Enamel Surface Damage following Debonding of Ceramic Brackets: A Hospital-Based Study.

METHODS: The current study includes 80 extracted premolars of human from the patient visiting for orthodontic treatment of Coorg Institute of Dental Sciences, Karnataka, India. The brackets were debonded using four different methods. The enamel surface damage after the procedure was assessed with the Enamel Surface Index (ESI); similarly, the Adhesive Remnant Index (ARI) score was used to determine the adhesive residual deposit. Scanning electron microscopy (SEM) was used to visualize better microporosities and micromechanical retention of adhesive remnants on the enamel surface. The normality of the data was tested using the Kolmogorov-Smirnov test. Depending upon the normality test result, the one-way ANOVA test or Kruskal-Wallis test was used to test the mean ESI and mean ARI differences among different debonding methods along with the appropriate post hoc tests. The necessary ethical clearance was obtained from the Ethics Committee of the institute. RESULTS: The ultrasonic scaler (US) technique led to more significant enamel surface damage, with 13 (65%) samples in the ESI scores III and IV against the satisfactory surface in 2 (10%) samples with the ligature cutter (LC) technique (ESI-I) reflecting LC as a better technique. The ESI scores (III and IV) for debonding plier (DP) and thermal method (TM) reflected a higher value in 12 (60%) and 10 (50%) samples and caused more damage to the enamel surface as compared to the LC technique. The ARI score was highest (ARI-1 = 40%) with the LC technique, followed by the US (ARI-1 = 20%), TM (ARI-1 = 15%), and DP (ARI-1 = 5%) methods. We have observed a significant association (p value <0.05) of the ARI score among four different debonding ways in terms of each tooth's residual adhesive after the bracket removal. CONCLUSION: The result establishes the LC technique as a more acceptable one as it causes minimal harm to the debonded surface. The adhesive left on the debonded area is also minimum as compared to the other three methods tested. Therefore, it can be suggested as an ideal method.

Cytotoxicity Study of UV-Laser-Irradiated PLLA Surfaces Subjected to Bio-Ceramisation: A New Way towards Implant Surface Modification.

In this research we subjected samples of poly(L-lactide) (PLLA) extruded film to ultraviolet (193 nm ArF excimer laser) radiation below the ablation threshold. The modified film was immersed in Simulated Body Fluid (SBF) at 37 °C for 1 day or 7 days to obtain a layer of apatite ceramic (CaP) coating on the modified PLLA surface. The samples were characterized by means of optical profilometry, which indicated an increase in average roughness (Ra) from 25 nm for the unmodified PLLA to over 580 nm for irradiated PLLA incubated in SBF for 1 day. At the same time, the water contact angle decreased from 78° for neat PLLA to 35° for irradiated PLLA incubated in SBF, which suggests its higher hydrophilicity. The obtained materials were investigated by means of cell response fibroblasts (3T3) and macrophage-like cells (RAW 264.7). Properties of the obtained composites were compared to the unmodified PLLA film as well as to the UV-laser irradiated PLLA. The activation of the PLLA surface by laser irradiation led to a distinct increase in cytotoxicity, while the treatment with SBF and the deposition of apatite ceramic had only a limited preventive effect on this harmful impact and depended on the cell type. Fibroblasts were found to have good tolerance for the irradiated and ceramic-covered PLLA, but macrophages seem to interact with the substrate leading to the release of cytotoxic products.

Distribution and Chemical Speciation of Exogenous Micro- and Nanoparticles in Inflamed Soft Tissue Adjacent to Titanium and Ceramic Dental Implants.

Degradation of the implant surface and particle release/formation as an inflammation catalyst mechanism is an emerging concept in dental medicine that may help explain the pathogenesis of peri-implantitis. The aim of the present study was a synchrotron-based characterization of micro- and nanosized implant-related particles in inflamed human tissues around titanium and ceramic dental implants that exhibited signs of peri-implantitis. Size, distribution, and chemical speciation of the exogenous micro- and nanosized particle content were evaluated using synchrotron µ-X-ray fluorescence spectroscopy (XRF), nano-XRF, and µ-X-ray absorption near-edge structure (XANES). Titanium particles, with variable speciation, were detected in all tissue sections associated with titanium implants. Ceramic particles were found in five out of eight tissue samples associated with ceramic implants. Particles ranged in size from micro- to nanoscale. The local density of both titanium and ceramic particles was calculated to be as high as ∼40 million particles/mm3. µ-XANES identified titanium in predominantly two different chemistries, including metallic and titanium dioxide (TiO2). The findings highlight the propensity for particle accumulation in the inflamed tissues around dental implants and will help in guiding toxicological studies to determine the biological significance of such exposures.

