Editorial Type:
Article Category: Laboratory Research
 | 
Online Publication Date: 01 May 2015

Localized and Generalized Simulated Wear of Resin Composites

,
,
,
,
, and
Page Range: 322 – 335
DOI: 10.2341/13-155-L
Save
Download PDF

SUMMARY

A laboratory study was conducted to examine the wear of resin composite materials using both a localized and generalized wear simulation model. Twenty specimens each of seven resin composites (Esthet•X HD [HD], Filtek Supreme Ultra [SU], Herculite Ultra [HU], SonicFill [SF], Tetric EvoCeram Bulk Fill [TB], Venus Diamond [VD], and Z100 Restorative [Z]) were subjected to a wear challenge of 400,000 cycles for both localized and generalized wear in a Leinfelder-Suzuki wear simulator (Alabama machine). The materials were placed in custom cylinder-shaped stainless steel fixtures. A stainless steel ball bearing (r=2.387 mm) was used as the antagonist for localized wear, and a stainless steel, cylindrical antagonist with a flat tip was used for generalized wear. A water slurry of polymethylmethacrylate (PMMA) beads was used as the abrasive media. A noncontact profilometer (Proscan 2100) with Proscan software was used to digitize the surface contours of the pretest and posttest specimens. AnSur 3D software was used for wear assessment. For localized testing, maximum facet depth (μm) and volume loss (mm3) were used to compare the materials. The mean depth of the facet surface (μm) and volume loss (mm3) were used for comparison of the generalized wear specimens. A one-way analysis of variance (ANOVA) and Tukey post hoc test were used for data analysis of volume loss for both localized and generalized wear, maximum facet depth for localized wear, and mean depth of the facet for generalized wear. The results for localized wear simulation were as follows [mean (standard deviation)]: maximum facet depth (μm)—Z, 59.5 (14.7); HU, 99.3 (16.3); SU, 102.8 (13.8); HD, 110.2 (13.3); VD, 114.0 (10.3); TB, 125.5 (12.1); SF, 195.9 (16.9); volume loss (mm3)— Z, 0.013 (0.002); SU, 0.026 (0.006); HU, 0.043 (0.008); VD, 0.057 (0.009); HD, 0.058 (0.014); TB, 0.061 (0.010); SF, 0.135 (0.024). Generalized wear simulation results were as follows: mean depth of facet (μm)—Z, 9.3 (3.4); SU, 12.8 (3.1); HU, 15.6 (3.2); TB, 19.2 (4.8); HD, 26.8 (6.5); VD, 29.1 (5.5); SF, 35.6 (8.4); volume loss (mm3)—Z, 0.132 (0.049); SU, 0.0179 (0.042); HU, 0.224 (0.044); TB, 0.274 (0.065); HD, 0.386 (0.101); VD, 0.417 (0.076); SF, 0.505 (0.105). The ANOVA showed a significant difference among materials (p<0.001) for facet depth and volume loss for both localized and generalized wear. The post hoc test revealed differences (p<0.05) in localized and generalized wear values among the seven resin composites examined in this study. The findings provide valuable information regarding the relative wear characteristics of the materials in this study.

INTRODUCTION

Wear of resin composite materials has been a concern of the dental profession since the materials were first advocated for the posterior dentition in the early 1970s. Early clinical trials of resin composite in the posterior region showed significant wear when compared with metallic restorations.1 Improvements in the resin matrix and filler components of resin composites have resulted in markedly better materials for the posterior dentition than the early-generation composites.2-11 Clinical studies over the years have shown steady improvements in the performance of later-generation resin composites.12-23

Due to the limited clinical information available to the profession regarding the performance of resin composite materials, laboratory wear simulation has evolved as a useful methodology for assessing relative wear resistance. Simulation models for both localized wear (occlusal contact area [OCA] wear) and generalized wear (contact-free area [CFA] wear) have been developed. Barkmeier and others24 recently recommended that a benchmark resin composite material (Z100 Restorative, 3M ESPE, St Paul, MN, USA) with good clinical and simulated wear performance be used as a standard for laboratory wear comparison with other resin composites. The recommendation is further strengthened by the good agreement of clinical and laboratory wear rates of the Z100 Restorative material.16,18

Additional information regarding wear characteristics of resin composites is needed. Limited data regarding the clinical wear performance of resin composite materials are available in the literature. The purpose of this study was to expand the information base on the simulated wear of resin composite materials and compare them with a benchmark material (Z100 Restorative). The materials selected for this study are current-generation materials, and little information about the relative performance of these materials is available to the profession. In addition, this study incorporated the use of a new computer software program for wear analysis.

METHODS AND MATERIALS

Wear Simulation

Seven resin composite materials were evaluated in this study: 1) Esthet•X HD (HD) (Dentsply Caulk, Milford, DE, USA); 2) Filtek Supreme Ultra (SU) (3M ESPE); 3) Herculite Ultra (HU) (Kerr Corporation Orange, CA, USA); 4 SonicFill (SF) (Kerr Corporation), 5) Tetric EvoCeram Bulk Fill (TB) (Ivoclar Vivadent AG, Schaan, Liechtenstein); 6) Venus Diamond (VD) (Heraeus Kulzer GmbH, Hanau, Germany); and 7) Z100 Restorative (Z) (3M ESPE). The resin composite materials and their components are listed in Tables 1 and 2.

