Denture Tooth Materials Research Articles

In vitro evaluation of the mechanical and optical properties of 3D printed vs CAD/CAM milled denture teeth materials

This laboratory research aimed to assess the Flexural strength, fracture toughness, Volumetric wear and optical properties of various recent 3D-printed denture tooth materials and compare them to CAD/CAM milled materials. Four 3D-printed denture tooth materials (Lucitone Tooth, OnX, Flexcera Ultra +, and VarseoSmile Crown Plus) and one CAD/CAM milled denture teeth material (Ivotion Dent) were used to fabricate fifteen specimens for each material (with total no. of 300 specimens). Tests were conducted according to ISO standards to assess flexural strength, fracture toughness, color staining, and volumetric wear. All materials were printed, washed, cured, or milled following the manufacturer’s instructions. Flexural strength and fracture toughness values were obtained by a universal testing machine. Volumetric wear was evaluated using a non-contact optical profilometer. Color stability outcomes were obtained via a spectrophotometer for determining L*a*b* values, with color change (ΔE2000) based on the CIEDE2000 formula. Data were analyzed using one-way ANOVA and Tukey post-hoc analysis (α = 0.05). All 3D-printed materials exhibited higher flexural strength values than the milled material (p < 0.05). For fracture toughness, two of the 3D-printed materials showed higher values than the milled material, while the other two had lower values. Insignificant variances in volumetric wear were detected between the materials (p > 0.05). Color staining results varied, with milled materials generally demonstrating better-staining resistance compared to the 3D-printed materials. 3D-printed denture tooth materials exhibit good mechanical and optical properties, presenting a cost-effective and efficient alternative to CAD/CAM milled materials for denture tooth fabrication.

In Vitro Analysis of Bonding and Wear Properties of 3D Printed Denture Tooth Materials.

While additive manufacturing (3D printing) has recently enhanced removable prosthodontics, the properties of new 3D printed materials are not well understood. This study aims to elucidate the physical properties of these materials, focusing on bonding to a 3D printed denture base material and wear resistance. For denture tooth-denture base bonding analyses, the same denture tooth material (Premium Teeth, Formlabs) was used with three denture base-bonding group assignments (n=6 each group) bonded using three protocols: Group A1 was bonded with Lucitone Digital Print-3D Denture Base using the Lucitone Fuse System (Dentsply), Group A2 with Formlabs Denture Base using the Formlabs Denture Base Bonding System, and Group A3 with Formlabs Denture Base using the Ivoclar Ivotion Bonding System (Ivoclar). Specimens were made according to the ISO-TS-19736-2027 standard. A 3D printed tooth mimicking a central incisor was bonded to the denture base and subjected to a palatal load at the incisal region at 90° from the long axis of the tooth until failure. The fracture surface was examined at 10× magnification. ANOVA with α=0.05 was used to determine statistically significant differences. For wear analysis, the same denture base material and bonding system (Lucitone Digital Print-3D Denture Base/Lucitone Fuse System, Dentsply) was used with four denture tooth material group assignments (n=8 each group): Group B1 used Formlabs Premium Teeth, Group B2 used SprintRay High Impact Denture Teeth, Group B3 used Lucitone Digital IPN Premium Tooth, and Group B4 used Ivotion Polymethyl Methacrylate (PMMA) Milled Teeth (Ivoclar). A premolar denture tooth bonded with the denture base was subjected to a chewing simulation cyclic loading of 1,200,000 cycles. Sample failures, vertical wear, and volume loss were documented. ANOVA with α=0.05 was used to determine statistically significant differences. The fracture load to failure values for A1, A2, and A3 were 175±106 N, 167±46.3 N, and 183±48.9 N, respectively (p=0.95). Most failure characteristics were mixed, except one of A2 was cohesive and half of A3 was cohesive. For cyclic loading, B4 was the only group where all specimens failed within 1,200,000 cycles, while B1, B2, and B3 had four, three, and five sample failures, respectively. Vertical wear was 0.93±0.34 mm, 1.22±0.37 mm, 1.05±0.27 mm, and 0.37±0.02 mm for B1, B2, B3, and B4, respectively (p<0.01). Abrasion volumes were 9.5±3.7 mm³, 12.2±4.7 mm³, 10.6±3.5 mm³, and 2.2±1.3 mm³ for B1, B2, B3, and B4, respectively. Vertical height loss per chewing cycle (μm/cycle) was 0.0022±0.0019, 0.0030±0.0029, 0.0012±0.00005, and 0.0080±0.0050 for B1, B2, B3, and B4, respectively (p<0.01). Abrasion volume per chewing cycle (μm³/cycle) was 17650.8±9682.9, 27263.4±24746.8, 11836.5±4200.8, and 70436.8±73602.5 for B1, B2, B3, and B4, respectively (p=0.02). The bonding strength and wear resistance of 3D printed denture materials vary by manufacturer. Formlabs Denture Base with Ivoclar Ivotion showed the highest fracture load, indicating superior bonding strength. In wear analysis, Ivoclar Ivotion PMMA Milled Teeth exhibited the least vertical wear and abrasion volume but had the highest failure rate under cyclic loading. While printed denture materials excel in bonding strength, their wear resistance may not be as good as milled denture teeth, highlighting the need to balance these properties in clinical applications.

