The use of PEEK in digital prosthodontics: A narrative review

Influence of the Peek Abutments on Mechanical Behavior of the Internal Connections Single Implant

The present study aimed to evaluate the biomechanical behavior of PEEK abutments with different heights on single titanium implants. To investigate the implant surface, different tests (scanning electron microscopy, energy-dispersive X-ray, and X-ray diffraction) were adopted. Herein, 20 implants received the 4.5 × 4.0 mm PEEK short abutment (SA) and 20 received the 4.5 × 5.5 mm PEEK long abutment (LA). The abutments were installed using dual-cure resin cement. To determine the fatigue test, two specimens from each group were submitted to the single load fracture test. For this, the samples were submitted to a compressive load of (0.5 mm/min; 30°) in a universal testing machine. For the fatigue test, the samples received 2,000,000 cycles (2 Hz; 30°). The number of cycles and the load test was analyzed by the reliability software SPSS statistics using Kaplan-Meier and Mantel-Cox tests (log-rank) (p < 0.05). The maximum load showed no statistically significant differences (p = 0.189) for the SA group (64.1 kgf) and the LA group (56.5 kgf). The study groups were statistically different regarding the number of cycles (p = 0.022) and fracture strength (p = 0.001). PEEK abutments can be indicated with caution for implant-supported rehabilitation and may be suitable as temporary rehabilitation.

Immunohistochemical analysis of soft tissue response to polyetheretherketone (PEEK) and titanium healing abutments on dental implants: a randomized pilot clinical study

Background

The data on polyetheretherketone (PEEK) influence on the peri-implant soft tissues in clinical settings are deficient. The aims of this pilot study were to analyze and compare soft tissues’ response to PEEK and titanium (Ti) healing abutments (HA) by means of histological and immunohistochemical analyses.

Methods

A total of 22 implants with PEEK or Ti HA were placed in 11 patients, applying the “split-mouth” study design. Three months later, soft tissue specimens were harvested from 20 implants for histology in order to qualitatively detect the inflammatory cells’ presence, to semi-qualitatively analyze the inflammation intensity and to assess the inflammatory responses type by immunohistochemical analysis using LCA, CD3, CD20 and CD68 antibodies.

Results

Epithelial infiltrate followed by an intensive inflammation in sub-epithelium was observed in 100% around PEEK HA. A number of LCA+ and CD 68+ cells was significantly higher in PEEK comparing to Ti group (p = 0.001 and p = 0.020, respectively), while CD 20+ and CD3+ counted cells were found in a significantly higher amount in Ti than in PEEK group (p = 0.006 and p = 0.010, respectively).

Conclusion

PEEK HA seems to evoke the more intense tissue inflammatory response demonstrated predominantly by histocytes’ and plasmacytes’ activation, while Ti HA triggers the inflammatory reaction of lower intensity, dominantly mediated by B-cells.

Trial registration

The study registered at ClinicalTrials.gov (NCT04436939).

Effects of Autoclave Sterilization and Multiple Use on Implant Scanbody Deformation In Vitro

In the intraoral scanner (IOS) impression technique for dental implants, a scanbody (SB) is connected to the implant and scanned. Poly(ether-ether-ketone) (PEEK) is a widely used material for SBs and it is recommended for single use. However, from the perspective of the Sustainable Development Goals, it is desirable to use these products multiple times. As SBs are used in patients' mouths, proper sterilization is necessary for multiple uses. In the present study, the effect of autoclave treatment and connection/disconnection on SB deformation was investigated. The SB was connected to the implant and stereolithography (STL) data were obtained. Then, the SB was disconnected and underwent autoclave treatment, or was connected and disconnected multiple times, or underwent a combination of both processes. The results showed that there were significant differences in the distance and angle when comparing SBs before and after the autoclave treatment, but repeated connections with or without autoclave treatment had no significant impact on the measured values. The surface texture, observed with scanning electron microscopy, showed that a groove was observed on the surface of the SB, but the groove did not show major changes after 10 connection/autoclave processes. These results indicate that autoclave sterilization has some impact on SB deformation but connection/disconnection itself may not have a huge impact on SB deformation.

Polyetheretherketone subperiosteal implant retaining a maxillary fixed prosthesis: A case series

STATEMENT OF PROBLEM

Patients needing dental rehabilitation of a complete atrophic maxilla would benefit from simplified treatment plans.

PURPOSE

The purpose of this case series was to demonstrate the prosthetic management of 4 edentulous patients with severe maxillary ridge resorption who declined multiple stage surgery and sought a fixed prosthesis in single-stage surgery.

MATERIAL AND METHODS

The patients were provided with completely digital computer-aided designed and computer-aided manufactured (CAD-CAM) polyetheretherketone (PEEK) maxillary subperiosteal frameworks, which were surgically placed in a 1-step procedure. The patients were followed up for 12 months and evaluated for signs of implant rejection, infection, prosthetic fracture or mobility, or implant exposure.

RESULTS

At the 12-month follow-up, all the implants were functionally stable with healthy soft tissue and showed no sign of prosthetic fracture, infection, or pus discharge.

CONCLUSIONS

PEEK subperiosteal implants for maxillary atrophied ridges can be considered a promising treatment option within the limitations of this clinical study with low patient numbers and a short observational time.

Comparison of Titanium and PEEK Medical Plastic Implant Materials for Their Bacterial Biofilm Formation Properties

This study investigated two of the most commonly used CAD–CAM materials for patient-specific reconstruction in craniomaxillofacial surgery. The aim of this study was to access the biofilm formation of Staphylococcus aureus, Streptococcus mutans, Enterococcus faecalis, and Escherichia coli on titanium and PEEK medical implant materials. Two titanium specimens (titanium grade 2 tooled with a Planmeca CAD–CAM milling device and titanium grade 5 tooled with a computer-aided design direct metal laser sintering device (CAD-DMLS)) and one PEEK specimen tooled with a Planmeca CAD–CAM milling device were studied. Bacterial adhesion on implants was evaluated in two groups (saliva-treated group and non-saliva-treated group) to imitate intraoral and extraoral surgical routes for implant placement. The PEEK medical implant material showed higher bacterial adhesion by S. aureus, S. mutans, and E. coli than titanium grade 2 and titanium grade 5, whereas E. faecalis showed higher adhesion to titanium as compared to PEEK. Saliva contamination of implants also effected bacterial attachment. Salivary coating enhanced biofilm formation by S. aureus, S. mutans, and E. faecalis. In conclusion, our findings imply that regardless of the implant material type or tooling techniques used, salivary coating plays a vital role in bacterial adhesion. In addition, the majority of the bacterial strains showed higher adhesion to PEEK than titanium.

