# Class III, IV and V Preparations > Class III, IV and V cavity preparations for BDS Operative Dentistry — anterior access designs, incisal retention for Class IV and the crescent Class V box. - Canonical URL: https://prepelephant.com/topics/bds/operative-dentistry/class-iii-iv-v-preparations - 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: "Class III, IV and V Preparations", PrepElephant, https://prepelephant.com/topics/bds/operative-dentistry/class-iii-iv-v-preparations ## Direct answer Anterior teeth and cervical-third defects demand geometry that posterior occlusal cavities never need: visibility, aesthetics and thin labial enamel dictate the design. A Class III preparation (proximal surface of an anterior tooth, incisal edge intact) is approached from the lingual side wherever aesthetics matter, shaped as a small box with retention grooves in the axiolabial line angle since no dovetail is possible. A Class IV preparation adds the lost incisal angle, so retention must be engineered with incisal coves, retention grooves extending along the labial and lingual margins, or today simply a bonded composite with bevelled enamel. A Class V preparation is a crescent or kidney-shaped cavity in the gingival third, its axial wall about 1 mm deep and following the tooth's convexity, with retention grooves along the occlusoaxial and gingivoaxial line angles for amalgam or a bonded bevelled design for composite. ## What you must remember - **Class III access:** lingual approach preserves labial enamel and aesthetics; the facial approach gives better visibility and is chosen when the lesion is buccally placed or the tooth is severely rotated. - **Class III retention:** grooves or coves in the axiogingival and axiolabial line angles, plus slightly converging labial and lingual walls — adhesives have made most of this geometry optional. - **Class IV problem:** the missing incisal angle removes the natural lock, so traditional designs added an incisal retention groove or labial shoulder; modern composite manages it with wide enamel bevels that multiply the bonding surface. - **Class V shape:** crescent (kidney or bean) with the convexity towards the incisal; occlusal and gingival walls meet the axial wall at obtuse angles, and the axial wall curves with the tooth, keeping depth uniform. - **Class V retention for amalgam:** retentive grooves along the occlusoaxial and gingivoaxial line angles, since the walls converge too little to lock the restoration mechanically. - **Class V margins:** bevel the enamel margins when restoring with composite for blending; keep butt joints for amalgam; always finish subgingival margins with clean, trimmed gingival walls. - **Non-carious lesions:** wedge erosions and abrasive cervical lesions need restorations mainly for sensitivity or aesthetics, and adhesive materials suit them better than mechanically retained amalgam. ## One canine, three problems Consider a maxillary canine with a mesial contact lesion, a distal defect carrying away the distoincisal angle, and a wedge-shaped cervical abrasion — Classes III, IV and V in one exam favourite. The mesial Class III is opened palatally with a small round bur, keeping the labial enamel shell intact; the box is conservative, caries is lifted with a spoon excavator, and a palatal margin bevel lets composite restore the contact against a mylar strip. The distal Class IV cannot hide palatally: the angle is gone, so enamel margins around the defect are broadly bevelled with a flame diamond and composite is built in increments — palatal shelf first, then body, then labial layer, finished with strips and discs. The cervical Class V from aggressive horizontal brushing is cleaned, bevelled at the enamel edges, and restored with a flowable or microfilled composite in one increment — moisture control decides survival, via retraction, drying and a bent matrix strip. The trio teaches the central lesson: design serves access and retention only after aesthetics and the gingiva. ## Where candidates lose the mark Theory papers set this as "compare Class III, IV and V preparations" and expect the comparison axes — access, retention, margin design — rather than three descriptions in turn. The viva trap is the Class III approach: the textbook answer is "lingual, for aesthetics", and the prepared student can name when facial access wins — a buccally placed lesion, a rotated tooth, failing old restorations. For Class IV, examiners probe why retention is difficult and expect the words "incisal angle lost". For Class V, the favourite question is why the axial wall follows the tooth's convexity: a flat cut drives into the pulp at one end and leaves unsupported dentine at the other — an exposure waiting to happen. ## Frequently asked questions ### Why is the lingual approach preferred for Class III cavity preparation? It conserves labial enamel and keeps the restoration invisible from the front; facial approach is reserved for buccally placed lesions and unfavourable tooth alignment. ### How is retention achieved in a Class IV preparation? Traditionally through incisal retention grooves, coves and a labial shoulder; contemporary practice relies on bonded composite with broad enamel bevels. ### What shape and depth define a Class V cavity? A crescent-shaped cavity in the gingival third with an axial wall about 1 mm deep, curving to follow the convexity of the tooth surface. ### Which retentive features secure a Class V amalgam? Retentive grooves placed along the occlusoaxial and gingivoaxial line angles, because the cavity's walls provide little inherent undercut. ### When does a non-carious cervical lesion require restoration? When dentine is exposed causing sensitivity, the defect is aesthetically unacceptable, weakening the tooth, or progressing despite preventive counselling.