Esthetic restorative materials and opposing enamel wear

This in vitro study compared the effects of a gold alloy (Degulor M), four dental ceramics (IPS Empress, IPS Empress 2, Duceram Plus, Duceram LFC) and a laboratory-processed composite (Targis) on the wear of human enamel. The amount of wear of the enamel (dental cusps) and restorative materials (disks) were tested in water at 37 degrees C under standard load (20 N), with a chewing rate of 1.3 Hz and was determined after 150,000 and 300,000 cycles. Before the test, the average surface roughness of the restorative materials was analyzed using the Ra parameter. The results of this study indicate that Targis caused enamel wear similar to Degulor M and resulted in significantly less wear than all the ceramics tested. IPS Empress provoked the greatest amount of enamel wear and Degulor M caused less vertical dimension loss. Targis could be an appropriate alternative material to ceramic, because it is esthetic and produces opposing enamel wear comparable to gold alloy.     

Relative wear of enamel opposing low-fusing dental porcelain

PURPOSE: This study evaluated the wear of human enamel opposing 5 low-fusing dental porcelains and a traditional feldspathic control. In a second experiment, the repeatability of the test method and the effect of ceramic overfiring on enamel wear were also evaluated. MATERIALS AND METHODS: Five low-fusing dental porcelains--Finesse (FI), Rhapsody (RP), IPS d.Sign (DS), Omega 900 (OM), and Duceram LFC (LFC)--and 1 traditional feldspathic porcelain--VMK 68 (VMK)--were formed into disks (n = 10) and used as substrate for the wear test. Enamel was harvested from extracted human molars and machined into cusps with a 5-mm spherical radius (n = 60). The Oregon Health Sciences University oral wear simulator was used to simulate chewing and the size of the resulting enamel wear facets (in mm(2)) were evaluated after a specified number of chewing cycles. A portion of the experiment was duplicated to assess the repeatability of the data and determine the effects of overfiring on enamel wear. Data were subjected to analysis of variance and post hoc tests to determine significant differences. After wear testing, scanning electron micrographs were made using representative ceramic samples from each group. RESULTS: The results indicate that none of the low-fusing ceramics resulted in significantly less wear than the VMK control. In fact, 3 of the low-fusing porcelains (OM, RP, LFC) resulted in significantly greater enamel wear than VMK. Enamel wear was not significantly affected (p = 0.29) by the increased ceramic firing temperature. Wear data were repeatable, with no significant difference (p = 0.56) between the enamel wear from 2 separate experiments. The results from both experiments indicated that ceramic material significantly affected enamel wear (p <0.001). There was significantly less enamel wear opposite DS than LFC. CONCLUSIONS: This work suggests that variations in ceramic composition and microstructure may affect the opposing enamel wear, but that low-fusing temperatures do not necessarily guarantee low enamel wear. Although the clinical relevance of this testing apparatus may be questioned, the testing method was repeatable.     

六种常用冠修复材料的摩擦磨耗性能比较

目的 探讨6种常用冠修复材料与滑石瓷对磨时的摩擦磨耗性能,为口腔常用冠修复材料的摩擦磨耗性能与牙釉质的匹配性提供依据.方法 使用MMJ-5G微机控制高温端面磨损实验机,以滑石瓷为对磨物,以15颗因正畸拔除的上颌第一前磨牙制作的10个试件为对照组,对纯钛(A组)、钴铬合金(B组)、Superporcelain Ti-22体瓷(C组)、喜美乐体瓷(D组)、松风饰瓷(E组)、e.max饰瓷(F组)(每组均为10个试件)与滑石瓷组成的摩擦副在37℃人工唾液润滑工况下进行摩擦磨耗实验.记录动态摩擦系数曲线、计算体积磨损百分比,扫描电镜观察表面磨损形貌.结果 试件体积磨损百分比由大至小为:对照组[(90.17×10-4)％]、A组[(79.23×10-4)％]、C组[(23.31 ×10-4)％]、D组[(20.41×10-4)％]、F组[(19.22 × 10-4)％]、E组[(8.53 × 10-4)％]、B组[(2.54×10-4)％].滑动摩擦系数由大到小依次是:D组(0.65)、C组(0.45)、E组(0.40)、A组(0.35)、B组和F组(0.30).扫描电镜观察显示,E组表面最光滑,以下依次是F组、D组、C组.结论 纯钛与天然牙磨耗性能相近,是理想的修复金属材料.4种瓷粉中Surperporcelain Ti-22体瓷磨损滑石瓷最少.     

