ABSTRACT: The aim of the study was to investigate the effect of internal bleaching on physical proprieties and ultrastructure of the bovine dentin.40 bovine incisors were used, divided in four experimental groups: control group, composed by teeth that did not receive the bleaching agent (G1); teeth submitted to a single internal bleaching session (G2); teeth submitted to two internal bleaching sessions (G3); teeth submitted to three internal bleaching sessions (G4). In each of the sessions, 35 % hydrogen peroxide was applied for 45 minutes on the dentin surface. Tests were performed (microhardness and roughness) and were analyzed using one-way analysis of variance (ANOVA) and Tukey’s post-hoc test (p≤0.05). Electromicrographs were captured for quality analysis. In the analysis of the superficial microhardness of the dentin, the internal bleaching reduced the Knoop microhardness since the first session, being observed statistically significant differences between the experimental groups and the control. The surface roughness gradually increased in the G2, G3 and G4 groups, but only G4 presented a statistically significant difference from the others. The qualitatively evaluated electromicrographs showed damage to the dentin ultrastructure, with areas of erosion and greater involvement of the intertubular when compared to peritubular dentin. Internal bleaching with 35 % hydrogen peroxide caused injuries in bovine dentin from the first treatment session. Both modifications in physical properties and dentin ultrastructure have been identified. These changes were intensified the higher the number of dentin internal bleaching sessions was exposed.

RESUMEN: El objetivo de este estudio fue investigar el efecto del blanqueamiento interno sobre las propiedades físicas y la ultraestructura de la dentina bovina. Se utilizaron 40 incisivos bovinos, divididos en cuatro grupos experimentales: grupo de control, compuesto por dientes que no recibieron el agente blanqueador (G1); dientes sometidos a una única sesión interna de blanqueamiento (G2); dientes sometidos a dos sesiones internas de blanqueamiento (G3); dientes sometidos a tres sesiones internas de blanqueamiento (G4). En cada una de las sesiones, se aplicó peróxido de hidrógeno al 35 % durante 45 minutos en la superficie de la dentina. Se realizaron pruebas (microdureza y rugosidad). Los datos se analizaron mediante análisis de varianza de una vía (ANOVA) y prueba post-hoc de Tukey (p≤0,05). Las electromicrografías fueron capturadas para el análisis cualitativo. En el análisis de la microdureza superficial de la dentina, el blanqueamiento interno redujo la microdureza de Knoop desde la primera sesión, observándose diferencias estadísticamente significativas entre los grupos experimentales y el control [NF2]. La rugosidad superficial aumentó gradualmente en los grupos G2, G3 y G4, pero solo G4 presentó una diferencia estadísticamente significativa con respecto a los otros [NF3]. Las electromicrografías evaluadas cualitativamente mostraron daño a la ultraestructura de la dentina, con áreas de erosión y una mayor participación de la dentina intertubular en comparación con la dentina peritubular. El blanqueamiento interno con peróxido de hidrógeno al 35 % causó lesiones en la dentina bovina en la primera sesión del tratamiento. Ambas modificaciones, en propiedades físicas y en la ultraestructura dentinaria, han sido identificadas. Estos cambios se intensificaron a medida que se expuso a mayor número de sesiones de blanqueamiento interno en la dentina.

RESUMO Introdução: os remanescentes epiteliais de Malassez (REM) se configuram como um grupo de células epiteliais presentes no ligamento periodontal, classicamente consideradas estruturas latentes ou quiescentes, associadas a processos patológicos. Entretanto, ao longo dos anos, esse paradigma vem sendo rompido e hoje não mais são consideradas apenas como restos celulares, mas sim uma importante estrutura tecidual, com funções na manutenção da homeostase do periodonto, inclusive durante a movimentação ortodôntica. Objetivo: na presente revisão da literatura, buscou-se apresentar as funções dessas estruturas, com ênfase nelas durante a movimentação ortodôntica, rompendo o conceito errôneo de que são meros restos celulares, e defendendo sua compreensão como uma estrutura funcional do periodonto. Conclusão: os REM possuem uma atividade funcional na modulação da movimentação ortodôntica, por meio de seu potencial para diferenciação, de suas funções de manutenção e de sua capacidade de reparação periodontal.

ABSTRACT Introduction: The epithelial rests of Malassez (ERM) represent a group of cells in the periodontal ligament classically consisting of latent or quiescent structures associated with pathological processes. However, recent evidence shows that these structures cannot be considered only as cellular debris. The ERM is a major tissue structure, with functions in maintaining the homeostasis of periodontal tissue, including the maintenance of orthodontic movement. Objective: The present literature review aims at presenting the potential functions of ERM, with emphasis on orthodontic movement and the functional structure of the periodontium. Conclusion: ERM cells have a functional activity in modulation of orthodontic movement, trough their potential for differentiation, maintenance functions and the capacity of repairing periodontium.

There are no studies in the literature reporting the prevalence of root canal ramifications in samples of lower incisors in the population of northern Brazil. The knowledge of the usual endodontic morphology and its possible anatomical variations is important. The aim of this study was to evaluate the prevalence of canals in the lower incisors in the population of northern Brazil using the descaling and diaphanization method. In addition, external measurements were performed and the direction of the apical foramen was observed. One hundred teeth were used for this study, and 18 % of them had two canals, with type 3 being the most prevalent, and the lowest incidence was type 5. The average length of the teeth was 18.5 mm, with 76.31 % of the teeth having a foramen that coincided with the long axis of the tooth. Prior knowledge of such changes should be considered before endodontic therapy.

