Comparison of the shaping ability of RaCe, FlexMaster, and ProFile nickel-titanium instruments in severely curved root canals

This in vitro study compared the shaping ability of RaCe, FlexMaster, and ProFile rotary nickel-titanium instruments in severely curved root canals of extracted teeth. Sixty maxillary molars with curvatures ranging from 25° to 65° were embedded in a muffle system and portioned into five horizontal sections (thickness 1.2 mm), starting from the apex. Canals were divided into three groups (n = 20, each) and were prepared with RaCe, FlexMaster, or ProFile rotary nickel-titanium instruments and the TriAuto ZX handpiece using a crown-down preparation technique. We evaluated the difference between pre- and postoperative root canal cross-sections, loss of working length, instrument failure, and preparation time. The root canal area before and after the intervention was determined using an area-measuring software. The data were analyzed statistically using a one-way ANOVA followed by a Kruskal-Wallis multiple-comparison Z-value test. Specimens treated with FlexMaster showed the greatest change from preoperative cross-sections, followed by RaCe and ProFile. The cross-sectional changes induced by RaCe and FlexMaster preparation differed significantly from those produced by ProFile. Loss of working length, instrument failure, and preparation time did not differ significantly between the groups. Root canal preparation with the three instruments did not lead to any significant alteration of the original root anatomy or working length. Thus, we conclude that RaCe, FlexMaster, and ProFile instruments are of comparable efficiency and usefulness in the preparation of severely curved root canals

Evaluating differently tutored groups in problem-based learning in a German dental curriculum: a mixed methods study

Background: It is still unclear to what extent the PBL tutor affects learning in PBL-sessions. This mixed-methods study (Part 1 and 2) evaluated the effects of facilitative (f) versus non-facilitative (nf) tutoring roles on knowledge-gain and group functioning in the field of endodontics. Methods: Part 1 was a quantitative assessment of tutor effectiveness within a prospective, experimental, single-blind, stratified, randomized, two-group intervention study. Participants attended PBL in the context of a hybrid curriculum. A validated questionnaire was used and knowledge assessments were conducted before and after the intervention. External observers rated tutor performance. Part 2 was a qualitative assessment of tutor effectiveness and consisted of semi-structured expert interviews with tutors and focus group discussions with students. Results: Part 1: f tutors obtained significantly higher scores than nf tutors with respect to learning motivation and tutor effectiveness (p ≤ 0.05). nf tuition resulted in a slightly larger knowledge gain (p = 0.08). External observers documented a significantly higher activity among facilitative tutors compared to non-facilitative tutors. Part 2: Tutors found the f role easier although this led to a less autonomous working climate. The students rated f tutoring as positive in all cases. Conclusions: With respect to PBL-group performance, students felt that groups guided in a non-facilitative fashion exhibited a higher level of independence and autonomy, especially with increasing PBL experience. In addition, students reported that more preparation was necessary for sessions guided by a non-facilitative tutor. Tutors were able to modify their role and influence group processes in a controlled manner. Results are useful for future “Train-the-Teacher” sessions

Reexamination In Vitro

Purpose. To introduce additional methods to detect and to quantify single pathogens in the complex biofilm formation on an antibacterial dental material. Materials and Methods. A conventional (ST) and an antibacterial dental composite (B) were manufactured. In vitro: specimens were incubated with a mixture of early colonizers. Bacterial adhesion was analyzed by TaqMan PCR after 8/24 h. In situ: TaqMan PCR and 16S rRNA Next Generation Sequencing (NGS) were performed. Results. In vitro: after 8 h incubation, B was covered by 58.6% of the bacterial amount that was attached to ST. After 24 h, the amount of attached bacteria to ST remained constant on ST only slightly lower on B. In situ: after 8 h the amount of adhering A. viscosus and S. mitis was prominent on ST and reduced on B. NGS revealed that S. sanguinis, S. parasanguinis, and Gemella sanguinis were the mainly attached species with S. sanguinis dominant on ST and S. parasanguinis and G. sanguinis dominant on B. Conclusions. Initial biofilm formation was altered by B. A shift between actinomycetes and streptococci was observed in situ. TaqMan PCR and 16S rRNA NGS revealed comparable results in situ and demonstrated the usefulness of NGS to characterize complex bacterial communities

Work shadowing in dental teaching practices: evaluation results of a collaborative study between university and general dental practices

