Transcript of “Restoration of Posterior Quadrants – Patient Selection and Treatment Planning”

 
1. John Beumer III DDS, MS Robert F. Faulkner, DDS Kumar C. Shah DDS, MS Division of Advanced Prosthodontics, UCLA Restora(on of posterior quadrants Pa(ent selec(on, and treatment planning This program of instruc(on is protected by copyright ©. No por(on of this program of instruc(on may be reproduced, recorded or transferred by any means electronic, digital, photographic, mechanical etc., or by any informa(on storage or retrieval system, without prior permission.
2. Table of Contents Treatment options –  RPD’s –  Fixed dental prostheses –  Endodontic therapy Implant biomechanics –  Number of implants per unit –  Staggered vs. linear configurations –  Length, implant diameter –  Cantilevers –  Occlusal factors –  Parafunctional activity –  Strategies to avoid biomechanical related problems Anatomic limitations and the role of preprosthetic surgery –  Grafting –  Distraction osteogenesis –  Socket augmentation and ridge preservation –  Placement of implants into fresh extraction sites
3. Implants vs RPD’s v Cost v Mas(ca(on efficiency (Kapur et al, 1987, 1989. 1991a, 1991b, 1997) Implants may not always be the best choice for the patient
4. RPD’s and Implants Position and lengths •  Implant site most favored – 1st molar position •  Lengths vary but in recent times some clinicians have reported successful outcomes when using implants as short as 6 mm in length (Gates et al, 2012). In extension base RPD’s (Kennedy Class I and II) to supplement the support, stability and reten(on provided by the exis(ng den((on.
5. RPD’s and Implants •  Unanticipated implant failures •  Poor quality bone •  Unfavorable biomechanics
6. Endodontics vs Implants v High level of predictability v Extraction of the tooth and replacement with an implant is based on volume and integrity of tooth structure remaining v Cost advantages to endo plus restoration v Esthetics – Retention of bone and soft tissue
7. Conventional fixed vs implants o  Predictable when abutments in good condi(on (Pietursson et al, 2007; Walton, 2009) o  Cost effec(ve o  Implants preferred when abutments are virgin or near virgin 15 year follow-up
8. Things can go wrong with implants Biomechanics – Partially Edentulous Patients !  Because of the curve of Spee and the distal angulation of the implants, the occlusal loads (arrow) are nonaxial. !  Note the bone loss around the implants. Linear configurations in the posterior region, such as in this patient, are particularly vulnerable to the effects of nonaxial loading, particularly brachycephalic individuals. Nonaxial loads and implant overload in posterior quadrants Semi-precision attachments usion of the natural tooth abutment ears after delivery the patient noticed the premolar o intrude. Exam revealed that the screw retaining the ad become loose, hence the rotation of this crown. Bruxism – Case Report This is a five year followup x-ray of a patient with an implant supported fixed partial denture. Closer exam revealed both implants to be fractured . The patient was a heavy bruxer. Six months later he presented with significant bone loss around both implants. Bruxism – Case Report This is a five year followup x-ray of a patient with an implant supported fixed partial denture. The patient was a heavy bruxer. Six months later he presented with significant bone loss around both implants. Implant overload Bone loss Implant fractures Peri-implantitis Impaction of cement Implant loss
9. How can we avoid these complications? Biomechanics – Partially Edentulous Patients !  Because of the curve of Spee and the distal angulation of the implants, the occlusal loads (arrow) are nonaxial. !  Note the bone loss around the implants. Linear configurations in the posterior region, such as in this patient, are particularly vulnerable to the effects of nonaxial loading, particularly brachycephalic individuals. Nonaxial loads and implant overload in posterior quadrants Semi-precision attachments usion of the natural tooth abutment ears after delivery the patient noticed the premolar o intrude. Exam revealed that the screw retaining the ad become loose, hence the rotation of this crown. Bruxism – Case Report This is a five year followup x-ray of a patient with an implant supported fixed partial denture. Closer exam revealed both implants to be fractured . The patient was a heavy bruxer. Six months later he presented with significant bone loss around both implants. Bruxism – Case Report This is a five year followup x-ray of a patient with an implant supported fixed partial denture. The patient was a heavy bruxer. Six months later he presented with significant bone loss around both implants. Implant overload Bone loss Implant fractures Peri-implantitis Impaction of cement Implant loss
10. Implant Biomechanics and Treatment Planning Why should we be concerned with implant biomechanics when we develop a plan of treatment? Because if we are not, we risk implant overload and prosthesis failures such as fracture and screw loosening. Implant overload can lead to bone loss around implants and eventually implant failure.
