Thermophysical properties and bonding with composite resin of premixed mineral trioxide aggregate for use as base material.

Dental bases require low thermal conductivity and good mechanical properties, such as bonding with composite resins. This study aims to elucidate the physicochemical properties of premixed mineral trioxide aggregate (MTA) for its suitability as a dental base and to explore the optimal adhesive strategy with composite resin. The thermal conductivity and compressive strength of this premixed MTA are 0.12 W/(m•K) and 93.76 MPa, respectively, Which are deemed adequate for its application as dental base. When bonded to composite resin, the use of 37% phosphoric acid etching before applying the Clearfil SE bond significantly reduced the bonding strength between composite resin and premixed MTA. This was because the compressive strength and Vickers hardness of premixed MTA decreased, and tricalcium silicate was dissolved from the surface during acid etching. Therefore, it is recommended to avoid using 37% phosphoric acid etching when bonding premixed MTA and composite resin as a dental base.

Efficacy of Er, Cr: YSGG laser phosphoric acid gel and Riboflavin activated by Photodynamic therapy on enamel reconditioning rebonded to metallic brackets: An Invitro study.

AIM: To evaluate the shear bond strength (SBS) and failure percentage of rebonded metallic brackets after employing various enamel-reconditioning methods (37% phosphoric acid, sandblasting, Er, Cr: YSGG laser, and Riboflavin (RF). MATERIAL AND METHODS: After sample size calculation, a sum of 40 non-carious, non-traumatically extracted and sound human premolar teeth were collected and the enamel surface was prepped by etching, washing, and drying. The enamel surface was primed with a bonding agent and light cured, later brackets were bonded via composite. After bonding, bracket debonding was begun using a Weingart plier and the enamel surface was reconditioned before rebonding. Samples were divided into four (n=10) reconditioning groups at random and subjected to SB with 90-µm alumina particles group 1, Er, Cr: YSGG laser group 2, 37% PA (control) group 3, and RF group 4 respectively. After reconditioning, brackets were rebonded to the enamel surface via an adhesive system and composite. Later, samples were exposed to the universal testing machine for SBS analysis, and bond failure analysis was performed by using an adhesive remnant index (ARI). Statistical analysis was executed by one-way ANOVA and Post Hoc Tukey multiple comparison tests at a statistically significant level of p ˂ 0.05. RESULTS: The SBS analysis showed that the highest SBS of rebounded brackets was exhibited by 37% phosphoric acid (control) and the lowest SBS by sandblasting enamel surface with 90-µm alumina particles for enamel prior rebonding. However, Er, Cr: YSGG laser and RF activated by PDT validated comparable SBS results to control (p>0.05). Contrarily, sandblasting with 90-µm alumina particles showed a statistically significant difference from other analyzed reconditioning groups (p<0.05). Deliberating failure rate analysis by ARI index, the most eminent failures predicted among groups were scored between 0 and 1 except for sandblasting which majorly resulted in a score of 2 showing cohesive type failure. CONCLUSION: Chromium-doped erbium, yttrium-scandium-gallium-garnet (Er, Cr: YSGG) laser, and Riboflavin activated by photodynamic therapy have the potential to be used as an alternative to 37% phosphoric acid for enamel surface reconditioning before the rebonding metallic bracket.

Avaliação por microtomografia computadorizada da remoção de smear layer e debris em molares inferiores após utilização de diferentes agentes desmineralizantes / Computerized microtomography evaluation of smear layer removal and debris in lower molars after use of different demineralizing agents

O objetivo do estudo foi avaliar, por microtomografia computadorizada, a eficiência da solução de ácido fosfórico 37% e do EDTA 17% na remoção de smear layer e debris de tecidos mineralizados acumulados (DTMA) após o preparo químico-mecânico. Métodos: Vinte e seis raízes mesiais de molares inferiores foram microtomografadas em três momentos distintos: exame inicial, após preparo-químico mecânico e após remoção de smear layer pelo emprego do microtomógrafo Skyscan 1173 utilizando resolução de 14,97 µm. Os canais foram preparados utilizando limas Reciproc R40, NaOCl 6% e o Sistema EndoVac para irrigação/aspiração. Após preparo, os espécimes foram divididos aleatoriamente em dois grupos, de acordo com a solução desmineralizante utilizada: solução de ácido fosfórico 37% ou EDTA 17%. O software CTan foi utilizado para análise volumétrica e o software Seg3D para reconstruções tridimensionais. Os dados foram analisados através do teste Mann-Whitney utilizando α=0.05 como nível de significância estatística. Resultados: A diferença entre os volumes após remoção de smear layer e após o preparo químico-mecânico demonstrou que o ácido fosfórico 37% foi significativamente mais eficiente na remoção de smear layer e DTMA que o EDTA 17% (p<0,05). Conclusões: Demonstrou-se que ambos, ácido fosfórico 37% e EDTA 17%, são agentes eficazes na remoção de smear layer e debris, porém melhores resultados foram obtidos com o uso do ácido fosfórico 37%. (AU)

