Progressive Tooth Wear Against Resin-Based Restorative Composites.

PURPOSE: The composition and properties of resin-based composite materials could affect tooth wear and lead to clinical problems. Therefore, the study objective was to characterize human tooth wear behavior against a bulk-fill restorative (BF) compared to a conventional resin composite (RC) and a CAD/CAM resin nano ceramic (RN). METHODS: Square-shaped specimens of each material were prepared and sub-divided according to the number of testing cycles (n=8): 100,000, 250,000, and 500,000 cycles. An occlusal wear test was performed using a chewing machine with 49 N, 2 Hz, in 37°C distilled water. Human premolar cusps were used as antagonists. Micro-CT and laser scanner were used to scan antagonists and specimens, respectively. Wear volume was assessed using a software and the wear pattern was examined with SEM. Softening in solvent analysis was performed by measuring the materials' Knoop microhardness (KHN) before and after immersion in ethanol. Wear volume data were analyzed with two-way ANOVA and Student-Neuman-Keuls test (α=0.05). RESULTS: For tooth and specimen wear volume, there was statistical significance for material and number of cycles, but not for the interaction between factors. BF resulted in less tooth (p=0.008) and specimen (p=0.030) wear than RN and RC, which were similar (p⟩0.05). Volume loss increased from 100,000 to 500,000 cycles. BF showed the lowest microhardness (KHN1); and %ΔKHN similar to RC, but greater than RN. CONCLUSION: BF induced less volume loss to the tooth than RC and RN, while presenting greater wear resistance. The tooth wear pattern and damage progression were mild for all materials. CLINICAL SIGNIFICANCE: Resin composites show favorable wear behavior, leading to low volume loss and mild structural damage of the tooth. Regular bulk-fill resin composite stands out for its efficient restorative technique, low wear susceptibility and reduced capacity to wear down the tooth.

Effect of polishing versus glazing of CAD-CAM ceramics on wear and surface roughness of opposing composite resin.

Background: This study aimed to assess the effect of polishing versus glazing of computer-aided design-computer-aided manufacturing (CAD-CAM) ceramics on depth of wear and surface roughness of opposing composite resin. Materials and Methods: This in vitro study was conducted on 40 Z250 composite and 40 CAD-CAM ceramic specimens including Celtra Duo, Vita Mark II, e.max CAD, and Vita Suprinity ceramics. All ceramic specimens were roughened by a fine-grit bur after primary glazing to simulate an adjusted surface in the clinical setting. They were then randomly assigned to two subgroups and underwent reglazing or polishing. All composite and ceramic specimens underwent profilometry after surface treatment and prior to the wear test, and the results were recorded quantitatively. Composite specimens were then subjected to 120,000 wear cycles against ceramic specimens in a chewing simulator, and the depth of wear was measured by a scanner. Data were statistically analyzed by repeated measures two-way analysis of variance (ANOVA) and one-way ANOVA (α = 0.05). Results: Comparison of the surface roughness of composite specimens before and after the wear test revealed significant differences in both glazed Suprinity (P = 0.048) and Vita Mark II (P = 0.026) ceramics groups. The change in surface roughness after the wear test (compared with baseline) was significant in glazed (P = 0.000) and polished (P = 0.013) Vita Mark II and polished Suprinity (P = 0.037) ceramics, but this change was not significant in other ceramics (P > 0.05). The depth of wear after the wear test was not significantly different among the ceramic and composite subgroups (P > 0.05). Conclusion: Assessment of depth of wear and surface roughness of composite specimens showed that the polishing kits of CAD-CAM ceramics can serve as a suitable alternative to reglazing.

Reliability of digital repeated-scan superimposition and single-scan techniques for wear volume loss assessment on flat surfaces.

OBJECTIVES: Evidence on the reliability of digital techniques for wear volume assessment using three-dimensional (3D) scan datasets is scarce. This study evaluated the reliability of a repeated-scan superimposition technique and two single-scan techniques in assessing wear volume loss on flat surfaces of 3D-printed resin specimens. METHODS: Cuboid-shaped (15×10×10 mm) resin specimens were 3D-printed (n = 14) and scanned before and after 200,000 cycles of masticatory simulation. For the repeated-scan superimposition technique, digital 3D models of specimens before and after masticatory simulation were superimposed, and the volume loss was determined. The first single-scan technique utilized a computer-aided design freeware program, while the second one employed a 3D-metrology software program. In the freeware program, the worn area of 3D objects was edited directly to obtain a flat surface. In the 3D-metrology software program, the worn area was deleted first and then filled to the flat surface. The volume differences before and after editing were calculated in each software program. Agreement between the three measurement techniques was determined through intraclass correlation coefficients (ICCs). One-way analysis of variance was performed to compare the wear volume loss assessed by the three techniques (α = 0.05). RESULTS: High inter-technique reliability was observed between the three assessment techniques (ICC = 0.998, p < .001). On pair-wise comparisons of two of the three techniques, all pairs showed high consistency (ICC ≥ 0.999, p < .001). No significant difference was found in the wear volume loss assessed using the three techniques (p = .996). CONCLUSIONS: Digital repeated-scan superimposition and two single-scan techniques demonstrated high reliability in assessing wear volume loss on flat surfaces. CLINICAL SIGNIFICANCE: The repeated-scan superimposition technique can be effectively utilized to assess wear volume loss of anatomically shaped specimens and flat surfaces. This study indicates that the single-scan techniques may serve as a suitable alternative to the repeated-scan superimposition technique when evaluating wear volume loss of flat surfaces.

