CAD/CAM milled removable complete dentures: an in vitro evaluation of trueness

Clinical use of duplicate complete dentures: A narrative review

Most reports on duplicate dentures are introduction to fabrication methods or clinical case reports. Only a few studies have verified their clinical effectiveness; hence, evidence to construct useful clinical guidelines for duplicate denture use is lacking. This review aimed to comprehensively investigate reports on duplicate dentures to accumulate evidences that will contribute to the formulation of clinical practice guidelines. Duplicate dentures are effectively used for impression making and bite registration when fabricating new dentures, thereby reducing the number of clinic visits and treatment time. Duplicate denture can also be used as temporary or new dentures. Older people in whom various adaptive abilities have declined, may find it difficult to adjust to new dentures and experience stress, even if the shape is appropriate. Duplicate dentures, which reproduces the shape of old dentures that they are used to, have the advantage of being more familiar to older people and less stressful. When manufacturing duplicate dentures, digital methods such as milling and three-dimensional printing are superior to conventional methods regarding working time and cost. A notable advantage of the digital method is that the denture shape can be saved as digital data, and the denture can be easily duplicated if lost.

Fit and retention of complete denture bases: Part II - conventional impressions versus digital scans: A clinical controlled crossover study

STATEMENT OF PROBLEM

Although the intraoral scanning of edentulous ridges is feasible, clinical evidence that the resulting denture retention is equivalent to that achieved with conventional impressions is lacking.

PURPOSE

The purpose of this clinical study was to determine the retention of complete denture bases fabricated from digital intraoral scans versus conventional impressions by using border molding and posterior palatal seal compression.

MATERIAL AND METHODS

Twenty volunteers with an edentulous maxilla were recruited. An intraoral scan of the maxilla and a conventionally border-molded impression with a custom tray were made. The conventional impression was poured; the definitive cast was scanned. Three-dimensionally (3D) printed (PB1) and milled bases (MB1) were fabricated based on the scan of the definitive cast. Based on the intraoral scan, a 3D printed (PB2) and a milled base (MB2) were fabricated. On each base, a platform with a hook consisting of a central notch orienting the force against the post dam (PD) and 2 lateral notches orienting the forces against the left (LT) and right (RT) tuberosities was set in the center of the outer surface of the base. A traction dynamometer was inserted in the hook and oriented into the corresponding notch by applying force until dislodgement. All bases were subsequently stored in artificial saliva for 2 weeks and scanned. Retention testing was repeated by using the same procedure. To evaluate trueness and to visualize the differences on a color map, the scan of the definitive cast and the intraoral scans were matched and compared in 3 dimensions. The Wilcoxon tests were used to compare the retention of the different bases (95% confidence interval, α=.05).

RESULTS

Nineteen participants with a mean ±standard deviation age of 64.1 ±14.7 years completed the 4 study sessions. The retention of printed bases (PD: 16.08 ±15.28 N; LT: 14.98 ±14.72 N; RT: 11.28 ±9.57 N) and milled bases (PD:14.52 ±17.07 N; RT: 11.99 ±12.10 N; LT: 13.55 ±15.53 N) fabricated from conventional impressions presented significantly higher retentive forces than those printed (PD: 6.21 ±4.72 N; RT:5.12 ±2.78 N; LT: 4.45 ±2.77 N) and milled (PD: 6.58 ±4.92 N; RT: 4.65 ±2.63 N; LT: 5.02 ±3.58 N) from the intraoral scans (P<.05). The differences were significant in all directions of dislodgement, as well as after storage in artificial saliva for 2 weeks. Comparison of the 3D distances between the intraoral scan and the definitive cast revealed a mean deviation of 0.45 ±0.11 mm.

CONCLUSIONS

Conventional impressions of the edentulous maxilla, including the clinical steps of border molding and posterior palatal seal compression, provide better retention than digital intraoral scans with both milled and 3D printed denture bases.

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.

Patient-reported outcome and cost-effectiveness analysis of milled and conventionally fabricated complete dentures in a university clinic: A retrospective study

STATEMENT OF PROBLEM

The custom disk is a novel method of complete denture fabrication; however, patient-reported outcomes and fabrication costs are unknown.

PURPOSE

The purpose of this retrospective study was to evaluate general patient satisfaction with complete dentures fabricated through the custom disk method. In addition, a comparative cost-effectiveness analysis was conducted for the custom disk method and conventional removable complete dentures.

MATERIAL AND METHODS

Complete dentures were fabricated for 44 edentulous participants by using the custom disk method (n=20) or the conventional removable complete denture (n=24). General patient satisfaction was measured by using visual analog scales before and after denture fabrication and compared by using the Wilcoxon signed-rank test (α=.05); the fabrication cost for each method was investigated and compared by using the Mann-Whitney U test (α=.05). Cost-effectiveness was analyzed with the incremental cost-effectiveness ratio as incremental cost per change in general patient satisfaction for the custom disk method with respect to the conventional removable complete denture.

RESULTS

The median general patient satisfaction with the custom disk method and conventional removable complete denture after the intervention was 84.0 mm and 91.0 mm, respectively. General patient satisfaction with the custom disk method was significantly higher after the intervention (P=.002). The median labor costs for the custom disk method and conventional removable complete denture were 24 516 and 36 583 Japanese yen, respectively, and the difference was statistically significant (P<.001). The median of the total cost of the custom disk method and the conventional removable complete denture was 41 104 and 45 276 Japanese yen, respectively, and the difference was statistically significant (P=.004). The incremental cost-effectiveness ratio was -251.4.

CONCLUSIONS

The custom disk method improved general patient satisfaction. The labor and total costs of the custom disk method were significantly lower than those of the conventional removable complete denture. The incremental cost-effectiveness ratio demonstrated that the custom disk method was more cost-effective than the conventional removable complete denture.

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.

Trueness assessment of additively manufactured maxillary complete denture bases produced at different orientations

STATEMENT OF PROBLEM

The trueness of the intaglio surface of an additively manufactured maxillary denture base may be influenced by the build orientation and the inclusion of support struts.

PURPOSE

The purpose of this in vitro study was to compare the trueness of a photopolymer additively manufactured maxillary complete denture base created at different orientations with different support strut designs. Optimizing the build is critical for adopting best practice when fabricating maxillary complete dentures through additive manufacturing techniques.

