Polymethylmethacrylate Group Research Articles

N-acetyl-L-cysteine Inhibits Wear Particle-Induced Prosthesis Loosening

To study whether N-acetyl-L-cysteine (NAC) has beneficial effects on wear particle-induced osteoclastogenesis and osteolysis. In vitro, cells were cultured for 5 d and were then exposed to polymethylmethacrylate (PMMA) particles or were pretreated with NAC 1 h prior to stimulation with optimal PMMA particles. After 48 h, the number of osteoclasts was determined by tartrate-resistant acid phosphatase (TRAP) staining. In vivo, a murine calvarial model of PMMA particle-induced osteolysis, was used. PMMA particles were implanted on the calvariae of C57BL/J6 mice, and NAC (10 and 50 mg/kg) was given intraperitoneally every day. Two weeks later, the calvariae were removed and processed for micro-CT and histomorphometry analysis. TRAP staining showed that the osteoclastogenic response was dose-dependent with PMMA particles. Compared with the PBS group, the PMMA group showed a significant decrease in bone mineral density (BMD), bone volume fraction (BVF), cortical mean thickness (CMT), and cortical area/total area (Ct) (P< 0.05). Treatment with NAC (10 and 50 mg/kg) attenuated the PMMA particle-induced decrease in BMD, BVF, CMT, and Ct (P < 0.05 versus PMMA group). NAC inhibited the osteoclastogenesis and osteolysis that is caused by wear particles. The TRAP (+) osteoclast number and the osteolysis area in PBS, PMMA, NAC (10 mg/kg), and NAC (50 mg/kg) were 6.0 ± 0.6, 22.5 ± 1.2, 15.8 ± 0.7, 8.7 ± 1.0 and 0.075 ± 0.011, 0.340 ± 0.014, 0.231 ± 0.018, 0.142 ± 0.026 mm(2), respectively (P< 0.05). Our in vitro and in vivo work shows that NAC may effectively inhibit osteoclastogenesis and may suppress wear particle-induced osteolysis, indicating that NAC may be useful in the prevention or treatment of wear particle-induced prosthesis loosening.

The short-term effects of PMMA and RGP contact lens wear on keratometric behaviour: a pilot study*

This article represents the preliminary findings of a larger study that included 24 subjects that were equally divided into three groups, namely, the PMMA (polymethyl methacrylate) group, the RGP(rigid gas permeable) group and the control group. The aim of this study was to establish the short term effects (if any) of PMMA and RGP contact lens wear on keratometric behaviour. A controlsubject was also included in the study to establish a reference fornormal diurnal changes in keratometric behaviour. Fifty successive auto-keratometric measurements were taken before and immediately after three hours of rigid contact lens wear for the first subject in the PMMA group and the first subject in the RGP group (experimental samples). Fifty successive auto-keratometric measurements were also taken on the first subject of the control group before and immediately after three hours of no lens wear (control sample). Data collected were analysed using multivariate statistical methods that in the past have been used infrequently in this area of study. This investigation revealed that, at least in these two randomly selected subjects, rigid contact lens wear appears to influence keratometric behaviour (PMMA contact lenses more so than RGP contact lenses). (S Afr Optom 2010 69(4) 173-181)

The degradation of bioactive bone cement for vertebroplasty and kyphoplasty in vivo

Objective To observe the degradation of calcium phosphate cements (CPC) and calcium sulfate cement (CSC) in vertebras, and explore the ideal filler for vertebroplasty and kyphoplasty.Methods Bone voids were created in L2-L5 vertebras of 24 female mature sheep. CPC, CSC and polymethylmethacrylate (PMMA) were injected into one bone void randomly, and the remaining voids served as the blank control, and L6 vertebra served as the normal control. Eight sheep were sacrificed at the 2nd,12th and 24th week after operation randomly. Gross observation, biomechanical test and undecalcified bone histology analyses were performed. Results Biomechanical analysis showed that the vertebras could be augmented by CPC and CSC. The mechanical properties of CSC group were decreased from the 2nd to 12th week, and increased from the 12th to 24th week after operation. The mechanical properties of CPC group were increased from the 2nd to 24th week, however, but lower than PMMA group. Histology analysis revealed CSC was mostly absorbed at the 12th week, and the bone voids were repaired only in large part at the 24th week. CPC was absorbed partly at the 24th week, and new bone was formed in contact with the surface of the CPC. Conclusion The vertebras can be augmented instantly by CPC and CSC. As time went on, CSC was absorbed fast and CPC was absorbed very slowly. Key words: Calcium phosphate cement; Polymethylmethacrylate; Vertebroplasty

