u Basis of osseointegration and prosthetic options- Dr. Ghaderi.pdf

Dr Pakhshan Ghaderi DDS, MSc Assistant Professor Department of Prosthodontics New York University college of Dental Medicine Basics of : Osseointegra0on, Anatomy, and Prosthe0c Op0ons . Lecture Objectives: The student will: 1. Learn basic terminology and concepts regarding implants and osseointegration 2. Learn bone quality and quantity classifications 3. Understand the critical anatomic features of maxilla and mandible 4. Learn key points in implant osteotomy 5. Understand basic sinus lifting and bone grafting procedures 6. Understand various prosthetic options with implants Literature Professor Per-Ingvar Branemark The actual titanium chamber imbedded in the rabbit tibia (Branemark 1952) Bone was fused to titanium surface Direct contact • Specimens obtained from these animals were examined with light microscopy and revealed a very close adapta8on between the surface of the 8tanium implant ﬁxture and adjacent bone(1950 to 1970) • This ﬁnding “a direct contact between bone and metallic implants, without interposed so@ 8ssues (connec8ve 8ssue)layers” revolu8onized den8stry and Branemark called the process Osseointegra*on(1969) Direct contact between bone and implant Osseointegration A direct structural and functional connection between ordered living bone and a load-carrying implant (1970) § In practice, this means that in osseointegration there is an anchorage mechanism whereby nonvital components can be reliably and predictably incorporated into living bone and this anchorage can persist under all normal conditions of loading Design Evolu6on After several years of research initially in dog and later in human ; as a consequence of these observational experiments, a screw design evolved. When an implant is manufactured a long rod of titanium is fed into a machine which turns the titanium into the screw .The surface that results is a" Machined " surface. Screw type implants may be left in this machined state.(T.Albrektsson) Macro-topography: screw shaped titanium implant fixture(a) Micro-topography: Machined surface(b,c) History In 1965 Brånemark operated his ﬁrst pa7ent with oral implants based on his belief that they would prove sa7sfactory due to implant bone anchorage . Gosta Laresson a pa7ent who had missing teeth due to sever jaw and chin deformi7es was the ﬁrst person in the world who received dental implant and with this surgery modern day implantology invented. When Larsson died in 2006, his ini7al set of implants were s7ll working as the founda7on for oral prostheses that had allowed him to eat and talk with ease Noble Biocare Blog Uniqueness of Titanium Most of the previous implant systems were made of cobalt-chrome alloys and were subject to corrosion and release of metallic ions into the adjacent tissues. The Presence of these ions cause acute and chronic inflammatory response which eventually result in fibrous encapsulation of offending material and rejection of implant . Failed subperiosteal implant Uniqueness of Titanium Ti is the ninth most abundant element found in the earth's crust and needs to be extracted from mineral ores such as ruFle and ilmenite • !"#$#%&'%(%)(*)++)#$)' • ,-)'%&'").#/0(1)+2#(&(*)&%$'3()1( %$%&'$.2(4$)5$4"6(78$*8($#(#%&9/"6(( 9$)/)3$*&//0($'"+%(&'4(-+)2)%"#(%8"( 4"-)#$%$)'()1(&(2$'"+&/$:"4(9)'"(2&%+$5( )'($%#(#.+1&*";( • <%($#(#%+)'36(&'4("&#$/0(2&*8$'"4($'%)(( .#"1./(#8&-"#;( The Bone-Titanium Implant Interface Original protocol for dental implant surgery In 1980 Professor Branemark published his 15 year clinical results using CP titanium; protocol was two stage surgery with screw shaped dental implants with machined surface to support full-arch screw-retained dental prosthesis. Factors For Reliable Osseointegration (Albrektsson, 1983) 1)IMPLANT BIOCOMPATIBILITY 2) IMPLANT DESIGN 3)IMPLANT SURFACE 4)STATE OF THE HOST BED 5)SURGICAL CONSIDERATIONS 6) LOADING CONDITIONS Implant Biocompatibility • Metals like commercially pure titanium are most well accepted in bone as they are covered with a very adherent, self-repairing and corrosion resistant oxide layer. • Metals like cobalt-chrome-molybdenum alloys, stainless steels are less well tolerated by bone. • Ceramics like calcium phosphate hydroxyapatite (HA) and various types of aluminum oxides are proved to be biocompatible but due to insufficient documentation and very less clinical trials, they are less commonly used. Implant Design The Macrodesign or shape of an implant has an important bearing on the bone response. Implant body designs is important : 1-Primary stability 2- Transferring load in bone implant interface a. Threaded implants provide more funcFonal area for stress distribuFon than the cylindrical implants and provide beSer primary stability. b. Longer the length, beSer the primary stability. c. Wide diameter implants exert less stress on crestal bone as compared to narrow