11. Bone is a dynamic structure. Excessive loads lead to a resorp(ve remodeling response   Hoshaw et al (1994) observed a resorptive remodeling of the bone around implants subjected to excessive axial loads (300N). Bone loss was observed at the crest around the neck of the implant and in the zone of bone adjacent to the body of the implant   Brunski et al, 2000   Recent studies by Myata et al (1998, 2000, 2008) and Nagasawa et al, (2013) have reconfirmed Hoshaw and Brunski’s original hypothesis Is it possible to overload the bone anchoring an osseointegrated implant?
12. Implant Overload – Basic Mechanism v Excessive occlusal loads, off angle loads, bending moments v Resul(ng microdamage (fractures, cracks, and delamina(ons) v Resorp(on remodeling response of bone is provoked v Increased porosity of bone in the interface zone secondary to remodeling v Vicious cycle of con(nued loading, more micro-­‐damage, more porosity un(l failure
13. Implant overload l  Implant alignment must consider the curve of Spee and the curve of Wilson l  In both situa(ons the implants will be exposed to bending moments and predispose to implant overload. Occlusal force
14. Implant overload •  In posterior quadrants when implants are aligned in a linear fashion they should be aligned consistent with the curve of Spee and the curve of Wilson Curve of Wilson
15. Implant Biomechanics   What is the load bearing capacity of osseointegrated implant supported restora(ons?   Is the load carrying capacity of implant prostheses influenced by the quality of the bone sites?   What factors control the magnitude of the loads that are delivered through the implant into the surrounding bone?   What loads should implant borne restora(ons be designed to resist?
16. Karnak The Great Wall Pont de Gard You must over engineer your implant restorations, particularly when restoring posterior quadrants with linear configurations in order achieve predictable long term results. Implant Biomechanics
17. Implant Biomechanics LOAD BEARING CAPACITY 1. Quality of bone site 2. Quality of bone implant interface 3. Implant microsurfaces   Machined vs microrough vs nano-­‐enhanced surfaces 4. Implant  Number and Arrangement Linear vs Curvilinear  Length and diameter  Angulation ANTICIPATED LOAD (Affected by)  Occlusal factors Cusp angles Width of occlusal table Guidance type Anterior guidance Group function  Cantilever forces Connection to natural dentition Size of occlusal table Cantilevered prostheses  Parafunctional habits (bruxism)  Brachycephalics
18. Load bearing capacity Implant number and arrangement •  Both the number and arrangement of implants affect the load carrying capacity of any par(cular implant supported restora(on. •  Curvilinear arrangements withstand more load than linear arrangements
19. Load bearing capacity Linear vs Curvilinear o  Curvilinear arrangements have the greatest load bearing capacity. o  Cross arch stabiliza(on
20. Load bearing capacity Linear vs Curvilinear v Curvilinear arrangements such as seen in this pa(ent are very predictable v This PFM fixed prosthesis is 12 years post inser(on. Occlusion: Group function 12 year follow-up12 year follow-up
21. Load bearing capacity Linear vs Curvilinear Linear configurations restoring the cuspid region, such as the patient on the right, are unpredictable, whereas curvilinear implant arrangements such as shown on the left are very predictable. Predictable Not predictable
22. Maxilla vs Mandible Bone quality v The size and shape of the trabeculae is different in the mandible as compared to the mandible. v This may be one of the reasons why the load carrying capacity of implant supported prostheses restoring posterior quadrants in the mandible appears to be superior to those in the maxilla. Courtesy Dr. C. Stanford
23. Number of Implants per Unit Posterior Maxilla When restoring posterior quadrants with implants we are forced to use linear arrangements by anatomic necessity. Therefore in most instances: *The third implant dramatically improves the biomechanics of the restoration  One implant for each dental unit.  At least three where possible in extension areas. One dental unit = premolar
24. Number of Implants per Unit Posterior Maxilla The distal implants failed 30 months after loading in both these patients because of implant overload.
