Titanium and hydroxyapatite coating of polyetheretherketone and carbon fiber-reinforced polyetheretherketone: A pilot study in sheep

Purpose: The purpose of this study was to evaluate the bone formation capability of polyetheretherketone (PEEK) and carbon fiber-reinforced PEEK (CFR-PEEK) implants coated with different titanium and hydroxyapatite plasma-sprayed layers after 2 and 12 weeks. Methods: In six sheep 108 implants were placed in the pelvis. Altogether six different surface modifications were tested. After 2 and 12 weeks, n = 3 implants per group were examined histologically and n = 6 implants per group were tested by a pull-out test. Results: Biomechanically (p = 0.001) as well as histologically (p > 0.05) surface coating of PEEK/CFR-PEEK led to an increase of osseointegration from 2 to 12 weeks. After 12 weeks, coated implants demonstrated significant (p < 0.001) higher pull-out values in comparison to uncoated implants. Overall, the double coating (titanium bond layer and hydroxyapatite top layer) showed the most favorable results after 2 and 12 weeks. Conclusions: Plasma-sprayed titanium and hydroxyapatite coatings on PEEK or CFR-PEEK demonstrated a significant improvement of osseointegration.

Compressive strength of interbody cages in the lumbar spine: the effect of cage shape, posterior instrumentation and bone density

One goal of interbody fusion is to increase the height of the degenerated disc space. Interbody cages in particular have been promoted with the claim that they can maintain the disc space better than other methods. There are many factors that can affect the disc height maintenance, including graft or cage design, the quality of the surrounding bone and the presence of supplementary posterior fixation. The present study is an in vitro biomechanical investigation of the compressive behaviour of three different interbody cage designs in a human cadaveric model. The effect of bone density and posterior instrumentation were assessed. Thirty-six lumbar functional spinal units were instrumented with one of three interbody cages: (1) a porous titanium implant with endplate fit (Stratec), (2) a porous, rectangular carbon-fibre implant (Brantigan) and (3) a porous, cylindrical threaded implant (Ray). Posterior instrumentation (USS) was applied to half of the specimens. All specimens were subjected to axial compression displacement until failure. Correlations between both the failure load and the load at 3 mm displacement with the bone density measurements were observed. Neither the cage design nor the presence of posterior instrumentation had a significant effect on the failure load. The loads at 3 mm were slightly less for the Stratec cage, implying lower axial stiffness, but were not different with posterior instrumentation. The large range of observed failure loads overlaps the potential in vivo compressive loads, implying that failure of the bone-implant interface may occur clinically. Preoperative measurements of bone density may be an effective tool to predict settling around interbody cages.

[The stamp technique for direct composite restoration]

The indications for direct resin composite restorations are nowadays extended due to the development of modern resin materials with improved material properties. However, there are still some difficulties regarding handling of resin composite material, especially in large restorations. The reconstruction of a functional and individual occlusion is difficult to achieve with direct application techniques. The aim of the present publication was to introduce a new "stamp"-technique for placing large composite restorations. The procedure of this "stamp"-technique is presented by three typical indications: large single-tooth restoration, occlusal rehabilitation of a compromised occlusal surface due to erosions and direct fibre-reinforced fixed partial denture. A step-by-step description of the technique and clinical figures illustrates the method. Large single-tooth restorations can be built-up with individual, two- piece silicone stamps. Large occlusal abrasive and/or erosive defects can be restored by copying the wax-up from the dental technician using the "stamp"-technique. Even fiber-reinforced resin-bonded fixed partial dentures can be formed with this intraoral technique with more precision and within a shorter treatment time. The presented "stamp"-technique facilitates the placement of large restoration with composite and can be recommended for the clinical use.

Single crowns versus conventional fillings for the restoration of root-filled teeth.

