Radiographic Evaluation of All Ceramic Crown Margins

Abstract

Statement of Problem: Radiographs aid in clinical determination of crown fit, specifically interproximal margins where tactile and visual methods can fail us. With the use of all ceramic materials surpassing ceramometal, it is beneficial to understand what limitations are present with this method to determine the correct marginal adaptation. Purpose: The purpose of this study was to assess if we can accurately identify crown margin closure via radiographs for all ceramic and ceramometal crown margins, and if not, to understand where the error lies. Materials and Methods: Individual IPS e.max, ZirPress, and ceramometal crowns were fabricated using a single prepared maxillary premolar and measured with light microscopy to ensure fit at the margin to below 20μm. The crowns were set up on a margin opening jig, and radiographs were made at 20μm increments starting at 0μm and finishing at 180μm for a total of 10 marginal adaptations. The threshold for closed versus open was >80μm. 80° and 90° radiographs were also made for each discrepancy to account for clinician variation in radiograph making. The 60 radiographs were then randomized and evaluated by prosthodontists and general dentists. Results: Individual evaluation accuracy of marginal adaptation was 48.8% for ceramometal crowns, 72.1% for e.max, and 76.9% for ZirPress. The scientific hypotheses were found to be true. When incorrectly evaluated, ceramometal crowns were significantly more likely to be evaluated acceptable when open margins were present, or as false positives. E.max and ZirPress were found to be more likely evaluated unacceptable with closed margins present. No significant difference was seen between general dentists and prosthodontists or between 80° and 90° variations except for ceramometal crowns which were more accurate for 90°. Conclusions: Within the limitations of this in vitro study, accuracy of marginal adaptation evaluations without clinical examination is not as high as would be expected. Ceramometal crowns tend to be incorrectly evaluated closed. Ceramic crowns (IPS e.max lithium disilicate and ZirPress) tend to be incorrectly evaluated open. No difference between prosthodontists and general dentists was evident in this study with relation to accuracy of evaluations. The goal of this study was to provide information to aid in marginal closure determination when evaluating crowns radiographically and guidance when examining crowns of different radiopacities with relation to the common inaccuracies found in the study.