Two-body wear of occlusal splint materials

Wear resistance of 3D printed occlusal device materials

STATEMENT OF PROBLEM

Three-dimensional (3D) printing offers an efficient method of producing occlusal devices; however, their wear resistance is poorly understood.

PURPOSE

The purpose of this in vitro study was to compare the wear resistance of flexible and rigid 3D printed occlusal device materials with milled and conventionally processed occlusal device materials.

MATERIAL AND METHODS

Blocks (n=8) of 3 flexible 3D printed materials (KeySplint Soft, NightGuard Flex 2, SmileGuard), 2 rigid 3D printed materials (KeySplint Hard, NightGuard Firm 2), 1 milled material (Ceramill A-Splint), 1 thermoform material (Erkoloc-Pro), 1 light-polymerized material (Eclipse Prosthetic Resin), 1 heat-polymerized material (Excel Formula Heat Cure Denture Base Material), and 1 autopolymerized material (Great Lakes Splint Resin Acrylic) were prepared and wet polished with 1200-grit SiC paper. The specimens were placed in a modified Alabama wear testing device with spherical zirconia antagonists. The devices applied a 20-N load and 2-mm horizontal slide for 400 000 cycles, and the test was run in a 33% glycerin solution. Following the wear test, the volumetric wear was measured with an optical profilometer. The Vickers microhardness of the materials was also measured (n=3). Volumetric wear and microhardness were compared with 1-way ANOVAs and Tukey post hoc analyses (α=.05).

RESULTS

Significant differences were found between the wear of the different occlusal device materials (P<.001). The rigid 3D printed materials experienced similar wear as the light-polymerized, heat-polymerized, and milled occlusal device materials. The autopolymerized and thermoformed occlusal device material experienced significantly more wear (P<.05). The flexible 3D printed materials had the significantly greatest wear (P<.05). A statistically significant, strong negative correlation between hardness and volumetric wear was found (r=-.93; P<.001).

CONCLUSIONS

Rigid 3D printed occlusal device materials exhibit a high degree of wear resistance; however, flexible 3D printed occlusal device materials exhibit relatively low wear resistance.

Effect of layer thickness and polishing on wear resistance of additively manufactured occlusal splints

OBJECTIVE

To evaluate the effect of polishing and layering thickness on the wear resistance of 3D-printed occlusal splint materials.

METHODS

Specimens with 3 different layer thicknesses (50, 75, 100 µm) were produced in the form of a disc 3 mm thick using V-Print splint resin on a 3D-printer with digital light processing technology. (n = 16 for each thickness) All specimens were washed and cured according to the manufacturer's instructions. Half of the specimens of each layer thickness were polished with silicon carbide papers. All specimens were subjected to 120.000 cycles of a chewing simulator for 2-body wear tests. Before and after the wear test, the specimens were scanned with a laser scanner, and the images were overlaid using a 3D analysis program and the volume loss was calculated. The wear patterns of the specimens were examined under a scanning electron microscope. Statistical evaluation was performed using a Shapiro-Wilk test, 2-way ANOVA, 1-way ANOVA, and Tukey post hoc test (α = 0.05).

RESULTS

While polishing had a significant effect (p = 0.003) on the wear volume of the occlusal splints, layer thickness (p = 0.105) and their interaction between polishing and layer thickness (p = 0.620) did not significantly affect the wear volume. Regardless of the polishing, the lowest mean wear was observed for D50 (0.064 mm3), followed by D75 (0.078 mm3), and D100 (0.096 mm3). However, a significant difference was observed only between polished D50 and unpolished D100.

CONCLUSION

The polished 3D-printed occlusal splint resin showed higher wear resistance than the unpolished one, regardless of the layer thickness.

CLINICAL SIGNIFICANCE

Since different layer thicknesses of 50 µm and greater had no effect on the wear resistance of the material, a layer thickness of 100 µm may be preferred for faster printing. However, polishing occlusal splints may reduce the amount of wear and improve clinical performance.

