Dental materials for primary dentition: are they suitable for occlusal restorations? A two-body wear study.

AIM: This was to evaluate the wear resistance of different materials, compomers, resin-modified glass ionomer cements (RMGICs), glass ionomer cements (GICs), used for posterior restorations in primary teeth and to compare the results with the reference material, amalgam. STUDY DESIGN: Eight specimens of each material were subjected to two-body wear test, using a chewing simulator. The wear region of each material was examined under a profilometer, measuring the vertical loss (µm) and the volume loss (mm(3)) of the materials. RESULTS: The results showed significant differences of vertical loss and volume loss of the test materials (p < 0.001). Amalgam had the highest wear resistance. Twinky Star (compomer) had the lowest vertical loss and volume loss. There was no significant difference of vertical loss among compomers, Dyract Extra, Dyract Flow and Dyract Posterior. Riva Self Cure (GIC) had no statistically significant difference compared with the compomers (except Twinky Star). No statistically significant difference was found also between Equia (GIC) and Ketac Moral (GIC) with Dyract Extra (Compomer). RMGICs were found to have the lowest wear resistance. STATISTICS: For the statistical analysis, the PASW 20.0 (SPSS Statistics, IBM, Chicago) package was used. Means and standard deviations were measured with descriptive statistics and analyzed using one-way ANOVA. CONCLUSION: Compomers and some GICs, that have moderate wear resistance, may be sufficient for occlusal restorations in primary dentitions.

A split-mouth randomized clinical trial of conventional and heavy flowable composites in class II restorations.

OBJECTIVE: The aim of this study was to evaluate the 2-year clinical performance of class II restorations made with a composite resin with two different viscosities. METHODS: 47 patients received two class II restorations (n=94), one made with GrandioSO (conventional viscosity - CV), and the other with GrandioSO Heavy Flow (flowable viscosity - FV), subjecting both materials to the same clinical conditions. The self-etching adhesive Futurabond M was used for all restorations. The composites were inserted using the incremental technique. The restorations were evaluated using the modified USPHS criteria according to the periods: baseline, 6 months, 1 year and 2 years after restorative procedures. RESULTS: After 24 months, 40 patients attended the recall and 78 restorations were evaluated. In all periods, no secondary caries was observed. After 6 months, there were slightly overall changes of scores for most parameters. After 24 months, the higher number of changes from score Alfa to Bravo was observed for marginal discolouration (32.5% - CV and 39.5% - FV) and colour match (15% - CV and 31.6% - FV), followed by proximal contact (25% - CV and 23.7% - FV) and marginal adaptation (20% - CV and 21.1% - FV). For wear, surface texture and postoperative sensitivity the changes were very small. Just two restorations were lost during the 24-month follow up. Less than 5% of all restorations showed postoperative sensitivity. Chi-square test showed no significant differences between the two materials for all parameters analysed. CONCLUSION: After 2 years of clinical service, no significant differences were observed between GrandioSO conventional and GrandioSO Heavy Flow for the parameters analysed. Both materials provided acceptable clinical behaviour in class II restorations. CLINICAL SIGNIFICANCE: This study presents the possibility of using a flowable composite with high filler content, for performing class II restorations.

Comparison of pattern of failure of resin composite restorations in non-carious cervical lesions with and without occlusal wear facets.

OBJECTIVES: Many studies have reported the clinical problems associated with resin composite restorations in NCCLs. None has compared these clinical problems in NCCLs with and without occlusal wear facets. The present study sets out to determine the proportion of NCCLs that presents occlusal wear facets, and to compare the failure pattern of resin composite restorations in NCCLs with and without occlusal wear facets. METHODS: Teeth with NCCLs were classified into two groups, those with and without occlusal wear facets. Both groups were restored using micro hybrid resin composite. The restorations were evaluated at the end of 2 years concerning post-operative sensitivity, retention, marginal integrity, marginal discolouration, wear, and secondary caries, using the USPHS criteria. Statistical analysis compared the ratings of each criterion between the two groups using Pearson's χ(2) or Fisher's exact test. RESULTS: About one-third (33.8%) of teeth with NCCLs presented with occlusal wear facets, more NCCLs with occlusal wear facets in mandibular teeth (44.7%) than maxillary teeth (24.5%). Retention rate of composite resin restorations in NCCLs with and without occlusal wear facets was 63.9% and 74.4% respectively at the end of 2 years. More marginal discolouration and defects were observed in restorations in NCCLs with occlusal wear facets, the differences were not statistically significant (p>0.05). CONCLUSIONS: The decline in ratings of marginal discolouration and defects, and the lower retention rate of restorations in NCCLs with occlusal wear facets may support the role of occlusal stress and tooth flexure as a cause of failure of restorations in NCCLs. CLINICAL SIGNIFICANCE: The ability to distinguish between stress induced lesions (with occlusal wear facets) and other cervical lesions will have important ramifications for the success of their restorations because they are not subjected to the same physical forces that are responsible for the deterioration of the restoration.