Table 1: Resin Composite Materials
Table 1:
Table 2: Information on Resin Composites
Table 2:

Twenty specimens of each of the seven resin composites were prepared for simulated localized wear (OCA wear) and 20 specimens of each material were prepared for generalized wear (CFA wear). Cylinder-shaped custom stainless steel fixtures used for the localized wear were machined with a cylindrical cavity 6.5 mm in diameter and 4 mm in depth. Stainless steel fixtures for generalized wear testing were machined with a cylindrical cavity 4.5 mm in diameter and 4 mm in depth. Two increments of the resin composite materials (approximately 2 mm in thickness) were cured for 40 seconds each with a Spectrum 800 curing unit (Dentsply Caulk) set at 600 mW/cm2. A SonicFill handpiece (Kerr Corporation) was used for insertion of the SF material into the cavity in the stainless custom fixtures, and the other six materials were inserted using a condenser. Twenty-four hours later, the composite surfaces were polished flat (Figures 1 and 2) to 4000-grit using a sequence of silicon carbide papers (Struers Inc, Cleveland, OH, USA).

Figure 1. Stainless steel custom fixture for localized wear.Figure 1. Stainless steel custom fixture for localized wear.Figure 1. Stainless steel custom fixture for localized wear.
Figure 1. Stainless steel custom fixture for localized wear.

Citation: Operative Dentistry 40, 3; 10.2341/13-155-L

Figure 2. Stainless steel custom fixture for generalized wear.Figure 2. Stainless steel custom fixture for generalized wear.Figure 2. Stainless steel custom fixture for generalized wear.
Figure 2. Stainless steel custom fixture for generalized wear.

Citation: Operative Dentistry 40, 3; 10.2341/13-155-L

A Leinfelder-Suzuki wear simulation device (Alabama machine) was used for this study. The simulator has a plastic water bath, and the custom wear fixtures were mounted inside the four-station bath. A brass cylinder was then placed around each fixture in the bath to serve as a reservoir for the abrasive media (water slurry of unplasticized polymethyl methacrylate [PMMA] with an average particle size of 44 μm). The media was placed inside the brass cylinders to cover the surface of the resin composite in the custom fixtures. The water slurry of PMMA inside the brass cylinders was approximately 6 mm in height over the surface of the resin composite.

Two different wear antagonists were used in this study. For localized (OCA) wear simulation, a stainless steel ball bearing (r=2.387 mm) was mounted inside a collet assembly (Figure 3). The antagonist for the generalized (CFA) wear simulation was a stainless steel cylinder (diameter, 6.5 mm) with a flat tip (Figure 4). The antagonist tips were mounted on spring-loaded pistons to deliver the wear challenges. During the application of the load, the antagonists rotated approximately 30° as the maximum force was reached (maximum load of 78.5 N at a rate of 2 Hz), and then they counterrotated back to the original starting position as the load was relaxed to complete the cycle. Each set of specimens was exposed to 400,000 cycles in the wear simulator.

Figure 3. Stainless steel antagonist tip for simulated localized wear.Figure 3. Stainless steel antagonist tip for simulated localized wear.Figure 3. Stainless steel antagonist tip for simulated localized wear.
Figure 3. Stainless steel antagonist tip for simulated localized wear.

Citation: Operative Dentistry 40, 3; 10.2341/13-155-L

Figure 4. Stainless steel antagonist tip for simulated generalized wear.Figure 4. Stainless steel antagonist tip for simulated generalized wear.Figure 4. Stainless steel antagonist tip for simulated generalized wear.
Figure 4. Stainless steel antagonist tip for simulated generalized wear.

Citation: Operative Dentistry 40, 3; 10.2341/13-155-L

Wear Measurements

Prior to wear simulation, each resin composite specimen was profiled using a Proscan 2100 noncontact optical profilometer (Scantron Industrial Products Ltd, Taunton, England) with Proscan software. These profiles provided the pretest digitized contours (20 test specimens each for the seven resin composite materials for both localized and generalized wear testing).

Following the 400,000 wear cycles, the specimens were ultrasonically cleaned (L&R Solid State Ultrasonic T-14B, South Orange, NJ, USA) in distilled water for three minutes and then profiled again using the Proscan 2100 unit. The x-, y-, and z-coordinates of the before and after scans from the Proscan software were exported to another computer for analysis with AnSur 3D software (Minnesota Dental Research Center for Biomaterials and Biomechanics, University of Minnesota, Minneapolis, MN, USA). The x-, y-, and z-coordinates generated with the Proscan software were saved as .prn files and then imported into the AnSur 3D program.

Wear measurements were determined from differences between the before and after data sets. A computerized fit was accomplished with the before and after data sets in AnSur 3D and volume loss measurements (mm3) were then determined for both localized and generalized wear simulation for each of the seven resin composites. Maximum depth of the wear facet (μm) was also determined for the localized wear specimens, and mean depth (μm) of the wear facet was determined for the generalized specimens. A one-way analysis of variance (ANOVA) and Tukey post hoc test were used for data analysis of volume loss for both localized and generalized wear, maximum facet depth for localized wear, and mean facet depth for generalized wear.

Scanning Electron Microscopy Observations

Specimens were prepared for argon-ion etching and scanning electron microscopy (SEM) examinations at Nihon University School of Dentistry in Tokyo, Japan. The seven resin composites examined in this manner may not have been from the same lot numbers as the resin materials subjected to the wear simulation studies at Creighton University School of Dentistry. The surfaces of the cured resin composites were polished to a high gloss with abrasive discs (Fuji Star Type DDC, Sankyo Rikagaky Co Ltd, Saitama, Japan), followed by a series of diamond pastes down to 0.25-μm particle size (DP-Paste, Struers, Ballerup, Denmark). The polished surfaces were subjected to argon-ion beam etching (IIS-200ER, Elionix, Tokyo, Japan) for 45 seconds with the ion beam directed at the polished surface (accelerating voltage of 1.0 kV, ion current density 0.4 mA/cm2). The surfaces were then coated in a vacuum evaporator with a thin film of gold . Observations were done with a SEM (FE-8000, Elionix, Tokyo, Japan) at an operating voltage of 10 kV and magnification of 5000×.

