Orthodontics Notes PDF

20 22 /20 23 20 22 /20 23  Faculty of Dentistry Cairo University 23 Orthodontic Department /20 Orthodontic Notes For Undergraduate Students 22 20  By Orthodontic Department Faculty member...

20 22 /20 23 20 22 /20 23  Faculty of Dentistry Cairo University 23 Orthodontic Department /20 Orthodontic Notes For Undergraduate Students 22 20  By Orthodontic Department Faculty members: Professors: 23 - Prof. Dr. Ahmed Abdel-Salam - Prof. Dr. Yehya Mostafa - Prof. Dr. Nagwa El-Mangouri - Prof. Dr. Wagih A. Kadry - Prof. Dr. Ehab El-Kattan - Prof. Dr. Hisham A. Afifi - Prof. Dr. Mohamed A. Bushnak /20 - Prof. Dr. Sanaa A. Soliman - Prof. Dr. Amgad Kaddah - Prof. Dr. Faten H. Eid - Prof. Dr. Sayed A. Hafez - Prof. Dr. Amr E. Labib - Prof. Dr. Amr E. Dakrouri - Prof. Dr. Fatma A. Abdel-Sayed - Prof. Dr. Hala M. Abdel-Meguid 22 - Prof. Dr. Hoda M. Abdel-Aziz - Prof. Dr. Amr M. Abou-El-Ezz - Prof. Dr. Sahar Taher - Prof. Essam Nasif - Prof. Dr. Manal Y. Fouda - Prof. Dr. Khaled H. Attia - Prof. Dr. Mona Salah. 20 Associate Professors: - Assistant Prof. Dr. Amany Hassan. - Assistant Prof. Dr. Fouad Sharaby - Associate Prof. Amr ElBialy - Associate Prof. Eman Mohie - Associate Prof. Fady Hussein - Associate Prof. Mai Aboelfotouh Lecturers 23 - Dr. Dalia ElBoughdadi -Dr. Amal ElAzab - Dr. Suzan Marzouk - Dr. Mostafa El Dawlalty - Dr. Sherif Elkordi - Dr.Heba Dehis - Dr.Nouran Fouad -Dr.Ahmed Medhat /20 - Dr.Amira Aboelnaga - Dr.Nada ELzawahry - Dr.Mohamed Abd El-Ghafour Demonstrators - Dr.Sally Magdy - Dr.Noha Ali 22 -Dr.Ahmed Fouda -Hadir AbouShady -Yasmin Mohsen -Heba Akl 20  Contents Page 23 Chapter 1: INTRODUCTION 09 Chapter 2: PRINCIPLES OF ETHICS 11 Chapter 3: GROWTH AND DEVELOPMENT 20 Chapter 4: DEVELOPMENT OF THE NORMAL OCCLUSION 45 Chapter 5: DESCRIPTION OF NORMAL OCCLUSION IN ADULTS 69 /20 Chapter 6: CLASSIFICATION OF MALOCCLUSION Chapter 7: DIAGNOSIS Chapter 8: ETIOLOGY OF MALOCCLUSION Chapter 9: SEQUELAE OF UNTREATED MALOCCLUSION Chapter 10: TREATMENT OF MALOCCLUSION 78 100 133 186 193 Chapter 11: ADJUNCTIVE TREATMENT FOR ADULTS 223 Chapter 12: BIOMECHANICS OF TOOTH MOVEMENT 232 22 Chapter 13: TISSUE CHANGES IN ORTHODONTICS 244 Chapter 14: ORTHODONTIC APPLIANCE DESIGN 255 Chapter 15: THERAPEUTIC EXTRACTION 269 Chapter 16: ORTHODONTIC RETENTION AND RELAPSE 290 Chapter 17: IATROGENIC EFFECTS OF ORTHODONTIC TREATMENT 20 301 REFERENCES 314  Faculty Vision and Mission 23 Vision Excellence in teaching, learning, research and community service at national, regional and international levels Mission Preparing qualified graduates and distinguished specialists /20 and consultants capable of meeting community needs at national and regional levels in different fields of oral and dental medicine through advanced teaching methods, supporting lifelong learning, innovation in scientific research and provision of preventive and therapeutic services to the surrounding community. 22 20  Orthodontic Department Vision and Mission 23 Vision The orthodontic department believes that orthodontics is central to the practice of dentistry looking for excellence in orthodontic teaching, learning, research and community service nationally, regionally and internationally /20 Mission To create an orthodontic academic program that encourages critical thinking and to communicate and transfer the orthodontic knowledge nationally, regionally and internationally. To create an environment to foster and support orthodontic research and postgraduate students. 22 To provide quality orthodontic care to a diverse community of patients. 20 20 22 /20 23 20 22 /20 23  Chapter 1 Introduction Definition of Orthodontic: 23 The word "Orthodontics" is derived from two Greek words, Orthos, meaning straight, and odontos, meaning tooth. Orthodontics is the branch of dentistry concerned with the growth of the face, development of the occlusion and the prevention and treatment of dentofacial abnormalities. Aim of Orthodontics: /20 Orthodontic therapy is directed to malocclusion, abnormal growth of dentofacial complex, and malfunction of orofacial musculature, which alone or in combination may cause any of the following: 1. Impaired mastication. 2. Bad facial esthetics. 3. Dysfunction of the temporomandibular joint. 4. Susceptibility to periodontal disease. 5. Susceptibility to dental caries. 6. Impaired speech. 22 20 11 20 22 /20 23 20 22 /20 23 Chapter 2 Principles of Ethics Intended Learning Outcomes (ILOs): Understand what is meant by ethics. 23 Understand why ethics are important. Understand the ethical obligations to patients. Understand how to apply ethical principles to the dental practice. Chapter Outline: A. Introduction B. Principles of Ethics: 1. Patient Autonomy 2. 3. 4. 5. C. D. Nonmaleficience Beneficience Justice Veracity /20 Code of professional conduct Advisory Opinion 22 20 14 Chapter 2 Principles of Ethics A. Introduction: Ethics are the moral principles or virtues that govern the character and conduct of an individual or a group. The study of ethics is the systematic study 23 of what is right and good with respect to character and conduct. The dental profession holds a specific position of trust within society. As a consequence, society affords the profession certain privileges that are not available to the public-at-large. In return, the profession makes a commitment to society that its members will adhere to high ethical standards of conduct. The code of ethics, in effect, is a written expression of the obligations arising from the implied contract between the dental profession and society. /20 Members of a dental union or association voluntarily agree to abide by its organization code as a condition for membership. Ethics affect relationships with patients, the public, office staff and other professionals. As a dentist, you have to make numerous decisions. Some decisions are straightforward and easy; others can be very difficult. When ethics are ignored, you risk making unethical or less ethical decisions. Unethical decisions lead to unethical conduct, which can seriously compromise your service to patients and undermines your ability to function as a professional. Without a solid ethical foundation, you simply cannot be a true professional. The code of ethics has three main components; principles of ethics, the code 22 of professional conduct and the advisory opinion. B. Principles of Ethics: These are the firm guideposts of our profession. They provide guidance and offer justification for the code of professional conduct. Principles can overlap each other as well as compete with each other for priority. More than one principle can justify a given element of the code of professional conduct. Principles of ethics include: 20 1. Patient Autonomy (Freedom ‫ﺔ‬%‫ﺮ‬#"‫)ا‬ 2. Nonmaleficience (No Harm ‫)اﻻﻳﺬاء ﻋﺪم‬ 3. Beneficence (of Benefit ‫)اﻹﺣﺴﺎن‬ 4. Justice (Fairness ‫)اﻟﻌﺪاﻟﺔ‬ 5. Veracity (Truth ‫ﻖ‬#"‫)ا‬ 15 Chapter 2 Principles of Ethics C. Code of professional conduct: ‫ ﻣﺪوﻧﺔ اﻟﺴﻠﻮك‬.-‫اﳌ‬ It is the expression of specific types of conduct that are either required or 23 prohibited. It is used as an instrument to help the dentist reach the goals of his/her profession. It's violation may result in disciplinary action. It is subject to change and modification. D. Advisory Opinion: ‫ﺎم‬1‫اﻷﺣ‬ Statement of a court on how it may rule on a legal issue. 1. Patient Autonomy: the dentist has a duty to treat the patient according to /20 the patient's desires, within the bounds of accepted treatment and to protect patient's confidentiality. Code: 1. The dentist should inform the patient of the proposed treatment and any reasonable alternatives. An informed consent should be presented to and signed by the patient prior to treatment. 2. The dentist is obliged to safeguard the confidentiality of patient records. Specific guidelines on transfer of patient’s records should be followed if a patient is moving or discontinuing treatment. Signed photo release forms are required before being used to market your 22 practice. Advisory opinion: A. Upon request, a dentist should provide copies of the patient's records either gratuitously or for a nominal fee to the new dentist. This obligation exists whether or not the patient's account is paid in full. B. The dentist should obtain the patient's written permission before forwarding health records which contain information of a sensitive nature e.g. HIV seropositivity, chemical dependency. 20 2. Nonmaleficience: The dentist has a duty to refrain from harming the patient. This is achieved by keeping knowledge and skill current, knowing one's limitations and when to refer to a specialist and when to delegate patient care to auxiliaries. 16 Chapter 2 Principles of Ethics Code: 1. All dentists are obliged to keep their knowledge and skills up to date 23 2. A dentist is obliged to refer the patient to a specialist, if necessary for the welfare of the patient. Then, the specialist should refer the patient back to the referring dentist upon completion of his care. 3. The dentist should protect the patient's health by only assigning to qualified auxiliaries those duties that can be legally delegated. The dentist should also supervise the patient care provided by all auxiliary personnel. 4. It is unethical for a dentist to practice while abusing substances, alcohol, etc. as this may impair the ability to practice. Also, a dentist who contracts a disease or becomes impaired in any way should limit activities /20 of practice to areas that do not endanger patients or staff. 