u.Biomechanics in implant dentistry_YKK_23_24.txt

Biomechanics in implant dentistry Prof. Young K. Kim, DMD, DMSc, FACP Diplomate & Fellow, American Board of Prosthodontics Clinical Assistant Professor, NYUCD, Dept. of Prosthodontics Editor & Co-leader, NYU Implant Restorative Protocol ’20 Editor & Co-leader, NYU Robotics Surgical Protocol ’21 / ’22 NEW YORK UNIVERSITY COLLEGE OF DENTISTRY UPDATE - Please see the yellow ﬂag under the left corner for its sign of FYI (= NOT on the exam) Engineering & Mechanics Photo by Matteo Colombo Engineering & Mechanics BIO Mechanics “ is the study of the structure, function and motion of the mechanical aspects of biological systems, at any level from whole organisms to organs, cells and cell organelles, using the methods of mechanics. “ (Alexander RM, 2005; Herbert H, 1974) Biomechanics & Implant dentistry I. C E L L U L A R im Kim YK & Spector M. Injectable bioactiveP r o s t h o d gelatin-hyaluronan-calcium phosphate (GH-CP) and its osteogenic potential for flapless guided bone regeneration (GBR). (DMedSc doctoral thesis dissertation). Harvard School of Dental Medicine, Boston, USA, 2019 YK o n t i s t Biomechanics & Implant dentistry P R O S T H E T I C YK P r o s t h o d o im t n t i s Biomechanics & Implant dentistry O C C L U S A L H o r i z o n t a l r e f e r e n c e p l a n e RESULTANT FORCE FULCRUM Cuspal Height Location of dentition LOAD YK P r o s t h o d o im t n t i s Biomechanics & Implant dentistry Computer-guided Prosthetically-driven Biomechanics & Implant dentistry Computer-guided Prosthetically-driven Biomechanics in implant dentistry C E L L U LA R PROSTHETIC O C C L U SA L Biomechanics in implant dentistry C E L L U LA R PROSTHETIC O C C L U SA L • Bone foundation • Principles of osteogenesis • Peri-implant endosseous healing • Implant features & surface science • Primary stability & insertion torque • Placement & loading protocol Biomechanics in implant dentistry C E L L U LA R PROSTHETIC • Dimensional planning • Inter-arch space • Implant-crown ratio • Connection systems • Splinting • Cantilever O C C L U SA L Biomechanics in implant dentistry C E L L U LA R PROSTHETIC O C C L U SA L • Non-axial forces • Overload • Principles of occlusion Biomechanics in implant dentistry I III II C E L L U LA R | PROSTHETIC O C C L U SA L Bone foundation “Hardness & Composition” Cortical bone Trabecular bone IV • Type I (oak wood) - very hard and dense + less blood supply + apprx 5 months for this type to osseointegrate • Type II (pine wood) - approx 4 months to osseointegrate • Type III (balsa wood) - more time to ﬁll in + approx 6 months to osseointegrate • Type IV (styrofoam) - least dense + 8 months to osseointegrate (Lekholm & Zarb & Albrektsson, 1985) Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Bone foundation “Hounsﬁeld units” • Type I - 1250 Hounsﬁeld units • Type II - 850 ~ 1250 HF • Type III - 350 ~ 850 HF • Type IV - 150 ~ 350 HF • Type V - 150 HF Misch (3 rd Ed) PROSTHETIC C E L L U LA R | O C C L U SA L Biomechanics in implant dentistry “The Paradox of poor quality bone” Bone foundation • Class IV bone • Almost trabecular • So-called “poor quality” • High surface area • More angiogenic & marrow • Rapid formation of new trabecular • Is it really “poor”? VS • Class I bone • Almost cortical • So-called “good quality” • Lamellar remodeling • Slow regeneration • Is it really “good”? (Davies JE, 2003) Md Ant Mx Post Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Principles of osteogenesis • Osteo-genesis • Condition of containing osteoprogenitor cells directly from host bone or grafting material, and only applicable with autogenous bone graft Kim YK & Spector M (DMedSc doctoral thesis dissertation), HSDM, 2019 Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Principles of osteogenesis • Osteo-genesis • Condition of containing osteoprogenitor cells directly from host bone or grafting material, and only applicable with autogenous bone graft • Osteo-induction • Signaling induction cascade of undifferentiated pluripotent stem cells getting differentiated into osteoblastlike cells through the presence of chemoattractants or signaling molecules Kim YK & Spector M (DMedSc doctoral thesis dissertation), HSDM, 2019 Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Principles of osteogenesis • Osteo-genesis • Condition of containing osteoprogenitor cells directly from host bone or grafting material, and only applicable with autogenous bone graft • Osteo-induction • Signaling induction cascade of undifferentiated pluripotent stem cells getting differentiated into osteoblastlike cells through the presence of chemoattractants or signaling molecules • Osteo-conduction • Implanted scaffolds, whether endosseous ﬁxtures or bone graft materials, attract a chemotactic migration of osteogenic cells followed by neovascularization through the extracellular ﬂuid and non-collagenous proteins within the provisional periimplant blood clot matrix Kim YK & Spector M (DMedSc doctoral thesis dissertation), HSDM, 2019 Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Principles of osteogenesis • Osteo-genesis • Condition of containing osteoprogenitor cells directly from host bone or grafting material, and only applicable with autogenous bone graft • Osteo-induction • Signaling induction cascade of undifferentiated pluripotent stem cells getting differentiated into osteoblastlike cells through the presence of chemoattractants or signaling molecules • Osteo-conduction • • Contact osteogenesis (CO) • Implanted scaffolds, whether endosseous ﬁxtures or bone • Osteogenesis from the implanted graft materials, attract