Comparative Influence of Marginal Design and Digital Scanning Accuracy on the Clinical Longevity of Ceramic Restorations: An Evidence-Based Approach. Consensus Statement From SSRD, SEPES, and PROSEC Conference on Minimally Invasive Restorations

OBJECTIVES

This consensus paper aims to evaluate the impact of vertical and horizontal finishing lines on the survival, success, and periodontal outcomes of veneer, crown, and fixed partial denture (FPD) restorations, as well as the accuracy of intraoral scanner (IOS) systems in fabricating inlay, onlay, and veneer restorations.

MATERIAL AND METHODS

Two systematic reviews with meta-analyses were conducted following PRISMA guidelines. The first review analyzed 15 studies comparing vertical and horizontal finishing lines. The second review included 33 studies on IOS accuracy for inlays, onlays, and veneers. Key findings, clinical recommendations, and unanswered research questions were synthesized into consensus statements.

RESULTS

Vertical and horizontal finish lines demonstrated no significant differences in restoration survival, success rates (65%-100%), or periodontal outcomes over 3-7 years. However, vertical designs were deemed technique-sensitive. IOSs reliably fabricated single-unit inlay and onlay restorations with high accuracy, but data on veneer restorations remained inconclusive due to limited studies.

CONCLUSIONS

Both finishing line designs are clinically viable, with material selection and planning being critical. IOSs offer reliable alternatives to conventional methods for inlays and onlays but require further evaluation for veneers. Future research should address clinical selection criteria, esthetic parameters, and patient-reported outcomes to refine restorative protocols.

In vitro assessment of an intraoral scanner accuracy on abutments with horizontal preparation geometries and subgingival margins

OBJECTIVES

This study evaluated the accuracy of the Medit i700 intraoral scanner (IOS) in capturing horizontal tooth preparations at different depths below the gingival margin and assessed its ability to detect surfaces beyond the finish line.

METHODS

Using CAD software, two abutments of a standard maxillary first molar were designed with horizontal preparation and 0.8 mm chamfer at 1 mm and 2 mm depths below the gingival margin. The abutment designs, created in DentalCAD 3.0 Galway (Exocad), were 3D printed and mounted on a typodont with simulated pink gum. An experienced operator conducted 20 scans, with each scan taking between 1 and 2 min. The scanning process began at the occlusal surface of the right third molar and proceeded longitudinally to the contralateral molar, then extended buccally and palatally, resulting in two experimental groups: H-1 (1 mm depth) and H-2 (2 mm depth). Accuracy was assessed using Geomagic Control X software, with descriptive statistics and independent sample tests (α = 0.05) employed for group comparisons.

RESULTS

No statistically significant difference was found in trueness between H-1 and H-2 (p=.053). However, precision differed significantly (p<.001). The IOS could not capture surfaces beyond the finish line in horizontal preparations.

CONCLUSIONS

Within study limitations, the horizontal preparation design hindered the IOS's ability to capture tooth anatomy beyond the finish line. Nonetheless, accuracy values at both 1 mm and 2 mm depths were clinically acceptable.

CLINICAL SIGNIFICANCE,

The present study shows that the tested intraoral scanner is accurate enough to scan abutments with horizontal margins placed 1 and 2 mm below the gingiva.

Fracture Resistance of Endodontically Treated Teeth Prepared With Biologically Oriented Preparation Technique Versus Horizontal Finish Lines: An In Vitro Study

INTRODUCTION

The biologically oriented preparation technique (BOPT) is a conservative tooth preparation method with no defined finish lines. Studies comparing the fracture resistance of endodontically treated teeth (ETT) prepared using BOPT or horizontal finish lines are lacking. The primary objective of this study was to compare the fracture resistance of ETT prepared using BOPT, chamfer finish line, or shoulder finish line and restored with monolithic zirconia (MZ) crowns. The secondary objective was to determine the modes of fracture of ETT with different finish lines.

METHODS

Forty-five maxillary premolar teeth were endodontically treated and randomly allotted to three tooth preparation methods: Group 1, BOPT; Group 2, chamfer finish line; and Group 3, shoulder finish line. MZ crowns were milled and cemented on their respective tooth preparations. The fracture resistance was tested using a universal testing machine. Maximum fracture load was recorded in Newtons (N). The fracture modes were classified using Burkey's codes and a newly proposed fracture grading.

RESULTS

The highest fracture resistance was seen in samples from Group 1, followed by Group 2, and the least in Group 3. Tukey's post hoc test showed a significant difference between Group 1 and Group 3 (p<0.05) and between Group 2 and Group 3 (p<0.05). No significant differences were found between Group 1 and Group 2 (p>0.05). Code V and Grade 3B fractures were highest in Group 3 samples.

CONCLUSIONS

Within the limitations of the present study, it can be concluded that ETT prepared with BOPT and chamfer finish lines had the greatest fracture resistance compared to shoulder finish lines. Teeth prepared with shoulder finish lines had more non-restorable fractures compared to BOPT or chamfer preparations.