Antimicrobial activity of cleanser tablets against S. mutans and C. Albicans on different denture base materials.

BACKGROUND: In this study, the antimicrobial activity of three different cleanser tablets on S. mutans and C. albicans adhesion to PMMA, polyamide and 3D printed resin was investigated. METHODS: 40 samples were prepared for PMMA (SR Triplex Hot), polyamide (Deflex) and 3D printed resin (PowerResins Denture) materials and divided into four subgroups for cleansers (Aktident™, Protefix™, Corega™ tablets and distilled water) (n = 5). After the surface preparations were completed, the samples were immersed separately in tubes containing the prepared microorganism suspension and incubated at 37˚C for 24 h. After the incubation, the samples were kept in the cleanser solutions. The samples were then transferred to sterile saline tubes. All the tubes were vortexed and 10 µl was taken from each of them. Sheep blood agar was inoculated for colony counting. The inoculated plates were incubated for 48 h for S. mutans and 24 h for C. albicans. After incubation, colonies observed on all plates were counted. Statistical analyses were done with three-way ANOVA and Tukey's multiple comparison test. RESULTS: Polyamide material registered the highest colony count of S. mutans, whereas PMMA registered the lowest. Significant differences in S. mutans adherence (p = 0.002) were found between the three denture base materials, but no such difference in C. albicans adherence (p = 0.221) was identified between the specimens. All three cleanser tablets eliminated 98% of S. mutans from all the material groups. In all these groups, as well, the antifungal effect of Corega™ on C. albicans was significantly higher than those of the other two cleanser tablets. CONCLUSIONS: According to the study's results, it may be better to pay attention to surface smoothness when using polyamide material to prevent microorganism retention. Cleanser tablets are clinically recommended to help maintain hygiene in removable denture users, especially Corega tablets that are more effective on C. albicans.

Comparison of three-dimensional printed resin crowns and preformed stainless steel crowns for primary molar restorations: a randomized controlled trial.

The importance of aesthetics in children has increased over time. Therefore, this multicenter randomized clinical trial aimed to analyze and compare three-dimensional (3D)-printed resin crowns (RCs) as a potential alternative to stainless-steel crowns (SSCs) for restoring primary molars with extensive carious lesions. According to the null hypothesis, no statistically significant difference was observed in restoration failure between RC and SSC groups. A total of 56 primary molars after pulp treatment at two dental hospitals were included. After pulp treatment, the teeth were randomly divided into two groups: SSCs (n = 28) and RCs (n = 28). At 1 week and 3, 6 and 12 months, the Quigley-Hein plaque index (QHI), gingival index (GI), occlusal wear, and survival rate were assessed by examination, radiography and alginate impressions. No significant difference in QHI was observed between the two groups. However, the GI at 12 months and occlusal wear in the RC group were significantly higher than those in the SSC group (p < 0.05). The survival rates were 100% in the SSC group and 82.1% in the RC group (p = 0.047). Cracks and discoloration were also observed in the RCs. Within the limitations of this study, 3D-printed RCs are aesthetically superior to SSCs and clinically easy to repair. However, if clinical effectiveness and safety are improved, RCs could potentially become a viable aesthetic alternative in the future.

Silver vanadate nanomaterial incorporated into heat-cured resin and coating in printed resin - Antimicrobial activity in two multi-species biofilms and wettability.

OBJECTIVES: To incorporate the nanostructured silver vanadate decorated with silver nanoparticles (AgVO3) into denture base materials: heat-cured (HC) and 3D printed (3DP) resins, at concentrations of 2.5 %, 5 %, and 10 %; and to evaluate the antimicrobial activity in two multi-species biofilm: (1) Candida albicans, Candida glabrata, and Streptococcus mutans, (2) Candida albicans, Pseudomonas aeruginosa, and Staphylococcus aureus, and the wettability. METHODS: The AgVO3 was added to the HC powder, and printed samples were coated with 3DP with AgVO3 incorporated. After biofilm formation, the antimicrobial activity was evaluated by colony forming units per milliliter (CFU/mL), metabolic activity, and epifluorescence microscopy. Wettability was assessed by the contact angles with water and artificial saliva. RESULTS: In biofilm (1), HC-5 % and HC-10 % showed activity against S. mutans, HC-10 % against C. glabrata, and HC-10 % and 3DP-10 % had higher CFU/mL of C. albicans. 3DP-5 % had lower metabolic activity than the 3DP control. In biofilm (2), HC-10 % reduced S. aureus and P. aeruginosa, and HC-5 %, 3DP-2.5 %, and 3DP-5 % reduced S. aureus. 3DP incorporated with AgVO3, HC-5 %, and HC-10 % reduced biofilm (2) metabolic activity. 3DP-5 % and 3DP-10 % increased wettability with water and saliva. CONCLUSION: HC-10 % was effective against C. glabrata, S. mutans, P. aeruginosa, and S. aureus, and HC-5 % reduced S. mutans and S. aureus. For 3DP, 2.5 % and 5 % reduced S. aureus. The incorporation of AgVO3 into both resins reduced the metabolic activity of biofilms but had no effect on C. albicans. The wettability of the 3DP with water and saliva increased with the addition of AgVO3. CLINICAL SIGNIFICANCE: The incorporation of silver vanadate into the denture base materials provides antimicrobial efficacy and can prevent the aggravation of oral and systemic diseases. The incorporation of nanomaterials into printed resins is challenging and the coating is an alternative to obtain the inner denture base with antimicrobial effect.

