In vitro occlusal wear of restorative materials on primary teeth

Since primary tooth enamel wears more rapidly than permanent tooth enamel, it is important to study the mechanical wear patterns of restorative materials used in the primary dentition. It is important that an in vitro evaluation of wear resistance of different restorative materials is done in order to establish a valid in vitro test protocol for use in pediatric dentistry.     

In vitro wear tests on macro-filled composite restorative materials*

Abstract — Minimum requirements to clinically relevant in vitro tests on macro-filled composites are suggested. Based on literature studies, it is demonstrated that none of the current known tests fulfil these requirements, a fact that probably explains their failing usefulness. Further and, as it appears, more detailed and critical studies are needed. With special emphasis on the abrasion by chewing of food, the maximum surface roughness of the composite as obtained by a specified method as well as the abrasion resistance of the resin matrix proper may be properties worthwhile exploring in future laboratory studies. Laboratory wear testing of micro-filled composites requires methods that in part are specific for this group of materials.     

Evaluation of wear behavior of dental restorative materials against zirconia in vitro

ObjectivesTo evaluate two-body wear (2BW) and three-body wear (3BW) of different CAD/CAM and direct restorative materials against zirconia using a dual-axis chewing simulator and an ACTA wear machine.Methods3 CAD-CAM resin-based composite or polymer infiltrated ceramic network blocs, 1 lithium disilicate CAD-CAM ceramic (LS₂), 3 direct resin composites, amalgam and bovine enamel were tested. For 2BW, 8 flat specimens per material were produced, grinded, polished, stored wet (37 °C, 28d) and tested (49 N, 37 °C, 1,200,000 cycles) against zirconia. For 3BW, specimens (n = 10) were stored accordingly, and tested against a zirconia antagonist wheel (3Y-TZP, d = 20 mm, h = 6 mm; 200,000 cycles, F = 15 N, f = 1 Hz, 15% slip) in millet seed suspension. Wear resistance was analysed in a 3D optical non-contact profilometer, measuring vertical wear depth and volume loss for 2BW and mean wear depth and roughness (R_a) for 3BW. Vickers hardness (15 s, HV2) was measured. Statistical analysis was performed using non-parametric tests (Mann-Whitney-U test, p < 0.05).Results2BW and 3BW have a different impact on material surfaces. Similar wear resistance was observed for direct and indirect resin based materials with analogous filler configurations in both methods. Bovine enamel exhibited the best wear resistance in 2BW, but the least wear resistance in 3BW against zirconia. Regarding 2BW, a direct/indirect composite material pair of the same manufacturer showed the significantly highest mean volume losses (2.72/2.85 mm³), followed by LS₂ (1.41 mm³). LS₂ presented the best wear resistance in 3BW (mean wear depth 2.85 µm), combined with the highest mean Vickers hardness (598 MPa). No linear correlation was found between Vickers hardness and both wear testing procedures. The zirconia antagonists showed no recordable signs of wear.SignificanceDental restorative materials behave differently in 2BW and 3BW laboratory testing. Vickers hardness testing alone cannot hold for a correlation with wear behavior of materials. Micromorphological investigation of material composition can reveal insights in wear mechanisms related to variations in filler technologies.     

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.     

Biodegradation and abrasive wear of nano restorative materials

The purpose of this study was to evaluate the biomechanical degradation of two nanofilled restorative materials (a resin-modified glass ionomer, Ketac N100 and a composite, Filtek Z350), compared with conventional materials (Vitremer and TPH Spectrum). Twenty specimens obtained from each material were divided into two storage groups (n=10): relative humidity (control) and Streptococcus mutans biofilm (biodegradation). After 7 days of storage, roughness values (Ra) and micrographs by scanning electron microscopy (SEM) were obtained. In a second experimental phase, the specimens previously subjected to biodegradation were fixed to the tooth-brushing device and abraded via toothbrushes, using dentifrice slurry (mechanical degradation). Next, these specimens were washed, dried, and reassessed by roughness and SEM. The data were submitted to repeated measures three-way analysis of variance (ANOVA) and Tukey tests (p<0.05). There was statistically significant interaction among factors: material, storage (humidity/biofilm), and abrasion (before/after). After biodegradation (S mutans biofilm storage), Ketac N100 presented the highest Ra values. Concerning bio plus mechanical challenge, TPH Spectrum, Ketac N100, and Vitremer presented the undesirable roughening of their surfaces, while the nano composite Filtek Z350 exhibited the best resistance to cumulative challenges proposed. The degraded aspect after biodegradation and the exposure of fillers after mechanical degradation were visualized in micrographs. This study demonstrated that the nanotechnology incorporated in restorative materials, as in composite resin and resin-modified glass ionomer, was important for the superior resistance to biomechanical degradation.     

