Dental Implantology PDF

DENTAL IMPLANTOLOGY Introduction Dr. Thair Abdul Lateef Generally the term implantation applies to the transplantation of non-viable tissue, it is the use of inert foreign body implants (alloplasts) in human body tissues. The term trans...

DENTAL IMPLANTOLOGY Introduction Dr. Thair Abdul Lateef Generally the term implantation applies to the transplantation of non-viable tissue, it is the use of inert foreign body implants (alloplasts) in human body tissues. The term transplant is usually preserved for a true transplantation of living tissue (soft tissue, cartilage and bone). Implantation can benefit patients psychologically and in terms of masticatory efficiency. A dental implant is "a non-viable device of biocompatible material(s) placed within or against the mandibular or maxillary bone to provide additional or enhanced support for a prosthesis or tooth". Implants are subjected to the same problems, except for caries, as the natural dentition. Therefore, the same care that must be given to the oral cavity prior to any rehabilitative procedure must be given prior to implantation. ********************************************************************* Bone remodeling Modeling is the appropriate term to characterize changes in bone morphology occur during growth (turnover & replacement). Ridge resorption and atrophy are misnomer because resorption is a part of normal turnover process occurring in all bones, whereas atrophy implies a passive process. Remodeling of bone involves 3 steps: ❖ Activation: begins as a result of specific local (i.e. stress) and systemic (i.e. hormonal) stimuli. ❖ Resorption: occur in all four of skeletal envelopes (periosteum, haversian, cortical- endosteal, trabecular). It is mediated strictly by osteoclasts which is the only cell in the body capable of resorbing bone. Often resorption occur parallel to the stress placed upon bone. Resorption also occurs in the absence of stress, but it does so in a less organized manner. Once resorption phase is complete, there is usually a delay period of 12-14 days after which formation begins. ❖ Formation: osteoblasts begin to lay down organic matrix, after 14 days osteoid begins mineralization. The site at which resorption ceases and formation begins is 1  termed as cement line. The time involved is about 3 months in compact bone and 2 months in trabecular bone (trabecular bone turnover is of higher rate). The progression of healing after a tooth extraction goes through certain resorptive stages of: 1. Fibrin clot organization (first 4 weeks) 2. Immature (woven) bone formation (4–8 weeks) 3. Mature (lamellar) bone development (8–12 weeks) 4. Bone stabilization stage (12–16 weeks or about 4 months) Post-extraction bone resorption is always three-dimensional, with the greatest loss of bone in the bucco-palatal or horizontal direction (the width) and occurring mainly on the buccal side of the alveolar ridge. Schropp et al reported that two thirds of the horizontal bone loss occurs within 3 months and one-third takes place within the remaining 9 months of the first year post-extraction. A mean reduction of the width of the ridge has been reported to be 5-7 mm within a 6-month period or 50% during the 12 months following tooth extraction. The loss of bone height is smaller, reported to be about 1 mm within the first 6 months post-extraction. ********************************************************************* Factors Influencing Edentulous Bone Loss A. Metabolic factors: metabolic bone disease is any process that influences the normal modeling of bone. Osteopenia is a clinical term for any loss in bone density. The common metabolic bone diseases are: 1. Osteoporosis → characterized by a reduction in the mass of bone per unit volume resulting in mechanical failure and pain, the ratio of mineral to organic matrix is usually normal. Clinical signs and symptoms of advanced osteoporosis include pain in the spine, loss of height and/or thoracic kyphosis due to vertebral compression and fractures due to secondary trauma, in most cases serum and urine biochemical examinations are normal. Osteoporosis seen in senile osteoporosis, postmenopausal osteoporosis, hyperparathyroidism and Cushing syndrome. 2. Osteomalacia → is any disease in which excess osteoid is not mineralized and impaired bone healing is present. Osteomalacia seen in vitamin D deficiency, malnutrition, renal osteodystrophy, secondary hyperparathyroidism and drug therapy (chronic corticosteroid therapy, chronic heparin therapy, anticonvulsant therapy, alcohol). B. Anatomic factors: 1. Facial morphology → peoples with long faces (dolichocephalic) have more voluminous anterior alveolar ridge than those with short faces (brachycephalic). Brachycephalic faces (low mandibular plane angle and gonial angle) are capable of 2  higher biting forces in both anterior and posterior regions, there is a direct correlation between short facial heights and edentulous bone loss. 2. Trauma and alveolectomy technique → maximum conservation of bone should be practiced during extraction and management of the trauma patients. C. Mechanical factors: 1. Disuse atrophy plays a role in the low-turnover type of remodeling. 