Journal of Dental Sciences
Volume 4, Issue 3 , Pages 110-117, September 2009

Fracture resistance and failure modes of CEREC endo-crowns and conventional post and core-supported CEREC crowns

  • Chia-Yu Chang

      Affiliations

    • Department of Operative Dentistry, Chang Gung Memorial Hospital, Tao-Yuan, Taiwan
    • ,
  • Jau-Shing Kuo

      Affiliations

    • Department of Operative Dentistry, Chang Gung Memorial Hospital, Tao-Yuan, Taiwan
    • ,
  • Yang-Sung Lin

      Affiliations

    • Department of Mechanical Engineering, Chang Gung University, Kweishan, Taoyuan, Taiwan
    • ,
  • Yen-Hsiang Chang

      Affiliations

    • Department of Operative Dentistry, Chang Gung Memorial Hospital, Tao-Yuan, Taiwan
    • Corresponding Author InformationCorresponding author. Department of Operative Dentistry, Chang Gung Memorial Hospital, 123, Ding-Hu Road, Kueishan, Taoyuan 33345, Taiwan

Received 14 May 2009; accepted 15 August 2009.

Article Outline

Background/Purpose

The purpose of this in vitro study was to compare the fracture resistance and failure modes of CEREC endo-crowns with the CEREC classic designed crown supported with glass fiber-reinforced composite posts and composite cores. The influences of thermal cycling and fatigue loading on both types of restorations were also investigated.

Materials and methods

Twenty extracted intact maxillary premolars were randomly divided into two groups (C and E). The crown portion of the specimens was removed to 1.5 mm above the cementoenamel junction (CEJ). All specimens were endodontically treated with a nickel-titanium rotary system and obturated with gutta-percha by a vertical compaction technique. In group C (n = 10), teeth were restored with glass fiber-reinforced composite posts and composite cores with a 1.0-mm wide circumferential shoulder margin at the CEJ and a 1.5-mm ferrule. In group E (n = 10), teeth were prepared for fabrication of CEREC endo-crowns. Both types of ceramic crowns were produced from ProCAD ceramic blocks utilizing a CEREC 3D CAD-CAM unit, and these were bonded to the preparations with an adhesive system and composite resin cement. Teeth were thermally cycled (2000 cycles of 5°C/55°C with a dwell time of 30 seconds,) and fatigue loaded (20,000 cycles at 5 kg and 3 Hz) in a custom-made fatigue simulator. All specimens were loaded in a universal testing machine with a cross-head speed of 0.5 mm/s until fracture occurred. Fracture resistance and failure modes were statistically evaluated with a t test and χ2 test.

Results

The mean fracture resistance ± standard deviation was recorded as follows: 1163.30±163.15 N for group C and 1446.68±200.34 N for group E. A significant difference was found between groups with respect to fracture resistance (P < 0.05). Regarding failure modes, most specimens of both groups exhibited unfavorable fractures, and no significant difference was found between the two groups.

Conclusion

The bonded ceramic endo-crowns showed a significantly higher fracture resistance than the classic reinforced and designed group and, therefore, offer a feasible alternative for severely damaged teeth.

Key Words:  CAD-CAM , CEREC , endo-crown , failure modes , fracture resistance

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PII: S1991-7902(09)60016-7

doi:10.1016/S1991-7902(09)60016-7

Journal of Dental Sciences
Volume 4, Issue 3 , Pages 110-117, September 2009

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