Three-year clinical evaluation of a silorane composite resin.

STATEMENT OF PROBLEM: Composite resins are still outperformed by amalgams in the clinical practice with secondary caries and fractures being their most common failures. A material that suffers less polymerization shrinkage might improve the clinical performance of composite resins. PURPOSE: To evaluate the clinical performance of a low-shrink silorane-based composite resin (Filtek LS Low Shrink Posterior Restorative, 3M ESPE, St. Paul, MN, USA) in comparison with a methacrylate-based composite resin (Tetric EvoCeram, Ivoclar Vivadent, Schaan, Principality of Liechtenstein) over time. MATERIALS AND METHODS: Candidates in need of Class II composite resin restorations participated in this randomized controlled clinical trial. Those were 25 female and six male subjects with average age of 44.3 ± 12.7 years. Participants received 82 restorations, being 54 in premolars and 28 in molars. Procedures, which included the restoration of primary caries lesions or replacement of failing restorations, were done using modified preparations with no bevels or additional retention. Restorations were placed using Filtek LS (and dedicated self-etch adhesive) or Tetric EvoCeram (with AdheSE, Ivoclar Vivadent), following manufacturers' instructions. Incremental placement technique was applied and the restorations were immediately finished. Follow-up evaluations occurred at six, 12, 24, and 36 months and were done using the Fédération Dentaire Internationale criteria. Statistical analysis was performed using generalized estimating equations. RESULTS: The recall rate at 36 months was 89%. All interaction terms were not significant. CONCLUSIONS: Filtek LS performs as well as Tetric EvoCeram performs in the clinical setting at 36 months. CLINICAL SIGNIFICANCE: The silorane-based composite resin Filtek LS and the conventional methacrylate-based composite resin Tetric EvoCeram performed similarly well in posterior restorations over at least 36 months of clinical service.

Clinical wear rate of direct and indirect posterior composite resin restorations.

The purpose of this randomized clinical trial was to determine the clinical wear behavior of three nanofilled composites (Filtek Supreme XT [FS], Tetric EvoCeram [TEC], and Aelite Aesthetic [AA]) with two indirect composites (Estenia [E] and Tescera ATL [TATL]) on permanent molar teeth. Fifty-four patients whose treatment plans included moderate Class I and/or II restorations on molar teeth were selected for inclusion in this study. Wear was measured by use of gypsum replicas at baseline and 6 and 12 months using three-dimensional scanning and rapid-form software to elucidate the wear mechanisms. For statistical analyses, one-way analysis of variance and the Scheffe test were used. Statistical results revealed that wear behavior of TATL was significantly different from that of AA (P < .05). No significant differences were detected between AA and E (P > .05) or between TEC, FS, and TATL composite resins (P > .05). The results showed similar clinical performance between the five composite resins evaluated. Therefore, composite resins may be indicated for the restoration of posterior teeth. However, the composition of the composite resin did affect the wear behavior of the composite material.

Wear of dental sealing materials using the replication technique.

AIM: The aim of the present study was an in vivo evaluation of the wear of different sealing materials using the replication technique. MATERIALS AND METHODS: Four different sealing materials were randomly applied on 2 out of 4 caries-free permanent first molars of each patient. Impressions were taken at T0: before the sealing material was applied; T1: right after the application; T2: 6 months after the application, and T3: 1 year after the application. The impressions were then processed for scanning electron microscopy analysis of the wear of the examined materials. Statistical analysis was used to evaluate differences among and within the 4 groups. RESULTS: At T2, the average ratio of residual material in all the groups was 62.37% ± 1.21%, while at T3 it was 49.63% ± 1.11%. At both T2 and T3 there were no statistically significant differences among the 4 groups examined (p=0.76 and p=0.50 respectively). Comparison within the same group at T2 and T3 showed that statistically significant differences were only detected in group D (p=0.015). CONCLUSION: Sealing materials do not undergo a complete loss after 1 year of application, thus indicating that they are suitable for caries prevention.

