Abstract
Analysis of marginal adaptation of dental adhesive interfaces using scanning electron microscopy has proven to be a powerful nondestructive method to evaluate the quality of adhesion. This methodology is, however, time-consuming and needs expensive equipment. The purpose of this study was to evaluate the possibility and efficiency of using a digital optical microscope (DOM) to perform marginal analysis and to compare it with the scanning electron microscope (SEM) analysis. Fifteen defect-free molars were selected for this study. Class V cavities were prepared and restored with resin composite, and epoxy replicas were obtained from silicone impressions of the restored teeth. Custom-made image analysis software was then used to measure the percentage of the noncontinuous margins (NCM) of each sample. To compare the DOM to the gold standard, SEM, each sample was analyzed 10 times using the DOM and three times using the SEM, by the same experienced operator. The repeatability coefficient and concordance were evaluated, and a Bland and Altman analysis was used for comparison of the two methods of measurements. To validate the DOM analysis method, an ANOVA approach (Gage R R) was used. Repeatability and reproducibility, which are two components of precision to validate the DOM analysis system, were calculated. For this, the same restorations were analyzed by two additional operators three times with the DOM. The duration of each step of the analysis using both methods was also recorded as a secondary outcome. Regarding the repeatability of each method, the Friedman test showed no statistically significant difference within the repetitions of measurements by SEM and DOM (p = 0.523 and p = 0.123, respectively). Moreover, the Bland-Altman analysis revealed a bias of 0.86 and concluded no statistically significant difference between the two methods, DOM and SEM. ANOVA evaluated DOM measurement system variation including the variances of repeatability and reproducibility that represented, respectively, 0.3% and 4% of the variance components. Reproducibility or inter-operator variability represented the principal source of variability with a statistically significant difference (p = 0.024). The time required for analysis with SEM was almost double that of DOM. The use of digital optical microscopy appears to be a valid alternative to the SEM for the analysis of marginal adaptation of dental adhesive interfaces. Further studies to evaluate the effect of training of operators in digital optical microscopy could reveal higher accuracy for this method and inter-operator agreement when experience is gained.
Highlights
Whether direct or indirect restorations, aging factors such as water, mechanical loads and staining elements have an important effect on the adhesive interface, which often leads to a worsening of the integrity of that margin from an esthetic and a biomechanical point of view [3,4]
Acceptance criteria for the ANOVA method are divided into three class: under 1%, it is an adequate measurement system; 1% to 9%, it is acceptable with modifications; and over 9% it is considered to be unacceptable [18]
This study shows that digital optical microscopy can be considered a promising, reliable and repeatable method to perform marginal analysis of adhesive dental restorations using the replica technique
Summary
Dental resin adhesives continue to evolve progressively, and new products are released almost every year. Whether direct or indirect restorations, aging factors such as water, mechanical loads and staining elements have an important effect on the adhesive interface, which often leads to a worsening of the integrity of that margin from an esthetic and a biomechanical point of view [3,4]. Such changes do not necessarily translate into debonding of the restoration, especially in newer generations of adhesive systems, but they constitute a major reason for retreatment due to secondary caries or appearance-related clinical failures [5–7]. Among the multiple tests that exist to evaluate the performance of adhesive systems, marginal integrity assessment appears to be relevant for the future, rather than bond strength tests that continue to report difficult-to-relate-to values, between adhesives that rarely fully debond clinically [8–11]
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