Application of 3 dimension-printed injection-molded polyether ether ketone lunate prosthesis in the treatment of stage III Kienböck’s disease: A case report

BACKGROUND

Polyether ether ketone (PEEK) is a high-performance medical polymer, and there are some clinical cases of PEEK prosthesis implantation. However, application of 3D-printed injection-molded PEEK lunate prosthesis for treatment of stage III Kienböck’s disease has not been reported. This study’s purpose was to analyze the clinical efficacy of 3D-printed injection-molded PEEK lunate prosthesis in the treatment of stage III Kienböck’s disease and thus provide a good therapeutic choice for Kienböck’s disease.

CASE SUMMARY

We report a patient with stage III Kienböck’s disease. With the healthy lunate bone as reference, 3D lunate reconstruction was performed using a mirroring technique. A PEEK lunate prosthesis was prepared by 3D printing and injection molding, and then it was inserted into the original anatomical position after removing the necrotic lunate bone. Wrist pain and function, anatomical suitability of the lunate prosthesis, and complications were evaluated and analyzed postoperatively. At the last visit (one year after surgery), the range of motion, grasp force, visual analog scale score and Cooney score of the affected wrist were significantly improved, and postoperative X-ray examination indicated that the lunate prosthesis had good anatomical suitability for adjacent bony structures.

CONCLUSION

The 3D-printed injection-molded PEEK lunate prosthesis demonstrated definite efficacy in treating stage III Kienböck’s disease.

Evaluation of the mechanical properties and fit of 3D-printed polyetheretherketone removable partial dentures

Compared with CAD/CAM, fused deposition modeling (FDM) 3D printing technology is simple and safe to operate and has a low cost and high material utilization rate; thus, it is widely used. The present investigation aimed to evaluate the mechanical properties and fit of polyetheretherketone (PEEK) removable partial dentures (RPDs) constructed by FDM. We analyzed mechanical properties of PEEK samples prepared by FDM, milling, or injection molding. RPDs were designed and finite element analysis models was constructed to evaluate maximum stress and strain in the RPDs, cortical bone and mucosa. Geomagic Qualify software was used to analyze gaps between the model and the tissue surface of the framework. The results showed that the compressive strength of the 3D-printed PRDs was greater than that of the injection-molded samples. Finite element analysis demonstrated that the maximum stress on the PRDs was less than the yield strength of the material. Overall, the mechanical properties and fit of the PEEK RPD fabricated by FDM technology essentially fulfilled clinical requirements.

Low-Cost Cranioplasty—A Systematic Review of 3D Printing in Medicine

The high cost of biofabricated titanium mesh plates can make them out of reach for hospitals in low-income countries. To increase the availability of cranioplasty, the authors of this work investigated the production of polymer-based endoprostheses. Recently, cheap, popular desktop 3D printers have generated sufficient opportunities to provide patients with on-demand and on-site help. This study also examines the technologies of 3D printing, including SLM, SLS, FFF, DLP, and SLA. The authors focused their interest on the materials in fabrication, which include PLA, ABS, PET-G, PEEK, and PMMA. Three-dimensional printed prostheses are modeled using widely available CAD software with the help of patient-specific DICOM files. Even though the topic is insufficiently researched, it can be perceived as a relatively safe procedure with a minimal complication rate. There have also been some initial studies on the costs and legal regulations. Early case studies provide information on dozens of patients living with self-made prostheses and who are experiencing significant improvements in their quality of life. Budget 3D-printed endoprostheses are reliable and are reported to be significantly cheaper than the popular counterparts manufactured from polypropylene polyester.

Insufficient Evidence to Ascertain the Long-Term Survival of PEEK Dental Prostheses: A Systematic Review of Clinical Studies

Introduction: Polyetheretherketone (PEEK) is a polymer that is used in the construction of orthopaedic and dental implants. It is also used to construct removable and fixed dental prostheses due to its superior mechanical and esthetic properties compared to conventional materials. This systematic review aims to analyse and appraise the literature concerning PEEK dental prostheses critically. Methods: The following focused question was constructed ‘Are dental prostheses made of PEEK inferior to those made of other materials in terms of clinical- and patient-reported outcomes?’. The CONSORT (Consolidated Standards of Reporting Trials) tool was used for the quality assessment of the randomised clinical trials. The STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) quality assessment tool was used to assess the quality of observational studies and the case reports were evaluated using the CARE (Case Report) guidelines. Results: A total of 12 studies were included in this review. Two case studies received an overall grade of medium and the overall quality of six studies was graded as ‘low’. All three observational studies and the only randomised controlled trial received scores of ‘medium’. Conclusion: PEEK-based dental prostheses may provide a viable and more esthetic alternative to conventional prosthodontic appliances. However, within the limitations of this study is the evidence to ascertain the long-term viability of PEEK-based dental prostheses. Future studies should focus on conducting large-scale, multicenter trials to compare the survival rate of PEEK prostheses to that of conventionally available prosthodontic appliances.

Biomechanical Analysis of Different Framework Design, Framework Material and Bone Density in the Edentulous Mandible With Fixed Implant-Supported Prostheses: A Three-Dimensional Finite Element Study

PURPOSE

The objective of this finite element study was to investigate the effect of different framework designs, framework materials, and bone densities on the stress distribution of fixed implant-supported prostheses for edentulous mandibles.

MATERIALS AND METHODS

Under the condition of 2-mm cortical bone, 16 models were created in the edentulous mandible to simulate different framework designs (1-piece or 3-piece frameworks) with different framework material (pure titanium, zirconia, polyetheretherketone, or carbon fiber-reinforced polyetheretherketone) in-high or low-density trabecular bone. Then, vertical loading and oblique loading at 75° were applied to the anterior and posterior regions. The stress distribution and stress concentration region of implant and peri-implant bone with different combinations were compared by finite element analysis.

RESULTS

The use of the 1-piece zirconia framework in high-density trabecular bone improved stress distribution on implants and peri-implant bone. The region of stress concentration is located in the buccal cervix of the distal implants and the distobuccal portion of the cortical bone in all models. To improve the stress distribution on fixed implant-supported dentures for edentulous mandibles, the 1-piece framework and zirconia represent the better combinations.

CONCLUSION

Under the condition of 2-mm cortical bone thickness, the full-arch zirconia framework had minimum von Mises stress on implants and peri-implant bone in all models, and high trabecular bone density greatly decreased the stress on cortical bone. This article is protected by copyright. All rights reserved.

