Retrieval analysis of PEEK rods pedicle screw system: three cases analysis.

PURPOSE: To analyze the characteristics of PEEK rods retrieved in vivo, specifically their wear and deformation, biodegradability, histocompatibility, and mechanical properties. METHOD: Six PEEK rods were retrieved from revision surgeries along with periprosthetic tissue. The retrieved PEEK rods were evaluated for surface damage and internal changes using Micro-CT, while light and electron microscopy were utilized to determine any histological changes in periprosthetic tissues. Patient history was gathered from medical records. Two intact and retrieved PEEK rods were used for fatigue testing analysis by sinusoidal load to the spinal construct. RESULTS: All implants showed evidence of plastic deformation around the screw-rod interface, while the inner structure of PEEK rods appeared unchanged with no visible voids or cracks. Examining images captured through light and electron microscopy indicated that phagocytosis of macrophages around PEEK rods was less severe in comparison to the screw-rod interface. The results of an energy spectrum analysis suggested that the distribution of tissue elements around PEEK rods did not differ significantly from normal tissue. During fatigue testing, it was found that the retrieved PEEK rods cracked after 1.36 million tests, whereas the intact PEEK rods completed 5 million fatigue tests without any failure. CONCLUSION: PEEK rods demonstrate satisfactory biocompatibility, corrosion resistance, chemical stability, and mechanical properties. Nevertheless, it is observed that the indentation at the junction between the nut and the rod exhibits relatively weak strength, making it susceptible to breakage. As a precautionary measure, it is recommended to secure the nut with a counter wrench, applying the preset torque to prevent overtightening.

Dental implant and abutment in PEEK: stress assessment in single crown retainers on anterior region.

OBJECTIVE: Stress distribution assessment by finite elements analysis in poly(etheretherketone) (PEEK) implant and abutment as retainers of single crowns in the anterior region. MATERIALS AND METHODS: Five 3D models were created, varying implant/abutment manufacturing materials: titanium (Ti), zirconia (Zr), pure PEEK (PEEKp), carbon fiber-reinforced PEEK (PEEKc), glass fiber-reinforced PEEK (PEEKg). A 50 N load was applied 30o off-axis at the incisal edge of the upper central incisor. The Von Mises stress (σvM) was evaluated on abutment, implant/screw, and minimum principal stress (σmin) and maximum shear stress (τmax) for cortical and cancellous bone. RESULTS: The abutment σvM lowest stress was observed in PEEKp group, being 70% lower than Ti and 74% than Zr. On the implant, PEEKp reduced 68% compared to Ti and a 71% to Zr. In the abutment screws, an increase of at least 33% was found in PEEKc compared to Ti, and of at least 81% to Zr. For cortical bone, the highest τmax values were in the PEEKp group, and a slight increase in stress was observed compared to all PEEK groups with Ti and Zr. For σmin, the highest stress was found in the PEEKc. Stress increased at least 7% in cancellous bone for all PEEK groups. CONCLUSION: Abutments and implants made by PEEKc concentrate less σvM stress, transmitting greater stress to the cortical and medullary bone. CLINICAL RELEVANCE: The best stress distribution in PEEKc components may contribute to decreased stress shielding; in vitro and in vivo research is recommended to investigate this.

Digital wear analysis and retention of poly-ether-ether-ketone retentive inserts versus conventional nylon inserts in locator retained mandibular overdentures: in-vitro study.