Effect of material and antagonist type on the wear of occlusal devices with different compositions fabricated by using conventional, additive, and subtractive manufacturing

STATEMENT OF PROBLEM

Additive (AM) and subtractive (SM) manufacturing have become popular for fabricating occlusal devices with materials of different chemical compositions. However, knowledge on the effect of material and antagonist type on the wear characteristics of occlusal devices fabricated by using different methods is limited.

PURPOSE

The purpose of this in vitro study was to evaluate the effect of material and antagonist type on the wear of occlusal devices fabricated by using conventional manufacturing, AM, and SM.

MATERIAL AND METHODS

Two-hundred and forty Ø10×2-mm disk-shaped specimens were fabricated by using heat-polymerized polymethylmethacrylate (control, CM), AM clear device resin fabricated in 3 different orientations (horizontal [AMH], diagonal [AMD], and vertical [AMV]), SM polymethylmethacrylate (SMP), and SM ceramic-reinforced polyetheretherketone (SMB) (n=40). Specimens were then divided into 4 groups based on the antagonists: steatite ceramic (SC); multilayered zirconia (ZR); lithium disilicate (EX); and zirconia-reinforced lithium silicate (ZLS) used for thermomechanical aging (n=10). After aging, the volume loss (mm3) and maximum wear depth (μm) were digitally evaluated. Data were analyzed with 2-way analysis of variance and Tukey honestly significant difference tests (α=.05).

RESULTS

The interaction between the device material and the antagonist affected volume loss and maximum depth of wear (P<.001). AMH had volume loss and depth of wear that was either similar to or higher than those of other materials (P≤.044). When SC was used, CM had higher volume loss and depth of wear than AMV, and, when EX was used, AMD had higher volume loss and depth of wear than SMP (P≤.013). SC and ZR led to higher volume loss of CM and AMH than EX and led to the highest depth of wear for these materials, while ZR also led to the highest volume loss and depth of wear of AMD and AMV (P≤.019). EX led to the lowest volume loss and depth of wear of AMV and SMP and to the lowest depth of wear of AMH (P≤.021). Regardless of the antagonist, SMB had the lowest volume loss and depth of wear (P≤.005).

CONCLUSIONS

AMH mostly had higher volume loss and depth of wear, while SMB had the lowest volume loss, and its depth of wear was not affected by the tested antagonists. ZR mostly led to higher volume loss and maximum depth of wear, while EX mostly led to lower volume loss and maximum depth of wear of the tested occlusal device materials.

Mechanical and chemical characterization of contemporary occlusal splint materials fabricated with different methods: a systematic review

OBJECTIVE

To systematically review studies on various occlusal splint materials and describe their mechanical and chemical properties.

METHODS

MEDLINE (PubMed), Scopus, and Web of Science searches were conducted for in vitro studies focusing on occlusal splint materials. Two reviewers performed an assessment of the identified studies and data abstraction independently, and this was complimented by an additional hand search. The articles were limited to those in the English language that were published between January 1st, 2012, and December 1st, 2022.

RESULTS

The initial search yielded 405 search results of which 274 were selected for full-text review following abstract evaluation. 250 articles that did not meet the inclusion criteria were excluded, and the remaining 25 articles (with 1 article identified from the reference lists of included articles) providing mechanical and chemical values were used in this review. Poly methyl methacrylate (PMMA) -based occlusal splint materials showed the highest values in terms of hardness, wear resistance, flexural strength, flexural modulus, e-modulus, and fracture toughness. The material group with the highest water sorption and water solubility was 3D printed (PR) splint materials. In addition, the lowest degree of double bond conversion was also observed in this group of materials.

CONCLUSIONS

The outcome of this review suggests that mechanically and chemically acceptable properties can be attained with PMMA-based occlusal splint materials using both conventional and digital production methods. PR splint materials should not be considered as the primary choice for long-term treatments due to their low mechanical and chemical properties.