25. Number of Implants per Unit Posterior Maxilla o  The distal implant failed 30 months after loading in both these patients because of implant overload. o  The patient was a bruxer
26. Number of Implants per Unit Posterior Maxilla These implants failed 66 months after loading because of implant overload. Group function was used to restore this patient. Result:  Application of excessive lateral forces  Implant failure Another problem: Cusp angles too steep and the occlusion was tripodized
27. Number of Implants per Unit Posterior Maxilla Space allowed only two implants to be placed in this patient. However, note anterior guidance. Design the occlusion to minimize the delivery of nonaxial forces
28. Number of Implants per Unit Posterior Maxilla Only two implants were placed. Note anterior guidance
29. Bone Augmentation – Horizontal Deficiencies  Predictable  Less occlusal force  Fixa(on of the grae is easy to accomplish  The blood supply to the grae is usually quite good
30. Bone Augmentation Vertical Defects Less predictable Problems:  Tension on the wound secondary to closure of (ssue flaps  Poor blood supply  Difficulty in achieving fixa(on Result:  Relapse (resorp(on) rate is 75%
31. Sinus Augmentation Advantages over onlay gra7s Resorp(on probably less than 25% Challenge Elevate the sinus membrane without perfora(on Sinus membrane Bone graft Bone of the residual allveolar ridge
32. Sinus Augmenta(on •  Implants can be placed simultaneous when there is 4-5 mm over the sinus and primary immobilization of the implants can be achieved •  Otherwise implant placement delayed for 6-9 months
33. Sinus augmentation  Predictable (Jensen et al, 1997; Aghaloo and Moy, 2007)  Sources of grae material include chin, ramus, and iliac crest some(mes mixed with bone subs(tutes. Complica(ons  Loss of grae material  Blockage of the os(um  Incomplete eleva(on of the sinus prevent normal sinus drainage
34. PRE-OP 4M POST-OP 2M POST-OP
35. Sinus augmention This patient was restored following a sinus lift and graft. Autogenous chin bone was used. She is 10 years post treatment and doing well. Note: Best results achieved when there is 4-5 mm of normal bone over the sinus before the procedure
36. Sinus augmentation § This pa(ent was restored following a bilateral sinus lie and grae. §  Freeze dried bone was used to grae the lee maxillary sinus. § The implants placed in this grae failed 18 months following delivery of the implant supported fixed par(al denture.
37. Crestal Augmenta(on Augmenta(on of ver(cal defects in posterior mandibular quadrants with free autogenous bone graes has been unpredictable. Following surgery the relapse rate is about 75% and further bone loss is also seen aeer loading. Why? a)  Tension on the wound upon closure b)  Poor blood supply c)  Difficulty is achieving proper fixa(on of the grae
38. Pterygoid implants •  As an alternative to sinus augmentation •  Success rates in excess of 90% Courtesy Dr. A. Pozzi
39. *Removable Partial Dentures* Removable partial dentures properly designed and fabricated provide the patient with masticatory function equivalent to that obtained with an implant supported fixed partial dentures (Kapur, et al, 1992) and this service should be offered to the patient before grafting is considered.
40. Number of Implants per Unit Posterior Mandible Two is sufficient for most patients Why? v The trabecular bone is more dense v Cortical layer is thicker
41. Number of Implants per Unit Posterior Mandible v There is bone over the nerve for only short implants v Bone quality is poor v When restoring four dental units Three are recommended when:
42. Number of Implants per Unit Posterior Mandible Three implants were used to restore four units in this patient
43. Posterior Mandible – Limiting Factors v Inferior alveolar nerve(arrow) v Insufficient bone over the nerve to permit placement of a 10 mm or longer implant v Uni-cortical anchorage (arrow)
44. Many patients such as this one, present with moderate to severe resorption precluding placement of implants unless the inferior alveolar nerve displaced. Posterior Mandible – Limiting Factors
45. Displacement of the Inferior Alveolar Nerve  This procedure enables placement of implants of sufficient length with bicor(cal anchorage.  Although the risk of nerve injury is rela(vely small the morbidi(es associated with injury may be severe.   Therefore, these issues must be thoroughly discussed with the pa(ent before proceeding with the procedure.
46. Crestal Augmentation Augmenta(on of ver(cal defects in posterior mandibular quadrants with free autogenous bone graes (A) has been unpredictable. Following surgery the relapse rate is about 75% and further bone loss is also seen aeer loading (B). Why? a) Tension on the wound upon closure b) Poor blood supply c) Difficulty is achieving proper fixa(on of the grae BA Presently, distrac(on osteogenesis is the only reasonably predictable method for enhancing this site ver(cally.