OBJECTIVE: this study aimed to digitally compare wear behavior and retention between PEEK and nylon retentive inserts used in locator-retained, mandibular implant overdentures when attachment design and size were standardized. MATERIALS AND METHODS: A total of sixty-four inserts (32 PEEK and 32 nylon inserts); were picked-up in implant overdentures. Overdentures of both groups were submerged in artificial saliva and mounted to chewing simulator. After 480,000 chewing cycles (equivalent to 2 years of clinical use) all inserts were scanned by scanning electron microscope (SEM), then all acquired images were digitally analyzed by software to detect and compare quantitative and qualitative changes of inserts in both groups. On the other hand, retention of both groups was measured by universal testing machine and the collected data was statistically analyzed using one-way Analysis of Variance (ANOVA) test with significance level set at P ≤ 0.05. RESULTS: PEEK inserts showed significantly higher mean retentive values compared to the nylon inserts in the control group. Also, PEEK retentive inserts exhibited statistically lower mean wear values than the control group P ≥ 0.000. Qualitative investigation revealed significant and more pronounced changes in the surface roughness of nylon inserts compared to PEEK ones. CONCLUSIONS: Regarding retention, wear behavior and dimension stability, PEEK can be recommended as retentive insert material in cases of locator-retained mandibular implant overdentures. CLINICAL RELEVANCE: PEEK inserts offer enhanced retention, reduced wear, and greater dimensional stability over two years time interval. Clinically, this reduces prosthodontic maintenance and adjustments, improving patient satisfaction and long-term prosthetic success.

Endoscopic-Assisted Forehead Augmentation with Polyetheretherketone (PEEK) Patient-Specific Implant (PSI) for Aesthetic Considerations.

BACKGROUND: Forehead augmentation have become popular aesthetic procedures among Asians in recent years. However, the use of polyetheretherketone (PEEK) patient-specific implant (PSI) in the facial contouring surgery for aesthetic considerations is not well documented in the existing studies. The purpose of this study was to develop a novel method for forehead augmentation and assess the clinical outcomes and complications in patients who underwent forehead augmentation with PEEK PSI assisted by endoscopy. METHODS: The PEEK PSIs were fabricated using the virtual surgical planning (VSP) and the computer-aided manufacturing (CAM) for each patient, preoperatively. The implant pockets were dissected in the subperiosteal plane, and PEEK PSIs were placed in their designed position and fixed assisting by endoscopy via small incision within the hairline. All patients were asked to complete the FACE-Q questionnaire before and 6 months after the operation. Pre- and postoperative demographics, photographs, and other clinical data of patients were collected and analyzed. RESULTS: 11 patients underwent forehead augmentation were enrolled in this study. All procedures were completed successfully with the help of endoscope. The average patient age was 30.63 ± 2.54 years. The mean thickness and size of PEEK PSI were 4.44 ± 1.77 mm and 38.43 ± 22.66 cm2, respectively. The mean operative time was 83.00 ± 29.44 min, and the mean postoperative follow-up period was 11.00 ± 6.50 months. No implant exposure, extrusion or removal were reported. The FACE-Q scores of patients in satisfaction with the forehead increased from 47.64 ± 7.15 to 78.81 ± 6.35. CONCLUSIONS: PEEK PSIs can be prefabricated to achieve accurate remodeling of the frontal contour with good esthetic outcomes. The endoscope provides direct and magnified vision, which allow easy access to the supraorbital rim and lateral edge of the eyebrow arch and confirming the position of the implants without damaging nerves and vessels. Endoscopic-assisted forehead augmentation with PEEK PSI is safe and effective. LEVEL OF EVIDENCE IV: This journal requires that authors assign a level of evidence to each article. For a full description of these evidence-based medicine ratings, please refer to the Table of contents or the online Instructions to Authors www.springer.com/00266 .

3D-printed intracoronal restorations, occlusal and laminate veneers: Clinical relevance, properties, and behavior compared to milled restorations; a systematic review and meta-analysis.