BACKGROUND Endodontic treatment involves removal of the dental pulp and its replacement by a root canal filling. Restoration of root filled teeth can be challenging due to structural differences between vital and non-vital root-filled teeth. Direct restoration involves placement of a restorative material e.g. amalgam or composite, directly into the tooth. Indirect restorations consist of cast metal or ceramic (porcelain) crowns. The choice of restoration depends on the amount of remaining tooth, and may influence durability and cost. The decision to use a post and core in addition to the crown is clinician driven. The comparative clinical performance of crowns or conventional fillings used to restore root-filled teeth is unknown. This review updates the original, which was published in 2012. OBJECTIVES To assess the effects of restoration of endodontically treated teeth (with or without post and core) by crowns versus conventional filling materials. SEARCH METHODS We searched the following databases: the Cochrane Oral Health Group's Trials Register, CENTRAL, MEDLINE via OVID, EMBASE via OVID, CINAHL via EBSCO, LILACS via BIREME. We also searched the reference lists of articles and ongoing trials registries.There were no restrictions regarding language or date of publication. The search is up-to-date as of 26 March 2015. SELECTION CRITERIA Randomised controlled trials (RCTs) or quasi-randomised controlled trials in participants with permanent teeth that have undergone endodontic treatment. Single full coverage crowns compared with any type of filling materials for direct restoration or indirect partial restorations (e.g. inlays and onlays). Comparisons considered the type of post and core used (cast or prefabricated post), if any. DATA COLLECTION AND ANALYSIS Two review authors independently extracted data from the included trial and assessed its risk of bias. We carried out data analysis using the 'treatment as allocated' patient population, expressing estimates of intervention effect for dichotomous data as risk ratios, with 95% confidence intervals (CI). MAIN RESULTS We included one trial, which was judged to be at high risk of performance, detection and attrition bias. The 117 participants with a root-filled, premolar tooth restored with a carbon fibre post, were randomised to either a full coverage metal-ceramic crown or direct adhesive composite restoration. None experienced a catastrophic failure (i.e. when the restoration cannot be repaired), although only 104 teeth were included in the final, three-year assessment. There was no clear difference between the crown and composite group and the composite only group for non-catastrophic failures of the restoration (1/54 versus 3/53; RR 0.33; 95% CI 0.04 to 3.05) or failures of the post (2/54 versus 1/53; RR 1.96; 95% CI 0.18 to 21.01) at three years. The quality of the evidence for these outcomes is very low. There was no evidence available for any of our secondary outcomes: patient satisfaction and quality of life, incidence or recurrence of caries, periodontal health status, and costs. AUTHORS' CONCLUSIONS There is insufficient evidence to assess the effects of crowns compared to conventional fillings for the restoration of root-filled teeth. Until more evidence becomes available, clinicians should continue to base decisions about how to restore root-filled teeth on their own clinical experience, whilst taking into consideration the individual circumstances and preferences of their patients.

The long-term mechanical integrity of non-reinforced PEEK-OPTIMA polymer for demanding spinal applications: experimental and finite-element analysis

Polyetheretherketone (PEEK) is a novel polymer with potential advantages for its use in demanding orthopaedic applications (e.g. intervertebral cages). However, the influence of a physiological environment on the mechanical stability of PEEK has not been reported. Furthermore, the suitability of the polymer for use in highly stressed spinal implants such as intervertebral cages has not been investigated. Therefore, a combined experimental and analytical study was performed to address these open questions. A quasi-static mechanical compression test was performed to compare the initial mechanical properties of PEEK-OPTIMA polymer in a dry, room-temperature and in an aqueous, 37 degrees C environment (n=10 per group). The creep behaviour of cylindrical PEEK polymer specimens (n=6) was measured in a simulated physiological environment at an applied stress level of 10 MPa for a loading duration of 2000 hours (12 weeks). To compare the biomechanical performance of different intervertebral cage types made from PEEK and titanium under complex loading conditions, a three-dimensional finite element model of a functional spinal unit was created. The elastic modulus of PEEK polymer specimens in a physiological environment was 1.8% lower than that of specimens tested at dry, room temperature conditions (P<0.001). The results from the creep test showed an average creep strain of less than 0.1% after 2000 hours of loading. The finite element analysis demonstrated high strain and stress concentrations at the bone/implant interface, emphasizing the importance of cage geometry for load distribution. The stress and strain maxima in the implants were well below the material strength limits of PEEK. In summary, the experimental results verified the mechanical stability of the PEEK-OPTIMA polymer in a simulated physiological environment, and over extended loading periods. Finite element analysis supported the use of PEEK-OPTIMA for load-bearing intervertebral implants.