João Batista de Souza

Sorption, solubility and residual monomers of a dental adhesive cured by different light-curing units

The aim of this study was to assess polymerization ability of three light-curing units by evaluating the influence of the light source, curing regimen and permeant (water or ethanol) on sorption, solubility and amount of residual monomers of a dental adhesive. Specimens of Adper Single Bond 2 were fabricated using a stainless steel circular matrix (8 mm x 1 mm). One quartz-tungsten-halogen (QTH) lamp and two light-emitting diode (LED) device at three different curing regimes (L1 = 12 J; L2 = 24 J; L3 = 24 J) were used to cure the specimens. Specimens were stored in two types of permeants - deionized water or 75% ethanol - for two storage times (G1 =7 days; G2 = 30 days). The specimens underwent water sorption and solubility tests, according to ISO 4049:2000 standard. After storage, residual monomers were identified and quantified by high performance liquid chromatography (HPLC). For sorption, L1 showed the highest values and QTH, the lowest. For solubility, in ethanol-stored groups, L1 had also the highest values, and QTH, the lowest, and findings were significantly different from the other curing regimens. L1 leached significantly more monomers than the others, and QTH had the lowest results. In conclusion, the type of light source, the curing regimen and the permeant affected sorption, solubility and amount of residual monomers of the adhesive under study.

Influence of pulse-delay curing on sorption and solubility of a composite resin

The purpose of this study was to evaluate the sorption and solubility of a composite resin (TPH3; Dentsply) cured with halogen light due to different storage media and curing modes. The methodology was based on the ISO 4049 standard. Two independent groups were established according to the storage time (7 days-G1; 60 days-G2). A stainless steel mould (2 mm x 8 mm ø) was used. The selected curing modes were: I (Conventional - C): 40s - 600 mW/cm2; II (Pulse I - PD): 3 s - 200 mW/cm2 + 2 min (delay) + 39 s - 600 mW/cm2; III (Pulse II): 10 s - 200 mW/cm2 + 2 min (delay) + 37 s - 600 mW/cm2; IV (Pulse III): 3 s- 600 mW/cm2 + 2 min (delay) + 37 s -600 mW/cm2. The media used were: distilled water, 75% ethanol and 100% chlorophorm. Five repetitions were made for each group. The specimens were placed in a desiccator at 37°C for 24 h and, after that, at 23°C for 1 h to be weighed until a constant mass (m1) was obtained. The discs were immersed separately into the 3 media for 7 days (G1) and 60 days (G2), and thereafter reweighed (m2). The reconditioning in the desiccator was done until a constant mass (m3) was obtained. Sorption and solubility were calculated and the data of G1 and the sorption data of G2 were subjected to two-way ANOVA and Tukeys tests (p=0.05). The solubility data of G2 were analyzed by Kruskal-Wallis test (p=0.05). For G1 and G2, no statistically significant differences were found in sorption among curing techniques (p>0.05). The solubility values were negative, which means that there was mass gain. Regarding the storage media, in G2 chlorophorm had the highest sorption values. It may be concluded that the curing modes (C and PD I, II and III) did not affect the sorption of the tested composite resin. However, different storage media influenced sorption behavior. The solubility test demonstrated negative data, masking the real solubility.

Evaluation of internal adaptation of Class V resin composite restorations using three techniques of polymerization.

Objective: The purpose of this in vitro study was to evaluate the internal adaptation of Class V composite restorations to the cavity walls using three different techniques of polymerization. Methods: Standard cavities were prepared on the buccal and lingual surfaces of 24 extracted human third molars with margins located above and below the cementoenamel junction. Restorations were placed in one increment using two restorative systems: 3M Filtek A110/ Single Bond (M) and 3M Filtek Z250/ Single Bond (H) in the same tooth, randomly in the buccal and lingual surfaces. Resin composites were polymerized using three techniques: Group 1 – Conventional (60 s - 600 mW/cm2); Group 2 – Soft-start (20 s – 200 mW/cm2, 40 s - 600 mW/cm2); Group 3 – Pulse Activation (3 s - 200 mW/cm2, 3-min hiatus, 57 s - 600 mW/cm2). Buccolingual sections were polished, impressions taken and replicated. Specimens were assessed under scanning electron microscopy up to X1000 magnification. Scores were given for presence or absence of gaps (0 – no gap; 1 – gap in one wall; 2 – gap in two walls; 3 – gap in three walls). Results: The mean scores of the groups were (±SD) were: G1M–3.0 (± 0.0); G2M–2.43 (± 0.8); G3M– 1.71 (± 0.9); G1H– 2.14 (± 1.2); G2H- 2.00 (± 0.8); G3H- 1.67 (± 1.1). Data were analyzed using Kruskal-Wallis and Dunnet’s tests. No statistically significant difference (p>0.05) was found among groups. Gaps were observed in all groups. Conclusions: The photocuring technique and the type of resin composite had no influence on the internal adaptation of the material to the cavity walls. A positive effect was observed when the slow polymerization techniques were used.