2. Excessive loading may contribute to high-turnover type of remodeling. In bone loss secondary to the influence of dentures, the denture-bearing area of the maxilla is 1.8 times than that of the mandible. Therefore, compression (in pound/inch2) are greater on the mandible resulting in increased bone loss which is 4 times that of the maxilla, in this situation edentulous bone loss can be reduced through decreasing occlusal contact area and balancing the occlusion during occlusal arrangement of dentures. 3. Parafunctional activity (clenching & bruxism) → contact during mastication occupies less than 15 minutes/day, whereas the teeth may be forcibly held together several hours/day in these activities, however the effects are not clearly understood. ********************************************************************** Classification Babbush 1985 classified implants according to the site into 4 types: 1. Mucosal Inserts: Was introduced to the dental profession in 1943 by Dahl. It has been discarded due to complicated and prolonged insertion technique and stormy post-operative periods. The mucosal inserts are composed of 2 parts the retentive base, which is placed into a prepared site in the prosthesis, and the vertical component (buttons), which enters the soft tissue receptor site in the oral mucosa. They were indicated in cases of severe atrophy of the alveolar ridge in maxilla that not permit the use of endosseous implant due to the presence of anatomical limitations which are the maxillary sinus and the nasal cavity. The use of mucosal inserts in complete mandibular dentures is not tenable because of thin friable non-retentive nature of the tissues. These appliances are designed to be inserted into surgically prepared sites in the mucoperiosteum. Preparation of oral mucosa done by bur and the receptor site should be narrower and deeper than the inserts. The denture should not be removed for longer than 8-12 hours at any time after insertion otherwise the receptor sites will begin to close, and the patient will have to be retreated. 3 2. Subperiosteal Implant: Was firstly introduced and performed in 1949. The design consist of 2 parts substructure which is a metallic framework that rests on bone under the periosteum, and superstructure which are abutment posts connected to the framework and penetrate the mucoperiosteum protruding in the oral cavity. The maxillary implant not done routinely. Transplantation of mucosal grafts (palatal patch grafts) or even split- thickness skin grafts may be required to enhance the soft tissue cuff-post interface. 3. Transmandibular Staple Bone Implant: was developed by small in 1975, it is placed into the anterior portion of the edentulous mandible. The purpose of this implant is to act as a stabilizer and fastener for mandibular full denture. It is mainly indicated for edentulous mandible with minimal alveolar ridge height of 8-9 mm, and to rehabilitate various types of mandibular deformities. The staple plate is inserted by drilling through the mandible using a specific set of instruments. The staple is composed of an inferior horizontal plate which acts as a base for the 3-5 vertically attached 9 mm retentive pins, and 2 completely threaded transosseous vertical components that penetrate the alveolar crest and mucoperiosteal tissue in the canine region. Each implant is equipped with 4 fasteners and 2 locknuts. The basic procedure has been done under GA through extra-oral approach or a modified intra-oral approach 4. Endosseous Implants: History → in 1950s and 1960s Linkow developed the blade implants, the mandibular staple implant developed by Small 1966. In 1951 Branemark began research leading to the development of an endosseous implant system that popularized the concept of osseointegration ( 15 years study work until the placement of the 1st dental implant in a human being ). It was until 1982 that Branemark encouraged the world to exposed to osseointegration, by the conference arranged by Zarb in Toronto that May. The successful treatment of edentulous and partially edentulous patients with osseointegrated implant has revolutionized dentistry. Babbush 1985 described 3 main types of endosseous implants: 1. Blade-vent implants: firstly introduced by Linkow 1967. 2. Hollow-basket implant system (C.E, H, K or F) 3. Screws and other implant systems: such as TPS-Screw (Titanium plasma-sprayed screw system). Vitreous Carbon Implant, Tubingen Aluminum Ceramic, TPC Implant (Tetracalcium Phosphate), IMZ Implant Branemark Osseointegrated Titanium Implant etc….. 4 Advantages of the screws over Subperiosteal and Staple implants: 1. Screws can be inserted under local anesthesia through a relatively small mucoperiosteal incision. 2. Can be placed against opposing natural teeth with less risk than other implants. 3. Permits final restoration of the case immediately or after few days. 4. In case of failure the screw can be easily removed and replaced without endangering the adjacent screws or without loss of the prosthesis. 