Trial fitting of a removable partial denture framework made using computer-aided design and rapid prototyping techniques

Recent Advances in 3D Printing of Polymers for Application in Prosthodontics

Contemporary mass media frequently depict 3D printing as a technology with widespread utilization in the creation of dental prosthetics. This paper endeavors to provide an evidence-based assessment of the current scope of 3D printing's integration within dental laboratories and practices. Its primary objective is to offer a systematic evaluation of the existing applications of 3D-printing technology within the realm of dental prosthetic restorations. Furthermore, this article delves into potential prospects, while also critically examining the sustained relevance of conventional dental laboratory services and manufacturing procedures. The central focus of this article is to expound upon the extent to which 3D printing is presently harnessed for crafting dental prosthetic appliances. By presenting verifiable data and factual insights, this article aspires to elucidate the actual implementation of 3D printing in prosthetic dentistry and its seamless integration into dental practices. The aim of this narrative review is twofold: firstly, to provide an informed and unbiased evaluation of the role that 3D printing currently plays within dental laboratories and practices; and secondly, to instigate contemplation on the transformative potential of this technology, both in terms of its contemporary impact and its future implications, while maintaining a balanced consideration of traditional dental approaches.

A Feasible and Innovative Method of Investing Wax Pattern for Removable Partial Dentures: An In Vitro Study

Background A dental prosthesis called a removable partial denture (RPD) is used to fill the gaps left by one or more lost teeth. It serves as an option to fixed bridges and restorations supported by implants. This research was on a simple and effective method of investing RPD wax pattern and an in vitro investigation into the creation of a cutting-edge RPD technique. Methodology The method outlines the straightforward steps for waxing an RPD and validating the precision of the cast framework. The use of a laminated paper ring rather than a metallic one for investing the wax patterns is the main distinction between the novel method and the traditional ringless technique. Results A total of 30 samples were considered for investigation, with 15 in the traditional and 15 in the experimental group. The innovative wax pattern investment method exhibited a higher mean geometric orientation (9.23 ± 0.42) compared to traditional investment casting (8.90 ± 0.37 mm). Conversely, the dimensional accuracy mean was lower for the innovative wax pattern investment method (0.28 ± 0.03 mm) compared to traditional investment casting (0.31 ± 0.05 mm). The p-value was less than 0.001 for both parameters, signifying that the differences between the means of the two methods were statistically significant. The statistical power (1-β) was the probability of rejecting the null hypothesis when it was false. The statistical power was 0.999 for both geometric orientation and dimensional accuracy, indicating that the study had a very high power to detect differences between the two methods. Conclusions This innovative method does away with the requirement for a commercially available plastic ring, reduces the price and time needed for RPD manufacturing, and offers decent marginal accuracy. However, it has some restrictions, such as the challenge of cutting and preparing the paper ring after investing, which could lower the finished product's quality.

Influence of fabrication method on the manufacturing accuracy and internal discrepancy of removable partial dentures: A systematic review and meta-analysis

STATEMENT OF PROBLEM

Removable partial dentures (RPDs) can be fabricated with conventional casting procedures or computer-aided design and computer-aided manufacturing (CAD-CAM) technologies; however, the manufacturing accuracy and internal discrepancy differences among these manufacturing methods remain uncertain.

PURPOSE

The purpose of this systematic review and meta-analysis was to assess the influence of the fabricating method (casting, milling, or additive manufacturing) on the accuracy and internal discrepancy of RPDs.

MATERIAL AND METHODS

An electronic search of the literature was performed in 6 databases: PubMed/Medline, Embase, Web of Science, Scopus, Cochrane, and Google Scholar. The studies that assessed the accuracy and internal discrepancy of RPDs fabricated from casting, milling, and additive manufacturing were included. Studies reporting gaps (mean) and standard deviations were included in the meta-analysis. Publication bias was identified using funnel plot asymmetry and the Egger test.

RESULTS

A total of 25 articles were included. The internal discrepancy of the additively manufactured RPDs ranged from 14.4 to 511 μm and from 7 to 419 μm in conventionally fabricated RPDs. For the milling method, 20 to 66 μm horizontal and 17 to 59 μm vertical discrepancies were reported. The Egger tests indicated no publication bias among the studies that were included in the meta-analysis. Four included studies resulted in more than the acceptable clinical gap (311 μm) for the CAD-CAM method. Independently of the manufacturing method, the greatest internal discrepancies reported were observed under the major connectors. RPDs fabricated by using CAD-CAM techniques required fewer clinical appointments, the RPD design was easier to reproduce, and laboratory time was less than with conventional procedures. However, the reviewed studies described several disadvantages, including limited RPD design programs, difficulties in defining the occlusal plane, expensive materials, and increased laboratory cost.

