Crown preparation – limited high quality evidence available


Tooth preparation for full-coverage restorations is a common element of dental practice and the clinical longevity is related to the quality of this preparation. The objective of this review was to assess the current knowledge about tooth preparation for full-coverage restorations regarding the following aspects: biological parameters, preparation geometry, and technical conditions.


Searches were conducted in the Medline, DIMDI (German Institute for Medical Documentation and 
and the Cochrane Library databases. Additional hand searching was conducted in some German language journals not indexed on Medline. Citations were classified according to the Oxford Centre for Evidence-Based Medicine levels of evidence.


  • 117 studies were included; 11 reviews, 23 clinical studies, 82 in vitro studies and 1 animal study.
  • A narrative summary biological parameters (tooth structure removal and periodontal tissues) Preparation geometry and technical aspects together with a table summarising the evidence grading for 21 statements was provided.


The authors concluded: –

The basic form of a preparation has not changed substantially over the years, although new materials like all-ceramic systems have their own demands with regard to the details of the preparation’s geometry. Estimating how much of the tooth structure can be removed without harming the tooth remains one of the biggest problems, if not the main difficulty, during tooth preparation. As the periodontal tissues may be affected by the restoration margin, a supragingival position of the margin should be preferred whenever possible. No finish line design has yet proven to be superior with regard to the marginal accuracy of the subsequent restoration. Instead, good detectability of the margin for the dental technician or intraoral scanning devices appears to be of primary importance in order to achieve a good fitting restoration.


This review has searched three relevant databases and all stages were carried out by the 3 authors, but it is not clear if this was done independently. In addition to clinical studies, animal and in vitro studies were included and although an overall evidence grading is given for each of the parameters the process for assessing individual study quality and allocating the evidence grading is not described.

This review covers a wide range of questions related to full coverage restorations and the limited number of clinical studies available should be noted. The best available evidence was for the positioning of gingival margins with a cohort and 4 other studies finding that, subgingivally placed restoration margins cause periodontal inflammations. The authors of this review were also in agreement with the findings of the review on the occlusal convergence angle of crown preparation we considered last week (Dental Elf – 17th March 2015).


Podhorsky A, Rehmann P, Wöstmann B. Tooth preparation for full-coverage restorations-a literature review. Clin Oral Investig. 2015 Mar 7. [Epub ahead of print] PubMed PMID: 25743567

Dental Elf -17th March 2015 – Tooth preparation for crowns

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