5. A dentist should immediately inform any patient who has been exposed to potentially infectious material in the dental office of the need for post exposure evaluation and follow up and to immediately refer the patient. 6. The dentist should never discontinue treatment without giving the patient adequate notice. The dentist may refrain from treatment if: i. He does not have the expertise or capability to provide competent treatment or to meet patient's expectations. ii. The dentist's professional ability is impaired from injury, illness, disability, medication or addiction. iii. The patient requests treatment that is contrary to the patient's best 22 interest. 7. A dentist should avoid personal relationships that could impair their professional judgement or risk the possibility of exploiting the confidence placed in them by a patient. 8. The dentist should avoid conditions or actions (physical, verbal or psychological) that promote harassment or abuse of patients, staff or other related parties. 20 3. Beneficience: The dentist has a duty to act for the benefit of others, by competent and timely delivery of dental care within the bounds of clinical circumstances. 17 Chapter 2 Principles of Ethics Code: 1. A dentist is obliged to use his skill, knowledge and experience for 23 improving the dental health of the public and is encouraged to be a leader in his community. 2. A dentist is obliged to be part of a professional society and to observe its rules of ethics. 3. A dentist is obliged to make the results & benefits of his research available to all. 4. A dentist my secure patents and copyrights, but should not restrict research or practice. 5. A dentist is obliged to report cases of abuse or neglect to the proper authorities. without prejudice. Code: /20 4. Justice: The dentist has a duty to treat people fairly and deliver dental care 1. A dentist shall not refuse to treat patients because of race, color, sex or national origin. 2. A dentist should provide emergency treatment to a patient of another dentist, if necessary. Following completion of care, the dentist should 22 return the patient to his regular dentist. 3. A dentist is obliged to report to the appropriate reviewing agency instances of gross or continued faulty treatment by another dentist. 4. A dentist may provide expert testimony, if necessary. 5. A dentist may provide an expert testimony when necessary without agreeing to a fee contingent upon the outcome of the litigation. 6. A dentist should never accept rebates or split in exchange for a referral. Advisory opinion: 20 A. A dentist has to provide treatment to those in need including patients with HIV, Hepatitis B and C, etc. B. A dentist may give a second opinion, but should excercise care that his comments are truthful, informed and justifiable "Justifiable criticism. He may consult with the previous dentist to determine the conditions under which the treatment was performed. A difference in opinion should not be 18 Chapter 2 Principles of Ethics communicated to the patient in a manner that would imply mistreatment. In fact, if disparaging comments are made, they can be the basis for a disciplinary proceeding against the dentist giving the second opinion 23 5. Veracity: A dentist has a duty to be honest and trust worthy while dealing with people. Code: 1. A dentist should not present the care being rendered to the patient in a false or misleading manner. 2. A dentist should not present his fees in a false or misleading manner. Fees should be consistent and fair to all parties i.e. a dentist should not /20 vary fees based on the patient's financial resources or insurance plans. 3. A dentist presenting a paper should disclose any monetary interest to the readers " disclosure of conflict of interest". 4. A dentist shall not prescribe or promote device or drugs unless their complete formulae are available to the dental profession. 5. Professional announcement and advertising should not be false or misleading. Practice name should not include any doctor who is no longer in the practice. 6. It is unethical to announce to the public specialized dental services without fulfilling the required training or certificate. Announcement of services by general dentists could be honest i.e. should not express or 22 imply specialization. Once announced as a specialist, the dentist should limit the dental practice to this field. Advisory opinion: A. Removal of amalgam from non allergic patients for the alleged purpose of removing toxic substances from the body is unethical. B. It is unethical to represent a treatment procedure to a patient as one that can cure a certain condition if not based on scientific evidence " unsubstantiated representation". 20 C. It is unethical to waive the patient payment without disclosing to the 3rd party" Deception & misrepresentation". D. It is unethical to overbill the patient because he is covered under a dental Benefits plan. Also, to change treatment dates is unethical for the sake of obtaining benefits under a dental plan. E. It is unethical to present uncovered procedure as one that is covered by 19 Chapter 2 Principles of Ethics the dental plan. F. It is unethical to recommend and perform unnecessary dental treatment. G. A dentist should s report a drug's adverse reaction to the adequate 23 authorities. H. A dentist should not exploit the trust inherent in the dentist-patient relationship for his own financial gain. I. A dentist should use academic degrees awarded only by accredited organizations only for advertising. The use of non academic degrees granted by some organizations is prohibited as it is misleading to the public Anyone who believes that a dentist has acted unethically may bring the /20 matter to the attention of the appropriate dental society for investigation. A member who is found guilty of unethical conduct may be placed under a sentence of censure or suspension or maybe even expelled from membership. 22 20 20 20 22 /20 23 20 22 /20 23 Chapter 3 Growth and Development Growth and Development 23 - Definitions - Prenatal development - Patterns (types) of growth throughout the body (Scammon's Curves): - Somatic growth - Neural growth - Lymphatic growth - /20 Genital growth - Changes in Outline Features of the Growing Face - Methods of Bone Formation (Osteogenisis: Types: - Endochondral bone formation - Intramembranous bone formation a) Growth by surface deposition b) Sutural growth - Growth movements: 22 a) Drift b) Displacement i) Primary displacement ii) Secondary displacement c) Remodeling - Post natal growth of the skull: 1) Growth of the cranium: 20 a) Growth of cranial vault b) Growth of the cranial base 2) Growth of the face: a) Middle face (naso-maxillary complex) b) The mandible. 23 Chapter 3 Growth and Development Growth and Development of the Skull Definitions: 23 Growth: Growth may be defined as the normal change in amount of living substance. Growth is the quantitative aspect of biological development and is measured in terms of increments. Development: Growth Increment: /20 Development can be defined as all normal sequential series of events between fertilization of the ovum and the adult state or maturation. Is the amount of growth per unit of time. Growth Spurt: Is the sudden increase in growth rate during the age of the organism (e.g. puberty spurt). Differential Growth: 22 Difference in growth rate and time of various organs of the organism. Prenatal Development The prenatal development may be divided into three periods: 1. The period of the ovum: from fertilization to the end of the fourteenth 20 day. 2. The period of the embryo: from the fourteenth day to about the fifty sixth day. 3. The period of the fetus: from eight weeks of birth. During the 4th week intrauterine of the embryonic period, the human face 24 Chapter 3 Growth and Development begins to take shape. The frontonasal, maxillary and mandibular processes of the 1st branchial arch bound the primitive oral cavity (stomadeum) (Fig. 1). The upper lip and premaxilla are formed by the fusion between globular process 23 and maxillary processes. Partial or complete failure of fusion between these two processes result in a condition known as cleft lip. Cleft lip may be either unilateral or bilateral. This will be apparent by the second month in-utero since this is the time where the fusion of the lip is usually completed. The palate is formed by the two palatine processes of the maxillary /20 processes, which are fused with each other and with the premaxilla region in a Y shaped pattern (Fig. 2). Failure of fusion between these two processes result in a condition called cleft palate which may be partial or complete. 22 Fig. 1 showing embryonic period 20 25 Chapter 3 Growth and Development Fig. 2: Palatal development: formed by fusion of two palatine processes of the maxillary processes with the pre-maxilla. Patterns (types) of growth throughout the body 23 (Scammon's curves) Four general patterns of growth can be distinguished among mammalian tissues (Fig. 3). 1. Somatic Growth: It is the increase in overall body size, which continues throughout the growth period. In man, this somatic growth does not cease until 18 to 20 years. It is /20 relatively rapid prenatally (weight 6-7 billion folds, height 5000 folds), accelerates in the first months after birth and then slowly declines until the pubertal growth spurt. The rate of growth accelerates reaching a peak (11-13 years in girls, 13-15 years in boys), then rate of growth declines again to virtually zero by about 20 years. The principal tissues showing somatic growth pattern are those of skeletal bones; maxilla, mandible, cartilage and other supporting connective tissues. 