Nanohybrid vs. fine hybrid composite in extended Class II cavities after six years.

OBJECTIVES: In a controlled prospective split-mouth study, clinical behavior of two different resin composites in extended Class II cavities was observed over six years. METHODS: Thirty patients received 68 direct resin composite restorations (Solobond M + Grandio: n=36; Syntac + Tetric Ceram: n=32) by one dentist in a private practice. All restorations were replacement fillings, 35% of cavities revealed no enamel at the bottom of the proximal box, in 48% of cavities remaining proximal enamel width was <0.5mm. Restorations were examined according to modified USPHS criteria at baseline, and after six months, one, two, four, and six years. RESULTS: Success rate was 100% after six years of clinical service, while the drop out of patients was 0%. Neither materials nor localization of the restoration (upper vs. lower jaw) had a significant influence on clinical outcome in any criterion after six years (p>0.05; Mann-Whitney U-test). Molar restorations performed worse regarding marginal integrity (4 years), filling integrity (6, 12, 24, 48 months), and tooth integrity (4 and 6 years). Irrespective of the resin composite used, significant changes over time were found for all criteria recorded (Friedman test; p<0.05). Marginal quality revealed a major portion of overhangs having been clearly reduced after the one year recall (baseline: 44%; 6 months: 65%; 1 year: 47%; 2 years: 6%; 4 years: 4%; and 6 years: 3%). Beyond the 1 year recall, negative step formations significantly increased due to wear (p<0.05), having been more pronounced in molars (87% bravo after 4 years) than in premolars (51% bravo after 4 years). Tooth integrity significantly deteriorated due to enamel cracks, which increased over time (p<0.05). Enamel chippings and cracks were significantly more frequent in molars (26% bravo after 4 years to 35% after six years) than in premolars (9% bravo after 4 years, 11% after six years). Restoration integrity over time mainly suffered surface roughness and wear (28% after one year, 75% after two years, 84% after four years, 91% after six years). SIGNIFICANCES: Both materials performed satisfactorily over the 6-year observation period. Due to the extension of the restorations, wear was clearly visible after six years of clinical service with 91% bravo ratings.

Erosion and abrasion of tooth-colored restorative materials and human enamel.

OBJECTIVES: The aim of this study was to investigate the effects of erosion and toothbrush abrasion on different restorative materials and human enamel. METHODS: Human enamel and 5 kinds of tooth-colored restorative materials were used. The restorative materials included three composite resins (Filtek Silorane, Tetric EvoCeram, and Tetric EvoFlow), a polyacid-modified composite (Dyract Extra), and a conventional glass-ionomer cement (Ketac Fil Plus). For each type of the material, 40 specimens were prepared and embedded in ceramic moulds and divided into four groups (n=10): control group (C), erosion group (E), abrasion group (A), and erosion-abrasion group (EA). The specimens were subjected to six daily erosive attacks (groups E and EA; citric acid, pH 2.3, 1 min) and/or six abrasive attacks (groups A and EA; toothbrush abrasion, 100 strokes, 1 min), while the control specimens (group C) were maintained in artificial saliva. After 10-day treatment, the substance loss and surface changes were determined by surface profilometry and scanning electron microscopy. RESULTS: Human enamel presented higher substance loss when compared to restorative materials. Generally, combined erosion-abrasion (EA) caused the highest substance loss, followed by erosion, abrasion, and storage in artificial saliva. Composite resin presented highest durability under erosive and/or abrasive attacks. Enamel and restorative materials showed degradation in groups E and EA through SEM observation. CONCLUSIONS: Toothbrush abrasion has a synergistic effect with erosion on substance loss of human enamel, polyacid-modified composite and glass-ionomer cement. The acid- and abrasive-resistance of human enamel was lower compared to restorative materials.

Confocal examination of subsurface cracking in ceramic materials.