Surface Micro-Hardness and Wear Resistance of a Self-Adhesive Flowable Composite in Comparison to Conventional Flowable Composites.

Objectives: The durability of composite restorations is directly affected by the mechanical properties of the composite. The aim of this study was to evaluate the hardness and wear resistance of self-adhesive flowable composite (SAF) in comparison with conventional flowable composites. Materials and Methods: In this in vitro study, 50 composite specimens were prepared in brass molds with 10mm ×10mm ×2mm and divided into five groups (n=10). Specimens included three conventional flowable composites (Grandio flow, Filtek flow and Admira fusion flow), one self-adhering flowable composite (SAF, Vertise flow) and a microhybrid composite (filtek z250). After polishing, the micro-hardness of the specimens was measured in a Vickers hardness device, and the specimens were then subjected to 5000, 10000, 20000, 40000, 80000 and 120000 wear cycles in a wear tester. One-way ANOVA/Games-Howell, Kruskal Wallis, and Friedman tests were used for statistical analysis. The significance level was set at P<0.05. Results: The surface micro-hardness of the SAF was significantly lower than that of the microhybrid composite (P=0.01). There was no significant difference between the surface hardness of the different tested flowable composites (P>0.05). Also, the wear resistance of the studied composites was not significantly different in various cycles (P>0.05). Conclusion: Based on our results, SAF would not be an ideal substitute for conventional flowable composites in high-stress areas.

Effect of staining layer on roughness after progressive wear of monolithic ceramics.

PURPOSE: The aim of this study was to evaluate staining layer behavior applied to high-translucency zirconia (YZHT), feldspathic ceramics (FD), and zirconia-reinforced lithium silicate (ZLS) surfaces against different antagonists. METHODS AND MATERIALS: Monolithic ceramic discs (n = 120) (ø 12 mm; thickness, 1.2 mm; ISO 6872) were obtained, 30 from YZHT and FD, and 60 from ZLS CAD/CAM blocks (staining layer applied before or after the crystallization procedure). The specimens were divided into 12 subgroups (n = 10) according to the antagonists: steatite, polymer-infiltrated ceramic, or zirconia. Mechanical cycling (1.5 × 104 cycles; 15 N; horizontal displacement, 6 mm; 1.7 Hz) and flexural strength tests (1 mm/min-1000 kg cell) were performed. The differences between final and initial roughnesses (Ra, Rz, and Rsm), the mass loss, and the flexural strength data were individually analyzed by two-way ANOVA and Tukey's test (α = 0.05). RESULTS: The roughnesses of all ceramics did not present a statistically significant difference before wear simulation: Ra (p = 0.3348), Rz (p = 0.5590), and Rsm (p = 0.5330). After the wear simulation, the Ra parameter was not affected by an interaction between ceramic and antagonist (p = 0.595). The Rz and Rsm parameters were affected only by the antagonist pistons (both, p = 0.000). The ceramics used in this study showed statistically significant differences in mass loss after the wear test (p < 0.0001). The additional firing (2 steps) of the ZLS2 led to a higher lost mass quantity. CONCLUSION: All ceramics presented similar initial roughnesses and similar roughnesses after the wear simulation. The zirconia antagonist showed better performance against ceramics with high crystalline content. CLINICAL SIGNIFICANCE: It is clear that restorative materials must be carefully selected by dental practitioners according to indications, properties, and antagonists. The steatite antagonist, that is, an enamel analog, showed better performance against vitreous ceramics, while the zirconia antagonist showed better performance against ceramics with high crystalline content. Wear affects the surface roughnesses of the ceramics. Additional firing for the staining of the zirconia-reinforced lithium silicate ceramic led to a greater loss of mass.

Evaluation of a novel restorative protocol to treat non-carious cervical lesion associated with gingival recession: a 2-year follow-up randomized clinical trial.