2. Neural growth: 22 The central nervous system grows rapidly during prenatal and early postnatal life completing most of its growth before the rest of the body. The human brain for example, attains more than 90% of its full adult size by 6 years although its functional maturation continues for much longer time. There is no evidence of any adolescent spurt in the neural pattern of growth. 3. Lymphatic Growth: 20 The lymphatic tissues grow rapidly in early life and reach their maximum extent to about 11 to 14 years, after which they decline. 4. Genital Growth: The primary and secondary sexual organs remain small until puberty then 26 Chapter 3 Growth and Development they grow to adult size. Of these four patterns, the first two are seen in the growing skull. The neurocranium and orbital cavities form a protecting box for the brain and eye 23 ball and their growth follows the neural pattern. /20 Fig. 3: Differential growth rate for different body tissues. Changes in Outline Features of the Growing Face 22 At birth the face forms only one-eighth of the bulk of the head, whereas in the adult it forms one-third to one-half. This proportion changes as the growth of the brain slows down considerably after about the third of fourth year of childhood, but the facial bones continue to enlarge markedly for many more years. By time, growth of the trunk and lower limbs reduce the head from 1/4th to 1/8th the body height. This trend continues postnatally along an axis of 20 increased growth from the head to the feet which is known as the cephalocaudal gradient. 27 Chapter 3 Growth and Development 23 Fig. 4: Proportional changes between child and adult face As the face matures with age, a number of characteristic age related In newly born Eyes Appear larger in the young /20 morphologic changes occur. The major changes observed in the facial features associated with growth are outlined below (Fig. 4): Adult Smaller in proportion when compared to the child. Due to nasal and jaw regions grow much faster and to a much greater extent than the orbit, child. 22 Ears In the adult, they are much Do the ears actually rise? No, higher with respect to the face. they in fact move downwards Ears of the infant and child during growth. However, the appear to be low face enlarges inferiorly even farther so that the relative position of the ears seems to rise Forehead Reduced and slanted The bulbous forehead is reduced by expansion of the supra orbital ridges, elevation of the Appears bulbous in the child. nasal bridge and elongation of the nose. 20 Cheeks The cheek area becomes much The zygomatic arches move more massive laterally away from each other, thereby increasing the breadth Are not prominent of the face. 28 Chapter 3 Growth and Development Nose longer and wider Increases noticeably in vertical size, and the nasal bridge becomes progressively more Small and short 23 prominent. Mandible large and square lower jaw Deposition of bone on posterior border of ramus Dimunitive mandible with obtuse angle, Chin Prominent Deposition of bone on chin and resorption above it. Receded chin /20 The entire face becomes longer in a vertical dimension as a composite result of mandibular ramus growth and downward growth of the nose and maxilla. The face as a whole is displaced downwards in relation the cranium (Fig. 5). 22 Fig. 5: The difference between child and adult face Methods of Bone Formation (Osteogenesis): Bone may be formed in two connective tissue sites: 1) Cartilage 2) Membranous connective tissue 20 1) Endochondral bone formation: (Fig. 6) It is a pressure-tolerant tissue located in specific skeletal areas where direct compression occurs (articular cartilage). It functions as a growth cartilage in conjunction with certain enlarging bones. 29 Chapter 3 Growth and Development Sites of endochondral bone growth: Synchondrosis * Nasal cartilage condylar cartilage 23 * epiphyseal plate During endochondral bone formation, the original mesenchymal tissue first becomes cartilage. Cartilage cells hyperplasia Cartilage cells hypertrophy, Their matrix becomes calcified. Cells degenerate replaces it. /20 Osteogenic tissue invades the dying and disintegrated cartilage and Thus, cartilage bone is not formed from cartilage, it invades the cartilage and replaces it. Cartilage tissues can grow by: Apposition on its surfaces as well as by Proliferation of cells and the intracellular matrix within its substance, thereby expanding the cartilage by interstitial growth. 22 20 Fig. 6 Endochondral bone formation Between individual bony centers, areas of growing cartilage form synchondrosis. The important synchondrosis include (Fig. 7 A): 30 Chapter 3 Growth and Development i. The spheno-occipital synchondrosis: It exists in the midline cranial base between the occipital and 23 sphenoidal bones. It persists up to 18-20 years of age closing a few years earlier in girls than in boys. ii. The intersphenoidal synchondrosis: It is present in the midline cranial base between the anterior and posterior parts of the body of the sphenoid. life. /20 In humans, it closes just before birth. In most other animals including monkeys, it persists until the beginning of adult iii. The spheno-ethmoidal synchondrosis: It exists between the sphenoid bone and the ethmoid bone. It closes at about 5-7 years. iv. The intra-occipital synchondrosis: It is present inside the occipital bone. It closes at 3-5 years. 22 In the maxillary complex, the nasal capsule is another region for endochondral growth where growing cartilage is converted into bone. In the mandible, midline symphysis and condyle of the mandible are other regions (Fig.7 B, C). 20 Fig. 7 A. Cranial Synchondrosis B. Nasal Cartilage C. Mandibular Symphysis 31 Chapter 3 Growth and Development Intra-membranous bone formation: (Fig. 8 A) In this type of bone formation: 23 i. The undifferentiated mesenchymal cells of the membranous connective tissue change to OSTEOBLASTS and elaborate OSTEOID MATRIX. ii. The matrix or intracellular substance becomes calcified and BONE results. Sites of intramembranous bone growth: Periodontal ligament Endosteum Periosteum Sutures /20 a) Growth by surface deposition: (Fig. 8 B) All skull bones depend on this method for their growth. It becomes more significant in the later periods of skull growth. The balance between bone deposition and resorption is an important factor in changing the form of individual bony elements of the skull. This growth is additive or appositional in nature. This process is responsible for the growth of cavities such as the: 22 i. Nasal cavity ii. Paranasal sinuses and iii. Medullary cavities of individual bones 20 A B 32 Chapter 3 Growth and Development Fig. 8 A. Intramembranous bone formation B. Growth by surface deposition b) Sutural growth (Fig. 9): 23 Sutures have an osteogenic process comparable to periosteal bone growth. The suture is an inward reflection of the periosteal membrane between the edges of adjacent bones. At a growing suture there are five layers of tissue: i. Cellular osteogenic layer of the periosteum associated with each of the two bones bounding the sutures. ii. Fibrous layer of the periosteum associated with each of the two bony units /20 and bounding the cellular osteogenic layer. iii. Intermediate layer between the adjacent fibrous layers containing connecting fibers and blood vessels. 22 Fig. 9: Sutural layers a. Fibrous layer b. Cellular Osteogenic layer c. Intermediate layer This means that there are two growth sites at each suture, one for each bony unit. These growth sites are independent of one another in their growth and thus at a suture, one bone may grow faster than the other. Two theories exist regarding the mechanism responsible for the separation of the bones bounding a suture: 20 1. The old classical theory: the proliferation of the soft tissues in the suture separating the bones bounding it thus, it considers the suture as a growth center (built-in). 2. The recent functional matrix theory (Moss): separation of the bones at 33 Chapter 3 Growth and Development sutures is produced by the growth of an organ such as the brain or eyeball or by growth of cartilage either at a synchondrosis between two bone elements or as in the case of nasal cartilage. According to this theory, the suture is a tension- 23 adapted growth region responding to the forces produced by the enlarging soft tissue associated with them thus, it considers the suture as a growth site (fill-in). Growth sites versus growth centers: Cartilage cells of growth plates are capable of creating a tissue separating force by virtue of interstitial expansion when such units are transplanted to /20 subcutaneous sites, they are capable of growing apart. Cells of sutures, however, are not capable of generating a tissue separating when transplanted to subcutaneous sites they are not capable of growing apart. Baume has given names to these two growth mechanisms. Growth center for endochondral ossification with tissue separating force, and growth site for suture bone formation. Growth movements: 22 During growth bone moves either in the same or opposite direction to its own growth or to the growth of other bones. In other words, during the enlargement of the craniofacial bones, two kinds of growth movements are seen: 1) Cortical Drift 20 2) Displacement 1) Drift: Relocation or movement of bone in the same direction of its own growth. It is produced by the deposition of bone on one side of the cortical plate while resorption occurs on the opposite side (Fig. 11 A). 