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INTRODUCTION: This study aimed to evaluate denture care and hygiene and oral health-related quality of life (OHRQoL) among complete denture (CD) wearers in the Eastern Province of Saudi Arabia. METHODOLOGY: This cross-sectional study was conducted on CD wearers in the Eastern Province of Saudi Arabia. A pre-tested questionnaire was administered among study participants. Questionnaire was divided in three sections: (1) patients' demographic data, (2) awareness and maintenance of CD and (3) OHRQoL. Independent sample t-test and one-way ANOVA test were performed. RESULTS: The study included data of 300 participants with 71% of males and 28% of females. Majority of participants (82.7%) cleaned CD daily, removed CD while sleeping (88.0%) and knew that unhygienic dentures can cause oral infection (92.7%). Only 19.3% used denture cleansing tables, 41% used toothpaste, and 60.7% rinsed CD with water. Regarding OHIP-DENT domains, highest score was for functional limitation domain (2.20 ± 1.67) and the lowest for handicap domain (0.94 ± 1.09). The mean OHIP-DENT score of the sample was 12.02 ± 8.52. Females (p = 0.006), participants below 65 years of age (p = 0.029), non-Saudis (p = 0.042), those with university education (p = 0.030) and low monthly income (p = 0.045) and participants who visited dentist due to problem with CD (p = 0.041) demonstrated significantly higher mean OHIP-DENT score. CONCLUSION: Majority of participants demonstrated appropriate denture care behaviours because they were aware of the importance of denture care and hygiene. Female gender, age below 65 years, non-Saudi nationality, university education, low monthly income and visiting dentist due to problem were related to poor OHRQoL.

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Saúde Bucal, Qualidade de Vida, Masculino, Humanos, Feminino, Idoso, Estudos Transversais, Arábia Saudita, Prótese Total

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Three-dimensionally (3D)-printed fabricated denture bases have shown inferior strength to conventional and subtractively fabricated ones. Several factors could significantly improve the strength of 3D-printed denture base resin, including the addition of nanoparticles and post-curing factors. This study evaluated the effect of TiO2 nanoparticle (TNP) addition and the post-curing time (PCT) on the flexural properties and hardness of three-dimensionally (3D)-printed denture base resins. A total of 360 specimens were fabricated, with 180 specimens from each type of resin. For evaluating the flexural properties, bar-shaped specimens measuring 64 × 10 × 3.3 mm were used, while, for the hardness testing, disc-shaped specimens measuring 15 × 2 mm were employed. The two 3D-printed resins utilized in this study were Asiga (DentaBASE) and NextDent (Vertex Dental B.V). Each resin was modified by adding TNPs at 1% and 2% concentrations, forming two groups and an additional unmodified group. Each group was divided into three subgroups according to the PCT (15, 60, and 90 min). All the specimens were subjected to artificial aging (5000 cycles), followed by testing of the flexural strength and elastic modulus using a universal testing machine, and the hardness using the Vickers hardness test. A three-way ANOVA was used for the data analysis, and a post hoc Tukey's test was used for the pairwise comparisons (α = 0.05). Scanning electron microscopy (SEM) was used for the fracture surface analysis. The addition of the TNPs increased the flexural strength in comparison to the unmodified groups (p < 0.001), while there was no significant difference in the elastic modulus and hardness with the 1% TNP concentration. Among the TNP groups, the 2% TNP concentration significantly decreased the elastic modulus and hardness (p < 0.001). The SEM showed a homogenous distribution of the TNPs, and the more irregular fracture surface displayed ductile fractures. The PCT significantly increased the flexural strength, elastic modulus, and hardness (p < 0.001), and this increase was time-dependent. The three-way ANOVA results revealed a significant difference between the material types, TNP concentrations, and PCT interactions (p < 0.001). Both concentrations of the TNPs increased the flexural strength, while the 2% TNP concentration decreased the elastic modulus and hardness of the 3D-printed nanocomposites. The flexural strength and hardness increased as the PCT increased. The material type, TNP concentration, and PCT are important factors that affect the strength of 3D-printed nanocomposites and could improve their mechanical performance.