OBJECTIVES: To assess the feasibility of producing 3D-printed intracoronal restorations, thin and ultrathin veneers, and to compare their mechanical behavior, accuracy, biological, and stain susceptibility to the currently applied milled restorations. MATERIALS AND METHODS: The databases were comprehensively searched for relevant records up to January 2024 without language restrictions. All studies that assessed 3D-printed partial coverage restorations including inlays, onlays, laminate, and occlusal veneers were retrieved. RESULTS: The web search yielded a total of 1142 records, with 8 additional records added from websites at a later stage. Only 17 records were ultimately included in the review. The included records compared 3D-printed; alumina-based- and zirconia ceramics, lithium disilicate ceramics, polymer infiltrated ceramics, polyetheretherketone (PEEK), resin composites, and acrylic resins to their CNC milled analogs. The pooled data indicated that it is possible to produce ultrathin restorations with a thickness of less than 0.2 mm. 3D-printed laminate veneers and intracoronal restorations exhibited superior trueness, as well as better marginal and internal fit compared to milled restorations (p < 0.05). However, it should be noted that the choice of materials and preparation design may influence these outcomes. In terms of cost, the initial investment and production expenses associated with 3D printing were significantly lower than those of CNC milling technology. Additionally, 3D printing was also shown to be more time-efficient. CONCLUSIONS: Using additive manufacturing technology to produce restorations with a thickness ranging from 0.1 to 0.2 mm is indeed feasible. The high accuracy of these restorations, contributes to their ability to resist caries progression, surpassing the minimum clinical threshold load of failure by a significant margin and reliable adhesion. However, before 3D-printed resin restorations can be widely adopted for clinical applications, further improvements are needed, particularly in terms of reducing their susceptibility to stains. CLINICAL SIGNIFICANCE: 3D-printed intracoronal restorations and veneers are more time and cost-efficient, more accurate, and could provide a considerable alternative to the currently applied CNC milling. Some limitations still accompany the resin materials, but this could be overcome by further development of the materials and printing technology.

Vapor-Phase-Deposited Ag/Ir and Ag/Au Film Heterostructures for Implant Materials: Cytotoxic, Antibacterial and Histological Studies.

Using gas-phase deposition (Physical Vapor Deposition (PVD) and Metal Organic Chemical Vapor Deposition (MOCVD)) methods, modern implant samples (Ti alloy and CFR-PEEK polymer, 30% carbon fiber) were functionalized with film heterostructures consisting of an iridium or gold sublayer, on the surface of which an antibacterial component (silver) was deposited: Ag/Ir(Au)/Ti(CFR-PEEK). The biocidal effect of the heterostructures was investigated, the effect of the surface relief of the carrier and the metal sublayer on antibacterial activity was established, and the dynamics of silver dissolution was evaluated. It has been shown that the activity of Ag/Ir heterostructures was due to high Ag+ release rates, which led to rapid (2-4 h) inhibition of P. aeruginosa growth. In the case of Ag/Au type heterostructures, the inhibition of the growth of P. aeruginosa and S. aureus occurred more slowly (from 6 h), and the antibacterial activity appeared to be due to the contribution of two agents (Ag+ and Au+ ions). It was found, according to the in vitro cytotoxicity study, that heterostructures did not exhibit toxic effects (cell viability > 95-98%). An in vivo biocompatibility assessment based on the results of a morphohistological study showed that after implantation for a period of 30 days, the samples were characterized by the presence of a thin fibrous capsule without volume thickening and signs of inflammation.

Comparison of the use of biocompatible materials and titanium in the treatment of midshaft clavicle fractures with a patient-specific plate: a finite element analysis study.

BACKGROUND: Clavicular midshaft fractures treated with titanium plates may encounter complications like implant failure. We assess if alternative biocompatible materials suchs as PLA, PLA/HA, PEEK offer comparable stability. Our study evaluates the biomechanical performance of these materials in surgical management of midshaft clavicle fractures. METHODS: We simulated a personalized fixation implant with four different materials and conducted finite element analysis in ANSYS to assess maximum von Mises stress (MvMs). RESULTS: The MvMs occurring on the plates, screws, clavicle, and fracture site were recorded. MvMs on titanium material at the 6th hole level (764.79 MPa) and the 6th screw level (503.38 MPa), with the highest stresses observed at 48.52 MPa on the lateral clavicle at the 1st hole level and 182.27 MPa on the medial clavicle at the 6th hole level. In PLA material analyses, the highest MvMs were observed at the 3rd hole level (340.6 MPa) and the 3rd screw level (157.83 MPa), with peak stresses at 379.63 MPa on the lateral clavicle fracture line and 505.44 MPa on the medial clavicle fracture line. In PLA/HA material analyses, the highest MvMs were at the 3rd hole (295.99 MPa) and 3rd screw (128.27 MPa), with peak stresses at 220.33 MPa on the lateral clavicle and 229.63 MPa on the medial clavicle fracture line. In PEEK material analyses, the highest MvMs were at the 3rd hole (234.74 MPa) and 6th screw (114.48 MPa), with peak stresses at 184.36 MPa on the lateral clavicle and 180.1 MPa on the medial clavicle. CONCLUSION: Our findings indicate that titanium material shows significantly higher stresses on plates and screws compared to those on the clavicle, suggesting a risk of implant failure. PLA and PLA/HA were inadequate for fixation. Although stress on the plate with PEEK material is higher than on the clavicle, it remains lower than titanium, indicating potential stability at fracture site. Further research is needed to confirm these findings.