The wear of enamel opposing shaded ceramic restorative materials: an in vitro study.

The wear rate of intact human enamel opposed by Olympia porcelain gold, Dicor, Ceramco porcelain, and externally shaded Dicor and Ceramco was investigated with an artificial oral environment. The enamel-material couples were subjected to 300,000 masticatory cycles at a maximal occlusal force of 13.4 N while they were continuously bathed with 37 degrees C deionized water. Both the enamel and material surfaces were analyzed by use of a three-dimensional surface monitoring computer program, AnSur, to record the removal of the material and the maximal loss of vertical height. The enamel opposing the externally shaded materials abraded two to five times more than that opposing the unshaded materials and 10 to 15 times more than enamel opposing gold. The wear rates for enamel opposing the gold and unshaded Dicor were similar both in the removal of material and in the loss in vertical height.     

Effects of carbamide peroxides on wear resistance and color change of enamel opposing porcelain

PURPOSE: This study evaluated the effects of a simulated 1- and 2-week night guard bleaching technique using various bleaching gel concentrations on wear resistance and color change of human enamel opposing a feldspathic porcelain substrate. MATERIALS AND METHODS: VMK 68 feldspathic porcelain was formed into 15-mm disks (n = 63) and fired according to manufacturer's recommendations. Enamel cusps were formed and shaped from extracted third molars and treated with 1 of 3 bleaching materials for 7 or 14 days. Specimens were kept at 37 degrees C in 100% humidity. The control group was subjected to identical conditions but with water replacing the bleaching gel between and during bleaching treatments. After simulated bleaching, the enamel cusp specimens were subjected to 3-body wear testing opposite a highly polished porcelain substrate. Enamel wear was evaluated using optical scanning methods, and color was measured with a small-aperture colorimeter. Data were subjected to a one-way repeated- measure analysis of variance and various post hoc statistics. RESULTS: Results indicated that the within effect of treatment time (7 or 14 days) did not significantly affect (p = 0.13) the size of the resulting enamel wear facet, whereas the between effect of bleaching concentration was significant (p = 0.01). Statistical analysis of unbleached control groups suggests that between-group differences can be explained by variations in wear rates of the 3 enamel groups, not by the concentration differences in bleaching gels. All bleaching treatments resulted in significant color changes (p = 0.04) compared to the unbleached control, but the bleach concentration did not significantly influence the magnitude of color change (p = 0.81). CONCLUSIONS: A simulated night guard vital bleaching treatment of 1 or 2 weeks had no significant effect on the wear resistance of human enamel in vitro. The increased bleaching treatment time and concentration did not significantly affect the amount of enamel color change.     

An in vitro assessment of the effect of load and pH on wear between opposing enamel and dentine surfaces

Objective

Previous in vitro studies have described the wear characteristics of specimens in which enamel has been opposed to enamel and dentine opposed to dentine. The aim of this study was to assess the characteristics of wear between specimens in which enamel was opposed to dentine at loads simulating attrition and at pH values simulating different erosive environments. It was hypothesized that enamel would wear more slowly than dentine under all conditions.

Design

Opposing enamel and dentine specimens from 57 human third molar teeth were worn in electromechanical machines with various loads (32, 62 and 100 N) and lubricants (pH 1.2, 3.0 and 6.1). Tooth wear was quantified by measuring reduction in dentine volume over time using a 3D profilometer. Qualitative assessment was also carried out using scanning electron microscopy.