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OBJECTIVE: The aim of this study was to evaluate the surface roughness, contact angle, and adhesion of Candida albicans to computer-aided designing/computer-aided manufacturing (CAD/CAM) and heat-polymerized (HP) denture base materials. MATERIALS AND METHODS: Specimens were allocated to six groups based on the composition of studied denture base materials, HP acrylic resin, milled resins (AvaDent and IvoCad), and 3D-printed resins (ASIGA, FormLabs, and NextDent). Ten specimens per group were used for each test (n = 10/test). Surface roughness and contact angles were analyzed using profilometer and goniometer, respectively. Adhesion of C. albicans was counted using colony-forming unit (CFU/mL). Means and standard deviations were calculated, and then one-way analysis of variance (ANOVA), followed by Tukey's post hoc test. Correlation of Candida adhesion and surface parameters was determined by using Pearson's correlation analysis. RESULTS: No statistically significant difference was noted in surface roughness between HP, milled, and 3D-printed denture base resins except NextDent, which showed significantly higher roughness in comparison to all other resins (p = 0.001). In terms of contact angle, milled resins had the lowest value, followed by HP, ASIGA, and FormLabs, whereas NextDent showed the highest contact angle (p = 0.001). C. albicans adhesion showed no significant difference between all denture base resins. A positive and significant correlation was found between C. albicans adhesion and contact angle (p = 0.003), while no correlation was reported between C. albicans adhesion and surface roughness (p = 0.523). CONCLUSION: Adhesion of C. albicans was similar in all tested specimens. Surface roughness showed no significant difference between all groups except NextDent, which had the highest value. Milled denture base resins had the lowest contact angle among all groups.

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PURPOSE: To assess the influence of denture brushing on the surface roughness, hardness, and color stability of conventional, thermoformed, and CAD-CAM denture base materials. MATERIALS AND METHODS: Seven different denture base materials were included in this study; conventional heat-polymerized acrylic resin (PMMA) served as control, polyamide, acetal, two categories of milled acrylic discs (AvaDent and IvoCad), and two categories of 3D-printed resins (NextDent and FormLabs). The specimens were constructed according to manufacturers' instructions and then subjected to simulated brushing (20,000 cycles). According to the brushing method, the specimens were split into three groups, no brushing, brushing with water, and brushing with toothpaste. Surface roughness, hardness, and color change were evaluated before and after brushing. Collected data were analyzed using ANOVA, and post-hoc Tukey's tests (α = 0.05). RESULTS: A significant difference was noted between the surface roughness of the tested materials before and after denture brushing (p < 0.05), and milled resin showed the least Ra values. Denture brushing with water significantly increased the Ra of PMMA (p = 0.004) and IvoCad (p = 0.032), while brushing using toothpaste did not show a significant increase. The brushing protocols did not alter the hardness of tested materials except that of PMMA (p = 0.001). The color stability of the tested materials showed comparable results with both brushing protocols. CONCLUSION: The tested properties showed variations between the types of denture base resins. Hardness and color stability of CAD-CAM and thermoformed denture base resins were not altered by denture brushing and showed comparable results with both brushing methods. Surface roughness was the only property that showed alteration after denture brushing.

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Objective: This bibliographic analysis was designed to review all dental publications in the Kingdom of Saudi Arabia (KSA) and evaluate the effect of international collaboration on the impact of published articles. Methods: The Web of Science (WOS) database was used to extract all related published articles in the KSA from 1982 to 2021. The keywords were connected using Boolean Operators to download related articles. Downloaded articles were screened according to the following inclusion criteria: collaboration journal category, journal discipline, number of citations, number of authors, and impact factor. After applying the inclusion criteria and excluding single-author articles, 5,689 documents were included in the final analysis. The chi-square test and two-independent samples t-test were used to determine the statistical significance between the variables. Results: A significantly higher proportion of articles with international collaboration (51.4%) were published in dental journals than those published nationally (43.3%) or within the institutional level (41.8%) (P < 0.0001). In addition, the average number of citations (9.28 ± 23.8) ranged from 0 to 749, received by an article and the impact factor of the journal in which the article was published, significantly higher in the case of internationally collaborative work compared with national or within institutional collaboration (P < 0.0001). Conclusion: International collaboration positively affected the impact factor, number of citations, and quartile rank of published articles. Moreover, the number of co-authors in different countries contributes to the international collaboration effect.