implants. d. PlaVorm-switching concept also preserves the crestal bone and prevents bone loss. This design uses a narrow diameter abutment over a wide diameter implant. Implant Design Implant with threaded features have the ability to convert occlusal loads into more favorable compressive loads at the bone interface; therefore thread shape is particularly important when considering long-term load transfer to the surrounding bone interface. The four basic thread shapes for implant design include: (A) V-thread, (B) buttress thread, (C) reverse buttress thread, and (D) square thread. V-shaped threads transfer the vertical forces in an angulated path, and thus may not be as efficient in stress distribution as the square shaped threads. IMPLANT SURFACE Surface topography relates to degree of roughness of the surface and the orientation of surface irregularities § Advantages of increased surface roughness: 1. Increased surface areas of the implant so increased bone at implant surface. 2. Increased biomechanical interaction of the implant with bone. . Biological response timeline on the implant surface During the early stages of healing. Proteins, blood, immune cells, and osteoprogenitor cells interact with the biomaterial, These interactions are surface dependent and can affect: osteoblastic differentiation, maturation, and local factor production and, finally, matrix formation and implant osseointegration. B.D. Boyan & co ;2016 IMPLANT SURFACE Micron/Submicron /Nano surface roughness, as well as surface roughness in combination with surface wettability. become an important parameter in clinical implant design for osseointegration Procedure for changing the surface roughness of implant can be Physical or chemical State of the host bed Bone quality and bone quantity The external and internal architecture of bone controls virtually every facet of the practice of implant dentistry. The available bone and the density of available bone in an edentulous site is a determining factor in treatment planning, surgical approach, implant design, healing time, and protocol for implant loading during prosthetic reconstruction. State of the host bed Bone quality The external (cortical) and internal (trabecular) structure of bone may be described in terms of quality or density, which reflects a number of biomechanical properties such as: • Strength • Modulus of elasticity • Bone–implant contact (BIC) percent • Stress distribution State of the host bed Bone quality Lekholm and Zarb described four bone quali0es for the anterior region of the jaws: Quality 1 is composed of homogenous compact bone. Quality 2has a thick layer of cor0cal bone surrounding dense trabecular bone. Quality 3 has a thin layer of cor0cal bone surrounded by dense trabecular bone of favorable strength. Quality 4 has a thin layer of cor0cal bone surrounding a core of low density trabecular bone. Misch described four bone densities found in the anterior and posterior edentulous regions of the maxilla and mandible. D1 bone is primarily dense cortical bone. D2 bone has dense to thick porous cortical bone on the crest and coarse trabecular bone underneath. D3 bone has a thinner porous cortical crest and fine trabecular bone within. D4 bone has almost no crestal cortical bone. The fine trabecular bone composes almost all of the total volume of bone. State of the host bed Bone quality Generalized Bone Density Location State of the host bed Bone quality Modeling or Remodeling • Cortical and trabecular bone throughout the body are constantly modified by either Modeling or Remodeling. • Modeling has independent sites of formation and resorption and results in the change of the shape or size of bone. • Remodeling is a process of resorption and formation at the same site that replaces previously existing bone and primarily affects the internal turnover of bone. Definition: • Stress is the force which develops within an object. • Strain is defined as the deformation that follows a stress application State of the host bed Bone quality Stress distribution Bone is a dynamic tissue able to respond to the external forces with the adaptation process of remodeling. Mechanical loads provoke a stress and a consequent strain on the tissues . The greater the magnitude of stress applied to the bone, the greater the strain observed in the bone. Frost defined four zones for bone related mechanical adaption to strain before spontaneous fracture. The acute disuse window is the lowest micro-strain amount. The adapted window is an ideal physiologic loading zone. The mild overload zone causes microfracture and triggers an increase in bone remodeling, which produces more woven bone. The pathologic overload zone causes increase in fatigue fractures, remodeling, and bone resorption. State of the host bed Bone quality ElasGc Modulus and Density : The elas7c modulus describes the amount of strain as a result of a par7cular amount of stress. The elas7c modulus