Comparison of Fracture Strengths of Three Provisional Prosthodontic CAD/CAM Materials: Laboratory Fatigue Tests

Influence of Popular Beverages on the Fracture Resistance of Implant-Supported Bis-Acrylic Resin Provisional Crowns: An In Vitro Study

Implant-supported provisional restorations are critical for improving the esthetics and shaping of the peri-implant tissue. The mechanical properties of these provisional materials can be influenced by saliva, food, beverages, and interactions between these materials in the oral environment. Therefore, the integrity of provisional restorations should be preserved throughout the treatment period. This study aimed to evaluate the fracture strength of implant-supported polymethyl methacrylate (PMMA) provisional restorations made of computer-aided design and computer-aided manufacturing when immersed in different solutions at a controlled temperature of 37 °C for 7 days. Each analog-pillar-crown set was submerged in different liquids: 10 pieces were placed in distilled water then in tea, coffee, red wine, and Coca Cola® for 1 week at a controlled oral temperature of 37 °C. The samples were then subjected to fracture forces. The moment of fracture of the crown was recorded and compared with those of the other samples. Specimens immersed in distilled water (control group) had the highest fracture resistance (mean [M] = 1331.00 ± 296.74 N), while those immersed in tea had the lowest mean resistance to fracture (mean [M] = 967.00 ± 281.86 N). Nutritional deficiency and inappropriate eating habits influence the fracture strength of temporary crowns, thereby rendering them more elastic or less resistant to fractures.

The Influence of Saliva pH on the Fracture Resistance of Two Types of Implant-Supported Bis-Acrylic Resin Provisional Crowns-An In Vitro Study

Temporary restorations play a fundamental role in oral rehabilitation. A properly adapted implant-supported provisional restoration implies better esthetics, contouring and architectural modeling of the upper peri-implant tissue. This study aimed to evaluate the influence of oral pH on the fracture resistance of implant-supported provisional restorations made with two brands of bis-acrylic resin (LuxaCrown^® and Protemp™ 4) and to compare the fracture resistance of these two materials. Twenty crowns (ten manufactured using each brand) served as a control, and another forty crowns (twenty of each brand) were aged using artificial saliva with pHs of 4 or 7, for 7 days at 37 °C, in an attempt to simulate the behavior of these materials inside the oral cavity. Subsequently, all crowns were subjected to the application of a force at a constant speed, in a universal testing machine, until fracture was achieved. The LuxaCrown^® brand showed greater resistance to fracture than the Protemp™ 4 brand. Salivary pH did not influence the fracture resistance of provisional LuxaCrown^® crowns but did influence the fracture resistance of provisional Protemp™ 4 crowns.

Digital Design of Different Transpalatal Arches Made of Polyether Ether Ketone (PEEK) and Determination of the Force Systems

The aim of this study was to investigate whether the polymer polyether ether ketone (PEEK), which is approved for (dental) medical appliances, is suitable for the production of orthodontic treatment appliances. Different geometries of transpalatal arches (TPAs) were designed by Computer Aided Design (CAD). Out of a number of different designs and dimensions, four devices were selected and manufactured by milling out of PEEK. A finite element analysis (FEA) and a mechanical in vitro testing were performed to analyze the force systems acting on the first upper molars. Up to an activation (transversal compression) of 4 mm per side (total 8 mm), the PEEK TPAs generated forces between 1.3 and 3.1 Newton (N) in the FEA and between 0.7 and 3.2 N in the mechanical testing. The moments in the oro-vestibular direction were measured between 2.1 and 6.6 Nmm in the FEA and between 1.1 and 6.0 Nmm in the mechanical testing, depending on the individual TPA geometry. With the help of the FEA, it was possible to calculate the von Mises stresses and the deformation patterns of the different TPAs. In some areas, local von Mises stresses exceeded 154–165 MPa, which could lead to a permanent deformation of the respective appliances. In the in vitro testing, however, none of the TPAs showed any visible deformation or fractures. With the help of the FEA and the mechanical testing, it could be shown that PEEK might be suitable as a material for the production of orthodontic TPAs.