3D printed denture base material: The effect of incorporating TiO2 nanoparticles and artificial ageing on the physical and mechanical properties.

OBJECTIVES: To evaluate the physical and mechanical properties of three-dimensional (3D) printed denture base resin incorporating TiO2 nanoparticles (NPs), subjected to a physical ageing process. METHODS: Acrylic denture base samples were prepared by a Stereolithography (SLA) 3D printing technique reinforced with different concentrations (0.10, 0.25, 0.50, and 0.75) of silanated TiO2 NPs. The resulting nanocomposite materials were characterized in terms of degree of conversion (DC), and sorption/solubility flexural strength, impact strength, Vickers hardness and Martens hardness and compared with unmodified resin and conventional heat-cured (HC) material. The nanocomposites were reassessed after subjecting them to ageing in artificial saliva. A fractured surface was studied under a scanning electron microscope (SEM). RESULTS: The addition of TiO2 NPs into 3D-printed resin significantly improved flexural strength/modulus, impact strength, Vickers hardness, and DC, while also slightly enhancing Martens hardness compared to the unmodified resin. Sorption values did not show any improvements, while solubility was reduced significantly. The addition of 0.10 wt% NPs provided the highest performance amongst the other concentrations, and 0.75 wt% NPs showed the lowest. Although ageing degraded the materials' performance to a certain extent, the trends remained the same. SEM images showed a homogenous distribution of the NPs at lower concentrations (0.10 and 0.25 wt%) but revealed agglomeration of the NPs with the higher concentrations (0.50 and 0.75 wt%). SIGNIFICANCE: The outcomes of this study suggested that the incorporation of TiO2 NPs (0.10 wt%) into 3D-printed denture base material showed superior performance compared to the unmodified 3D-printed resin even after ageing in artificial saliva. The nanocomposite has the potential to extend service life of denture bases in future clinical use.

Evaluation of Prosthetic Outcomes and Patient Satisfaction With 3D-Printed Implant-Supported Fixed Prosthesis.

OBJECTIVES: The objectives of this study were to quantify the number and type of prosthetic complications associated with 3D-printed implant-supported fixed prostheses (3DISFP) and to evaluate patient satisfaction and oral health-related quality of life over a four-month period. METHODS:  Fifteen edentulous patients who underwent implant therapy were included in the study. Each patient received a 3D-printed prosthesis using OnX dental resin. Prosthetic complications were documented, and data from the 14-item Oral Health Impact Profile (OHIP) questionnaire were collected at two time points: at enrollment and during a four-month recall. RESULTS: During the four-month evaluation period, a total of nine complications were recorded, with three classified as catastrophic failures. Statistical analysis revealed statistically significant differences in OHIP scores between the preoperative and postoperative assessments (p<0.001). CONCLUSION: Within the limitations of this study, it can be concluded that utilizing 3D-printed prostheses with OnX resin represents a viable alternative for long-term implant-supported temporaries. The patients experienced a significant improvement in their oral health-related quality of life. These results suggest that 3D printing technology, combined with the use of OnX resin, holds promise in providing satisfactory clinical outcomes and enhanced patient satisfaction. However, it is important to acknowledge the limitations of this study, and further research is warranted to validate these findings and explore the long-term performance and durability of 3D-printed implant-supported fixed prostheses. This study contributes to the growing body of evidence supporting the effectiveness of 3D printing technology in implant dentistry. The results highlight the potential of 3DISFP with OnX resin to improve oral health-related quality of life in edentulous patients. Continued advancements in 3D printing materials and techniques will likely expand the utilization of these prostheses, ultimately benefiting patients in need of implant-supported restorations.

Flexural strength, surface roughness, micro-CT analysis, and microbiological adhesion of a 3D-printed temporary crown material.

OBJECTIVE: To evaluate the thermocycling effect of 3D-printed resins on flexural strength, surface roughness, microbiological adhesion, and porosity. MATERIALS AND METHODS: 150 bars (8 × 2 × 2 mm) and 100 blocks (8 × 8 × 2 mm) were made and divided into 5 groups, according to two factors: "material" (AR: acrylic resin, CR: composite resin, BIS: bis-acryl resin, CAD: CAD/CAM resin, and PRINT: 3D-printed resin) and "aging" (non-aged and aged - TC). Half of them were subjected to thermocycling (10,000 cycles). The bars were subjected to mini-flexural strength (σ) test (1 mm/min). All the blocks were subjected to roughness analysis (Ra/Rq/Rz). The non-aged blocks were subjected to porosity analysis (micro-CT; n = 5) and fungal adherence (n = 10). Data were statistically analyzed (one-way ANOVA, two-way ANOVA; Tukey's test, α = 0.05). RESULTS: For σ, "material" and "aging" factors were statistically significant (p < 0.0001). The BIS (118.23 ± 16.26A) presented a higher σ and the PRINT group (49.87 ± 7.55E) had the lowest mean σ. All groups showed a decrease in σ after TC, except for PRINT. The CRTC showed the lowest Weibull modulus. The AR showed higher roughness than BIS. Porosity revealed that the AR (1.369%) and BIS (6.339%) presented the highest porosity, and the CAD (0.002%) had the lowest porosity. Cell adhesion was significantly different between the CR (6.81) and CAD (6.37). CONCLUSION: Thermocycling reduced the flexural strength of most provisional materials, except for 3D-printed resin. However, it did not influence the surface roughness. The CR showed higher microbiological adherence than CAD group. The BIS group reached the highest porosity while the CAD group had the lowest values. CLINICAL RELEVANCE: 3D-printed resins are promising materials for clinical applications because they have good mechanical properties and low fungal adhesion.