CONCLUSIONS

Additive and subtractive technologies provide accurate methods for RPD fabrication; however, all challenges, including limited design software programs have not yet been overcome, and casting is still needed when the framework pattern is milled or printed.

Evaluation of trueness and precision of removable partial denture metal frameworks manufactured with digital technology and different materials

PURPOSE

The aim of this study is to evaluate the accuracy of removable partial denture (RPD) frameworks produced using different digital protocols.

MATERIALS AND METHODS

80 frameworks for RPDs were produced using CAD-CAM technology and divided into four groups of twenty (n = 20): Group 1, Titanium frameworks manufactured by digital metal laser sintering (DMLS); Group 2, Co-Cr frameworks manufactured by DMLS; Group 3, Polyamide PA12 castable resin manufactured by multi-jet fusion (MJF); and Group 4, Metal (Co-Cr) casting by using lost-wax technique. After the digital acquisition, eight specific areas were selected in order to measure the Δ-error value at the intaglio surface of RPD. The minimum value required for point sampling density (0.4 mm) was derived from the sensitivity analysis. The obtained Δ-error mean value was used for comparisons: 1. between different manufacturing processes; 2. between different manufacturing techniques in the same area of interest (AOI); and 3. between different AOI of the same group.

RESULTS

The Δ-error mean value of each group ranged between -0.002 (Ti) and 0.041 (Co-Cr) mm. The Pearson's Chi-squared test revealed significant differences considering all groups paired two by two, except for group 3 and 4. The multiple comparison test documented a significant difference for each AOI among group 1, 3, and 4. The multiple comparison test showed significant differences among almost all different AOIs of each group.

CONCLUSION

All Δ-mean error values of all digital protocols for manufacturing RPD frameworks optimally fit within the clinical tolerance limit of trueness and precision.

Optimization of the dimension of computer numerical control-milled polyetheretherketone clasps: An in vitro evaluation of accuracy

STATEMENT OF PROBLEM

The accuracy and optimal dimensions of computer numerical control (CNC)-milled polyetheretherketone (PEEK) removable partial denture (RPD) clasps are unclear.

PURPOSE

The purpose of this in vitro study was to investigate the trueness and precision of CNC-milled PEEK clasps with different thicknesses and lengths.

MATERIAL AND METHODS

Ladder-shaped specimens of 2 thicknesses with 5 lengths of clasps were designed and milled with PEEK and commercially pure titanium (CP Ti) (n=6). All milled specimens were scanned and superimposed onto the design data. Three-dimensional and 2-dimensional deviation analyses were carried out to evaluate the trueness of milled PEEK clasps. The scanning data of each group were superimposed pairwise, and the 3-dimensional deviations were analyzed to evaluate the precision. Nonparametric tests, ANOVA, the Pearson correlation, and univariate linear regression were used for statistical analysis (α=.05).

RESULTS

The deviation of trueness of the PEEK clasps (0.047 to 0.164 mm) was higher than that of the CP Ti clasps (0.037 to 0.060 mm) (P<.001). Increasing the length of the clasps increased the deviations (P<.001). Deviation in the 2 thicknesses was not significantly different (P=.210). The correlation coefficients of 1.0-mm-thick and 1.5-mm-thick PEEK and CP Ti clasps were 0.843, 0.794, 0.638, and 0.405. The positive correlation coefficients of PEEK were higher than those of CP Ti and those of 1.0-mm-thick clasps was higher than those of 1.5-mm-thick clasps. The deviations were evenly distributed in the 9-mm length of the clasp for CP Ti and in the 6-mm length of the clasp for PEEK. Beyond these lengths, deviations increased with increased length. The increasing amplitude of CP Ti was smaller than that of the PEEK group, and that of the 1.5-mm-thick clasp was smaller than that of the1.0-mm-thick clasp. The measured range of precision of PEEK clasps was 0.079 to 0.152 mm, while that of CP Ti clasps was 0.036 to 0.096 mm. CP Ti clasps tended to have better precision than PEEK clasps, except for the 1.0-mm-thick clasps with a length greater than 9 mm and the 1.5-mm-thick clasp with a 12-mm length. The correlation of the clasp length with precision showed that the lengths of 1.0-mm-thick clasps strongly influenced precision (PEEK, P=.020; CP Ti, P<.001); this correlation decreased sharply when the thickness of clasps was 1.5 mm (PEEK, P=.199; CP Ti, P=.107).

