CAD/CAM produces dentures with improved fit

Digital versus conventional complete dentures: A randomized, controlled, double-blinded crossover trial

STATEMENT OF PROBLEM

The Baltic Denture System provides a digital way to fabricate complete dentures in 2 visits. Conventional dentures using injection or compression molding require additional visits and complex laboratory procedures. However, how the fabrication method affects clinical outcomes is unclear.

PURPOSE

The purpose of this clinical, randomized, controlled, double-blinded crossover trial was to evaluate the impact of the fabrication method (digital versus conventional production) of complete dentures on clinical outcomes.

MATERIAL AND METHODS

Sixteen participants received 2 pairs of new complete dentures, produced in a digital and a conventional workflow. Each complete denture was worn for an observation period of 3 months. The order of the dentures was randomized. The primary outcome was the clinical assessment of the dentures by a blinded examiner, including peripheral extension, cutout for buccal and labial frenula, denture extension, and denture thickness. Denture esthetics were evaluated by the midline, position of anterior teeth, buccal corridor, and smile arc, and occlusal relationships were evaluated by the vertical dimension, sagittal relation, the Camper plane, and occlusion. In addition, the retention of maxillary and mandibular dentures and phonetics was evaluated. Differences between the prostheses were statistically analyzed with the McNemar test (α=.05).

RESULTS

The borders of the digital dentures were significantly more often overextended at the time of insertion (P=.021), reducing the retention of the digital dentures, especially the maxillary dentures (P=.016). The borders of the dentures could be corrected so that after 2 weeks and 3 months, no significant differences could be seen between digital dentures and conventional dentures.

CONCLUSIONS

The fabrication method has a significant influence only on the dimension of the denture border. It was significantly more often overextended in digital dentures and impaired retention, especially of the maxillary dentures, at the time of insertion. As this parameter is correctable, no significant clinical differences could be observed over the observation time of 3 months between digital dentures and conventional dentures.

Flexural strength of repaired denture base materials manufactured for the CAD-CAM technique

PURPOSE

To evaluate the flexural properties of repaired poly(methylmethacrylate) (PMMA) denture base materials for computer-aided design/computer-aided manufacturing (CAD-CAM) and to compare them with heat-activated polymerized PMMA.

METHODS

A total of 288 specimens (65 × 10 × 2.5 mm) were prepared using both CAD-CAM and conventional blocks and repaired using autopolymerizing and visible-light polymerizing (VLC) materials. Microwave energy, water storage and hydroflask polymerization were applied as additional post-polymerization cycles after the repair process. The flexural strength (FS) of the specimens was evaluated using the three-point bending test. Data were evaluated statistically using 2-way ANOVA followed by Bonferroni's correction to determine the significance of differences between the groups (P ≤ 0.05).

RESULTS

The FS of the denture base materials for CAD-CAM was significantly higher than that for the heat-activated group (P ≤ 0.05). The FS was significantly highest when microwave energy was used for the post-polymerization cycle. The FS values for all groups repaired with VLC resin were significantly lower than for the autopolymerization group (P ≤ 0.05).

CONCLUSION

The flexural properties of denture base materials for CAD-CAM repaired using autopolymerizing acrylic resins can recover by 50-70%. Additional post-polymerization cycles for autopolymerizing repair resin can be suggested to improve the clinical service properties of repaired dentures.

Fit and retention of complete denture bases: Part I - Conventional versus CAD-CAM methods: A clinical controlled crossover study

STATEMENT OF PROBLEM

Clinical evidence is sparse on whether dentures fabricated by computer-aided design and computer-aided manufacturing (CAD-CAM) methods afford superior fit and retention when compared with those fabricated conventionally.

PURPOSE

The purpose of this clinical controlled crossover study was to evaluate the peak retention force and fit of CAD-CAM manufactured (3D printed and milled) maxillary complete denture bases and conventional heat-polymerized bases (control).

MATERIAL AND METHODS

Twenty participants with edentulous maxillary arches were recruited. Impressions were made with a border-molded custom tray, and the resulting definitive cast was scanned. The conventional base was manufactured on the definitive cast with a hook and a 45-degree platform with a central notch and 2 lateral notches. The scan of the definitive cast was used for the fabrication of a milled and a printed base. The platform and hook position on the conventional base were transferred digitally to the milled and printed bases. All bases were scanned. A traction dynamometer was orientated into the notches, and retention was evaluated in the post dam and tuberosity areas. Scans were imported into a comparison software program which matched scans to their corresponding reference and performed a 3-dimensional comparison. The Friedman and Wilcoxon tests were used to compare between groups (confidence interval: 95%, α=.05).

RESULTS

Nineteen participants with a mean ±standard deviation age of 64.1 ±14.7 years completed all clinical sessions. No significant difference in peak retention was measured between milled (MB1), printed (PB1), and conventional (CB) bases in the post dam (CB: 12.44 ±9.62 N, PB1: 16.08 ±15.28 N, MB1: 14.52 ±17.07 N) and right tuberosity area (CB: 8.99 ±7.82 N, PB1: 11.28 ±9.57 N, MB1: 11.99 ±12.10 N). In the left tuberosity area, peak retention was lower for CB (10.03 ±8.39 N) than PB1 (14.98 ±14.72 N) and MB1 (13.55 ±15.53 N; P=.05). Compared with the definitive cast, the fit of the conventional base (0.18 ±0.01 mm) was closer than the printed (0.21 ±0.03 mm) and milled bases (0.21 ±0.02 mm) (P<.001).

CONCLUSIONS

The CD bases manufactured by CAD-CAM techniques provided retention and fit similar to that of conventionally manufactured bases and can therefore be considered suitable techniques.

Challenges and Solutions in Clinical Workflow for the Rehabilitation of Completely Edentulous Patients Through CAD/CAM Dentures: A Case Study

In the field of removable prosthodontics, computer-aided design and computer-aided manufacturing (CAD/CAM) have become widely recognized. The traditional method, which uses heat-polymerized resins for injection or compression molding, necessitates up to five patient visits and laborious laboratory processes. A digital workflow combined with a CAD/CAM methodology can provide prompt prosthesis delivery for patients with time constraints. This article's goal is to outline the steps and the limitations in the fabrication of digital dentures as well as the challenges, limitations, and solutions developed while developing a clinical workflow for the rehabilitation of completely edentulous patients with the CAD/CAM System.

Denture relining using digital replication method: A dental technique

The aim of this report was to digitize traditional denture relining using a digital duplication method, in addition to assessing the wear resistance of three-dimensional (3D) printed denture teeth. A complete denture was relined using light body impression. The denture with impression was scanned yielding a standard tessellation language file that was designed to print the denture base and teeth. The printed teeth were fitted into the sockets of the printed denture base and then bonded using auto-polymerized acrylic resins, followed by finishing and polishing. Dentures were inserted and fit and occlusion were adjusted as needed, and the patient was scheduled for follow-up appointments at one week, three months, and six months. At each follow-up visit, dentures were scanned using a 3Shape E3 desktop scanner and scans were superimposed. The occlusal wear was assessed in reference to the first scan after the denture insertion visit. The accuracy of the intaglio surface of dentures was within clinically acceptable limits. The clinical evaluation of inserted dentures in terms of retention, occlusion, esthetic, and patient satisfaction was encouraging. Using digital duplication, conventional dentures could be relined. The advantages of digital records include eliminating polymerization dimensional changes, and reducing cost and clinical time by minimizing the number of visits, which is particularly helpful with geriatric patients.

Effect of repair and surface treatments on the strength of digitally fabricated resin-based dental prostheses: A systematic review of in vitro studies

OBJECTIVE

This review investigated the current literature pertaining to the repairability of computer-aided design-computer-aided manufacturing (CAD-CAM) milled and three-dimensional (3D) printed resin-based dental prostheses (RBDPs) as well as the appropriate surface treatment for each repair material that will produce adequate repair bond strength.

DATA/SOURCES

PubMed, Web of Science, and Scopus databases were searched for published articles involving repair of CAD-CAM RBDPs between January 2010 and June 2023. Data were collected and analyzed to reveal the surface treatment effects, suggested repair materials, and strength of repaired RBDPs.

STUDY SELECTION

Out of 164 retrieved titles, 11 studies were included, of which five investigated the repair of 3D-printed RBDPs, three investigated the repair of CAD-CAM milled resins, and three investigated both materials. Additionally, of the included studies, seven investigated denture base resins, three studied provisional restoration resins, and one evaluated 3D-printed intraoral splints. Various surface treatments were suggested, with air-abrasive methods being the most commonly used. Different materials for resin repair were proposed and used, including auto-polymerized, reline, and composite resins. For 3D-printed resins, repair with Bis-acrylic/Bis-GMA composites improved repair strength.

