Comparison of CAD/CAM and Conventional Denture Base Resins: A Systematic Review

Analog and digital complete denture bases accuracy and dimensional stability: an in-vitro evaluation at 24 hours and 6 months

OBJECTIVES

The study aimed to evaluate the accuracy of 3D printed complete denture bases compared to analog and milling manufacturing.

METHODS

Denture bases (n=60) were created using three methods: milling (n=10), analog (flasking) (n=10), and 3D printing (n=40). The 3D printing group was further divided into subgroups and each of the material groups. All samples were scanned, and their surfaces were analyzed using 3D software (Geomagic Control X software, 3D Systems) to compare them to the reference model. The accuracy was assessed using root mean square (RMS) values, reflecting the average deviation between the denture bases and the reference model.

RESULTS

At 24 hours, the "Temp Print", from 3D printing group had the lowest RMS values (54.20±9.44 µm), indicating higher accuracy, while the "ProBase Hot" from the anlog group showed the highest discrepancies, particularly in the border areas. Over six months, all groups experienced increased RMS values, with the 3d pronted "Denture 3d+" group showing the most significant variations (194.1±49.63 µm). The "Temp Print" group maintained the lowest RMS values, indicating better stability at 6 months.

CONCLUSION

Despite some discrepancies, all denture bases remained within clinically acceptable limits (300 µm). Milled bases were the most stable between 24 hours and six months. In terms of accuracy and stability, 3D printed resins are suitable for both prototypes and definitive dentures. Further research is required to confirm the clinical acceptability of these materials.

CLINICAL SIGNIFICANCE

Accuracy in the fabrication of denture bases is paramount for ensuring proper fit, function, and comfort for patients. Analog, addictive and subtractive manufacturing methods of production obtained good dentures accuracy.

Comparison between relining of ill-fitted maxillary complete denture versus CAD/CAM milling of new one regarding patient satisfaction, denture retention and adaptation

PURPOSE

This study aimed to compare different treatment modalities to correct ill-fitted maxillary complete denture either by the conventional relining method or by scanning the relining impression and digitally construct a new denture regarding patient satisfaction, denture retention, and adaptation.

MATERIALS AND METHODS

Twelve edentulous patients suffering from loose maxillary complete dentures were selected, dentures' borders and fitting surfaces were prepared, and relining impressions were taken, the impressions were scanned and the STL files were used for CAD/CAM milling ( computer aided designing/ computer aided manufacturing) of new maxillary dentures (Group A), then the relining impression went through the conventional laboratory steps to fabricate (Group B) maxillary dentures. Both groups were evaluated regarding patient satisfaction by a specially designed questionnaire, retention values were measured by a digital force gauge at denture insertion appointment and two weeks later, geomagic software was used to evaluate dentures adaptation to oral tissues.

RESULTS

Both groups (A and B) were completely satisfied with their dentures except regarding esthetics, all group A and 50% of group B were satisfied. Both groups showed a statistically significant increase in retention values at the two-week follow-up period compared to those at denture insertion time, with higher values were for group B. Finally, the relined dentures showed better oral tissue adaptation than digitally constructed dentures.

CONCLUSION

Relined maxillary dentures showed better retention, esthetics, and denture adaptation with lower cost than digitally constructed maxillary dentures which showed acceptable retention and adaptation, with better time and data saving.

TRIAL REGISTRATION

Clinical trials number: NCT06366321. With registration date on ClinicalTrials.gov public website: 13/ 4/ 2024.

Effect of toothbrushing on surface roughness and gloss of CAD-CAM versus conventional interim materials with different surface treatments

STATEMENT OF PROBLEM

Characterizing interim restorations promotes esthetics. However, studies on the effects of characterization materials on the surface roughness and gloss of interim materials after toothbrushing are lacking.

PURPOSE

The purpose of this in vitro study was to evaluate the surface roughness and gloss of 5 different interim materials with different surface treatments after 1 year of simulated toothbrushing.