a chemotactic migration of osteogenic material’s surface cells followed by neovascularization through the extracellular ﬂuid and non-collagenous proteins within the provisional periDistant osteogenesis (DO) implant blood clot matrix • Osteogenesis from the surrounding bone surface towards the implanted material’s surface Kim YK & Spector M (DMedSc doctoral thesis dissertation), HSDM, 2019 PROSTHETIC C E L L U LA R | O C C L U SA L Biomechanics in implant dentistry Peri-implant endosseous healing “Osseointegration” (Davies JE, 2003) I. Osteoconduction, relies on the recruitment and migration of osteogenic cells to the implant surface, through the residue of the periimplant blood clot • Initiation of platelet activation → directed osteogenic cell migration Kim YK & Spector M (DMedSc doctoral thesis dissertation), 2019 PROSTHETIC C E L L U LA R | O C C L U SA L Biomechanics in implant dentistry Peri-implant endosseous healing “Osseointegration” (Davies JE, 2003) I. Osteoconduction, relies on the recruitment and migration of osteogenic cells to the implant surface, through the residue of the periimplant blood clot • Initiation of platelet activation → directed osteogenic cell migration De novo bone formation, results in a mineralized interfacial matrix equivalent to that seen in the cement line in natural bone tissue. Kim YK & Spector M (DMedSc doctoral thesis dissertation), 2019 PROSTHETIC C E L L U LA R | O C C L U SA L Biomechanics in implant dentistry Peri-implant endosseous healing “Osseointegration” (Davies JE, 2003) I. Osteoconduction, relies on the recruitment and migration of osteogenic cells to the implant surface, through the residue of the periimplant blood clot • Initiation of platelet activation → directed osteogenic cell migration De novo bone formation, results in a mineralized interfacial matrix equivalent to that seen in the cement line in natural bone tissue. Osteoconduction and de novo bone formation → contact osteogenesis → bone bonding Kim YK & Spector M (DMedSc doctoral thesis dissertation), 2019 PROSTHETIC C E L L U LA R | O C C L U SA L Biomechanics in implant dentistry Peri-implant endosseous healing “Osseointegration” (Davies JE, 2003) I. Osteoconduction, relies on the recruitment and migration of osteogenic cells to the implant surface, through the residue of the periimplant blood clot • Initiation of platelet activation → directed osteogenic cell migration De novo bone formation, results in a mineralized interfacial matrix equivalent to that seen in the cement line in natural bone tissue. Osteoconduction and de novo bone formation → contact osteogenesis → bone bonding V. Bone remodeling Kim YK & Spector M (DMedSc doctoral thesis dissertation), 2019 PROSTHETIC C E L L U LA R | O C C L U SA L Biomechanics in implant dentistry “De novo bone formation” (Davies JE, 2003) Peri-implant endosseous healing I. Osteogenic cells excreting collagen-free bone matrix proteins such as osteopontin and bone sialoprotein Kim YK & Spector M (DMedSc doctoral thesis dissertation), 2019 PROSTHETIC C E L L U LA R | O C C L U SA L Biomechanics in implant dentistry “De novo bone formation” (Davies JE, 2003) Peri-implant endosseous healing I. Osteogenic cells excreting collagen-free bone matrix proteins such as osteopontin and bone sialoprotein These organic matrices initiating calcium phosphate nucleation for further mineralization Kim YK & Spector M (DMedSc doctoral thesis dissertation), 2019 PROSTHETIC C E L L U LA R | O C C L U SA L Biomechanics in implant dentistry “De novo bone formation” (Davies JE, 2003) Peri-implant endosseous healing I. Osteogenic cells excreting collagen-free bone matrix proteins such as osteopontin and bone sialoprotein These organic matrices initiating calcium phosphate nucleation for further mineralization Crystallization of elongated calcium phosphates followed by assembly of collagen ﬁbers Kim YK & Spector M (DMedSc doctoral thesis dissertation), 2019 PROSTHETIC C E L L U LA R | O C C L U SA L Biomechanics in implant dentistry “De novo bone formation” (Davies JE, 2003) Peri-implant endosseous healing I. Osteogenic cells excreting collagen-free bone matrix proteins such as osteopontin and bone sialoprotein These organic matrices initiating calcium phosphate nucleation for further mineralization Crystallization of elongated calcium phosphates followed by assembly of collagen ﬁbers Each collagen ﬁbril’s calciﬁcation process amongst collagen free calciﬁed layers with non-collagen proteins Kim YK & Spector M (DMedSc doctoral thesis dissertation), 2019 Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Implant features & surface science “Implant surface topography” • Implant surface roughness modulates bone matrix-related gene expression → enhanced bone apposition (Ogawa & Nishimura, 2003; Jokstad, 2003) Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Implant features & surface science “Implant surface topography” • Implant surface roughness modulates bone matrix-related gene expression → enhanced bone apposition • Different methods exist (i.e. acid etch, blasted surface, blasted + acid etch, hydroxyapatite coating, oxidized surface, titanium plasma-spray, turned surfaces) (Ogawa & Nishimura, 2003; Jokstad, 2003) Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Implant features & surface science “Implant surface topography” • Implant surface roughness modulates bone matrix-related gene expression → enhanced bone apposition • Different methods exist (i.e. acid etch, blasted surface, blasted + acid etch, hydroxyapatite coating, oxidized surface, titanium plasma-spray, turned surfaces) • Implant surface topography inﬂuencing