Tensile Strength and Elastic Modulus of Gutta-percha Cones Disinfected with Sodium Hypochlorite at Different Immersion Times: An In Vitro Comparative Study.

Aim: The tensile strength and modulus of elasticity of gutta-percha cones can be chemically altered due to disinfectant solutions. Therefore, the aim of the present study was to compare tensile strength and elastic modulus of gutta-percha cones subjected to sodium hypochlorite (NaOCl) disinfection at different times. Materials and Methods: This in vitro and longitudinal experimental study consisted of 45 gutta-percha cones, divided equally into three groups: Group 1 (disinfection with 2.5% NaOCl), Group 2 (disinfection with 5.25% NaOCl), and control group. All groups were subdivided according to immersion times for 1, 5, and 10 minutes. Tensile strength and elastic modulus were measured with a universal testing machine. For comparing more than two independent groups, parametric analysis of variance test with Sheffe's post hoc was used and for multivariate analysis, and multivariate analysis of variance test based on Pillai's Trace was used. In all statistical analysis, a significance level P ≤ 0.05 was considered. Results: When comparing the tensile strength of gutta-percha cones, no significant differences were observed after being immersed at 1, 5, and 10 minutes in NaOCl 2.5% (P = 0.715) and 5.25% (P = 0.585). Regarding the elastic modulus, a significant decrease (P < 0.05) was observed in those that were immersed in NaOCl 2.5% and 5.25% for 1, 5, and 10 minutes. Furthermore, increased NaOCl concentration significantly reduced the elastic modulus (P < 0.001). However, there were no significant differences in tensile strength (P > 0.05) and elastic modulus (P > 0.05), when evaluating the interaction between NaOCl concentration and time. Conclusion: Increasing NaOCl concentration significantly reduced the modulus of elasticity without affecting the tensile strength of gutta-percha cones, regardless of immersion time. Furthermore, the interaction of time and NaOCl concentration did not significantly affect the tensile strength and elastic modulus.

Microleakage in indirect onlay restorations cemented with three different types of adhesives: An in vitro study.

Background: To evaluate the in vitro degree of marginal microleakage in indirect Class II onlay restorations cemented with dual self-adhesive, universal adhesive and dual adhesive. Material and Methods: In the present in vitro experimental study, a total of 54 human premolar teeth were prepared and divided into three equal groups (n = 18) for placement of onlay-type restorations cemented with A: Allcem™ dual-cure adhesive cement), B: RelyX™U200 dual-cure self-adhesive cement and C: RelyX™ Ultimate universal adhesive cement. All restorations were subjected to 10,000 thermocycles between 5°C and 55°C and immersed in a 1M silver nitrate solution for 6 hours. The crowns were then sectioned mesiodistally and observed under a stereo microscope to determine the degree of marginal microleakage in the cervical area. Results: The onlay restorations cemented with RelyX Ultimate did not present microleakage in the majority of cases (77.8%). Restorations cemented with RelyX U200 showed predominantly microleakage up to the pulp floor in 83.3% of the total, being this significantly higher microleakage than in restorations cemented with RelyX Ultimate and Allcem Dual (p<0.001 and p<0.001 respectively). There was no significant difference in microleakage between the last two mentioned cements (p=0.255). Conclusions: Allcem dual adhesive cement and RelyX Ultimate universal adhesive showed significantly less microleakage than RelyX U200 dual-curing self-adhesive cement at the cervical level, with predominantly no microleakage and microleakage down to the enamel, respectively. The use of RelyX Ultimate cement in indirect restorations is recommended as it showed better marginal adaptation. Key words:Microleakage, human teeth, adhesion, adhesive cement, thermal cycling, onlay restoration.

In Vitro Color Stability Evaluation of Three Polished and Unpolished Nanohybrid Resin Composites Immersed in a 0.12% Chlorhexidine-Based Mouthwash at Different Times.