SEM examinations were completed at the Creighton University School of Dentistry on the wear facets of the seven resin composite materials after both localized and generalized wear simulation. Following the wear analysis, representative samples of each material were sputter coated with gold and palladium (Emitech SC7620 Mini Sputter Coater, Quorum Technologies, Ashford, UK). The coated specimens were then examined with a TM3000 Tabletop Microscope (Hitachi-High Technologies Corporation, Tokyo, Japan) using an accelerating voltage of 15 kV and magnification of 5000×.

RESULTS

Wear Measurements

The one-way ANOVA tests showed a significant effect for material for both simulated localized wear and simulated generalized wear for both facet depth and volume loss (p<0.001). The results of the ANOVA testing are shown in Tables 3-6.

Table 3: Analysis of Variance of Simulated Localized Wear—Facet Depth
Table 3:
Table 4: Analysis of Variance for Simulated Localized Wear—Volume Loss
Table 4:
Table 5: Analysis of Variance for Simulated Generalized Wear—Mean Facet Depth
Table 5:
Table 6: Analysis of Variance for Simulated Generalized Wear—Volume Loss
Table 6:

The localized wear values (maximum facet depth and volume loss) for the seven resin composite materials evaluated are presented in Tables 7 and 8. The statistical differences (p<0.05) in localized wear among the seven materials using the Tukey post hoc test are also shown in the same tables.

Table 7: Simulated Localized Wear—Maximum Facet Depth (μm) and SD
Table 7:
Table 8: Simulated Localized Wear—Volume Loss (mm3) and SD
Table 8:

For the seven materials examined, values for the mean (standard deviation) of maximum facet depth (μm) for localized wear ranged from 59.5 (14.7) to 195.9 (16.9). The localized wear facet depth of Z was significantly less (p<0.05) than the other six materials in this study. The mean facet depth of SF was significantly greater (p<0.05) than the other six materials.

The localized wear mean volumetric loss (mm3) ranged from 0.003 (0.002) to 0.135 (0.024). The localized wear volumetric loss of Z was significantly less (p<0.05) than of the other six materials. The volumetric loss of SF was significantly greater (p<0.05) than of the other six materials.

The generalized wear values (mean facet depth and volume loss) are presented in Tables 9 and 10. The results of the Tukey test for significant differences among the materials tested are shown in the same tables.

Table 9: Simulated Generalized Wear—Mean Facet Depth (μm) and SD
Table 9:
Table 10: Simulated Generalized Wear—Volume Loss (mm3) and SD
Table 10:

The mean depth (μm) of the wear facets for generalized wear ranged from 9.3 (3.4) to 35.6 (8.4). The benchmark material (Z) exhibited the least facet wear depth using the generalized wear model. SU ranked second in wear resistance and was not significantly different (p>0.05) from Z. The generalized facet wear depth of SF was significantly greater (p<0.05) than of the other six materials evaluated.

The rank order of all seven materials was the same for generalized volumetric loss and generalized facet wear depth. The Z resin composite exhibited the least volumetric loss during generalized wear simulation but was not statistically different (p>0.05) from SU. The volume loss of SF was significantly greater (p<0.05) than of the other six materials in this study.

SEM Observations

SEM examinations of the seven resin composite materials evaluated by argon-ion etching are presented in Figure 5A-G. This figure demonstrates the differences in the shape and size of the filler components of the materials subjected to wear challenges in this study. The argon-ion etching shows clear differences in filler particle size, shape, and distribution. Z and SU have zirconia/silica filler particles that are more rounded or cylindrical (Figure 5B,G) than the typical ground glass particle contained in many resin composite systems. The glass filler particles of SF (Figure 5D) and VD (Figure 5F) appeared to be larger than the fillers in the other resin composite systems with ground (milled) glass filler particles (HD, Figure 5A; TB, Figure 5E; and HU, Figure 5C). The ground/milled glass particles (VD, TB, SF, HU, and HD) are more irregular in shape, when compared with the agglomerated filler particles in Z and SU.

Figure 5. (A): Esthet•X HD—argon-ion etched surface at 5000×. (B): Filtek Supreme Ultra—argon-ion etched surface at 5000×. (C): Herculite Ultra—argon-ion etched surface at 5000×. (D): SonicFill—argon-ion etched surface at 5000×. (E): Tetric EvoCeram Bulk Fill—argon-ion etched surface at 5000×. (F): Venus Diamond—argon-ion etched surface at 5000×. (G): Z100 Restorative—argon-ion etched surface at 5000×.Figure 5. (A): Esthet•X HD—argon-ion etched surface at 5000×. (B): Filtek Supreme Ultra—argon-ion etched surface at 5000×. (C): Herculite Ultra—argon-ion etched surface at 5000×. (D): SonicFill—argon-ion etched surface at 5000×. (E): Tetric EvoCeram Bulk Fill—argon-ion etched surface at 5000×. (F): Venus Diamond—argon-ion etched surface at 5000×. (G): Z100 Restorative—argon-ion etched surface at 5000×.Figure 5. (A): Esthet•X HD—argon-ion etched surface at 5000×. (B): Filtek Supreme Ultra—argon-ion etched surface at 5000×. (C): Herculite Ultra—argon-ion etched surface at 5000×. (D): SonicFill—argon-ion etched surface at 5000×. (E): Tetric EvoCeram Bulk Fill—argon-ion etched surface at 5000×. (F): Venus Diamond—argon-ion etched surface at 5000×. (G): Z100 Restorative—argon-ion etched surface at 5000×.
Figure 5. (A): Esthet•X HD—argon-ion etched surface at 5000×. (B): Filtek Supreme Ultra—argon-ion etched surface at 5000×. (C): Herculite Ultra—argon-ion etched surface at 5000×. (D): SonicFill—argon-ion etched surface at 5000×. (E): Tetric EvoCeram Bulk Fill—argon-ion etched surface at 5000×. (F): Venus Diamond—argon-ion etched surface at 5000×. (G): Z100 Restorative—argon-ion etched surface at 5000×.

