RPROSD 411 (1) Removable Prosthodontics PDF - جامعة التكنولوجيا والمعلومات

Complete DENTURE PROSTHODONTICS For 4 year students th Course NAME: removable Prosthodontics (2) Course code: RPROSD 411 Removable Prosthodontics Department 2024-2025 by Assoc. Prof. Iman Adel ‫رؤية ورسالة الجامعة‬ ‫الرؤية‬ ‫تسعى الجامعة الحديثة للتكنولوجيا والمعلومات ان تكون احدى الجامعات الخاصة المتميزة‬ ‫والمؤثرة على المستوى المحلى واالقليمى‬ ‫الرسالة‬ ‫تعمل الجامعة الحديثة للتكنولوجيا والمعلومات على االرتقاء بالمستوى العلمى والجودة للخريج من‬ ‫خالل تقديم برامج تعليمية متطورة من اجل تلبية احتياجات سوق العمل الحالى والمستقبلى وتقديم‬ ‫خدمات للمجتمع واستشارات وابحاث اكاديمية وتطبيقية متميزة ومن خالل شراكة مع جامعات‬ ‫محلية واجنبية‪.‬‬ ‫رؤية ورسالة الكلية‬ ‫الرؤية‬ ‫تتطلع كلية طب الفم و األسنان – الجامعة الحديثة للتكنولوجيا و المعلومات إلى أن تكون من‬ ‫أكثر الكليات تميزا على المستوى المحلي و اإلقليمي في مجال طب األسنان‬ ‫الرسالة‬ ‫تلتزم الكلية بإعداد أطباء أسنان يتميزون بالجدارة المهنية قادرين على التوافق مع متطلبات‬ ‫سوق العمل ومواكبة التطور العلمي واإلسهام فيه باألنشطة البحثية مع تلبية إحتياجات المجتمع‬ ‫في إطار قيم أخالقية‬ ‫‪i‬‬ Vision The College of Oral and Dental Medicine - Modern University for Technology and Information aspires to be one of the most distinguished colleges at the local and regional levels in the field of dentistry. Mission The college is committed to prepare dentists who are distinguished by professional merit, able to comply with the requirements of the labor market and keep pace with scientific development and contribute to it through research activities while meeting the needs of the surrounding community within the framework of ethical values. ii ‫الغايات واألهداف اإلستراتيجية‬ ‫الغاية األولى‪ :‬تحقيق قدرة تنافسية متميزة فى تعليم طب األسنان‬ ‫الهدف األول‪:‬‬ ‫تطوير إستراتيجيات التدريس والتعلم بما يتفق مع اتجاه الدولة المصرية لتطوير التعليم الجامعي‪.‬‬ ‫الهدف الثاني‪:‬‬ ‫تطوير المحتوى العلمي للبرنامج ونظم التقويم والكتاب الجامعي واألنشطة الطالبية لتنمية مهارات طالب‬ ‫وخريجي الكلية بما يتفق مع متغيرات سوق العمل‪.‬‬ ‫الهدف الثالث‪:‬‬ ‫استيفاء أعداد أعضاء هيئة التدريس والهيئة المعاونة بما يتناسب مع أعداد الطالب‪.‬‬ ‫الهدف الرابع‪:‬‬ ‫استخدام تكنولوجيا المعلومات وأساليب التعلم الحديثة‪.‬‬ ‫الغاية الثانية ‪ :‬التميز واإلبداع في مجال البحث العلمي‬ ‫الهدف األول‪:‬‬ ‫تحفيز منظومة البحث العلمي بما يدعم تقديم خدمات بحثية ذات تطبيقات عالجية تلبي حاجة المجتمع المحلي‬ ‫والدولي‪.‬‬ ‫الهدف الثاني‪:‬‬ ‫توسيع مجاالت التعاون والشراكة البحثية محليا واقليميا وعالميا‪.‬‬ ‫الهدف الثالث‪:‬‬ ‫تطوير البنية البحثية والتكنولوجية للكلية‪.‬‬ ‫الهدف الرابع‪:‬‬ ‫االلتزام بأخالقيات البحث العلمي وضمان حقوق الملكية الفكرية‬ ‫الهدف الخامس‪:‬‬ ‫تشجيع أعضاء هيئة التدريس والهيئة المعاونة على نشر األبحاث العلمية المحلية والدولية والحث على‬ ‫المشاركة العلمية في المؤتمرات‪.‬‬ ‫الهدف السادس‪:‬‬ ‫إنشاء برامج تعليمية لمرحلة الدراسات العليا تلبي احتياجات الخريجين في سوق العمل‪.‬‬ ‫‪iii‬‬ ‫الغاية الثالثة ‪ :‬التكامل مع المجتمع المدني لتقديم خدمات عالجية فى طب األسنان‬ ‫الهدف األول‪:‬‬ ‫التوسع في التعاون مع مؤسسات المجتمع المدني المحيط لتلبية احتياجات المجتمع‪.‬‬ ‫الهدف الثاني‪:‬‬ ‫التوعية التثقيفية المستمرة داخليا وخارجيا لتلبية احتياجات المجتمع المحيط بالرعاية الصحية لألسنان‪.‬‬ ‫الهدف الثالث‪:‬‬ ‫التطوير المستمر للخدمات العالجية بالعيادات الخارجية للكلية‪.‬‬ ‫الهدف الرابع‪:‬‬ ‫دعم برامج التواصل مع الخريجين‪.‬‬ ‫الغايــة الــرابعة‪ :‬التــ ُميز واإلبــداع الـمؤســسي‬ ‫الهدف األول‪:‬‬ ‫تطوير البنية التحتية والتكنولوجية للكلية‪.‬‬ ‫الهدف الثاني‪:‬‬ ‫تنمية قدرات القيادات االكاديمية واالدارية الحالية والمستقبلية‪.‬‬ ‫الهدف الثالث‪:‬‬ ‫تنمية قدرات اعضاء هيئة التدريس والهيئة المعاونة والجهاز اإلداري‪.‬‬ ‫‪iv‬‬ Strategic goals and objectives The first aim: achieving distinct competitiveness in dental education First goal: Developing teaching and learning strategies in line with the Egyptian state’s direction to develop university education. Second goal: Developing the program’s scientific content, evaluation systems, university book, and student activities to develop the skills of college students and graduates in accordance with labor market variables. Third goal: Fulfilling the numbers of faculty members and supporting staff in proportion to the numbers of students. Fourth goal: Using information technology and modern learning methods. The second aim: excellence and creativity in the field of scientific research First goal: Stimulating the scientific research system to support the provision of research services with therapeutic applications that meet the needs of the local and international community. Second goal: Expanding areas of cooperation and research partnerships locally, regionally and globally. Third goal: Developing the college’s research and technological infrastructure. Fourth goal: Commitment to scientific research ethics and ensuring intellectual property rights. Fifth goal: Encouraging faculty members and supporting staff to publish local and international scientific research and encouraging scientific participation in conferences. sixth goal: Establishing postgraduate educational programs that meet the needs of graduates in the labor market. v The third aim: Integration with civil society to provide therapeutic services in dentistry First goal: Expanding cooperation with surrounding civil society institutions to meet community needs. Second goal: Continuous educational awareness, internally and externally, to meet the needs of the community surrounding dental health care Third goal: Supporting alumni communication programs. Fourth goal: Commitment to scientific research ethics and ensuring intellectual property rights.. The fourth aim: Institutional excellence and creativity First goal: Developing the college’s infrastructure and technology. Second goal: Developing the capabilities of current and future academic and administrative leaders. Third goal: Developing the capabilities of faculty members, supporting staff, and the administrative staff. vi Table of contents CHAPTER TOPIC PAGE NUMBER 1 Diagnosis and treatment planning of 1 completely edentulous cases 2 Complete denture impressions 36 3 Recording the maxillo-mandibular relations 71 4 Try- in of complete denture 106 5 Denture insertion and remounting 127 techniques 6 Denture problems and patient’s 144 complaints vii Diagnosis and treatment planning of completely edentulous cases Diagnosis and treatment planning of completely edentulous cases To construct a successful denture, a thorough extra and intra oral examination of the mouth should be conducted; including the condition of the existing denture, denture- supporting areas, the condition of the temporomandibular joint and the appearance. As most edentulous patients are old, the examination must be carried out not only regarding the condition of the oral cavity but also in relation to their general health. Examination: It is the first clinical step in complete denture treatment to reach a proper diagnosis & to list a suit ble treatment planning. Diagnosis: It is the determination of the nature, location and causes of diseases. 1 Diagnosis and treatment planning of completely edentulous cases Objectives: 1) Assessment of the patient's genera health condition. 2) Evaluation of the condition of the oral tissues before making prosthesis. 3) Psychological & mental evaluation of the subj ect under treatment. 4) Determination of the possible difficulties expected for the case. 5) Reaching the highest level of success for the definite case. A- History Taking: I-Patient History and personal informations: 1- Patient’s Social Information: Knowledge of a patient's social status can help the dentist to understand the patient's expectations and may also indicate the socioeconomic level of the patient. 2 Diagnosis and treatment planning of completely edentulous cases A- The Patient's Age: In general, though there are many exceptions, increasing age decreases the readiness to form new habits and also muscular efficiency is often impaired. B- The Patient's Occupation: This will frequently have a relation to the design of the dentures and the technique used in impression making, for example. 1- With most professional men and many others whose occupation entails intimate contact with their fellows, appearance and retention are more important than efficiency. 2- Public speakers and singers require not only perfect retention but also particular attention to palatal shape and thickness because of the importance of these in phonation. C- The Patient's Attitude to Appearance: This is often a matter of supreme importance to the individual and where this is the case the operator must be prepared to devote extra time and care to this part of denture construction. 3 Diagnosis and treatment planning of completely edentulous cases 2-Patient Past Medical History: The dentist not only must be aware of the systemic diseases but must also consider them in the treatment plan. These diseases such as: Diabetes, tuberculosis, and blood dyscrasias are examples. These patients may require extra instructions in oral hygiene, eating habits and tissue rest. Since the supporting bone may be affected by the disease, frequent recall appointments should be arranged to keep the denture base adapted and the occlusion corrected. 3- Patient’s Mental Attitude House (1978) classified patients as: A- Philosophical Patient The best mental attitude for denture acceptance is the philosophical type. These patients are rational, sensible, calm, and cooperative in difficult situations. Their motivation is generalized, as they desire dentures for the maintenance of health and appearance and feel that having teeth replaced is a normal, acceptable proce- 4 Diagnosis and treatment planning of completely edentulous cases dure. They eliminate frustrations and learn to adjust rapidly. B- Exacting Patient The exacting type may have all of the good attributes of the philosophical patients; however, they may require extreme care, effort and patience on the part of the dentist. These patients are methodical, precise, and accurate and at times make severe demands. They like each step in the procedure explained in detail. C- Indifferent Patient The indifferent type of patient presents a questionable or unfavorable prognosis. These patients evidence little if any concern; they are apathetic and uninterested and lack motivation. Indifferent patients pay no attention to instructions, will not cooperate, and are prone to blame the dentist for poor dental health. Unfortunately, many young patients are this type. An education program in dental conditions and dental treatment is the recommended treatment plan before denture construction. D- Hysterical Patient 5 Diagnosis and treatment planning of completely edentulous cases The hysterical type is emotionally unstable, excitable, excessively apprehensive, and hypertensive. The prognosis is often unfavorable, and additional profes- sional help (psychiatric) is required prior to and during treatment. These patients must be made aware that their problem is primarily systemic and that many of their symptoms are not the result of dentures. The behavior profile of the patient includes 1. Ideal patient. 