The use of chlorhexidine-based mouthwashes on resin composites with rough surfaces can cause discoloration which compromises the esthetic of patients. The present study aimed to evaluate the in vitro color stability of Forma (Ultradent Products, Inc., South Jordan), Tetric N-Ceram (Ivoclar Vivadent, Schaan, Liechtenstein) and Filtek Z350XT (3M, ESPE, St. Paul, MN, USA) resin composites, with and without polishing, after being immersed in a 0.12% chlorhexidine (CHX)-based mouthwash at different times. The present in vitro experimental and longitudinal study used 96 nanohybrid resin composite blocks (Forma, Tetric N-Ceram and Filtek Z350XT) 8 mm in diameter and 2 mm thick, evenly distributed. Each resin composite group was divided into two subgroups (n = 16) with and without polishing and then immersed in a 0.12% CHX-based mouthwash for 7, 14, 21 and 28 days. Color measurements were performed with a calibrated digital spectrophotometer. Nonparametric tests were used to compare independent (Mann-Whitney U and Kruskal-Wallis) and related (Friedman) measures. In addition, the Bonferroni post hoc correction was used considering a significance level of p < 0.05. All polished and unpolished resin composites presented color variation < 3.3 when immersed for up to 14 days in 0.12% CHX-based mouthwash. The polished resin composite with the lowest color variation (ΔE) values over time was Forma, and the one with the highest values was Tetric N-Ceram. When comparing the color variation (ΔE) over time, it was observed that the three resin composites, with and without polishing, presented a significant change (p < 0.001), although these changes in color variation (ΔE) were evident from 14 days between each color acquisition (p < 0.05). The unpolished Forma and Filtek Z350XT resin composites showed significantly more color variation than the same polished ones at all times when immersed in a 0.12% CHX-based mouthwash for 30 s daily. In addition, every 14 days, all three resin composites with and without polishing showed a significant color change, while, every 7 days, color stability was maintained. All the resin composites showed clinically acceptable color stability when exposed for up to 14 days to the above-mentioned mouthwash.

The Microhardness and Surface Roughness Assessment of Bulk-Fill Resin Composites Treated with and without the Application of an Oxygen-Inhibited Layer and a Polishing System: An In Vitro Study.

The aim of this study was to assess the microhardness and surface roughness of bulk-fill resin composites treated with and without the application of an oxygen-inhibited layer (OIL) and a polishing system. This in vitro experimental study consisted of 72 resin composite blocks divided into three groups: Tetric N-Ceram Bulk Fill, Opus Bulk Fill APS, and Filtek Bulk Fill. Each resin composite group was further divided into two subgroups: with and without OIL control. Subsequently, surface roughness and microhardness were measured before and after polishing. A t-test was used to compare independent and related measures. For the intergroup comparison of variation before and after polishing, the Kruskal−Wallis test with Bonferroni post hoc was used considering a significance level of p < 0.05. When comparing surface roughness, significant differences were observed between Opus Bulk Fill resin composite with and without OIL control (p = 0.003) before polishing. The same occurred when comparing Tetric N-Ceram resin composite with and without OIL control (p = 0.039) after polishing. In addition, the surface roughness of Filtek Bulk Fill, Opus Bulk Fill, and Tetric N-Ceram Bulk Fill resin composites, with and without OIL control, decreased significantly after polishing (p < 0.001), while surface microhardness significantly increased (p < 0.05), with the exception of Opus Bulk Fill resin with OIL control (p = 0.413). In conclusion, OIL control and polishing significantly improved the surface roughness and surface microhardness of Filtek Bulk Fill and Tetric N-Ceram Bulk Fill resin composites. However, in the case of Opus Bulk Fill resin composite, only its surface roughness was significantly improved.

Microleakage in class II restorations of two bulk fill resin composites and a conventional nanohybrid resin composite: an in vitro study at 10,000 thermocycles.

