OBJECTIVES: This study evaluated the effectiveness of different home bleaching agents on color alteration and their influence on surface and subsurface microhardness of discolored bovine enamel. MATERIAL AND METHODS: Forty-five fragments of bovine incisors were randomly allocated into 3 groups (n=15) according to the bleaching agent: 10% carbamide peroxide gel (CP10), 16% carbamide peroxide gel (CP16) and 6.5%-hydrogen-peroxide-based strip (HP6.5). Before bleaching treatment, initial values of Knoop surface microhardness and color (CIEL*a*b*) were obtained and the fragments were artificially stained in hemolyzed rat blood. Then, bleaching treatments were performed over a 21-day period. Color changes (ΔE) were assessed at 7, 14 and 21 days, and final surface microhardness reading was done after 21 days. Thereafter, the fragments were bisected to obtain subsurface microhardness. Data were subjected to ANOVA and Tukey's tests (α=5%). RESULTS: Color changes produced by CP16 were similar to those of CP10, and the color changes produced by these materials were significantly superior to those produced by HP6.5. Color changes at 21 days were superior to 7 days and similar to 14 days. The time did not influence color changes for CP16, which showed similarity between the 14- and 21-day results. No statistically significant differences were found among the home bleaching agents for surface and subsurface microhardness. CONCLUSIONS: Microhardness of bovine enamel was not affected by the bleaching agents. The 16% carbamide peroxide gel was the most effective for bleaching the stained substrate.

This study evaluated in vitro the pulp chamber temperature rise induced by the light-activated dental bleaching technique using different light sources. The root portions of 78 extracted sound human mandibular incisors were sectioned approximately 2 mm below the cementoenamel junction. The root cavities of the crowns were enlarged to facilitate the correct placing of the sensor into the pulp chamber. Half of specimens (n=39) was assigned to receive a 35% hydrogen peroxide gel on the buccal surface and the other halt (n=39) not to receive the bleaching agent. Three groups (n=13) were formed for each condition (bleach or no bleach) according to the use of 3 light sources recommended for dental bleaching: a light-emitting diode (LED)laser system, a LED unit and a conventional halogen light. The light sources were positioned perpendicular to the buccal surface at a distance of 5 mm and activated during 30 s. The differences between the initial and the highest temperature readings for each specimen were obtained, and, from the temperature changes, the means for each specimen and each group were calculated. The values of temperature rise were compared using Kruskal-Wallis test at 1% significance level. Temperature rise varied significantly depending on the light-curing unit, with statistically significant differences (p<0.01) among the groups. When the bleaching agent was not applied, the halogen light induced the highest temperature rise (2.38±0.66ºC). The LED unit produced the lowest temperature increase (0.29±0.13ºC); but there was no significant difference between LED unit and LED-laser system (0.35±0.15ºC) (p>0.01). When the bleaching agent was applied, there were significant differences among groups (p<0.01): halogen light induced the highest temperature rise (1.41±0.64ºC), and LED-laser system the lowest (0.33±0.12ºC); however, there was no difference between LED-laser system and LED unit (0.44±0.11ºC). LED and LED-laser system did not differ significantly from each other regardless the temperature rise occurred with or without bleaching agent application. It may be concluded that during light-activated tooth bleaching, with or without the bleaching agent, halogen light promoted higher pulp chamber temperature rise than LED unit and LED-laser system. The tested light-curing units provided increases in the pulp chamber temperature that were compatible with pulpal health.

A proposta deste estudo foi avaliar, por meio de microscopia eletrônica de varredura (MEV), a efetividade dos irrigantes endodônticos na remoção da "smear layer" das paredes dos canais radiculares instrumentados. Os irrigantes endodônticos utilizados foram: solução de hipoclorito de sódio a 1%; solução de hipoclorito de sódio a 1% misturado ao EDTAC a 17%, gel de clorexidina a 2% e gel de Ricinus communis. Fotomicrografias dos terços médio e apical foram avaliadas com o auxílio do software Fotoscore - versão 2.0. Os resultados indicaram que a mistura da solução de hipoclorito de sódio e EDTAC removeu eficientemente a "smear layer" das paredes dentinárias. Os demais irrigantes endodônticos não foram tão eficientes na limpeza dos canais.

The purpose of this study was to assess the effectiveness of endodontic irrigants in removing the smear layer from instrumented root canal walls using Scanning Electron Microscopy (SEM). The endodontic irrigants used were: 1% sodium hypochlorite (NaOCl); 1% NaOCl mixed to 17% EDTAC; 2% chlorhexidine gel; and Ricinus communis gel. Photomicrographs of the middle and apical thirds were evaluated with the aid of the Fotoscore - v. 2.0 software. The results indicated that the mixture of sodium hypochlorite and EDTAC completely removed the smear layer from dentinal walls. The other endodontic irrigants were not as efficient in cleansing the root canals.