CONCLUSION

Surface treatments positively affected the repair strength of conventional and milled RBDPs. However, challenges remain relevant to the repair of 3D-printed resins owing to composition mismatches and fabrication techniques. Therefore, further investigation is required to develop new 3D-printed resins.

CLINICAL SIGNIFICANCE

CAD-CAM milled resins have satisfactory repair strength, which increases with surface treatment. The repair of 3D-printed resins has proven challenging even with surface treatments. However, composite resins are the materials of choice.

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.

Effect of digital complete dentures manufactured using the custom disk method on masticatory function

Statement of problem

The effect of using the custom disk method (CDM) for fabricating digital dentures on patients' masticatory function should be studied to support its use in clinical practice.

Purpose

To investigate the effect of digital dentures fabricated using CDM on patients' masticatory function.

Material and methods

This single-center prospective clinical study included 20 patients with edentulous maxillary and mandibular arches who used a complete denture. The digital impression and complete denture manufacturing procedures using CDM have already been reported by Kanazawa et al. (2018) [32] and Soeda et al. (2022) [18] Thedigital dentures fabricated with CDM were delivered to the participants, and periodic adjustments were made until the patient could use the denture without pain. A color-changeable chewing gum, two types of gummy jellies that can evaluate the masticatory function, and pressure-sensitive sheets were used to evaluate the participants' masticatory function at baseline, 1 month, and 6 months following adjustment of the new digital complete dentures fabricated with CDM. These masticatory function values had already been measured in the previous conventional dentures and were recorded as baseline values.

Results

The study participants included 8 women and 12 men (mean age, 77.6 years). The color-changeable chewing gum analysis indicated that there was no significant improvement of masticatory function from baseline to 1 M (P = .083) and 6 M (P = .157).The gummy jelly analysis indicated no significant differences between the masticatory function baseline and 1 month (P = .387); however, a significant improvement was observed from baseline to 6 months (P = .020). Tests with Glucolum indicated a significant improvement from baseline to 1 month (P = .012) and 6 months (P = .003). The maximum bite force and occlusal contact area showed no significant difference at any time point.

Conclusions

Significant improvement in masticatory function was observed upon evaluation with gummy jelly and Glucolum 6 months after delivering the new digital complete dentures. Under limited conditions, the digital denture fabricated using CDM resulted in good recovery of the masticatory function in elderly edentulous patients. The present results combined with the cost-effectiveness and patient satisfaction associated with CDM indicate its clinical utility.

Additively manufactured CAD-CAM complete dentures with intraoral scanning and cast digitization: A controlled clinical trial

PURPOSE

To assess, clinically, patient satisfaction of additively manufactured complete dentures with intraoral scanning and hybrid cast digitization in comparison with conventional complete dentures.

MATERIALS AND METHODS

Participants who were edentulous in both arches were recruited and received three types of complete dentures (CDs): conventionally manufactured with conventional impression (CC), additively manufactured with intraoral scanning (AMI), and additively manufactured with cast digitization (AMH). Definitive impressions of the edentulous arches were made with medium viscosity polyvinyl siloxane (Hydrorise Monophase; Zhermack, Italy) for the CC group, intraoral scanning (TRIOS 4; 3Shape, Copenhagen, Denmark) for the AMI group, and laboratory scanning of the definitive casts (Ceramill Map400 AMANNGIRRBACH, Pforzheim, Deutschland) for the AMH group. The trial dentures of the CC group were scanned for occlusion registrations of the AMI and AMH groups and were used to guide the designing process (Exocad 3.0 Galway; Exocad GmbH). The AMI and AMH dentures were additively manufactured with a vat-polymerization 3D printer (Sonic XL 4K; phrozen, Taiwan). Patient satisfaction and clinical outcome were assessed with OHIP EDENT, and 14-factor criteria, respectively. Statistical analyses were performed with paired sample t-test and one-way repeated measure ANOVA for satisfaction, Wilcoxon signed rank test for clinical outcome, and Pearson's r (r) for effect size, with α = 0.05.

RESULTS

A total of 20 participants were included. Satisfaction had no statistically significant difference within or among the groups (p < 0.105). Within-group comparison between the two arches showed no statistical significance for the clinical outcome except for a significantly higher maxillary AMI score (p = 0.01, r = -0.40 with medium effect size). For among group's comparison; AMI had a significantly lower score than CC for the maxillary and mandibular arches (p = 0.01, r = -0.40, medium effect size, and p = 0.003, r = -0.47, medium effect size), and significantly lower score than the mandibular AMH (p = 0.03, r = -0.47, medium effect size), with significantly lower quality in teeth arrangement and retention domains for the AMI, and teeth arrangement for the AMH, in comparison with CC.

CONCLUSIONS

Patient satisfaction with both types of additively manufactured dentures is comparable to conventional dentures. The comparable overall clinical outcomes between hybrid and conventional dentures indicate that additive manufacturing is an acceptable clinical substitute for the conventional methods. However, additively manufactured dentures made with intraoral scanning have lower clinical quality and retention than hybrid and conventional dentures, particularly for the mandibular arch. Teeth arrangement of both additively manufactured dentures is clinically inferior to the conventional denture.

CAD/CAM full-mouth rehabilitation of an elderly patient: One-piece digital complete denture meets multilayered zirconia with gradient technology

OBJECTIVE

This article highlights a CAD/CAM complete-mouth rehabilitation in an 82-year-old patient by means of a complete maxillary prosthesis and mandibular implant- and tooth-supported fixed restorations made from multilayered zirconia.

CLINICAL CONSIDERATIONS

Comprehensive complete-mouth rehabilitations in elderly patients with adaptation of the occlusal vertical dimension (OVD) often present particular challenges. This applies especially when exacting functional and esthetic requirements are to be met and the treatment should not cause the patient too much effort, still ensuring the highest level of quality and efficiency and a low intervention rate.

CONCLUSION

The digital approach used for the present patient allowed for an efficient treatment procedure, facilitated virtual evaluations using a face-scan, and enhanced the predictability of the prosthodontic outcome. The approach enabled some steps required in the conventional protocol to be omitted, resulting in a straightforward clinical treatment with minimal strain on the patient.

CLINICAL SIGNIFICANCE

Because of the comprehensive recording of extraoral and intraoral data, for example with a facial scanner, it was possible to transfer a digital replica of the patient to the dental laboratory technician. With this protocol, many steps can be performed in the absence of the real patient.

Comparative Evaluation of the Digital Workflow and Conventional Method in Manufacturing Complete Removal Prostheses

The aging population in developed countries has increased the number of edentulous patients and, therefore, the need for prosthetic rehabilitation to improve their quality of life. Complete dentures are the main treatment option in these cases. The use of CAD/CAM (Computer Aided Design/Computer Aided Manufacturing) in dentistry has improved clinical protocols and outcomes, achieving a reduction in work time and economic costs for the patients. The main objective of this review was to compare the characteristics of conventional and digital dentures, attempting to determine whether the use of new technologies represents an improvement in the properties of removable complete dentures. A bibliographic review was carried out in the PubMed/MEDLINE, Cochrane Library, Scielo, and Embase databases. With the initial search, 157 articles were obtained. After applying the inclusion and exclusion criteria, 64 publications were selected for this bibliographic review. The different conclusions of the studies consulted were compared regarding fit and retention, fracture resistance, surface roughness, biocompatibility, and aesthetics, taking into account the different methods of prostheses fabrication. In general, digital prostheses have shown better mechanical properties and, consequently, better biocompatibility and aesthetics than conventional prostheses. However, the obtained results were very heterogeneous, preventing a supported conclusion.

Flexural Strength Analysis of Different Complete Denture Resin-Based Materials Obtained by Conventional and Digital Manufacturing

PMMA (Polymethylmethacrylate) is the material of choice to fabricate denture bases. Recently, with the introduction of CAD-CAM and 3D printers in dentistry, new materials have been proposed for complete denture manufacturing.

AIM

This study compared the flexural strength of different resins fabricated using different technologies (conventional, CAD-CAM-milled, and 3D-printed) and polymerization techniques.

METHODS

A total of 11 different resins were tested: six PMMA conventional (Acrypol R, Acrypol LL, Acrypol HI, Acrypol Fast, Acryself and Acryslef P), two milled obtained from UDMA PMMA disks (Ivotion disk and Aadva disk, control groups), two 3D-printed PMMA resins (NextDent Denture 3D+, and SprintRayEU Denture Base), and one 3D-printed composite resin (GC Temp Print). Flexural strength was measured using a universal testing machine. One-way ANOVA and Bonferroni post hoc tests were performed; the p-value was set at 0.05 to consider statistically significant differences among the groups. Spearman test was used to evaluate the correlation between polymerization technique and the flexural strength of 3D-printed resins.

