# Comparison of Marginal Adaptation in Lithium Disilicate Crowns Using Three Fabrication Techniques: An In Vitro Study

## TL;DR

This study compares how well different methods of making lithium disilicate crowns fit at their edges, finding that fully digital methods provide the best precision.

## Contribution

The study introduces a direct comparison of three fabrication techniques for lithium disilicate crowns focusing on marginal adaptation.

## Key findings

- Fully digital CAD/CAM milling showed the smallest mean marginal gap compared to other methods.
- CAD-milled wax patterns improved fit over conventional manual waxing.
- No significant difference was found between conventional and digital methods on the labial surface.

## Abstract

Introduction

The durability of all-ceramic crowns in clinical settings is fundamentally influenced by the precision of their margins, as significant marginal discrepancies can lead to the dissolution of cement, microleakage, the development of secondary caries, and periodontal issues. This research sought to evaluate the vertical marginal precision of lithium disilicate crowns fabricated via the traditional heat-press methodology, the computer-aided design-milled wax pattern subsequently subjected to heat-pressing, and the fully digital computer-aided design/computer-aided manufacturing (CAD/CAM) milling of lithium disilicate materials.

Materials and methods

Thirty lithium disilicate crowns were fabricated on an identical master die of a prepared maxillary left second premolar and equally divided into three groups (n = 10): Group 1, conventional heat press using manually waxed patterns (control); Group 2, heat-press using CAD-milled wax patterns; and Group 3, fully digital CAD/CAM milling of lithium disilicate blocks (IPS e.max CAD LT A2, Ivoclar Vivadent, Schaan, Liechtenstein) followed by crystallization firing. All procedures were performed by a single operator. Vertical marginal gaps were measured at four indexed points using a stereomicroscope at 20x magnification (Leica M205 C; Leica Microsystems GmbH, Wetzlar, Germany). Data were then analyzed (α = 0.05).

Results

Significant intergroup differences were observed (p = 0.0001). Group 3 (fully digital) exhibited the smallest mean marginal gap, followed by Groups 2 and 1. Post-hoc analysis confirmed significant differences between all pairs on the mesial, distal, and palatal surfaces (p < 0.05). On the labial surface, Group 3 remained superior to Group 2 (p = 0.0021); however, no significant difference was noted between Groups 1 and 3 (p = 0.8739).

Conclusion

Fully digital CAD/CAM milling of lithium disilicate provided superior vertical marginal accuracy compared to heat-pressed techniques. Incorporating CAD-milled wax patterns significantly improved the fit compared to conventional manual waxing.