Grinding of composite cores using diamond burs with different grit sizes: the effects on the retentive strength of zirconia crowns

Aim: To evaluate the retention of Y-TZP crowns cemented in aged composite cores ground with burs of different grit sizes. Methods: Sixty composite resin simplified full-crown preparations were scanned, while 60 Y-TZP crowns with occlusal retentions were milled. The composite preparations were stored for 120 days (wet environment-37°C) and randomly distributed into three groups (n=20) according to the type of composite core surface treatment. The groups were defined as: CTRL (control: No treatment), EFB (extra-fine diamond bur [25µm]), and CB (coarse diamond bur [107µm]). The grinding was performed with an adapted surveyor standardizing the speed and pressure of the grinding. The intaglio surfaces on the crowns were air-abraded with silica-coated alumina particles (30 µm) and then a silane was applied. The crowns were cemented with self-adhesive resin cement, thermocycled (12,000 cycles; 5/55°C), stored (120 days) and submitted to a retention test (0.5mm/min). The retentive strength data (MPa) were analyzed using one-way analysis of variance and Tukey test, as well as Weibull analysis. Failures were classified as 50C (above 50% of cement in the crown), 50S (above 50% of cement in the substrate) and COE (composite core cohesive failure). Results: No statistical difference was observed among the retention values (p=0.975). However, a higher Weibull modulus was observed in the CTRL group. The predominant type of failure was 50S (above 50% of cement in the substrate composite). Conclusion: The retention of zirconia crowns was not affected by grinding using diamond burs with different grit sizes (coarse/extra-fine) or when no grinding was performed

Y-TZP surface treatments and their effects on the bond strength to resin cement

Aim: This study evaluated the effect of surface treatments of yttria-stabilized tetragonal zirconia polycrystal (Y-TZP) ceramics on their bond strength to a resin cement. Methods: Seventy zirconia blocks (6 × 6 × 2 mm3, IPS e.max ZirCAD) were assigned into 7 groups (n=10) ­ as-sintered (AS), no treatment; tribochemical silica coating + silanization (TBS; Cojet-sand; ProSil); airabrasion with 45 µm alumina particles + universal primer (AAP; Monobond®Plus); fusion sputtering (FS); SiO2 nanofilm + silanization (SN; ProSil); FS+SN+ silanization (FSSN; ProSil); FS+SN+Universal Primer (FSSNP; Monobond®Plus). Afterwards, a resin cement (RelyX™ ARC) was applied inside cylinders (Ø = 0.96 mm × 1 mm height) placed on the zirconia surfaces. Microshear bond strength tests (µSBS) were carried out (1 mm/min). Failure and phase transformation analysis were performed. Bond strength data (MPa) were subjected to Kruskal-Wallis/Mann Whitney tests. Results: TBS (27 ± 1.2) and AAP (24.7 ± 0.8) showed higher bond strengths than the other groups, followed by FSSNP (15.5 ± 4.2) and FSSN (13.3 ± 3.6). FS (3.4 ± 0.44) and SN (9.5 ± 2.7) showed the lowest values (p < 0.001). Most of the specimens exhibited an adhesive failure. Conclusion: Air-abrasion by silica-coated alumina particles followed by silanization or by alumina particles followed by universal primer resulted in the highest resin bond strength to zirconia. Fusion sputtering and silica nanofilm deposition induced low strengths. However, when these methods are applied in combination and with a primer (FSSN and FSSNP), higher bond strengths may be achieved. Low bond strengths are obtained when no zirconia treatment is performed

Influence of elastic modulus of intraradicular posts on the fracture load of roots restored with full crowns / Influência do modulo de elasticidade de retentores intrarradiculares na carga para fratura de raízes restauradas com coroas totais

Objective: This study aimed to evaluate the fracture load and displacement of roots restored with posts of different elastic modulus. Material and method: Thirty-six replicas of epoxy resin mixed with glass microfibers were made from an endodontically-treated human premolar root prepared to a length of 12 mm with a custom drill, leaving the apical 4 mm unprepared. Replicas were randomly restored with (n = 12): FP-LM (fiber post with low elastic modulus- 50 GPa), FP-HM (fiber post with high elastic modulus - 67 GPa) and MP (metallic post - 208 GPa), using self-curing adhesive and dual resin cement. Cores were built up with composite resin and metallic crowns were cemented in all the roots with self-adhesive resin cement with self-curing mode. Specimens were subjected to a fracture load test (45° inclination/0.5 mm/min) and displacement was registered at 100 N. Result: One-way ANOVA showed that elastic modulus of the post did not affect the fracture load means (p = 0.203) (FP-LM: 237.4 ± 65.11 N; FP-HM: 236.7 ± 92.85 N; MP: 295.8 ± 108.7 N) but was statistically significant for the displacement (p < 0.00): Tukey's test showed that FP-LM displacement mean (0.81 ± 0.15 mm) was significantly higher than those for FP-HM (0.46 ± 0.26 mm; p = 0.00) and MP (0.62 ± 0.07 mm; p = 0.04). Conclusion: Posts with different elastic modulus exhibit similar fracture loads, but a lower displacement is achieved when fiber posts with a high elastic modulus and metallic posts are used.

