Leonardo Gonçalves Cunha

Association of photoactivation methods and low modulus liners on marginal adaptation of composite restorations

The aim of this study was to evaluate the effect of photoactivation methods, resin liners, and the association of these techniques on the marginal adaptation of composite restorations. One‐hundred‐and‐twenty bovine incisors were selected. A circular cavity was prepared in a flat dentin area on the buccal surface and the Scotchbond Multi Purpose system was applied. These teeth were assigned to four groups in accordance with lining technique: control (one adhesive layer), three adhesive layers individually photoactivated, Filtek Flow, and Protect Liner F. Each group was subdivided depending on the photoactivation method: continuous light, soft‐start, or intermittent light. All cavities were restored with Filtek Z250 and then polished. Caries detector was applied on each specimen for 5 s in order to verify marginal adaptation through dye‐staining of the gaps formed on the outer margins. Images of the stained gaps were observed under the stereomicroscope, and transferred to a computer measurement program in order to determine gap length. Data were submitted to ANOVA and Tukeys test (P < 0.05). Significant differences among the lining techniques were only observed using the photoactivation method with continuous light. In this case, the lining technique with Filtek Flow significantly increased marginal adaptation of the composite to the outer dentin margins compared with the results of the control group. The other lining techniques showed intermediate values and no statistical difference from the other groups. For the photoactivation methods, intermittent light showed the best marginal quality of all the methods. This was statistically significant only for the control lining technique.

Relationship between bond strength and marginal and internal adaptation of composite restorations photocured by different methods

Objective. This study evaluated the relationship between bond strength and marginal and internal adaptation of composite restorations photocured using different methods with a quartz-tungsten-halogen light. Material and Methods. A push-out test was performed to evaluate bond strength of conical restorations in 50 bovine incisors. To evaluate marginal (external) and internal restoration adaptation, 50 circular all-enamel margin preparations were done in bovine incisors. For both tests, the preparations were filled with Esthet•X resin composite. Specimens were distributed into 5 groups (n=10) depending on photoactivation method: G1: continuous light 700; G2: continuous light 150; G3: soft-start; G4: intermittent light; and G5: pulse-delay. The energy density for each method was standardized: 14 J/cm2. Caries Detector® (Kuraray) was placed in restoration margins for detection of marginal adaptation. The percentage of interfaces present as gaps was determined using digital images. Specimens were then sectioned, stained, and the internal adaptation was recorded in a similar manner. Data were submitted to ANOVA and the Tukey HSD test, pre-set α = 0.05. Results. Bond strength G5 (7.2 MPa±1.3) was significantly greater (p=0.00280) than G1 (4.6 MPa±1.5). G2, G3, and G4 showed equivalent, intermediate strength values. No significant difference was found in marginal adaptation of any of the groups (p=0.16911). Internal adaptation results were the inverse of strength results: G5 (2.8%±4.9) showed significantly less (p=0.00979) gap formation compared to G1 (10.1%±6.2). Conclusion. Some modulated photocuring methods can increase bond strength while decreasing internal gap formation. An inverse relationship was found between push-out bond strength and internal adaptation. Marginal adaptation was not affected by any photoactivation method.

Dye staining gap test: An alternative method for assessing marginal gap formation in composite restorations

