Disc-shaped specimens with a diameter of 16 mm and thickness of 3 mm were fabricated to quantify the wear of different materials. Sixteen specimens of each splint material were tested. The composition of the materials and the associated information from the manufacturers are listed in Table 1.
Table 1
The materials used in this study
Occlusal splint material | Code | Manufacturer | Composition | Lot no |
Sr Ivocap Heat Cured | SRI | Ivoclar Vivadent, Shaan, Liechtenstein | Methyl Methacrylate Ethylene Dimethacrylate | YC353P07 |
Valplast | VP | Valplast International Corp., Long Beach, NY, USA | Polyamide | 3009A |
SR Ivocap Elastomer | SRE | Ivoclar Vivadent, Shaan, Liechtenstein | Methyl Methacrylate | YG072L04 |
Eclipse | EC | Dentsply International, York, PA | Urethane Oligomers | 070228 |
Antagonist material | Code | Manufacturer | Composition | Lot no |
inCoris TZI | TZI | SironaDental Systems, Bensheim, German | Monoblock zirconia, ZrO2 + HfO2 + Y2O3 (≥ 99.0), Y2O3 (> 4.5−≤6.0),HfO2 (≤ 5), Al2O3 (≤ 0.5), Other oxides (≤ 0.5) | 2014161366 |
IPS e.max Press | IM | Ivoclar Vivadent, Shaan, Liechtenstein | Lithium disilicate glass-ceramic SiO2(57–80%)Li2O(11–19%), K2O (0–13%), P2O5( 0–11%) ZrO2 (0–8%), ZnO (0–8%), other oxides and ceramic pigments | U51802 |
Enamel | E | Maxillary Human third molar tubercle | 96 wt.% inorganic material (Ca10(PO4)6·2(OH) )and 4 wt.% organic material and water | |
The test surfaces of all specimens were smoothened using waterproof silicon carbide grinding papers of 220, 500, 800, and 1200 grit (Struers A/S, Ballerup, Denmark). The specimens were finished with a
rag wheel and fine pumice slurry, followed by the application of a universal polishing paste. The specimens were finished with a cloth and thin pomade, followed by polishing paste application. All specimens were stored in distilled water at 25 °C for 2 weeks before testing. The specimen surfaces was polished by a single operator using an OptraFine ceramic polishing system (Ivoclar Vivadent), based on the manufacturer’s recommendations. OptraFine F finishers (light blue) were used with water to smoothen the ceramic surface. OptraFine P polishers (dark blue) were used with water to polish the ceramic surface. Finally, the OptraFine HP high polishing brush and paste were used without water to obtain a high-luster gloss on the ceramic surface.
InCoris TZI C (Dentsply Sirona) and IPS e.max Press (Ivoclar Vivadent) specimens were fabricated as spheres with a height of 5 mm and a diameter of 4 mm according to the manufacturer's manual. After the surfaces of the specimens were free of roughness, pre-polishing was performed with a diamond rubber brightener (OptraFine F). Fine polishing was performed with a very bright rubber polish (OptraFine P).
Calculus and periodontal tissues on enamel and cementum surfaces were removed from the teeth using the cavitron device (Scalex 800, Dentamerica, California, USA). The cleaned teeth were shaped in exactly the same type as the other antagonists with the help of diamond burs. After polishing (Prophet Paste, Sultan Chemist Inc., York, USA) and brushing (Stoddard, Hertfordshire, England) the cutting line is marked with a pen so that teeth are angled about 90 degrees below the level of the cervical line and cut with a diamond disc (Horico discs Diaflex F 358F, Horico Dental Hopf, Ringleb & Co. GmbH & Cie, Berlin, Germany).
All antagonist specimens were embedded in autopolymerizing acrylic resin (Technovit 4000; Heraeus Kulzer). The acrylic resin was mixed and poured in custom-made Teflon holders (Analitik Mühendislik, Gaziantep, Türkiye).
The wear test was performed using the Chewing Simulator CS-4 (Willytec ⁄ SD Mechatronik GmbH, Feldkirchen-Westerham, Germany) (Fig. 1), which is a three-body wear machine, in which water or other conditions can be used with programmable (5–55 °C) thermocycling. The CS-4 can make gnashing, slipping, and striking movements with a 50-N force when loaded with weight, for up to 120,000 cycles.
The specimens were prepared according the plastic specimen holders. Occlusal splint specimens were embedded in acrylic resin in the sub-specimen holder in the chewing simulator. The enamel, IPS e.max Press, and InCoris TZI C specimens were embedded in acrylic resin in the upper specimen holder for use as antagonist materials and fixed with fixing screws. All test groups to were subjected to a load of 50 N.
The specimens were subjected to 30,000 loading cycles and each surface was analyzed after 10,000 cycles. Notably, 10,000 cycles are approximately equal to the maximum total number of chewing cycles experienced in 1 week by all-day splint users, and 2 weeks for night-time users, given the established range of 800–1400 chewing cycles per day 12. A vertical load of 50 N was applied at a frequency of 1.6 Hz. After vertical loading, horizontal movement of 2 mm was performed. Half of the specimens underwent an aging procedure in a dry condition. During wet aging, demineralized water at 30 °C was used for continuous rinsing to remove the abraded particles from the sample (and to avoid any three-body wear processes) and to simulate the wet condition of the oral cavity. Owing to the uncertainty of the temperature used in other studies (temperatures of 25–37 °C were used), the default temperature of the simulator was set at 30 °C9,10,13.
Each specimen was analyzed with a three-dimensional (3D) laser scanner (LAS-20, SD Mechatronik GMBH) and surface analysis program (Geomagic Control of 3D Systems; SD Mechatronik GMBH,) after removing it from the cyclic wear device.
Data were analyzed using IBM SPSS V23. The Shapiro-Wilk test was used for testing the normal distribution of the variables. The main effects and interactions of the average antagonist wear quantities with the material, cycle, and condition factors were investigated using univariate variance analysis. Multiple comparisons were performed using the Games-Howell test. The results of the analyses were presented as arithmetic mean ± standard error. p < 0.05 was considered statistically significant.