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Occlusal rest provides support for removable partial dentures (RPD). Rest seats are ideally prepared in enamel, but the abutment teeth might be restored or need restorations. This study compared the fracture strength of abutments restored with composite to amalgam restorations after rest seat preparation. Disto-occlusal cavities were prepared in 30 extracted human maxillary premolars. The specimens were allocated in three groups (n = 10) based on the type of restoration. All the specimens were exposed to thermomechanical aging followed by cycling loading. Fracture strength was tested using a universal testing machine, and then, the fracture mode was recorded. The data were analyzed using Kruskal-Wallis test with a significance level set at 0.05. The fracture mode was recorded as catastrophic or non-catastrophic. The fracture strength between all tested groups showed no significant difference. The highest and lowest fracture strength were recorded on amalgam and Tetric N-Ceram groups, respectively. Composite Tetric N-Ceram showed equal distribution of fracture sites on the restorative materials and teeth, it also displayed the highest number of non-catastrophic fractures unlike other groups where the fracture occurred more within the restorations. The fracture strength of composite was comparable to that of amalgam restorations with prepared rest seats.

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Background: This study aimed to evaluate the effects of different denture cleansing solutions (DCSs) on the retention of Locator and Locator R-Tx attachment systems of implant retained overdentures (IRO). Methods: Two part acrylic resin blocks were fabricated, upper part contained metal housing and plastic inserts and lower part contained implant analogs and abutments. Eighty pink plastic inserts (40/attachment, 10/solution) were immersed in Corega, Fittydent, sodium hypochlorite, and water for a time simulating upto 1-year of clinical usage. Acrylic blocks were held on a universal testing machine for a pull-out test to record the dislodgement force. Measurements were conducted after 6 months (T1) and 12 months (T2). One-way ANOVA followed by Tukey's HSD test was used to analyze the results (α = 0.05). Results: For both attachments, retention significantly decreased after immersion in different solutions at T2 (P < 0.001). Locator R-Tx attachment in NaOCl showed a significant decrease in retention compared with other solutions at T1. At T2, there was a significant decrease in retention for all DCS compared with water (P < 0.001). Locator R-TX showed higher retention values per solution compared to Locator attachment (P < 0.001). In terms of retention loss %, NaOCl recorded the highest (61.87%) loss, followed by Corega (55.54%) and Fittydent (43.13%), whereas water demonstrated the best retention (16.13%) in both groups. Conclusion: Locator R-TX has better retention with different DCS immersion. The loss of retention varied with different types of DCS and NaOCl recorded the highest retention loss. Therefore, denture cleanser selection must be guided by the type of IRO attachment.

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Objective: This in vitro study compares the accuracy and trueness of various 3D-printed denture teeth. Methods: A total of 30 specimens were created using various 3D-printed resins, 10 each using Asiga DentaTOOTH resin (Asiga, Australia), Formlabs Denture Teeth Resin (Formlabs GmbH, Germany), and NextDent C&B MFH (Micro Filled Hybrid) resin (Nextdent B.V., Netherlands), respectively. A prefabricated mandibular first molar was scanned using a desktop laser scanner (E3, 3Shape A/S) to create a standard tessellation language file, which served as a "reference tooth" scan. That file was sent to each corresponding printer for printing according to manufacturer recommendations. The printed teeth were scanned with an intraoral scanner (TRIOS 3, 3shape, Copenhagen, Denmark). Trueness and precision were assessed using 3D morphometric analysis software (Geomagic Control X, 3D Systems, Rock Hill, SC, USA). One-way ANOVA was used to analyze the data (α = 0.05). Root mean square error and mean deviations were also calculated. Data analysis was carried out using SPSS (IBM Corp., New York, NY, USA) software. One-way ANOVA with Tukey's post hoc analysis was used. P-values of<0.05 were regarded as statistically significant. Results: The overall trueness of teeth followed a similar pattern, with the highest trueness recorded with NextDent specimens, while ASIGA specimens had the lowest. When precision was assessed, there were significant differences in occlusal areas between FormLabs and NextDent specimens (p = 0.01) and between FormLabs and ASIGA specimens (p = 0.002). However, ASIGA and NextDent did not differ from one another (p = 0.9). The precision analysis shows that all tested groups had similar values, with no significant differences among them. Conclusion: The trueness values of the tested printing systems varied, although the precision values were similar. All evaluated printing systems achieved printing accuracy falling within the clinically acceptable range.