Analysis of the Surface Roughness of Different Denture Teeth Materials: A Quantitative In-Vitro Study.

The surface roughness of denture teeth materials significantly influences their clinical performance and patient satisfaction. Understanding the variations in surface roughness among different materials is crucial for optimizing denture fabrication processes. In this quantitative in-vitro study, three commonly used denture teeth materials, namely acrylic resin, composite resin, and porcelain, were evaluated for surface roughness. Twenty samples of each material were prepared and subjected to profilometric analysis. The surface roughness parameters Ra and Rz were measured using a contact profilometer. Statistical analysis was performed to compare the surface roughness among the different materials. The mean surface roughness (Ra) values were found to be 0.32 μm for acrylic resin, 0.25 μm for composite resin, and 0.18 μm for porcelain. Similarly, the mean Rz values were 2.45 μm for acrylic resin, 1.98 μm for composite resin, and 1.62 μm for porcelain. Statistical analysis revealed significant differences in surface roughness among the three materials (P < 0.05). Porcelain denture teeth exhibited the smoothest surface, followed by composite resin and acrylic resin. These findings suggest that material selection plays a crucial role in determining the surface roughness of denture teeth. Porcelain may offer superior aesthetics and reduced plaque accumulation compared with acrylic and composite resin materials. Clinicians should consider these differences when choosing denture materials to achieve optimal clinical outcomes and patient satisfaction.

Investigation of the Surface Roughness and Hardness of Different Denture Teeth Materials: An In vitro Study

ABSTRACT Background: Surface roughness and hardness are key factors that influence the clinical performance and durability of denture teeth. Understanding variations in these properties among different denture teeth materials can assist in selecting the most suitable materials for optimal patient outcomes. This study aimed to investigate the surface roughness and hardness of four commonly used denture teeth materials: acrylic resin, composite resin, porcelain, and nanohybrid composite. Materials and Methods: Ten specimens were prepared for each denture teeth material, resulting in a total of 40 specimens. Surface roughness was assessed using a profilometer, and measurements were recorded in micrometers (μm). Hardness was determined using a Vickers hardness tester, and results were expressed as Vickers hardness numbers (VHN). The surface roughness and hardness data were analyzed using appropriate statistical tests (e.g., analysis of variance), with significance set at P &lt; 0.05. Results: The results revealed significant differences in both surface roughness and hardness among the different denture teeth materials (P &lt; 0.05). Acrylic resin exhibited the highest surface roughness (mean ± standard deviation: 3.45 ± 0.78 μm) and the lowest hardness (mean ± standard deviation: 45.6 ± 2.3 VHN). Composite resin demonstrated intermediate values of surface roughness (mean ± standard deviation: 1.87 ± 0.54 μm) and hardness (mean ± standard deviation: 65.2 ± 3.9 VHN). Porcelain demonstrated the smoothest surface (mean ± standard deviation: 0.94 ± 0.28 μm) and the highest hardness (mean ± standard deviation: 78.5 ± 4.1 VHN). Nanohybrid composite displayed surface roughness and hardness values similar to composite resin. Conclusion: This study demonstrated significant variations in surface roughness and hardness among the different denture teeth materials evaluated. Acrylic resin exhibited the roughest surface and lowest hardness, while porcelain demonstrated the smoothest surface and highest hardness. Composite resin and nanohybrid composite exhibited intermediate values. These findings provide valuable insights for prosthodontic practitioners in selecting denture teeth materials based on specific clinical requirements, aiming to achieve optimal aesthetics, reduced plaque accumulation, and improved wear resistance.

