In vitro wear resistance of three types of composite resin denture teeth

Effect of build orientation on the wear resistance and hardness of denture teeth fabricated using digital light processing: An in vitro study

PURPOSE

This in vitro study investigated the effect of build orientation on the wear resistance and hardness of denture teeth fabricated using digital light processing (DLP) compared to other denture tooth materials.

METHODS

Disc-shaped specimens were prepared using denture tooth monomers and DLP devices in three build orientations: 0°, 45°, and 90°. Specimens of the same shape were fabricated using denture tooth materials for subtractive manufacturing, commercially available polymethylmethacrylate (PMMA) resin, and composite resin. The wear resistance was evaluated as the wear volume loss after 50,000 wear cycles using a ball-on-disc wear device in water for two-body wear and poppy seed slurry for three-body wear. The Vickers hardness values of the materials were measured. Two-way and one-way analyses of variance were performed for wear resistance and hardness, respectively, followed by Tukey's honest significance test.

RESULTS

The interaction between the denture tooth resins and maximum wear volume was significant (P < 0.01). The 0° build orientation exhibited the lowest wear volume in the three-body wear test and the highest hardness among the three build orientations. The 0° DLP-fabricated specimens demonstrated significantly less wear volume than that of the PMMA specimens and a wear volume comparable to that of the milled specimens. However, the 0° DLP-fabricated specimens showed significantly lower hardness than that of the milled and PMMA specimens. The composite resin specimens exhibited the highest wear resistance and hardness.

CONCLUSIONS

A 0° build orientation is recommended for DLP-fabricated denture teeth compared to 45° and 90° orientations to achieve greater wear resistance and hardness.

Surface hardness and wear resistance of prefabricated and CAD-CAM milled artificial teeth: A cross-over clinical study

PURPOSE

To clinically evaluate the surface roughness and wear resistance of prefabricated and CAD-CAM milled acrylic resin teeth for complete dentures.

MATERIALS AND METHODS

In a cross-over study design, 10 completely edentulous patients were randomly included in this study and given two complete dentures. The first complete denture was made using prefabricated teeth, while the second was constructed using CAD-CAM milled teeth. Following insertion (T0), 3 months (T3), and 6 months (T6), the complete dentures were scanned. Utilizing 3D surface super-imposition techniques, the vertical (2D wear), and volumetric (3D wear) material loss were measured. The hardness of the teeth was evaluated at the time of denture insertion (T0) and then after 6 months (T6) of denture insertion by digital Vickers hardness tester. Statistical analysis was done using SPSS software. Paired groups were compared by paired t-test. Also, a repeated measure test was used. The significant difference was considered if p ≤ 0.05.

RESULTS

The time of denture function was linearly correlated with the wear of the prefabricated and CAD-CAM milled denture tooth. Prefabricated acrylic teeth had significantly more vertical and volumetric wear after 3 and 6 months, compared to CAD-CAM milled denture teeth where p-values were 0.01, 0.009, 0.003, and 0.024, respectively. Additionally, CAD-CAM milled teeth displayed significantly higher hardness values than prefabricated teeth both before and after 6 months of use where p-values were 0.001. After 6 months, all studied teeth showed a decrease in their hardness.

CONCLUSIONS

In terms of wear resistance and surface hardness, CAD-CAM milled acrylic resin teeth were superior to prefabricated acrylic resin artificial teeth once the complete denture functions.

Investigation of Bruxism wear behavior of titanium alloy biomaterials; experimental and 3D finite element simulation

Bruxism can be defined as the process of direct contact with teeth and dental materials with an involuntary jaw-tightening movement. In this process, teeth and dental materials can be exposed to various damage mechanisms. This study aims to realize the mechanism of bruxism with finite element analysis and in vitro rotating chewing movement analysis. Within the scope of the study, cp-Ti, Ti-5Zr, and Ti-5Ta materials were subjected to wear tests in the finite element analysis and in vitro rotating chewing movement method under the determined Bruxism chewing test conditions. Test specimens with cylindrical geometry were exposed to a direct every-contact wear mechanism for 30 s under 150 N bruxism chewing bite force. The bruxism chewing cycle continued for 300 min at a frequency of 2 Hz. Microanalysis of the wear surfaces of the samples after the experimental study was carried out with Scanning Electron Microscopy. The results obtained within the scope of this study showed that the Bruxism wear resistance increased by adding zirconium and tantalum to pure titanium material. This result shows that pure titanium material, which is known to have poor wear resistance, can be improved with Zr and Ta alloys. It is clinically important that the success rate in the treatment process increases with the increase in wear resistance. However, the micro-cracks observed in the microstructure may have occurred in the sub-surface, which is a show of the fatigue wear mechanism.

Digital workflow for duplication of gold onlay anatomy to monolithic zirconia onlay for a complete denture: A technique paper

Digital replication of an existing cast gold onlay anatomy to a more esthetic material for a new complete denture is challenging. A technique is presented that uses digital technology to fabricate a new maxillary complete denture with monolithic zirconia onlays that duplicate the anatomy of an existing complete denture with cast gold onlays.