CLINICAL RELEVANCE

This review provides clinical recommendations for selecting the appropriate material and fabrication method for occlusal splints while taking the patients' needs and the materials´ mechanical and chemical properties into account.

CAD-CAM and analog occlusal splints comparison based on the amount of occlusal adjustments. 3D analysis of the volumetric changes: A pilot study

OBJECTIVE

To evaluate the volumetric changes on occlusal surface of computer-aided design and computer-aided manufacturing (CAD-CAM) occlusal devices fabricated following a fully digital workflow after occlusal adjustment, compared to those fabricated with an analog workflow.

MATERIALS AND METHODS

Eight participants were included in this clinical pilot study, receiving two different occlusal devices fabricated with two different workflows, fully analog and fully digital. Every occlusal device was scanned before and after the occlusal adjustments to compare the volumetric changes using a reverse engineering software program. Moreover, three independent evaluators assessed a semi-quantitative and qualitative comparison using visual analog scale and dichotomous evaluation. The Shapiro-Wilk test was performed to validate normal distribution assumption, and a dependent t-Student test for paired variables was used to determine statistically significant differences (p-value < 0.05).

RESULTS

The root mean square value was extracted from the 3-Dimensional (3D) analysis of the occlusal devices. The average values of the root mean square were higher for the analogic technique (0.23 ± 0.10 mm) than the digital technique (0.14 ± 0.07 mm) but the differences were not statistically significant (paired t-Student test; p = 0.106) between the two fabrication techniques. The semiquantitative visual analog scale values between the impression for the digital (5.08 ± 2.4 cm) and analog (3.80 ± 3.3 cm) technique were significant (p < 0.001), and statistically significant differences values were assessed for evaluator 3 compared to the other evaluators (p < 0.05). However, the three evaluators agreed on the qualitative dichotomous evaluation in 62% of the cases, and at least two evaluators agreed in 100% of the evaluations.

CONCLUSIONS

Occlusal devices fabricated following a fully digital workflow resulted in fewer occlusal adjustments, as they could be a valid alternative to those fabricated following an analog workflow.

CLINICAL SIGNIFICANCE

Fabricated occlusal devices following a fully digital workflow could have some advantages over analog workflow such reduce occlusal adjustments at delivery appointment, which can result in reduced chair time and therefore increased comfort for the patient and clinician.

Evaluation of enamel wear by 3 occlusal splint materials: An in vitro study

STATEMENT OF PROBLEM

Occlusal devices used to manage bruxism have been commonly fabricated from polymethyl methacrylate with the powder-liquid technique. More recently, Vertex ThermoSens (VTS) and the biocompatible high-performance polymer (BioHPP), an optimized material having polyetheretherketone (PEEK) as its basis, have been used, but little is known about the wear of these materials on human enamel.

PURPOSE

The purpose of this in vitro study was to assess via a mastication simulation test how 3 occlusal device materials affected the wear and roughness of enamel antagonists.

MATERIAL AND METHODS

A noncontact 3D optical profilometer was used to measure the enamel surface roughness (Ra) against 3 occlusal device materials: vertex regular, VTS, and PEEK high-performance polymer (BioHPP). A dual-axis mastication simulator was used to perform a 2-body wear test on specimens from each group. The test consisted of 10 000 cycles with a 70-N force and 5 to 55 °C thermocycling. Following simulated mastication, the weight of each specimen and the Ra change were compared with the Kolmogorov-Smirnov test, paired specimens t test, Wilcoxon signed-rank test, and 1-way analysis of variance (α=.05).

RESULTS

The polyamide group caused the lowest amount of enamel wear (P<.05), while the heat-polymerized acrylic resin group induced the largest amount of enamel wear (P<.05). For polyamide and PEEK, the change in enamel surface roughness exhibited a smooth texture, whereas it found a rougher surface for the heat-polymerized acrylic resin.

CONCLUSIONS

According to this study, surface roughness and wear on human enamel were not correlated. PEEK is a promising material for the fabrication of occlusal devices.

