Wear Of Restorations Research Articles

In vivo prospective randomised study of the wear of dental restorations using an intraoral scanner and its correlation with visual assessment.

Objectives: To evaluate the efficacy of the True Definition®intraoral scanner in quantifying the wear of the glass ionomer restorative material (KetacTM Universal and KetacTM Molar) over 1 year. We also studied the correlation between visual and digital assessments of restoration wear. Materials and Methods: This was a clinical follow-up study of a post-marketed material with a prospective, controlled, randomised, split-mouth, and blinded assessment design. Intraoral optical impression and visual assessment were carried out over three appointments over 12 months, starting with 36 patients.Results: According to the visual indices, all restorations in this study were clinically healthy. However, in the digital measurement of wear, 94.74% and 94.44% of the restorations during the T0-T6 and T6-T12 observation periods, respectively, showed deterioration greater than 41 microns. Moreover, in the analysis of agreement between measurement techniques, no agreement was obtained in the two analysed time periods: T0-T6 yielded a kappa (k) value of 0.000, and T6-T12 yielded k=0.0030. Discordant results were obtained in the correlation analysis. In T0-T6, the results were not considered statistically significant (p=0.838); however, the results obtained during T6-T12 showed a correlation (p-value <0.001).Conclusions: The wear of dental materials as observed by the human eye did not agree with that observed by intraoral scanning. The scanner effectively measures wear, detecting details that are beyond the capability of the human eye and conventional photographs. The surface deterioration of the restorations at both observation times can be considered non-physiological, potentially leading to premature occlusal alterations and accelerated physiological ageing.Clinical Relevance: Early diagnosis is crucial for avoiding alterations in the function of the stomatognathic system due to the wear of dental restorations. Additionally, since most of the tools applied are qualitative in nature, such as visual inspection, it is essential to find a standardised and precise tool that offers diagnosis, monitoring, and records of the evolution of tooth wear. This study has been registered at https://www.ClinicalTrials.gov, under the identifier NCT06275581.

Performance and durability of additively and subtractively manufactured resin-based onlay restorations after thermomechanical aging.

To evaluate the effect of material type on dimensional stability, occlusal surface wear, fracture resistance, and failure behavior of resin-based onlay restorations. A mandibular right first molar typodont was prepared and digitized using an intraoral scanner to virtually design an onlay restoration with the minimum occlusal thickness of 1.5mm. Resin-based onlay restorations (n = 15 per group) were fabricated either additively from 2 different resins indicated either for definitive or interim use or subtractively with a composite resin. After cementing onlays to corresponding dies, each of them was digitized before and after thermomechanical aging (B-STL and A-STL), and then subjected to load-to-failure test to evaluate fracture resistance. The B-STL and A-STL of each onlay were also compared to assess the dimensional stability and occlusal surface wear. One-way analysis of variance and Tukey honestly significant difference tests were used to evaluate dimensional stability, occlusal surface wear, and fracture resistance. The chi-square test was used to evaluate the Weibull modulus and characteristic strength among the groups (α = 0.05). Material type affected investigated outcomes (p<0.001). The additively manufactured resin indicated for definitive use led to the highest external surface deviations and the additively manufactured resin indicated for interim use led to the highest mesiodistal width deviations (p≤0.033). The onlays fabricated from the additively manufactured resin indicated for definitive use had the highest occlusal surface wear, while those in composite resin had the lowest (p≤0.006). The composite resin onlays had the highest fracture resistance values and reliability (p≤0.035). Tested subtractively manufactured composite resin had the lowest occlusal surface wear with the highest fracture resistance and reliability. Additively manufactured resins had lower dimensional stability, while tested resin for additively manufactured definitive restorations had the highest occlusal surface wear.

An In Vitro Study regarding the Wear of Composite Materials Following the Use of Dental Bleaching Protocols.