Early failure for wear after ceramic-on-highly cross-linked polyethylene total hip arthroplasty: a case report.

BACKGROUND: Highly cross-linked polyethylene (HXLPE) enhances the anti-wear characteristics of the conventional polyethylene (PE). Early failure for wear after ceramic-on-highly cross-linked polyethylene (CoHXLPE) total hip arthroplasty (THA) is extremely rare. CASE PRESENTATION: We described the case of a 60-year-old man who underwent right CoHXLPE THA because of the developmental dysplasia hip (DDH) complained pain 32 months after this procedure. Plain radiographs showed that eccentric wear existed at the polyethylene insert. However, the patient refused surgery at that time and did not stop weight-bearing. The right hip pain continued for 7 months. Plain radiographs of the pelvis showed that the HXLPE liner was penetrated and partial inner wall of acetabular shell was worn. Acetabular cup revision was performed, and the ceramic head and HXLPE were exchanged. CONCLUSIONS: Difficult reduction during primary THA, especially for DDH, can result in higher abductor tension, which may lead to early eccentric wear of the prosthesis. Whenever eccentric wear of HXLPE liner was found, weight-bearing must be stopped to avoid the accelerated wear and adverse reactions to metal debris (ARMD).

Hemiarthroplasties: the choice of prosthetic material causes different levels of damage in the articular cartilage.

BACKGROUND: Hemiarthroplasty has clear advantages over alternative procedures and is used in 20% of all shoulder joint replacements. Because of cartilage wear, the clinical outcome of hemiarthroplasty is unreliable and controversial. This paper suggests that the optimal choice of prosthetic material may reduce cartilage degeneration and improve the reliability of the procedure. The specific objectives were to assess 3 materials and assess how the severity of arthritis might affect the choice of prosthetic material. METHODS: A CoCr alloy, an AL2O3 ceramic, and a polycarbonate urethane polymer (PCU) were mechanically tested against 5 levels of human osteoarthritic cartilage (from intact to severely arthritic, n = 45). A high friction coefficient, a decrease in Young's modulus, an increase in permeability, a decrease in relaxation time, an increase in surface roughness, and a disrupted appearance of the cartilage after testing were used as measures of cartilage damage. The biomaterial that caused minimal cartilage damage was defined as superior. RESULTS: The CoCr caused the most damage. This was followed by the AL2O3 ceramic, whereas the PCU caused the least amount of damage. Although the degree of arthritis had an effect on the results, it did not change the trend that CoCr performed worst and PCU the best. DISCUSSION AND CONCLUSION: This study indicates that ceramic implants may be a better choice than metals, and the articulating surface should be as smooth as possible. Although our results indicate that the degree of arthritis should not affect the choice of prosthetic material, this suggestion needs to be further investigated.

Alumina Ceramic Exacerbates the Inflammatory Disease by Activation of Macrophages and T Cells.

(1) Background: Aluminum oxide (Al2O3) ceramic is one of the materials used for artificial joints, and it has been known that their fine particles (FPs) are provided by the wear of the ceramic. Al2O3 FPs have been shown to induce macrophage activation in vitro; however, the inflammatory effect in vivo has not been studied. (2) Methods: We examined the in vivo effect of Al2O3 FPs on the innate and adaptive immune cells in the mice. (3) Results: Al2O3 FPs promoted the activation of spleen macrophages; however, conventional dendritic cells (cDCs), plasmacytoid DCs (pDCs), and natural killer (NK) cells were not activated. In addition, increases in the CD4 and CD8 T cells was induced in the spleens of the mice treated with Al2O3 FPs, which differentiated into interferon-gamma (IFN-γ)-producing helper T1 (Th1) and cytotoxic T1 (Tc1) cells. Finally, the injection of Al2O3 FPs exacerbated dextran sulfate sodium (DSS)-induced inflammation in the colon, mediated by activated and increased number of CD4 and CD8 T cells. (4) Conclusions: These data demonstrate that FPs of Al2O3 ceramic may contribute to the exacerbation of inflammatory diseases in the patients.