OBJECTIVE: To compare 2 different resin composites and 2 adhesive systems used in a new restorative protocol (partial restoration) to treat non-carious cervical lesions associated with gingival recession type 1 (RT1). MATERIAL AND METHODS: Eighty combined defects (CDs) were treated with a partial restoration and periodontal plastic surgery for root coverage. The CDs were randomly assigned to one of the following groups: NP + TE (n = 20), nanofilled composite and 2-step total-etch adhesive system; NP + UA (n = 20), nanofilled composite and universal adhesive system; MH + TE (n = 20), microhybrid composite and 2-step total-etch adhesive; MH + UA (n = 20), microhybrid composite and universal adhesive. Restorations were assessed using the United States Public Health Service (USPHS) criteria at 1 week (baseline) and 6, 12, and 24 months. Survival rate, periodontal parameters, dentin hypersensitivity (DH), and aesthetics were also evaluated. RESULTS: After 24 months, only the MH + TE group did not lose any restoration, with no significant differences between groups. For surface roughness parameter, MH presented 83.3% of the restorations scoring Bravo, whereas NP presented 48.5% of the restorations scoring Bravo. All groups presented restorations with marginal discoloration. All periodontal parameters behaved similarly, regardless of the restorative material. All groups presented significant reductions of dentin hypersensitivity and improved aesthetic perceptions (p < 0.05). CONCLUSION: Both resin composites and adhesives tested can be combined for partial restorations to treat CDs. CLINICAL RELEVANCE: This new restorative-surgical protocol to treat CDs presents satisfactory outcomes. The partial restorations can be successfully executed with both combinations of adhesives and resin composites evaluated in this investigation. TRN : ClinicalTrial.gov: NCT03215615; registration date July 12, 2017.

Análise da resistência ao desgaste de uma resina temporária para impressão 3D frente a diferentes antagonistas / Analysis of the wear resistance of a temporary resin for 3D printing against different antagonists

A impressão 3D surge como uma nova alternativa para confecção de próteses provisórias através do uso de resinas temporárias, visando otimizar e simplificar a técnica de confecção e sua aplicação. Este trabalho analisou o comportamento de uma resina provisória de impressão 3D sob simulação de desgaste frente a três diferentes antagonistas. Para isso, foram confeccionados 60 discos de resina provisória de impressão 3D (Resilab Temp) nas dimensões 12 x 2 mm. Os modelos 3D foram previamente desenhados no software Rhinoceros (Robert McNeel & Associates, Seattle, WA, EUA); versão 5, e processados no software de uma impressora 3D, produzidos utilizando impressora com processamento digital de luz (DLP). Metade das amostras recebeu uma camada de glaze na superfície da resina. Os espécimes foram submetidos à simulação de desgaste em cicladora mecânica com sliding (Byocicle V2, Biopdi, São Carlos, SP). Foram utilizados como antagonistas: esteatita, resina de impressão 3D e resina acrílica termicamente ativada, adaptados a mandris personalizados. O protocolo utilizado para a simulação do desgaste foi de 30 N ‭̸1,7 Hz ‭̸2x103 ciclos ‭̸37ºC, imersos em água. Realizou-se os testes de rugosidade, análise de superfície com microscopia eletrônica de varredura (MEV) e análise digital de varredura única de perda de volume de desgaste. O desgaste dos antagonistas foi avaliado através de estereomicroscópio óptico. A análise estatística foi realizada aplicando-se o teste de ANOVA 2 fatores para todos os grupos analisados. Na rugosidade, foram observadas diferenças estatisticamente significantes entre todos os grupos (p<0,05), exceto Rz do grupo com glaze, em que todas as variáveis foram iguais (p=0,377). Para perda de volume em desgaste, observou-se diferenças estatisticamente significantes entre os antagonistas (p=0,015) e para o tratamento com glaze (p=0,001). No desgaste dos antagonistas, observou-se diferenças estatisticamente significantes entre eles (p=0,001) e o tratamento com glaze (p=0,001). A resina em estudo apresenta resistência ao desgaste adequada para uso a curto prazo, sendo essa resistência influenciada pelo material antagonista. A aplicação da camada de glaze sobre a resina diminui a rugosidade superficial média do material e melhora a resistência ao desgaste (AU)

3D printing emerges as a new alternative for making provisional prostheses through the use of temporary resins, aiming to optimize and simplify the manufacturing technique and its application. This work analyzed the behavior of a provisional 3D printing resin under wear simulation against three different antagonists. For this, 60 discs of temporary 3D printing resin (Resilab Temp) in dimensions 12 x 2 mm were made. The 3D models were previously designed in Rhinoceros software (Robert McNeel & Associates, Seattle, WA, USA); version 5, and processed in the software of a 3D printer, produced using a printer with digital light processing (DLP). Half of the samples received a glaze layer on the resin surface. The specimens were submitted to wear simulation in a mechanical cycler with sliding (Byocicle V2, Biopdi, São Carlos, SP). The following antagonists were used: steatite, 3D printing resin and thermally activated acrylic resin, adapted to customized mandrels. The protocol used for the simulation of wear was 30 N ‭̸1.7 Hz ‭̸2x103 cycles ‭̸37ºC, immersed in water. Roughness tests, surface analysis with scanning electron microscopy (SEM) and single-scan digital analysis of wear volume loss were performed. The wear of the antagonists was evaluated using an optical stereomicroscope. Statistical analysis was performed by applying the 2-way ANOVA test for all analyzed groups. In terms of roughness, statistically significant differences were observed between all groups (p<0.05), except for the Rz group with glaze, in which all variables were equal (p=0.377). For volume loss in grinding, statistically significant differences were observed between antagonists (p=0.015) and for treatment with glaze (p=0.001). In the wear of the antagonists, statistically significant differences were observed between them (p=0.001) and the treatment with glaze (p=0.001). The resin under study has adequate wear resistance for short-term use, and this resistance is influenced by the antagonist material. The application of the glaze layer over the resin decreases the average surface roughness of the material and improves wear resistance. (AU)

