restorative dentistry

Key Points

In brief

• The resin-bonded all-ceramic crown (RBC) has been in use for the past 10 years. The majority are placed in general practice.

• A variety of guidelines have been advocated for the design of preparations — these are essentially from the manufacturers of the ceramics.

• This study examined 180 dies for RBCs on 132 working models sent to four large dental laboratories.

• It was found that there was a tendancy that the guidelines are not being fully adhered to.

• Postgraduate training of clinicians in general dental practice is probably necessary to improve the knowledge of the required preparation designs.

Abstract

Objective

To investigate variations in tooth preparations for resin-bonded all-ceramic crowns (RBCs) in general dental practice (GDP).

Design

Laboratory-based retrospective analysis of dies for RBCs.

Setting

General dental practice in the UK and Ireland (2000).

Methods

A sample (n = 132) of laboratory models containing 180 tooth preparations for RBCs, featuring work from different general dental practitioners was obtained from four commercial dental laboratories. Aspects of the preparations were quantified and compared with accepted criteria defined following a review of the literature.

Results

The teeth found to be most frequently prepared for RBCs were maxillary incisors (41%). Margin positions were variably positioned with 29% of the preparations on the buccal aspect having subgingival margins. There were many tooth preparation dies for low fusing RBCs (47%) and Chameleon Fortress RBCs (62%) demonstrating overpreparation in the mesiodistal plane. The majority of the margins (84% buccally and 79% lingually) of the dies examined, exhibited appropriate shoulder or chamfer finishes. Of the Chameleon Fortress preparations analysed, 86% had been underprepared occlusally. 42% of the teeth had been prepared with no regard to tooth morphology and demonstrated just one plane of reduction. The majority (93%) of the clinicians failed to provide any information regarding the shade of the prepared tooth stump.

Conclusions

On the evidence of this survey of this sample of general dental practitioner's work, it was found that relevant guidelines for the preparations of RBCs are not being fully adhered to.

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