The degradation of bioactive bone cement for vertebroplasty and kyphoplasty in vivo

Objective To observe the degradation of calcium phosphate cements (CPC) and calcium sulfate cement (CSC) in vertebras, and explore the ideal filler for vertebroplasty and kyphoplasty.Methods Bone voids were created in L2-L5 vertebras of 24 female mature sheep. CPC, CSC and polymethylmethacrylate (PMMA) were injected into one bone void randomly, and the remaining voids served as the blank control, and L6 vertebra served as the normal control. Eight sheep were sacrificed at the 2nd,12th and 24th week after operation randomly. Gross observation, biomechanical test and undecalcified bone histology analyses were performed. Results Biomechanical analysis showed that the vertebras could be augmented by CPC and CSC. The mechanical properties of CSC group were decreased from the 2nd to 12th week, and increased from the 12th to 24th week after operation. The mechanical properties of CPC group were increased from the 2nd to 24th week, however, but lower than PMMA group. Histology analysis revealed CSC was mostly absorbed at the 12th week, and the bone voids were repaired only in large part at the 24th week. CPC was absorbed partly at the 24th week, and new bone was formed in contact with the surface of the CPC. Conclusion The vertebras can be augmented instantly by CPC and CSC. As time went on, CSC was absorbed fast and CPC was absorbed very slowly. Key words: Calcium phosphate cement; Polymethylmethacrylate; Vertebroplasty

A Prospective, Randomized Clinical Trial Comparing an Antibiotic-Impregnated Bioabsorbable Bone Substitute With Standard Antibiotic-Impregnated Cement Beads in the Treatment of Chronic Osteomyelitis and Infected Nonunion

We sought to compare the effectiveness of an antibiotic-impregnated bioabsorbable bone substitute (BBS, tobramycin-impregnated medical-grade calcium sulfate) with antibiotic-impregnated polymethylmethacrylate (PMMA) cement beads after surgical débridement in patients with chronic nonhematogenous osteomyelitis and/or infected nonunion. A prospective, randomized clinical trial. A university-affiliated teaching hospital. Thirty patients requiring surgical treatment for chronic long bone infection or infected nonunion were included: BBS (15 patients, mean age 44.1 years) PMMA (15 patients, mean age 45.6 years). Patients were randomized to receive either BBS or PMMA to the bone void created by surgical débridement. Eradication of infection, new bone growth, rate of union, repeat operative procedures complications. Patients were followed for a mean 38 months (range, 24-60 months). One patient was lost to follow-up in each group. In the BBS group, infection was eradicated in 86% (12 of 14) of patients. Seven of eight patients achieved union of their nonunion, and five patients underwent seven further surgical procedures. In the PMMA group, infection was eradicated in 86% (12 of 14) of patients. Six of eight patients achieved union of their nonunion, and nine patients required 15 further surgical procedures. There were more reoperations in the PMMA group (15 versus seven, P = 0.04), and these procedures tended to be of greater magnitude. The results of this preliminary study suggest that, in the treatment of chronic osteomyelitis and infected nonunion, the use of an antibiotic-impregnated BBS is equivalent to standard surgical therapy in eradicating infection and that it may reduce the number of subsequent surgical procedures. A larger, definitive study on this topic is required.