34 Chapter 3 Growth and Development 2) Displacement: 23 The movement of the whole bone as a unit. Two types of displacements exist: i. Primary displacement: The movement of bone in opposite direction to its own growth. This type of growth functions to maintain the relationship of bones to each other as they are carried away from their articulation with each other (Fig. 11 B). ii. Secondary displacement: The movement of the bone in the same 11 C). 3) Remodeling: /20 direction of growth of other adjacent or distant bone. It is the movement of the bone in relation to enlargement of other bones (Fig. It is the change is size and shape of the bone as a result of differential resorption and deposition of the inner and outer surfaces (Fig. 11 D). 22 A. Drift B. Primary Displacement 20 35 Chapter 3 Growth and Development 23 C. Secondary Displacement D. Remodeling Fig. 11 Growth Movements Postnatal growth of the skull /20 Growth of the skull may be subdivided into: 1) Growth of the cranium: a) Growth of cranial vault b) Growth of the cranial base 2) Growth of the face a) Middle face (naso-maxillary complex) b) The mandible 22 1) Growth of the cranium: a) Growth of the vault: The cranium grows secondary to brain growth. This growth is accelerated during infancy. The increase in size under the influence of an expanding brain is accomplished primarily by proliferation and ossification of sutural connective tissue and by appositional growth of the individual bones that make up the cranial vault. Some selective resorption occurs early in postnatal 20 life of the inner surface of the cranial bones to help flatten them out as they expand. Apposition can be seen on both the internal and external tables of the cranial bones as they become thicker. This increase in thickness is not uniform due to the inner cranial table being primarily under the influence of the growth of the 36 Chapter 3 Growth and Development brain while the outer plate has certain mechanical influences operating upon it. These mechanical influences contribute to the growth of the cranial superstructures (supra orbital and mastoid structures). These structures are 23 usually more marked in males than in females. The newborn has his frontal bone separated by the metopic suture and has no frontal sinus. The developing frontal sinus gradually replaces the spongy bone between the external plates. The cranial vault increases in width primarily through filling ossification of the proliferating connective tissue in the interparietal, parieto-sphenoid and parieto-temporal sutures. /20 The mid-sagittal suture does not close until the middle of the third decade of life. Increase in length of the vault may be primarily due to the growth of the cranial base with active response at the coronal suture and lamboidal sutures (Fig. 12). a. Growth of Cranial Base: The cranial base grows primarily by cartilage growth in the synchondrosis (sphenoethmoidal, intersphenoidal, spheno-occipital and intra - occipital 22 synchondrosis). These synchondrosis share in adjusting the cranial base to the need of the growing brain and the upper respiratory area. At the center of the cartilage, the cartilaginous growth separates the growing bones. It acts as a double epiphyseal plate like fibrous suture. The separating mechanism is built between the adjacent bones (fibrous suture is filling). When the cranial base grows anteroposteriorly, this brings the maxillary 20 complex forward and downward (secondary displacement). Also, the maxilla leaves a space for the oropharynx. On the other hand, increase in length of the cranial base gives a chance for the growth of the naso-maxillary complex and alveolar region to grow vertically. 37 Chapter 3 Growth and Development 23 Fig. 12 Sutures of the Cranial vault Growth of the face /20 a) Growth of the Middle Face: The middle face consists of the orbits and their contents, the nasal cavity, the maxillary sinuses, upper alveolar process and palate (Fig. 13). It follows the somatic curve of growth and undergoes a dramatic increase in absolute term but particularly in relation to the cranium that is more complex at birth 22 (follows the neural curve). The middle face expands in width, depth and height but the last dimension is more remarkable. 20 Fig. 13: Bones forming the face 38 Chapter 3 Growth and Development 1. Growth in Width: Before Seven Years: Comparing the face of the newborn to that of an adult, an obvious lateral 23 expansion is seen. The principles of bone growth responsible for the lateral growth of the face involve displacement and drift. The former is dominant during the early stages of growth as the skull is divided to two halves by the sagittal suture system (interparietal, metopic, nasal, middle palatine, symphysis of the mandible and cranial base cartilage). Brain growth and cranial base cartilage growth lead to an increase in facial width through unit. After seven years: /20 displacement. However, during the first year, the frontal bone and the mandible become continuous bones, as the metopic suture and the symphysis The neural growth is completed and growth in width by displacement ceases. Further enlargement will be by bone drift. The combined lateral growth movements of the orbits, the nasal walls, maxillary sinuses, and malar regions are produced by bone deposition on 22 their lateral facing surfaces, together with resorption from the various medial facing surfaces (Fig. 14). 20 Fig. 14: Lateral & posterior drift of the zygomatic bone. - - Resorptive (ant. & inner) surface. ++ Depository (post & lateral) surface 39 Chapter 3 Growth and Development 2- Growth in Height: 23 Increase in height is remarkable during the postnatal period. Roughly half of the vertical growth results from displacement, while the other half results from drift. At birth the nasal floor is at the same level of the orbital floors. During the first seven years: Secondary displacement of the nasomaxillary complex is in a downward direction following growth of the anterior cranial base. Growth of the nasal cartilage is downward as a result of increase in respiratory demand (function matrix theory). After seven years: /20 Drift accounts for about half of the vertical growth in the midface. The nasal floor is resorptive while the palate and alveolar process are depository in nature. The result is drift of the naso-maxillary complex downward where the nasal floor becomes at a lower position than the orbital floor as resorption in the nasal floor exceeds that of the orbit (Fig. 15). 22 20 Fig. 15: Downward drift of the nasomaxillary Complex 3- Growth in Depth (Antero-Posterior): The nasomaxillary complex is united with the cranial base through a group of sutures (Fig. 16): a) Frontonasal 40 Chapter 3 Growth and Development b) Fronto-maxillary c) Zygomaticomaxillary d) Zygomatico-temporal and 23 e) Pterygo palatine sutures These sutures are aligned in such a way that any growth in the cranial base would displace the middle face downward and forward in this manner. The middle face could maintain its anteroposterior relationship to the growing anterior cranial base and at the same time its depth increases by displacement. /20 22 Fig. 16: Craniofacial Sutures Before seven years The anteroposterior growth occurs by secondary displacement of the nasomaxillary complex in a downward and forward direction following growth of: 1.The anterior cranial base (synchondrosis) and; 2. Growth of the nasal cartilage which is downward as a result of increase 20 in respiratory demand (functional matrix theory). After seven years Growth of the surrounding soft tissue translates the maxilla downward and forward, 41 Chapter 3 Growth and Development opening spaces in the sutures where bone is added. If a bone gets displaced as a result of its own growth, it is called “primary displacement”. The maxilla does not grow forward or make room for the erupting teeth by 23 depositing new bone on its anterior surface, but instead, new growth is deposited posteriorly in the maxillary tuberosity area, followed by anterior displacement (primary displacement) making room for the erupting molar teeth successively (Fig.17). In this way some remodeling can occur on the anterior surface by resorption. The molar region grows in a progressive posterior direction relative to the orbit and the maxilla receives new bone deposition posteriorly. /20 So, the process of displacement (which is produced by the expanding soft tissue) produces the space within which bone enlargement occurs. sutural bone growth does not push the nasomaxillary complex away from the cranial floor. This places all the bones in new positions in pace with the So, expanding soft tissue matrix and maintains continuous sutural contact as bone becomes separated. 22 20 Fig. 17. Posterior drift-anterior displacement of the maxillary arch b) Growth of the Mandible: 42 Chapter 3 Growth and Development At birth, the mandible appears to be a little more than a curved bar of bone. The body is ill defined. The alveolar process is scarcely present. The rami are proportionally short and the condyles have not yet become well 23 developed. Growth in Width: Symphyseal cartilage growth contributes to growth in width during the first year of life. The mandibular condyle grows in a posterior superior and lateral direction through a process of endochondral bone formation. Additive V Principle of Growth /20 growth at the coronoid process and condyle increases the superior inter- ramus dimension (V principle). According to this growth concept, bone is deposited on the inner surface of the “V” shaped bone and resorbed on the outer surface. Bone is deposited towards the surface of growth (Fig. 18). 