Citation: Operative Dentistry 40, 3; 10.2341/13-155-L

SEM examinations of the localized wear facets (Figure 6A-6G) also demonstrated the differences in the filler systems of the resin composites in this study. SEM observations of Z and SU revealed a similar wear pattern with some fracturing of the resin matrix, resulting in micron size filler particles being fractured out on the surface. Despite this fracturing process, the localized wear of Z and SU was less than that of the other materials in this study. The SEM observations of SF (Figure 6D) showed larger glass filler particles and some fracturing of the particles resulting from the concentrated force applied with the localized antagonist. The VD SEM observations (Figure 6F) showed evidence of fatigue cracks in the resin matrix and plucking of glass filler particles from the surface. The SEM observations of HU (Figure 6C) and TB (Figure 6E) appeared to show evidence of the prepolymerized filler components of these systems.

Figure 6. (A): Esthet•X HD—localized wear near center of facet at 5000×. (B): Filtek Supreme Ultra—localized wear near center of facet at 5000×. (C): Herculite Ultra—localized wear near center of facet at 5000×. (D): SonicFill—localized wear near center of facet at 5000×. (E): Tetric EvoCeram Bulk Fill—localized wear near center of facet at 5000×. (F): Venus Diamond—localized wear near center of facet at 5000×. (G): Z100 Restorative—localized wear near center of facet at 5000×.Figure 6. (A): Esthet•X HD—localized wear near center of facet at 5000×. (B): Filtek Supreme Ultra—localized wear near center of facet at 5000×. (C): Herculite Ultra—localized wear near center of facet at 5000×. (D): SonicFill—localized wear near center of facet at 5000×. (E): Tetric EvoCeram Bulk Fill—localized wear near center of facet at 5000×. (F): Venus Diamond—localized wear near center of facet at 5000×. (G): Z100 Restorative—localized wear near center of facet at 5000×.Figure 6. (A): Esthet•X HD—localized wear near center of facet at 5000×. (B): Filtek Supreme Ultra—localized wear near center of facet at 5000×. (C): Herculite Ultra—localized wear near center of facet at 5000×. (D): SonicFill—localized wear near center of facet at 5000×. (E): Tetric EvoCeram Bulk Fill—localized wear near center of facet at 5000×. (F): Venus Diamond—localized wear near center of facet at 5000×. (G): Z100 Restorative—localized wear near center of facet at 5000×.
Figure 6. (A): Esthet•X HD—localized wear near center of facet at 5000×. (B): Filtek Supreme Ultra—localized wear near center of facet at 5000×. (C): Herculite Ultra—localized wear near center of facet at 5000×. (D): SonicFill—localized wear near center of facet at 5000×. (E): Tetric EvoCeram Bulk Fill—localized wear near center of facet at 5000×. (F): Venus Diamond—localized wear near center of facet at 5000×. (G): Z100 Restorative—localized wear near center of facet at 5000×.

Citation: Operative Dentistry 40, 3; 10.2341/13-155-L

SEM examinations (Figures 7A-G) of the surfaces of the generalized wear simulation specimens also demonstrated differences in the resin composite systems. Cracking of the glass filler component of SF (Figure 7D) was observed, as was plucking of filler particles from the surface. SU (Figure 7B), VD (Figure 7F), and Z (Figure 7G) also showed plucking of filler particles resulting from simulated generalized wear. There also was some evidence of cracks in the resin matrix of SU. The SEM examinations of TB (Figure 7E) revealed the various filler components on the worn surface of this resin composite. Prepolymerized particles were evident on the surface of HU (Figure 7C) after simulated generalized wear.

Figure 7. (A): Esthet•X HD—generalized wear near center of facet at 5000×. (B): Filtek Supreme Ultra—generalized wear near center of facet at 5000×. (C): Herculite Ultra—generalized wear near center of facet at 5000×. (D): SonicFill—generalized wear near center of facet at 5000×. (E): Tetric EvoCeram Bulk Fill—generalized wear near center of facet at 5000×. (F): Venus Diamond—generalized wear near center of facet at 5000×. (G): Z100 Restorative—generalized wear near center of facet at 5000×.Figure 7. (A): Esthet•X HD—generalized wear near center of facet at 5000×. (B): Filtek Supreme Ultra—generalized wear near center of facet at 5000×. (C): Herculite Ultra—generalized wear near center of facet at 5000×. (D): SonicFill—generalized wear near center of facet at 5000×. (E): Tetric EvoCeram Bulk Fill—generalized wear near center of facet at 5000×. (F): Venus Diamond—generalized wear near center of facet at 5000×. (G): Z100 Restorative—generalized wear near center of facet at 5000×.Figure 7. (A): Esthet•X HD—generalized wear near center of facet at 5000×. (B): Filtek Supreme Ultra—generalized wear near center of facet at 5000×. (C): Herculite Ultra—generalized wear near center of facet at 5000×. (D): SonicFill—generalized wear near center of facet at 5000×. (E): Tetric EvoCeram Bulk Fill—generalized wear near center of facet at 5000×. (F): Venus Diamond—generalized wear near center of facet at 5000×. (G): Z100 Restorative—generalized wear near center of facet at 5000×.
Figure 7. (A): Esthet•X HD—generalized wear near center of facet at 5000×. (B): Filtek Supreme Ultra—generalized wear near center of facet at 5000×. (C): Herculite Ultra—generalized wear near center of facet at 5000×. (D): SonicFill—generalized wear near center of facet at 5000×. (E): Tetric EvoCeram Bulk Fill—generalized wear near center of facet at 5000×. (F): Venus Diamond—generalized wear near center of facet at 5000×. (G): Z100 Restorative—generalized wear near center of facet at 5000×.