MATERIAL AND METHODS

Denture bases (N=70) were additively manufactured at 5 different build orientations (0-, 15-, 45-, 60-, and 90-degrees) with 10 specimens per orientation. Another 2 groups of 10 were manufactured by using the optimal printing orientation with and without support struts. The denture bases were scanned after storage in artificial saliva at 37 °C, and the scan data were analyzed with a 3D metrology software program. Statistical differences were determined with 1-way analysis of variance (ANOVA) and the Kruskal-Wallis test (α=.05). Color deviation heat maps were used to determine areas of clinically significant dimensional errors.

RESULTS

Significant differences were found among groups for positive mean deviation (F=44.09, P<.001), negative mean deviation (F=11.69, P<.001), and root mean square deviation (F=17.11, P<.001) for the different orientations. One-way ANOVA revealed significant differences with the use of support struts in relation to negative mean deviation (F=3.857, P<.001) and RMSE (F=11.215, P<.001) and positive mean deviation (Kruskal-Wallis H=0.070, P=.007). The color deviation maps showed that a 45- to 90-degree print orientation was truest overall and that the addition of support struts to the cameo and intaglio surfaces improved the trueness of the maxillary denture bases.

CONCLUSIONS

The build orientation and inclusion of support struts influenced the accuracy of the intaglio surface of additively manufactured maxillary denture bases. A 45- to 90-degree build orientation with support struts on the cameo and intaglio surfaces resulted in the truest denture base.

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.

Fabrication of milled removable partial dentures using a custom plate with prefabricated artificial teeth

PURPOSE

Although digital removable partial dentures have been previously described, there have been no reports on how to fabricate them in one piece. This study proposes a new method for fabricating patient-specific digital removable partial dentures using a custom plate.

METHODS

First, a gypsum model was scanned using a laboratory scanner and a removable partial denture was designed using computer-aided design (CAD) software based on standard tessellation language data. The metal clasp was fabricated from Ti-6Al-4V using a 3D printer. For custom plate fabrication, a resin plate frame was designed using computer-aided design (CAD) software and fabricated using a 3D printer. An artificial tooth and metal clasp were fixed on the base surface of the frame, an auto-polymerizing resin was poured into the frame for the denture base, and the artificial tooth and metal clasp were packed to form a custom plate. The plate was cut using a milling machine. Subsequently, the support attached to the denture was removed and polished for complete fabrication of the denture.

CONCLUSIONS

Our novel removable partial denture fabrication method is more efficient than the conventional method. The obtained removable partial dentures demonstrated satisfactory accuracy.

Influence of postpolymerization time and atmosphere on the mechanical properties, degree of conversion, and cytotoxicity of denture bases produced by digital light processing

STATEMENT OF PROBLEM

Studies on the effects of postprocessing conditions on the physical properties, degree of conversion (DC), and biocompatibility of denture bases produced by digital light processing are lacking.

PURPOSE

The purpose of this in vitro study was to evaluate the effects of the atmosphere during postpolymerization and of postpolymerization time on the flexural strength, Vickers hardness, DC, cytotoxicity, and residual monomer content of denture bases.

MATERIAL AND METHODS

Six different groups of bar- and disk-shaped specimens from the denture base resin were produced, considering 2 different atmospheres (air and nitrogen) and 3 different postpolymerization times (5, 10, and 20 minutes). To determine the physical properties, the flexural strength and Vickers hardness were measured. Fourier transform infrared spectrometry was used to calculate DC. Cytotoxicity was assessed from the effect on human gingival fibroblasts. The residual monomer content was determined by using high-performance liquid chromatography. Based on the normality test by the Shapiro-Wilk method, a nonparametric factorial analysis of variances was conducted (α=.05).

RESULTS

A significant interaction was detected between the atmosphere and postpolymerization time for hardness (P<.001) but no interaction for strength, DC, or cytotoxicity (P=.826, P=.786, and P=.563, respectively). Hardness was significantly affected by the postpolymerization time in the groups with the nitrogen atmosphere (P<.001). DC was significantly affected by the atmosphere (P=.012), whereas strength and cytotoxicity were not (P=.500 and P=.299, respectively). Cytotoxicity was significantly affected by the postpolymerization time (P<.001), but strength and DC were not (P=.482 and P=.167, respectively). Residual monomers were not detected after ≥10-minute postpolymerization time.

CONCLUSIONS

The atmosphere significantly affected hardness and DC, whereas the postpolymerization time significantly affected hardness, DC, cytotoxicity, and residual monomer content. Denture bases produced in a nitrogen atmosphere and with the 10-minute postpolymerization time showed sufficient hardness, DC, and no cytotoxicity.

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.

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.

A review on clinical use of CAD/CAM and 3D printed dentures

Aim The aim of this article was to review the current clinical application of computer-aided design/computer-aided manufacturing (CAD/CAM) and three-dimensional (3D) printed dentures in dental clinics.Methods A systematic approach for searching PubMed, Embase, Scopus, and Web of Science databases. The search was performed using a variety of keywords including clinical use AND 3D printed removable dentures OR clinical use AND CAD/CAM removable dentures OR clinical use AND digital removable dentures. Selection criteria included articles written in English and reporting information on clinical applications of digital dentures between 2010 to January 2022.Results The findings outlined the main clinical advantages of digital dentures such as saving working time, satisfying clinical results and securing patients' records, and also requirement of additional visits to secure aesthetic patient satisfaction, good retention and ideal vertical dimension. Many studies recommended performing clinical try-in with regards to providing better results. It was also established that 3D printers are less expensive than milling centres and therefore can be afforded by individual dental professionals.Conclusion Digital dentures are a promising option in treating edentulous patients, especially in remote areas where skilful technicians are rare. However, there are some limitations in their applications.

CAD-CAM Fabricated Denture Base Resins: In Vitro Investigation of the Minimum Acceptable Denture Base Thickness

PURPOSE

To investigate the influence of reducing material thickness on flexural properties of computer-aided design and computer-aided manufacturing (CAD-CAM) denture base resins.

MATERIALS AND METHODS

Four CAD-CAM denture base acrylic resin materials were selected; two were made via the subtractive method (AvaDent and IvoCad) and two were made with the additive method (FormLabs and NextDent). One heat-polymerized denture base material was used as a control. Specimens were fabricated with varying thicknesses (n = 10/group): 3.3 mm, 2.5 mm, 2 mm, or 1.5 mm. Flexural strength was evaluated via a three-point bending test. One- and two-way ANOVA were used for data analysis along with Tukey's post hoc comparison (α = 0.05).