Effects of gamma radiation on the in vitro wear of composite restorative materials.

The effects of gamma radiation at therapeutic dosage levels on the wear of three anterior (two light-cured and one autocured) composites and a light-cured posterior composite were studied in vitro. Specimens were subjected to successive sets of 100 abrades to a maximum of 500 abrades on a reciprocating arm abrader, with the dimensional change being recorded between the sets of abrades. The data showed that there were no significant effects on the wear rates of any of the materials tested. The rate of height loss was similar for the two hybrid composites tested (P less than 0.05), as was that for the microfilled and conventional material (P less than 0.05). There was, however, a significant difference (P greater than 0.001) in the wear behaviour between the two groups.     

An in vitro investigation into the wear effects of selected restorative materials on dentine

SUMMARY Wear testing of five restorative materials was carried out against plates of human dentine using a wear machine specifically designed to simulate the masticatory cycle. The results showed that dentine is substantially less wear resistant than enamel when compared to previous findings. Amalgam produced no measurable wear of dentine, conventional composite produced extreme destruction and porcelain produced the greatest amount of wear. Great care should be taken with the choice of restorative material when opposing dentine.     

An in vitro investigation into the wear effects of selected restorative materials on enamel

SUMMARY Abrasive wear testing of five restorative materials was carried otu with human enamel as the opposing surface using a wear machine specifically designed to simulate the masticatory cycle. The results showed that enamel demonstrated good abrasion resistance against amalgam and microfine composite and moderate abrasion resistance against gold. Conventional composite produced marked destruction of enamel and the greatest amount of enamel wear was produced by porcelain. The ranking order compared favourably with results from in vivo studies.     

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.     

Comparative wear ranking of dental restorative materials utilizing different wear simulation modes

summary The aim of this study was to compare the wear of seven different restorative materials using two different wear simulation modes. This included a non-impact sliding wear test (rotary pin and disc) and an impact-cum-sliding wear test (masticatory simulator). The difference in wear ranking between the two wear tests was compared as well as the correlation of wear to the hardness of the materials. Hardness ranking in the order of decreasing hardness was as follows: Dispersalloy^® (DA), P50^® (P50), Hi-Dense^(r) (HD), TPH^® (TPH), Fuji II LC^® (FJ), Dyract^® (DR) and Vitremer^® (VM). For volumetric wear using the non-impact sliding test, the following ranking in the order of decreasing wear resistance was obtained: DA, TPH, DR, HD, VM, FJ, P50. The results for volumetric wear with impact-cum-sliding wear testing in the order of decreasing wear resistance were: TPH, DR, P50, AR, FJ, VM, HD. Results showed that there is no correlation between hardness and wear resistance. There is also no correlation between impact-cum-sliding wear and non-impact sliding wear. Impact wear should be considered in future two-body wear assessment of materials.     

The comparison of wear characteristics of prosthodontic restorative materials

AIM: To assess the mutual wear characteristics of various prosthodontic restorative materials. MATERIALS AND METHODS: Samples were prepared using base metal alloy, ceramics and aesthetic methyl metacrylate resin materials in cylinders with a diameter of 30 mm, height 4 mm, and a spherical shape with a diameter of 5 mm and length of 6 mm.The mutual wearing process of samples on each other in groups was tested using a pin-on disc wear tester machine. RESULTS: The data obtained were evaluated by means of variance analysis and T-test. It was determined that the percentages of the mutual wearing of the restorative materials were statistically significant (p<0.001), but whether the samples were in the upper or lower position had no statistical significance. CONCLUSION: Various prosthodontic restorative materials had wear characteristics affecting each other.     