5. Relative simplicity of the superstructure. 6. Can be used as support for Cranio-Facial prosthesis that applied in cases of craniofacial deformities (auricle, nose, orbit, maxilla and mandible). 7. Can be applied for treatment of some orthodontic problems such as correction of simple cross-bite. ********************************************************************* Parts of DI: Fixture (DI): consist of 3 parts → crest module, body and apex Cover screw: which is placed into the top of the implant, in first stage surgery. Permucosal extension (healing abutment, gingival former): is the transepithelial portion which extends above the soft tissue and results in the development of a permucosal seal around the implant. Abutment: is the portion of the implant that supports or retains a prosthesis or implant superstructure. Transfer coping: the component used to transfer the position and the design of the implant or the abutment to the master cast for prosthesis fabrication. It is either indirect transfer coping used in closed tray impression or direct used in open tray impression. Analog: used in the fabrication of the master cast to replicate the retentive portion of the implant body or abutment (implant body analog, implant abutment analog). ************************************************************* Tissue Reactions to Implants 1. Ankylosis → or direct apposition of bone to the implant which is accepted as the most desirable alternative to true periodontal attachment and can provide effective load transmission. 2. Fibrous encapsulation → fibrous capsule around implants are associated with numerous factors including implant mobility, shape and toxicity. 5  3. Epithelial down growth → has been observed around both endosseous and subperiosteal implants which cause breakdown of the bond between the implant and the surrounding bone. ********************************************************************** Factors Influencing Tissue Behavior 1. Site preparation: it is important to avoid overheating when placing the implant which may lead to osteonecrosis or delayed bone regeneration and replacement by fibrous connective tissue. 2. Implant material: the material from which an implant is made has a profound effect on the type of tissue which forms around it and the stability of the implant- tissue interface. There are 3 basic types of interaction between host and implant: a. Bio-tolerance → where there is a mild reaction to the implant, as seen around stainless steel. b. Bio-inertness → where the implant is ignored, as seen around vitreous carbon. c. Bio-activity → where the implant interacts chemically with the body in a controlled fashion so as to become incorporated into the tissues. 3. Implant design: there is a little evidence that variations in implant surface texture at a microscopic level influence the subsequent tissue response. Implants with sharp corners elicit a fibrous reaction, and there is evidence that implant shape in the cervical region can also influence pattern of bone behavior. ********************************************************************** Osseointegration According to Branemark 1982 it was defined as a "direct structural and functional connection between living bone and a load carrying endosseous implant at the light microscopic level". The term osseointegration indicates a situation in which living bone tissue is induced to incorporate permanently a synthetic anchorage element. Reliable stability must be achieved by incorporation of the anchorage element into normal bone tissue providing both adequate resistance to load and load distribution resulting in bone remodeling. An implant is said to be biomechanically osseointegrated if there no progressive relative motion of living bone and implant under functional levels and types of loading 6 for the entire life of the patient. Osseointegration is not a static but a highly dynamic condition. Even very gentle drilling, cutting and threading of bone tissue is accompanied by some tissue injury, both thermal and mechanical. Initial stability and successive remodeling of bone tissue depend on: 1. Gentle surgical technique 2. Controlled application of functional load It is crucial to recognize and respect time as a critical factor in a protocol for surgical and prosthetic procedures. The continuous remodeling of bone varies in quantity and quality between individuals. In load-bearing reconstruction one should avoid unnecessary risks of overloading and possible displacement of bone tissue at the interface relative to the anchorage element during healing phase, this means that, in the majority of situations, a two-stage procedure is recommended. In other cases of non-load-bearing reconstruction (ear prostheses or bone conduction. hearing aids), a modified one-stage procedure may be satisfactory. In other cases, such as when a performed bone graft with integrated anchorage element is used, a three-stage procedure may be necessary. In spite of the widespread use of titanium implants, little is known about the events taking place in the tissue at different times after insertion (hypothesis): 1. A general concept appears to be that the implant surface serves to support osteogenic cells, thus providing favorable conditions for bone formation leading to osseointegration. 