RESULTS

Reducing the thickness of materials made via the subtractive method did not influence flexural strength up to 2 mm (p > 0.05). However, the difference was significant at a 1.5 mm thickness (p ˂ 0.001). For materials made via the additive method, NextDent specimens had no significant decrease in flexural strength when the thickness was reduced to 2 mm (p = 0.58). FormLabs specimens showed a significant decrease (p ˂ 0.001), although the values of flexural strength were clinically acceptable. During testing, specimens manufactured via the additive method at a 1.5 mm thickness bent without fracturing and were therefore excluded. All materials showed a reduction in elastic modulus as the thickness decreased (p ˂ 0.001).

CONCLUSION

Heat-polymerized, AvaDent, and IvoCad materials may be used for denture base fabrication at a minimum thickness of 1.5 mm. FormLabs and NextDent may be fabricated at a 2 mm minimum thickness, with clinically acceptable flexural properties.

Contemporary Evidence of CAD-CAM in Dentistry: A Systematic Review

In this systematic review, we compare the quality and accuracy of computer-aided design (CAD)/computer-aided manufacturing (CAM) techniques currently employed in dentistry with those of traditional materials. Published literature on the study topic was searched in the online MEDLINE, PsycINFO, PubMed, and Cochrane library databases and the database of Indian Council of Medical Research. For this systematic review, the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) framework was applied for the assessment of studies fit for investigation. Of the total 103 papers searched, 54 underwent in-depth evaluation. Using criteria for what to include and what to leave out, we chose research that was relevant to our review and narrowed it down to 14 papers that met the review's guidelines. According to our findings and the analysis of the chosen articles, the prospects and current advances of CAD/CAM technology are fascinating and are revolutionizing the field of dentistry. Even though researchers are excited, it is important to make sure that different materials have been tested and looked at well enough before making firm claims and choices to replace materials that have been made in the past. Based on previous research, it has been determined that the CAD/CAM methodology used in the dental field is the most popular method at the moment since it is quick, simple, and efficient. Since there are different kinds of CAD/CAM systems, it is very important to choose the right one and come up with a good plan for treating a patient.

Misfit of Complete Maxillary Dentures' Posterior Palatal Seal following Polymerisation with Four Different Autopolymerising Resins: An In Vitro Study

BACKGROUND

The majority of complete dentures are still conventionally manufactured using a flask-and-pack technique. However, the polymerization process may introduce a distortion of the denture body. The aim of this study was to evaluate the three-dimensional fit of the posterior palatal seal of maxillary complete dentures with the original impression, and to give recommendations for scraping.

METHODS

Four autopolymerising resins were used to manufacture 40 palatal plates each for high, medium and flat palates (total n = 120). The misfit was captured by taking a reline impression with a highly fluid silicone, the dimensions of which were measured with a flat-bed scanner.

RESULTS

The shape of the palate had a significant impact (median p = 0.0435), but not the resin type (median p = 0.2575). It was largest for the flat palate and smallest for the high palate. The largest misfit was observed in the palatal midline area (flat-palate average median: 685 µm; high and medium palates: 620 µm) decreasing towards the lateral and anterior regions.

CONCLUSIONS

The results suggest compensating for the palatal misfit that occurs with autopolymerising resins by scraping a postdam of an approximately 0.7 mm depth to the master cast, decreasing towards the anterior and lateral areas. In high and medium palates, the scraping could be less pronounced.

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.

Analysis of the residual monomer content in milled and 3D-printed removable CAD-CAM Murali complete dentures: an in vitro study

OBJECTIVE

The study aimed to quantitatively evaluate the elution of methylmethacrylate from CAD-CAM manufactured removable complete dentures (RCDs) using high performance liquid chromatography (HPLC).

METHODS

Thirty-two RCDs were manufactured following either the CNC-milling (Milled: n=8) or the 3D-printing (n=24) protocols. The 3D-printed dentures were further categorized into three groups based on their post-production rinsing cycles [Extended wash cycle (EWC), Standard wash cycle (SWC), and SWC and additional Durécon coating (SWC2)]. HPLC was used to evaluate the methylmethacrylate concentrations (MMCs) eluted from the dentures in each group for different time periods (1, 2, 4, 8, and 24 hours). Mean and standard deviations were calculated for the MMCs; data was verified for normal distribution, ANOVA and post hoc tests were applied for statistical analyses (⍺=0.05).

RESULTS

The HPLC revealed that all the denture groups recorded some amounts of MMCs, with significant differences [F (3, 31) = 23.646, p<0.0001]. The milled denture group had the highest MMCs at 24 hours when compared to the EWC (p<0.0001), SWC (p=0.001), and SWC2 (p<0.0001) denture groups. SWC had a higher MMC than EWC (p=0.032) and SWC2 (p=0.015). No differences were found in MMCs when comparing EWC and SWC2 (p=0.989).

CONCLUSION

Methylmethacrylate concentrations were significantly lower in 3D-printed RCDs than in milled RCDs when using the resins employed in this study. Furthermore, the MMCs can be further decreased in the 3D-printed RCDs when coated with an additional thin protective layer (Durécon) by following the manufacturer-recommended rinsing protocol or when an extended isopropanol wash cycle is adopted.

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.

Comparison of the flexural and surface properties of milled, 3D-printed, and heat polymerized PMMA resins for denture bases: an in vitro study

PURPOSE

To compare the flexural properties and the adhesion of Lactobacillus salivarius (LS), Streptococcus mutans (SM), and Candida albicans (CA) on heat-polymerized (CV), CAD-CAM milled (CAD), or 3D-printed (3D) Poly (methylmethacrylate) (PMMA).

METHODS

Ultimate Flexural Strength (UFS), Flexural Strain (FS) (%) at Flexural Strength, and Flexural Modulus (FM) of specimens (65.0×10.0×3.3 mm) from each PMMA group (n=6) were calculated by using the 3-point bending test. The surface roughness profiles (R) were measured before and after polishing with a contact profilometer. LS, SM, and CA adhesion on PMMA specimens (n=18) (10 mm in diameter, 3 mm in height) was assessed after 90 minutes and 16 hours by using scanning electron microscopy. The Kruskal-Wallis test with post hoc analysis was performed to compare the groups (alpha=0.05).

