Dental Arches and Occlusion

Flashcards about dental arches and occlusion.

Centric occlusion of permanent teeth

The relation of the upper and lower teeth when they are in maximal intercuspation and the condyles are resting in the most unstrained retrusive position in the glenoid fossa.

Centric Occlusion Tooth Contact

Each tooth occludes with two opposing teeth except lower central incisors and upper third molars, preserving normal occlusion after tooth loss.

Key of Occlusion

The permanent upper and lower first molars.

First Molars Eruption

They are the first permanent teeth erupted in the oral cavity.

First Molars Size

The upper 6 is the largest tooth buccolingually, while lower 6 is the largest mesiodistally.

Distobuccal Cusps of Upper Molars

Upper first and second molars: Distobuccal cusps are free from occlusion, triangular ridges in buccal embrasures between lower 6 & 7 and 7 & 8 respectively. Upper third molar: Distobuccal cusp is free, triangular ridge strikes the distal slope of the distobuccal cusp of lower 8.

Mesiolingual Cusps of Upper Molars

First, second and third molars: Mesiolingual cusps rest in the central fossae of lower 6, 7 and 8 respectively.

Distolingual Cusps of Upper Molars

Upper first molar: Distolingual cusp strikes the mesial marginal ridge of lower 7. Second & Third molars: Distolingual cusps strike the distal marginal ridges of lower 7 and 8 respectively.

Mesiobuccal Cusps of Lower Molars

First molar: Mesiobuccal cusp strikes the distal marginal ridge of upper 5 and mesial marginal ridge of upper 6. Second molar: Mesiobuccal cusp strikes the distal marginal ridges of upper 6 and mesial marginal ridge of upper 7. Third molar: Mesiobuccal cusp is located in the mesial triangular fossa of upper 8.

Distobuccal Cusps of Lower Molars

First, second and third molars: Distobuccal cusps rest in the central fossae of upper 6, 7 and 8 respectively. First molar: Distal cusp rests in the distal triangular fossa of upper 6.

Mesiolingual Cusps of Lower Molars

First, second & third molars: Mesiolingual cusps are free from occlusion and are located at the embrasures between upper 5&6, between upper 6&7 and between upper 7&8 respectively.

Distolingual Cusps of Lower Molars

First, second & third molars: Distolingual cusps are free from occlusion and their triangular ridges are located at the lingual developmental grooves of upper 6, 7 and 8 respectively.

Centric Occlusion of Incisors

Incisal edges of upper incisors are free from occlusion, covering the incisal third of opposing teeth. Incisal edges of lower incisors strike the opposing teeth at the junction of the incisal and middle thirds on the lingual surfaces.

Centric Occlusion of Upper Central Incisor

Incisal edge is free from contact and has labial relation to the incisal thirds of lower 1 and lower 2 (mesial half). Cingulum is free and above the lingual embrasure between lower 1&2. Mesial outline is in line with the mesial outline of lower 1. Distal outline is centered above the labial surface of lower 2.

Centric Occlusion of Upper Lateral Incisor

Incisal edge is free from occlusion and has labial relation to the incisal thirds of lower 2 (distal half) and lower 3 (mesial half). Cingulum is free and above the lingual embrasure between lower 2&3. Mesial outline is centered above the labial surface of lower 2. Distal outline is centered above the labial ridge of lower 3.

Centric Occlusion of Posterior Teeth

Upper posterior teeth are slightly distal to the lower teeth. Buccal cusps of the upper teeth are free from contact, triangular ridges lie in buccal relation to those of the lower teeth. Lingual cusps of the upper teeth strike the occlusal surfaces of lower teeth. Buccal cusps of the lower teeth strike the occlusal surfaces of upper teeth. Lingual cusps of the lower teeth are free and lingual to the upper teeth.

Buccal Cusps of Upper Premolars

First premolar: Buccal cusp is free from contact, triangular ridge is located in the buccal embrasure between lower 4 and 5. Second premolar: Buccal cusp is free from contact, triangular ridge is located in buccal embrasure between lower 5 and 6.

Lingual Cusps of Upper Premolars

First premolar: Lingual cusp strikes the distal marginal ridge of lower 4. Second premolar: Lingual cusp strikes the distal triangular fossa of the 2 cusp type lower 5 or the distal slope of the distolingual cusp of 3 cusp type lower 5.

Outlines of Upper Premolars

First premolar: Mesial outline is in line with the buccal cusp of lower 4, for upper second premolar it is in line with the buccal cusp of lower 5. First premolar: Distal outline is in line with the buccal cusp of lower 5, for upper second premolar it is in line with the mesiobuccal cusp tip of lower 6.

Anterior Masticatory Cycle

Mandible moves downward from centric occlusion to separate teeth, then forward, anterior teeth are in anterior relation by 1-2mm. Incisal ridges of lower incisors (contact with lingual incisal thirds of upper incisors) show tip to tip incisal edges, slight depression/protrusion of mandible, posterior teeth show anterior relation. Also known as masticatory cycle of anterior teeth.

Lateral Sides Occlusal Relation (Posterior Masticatory Cycle)

Mandibular dental arch is in a right or left lateral relation to centric occlusion with maxillary teeth. Working side: buccal cusps of maxillary and mandibular teeth in contact. Balancing side: contact of lingual cusps of maxillary teeth with the buccal cusps of mandibular teeth. Both sides move to centric occlusion, alterations performed by depression of the mandible and side movement. Also known as masticatory cycle of posterior teeth.