Polytetrafluoroethylene Group Research Articles

Compari̇son of PTFE sutures with polypropylene sutures in suprapopliteal femoropopliteal bypass with PTFE grafts

Aim: Infrainguinal bypass surgery stands as the predominant open surgical procedure for lower limb revascularization and is reserved for cases of intermittent claudication (IC) that have proven unresponsive to maximal medical management. Polypropylene monofilament sutures have been widely used for peripheral vascular surgery operations. Aim of this study is comparing this new type of suture with propylene sutures. Material and Methods: Between January 2022 and December 2022, two cohorts who underwent suprapopliteal femoropopliteal bypass surgery, each comprising 15 patients were included in the study. In Group I (polytetrafluoroethylene (PTFE) Group), PTFE served as the suture material, whereas in Group 2 (Non PTFE Group), polypropylene sutures were employed. All preoperative demographics, perioperative and postoperative data were collected carefully. Results: All patients underwent surgical interventions due to either rest pain or ischemic ulcers. Among the 30 patients, 11 fell into Fontaine class 4, while 19 were categorized as Fontaine class 3. Out of the 30 patients, 18 received cilostazol treatment. The mean age of the patient cohort was 66.97±7.4 years, with a mean body mass index of 29.03±6.2. When we compared the two groups, no statistically significant difference was found between groups according to demographic data. In the evaluation of intraoperative data, the mean operation time was 88.7±9.37 minutes, and the mean hemostasis time was 5.8±2.8 minutes. Group I (PTFE group) exhibited significantly lower hemostasis time and drainage levels on the first and second postoperative days (p<0.0001, p=0.03, and p=0.017, respectively). The use of absorbable hemostats were significantly less in PTFE suture group. Conclusion: The selection of sutures significantly influences the achievement of soft tissue approximation, reduced inflammation, suture hole leakage and capsule formation.

Preload and Removal Torque of Two Different Prosthetic Screw Coatings-A Laboratory Study.

This study aimed to evaluate the effect of two coating materials, a silicone sealing gel and a polytetrafluoroethylene (PTFE) tape, on the screw preload and removal torque value (RTV) to develop strategies to prevent prosthetic screw loosening. We examined 45 complexes comprising an implant, abutment, and prosthetic screw, of which 15 samples were uncoated, 15 were coated with GapSeal® (Hager & Werken GmbH & Co., Duisburg, Germany), and 15 were coated with PTFE tape (MIARCO®, Valencia, Spain). The screws were tightened to register the preload and then untightened to register the RTV. The preload values showed a statistically significant difference only in the PTFE group, suggesting that this lubricant negatively affects the preload. The RTVs showed statistically significant differences among all groups, with the GapSeal® group and PTFE group showing the highest and lowest values, respectively. It can be concluded that the application of the PTFE tape on the screw significantly reduced the preload and RTV. The silicone sealing gel did not affect the preload but increased the RTV. Therefore, the use of GapSeal® should be considered to prevent prosthetic screw loosening, while the use of PTFE tape should be avoided.

Transvaginal Polytetrafluoroethylene Mesh Surgery for Pelvic Organ Prolapse: One-Year Safety and Efficacy Results

ObjectivesTo evaluate the efficacy and safety of the polytetrafluoroethylene (PTFE) mesh by comparing conventionally used polypropylene (PP) mesh in tension-free vaginal mesh (TVM) surgery for pelvic organ prolapse (POP). MethodsWe conducted an observational cohort study of patients who underwent TVM using a PTFE or PP mesh. PTFE was used from June 2019 to May 2021, and PP mesh from January 2018 to May 2019. Outcomes included POP recurrence, perioperative complications, and patient satisfaction. Restricted mean survival time (RMST) was used to analyze POP recurrence, comparing the time to recurrence between the two groups at 1 year after TVM. ResultsOf 171 patients, 104 underwent PP mesh placement (PP group) and 67 underwent PTFE mesh placement (PTFE group). POP recurrence was observed in 10 and nine patients in the PP and PTFE groups, respectively. The mean time until the recurrence in the PTFE group was significantly shorter than that in the PP group (RMST difference: -20.3 days; 95% CI, -40.1 to -0.5; P=0.044). Subgroup analysis revealed the mean time until recurrence was significantly shorter in the PTFE group for postoperative periods 3 months or less, ages >70 yrs, and POP stage ≥3. There were no intervention cases in either group and no significant differences in the perioperative complications. Patient satisfaction was greater in the PTFE group after three months postoperatively. ConclusionTVM surgery with a PTFE mesh is more prone to recurrence than that with a PP mesh, but with higher patient satisfaction. Within three months of surgery, elderly patients and those with advanced stage POP require care to prevent recurrence.