RESULTS

Mean UFS values were 80.79±7.64 MPa for CV, 110.23±5.03 MPa for CAD, and 87.34±6.39 MPa for 3D. Mean FS values were 4.37±1.04% for CV, 4.71±0.62% for CAD, and 6.19±0.13 % for 3D. Mean FM values were 2542±301 MPa for CV, 3435±346 MPa for CAD, and 2371±197 MPa for 3D. CAD had the lowest average R value (0.29±0.16 µm) before polishing, and bacterial adhesion after 90 minutes of incubation. R value and microbial adhesion were not different amongst groups after polishing and 16 hours of incubation, respectively.

CONCLUSION

The CAD group displayed the best flexural properties, except for FS, the lowest roughness before polishing and bacterial adhesion after 90 minutes of incubation. All tested PMMAs had similar surface roughness after polishing, and microbial adhesion after 16 hours of incubation.

Effect of post-curing time on the color stability and related properties of a tooth-colored 3D-printed resin material

This study investigated the effect of post-curing time on the color stability and related properties, such as degree of conversion (DC), surface roughness, water contact angle, water sorption (W_sp), and water solubility (W_sl) of 3D-printed resin for dental restorations. The 3D-printed specimens were divided into four groups according to the post-curing time (0, 5, 10, and 20 min). Color changes (ΔE₀₀) of the specimens immersed in aging media were measured using a spectrophotometer at different aging times. The DC of the resin was measured using a FTIR. The surface roughness (Ra) of the resin immersed in coffee was measured at different aging times. Water contact angle was evaluated using the sessile drop method, and W_sp and W_sl were tested according to the ISO 4049:2019. The ΔE₀₀ values of the specimens immersed in coffee and red wine decreased with increasing post-curing time. As the post-curing time increased up to 10 min, the DC increased and water contact angle decreased. The Ra value of the group without post-curing (0 min) increased gradually for 30 days, except between 7 and 15 days. However, when the post-curing time increased to greater than 10 min, no apparent change in Ra value was detected. The W_sp and W_sl of the group without post-curing were significantly lower and larger than that of the other groups, respectively. The longer the post-curing time of the tooth-colored 3D-printed resin, the better the color stability. The post-curing time of the 3D-printed resin affected the DC, surface roughness after aging in the staining media, water contact angle, water sorption, and water solubility.

Extra-oral assessment of conventional and CAD-CAM complete denture appearance by dental professionals and CRDP wearers: A randomized survey

INTRODUCTION

Complete removable dental prostheses' (CRDPs) appearance may vary between conventional and contemporary CAD-CAM manufacturing techniques.

OBJECTIVES

The aim of this randomized survey was to analyze appreciation of CRDPs, manufactured with different techniques, by dental professionals and elder CRDP wearers.

METHODS

Four participant groups, comprised of undergraduate students (n=10), postgraduate residents (n=10), dental technicians (n=10) and elder CRDP wearers (n=10), evaluated the appearance of maxillary CRDPs manufactured by six different techniques: three conventional methods 1. flask-pack-press (FP), 2. Injection-molded (IM), 3. intrinsically colored natural gingiva finish before injection-molded (NG) and three CAD-CAM methods 4. milled base with bonded prefabricated teeth (M), 5. fully milled including milled teeth (FM) and 6. rapid-prototyped including printed teeth (P). A randomized, blinded survey included 18 pairwise comparative assessments and 12 individual judgements of the CRDPs on general appearance as well as pink and white aspects. Statistical analyses included parametric- and nonparametric tests as well as linear regression models; the level of statistical significance was set at p<.05.

RESULTS

NG was preferred by the professional groups but not by the elder CRDP wearers (p<.05). P was scored lowest by all four participant groups (p<.05). CRDP wearers' ratings were less severe and within a narrower range. The ratings of the two CAD-CAM milled CRDPs (M and FM) were ranked closer to FP and IM); the order of preference was different depending on the participant groups.

CONCLUSIONS

The findings of this study revealed marked differences in the assessment of CRDP appearances between dental professionals and older CRDP wearers.

CLINICAL SIGNIFICANCE

A shared and informed approach to decision making concerning the CRDP appearance might foster denture acceptance and treatment success.

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 complete denture resins: an evaluation of biocompatibility, mechanical properties, and surface characteristics

OBJECTIVES

This study evaluated the biocompatibility, mechanical properties, and surface roughness of CAD-CAM milled and rapidly-prototyped/3D-printed resins used for manufacturing complete dentures.

METHODS

Six groups of resin specimens were prepared, milled-base (MB), milled-tooth shade (MT), printed-tooth shade (PT), printed-base with manufacturer-recommended 3D-printer (PB1), printed-base with third-party 3D-printer (PB2), printed-base in a vertical orientation (PB2V). Human epithelial (A-431) and gingival (HGF-1) cells were cultured and tested for biocompatibility using Resazurin assays. Three-point bending and nanoindentation tests measured the mechanical properties of the resin groups. Surface roughness was evaluated using a high-resolution laser profilometer. ANOVA and post-hoc tests were used for statistical analyses (α = 0.05).

RESULTS

There were no significant differences in biocompatibility between any of the investigated groups. MB revealed a higher ultimate strength (p = 0.008), elastic modulus (p = 0.002), and toughness (p = 0.014) than PB1. MT had significantly higher elastic modulus than PT (p < 0.001). Rapidly-prototyped resin samples with a manufacturer-recommended 3D-printer (PB1) demonstrated higher ultimate strength (p = 0.008), elastic modulus (p < 0.001), hardness (p < 0.001) and a reduced surface roughness (p < 0.05) when compared with rapidly-prototyped groups using a third-party 3D-printer (PB2). Rapidly-prototyped samples manufactured with a vertical printing orientation (PB2V) revealed a significantly lower elastic modulus than samples groups manufactured using horizontal printing orientation (PB2) (p = 0.011).

CONCLUSIONS

Within the limits of this present study, CAD-CAM milled and rapidly-prototyped complete denture resins performed similarly in terms of biocompatibility and surface roughness. However, the milled denture resins were superior to the rapidly-prototyped denture resins with regard to their mechanical properties. Printing orientation and type of 3D-printer can affect the resin strength and surface roughness.

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.

Dimensional changes of complete dentures fabricated by milled and printed techniques: An in vitro study

STATEMENT OF PROBLEM

Information on the dimensional changes in maxillary and mandibular dentures made by using computer-aided design and computer-aided manufacturing (CAD-CAM) techniques under uniform testing conditions is lacking.