22 20 Fig.18 Increase in inter-ramal width by outer resorption & Inner deposition (V principle of Growth) Increase in Length The increase in the length of the mandible is by condylar growth and apposition 43 Chapter 3 Growth and Development of bone on the posterior border of the ramus. The posterior border of the ramus grows in a backward course by progressive addition of new bone, which is an example of drift. 23 This ramus drift gives room for the developing posterior teeth, thus the ramus becomes deeper in its anteroposterior dimension (Fig. 19 A). In general, the growth at the head of the condyle occurs in an upward and backward direction where mandibular growth is expressed as a downward and forward displacement, which is an example of primary displacement and hence the mandibular length increases (Fig. 19 B). /20 22 A. Drift B. primary displacement Fig. 19 Increase in length of mandible Increase in Height 20 The ramus also increases significantly in vertical dimension, to accommodate the marked downward growth of the naso-maxillary complex as well as eruption of teeth. Alveolar bone growth along the superior of border of the mandibular body brings about an increase in vertical dimension. Bone is deposited along the entire inferior surface of the mandibular body except for the 44 Chapter 3 Growth and Development antegonial notch. Chin 23 The area of the chin receives thick deposits of periosteol bone. The alveolar area just above the mental protuberance however is usually resorptive. This results in a protruding chin. Mandibular angle The region of the angle of the mandible is augmented by addition of bone to the Mental Foramen /20 posterior border of the ramus as a result, the angle of the mandible decreases from 175 degrees at birth to 115 degrees in adult. The mental foramen during the early years of life is situated under the mesial cusp of the first deciduous molar. In the adult it lies below and between the first and second premolars. This change in position is due to the backward and outward inclination of the canal. As bone is added to the outer surface of the 22 body of the mandible, the foramen is carried backwards (Fig. 20). 20 Fig.20 Change in mental foramen position 45 Chapter 3 Growth and Development 23 /20 22 20 46 20 22 /20 23 20 22 /20 23 Chapter 4 Development of the Normal Occlusion Development of the Normal Occlusion 23 Intended Learning Outcomes (ILOs): To identify the normal development & characteristic features of deciduous dentition stage. To know the normal development & characteristic features of mixed dentition. To recognize the normal development & characteristic features of permanent dentition stage. Identify the timing of eruption of deciduous & permanent dentition. /20 The importance of the deciduous dentition and early treatment to prevent developing malocclusion. Define the dimensional changes seen in maxillary & mandibular arches regarding shape, size and relationships & to understand their importance. To understand the transient pattern of different of malocclusion during different stages. To be skilled to spot and diagnose any abnormalities. 22 20 49 Chapter 4 Development of the Normal Occlusion Chapter Outline: 23 A. Gum pads stage 1. At birth. 2. Eruption of deciduous dentition. B. Deciduous dentition stage 1. Overbite in deciduous dentition 2. Spacing in deciduous dentition 3. Anteroposterior relationship of deciduous dentition C. Mixed dentition stage 1. Stages of teething in permanent dentition. /20 2. Eruption of canines and premolars. D. Early permanent dentition stage E. Adult dentition stage 1. Criteria of Normal Occlusion 2. Dental arch dimension. 3. Dimensional changes in dental arches. F. Transient malocclusions Definition: Occlusion is the articulation of the maxillary and mandibular teeth. It is a complex procedure as it involves teeth, their morphology, angulations & muscles of mastication, skeletal structures, TMJ and also functional jaw movements. 22 20 50 Chapter 4 Development of the Normal Occlusion Stages of development of normal occlusion: 23 A. Gum pads stage (Fig. 1): It starts from birth until end of eruption of the deciduous dentition (0 to 2.5 years). Fig. 1: gum pad stage 1. At birth: /20 In the mouth of the newborn fetus, gum pads cover the alveolar processes. These are greatly thickened oral mucous membrane and covered with fibrous periosteum, which soon become segmented by transverse grooves into 10 segments. Each segment is a developing tooth site. The maxillary gum pad (Fig. 2) is horseshoe shaped with a very shallow vault, while the mandibular (Fig. 3) one is U –shaped. There are no teeth for the first 6-month. 22 Fig. 2: Maxillary gum pad Fig. 3: Mandibular gum pad 20 The gum pads show elevations and grooves (Fig. 4) that outline the position of primary teeth. They are apart during function, while at rest there is a contact only posteriorly. 51 Chapter 4 Development of the Normal Occlusion 23 Fig. 4: gum pads showing elevations & grooves. Relationship between upper & lower gum pads: In physiologic rest position, tongue protrudes most of the time. /20 forward and maintains in contact with the lips The upper lip appears to be short and flaccid. Mandibular gum pad is distal to maxillary to a variable degree In the first year; the gum pads are not wide enough to occupy the developing incisors that are rotated & crowded in their crypts (Fig. 5). Fig. 5: Radiograph of gum pads demonstrating 22 positions of the unerupted teeth in their crypts. They will grow rapidly especially in lateral direction; which will give an increase in arch width; which will allow eruption of teeth in good alignment. 2. Eruption of deciduous teeth: During the 4th month intrauterine life, calcification of the deciduous teeth begins. At birth ¼ to ½ the crowns of the deciduous teeth have been calcified 20 with the tips of the first permanent molar cusps. Eruption of deciduous teeth starts at 6 to 7 months. At age 2.5 years, all primary teeth erupted and at 4 years old, their roots are completed. 52 Chapter 4 Development of the Normal Occlusion 23 Fig. 6: maxillary & mandibular deciduous teeth. Table 1 represents the average date of eruption of deciduous dentition in months (up to 6 months earlier or later is considered to be normal): LA 6 months UA 8 /20 LB LC LD LE 7 months 16 months 12 months 20 months UB UC UD UE 9 18 14 24 Table 1: Average eruption dates of deciduous teeth The six/four rule for primary tooth emergence; 4 teeth emerge for each 6 month: 1. 6 m.: 4 teeth (lower & upper centrals). 22 2. 12 m.: 8 teeth (1. + upper & lower laterals). 3. 18 m.: 12 teeth (2. + upper first & lower first molars). 4. 24 m.: 16 teeth (3. + upper & lower canines) 5. 30 m.: 20 teeth (4. + lower 2nd & upper 2nd molars). B. Deciduous dentition stage: It covers the period from the finishing of the 20 eruption deciduous dentition up to the eruption of the first permanent tooth (2.5 to 6 years), which is either a first molar or a mandibular central incisor (Fig. 7). Fig. 7: Deciduous dentition stage 53 Chapter 4 Development of the Normal Occlusion During the first year the gum pads enlarge and the arches widen slightly to have room for erupting teeth. 23 Teeth start to appear by age of 6 month, usually in lower arch followed by upper arch. Deciduous incisors are smaller, whiter and more upright than their successors (Fig. 8). /20 Fig. 8: maxillary & mandibular deciduous teeth Three important features are presented in this stage: 1. Overbite in deciduous dentition. 2. Spacing in deciduous dentition. 3. Anteroposterior relationship of deciduous dentition. 1. Overbite in deciduous dentition: Normal overbite (Fig. 9) is the amount of vertical overlap between maxillary & mandibular central incisors or primary one, when teeth are in 22 centric occlusion. It varies in primary dentition from 10 to 40 %. Overbite tends to be deep normally at 3 years, but it will be reduced at age 5 y. It is reduced by rapid attrition of incisors, so at age of 5 to 6 years an edge-to-edge relationship is seen. This will facilitate the forward growth movement 20 of the mandible. Fig. 9: normal overbite. These photographs (Fig. 10&11) represent two cases with primary dentition at age of 5 years; the first one is favorable condition and known as spaced dentition. The 2nd case is unfavorable condition and known as closed 54 Chapter 4 Development of the Normal Occlusion dentition. 23 Fig. 10: favorable condition Fig. 11: unfavorable condition 2- Spacing in deciduous dentition: a) Generalized spacing; usually present in the incisor region to allow for difference in size /20 between primary and permanent teeth. The crowns of the permanent incisors lie lingual to the crowns of the primary incisors. Fig. 12: generalized spacing in deciduous teeth Presence of permanent teeth in lingual relation to primary one (Fig. 13): The mesiodistal crown dimensions of permanent incisors are considerably greater than that of the primary incisors. This difference in the mesiodistal crown dimension between them is termed as Incisal liability. 22 20 Fig. 13: presence of permanent teeth in lingual relation to the primary one. b) Primate spaces (Figs. 14&15): present mesial to upper primary canine and distal to lower primary canine. 