Objectives: Restoration of primary incisors presents a challenge to the clinician. Class III restorations have been studied extensively, leading to concerns relative to limited durability due to poor retention, tooth morphology, and limited primary enamel for bonding. The purpose of this investigation was to photoelastically analyze the load generating characteristics of two Class III preparations. Methods: Composite photoelastic models of a typical maxillary primary central incisor were fabricated using individual simulant materials for enamel, dentin, periodontal ligament, and alveolar bone. The models included either a standard Class III preparation or a facial dovetail modification. Cavity walls were prepared by air abrasion, cleansed, primed, and coated with unfilled resin. The model teeth were then restored utilizing hybrid composite resin (Herculite XRV). Five replications of each type of restored tooth were fabricated. Simulated masticatory forces were applied on the central portion of the incisal edge, the most mesial portion of the incisal edge, and the cingulum of each tooth. The resulting stress patterns were observed and recorded photographically in the field of a circular polariscope. Results: Comparison of modified and conventional preparations demonstrated higher stress concentrations with the conventional preparation. Force directed on the center of the incisal edge produced a more uniform stress distribution with the dovetail modification. Force directed on the mesial incisal angle caused a more even distribution of stresses on the modified preparation when viewed from the facial and mesial surfaces. Loading on the cingulum revealed similar force distribution patterns for the two preparation designs. Conclusions: A difference in stresses was observed between the restored model teeth. Even though additional tooth structure is removed, the modification made to the Class III aids in force distribution. This advantage may be clinically significant when restoring Class III primary incisor lesions especially with respect to loading on the mesial incisal edge.

Back to the Dental Materials: VIII - Others-Non-metallic Program
Back to the 81st General Session of the International Association for Dental Research (June 25-28, 2003)

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