PURPOSE

The purpose of this in vitro study was to evaluate the dimensional changes and reproducibility of maxillary and mandibular dentures by using CAD-CAM-milled and 3D-printed techniques.

MATERIAL AND METHODS

Maxillary and mandibular edentulous models with wax occlusal rims were scanned, and dentures were designed by using a CAD software program and fabricated by using 2 techniques and materials: CAD-CAM-milled (CCM) and 3D-printed (3DP). The 3DP fabrications included 4 subgroups: dentures printed with a 90-degree build angle with UV light polymerization on the reference model (3DP 90M), dentures printed with a 90-degree build angle and light polymerization without the reference model (3DP 90), dentures printed with a 45-degree build angle with light polymerization on the reference model (3DP 45M), and dentures printed with a 45-degree build angle and light polymerization without the reference model (3DP 45). The preprocessing and postprocessing scan files of each denture produced by CCM and 3DP were superimposed by using a surface matching software program. Ten points each on maxillary and mandibular dentures were measured for deviations after processing. Additionally, for each denture, the widths were measured between the canines and molars, the anteroposterior plane from cusp tips between the canines and molars, and the vertical plane from the cusp tip of the canines to the marginal gingiva. They were then compared with those in the denture design CAD cast. The Kruskal-Wallis analysis of variance test was used for statistical analyses (α=.05).

RESULTS

According to digital superimposition, CCM had the smallest values of deviation with no statistical difference (P>.05), indicating more uniform results from measurement points in both maxillary and mandibular dentures, followed by 3DP 90M, 3DP 90, 3DP 45M, and 3DP 45. Regarding the width measurements, CCM had the smallest values of deviation (P<.05). In 3DP, smaller deviation values were observed at the vertical plane from the tip of the canine to the marginal gingiva, and larger values were observed in the intermolar width (P<.05).

CONCLUSIONS

CCM exhibited smaller dimensional changes and better reproducibility among the tested techniques. In 3DP, the build angle and methods of light postprocessing influenced the dimensional stability. The 90-degree build angle with additional light polymerization on the cast improved the dimensional deviations.

Comparison of Intaglio Surface Trueness of Interim Dental Crowns Fabricated with SLA 3D Printing, DLP 3D Printing, and Milling Technologies

This study aimed to evaluate the intaglio surface trueness of interim dental crowns fabricated with three 3-dimensional (3D) printing and milling technologies. Dental crown was designated and assigned as a computer-aided design (CAD) reference model (CRM). Interim dental crowns were fabricated based on CRM using two types of 3D printer technologies (stereolithography apparatus and digital light processing) and one type of milling machine (n = 15 per technology). The fabricated interim dental crowns were obtained via 3D modeling of the intaglio surface using a laboratory scanner and designated as CAD test models (CTMs). The alignment and 3D comparison of CRM and CTM were performed based on the intaglio surface using a 3D inspection software program (Geomagic Control X). Statistical analysis was validated using one-way analysis of variance and Tukey HSD test (α = 0.05). There were significant differences in intaglio surface trueness between the three different fabrication technologies, and high trueness values were observed in the milling group (p < 0.05). In the milling group, there was a significant difference in trueness according to the location of the intaglio surface (p < 0.001). In the manufacturing process of interim dental crowns, 3D printing technologies showed superior and uniform manufacturing accuracy than milling technology.

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.

Effect of thermocycling on the surface properties of CAD-CAM denture base materials after different surface treatments

PURPOSE

To evaluate the effect of thermocycling on the water contact angle (WCA), surface roughness (SR), and microhardness (MH) of different CAD-CAM PMMA denture base materials after different surface treatments (conventional laboratory polishing, polishing kit, or surface sealant).

MATERIALS AND METHODS

Disk-shaped specimens (10 × 2 mm) of 3 different CAD-CAM PMMAs, AvaDent (AV); Merz M-PM (M-PM); Polident (Poli), and a conventional heat-polymerized PMMA (Vynacron) (CV) (n=21) were divided into 3 different surface treatment groups (n=7): conventional laboratory polishing (CLP), polishing with acrylic resin polisher kit (PK), and a surface sealant (Palaseal) (SSC). Stereomicroscopic images were taken both before and after thermocycling. WCA, SR, and MH of all specimens were measured before and after thermocycling and compared by using a 2-way ANOVA (α=0.05).

RESULTS

After thermocycling, WCA significantly increased for CLP- or PK -applied (P<.001) specimens of all materials and SSC-applied M-PM (P=.002), SR significantly increased for CLP-applied M-PM (P=.027) and PK-applied Poli (P=.041), and MH significantly decreased for CLP- or PK-applied AV (P = .001, P < .001, respectively), CV (P=.033, P=.023, respectively), and M-PM (P=.003, P=.001, respectively), SSC-applied M-PM (P<.001), and CLP-applied Poli (P<.001). Stereomicroscopic images revealed rougher surfaces for PK-applied specimens.

CONCLUSIONS

After thermocycling, surface treatment had a significant effect on water contact angle and surface roughness. CLP or PK application resulted in hydrophobic surfaces compared with before thermocycling. CLP or SSC application on CAD-CAM PMMAs resulted in smoother surfaces. Thermocycling lowered the microhardness of all PMMAs, and the decrease was significant in CLP- or PK-applied PMMAs, except for PK-applied Poli.

Conversion of Digital Dentures for Immediate Loading of Complete Arch Implant Prostheses

The development and expanded use of digital dentures has led to their use in the immediate loading of complete arch implant prostheses. This paper reviews the prosthetic complications that can occur with immediately loaded conversion prostheses along with the advantages afforded by digital dentures in minimizing or eliminating these complications. The process of using digital dentures in the fabrication of conversion dentures for immediate loading of complete arch implant prostheses is presented as well as the use of digital dentures for definitive prostheses. The described procedures include methods of obtaining clinical records, the fabrication of conversion dentures, the immediate loading procedure using a conversion prosthesis, and use of a conversion denture in the fabrication of a definitive prosthesis.