55 Chapter 4 Development of the Normal Occlusion Primate spaces in the upper close by 23 eruption of maxillary permanent incisors, while the lower close by eruption of mandibular first molar and by their early mesial shift. Absence of these spacing, indicates potential crowding Fig. 14: generalized spacing and primate space. /20 Fig. 15: primate space in maxillary and mandibular arches. 3. Anteroposterior relationship of deciduous dentition: Classified according to: 22 a) The distal aspect of the upper second primary molar may show: 1) Flush terminal plane 2) Mesial step 3) Distal step b) The long axis of the upper primary canine may show: 1) Neutro cuspid (Class I), 2) Disto cuspid (Class II) and 3) Mesio cuspid (Class III). 20 a) The distal aspect of the upper second primary molar may shows: 1) Flush Terminal Plane relation (Fig. 16): a. The primary posterior teeth occlude so that the mesiolingual cusp of the maxillary primary molar occludes in the central fossa of the mandibular 56 Chapter 4 Development of the Normal Occlusion primary molar. b. The primary mandibular molar is usually wide mesiodistally than maxillary one giving rise to flush terminal plane. 23 Flush terminal plane is an imaginary line dropped tangent to the distal surface of the upper E that passes through the distal surface of lower E. It is also called end-to-end occlusion.. /20 Fig. 16: flush terminal plane relation 2) Mesial Step (Fig. 17): distal surface of lower E is mesial the line dropped from the distal surface of the upper E. 22 Fig. 17: mesial step relation. The effects of mesial step, the first permanent molars directly erupt into class I molar relationship. Few cases may progress to class III molar relations, if forward growth of the mandible is more than normal. 20 3) Distal Step: the distal surface of lower E is distal to the line dropped from distal surface of upper E. The Effect of distal step usually leads to Angle’s class II molar relationship, a few cases may go into class I. 57 Chapter 4 Development of the Normal Occlusion 23 Fig. 18: distal step relation. b) The long axis of the upper primary canine may show: /20 1) Neutro cuspid (Fig. 19): The long axis of maxillary cuspid passes through the embrasure between lower cupid and primary first molar (star). D C C 22 Fig. 19: neutro cuspid relation. 2) Disto cuspid (Fig. 20): The embrasure between lower cupid and primary first molar (star) is located distal to long axis of maxillary cuspid. 20 Fig. 20: disto cuspid relation. 58 Chapter 4 Development of the Normal Occlusion 3) Mesio cuspid (Fig. 21): The embrasure between lower cupid and primary first molar (star) is located 23 mesial to long axis of maxillary cuspid. /20Fig. 21: mesio cuspid relation. Early correction of flush terminal plane (Fig. 22): The erupting first mandibular permanent molars are guided by distal surface of 2nd primary molars and move forward by closure of the primate space. The flush terminal plane is no longer present due to forward movement of the mandible and closure of lower primate space. This step is known as 22 early mesial shift. Attrition of incisors will facilitate forward growth of the mandible more than the maxilla. Fig. 22: correction of flush terminal plane 20 59 Chapter 4 Development of the Normal Occlusion 23 Fig. 23: Occlusion at age of 6 years; eruption of mandibular central incisors & first permanent molar C. Mixed dentition stage: /20 It begins from the eruption of the first permanent tooth to the final shedding of the deciduous teeth (6 to 12 years) (Figs. 23&26). Ø Stages of teething in permanent dentition: Permanent teeth start calcification after birth except cusp tips of first permanent molars. Eruptive movement starts after half of the root has been formed. Tooth pierce alveolar crest after 2/3 of its root has been formed. Tooth emerges into oral cavity through gum tissues after ¾ of the root formation. Lower incisors usually erupt before upper one. 22 Upper teeth develop on the palatal aspects of their predecessors. They erupt downwards, outwards and forwards (Fig. 24). Fig. 24: position of upper permanent incisor in relation to primary one & it tends to erupt in 20 outwards & forward position. Table 2 represents the sequence of average date of eruption of permanent dentition with a range of variation up to 6 months earlier or later is considered to be normal: 60 Chapter 4 Development of the Normal Occlusion L6 6 years U6 6 years L1 6 years U1 7 years 23 L2 7 years U2 8 years L3 9 years U4 12 years L4 10 years U5 11 years L5 11 years U3 12 years L7 12 years U7 12 years Table 2: the average sequence of eruption of permanent dentition /20 22 Fig. 26: occlusion at 8 years The rules of “Fours” for permanent tooth development (3rd molars not included): ü At birth, four first molars have initiated calcification, ü At 4 y., all crowns have initiated calcification. ü At 8 y., all crowns are completed, ü At 12 y., all crowns emerge & ü At 16 y., all roots are complete. 20 Eruptive tooth movement is the occlusal movement of the tooth from its developmental position within the jaw to its final functional position in the occlusal plane. Active eruption: bodily movement of tooth from its site of development to its functional position in the oral cavity. 61 Chapter 4 Development of the Normal Occlusion Passive eruption: apparent lengthening of the crown due to loss of attachment or recession of gingiva. 23 Ø Stages of eruption in permanent dentition It is divided into 4 stages: 1- Pre-emergent eruption: Eruptive movements begin with the start of root development. For eruption to occur, the dental follicle must resorb the overlying bone & primary tooth root, & the eruptive mechanism cause tooth movement. Normally both these mechanisms are coordinated, however if not, failure of eruption may result. 2- Post-emergent eruption: /20 Tooth eruption normally occurs when root formation is ¾ complete. Eruption is rapid (0.3-0.5 mm/week) until the tooth reaches close to the occlusal plane: (post-emergent spurt). There are many factors opposing eruption as occlusal contacts & pressure from the tongue & cheeks. 3- Juvenile occlusal equilibrium: once a tooth has moved into occlusion, eruption continues at a slower rate to keep proportion with vertical skeletal growth. 4- Adult occlusal equilibrium: starts after the adolescent growth spurt. 22 § Teeth continue to erupt throughout adult life to compensate for occlusal wear & residual vertical skeletal growth. § Over eruption can also occur if an opposing occlusal contact is lost. Ø The difference in size between permanent and deciduous teeth could be housed as follows: 1. The presence of normal interdental spaces between deciduous incisors; generalized spacing. 2. Permanent incisors are larger, more proclined and erupt outwards and 20 forward. 3. Increase in intercanine width, in mandible from age 6-8years and in maxilla increases up to 12 years in females and 16 years in male. Ø Eruption of permanent canines and premolars: The sum of the mesiodistal dimension of the primary canine, first & 2nd molars 62 Chapter 4 Development of the Normal Occlusion is larger than the sum their successors (3, 4, 5). This difference is known as Leeway space. 23 a) Utilization of Lee way space (Fig. 27&28): Upper permanent teeth (3, 4, and 5) are smaller about 1mm on each side. Lower permanent teeth (3, 4, and 5) are smaller about 2mm on each side. Partially larger permanent canine falling back to the space. The other part is taken by the late mesial shift of first mandibular permanent molars. /20 Fig. 27: Leeway space This “Leeway space" is to 1.7 mm. in the mandibular buccal segment on 22 each side; (3.4 mm bilaterally). While in the maxillary buccal segment is 0.9 mm. on each side; (1.8 mm bilaterally). 20 Fig. 28: Leeway space may relief incisor crowding. b) Intercanine growth may relief incisors crowding (Fig. 29): There is an increase in the intercanine width 1-2mm during the presence of deciduous incisors. Also, during the eruption of the permanent incisors and 63 Chapter 4 Development of the Normal Occlusion canines, 3-5 mm increase in upper arch and less in lower arch occur. Fig. 29: Intercanine growth, may relief incisors crowding. 23 c) Ugly Duckling stage (Fig. 30): The maxillary canines develop distant from the dental arch and close to the floor of the orbit. At 9-10 years as it moves downward and forward towards occlusion, it come to lie against the apices of the erupting permanent lateral incisors and central incisors causing mesial pressure on their roots. The centrals respond to that pressure by central diastama and distal crown flaring, while laterals show labial and distal tipping. This phenomena is called /20 Ugly Duckling stage, it is a temporary clinical picture that is improved by eruption of permanent canines (NO treatment). 22 Fig. 30: Ugly Duckling stage 20 d) Early mesial shift (Fig. 31): In case of spaced primary dentition and flush terminal plane; as the first mandibular permanent molar erupts; the primary molars move mesially to close the space distal to the primary canine (primate space). 64 Chapter 4 Development of the Normal Occlusion 23 Fig. 31: early mesial shift. e) Late Mesial Shift (Fig. 32): In case of closed primary dentition & flush terminal plane; the first maxillary and mandibular permanent molar erupts into cusp to cusp relationship ( no space); at 11 y. the primary mandibular 2nd molar exfoliate and this allow for /20 mesial migration of mandibular first permanent molar. Fig. 32: late mesial shift: forward movement of mandibular first molar to occupy Leeway space. 