Effect of Indirect Visual Course on Full Crown Preparation Skills in Preclinical Dental Students

OBJECTIVES

Indirect vision is a crucial skill for dentists and should be developed during undergraduate training. This study aimed to evaluate the impact of an indirect visual course on students' competence in abutment tooth preparation and compare their self-assessments with instructor assessments.

METHODS

Thirty-seven third-year dental students participated in an indirect vision preclinical training course, which involved drawing shapes in a reflection box. Before and after the course, students performed 296 full crown preparations on canine teeth over four practical sessions. Students self-assessed their performance using a 5-item scoring rubric, and their scores were compared with the instructor's technical assessments. Data were analyzed using one-way ANOVA, post hoc tests, paired samples t-tests, and Spearman's rho (∝ = 0.05).

RESULTS

Both self-assessment and technical assessment scores improved significantly after the indirect visual course (p < 0.001). The correlation between self-assessments and instructor assessments was moderate both before (Spearman's rho 0.48) and after the course (Spearman's rho 0.42) (p < 0.001). Repetitive practical sessions did not further improve the scores (p > 0.05). However, the average time for crown preparation decreased significantly, from 46 to 38 min, showing an 18% improvement (p < 0.001).

CONCLUSION

The indirect visual course significantly enhanced students' crown preparation skills and reduced preparation time. The course also improved the overall agreement between students' self-assessments and instructor assessments, indicating a better understanding of their performance.

Comparison of digitally assessed quality of posterior crown preparations performed with and without previous practice on patient-specific three-dimensional-printed teeth models

INTRODUCTION

Three-dimensional (3D)-printing technology can provide customizable simulations, but its effects on patient care quality have not been well studied. This study aimed to assess the impact of practicing with patient-specific 3D-printed teeth models on the quality of patients' dental preparations performed by students transitioning to clinical training. Accordingly, the quality of posterior crown preparations was evaluated by objectively analyzing digital scans and grades in two groups: the study group, which practiced beforehand with patient-specific 3D-printed teeth models, and the control group, which did not practice with these models.

METHODS

All 78 fourth-year dental students who had just finished their fixed prosthodontics course at the simulation laboratory with training on phantom heads and without previous clinical experience in crown preparations were invited to participate in the study. Sixty-eight agreed to take part and were randomly divided into a study group that practiced crown preparations on 3D-printed models of their own patient's teeth and a control group that did not practice with 3D-printed models and started their clinical work straightforwardly after simulation training. Students completed validated perception questionnaires on self-confidence and clinical skills before and after the protocol, which were compared using a chi-squared test. Crown preparations performed on 3D-printed models and then on patients were digitally scanned and objectively graded by prepCheck software for critical parameters, such as undercuts, taper, and occlusion reduction. Non-parametric tests were used to compare preparations on 3D-printed models and on patients performed by the study group and those on patients made by the control group.

RESULTS

Initially, both groups reported similar perceptions of self-confidence and clinical skills levels. The study group significantly improved both aspects after the protocol. Analysis of the scanned preparations demonstrated that the study group removed less tooth structure from actual patients than from the initial 3D-printed models. In contrast, the control group showed excess occlusal clearance in their patients compared to the study group.

CONCLUSIONS

Practicing patient-specific 3D-printed teeth before performing procedures clinically appears to enhance preparation quality and minimize unnecessary tooth reduction in early clinical experiences.

Effect of the haptic 3D virtual reality dental training simulator on assessment of tooth preparation

Background/purpose

The haptic 3D virtual reality dental training simulator has been drawn attention as a educational strategy in Covid-19 pandemic. The purpose of this study is to investigate the feature of the haptics simulator in comparison with a conventional mannequin simulator by analyzing the assessment of products prepared by dental students using these two kinds of simulator.

Materials and methods

The subjects were 30 students in the sixth-year classes of the faculty of dentistry. Abutments for a full cast crown were prepared by each subject using two kinds of simulator; one is the haptics simulator and the other is a mannequin simulator. For the resulted products, occlusal surface form, margin design, surface smoothness, taper angle, total cut volume and overall impression were rated by 3 evaluators. Score differences between two simulators were statistically analyzed.

Results

The kinds of simulator affected subject performance for margin design and total cut volume. The differences in cutting feeling between the simulators as well as variation of stereoscopic ability in subjects were considerable reasons. Evaluators' rating was affected by difference in simulators for occlusal surface form, total cut volume, and overall impression. This may have been due to variation of stereoscopic ability in evaluators.

Conclusion

The unique characteristics of virtual reality, such as the simulated cutting sensation and the simulated three-dimensional images created by stereo viewers, affect operators' performance and evaluators' rating. It was suggested that educational programs need to be constructed taking account of the characteristics of virtual reality to make the best use of the haptics simulator.

Convergence Angle of Preparations for Lithium Disilicate Glass-Ceramic Crowns by Dental Students and Its Effect on Crown Retention

The aims of this study were to determine the convergence angles of posterior teeth prepared by dental students at the University of Toronto for lithium disilicate glass-ceramic (LDGC) CAD/CAM crowns and to investigate their effect on loss of retention rate. A total of 280 preparations for posterior monolithic LDGC CAD/CAM crowns were performed on 270 patients (169 women and 101 men). Crowns were cemented with RelyX Unicem and Calibra Universal resin cements. Mesial, distal, and angle of convergence were measured on the bitewing radiographs. Cemented crowns were followed for up to six years. Data were analyzed for tooth type and location and for operator experience. The results showed the majority of convergence angles were greater than the recommended guidelines but fell within a clinically acceptable range (20 to 24 degrees). However, angles of convergence for mandibular molar preparations were highest (28.06±5.50 degrees), while maxillary premolars exhibited the lowest values (24.72±6.59 degrees). No significant difference was found between the results of dental students and foreign-trained dentists. Over a six-year observation period, only two crowns lost retention. The findings of this study indicated that ideal taper angles were impractical and difficult to achieve in clinical education settings.

Crown Taper Angles Achieved by Dental Students: A Systematic Review

The aim of this systematic review was to examine the literature on clinical taper angles achieved by dental students during crown preparation to determine the theoretical and clinically acceptable values identified in research studies. Medline, Embase, Web of Knowledge, the Cochrane Library, the British Dental Journal, and the Journal of the American Dental Association were searched to identify relevant studies. Studies were included if they were in vivo research on full crown preparations by dental students and published in English. Data extracted were country, year of publication, model selection and measurement methods, tests for reproducibility, tooth type, number of teeth assessed, and tapers achieved. The search resulted in 12 included articles from 11 countries published between 1978 and 2014 featuring a total of 2,306 preparations. In those studies, students failed to achieve ideal convergence angles (between 4° and 14°) but produced clinically acceptable results (between 10° and 20°). These findings should be taken into account when assessing dental students during their training programs.