Multimethod analysis of large- and low-tapered single file reciprocating instruments: Design, metallurgy, mechanical performance, and irrigation flow.

AIM: To compare eight large- and low-tapered heat-treated reciprocating instruments regarding their design, metallurgy, mechanical properties, and irrigation flow through an in silico model. METHODOLOGY: A total of 472 new 25-mm E-Flex Rex (25/.04 and 25/.06), Excalibur (25/.05), Procodile (25/.06), Reciproc Blue R25 (25/.08v), WaveOne Gold Primary (25/.07v), and Univy Sense (25/.04 and 25/.06) instruments were evaluated regarding their design (stereomicroscopy, scanning electron microscopy, and 3D surface scanning), metallurgy (energy-dispersive X-ray spectroscopy and differential scanning calorimetry), and mechanical performance (cyclic fatigue, torsional resistance, cutting ability, bending and buckling resistance). Computational fluid dynamics assessment was also conducted to determine the irrigation flow pattern, apical pressure, and wall shear stress in simulated canal preparations. Kruskal-Wallis and one-way anova post hoc Tukey tests were used for statistical comparisons (α = 5%). RESULTS: Instruments presented variations in blade numbers, helical angles, and tip designs, with all featuring non-active tips, symmetrical blades, and equiatomic nickel-titanium ratios. Cross-sectional designs exhibited an S-shaped geometry, except for WaveOne Gold. Univy 25/.04 and Reciproc Blue displayed the smallest and largest core diameters at D3. Univy 25/.04 and E-Flex Rec 25/.04 demonstrated the longest time to fracture (p < .05). Reciproc Blue and Univy 25/.04 exhibited the highest and lowest torque to fracture, respectively (p < .05). Univy 25/.04 and Reciproc Blue had the highest rotation angles, whilst E-Flex Rec 25/.06 showed the lowest angle (p < .05). The better cutting ability was observed with E-Flex Rec 25/.06, Procodile, Excalibur, and Reciproc Blue (p > .05). Reciproc R25 and E-Flex Rec showed the highest buckling resistance values (p < .05), with WaveOne Gold being the least flexible instrument. The impact of instruments' size and taper on wall shear stress and apical pressure did not follow a distinct pattern, although Univy 25/.04 and E-Flex Rec 25/.06 yielded the highest and lowest values for both parameters, respectively. CONCLUSIONS: Low-tapered reciprocating instruments exhibit increased flexibility, higher time to fracture, and greater angles of rotation, coupled with reduced maximum bending loads and buckling strength compared to large-tapered instruments. Nevertheless, low-tapered systems also exhibit lower maximum torque to fracture and inferior cutting ability, contributing to a narrower apical canal enlargement that may compromise the penetration of irrigants in that region.

Comparative in vitro analysis of the antifungal activity of different calcium silicate-based endodontic sealers

Aim: This study aimed to perform an in vitro comparative analysis of the antifungal activity of different calcium silicate-based endodontic sealers against three fungal species. Methods: The antifungal properties of three calcium silicate-based sealers were tested: Bio-C Sealer, Cambiar a Sealer Plus BC, and MTA-Fillapex. Two commonly used sealers were used as controls: AH Plus and Endomethasone. An agar diffusion test was performed to analyze the antifungal activity of the sealers against Candida albicans, Candida glabrata, Candida tropicalis, and a mixed microbial culture medium. The results were analyzed using ANOVA (p <0.05). Results: Endomethasone exhibited the highest inhibition against all strains examined, maintaining a consistent level of inhibition throughout 7 days. MTA-Fillapex demonstrated the best performance among the calcium silicate-based sealers for the three fungal species (p < 0.05), maintaining stable values over the 7 days, surpassing that of Endomethasone. Nevertheless, MTA-Fillapex only exhibited antimicrobial effect against the mixed culture for the first 24 hours, and no antimicrobial activity was observed at 48 hours, being surpassed by all tested sealers (p < 0.05). Conclusion: Of all silicate-based sealers tested, only MTA-Fillapex exhibited promising antifungal activity. Nevertheless, care must be taken when extrapolating these results, as MTA-Fillapex exhibited poor antimicrobial activity when tested in mixed microbial cultures