Wear effects between polymethyl methacrylate occlusal splints and opposing dentin surfaces during bruxism mimicking events

OBJECTIVES

To compare the surface wear rate between polymethyl methacrylate (PMMA)-based occlusal splints and opposing dentin-exposed teeth in bruxism simulating models.

MATERIALS AND METHODS

PMMA-based occlusal splints and extracted premolars were tested on a chewing stimulator at 30,000 or 60,000 cycles. Dentin wear was measured under a stereomicroscope and PMMA wear was determined with an optical profilometer. In addition, wear surface topography was assessed and quantified by scanning electron microscopy (SEM).

RESULTS

Wear rate of PMMA was significantly greater (11 times) than that of dentin specimens at 60,000 cycles, though these findings were not observed at 30,000 cycles. When comparing wear rates within each group at different duration cycles, PMMA surfaces exhibited an average wear rate 1.4 times higher with high duration cycles, while dentin surfaces displayed a marginal decrease in wear. In SEM micrographs, PMMA surfaces displayed more wear abrasion lines with higher duration cycles. However, dentin surfaces did not exhibit major differences between low and high duration cycles.

CONCLUSION

Wear rate on PMMA-based occlusal splints remarkably increases upon high chewing cycles mimicking bruxism comparing with the rate on dentin. Hence, it is reasonable for bruxing patients to wear single-arch PMMA-based occlusal splints to protect opposing dentin-exposed teeth.

Effect of 3D printing system and post-curing atmosphere on micro- and nano-wear of additive-manufactured occlusal splint materials

Although additive manufacturing has been widely applied for occlusal splint (OS) fabrication, it is still unclear whether 3D printing system and post-curing atmosphere would play a role in the wear resistance of additive-manufactured OS. Therefore, the aim of this study was to evaluate the effect of 3D printing system (liquid crystal display (LCD) and digital light processing (DLP)) and post-curing atmosphere (air and nitrogen gas (N₂)) on the wear resistance of hard and soft OS materials for additive-manufactured OSs (KeySplint® Hard and Soft). The evaluated properties were microwear (by two-body wear test) and nano-wear resistances (by nanoindentation wear test) as well as flexural strength and flexural modulus (by three-point bending test), surface microhardness (by Vickers hardness test), and nanoscale elastic modulus (reduced elastic modulus) and nano surface hardness (by nanoindentation test). For the hard material, the surface microhardness, microwear resistance, reduced elastic modulus, nano surface hardness, and nano-wear resistance were significantly affected by the printing system (p < 0.05), while all the evaluated properties except flexural modulus were significantly affected by the post-curing atmosphere (p < 0.05). Meanwhile, both the printing system and post-curing atmosphere significantly affected all the evaluated properties (p < 0.05). The specimens additive-manufactured by DLP printer tended to show higher wear resistance in the hard material groups and lower wear resistance in the soft material groups when compared to those by LCD printer. The post-curing at N₂ atmosphere significantly enhanced the microwear resistance of hard material groups additive-manufactured by the DLP printer (p < 0.05) and soft material groups additive-manufactured by the LCD printer (p < 0.01), while it significantly enhanced the nano-wear resistance of both hard and soft material groups regardless of the printing system (p < 0.01). It can be concluded that 3D printing system and post-curing atmosphere affect the micro- and nano-wear resistance of tested additively manufactured OS materials. In addition, it can be also concluded that the optical printing system providing higher wear resistance depends on the material type, and using nitrogen gas as a protection gas during post-curing enhances the wear resistance of tested materials.

Evaluation of wear behaviour of various occlusal splint materials and manufacturing processes

OBJECTIVES

To investigate the volumetric and vertical loss of occlusal splints manufactured by conventional (heat-cure), subtractive (CAD/CAM) and additive (3D-printing) methods.