47. Mandibular Onlay Grafting
 Patients = 13 Total grafts = 21 •  Follow-up: 3 mos – 72 mos Avg. = 26 mos •  Avg. height gained with block graft = 4.21 mm •  Avg. height of graft remaining on f/u = 1.05 mm •  Overall, 75% of initial graft height was lost •  Complication(s) –  6 of 21 sites demonstrated wound dehiscence •  28.6% complication rate
48. Distraction Osteogenesis §  4-5 mm of bone required over the nerve §  Distract 1mm per day §  Relapse rate is 25 % §  Wait 6 months for consolidation before implant placement
49. Horizontal vs vertical augmentation Predictable
50. Use of Short Wide Diameter Implants in the Posterior Mandible This practice has not been predictable. The short implants are particularly prone to occlusal overload and bone loss. This is a 2 and 7 year follow-up x-ray of two 6 mm diameter implants.
51. Use of Short Wide Diameter Implants in the Posterior Mandible The implants failed 15 years after insertion.
52. If implants of adequate length cannot be used, consider removable partial dentures Mastication efficiency of distal extension RPD’s is equivalent to implant supported fixed partial dentures.
53.  When in doubt add the 3rd implant in posterior quadrant cases.  Minimize the length and width of the occlusal table Linear configura(ons Over engineer your cases
54. Over-engineer your linear quadrant cases v When in doubt re: the quality of the implant site bone, history of parafunction etc., add the third implant
55. Over-engineer your linear quadrant cases v Minimize the width of the occlusal surfaces. They should be no wider than a premolar Note: The buccal-lingual dimension is excessive However, there is a flaw in the design of this case. What is it?
56. Staggered vs linear configuration in posterior quadrants This has been studied using a photoelastic model by Itoh, et al, 2003 Staggered implant configuration 1.5 mm 1.5 mm 1.5 mm Straight line implant configuration
57. Staggered vs linear configuration Staggered implant configuration 1.5 mm 1.5 mm 1.5 mm Straight line implant configuration Itoh and Caputo, et al 2003 Is it biomechanically more favorable? v Yes, par(cularly with specific chewing cycles. Nonlinear arrangements resist lateral forces more effec(vely v Is the improvement clinically significant? This is unknown
58. Staggered vs linear configuration Staggered implant configuration 1.5 mm 1.5 mm 1.5 mm Straight line implant configuration Probably not. In the posterior quadrants you can’t get enough stagger to make much of a difference biomechanically. Itoh and Caputo, et al 2003 Is it feasible in the posterior quadrants?
59. Implants in Compromised Sites  Posterior maxilla  Posterior mandible over the inferior alveolar nerve in partially edentulous patients  Craniofacial application Theore(cally perhaps. However we need well designed clinical outcome studies to determine predictability Can we use shorter implants?
60. Length and diameter of Implants v Short implants, such as this 7 mm screw shaped implant, demonstrate unfavorable stress distribution patterns as seen in this study performed with finite element analysis. Longer implants distribute stresses more favorably. v Given the bone anchorage achieved with modern surfaces, failures are most likely to occur in the trabecular bone v Failure rates approach 25% for machine surface implants 7 mm in length (Wyatt and Zarb, 1998; Winklet et al, 2000) Avoid the use of implants less than 10 mm in length and 4mm in diameter when restoring posterior quadrants. Cho et al, 1993
61. • Two year followup data from Moy and Sze,’93 • Note the high failure rates with the 7 mm and 10 mm implants in the posterior maxilla. Length and diameter of Implants
62. Implant length vs diameter Using a photoelastic model, Caputo et al, 2002 attempted to determine whether increasing the diameter of the implant or increasing the length of the implant had a significant impact on stress distribution. They concluded that: Does increasing the diameter compensate for the lack of sufficient length?
63. Implant length vs diameter Lingual load Axial load Buccal load  Most equitable load transfer with axially directed loads.  Under comparable loading conditions, the stresses transferred by the wide diameter implant were only slightly lower than the same length narrow implant.  For implants tested, increased length was more important than diameter in stress reduction. Caputo et al,2002
64. Implant length vs width § Failure rates of short wide diameter implants approaches 20%. 2 years 8 years Cho,In Ho et al, 1992 14 years
65. Implant length vs width l  Over-­‐prepara(on and/or over hea(ng of the osteotomy site. This may precipitate early loss of bone, par(cularly around the neck of the implant. l  Implant overload. l  Insufficient trabecular bone encasing the implant on its buccal and lingual aspect leading to progressive bone loss.