Objetivo: Este trabalho avaliou a carga para fratura e deslocamento de raízes restauradas com pinos de diferentes módulos de elasticidade. Material e método: Trinta e seis réplicas de microfibras de vidro embutidas em resina epóxi foram fabricadas a partir de uma raiz de um pré-molar tratado endodonticamente preparado em 12 mm de comprimento com brocas customizadas, deixando 4 mm apicais sem preparo. As raízes foram randomicamente restauradas com (n = 12): FP-LM (pino de fibra com um baixo módulo de elasticidade - 50 GPa), FP-HM (pino de fibra com um alto módulo de elasticidade - 67 GPa) e MP (pinos metálicos - 208 GPa), usando adesivo autopolimerizável e cimento resinoso dual. Núcleos foram confeccionados com resina composta e coroas metálicas foram cimentadas em todas as raízes com cimento resinoso autoadesivo com modo de polimerização químico. Os espécimes foram submetidos ao teste de fratura em 45° (inclinação de 45° / 0,5 mm/min) e o deslocamento foi registrado aos 100 N. Resultado: Anova 1 fator mostrou que o módulo de elasticidade dos retentores não afetou as médias de fratura (p = 0,203) (FP-LM: 237,4 ± 65,11 N; FP-HM: 236,7 ± 92,85 N; MP: 295,8 ± 108,7 N) mas foi estatisticamente significante para o deslocamento (p < 0,00): o teste de Tukey mostrou que a média de deslocamento do grupo FP-LM (0,81 ± 0,15 mm) foi significativamente maior do que o grupo FP-HM (0,46 ± 0,26 mm; p = 0,00) e MP (0,62 ± 0,07 mm; p = 0,47). Conclusão: Pinos com diferentes módulos de elasticidade mostram resistência similar, porém um menor deslocamento é obtido quando pinos de fibra com alto módulo de elasticidade (FP-HM/MP) são usados.

Clinical performance and failure modes of pulpless teeth restored with posts: a systematic review

Abstract The aim of this systematic review was to compare the clinical performance and failure modes of teeth restored with intra-radicular retainers. A search was performed on PubMed/Medline, Central and ClinicalTrials databases for randomized clinical trials comparing clinical behavior and failures of at least two types of retainers. From 341 detected papers, 16 were selected for full-text analysis, of which 9 met the eligibility criteria. A manual search added 2 more studies, totalizing 11 studies that were included in this review. Evaluated retainers were fiber (prefabricated and customized) and metal (prefabricated and cast) posts, and follow-up ranged from 6 months to 10 years. Most studies showed good clinical behavior for evaluated intra-radicular retainers. Reported survival rates varied from 71 to 100% for fiber posts and 50 to 97.1% for metal posts. Studies found no difference in the survival among different metal posts and most studies found no difference between fiber and metal posts. Two studies also showed that remaining dentine height, number of walls and ferrule increased the longevity of the restored teeth. Failures of fiber posts were mainly due to post loss of retention, while metal post failures were mostly related to root fracture, post fracture and crown and/or post loss of retention. In conclusion, metal and fiber posts present similar clinical behavior at short to medium term follow-up. Remaining dental structure and ferrule increase the survival of restored pulpless teeth. Studies with longer follow-up are needed.

Influence of periodontal ligament simulation on bond strength and fracture resistance of roots restored with fiber posts

Objective: Considering that periodontal ligament simulation may influence the stress distribution over teeth restored with intraradicular retainers, this study aimed to assess the combined effect of mechanical cycling and periodontal ligament simulation on both the bond strength between fiber posts and root dentin and the fracture resistance of teeth restored using glass fiber posts. Material and Methods: Ninety roots were randomly distributed into 3 groups (n=10) (C-MC: control; P-MC: polyether; AS-MC: addition silicone) to test bond strength and 6 groups (n=10) (C: control; P: polyether; AS: addition silicone, without mechanical cycling, and C-MC, P-MC and AS-MC with mechanical cycling) to test fracture strength, according to the material used to simulate the periodontal ligament. For the bond strength test, fiber posts were cemented, cores were built, mechanical cycling was applied (2×106 cycles, 88 N, 2.2 Hz, and 45º incline), and the teeth cut into 3 slices (2 mm), which were then subjected to the push-out test at 1 mm/min. For the fracture strength test, fiber posts were cemented, cores were built, and half of the groups received mechanical cycling, followed by the compressive strength (45° to the long axis and 1 mm/min) performed on all groups. Results: Periodontal ligament simulation did not affect the bond strength (p=0.244) between post and dentin. Simulation of periodontal ligament (p=0.153) and application of mechanical cycling (p=0.97) did not affect fracture resistance. Conclusions: The materials used to simulate the periodontal ligament did not affect fracture or bond strength, therefore periodontal ligament simulation using the tested materials could be considered optional in the conditions of the study. .

