Comparison of load bearing capacity of ceramic crowns with zirconia or polyetherketoneketone frameworks.

AIM: The aim of the present study was to compare the load bearing capacity of monolithic or bilayered single crowns with zirconia or polyetherketoneketone frameworks designed and fabricated using CAD/CAM systems. MATERIALS AND METHODS: Cr-Co-based metal dies (n = 60) were duplicated from an extracted and prepared premolar and then restored with different CAD/CAM materials. The specimens were divided into five groups (n = 12) according to the type of materials: group S: monolithic zirconia-reinforced lithium disilicate; group ZI: bilayered zirconia framework with lithium disilicate; group ZE: bilayered zirconia framework with resin-infiltrated hybrid ceramic; group PI: bilayered polyetherketoneketone (PEKK) framework with lithium disilicate; group PE: bilayered PEKK framework with resin-infiltrated hybrid ceramic. The crown specimens were cemented on Cr-Co metal dies with a resin cement (Multilink N). The specimens were subjected to cyclic mechanical loading followed by load bearing testing. Data were analyzed using the Kruskal-Wallis and Mann-Whitney U tests (α = 0.05). RESULTS: The monolithic crowns in group S (1930 ± 452.18 N) presented significantly higher load bearing capacity than those of the other groups (P < 0.05). This was followed by group ZI (1165.41 ± 264.04 N). The remaining groups demonstrated comparable results. Failure types were more frequent in all zirconia specimens that included veneering ceramic. CONCLUSIONS: Monolithic zirconia-reinforced lithium disilicate CAD/CAM ceramics showed superior load bearing capacity compared with all other bilayered counterparts. All CAD/CAM materials tested remarkably exceeded the average occlusal force in the posterior region.

Effects of sintering protocol and dipping time on the optical properties of monolithic zirconia.

STATEMENT OF PROBLEM: The use of monolithic zirconia for restorations has become popular. However, the effects of the coloring process and sintering procedure on the optical properties of monolithic zirconia remain unclear. PURPOSE: The purpose of this in vitro study was to evaluate the effects of the different sintering protocols and dipping times on the CIELab color parameters, color difference (ΔE00), translucency parameter (TP00), opalescence parameter (OP), and contrast ratio (CR) of monolithic zirconia. MATERIAL AND METHODS: One hundred and fifty monolithic zirconia specimens were prepared and divided into 5 groups according to different dipping times in A2 shade coloring liquid: no immersion (D0), 3 minutes (D3), 5 minutes (D5), 7 minutes (D7), and 9 minutes (D9). The specimens were further divided into 3 subgroups according to different sintering protocols (n=10): classic (C); speed (S); and super-speed sintering (SS). The CIE L∗a∗b∗ values, ΔE00, TP00, OP, and CR values were determined with a spectrophotometer. The data were analyzed with 2-way ANOVA and Bonferroni post hoc tests (α=.05). RESULTS: The effects of the sintering protocol, dipping time, and interaction of the sintering protocol and dipping time were significant for the L∗, a∗, b∗, ΔE00, TP00, OP, and CR parameters (P<.001). The ΔE00 values of the SS groups were significantly higher than those of the C and S groups for all the dipping times assessed. However, only the CD3 and CD5 groups had ΔE00 values below the acceptability threshold (<1.8). Coloring significantly reduced TP00 values and significantly increased OP and CR values in the colored groups compared with those in the D0 groups. The C and S protocols for different dipping times showed similar optical properties in TP00, OP, CR, and ΔE00 (excluding the D0 and D9 groups) compared with the SS protocol. CONCLUSIONS: Different sintering protocols combined with various dipping times significantly affected the optical properties of monolithic zirconia. However, C and S sintering with a 3-minute and 5-minute coloring process yielded more favorable optical results than SS sintering and prolonged dipping times.

Evaluation of various denture cleansers on color stability and surface topography of polyetherketoneketone, polyamide, and polymethylmethacrylate.

The aim of this study was to evaluate the effect of sodium perborate effervescent tablets and citric acid solution on the color stability and surface topography of a new generation of high-performance polymer polyetherketoneketone (PEKK), thermoinjection-molded polyamide, and polymethylmethacrylate (PMMA). Fifty disc-shaped specimens were fabricated (10 mm × 2 mm) from PEKK (P group), polyamide (D group), and PMMA (M group). These groups were divided into five subgroups (n = 10) according to the storage media. The test groups were immersed in the following solutions: distilled water (Control), Corega, Protefix, Perlodent, and Curaprox. The color stability values (ΔE) were measured using a spectrophotometer before and after immersion in distilled water and four different denture cleansers for 8 hr/day for 140 days. Topography alterations after treatments were assessed with scanning electron microscopy (SEM). Data were analyzed by one-way analysis of variance (ANOVA) followed by Tukey's Honest Significant Difference test. The p < .05 was considered significant. All denture cleansers increased the ΔE values relative to the baseline values in the M, D, and P groups (p < .05). The Perlodent denture cleanser demonstrated the highest ΔE value in all groups, which was unacceptable. Curaprox denture cleanser showed the lowest ΔE value in the M and D groups (p < .05). Curaprox in all groups showed a ∆E value less than 3.7. For patients who have PEKK- and polyamide-based prosthesis, the use of citric acid-based cleansers may be more recommended than sodium perborate-containing cleansers because of its clinically acceptable color changes on polymers in terms of color stability.