METHODS

Six occlusal splint materials were investigated (n = 126), using three manufacturing methods: heat-cured, CAD/CAM and 3D-printed built-in three different printing angles (0°,45°and 90°). Block-on-ring wear testing was performed with extracted human molars as the antagonist. All samples were tested with an applied force of 49N at 1 Hz and 60RPM in artificial saliva at 37 °C for six and 12 months. Scanning electron microscopy images were analysed to evaluate the wear on the tooth enamel and in the splint material. Volumetric and vertical wear loss were statistically analysed.

RESULTS

The lowest volumetric and vertical loss was observed in CAD-CAM materials (6.44 ± 1.77 mm³ and 48.3 ± 7.14 μm) with no statistical significance to the heat-cured material (17.22 ± 9.23 mm³ and 148 ± 121.1 μm) after 12 months (p < 0.172). The mean volumetric loss of 3D printed materials ranged from 0.25 ± 0.15 mm³ to 0.29 ± 0.1 4mm³ with no statistical difference, whereas, the differences in vertical loss from 131.63 ± 44.1 μm to 493 ± 79.19 μm were statistically significant (p < 0.001). The highest vertical loss was observed in the KeySplint Soft 3D printed at 90° (385.35 ± 82.37 μm), whereas FreePrint Splint 2.0 with a build angle of 0° had the highest volumetric loss (204.59 ± 25.67 mm³).

CONCLUSION

CAD-CAM material had the highest wear resistance followed by heat-cured material.KeySplint Soft and FreePrint Splint 2.0 3D printed materials would be preferred for patients that do not have severe bruxing episodes. No significant wear of human enamel after six and 12 months was observed under SEM for any tested materials.

Characterization of occlusal splint materials: CAD-CAM versus conventional resins

AIM

The aim of this in vitro study was to assess the mechanical properties of five commercially available subtractive computer-aided design and computer-aided manufacturing (CAD-CAM) milled splint materials, as well as to compare them with conventional heat-polymerized and autopolymerizing resins used in the construction of conventional splints.

MATERIAL AND METHODS

Five CAD-CAM milled (ProArt CAD Splint, Therapon Transpa, Temp Premium Flexible Transpa, Cast, and Aqua), one autopolymerizing (Palapress), and one heat-polymerized (Paladon 65) resin materials were evaluated. Flexural strength, E-modulus, Vickers hardness, fracture toughness, fracture work, water sorption, and water solubility were measured. Samples were evaluated after dry and water storage for 30 days at 37 °C. Data were collected and statistically analyzed.

RESULTS

Under both storage circumstances, the flexural strength values of Paladon 65, Therapon Transpa, Temp Premium Flexible Transpa, and Aqua were statistically non-significant (P=0.055). The polycarbonate-based CAD-CAM material Temp Premium Flexible Transpa had the highest statistically significant values of the fracture toughness and fracture work (P<0.001). Moreover, it exhibited the lowest percentages of water sorption and water solubility among the investigated materials (P<0.001). All of the CAD-CAM materials exhibited dry elastic moduli greater than Palapress and lower than Paladon 65. One of the CAD-CAM materials, Cast, had the highest dry Vickers hardness value, which was non-significant when compared to Therapon Transpa (P=0.762).

CONCLUSION

CAD-CAM polycarbonate-based splint materials exhibit higher fracture toughness and fracture work as well as lower water sorption and solubility than polymethyl methacrylate-based ones. The mechanical characteristics of the assessed CAD-CAM milled splint materials were not typically superior to those of the conventional heat-polymerized resin. However, some of them outperformed the autopolymerizing acrylic resin in terms of flexural strength, surface microhardness, water sorption, and water solubility.

Wear Behavior of Occlusal Splint Materials Manufactured By Various Methods: A Systematic Review

PURPOSE

To systematically review studies on various materials and methods used for wear testing of occlusal devices and their antagonists in vitro and in vivo.