Wear of dental ceramics / Desgaste das cerâmicas odontológicas

Com base no desenvolvimento da odontologia adesiva, restaurações minimamente invasivas em cerâmica são utilizadas como alternativas para restaurar um dente. As cerâmicas odontológicas são amplamente aplicadas na área odontológica principalmente devido à sua estética e resistência mecânica. Uma das propriedades da cerâmica a ser bem conhecida antes de seu uso, é a resistência ao desgaste que deve ser compatível com o comportamento de desgaste do antagonista para evitar desempenhos indesejados. Portanto, vários métodos têm sido realizados para avaliar o comportamento do desgaste dos materiais cerâmicos considerando diferentes condições presentes no complexo meio oral. Este estudo teve como objetivo compilar os métodos utilizados para investigar o desgaste das cerâmicas odontológicas e descrever os mecanismos de desgaste envolvidos nos mesmos. A obtenção e análise de dados também é abordada para discutir os resultados obtidos a partir de diferentes métodos, bem como a análise clínica do desgaste e perspectivas futuras sobre esse tema. Em conclusão, muitas metodologias estão disponíveis para medir o desgaste cerâmico. Portanto, os métodos devem ser selecionados com base na relevência clínica de cada estudo e devem seguir parâmetros previamente relatados para padronização, permitindo a comparação da literatura (AU)

Based on the development of adhesive dentistry, minimally invasive restorations in ceramics are used as alternatives to restore a tooth. Dental ceramics are largely applied in the dentistry field mainly due to their esthetic and mechanical strength. One of the ceramic properties to be well known before its use is the wear resistance that should be compatible with the antagonist wear behavior to avoid unwanted performance. Therefore, several methods have been performed to assess the ceramic materials wear behavior considering different conditions present in the complex oral medium. This study aimed to compile the methods used to investigate dental ceramics wear and to describe the wear mechanisms involved on them. Obtaining and analyzing data is also addressed to discuss the results obtained from different methods, as well as the clinical analysis of wear and future perspectives on this topic. In conclusion, many methodologies are available to measure the ceramic wear. Therefore, the methods must be selected based on the clinical significance of each study and should follow previously reported parameters for standardization, allowing literature comparison. (AU)

12-months Clinical Evaluation of Fiber Reinforced Bulk Fill Resin Composite versus Incremental Packing of Nanohybrid Resin Composite in Restoration of Deep Proximal Lesions of Permanent Molars: A Randomized Controlled Trial.

Objective: The present clinical trial was conducted to evaluate the clinical performance of the biomimetic, bilayered structure utilizing a fiber reinforced bulk fill resin composite with a nanohybrid capping layer, compared to incremental packing of nanohybrid resin composite, in deep proximal cavities in permanent molars. Material and methods: A total of 36 deep proximal cavities in vital molars were restored either with a bilayered structure of fiber reinforced composite resin as a dentine substitute and a capping layer of nanohybrid composite resin (n=18) or conventional, nanohybrid composite resin incrementation (n=18). The restorations were assessed over a period of 12 months using the modified USPHS criteria. The criteria evaluated were: fracture and retention, marginal integrity, marginal discoloration, anatomic form, proximal contact, surface texture, radiographic evaluation, postoperative sensitivity and secondary caries. Results: There was no statistically or clinically significant difference between fiber-reinforced resin composite and conventional incremental resin composite. There was no risk for failure regarding all the evaluated modified USPHS criteria for both materials after 12 months (RR= 1(95% CI 0.0209 to 47.8503; P =1.0000)). Conclusion: The biomimetic approach utilizing a fiber reinforced resin composite dentine substitute showed a comparable clinical performance to nanohybrid resin composite incrementation. Bulk fill fiber reinforced resin composite is an efficient alternative in restoration of deep proximal cavities in posterior teeth. Further long-term studies are necessary to confirm these results.