Abstract Background The aim of this study was to investigate the acceptance and assessment of work shadowing carried out by students and dentists in dental practices. Furthermore, the extent to which students perceive an improvement in their specialised, communication and social competencies, was to be examined. Methods 61 dental students in their clinical semesters at a German university participated in work shadowing placements at 27 different general dental practices. Before beginning, they received checklists of various competencies that they self-assessed using school grades (from 1 = ‘very good’, to 6 = ‘failed’), which they also repeated after completion. The dentists supplemented this with their external assessments. In addition, the students were requested to fill out a 54-item questionnaire and compose a freely-structured report after the work shadowing; the dentists filled out a questionnaire containing 16 items. The statistical analysis was carried out by means of the Friedman Test, including a post-hoc test (Bonferroni-Holm correction). Results The analysis showed a significant overall improvement in the students’ self-assessed competencies by 0.71* ± 0.43 grades. With an average of 0.33* ± 0.36, the dentists’ external assessment proved significantly higher than the self-assessment. The greatest improvements were perceived by the students in the areas of accounting (1.17* ± 0.77), practice organisation (1.05* ± 0.61) and dentist’s discussions (0.94* ±0.80) [*p < 0.05]. The students confirmed experiencing an expansion of knowledge, an improvement in their communication skills and indicated a high degree of satisfaction in regard to the dentists (school grade 1.58 ± 0.93). A maximum amount of satisfaction towards the work shadow students was demonstrated by the dentists, and this form of teaching was assessed with a school grade of 1.69 ± 0.89. Conclusion Both students and dental practitioners demonstrated a high level of satisfaction in regard to the work shadowing. The students felt their knowledge had increased, viewed the dentists as motivating role models and acknowledged a significant improvement in their specialised, communication and social competencies. Work shadowing in dental teaching practices presents a sensible addition to academic teaching at a university

Work shadowing in dental teaching practices : evaluation results of a collaborative study between university and general dental practices

Background: The aim of this study was to investigate the acceptance and assessment of work shadowing carried out by students and dentists in dental practices. Furthermore, the extent to which students perceive an improvement in their specialised, communication and social competencies, was to be examined. Methods: 61 dental students in their clinical semesters at a German university participated in work shadowing placements at 27 different general dental practices. Before beginning, they received checklists of various competencies that they self-assessed using school grades (from 1 = "very good", to 6 = "failed"), which they also repeated after completion. The dentists supplemented this with their external assessments. In addition, the students were requested to fill out a 54-item questionnaire and compose a freely-structured report after the work shadowing; the dentists filled out a questionnaire containing 16 items. The statistical analysis was carried out by means of the Friedman Test, including a post-hoc test (Bonferroni-Holm correction). Results: The analysis showed a significant overall improvement in the students’ self-assessed competencies by 0.71* ± 0.43 grades. With an average of 0.33* ± 0.36, the dentists’ external assessment proved significantly higher than the self-assessment. The greatest improvements were perceived by the students in the areas of accounting (1.17* ± 0.77), practice organisation (1.05* ± 0.61) and dentist’s discussions (0.94* ±0.80) [*p < 0.05]. The students confirmed experiencing an expansion of knowledge, an improvement in their communication skills and indicated a high degree of satisfaction in regard to the dentists (school grade 1.58 ± 0.93). A maximum amount of satisfaction towards the work shadow students was demonstrated by the dentists, and this form of teaching was assessed with a school grade of 1.69 ± 0.89. Conclusion: Both students and dental practitioners demonstrated a high level of satisfaction in regard to the work shadowing. The students felt their knowledge had increased, viewed the dentists as motivating role models and acknowledged a significant improvement in their specialised, communication and social competencies. Work shadowing in dental teaching practices presents a sensible addition to academic teaching at a university

Shear Bond Strength and Fracture Analysis of Human vs. Bovine Teeth

PURPOSE: To evaluate if bovine enamel and dentin are appropriate substitutes for the respective human hard tooth tissues to test shear bond strength (SBS) and fracture analysis. MATERIALS AND METHODS: 80 sound and caries-free human erupted third molars and 80 freshly extracted bovine permanent central incisors (10 specimens for each group) were used to investigate enamel and dentine adhesion of one 2-step self-etch (SE) and one 3-step etch and rinse (E&R) product. To test SBS the buccal or labial areas were ground plane to obtain appropriate enamel or dentine areas. SE and E&R were applied and SBS was measured prior to and after 500 thermocycles between +5 and +55°C. Fracture analysis was performed for all debonded areas. RESULTS: ANOVA revealed significant differences of enamel and dentin SBS prior to and after thermocycling for both of the adhesives. SBS- of E&R-bonded human enamel increased after thermocycling but SE-bonded did not. Bovine enamel SE-bonded showed higher SBS after TC but E&R-bonded had lower SBS. No differences were found for human dentin SE- or E&R-bonded prior to or after thermocycling but bovine dentin SE-bonded increased whereas bovine dentine E&R-bonded decreased. Considering the totalized and adhesive failures, fracture analysis did not show significances between the adhesives or the respective tooth tissues prior to or after thermocycling. CONCLUSION: Although SBS was different on human and bovine teeth, no differences were found for fracture analysis. This indicates that solely conducted SBS on bovine substrate are not sufficient to judge the perfomance of adhesives, thus bovine teeth are questionnable as a substrate for shear bond testing