A Comparison of the Surface and Mechanical Properties of 3D Printable Denture-Base Resin Material and Conventional Polymethylmethacrylate (PMMA).

PURPOSE: To study the surface and mechanical properties of 3D printed denture-base resin materials and compare them with conventional heat-cured polymethylmethacrylate (PMMA). MATERIALS AND METHODS: Three brands of 3D printed denture-base resin materials and one conventional heat-cured PMMA were tested in this study: NextDent 3D printed resin, Dentona 3D printed resin, ASIGA 3D printed resin, and Meliodent conventional PMMA. Sixty specimens (25 × 25 × 3 mm) were fabricated (n=15 per group) to perform the following tests: wettability, surface roughness, and microhardness. One hundred twenty specimens (65 × 10 × 3 mm) were fabricated (n=30 per group) and stored in distilled water at (37 ±1°C) for 7 days. Specimens (N = 15) in each group were subjected to the three-point bending test and impact strength test, employing the Charpy configuration on un-notched specimens. The morphology of the fractured specimens was studied under scanning electron microscope (SEM). Statistical analysis was performed using one-way ANOVA and Tukey-pairwise multiple comparisons with 95% confidence interval. P-values of ≤0.05 were considered significant. RESULTS: The conventional heat-cured specimens demonstrated the highest means of surface roughness (0.23 ± 0.07 µm), Vickers hardness number (18.11 ±0.65) and flexural strength (92.44 ±7.91 MPa), and the lowest mean of contact angle (66.71° ±3.38°). ASIGA group showed the highest mean of contact angle (73.44° ±2.74°) and the lowest mean of surface roughness (0.19 ±0.03 µm). The highest mean of impact strength was recorded in the Dentona group (17.98 ±1.76 kg/m2 ). NextDent specimens showed the lowest means of Vickers hardness number (16.20 ±0.93), flexural strength (74.89 ±8.44 MPa), impact strength (15.20 ±0.69 kg/m2 ), and recorded the highest mean of bending modulus (2,115.80 ±178.95 MPa). CONCLUSIONS: 3D printed resin exhibited noticeable differences in surface and mechanical properties between different brands and with conventional heat-polymerized PMMA.

Shaping ability of different NiTi rotary systems during the preparation of printed mandibular molars.

This study aimed to evaluate the shaping ability of XP-endo Shaper, TruNatomy and EdgeFile X3 during the preparation of resin-printed mandibular molar mesial root canals. Thirty-three resin-based mandibular mesial roots with two canals, obtained from extracted tooth cone-beam computed tomography (CBCT) image and printed on a three-dimensional (3D) printer, were divided into three experimental groups according to the different nickel-titanium (NiTi) systems used for root canal preparation. The specimens were scanned using CBCT imaging before and after root canal preparation. Then images were registered using a dedicated software and changes in the canal area, volume, untouched canal surface and the maximum and minimum dentine wall wear were calculated. The XP-endo Shaper instruments showed improved shaping ability with lower untouched root canal surface and better preservation of root canal anatomy during the preparation of resin-printed mandibular mesial root canals compared with TruNatomy and EdgeFile X3 systems.

Shaping ability of novel nickel-titanium systems in printed primary molars.

BACKGROUND: Manual or mechanized instruments can be used for root canal preparation. Manual instrumentation using K-files is widely used in primary teeth, but there are many limitations. Mechanized root canal preparation can lead to easy access to all canals, decrease instrumentation time, and result in more funnel-shaped root canals, resulting in a more predictable uniform paste fill. AIM: This study aimed to evaluate the shaping ability and instrumentation time of VDW.ROTATE™ and EdgeTaper Platinum™ during the preparation of resin-printed primary molars. Hand K-files were used as a reference for comparison. DESIGN: Sixty-six resin-based maxillary second primary molars, obtained from extracted tooth cone-beam computed tomography (CBCT) image and printed on a three-dimensional printer, were divided into three groups: VDW.ROTATE™, EdgeTaper Platinum™, and K-files. The specimens were scanned using CBCT imaging before and after root canal preparation. Images were registered using a dedicated software, and changes (Δ) in the canal area, volume, and untouched canal surface were calculated. Instrumentation time was evaluated. Data were statistically analyzed using the SPSS program. RESULTS: There was no significant difference among the tested file systems for Δ canal volume and area (p > .05). VDW.ROTATE™, however, showed significantly lower untouched canal surface area than other systems in all roots (p < .001). The VDW.ROTATE™ was found to be significantly faster (6.47 ± 0.39 min) than EdgeTaper Platinum™ (7.71 ± 0.73 min) and K-files (8.22 ± 0.72 min), (p < .05). CONCLUSIONS: The shaping ability and the instrumentation time were directly influenced by the root canal instrumentation system used during the preparation of resin-printed primary molars, with VDW.ROTATE™ being the faster system and associated with the lower amount of untouched canal surface area.