No hay estudios en la literatura que reporten la prevalencia de las ramificaciones del canal radicular en muestras de incisivos inferiores en la población del Norte de Brasil. El conocimiento de la morfología dentaria en endodoncia y sus posibles variaciones anatómicas es importante. El objetivo del estudio fue evaluar la prevalencia de canales en los incisivos inferiores en la población del Norte de Brasil utilizando el método de descalcificación y diafanización. Además, se realizaron mediciones externas y se observó la dirección del foramen apical. Cien dientes fueron utilizados en este estudio, 18 % tenían dos canales, siendo el tipo 3 el más prevalente, y solo un diente presentó el tipo 5. La longitud promedio de los dientes fue de 18,5 mm, de los cuales en el 76,31 % de éstos se observó un foramen que coincidió con el eje longitudinal del diente. El conocimiento previo de éstas variaciones debe ser considerado antes de la terapia endodóntica.

RESUMO Introdução: o acúmulo de detritos na interface braquete-arco pode influenciar no atrito, mas a limpeza dos braquetes usando jatos de bicarbonato de sódio pode interferir nesse processo. Objetivo: o objetivo desse estudo foi avaliar a força de atrito e a quantidade de detritos remanescentes em braquetes ortodônticos submetidos à profilaxia com jatos de bicarbonato de sódio. Material e Métodos: avaliou-se, ao final do tratamento ortodôntico, a força de atrito e o acúmulo de detritos na superfície de 28 braquetes de pré-molares. Em uma hemiarcada, os braquetes foram jateados com bicarbonato de sódio (n = 14) por 5 segundos, enquanto a hemiarcada contralateral serviu de controle (n = 14). Foram realizados ensaios mecânicos de atrito e análise imagiológica dos braquetes de ambas as hemiarcadas, a jateada e a controle. O teste de Wilcoxon foi utilizado para a análise comparativa entre as hemiarcadas, com p < 0,05. Resultados: os braquetes submetidos à limpeza com jatos de bicarbonato de sódio apresentaram menor atrito (mediana = 1,27N), quando comparados aos do lado controle (mediana = 4,52N) (p < 0,01). A análise imagiológica demonstrou que o grupo controle apresentou maior acúmulo de detritos (mediana = 2,0), em comparação ao grupo que recebeu profilaxia com jatos de bicarbonato (mediana = 0,5) (p < 0,05). Conclusão: a limpeza dos braquetes ortodônticos por meio do jateamento com bicarbonato de sódio reduz significativamente o acúmulo de detritos na superfície deles, bem como os níveis de atrito observados durante a mecânica de deslizamento.

ABSTRACT Introduction: Debris buildup on the bracket-wire interface can influence friction. Cleansing brackets with air-powder polishing can affect this process. Objective: The aim of this study was to evaluate the frictional force and amount of debris remaining on orthodontic brackets subjected to prophylaxis with air-powder polishing. Methods: Frictional force and debris buildup on the surface of 28 premolar brackets were evaluated after orthodontic treatment. In one hemiarch, each bracket was subjected to air-powder polishing (n = 14) for five seconds, while the contralateral hemiarch (n = 14) served as control. Mechanical friction tests were performed and images of the polished bracket surfaces and control surfaces were examined. Wilcoxon test was applied for comparative analysis between hemiarches at p < 0.05. Results: Brackets that had been cleaned with air-powder polishing showed lower friction (median = 1.27 N) when compared to the control surfaces (median = 4.52 N) (p < 0.01). Image analysis showed that the control group exhibited greater debris buildup (median = 2.0) compared with the group that received prophylaxis with air-powder polishing (median = 0.5) (p < 0.05). Conclusion: Cleansing orthodontic brackets with air-powder polishing significantly reduces debris buildup on the bracket surface while decreasing friction levels observed during sliding mechanics.

Remnants of calcium hydroxide (Ca(OH)2) post-irrigation can compromise cleansing and permeability of dentinal walls in endodontic therapy. The aim of this study was to evaluate effectiveness of irrigation needle NaviTip FX on intracanal Calcium Hydroxide removal. Twenty-two single-rooted human teeth were randomly assigned according to irrigation needle used after calcium hydroxide removal: G1- NaviTip; G2- NaviTip FX, both with n= 9; as well as negative and positive control groups, with n= 2. The samples were analyzed in scanning electron microscopy, with 500x magnification. The difference between groups were analysed by Student t test, for p 0.01. In apical third, G2 group presents better cleaning in comparison with G1 (p= 0.0007). In middle third, no differences between groups were observed. NaviTip FX irrigation needle shows greater effectiveness in removing calcium hydroxide medication than NaviTip needle in the apical third of the canal.

La presencia de hidróxido de calcio post-irrigación compromete la limpieza y la permeabilidad de la pared de la dentina durante el tratamiento endodóntico. El objetivo deste estudio fue evaluar la eficacia de la cánula de irrigación Navitip Fx en la eliminación de hidróxido de cálcio intracanalicular. Veintidós dientes unirradiculares humanos fueron divididos aleatoriamente de acuerdo con la cánula de irrigación, después de la eliminación del hidróxido de calcio, en grupos: G1- Navitip; G2- Navitip FX, ambos con n= 9; así como los grupos de control positivos y negativos, con n= 2. Las muestras fueron analizadas bajo microscopía electrónica de barrido, con magnificación de 500x. La diferencia entre los grupos fue analizada con la prueba t de Student (p 0,01). En el tercio apical, el grupo G2 presentó mejor limpieza en comparación con el grupo G1 (p= 0,0007). En el tercio medio, no se observaron diferencias entre los grupos. La cánula de irrigación Navitip FX muestra una mayor eficiencia en la eliminación de la medicación hidróxido de calcio en comparación con Navitip cánula en el tercio apical del canal.