2. Titanium oxide forming the surface of the implant has certain properties favorable for mineralization (bind with calcium which might be beneficial for bone formation). Types of Stability: 1. Primary stability → is largely a mechanical parameter, a function of bone quantity & quality. 2. Secondary stability → viewed as increased stability (biological) after placement. 7 Factors Control (affecting) Osseointegration A- Surgical: primary stability and surgical technique B- Tissular: bone quality & quantity, healing, remodeling C-Implantological: macrostructure (implant design and surface treatment), microstructure and dimensions D- Occlusal ̸ Mechanical: forces (loading) & prosthetic design Measurement of OI : 1. Tensional test (lateral load) 2. Push-out/Pull-out test (only for non-threaded cylinder DI) 3. Percussion test (subjective) 4. Insertion torque 5. Removal torque (reverse) 6. Thread cutting force 7. Periotest (1986) 8. Resonance Frequency Analysis 1998 (Osstell ISQ) → (produce alternating sine waves in a specific frequency range by uniform amplitude. Resonance frequency between 3.5 KHz and 8.5 KHz formed from magnetic field is converted into ISQ values) 9. Radiographic evaluation (difficult to perceive changes in bone structure & morphology of bone-implant interface unless over 30% bone loss occur) 10. Histology & Histomorphometry (non-clinical studies & experiments) Surface Characteristics of Titanium Implants: For most metal surfaces (except those of the noble metals) exposed to air or other oxidizing media, this results in the formation of a thin surface oxide (10 nm in thickness). The composition of surface oxide is in most cases Titanium oxide. The surface of Titanium implants prior to implantation consist of a thin surface oxide which is covered by a hydrocarbon-dominated contamination layer. Roughness at implant surface can be modified by 1. Sandblasting → the surface is bombarded by fast hard particles in order to remove gross surface defects and contamination. 2. Plasma spraying → in which the surface is coated by spraying molten drops of metal onto the surface at a high velocity. ************************************************************************ 8  Clinical and Radiological Assessment for Dental Implants ❖ CLINICAL: A. History 1. Patient’s complaints and expectations: a. Elicit the patient chief complaints b. Major concerns c. Treatment requests 2. Medical: a. The general health status b. Contraindications : Absolute V/S Relative Implants are not recommended for elderly infirm persons Drug or alcohol dependence, uncontrolled depression and those with some psychiatric disorders Heart failure, uncontrolled diabetes and blood dyscrasias, immunocompromised Heavy smokers , irradiation of the face and jaws, osteoporosis in the oral region, parafunctional habits Unfinished cranial growth and teeth eruption 3. Dental History: a. Cause of teeth loss b. Compliance 4. Social History B. Examination: 1. Extraoral a. Facial proportions b. Mouth opening c. Jaw relationship d. Morphology and function of the lips e. Facial muscles hypertrophy 2. Intraoral a. Oral hygiene assessment b. Condition of the remaining dentition c. Palpation of the alveolar ridge at the prospective implant sites: 9  Ridge defect class (horizontal as vestibular concavity, vertical, combined), bony profile of the ridge, gingival profile d. Space analysis of edentulous areas: Height, Width, and Length (Inter-coronal distance) → Osteometer (bone caliper), alveolar ridge mapping Inter-arch distance (Rule of 6) Thickness of the soft tissue ❖ RADIOLOGICAL: Radiographic Presurgical Assessment of Endosseous Implants; the specific imaging objectives for implant surgery are: 1. Jaw Size (height & width) the horizontal and vertical dimensions of the alveolar and basal bone are important for treatment planning and implant retention. The larger and denser alveolar ridge the better the long-term success for implant integration. It is ideal to have at least 1 mm of bone on all sides of the implant and therefore the cross- sectional dimension of the alveolar ridge should be at least 6 mm. Implants that have bicortical anchorage are more successful than those that are suspended in trabecular bone. Therefore, determination of the implant length is necessary to allow for engagement of the terminal end in cortical bone. 2. Orientation of the Vertical Long Axis of the Jaw → The axis orientation can be determined only with cross-sectional imaging techniques. 3. Jaw Boundaries → the buccal and lingual walls of the maxilla and mandible are not always parallel, the canine fosse on the buccal surface of the anterior maxilla and the submandibular fossa on the lingual surface of the mandible arc common normal anatomic depressions. 4. Internal Anatomy → to reveal the location of neurovascular structures, cortices, sinuses, nasal fossae and nasopalatine duct. 5. Soft-tissue Morphology → it is important to determine the thickness of the soft tissues overlying the alveolar ridge for accurate determination of the location and alignment of the prosthetic element that attached to the implant. 