Segundo Conducto Mesiovestibular en Molares Superiores: Prevalencia y Análisis Anatómico Mediante Tomografía Computarizada de Haz Cónico / Second Mesiobuccal Canal in Maxillary Molars: Prevalence and Anatomical Analysis Through Cone Beam Computed Tomography

El objetivo de este estudio fue utilizar la Tomografía Computarizada de Haz Cónico (TCHC) para investigar la configuración anatómica, prevalencia y distribución del conducto mesiovestibular Dos (MV2) en molares superiores de una subpoblación chilena, considerando variables como la presencia del conducto MV2, la clasificación de Vertucci, el género y edad. Estudio observacional de corte transversal. La muestra consistió en Tomografías Computarizadas de Haz Cónico tomadas en la clínica odontológica de la Universidad Andrés Bello (Viña del Mar). Se calculó el tamaño muestral utilizando la fórmula de población conocida, lo que resultó en 262 tomografías. Los examinadores se calibraron utilizando el coeficiente Kappa de Cohen, para luego analizar las variables mediante un estudio imagenológico utilizando el software I-CAT Visión. Se analizaron 439 primeros y segundos molares superiores. La prevalencia del conducto MV2 en primeros molares fue del 63,74 %, mientras que, en segundos molares, fue del 20,04 %. La prevalencia en primeros molares fue mayor en hombres (73,86 %) que en mujeres (58,62 %), mientras que, en segundos molares, fue del 15,81 % en mujeres y del 28,41 % en hombres. En relación con la edad, en los primeros molares la diferencia fue significativa en el rango de 18 a 40 años (66,49 %). En cuanto al tipo de configuración según Vertucci (2005), el 70 % de los primeros molares presentó una configuración Tipo II, y un 23,65 % Tipo IV, con resultados similares en los segundos molares. El presente estudio demostró que los conductos MV2 son frecuentes en la población analizada, especialmente en los primeros molares, y que la configuración Tipo II es la más prevalente. Además, se observó una mayor prevalencia en hombres y en el rango de 18 a 40 años. Estos hallazgos proporcionan información relevante sobre la anatomía radicular en la población y pueden contribuir a mejorar los resultados de tratamiento.

SUMMARY: The aim of this study was to use Cone-beam Computed Tomography (TCHC) to investigate the anatomical configuration, prevalence, and distribution of the Second Mesiobuccal (MB2) canal in upper molars of a Chilean subpopulation, considering variables such as the presence of MB2 canal, Vertucci classification, gender, and age. Cross-sectional observational study. The sample consisted of TCHC scans taken at the dental clinic of Universidad Andrés Bello (Viña del Mar). The sample size was calculated using the formula for known population, resulting in 262 scans. The examiners were calibrated using Cohen's Kappa coefficient, then the variables were analyzed through an imaging study using I-CAT Vision software. 439 first and second upper molars were analyzed. The prevalence of MB2 canal in first molars was 63.74 %, while in second molars, it was 20.04 %. The prevalence in first molars was higher in males (73.86 %) than in females (58.62 %), while in second molars, it was 15.81 % in females and 28.41 % in males. Regarding age, in first molars the difference was significant between the age range of 18 to 40 years (66.49 %). Regarding the type of configuration according to Vertucci, 70 % of the first molars had Type II configuration, and 23.65 % had Type IV, with similar results in second molars. The present study demonstrated that MB2 canals are frequent in the analyzed population, especially in first molars, and Type II configuration is the most prevalent. Additionally, a higher prevalence was observed in males and in the age range of 18 to 40 years. These findings provide relevant information about root anatomy in the studied population and can contribute to improving treatment outcomes.

Association between second mesiobuccal missed canals and apical periodontitis in maxillary molars of a Chilean subpopulation.