A Full Digital Workflow for the Duplication of an Existing Implant Retained Overdenture Prosthesis: A Novel Approach

The purpose of this clinical case report is to describe a fully digital workflow for the duplication of an existing implant retained overdenture, highlighting the benefits of digitally fabricated dentures. The patient presented with an existing mandibular implant retained overdenture on Locator attachments that needed to be replaced. The existing overdenture was duplicated/scanned with the use of an intraoral scanner and was 3D printed using acrylic resin. This resin duplicate was sectioned in the midline and served as a unilateral record base to digitally record maxillo-mandibular relationship. The occlusal relationship was scanned unilaterally with the record base (sectioned duplicate) in place, and the procedure was repeated for the opposite side. All scans (edentulous, bite registrations and preliminary scan) were superimposed and the software managed to position and stich everything together. A try-in copy denture (ProArtCAD Try in, Ivoclar Vivadent AG, Schaan, Liechtenstein) was milled in order to imitate the conventional wax teeth try-in. A definitive milled overdenture was fabricated and delivered. A reinforcing polyetheretherketone mesh was fabricated, utilizing computer assisted design/computer assisted manufacturing technology and was incorporated into the pre-designed customized space into the polymethylmethacrylate base, using indirect light-polymerized nano-filled composite resin (crea.lign; bredent GmbH & Co. KG). Occlusion was verified and the patient was instructed oral hygiene, home maintenance and was informed for the required recall visits.

Trueness and precision of artificial teeth in CAD-CAM milled complete dentures with custom disks

STATEMENT OF PROBLEM

Insufficient information is available regarding the trueness and precision of artificial teeth in computer-aided design and computer-aided manufacturing (CAD-CAM) milled complete dentures fabricated from custom disks, including prefabricated teeth.

PURPOSE

The purpose of this in vitro study was to determine the trueness and precision of the position of the artificial teeth arranged in CAD-CAM milled complete dentures manufactured by using a custom disk method and to compare the trueness and precision of different tooth types and the occlusal surface and entire surface of the teeth.

MATERIAL AND METHODS

The milling data were designed by using a CAD software program. Four types of artificial teeth (maxillary-left central incisor, mandibular-left central incisor, maxillary-left first premolar, and maxillary-left first molar) were arranged concentrically in the disk with 3 corresponding teeth per disk. Five custom disks were milled based on the milling data. The sample size for maxillary-left central incisor, mandibular-left central incisor, maxillary-left first premolar, and maxillary-left first molar was 15. The standard tessellation language data were obtained by scanning the milled disks with cone beam computed tomography. The obtained data were superimposed by using a CAD software program to assess the trueness and precision of the tooth positions. For the occlusal surface, the data were superimposed after trimming to assess the trueness and precision of the tooth position with respect to the entire tooth surface. After data superimposition, the deviation was analyzed by using a 3-dimensional analysis software program to obtain the mean absolute error values and color maps. The data were analyzed by using 2-way ANOVA and the Games-Howell post hoc test (α=.05).

RESULTS

Significant differences were found in the mean absolute error values of the position trueness of the entire surface between the different teeth, except for maxillary-left first premolar and maxillary-left first molar (P<.05). Moreover, significant differences in the mean absolute error values of the precision for the entire surface were observed between mandibular-left central incisor and maxillary-left first premolar, as well as between mandibular-left central incisor and maxillary-left first molar (P<.05). The mean absolute error values of the position trueness of the occlusal surface were significantly smaller than those for the entire tooth surface for mandibular-left central incisor, maxillary-left first premolar, and maxillary-left first molar (P<.05). Finally, the mean absolute error values of the position precision of the occlusal surface were significantly smaller than those for the entire tooth surface for mandibular-left central incisor and maxillary-left first premolar (P<.05).

CONCLUSIONS

The trueness and precision of the posterior teeth were higher than that of anterior teeth. The trueness of the movement of the artificial teeth during the manufacturing of dentures by using the custom disk method was found to be within a clinically acceptable range.

Clinical analysis of CAD-CAM milled and printed complete dentures using computerized occlusal force analyser

BACKGROUND

Digital complete dentures (CDs) by computer-aided designing and computer-aided manufacturing (CAD-CAM) techniques (milling and three-dimensional (3-D) printing) have been evaluated clinically and provided satisfactory results. But clinical studies assessing occlusal forces by digital dentures are lacking.

OBJECTIVES

To compare the occlusal force parameters in complete dentures (CDs) fabricated by milling, 3-D printing and conventional techniques having 3 commonly used occlusal schemes, using computerized occlusal force analysis system (Tech-Scan III- T-Scan III).

METHODS

A total of 45 CDs were fabricated for 5 patients. Nine sets of CDs were made for each patient and were divided into 3 groups: Conventional CDs (CCD), Milled CDs (MCD), and 3-D printed CDs (3-DP CD). The CDs in each group were further divided into 3 sub-groups based on occlusion schemes - bilateral balanced (BBO), lingualized (LO) and mono plane (MP). Occlusal force analysis [percentage (%) of occlusal force applied on the right and left sides of the arch difference between them, centralization of forces and % of maximum occlusal/bite force] was done using computerized occlusal analysis system (T-Scan III) at the time of denture insertion. Univariate regression analysis and logistic regression analysis were performed (p< 0.05).

RESULTS

The intergroup comparison of force distribution on right and left side in CDs fabricated by various techniques showed insignificant differences (p> 0.05) but statistically significant differences (p< 0.01) were found in right-left side force difference, maximum bite force % and centralization of forces. The maximum force difference on right and left side was observed CCD with MO (37.48 ± 1.03 N) and maximum occlusal-bite force % was observed for 3-DPCD with LO (95.40 ± 1.30 N). In comparison to 3-DP CD, the chances of centre of force out of ellipse (centralization of forces) was 3.36 and 2.15 times more in CCD and MCD techniques made CDs respectively.

CONCLUSIONS

The occlusal parameters in CDs were affected by the fabrication techniques and occlusal schemes of CDs. The digital CDs retain adjusted occlusal schemes better and 3-DP CDs with BBO and LO occlusal schemes provided centralization of forces, better distribution and high maximum occlusal force % respectively.

Computerized occlusal forces analysis in complete dentures fabricated by additive and subtractive techniques

BACKGROUND

Fabrication of complete dentures by computer-aided designing and computer-aided manufacturing (CAD-CAM) techniques are now common. Subtractive and Additive are the two principal CAD-CAM techniques used for this purpose. However, studies that evaluated the occlusal forces by CDs manufactured by these techniques are lacking.

OBJECTIVES

To compare the occlusal forces in complete dentures fabricated by additive, subtractive and conventional techniques with different occlusal schemes, using computerized occlusal force analysis system [Tech-Scan III (T-Scan III)].

