A microscopia eletrônica de varredura pode ser usada para medir quantitativamente a rugosidade da dentina? / Can Scanning Electron Microscopy be used to quantitatively measure dentine roughness?

Objective: The aim of this study was to determine if SEM used with imaging software could be used to quantitatively determine the extent of dentine roughness due to tooth-brushing. Material and methods: Flat, polished dentine surfaces were subjected to 25,000 cycles of simulated tooth-brushing at 2 strokes per second with a load of 200 g. At the end of the brushing cycle, dentine surfaces were first assessed using profilometry and then subjected to SEM analysis. Ra (average roughness) readings were obtained for profilometric assessment. Using imaging software, the horizontal distance between adjacent characteristic grooves noted on micrographs was measured, ensuring that the middle of each crest of the associated groove was used as the reference point, the Crest-to-Crest distance (C-C distance). These two parameters were examined statistically for correlation. Results: When Spearman Rank tests were utilized the correlation between average Ra and crest to crest measurements was 0.709 (p <0.01). The Bland Altman plot, however, showed poor agreement between the two test parameters. Conclusion: Further work is needed to validate the use of this methodology in the quantitative assessment of tooth surface loss due to abrasion (AU)

Objetivo: O objetivo deste estudo foi determinar se o MEV usado com software de imagem poderia ser usado para determinar quantitativamente a extensão da rugosidade da dentina devido à escovação dentária. Material e Métodos: Superfícies dentinárias planas e polidas foram submetidas a 25.000 ciclos de escovação dentária simulada a 2 movimentos por segundo com uma carga de 200g. No final do ciclo de escovação, as superfícies dentinárias foram primeiro avaliadas por perfilometria e depois submetidas à análise MEV. Leituras de Ra (rugosidade média) foram obtidas para avaliação perfilométrica. Utilizando um software de imagem, foi medida a distância horizontal entre sulcos característicos adjacentes observados nas micrografias, garantindo que o meio de cada crista do sulco associado fosse usado como ponto de referência, a distância crista a crista (distância CC). Esses dois parâmetros foram examinados estatisticamente para correlação. Resultados: Quando foram utilizados os testes de Spearman Rank, a correlação entre a média de Ra e as medidas de crista a crista foi de 0,709 (p<0,01). O gráfico de Bland Altman, no entanto, mostrou fraca concordância entre os dois parâmetros de teste. Conclusão: Mais trabalhos são necessários para validar o uso desta metodologia na avaliação quantitativa da perda da superfície dentária devido à abrasão(AU)

Qualitative Characterization of the Abrasive Component of Charcoal-Containing Toothpastes and the Effect on Dentin Roughness / Caracterización Cualitativa del Componente Abrasivo de las Pastas Dentales que Contienen Carbón Vegetal y la Rugosidad de la Dentina

This study investigated the effect of commercially available whitening toothpastes containing charcoal on dentin. Nine charcoal-containing toothpastes were compared with 3 whitening toothpastes (positive control) and distilled water (negative control). Periodontally hopeless molars were cleaned and washed and the occlusal table removed to expose dentin. The teeth were mounted in auto-polymerizing resin and exposed dentine surfaces polished with water-cooled decreasing grits of silica carbide paper up to 1500 grit. Baseline average roughness (Ra) measurements were taken. Specimens were then mounted in an automatic tooth-brushing machine and brushed for 5000 cycles. Repeat Ra measurements were taken. Specimens were brushed in 5000-cycle increments up to 25,000 cycles with Ra measurements being taken at each time point. Between abrasive challenges specimens were stored in distilled water. All toothpaste samples were sputter coated and examined under a scanning electron microscope to qualify the shape and size of the abrasive components of the formulations. Data were analyzed using a two-way analysis of variance with post hoc Bonferroni. The results demonstrated that the abrasive effect, in terms of increasing Ra, on dentin was noted as early as 5000 cycles for all the tested toothpastes (p<0.05). The effect of continued brushing showed an overall cumulative effect on dentine roughness up to 25000 cycles. When toothpastes were compared between groups at each time-point, dentin specimens brushed with Pursito were statistically similar to the control group. At 25,000 cycles all dentin samples were significantly rougher compared to Pursito and the control groups. It may be concluded that all the tested toothpastes have an abrasive effect on dentin surfaces.

