For a crescent rest, which option lists the correct dimensions: mesiodistal length, labiolingual width, and incisal-apical depth?

For a crescent rest, which option lists the correct dimensions: mesiodistal length, labiolingual width, and incisal-apical depth?

• A. 2.0-2.5 mm; 1.0 mm; 1.0 mm
• B. 3.0-3.5 mm; 2.0 mm; 2.0 mm
• C. 2.5-3 mm; 1.5 mm; 1.5 mm
• D. 4.0-4.5 mm; 1.0 mm; 0.5 mm

Answer: (C)

A crescent rest is sized to provide enough surface area for vertical support while preserving tooth structure and avoiding interference with neighboring teeth. The mesiodistal length should be about 2.5 to 3 mm, giving sufficient contact area without crossing into adjacent contacts. The labiolingual width is typically around 1.5 mm, providing enough thickness for strength without removing excess tooth structure. The incisal-apical depth, about 1.5 mm, ensures the rest seat seats properly and has adequate material thickness without approaching the pulp or creating a bulky restoration. Therefore, the combination of 2.5–3 mm for mesiodistal length, 1.5 mm for width, and 1.5 mm for depth best fits these requirements. Other options deviate from these practical ranges and could compromise retention or tooth health.

A crescent rest is sized to provide enough surface area for vertical support while preserving tooth structure and avoiding interference with neighboring teeth. The mesiodistal length should be about 2.5 to 3 mm, giving sufficient contact area without crossing into adjacent contacts. The labiolingual width is typically around 1.5 mm, providing enough thickness for strength without removing excess tooth structure. The incisal-apical depth, about 1.5 mm, ensures the rest seat seats properly and has adequate material thickness without approaching the pulp or creating a bulky restoration. Therefore, the combination of 2.5–3 mm for mesiodistal length, 1.5 mm for width, and 1.5 mm for depth best fits these requirements. Other options deviate from these practical ranges and could compromise retention or tooth health.