RESULTS

CAD-CAM-milled specimens showed the highest flexural strength (107.87 MPa for UDMA) followed by 3D-printed composite resins (102.96 MPa). Furthermore, 3D-printed resins polymerized for 40 min with the BB cure unit showed no statistically significant differences with conventional resin groups. Moreover, in all the 3D-printed specimens, a high correlation between polymerization technique and flexural strength was found.

CONCLUSIONS

In terms of flexural strength, the polymerization technique is a determinant for both acrylic and composite resins. Temp Print can be a potential alternative to fabricating removable dentures and showed promising results when used in combination with pink color resin powder.

The effects of different surface treatments applied to milled PMMA denture base material on repair bond strength

The high cost of CAD/CAM systems and materials is a severe economic burden. Therefore, repair of CAD/CAM PMMA, selecting appropriate repair materials, and surface modifications are clinically important. This study aims to evaluate the shear bond strength of PMMA repair materials after various surface treatments on CAD/CAM PMMA denture base material. For this purpose, a total of 480 CAD/CAM PMMA denture base test specimens were manufactured. Then all test specimens were divided into 6 groups, and different surface treatments were applied. Group A: sandblasting, Group B: 4% hydro fluoric acid, Group C: tungsten carbide bur, Group D: dichloromethane + methyl methacrylate mixture, Group E: dichloromethane and methyl methacrylate, Group F: no surface treatment. Each group is then divided into 4 different subcategories; repair processes were performed using; heat-cured acrylic resin (n:20), auto-polymerized acrylic resin (n:20), gingiva composite (n:20), and CAD/CAM PMMA tooth material (n:20). After repairs, thermal aging was applied to half of the test specimens in each subcategory. The shear bond strength value was measured with a universal test device. Sandblasting group showed the highest surface roughness value in all test specimens (p < 0.001). Heat-cured acrylic resin with sandblasting exhibited the highest bond strength, while the untreated gingiva composite resin exhibited the lowest value. Thermal aging decreased bond strength in all repair materials (p < 0.001). Among the surface treatment groups, sandblasting with Al2O3 particles exhibited the highest surface roughness value and repair bond strength. The application of organic solvents to the surface increased the surface roughness and repair bond strength. Applying dichloromethane and methyl methacrylate monomer separately is more effective than applying it as a mixture. The ideal bonding among repair materials was obtained with heat-cured acrylic resin.

Fit Accuracy of Complete Denture Base Fabricated by CAD/CAM Milling and 3D-Printing Methods

OBJECTIVE

 Digital complete denture fabrication can be accomplished by either milling or three-dimensional (3D)-printing approach in which minimal distortion during processing contributes to effective denture base adaption, which leads to good denture retention. The purpose of this study was to compare the fit accuracy of milled and 3D-printed complete denture bases.

MATERIALS AND METHODS

 The reference edentulous maxillary arch model was scanned to generate virtual denture bases using computer-aided manufacturing software that exports as standard tessellation language files. Denture bases were constructed using a milling and 3D-printing technique using digital light processing method (n = 10). Intaglio surfaces of denture bases were scanned and superimposed on the reference model. The fit accuracy was quantified as root mean square error and evaluated statistically using independent t-test comparisons with a significance level of 0.05.

RESULTS

 Milled denture bases were significantly more accurate in adaptation than 3D-printed dentures in the overall intaglio area and primary bearing area of denture bases. 3D-printed denture bases demonstrated significantly greater accuracy in adaptation than milled denture bases in the peripheral/posterior palatal seal area.

CONCLUSION

 Milled denture bases fit better in the overall and primary stress-bearing areas than 3D-printed dentures, while 3D-printed dentures appeared more accurate in the peripheral seal area, which had a minor undercut that is not suitable for using milling technology.

Experimental Study on Mechanical Properties of Different Resins Used in Oral Environments

Background and Objectives: Acrylic resins remain the materials of choice for removable prosthesis due to their indisputable qualities. The continuous evolution in the field of dental materials offers practitioners today a multitude of therapeutic options. With the development of digital technologies, including both subtractive and additive methods, workflow has been considerably reduced and the precision of prosthetic devices has increased. The superiority of prostheses made by digital methods compared to conventional prostheses is much debated in the literature. Our study's objective was to compare the mechanical and surface properties of three types of resins used in conventional, subtractive, and additive technologies and to determine the optimal material and the most appropriate technology to obtain removable dentures with the highest mechanical longevity over time. Materials and Methods: For the mechanical tests, 90 samples were fabricated using the conventional method (heat curing), CAD/CAM milling, and 3D printing technology. The samples were analyzed for hardness, roughness, and tensile tests, and the data were statistically compared using Stata 16.1 software (StataCorp, College Station, TX, USA). A finite element method was used to show the behavior of the experimental samples in terms of the crack shape and its direction of propagation. For this assessment the materials had to be designed inside simulation software that has similar mechanical properties to those used for obtaining specimens for tensile tests. Results: The results of this study suggested that CAD/CAM milled samples showed superior surface characteristics and mechanical properties, comparable with conventional heat-cured resin samples. The propagation direction predicted by the finite element analysis (FEA) software was similar to that observed in a real-life specimen subjected to a tensile test. Conclusions: Removable dentures made from heat-cured resins remain a clinically acceptable option due to their surface quality, mechanical properties, and affordability. Three-dimensional printing technology can be successfully used as a provisional or emergency therapeutic solution. CAD/CAM milled resins exhibit the best mechanical properties with great surface finishes compared to the other two processing methods.

Accuracy of tooth positioning in 3D-printing aided manufactured complete dentures: An in vitro study

PURPOSE

In this study, we propose a 3D printing-aided method for manufacturing complete dentures and evaluate its accuracy of artificial tooth positioning.

METHODS

Complete dentures were designed and 3D printed and put on a plaster cast; and pack and press technique was used to fabricate the final denture during which artificial teeth were inserted in the teeth holes formed by the printed denture. In this study, fused deposition moulding (FDM) and stereolithography (SLA) techniques were used to fabricate complete dentures (10 pairs of maxillary and mandibular dentures each). After 3D scanning the final dentures, 3D comparison between the scanned teeth on the denture and its computer-aided design (CAD) data was made and single-tooth deflection angles were measured to evaluate the tooth position. Values were compared using independent-sample t-tests or the Mann-Whitney U test.

RESULTS

In the result of 3D comparison, the root mean square values of artificial teeth were 0.107 ± 0.018 mm (SLA group) and 0.136 ± 0.023 mm (FDM group; P < 0.05). In the result of single-tooth deflection angles, the mandibular anterior teeth demonstrated the maximum deflection angle, followed by the molars, premolars, and maxillary anterior teeth.

CONCLUSIONS

It is feasible to fabricate complete dentures using 3D-printed complete dentures as prototypes and combine conventional methods. The accuracy of the final denture fabricated using SLA printing was better than that of dentures produced using the FDM method.

CLINICAL SIGNIFICANCE

The 3D printing-aided manufacturing for complete dentures refers to using the 3D-printed dentures as a prototype along with the traditional process to fabricate final dentures and is an effective alternative when the dentures cannot be directly processed using computer-aided manufacturing (CAM).

Analysis of the trueness and precision of complete denture bases manufactured using digital and analog technologies

PURPOSE

Digital technology has enabled improvements in the fitting accuracy of denture bases via milling techniques. The aim of this study was to evaluate the trueness and precision of digital and analog techniques for manufacturing complete dentures (CDs).

MATERIALS AND METHODS

Sixty identical CDs were manufactured using different production protocols. Digital and analog technologies were compared using the reference geometric approach, and the Δ-error values of eight areas of interest (AOI) were calculated. For each AOI, a precise number of measurement points was selected according to sensitivity analyses to compare the Δ-error of trueness and precision between the original model and manufactured prosthesis. Three types of statistical analysis were performed: to calculate the intergroup cumulative difference among the three protocols, the intergroup among the AOIs, and the intragroup difference among AOIs.

RESULTS

There was a statistically significant difference between the dentures made using the oversize process and injection molding process (P < .001), but no significant difference between the other two manufacturing methods (P = .1227). There was also a statistically significant difference between the dentures made using the monolithic process and the other two processes for all AOIs (P = .0061), but there was no significant difference between the other two processes (P = 1). Within each group, significant differences among the AOIs were observed.