CONCLUSIONS

Greater elasticity increased the deviations of milled clasps. The increased thickness helped the clasp remain stable during the milling process. The 1.5-mm-thick PEEK clasps in the 3-mm and 6-mm lengths were the optimal design tested.

Additive Manufactured Polymers in Dentistry, Current State-of-the-Art and Future Perspectives-A Review

3D-printing application in dentistry not only enables the manufacture of patient-specific devices and tissue constructs, but also allows mass customization, as well as digital workflow, with predictable lower cost and rapid turnaround times. 4D printing also shows a good impact in dentistry, as it can produce dynamic and adaptable materials, which have proven effective in the oral environment, under its continuously changing thermal and humidity conditions. It is expected to further boost the research into producing a whole tooth, capable to harmoniously integrate with the surrounding periodontium, which represents the ultimate goal of tissue engineering in dentistry. Because of their high versatility associated with the wide variety of available materials, additive manufacturing in dentistry predominantly targets the production of polymeric constructs. The aim of this narrative review is to catch a glimpse of the current state-of-the-art of additive manufacturing in dentistry, and the future perspectives of this modern technology, focusing on the specific polymeric materials.

Fit Accuracy of Removable Partial Denture Frameworks Fabricated with CAD/CAM, Rapid Prototyping, and Conventional Techniques: A Systematic Review

Objective

Analyzing and comparing the fit and accuracy of removable partial denture (RPDs) frameworks fabricated with CAD/CAM and rapid prototyping methods with conventional techniques.

Materials and Methods

The present systematic review was carried out according to PRISMA guidelines. The search was carried out on PubMed/MEDLINE, Cochrane collaboration, Science direct, and Scopus scientific engines using selected MeSH keywords. The articles fulfilling the predefined selection criteria based on the fit and accuracy of removable partial denture (RPD) frameworks constructed from digital workflow (CAD/CAM; rapid prototyping) and conventional techniques were included.

Results

Nine full-text articles comprising 6 in vitro and 3 in vivo studies were included in this review. The digital RPDs were fabricated in all articles by CAD/CAM selective laser sintering and selective laser melting techniques. The articles that have used CAD/CAM and rapid prototyping technique demonstrated better fit and accuracy as compared to the RPDs fabricated through conventional techniques. The least gaps between the framework and cast (41.677 ± 15.546 μm) were found in RPDs constructed through digital CAD/CAM systems.

Conclusion

A better accuracy was achieved using CAD/CAM and rapid prototyping techniques. The RPD frameworks fabricated by CAD/CAM and rapid prototyping techniques had clinically acceptable fit, superior precision, and better accuracy than conventionally fabricated RPD frameworks.

Computer-aided technology for fabricating removable partial denture frameworks: A systematic review and meta-analysis

STATEMENT OF PROBLEM

A consensus that establishes the indications and clinical performance of removable partial denture (RPD) frameworks designed and manufactured with computer-aided design and computer-aided manufacturing (CAD-CAM) systems is lacking.

PURPOSE

The purpose of this systematic review and meta-analysis was to evaluate the currently published literature investigating different CAD-CAM methods and techniques for RPD manufacturing and their clinical performance.

MATERIAL AND METHODS

A comprehensive search of studies published up to September 2019 was performed in PubMed/MEDLINE, Web of Science, Cochrane Library, and SciELO databases according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA Statement) criteria and was registered and approved in the International Prospective Register of Systematic Reviews (PROSPERO: CRD42020152197). The population, intervention, comparison, outcome (PICO) question was "Do the CAD-CAM frameworks have similar performances to those fabricated by conventional techniques?" The meta-analysis included clinical and in vitro studies based on the effect size and test of Null (2-Tail) with 95% confidence interval (CI). Clinical and in vitro studies were selected and analyzed separately.