The risk of revision after total hip arthroplasty in young patients depends on surgical approach, femoral head size and bearing type; an analysis of 19,682 operations in the Dutch arthroplasty register.

BACKGROUND: Total hip arthroplasty (THA) is used increasingly in younger patients. There is little knowledge about the effect of THA characteristics on risk of revision, especially in young patients. Therefore, we studied the influence of both patient-related and surgical factors on the risk of revision using data from the Dutch Arthroplasty Registry (LROI). METHODS: All patients younger than 55 years with a primary THA implanted in the Netherlands between 2007 and 2017 were selected (n = 19,682). The covariates age, sex, primary diagnosis, ASA-classification, surgical approach, fixation method, bearing type, head size and year of surgery were entered into Cox proportional hazards models to calculate hazard ratios for the risk of revision. RESULTS: The overall 5-year survival of primary THA was 95.3% (95% CI, 94.9-95.6). Use of the anterior approach resulted in a lower risk of revision than the use of the posterolateral approach (HR: 0.66, 95% CI: 0.47-0.92). THAs with a head diameter ≥ 38 mm had a higher risk of revision (HR: 1.90, 95% CI: 1.33-2.72) than THAs with 32 mm heads. Use of MoM bearings resulted in an increased risk when compared to C-PE (HR: 1.76, 95% CI: 1.27-2.43). CONCLUSION: The risk of revision in patients younger than 55 years depends on surgical approach, head size and bearing type. The anterior approach resulted in a decreased risk of revision, whereas use of ≥38 mm heads and MoM bearings resulted in an increased risk of revision for any reason.

Fatigue Behavior of Crystalline-Reinforced Glass-Ceramics.

PURPOSE: To evaluate the fatigue behavior of two crystalline-reinforced ceramics: leucite-reinforced (VL) and lithium disilicate-based (VD) glass-ceramics. MATERIALS AND METHODS: Bar-shaped specimens (16 × 4 × 1.2 mm) were produced for each ceramic using prefabricated CAD/CAM blocks. For each group, 30 specimens were subjected to a three-point flexural strength test in a universal testing machine. For VL and VD, 36 and 41 specimens were subjected to a cyclic fatigue test, respectively. The cyclic fatigue test was performed with a pneumatic mechanical cycling machine (1 Hz; 37°C distilled water). Specimens were tested at two stress levels for each preset lifetime (103 and 104 cycles for VL; 104 and 105 cycles for VD) following the boundary technique. Fractography was performed with a scanning electron microscope. Data were analyzed with Weibull analysis. RESULTS: There were significant differences among groups for characteristic strength (σ0 ) and Weibull modulus (m), as the confidence intervals did not overlap. The VD group presented the highest values of σ0 , but the lowest Weibull modulus. Both groups showed a reduction of approximately 60% of the initial flexural strength (σf ) after cycling for 104 cycles. For VD tested in fatigue, there was no degradation of σf when the number of cycles was increased from 104 to 105 . The VL group showed an 18% decrease in σf when the number of cycles increased from 103 to 104 . Flexural strength values estimated for a 5% probability of failure were 36 MPa for VL and 55 MPa for VD, after 104 cycles. CONCLUSION: Both glass-ceramics showed similar strength degradation (60%) after a lifetime of 104 cycles, despite their distinct mechanical properties. Mechanical cycling in humid conditions proved to be an important factor for the degradation of the mechanical properties of crystalline-reinforced glass-ceramics.

Effects of New Generation All-Ceramic and Provisional Materials on Fibroblast Cells.