Results

Dentine wear increased with increasing load, and dentine wear was faster at pH 1.2 than at pH 3.0 or 6.1 for all loads tested. Interestingly, enamel wore more rapidly than dentine at pH 1.2 under all loads. At pH values of 3.0 and 6.1, enamel wear rates were not measurably different from zero and they were less than wear rates for opposing dentine specimens at all loads. Micrographic assessment showed extensive surface destruction of dentine wear facets due to erosion at pH 1.2. Dentine wear facets were smoother at pH 3.0 that at pH 6.1.

Conclusions

When enamel wears against dentine in an acidic environment enamel will wear more rapidly at very low pH, while under less acid conditions dentine will wear faster than enamel.     

Three-body wear associated with three ceramics and enamel.

STATEMENT OF PROBLEM: Wear of human enamel is a clinical concern whenever opposing teeth need to be restored using ceramic restorations. PURPOSE: This in vitro study investigated wear of human enamel and 3 dental ceramics: a conventional porcelain (Vitadur Alpha), a low-fusing hydrothermal ceramic (Duceram-LFC), and a machinable ceramic (Vita Mark II) in a 3-body wear test. MATERIAL AND METHODS: Thirty pairs of tooth-ceramic specimens were tested in a dental wear machine, under a standard load (40 N), rate (80 cycles/minute), and for 25,000 cycles in a simulated food slurry medium. Amount of wear was determined by measuring the height loss of the tooth and depth of wear track of the ceramic materials. Analysis of variance (ANOVA) was used to analyze the data, followed by Bonferroni multiple comparisons method to produce sets of simultaneous 95% confidence intervals. RESULTS: ANOVA revealed significant differences between the groups for both enamel wear (P =. 002) and ceramic wear (P <.001). Further comparisons (95% CI significance level) revealed that the difference in enamel wear produced by Alpha porcelain and Duceram-LFC ceramic material was not statistically significant, whereas that produced by Vita Mark II ceramic was significantly less. Vita Mark II ceramic was significantly more resistant to wear than Alpha porcelain and Duceram-LFC ceramic. Furthermore, Alpha porcelain was significantly more resistant to wear than Duceram-LFC ceramic. CONCLUSION: The abrasiveness of Alpha porcelain and Duceram-LFC ceramic was similar, yet both were significantly more abrasive than Vita Mark II ceramic. In addition, Vita Mark II was the most wear-resistant ceramic and Duceram-LFC ceramic the least resistant.     

Wear of enamel opposing low-fusing and conventional ceramic restorative materials

PURPOSE: This study evaluated the wear area of human enamel opposing 2 conventional and 2 low-fusing dental porcelains, as well as abrasive wear, attrition, surface hardness, and fracture toughness for the 4 porcelain substrates. MATERIALS AND METHODS: Two low-fusing and 2 conventional metal-ceramic porcelains were used to form 15-mm-diameter disks (n = 10), which were fired according to manufacturer's recommendations. Enamel cusps (n = 40) were formed from extracted third molars. All ceramic and enamel specimens were finished to a 1000-grit silicon carbide surface. The Oregon Health Sciences University (Portland, OR) oral wear simulator was used to deliver a 20-N load from the cusps to the ceramic substrates through a food-like slurry. The sliding action of the cusps over an 8-mm linear path produced abrasive wear. A static 70-N load was applied at the end of the path to create attrition. This sequence was repeated at 1.0 Hz for 50,000 cycles. Ceramic wear was measured with a profilometer (+/-2 micrometers), and enamel wear was evaluated using optical scanning methods. After wear testing, the hardness and fracture toughness of the ceramic surfaces were determined, and scanning electron photomicrographs were made using representative ceramic and enamel specimens from each group. Enamel wear areas, abrasion and attrition depths, hardness, and fracture toughness values were subjected to analysis of variance and Tukey-Kramer post hoc tests to determine significant differences. RESULTS: Enamel wear was not significantly different for low-fusing and conventional porcelains (p =.29). The wear of conventional and low-fusing ceramic substrates was also not significantly different (p =.79). However, depth of porcelain wear caused by attrition was in general significantly greater than abrasive wear (p =.0004). Although no significant differences were found in the measured porcelain hardness values (p =.08), 1 conventional porcelain exhibited fracture toughness significantly greater than 1 low-fusing porcelain (p <.01). CONCLUSIONS: No differences in wear patterns were noted among low-fusing compared with conventional metal-ceramic porcelains, but static loading resulted in significantly greater attrition compared with the observed sliding abrasive wear. J Prosthodont 2001;10:8-15.     