Comparison of wear and marginal fitness of 3D-printed deciduous molar crowns: An in vitro study

This study aimed to evaluate the wear resistance of primary tooth enamel and 3 kinds of 3D printing materials and to compare the marginal fitness and internal suitability of prefabricated all-ceramic crowns, computer-aided design/manufacturing (CAD/CAM) all-ceramic crowns, and three 3D-printed deciduous molar crowns. Multifunctional friction wear testing machine was used to image the wear surface of the sample and calculate the maximum wear depth and volume loss value of each sample. The internal fit evaluation used the silicon replica method, The four points were measured using scanning electron microscopy (SEM). The obtained data were statistically analyzed using ANOVA and Tukey HSD-test with a fully randomized design (p<0.05). The results showed the wear resistance of E-Dent400 was better than that of PEEK and three different 3D printed materials have good wear resistance compared with the primary tooth enamel. The measured values at M1 and M4 of E-Dent400 were both the smallest.

Clinical wear of different types of denture teeth after one year in service: A clinical study

STATEMENT OF PROBLEM

Worn denture teeth are a common reason for replacing complete dentures. However, clinical studies on the amount of denture tooth wear are lacking.

PURPOSE

The purpose of this clinical study was to compare the clinical wear of denture teeth made from double cross-linked (DCL) versus highly cross-linked (HCL) materials after 1 year in service.

MATERIAL AND METHODS

Fourteen participants received maxillary and mandibular removable complete dentures (RCDs). The participants randomly received either DCL or HCL teeth. Each RCD was scanned with an intraoral scanner 1 week after finishing any occlusal adjustment and after 1 year. Occlusal contact marks were recorded using articulating paper, and photographs were made in centric and eccentric movements. The generated 1-week and 1-year standard tessellation language (STL) files of the scans were obtained and trimmed using the Geomagic X software program. After merging the files, the depth of the wear facets was measured using the software program tool that measures the vertical gap distance in micrometers at 100 points distributed on the contact areas. These areas were identified by using the segment tools in the software program. Repeated measures ANOVA was used to analyze the differences between the collected data (α=.05).

RESULTS

The DCL had higher mean ±standard deviation wear (62.7 ±40 µm) than the HCL (37 ±31 µm) after 1 year in service (P<.001).

CONCLUSIONS

Both DCL and HCL denture teeth showed acceptable clinical wear after 1 year of clinical use. HCL denture teeth showed more resistance to occlusal wear than DCL denture teeth.

Influence of abrasive dentifrices on polymeric reconstructive material properties after simulated toothbrushing

To assess the influence of dentifrices with different abrasiveness levels on the properties of dental reconstructive materials. Forty-eight cylinders were obtained from four polymeric materials, being two CAD/CAM acrylic resins (Ivotion-Dent and Ivotion-Base), one injected acrylic resin (IvoBase-Hydrid) and one light-cured resin composite (Empress Direct). Specimens were allocated to four subgroups for toothbrushing simulation according to the dentifrice relative dentin abrasivity (RDA) and silica content: (i) RDA 0 = 0%; (ii) RDA 50 = 3%; (iii) RDA 100 = 10%; and (iv) RDA 120 = 25%. Specimens were then subjected to toothbrushing. Surface analyses [surface roughness Ra (SR) and scanning electron microscopy (SEM)] along with hardness and optical properties [translucency parameter (TP) and contrast ratio (CR)] were evaluated before and after toothbrushing. Statistical analyses were performed using ANOVA and Tukey test. A significant increase in SR was observed after toothbrushing with higher RDA toothpastes for Ivotion-Dent (100 and 120) and IvoBase-Hybrid (120). Ivotion-Base and Empress Direct presented no significant differences in SR when analyzed as a function of timepoint and RDA levels. Hardness was not influenced by toothbrushing with different RDA dentifrices, except for Empress Direct with RDA 0 toothpaste, where a decrease in the hardness was observed. TP of Ivotion-Dent and Empress Direct significantly decreased after toothbrushing with higher RDA dentifrices and CR of Ivotion-Dent, Empress Direct and IvoBase-Hybrid significantly increased with higher RDA dentifrices. The levels of dentifrice abrasiveness affected differently the SR, hardness and optical properties of polymeric reconstructive materials after toothbrushing.

Fracture toughness of 3D printed denture teeth

BACKGROUND

Advances in digital dentistry lead to use of three-dimensional (3D) printed resin denture teeth. Fracture toughness of these teeth must be assessed.

OBJECTIVE

This study aimed to compare the chipping and indirect tensile fracture resistance of denture teeth fabricated by 3D printing technique with traditionally fabricated resin denture teeth.