Caracterização de resina impressa para restaurações definitivas / Characterization of imprinted resin for definitive restorations

Este estudo teve como objetivo avaliar o comportamento de uma resina composta feita por impressão 3D (BPC 66, Smart Dent, São Carlos, Brasil), submetidas a diversos testes mecânicos, comparada com uma resina composta usinável (Grandio Blocs, Voco GmbH, Cuxhaven, Alemanha). Os espécime foram submetidos aos testes de Dureza Knoop (n=5), desgaste (n=10), resistência à flexão (n=25), módulo de elasticidade (n=3), a alteração de cor e translucidez (n=15), rugosidade (n=15) e resistência de união (n=15). Também foram analisados em microscopia eletrônica de varredura (MEV) para determinação da estrutura. Os valores de dureza (132,76 (16,32) HK- Grandio e 35,87 (2,78) HK ­ impressa), resistência à flexão (172,17 (26,99) MPa - Grandio e 88,69 (8,39) MPa - impressa) e alteração de cor/ translucidez de 1,86 (0,31)/0,06 - Grandio e 3,73 (0,36)/9,16- impressa e profundidade de desgaste (24,97 mm (3,60)- Grandio e 7,16 mm (2,84)- impressa)foram estatisticamente diferentes. Não foram observadas diferenças estatísticas para a rugosidade média (Ra) entre os materiais. Para a resistência de união, observou-se os valores de 16,23 (3,68) MPa para o cimento Bifix (Voco GmbH, Cuxhaven, Alemanha) e 25,33 (3,86) MPa para o cimento Variolink (Ivoclar Vivadent, Schaan, Liechtenstein) na resina impressa e 17,96 (4,88) MPa para o cimento Bifix e 20,76 (8,38) MPa para o cimento Variolink na Grandio. De um lado, o fator material não afetou a resistência adesiva (p=0,75), mas o fator cimento afetou (p=0,05), não sendo observada interação significante entre os fatores (p=0,07). A melhor dispersão e o maior tamanho das partículas inorgânicas na Grandio foram contrastados com partículas aglomeradas e de menor dimensão da resina impressa, em microscopia eletrônica de varredura. Dessa forma, as propriedades mecânicas e estabilidade de cor da resina usinável ainda foram superiores aos da resina impressa, provavelmente devido à maior quantidade e dispersão de partículas inorgânicas da resina usinável. (AU)

This study aimed to evaluate the behavior of a composite resin made by 3D printing (BPC 66, Smart Dent, São Carlos, Brazil), subjected to several mechanical tests, compared with a machinable composite resin (Grandio Blocs, Voco GmbH, Cuxhaven, Germany). The specimens were submitted to Knoop Hardness (n=5), wear (n=10), flexural strength (n=25), modulus of elasticity (n=3), color change and translucency (n=15) tests.), roughness (n=15) and bond strength (n=15). They were also analyzed by scanning electron microscopy (SEM) to determine the structure. Hardness values (132.76 (16.32) HK- Grandio and 35.87 (2.78) HK - printed), flexural strength (172.17 (26.99) MPa - Grandio and 88.69 (8.39) MPa - printed) and color/translucency change of 1.86 (0.31)/0.06 - Grandio and 3.73 (0.36)/9.16-printed and depth of wear (24 .97 mm (3.60) - grandiose and 7.16 mm (2.84) - printed) were statistically different. No statistical differences were observed for mean roughness (Ra) between materials. For bond strength, values of 16.23 (3.68) MPa were observed for Bifix cement (Voco GmbH, Cuxhaven, Germany) and 25.33 (3.86) MPa for Variolink cement (Ivoclar Vivadent, Schaan, Liechtenstein) in printed resin and 17.96 (4.88) MPa for Bifix cement and 20.76 (8.38) MPa for Variolink cement in Grandio. On the one hand, the material factor did not affect bond strength (p=0.75), but the cement factor did (p=0.05), with no significant interaction between the factors being observed (p=0.07). The better dispersion and larger size of the inorganic particles in the Grandio were contrasted with the agglomerated and smaller particles of the printed resin, in scanning electron microscopy. Thus, the mechanical properties and color stability of the machinable resin were still superior to those of the printed resin, probably due to the greater amount and dispersion of inorganic particles in the machinable resin (AU)

Shaping ability of modern Nickel-Titanium rotary systems on the preparation of printed mandibular molars.