Este estudio investigó el efecto sobre la dentina de las pastas dentales blanqueadoras disponibles en el mercado que contienen carbón vegetal. Se compararon nueve dentífricos que contenían carbón vegetal con 3 dentífricos blanqueadores (control positivo) y agua destilada (control negativo). Los molares sin material periodontal se limpiaron y lavaron y se retiró la tabla oclusal para exponer la dentina. Los dientes se montaron en resina autopolimerizable y las superficies expuestas de la dentina se pulieron con papel de carburo de sílice de grano decreciente enfriado con agua hasta grano 1500. Se tomaron medidas de rugosidad promedio (Ra) de referencia. Luego, las muestras se montaron en una máquina automática de cepillado de dientes y se cepillaron durante 5000 ciclos. Se tomaron medidas repetidas de Ra. Las muestras se cepillaron en incrementos de 5000 ciclos hasta 25 000 ciclos y se tomaron medidas de Ra en cada punto de tiempo. Entre periodos abrasivos, las muestras se almacenaron en agua destilada. Todas las muestras de pasta de dientes se recubrieron por pulverización catódica y se examinaron bajo un microscopio electrónico de barrido para calificar la forma y el tamaño de los componentes abrasivos de las formulaciones. Los datos se analizaron utilizando un análisis de varianza de dos vías de Bonferroni post hoc. Los resultados demostraron que el efecto abrasivo, en términos de aumento de Ra, sobre la dentina se notó ya en 5000 ciclos para todas las pastas dentales probadas (p<0,05). El efecto del cepillado continuo mostró un efecto acumulativo general sobre la rugosidad de la dentina hasta 25.000 ciclos. Cuando se compararon las pastas dentales entre los grupos en cada momento, las muestras de dentina cepilladas con Pursito fueron estadísticamente similares al grupo de control. A los 25.000 ciclos, todas las muestras de dentina eran significativamente más ásperas en comparación con Pursito y los grupos controles. Se puede concluir que todas las pastas dentales probadas tienen un efecto abrasivo sobre las superficies dentinarias.

An evaluation of the relationship between clinical requirements and tests of competence in a competency-based curriculum in dentistry.

BACKGROUND: The development of competencies in dentistry is a complicated process that calls for the development of not just cognitive and psychomotor abilities but also behaviors and attitudes that change as technical proficiency increases and meaningful patient encounters occur. This study examined the relationship between the number of clinical requirements completed by dental students and subsequent performance on tests of competence. The null hypothesis stated there would be no significant linear relationship different from zero between absolute clinical requirements and grades attained in various tests of clinical competence. METHODS: Retrospective assessment data for 81 students were used in this analysis. Data included the amounts of clinical requirements completed for operative dentistry, endodontics, periodontics, and fixed prosthodontics together with data on the respective performance in tests of competence. Correlation was ascertained between grades for tests of competence and the corresponding clinical requirements using a non-parametric Spearman's Rho test at an alpha level of 0.05. RESULTS: Fixed prosthodontics and posterior endodontics were the least common procedures completed by dental students. Statistically significant weak correlations were found between the amounts of clinical requirements performed for posterior endodontic(p = 0.005) and operative procedures (p = 0.006) and associated performance in tests of competence. A moderate correlation was found between the number of fixed prosthodontic procedures completed and associated performance in tests of competence. This latter correlation, however, was not statistically significant (p = 0.654). A significant weak correlation was found between requirements completed for periodontics and the associated test of competence (p = 0.04). A highly statistically significant moderate correlation was found between clinical requirements for anterior endodontics and the associated performance in the tests of competence (p < 0.001). CONCLUSION: The null hypothesis was rejected since a positive correlation was found between the absolute clinical requirements completed and grades in tests of competence. However, only a weak to moderate degree of correlation was found between the completion of clinical requirements and performance in tests of competence for common clinical procedures that new dental graduates should be able to perform.

Case Report: Case report: Rapidly progressing tooth wear dominated by intrinsic and extrinsic erosion.

Tooth wear is multi-factorial presenting as a combination of abrasion, attrition, and erosion. This case report represents a case of combined tooth wear in a 46-year-old Indo-Trinidadian male, with a predominant erosive component with both the clinical signs and features of intrinsic and extrinsic erosion. This patient case is unique since the wear predominated by dental erosion has occurred rapidly evidenced by the physical clinical appearance of a lack of compensation and the upper left premolars and molars relatively unaffected by the overall effects of tooth wear. This lack of compensation, where opposing teeth have not supra-erupted to maintain inter-arch stability, and the maintenance of occlusal vertical dimension on the left due to the non-worn posterior maxillary teeth, provides the benefit of simplifying subsequent restorative management. The medical and diet history corroborates the diagnoses of intrinsic and extrinsic erosion respectively. Complications noted with rapid tooth wear, such as dentine sensitivity and pulpal necrosis are known sequelae of tooth wear however the patient presented in this case report shows a concomitant high caries experience and poor oral hygiene. Cases such as the one presented here require not only comprehensive dental management, utilizing a restorative approach but also medical referral for confirmation of a diagnosis and management of gastroesophageal reflux disease. Inherent to the management of this patient should be a multidisciplinary medical and dental approach, with confirmation and management of the cause of the intrinsic erosion as well as restorative dental management, together with dietary counseling to mitigate the effect of intrinsic and extrinsic sources of acid on dental hard tissue. A key lesson learned from this case is the importance of history and targeted questioning when trying to determine the cause of tooth wear dominated by intrinsic and extrinsic erosion.