BACKGROUND: The contraction presented by resin composites causes an increase in stress at the tooth-resin interface, causing micro-gaps that allow microleakage. This study aims to evaluate the degree of in vitro marginal microleakage in class II restorations with two bulk fill resin composites compared to a conventional nanohybrid resin composite. METHODS: The present study was an in vitro experimental design. A total of 30 standardized class II cavities were prepared in 15 human molars (mesially and distally). These cavities were later distributed in 3 groups according to the type of resin. Groups A and B were restored with bulk fill resin composites (Filtek-3 M/ESPE and Tetric N-Ceram-Ivoclar/Vivadent respectively) in a single increment of 4 mm. Group C was restored with the Filtek Z350 XT - 3 M/ESPE resin composite and two increments of 2 mm. Later, the restorations were subjected to 10,000 thermocycles between 5 °C to 55 °C and immersed in a silver nitrate solution (1 M for 24 h). The crowns were then sectioned mesiodistally and observed under the stereomicroscope to determine the degree of marginal microleakage at the occlusal and cervical areas. The results were analyzed with the Kruskal-Wallis and the Mann-Whitney U statistical tests. RESULTS: There were no statistically significant differences regarding the degree of microleakage between the three types of resin composites in the occlusal and cervical areas (p > 0.05). Similarly, there were no significant differences after comparing each resin type in its occlusal and cervical area (p > 0.05). CONCLUSION: Filtek Bulk Fill and Tetric N-Ceram Bulk Fill resin composites showed no statistically significant differences with the conventional nanohybrid resin composite Filtek Z350XT at both occlusal and cervical areas.

Cambios del pH salival por ingesta cariogénica y no cariogénica en preescolares de Huaura, Perú / Salivary pH changes caused by cariogenic and non-cariogenic food intake in preschoolers from Huaura, Peru

Introducción: El tipo de dieta influye directamente en el valor del pH salival, el cual es un factor importante para evitar la formación de caries. Objetivo: Evaluar el cambio del pH salival por ingesta cariogénica y no cariogénica en preescolares de una institución educativa de Huaura, Perú. Métodos: Esta investigación fue de tipo observacional, comparativo y longitudinal. El tamaño de muestra fue de 30 preescolares. Después que los niños consumieron dieta cariogénica y no cariogénica, se evaluó su pH a diferentes tiempos. Para el contraste de resultados se utilizó la prueba T Student y U de Mann-Whitney. Resultados: El pH salival con dieta no cariogénica a los cinco minutos fue 7,11 ± 0,19 y 7,09 ± 0,20, y, a los 40 minutos, 7,46 ± 0,19 y 7,42 ± 0,22, en mujeres y hombres, respectivamente. El pH salival con dieta cariogénica en mujeres fue 6,56 ± 0,21 a los cinco minutos y 7,15 ± 0,12 a los 60 minutos; mientras que, en los hombres, para iguales rangos de tiempos fue 6,47 ± 0,32 y 7,23 ± 0,22, respectivamente. Al realizar las comparaciones entre grupos de dieta cariogénica y no cariogénica se observaron diferencias muy significativas (p < 0,01). Conclusiones: Para la dieta cariogénica el pH disminuye como máximo a los cinco minutos y se restablece a partir de los 60 minutos. Para la dieta no cariogénica disminuye en el mismo tiempo pero se recupera a los 40 minutos, siendo este proceso similar en ambos géneros(AU)

Introduction: Salivary pH, an important factor in caries prevention, is under the direct influence of diet type. Objective: Evaluate salivary pH changes caused by cariogenic and non-cariogenic food intake in preschoolers from an educational institution in Huaura, Peru. Methods: An observational longitudinal comparative study was conducted of a sample of 30 preschoolers. After the children consumed cariogenic and non-cariogenic food, their salivary pH was evaluated at various times. Student's t-test and the Mann-Whitney U test were used to contrast results. Results: Salivary pH with a non-cariogenic diet at five minutes was 7.11 ± 0.19 and 7.09 ± 0.20; whereas at 40 minutes it was 7.46 ± 0.19 and 7.42 ± 0.22, in female and male participants, respectively. Salivary pH with a cariogenic diet in women was 6.56 ± 0.21 at five minutes and 7.15 ± 0.12 at 60 minutes, whereas values in men for the same time ranges were 6.47 ± 0.32 and 7.23 ± 0.22, respectively. Comparison between the cariogenic and non-cariogenic diet groups revealed very significant differences (p < 0.01). Conclusions: With a cariogenic diet, pH is reduced at five minutes maximum, and is restored as of 60 minutes. With a non-cariogenic diet, pH is reduced in the same time period, but is restored at 40 minutes. This process is similar in the two genders(AU)

Knowledge about oral health, salivary PH, body mass index and its relationship with dental caries in preschool children / Conocimiento en salud bucal, PH salival, índice de masa corporal y su relación con caries dental en preescolares