Introduction: This study aimed to evaluate the shaping ability of TruNatomy (Dentsply Maillefer, Ballaigues, Switzerland), VDW.ROTATE (VDW GmbH, Munich, Germany) and ProTaper Gold (Dentsply Maillefer, Ballaigues, Switzerland) during the preparation of resin-printed mandibular molar mesial root canals. Materials and Methods: Thirty-three printed resin-based mandibular mesial roots with two canals were obtained from extract tooth cone-beam computed tomography (CBCT) image. The printed teeth were divided into three groups (n = 11) according to the system used for root canal preparation: TruNatomy, VDW.ROTATE, and ProTaper Gold. The specimens were scanned using CBCT imaging before and after root canal preparation. Then images were registered using a dedicated software and changes in the canal area, volume, untouched canal surface, and the maximum and minimum dentin wall wear were calculated. Statistical Analysis Used: Data were statistically analyzed using Shapiro-Wilk for normality, one-way ANOVA, and Tukey or Kruskal-Wallis H tests with alpha set at 5%. Results: No differences were observed for changes in the canal area, volume, untouched canal surface area, and minimum dentine wall wear parameters for the whole canal length (P > 0.05). The mean of untouched canal surface area for the TruNatomy, VDW.ROTATE, and ProTaper Gold was 40%, 44%, and 44%, respectively. The maximum dentine wall wear was significantly lower in the ProTaper Gold group than in the TruNatomy and VDW.ROTATE groups (P < 0.05). Conclusions: TruNatomy, VDW.ROTATE, and ProTaper Gold systems showed similar shaping ability in printed resin-based mandibular mesial roots without clinically significant errors. A large amount of untouched canal surface area was observed for all systems.

Development of 3D printed dental resin nanocomposite with graphene nanoplatelets enhanced mechanical properties and induced drug-free antimicrobial activity.

OBJECTIVES: Oral prosthetic rehabilitation has been used for a long time to restore function and natural appearance; however, it is still one of the most challenging areas in dentistry due to its technical fabrication process and biological behavior. Considering the advantages of additive manufacturing technology, this study introduced the feasibility of developing a 3D printed resin-based composition modified with graphene nanoplatelets (GNPs) to improve properties. METHODS: Acrylate-based resin was impregnated with different concentrations of GNPs (0.0-0.25 wt%), and then different aspects such as mechanical, physical, biological and antimicrobial were analyzed to evaluate the effectiveness. TEM and SEM were used to characterize GNPs and their existence within the resin. Surface topography and roughness were evaluated using AFM. The degree of conversion and composition were confirmed by FTIR. Mechanical properties were detected using bending strength, microhardness and nanoindentation. Biocompatibility and antimicrobial activities were assessed with oral fibroblast and Candida albicans (C. albicans), respectively. In addition, most of the measurements were performed repeatedly after 3 months of storage in artificial saliva to evaluate performance. RESULTS: GNPs improved strength significantly at low concentrations ≤ 0.05 wt%, while the addition up to 0.25 wt% enhanced printed nanocomposite hardness and elasticity. The modification did not induce a toxic response, as its biocompatibility was within the recommended range of biomedical devices. Antimicrobial activity was of prominence, as GNPs showed an outstanding route of reducing C. albicans activity associated with filler proportion. SIGNIFICANCE: The embedment of GNPs in 3D printed resin can become a key material for customized applications that require high antimicrobial, stiffness and strength properties.

Novel 3D Printed Resin Crowns for Primary Molars: In Vitro Study of Fracture Resistance, Biaxial Flexural Strength, and Dynamic Mechanical Analysis.

This study evaluated the fracture resistance, biaxial flexural strength (BFS), and dynamic mechanical analysis (DMA) of three-dimensional (3D) printing resins for the esthetic restoration of primary molars. Two 3D printing resins, Graphy (GP) and NextDent (NXT), and a prefabricated zirconia crown, NuSmile (NS), were tested. GP and NXT samples were 3D printed using the workflow recommended by each manufacturer. Data were collected and statistically analyzed. As a result of the fracture resistance test of 0.7-mm-thick 3D printed resin crowns with a thickness similar to that of the NS crown, there was no statistically significant difference among GP (1491.6 ± 394.6 N), NXT (1634.4 ± 289.3 N), and NS (1622.8 ± 323.9 N). The BFS of GP was higher for all thicknesses than that of NXT. Both resins showed high survival probabilities (more than 90%) when subjected to 50 and 150 MPa. Through DMA, the glass transition temperatures of GP and NXT were above 120 °C and the rheological behavior of GP and NXT according to temperature and frequency were analyzed. In conclusion, GP and NXT showed optimum strength to withstand bite forces in children, and 3D printed resin crowns could be an acceptable option for fixed prostheses of primary teeth.

