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

PURPOSE

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSION

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

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

PURPOSE

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

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.

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.

3D printed complete removable dental prostheses: a narrative review

Background

The purpose of this paper is to review the available literature on three-dimensionally printed complete dentures in terms of novel biomaterials, fabrication techniques and workflow, clinical performance and patient satisfaction.

Methods

The methodology included applying a search strategy, defining inclusion and exclusion criteria, selecting studies and forming tables to summarize the results. Searches of PubMed, Scopus, and Embase databases were performed independently by two reviewers to gather literature published between 2010 and 2020.

Results

A total of 126 titles were obtained from the electronic database, and the application of exclusion criteria resulted in the identification of 21 articles pertaining to printed technology for complete dentures. Current innovations and developments in digital dentistry have successfully led to the fabrication of removable dental prostheses using CAD/CAM technologies. Milled dentures have been studied more than 3D printed ones in the currently available literature. The limited number of clinical studies, mainly case reports, suggest current indications of 3D printing in denture fabrication process to be custom tray, record bases, trial, interim or immediate dentures but not definitive prostheses fabrication. Limitations include poor esthetics and retention, inability to balance occlusion and low printer resolution.

Conclusions

Initial studies on digital dentures have shown promising short-term clinical performance, positive patient-related results and reasonable cost-effectiveness. 3D printing has potential to modernize and streamline the denture fabrication techniques, materials and workflows. However, more research is required on the existing and developing materials and printers to allow for advancement and increase its application in removable prosthodontics.

Incorporating Digital Dentures into Clinical Practice: Flexible Workflows and Improved Clinical Outcomes

Replacement of missing teeth with complete denture prostheses have been successfully accomplished for decades. However, limitations of denture materials and the number of appointments required to fabricate new or replacement complete dentures preclude practicality. New innovations involving a partially or completely digital workflow facilitate the fabrication of complete dentures in fewer, shorter appointments, and by incorporating materials that exhibit improved physical properties. The purpose of this manuscript is to describe the variety of workflows that can be implemented to incorporate digital denture fabrication into clinical practice.

A first experience with digital complete overdentures

The development of computer-aided design/computer-aided manufacturing systems for dentistry in the 1980s resulted in the successful fabrication of crowns, fixed dental prostheses, and superstructures for both natural teeth and dental implants. Today, this technology is available for constructing digitally designed and milled, completely removable dental prostheses. The procedure uses clinical and laboratory protocols that allow fabrication of completely removable prostheses within two clinical appointments. The aim of this clinical report is to present the author's first experience with digital complete overdentures, the practicality of this technology, and patient feedback. Compared with conventional overdentures, the fit of the digital prostheses was improved because the cameo and flanges of the prostheses were nicely shaped and rolled, and this enhanced their stability and retention. Occlusion was also excellent. However, aesthetics in terms of the alignment, shape, and size of the maxillary overdenture teeth were inacceptable. Despite some of the drawbacks identified in our study, the use of removable digital dentures does provide excellent adaptation of the denture base and requires fewer clinic visits. We anticipate that the unsatisfactory aesthetic outcomes presented in this report can be corrected with more experience. We also believe that acquiring an in-house scanning machine would be beneficial. We highly recommend including this technique in dental school curriculums at both the undergraduate and graduate levels in order to keep students and residents up to date on the latest technology available.