MATERIAL AND METHODS

Cuboid specimens (10×12×2 mm) were fabricated from each interim material: autopolymerized polymethyl methacrylate (UNIFAST Trad), autopolymerized bis-acryl composite resin (Protemp 4), light-activated composite resin (REVOTEK LC), milled polymethyl methacrylate block (DD provi P HI), and 3-dimensionally printed methacrylate oligomer (Nextdent C&B MFH). Each material was divided into 3 groups based on surface treatment (n=10): polishing, application of Lite Art and Resin Glaze, and application of OPTIGLAZE color. The specimens were subjected to 5000 and 10000 cycles of toothbrushing. The surface roughness and gloss were measured and separately analyzed by using 3-way repeated measures ANOVA (α=.05).

RESULTS

Significant interactions of the surface roughness and gloss among interim materials, surface treatments, and toothbrushing durations were found (P<.001). After 5000 and 10000 cycles, each polished material showed no significant difference in surface roughness compared with baseline: Protemp 4 (P>.999), REVOTEK LC (P>.999, P=.922), and Nextdent C&B MFH (P>.999), except for UNIFAST Trad and DD provi P HI (P<.001). Coating with Lite Art and Resin Glaze, as well as OPTIGLAZE color, significantly reduced surface roughness after both 5000 and 10000 cycles for all materials (application of Lite Art and Resin Glaze with UNIFAST TRAD (P<.001), Protemp 4 (P<.001), REVOTEK LC (P<.001), DD provi P HI (P<.001), and Nextdent C&B MFH (P<.001, P=.002), and application of OPTIGLAZE color with UNIFAST TRAD (P<.001), Protemp 4 (P<.001), REVOTEK LC (P<.001, P=.002), DD provi P HI (P<.001), and Nextdent C&B MFH (P<.001, P=.008)). Specimens with these treatments also exhibited significantly better gloss compared with the polished specimens (P<.001).

CONCLUSIONS

After 5000 to 10000 cycles of toothbrushing, Protemp 4, REVOTEK LC, and Nextdent C&B MFH, interim materials containing fillers, exhibited smoother surfaces compared with UNIFAST Trad and DD provi P HI, interim materials without fillers. Coating of all materials reduced surface roughness and increased gloss. After 5000 to 10000 cycles of toothbrushing, the surface roughness of each material remained stable; while the gloss decreased slightly, it remained within clinically acceptable levels.

Are There Clinical Differences Between 3D-Printed and Milled Complete Dentures? A Systematic Review and Meta-analysis

Limited studies assess clinical key factors in the success of digitally fabricated complete dentures between additive and subtractive methods. This study aimed to compare 2 determinants of clinical success-retention and patient satisfaction- in complete dentures fabricated using additive and subtractive approaches. PubMed, Scopus, Web of Science, Embase, Cochrane Library, and Google Scholar were searched up to August 2024. Records were screened by title, abstract, and full text against the eligibility criteria. The standardized mean difference (SMD) was calculated using the data extracted from each included study. A random effects model pooled the effect sizes, and heterogeneity was assessed with Cochran's Q test, I-squared, and Tau-squared indices; publication bias was evaluated using Begg's funnel plot and the Egger test, while sensitivity analyses checked result robustness. The risk of bias was assessed using the Cochrane RoB 2 and ROBINS-I tools. Of the initial 1098 records, a total of 4 articles were deemed eligible. Although mean denture retention was higher in the additive compared to the subtractive method, the difference was not statistically significant (SMD = 0.165 N, 95% CI = [-0.176, 0.506], P = .343, I² = 58.72%). Similarly, mean satisfaction was lower in the additive compared to the subtractive method, but this difference was not statistically significant (SMD = -0.595, 95% CI = [-1.579, 0.389], P = .236, I² = 85.94%). Considering the high heterogeneity and the small number of studies, it can be cautiously concluded that there is no significant difference between complete dentures fabricated by 3D printing and milling approaches.

Assessing the Current Landscape and Future Directions of Digital Denture Technology

Digital dentures are removable dental prostheses fabricated using computer-aided design/computer-aided manufacturing (CAD/CAM) technology. This study aimed to explore the trends in digital dentures. A comprehensive four-phase search and selection strategy was framed.

Dimensions and Lens.org databases were used. Boolean operators were used to combine keywords.