Influência da angulação e espessura da camada de impressão na resistência à flexão, estabilidade dimensional e rugosidade de uma resina impressa / Influence of the angulation and thickness of the printing layer on the flexural strength, dimensional stability and roughness of a printed resin

Objetivo: Avaliar a influência da angulação e espessura da camada de impressão na resistência à flexão de três pontos (), estabilidade dimensional e rugosidade de uma resina provisória impressa. Metodologia: A partir da modelagem de uma barra (26 x 2,2 x 2,2mm) em software Meshmixer (Autodesk) e obtenção de arquivo STL, este foi exportado para o software da impressora 3D SLA (Forms2/Formlabs), onde 225 barras nas mesmas dimensões foram impressas com a resina Cosmos Temp, Yller (n=15) de acordo com os fatores "espessura da camada de impressão" (25µm;50µm;100µm) e "angulação" (0°; 30°; 45°; 60° e 90°). Após impressão, as amostras foram limpas com álcool isopropílico e encaminhadas ao pós-processamento em forno ultravioleta (Anycubic Wash e Cure Plus, Anycubic), por 15 minutos. As barras foram submetidas ao teste de  em máquina de ensaio universal (100KgF,1mm/min) e os dados (MPa) analisados com teste ANOVA 2 fatores, Tukey (5%) e análise de Weibull. Também foram realizadas as análises de rugosidade e estabilidade dimensional, cujos dados foram analisados pela ANOVA 2 fatores e Tukey (5%), além do MEV das superfícies. Resultados: Para a resistência à flexão, ANOVA 2 fatores revelou que o fator "Espessura da camada de impressão" (p<0,0001) foi estatisticamente significante, já o fator "Angulação" (p=0,8074) não apresentou significância estatística. Os grupos 30°/25µm (51,2±4,6AMPa), 60°/25µm (49,1±4,3ABMPa), 0°/25µm (48,6±6,6ABMPa), 90°/50µm (46,8±4,1ABCMPa) e 90°/25µm (46,2±4,9ABCMPa) apresentaram valores de  estatisticamente superiores aos grupos 0°/100µm (39,4±5,4DEFMPa), 60°/100µm (37,7±4,2DEFMPa), 90°/100µm (37,1±4,1EFMPa) e 30°/100µm (34,8±4,5FMPa), os quais foram semelhantes entre si. Para estabilidade dimensional, os grupos 0°/50µm (1746.9±61.80Aµm) e 0°/100µm (1704.7±84.30Aµm) apresentaram maiores alterações dimensionais, enquanto o grupo 90°/25µm (401.1±48.61Gµm) apresentou as menores alterações. Para rugosidade superficial, ANOVA relevou que os grupos 30°/100µm (0.90±0.10Aµm), 45°/100µm (0.79±0.07ABµm) e 60°/100µm (0.88±0.08Aµm) foram semelhantes entre si e apresentaram os maiores valores, enquanto a configuração 90°/100µm (0.23±0.08F) mostrou os menores valores. Conclusão: Quanto menor a espessura da camada de impressão, maior a resistência à flexão, independente da angulação escolhida. Adicionalmente, quanto menor a espessura da camada de impressão, maior foi a alteração dimensional, enquanto que objetos impressos verticalmente (90°) apresentam maior estabilidade dimensional. Para rugosidade superficial, quanto maior espessura da camada, maior rugosidade (AU).

Objective: To evaluate the influence of printing layer angulation and thickness on the three-point flexural strength (), dimensional stability and roughness of a printed provisional resin. Methodology: From the modeling of a bar (26 x 2.2 x 2.2mm) in Meshmixer software (Autodesk) and obtaining an STL file, it was exported to the SLA 3D printer software (Forms2/Formlabs), where 225 bars of the same dimensions were printed with Cosmos Temp resin, Yller (n=15) according to the factors "print layer thickness" (25µm;50µm;100µm) and "angulation" (0°; 30°; 45°; 60° e 90°). After printing, the samples were cleaned with isopropyl alcohol and sent to post-processing in an ultraviolet oven (Anycubic Wash and Cure Plus, Anycubic) for 15 minutes. The bars were submitted to the  test in a universal testing machine (100KgF,1mm/min) and the data (MPa) analyzed with 2-way ANOVA, Tukey (5%) and Weibull analysis. Roughness and dimensional stability analyzes were also performed, whose data were analyzed by 2- way ANOVA and Tukey (5%), in addition to the SEM of the surfaces. Results: For the flexural strength, 2-way ANOVA revealed that the factor "Print layer thickness" (p<0.0001) was statistically significant, while the factor "Angulation" (p=0.8074) did not show statistical significance. The 30°/25µm (51.2±4.6AMPa), 60°/25µm (49.1±4.3ABMPa), 0°/25µm (48.6±6.6ABMPa), 90°/50µm (46.8±4.1ABCMPa) and 90°/25µm (46.2±4.9ABCMPa) showed  values statistically higher than the 0°/100µm (39.4±5.4DEFMPa), 60°/100µm (37, 7±4.2DEFMPa), 90°/100µm (37.1±4.1EFMPa) and 30°/100µm (34.8±4.5FMPa), which were similar to each other. For dimensional stability, the 0°/50µm (1746.9±61.80Aµm) and 0°/100µm (1704.7±84.30Aµm) groups showed greater dimensional changes, while the 90°/25µm group (401.1±48.61Gµm) showed the smallest changes. For surface roughness, ANOVA revealed that the 30°/100µm (0.90±0.10Aµm), 45°/100µm (0.79±0.07ABµm) and 60°/100µm (0.88±0.08Aµm) groups were similar to each other and presented the highest values, while the 90°/100µm (0.23±0.08F) configuration showed the lowest values. Conclusion: The lower the printing layer thickness, the greater the flexural strength, regardless of the chosen angle. Additionally, the thinner the printing layer, the greater the dimensional change, while objects printed vertically (90°) have greater dimensional stability. For surface roughness, the greater the layer thickness, the greater the roughness (AU).

