No abstract

In a within-subject cross-over clinical trial, psychometric and functional measurements were taken while 15 completely edentulous subjects wore mandibular fixed prostheses and long-bar removable implant-supported prostheses. In this paper, the results of a psychometric assessment are presented. Eight subjects first received the fixed bridge and seven the removable type. After having worn a prosthesis for a minimum of two months, subjects responded to psychometric scales that measured their perceptions of various factors associated with prostheses. They also chewed test foods while masticatory activity was recorded. The prostheses were then changed and the procedures repeated. At the end of the study, patients were asked to choose the prosthesis that they wished to keep. Patients assigned significantly higher scores, on visual analogue scales, to both types of implant-supported prostheses than to their original conventional prostheses for all factors tested, including general satisfaction. However, no statistically significant differences between the two implant-supported prostheses were detected except for the difficulty of chewing carrot, apple, and sausage. For these foods, the fixed prostheses were rated higher. Subjects' responses to category scales were consistent with their responses to the visual analogue scales. These results suggest that, although patients find the fixed bridge to be significantly better for chewing harder foods, there is no difference in their general satisfaction with the two types of prostheses.

In the past, fixed prostheses were believed to be more efficient implant-supported devices than removable types for edentulous patients. However, this hypothesis was never properly tested. Therefore, a within-subject crossover clinical trial was designed in which 145 completely edentulous subjects were tested wearing implant-supported mandibular fixed prostheses and long-bar overdentures. Eight subjects received the fixed appliance first and seven the removable type. The patients' perceptions of various characteristics of the implant-supported prostheses were measured after a minimum of two months' adaptation. Mandibular movements and jaw muscle electromyographic activity were recorded while the patients chewed five standard-sized test foods: bread, apple, hard cheese, sausage, and raw carrot. The prostheses were then changed, worn for the same period of adaptation, and the procedures repeated. There were three test sessions per prosthesis, and each included five trials per food. The measurements were repeated three times at one-week intervals. Mastication time was found to be shorter for three foods (bread, cheese, and sausage) when subjects wore the long-bar overdenture. The vertical amplitude of the masticatory strokes was significantly less with the overdenture for all foods except carrot. Cycle duration was significantly longer with the overdenture for sausage and carrot. Contrary to what might be expected, the long-bar overdenture appears to be no less efficient than the fixed prosthesis. Furthermore, these data suggest that patients are capable of adapting their masticatory movements to the characteristics of the two prostheses.

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 ؋ 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.

Bilateral agenesis was encountered in about 9% of the cases, with no significant sexual difference. The right and left mandibular third molars had the same pattern of development and emergence. The slight advance of girls over boys at the crown-completion stage was similar to previous observations on other mandibular teeth, particularly the second molar. The root development course of the third molar was faster in males than in females; this sexual dimorphism was much greater for retarded cases than for advanced cases. At the apex closure, the difference between median ages of males and females was 1.5 yr. Alveolar emergence tended to occur at a lower developmental stage in advanced cases compared with retarded cases.