Effect of contact area size on enamel and composite wear.

The effect of contact area dimensions on the wear of composite specimens and their opposing enamel cusps was evaluated in vitro. Thirty-six standardized cylindrical composite specimens were placed into metal cavities (8 mm x 2 mm) and divided randomly into five groups. The composite used was a fine-particle hybrid and was stressed as follows: storage in 75% aqueous ethanol solution for 24 h, toothbrush/toothpaste-abrasion for 30 min, followed by 300 thermal cycles in water ranging from 5 degrees to 55 degrees C and simultaneous 120,000 occlusal chewing loads at a frequency of 1.7 Hz at 53 N maximum force. In group 1 (n = 12), the occlusal chewing loads were applied by palatal cusps of extracted human maxillary molars with natural morphology. In groups 2 to 5 (n = 6), the cusp tips had standardized contact area dimensions of 0.26, 0.38, 1.18, and 4.10 mm2, respectively. Wear of composite specimens and antagonistic enamel cusps (means +/- SD) was assessed in microns by means of a 3-D scanner. Additionally, the contact surfaces of the restorations and of the antagonistic enamel cusps were evaluated by SEM. Increases in enamel contact areas after being loaded were measured by means of a digitizer and expressed in percent of the initial size before stress exposure. The wear of the composite specimens varied from 69.8 +/- 19.9 to 9.5 +/- 3.6 microns, and that of antagonistic enamel cusps from 31.3 +/- 3.4 to 8.8 +/- 1.5 microns. The increase in contact area varied between 27.8 and 0.1%.(ABSTRACT TRUNCATED AT 250 WORDS)     

In vitro contact wear of dental composites.

OBJECTIVE: The aim of this study is to determine the in vitro two-body contact wear mechanisms of three medium filled composites and compare these with a highly filled composite previously investigated. MATERIALS AND METHODS: Three commercial dental composites with filler mass fraction loading of 75-76% were evaluated. Two of the composites contained Ba-B-Al-silicate glass fillers and fumed silica with different particle sizes and distributions. One of these composites contained a fairly uniform distribution of filler particles ranging in size from 1 to 5 microm, whereas the particle size distribution in the second composite was bimodal consisting of small (less than 1 microm) and large (about 10 microm) particles. The third composite contained Ba-Al-silicate glass and silica with a filler particle size of approximately 1 microm. The composite disks were tested for wear against harder alumina counterfaces. Wear tests were conducted in distilled water using a pin-on-disk tribometer under conditions that represented typical oral conditions (sliding speed of 2.5 mm/s and contact loads ranging from 1 to 20 N). The wear tracks were analyzed by scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy to elucidate the wear mechanisms. The chemical composition of the water solution collected after the tests was determined using an inductively coupled plasma-mass spectrometer (ICP-MS) to detect possible chemical changes, e.g. dissolution of trace elements due to submersion or wear. The wear results were compared with those reported in an earlier study on a highly filled composite containing predominately alumino-silicate glass fillers and alumina at a filler loading of 92%. RESULTS: The differences in two-body wear rates between the three medium filled composites were not statistically significant (p<0.05) indicating that the variations in filler particle size and slight differences in chemical composition of the glass fillers do not affect the in vitro wear rates of these composites. Wear rates of these medium filled composites, however, were significantly lower than the highly filled composite (p<0.05). SEM, FTIR and ICP-MS analyses suggested that wear in the medium filled composites occurs by a complex set of processes involving tribochemical reactions between filler particles and water, formation of surface films containing a mixture of filler fragments and reaction products, and film delamination, as well as dissolution of the reaction products. SIGNIFICANCE: This study reveals that subtle changes in the filler particle size and small differences in filler composition do not significantly affect the two-body wear behavior of medium filled composites. However, the chemistry of filler particles plays an important role in altering the wear performance of composites when significant changes are made in the chemical composition of the fillers and when the filler loading is increased.     