on osseointegration (Ogawa & Nishimura, 2003; Jokstad, 2003) Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Implant features & surface science “SLA” • SLA = Sandblasted, large grit, acid-etched surface treatment • Sandblasting with aluminous oxide Straumann (ITI) Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Implant features & surface science “SLA” • SLA = Sandblasted, large grit, acid-etched surface treatment • Sandblasting with aluminous oxide • Acid etching with hydrogen sulfate or hydrogen chloride • Protected from air/carbon contamination via submerging in saline Straumann (ITI) Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Implant features & surface science “SLA” • SLA = Sandblasted, large grit, acid-etched surface treatment • Sandblasting with aluminous oxide • Acid etching with hydrogen sulfate or hydrogen chloride • Protected from air/carbon contamination via submerging in saline • Greater alkaline phosphatase activity (i.e. enhanced osteogenesis) on SLA surfaces than conventional TPS (titanium plasma spray) • Less bone resorption (3 yr follow up) than on TPS Straumann (ITI) Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Primary stability & insertion torque • Implant geometry + thread proﬁle and contact with bone dictate load distribution • Primary stability and insertion torque are NOT the same (Norton MR 2013; Barewal RM, et al, 2012) Biomechanics in implant dentistry Net stability Primary stability (old bone) Secondary stability (new bone) C E L L U LA R | PROSTHETIC O C C L U SA L Primary stability & insertion torque 100 75 50 25 0 • Implant geometry + thread proﬁle and contact with bone dictate load distribution • Primary stability and insertion torque are NOT the same “Primary stability” • Subjective assessment • Maximum insertion torque • Resonance frequency analysis 1 2 3 4 5 6 7 8 Time (weeks) (Raghavendra S, et al, 2005) Stability (%) Biomechanics in implant dentistry “Insertion torque” C E L L U LA R | PROSTHETIC O C C L U SA L Primary stability & insertion torque Implant insertion torque may portray bone quality around implants during the placement, yet its correlation with clinical efﬁcacy remains polemical Biomechanics in implant dentistry P L A C E M E N T P R O T O C O L (Harmmerle, 2004) C E L L U LA R | PROSTHETIC O C C L U SA L Placement & loading protocol Classiﬁcation Type 1 Type II Type III Type IV Implant placement Same day as extraction After complete soft tissue coverage of the socket (4-8 wks) After substantial clinical and/or radiographic bone ﬁll of the socket (12 - 16 wks) In a healed socket (> 16 wks) Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Placement & loading protocol L O A D I N G P R O T O C O L (Cochran 2004) Classiﬁcation Immediate restoration or Immediate non-functional (nonocclusal) loading Immediate loading or Immediate functional loading Progressive loading Early loading Conventional loading Delayed loading Implant loading 48hr of implant placement but not in occlusal contact with the opposing dentition during healing Into occlusal loading within 48hr of implant placement Light occlusal contact initially then gradually into full occlusal contact Between 48hr and not later than 3 months after implant placement In a second procedure after a healing period of 3-6 months After a conventional healing period of 6 months Biomechanics in implant dentistry “Dental implant” C E L L U LA R | PROSTHETIC O C C L U SA L Dimensional planning “A prosthetic device made of alloplastic material(s) implanted into the oral tissues beneath the mucosal and/or periosteal layer” - GPT 9th Ed Biomechanics in implant dentistry “Dental implant” C E L L U LA R | PROSTHETIC O C C L U SA L Dimensional planning “A prosthetic device made of alloplastic material(s) implanted into the oral tissues beneath the mucosal and/or periosteal layer” - GPT 9th Ed “Principles of Prosthodontics should be applied for the surgical placement!” Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Dimensional planning 1.5mm “Mesiodistal implant position” • Distance to adjacent tooth at bone level: • a minimum distance of 1.5mm from the implant shoulder to the adjacent tooth at bone level (mesiodistal) is required Kim YK, et al, NYU Predoctoral Implant Manual – Restorative. NYUCD, 2021 Biomechanics in implant dentistry 3mm C E L L U LA R | PROSTHETIC O C C L U SA L Dimensional planning “Mesiodistal implant position” • Distance to adjacent tooth at bone level: • a minimum distance of 1.5mm from the implant shoulder to the adjacent tooth at bone level (mesiodistal) is required • Distance to adjacent implants at bone level: • a minimum distance of 3mm between two adjacent implant shoulders (mesiodistal) is required Kim YK, et al, NYU Predoctoral Implant Manual – Restorative. NYUCD, 2021 Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Dimensional planning “Orofacial implant position” • The layer of bone must be at least 1-2mm thick Kim YK, et al, NYU Predoctoral Implant Manual – Restorative. NYUCD, 2021 Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Dimensional planning “Orofacial implant position” • The layer of bone must be at least 1-2mm thick • Choose the orofacial implant position and axis so that the screw channel of the screw-retained restoration is located behind the incised edge (anterior position) or at the center (posterior position) Kim YK, et al, NYU Predoctoral Implant Manual – Restorative. NYUCD, 2021 PROSTHETIC C E L L U LA R | O C C L U SA L Biomechanics in implant dentistry Dimensional planning “Coronoapical implant position” • The implant shoulder (for bone-level implants) should be sinked around 