Predictors of amputation-free survival and wound healing after infrainguinal bypass with alternative conduits

ObjectiveInadequate vein quality or prior harvest precludes use of autologous single segment greater saphenous vein (ssGSV) in many patients with chronic limb-threatening ischemia (CLTI). Predictors of patient outcome after infrainguinal bypass with alternative (non-ssGSV) conduits are not well-understood. We explored whether limb presentation, bypass target, and conduit type were associated with amputation-free survival (AFS) after infrainguinal bypass using alternative conduits. MethodsA single-center retrospective study (2013-2020) was conducted of 139 infrainguinal bypasses performed for CLTI with cryopreserved ssGSV (cryovein) (n = 71), polytetrafluoroethylene (PTFE) (n = 23), or arm/spliced vein grafts (n = 45). Characteristics, Wound, Ischemia, and foot Infection (WIfI) stage, and outcomes were recorded. Multivariable Cox proportional hazards and classification and regression tree analysis modeled predictors of AFS. ResultsWithin 139 cases, the mean age was 71 years, 59% of patients were male, and 51% of cases were nonelective. More patients undergoing bypass with cryovein were WIfI stage 4 (41%) compared with PTFE (13%) or arm/spliced vein (27%) (P = .04). Across groups, AFS at 2 years was 78% for spliced/arm, 79% for PTFE, and 53% for cryovein (adjusted hazard ratio for cryovein, 2.5; P = .02). Among cases using cryovein, classification and regression tree analysis showed that WIfI stage 3 or 4, age >70 years, and prior failed bypass were predictive of the lowest AFS at 2 years of 36% vs AFS of 58% to 76% among subgroups with less than two of these factors. Although secondary patency at 2 years was worse in the cryovein group (26% vs 68% and 89% in arm/spliced and PTFE groups; P < .01), in patients with tissue loss there was no statistically significant difference in wound healing in the cryovein group (72%) compared with other bypass types (72% vs 87%, respectively; P = .12). ConclusionsIn patients with CLTI lacking suitable ssGSV, bypass with autogenous arm/spliced vein or PTFE has superior AFS compared with cryovein, although data were limited for PTFE conduits for distal targets. Despite poor patency with cryovein, wound healing is achieved in a majority of cases, although it should be used with caution in older patients with high WIfI stage and prior failed bypass, given the low rates of AFS.

Prevalence of type II endoleak after elective endovascular aneurysm repair with polytetrafluoroethylene- or polyester-based endografts

ObjectiveType II endoleak is the most frequent complication after endovascular abdominal aneurysm repair. Polytetrafluoroethylene and polyester (PE) are the two most commonly used graft materials in endovascular aneurysm repair (EVAR) devices. Biological properties of the material might influence the appearance and persistence of type II endoleak (T2EL). Therefore, the aim of this study was to evaluate potential differences in the prevalence of T2EL after EVAR between polytetrafluoroethylene (PTFE) and PE endografts in patients electively treated for an infrarenal abdominal aortic aneurysm. MethodsA single-center, retrospective, observational study was conducted between January 2011 and January 2022. Preoperative, procedural, and follow-up data were derived from electronic health records. Imaging included computed tomography scans, and/or duplex ultrasound examination. The primary end point was the prevalence of T2EL diagnosed within 1 year after EVAR. Secondary end points included the prevalence of T2EL throughout follow-up, early (≤30 days) and late (>30 days) T2EL, the rate of T2EL disappearance during the follow-up period, the prevalence of type I and III endoleak, and T2EL-related reinterventions. ResultsFollow-up was available for 394 patients, 245 in the PE and 149 in the PTFE group. The prevalence of T2EL diagnosed within 1 year after endovascular repair was 11.8% in the PE group and 21.5% in the PTFE group (P = .010). There was no significant difference in early (≤30 days) and late (>30 days) T2EL between groups (P = .270 and P = .311). There was no difference in the freedom from endoleak type II reinterventions between groups (P = .877). ConclusionsThe prevalence of T2EL after elective EVAR is significantly higher with the use of PTFE-based endografts compared with PE-based endografts. This difference is mostly based on T2EL diagnosed after 30 days of follow-up.