Clinical follow-up at 18 months of two bulk fill occlusal composite resins: a double-blind randomized clinical study / Seguimiento clínico a 18 meses de dos resinas compuestas oclusales bulk fill: estudio clínico aleatorio doble ciego

Objetive: To compare the clinical behavior of two types of Bulk Fill composite resins and a nanohybrid resin at 18 months in occlusal restorations. Material and Methods: Three occlusal restorations were performed in each one of the 55 participants. They were randomly distributed into three groups, TN: Tetric-N-Ceram Bulk-Fill, FK: Filtek Bulk-Fill, and Z350: Filtek Z350XT. Adhesive techniques and restorative procedures were performed according to the manufacturer's instructions for each restorative material used. In TN and FK an increment of 4mm was applied, and in Z350 increments of ≤2mm depth were applied. Two calibrated operators evaluated the restorations at baseline and at 18 months using the FDI World Dental Federations system (1: excellent, 2: good, 3: satisfactory, 4: unsatisfactory, 5: poor) for clinical marginal staining (MS) properties, fracture-retention (FR), superficial texture (ST), marginal integrity (MI), postoperative sensitivity (PS) and caries (C). Kruskal-Wallis and Wilcoxon were used to compare the 3 groups at 18 months (5% significance). Results: 38 patients with a total of 114 restorations were assessed, being evaluated with excellent clinical behavior; MI, 78.9% in Z350, 89.51% in TN and 81.6% in FK; ST 73.5% in Z350, 86.8% in TN, and 84.2% in FK; MS 84.2% in Z350, 84.2% in TN, and 91.2% in FK; PS 100% in Z350 and 97.3% in TN and FK; in C and FR, 100% in the 3 groups. There were no significant differences between the three groups (p>0.05). Conclusion: The three resins studied presented a good clinical performance at 18 months without showing significant differences in the clinical properties evaluated.

Objetivo: Comparar el comportamiento clínico a 18 meses en restauraciones oclusales entre dos tipos de resinas compuestas Bulk Fill y una resina nanohíbrida. Material y Métodos: En 55 participantes se realizaron 3 restauraciones oclusales en cada paciente, distribuidas aleatoriamente en 3 grupos, TN: Tetric-N-Ceram Bulk-Fill, FK: Filtek Bulk-Fill y Z350: Filtek Z350XT. Las técnicas adhesivas y procedimientos restauradores fueron realizados según las instrucciones de los fabricantes de cada material restaurador utilizado. En TN y FK se aplicó un incremento de 4mm y en Z350 se aplicó incrementos ≤ 2 mm de profundidad. Dos operadores calibrados evaluaron las restauraciones al baseline y a los 18 meses mediante el sistema FDI World Dental Federations (1: excelente, 2: aceptable, 3: suficiente, 4: insatisfactorio, 5: inaceptable) en las propiedades clínicas de tinción marginal (TM), fractura-retención (FR), textura superficial (TS), integridad marginal (IM), sensibilidad postoperatoria (SP) y caries (C). Se utilizó Kruskal-Wallis y Wilcoxon para la comparación de los 3 grupos a 18 meses (significancia de 5%). Resultados: Se controlaron 38 pacientes con un total de 114 restauraciones, siendo evaluados con comportamiento clínico excelente; IM, 78.9% en Z350, 89.51% en TN y 81.6% en FK; TS 73.5%, en Z350, 86.8% en TN y 84.2% en FK; TM, 84.2% en Z350, 84.2% en TN y 91.2% en FK; SP 100% en Z350 y 97,3% en TN y FK; en C y FR 100% en los 3 grupos. No hubo diferencias significativas entre los 3 grupos (p>0,05). Conclusión: Las 3 resinas estudiadas presentaron un buen desempeño clínico a 18 meses sin mostrar diferencias significativas en las propiedades clínicas evaluadas.

A comparative evaluation of wear resistance of three types of artificial acrylic teeth after removing the glaze layer.

Background: The posterior denture teeth wear faster than the anterior teeth, which can result in occlusal interferences, loss of vertical dimension of occlusion, greater stress accumulation in the anterior region, and higher ridge resorption. This study aimed to compare the wear resistance of three types of artificial acrylic teeth before and after removing the glaze layer. Materials and Methods: This in vitro study compared three types of artificial acrylic teeth, namely, Finex (F), SR Orthotyp DCL (S), and Vita Physiodents (V) in six groups (n = 10). Half of the artificial teeth of each brand underwent 0.5-mm buccal reduction to remove the glaze layer (groups FC, SC, and VC). The teeth were thermocycled and placed in a chewing simulator. The teeth with and without the glaze layer were weighed before and after the wear test. The data were analyzed using ANCOVA (the level of significance was 0.05). Results: The weight reduction (indicative of wear) was 0.03 ± 0.02 and 0.12 ± 0.03 mg in Groups S and SC, 0.03 ± 0.02 and 0.25 ± 0.04 mg in Groups V and VC, and 0.11 ± 0.15 and 0.28 ± 0.1 mg in groups F and FC, respectively. Removing the glaze layer (P < 0.01), type and brand of acrylic tooth (P < 0.01), and the baseline weight of artificial teeth (P < 0.01) had significant effects on wear resistance of artificial teeth. Conclusion: The wear of artificial teeth was greater after removing the glaze layer, and the magnitude of wear was also significantly different among the three brands. The group FC showed maximum wear while the groups S and V showed minimum wear.