66. Ideal Implant Diameter 4-5 mm in diameter Less than 4 mm the rate of implant fracture is unacceptably high Implants 3.75 mm in diameter have a 5-7% fracture rate More than 5 mm the higher the failure rate. Implants 6 mm in diameter have a 20% failure rate Implants 4-5 mm in diameter have a less than 5% failure rate
67. Implant Angulation – Posterior vs Anterior v  Implants in the posterior quadrants should be placed so that occlusal loads can be directed axially in the posterior quadrants. v  In the anterior region, anatomic necessity precludes implant placement perpendicular to the occlusal plane. v  However, the forces used to incise the bolus are only about ¼ of those used posteriorly to masticate the bolus. For this and other reasons implant overload is rarely seen in the anterior regions.
68. v Nonaxial loads result in load magnification. Kinni et al (1987), using photoelastic analysis and Cho et al (1993), using finite element analysis, demonstrated that nonaxial loads concentrated potentially clinically significant stresses around the neck and at the tip of the implant. Implant angulation Cho,In Ho et al, 1992
69. Curve of Wilson Implant Angula(on Curve of Wilson Curve of Spee
70. Implant angulation v Implant alignment must consider the curve of Spee and the curve of Wilson Nonaxial loads and implant overload in posterior quadrants
71. Implant Angula(on CAC-­‐CAM technologies permit: l Development of virtual diagnos(c wax-­‐ups l Surgical drill guides which permit controlled direc(onal drilling as opposed to free hand drilling
72. Implant Angula(on •  Controlled directional drilling is preferred because it results in few errors in implant angulation and position as opposed to free hand drilling
73. Implant Angula(on •  CAD-CAM can also be used to design and mill custom abutments and prototype restorations
74. Cantilevers and Linear Configurations in Posterior Quadrants •  They are particularly detrimental and are therefore contraindicated when using linear configurations to restore posterior quadrants. They cause subject the implants to bending, load magnification and overload the bone around the implant adjacent to the cantilever. Mesial and distal canClevers
75. They are well tolerated when implant supported restora(ons are used to restore the edentulous mandible, so long as: –  The can(levered sec(on is within a reasonable limit –  The implants are arranged in a reasonable arc of curvature. –  Rigid frameworks with cross arch stabiliza(on are used Cantilever forces Cantilever section
76. Cantilevers – Implant Overload •  Note the bone loss around the dental implants adjacent to the cantilever. Restorations designed in this fashion, especially in the posterior maxilla, have a poor prognosis.
77. Limit buccal, lingual and cantilevers The occlusal tables are excessively wide in this case. Buccal and lingual cantilever forces may lead in selected patients to: Prosthesis failures • Porcelain fractures • Screw fractures Implant overload and bone loss
78. Occlusal Anatomy and Biomechanics v Narrow occlusal table Goal: Reduce the buccal – lingual cantilever effect
79. Avoid buccal and lingual can(levers The occlusal table must be narrowed to avoid buccal and lingual cantilevers. Molars should be no wider than premolars as shown in these two examples.
80. Solitary implants restoring single molars – Cantilever effect When the food bolus is applied to the marginal ridge (B), the restoration is easily tipped because the crown is supported by such a narrow platform. Result: Cantilever forces lead to screw loosening, implant fracture and overload the bone anchoring the implant. BA
81. Fracture Implant fractured after 30 months of function Solitary implants restoring single molars Cantilever effect
82. Single tooth restorations in the molar region – Cantilever effect This implant was too short and too narrow to withstand occlusal loads and bone loss caused by the resorptive remodeling response led to its loss. 4 mm diameter implant Mesial canClever
83. Single Tooth Restorations Distal Extension Defects
84. Distal Extension Defects
85. Restoration of single molar sites – Solutions In this patient a wide diameter implant was used to restore the first molar. Eliminate the can(lever by using   Wide diameter   Mul(ple implants
86. Restoration of single molar sites Custom abutment Lingual set screw In this pa(ent, two 4 mm diameter implant were used to restore the first molar. The width of the occlusal table was limited to the width of the natural premolar, thereby elimina(ng any possible buccal or lingual can(levers.