3D-Printed Nanocomposite Denture-Base Resins: Effect of ZrO2 Nanoparticles on the Mechanical and Surface Properties In Vitro.

Due to the low mechanical performances of 3D-printed denture base resins, ZrO2 nanoparticles (ZrO2NPs) were incorporated into different 3D-printed resins and their effects on the flexure strength, elastic modulus, impact strength, hardness, and surface roughness were evaluated. A total of 286 specimens were fabricated in dimensions per respective test and divided according to materials into three groups: heat-polymerized as a control group and two 3D-printed resins (NextDent and ASIGA) which were modified with 0.5 wt.%, 1 wt.%, 3 wt.%, and 5 wt.% ZrO2NPs. The flexure strength and elastic modulus, impact strength, hardness, and surface roughness (µm) were measured using the three-point bending test, Charpy's impact test, Vickers hardness test, and a profilometer, respectively. The data were analyzed by ANOVA and Tukey's post hoc test (α = 0.05). The results showed that, in comparison to heat-polymerized resin, the unmodified 3D-printed resins showed a significant decrease in all tested properties (p < 0.001) except surface roughness (p = 0.11). In between 3D-printed resins, the addition of ZrO2NPs to 3D-printed resins showed a significant increase in flexure strength, impact strength, and hardness (p < 0.05) while showing no significant differences in surface roughness and elastic modulus (p > 0.05). Our study demonstrated that the unmodified 3D-printed resins showed inferior mechanical behavior when compared with heat-polymerized acrylic resin while the addition of ZrO2NPs improved the properties of 3D-printed resins. Therefore, the introduced 3D-printable nanocomposite denture-base resins are suitable for clinical use.

Cytotoxicity and antimicrobial efficiency of ZrO2 nanoparticles reinforced 3D printed resins.

OBJECTIVE: The aim of this study was to investigate the potential antimicrobial and cytotoxic effect of modified 3D printed resin with ZrO2 nanoparticles, as long-term provisional restoration. In addition, the study involved artificial aging process for three months to observe stability of 3D printed resin. METHODS: Functionalized ZrO2 nanoparticles with γ-MPS were characterized using transmission electron microscopy, scanning electron microscope and Fourier-transform infrared spectroscopy. Dental resin was incrementally impregnated with γ-MPS modified nanoparticles at different concentrations (0, 1, 3, and 5 wt%). Specimens were printed, post-cured and placed in artificial saliva at 37 oC for 48 h or aged for 3 months. Discrepancy in composition and roughness were monitored using FTIR and AFM, respectively. Biocompatibility was evaluated using human oral fibroblasts. Antimicrobials capacity and biofilm adhesion were measured with Streptococcus mutans and Candida albicans. RESULTS: The microscopic and spectroscopic analyses confirmed γ-MPS coating around ZrO2 nanoparticles. The addition of nanoparticles (>1 wt%) significantly increased the surface roughness. Cytotoxicity results were in agreement with the recommended range of oral biomaterials standard. Moreover, the antimicrobial activity significantly improved with increasing the filler concentration. Despite the decrease in antimicrobial efficacy after 3 months of aging, modified resin revealed a critical ability to dominate biofilm formation. SIGNIFICANCE: The addition of ZrO2 nanoparticles showed significant antimicrobial capability of a 3D printed resin without inducing any cellular side effects. Thus, the modification of a 3D printed resin with ZrO2 nanoparticles has a promising future in the dental field for fabricating long-term provisional restorations.

Influence of different postcuring parameters on mechanical properties and biocompatibility of 3D printed crown and bridge resin for temporary restorations.

This study analyzed the flexural properties, Vickers hardness, degree of conversion (DC), and cell viability of 3D printed crown and bridge resin postcured using various types of postcuring equipment (PCE). 3D printed specimens were postcured for various times using different types of 3D printing PCE [for 5, 15, and 30 min using LC 3D Print Box (LC), Form Cure (FC), Cure M (CM), and Veltz 3D (VE) devices] and the VALO handheld light-curing (VA) device for 20, 40, and 60 s. Neither the flexural strength (132.27-145.79 MPa) nor the flexural modulus (1.52-1.83 GPa) differed significantly when postcuring for 30 min using the LC, FC, CM, or VE device, or for 20, 40, or 60 s of postcuring using the VA device (p > 0.05). The Vickers hardness was highest after 30 min of postcuring for all groups, and varied significantly with the postcuring time in the LC (p < 0.001) and CM (p < 0.001) groups. DC was significantly higher for the 5-min CM group (84.97 ± 4.02%) than for the GS, 30-min FC, 5-min VE, and 20-s VA groups. Cell viability of the postcured resin specimens was 56.46-92.29%, and varied significantly in the CM and VE groups according to the postcuring time (p < 0.05). Confocal laser scanning microscopy observations showed well-developed cell morphology and numerous cell-cell contacts in all groups except the GS group. This study found that the use of different types of PCE did not significantly affect the flexural properties of 3D printed crown and bridge resin, whereas there were significant variations in DC, Vickers hardness, and cell viability.