Composite materials used in dental restorations are considered resistant, long-lasting and aesthetic. As the wear of restorations is an important element in long-term use, the aim of this study was to evaluate the surface condition of nanohybrid and microfilled composite resins, after being subjected to the erosive action of dental bleaching protocols. This paper reflects a comparative study between one nanofilled composite and three microfilled composites used in restorations. For each composite, three sets of samples (under the form of composite discs) were created: a control group, an "office bleach" group with discs bleached with 40% hydrogen peroxide gel, and a "home bleach" group with discs bleached with 16% carbamide peroxide gel. Wear was numerically determined as the trace and the coefficients of friction obtained using a tribometer, the ball-on-disk test method, and two balls: alumina and sapphire. For all composite groups, there were statistically significant differences between the wear corresponding to the control and bleaching groups, for both testing balls. Regarding the composite type, the largest traces were recorded for GC Gradia direct anterior, for all groups, using the alumina ball. In contrast, for the sapphire ball, 3M ESPE Filtek Z550 was characterized by the largest traces. With respect to the friction coefficients, the "office bleach" group recorded the largest values, no matter the composite or the ball type used. The 3M ESPE Valux Plus composite recorded the largest friction coefficients for the alumina ball, and 3M ESPE Filtek Z550 for the sapphire ball. Overall, the "office bleach" group was characterized by higher composite wear, compared to the "home bleach" protocol or control group. Nanofilled composite resins showed superior wear resistance to microfilled resins after undergoing a bleaching protocol.

Influence of filler types on wear and surface hardness of composite resin restorations.

Wear and surface hardness of resin composites are of relevance from the clinical standpoint. With the incorporation of novel filler system, more studies need to be performed to investigate newly marketed resin composites. The objective of this study was to investigate the abrasive wear and surface hardness of dental restorative with different filler types. Nanohybrid filled Harmonize (HM) and Tetric N-Ceram (TNC), microhybrid filled Filtek Z250 (Z250), nanofilled Filtek Z350 (Z350) were included in the study. Twelve cylindrical resin composites specimens with 10 mm in diameter and 6 mm in thickness were prepared for abrasive wear test. Eight hundred cycles under 17 kg load were conducted for final wear by CW3-1 wear machine. The specimen was cleaned with an ultrasonic unit for 3 min followed with drying procedure. After measurement of weight loss and the density of specimens, the specimens were kept for measurement of surface hardness. Surface hardness was measured using a micro-hardness tester with a Vickers diamond indenter after polishing. Three specimens of each material were observed by scanning electron microscopy (SEM) after the abrasion to evaluate the morphology of the surface. Data were analyzed using one-way analysis of variance (ANOVA), followed by Tukey HSD test (α = .05). Z250 performed the least volume wear loss (41.1 ± 2.1 mm3), as well as the hardest value (102.7 ± 2.9 HV). There was no significant difference with the volume wear loss (p = 1.000) and surface hardness (p = 0.874) of HM and TNC. SEM images of nanohybrid filled HM and TNC represented smoother surface compared with other types of resin composites. Microhybrid Z250 showed the highest wear resistance and surface hardness, nanofilled and nanohybrid resin composites may still face the insufficient of wear and surface hardness quality.

Wear of dental ceramics

Based on the development of adhesive dentistry, minimally invasive restorations in ceramics are used as alternativesto restore a tooth. Dental ceramics are largely applied in the dentistry field mainly due to their esthetic andmechanical strength. One of the ceramic properties to be well known before its use is the wear resistance thatshould be compatible with the antagonist wear behavior to avoid unwanted performance. Therefore, severalmethods have been performed to assess the ceramic materials wear behavior considering different conditionspresent in the complex oral medium. This study aimed to compile the methods used to investigate dental ceramicswear and to describe the wear mechanisms involved on them. Obtaining and analyzing data is also addressed todiscuss the results obtained from different methods, as well as the clinical analysis of wear and future perspectiveson this topic. In conclusion, many methodologies are available to measure the ceramic wear. Therefore, themethods must be selected based on the clinical significance of each study and should follow previously reportedparameters for standardization, allowing literature comparison. KEYWORDSDental Materials; Ceramics; Dental wear; Dental restoration wear; Methods.