The most significant growth occurred by 2021, with 71 publications and 984 citations. Egypt had the highest publication rankings, with 46 total publications (TP) and 45 total citations (TC). The University of Geneva played a significant role in contributing to 16 TP and 491 TC. Egyptian Dental Journal ranked at the top. The group with four authors had an even higher number of authorships, with a total of 60. The top four keywords were CAD/CAM, 3D printing, CAD-CAM, complete denture, and digital dentistry. The Glossary of Prosthodontic Terms, Ninth Edition, was referenced 614 times and had the highest average number of citations (75.2). The top three writers had strong relationships with the three sources and preferred to publish using four keywords. The 11-author group, cluster 6, had the highest level of network cooperation.

In conclusion, research on digital dentures has grown in terms of number of articles and citations.

Time efficiency and cost of fabricating removable complete dentures using digital, hybrid, and conventional workflows: A systematic review

STATEMENT OF PROBLEM

Analysis of the cost and time efficiency of removable complete dentures (RCDs) fabricated using conventional and computer-aided design and computer-aided manufacturing (CAD-CAM) processes remains limited.

PURPOSE

The purpose of this systematic review was to evaluate the time efficiency and cost of conventional, hybrid, and completely digital workflows throughout the entire process of RCD fabrication.

MATERIAL AND METHODS

Article selection followed the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols (PRISMA-P) 2015 guidelines and was registered with the international prospective register of systematic reviews (PROSPERO). The bibliographic search covered the PubMed and Cochrane databases using keywords related to removable complete dentures, digital workflows, and economic factors and covered articles from January 2010 to June 2024. In total, 1188 articles were identified and assessed. A bottom-up search identified an additional 10 articles through cited works. Data on cost and time analyses were reported in a qualitative synthesis.

RESULTS

The qualitative synthesis included 8 articles published between 2015 and 2024 showing that digital and hybrid workflows generally reduced both clinical and laboratory time and overall costs compared with conventional workflows. The hybrid protocol required significantly less clinical time, with reductions ranging from approximately 1 to 4 hours. Hybrid and completely digital workflows reduced laboratory manufacturing time by approximately 6 to 7 hours compared with conventional workflows. Cost analyses revealed that digital and hybrid workflows were more profitable and cost effective than conventional workflows.

CONCLUSIONS

The findings suggest that digital and hybrid workflows for RCD fabrication are more time efficient and cost effective than conventional methods.

Influence of nanohydroxyapatite mouthwash on the growth of Candida albicans biofilm on milled denture surfaces: An in vitro study

PURPOSE

There is a need for effective solutions for the persistent prevalence of denture stomatitis (DS) in denture-wearing populations. This study assessed the impact of nanohydroxyapatite (nanoHAP) nanoparticles on Candida albicans biofilm formation on milled polymethylmethacrylate (PMMA) denture bases.

MATERIALS AND METHODS

Acquired salivary pellicle was formed on disks milled from a prepolymerized PMMA puck. The disks were assigned to two groups, A (n = 18) and B (n = 18), and each group was further subdivided into three subgroups (6/subgroup), each treated with either Polident solution (antibacterial denture cleanser), nanoHAP mouthwash, or distilled water. Disks in group A subgroups were soaked in their respective treatment solutions for 8 h, followed by biofilm formation on the disk for 24 h. Disks in group B subgroups had C. albicans biofilm formed on them for 24 h, followed by soaking in their respective treatment solutions for 8 h. Biofilm thickness, biomass, and live/dead cell ratio were determined using a confocal laser scanning microscope. Biofilm morphology was examined with a scanning electron microscope (SEM). Data were analyzed by ANOVA and Tukey-Kramer multiple comparisons (α = 0.05).

RESULTS

In group A, nanoHAP mouthwash displayed significant anti-adhesive properties. In group B, biofilm biomass and thickness significantly decreased (p < 0.05), with the nanoHAP showing the most substantial reduction in existing biofilm compared to other solutions, but it did not significantly affect cell viability.

CONCLUSIONS

This study demonstrated the efficacy of nanoHAP mouthwash in inhibiting C. albicans biofilm formation when used as a storage medium for acrylic dentures. It suggests its potential clinical application for preventing denture stomatitis in patients.

