Changes of cement properties caused by mixing errors: the therapeutic range of different cement types.

OBJECTIVE: The hypothesis was that low grade variations of mixing ratios of luting agents have negligible influence, while high grade variations cause severe property changes independent from the cement type used. MATERIAL AND METHODS: A zinc oxide phosphate, carboxylate, glass ionomer, resin-modified glass ionomer, dual-curing composite and self-adhesive composite cement were mixed using various mixing ratios. Beside the recommended ratio, samples were mixed with ratios between 10 and 25% (low grade) up to 60% (high grade) variation of powder/liquid, respectively base/catalyst pastes. The samples underwent a Vickers hardness, flexural strength and three-body abrasion test. Their extent of cure reaction was characterized using differential scanning calorimetry. RESULTS: This study indicates that dual-curing composite cements and resin-modified glass ionomers have a wide therapeutic range, followed by zinc oxide phosphate, carboyxlate and classical glass ionomer cements. Dual-curing composite cement showed less property changes, if they were exclusively light-cured in contrast to dark-curing. The classic glass ionomer and the carboxylate cements reacted more sensible to higher liquid content than higher powder content, while zinc oxide phosphate cement was lower sensitive to higher powder content. The investigated self-adhesive composite cement reacted very sensitive even to low grade mixing errors. CONCLUSIONS: . Most of the established luting agents seem to tolerate low grade mixing errors, while this is not the case for recently developed self-adhesive composite cement.

A contact-free volumetric measurement of facial volume after third molar osteotomy: proof of concept.

OBJECTIVE: The present study tested the reliability of an optical scanning device for the objective assessment of postoperative facial swelling. STUDY DESIGN: Twenty control subjects bearing a defined volume of water (10-30 mL) in an intraorally carried balloon were tested to assess the measurement accuracy of the device. As a proof of concept, facial volumes of 59 surgical cases were recorded before osteotomy and 1 and 7 days after intervention with the use of a structured light scanner. RESULTS: The median difference between the applied and the measured volumes was 0.67 mL for the control test with the artificial swelling simulated using water balloons. For subjects having third molar osteotomy, extraoral volume increased to 5.29 cm(3) 1 day after surgery (95% CI 5.22-8.52) and decreased to 0.00 mL (95% CI 0.85-2.55) after 7 days. CONCLUSIONS: Contact-free visible-light 3-dimensional scanning is reliable for the objective assessment of postoperative facial swelling.

Two-body wear of dental restorative materials.

AIM: The aim of this in vitro study was to determine the two-body wear resistance of modern direct dental restorative materials. METHODS: Eight standardized specimens were prepared from 14 dental restorative materials (nano-, micro-, hybrid-, macrofilled composites; compomer, silorane, ormocer); a veneering composite (Sinfony) and enamel were used for reference. Vickers hardness (HV) and inorganic filler weight were determined. Specimens were subjected to mastication simulation using a mastication simulator (50 N, 1.2×10(5) cycles, 1.2 Hz) in a pin-on-block design and simultaneous thermal cycling (600 cycles, 5/55 °C, 2 min/cycle). Steatite balls were used as antagonists. Vertical substance and volume loss were determined using cast replicas and a 3D laser scanning device. Means and standard deviations were calculated, and statistical analysis was performed using one-way ANOVA and the Games-Howell test for post hoc analysis (α=.05). RESULTS: HV ranged between 19 and 76; inorganic filler weight ranged between 44% and 88%. Significantly lowest vertical substance and volume loss were detected for the microfilled composite Heliomolar; enamel yielded similar vertical substance and volume loss. Intermediate wear was found for the other microfilled and hybrid composites as well as the silorane and the ormocers. Significantly highest wear was found for the macrofilled composite Quixfil and the compomer Compoglass F. DISCUSSION: Within the limitations of an in vitro study, the findings indicate similar wear behaviour for silorane- and ormocer-based dental restorative materials. However, correlations between HV, filler content, and wear resistance were poor.