The purpose of this study was to evaluate the clinical performance of laminate porcelain veneers bonded with a light-cured composite. Thirty patients were restored with 119 porcelain laminate veneers. The veneers were studied for an observation time of 7 years. Marginal adaptation, marginal discoloration, secondary caries, color match, and anatomic form were clinically examined following modified United States Public Health Service (USPHS) criteria. Each restoration was also examined for cracks, fractures, and debonding. Pulp vitality was verified. In addition, plaque and gingival indexes and increase in gingival recession were recorded. Survival rate evaluating absolute failures and success rate describing relative failures were statistically determined, using both restoration and patient-related analyses. On the basis of the criteria used, most of the veneers rated Alfa. After 7 years, the results of the clinical investigation regarding marginal adaptation and marginal discoloration revealed only 2.5% and 4.2% Bravo ratings, respectively, among the 119 initially placed veneers. Using the restoration as the statistical unit, the survival rate was 97.5%, with a high estimated success probability of 0.843 after 7 years. Using the patient as the statistical unit, the survival rate was 90.0% and the estimated success probability after 7 years was 0.824. Gingival response to the veneers was all in the satisfactory range. Porcelain laminate veneers offer a predictable and successful treatment modality giving a maximum preservation of sound tooth. The preparation, cementation, and finishing procedures adopted are considered key factors for the long-term success and aesthetical result of the veneer restorations.

Clinical evaluation on porcelain laminate veneers bonded with light-cured composite: results up to 7 years

Resin-based cements have been frequently employed in clinical practice to lute indirect restorations. However, there are numerous factors that may compromise the clinical performance of those cements. The aim of this literature review is to present and discuss some of the clinical factors that may affect the performance of current resin-based luting systems. Resin cements may have three different curing mechanisms: chemical curing, photo curing or a combination of both. Chemically cured systems are recommended to be used under opaque or thick restorations, due to the reduced access of the light. Photo-cured cements are mainly indicated for translucent veneers, due to the possibility of light transmission through the restoration. Dual-cured are more versatile systems and, theoretically, can be used in either situation, since the presence of both curing mechanisms might guarantee a high degree of conversion (DC) under every condition. However, it has been demonstrated that clinical procedures and characteristics of the materials may have many different implications in the DC of currently available resin cements, affecting their mechanical properties, bond strength to the substrate and the esthetic results of the restoration. Factors such as curing mechanism, choice of adhesive system, indirect restorative material and light-curing device may affect the degree of conversion of the cement and, therefore, have an effect on the clinical performance of resin-based cements. Specific measures are to be taken to ensure a higher DC of the luting system to be used.

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Correlation between clinical performance and degree of conversion of resin cements: a literature review

https://cyberleninka.org/article/n/464909.pdf

Degree of conversion and surface hardness of bulk-fill composite versus incremental-fill composite

Monomer elution in relation to degree of conversion for different types of composite.

Statement of problem Dental laboratories use different computer-aided design and computer-aided manufacturing (CAD-CAM) systems to fabricate fixed prostheses; however, limited evidence is available concerning which system provides the best marginal discrepancy. Purpose The purpose of this in vitro study was to evaluate the marginal fit of 5 different monolithic zirconia restorations milled with different CAD-CAM systems. Material and methods Thirty monolithic zirconia crowns were fabricated on a custom-designed stainless steel die and were divided into 5 groups according to the type of monolithic zirconia crown and the CAD-CAM system used: group TZ, milled with an MCXL milling machine; group CZ, translucent zirconia milled with a motion milling machine; group ZZ, zirconia milled with a dental milling unit; group PZ, translucent zirconia milled with a zirconia milling unit; and group BZ, solid zirconia milled using an S1 VHF milling machine. The marginal fit was measured with a binocular microscope at an original magnification of ×100. The results were tabulated and statistically analyzed with 1-way ANOVA and post hoc surface range test, and pairwise multiple comparisons were made using Bonferroni correction (α=.05). Results The type of CAD-CAM used affected the marginal fit of the monolithic restoration. The mean (±SD) highest marginal discrepancy was recorded in group TZI at 39.3 ±2.3 μm, while the least mean marginal discrepancy was recorded in group IZ (22.8 ±8.9 μm). The Bonferroni post hoc test showed that group TZI was significantly different from all other groups tested ( P Conclusions Within the limitation of this in vitro study, all tested CAD-CAM systems produced monolithic zirconia restorations with clinically acceptable marginal discrepancies; however, the CAD-CAM system with the 5-axis milling unit produced the best marginal fit.

In vitro evaluation of marginal discrepancy of monolithic zirconia restorations fabricated with different CAD-CAM systems

Degree of conversion of three composite materials employed in the adhesive cementation of indirect restorations: a micro-Raman analysis.