Abstract Introduction: Dental caries is a disease caused by the interaction of several factors, including diet, since the development of the biological environment that promotes cariogenic bacterial metabolism often depends on it. Objectives: To determine the prevalence of caries in preschool children from Huaura, Peru, and to confirm if there is an association between their salivary pH and body mass index (BMI) and the level of knowledge about oral health of one of their parents. Materials and methods: A non-experimental, correlational, and cross-sectional study was conducted in 126 preschoolers equally distributed in 3 age groups (3, 4, and 5 years old). The association between the presence of caries and the variables considered was determined by means of the chi-square test of independence, with a confidence level of 95% and a type I error of 5%. In addition, a multiple logistic regression analysis was performed to calculate the probability of caries development in relation to each risk factor. Results: The prevalence of caries was 80.2% (95%CI:73.2-87.2); furthermore, salivary pH (p=0.012) and the level of parental knowledge (p<0.001) were significantly associated with caries occurrence. Regarding the multiple regression analysis, an OR=0.12 (95%CI:0.02-0.63) was obtained for pH and an OR=0.50 (95%CI:0.35-0.74) for the level of parental knowledge in relation to the probability of caries development. Conclusion: The level of parental knowledge about oral health and high salivary pH levels of preschoolers were protective factors against caries development in the study population. On the other hand, no association was found between BMI and the presence of caries in 5-year-old preschoolers.

Resumen Introducción. La caries dental es una condición causada por la interacción de múltiples factores, entre ellos la dieta, ya que, con frecuencia, de ella depende el desarrollo del medio biológico propicio para el metabolismo bacteriano cariogénico. Objetivo. Determinar la prevalencia de caries en preescolares de Huaura, Perú, y confirmar si hay una asociación con el pH salival y el índice de masa corporal (IMC) de los preescolares, y con el nivel de conocimiento en salud bucal de uno de sus padres. Materiales y métodos. Estudio no experimental, correlacional y transversal realizado en 126 preescolares distribuidos equitativamente en 3 grupos etarios (3, 4 y 5 años). La asociación entre presencia de caries y las variables consideradas se determinó mediante la prueba de independencia de chi cuadrado, con un nivel de confianza del 95% y error tipo I del 5%; además, se realizó un análisis de regresión logística múltiple para calcular la probabilidad de ocurrencia de caries en relación con cada factor de riesgo. Resultados. La prevalencia de caries fue de 80.2% (IC95%:73.2-87.2); además, el pH salival (p=0.012) y el nivel de conocimiento de los padres (p<0.001) se asociaron significativamente con la ocurrencia de caries. En cuanto al análisis de regresión múltiple, se obtuvo un 0R=0.12 (IC95%:0.02-0.63) para el pH y un 0R=0.50 (IC95%:0.35-0.74) para el nivel de conocimiento de los padres en relación con la probabilidad de presentar caries. Conclusión. El nivel de conocimiento sobre salud bucal de los padres y los niveles altos de pH salival de los preescolares fueron factores protectores frente al desarrollo de caries en la población de estudio. Por otra parte, no se encontró asociación entre IMC y presencia de caries en los preescolares de 5 años.

Cleaning of endodontic files with and without enzymatic detergent by means of the manual method versus the ultrasonic method: An experimental study.

AIM: The aim of this article is to evaluate the cleanliness level achieved with and without the application of enzymatic detergent for the manual method versus the ultrasonic method, applied to Flexoreamer K-type files No. 25, No. 30, and No. 35. MATERIALS AND METHODS: 192 K-type Flexoreamer files were divided into four categories: A1 (ultrasonic method with enzymatic detergent), A2 (ultrasonic method without enzymatic detergent), B1 (manual method with enzymatic detergent), and B2 (manual method without enzymatic detergent). Each category was randomly distributed in three groups of 16 files each (No. 25, No. 30, and No. 35). The files were used for biomechanical instrumentation of the root canal in premolars. The active part of the files was examined under a stereomicroscope, considering four cleaning levels: 4 (100% cleanliness), 3 (95-99% cleanliness), 2 (85-94% cleanliness), 1 (75-84% cleanliness), and 0 (less than 75% cleanliness). For hypothesis testing, the Mann-Whitney U-test was used to differentiate between techniques, and the Kruskal-Wallis multiple comparison test was used to compare pairs of files within each cleaning method. RESULTS: When using enzymatic detergents, the manual and ultrasonic methods did not show significant differences when comparing each group of the files analyzed (P > 0.05). However, when comparing the cleaning level without enzymatic detergent between the manual and ultrasonic methods, we observed that it obtained a superior result when compared with the manual method for each type of file: No. 25 (P = 0.021), No. 30 (P < 0.001), and No. 35 (P < 0.001). Both methods achieved a significantly higher level of cleaning with the application of the enzymatic detergent (P < 0.05) than without applying it. CONCLUSION: The ultrasonic cleaning method proved to be the most effective method for the removal of biologic waste when compared with the manual method using a nylon brush. However, there was no significant difference between these two methods when enzymatic detergent was used.