6. Three-dimensional Spatial Localization → 2 planes perpendicular to each other (longitudinal and cross-sectional images), this allow localization of relevant anatomic structures. 10 7. Pathology Detection → any disease process or abnormal condition may diminish the probability of successful implant placement and retention (root tips, inflammatory processes, cysts and tumors). 8. Bone Quality → the amount of mineralized bone / unit area at implant site affect the success of implant integration (I-e: maxillary tuberosity is a poor implant site because of the paucity of trabeculated bone). Imaging Modalities A. Conventional Imaging: 1. Panoramic Projections → provide information about the vertical height of the mandible and location of the mental foramina. It may give improper size if the target anatomy misaligned toward the film the image is reduced in size, and conversely magnified if it is misaligned farther away from the film. There may also vertical and horizontal distortion. All panoramic beam angles are approximately at 8 degrees, which gives the image inherent magnification (20 -30%). Effective dose 10-14 µ SV. 2. Cephalometric Projections → lateral cephalometry provide information about the cross-sectional dimensions of the mandible. The main disadvantage is the significant superimposition. 3. Periapical projections→ produce excellent anatomic detail and information related to bone quality, but it 1) does not provide information about cross-sectional anatomy of the jaws, 2) nor does it demonstrate all regions of the law, 3) relatively high radiation dose per image. 4. Occlusal projections→ the same to periapical but demonstrates larger areas. This image can evaluate 1) curve of the jaws 2) bone quality 3) largest buccolingual dimensions of the mandible. 5. Tomographic projections → it is an imaging technique that provides an image of a tissue plane or layer. The main disadvantage due to this single image plane is blurred image. B. Digital Imaging: I. Computed Tomography CT → produce image with contrast sensitivity much greater than that of images produced by conventional methods, the images are superior because there is no superimposition. The main disadvantage is the high radiation dose and cost. 2. Cone Beam Computed Tomography CBCT → less dose than CT. 11 CT or CBCT give 3-dimensional images, and applied when cross-sectional images required. 3. Intraoral Detectors → allow direct digital capture and display of intraoral images on a video monitor, once the images have been captured they can be enhanced, archived, retrieved, transmitted and printed. It may be very useful to the surgeon as an operative imaging tool during the surgical placement of implants. Post-implant Imaging Objectives: 1. Implant Placement → location is considered ideal when the implant located within the boundaries of the jaws and is terminated in thick cortical bone. 2. Integration of the implant. ********************************************************************* Bone Density (bone volume, bone quantity) There are various conditions of residual ridge depending on history and duration of edentulism. A tooth loss due to advanced periodontal disease lead to rapid resorption to the apex 13-15 mm, while a tooth loss due to apical ostietis or trauma may preserve the alveolar process for longer period of time. In infraforaminal region there is a visible angle between the axial inclination of the teeth/alveolar process and the basal bone, this angle must be taken into account in order to prevent perforation of the lingual cortical bone and possible trauma to lingual artery. A ridge width of at least 6 mm is necessary for placing implant of a 3.5 mm diameter. Bone density varies substantially from one anatomic region to another, the failure rate of implantation is greater for regions with very low density which result in → low primary stability, or regions with very high density → risk of overheating during drilling. A good evaluation of bone density allows the surgeon to do the following: 1. Select the proper implant diameter. 2. Decide about the optimal drilling sequence, in soft bone → use of final drill of half depth only with minimal use of countersink and use of smaller drill diameter than standard, while in hard (dense) bone → use of oversized drill diameters. 3. Determine the length of healing period. 4. Evaluate occlusal loading capacity of different implants. 12 Classification of bone density ( Lekholms & Zarb ) 1. Type I → essentially cortical bone 2. Type II → dense corticocancellous bone 3. Type III → sparse corticocancellous bone 4. Type IV → thin cortical bone and very sparse medullary bone Bone Quality (Structure) Classification of bone quality from biological point of view (BHP bone healing potential): 1. BHP1 → bone with normal bone healing 2. BHP 2 → bone with moderately reduced healing potential (as in moderate smoking 10 Cigarette / day, controlled diabetes mellitus, long-term corticosteroid treatment, regenerated bone, long-term non-steroidal anti-inflammatory agents like indomethacin). 