Effect of aging on dimensional accuracy and color stability of CAD-CAM milled and 3D-printed denture base resins: a comparative in-vitro study

BACKGROUND

There is a lack of studies comparing the dimensional accuracy and color stability of denture base resins made using computer-aided design and computer-aided manufacturing (CAD-CAM) milling, 3-dimensional (3D) printing, and conventional denture processing techniques. This makes it challenging to determine the best method to fabricate complete dentures. The objective of this in vitro investigation was to assess and contrast the color stability and dimensional accuracy of denture base resins that were 3D printed and CAD-CAM milled, both before and after aging by thermocycling using digital surface matching technology and a benchtop laser scanner without using a spray, to optimize adaptation of the denture base and cast to minimize any imperfections and to evaluate the impact of the denture cleansing solution on the stability of color.

METHODS

Evaluation of the dimensional accuracy (n = 27) was completed on a sectional maxillary stone cast using a digital 3D-surface matching software before and after 5000 thermocycles. A spectrophotometer was used to measure the color change (△E00) of all disc specimens (N = 54) before and after 500 thermocycles and immersion in denture cleansing solution for 30 cycles (3 min each) daily for 6 days. The Kruskal Wallis test, Dunn's post hoc test, Tukey's test with Bonferroni adjustment, one sample t test and independent t test were used to statistically analyze the data (α < 0.05).

RESULTS

Thermocycling decreased the dimensional accuracy of the heat polymerized group at all 5 locations and the 3D-printed group at locations 1, 3 and 5 (P > .05), while it had no significant difference on the CAD-CAM milled group at all locations (P < .05). The color change (△E00) was lowest in the CAD-CAM milled group, moderate in the heat-polymerized group and highest in the 3D-printed group. After immersion in denture cleanser, the color change (△E00) was significantly higher in the 3 groups compared with after thermocycling (P > .001).

CONCLUSIONS

CAD-CAM milled resins had the highest dimensional accuracy and the best color stability, conventional heat polymerized acrylic resins showed moderate change in dimensional accuracy and color stability, while the 3D- printed resin had the lowest dimensional accuracy and color stability after aging by thermocycling.

The wettability of complete denture base materials constructed by conventional versus digital techniques: an in-vitro study

BACKGROUND

Decreased salivary flow can make the patients uncomfortable with their complete dentures and affects the retention of the dentures. Milling and 3D printing have become an alternative to conventional denture construction techniques. The goal of this study was to evaluate the effect of conventional and digital techniques of the complete denture construction on the denture surface wettability with distilled water and saliva substitute before and after thermocycling.

METHODS

A total of 30 specimens were utilized in the present study. Specimens were divided according to the construction techniques into 3 groups (n = 10 each). Group I: Heat-polymerized polymethylmethacrylate (PMMA) group, group II: Milled group, and group III: 3-dimensional (3D)-printed group. All the specimens were subjected to 2000 cycles of thermal aging in a thermocycler. The wettability of all specimens to water and saliva substitute was measured via a contact angle goniometer (Olympus TGHM, Rame-hart Inc, USA) before and after thermocycling. Descriptive statistical analysis, plots, and the Shapiro-Wilk test were used to verify normality for each variable. One-way ANOVA was used to compare the 3 study groups, while paired samples t-test was used to compare the differences within each group (P < .05).

RESULTS

The smallest contact angle of drop of water to the denture base specimens before and after thermocycling were recorded in the milled group (53.0 ± 4.77 and 50.27 ± 2.30, respectively), followed by the heat polymerized PMMA group (85.65 ± 4.71 and 65.06 ± 2.27, respectively), and the 3D-printed group (91.34 ± 6.74 and 90.86 ± 8.57, respectively). While the smallest contact angle of drop of saliva substitute to denture base specimens was recorded in the milled group (56.82 ± 2.29 and 34.85 ± 7.51, respectively), followed by the 3D-printed group (72.87 ± 4.83 and 58.14 ± 9.58, respectively) and the heat polymerized PMMA group (83.62 ± 4.12 and 67.82 ± 4.93, respectively). There was statistically significant difference between the groups (P < .05). A significant decline in the average contact angle of drop of saliva has been reported in all groups after thermocycling. The contact angle values differed significantly between saliva substitute and distilled water in both 3D-printed and milled groups after thermocycling (P < .001).

CONCLUSIONS

The milled denture base material presented the best wettability to water and saliva substitute than the 3D-printed and the heat-polymerized PMMA materials. Saliva substitutes improve the wetting ability of denture base materials manufactured by CAD/CAM compared with water.