Implant and Prosthesis Movement after Enucleation: A Randomized Controlled Trial

To evaluate implant and prosthesis movement after myoconjunctival enucleation and subsequent polymethyl methacrylate (PMMA) implantation, compared with the traditional enucleation with muscle imbrication using a PMMA implant and with enucleation accompanied by porous polyethylene implantation. Randomized, controlled, observer-masked, interventional study. One hundred fifty patients, equally and randomly allocated to the 3 groups. Group 1 consisted of patients in whom a PMMA implant was used after enucleation with muscle imbrication (traditional PMMA group). Group 2 consisted of patients in whom a PMMA implant was used after enucleation with a myoconjunctival technique (myoconjunctival PMMA group). Group 3 consisted of patients in whom a porous polyethylene implant was used after enucleation by the scleral cap technique (porous polyethylene group). Fifty patients were included in each group. Patients were allocated to 1 of the 3 groups using stratified randomization. Informed consent was obtained. Acrylic prostheses custom made by a trained ocularist were fitted 6 weeks after surgery in all patients. A masked observer measured implant and prosthesis movement 6 weeks after surgery using a slit-lamp device with real-time video and still photographic documentation. Analysis of implant and prosthesis movement was carried out using the Mann-Whitney U test, and a P value of < or =0.03 was considered significant. Complications including implant displacement and exposure also were noted. Implant and prosthesis movement. Myoconjunctival PMMA implant movement was better than the traditional PMMA implant (P = 0.001), but was similar to that of the porous polyethylene implant. Prosthesis movement with the myoconjunctival PMMA implant was better than that of either the traditional PMMA (P = 0.001) or porous polyethylene (P = 0.002) implants. Myoconjunctival enucleation technique with a PMMA implant provides statistically and clinically significantly better implant and prosthesis movement than the traditional PMMA implant and better prosthesis movement than the porous polyethylene implant.

Effect of blockade of calcineurin/nuclear factor of activated T cells paths by VIVIT peptide on inhibition of osteoprogenitor differentiation by polymethylmethacrylate particles

Objective To investigate the effect of blockade of calcineurin/nuclear factor of activated T cells (Cn/NFAT) paths by Valine Isoleucine Valine Isoleucine Threonine (VIVIT) peptide on the inhibition of osteoprogenitor differentiation by polymethylmethacrylate (PMMA) particles. Methods The rat calvaria (RC) cells were isolated and cultured in vitro in four groups: 1) supplemented with neither PMMA particles nor 11R-VIVIT peptide (control); 2) supplemented with PMMA particles only (PMMA); 3) supplemented with both PMMA particles and 11R-VIVIT peptide (PMMA/VIVIT); and 4) supplemented with 11R-VIVIT peptide only (VIVIT) . 3-(4, 5-dimethyhhiazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT) test was conducted at 2, 4, 7, 14 days to assess the proliferation ofosteoblasts. The alkaline phosphatase (ALP) activity was measured at days 7 and 14 and alizarin red staining was performed at day 14 to assess the differentiation and mineralization of RC cells respectively. The mRNA expressions of ALP osteocalcin (OC), collagen Ⅰ (Col Ⅰ), fos related antigen-2 (Fra-2) and NFATc1 extracted from the cells were detected by RT-PCR. The protein expression of NFATc1 in cytosol and nucleus were detected by Western Blot. Results Compared with the control group,the gene and protein expressions of NFATc1 increased while the ALP activity, mineralization and the gene ex-pressions of ALP, OC, Col Ⅰ, Fra-2 decreased significantly in the PMMA group. Compared with the PMMA group,the ALP activity, mineralization and the expressions of osteogenesis related gene increased while the protein ex-pression of NFATc1 in nucleus decreased in PMMA/VIVIT group. However, the cell proliferation showed no significant difference between groups. Conclusions Cn/NFAT paths play a critical role in the inhibition of osteoprogenitor differentiation by PMMA particles. Blockade of Cn/NFAT paths by VIVIT peptide may increase osteoprogenitor differentiation and mineralization inhibited by the PMMA particles. Key words: Osteoblasts; Celldifferentiation; Osteoprogenitor; Peptides; Polymethacrylic acids

Incidence of early-onset glaucoma after infant cataract extraction with and without intraocular lens implantation

Aims:To determine the incidence of glaucoma, with onset within 1 year after the date of cataract surgery (early onset) performed in the first year of life, with or without intraocular...

