The effect of endodontic access on the failure load of lithium disilicate and resin nanoceramic CAD/CAM crowns.

Currently, there is no consensus on whether crowns fabricated via computer-aided design/computer-aided manufacturing (CAD/CAM) need to be replaced following an endodontic procedure. The aim of this in vitro study was to evaluate the effect of endodontic access preparation and repair on the failure load of lithium disilicate and resin nanoceramic crowns. The hypothesis was that there would be no difference in the failure load between the intact and repaired crowns. Eighty identical mandibular CAD/CAM crowns (40 lithium disilicate glass ceramic [IPS e.max CAD] and 40 resin nanoceramic [Lava Ultimate]) were milled and cemented on 80 identical polymethyl methacrylate resin dies. A standardized endodontic access preparation was made in half the specimens and restored with composite resin. All crowns were subjected to an occlusal load with a hydraulic testing machine until failure. Based on the Wilcoxon rank sum test, the load to failure was significantly higher for the lithium disilicate crowns than for resin nanoceramic crowns in both the intact and repaired groups (P < 0.001). For the lithium disilicate crowns, the failure load was significantly higher for intact than for repaired specimens (P = 0.002). However, there was no significant difference between intact and repaired specimens for resin nanoceramic. The repair of lithium disilicate and resin nanoceramic CAD/CAM crowns may provide a serviceable restoration under normal occlusal loads. However, replacement would be prudent in cases where parafunctional occlusal loading is suspected, the crown was not adhesively cemented, or there is an obvious defect in the existing crown.

A comparison of marginal fit between press-fabricated and CAD/CAM lithium disilicate crowns.

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.

Placement and replacement rates of amalgam and composite restorations on posterior teeth in a military population.

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.

Microcomputed tomographic comparison of posterior composite resin restorative techniques: sonicated bulk fill versus incremental fill.

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.

An Evaluation of Common Cleaning Methods for the Removal of a Clinical Isolate of Escherichia coli in Personal Hydration System Water Reservoirs.

Waterborne infection is an important cause of morbidity and mortality throughout the world. Personal hydration packs have been used by military personnel since the Gulf War and are now a common issue item. Since military personnel tend to operate under austere conditions and may use a variety of water sources, preventing the acquisition of waterborne infections is extremely important. Further, since hydration pack water reservoir replacements may not be available during combat operations, the development of a reliable cleaning protocol for use in the field is essential. Several methods for cleaning have been described. In the current study, three common cleaning methodologies-bleach treatment, baking soda treatment, and proprietary CAMELBAK Cleaning Tabs™-were evaluated for the ability to remove Escherichia coli contamination from hydration pack water reservoirs. The study results suggest that the use of bleach and proprietary CAMELBAK tablets should be encouraged since they both operate by releasing bactericidal chlorine compounds into solution, which is more effective at reducing post-treatment bacterial burden. It should be noted that no method was 100% effective at completely eliminating bacteria from the reservoirs and that mechanical cleaning was not attempted.

The inhibitory activity of typified propolis against Enterococcus species.

Propolis, a natural bee product widely used for its antimicrobial activity, was tested against isolates of Enterococcus from humans, pig-tailed macaques, isolates of refractory endodontic treatment cases, and isolates from Lactobacillus-containing food supplements. Typification of the propolis was performed by high-performance liquid chromatography (HPLC) by which prenylated compounds, cinnamic acid derivatives, and flavonoids were detected as the main constituents. Minimum inhibitory concentrations (MIC) were determined using the agar dilution method. All human and animal Enterococcus isolates demonstrated MIC values of 1600 microg/mL. Enterococcal species of human and animal origin were inhibited by propolis. Particularly, human isolates of E. faecium and E. faecalis of refractory endodontic treatment cases were susceptible to propolis of Brazilian origin.