Citation: Operative Dentistry 40, 3; 10.2341/13-155-L

DISCUSSION

The use of wear simulation to predict clinical performance has been a challenge for dental materials researchers for many years. Leinfelder and Suzuki6 published much of the early work in trying to relate simulated wear with clinical wear by using a spring-loaded piston wear simulator. This device was a modification of a wear simulator developed by Roulet.25 In their early work, Leinfelder and Suzuki6 (1999) used a cylinder-shaped cavity in extracted human molar teeth (enamel margins) for placement of a restorative resin material and used a flat polyacetal antagonist to simulate generalized wear (Alabama method). They used 400,000 cycles for simulated, generalized wear studies. The results of their published work6 found an excellent correlation between 400,000 cycles in the wear testing device (generalized wear simulation) and three years of clinical services for 10 resin composites. The results of their work and the reported correlation of in vitro and in vivo wear led researchers to routinely use 400,000 cycles with the Alabama testing machine.

Barkmeier and others18 modified the testing methods for simulated generalized wear with the Alabama machine. They developed custom stainless steel fixtures to hold the test material and moved to a flat stainless steel antagonist. This improvement essentially eliminated the problem of both antagonist and tooth surface wear during the cycling procedure. In addition to simulating generalized wear, the Alabama simulator has also been used for localized wear testing using a hardened steel, cone-shaped antagonist. More recently, a collet device for holding a stainless steel ball bearing has been introduced. The ball bearings allow a new antagonist tip to be used for each specimen because of the cost differential between a chrome-plated, hardened steel antagonist and a stainless steel ball bearing. Whereas other antagonist tips, such as enamel, ceramic, or resin composite, may add additional information in wear testing, stainless steel has routinely been used to provide consistency in the wear challenges for both localized and generalized wear simulation studies. However, although a steel antagonist offers many advantages, the clinical relevance is sometimes brought into question.

Much has been published* in recent years regarding the correlation of simulated wear and clinical wear. Barkmeier and others16 using clinical data from two study sites on two resin composite materials found a good relationship between localized simulated wear in the laboratory and OCA clinical wear. A subsequent study18 compared simulated generalized wear and CFA clinical wear of the same two resin composites and again found a good relationship between laboratory and clinical wear values. Heintze and others11,23 have published on the relationship of simulated wear to clinical wear using multiple laboratory wear simulators. These studies have compared wear simulation data from multiple testing centers with published clinical data for the same materials. These investigators, when examining data from several sites, have found a wide range of correlations between laboratory and clinical data for both generalized and localized wear. The correlations for the Alabama method have been reported11 as being better for generalized wear than for localized wear. However, it should be noted that various sites doing wear simulation studies with the Alabama machine use different methodologies for generating localized and generalized simulated wear. Although the absolute wear values may not be the same, depending on site methodologies and analysis tools, the relative wear ranking of materials from site to site should be similar.

Analysis methods for determining wear of laboratory specimens have evolved over the years. Various profiling and 3D measurement techniques have been used for wear analysis.3,6,9,11-12,23-37 Typically, a pretest surface is compared with a posttest surface, and wear (facet depth and/or volume loss) is determined from the differences between the pretest and posttest digitized surfaces.

In the present study a Proscan 2100 noncontact profilometer with Proscan software was used to digitize the surface contours of the pretest and posttest data sets. The x-, y-, and z-coordinates of the pretest and posttest specimens were exported from the Proscan software onto a computer with AnSur 3D software. The AnSur 3D software was recently modified to be used with the digitized surface contour files generated with the Proscan software. After exporting the x-, y-, and z-coordinates, a computerized “fit” of the before and after data sets was accomplished using the AnSur 3D software. A goodness-of-fit value (root-mean-square of the difference of similar points) is also provided by the software. Four wear parameters are then generated by the software: 1) volume loss (mm3); 2) maximum depth (μm)—lowest point on the posttest surface; 3) mean maximum depth (μm)—average of all the lowest points from the individual profiles examined; 4) mean depth (μm)—average depth of the posttest surface. The use of the Proscan 2100 noncontact profilometer and AnSur 3D analysis software produces excellent results combined with ease of use.

Barkmeier and others24 recently proposed that Z100 Restorative (Z) be used as a benchmark material when wear simulation studies are done on resin composite materials. This recommendation was based on the performance of Z in laboratory wear simulation studies and also on excellent wear values reported from clinical studies.16,18 In the present study, Z again produced the lowest localized and generalized wear values of the seven materials evaluated. This performance strengthens the recommendation that Z be used as a benchmark, or reference material, in future wear studies. If wear simulation studies show wear resistance in the range of Z exhibited in this study and other simulation studies,16,18 then there should be good confidence that the material will perform well in a clinical setting.

