Evaluation of mechanical properties of different polyetheretherketone endodontic post systems: an in vitro study

BACKGROUND

Survival of endodontically treated teeth depends on an efficient restoration of the missing tooth structure.

OBJECTIVES

This study aimed to investigate the mechanical properties of different endodontic post systems.

MATERIALS AND METHODS

Human permanent maxillary central incisors (no.=58) were decoronated and root-filled. The specimens with prepared root canals were randomly divided into Group P: Polyether Ether Ketone (PEEK) post and composite core and Group C: custom-made post-core of PEEK. The cementation of the posts was carried out using self-adhesive resin cement. Nano-hybrid composite resin was used for core fabrication. After cementation, the specimens from each group were randomly divided into two subgroups according to the types of tests utilized: 14 from each group were for the fracture strength test, which was restored with IPS e-max CAD crown, and 15 from each group for the pullout resistance test. A universal testing machine was used for the test performance.

RESULTS

The fracture resistance test showed that the values significantly differed among tested posts (P = 0.013). Group P showed the highest fracture resistance. Group C exhibited higher mean pullout resistance values than the other group (P) (P = 0.059). In the two-piece PEEK post and composite core, the predominant type of failure was a core fracture, while in the one-piece PEEK post-core, most types of failures were either in the crown or in the post.

CONCLUSIONS

The prefabricated posts are more resistant to fracture than the custom-made posts, with fracture and displacement mainly of the core. In contrast, both showed similar pullout resistance.

How to place a cephalomedullary screw when visualization is obscured by the jig in peritrochanteric hip fractures using "peek radiographs."

Lag screw positioning can be difficult to discern intraoperatively on lateral fluoroscopic imaging during intramedullary fixation of proximal femur fractures in some nailing systems due to the drill guide handle obstructing the view. We have described a method of obtaining non-obstructed lateral-oblique "peek" views that reliably assist in obtaining adequate tip-apex distance (TAD) measurements when using intramedullary fixation for these fractures. The purpose of this study was (1) to describe an intraoperative radiographic technique to obtain non-obscured views for appropriate center-center placement of the lag screw(s) within the femoral head during jig-aided cephalomedullary nailing of peritrochanteric hip fractures and (2) to present a case series detailing the radiographic results using this technique. This clinical series of sixty-five patients with intertrochanteric or subtrochanteric proximal femur fractures stabilized with a cephalomedullary nail had an average TAD of 15.1 ± 3.3mm (range: 9.4mm-26.2mm). This suggests that our technical trick of obtaining "peek" radiographs intraoperatively may aid in a precise lag-screw placement.

Self-reinforced poly(ether ether ketone) and polyethylene composite gaskets for prevention of mechanically-assisted corrosion in modular taper junctions: Seating, micromotion and short-term fretting corrosion

Mechanically-assisted crevice corrosion (MACC) is a phenomenon known to cause complications in modular orthopedic implants, particularly at metal-metal taper junctions. Previous studies of the properties and corrosion performance of an interfacial polymeric self-reinforced composite (SRC) gaskets have shown its capability as a high-strength, insulating barrier against oxide abrasion and metal degradation of metal-metal (or metal-hard) contacts in MACC conditions. This study characterizes the short-term tribocorrosion performance of poly (ether ether ketone) SRCs (SRC-PEEK) and polyethylene SRC (SRC-PE) films under in vitro test conditions for head-neck modular junction designs in hip replacement devices. SRC films composed of SRC-PEEK and SRC-PE were seated between 9/10 femoral head bores and stem tapers as thin interfacial gaskets and tested against metal-metal controls under short-term cyclic loading conditions in a custom in vitro test setup. Head-neck seating mechanics were measured, followed by incremental cyclic fretting corrosion testing with monitoring of fretting current, force, and relative micromotion between head and neck components during cyclic loading. SRC-PEEK tapers had a seating subsidence that was approximately three times that of the SRC-PE tapers and nine times that of controls. SRC-PE tapers, likely due to low friction, partially failed to lock during seating resulting in a pushing up of the head on the taper. Average fretting currents were significantly lower for both SRC groups (less than 0.3 μA at 4000 N) compared to control tapers experiencing fretting corrosion currents between 1.7 μA and 32 μA, (p < 0.05). SRC-PEEK gaskets exhibited similar subsidence and micromotion performance as controls while SRC-PE tapers experienced over 240 μm of subsidence during seating and loading conditions. The SRC-PE low-friction properties likely caused insufficient taper locking, which may increase the risk of improper head seating or head disassociation. These results show that SRC-PEEK gaskets, unlike SRC-PE gaskets, can maintain adequate frictional locking at the taper junction and prevent the onset of MACC. SRC-PEEK gaskets improve the performance of modular taper junctions and could be considered as a potential solution to mitigate fretting corrosion.

Influence of implant scanbody material, position and operator on the accuracy of digital impression for complete-arch: A randomized in vitro trial

PURPOSE

To evaluate the influence of implant scanbody (ISB) material, position and operator on the accuracy of a confocal microscopy intraoral scanning (IOS) for complete-arch implant impression.

METHODS

An edentulous maxillary model with 6 internal hexagonal connection analogues was scanned with an extraoral optical scanner to achieve a reference file. Three ISBs made of different materials (polyetheretherketone (Pk), titanium (T) and Pk with a titanium base (Pkt)) were scanned with IOS by 3 operators. The resulting 45 test files were aligned to the reference file with a best fit algorithm. Linear (ΔX, ΔY and ΔZ-axis) and angular deviations (ΔANGLE) were assessed. Absolute values of the linear discrepancies were summed up to obtain a global measure of linear absolute error (ΔASS). Influence of ISB material, position and operator was statistically assessed using the mixed general linear model.