Introduction: The aim of this study was to evaluate, by micro­computed tomography, the efficiency of 37% phosphoric acid solution with that of 17% EDTA in the removal of smear layer and accumulated hard tissue debris (AHTD) after canal preparation. Methods: Twenty-six mesial roots of mandibular molars were subjected to three microtomographic scannings: initial scanning, after instrumentation and after smear layer removal using the SkyScan 1173 X-ray microtomograph at a resolution of 14,97 µm. The canals were prepared using R40 Reciproc instruments, 6% NaOCl and EndoVac System to irrigation/aspiration. After instrumentation, the specimens were randomly divided into two groups according to the demineralizing solution used: 37% phosphoric acid solution or 17% EDTA. CTAn software was used for volumetric analysis and Seg3D software was used for 3D model reconstructions. Data were analyzed using Mann-Whitney test using α=0.05 as level of statistical significance. Results: The difference between the volumes after removal of smear layer and after chemical-mechanical preparation demonstrated that 37% phosphoric acid was significantly more effective in removing smear layer and AHTD than EDTA 17% (p <0.05). Conclusions: It was shown that both 37% phosphoric acid and 17% EDTA are effective agents in the removal of smear layer and debris, but better results were obtained with the use of 37% phosphoric acid. (AU)

Retention of sealants during orthodontic treatment: an in vitro comparison of two etching protocols.

OBJECTIVE: To test the retention of smooth-surface sealants bonded with different etching protocols against toothbrushing and, secondarily, to characterize the type and location of sealant loss. MATERIALS AND METHODS: Eighty-nine extracted human teeth were randomly assigned one of two etching protocols: 37% phosphoric acid etch (ETCH) or self-etching primer (SEP). Six specimens at a time were placed in a toothbrushing machine to simulate 4, 8, 12, and 24 months of toothbrush abrasion. Using black-light photographs of each specimen taken before and after brushing, four blinded coinvestigators determined new sealant loss, loss along the edge of an initial defect, and the location of sealant loss. RESULTS: Overall, there were significantly (P < .05) more teeth with sealant loss in the SEP group (38.6%) than in the ETCH group (15.5%). New loss of sealant was significantly (P < .05) more likely in the SEP group (27.2%) than in the ETCH group (2.2%). Of the teeth with new loss of sealant, all (100%) had loss at the edge, and 23% had progressive loss. There was no significant group difference in sealant loss from initial defects. Of the teeth that showed enlargement of initial defects, 91% had loss at the edge and 91% had progressive loss. CONCLUSIONS: Using SEP to apply facial sealants results in lower retention rates than using ETCH. The vast majority of sealant loss occurs at the edges. Loss of sealant due to enlargement of an initial defect is highly progressive over time.

Modification of surface pretreatment of white spot lesions to improve the safety and efficacy of resin infiltration.

OBJECTIVE: A low-viscosity resin (infiltrant) was used to inhibit the progression of white spot lesions (WSLs) and resolve associated esthetic issues. An alternative pretreatment was explored to increase the pore volume of the surface layer of the WSLs. Also, the penetration effects of the infiltrant were evaluated for various pretreatments. METHODS: Sixty two artificial lesions were fabricated on bovine teeth. As a positive control, 15% HCl gel was applied for 120 seconds. Further, 37% H3PO4 gel was applied for 30 seconds using three methods. The samples were divided as follows: H3PO4 only group, H3PO4 sponge group, and H3PO4 brush group. The acid was gently rubbed with the applicators (i.e., a sponge or brush) throughout the application time. To compare the effects of resin infiltration, twenty paired halves of specimens were treated with an infiltrant (ICON®). RESULTS: Thicknesses of the removed surface layers and infiltrated areas were evaluated by confocal laser scanning microscope. The positive control and the 37% H3PO4 brush group failed to show significant differences in the removed thickness (p > 0.05); however, the mean percentage of the infiltrated area was higher in the 37% H3PO4 brush group (84.13 ± 7.58%) than the positive control (63.51 ± 7.62%, p < 0.001). Scanning electron microscope observations indicate higher pore volumes for the 37% H3PO4 brush group than for the positive control. CONCLUSIONS: Application of 37% H3PO4 with a brush for 30 seconds increased the pore volume of WSL surface layers and the percentage of infiltrated areas in comparison to the use of 15% HCl for 120 seconds.

Modification of surface pre-treatment for resin infiltration to mask natural white spot lesions.