Lambrechts and others have reported38-39 that a restoration should ideally exhibit wear similar to enamel. They used their computerized 3D measuring technique to quantitatively measure OCA wear of human enamel. Over a four-year period, they measured enamel-to-enamel contact of premolar and molar teeth and recorded the vertical loss of enamel. Wear rates were calculated using logarithmic data of the polynomial fourth-degree function after regression analysis. Their in vivo wear rate of enamel was 29 μm per year for molar teeth and 15 μm per year for premolars. In 1997, Lambrechts40 also reported that the wear of Z in occlusal contact areas is comparable with the OCA wear of enamel. In a previous study, Barkmeier and others16 used regression analysis to examine localized simulated wear of Z (conical, hardened steel antagonist; r=1.575 mm) and found 9.6 μm of vertical loss per 100,000 cycles. Thus, 300,000 cycles of localized wear in the simulator (conical antagonist) would approximate one year of clinical tooth-to-tooth contact (OCA) wear of human molars, when using data from the Lambrechts studies.39-40 In the present study, the average localized simulated wear rate of Z for 100,000 cycles was 14.9 μm using a stainless steel ball-bearing antagonist (r=2.387 mm). This value was calculated from the total wear of Z after 400,000 cycles, versus the earlier study of Z in which the slope of the regression curve was used for predicting the wear rate per 100,000 cycles. The wear rate per 100,000 cycles in the current study is greater than the previous study using regression analysis because it includes the initial rapid wear that is always present in these types of studies and is not indicative of long-term wear rates. Clinical wear studies of resin composite materials exhibit the same issues related to the initial wear-in period. Using the current study, the wear rate for localized wear simulation for 200,000 cycles would be approximately equivalent to the one-year wear rate of molar enamel (29 μm) reported in the Lambrechts studies.39-40 The above comparisons are useful in helping to relate simulated localized wear testing of Z to natural enamel loss from tooth-to-tooth contact.

The components of the materials evaluated in this study are quite different. The SEM observations revealed differences in filler particle size and shape. Studies have shown that the type of glass, shape, and size of filler components, resin matrix formulation, and degree of polymerization have a significant effect on the wear characteristics of resin composite materials.41-42 It is interesting to note the similarity of Z and SU on the argon-etched SEM examinations (Figure 5B,G). The manufacturing process appears to result in similarly shaped filler particles, which are mostly rounded. Table 2 shows that these materials of the same manufacturer both contain zirconia/silica filler particles. The study results (Tables 7-10) indicate that these two materials are very wear resistant in both localized and generalized wear simulation. It is also interesting to observe the similarity of the worn surfaces of these two materials after localized wear simulation. Both of these materials exhibit what appear to be fatigue cracks from the aggressive pounding of the stainless steel ball-bearing antagonist. Although these cracks might initially appear to result from a rapid breakdown of the material, the resistance to wear of these two materials suggests that these cracks are a result of a very wear-resistant material that eventually develops fatigue cracks after repeated challenges from the antagonist. Materials that are not as wear resistant may lose surface area faster and not develop crack formation on the surface.

The localized and generalized wear of SF was significantly greater (p<0.05) than that of the other materials evaluated in this study. In examining the scanning electron micrographs of SF after both localized and generalized wear simulation, there appears to be similarities in the surface characteristics. The observations of both localized (Figure 6D) and generalized (Figure 6D) wear show a surface with large glass filler particles and plucking of glass from the surface. In addition there is fracturing of the larger glass filler particles from both localized and generalized wear simulation.

This study demonstrated differences in the resistance to wear among modern resin composites and adds useful information regarding the relative wear performance of seven commonly used materials. The study results show clear differences in the wear characteristics among the materials examined (Tables 7-10). Although concern exists that these differences may not be predictive of clinical performance, the results are useful for practicing dentists in assessing the overall performance of the materials evaluated. However, there is good evidence that the relative wear resistance of resin composite materials found in wear simulation studies may translate well to the clinical setting.11,16,18,23 Parameters other than wear may also guide practitioners in selecting restorative materials. But, because wear is so important in the long-term clinical performance of a resin composite material, the results of this study should be carefully considered by clinicians when selecting a resin composite material for patient care.

CONCLUSIONS

Seven resin composite materials were subjected to both simulated localized and generalized wear in a Leinfelder-Suzuki (Alabama) wear machine. Z was used as a benchmark material in this study due to excellent results in past simulated wear studies and clinical trials.

The results of this study provide useful additional information on the wear characteristics of modern-day resin composite materials. The benchmark material, Z, exhibited the least amount of wear in both localized and generalized wear simulations. The testing was able to discriminate wear performance among the seven materials tested. The results of this study, coupled with the results of previous laboratory and clinical wear studies, augment the information base available to the profession and provide guidance for clinicians in the selection of a resin composite material for patient care.

Conflict of Interest

The authors of this manuscript certify that they have no proprietary, financial, or other personal interest of any nature or kind in any product, service, and/or company that is presented in this article.