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BACKGROUND: Enhancement of students' knowledge is essential in improving their clinical skills and performance. Thus, the curriculum should be prepared to achieve a better outcome. The current study aimed to determine the dental students' and interns' basic knowledge towards dental luting cements and their application in dental practice to improve the theoretical and clinical training sections. MATERIALS AND METHODS: A cross-sectional study was conducted among dental students and interns at three Colleges of Dentistry in the Kingdom of Saudi Arabia between September 2019-June 2020. An online questionnaire was used which included demographic data, questions about luting cement usage, cementation techniques, and commonly used cements in dental clinics. Descriptive analysis and chi-square test were used to show the association between level of dental education and the use of dental cements using SPSS software. The significance level was set at 5%. RESULTS: The total respondents were 626 dental students/interns of whom 78.8% were undergraduate dental students. Participants who reported undergraduate studies as the source of information were 79.7%. The type of restoration was the main factor in luting cement selection (62.6%). Concerning the isolation technique in cementing laminate veneers, 49.7% used dri-angles, cotton rolls and saliva ejectors. Dual-cure resin cement was the most common cement used in all the mentioned restorations except in pressed porcelain laminate veneers and cement-retained implant-supported restorations. CONCLUSIONS: Students' knowledge and practice in managing dental implants and porcelain laminate veneers need to be improved. The selection of a luting agent for a given restoration by students and interns was based on the basic knowledge, available cement, and the type of restoration. Awareness towards the management of short prepared teeth and custom-made cast posts and cores is also limited.

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Cimentos Dentários, Porcelana Dentária, Humanos, Prostodontia, Estudos Transversais, Arábia Saudita, Estudantes de Odontologia, Cimentos de Resina, Cimentos de Ionômeros de Vidro, Teste de Materiais

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BACKGROUND: Denture adhesives (DAs) enhance denture retention and stability, thus improving functions of removable prostheses. However, the adverse effects of DAs on denture foundation area were also reported. The clinical use of DAs among dentists has not been investigated in Saudi Arabia. Therefore, this study aimed to evaluate utilization of DAs and associated factors among dental practitioners in Saudi Arabia. METHODS: This cross-sectional study included dental professionals practicing in both public and private sectors in the Eastern Province of Saudi Arabia. A self-administered pilot tested questionnaire was distributed among participants. The questionnaire has questions related to demographic information, knowledge and awareness, and the utilization of DAs. Bivariate and multiple logistic regression analyses were performed. RESULTS: The study included 279 participants with a response rate of 79.03%. The majority of participants (61.6%) were below 35 years of age, males (56.6%), general dentists (57.3%), and worked in the private sector (59.9%). Less than half of the participants (39.4%) used DAs in their dental practice, and 64.5% recommended using DAs when needed. The most reported complications of DAs included inflammation (58.40%), ulcers (35.10%), and whitish color (31.20%) of denture foundation area. A vast majority (83.90%) reported that DAs improve retention of the dentures. About 55.2% of the participants were taught about DAs in their undergraduate programs, 12.5% attended continuing education, and 21.5% updated their knowledge about DAs. Multiple logistic regression showed that those who attended continuing education activities (adjusted OR = 2.41, p = 0.036) and updated their knowledge about DAs (adjusted OR = 4.43, p = < 0.001) were significantly more likely to use DAs in their dental practice. CONCLUSION: A minority of dental practitioners used DAs in their practices. Attending continuing education programs and updating knowledge of DAs were significantly associated with DAs utilization.

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Odontólogos, Papel Profissional, Masculino, Humanos, Arábia Saudita, Estudos Transversais, Dentaduras

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Background: Denture stomatitis is a clinical condition that affects people who wear removable maxillary dentures. It causes redness, soreness, and erythema and ultimately affects the general condition of the patient. The objective of this study was to analyze the leading countries, journals, organizations, and authors and the frequently used keywords associated with denture stomatitis. Material and Methods: A bibliometric analysis of publications indexed in the Scopus database was conducted, and the article titles, abstracts, and keywords were analyzed using the VOSviewer software. Denture stomatitis-related publications from 1960 to 2021 were collected. This study included only research papers published in English with "article" as the paper type and dentistry as the subject area. Results: Data from a total of 461 articles and 10 different journals were obtained. The papers were published in 64 different countries. Brazil and the United States of America were the top contributing countries, and the University of Sydney was the leading organization. Papers published in the Journal of Oral Rehabilitation received the highest number of citations, while author Gordon Ramage from the University of Glasgow received the highest number of citations. Conclusions: The bibliometric analysis revealed that the number of denture stomatitis-related publications indexed in the Scopus database is increasing globally. Since 2007, there has been an increase in research interest regarding denture stomatitis, with more publications from several countries expected to be published in different journals. Key words:Bibliometric analysis, denture, candida, VOSviewer, maxilla.