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

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

Development of predictive algorithms for the wear resistance of denture teeth materials

ObjectivesTo investigate the wear resistance of conventional, CAD-milled and 3D-printed denture teeth in vitro with simulated aging. To use the collected data to train single time series sample model LSTM and provide proof of concept. MethodsSix denture teeth materials (Three Conventional; Double-cross linked PMMA (G1), Nanohybrid composite (G2), PMMA with microfillers (G3), CAD-milled (G4), two 3D-printed teeth (G5, G6) (Total n = 60) underwent simulation for 24 and 48 months of linear reciprocating wear using a universal testing machine (UFW200, NeoPlus) under 49 N load, 1 Hz and linear stroke of 2 mm in an artificial saliva medium. Single samples were parsed through Long Short-Term Memory (LSTM) neural network model using Python. To determine minimal simulation times, multiple data splits for training were trialled (10/20/30/40%). Scanning electron microscopy (SEM) was performed for material surface evaluation. Results3D printed tooth material (G5) had the lowest wear resistance (59 ± 35.71 μm) whereas conventional PMMA with microfillers (G3) shown the highest wear rate (303 ± 0.06 μm) after 48 months of simulation. The LSTM model successfully predicted up to 48 months wear using 30% of the collected data. Compared with the actual data, the model had a root-mean-square error range between 6.23 and 88.56 μm, mean-absolute-percentage-error 12.43-23.02% and mean-absolute-error 7.47-70.71 μm. SEM images revealed additional plastic deformations and chipping of materials, that may have introduced data artifacts. Conclusions3D printed denture teeth materials showed the lowest wear out of all studied for 48 months simulation. LSTM model was successfully developed to predict wear of various denture teeth. The developed LSTM model has the potential to reduce simulation duration and specimen number for wear testing of various dental materials, while potentially improving the accuracy and reliability of wear testing predictions. This work paves the way for generalized multi-sample models enhanced with empirical information.

Comparative in-vivo study on the wear resistance of three different denture teeth materials -1-year study

Comparative in-vivo study on the wear resistance of three different denture teeth materials -1-year study

Colour Stability of Different Denture Teeth Stored in Various Beverages

Aim: New types of denture teeth using modified acrylic resin that incorporate cross-linking agents and composite resin containing different types of filler have become increasingly common. It has been possible to produce nano-sized filler particles with nanotechnology. However, evidence-based information regarding composition and properties is lacking. The purpose of this study was to evaluate the colour stability of four commercially available denture tooth materials with different chemical structure when subjected to various beverages.&#x0D; Methods: Conventional acrylic resin, reinforced acrylic resin, microfiller composite resin, and nanofiller composite resin teeth with different brands were used, for a total of four different denture teeth groups. Denture teeth were subjected to four beverages (tea, filtered coffee, cola, and cherry juice) and distilled water as control. The test period of 24 hours appears comparable to approximately 1 month of normal beverage consumption. The test periods used in this study were arranged according to this protocol and 1 week, 1 month, 3 months and 6 months of normal beverage consumptions were simulated. From each group, 10 maxillary first molar denture teeth were immersed in each of the five solutions. The baseline, 1st week, 1st month, 3rd month and 6th month values for colour change of denture teeth were measured. &#x0D; Results: The differences of each value were calculated by one-way ANOVA statistically. For colour changes (ΔE) there was no significant difference among the specimens immersed in distilled water (Tukey HSD test, p&gt;0.01). The highest colour changes were recorded for the specimens of Integral and Major immersed in cola, whereas for the specimens of Veracia and Orthosit immersed in tea (Tukey HSD test, p

Effect of Two Denture Teeth Materials on Masticatory Efficiency, Wear, Bonding to Denture Base

Effect of Two Denture Teeth Materials on Masticatory Efficiency, Wear, Bonding to Denture Base

The Effect of Nano-hybrid Composite Resin Denture Teeth on Mandibular Residual Ridge