Effect of Polishing on the Surface Microhardness of Nanohybrid Composite Resins Subjected to 35% Hydrogen Peroxide: An In vitro Study.

AIM: The use of bleaching agents, despite being a conservative treatment, can cause a decrease in the surface microhardness of dental resins, affecting their aesthetics and performance. The aim of this study was to evaluate the in vitro effect of polishing on the surface microhardness of nanohybrid composite resins that were subjected to bleaching with 35% hydrogen peroxide. MATERIALS AND METHODS: This cross-sectional, in vitro experimental study consisted of 30 composite resin samples made according to ISO 4049-2019 and divided equally into two groups (A and B) which were subjected to 35% hydrogen peroxide bleaching. Group A was subjected to polishing procedure, whereas group B was the control group. The samples were stored in distilled water at 37°C for 24 h. The Vickers microhardness was determined with a load of 100 g-f for 10 s. The data were analyzed with Student's t-test for independent samples at a confidence level of 95%. RESULTS: The surface microhardness of the group that was subjected to polishing (A) obtained a mean of 78.07 ± 7.96 HV, whereas for the group that was not subjected to polishing (B) the mean was 65.67 ± 5.22 HV. The difference between groups (A and B) was statistically significant (P < 0.001). CONCLUSION: Nanohybrid composite resins previously subjected to 35% hydrogen peroxide gel significantly increased their surface microhardness when subjected to polishing when compared with unpolished nanohybrid composite resins.

Impact of COVID-19 Mandatory Social Isolation on the Development of Anxiety in Peruvian Dentistry Students: A Logistic Regression Analysis.

AIM: The COVID-19 pandemic has generated much concern worldwide. Due to its high transmissibility, many young university students have had to carry out their academic activities in mandatory social isolation, which could generate excessive anxiety. Therefore, the aim of this study was to evaluate the anxiety levels in Peruvian dentistry students developed during COVID-19 mandatory social isolation. MATERIALS AND METHODS: An analytical, observational, and transversal study was carried out in 403 dentistry students in the last two years from three Peruvian universities from May to July 2020. The Zung Self-Rating Anxiety Scale was used to detect anxiety symptoms and their respective diagnoses. A logit model was used to evaluate the association of the variables: age group (X1), gender (X2), type of university (X3), and marital status (X4), with the anxiety levels of the students, considering a p-value less than 0.05. RESULTS: The prevalence of anxiety resulted in 56.8% (95% confidence interval (CI): 51.9-61.7) of 403 dentistry students. According to the multivariate logistic regression analysis, the type of university was the only variable that demonstrated to have a significant influence on the development of anxiety with an odds ratio (OR = 1.98; CI: 1.29-3.02); whereas the other variables such as age group (OR = 0.77; CI: 0.49-1.20), gender (OR = 1.15; CI: 0.72-1.84), and marital status (OR = 0.75; CI: 0.35-1.60) were not considered factors that influenced the development of anxiety. CONCLUSION: More than a half of the Peruvian dentistry students from three universities showed mild-to-severe anxiety levels. Students from a private university have a 98% higher chance of developing anxiety in comparison to students from public universities. Other variables such as gender, age group, or marital status were not considered influencing factors to develop anxiety.