RESULTS

A total of 15 articles out of 358 were selected. For clinical studies, quantitative analysis with a sample of 25 participants showed a mean discrepancy between occlusal rests and rest seats of 184.91 μm (95% CI: 152.6 μm-217.15 μm) and heterogeneity (I²) of 0%. Clinical data considered that frameworks were acceptable for continuity of treatment. The predominant materials were cobalt-chromium (Co-Cr) and polyetheretherketone (PEEK), and studies using Co-Cr reported that the structure required adjustments. In addition, it has been reported that the indirect technique was time-consuming and selective laser melting (SLM) can be costly. PEEK structures have been more widely accepted because of improved esthetics. Quantitative data from the in vitro studies revealed that the additive manufacturing technique (2.006 mm: 95% CI: -2.021 mm to 6.032 mm) was not significantly different from the indirect technique (0.026 mm; P=.455; random: I²: 98.402%).

CONCLUSIONS

Clinical studies and in vitro research on CAD-CAM planning and manufacturing of removable prosthesis frameworks are still sparse. However, preliminary data indicate a similar fit and esthetic improvement when compared with the conventional technique.

A systematic review of digital removable partial dentures. Part II: CAD/CAM framework, artificial teeth, and denture base

PURPOSE

This study comprehensively reviewed the current status of the digital workflow of removable partial dentures (RPDs) and summarized information about the fabrication methods and material properties of the dental framework, artificial teeth, and denture base.

STUDY SELECTION

We performed a systematic review of the literature published in online databases from January 1980 to April 2020 regarding RPD fabrication and materials used in the related digital technology. We selected eligible articles, retrieved information regarding digital RPDs, and conducted qualitative/quantitative analyses. In this paper, the computer-aided design/computer-aided manufacturing (CAD/CAM) framework, artificial teeth, and denture base materials are reported.

RESULTS

A variety of materials, such as cobalt-chromium alloy, titanium, zirconia, and polyether ether ketone, are used for dental CAD/CAM frameworks. The mechanical strength of the metal materials used for the CAD/CAM framework was superior to that of the cast framework. However, the fitness and surface roughness of the framework and clasp fabricated using a selective laser melting (SLM) method were not superior to those obtained via cast fabrication. Most material properties and the surface roughness of poly methyl methacrylate (PMMA) discs used for digital RPDs were superior to those of heat-cured PMMA.

CONCLUSIONS

The use of a CAD/CAM framework and PMMA disc for digital RPDs offers numerous advantages over conventional RPDs. However, technical challenges regarding the accuracy and durability of adhesion between the framework and denture base remain to be solved. In digital fabrication, human technical factors influence the quality of the framework.

A Scoping Review on the Accuracy of Fit of Removable Partial Dentures in a Developing Digital Context

Purpose

The aim of this paper is to evaluate studies on the quality of fit of alloy removable-partial-dentures (RPDs) produced by computer-aided design/computer-aided manufacturing (CAD/CAM) and rapid prototyping (RP) technology. This paper offers a comprehensive scoping review of various methods of assessing the quality of fit of RPDs in the context of a developing digital approach to manufacturing and assessment.

Methodology/Approach

A search was made using MEDLINE/PubMed, Scopus, and Science Direct to identify the studies of the accuracy of fit of RPDs.

Findings

Optical and physical examination of dentures “in situ” on the model or in the patient’s oral cavity were the most commonly used methods for the assessment of fit of RPDs. Eighteen of the included studies assessed the internal fit between RPDs and oral tissues or models using either polyvinyl silicone materials as filler, calipers, photographs, and microscopes or a combination of these. Two studies used visual assessment. Most studies reported that the fit of RPDs ranged from satisfactory to excellent. However, many of these assessments seemed somewhat subjective and flawed with regard to assessing indentations of the framework into a model or distortion. Two papers used a new method of computer-based superimposition which included a color map of discrepancies to assess the fit of the machine-produced RPDs offering possibilities to quantify the assessment of fit, perhaps leading to a more objective assessment. Despite the limited number of clinical trials, the available evidence was thought to reinforce the claim that the fit of RPDs fabricated digitally was acceptable.

Conclusion

The recent introduction of color maps to compare the differences between the fitting surface and the model is promising. However, a new method for displaying discrepancies shown by color maps is introduced, which could lead to a more quantitative assessment.