Introduction:Progressive ridge resorption is one of the main causes of loss of stability and retention of mandibular complete dentures with subsequent loss of masticatory efficiency and patient discomfort. Aim: This study was conducted to evaluate radiographically the effect of nano-hybrid composite resin teeth on mandibular residual ridge using cone beam computerized tomography (CBCT). A comparative study. Materials and Methods: Twelve completely edentulous male patients were randomly divided into two groups according to the artificial tooth material used in complete denture construction. One group received complete dentures with nano-hybrid composite resin teeth and the other group received complete dentures with cross-linked acrylic resin teeth. CBCT was taken at the delivery, 6 months and 12 months follow -up appointments. The evaluation was done for height and width changes of the mandibular residual alveolar ridge at different anatomical sites either in the anterior or posterior part of the mandible. Results: Analysis was done by using two-tailed t-test revealed that increase in amount of bone loss in both groups which is in favor to patients wearing dentures with nano-hybrid composite resin teeth, with no statistically significant difference between the two groups. Conclusion: Despite of introduction of new denture tooth material as nano-hybrid composite resin teeth, the cross-linked acrylic resin teeth still considered the gold standard denture teeth regarding the degree of occlusal force transmission and preservation of residual alveolar ridge.

Wear Resistance of 3D Printed and Prefabricated Denture Teeth Opposing Zirconia.

To evaluate the wear resistance of a recently developed three-dimensional (3D) printed denture teeth resin compared to three commercially available prefabricated denture teeth. A total of 88 maxillary first molar denture teeth were evaluated: C (Classic; Dentsply Sirona, York, PA), DCL (SR Postaris DCL; Ivoclar Vivadent, Schaan, Liechtenstein), IPN (Portrait IPN; Dentsply Sirona, York, PA), and F (Denture Teeth A2 Resin 1 L; Formlabs, Somerville, MA). The 3D printed denture tooth specimens were fabricated from a methacrylate-based photopolymerizing resin using stereolithography (SLA). Denture teeth were subjected to a three-body wear test with a poly(methylmethacrylate) (PMMA) abrasive slurry. A Leinfelder-style four station wear apparatus with custom bullet-shaped milled zirconia styli was utilized with a load force of 36-40 N at 1.7 Hz for 200,000 cycles. Maximum depth of wear was measured using a lab grade scanner and analyzing software program. Data were analyzed using a one-way ANOVA followed by the Tukey's Multiple Comparisons post hoc test (α = 0.05). A statistically significant difference in depth of wear was found between denture tooth materials (p < 0.001). The mean vertical depth of wear for the 3D printed denture teeth (0.016 ± 0.010 mm) was statistically significantly less than the prefabricated denture teeth. The highly cross-linked denture teeth, DCL (0.036 ± 0.011 mm) and IPN (0.035 ± 0.014 mm), exhibited statistically significantly less wear than the conventional acrylic denture teeth. The conventional acrylic denture teeth demonstrated the greatest wear (0.058 ± 0.014 mm). No significant difference in depth of wear was found between DCL and IPN (p > 0.001). Denture tooth material significantly influences the depth of wear. The 3D printed denture teeth demonstrated superior wear resistance compared to the commercially available prefabricated denture teeth when opposed to zirconia. Denture teeth fabricated with SLA technology may have a promising future in prosthetic dentistry.

Bond Strength of Acrylic Denture Tooth to a Novel Thermo-Polymerized Denture Base Copolymer Containing Cycloaliphatic Comonomer after Mechanical and Thermal Aging.

Background:There are numerous artificial denture tooth materials available of which acrylic resin teeth were used widely. The resin teeth bond chemically to the denture base resin, and this bonding is affected by numerous intrinsic and extrinsic factors. The type of cross-linker in the denture base monomer is one such factor which has a questionable influence on the bond strength. Recently, cycloaliphatic comonomer was added in the methyl methacrylate monomer and the resultant novel copolymer possessed good physico-mechanical and biological properties.Purpose:The purpose of this study was to evaluate the shear bond strength (SBS) between acrylic denture tooth and resultant novel copolymer after cyclic loading and thermal aging.Materials and Methods:Sixty central incisor denture teeth were bonded to three types of acrylic denture base resin groups (n = 20 per group) categorized based on the presence of the cycloaliphatic comonomer – Control group (G0): denture bases without cycloaliphatic comonomer and trial groups G10 and G20 contain 10 vol.% and 20 vol.% comonomer, respectively, substituted in the denture base monomer component. The specimens were processed and subjected to cyclic loading and thermal aging which was then followed by SBS testing.Results:G20 possessed the highest SBS followed by G10. G0 had the least SBS. All the specimens of the control and trial groups exhibited adhesive–cohesive mixed failure at the resin tooth–base resin interface.Conclusion:The addition of cycloaliphatic comonomer increased the SBS between the resultant novel copolymer and the resin teeth after cyclic loading and thermal aging.