1~1.5mm subcrestally Kim YK, et al, NYU Predoctoral Implant Manual – Restorative. NYUCD, 2021 1~1.5mm PROSTHETIC C E L L U LA R | O C C L U SA L Biomechanics in implant dentistry Dimensional planning “Coronoapical implant position” • The implant shoulder (for bone-level implants) should be sinked around 1~1.5mm subcrestally • Crestal bone should be in sloping edge (i.e. chamfer) for allowing prosthetic components Kim YK, et al, NYU Predoctoral Implant Manual – Restorative. NYUCD, 2021 PROSTHETIC C E L L U LA R | O C C L U SA L Biomechanics in implant dentistry Dimensional planning “Occlusal plane & its implication” PROSTHETIC C E L L U LA R | O C C L U SA L Biomechanics in implant dentistry Dimensional planning “Occlusal plane & its implication” PROSTHETIC C E L L U LA R | O C C L U SA L Biomechanics in implant dentistry Dimensional planning “Occlusal plane & its implication” Kim YK, Wiedemann TG, Talib H, Under Review PROSTHETIC C E L L U LA R | O C C L U SA L Biomechanics in implant dentistry Dimensional planning “Occlusal plane & its implication” Kim YK, Wiedemann TG, Talib H, Under Review PROSTHETIC C E L L U LA R | O C C L U SA L Biomechanics in implant dentistry “Lip contour & its implication” Dimensional planning PROSTHETIC C E L L U LA R | O C C L U SA L Biomechanics in implant dentistry “Lip contour & its implication” Dimensional planning Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Inter-arch space “Fixed crowns” • For cement-retained crowns, a minimum of 4mm of abutment height is recommended for proper retention, along with available restoration space (all metal = 1mm; metal-ceramic or all-ceramic = 2mm). • For NYU DDS, 7mm space is recommended. Kim YK, et al, NYU Predoctoral Implant Manual – Restorative. NYUCD, 2021 Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Inter-arch space “Fixed crowns” • For cement-retained crowns, a minimum of 4mm of abutment height is recommended for proper retention, along with available restoration space (all metal = 1mm; metal-ceramic or all-ceramic = 2mm). • For NYU DDS, 7mm space is recommended. • With insufﬁcient inter-arch space, all-metal crown options (or screw-retained) can be chosen, yet achieving a proper emergence proﬁle may be challenging. • Please consult with Pros faculty. Kim YK, et al, NYU Predoctoral Implant Manual – Restorative. NYUCD, 2021 Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Inter-arch space “Overdenture” • Analysis at established occlusal vertical dimension (OVD) needed before the surgical implant placement • Suggested implant-retained overdenture vertical space (distance between the edentulous ridge crest and the position where the incisal edges of the denture teeth) requirement is 10- 12mm for non-splinted (such as locator or ball) and 15-20mm for splinted (i.e. bar or bar with locator). Kim YK, et al, NYU Predoctoral Implant Manual – Restorative. NYUCD, 2021 Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Implant-crown ratio “Crown-to-root ratio” • Minimum 1:1 & ideal 1:2 (Penny) • 1:1 (Shillingburg) • Resistance & retention • Taper & total occlusal convergence (TOC) • Critical convergence Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Implant-crown ratio “Crown-to-root ratio” “Not applied in implant dentistry!” • Short implants with moderately rough surface are as successful as long implants (Kotsovilis, et al, 2009) Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Implant-crown ratio “Crown-to-root ratio” “Not applied in implant dentistry!” • Short implants with moderately rough surface are as successful as long implants (Kotsovilis, et al, 2009) • Short implant survival is high and are a viable option to long implants when additional surgical augmentation procedures are considered (Atieh MA et al, 2012) Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Implant-crown ratio “Crown-to-root ratio” “Not applied in implant dentistry!” • Short implants with moderately rough surface are as successful as long implants (Kotsovilis, et al, 2009) • Short implant survival is high and are a viable option to long implants when additional surgical augmentation procedures are considered (Atieh MA et al, 2012) • Greater crown-to-implant (i.e. C/I) ratios tended to exhibit less bone loss with time (Garaicoa-Pazmino C, et al, 2014) Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Implant-crown ratio “Crown-to-root ratio” “Not applied in implant dentistry!” • Short implants with moderately rough surface are as successful as long implants (Kotsovilis, et al, 2009) • Short implant survival is high and are a viable option to long implants when additional surgical augmentation procedures are considered (Atieh MA et al, 2012) • Greater crown-to-implant (i.e. C/I) ratios tended to exhibit less bone loss with time (Garaicoa-Pazmino C, et al, 2014) • However, crown height magniﬁes the force on the abutment screw (Boggan, 1999) Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Implant-crown ratio “Crown-to-root ratio” “Not applied in implant dentistry!” • Short implants with moderately rough surface are as successful as long implants (Kotsovilis, et al, 2009) • Short implant survival is high and are a viable option to long implants when additional surgical augmentation procedures are considered (Atieh MA et al, 2012) • Greater crown-to-implant (i.e. C/I) ratios tended to exhibit less bone loss with time (Garaicoa-Pazmino C, et al, 2014) • However, crown height magniﬁes the force on the abutment screw (Boggan, 1999) • Increased C/I ratio can still achieve a long-term survival rate as long as the occlusion and parafunctional habits are controlled (Tawil G, et al, 