Nd:YAG laser capsulotomy rates following implantation of square-edged intraocular lenses: polymethyl methacrylate versus silicone versus acrylic

Objective: To study the influence of square-edged intraocular lenses (lOLs) on the development of posterior capsule opacification (PCO) and the requirement for laser capsulotomy. Design: Retrospective study. Participants: Three hundred seventy-seven eyes of 377 patients were included. Methods: All these patients underwent phacoemulsification and implantation of square polymethyl methacrylate (PMMA) (Aurolab), silicone (Tecnis Z9000), acrylic hydrophobic (AcrySof MA60AC and Sensar Optiedge), or acrylic hydrophilic (Akreos Adapt) lOLs with a minimum of 2 years’ follow-up. Only those cases in which Nd:YAG laser capsulotomy had been performed for visually significant PCO were evaluated. Results: Three hundred seventy-seven eyes of 377 patients were included in the study. Follow-up duration ranged from 24 to 54 (mean 40.27, SD 8.42) months. The incidence of PCO requiring Nd:YAG laser capsulotomy was found to be significantly less in the silicone lens group: 1.4% as compared with an incidence of 11.7% in the PMMA lens group (p = 0.018). In the square-edged acrylic group, visually significant PCO requiring Nd:YAG laser capsulotomy was observed in 3.6%, 4.8%, and 6.8% of eyes implanted with AcrySof MA60AC, Sensar Optiedge, and Akreos Adapt lOLs, respectively. In 5 of the 7 eyes (71.4%) exhibiting PCO in the PMMA group, the condition developed within the first 6 months. In the silicone and acrylic group, development of PCO was delayed. Conclusions: The rate of visually significant PCO as well as the need for Nd:YAG laser capsulotomy is influenced by IOL biomaterial in addition to square edge. It is significantly delayed with square-edged foldable acrylic and silicone lOLs compared with square-edged PMMA IOLs.

Biomechanical evaluation of internal fixation augmented with calcium phosphate cement in treatment of proximal humeral fractures

Objective To compare injectable calcium phosphate cement (CPC) and polymethyl-methacrylate (PMMA) in their biomechanical performances in augmenting the fixation for osteoporotic proximal humeral fractures. Methods Forty-two humeral specimens were obtained from aged female corpses soaked in the formaldehyde. They were made models of three-part proximal humeral fracture. The specimens were randomized evenly into CPC group, PMMA group and control group. Biomechanical tests involving compression, stretching and axial pulling-out of cancellous screw were conducted to determine the maxiulum compression load, tensile load and initial loosening load of screw. Results The values of maximum compression load, tensile load and initial loosening load of screw in CPC and PMMA groups were significantly higher than those in control group (P 0.05) . Conclusion Since the biomechanical performances of injectable CPC are similar to those of PMMA, injectable CPC may be used as a fine substitute of PMMA to enhance the in-ternal fixation for osteoporotic proximal humeral fractures. Key words: Calcium phosphate cement (CPC); Osteoporosis; Humeral fracture; Biome-chanics

Augmentation of Pedicle Screw Fixation Strength Using an Injectable Calcium Sulfate Cement