Mechanical failure of distal femur mega prosthesis due to polyaryl-ether-ether-ketone (PEEK) hinge component.

BACKGROUND: Polyaryl-ether-ether-ketone (PEEK) has gained popularity as a substrate for orthopaedic hardware due to its desirable properties such as heat and deformation resistance, low weight, and ease of manufacturing. However, we observed a relatively high failure rate of PEEK-based hinges in a distal femur reconstruction system. In this study, we aimed to evaluate the proportion of patients who experienced implant failure, analyse the mechanism of failure, and document the associated clinical findings. METHODS: We conducted a retrospective cohort study, reviewing the medical charts of 56 patients who underwent distal femur resection and reconstruction with a PEEK Optima hinge-based prosthesis between 2004 and 2018. Concurrently, we performed a clinical and biomechanical failure analysis. RESULTS: PEEK component failure occurred in 21 out of 56 patients (37.5%), with a mean time to failure of 63.2 months (range: 13-144 months, SD: 37.9). The survival distributions of PEEK hinges for males and females were significantly different (chi-square test, p-value = 0.005). Patient weight was also significantly associated with the hazard of failure (Wald's test statistic, p-value = 0.031). DISCUSSION: Our findings suggest that PEEK hinge failure in a distal femur reconstruction system is correlated with patient weight and male gender. Retrieval analysis revealed that failure was related to fretting and microscopic fractures due to cyclic loading, leading to instability and mechanical failure of the PEEK component in full extension. Further assessment of PEEK-based weight bearing articulating components against metal is warranted.

Poly-ether-ether-ketone (PEEK) versus dead-soft coaxial bonded retainers: a randomized clinical trial. Part 1. Stability, retainer failure, and participant satisfaction.

BACKGROUND: Poly-ether-ether-ketone (PEEK) was introduced in dentistry as an alternative to metal alloys. OBJECTIVE: To assess the effectiveness of PEEK-fixed retainers in preserving the stability of mandibular anterior and participant satisfaction as compared to the Dead-soft coaxial fixed retainer (DSC). TRIAL DESIGN: A single-centre, two-arm parallel groups randomized clinical trial. METHODS: The patients treated with pre-adjusted orthodontic appliances who have a Little's Irregularity Index (LII) ≤ 0.5 mm have been enrolled in the trial. PEEK retainers were prepared to round 0.8 mm wire by computer-aided design and manufacturing, and the DSC wire was carefully adapted to the lingual surface of the lower anterior teeth. The primary outcome was the stability of lower anterior teeth as assessed by LII, while the secondary outcomes were changes in occlusal parameters, retainer failure, and patient satisfaction. The data were collected at the debonding stage (T0), 1 month (T1), 3 months (T3), and 6 months (T6) after starting the trial, except for patient's satisfaction, which was recorded using an electronic form at T1 and T6. BLINDING: Single blinding of participants. RESULTS: A total of 46 participants with an age range of 12-28 years old were randomly allocated to the two groups (n = 23 in each). Only one participant dropped out; therefore, 45 participants were analysed. The DSC group showed a significant increase in LII at T3. Both retainer groups had comparable occlusal measurements, failure frequency, and survival time, with no significant difference. The patients in the DSC group reported a statistically significant perception of change in the position of their teeth compared to those in the PEEK group. HARMS: No harmful effects have been reported. LIMITATIONS: Limited follow-up duration and the inability to blind the operator due to the nature of the intervention. CONCLUSIONS: After 6-month retention, the PEEK retainer was equally effective to DSC retainers in maintaining the teeth alignment, with no significant differences regarding the failure frequency, survival rate, and general patient satisfaction. TRIAL REGISTRATION: https://register.clinicaltrials.gov. (NCT05557136).