Comparative effectiveness of bovine carotid artery xenograft and polytetrafluoroethylene in hemodialysis access revision.

When hemodialysis arteriovenous accesses fail, autogenous options are often limited. Non-autogenous conduit choices include bovine carotid artery xenografts (BCAG) and expanded polytetrafluoroethylene (PTFE), yet their comparative effectiveness in hemodialysis access revision remains largely unknown. A cohort study was performed from a prospectively collected institutional database from August 2010 to July 2021. All patients undergoing an arteriovenous access revision with either BCAG or PTFE were followed for up to 3 years from their index access revision. Revision was defined as graft placement to address a specific problem of an existing arteriovenous access while maintaining one or more of the key components of the original access (e.g. inflow, outflow, and cannulation zone). Outcomes were measured starting at the date of the index revision procedure. The primary outcome was loss of secondary patency at 3 years. Secondary outcomes included loss of post-intervention primary patency, rates of recurrent interventions, and 30-day complications. Pooled logistic regression was used to estimate inverse probability weighted marginal structural models for the time-to-event outcomes of interest. A total of 159 patients were included in the study, and 58% received access revision with BCAG. Common indications for revision included worn out cannulation zones (32%), thrombosis (18%), outflow augmentation (16%), and inflow augmentation (13%). Estimated risk of secondary patency loss at 3 years was lower in the BCAG group (8.6%, 3.9-15.1) compared to the PTFE group (24.8%, 12.4-38.7). Patients receiving BCAG experienced a 60% decreased relative risk of secondary patency loss at 3 years (risk ratio 0.40, 0.14-0.86). Recurrent interventions occurred at similar rates in the BCAG and PTFE groups, with 1.86 (1.31-2.43) and 1.60 (1.07-2.14) interventions at 1 year, respectively (hazard ratio 1.22, 0.74-1.96). Under the conditions of this contemporary cohort study, use of BCAG in upper extremity hemodialysis access revision decreased access abandonment when compared to PTFE.

