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The purpose of this study was to compare the marginal fit of press-fabricated lithium disilicate crowns with that of computer-aided design/computer-aided manufacturing (CAD/CAM) lithium disilicate crowns to determine if the fabrication method has an influence on marginal fit. The marginal fit of 25 pressed and 25 CAD/CAM crowns was measured using the replica technique. The sites measured were the mesial, distal, facial, and lingual margins. A microscope at 10× magnification was used to obtain the measurements. Each site was measured 4 times, and intraclass correlation coefficients were used to assess measurement errors. An unpaired t test was used to evaluate the differences between the 2 groups. Mean marginal gap measurements were greater for CAD/CAM crowns than for pressed crowns at all sites. Only the difference in mean gap at the facial margin was statistically significant (P < 0.001). Press-fabricated lithium disilicate crowns provided a better marginal fit than those fabricated by CAD/CAM, but both fabrication methods provided crowns with a clinically acceptable marginal fit.

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OBJECTIVE: Replacement rates of direct dental restorations have been reported to be 37% to 70%, occupying a large proportion of a general dentist's time. Variations in the rate of initial placement and replacement of direct dental restorations may be associated with material placed (amalgam or composite), age, caries risk of the patient, and other factors. The purpose of this research was to clarify where the majority of patient care time is spent as a restorative Army dentist regarding either the initial placement or replacement of failed restorations; and how the location, caries risk, and material used (amalgam or composite) affects replacement rates. METHODS: This retrospective cross-sectional study gathered data from 600 randomly selected military patient dental records. All paper records were reviewed and cross checked with the digital record and digital x-ray databases. Record review was limited to all direct dental restorations placed in the posterior dentition within the past 2 years (March 2011 to March 2013). Statistical analysis was accomplished using chi-square tests and logistic regression analyses. RESULTS: Of the 600 charts reviewed, 525 were male, 75 were female, with an average age of 26 years (SD=6), ranging from 17 to 54 years. A third of the patients were classified as high, moderate, and low caries risk, respectively. The total number of posterior direct dental restorations placed was 2,117. Initial restorations totaled 1,429 (67.5%), and replacement restorations placed totaled 688 (32.5%). Four hundred forty-one of the 688 direct dental restorations replaced were amalgam (64%), the 247 remaining direct restorations replaced were composite (36%). Mandibular first molar dental restorations were replaced the most often (23.1%) while mandibular first premolar restorations were replaced the least often (0.9%). Older patients were more likely to have replacement of an existing restoration. CONCLUSIONS: Military dentists spend about one-third (32.5%) of their time replacing existing direct dental restorations. The majority of direct dental restorations placed and replaced were amalgam. No significant difference was found between composite and amalgam restorations. Location was shown to be significant with first molars and second molar restorations failing with the highest frequency. There was no significant difference found between male and female patients. As patient's age increased, the number of replacement restorations also increased.

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Sonication technology has recently been touted to decrease composite viscosity during delivery and may allow better cavity preparation adaptation and minimize voids. The purpose of this investigation was to evaluate the difference between conventional, hand-placed, incremental application of a standard hybrid resin-based composite (RBC) and sonicated application of a bulk-fill RBC in box-type and cylindrical cavity preparations. Experimental restorations were fabricated using molds of box-type or cylindrical preparations. For bulk-filled specimens, a single compule of bulk-fill composite was dispensed with a sonic handpiece. The conventional hybrid material was placed in 3 increments (2 mm, 2 mm, and 1 mm). Microfocus x-ray computed tomography was used to analyze voids for percentage and total volume porosity as well as number of actual pores. An analysis of variance indicated that RBC restorations that were applied to cylindrical cavities using a sonicated bulk-filled application method exhibited significantly less porosity (1.42%; P < 0.001) than incrementally placed cylindrical restorations (2.87%); sonicated bulk-filled, cube-shaped restorations (3.12%); and incrementally placed cube-shaped restorations (5.16%). When the groups were subcategorized into the specific characteristics of shape (cube vs cylinder) and application method (bulk vs incremental), the cylindrical group, which included both bulk-filled and incrementally placed specimens, demonstrated significantly less porosity (2.00%; P < 0.001) than other groups. Restorations that were incrementally placed into cube-shaped cavities produced the largest amount of porosity.

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