3. BHP3 → bone with substantially reduced healing potential (heavy smoking 20 cigarettes or more/ day, diabetes mellitus, severe anemia, Gauchers disease, severe osteoporosis, Paget’s disease, fibrous dysplasia, hyperparathyroidism, thalassemia, irradiated bone, rheumatoid arthritis and antimitotic drugs). ********************************************************************* SURGICAL TECHNIQUE: Strict aseptic surgical technique should be followed in dental implant surgery. The patient is draped as for other oral surgical procedures, cleaning of the perioral area with suitable antiseptic solution to eliminate contamination during surgery, and it is convenient to use sterile disposable suction tubing and stents. Chlorhexidine 0.12% is used as a pre-operative mouth wash and skin preparation circum-orally. Autoclaving of surgical instruments is essential with the use of sterilization pouch. Approach: ❖ Flapped Approach ❖ Flapless Approach (minimally invasive approach) ❖ Flapped Approach: 1. Extensive flap design (conventional three or two-sided( 2. Envelope flap 3. Conserved flap (limited flap design, papilla-saving incision) 13 In maxilla, an incision placed slightly palatal (palatal bias) which allows better vision, reduce the possibility of flap trauma, and avoid incision and sutures to be directly over fixture and hence reducing the possibility of contamination. In posterior mandible, the incision may be placed toward buccal aspect of the ridge to allow the flap for better retraction by a tractional suture and produce excellent access, avoid injury to the lingual nerve and for better coverage of the fixture postoperatively. In edentulous mandible care taken not to injure the mental nerve with crestal incision especially in severely resorbed alveolar ridges. Preparation of implant site: The implant fixtures are installed into a carefully made recipient site (osteotomy site) in the jaw bones created by: Bone drilling technique Bone expanders and condensers (screws or osteotomes) Bone drilling technique: Atraumatic preparation and removal of bone from the recipient site must be accomplished with minimal violence. Heat production during bone preparation is a critical factor, a maximum temperature of 47 C for 1 minute is commonly quoted as a threshold temperature (heat with external cooling reach to 55 C° while heat during internal cooling reach to 40 C°). In order to avoid an irreversible bone damage that can lead to failure of osseointergartion, use: A low-speed (600-1000 rpm) High-torque handpiece Intermittent drilling technique → allow the irrigant to reach the depth of the preparation and allow the bone chips to be removed and to prevent the heat buildup Sharp drills Copious saline irrigation (external, internal, manual ) Unless the recipient site is quite dense, it is desirable to drill deep enough to engage the cortex (bicortical) at the apical area of the site. This applies to the antral area, floor 14 of the nose and the anterior region of the mandible unless the mandible has a dense medullary area. Procedure: after soft tissue reflection → if available, using the surgical template (stent) which also assist in directing the angulations of the implant. With the initial drill (usually with a round bur) the center of the implant recipient site is marked and the initial pilot hole is prepared and paralleling pin is placed in the initial preparation to check the alignment and angulations. If template is not available the angulation of the drill may be estimated from the position of the adjacent teeth or opposing teeth and ridge, however, it is usually best to have a template as a guide → depth of the implant site is determined by amount, density of bone and relation to the crest of bone. One should keep in mind that the polished portion of the implant does not integrate. Therefore, if the bone height at the implant site is minimal, it is prudent to have little or none of the polished portion of the implant within bone. If only a small portion of the osseointegratable portion of the implant is exposed, it may be not necessary to cover it with bone. However, if the exposed area is large or is at the coronal portion of the implant (dehiscence or fenestration), bone coverage is required to enhance peri- implant strength and increase support for lateral loading by using locally harvested bone or with the use of barrier membrane. Adequate bone should be present between adjacent implants (about 3 mm), and between implants and adjacent teeth (1-1.5 mm). Care should take not to damage adjacent structures such as teeth, nerves, and nasal or sinus cavities. It is acceptable to engage the nasal or sinus floor with a small degree of penetration (e.g. 1 to 2 mm). An adequate safety margin of about 2 mm above the inferior dental canal is recommended. In maxillary posterior area → I) Bone is soft here and subject to over enlargement during drilling process. If a loose fit is encountered, it is desirable to remove the implant and replace it with one of larger diameter. It is appropriate not to tap on screw shape systems. 