Dental versus zygomatic implants in the treatment of maxillectomy: a finite element analysis.

PURPOSE: This study analyzed the stress distributions on zygomatic and dental implants placed in the zygomatic bone, supporting bones, and superstructures under occlusal loads after maxillary reconstruction with obturator prostheses. MATERIALS AND METHODS: 12 scenarios of three-dimensional finite element models were constructed based on computed tomography scans of a patient who had hemimaxillectomy. Two obturator prostheses were analyzed for each model. A total force of 600 N was applied from the palatal to buccal bones at an angle of 45°. The maximum and minimum principal stress values for bone and also the von Misses stress values for dental implants and prostheses were calculated. RESULTS: When zygomatic implants were applied to the defect area, the maximum principal stresses were similar in intensity to the other models; however, the minimum principal stress values were higher than in scenarios without zygomatic implants. In models that used zygomatic implants in the defect area, von Misses stress levels were significantly higher in zygomatic implants than in dental implants. In scenarios where the prosthesis was supported by tissue in the non-defect area, the maximum and minimum principal stress values on cortical bone were higher than in scenarios where implants were applied to both defect and non-defect areas. CONCLUSIONS: In patients who lack an alveolar crest after maxillectomy, reduced stress on the zygomatic bone is expected if a custom bar-retained prosthesis is placed on the dental implant. The stress was higher on zygomatic implants without alveolar crest support than on dental implants.

Effect of surface treatment and resin cement type on the bond strength of polyetheretherketone to lithium disilicate ceramic.

BACKGROUND: This study aims to evaluate the effect of surface treatment and resin cement on the shear bond strength (SBS) and mode of failure of polyetheretherketone (PEEK) to lithium disilicate ceramic (LDC). This is suggested to study alternative veneering of PEEK frameworks with a ceramic material. METHODS: eighty discs were prepared from PEEK blank and from lithium disilicate ceramic. Samples were divided into four groups according to surface treatment: Group (A) air abraded with 110 µm Al2O3, Group (AP) air abrasion and primer application, Group (S) 98% sulfuric acid etching for 60 s, Group (SP) Sulfuric acid and primer. Each group was subdivided into two subgroups based on resin cement type used for bonding LDC:1) subgroup (L) self- adhesive resin cement and 2) subgroup (B) conventional resin cement (n = 10). Thermocycling was done for all samples. The bond strength was assessed using the shear bond strength test (SBS). Failure mode analysis was done at 50X magnification with a stereomicroscope. Samples were chosen from each group for scanning electron microscope (SEM). The three-way nested ANOVA followed by Tukey's post hoc test were used for statistical analysis of results. Comparisons of effects were done utilizing one way ANOVA and (p < 0.05). RESULTS: The highest mean of shear bond strength values was demonstrated in Group of air abrasion with primer application using conventional resin cement (APB) (12.21 ± 2.14 MPa). Sulfuric acid groups showed lower shear bond strength values and the majority failed in thermocycling especially when no primer was applied. The failure mode analysis showed that the predominant failure type was adhesive failure between cement and PEEK, while the remaining was mixed failure between cement and PEEK. CONCLUSION: The air abrasion followed by primer application and conventional resin cement used for bonding Lithium Disilicate to PEEK achieved the best bond strength. Primer application did not have an effect when self-adhesive resin cement was used in air-abraded groups. Priming step is mandatory whenever sulfuric acid etching surface treatment is utilized for PEEK.

Comparison of the shear bond strengths of two different polyetheretherketone (PEEK) framework materials and CAD-CAM veneer materials.