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The fracture resistance of 3-unit interim fixed dental prostheses (IFDPs) fabricated using digital light processing (DLP) additive technology with different printing parameters is neglected. Therefore, this study investigates the effect of different printing orientations and different post-curing times on the fracture resistance of 3-unit IFDPs fabricated from two three-dimensional (3D) printed resins, NextDent, C&B (CB), ASIGA, and DentaTOOTH. A 3-unit dye was scanned, and an IFDP was designed. A total of 300 specimens (150/materials, n = 10) were printed and divided into three groups according to printing orientations (0°, 45°, 90°) per material. Each orientation was subdivided into five groups (n = 10) considering the post-curing time (green state as control, 30, 60, 90, and 120 min). All specimens underwent thermocycling (5000 cycles). Each specimen was fitted onto the die and loaded until fracture using a universal testing machine with a loading rate of 1 m/min. Data were analyzed using ANOVA and post hoc Tukey test (α = 0.05). The result showed that printing orientation had a significant effect on the fracture load for both ASIGA and NextDent materials (p < 0.05). The highest fracture load was recorded with 45° orientation, followed by 0° orientation and 90° orientation showed the lowest values per respective post-curing time. Post-curing time increased the fracture load (p < 0.05). Post-curing time had a positive effect on the fracture load. As the post-curing time increased, the fracture resistance load increased (p < 0.05), with 90 and 120 min showing the highest fracture load. The 0° and 45° printing orientations have a high fracture load for 3D-printed IFDPs, and an increased post-curing time is recommended.

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Pressable ceramic restorations have been introduced and investigated, and found comparable to CAD/CAM ceramic in terms of mechanical properties; however, the effect of toothbrushing on the pressable ceramic has not been thoroughly investigated. The objective of the current study was to assess the effect of artificial toothbrushing simulation on the surface roughness, microhardness, and color stability of different ceramic materials. Three lithium disilicate-based ceramics (IPS Emax CAD [EC], IPS Emax Press [EP]; (Ivoclar Vivadent AG), and LiSi Press [LP] (GC Corp, Tokyo, Japan)) were examined. For each ceramic material, eight bar-shaped specimens were prepared and subjected to 10,000 brushing cycles. Surface roughness, microhardness, and color stability (∆E) were measured before and after brushing. Scanning electron microscopy (SEM) was used for surface profile analysis. The results were analyzed using one-way ANOVA, Tukey's post hoc test, and paired sample t-test α = 0.05. The findings revealed a non-significant decrease in the surface roughness of EC, EP, and LP groups (p > 0.05), and both LP and EP have the lowest surface roughness values (0.64 ± 0.13, 0.64 ± 0.08 µm) after brushing, respectively. Toothbrushing showed a decrease in the microhardness of the three groups: EC and LP, p < 0.001; EP, p = 0.012). EP showed the lowest hardness value after brushing (862.45 ± 273.83). No significant changes (∆E) were observed in all groups (p > 0.05); however, the EC group was found to be considerably affected by color changes, in comparison to the EC and LP groups. Toothbrushing had no effect on surface roughness and color stability of all tested materials, but it decreased the microhardness. Material type, surface treatments, and glazing of ceramic materials contributed to the surface changes in the ceramic materials, necessitating further investigations in terms of the toothbrushing effect with different glazing as variables.

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Denture care and maintenance are necessary for both denture longevity and underlying tissue health. However, the effects of disinfectants on the strength of 3D-printed denture base resins are unclear. Herein, distilled water (DW), effervescent tablet, and sodium hypochlorite (NaOCl) immersion solutions were used to investigate the flexural properties and hardness of two 3D-printed resins (NextDent and FormLabs) compared with a heat-polymerized resin. The flexural strength and elastic modulus were investigated using the three-point bending test and Vickers hardness test before (baseline) immersion and 180 days after immersion. The data were analyzed using ANOVA and Tukey's post hoc test (α = 0.05), and further verified by using electron microscopy and infrared spectroscopy. The flexural strength of all the materials decreased after solution immersion (p < 0.001). The effervescent tablet and NaOCl immersion reduced the flexural strength (p < 0.001), with the lowest values recorded with the NaOCl immersion. The elastic modulus did not significantly differ between the baseline and after the DW immersion (p > 0.05), but significantly decreased after the effervescent tablet and NaOCl immersion (p < 0.001). The hardness significantly decreased after immersion in all the solutions (p < 0.001). The immersion of the heat-polymerized and 3D-printed resins in the DW and disinfectant solutions decreased the flexural properties and hardness.