Wear Resistance and Biocompatibility of Co-Cr Dental Alloys Fabricated with CAST and SLM Techniques.

Cobalt-chromium (Co-Cr) alloys have been widely used as dental-restoration materials for many years. This study sought to investigate whether selective laser melting (SLM) is a more appropriate process than traditional casting (CAST) for fabricating dental Co-Cr alloys. Metallurgical microscopy, X-ray photoelectron spectroscopy (XPS), Vickers hardness and nanoindentation tests, and friction and wear tests were used to evaluate the microstructure, surface compositions, mechanical properties, and wear resistance, respectively. Additionally, the biocompatibilities and cell adhesion of the alloys were evaluated with L-929 fibroblasts via CCK-8 assay, Live/Dead staining, flow cytometric analysis, scanning electron microscopy (SEM) observation and real-time PCR (RT-PCR) assay. The XPS results showed that the two alloys were all mainly comprised of Co, Cr, and O. The hardness in the CAST group equaled 7.15 ± 0.48 GPa, while in the SLM group, it equaled 9.06 ± 0.49 GPa. The friction coefficient of SLM alloys remained at approximately 0.46, but the CAST specimens fluctuated significantly. SLM alloys exhibited shallower wear scars and less wear debris compared with CAST alloys, simultaneously. Additionally, there were higher survival and expression of cell-adhesion-related genes on SLM alloys of L-929 cells, which meant that the deleterious effect on L-929 cells was significantly reduced compared with that for the CAST alloys. Overall, the wear resistances and biocompatibilities of the Co-Cr dental alloys were dramatically affected by the fabrication technique. The SLM technique is advantageous over the CAST technique for fabricating Co-Cr dental alloys.

A digital method for wear volume loss analysis using a single-scan three-dimensional dataset.

A straightforward digital method of evaluating wear volume loss is described. This method allows the measurement of the wear by analyzing only the three-dimensional scan dataset of the worn specimen without needing a separate baseline scan. Compared to the conventional method, involving superimposition of the two datasets scanned before and after the wear test, this method can reduce labor and accuracy errors caused by repeated scans and superimposition procedures. Further, this analysis can be conducted using free computer-aided design software, which makes it more efficient for the analysis of wear volume loss of restorative materials.

Registro cefalométrico de la dimensión vertical oclusiva en pacientes bruxópatas con trastornos temporomandibulares / Cephalometric register of the occlussive vertical dimension in bruxist patients with temporomandibular disorders

RESUMEN Fundamento: el registro de la dimensión vertical oclusiva se complejiza en los pacientes con bruxismo en los que se impone restablecer la misma. Objetivo: determinar la utilidad clínica del registro cefalométrico de la dimensión vertical oclusiva en pacientes con bruxismo y trastornos temporomandibulares tributarios de tratamiento rehabilitador integral. Métodos: se desarrolló un estudio cuasi experimental antes y después con grupo control en la consulta del tercer nivel de atención estomatológica de Oclusión Dentaria y Articulación Temporomandibular en la Clínica Estomatológica Docente Ismael Clark y Mascaró, de septiembre de 2015 a mayo de 2018 en la provincia Camagüey. El universo de estudio lo conformaron los 73 pacientes remitidos con diagnóstico de bruxismo, presencia de facetas de desgastes, pérdida de la dimensión vertical oclusiva, signos y síntomas de trastornos temporomandibulares, desdentados parciales, mayores de 19 años, sin distinción en cuanto al sexo y desprovistos de procesos periodontales activos. La muestra no probabilística finita y heterogénea quedó representada por los primeros 50 pacientes asistidos que integraron en la misma proporción el grupo estudio y el grupo control. La investigación se realizó en tres momentos: organización, intervención y evaluación. Resultados: predominaron los pacientes con desgaste dentario tipo E 2, resaltó la dimensión vertical disminuida y la conservación de la dimensión vertical oclusiva a los seis meses de concluir el tratamiento rehabilitador integral. Conclusiones: útil se consideró el registro cefalométrico de la dimensión vertical oclusiva para pacientes con bruxismo y trastornos temporomandibulares.

ABSTRACT Background: the register of the occlusive vertical dimension is a complex issue in patients with bruxism who need to restore it. Objective: to determine the clinical use of the cephalometric register of the occlussive vertical dimension in patients with bruxism and temporomandibular disorders tributary of integral rehabilitator treatment. Methods: a quasi-experimental study was performed before and after with a control group in the third level consultation of dentistry assistance of Dental Occlusion and Temporomandibular Joint at Ismael Clark y Mascaró teaching dental clinic from September 2015 to May 2018 in Camagüey province. The universe of study consisted of 73 patients referred with a diagnosis of bruxism, presence of wear facets, loss of the occlusive vertical dimension, signs and symptoms of temporomandibular disorders, partial edentulous, older than 19 years old, regardless of sex and devoid of active periodontal processes. The finite and heterogenous non-probabilistic sample was represented by the first 50 assisted patients who made up the study group and the control one in the same proportion. The research was carried out in three moments: organization, intervention and assessment. Results: patients with wear facets type E 2 predominated, the diminished vertical dimension and the conservation of the occlusive vertical dimension and six months later of the integral rehabilitator treatment stand out. Conclusions: the cephalometric register of the occlussive vertical dimension for patients with bruxism and temporomandibular disorders was considered useful.

