An in vitro study of dentin exposure during resin-bonded fixed partial denture preparation

Objectives: The aim of this in vitro study was to investigate whether dentin is exposed during tooth preparation for resin-bonded fixed partial dentures and, if so, to quantify the amount of dentin exposure. Method and materials: Twenty extracted premolars were prepared in the following manner: The palatolingual and proximal axial surfaces were reduced by 0.50 mm. Mesial and distal grooves, 1.00 mm in depth, and mesial and distal occlusal rest seats, measuring 2.00 mm buccolingually × 1.50 mm mesiodistally × 1.00 mm deep, were prepared. The specimens were stained with a modified van Gieson's stain to identify dentin exposure, mounted on a jig to allow standardization, and photographed after 30-degree rotation to create a panoramic image of each tooth. The image was modified and analyzed to measure the percentage of the preparation area that exhibited dentin exposure. Results: Dentin exposure was noted in all specimens. The mean area of dentin exposure was 11.06 mm² (16.15% of the preparation area). The minimum and maximum areas of dentin exposure were 4.07 mm² (7.03%) and 19.73 mm2 (27.28%), respectively. Conclusion: Dentin is exposed during resin-bonded fixed partial denture preparation if current tooth preparation guidelines are followed, despite the commonly made recommendation that the preparation remain within enamel. The region of the grooves consistently exhibited exposed dentin; exposure at the cervical margin was variable.