The Cleaning and Whitening Ability of Charcoal Containing Toothpastes and Homeopathic Remedies on Human Tooth Enamel

ABSTRACT: The purpose of this research was to determine the cleaning and whitening ability of two charcoal containing toothpastes compared with baking soda, activated charcoal and a hydrogen peroxide containing whitening toothpaste. Tea-stained enamel/dentin slices were mounted dentin side down in cylinders of auto-polymerizing acrylic and subjected to simulated brushin g. Total color, ΔE, and stained area were measured using a reflectance spectrophotometer and ImageJ software using a Hue, Chroma, and Brightness color threshold method; respectively, at prescribed brushing intervals of baseline, months 1, 6 and 12. A two- w ay repeated measure analysis of variance was performed, with included factors being toothpaste group and time. Statistical analys is revealed the included factor of brushing time interval was significant (p<0.05) for both ΔE and stained area. There was significant interaction for both main effects (p<0.05) for the dependent variable of stained area alone. Significant reduction in ΔE values occurred in all groups except Optic White at the 1-month interval. Statistically significant reduction in stained area occurred at 1-mon th for the baking soda group only. Post-hoc Tukey HSD tests revealed there was significant group*time interaction for baking soda at month 1 for the variable stained area. The charcoal containing (Crest 3D with Charcoal and Colgate Essentials) and non-charcoal contai ning toothpastes (Optic White) only produced a significant stain removal at the 6-month interval.

RESUMEN: El propósito de esta investigación fue determinar la capacidad de limpieza y blanqueamiento de dos pastas dentales que contienen carbón en comparación con bicarbonato de sodio, carbón activado y una pasta dental blanqueadora que contiene peróxido de hidrógeno. Los cortes de esmalte/dentina teñidos con té se montaron con el lado de la dentina hacia abajo, en cilindros de acrílico autopolimerizable y se sometieron a un cepillado simulado. El color total, ΔE y el área teñida se midieron usando un espectrofotómetro de reflectancia y el software ImageJ usando un método de umbral de color de tono, croma y brillo; respectivamente, en los intervalos de cepillado prescritos al inicio, los meses 1, 6 y 12. Se realizó un análisis de varianza de medidas repetidas de dos vías, con factores incluidos como el grupo de pasta de dientes y el tiempo. El análisis estadístico reveló que el factor incluido del intervalo de tiempo de cepillado fue significativo (p<0,05) tanto para ΔE como para el área manchada. Hubo interacción significativa para ambos efectos principales (p<0,05) para la variable dependiente del área teñida sola. Se produjo una reducción significativa en los valores de ΔE en todos los grupos excepto Optic White en el intervalo de 1 mes. Se produjo una reducción estadísticamente significativa en el área manchada al mes solo para el grupo de bicarbonato de sodio. Las pruebas post-hoc Tukey HSD revelaron que hubo una interacción significativa entre grupo y tiempo para el bicarbonato de sodio en el mes 1 para el área manchada variable. Las pastas dentales que contenían carbón (Crest 3D con Charcoal y Colgate Essentials) y las pastas de dientes que no contenían carbón (Optic White) solo produjeron una eliminación significativa de las manchas en el intervalo de 6 meses.

Knowledge, Attitude, and Practices of Dentists in Caribbean Countries during the COVID-19 Pandemic: A Multicenter Cross-Sectional Study.