An in vivo landrace model of cement augmentation of pedicle screw was established, and axial pull-out tests and histological analysis were performed. To investigate the long-term in vivo biomechanical performance of pedicle screws augmented with calcium sulfate cement. Little information is available on the long-term biomechanical performance of pedicle screws augmented with calcium sulfate cement in vivo. Ten pedicle screws were implanted into the lumbar vertebrae of 15 adult females landraces weighing 105 to 115 kg. The pedicle screws were augmented with Polymethyl methacrylate (PMMA), augmented with the calcium sulfate cement, or not augmented. The landraces were randomized into 3 study periods of day 1, 6 weeks, and 12 weeks. At the end of the assigned study periods, the animals were killed and axial pull-out tests and histological analyses were conducted on the isolated specimen vertebrae. No significant difference was found among the 1-day, 6-week,and 12-week control group (P > 0.18), no significant difference was found among the 1-day, 6-week and 12-week PMMA group (P > 0.59), and no significant difference was found among the 1-day, 6-week and 12-week calcium sulfate group (P > 0.27). The maximum POS of the PMMA groups was significantly greater than that of the calcium sulfate groups (P < 0.002), the maximum POS of the calcium sulfate groups was significantly greater than that of the control groups (P < 0.004). Histologically progressive absorption of the calcium sulfate was evident. The bone walls around the screws in the 12-week calcium sulfate group were statistically significantly thicker than that of the 12-week control group and that of the 12-week PMMA group. Results of this study demonstrate that the injectable calcium sulfate cement can significantly improve the immediate POS of pedicle screw fixation, and this effect can be maintained even if the calcium sulfate cement has been absorbed completely, which may result from that the calcium sulfate cement resorption paralleled bone ingrowth.

A Novel Technique of Intra-Spinous Process Injection of PMMA to Augment the Strength of an Inter-Spinous Process Device Such as the X STOP

Biomechanical. To determine if cement injection into the spinous process will improve compression strength. The X STOP (St. Francis Medical Technologies) has been shown to be a safe and effective means for decompressing 1- or 2-level lumbar spinal stenosis (LSS). The X STOP is indicated for LSS patients with osteoporosis, but contraindicated for patients with severe osteoporosis. In an attempt to address these LSS patients with demonstrably weaker bone, a technique to strengthen the spinous process with polymethylmethacrylate (PMMA) injection is presented. Nine pairs of adjacent fresh frozen cadaveric lumbar vertebrae were DEXA scanned before testing. They were randomly assigned to the PMMA group and a control group. Nine of the specimens were injected with PMMA. Each spinous process was then compressed between 2 X STOPs. The testing model was designed to simulate the loading of a 2-level X STOP placement. The mean load to failure and stiffness values of the treated and untreated groups were calculated. The specimens were inspected carefully for PMMA infiltration and extrusion. The mean bone mineral density (BMD) values of the control and PMMA treatment groups were 0.99 +/- 0.13 g/cm and 0.98 +/- 0.10 g/cm, respectively; P > 0.616. The mean volume of cement injected was 2.2 +/- 0.3 cc. The mean failure load values of the control and PMMA treatment groups were 1250 +/- 627 N and 2386 +/- 1034 N, respectively; P < 0.001. The mean stiffness values of the control and PMMA treatment groups were 296 +/- 139 N/mm and 381 +/- 131 N/mm, respectively; P > 0.059. Most specimens had flow of the cement into the laminae and some into the facet and pedicle. No PMMA was found within the spinal canal. This first reported technique of posterior element vertebroplasty may increase the indications and success for patients with decreased BMD who seek an interspinous implant such as the X STOP. A possible role may exist in increasing the effectiveness of such devices. However, clinical trials have yet been performed. These results demonstrate that PMMA injection in the spinous processes is effective in increasing resistance to compressive forces in an X STOP model.

Comparison of PMMA, silicone and acrylic intraocular lenses in combined phacoemulsification and trabeculectomy

目的 比较青光眼白内障联合术中植入不同材料人工晶状体(IOL)的临床效果.方法 回顾性分析行青光眼白内障联合术70例(76眼),其中植入PMMA IOL 30例(36眼),硅胶IOL 23例(23眼),丙烯酸酯折叠IOL 17例(17眼).对治疗效果进行评价,平均随访期限为10.5月.结果 3组间术后眼压和最佳矫正视力差异无统计学意义.前房纤维素样渗出物和IOL表面沉积物发生率,硅胶组高于PMMA组和丙烯酸酯组,但差异无统计学意义.后发障发生率,丙烯酸酯组和硅胶组显著低于PMMA组,差异有统计学意义.结论 行青光眼白内障联合术植入PMMA,硅胶与丙烯酸酯IOL在降眼压和提高视力方面具有相似的效果.但硅胶IOL的前房纤维素样渗出物及IOL表面沉积物发生率高于PMMA和丙烯酸酯IOL.丙烯酸酯和硅胶IOL的后发障发生率低于PMMA IOL。