METHODS

An electronic search in OVID, Web of Science, PubMed and Scopus was conducted using the following terms (MeSH words) with any synonyms and closed terms: "Splint*" OR "occlusal splint*" OR "night guard" OR "occlusal device" OR "occlusal devices" OR "deprogrammer" OR "bite splint" OR "bite plane" OR "orthotic appliance*" OR "orthotic devices" AND "wear" OR "two-body wear" OR "three-body wear" OR "tooth wear" OR "wear measurement*" OR "wear behaviour" OR "wear behavior" OR "abrasion" AND "Polymethyl Methacrylate" OR "PMMA" OR "acrylic resin*" OR "dental material*" OR "dental enamel" OR "CAD" OR "CAM" OR "PEEK" OR "material* testing". Database search was limited to English-language publications and published between 2001 and 1st of September 2021. A further hand search was done to ensure all materials were captured.

RESULTS

After the removal of duplicates, 115 studies were identified, and 11 were chosen for review. Studies showed that the lowest volumetric loss was observed in PEEK occlusal device materials, whereas heat-cure, CAD-milled, and 3D printed occlusal device materials had no significant difference in wear. Vacuum-formed materials showed the highest wear among all groups. Testing parameters were found to be inconsistent across all studies.

CONCLUSION

There is a need for standardization of in vitro and in vivo wear measurement and testing protocols as this study revealed a wide variety of testing protocols which potentially could influence the outcome. Polishing procedures are required for the material. Limited studies are available on 3D printed occlusal device materials and would therefore require further investigation, especially on printing build angles and settings. Further clinical studies would be advantageous to provide guidance on the selection of the best occlusal device material that would last the longest without remake.

Investigating the mechanical and optical properties of novel Urethandimethacrylate (UDMA) and Urethanmethacrylate (UMA) based rapid prototyping materials

OBJECTIVE

This study is focused on testing experimental rapid prototyping materials for occlusal splints made from Urethandimethacrylate (UDMA) and Urethanmethacrylate (UMA).

METHODS

Materials were mixed from UDMA and UMA in ratios of 1.0:0.0, 0.75:0.25, 0.5:0.5, 0.25:0.75 and 0.0:1.0. Specimens were printed using digital light processing (DLP). After post-processing, the specimens underwent testing on flexural strength, modulus of elasticity, hardness, wear behavior, surface roughness, gloss and color stability. All tests were performed after 24 h (baseline) and 10 days of water storage (aging). Splints underwent cyclic pull-off and insertion testing, which was alongside simulated using finite element analysis.

RESULTS

The mechanical properties were significantly influenced by changes in the UDMA:UMA ratio. Statistical analysis revealed that increased amounts of UMA correlated with a decrease in flexural strength (92.0 to 30.7 MPa), modulus of elasticity (2.4 to 0.6 GPa), hardness (155.1 to 102.0 N/mm²) and wear resistance (-1394.9 to -1742.1 μm). Materials with higher amounts of UMA were also more likely to be influenced by water storage. Specimens with 75% and 100% UMA content were partly not analyzable due to soft consistency. Optical properties showed only minor influence from UMA content and aging. Differences in surface roughness (3.9 to 2.4 μm) and color stability were insignificant. Gloss was partly influenced by the UDMA:UMA ratio and water storage. Mean survival rates for cyclic pull-off and insertion testing ranged from 2537 to 23,857 cycles. A correlation between the amount of UMA and survival rates was observed.

SIGNIFICANCE

The addition of up to 25% UMA showed promising results, complying with clinical standards and delivering acceptable results in the cyclic pull-off and insertion test. Further investigation on increments between 0 and 25% UMA could help to find an optimum.

Polymers for conventional, subtractive, and additive manufacturing of occlusal devices differ in hardness and flexural properties but not in wear resistance

OBJECTIVES

To investigate the wear resistance of polymers for injection molding, subtractive and additive manufacturing of occlusal devices in comparison with enamel antagonist wear and material properties (i.e., hardness, flexural strength, and flexural modulus).