A Retrospective Review of Bovine Artery Graft Patency: A Single-Site Study

The hemodialysis-dependent population is increasing in the United States. Dialysis access complications are a significant source of morbidity and mortality for patients with end-stage renal disease. A surgically created autogenous arteriovenous fistula has been the gold standard for dialysis access. However, for patients who are not candidates for arteriovenous fistula, arteriovenous grafts using various conduits have widely been used. In this study, we report the outcomes of bovine carotid artery (BCA) grafts for dialysis access at a single institution and compare these results to those for polytetrafluoroethylene (PTFE) grafts. A single-institution, retrospective review of all patients undergoing surgical placement of a bovine carotid artery graft for dialysis access from 2017-2018 was performed under an institutional review board-approved protocol. The primary, primary-assisted, and secondary patency were calculated for the whole cohort and results determined based on gender, body mass index (BMI), and indication for use. Comparison was performed to PTFE grafts at same institution from 2013 to2016. One hundred and twenty two patients were included in this study. Seventy four patients had a BCA graft placed while 48 had a PTFE graft placed. . The mean age was 59.7±13.5years in the BCA group, 55.8±14.5 in the PTFE group, and the mean BMI was 29.8±9.2kg/m2 in the BCA group and 28.1±9.7 in the PTFE group. Comparison of the comorbidities present in BCA/PTFE groups included hypertension (92%/100%), diabetes (57%/54%), congestive heart failure (28%/10%), lupus (5%/7%), and chronic obstructive pulmonary disease (4%/8%). The various configurations were reviewed (BCA/PTFE): interposition/access salvage (40.5%/13%), axillary-axillary (18.9%, 7%), brachial-basilic (5.4%, 6%), brachial-brachial (4.1%, 4%), brachial-cephalic (1.4%, 0%), axillary-brachial (1.4%, 0%), brachial-axillary (23%, 62%), and femoral-femoral (5.4%, 6%). Overall, 12-month primary patency was 50% in the BCA group and 18% in the PTFE group (P=0.001). Twelve-month primary-assisted patency was 66% in the BCA group and 37% in the PTFE group (P=0.003). Twelve-month secondary patency was 81% in the BCA group and 36% in the PTFE group (P=0.07). When comparing BCA graft survival probability among male and female gender, males had better primary-assisted patency (P=0.042). Secondary patency among the 2 genders was similar. There was no statistically significant difference in primary, primary-assisted, and secondary patency of BCA grafts between different BMI groups and indication for use. The average patency of a bovine graft was 17.8±8months. Sixty one percent of the BCA grafts needed intervention with 24% needing multiple interventions. There was an average of 7±5months to first intervention. The infection rate was 8.1% in the BCA group and 10.4% in the PTFE group with no statistical difference. Primary and primary-assisted patency rates at 12months in our study were higher than those for PTFE at our institution. There was higher primary-assisted patency of BCA grafts among males at 12months compared to PTFE. Obesity and indication for BCA graft use did not appear to affect patency in our population.

Polytetrafluorethylene (PTFE) vs. Polyester (Dacron®) Grafts in Critical Limb Ischemia Salvage.

Critical ischemia of the lower limbs refers to the last stages of peripheral arterial disease. It is characterized by resting discomfort or trophic disorders such as ulceration, skin necrosis, or gangrene in the lower limbs. Critical ischemia corresponds to Leriche-Fontaine (LF) stages III-IV and Rutherford stages 4-6. The purpose of this study was to observe the patency and postoperative complications of patients who have had infra-inguinal surgical revascularization and compare the results based on the kind of graft utilized. The present study was designed as an observational retrospective cohort study, including all patients from 2018 to 2019 diagnosed with severe ischemia of the lower limbs who were hospitalized at the Vascular Surgery Clinic of the County Emergency Clinical Hospital of Targu Mures. Patients with a polytetrafluoroethylene (PTFE) graft had a higher incidence of chronic obstructive pulmonary disease (p = 0.01), stage III LF (70.41% vs. 55.29%), p = 0.03), and a lower incidence of stage IV LF (29.95% vs. 44.71%, p = 0.03). As for complications, the PTFE group showed a lower incidence of bypass thrombosis (29.59% vs. 44.71%; p = 0.03) and graft infection (9.18% vs. 21.18%; p = 0.02), but no statistical significance in the event of bleeding (p = 0.40). Regarding the outcomes, no statistical significance was seen for below-the-knee amputations or death. However, the PTFE group had a lower incidence of above-the-knee amputations (11.22% vs. 24.71%; p = 0.01). At multivariate analysis, the PTFE graft is an independent predictor of primary patency at 6, 12, and 24 months (OR: 2.15, p = 0.02; OR: 1.84, p = 0.04; and OR: 1.89, p = 0.03), as well as a protective factor against bypass thrombosis (OR: 0.52; p = 0.03), graft infection (OR: 0.37; p = 0.02), and above-the-knee amputation (OR: 0.38; p = 0.01).; Conclusions: According to this study's findings, there were minor differences regarding the long-term patency, bypass thrombosis, graft infections, and above-the-knee amputations. In addition, the PTFE graft group had a higher incidence of primary patency at 6, 12, and 24 months, as well as a lower incidence of bypass thrombosis, graft infection, and above-the-knee amputations.