2. Submitter. 3. Reluctant 4. Indifferent. 5. Resistant. 1. Ideal patient Reasonably engaged and reasonably willing to trust the dentist. 2. Submitter. The patient lacks discrimination and tend to idealize the dentist which result in high degree of engagement. 3. Reluctant The patient is always leery of the dentist and skeptical of the treatment plan 4. Indifferent 6 Diagnosis and treatment planning of completely edentulous cases Patient is minimally engaged and the patient’s willingness to trust the dentist is not an issue to him 5. Resistant These patients are skeptical of the dentist as a person and of being helped by anyone under any circumstances. 4-Patient’s Past Dental history An attitude of mind will have been formed by the patient's own past experience of dentures, if any, or from his observation of friends or relatives who wear dentures. A- The Patient's Attitude to Dentures: 1- If the patient has worn partial dentures with comfort and efficiency, prior to being rendered edentulous, the same will be expected of complete dentures. 2- If complete dentures are already being worn and they have been comfortable and efficient, the same will be expected of the new dentures. If the old complete dentures were troublesome, the attitude may be expectant of better results with the new dentures or pessimism that nothing better can be hoped for. 7 Diagnosis and treatment planning of completely edentulous cases 3- If no previous denture experience exists, friends or relations may have colored the patient's mind with their own attitudes. In such cases the efficient control and use of complete dentures depend to a very large extent on the formation of new habits and a new pattern of muscular movement. This demands time and some patience on the part of the wearer. Many complete denture troubles can be traced to the fact that no 4- preparation of the patient's mind preceded the fitting of the dentures. B- Information Regarding the Loss of the Natural Teeth: A history of difficult extractions should be followed by a radiographic examination of the jaws to verify the absence of retained roots. Questioning should be directed to eliciting the general order in which the teeth were lost. For example, if all the posterior teeth were extracted some years before the anterior ones and no partial dentures were worn in the meantime, then a habit of eating with the front teeth will have been formed which, if persisted in, will have a pronounced unstablizing effect on complete dentures. A similar condition will exist in individuals who have been edentulous for a considerable length of time and have not worn dentures, for thus they are only able to 8 Diagnosis and treatment planning of completely edentulous cases approximate their jaws in the anterior region and consequently forward travel of the mandible is necessary all the time during eating. When there is a history of abnormal mandibular function or movement, then difficulty can be anticipated when registering the antero-posterior occlusal relationship. B-Extra-Oral Examination 1- The patient’s head and neck region should be first examined for the presence of any pathological condition related to nondental or systemic disease. 2- Hair and eyes color and complexion are noted because these factors, along with the patient’s age, are important in determining the teeth shade. 3- The lips should be examined for cracking, fissuring at the corners of the mouth, and ulceration. The apparent support of the lip is noted. The philtrum, nasolabial fold and mentolabial grooves are observed for fullness. Loose wrinkled skin may be impossible to be properly supported with artificial anterior teeth. Thickness of the lip is an important factor for tooth placement. Thin lips are highly sensitive to the position of anterior teeth. A thick lip gives more freedom in 9 Diagnosis and treatment planning of completely edentulous cases setting the teeth before changing the lip contour. The length of the lip will affect how much tooth will be exposed. 5- A patient’s profile appears not only as flat or curved, it also can be an early indicator of the patient’s jaw relation (classification; fig 1, 2). a, Angle Class I: a normal ridge relationship, the mento-labial sulcus shows a gentle curvature with an obtuse angle. b, b, Angle Class II: a retn1ded mandibular position, the mento-labial sulcus shows an acute angle. c, Angle Class III: protruded maxillo- mandibular relationship, the mento-labial sulcus forms nearly a straight angle (180°). 10 Diagnosis and treatment planning of completely edentulous cases Fig. (1); a- Angle class I (Normal), b- Angle class II(retrognathic), c- Angle class III (prognathic) A 11 Diagnosis and treatment planning of completely edentulous cases B Fig. (2): A- Angle Class II, B- Angle Class III 5- Temporomandibular joint examination (TMJ): The TMJ and muscles of mastication should be evaluated for pain by palpation or mandibular movement. As the mandible is opened and closed, the range of opening, any deviation or joint sound should be noted. The presence of any of these symptoms is an indicator of TMJ disorder. Fig (3) 12 Diagnosis and treatment planning of completely edentulous cases Fig (3): TMJ Examination 6- Angle of the mouth (commissure) It is the point of meeting between the maxillary and mandibular lips. Inflammation due to drooping of saliva from the angle of the mouth is termed Angular cheilitis. It may be the result of: a. Prolonged edentulism, b. Denture with reduced ve1iical dimension. c. Vitamin B12 deficiency. d. Fungal infection In the first two conditions, construction of the denture with proper vertical dimension and proper positioning of the anterior teeth will suppmi the angle of the mouth and hence improve the case. Inflammation due to vitamin B12 deficiency can be treated by administration of B12. 8- Modiolus 13 Diagnosis and treatment planning of completely edentulous cases It is the point of meeting of facial muscle fibers. It 1s a depression located below and distal to the angle of mouth. After loss of teeth and alveolar bone resorption, the modiolus drops inward resulting in the characteristic appearance of edentulism. Proper denture construction restores its natural appearance 9- Extra-oral Pathological lesions: The examination should also include an extra-oral assessment of any pathological lesions such as abscesses, cysts, herpes, ulcers or any facial asymmetry. C-Intra-Oral Examination 1- Color of the Mucous Membrane: Any variation from the normal must be investigated, and though whitish patches or spots of hyper- keratinization are not uncommon, the most usual variation found is an increased redness due to inflammation Fig (4) caused by irritation whether mechanical, chemical or bacteriological. This is done by following a tissue health rehabilitation program. For good prognosis, the cause should be first removed. Tissues are then allowed to rest and recover either by simply keeping the dentures out. of the mouth or by using soft lining denture materials. Surgery may 14 Diagnosis and treatment planning of completely edentulous cases sometimes be required to ensure the presence of healthy foundation tissues. Palpation is necessary to detect the resiliency and displaceability of the oral tissues. - Denture supporting tissues should exhibit 1-2 mm resiliency which is necessary to aid in denture retention. Non displaceable tissues are unfavorable for attaining denture retention and easily damaged by pressure from the denture. Localized areas of non-resilient tissues require relief. However, tissues exhibiting more than 2 mm displaceability present an unstable denture foundation. These tissues are either in the form of flabby tissues overlying ridge crests or hypertrophied tissues forming tissue folds. -Localized areas of flabby tissues and localized areas of non-resilient tissues require suitable impression technique usually selective pressure impression technique should be planned. Cuspless teeth should also be used to eliminate horizontal forces. In cases of excessively thick generalized flabby tissues surgery should be considered. 15 Diagnosis and treatment planning of completely edentulous cases Fig. (4): Inflamed Mucosa Common Prosthetic Causes for color variation: a- Overextension of the periphery of the denture: - This is frequently seen as a bright red line, which may lead to ulceration if the irritation is continued. It may be due to overextension of the periphery of new dentures or the altered position of existing dentures due to alveolar absorption. In some cases, this irritation if continued over a long period of time, will cause a proliferation of the mucous membrane, which is visible as a ridge, flap, or series of flaps. 16 Diagnosis and treatment planning of completely edentulous cases b- Ill-fitting dentures (stained, bad denture hygiene): The inflammation usually appears as an ill-defined red area which varies with the extent of the mucous membrane most constantly in contact with the denture. c- Continuous wearing of the denture: It may cause a chronic inflammation of the underlying mucosa. d- Faulty articulation of teeth: Inflammation may be found on the crest of the alveolar ridge if the occlusion is too heavy in one particular spot or on the sides of the ridge if there is a lateral drag caused by cuspal interference. e-Traumatic injury: The edentulous mouth frequently sustains trifling injuries to the mucosa from sharp pieces of food such as crusts or small bones. f-Small spicules of alveolar bone: Sharp edges of tooth sockets not yet rounded by absorption frequently cause inflammation of the mucosa covering them. Also, small pieces of bone fractured during the extraction of the teeth and in the process of being exfoliated may cause inflammation. g-Allergy: 17 Diagnosis and treatment planning of completely edentulous cases It is very rare. Most of the cases are due to dirty, ill- fitting dentures. Other Causes of Color Variation: These are most frequently a sign of some general systemic disturbances for which reference to an oral Pathologist is recommended, and the only safe rule to follow is never to proceed with prosthetic work until the cause of color variation has been investigated. 