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Fakhr MWZF, Alansary H, Hassanien EEY. Internal fit and marginal adaptation of all-ceramic implant-supported hybrid abutment crowns with custom-milled screw-channels on Titanium-base: in-vitro study. BMC Oral Health 2024; 24:1073. [PMID: 39261788 PMCID: PMC11391652 DOI: 10.1186/s12903-024-04810-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2024] [Accepted: 08/26/2024] [Indexed: 09/13/2024] Open
Abstract
BACKGROUND Advancements in digital dentistry helped in custom-milling screw-channels in implant-supported restorations; however, the fit of these restorations is still unclear especially for contemporary computer aided designing/computer aided manufacturing (CAD/CAM) materials. This study aimed to compare the internal and marginal fit of Ultra translucent multilayered zirconia versus lithium disilicate implant-supported hybrid abutment crowns (HACs) constructed with custom-milled screw-channels on Titanium-base. MATERIALS AND METHODS A total of 24 HACs with custom-milled screw-channels were constructed from lithium disilicate (Group LDS) and Ultra translucent multilayered zirconia (Group UT) using digital workflow (n = 12). The internal and marginal gaps of HACs on their corresponding Titanium-bases were assessed using replica technique and stereomicroscope, respectively. After testing for normality, quantitative data were expressed as mean and standard deviation and compared using independent t-test at a level of significance (P ≤ 0.05). RESULTS There was no statistically significant difference between Group LDS and Group UT in terms of marginal and internal fit. The internal and marginal gaps in both groups were within the accepted values reported in literature. CONCLUSIONS UT and LDS HACs with custom-milled screw-channels demonstrated comparable and acceptable internal fit and marginal adaptations to Ti-base, which lied within the range reported in literature.
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Affiliation(s)
- Marwa Wagih Zaky Fouad Fakhr
- Fixed Prosthodontics Department, Faculty of Dentistry, Cairo University, 11 EL-Saraya St. Manial, Cairo, 11553, Egypt.
| | - Hesham Alansary
- Fixed Prosthodontics Department, Faculty of Dentistry, Cairo University, 11 EL-Saraya St. Manial, Cairo, 11553, Egypt
| | - Eman Ezzat Youssef Hassanien
- Fixed Prosthodontics Department, Faculty of Dentistry, Cairo University, 11 EL-Saraya St. Manial, Cairo, 11553, Egypt
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Rizk A, Abdou A, Samy AM, Mahmoud N, Omar S. Vertical marginal gap and internal fit of virgilite-based lithium disilicate glass ceramic veneers with different preparation designs. J Prosthodont 2024. [PMID: 39248202 DOI: 10.1111/jopr.13937] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2023] [Accepted: 08/17/2024] [Indexed: 09/10/2024] Open
Abstract
PURPOSE To evaluate and compare internal fit and marginal adaptation of conventional lithium disilicate (LDS) glass ceramics and LDS containing virgilite computer-aided design and manufacturing (CAD-CAM) blocks before and after aging. MATERIALS AND METHODS Seventy-two epoxy replicated dies from two prepared maxillary right central incisors acrylic typodont were divided into two groups of different preparation designs (n = 36): Group I, incisal butt-joint, and Group P, incisal overlap. Each group was further subdivided into two equal groups according to ceramic material (n = 18): Group E, IPS e.max CAD, and Group T, Tessera advanced lithium disilicate (ALD) CAD-CAM blocks. The replica technique was used to assess the internal fit using a stereomicroscope at 45× magnification. Laminate veneers were cemented to their corresponding epoxy dies, then the vertical marginal gap was evaluated before and after thermal cycling. Repeated measures analysis of variance (ANOVA) were used for marginal fit data and 2-way ANOVA for internal fit measurements (α = 0.05). RESULTS For internal fit, there were no significant differences between tested groups. For vertical marginal gap results, two-way ANOVA showed that only aging had a significant effect on the vertical marginal gap (p < 0.001), while different CAD-CAM materials and preparation designs did not affect the vertical marginal gap. CONCLUSIONS The vertical marginal gap and internal fits of IPS e.max CAD and CEREC Tessera CAD for both preparation designs were comparable. Aging significantly affected the vertical marginal gap of the laminate veneers of both materials and both preparation designs; however, all were within clinically acceptable ranges before and after aging.