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Poly(methyl methacrylate) (PMMA) is a commonly used material, as it is biocompatible and relatively cheap. However, its mechanical properties and weak antibiofilm activity are major concerns. With the development of new technology, 3D-printed resins are emerging as replacements for PMMA. Few studies have investigated the antibiofilm activity of 3D-printed resins. Therefore, this study aimed to investigate the antibiofilm activity and surface roughness of a 3D-printed denture base resin modified with different concentrations of zirconium dioxide nanoparticles (ZrO2 NPs). A total of 60 resin disc specimens (15 × 2 mm) were fabricated and divided into six groups (n = 10). The groups comprised a heat-polymerized resin (PMMA) group, an unmodified 3D-printed resin (NextDent) group, and four 3D-printed resin groups that were modified with ZrO2 NPs at various concentrations (0.5 wt%, 1 wt%, 3 wt%, and 5 wt%). All specimens were polished using a conventional method and then placed in a thermocycler machine for 5000 cycles. Surface roughness (Ra, µm) was measured using a non-contact profilometer. The adhesion of Candida albicans (C. albicans) was measured using a fungal adhesion assay that consisted of a colony forming unit assay and a cell proliferation assay. The data were analyzed using Shapiro-Wilk and Kruskal-Wallis tests. A Mann-Whitney U test was used for pairwise comparison, and p-values of less than 0.05 were considered statistically significant. The lowest Ra value (0.88 ± 0.087 µm) was recorded for the PMMA group. In comparison to the PMMA group, the 3% ZrO2 NPs 3D-printed group showed a significant increase in Ra (p < 0.025). For the 3D-printed resins, significant differences were found between the groups with 0% vs. 3% ZrO2 NPs and 3% vs. 5% ZrO2 NPs (p < 0.025). The highest Ra value (0.96 ± 0.06 µm) was recorded for the 3% ZrO2 NPs group, and the lowest Ra values (0.91 ± 0.03 µm) were recorded for the 0.5% and 5% ZrO2 NPs groups. In terms of antifungal activity, the cell proliferation assay showed a significant decrease in the C. albicans count for the 0.5% ZrO2 NPs group when compared with PMMA and all other groups of 3D-printed resins. The group with the lowest concentration of ZrO2 NPs (0.5%) showed the lowest level of C. albicans adhesion of all the tested groups and showed the lowest Candida count (0.29 ± 0.03). The addition of ZrO2 NPs in low concentrations did not affect the surface roughness of the 3D-printed resins. These 3D-printed resins with low concentrations of nanocomposites could be used as possible materials for the prevention and treatment of denture stomatitis, due to their antibiofilm activities.

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OBJECTIVES: With advanced technology for complete denture fabrication, there is a lack of knowledge on the mechanical behavior of three-dimensional (3D) printed teeth despite the development of complete denture fabrication technologies. This study aimed to compare different types of 3D-printed teeth in terms of wear and fracture resistance in comparison to control prefabricated denture teeth. MATERIALS AND METHODS: One prefabricated tooth was selected and fixed in a resin holder and half of the tooth remained in anatomic form, while the other half was flattened for the wear test. One from each type was scanned and then printed with different resins; Asiga (DentaTOOTH, Asiga, Alexandria 2015,NSW, Australia), FormLabs (Denture Base LP, FormLabs, Berlin, Germany), and NextDent (NextDent C&B MFH, NextDent B.V., Soesterberg, the Netherlands) according to manufacturer recommendations. A total of 60 specimens (20/resin, n = 10) were thermo cycled (5,000 cycles) and wear test samples were further subjected to cyclic loading (1,70,000 cycles) in a chewing simulator machine CS-4.2 (SD Mechatronik GmbH, Germany). The fracture strength of anatomic teeth was measured using a universal testing machine (Instron model 5965, Massachusetts, United States), while Geomagic Control X software was used to assess the amount of wear of flattened teeth. Statistical analyses were performed with one-way analysis of variance with Tukey's post hoc test at significance level of α = 0.05. RESULTS: NextDent specimens showed the greatest volume loss, whereas FormLabs specimens showed the least volume loss. Comparing NextDent specimens to FromLabs specimens, FromLabs showed statistically significantly less volume loss (p < 0.001). No other group pairs differed significantly from one another in terms of volume loss (p > 0.06). CONCLUSION: 3D-printed denture teeth showed comparable strength and wear resistance with the prefabricated denture teeth and were suitable for long-term clinical usage except for NextDent that significantly showed the lowest fracture resistance.