In vitro wear of four ceramic materials and human enamel on enamel antagonist

The purpose of the present study was to evaluate the wear of four different ceramics and human enamel. The ceramics used were lithium disilicate glass (e.max Press), leucite‐reinforced glass (GN‐Ceram), yttria‐stabilized zirconia (Aadva Zr), and feldspathic porcelain (Porcelain AAA). Hemispherical styli were fabricated with these ceramics and with tooth enamel. Flattened enamel was used for antagonistic specimens. After 100,000 wear cycles of a two‐body wear test, the height and volume losses of the styli and enamel antagonists were determined. The mean and standard deviation for eight specimens were calculated and statistically analyzed using a non‐parametric (Steel–Dwass) test (α = 0.05). GN‐Ceram exhibited greater stylus height and volume losses than did Porcelain AAA. E.max Press, Porcelain AAA, and enamel styli showed no significant differences, and Aadva Zr exhibited the smallest stylus height and volume losses. The wear of the enamel antagonist was not significantly different among GN‐Ceram, e.max Press, Porcelain AAA, and enamel styli. Aadva Zr resulted in significantly lower wear values of the enamel antagonist than did GN‐Ceram, Porcelain AAA, and enamel styli. In conclusion, leucite‐reinforced glass, lithium disilicate glass, and feldspathic porcelain showed wear values closer to those for human enamel than did yttria‐stabilized zirconia.     

Bond strength of composites applied to acid-etched enamel.

The adhesion to acid-etched enamel of a four-component composite, Concise Enamel Bond System, was studied. The composite was applied undiluted over an intermediate resin layer and diluted with different amounts of resin. Corresponding surfaces of contralateral premolars were used to ensure that the composite samples were tested on areas with similar enamel etch patterns. Eighty specimens were tested. The results of this study indicated that the adherence of undiluted composite to etched enamel surfaces was not improved by using an intermediate layer of low-viscous resin. Composite diluted with liquid resin had poorer adherence than undiluted composite. There was no difference in the results from two degrees of dilution.     

Quantitative in vivo wear of human enamel

In this study, the attrition wear, also called occlusal-contact-area wear, of human enamel was measured quantitatively with a computerized three-dimensional measuring technique over a period of four years. Tooth replicas from a clinical trial were used. A running-in wear period after restorative treatment, followed by steady-state wear, was suggested. The average steady-wear rate on occlusal contact areas was about 29 microns per year for molars and about 15 microns per year for premolars.     

