Occlusion PDF

OCCLUSION  What is occlusion? Is contacting of occlusal and incising surfaces of opposing maxillary and mandibular teeth. Ideal occlusion- the harmonious static and dynamic relationship of teeth and jaws. Stable occlusion - do not have too much force on any particular teeth,...

OCCLUSION  What is occlusion? Is contacting of occlusal and incising surfaces of opposing maxillary and mandibular teeth. Ideal occlusion- the harmonious static and dynamic relationship of teeth and jaws. Stable occlusion - do not have too much force on any particular teeth, which could damage the teeth in the short or long term.  Importance Good general and dental health Mastication Ability to speak Esthetics Allows better differential diagnosis in complicated cases.  Determinants of occlusion Posterior determinant TMJ-inclination of the articular eminence, morphology of the medial wall of the glenoid fossa and the shape of the condyle) Anterior determinant Teeth Overall neuro-masticatory system Angle’s Classification of Occlusion Class 1 Class II – Division I - Division II Class III  Class I- Skeletal Relationship Straight facial profile. Aka orthognathic or mesognathic profile  Molar Relationship Where the mesiobuccal cusp of the maxillary first molar is aligned directly over the mesiobuccal groove on the mandibular first molar. Incisor relationship Incisal edges of maxillary teeth are labial to the incisal edges of the mandibular teeth. Incisal margins of the mandibular incisors occlude with or directly lie below the palatal surfaces of the maxillary incisors (ie. On the cingulum plateau) Normal horizontal alignment Normal vertical alignme  Class II- Skeletal Relationship Small mandible, large maxilla, or both. Convex facial profile. Retrognathic Molar Relationship Mandibular teeth are distal to their normal maxillary teeth. Maxillary teeth occludes at least half a cusp more mesial to the mandibular first permanent molar. Incisor Relationship Abnormally large overlap of maxillary incisors over mandibular. Incisal margins of the mandibilar incisors lie behind the cingulum plateau on the palatal surfaces of the maxillary incisors. Div I- Maxillary incisors have a labial inclination (proclined) Div II- Maxillary incisors have lingual inclination (retroclined)  Class III- Skeletal Relationship Large mandible to maxillae. Concave facial profile. Prognathic. Molar Relationship Mandibular molars are mesial to the class I relationship. Maxillary first permanent molars occludes at least half a cusp more distal to the mandibular first permanent molars than the standard anatomical position. Incisor Relationship Lower anterior incisors are in edge to edge or labial to upper anteriors. Incisal margins of the mandibular incisors lie in front of the maxillary incisors.  Terms related to Malocclusion Infraocclusion (or infraversion) - if a tooth is abnormally short relative to the rest of the occlusal plane.  Posterior crossbite With mandibular molars totally to the lingual of the maxillary molars. Common in persons with class ii malocclusion. Posterior Crossbite(Reverse articulation) mandibular molars too buccal or maxillary molars placed too lingual. Common in persons with class iii malocclusion Anterior crossbite When mandibular anterior teeth are facial to maxillary anterior teeth. Overbite This is when the maxillary incisors are completely overlapping (covering up) the mandibular incisors Overjet where the maxillary incisors are considerably anterior to the mandibular incisors. Premature contact A condition of teeth contacts that diverts the mandible from a normal path of closure to centric jaw relation.  Jaw Relationships Is also known as the maxillomandibular relationship. Refers to the position of the mandible relative to the maxillae. Can be described as a tooth-to-tooth relationship between maxillary and mandibular teeth. Can be described as bone-to-bone relationship between the maxillae and mandible. A. Maximal Intercuspal position (MIP) It is the tightest or best fit between maxillary and mandibular posterior teeth This can also be called maximal intercuspation. Is a tooth-to tooth relationship.  B. Centric relation (Retruded contact position) Is an important reproducible and repeatable relationship of the mandible to the maxillae. This jaw relationship is not affected by the presence (or absence) of teeth. Mandible closes with both condyles remaining in rear- most, upper most and mid most (rum). SLIDE = Movement from CR to CO  C. Physiologic Rest Position Occlusal vertical dimension- refers to the distance between a selected point on the mandible and a selected point on the maxillae. Resting vertical dimension- is the position of the mandible when all of its supporting muscles are in their resting posture. Freeway space- space between the occlusal surfaces of the maxillary and mandibular teeth. [RVD-OVD=FWS] D. Jaw relationships during horizontal movements of the mandible 1. Protrusive jaw relation and occlusion 2. Lateral mandibular relation and occlusion Canine-protected articulation Group function  1. Protrusive jaw relation Occurs when the mandible moves anteriorly. Both mandibular condyles and discs move forward together in their articular fossa- downwards and forwards. Incisal guidance (anterior guidance or anterior protected occlusion)- the incisal edges of the mandibular anterior teeth glide against the lingual surfaces of the maxillary anterior teeth. Causes disocclusion of the posterior teeth. Retrusion (retraction)- when the mandible moves posteriorly toward its maximum intercuspal position. 2. Lateral mandibular relation Movement of mandible to the right or left Working side is the side toward which the mandible moves during lateral excursion. Opposite side is called the nonworking side. Bennett’s movement- The condyle on the working side does not move much; it rotates on its vertical axis and moves laterally only about 1 to 2 mm. Canine-protected articulation vertical overlap of the maxillary and mandibular canines produces a disocclusion (separation) of all of the posterior teeth when the mandible moves to either side. Interferences- refer to the tooth contacts on the nonworking side. Group function (or unilateral balanced occlusion) is an occlusal relationship in which multiple teeth on a working side contact evenly as the jaw is moved toward that side. Bilateral Balanced Occlusion Occurs when all posterior teeth contact on the working side and one or more teeth on the balancing side contact simultaneously. Produced in complete dentures as it helps to prevent the dentures from tipping and coming loose. Potentially bad for a patient with natural teeth to have any contact on the non working side. Occlusal curvatures Do not conform to a flat plane Curve of Spee – when viewed from the lateral aspect the incisal and cusp edges follow a curve which curves upwards from anterior to posterior. Occlusal curvatures Monsons (Wilsons) curve – when viewed from the coronal plane there is a curve in the posterior region which is concave and the cusps of the right and left side teeth lie on this curve Advantages of occlusal curvatures 1. Allow tooth contact 2. Withstand masticatory forces 3. Occlusal Harmony 4. Self adaptation of teeth to occlusal curvatures allows for axial loading which enhances stability in the dental arches. Reference Scheid R.C & Weiss G. (2012). Woelfel’s Dental Anatomy (8th Ed.), Chapter 1.