Fracture resistance of weakened roots restored with composite resin and glass fiber post

This study evaluated the fracture resistance of weakened roots restored with glass fiber posts, composite resin cores and complete metal crowns. Thirty maxillary canines were randomly divided into 3 groups of 10 teeth each: teeth without weakened roots (control); teeth with partially weakened roots (PWR) and teeth with and largely weakened roots (LWR). The control group was restored with glass fiber posts and a composite resin core. Teeth in the PWR and LWR groups were flared internally to standardized dimensions in order to simulate root weakness. Thereafter, the roots were partially filled with composite resin and restored in the same way as in the control group. The specimens were exposed to 250,000 cycles in a controlled chewing simulator. All intact specimens were subjected to a static load (N) in a universal testing machine at 45 degrees to the long axis of the tooth until failure. Data were analyzed by one-way ANOVA and Dunnett's test for multiple comparisons (p=0.05). There were statistically significant difference differences (p<0.01) among the groups (control group = 566.73 N; PWR = 409.64 N; and LWR = 410.91 N), with significantly higher fracture strength for the control group. There was no statistically significant difference (p>0.05) between the weakened groups. The results of this study showed that thicker root dentin walls significantly increase the fracture resistance of endodontically treated teeth.Este estudo avaliou a resistência à fratura de raízes fragilizadas restauradas com pinos de fibra de vidro, núcleos de resina composta e coroas totais metálicas. Trinta caninos superiores foram aleatoriamente divididos em 3 grupos. Dentes sem enfraquecimento (grupo controle); grupo de raízes parcialmente enfraquecidas e amplamente enfraquecidas. O grupo controle foi restaurado com pinos de fibra de vidro e núcleo em resina composta. Os dentes dos grupos de raízes parcialmente e amplamente enfraquecidas foram internamente preparadas de maneira padronizada simulando enfraquecimento. Após isto, as raízes foram parcialmente preenchidas com resina composta e restauradas como no grupo controle. Os espécimes foram expostos a 250.000 ciclos em uma máquina de ciclagem mecânica. Todos os dentes intactos foram submetidos à carga estática (N) em uma máquina de ensaio universal a 45 graus ao longo eixo do dente até a sua falha. Os resultados foram analisados através do teste ANOVA a 1 critério e teste de Dunnett para comparações múltiplas (p=0,05). A análise estatística revelou diferenças significantes (p<0,01) entre os três grupos (grupo controle = 566,73 N; RPE = 409,64 N; e ERA = 410,91 N). Quando as três médias de resistência a fratura são ranqueadas as duas menores não se diferem. Os resultados deste estudo mostraram que uma maior espessura de paredes dentinárias aumenta significantemente a resistência à fratura de dentes tratados endodonticamente

Resistance to fracture of weakened roots restored with composite resin and glass fiber post submitted to cyclic loading