CONCLUSION

The monolithic process yielded better results, in terms of accuracy (trueness and precision), than the other groups, although all three processes led to dentures with Δ-error values well within the clinical tolerance limit.

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.

Intaglio surface trueness of milled and 3D-printed digital maxillary and mandibular dentures: A clinical study

STATEMENT OF PROBLEM

While the dimensional accuracy of the intaglio surface of a removable complete denture is key to its adaptation, comfort, and clinical performance, information on the ability of milling and 3D-printing workflows to accurately reproduce this surface is lacking.

PURPOSE

The purpose of this clinical study was to compare the trueness of the intaglio surface of milled and 3D-printed removable complete digital dentures.

MATERIAL AND METHODS

Intraoral scans were obtained from 14 participants for a total of 20 edentulous arches. Ten maxillary and 10 mandibular denture bases were then designed and fabricated with a completely digital workflow, both with milling and 3D-printing. Fabricated dentures were digitized with the same intraoral scanner used to obtain intraoral digital scans of the edentulous arches. Standard tessellation language (STL) files of the printed and milled denture bases were used for 3D analysis and comparisons with the STL file of the corresponding designed denture base. Specifically, a reverse engineering software program was used to trim and extract intaglio surfaces, align them, and measure their global mean 3D distance. In order to evaluate the homogeneity of production accuracy of each manufacturing process, the intaglio surfaces were also divided into several regions of interest and the corresponding 3D distances measured. Within- and between-group differences and maxillary and mandibular dentures differences were assessed with parametric and nonparametric tests (α=.05).

RESULTS

Milling showed a global better trueness of the entire intaglio surface (-0.002 mm) than 3D-printing (0.018 mm), both for the whole data set (P<.001) and for maxillary (P=.032) or mandibular (P=.049) denture base subgroups. Within each fabrication technology, maxillary (P<.11) and mandibular dentures (P=.2) showed no significant difference in trueness. Measured deviations were significantly different from zero for the 3D-printed dentures (P<.001), but not for the milled dentures (P=.487). Additionally, for milled dentures, no significant difference in trueness was found among the 11 regions of interest identified for the maxillary dentures (P=.085) and the 13 regions of interest for the mandibular dentures (P=.211). Conversely, 3D-printing showed significant variations in trueness among the same zones of interest, both in maxillary (P<.001) and mandibular (P=.004) dentures.

CONCLUSIONS

Within the limits of the manufacturing methodologies used for complete dentures, milling can provide a slightly better trueness of the intaglio surface than 3D-printing, with less variation across several zones of interest. However, given the magnitude of such differences, they may be reasonably considered to be of limited, if any, clinical significance.

Does Multifunctional Acrylate's Addition to Methacrylate Improve Its Flexural Properties and Bond Ability to CAD/CAM PMMA Block?

This study investigated the effects of a multifunctional acrylate copolymer-Trimethylolpropane Triacrylate (TMPTA) and Di-pentaerythritol Polyacrylate (A-DPH)-on the mechanical properties of chemically polymerized acrylic resin and its bond strength to a CAD/CAM polymethyl methacrylate (PMMA) disk. The methyl methacrylate (MMA) samples were doped with one of the following comonomers: TMPTA, A-DPH, or Trimethylolpropane Trimethacrylate (TMPTMA). The doping ratio ranged from 10 wt% to 50 wt% in 10 wt% increments. The flexural strength (FS) and modulus (FM) of PMMA with and without comonomer doping, as well as the shear bond strength (SBS) between the comonomer-doped PMMA and CAD/CAM PMMA disk, were evaluated. The highest FS (93.2 ± 4.2 MPa) was obtained when doped with 20 wt% of TMPTA. For TMPTMA, the FS decreased with the increase in the doping ratio. For SBS, TMPTA showed almost constant values (ranging from 7.0 to 8.2 MPa) regardless of the doping amount, and A-DPH peaked at 10 wt% doping (8.7 ± 2.2 MPa). TMPTMA showed two peaks at 10 wt% (7.2 ± 2.6 MPa) and 40 wt% (6.5 ± 2.3 MPa). Regarding the failure mode, TMPTMA showed mostly adhesive failure between the CAD/CAM PMMA disk and acrylic resin while TMPTA and A-DPH showed an increased rate of cohesive or mixed failures. Acrylate's addition as a comonomer to PMMA provided improved mechanical properties and bond strength to the CAD/CAM PMMA disk.

Evaluation of a novel 3D-printed custom tray for the impressions of edentulous jaws

PURPOSE

The purpose of this study was to evaluate a novel 3D-printed custom tray for impressions of edentulous jaws, and to compare it with conventional impression trays.

METHODS

Fifteen edentulous patients were enroled to evaluate the accuracy and border extension of a novel custom tray in the shape of a complete denture. Four impressions were made for each patient. Impressions made using novel custom trays were considered the experimental group, impressions made using conventional custom trays were considered the control group, and impressions made using final dentures and non-pressure custom trays were considered the reference groups. The experimental and control groups were compared with the reference groups using three-dimensional (3D) comparison analysis, and the impressions were further divided into regions. The root mean square (RMS) value was calculated to analyse the differences in impression morphology. Additionally, the experimental and control groups were compared to analyse border extension at standard locations.

RESULTS

Compared to the final denture impression as a reference, the diagnostic denture impression (RMS:0.146 ± 0.024 mm) was closer to the reference than the conventional impression (RMS:0.176 ± 0.047 mm), with a significant difference only in the secondary stress-bearing area. The border extension of the diagnostic denture impression was slightly longer than the conventional impression; however, the difference was not statistically significant.

CONCLUSIONS

The impressions made using the novel custom tray were similar to those made with a definitive complete denture. However, no significant differences were noted when compared with the conventional impressions.

Misfit of Implant-Supported Zirconia (Y-TZP) CAD-CAM Framework Compared to Non-Zirconia Frameworks: A Systematic Review

Objective: The aim of the study was to systematically review the overall outcomes of studies comparing the misfit of yttria-stabilized zirconia (Y-TZP) CAD-CAM implant-supported frameworks with frameworks fabricated with other materials and techniques. Methods: An electronic literature search of English literature was performed using Google Scholar, Scopus, Web of Science, MEDLINE (OVID), EMBASE, and PubMed, using predetermined inclusion criteria. Specific terms were utilized in conducting a search from the inception of the respective database up to May 2022. After the search strategy was applied, the data were extracted and the results were analyzed. The focused question was: Is the misfit of the implant-supported zirconia CAD-CAM framework lower than that of non-Y-TZP implant-supported fixed restorations? Results: Eleven articles were included for qualitative assessment and critical appraisal in this review. In the included studies, Y-TZP CAD-CAM implant-supported frameworks were compared to Titanium (Ti), Ni-Cr, Co-Cr, PEEK and high-density polymer, and cast and CAD-CAM frameworks. The studies used scanning electron microscopy, one-screw tests, digital or optical microscopy, 3D virtual assessment, and replica techniques for analyzing the misfit of frameworks. Six studies showed comparable misfits among the Y-TZP CAD-CAM frameworks and the controls. Three studies showed higher misfits for the Y-TZP CAD-CAM frameworks, whereas two studies reported lower misfits for Y-TZP CAD-CAM implant frameworks compared to controls. Conclusion: Y-TZP CAD-CAM implant-supported frameworks have comparable misfits to other implant-supported frameworks. However, due to heterogeneity in the methodologies of the included studies, the overall numerical misfit of the frameworks assessed in the reviewed studies is debatable.

An Updated Review of Salivary pH Effects on Polymethyl Methacrylate (PMMA)-Based Removable Dental Prostheses

Salivary pH is a neglected factor that may affect the performance of removable dental prostheses (RDP). This study aimed to review literature in reference to the role of salivary pH on the performance of RDP and materials used for their fabrication. From January 1990 until December 2021, a search was done on PubMed, Scopus, and Web of Science databases using removable dental prostheses, salivary pH, PMMA, Denture base, and physical properties as keywords. Articles that met the inclusion criteria (full-length articles have investigated the effect of salivary pH on RDP materials in vitro and in vivo) were included. Out of 433 articles, 8 articles that met the inclusion criteria were included. All studies used artificial saliva with different salivary pH ranging between 3 and 14. Two articles investigated the role of salivary pH on the cytotoxicity of denture base resins and soft liner. One article studied the durability and retention of attachments, one article analyzed the performance of PEEK materials, one article researched the fatigue resistance of a denture base, one article investigated the corrosion of RPD framework cast and milled Co–Cr, one article studied the strength and clasp retention and deformation of acetal and PEEK materials, and one evaluated changes in mass and surface morphology of CAD–CAM fiber-reinforced composites for the prosthetic framework. Different salivary pH affected all included materials in this review except PEEK materials. The most adverse effect was reported with alkaline and acidic; however, the acidic showed the most deterioration effect. Salivary pH has a role in the selection of material used for RDP fabrication.

