The Effect of the Digital Manufacturing Technique, Preparation Taper, and Cement Type on the Retention of Aged Anterior Provisional Crowns: An In Vitro Study

Abstract

A well-made provisional fixed prosthesis must present as a preview of the future prosthesis and may also augment the health of the abutments and periodontium. Provisional restorations have been prepared chairside with polymethyl methacrylate (PMMA) since time immemorial. CAD/CAM additive and subtractive technologies have revolutionized the fabrication of interim restorations in dental clinics. The current literature lacks substantial data about retention of provisional crowns manufactured using Computer-Aided Design/Computer-Aided Manufacturing (CAD/CAM) additive and subtractive techniques with various temporary cements. This in vitro study aims to assess and compare the retention of temporary/provisional anterior crowns based on the combined effect of different digital manufacturing techniques, preparation tapers, and the temporary cements used for cementation. Two maxillary right central incisor typodont teeth were prepared to receive all-ceramic crowns, one with a 10-degree taper and the other with a 20-degree taper. Forty 3D-printed working models with the 10° taper and forty working models with the 20° taper were prepared to receive the temporary crowns. Forty temporary crowns were 3D-printed and forty crowns were milled (20 from each taper group). Kerr Temp-Bond NE conventional cement and Kerr Temp-Bond clear cement were used for cementation in the two groups. The number of samples per test group was 10. All samples were thermocycled and subjected to a universal testing machine to measure the pull-off force until retention loss (N) under tension with a crosshead speed of 5 mm/min. The pull-off force was highest for group 8, i.e., 3D-printed crowns with a 20° taper and cemented with Kerr Temp-Bond clear cement, followed by groups 6, 7, 4, 5, 3, and 2. Group 1, i.e., milled crowns with 10° taper cemented with Kerr Temp-Bond NE conventional cement, exhibited the lowest pull-off retentive force. The clinical selection of long-term provisional crowns fabricated using 3D-printing technology, prepared with 10° or 20° tapers, and cemented with clear cement, is the most favorable in terms of the retention of provisional crowns. 3D-printed provisional crowns can be used as an alternative to conventional and CAD/CAM-milled crowns for long-term provisionalization.

Keywords

• provisional crowns
• 3D printing
• CAD/CAM milling
• taper
• temporary cement
• retention