Background: To determine the frequency of missed second mesiobuccal canals (MB2) and apical periodontitis in maxillary molars of a Chilean subpopulation using cone beam computed tomography (CBCT). Material and Methods: Two previously calibrated operators evaluated CBCTs with a total of 588 upper molars, of which 179 endodontically treated molars were selected. Axial tomographic slices were used to study the frequency and association between the presence of apical periodontitis and untreated MB2 canals. Results: Of the 179 endodontically treated molars, 45.78% (84) presented MB2 missed canals. Of the upper molars that presented MB2 missed canals, 70% were associated with apical periodontitis, which was statistically significant (p< 0.0001). Sixty-two corresponded to first molars (74%) and 22 to second molars (26%). Of the first molars, 34 (54.8%) presented with apical periodontitis and MB2 missed canals (p< 0.0001), while 12 (54.4%) of the second molars presented this association (p = 0.081). Conclusions: MB2 missed canals are associated with a high degree of apical periodontitis and may be an important predictor of endodontic prognosis of upper molars. Key words:Endodontics, apical periodontitis, cone beam computed tomography, missed canals, maxillary molars.

Effect of Ultrasonic Activation on Dentinal Tubule Penetration of Bio-C Temp and Ultracal XS: A Comparative CLSM Assessment.

OBJECTIVE: The aim of this study was to compare the effect of ultrasonic activation (UA) on tubular penetration between Bio-C Temp and Ultracal XS intracanal medicaments. METHODS: Forty single-rooted human premolars were endodontically prepared and divided into 4 experimental groups (n=10): Bio-C Temp, Bio-C Temp+UA, UltraCal XS and UltraCal XS+UA. All medicaments were previously mixed with a specific calcium marker (Fluo-3) and passively injected into the canals. The samples were incubated for 7 days. For each tooth, 1 mm thick sections were obtained from the middle and apical thirds of the canals. The samples were examined by confocal laser scanning microscopy (CLSM) and the depth and area of penetration were determined for each group. The Student t test was used to compare results between groups (p<0.05). RESULTS: UA increased the depth and penetration area of Bio-C Temp and Ultracal XS, showing significant differences in the penetration area of the apical third for Bio-C Temp (p<0.0339). Bio-C Temp presented greater tubular penetration than Ultracal XS, showing significant differences in the depth of penetration in the apical third (p<0.0005), and in the penetration area in the middle (p<0.0016) and apical third (p<0.0339) after UA. CONCLUSION: UA increases tubular penetration (both depth and area) of Bio-C Temp at the apical third but has no significant effect on Ultracal XS. Bio-C Temp has a greater depth and tubular penetration area than Ultracal XS after UA. (EEJ-2023-02-024).

Prevalence and C-shaped root canal configuration in lower molars in the metropolitan region, Chile / Prevalencia y configuración de conductos en C en molares inferiores de la región metropolitana, Chile

Objetive: The aim of this study was to determine the prevalence, demographics, and root configuration of C-shaped canals of mandibular molars by means of cone beam computed tomography in the population of the Metropolitan Region, Chile. Material and Methods: 912 molars (456 first and 456 second molars) resulting from the analysis of 228 mandibular CT scans were evaluated. The root configuration was established by means of a panoramic reconstruction and axial tomographic sections, classifying the presence and type of canals through the analysis of five sections or cuts along the root. Data were statistically analyzed using a 5% confidence interval. Results: Of the 912 molars analyzed, 70 were classified as C-shaped canals (7.68%), corresponding to 58.33% of those molars that presented fused roots. 95.7% of this root canal configuration was observed in lower second molars, occurring more frequently in females (n=45, 64.29%). 45.65% of the cases that presented C-shaped canals were bilateral and the most frequent configuration was C3 (n=401, 66.63%) according to the Melton classification.Conclusion: The C-shaped canals of the mandibular molars in the studied population were observed mainly in second molars, showing a clear prevalence among females and a high percentage of bilaterality. The presence of fused roots significantly increases the possibility of finding this type of root configuration.

