Remaining Dentin Thickness of Teeth after Metal-Ceramic Crown Preparation

Objectives: To compare the remaining dentine thickness (RDT) between well-aligned and rotated maxillary central incisors and first premolars after metal-ceramic crown preparation. To identify areas of thin dentine after crown preparation. Methods: Twenty each of freshly extracted sound human maxillary central incisors (MD=8.70±0.26mm, LP=7.18±0.47mm) and first premolars (MD=7.73±0.12mm, BP=9.93±0.30mm) were randomly selected and mounted with their adjacent in good alignment for one group and at 45º mesio-buccal rotation for another group (n=10). Metal-ceramic crown preparation was carried out by a single operator. Rotated teeth were prepared to correct its malalignment with final restoration. The teeth were sectioned transversely at various levels of the crowns and RDT was measured. Areas of thinnest dentin were identified and data analyzed using Student's t-test. Results: The RDT was significantly less on the palatal and mesial of mid-incisal portion and on labial and mesial of the mid-cervical portion for the rotated than the well-aligned central incisors. The RDT was significantly less on the mesio-buccal of the occlusal portion and on the mesio-buccal and mesio-palatal of the middle portion for the rotated than the well-aligned premolars (p<0.05). The thinnest area among all the specimens studied was the mesial aspect of the mid-incisal portion of the rotated maxillary central incisors (0.30 ± 0.15mm). RDT of the premolars exceeded 1.00mm. Conclusions: The thin areas with high risk of pulpal exposure is the mesio-buccal aspects of well-aligned central incisors at incisal third of prepared crown. With correction of alignment in preparing rotated incisors, there is increased risk of pulpal exposure at mesial aspect of incisal third and mid-crown levels. The thinnest RDT is at the mesial aspect of incisal third of rotated central incisors. There is less risk of pulpal injury to well-aligned or rotated premolars.