Objective. The aim of this study was to evaluate and compare marginal adaptation of composite restorations assessed by a dye staining method and by scanning electron microscopy (SEM) analysis. Material and methods. Twenty bovine incisors were selected and ground flat to expose dentin. Two cylindrical cavities were prepared on the central area of flattened surfaces. Single bond adhesive system was applied in accordance with the manufacturers instructions and the cavities were filled with Filtek Z250 or Filtek Flow. The specimens were polished and replicas were obtained in epoxy resin. The replicas were observed by SEM for marginal quality/quantity evaluation. Caries detector was then applied on each specimen for 5 s to verify marginal adaptation through dye staining of the formed gaps on the outer margins. Images of the stained gaps were transferred to a computer measurement program to determine gap length. The length of the gap was expressed as the percentage of total length of the margins observed. Data were submitted to two-way ANOVA and Pearson correlation. Results. Filtek flow showed 36% and 34% and Filtek Z250 27% and 29% of gap in the margins when evaluated by SEM analysis and by the dye staining test, respectively. There was no difference between the composites, regardless of the evaluation technique. There was a strong positive correlation (r=0.83) between the results obtained with the tested methods to assess marginal gap. Conclusion. Dye staining the gaps can be used with good reliability to evaluate the gap formation in composite restorations.Objective. The aim of this study was to evaluate and compare marginal adaptation of composite restorations assessed by a dye staining method and by scanning electron microscopy (SEM) analysis. Material and methods. Twenty bovine incisors were selected and ground flat to expose dentin. Two cylindrical cavities were prepared on the central area of flattened surfaces. Single bond adhesive system was applied in accordance with the manufacturers instructions and the cavities were filled with Filtek Z250 or Filtek Flow. The specimens were polished and replicas were obtained in epoxy resin. The replicas were observed by SEM for marginal quality/quantity evaluation. Caries detector was then applied on each specimen for 5 s to verify marginal adaptation through dye staining of the formed gaps on the outer margins. Images of the stained gaps were transferred to a computer measurement program to determine gap length. The length of the gap was expressed as the percentage of total length of the margins observed. Data...

Comparative study of the surface roughness of Ormocer-based and conventional composites

The aim of this study was to evaluate the surface roughness of two Ormocer-based resin composites before and after mechanical toothbrushing. The study compared the brands Admira and Definite with composites based on conventional monomer systems (Bis-GMA, Bis-EMA, UEDMA e TEGDMA), Z250 and A110. Eight samples of each material with 4mm in diameter and 2mm in height were prepared using a metallic mold. After 24 hours they were polished and examined with a profilometer for measurement of the initial surface roughness (Ra, mm) before mechanical toothbrushing (30,000 cycles). After toothbrushing, the samples were taken to the profilometer once again to check the final surface roughness. The results were submitted to ANOVA and Tukey test (5%). The Admira composite presented a higher mean of surface roughness before toothbrushing (0.132mm), with a statistical difference from the composite A110 (0.082mm). Definite (0.110mm) and Z250 (0.105mm) composites showed no differences between themselves or among the other composites. No statistical differences were observed after toothbrushing between the composites Definite (0.178mm), Z250 (0.187mm), Admira (0.181mm), and A110 (0.193mm). All composites showed a statistically significant increase in the surface roughness after toothbrushing.

Effect of Resin Liners and Photoactivation Methods on the Shrinkage Stress of a Resin Composite

PURPOSE This study was undertaken to evaluate the effect of three different photoactivation methods on the polymerization shrinkage stress of a resin composite using different resin liners. MATERIALS AND METHODS Three photoactivation methods using a quartz-tungsten-halogen light were evaluated: continuous light, soft start, and intermittent light. Three lining groups were tested: one or three coats of adhesive, and flowable composite. The stress was measured using a universal testing machine. After the stress measurement, Knoop hardness numbers (KHNs) were evaluated to verify indirectly the degree of conversion of the composite using the three photoactivation methods. The data were submitted to analysis of variance and Tukeys test (p < .05). RESULTS Intermittent light was always associated with statistically lower stress values when compared with continuous light. Statistical differences were not observed when continuous light and soft start were compared. The use of a flowable composite liner significantly reduced the stress generation when compared with the use of one adhesive coat. The three adhesive coats groups showed intermediate stress values. The hardness test showed no statistical difference between that achieved with continuous light and soft start. These two methods showed statistically higher KHNs when compared with results with intermittent light. CLINICAL SIGNIFICANCE Photoactivation using intermittent light may lead to a significant reduction in shrinkage stress levels. This effect could be attributed to a significant reduction of the polymerization rate and/or a decrease in the degree of conversion. The use of a flowable composite liner reduced the stress levels when compared with levels when one coat of adhesive was used. This is possibly related to the higher thickness of the flowable composite layer.