METHOD

Four groups (Gr) were made (n= 50/group): Gr-1 3D printed denture teeth (denture teeth; Formlabs Inc., Somerville, MA, USA), Gr-2 SR-Orthosit-PE (Ivoclar Vivadent AG), Gr-3 Portrait IPN (Dentsply Sirona), Gr-4 Pala Premium 8 (Heraeus Kulzer GmbH). Stereolithography 3D printing was used to create the methacrylate-based photopolymerized resin teeth models and remaining group teeth were collected commercially. A 1 mm/min chipping and indirect tensile fracture speed tests were carried out till fracture occurred. The data so obtained were statistically analysed using one-way analysis of variance with Tukey's honestly significant difference multiple comparisons test (p< 0.05). At the end of the test, the fractured areas of the specimens were evaluated by the chief researcher to assess the fracture pattern of the teeth.

RESULTS

The indirect tensile fracture values of the 3D printed teeth were more than that of Pala Premium-8 and SR-Orthosit-PE but it was lower than that of Portrait IPN teeth. In chipping test, buccal chipping of the loaded cusp was seen in 3D printed resin without distortion and in indirect tensile test in 3D printed resin teeth, line of fracture emerges near the loading point propagates from the inner incline of both cusps and extends cervically, unlike in other groups where first deformation occurs then fracture.

CONCLUSION

Prosthetic teeth fabricated by the 3D printing technique using printable resin material provide adequate fracture resistance as denture teeth.

Wear Properties of Conventional and High-Translucent Zirconia-Based Materials

This study investigated the two-body wear resistance of a first generation 3 mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP), a second generation 3Y-TZP, a third generation 4 mol% yttria partially stabilized zirconia (4Y-PSZ), a 5 mol% yttria partially stabilized zirconia (5Y-PSZ), and a type III gold alloy (Aurocast 8), performed using opposing antagonistic cusps made out of the same material. Eight cylindrical specimens were prepared for each material (n = 8) for a total of forty specimens (N = 40). Conical cusps were fabricated for each material. Each cylinder−cusp pair was arranged inside a two-axis chewing simulator over up to 360,000 loading cycles. The wear resistance was analyzed by measuring the vertical substance loss (mm) and the volume loss (mm3). The antagonist wear (mm) was recorded before and after the wear test to evaluate the linear difference. Statistical analysis was performed using one-way analysis of variance (ANOVA); multiple comparisons were performed according to Tukey’s method. No statistically significant differences (p > 0.05) among the first generation 3Y-TZP, second generation 3Y-TZP, and 4Y-PSZ wear were found. 5Y-PSZ showed statistically significant higher wear compared to other the zirconias. Aurocast 8 displayed the highest values in terms of vertical wear, antagonist cusp wear, and volumetric loss. Although still not statistically comparable, the wear behavior of the latest 5Y-PSZ was the closest to the widely recognized gold standard represented by the type III gold alloy.

Comparison of Microhardness of Artificial Teeth with Different Contents After Waiting in Various Liquids

Objectives: This study aimed to assess the long-term microhardness of different artificial teeth after waiting in liquids of various pH values. Materials and Methods: Four different artificial teeth [conventional PMMA(Ivostar) as control group), double cross-linked PMMA(DCL), micro-filled composite resin(VivodentPE), nanohybrid composite resin(PhonaresiII)] were used for the study. After the samples fixed on acrylic blocks were immersed in distilled water at 37˚C for 24 hours, initial microhardness (T0) measurements were performed. Randomly selected samples from each group were immersed in liquids with different pH values (artificial saliva, kefir, orange juice, cola). Measurements repeated on the 7th day on the same samples were recorded as T1, and measurements repeated on the 14th day were recorded as T2. The data obtained were evaluated in the SPSS 22.0 program. Friedman and Kruskall Wallis tests were used to compare of the groups. Results: While the highest initial microhardness averages were found in the Phonares II group, the lowest average belongs to the Ivostar group. Microhardness findings of all materials measured at different times were obtained in the order of T0>T1>T2. When the data of samples aged in different liquids are compared, significant differences are observed (p0.05) Conclusions: A decrease in microhardness of materials that are immersed in liquids with different pH values for a long time was observed, and the microhardness of the materials exposed to these solutions is adversely affected.

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.

Shear bond strength between CAD/CAM denture base resin and denture artificial teeth when bonded with resin cement

PURPOSE

The bond strengths between resin denture teeth with various compositions and denture base resins including conventional and AD/CAM purposed materials were evaluated to find influence of each material.

MATERIALS AND METHODS

Cylindrical rods (6.0 mm diameter × 8.0 mm length) prepared from pre-polymerized CAD/CAM denture base resin blocks (PMMA Block-pink; Huge Dental Material, Vipi Block-Pink; Vipi Industria) were bonded to the basal surface of resin teeth from three different companies (VITA MFT®; VITA Zahnfabrik, Endura Posterio®; SHOFU Dental, Duracross Physio®; Nissin Dental Products Inc.) using resin cement (Super-Bond C&B; SUN MEDICAL). As a control group, rods from a conventional heat-polymerizing denture base resin (Vertex™ Rapid Simplified; Vertex-Dental B.V. Co.) were attached to the resin teeth using the conventional flasking and curing method. Furthermore, the effect of air abrasion was studied with the highly cross-linked resin teeth (VITA MFT®) groups. The shear bond strengths were measured, and then the fractured surfaces were examined to analyze the mode of failure.