METHODS

Injection molding was compared with milling and the additive technologies stereolithography, low force stereolithography, and digital light processing. For each material, eight specimens were produced for wear measurements. Extracted human premolars served as indenters. All samples were subjected to two series of a 2-body wear test consisting of 200,000 circular loading cycles with an applied load of 1) 20 N and 2) 50 N in a thermocycling environment (5/55 °C, 30 s, 3860 cycles, H₂O). Wear resistance was characterized by means of maximum depth and volume of the resulting traces. In addition, enamel wear of the indenters and Vickers hardness, flexural strength, and flexural modulus of the polymers were determined. Wear was statistically analyzed with linear general models for repeated measures and material properties with one-way ANOVA with post-hoc Tukey-HSD tests.

RESULTS

Wear of the antagonists was not influenced by the material (P ≥ 0.343). Likewise, no differences in wear resistance were found between materials after cyclic loading with 20 N or 50 N (P ≥ 0.074). Material properties investigated revealed decreased values for the resins for the additive manufacturing with the exception of flexural strength of one material.

SIGNIFICANCE

Within the limitations of this in-vitro study, arylates for conventional, subtractive, and additive manufacturing of occlusal devices differ in material properties but not in wear resistance and antagonist wear.

Two-body wear of occlusal splint materials against different antagonists

Background

This study aimed to demonstrate that the material of the occlusal splint can be chosen according to the needs of individual patients and contribute to the knowledge of the wear rate of these materials.

Methods

In this study, four occlusal splint materials (Sr Ivocap Heat Cured, Valplast, SR Ivocap Elastomer and Eclipse) and three antagonists (natural tooth enamel, inCoris TZI and IPS e.max Press ceramic materials) were used. Each wear test was performed using a chewing simulator (n = 16; test load: 50 N; number of cycles: 10,000, 20,000 and 30,000; continuous rinsing with water at 30 °C for the wet condition). The Shapiro Wilk test was used for normal distribution suitability. Antagonist on average wear quantities both main effects and interactions of material, cycle and condition factors were investigated by Univariate variance analysis. Multiple comparisons were examined using the Games-Howell test.

Results

There was a statistically significant effect of the difference in materials on the amount of wear (p < 0.001). Furthermore, there was a statistically significant difference among the mean values of all materials (p > 0.001). The highest mean value was obtained with Eclipse (0,318 μm³), and the lowest mean value was obtained with Valplast (0,134 μm³).

Conclusion

Our study found differences in the in vitro wear rate among various occlusal splint materials.

Surface roughness and wear behavior of occlusal splint materials made of contemporary and high-performance polymers

With the development of a digital technology of computer-assisted manufacturing (CAD/CAM) and new age materials, the use of new types of occlusal splint is to consider. The aim of the present study was to evaluate the surface roughness (Ra) and wear behavior of different CAD/CAM materials against enamel antagonist through a simulated chewing test. A total of 75 specimens made from ethylene vinyl acetate (EVA), polymethyl methacrylate (PMMA), polycarbonate (PC), polyetheretherketone (PEEK), and polyethyleneterephthalate (PETG) as a control were polished to evaluate the Ra before loading by optical profilometry and further analyzed by scanning electron microscopy (SEM). Specimens of each group were subjected to thermomechanical fatigue loading in a chewing simulator (60000 cycles at 49 N with 5-55 °C thermocycling). The wear volume loss and change in Ra of each specimen after the simulated chewing were analyzed. One-way ANOVA, paired samples t test, and Pearson correlation analysis were performed for statistical analyzes. The result showed that the volume loss and Ra varied among the materials tested. EVA exhibited the greatest amount of Ra and volume loss (p < 0.001), while PEEK had the lowest values for both (p < 0.001). In terms of volume loss, there was no significant difference between PC and PMMA (p > 0.05). SEM investigations revealed different wear behaviors, especially in EVA. As PEEK showed significantly more favorable results, PEEK splints should be considered as a new therapeutic option for occlusal splint.