Effect of thermocycling on surface topography and fracture toughness of milled and additively manufactured denture base materials: an in-vitro study

BACKGROUND

Studies investigating thermocycling effect on surface topography and fracture toughness of resins used in digitally manufactured denture bases are few. The study aimed to assess the impact of thermocycling on surface topography and fracture toughness of materials used for digitally manufactured denture bases.

METHODS

Water sorption, solubility, hardness, surface roughness, and fracture toughness of both three-dimensional (3D)-printed and computer-aided design, computer-aided manufacturing (CAD-CAM) milled specimens (n = 50) were assessed both prior to and following 2000 thermocycles, simulating 2 years of clinical aging. Surface hardness (n = 10) was measured using a Vickers hardness testing machine, surface roughness (n = 10) was determined by a contact profilometer, and fracture toughness (n = 20) was measured using the 3-point bend test, then studying the fractured surfaces was done via a scanning electron microscope (SEM). Prior to and following thermocycling, water sorption and solubility (n = 10) were assessed. Normally distributed data was tested using two-way repeated ANOVA and two-way ANOVA, while Mann Whitney U test and the Wilcoxon signed ranks test were used to analyze data that was not normally distributed (α < 0.05).

RESULTS

Following thermocycling, Vickers hardness and fracture toughness of both groups declined, with a significant reduction in values of the 3D-printed resin (P < .001). The 3D-printed denture base resins had a rougher surface following thermocycling with a significant difference (P < .001). The sorption and solubility of water of both materials were not affected by thermocycling.

CONCLUSIONS

Before and after thermocycling, milled specimens had lower surface roughness and a greater degree of hardness and fracture toughness than 3D-printed specimens. Thermocycling lowered hardness and fracture toughness, and increased surface roughness in both groups, but had no effect on water sorption and solubility.

Effect of support structures on the trueness and precision of 3D printing dentures: An in vitro study

Purpose Additive manufacturing has revolutionized the fabrication of complete dentures. However, this process involves support structure, which is a construction part that holds the specimen during printing, and may prove to be disadvantageous. Therefore, this in vitro study compared the effect of support structure reduction on various volume and area distributions of a 3D-printed denture base to determine optimal parameters based on accuracy.Methods A complete maxillary denture base construction file was used as reference. Twenty denture bases were 3D printed under four conditions (total n=80): no support structure reduction (control), palatal support structure reduction (Condition P), border support structure reduction (Condition B), and palatal and border support structure reduction (Condition PB). Printing time and resin consumption were also recorded. The intaglio surface trueness and precision of all acquired data were exported to a 3D analysis software, and the dimensional changes to the denture base were analyzed using the root-mean-square estimate (RMSE) to assess geometric accuracy and generate color map patterns. Nonparametric Kruskal-Wallis and Steel-Dwass tests (α=0.05) analyzed the accumulated data.Results Control had the lowest RMSE values for trueness and precision. Nevertheless, it demonstrated a significantly lower RMSE than that of Condition B (P=0.02) in precision. Owing to negative deviation at the palatal region, Conditions P and PB had higher retention than Control and Condition B regarding the color map pattern.Conclusions Within the limitations of this study, the reduction of palatal and border support structures showed optimal accuracy with resource and cost savings.

Assessing the effect of Artemisia sieberi extracts on surface roughness and candida growth of digitally processed denture acrylic materials

BACKGROUND

Denture stomatitis, frequently encountered, is generally addressed symptomatically, with limited exploration of preventive approaches involving antifungal medicinal plants.

OBJECTIVE

This study assessed the impact of Artemisia sieberi extracts on the candida growth of conventional and digitally processed acrylic materials.

METHOD

Thirty acrylic resin discs (3 mm thickness × 10 mm diameter) were prepared by conventional or CAD/CAM technology (milling and 3D printing). The resin discs were exposed to simulated brushing, thermocycling, and immersion in Artemisia sieberi extract for 8 hours. The surface roughness of the discs was assessed at baseline and after immersion in Artemisia sieberi extract. Candida growth was quantified through colony-forming units (CFU/mL). Data was analyzed using SPSS v.22 (α⩽ 0.05).