PEEK Biomaterial in Long-Term Provisional Implant Restorations: A Review

Polyetheretherketone (PEEK) has become a useful polymeric biomaterial due to its superior properties and has been increasingly used in dentistry, especially in prosthetic dentistry and dental implantology. Promising applications of PEEK in dentistry are dental implants, temporary abutment, implant-supported provisional crowns, fixed prosthesis, removable denture framework, and finger prosthesis. PEEK as a long-term provisional implant restoration has not been studied much. Hence, this review article aims to review PEEK as a long-term provisional implant restoration for applications focusing on implant dentistry. Articles published in English on PEEK biomaterial for long-term provisional implant restoration were searched in Google Scholar, ScienceDirect, PubMed/MEDLINE, and Scopus. Then, relevant articles were selected and included in this literature review. PEEK presents suitable properties for various implant components in implant dentistry, including temporary and long-term provisional restorations. The modifications of PEEK result in wider applications in clinical dentistry. The PEEK reinforced by 30-50% carbon fibers can be a suitable material for the various implant components in dentistry.

Adaptive Mechanism for Designing a Personalized Cranial Implant and Its 3D Printing Using PEEK

The rehabilitation of the skull’s bones is a difficult process that poses a challenge to the surgical team. Due to the range of design methods and the availability of materials, the main concerns are the implant design and material selection. Mirror-image reconstruction is one of the widely used implant reconstruction techniques, but it is not a feasible option in asymmetrical regions. The ideal design approach and material should result in an implant outcome that is compact, easy to fit, resilient, and provides the perfect aesthetic and functional outcomes irrespective of the location. The design technique for the making of the personalized implant must be easy to use and independent of the defect’s position on the skull. As a result, this article proposes a hybrid system that incorporates computer tomography acquisition, an adaptive design (or modeling) scheme, computational analysis, and accuracy assessment. The newly developed hybrid approach aims to obtain ideal cranial implants that are unique to each patient and defect. Polyetheretherketone (PEEK) is chosen to fabricate the implant because it is a viable alternative to titanium implants for personalized implants, and because it is simpler to use, lighter, and sturdy enough to shield the brain. The aesthetic result or the fitting accuracy is adequate, with a maximum deviation of 0.59 mm in the outside direction. The results of the biomechanical analysis demonstrate that the maximum Von Mises stress (8.15 MPa), Von Mises strain (0.002), and deformation (0.18 mm) are all extremely low, and the factor of safety is reasonably high, highlighting the implant’s load resistance potential and safety under high loading. Moreover, the time it takes to develop an implant model for any cranial defect using the proposed modeling scheme is very fast, at around one hour. This study illustrates that the utilized 3D reconstruction method and PEEK material would minimize time-consuming alterations while also improving the implant’s fit, stability, and strength.

A Comparative Evaluation of the Radiopacity of Contemporary Restorative CAD/CAM Blocks Using Digital Radiography Based on the Impact of Material Composition

Purpose

The main purpose of this study was to assess the radiopacity of contemporary restorative computer-aided design (CAD)/computer-aided manufacturing (CAM) materials and the impact of material composition as measured by energy-dispersive X-ray spectrophotometry (EDX) on radiopacity.

Materials and Methods

Ten specimens of six CAD/CAM materials with 1 mm thickness were produced and then digitally radiographed with an aluminum (Al) step-wedge (SW) and 1 mm thick tooth slice. The specimen mean gray values (MGVs) were recorded in pixels and compared to an Al-SW, dentin, and enamel of equal thickness. For the elementary analysis of the composition of the materials, EDX was performed.

Results

The recorded MGVs ranged between 21.20 ± 4.94 and 238.5 ± 13.61 pixels. Materials were sorted according to the MGVs descendingly, Prettau, Vita Suprinity, Vita Enamic, Shofu, Pekkton, and BioHPP. Prettau and Vita Suprinity had significantly higher MGV than dentin and 1 mm thick Al. In comparison, Vita Enamic had a slightly higher value than dentin and 1 mm thick Al. Although Pekkton and BioHPP had MGV significantly lower than dentin and 1 mm thick Al, Shofu had a significantly lower value than dentin and nonsignificantly lower than 1 mm thick Al (p < 0.05). According to EDX analysis, the examined materials contained several components in varying quantities of radiopacity.

Conclusions

The radiopacity of only three studied materials exceeded the International Organization for Standardization's minimum standards (ISO).

Investigation of stress distribution within an endodontically treated tooth restored with different restorations

Background/purpose

Recently, metal-free restoration has become the standard in prosthetic treatment. However, it is still unclear which combination is most effective in preventing root fracture and secondary caries. The purpose of this study was to evaluate the influence of different post systems, crown materials, crown thickness and luting agents on the stress distribution around the crown margins, cervical dentin and the tip of the post.

Materials and methods

Ninety-six mandibular first premolar models were developed and analyzed using finite element analysis (FEA). Two designs of crowns, six kinds of crown materials, four types of post and core systems and two kinds of luting agents were included and evaluated for the stress distribution within the abutment teeth. The Von Mises stress magnitudes were compared among all models.

Results

The stress at the tip of the post decreased as the young's modulus of luting agent decreased; The stress concentrated more at the cervical area (dentin and crown), as the physical properties of the crown material increased.

Conclusion

Crowns fabricated using polyetheretherketone (PEEK) can reduce the stress concentration at the cervical area, so it may be possible to reduce the amount of tooth reduction during abutment tooth preparation. The stress distribution around the post tip is affected by the post and core systems and luting agent, regardless of crown materials and thickness. When inserting a post of the higher Young's modulus such as zirconia post, methyl methacrylate luting cement can reduce the stress concentration at the tip of the post.

Influence of Framework Material and Posterior Implant Angulation in Full-Arch All-on-4 Implant-Supported Prosthesis Stress Concentration

This study evaluated the influence of distal implants angulation and framework material in the stress concentration of an All-on-4 full-arch prosthesis. A full-arch implant-supported prosthesis 3D model was created with different distal implant angulations and cantilever arms (30° with 10-mm cantilever; 45° with 10-mm cantilever and 45° with 6-mm cantilever) and framework materials (Cobalt–chrome [CoCr alloy], Yttria-stabilized tetragonal zirconia polycrystal [Y-TZP] and polyetheretherketone [PEEK]). Each solid was imported to computer-aided engineering software, and tetrahedral elements formed the mesh. Material properties were assigned to each solid with isotropic and homogeneous behavior. The contacts were considered bonded. A vertical load of 200 N was applied in the distal region of the cantilever arm, and stress was evaluated in Von Misses (σVM) for prosthesis components and the Maximum (σMAX) and Minimum (σMIN) Principal Stresses for the bone. Distal implants angled in 45° with a 10-mm cantilever arm showed the highest stress concentration for all structures with higher stress magnitudes when the PEEK framework was considered. However, distal implants angled in 45° with a 6-mm cantilever arm showed promising mechanical responses with the lowest stress peaks. For the All-on-4 concept, a 45° distal implants angulation is only beneficial if it is possible to reduce the cantilever’s length; otherwise, the use of 30° should be considered. Comparing with PEEK, the YTZP and CoCr concentrated stress in the framework structure, reducing the stress in the prosthetic screw.