A preservação e a restauração de dentes severamente debilitados sem suporte dentinário no terço cervical do canal radicular é um procedimento difícil e de prognóstico duvidoso. Avaliou-se, por meio de ciclagem mecânica e compressão, a resistência à fratura e o padrão de fratura de raízes íntegras e fragilizadas, reconstruídas internamente com resina composta (Z 250) e pinos de fibra de vidro (Reforpost). Trinta caninos superiores humanos com anatomia radicular semelhante foram divididos em três grupos de acordo com a espessura do terço cervical: grupo I - raízes íntegras sem simulação de enfraquecimento e grupos II e III simularam raízes parcial e amplamente enfraquecidas. Estas foram reconstruídas através de preenchimento com resina composta fotopolimerizável por meio de um pino translumínico (Luminex). Todos os grupos tiveram coroas totais metálicas cimentadas sobre os núcleos em resina composta. Os pinos e coroas foram cimentados com cimento resinoso dual. Os corpos de prova foram submetidos à 250.000 ciclos numa freqüência de 2.6 Hz e carga de 3Kg. Posteriormente, os mesmos foram carregados numa máquina de ensaio universal à uma velocidade de carga de 0,5 mm/min até sua fratura. Em ambos os testes a angulação de carga foi de 135º em relação ao longo eixo do dente sobre a face palatina. Os valores de resistência à fratura foram: Grupo I-57,83Kgf; Grupo II-41,80 Kgf; Grupo III-41,93 Kgf. A análise de variância (ANOVA) (p<0,05) a um critério mostrou diferença estatisticamente significante entre os grupos. A comparação individual das médias revelou diferença somente entre o grupo I e os grupos II e III. O percentual de raízes com prognóstico favorável após a fratura foi: Grupo I -80%; Grupo II -40%; Grupo III -30%. Raízes fragilizadas foram menos resistentes à fratura e apresentaram menos fraturas favoráveis a reabilitação do que aa raízes íntegras.The preservation and restoration of severely weakened pulpless teeth is a difficult and unpredictable procedure. This study evaluated the resistance to fracture and fracture patterns of weakened roots after restoration with glass fiber post, filling core of composite resin and total metallic crown submitted to cyclical and compressive load. Thirty upper canine teeth with similar dimensions were selected, being endodontic treatment performed. Samples were embedded and placed in a positioning jig. The teeth were divided into three groups in agreement with their cervical third thickness: group I (no weaken); Groups II (1.0mm) and III (0.5mm) simulated roots partial and largely weakened. The roots of groups II and III were reconstructed with composite resin through transparent plastic post (Luminex System-Dentatus). All groups received nickel-chrome cast metallic crowns. Both posts and crowns were cemented with a dual resinous cement. The specimens were impacted at 45 degrees to the long axis of the tooth with a force of 30 N at a frequency of 2.6 Hz for a total of 250.000 impacts. After were taken to the Universal Testing Machine for the fracture resistance test in a 135º and 0,5 mm/min speed. The fracture resistance values were: Group I -54,71 Kgf; Group II -40,04 Kgf; Group III -44,56 Kgf. Result show statistically significant differences in relation to the root conditions (ANOVA at one criterion p < 0,05). The samples with a favorable repair were: Group I -100%; Group II - 40%; Group III - 30%. The presence of more bulk of dentinal structure increased the resistance to fracture

Efeito da neutralização e remoção sônica do precipitado do ácido fluorídrico na resistência à fratura de coroas cerâmicas