Objetivo: El objetivo del presente estudio fue determinar, por medio de tomografía computarizada de haz cónico, la prevalencia, demografía y configuración radicular de los conductos en forma de C de molares inferiores en la población de la Región Metropolitana, Chile. Material y Métodos: 912 molares (456 primeros y 456 segundos molares) resultantes del análisis de 228 tomografías mandibulares fueron evaluados. Mediante una reconstrucción panorámica y cortes tomográficos axiales se estableció la configuración radicular, clasificando la presencia y tipo de conducto por medio del análisis de 5 cortes a lo largo de la raíz. Los datos fueron analizados estadísticamente con un intervalo de confianza del 5%. Resultados: De los 912 molares analizados, 70 fueron clasificados como conductos en forma de C (7.68%), correspondiendo al 58.33% de aquellos molares que presentaron raíces fusionadas. El 95.7% de esta configuración de conductos fue observada en segundos molares inferiores, presentándose con mayor frecuencia en mujeres (n=45, 64.29%). El 45.65% de los casos que presentaron conductos en C se manifestaron bilateralmente y la configuración más frecuente observada fue la C3 (n=401, 66.63%) según la clasificación de Melton. Conclusión: Los conductos en forma de C de los molares mandibulares en la población estudiada fueron observados principalmente en segundos molares, marcando una clara predilección por el sexo femenino y un alto porcentaje de bilateralidad. La presencia de raíces fusionadas aumenta significativamente la posibilidad de encontrar este tipo de configuración radicular.

Alargamento do forame como complemento no tratamento endodôntico para regeneração de uma lesão periapical extensa: relato de caso / Foraminal enlargement as a complement in the endodontic treatment for the regeneration of an extensive periapical lesion. A case report

Introdução: O alargamento do forame refere-se ao alargamento mecânico intencional do forame para reduzir a carga bacteriana em uma área afetada frequentemente por infecções endodônticas além do limite da constrição apical. Objetivo: O objetivo do presente relato de caso é apresentar a técnica de alargamento do forame de um dente com lesão periapical extensa, como complemento do tratamento endodôntico e alternativa precoce à microcirurgia periapical. Métodos: É apresentado o caso de um incisivo lateral superior endodonticamente tratado, com uma extensa lesão periapical associada. Devido à história clínica e radiográfica, tempo decorrido desde o tratamento endodôntico inicial e alta probabilidade de áreas de reabsorção apical com biofilme extrarradicular, o retratamento endodôntico com alargamento do forame foi indicado como primeira opção, adiando a indicação de cirurgia endodôntica de acordo com a evolução. Resultados: Na avaliação de acompanhamento de dois anos, por exame de imagem, observou-se evolução clínica favorável ao retratamento, com aumento total da densidade óssea. O procedimento cirúrgico endodôntico complementar foi descartado. Conclusão: O alargamento do forame é uma alternativa complementar viável em casos de periodontite apical de longa duração com suspeita de biofilme no nível do forame. Pode ser considerado uma opção antes da indicação de retratamento endodôntico cirúrgico (AU).

Introduction: Foraminal enlargement refers to intentional mechanical enlargement of the foramen to reduce the bacterial load in an area frequently affected by endodontic infections beyond the limits of the apical constriction. The objective of this case report is to present the foraminal enlargement technique of a tooth with an extensive periapical lesion as a complement in the endodontic treatment and an early alternative to periapical microsurgery. Materials and methods: The case is presented of an endodontically treated upper lateral incisor with an extensive associated periapical lesion. Due to the clinical and radiographic history, the time elapsed since the initial endodontic treatment, and the high probability of areas of apical resorption with extra-radicular biofilm, endodontic retreatment with foraminal enlargement was indicated as the first option, postponing the indication for endodontic surgery according to evolution. Results: In the follow-up appointment at 2 years, a favorable clinical imaging evolution of retreatment was observed, with a total increase in bone density. The complementary endodontic surgical procedure was discarded. Conclusion: Foraminal enlargement is a viable complementary alternative in cases of long-term apical periodontitis with suspicion of biofilm at the foramen level. It can be considered an option before the indication of surgical endodontic retreatment (AU).