Effect of SiO2 and Al2O3 nanoparticles on wear resistance of PMMA acrylic denture teeth

Objective: This study aimed to evaluate the wear resistance of acrylic denture teeth containing silicon dioxide (nano-SiO2) and aluminum dioxide (nano-Al2O3) nanoparticles. Material and Methods: Poly methyl methacrylate (PMMA) denture tooth material was used to denture tooth material was used to fabricate 84 specimens (n=10) containing nano-SiO2 and nano-Al2O3 in concentrations 0.1wt%, 0.3wt%, and 0.5wt% of acrylic powder. A two-body wear testing machine and digital microscope were used to measure the changes in weight loss and surface roughness respectively. One-way ANOVA and pair-wise Tukey’s post-hoc tests were used for data analysis (? = 0.05). Results: Nano-SiO2 modified teeth material demonstrated a significant increase in weight loss in comparison conventional artificial acrylic teeth material (p ? 0.05) while nano- Al2O3 modified teeth material demonstrated non-significant increase in weight loss except for 0.5% subgroup (p ? 0.05). There is no significant differences regarding roughness change after wear simulation among all tested groups (p &gt; 0.05). Conclusion: Nano-Al2O3 nanoparticles exhibit less negative effect than nano-SiO2 so; it could be used with caution if necessary.KeywordsAcrylic denture teeth; Al2O3 nanoparticles; SiO2 nanoparticles; wear resistance; surface roughness.

The Effect of Different Beverage Solutions on the Hardness of Different Acrylic Denture Teeth

Aims: To determine the effect of different beverage solutions on the hardness of different acrylic denture teeth which are commercially available. Materials and Methods: Sixty samples were prepared from three brands of artificial teeth in this study. The posterior teeth of each brand were placed in auto polymerizing acrylic resin and the occlusal surfaces were ground flat, then immersed in distilled water (control), Pepsi, coffee and tea solutions for 30 days and then the hardness were tested using Vickers microhardness tester. Results: The RMH denture teeth materials showed the highest hardness than other denture teeth materials. Pepsi was more effective than tea and coffee in reducing the hardness of different acrylic teeth materials. Conclusions: Pepsi reduced the hardness of different acrylic teeth materials during the 30 days immersion. The hardness of RMH denture teeth materials was less affective by the different beverage solutions.

Wear of resin teeth opposing zirconia

Statement of problemThe use of dissimilar materials for opposing complete-mouth implant-supported prosthesis has become popular, especially when one arch is made from anatomical contour zirconia. However, the amount of wear zirconia causes on resin and other denture tooth materials is largely unknown. PurposeThe purpose of this in vitro study was to determine the volumetric wear of 4 commercially available resin materials used for denture teeth in complete-arch implant-supported prostheses opposed by zirconia. Material and methodsA total of 32 maxillary central incisor denture teeth were evaluated (n=8): double crosslinked polymethyl methacrylate (PMMA) (DCL), nanohybrid composite resin (PHO), and computer-aided design and computer-aided manufacturing (CAD-CAM)-fabricated teeth made from crosslinked PMMA (TEL) and acrylate polymer (ZCAD). Antagonist cone-shaped specimens were milled from zirconia. Specimens were mounted in acrylic resin, polished to a flat surface by using 1200-grit SiC paper, and stored in water (37 °C for 24 hours) before exposure in a custom dual-axis wear simulator for 200 000 cycles with a vertical load of 20 N, a horizontal slide of 2 mm, and a frequency of 1 Hz. Volumetric wear was measured by using a noncontact profilometer and a superimposition software program. Data were analyzed with a 1-way analysis of variance (ANOVA) and the Tukey Honestly Significant Difference (HSD) post hoc test (α=.05). ResultsA statistically significant difference in volumetric wear was found between groups (P<.001), with PHO (4.3 ±1.0 mm3)<TEL (11.9 ±2.0 mm3)<ZCAD (14.2 ±0.8)<DCL (17.3 ±1.0 mm3). ConclusionsDenture teeth made from different materials demonstrate significantly different volumetric substance loss when subjected to occlusal wear by zirconia antagonists. Nanohybrid composite resin denture teeth had the least amount of volumetric substance loss.

