Preclinics of Conservative Dental Medicine · MU Sofia
15. Class three cavity preparations – proximo-buccal and proximo-bucco-lingual configuration.
Covers labially approached Class III cavities on incisors and canines, starting with when a labial route is preferred over the default lingual one. It compares the proximo-buccal and proximo-bucco-lingual (through-and-through) configurations in a table, then walks through preparation step by step, from shade choice and isolation to axial wall depth, retention, bevel and finishing. It closes with aesthetic points, common mistakes and a key-points summary.
Topic 15 of 53 in the MU Sofia syllabus for Preclinics of Conservative Dental Medicine (Dental Medicine, Year 3). The free AceMed note covers it in 7 sections, about 856 words (7 min of reading), with 17 flashcards.
In this note
Introduction
When the labial approach is indicated
The two configurations
Preparation step by step
Esthetic considerations
Main mistakes
Key points
Introduction
Class III cavities lie on the proximal surfaces of incisors and canines without involving the incisal angle. This topic covers the two configurations opened from the labial side: the proximo-buccal cavity (proximo-labial or proximo-vestibular; on anterior teeth “buccal” means the labial surface) and the proximo-bucco-lingual or through-and-through cavity. Their margins are visible, so the outline, the bevel and the shade decide whether the composite restoration looks natural.
When the labial approach is indicated
The lingual approach (topic 14) is the default for Class III: it keeps the labial enamel and hides the margin. A labial approach is chosen only when the lesion or the position of the tooth makes it the more conservative route.
Caries lies labially or has already spread onto the labial surface, so lingual access would sacrifice sound tooth.
The labial wall is already broken, cavitated or chalky.
Crowded or rotated teeth, where the proximal surface faces labially or the lingual side cannot be reached.
A faulty restoration placed from the labial is being replaced.
The price: a visible margin, critical shade matching and more labial enamel lost.
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