Strain Induced by Bio-High-Performance Polymers and Cobalt-Chromium Digitally Constructed Telescopic Partial Dentures after 1 Year Simulation of Function

BACKGROUND: Numerous attempts were made to reduce the adverse effects of the distal extension removable partial dentures (RPDs) and enhance their prognosis. High-performance polymers (HPP) were utilized in the construction of RPDs to maintain the health of the supporting structures. AIM: Thus, this study was prompted to compare the strains induced by Bio HPP and Cobalt- Chromium (Co Cr) Computer Assisted Design and Computer Assisted Manufacturing telescopic RPDs after 1 year of function. MATERIALS AND METHODS: A maxillary Kennedy class I was used in this study. Twelve telescopic RPDs were fabricated from two different materials. In Group A, six telescopic RPDs were milled from Co-Cr and in Group B, six telescopic retained RPDs were milled from Bio-HPP. Each partial denture was seated on the cast and introduced into the chewing simulator. The strain values were recorded using four strain gauges connected to a four-channel strain indicator. Statistical analysis of the resultant data was done using one-way ANOVA, followed by Tukey’s HSD for comparison within the same group. Student t-test was used for comparison between the different groups. The significance level was set at p ≤ 0.05. RESULTS: During unilateral loading, the results showed higher strains in Group A at the abutments (473.33 μm/m ± 10.8, 193.39 μm/m ± 10.8) and at the distal aspect of the ridge (470.83 μm/m ± 13.93, 185 μm/m ± 20.83) than Group B. Independent t-test showed statistically significant difference between strains at the abutments of both groups (t = 70.4, p ≤ 0.0001), (t = 36.84, p ≤ 0.0001). Furthermore, there was a statistically significant difference between strains at the saddles of both groups (t = 51.62, p ≤ 0.0001), (t = 34.72, p ≤ 0.0001) respectively (DOF = 10). CONCLUSIONS: In telescopic RPDs, Co Cr induces higher strain values on the abutments and the distal aspect of the ridge than Bio-HPP during bilateral and unilateral loading. During unilateral loading, Bio-HPP telescopic RPDs direct high strain values on the distal aspect of the ridge of the loaded side. CLINICAL IMPLICATIONS: The materials that induce less stresses on the supporting structures of telescopic partial dentures on the long-term can be used to maintain the health of periodontally affected abutments.

Lithium disilicate and peek implant-retained single crowns - a randomized, prospective clinical study

Introduction/Objective. Comparing two materials under the same conditions is the best way to define differences between them. PEEK is a polymer that has many possible uses in dentistry as already well-known lithium disilicate ceramics. The aim of this study was to compare peri-implant soft tissue healing and evaluate patient satisfaction with esthetics in different observation periods, as well as the success and survival rate of both types of crowns. Methods. The study was conducted as a clinical, prospective, randomized split-mouth study on 17 patients with bilaterally missing upper teeth of the same type, replaced with dental implants. Study outcomes have been analyzed with subjective (VAS scale) and objective parameters (MBI, MPI and PPD) baseline, six and twelve months after fixing crowns onto the implants. Results. Comparison of the results between PEEK and lithium disilicate crowns showed no statistical differences in terms of MPI, MBI and PPD in the observed periods. Analyzing MPI during observation periods in the PEEK group of crowns, statistical significance was registered between baseline values and after 6 months. Also, statistical significance was noticed in terms of PPD during the observation time both in the study and control group of crowns. Results for VAS for the esthetics showed no statistically significant difference between the groups, while VAS for restoration satisfaction showed a statistically significant difference. Conclusion. This study showed that scores of the applied subjective and objective parameters can be a reliable tool to rate the clinical outcome of implant-retained single crowns over time.

Icariin-loaded Sulfonated Polyetheretherketone with Osteogenesis Promotion and Osteoclastogenesis Inhibition Properties via Immunomodulation for Advanced Osseointegration

Preventing prosthesis loosening due to insufficient osseointegration is critical for patients with osteoporosis. Endowing implants with immunomodulatory function can effectively enhance osseointegration. In this work, we loaded icariin (ICA) onto...

The use of PEEK as an occlusal splint in a patient with histaminosis: A case report

Poly-(etheretherketone) (PEEK) began to be used in the field of odontology more than 10 years ago, especially in relation to the creation of removable partial dentures. Here we report the case of a 62 years old woman diagnosed with histamine intolerance (or histaminosis), who presented a very particular set of oral symptoms. She described a certain tingling, burning, and swelling of the mucous membranes. These symptoms seem to be linked with the wearing of a resin occlusal splint which was initially prescribed to compensate for the absence of a meniscus in the left temporomandibular joint of the patient. After a multidisciplinary concertation, it was decided to create a new splint with a resin-free material. For this reason, the production of a PEEK prosthesis was considered. Following the installation of the occlusal splint in the patient, and after clinical adjustments, she described the occlusion positioning as correct and a disappearance of the symptomatology. Mechanically, PEEK seems to have higher mechanical resistance than PMMA. Despite these characteristics, the use of PEEK still presents some limitations, especially concerning the overall aesthetic. Additionally, the prescription of the occlusal splint seems to be limited to patients who need special care. The case presented here thus confirms a new perspective concerning the use of PEEK as an occlusal splint.