METHODS

Three groups (Gr) were made on the basis of techniques of fabrication of CDs: Conventional CDs (CCD), Subtractive CDs (SCD), and Additive CDs (ACD). Each group CDs were further divided into three sub groups based on occlusion schemes: bilateral balanced occlusion (BBO), lingualized occlusion (LO) and mono plane occlusion (MO). A total of 45 CDs were made: 15 in each group with 5 CDs of each occlusal scheme. For all samples, occlusal force analysis (percentage of occlusal force applied on the right and left sides of the arch, centralization of forces and percentage of maximum occlusal force) was done using computerized occlusal analysis system: T-Scan III. Univariate regression analysis and logistic regression analysis were used to find the effects of the technique of fabrication and occlusion scheme over the occlusal forces (p< 0.05).

RESULTS

The intergroup comparison revealed statistically significant differences (p< 0.01) in right-left side force difference, maximum bite force in CDs fabricated by various techniques and with different occlusion schemes. Though the effect of occlusion scheme was more than the technique of fabrication (according to effect size estimation). The maximum force difference between right-left side was observed in combination of CCD technique and MO scheme (36.88 ± 2.82 N). Furthermore, the maximum bite force was observed for SCD technique (89.14 ± 6.08 N) and LO scheme (92.17 ± 3.22 N). In comparison to ACD, the chances of centre of force out of ellipse was 2.53 time more in CCS and 0.75 times less in SCD techniques and in comparison to MO, the chances of out of ellipse was 0.298 times less in BBO and 0.396 times less in LO schemes, though these chances were not statistically significant (p> 0.05).

CONCLUSIONS

The digital CDs fabricated by subtractive technique were proved to be superior to additive technique in terms of occlusal force analysis on tested parameters. However, further research is needed on patients to determine the exact superiority of one technique over the other.

Evaluation of trueness and precision of stereolithography-fabricated photopolymer-resin dentures under different postpolymerization conditions: An in vitro study

STATEMENT OF PROBLEM

Stereolithography (SLA) additive manufacturing (AM) technologies have become popular for the fabrication of complete dentures; however, the trueness and precision of the dentures under different postpolymerization conditions remain unclear.

PURPOSE

The purpose of this in vitro study was to investigate the effect of different postpolymerization times and temperatures on the trueness and precision of SLA dentures.

MATERIAL AND METHODS

Specimens simulating maxillary complete dentures were fabricated by SLA 3D printing. They were polymerized for 15 minutes or 30 minutes at different temperatures (40 °C, 60 °C, and 80 °C). The intaglio surface trueness of the specimens was evaluated by superimposing the postpolymerization standard tessellation language (STL) file on the original STL file for each specimen via a best-fit method (n=10). The precision was measured across specimens by superimposing the postpolymerization STL file from each specimen group and using the combination formula (n=45). Subsequently, root-mean-square estimates (RMSEs) and color map data were obtained, and a normality test was conducted on the obtained data. The results indicated that the distributions were not normal; therefore, nonparametric Kruskal-Wallis and Mann-Whitney tests were used to analyze the data (α=.05).

RESULTS

For trueness, the lowest RMSE corresponded to the postpolymerization time of 30 minutes and a temperature of 40 °C. This result was significantly different from specimens those of the 15-minute and 60 °C, 15-minute and 80 °C, and 30-minute and 80 °C specimens (P<.001). For precision, the median of the lowest RMSE corresponded to the 30-minute and 40 °C specimens. This median value was significantly different from those of other specimens (P<.001). The findings indicate that the postpolymerization condition of 30 minutes and 40 °C affords the highest trueness and precision and the most favorable intaglio surface adaptation of the denture.

CONCLUSIONS

The postpolymerization conditions influenced the RMSE values of the trueness and precision of a clear photopolymer resin. The RMSE and color map data associated with the 30-minute and 40 °C condition corresponded to the greatest trueness and precision of all the SLA denture specimens considered.

CAD-CAM milled complete dentures with custom disks and prefabricated artificial teeth: A dental technique

A digital complete denture was manufactured from a disk customized for each patient. The custom disk was made of resin and contained prefabricated artificial teeth. Both the denture base and the artificial teeth in the custom disk were milled in this technique, resulting in dentures with a high bond strength between the artificial teeth and denture base, excellent esthetics because of the prefabricated artificial teeth, and accurate occlusion because of the custom occlusal surface.

Evaluation of the Milling Accuracy of Zirconia-Reinforced Lithium Silicate Crowns Fabricated Using the Dental Medical Device System: A Three-Dimensional Analysis

This study aimed to analyze the milling accuracy of lithium disilicate and zirconia-reinforced silicate crown fabricated using chairside computer-aided design/manufacturing (CAD/CAM) system. Mandibular left first premolar was selected for abutment. A master model was obtained for digital impression using an intraoral scanner, and crowns were designed using a CAD software design program. Amber Mill (AM), IPS e max CAD (IPS), and CELTRA DUO (CEL) were used in the CAD/CAM system, and a total 45 crowns (15 crowns each for AM, IPS, and CEL) was fabricated. Milling accuracy was analyzed with respect to trueness, measured by superimposing CAD design data and scan data through a three-dimensional program to compare the outer and inner surfaces and internal and external parts, thereby acquiring both quantitative and qualitative data. Data were analyzed using the non-parametric test and Kruskal–Wallis H test. In addition, the Mann–Whitney U test was used by applying the level of significance (0.05/3 = 0.016) adjusted by post-analysis Bonferroni correction. All the measured parts of the lithium disilicate and zirconia-reinforced silicate crowns showed statistically significant differences (p < 0.05). The lithium disilicate (AM and IPS) materials showed superior milling accuracy than the zirconia-reinforced lithium silicate (CEL) materials.

A Comparison of Conventionally Versus Digitally Fabricated Denture Outcomes in a University Dental Clinic

PURPOSE

The purpose of this retrospective, cross-sectional study is to evaluate if there is a difference in number of visits (including fabrication and postoperative) and remake rate when comparing conventionally fabricated and digitally fabricated complete dentures by dental students in a predoctoral student dental clinic.

