J Korean Acad Prosthodont.  2016 Jul;54(3):253-258. 10.4047/jkap.2016.54.3.253.

Superimposition: a simple method to minimize occlusal adjustment of monolithic restoration

• Choi C
• Kim S

• KMID: 2344864
• DOI: http://doi.org/10.4047/jkap.2016.54.3.253

Abstract

The development of translucent zirconia enabled clinicians to choose a monolithic zirconia crown as one treatment modality in the posterior dentition. Careful occlusal adjustments are recommended for monolithic zirconia crowns because grinding zirconia inevitably causes phase transformation, which may deteriorate mechanical properties. intraoral scanners enable the clinician to scan and superimpose a complete tooth structure before preparation onto the prepared abutment. This technique helps to reproduce the original tooth form and occlusion of the patient. In this case report, prostheses were fabricated for patients with cracked or fractured tooth by applying intraoral scanner, Computer aided design-computer aided manufacturing (CAD-CAM) and monolithic zirconia crown to reproduce the occlusion of original tooth and to minimize occlusal adjustment. The clinical results were satisfactory in both esthetic and functional aspects.

Keyword

Computer aided design-computer aided manufacturing (CAD-CAM); Superimposition; Monolithic zirconia; Intraoral scanner

MeSH Terms

Crowns
Dentition
Humans
Methods*
Occlusal Adjustment*
Prostheses and Implants
Tooth

Figure

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  Fig. 1. Digital shade matching.

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  Fig. 2. Scanning tooth before preparation (maxillary left first molar).

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  Fig. 3. Digital image of the prepared tooth.

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  Fig. 4. (A) Image of tooth before preparation was superimposed onto the abutment, (B) Designed crown using superimposition.

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  Fig. 5. Delivery of zirconia crown.

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  Fig. 6. Cracked tooth case of maxillary right first molar. (A) A definite crack line was observed on the palatal surface of maxillary right first molar, (B) Occlusal view of maxillary right first molar before preparation, (C) Biogeneric copy of entire crown (superimposition), (D) The occlusion before tooth preparation was completely reproduced on the new restoration design by superimposition, (E) Delivery of zirconia crown.

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  Fig. 7. Crown fracture case of maxillary right first molar. (A) Crown fracture of distopalatal cusp on maxillary right first molar, (B) Occlusal view of maxillary right first molar before preparation, (C) Bio-copy excluding cusp of fractured area (occlusal view), (D) Bio-copy excluding cusp of fractured area (palatal view), (E) Superimposed images of the prepared abutment and biogeneric copy image excluding cusp fracture area, (F) Designed crown using double scanning, (G) Delivery of zirconia crown.

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  Fig. 8. (A) Occlusal contact point before tooth preparation, (B) Occlusal contact point of zirconia resoration after adjsutment.

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