Canine guidance reconstruction with ceramic or composite resin: A 3D finite element analysis and in vitro wear study

Statement of problemWear of the maxillary canine cusps is a common clinical condition which can affect function and esthetics and, in some situations, lead to occlusal pathology. The mechanical behavior of different restorative techniques for the condition is unclear. PurposeThe purpose of this in vitro study was to evaluate the biomechanical behavior of direct or indirect restorative techniques used in restoring canine guidance. Material and methodsThree-dimensional models obtained from 10 extracted undamaged maxillary canines were modeled by using reverse engineering. Each model received 2 different preparations: incisal (I) or incisal and labial (IL), restored with composite resin (CR) or ceramic (C), compared with unrestored teeth (U). Finite element analysis was used to evaluate the total deformation and the maximum principal stress. For the in vitro wear test, 30 teeth were divided into groups: U (control), I-CR, and IL-C. The teeth were wear tested for 240 000 cycles with a 2-mm sliding contact, a load of 49 N applied, with a 4-Hz cycle with a composite resin piston as antagonist. The wear of restorations and antagonists was quantified by the digital image correlation technique. The 1-way analysis of variance test for total deformation and the Tukey test for the maximum principal stress were used (α=.05) to statistically analyze the data. The Friedman test was applied in the comparison between wear cycles, and the Tukey test was used in the comparison among groups. ResultsNo significant difference was found among groups (P>.05) for the total deformation. IL-CR showed a higher failure probability, reaching stress peaks which exceeded the tensile strength of the material. I-CR showed greater wear in the in vitro test than IL-C (P=.02). No difference was found among groups in antagonist wear (P=.074). ConclusionsCeramic restorations with labial involvement show biomechanical behavior closer to that of unrestored teeth in restoring canine guidance compared with composite resin.

Laminate veneer ceramics in aesthetic rehabilitation of teeth with fluorosis: a 10-year follow-up study

BackgroundFluorosis is one of the color anomalies seen in teeth. White lines and blurred areas associated with mild fluorosis are barely noticeable; in its severe form, tooth enamel surface changes ranging from staining and pitting may be observed. The treatment of fluorosis not only provides aesthetic and functional correction but also helps to improve the patient's self-esteem.MethodsThe present retrospective study evaluated the clinical quality, success rate, and estimated survival of porcelain laminate veneers in teeth with anterior fluorosis. Three hundred fifty-eight porcelain laminate veneers (254 in the anterior maxilla and 104 in the mandible) were "functional" restorations that covered the incisal edge and part of the palatal/lingual side of the tooth with a 1 mm high palatal bevel. Ceramic veneers were fabricated with lithium disilicate reinforced glass–ceramic material (IPS e.max Press, Ivoclar Vivadent, Schaan, Liechtenstein). The modified United States Public Health Service criteria were used for clinical evaluation of the restorations.ResultsOn the basis of these criteria, marginal adaptation, color match, marginal discoloration, surface roughness, restoration fracture, tooth fracture, restoration wear, antagonist tooth wear, caries and postoperative sensitivity were evaluated yearly. The survival rate in the current study was ≥ 0.997 for 10 years.ConclusionsThe results of this clinical study should encourage clinicians to consider ceramic veneers over crown restorations when restoring the smile of patients with advanced fluorosis.

Influence of Conventional, CAD-CAM, and 3D Printing Fabrication Techniques on the Marginal Integrity and Surface Roughness and Wear of Interim Crowns