2- Size and Shape of the Arches and Alveolar Ridges: 1-The arch size and form: The form, size and condition of the bony foundation greatly affect the support, retention and stability of complete dentures. Therefore, proper examination is essential in planning and designing the denture. -The size of the mandibular and maxillary arches determines the support available for complete dentures. The greater the size the more the support. -The larger the size, the more the area covered by the denture, the better the retention and stability. Tapered squared ovoid 18 Diagnosis and treatment planning of completely edentulous cases Fig. (5): Different arch forms & ridge Contour 3- Shape of the Hard Palate: a. Hard palate. b. soft palate. a-Hard Palate: The Palatal Vault: The most favorable palatal vault form is the one with medium depth and exhibiting a well-defined rugae area. - A flat palatal vault presents insufficient resistance to forward (lateral) movement of the maxillary denture, loss of stability and hence loss of retention. - Such dentures can be easily dislodged by lateral or anteriorly directed forces. Balanced occlusion is necessary for these dentures. - A high (v- shaped) palatal vault is also unfavorable for denture retention. The denture presses against the sides of the vault (may offer better resistance to lateral forces than flat palatal vault) but it may become unretained and loose. Metallic denture baes can be used in these cases. 19 Diagnosis and treatment planning of completely edentulous cases Fig. (6): V- shaped palate Flat palate with flat ridges (left) ( Right) b- Soft palate and Throat Form: The throat form is classified according to the curvature of the soft palate into three classes. The soft palate with gentle curvature is the most favorable for obtaining adequate post darning, while the soft palate with sharp curvature (curtain type) provides a narrow posterior palatal seal area which adversely affects denture. Types of soft palate Class I soft palate of gentle curve gives broad posterior palatal seal (favorable). Class II Medium curvature offers medium width posterior palatal seal. · Class III Abrupt curvature with narrow posterior palatal seal. 20 Diagnosis and treatment planning of completely edentulous cases Fig. (7): Soft palate curvatures 4- Depth of the Sulci: Whenever a very shallow sulcus is encountered a special impression technique will be required to obtain an adequate peripheral seal and so utilize atmospheric pressure to the full as a retentive force. The oral vestibule should be examined to insure the presence of displaceable tissues at the mucous reflection area. The border of the denture flange should lie on slightly compressible (resilient) but immovable tissues to provide adequate peripheral seal necessary for denture retention. Encroachment of the denture border 21 Diagnosis and treatment planning of completely edentulous cases on non-resilient tissues results in soreness and instability. This usually occurs if the denture is overextended in the area of the zygoma. -Examination of the frenal attachments is necessary. A broad frenum occupying a position near the ridge crest requires surgical correction (frenectomy) rather than excessively relieving the denture by a deep and wide V- shaped notch. Excessive relief in this area causes loss of peripheral seal and results in a weak denture base prone to midline fracture. 5- Interference Factors: The size of the tongue, tightness of the lips and any abnormal muscular or frenal attachments must be noted as they will influence the design of the dentures, and the type and position of the artificial teeth used. a) The Tongue size and type: -The tongue is a muscular organ whose size, form, position and function influences impression making and affects the prognosis of complete dentures. A broad thick tongue helps in creating a good peripheral seal. However, an abnormal tongue may hinder proper denture construction( difficult 22 Diagnosis and treatment planning of completely edentulous cases impression making). A small tongue simplifies impression making but cannot provide good peripheral seal and so impairs retention. -Abnormal tongue conditions can be improved by patient education. The tongue seems to become larger and more powerful when a person has been wearing an inadequate denture or spent a long time without having a complete denture constructed to replace his teeth. The tongue also tends to spread to fill spaces occupied by mandibular molars that have been missing for a long time. 6- Ridge relations: a) types of maxilla-mandibular relationships -Normal relationship between maxillary and mandibular arches indicates favorable prognosis. Disharmony in jaw sizes may be due to genetic factors or due to improper growth and development. - Angle class I (normal) - Angle class II (retrognathia) - Angle class III (Prognathia) -Angle's class II (retruded mandible) and class III (protruded mandible) present a problem in the placement of teeth. This problem should be recognized and handled during denture 23 Diagnosis and treatment planning of completely edentulous cases construction. Surgical correction may sometimes be required to correct extreme protrusion of either ridge to enhance the prognosis of the denture. -Maxillary protrusion (class II) is the least favorable because the area covered by the mandibular denture is always less than that of the maxillary. -Mandibular protrusion (class Ill) causes marked trauma to the anterior maxillary ridge due to concentration of biting and masticatory forces in this area. b) Inter-arch distance: The anteroposterior and lateral relationships of the maxillary and mandibular ridges should be observed at the appropriate occlusal vertical dimension.The amount of inter-ridge distance should also be noted. A moderate space should exist between n1axillary and mandibular ridges. It is rather difficult to detect the inter-ridge space by visual examination and is better diagnosed by mounted study casts. -Insufficient inter-ridge distance is usually accentuated between the maxillary tuberosity and the retromolar pad area. Although insufficient inter-ridge distance 24 Diagnosis and treatment planning of completely edentulous cases enhances denture retention and stability, it presents a problem during setting-up of teeth, hence it is advisable to use teeth which chemically binds to the denture base. -An excessive amount of inter-arch (inter-ridge) distance will result in poor stability and retention because of increased leverage. A small amount of interridge distance will lead to difficulty in setting teeth and maintaining a proper free-way space In such condition, proper selection and placement of teeth is necessary. Posterior teeth are preferably set near the mandibular ridge (most commonly it is the weaker ridge due to lower surface area compared to maxillary) to enhance denture stability. 7- Unextracted Roots: These may be flush with, or protruding above, the surrounding mucous membrane, with or without an obvious area of inflammation round them. They may be loose or firm, and in the latter case it is always wise to take X-ray radiograph. 8- Sinuses: An infected area in the bone, such as surrounds the retained broken off apex of a tooth, usually 25 Diagnosis and treatment planning of completely edentulous cases communicates with the surface through a channel known as a sinus. 9- 0ral lesions: a. Sharp Bony Spicules. Sharp Bony Spicules Bony spicules should be surgically removed before impression procedures because they should be. undesirable sources of tissue injury and patient discomfort b. Simple ulceration of the mucous membrane c. Hyperplasia or hypertrophy (epulis fissuratum) as fibrous tuberosities, papillary hyperplasia in the palatal vault, epulis fissuratum in the sulcular epithelium resulting from ill-fitting denture flanges or hypermobile ridge tissues· covering atrophic knife-edge ridges. - These abnormalities (tissue recovery program) are first treated by a conservative method in which the cause for this abnormality is eliminated, tissues are allowed to rest. A soft-liner conditioning material may then be used to allow tissues to collapse and regain their form. Surgical removal of abnormal tissues will only be indicated in cases resisting conservative treatment. d. Remaining roots/impacted teeth 26 Diagnosis and treatment planning of completely edentulous cases e. Sinuses f. Cysts g. Neoplastic changes Any abnormal swellings in the mouth must be investigated and diagnosed, and when found only on one side they are much more likely to be pathological than when they are bilateral. 10- kind of alveolar ridge -The alveolar ridge is either: Normal ridge, Flat ridge, Knife edge ridge or Flabby ridge. The ridge form affects the retention and stability of complete dentures. It also influences the choice of the type of artificial teeth. The U-shaped ridge is the most favorable because its height resists lateral displacement, and the parallelism of its sides resists vertical displacement. -Flat severely resorbed ridges lack lateral stability due to the absence of ridge height. The mental foramen usually attains a position near the ridge crest and hence should be relieved. A special impression. technique is usually required. -The crest and slopes of knife edged ridges offer poor prognosis due to lack of proper denture supporting 27 Diagnosis and treatment planning of completely edentulous cases foundation area. Selective pressure impression may be required to eliminate pressure on the ridge crest. 