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Affiliation(s)
- Amr Rizk
- Department of Prosthetic Dentistry, Faculty of Dentistry, King Salman International University, South Sinai, Egypt
| | - Ahmed Abdou
- Department of Restorative Dentistry, Faculty of Dentistry, Universiti Malaya, Kuala Lumpur, Malaysia
| | - Amira Mohammad Samy
- Department of Conservative Dentistry, Faculty of Oral and Dental Medicine, Badr University in Cairo, Cairo, Egypt
| | - Nouran Mahmoud
- Department of Prosthodontics, Faculty of Oral and Dental Medicine, Badr University in Cairo, Cairo, Egypt
| | - Sarah Omar
- Department of Prosthodontics, Faculty of Oral and Dental Medicine, Badr University in Cairo, Cairo, Egypt
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Silva SEGD, Silva NRD, Santos JVDN, Moreira FGDG, Özcan M, Souza RODAE. Accuracy, adaptation and margin quality of monolithic zirconia crowns fabricated by 3D printing versus subtractive manufacturing technique: A systematic review and meta-analysis of in vitro studies. J Dent 2024; 147:105089. [PMID: 38772449 DOI: 10.1016/j.jdent.2024.105089] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2024] [Revised: 04/28/2024] [Accepted: 05/18/2024] [Indexed: 05/23/2024] Open
Abstract
OBJECTIVE The purpose of this systematic review and meta-analysis was to evaluate the accuracy (trueness and precision), marginal and internal adaptation, and margin quality of zirconia crowns made by additive manufacturing compared to subtractive manufacturing technology. METHODS The investigation adhered to the PRISMA-ScR guidelines for systematic reviews and was registered at the Prospero database (n°CRD42023452927). Four electronic databases, including PubMed, Scopus, Embase, and Web of Science and manual search was conducted to find relevant studies published until September 2023. In vitro studies that assessed the trueness and precision, marginal and internal adaptation, and margin quality of printed crowns compared to milled ones were included. Studies on crowns over implants, pontics, temporary restorations, laminates, or exclusively experimental materials were excluded. RESULTS A total of 9 studies were included in the descriptive reporting and 7 for meta-analysis. The global meta-analysis of the trueness (P<0.74,I2=90 %) and the margin quality (P<0.61,I2=0 %) indicated no significant difference between the root mean square of printed and milled zirconia crowns. The subgroup analysis for the printing system showed a significant effect (P<0.01). The meta-analysis of the crown areas indicated no significant difference in most of the areas, except for the marginal (favoring milled crowns) and axial (favoring printed crowns) areas. For precision and adaptation, both methods showed a clinically acceptable level. CONCLUSIONS Additive manufacturing technology produces crowns with trueness and margin quality comparable to subtractive manufacturing. Both techniques have demonstrated the ability to produce crowns with precision levels, internal discrepancy, and marginal fit within clinically acceptable limits. CLINICAL SIGNIFICANCE 3D printing emerges as a promising and potentially applicable alternative method for manufacturing zirconia crowns, as it shows trueness and margin quality comparable to restorations produced by the subtractive method.