The aim is to assess the influence of fabrication techniques—conventional (CN), CAD-CAM (CC), and 3D printing (3D)—on the marginal fit, adaptation, surface roughness, and wear of interim restorations of crowns. Thirty interim crowns were fabricated using CN, CC, and 3D techniques. Sixty discs were fabricated to evaluate surface wear and surface roughness properties, with 10 disc samples in each group (n = 10). Internal adaptation and marginal integrity of interim crowns were analyzed with micro CT to detect microgaps at selected points. Average surface micro-roughness (Ra) was calculated in micrometers (μm) using an optical non-contact surface microscope under cyclic loading. Surface wear was evaluated by surface area measurements (mm3) using a micro CT. Analysis of variance (ANOVA) and Tukey’s post hoc comparison tests with Pearson correlation were performed for data analysis. The highest adaptation means were for CN (269.94 ± 64 μm), and the lowest mean value was observed for 3D (197.82 ± 11.72 μm) crowns. CN and CC specimens showed comparable adaptation (p &gt; 0.05), which were significantly higher (p &lt; 0.05) than 3D crowns. CN crowns showed significantly higher marginal misfit compared to 3D (p &lt; 0.05) and CC (p &lt; 0.05) crowns. The highest mean surface roughness was observed in the 3D crowns (5.61 ± 0.33 µm), whereas the lowest was found in CC crowns (3.28 ± 0.34 µm). Better restoration Ra was observed using the CC method followed by CN. CN had the highest wear (17.79 ± 2.78 mm3), and the lowest wear was observed in the 3D (10.81 ± 2.00 mm3) specimen. Low surface wear was observed using 3D printing, followed by CN and CC techniques. The printed specimen showed comparable outcomes to CAD-CAM restoration; however, they were better than CN restoration. A positive correlation between adaptation and surface roughness was observed, indicating an effect of the fabrication technique on material physical property.

In-vivo-wear in composite and ceramic full mouth rehabilitations over 3 years

The aim of this study was to quantify and to compare the wear rates of premolar (PM) and molar (M) restorations of lithium disilicate ceramic (LS2) and an experimental CAD/CAM polymer (COMP) in cases of complex rehabilitations with changes in vertical dimension of occlusion (VDO). Twelve patients with severe tooth wear underwent prosthetic rehabilitation, restoring the VDO with antagonistic occlusal coverage restorations either out of LS2 (n = 6 patients, n = 16 posterior restorations/patient; N = 96 restorations/year) or COMP (n = 6 patients; n = 16 posterior restorations/patient; N = 96 restorations/year). Data was obtained by digitalization of plaster casts with a laboratory scanner at annual recalls (350 ± 86 days; 755 ± 92 days; 1102 ± 97 days). Each annual recall dataset of premolar and molar restorations (N = 192) was overlaid individually with the corresponding baseline dataset using an iterative best-fit method. Mean vertical loss of the occlusal contact areas (OCAs) was calculated for each restoration and recall time. For LS2 restorations, the mean wear rate per month over 1 year was 7.5 ± 3.4 μm (PM), 7.8 ± 2.0 μm (M), over 2 years 3.8 ± 1.6 µm (PM), 4.4 ± 1.5 µm (M), over 3 years 2.8 ± 1.3 µm (PM), 3.4 ± 1.7 µm (M). For COMP restorations, the mean wear rate per month over 1 year was 15.5 ± 8.9 μm (PM), 28.5 ± 20.2 μm (M), over 2 years 9.2 ± 5.9 µm (PM), 16.7 ± 14.9 µm (M), over 3 years 8.6 ± 5.3 µm (PM), 9.5 ± 8.0 µm (M). Three COMP restorations fractured after two years and therefore were not considered in the 3-year results. The wear rates in the LS2 group showed significant differences between premolars and molars restorations (p = 0.041; p = 0.023; p = 0.045). The wear rates in COMP group differed significantly between premolars and molars only in the first two years (p < 0.0001; p = 0.007). COMP restorations show much higher wear rates compared to LS2. The presented results suggest that with increasing time in situ, the monthly wear rates for both materials decreased over time. On the basis of this limited dataset, both LS2 and COMP restorations show reasonable clinical wear rates after 3 years follow-up. Wear of COMP restorations was higher, however prosthodontic treatment was less invasive. LS2 showed less wear, yet tooth preparation was necessary. Clinicians should balance well between necessary preparation invasiveness and long-term occlusal stability in patients with worn dentitions.

HAZ Structure Formation of Carbonaceous Steel at Impulse Welding

For increase of mining technique capacity at production and restoration wear resistant facings are widely applied. In this work, impacts of impulse welding of an intermediate layer on structural factors and facture toughness of wear resistant surfacing are studied. It, is established, that applying an intermediate layer with periodic impulse «teeth» forms a heterogeneous texture of intermediate layer, causing higher fracture toughness of wear resistant surfacing. It, is shown that defects made by current impulse have promoted a fine-grained structure of HAZ facing and grain-boundary allocation of grainy pearlite.

