J Korean Acad Prosthodont.  2016 Jul;54(3):226-233. 10.4047/jkap.2016.54.3.226.

Comparison of micro CT and cross-section technique for evaluation of marginal and internal fit of lithium disilicate crowns

• Ko IS
• Kim JM
• Cho HW

• KMID: 2344860
• DOI: http://doi.org/10.4047/jkap.2016.54.3.226

Abstract

PURPOSE
The purpose of this study was to evaluate the adaptation of lithium disilicate crowns fabricated by CAD-CAM (computer aided design-computer aided manufacturing) and heat-press technique to compare two different measurement methods in assessing fit of the ceramic crowns: micro CT and cross-section technique.
MATERIALS AND METHODS
A prepared typodont mandibular molar for ceramic crown was duplicated and ten dies were produced by milling the PMMA (polymethylmethacrylate) resin. Ten vinyl polysiloxane impressions were made and stone casts were produced. Five dies were used for IPS e.max Press crowns with heat-press technique. The other five dies were used for IPS e.max CAD crowns with CAD-CAM technique. Ten lithium disilicate crowns were cemented on the resin dies using zinc phosphate cement with finger pressure. The marginal and internal fits in central buccolingual plane were evaluated using a micro CT. Then the specimens were embedded and cross-sectioned and the marginal and internal fits were measured using scanning electronic microscope. The two measurement methods and two manufacturing methods were compared using Mann-Whitney U test (SPSS 22.0).
RESULTS
The marginal and internal fit values using micro CT and cross-section technique were similar, showing no significant differences. There were no significant differences in adaptation between lithium disilicate crowns fabricated with CAD-CAM and heat-press technique.
CONCLUSION
Both micro CT and cross-section technique were acceptable methods in the evaluation of marginal and internal fit of lithium disilicate crown. There was no difference in adaptation between lithium disilicate crowns fabricated with CAD-CAM and heat-press technique except occlusal fit.

Keyword

Micro CT; Marginal fit; Internal fit; Computer aided design-computer aided manufacturing (CAD-CAM)

MeSH Terms

Ceramics
Computer-Aided Design
Crowns*
Fingers
Lithium*
Molar
Polymethyl Methacrylate
Siloxanes
Zinc Phosphate Cement
Lithium
Polymethyl Methacrylate
Siloxanes
Zinc Phosphate Cement

Figure

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  Fig. 1. Prepared resin master die.

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  Fig. 2. Micro CT analysis of adaptation.

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  Fig. 3. Eight reference points showing sites of marginal fit (1, 8), cervical fit (2, 7), axial fit (3, 6) and occlusal fit (4, 5).

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  Fig. 4. Cross-sectioning of resin die-ceramic crown complex.

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  Fig. 5. SEM analysis of adaptation. LDS: lithium disilicate.

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