PURPOSE Marginal fit is valued as one of the most important criteria for the clinical quality and success of all-ceramic crowns. The aim of this in vitro study was to investigate the marginal fit of Lava Zirconia crown-copings on chamfer and shoulder preparations. METHODS Two acrylic model teeth were selected to simulate the clinical preparations: one molar was prepared with a chamfer finish line (C) and one premolar was prepared with a rounded shoulder finish line (RS). Each resin model was duplicated 10 times using silicon-based impression material and poured in type IV dental stone for the fabrication of working dies. A total of 20 copings were divided into two groups (n = 10 for each finish line). Fifty measuring locations were chosen randomly along the margin on the dies and the gap width - vertical marginal discrepancy - was measured under a light microscope with a magnification of x100. Measurements were made without cementation. The mean marginal gap widths and standard deviations were calculated and a one-way analysis of variance (ANOVA) was performed for different types of preparations in order to detect differences (α = 0.05). RESULTS The mean marginal gap was 30 ± 3 μm for the C group and 28 ± 4 μm for the RS group. The one-way ANOVA showed no statistical significant difference between the two groups (P = 0.23). CONCLUSIONS Within the limitations of this study, the marginal discrepancies were all within the clinical acceptable standard set at 120 μm. Chamfer and shoulder preparations did not show differences regarding the gap dimension. CLINICAL SIGNIFICANCE Bur design is an easily selected parameter before natural tooth preparation. Both tested finish lines are able to help clinicians in obtaining acceptable marginal fit values for the investigated zirconia copings.

Comparison of marginal fit of Lava CAD/CAM crown-copings with two finish lines.

PURPOSE: To evaluate the degree of conversion (DC) of dual-curing materials used to lute glass-fiber posts in a simulated root canal polymerized by two different modalities.

METHODS: Artificial root canals were used to simulate a clinical condition to lute 45 posts by three different dual curing luting cements (Calibra, Multilink Automix and Variolink II). Two light cure modalities were chosen for each luting cement: standard (S group) 400 mW/cm2 for 120 seconds and high-power (H group) 1200 mW/cm2 for 40 seconds. Raman spectra were collected at different positions in the post surface (1, 3, 5 and 7 mm from the coronal-most portion of the post covered in cement) and the percentage degree of conversion was computed. The data were analyzed using ANOVA and post-hoc Student-Neuman-Keuls t-test (P = 0.05).

RESULTS: The DC of the tested luting composites decreased progressively while increasing the distance from the light tip. Regardless of the polymerization modality (H or S) applied. Conversely, the curing modality significantly influenced the DC of the tested materials, evidencing different responses to the same energy density: Calibra seemed to be less dependent on light-curing than the other tested materials, showing a constant behavior. Multilink Automix reached the highest DCs in the S group compared to the H mode. Variolink II showed an interesting drawback in DC at 7 mm when cured in the H model. Dual-cure materials show adequate monomer conversion but when the distance from the curing light increased, a variable, but significant lowering in conversion rate was observed. In addition, the time and power of curing appeared to be material-dependent and should be calibrated individually.

Degree of conversion of dual-cure resins light-cured through glass-fiber posts.

Introduction: The aim of the present study was to compare two obturation techniques, i.e. Thermafil ® and cold lateral condensation, in order to determine which one was most easily and rapidly learnt and applied by dental students. Methods: Fifty single-rooted teeth were instrumented by the crown-down technique. Five students were requested to obturate five teeth using the Thermafil technique and five using lateral condensation. A microleakage study was performed using a 2% aqueous methylene blue dye solution. The apical portion of teeth was sectioned into six sections and evaluated under a stereomicroscope. The presence of dye microleakage was considered when assessing every section. Results: Results were processed statistically by frequence of distribution and the Mann-Whitney test. A highly significant difference (P < 0.0001) was observed between Thermafil and cold lateral condensation techniques, the former resulting in lower leakage. Conclusion: The present study, though limited and only referring to a small group, suggested that characteristics of operators and the early repeated use of a technique may influence performance.

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A Study of undergraduate learning of two obturation techniques : Thermafil versus lateral condensation

Summary Adhesion is the pivot of the modern restorative dentistry. Inlays, onlays and veneers have become a valid alternative to the traditional prosthetic treatments even in the rehabilitation of extremely damaged teeth, allowing a consistent saving of sound tooth tissues. Composite resins and dental adhesive are continously investigated and improved, nevertheless the optimization of the tooth-adhesive interface has to be considered: in fact, the long-term stability of adhesion between tooth and composite material depends on the treatment of the amelo-dentinal surfaces. This study investigated the quality of the occlusal walls of a cavity prepared to receive an inlay and finished with four different systems: thin and extra-thin diamond coated burs, a 12-blades carbide burs and a diamond-coated tip driven by sonic instrument. Consequently, prophylometric and SEM analyses were performed on the samples. The average roughness values recorded by the prophylometer were expressed by the parameters Ra and RZ: there is a correspondence between the numeric values and the pictures of the SEM. The results show a better quality (low roughness values) of the surface treated with multi-blade burs, followed by the this and extra-thin diamond coated burs. The 25 micron diamond-coated tip of the sonic instrument obtains the roughest surface and a sensibly higher amount of smear layer than the other tested systems.

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Francesca Cerutti

Papers

Degree of conversion of three composite materials employed in the adhesive cementation of indirect restorations: a micro-Raman analysis.

Comparison of marginal fit of Lava CAD/CAM crown-copings with two finish lines.

Degree of conversion of dual-cure resins light-cured through glass-fiber posts.

A Study of undergraduate learning of two obturation techniques : Thermafil versus lateral condensation

Prophylometric and SEM analyses of four different finishing methods.