Computer-aided design of polyetheretherketone for application to removable pediatric space maintainers

Background

The premature loss of primary teeth is a common problem in pediatric dentistry, resulting in disruption of the arch integrity. Hence, space maintainers (SM) used for maintaining spaces are necessary. However, current methods of making removable space maintainers (RSM) have some limitations.

Methods

Digital models of dentition defects were obtained by using a scanning technique coupled with laser medical image reconstruction. The digital RSMs were designed using the 3Shape software. They were manufactured using two methods: polyetheretherketone (PEEK), and conventional methods (20 RSMs per group). For qualitative evaluation, the Likert five-point scale was used by 10 experts to obtain a score for 40 RSMs. The spaces between the tissue surfaces of the RSMs and the models were replaced using silicone, and the maximum and mean distances, as well as the standard deviation, were measured. A three-dimensional variation analysis was used to measure these spaces. The student’s t-test and Satterthwaite t-test were used to compare the differences in the spaces for the various materials.

Results

The PEEK RSMs were found to fit the models well. In the qualitative assessment, the mean experts’ scores for the PEEK and conventional groups were 1.80 ± 0.40 and 1.82 ± 0.40, and there was no significant difference between the two groups (p = 0.875). In the quantitative assessment, the mean spaces for the PEEK digital RSMs and the conventional RSMs were 44.32 ± 1.75 μm, and 137.36 ± 18.63 μm, respectively, and the differences were statistically significant (p < 0.001). In addition, there were significant differences in the maximum space and the standard deviation between the two groups.

Conclusion

Digitally designed and integrated RSMs were found to be superior to those produced using the conventional method. 3D variation analysis results showed that the mean distances and standard deviations of the PEEK groups were significantly smaller than those of conventional group (p < 0.01). A PEEK-manufactured RSM produced using CAD/CAM would be extremely suitable for clinical applications.

A novel digital altered cast impression technique for fabricating a removable partial denture with a distal extension

BACKGROUND

Although computer-aided design and computer-aided manufacturing has been successfully used in fabricating removable partial dentures (RPDs), making altered cast impressions is still a time-consuming and labor-intensive process for fabricating RPDs with a distal extension. An alternative digital technique has been developed to simplify this process.

METHODS

The authors present a case in which they sought to improve the efficiency and simplicity in obtaining altered cast impressions by means of digital technology. Initially, a primary plaster cast was scanned as a digital cast. Based on the digital cast, a novel custom tray was designed and fabricated using a 3-dimensional printing method. With the custom tray, the novel altered cast impression was fabricated and scanned, and the final virtual altered cast was reconstructed by a stitching method.

RESULTS

Based on the virtual altered cast, the authors designed the virtual RPD framework. Finally, the titanium alloy framework was fabricated using a 3-dimensional printing process, and the authors fit the final RPD to the patient.

CONCLUSIONS

This novel digital altered cast impression technique may eliminate interoperator variability and increase precision compared with the traditional technique.

PRACTICAL IMPLICATIONS

This technique showed the potential for reducing clinical appointments, chair time, and laboratory procedures.

Additive manufacturing of dental polymers: An overview on processes, materials and applications

Additive manufacturing (AM) processes are increasingly used in dentistry. The underlying process is the joining of material layer by layer based on 3D data models. Four additive processes (laser stereolithography, polymer jetting, digital light processing, fused deposition modeling) are mainly used for processing dental polymers. The number of polymer materials that can be used for AM in dentistry is small compared to other areas. Applications in dentistry using AM are limited (e.g. study models, maxillo-facial prostheses, orthodontic appliances etc.). New and further developments of materials are currently taking place due to the increasing demand for safer and other applications. Biocompatibility and the possibility of using materials not only as temporarily but as definitive reconstructions under oral conditions, mechanically more stable materials where less or no post-processing is needed are current targets in AM technologies. Printing parameters are also open for further development where optical aspects are also important.

Internal porosities, retentive force, and survival of cobalt-chromium alloy clasps fabricated by selective laser-sintering

PURPOSE

The purpose of this study was to evaluate internal porosities, retentive force values and survival of cobalt-chromium (Co-Cr) alloy clasps fabricated by direct metal laser-sintering (DMLS) and compare them to conventionally cast clasps.