THEORETICAL SUBSTANTIATION OF CAVITATION WEAR INTENSITY REDUCTION OF CYLINDER SLEEVE WALLS BY APPLICATION OF ANTI-CAVITATION COATING

One of the ways to increase service life of internal combustion engines is to reduce cavitation wear intensity of the outer wall of the cylinder sleeves. The most promising, at present, method is application of anti-cavitation coating on the outer surface of the cylinder sleeve. The aim of the research was to establish theoretical dependencies that allow to substantiate the properties and thickness of the anti-cavitation material applied to the outer wall of the cylinder sleeve. Theoretical studies of cavitation wear intensity along the destruction depth of the cylinder sleeve wall established that when choosing cavitation-resistant materials, it is necessary to have regard to material structure and give preference to those materials that are characterized by high resistance to microvolumes of plastic deformation under microshock action and are capable of withstanding operating modes over a wide temperature range. The materials of the polytetrafluoroethylene group - fluoroplasts - most fully meet these requirements. Studies of the fluoroplastic coating applied to the outer wall of the cylinder sleeve, using the obtained theoretical dependencies, showed that the minimum wear rate of the cylinder sleeve of 0.0006 mm3/cycle is achieved with a fluoroplastic coating thickness of the outer surface of the cylinder sleeve with a thickness of 1.8 mm. In this case, the difference in heating of a typical sleeve and a sleeve with a fluoroplastic coating with an increase of the heating temperature of the inner wall of the sleeve decreases from 15% at a temperature of 50 °C to 5.7% at a heating temperature of 150 °C, that is, the application of a fluoroplastic coating on the outer wall of the cylinder sleeve does not lead to a change in the heat stress of the cylinder sleeve and will not affect the heat balance of the internal combustion engine. Thus, the obtained theoretical dependences make it possible to establish and justify not only the properties of the anti-cavitation material, but also the thickness of its application to the outer surface of the cylinder sleeve.

Comparison of autogenous basilic vein, polytetrafluoroethylene and polycarbonate grafts for haemodialysis access

This study aims to present data obtained by comparing the results of three different kinds of arterio-venous fistula (AVF) in hemodialysis patients. One hundred twenty (120) patients were operated with autogenous brachiobasilic (BBF) AVF, upper arm polytetrafluoroethylene (PTFE) or polycarbonate-urethane (PCU) graft AVF in our centre between January 2015 and January 2018. They were enrolled for a retrospective study into three groups; BBF Group (n=54), PTFE Graft Group (n=36), PCU Graft Group (n=30). Their data was analyzed, primary and secondary patency rates, complications and cannulation time were calculated. Primary patency rates of the 1st, 2nd and 3rd years were recorded to be respectively 81.4%, 72.2% and 59.2% in the Autogenous Arteriovenous Fistula (BBF) Group; 61.1%, 55.5% and 44.4% in the PTFE Group and 63.3%, 60% and 46.6% in the PCU Group. Infections occurred in 3.7% of BBF patients, in 8.3% of PTFE patients and 10% of PCU patients. First cannulation times were: 69± 17 (day) in BBF Group, 20 ± 5 (day) in PTFE Group and 10± 3(day) in PCU Group. BBF was observed to perform better than AVG in terms of primary and secondary patency and to result in low infection rates. On the other hand, first cannulation was performed earlier in both graft AVFs. There was no significant difference between PTFE and PCU in terms of our outcomes.

Outcomes of pulmonary valve replacement using a bioprosthetic valve and polytetrafluoroethylene bicuspid valve for pulmonary valve regurgitation after intracardiac repair of tetralogy of Fallot.