Effect of hydroxyapatite coating and polymethylmethacrylate on stainless steel implant‐site infection with Staphylococcus epidermidis in a sheep model

We aimed to study the influence of hydroxyapatite (HA) coating and polymethylmethacrylate (PMMA) cement on the risk of development of stainless steel implant-site infection with Staphylococcus epidermidis in a sheep model. Uncoated, HA-coated, and PMMA-cemented stainless steel implants were inserted in the left femur of 30 sheep. For each type of implant, sheep were inoculated with S. epidermidis in the intramedullary canal and one non-inoculated group was used as control. After 6 weeks, infection was evaluated using clinical, radiological, bacteriological, and histological criteria. Radiological and clinical results were normal. Cultures were negative in the control sheep. In the inoculated sheep, interposition tissue and bone cultures were positive in 2 of 6 uncoated, 6 of 6 HA, and 6 of 6 PMMA implants with a mean bacteria count of 5.2 +/- 1.17, 3.5 +/- 0.7, and 3.9 +/- 0.9 log10 cfu/g, respectively (NS), for interposition tissue, and 4 +/- 0.01, 2.9 +/- 0.6, and 2.5 +/- 1.3 log10 cfu/g, respectively (NS) for bone. The polymorphonuclear leukocyte (PMN) score (mean number of PMN per 10 different microscopic high-power fields >or=5) in interposition tissue was >or=3 in 6 of 6 HA, significantly different from uncoated (3 of 6) and PMMA (2 of 6) groups (p = 0.04). The HA and PMMA inoculated groups had a higher infection rate than the uncoated inoculated group (p = 0.06). In this experimental sheep model of S. epidermidis infection at the bone-biomaterial interface, HA seems to be at higher risk of infection compared with uncoated or PMMA-cemented stainless steel, when inoculation is intramedullary and contemporary with implantation.

Vertebroplasty comparing injectable calcium phosphate cement compared with polymethylmethacrylate in a unique canine vertebral body large defect model

Background context Vertebroplasty was developed to mechanically reinforce weakened vertebral bodies. Polymethylmethacrylate (PMMA) bone cement has been most commonly used but carries risks of thermal injury and respiratory and cardiovascular complications. Calcium phosphate (CaP) offers the potential for biological resorption and replacement with new bone, restoring vertebral body mass and height. Purpose To compare compressive strength, elastic modulus of the adjacent motion segments, and histologic response of vertebral bodies injected with either CaP or PMMA in a canine vertebroplasty model. Study design By using a canine vertebroplasty model, two level vertebroplasties were performed at L1 and L3 and studied for 1 month (n=10) and 6 months (n=10). In each canine, one vertebral defect was randomly injected with either CaP cement (BoneSource; Stryker, Freiberg, Germany) or PMMA. Methods Twenty dogs had an iatrogenically created cavitary lesion at two nonadjacent levels injected with either CaP or PMMA. Canines from each group were tested mechanically (n=5) and histologically (n=5). Histology consisted of axial sections of the L1 and L3 vertebral bodies and high-resolution contact radiographs. Sections from each specimen were embedded in plastic without decalcification to study the bone-cement interface. Bone-cement interfaces were compared for evidence of necrosis, fibrosis, foreign body response, cement resorption, and new bone formation between the PMMA and CaP treatments groups. Mechanical compression testing was performed on specimens from the 1-month (n=5) and 6-month (n=5) time periods. The T13 vertebral body was used as an intact control for the destructive compression testing of L1 and L3. Each vertebral body was compressed to 50% of its original height under displacement control at 15 mm/min to simulate a nontraumatic loading situation. Force and displacement data were recorded in real time. Results Vertebral sites containing PMMA were characterized by a thin fibrous membrane. PMMA was detected within the trabeculae, vascular channels, and the spinal canal. Unlike PMMA, CaP underwent resorption and remodeling with vascular invasion and bone ingrowth. Woven and lamellar bone was found on the CaP cement surface, within the remodeled material, and on the surrounding trabeculae. Vertebral body compression strength testing revealed no significant difference in vertebral body height and compressive strength between PMMA and CaP. There was a trend for CaP-treated vertebrae to increase in compressive strength from 1 month to 6 months, whereas PMMA decreased compressive strength when compared with adjacent nontreated vertebrae. Conclusion For both short and intermediate time periods, the injection of CaP cement can be an effective method to treat large vertebral defects. Early results indicate that CaP remodeling might result in the resorption of the majority of the cement with replacement by lamellar bone.