Dentinal Tubule Penetration and Adaptation of Bio-C Sealer and AH-Plus: A Comparative SEM Evaluation.

OBJECTIVE: The aim of this study was to compare and evaluate the dentinal tubule penetration and adaptation of a premixed bioceramic sealer and an epoxy-resin based sealer in the three radicular thirds. METHODS: 30 wide roots, with single straight canals and totally formed apexes, were endodontically prepared and divided into two groups (n=14) according to the sealer used for root canal filling: AH-Plus (AHP) and Bio-C Sealer (BIOC). Two samples were left as controls. After the canals were filled, the samples were cut and viewed under Scanning Electron Microscopy by taking images to analyse the tubular penetration and adaptation of the sealers. The results were statistically analysed with the Shapiro Wilk, Levene and Mann-Whitney tests (P<0.05). RESULTS: BIOC showed significantly higher penetration in dentinal tubules than AHP in the cervical, middle and apical thirds of the root canal (P<0.05) and better adaptation to the dentinal tubule walls. CONCLUSION: Under the parameters of this study, BIOC exhibits higher penetration and better adaptation to the dentinal tubules compared to AHP.

Prevalence and Configuration of C-shaped Canals in Lower Molars from a Chilean Subpopulation / Prevalência e configuração de canais em forma de C em molares inferiores em subpopulação Chilena

Objective: To determine the prevalence of C-shaped canals in lower molars (first and second molars) in a Chilean subpopulation, and to identify root configuration and demographic characteristics using cone beam tomography.Materials and method: 912 molars (456 first and 456 second molars) resulting from the analysis of 228 mandibular CBCT scans (89 men and 139 women between 15 and 80 years old) were evaluated. Through panoramic reconstruction and axial tomographic sections, the root configuration was established, and the presence and type of C-shaped canal were classified, analyzing 5 levels along the root canal. Data were statistically analyzed with a 5% significance level. Results: Of the 912 molars analyzed, 69 were classified as C-shaped (7.57%), constituting 65.72% of those molars that presented fused roots. 100% of this configuration of canals was observed in lower second molars, presenting a higher prevalence in women (n = 49, 71.01%). 40.82% of the cases that presented a C-shaped configuration manifested bilaterally. The most frequent C-shaped canal configuration was C3 (n = 347, 66.10%), according to Melton's classification. Conclusion: The C-shaped canals in the studied population were observed entirely in lower second molars, showing a clear predilection for the female sex and a high rate of bilaterality (AU)

Objetivo: Determinar a prevalência de canais em forma de C em molares inferiores (primeiros e segundos molares) em uma subpopulação chilena e identificar a configuração radiculares e características demográficas utilizando tomografia feixe cônico. Material e Métodos: Foram avaliados 912 molares ( 456 primeiros e 456 segundos molares) resultando da análise de 228 tomografias de feixe cônico de mandíbulas (89 homens e 139 mulheres entre 15 e 80 anos). Através da reconstrução panorâmica e secções axiais de tomografias, a configuração da raiz foi estabelecida e a classificada a presença e tipo de canal em forma de C, analisando 5 níveis ao longo do canal radicular. Os dados foram analisados estatisticamente com significância de 5%. Resultados: Dos 912 molares analisados, 69 foram classificados como formato de C (7,57%), constituindo 65,72% dos molares que apresentavam raiz fusionadas. 100% dessas configurações de canais foram observados em segundos molares inferiores, com maior prevalência em mulheres (n=49, 71,01%). 40,82% dos casos presentes como formato de C manifestaram-se bilateralmente. A maior frequência das configurações do canal em forma de C no canal foram C3 ( n=347, 66.10%) de acordo com a classificação de Melton. Conclusão: Canais em forma de C no estudo populacional foram observados em sua totalidade nos segundos molares inferiores, demonstrando nítida predileção pelo sexo feminino e alto índice de bilateralidade. (AU)