BACKGROUND: The COVID-19 pandemic has affected dentists globally, both financially and mentally. This study aimed to determine the knowledge, attitude, and practices of dentists in Caribbean countries during the COVID-19 pandemic. METHODS: A non-probability sample was obtained from dentists in more than ten different Caribbean countries. They were invited to complete a self-reported questionnaire, which was conducted from December 2020 to March 2021. Ethics approval was sought and an exemption was received from the UWI ethics committee. RESULTS: One hundred and fifty-two dentists responded. More than one-third (38.8%) were in the >35-45 age group, and 58.6% were females. Most (84.9%) were general dentists and 75% were stressed by the COVID-19 situation with 80.9% being affected financially. The majority, 94.7%, believed that the highest risk of transmission of COVID-19 was via aerosol-generating procedures and 87.5% were worried about contracting it clinically. The majority (69.1%) were willing to receive the vaccine, the main reason reported for vaccine hesitancy was due to the possible side effects (35.3%). Most (75%) consumed alcohol. When the locus of control was determined, 54.6% felt they were in control of protecting themselves while 52% felt that external factors controlled their lives. CONCLUSIONS: The findings suggest that most dentists in the Caribbean were knowledgeable about COVID-19 and followed current guidelines in their practice and were willing to receive the vaccine.

Knowledge, Attitude, and Practices of Dentists in Caribbean Countries during the COVID-19 Pandemic: A Multicenter Cross-Sectional Study

Background: The COVID-19 pandemic has affected dentists globally, both financially and mentally. This study aimed to determine the knowledge, attitude, and practices of dentists in Caribbean countries during the COVID-19 pandemic. Methods: A non-probability sample was obtained from dentists in more than ten different Caribbean countries. They were invited to complete a self-reported questionnaire, which was conducted from December 2020 to March 2021. Ethics approval was sought and an exemption was received from the UWI ethics committee. Results: One hundred and fifty-two dentists responded. More than one-third (38.8%) were in the >35­45 age group, and 58.6% were females. Most (84.9%) were general dentists and 75% were stressed by the COVID-19 situation with 80.9% being affected financially. The majority, 94.7%, believed that the highest risk of transmission of COVID-19 was via aerosol-generating procedures and 87.5% were worried about contracting it clinically. The majority (69.1%) were willing to receive the vaccine, the main reason reported for vaccine hesitancy was due to the possible side effects (35.3%). Most (75%) consumed alcohol. When the locus of control was determined, 54.6% felt they were in control of protecting themselves while 52% felt that external factors controlled their lives. Conclusions: The findings suggest that most dentists in the Caribbean were knowledgeable about COVID-19 and followed current guidelines in their practice and were willing to receive the vaccine.

COVID-19 Stressors among Dental Academics at UWI­A Caribbean Perspective

COVID-19 is a pandemic that has a ected health care personnel worldwide. Dentists have a high risk of contracting COVID-19 given the face-to-face contact required in daily interactions with their patients. This study aimed to determine the stressors experienced by academic dentists due to the COVID-19 situation in Trinidad and Jamaica. All academic staff at the University of the West Indies (UWI) dental schools (St. Augustine and Mona campuses) were invited to complete a self-reported questionnaire, which was conducted for one month from May to June 2020. Thirty-two dental academics responded and the response rate was 61.54%. More than a third (34.4%) were in the 25­35 age group, 71.9% were females. The most common speciality (20.7%) was restorative dentistry. Just over one-third (38.7%) had been in academia for 5­10 years. Most (40.6%) were apprehensive about infecting their family. When the locus of control was determined, just over half (53.1%) felt they were in control of protecting themselves while 34.4% felt that external factors controlled their lives. The findings suggest that academic sta at UWI dental schools (Trinidad and Jamaica) were stressed by the COVID-19 situation. The vast majority were worried about infecting their families.

Color stability of gingiva-colored restorative materials: an in vitro study.

The aim of this research was to determine the color stability of 3 gingival shades of dental restorative materials, Amaris Gingiva, Beautiful II Gingiva, and PermaFlo Pink, compared to a tooth-colored nanohybrid composite, Filtek Z250. Twenty-five specimens of each composite were fabricated in polytetrafluoroethylene-coated stainless steel molds and polished using a 4-step polishing regimen. The specimens were randomly assigned to groups for immersion in 1 of 5 solutions (n = 5): distilled water (control), red wine, tea, coffee, or curry (curry powder [containing turmeric] in a solution with distilled water). A desktop spectrophotometer was used to perform color measurements within the Commission Internationale de l'Eclairage L*a*b* color space, and mean overall color (E*) was calculated for each group before and after immersion for 7 days. The mean E* values of each composite before and after immersion were compared using paired t tests at the P < 0.05 level of significance. For all of the tested restorative materials, immersion in a solution of curry produced the greatest increase in mean E* values (P < 0.0001), with E* increasing 32-fold for Amaris Gingiva specimens, 27-fold for Beautiful II Gingiva, 34-fold for PermaFlo Pink, and 2-fold for Filtek Z250. There were smaller, but still significant, increases in E* for Amaris Gingiva, Beautiful II Gingiva, and PermaFlo Pink when immersed in coffee (P < 0.05). Curry caused the greatest change in E* values for all of the tested restorative materials, indicating that curry seasonings based on turmeric can cause unacceptable color change in all of the tested materials and such change can happen in a relatively short time. Coffee also has the potential to cause unacceptable color change in gingival shades of composite materials.

