Custom total occlusal convergence angle sticker fabrication.

This article describes a method of fabricating a custom total occlusal convergence angle sticker with photo editing software and label stickers. The custom total occlusal convergence angle sticker can help clinicians achieve an accurate degree of taper during axial wall reduction of tooth preparation.

Dental students' self-assessment of operative preparations using CAD/CAM: a preliminary analysis.

The Commission on Dental Accreditation (CODA)'s accreditation standards for dental schools state that "graduates must demonstrate the ability to self-assess." Therefore, dental schools have developed preclinical and clinical self-assessment (SA) protocols aimed at fostering a reflective process. This study comparing students' visual SA with students' digital SA and with faculty assessment was designed to test the hypothesis that higher agreement would occur when utilizing a digital evaluation. Twenty-five first-year dental students at one dental school participated by preparing a mesial occlusal preparation on tooth #30 and performing both types of SAs. A faculty evaluation was then performed both visually and digitally using the same evaluation criteria. The Kappa statistic was used to measure agreement between evaluators. The results showed statistically significant moderate agreement between the faculty visual and faculty digital modes of evaluation for occlusal shape (K=0.507, p=0.002), proximal shape (K=0.564, p=0.001), orientation (K=0.425, p=0.001), and definition (K=0.480, p=0.001). There was slight to poor agreement between the student visual and faculty visual assessment, except for preparation orientation occlusal shape (K=0.164, p=0.022), proximal shape (K=-0.227, p=0.032), orientation (K=0.253, p=0.041), and definition (K=-0.027, p=0.824). This study showed that the students had challenges in self-assessing even when using CAD/CAM and the digital assessment did not improve the amount of student/faculty agreement.

Changes in the cutting efficiency of different types of dental diamond rotary instrument with repeated cuts and disinfection.

STATEMENT OF PROBLEM: Cutting efficiency is one of the most important factors to consider when a specific dental diamond rotary instrument is selected. However, the selection of a dental diamond rotary instrument is based on clinical experience rather than any scientific evidence. PURPOSE: The purpose of this study was to identify how the cutting efficiency of different types of dental diamond rotary instrument changed with repeated cuts and disinfection. MATERIAL AND METHODS: Four types of diamond rotary instrument from 2 dental manufacturers (Shofu, Jin Dental) were investigated with a high-speed air-turbine handpiece. The groups were as follows: S cham group (n=10): chamfer design from Shofu; J cham group (n=10): chamfer design from Jin Dental; S thin group (n=10): thin tapered design from Shofu; J thin group (n=10): thin tapered design from Jin Dental. Changes in the cutting efficiency of diamond rotary instruments on glass ceramic blocks were measured after repeated cuts. Changes in cutting efficiency also were measured for 30 diamond rotary instruments, the same type as those used in group J cham after disinfection with ethylene oxide gas, immersion in solution, or autoclaving. One-way ANOVA, 2-way ANOVA, and repeated-measures ANOVA were used to identify differences in cutting efficiency, in total cutting efficiency, and change trend in cutting efficiency (α=.05). The Tukey honestly significant difference method was used for the post hoc tests. The principal metal components of the diamond rotary instruments were detected with x-ray spectrometry. RESULTS: The mean (standard deviation [SD]) total cutting efficiency after 10 cuts in the 4 groups was in the following order: J cham group (0.210 ± 0.064 g/min) > S cham group (0.170 ± 0.064 g/min) > J thin group (0.130 ± 0.042 g/min) > S thin group (0.010 ± 0.040 g/min) (P<.05).The decrease in the cutting efficiency was greatest after the first cut. The cutting efficiency was not influenced by repeated disinfection. CONCLUSION: The cutting efficiencies of diamond rotary instruments with different designs and particle sizes showed a decreasing trend after repeated cuts but did not show any change after various disinfecting procedures.

Performance of single-use and multiuse diamond rotary cutting instruments with turbine and electric handpieces.