PURPOSE: The original ceramic surface finish and its microstructure may have an effect on crack propagation. The purpose of this study was to investigate the relation between crack propagation and ceramic microstructure following cyclic fatigue loading, and to qualitatively evaluate and quantitatively measure the surface and subsurface crack depths of three types of ceramic restorations with different microstructures using a Confocal Laser Scanning Microscope (CLSM) and Scanning Electron Microscope (SEM). MATERIALS AND METHODS: Twenty (8 x 4 x 2 mm(3)) blocks of AllCeram (AC), experimental ceramic (EC, IPS e.max Press), and Sensation SL (SSL) were prepared, ten glazed and ten polished of each material. Sixty antagonist enamel specimens were made from the labial surfaces of permanent incisors. The ceramic abraders were attached to a wear machine, so that each enamel specimen presented at 45 degrees to the vertical movement of the abraders, and immersed in artificial saliva. Wear was induced for 80K cycles at 60 cycles/min with a load of 40 N and 2-mm horizontal deflection. The specimens were examined for cracks at baseline, 5K, 10K, 20K, 40K, and 80K cycles. RESULTS: Twenty- to 30-microm deep subsurface cracking appeared in SSL, with 8 to 10 microm in AC, and 7 microm close to the margin of the wear facets in glazed EC after 5K cycles. The EC showed no cracks with increasing wear cycles. Seventy-microm deep subsurface cracks were detected in SSL and 45 microm in AC after 80K cycles. Statistically, there was significant difference among the three materials (p < 0.05). Bonferroni multiple comparison of means test confirmed the ANOVA test and showed that there was no statistical difference (p > 0.05) in crack depth within the same ceramic material with different surface finishes. CONCLUSIONS: The ceramic materials with different microstructures showed different patterns of subsurface cracking.

Evaluation of the wear resistance of new nanocomposite resin restorative materials.

STATEMENT OF PROBLEM: The use of composite resins for the restoration of posterior teeth is popular because of the improved performance and appearance of these materials. Wear resistance continues to be of particular importance when restoring large occlusal areas in posterior teeth. PURPOSE: The purpose of this study was to evaluate the relative wear characteristics of 2 recently introduced nanofiller-based composite resins (Filtek Supreme, Premise) and compare them to the more traditional microhybrid (Point 4) and microfill (Heliomolar RO) materials that have been used for many years. MATERIAL AND METHODS: Six specimens (2 mm thick and 15 mm in diameter) of each material were subjected to 3-body wear tests using the Oregon Health Sciences University Oral Wear Simulator to produce abrasive wear and attrition for all specimens using human enamel as the opposing cusp. Profilometric tracings of the worn surfaces were used to determine the relative abrasive wear, attrition wear, and roughness (Ra) of the composite resin substrate. The mean diameter of the antagonist enamel wear facets was determined under a measuring microscope. Qualitative SEM analysis was also used to assess the surface appearance of the resulting enamel and composite resin wear facets. The data were analyzed by 1-way ANOVA and Tukey's multiple range post hoc test (alpha=.05). RESULTS: The results indicated that the composite resin type did not significantly affect the amount of measured attrition (P=.15) but did significantly affect abrasive wear (P=.02). The conventional microfill composite resin (Heliomolar RO) exhibited significantly less abrasive wear than the nanohybrid material (Premise). There was no significant difference in the average size of the opposing enamel wear facet generated by the different composite resin materials. Heliomolar RO resulted in a significantly rougher surface within the wear track than either nanohybrid composite resin (Premise) or microhybrid composite resin (Point 4) but was not significantly different than nanofilled composite resin (Filtek Supreme). CONCLUSIONS: The incorporation of nanofillers in 2 of the composite resin materials tested did not significantly improve their wear resistance or the amount of opposing cusp wear when compared to the traditional materials tested.

Quantitative measurement of tooth and ceramic wear: in vivo study.

PURPOSE: The aim of this study was to quantitatively measure tooth and ceramic wear over a 2-year period using a novel superimposition technique. Three ceramic systems--experimental hot-pressed ceramic (EC), Procera AllCeram (PA), and metal-ceramic--were used. MATERIALS AND METHODS: A total of 90 posterior crowns in 48 patients were randomized into 3 groups, and impressions were made at baseline and at 6-month intervals for 2 years. Clinical images were taken after using a dye to highlight surface changes. The impressions were digitized and modeled as superimposable 3-dimensional colored surface images. The depth of wear at the occlusal contact areas was quantitatively measured at 6, 12, 18, and 24 months. RESULTS: The quantitative evaluation showed more wear in Procera AllCeram at the occlusal contact areas, whereas the experimental and metal-ceramic systems showed less wear. There was a significant difference in the amount of enamel worn between all types of restorations (P < .05). There was a statistically significant difference (P < .05) in the mean depth of wear between all systems. CONCLUSIONS: The metal-ceramic and experimental systems showed less change, indicating improved wear resistance compared with Procera AllCeram. In addition, enamel opposing metal-ceramic and experimental crowns showed less wear compared to enamel opposed by Procera AIICeram crowns.