Wear evaluation of porcelain opposing gold, composite resin, and enamel

STATEMENT OF PROBLEM: When porcelain surfaces oppose gold and composite resin restorations as well as enamel, wear resistance and abrasiveness of the porcelain are clinical concerns to maintain the occlusal relationship. However, there is limited information on comparison of mutual wear rates when these materials oppose in 2-body and 3-body conditions. PURPOSE: The purpose of this study was to evaluate mutual wear rates of dental porcelain and opposing materials, including a gold alloy, a composite resin, and human enamel, using an in vitro wear test. MATERIAL AND METHODS: Mutual wear between high-fusing dental porcelain (Ceramco II) disks (9 x 5-mm thick) with a rough or smooth surface and opposing styli made of gold alloy, composite resin, or human enamel was evaluated in 2-body and 3-body conditions using a wear simulator (n=8). Wear depths (microm) of porcelain disks were determined using a profilometer. Wear depths (microm) of the opposing materials were obtained by converting the worn surface areas into wear depths using image-analysis software. All data were statistically analyzed by 3-way analysis of variance and Bonferroni-Dunn test (alpha=.05). The worn surfaces were observed by scanning electron microscope (SEM). RESULTS: The wear values for porcelain opposing composite resin or enamel in the 2-body condition were significantly greater than those in the 3-body condition, regardless of the surface condition of the porcelain (P<.001). For stylus specimens, all values in the 2-body condition were significantly greater than those in the 3-body condition, regardless of the surface condition of the opposing porcelain (P<.001). These results are supported by SEM observations of worn surfaces. CONCLUSION: The results of this study suggest that mutual wear rates, when porcelain opposes gold, composite resin, and enamel, are influenced by 2-body and 3-body wear conditions.     

In vitro wear of primary and permanent enamel. Simultaneous erosion and abrasion

PURPOSE: To evaluate the wear differences between primary and permanent enamel caused by the association of abrasion and erosion. METHODS: Fragments of 40 human teeth (20 primary and 20 permanent) were cast in acrylic rings, polished to expose a flat enamel area, and evaluated with a 3D profiler. Antagonists were made from primary and permanent molars. The specimens were distributed into four groups (n = 10) according to type of substrate and slurry (neutral and acidic), and cycled 100,000 times in the OHSU oral wear simulator. Specimens were cleaned and re-profiled. Volume loss and maximum depth were determined on the polished specimens. Data were submitted to ANOVA and Tukey's test. The area of the wear facet on the antagonist was measured. RESULTS: Primary enamel showed more wear than permanent enamel, regardless of the slurry type. The acidic environment increased the wear rate compared to the neutral slurry. The association of abrasion and erosion increased the wear rate for the primary teeth only. There was no significant difference among groups for cusp wear and no correlation between cusp wear and the enamel wear.     

In vitro wear of microfilled and visible light-cured composites.

Wear of microfilled composites, a visible light-cured composite, and a conventional composite were characterized by two-body abrasion and single-pass sliding. There were differences in abrasion rates among the materials. Tangential forces, wear track widths, and surface failure modes were different among materials. Wear characteristics are combinations of these properties.     

Water and abrasive effects on three-body wear of composites.

The degrees of in vitro three-body wear resistance of a hybrid, a small-particle, and a microfilled composite were determined after water storage for up to 24 months. The hybrid composite was the most wear-resistant, while the microfilled composite showed the most wear. The hybrid composite showed no loss of wear resistance as a result of water storage. The small-particle composite showed a decrease in wear resistance after water storage only when tested with silicon carbide abrasive. The wear resistance of the microfilled composite decreased following water storage when tested with either a soft (CaCO3) or a hard (SiC) abrasive. For all composites, the soft abrasive was not capable of causing preferential wear of the polymer matrix, as observed on in vivo specimens. Instead, the filler particles became flattened, with minimal loss of interparticle substance. The hard abrasive did cause preferential wear of the matrix. All composites absorbed water and leached silicon during water storage, indicating that the filler-polymer bond was attacked by hydrolytic degradation. Scanning electron microscopic evaluation of the three-body wear specimens indicated that the in vitro wear method did not duplicate in vivo wear conditions (e.g., the hard abrasive caused excessive wear and chipping of the filler particles in vitro, a pattern that was not usually observed in vivo). Filler-polymer de-bonding was observed on in vivo specimens of all the composites, while it was found only on the in vitro microfilled composite specimens. These findings suggest that filler dislodging is a complex process that cannot be simulated with the in vitro wear method used in this study, not even after prolonged water storage.