Influence of the curing method on the post-polymerization shrinkage stress of a composite resin

The aim of this study was to evaluate the effect of different curing methods on the stress generated by the polymerization shrinkage of a restorative composite in two moments: immediately after light exposure and after 5 min. Photoactivation was performed using two different light sources: (1) xenon plasma arc (PAC) light (1,500 mW/cm2 – 3s) and (2) a quartz-tungsten-halogen (QTH) light with three light-curing regimens: continuous exposure (40 s at 800 mW/cm2 – CL); soft-start (10 s at 150 mW/cm2 and 30 s at 800 mW/cm2 - SS) and intermittent light [cycles of 4 s (2 s with light on at 600 mW/cm2 and 2 s of light off), for 80s – IL]. The composite resin was applied between two 5-mm diameter metallic rods, mounted in a servohydraulic machine. The maximum stress was recorded immediately after light exposure (FF) and after 5 min (5F). The results were submitted to ANOVA and Tukeys test (5%). For each method, the results obtained in FF and 5F were, respectively: CL (3.58 and 4.46 MPa); SS (2.99 and 4.36 MPa); IL (3.11 and 4.32 MPa) and PAC (0.72 and 3.27 MPa). The stress generated by the polymerization shrinkage during light exposure can be associated with the photoactivation method used. A significant increase in the stress level was observed during the post-curing period up to 5 min, for all evaluated methods.

Concurrence Between the Maxillary Midline and Bisector to the Interpupillary Line

PURPOSE Symmetry is one of the factors that contributes to facial harmony, and in oral rehabilitation it determines the success of esthetic treatment. Therefore, the aim of the present study was to analyze the axial symmetry between the bipupillar midline and maxillary central incisors midline of 102 dental students (both genders) distributed across five Brazilian dental schools. MATERIALS AND METHODS Students with no teeth missing and who had never been subjected to any dental treatment were selected. Photographs were taken with a Dental Eye III camera with a 100-mm macro objective and ratio of 1:10 from natural size, recorded on an Ektachrome ASA/ISO 100 film. The images were developed and applied to Microsoft Office Power Point 2007 software. The results were analyzed by analysis of variance and Students t-test (alpha = 0.05). RESULTS There was no significant correlation between bipupillar midline and the maxillary dental midline, irrespective of gender. CONCLUSION No significant coincidence was observed between the interpupillary and dental midline. However, the interpupillar distance and its relationship with other anatomic structures may be used as a reference in treatment, but measurements must be assessed individually. CLINICAL SIGNIFICANCE Anatomic measurements and facial proportions can be helpful during the planning of esthetic oral rehabilitation.

Influence of anatomic reference on the buccal contour of prosthetic crowns

During clinical practice, when performing prosthetic rehabilitation with single crowns, improper reproduction of the dental contour by the dental laboratory is a common occurrence. Therefore, the present study evaluated the fidelity of the reproduction of the buccal contour in an upper left canine performed by three Dental Prosthesis Technicians (DPT) using the indirect laminate veneer technique. First, the DPTs confected the veneers based on a model obtained from the upper arch of a dental dummy, containing a replica of an upper left canine with a prosthetic preparation for a laminate veneer. Then, the same DPTs received other identical models, now with the replica of the upper left canine with no preparation, to be used as an anatomical reference for confecting the laminate veneers. The laminate veneers were then bonded to the plaster models and had their buccal contour individually measured. Measurements were also made of the buccal contour of the reference canine. The data were analyzed by ANOVA and the t-test (p = 0.05). Results showed 100% of buccal overcontour when the laminate veneers were compared to the reference canine, regardless of which DPT confected the veneer and regardless of using or not the anatomical reference. The DPTs who participated in the present study were unable to acomplish a faithful anatomical reproduction of the buccal contour, creating an overcontour in all samples. This situation may be responsible for increasing the probability of periodontal and esthetic harm in clinical practice.