BACKGROUND: This study evaluated the shear bond strength (SBS) of two different polyetheretherketone (PEEK) and CAD-CAM materials after aging. METHODS: A total of 42 frameworks were designed and milled from 2 different PEEK discs (Copra Peek, P and BioHPP, B). P and B frameworks were divided into 3 subgroups (n = 7). 14 slices were prepared each from feldspathic ceramic (Vitablocs Mark II, VM), hybrid nanoceramic (Cerasmart, CS), and polymer-infiltrated ceramic (Vita Enamic, VE) blocks. After surface preparations, the slices were cemented to P and B surfaces. The samples were subjected to thermal aging (5000 cycles). SBS of all the samples was measured. Fractured surfaces were examined by SEM/EDX analysis. The Shapiro-Wilk, Two-way Robust ANOVA and Bonferroni correction tests were used to analyze the data (a = .05). RESULTS: Frameworks, ceramics, and frameworks x ceramics had significant differences (p < 0.05). The highest SBS value was seen in B-VM (p < 0.05). VM offered the highest SBS with both P and B. The differences between P-VM, P-CS, P-VE and B-CS and B-VE were insignificant (p > 0.05). According to EDX analysis, ytterbium and fluorine was seen in B content, unlike P. While VM and CS contained fluorine, barium, and aluminum; sodium and aluminum were observed in the VE structure. CONCLUSION: Bonding of P and B with VM offers higher SBS. VM, CS and VE did not make any difference in SBS for P, however VM showed a significant difference for B.

Five years of radiographic evaluation for the peri-implant bone changes of all-on-four implant prostheses constructed from different framework materials using different digital construction techniques.

BACKGROUND: There is insufficient evidence recommending a framework material and a CAD/CAM manufacturing technique for mandibular implant-supported prostheses. The study objective was to evaluate the clinical application of different materials and construction techniques used for mandibular All-on-4 prosthesis on circumferential peri-implant bony changes after 5 years. METHODS: Thirty-six male patients with all-on-4 mandibular implant-supported prostheses were recalled and divided into three groups. Group PK (patients with frameworks milled from PEEK blocks), Group PSM (patients with frameworks milled from soft metal blocks), and Group SLM (patients with frameworks constructed with additive manufacturing; selective laser melting). The circumferential bone level on all implant faces was assessed with a CBCT. Two-way repeated measures ANOVA was used to compare vertical bone loss (VBL) and horizontal bone loss (HBL) between different groups, implant positions, and observation times followed by Tukey's multiple comparisons. RESULTS: For all observation times, there was a significant difference in VBL between groups for both anterior and posterior implants (P < .001). For anterior implants, group PSM showed the lowest VBL while group PK showed the highest for anterior and posterior implants. For all groups, HBL significantly increased after 5 years for both anterior and posterior implants (P < .001). For anterior implants, group PSM showed the highest HBL. For posterior implants, group PK and SLM showed the highest. CONCLUSION: Within the study's limitations, mandibular implant-supported fixed frameworks fabricated with either milling from PEEK or soft metal blocks, or additive manufacturing (laser melting technology) exhibited significant vertical and horizontal bone height changes after 5 years. CLINICAL TRIAL REGISTRY NUMBER: (NCT06071689) (11/10/2023).

Evaluation and assessment of the wettabilty and water contact angle of modified poly methyl methacrylate denture base materials against PEEK in cast partial denture framework: an in vitro study.