Optical Properties and Color Stability of Dental PEEK Related to Artificial Ageing and Staining

Considering that the processes of PEEK discoloration caused by either intrinsic or extrinsic factors require elucidation, the aim of this study was to investigate the long-term effect of the combined action of ageing and immersing solutions on the optical properties and color stability of PEEK material, related to surface processing (polishing or glazing). (2) Methods: This study aims to determine the influence of different ageing and staining protocols on optical properties, color changes, and surface roughness of a reinforced PEEK material (bioHPP, Bredent, Senden, Germany). For ageing, specimens were submitted to 5000 cycles in a 55 °C bath and a 5 °C bath filled with distilled water. For staining, thermal cycling was performed in a hot coffee bath (55 °C) and a bath filled with distilled water (37 °C) and in a cold juice bath (5 °C) and a bath filled with distilled water (37 °C). Translucency (TP) and opalescence (OP) parameters were determined, the total color change value (ΔΕ*) was calculated, specimens’ surface roughness was analyzed, and statistical analyses were performed. (3) Results: The mean TP values of the studied samples were in the interval of 1.25–3.60, which is lower than those reported for natural teeth or other aesthetic restoration materials. The OP values of PEEK were registered in the range of 0.27–0.75, being also lower than those of natural teeth or other aesthetic restoration materials. OP has a very strong positive relationship with TP. The mean registered Ra values for all subgroups were below 0.13 µm. Artificial ageing and staining in hot coffee proved to increase the roughness values. (4) Conclusions: The glazing of PEEK has a favorable effect on surface roughness and opalescence, irrespective of the artificial ageing or staining protocols. Artificial ageing damages the color stability and roughness of PEEK, regardless of surface processing, and decreases the translucency and opalescence of glazed surfaces. Immersion in hot coffee leads to perceivable discolorations.

The effect of thermo-mechanical fatigue on the retentive force and dimensional changes in polyetheretherketone clasps with different thickness and undercut

PURPOSE

Esthetic expectations have increased the use of polyetheretherketone (PEEK) clasps as alternatives to Cr-Co in removable partial dentures (RPDs). The objective of this study was to evaluate the retentive force and dimensional change of clasps with different thickness and undercut made from PEEK by the thermo-mechanical fatigue.

MATERIALS AND METHODS

PEEK clasps (N = 48) with thicknesses of 1 or 1.50 mm and 48 premolar monolithic zirconia crowns with undercuts of 0.25 mm or 0.50 mm were fabricated. Samples are divided into four groups (C1-C4) and were subjected to 7200 thermal aging cycles (at 5 - 55℃). The changes in the retentive force and dimensions of the clasps were measured by micro-stress testing and micro-CT devices from five measurement points (M1 - M5). One-way ANOVA, paired t-test, two-way repeated ANOVA, and post-hoc tests were used to analyze the data (P < .05).

RESULTS

The retentive forces of C1, C2, C3, and C4 groups in initial and final test were found to be 4.389-3.388 N, 4.67 - 3.396 N, 5.161 - 4.096 N, 5.459 - 4.141 N, respectively. The effects of retentive force of all PEEK clasps groups were significant decreased. Thermo-mechanical cycles caused significant dimensional changes at points with M2, M4, and M5, and abraded the clasp corners and increased the distance between the ends of the clasp, resulting in reduced retentive forces (P^* = .016, P^* = .042, P < .001, respectively).

CONCLUSION

Thermo-mechanical aging decreases the retentive forces in PEEK clasps. Increasing the thickness and undercut amount of clasps decreases the amount of dimensional change. The values measured after aging are within the clinically acceptable limits.

Wear Resistance, Color Stability and Displacement Resistance of Milled PEEK Crowns Compared to Zirconia Crowns under Stimulated Chewing and High-Performance Aging

Recently, polyetheretherketone (PEEK) has been introduced to the dental market as a high-performance and chemically inert biomaterial. This study aimed to compare the wear resistance, abrasiveness, color stability, and displacement resistance of zirconia and PEEK milled crowns. An ideal tooth preparation of a first maxillary molar was done and scanned by an intraoral scanner to make a digital model. Then, the prosthetic crown was digitally designed on the CAD software, and the STL file was milled in zirconia (CaroZiir S, Carol Zircolite Pvt. Ltd., Gujarat, India) and PEEK (BioHpp, Bredent GmbH, Senden, Germany) crowns using five-axis CNC milling machines. The wear resistance, color stability, and displacement resistance of the milled monolithic zirconia with unfilled PEEK crowns using a chewing simulator with thermocyclic aging (120,000 cycles) were compared. The antagonist wear, material wear, color stability, and displacement were evaluated and compared among the groups using the Wilcoxon-Mann-Whitney U-test. Zirconia was shown to be three times more abrasive than PEEK (p value < 0.05). Zirconia had twice the wear resistance of PEEK (p value < 0.05). Zirconia was more color stable than PEEK (p value < 0.05). PEEK had more displacement resistance than zirconia (p value < 0.05). PEEK offers minimal abrasion, better stress modulation through plastic deformation, and good color stability, which make it a promising alternative to zirconia crown.

Comparison of Fracture Strengths of Three Provisional Prosthodontic CAD/CAM Materials: Laboratory Fatigue Tests

Temporary restorations play a fundamental role in oral rehabilitation. They can be used on teeth or implants for a variable period of time during the period prior to rehabilitation with definitive restorations. Temporary or provisional restorations manufactured via CAD/CAM methods are becoming increasingly used in the intermediate phase of the treatment of complex cases. The main objective of this study was to compare the fracture resistance of three materials used in the creation of provisional crowns on implants: polymethyl methacrylate (PMMA), composite resin, and polyether ether ketone (PEEK). Fracture resistance in PMMA (Zirkonzahn Temp Basic® , Gais, South Tyrol, Italy) ranged from 1216.0 N to 1461.2 N, with a mean of 1300.4 N (SD = 97.09). In the composite material (3M Lava Ultimate®, Minnesota, USA), fracture resistance varied between 1343.5 N and 1490.6 N, with a mean of 1425.9 N (SD = 49.03). Lastly, in PEEK (Tecno Med Mineral®, Zirkonzahn®, Gais, South Tyrol, Italy), fracture resistance ranged from 2294.8 N to 2451.7 N, with a mean of 2359.5 (SD = 50.01). The crowns made with the PEEK Tecno Med Mineral® (Zirkonzahn®, Tyrol, Italy) material presented the best fracture resistance, followed by the crowns made with the Lava Ultimate® (3M® ESPE, Minnesota, USA) composite resin material and, finally, those made with the PMMA Temp Basic® (Zirkonzahn®, Tyrol, Italy) material.

