2-Centric Occlusal Contact PDF

THE OCCLUSAL CONTACTS IN CENTRIC POSITION THE FUNCTIONAL FORM OF THE TEETH C; cusp. CR; cusp ridge. MR; marginal ridge. TR; triangular ridge. OR; oblique ridge. CF; central fossa. MRF; marginal ridge fissure. THE FUNCTIONAL FORM OF THE TEETH C; cusp. CR; cusp ridge. MR;...

THE OCCLUSAL CONTACTS IN CENTRIC POSITION THE FUNCTIONAL FORM OF THE TEETH C; cusp. CR; cusp ridge. MR; marginal ridge. TR; triangular ridge. OR; oblique ridge. CF; central fossa. MRF; marginal ridge fissure. THE FUNCTIONAL FORM OF THE TEETH C; cusp. CR; cusp ridge. MR; marginal ridge. TR; triangular ridge. CF; central fossa.  THE FACIAL AND LINGUAL RELATIONS OF EACH TOOTH TO ITS ANTAGONIST In centric occlusion, each tooth of one arch in occlusal with portions of two others in the opposing arch Except mandibular central incisors and the maxillary third molars which has one antagonist only. HORIZONTAL OVERLAP (OVERJET) The incisal ridges or buccal cusp ridges of the maxillary teeth extend labially or buccally to the incisal ridges or buccal cusp ridges of the mandibular teeth when the teeth are in centric occlusion.  VERTICAL OVERLAP (OVERBITE) The incisal ridges of the maxillary anterior teeth extend below the incisal ridges of the mandibular anterior teeth when the teeth are placed in centric occlusal relation VERTICAL AND HORIZONTAL OVERLAP IN DIFFERENT JAW RELATIONS  CENTRIC HOLDING CUSPS (THE SUPPORTING OR STAMP) CUSPS AND CENTRIC STOPS The supporting cusps (PU-BL) are the lingual cusps of the maxillary posterior teeth and the buccal cusps of the posterior mandibular teeth. Centric stops are areas of contact that a supporting cusp makes with opposing teeth.  NON-CENTRIC (GUIDING OR SHEAR) CUSPS Guiding cusps (BU-LL) (Mandibular lingual and maxillary buccal) are sharper and more outward placed than the supporting cusps and provide horizontal and vertical overlap over them. CENTRIC HOLDING CUSPS IN POSTERIOR CROSS BITE RELATIONSHIP  A, B AND C CONTACTS Contact between the buccal cusps of the posterior teeth is an A contact. The common contact between the stamp cusps is a B contact. Contact between the lingual cusps of the posterior teeth is a C contact. The B contacts in centric occlusion must be obtained and maintained for occlusal stability. CLOSURE STOPPERS AND EQUALIZERS The closure of the mandible occurs in a curved upward path. Upon closure, mesial inclines of lower teeth contact distal inclines of uppers. These contacts are called: Closure Stoppers (ML-DU). Also, the distal inclines of the lowers contact the mesial inclines of the uppers. These contacts are known as the Equalizers (MU-DL). Simultaneous contacts between the Equalizers and Stoppers should occurs in centric occlusion.  CUSP – MARGINAL RIDGE OCCLUSION One stamp cusp fits in a fossa and another stamp cusp of the same tooth fits into the embrasure area of two of the opposing teeth “tooth-to- two-teeth” occlusion, or a “cusp-embrasure” occlusal pattern. Present in 95% of natural teeth. -Plunger cusp effect CUSP – MARGINAL RIDGE OCCLUSION Maxillary 1st molar: Mesio-palatal cusp fits into central fossa of lower 1st molar. Disto-palatal cusp fits into distal MR of 1st lower molar and mesial MR of 2nd molar. Lingual view  CUSP- MARGINAL RIDGE OCCLUSION Mandibular 1st molar: Mesio-buccal cusp fits into distal MR of 2nd premolar and mesial MR of 1st max. molar. Disto-buccal cusp fits into maxillary central fossa. Buccal view  CUSP FOSSA OCCLUSION Most or all of the stamp cusps fit into fossae. The cusps and fossae of one tooth interdigitate with the cusps and fossae of only one opposing tooth “tooth - to-one-tooth” occlusion. Present in 5% of natural teeth.  TRIPOD CONTACT IN CUSP FOSSA OCCLUSION The cusp ridges make a tripod of contact with the fossa leaving the cusp apex out of occlusion. A tripod is the most stable system in mechanics This contact provide escapements spaces. These spaces are needed for efficient mastication.  CUSP- FOSSAE OCCLUSION Maxillary 1st molar: Mesio-palatal cusp fits into central fossa of lower one. Disto-palatal cusp fits into distal fossa of lower one. Lingual view  CUSP- FOSSAE OCCLUSION Mandibular 1st molar: Mesio-buccal cusp fits into mesial fossa of maxillary one. Disto-buccal cusp fits into maxillary central fossa. Buccal view  ADVANTAGES OF CUP FOSSA OCCLUSION Food impaction is prevented Centric relation closure forces are nearer the long axes of the tooth Improve stability Used when: Mesiodistal relationship of opposing teeth favor it. Full mouth/full arch reconstruction  REFERENCES Academy of Prosthodontics (2013): The glossary of prosthodontic terms, J. Prosthet. Dent. 1- Howat A.P, Capp N.J, Parrett N.V.J: A color atlas of occlusion and mal occlusion. Wolf publishing LTD, London, 1991 2- Dawson P. E: Functional occlusion from TMJ to smile design. Mosby Inc., St. Louis, 2007. 4. Ramfjord SP, Ash MM: Occlusion, ed 4, Philadelphia, 1983, WB Saunders. 5- Thomson H.: Occlusion in clinical practice, Bristol, London and Boston, Whright P.S.G. 1981. 6- Simpson G.W.: On Johnson's Modem Practice in Fixed prosthodontics, 4th. Ed, Philadelphia, Toronto, W.B. Saunders Co., 1986.