A Novel Design for Full-coverage Crown to Assist for Future Endodontic Treatment: A Survey on Difficulties of Access Cavity through Crowns and Pilot In-vitro Study Testing the New Design

Many challenges are faced during opening cavity access through crowns. This study aimed to present a novel design for a full-coverage crown to overcome the difficulties of opening endodontic access and to facilitate root canal treatment.

This study comprised two parts: (I) the survey, a cross-sectional questionnaire-based survey was conducted among dentists to assess the degree and type of challenges, complications and difficulties of opening the endodontic access cavity through zirconia and porcelain-fused-to-metal (PFM) crowns, and (II) the experiment, a novel crown design that include a mark occlusally as a guide to access precisely into the pulp chamber was fabricated by taking cone-beam computed tomography scans along with digital impressions of teeth prepared to receive zirconia crowns. The scans were merged with the digital impressions to detect the exact location of the pulp chamber and to make a guide on the crown over the pulp. Subsequently, the crowns were cut using a computer-aided design/computer-aided milling machine. Twenty-one samples in three equal groups (control 1, natural teeth; control 2, full zirconia crowns; and the experimental group, the novel design) were accessed by one operator. The following criteria were evaluated: time spent, quality, and size of the access cavity. The data were collected and analyzed using the SPSS software program at a significance level of P-value < 0.05.

In total, 440 dentists from 28 countries participated in this survey. Generally, the participants reported moderate and difficult degrees of opening through crowns. The most reported challenges and complications were the time spent in the opening and the fracture or chipping of the crown material. For the experiment, no significant difference was found among the groups in relation to the time spent for opening (P = 0.57), with the least required time of access for the experimental group. In addition, no significant difference was found in the quality and size of the access cavity (P = 0.775) among the groups.

Endodontic cavity access through zirconia and PFM crowns is difficult and time-consuming. The novel proposed design utilizing digital dental technology can overcome these issues by preserving the crown, decreasing chair time, and providing less complicated treatment.