Comparative evaluation of fracture resistance of anterior provisional restorations fabricated using conventional and digital techniques - An in vitro study

Abstract

Aim: Comparative evaluation of the fracture resistance of anterior provisional crowns fabricated by conventional and digital techniques.

Settings and design: Department of Prosthodontic, PGIDS, Rohtak, An in-vitro - Comparative study.

Materials and methods: Thirty recently extracted maxillary central incisors were handpicked. Tooth preparation was done according to the principles of tooth preparation. A single-step impression technique was used for impression making of the prepared tooth and stone models were poured. Extracted teeth were divided into 3 groups (n = 10 each) based on provisional crown fabrication technique. A bis-acryl-based (Protemp 4 3M ESPE) resin was used to fabricate the provisional crowns by the conventional indirect technique. The rest of the stone models (20) were scanned using lab scanner (Dentsply Sirona InLab EOS X5). CAD/CAM provisional material (Dentsply Sirona multilayer PolyMethyl Methacrylate) PMMA disc was used for fabrication of provisional restoration through milling technique. 3D printed temporary provisional material (NextDent C&B resin) was utilized for 3D printed provisional crowns. Cementation of provisional crowns was done using eugenol free temporary luting cement (Templute, Prime dental). All cemented provisional crowns were subjected to load under Universal Testing Machine. The maximum load to produce fracture for each specimen was recorded in Newton (N).

Statistical analysis used: Shapiro-Wilk test was employed to test the normality of data. Kruskal- Wallis Test was used to compare the mean fracture resistance between all the groups. For intergroup comparison Mann-Whitney U Test was used.

Results: The mean fracture resistance of group I (Conventional technique) was found to be 558.8459700 ± 22.33 N; for group II (CAD/CAM technique) 960.8427200 ± 37.49 N and for group III (3D Printed technique) 1243.1774000 ± 68.18 N. Group I had the least fracture resistance value while group III showed maximum value.

Conclusion: Provisional crowns fabricated using 3-D printing technique showed higher fracture resistance followed by CAD/CAM technique and conventional technique. Additive manufacturing of provisional crowns using 3-D printing technique could be considered a reliable and conservative method for the fabrication of stronger provisional restorations.

Keywords: Computer-aided design and computer/aided manufacturing technology; fracture resistance; provisional restoration; three-dimensional printing.

Figure 1

(a) Scanning of the stone die, (b) STL file of scanned stone die, (c) Designing of provisional crowns, (d) Milled provisional crowns, STL: Surface tessellation language

Figure 2

(a) Activation of NextDent C and B resin, (b) Orientation of provisional crown STL files on printing table, (c) 3D Printed crowns, (d) Post curing of 3D printed crown, 3D: Three-dimensional

Figure 3

(a) Testing of specimen under Universal Testing Machine, (b) Fracture crown after testing

Graph 1

Fracture resistance of provisional crowns fabricated by conventional, CAD/CAM and 3D printed techniques. CAD/CAM: Computer-aided design and computer-aided manufacturing, 3D: Three-dimensional