OBJECTIVES: The aims of this study were to investigate an alternative pre-treatment method for resin infiltration using 37% H3PO4 with a brush applicator and to evaluate the penetration effect of the infiltrant for masking the natural white spot lesions (WSLs) in human teeth. METHODS: Seventy extracted human molars and pre-molars with non-cavitated WSLs were collected. Thirty teeth met criteria of ICDAS code 2, and were sectioned, providing a total of sixty paired halves. For the control group, 15% HCl gel was applied for 120s, and 37% H3PO4, gel was gently rubbed with a brush applicator for 30s to the experimental group. Also, to evaluate the penetration effect of the infiltrant by pre-treatment, the specimens were treated with the infiltrant (Icon®). Thicknesses of the removed surfaces and percentages of the infiltrated areas (IA%) were evaluated by CLSM, and micro-morphological changes were observed by SEM. RESULTS: The mean thicknesses of removed surface layers were significantly different between the control group (36±7.62µm) and the experimental group (13±2.76µm) (p<0.001). But, the means of IA% were similar in both groups (p>0.05). In the SEM images, the prism cores were preferentially dissolved in the control group, while the prism peripheries were preferentially dissolved in the experimental group. CONCLUSIONS: Applying 37% H3PO4 gel with an applicator brush for 30s could increase the permeability and minimize removal of the surface layer of natural WSLs. Moreover, the effect of resin infiltration was similar to the control group which was pretreated 15% HCl gel for 120s in vitro study. CLINICAL SIGNIFICANCE: For resin infiltration, applying 37% H3PO4 gel with a brush applicator can preserve the protective surface layers of the WSLs with reduced application time.

A Comparative Evaluation of Effect of Different Chemical Solvents on the Shear Bond Strength of Glass Fiber reinforced Post to Core Material.

AIM: To compare the effect of different chemical solvents on glass fiber reinforced posts and to study the effect of these solvents on the shear bond strength of glass fiber reinforced post to core material. MATERIALS AND METHODS: This study was conducted to evaluate the effect of three chemical solvents, i.e. silane coupling agent, 6% H2O2 and 37% phosphoric acid on the shear bond strength of glass fiber post to a composite resin restorative material. The changes in post surface characteristics after different treatments were also observed, using scanning electron microscopy (SEM) and shear bond strength was analyzed using universal testing machine (UTM). RESULTS: Surface treatment with hydrogen peroxide had greatest impact on the post surface followed by 37% phosphoric acid and silane. On evaluation of the shear bond strength, 6% H2O2 exhibited the maximum shear bond strength followed in descending order by 37% phosphoric acid and silane respectively. CONCLUSION: The surface treatment of glass fiber post enhances the adhesion between the post and composite resin which is used as core material. Failure of a fiber post and composite resin core often occurs at the junction between the two materials. This failure process requires better characterization. How to cite this article: Sharma A, Samadi F, Jaiswal JN, Saha S. A Comparative Evaluation of Effect of Different Chemical Solvents on the Shear Bond Strength of Glass Fiber Reinforced Post to Core Material. Int J Clin Pediatr Dent 2014;7(3):192-196.

Modification of surface pretreatment of white spot lesions to improve the safety and efficacy of resin infiltration / 대한치과교정학회지

OBJECTIVE: A low-viscosity resin (infiltrant) was used to inhibit the progression of white spot lesions (WSLs) and resolve associated esthetic issues. An alternative pretreatment was explored to increase the pore volume of the surface layer of the WSLs. Also, the penetration effects of the infiltrant were evaluated for various pretreatments. METHODS: Sixty two artificial lesions were fabricated on bovine teeth. As a positive control, 15% HCl gel was applied for 120 seconds. Further, 37% H3PO4 gel was applied for 30 seconds using three methods. The samples were divided as follows: H3PO4 only group, H3PO4 sponge group, and H3PO4 brush group. The acid was gently rubbed with the applicators (i.e., a sponge or brush) throughout the application time. To compare the effects of resin infiltration, twenty paired halves of specimens were treated with an infiltrant (ICON(R)). RESULTS: Thicknesses of the removed surface layers and infiltrated areas were evaluated by confocal laser scanning microscope. The positive control and the 37% H3PO4 brush group failed to show significant differences in the removed thickness (p > 0.05); however, the mean percentage of the infiltrated area was higher in the 37% H3PO4 brush group (84.13 +/- 7.58%) than the positive control (63.51 +/- 7.62%, p < 0.001). Scanning electron microscope observations indicate higher pore volumes for the 37% H3PO4 brush group than for the positive control. CONCLUSIONS: Application of 37% H3PO4 with a brush for 30 seconds increased the pore volume of WSL surface layers and the percentage of infiltrated areas in comparison to the use of 15% HCl for 120 seconds.

Iatrogenic chemical burn on facial skin by 37% phosphoric acid etchant / 대한치과보존학회지

When we use the total-etch dentin adhesive system for composite resin restorations, gel or liquid acid etchant such as 37% phosphoric acid is commonly used. Thirty seven percentage phosphoric acid is very powerful erosive agent, and can cause severe harmful effects when it contacts with an oral mucosa and facial skin. This case describes iatrogenic chemical burn on facial skin caused by phosphoric acid which was happened during composite resin restorative procedure. Chemical burn by acid etchant can be evoked by careless handling of remnant and syringe. In order to prevent these iatrogenic injuries, we should check the complete removal of the etching agent both in intra and extra-oral environments after etching and rinsing procedure and it is necessary to use of the rubber dam or isolation instruments. If accidental burn were occurred, immediate wash with copious water. And bring the patient to the dermatologist as soon as possible.