Real-time measurement of temperature variation during nanosecond pulsed-laser-induced contamination deposition.

In this paper, a study of heat generation during UV laser-induced contamination (LIC) and potentially resulting subsequent thermal damage are presented. This becomes increasingly interesting when optics with delicate coatings are involved. During LIC, radiation can interact with outgassing molecules, both in the gas phase and at the surface, thus triggering chemical and photo-fixation reactions. This is a major hazard, in particular for laser units operating under vacuum conditions such as in space applications. The intense photon flux not only affects the contaminant deposition rate but also alters their chemical structure, which can increase their absorption coefficient. Over cumulative irradiation shots, these molecules formed deposits that increasingly absorb photons and produce heat as a by-product of de-excitation, eventually leading to thermal damage. One could better assess the risk of the latter with the knowledge of temperature during the contamination process. For this purpose, a thermoreflectance technique is used here to estimate the temperature variation from pulse to pulse during contamination deposition through the analysis of a temperature-dependent surface reflectance signal.

Silane influence on bonding to CAD-CAM composites: An interfacial fracture toughness study.

OBJECTIVES: To evaluate silane influence on the interfacial fracture toughness (IFT) of composite cement, with the two sub-classes of CAD-CAM composites, polymer-infiltrated ceramic networks (PICN) and dispersed fillers (DF), after hydrofluoric acid etching (HF) or airborne-particle abrasion (AB). A secondary objective was to correlate results with developed interfacial area ratio (Sdr) and surface wettability. METHODS: Experimental PICN and DF blocks were cut into equilateral half-prisms, which were treated with HF or AB, then treated with an experimental silane or not and bonded to their counterparts with an experimental light-cure resin cement. After thermocycling, samples (n=30 per group) were tested for IFT using the notchless triangular prism test in a water bath at 36°C. Moreover, profilometry and contact angle measurement were performed on rectangular samples of each group. Finally, bonding interface was analysed by SEM. RESULTS: PICN-HF treated with silane showed the highest IFT significantly. Three-way ANOVA revealed the influence of silane, material class and surface pre-treatment (HF or AB) on IFT (p<0.05). When silane was used, IFT was correlated with Sdr, while surface wettability was increased. Silane application significantly increased IFT for PICN but not for DF, while PICN performed better with HF and DF with AB. SIGNIFICANCE: Silane increases IFT of composite cement with PICNs, but not with DF materials. Results suggest that silane increases the micromechanical bond by promoting resin cement spreading and penetration in surface roughness. This roughness is significantly higher for pre-treated PICNs than for DF due to their specific honeycomb microstructure when etched, which explains their better bonding properties.

Biocompatibility of polymer-infiltrated-ceramic-network (PICN) materials with Human Gingival Fibroblasts (HGFs).

OBJECTIVES: Polymer-infiltrated-ceramic-network (PICN) materials constitute an innovative class of CAD-CAM materials offering promising perspectives in prosthodontics, but no data are available in the literature regarding their biological properties. The objective of the present study was to evaluate the in vitro biocompatibility of PICNs with human gingival fibroblasts (HGFs) in comparison with materials typically used for implant prostheses and abutments. METHODS: HGF attachment, proliferation and spreading on discs made of PICN, grade V titanium (Ti), yttrium zirconia (Zi), lithium disilicate glass-ceramic (eM) and polytetrafluoroethylene (negative control), were evaluated using a specific insert-based culture system (IBS-R). Sample surface properties were characterized by XPS, contact angle measurement, profilometry and SEM. RESULTS: Ti and Zi gave the best results regarding HGF viability, morphology, number and coverage increase with time in comparison with the negative control, while PICN and eM gave intermediate results, cell spreading being comparable for PICN, Ti, Zi and eM. Despite the presence of polymers and their related hydrophobicity, PICN exhibited comparable results to glass-ceramic materials, which could be explained by the mode of polymerization of the monomers. SIGNIFICANCE: The results of the present study confirm that the currently employed materials, i.e. Ti and Zi, can be considered to be the gold standard of materials in terms of HGF behavior, while PICN gave intermediate results comparable to eM. The impact of the present in vitro results needs to be further investigated clinically, particularly in the view of the utilization of PICNs for prostheses on bone-level implants.