Tissue Surface Adaptation and Clinical Performance of CAD-CAM Milled versus Conventional Implant-Assisted Mandibular Overdenture

Purpose

To evaluate the surface adaptation and maximal biting force of CAD-CAM milled mandibular overdenture (CAD-CAM MOD) compared to conventional compression mold mandibular overdenture (CC MOD).

Materials and Methods

Ten completely edentulous subjects with persistent complaints of their complete mandibular dentures were received four dental implants in the anterior mandible. Three months after osseointegration, subjects were randomly received either conventional compression mold or CAD-CAM MOD in a crossover design. To assess tissue surface adaptation, the fitting surfaces of each denture base were scanned and placed on the reference master cast. Three and six months after each overdenture was inserted, clinical performance in the form of maximum biting force was evaluated.

Results

The results of this study indicated that the tissue surface adaptation of the CAD-CAM MOD bases was significantly better than the conventional (compression mold technique) processed bases where (P=0.0001). Regarding clinical performance (maximum biting force), the CAD-CAM MOD exhibited better clinical performance (P=0.0001).

Conclusions

In denture processing methods, the CAD-CAM overdenture delivered more precise adaption and clinical performance than the compression mold technique.

In Vitro Analysis of Shear Stress: CAD Milled vs Printed Denture Base Resins with Bonded Denture Tooth

PURPOSE

As the fabrication of computer-aided design (CAD) milled and 3D printed denture base resins with bonded denture teeth increase in popularity, there is a need for research comparing the shear bond stress of milled and printed denture base resins with bonded denture teeth to that of a conventional heat processed denture base.

MATERIALS AND METHODS

Denture base resin specimens (n = 9) were fabricated according to manufacturers' instructions using a novel test design. Two milled (Ivobase CAD PMMA, Ivoclar Vivadent and Polident PMMA, Polident Dental) and two 3D printed (Denture Base LP Resin, Formlabs and Lucitone Digital Print, Dentsply Sirona) materials were used. Conventional heat processed polymethylmethacrylate was used as the control (Lucitone 199, Dentsply Sirona). Denture teeth (VITA Vitapan XL T44, #8, VITA Zahnfabrik) were bonded to their respective bases using denture tooth bonding agent (Ivobase CAD bonding system, Ivoclar). Specimens were aged in water for 600 hours at 37°C and loaded until failure in a Universal testing machine. Shear bond stress was calculated. All specimens were evaluated for mode of failure and select specimens under scanning electron microscope and vertical scanning interferometry. Data were analyzed with one-way ANOVA followed by Tukey test (IBM SPSS) and fracture analysis performed.

RESULTS

Shear stress was highest for the heat processed control (mean = 180 N ±26.76) and Polident test groups (mean = 180 N ± 34.90). Milled specimens were not significantly different from the control (p = 0.076 for IvoBase CAD and 1.00 for Polident), while the printed groups were significantly different from the control (p = 0.012 for Formlabs Denture Base Resin and p = 0.00 for Carbon Lucitone Digital Print). Milled denture base resins performed similarly to heat processed denture base resin and better than 3D printed denture bases.

CONCLUSION

For complete denture wearers, all resin materials used in this study may be clinically acceptable, as the sheer stress for all groups was higher than the reported maximum biting force of complete denture patients. However, for implant retained prostheses, the incorporation of additional retentive features should be considered when bonding denture teeth to printed bases. More research is needed to evaluate methods to increase the bond strength of denture teeth to printed denture base resins.

Assessment of Conventionally and Digitally Fabricated Complete Dentures: A Comprehensive Review

CAD/CAM technology is gaining popularity and replacing archaic conventional procedures for fabricating dentures. CAD/CAM supports using a digital workflow reduce the number of visits, chair time, and laboratory time, making it attractive to patients. This study aimed to provide a comparative review of complete dentures manufactured using CAD/CAM and conventional methods. The PubMed/Medline, Science Direct, Cochrane, and Google Scholar databases were searched for studies published in English within the last 11 years (from 2011 to 2021). The keywords used were “computer-engineered complete dentures”, “CAD/CAM complete dentures”, “computer-aided engineering complete dentures”, and “digital complete dentures”. The search yielded 102 articles. Eighteen relevant articles were included in this review. Overall, computer-engineered complete dentures have several advantages over conventional dentures. Patients reported greater satisfaction with computer-engineered complete dentures (CECDs) due to better fit, reduced chair time, shorter appointments, and fewer post-insertion visits. CAD/CAM allows for precision and reproducibility with fewer procedures compared to conventional dentures. Polymethyl methacrylate is used as the denture base material for conventional dentures. For CECDs, the resin can be modified and cross-linked to improve its mechanical properties. The advantages of CECDs include a reduced number of appointments, saving chairside time, a digital workflow allowing easy reproducibility and greater patient satisfaction with a better fit.

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.

Comparison of Dimensional Changes Between CAD-CAM Milled Complete Denture Bases and 3D Printed Complete Denture Bases: An In Vitro Study

PURPOSE

This study compared the dimensional changes between the computer-aided design and computer-aided manufacturing (CAD-CAM) milled complete denture bases (CDBs) and three-dimensional (3D) printed CDBs.

MATERIALS AND METHODS

One maxillary completely edentulous stone model was fabricated with three reference points at the incisive papilla, right molar, and left molar areas marked as X, Y, and Z, respectively. It was scanned to produce a standard tessellation language (STL) file, which was imported to a metal milling machine software to produce the metal model. This metal model was used to fabricate 30 CDBs for analysis in this study. The CDBs were divided into three groups (n = 10 each) according to the fabrication method used as follows: Group 1, CAD-CAM milled CDBs; Group 2, 3D printed CDBs; and Group 3, conventional compression molded CDBs. The CDBs of all groups were scanned after fabrication, and the dimensional changes in each were evaluated by two methods. The first was the two-dimensional evaluation method that involved linear measurement of the distances between the reference points (X-Y, X-Z, and Y-Z) of the scanned reference cast and dentures. The second method was the 3D evaluation method that involved the superimposition of the STL files of the dentures on the STL file of the reference cast. Data were calculated and were statistically analyzed using one-way analysis of variance and Tukey's pairwise post hoc tests.

RESULTS

There was a significant difference in the dimensional accuracy between the CAD-CAM milled, 3D printed, and conventional compression molded CDBs (P<0.05).

CONCLUSION

The dimensional accuracy of the CAD-CAM milling system in complete denture fabrication is superior to that of the compression molding and 3D printing systems. This article is protected by copyright. All rights reserved.

Comparison of the Accuracy between Denture Bases Produced by Subtractive and Additive Manufacturing Methods: A Pilot Study

Today, two different types of CAD-CAM fabrication methods for complete denture bases are available besides the conventional protocols: a subtractive milling process from a prepolymerized block of polymethylmethacrylate and an additive manufacturing process that built the denture base using a light-cured liquid in a VAT-polymerization process. The aim of this study was to evaluate and to compare the accuracy and precision of denture prosthetic bases made with subtractive and additive manufacturing technologies and to compare them with a denture base with the conventional method in muffle. From the results obtained, 3D printing dentures show a statistically significant higher accuracy than milled prosthetic bases. Milled prosthetic bases have similar accuracy than conventional fabricated dentures.

Additive Manufacturing for Complete Denture Fabrication: A Narrative Review

PURPOSE

To evaluate and compare the benefits and limitations of additive manufacturing for complete denture fabrication.

METHODS

A PubMed and Google Scholar search for topics pertaining to additive manufacturing for complete dentures was performed. The resulting articles were then divided into topics to allow a narrative review.

DISCUSSION

Determining how printing compares with conventional and milled dentures is critical for the widespread adoption of this fabrication technique. Physical properties, denture tooth bond strength, denture base adaptation and soft-liner bond strength are discussed to establish how printing compares.