Evaluation of Internal bleaching with 35% hydrogen peroxide in dentin conditioned with 37% phosphoric acid and 17% EDTA / Evaluación del blanqueamiento interno con peróxido de hidrógeno al 35% en dentina acondicionada con ácido fosfórico al 37% y EDTA al 17%

Introduction: This study aimed to evaluate the effect of dentin surface treatment with 37% phosphoric acid or 17% ethylenedia-minetetraacetic acid (EDTA) before Internal Bleaching with 35% hydrogen peroxide using the walking bleach technique. Material and Methods: This experimental in vitro study used 66 human premolars extracted for orthodontic reasons, which were debrided, endodontically prepared, and pigmented with chromogens derived from blood decomposition. The samples were randomly divided into three groups (n=22). Group A: bleaching agent without dentin conditioning; group B: bleaching agent in dentin conditioned with phosphoric acid 37%; group C: bleaching agent in dentin conditioned with 17% EDTA. 4 applications of bleaching agent were used with a separation of 4 days between each session. The initial color (baseline) and after each application was determined by spectrophotometry, recording the CIE L*a*b* values and the total color variation between the initial parameters and the different evaluation times. Results: Data were statistically analyzed with the Wilcoxon test. This showed statistically significant differences for the total variation of the color between the study groups, with the control group in no case inferior to the rest. Conclusion: The application of 37% phosphoric acid increased the effectiveness of the bleaching agent when compared to 17% EDTA. However, these did not increase the effectiveness compared to the application of the bleaching agent without a previous dentin surface treatment.

Introducción: El objetivo de este estudio fue evaluar el efecto del tratamiento de superficie dentinaria con ácido fosfórico al 37% o EDTA al 17% previo al blanqueamiento Interno con peróxido de hidrógeno al 35% por medio de la técnica Walking Bleach. Material y Métodos:Para este estudio experimental in vitro, se utilizaron 66 premolares humanos extraídos por indicación ortodóncica, los cuales fueron desbridados, preparados endodónticamente, y pigmentados con cromógenos derivados de la descomposición sanguínea. Las muestras fueron divididas aleatoriamente en 3 grupos (n=22). Grupo A: agente blanqueador sin acondicionamiento dentinario, grupo B: agente blanqueador en dentina acondicionada con ácido fosfórico 37% y grupo C: agente blanqueador en dentina acondicionada con EDTA 17%. Se utilizaron 4 aplicaciones de agente blanqueador con una separación de 4 días entre cada sesión. El color inicial (baseline) y tras cada aplicación fue determinado mediante espectrofotometría, registrando los valores CIE L*a*b* y la variación total de color entre los parámetros iniciales y los diferentes tiempos de evaluación. Resultados: Los datos fueron analizados estadísticamente con la prueba de Wilcoxon, arrojando diferencias estadísticamente significativas para la variación total del color entre los grupos de estudio, siendo en ningún caso el grupo control inferior al resto. Conclusión: La aplicación de ácido fosfórico al 37% aumenta la eficacia del agente blanqueador al compararlo con el EDTA 17%, sin embargo, no aumentan la eficacia respecto a la aplicación del agente blanqueador sin un tratamiento de superficie dentinaria previo.

Effect of ultrasonic cleaning on the bond strength of fiber posts in oval canals filled with a premixed bioceramic root canal sealer.

