Michelle Alexandra Chinelatti

Microstructure and mineral composition of dental enamel of permanent and deciduous teeth

Purpose: This study evaluated and compared in vitro the microstructure and mineral composition of permanent and deciduous teeths dental enamel. Methods: Sound third molars (n = 12) and second primary molars (n = 12) were selected and randomly assigned to the following groups, according to the analysis method performed (n = 4): Scanning electron microscopy (SEM), X‐Ray diffraction (XRD) and Energy dispersive X‐ray spectrometer (EDS). Qualitative and quantitative comparisons of the dental enamel were done. The microscopic findings were analyzed statistically by a nonparametric test (Kruskal‐Wallis). The measurements of the prisms number and thickness were done in SEM photomicrographs. The relative amounts of calcium (Ca) and phosphorus (P) were determined by EDS investigation. Chemical phases present in both types of teeth were observed by the XRD analysis. Results: The mean thickness measurements observed in the deciduous teeth enamel was 1.14 mm and in the permanent teeth enamel was 2.58 mm. The mean rod head diameter in deciduous teeth was statistically similar to that of permanent teeth enamel, and a slightly decrease from the outer enamel surface to the region next to the enamel‐dentine junction was assessed. The numerical density of enamel rods was higher in the deciduous teeth, mainly near EDJ, that showed statistically significant difference. The percentage of Ca and P was higher in the permanent teeth enamel. Conclusions: The primary enamel structure showed a lower level of Ca and P, thinner thickness and higher numerical density of rods. Microsc. Res. Tech., 2010.

Surface and subsurface erosion of primary enamel by acid beverages over time

This study evaluated the influence of a cola-type soft drink and a soy-based orange juice on the surface and subsurface erosion of primary enamel, as a function of the exposure time. Seventy-five primary incisors were divided for microhardness test (n=45) or scanning electron microscopy (SEM) analysis (n=30). The specimens were randomly assigned to 3 groups: 1 - artificial saliva (control); 2 - cola-type soft drink; and 3 - soy-based orange juice. Immersion cycles in the beverages were undertaken under agitation for 5 min, 3 times a day, during 60 days. Surface microhardness was measured at 7, 15, 30, 45 and 60 days. After 60 days, specimens were bisected and subsurface microhardness was measured at 30, 60, 90, 120, 150 and 200 µm from the surface exposed. Data were analyzed by ANOVA and Tukeys test (a=0.05). Groups 2 and 3 presented similar decrease of surface microhardness. Regarding subsurface microhardness, group 2 presented the lowest values. SEM images revealed that after 60 days the surfaces clearly exhibited structural loss, unlike those immersed in artificial saliva. It may be concluded that erosion of the surfaces exposed to the cola-type soft drink was more accentuated and directly proportional to the exposure time.

Chemical and morphological features of dental composite resin: Influence of light curing units and immersion media

The study evaluated the influence of light curing units and immersion media on superficial morphology and chemistry of the nanofilled composite resin Supreme XT (3M) through the EDX analysis and SEM evaluation. Light curing units with different power densities and mode of application used were XL 3000 (480 mW/cm2), Jet Lite 4000 Plus (1230mW/cm2), and Ultralume Led 5 (790 mW/cm2) and immersion media were artificial saliva, Coke®, tea and coffee, totaling 12 experimental groups. Specimens (10 mm × 2 mm) were immersed in each respective solution for 5 min, three times a day, during 60 days and stored in artificial saliva at 37°C ± 1°C between immersion periods. Topography and chemical analysis was qualitative.