CONCLUSIONS

Printing offers many advantages over milled and conventionally processed dentures; however, many questions need to be answered by research. The advantages include reduced cost of most printers compared to milling machines, less material waste, ability to print multiple dentures simultaneously, and complex designs can be fabricated that otherwise could not be milled. Current research has shown flexural strength, fracture toughness, color stability, and denture base adaptation are reduced for printed dentures when compared with milled dentures. Print orientation has been shown to influence accuracy, strength, surface roughness and C. albicans adherence which is not seen with conventional or milled denture materials. These factors do not represent a criticism of printing but rather indicate the need for more research with this new and promising denture fabrication technique. Since printing offers numerous benefits to complete denture fabrication it is likely to have a more significant role in complete denture fabrication in years to come as knowledge increases and materials/techniques continue to advance.

The Neutral Zone Approach with CAD/CAM Record Bases

Lack of adequate retention, support, and stability in the complete denture can be attributed to a poor fit or incorrect shape of the polished surfaces. This article presents a case using the neutral zone technique effectively with the fabrication of computer-aided design and computer-aided manufacturing (CAD-CAM) record bases in an edentulous patient with severely resorbed alveolar ridges and discusses the overall treatment steps and clinical implications of this technique. A stable neutral zone and an accurate jaw relation were recorded using CAD-CAM record bases and stability of complete denture was optimized by arranging denture teeth and reforming polishing surfaces in the neutral zone. A new complete denture was fabricated for a patient with atrophic alveolar ridges by a technique utilizing the neutral zone with CAD-CAM record bases. This article is protected by copyright. All rights reserved.

Duplicating Complete Dentures with Conventional and Digital Methods: Comparisons of Trueness and Efficiency

Background: A complete denture (CD) can be duplicated with a conventional or digital protocol. However, there are no comparative studies of these methods. This study aimed to compare the trueness and efficiency of conventional and digital CD duplication methods. Methods: A mandibular CD was digitized as the virtual reference model and duplicated using five methods (n = 10). The trueness (root mean square (RMS)) was calculated for the whole denture and across the dentition, cameo denture extension, and intaglio portions. The manual labor time spent during denture duplication was also recorded at different steps. The trueness and labor time comparisons were statistically analyzed among the five groups (α = 0.05). Results: The conventional group was the least true with the largest RMS (mean, 95% CI) in all of the comparisons. The four digital groups yielded similar trueness values across the dentition, cameo denture extension, and intaglio areas, yet they had a significant difference in the whole denture comparison between the Digital-CBCT-SLA printer (0.17, 0.15–0.19 mm) and Digital-Laboratory Scanner-SLA printer (0.13, 0.11–0.15 mm). The conventional protocol required longer trimming and finishing time (7.55 ± 1.02 min), as well as total labor time (27.64 ± 1.72 min) than the other four digital techniques. Conclusions: The conventional CD duplication method was less true and efficient than digital techniques.

Is the Number of Appointments for Complete Denture Fabrication Reduced with CAD-CAM? A Literature Review

One of the key arguments in favor of digitally produced complete dentures (CDs) is the requirement for less patient visits in comparison to the conventional workflow. However, it is not yet clear if this argument is accurate; nor, if indeed the insertion of the complete dentures is achieved in fewer appointments, how many are required. The purpose of this literature review was to investigate the reported number of required patient visits for the production of digitally fabricated CDs. An electronic search was performed in PubMed/MEDLINE using three groups of keywords: “complete dentures”, “CAD/CAM”, and “Appointments” with their alternative forms. Out of the initial 157 results, 36 articles were automatically selected utilizing exclusion keywords. After consensus between the two examiners, eight articles were finally analyzed and presented in a table. The majority (75%) of the reports came from institutions, and the average number of appointments up to complete denture insertion was 4.1, not always including try-in dentures. In this study, it can be concluded that, with a digital workflow, the insertion appointment is reached in fewer visits than the conventional five-visit procedure which is commonly taught in dental schools.

Computer-Aided Design and Computer-Aided Manufacturing (CAD/CAM) Complete Dentures for Atrophic Alveolar Ridges: Workflow Combining Conventional and Novel Techniques

Extreme residual ridge resorption is a challenging clinical situation for the fabrication of complete dental prostheses. Computer-aided design and computer-aided manufacturing (CAD/CAM) complete dentures have been shown to have superior fit and material strength to conventionally fabricated dentures, but no clinical protocols have been described for cases of extreme residual ridge resorption. This report describes a workflow combining conventional and novel techniques for CAD/CAM complete dentures fabrication for atrophic alveolar ridges and demonstrates that a CAD/CAM workflow is an effective tool for solving this complex situation.

Flexural strength of CAD/CAM denture base materials: Systematic review and meta-analysis of in-vitro studies

Introduction:

Digital complete dentures fabrication techniques are expanding. This study aimed to review flexural strength (FS) of milled and 3D-printed denture base materials to answer the study question: is FS of computer-aided designing/computer-aided manufacturing (CAD/CAM) denture base comparable to conventional heat-polymerized materials?

Materials and Methods:

Search was done within different databases for articles published between January 2010 and June 2021 using specific keywords. Articles of in-vitro studies in English language with methods following International Standards Organization standardization/ADA specifications for flexural testing of conventional and CAD/CAM (milled or printed) polymethyl methacrylate (PMMA) materials were included.

Results:

Out of the 61 studies, 9 were processed for data extraction and only 7 underwent meta-analysis. Two, six, and one study showed high, moderate, and low risk of bias, respectively. Random-effects model was used for analysis and resulted in the average FS of 120.61 MPa [95% confidence interval (CI): 109.81−131.41] and 92.16 MPa (CI: 75.12−109.19) for CAD/CAM milled and heat-polymerized PMMA, respectively.

Conclusion:

Subtractive CAD/CAM technique of denture fabrication showed satisfactory FS values, whereas additive CAD/CAM method was comparable to conventional heat-polymerized technique with lower value, requiring further investigations and improvement. The clinical use of milled denture bases is an acceptable substitution to heat-polymerized PMMA, making the denture fabrication an easier and faster process.

Effect of post-rinsing time and method on accuracy of denture base manufactured with stereolithography

PURPOSE

MATERIALS AND METHODS

RESULTS

CONCLUSION

Influence of molding angle on the trueness and defects of removable partial denture frameworks fabricated by selective laser melting

PURPOSE

To examine the effect of molding angle on the trueness and defects associated with removable partial denture (RPD) frameworks fabricated by selective laser melting (SLM).

METHODS

A plaster model of a partially edentulous mandibular arch classified as Kennedy class II modification 1 was used. After obtaining the 3D data of the model (design data), a framework was designed using CAD software. Based on the design data, three different molding angle conditions (0°, 45°, and -45°) were set in the CAM software. The frameworks were fabricated by SLM under each condition, and 3D data were captured (fabrication data). The design and fabrication data were superimposed using 3D inspection software to verify the shape errors. The number of support structures was then measured. To examine the internal defects, micro-computed tomography (µCT) was performed for void analysis. Surface roughness was measured using a laser microscope.

RESULTS

The overall shape errors of the RPD framework were smaller under the 0° condition compared with the others, and the largest number of support structures was observed at 0°. Many internal defects were observed in the large components of the framework at 45° and -45°. The surface roughness was the smallest at -45°.

CONCLUSION

The trueness and defects associated with the RPD frameworks were affected by the difference in the SLM molding angle.

CAD-CAM complete removable dental prostheses: A double-blind, randomized, crossover clinical trial evaluating milled and 3D-printed dentures

OBJECTIVE

This double-blind, randomized, crossover, clinical trial aimed to evaluate and compare the differences between milled and 3D-printed complete removable dental prostheses (CRDPs).

METHODS

Fifteen edentulous patients (men: n = 10, women: n = 5; age: 66.7 ± 8.0 years) rehabilitated with conventional CRDPs were recruited for this trial. Participants were randomized to first receiving either the milled or 3D-printed CAD-CAM manufactured CRDPs and then after 6-weeks cross over to the other set. Both, clinicians and participants were blinded to the group allocation. Outcomes included patient's denture satisfaction (PDS), oral-health related quality of life (OHIP-EDENT), willingness-to-pay analysis, final choice (FC) of CRDPs, clinician's denture quality evaluation (CDQE), chewing efficiency (CE), maximum-voluntary-bite-force (MBF), and prosthodontic maintenance needs. The outcomes were measured at baseline (with old CRDPs), at 1 and 6 weeks after new CRDP insertion; following crossover with the second set of CRDPs, an identical protocol was followed. Generalized linear regression for repeated measures was used for statistical analysis with α=0.05.

RESULTS

All participants completed the trial. 3D-printed CRDPs required more maintenance visits, adjustment time (p = 0.0003), and adjustment costs (p = 0.021). Patients were willing-to-pay an average of 606.67 Swiss Francs more than the actual cost for the milled CRDPs. There were no differences in the PDS, OHIP, FC, CDQE, CE, and MBF between the two CRDPs groups.