OBJECTIVE: This study aimed to evaluate the effect of ultrasonic cleaning of the intracanal post space on the bond strength of fiber posts in oval canals filled with a premixed bioceramic (Bio-C Sealer [BIOC]) root canal sealer. MATERIALS AND METHODS: Fifty premolars were endodontically prepared and divided into 5 groups (n = 10), based on the type of root canal filling material used and the post space cleaning protocol. A1: gutta-percha + AH Plus (AHP) and post space preparation with ultrasonic cleaning, A2: gutta-percha + BIOC and post space preparation with ultrasonic cleaning, B1: gutta-percha + AHP and post space preparation, B2: gutta-percha + BIOC and post space preparation, C: control group. Fiber posts were cemented with a self-adhesive luting material, and 1 mm thick slices were sectioned from the middle and cervical third to evaluate the remaining filling material microscopically. The samples were subjected to a push-out test to analyze the bond strength of the fiber post, and the results were analyzed with the Shapiro-Wilk, Bonferroni, Kruskal-Wallis, and Mann-Whitney tests (p < 0.05). Failure modes were evaluated using optical microscopy. RESULTS: The results showed that the fiber posts cemented in canals sealed with BIOC had lower bond strength than those sealed with AHP. The ultrasonic cleaning of the post space improved the bond strength of fiber posts in canals sealed with AHP, but not with BIOC. CONCLUSIONS: BIOC decreased the bond strength of fiber posts in oval canals, regardless of ultrasonic cleaning.

Preparación Ultrasónica del Espacio Protésico y su Influencia en la Resistencia Adhesiva de Postes de Fibroresina en Conductos Ovalados / Ultrasonic Preparation of the Prosthetic Space and its Influence on the Bond Strength of Fiber Post in Oval-Shaped Canals

RESUMEN: Paredes sin instrumentar y con material obturador endodóntico residual pueden elevar la posibilidad de la falla adhesiva de postes de fibroresina. Las fresas de desobturación y conformación del espacio protésico poseen una sección circular, lo que dificulta una adecuada preparación y limpieza de las paredes de los conductos ovales. El objetivo del presente estudio fue evaluar la capacidad de limpieza ultrasónica del espacio protésico y cómo ésta influyó en la resistencia a la tracción de postes de fibroresina en conductos ovales. Se utilizaron 30 premolares con conducto ovalado divididos aleatoriamente en 3 grupos de estudio (n=10), siendo: grupo A: preparación rotatoria con complemento ultrasónico, grupo B: preparación rotatoria y grupo C: grupo control. Postes de fibra de vidrio fueron cementados y luego de 7 días se realizaron cortes de un milímetro de grosor del tercio cervical y medio de cada muestra y se evaluó microscópicamente el área de gutapercha remanente y área efectiva de adhesión. Estos fueron sometidos a una prueba de push out evaluando la resistencia adhesiva de los postes. Finalmente fueron observados microscópicamente para analizar tipo de falla. Los resultados se analizaron mediante el test de ANOVA, Bonferroni, Kruskal-Wallis y Mann Whitney (p < 0.05), registrando diferencias estadísticamente significativas en la resistencia a tracción, área de gutapercha remanente y área disponible para la adhesión; además de una relación directa entre gutapercha remanente y menor resistencia a la tracción. Conclusiones: La preparación ultrasónica del espacio protésico aumenta la resistencia a la tracción de postes de fibroresinas cementados en conductos ovalados.

ABSTRACT: Untouched canal walls with residual filling materials can increase the probability of adhesive failure of fiber posts. The drills used for desobturation and conformation of the prosthetic space, has a circular cross section, which does not allow a proper preparation and cleaning of oval-shaped canal walls. The objective of the study was to evaluate the ultrasonic cleaning of the prosthetic space and how this influences the adhesive strength of fiber posts in oval-shaped canals. Thirty (30) oval-shaped canal premolars were randomly divided into 3 groups (n = 10): Group A: rotary desobturation with ultrasonic complement, group B: rotary desobturation without ultrasonic complement and group C: control group. Fiberglass posts were cemented; after 7 days, one-millimeter slices were performed, one of the cervical and another from the middle third of the root. The slices were analyzed under an optical microscope to evaluate remaining gutta percha and effective adhesion area. Samples were subjected to a push-out test to evaluate bond strength of the fiber resin posts. Finally, samples were evaluated microscopically to analyze the type of failure. The results were analyzed using ANOVA, Bonferroni, KruskalWallis and Mann Whitney test (p < 0.05), recording statistically significant differences in bond strength, remaining gutta-percha area and clean walls for adhesion; In addition, to a direct relationship between remaining gutta percha and lower adhesive strength, the ultrasonic preparation of the prosthetic space increases bond strength of fiber posts in oval canals.