RESULTS

The shear bond strengths of the conventional heat-polymerizing PMMA denture resin group and the CAD/CAM denture base resin groups were similar. Air abrasion to VITA MFT® did not improve shear bond strengths. Interfacial failure was the dominant cause of failure for all specimens.

CONCLUSION

Shear bond strengths of CAD/CAM denture base materials and resin denture teeth using resin cement are comparable to those of conventional methods.

Quantify the Protein-Protein Interaction Effects on Adsorption Related Lubricating Behaviors of α-Amylase on a Glass Surface

Dental ceramic material is one of the widely preferred restorative materials to mimic the natural tooth enamel surface. However, it has continuously been degraded because of low wear resistance during mastication in the oral cavity. The friction involved was reduced by introducing the lubricant saliva protein layers to improve the wear resistance of the dental materials. However, little is understood regarding how the protein-protein interactions (PPI) influence the adsorbed-state structures and lubricating behaviors of saliva proteins on the ceramic material surface. The objective of this study is to quantify the influences of PPI effects on the structural changes and corresponding oral lubrications of adsorbed α-amylase, one of the abundant proteins in the saliva, on the dental ceramic material with glass as a model surface. α-Amylase was first adsorbed to glass surface under varying protein solution concentrations to saturate the surface to vary the PPI effects over a wide range. The areal density of the adsorbed protein was measured as an indicator of the level of PPI effects within the layer, and these values were then correlated with the measurements of the adsorbed protein's secondary structure and corresponding friction coefficient. The decreased friction coefficient value was an indicator of the lubricated surfaces with higher wear resistance. Our results indicate that PPI effects help stabilize the structure of α-amylase adsorbed on glass, and the correlation observed between the friction coefficient and the conformational state of adsorbed α-amylase was apparent. This study thus provides new molecular-level insights into how PPI influences the structure and lubricating behaviors of adsorbed protein, which is critical for the innovations of dental ceramic material designs with improved wear resistance.

Wear Properties of Different Additive Restorative Materials Used for Onlay/Overlay Posterior Restorations

The purpose of this laboratory study was to compare the two-body wear resistance of different restorative materials commonly used for the indirect restoration of posterior teeth. The tested materials, based on ceramic (Imagine Press X, IPS e.max CAD, Milled Celtra Duo, Glaze-Fired Celtra Duo, Vita Mark II) and composite (Enamel Plus HRi, Enamel Plus HRi Bio-Function, Filtek Supreme XTE, Lava Ultimate), were compared with the wear properties of a type III gold alloy (Aurocast 8). Flat samples were prepared with a 6-mm thickness (n=10). Composite samples were tested after a heat polymerization cycle. All samples were exposed to a two-body wear test in a dual axis chewing simulator performing over 120,000 loading cycles. The opposing abrader cusps were fabricated from yttria-stabilized tetragonal zirconia polycrystal. The vertical substance loss (mm) and the volume loss (mm3) were recorded, as was the wear of the antagonist cusp (mm). Mean values were analyzed by one-way analysis of variance. Significant differences among materials were detected. The heat-cured resin-based composite material Enamel Plus Bio-Function and the type III gold alloy demonstrated similar mean values for wear depth and volumetric loss.

Wear resistance of 3D-printed denture tooth resin opposing zirconia and metal antagonists

STATEMENT OF PROBLEM

Additive manufacturing technology can be used for denture bases and also denture teeth. Therefore, the mechanical properties of 3D-printed resin denture teeth should be evaluated.

PURPOSE

The purpose of this in vitro study was to compare the wear resistance of 3D-printed denture tooth resin with that of conventionally prefabricated denture teeth.

MATERIAL AND METHODS

Eighty substrate specimens were prepared with 5 kinds of resin denture teeth: 3D-printed denture tooth resin (DENTCA denture tooth resin; DENTCA, Inc), Artic 6 (Kulzer GmbH), Preference (Candulor AG), Premium 6 (Kulzer GmbH), and Surpass (GC Corp). The 3D-printed denture tooth specimens were made of methacrylate-based photopolymerized resin by stereolithography 3D printing. Antagonistic surfaces were made from zirconia by milling and from cobalt-chromium (Co-Cr) alloy by 3D printing and casting. The specimens were loaded at 49 N for 30 000 cycles under thermocycling conditions in a mastication simulator. Wear resistance was measured by calculating the volume of substance lost. Wear surface characteristics were observed by using a scanning electron microscope (SEM). Two-way ANOVA was used to analyze the data (α=.05).

RESULTS

The influence of the resin denture teeth and the type of antagonist were both statistically significant. The wear volume loss of the 3D-printed denture tooth resin was higher than that of Artic 6 and Preference when opposing the zirconia and the metal antagonists (P<.05). The 3D-printed denture tooth resin did not show a significant difference from Premium 6 with the zirconia and the metal antagonists or Surpass with the zirconia antagonist. From the SEM images, the specimens of the 3D-printed denture tooth resin showed a relatively smooth surface with the zirconia antagonist and exhibited cracks when opposed by the metal antagonist.