METHODS

Embrasure clasps were digitally designed fitting teeth 35 and 36 on identical metal models (N = 32). Sixteen clasps were fabricated using DMLS (group DMLS) and another sixteen clasps were additively manufactured from wax and then cast from a Co-Cr alloy (group CAST). Internal porosities were examined using micro-focus X-ray (micro-CT) and analyzed applying Kolmogorov-Smirnov test, Mann-Whitney test, and T test (significance level: p < 0.050). A universal testing machine was used to determine the retentive force values at baseline and after 1095, 5475, 10,950 and 65,000 cycles of simulated aging. Data were analyzed employing Kolmogorov-Smirnov test, one-way ANOVA, and Scheffé's post-hoc test (significance level: p < 0.050). Survival was estimated for 65,000 cycles of artificial aging using Kaplan-Meier analysis.

RESULTS

Micro-CT analysis revealed a higher prevalence (p < 0.001), but a more homogeneous size and a significantly smaller mean (p = 0.009) and total volume (p < 0.001) of internal porosities for group DMLS. The groups showed mean initial retentive force values of 13.57 N (CAST) and 15.74 N (DMLS), which significantly declined over aging for group CAST (p = 0.003), but not for group DMLS (p = 0.107). Survival was considerably higher for group DMLS (93.8%) than for group CAST (43.8%) after 65,000 cycles of aging.

CONCLUSIONS

Clasps made by laser-sintering could be an alternative to conventional cast clasps for the fabrication of removable partial denture frameworks.

Assessing the Accuracy of Casting and Additive Manufacturing Techniques for Fabrication of a Complete Palatal Coverage Metal Framework

PURPOSE

To provide information regarding the accuracy of additive manufacturing in comparison to conventional casting, specifically for fabrication of complete palatal coverage metal frameworks.

MATERIALS AND METHODS

Three additive manufacturing techniques were tested: selective laser melting (SLM), electron beam melting (EBM), and computer-aided design/cast (CADcast), with conventional casting as the control. Both the SLM and EBM groups were tested pre- and post-finishing, for a total of six test groups (n = 10/group). A digital master design was used as the standard to which all frameworks were digitally compared by best-fit analysis, which generated root mean square values using proprietary software. A one-way ANOVA was conducted to test for statistical differences among materials, followed by a post-hoc multiple comparison test (Tukey's test HSD). Surface roughness for one framework arbitrarily selected from each group was analyzed using a profilometer.

RESULTS

There was a significant difference in accuracy among the materials (F = 99.79, p < 0.0001). A post-hoc Tukey test indicated that CADcast differed significantly from the other five materials (i.e., most accurate, p < 0.01). EBM prefinished and EBM finished were both significantly different from the other materials (i.e., least accurate). Color mapping images help visualize the differences between each framework compared to the master design. The surface roughness values ranged from 22 to 63.5 µm, with CADcast being the smoothest, and EBM prefinished the roughest.

CONCLUSIONS

CADcast and SLM techniques were as or more accurate than the conventional technique for producing an uncomplicated framework design. Further investigation is recommended regarding the surface roughness of additive manufacturing products and potential biological complications.

Obturator fabrication incorporating computer-aided design and 3-dimensional printing technology: A clinical report

This article reports an approach to fabricating a maxillary obturator using the computer-aided design and computer-aided manufacturing (CAD-CAM) process. The maxillary definitive cast and the trial tooth arrangement were separately scanned and superimposed. The virtual cast created from the scan data was surveyed, and the framework was designed using specific software. The definitive cobalt-chromium framework was fabricated by using 3-dimensional (3D) selective laser sintering (SLS) technology. After framework trial placement, the definitive obturator prosthesis was processed using conventional heat-polymerizing resin with the lost-wax processing technique. Using CAD technology and 3D metal printing resulted in improved fit, function, and esthetics for the definitive obturator prosthesis.

Assessment of the fit of removable partial denture fabricated by computer-aided designing/computer aided manufacturing technology

Objective:

To assess the level of evidence that supports the quality of fit for removable partial denture (RPD) fabricated by computer-aided designing/computer aided manufacturing (CAD/CAM) and rapid prototyping (RP) technology.

Methods:

An electronic search was performed in Google Scholar, PubMed, and Cochrane library search engines, using Boolean operators. All articles published in English and published in the period from 1950 until April 2017 were eligible to be included in this review. The total number of articles contained the search terms in any part of the article (including titles, abstracts, or article texts) were screened, which resulted in 214 articles. After exclusion of irrelevant and duplicated articles, 12 papers were included in this systematic review.