22 Fig. 33: occlusion at age of 12 years Fig. 34: occlusion at age of 15 years. 20 D. Early permanent dentition stage (Figs. 33&34): It begins after the eruption of the permanent canines, premolars and permanent 2nd molars (12 to 17 years). After eruption of 2nd molars, there will be some proclination of the 65 Chapter 4 Development of the Normal Occlusion incisors; MOUTH FULLNESS; with increase in the facial convexity. This is related to larger tongue size relative to the surrounding skeleton of jaw. As the jaws catch up to the tongue in growth, the incisors are more 23 upright and less facial convexity occurs. LATE TEEN CROWDING (Fig. 35): As the mandible continues to grow downward and forward more than maxilla, the mandibular incisors are locked lingually to the upper. So, they tip lingually and the mandibular arch perimeter decreases more. /20 Fig. 35: late teen crowding. E. Adult dentition stage (Fig. 36): It starts by the eruption of the 3rd molars (17 to 21 years onwards). 22 Fig. 36: adult dentition stage. 20 1. Criteria of normal occlusion: Upper arch wider than lower arch. Individual articulation of the teeth. No spacing, crowding or rotation. Slightly curved occlusal plane. 66 Chapter 4 Development of the Normal Occlusion Anteroposterior molar relationships. The mesiobuccal cusp of upper first permanent molar is received in the 23 sulcus between the mesial and distal buccal cusps of the lower first permanent molar Normal overjet; is the horizontal relationship between upper and lower incisors. The distance is measured between the most protruded maxillary central incisors and opposing mandibular incisors, normally 0 - 4 mm. Normal overbite; is the amount of vertical overlap between the maxillary and mandibular central incisors. /20 2. Dental arch dimension (Fig. 37): It includes: width, length & perimeter: A: representing arch length. B1: representing intercanine width (arch width). B2: representing intermolar width (arch width). C: representing arch circumference. Fig. 37: dental arch dimension. 1. Width: it is the transverse linear measurement between two contra lateral 22 teeth; inter-canine, inter-molar or inter premolar width. 2. Length: it is the depth of the dental arch; it is measured from a line drawn at the midpoint between central incisors perpendicular to a line connecting the mesial contact points of first permanent molars. 3. Perimeter: it is a curved line connecting the mesial contact point of one first permanent molar passing over the contact points between premolars or deciduous molars and incisal edges of incisors to the mesial contact point of the contra lateral first permanent molar 20 3. Dimensional changes in dental arches: a) In the maxilla (Figs. 38-40): Maxillary arch length & perimeter: there is a slight increase in length and perimeter, followed by a decrease after age of 10 years. Maxillary width: between 3 to 14 y. inter-canine width increases 3-5 67 Chapter 4 Development of the Normal Occlusion mm. 23 Fig. 38: Dimensional changes in maxillary arch /20 Fig. 39: growth in height of the maxillary alveolar processes 22 Fig. 40: Lengthening of the maxilla by apposition of bone to the maxillary tuberosities. b) In the mandible: The width shows a lesser increase between 3 to 4 years. Mandibular length and perimeter show no change between 6 and 10 20 years. c) After 10 years there is a remarkable decrease due to: 1. Late mesial shift, 2. Inter-proximal wear, 3. Mesial drift tendency, and 68 Chapter 4 Development of the Normal Occlusion 4. Lingual tipping of mandibular incisors. F. Transient malocclusions: 23 These are self-correcting malocclusions that occurred during the development of the dental occlusion; which are normal for that age in the five dentitions stages. 1. Gum pads stage: a) Infantile swallowing: as the baby is sucking; the tongue lies over the lower gum pads & protrudes between the upper & lower lip. b) Retrognathic mandible & anterior open bite: on closure; there is contact only in the posterior region of the gum pads & the mandible is retruded in /20 relation to the maxilla. 2. Deciduous dentition stage: a) Spacing in deciduous dentition; generalized spacing & primate spaces b) Anterior deep overbite normally present at 3 years, but it will be reduced at age of 5 years to show edge to edge occlusion. c) When the distal surface of maxillary & mandibular deciduous second molar is in the same vertical plane. This is the normal molar relationship in the primary dentition because the mesiodistal width of mandibular molar is greater than maxillary molar known as flush terminal plane. 22 3. Mixed dentition stage a) Anterior deep bite because of larger permanent incisors & shedding of primary molars, which is usually, corrected following exfoliation of second primary molars and eruption of 2nd permanent molar. b) Ugly duckling stage. c) Crowding in lower anterior region 4. Early permanent dentition stage: 20 a) Mouth fullness & increase in the facial convexity; this is related to larger tongue size relative to the surrounding skeleton of jaw. b) Late teen crowding. 69 20 22 /20 23 20 22 /20 23 Chapter 5 Six keys to Normal Occlusion Six keys to Normal Occlusion 23 Intended Learning Outcomes (ILOs): Recognize a developing normal occlusion and be able to distinguish abnormal deviation that necessitates treatment Chapter Outline: A. B. C. D. Introduction /20 Prevalence of normal occlusion in Egypt. Static occlusion ''Larry Andrews' six keys to normal occlusion''. Functional occlusion ''Ronald Roth's concepts''. 22 20 72 Chapter 5 Six keys to Normal Occlusion A. Introduction: Physiologically speaking, the word '' normal'' designates a range rather 23 than a single point. Literally, the word ''occlusion'' means closing up (oc = up, and clusion = closing). The description of normal occlusion at different ages was previously lectured (i.e., normal growth and development of the dental arches and occlusion). The purpose of this chapter is to describe normal occlusion in adult subjects. A long time ago, it was stated that there are 138 surface contact spots /20 in normal occlusion in adults. Recently, normal occlusion was statically and functionally described. B. Prevalence of Normal Occlusion in Egypt Published research has shown that the prevalence of normal occlusion among adult Egyptians is 34.3%. It is significantly more common in females (36.7%) than males (31.6%). The prevalence of normal occlusion among Egyptians is lower than that of the Indians. However, it is higher than that of the Americans, Swedish, 22 Kenyans, Eskimos, and Danes C. Static Occlusion: Larry Andrews' Six Keys To Normal Occlusion Lawrence F. Andrews studied dental casts of 120 nonorthodontic subjects having normal occlusion. Following his study, he described six dynamically- interrelated characteristics of normal occlusion designed by nature without any orthodontic intervention. He called these characteristics the ''six keys''. These 20 keys are: molar relationship, crown angulation, crown inclination, rotations, tight contacts, and occlusal plane. 73 Chapter 5 Six keys to Normal Occlusion Key I. Molar Relationship (Fig. 1): The maxillary first permanent molar displayed a solid three-point contact 23 with opposing teeth. 1. The distal surface of the distal marginal ridge of the maxillary permanent first molar made contact and occluded with the mesial surface of the mesial marginal ridge of the mandibular permanent second molar. 2. The mesiobuccal cusp of the maxillary permanent first molar fell within the buccal groove located between the mesial and middle cusps of the mandibular permanent first molar- as indicated by Angle. 3. The mesiolingual cusp of the maxillary permanent first molar was seated /20 in the central fossa of the mandibular permanent first molar. (The molars and premolars enjoyed a cusp-embrasure relationship buccally, and a cusp-fossa relationship lingually. The tips of the maxillary canines were slightly mesial to the mandibular canine-premolar embrasure - which is consistent with the canine-rise concept). 22 20 Fig. 1: 1, Improper molar relationship. 2, Improved molar relationship. 3, More improved molar relationship. 4, Proper molar relationship. 74 Chapter 5 Six keys to Normal Occlusion Key II. Crown Angulation (MESIODISTAL TIP) (Fig. 2): By definition, the crown angulation is the mesiodistal tip of the long axis 23 of the crown. It is the angle formed between the long axis of the crown (as viewed from a facial perspective) and a perpendicular line erected from the occlusal plane. It is positive when the gingival portion of the long axis of the crown is distal to the incisal portion and vice versa. In normal occlusion, the crown angulation was positive for all the teeth. /20 Fig. 2: Crown angulation (tip) long axis of crown measured from line 90 degrees to occlusal 22 plane Key lll. Crown Inclination (Faciolingual Torque) (Fig. 3): By definition, the crown inclination is the faciolingual torque of the long axis of the crown. It is the angle formed between the facial long axis of the crown (as viewed from a proximal perspective) and a perpendicular line erected from the occlusal plane. It is positive when the gingival portion of the long axis of the crown is lingual to the incisal portion, and vice versa. In normal occlusion, the crown inclination was negative for all the teeth except the 20 maxillary central and lateral incisors. Further, the lingual crown inclination was similar for the maxillary canines through the maxillary second premolars, and was slightly more pronounced in the maxillary molars. Furthermore, the lingual crown inclination 75 Chapter 5 Six keys to Normal Occlusion progressively increased from the mandibular canines through the mandibular second molars. 