In vitro investigation on extensively destroyed vital teeth: is fracture force a limiting factor for direct restoration?

Abstract

To evaluate the in vitro fracture load of extensively damaged vital teeth after either direct or indirect restauration, severe tooth substance loss was simulated for 96 molars. Subsequently, two cavities were prepared with little (design 1) or more substantial (design 2) residual tooth support. All molars were provided with a 2-mm ferrule design and then divided into 12 test groups based on their occlusal surface size. They were restored with composite or with either of two types of single crown (cast metal or milled zirconia). After thermal ageing (10,000 cycles at 6.5 and 60 °C), 1.2 million cycles of chewing simulation were applied (64 N). Maximum fracture load was determined with a loading angle of 45°. Statistical analysis was performed by use of Kaplan-Meier modelling, Student's t-tests, one-way anova, post hoc Tukey's HSD tests and linear regression analysis. Regarding mean fracture load without ageing, the indirect restorations outperformed composite (design 1: direct: 508 ± 123 N, indirect: 741 ± 248 N; design 2: direct: 554 ± 167 N, indirect: 903 ± 221 N). After artificial ageing, however, these differences were no longer significant (design 1: direct: 328 ± 189 N, indirect: 506 ± 352 N; design 2: direct 399 ± 208 N, indirect 577 ± 292 N). Instead, the fracture load of the aged composite restorations was comparable with that for zirconia (design 1) and cast metal (design 2) crowns. Fracture loads of direct composite restorations after artificial ageing might fulfil clinical requirements.

Stress Distribution, Tooth Remaining Strain, and Fracture Resistance of Endodontically Treated Molars Restored Without or With One or Two Fiberglass Posts And Direct Composite Resin

“…37 In this investigation, a force of 100 N was chosen to simulate the effect of chewing on TrSt and for the stress analysis because physiological biting forces during eating were found to be between 20 and 160 N. 37,38 The periodontal ligament simulation using elastomeric material and embedding of the root inside the polystyrene resin cylinder, which has a similar elastic modulus to bone tissue, offered more similarities to the oral environment than to the in vitro experiment. 37,38 The combination of using destructive and nondestructive methods on the same specimen, such as the strain gauge method, the fracture resistance, and fracture mode analysis, permits the sequential understanding of failure. 28,39 Measuring strain before fracture may contribute to a better understanding of the entire fracture process, from initiation to ultimate rupture.…”

Finite element analysis of stress distribution in four different endodontic post systems in a model canine

“…The elastic properties of the materials [14] are shown in Table 1. A force of 100 N was applied 3 mm below the incisal edge of the crown at a 45° angle [15]. The maximum von Mises stresses were calculated under different conditions and in different regions.…”

Efeito do número de pinos de fibra de vidro na resistência à fratura, deformação estrutural e distribuição de tensão em molares tratados endodonticamente

“…Supondo que ocorrem de 240.000 a 250.000 por ano de contatos oclusais, 1,2 milhões de ciclos é equivalente a simulação mastigatória de 5 anos (Schwindling et al, 2014), fator importante para um experimento in vitro. Nesta investigação, a força de 100 N foi escolhida para simular o processo de mastigação durante análise de deformação e tensão, devido a magnitude das forças mastigatórias fisiológicas terem sido mensuradas entre 20 e 160 N (De Boever et al 1978;Schwindling et al 2014).…”

“…Supondo que ocorrem de 240.000 a 250.000 por ano de contatos oclusais, 1,2 milhões de ciclos é equivalente a simulação mastigatória de 5 anos (Schwindling et al, 2014), fator importante para um experimento in vitro. Nesta investigação, a força de 100 N foi escolhida para simular o processo de mastigação durante análise de deformação e tensão, devido a magnitude das forças mastigatórias fisiológicas terem sido mensuradas entre 20 e 160 N (De Boever et al 1978;Schwindling et al 2014). O ligamento periodontal com material elastomérico envolvendo a raiz em um cilindro de resina de poliestireno com módulo de elasticidade próximo ao do tecido ósseo determina mais semelhança entre o experimento in vitro e o ambiente oral (Soares et al, 2005;Schwindling et al 2014).…”

“…Nesta investigação, a força de 100 N foi escolhida para simular o processo de mastigação durante análise de deformação e tensão, devido a magnitude das forças mastigatórias fisiológicas terem sido mensuradas entre 20 e 160 N (De Boever et al 1978;Schwindling et al 2014). O ligamento periodontal com material elastomérico envolvendo a raiz em um cilindro de resina de poliestireno com módulo de elasticidade próximo ao do tecido ósseo determina mais semelhança entre o experimento in vitro e o ambiente oral (Soares et al, 2005;Schwindling et al 2014). A ponta aplicadora contatando a maior área da superfície oclusal para distribuir homogeneamente os contatos, proporciona maior abrangência do esforço aplicado sobre o conjunto restaurado .…”