of a material is a value that relates to the s7ﬀness of the material. When higher stresses are applied to an implant prosthesis, the 7tanium has lower strain (change in shape) compared with the bone. The diﬀerence between the two materials may create macrostrains condi7ons of pathologic overload The microstrain difference between titanium and D4 bone is great and may be in the pathologic overload zone, whereas at the same stress level, the microstrain difference between titanium and D2 bone may be within the ideal adapted window zone. State of the host bed Bone quality Bone-Implant Contact and Density • Bone-to-implant contact (BIC) is defined as the percentage of bone found in direct contact over the implant surface; this parameter is considered to be important in defining the degree of osseointegration and may play a role in both short and long term treatment outcomes. • The initial bone density not only provides mechanical immobilization of the implant during healing(primary stability), but after healing also permits distribution and transmission of stresses from the prosthesis to the implant-bone interface. The mechanical distribution of stress occurs primarily where bone is in contact with the implant. Therefore the boneimplant contact percent may influence the amount of stress/strain at the interface. D4 bone has the least bone-implant contact. As a result, the stress is greatest for the D4 bone-implant interface. • D1(BIC)=80% .D2 (BIC) =70% .D3 (BIC) = 50% In D2 bone density, one finds primarily coarse trabecular bone next to the implant. The boneimplant contact is greater than D3 bone but less than D1 bone. State of the host bed Bone quantity Available bone is parGcularly important in implant denGstry and describes the external architecture or volume of the edentulous area considered for implants In 1985 Misch and Judy presented a classiﬁcaGon of available bone : Divisions A(Abundant Bone), B(barely suﬃcient Bone), C(compromised Bone), and D(Deﬁcient Bone), which is similar in both arches. Implant, bone graPing methods, and prosthodonGc-related treatment were suggested for each category of bone. h, Inadequate height; w, inadequate width. State of the host bed Bone quantity 1-Available bone measured in: height (H),Width(w),length(L) 2-Crown height space is related to bone quantity. Crown height space (CHS)is measured from occlusal plane to the level of the bone. , so more resorption produce more crown height space and affect prosthetic options State of the host bed Bone quantity To understand the available bone classification, the clinician must first have a knowledge of dental implant size . Manufacturers describe the root form implant in dimensions of diameter and length (e.g., 4.1mm × 12.0 mm). .5 .5 The Mesio-distal length of available bone in an edentulous area is often limited by adjacent teeth or implants. As a general rule, the implant should be at least 1.5 mm from an adjacent tooth and 3 mm from an adjacent implant. This dimension not only compensate for surgical error, but also compensates for implant or tooth crestal defect. for Buccolingual evaluation, patient should have at least 1.5 to 2mm bone buccal to implant. The Height of available bone is measured from the crest of the edentulous ridge to opposing landmark . The opposing landmark maybe in the maxillary canine region(A) ﬂoor of the nares(B) maxillary sinus(c) tuberosity(D) Bone above the inferior mandibular canal(E) anterior mandible(F) or mandibular canal region(G) Minimum distance between an implant and an anatomic structure (nerve, etc.) is 2mm Anatomy Inferior alveolar nerve The inferior alveolar nerve is a branch of the mandibular nerve, which is itself the third branch (V3) of the trigeminal nerve (cranial nerve V). • Inferior nerve injury most commonly occurs during surgery including wisdom tooth, dental implant placement in the mandible. Trigeminal sensory nerve injuries are associated with numbness, pain, altered sensation and usually a combination of all three. This can result in a significant reduction in quality of life for the patient with functional difficulties and psychological impact. Anatomy Lingual (sublingual) artery The lingual artery is a branch of the external carotid artery. It is the principal artery supplying the tongue, sublingual gland, gingiva and oral mucosa of the floor of the mouth. Within the tongue, it is located deep to the hyoglossus muscle. damage during implant placement in the mandibular anterior region is rare. However, if it happens, it may cause a lifethreatening (sublingual hematoma and difficulty in breathing) condition. Anatomy The maxillary sinus lies within the body of the maxillary bone and is the largest and first to develop of the paranasal sinuses. The maxillary sinus features six bony walls, each of which contain important anatomic structures that play a significant role in the treatment of the maxillary posterior region. The