23 Fig. 3: Crown inclination is determined by the resulting angle between a line 90 degrees to /20 the occlusal plane and a line tangent to the middle of the labial or buccal clinical crown. Key IV. Rotations (Fig. 4): In normal occlusion, the dentition should be free from undesirable rotations. If a molar is rotated, it would occupy more space than normal within the dental arch the reverse is true for the anterior teeth. 22 Fig. 4: A rotated molar occupies more mesiodistal space, creating a situation unreceptive to normal occlusion 20 Key V. Tight Contacts: In normal occlusion, the contact areas should be tight. Key VI. Occlusal Plane (Fig. 5): By definition, the occlusal plane is the imaginary plane on which the teeth meet in occlusion. (It is indeed a curved compound surface which is 76 Chapter 5 Six keys to Normal Occlusion commonly approximated by a plane - straight lines on lateral views-based on specific reference points within the dental arches). In normal occlusion, the occlusal plane should be flat or nearly flat. 23 A deep curve of Spee results in a more confined area for the maxillary teeth, creating spillage of the maxillary teeth mesially and distally. On the other hand, a reverse curve of Spee results in excessive room for the maxillary teeth. In other words, if the curve of Spee is not relatively flat, teeth in one arch will tend to be crowded while those in the other will be spaced. /20 22 Fig. 5: A, A deep curve of Spee results in a more confined area for the upper teeth, creating spillage of the upper teeth progressively mesially and distally. B, A flat plane of occlusion is most receptive to normal occlusion. C, A reverse curve of Spee results in excessive room for the upper teeth. C. Functional Occlusion: Ronald Roth's Concepts Ronald Roth applied gnathologhical concepts to orthodontics. He has shown that functional occlusion can be orthodontically achieved even after 20 therapeutic extractions. Roth described the mutually-protective occlusal scheme in which maximum dental interdigitation occurs when the mandible is in its rearmost, midmost, and uppermost position. The occlusal stops are equally distributed among the posterior teeth on their centric cusps. The anterior teeth are not in 77 Chapter 5 Six keys to Normal Occlusion positive contact but may elicit a mark with an articulation paper. However, when the posterior teeth are in occlusion, a thin mylar strip will not be held by the anterior teeth. 23 In protrusive movements, the maxillary anterior teeth articulate equally and evenly with the mandibular anterior teeth and the first premolars (or the second premolars in first premolars extraction cases) to gently dis-occlude the posterior teeth. In lateral movements, the maxillary anterior teeth articulate with the same mandibular teeth to dis-occlude the posterior teeth on any movement out of centric. The canines serve as the main guiding inclines the rate of canine-rise is /20 very gentle and harmonious with the lateral excursions. 22 20 78 Chapter 6 Classification of Malocclusion 23 /20 22 20 79 Chapter 6 Classification of Malocclusion Intended Learning Outcomes (ILOs): 23 Define the terminology of malposed teeth and different types of classifications of malocclusion Chapter Outline: A. Terminology of Malocclusion B. Malpositioning of individual teeth C. Malrelation of dental arches themselves 1. Anteroposterior Variations /20 2. Transverse Variations 3. Vertical Variations D. Malrelation of the bony bases themselves E. Classification of malocclusion 1. Definition 2. Objectives of Classification 3. Classification a) According to Body Type b) Simon’s Classification of Malocclusion c) Skeletal Classification d) British Standard Classification of Incisior Relationship: 22 e) Classification According to Dental Arch Relationship “Angle’s Classification” 1) Advantages of Angle’s Classification: 2) Disadvantages of Angle’s Classification: 3) The validity of angle’s classification 4) Dewey Modifications of Angle’s Classification 5) Prevalence of Angle's Classes in Egypt 20 80 Chapter 6 Classification of Malocclusion A. Terminology of Malocclusion: Malocclusion means a deviation in intra-maxillary and/or 23 intermaxillary relations of teeth presenting a hazard to the individual’s well being. Malocclusion of the teeth may be associated with one or more of the following conditions: 1. Malpositioning of individual teeth in arches which are themselves normally related to one another. 2. Malrelation of dental arches to one another upon bony bases which are normally related teeth: /20 3. Malrelation of the bony bases themselves B. Malpositioning of individual teeth: There are different positions of malocclusion of the individual 1. Labial (Facial) inclination (Fig. 1): Outward tilting of incisor and canine teeth toward the lips, i.e., proclination. In the case of the molars and premolars, the term Buccal (Facial) proclination is used. 2. Labial and Buccal Displacement (Fig. 2): (Facial displacement): i.e.bodily displacement of teeth in a facial direction. 22 3. Lingual inclination (Fig. 3): The crown of the tooth is tilted towards the tongue. Retroclination refers to lingual tilting of the anterior teeth. 4. Lingual Displacement (Fig. 4): A teeth bodily displaced towards the tongue. 5. Medial inclination (Fig. 5): A tooth having its crown abnormally tilted towards the mid-line. 6. Medial displacement: A tooth, which is bodily displaced towards the mid-line. 7. Distal inclination (Fig. 6): A tooth having its crown abnormally tilted 20 away from the mid-line. 8. Distal Displacement: A tooth, which is bodily, displaced in a direction away from the mid-line. 9. Infra-occlusion: A tooth has not reached the line of occlusion, i.e. has not erupted sufficiently. 10. Supraocclusion: A tooth that has passed the line of occlusion,i.e., 81 Chapter 6 Classification of Malocclusion overerupted. 11. Medio-lingual rotation (Fig. 7): A tooth which is rotated around its long axis so that its medial aspect is turned towards the tongue, i.e., torsi- 23 version. 12. Disto-lingual rotation (Fig. 7): A tooth which is rotated around its long axis so that its distal aspect is turned towards the tongue, i.e., torsi- version. 13. Transposition: A tooth that has appeared in abnormal numerical order, e.g., an upper canine and a lateral incisor changing place. 14. Perversion: A tooth completely misplaced or impacted, e.g., a lower third molar placed in the ascending ramus or a maxillary canine erupting in the nasal fossa. /20 15. Imbrication: Describes teeth which are irregularly arranged within the arch due to lack of space for them. Combination of these individual malpositions may occur, e.g., infra-labial mesio-lingual or even mesio- lingtorsi infraocclusion. 22 Fig. 1: Labially Inclined Fig. 2: Labial displacement Fig. 3: Lingually inclined Fig. 4: Lingual displacement 20 82 Chapter 6 Classification of Malocclusion Fig. 5: Mesially Inclined Fig. 6: Distally Inclined 23 Fig. 7: Mesio/disto-lingual rotation Lischer’s terminology (Fig. 8): Lischer used the suffix version to identify the Malpositioning of individual teeth in relation to the line of occlusion. /20 1. Labioversion or buccoversion (facioversion): facial to the line of occlusion (i.e. toward the lips or cheeks). 2. Linguoversion: Lingual to the line of occlusion (i.e., toward the tongue). 3. Mesioversion: Mesial to the normal position. 4. Distoversion: Distal to the normal position 5. Supraversion (Fig. 9): Past the line of occlusion. Thus, above in the mandible) or below (in the maxilla) the line of occlusion. 6. Infraversion (Fig. 10_: Away from the line of occlusion. Thus, above (in the maxilla) or below (in the mandible) the line of occlusion. 7. Axiversion: Wrong axial inclination 22 8. Torsiversion (Fig. 12): Rotated on its long axis 9. Transversion (Fig. 11): Wrong sequential order 20 Fig. 8: Lischer’s Terminology 83 Chapter 6 Classification of Malocclusion 23 Fig. 9: Supraversion Fig. 10: Infraversion /20 Fig. 11: Transversion C. Malrelation of dental arches themselves: Fig. 12: Torsiversion The following terms are used to describe variation from the normal relations of the dental arches or segments of the arches to one another: 1 - Post-Normal Occlusion: It is used to describe a condition when the lower dental arch appears to lie too far back in relation to the upper arch when the teeth are closed in centric occlusion. The term applied to the dental arches relations only and does include the relation of the mandibular basal bone to 22 the maxillary basal bone. Also it includes conditions when either the lower arch appears distal or the upper arch in a forward position or when both conditions coexist. 2 - Pre- Normal Occlusion: This describes a condition where the lower dental arch is in advance of the upper when the teeth are closed in centric occlusion and the condyles are in their normal position within the glenoid fossae. Postural prenormal occlusion describes a condition which though 20 appearing similar from a view of plaster casts alone, is created by the lingual inclinations or lingual displacement of the upper incisor to such an extent that when the jaws are closed, the mandible assumes a forward position and both condyles will be drawn forward onto the