PURPOSE: The purpose of this in vitro study was to evaluate the cytotoxic and apoptotic effects of seven new-generation all-ceramic materials for CAD/CAM (Lava Ultimate [LU], VITA Mark II [VM], InCoris TZI [IC], IPS e.max CAD [EM], VITA Suprinity [VS], Cerasmart [CS], IPS Empress CAD [EC]) and six provisional materials (Protemp 4 [PT], Telio CAD [TC], CAD-Temp [CT], Telio Lab [TL], Temdent Classic [TD], Telio CS C&B [TS]) on L929 mouse fibroblast cells. MATERIALS AND METHODS: 24 disc-shaped specimens (∅ = 5 mm, h = 2 mm) were prepared from each test material. Medium extracts were collected at the 1st, 3rd, and 7th days for each group and tested using the L929 cell line. Cytotoxicity was evaluated using XTT assay, and apoptosis was determined by Annexin-V/PI staining. Data were analyzed using one-way ANOVA, Tukey's multiple comparison tests at a significance level of p < 0.05. RESULTS: The cell viability results among all-ceramic material groups after the 1st and 7th days of incubation periods showed statistically significant differences (p < 0.05). There were significant differences within the ceramic groups in different incubation periods regarding apoptosis rate (p < 0.05). Throughout the entire test period, LU and VM from the CAD/CAM all-ceramic materials and PT and TC from the provisional restoration materials showed cell viability higher than 90%. EC and TD showed the lowest cell viability and highest apoptosis rates in their own groups. For the provisional materials, there were significant differences in cell viability and apoptosis rate in all the incubation periods for each material (p < 0.05). CONCLUSIONS: Although some new-generation CAD/CAM and provisional restoration materials display slight cytotoxicity values, the results are still within the reliable range, and they can safely be used in clinical conditions.

Clinical and radiographic evaluation of bioactive glass in posterior cervical and lumbar spinal fusion.

INTRODUCTION: Spinal surgery of degenerative painful segments is a valuable treatment option in the management of chronic cervical and low back pain. The surgery consists in stabilizing and fusing painful vertebral segment(s). The objective of the study was to report our experience with 45S5 bioactive glass (BAG) to obtain inter-vertebral fusion in the context of posterior spine surgery. MATERIAL AND METHOD: In this retrospective study, 30 patients with a wide range of degenerative and traumatic conditions of the cervical or lumbar spine underwent spinal fusion utilizing a synthetic bone graft substitute of BAG (GlassBone™, Noraker, Lyon-Villeurbanne, France). The pain was evaluated by VAS score, and graft consolidation was assessed on according radiographic images at 1-year post-op. RESULTS: All patients underwent posterior spinal fusion either in the cervical or the thoraco-lumbar spine. Multi-level fusions represented the majority of the cohort (43% of patients with more than seven levels treated). Radiographic imaging demonstrated excellent fusion rates (93%) at final follow-up, equivalent to the outcomes reported in the literature for autogenous bone, with excellent bone bridging and no spinal implant loosening. Only two cases of non-union were encountered. Additionally, 90% of the patients demonstrated recovery at 1 year after surgery with a pain reduction of 60%. CONCLUSION: The results of this retrospective study suggest that the 45S5 BAG may be an interesting alternative option to autologous graft, in terms of safety and bone fusion efficiency. LEVEL OF EVIDENCE: IV Retrospective study.

Clinical outcomes of partial and full-arch all-ceramic implant-supported fixed dental prostheses. A systematic review and meta-analysis.

OBJECTIVE: To assess the survival and technical complication rate of partial and full-arch all-ceramic implant-supported fixed dental prostheses (P-FDP/FA-FDP) and supporting implants. MATERIALS AND METHODS: An electronic search through three databases (MEDLINE/Pubmed, Cochrane Library, Embase) was conducted to identify relevant clinical studies with an observation period of at least 12 months, including ≥15 patients. Reconstruction and implant survival rates, technical complications and confounding variables such as processed/installed materials, retention mode and location in the mouth were obtained. Failure and complication rates were analyzed using standard Poisson regression models to calculate 5-year survival and complication estimates. RESULTS: A total of five studies for the P-FDP group and seven studies for the FA-FDP group were included, throughout evaluating veneered zirconia reconstructions. In the P-FDP group, reconstructions were located in posterior regions. Meta-analysis indicated survival estimates on the reconstruction level of 98.3% and 97.7% for P- and FA-FDPs after 5 years. However, chipping of the veneering ceramic was frequent, resulting in estimated 5-year complication rates of 22.8% (P-FDPs) and 34.8% (FA-FDPs). Five-year survival estimates of implants supporting P-FDPs and FA-FDPs of 98.5% and 99.4% were calculated, respectively. Including a total of 540 FDPs, one screw-loosening and 11 de-cementations were reported. Confounding variables were not found to have a significant influence on survival and complication rates. CONCLUSIONS: All-ceramic implant-supported P- and FA-FDPs comprising veneered zirconia frameworks showed high survival but clinically inacceptable fracture rates of the veneering ceramic. Their suitability with regard to this indication and a successful long-term outcome needs to be further evaluated.