CONCLUSIONS

The results suggest that 3D-printing by using resin materials provides adequate wear resistance for denture tooth use.

Evaluating the Wear of Resin Teeth by Different Opposing Restorative Materials

The aim of this study was to evaluate the wear properties of resin teeth with different opposing dental restorative materials. One type of resin tooth (Trubyte Biotone) was tested against six types of restorative materials including type III gold alloy (GO), monolithic zirconia (MZ), lithium disilicate glass ceramic (LD), nickel-chromium alloy (NC), feldspathic ceramic (FC), and steatite (ST). Two-body wear tests were performed under a vertical load of 5 kgf and thermo-cycling at 5/55 °C with a total of 120,000 cycles. The wear amount was quantified by measuring the volume loss of the resin teeth and the vertical substance loss of the opposing materials using three-dimensional images. The FC group showed a significantly greater amount of wear of the resin teeth, followed by the ST, NC, LD, MZ, and GO groups. The GO group showed significantly less wear of resin teeth than the other groups. There were no statistically significant differences in the wear of opposing restorative materials between groups. Within the limits of this study, it is recommended that zirconia, rather than feldspathic ceramic, should be used for restorations in the esthetic zone, and gold alloy should be used for areas with little or no esthetic demand.

3D Printing of Resin Material for Denture Artificial Teeth: Chipping and Indirect Tensile Fracture Resistance

3D printing of denture artificial teeth with resin materials is worthy of study in a novel way. This study evaluated chipping and indirect tensile fracture resistance of 3D printing resin material (Dentca 3D printing denture teeth resin) compared with conventionally prefabricated resin denture teeth (Premium-8, Surpass, SR-Orthosit-PE, and Preference). One hundred tooth specimens were prepared for testing. The 3D printed tooth specimens were printed at a 50 µm layer thickness with methacrylate-based photopolymerized resin by stereolithography 3D printing. Chipping and indirect tensile fracture tests were conducted at a speed of 1 mm/min until fracture. The indirect tensile fracture loads of the 3D printed resin teeth were higher than those of Premium-8, Surpass, and SR-Orthosit-PE, and lower than those of Preference teeth. Regarding chipping resistance, the 3D printed resin teeth were not different from Surpass and SR-Orthosit-PE, and were lower than Premium-8 and Preference teeth. The 3D printed resin teeth exhibited vertical fracture of the loaded cusp without deformation in chipping. The 3D printed resin teeth showed simultaneous fracture of two cusps in indirect tensile fracture, unlike other teeth. The results of this study suggest that 3D printing technology using resin materials provides adequate fracture resistance for denture artificial tooth use.

Wear resistance of injection-molded thermoplastic denture base resins

Objective This study investigated the wear resistance of injection-molded thermoplastic denture base resins using nanoindentation instrument.

Materials and methods Six injection-molded thermoplastic denture base resins (two polyamides, two polyesters, one polycarbonate, one polymethylmethacrylate [PMMA]) and a PMMA conventional heat-polymerized denture-based polymer control were tested. Elastic modulus, hardness, wear depth, and roughness were calculated using a nanoindentation instrument.

Results Elastic modulus and hardness of the injection-molded thermoplastic denture base resins were significantly lower than those of the PMMA conventional heat-polymerized denture-based polymer. Wear depth of polycarbonate and PMMA conventional heat-polymerized denture-based polymer were significantly higher than that of other injection-molded thermoplastic denture base resins. The roughness of injection-molded thermoplastic denture base resins was significantly more than that of PMMA conventional heat-polymerized denture-based polymer after testing.

Conclusions Wear resistance of injection-molded thermoplastic denture base was low compared to PMMA conventional heat-polymerized denture-based polymers.

A direct bonded fixed partial dental prosthesis: a clinical report

A direct bonded fixed partial dental prosthesis, with a composite resin denture tooth as a pontic, a tri-n-butylborane initiated adhesive resin, and screw posts for reinforcement, was still functioning after an observation period of 20 years. The prosthesis was found to be reliable for long-term clinical use when chemically and mechanically reinforced.

Wear properties of a novel resin composite compared to human enamel and other restorative materials

The purpose of this in vitro study was to compare the two-body wear resistance of human enamel, a pressable glass-ceramic (Imagine PressX), a type 3 gold alloy (Aurocast8), three resins composites currently available on the market (Enamel plus HRi, Filtek Supreme XTE, Ceram.X duo), and one recently introduced resin composite (Enamel plus HRi-Function). Resin composites were tested after simple light curing and after a further heat polymerization cycle. Ten cylindrical specimens (7 mm in diameter) were manufactured with each dental material according to standard laboratory procedures. Ten flat enamel specimens were obtained from freshly extracted human molars and included in the control group. All samples were subjected to a two-body wear test in a dual-axis chewing simulator over up to 120,000 loading cycles, against yttria stabilized tetragonal zirconia polycrystal cusps. Wear resistance was analyzed by measuring the vertical substance loss (mm) and the volume loss (mm(3)). Antagonist wear (mm) was also recorded. Data were statistically analyzed using one-way analysis of variance (ANOVA) (wear depth and volume loss) and Kruskal-Wallis one-way ANOVA on ranks (antagonist wear). Heat-cured HRi function and Aurocast8 showed similar mean values for wear depth and volumetric loss, and their results did not statistically differ in comparison with the human enamel.