2006) Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Implant-crown ratio “Crown-to-root ratio” “Not applied in implant dentistry!” Yet! • Short implants with moderately rough surface are as successful as long implants (Kotsovilis, et al, 2009) • Short implant survival is high and are a viable option to long implants when additional surgical augmentation procedures are considered (Atieh MA et al, 2012) • Greater crown-to-implant (i.e. C/I) ratios tended to exhibit less bone loss with time (Garaicoa-Pazmino C, et al, 2014) • However, crown height magniﬁes the force on the abutment (Boggan, 1999) screw “More systematic in vitro / in vivo research israte needed” • Increased C/I ratio can still achieve a long-term survival as long as the occlusion and parafunctional habits are controlled (Tawil G, et al, 2006) Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Connection systems “External vs. internal hex” PROSTHETIC C E L L U LA R | O C C L U SA L Biomechanics in implant dentistry “Beneﬁts of internal connections” Connection systems • High resistance to non-axial loading PROSTHETIC C E L L U LA R | O C C L U SA L Biomechanics in implant dentistry “Beneﬁts of internal connections” Connection systems • High resistance to non-axial loading • Clamping force (i.e. preload) becomes less critical PROSTHETIC C E L L U LA R | O C C L U SA L Biomechanics in implant dentistry “Beneﬁts of internal connections” Connection systems • High resistance to non-axial loading • Clamping force (i.e. preload) becomes less critical • Minor or no rotational “slop” PROSTHETIC C E L L U LA R | O C C L U SA L Biomechanics in implant dentistry “Beneﬁts of internal connections” Connection systems • High resistance to non-axial loading • Clamping force (i.e. preload) becomes less critical • Minor or no rotational “slop” • Excellent anti-rotational resistance Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Connection systems “Risks of internal tapered” • Hoop stress generated in implant body (Shigley and Mitchell, 1992) Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Connection systems “Risks of internal tapered” • Hoop stress generated in implant body • Extensive load applying to the walls of implant (Shigley and Mitchell, 1992) Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Connection systems “Risks of internal tapered” • Hoop stress generated in implant body • Extensive load applying to the walls of implant • With resorbed peri-implant crestal bone, implant may fracture (Shigley and Mitchell, 1992) Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Splinting “Individuals vs. splinting” • Splinted acted favorably in stress distribution (Pellizzer 2015) Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Splinting “Individuals vs. splinting” • Splinted acted favorably in stress distribution (Pellizzer 2015) • Not clinically signiﬁcant bone loss between splinted vs. non-splinted (Vigolo 2015) Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Splinting “Individuals vs. splinting” • Splinted acted favorably in stress distribution (Pellizzer 2015) • Not clinically signiﬁcant bone loss between splinted vs. non-splinted (Vigolo 2015) • In vitro higher strains for non-splinted with oblique loading (Yilmaz 2011) PROSTHETIC C E L L U LA R | O C C L U SA L Biomechanics in implant dentistry Cantilever “Full-arch implant prosthesis with cantilever” Scientiﬁcally and clinically validated ! (ITI Treatment Guide Vol. 4., 2010) Biomechanics in implant dentistry 1 1.5 C E L L U LA R | PROSTHETIC O C C L U SA L Cantilever “A-P spread” A-P spread Cantilever Def : the distance between a linear line connecting the most terminal aspects of implant platform to the center of the most anteriorly distant implant (English CE, 1990) Biomechanics in implant dentistry 1 1.5 C E L L U LA R | PROSTHETIC O C C L U SA L Cantilever “A-P spread” A-P spread Cantilever “1.5 A-P spread rule using 4 implants” (English CE, 1997) Biomechanics in implant dentistry 1 1.5 C E L L U LA R | PROSTHETIC O C C L U SA L Cantilever “Inconsistency of A-P spread” Biomechanics in implant dentistry 1 1.5 C E L L U LA R | PROSTHETIC O C C L U SA L Cantilever “Inconsistency of A-P spread” Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Cantilever “PIAAR (new concept)” Kim YK. Prosthesis-Implant Arch Area Ratio (PIAAR) – A New Geometric Paradigm, Replacing the Current ‘A-P Spread’ of a Cantilever in Full-Arch Implant Prosthesis: A Proof-of-Concept Experiment. Journal of Prosthodontics, 2022;1-7. Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Cantilever “PIAAR (new concept)” “Heron’s formula” x z Area y S = 1/2 (x + y + z) Area = root {S * (S - x) (S - y) (S - z) } Kim YK. Prosthesis-Implant Arch Area Ratio (PIAAR) – A New Geometric Paradigm, Replacing the Current ‘A-P Spread’ of a Cantilever in Full-Arch Implant Prosthesis: A Proof-of-Concept Experiment. Journal of Prosthodontics, 2022;1-7. Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Cantilever “PIAAR (new concept)” Kim YK. Prosthesis-Implant Arch Area Ratio (PIAAR) – A New Geometric Paradigm, Replacing the Current ‘A-P Spread’ of a Cantilever in Full-Arch Implant Prosthesis: A Proof-of-Concept Experiment. Journal of Prosthodontics, 2022;1-7. Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Cantilever “PIAAR (new concept)” Kim YK. Prosthesis-Implant Arch Area Ratio (PIAAR) – A New Geometric Paradigm, Replacing the Current ‘A-P Spread’ of a Cantilever in Full-Arch Implant Prosthesis: A Proof-of-Concept Experiment. Journal of Prosthodontics, 2022;1-7. Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Cantilever “PIAAR (new concept)” PIAAR-ant (anterior cantilever) = Pros-AA-ant / (Pros-AA-ant + Plat AA) PIAAR-lat (lateral cantilever) = Pros-AA-lat / (Pros-AA-lat + Plat-AA) PIAAR-post (posterior cantilever) = Pros-AA-post / (Pros-AA-post + Plat-AA) Kim YK. Prosthesis-Implant Arch Area Ratio (PIAAR) – A New Geometric Paradigm, Replacing the Current ‘A-P Spread’ of a Cantilever in Full-Arch Implant Prosthesis: A Proof-of-Concept Experiment. Journal of Prosthodontics, 2022;1-7. Biomechanics in implant dentistry 1 1.5 C E L L U LA R | PROSTHETIC O C C L U SA L Cantilever “PIAAR (new concept)” Ar Ar Ar Ar Ar Ar Ar Ar Ar Ar Ar Ar Ar Ar Ar Kim YK. Prosthesis-Implant Arch Area Ratio (PIAAR) – A New Geometric Paradigm, Replacing the Current ‘A-P Spread’ of a Cantilever in Full-Arch Implant Prosthesis: A Proof-of-Concept Experiment. Journal of Prosthodontics, 2022;1-7. Biomechanics in implant dentistry 1 1.5 C E L L U LA R | PROSTHETIC O C C L U SA L Cantilever “PIAAR (new concept)” Ar Ar Ar Ar Ar Ar 1 Plat-AA Width 1 1 Plat-AA Width 1.25:1 1 Plat-AA 1 1.5 1.5 1.5 1.5 Ar Ar Ar Ar Width 1.5:1 Ar Ar Ar Ar Ar Kim YK. Prosthesis-Implant Arch Area Ratio (PIAAR) – A New Geometric Paradigm, Replacing the Current ‘A-P Spread’ of a Cantilever in Full-Arch Implant Prosthesis: A Proof-of-Concept Experiment. Journal of Prosthodontics, 2022;1-7. Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Cantilever “PIAAR (new concept)” Kim YK. Prosthesis-Implant Arch Area Ratio (PIAAR) – A New Geometric Paradigm, Replacing the Current ‘A-P Spread’ of a Cantilever in Full-Arch Implant Prosthesis: A Proof-of-Concept Experiment. Journal of Prosthodontics, 2022;1-7. Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Cantilever “PIAAR (new concept)” • Compared to the preexisting anterior-posterior spread concept, a new prosthesis-implant arch area ratio seemed to be a more categorized, geometric, and perceptive modality of assessing the prosthetic cantilever in a full-arch implant-supported prosthesis Kim YK. Prosthesis-Implant Arch Area Ratio (PIAAR) – A New Geometric Paradigm, Replacing the Current ‘A-P Spread’ of a Cantilever in Full-Arch Implant Prosthesis: A Proof-of-Concept Experiment. Journal of Prosthodontics, 2022;1-7. Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Cantilever “PIAAR (new concept)” • Compared to the preexisting anterior-posterior spread concept, a new prosthesis-implant arch area ratio seemed to be a more categorized, geometric, and perceptive modality of assessing the prosthetic cantilever in a full-arch implant-supported prosthesis • allowing a more systematic indexing of different full-arch implant clinical scenarios with greater speciﬁcity and consistency. Kim YK. Prosthesis-Implant Arch Area Ratio (PIAAR) – A New Geometric Paradigm, Replacing the Current ‘A-P Spread’ of a Cantilever in Full-Arch Implant Prosthesis: A Proof-of-Concept Experiment. Journal of Prosthodontics, 2022;1-7. Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Non-axial forces “Cuspal inclination” • Abutment screw torque = T = F x ASD Abutment screw distance (ASD) • 10 degree increase of cuspal inclination → 30% increase of torque • Thus, ﬂatter cusp is desirable 90’ horizontal force (F) Cuspal inclination Occlusal loading (Weinberg, 1995) Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Non-axial forces “Implant inclination” Implant inclination • Implant inclination (i.e. angled abutment) → No signiﬁcant changes in torque 90’ horizontal force (F) Occlusal loading (Weinberg, 1995) Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Non-axial forces “Lingual offset” Lingual offset • Every 1mm of offset → 15% increase of torque • Thus, minimum cantilever length is recommended 90’ horizontal force (F) Occlusal loading (Weinberg, 1995) Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Non-axial forces “Apical offset” Apical offset 90’ horizontal force (F) • No signiﬁcant changes in torque Occlusal loading (Weinberg, 1995) Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Non-axial forces “Insights” Once osseointegrated… “Non-Axial loading is NOT biologically detrimental to the integration of the implant, even when non-axial occlusal forces are greatly exaggerated” (Celleti, Asikainen, Miyata) (Taylor TD et al, 2000) Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Non-axial forces “Insights” Once osseointegrated… “Non-Axial loading is NOT biologically detrimental to the integration of the implant, even when non-axial occlusal forces are greatly exaggerated” (Celleti, Asikainen, Miyata) “However, non-axial loading puts implant components at greater risk for mechanical failure” (Taylor TD et al, 2000) Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Non-axial forces “Insights” Once osseointegrated… “Non-Axial loading is NOT biologically detrimental to the integration of the implant, even when non-axial occlusal forces are greatly exaggerated” (Celleti, Asikainen, Miyata) “However, non-axial loading puts implant components at greater risk for mechanical failure” “Screw-retained components are much less able to withstand non-axial forces (McGlumphy, Binon, Rangert) (Taylor TD et al, 2000) Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Non-axial forces “Flexure fatigue” Preload • Maximum stress strain concentrated at the implant-abutment interface (via off-axial forces) Maximum stress Clamping force (N) Torque (Ncm) Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Non-axial forces “Flexure fatigue” Preload • Maximum stress strain concentrated at the implant-abutment interface (via off-axial forces) Maximum stress • Tightening force = preload → generating clamping force (i.e. compressive stress) Clamping force (N) Torque (Ncm) Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Non-axial forces “Flexure fatigue” Preload • Maximum stress strain concentrated at the implant-abutment interface (via off-axial forces) Maximum stress • Tightening force = preload → generating clamping force (i.e. compressive stress) • Clamping force shields the abutment screw from ﬂexure Clamping force (N) Torque (Ncm) Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Non-axial forces “Flexure fatigue” Preload • Maximum stress strain concentrated at the implant-abutment interface (via off-axial forces) Maximum stress • Tightening force = preload → generating clamping force (i.e. compressive stress) • Clamping force shields the abutment screw from ﬂexure • Loss of preload → increasing the bending load of the screw Clamping force (N) Torque (Ncm) Biomechanics in implant dentistry • Common prosthetic complication in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Non-axial forces “Screw loosening” • Non-axial force serves as a critical factor affecting screw loosening (i.e. prematurity, eccentric excursive interferences, and bruxism) Biomechanics in implant dentistry • Common prosthetic complication in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Non-axial forces “Screw loosening” • Non-axial force serves as a critical factor affecting screw loosening (i.e. prematurity, eccentric excursive interferences, and bruxism) • Wide diameter implants → reducing the screw loosening and component fracture (Boggan, 1999) • Crown height magniﬁes the force on the abutment screw (Boggan, 1999) • Narrowing the occlusal table is critical for a single unit to prevent screw loosening (Bakaeen, 2001) Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Non-axial forces “Screw loosening” • Retightening abutment screws 10 min after the initial torque applications improve the tightening of screw and to decrease screw loosening (Siamos, 2002) • Repeated opening and closing of implant abutment screws → progressive loss of torque retention with variations between systems → decrease in the coefﬁcient of friction of the screw head and threads (Weiss, 2000) Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Non-axial forces “Screw loosening” • Retightening abutment screws 10 min after the initial torque applications improve the tightening of screw and to decrease screw loosening (Siamos, 2002) • Repeated opening and closing of implant abutment screws → progressive loss of torque retention with variations between systems → decrease in the coefﬁcient of friction of the screw head and threads (Weiss, 2000) • Preventing the misﬁt through proper impression & laboratory workﬂows and veriﬁcation = the key ! Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Overload “Tooth vs. implant” Classiﬁcation Biologic system Mobility Tactile sensitivity Load bearing mechanism Fulcrum to lateral forces Signs of overloading Tooth Periodontal ligament (PDL) 25-100 microns High Shock-absorption Apical 1/3 of root PDL thickening, mobility, wear facets, fremitus, pain Implant Direct bone implant contact (osseointegration) 5-10 microns Low Supporting bone Crestal bone Screw loosening or fracture, abutment or prosthesis fracture, implant fracture, bone loss (Lang, 2001; Misch, 1994; Schulte, 1995, Zarb 1990) Biomechanics in implant dentistry Distribution Occlusal morphology Implant size & length C E L L U LA R | PROSTHETIC O C C L U SA L Overload “Multi-factorial” Duration Parafunctional habit Bruxism (i.e. clenching) Direction Off-axis loading Position Cantilever Magnitude Occlusal force Bruxism Complication risk PROSTHETIC C E L L U LA R | O C C L U SA L Biomechanics in implant dentistry Overload “Occlusion & biological outcomes” • Controversy persists as to the role of occlusal overload in peri-implantitis • No controlled studies evaluating the effect of occlusion on implants in humans, following the Helsinki accords (Graves CV et al, 2016) (Sadowsky SJ, 2019) PROSTHETIC C E L L U LA R | O C C L U SA L Biomechanics in implant dentistry Overload “Occlusion & biological outcomes” • Controversy persists as to the role of occlusal overload in peri-implantitis • No controlled studies evaluating the effect of occlusion on implants in humans, following the Helsinki accords (Graves CV et al, 2016) • Available body of evidence → broad and heterogenous • Lacking a study that reveals the link between speciﬁc mechanical loads and histological changes (Sadowsky SJ, 2019) Biomechanics in implant dentistry • Lack of scientiﬁc evidence supporting that overload itself is a substantial risk factor for loss of osseointegration and implant failure C E L L U LA R | PROSTHETIC O C C L U SA L Overload “Evidence-based” (Chen, 2005; Kim, 2005; Taylor, 2000, 2002, 2005) Biomechanics in implant dentistry • Lack of scientiﬁc evidence supporting that overload itself is a substantial risk factor for loss of osseointegration and implant failure C E L L U LA R | PROSTHETIC O C C L U SA L Overload “Evidence-based” (Chen, 2005; Kim, 2005; Taylor, 2000, 2002, 2005) • May be an additional contributing factor to implant-bone loss in the presence of plaque-induced inﬂammation (i.e. biological complications) (Chambrone, 2010; Kozlovsky, 2007; Wennergberg, 2011) PROSTHETIC C E L L U LA R | O C C L U SA L Biomechanics in implant dentistry Overload “Occlusion & biological outcomes” • Evidence-based fact - increased mechanical stress (below a certain threshold) → increasing bone density or bone apposition → following the “Wolff’s law” strengthening the bone (Frost HM, 2003; Frost HM, 1994) • Non-evidence-based expert opinion - mechanical stress + fatigue micro-damage → biological