INTRODUCTION: The prevalence of adults with partially dental arches is expected to be more than imagined and patients requiring replacement of missing teeth are slowly increasing in number too. Removable partial dentures are known to provide for substantial replacement for the missing teeth with also added advantages when compared to fixed or implant prosthesis, mainly in elderly patients. Denture base material performance and durability are greatly influenced by wettability and water contact angle. In the case of dentures; adequate moisture distribution is necessary to ensure excellent wettability which has an influence on comfort and oral health. The purpose of conducting this study was to find out whether the advancements made using PEEK (Polyether ether ketone) would prove to be more beneficial than the current upgrades in the current material spectrum. MATERIALS AND METHODS: This study was performed under in vitro conditions. All the fabrication and processing was done only by one operator. The materials used were divided into three groups each comprising 20 samples. Group A was modified polymethylmethacrylate (Bredent Polyan), Group B was polyoxymethylene acetal resin (Biodentaplast) and Group C was PEEK. An Ossila Goniometer was used to measure the contact angle. The three types of liquids used for the testing included distilled water, natural saliva and mouth wetting solution (Wet Mouth Liquid, ICPA India). Human saliva was collected from an individual with no medical conditions and normal salivary secretion. RESULTS: The data was analyzed using One-way ANOVA test and a pairwise comparison using the Post Hoc Tukey's Honest Significant Difference. Table 1 consists of the mean water contact angles of the denture base materials and mean contact angles of various denture base materials. In saliva, mouth wetting solution and distilled water, the highest mean and least mean contact angle was seen in Polyan and Biodentaplast respectively. A signicant difference was seen between PEEK and Polyan and Biodentaplast and Polyan on further comparison. CONCLUSION: From the resources and the materials at our disposal, it could be concluded that Polyan, Biodentaplast and PEEK and could be used as viable options in cast partial denture framework.

Effect of acidic environment on color and translucency of different indirect restorative materials.

PURPOSE: The aim of the current study was to evaluate the effect of simulated gastric acid on the color and translucency of different indirect restorative materials. MATERIALS AND METHODS: A total of 36 disc-shaped samples were cut by using an isomet saw and divided into four equal groups (n = 9) according to the material type: Group Z: translucent zirconia (Ceramill® Zolid ht.+ preshade, Amann Girrbach, Koblach, Austria); Group E: lithium disilicate (IPS e.max CAD, Ivoclar Vivadent AG, Schaan, Liechtenstein); Group C: resin nanoceramic (Cerasmart, GC, Tokyo, Japan); Group P: polyether ether ketone (PEEK) (Bettin Zirconia Dentale Italy) veneered with indirect high impact polymer composite (HIPC) (breCAM HIPC, Bredent GmbH & Co. KG, Germany). The samples were immersed in simulated gastric acid (HCl, pH 1.2) for 96 hours at 37 °C in an incubator. The color change (ΔE00) and translucency (RTP00) were measured every 9.6 hours (one-year clinical simulation) of immersion in simulated gastric acid. RESULTS: For color change (∆E00) and translucency (RTP00) among the tested materials, there was a highly statistically significant difference (P < 0.001) after every year of follow-up. The color change in both Z and G groups was the lowest after 1 year of acid immersion, followed by that in group H, and the highest change in color was recorded in group P. CONCLUSION: High translucent zirconia is recommended in patients who are concerned about esthetic, especially with acidic oral environment.

In vitro measurement of the retention force of two stud attachment systems during cyclic load.

PURPOSE: To investigate the retentive behavior of the Locator legacy and Novaloc attachment systems with different retention inserts both within and across systems under cyclic load. MATERIALS AND METHODS: Three retention inserts of each system (green, yellow, and white for Novaloc; green, orange, and red inserts for extended range for legacy Locator) were tested on abutments of both systems with a sample number of 10 per force and 10,000 cycles of insertion and removal. The loading was applied in the axial direction of the abutments, which were placed in artificial saliva. The retention force was measured in each cycle. The results were compared with the manufacturer's specifications and evaluated for a simulated period of use of 10 years. Characteristic time constants were determined, and subsequently, the two systems were compared regarding their wear behavior. RESULTS: The manufacturer's specifications could only be confirmed for the green Novaloc retention insert on a Novaloc abutment (t-test: p = 0.50); for all other inserts, the baseline exceeded the manufacturer's specifications by 30%-75% (Novaloc; t-test: p < 0.001) and 75%-550% (Locator; t-test: p < 0.001). After 10,000 cycles performed, the manufacturer's specifications were confirmed on a Novaloc abutment for the white Novaloc retention insert (t-test: p = 0.86) and on a Locator abutment for the green Novaloc retention insert (t-test: p = 0.32). Both systems lost retention force during the experiment. Overall, Novaloc inserts on both abutments showed less wear (decrease to 56%-85% of initial force) and a slower decrease in retention force compared to Locator inserts (decrease to 6%-31% of initial force). CONCLUSIONS: In both systems, wear leads to a varying loss of retention; therefore, regular checks with possible replacement of the inserts are necessary in clinical use. Novaloc attachments seem to be more resistant to the loss of retention than Locator attachments. A cross-combination may be clinically useful in some cases.

