Evaluation of Stress Distribution in Endodontically Weakened Teeth Restored with Different Crown Materials: 3D-FEA Analysis

Abstract This study evaluated the stress distribution in endodontically treated teeth, weakened (W) or not weakened (NW), restored with different materials of prosthetic crown using 3D-FEA. Models of a maxillary canine were constructed based on micro-CT images and divided into the groups: G1 (control) - sound tooth; G2 to G7 - endodontically treated teeth restored with glass fiber post (GFP); which G2 to G4 simulated NW root and G5 to G7 simulated W root. For crown material the teeth were restored with: G2 and G5: metallic coping and ceramic veneering, G3 and G6: zirconia coping and ceramic veneering, G4 and G7: alumina coping and ceramic veneering. Load of 180 N was applied at the incisal third of lingual surface at 45º. Models were supported by the periodontal ligament (x=y=z=0). The von Mises stress (VMS) values were calculated. The W teeth presented higher VMS at coping when compared to NW teeth and group G1 showed lower VMS value. For crown material, for both W or NW teeth, increasing VMS was found at metallic, zirconia and alumina coping, respectively. Metallic coping showed a better performance despite its unfavorable esthetics, suggesting as an appropriate material for prosthetic restoration of endodontically treated teeth.

Resumo Este estudo avaliou a distribuição de tensão em dentes tratados endodonticamente, fragilizados (F) ou não fragilizados (NF), restaurados com diferentes materiais para a coroa protética utilizando 3D-FEA. Modelos de um canino maxilar foram construídos baseados em imagens de micro-CT e divididos em grupos: G1 (controle) - dente hígido; G2 a G7 - dentes tratados endodonticamente com pino de fibra de vidro (PFV), sendo que G2 a G4 simularam raízes NF e G5 a G7 simularam raízes F. Para o material das coroas os dentes foram restaurados com: G2 e G5: coping metálico e revestimento cerâmico, G3 e G6: coping de zirconia e revestimento cerâmico, G4 e G7: coping de alumina e revestimento cerâmico. Carregamento de 180 N foi aplicado na superfície lingual em seu terço incisal com 45 graus de inclinação. Os modelos foram suportados pelo ligamento periodontal (x=y=z=0). Os valores da tensão de von Mises (VMS) foram calculados. Os dentes F apresentaram maiores valores VMS para o coping quando comparados aos dentes NF, sendo que o G1 apresentou menores valores VMS. Para o material das coroas, ambos F ou NF aumentaram VMS no coping metálico, zirconia e alumina, respectivamente. Copings metálicos apresentaram melhor comportamento mecânico apesar de não favorecerem a estética, o que sugere ser um material apropriado para a restauração de dentes tratados endodonticamente.

Factors affecting the periapical healing process of endodontically treated teeth

Abstract Tissue repair is an essential process that reestablishes tissue integrity and regular function. Nevertheless, different therapeutic factors and clinical conditions may interfere in this process of periapical healing. This review aims to discuss the important therapeutic factors associated with the clinical protocol used during root canal treatment and to highlight the systemic conditions associated with the periapical healing process of endodontically treated teeth. The antibacterial strategies indicated in the conventional treatment of an inflamed and infected pulp and the modulation of the host's immune response may assist in tissue repair, if wound healing has been hindered by infection. Systemic conditions, such as diabetes mellitus and hypertension, can also inhibit wound healing. The success of root canal treatment is affected by the correct choice of clinical protocol. These factors are dependent on the sanitization process (instrumentation, irrigant solution, irrigating strategies, and intracanal dressing), the apical limit of the root canal preparation and obturation, and the quality of the sealer. The challenges affecting the healing process of endodontically treated teeth include control of the inflammation of pulp or infectious processes and simultaneous neutralization of unpredictable provocations to the periapical tissue. Along with these factors, one must understand the local and general clinical conditions (systemic health of the patient) that affect the outcome of root canal treatment prediction.

Monobloque aspecto funcional: postes de fibra de vidrio / Monoblocks and functionality: the case for fiberglass posts

Durante muchos años se han utilizado los postes colados, considerados como un estándar en la odontología protésica, pero presentan limitantes técnicas y mecánicas, ya que exhiben altos módulos de elasticidad y, por lo mismo, imposibilitan la capacidad de disipar las fuerzas con efectividad, lo que significa concentrar tensiones dentro del conducto radicular. Literatura basada en evidencia científica describe a los postes de fibra de vidrio con módulos de elasticidad semejantes o próximos a la dentina, presentando propiedades anisotrópicas, en comparación con los postes tradicionales, que presentan propiedades isotrópicas. Se propone un concepto restaurador que involucra el poste, el cemento y la dentina, constituyendo un complejo homogéneo denominado ®monobloque¼ que permite un mejor comportamiento mecánico benéfico para el remanente dentario

For many years now, cast posts have been regarded as standard in prosthetics despite the technical and mechanical limitations caused by their high moduli of elasticity, which prevent the forces involved from being effectively dissipated and, therefore, concentrate stress within the root canal. Scientifi c evidence-based literature describes fi berglass posts with moduli of elasticity similar to or approaching that of dentin as having anisotropic properties, as opposed to the isotropic properties of traditional posts. We propose a restorative approach that involves the post, the cement, and the dentin, forming a homogeneous complex known as a ®monobloc¼ that enables enhanced mechanical behavior that benefits the remaining tooth structure.