CONCLUSIONS

The findings of this double-blind randomized crossover clinical trial confirm that both milled and 3D-printed CRDPs are valid treatment modalities for edentulous patients, with the latter performing inferiorly with regard to the time and costs involved with the prosthodontic aftercare, as well as the patients' willingness-to-pay.

CLINICAL RELEVANCE

The findings of this trial provide evidence to help the clinician in choosing the appropriate CAD-CAM manufacturing process for fabricating the CRDPs.

Accuracy of a titanium maxillary complete denture baseplate fabricated by using the electron beam melting technique: An in vitro study

STATEMENT OF PROBLEM

Electron beam melting (EBM) is a promising additive manufacturing technique for fabricating denture baseplates; however, studies evaluating its accuracy are sparse.

PURPOSE

The purpose of this in vitro study was to compare the fit accuracy of titanium maxillary complete denture baseplates fabricated by using the EBM technique with those fabricated by using the conventional casting technique and to evaluate the dimensional accuracy of the EBM baseplate by using a 3-dimensional inspection software program.

MATERIAL AND METHODS

Definitive casts of an edentulous maxilla were prepared. After the casts were optically scanned, computer-aided designs for the EBM baseplate were created by using a software program for standard tessellation language file editing. The EBM baseplates were fabricated with an EBM machine by using a Grade II titanium powder as the raw material. The cast baseplates were fabricated with a lost-wax casting technique by using refractory casts duplicated from the definitive casts. After fitting the EBM and cast baseplates to their corresponding definitive cast, they were embedded in a Type IV stone. The embedded baseplates on the casts were sectioned at 3 regions: posterior palatal seal, molar, and premolar. The maximum gaps between the baseplate and definitive cast were measured in these 3 regions. The virtual casts obtained by scanning the EBM baseplate were superimposed on the computer-aided design to evaluate the dimensional accuracy. Distribution color maps were then generated, and the mean absolute deviations and root mean square deviations were calculated. One-way analysis of variance and t tests were used for statistical analysis (α=.05).

RESULTS

No significant differences in the maximum gaps among the 3 regions were found in the cast or EBM baseplate groups (P>.05). The EBM baseplate group showed significantly lower values than the cast baseplate group in all regions (premolar: P=.008; molar: P=.003; posterior palatal seal: P=.004). The mean maximum gap for the 3 regions in the cast baseplates was 168.0 μm and that in the EBM baseplates was 60.7 μm. The distribution color map of the EBM baseplate showed a favorable dimensional accuracy. The mean absolute deviation value was 19.7 μm, and the root mean square deviation value was 25.1 μm.

CONCLUSIONS

The EBM baseplates had a significantly higher fit accuracy than the cast baseplates. Thus, the fit accuracy of the EBM technique is suitable for fabricating metal baseplates.

Current Status of Digital Complete Dentures Technology

Fabrication of complete dentures (CDs) utilizing computer-aided design and computer-aided manufacturing (CAD/CAM) methods has attracted a lot of attention. The purpose of this paper was to summarize current knowledge about digital CDs and the relevant technology, and to present the application of the new technology in a dental geriatrics case. Initially, some of the challenges regarding digitization of the oral mucosa as a supporting surface of the CDs’ intaglio surface are listed. Next, a brief introduction of the CAD software capabilities regarding CDs is presented. The latest CAM additive and subtractive techniques for CDs are following. Subsequently, the consecutive steps for the construction of a digital CD as part of the prosthodontic treatment of a 90-year-old ambulative female patient are presented. Finally, some considerations about the digital workflow in CD manufacturing are discussed. In conclusion, the new digital technology has clear advantages; however, implementation requires careful planning. The digital workflow is applicable and versatile.

CAD-CAM removable complete dentures: A systematic review and meta-analysis of trueness of fit, biocompatibility, mechanical properties, surface characteristics, color stability, time-cost analysis, clinical and patient-reported outcomes

OBJECTIVES

This review compared Computer-aided designand Computer-aided manufactured (CAD-CAM) and conventionally constructed removable complete dentures (CDs).

DATA

Seventy-three studies reporting on CAD-CAM (milled/3D-printed) CDs were included in this review. The most recent literature search was performed on 15/03/2021.

SOURCES

Two investigators searched electronic databases [PubMed (MEDLINE), Embase, CENTRAL], online search engines (Google) and research portals. Hand searches were performed to identify literature not available online.

STUDY SELECTION

Studies on CAD-CAM CDs were included if they reported on trueness of fit, biocompatibility, mechanical, surface, chemical, color , microbiological properties, time-cost analysis, and clinical outcomes. Inter-investigator reliability was assessed using kappa scores. Meta-analyses were performed on the extracted data .

RESULTS

The kappa score ranged between 0.897-1.000. Meta-analyses revealed that 3D-printed CDs were more true than conventional CDs (p = 0.039). Milled CDs had a higher flexural-strength than conventional and 3D-printed CDs (p < 0.0001). Milled CDs had a higher flexural-modulus than 3D-printed CDs (p < 0.0001). Milled CDs had a higher yield-strength than injection-molded (p = 0.004), and 3D-printed CDs (p = 0.001). Milled CDs had superior toughness (p < 0.0001) and surface roughness characteristics (p < 0.0001) than other CDs . Rapidly-prototyped CDs displayed poor color-stability compared to other CDs (p = 0.029). CAD-CAM CDs d displayed better retention than conventional CDs (p = 0.015). Conventional CDs had a higher strain at yield point than milled CDs (p < 0.0001), and had superior esthetics than 3D-printed (p < 0.0001). Fabrication of CAD-CAM CDs required less chairside time (p = 0.037) and lower overall costs (p < 0.0001) than conventional CDs.

CONCLUSIONS

This systematic review concludes that CAD-CAM CDs offer a number of improved mechanical/surface properties and are not inferior when compared to conventional CDs.

CLINICAL SIGNIFICANCE

CAD-CAM CDs should be considered for completely edentulous patients whenever possible, since this technique offers numerous advantages including better retention, mechanical and surface properties but most importantly preserves a digital record. This can be a great advantage for older adults with limited access to dental care.

Effect of different fabrication methods of occlusal devices on periradicular stress distribution: A photoelastic analysis

STATEMENT OF PROBLEM

Investigations on the effectiveness of new methods for optimizing the fabrication of oral devices are lacking.

PURPOSE

The purpose of this in vitro study was to evaluate stress distribution with photoelastic analysis in the periradicular area of teeth supporting occlusal devices fabricated by 5 different processes.

MATERIAL AND METHODS

The occlusal devices were fabricated by vacuum thermoforming, heat-polymerized acrylic resin, chemical polymerized acrylic resin, 3-dimensional printing, and milling (computer-aided manufacturing). The devices were evaluated regarding initial fit, number of adjustments for passive fit, and stress distribution under 100-N and 400-N loads in the periradicular locations of posterior teeth.

RESULTS

The 3-dimensional printing device did not require any adjustment for initial adaptation to the photoelastic model and presented a little friction with the model. The heat-polymerized acrylic resin device did not seat initially, requiring more sites of adjustment until passive adaptation. At 100-N and 400-N loads, the use of the computer-aided manufacturing occlusal device resulted in the lowest stresses in periradicular areas (0.744 and 1.583, respectively), and the 3-dimensional printing occlusal device produced the highest stresses with a 400-N load application (2.427). The lowest mean of fringe pattern was observed for the computer-aided manufacturing device, and the highest mean of fringe pattern was observed for the vacuum thermoforming device.

CONCLUSIONS

The computer-aided design and computer-aided manufacturing milled occlusal device presented the best initial adaptation and transferred lower stresses to the periradicular areas than the other evaluated devices.

Evaluation of the clinical performance of dentures manufactured by computer-aided technology and conventional techniques: A systematic review

STATEMENT OF PROBLEM

The introduction of computer-aided design and computer-aided manufacturing (CAD-CAM) technology for complete denture fabrication may have improved clinical outcomes compared with conventional techniques. However, systematic reviews comparing these techniques are lacking.

PURPOSE

The purpose of this systematic review was to identify, compare, and synthesize the outcomes of published clinical studies related to complete denture fabrication, with respect to the differences between CAD-CAM technology and conventional techniques.

MATERIAL AND METHODS

A comprehensive search of studies published up to March 16, 2020, was conducted by using the PubMed/MEDLINE, Web of Science, Cochrane Library, SciELO, and Embase databases according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement criteria and was registered in the International Prospective Register of Systematic Reviews (PROSPERO ID 42020202614). The population, intervention, comparison, and outcome (PICO) question was: Do CAD-CAM complete dentures have a similar functional performance to those fabricated by conventional techniques? The quality of publications was appraised by using the Critical Appraisal Skills Program (CASP) checklists.