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.

Fracture resistance of cement-retained lithium disilicate implant-supported crowns: Effect of material used for two-piece abutments.

PURPOSE: This study compared the fracture strength of single lithium disilicate implant-supported crowns fabricated on two-piece abutments with various materials: ceramic-reinforced PEEK, zirconia, and lithium disilicate. MATERIALS AND METHODS: Thirty-six implants were embedded in acrylic cylinders. A two-piece abutment and a crown were designed following a pre-operation scan for a maxillary left central incisor. The designed crown was used to fabricate 36 lithium disilicate crowns. The designed abutment was used to manufacture 36 abutments from 3 materials, 12 each: (A) zirconia; (B) lithium disilicate; and (C) ceramic-reinforced PEEK. Abutments were surface treated and bonded on the titanium base abutments with resin cement. Then, lithium disilicate crowns were bonded on the assigned abutments. Specimens were then subjected to dynamic loading for 1,200,000 cycles. The fracture strength (N) of the assembly was assessed using a universal testing machine. One-way ANOVA followed by multiple comparison tests was used to evaluate the effect of abutment material on the fracture strength of single implant-supported restorations at a significance of .05. RESULTS: The average fracture strength for the groups with zirconia, PEEK, and lithium disilicate two-piece abutments were 1362N ± 218N, 1235N ± 115N, and 1472N ± 171N, respectively. There was a significant (p < 0.05) difference in fracture strength among the groups. The lithium disilicate group had significantly higher fracture strength (p = 0.0058) than the group with PEEK; however, there was no significant (p > 0.05) difference between the other groups. CONCLUSIONS: Two-piece abutments restored with lithium disilicate crowns investigated in the study have the potential to withstand the average physiological occlusal forces in the anterior region.

Experimental Modeling of Cranial Injury and Defect Reconstruction Using Superconstructive Polymers (PEEK).

Experimental model of resection craniotomy with subsequent reconstruction of the defect with a polymer implant enables comprehensive assessment of functional and ultrastructural changes during replacement of the damaged tissue. Reconstruction of a skull defect was accompanied by transient motor disturbance in the acute period and did not cause functional disorders and neurological deficits in a delayed period. Histological examination of osteal and brain tissue revealed no pathological reactions that could be associated with the response to the chemical components of the implant.

Comparative in vitro study on biomechanical behavior of zirconia and polyetheretherketone biomaterials exposed to experimental loading conditions in a prototypal simulator.

Zirconia and polyetheretherketone (PEEK) are two biomaterials widely investigated as substitute for metals in oral prosthetic rehabilitation. To achieve a proper biomechanical behavior, the prosthetic biomaterials must ensure a good resistance to loads, as this is a crucial characteristic enabling their use in dental applications. The aim of this study was to investigate differences in the fracture resistance of different biomaterials in an experimental environment: fixed partial dentures (FPDs) screwed in a prototype of biomimetic mandible. 10 Samples of FPDs were allocated in 2 groups (A and B): Group A (n=5) involved FPDs in zirconia-ceramic, and Group B (n=5) involved FPDs in PEEK-composite. The samples were loaded by means of a three-point bending mechanical test, and the load to fracture has been evaluated generating a point-by-point graphics (speed/load and time/deformation). The samples were further analyzed by micro-computed tomography (micro-CT) and described under experimental loading conditions. Zirconia-ceramic FDPs were the samples reporting the worst results, showing a lower value of vertical displacement with respect to PEEK-based samples. The micro-CT results have further confirmed the preliminary results previously described. This in vitro study aims to give analytic data on the reliability of PEEK as a reliable and strong biomaterial for prosthetic treatments.