bone resorption (Isidor F, 2006) Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Principles of occlusion “Occlusal schemes” • Different occlusal schemes exist such as: 1) mutually protected canine guidance (ideal for ﬁxed rehabilitation); 2) unilateral balanced occlusion (i.e. group function or working side interference); 3) bilateral balanced occlusion (ideal for denture occlusion; unideal for ﬁxed rehabilitation). Kim YK, et al, NYU Predoctoral Implant Manual – Restorative. NYUCD, 2021 Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Principles of occlusion “Occlusal schemes” • Different occlusal schemes exist such as: 1) mutually protected canine guidance (ideal for ﬁxed rehabilitation); 2) unilateral balanced occlusion (i.e. group function or working side interference); 3) bilateral balanced occlusion (ideal for denture occlusion; unideal for ﬁxed rehabilitation). • Ideally, anterior guidance & mutually protected canine guidance is preferable or should be established so that posterior implants are not at risk of occlusal damage once restored Kim YK, et al, NYU Predoctoral Implant Manual – Restorative. NYUCD, 2021 Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Principles of occlusion “Mutually-protected occlusion” • Anterior guidance + mutually protected occlusion → least traumatic occlusal scheme from electromyography (EMG) activity (Williamson, 1983) Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Principles of occlusion “Mutually-protected occlusion” • Anterior guidance + mutually protected occlusion → least traumatic occlusal scheme from electromyography (EMG) activity (Williamson, 1983) • Canine guidance → least muscle activity + lessening the tension + decreasing force magnitude (DiAmico, 1961; Shupe, 1984) Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Principles of occlusion “Bilateral balanced occlusion” Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Principles of occlusion “Armamentarium” Biomechanics in implant dentistry • 8 microns (human RBC diameter) • Pre-assessment (i.e. prematurity & interferences) C E L L U LA R | PROSTHETIC O C C L U SA L Principles of occlusion “Armamentarium” • Inter-proximal assessment • Bite registration veriﬁcation in ﬁxed rehab • Static/dynamic occlusion check during ﬁnal delivery Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Principles of occlusion “Armamentarium” • 21 microns • Prematurity/eccentric interferences (red color) • Static MIP contacts (black color) Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Principles of occlusion “Armamentarium” • 79 microns • Marking hyper-occluding contacts (i.e. areas for adjustments) • Removable prosthesis occlusion Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Principles of occlusion “Deﬂective occlusal contact” • Def: a contact that displaces a tooth, diverts the mandible from its intended movement” - GPT 9th Ed Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Principles of occlusion “Deﬂective occlusal contact” • Def: a contact that displaces a tooth, diverts the mandible from its intended movement” - GPT 9th Ed “Eccentric excursive interferences” • Non-working side interference • Working side interference (i.e. group function) • Mutually protected canine guidance (= protective) Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Principles of occlusion “Deﬂective occlusal contact” • Incrementally loading leaf-gauge • Check the initial centric occlusion (CO) with shimstock • Mark CO with the articulating paper • Def: a contact that displaces a tooth, diverts the mandible from its intended movement” - GPT 9th Ed “Eccentric excursive interferences” • Non-working side interference • Working side interference (i.e. group function) • Mutually protected canine guidance (= protective) Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Principles of occlusion “Deﬂective occlusal contact” • Incrementally loading leaf-gauge • Check the initial centric occlusion (CO) with shimstock • Mark CO with the articulating paper • Def: a contact that displaces a tooth, diverts the mandible from its intended movement” - GPT 9th Ed “Eccentric excursive interferences” • Non-working side interference • Working side interference (i.e. group function) • Mutually protected canine guidance (= protective) Biomechanics in implant dentistry C E L L U LA R | PROSTHETIC O C C L U SA L Principles of occlusion “Deﬂective occlusal contact” • Def: a contact that displaces a tooth, diverts the mandible from its intended movement” - GPT 9th Ed “Causing the non-axial forces” • Leading to mechanical complications • Screw-loosening and/or fracture “Eccentric excursive interferences” • Prosthetic fracture • Implant fracture (with insufﬁcient crestal bone around the platform) • Non-working side interference • Working side interference (i.e. group function) • Mutually protected canine guidance (= protective) Biomechanics in implant dentistry “Hanau quint (Theilman’s formula)” (Condylar inclination) x (Incisal guidance) (Compensating curve) x (Cuspal height) x (Occlusal plane) 1= C E L L U LA R | PROSTHETIC O C C L U SA L Principles of occlusion Biomechanics in implant dentistry “Hanau quint (Theilman’s formula)” (Condylar inclination) x (Incisal guidance) (Compensating curve) x (Cuspal height) x (Occlusal plane) 1= C E L L U LA R | PROSTHETIC O C C L U SA L Principles of occlusion H o r i z o n t a l r e f e r e n c e p l a n e Cuspal Height Visualizing Location of dentition Dynamics YK P r o s t h o d Thank you Instagram Youtube Linkedin YKK Website [email protected] @ykk_pros YKP r o s t h o d im s tonti

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