Cast-free fabrication of a digital removable partial denture with a polyetheretherketone framework

A technical and clinical digital approach to the altered cast technique with an intraoral scanner and polyvinyl siloxane impression material

This technique digitalizes the clinical and laboratory steps of fabricating removable partial dentures (RPDs) with the altered cast technique. An intraoral scanner was used to capture the mandibular Kennedy class II partially edentulous arch. An RPD framework was fabricated digitally and then combined with a custom tray with a wax occlusal rim. A conventional polyvinyl siloxane altered cast impression was made and then digitalized both intraorally and extraorally, followed by a digital interocclusal record. The resulting scan was modified to produce an additively manufactured cast. The teeth and gingival components were then designed and fabricated with a combination of additive and subtractive manufacturing, followed by the conventional acrylic resin pour technique. The definitive prosthesis was completed with minimal conventional techniques and without the use of gypsum, prefabricated teeth, or a physical articulator. The technique reduces the number of appointments and achieves the functional extension of the prosthesis through border molding, which is not possible with intraoral scanning.

Clinical evaluation of a one-piece polyetheretherketone removable partial denture fabricated using a novel digital workflow: A self-controlled clinical trial

PURPOSE

To explore the clinical application of one-piece polyetheretherketone (PEEK) removable partial dentures (RPDs) fabricated using a novel digital workflow and to evaluate their weights and fits in vivo and patient satisfaction.

MATERIALS AND METHODS

Fifteen cases with posterior partially edentulous situations were selected, and each patient received two types of RPDs, including a novel digital workflow (test group) and a conventional workflow (control group). For the test group, one-piece RPDs were designed through three-dimensional (3D) methods by scanning stone casts and fabricated by milling PEEK discs. Each RPD was weighed. The gaps between the oral tissue and RPDs in each group were duplicated using a polyvinylsiloxane (PVS) replica and measured by 3D analysis. A visual analog scale (VAS) was used to evaluate the patient's satisfaction. Paired t-tests were used to compare the differences in the weight, the gaps of each RPD, and VAS values between the two groups. One-way analysis of variance tests was used to compare the differences in the gap among different components in each group.

RESULTS

The RPD in the test group weighed less than that in the control group (p < 0.01). No statistically significant differences in the gaps of denture bases and rests (p > 0.05) were found between the two groups, but the gaps of major connectors in the test group were significantly smaller than in the control group (p < 0.05). The VAS scores for comfortableness and masticatory efficiency were not significantly different between the two groups (p > 0.05) but the scores for the aesthetic appearance of the clasps in the test group were significantly higher than that in the control group (p < 0.05).

CONCLUSIONS

One-piece PEEK RPDs manufactured using a novel digital workflow weighed less than conventional RPDs and exhibited a clinically acceptable internal fit. Although the aesthetic appearance of the PEEK clasps was superior to the control, there is still room for improvement.

A digital workflow for designing and manufacturing metal frameworks and removable partial dentures: A novel dental technique

The purpose of this technical report is to demonstrate a fully digital workflow for designing and fabricating metal frameworks and removable partial dentures. After obtaining a digital cast of the dental arch with bilateral distal extension defect, computer-aided design software and 3D printing technology are used for the design and fabrication of the removable partial denture frameworks, denture teeth, and denture bases, instead of the traditional workflow. The assembly of the three components is facilitated through a meticulously structured framework. The technology, which prints metal frameworks, denture bases, and denture teeth through different processes with different materials, achieves full 3D printing technology for making removable partial dentures.

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.

Removable complete denture with a metal base: Integration of digital design and conventional fabrication techniques

OBJECTIVE

Digitally-designed removable complete dentures are typically composed of a resin denture base without a metal framework. However, metal denture bases are preferable as resin bases are more susceptible to fracture. Therefore, this article introduces a unique technique that integrates computer-aided design (CAD) and conventional resin processing for the fabrication of removable complete dentures with a metal framework.

CLINICAL CONSIDERATIONS

A maxillary complete denture with a metal base and a mandibular implant-retained overdenture reinforced with a metal framework were fabricated. The dentures were designed using CAD software and a tooth library. The denture bases were milled from wax disks, and artificial teeth were placed to complete the wax dentures. The metal frameworks were also designed using CAD software and produced via casting of printed resin patterns. Finally, conventional denture processing techniques were applied to obtain dentures with metal frameworks.

CONCLUSIONS

A digitally designed, removable complete denture with a metal base can be successfully fabricated using the described technique, which merges digital design and conventional methods. This article demonstrates the feasibility and potential advantages of this innovative approach in denture fabrication.

