Acid erosion is a superficial loss of enamel caused by chemical processes that do not involve bacteria. Intrinsic and extrinsic factors, such as the presence of acid substances in the oral cavity, may cause a pH reduction, thus potentially increasing acid erosion. The aim of this study was to evaluate the microhardness of bleached and unbleached bovine enamel after immersion in a soda beverage, artificial powder juice and hydrochloric acid. The results obtained for the variables of exposure time, acid solution and substrate condition (bleached or unbleached enamel) were statistically analyzed by the ANOVA and Tukey tests. It was concluded that a decrease in microhardness renders dental structures more susceptible to erosion and mineral loss, and that teeth left unbleached show higher values of microhardness compared to bleached teeth.

The aim of this in vitro study was to compare the photoactivation effects of QTH (Quartz-Tungsten-Halogen) and LED (Light-Emitting Diode) on the SBS (Shear Bond Strength) of orthodontic brackets at different debond times. Seventy-two bovine lower incisors were randomly divided into two groups according to the photoactivation system used (QTH or LED). The enamel surfaces were conditioned with Transbond self-etching primer, and APC (Adhesive Pre-Coated) brackets were used in all specimens. Group I was cured with QTH for 20 s and Group II with LED for 10 s. Both groups were subdivided according to the different experimental times after bonding (immediately, 24 h and 7 days). The specimens were tested for SBS and the enamel surfaces were analyzed according to the Adhesive Remnant Index (ARI). The statistical analysis included the Tukey's test to evaluate the main effects of photoactivation and debond time on SBS. The Chi-square test was used to compare the ARI values found for each group, and no statistically significant difference was observed. The debond time of 7 days for QTH photoactivation showed statistically greater values of SBS when compared to the immediate and 24 h periods. There was no statistically significant difference between the QTH and LED groups immediately and after the 24 h period. In conclusion, bonding orthodontic brackets with LED photoactivation for 10 s is suggested because it requires a reduced clinical chair time.

El objetivo del estudio era el de analizar radiográficamente los efectos del risedronato de sodio (OSG Norwich Pharmaceticals, U. S. UN.) y del raloxifeno clorhidrato (Eli Lirio & Compañía Ltda, ING. ) En la reparación ósea en ratones osteopénicos. Se utilizó cincuenta ratones divididos en cinco grupos de 10 animales: (I) SHAM, (II) Castrado, (III) Castrados y tratados con risedronato 1mg/kg/dia, (IV) Castrados y tratados con raloxifeno 1mg/kg/día y (V) Castrados y tratados con raloxifeno 3mg/kg/día. Después de treinta días de la castración se les produjo heridas en el hueso de 3 mm de en las de tibias derechas. Entre 7 y 28 días de tratamiento los ratones fueron sacrificados y las tibias evaluadas considerando la densidad óptica radiográfica de la región de la reparación del defecto óseo por medio del sistema digital RVG Trophy y Programa de Imagen Tool® 2,03. Los resultados fueron sometidos al ANOVA y al Test de Tukey (p?0,05). Los datos mostraron que a los 7 días de observación los grupos I y II fueron estadísticamente semejantes en relación al grado de densidad radiográfica, así como los demás grupos entre sí. A los 28 días el grupo V presentó los valores de densidad radiográfica superior y estadísticamente significativos con respecto a los grupos II, III y IV y semejante al grupo I. Los grupos III y IV fueron semejantes entre sí y estadísticamente superior al grupo II. Se concluyó que el raloxifeno en dosis de 3mg/kg/dia presentó mejor desempeño en el proceso de reparación ósea, siendo semejante al grupo SHAM a los 28 días. El efecto del raloxifeno se mostró dosis dependiente, a los 28 días, en las posologias testadas.

The aim of this study was to analyse radiographically the effects of sodium risedronate (OSG Norwich Pharmaceticals, EUA) and raloxifene hydrochloride (Eli Lilly & Company Ltd; ING.) in bone repair of male rats with osteopenia. 50 animals were divided in 5 groups of 10: (I) SHAM, (II) Castrated rats, (III) Castrated rats treated with 1mg/kg/day risedronate, (IV) Castrated rats treated with 1mg/kg/day raloxifene and (V) Castrated rats treated with 3mg/kg/day raloxifene. 30 days after castration, a 3 mm bone defect was made in the right tibia of the animals. After 7 and 28 days of treatment, the animals were sacrificed and the tibias were removed for analysis of radiographic optical density by the digital system RVG Trophy and the Image Programme Tool 2.03®. All data collected were analysed by ANOVA and the Tukey´s Test (p?0.05). The results showed that at 7 days of bone repair, groups I and II had similar and statistically significant values of optical density while the other groups had similar values among themselves. At 28 days of bone repair, group V showed greater and statistically significant values of optical density compared to groups II, III and IV, but similar values to group I. Groups III and IV had similar values between themselves but greater and statistically significant values than group II. It could be concluded that 3 mg/kg/day raloxifene had a better performance in bone repair when compared to the other groups, similar results to group I and a dose-dependent relation at 28 days.