A systematic review of the influence of the implant-abutment connection on the clinical outcomes of ceramic and metal implant abutments supporting fixed implant reconstructions.

OBJECTIVES: The objective of this systematic review was to assess the influence of implant-abutment connection and abutment material on the outcome of implant-supported single crowns (SCs) and fixed dental prostheses (FDPs). METHODS: An electronic Medline search complemented by manual searching was conducted to identify randomized controlled clinical trials, prospective and retrospective studies with a mean follow-up time of at least 3 years. Patients had to have been examined clinically at the follow-up visit. Failure and complication rates were analyzed using robust Poisson regression, and comparisons were made with multivariable Poisson regression models. RESULTS: The search provided 1511 titles and 177 abstracts. Full-text analysis was performed for 147 articles resulting in 60 studies meeting the inclusion criteria. Meta-analysis of these studies indicated an estimated 5-year survival rate of 97.6% for SCs and 97.0% for FDPs supported by implants with internal implant-abutment connection and 95.7% for SCs and 95.8% for FDPs supported by implants with external connection. The 5-year abutment failure rate ranged from 0.7% to 2.8% for different connections with no differences between the types of connections. The total number of complications was similar between the two connections, yet, at external connections, abutment or occlusal screw loosening was more predominant. Ceramic abutments, both internally and externally connected, demonstrated a significantly higher incidence of abutment fractures compared with metal abutments. CONCLUSION: For implant-supported SCs, both metal and ceramic abutments with internal and external connections exhibited high survival rates. Moreover, implant-supported FDPs with metal abutments with internal and external connections for also showed high survival rates.

Ion release in ceramic bearings for total hip replacement: Results from an in vitro and an in vivo study.

INTRODUCTION: Literature on the potential release of trace elements following implantation of Zirconia-platelet toughened alumina (ZPTA) ceramic components is scant. The present study therefore analysed the in vitro and in vivo potential release of ions from ZPTA bearings. MATERIAL AND METHODS: An in vitro and in vivo study was conducted. The in vitro study compared leaching in bovine serum from two groups: ZPTA ceramic heads and Co-28Cr-6Mo alloy heads, both 28-mm diameter. A third group without implant served as reference group. An in vivo clinical study compared trace elements in the whole blood of patients with 36-mm diameter ZPTA ceramic-on-ceramic articulation after three and 12 months. A cohort of subjects without any prosthesis was used as control group. The release of ions was determined by high resolution-inductively coupled plasma-mass spectrometry. RESULTS: In the in vitro experiment, significant differences (p ≤ 0.01) in trace element release for chromium, cobalt and molybdenum were found, with increased levels of ion release in the Co-28Cr-6Mo metal group. The very low detection limit for yttrium allowed detection of a small yttrium release from the ZPTA heads, which was not confirmed by the in vivo study. No significant difference between the groups was found for strontium, aluminium, and zirconium. In the in vivo study, no relevant differences in ion levels between the reference group without any implant and the study group were found at the three and 12-month follow-up. CONCLUSION: This study supports that ZPTA ceramic articulation components are safe in terms of ion release, and may be an excellent alternative to bearings based on Co-28Cr-6Mo alloys.

Higher prevalence of periprosthetic fractures with ceramic on polyethylene hip bearing compared with ceramic on ceramic on the contralateral side: a forty year experience with hip osteonecrosis.

