Quality and Survival of Direct Light-Activated Composite Resin Restorations in Posterior Teeth: A 5- to 20-Year Retrospective Longitudinal Study

Comparison of the Shear Bond Strength of Metal Orthodontic Brackets Bonded to Long-term Water-aged and Fresh Porcelain and Composite Surfaces

Objective

The aim of the present study was to compare the shear bond strength (SBS) of metal orthodontic brackets bonded to long-term water-aged and fresh porcelain and composite surfaces.

Methods

One porcelain (Vitadur Alpha (VA)) and three composite (Filtek Ultimate (FU), Tetric EvoCeram (TEC), and Gradia Direct Anterior (GDA)) materials were evaluated in the present study. First, 10 discs from each material were prepared and subjected to the aging procedure for 5 years. Then, for comparison, another 10 discs from each material were prepared as fresh surfaces and stored in distilled water for 24 h. Metal brackets were bonded to the prepared disc surfaces, and after being stored in water for 24 h, they were subjected to shear bond test using a universal testing machine. Adhesive remnant index (ARI) scores were obtained by examining the disc surfaces under a stereomicroscope at 10× magnification. Kruskal-Wallis test was used to compare the aged and fresh groups.

Results

Although the difference between the SBS between the aged and fresh groups with VA, FU, and TEC was not significant, the SBS was significantly higher in the fresh group with GDA. With regard to ARI scores, there was no significant difference between the aged and fresh groups with FU and GDA, whereas the ARI scores of the aged groups with VA and TEC were higher.

Conclusion

It was concluded that the aged restoration materials have a distinctive influence on the SBS of metal orthodontic brackets.

Two-body wear behavior of human enamel versus monolithic zirconia, lithium disilicate, ceramometal and composite resin

PURPOSE

To investigate and compare the surface roughness (SR), weight and height of monolithic zirconia (MZ), ceramometal (CM), lithium disilicate glass ceramic (LD), composite resin (CR), and their antagonistic human teeth enamel.

MATERIALS AND METHODS

32 disc shaped specimens for the four test materials (n=8) and 32 premolars were prepared and randomly divided. SR, weight and height of the materials and the antagonist enamel were recorded before and after subjecting the specimens to 240,000 wear-cycles (49 N/0.8 Hz/5℃/50℃). SR, height, weight, and digital microscopic qualitative evaluation were measured.

RESULTS

CM (0.23 + 0.08 µm) and LD (0.68 + 0.16 µm) exhibited the least and highest mean difference in the SR, respectively. ANOVA revealed significance (P=.001) between the materials for the SR. Paired T-Test showed significance (P<.05) for the pre- and post-SR for all the materials. For the antagonistic enamel, no significance (P=.987) was found between the groups. However, the pre- and post-SR values of all the enamel groups were significant (P<.05). Wear cycles had significant effect on enamel weight loss against all the materials (P<.05). CR and MZ showed the lowest and highest height loss of 0.14 mm and 0.46 mm, respectively.

CONCLUSION

MZ and CM are more resistant to SR against the enamel than LD and CR. Enamel worn against test materials showed similar SR. Significant variations in SR values for the tested materials (MZ, LD, CM, and CR) against the enamel were found. Wear simulation significantly affected the enamel weight loss against all the materials, and enamel antagonist against MZ and CM showed more height loss.

Real-time in-depth imaging of gap formation in bulk-fill resin composites

OBJECTIVES

This study visualized in real-time the gap forming of bulk-fill resin composites during polymerization using optical coherence tomography (OCT).

METHODS

Light-cured bulk-fill resin composites; Tetric N-ceram Bulk Fill (TNB), SonicFill (SNF), Surefil SDR (SDR), dual-cured bulk-fill resin composite Bulk EZ (BEZ), and light-cured core resin composite Clearfil Photo Core (CPC) were investigated. Swept-source OCT real-time cross-sectional monitoring was obtained during resin composite placement and curing procedure. Gap formation was observed in bonded cylindrical resin composite molds (4-mm depth, 3-mm diameter) and free shrinkage volume was observed at the top and bottom of a tube with similar dimensions (n=10). OCT 3D data were analyzed to calculate sealing floor area percentage (SFA%) and volumetric shrinkage in bonded tube (VS%). Data were analyzed by ANOVA at significance level of 0.05. The bottom-top degree of conversion ratio (DC%-R) through 4-mm depth was measured using the XploRA Plus micro-Raman spectroscopy.

RESULTS

BEZ showed no gap formation at the cavity floor in any specimens while SNF showed the highest gap formation; the statistical order in terms of SFA% was BEZ (100±0)>TNB (84.97±2.98)>CPC (52.13±8.23)=SDR (45.97±9.21)>SNF (16.23±6.00) (p<0.05). On the other hand, total VS% was statistically ordered as BEZ (3.40±0.14)>SDR (3.22±0.09)>TNB (1.82±0.11)>SNF (1.65±0.04)=CPC (1.56±0.04) (p<0.05). Unlike BEZ, the light-cured resin composites showed larger shrinkage at specimen bottom than top. TNB showed the lowest DC%-R followed by SNF (p<0.05).

SIGNIFICANCE

Light-cured bulk-fill resin composites showed various degrees of gap formation and shrinkage at 4-mm deep cavity. The dual-cured bulk-filled resin composite showed no decrease of degree of conversion through the depth and the highest cavity adaptation despite its tendency for higher volumetric shrinkage.

A Novel Technique for Bulk-Fill Resin-Based Restorations: Achieving Function and Esthetics in Posterior Teeth

Advances in the mechanical properties of composite resins have allowed for their use in posterior teeth. Conventional resins have several problems associated with polymerization shrinkage stress. The development of “bulk-fill” resins has allowed for their use in single increments up to depths of 4 mm, with very low polymerization shrinkage stress. Nevertheless, differences in anatomy and the desire for optimal esthetics present unique difficulties. This article describes a step-by-step technique using flowable bulk-fill resin as a substitute for dentin in a single increment, together with a high-reflective-index resin to restore enamel and decrease clinical time, obtaining anatomically and esthetically acceptable results without detriment to the mechanical properties required to restore the functionality of the posterior teeth.