Resin adjustment of three-dimensional printed thermoset occlusal splints: Bonding properties - Short communication

OBJECTIVES

To evaluate the interfacial adhesion of an autopolymerizing acrylic resin to 3D printed thermoset occlusal splints compared to thermoplastic occlusal splints.

MATERIALS AND METHODS

Cylinders made of an autopolymerizing acrylic resin were adhered to 3D printed thermoset and also to thermoplastic plates. A different surface treatment and three storage conditions were used: dry, 7 days water-storage and 14 days water-storage. Bond strength test (so-called shear-bond strength test) was afterward performed.

RESULTS

ANOVA (R2 = 0.764) revealed significant differences in bond strength according to material (p < 0.001) and storage (p < 0.001) but not for surface treatment (p = 0.202).

CONCLUSIONS

The bond strength of autopolymerizing acrylic resin to 3D printed thermoset plates is higher when compared to thermoplastic plates. Bonding between acrylic resin and 3D printed splints was high enough for clinical applications.conclusion CLINICAL RELEVANCE: The bond strength values obtained in this study with 3D printed plates were at the level of generally accepted adequate bonding values for prosthetic materials.

Evaluation of sleep bruxism with a novel designed occlusal splint

PURPOSE

This report presents our evaluation system that assesses sleep bruxism. The characteristics and fabrication process of our novel designed splint, and the analysis process of our system are presented.

METHODS

The subjects were 17 volunteers. The splint was fabricated with a self-curing resin compounded with an amino-acid powder for easy wear on the semi-adjustable articulator, and adjusted for a full-balanced occlusion. An impression of the splint, located on the cast, was taken before and after it was worn. The analytical casts were made and scanned via a dental 3D scanner. The datasets were superimposed using two kinds of regions of interest (palate and occlusal surface). The differences between the two datasets were quantitatively presented with pseudo-color mapping. The maximum differences in coronal and apical directions were calculated on the selected area in the occlusal surface when the occlusal surface was used as a region of interest for registration. The relationship between the EMG activities and the change of occlusal surface of the splint were investigated.

RESULTS

In all subjects, deformation and wear facets on the splint were observed. The differences in the apical direction, which indicate wear depth, were correlated with the maximum muscle activity during sleep (p=0.036).

CONCLUSION

From our results, it is suggested that we are not able to eliminate the influence of parafunction for the prosthesis only by designing the surface of occlusal splint using the semi-adjustable articulator. Our splint may have the potential to detect specific facets due to parafunctions as nocturnal bruxism.

Effect of thermocycling on the shear bond strength of different resins bonded to thermoplastic foil applied in occlusal splint therapy

PURPOSE

Temporomandibular disorders are a group of symptoms related to the impaired function of the temporomandibular joints and associated muscles. Occlusal splint therapy is a common treatment in the aforementioned syndrome. One of the methods of manufacturing occlusal splints is to place a polymer on thermoplastic foil. The aim of this study was to evaluate the shear bond strength of light- and self-cured resins bonded to thermoplastic foil dependent on artificial aging.

MATERIALS AND METHODS

Thirty cylinders composed of light-cured resin and 30 cylinders made of self-cured resin were attached to 60 rectangular thermoplastic plates. All specimens were divided into six groups. A control study was conducted for groups 1 and 2. The other preparation groups were subjected to thermocycling by setting appropriately 1000 cycles for groups 3 and 4 and 3000 cycles for groups 5 and 6 in distilled water. Bond strength was measured in a universal testing machine. The results were subjected to statistical analysis using the Mann-Whitney U test (p ≤ 0.05).

RESULTS

The statistics revealed that the values of the shear bond strength for specimens composed of self-cured resin after 1000 and 3000 thermocycles were significantly higher than on those made of light-cured resin (p = 0.003 and p = 0.002).

CONCLUSION

The shear bond strength between the self-cured resin and the thermoplastic foil was higher and more resistant to aging than the shear bond strength between the light-cured resin and the thermoplastic foil.