Patient-Centered Treatment Outcomes with Full-Arch PEEK Rehabilitation Supported on Four Immediate or Conventionally Loaded Implants. A Randomized Clinical Trial

This study aims to assess the treatment outcomes (functional and subjective) of full-arch fixed hybrid rehabilitations made of PEEK (poly-ether-ether-ketone) with milled crowns of nano-filled composite (NFC) supported on four to six implants. In this randomized clinical trial, 34 edentate patients in the upper and/or the lower jaws were treated with the fixed hybrid dentures. In 16 patients (47.1% of the sample), the implants were loaded immediately (IL) by means of a provisional fixed rehabilitation made of PMMA (polymethylmethacrylate) screwed on Multi-Unit (MU) abutments connected after emplacement of the implant; however, in the counterparts (n = 18) these MU abutments were covered by healing caps and were left unloaded during two months (conventional loading protocol—CL), when all patients received a fixed hybrid PEEK-NFC rehabilitation on the upper and/or the lower jaw. Treatment outcomes were assessed 12 months after prostheses delivery. Functional outcomes were calculated according to masticatory performance, estimated by mixing ability tests of two colored chewing gums after ten chewing strokes, by the occlusal force/area recorded by pressure-sensitive sheets, and by electromyography of masseters and temporal muscles at maximum biteforce. The subjective outcomes of the treatment were assessed using both the oral satisfaction scale (visual analog scale) and the Spanish version of the Oral Health Impact Profile (OHIP-20). The findings of the present study showed that treatment with fixed PEEK-NFC hybrid prostheses significantly improved the masticatory performance, bite force, occlusal pattern, quality of life, and satisfaction, with the IL group being those with significantly higher occlusal bite forces and greater satisfaction in comparison with CL group. It should be concluded that PEEK-NFC hybrid prostheses can improve several patient-centered outcomes and that loading protocol significantly affects the patient’s self-rated satisfaction.

Trueness and marginal fit of implant-supported complete-arch fixed prosthesis frameworks made of high-performance polymers and titanium: An explorative in-vitro study

PURPOSE

To investigate the trueness and marginal fit of computer-aided design-computer-aided manufactured (CAD-CAM) complete-arch implant-supported screw-retained fixed prosthesis (CAISFP) made of polyetheretherketone (PEEK), polyetherketoneketone (PEKK) and titanium (Ti) MATERIAL AND METHODS: A typodont model with four implants, their multiunit abutments (MUAs), and MUA scanbodies were digitized by using a laboratory scanner. The generated CAD was used to mill CAISFP frameworks in Ti, PEEK, or PEKK (each n = 10). The frameworks were digitized with an industrial light scanner to superimpose resulting standard tessellation language (STL) file with the CAD file. Deviations at five points at the abutment-framework interface of each of the four abutment sites (1:left first molar, 2:left canine, 3:right canine, 4:right first molar sites) were calculated (trueness). Marginal gaps were measured using the triple scan technique. A nonparametric repeated measures ANOVA by Brunner and Puri with factors being abutment location and material was performed to assess the mean deviations for trueness and mean marginal gaps, followed by Mann-Whitney or exact Wilcoxon Signed-Rank tests (alpha=.05).

RESULTS

Material type significantly affected the trueness (p<0.0001). PEEK had the lowest deviations (0.039 +/-0.01mm) followed by PEKK (0,049 +/-0.009mm), and Ti (0.074 +/-0.011mm). For marginal gaps, only abutment location's effect was significant (p = 0.003). Within PEKK, gaps at abutment 4 were significantly larger, compared with abutments 2 (p = 0.04) and 3 (p = 0.02).

CONCLUSIONS

The trueness of PEEK, PEKK, and Ti frameworks was different after milled. PEEK had the highest trueness. However, the marginal fit of the frameworks was similar and smaller than 90 µm in average.

CLINICAL RELEVANCE

PEEK, PEKK, and Ti complete-arch frameworks had clinically acceptable gaps and may therefore be recommended when their fit is considered. Higher trueness after milling did not result in better marginal fit.

Comparison of marginal and internal fit of three-unit implant-supported fixed prosthetic substructures fabricated using CAD/CAM systems

OBJECTIVE

This study compared the marginal and internal fit of implant-supported fixed dentures fabricated using CAD/CAM systems.

MATERIALS AND METHODS

A lower jaw model representing partial edentulism was produced. Two dental implants were inserted in the area of teeth 35 and 37, onto which cemented abutments were screwed. The model was scanned using a laboratory scanner and transferred to a design software program for substructure fabrication. Sixty substructures were fabricated out of each group for six substructure types (n = 10), cast Co-Cr (control), milling Co-Cr, laser sintering Co-Cr, titanium (Ti), zirconium, and polyetheretherketone (PEEK) substructures. The marginal and internal fit was evaluated using a silicone replica viewed under a stereomicroscope. The data were analyzed using the statistical package program for social sciences (SPSS, Chicago, IL, USA, v. 17) at a significance level of 0.05. Marginal and internal gaps were compared using the one-way ANOVA test and Tukey's post hoc test. The differences between abutment teeth were determined using the independent sample t-test.

RESULTS

There was a significant difference in the marginal gap between PEEK and Ti groups (p < 0.05) but no difference between other groups (p > 0.05). There was a significant difference in the internal gap between PEEK, laser sintering Co-Cr, and milling Co-Cr groups (p < 0.05) but no difference between other groups (p > 0.05). The PEEK group had a higher marginal gap than the Ti group and a higher internal gap than the DMLS Co-Cr group (p < 0.05).

CONCLUSION

All substructures have a marginal and internal fit within acceptable clinical limits.

CLINICAL RELEVANCE

This in vitro study suggests that materials and techniques used in CAD/CAM systems improve the fitting accuracy of implant-supported fixed restorations.

Removable Partial Dentures with Polyetheretherketone Framework: The Influence on Residual Ridge Stability

PURPOSE

To provide, in a clinical case-control study, 1-year data on edentulous residual ridge dimensional changes for patients wearing removable partial dentures (RPD) with Polyetheretherketone (PEEK) framework, fabricated with a digital workflow, and a control group of untreated patients.

MATERIALS AND METHODS

Ten patients were treated with PEEK RPD, and six controls were studied. Intraoral scans at baseline (T0) and after a median period of 1 year (T1) were superimposed, trimmed, and reoriented (T0r and T1r), moved to a metrology software, and realigned. A curve (C0) was then traced on T0r, along the residual ridge crest; its projection (C1) on T1r was obtained. The mean distance C0-C1 was the dependent variable of interest and represented the 1-year changes in the height of the edentulous ridge. In addition, mean 3D distance between T0 and T1 at each edentulous area was measured. Differences in these outcomes measured between RPD treated and control groups were statistically assessed.

RESULTS

Twenty-six and 14 edentulous areas were investigated in the RPD treated and control groups, respectively. No significant differences were observed for potentially confounding variables, such as median follow-up time (12.5 vs. 13 months, respectively), the alignment accuracy between T0r and T1r (0.01 mm vs. 0 mm, respectively), the median number of remaining teeth (6 vs. 8.5, respectively), and the median length of edentulous areas (25.5 mm vs. 22.8 mm, respectively). For the outcomes of interest, no statistically significant difference was seen in the mean distance between C0 and C1 (i.e., changes in residual ridge height: -0.39 ± 0.52 mm vs. -0.52 ± 0.54 mm, respectively) or in the mean 3D distance at corresponding points of the denture bearing areas (-0.3 ± 0.46 mm vs. -0.4 ± 0.35, respectively).