PURPOSE: It is unclear whether late THA periprosthetic femoral fractures are related to a mechanical mechanism that decreases strength of the femur (for example, loosening) or to a biological problem as osteolysis. It is also unknown if ceramic on ceramic bearing couples decrease the risk of late periprosthetic fractures as a result of the absence of wear and osteolysis. MATERIAL AND METHODS: We therefore asked whether the cumulative long-term fractures were different according to the couple of friction ceramic on ceramic or ceramic on polyethylene in 327 patients (654 hips) with bilateral THA (one ceramic-ceramic, and the contralateral ceramic-polyethylene) who had THA with cemented stems performed between from 1978 to 2000 for osteonecrosis. RESULTS: There were two intra-operative fractures (0.3%). The median follow-up was 22 years (range, 15-40 years), and at the most recent follow-up, the cumulative number of late (after 7 years of follow-up) post-operative fractures was 32 (5% of 654 hips). Fractures were unilateral, which means for the 327 patients, a 10% rate of fractures. Periprosthetic fractures increased in number with follow-up: seven fractures (1% of 654 hips) occurred within ten years of THA implantation, 20 (3%) within 20 years, 26 (4%) within 30 years, and 32 (5%) within 40 years. The risk of fracture was influenced (p < 0.001) by the bearing surfaces at the time of prosthetic implantation, low (0.3%) for ceramic on ceramic (1/32 fractures; 1/327 hips), high (10%) for ceramic on PE (31/32 fractures; 31/327 hips). CONCLUSION: In summary, when the contralateral hip of the same patient is the control, after 40 years of follow-up, post-operative fractures occur 30 times more often on the side with PE cup than on the side with ceramic/ceramic bearing.

Fatigue failure load of feldspathic ceramic crowns after hydrofluoric acid etching at different concentrations.

STATEMENT OF PROBLEM: Hydrofluoric acid etching modifies the cementation surface of ceramic restorations, which is the same surface where failure is initiated. Information regarding the influence of hydrofluoric acid etching on the cyclic loads to failure of ceramic crowns is lacking. PURPOSE: The purpose of this in vitro study was to evaluate the influence of different hydrofluoric acid concentrations on the fatigue failure loads of feldspathic ceramic crowns. MATERIAL AND METHODS: Eighty feldspathic ceramic crowns were cemented with resin cement to identical simplified complete crown preparations machined in a dentin-like polymer. The preparations were etched with 10% hydrofluoric acid for 60 seconds and received a primer coating. Before cementation, the intaglio of the ceramic crowns was treated with 1 of 4 surface conditionings (n=20): nonconditioned (control, CTRL), or etched for 60 seconds with different hydrofluoric acid concentrations: 1% (HF1), 5% (HF5), and 10% (HF10). A silane coupling agent was applied on this surface of all crowns, which were cemented to the preparations. Each crown was cyclically loaded in water with a G10 epoxy-glass piston positioned in the center of the occlusal surface. Fatigue failure loads of ceramic crowns were obtained by the staircase approach after 500000 cycles at 20 Hz. Mean failure loads were analyzed by 1-way ANOVA and the Tukey test (α=.05). RESULTS: Mean failure loads of groups CTRL (245.0 ±15.1 N), HF1 (242.5 ±24.7 N), and HF10 (255.7 ±53.8 N) were statistically similar (P>.05), while that of the HF5 group (216.7 ±22.5 N) was significantly lower (P<.05). CONCLUSIONS: HF5 acid had a negative effect on the fatigue loads of the tested feldspathic ceramic crowns, while HF1 and HF10 acids did not change the fatigue resistance.

Enamel wear by antagonistic restorative materials under erosive conditions.

OBJECTIVES: This study aimed to analyse loss of enamel worn against composite, leucite glass ceramic or enamel antagonists under non-erosive and alternating or simultanuous erosive-attritive conditions. MATERIALS AND METHODS: Flat human enamel specimens were loaded (1 Hz, 300 g loading weight, each subgroup n = 12) with antagonists made from a hybrid-composite (Z250, 3 M Espe), a nano-composite (Filtek Supreme XTE, 3 M Espe), leucite glass ceramic (IPS Empress CAD LT, Ivoclar Vivadent) or enamel. Specimens were either submitted to mechanical loading in mineral solution (60 s) or to loading under alternating or simultaneous erosive conditions. For alternating erosion-attrition, specimens were eroded by citric acid (pH 2.6, 60 s) and then loaded with the respective antagonist for 60s. For simultaneous erosion-attrition, specimens were loaded with the respective antagonist while being immersed in citric acid (pH 2.6, 60 s). After each cycle, specimens were stored in water for 1 h. After 18 cycles, enamel loss was calculated profilometrically and statistically analysed by two-way ANOVA and Tukey's post-hoc tests (p < 0.05). RESULTS: Enamel loss (µm, mean ± standard deviation) was significantly highest for simultaneous erosion-attrition (ceramic 9.4 ± 1.1, hybrid-composite 8.3 ± 0.7, nano-composite 7.8 ± 1.2, enamel 7.4 ± 0.8) followed by alternating erosion-attrition (ceramic 3.5 ± 0.5, hybrid-composite 2.1 ± 0.8, nano-composite 1.0 ± 0.2, enamel 2.5 ± 0.7) and attrition in mineral solution (ceramic 0.5 ± 0.3, hybrid composite 0.3 ± 0.1, nano composite 0.1 ± 0.2, enamel 0.1 ± 0.1). Ceramic antagonists resulted in significantly higher loss than the remaining antagonistic materials when alternating or simultaneous erosion-attrition was performed. CONCLUSION: Erosive conditions had a massive impact on enamel worn against different antagonistic materials, with simultaneous erosive-attritive conditions being more detrimental than alternating erosive-attritive conditions. CLINICAL RELEVANCE: Enamel wear by antagonistic restorative materials is significantly influenced by erosive conditions.

