# Dental Anatomy and Occlusion Basics > Dental anatomy and occlusion for BDS Operative Dentistry — contacts, contour, embrasures, cusp function, curves of occlusion and Angle classes. - Canonical URL: https://prepelephant.com/topics/bds/operative-dentistry/dental-anatomy-occlusion-basics - Exam / course: BDS · Subject: Operative Dentistry - Publisher: PrepElephant (https://prepelephant.com) — Prepared and reviewed by the PrepElephant Academic Review Team - First published: 2026-10-02 - Last updated: 2026-10-02 - How to cite: "Dental Anatomy and Occlusion Basics", PrepElephant, https://prepelephant.com/topics/bds/operative-dentistry/dental-anatomy-occlusion-basics ## Direct answer A restoration succeeds or fails against the anatomy it has to replace: contact areas that prevent food impaction, embrasures that let food spill away, contour that protects the gingiva, and cusps that mesh with the opponents in a stable occlusion. A normal dentition shows an Angle Class I molar relationship, an overjet of roughly 2–3 mm, a slight overbite, and posterior contacts distributed so that the mandibular buccal and maxillary palatal cusps — the supporting cusps — seat into opposing fossae while guiding cusps shear food. Restorations that ignore these details produce overhangs, food trapping, gingivitis and fractured margins, however excellent the material. ## What you must remember - Contact areas: anterior teeth touch in the incisal third; posterior contacts lie in the middle third close to its junction with the occlusal third, slightly buccal to a line drawn through the central fossae. - Height of contour is most convex in the cervical third of facial surfaces; on the lingual side it sits in the cervical third of anteriors but the middle third of posteriors — under-contouring invites impaction and gingivitis, over-contouring shelters plaque. - Embrasures are the V-shaped spillway spaces (occlusal, facial, lingual, gingival) around each contact; the lingual embrasure of posterior teeth is wider because the contact sits buccal, deflecting food towards the tongue. - Supporting or "stamp" cusps are the mandibular buccal and maxillary palatal cusps; guiding or "shear" cusps are the maxillary buccal and mandibular lingual cusps. - Curve of Spee is the anteroposterior curve through the cusp tips; Curve of Wilson is the transverse curve across molar cusps, tilted because mandibular lingual cusps ride higher; together they generate the compensating sphere of Monson and distribute load. - Bonwill's triangle joins the two condyles and the mandibular incisor contact point as an equilateral triangle with 4-inch (10 cm) sides — a favourite short viva question. - Centric occlusion (maximum intercuspation) is a tooth relationship; centric relation is the condyle position with the heads most superior and anterior against the eminence — restorations must be stable in both. - Pulp horns project beneath each cusp and are tallest in young teeth, which limits safe preparation depth near cusps in adolescents. ## How anatomy dictates a Class II restoration Suppose you have just condensed the amalgam in a distal occlusal cavity of a mandibular first molar. The matrix band was wedged from the wider lingual embrasure, pulling it tight against the gingival margin. Now carve deliberately: drop the marginal ridge to the same height as the neighbouring tooth, keep it continuous mesiodistally, and re-create the occlusal embrasure so the ridges do not form a flat plateau. Proximal to the contact, the surface should be slightly concave gingivally — a dead-flat proximal wall is a food impaction machine. Finally, check the restoration in centric occlusion and in excursive movements with articulating paper: because the mandibular buccal cusp is a supporting cusp, a fraction of a millimetre of error there registers as premature contact, so those inclines are checked first. Floss should snap through the contact with slight resistance and emerge clean. ## Where students slip The recurring viva trap is mixing up supporting and guiding cusps. Examiners frame it as a treatment question: "You have just placed a high spot on the maxillary buccal cusp of a first molar — what does the patient feel?" The answer is that a maxillary buccal cusp is a guiding cusp, so it loads mainly in excursive movement and the patient complains of pain on chewing sideways, not on closure. The mirror-image error occurs clinically when students check only centric occlusion after placing a large restoration and send the patient home with an unbalanced lateral guidance. A second slip is equating centric relation with centric occlusion in written answers — one is a jaw relationship defined by the condyles, the other by the teeth, and only a phrase such as "CO equals MI in most natural dentitions" earns the mark. ## Frequently asked questions ### Where is the proximal contact area of a mandibular first molar? In the middle third close to the junction with the occlusal third, positioned slightly buccal to the line of the central fossa — which is why the lingual embrasure is the larger one. ### Which cusps are the supporting cusps? The mandibular buccal cusps and the maxillary palatal cusps; they stamp into the opposing central fossae and carry occlusal load. ### What do the curves of Spee and Wilson achieve? Together with the sphere of Monson they create a curved occlusal plane that keeps tooth contact balanced during mandibular movement and distributes masticatory forces across the arch. ### Why does a broad, flat proximal contact cause food impaction? Food needs defined spillway embrasures around a firm, point contact; a flat wide contact with no embrature traps food against the gingiva, exactly the situation Black's extension for prevention was designed to avoid. ### How is centric occlusion different from centric relation? Centric occlusion is maximum intercuspation of teeth; centric relation is the most superior and anterior condylar position against the articular eminence with the disc in place, independent of tooth contact.