Results:

All the included studies were case reports, except one study, which was a case series that recruited 10 study participants. The visual and tactile examination in the cast or clinically in the patient’s mouth was the most-used method for assessment of the fit of RPDs. From all included studies, only one has assessed the internal fit between RPDs and oral tissues using silicone registration material. The vast majority of included studies found that the fit of RPDs ranged from satisfactory to excellent fit.

Conclusion:

Despite the lack of clinical trials that provide strong evidence, the available evidence supported the claim of good fit of RPDs fabricated by new technologies using CAD/CAM.

Fitness and retentive force of cobalt-chromium alloy clasps fabricated with repeated laser sintering and milling

PURPOSE

With computer-aided design and computer-aided manufacturing (CAD/CAM), the study was conducted to create a removable partial denture (RPD) framework using repeated laser sintering rather than milling and casting techniques. This study experimentally evaluated the CAM clasp and compared it to a conventional cast clasp.

METHODS

After the tooth die was scanned, an Akers clasp was designed using CAD with and without 50μm of digital relief on the occlusal surface of the tooth die. Cobalt-chromium (Co-Cr) alloy clasps were fabricated using repeated laser sintering (RLS) and milling as one process simultaneously (hybrid manufacturing; HM). The surface roughness of the rest region, gap distances between clasp and tooth die, initial retentive forces, and changes of retentive forces up to 10,000 insertion/removal cycles were measured before and after heat treatment. The HM clasp was compared to the cast clasp and the clasp made by repeated laser sintering only without a milling process.

RESULTS

The HM clasp surface was smoother than those of cast and RLS clasps. With the digital relief, the fitness accuracy of the HM clasp improved. The retentive forces of the HM clasps with relief and after heat treatment were significantly greater than for the cast clasp. HM clasps demonstrated a constant or slight decrease of retention up to 10,000 cycles.

CONCLUSIONS

HM clasp exhibited better fitness accuracy and retentive forces. The possibility of clinically using HM clasps as well as conventional cast clasps can be suggested.

Titanium removable denture based on a one-metal rehabilitation concept

The use of a single metal for all restorations would be necessary because it protects against metal corrosion caused by the contact of different metals. For this "one-metal rehabilitation" concept, non-alloyed commercially pure (CP) titanium should be used for all restorations. Titanium frameworks have been cast and used for the long term without catastrophic failure, whereas they have been fabricated recently using computer-aided design/computer-aided manufacturing (CAD/CAM). However, the milling process for the frameworks of removable partial dentures (RPDs) is not easy because they have very complicated shapes and consist of many components. Currently, the fabrication of RPD frameworks has been challenged by one-process molding using repeated laser sintering and high-speed milling. Laser welding has also been used typically for repairing and rebuilding titanium frameworks. Although laboratory and clinical problems still remain, the one-metal rehabilitation concept using CP titanium as a bioinert metal can be recommended for all restorations.

Clasp fabrication using one-process molding by repeated laser sintering and high-speed milling

PURPOSE

A single machine platform that integrates repeated laser sintering and high-speed milling for one-process molding has been developed.

METHODS

The Akers clasp was designed using the CAD system (DWOS Partial Frameworks, Dental Wings) and fabricated using repeated laser sintering and a high-speed milling machine (LUMEX Advance-25, Matsuura) with 50-μm Co-Cr particles (CAM clasp). As controls, cast clasps of the same forms were also prepared using conventional casting methods with a Co-Cr alloy and CP titanium Grade 3. After the surface roughness was measured, the gap distance between the clasps and the tooth die was assessed using the silicone film method. The initial retentive force and changes in retention up to 10,000 cycles were also measured. The data were analyzed using two-way ANOVA and Tukey's multiple comparison test (α=0.05).

RESULTS

CAM clasps exhibited significantly smoother surfaces than those of cast Co-Cr and CP Ti clasps (p<0.05). However, the gap distances of the CAM clasps were significantly greater than those of the cast clasps (p<0.05). The retentive forces of both CAM and cast Co-Cr clasps were significantly higher than those of CP Ti clasps. (p<0.05). The retention of CAM clasps demonstrated a constant or slight decrease from 1000 up to 10,000 cycles.

CONCLUSIONS

The CAM clasp made by repeated laser sintering and high-speed milling can be used effectively as an RPD component.