Retrieval analysis of ceramic-coated metal-on-polyethylene total hip replacements.

PURPOSE: Ceramic coatings have been used in metal-on-polyethylene (MOP) hips to reduce the risk of wear and also infection; the clinical efficacy of this remains unclear. This retrieval study sought to better understand the performance of coated bearing surfaces. METHODS: Forty-three coated MOP components were analysed post-retrieval for evidence of coating loss and gross polyethylene wear. Coating loss was graded using a visual semi-quantitative protocol. Evidence of gross polyethylene wear was determined by radiographic analysis and visual inspection of the retrieved implants. RESULTS: All components with gross polyethylene wear (n = 10) were revised due to a malfunctioning acetabular component; 35 % (n = 15) of implants exhibited visible coating loss and the incidence of polyethylene wear in samples with coating loss was 54 %, significantly (p = 0.02) elevated compared to samples with intact coatings (14 %). CONCLUSIONS: In this study we found evidence of coating loss on metal femoral heads which was associated with increased wear of the corresponding polyethylene acetabular cups.

Quantitative analysis of enamel on debonded orthodontic brackets.

INTRODUCTION: Iatrogenic damage to the tooth surface in the form of enamel tearouts can occur during removal of fixed orthodontic appliances. The aim of this study was to assess debonded metal and ceramic brackets attached with a variety of bonding materials to determine how frequently this type of damage occurs. METHODS: Eighty-one patients close to finishing fixed orthodontic treatment were recruited. They had metal brackets bonded with composite resin and a 2-step etch-and-bond technique or ceramic brackets bonded with composite resin and a 2-step etch-and- bond technique, and composite resin with a self-etching primer or resin-modified glass ionomer cement. Debonded brackets were examined by backscattered scanning electron microscopy with energy dispersive x-ray spectroscopy to determine the presence and area of enamel on the base pad. RESULTS: Of the 486 brackets collected, 26.1% exhibited enamel on the bonding material on the bracket base pad. The incidences of enamel tearouts for each group were metal brackets, 13.3%; ceramic brackets, 30.2%; composite resin with self-etching primer, 38.2%; and resin-modified glass ionomer cement, 21.2%. The percentage of the bracket base pad covered in enamel was highly variable, ranging from 0% to 46.1%. CONCLUSIONS: Enamel damage regularly occurred during the debonding process with the degree of damage being highly variable. Damage occurred more frequently when ceramic brackets were used (31.9%) compared with metal brackets (13.3%). Removal of ceramic brackets bonded with resin-modified glass ionomer cement resulted in less damage compared with the resin bonding systems.

Comparison of Hypersensitivity in Metal Ceramic Crowns cemented with Zinc Phosphate and Self-adhesive Resin: A Prospective Study.