11- maxillary tuberosities: -The maxillary tuberosities provide support and retention to the maxillary denture; hence the denture should completely cover them. Large tuberosities are usually associated with undercut areas that may interfere with denture insertion. If moderately enlarged bilateral tuberosities, one of them can be blocked (relieved) and the other one used to be engaged as an undercut to enhance denture retention. If large undercuts are present bilaterally, one of them should be surgically eliminated. If large bilateral undercuts are present together with undercuts on the labial slope of the anterior ridge, it is usually more conservative to remove the two opposing undercuts in the tuberosity areas. The presence of undercut areas may interfere with denture retention and insertion. Large, sharp, extensive, numerous or bilaterally opposed undercuts present problems in denture construction which may sometimes necessitates surgical elimination -A unilateral undercut can be avoided by inserting and removing the denture in a rotating path. This enhances denture retention. Fig (8) 28 Diagnosis and treatment planning of completely edentulous cases -A large unilateral tuberosity undercut should sometimes be surgically reduced to avoid resistance exerted by the coronoid process on the denture flange in this area. The maxillary tuberosity may often extend inferiorly to occlude with the retromolar pad obliterating the inter-ridge space in this area. In such cases surgical removal of the tuberosity is necessary. -The maxillary tuberosity may sometimes be covered with large pendulous fibrous tissues that may contribute to excessive vertical and horizontal movement which in tum affects denture retention and stability. These fibrous tissues should be surgically removed. Fig. (8): rotational insertion path of denture 12- Tori Tori are hard bony protuberances covered by thin, non- resilient soft tissues which can be easily irritated. S1nall 29 Diagnosis and treatment planning of completely edentulous cases tori are usually relieved to avoid rocking and instability of dentures. While large tori are surgically removed or reduced in size. 13- Saliva: -Through aging, salivary flow decreases and its contents change. The quantity and quality of saliva are among the important diagnostic data because of their effect on denture retention. -As saliva (thin serous) enhances denture retention by intervening between the dentures and the mucosa, a patient with scanty (low amount) saliva will have poor denture retention. Also in a dry oral cavity, the mucosa lying beneath the denture base may be easily traumatized and therefore the impression surface of the denture must be polished more smoothly. -Xerostomia (dry mouth) also hinders denture retention “and the lips and cheeks may stick to the denture base. - The diminution in salivary flow will not moisten the oral mucosa and will interfere with the functions of mastication, swallowing and phonetics. In some cases, the use of artificial saliva or medications promoting salivary secretion should be recommended. 30 Diagnosis and treatment planning of completely edentulous cases -Copious thick ropy saliva interferes with the accuracy of the impression procedures, initiates nausea and gagging reflex and hinders denture retention D- Digital Examination: Before starting to explore the mouth with the finger tips the patient should be asked to indicate immediately if any pain is felt and the cause of such pain must be found. Any area which is painful to the pressure of a soft finger is unlikely to tolerate the pressure of a hard denture. 1-Firmness of the Ridge: This is most conveniently tested by placing a finger on each side of the ridge and applying alternate lateral pressure. Flabby fibrous ridge may be encountered in all parts both of upper and lower jaws. 2- Irregularities of the Alveolar Ridge: Alveolar absorption is never uniform and hard nodules, sharp edges, spikes and irregularities are frequently felt and pain on pressure over these areas is common. The prosthodontist must at this stage decide whether surgical correction is needed, whether they will remedy themselves in time in course of normal absorption or whether relief of the denture alone will be satisfactory. 31 Diagnosis and treatment planning of completely edentulous cases 3- Variations of Mucous Membrane: The ideal mucosa on which to seat complete dentures should be: a- Firmly bound down to the sub-adjacent bone by union with the periosteum which will thus prevent the denture and mucosa moving together in relation to the supporting bone. b- Slightly compressible. This will allow the denture to bed comfortably into place because the mucosa will adjust itself slightly to the fitting surface of the denture. c- Of an even thickness. This condition is never realized. 4- Maxillary Tuberosities: These may be found on visual examination to be bulbous and to have a definite undercut area above them, but only by palpation can it be determined whether the bulbous portion is composed of hard or soft tissues. 5- Mylohyoid Ridges: Some of these ridges are felt to be pronounced and sharp and others are felt ill defined and rounded. 6- Lingual Pouch: 32 Diagnosis and treatment planning of completely edentulous cases The extent of the pouch with the tongue at rest and with tongue protruded sufficiently to lick the lips and also during the act of swallowing should be noted. This is most conveniently done by gently inserting the index finger into the pouch and asking the patient to perform the above actions when the alterations in the extent of the pouch can be felt. E- Radiographic Examination: Ideally a panoramic or cephalometric X-ray examination should be made for every edentulous patient prior to starting denture construction. When it is considered that the routine is uneconomic or too time- consuming, X-ray photographs should still be taken to confirm or assist in diagnosis in the following cases: 1- Remaining roots. 2- Sinuses. 3- Unilateral swellings. 4- Rough alveolar ridges. 5- Areas painful to pressure. 6- Impacted teeth. 7- Cysts. 33 Diagnosis and treatment planning of completely edentulous cases F- Pre-extraction Records and Helpful aids Records Records taken from the patient before reaching complete edentulism. These records are a useful guide in restoring the patient's natural appearance and facial contour, these records include: 1 - Radiographs. 2- Photographs of the patient's face before extraction of teeth. 3- Record of the shade and color of the natural teeth will help and guide in proper tooth selection. 4-Diagnostic casts which may or may not be mounted on an articulator. Mounted casts will help to visualize the position and the relationship between teeth. They also help to evaluate the inter-ridge space. 5- Measurements made between landmarks on the patient's face. 7- Contoured wire profile or silhouettes. 8- Face masks obtained by making a hydrocolloid impression of the facial structures especially around the mouth, chin and nose. 9- Some investigations (blood pressure,cbc and sugar analysis... etc.). 34 Diagnosis and treatment planning of completely edentulous cases 9- Biopsy. G- Old Dentures Moreover, if the patient has an old denture, it is examined for the following: a. Denture age and condition. b. Denture extension. c. Vertical dimension of occlusion and interocclusal distance. d. Retention and stability. e. Esthetics and soft tissue support by the denture. f. Masticatory stability. g. Hard and soft microbial deposit on the denture. h. Phonation. i. Pattern of tooth wear. Development of the Treatment Plan A thorough and careful diagnosis is the key of a successful treatment plan. Data collected during diagnosis are studied and analyzed to develop the best suitable treatment plan and offers the correct prognosis for each case. 35 Complete denture impressions Complete denture impressions Impression: Is a negative imprint or reproduction of the entire denture bearing areas and the border limiting structures. An impression is made to reproduce a positive form of the oral tissue (cast or model) which is either primary (study or diagnostic) or secondary (final or master). Requirements of an ideal denture with an ideal impression: Maximum area of coverage within anatomic-physiological limits. Intimate adaptation with the tissue surface to reproduce the foundation and border tissues accurately. Extension into the vestibule to create a border seal. No impingement on the action of the muscles. Equalization of forces on the denture foundation area. To achieve a successful impression the following conditions should be achieved 1- The tissues of the mouth must be healthy. 2- Proper space for the selected impression material should be provided within the impression tray 3- The impression should extend to include all the supporting and limiting structures. 4- A physiological type of border molding should be performed. 5- The impression must determine the selective placement of forces by the denture base on the supporting structures. 6- The impression must record the fine details of the surface of the soft tissues to be covered. Complete denture impressions Objectives of an impression 1-Retention 2- Support 3- Stability 4- Providing improved lip support and Esthetics 5- Preservation of the remaining residual alveolar ridge 1-Retention If the other objectives are achieved, retention will be adequate. 2-Support Maximum coverage provides distribution of the load over wide area so that load per unit area will be reduced. 3-Stability Stability is the resistance to horizontal movement. Denture stability is important to the preservation of the denture supporting structures (soft tissues and bone). 4-Providing improved lip support and Esthetics: In patients with severely resorbed maxillary ridges, the flanges and borders of the denture should have sufficient thickness to provide proper lip support and proper arrangement of artificial teeth. Border thickness should be varied with the needs of each patient in accordance with the extent of residual ridge loss. 5-Preservation of the remaining residual alveolar ridge: The primary goal for any step in complete denture construction is preservation of remaining oral tissues. The impression technique and impression material influence the accuracy of denture base which has an effect on the continued health of both the soft and hard tissues of the jaws. Pressure in the impression technique is reflected as pressure from the denture base to soft tissue and bone. This pressure could lead to tissue damage and bone resorption. Complete denture impressions For construction of complete dentures, two impressions are required: 1- Primary (Preliminary) impression using stock tray to obtain a study cast on which a custom tray is constructed. 2- Secondary (Final or definitive) impression Using special (custom) tray to obtain a master cast on which the denture is constructed. Types of Secondary Impression techniques: 1. Minimal pressure impression technique (impression theory) 2. Definitive Pressure (functional) impression technique (impression theory) 3. Selective pressure techniques (impression theory) 4. Reline and rebase techniques 5. Conventional techniques Before Taking any impression, A tissue recovery program should be executed; The oral tissues should be healthy before impressions are taken. Any distortion or inflammation of the denture foundation tissues must be eliminated before the impressions are made as the following: 1- The patients must leave their old dentures out of the mouth for at least 24 hours before the impressions are made. 2- Use of tissue conditioners if the patient cannot leave the dentures outside the mouth. Complete denture impressions Primary Impression Primary impressions are made with alginate impression material in perforated stock trays or with modeling compound in plain stock trays. Trays used for primary impression: ' Trays for primary impressions tend to be selected from a supply of 'stock' trays which are designed to cover a broad range of arch forms and Sizes. Some trays are metallic and have fixed handles; some are plastic with fixed or attachable handles. Although any tray could be used, consistently successful results tend to be produced when rigid trays of appropriate extension are used, especially when recording impressions of the mandibular arch. Fig (1): perforated stock tray for alginate (left), non-perforated stock trayfor impression compound (right) The Position of the Patient and the operator: 1- The patient is seated in an upright position with the head in line with the body. The back and the head rest should be adjusted to give support. 