REFERENCES

  • 1
    Phillips RW,
    Avery DR,
    Mehra R,
    Swartz ML,
    &
    McCuneRJ
    (1973) Observations on a composite resin for Class II restorations: Three-year reportJournal of Prosthetic Dentistry30(
    6
    ) 891-897.
  • 2
    Lutz F,
    Phillips RW,
    Roulet JF,
    &
    SetcosJC
    (1984) In vivo and in vitro wear of potential posterior compositesJournal of Dental Research63(
    6
    ) 914-920.
  • 3
    Sakaguchi RL,
    Douglas WH,
    Delong R,
    &
    PintadoMR
    (1986) The wear of a posterior composite in an artificial mouth: A clinical correlationDental Materials2(
    6
    ) 235-240.
  • 4
    Lewis G
    (1991) In vivo occlusal wear of posterior composite restorationsOperative Dentistry16(
    2
    ) 61-69.
  • 5
    Kawai K,
    &
    LeinfelderK
    (1995) In vitro evaluation of OCA wear resistance of posterior compositesDental Materials11(
    4
    ) 246-251.
  • 6
    Leinfelder KF,
    &
    SuzukiS
    (1999)
    In vitro wear device for determining posterior composite wear Journal of the American Dental Association 130(9) 1347-1353
    .
  • 7
    Barkmeier WW,
    Latta MA,
    Wilwerding TM,
    &
    BlakeSM
    (2001) Wear assessment of high viscosity and conventional composite restorative materialsOperative Dentistry26(
    2
    ) 152-156.
  • 8
    Nagarajan VS,
    Jahanmir S,
    &
    ThompsonVP
    (2004) In vitro contact wear of dental compositesDental Materials20(
    1
    ) 63-71.
  • 9
    Zantner C,
    Kielbassa AM,
    Martus P,
    &
    KunzelmannKH
    (2004) Sliding wear of 19 commercially available composites and compomersDental Materials20(
    3
    ) 277-285.
  • 10
    Ferracane JL
    (2006) Is the wear of dental composites still a clinical concern? Is there still a need for in vitro wear simulating devices?Dental Materials22(
    8
    ) 689-692.
  • 11
    Heintze SD,
    Barkmeier WW,
    Latta MA,
    &
    RoussonV
    (2011) Round robin test: Wear of nine restorative materials in six different wear simulators—Supplement to the round robin test of 2005Dental Materials27(
    2
    ) e1-e9.
  • 12
    Braem M,
    Lambrechts P,
    Van Doren V,
    &
    VanherleG
    (1985) In vivo evaluation of four posterior composites: Quantitative wear measurements and clinical behaviorDental Materials2(
    3
    ) 106-113.
  • 13
    Stangel I,
    Barolet RY,
    &
    RobertD
    (1990) A five-year evaluation of two posterior composites and amalgamJournal of Dental Research
    69(Special issue)
    Abstract #1600p308.
  • 14
    Tyas MJ,
    &
    WassenaarP
    (1991) Clinical evaluation of four composite resins in posterior teeth: Five-year results. Australian Dental Journal36(
    5
    ) 369-373.
  • 15
    Barnes DM,
    Blank LW,
    Thompson VP,
    Holston AM,
    &
    GingellJC
    (1991) A 5- and 8-year clinical evaluation of a posterior composite resinQuintessence International22(
    2
    ) 143-151.
  • 16
    Barkmeier WW,
    Latta MA,
    Erickson RL,
    &
    LambrechtsP
    (2004) Comparison of laboratory and clinical wear rates of resin compositesQuintessence International35(
    4
    ) 269-274.
  • 17
    Sarrett DC,
    Brooks CN,
    &
    RoseJT
    (2006)
    Clinical performance evaluation of a packable posterior composite in bulk-cured restorations Journal of the American Dental Association 137(1) 71-80
    .
  • 18
    Barkmeier WW,
    Erickson RL,
    Latta MA,
    &
    WilwerdingTM
    (2008) Wear simulation of resin composites and the relationship to clinical wearOperative Dentistry33(
    2
    ) 177-182.
  • 19
    Palaniappan S,
    Bharadwaj D,
    Mattar DL,
    Peumans M,
    Van Meerbeek B,
    &
    LambrechtsP
    (2009) Three-year randomized clinical trial to evaluate the clinical performance and wear of a nanocomposite versus a hybrid compositeDental Materials25(
    11
    ) 1302-1314.
  • 20
    Opdam, NJ,
    Bronkhorst BA,
    &
    HuysmansMC
    (2010) 12-year survival of composite vs. amalgam restorationsJournal of Dental Research89(
    10
    ) 1063-1067.
  • 21
    Palaniappan S,
    Bharadwaj D,
    Mattar DL,
    Peumans M,
    Van Meerbeek B,
    &
    LambrechtsP
    (2011) Nanofilled and microhybrid composite restorations: Five-year clinical wear performancesDental Materials27(
    7
    ) 692-700.
  • 22
    Da Rosa Rodolpho PA,
    Donassollo TA,
    Cenci MS,
    Loguércio AD,
    Moraes RR,
    Bronkhorst EM,
    Opdam NJ,
    &
    DemarcoFF
    (2011) 22-year clinical evaluation of the performance of two posterior composites with different filler characteristicsDental Materials27(
    10
    ) 955-963.
  • 23
    Heintze SD,
    Faouri M,
    Rousson V,
    &
    ÖzcanM
    (2012) Correlation of wear in vivo and six laboratory wear methodsDental Materials28(
    9
    ) 961-973.
  • 24
    Barkmeier WW,
    Erickson RL,
    Latta MA,
    &
    WilwerdingTM
    (2013) Wear rates of resin compositesOperative Dentistry38(
    2
    ) 226-233.
  • 25
    Roulet JF
    (1987) Degradation of Dental Polymers
    Karger Press
    ,
    Basel
    .
  • 26
    Lambrechts P,
    Vuylsteke M,
    Vanherle G,
    &
    DavidsonCL
    (1984) Quantitative evaluation of the wear resistance of posterior dental restorations. A new three-dimensional measuring techniqueJournal of Dentistry12(
    3
    ) 252-256.
  • 27
    Leinfelder KF,
    Taylor DR,
    Barkmeier WW,
    &
    GoldbergAJ
    (1986) Quantitative wear measurements of posterior composite resinsDental Materials2(
    5
    ) 198-201.
  • 28
    de Gee AJ,
    Pallav P,
    &
    DavidsonCL
    (1986) Effect of abrasion medium on wear of stress-bearing composites and amalgam in vitroJournal of Dental Research65(
    5
    ) 654-658.
  • 29
    Pallav P,
    Davidson CL,
    &
    de GeeAJ
    (1988) Wear rates of composites, an amalgam, and enamel under stress-bearing conditionsJournal of Prosthetic Dentistry59(
    4
    ) 426-429.
  • 30
    Leinfelder KF,
    Beaudreau RW,
    &
    MazerRB
    (1989) An in vitro device for predicting wearQuintessence International20(
    10
    ) 755-761.
  • 31
    de Gee AJ,
    &
    PallavP
     Occlusal wear simulation with the ACTA wear machine Journal of Dentistry
    22(Supplement 1)
    S21-S27.
  • 32
    Condon JR,
    &
    FerracaneJL.
    (1996) Evaluation of composite wear with a new multi-mode oral wear simulatorDental Materials12(
    4
    ) 218-226.
  • 33
    Perry R,
    Kugel G,
    Kunzelmann KH,
    Flessa HP,
    &
    EstafanD
    (2000) Composite restoration wear analysis: Conventional methods vs three-dimensional laser digitizerJournal of the American Dental Association131(
    10
    ) 1472-1477.
  • 34
    Suzuki S,
    Nagai E,
    Taira Y,
    &
    MinesakiY
    (2002) In vitro wear of indirect restorativesJournal of Prosthetic Dentistry88(
    40
    ) 431-436.
  • 35
    Heintze SD
    (2006) How to qualify and validate wear simulation devices and methodsDental Materials22(
    8
    ) 712-734.
  • 36
    Rodriguez JM,
    Austin RS,
    &
    BartlettDW
    (2012) A methods to evaluate profilometric tooth wear measurementsDental Materials28(
    4
    ) 245-251.
  • 37
    Latta MA,
    Barkmeier WW,
    Wilwerding TM,
    &
    BlakeSM
    (2001) Localized wear of compomer restorative materialsAmerican Journal of Dentistry14(
    4
    ) 238-240.
  • 38
    Lambrechts P,
    Debels E,
    Van Landuyt K,
    Peumans M,
    &
    Van MeerbeekB
    (2006) How to simulate wear? Overview of existing methodDental Materials22(
    8
    ) 693-701.
  • 39
    Lambrechts P,
    Braem M,
    Vuylsteke-Wauters M,
    Vanherle G
    (1989) Quantitative in vivo wear of human enamelJournal of Dental Research68(
    12
    ) 1752-1753.
  • 40
    Lambrechts P
    (1997) Clinical update, 3M Restorative Z100 four-year quantitative wear. Report to 3M; Retrieved online Month Date, Year from: http://multimedia.3m.com/mws/mediawebserver?mwsId=66666UgxGCuNyXTtOxTcoxz6EVtQEcuZgVs6EVs6E666666--&fn=z100 clinical 4 year wear.pdf
  • 41
    Suzuki S,
    Leinfelder KF,
    Kawai K,
    &
    TsuchitaniY
    (1995) Effect of particle size variation on wear rates of posterior compositesAmerican Journal of Dentistry8(
    4
    ) 173-178.
  • 42
    Oliveira GU,
    Mondelli RF,
    Charantola RM,
    Franco EB,
    Ishikiriama SK,
    &
    WangL
    (2012) Impact of filler size and distribution on roughness and wear of composite resin after simulated toothbrushingJournal of Applied Oral Science20(
    5
    ) 510-516.
  1. *