Excellent results have been reported regarding pulmonary valve replacement (PVR) for pulmonary valve regurgitation (PR) after intracardiac repair (ICR) in patients with tetralogy of Fallot (TOF). However, there are apparently no reports comparing the following procedures: PVR using a bioprosthetic valve and PVR using a polytetrafluoroethylene (PTFE) bicuspid valve. Herein, we retrospectively analyzed the outcomes of PVR for PR after ICR of TOF in our institution and assessed which of the two PVR procedures was better. From June 2008 to December 2017, we performed PVR for PR after ICR of TOF in 34 patients. Patients with the right ventricle to the pulmonary artery conduits were excluded. Preoperative and postoperative cardiac magnetic resonance imagings (cMRIs) were performed in all patients. The patients were divided into the bioprosthetic valve group (BV group, n = 17) and the PTFE bicuspid valve group (PTFE group, n = 17). There were no significant differences in the preoperative cMRI data and perioperative factors between the two groups. There were no deaths in either group. Postoperative cMRI showed that the PR fraction and the right ventricular end-diastolic volume index (RVEDVI)/left ventricular end-diastolic volume index ratio were significantly improved in both groups. However, RVEDVI was significantly improved only in the BV group. Re-PVR was required in four patients in the PTFE group. PVR using a bioprosthetic valve was more effective for PR treatment after ICR of TOF than PVR using a PTFE bicuspid valve.

Preliminary evaluation of the short-term outcomes of polytetrafluoroethylene mesh for pelvic organ prolapse.

Tension-free vaginal mesh (TVM) surgery using synthetic polypropylene (PP) soft mesh had spread rapidly. However, the frequency of mesh-related postoperative complications had increased, and PP was banned in April 2019. In Japan, however, transvaginal surgery using polytetrafluoroethylene (PTFE) mesh had been approved. In this study, we evaluated the clinical outcome and quality of life (QOL) of the postoperative course using PP mesh and PTFE mesh (named "ORIHIME™" ) in a combination surgery for utero-sacral ligament suspension and anterior vaginal support using anterior TVM. The vaginal hysterectomy and utero-sacral ligament colpopexy augmented by anterior vaginal mesh implants using PP mesh and PTFE mesh were performed on patients with stage III to IV cystocele and uterine prolapse. The clinical outcome and QOL changes in their postoperative course were evaluated by comparing 15 cases of PP mesh and 13 cases of PTFE mesh. There was no difference between the PP group and PTFE group in characteristics. No mesh-related complications occurred during the follow-up period. With regard to the pelvic organ prolapse quantification (POP-Q) score, no significant difference was found between the two groups. Comparing the postoperative QOL of both groups, the PTFE group had significantly higher values in two domains than PP group (SF-12v2 questionnaire). We used the world's first PTFE mesh to compare PP mesh with postoperative POP-Q and QOL after the same surgery, with the same operator, and at the same institution. The results showed no significant difference between both mesh materials in the short-term.

Polytetrafluoroethylene (PTFE) suture vs fiberwire and polypropylene in flexor tendon repair

BackgroundIn this study, we evaluate the value of novel suture material based on monofilamentous-extruded polyfluoroethylene (PTFE) compared to polypropylene (PPL) and Fiberwire (FW).Materials and methods60 flexor tendons were harvested from fresh cadaveric upper extremities. 4–0 sutures strands were used in the PPL, FW and PTFE group. Knotting properties and mechanical characteristics of the suture materials were evaluated. A 4-strand locked cruciate (Adelaide) or a 6-strand (M-Tang) suture technique was applied as core sutures for a tendon repair. Two-way ANOVA tests were performed with the Bonferroni correction.ResultsStable knotting was achieved with 5 throws with the PPL material, 7 throws for FW and 9 throws for PTFE. In the PPL group, linear tensile strength was 45.92 ± 12.53 N, in the FW group 80.11 ± 18.34 N and in the PTFE group 76.16 ± 29.10 N. FW and PTFE are significantly stronger than PPL but show no significant difference among each other. Similar results were obtained in the subgroup comparisons for different repair techniques. The Adelaide and the M-Tang knotting technique showed no significant difference.ConclusionFiberwire showed superior handling and knotting properties in comparison to PTFE. However, PTFE allows easier approximation of the stumps. In both, M-Tang and Adelaide repairs, PTFE was equal to FW in terms of repair strength. Both PTFE and FW provide for a robust tendon repair so that early active motion regimens for rehabilitation can be applied.

