Flexural strength of composites: influences of polyethylene fiber reinforcement and type of composite

MAIN PROBLEM: The microfill veneering of hybrid composite restorations has been indicated to improve esthetics. Also, polyethylene fiber reinforcement has been proposed for use in composite restorations in high-stress clinical situations. However, minimal information in the literature addresses the influence of such combinations on the resistance to fracture. The purpose of this study was to investigate the flexural strength of two composites, a microfill and a hybrid, the effect of their combination, and the influence of polyethylene fiber reinforcement. MATERIALS AND METHODS: Twenty-eight specimens were prepared using a standard metallic mold (20x2x2 mm) and divided into groups of seven each: Filtek Z-250 (3M ESPE, St. Paul, Minn., USA) (group I), Filtek A-110 (3M ESPE) (group II), Filtek Z-250 combined with Filtek A-110 (group III), and Filtek Z-250 combined with polyethylene fiber (Ribbond, Seattle, Wash., USA) (group IV). The specimens were stress-loaded to fracture in a three-point bending device according to International Standardization Organization (ISO) 4049. RESULTS: Data were analyzed using analysis of variance and Tukey's test at a 0.05 level of significance. No statistically significant differences were observed between groups I and IV. Group II, however, exhibited statistically lower resistance to fracture than the other groups. Group III presented intermediate results, showing statistically higher fracture resistance than group II but lower than group I. CONCLUSIONS: With the methodology employed, microfill composite presented the lowest flexural strength, but its association with hybrid composite increased the resistance to fracture. The combination of polyethylene fiber and hybrid composite did not present higher flexural strength than hybrid composite alone.     

Clinical study of the use of the laser fluorescence device DIAGNOdent for detection of occlusal caries in children

Diagnosis of non-cavitated occlusal caries is generally considered problematic. The aim of this study was to evaluate the utility of the laser fluorescence device DIAGNOdent as part of routine dental check-ups in children. A total of 613 occlusal surfaces on permanent molars and 436 surfaces on primary molars in children aged 7-8 (n = 55) and 13-14 years (n = 54) were examined visually, using DIAGNOdent and for most 13- to 14-year-olds also using radiographs. The teeth were not cleaned professionally before examination. To provide a gold standard for carious teeth, the depth of the caries lesion was determined in those lesions that were judged visually to need opening by drilling (51 teeth). The higher the visual score, the higher were the mean DIAGNOdent values, but in each visual category the variation among values was large. The presence of a clear sealant did not affect DIAGNOdent measurements. The values for permanent and primary molars differed slightly. For permanent teeth, Youden's index value was highest (60%) at a cut-off value of 30, which indicates that the overall performance for DIAGNOdent in detecting dentinal caries was best at this point. Using this cut-off, sensitivity was 92% and specificity 69% with visual examination for validation, while sensitivity was 92% and specificity 82% with validation by fissure opening. Of the three methods, radiographic examination was the least accurate. In routine dental check-ups of children, DIAGNOdent appears to be useful as an adjunct to visual examination.     

The effect of three different periodontal pre-treatment procedures on the success of telescopic removable partial dentures

In this prospective study, 120 teeth consisting of maxillary and mandibular canines and premolars were divided into three groups each containing 40 teeth. The teeth were assigned randomly in quadrants to three different periodontal treatment protocols. The first group was treated with professional prophylaxis only. The second group received additional deep scaling. With the third group, additional surgical periodontal flap surgery and scaling was performed. Both papillary bleeding index (PBI) and probing depth (PD) were evaluated before, during and after treatment. During the subsequent prosthetic treatment phase all teeth were then used as telescope abutments supporting a removable prosthesis. The documentation of the attachment level (AL) was then used as a clinical parameter. One year after the incorporation of telescopic removable partial dentures (RPDs), PD, PBI and AL were again evaluated. The resulting periodontal parameters were compared between the different groups using the general linear model (GLM) repeated measures and the Kruskal-Wallis test for non-parametric variables. Differences within the three treatment groups were determined using the t-test, e.g. the Wilcoxon test for dependent variables (P < 0.05). A significant decrease in inflammatory indices (PBI) was found for all types of periodontal treatment (P < 0.03 for all groups). Additionally, the reduction in PD was significant for all of the three groups (P < 0.001 for all groups). The greatest reduction in PD was observed in the group in which a surgical approach was used. Evaluation of the attachment level after the incorporation of the telescopic RPDs showed that tooth position did not influence the periodontal prognosis and that the use of telescopic RPDs exerted no ascertainable negative influence on the periodontium of the abutment teeth.     

Alumni perspectives on community-based and traditional curricula

In 1994, the University of Medicine and Dentistry of New Jersey-New Jersey Dental School (UMDNJ-NJDS) launched the Community-Oriented Dental Education (CODE) program. The CODE program provides senior dental students the opportunity to spend four days per week providing dental care in a community-based clinic. A survey of graduates of CODE (n = 55) and randomly selected graduates of the traditional curriculum (n = 110) was conducted via mail to determine attitudes relating to community service (CS), community-based learning (CBL), reasons for participating in their clinical program, perceived levels of clinical preparedness at graduation, and practice choices. A total of 111 surveys (66.9 percent) were returned to NJDS, with 84.6 percent of CODE alumni responding and 59.0 percent of traditional alumni (TA) responding. Of the 111 surveys returned, sixty-five (58.6 percent) were completed by TA, and forty-six (41.4 percent) were completed by CODE alumni. There were no differences among CODE and TA regarding attitudes toward CS and tendency to practice in underserved areas or to accept Medicaid payments. There were, however, some differences in attitudes toward CBL, reasons for applying or not applying to the CODE program, perceived impact of clinical education on graduates' preparedness, views of the extent to which the programs encouraged students to choose public or private areas of practice, and perceptions of how the desire to help communities influenced career and practice decisions. Some of these findings may be useful to schools as they plan extramural education programs.     

Hydrolytic stability of experimental hydroxyapatite-filled dental composite materials.

OBJECTIVES: The purpose of this study was to analyze the behavior in water, related to mechanical properties, of experimental composites for dental restoration. METHODS: The studied materials were composed of a visible-light-curing monomer mixture (Bis-GMA and TEGDMA or HEMA) and micrometric, nanometric or a mixture of both sizes hydroxyapatite particles as a reinforcing filler. Filler particles were modified with a coupling agent (citric, hydrosuccinic, acrylic or methacrylic acid or silane). The hydrolytic stability of the evaluated materials was studied through total elution and water-uptake tests. Percent net-mass variation was daily monitored and analyzed as a function of time. Mechanical performance was examined through flexural properties and Vickers hardness. Morphological surface changes were observed with scanning electron microscopy. ANOVA statistical analysis was performed (P<0.05). RESULTS: In general, the use of HEMA instead of TEGDMA did not substantially worsen the composite quality. Dental composites containing only nanometric particles of hydroxyapatite as a filler are unsuitable for clinical performance. Midway-filled composite resins loaded with micro-HAP particles, coated with citric, acrylic or methacrylic acid displayed low percent elution and water-uptake values. Mechanical properties were similar or even superior to those measured for silane treated particles. SIGNIFICANCE: More research is needed to further improve the interaction of nano-HAP particles with the polymeric matrix, either as a single filler or, preferentially, mixed with micro-HAP, that will allow to increase the total loading of reinforcing filler and, hence, to improve the mechanical properties.