Effect of erosive pH cycling on different restorative materials and on enamel restored with these materials.

This in vitro study evaluated the effect of erosive pH cycling on the percentage of surface micro-hardness change (%SMHC) and wear of different restorative materials and bovine enamel restored with these materials. Eighty enamel specimens were randomly divided into eight groups according to the restorative materials and immersion media used: GI/GV-resin-modified glass-ionomer, GII/GVI-conventional glass-ionomer, GIII/GVII-resin composite and GIV/GVIII-amalgam. Over a period of seven days, groups GI to GIV were immersed in a cola drink (ERO) for 5 minutes, 3x/day and kept in artificial saliva between erosive cycles. Groups GV to GVIII were immersed in artificial saliva (SAL) throughout the entire experimental period (control). Data were tested for significant differences using ANOVA and Tukey's tests (p<0.05). For %SMHC, considering the restorative materials, no significant differences were detected among the materials and immersion media. Mean wear was higher for the resin modified glass ionomer cement when compared to conventional cement, but those materials did not significantly differ from the others. For enamel analyses, erosive pH cycling promoted higher wear and %SMHC compared to saliva. There were no significant differences in wear and %SMHC of enamel around the different restorative materials, regardless of the distance from the restorative material (50, 150 or 300 microm). In conclusion, there were only subtle differences among the materials, and these differences were not able to protect the surrounding enamel from erosion.

Wear simulation of resin composites and the relationship to clinical wear.

This study used a new generalized wear model to examine the relationship between wear simulation and the clinical wear of two resin composites. Ten specimens each of P50 and Z100, were subjected to 100,000, 400,000 and 800,000 cycles in a spring-loaded piston-type wear simulator. Wear was generated using flat, cylindrically-shaped stainless steel antagonists on the resin composites, which were placed in custom stainless steel fixtures. A slurry of polymethyl methacrylate beads was used as the abrasive media. Wear was determined using profilometry, and the parameters examined included volume loss (mm3), maximum depth (microm), mean maximum depth (microm) and mean depth (microm). Statistical analysis of the laboratory wear data using ANOVA and Tukey's post hoc test showed a significant difference (p<0.05) for wear between the two materials and the number of cycles. Mean maximum wear (microm) values (100K--P50--11.5 +/- 1.8; Z100--4.9 +/- 1.0; 400K--P50--17.2 +/- 2.7; Z100--6.0 +/- 1.7; 800K--P50--20.5 +/- 4.6; Z100--9.6 +/- 2.5) were used for comparisons with clinical data. Previous clinical studies of P50 and Z100 were used to examine the relationship between laboratory and clinical wear. Linear regression analysis was used to predict laboratory and clinical wear rates. The laboratory wear rate for P50 was 1.3 microm/100K cycles and the rate for Z100 was 0.7 microm/100K cycles. The clinical wear rates for P50 and Z100 were 8.3 microm/year and 4.0 microm/year, respectively. The ratio of wear rates of P50 to Z100 for wear simulation was 1.9 and the ratio of P50 to Z100 for clinical rates was 2.1. These ratios showed good agreement between the relative wear rates of laboratory and clinical wear. For the two composite materials examined, this new simulation model appears to be effective for evaluating the relative wear of resin composites.

Influence of bonded composite resin cingulum rest seats on abutment tooth periodontal tissues: a longitudinal prospective study.