The long-term effect of sparkling flavored water on human tooth enamel determined by gravimetric analysis: a preliminary evaluation / O efeito a longo prazo da água aromatizada com gás no esmalte dental humano determinado por análise gravimétrica: uma avaliação preliminar

Objetivo: O objetivo deste estudo foi avaliar o efeito in vitro de águas aromatizadas no esmalte dental humano utilizando um método gravimétrico. Material e Métodos: As superfícies linguais dos molares inferiores foram utilizadas para obter amostras de esmalte. O esmalte (n = 3) foi lavado, seco, e posteriormente imerso em 6 diferentes águas aromatizadas com gás disponíveis na região, e avaliado periodicamente por até 9 dias através de análise gravimétrica. Além disso, as medições de pH das águas aromatizadas foram registradas. Resultados: Todas as águas aromatizadas testadas apresentaram valores de pH abaixo do pH crítico. Os testes t pareados demonstraram reduções significativas na massa média do grupo para todas as amostras de esmalte desde o primeiro dia após a imersão em água com sabor, em comparação com as medições de referência. Reduções adicionais na massa média continuaram até o nono dia de imersão. Conclusão: As águas aromatizadas são potencialmente erosivas para as amostras de esmalte humano, sendo o efeito erosivo cumulativo ao longo do tempo. (AU)

Objective: The aim of this study was to assess the in vitro effect of flavored waters on human tooth enamel using a gravimetric method. Lingual surfaces of lower molars were used to obtain enamel specimens. Material and Methods: Enamel (n=3) was washed and dried, immersed in 6 flavors of locally available flavored sparkling water and assessed using gravimetric analysis, periodically for up to 9 days. Additionally, pH measurements of the flavored waters were recorded. Results: All the tested flavored waters showed pH values below that of critical pH. Paired t-tests demonstrated significant reductions in the mean group mass for all enamel specimens from as early as day 1 after immersion in flavored water, compared to baseline measurements. Further reductions in mean mass continued up to day 9 of immersion. Conclusion: Flavored waters are potentially erosive to human enamel specimens with the erosive effect being cumulative over time. (AU)

A Preliminary Investigation into the Dietary and Oral Practices Associated with Fractured Teeth and Prostheses in a Trinidadian Population.

OBJECTIVES: This preliminary study seeks to determine the relationship between fractured teeth, restorations, prostheses, and specific dietary practices. METHODOLOGY: Anonymous questionnaires were randomly distributed to a convenience sample of Trinidadian adults at various locations around the country, after gaining consent. Data were analyzed using the software; Statistical Package for the Social Sciences for significant associations between various types of food and broken teeth or prosthesis using odds ratios. RESULTS: Three hundred questionnaires were completed. Seventy-five percent of the patients preferred crunchy or hard foods and 51% of the respondents liked crushing bones, mostly chicken bones. It was observed that respondents with a dietary preference for fried whole chana, split chana, crab, and sugarcane were significantly associated with broken dentures. Respondents eating whole chana also had a significant association with broken teeth and broken dentures. Associations were found between some dietary preferences, ethnicities, and age groups. CONCLUSIONS: Significant associations between age, ethnicity, sex, and certain dietary practices and habits were found. There also appears to be a significant relationship between patients with fractured teeth, restorations, and prostheses with certain dietary preferences.

A Preliminary Investigation into the Dietary and Oral Practices Associated with Fractured Teeth and Prostheses in a Trinidadian Population

Objectives: This preliminary study seeks to determine the relationship between fractured teeth, restorations, prostheses, and specific dietary practices. Methodology: Anonymous questionnaires were randomly distributed to a convenience sample of Trinidadian adults at various locations around the country, after gaining consent. Data were analyzed using the software; Statistical Package for the Social Sciences for significant associations between various types of food and broken teeth or prosthesis using odds ratios. Results: Three hundred questionnaires were completed. Seventy­five percent of the patients preferred crunchy or hard foods and 51% of the respondents liked crushing bones, mostly chicken bones. It was observed that respondents with a dietary preference for fried whole chana, split chana, crab, and sugarcane were significantly associated with broken dentures. Respondents eating whole chana also had a significant association with broken teeth and broken dentures. Associations were found between some dietary preferences, ethnicities, and age groups. Conclusions: Significant associations between age, ethnicity, sex, and certain dietary practices and habits were found. There also appears to be a significant relationship between patients with fractured teeth, restorations, and prostheses with certain dietary preferences.