STATEMENT OF PROBLEM: As single-use rotary cutting instruments and electric handpieces become more available, the performance of these instruments with electric as compared to turbine handpieces requires evaluation. In addition, if rotary cutting instruments marketed as single-use instruments are used for multiple patients, the effects on their performance of cleaning, sterilization, and repeated use are of interest to the clinician. PURPOSE: The purpose of the study was to evaluate how the cleaning, autoclaving, and repeated use of single-use and multiuse rotary cutting instruments, with either a turbine or electric handpiece, affected their performance. MATERIAL AND METHODS: The effects on cutting performance of 2 handpieces (turbine and electric), 2 cleaning and sterilization conditions (cleaned and autoclaved versus noncleaned and nonautoclaved), and 6 different diamond rotary cutting instruments (4 single-use and 2 multiuse) during simulated tooth preparations were evaluated by using a 24-treatment condition full-factorial experimental design. A computer-controlled dedicated testing apparatus was used to simulate the cutting procedures, and machinable glass ceramic blocks were used as the cutting substrate for tangential cuts. In addition, for each treatment condition, 8 consecutive cuts, for a total of 192 cuts, were measured to assess the durability of the rotary cutting instruments. A linear mixed model was used to study the effect of instrument type, handpiece, cleaning, and sterilization, as well as the status and number of cuts on the outcome variables. The Tukey honestly significant difference test was used for the post hoc pairwise comparisons (α=.05). RESULTS: Performance, as measured by the rate of advancement, decreased with the repeated use of rotary cutting instruments (P<.001), while cleaning and sterilization procedures improved the average performance of the 8 cuts (P=.002). The electric handpiece showed a greater load than the turbine (P<.001) and a lower rate/load metric, but no differences in the rate of advancement. Significant differences were also detected among the different rotary cutting instruments tested with the Two Striper, which showed the highest cumulative performance of all groups. CONCLUSIONS: The repeated use of both single-use and multiuse rotary cutting instruments decreased cutting performance. The use of a cleaning and sterilization procedure between cuts improved the average cutting performance. During a tangential cutting process, although the ease of advancement (rate/load) was greater for the turbine, the electric handpiece did not produce a statistically different cutting rate.

E4D compare software: an alternative to faculty grading in dental education.

The traditional method of evaluating student tooth preparations in preclinical courses has relied on the judgment of experienced clinicians primarily utilizing visual inspection. At times, certain aids such as reduction matrices or reduction instruments of known dimension are used to assist the evaluator in determining the grade. Despite the skill and experience of the evaluator, there is still a significant element of uncertainty and inconsistency in these methods. Students may perceive this inconsistency as a form of subjective, arbitrary, and empirical evaluation, which often results in students' focusing more on the grade than the actual learning or developing skills necessary to accomplish the preparation properly. Perceptions of favoritism, discrimination, and unfairness (whether verbalized or not) may interfere with the learning process. This study reports the use of a new experimental scanning and evaluation software program (E4D Compare) that can consistently and reliably scan a student's tooth preparation and compare it to a known (faculty-determined) standardized preparation. An actual numerical evaluation is generated by the E4D Compare software, thereby making subjective judgments by the faculty unnecessary. In this study, the computer-generated result was found to be more precise than the hand-graded method.

Pascal Magne: 'It should not be about aesthetics but tooth-conserving dentistry'. Interview by Ruth Doherty.

Pascal Magne, lecturer in adhesive and aesthetic dentistry at the University of Southern California in the USA, on biomimetics, mentorship and the future for the profession.

The chamfer finish line: preclinical student performance using different bur designs.

The primary purposes of this investigation were to evaluate sophomore dental student performance in the production of a chamfer finish line using two diamond bur types-a round-ended bur and a torpedo-shaped bur-and to gain student feedback about their preferences for bur type. Fifty students took part in the study, each of whom prepared the buccal surfaces of two mandibular molar typodont teeth, producing chamfer finish lines. Students prepared both teeth in the same laboratory session and were randomly assigned to two groups that were required to prepare the first of the two molars with a specific bur type. The prepared chamfer finish lines were scored and the data analyzed using the Wilcoxon signed-rank test. Student performance was significantly better when the round-ended bur was used (p=0.005). Student feedback was collected with a survey that consisted of four questions and the opportunity to provide write-in comments. In response to the question "Overall, was one bur type better?" 58 percent of the students preferred the round-ended bur for creating a chamfer finish line. The most frequent write-in comment, made by twelve of the fifty students, criticized the torpedo-shaped bur for creating finish lines that were too shallow or too long.