Schneiderian membrane, also called the Schneiderian epithelium, is the lining of the paranasal sinuses and nasal cavity Anatomy • The posterior maxilla loses bone height more rapidly than any other region because the maxillary sinus expands after tooth loss. Hence, the bone height is lost from both the crestal and apical regions. SURGICAL CONSIDERATIONS • Implant Osteotomy • Sinus li1 • Bone Gra1 & Membrane Implant Osteotomy Implant specification (BL Straumann) Length Width 6 7 The implant diameter, implant type, posiFon and number of implants should be selected individually taking the anatomy and spaFal circumstances into account Implant Osteotomy Mesio-distal Position of Implant The Mesio-distal length of available bone in an edentulous area is often limited by adjacent teeth or implants. As a general rule, the mesio-distal implant should be at least 1.5 mm from an adjacent tooth (at the bone level)and 3 mm from an adjacent implant. For example if treatment plan is (b) placing two implant with diameter of 4.1,available mesio-distal bone should be: 1.5+4.1+3+4.1+1.5#14.5 (c) Placing 3 implant with diameter of 3.3 and 4.1 and 4.8 available mesio-distal bone should be: 1.5+3.3+3+4.1+3+4.8+1.5#21.5 mm a b Implant Osteotomy Bucco-lingual Position of Implant The bone buccal to implant at least should be 1.5 mm Implant Osteotomy Corono-apical posiOon of shoulder of implant The ideal depth of the implant plaVorm is 2 mm below the natural tooth cement-enamel juncFon (CEJ) or 3 mm below the free gingival margin. This provides adequate emergence proﬁle for the implant crown and creates an environment for sog Fssue health around the implant. The round markings in the LoximTM Transfer Piece indicate the distance to the implant shoulder in 1 mm steps. Implant Osteotomy BLT Pilot Drill Alignment Pin BLT Drill Implant Osteotomy All Straumann dental implants are placed using one instrument kit – the Straumann® Surgical casseSe The uniﬁed color code represents the workﬂow you need to follow. Implant Osteotomy Implant Osteotomy A 2-mm-diameter, twist drill (pilot drill) is used in the mesio-distal and buccolingual centers of the crestal bone for implants in the mandible or out of the esthetic zone in the maxilla. The osteotomy is made with an electric motor at a preferred speed of 800 rpm under copious amounts of saline irrigation Implant Osteotomy The initial bone density provides mechanical immobilization of the implant during healing which is called primary stability ,Primary implant stability between bone and implant is the essential feature that permits the transfer of stress from the implant to the bone without any relative motion. Minimum distance between an implant and an anatomic structure (nerve, etc.): 2mm Bone Graft The presence of an adequate volume of available bone is one of the most important prerequisites for predictable implant placement and osseointegraFon. Although loss in bone volume may result from trauma, bone deﬁciency is most frequently due to the normal physiologic process that occurs ager tooth loss or extracFon. Bone Graft 1) Autogra* The gold standard of bone gra0ing materials is autogra0s. Autogra0s are obtained from the same pa7ent, taken from one site and placed in another site and forms the bone by the process of osteogenesis and osteoinduc7on. Autogra0 materials are obtained intraorally from edentulous areas such as maxillary tuberosity, mandibular symphysis, and mandibular ramus. Extraoral autogra0s are obtained from iliac crest, rib, 7bia, and calvarium. The advantages of autogra0 bone material are that it maintains bone structures such as minerals, collagen, and viable osteoblasts and bone morphogenic proteins (BMPs) 2) Allogra* Allogra0 bone, like autogenous bone, is derived from humans; the diﬀerence is that allogra0 is harvested from an individual other than the one receiving the gra0. Allogra0 bone is taken from cadavers . A wide range of gra0s is available, which may be par7culate, thin sheets of cor7cal plate, or much larger bone blocks • There are three types of bone allogra0 available: - Fresh or fresh-frozen bone - Freeze-dried bone allogra0 (FDBA) - Demineralized freeze-dried bone allogra0 (DFDBA) Bone Graft 3) Xenografts Xenograft bone substitute has its origin from a species other than human, such as bovine (Bioss). Xenografts are usually only distributed as a calcified matrix . 