Nanoparticles in dentistry - An updated review

Nanoparticles having a size from 1 nm to 100 nm are present in nature and are successfully used in many products of daily life. In dental materials, nanoparticles are typically embedded but they may also exist as by-products from milling processes. Possible adverse effects of nanoparticles have gained increased interest, with the lungs being the main target organ. Exposure to nanoparticles in the dental laboratory is addressed by legal regulations. In dental practice, nanoparticles are mainly produced by intra-oral grinding/polishing and removal of materials, by wear of restorations or release from dental implants. Based on worst-case mass-based calculations, the additional risk as a result of exposure to nanoparticles is considered to be low. However, more research is needed, especially on vulnerable groups (patients with asthma or chronic obstructive pulmonary disease). An assessment of risks for the environment is not possible because of lack of data. Exposure-reduction measures mainly include avoidance of abrasive processes (e.g., by proper sculpturing), cooling by the use of water spray, and sufficient ventilation of treatment areas.

Clinical Evaluation of Lithium Disilicate Veneers Manufactured by CAD/CAM Compared with Heat-pressed Methods: Randomized Controlled Clinical Trial.

Lithium disilicate veneers for esthetic restorations show great accuracy and similarity, regardless of the type of fabrication technique.

Evaluation of friction in different oral restoration materials and its influencing factors

This research uses nanotechnology and molecular assembly technology, using biocompatible hydroxyapatite material as the inorganic filler, organically compound and assemble with the organic resin matrix to achieve the performance shear of the composite material, thus developing strength High-resistance, easy-to-process and good biocompatibility composite resin dental restoration materials, and the nano-composite resin material flexural strength, compressive strength and water absorption value were characterized in laboratory stage, the performance fully reached the current clinical use Various indicators of imported composite resin. This study analyzed the differences in the effects and friction properties of different prosthetic materials in oral repair. In order to better simulate the friction and wear performance of dental restoration materials in the oral environment, this paper studied under two conditions of oil lubrication and artificial saliva lubrication, and the wear mechanism from the macro aspects of friction coefficient, wear rate, wear resistance, etc. The research results show that the abrasion performance of the nanocomposite resin is closely related to its surface morphology and characteristics. The comparison with the performance of ceramic and composite resin restoration materials shows that nanocomposite resin materials have better mechanical properties and resistance than other dental restoration wear performance.

The effect of toothbrush abrasion on wear and surface roughness of direct and indirect composite laminate veneer restorations

Direct and indirect composite laminate veneers have been frequently used, however the wear of composite restorative materials is still a major problem. Objective: This study aimed to investigate the surface roughness and wear of composite laminate veneers made by two different methods after toothbrushing simulation. Material and Methods: Ninety-six upper incisors and canines were divided into two groups: 1-Componeer prefabricated composite veneer (CPV), 2- Uveneer direct composite veneer (UDV). At the UDV group, restorations were made by using Uveneer template system with the same nanofilled composite material (Synergy D6, Coltène, Altstatten, Switzerland) of the prefabricated Componeers’. The initial surface roughness was measured with a profilometer, then the weight was measured. Before the simulation, samples were screened with a 3D extra-oral scanner. Toothbrush simulation was performed at 10,000 rotational strokes with 2.5 N. The measurements were repeated after toothbrushing simulation. Data were analyzed using variance analyses and t-tests (p < 0.05). Results: Before and after polishing, a significant difference was found between two groups’ surface roughness in both lateral incisors (p = 0.000, p = 0.000) and canines (p = 0.048, p = 0.001), respectively. After toothbrushing simulation, significant increases were observed in central and lateral incisors’ surface roughness with two methods. There was no significant difference between weight loss (p > 0.05). In 3D scans, wear rate was quite similar except UDV group central incisors. Conclusions: Surface roughness of the CPV restorations were less affected after toothbrushing simulation. However, the Uveneer template system, a facilitated treatment procedure compared to the manual buildup of direct restoration, has shown comparable results with CPV’s.

Clinical wear of approximal glass ionomer restorations protected with a nanofilled self-adhesive light-cured protective coating.