2) In this area there is lack of dense cortices in both the occlusal surface and the floor of antrum. To make use of little cortex available, it may be best not to countersink the implant. Mandibular Anterior Area: an anatomic problem in this area may be the slope of lingual surface of the mandible, often in the lateral-cuspid areas, the lingual surface of the mandible slopes anteriorly from crest to the inferior border. If angulation is directed more vertically for a better loading axis, the drill may engage and penetrate 15 the lingual cortex. Penetration of the lingual cortex usually does not create a problem, but lacerating an artery in the lingual soft tissue (sublingual A) is possible. Remember that mental nerve usually leaves inferior alveolar nerve in a plane anterior to mental foramen then courses posteriorly and superiorly before it exits the mental nerve → thus the implant site in this region should be placed a few millimeters anterior to the mental foramen. Mandibular Posterior Area → bone above inferior alveolar nerve often insufficient for implants of adequate length as suggested in a panoramic radiograph. There are 2 solutions for this problem: 1) Grafting, however grafting the crest of the ridge may not be feasible, as the intermaxillary space may restrict the amount of bone to be added. 2) Lateralizing or transposition of the IAN temporarily to allow an implant of adequate length. 3) Short wide plat-form DI The implant should not touch anything (other than a sterile titanium surface) before its delivery to the prepared bone site. Contaminations by touching with dissimilar instrument, cloth, soft tissue, and even surgical gloves, gloves powder, oil may affect the degree of ossointegration (uncontaminated oxide layer is necessary for osseointegration). The insertion of the implants should be done with the same care as the preparation of the site by maintaining the cooling irrigation and placing the implant at slow speed. Screw shaped implants and tapping of sites are performed at speeds of less than 20 rpm. The mucoperiosteal flaps are carefully closed with multiple sutures either to bury the implant completely or around the neck of the implant in non-submerged systems. Silk sutures are satisfactory and others such resorbables are good alternatives. Exposure Procedure The procedure selected to expose the implants (after the healing period usually 3-6 months) will depend on the esthetic and functional requirement. There are 3 basic soft tissue procedures for exposing the implant: 1. Coring out the mucosa overlying the implant. 2. Elevation of facial flaps with some slight release of the lingual and palatal mucosa. 3. Mobilizing and moving of facial &/or lingual flaps with or without mucosal or skin grafting ********************************************************************* 16 Various treatment options devised over the years for inadequate ridge width are: 1. Increase width by osteoplasty 2. Utilize narrower diameter implants 3. Increase width by augmentation 4. Bone expansion 5. Ridge splitting 6. Horizontal distraction osteogenesis ******************************************************************** Treatment Protocols (Treatment Sequence) The timing of implant placement falls into 3 categories: A. Delayed Placement (late implant placement, traditional protocol) → in which delay placement until an extraction site was completely filled with bone (6 month or longer). A covered non loaded healing phase requiring a stress-free OI period of approximately 4 months guarantees a high degree of safety if the classic surgical protocol is followed. Edentulous patients have also been required to go out their removable prosthesis for the 1st 2 weeks after implant placement. The 2nd stage involving uncovering the implants and prosthetic restoration can take at least another 2 months or more to complete. Healing Phase: Today 3 - 6 months non-loaded phase for dental implants is generally accepted for safe bone apposition to implant interface. The resulting loading periods of 3 months for the mandible and 6 months for the maxilla were based on purely empirical data of 45-175 days trials. The regeneration process at the implant-bone interface is a biologic process characterized by different phases → hemorrhagic phase - cell migration & differentiation-extracellular matrix synthesis - mineralization & bone growth. The process is influenced by: 1. Biocompatibility of the implant material 2. Implant surface structure 3. The application of atraumatic surgical protocol 4. Prevention of micro-movement at the interface Micro-movement can negatively influence the regeneration process at the implant interface by causing fibrous repair rather than direct bone apposition. However not every movement of an implant during healing phase necessarily lead to tissue ingrowth, the critical value of tolerable micromovement is 50-150 µm for endosseous implants with a biocompatible surface. 