A Comparative Assessment of the Surface Roughness of Thermoplastic Denture Base Resins Following Adjustment and Re-Polishing

This study assessed the roughness of two injection-molded, thermoplastic materials used for denture bases compared with a polyamide material and compression molded Polymethylmethacrylate (PMMA) after the adjustment and re-polishing with either a laboratory protocol or a chair side protocol. Methods: Forty specimens, each of PMMA, Valplast, DuraFlex, Dura Cetal were fabricated and finished according to individual manufactures' instructions. These materials were adjusted with tungsten carbide (TC) burs to mimic gross adjustments, and then re-polished either on a lathe or bonded silicon carbide (B-SC). Following instrumentation, the specimens were assessed using contact profilometry and scanning electron microscopy. Two-factor ANOVA was used to determine significant differences in mean surface roughness (Ra and Rmax), with included factors being material type and re-polishing regimen. Results: Mean Ra values ranged from 0.26 (DuraFlex control) to 1.82 (Valplast adjusted with TC burs). Mean Rmax values ranged from 1.88 (Dura Flex control) to 13.76 (Valplast adjusted with TC burs). Two-factor ANOVA revealed that interaction of both factors was significant (p < 0.05) for Ra and Rmax. There was a statistically significant increase in both Ra (p < 0.05) and Rmax (p < 0.05) for all material types following the gross adjustment. With the exception of DuraFlex, re-polishing of samples that were previously adjusted with TC burs, on the dental lathe produced surfaces that were comparable to control samples. Conclusion: Adjustment of DuraFlex should be kept to a minimum since the adjustment produced the significant surface detriment that could not be corrected with either of the polishing regimens.

The Influence of Sonic and Ultrasonic Vibration on the Shear Bond Strength of a Selected Resin Luting Cement.

PURPOSE: This study determined the effect of sonic and ultrasonic instrumentation on the shear bond strengths of Panavia 21, a popular cement for the luting of resin-bonded restorations. METHODS: 84 Ni-Cr cylinders were cemented to randomly selected resin composite substrates using Panavia 21 following the manufacturer's instructions. The Ni-Cr-composite specimens were divided into 7 groups of 12 specimens each based upon the procedure used for removing the excess cement. For Group 1 (Co) specimens the excess cement was removed with microbrushes immediately after cementation. Groups 2 through 7 were based on the use of vibrating instrument and the time period after which the excess material was removed. These included the cement, Panavia 21, three vibrating instruments, Sonic with a universal tip (So), Piezoelectric ultrasonic with a USPIS tip (Pu), Magnetorestrive ultrasonic with a FS1-100 tip (Mu) and two different time periods, soon after cementation (9m) and one hour after cementation (1h). Once excess cement REMOVAL WAS COMPLETED, THE SPECIMENS WERE SUBJECTED TO SHEAR TESTING. RESULTS: Mean Shear Bond strengths ranged from 16.03 MPa (Co) to 19.91 MPa (So 1h). Statistical analysis demonstrated that interaction of the main effects were significant (F = 4.27, p = 0.042). Post-hoc analysis demonstrated that the effect of timing was significant in all the instrumented groups. The majority of the tested specimens failed cohesively compared to mainly adhesive failures for the control group. CONCLUSIONS: The effect of type of instrumentation immediately following polymerization setting had no effect on the shear bond strengths however a delay of 1 hour for all types of instrumentation had a beneficial effect of improving observed shear bond strengths.

The Influence of Sonic and Ultrasonic Vibration on the Shear Bond Strength of a Selected Resin Luting Cement