2- The patient’s mouth should be on a level with the operator’s elbow when making the lower impression. 3- The patient’s mouth should be on a level with the operator’s elbow when making the upper impression. The operator Complete denture impressions should be in front of the patient and on the right side when making the lower impression. 5- The operator should be to the right and a little behind the patient when making the upper impression. The Impression materials: The Impression materials generally used for primary impression are: 1- Impression compound. 2- Irreversible hydrocolloid (alginate). Selection of the Stock Tray: o Stock trays are supplied in different sizes, forms , materials (metallic or plastics) and they either perforated or non-perforated according to the selected impression material o The alveolar ridges and palate are examined for shape and size, o Stock trays with suitable size and shape were selected and tested in the mouth for their approximation to the oral structures. o Stock trays should have 3-5 mm space between the ridge and the tray o Tray is placed in mouth by centering the labial notch of the tray over the labial frenum o Once the tray is anteriorly positioned , it is observed posteriorly for extension. Maxillary trays should extend slightly beyond the vibrating line while mandibular trays should cover retromolar pads Complete denture impressions If the tray is too large, this will: 1- Distort the tissues around the borders of the impression. 2- Pull the soft tissues under the impression away from the bone. 3- Distort the dimensions of the sulcus. If it is too small:- The border tissue will collapse inward onto the residual ridge. Modification of stock tray Over extended flanges of the trays can be modified by bending the tray slightly with pliers or cutting the flange with a scissor to accommodate frena and prevent pressure on bony structures such as the zygomatic process of the maxilla. In case of alginate impression, shortness in the flanges can be corrected by the addition of a little warmed composition (impression compound), or soft base plate wax in order to correct border under extension (In case of using impression compound as a primary impression material, the material itself act as both border modification and impression materials) For upper trays, base plate wax may be added across the posterior border. If the palatal vault is deep, the central portion of the tray is built-up with base plate wax to ensure a relative uniform thickness of impression material and to guard against slumping of the impression material away from the palate. The corrected tray is reinserted in the mouth and the periphery is molded while the border modification material is soft. Complete denture impressions The sequence of impression making: It is generally advisable that the lower impression should be made first for two reasons: 1. The upper impression causes greater discomfort and anxiety, through stimulation of gag reflex 2. A foreign body placed in the mouth produces an increase in the rate of salivation. Therefore, it is preferable to have the lower impression seated in position before this takes place. Materials for primary impression Making: I- Compound impression Impression Compound is a thermoplastic material which is suitable for use in obtaining preliminary impressions for edentulous mouth specially of patients with flat ridges or for patients who have gagging problem. impression compound is supplied in flat sheets. The material is incapable of reproducing undercuts. In general, compounds are not considered as an accurate impression material, and it should never be reused because of fear of cross infection. To prepare the material for use, its heated in water bath at 55-60c. Since the material has a low thermal conductivity, it must be immersed in the water bath for sufficient time to ensure complete softening. The compound is, then, removed from the water bath, folded repeatedly from the edges to the center then replaced back into the water path as quickly as possible to prevent loss of heat. kneading the compound (folding it repeatedly )incorporates water into the mass which act as a plasticizer. Complete denture impressions This procedure is repeated until the material has acquired a uniform softness For mandibular impression, the soft compound is shaped in the form of a roll , that must be thicker posteriorly and in the lingual side to help in producing lingual sulcus depth. A trough may be formed in the compound with the finger to simulate the ridge. For maxillary impression, the compound is softened , molded in the form of ball , placed in the center of palatal region. The compound is spread in the tray until the whole tray is filled. Then a trough is formed in the compound with the finger to simulate the ridge. The loaded stock tray then the tray is placed into the mouth The patient is asked to do functional movements The tray is held in place for one minute or two, removed and chilled thoroughly in cold water. Advantages of compound impression: 1- Addition and correction can be done. 2- Ease of manipulation. 3- Well tolerated by the patients. II- Alginate impression Indications 1- Some authors recommend the use of alginate for all completely edentulous cases. 2- Severe undercuts Complete denture impressions Contra-indications: 1- Nausea to the patient. 2- Flat ridges. Advantages: 1- Alginate produces excellent surface details. 2- It is elastic and can be withdrawn over undercuts. Disadvantages: 1- It does not accept addition. 2-Dimensional instability due to syneresis or imbibition. 3-The stresses induced in the material are released slowly, so alginate impression should be poured rapidly. 4- The alginates will not adhere to the tray. -Attachment of the alginate to the tray is essential because if it pulls away from the tray flange, a distorted impression will result which may pass unnoticed since the detail of the surface will remain unchanged. Fixation may be affected by small holes in the tray through which some of the alginate will flow securing the impression firmly to the tray. Precautions for alginate impression: When alginate is used as an impression material the following points should be observed in order to obtain the best results: 1- The clearance space between the tray and the model should be approximately 4- 5 mm. 2-The under-extended borders of the tray can be corrected by impression compound or base plate wax, Also, the palatal portion of the tray is built by compound or wax in case of high palatal vault. Complete denture impressions 2- The container of powder should be shaken before use to get an even distribution of constituents. 3- The powder and water should be measured, as directed by the manufacturer. 4- Room temperature water is usually used, slower or faster setting time can be achieved, if required, by using cooler or warmer water, respectively. 5- Vigorous mixing by spreading the material against the side of the bowl. 6- During setting of the material, it is important that the impression should not be moved. As the material in contact with the tissues sets first so pressure on the gel due to tray movement will set up stresses within the material, which will distort the alginate after its removal from the mouth. 7- Before removing the impression, the seal should be freed by running the finger round the periphery. 8- An alginate impression should be displaced sharply from the tissues to ensure the best elastic behavior. This is to avoid tearing or pulling the alginate away from the tray. 9- On removal from the mouth, the impression should be washed with cold water to remove saliva, covered with a damp napkin to prevent syneresis, and poured as soon as possible, preferably not more than 15 minutes after making the impression , to avoid syneresis or imbibition. Maxillary preliminary impression Procedures: 1 -The shape, size and form of the residual ridge and palate are examined to estimate the size of the tray. The width and depth of the vestibular space should be evaluated with the mouth half opened and the upper lip held slightly outward and downward. 2-A suitable sized perforated stock tray that matches the size and form the dental arch is selected. The selected tray is inserted in the mouth by a rotating motion, oriented in position and centered over Complete denture impressions the residual ridge. The size of the tray is checked by positioning the posterior border of the tray on the hamular notches. The tray should be a-Large enough to provide 4-5mm space for the impression. b- The borders of the tray should be 3-4mm short of the tissue reflection to allow for accurate registration and normal function of the limiting structures. c- Posteriorly the tray has to be extended into the buccal space and must contain both hamular notches and extend posteriorly to the vibrating line. 3·The short tray borders are corrected by adding wax. Over extended tray ' borders can be reduced with a scissors. Roughened edges should be ' smoothed with file or covered by wax. 4-If the space between the ridge and tray is too large at the periphery, as in cases with labial undercut the tray should be adjusted by bending or by the addition of wax on the tissue surface of the tray. If the patient has a high palatal vault, the palatal portion of the tray should be built up with wax or modeling compound to prevent the material from sagging away from the palatal portion 5-Before making the preliminary impression, the operator should practice placing the tray in position correctly on the maxillary ridge. The cheek is retracted on the side away from the operator and the tray is rotated into the mouth from the near side. The tray is first seated on the side away from the operator, next on the anterior area while reflecting the lip and then on the near side and the tray is centered below the residual ridge. The upper lip is elevated, and the tray is carried upward with the labial frenum used as a centering guide. When the tray is located properly anteriorly, the index fingers are placed on the molar region on both sides and pressure is applied upward until the posterior border of the tray comes into contact with the tissues in the posterior palatal seal area. 6-The measured amount of water is placed in a clean dry rubber mixing bowl. The correct measure of powder is added, spatulated rapidly against the side of the bowl to obtain a thick creamy mix. The patient is instructed to rinse his mouth with water to eliminate excess saliva, while the impression is being mixed and the tray is being loaded. The mixed impression material is placed in the tray and evenly distributed to fill the tray to the level of the border. 