Novel methodology for measuring intraoral wear in enamel and dental restorative materials.

OBJECTIVES: To test the hypotheses that (a) the chairside/handheld dental scanner combined with a metrology software will measure clinical wear in vivo in agreement with measurements from X-ray computed microtomography and; (b) polished monolithic zirconia does not cause accelerated wear of opposing enamel. MATERIALS AND METHODS: Thirty single crowns were randomized to receive a monolithic zirconia or metal-ceramic crown. Two non-restored opposing teeth in the same quadrants were identified to serve as enamel controls. After cementation, quadrants were scanned using an intraoral dental scanner. Patients were recalled at 6-months and 1-year for re-scanning. Scanned images were compared using a metrology software to determine maximum vertical wear of teeth. The accuracy of the scanning measurements from this new method was compared with X-ray computed microtomography (micro-CT) measurements. Statistical analysis was performed using Mann-Whitney U test to determine significant differences between wear of enamel against zirconia, metal-ceramic or enamel. Linear regression analysis determined agreement between measurements obtained using intraoral scanning and micro-CT. RESULTS: Regression analysis demonstrated that there is a quantitative agreement between depth and volume measurements produced using intraoral scanning and the micro-CT methodologies. There was no significant difference between the wear of enamel against polished monolithic zirconia crowns and enamel against enamel. CONCLUSIONS: Intraoral scanning combined with a matching software can accurately quantify clinical wear to verify that monolithic zirconia exhibited comparable wear of enamel compared with metal-ceramic crowns and control enamel. Agreement between the intraoral scanner and the micro-CT was 99.8%. Clinical Trials.gov NCT02289781.

Incorporation of polymerizable surfactants in hydroxyethyl methacrylate lenses for improving wettability and lubricity.

Dryness and discomfort are the main reasons for dropouts in contact lens wearers. Incorporating surfactants in lens formulations could improve wettability and lubricity, which can improve comfort. We have focused on incorporating polymerizable surfactants in hydroxyethyl methacrylate lenses to improve comfort, while minimizing the potential for surfactant release into the tears. The surfactants were added to the polymerization mixture, followed by UV curing and extraction of leachables in hot water. Wettability and lubricity were characterized by measuring the contact angle and coefficient of friction. Lenses were also characterized by measuring transmittance, loss and storage moduli and ion permeability. Incorporation of surfactants significantly reduced contact angle from 90° for p-HEMA gels to about 10° for 2.43% (w/w) surfactant loading in hydrated gel. The coefficient of friction also decreased from about 0.16 for HEMA gels to 0.05 for the gels with 2.43% surfactant loading. There was a good correlation between the contact angle and coefficient of friction suggesting that both effects can be related to the stretching of the surfactant tails near the surface into the aqueous phase. The water content was also correlated with the surfactant loading but the contact angle was more sensitive suggesting that the observed improvements in wettability and lubricity arise from the protrusion of the surfactant tails in into the liquid, and not purely from the increase in the water content. The gels were clear and certain compositions also have the capability to block UVC and UVB radiation. The results suggest that incorporation of polymerizable surfactants could be useful in improving surface properties without significantly impacting any bulk property.