STUDY OF COLOR STABILITY OF SOME DENTURE TEETH MATERIALS

Objective: To study the color stability of some denture teeth materials (acrylic &porcelain) and to evaluate some mechanical properties of these denture teeth materials. Material and methods: Forty samples of both acrylic and porcelain teeth were immersed in three staining solutions and distilled water. Color measurements were performed by using spectrophotometer. Before immersion, the initial color value of each tooth was recorded. Color change values were determined after 1 day, 1 week, 2 weeks, 4weeks and 6 weeks of immersion. Color differences were characterized using the CIE L*a*b* color space. Also water sorption and surface roughness were evaluated. Results: showing significant color changes of the different denture teeth materials upon immersion in tea, coffee, cola, or distilled water. This color change was greater in case of immersion in either tea or coffee solutions. The least color change was obtained from samples immersed in distilled water. The different materials used showed no significant statistical difference in water sorption values. Finally the results showed that, there were significant statistical differences in surface roughness of all tested materials after immersion in any of the tested solutions. Conclusion: The acrylic denture teeth material is much more subjected to discoloration than the porcelain denture teeth material. Water sorption of the tested materials was of close values. Surface roughness of the denture teeth material show significant statistical difference by immersion in staining solutions

Do denture processing techniques affect the mechanical properties of denture teeth?

Statement of problemDenture tooth fracture may limit the longevity of dental prostheses. Whether the strength of the denture tooth material is affected by the denture processing technique is unclear. PurposeThe purpose of this in vitro study was to investigate whether the denture processing technique affects the mechanical properties of denture tooth materials. Material and methodsTwo denture processing techniques, injection and compression molding, were tested for 3 types of denture teeth: nanohybrid composite (NHC), interpenetrating network (IPN), and microfiller-reinforced polyacrylic (MRP). Denture teeth were processed by using an injection-molded resin or a compression-molded resin. Unprocessed denture teeth served as the control. After teeth were processed, they were sectioned into rectangular beams for 3-point bend testing (n=20 to 24). Elastic moduli were determined from load deflection and maximum stress from maximum bending load. The results were statistically analyzed by using 2-way ANOVA and multiple comparisons (α=.05). ResultsThe processing technique and the type of denture tooth affected both the elastic modulus and the maximum stress. The injection-molded technique resulted in significantly higher (24% to 26%) elastic modulus for NHC and IPN (12% higher in MRP, but not statistically significant) and higher (12% to 17%) maximum stresses for IPN and MRP (3% lower in NHC, but not statistically significant). Compression-molded technique increased the elastic modulus of IPN and NHC by 10% to 17% (3% lower in MRP but not statistically significant), but maximum stresses were not statistically significantly different in any of the tested teeth. Regardless of processing, MRP teeth had the highest elastic modulus (8.0 to 9.2 GPa) but the lowest maximum stresses (97 to 124 MPa), whereas IPN teeth had the lowest elastic modulus (5.5 GPa) but high or highest maximum stress (171 to 192 MPa). ConclusionsThe injection-molded technique significantly increased the elastic modulus of NHC and IPN teeth and significantly increased the maximum stress of IPN teeth. The compression-molded technique did not significantly affect mechanical properties of denture teeth.

In Vitro Wear Resistance of Nano-Hybrid Composite Denture Teeth.