High viscous glass ionomer cement (GIC) has gained popularity as a restorative material; however, high wear is pointed as one of the major drawbacks of this material. Protective surface coatings were developed to protect GIC from water contamination with the additional advantage of occluding any surface cracks or porosities commonly found in this material, possibly resulting in an increased wear resistance of the restorations.Objective:The objective of this study was to investigate the clinical wear of GIC approximal restorations in primary molars protected either with a nanofilled self-adhesive light-cured protective coating (NPC) or with petroleum jelly.Material and Methods:Approximal caries lesions in primary molars from 32 schoolchildren previously enrolled in another clinical trial were included in this investigation. GIC restorations were performed according to the Atraumatic Restorative Treatment approach and protected with either petroleum jelly or a NPC. Impressions of the restored hemiarch were done after 1 day and 6, 12, 24 and 36 months. The impressions were scanned in a 3-D appliance and the obtained images were superimposed using an appropriate computer software. Two-way ANOVA for repeated measures and Tukey's post-hoc test were used to analyze the wear of restorations (α=5%).Results:A significant difference was found between the two groups, with a wear protection offered by the application of a NPC. Conclusion: These results suggest that the application of a NPC has a protective effect on the clinical wear of approximal GIC restorations in primary teeth.

REPARAÇÃO EM RESINA COMPOSTA: REVISÃO SISTEMÁTICA

Introdução: A substituição total de restaurações de resina composta é uma das técnicas mais utilizadas por cirurgiões dentistas quando estas restaurações apresentam alguma falha. Essa técnica amplia o preparo cavitário, removendo tecido dentário sadio, podendo gerar danos pulpares. A reparação de resina composta substitui parcialmente a restauração preservando estrutura dental e o substrato remanescente de resina composta. Objetivo: Realizar uma revisão sistemática por meio de estudos que descrevessem a eficácia clínica e laboratorial da reparação em restaurações de resina composta defeituosas. Método: Como base para a pesquisa, foram acessados os bancos de dados PubMed, Scopus, BVS e SciELO, os descritores selecionados através do DesC e MeSH foram, Resinas compostas, Desgaste de restauração dentária, Falha de restauração dentária, Reparação de restauração dentária. Resultados: Foram incluídos todos os artigos que abordassem sobre a técnica de reparação. Conclusão: Existem poucas evidências cientificas que mostrem o sucesso e vantagens desse método sobre a substituição total, porém os estudos analisados já apresentam bons resultados.

Influence of abrasive solutions on direct restorative composites wear

Tribological characterization of dental restorative materials is very hard because it is difficult to reproduce the actual test conditions which occur in the mouth. Despite the wide variety of wear test equipment, there are no wear test standards. The guide provided by the International Organization for Standardization (ISO), entitled “ Dental materials—guidance on testing of wear—part 2: Wear by two- and/or three body contact, Technical Specification 14569-2 number 2001 focuses only on a technical description of the procedures. This standard doesn’t evaluate or demonstrate any of the advantages or disadvantages of the existing tests or their procedures. This work is focused on the evaluation of the effect of abrasion solution. Three abrasive of the most common used were select. Test condition such as load and number of cycles were established, in order to attain specific wear rates similar to the ones in the mouth. From a soft organic abrasive to more severe abrasive several solutions were tested. Wear analyses was done using two distinct approaches; a classical and an energetic. A glass sphere against a flat direct restorative composite surface on a reciprocating sliding contact were selected for the evaluation, initial conditions were set based on previous studies which provided decisive information for the selection of adequate laboratorial parameters. It was found that the wear evolution of the composite and antagonist materials depends directly on the abrasive solution and test conditions used. It was necessary to fix a standard parameter to compare abrasive solutions, wear rate (mm3/cycle) of natural teeth. The use of each abrasive solution can be made depending on the purpose of the study, i.e., if it is comparative performance of a particular material or if you want to simulate more closely what goes into the mouth. If the purpose of the study is to compare performance of particular materials (more severe abrasive solution) or if we want to simulate more closely what happens in the mouth (mild abrasive solution). A morphological and wear mechanisms analysis were done using SEM, this allowed to compare qualitatively the effect of abrasive solution on the material pair.