RESULTS

At multivariate analysis, whenΔASS was considered as response variable, it was identified a significant influence of material (p<0.0001) and position (p=0.0009) while no significant operator effect was detected. When ΔANGLE was considered as response variable, material and position significantly influenced the expected ΔANGLE (p=0.0232 and p<0.0001) and no operator effect was identified.

CONCLUSIONS

The investigated IOS for complete-arch digital impression was influenced by the ISB material with peek reporting the best results on both linear and angular measurements followed by titanium, peek-titanium resulting as the less accurate. Implant angulation affected significantly the linear deviations while implant position the angular deviations. Operator did not show any significant effect on the IOS accuracy.

Physicochemical and biological assessment of PEEK composites embedding natural amorphous silica fibers for biomedical applications

The main aim of this study was to assess the physicochemical and biological properties of a novel poly(ether ether ketone) (PEEK) composite containing 30%wt natural amorphous silica fibers (NASF). PEEK and NASF powders were previously functionalized by atomization and citric acid in order to enhance adhesion between polymeric matrix and fillers. Then, composites were produced by cold compression molding technique at 350°C for 3h. Materials were characterized by chemical, microstructural, thermophysical, mechanical and cytotoxic analysis. The results of the mechanical assays showed that the incorporation fibers increased the elastic modulus of the resultant PEEK composite in 56% while its microhardness increased in 26.7%. Chemical and microscopic analyses detected a good interfacial adhesion between PEEK and NASF. The results of the cytotoxicity assays indicated that PEEK/NASF composites stimulated the metabolic activity of fibroblasts and therefore a high cytocompatibility was noticed. PEEK composites embedding natural amorphous silica fibers revealed a high potential to be used in medicine and dentistry replacing several polymeric and composite materials.

Effectiveness of a novel mobile health education intervention (Peek) on spectacle wear among children in India: study protocol for a randomized controlled trial

Background

Uncorrected refractive errors are the commonest cause of visual loss in children despite spectacle correction being highly cost-effective. Many affected children do not benefit from correction as a high proportion do not wear their spectacles. Reasons for non-wear include parental attitudes, overprescribing and children being teased/bullied. Most school programmes do not provide health education for affected children, their peers, teachers or parents.

The Portable Eye Examination Kit (Peek) will be used in this study. Peek has applications for measuring visual acuity with software for data entry and sending automated messages to inform providers and parents. Peek also has an application which simulates the visual blur of uncorrected refractive error (SightSim).

The hypothesis is that higher proportion of children with uncorrected refractive errors in schools allocated to the Peek educational package will wear their spectacles 3–4 months after they are dispensed, and a higher proportion of children identified with other eye conditions will access services, compared with schools receiving standard school screening.

Methods/Design

Cluster randomized, double-masked trial of children with and without uncorrected refractive errors or other eye conditions. Government schools in Hyderabad, India will be allocated to intervention (Peek) or comparator (standard programme) arms before vision screening. In the intervention arm Peek will be used for vision screening, SightSim images will be used in classroom teaching and will be taken home by children, and voice messages will be sent to parents of children requiring spectacles or referral.

In both arms the same criteria for recruitment, prescribing and dispensing spectacles will be used. After 3–4 months children dispensed spectacles will be followed up to assess spectacle wear, and uptake of referrals will be ascertained.

The cost of developing and delivering the Peek package will be assessed. The cost per child wearing their spectacles or accessing services will be compared.

Discussion

Educating parents, teachers and children about refractive errors and the importance of wearing spectacles has the potential to increase spectacle wear amongst children. Innovative, potentially scalable mobile technology (Peek) will be used to screen, provide health education, track spectacle wear and adherence to follow-up amongst children referred.

Trial registration

Controlled-Trials.com, ISRCTN78134921. Registered on 29 June 2016.

Electronic supplementary material

The online version of this article (doi:10.1186/s13063-017-1888-5) contains supplementary material, which is available to authorized users.

Primary and secondary reconstruction of complex craniofacial defects using polyetheretherketone custom-made implants

PURPOSE

The aim of this study was to evaluate the surgical outcomes using polyetheretherketone (PEEK) patient-specific prostheses produced by computer-aided design and manufacturing for primary and secondary reconstruction in patients with craniofacial defects.

MATERIAL AND METHODS

The study included 13 patients who underwent reconstruction for craniofacial defects using PEEK patient-specific implants (PSI). Eight patients underwent single-step primary reconstruction using individual custom-made surgical guides and custom-made prostheses during the same surgery; five patients underwent delayed reconstruction. The material used to manufacture the implants was PEEK in 13 cases. All patients underwent esthetic examination, ophthalmological examination, and radiological evaluation during the preoperative and follow-up periods. The operation duration and short- and long-term complications were recorded.

RESULTS

The shape and global position of the implants were satisfactory in each case. Fitting of the implant during surgery required extensive adaptation in 1 case and minor in 11 cases. Of 13 implants, 11 adequately restored a morphological complex area with satisfactory cosmetic results. No complications related to the implants were reported.

CONCLUSION

Reconstruction for cranio-facial defects using PEEK computer-aided designed and manufactured implants is a promising new technique that allows for accurate restoration of the complex 3D anatomy of the craniofacial region.