Wear behavior of seven artificial resin teeth assessed with three-dimensional measurements

STATEMENT OF PROBLEM

Artificial resin teeth are widely used for removable dental prostheses because of their excellent properties. An evaluation of their wear behavior is important for predicting good clinical performance.

PURPOSE

The purpose of the study was to examine the wear behavior of 7 different artificial resin teeth with 3-dimensional measurements.

MATERIAL AND METHODS

The artificial denture teeth tested were 2 composite resin teeth (Yamahachi PX, Huge Kaijing), 3 cross-linked acrylic resin teeth (Cosmo HXL, Premium 8, Vita Lingoform), and 2 conventional acrylic resin teeth (Yamahachi FX, Shengjian). The specimens were subjected to an abrasive tester for masticatory simulation. The wear loss (vertical loss and volume loss) was determined with a confocal laser scanning microscope. Data were analyzed with 1-way ANOVA followed by the Games-Howell post hoc test (α=.05).

RESULTS

The mean vertical loss and volume loss for all cross-linked acrylic resin teeth (0.987-1.03 μm, 0.858-0.939 mm(3) × 10(-3)) were higher than for all composite resin teeth (0.636-0.698 μm, 0.507-0.650 mm(3) × 10(-3), P<.001) but lower than those for conventional acrylic resin teeth Yamahachi FX and Shengjian (1.39 μm, 1.24 mm(3) × 10(-3); 12.1 μm, 16.4 mm(3) × 10(-3); P<.001). No significant differences for wear loss were found between the Vita Lingoform group and the other cross-linked acrylic resin teeth (P>.05).

CONCLUSION

The wear behavior of the artificial teeth examined differed with regard to their compositions. The composite resin teeth and high cross-linked acrylic resin teeth found superior wear resistance over the conventional acrylic resin teeth.

A conservative approach to rebasing an implant-retained fixed complete denture

After years of service, the acrylic resin base of an implant-retained fixed complete dental prosthesis may need to be replaced because of the wear of the acrylic resin teeth. The most common methods used by dental laboratories to remove the acrylic resin from the metal framework are either burning with a flame or grinding. Both of these methods risk exposing the dental laboratory technician to hazardous by-products and damaging or contaminating the metal framework or the gold cylinders. This article presents a safe approach to removing acrylic resin while preserving the integrity of the framework. The technique involves heating the prosthesis to beyond the glass transitional temperature of the acrylic resin to allow the resin to be safely peeled off the framework.

Wear resistance of experimental titanium alloys for dental applications

The present study evaluated microstructure, microhardness and wear resistance of experimental titanium alloys containing zirconium and tantalum. Alloys were melted in arc melting furnace according to the following compositions: Ti-5Zr, Ti-5Ta and Ti-5Ta-5Zr (%wt). Hemispheres and disks were obtained from wax patterns that were invested and cast by plasma. Microstructures were evaluated using optical microscopy and X-ray diffraction (XRD) analysis and also Vickers microhardness was measured. Hemispherical samples and disks were used for 2-body wear tests, performed by repeated grinding of the samples. Wear resistance was assessed as height loss after 40,000 cycles. The data were compared using ANOVA and post-hoc Tukey test. Ti-5Zr presented a Widmanstätten structure and the identified phases were α and α' while Ti-5Ta and Ti-5Ta-5Zr presented α, β, α' and α" phases, but the former presented a lamellar structure, and the other, acicular. The microhardness of Ti-5Zr was significantly greater than other materials and cp Ti presented wear resistance significantly lower than experimental alloys. It was concluded that wear resistance was improved when adding Ta and Zr to titanium and Zr increased microhardness of Ti-5Zr alloy.

Indentation Testing of Bulk Zr0.5Hf0.5Co1-xIrxSb0.99Sn0.01 Half-Heusler Alloys

Indentation tests were performed to assess the influence of compositional changes on the mechanical properties of several half-Heusler compounds with the general composition Zr0.5Hf0.5Co1-xIrxSb0.99Sn0.01 (x=0.0,0.1,0.3,0.5,0.7). These samples were synthesized by high temperature solid-state reactions and were consolidated by hot-pressing. Indentation measurements were obtained using both microhardness testing (Vickers) and depth-sensing nanoindentation. These measurements were used to determine the microhardness and the elastic modulus of each half-Heusler compound. The Vickers hardness values were found to range between 876 and 964. A slight increase in hardness was observed with the addition of iridium. The elastic stiffness values ranged from 229 GPa to 246 GPa. Here, a slight decrease in stiffness was observed with the addition of iridium.