Effects of porcine small intestinal submucosa on elution characteristics of gentamicin-impregnated plaster of Paris

To evaluate effects of small intestinal submucosa (SIS) on elution properties of plaster of Paris (POP). 27 POP cylinders, 27 POP spheres, and 9 polymethylmethacrylate (PMMA) spheres. Pellets were loaded with gentamicin (50 mg/g) and divided into 7 groups of 9 beads each: PMMA spheres; POP cylinders coated with 0, 4, or 8 layers of SIS; and POP spheres coated with 0, 4, or 8 layers of SIS. Gentamicin concentration was measured 6, 12, 18, 24, 32, 40, and 48 hours and 3, 4, 5, 7, 14, 21, 28, 35, and 42 days after wrapping. Porosity was evaluated via scanning electron microscopy. Curvature factor of elution curves, total amount of drug released (TDR), time required to reach 50% of total release (TDR(t50)), and number of days with concentrations > or = 1 microg/mL were compared among groups. SIS decreased the curvature factor and increased the TDR(t50) and TDR of POP spheres and cylinders. Curvature factor of the PMMA-release curve remained lower than that for any POP group, but all POP groups wrapped in SIS released more gentamicin than PMMA spheres. Gentamicin concentrations remained > or = 1 microg/mL in SIS-wrapped POP and PMMA groups throughout the study. Wrapping POP in SIS minimized the increase in porosity of pellets. Wrapping POP with SIS slows the release and increases the amount of gentamicin leaching from spheres and cylinders. All groups wrapped in SIS maintained antimicrobial concentrations greater than the minimum inhibitory concentration of most pathogens.

NEODYMIUM: YAG;

Objective: To evaluate the incidence of posterior capsule opacificationafter phacoemulsification, between acrylic and polymethylmethacrylate intraocular lenses, by comparing their YAG lasercapsulotomy rates. Design: It was a randomized clinical trial. Place and duration of study: Department ofOphthalmology, Military Hospital Rawalpindi, between March 2002-04. Patients and Methods: One hundred and fivepatients were randomized to receive either a foldable acrylic lens (fifty-two cases), or rigid polymethylmethacrylate lens(fifty-three cases) following phacoemulsification for cataracts. Postoperatively their visual acuities were recorded alongwith the presence of posterior capsular opacification. Laser capsulotomy was performed if the eyes had lost 2 or morelines of visual acuity. Results: The visual acuity loss at six months in the PMMA group was greater than that in theacrylic group (p&lt; 0.001,Chi-square test).65% cases exhibiting PCO in the Polymethylmethacrylate group developedit within the first six months, whereas in the acrylic group the development of posterior capsular opacification was seeneighteen months after surgery in 60% cases. Nd: YAG laser capsulotomy was performed in 28% of cases in the PMMAgroup compared to 6% in the AcrySof group (p &lt; 0.005). Conclusion: Acrylic intraocular lenses is associated with lessincidence of posterior capsular opacification and with a significantly reduced rate of YAG laser capsulotomy comparedwith Polymethylmethacrylate lenses.