Lingual retainer materials: Comparative evaluation of wear resistance of flowable nanocomposites and universal composite: An in vitro study.

BACKGROUND: A bonded fixed retainer is used to stabilize the alignment of the teeth. Different composites have been introduced for this purpose. This study aimed to investigate the wear resistance of flowable nanocomposite in comparison with microhybrid composite in an in vitro situation. MATERIALS AND METHODS: In this in vitro study, 46 disk-shaped specimens were divided into two groups: Filtek Ultimate flowable composite and Z250 microhybrid composite. The samples were prepared in 8 mm diameter and 3 mm thickness in an aluminum mold and light cured. They were polished with 600 grit sandpaper to achieve a smooth surface. Two-body wear test was accomplished by the pin-on-disk device (under 15 N, 20 rpm for 1 h). Analyzing the weight and thickness of specimens before and after the assay demonstrates the wear resistance. Data were analyzed using the t-test. P ≤ 0.05 was considered statistically significant. RESULTS: The Filtek Ultimate flowable composite shows no significant difference compared to Z250 microhybrid composite in thickness (P = 0.701) and weight (P = 0.939) of specimens. CONCLUSION: Due to wear resistance of both materials, flowable composite can be recommended as an alternative material for bonded fixed retainers.

Wear of 3D printed and CAD/CAM milled interim resin materials after chewing simulation.

PURPOSE: The purpose of this in vitro study was to investigate the wear resistance and surface roughness of three interim resin materials, which were subjected to chewing simulation. MATERIALS AND METHODS: Three interim resin materials were evaluated: (1) three-dimensional (3D) printed (digital light processing type), (2) computer-aided design and computer-aided manufacturing (CAD/CAM) milled, and (3) conventional polymethyl methacrylate interim resin materials. A total of 48 substrate specimens were prepared. The specimens were divided into two subgroups and subjected to 30,000 or 60,000 cycles of chewing simulation (n = 8). The wear volume loss and surface roughness of the materials were compared. Statistical analysis was performed using one-way analysis of variance and Tukey's post-hoc test (α=.05). RESULTS: The mean ± standard deviation values of wear volume loss (in mm3) against the metal abrader after 60,000 cycles were 0.10 ± 0.01 for the 3D printed resin, 0.21 ± 0.02 for the milled resin, and 0.44 ± 0.01 for the conventional resin. Statistically significant differences among volume losses were found in the order of 3D printed, milled, and conventional interim materials (P<.001). After 60,000 cycles of simulated chewing, the mean surface roughness (Ra; µm) values for 3D printed, milled, and conventional materials were 0.59 ± 0.06, 1.27 ± 0.49, and 1.64 ± 0.44, respectively. A significant difference was found in the Ra value between 3D printed and conventional materials (P=.01). CONCLUSION: The interim restorative materials for additive and subtractive manufacturing digital technologies exhibited less wear volume loss than the conventional interim resin. The 3D printed interim restorative material showed a smoother surface than the conventional interim material after simulated chewing.

Polyoxymethylene as Material for Removable Partial Dentures-A Literature Review and Illustrating Case Report.

Compared to thermoplastic manufacturing techniques, computer-aided design (CAD) and computer-aided manufacturing (CAM) technologies make it easier to process modern restorative and prosthetic materials with improved material properties. In dentistry, tooth-colored alternatives to metal-based frameworks for application in removable dental prostheses (RDP) emerged. With regard to this aspect, the current article provides an overview of the specific material properties of polyoxymethylene (POM). Furthermore, it reviews scientific literature indexed in PubMed and Web of Science that focuses on RDPs fabricated from POM within the last 10 years. Finally, a prosthetic rehabilitation of a patient with a RDP fabricated from POM is illustrated and observations during a follow-up over 10 months are described. Scientific data and clinical observations indicate that polyoxymethylene is a promising material that bridges gaps in dental therapeutic options. While survival time may be limited due to wear, POM might be a favorable option for application in semi-permanent restorations.