Evaluación antibacteriana del peróxido de hidrógeno comparado con hipoclorito de sodio sobre cepillos dentales inoculados con Streptococcus mutans / Antibacterial Evaluation of Hydrogen Peroxide Compared to Sodium Hypochlorite on Dental Brushes Inoculated with Streptococcus Mutans / Avaliação do efeito antibacteriano do peróxido de hidrogênio em comparação ao hipoclorito de sódio em escovas de dente inoculadas com Streptococcus mutans

Resumen Objetivo: evaluar el efecto antibacteriano del peróxido de hidrógeno (H2O2) al 6 % comparado con hipoclorito de sodio (NaClO) al 1 % y al 2 %, sobre cepillos dentales inoculados con Streptococcus mutans ATCC® 25175™. Materiales y métodos: estudio experimental in vitro, transversal y comparativo. Se utilizaron 60 cepillos dentales, divididos en 4 grupos de 15 cepillos cada uno. El número de muestra lo determinó la fórmula de comparación de medias, después de realizar un estudio piloto, y se seleccionaron por muestreo aleatorio simple. Se aplicaron las pruebas de normalidad de Shapiro-Wilk, y para la prueba de hipótesis, la U de Mann-Whitney. Resultados: el H2O2 al 6 % presentó una media de crecimiento de 2 * 109 UFC/mL, lo que indica que su efectividad es mayor comparada con el NaClO al 1 %>, que presentó una media de crecimiento de 4 * 109 UFC/mL, y esta es menor al NaClO al 2 %, que tuvo 0 UFC /mL de Streptococcus mutans (p = 0,004). Conclusión: el H2O2 al 6 % y el NaClO al 1 % y al 2 % evidenciaron efectividad antibacteriana, aun cuando fue el NaClO al 2 % el más efectivo.

Abstract Objective: To assess the antibacterial effect of 6% hydrogen peroxide (H2O2) compared with 1% and 2% sodium hypochlorite, on toothbrushes inoculated with Streptococcus mutans ATCC® 25175™. Materials and methods: The study design was an experimental in vitro, cross-sectional prospective and comparative study. Sixty toothbrushes were used, which were divided into four groups of 15 brushes. After conducting a pilot study, the sample number was determined by the means comparison formula and these were selected by simple random sampling. These brushes were inoculated with strains of S. mutans ATCC® 25175™. The disinfectants included H2O2 at 6% and sodium hypochlorite (NaOCl) at 1% and 2%. The Shapiro-Wilk test was used to assess normality and the Mann-Whitney U test was applied for the hypothesis test. Results: The 6% H2O2 showed an average growth of 2 * 109 CFU/mL, which indicates that its effectiveness is greater compared to the 1% NaClO that showed a growth average of 4 * 109 CFU/mL which is less than the 2% NaClO that presented 0 CFU/mL of S. mutans (p = 0.004). Conclusion: Between 6% H2O2 and 1% and 2% NaClO, specifically antibacterial detection, 2% NaClO was concluded as being the most effective.

Resumo Objetivo: avaliar o efeito antibacteriano do peróxido de hidrogênio 6% em comparação ao hipoclorito de sódio 1% e 2%, em escovas de dente inoculadas com Streptococcus mutans ATCC® 25175™. Materiais e métodos: estudo experimental in vitro, transversal e comparativo. Foram utilizadas 60 escovas de dente, as quais foram divididas em 4 grupos de 15 escovas cada um. O número amostral foi determinado pela fórmula de comparação de médias, após realização de um estudo piloto, sendo selecionado por meio de amostragem aleatória simples. As escovas foram inoculadas com cepas de Streptococcus mutans ATCC® 25175™. Os desinfetantes utilizados foram peróxido de hidrogênio (H202) 6% em comparação ao hipo-clorito de sódio (NaClO) 1% e 2%. Aplicou-se a prova de normalidade de Shapiro-Wilk e como teste de hipótese utilizou-se o U de Mann-Whitney. Resultados: o H202 6% apresentou uma média de crescimento de 2*109 UFC/mL, indicando uma efetividade maior em comparação com o NaClO 1% que apresentou uma média de crescimento de 4*109 UFC/mL, que por sua vez foi menos efetivo que o NaClO 2% que apresentou uma contagem de 0 UFC/mL de Streptococcus mutans (p=0,004). Conclusão: o H2O2 6% e o NaClO 1% e 2%, apresentaram efetividade antibacteriana, sendo que o NaClO 2% foi totalmente efetivo.