J Dent Rehabil Appl Sci.  2024 May;40(2):72-81. 10.14368/jdras.2024.40.2.72.

Comparison of marginal and internal fit of 3-unit monolithic zirconia fixed partial dentures fabricated from solid working casts and working casts from a removable die system

• Lee WS

• KMID: 2562751
• DOI: http://doi.org/10.14368/jdras.2024.40.2.72

Abstract

Purpose
This study aimed to assess the marginal and internal fit of 3-unit monolithic zirconia fixed partial dentures (FPDs) fabricated via computer-aided design and computer-aided manufacturing (CAD/CAM) from solid working casts and removable die system.
Materials and Methods
The tooth preparation protocol for a zirconia crown was executed on the mandibular right first premolar and mandibular right first molar, with the creation of a reference cast featuring an absent mandibular right second premolar. The reference cast was duplicated using polyvinyl siloxane impression, from which 20 working casts were fabricated following typical dental laboratory procedures. For comparative analysis, 10 FPDs were produced from a removable die system (RD group) and the remaining 10 FPDs from the solid working casts (S group). The casts were digitized using a dental desktop scanner to establish virtual casts and design the FPDs using CAD. The definitive 3-unit monolithic zirconia FPDs were fabricated via a CAM milling process. The seated FPDs on the reference cast underwent digital evaluation for marginal and internal fit. The Mann-Whitney U test was applied for statistical comparison between the two groups (α = 0.05).
Results
The RD group showed significantly higher discrepancies in fit for both premolars and molars compared to the S group (P < 0.05), particularly in terms of marginal and occlusal gaps. Color mapping also highlighted more significant deviations in the RD group, especially in the marginal and occlusal regions.
Conclusion
The study found that the discrepancies in marginal and occlusal fits of 3-unit monolithic zirconia FPDs were primarily associated with those fabricated using the removable die system. This indicates the significant impact of the fabrication method on the accuracy of FPDs.

Keyword

monolithic zirconia fixed partial dentures; dental working cast; computer-aided design and manufacturing; marginal and internal fit; removable die system

Figure

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  Fig. 1 Study diagram. FPD: fixed partial denture; CAD/CAM: computer-aided design and computer-aided manufacturing.

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  Fig. 2 Working casts. (A) Solid working cast, (B) Working cast with removable dies.

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  Fig. 3 Analysis region of the marginal and internal fit.

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  Fig. 4 Comparison of the marginal and internal fit of the three-unit monolithic zirconia FPDs fabricated via solid working casts and removable die system. (A) Overall region, (B) Marginal gap, (C) Axial gap, (D) Occlusal gap.

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  Fig. 5 Comparison of deviations in the color difference map of the 3-unit monolithic zirconia FPDs fabricated via solid working casts (A) and removable die system (B).

Reference

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