4) Alloplastic grafts • Alloplastic bone grafts are synthetic materials that have developed to replace human bone. They are biocompatible and osteoconductive materials. The most common types of alloplasts used are calcium phosphates, bioactive glasses Membrane Barrier membranes are generally used in guided bone regeneration procedures. During the bone regeneration process, there is a competition between soft-tissue and bone-forming cells to invade the surgical site. Membrane act as biological and mechanical barriers against the invasion of fibrous tissue into the developing graft site but will allow for the migration of the slower-migrating bone-forming cells into the defect sites . Types of Membranes: Membranes are typically classified as resorbable or nonresorbable. • Nonresorbable membranes have included titanium foils, expanded polytetrafluoroethylene (e-PTFE), and dense polytetrafluoroethylene (d-PTFE) with or without titanium reinforcement. • Resorbable membranes are typically made of polyesters or tissue-derived collagens (AlloDerm) Clinical view of d-PTFE membrane Sinus liU Sinus augmentation procedure is a surgical intervention aimed at increasing the height of residual bone in the posterior maxilla by repositioning the floor of maxillary sinus in an upward direction, creating an appropriate bone height that would allow the placement of functional dental implants Classification of maxillary sinus based on residual bone height( In 1987, Misch developed a classification system based on the amount of residual bone available below the antrum and the treatment options accordingly SA 1:Adequate verFcal bone for endosteal implants(>12mm) and no surgical intervenFon required SA 2: 0-2mm less than ideal height of bone (10-12mm) and may require surgical manipulaFon SA 3: 5-10mm of bone below the antrum SA 4: <5mm of verFcal bone below the antrum Sinus lift 22) TREATMENT MODALITIES: Over the years, several strategies have been advocated to restore the posterior maxilla and address the deficiency of bone volume. The type of sinus floor elevation technique selected is based mainly on residual vertical bone height, marginal bone width, local intra sinus anatomy and the number of teeth to be replaced, although other factors, such as surgical training and experience, may have an impact. Different techniques that are used for maxillary sinus floor augmentation are: 1. Maxillary sinus floor augmentation applying the lateral window technique 2. Crestal approach for sinuslift Sinus liU Lateral Window technique For SA3 & SA4 A, showing a crestal incision and lateral osteotomy. B, Creation of an osteotomy along the lateral aspect of the right maxillary sinus wall. C, Sinus curette in place, beginning the elevation of the sinus membrane. D, the sinus membrane has been elevated, and the lateral window has been infractured. Sinus lift Lateral Window technique For SA3 & SA4 E, Infracture of the lateral sinus window with sinus membrane elevaFon. F, ParFculate bone grag in place. G, ParFculate bone grag has been placed along the sinus ﬂoor of the right maxillary sinus. H, Panoramic radiograph approximately 8 months ager the sinus lig. Note the excellent bone in the posterior maxilla bilaterally. I, Second- phase surgery with mature bone grag and implant in place. J, PostoperaFve panoramic radiograph showing implants in good posiFon. Sinus lift Trans-Crestal Approach technique For SA2 A Showing that a crestal incision has been made, and buccal and palatal flaps have been elevated. B Start is with pilot drill and the bone is prepared using the twist drills in accordance with the desired implant diameter. The surgeon feels the way very carefully up to the cortical bone of the sinus floor. Pilot drill stopped about 2 mm below the maxillary sinus floor . This process requires precise radiological planning. C The final osteotome, which is undersized to ensure initial implant stability, is used to tap the sinus floor up. It can also be done by placing the graft material in the osteotomy and tapping it upward to begin to elevate the sinus floor. D Implant is placed and used to elevate the sinus floor about 3 to 5 mm to help tent the sinus membrane superiorly. . Sinus liU Healing time for treatment categories LOADING CONDITIONS Loading of implant with its implant supported prosthesis can be discussed from two perspective Loading time Loading time of the prosthetic part of dental implants is as follows: 1) Immediate loading: the prosthesis is attached to the implants the same day the implants are placed. 2) Early loading: the prosthesis is attached at a second procedure, earlier than the conventional healing period of 3 to 6 months. The time of loading is started after some days/weeks. 3) Delayed loading the prosthesis is attached at a second procedure after a conventional healing period of 3 to 6 months. Loading force Forces applied to the implant by implant supported prosthesis may be evaluated in type, direction, magnitude and duration. Prosthetic Options In 1989, Dr. Misch proposed five prosthetic options for implant dentistry. - The first three options are Fixed Prosthesis: These three options may replace partial (one tooth or several) or total dentitions , it can be cemented or screw retained and Common to all fixed options is the inability of the patient to remove the prosthesis. These options depend on the amount of hard and soft tissue structures replaced by restoration which effect the aspects of the prosthesis in