RESULTS

Of the 1232 titles, 6 articles were selected. The studies reported better retention of digitally manufactured complete dentures without denture adhesives than that of conventional complete dentures with or without denture adhesives. Other studies reported that dentures manufactured with digital systems were better adapted to tissue surfaces, required less clinical time, were lower in cost, and provided better experience and satisfaction to patients.

CONCLUSIONS

The assessment of CAD-CAM planning and manufacturing through clinical studies is ongoing. However, preliminary results indicate better clinical performance and lower overall costs of digital complete dentures than conventional dentures.

Accuracy Evaluation of Additively and Subtractively Fabricated Palatal Plate Orthodontic Appliances for Newborns and Infants-An In Vitro Study

Different approaches for digital workflows have already been presented for their use in palatal plates for newborns and infants. However, there is no evidence on the accuracy of CAD/CAM manufactured orthodontic appliances for this kind of application. This study evaluates trueness and precision provided by different CAM technologies and materials for these appliances. Samples of a standard palatal stimulation plate were manufactured using stereolithography (SLA), direct light processing (DLP) and subtractive manufacturing (SM). The effect of material (for SM) and layer thickness (for DLP) were also investigated. Specimens were digitized with a laboratory scanner (D2000, 3Shape) and analyzed with a 3D inspection software (Geomagic Control X, 3D systems). For quantitative analysis, differences between 3D datasets were measured using root mean square (RMS) error values for trueness and precision. For qualitative analysis, color maps were generated to detect locations of deviations within each sample. SM showed higher trueness and precision than AM technologies. Reducing layer thickness in DLP did not significantly increase accuracy, but prolonged manufacturing time. All materials and technologies met the clinically acceptable range and are appropriate for their use. DLP with 100 µm layer thickness showed the highest efficiency, obtaining high trueness and precision within the lowest manufacturing time.

Bonding Behavior of Conventional PMMA towards Industrial CAD/CAM PMMA and Artificial Resin Teeth for Complete Denture Manufacturing in a Digital Workflow

When applying a digital workflow, custom artificial resin teeth have to be integrated into a milled complete denture base, using polymethylmethacrylate (PMMA) applied with a powder–liquid technique. Debonding of denture teeth from dentures is reported to be a frequent complication. No evidence is provided as to which method of surface treatment may enhance the bonding strength. The bonding strength between artificial teeth and PMMA (Group A, n = 60), as well as between the PMMA and industrial PMMA (Group B, n = 60), was investigated following no treatment, monomer application, sandblasting, oxygen plasma, and nitrogen plasma treatment. Surface-roughness values and SEM images were obtained for each group. Shear bond strength (SBS) and fracture mode were analyzed after thermocycling. Within Group A, statistically significant higher SBS was found for all surface treatments, except for nitrogen plasma. In Group B, only nitrogen plasma showed a statistically lower SBS compared to the reference group which was equivalent to all surface treatments. Conclusions: Within the limitations of the present study, the monomer application can be proposed as the most effective surface-treatment method to bond custom artificial teeth into a milled PMMA denture base, whereas nitrogen plasma impairs the bonding strength.

Trueness of Intaglio Surface of Milled Digital Dentures Designed from Intraoral Scans

PURPOSE

To asses trueness of the intaglio surface of milled dentures fabricated according to a fully digital protocol starting from intraoral scans in a clinical study by means of 3-dimensional (3D) digital analysis.

MATERIALS AND METHODS

Ten maxillary and 10 mandibular dentures, designed from intraoral scans and milled in-house, were studied. Intraoral scans were compared with the scans of intaglio surface of milled dentures. To this end, they were aligned, trimmed and used in a metrology software to measure their mean 3D distance, absolute mean deviation, and other parameters. Measured differences for all parameters were statistically investigated. Subgroup analysis for the maxillary and mandibular dentures was performed using independent samples t-test or, in case of non-normal distribution, by means of Mann-Whitney test.

RESULTS

Using a mean of 24.9 ±2.8 measurement points/mm² , a mean 3D distance of 0.0006 ±0.007 mm between intraoral scans and the scans of the intaglio surface of milled dentures was measured. The corresponding absolute mean deviation was 0.055 ±0.032 for maxillary dentures and 0.061 ±0.016 for mandibular dentures; such a difference between arches was statistically significant (p = 0.035).

CONCLUSIONS

Milled dentures fabricated using a fully digital protocol and intraoral scans have accurate intaglio surfaces. It is reasonable to assume that they may achieve an adequate fit.

Mechanical properties of polymethyl methacrylate as a denture base: Conventional versus CAD-CAM resin - A systematic review and meta-analysis of in vitro studies

STATEMENT OF PROBLEM

The development of polymethyl methacrylate (PMMA) computer-aided design and computer-aided manufacturing (CAD-CAM) resin blocks with reported improved mechanical properties has simplified complete denture production. However, whether the objective of improved mechanical properties has been achieved compared with conventional heat-polymerized PMMA is not yet clear.

PURPOSE

The purpose of this systematic review and meta-analysis was to evaluate the mechanical properties of denture base resins manufactured by conventional heat-polymerization and by CAD-CAM in terms of flexural strength, flexural modulus, and surface roughness.

MATERIAL AND METHODS

Electronic databases (PubMed/MEDLINE, Scopus, Web of Science) were independently searched by 2 researchers for relevant studies published up to November 2020. The population, intervention, comparison, and outcome (PICO) question was, "Does the conventionally manufactured, heat-polymerized PMMA resin, as a denture base, demonstrate the same mechanical properties as the CAD-CAM resin block?" In addition, a meta-analysis was based on the inverse variance method. Flexural strength, flexural modulus, and surface roughness were analyzed through the continuous outcome evaluated by mean difference and standard deviation, with 95% confidence intervals. To evaluated heterogeneity, the I² value (≤25%=low, ≥50%=moderate and ≥75%=high) and the P value were considered. P<.10 indicated statistical difference for heterogeneity. The effects of meta-analysis were based on the results of heterogeneity as per the studies.

RESULTS

Thirteen in vitro studies were included in the analysis. A total of 507 specimens were evaluated, 222 conventional and 285 CAD-CAM. In terms of flexural strength, the data showed no significant difference when conventional heat-polymerized PMMA was compared with CAD-CAM PMMA resins (P=.06; mean difference=18.28; 95% confidence interval:-0.42 to 36.97). In terms of flexural modulus, there was a significant difference for the CAD-CAM PMMA group (P=.01; mean difference=589.22; 95% confidence interval: 117.95 to 1060.48). In terms of surface roughness, a significant difference was observed between the groups (P=.02; mean difference=-0.53; 95% confidence interval: -0.97 to -0.09) with the conventional heat-polymerized PMMA resin having higher surface roughness values.

CONCLUSIONS

The mechanical properties of CAD-CAM PMMA resins were generally improved when compared with heat-polymerized polymethyl methacrylate resin.

Comparing volumetric and biological aspects of 3D-printed interim restorations under various post-curing modes

PURPOSE

This study aims to compare the volumetric change, degree of conversion (DOC), and cytotoxicity of 3D-printed restorations post-cured under three different conditions.

MATERIALS AND METHODS

3D-printed interim restorations were post-cured under three different conditions and systems: 5 min, 30 min, and 24 h. Three-unit and six-unit fixed dental prostheses (n = 30 for each case) were printed; ten specimens from each group were post-cured and then scanned to compare their volumetric changes. Root-mean-squared (RMS) values of the data were acquired by superimposing the scanned files with original files. Thirty disk-shaped specimens were printed to evaluate the DOC ratio. Fourier transform infrared spectroscopy was used to compare the DOCs of 10 specimens from each group. Human gingival fibroblasts were used to measure the cell viability of every specimen (n = 7). The data from this experiment were employed for one-way analysis of variance and Tukey's post-hoc comparisons.

RESULTS

Differences between the three-unit restorations were statistically insignificant, regardless of the post-curing conditions. However, for the six-unit restorations, a high RMS value was acquired when the post-curing duration was 30 min. The average DOC was approximately 56 - 62%; the difference between each group was statistically insignificant. All the groups exhibited cell viability greater than 70%, rendering them clinically acceptable.

CONCLUSION

The post-curing conditions influenced the volume when the length of the restoration was increased. However, this deviation was found to be clinically acceptable. Additionally, post-curing did not significantly influence the DOC and cytotoxicity of the restorations.