Influence of dental prophylaxis procedures on the tooth veneer interface in resin-based composite and polymer-infiltrated ceramic veneer restorations: an in vitro study

OBJECTIVES

The aim of this study was to investigate the influence of dental prophylaxis cleaning procedures and artificial aging on veneers in human teeth. The external marginal and internal tooth veneer as well as the restoration surfaces were examined.

MATERIAL AND METHODS

Thirty-two extracted premolars were restored with resin-based composite (RBC) and polymer-infiltrated ceramic network (PICN) veneers. Artificial aging by alternating thermocycling and subsequent prophylaxis procedure (glycine-based powder air polishing or ultrasonic scaling) was conducted for five consecutive cycles. The external marginal interface was examined by height profile measurements and the internal interface was investigated using micro X-ray computed tomography. In addition, the surface texture of the veneer surface was analyzed using confocal laser scanning microscopy.

RESULTS

The application of both prophylaxis procedures resulted in a deepening of the marginal interface (10 µm ± 8 µm) for materials. Furthermore, the internal interface of PICN restorations showed marginal gaps after both treatments and artificial aging (16 µm ± 3 µm). In contrast to the RBC specimens, a significant increase in surface roughness was identified for PICN veneers after ultrasonic scaling.

CONCLUSIONS

The marginal and internal interface regions in veneers fabricated from PICN and RBC were affected by prophylaxis procedures. Furthermore, it may result in increased veneer surface roughness, especially in PICN and after ultrasonic scaling, which might affect bioadhesion and longevity.

CLINICAL RELEVANCE

After dental prophylaxis procedures, examination of the marginal and the internal interface as well as the veneer surface provides a precise insight into damage mechanisms and offers an assessment of longevity.

Rewarding and aversive properties of IP and SC cocaine: assessment by place and taste conditioning

Three experiments were conducted to compare the effectiveness of intraperitoneally (IP) administered or subcutaneously (SC) administered cocaine to produce place and/or taste conditioning after four conditioning trials. In each experiment, IP (5-20 mg/kg) cocaine produced a place preference, but SC (0.5-20 mg/kg) cocaine at concentrations that prevented necrosis, did not produce a place preference. The failure of SC cocaine to produce a place preference was not a function of conditioning trial duration. On the other hand, SC cocaine (20 mg/kg) produced conditioned taste avoidance, but IP cocaine (20 mg/kg) did not produce conditioned taste avoidance. The results suggest that IP cocaine, but not SC cocaine, is rewarding.

Equatorial Pacific Seismic Reflectors as Indicators of Global Oceanographic Events

The origin of a series of regionally correlatable seismic horizons in the Neogene sediments of the central equatorial Pacific is examined through seismic modeling and the detailed analyses of stratigraphic and physical property relationships in Deep Sea Drilling Project cores. These regionally traceable reflectors are synchronous; the younger reflectors are the direct result of carbonate dissolution events, the older ones of stratigraphically selective diagenetic processes. The changes in ocean chemistry associated with these events appear to be linked to global reorganizations of surface and bottom-water circulation patterns, the most dramatic of which are associated with reorganizations of North Atlantic bottom waters. These deepwater seismic horizons appear to correlate with the major events on the "relative sea-level" curve of Vail et al. for the Neogene.

Morphologic responses to a murine erythroblastosis virus

A recently described mouse erythroblastosis virus (MEV) was passed to newborn W/Fu rats. The rats developed generalized malignant lymphomas after 6-7 months. Two separate serial cell-free passage series were initiated. Rat lymphomas induced erythroblastosis in less than 20% of the rats that died within 4 weeks after inoculation. The surviving rats remained apparently healthy for months until they died from lymphomas. Inoculation of newborn C3Hf/Gs mice with the same Filtrates caused only lymphomas in 35-50% of the mice after 3-8 months. The lymphomas were morphologically indistinguishable from thymic lymphomas induced in mice and rats by Gross' leukemia virus. A different morphologic response was observed by serial passages of spleen filtrates or plasma from rats with erythroblastosis. All rats died within 4 weeks with erythroblastosis. In addition, multiple sarcomas and polyostotic osteolytic lesions were found in most rats of such erythroblastosis passages. The same rat erythroblastosis filtrates induced erythroblastosis and sarcomas but no osteolytic lesions in C3Hf/Gs mice. Erythroblastosis in rats was similar to the disease previously described in mice, except for a marked normoblastosis and cerebral hemorrhages which did not occur in erythroblastotic mice. The sarcomas arose in multiple sites and were histologically undifferentiated. The osteolytic lesions were likewise multicentric in origin, affecting particularly the vertebrae and long bones. Their exact nature could not be determined.