Effect of ultrasonic vibration on the presence of voids in core build-up materials.

The core build-up procedure is utilized to restore teeth with limited remaining coronal tooth structure. However, voids have been observed radiographically within composite resin- and glass ionomer-based core build-ups, potentially compromising the mechanical strength of a fully restored tooth and requiring build-up replacement before a final restoration can be delivered. The purpose of this in vitro study was to determine whether applying ultrasonic vibration during core build-up placement reduces the presence of radiographically detectable voids. A total of 120 acrylic resin mandibular premolar analogs were fabricated using a 3-dimensional printer and randomly allocated into 4 groups (n = 30). Dual-cured composite resin or glass ionomer core build-ups were placed with or without vibration. The final build-ups were assessed radiographically and rated by 3 independent calibrated clinicians based on a 4-category scale for the severity of voids. In an ordinal logistic regression model with the void severity rating as the outcome, a significant interaction was found for glass ionomer, composite resin, and the use of ultrasonic vibration (P = 0.03). Vibration was associated with worse void severity ratings in glass ionomer specimens (P < 0.01). No effect of vibration was found in the composite resin specimens. The Fleiss kappa score (κ = 0.36) indicated fair agreement in all severity ratings among the 3 raters. These results suggest that the application of ultrasonic vibration during core build-up placement may not be clinically advantageous for improving restorative outcomes.

Shade matching and blending capabilities of a new single-shade composite: an in vivo study.

Demand for direct esthetic restorations is high, but shade matching can be challenging. Some manufacturers claim that a single product is able to match all colors of the human dentition, eliminating shade matching challenges. This in vivo study, which followed the International Commission on Illumination's (CIE) CIEDE2000 color difference standard (ΔE00), aimed to quantify the shade matching and blending capabilities of a single-shade composite (Omnichroma PLT) used as a direct veneer. A color difference of ΔE00 ≤ 1.8 was set as the acceptability threshold. Ten participants with an unrestored and noncarious maxillary left central incisor were enrolled in the study. Direct spectrophotometric measurements (CIE L*a*b*) were made on the tooth and then on composite cured on the tooth. Consistency in measurements and composite resin placement were attained through the use of a specially designed jig. A digital photograph was then taken with the composite in place, and colorimetric software was used to obtain the L*a*b* values at the most incisal and cervical edges of the restoration. These values were compared to those of the natural tooth structure immediately adjacent to the composite resin. The ΔE00 scores were calculated to determine the composite's ability to match the tooth shade beneath it (ΔEm) and to blend with the incisal (ΔEi) and cervical (ΔEc) tooth shades. Mean scores for ΔEm, ΔEi, and ΔEc were calculated, and an independent t test (α = 0.05) was used to compare means for ΔEi and ΔEc. The mean (SD) ΔE00 values were 6.16 (2.38), 3.90 (2.47), and 6.84 (1.80) for ΔEm, ΔEi, and ΔEc, respectively. A statistically significant difference (P = 0.008) was observed between ΔEi and ΔEc. As a direct veneer, the tested composite did not meet the acceptability threshold for any ΔE00 measurement; however, it was better at matching the incisal third of the tooth than it was the other thirds. More in vivo studies are needed to verify and expand on these results.