Evaluation of a reinforced slot design for CEREC system to restore extensively compromised premolars

Lin, Chun-Li; Chang, Yen-Hsiang; Chang, Wen-Jen; Cheng, Ming-Hsiang

doi:10.1016/j.jdent.2005.05.009

« Previous Next »Journal of Dentistry
Volume 34, Issue 3 , Pages 221-229, March 2006

Evaluation of a reinforced slot design for CEREC system to restore extensively compromised premolars

Chun-Li Lin
- Department of Mechanical Engineering, Graduate Institute of Medical Mechatronics, Chang Gung University, 259 Wen-Hua 1st Road, Kwei-Shan, Tao-Yuan 333, Taiwan
- Corresponding author. Tel.: +886 3 211 8800x5759; fax: +886 3 211 8700.
Yen-Hsiang Chang
- Operative Dentistry, Chang Gung Memorial Hospital, 5, Fu-Hsing St., Kuei-Shan, Tao-Yuan, Taiwan
- Tel.: +886 3 328 1200x8328; fax: +886 3 327 8928.
Wen-Jen Chang
- Department of Industrial Engineering and Management, Ta-Hwa Institute of Technology, No. 1 Ta-Hwa Road, Hsiung-Lin, Hsinchu County, 307, Taiwan
- Tel.: +886 3 592 7700x2959; fax: +886 3 592 6848.
Ming-Hsiang Cheng
- Graduate Institute of Medical Mechatronics, Chang Gung University, 259 Wen-Hua 1st Road, Kwei-Shan, Tao-Yuan 333, Taiwan
- Tel: +886 3 211 8800x3197; fax: +886 3 211 8700.

Received 1 March 2004; received in revised form 16 May 2005; accepted 19 May 2005.

Summary

Objectives

The structural stability and adhesive strength of a large-cavity premolar with a CEREC restoration is a frequent problem in long-term use. This study sought to determine whether an additional reinforced slot could increase tooth/ceramic retention using finite element (FE) analysis and fracture testing.

Methods

The cavity was designed in a typical MODL restoration failure shape when the lingual cusp has been lost. Two FE restored-tooth models with different cavity designs were created using image processing, contour stacking, and mesh generation. Interfacial (normal and shear) stresses were then calculated with and without the slot design for restored teeth under lateral and axial forces and different interfacial conditions (bonded and de-bonding). For validation, a fracture experiment was performed with and without reinforced slot designs for large ceramic CEREC restorations.

Results

The maximum stresses at the buccal wall increased when a lateral occlusal force acted on the restored tooth with a slot design. Conversely, the interfacial stresses decreased when the restored tooth received a uniform axial occlusal force. After de-bonding on the buccal tooth/ceramic interface, the stresses increased by an average factor of three over those obtained with a bonded interface. The fracture forces were consistent with the tendencies predicted in FE analyses.

Conclusions

An additional reinforced slot for the CEREC restoration of a large cavity could increase retention when a restored tooth receives an axial occlusal load. However, the benefits of a slot seem to be doubtful for a premolar often subjected to a lateral load.

Keywords: CEREC, Finite element analysis, Slot, Biomechanics