Inflammatory response of human dental pulp to at-home and in-office tooth bleaching

ABSTRACT Tooth bleaching is a technique of choice to obtain a harmonious smile, but bleaching agents may damage the dental pulp. Objective: This study evaluated the inflammatory responses of human dental pulp after the use of two bleaching techniques. Material and Methods: Pulp samples were collected from human third molars extracted for orthodontic reasons and divided into three groups: control - no tooth bleaching (CG) (n=7); at-home bleaching with 15% carbamide peroxide (AH) (n = 10), and in-office bleaching with 38% hydrogen peroxide (IO) (n=12). Pulps were removed and stained with hematoxylin-eosin for microscopic analysis of inflammation intensity, collagen degradation, and pulp tissue organization. Immunohistochemistry was used to detect mast cells (tryptase+), blood vessels (CD31+), and macrophages (CD68+). Chi-square, Kruskal-Wallis, and Mann Whitney tests were used for statistical analysis. The level of significance was set at p<.05. Results: The inflammation intensity and the number of macrophages were significantly greater in IO than in AH and CG (p<0.05). The results of CD31+ (blood vessels per mm2) were similar in CG (61.39±20.03), AH (52.29±27.62), and IO (57.43±8.69) groups (p>0.05). No mast cells were found in the pulp samples analyzed. Conclusion: In-office bleaching with 38% hydrogen peroxide resulted in more intense inflammation, higher macrophages migration, and greater pulp damage then at-home bleaching with 15% carbamide peroxide, however, these bleaching techniques did not induce migration of mast cells and increased the number of blood vessels.

Effect of light sources and curing mode techniques on sorption, solubility and biaxial flexural strength of a composite resin

Adequate polymerization plays an important role on the longevity of the composite resin restorations. Objectives The aim of this study was to evaluate the effect of light-curing units, curing mode techniques and storage media on sorption, solubility and biaxial flexural strength (BFS) of a composite resin. Material and Methods Two hundred and forty specimens were made of one composite resin (Esthet-X) in a stainless steel mold (2 mm x 8 mm Ø), and divided into 24 groups (n=10) established according to the 4 study factors: light-curing units: quartz tungsten halogen (QTH) lamp and light-emitting diodes (LED); energy densities: 16 J/cm2 and 20 J/cm2; curing modes: conventional (CM) and pulse-delay (PD); and permeants: deionized water and 75% ethanol for 28 days. Sorption and solubility tests were performed according to ISO 4049:2000 specifications. All specimens were then tested for BFS according to ASTM F394-78 specification. Data were analyzed by three-way ANOVA followed by Tukey, Kruskal-Wallis and Mann-Whitney tests (α=0.05). Results In general, no significant differences were found regarding sorption, solubility or BFS means for the light-curing units and curing modes (p>0.05). Only LED unit using 16 J/cm2 and PD using 10 s produced higher sorption and solubility values than QTH. Otherwise, using CM (16 J/cm2), LED produced lower values of BFS than QTH (p<0.05). 75% ethanol permeant produced higher values of sorption and solubility and lower values of BFS than water (p<0.05). Conclusion Ethanol storage media produced more damage on composite resin than water. In general the LED and QTH curing units using 16 and 20 J/cm2 by CM and PD curing modes produced no influence on the sorption, solubility or BFS of the tested resin.

Marginal microleakage of class II composite resin restorations due to restorative techniques

PURPOSE: To evaluate the marginal microleakage of class II composite resin (CR) restorations due to restorative techniques. METHODS: Forty human extracted premolars were assigned to 4 groups (n=10). Class II cavities were prepared (4-mm wide, 2-mm axially, with the gingival margin located 1 mm beyond the cementum-enamel-junction), and the restorative adhesive system Prime & Bond 2.1/TPH3 (Dentsply) was used. CR was inserted by the oblique incremental technique (OIT) and cured in continuous exposure. The restoratives techniques were: group 1 (control): OIT; group 2: flowable resin (1 mm) applied in the gingival wall + OIT; group 3: OIT + three pre-cured spheres inserted in the first increment of CR; and, group 4: OIT + strip of fiberglass inserted in the first increment of CR. The specimens were subjected to a thermocycling regimen of 500 cycles (1 min at 5o-37o-55oC), coated with two layers of nail varnish up to 1 mm from the restoration margins, and immersed in 0.5% basic fuchsine solution for 24 h. The extension of dye penetration at the cervical wall (µm) was evaluated using an optic microscope at x40. Data were analyzed using analysis of variance (ANOVA) (α=0.05). RESULTS: The microleakage values were: G1: 370 µm ± 241; G2: 398 µm ± 354; G3: 205 µm ± 119; and G4: 413 µm ± 340. No statistically significant differences were found among the restorative techniques (P=0.081). CONCLUSION: Marginal microleakage values were not influenced by the different restorative techniques tested.