17  B. Immediate Placement → placing the implant at the same time as tooth extraction. The advantage → preserve more residual alveolar bone by providing the internal tensional load that alveolar bone requires to maintain itself this consequently result in improved esthetic and better emergence profile, also the time between extraction and implant placement will be significantly reduced. This technique is most often used when multiple teeth to be extracted /or primary soft-tissue closure can easily be achieved (usually in anterior mandible or maxilla). Contraindications: 1. Bony or soft tissue infection 2. Inadequate bone apical to extraction site for implant stabilization 3. Inability to provide occlusion from oral contamination 4. Chronic problems such as granuloma or radicular cyst Technique. once the tooth is removed as atraumatically as possible, intrabony soft tissue should be carefully excavated (periodontal ligament C.T. & epithelial remnants may interfere with integration process) → extracted tooth can be used as a template for implant selection and preparation size, the tooth root can be a very helpful guide to implant length by measuring root length + length of available bone apical to the tooth socket. To fill the void between portion of the implant and the wall of alveolus, autogenous, allogeneic or xenografting materials may be used with same success, this may: 1. Minimize soft-tissue ingrowth 2. Improve bony apposition 3. Aid in alveolar bone preservation. When primary closure cannot obtained a: 1. Collagen material such as collotape can be considered over the graft 2. Barrier membrane C. Semi-immediate Placement → placement of implant is delayed until the mucosa has regenerated over the socket, allowing a more predictable soft-tissue covering over the implant site. It is indicated in situation in which closure by flap mobilization cannot be done owing to lack of tissue or distortion of esthetic gingival contours. This frequently occurs when one or two teeth are lost adjacent to natural teeth → this require 2 months of epithelial healing and maturation. There will be some bone resorption which make necessary to position the implant slightly more apically (additional depth of 1-2 mm is usually adequate). 18 Complications of Dental Implants: A- Intraoperative: 1. Poorly positioned Implant 2. Damage to mucosa and adjacent teeth 3. Damage to bone ( lateral perforation, alveolar bone fracture or jaw fracture ) 4. Perforation into adjacent areas ( lower border of the mandible, nasal cavity or maxillary antrum) 5. Damage to nerves 6. Loose implant ( poor primary stability ) 7. Contamination of implant and bone during surgery 8. Damage to the implant ( crossed threads or surface defect ) 9. Hemorrhage during surgery ( especially in the anterior mandible and possible airway compromise ) B- Postoperative: 1. Pain 2. Swelling 3. Reactionary or secondary hemorrhage 4. Infection of peri-implant soft tissue or bone ( peri-implant mucositis or peri-implantitis ) 5. Exposed or loose cover screw ( healing screw ) C- Late: 1. Mucosal recession 2. Bone resorption 3. Mobility 4. Implant fracture ******************************************************************** Criteria for Success The term implant success may be used to describe ideal clinical conditions. It should include a time period of at least 12 months for implant serving an implant as prosthetic abutments. Implant success is suggested for a span of: ❖ 1-3 years → early implant success ❖ 3-7 years → intermediate implant success ❖ More than 7 years → long-term implant success 19 The primary function of a DI is to act as an abutment for a prosthetic device, similar to a natural tooth root and crown. Any success criteria, therefore, must include first and foremost support of a functional prosthesis. Assessment of failure according to the time when occurred: (1) Early failures or failures during the osseointegration period (usually within the first year after an implant insertion, during the healing period and initial loading), and (2) Late failures or failures after the osseointegration period (usually about a year after implant insertion, when an osseointegration process is complete and implant function is established). Causes of early implant failures: 1. Poor quality and quantity of bone and soft tissue 2. Patient medical condition 3. Unfavorable patient habits (bruxism, heavy long-term smoking, poor oral hygiene, others) 4. Inadequate surgical analysis and technique 5. Inadequate prosthetic analysis and technique 6. Suboptimal implant design and surface characteristics 7. Implant position or location (functional implant zones) 8. Unknown factors *********************************************************** 20  Health Scale for Dental Implants, Misch Criteria of Success 2008 Implant Quality Scale Group Clinical Conditions I. Success (optimum health) a) No pain or tenderness upon function b) 0 mobility c) 4 mm (less than 1/2 of implant body) d) Probing depth > 7 mm e) May have exudates history a) Pain on function IV. Failure (clinical or absolute failure) → any of the following b) Mobility c) Radiographic bone loss > 1/2 length of implant d) Uncontrolled exudate e) No longer in mouth 21 22