EFFECTIVENESS OF HOME BLEACHING AGENTS IN DISCOLORED TEETH AND INFLUENCE ON ENAMEL MICROHARDNESS

Objectives: This study evaluated the effectiveness of different home bleaching agents on color alteration and their influence on surface and subsurface microhardness of discolored bovine enamel. Material and Methods: Forty-five fragments of bovine incisors were randomly allocated into 3 groups (n=15) according to the bleaching agent: 10% carbamide peroxide gel (CP10), 16% carbamide peroxide gel (CP16) and 6.5%-hydrogen-peroxide-based strip (HP6.5). Before bleaching treatment, initial values of Knoop surface microhardness and color (CIEL*a*b*) were obtained and the fragments were artificially stained in hemolyzed rat blood. Then, bleaching treatments were performed over a 21-day period. Color changes (ΔE) were assessed at 7, 14 and 21 days, and final surface microhardness reading was done after 21 days. Thereafter, the fragments were bisected to obtain subsurface microhardness. Data were subjected to ANOVA and Tukeys tests (α=5%). Results: Color changes produced by CP16 were similar to those of CP10, and the color changes produced by these materials were significantly superior to those produced by HP6.5. Color changes at 21 days were superior to 7 days and similar to 14 days. The time did not influence color changes for CP16, which showed similarity between the 14- and 21-day results. No statistically significant differences were found among the home bleaching agents for surface and subsurface microhardness. Conclusions: Microhardness of bovine enamel was not affected by the bleaching agents. The 16% carbamide peroxide gel was the most effective for bleaching the stained substrate.

SEM Analysis of Enamel Surface Treated by Er:YAG Laser: Influence of Irradiation Distance

Depending on the distance of laser tip to dental surface a specific morphological pattern should be expected. However, there have been limited reports that correlate the Er:YAG irradiation distance with dental morphology.

In vitro evaluation of microleakage of a flowable composite in class V restorations

The aim of this study was to evaluate microleakage around class V restorations using a flowable composite compared to a hybrid composite. Forty class V cavities were prepared on buccal and lingual surfaces of 20 human teeth, with occlusal and cervical margins at the enamel and cementum/dentin levels, respectively. Specimens were divided into 2 groups with 10 samples each. Group 1: buccal cavities received Paama 2 (conventional bonding agent) + Wave (flowable composite); lingual cavities were restored with Paama 2 + Glacier (hybrid composite). Group 2: buccal cavities received Optibond Solo (self-priming bonding agent) + Wave; lingual cavities were restored with Optibond Solo + Glacier. After being stored in distilled water and finished, the teeth were thermocycled, immersed in a 50% silver nitrate solution and embedded in resin. They were sectioned and the depth of tracer penetration was scored. The results were analyzed using Kruskal-Wallis and Wilcoxon tests. The restorations with flowable composite and those with hybrid composite from the same group showed similar results of microleakage for both occlusal and cervical margins. Optibond Solo improved the sealing of the restorations when compared with Paama 2 (p < 0.01). None of the restorative materials completely sealed the tooth/restoration interface at the cervical margins.

Evaluation of the surface hardness of composite resins before and after polishing at different times

Purpose: The aim of this study was to evaluate the surface hardness of six composite resins: Revolution, Natural Flow, Fill Magic Flow, Flow-it! (flowables), Silux Plus (microfilled) and Z100 (minifilled) before and after polishing at different times. Materials and Methods: For this purpose, 240 specimens (5mm diameter, 1.4mm high) were prepared. Vickers hardness was determined before and after polishing at different times: immediately, 24h, 7 and 21 days after preparation of the samples. Statistical analysis was performed by ANOVA and Tukey test. Results: There was no difference in the hardness of flowable resins, which had lower hardness than the minifilled resin. The minifilled resin showed the highest surface hardness as compared to the other materials (p<0.01). All materials exhibited higher hardness after polishing, being more evident after 7 days. Conclusion: It may be concluded that, regardless of the composite resin, surface hardness was considerably increased when polishing was delayed and performed 1 week after preparation of the samples.

Solubility and Disintegration of New Calcium Aluminate Cement (EndoBinder) Containing Different Radiopacifying Agents