Comparative Evaluation of Retention and Vertical Marginal Accuracy of Co-Cr Copings Fabricated Using Three Different Techniques: An In Vitro Study.

AIM: This study was conducted to comparatively assess the retention and vertical marginal fit of cobalt-chromium copings fabricated by the conventional casting technique, 3D-printed resin pattern, and with direct metal laser sintering (DMLS) technique. MATERIALS AND METHODS: Out of the total 60 test samples, 20 copings were obtained from inlay-casting wax and 20 from casting of 3D-printed resin patterns. In total, 20 copings were obtained from the laser sintering technique. All 60 test samples were then cemented serially on the prepared maxillary-extracted premolars and were evaluated for vertical marginal gap in 8 pre-established reference areas. Retention was evaluated using a universal testing machine. RESULTS: Results obtained for both marginal gap and retention were statistically analyzed, and the values fall within the clinically acceptable range. The DMLS technique proved precedence over the other two techniques used, as it exhibited maximum retention and marginal accuracy, which is an area of prime concern. CONCLUSION: The results from this study encourage further research with different pattern-forming materials and techniques and the need to identify the factors that facilitate better marginal fit and retention of cast restorations. CLINICAL SIGNIFICANCE: This study has myriad of applications in clinical dentistry mainly in decision-making for casting procedure to provide better retention and marginal accuracy for fabrication of Co-Cr crowns. It also aims to aid the clinician to minimize errors by using different techniques for fabrication of wax pattern as well as the coping, keeping abreast with the recent technology to evaluate the accuracy of 3D-printed resin pattern over conventional wax pattern.

Shaping ability of protaper next compared with waveone in late-model three-dimensional printed teeth.

BACKGROUND: Comparison of the shaping ability of advanced nickel-titanium (Ni-Ti) instruments is of great interest to the field of endodontics. However, the models used to study canal preparation still lack uniformity, relevance to reality and complexity. The aim of this study was thus to compare the shaping abilities of the ProTaper Next (PN) and WaveOne (WO) Ni-Ti instruments in three-dimensional (3D)-printed teeth, which may overcome the present defects of most real teeth and model teeth including 3D S-shaped canals. METHODS: Six teeth and their corresponding 3D-printed replicas were prepared using the same kind of Ni-Ti instrument. The pre- and post-preparation volumes, surface areas and transportation of the canals were measured to compare the teeth with their replicas. Twenty 3D-printed teeth with S-shaped canals were used to support the preparation study. The S-shaped canals were then scanned to measure their volumes and surface areas. Next, the two kinds of instruments were used to prepare the 3D-printed canals (n = 10 per group). The volume and surface area of the canals, the transportation along the two curvatures and the percentage of unprepared surface area were measured. Micro-CT and VGstudio2.2 (VG2.2) software were used to perform scans and collect data throughout the research. The paired-samples T test and Kruskal-Wallis H test were used for statistical analysis. RESULTS: There was no significant difference between the real canals and the printed ones post-preparation (P > .05). The printed S-shaped root canals had a unified shape, with a small standard deviation and range. The WO group had higher mean values for the volume and superficial area measurements compared with the PN group (P < .05). No differences in the untouched areas were found between the two systems (P > .05). PN caused less transportation at the apical curve than WO did (P < .05). CONCLUSIONS: In conclusion, 3D-printed teeth are suitable for the study of Ni-Ti rotary instruments. Furthermore, the PN rotary system caused less transportation at the apical curve than the WO system did in complicated root canal procedures.

Comparative Evaluation of Marginal and Internal Gap of Co-Cr Copings Fabricated from Conventional Wax Pattern, 3D Printed Resin Pattern and DMLS Tech: An In Vitro Study.

Accuracy of the fit of the restoration has always remained as one of the primary factors in determining success of the restoration. A well fitting restoration needs to be accurate both along its margins and internal surface. This study was conducted to comparatively evaluate the marginal gap and internal gap of cobalt-chromium (Co-Cr) copings fabricated by conventional casting procedures and with direct metal laser sintering (DMLS) technique. Among the total of 30 test samples 10 cast copings were made from inlay casting wax and 10 from 3D printed resin pattern. 10 copings were obtained from DMLS technique. All the 30 test samples were then cemented sequentially on stainless steel model using pressure indicating paste and evaluated for vertical marginal gap in 8 predetermined reference areas. All copings were then removed and partially sectioned and cemented sequentially on same master model for evaluation of internal gap at 4 predetermined reference areas. Both marginal gap and internal gap were measured in microns using video measuring system (VMS2010F). The results obtained for both marginal and internal gap were statistically analyzed and the values fall within the clinically acceptable range. The DMLS technique had an edge over the other two techniques used, as it exhibited minimal gap in the marginal region which is an area of chief concern.