CONCLUSIONS

Although 1 year is a relatively short observation period, this clinical study shows that there are no short-term differences in edentulous residual ridge height and overall dimensions between patients wearing PEEK RPD, fabricated with a digital workflow, and controls without an RPD.

Effect of Staining Solutions on Color Stability, Gloss and Surface Roughness of Removable Partial Dental Prosthetic Polymers

PURPOSE

To assess the effect of commonly used solutions on color stability, gloss, and surface roughness of removable partial dental prostheses polymers.

MATERIALS AND METHODS

Discs (n = 112) were made of a poly(etheretherketone) (PEEK) polymer, a polyamide, an acetal resin and a heat-cured poly(methylmethacrylate) PMMA acrylic resin polished according to manufacturers' instructions. Seven specimens of each material were immersed in coffee, red wine, coca cola and distilled water for 30 days at 37^ο C. Changes of color (ΔΕ*) and color coordinates L*α*b* after immersion were calculated with a colorimeter. Changes in the values of gloss and surface roughness parameters (Sa, Sz, Str, Sdr, Sci, Svi) were also measured. Two-way ANOVA and pairwise comparisons were used to evaluate the effect of material and staining solution on parameter value alterations (α = 0.05).

RESULTS

The two-way ANOVA revealed that the interaction between material and staining solution significantly affected color changes after immersion [F(9,96) = 44.67, p < 0.001]. PEEK presented the lowest color change (ΔΕ* = 3.83 ± 2) while polyamide had the highest color change overall (ΔΕ* = 14.59 ± 8.65) (p < 0.001). Coffee caused the highest color (ΔΕ* = 13.08 ± 6.98) and gloss changes (ΔG = -6.36 ± 19.2 GU) among different solutions (p < 0.001). PEEK showed the highest alteration of gloss (ΔG = -11.31 ± 15.49 GU), with significant difference with the other three materials (p < 0.001). Insignificant interaction of material and immersing solution was found for surface roughness parameters (p > 0.05).

CONCLUSIONS

Among the materials tested, PEEK seemed to be the most stable material when subjected to common, everyday staining solutions. Therefore, PEEK could be a viable solution for an RPDP framework fabrication, expanding the material list of prosthetic options. Further research and clinical trials are required to confirm the above statement.

Can polylactic acid be a CAD/CAM material for provisional crown restorations in terms of fit and fracture strength?

This study aimed to evaluate polylactic acid (PLA) as a provisional crown material. Lower right first molar phantom tooth was used for the fabrication of 60 crowns. Samples were divided into three groups (n=20) according to the material: Group PL (PLA), Group PM (polymethyl methacrylate), and Group PE (polyetheretherketone). Each group was investigated for internal and marginal fit, fracture strength, and fracture mode. Data were analyzed using ANOVA, chi-squared test, and Tukey's tests (p≤0.05). The average marginal gap value of each group was: PE 56.00±4.67 µm, PM 61.15±4.44 µm, and PL 60.40±2.85 µm (p<0.001). The average internal gap value for each group was: PE 128.90±8.39 µm, PM 132.40±7.51 µm, and PL 130.75±9.76 µm (p=0.442). The average fracture strength of each group was: PE 840.90±13.23 N, PM 733.30±9.00 N, and PL 664.50±10.79 N (p<0.001). Results demonstrated that PLA may be a good option as a provisional crown material.

Fracture Load of Metal, Zirconia and Polyetheretherketone Posterior CAD-CAM Milled Fixed Partial Denture Frameworks

The aim of this study was to investigate the load to fracture and fracture pattern of prosthetic frameworks for tooth-supported fixed partial dentures (FPDs) fabricated with different subtractive computer-aided design and computer-aided manufacturing (CAD-CAM) materials. Materials and Methods: Thirty standardized specimens with two abutments were fabricated to receive three-unit posterior FDP frameworks with an intermediate pontic. Specimens were randomly divided into three groups (n = 10 each) according to the material: group 1 (MM)—milled metal; group 2 (L)—zirconia; and group 3 (P)—Polyetheretherketone (PEEK). The specimens were thermo-cycled and subjected to a three-point bending test until fracture using a universal testing machine (cross-head speed: 1 mm/min). Axial compressive loads were applied at the central fossa of the pontics. Data analysis was made using one-way analysis of variance, Tamhane post hoc test, and Weibull statistics (α = 0.05). Results: Significant differences were observed among the groups for the fracture load (p < 0.0001). MM frameworks showed the highest fracture load values. The PEEK group registered higher fracture load values than zirconia samples. The Weibull statistics corroborated these results. The fracture pattern was different among the groups. Conclusions: Milled metal provided the highest fracture load values, followed by PEEK, and zirconia. However, all tested groups demonstrated clinically acceptable fracture load values higher than 1000 N. PEEK might be considered a promising alternative for posterior FPDs.

Combination of Polydopamine Coating and Plasma Pretreatment to Improve Bond Ability Between PEEK and Primary Teeth

Preformed crowns are preferred to reduce the failure risk of restoration of primary teeth, but some drawback of conventional material is still a main barrier for their clinical use. Polyether etherketone (PEEK), a tooth colored, high-performance thermoplastic polymer, has been recognized as a promising alternative to manufacture the restoration of primary teeth. However, the hydrophobic surface and low surface energy of PEEK make it hard to establish a strong and durable adhesion. In this study, we have evaluated a modification method of polydopamine (PDA) coating with plasma pretreatment for the PEEK films by physical and chemical characterization, bonding properties, and biocompatibility. The surface properties of PEEK were well-characterized by scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). The adhesive strength of the PEEK films was greatly improved without significant reduction of the proliferation rate of human gingival fibroblast cells in MTT and Live/Dead assays. Therefore, PDA coating with plasma pretreatment may give a new solution for effective clinical application of PEEK in primary performed crowns.