Influence of Activation Mode of Resin Cement on the Shade of Porcelain Veneers

PURPOSE The aim of this study was to evaluate the influence of resin luting cements activation mode in the final shade of porcelain veneers after accelerated artificial aging (AAA). MATERIALS AND METHODS Porcelain veneers (IPS Empress Esthetic) were produced using a standardized shade (ET1) and thickness (0.6 mm). Twenty bovine teeth were collected, prepared, and divided into two groups: group I (n = 10)-light-cured group, only base paste was applied to the veneers; group II (n = 10)-dual-cured group, in which the same base paste used in group I and a transparent catalyst were proportionally mixed for 20 seconds and then applied to the veneers. The specimens were light-cured for 60 seconds each and were next subjected to AAA. They were submitted to color readings with a spectrophotometer in three instances: in the tooth surface (only the substrate), after the cementation and polymerization of the veneers, and after the AAA. The values of L*, a*, and b* were obtained and the total color change was calculated (∆E*). Values obtained were subjected to statistical analysis, with a significance of 0.05. RESULTS There were no significant differences between dual- and light-cured modes considering ∆E*, L*, a*, and b* values obtained after aging (p > 0.05). Within the dual-cured mode there were no significant differences in ∆E*, L*, a*, and b* values (p > 0.05). CONCLUSION No relevant differences were found between the two activation modes in color change. When submitted to aging, dual- and light-cured modes of the resin cement showed visually perceptible (∆E* > 1.0) color changes; however, within the threshold of clinical acceptance (∆E* > 3.3).

Oxygen Saturation in the Dental Pulp of Maxillary Premolars in Different Age Groups - Part 1

The aim of this study was to determine oxygen saturation levels in the dental pulp of maxillary premolars in different age groups. A total of 120 human maxillary premolars with normal dental pulps were selected covering the following age groups: 20-24, 25-29, 30-34, 35-39 and 40-44 years (n=24 each group). Oxygen saturation was assessed using pulse oximetry. Analysis of variance was used to assess differences in oxygen saturation levels and Tukeys test was used to identify the age groups that differed from each other. Significance was set at 0.05. Mean oxygen saturation of 120 premolars was 86.20% considering all age groups. Significantly reduced levels were found in the oldest group compared to the other groups: 40 to 44 years - 80.00% vs. 89.71, 87.67, 88.71, and 84.80% for age groups 20-24, 25-29, 30-34, 35-39 years, respectively. The mean oxygen saturation levels were similar between 20 and 39 years of age (86.20%) in the whole sample, but reduced significantly in the 40-44-year age group, suggesting that older patients present lower oxygen saturation results even in the absence of pulp tissue injury.

Resin Cement: Correspondence with Try-In Paste and Influence on the Immediate Final Color of Veneers: Resin Cement vs Try-In Pastes

PURPOSE To assess the correspondence of shades between try-in pastes and resin cements and their influence on the final color of veneers. MATERIALS AND METHODS Bovine teeth (n = 140) were prepared and divided into 2 groups (a or b) according to ceramic veneer thickness (0.35 or 0.70 mm). Seventy teeth (n = 70) were distributed in 7 groups (groups 1 to 7a and groups 1 to 7b; n = 10). Try-in pastes and their corresponding resin cements were used according to the value: groups 1a and 1b (value -3); groups 2a and 2b (-2); groups 3a and 3b (-1); groups 4a and 4b (0); groups 5a and 5b (+1); groups 6a and 6b (+2); groups 7a and 7b (+3). Color measurements were performed with spectrophotometer, and the coordinates L* , a* , and b* were obtained. The final color change (ΔE) was calculated from these coordinates: ΔE0 (trial - substrate), ΔE1 (cementation - substrate), and ΔE2 (cementation - trial). The data were analyzed using the Kolmogorov-Smirnov test, the Wilcoxon test, or t-test for paired samples and repeated-measures ANOVA, post hoc Bonferroni, or the Friedman test (p < 0.05). RESULTS The results indicated no statistically significant difference between the groups comparing ΔE0 and ΔE1 for 0.35 mm thickness laminate veneers, except for groups 2a and 5a. For 0.70 mm thickness laminate veneers, no statistically significant differences were observed between the groups comparing ΔE0 and ΔE1. ΔE2 values for 0.35 mm and 0.70 mm thickness laminate veneers ranged from 1.77 ± 0.81 to 4.99 ± 3.80 and from 1.01 ± 0.73 to 4.66 ± 2.96, respectively. CONCLUSIONS Try-in pastes correspond with their respective resin cements for most colors investigated. The color of the resin cement may influence the final color of laminate veneers. Thickness of the ceramic was the most relevant variable for color change.

Unilateral Fusion of Maxillary Lateral Incisor: Diagnosis Using Cone Beam Computed Tomography

Objective. The objective of this paper is to report a dental fusion case focusing on clinical and radiographic features for the diagnosis. Method. To report a case of right maxillary lateral incisor fusion and a supernumerary tooth, the anatomy of the root canal and dental united portion were assessed by cone beam computed tomography (CBCT). Results. The clinical examination showed dental juxtaposition with the absence of interdental papilla and esthetic impairment in the right maxillary lateral incisor region. The periapical radiography did not provide enough information for the differential diagnosis due to the inherent limitations of this technique. CBCT confirmed the presence of tooth fusion. Conclusion. CBCT examination supports the diagnosis and provides both the identification of changes in tooth development and the visualization of their extent and limits.