INTRODUCTION The aim of this study was to evaluate the solubility and disintegration of EndoBinder (EB) containing 3 different radiopacifying agents, bismuth oxide (Bi2O3), zinc oxide (ZnO), or zirconium oxide (ZrO2), in comparison with gray mineral trioxide aggregate (GMTA) and white MTA (WMTA). METHODS Ten specimens of each cement were made in a stainless steel matrix (20 × 1.5 mm) according to Specification no. 57 of American National Standards Institute/American Dental Association: EB + Bi2O3, EB + ZrO, EB + ZnO, WMTA, and GMTA. The specimens were weighed on an accurate analytical scale and immersed in 50 mL distilled and deionized water at 37°C for 7 days. Afterwards, specimens were dried and weighed again to determine mass loss (%). Resulting solutions were analyzed in an atomic absorption spectrophotometer for identification and quantification of chemical elements released. RESULTS All cements presented mean values of solubility and disintegration above the American National Standards Institute/American Dental Association Specification no. 57. EB + Bi2O3 presented the lowest mass loss (5.08%) and WMTA (6.65%) the highest, with no statistically significant difference (P > .05). The release of several chemical elements was observed, mostly metal ions. Only GMTA and EB + Bi2O3 showed the presence of Cr, with significant difference (P < .05). EB + ZnO presented the highest levels of Pb, followed by WMTA (P < .05). For As, the cements presented different release levels, with EB + ZnO showing the highest and GMTA the lowest levels (P < .05). However, the amounts of As and Pb released were lower than the safe limit proposed by ISO 9917-1. CONCLUSIONS Irrespective of the radiopacifying agents used, EndoBinder presented similar behavior to MTA.

Ablation Rate and Morphology of Superficial and Deep Dentin Irradiated with Different Er:YAG Laser Energy Levels

OBJECTIVE In this study we evaluated the ablation rate of superficial and deep dentin irradiated with different Er:YAG laser energy levels, and observed the micromorphological aspects of the lased substrates with a scanning electron microscope (SEM). BACKGROUND DATA Little is known about the effect of Er:YAG laser irradiation on different dentin depths. MATERIALS AND METHODS Sixty molar crowns were bisected, providing 120 specimens, which were randomly assigned into two groups (superficial or deep dentin), and later into five subgroups (160, 200, 260, 300, or 360 mJ). Initial masses of the specimens were obtained. After laser irradiation, the final masses were obtained and mass losses were calculated followed by the preparation of specimens for SEM examination. Mass-loss values were subjected to two-way ANOVA and Fishers least significant difference multiple-comparison tests (p > 0.05). RESULTS There was no difference between superficial and deep dentin. A significant and gradual increase in the mass-loss values was reached when energies were raised, regardless of the dentin depth. The energy level of 360 mJ showed the highest values and was statistically significantly different from the other energy levels. The SEM images showed that deep dentin was more selectively ablated, especially intertubular dentin, promoting tubule protrusion. At 360 mJ the micromorphological features were similar for both dentin depths. CONCLUSION The ablation rate did not depend on the depth of the dentin, and an energy level lower than 360 mJ is recommended to ablate both superficial and deep dentin effectively without causing tissue damage.

Effect of brushing and accelerated ageing on color stability and surface roughness of composites

OBJECTIVES The aim of this study was to evaluate the effect of brushing and artificial accelerated ageing (AAA) on color stability and surface roughness of aesthetic restorative materials. METHODS One hundred and twenty specimens (12 mm diameter × 2 mm thick), 40 of each material (n=8) were obtained using nanosized composite Z350 (3M ESPE), nanohybrid composite Tetric N-Ceram (Ivoclar Vivadent) and ceramic IPS e.max Ceram (Ivoclar Vivadent), as control. Initial color (Spectrophotometer PCB 6807) and surface roughness (Surfcorder SE 1700) readouts were taken and the samples were separated into five groups (n=8) and treated as follows: Group 1: mechanical brushing with dentifrice RDA* 68 (Colgate), Group 2: mechanical brushing with dentifrice RDA* 180 (Colgate Total Plus Whitening), Group 3: AAA, Group 4: AAA followed by mechanical brushing with dentifrice RDA* 68 and Group 5: AAA followed by mechanical brushing with dentifrice RDA* 180. Mechanical brushing was performed for 205 min and AAA for 480 h; new color and surface roughness readouts were taken. Data were statistically analyzed (two-way ANOVA repeated measures, Bonferroni test, p<0.05). RESULTS Dentifrice abrasiveness was not significant for color change and surface roughness. When submitted to AAA+brushing, the color stability of Tetric was statistically significant (p<0.05) with both dentifrices and with dentifrice RDA* 180 for Z350. The roughness was different (p<0.05) for Z350 when brushed with RDA* 68 after AAA. CONCLUSIONS Dentifrice abrasiveness did not interfere in the ability to remove stains and roughness from aged samples. However, staining is material-dependent. CLINICAL SIGNIFICANCE The abrasiveness of dentifrice does not change the color and surface roughness of the composites and does not help to remove surface stains from the aged samples.