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Affiliation(s)
- Sarah Emille Gomes da Silva
- Federal University of Rio Grande do Norte (UFRN), Department of Dentistry, Av. Salgado Filho, 1787, Lagoa Nova, Natal, RN, CEP 59056-000, Brazil
| | - Nathalia Ramos da Silva
- Federal University of Rio Grande do Norte (UFRN), Department of Dentistry, Av. Salgado Filho, 1787, Lagoa Nova, Natal, RN, CEP 59056-000, Brazil
| | - João Vitor do Nascimento Santos
- Federal University of Rio Grande do Norte (UFRN), Department of Dentistry, Av. Salgado Filho, 1787, Lagoa Nova, Natal, RN, CEP 59056-000, Brazil
| | - Fernanda Gurgel de Gois Moreira
- Federal University of Rio Grande do Norte (UFRN), Department of Dentistry, Av. Salgado Filho, 1787, Lagoa Nova, Natal, RN, CEP 59056-000, Brazil
| | - Mutlu Özcan
- University of Zurich, Clinic for Masticatory Disorders and Dental Biomaterials, Center for Dental Medicine, Zentrum für Zahnmedizin, Plattenstrasse, 11, 8032 Zurich, Switzerland
| | - Rodrigo Othávio de Assunção E Souza
- Federal University of Rio Grande do Norte (UFRN), Department of Dentistry, Av. Salgado Filho, 1787, Lagoa Nova, Natal, RN, CEP 59056-000, Brazil.
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Mosaddad SA, Peláez J, Panadero RA, Ghodsi S, Akhlaghian M, Suárez MJ. Do 3D-printed and milled tooth-supported complete monolithic zirconia crowns differ in accuracy and fit? A systematic review and meta-analysis of in vitro studies. J Prosthet Dent 2024:S0022-3913(24)00283-X. [PMID: 38772783 DOI: 10.1016/j.prosdent.2024.04.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2023] [Revised: 04/03/2024] [Accepted: 04/04/2024] [Indexed: 05/23/2024]
Abstract
STATEMENT OF PROBLEM Additive (3-dimensional printing) and subtractive (milling) methods are digital approaches to fabricating zirconia restorations. Comparisons of their resultant fabrication accuracy and restoration fit are lacking. PURPOSE The purpose of this systematic review and meta-analysis was to evaluate the accuracy and fit of monolithic zirconia crowns fabricated by 3-dimensional printing and milling. MATERIAL AND METHODS The PubMed (Medline), Scopus, Embase, Web of Science, Cochrane Library, and Google Scholar databases were searched up to August 2023. Eligible records were included, and the standardized mean difference (SMD) analyzed 4 outcomes: marginal fit, intaglio fit, trueness, and precision. Publication bias was analyzed with Trim-and-fill, the Egger regression test, and Begg funnel plot. Methodological quality was rated using the QUIN tool. RESULTS A total of 15 publications were found eligible out of the initial 6539 records. The 3-dimensional printing group demonstrated a lower marginal fit (SMD=1.46, 95% CI=[0.67, 2.26], P<.001; I2=83%, P<.001) and trueness (SMD=0.69, 95% CI=[0.20, 1.18], P=.006; I2=88%, P<.001) and a significantly higher precision (SMD=-2.19, 95% CI=[-2.90, -1.48], P<.001; I2=56%, P=.045). The intaglio fit did not differ significantly across the study groups (SMD=0.77, 95% CI=[-0.22, 1.77], P=.127; I2=87%, P<.001). CONCLUSIONS Given the high degree of heterogeneity, it can be cautiously concluded that while 3-dimensional printing led to greater precision, the outcomes of the 2 accuracy and adaptation parameters most crucial to the longevity of the restorations-trueness and marginal fit-showed the superiority of the milling technique.
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Affiliation(s)
- Seyed Ali Mosaddad
- Researcher, Department of Conservative Dentistry and Bucofacial Prosthesis, Faculty of Odontology, Complutense University of Madrid, Madrid, Spain; and Adjunct Faculty Member, Department of Research Analytics, Saveetha Dental College and Hospitals, Saveetha Institute of Medical and Technical Sciences, Saveetha University, Chennai, India.
| | - Jesús Peláez
- Adjunct Professor, Department of Conservative Dentistry and Bucofacial Prosthesis, Faculty of Odontology, Complutense University of Madrid, Madrid, Spain.