PMMA versus Titanium Cage after Anterior Cervical Discectomy - A Prospective Randomized Trial

Nonautologous interbody fusion materials are utilised in increasing numbers after anterior cervical disc surgery to overcome the problem of donor site morbidity of autologous bone grafts. This study investigates the performance of two nonautologous materials, the bone cement Polymethylmethacrylate (PMMA) and titanium cages. This prospective randomised trial, with assessment of the results by an independent observer, evaluates whether a Polymethylmethacrylate (PMMA) spacer or a titanium cage provides a better fusion rate around the implant and a better clinical outcome. Between 2000 and 2002, 115 patients with monoradicular cervical nerve root compression syndrome caused by soft cervical disc herniation were eligible for this study. Myelopathy, excessive osteophyte formation, and adjacent level degeneration were exclusion criteria. A block-restricted randomisation was applied. The 2-year clinical outcome served as the primary endpoint of the study. Clinical outcome was assessed according to the Odom scale by an independent observer at the follow-up examination. Preoperative, postoperative, and follow-up radiographs were taken. The study was completed by 107 patients (53 with PMMA and 54 with titanium cage). No significant difference between the two groups could be established with respect to the clinical outcome. In each group, 26 patients scored excellent. Good results were found in 19 PMMA patients and 16 titanium cage patients; satisfactory results were found in 8 PMMA patients and 9 titanium cage patients; bad results were found in 3 titanium cage patients. In 47 titanium cage cases (87%), fusion occurred radiologically as bony bridging around the implant. The fusion rate was significantly lower (p=0.011) in the PMMA group, with 35 cases (66%) united at follow-up. The radiological result of the titanium cage is superior to that of PMMA with respect to the fusion rate. Although the titanium cage achieves a better fusion rate, there is no difference between titanium cages and PMMA with respect to the clinical outcome.

Kinetics of In Vitro Lysozyme Deposition on Silicone Hydrogel, PMMA, and FDA Groups I, II, and IV Contact Lens Materials

We sought to compare the kinetics of in vitro lysozyme deposition on silicone hydrogel (SH), polymethyl methacrylate (PMMA), and FDA groups I, II, and IV contact lenses. Lenses were incubated in 125I-labeled lysozyme for time periods ranging from 1 hr to 28 days, and radioactive counts were determined. SH lenses and PMMA deposited less lysozyme than conventional hydrogel lenses (p < 0.05). Lysozyme accumulation on group IV lenses reached a maximum on the seventh day and then plateaued, whereas on groups I, II, and SH lenses, deposition continued to increase across all time periods, reiterating that kinetics of lysozyme deposition is highly material dependent.

The sustaining effect of three polymers on the release of chlorhexidine from a controlled release drug device for root canal disinfection

The aim of this in vitro study was to evaluate the suitability of using chitosan, poly (lactide-co-glycolide) (PLGA), and polymethyl methacrylate (PMMA) to control the release of chlorhexidine digluconate (CHX) from a prototype of controlled release drug device for root canal disinfection. Four different prototypes with different formulations were prepared. Group A (n = 12): the device (absorbent paper point) was loaded with CHX as control. Group B (n = 12): same as group A, but the device was coated with chitosan (Texan MedTech). In Groups C and D, the device was treated in the same way as group A and then coated 3 times with 5% PMMA (Group C, n = 12, Aldrich), or coated 3 times with 3% PLGA (Group D, n = 12, Sigma). The devices were randomly allocated to experimental groups of 12 each. All the prototypes of controlled release drug device were soaked in 3 mL distilled water. The concentrations of CHX were determined using a UV spectrophotometer. The surface characteristics of each prototype were observed using a scanning electron microscope. The result showed that release rate of CHX was the greatest in the noncoated group, followed by the chitosan-coated group, the PLGA-coated group, and the PMMA-coated group (P < 0.05). Pores were observed on the surface of the prototypes that were coated with PLGA and PMMA. When the pore size was smaller, the release rate was lower. These data indicate that polymer coating can control the release rate of CHX from the prototypes of controlled release drug device.