Effect of handpiece light and material used in pulp chamber on dentin removal during root canal retreatment

Abstract This study evaluated the effect of the use of glass ionomer cement (GIC) and flowable bulk-fill resin composite (BFRC) for filling pulp chambers and the type of high-speed handpiece light used on dentin removal during access preparation for endodontic retreatment in molar teeth. Twenty maxillary molars were treated endodontically. BFRC (Opus Bulk Fill Flow APS, FGM) was used to fill the pulp chamber and replace coronal dentin (n = 10). In the remaining teeth, the pulp chamber was filled with GIC (Maxion R, FGM). Conventional resin composite (Opallis, FGM) was used to restore the enamel layer in all teeth. The samples in each group were divided into two subgroups, and the root canals were reaccessed using a handpiece with white or ultraviolet light. The teeth were scanned using micro-CT before and after root canal reaccess. The dentin volume removed was calculated and analyzed using 2-way analysis of variance and Tukey's test (α = 0.05). The crown and pulp chamber locations with dentin removal are described using frequency distribution. During the access, fewer pulp chamber walls were affected and a lower volume of dentin was removed from the pulpal floor in the group restored with GIC than in the group restored with BFRC. No effect was observed on the coronal dentin walls with respect to the filling protocols and type of light used. For dentin removal from the pulp chamber, handpieces with white light performed better than those with ultraviolet light, irrespective of the filling protocol used. The use of GIC to fill the pulp chamber and use of white handpiece light reduced dentin removal from the pulpal floor and resulted in fewer affected dentin walls.

Resumo Este estudo avaliou os efeitos do cimento de ionômero de vidro (GIC) e da resina composta fluida bulk fill (BFRC) usados como preenchimento da câmara pulpar; e o tipo de iluminação das turbinas de alta rotação na remoção dentinária após cavidades de acesso para retratamento endodôntico em dentes molares. Vinte molares superiores foram tratados endodonticamente. Dez dentes foram restaurados usando BFRC (Opus Bulk Fill Flow APS, FGM) para preencher a câmara pulpar e dentina coronária; e resina composta convencional (Opallis, FGM) para restaurar a camada de esmalte. Os outros dentes foram restaurados usando GIC (Maxion R, FGM) para preencher a câmara pulpar e resina composta (Opallis, FGM). As amostras foram divididas em dois grupos e os canais radiculares foram novamente acessados com turbina de alta-rotação com iluminação branca ou ultravioleta. Os dentes foram escaneados usando micro-CT antes e após o novo acesso ao canal radicular. O volume de dentina removida foi calculado e os dados foram analisados por ANOVA bidirecional e teste de Tukey (α=0,05). As regiões na coroa e na câmara pulpar que apresentaram dentina removida no acesso dos canais foram descritas por meio de distribuição por frequência. A reabertura do canal radicular com GIC resultou em menos paredes afetadas da câmara pulpar e menor volume de dentina removida no assoalho. Nenhum efeito foi observado nas paredes de dentina coronária considerando aos protocolos de preenchimento. A turbina de alta rotação com iluminação branca reduziu a remoção de dentina da câmara pulpar, independentemente do protocolo de restauração utilizado. O uso de turbina de alta rotação com iluminação branca e GIC para preencher a câmara pulpar reduziram a remoção de dentina do assoalho e afetaram menos paredes dentinárias.

Direct resin composite restoration of endodontically-treated permanent molars in adolescents: bite force and patient-specific finite element analysis

Abstract Objective To evaluate the influence of three levels of dental structure loss on stress distribution and bite load in root canal-treated young molar teeth that were filled with bulk-fill resin composite, using finite element analysis (FEA) to predict clinical failure. Methodology Three first mandibular molars with extensive caries lesions were selected in teenager patients. The habitual occlusion bite force was measured using gnathodynamometer before and after endodontic/restoration procedures. The recorded bite forces were used as input for patient-specific FEA models, generated from cone-beam computed tomographic (CT) scans of the teeth before and after treatment. Loads were simulated using the contact loading of the antagonist molars selected based on the CT scans and clinical evaluation. Pre and post treatment bite forces (N) in the 3 patients were 30.1/136.6, 34.3/133.4, and 47.9/124.1. Results Bite force increased 260% (from 36.7±11.6 to 131.9±17.8 N) after endodontic and direct restoration. Before endodontic intervention, the stress concentration was located in coronal tooth structure; after rehabilitation, the stresses were located in root dentin, regardless of the level of tooth structure loss. The bite force used on molar teeth after pulp removal during endodontic treatment resulted in high stress concentrations in weakened tooth areas and at the furcation. Conclusion Extensive caries negatively affected the bite force. After pulp removal and endodontic treatment, stress and strain concentrations were higher in the weakened dental structure. Root canal treatment associated with direct resin composite restorative procedure could restore the stress-strain conditions in permanent young molar teeth.