CLINICAL SIGNIFICANCE

The presented technique provides the following advantages: digital design features, precise space above implant overdenture attachments for a metal framework, convenience of esthetic evaluation with printed trial dentures, long-term data storage and duplication, reliable bond between the artificial teeth and denture base, and enhanced strength of the removable complete denture due to the metal reinforcement.

A digital chairside repair protocol for removable partial dentures with polyetheretherketone frameworks

Polyetheretherketone (PEEK) has become popular for removable partial denture (RPD) frameworks but reports on their clinical follow-up and repair are lacking. Two defective PEEK-framework RPDs were repaired with computer-aided design and manufacturing technology, saving costs and time and simplifying the treatment process.

Survival analysis up to 7 years of 621 zirconia monolithic single crowns with feather-edge margins fabricated with a cast-free workflow starting from intraoral scans: A multicentric retrospective study

STATEMENT OF PROBLEM

Clinical studies on the fabrication of monolithic zirconia restorations with a feather-edge tooth preparation from digital scans and a cast-free fully digital workflow are lacking.

PURPOSE

The purpose of this retrospective multicentric study in private practices was to evaluate the outcomes of monolithic zirconia crowns fabricated with feather-edge margins and a cast-free approach.

MATERIAL AND METHODS

A total of 621 teeth were prepared with feather-edge margins and restored with monolithic zirconia crowns fabricated with a fully digital cast-free workflow. Data were analyzed by using the Kaplan-Meier test and descriptive statistics. The clinical evaluation adopted the California Dental Association-modified criteria after recalling all patients between April and July 2021.

RESULTS

The clinical survival of 619 of 621 crowns, including recemented crowns placed in 427 patients (217 men, 220 women) over 5 years (2014 to 2019 with crowns in service between 12 and 85 months), was analyzed. The 2 excluded crowns were delivered to patients who dropped out of the study. Of the 619 crowns, 5 failed during the follow-up period: 4 teeth were extracted because of fracture and 1 restoration fractured. No other technical or biological failures were observed. The mean overall survival time was 84.4 months (standard error, 0.255; 95% confidence interval for the mean, 83.92 to 84.92). The overall survival probability was 99.1% up to 85 months.

CONCLUSIONS

The clinical outcomes of the monolithic zirconia crowns with feather-edge margins evaluated were comparable with outcomes reported using other margin designs and materials.

Clinical Applications of Polyetheretherketone in Removable Dental Prostheses: Accuracy, Characteristics, and Performance

The high-performance thermoplastic polyetheretherketone (PEEK) has excellent mechanical properties, biocompatibility, chemical stability, and radiolucency. The present article comprehensively reviews various applications of PEEK in removable dental prostheses, including in removable partial dentures (RPDs) (frameworks and clasps), double-crown RPDs, and obturators. The clinical performance of PEEK in removable dental prostheses is shown to be satisfactory and promising based on the short-term clinical evidence and technical complications are scarce. Moreover, the accuracy of RPDs is a vital factor for their long-term success rate. PEEK in removable dental prostheses is fabricated using the conventional lost-wax technique and CAD/CAM milling, which produces a good fit. Furthermore, fused deposition modeling is considered to be one of the most practical additive techniques. PEEK in removable prostheses produced by this technique exhibits good results in terms of the framework fit. However, in light of the paucity of evidence regarding other additive techniques, these manufacturers cannot yet be endorsed. Surface roughness, bacterial retention, color stability, and wear resistance should also be considered when attempting to increase the survival rates of PEEK removable prostheses. In addition, pastes represent an effective method for PEEK polishing to obtain a reduced surface roughness, which facilitates lower bacterial retention. As compared to other composite materials, PEEK is less likely to become discolored or deteriorate due to wear abrasion.

A Digital Workflow for the Fabrication of a Milled Removable Partial Denture

Complete dentures fabricated with the additive or subtractive method have been widely used and proven to be clinically acceptable. However, fabrication of removable partial dentures (RPDs) using computer-aided design and computer-aided manufacturing is limited by its technique sensitivity as the pink resin, which encases part of metal framework, cannot be fabricated digitally. This article introduces a digital workflow to fabricate an RPD with the subtractive method. A complex structure of the offset metal framework and denture base with teeth sockets was milled with this technique. Artificial teeth were milled with a resin disk according to the computer-aided design data, resulting in the customized occlusal surface. This digital technique can be an alternative to the analog fabrication method as the RPD was fabricated digitally, keeping the original structures and reducing resin shrinkage on the intaglio surface.