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PURPOSE: The strength of 3D-printed resins is affected by different factors, but review articles clarifying these factors are limited. This review lists the factors affecting the strength of 3D-printed resins and the possible correlations between them to answer the study question: What are the factors affecting the flexural strength of 3D-printed resins? METHODS: A database search (PubMed, Google Scholar, and Scopus) was performed, limited to English-language publications between 2010 and February 1, 2022. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were used for study selection. The modified Consolidated Standards of Reporting Trials (CONSORT) checklist was used to determine the risk of bias of the included studies in this review. The data analysis was descriptive due to the presence of many variables in the included studies. RESULTS: Out of 123 studies, 26 were reviewed for full-text analysis, and 19 met the inclusion criteria and were thus included in this systematic review. The included studies were divided according to the investigated resin: 5 studies tested provisional restorations, seven tested denture base resins, 2 tested occlusal devices, 3 tested orthodontic appliances, 1 tested denture teeth, and 1 tested surgical guide resins. These studies investigated the flexural strength of 3D-printed resins, with different factors, such as reinforcement with fillers or nanofillers; printing orientation, angulation, and directions; post-polymerization time and temperature; third-party printing (switching between printers and materials); printing layer thickness; and post-printing rinsing time. Most factors significantly affected the flexural strength of 3D-printed resin. CONCLUSIONS: The strength of 3D-printed resins could be improved with one or more of the following factors: filler or nanofiller addition; printing orientation, angulation, or directions; printing layer thickness; and post-polymerization time and temperature. However, further studies combining these factors are recommended.

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Resistência à Flexão, Impressão Tridimensional, Teste de Materiais, Propriedades de Superfície, Temperatura

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OBJECTIVES: This study aimed to evaluate the influence of different salivary pH on flexural strength, hardness, and surface roughness of computer-aided design and computer-aided manufacturing (CAD/CAM) milled and three-dimensional (3D)-printed denture base resins. METHODS: One heat-polymerized, two CAD/CAM milled (IvoCad, AvaDent), and two 3D-printed (FormLabs, NextDent) denture base resins were fabricated and divided into five groups (n = 10) according to the solutions: three groups were immersed in different salivary pH (5.7, 7.0, or 8.3), one group was immersed in distilled water (DW) as a positive control, and one group had no immersion (negative control). All immersions were performed at 37°C for 90 days. Flexural strength, hardness, and surface roughness were measured before and after immersion. Data was analyzed with analysis of variance and post hoc Tukey's test (α = 0.05). RESULTS: After immersion, all specimens had lower flexural strength values when compared with those with no immersion. Comparing the immersion groups, the highest flexural strength value (93.96 ± 3.18 MPa) was recorded with IvoCad after immersion in DW while the lowest value (60.43 ± 2.66 MPa) was recorded with NextDent after being immersed in 7.0 pH saliva. All specimens had significant decrease in hardness except IvoCad and AvaDent specimens where both presented the highest surface hardness (53.76 ± 1.60 Vickers hardness number [VHN]) after immersion in DW while NextDent showed the lowest hardness value (24.91 ± 2.13 VHN) after being immersed in 8.3 pH saliva. There was statistically significant difference between the baseline and different artificial salivary pH solutions in terms of surfaces roughness, with the highest surface roughness were found in 3D-printed resin materials. CONCLUSION: After exposure to artificial saliva with different salivary pH, the milled CAD/CAM denture base resins showed higher flexural strength, hardness, and lesser surface roughness than conventional and 3D-printed denture base resins.