Análise do comportamento da resina composta frente aos diferentes mecanismos de desgaste: uma revisão de literatura / Analysis of the composite resin behavior against different wear mechanisms: a literature review

Introdução:Com o avanço da odontologia e dos materiais dentários, as resinas compostas têm sido amplamente utilizadas nas diversas variedades de restaurações, sejam elas diretas ou indiretas, devido às suas propriedades estéticas. No entanto, existem fatores significati-vos que contribuem para o fracasso das resinas compostas ao longo do tempo, dentre eles, o desgaste.Objetivo:Este trabalho consiste em uma revisão da literatura que objetiva discor-rer acerca dos principais mecanismos de desgaste da resina composta e suas consequências.Metodologia:O presente estudo trata-se de uma revisão da literatura narrativa realizada através de um levantamento bibliográfico de 53 artigos científicos, publicados entre 2010 e 2021. Tendo como fonte as seguintes bases de dados eletrônicos nacionais e internacionais: PubMed, SciELO e Google Acadêmico.Resultados: Perda de brilho, manchamento, infil-tração marginal, cárie recorrente e desgaste (desgaste adesivo, desgaste abrasivo, desgaste por fadiga e desgaste corrosivo) são os principais fatores que contribuem para o fracasso das resinas compostas ao longo do tempo. Conclusão:Os mecanismos de desgaste, sejam de natureza mecânica (física) e/ou química: desgaste adesivo, desgaste por atrito, desgaste abrasivo, desgaste por fadiga e desgaste corrosivo, assim como procedimentos de acaba-mento e polimento e hábitos parafuncionais implicam na perda gradual da resina composta e, consequentemente, geram acúmulo de biofilme, comprometimento gradual da função e estética, redução da dureza e resistência à flexão, que juntos resultam na diminuição da durabilidade clínica das restaurações e geram a necessidade de reparo e/ou substituição da restauração ao longo do tempo.

Introduction: With the advancement of dentistry and dental materials, composite resins have been widely used in different varieties of restorations, whether direct or indirect, due to their aesthetic properties. However, some calculated factors contribute to the failure of composite resins over time, including wear. Objective: This literature review aims to discuss the main wear factors of composite resin and its consequences. Methodology: This is a review of narrative literature carried out through a bibliographic survey of 53 scien-tific articles published between 2010 and 2021. The following national and international electronic databases were used: PubMed, SciELO, and Academic Google. Results: Loss of gloss, staining, marginal infiltration, recurrent caries, and wear (adhesive wear, abrasive wear, fatigue wear, and corrosive wear) are the main factors that contribute to the failure of composite resins over time. Conclusion: The wear mechanisms are of a physical and/or chemical nature: adhesive wear, friction wear, abrasive wear, fatigue wear, and corrosive wear, as well as finishing and polishing procedures, and parafunctional habits imply the gradual loss of the composite resin and, consequently, generate biofilm accumulation, gra-dual impairment of function and esthetics, reduction in hardness, and resistance to flexion, which together result in a decrease in the clinical durability of the restorations, generating the need for restoration and/or replacement over time.Keywords: Composite Resin. Wear. Dental Restoration Wear.

[Evaluation of wear property of Giomer and universal composite in vivo].

OBJECTIVE: To observe the wear performance of Giomer and universal composite for posterior restorations by 3D laser scan method, in order to guide the material selection in clinic. METHODS: In this study, 48 patients (108 teeth) were selected according to the inclusion and exclusion criteria. All the patients in need of a minimum of 2 Class Ⅰ and/or Class Ⅱ restorations were invited to join the study. The teeth were restored with Giomer (Beautifil Ⅱ, BF) and universal composite (Filtek Z350, Z350) randomly. The restorations were evaluated at baseline and after 6-, 18-, 48-month using the modified United States Public Health Service (USPHS) criteria for clinical performance. The in vivo images and gypsum replicas were taken at each recall. A 3D-laser scanner and Geomagic Studio 12 were used to analyze the wear depth quantitatively. Statistical analysis was performed with SPSS 20.0. RESULTS: After 4 years, 89.6% patients were recalled. The survival rate of both materials was 95.8% (Kaplan-Meier survival analysis). Seven restorations of the two materials failed due to loss of restoration, bulk fracture, secondary caries and pulp necrosis. The wear patterns of restorations were divided into 2 classes. Pattern Ⅰ: occlusal contact areas showed the deepest and fastest wear depth; pattern Ⅱ: the wear depth was slow and uniform. Both materials showed a rapid wear in the first 6 months. Then the wear rate was decreased. The occlusal wear depth after 4 years were (58±22) µm and (54±16) µm for BF group and Z350 group respectively, which were in accordance with the American Dental Association (ADA) guidelines (wear depth for 3 years < 100 µm). No significant differences (P>0.05) were observed between the two groups. Regarding the restorations with wear pattern Ⅰ, the wear depth of BF group was higher than Z350 group at 6- and 48-month (P < 0.05), while there was no significant difference between restorations with wear pattern Ⅱ (P>0.05). CONCLUSION: Within the limitation of the study, after 4 years, the survival rate and wear resistance of Giomer met ADA guidelines for tooth-colored restorative materials for posterior teeth. When the two materials were applied in occlusal contact areas, wear resistance of Giomer was slightly lower than universal composite resin. No significant difference was found when they were applied in none of the occlusal contact areas.