Abrasion wear resistance of different artificial teeth opposed to metal and composite antagonists

One of the most important properties of artificial teeth is the abrasion wear resistance, which is determinant in the maintenance of the rehabilitation's occlusal pattern.

Influence of flowable resins on the shear bond strength of orthodontic brackets

The present study tested the shear bond strength (SBS) of orthodontic brackets bonded to teeth using flowable resins. A total of 105 human teeth were divided into seven groups. The brackets in each group were bonded to the tooth substrates using a Transbond XT adhesive and six other different flowable resins, respectively. Each adhesive resin was light-cured using a quartz-tungsten-halogen (QTH) light for 40 seconds. The brackets were debonded in shear mode using a universal testing machine. The brackets bonded using Tetric Flow and Grandio Flow showed slightly greater SBS values (13.0+/-1.8 and 12.2+/-1.2 MPa, respectively) than the Transbond XT adhesive (12.1+/-1.2 MPa). However, the SBS values of Transbond XT, X-flow, Tetric Flow, Grandio Flow, and Filtek Z350 flow were not significantly different. As for Admira Flow and Aelite Flow, they scored significantly lower SBS values (7.0+/-2.1 and 9.2+/-1.3 MPa, respectively) than the other groups. On bracket failure mode, statistical analysis revealed a similar failure mode among all the seven test groups.

Two-body wear of artificial acrylic and composite resin teeth in relation to antagonist material

STATEMENT OF PROBLEM

Wear resistance is one of the most important physical properties of artificial resin teeth, and its dependence on the antagonist material has not been clearly established.

PURPOSE

The purpose of this in vitro study was to investigate the wear resistance of representative artificial resin teeth in relation to antagonist material.

MATERIAL AND METHODS

Twenty-four standardized specimens were prepared for each of 8 tooth types representative of anterior and posterior artificial acrylic and composite resin teeth (Gnathostar, SR Orthosit PE, Condyloform II NFC, SR Postaris DCL, SR Vivodent PE, VITA Physiodens, SR Antaris DCL, Bioplus), for a total of 192 specimens. Each specimen was prepared to a diameter of 5 mm and a thickness of 2 mm on the buccal/facial tooth surfaces. The specimens were then polished and subjected to simulated mastication (50 N, 1.2 x 10(5) cycles, 1.2 Hz) using a pin-on-block design and additional thermocycling (600 cycles, 5/55 degrees C, 2 min/cycle). Three antagonists (artificial resin teeth, steel, steatite) were prepared, and 8 specimens per tooth type were tested for each antagonist. Vertical substance and volume loss were analyzed using cast replicas and an optical 3-dimensional (3-D) surface profilometer, as well as scanning electron microscopy. Data were analyzed using 2- and 1-way ANOVA and the Games-Howell test (alpha=.05).

RESULTS

For both vertical substance and volume loss, significant differences were found for the various antagonists. Lowest overall mean values (SD) for vertical substance and volume loss were measured for artificial tooth antagonists (26 (10) microm to 95 (46) microm, 1.5 (1.5) microm(3) to 10.5 (9) microm(3)), and the highest values were measured for steatite antagonists (95 (23) microm to 723 (168) microm, 8 (4) microm(3) to 245 (109) microm(3)). Intermediate mean values (SD) for vertical substance and volume loss were measured for steel antagonists (118 (88) microm to 205 (120) microm, 9 (7) microm(3) to 28 (24) microm(3)). Using artificial teeth and steel antagonists, few significant differences in wear resistance were found between the various resin teeth. In contrast, significant differences were observed with steatite antagonists.

CONCLUSIONS

The use of steatite antagonists allowed for significantly better differentiation of wear behavior between various artificial teeth than the use of artificial resin teeth or steel antagonists.

Wear of feldspathic ceramic, nano-filled composite resin and acrylic resin artificial teeth when opposed to different antagonists

The aim of this study was to evaluate the wear of denture teeth and their antagonists produced by two-body and three-body wear tests. Three types of denture teeth, namely feldspathic ceramic (FC), nano-filled composite resin (NCR), and experimental acrylic resin teeth (AR), were tested. For each type two groups of eight upper premolars each were prepared. The first group was tested against cusps from the same material and the second group was tested against human enamel cusps. Each group was loaded with a total of 200,000 chewing cycles (two-body wear 100,000 cycles and three-body wear 100,000 cycles). Wear was analyzed by measuring the maximum depth and volume loss of the denture teeth using a laser scanner and by measuring the vertical loss of the antagonists using an optical macroscope. Statistically, there was no significant difference between the following combinations: FC-FC and NCR-NCR regarding the vertical and volume loss; and FC-enamel and NCR-enamel regarding the total vertical substance loss. The combinations AR-AR and AR-enamel showed higher wear values than the other combinations. For complete dentures, composite resin and ceramic teeth showed similar vertical and volume loss, whereas composite resin teeth seemed to be more suitable for partial dentures opposing natural teeth in terms of wear of teeth and antagonists.