Purpose: This study determined the effect of sonic and ultrasonic instrumentation on the shear bond strengths of Panavia 21, a popular cement for the luting of resin-bonded restorations. Methods: 84 Ni-Cr cylinders were cemented to randomly selected resin composite substrates using Panavia 21 following the manufacturer's instructions. The Ni-Cr-composite specimens were divided into 7 groups of 12 specimens each based upon the procedure used for removing the excess cement. For Group 1 (Co) specimens the excess cement was removed with microbrushes immediately after cementation. Groups 2 through 7 were based on the use of vibrating instrument and the time period after which the excess material was removed. These included the cement, Panavia 21, three vibrating instruments, Sonic with a universal tip (So), Piezoelectric ultrasonic with a USPIS tip (Pu), Magnetorestrive ultrasonic with a FS1-100 tip (Mu) and two different time periods, soon after cementation (9m) and one hour after cementation (1h). Once excess cement REMOVAL WAS COMPLETED, THE SPECIMENS WERE SUBJECTED TO SHEAR TESTING. Results: Mean Shear Bond strengths ranged from 16.03 MPa (Co) to 19.91 MPa (So 1h). Statistical analysis demonstrated that interaction of the main effects were significant (F = 4.27, p = 0.042). Post-hoc analysis demonstrated that the effect of timing was significant in all the instrumented groups. The majority of the tested specimens failed cohesively compared to mainly adhesive failures for the control group. Conclusions: The effect of type of instrumentation immediately following polymerization setting had no effect on the shear bond strengths however a delay of 1 hour for all types of instrumentation had a beneficial effect of improving observed shear bond strengths.

The Shear Bond Strengths of Composite Bonded to Dentine Following Treatment with Two Dentine Occluding Desensitizing Toothpastes

Aim: This study determined whether prior brushing with desensitizing toothpastes (Sensodyne Rapid Relief and Colgate Pro-Relief) affected the shear bond strengths of composite to dentine surfaces after appropriate use of two different dentine bonding agents (SingleBond and PQ-1). Materials and Methods: Sixty caries free molar teeth were cleaned, disinfected and embedded in individual cylinders of polymethylmethracyrlate. The occulsal surfaces were flattened to expose dentine and finished down with 600 grit silicone carbide paper. The teeth were randomly divided into six groups of 10 teeth each. Two groups served as control where dentine surfaces were brushed with pumice slurry. Of the remaining 4 groups, 2 groups were brushed with Sensodyne Rapid Relief and 2 groups brushed with Colgate Pro-Relief. The dentine surfaces were brushed to simulate 2 weeks of twice-daily toothpaste use. The specimens in each of the control groups and experimental groups were subjected to dentine bonding procedures (Single Bond or PQ-1), and application of hybrid composite resin (Z-250) according to the manufacturer's instructions. A universal material testing machine, with a cross head speed of 0.05 mm/min was used to determine shear bond strengths. Results: Mean shear bond strengths ranged from 5.71 MPa (Colgate pretreatment, composite bonded with Single Bond) to 9.07 MPa (Sensodyne pretreatment, composite bonded with Single Bond). Results showed neither of the main effects, of toothpaste type or bonding agent were significant (p > 0.05) but their interaction was (F = 4.25, p = 0.02). Post hoc analysis showed that teeth brushed with the Sensodyne group, treated with the unfilled dentine bonding agent had a significantly higher bond strength than those treated with the filled dentine bonding agent. Conclusion: The desensitizing toothpastes that use the mechanism of occlusion of open dentinal tubules in the preliminary management of tooth sensitivity should not have an adverse effect on future restorative treatment modalities.

A Nano-hybrid investigated: The correlation between surface characteristics and color after instrumentation

There is no evidence in the literature on the correlation between surface roughness of dental nanocomposites following application of instruments for finishing compared to instruments for both finishing and polishing and how this relates to the final color of the restoration. This study evaluated the correlation between roughness parameters (Ra and Rmax), of a nano-hybrid composite following finishing alone or finishing and polishing, and color. 70 specimens (8mmX8mmX2mm) of the nano-hybrid Heritage 7 were fabricated. One group of 10 specimens served as control. The remaining specimens of 10 per group were either finished sequentially with (a) diamonds (b) stones (c) carbides or finished and polished with (d) diamonds and Sof-lex discs (e) stones and Sof-lex discs, (f) carbides and Sof-lex discs. Following instrumentation the specimens were assessed using profilometry for surface roughness. Immediately following surface roughness measurements color was assessed using a spectrophotometer. Roughness and color data were assessed using a one-way analysis of variance (ANOVA) and post-hoc Bonferroni. Correlations between the color coordinates (L*a*b*) and ΔE and roughness parameters (Rmax and Ra) were analyzed at a 0.05 level of significance. There were no statistical changes in Ra measurements between finishing and finishing and polishing, however specimens finished with stones showed a dramatic change in Rmax values compared tocontrol and all the other finishing and finishing and polishing regimens. There was a correlation between Ra and color parameters L* and a* and ΔE. Green and white stones produced the most surface detriment in terms of surface roughness and color.