Effect of cleansers on denture base resins' structural properties.

INTRODUCTION:: We assessed the effect of different available denture cleansers on the roughness and hardness of polyetherketoneketone, thermoinjection-molded polyamide, and polymethylmethacrylate. MATERIALS AND METHODS:: A total of 150 disc-shaped specimens were fabricated (10 mm × 2 mm) from these three denture base resins, and divided into five subgroups ( n = 10) according to immersion procedures. One of these groups subjected to distilled water served as control, whereas other groups were subjected to daily cleansing with four denture cleansers (Corega, Protefix, Curaprox, and Perlodent) for 8 h a day for 140 days. The surface roughness and hardness values of specimens were recorded by measuring twice at baseline, and again after application of chemical solutions. Topography alterations after treatments were assessed with scanning electron microscopy. The data were subjected to statistical analysis and comparison among groups was done using Kruskal Wallis and Wilcoxon Signed Ranks tests. P-value <0.05 was considered significant. RESULTS:: The surface roughness of polyetherketoneketone, polymethylmethacrylate, and polyamide dentures was increased significantly by chemical solutions of denture cleansers. While the hardness value of polyetherketoneketone was not affected significantly after immersion in denture cleansers, those of polymethylmethacrylate and polyamide decreased significantly. Compared with Curaprox, the effervescent tablets significantly altered the surface hardness and roughness of polyamide. CONCLUSION:: Denture cleansers can considerably alter the surface roughness and hardness of denture base resins and should be used carefully depending on the material.

Adult case of acrodysostosis with severe neurologic involvement.

OBJECTIVE: Acrodysostosis is a rare syndrome characterized by peripheral dysostosis, nasal hypoplasia and frequently mental retardation. Only one adult case of acrodysostosis has been reported to have neurologic symptoms. We report one further adult case of acrodysostosis with severe neurologic findings including myelopathy and spastic paraparesis due to diffuse spinal stenosis and recurrent deep vein thrombosis possibly caused by neurologic deficits. RESULTS: We report a 43-year-old woman who had back and neck pain with weakness in the extremities of several years. 1~year before admission to our hospital, she had been treated with a missed diagnosis of sero (-) spondyloarthropathy but had not benefited. She became unable to walk, thereafter she underwent decompression surgery with a diagnosis of degenerative spinal stenosis. She presented at our outpatient department complaining of lowback pain and difficulty walking. She had marked facial and peripheral appearance of acrodysostosis. Spinal MRI revealed extensive spinal stenosis. A diagnosis was made through the genetic investigation, clinical and radiological findings. Spastic paraparesis were detected. There was widespread neuropathic pain. 15 days after admission, she developed swelling and redness of the left lower extremity and the venous doppler ultrasonography showed left acute and right past DVT. We treated DVT with anticoagulant therapy. Gabapentin and Baclofen were initiated for neuropathic pain and spasticity. A conventional rehabilitation program was performed. She left walking with a walker without pain and spasticity. CONCLUSIONS: We would like to remind physicians to be aware of peripheral malformations as signs of skeletal dysplasias and to consider acrodysostosis in the differential diagnosis. Although it is a rare condition, if diagnosed early, possible complications can be treated and outcomes may be improved.

Spinal cord injury associated with thoracic osteoporotic fracture.

This report details a case of sudden neurologic deficit attributable to acute thoracic fractures associated with senile osteoporosis. A 73-yr-old female patient with a history of occasional back pain during the past 4 mos had sudden thoracic vertebral fracture with spinal cord injury. The patient, who had a benign past medical history, had not been evaluated for osteoporosis. Thoracic spine radiographs showed a compression fracture at T8. Thoracic magnetic resonance imaging exposed a compression fracture at T7-T8. She was treated operatively. She was found to have spinal cord injury with American Spinal Injury Association classification C (T7), and she had poor sitting balance. She was discharged in a wheelchair and was administered clean intermittent catheterization every 6 hrs. Six months after discharge, she ambulated with a walker and had spontaneous micturition. Vertebral fractures are a common presentation of senile osteoporosis. The risk of neurologic impairment attributable to vertebral fracture is a rare but potentially severe complication. Besides medical therapy and suitable rehabilitation programs, surgical treatment is an integral part of the management of patients with osteoporotic vertebral fractures.