7 -After loading the tray, some material is quickly placed with finger on any critical areas such as deep labial and/ or buccal vestibules in the highest aspect of the palate and over the rugae. Placement of alginate in the rugae area also prevents air from being trapped in this part of the impression. Complete denture impressions 8-The tray containing the impression is carried and positioned in the mouth by a rotating motion. Then positioned anteriorly by centering the labial notch in relation to the labial frenum so that it can be seated in a correct position. The tray is carried upward and seated posteriorly by the index finger in the region of the first molar. The seating pressure is stopped when the alginate can be observed along the entire posterior border of the tray. 9-During insertion and seating of the tray the patient is instructed to slightly close his mouth to retrude the coronoid process of the mandible and permit proper positioning of the tray in the buccal vestibule. 10-The tray is held firmly in position by steady finger pressure applied on the palatal part of the tray and border molding is carried out with the other hand as follows; 11-Border molding (can be active by the patient or passive by the dentist) The cheeks are pulled upward and downward to release the lip and cheeks and free any trapped fold of tissue. The lip and cheeks are then moved downward, inward and backward to stimulate their functional movements. The patient is asked to: - Purse his lips, retract them and move them downward and to suck the operator’s finger. - Moves his Jaws laterally to functionally mold the width of the impression in the distobuccal space caused by movement of the coronoid process. - Bend his head forward, move the head to the right and left sides and swallow to record the functional position of the palate and can do the Valsalva maneuver. 12-When the impression material has completely set (Alginate or Impression compound); the cheeks and upper lip are elevated above the borders of the impression to introduce air at the reflection and the border of the impression. After releasing the surface tension, the impression is removed from the mouth. The completed maxillary impression is inspected. It should record all the anatomical landmarks and have rounded and molded peripheries. 13-The denture outline is marked on the impression with indelible pencil by referring to anatomical landmarks in the mouth of the patient. The indelible pencil outline will also be transferred onto the Complete denture impressions cast and act as a guide to the technician when the special tray is made. Fig. (2): Alginate maxillary primary impression Fig. (3): Impression compound maxillary primary impression Complete denture impressions Mandibular preliminary impression Procedures: 1 -The shape, size and form of the residual ridge and the width and depth of the vestibule should be examined carefully to estimate the size of the stock tray. 2-A suitable sized perforated stock tray that conforms to the size and shape of the arch is selected. The tray should cover all the landmarks indicating the denture bearing area; and provide 4-5mm clearance space between the ridge and the tray for the impression material. 3-The selected tray is inserted in the mouth by a rotating motion, oriented in position and centered over the residual ridge. a-The patient is asked to raise his tongue slightly as the tray is placed in the mouth and. the position the tongue in the tongue space of the tray. The tray is checked by referring to the anatomical landmarks in the mouth. b- Posteriorly, the retromolar pad should be covered by the tray. c- Labial and buccally, the tray should be 3-4mm shorter than limiting anatomic structures to allow for normal function of the limiting structures around it. d- Lingually, the distolingual portion of the tray should contain the retro-mylohyoid fossa and extend about 1 0-1 2mm distal to the end of the mylohyoid ridge. In the posterior alveo-lingual sulcus, the tray - should extend 3-5mm below mylohyoid ridge. 4-Deficient tray borders are corrected by adding wax. The lingual flange of the tray frequently must be extended with wax in the retro- mylohyoid area and posteriorly to cover the retromolar pad region. In cases of severely resorbed ridge, the tray should be adjusted by bending and/or cutting the tray with scissors. If the tray border is too long, the impression will be over extended and too wide making it impossible to identify the position of the reflection area. The roughened edge should be smoothed with a file or covered by wax. 5-The Impression material is mixed according to the direction of the Complete denture impressions manufacture, loaded into the mandibular stock tray from the lingual surface and evenly distributed to fill the tray to the level of the borders. 6-The tray is rotated and centered over the residual ridge. The position of the tray handle should be kept at the midline of the face and used as a centering guide so that the tray can be seated in the correct position. The tray is gently seated by alternating finger pressure on either side of the tray in the first molar region. Border molding: a-Labially: The fingers are used to gently mold the labial and buccal borders. The lower lip is lifted downward outward and upward. b-Posteriorly: The buccal flange is border molded when the cheek is moved downward outward and upward meanwhile, the patient is asked to close his mouth against resistance created by the operator in the opposite direction to form the massteric notch (distobuccal corner). The distobuccal border is extended into the functioning area of the masseter muscle. Movement of the masseter muscle is recorded in the impression by creating its reactive contraction through asking the patient to close against resistance during the border molding procedure. c-Lingually: The lingual borders of the impression are functionally trimmed by active movement of the tongue; the patient is instructed to protrude his tongue. This movement creates functional activity of the anterior part of the floor of the mouth including the lingual frenum and determines the length of the border in this region. It also activates the superior constrictor muscle which supports the retro-mylohyoid curtain and limits the distal extension of the impression in the retro-mylohyoid fossa. The patient is also instructed to move the tongue from side to side. This permits the mylohyoid muscle to function normally which raises the floor of the mouth and determines the length of the borders in the molar region. The patient is then instructed to push the tongue forcefully against the anterior part of the palate to regulate the thickness of the anterior lingual flange. Since the posterior fibers mylohyoid muscle contracts during swallowing, the patients is instructed to swallow so that the impression slopes medially parallel to the mylohyoid muscle. (s- shaped contour of the lingual flange) and to prevent pressure from being applied on the sharp mylohyoid ridge. Complete denture impressions Finally, the patient is instructed to widely open his mouth to activate the I pterygomandibular raphe and produced the desired posterior extension. When the impression material has completely set, the tray is removed after releasing the surface tension. The impression is checked to ensure accurate reproduction of all dentures' bearing area by referring to the anatomical landmarks. The estimated denture outline is marked with an indelible pencil on the impression surface. This procedure is essential for providing information about the denture bearing area for the technician Fig. (4): Alginate mandibular primary impression Fig. (5): Impression Compound mandibular primary impression Complete denture impressions Causes of Inaccurate (faulty) Impression: 1 -impression made on inflamed tissues: It is important that the oral tissues are healthy before impressions are made. Edematous inflamed tissues from trauma change the form of the surface to be recorded in the impression. Dentures will not fit to the tissues after they are no longer distorted by inflammation. Distorted oral tissues must regain their healthy form before impressions are made. This can be achieved by keeping old dentures out of the mouth until the tissue is healthy and the use of tissue conditioning lining material. The old denture must be kept out of mouth at least for 24 hours before impressions are made. 2-lmproper selection of the tray: a- The use of short tray: The use of short tray posteriorly will cause rolling and sagging of the impression. The impression will not contact and record the surface details of the ridge across the posterior palatal seal area and retro-molar area. Short tray labially, buccally and or lingually will result in unsupported impression borders. The weight of the stone of the cast will distort the borders of the impressions. b-The use of too large tray: A large tray causes fullness of the lip and checks, shortening of the vestibular sulcus and distortion of the tissues that fit against the borders of the impression. This results in an impression with excessively thick borders and difficulties identifying the exact position of the reflection area. c-The use of too small tray: The use of too small tray may cause tearing of the impression during removal from the mouth and the presence of pressure spots, in which the tray shows through the impression material. Pressure spots indicate displacement of the tissue by pressure from the tray. These lesions of extra pressure will tend to dislodge the denture when completed and impair the health of the tissues that come into Complete denture impressions contact. d-The use of too long tray: Long tray causes excessive displacement of the resilient tissues in the depth of the vestibule and interferes with the action of the muscles that surround it. 3-lmproper positioning of the tray: a. Incorrect centralization of the tray results in a thick border on one side and a thin border on the opposite side. This indicates that the tray is shifted towards the thick border. b. Maxillary tray placed too far forward in relation to the ridge. Forward positioning of the tray results in excessive thickness of the labial border or the borders of the tray may show through the impression. c. Maxillary