RESULTS

Irrespective of the material type, the post-immersion surface roughness was significantly higher compared to pre-immersion values (p< 0.05). Candida growth was significantly higher in conventional acrylic materials than digitally fabricated acrylics (p< 0.05). At × 3, Ra and CFU were found to be moderately positive and non-significantly correlated (R= 0.664, p= 0.149). At × 4, Ra and CFU were found to be weak positive and non-significantly correlated (R= 0.344, p= 0.503).

CONCLUSION

Artemisia sieberi extracts had a notable impact on digitally fabricated denture acrylics, reducing candida albicans growth compared to conventional heat-cured acrylic. This suggests a potential role for these extracts in improving denture hygiene and preventing denture stomatitis, particularly in the context of digitally fabricated dentures.

The Shear Bond Strength between Milled Denture Base Materials and Artificial Teeth: A Systematic Review

The data about bond strength between digitally produced denture base resins and artificial teeth are scarce. Several studies investigated shear bond strength values of milled denture base resins and different types of artificial teeth. The purpose of the present study was to compare and evaluate the available evidence through a systematic review. A bibliographic search was conducted in PubMed, Scopus, and Web of Science to assess adequate studies published up to 1 June 2022. This review followed the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. The appropriate studies that determined the shear bond strength values between milled denture base resins and artificial teeth were selected. The initial search identified 103 studies, which were included in the PRISMA 2020 flow diagram for new systematic reviews. Three studies met the inclusion criteria, and all of them present a moderate risk of bias (score 6). Two studies found no statistical differences between heat-polymerized and CAD/CAM (milled) denture base materials when attached with different types of artificial teeth, while one study showed higher values of CAD/CAM (milled) denture base materials. Bonding agents ensure bonding strength at least similar to the conventional methods. In order to improve the quality of future studies, it would be advantageous to use a larger number of specimens with standardized dimensions and a blinded testing machine operator to decrease the risk of bias.

Hardness and surface roughness of differently processed denture base acrylic resins after immersion in simulated gastric acid

STATEMENT OF PROBLEM

The effect of gastric acid on the surface properties of denture base acrylic resin is unknown.

PURPOSE

The purpose of this in vitro study was to evaluate changes in the surface roughness and hardness of denture base acrylic resins after immersion in simulated gastric acid.

MATERIAL AND METHODS

Acrylic resin specimens (n=10) were prepared with 3 different processing techniques (compression-molded, injection-molded, and computer-aided design and computer-aided manufacturing [CAD-CAM] milled) and exposed to either gastric acid or artificial saliva (control). Surface roughness and hardness were measured at baseline (T0) and after 24-hour (T24) and 96-hour (T96) immersion in the solutions. The surface roughness and hardness data were analyzed by 3-way ANOVA and the Tukey HSD test (α=.05).

RESULTS

At T24, the greatest change in surface hardness was observed for compression-molded specimens in gastric acid (P<.05). At T96, changes in hardness values were higher in compression-molded specimens than those in milled specimens (P<.05). Regarding surface roughness, at T24, compression-molded and injection-molded specimens showed higher values than milled specimens in gastric acid (P<.05). Concerning specimens in artificial saliva, compression-molded specimens showed significantly higher changes in roughness than those of the others (P<.05). At T96, injection-molded specimens had the greatest roughness values (P<.05). Among specimens immersed in artificial saliva, milled specimens showed lower roughness values than the injection-molded or compression-molded specimens (P<.05).

CONCLUSIONS

Gastric acid exposure adversely affected the roughness and hardness of all the acrylic resins evaluated. CAD-CAM milled specimens showed better resistance to acid exposure after 24 and 96 hours in terms of roughness and hardness.

Color Stability Determination of CAD/CAM Milled and 3D Printed Acrylic Resins for Denture Bases: A Narrative Review

The aim of this paper is to review the available literature on the different methods for color stability determination of CAD/CAM milled and 3D printed resins for denture bases. The methodology included applying a search strategy, defining inclusion and exclusion criteria and selecting studies to summarize the results. Searches of PubMed, Scopus, and Embase databases were performed independently by three reviewers to gather the literature published between 1998 and 2022. A total of 186 titles were obtained from the electronic database, and the application of exclusion criteria resulted in the identification of 66 articles pertaining to the different methods for color stability determination of CAD/CAM acrylic resins for denture bases. Color change in dental materials is clinically very important for the dental operator, as it determines the clinical serviceability of the material. Discoloration of the denture bases can be evaluated with various instruments and methods. Dental resins may undergo color changes over time due to intrinsic and/or extrinsic factors. The extrinsic factors are considered the more frequent causes of color changes. According to a number of studies, CAD/CAM fabricated acrylics have achieved better color stability than the conventional PMMA (polymethyl methacrylate) resins.

