3D analysis of occlusal registration through geometry embedded library matching between quadrant and full-arch digital impression.

OBJECTIVE: This study aimed to compare the accuracy of occlusal registration for single-unit restorations in the posterior area of the jaw using the complete-arch or quadrant scan techniques. MATERIALS AND METHODS: A master cast was prepared and articulated on a nonadjustable articulator, and the maxillary left first molar was prepared for a full-coverage crown. The master cast was digitized as the reference data using a laboratory scanner (E3 scanner, 3Shape, Copenhagen, Denmark). It was scanned 10 times in the complete arch and 10 times in the quadrant, with an occlusal registration in each, using four intraoral scanners (i500, Primescan, TRIOS 3, and TRIOS 4). The scanned data were aligned to the reference data using GOM Inspect software. A three-dimensional analysis of the surface-based occlusal clearance and angular deviation, focusing on the prepared tooth, was performed. RESULTS: The mean surface-based occlusal clearance in the quadrant and complete-arch scans was 1.622 ± 0.032 mm and 1.642 ± 0.043 mm, respectively. Angular deviations compared to the reference cast showed a difference of 0.10° distally and 0.09° buccally for the quadrant scan and 0.12° distally and buccally for the complete-arch scan. Statistical analysis was performed using one-way analysis of variance and post hoc Scheffe's test. No significant differences were observed between the test groups. CONCLUSIONS: No significant differences were found between occlusal registrations of the complete-arch and quadrant scans. Therefore, a quadrant scan can achieve the same outcome as a complete-arch scan for single-unit restoration in the posterior area of the jaw. CLINICAL RELEVANCE: Quadrant scanning for single-unit restoration showed similar outcomes as complete-arch scans.

Comparison of digital and conventional assessment methods for a single tooth preparation and educational satisfaction.

INTRODUCTION: Digital feedback for tooth preparation can provide dental practitioners with more objective and accurate evaluations compared to conventional methods. This study aimed to evaluate the educational effect and satisfaction of digital feedback compared with those of the conventional putty index method for tooth preparation. MATERIAL AND METHODS: Forty-eight third-grade dental students were selected. All students performed a full-coverage preparation on a right mandibular first molar resin tooth. They were randomly divided into four groups (n = 12)-no guide (control), putty index, digital feedback, and digital and putty index assessment. Three-dimensional analysis was performed using an analysis software (GomInspect 2018, Gom) to evaluate the amount of tooth structure removed. At the end of the practice, the students completed a questionnaire to evaluate the educational satisfaction of the respective methods. RESULTS: There was no statistical significance of the amount of preparation amongst groups in most of the measured areas only except for several specific points. Overall occlusal surface showed 0.99 ± 0.27 mm in the N group (no guide) and 1.15 ± 0.31 mm in the D group (digital feedback), and overall axial surface showed no statistical differences (p > .05). The groups that used digital assessment showed a high level of satisfaction compared with conventional assessment. CONCLUSIONS: It was difficult to confirm that the digital-based feedback promotes accurate tooth preparation compared to conventional feedback within the limitation of this study. However, it improved educational satisfaction and permitted objective evaluation.

[Epidemiological Studies On The Acaroid Mite]

Epidemiological study on Acaroid mite in dust different sites were carried out and the following results were obtained. 1. Tyrophagus dimidiatus, Chibidania tokyoensis and Ornithonyssus nagayoi were found in living room(46.2 %), bath room(36.7 %), garden(27.0 %), shopping-store(28.8 %) and ware-house (29.2 %) in the Pusan area. 2. Dermanyssus gallinae and Rhizoglyphus echinopus were found mainly in class rooms of girl's high school(34.0 %) and class room of girl's middle school(40.0 %) as well as in primary school(13.2 %), but they are not found in class rooms of boys high school. 3. Generally, the various mites were found in the living room(57.0 %), under the carpet(50 %), under the furniture(52.0 %), on the furniture(27.5 %), lavatory(35.7 %) and garden(23.8 %).