87. Restoration of single molar sites Note:   Hygiene access for proxy brush   Note width of occlusal table
88. Splinted vs Nonsplinted Pa(ent presented with a failed endodon(cally treated #30. This tooth was extracted and the space restored with an implant. Several years later the endodon(c therapy on #29 failed and this too was replaced with and implant restora(on.
89. Splinted vs Nonsplinted •  These implants were not splinted •  Note the anterior group func(on •  Mandibular bone sites favorable •  Pa(ent did not demonstrate evidence of parafunc(onal ac(vity •  Long implants
90. Splinted vs Nonsplinted From a theoretical biomechanical perspective splinted designs are more favorable than unsplinted designs, but whether this difference is clinically significant has yet to be determined with properly desinged clinical outcome studies.
91. Criteria for splinting •  If the patient shows signs of parafunctional activities. •  If the quality of bone anchoring the implants is questionable (type IV bone, or if the implants are in grafted sites). •  Misangled implants ie, implants that are not perpindicular to the plane of occlusion. •  If relatively short implants have been employed (less than 10 mm in length). •  If the patient presents with or is to be restored with group function. Linear configurations of implants lack cross arch stabilization and are less able to resist bending moments (nonaxial loads) and implant angulations that are not ideal result in the application of bending moments. •  All maxillary posterior quadrant cases.
92. l When implants of 10 in length or longer are placed. l When the quality of bone is good. l Implants placed with perfect angula(on (perpendicular to the plane of occlusion) l Absence of parafunc(onal ac(vity. Nonsplinted designs are used when restoring posterior quadrants only in the mandible and under the following circumstances:
93. Connecting Implants to Natural Dentition How do you minimize cantilever forces? Semiprecision (nonrigid) vs rigid attachments
94. Connecting Implants to Natural Dentition Posterior implant apached to anterior abutment Rigid apachment Nonrigid apachment Nishimura et al, 1999 Loads applied in the pontic area
95. Connecting Implants to Natural Dentition Rigid vs non rigid apachments No difference as long as the nonrigid (semi-­‐precision) apachments remain fully seated
96. Semi-precision Attachments Problems v Intrusion of the natural tooth leading to: v Cantilever affect v Load magnification v Resorptive remodeling response v Bone loss (arrows) Semi-precision attachment
97. Semi-precision attachments Intrusion of the natural tooth abutment •  Eleven years after delivery the patient noticed the premolar began to intrude. Exam revealed that the screw retaining the molar had become loose, hence the rotation of this crown.
98. Rigid Attachments* Intrusion is prevented with rigid attachments Screw retained tube lock attachment *Shared support
99. Rigid Attachments* Screw retained tube lock apachment *Shared support
100. Occlusal Anatomy and Biomechanics •  Narrow occlusal table •  Flat cusp angles •  Lingualize or buccalize
101. Occlusal Anatomy and Biomechanics v Narrow occlusal table Goal: Reduce the cantilever effect
102. Parafunctional activity This is a five year followup x-­‐ray of a pa(ent with an implant supported fixed par(al denture. Closer exam revealed both implants to be fractured . The patient was a heavy bruxer. Six months later he presented with significant bone loss around both implants.
103. Parafunctional activity This patient did well with this implant supported fixed partial denture for more than four years (note 4 year follow-up x-ray). However, soon thereafter, the anterior implant fractured, the bridge was removed and a trephine used to remove the implant.
104. Occlusion Partially edentulous patients when restoring posterior quadrants with implants – Anterior guidance – Anterior group function – Group function Courtesy Dr. M. Hamada
105. Implants in the Maxillary Cuspid Region Mutually Protected Occlusion (Group Function) Patient in right working position. Note lateral guidance is provided by the premolars and the central incisor. Result: Lateral forces on the implants are minimized. Courtesy Dr. M. Hamada
106. Anterior (canine) guidance Space allowed only two implants to be placed in this patient. However, note anterior guidance. Design the occlusion to minimize the delivery of nonaxial forces
107. Mutually Protected Occlusion Only two implants have been placed to restore the corner of the arch in this patient. (b,c) The implants were inclined towards the labial and milled customized abutments were used. Note that the minimal height of the buccal wall of the posterior abutment. As a result retention was designed to be achieved with lingual set screws as opposed to cement.
108. Mutually Protected Occlusion (d) The finished prosthesis. (e) It is adjusted so that contact during lateral excursion is provided by the natural den((on and not the implants.