RESUMO

PURPOSE: To introduce a new technique, denture base layering, for the addition of titanium dioxide nanoparticles (TiO2 NPs) to polymethylmethacrylate (PMMA) and to investigate the effects of the layering technique on Candida albicans (C. albicans) adhesion and on surface roughness, hardness, translucency, and flexural strength. MATERIALS AND METHODS: In total, 210 heat-polymerized acrylic resin specimens were prepared as discs (15 × 2 mm) for testing C. albicans adhesion (n = 70) and surface roughness, hardness, and translucency (n = 70); and as acrylic plates (65 × 10 × 2.5 mm) for testing flexural strength (n = 70). Specimens were divided into 4 groups: control (n = 30), one-layer (n = 60), double-layer (n = 60), and dotted-layer (n = 60) according to the packing and layering technique. Each group was divided according to the concentration of TiO2 NPs 1% and 2.5% (n = 10). The control group comprised one layer of unmodified resin. The one-layer group comprised one layer of a mixture of PMMA/TiO2 NPs packed conventionally. The double-layer group consisted of two different layers packed in two steps, as follows: unmodified resin first, followed by a continuous thin layer of the PMMA/TiO2 NPs mixture. Similarly, the dotted-layer group consisted of two different layers packed in two steps, as follows: unmodified resin first, followed by a thin layer of the PMMA/TiO2 NPs. However, the second mixture was added in a dotted manner. The direct culture method for C. albicans adhesion before and after ultraviolet light activation, and surface roughness, hardness, translucency, and flexural strength were measured. An analysis of variance and Tukey's post hoc test were used for data analysis (α = 0.05). RESULTS: The addition of TiO2 NPs reduced C. albicans adhesion (p < 0.001). However, no significant difference was found between both concentrations within the same group before and after ultraviolet light activation (p > 0.05), except in the 1% dotted-layer (p = 0.022). Surface roughness and hardness were not affected by the additions of different concentrations of TiO2 NPs (p = 0.905) and (p = 0.059), respectively. Translucency was significantly reduced in all the groups (p < 0.001) except in the 1% dotted-layer (p = 0.332). Flexural strength decreased as the TiO2 NPs concentration increased, with the greatest reduction in strength observed in the one-layer group (p < 0.001). CONCLUSIONS: The double and dotted layering techniques were effective in reducing C. albicans adhesion, without affecting surface roughness, hardness, or flexural strength. However, translucency was reduced in all the groups, except the 1% dotted-layer group.

Assuntos

Antifúngicos, Polimetil Metacrilato, Polimetil Metacrilato/farmacologia, Teste de Materiais, Antifúngicos/farmacologia, Propriedades de Superfície, Bases de Dentadura, Candida albicans

RESUMO

STATEMENT OF PROBLEM: Fractures of interim fixed restorations are a common complication. The autopolymerized polymethyl methacrylate resin materials used for interim fixed restorations have limited mechanical properties, but whether adding treated zirconium dioxide nanoparticles improves mechanical properties is unclear. PURPOSE: The purpose of this in vitro study was to evaluate the effect of treated zirconium dioxide nanoparticles on the flexural strength and elastic modulus of autopolymerized polymethyl methacrylate resin. MATERIAL AND METHODS: A split-metal mold (60×10×3.3 mm) was used to fabricate 40 autopolymerized acrylic resin specimens. The specimens were divided into 4 groups (n=10) according to zirconium dioxide nanoparticle concentration: control (unmodified resin) and zirconium dioxide nanoparticle contents of 1, 2.5, and 5 wt%. The specimens were mixed and polymerized according to the manufacturer's instructions and stored in distilled water for 48 ±2 hours at 37 °C. The flexural strength and elastic modulus were evaluated based on the 3-point bend test where data were analyzed by using 1-way analysis of variance and Tukey post hoc tests (α=.05). RESULTS: The flexural strength of the 1-wt% zirconium dioxide nanoparticle specimens was significantly higher than that of the control group (P<.001) but did not significantly increase further with the higher nanoparticle content (P>.05). Elastic modulus significantly decreased with 2.5-wt% zirconium dioxide nanoparticles (P=.019), while no significant changes were found with other test groups (P>.05). CONCLUSIONS: The addition of treated zirconium dioxide nanoparticles at low concentrations increased the flexural strength of autopolymerized polymethyl methacrylate resins used in fixed interim restorations.

Assuntos

Resistência à Flexão, Nanopartículas, Polimetil Metacrilato, Teste de Materiais, Nanopartículas/uso terapêutico, Propriedades de Superfície, Maleabilidade, Estresse Mecânico