RESUMO

OBJECTIVE: To evaluate the effect of the labiolingual diameter and construction of an endodontically treated (ET) anterior tooth with crown restoration on stress distribution and biomechanical safety under occlusal loading. METHODOLOGY: Three-dimensional finite element models were generated for maxillary central incisors with all-ceramic crown restorations. The labiolingual diameters of the tooth, defined as the horizontal distance between the protrusion of the labial and lingual surfaces, were changed as follows: (D1) 6.85 mm, (D2) 6.35 mm, and (D3) 5.85 mm. The model was constructed as follows: (S0) vital pulp tooth; (S1) ET tooth; (S2) ET tooth with a 2 mm ferrule, restored with a fiber post and composite resin core; (S3) ET tooth without a ferrule, restored with a fiber post and composite resin core. A total of 12 models were developed. In total, two force loads (100 N) were applied to the crown's incisal edge and palatal surface at a 45° oblique angle to the longitudinal axis of the teeth. The Von Mises stress distribution and maximum stress of the models were analyzed. RESULTS: Regardless of the loading location, stress concentration and maximum stress (34.07~66.78MPa) in all models occurred in the labial cervical 1/3 of each root. Both labiolingual diameter and construction influenced the maximum stress of the residual tooth tissue, with the impact of the labiolingual diameter being greater. A reduction in labiolingual diameter led to increased maximum stress throughout the tooth. The ferrule reduced the maximum stress of the core of S2 models (7.15~10.69 MPa), which is lower compared with that of S3 models (19.45~43.67 MPa). CONCLUSION: The labiolingual diameter exerts a greater impact on the biomechanical characteristics of ET anterior teeth with crown restoration, surpassing the influence of the construction. The ferrule can reduce the maximum stress of the core and maintain the uniformity of stress distribution.

Assuntos

Resinas Compostas , Coroas , Análise do Estresse Dentário , Análise de Elementos Finitos , Incisivo , Dente não Vital , Dente não Vital/fisiopatologia , Humanos , Fenômenos Biomecânicos , Incisivo/anatomia & histologia , Incisivo/fisiologia , Resinas Compostas/química , Análise do Estresse Dentário/métodos , Técnica para Retentor Intrarradicular , Reprodutibilidade dos Testes , Estresse Mecânico , Valores de Referência , Força de Mordida , Imageamento Tridimensional/métodos , Planejamento de Prótese Dentária , Teste de Materiais , Coroa do Dente/anatomia & histologia , Coroa do Dente/fisiologia

RESUMO

PURPOSE: This study aimed to assess the impact of ypT stage and tumor regression grade (TRG) on the long-term prognosis of patients with locally advanced rectal cancer (LARC) stage ypT1-4N0 after neoadjuvant chemoradiotherapy (NCRT). METHODS: We retrospectively analyzed 585 patients with histologically diagnosed middle-low LARC (cT3-4 or cN + by pelvic MRI) from 2014 to 2019. All patients underwent NCRT, followed by total mesorectal excision. Disease-free survival (DFS) rates were compared among patients with different ypT stages and TRGs by Kaplan-Meier survival analysis. The chi-square test was used to analyze the relationship between clinicopathological or therapeutic factors and ypT stage. RESULTS: The median follow-up was 35.8 months (range 2.8-71.8 months). The 3-year DFS was 79.5%. A better 3-year DFS was achieved in patients with a pathologic complete response (94.0% vs. 74.3%, p < 0.001) and those in the ypT0-2 (86.5% vs. 66.6%, p < 0.001), ypN0 (85.0% vs. 60.2%, p < 0.001), and TRG0 + 1 (83.1% vs. 73.0%, p = 0.004) subgroups. A total of 309 patients (52.8%) achieved stage ypT1-4N0 after surgery. Among these patients, the ypT1-2N0 subgroup achieved a significantly higher 3-year DFS than the ypT3-4N0 subgroup (85.4% vs. 72.8%, p = 0.018); in contrast, the 3-year DFS did not significantly differ between the TRG1 and TRG2 + 3 subgroups (79.9% vs. 81.1%, p = 0.833). In the ypT1-2N0 or ypT3-4N0 subgroup, different TRG had no significant effect on failure patterns. CONCLUSIONS: For LARC patients with a ypT1-4N0 status after NCRT, ypT stage may be a more effective predictor of long-term prognosis than TRG.

Assuntos

Terapia Neoadjuvante , Neoplasias Retais , Humanos , Resultado do Tratamento , Estudos Retrospectivos , Estadiamento de Neoplasias , Quimiorradioterapia , Prognóstico , Neoplasias Retais/patologia

RESUMO

Abstract Objective To evaluate the effect of the labiolingual diameter and construction of an endodontically treated (ET) anterior tooth with crown restoration on stress distribution and biomechanical safety under occlusal loading. Methodology Three-dimensional finite element models were generated for maxillary central incisors with all-ceramic crown restorations. The labiolingual diameters of the tooth, defined as the horizontal distance between the protrusion of the labial and lingual surfaces, were changed as follows: (D1) 6.85 mm, (D2) 6.35 mm, and (D3) 5.85 mm. The model was constructed as follows: (S0) vital pulp tooth; (S1) ET tooth; (S2) ET tooth with a 2 mm ferrule, restored with a fiber post and composite resin core; (S3) ET tooth without a ferrule, restored with a fiber post and composite resin core. A total of 12 models were developed. In total, two force loads (100 N) were applied to the crown's incisal edge and palatal surface at a 45° oblique angle to the longitudinal axis of the teeth. The Von Mises stress distribution and maximum stress of the models were analyzed. Results Regardless of the loading location, stress concentration and maximum stress (34.07~66.78MPa) in all models occurred in the labial cervical 1/3 of each root. Both labiolingual diameter and construction influenced the maximum stress of the residual tooth tissue, with the impact of the labiolingual diameter being greater. A reduction in labiolingual diameter led to increased maximum stress throughout the tooth. The ferrule reduced the maximum stress of the core of S2 models (7.15~10.69 MPa), which is lower compared with that of S3 models (19.45~43.67 MPa). Conclusion The labiolingual diameter exerts a greater impact on the biomechanical characteristics of ET anterior teeth with crown restoration, surpassing the influence of the construction. The ferrule can reduce the maximum stress of the core and maintain the uniformity of stress distribution.