Physical and Mechanical Properties of 3D-Printed Provisional Crowns and Fixed Dental Prosthesis Resins Compared to CAD/CAM Milled and Conventional Provisional Resins: A Systematic Review and Meta-Analysis

Newly introduced provisional crowns and fixed dental prostheses (FDP) materials should exhibit good physical and mechanical properties necessary to serve the purpose of their fabrication. The aim of this systematic literature review and meta-analysis is to evaluate the articles comparing the physical and mechanical properties of 3D-printed provisional crown and FDP resin materials with CAD/CAM (Computer-Aided Designing/Computer-Aided Manufacturing) milled and conventional provisional resins. Indexed English literature up to April 2022 was systematically searched for articles using the following electronic databases: MEDLINE-PubMed, Web of Science (core collection), Scopus, and the Cochrane library. This systematic review was structured based on the guidelines given by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). The focused PICO/PECO (Participant, Intervention/exposure, Comparison, Outcome) question was: ‘Do 3D-printed (P) provisional crowns and FDPs (I) have similar physical and mechanical properties (O) when compared to CAD/CAM milled and other conventionally fabricated ones (C)’. Out of eight hundred and ninety-six titles, which were recognized after a primary search, twenty-five articles were included in the qualitative analysis, and their quality analysis was performed using the modified CONSORT scale. Due to the heterogeneity of the studies, only twelve articles were included for quantitative analysis. Within the limitations of this study, it can be concluded that 3D-printed provisional crown and FDP resin materials have superior mechanical properties but inferior physical properties compared to CAD/CAM milled and other conventionally fabricated ones. Three-dimensionally printed provisional crowns and FDP materials can be used as an alternative to conventional and CAD/CAM milled long-term provisional materials.

Flexural Properties and Hardness of CAD-CAM Denture Base Materials

PURPOSE

To compare flexural strength, elastic modulus, and surface hardness of CAD-CAM milled, 3D-printed, and heat-polymerized denture base resins.

MATERIALS AND METHODS

A total of 120 specimens were fabricated from heat-polymerized acrylic resin (HP), milled resin (Avadent and IvoCad), and 3D-printed resin (ASIGA, FormLabs, and NextDent). The specimens were divided into 6 groups according to the type of denture base material n = 20/material, (10/flexural properties and 10/hardness). Flexural strength and elastic modulus of the specimens were evaluated by 3-point bending test and surface hardness by Vickers hardness test. To test flexural properties, the specimens were fabricated according to ISO 20795-1:2013 standards (64×10×3.3 ±0.2 mm). The dimensions for hardness test were 15×10×2.5 ±0.2 mm. Scanning electron microscope was used to evaluate the surface morphology of the fractured specimens. The means and standard deviations were calculated, followed by one-way ANOVA and Tukey post-hoc test (α = 0.05).

RESULTS

Milled resins showed significantly higher values for flexural strength, elastic modulus, and surface hardness, followed by HP then 3D-printed resins (P<0.001). In between milled groups, flexural strength of AvaDent was significantly higher than IvoCad (P<0.001), while elastic modulus and hardness didn't show significant difference. In between 3D-printed resins, ASIGA showed the highest flexural strength and elastic modulus, insignificantly with FormLabs (P = 0.595) and significantly with NextDent (P = 0.008). ASIGA also showed significantly the highest hardness among the 3D-printed groups. No significant difference was found between FormLabs and NextDent flexural strength (P = 0.357), elastic modulus (P = 1.00) and surface hardness (P = 0.987).

CONCLUSION

CAD-CAM milled resins had greater flexural properties and hardness compared to heat-polymerized acrylic resin and 3D-printed resins. Although 3D-printed samples showed the lowest values of tested properties, the flexural strength and modulus were above the clinically acceptable values. This article is protected by copyright. All rights reserved.