Biological versus synthetic patch for the repair of congenital diaphragmatic hernia: 8-year experience at a tertiary center

PurposeThe aim of this study is to compare outcome between small intestinal submucosal (SIS) and polytetrafluoroethylene (PTFE) patches in patients with congenital diaphragmatic hernia (CDH) with large muscular defects. Material and methodsWe performed a retrospective review of prospectively collected data of patients who underwent CDH repair from January 2011 to June 2019, with a minimum follow-up of 1 year. Data were collected regarding length of stay (LOS), mortality and recurrence. Kaplan-Meier analyses was used. ResultsIn the study period, 195 patients with CDH were admitted, 176 underwent surgical repair and 19 died before surgery. Sixty-two (35%) required a patch. Over the last 5 years, our institution transitioned from the use of all SIS to all PTFE. SIS was used in 18 cases and PTFE in 25. Overall survival rate was 89% (174/195). There was no significant difference regarding LOS and mortality. Nine patients (50%) of SIS and 1 (4%) of PTFE repairs recurred (P < 0.01; log-rank test P < 0.01), with a time course of recurrence of 18 (SD = 13) and 8 months, respectively. Median follow-up was 60 months (SD: 23) for the SIS group and 26 (SD: 10) for the PTFE group. ConclusionA significant lower recurrence was found using PTFE patches instead of SIS for the repair of large CDH. Level of evidenceLevel 3. Retrospective comparative study.

A Novel Technique Using Polytetrafluoroethylene Tape to Solve Screw Loosening Complication in Implant-Supported Single Crowns.

This study aimed to analyze a novel technique to make screws with greater untightening resistance and to solve screw loosening in implant-supported single crowns. Thirty grade IV titanium straight abutments were screwed onto 30 external hex implants using grade IV titanium screws (30 Ncm). They were exposed to cyclic loading (300,000 cycles, 200 N). Samples were divided into 4 groups (15 samples per group): new screws (SCREW group) (control), reused screws (rSCREW group), new screws wrapped with polytetrafluoroethylene (PTFE) tape (PTFE group), and reused screws wrapped with PTFE tape (rPTFE group). Reverse torque values (RTVs) were recorded with a digitally calibrated implant motor. Mean RTVs observed were 14.46 N (±1.10 N) for the control group, 14.42 N (±1.22 N) for the rSCREW group, 19.97 N (±1.16 N) for the PTFE group, and 19.13 N (±2.38 N) for the rPTFE group. Statistically significant differences were found between RTVs of both groups employing screws without PTFE tape (SCREW and rSCREW groups) compared with those using screws wrapped with PTFE tape (PTFE and rPTFE) (p < 0.001). These results suggest that wrapping the implant–abutment screw with PTFE tape may effectively lower the risk of loosening and even constitute a solution when this complication occurs in implant single crowns.

Clinical Outcomes after Biologic Graft Use for the Creation of Blalock-Taussig Shunt in Critically Ill Patients with Thrombophilia.