| | - Rubén Agustín Panadero
- Professor, Department of Stomatology, Faculty of Medicine and Dentistry, Valencia University, Valencia, Spain
| | - Safoura Ghodsi
- Associate Professor, Dental Research Center, Dentistry Research Institute, Department of Prosthodontics, Tehran University of Medical Sciences, Tehran, Iran
| | - Marzieh Akhlaghian
- Assistant Professor, Department of Prosthodontics, School of Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran
| | - María J Suárez
- Professor, Department of Conservative Dentistry and Bucofacial Prosthesis, Faculty of Odontology, Complutense University of Madrid, Madrid, Spain
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Baig MR, Qasim SSB, Baskaradoss JK. Marginal and internal fit of porcelain laminate veneers: A systematic review and meta-analysis. J Prosthet Dent 2024; 131:13-24. [PMID: 35260253 DOI: 10.1016/j.prosdent.2022.01.009] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Revised: 01/01/2022] [Accepted: 01/04/2022] [Indexed: 11/22/2022]
Abstract
STATEMENT OF PROBLEM Marginal integrity and internal adaptation are key to the long-term success of porcelain laminate veneers. Evidence for their marginal and internal fit is unclear, and the factors affecting such fit have not been identified. PURPOSE The purpose of this systematic review and meta-analysis was to summarize the scientific literature assessing the effects of various parameters on the marginal and internal fit of porcelain laminate veneers. MATERIAL AND METHODS An electronic search was conducted to identify all relevant published articles on the fit accuracy of ceramic veneers between January 2000 and June 2021 in the PubMed-MEDLINE, Scopus, Embase, Google Scholar, and Web of Science databases. Information, including the study outcomes, in terms of the mean marginal gap, internal gap, and absolute marginal discrepancies of porcelain laminate veneers, was extracted from the selected studies. The inverse-variance random effects model was used to analyze the pooled results and estimate the overall effect based on the heterogeneity of studies (α=.05). RESULTS Twenty-one studies were selected for analysis, 2 clinical and 19 in vitro. The risk of bias was "medium" for most studies (19 of 21), and only 2 studies were classified as "high risk." A mean difference of -4.53 μm (95% CI: -21.46 to 12.41) was found, with no statistically significant difference in marginal gap between the pressed and milled fabrication modes (P=.600). As for the internal gap, significant differences were found (mean difference=-40.56 μm; 95% CI: -76.54 to -4.58), with pressed veneers performing better (P=.030). Butt joint preparation design produced significantly (P=.002) lower marginal gaps than the palatal chamfer (mean difference=-14.02 μm; 95% CI: -23.07 to -4.98). CONCLUSIONS No significant differences were found between the pressed and milled porcelain laminate veneers for marginal gap, but for the internal gap, the differences were significantly in favor of the pressed type. The butt joint veneer preparation design was significantly better than the palatal chamfer design in terms of marginal fit.
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Affiliation(s)
- Mirza Rustum Baig
- Associate Professor, Department of Restorative Sciences (Prosthodontics), Faculty of Dentistry, Kuwait University, Kuwait City, Kuwait.
| | - Sayed Saad Bin Qasim
- Assistant Professor, Department of Bioclinical Sciences (Dental Materials), Faculty of Dentistry, Kuwait University, Kuwait City, Kuwait
| | - Jagan Kumar Baskaradoss
- Assistant Professor, Department of Developmental and Preventive Sciences (Dental Public Health), Faculty of Dentistry, Kuwait University, Kuwait City, Kuwait
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Chantler JGM, Evans CDJ, Zitzmann NU, Derksen W. Clinical performance of single implant prostheses restored using titanium base abutments: A systematic review and meta-analysis. Clin Oral Implants Res 2023; 34 Suppl 26:64-85. [PMID: 37750524 DOI: 10.1111/clr.14128] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Revised: 06/16/2023] [Accepted: 06/21/2023] [Indexed: 09/27/2023]
Abstract
PURPOSE The aim of this review was to evaluate the survival rates of restorations utilizing titanium base abutments (TBA) for restoring single-unit implant prostheses. MATERIALS AND METHODS This review was conducted following the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines. The focus question was: In patients who require the restoration of a single dental implant utilizing a titanium base abutment, what are the determining factors and outcomes relating to implant prosthesis prognosis and survival? A comprehensive search of databases (PubMed, EMBASE, and Cochrane Library) was conducted on 16 April 2023 and updated on 5 May 2023. Randomized clinical trials (RCT), retrospective studies and prospective studies, reporting on the use of TBA for single implant prostheses, were reviewed. A Cochrane collaboration risk of bias assessment analysis was performed for randomized clinical studies, and the Newcastle-Ottawa Scale tool was applied for non-randomized studies. A meta-analysis was performed on clinical trials reporting on survival rates of both TBA and other abutments. Other clinical studies, reporting on TBA only, were included for descriptive statistics. RESULTS The search provided 1159 titles after duplicates were removed. Six RCTs were included to perform a meta-analysis and compare the survival of the TBA to other abutments [OR 0.74; 95% CI: 0.21-2.63, heterogeneity; I2 0%; p = .99]. Twenty-three prospective and retrospective studies fulfilled the criteria and were included in the meta-analysis after 12 months of function. A total of 857 single implant-supported prostheses fabricated with a TBA were included. TBA abutments have an estimate 98.6% survival rate after 1 year in function (95% CI: 97.9%-99.4%). The mean follow-up period was 31.2 ± 16.9 months. CONCLUSIONS Single implant prosthesis restored with titanium base abutments showed favourable short-term survival rates.