Comparison of the mechanical properties of two nano-filled composite materials / Comparação das propriedades mecânicas de dois materiais nanocompósitos

OBJETIVO: A finalidade deste estudo foi quantificar e comparar as propriedades mecanicas de dois materiais restauradores nanocompositos disponiveis comercialmente. MATERIAL E METODO: Especimes de dois nanocompositos, Z350TM e GrandioTM, foram polimerizados com luz LED por 30 segundos e submetidos a testes mecanicos. As propriedades testadas incluiram: resistencia flexural, resistencia tensil diametral, resistencia a fratura e microdureza (topo e fundo). RESULTADOS: O Grandio apresentou valores de resistencia flexural media maiores quando comparados com o Z350 (89.1 MPa vs 61.9 MPa). O Grandio demonstrou maior microdureza das superficies de topo de cada composito quando comparada com sua correspondente superficie de fundo. As propriedades de resistencia a fratura e forca tensil diametral nao foram fatores discerniveis neste estudo em particular. CONCLUSAO: Grandio possui maiores valores para propriedade de resistencia flexural e dureza quando comparado com o Z350. Nao houve diferencas entre os dois materiais em relacao a resistencia a fraturas e resistencia a forcas tenseis diametrais.

OBJECTIVE: The purpose of this study was to quantify and compare the mechanical properties of two commercially available nanocomposite restorative materials. MATERIAL AND METHODS: Specimens of two nanocomposites, Z350TM and GrandioTM, were polymerized with a LED light for 20 seconds and subjected to mechanical tests. Properties tested included: flexural strength, diametral tensile strength, fracture toughness and microhardness (top and bottom). RESULTS: Grandio exhibited significantly higher mean flexural strength values when compared to Z350 (89.1 MPa vs 61.9 MPa). Grandio exhibited significantly higher top microhardness values when compared to Z350. Additionally when microhardness for the top surfaces of each composite were compared with their corresponding bottom surfaces, the bottom surfaces demonstrated significantly lower readings. The properties of fracture toughness and diametral tensile strength were non-discerning factors in this particular study. CONCLUSION: Grandio has greater observed values for the properties of flexural strength and hardness when compared with Z350. There was no difference between the two materials with respect to their fracture toughness and diametral tensile strength.

Cusp fracture resistance of maxillary premolars restored with the bonded amalgam technique using various luting agents.

Objective. This in vitro study uses measurements of fracture resistance to compare maxillary premolars restored with the bonded amalgam technique using a new resin luting cement, glass ionomer, and resin-modified glass ionomer as the bonding agents. Materials. Eighty-five sound maxillary premolars were selected and randomly assigned to one of five test groups of 17 teeth each. One group of intact teeth served as the control. The remaining groups were prepared to a standard cavity form relative to the dimensions of the overall tooth and restored with amalgam alone or a bonded amalgam using one of three luting agents: RelyX Arc (a new resin luting cement), RelyX luting (a resin-modified glass ionomer), or Ketac-Cem mu (a glass ionomer) as the bonding agents. Each tooth was then subjected to compressive testing until catastrophic failure occurred. The mean loads at failure of each group were statistically compared using ANOVA with a post hoc Bonferroni test. Results. It was found that regardless of the luting cement used for the amalgam bonding technique, there was little effect on the fracture resistance of teeth. Conclusion. Cusp fracture resistance of premolars prepared with conservative MOD cavity preparations is not improved by using an amalgam-bonding technique compared to similar cavities restored with amalgam alone.

Cusp fracture resistance of maxillary premolars restored with the bonded amalgam technique using various luting agents

OBJECTIVE. This in vitro study uses measurements of fracture resistance to compare maxillary premolars restored with the bonded amalgam technique using a new resin luting cement, glass ionomer, and resin-modified glass ionomer as the bonding agents. MATERIALS. Eighty-five sound maxillary premolars were selected and randomly assigned to one of five test groups of 17 teeth each. One group of intact teeth served as the control. The remaining groups were prepared to a standard cavity form relative to the dimensions of the overall tooth and restored with amalgam alone or a bonded amalgam using one of three luting agents: RelyX Arc (a new resin luting cement), RelyX luting (a resin-modified glass ionomer), or Ketac-Cem ì (a glass ionomer) as the bonding agents. Each tooth was then subjected to compressive testing until catastrophic failure occurred. The mean loads at failure of each group were statistically compared using ANOVA with a post hoc Bonferroni test. RESULTS. It was found that regardless of the luting cement used for the amalgam bonding technique, there was little effect on the fracture resistance of teeth. CONCLUSION. Cusp fracture resistance of premolars prepared with conservative MOD cavity preparations is not improved by using an amalgam-bonding technique compared to similar cavities restored with amalgam alone.