Comparación Espectrofotométrica de las Sesiones de Blanqueamiento Intracameral con Peróxido de Hidrógeno y Carbamida a Diferentes Concentraciones / Spectrophotometric Comparison of Intracameral Tooth-Bleaching Sessions Using Hydrogen Peroxide, and Carbamide Peroxide at Different Concentrations

RESUMEN: El objetivo del presente trabajo fue comparar espectrofotométricamente el número de sesiones para un cambio efectivo de coloración con peróxido de carbamida al 100 %, 37 % y peróxido de hidrógeno al 35 %, a través de la técnica Walking Bleach. Este fue un estudio experimental, in vitro, en paralelo, con ciego en la medición del efecto y en el análisis de datos. Se utilizaron 88 premolares extraídos por indicación ortodóncica. Estos fueron tratados endodónticamente y artificialmente pigmentados con cromógenos derivados de productos de descomposición de la sangre. Se dividieron aleatoriamente en 4 grupos de 22 dientes (un grupo por cada agente blanqueador, más un grupo control con agua destilada). El régimen de tratamiento para cada grupo fue de 4 sesiones existiendo una separación de 4 días entre cada una. El registro de color previo (baseline) y posterior a cada aplicación fue realizado mediante el espectrofotómetro dental Vita Easyshade V, con el cual se registraron los colores en espacio de color CIE L*a*b*. Se calcularon posteriormente los valores de la variación total de color (DE) entre los parámetros iniciales y los distintos tiempos de evaluación. El análisis de significancia se realizó mediante la prueba Kruskal-Wallis y para comparar las diferencias se usó el test de comparaciones múltiples por pares mediante el procedimiento de Steel-Dwass-Critchlow-Fligner, registrando diferencias estadísticamente significativas en la variación total del color desde la primera sesión de blanqueamiento. En conclusión, utilizando peróxido de carbamida al 100 %, la técnica Walking Bleach no requiere un menor número de sesiones para un cambio efectivo de coloración al compararlo con peróxido de hidrógeno al 35 %, pero si con relación al peróxido de carbamida al 37 %, donde el objetivo se consigue en un menor número de sesiones.

ABSTRACT: The objective of this study was to spectrophotometrically compare the number of sessions for an effective color change using 100 % and 37 % carbamide peroxide, and 35 % hydrogen peroxide, applying the Walking Bleach technique. This was an experimental study, performed in vitro, in parallel, and was a blind study in relation to the measurement of the effect and the analysis of data. 88 premolars extracted by orthodontics indications were used. These were endodontically treated and artificially pigmented with chromogens derived from blood decomposition products. They were randomly divided into 4 groups of 22 teeth (one group for each whitening agent, plus a control group with distilled water). The treatment regime for each group was 4 sessions, with a separation of 4 days between each session. The registration of color before (baseline) and after each application was done using the dental spectrophotometer Vita Easyshade V, with which the colors were registered in the CIE L*a*b* color space. The values of total color variation (DE) were later calculated between the initial parameters and the different stages of evaluation. Significance testing was undertaken using Kruskal-Wallis and to compare the differences the method used was Steel-Dwass-Critchlow- Fligner, registering significant statistical differences in the total color variation from the first bleaching session. In conclusion, using 100 % carbamide peroxide, the Walking Bleach technique does not require fewer sessions for an effective change in coloration when compared to 35 % hydrogen peroxide, however, it does using 37 % carbamide peroxide, where the result is achieved in a lower number of sessions.