In vitro comparison of the cutting efficiency and temperature production of 10 different rotary cutting instruments. Part I: Turbine.

STATEMENT OF PROBLEM: Standards to test the cutting efficiency of dental rotary cutting instruments are either nonexistent or inappropriate, and knowledge of the factors that affect their cutting performance is limited. Therefore, rotary cutting instruments for crown preparation are generally marketed with weak or unsupported claims of superior performance. PURPOSE: The purpose of this study was to examine the cutting behavior of a wide selection of rotary cutting instruments under carefully controlled and reproducible conditions with an air-turbine handpiece. MATERIAL AND METHODS: Ten groups of rotary cutting instruments (n=30) designed for tooth preparation were selected: 9 diamond rotary cutting instruments (7 multi-use, 2 disposable) and 1 carbide bur. One bur per group was imaged with a scanning electron microscope (SEM) at different magnifications. Macor blocks (n=75) were used as a substrate, and 4 cuts were made on each specimen, using a new rotary cutting instrument each time, for a total of 300 cuts. The cuts were performed with an air-turbine handpiece (Midwest Quiet Air). A computer-controlled, custom-made testing apparatus was used to monitor all sensors and control the cutting action. The data were analyzed to compare the correlation of rotary cutting instrument type, grit, amount of pressure, cutting rate, revolutions per minute (rpm), temperature, and type of handpiece, using 1-way ANOVA and Tukey's Studentized Range test (alpha=.05). RESULTS: Compared to the baseline temperature, all rotary cutting instruments showed a reduction of temperature in the simulated pulp chamber. The Great White Ultra (carbide bur) showed a significantly higher rate of advancement (0.15 mm/s) and lower applied load (106.46 g) and rpm (304,375.97). CONCLUSIONS: Tooth preparation with an adequate water flow does not cause harmful temperature changes in the pulp chamber, regardless of rotary cutting instrument type. The tested carbide bur showed greater cutting efficiency than all diamond rotary cutting instruments.

PREPassistant: a system for evaluating tooth preparations.

Learning the widely differing forms of tooth preparation, especially in restorative dentistry, places high demands on both trainees and instructors with regard to precision, reproducibility, assessment, evaluation and three-dimensional conceptualization. In the past, evaluation of such preparations has been against subjective parameters and their interpretation by the assessor (usually the instructor). The use of CAD systems in teaching seminars and courses allows an objective assessment of tooth preparations and offers the trainee the possibility of measuring him/herself against a standard, of detecting errors, and of achieving perfection in the required tasks. The PREPassistant system described in this article is one such CAD-assisted learning system. It is recommended both for students in dental schools and for the continuing education of established dentists. Its strengths are that it produces a design for a tooth preparation, enables exact comparison with an ideal preparation, detects errors, and promotes improvements and perfection.

The quality of dental casts used in crown and bridgework.

OBJECTIVE: To assess the quality of dental casts used in crown and bridge construction. DESIGN: Observational cross-sectional study of dental casts. SETTING: Commercial dental laboratories and a university dental hospital laboratory in the UK. MATERIALS AND METHODS: A sample (n = 150) of working and opposing casts used for crown and bridgework prescribed by general dental practices and a dental hospital were sampled from two commercial dental laboratories and an 'on-site' university dental hospital laboratory respectively. A simple '3 point' assessment scale of quality (good, fair and poor) was used to categorise the casts depending on the clarity of reproduction of soft and hard tissues. RESULTS: The quality of opposing casts used for articulation purposes was significantly better (P<0.001) than that of the working casts. In addition it was found that for working casts the quality in the preparation area(s) was significantly better (p<0.001) than that in areas remote from preparation(s) in the same arch. In general, the quality of casts in the incisal or occlusal surfaces was better than the buccal and lingual surfaces. CONCLUSIONS: This study has demonstrated that variation exists in the quality of casts used in crown and bridgework, specifically those used in the construction of indirect restorations and also those used for articulation purposes. This study highlights the need for clinicians to exercise continued vigilance with crown and bridge impressions, and casts, particularly in areas away from the prepared teeth.