To evaluate the wear resistance of nano-hybrid composite denture teeth as compared to two commonly used denture teeth: interpenetrating polymer network (IPN) and double crosslinking polymethylmethacrylate (PMMA) denture teeth. 18 styli and 18 disk specimens were prepared from the three denture tooth materials: nano-hybrid composite, IPN, and double crosslinking PMMA. The specimens were mounted in a two-body wear testing machine to simulate chewing in the complete denture. The amount of wear from the styli specimens were measured before and after using a digital micrometer, and the depth of the wear track from the disk specimens was measured using a noncontact 3D optical profilometer. The total wear from each denture tooth group was compared using one-way ANOVA with a 0.05 significance level. A Tukey post hoc test was used to determine differences between the three groups. The mean total wear in the nano-hybrid composite teeth group was 1.16 mm, SD = 0.5 mm, statistically significantly higher (p ≤ 0.0001) than the IPN (mean = 0.13 mm, SD = 0.05) and double crosslinking PMMA tooth groups (mean = 0.31 mm, SD = 0.19). There was no statistically significant difference between IPN denture teeth and double crosslinking PMMA denture teeth in the amount of wear. Nano-hybrid composite denture teeth exhibited statistically significantly more wear than the IPN and double crosslinking PMMA denture teeth.

Fatigue resistance of denture teeth

AimsThere is no standard test to determine the fatigue resistance of denture teeth. With the increasing number of patients with implant-retained dentures the mechanical strength of the denture teeth requires more attention and valid laboratory test set-ups. The purpose of the present study was to determine the fatigue resistance of various denture teeth using a dynamic load testing machine. MethodsFour denture teeth were used: Bonartic II (Candulor), Physiodens (Vita), SR Phonares II (Ivoclar Vivadent) and Trubyte (Dentsply). For dynamic load testing, first upper molars with a similar shape and cusp inclination were selected. The molar teeth were embedded in cylindrical steel molds with denture base material (ProBase, Ivoclar Vivadent). Dynamic fatigue loading was carried out on the mesio-buccal cusp at a 45° angle using dynamic testing machines and 2,000,000 cycles at 2Hz in water (37°C). Three specimens per group and load were submitted to decreasing load levels (at least 4) until all the three specimens no longer showed any failures. All the specimens were evaluated under a stereo microscope (20× magnification). The number of cycles reached before observing a failure, and its dependence on the load and on the material, has been modeled using a parametric survival regression model with a lognormal distribution. This allowed to estimate the fatigue resistance for a given material as the maximal load for which one would observe less than 1% failure after 2,000,000 cycles. ResultsThe failure pattern was similar for all denture teeth, showing a large chipping of the loaded mesio-buccal cusp. In our regression model, there were statistically significant differences among the different materials, with SR Phonares II and Bonartic II showing a higher resistance than Physiodens and Trubyte, the fatigue resistance being estimated at around 110N for the former two, and at about 60N for the latter two materials. ConclusionThe fatigue resistance may be a useful parameter to assess and to compare the clinical risk of chipping and fracture of denture tooth materials.

Influence of surface sealant agents on the surface roughness and color stability of artificial teeth

Statement of problemAlthough various surface sealant agents are available and recommended for chairside polishing procedures, their effect on the surface roughness and color stability of denture teeth is not clear. PurposeThe purpose of this in vitro study was to evaluate the effect of sealant agents on the surface roughness and color stability of various denture tooth materials. Material and methodsEighty disk-shaped specimens were prepared for each type of denture tooth material (SR Vivodent, PMMA; Vitapan, reinforced-PMMA; SR Phonares II, composite resin). The specimens were assigned to 4 groups according to the surface treatment used (n=20): surface sealant agents (Palaseal; Heraeus Kulzer GmbH, Optiglaze; GC Corp Biscover; Bisco Inc) and a conventional laboratory polishing technique (control group). A thermal cycling procedure was applied for half of the specimens (n=10). The surface roughness (Ra) values of thermocycled and nonthermocycled specimens were measured with a profilometer. The CIELab color parameters of both thermocycled and nonthermocycled specimens were measured with a spectrophotometer at baseline and after 7-day storage in a coffee solution. The color differences were calculated from the CIEDE2000 (ΔE00) formula. Data were statistically analyzed with 3-way ANOVA and the Tukey HSD test (α=.05). ResultsThe type of tooth material, surface treatment technique, and their interactions were significant for Ra values, and each variable and their interactions were also significant for ΔE00 values (P<.05). Thermal cycling had a significant effect only on ΔE00 values (P<.05). ConclusionsPalaseal and Optiglaze sealant agents provided smoother and more color-stable denture tooth surfaces than the conventional polishing technique. The use of the Biscover agent with SR Vivodent and Phonares II teeth increased the Ra values. The color of conventionally polished SR Vivodent and Phonares II teeth changed more with thermal cycling.