RESUMO
STATEMENT OF PROBLEM: Customized glass fiber posts using CAD-CAM technology have been suggested for restoring endodontically treated teeth. However, how weakened or non-weakened roots restored with anatomical CAD-CAM posts behave under cyclic fatigue is not clear. OBJECTIVE: To evaluate the load-bearing capacity under fatigue (fatigue failure load [FFL], the number of cycles for failure [CFF], and survival probabilities) and fracture pattern of weakened and non-weakened roots restored with CAD-CAM fiber post and cores, metal cast-post-core, and prefabricated fiber post and resin core. METHODS AND MATERIALS: A total of 60 crack-free bovine incisor roots (13 mm in length) with standard geometry were obtained and randomly allocated considering the factor "root condition" in two levels (weakened and non-weakened). Thus, half of the roots were weakened to obtain a wall thickness of 0.5 mm. After that, the endodontic treatment was executed, all roots embedded with acrylic resin and the specimens randomly allocated (n=10) considering the factor "post system" in three levels (CAD-CAM: CAD-CAM milled glass-fiber post and core; MBC: metallic-based post and core; and FRC: prefabricated glass-fiber post and composite resin core). The posts were luted with a dual-cure self-adhesive luting agent. Then, all teeth received a metallic crown. An initial load of 100 N at 20 Hz for 5000 cycles was applied for the step-stress fatigue test, followed by incremental steps of 50 N for 20,000 cycles each step, up to failure. A fracture pattern analysis was performed. RESULTS: CAD-CAM fiber post (FFL: 865 N; CFF: 311,000 cycles) presented similar fatigue performance (p>0.05) to FRC (FFL: 925 N; CFF: 335,000 cycles), with 100% of repairable fractures for non-weakened roots; however, both groups presented worse performance than MBC (p<0.05; FFL: 1265 N; CFF: 471,000 cycles) which led to 100% of catastrophic failures. No statistical difference was found in fatigue performance among the three systems for weakened roots (p>0.05; FFL: 1035-1170 N; CFF: 379,000-433,000 cycles), with a high rate of catastrophic failures. CONCLUSIONS: CAD-CAM fiber post presented similar fatigue performance to MBC and FRC approaches when restoring weakened roots. CADCAM was similar to FRC when restoring non-weakened roots, while MBC enhanced fatigue properties in this scenario.
Assuntos
Técnica para Retentor Intrarradicular , Fraturas dos Dentes , Dente não Vital , Animais , Bovinos , Cerâmica , Resinas Compostas/uso terapêutico , Desenho Assistido por Computador , Análise do Estresse Dentário , Vidro , Teste de Materiais , Propriedades de Superfície , Dente não Vital/terapia , Estudos Cross-OverRESUMO
AIM: To compare stress distribution between a fractured maxillary central incisor restored with direct composite resin only (CR) or associated with different post materials, using finite element analysis. METHODOLOGY: A three-dimensional model of a sound maxillary central incisor and supporting structures was constructed, using data from the dental literature. Changes were made in the crown region to create a tooth with a restored crown fracture. A composite resin restoration only and restorations associated with different tapered post systems (glass fibre, carbon fibre, titanium and zirconia ceramic) were also evaluated, resulting in six experimental models. A static chewing pressure of 2.16Nmm(-2) was applied to two areas of the palatal surface of the tooth. Stress distribution was analysed under a general condition and in the structures of the models separately. RESULTS: The maximum stresses were concentrated as follows: at the cemento-enamel junction in the model with a sound maxillary central incisor, restored with CR and with a composite resin restoration associated with fibre posts; in the enamel at the post-enamel interface on the palatal surface of the model with a titanium post; and in the post of the model with zirconia ceramic post. CONCLUSIONS: None of the restorations evaluated was able to recover the stress distribution of the sound tooth. The models restored with composite resin associated with a glass or carbon fibre post had similar stress distributions to that of the model restored with CR. The different post materials were shown to have a substantial influence on stress distribution, with less stress concentration when fibre posts were used.
Assuntos
Resinas Compostas/uso terapêutico , Restauração Dentária Permanente/métodos , Incisivo/lesões , Técnica para Retentor Intrarradicular/instrumentação , Fraturas dos Dentes/terapia , Fenômenos Biomecânicos , Carbono , Fibra de Carbono , Porcelana Dentária , Planejamento de Prótese Dentária , Falha de Restauração Dentária , Análise do Estresse Dentário , Análise de Elementos Finitos , Vidro , Humanos , Maxila , Titânio , Dente não Vital , ZircônioRESUMO
The current study evaluated the influence of two endodontic post systems and the elastic modulus and film thickness of resin cement on stress distribution in a maxillary central incisor (MCI) restored with direct resin composite using finite element analysis (FEA). A three-dimensional model of an MCI with a coronary fracture and supporting structures was performed. A static chewing pressure of 2.16 N/mm2 was applied to two areas on the palatal surface of the composite restoration. Zirconia ceramic (ZC) and glass fiber (GF) posts were considered. The stress distribution was analyzed in the post, dentin and cement layer when ZC and GF posts were fixed to the root canals using resin cements of different elastic moduli (7.0 and 18.6 GPa) and different layer thicknesses (70 and 200 microm). The different post materials presented a significant influence on stress distribution with lesser stress concentration when using the GF post. The higher elastic modulus cement created higher stress levels within itself. The cement thicknesses did not present significant changes.