The dental alloys determine the choice of composite resins to be used.

Objective: The aim of the present study was to evaluate wear resistance of two composites resins against alternative alloys. Material and Methods: Fifteen stylus tips samples of composite resin were obtained for each resin Z250 and charisma (CHA). Samples were divided into three groups according to the disk of alloy to be used as antagonist: Nickel-Chromium (Ni-Cr), Cobalt- Chromium (Co-Cr) and commercially pure titanium (cp Ti). Wear tests were performed at a speed of 265 cycles/min and distance of 10mm, in a total of 40,000 cycles. Before and after wear tests, samples were weighed and had their profile designed in an optical comparator to evaluate weight and height loss, respectively. Results: For weight and height loss, wear of Z250 was lower than CHA for Co-Cr antagonist, but greater for cp Ti. CHA presents a more regular surface without cracks and similar aspect for all antagonists. Z250 showed some cracks, mainly against cp Ti and Ni-Cr. Conclusion: Within the results of the present study, it was concluded that CHA is suitable against cp Ti, and Z250 for association with Co-Cr alloy while any composite resin can be used against Ni-Cr.KeywordsComposite resins; Dental alloys; Dental restoration wear.

Effect of addition of Nano hydroxyapatite particles on wear of resin modified glass ionomer by tooth brushing simulation

BackgroundRecently, incorporation of nanohydroxyapatite (NHA) has been suggested to improve the mechanical properties of glass ionomers (GIs). This study aimed to assess the effect of addition of NHA on wear of resin modified glass ionomer (RMGI) by tooth brushing simulation.Material and MethodsIn this in vitro, experimental study, NHA in 1, 2, 5, 7 and 10wt% concentrations was added to Fuji II LC RMGI powder, and 48 samples (5×5mm) in five experimental and one control group (n=8) were fabricated. After polishing, cleaning and incubation at 37°C for three weeks, the samples were weighed and subjected to tooth brushing simulation in a toothpaste slurry according to ISO14569-1. Then, they were weighed again and the weight loss was calculated. The data were analyzed using one-way ANOVA and Tukey’s test.ResultsThe highest and the lowest weight loss was found in the 0% NHA (-1.052±0.176) and 5% NHA (-0.370±0.143) groups, respectively. Wear was significantly higher in 0% NHA group (P<0.05). No difference was detected in wear between 2 and 5wt% NHA or among 1, 7 and 10wt% NHA groups. Significant differences were noted in wear between 2 and 5wt% NHA and 1, 7 and 10wt% NHA groups (P<0.001).ConclusionsIncorporation of up to 10wt% of NHA increases the wear resistance of Fuji II LC RMGI. This increase was the highest when 2 and 5wt% NHA were added. Key words:Glass ionomer, hydroxyapatites, nanoparticles, dental restoration wear.

Evaluation of Wear and Hardness of Zirconia with Different Surface Treatment Protocols a Systematic Review

Objective: The objective of this systematic review is to assess the wear and hardness of surface treated zirconia. Methods: Two automated databases were investigated till July 2015 with no limits. The scientific terms: “Dental enamel”, “Yttria stabilized tetragonal zirconia”, “Tooth wear”, “Enamel wear”, “Hardness”, “Translucent zirconia’ and “Dental restoration wear” were used in this study. Initially screening was performed for the retrieved articles through title and abstract after that, full-text assessment was done to those articles that fulfilled the inclusion criteria. Findings: Sixty-nine potentially eligible studies were retrieved from the data base search; after duplicate removal the studies became sixty-three. Full-text assessment was performed for all titles and abstracts that met the inclusion criteria. Finally, seventeen studies met the inclusion criteria, and so their references were also screened. Applications/Improvements: Although studies applied different wear testing methodologies; wear testing devices, number of cycles, magnitude of force, number of samples, sample preparation for zirconia and enamel antagonist surface, as well as hardness measurement protocol, full contoured polished zirconia and human enamel (as antagonist) showed high resistance to wear. It was also concluded that zirconia showed high hardness as a surface property. It is recommended to polish the surface of restorations made of full-contour zirconia because this polishing favours the surface properties (wear and hardness) to opposing enamel.