A review of computer-aided design/computer-aided manufacture techniques for removable denture fabrication

The aim of this review was to investigate usage of computer-aided design/computer-aided manufacture (CAD/CAM) such as milling and rapid prototyping (RP) technologies for removable denture fabrication. An electronic search was conducted in the PubMed/MEDLINE, ScienceDirect, Google Scholar, and Web of Science databases. Databases were searched from 1987 to 2014. The search was performed using a variety of keywords including CAD/CAM, complete/partial dentures, RP, rapid manufacturing, digitally designed, milled, computerized, and machined. The identified developments (in chronological order), techniques, advantages, and disadvantages of CAD/CAM and RP for removable denture fabrication are summarized. Using a variety of keywords and aiming to find the topic, 78 publications were initially searched. For the main topic, the abstract of these 78 articles were scanned, and 52 publications were selected for reading in detail. Full-text of these articles was gained and searched in detail. Totally, 40 articles that discussed the techniques, advantages, and disadvantages of CAD/CAM and RP for removable denture fabrication and the articles were incorporated in this review. Totally, 16 of the papers summarized in the table. Following review of all relevant publications, it can be concluded that current innovations and technological developments of CAD/CAM and RP allow the digitally planning and manufacturing of removable dentures from start to finish. As a result according to the literature review CAD/CAM techniques and supportive maxillomandibular relationship transfer devices are growing fast. In the close future, fabricating removable dentures will become medical informatics instead of needing a technical staff and procedures. However the methods have several limitations for now.

Evaluation of the flexural strength and microhardness of provisional crown and bridge materials fabricated by different methods

Purpose:

The purpose of this study was to evaluate and compare the flexural strength and microhardness of provisional restorative materials fabricated utilizing rapid prototyping (RP), Computer Assisted Designing and Computer Assisted Milling (CAD-CAM) and conventional method.

Materials and Methods:

Twenty specimens of dimensions 25 mm × 2 mm × 2 mm (ADA-ANSI specification #27) were fabricated each using: (1) Three dimensional (3D) printed light-cured micro-hybrid filled composite by RP resin group, (2) a milled polymethyl methacrylate (CH) using CAD-CAM (CC resin group), and (3) a conventionally fabricated heat activated polymerized CH resin group. Flexural strength and microhardness were measured and values obtained were evaluated.

Results:

The measured mean flexural strength values (MegaPascals) were 79.54 (RP resin group), 104.20 (CC resin group), and 95.58 (CH resin group). The measured mean microhardness values (Knoop hardness number) were 32.77 (RP resin group), 25.33 (CC resin group), and 27.36 (CH resin group). The analysis of variance (ANOVA) test shows that there is statistically significant difference in the flexural strength values of the three groups (P < 0.05). According to the pairwise comparison of Tukey's honest significant difference (HSD) test, flexural strength values of CC resin group and CH resin group were higher and statistically significant than those of the RP resin group (P < 0.05). However, there was no significant difference between flexural strength values of CC resin and CH resin group (P = 0.64). The difference in microhardness values of the three groups was statistically significant according to ANOVA as well as the intergroup comparison done using the Tukey's HSD (post hoc) test (P < 0.05).

Conclusions:

CC-based CH had the highest flexural strength whereas RP-based 3D printed and light cured micro-hybrid filled composite had the highest microhardness.

A critically appraised topic review of computer-aided design/computer-aided machining of removable partial denture frameworks

A critically appraised topic (CAT) review is presented about the use of computer-aided design (CAD)/computer-aided machining (CAM) removable partial denture (RPD) frameworks. A systematic search of the literature supporting CAD/CAM RPD systems revealed no randomized clinical trials, hence the CAT review was performed. A PubMed search yielded 9 articles meeting the inclusion criteria. Each article was characterized by study design and level of evidence. No clinical outcomes research has been published on the use of CAD/CAM RPDs. Low levels of evidence were found in the available literature. Clinical research studies are needed to determine the efficacy of this treatment modality.

Microtechnologies in implant and restorative dentistry: A stroll through a digital dental landscape

This is an explanatory article introducing the combination of various technologies used in implant and restorative dentistry. The aim of the article is to provide an overview of some of the techniques supporting the restorative treatment plan at various stages to provide contemporary, state-of-the-art bridgework based on dental implants. It is a discussion of the way existing technologies used in fields of engineering and medicine are brought together to form a complete process.