This study aimed to examine the longitudinal influence of bonded composite resin cingulum rest seats on abutment tooth periodontal tissues in removable partial dentures (RPDs). Twenty-eight patients with RPDs were enrolled in the study. Thirty-one cingulum rest seats were prepared for an anterior tooth using composite resin and a standardized method for each patient. Periodontal indices such as probing pocket depth (PD), bleeding on probing (BoP), and tooth mobility (TM) were measured at the time of denture insertion (baseline) and at least 3 months postinsertion (up to 8 years). Control data were obtained from the remaining nonprepared anterior teeth on the other side of the arch. None of the bonded resin rest seats failed, but slight abrasion was observed in 3 rest seats. No significant differences were found in terms of PD, BoP, and TM between baseline and postinsertion data for abutments with bonded resin rest seats and controls. It is suggested that bonded composite resin cingulum rest seats can be used longitudinally without damaging the periodontal tissues of abutment teeth.

In situ effect of an erosive challenge on different restorative materials and on enamel adjacent to these materials.

OBJECTIVES: This in situ study evaluated the effect of an erosive challenge on different restorative materials and on enamel restored with these materials, as well as the ability of these materials to protect the adjacent enamel against erosion. METHODS: Ten volunteers wore palatal devices with eight bovine enamel blocks, randomly selected and distributed into two vertical rows, corresponding to the following groups: GI/GV, resin-modified glass ionomer; GII/GVI, conventional glass ionomer; GIII/GVII, composite resin; GIV/GVIII, amalgam. One row (corresponding to groups I-IV) was immersed in a cola drink and the other row (corresponding to groups V-VIII) was subjected to saliva only. The palatal device was continuously worn for 7 days and only half of the appliance (groups I-IV) was immersed in the soft drink (Coca-Cola), 150 mL) for 5 min, three times a day. The study variables comprised the wear (profilometry, microm) and the percentage of surface microhardness change (%SMHC). Data were tested for significant differences by two-way ANOVA and Tukey's tests (p<0.05). RESULTS: Considering the restorative materials, for %SMHC and wear, there were no differences among the materials and between the saliva and the erosive challenge. For enamel analyses, the erosive challenge promoted a higher wear and %SMHC of the enamel than did the saliva. There were no significant differences in wear and %SMHC of the enamel adjacent to the different restorative materials. CONCLUSION: This research data suggest that there is little %SMHC and wear of the studied restorative materials and none of them had a preventive effect against erosion on adjacent enamel, which showed a pronounced wear.

Morphological and compositional alterations of in vivo aged prefabricated pediatric metal crowns (PMCs).

OBJECTIVES: The purpose of the present study was to assess the morphological and elemental alterations of retrieved prefabricated metal crowns (PMCs) after intraoral exposure. METHODS: Seventeen in vivo aged stainless steel crowns (3M ESPE) were collected. The intraoral exposure time varied from 3 to 101 months. For every retrieved crown one new crown of the same type was used as a reference. The reference and in vivo aged crowns were examined by high-vacuum scanning electron microscopy and energy-dispersive X-ray microanalysis. The elemental composition between the as-received and in vivo aged crowns was statistically analyzed by t-test (a=0.05). RESULTS: In vivo aged crown surfaces demonstrated significantly morphological alterations with accumulation of amorphous intraoral integuments, biting imprints, wear and occlusal perforations. The results of microanalysis showed that there were no statistically significant differences in the elemental composition of the stainless steel crowns between the two conditions. SIGNIFICANCE: Under the conditions of the present study, retrieved prefabricated pediatric stainless steel crowns exhibit morphological changes mainly due to plastic deformation, without changes in elemental composition.

Developments in denture teeth to prevent softening by food solvents.

The effect of various food-simulating solvents on the hardness of denture teeth after varying storage times, using a Martens hardness test was determined. Martens hardness (HM) was assessed at baseline and during storage up to 1 month in distilled water (DW), peppermint oil (PO), heptane (HT) and 75% ethanol (ET) for four commercially-available denture teeth; Vivodent (VIV), Double-cross-linked Postaris (DCL), Orthosit (ORT), Candulor porcelain (POR) and two polymer based experimental denture teeth: Experimental 1 (EXP1); a hybrid nanocomposite with two different sized silanated filler particles and Experimental 2 (EXP2); containing an organic copolymer based upon urethanedimethacrylate and polymethyl methacrylate. Hardness [mean (sd)] at baseline was: VIV 142 (1), DCL 142 (1), ORT 209 (9), POR 2926 (101), EXP1 285 (11), and EXP2 146 (12). One-way ANOVA using Tukey's test on polymer-based materials showed that the hardness values of ORT and EXP1 were significantly higher than those of VIV, DCL and EXP2 (P < 0.05). Moreover, EXP1 had a significantly higher hardness value than ORT (P < 0.05). Except for EXP1, all polymer based materials showed a significant drop in hardness after storage in ET (P < 0.05). Specimens stored in water, heptane and peppermint oil showed minor fluctuations in hardness, which were not statistically significant.