tray placed too for backward. This results in thin borders of the impression with failure to record the proper depth and width of the vestibule accurately. d. Mandibular tray placed too far forward in relation to the residual ridge, causes pressure spots on the anterior part of the lingual flange. e. Insufficient seating pressure. Inadequately seated tray will cause lack of tissue detail and excessive length of impression material on the flange of the tray. f. Excessive seating pressure. This causes the presence of pressure spots, where the tray shows through the impression 4-The presence of voids on the impression: Voids on the borders of the impression may be due to: a- The use of too soft impression mix. b- Labial and buccal tissues are trapped between the impression. c- The use of insufficient seating pressure. d- Excessive space between the tray and the oral tissues causes sagging of the impression. This is most seen in patients with high palatal vault. The palatal area should be built up with wax before impression making. Complete denture impressions 5-Partial dislodgement of the impression from the tray: Partial displacement of the impression from the tray may be due to forcibly removal of the impression without care. Factors that may complicate impression making: 1 -Amount and consistency of saliva: 1-Excessive salivation and thick ropy saliva complicates impression making by forming voids in the impression and can cause the patient to gag while impressions are made. The palatal surface should be wiped free of saliva with a piece of gauze before the impression is made. 2-Thick cheeks: Patients with thick cheeks may present problems during impression making. They do not allow easy manipulation at the proper time for border molding of impression material. 3-Tone of the facial muscles. I-Too tense or too weak muscle tone is unfavorable. Tense muscle interferes with proper extension of the denture borders. Extra time will be needed to functionally mold the borders of the impression. In patients exhibiting strong muscle tension, the vestibule will be too shallow, and the impression border becomes thin and short. As a result, the completed denture will have an insufficient peripheral seal. 4-Muscular control : Good muscular control and coordination are essential to effective border molding of impression materials. Tongue movements are used for border molding the lingual flange of the mandibular impression. The timing, direction and amount of movement are important for correct shape and extension of the lingual flange. -If the tongue movements are too slow, too fast, too little, too great or wrong in direction problem in recording the movement of the floor of the mouth will occur. Exaggerated tongue movements will cause under extended lingual borders. In such conditions proper training can help the patient in learning the proper location of the Complete denture impressions tongue. 5-Gagging (Nausea During Impression): Active gag reflex complicates impression making. Gagging can be triggered by: Encroaching upon the palatoglossal muscle by long tray. Distal portion of the lingual tray that makes excessive contact with the posterior third of the tongue. Maxillary tray that is too short or too long. Short tray causes sagging of the impression on the dorsal surface of the tongue, that triggers gagging. Treatment: When treating gaggers carefully manipulate the trays, 1. keeping the patient's head forward over a Bowl held under the chin to catch any saliva that may run out of the mouth. 2. the use of minimal amount of impression material, 3. Instructing the patient to breathe deeply through the nose and diverting the patient from the actual work are helpful. 4. Self-confidence of the operator with firm sympathetic manner 5. Assure the patient. 6. Avoid touching the dorsum of the tongue with impression tray. Seat the impression quickly. 7. Desensitize the surface of the mucous membrane with: a- Phenol mouth washes. b- Sucking a tablet made for this purpose. c- c-local anesthetic cream or spray. - In such cases mandibular impression is preferably made before the maxillary impression local anesthesia can be used in severe cases. 6-The presence of undercuts: The presence of undercut areas interferes with the insertion and removal of the tray. This requires a suitable path of insertion and the use of elastic impression material. Complete denture impressions Secondary Impression (Final Impression, Definitive impressions) Using special (custom) tray to obtain a master cast on which the denture is constructed. Types of Secondary Impression techniques: 1. Minimal pressure impression technique (impression theory) 2. Definitive Pressure (functional) impression technique (impression theory) 3. Selective pressure techniques (impression theory) 4. Reline and rebase techniques 5. Conventional techniques 1- Minimal pressure impression technique (impression theory) The minimal pressure impression technique is also called mucostatic impression technique or passive non pressure technique or open mouth technique In this technique, the impression is made under minimal pressure while the patient is opening his mouth The denture bearing tissues are recorded at a state of relative rest with minimal displacement. Material: Materials having high flow properties and low viscosity for example: Plaster of Paris Tray: Trays constructed for this technique require a spacer with stops Complete denture impressions and holes to allow escape of the material to avoid pressure on tissues. Advantages: 1- As it is an open mouth technique, the operator the borders and insures proper border molding. 2- There is less distortion to the mucosa and accordingly the tissues do not exert a displacing force on the denture, this results in a more stable denture during rest 3- It is the technique of choice for flabby and thin wiry ridges where minimal pressure is essential. 4- The tissues beneath the denture are not subjected to a continuous pressure which often results in bone resorption. 5- Minimal interference with the blood supply. Disadvantages 1- The denture may not fit the mucosa all times. This is because the mucosal topography is not static over a 24- hours period. 2- The denture is not stable during function. 3- It neglects the principle of distributing masticatory forces over the largest possible basal seat area. 2- Definitive pressure impression technique (impression theory) It is also called muco-compressive or functional or Closed mouth impression technique) It is the negative representation of the denture bearing tissues at function, under the patient’s biting force. Impression material: viscous impression material to allow transmission of pressure to the mucosa. The material used is zinc oxide and eugenol Complete denture impressions paste or medium body rubber base (Zinc oxide eugenol material is a viscous material, have a long setting time to allow functional movement and border molding.) Impression tray: special tray without spacer with occlusion rims set at the proper vertical dimension. Advantages: 1- The patient can exert his own masticatory force on the impression material. 2- It permits adequate trimming of the lingual borders of the lower impression. This is because tongue movement required to trim the lingual border are more forceful when the mouth is closed than when the mouth is opened and the tongue is protruded. Disadvantages: 1- Dentures constructed from such an impression do not fit well at rest, as the compressed tissues tend to rebound and regain their form when pressure is released. 2- An overextended denture may result due to improper border molding. 3- Prolonged pressure exerted on tissues may interfere with blood supply and accelerates ridge resorption. -Functional Impression Technique is a type of Definitive pressure impression technique Functional impression technique may be used in the presence denture instability problem. When the patient suffers from denture looseness due to the presence of localized areas of poor functional adaptation. In these cases, the application of a thin mix of a chairside Complete denture impressions resilient lining material may be beneficial (e.g Visco-Gel) Procedures: The chair side relining material is mixed according to the manufacturer instructions. The material is added to the fitting surface of the denture & the patient is instructed to wear the denture for one hour. After one hour of functional molding, the denture is removed from the patient mouth & the conventional relining process completed 3- Selective pressure impressions (impression theory) This technique combines pressures over areas and little pressure on others. The technique presumes that certain areas of the ridges are better adapted to withstand extra load falling on the denture so they are recorded with a definite pressure while the other tissues are recorded in relaxed undistorted state. The selective pressure impression technique is used when the flabby tissue is in the anterior part of the mouth (localized tissues and not expected to interfere with the stability of the denture) If the flabby tissues are generalized (cover the whole denture bearing area which may interfere with denture stability) , mucostatic impression technique is used. Methods: 1- Window technique: a. Displaceable (Flabby) Anterior Maxillary Ridge 1. A zinc oxide/eugenol impression is made with a special tray for the whole ridge. A window is made over the flabby area. Complete denture impressions Impression plaster is painted over the flabby area with a brush. 2. The impression is made with medium body rubber base or Plaster of Paris material. A window is made over the anterior flabby area and the impression material (medium rubber base) was removed in the region of flabby tissue using a scalpel. Light body rubber base (or Plaster of Paris) impression material is injected over the flabby tissue to record it. Fig. (6): Window Technique ( maxillary) Complete denture impressions b. Fibrous (Fibrous) posterior Mandibular Ridge - Fig. (7): Window Technique ( Mandibular) - The Mandibular ridge may have a posterior fibrous area , a window can be opeded at this area and a selective pressure impression technique is done. 2- preliminary compound impression is made in a stock tray. then scrapped to be relieved over hard and sensitive areas. Zinc oxide paste is used as wash impression over the preliminary compound impression. Fig. (8): Selective pressuire technique on an impression compound primary impression Complete denture impressions 4.Reline and rebase techniques This impression technique is performed in an old denture. The denture to be relined should be modified peripherally to ensure that the peripheral seal has been established Undercuts are removed from the impression surface of the denture, to ensure that the master cast is not damaged on removal of the denture. Zinc oxide eugenol impression material was generally used here although clinicians now prefer to use polyether, polysulphide or polyvinylsiloxane. Before recording the definitive impression, there is merit in placing tracing compound as spacing on the denture in the region corresponding to the ridges of the canine areas. In the case of the maxillary impression, there is also merit in perforating the palate in the midline of the rugae to prevent any possibility of imperfections in the impression, e.g. air bubbles. Fig. (9): Reline and rebase techniques Complete denture impressions 5. Conventional secondary impression technique Clinical procedures 1- Check the special tray extension: The borders of the special tray should be checked intraorally to make sure that they are 2 mm short of the depth of the vestibule except posteriorly it should extend to the vibrating line. Trim the borders If they are overextended. 