Biomedical subjects
Publications and source records attributed to A P Prévost.
The correlation technique explained here shows one of the possibilities for occlusal reconstruction offered by the Cerec approach. The various stages of this technique are described and illustrated. The most current applications are reviewed.
It has been postulated that evacuation systems used in dentistry could be a source of cross-contamination between patients through backflow of bacteria dislodged from the saliva ejector tubings. The bacterial microflora associated with these systems was characterized using transmission electron microscopy (TEM) and microbiological cultures. The potential for backflow was investigated by a study of pressure differentials in evacuation system tubing and by the presence of bacteria in backflow samples. Evacuation lines were coated with microbial biofilms in which microcolonies of Gram-positive cocci and Gram-negative bacilli predominated, embedded in an extensive polysaccharide matrix. Most bacteria were metabolically active. Occasionally, buccal material such as collagen, fibrin and eukaryotic cell debris was observed. In other experiments, flow reversal was detected several times during saliva ejector use though each of these events was brief (less than 0.1 s). Aspiration of saliva, or occlusion of the mouthpiece opening by the oral mucosa, were the major factors leading to backflow episodes. Bacteria associated with backflow were found in almost 25% assays, with counts ranging from 1-300 cfu/occurrence. The majority of the bacteria isolated from biofilm or backflow samples were staphylococci, micrococci and non-fermentive Gram-negative rods. Pathogens such as Pseudomonas aeruginosa and Staphylococcus aureus were also isolated from backflow fluids. No oral streptococci could be recovered from biofilms in the tubing beyond 15 min from the last saliva ejector use however, suggesting that these species did not survive in the biofilms. These data suggest, although without direct proof of cross-contamination, the possible existence of an infectious risk associated with oral evacuation systems, as potential pathogens may be shed from tubing biofilms following backflow. Even if the risk of cross-contamination between patients is considered to be low, the necessity for regular disinfection of these systems must be stressed, since biofilms can serve as a reservoir for pathogens or harbor potentially infectious material.
Microbial contamination of dental unit waterlines is thought to be the result of biofilm formation within the small-bore tubing used for these conduits. Systematic sampling of 121 dental units located at the dental school of Université de Montréal showed that none of the waterlines was spared from bacterial contamination. Multilevel statistical analyses showed significant differences between samples taken at the beginning of the day and samples taken after a 2-min purge. Differences were also found between water from the turbine and the air/water syringe. Random variation occurred mainly between measurements (80%) and to a lesser extent between dental units (20%). In other analyses, it was observed to take less than 5 days before initial bacterial counts reached a plateau of 2 x 10(5) CFU/ml in newly installed waterlines. Sphyngomonas paucimobilis, Acinetobacter calcoaceticus, Methylobacterium mesophilicum, and Pseudomonas aeruginosa were the predominant isolates. P. aeruginosa showed a nonrandom distribution in dental unit waterlines, since 89.5% of the all the isolates were located in only three of the nine clinics tested. Dental units contaminated by P. aeruginosa showed significantly higher total bacterial counts than the others. By comparison, P. aeruginosa was never isolated in tap water remote from or near the contaminated dental unit waterlines. In conclusion, dental unit waterlines should be considered an aquatic ecosystem in which opportunistic pathogens successfully colonize synthetic surfaces, increasing the concentration of the pathogens in water to potentially dangerous levels. The clinical significance of these findings in relation to routine dental procedures is discussed.
This study attempts to measure the adhesive resistance between VitreBond and P-50 composite resin when the VitreBond surface is submitted to grinding and to the application of Scotchprep. The results indicate that this adhesion is superior to the cohesive resistance of VitreBond independently from grinding and from the application of Scotchprep.
Enamel Micro-abrasion is a technique where an acid is used in combination with an abrasive to remove the superficial layer of enamel which has certain dental colorants within its structure. It is indicated as the treatment of choice for superficial enamel stains and is a technique which every dentist should offer to their patients. It is a simple, conservative, efficient and durable procedure.
The radiopacity of glass ionomer dental materials is quite variable. The use of a poorly radiopaque material as a base under other restorative materials can mislead the dentist to a diagnosis of recurrent decay. This study investigates the radiopacity of these materials and proposes a minimal radiopacity under which a material should not be used as a base or liner. All base, liner, and core formulations of glass ionomer under investigation were more radiopaque than dentin. All restorative and luting formulations of glass ionomer under investigation were less radiopaque than dentin and therefore should be avoided as bases or liners.
Diastema closure by simple direct techniques has to take advantage of modern photo-cure systems. This paper reviews the basic concepts of diastema closure and describes a technique that does not necessitate the use a conventional matrix.
For 18 years, the acid-etched bridge has been put to good use. Clinical observations over this period of time allow us to take a step back and review this conservative technique. Using the results of clinical research, this article aims to evaluate the performance and basic principles relative to the acid-etched bridge. The primary and secondary causes of debonding are also identified.
The adhesion to enamel of composite resin inlays are not documented as much as porcelain inlays and direct composite resins. This study evaluates the adhesion of a light cured composite resin (P-50) used in an indirect technique and secondarily polymerized by heat. No significant differences were found between adhesion of P-50 used with an indirect technique and adhesion of porcelain (Mirage). P-50 used with the direct technique yield adhesion values significantly lower than the indirect techniques.
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Three composite resin systems, one conventional (Concise) and two microfilled (IsoPast and Silar), used with and without an intermediate resin (Concise Enamel Bond), were evaluated with and without thermal stress for in vitro retentive strength and sealing ability to acid-etched human enamel. All three materials yielded significantly different shear strength values. The use of an intermediate resin significantly improved both the shear strength and resistance to microleakage of Silar, while no differences were observed for Concise and IsoPast. The thermocycling procedure did not generally or consistently affect the results. The failure mode of the three acid-etched composite resins was studied by evaluation of the failure surface and by describing the percentage of enamel, composite, and interface which were present. The use of an intermediate resin did not significantly influence the failure mode, and the correlation between the failure mode and retentive strength, although significant was low. The study confirmed the importance of adequate wetting action of a resin on the etched enamel to ensure proper bonding.
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