Surgical treatment of transmigration of mandibular canine

Introduction: The occurrence of canine impaction is not a rare phenomenon, but transmigration of the tooth across the midline is a less common event. The finding is normally asymptomatic and the etiologic factors involved in the transmigration process are still unclear. Objective: To present a clinical case of surgical treatment of a transmigrated mandibular canine. Case report: A 17-year-old male patient presented to the dental clinic to remove an unerupted canine. Clinical and radiological examinations led to the diagnosis of a transmigrated canine in the mental region. Surgical removal was the treatment of choice and further radiographs were needed to complement the clinical exam and to determine the location of the tooth precisely for the surgical procedure. Postoperative period was uneventful. Canine transmigration is a rare finding and symptoms are usually absent. Conclusion: An early detection is important to plan the treatment and mainly to avoid future complications.

Associação entre a duração do aleitamento materno e sua influência sobre o desenvolvimento de hábitos orais deletérios / Association between duration of breast feeding and its influence upon the development of harmful oral habits

Introdução e objetivo: O objetivo deste estudo foi identificar a presença de hábitos bucais deletérios e relacioná-la com a duração de aleitamento materno. Material e métodos: Foi realizado um estudo retrospectivo,utilizando-se dados secundários contidos em 143 prontuáriosde crianças entre 0 e 59 meses, assistidas em clínica pública de Odontopediatria. Nos prontuários, constavam perguntas sobre a presença de hábitos bucais e sua frequência, bem como o período de duração do aleitamento materno. Os dados foram analisados pelo emprego do teste do qui-quadrado, com nível de significância de5%. Resultados: Verificou-se a presença de sucção de chupeta em 94crianças (76,4%), respiração bucal em 28 (22,7%), bruxismo em 18(14,7%) e sucção digital em 15 (12,2%). Dos 143 prontuários analisados,em 94 (65,7%) a duração relatada do aleitamento materno foi inferior a seis meses. Houve associação estatisticamente significante entre tempo de aleitamento materno e presença de hábito bucal deletério.Conclusão: O tempo insuficiente de aleitamento no peito está associado à presença de hábitos bucais deletérios.

Introduction and objective: This study aimed to identify harmful oral habits and relate them to the duration of breast feeding. Material and methods: This was a retrospective study, using data from 143 dentalcharts of 0-59 months-old children of a public pediatric dental clinic.The charts contained information about presence of harmful oral habits and its frequency, as well as the duration of breast feeding. Data were analyzed through chi-square test with significance level of 5%. Results:It was observed that 94 children (76.4%) used pacifiers, 28 (22.7%)presented oral breathing, 18 (14.7%) had bruxism and 15 (12.2%) bittheir nails. Data from 143 dental charts indicated that 94 children(65.7%) were breastfed for less than 6 months. There was a statistical significant association between duration of breast feeding and harmful oral habits. Conclusion: The insufficient duration of breast feeding is associated with the presence of harmful oral habits.

Vitamina D y cáncer / Cancer and vitamin D

El cáncer es una de las mayores causas de muerte en el mundo. Si bien la vitamina D (colecalciferol) ha sido asociada a la regulación de la homeostasis de calcio, muchos son los datos epidemiológicos, bioquímicos y genéticos sobre otros efectos importantes de la vitamina D, como el desarrollo y la progresión de diferentes cánceres. El objetivo del presente artículo es revisar distintos aspectos acerca de los mecanismos de acción y efectos moleculares de la vitamina D o sus metabolitos y de los indicadores epidemiológicos que los correlacionan con el cáncer, su prevención y tratamiento. El estudio de los efectos de la vitamina D se ha vuelto muy amplio: nuevos genes, nuevos blancos, mecanismos diferentes. Niveles adecuados de vitamina D son necesarios para una gran cantidad de procesos fisiológicos y no solamente para el mantenimiento de la homeostasis del calcio. Los estudios clínicos podrían revisar las recomendaciones sobre las dosis de vitamina D que puedan proteger también contra el desarrollo del cáncer.