the esthetic zone and also the magnitude of force on implant. - Two types of final implant restorations are removable Prosthesis that replace total dentition; they depend on the amount of implant support, retention, and stability, not the appearance of the prosthesis . From Mish CE.Bone classification training keys.Dent Today 1989.8:39-44 Anatomical Crown Crown Hight space FP-1 Fixed prosthesis; replaces only the crown; looks like a natural tooth FP-2 Fixed prosthesis; replaces the crown and a porGon of the root; crown contour appears normal in the occlusal half but is elongated or hyper contoured in the gingival half FP-3 Fixed prosthesis; replaces missing crowns and gingival color and a porGon of the edentulous site; prosthesis most oPen uses denture teeth and acrylic gingiva but may be porcelain to metal FP-1 • Replace Anatomical crown s • Minimal loss of hard and soft tissues • The bone and soft tissue must be ideal in volume and position to obtain an FP-1 for final restoration • Very desired in maxillary anterior restoration FP-2 • Restore the anatomical crown & a portion of root • The volume and topography of the available bone is more apical • Incisal edge in correct position ,but gingival third overextended FP-3 Restore the anatomical crown & a portion of root The volume and topography of the available bone is more apical Incisal edge in correct position ,but gingival third overextended and a part of that is replaced by pink porcelain to look natural Lip Line Lip line can be defined as the vertical position of the lower border of the upper lip during smile: a.High lip line: which exposes the teeth in full in display as well as the gingival tissues beyond the gingival margins, often referred to as ‘gummy smile b.Medium lip line : where lip movement culminates in the display of between 75% and 100% of the anterior teeth as well as the interdental papillae c.Low lip line: where the motility of the upper lip exposes the anterior teeth by no more than 75%, with no display of gingival tissue The selection of FP2 and FP3 is often based on evaluation of the lip line The selection of FP2 and FP3 is often based on evaluation of the lip line Pt is low lip line FP2 Pt is high lip line FP3 • • • • • • Crown Height Space(CHS) CHS=distance between bone level and occlusal plane or Incisal Plane Ideal CHS for FP1 implant is 812mm CHS is excessive when is more than 15 mm Excessive CHS is a force magniﬁer and increase load on implant Biomechanics of CHS are related to lever mechanics CHS is a ver8cal can8lever so it is a force magniﬁer • CHS (Crown height space) is a vertical cantilever to any angled load. The FP-3 on the right will deliver greater stresses to the implant compared with the implant on the left. Therefore, a wider-diameter implant is of benefit to support the implant restoration on the right. Treatment for Excessive CHS • Crown height is a force magnifier to any lateral load or horizontal cantilever. Therefore, when available bone height decreases with a greater crown height, more implants should be inserted • Fabrication of removable implant supported prosthesis instead of fix can be a solution for managing excessive crown height space RP-4 Removable prosthesis; overdenture supported completely by implants (usually with a superstructure bar) RP-5 Removable prosthesis; overdenture supported by both soft tissue and implants (may or may not have a superstructure bar ) RP-4 is an Removable prosthesis completely supported by the implants. overdenture attachments usually connect the RP to a low-profile tissue bar or superstructure that splints the implant abutments. Usually 5-7 implants in the mandible and 6-8 implants in the maxilla are required to fabricate completely implant-supported RP-4 prostheses in patients with favorable dental criteria. RP-5 is a Removable prosthesis combining implant and soft tissue support. A completely edentulous overdenture may have: 1- Implants independent of each other primarily for retention 2-Splinted implants to enhance retention and stability The primary advantage of an RP-5 restoration is the reduced cost because fewer implants may be inserted compared with a fixed restoration and there is less demand for bone augmentation. Maxilla overdenture retained by 4 independent implants (#3,5,12,14) and locater abutments. Mandible overdenture supported by two splinted implant with two independent implant and locator Mandible overdenture supported by two splinted implant with bar Position of implant Ideal situation is one implant per missing tooth but in the case we restore with less implants there is some teeth that should be replaced by implant and can not be pontic position of implant is important to decrease Force magnification Key Implant Positions: Rule#1: No cantilever • When three adjacent teeth are being replaced, two implants may be adequate to replace the three missing teeth. In this scenario the terminal missing teeth