2. Border molding It is the process by which the shape of the borders of the tray is made to conform accurately to the contours of the buccal and labial vestibules. It is performed by manipulation of the border tissues against a moldable impression material that is properly supported by the tray. It is done using a tracing compound (green stick compound) that is added in sections to the shortened borders of the tray and molded to a form that will be in harmony with the physiologic action of the limiting anatomic structures. The procedures of border molding: Flame the tracing compound until it becomes soft then apply on the border of the special tray after drying it Temper the compound by immersing it in a warm water before inserting the tray inside the patient mouth. Ask the patient to perform the movement required to mold the green stick compound. Complete denture impressions Border molding of the maxillary special tray D Fig. (10): Border molding of the maxillary special tray - The labial flange (section C) is border molded by elevating the lip and pulling it outward, downward, and inward. Then move it right and left (labial frenum) - The buccal flange (section B) is border molded by elevating the cheek and pulling it outward, downward, inward. In addition, move the check at the area of buccal frenum forward and backward to simulate movement of the frenum. - Posteriorly, the distobuccal border is border molded by introducing the tray while the patient half open (to give a space for the compound as wide opening will result in movement of the coronoid toward the maxillary tuberosity preventing the entrance of compound to this area) then ask the patient move the mandible from side to side. The coronoid limit the length and thickness of flanges in this area. - At the posterior palatal seal area (section D), make sure that the Complete denture impressions tray extends to the vibrating line. Place 2-3 mm of compound on top of the tray in a butterfly configuration then seat the tray. Ask the patient to say ah in prolonged manner, or swallow or blow from the nose while supporting the tray ( Valsalva maneuver) Border molding of the mandibular special tray D Fig. (11): Border molding of the mandibular special tray - The labial flange (section C) is border molded by elevating the lip and pulling it outward, upward, and inward (labial frenum) - The buccal flange (section A) is border molded by elevating the cheek and pulling it outward, upward, inward. In addition, move the check at the area of buccal frenum forward and backward to simulate movement of the frenum. - The disto buccal corner A-B (masseter muscle influencing area as the masseter contraction force the buccinators to mold this Complete denture impressions part) This area is molded by asking the patient to exert a closing force while a downward pressure is exerted on the tray by the dentist (force by the dentist against resistance from the patient). - Retr omolar pad (B) ; the compound is added on the fitting surface of tray opposing retromolar pad and slight pressure is applied to mold this area. Finally, the patient is asked to open wide. If the tray is over extended distally beyond the retromolar pad, a notch will be formed in the compound that present at the distal end of the tray. This notch is created by the action of pterygo-mandibular raphe if the tray is over- extended distally. - The anterior lingual flange (section D) is molded by asking the patient to protrude the tongue and then to push the dentist finger that is placed on the tray handle. - The lingual pouch area (section E) at distal end of the lingual flange is molded by asking the patient to protrude the tongue and move it laterally to the opposite side, or repeat letter “K” several times. If it is properly molded it will be S- shaped. In each section of border molding, the tray is removed from the mouth, the border molding is examined to determine that it is adequate. The contour of the border should be smooth, rounded and dull. If not this means that you have to repeat border molding procedures again. After achieving smooth, rounded and dull borders, remove the excess tracing compound that is present on the fitting surface of the tray using scalpel. Check the peripheral seal: after completing the border molding, insert the tray inside the patient mouth and check the peripheral seal (retention) while trying to pull the tray vertically and horizontally Cut back: scrap back a thin layer of compound from the border molded periphery using a scalpel. This will create space for the impression material and avoid undesirable tissue displacement. Complete denture impressions Clinical procedures for making final impression using rubber base material: 1. After the compound (border Molding can also be made in this technique by putty rubber base consistency) is scraped back, apply a thin layer of tray adhesive to the surface of the tray. Be sure to apply the adhesive 3-4 mm beyond the border. 2. Put equal lengths of rubber base material on the mixing pad. 3. Keep the strips of material widely separated so they do not flow in contact and set prematurely 4. A stable immobile mixing pad ill make it easier to mix the material 5. Use flat wide spatula for mixing, 6. Begin mixing with the tip of your spatula 7. Attempt to confine the impression material to a small area of the pad 8. Finish mixing the rubber base with the flat edge of the blade. This technique will minimize the number of air bubbles into the material 9. Apply a thin layer of impression material, do not overload the tray. 10. Close inspection should reveal that there are no bubbles associated with the impression material and all surfaces are coated 11. Retract the lips with your index finger or mouth mirror and seat the loaded impression tray in patient mouth and go through the soft tissue manipulation process as during border molding Complete denture impressions 12. Hold the tray in position until the impression material set. 13. Trim the excess unsupported impression material. 14. Spray the impression with the appropriate disinfectant. N B: It is preferable to perform border check before the final impression by applying the rubber base of Zinc Oxide final impression materials) over the border molded border to check and correct pressure areas. the Posterior Palatal Border( Post-Damming) In the region of compressible tissue just distal to the hard palate and anterior to the vibrating line. (On the immovable part of soft palate) Functions of posterior palatal seal: 1- It increases retention of the denture by offering negative atmospheric pressure. 2- It prevents air and food from getting under the denture. 3- It reduces reflex irritation and gag by: a) Reducing patient awareness of this area, no separation of the denture base and soft palate. b)Making the thickness of the base less conspicuous to the tongue. 4- It compensates for dimensional changes that are inherent in the laboratory procedures Complete denture impressions Errors in Secondary impression 1-A thick buccal border on one side with a thin buccal border on the opposite side. (poorly centralized tray----- as the tray was out of position in the direction of the thick border). 2-A thin labial border with the tray showing on the inside surface of the labial flange. This indicates that the tray was placed too far posteriorly and not centered correctly over the anterior ridge. 3-A thick lingual border on one side with a thin lingual border on the opposite side. This indicates that the lower tray was out of position in the direction of the thin border. 4-A thin anterior lingual border with the tray showing on the inside surface of the lingual flange. This suggests that the lower tray was too far forward in relation to the residual ridge. It will be accompanied by a thick labial border. In a similar manner, a thick labial border in the upper arch with the tray showing through over the anterior slope of the palate. This indicates that the tray was too far forward in relation to the residual ridge. 5- Excess thickness of impression material over the fitting surface of the tray and material unsupported by the borders of the tray. This indicates that the tray was not seated down sufficiently on the residual ridge (insufficient pressure). -The correct thickness of material over the fitting surface of the tray, but material extending beyond the border of the tray so that it is unsupported by the tray, suggests that the tray is under extended in that area. Complete denture impressions 6- The tray showing through the impression material over the fitting surface of the tray and the borders showing through the final impression material. This indicates that the tray has been seated on the residual ridge with too much pressure. The correct thickness of material over the fitting surface of the tray, but with the border showing through the final impression material, suggests that the tray is overextended in that area. 7- Voids or discrepancies that are too large to be corrected accurately 8- Incorrect consistency of the final impression material (granular impression with poor tissue details). 9- Movement of the tray while the final impression material was setting 10- Incorrect border molding procedures. (For example, unsupported impression material by the tray) 11- Using either too much or too little impression material. 6- Sticking the impression material to the teeth. 12- Pulling the impression material away from any area of the tray. 8- Layered impression. 13- Trapping lip, cheek, tongue or floor of the mouth. 14- - Tearing of important

RPROSD 411 (1) Removable Prosthodontics PDF - جامعة التكنولوجيا والمعلومات

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