O objetivo deste trabalho foi comparar in vitro a alteração de temperatura na superfície radicular externa durante o preparo para contenção intra-radicular utilizando 4 técnicas de remoção da guta-percha: condensadores aquecidos, brocas de Peeso, Gates-Glidden e Largo, em 40 dentes pré-molares inferiores (unirradiculares) tratados endodonticamente. O experimento foi realizado em uma câmara com temperatura controlada em torno de 26°C. Para a remoção da guta-percha do interior dos canais, foram calculados dois terços do comprimento da raiz, deixando em torno de 4 mm de obturação apical. As medições da temperatura radicular externa foram realizadas com um termopar acoplado a um multímetro e efetuadas em 3 regiões: cervical (em torno de 3 mm abaixo da junção cemento-esmalte), média e apical. A análise de variância indicou diferenças significantes (p < 0,01) entre as regiões e as técnicas utilizadas. O teste complementar de Tukey indicou que os condensadores aquecidos produziram o maior aumento de temperatura dentre as técnicas, e a broca de Peeso dentre as brocas, seguida pela de Largo e de Gates-Glidden. Dentre as regiões, a apical apresentou a maior alteração de temperatura em todas as técnicas avaliadas.

The objective of the present study was to compare the change in temperature on the external surface of the root in vitro during post and core preparation using 4 different techniques. Forty lower single-root premolars instrumented and filled with gutta-percha and stored in 10% formalin were divided into 4 groups according to the technique of gutta-percha removal employed, using heated endodontic pluggers and Peeso, Largo and Gates-Glidden burs. The experiment was performed in a chamber with controlled temperature maintained at about 26°C. For gutta-percha removal from the canals, 2/3 of the root length was calculated and approximately 4 mm of apical filling was left. The temperature of the external surface of the root was measured with a thermo-couple connected to a multimeter and measurements were made in 3 regions: cervical (about 3 mm below the cementum-enamel junction), middle and apical regions of a predetermined measurent. Analysis of variance indicated significant differences (p < 0.01) between regions and techniques. The complementary Tukey test indicated that the heated endodontic pluggers produced the greatest increased in temperature among the three techniques, and the Peeso bur produced the greatest increase in temperature among the burs used. Among regions, the apical one presented the greatest change in temperature for all the techniques evaluated.

A presente pesquisa analisa in vitro as alterações anatômicas dos 4 mm apicais de 68 raízes mesiais de molares inferiores permanentes humanos, utilizando-se de microscópio esterioscópio. Cada raiz foi incluida em bloco de resina acrílica autopolimerizável, cortada transversalmente à partir de 1 mm apical obtendo-se 4 cortes em sentido cervical. Os resultados demonstraram a complexidade anatômica do terço apical da raiz mesial dos molares inferiores, com a presença de um ou dois canais radiculares. Quando da presença de dois canais radiculares estes podem apresenta-se totalmente independentes em toda extensão da raiz ou unirem-se em diferentes níveis para terminar em canal único. Verificou-se presença de istmo entre os canais mesio-vestibular e mesio-lingual. Em raízes com canal único, observou-se a alteração da forma do canal a medida que se aproxima do extremo apical.

The anatomical apex of the mesial root of the lower molars presents a morphological complexity related to the number and shape of the root canals as well as of the apical foramen and isthmus presence. The knowledge of the complexity of the endodontic system of the molar root area is essencial to select more carefully the best instrumentation and obturation technique, to obtain a more successful endodontic therapy.

Uma das dificuldades durante o tratamento endodôntico é a determinação do comprimento de trabalho, devido às limitações impostas pela imagem radiográfica. Muitas técnicas têm sido desenvolvidas com o intuito de facilitar a execução da odontometria durante o tratamento endodôntico. Nosso objetivo foi comparar clinicamente a eficácia de dois métodos auxiliares na odontometria: a tela milimetrada e o localizador apical eletrônico (APIT, Osada, Japão). Os resultados foram concordantes em 76,47% dos casos quando se tratava de dentes com polpa vital, e em dentes com polpa em estado necrótico os resultados foram concordantes em 83,64% dos casos. O APIT não foi eficiente na determinação do comprimento radicular somente nos canais obliterados ou com ápices que apresentavam grandes reabsorções. A tela milimetrada apresentou menor eficácia na determinação do comprimento de trabalho devido à própria limitação radiográfica. O localizador eletrônico mostrou-se mais eficiente que a tela milimetrada, porém apresenta um custo elevado.

One of the greatest difficulties in endodontic treatment is to determine the working length, due to the limitations imposed by radiographic images. Many techniques have been developed with the intention of facilitating dental measurement during endodontic treatment. Our objective was to carry out a clinical comparison of the efficacy of two methods often used in dental measurement: grid pattern and electronic apex locator (APIT, Osada, Japan). Similar results were found in 76,46% of the cases, in teeth with the vital pulp preserved; and in teeth with necrotic pulp, results agreed in 83,64% of the cases. APIT was not efficient to determine the radicular length only in obliterated root canal, or with apexes which had large resorptions. The grid pattern presented less efficiency in determining the working length due to its own radiographic limitations. The electronic positioner was more efficient than the grid pattern but it has a higher cost.