MATERIALS AND METHODS

This two-year retrospective cross-sectional study consisted of a chart review for patients receiving maxillary and/or mandibular complete dentures between 2017 and 2019 (n = 314) at the UNC Adams School of Dentistry predoctoral student clinic. No control group was determined for this study. Data were extracted for 242 conventional dentures and 39 digital dentures. Objective treatment outcomes were obtained for each included denture: the number of patient appointments from preliminary impressions to denture placement, the number of postoperative visits, any complications noted, and any need for remakes. Fisher's Exact Test and Cochran-Mantel-Haenszel analysis were completed with statistical significance set at p < 0.05.

RESULTS

For the number of visits from preliminary impression to placement, 50% of conventionally fabricated dentures had 6 or more visits, while only 5% of digitally fabricated dentures had 6 or more visits. This difference for the number of patient visits was statistically significant (p < 0.05). Additionally, conventionally fabricated dentures required an average of 2-3 postoperative visits, whereas digitally fabricated dentures required 1-2 postoperative visits. This difference was also statistically significant (p < 0.05). For the number of dentures requiring remake, there was no statistical difference (p = 0.1904).

CONCLUSIONS

When comparing conventionally fabricated and digitally fabricated dentures in the predoctoral clinic, the digitally fabricated dentures required fewer patient appointments from start to finish, and fewer postoperative appointments than conventionally fabricated dentures. Fewer visits may be an important consideration for patients, especially those with limited access to care.

Effect of Printing Direction on the Accuracy of 3D-Printed Dentures Using Stereolithography Technology

This study evaluated the effects of the differences in the printing directions of stereolithography (SLA) three-dimensional (3D)-printed dentures on accuracy (trueness and precision). The maxillary denture was designed using computer-aided design (CAD) software with an STL file (master data) as the output. Three different printing directions (0°, 45°, and 90°) were used. Photopolymer resin was 3D-printed (n = 6/group). After scanning all dentures, the scanning data were saved/output as STL files (experimental data). For trueness, the experimental data were superimposed on the master data sets. For precision, the experimental data were selected from six dentures with three different printing directions and superimposed. The root mean square error (RMSE) and color map data were obtained using a deviation analysis. The averages of the RMSE values of trueness and precision at 0°, 45°, and 90° were statistically compared. The RMSE of trueness and precision were lowest at 45°, followed by 90°; the highest occurred at 0°. The RMSE of trueness and precision were significantly different among all printing directions (p < 0.05). The highest trueness and precision and the most favorable surface adaptation occurred when the printing direction was 45°; therefore, this may be the most effective direction for manufacturing SLA 3D-printed dentures.

Do hydrothermal aging and microwave sterilization affect the trueness of milled, additive manufactured and injection molded denture bases?

Concepts for digital denture manufacturing are market-available but studies comparing the trueness of such dentures, either milled (MIL) or additive manufactured, compared to injection molded (IM) ones are still limited. Regarding the impact of artificial aging and microwave sterilization on this parameter, no data are available. Therefore, the purpose of this investigation was to assess the trueness of IM, MIL, and stereolithography (SLA) printed denture bases after manufacturing, hydrothermal cycling, and microwave sterilization. Sixteen edentulous maxillary plaster models were poured using a silicone mold and digitized by means of a desktop scanner. For group IM, 16 denture bases were injection molded using these models. For group MIL and SLA, the denture bases were virtually designed and manufactured referring to the digitized data. A total of 48 samples were scanned 1) after manufacturing, 2) after hydrothermal cycling (5-55 °C, N = 5,000), and after 3) three as well as 4) six cycles of microwave sterilization for 6 min each at 640 W. The 3D surface deviation of the total intaglio surface, the palate, the alveolar ridge, and the border seal region was evaluated on the basis of the root mean square estimation (RMSE) and positive and negative mean deviations with an inspection software. For statistical analysis, ANOVA and post hoc Tukey tests were performed (α = 0.05). MIL showed the lowest deviations of the total RMSE (P ≤ .006) compared with the scans of the plaster models. In comparison, IM showed increased, mainly positive, deviations (P = .006) at the border seal. SLA presented the highest total RMSE (P = .001) with increased negative deviations, likewise at the border seal. In contrast to SLA (P = .001), no differences between IM and MIL (P = .816) were measured after hydrothermal cycling. Following microwave sterilization, the trueness of SLA was higher compared to IM and MIL (P = .001), with no differences between MIL and IM (P = .153). Distortion of IM and MIL was measured after the 3rd cycle with no further changes observed thereafter (P ≥ .385). It can be concluded, that subtractive manufacturing of denture bases results in the highest trueness, followed by IM and SLA. In contrast to IM and SLA, hydrothermal cycling did not affect MIL. Solely SLA printed denture bases remained dimensionally stable after microwave sterilization.

In silico evaluation of the peripheral and inner seals in complete denture master impressions using a custom-developed 3D software

OBJECTIVES

Despite the complexity of the edentulous anatomy, little evidence exists as to what impression techniques and materials should be employed for an optimal result. The aim of this in silico study was to evaluate the trueness of peripheral and inner seals of different edentulous jaw impressions.

MATERIALS AND METHODS

Twelve maxillary edentulous participants (male = 8, female = 4; age 68.5 ± 11.7 years) participated in this study. Four different impression materials and techniques, irreversible hydrocolloid (Alginate; Blueprint X-Crème, Dentsply Sirona, PA, USA), polyvinyl siloxane impression (PVS; Aquasil Ultra+ Medium, Dentsply Sirona, PA, USA), and subsequently modified with ZnOE (PVSM) and an optical impression (Optical; 3Shape A/S, Copenhagen, Denmark), were tested against a control impression: low-fusing impression compound border molding (Kerr Corp., CA, USA) followed by a ZnOE impression (ZnOE; SS White impression paste, S.S. White Group, Gloucester, England). All impressions were scanned and analyzed using a custom-built 3D comparison software analyzing the vertical and horizontal trueness.

RESULTS

The vertical discrepancy (peripheral seal) of the impression surface was significantly more true for PVSM than Alginate (p = 0.001), PVS (p = 0.019), and Optical groups (p < 0.001). Where the horizontal discrepancy (inner seal) was compared, the impression surface was more true for PVSM than Alginate (p < 0.001) and Optical (p < 0.001). PVS group was also significantly more true than Optical (p = 0.015).

CONCLUSION

Impression techniques and materials may significantly influence the peripheral and inner seal of an edentulous jaw impression.

CLINICAL RELEVANCE

When using a polyvinylsiloxane impression material for master edentulous impressions, a selective inner seal reline with a conventional zinc oxide eugenol impression paste can improve the inner seal.