BACKGROUND: Luting agents used to fix artificial prostheses, such as fixed partial denture (FPD) to tooth are basically viscous in nature and show chemical reaction for fixation. Postcementation hypersensitivity is a frequent complaint of patients. The present study was conducted to compare postcementation hypersensitivity with zinc phosphate and self-adhesive resin in complete coverage crown. MATERIALS AND METHODS: This study included 30 patients in which 60 porcelein fused to metal crowns was placed. Two metal crowns were placed in each patient in nonantagonis-tic contralateral quadrants. First crown was cemented with zinc phosphate cement, while the other was cemented with self-adhesive resin. Hypersensitivity was evaluated by visual analog scale (VAS) score and by clinical test. For clinical evaluation of sensitivity, hot and cold water was applied to the cervical margin of restoration for 5 seconds and response was recorded. RESULTS: This study consisted of 30 patients in which 60 crowns were given. There was no statistical difference in VAS score of mastication in zinc phosphate cement recorded at baseline, 1 week, 4 weeks, 6 months, 1 year, and 2 years (p > 0.05). Cold response also did not show a significant difference at six time points. Warm response showed slight decrease in subsequent time points but was nonsignificant (p > 0.05). Similarly, with self-adhesive resin cement, VAS score during mastication, hot and cold response was statistically nonsignificant (p > 0.05). CONCLUSION: Postcementation hypersensitivity is a frequent complaint that patient may experience. However, we found no statistically significant difference in both cements tested. CLINICAL SIGNIFICANCE: Postcementation hypersensitivity is an unpleasant sensation experienced by patients. This may affect the success of any prosthesis. Thus, selection of luting agent for cementation plays an important role to eliminate this symptom.

Periprosthetic Joint Infection in Hip Arthroplasty: Is There an Association Between Infection and Bearing Surface Type?

BACKGROUND: Preliminary studies have raised the question of whether certain prosthetic biomaterials used in total hip arthroplasty (THA) bearings are associated with increased risk of periprosthetic joint infection (PJI). For example, some observational data suggest the risk of PJI is higher with metal-on-metal bearings. However, it is not known whether other bearings-including ceramic bearings or metal-on-polyethylene bearings-may be associated with a higher or lower risk of PJI. QUESTIONS/PURPOSES: The objective of this study was to use a national arthroplasty registry to assess whether the choice of bearings-metal-on-polyethylene (MoP), ceramic-on-polyethylene (CoP), ceramic-on-ceramic (CoC), or metal-on-metal (MoM)-is associated with differences in the risk of revision for deep infection, either (1) within 6 months or (2) over the entire period of observation, which spanned 15 years. METHODS: Data from primary THAs were extracted from the New Zealand Joint Registry over a 15-year period. A total of 97,889 hips were available for analysis. Inclusion criterion was degenerative joint disease; exclusion criteria were previous surgery, trauma, and any other diagnosis (12,566 hips). We also excluded a small group of ceramic-on-metal THAs (429) with short followup. The median observation period of the selected group of hips (84,894) was 9 years (range, 1-15 years). The mean age of patients was 68 years (SD ± 11 years), and 52% were women. There were 54,409 (64%) MoP, 16,503 (19%) CoP, 9051 (11%) CoC, and 4931 (6%) MoM hip arthroplasties. Four hundred one hips were revised for deep infection. A multivariate assessment was carried out including the following risks factors available for analysis: age, sex, operating room type, use of body exhaust suits, THA fixation mode, and surgeon volume. Because of late introduction of data collection in the Registry, we were unable to include body mass index (BMI, recording started 2010) and medical comorbidities according to the American Society of Anesthesiologists class (ASA, recording started 2005) in the multivariate analysis. RESULTS: The rate of early PJI (< 6 months) did not differ by bearing surface. In contrast, we observed a difference over the total observation period. Within the first 6 months after the index surgery, CoC THAs were not associated with a lower risk of revision for PJI (p = 0.118) when compared with CoP (hazard ratio [HR], 1.31; 95% confidence interval [CI], 0.50-3.41), MoP (HR, 2.10; CI, 0.91-4.82), and MoM (HR, 2.04; CI, 0.69-6.09). When the whole observation period was considered, CoC hips were associated with a lower risk of revision for deep infection when compared with CoP (HR, 1.30; CI, 0.78-2.18; p = 0.01), MoP (HR, 1.75; CI, 1.07-2.86; p = 0.02), and MoM (HR, 2.12; CI, 1.23-3.65; p = 0.008). CONCLUSIONS: Our finding associating CoC THA bearings with a lower risk of infection after THA must be considered very preliminary, and we caution readers against attributing all of the observed difference to the bearing surface. It is possible that some or all of the observed difference associated with bearing type may have been driven by other factors such as ASA and BMI, which could not be included in our multivariate analysis, and so future registry studies on this topic must assess those variables carefully. LEVEL OF EVIDENCE: Level III, therapeutic study.