In vitro wear resistance of three types of polymethyl methacrylate denture teeth

The wear resistance of denture teeth is important to the longevity of removable prostheses of edentulous patients. The ability of denture teeth to maintain a stable occlusal relationship over time may be influenced by this property. The purpose of this in vitro study was to evaluate the wear resistance of polymethyl methacrylate (PMMA) denture teeth based on their chemical composition when opposed by a ceramic antagonist. The maxillary canines (n=10) of 3 PMMA denture teeth (Trubyte Biotone, cross-linked PMMA; Trilux, highly cross-linked IPN (interpenetrating polymer network)-PMMA; and Vivodent, highly cross-linked PMMA) were secured in an in vitro 2-body wear-testing apparatus that produced sliding contact of the specimens (4.5 cycles/s, sliding distance of 20 mm, under 37°C running water) against glazed or airborne particle abraded ceramic. Wear resistance was measured as height loss (mm) under 300 g (sliding force) after 100,000 cycles, using a digital measuring microscope. Mean values were analyzed by 2-way ANOVA and Tukey's test (α=0.05). The wear of Trubyte Biotone (0.93 ± 0.14 mm) was significantly higher than that of both other types of teeth tested against abraded ceramic (p<0.05). The Vivodent tooth (0.64 ± 0.17 mm) exhibited the best wear resistance among the denture teeth tested against airborne particle abraded ceramic. There were no statistically significant differences (p>0.05) in wear among the 3 denture teeth evaluated against glazed ceramic. Trilux and Vivodent teeth tested against either glazed or airborne particle abraded ceramic did not differ significantly from each other (p<0.05). All teeth showed significantly more wear against airborne particle abraded ceramic than against glazed ceramic (p<0.05). In conclusion, the three types of PMMA denture teeth presented significantly different wear resistance against the abraded ceramic. The high-strength PMMA denture teeth were more wear-resistant than the conventional PMMA denture tooth.

Two-body wear of resin and ceramic denture teeth in comparison to human enamel

OBJECTIVES

To evaluate the two-body wear resistance of different artificial denture teeth when opposed to steatite ceramic balls in a dual-axis chewing simulator.

METHODS

Artificial denture teeth including the ceramic tooth Bonartic CT, the composite resin tooth Condyloform II NFC, the acrylic resin teeth Bonartic TCR, Orthognath, Polystar Selection, SR Orthotyp DCL, and Vitapan Cuspiform, and human maxillary premolars were tested in a chewing simulator. Wear resistance was analyzed measuring vertical substance loss and volume loss using profilometry and an optical macroscope after various chewing cycles (49N, up to 1,200,000 cycles). Data were statistically analyzed using one-way analysis of variance (ANOVA) followed by the Fisher test (LSD) at p< or =0.05.

RESULTS

After 1,200,000 chewing cycles the mean vertical substance loss and volume loss for the composite resin teeth (117microm and 0.144mm3) were significantly lower than for all acrylic resin teeth (149-166microm and 0.220-0.292mm3) (p< or =0.05), but higher than for ceramic teeth (36microm and 0.029mm3) and for enamel (56microm and 0.033mm3) (p< or =0.05). No significant differences were found among the acrylic resin teeth for both parameters (p>0.05).

SIGNIFICANCE

The composite resin showed improved in vitro two-body wear resistance compared to modern acrylic resin denture teeth; however, it showed less wear resistance than ceramic teeth and human enamel. Ceramic teeth should be preferred over natural teeth when occlusal stability is considered a high priority.

Compositional characteristics and hardness of acrylic and composite resin artificial teeth

STATEMENT OF PROBLEM

New types of artificial teeth are commercially available; however, evidence-based information regarding composition and properties is lacking.

PURPOSE

The purpose of this study was to qualify the compositional characteristics and hardness of new commercially available types of acrylic resin and composite resin artificial teeth.

MATERIAL AND METHODS

Twelve brands of 3 types (2 conventional acrylic resins, 3 cross-linked acrylic resins, and 7 composite resins) of artificial teeth were examined. The filler geometry and composition were observed using scanning electron microscopy and energy disperse x-ray analysis, respectively. Vickers hardness was determined for each layer of the polished cross-sectioned teeth. The inorganic content of the enamel layer was determined by thermogravimetric analysis with an ash method. The swelling behavior of the artificial teeth after 12 hours of methyl methacrylate immersion was observed to determine the cross-linking structure. The data were statistically analyzed using 1-way analysis of variance and Tukey's multiple comparison (alpha=.05).

RESULTS

Examined teeth were composed of 2, 3, or 4 layers of resin. Different sizes and shapes of filler were found but were composed only of silicon oxide. Vickers hardness ranged from 17.4 to 47.0 kgf/mm(2). The inorganic content ranged from 0 to 42.8 mass%. The enamel layer of all teeth, except for 3 products, produced negligible swelling, and the base layer of all the teeth, except for 2 products, produced obvious swelling. A significant linear correlation was observed between hardness and inorganic content.

CONCLUSIONS

Within the limitations of this study, differences in size, shape, distribution, and content of the silica filler and the cross-linking nature of the resin matrix were found among the commercial brands of artificial teeth evaluated.