Differential wear of teeth and restorative materials: clinical implications

PURPOSE: This study reviewed the wear of commonly used dental restorative materials and their effects on the opposing dentition. MATERIALS AND METHODS: Key words were used with PubMed to retrieve pertinent references to publications on tooth and restoration wear. RESULTS: The wear resistance of newer esthetic restorative materials has generally improved, and the damage caused by several materials to the opposing dentition has been reduced. However, the different structures and physical properties of tooth substance and restorative materials will eventually lead to varying degrees of differential wear. The extent and rate of wear are influenced by many intraoral factors. CONCLUSION: Selection of restorative materials must be based on knowledge of their wear behavior and the individual needs of each patient. The lowest wear rates for restorations and the opposing dentition occur with metal alloys, machined ceramics, and microfilled and microfine hybrid resin composites.     

Comparative wear resistance of reinforced glass ionomer restorative materials

This study investigated the wear resistance of three restorative reinforced glass ionomer cements (Fuji IX GP FAST [FJ], Miracle Mix [MM] and Ketac Silver [KS]). Microfilled (Silux [SX]) and mini-filled (Z100 [ZO]) composites were used for comparison. Six specimens were made for each material. The specimens were conditioned for one week in distilled water at 37 degrees C and subjected to wear testing at 20 MPa contact stress against SS304 counterbodies using a reciprocal compression-sliding wear instrumentation. Distilled water was used as lubricant. Wear depth (microm) was measured using profilometry every 2,000 cycles up to 10,000 cycles. Results were analyzed using ANOVA/Scheffe's test (p<0.05). After 10,000 cycles of wear testing, ranking was as follows: KS>ZO>MM>FJ>SX. Wear ranged from 26.1 microm for SX to 71.5 microm for KS. The wear resistance of KS was significantly lower than FJ, MM and SX at all wear intervals. Although KS had significantly more wear than ZO at 2,000 to 6,000 cycles, no significant difference in wear was observed between these two materials at 8,000 and 10,000 cycles. Sintering of silver particles to glass ionomer cement (KS) did not appear to improve wear resistance. The simple addition of amalgam alloy to glass ionomer may improve wear resistance but results in poor aesthetics (silver-black color). FJ, which relies on improved chemistry instead of metal fillers, showed comparable wear resistance to the composites evaluated and is tooth-colored. It may serve as a potential substitute for composites in low-stress situations where fluoride release is desirable and aesthetic requirements are not high.     

Hardness and in vitro wear of a novel ceramic restorative cement

The aim of the present work was to compare a new ceramic restorative cement for posterior restorations, DoxaDent, with other types of tooth-colored materials for direct use as regards hardness and in vitro wear. Four hybrid resin composites, one polyacid-modified resin composite, one resin-modified glass ionomer cement, one conventional glass ionomer cement, one zinc phosphate cement, an experimental version as well as the marketed version of the ceramic restorative cement, were investigated. Hardness of the materials was tested with the Wallace indentation tester and wear was tested with the ACTA wear machine. All tests were carried out on 2-wk-old specimens. DoxaDent was as hard as the zinc phosphate cement and the hardest resin composite. The ceramic restorative cement wore significantly more than the resin composites, the same as the zinc phosphate cement, and less than the glass ionomer cements. No correlation between hardness and wear was found. It can be concluded that the ceramic restorative cement is a rather hard material but with a relatively low wear resistance.     

Wear of dental restorative and prosthetic materials in vitro

The aim of this study was to evaluate the wear of some modern materials for fixed crown and bridge restorations and fillings in vitro. Eighteen commercial materials (8 composites, 4 alloys, 4 fa?ade materials, and 2 denture-base resins) were tested. Enamel was used as the control. Test specimens were abraded on abrasion discs under water or in artificial saliva. There was a great variation in the wear rates of the tested materials. The greatest wear was shown by resins used for base material and the smallest by gold and Cr-Co alloys and porcelain. Most of the composites had a wear rate near that of enamel. The wear for amalgam was slightly greater than for most of the composites. When one is using several different materials for reconstructing occlusion, differences in wear resistance should be taken into account.