Tooth-Colored CAD/CAM Materials for Application in 3-Unit Fixed Dental Prostheses in the Molar Area: An Illustrated Clinical Comparison

The aim of this study was to compare the clinical properties of tooth-colored computer-aided design/computer-aided manufacturing (CAD/CAM) materials for the fabrication of a 3-unit fixed dental prostheses (FDPs) in the same clinical scenario. A 53-year-old female patient was supplied with a 3-unit FDP to replace a second premolar in the upper jaw. Restorations were fabricated from 3 mol%, 4 mol%, and 5 mol% yttrium oxide zirconia, zirconia with translucency gradient, indirect composite resin, polyetheretherketone (PEEK), and polyetherketoneketone (PEKK). Milling time, weight, and radiopacity were investigated. Esthetics were examined following the US Public Health Service criteria (USPHS). The milling time for zirconia was twice as high as for the indirect composite resin, PEEK, or PEKK. The latter materials had a weight of 2 g each, while zirconia restorations yielded 5 g. Zirconia presented intense radiopacity. PEEK and PEKK required veneering and an opaquer was applied to the PEKK framework. All FDPs showed acceptable esthetics. PEEK and PEKK restorations were featured by a grayish shimmering. A variety of CAD/CAM materials are available to fabricate 3-unit FDPs with esthetically acceptable results. In the esthetic zone, PEEK and PEKK require veneering and an opaquer might be applied. Milling time, weight, and radiopacity were relatively high for zirconia FDPs.

The Effect of Different Cleaning Protocols of Polymer-Based Prosthetic Materials on the Behavior of Human Gingival Fibroblasts

Dental implant abutment and prosthetic materials, their surface treatment, and cleaning modalities are important factors for the formation of a peri-implant soft tissue seal and long-term stability of bone around the implant. This study aimed to investigate the influence of a polymeric material surface cleaning method on the surface roughness, water contact angle, and human gingival fibroblasts (HGF) proliferation. Polymeric materials tested: two types of milled polymethylmethacrylate (PMMA-Ker and PMMA-Bre), three-dimensionally (3D) printed polymethylmethacrylate (PMMA-3D), polyetheretherketone (PEEK), and polyetherketoneketone (PEKK). Titanium (Ti) and zirconia oxide ceramics (ZrO-HT) were used as positive controls. A conventional surface cleaning protocol (CCP) was compared to a multi-step research cleaning method (RCP). Application of the RCP method allowed to reduce S_a values in all groups from 0.14-0.28 µm to 0.08-0.17 µm (p < 0.05 in PMMA-Ker and PEEK groups). Moreover, the water contact angle increased in all groups from 74-91° to 83-101° (p < 0.05 in the PEKK group), except ZrO-HT-it was reduced from 98.7 ± 4.5° to 69.9 ± 6.4° (p < 0.05). CCP resulted in higher variability of HGF viability after 48 and 72 h. RCP application led to higher HGF viability in PMMA-3D and PEKK groups after 48 h, but lower for the PMMA-Ker group (p < 0.05). After 72 h, no significant differences in HGF viability between both cleaning methods were observed. It can be concluded that the cleaning method of the polymeric materials affected surface roughness, contact angle, and HGF viability at 48 h.

Retention force of polyetheretherketone and cobalt-chrome-molybdenum removable dental prosthesis clasps after artificial aging

OBJECTIVES

To examine the retention force of removable dental prosthesis (RDP) clasps made from polyetheretherketone (PEEK) and cobalt-chrome-molybdenum (CoCrMo, control group) after storage in water and artificial aging.

MATERIALS AND METHODS

For each material, 15 Bonwill clasps with retentive buccal and reciprocal lingual arms situated between the second pre- and first molar were manufactured by milling (Dentokeep [PEEKmilled1], NT digital implant technology; breCAM BioHPP Blank [PEEKmilled2], bredent), pressing (BioHPP Granulat for 2 press [PEEKpressed], bredent), or casting (remanium GM 800+ [CoCrMo], Dentaurum); N = 60, n = 15/subgroup. A total of 50 retention force measurements were performed for each specimen per aging level (initial; after storage [30 days, 37 °C] and 10,000 thermal cycles; after storage [60 days, 37 °C] and 20,000 thermal cycles) in a pull-off test. Data were statistically analyzed using one-way ANOVA, post hoc Scheffé and mixed models (p < 0.05).

RESULTS

Initial, PEEKpressed (80.2 ± 35.2) and PEEKmilled1 (98.9 ± 40.3) presented the lowest results, while PEEKmilled2 (170.2 ± 51.8) showed the highest values. After artificial aging, the highest retention force was observed for the control group (131.4 ± 56.8). The influence of artificial aging was significantly higher for PEEK-based materials. While PEEKmilled2 and PEEKpressed showed an initial decline in retention force, all other groups presented no impact or an increase in retention force over a repetitive insertion and removal of the clasps.

CONCLUSIONS

Within the tested PEEK materials, PEEKmilled2 presented superior results than PEEKpressed. Although CoCrMo showed higher values after artificial aging, all materials exhibited sufficient retention to recommend usage under clinical conditions.

CLINICAL RELEVANCE

As RDPs are still employed for a wide range of indications, esthetic alternatives to conventional CoCrMo clasps are sought.

Is the high-performance thermoplastic polyetheretherketone indicated as a clasp material for removable dental prostheses?

Objectives

To investigate the retention force of polyetheretherketone (PEEK) removable dental prosthesis clasps in comparison with a cobalt-chrome-molybdenum control group after storage in artificial saliva.

Materials and Methods

Clasps were milled (Dentokeep (PEEKmilled1), NT digital implant technology; breCAM BioHPP Blank (PEEKmilled2), bredent), pressed (BioHPP Granulat for 2 press (PEEKpressed), bredent), or cast (remanium GM 800+ (cobalt-chrome-molybdenum), Dentaurum); N = 60, n = 15/subgroup. Retention force was examined 50 times/specimen in a pull-off test using the universal testing machine (Zwick 1445), where pull-off force was applied with a crosshead speed of 5 mm/minute until the maximum force dropped by 10%, at different aging levels: (1) initial, after storage in artificial saliva for (2) 90 and (3) 180 days. Statistical analysis was performed using one-way ANOVA followed by post hoc Scheffé-test and mixed models (p < 0.05).

Results

Cobalt-chrome-molybdenum presented the highest retention force. No differences were observed between polyetheretherketone materials. Cobalt-chrome-molybdenum showed a significant decrease of its values after artificial aging, while polyetheretherketone materials presented similar results over the course of aging. Regarding a repetitive insertion and removal, even though PEEKmilled2 and cobalt-chrome-molybdenum showed an initial increase, ultimately, a decrease in retention force was observed for all tested groups.

Conclusions

Although the control group showed significantly higher results, the retention force of polyetheretherketone materials indicate a potential clinical application. Neither the manufacturing process nor artificial aging showed an impact on the retention force of polyetheretherketone clasps.

Clinical relevance

Mechanical properties of novel removable dental prosthesis clasp materials devised to meet the growing esthetic demands of patients need to be investigated to ensure a successful long-term clinical application.