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Affiliation(s)
| | | | - Nicola U Zitzmann
- Department of Reconstructive Dentistry, University of Basel, Basel, Switzerland
| | - Wiebe Derksen
- Department of Oral Implantology and Prosthetic Dentistry, Amsterdam, Netherlands
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Abualsaud R, Alalawi H. Fit, Precision, and Trueness of 3D-Printed Zirconia Crowns Compared to Milled Counterparts. Dent J (Basel) 2022; 10:dj10110215. [PMID: 36421402 PMCID: PMC9689223 DOI: 10.3390/dj10110215] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2022] [Revised: 11/08/2022] [Accepted: 11/09/2022] [Indexed: 11/13/2022] Open
Abstract
Precise fit of a crown and accurate reproduction of the digital design are paramount for successful treatment outcomes and preservation of clinician and technician time. The study aimed to compare the internal fit, marginal adaptation, precision, and trueness of 3D-printed zirconia crowns compared to their milled counterpart. A total of 20 monolithic 3 mol% yttria stabilized-zirconia crowns (n = 10) were made using computer-assisted design (CAD) followed by additive (3D-printed) and subtractive (milled) manufacturing. Digital scanning of the master die with and without a fit checker followed by image superimposition, and analysis was performed to evaluate internal and marginal adaptation in four areas (occlusal, axial, marginal, and overall). ISO 12836:2015 standard was followed for precision and trueness evaluation. Statistical analysis was achieved using a t-test at α = 0.05. Internal fit and marginal adaptation revealed no significant difference between the two test groups (p > 0.05). The significant difference in trueness (p < 0.05) was found between the two groups in three areas (occlusal, axial, and internal). The best and worst trueness values were seen with 3D-printed crowns at occlusal (8.77 ± 0.89 µm) and Intaglio (23.90 ± 1.60 µm), respectively. The overall precision was statistically better (p < 0.05) in the 3D-printed crowns (9.59 ± 0.75 µm) than the milled (17.31 ± 3.39 µm). 3D-printed and milled zirconia crowns were comparable to each other in terms of internal fit and marginal adaptation. The trueness of the occlusal and axial surfaces of 3D-printed crowns was better, whereas the trueness of fitting surface of milled crowns was better. 3D-printed crowns provided a higher level of precision than milled crowns. Although the internal and marginal fit of both production techniques were comparable, 3D printing of zirconia produced more precise crowns.