109. Anterior Group function with Centric Only Contact Note: The cusp angles are flat and the occlusal tables are narrow Result: Lateral forces on the implants are minimized
110. Restoring the Cuspids: Mutually Protected Occlusion (Group Function) Patient in right and left working position. Note lateral guidance is provided by the premolars and the central incisor. Result: Lateral forces on the implants are minimized. Right working Left working
111. Restoring the corner of the arch : Mutually protected occlusion plus implants Group function was used to distribute lateral loads as widely as possible in order to reduce the risk of implant overload
112. Materials for the occlusal surfaces o  Layered porcelains o  Susceptable to fracture o  Milled monolithic zirconia o  Metal occlusal surfaces
113. •  Metal •  Ceramic •  Resin Materials for the occlusal surfaces
114. Strategies to Avoid Implant Complications Place implants perpendicular to the occlusal plane (Note that the occlusal plane is not flat – Curve of Wilson, Curve of Spee) Posterior quadrants of partially edentulous patients Place implants in tooth posi(ons When in doubt, always add the third implant Avoid use of cantilevers in linear configurations
115. Strategies to Avoid Implant Complications Restore anterior guidance Posterior quadrants of parCally edentulous paCents  If required to attach to natural dentition, do so with a rigid attachment system Control the occlusal factors (cusp angles, width of the occlusal table) Avoid use of short implants (less than 10 mm
116. Preservation of bone and soft tissues following extraction l Socket augmenta(on -­‐ treatment of fresh extrac(on sockets with intact buccal and lingual bone walls. l Ridge preserva(on -­‐ treatment of fresh extrac(on sockets with deficient bone walls in order to maintain ridge contours. l Ridge augmenta(on -­‐ augmen(ng edentulous sites that are insufficient for implant placement.
117. Socket augmentation Socket augmenta(on is defined as treatment of fresh extrac(on sockets with intact buccal and lingual bone walls. v Many methods attempted v No consensus re: its value or the best method Courtesy Dr. T. Han
118. Socket augmenta(on v When successful, following healing implants can be placed in ideal positions with proper angulation v Many methods attempted v No consensus re: its value or the best method Courtesy Dr. T. Han
119. Ridge preservation Ridge preserva(on is defined as treatment of fresh extrac(on sockets with deficient bone walls in order to maintain ridge contours. v  Many methods attempted v  No consensus re: its value or the best method Courtesy Dr. D. Krill
120. Ridge preservation Ridge preserva(on is defined as treatment of fresh extrac(on sockets with deficient bone walls in order to maintain ridge contours. v  Problematic in patient presenting with active infection. Courtesy Dr. D. Krill
121. Ridge augmentation l  Ridge augmenta(on is defined as augmen(ng edentulous sites that are insufficient for implant placement. •  Appears to the most predictable Courtesy Dr. P. Moy
122. Loss of vertical and horizontal bone volume following extraction can be significant v 3-4 mm of resorption can occur during the first 6 months post- extraction (Atwood et al, 1971 and others) v Probably secondary to expession of specific genes in oral mucosa to promote wound contraction and closure (Sukotjo et al, 2002; Suwanwela et al, 2011) Placement of Implants into Fresh Extraction Sites
123. Placement of Implants into Fresh Extrac(on Sites Will placement of an implant impact the process of resorption? It appears not. There will still be resorption of the facial plate of bone even in the presence of an implant placed immediately upon exstraction Radiographic finding of root resorption Courtesy Dr. TL Chang
124. Implants in fresh extraction sites Atrauma(c extrac(on and flapless surgery l Remember that the vasculature of the labial plate associated with the PDL has been significantly compromised by the extrac(on l Even under the best of circumstances there will be resorp(on of the facial plate of bone Courtesy Dr. T. Han
125. Mucosal advancement flaps •  Facilitates hygiene •  The more keratinized tissue the better because over time the patient slowly loose the attached tissue, particularly on the buccal side of the mandibular molars
126. v Visit ffofr.org for hundreds of addi(onal lectures on Complete Dentures, Fixed Prosthodon(cs, Implant Den(stry, Removable Par(al Dentures, Esthe(c Den(stry and Maxillofacial Prosthe(cs. v The lectures are free. v Our objec(ve is to create the best and most comprehensive online programs of instruc(on in Prosthodon(cs