Testou-se o efeito de diferentes formas de tratamento da superfície cerâmica após condicionamento com ácido hidrofluorídrico (HF) na resistência à fratura de coroas cerâmicas à base de dissilicato de lítio. Quarenta terceiros molares humanos receberam um preparo convencional para coroa total. Após escaneamento digital dos preparos, blocos cerâmicos foram usinados pelo sistema CAD/CAM para obtenção das coroas. A espessura da película de cimento das coroas ao preparo foi verificada com silicone de adição. As coroas foram distribuídas nos 4 grupos conforme o tratamento da superfície cerâmica (n=10): (HF)- HF à 4.9% por 20s + spray ar-água por 30s; (HFN)– HF + agente neutralizador por 5 min (N); (HFU) – HF + banho sônico por 5 min (U); e (HFNU)– HF + N + U. Após aplicação de uma camada de silano (60s), as coroas foram cimentadas com cimento resinoso dual. Uma carga compressiva de 1000Kg foi aplicada no centro da face oclusal da coroa com velocidade de 1 mm/min até a fratura. Os dados foram analisados por ANOVA e Tukey (α=0,05). A carga média de fratura (Kgf) foi: HF = 169,92 ± 21,37; HFN = 187,34 ± 34,79; HFU = 166,63 ± 40,22 e HFNU = 175,26 ± 40,22. O tratamento da superfície cerâmica após condicionamento ácido não influenciou significativamente (p>0.05) na resistência à fratura das coroas cerâmicas testadas, sugerindo que é desnecessário qualquer tratamento adicional para remoção de resíduos após o uso de HF e lavagem com jato de água-arThe effect of different ceramic surface post hydrofluoric acid (HF) etching cleaning protocols in the fracture strength of lithium dissilicate glass ceramic crowns were evaluated. Forty maxillary third human molars received a conventional full preparation. Crowns were obtained from the digital scanning of the preparations and CAD/CAM blocks machining. Crown cement film thickness was evaluated with vinyl polysiloxane. The crowns were allocated in 4 groups according to the ceramic surface treatment (n=10): (HF)- 4.9% HF for 20s + water spray for 30s; (HFN)- HF + neutralizing agent for 5 min (N); (HFU) -: HF+ sonic bath for 5 min (U) and (HFNU): HF + N + U. After a silane coat (60s), crowns were cemented with dual cure cement. A compressive load of 1000Kg was applied in the occlusal surface center at crosshead speed of 1mm/min until the fracture. Data were analyzed by one-way ANOVA and Tukey tests (α = 0.05). Fracture strength mean for each group was (Kgf): HF = 169.92 ± 21.37; HFN = 187.34 ± 34.79; HFU = 166.63 ± 40.22 e HFNU = 175.26 ± 40.22. There was no statistical difference as the surface treatment (p>0.05) suggesting that it is not necessary any additional ceramic surface treatment in order to remove debris after using of HF and air-water spray rinsingCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

Fracture resistance of endodontically treated teeth with different heights of crown ferrule restored with prefabricated carbon fiber post and composite resin core by intermittent loading

This study evaluated the fracture resistance of endodontically treated teeth restored with prefabricated carbon fiber posts and varying quantities of coronal dentin. Sixty freshly extracted upper canines were randomly divided into groups of 10 teeth each. The specimens were exposed to 250,000 cycles in a controlled chewing simulator. All intact specimens were subjected to a static load (N) in a universal testing machine at 45 degrees to the long axis. Data were analyzed by 1-way analysis of variance and Tukey test (alpha = .05). Significant differences (P < .001) were found among the mean fracture forces of the test groups (positive control, 0 mm, 1 mm, 2 mm, 3 mm, and negative control groups: 1022.82 N, 1008.22 N, 1292.52 N, 1289.19 N, 1255.38 N, and 1582.11, respectively). These results suggested that the amount of coronal dentin did not significantly increase the fracture resistance of endodontically treated teeth restored with prefabricated carbon fiber post and composite resin core. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2008;106:e52-e57

Fracture resistance of bovine incisors restored with different glass fiber posts: Effect of the diameter of fiber post

Aim: Compare the effect of three post designs on the fracture resistance and failure modes of composite core-fiber post-crownless tooth sets. Materials and Methods: Ninety bovine incisors were selected and divided into nine groups of 10 specimens. The teeth were assigned to three groups based on the post design: Cylindrical, tapered, and double-tapered. Each group was subdivided into three subgroups in accordance with the diameter of the post: Small (No.1), medium (No.2), and large (No.3). The Panavia F system was used for post cementation. The specimens were mounted in acrylic resin blocks with a layer of silicone rubber covering the roots. A universal testing machine compressively loaded the specimens from the palatal side at a crosshead speed of 1 mm/min and at an angle of 135I to the long axis of the teeth, until failure occurred. The failure mode was determined by a stereomicroscope inspection of all the specimens. Data were analyzed by one-way ANOVA and the Tukey test (P < 0.05). Results: The fracture resistance was affected by the type of post (P < 0.0001). A narrower diameter for all of the post systems allowed for higher resistance. The main failure mode in the large cylindrical group was catastrophic fractures, while the main failures in the other eight groups were favorable. Conclusion: Narrower diameter posts showed higher fracture resistance. The dominant failure pattern was repairable fracture, except for those with large cylindrical groups