are key implant positions and implant should be inserted there. Key Implant Positions Rule # 2: Limit the Number of Adjacent Pontics In most prostheses designs, greater than three adjacent ponGcs are contraindicated on implants. • The adjacent abutments are subjected to considerable addiGonal force when they must support ponGc, especially in the posterior regions of the mouth. • All ponGc spans between abutments ﬂex under load. The greater the span between abutments, the greater the ﬂexibility in the prosthesis under load and this cause the increased risk for porcelain/zirconia fracture A-When one ponIc is present, the metal ﬂexes (x). B,-When the ﬁxed prosthesis has two ponIcs (2×), the metal ﬂexes 2 × 2 × 2 = 8 Imes more. C-When three ponIcs exist (3×), the metal ﬂexes 3 × 3 × 3 = 27 Imes more than a one-ponIc restoraIon. Key Implant Positions Rule # 3: Implant Positioned in Canine Site • A fixed restoration replacing a canine is at greater risk than nearly any other restoration in the mouth. • In the missing (1) the first premolar, canine, and lateral incisor; (2) the second premolar, first premolar, and canine; and (3) the canine, lateral, and central incisors and plan is restoring with two implant always one implant should be in canine Position Force/Load Directions When an angled load is placed on an implant body, the compressive stresses on the opposite side of the implant increase and the tensile and shear loads on the same side of the implant increase. Because bone is weaker to tensile and shear forces, the risks to the bone are increased for two reasons: 1- the amount of the stress increases, 2- the type of stress is changed to more tensile and shear conditions. Avoiding shearing force on implant 1-Placing implant in long axis of tooth 2- Guiding occlusal force to central fossa of implant crown The periodontal ligament around a natural tooth has “shock absorbing capacity” but implant does not have this protecTve system so implant is more sensiTve to traumaTc occlusion Avoiding excessive force on implant Ideal occlusion for single tooth implant • Light load (infra-occlusion by 30 μm) under heavy clenching • Occlusal force directed down the long axis of implant • Light or no occlusal contact during eccentric movement. THE DESIGN OF THE OCCLUSION FOR IMPLANT PROTHESIS IS AN INTEGRAL PART OF TREARTMENT PLANING AND SHOULD BEGIN BEFROE IMPLANT INSERTION CONSEQUENCES OF BIOMECHANICAL OVERLOAD • Early implant failure • Early crestal bone loss • Intermediate to late implant failure • Intermediate to late implant bone loss • Screw loosening (abutment and prosthesis coping) • Uncemented restoration • Component fracture • Porcelain fracture • Prosthesis fracture • Peri implant disease from bone loss The patient force factor evaluated The bone density evaluated The available bone measured The crown height space(CHS) measured The key implant position and implant number selected Final prosthesis can be planed: • • • • • The ideal goal of implant dentistry is to replace patient’s missing teeth to normal contour ,comfort,function esthetics,speech and health,regardless of previous atrophy,disease or injury of the stomatognatic system with: single implant,partialy edentulous,fully edentolous Partially edentulous patient Implant Supported prosthesis Fixed Metal ceramic All ceramic Removable RARE ConvenGonal Fixed Removable Implant Supported prosthesis for par6ally edentulous pa6ent Fixed Retention systems for fix implant supported prostheses can be obtained via screw retaining or through cementation. These two options gave distinct advantages and disadvantages in clinical practice Cement Retained Screw Retained Fully edentulous patient Implant Supported prosthesis Fixed Metal ceramic Metal Resin(hybrid) Full zirconia Complete denture Removable Over Denture Implant Supported prosthesis for edentulous patient Fixed PFM Zirconia Acrylic Implant Supported prosthesis for fully edentulous patient Removable: Over Denture Locator Bar with two implant Bar with ﬁve implant The preimplant prosthodonTc evaluaTon of the paTent's overall condiTon closely resembles tradiTonal denTstry. When a restoring denTst ﬁrst evaluates the prostheTc needs of a paTent, an orderly process is required, regardless of the current state of the denTTon. specific criteria Lip lines Maxillomandibular arch relationship Existing occlusion Crown height space Temporomandibular joint status Extraction of hopeless or guarded-prognosis existing teeth Existing prostheses Arch form (ovoid, tapering, square) Natural tooth adjacent to implant site Soft tissue evaluation of edentulous sites Misch, Carl E. Contemporary Implant Dentistry, 3rd Edition. Mosby, Chapter 12, Preimplant Prosthodontics: Overall Evaluation, Specific Criteria, and Pretreatment Prostheses. Thank you [email protected]

u Basis of osseointegration and prosthetic options- Dr. Ghaderi.pdf

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