    References 3,6,10,11,16,18,23,24,26,36-40.

Copyright: Operative Dentistry, Inc. 2015
Figure 1.
Figure 1.

Stainless steel custom fixture for localized wear.

Figure 2.
Figure 2.

Stainless steel custom fixture for generalized wear.

Figure 3.
Figure 3.

Stainless steel antagonist tip for simulated localized wear.

Figure 4.
Figure 4.

Stainless steel antagonist tip for simulated generalized wear.

Figure 5.
Figure 5.

(A): Esthet•X HD—argon-ion etched surface at 5000×. (B): Filtek Supreme Ultra—argon-ion etched surface at 5000×. (C): Herculite Ultra—argon-ion etched surface at 5000×. (D): SonicFill—argon-ion etched surface at 5000×. (E): Tetric EvoCeram Bulk Fill—argon-ion etched surface at 5000×. (F): Venus Diamond—argon-ion etched surface at 5000×. (G): Z100 Restorative—argon-ion etched surface at 5000×.

Figure 6.
Figure 6.

(A): Esthet•X HD—localized wear near center of facet at 5000×. (B): Filtek Supreme Ultra—localized wear near center of facet at 5000×. (C): Herculite Ultra—localized wear near center of facet at 5000×. (D): SonicFill—localized wear near center of facet at 5000×. (E): Tetric EvoCeram Bulk Fill—localized wear near center of facet at 5000×. (F): Venus Diamond—localized wear near center of facet at 5000×. (G): Z100 Restorative—localized wear near center of facet at 5000×.

Figure 7.
Figure 7.

(A): Esthet•X HD—generalized wear near center of facet at 5000×. (B): Filtek Supreme Ultra—generalized wear near center of facet at 5000×. (C): Herculite Ultra—generalized wear near center of facet at 5000×. (D): SonicFill—generalized wear near center of facet at 5000×. (E): Tetric EvoCeram Bulk Fill—generalized wear near center of facet at 5000×. (F): Venus Diamond—generalized wear near center of facet at 5000×. (G): Z100 Restorative—generalized wear near center of facet at 5000×.

Contributor Notes

*Corresponding author: 2500 California Plaza, Omaha, NE 68178; e-mail: wbark@creighton.edu
Accepted: 05 Nov 2013
  • Download PDF