"Denture Tooth Forms and Occlusal Forms (PowerPoint download)"
Philosophies of Occlusion for Implants Implant Occlusion Single Crown Fixed Partial Dentures Full arch prostheses (screw retained) Overdentures Many Philosophies of Occlusion No definitive scientific studies to prove: one type of tooth form one type of occlusal scheme to be clearly preferred by patients to be more efficient than another Tooth Forms Occlusal Schemes Anatomic Canine Guidance Non Anatomic (Mutually Protected) Group Function Lingualized (Balanced) Monoplane Denture Tooth Forms and Occlusal Forms QuickTime™ and a TIFF (LZW) decompressor are needed to see this picture. Occlusal Scheme & Axial Loading Evidence Based Reviews • Taylor, Wiens et al. J Prosthet Dent 2005;94:555-560 • Carlsson. Odontology 2009; 97:8-17 No Preferred occlusal scheme Clinicians advocate axial loading of implants, but no evidence, at present, demonstrating benefits Loading and Overloading Evidence Based Review Taylor, Wiens et al. J Prosthet Dent 2005;94:555-560 No evidence at present that progressive occlusal loading of implant is beneficial occlusal overload is detrimental to implants* * At least one case study now - unstable prosthesis, bone loss reversed Int J Oral Maxillofac Impl 2008;23:153-157. Occlusal Table & C/R Ratios Evidence Based Review Carlsson 2008 No evidence of risk at present from: Increased Crown/Root Ratio Increased occlusal table Porcelain vs. Acrylic Absence of Scientific Evidence Not proof against! Follow best available clinical principles Do not build in heavy non-axial loading or overloading Clinical Principles for Occlusion Based on Clinical Experience Not Scientific Evidence General Principles Improve denture stability or axial loading of single teeth Centric contacts on flat surfaces, not inclines General Principles Center over lower ridge Posterior Overjet to 1-2 mm Avoid Cheek 1-2 mm Biting Anatomic setup Nonanatomic setup General Principles Improve denture stability or single tooth loading Center occlusal contacts over ridge Simultaneous posterior contacts in centric General Occlusal Principles For overdentures or full arch prostheses opposing a CD: No anterior contacts in centric Minimizes anterior resorption Grazing anterior contacts in excursions Incising Occlusal Schemes Canine Guidance Single Teeth Group Function FPD’s Lingualized Monoplane Dentures Crowns or FPD’s Either canine guidance or group function works - no preference Use what the patient has Use what would be easiest Overdentures or Full Arch Prostheses ALL Occlusal Schemes Devised to Maximize Denture Stability Lingualized Occlusion Maxillary cusped tooth Mandibular cuspless or shallow cusped tooth Maxillary lingual cusp balances like a mortar in a pestle Lingualized Occlusion • Lingual cusp contacts opposing central fossae • Mandibular cuspal inclines are shallow (0°, 10°) • Less lateral displacement Lingualized Occlusion How Stability is Improved Simultaneous bilateral anterior and posterior in all excursions Tilting forces theoretically neutralized Enter Bolus Exit Balance? Many patients chew bilaterally Biting forces maximum close to intercuspation (where balance most effective) Non-functional aspects (swallow) Point of Loading Affects Stability Browning, 1986 Loaded centrally, M, D, L, B M B caused unseating B C Central loading better than L distal loading D Lingualized Contacts Working Side Only buccal cusp contact is inner incline of mandibular teeth (balancing) Balancing Side ‘IIF’ Rule IIF you have contacts on the Inner Inclines of Functional cusps they are balancing contacts B L B Working Contacts L Inner Inclines (inside of cusp) Outer Inclines(outside of cusp) Test! Rules for Balancing Contacts Balancing contacts should be lines, not points Balancing contacts should never be heavier than working contacts Balanced Occlusion (Lingualized) Indirect evidence that balanced occlusion may: reduce ridge resorption (Maeda & Wood , 1989) allow for increased functional forces in excursions (Miralles et al, 1989) Lingualized Cusp Angles Always use steep cusped maxillary tooth (33°) When condylar guidance is steeper use more cusp angle in mandible (10°) Lingualized Occlusion Balance cannot be set without an articulator Clinical remount on an articulator - fewer adjustments Condylar Inclination Posterior teeth separate as working condyle moves forward (and downward) Anterior teeth contact Closer to condyle, more separation More anterior separation of Premolars if steep anterior guidance Effect of Mandible Moving Downward During Excursions Maintaining Balancing Contacts Change occlusal plane angle Increase compensating curves Increase cusp angles or effective cusp angles Checking for Balance Feels Smooooooth in excursions - Fingers on max. canines - Check on articulator Assess Contacts: Centric Stops Excursions Improving Denture Occlusion Most important cusp - maxillary lingual Mandibular buccal cusps more lateral - more tipping When Not to Balance Difficulty in obtaining repeatable centric record incoordination, muscle splinting Dramatic malocclusions Severe ridge resorption lateral forces displace the denture Implants tend to negate this factor Monoplane Occlusion Cuspless teeth set on a flat plane with 1.5- 2 mm overjet No cusp to fossa relationship No anterior contacts present in centric position No overbite Monoplane Occlusion How Stability is Improved Elimination of cusps Lateral forces reduced, improving stability Simplifies denture tooth arrangement Monoplane Occlusion With Condylar Inclination Monoplane Occlusion With Condylar Inclination Ensure Teeth Set Over Ridge Minimize tilting/tipping Maximize stability Minimize contacts on buccal of flat cusps Monoplane Occlusion Functional, but unesthetic Not balanced - flat Zero degree teeth can be balanced if condylar inclinations are shallow Monoplane Occlussion - When? Jaw size discrepancies, malocclusions cross-bite, Cl II, III Minimal ridge reduces horizontal forces implants help Uncoordinated jaw movements Summary No definitive studies to show one type of occlusion is best Follow established clinical principles Assess each case - adapt to clinical situation Continue to read the literature