Fracture resistance of teeth subjected to internal bleaching and restored with different procedures

This study evaluated the fracture resistance of teeth submitted to internal bleaching and restored with different procedures. Forty maxillary incisors were endodontically treated and assigned to 4 groups (n=10): G1- restored with composite resin (CR), G2- bleached with hydrogen peroxide (HP) and restored with CR, G3- restored with CR and fiberglass posts (CR + posts) and G4- bleached and restored with CR + posts. HP was applied in the buccal surface and pulp chamber 3 times at each one of 2 sessions with an interval of 7 days between them. Additional 10 sound incisors were subjected to fracture strength test (gold standard). The fracture strength (kN) was determined in an Instron machine. Data were analyzed by ANOVA and Tukey-Kramer test (α=0.05). The untreated teeth (gold standard) showed the highest (p<0.05) fracture strength (0.43 ± 0.16). Teeth restored with CR (G1) without internal bleaching had the lowest (p<0.05) fracture strength (0.23 ± 0.11). Teeth bleached and restored with CR (G2) (0.26 ± 0.10), restored with CR + posts ithout internal bleaching (G3) (0.31 ± 0.17) and, bleached and restored with CR + posts (G4) (0.33 ± 0.12) had intermediate values, sometimes similar to the group with the highest value, sometimes similar to the group with the lowest value. In conclusion, as far as the fracture strength is concerned, teeth subjected to internal bleaching can be restored with composite resin alone, as the use of posts in these teeth did not increase their resistance.

Este estudo avaliou a resistência à fratura de dentes submetidos ao clareamento interno restaurados com diferentes procedimentos. Quarenta incisivos superiores foram tratados endodonticamente e divididos em 4 grupos (n = 10): G1- restaurados com resina composta (RC), G2- clareados com peróxido de hidrogênio (PH) e restaurados com o RC, G3- restaurado com RC e pinos de fibra de vidro (RC + pinos) e G4- clareados e restaurados com RC + pinos. O PH foi aplicado na superfície vestibular e câmara pulpar 3 vezes por sessão, por 2 sessões com intervalo de 7 dias entre elas. Dez dentes hígidos adicionais foram submetidos a teste fratura (padrão ouro). A resistência à fratura (kN) foi determinada em máquina Instron. Os dados foram analisados por Análise de Variânica e teste de Tukey-Krammer (α= 0,05). Os dentes não tratados (padrão ouro) apresentaram a maior resistência à fratura (0,43 ± 0,16) (p <0,05). Os dentes restaurados com RC (G1) apresentaram a menor resistência à fratura (0,23 ± 0,11) (p <0,05). Os dentes clareados e restaurados com RC (G2) (0,26 ± 0,10), restaurado com RC + pinos (G3) (0,31 ± 0,17) e os clareados e restaurados com RC + pinos (G4) (0,33 ± 0,12) apresentaram valores intermediários, ora semelhantes ao do grupo com o maior valor, ora similares ao grupo de valores mais baixos. Pode-se concluir que os dentes submetidos ao clareamento interno podem ser restaurados com apenas resina composta.

Influence of ferrule preparation with or without glass fiber post on fracture resistance of endodontically treated teeth

OBJECTIVE: This study evaluated the effect of ferrule preparation (Fp) on the fracture resistance of endodontically treated teeth, restored with composite resin cores with or without glass fiber posts. MATERIAL AND METHODS: Forty-four bovine teeth were sectioned 19 or 17 mm (2 mm ferrule) from the apex, endodontically treated and assigned to four groups (n = 11): Group 1: Fp and post; Group 2: Fp and without post; Group 3: without Fp and with post; Group 4: without Fp and without post. All specimens were restored with composite resin core and metal crown. Specimens were subjected to fracture resistance testing in a universal testing machine at a crosshead speed of 0.5 mm/min. The data were analyzed by two-way ANOVA and Tukey's tests (α=0.05). RESULTS: The mean fracture resistance values were as follows: Group 1: 573.3 N; Group 2: 552.5 N; Group 3: 275.3 N; Group 4: 258.6 N. Significantly higher fracture resistance was found for the groups with Fp (p<0.001). CONCLUSION: There was no statistically significant interaction between the "Fp" and "post" factors (p = 0.954). The ferrule preparation increased the fracture resistance of endodontically treated teeth. However, the use of glass fiber post showed no significant influence on the fracture resistance.

Influence of different post design and composition on stress distribution in maxillary central incisor: Finite element analysis.

Background: Post design and material has very important effects on dentinal stress distribution since the post placement can create stresses that lead to root fracture. Materials and Methods: In this study we use finite element analysis (FEA) to evaluate stress distribution on endodontically treated maxillary central incisors that have been restored with different prefabricated posts. Six models were generated from the image of anatomical plate: Four metallic posts (ParaPost XH, ParaPost XT, ParaPost XP, and Flexi-Flange) and one fiberglass post (ParaPost Fiber Lux). The sixth model was a control-a sound maxillary central incisor. We used CAD software and exported the models to ANSYS 9.0. All the materials and structures were considered elastic, isotropic, homogeneous, and linear except the fiberglass post which was considered orthotropic. The values for the mechanical properties were obtained by a review of the literature and the model was meshed with 8-node tetrahedral elements. A load of 2N was applied to the lingual surface at an angle of 135°. Results: The stress results were recorded by shear stress and von Mises criteria; it was observed that there was no difference for stress distribution among the titanium posts in the radicular portions and into posts. There was higher stress concentration on the coronary portion with the titanium posts than with the glass fiber post. It seems that the metallic posts' external configuration does not influence the stress distribution. Conclusion: Fiber posts show more homogeneous stress distribution than metallic posts. The post material seems to be more relevant for the stress distribution in endodontically treated teeth than the posts' external configuration.