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Effect of repeated millings on the surface integrity of diamond burs and roughness of different CAD/CAM materials. Clin Oral Investig 2022; 26:5325-5337. [PMID: 35449245 DOI: 10.1007/s00784-022-04500-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Accepted: 04/13/2022] [Indexed: 11/03/2022]
Abstract
OBJECTIVES This study evaluated the surface integrity of two types of diamond burs and their effect on the roughness of different CAD/CAM materials. MATERIALS AND METHODS CAD/CAM materials, Vita Mark II (VM), IPS e.max CAD (EM), Celtra Duo (CD), G-Ceram (GC), and Lava Ultimate (LU) blocks were milled with CEREC MCXL. Five pairs of pointed cylinder burs (CB) and step burs (SB) were used repeatedly. The wear rate of burs was analyzed before and after milling with a scanning electron microscope (SEM) and weighing the burs. The milling time of the blocks at different milling stages was recorded from 2 (M2) to 8 times (M8) of use. The surface roughness (Ra) of blocks was measured with a profilometer. Data from the differences in surface roughness were analyzed using univariate analyses of variance and Kruskal-Wallis tests (alpha = 0.05). RESULTS For M2, the highest roughness (2.12 ± 0.1 μm) was observed with the VM block. EM blocks presented the highest roughness values (1.82 ± 0.3 μm, 1.85 ± 0.1 μm, and 1.86 ± 0.04 μm) at M4, M6, and M8, respectively. While the highest Ra values were observed for VM (2.12 to 1.43 µm), LU provided the lowest mean Ra (1.62 to 1.33 µm) among the tested materials. After the repeated use of burs up to 8 times, the surface roughness of all the tested materials decreased. Milling of LU resulted in chip deposits on the CB surface in SEM images. The duration of cutting was higher for CD and EM materials than those of other materials, but the milling duration for VM, GC, and LU blocks was similar. SB burs exhibited more wear than CB after repeated milling. CONCLUSIONS A repeated number of millings more than 4 times decreased the surface integrity of the milling burs, increased the surface roughness of CAD/CAM blocks except for LU, and increased the milling duration. Increased material hardness was more detrimental on bur surface integrity. CLINICAL RELEVANCE During milling CAD/CAM blocks, clinicians should note that the surface integrity of milling burs decreases after 4 times of use as a function of material hardness where step burs wear quicker than pointed cylinder burs.
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Effects of repeated use of tungsten carbide burs on the surface roughness and contact angles of a CAD-CAM PMMA denture base resin. J Prosthet Dent 2022; 128:1358-1362. [PMID: 35012770 DOI: 10.1016/j.prosdent.2021.11.032] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Revised: 11/30/2021] [Accepted: 11/30/2021] [Indexed: 11/22/2022]
Abstract
STATEMENT OF PROBLEM The surface roughness (Ra) and wettability of complete denture base materials must meet certain clinical requirements. Although computer-aided design and computer-aided manufacturing (CAD-CAM) systems have recently become popular for the fabrication of complete dentures, the effects of the repeated usage of milling burs on the surface properties of CAD-CAM denture base acrylic resins have not yet been fully investigated. PURPOSE The purpose of this in vitro study was to evaluate the effects of new and used burs on the Ra and contact angles (wettability) of a CAD-CAM polymethylmethacrylate (PMMA) denture base material. MATERIAL AND METHODS A total of 40 Ø2×10-mm disks were fabricated from 1 brand of CAD-CAM PMMA resin (Polident). Half of the specimens (group N) were milled with a new tungsten carbide bur set, while the other half (group U) was milled with a used tungsten carbide bur set. Moreover, half of the specimens (groups NT and UT) were subjected to thermocycling before Ra and contact angle testing. Ra was tested by using a profilometer, and the surfaces were also examined by scanning electron microscopy (SEM). The contact angle was measured by using the sessile drop method. Data were analyzed with the Kruskal-Wallis and Dunn Pairwise Comparison tests (α=.05). RESULTS The mean contact angle was highest for group U (80 degrees) and lowest for group UT (66 degrees) (P<.05). Ra values were highest for group N (1.3 μm) and lowest for group U (0.93 μm) (P<.05). CONCLUSIONS Specimens milled with new tungsten carbide burs had lower mean contact angles and higher Ra values than specimens milled with used burs. The contact angles of CAD-CAM PMMA resin specimens milled with used burs decreased significantly after thermocycling. Regardless of whether or not thermocycling was performed, contact angle values decreased as Ra values increased.
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