Effect of Tooth Position on Molar Zirconia Crown Restoration with a Modified Dental Measurement Software

Summary

This study investigates a modified digital technique for the individualized zirconia crown restoration of posterior teeth.

Abstract

This study employed a modified digital technique to evaluate parameters of molar preparations for monolithic zirconia crown restoration, investigating whether clinical preparations with different tooth positions influence restorative outcomes. A total of 238 prepared posterior abutments were analyzed using an intraoral scanner, with parameters including total occlusal convergence (TOC) angle, margin perimeter, and mean abutment height assessed for statistical analysis. The results revealed that the average TOC angle of each posterior tooth exceeded 6°, with the maximum average observed in the mandibular left second molar (35.96 ± 20.21°) and the minimum in the maxillary right first premolar (10.97 ± 6.84°). Statistically significant differences were found in the TOC angle of homonymous second premolars (p < 0.05), where the mandibular left second molar was significantly larger than the other homonymous teeth. Additionally, significant differences existed between teeth in the same quadrant with different positions (p < 0.05), showing a linear increase in TOC angle as the tooth position moved backward. A positive correlation was observed between TOC angle and margin perimeter, while a negative correlation existed between TOC angle and mean abutment height. The findings indicate that clinical zirconia crown preparations often deviate from theoretical TOC recommendations, particularly requiring tailored criteria for mandibular teeth. The developed software integrates digital acquisition with clinical analysis, demonstrating its relevance in prosthodontic practice and education.

Introduction

High-quality zirconia-crown preparation is crucial for the long-term success of dental restoration^1,2,3. It has been observed that the total occlusal convergence (TOC) angle, diameter, and abutment height are correlated^1,4,5. Several in vitro studies have indicated that these factors substantially influence the fit, retention, resistance, and longevity of restoration^5,6,7. The TOC a....

Protocol

All experiments were conducted in accordance with a protocol approved by the Institutional Review Board (IRB) of Beijing Shijitan Hospital, Capital Medical University. The ethical approval reference number was IIT2023-021-001.

1. Experiment preparation

1. Software preparation
   1. Employ the IOS, 3D inspection software, and dental measurement software.
2. Personnel preparation
   1. Perform measurement procedures with three board-certified prosthodontists (mean clinical experience: 12.4 ± 2.1 years).
   2. Conduct sample preparation with a team of nineteen qualified prost....

Results

General characteristics
The number of maxillary specimens (n = 132) was greater than that of mandibular specimens (n = 106), with the maxillary right first molar being the most frequently prepared tooth (n = 24). The angles exhibiting a negative value were deemed invalid and omitted from statistical analysis. Table 2 delineates the quantity and classification of invalid TOC angle specimens. Table 3 presents the mean TOC angle for each posterior tooth. Furthermore, clinical TOC angles are compared wit.......

Discussion

This study aimed to evaluate the total occlusal convergence (TOC) angle of monolithic zirconia crowns using digital technology and analyze its relationship with tooth position, an area still lacking in research. Additionally, the application of digital techniques in the preparation and assessment of these crowns remains underexplored. Clinical samples were collected based on tooth location, and for each posterior tooth, the TOC angle, margin perimeter, and mean abutment height were measured. The findings revealed that mo.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
DentalEngineerV1.0	SuZhou, China	Dental measurement software
3Shape TRIOS3	3Shape, Danmark	Intraoral scanner
Geomagic Studio12.0	3D Systems, USA	Intraoral scanning data processing