Clinical wear of posterior metal-free polymer crowns. One-year results from a randomized clinical trial.

OBJECTIVES: The purpose of this randomized clinical trial was to evaluate the clinical wear behavior of posterior, metal-free polymer crowns, with and without a glass-fiber framework, and to compare it with that of metal-ceramic crowns. METHODS: Eighty single crowns manufactured from a newly designed polymer composite were set in posterior teeth. Half of these received a glass-fiber framework (group 1) whereas half were prepared without framework stabilization (group 2). All polymer crowns were adhesively luted with resin cement. As the control group, 40 conventional metal-ceramic crowns were inserted with hybrid cement. Wear was measured, by use of gypsum replicas, at baseline and after 12 months, by use of a 3D laser scanner. Statistical analysis was performed using mixed-effects regression model analyses. RESULTS: The mean total wear of posterior single crowns was -8.1 microm (+/-9.7 microm) in group 1, -7.0 microm (+/-9.1 microm) in group 2, and -3.4 microm (+/-6.3 microm) in the control group. Statistical analysis revealed wear behavior was significantly different from the control group for group 1 (p=0.014) and group 2 (p<0.01). No significant difference was detected between groups 1 and 2. Age, gender, and opposing teeth had no significant effect on wear behavior. CONCLUSIONS: Within a 12-month observation period mean total wear of posterior polymer crowns with and without a glass-fiber framework was significantly greater than for metal-ceramic crowns. The selection of restorative materials should be based on knowledge of clinical wear in order to preserve occlusal stability.

Antagonist enamel wears more than ceramic inlays.

Wear phenomena of ceramic inlays are not fully understood. The aim of the present study was to evaluate ceramic wear, antagonist enamel wear, and luting cement wear over 8 years. The two-fold null hypothesis was that there would be (1) no difference in wear behavior between ceramic and enamel, and (2) no influence of filler content of luting composites on composite wear. From 96 restorations, 36 Class II inlays from 16 participants were selected. For inlays with opposing enamel cusps (n=17), replicas of inlays and enamel were scanned with a 3-D laser scanner. Luting gaps of inlays (n=36) were analyzed with a profilometer, including 3-D data analysis. Ceramic and enamel wear increased between 4 and 8 years, with significantly higher values for enamel after 6 years (p<0.05). Luting gap wear increased continuously up to 8 years (p<0.05), with no influence of luting composites (p>0.05) and location of teeth (p>0.05).

A comparison of three different methods for the quantification of the in vitro wear of dental materials.

OBJECTIVE: Different approaches are utilized to quantify the wear generated on flat specimens with a wear simulator. However, there are no systematic studies comparing different wear quantification methods with a series of materials that exhibit different wear rates. METHODS: Sixteen restorative materials, including 14 composites (BelleGlass, Chromasit, Estenia, Esthet-X, Four Seasons, Heliomolar RO, Heliomolar HB, Herculite XRV, InTen-S, Point 4, SureFil, Targis cured at 95 and 130 degrees C, Tetric Ceram) as well as an amalgam (Amalcap) and a ceramic (Empress) material, were subjected to attrition wear against standardized Empress antagonists in the Willytec wear simulator (120,000 cycles, 5 kg, 1.6 Hz). The volume and maximal vertical loss were quantified directly on the specimens with a profilometry device (Perthometer) and the FRT MicroProf optical sensor. After the fabrication of plaster replicas, the loss was also determined with a 3D laser scanning device. For the statistical analysis, the data were subjected to a logarithmic transformation. Intraclass correlation was calculated to measure the agreement among all three methods, while limits of agreement were used to compare one method against another. RESULTS: There was a very good agreement between all three quantification methods for both volume and vertical loss. The mechanical sensor measured consistently higher values compared to the optical sensors for the volume loss (correction factor 0.95), whereas for the vertical loss, consistently lower values were obtained (correction factor 1.17). However, the ranking of the materials was only marginally influenced by the quantification method. SIGNIFICANCE: All three sensors are suitable for the quantification of wear facets. Due to speed and simplicity, the laser sensor has greater advantages over the two other sensors.