The modified systemic to pulmonary artery shunt (mSPS) is an effective palliative procedure in children with cyanotic congenital heart disease (CCHD) who are not suited for total correction. Early graft failure related to hereditary thrombophilic disorder is one cause of mortality. The aim of this study is to compare the clinical outcomes and rate of graft failure after mSPS in cyanotic infants with hereditary thrombophilia using bovine mesenteric venous graft (BMVG) and polytetrafluoroethylene (PTFE). 60 cyanotic patients (28 neonates, mean age 19 ± 11.3 days; range 1 to 27) who had thrombophilic risk factors were divided into 2 groups: BMVG (n = 30) and PTFE (n = 30). Preoperative thrombophilic factors were measured for each patient. The most common thrombophilic factors were protein C and S deficiency and Factor V Leiden mutation. We also investigated D-dimer, positivity of prothrombin G20210A, factor XII and antithrombin III deficiency, and homocysteinemia in both groups. The mean age of patients was 4.6 ± 1.09 months (range 1 day to 6 months) in the BMVG group and 3.9 ± 1.02 months (range 2 days to 9 months) in the PTFE group (P = .67). mSPS procedures were performed via left thoracotomy (n = 19 in the BMVG group and n = 22 in the PTFE group) or right anterior thoracotomy (n = 3 in the BMVG group and n = 3 in the PTFE group). Median sternotomy was performed to create a central shunt in 8 neonates in the BMVG group. In the PTFE group, we performed a central shunt in 5 patients via median sternotomy. Low molecular weight heparin in combination with acetylsalicylic acid (aspirin) were administered after surgery in both groups. The patients received aspirin combined with warfarin (Coumadin) after being discharged from hospital. We performed revision surgery to observe whether any patient had a significant drop in saturation with inaudible mSPS murmur. 7 patients died early after surgery (n = 2 in the BMVG group [6.6%] and n = 5 in the PTFE group [16.5%]; P = .022). 53 patients were discharged home in good clinical condition. Early graft thromboses were observed in 2 patients in the BMVG group (6.6%) and 8 patients in the PTFE group (26.6%) (P = .001). In a case from the BMVG group, the reason for graft thrombosis was entanglement of the graft. Revision surgery was performed successfully without any complication. Cil et collegues has been reported a successful percutaneous balloon angioplasty after an acute thrombosis of BMVG previously [Cil 2010]. In another patient who had acute BMVG thrombosis, we performed transluminal graft angioplasty using successful thrombolytic administration in the catheterization laboratory. There were no complications due to graft materials such as hematoma, seroma, or infection in the BMVG group. Bleeding from the needle hole was seen in 1 patient in the BMVG group. PTFE thrombosis developed in 3 patients within 24 hours (10%). We detected total or partial PTFE graft thrombosis in 5 patients during the follow-up period (20%). Revision surgeries in 3 patients were performed immediately after diagnosis. Transluminal balloon angioplasty combined with thrombolysis was performed in infants with partial or total PTFE occlusion in 5 patients. In the PTFE group, perigraft seroma (n = 5 [16.6%)] and hematoma (n = 2 [6.6%]) were detected. We performed revision surgery because of bleeding from the needle hole in 3 patients in the PTFE group (10%) in the early period after surgery. We detected a graft infection in 1 patient (3.3%) 6 months after surgery in the PTFE group. The rate of overall complications including pseudoaneurysm, seroma formation, graft infection, or partial or total graft occlusion in the early and follow-up periods was 6.6% in the BMVG group and 53.3% in the PTFE group (P = .0001). The rate of freedom from shunt failure was 92.6% ± 2.1% and 76.2% ± 4.8% during follow-up in BMVG and PTFE groups, respectively (P = .034). The rate of shunt-related mortality was 10.7% (n = 3) in the BMVG group and 20% in the PTFE group (P = .01). Regular physical examinations, transcutaneous oxygen saturation, and echocardiographic study were performed for shunt control during follow-up. Shunt occlusion or thrombosis was not seen in the BMVG group; 5 patients in the PTFE group (20%) had shunt occlusion during follow-up (P = .001). Our study shows that BMVG, as a biological material, may be used as an alternative material for creating mSPS. It decreases postoperative life-threatening complications after shunt procedures, including graft thrombosis, bleeding from the needle hole, perigraft hematoma, and seroma in patients with hereditary thrombophilia. To our knowledge, we report the first clinical comparison of the 2 grafts in our case series with thrombophilic risk factors.

Comparison of cytotoxicity of vascular prostheses in vitro

Aim. To study and compare cytotoxicity of the main types of synthetic prostheses used in arterial reconstructive surgery, including polytetrafluoroethylene (PTFE) and polyethylene-terephthalate (Dacron).&#x0D; Materials and Methods. On the culture of human umbilical vein endothelial cells (HUVEC) of the 3rd passage, MTS test was conducted that is used in laboratory examinations with attraction of cellular technologies to study cytotoxicity of medical drugs and medical products. The test implies use of MTS reagent that is 3-(4,5-dimethylthiazol-2-il)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium; additionally phenazine methosulfate (PMS) was used that plays the role of electron-binding reagent. In the experiment, cells were incubated with PTFE and Dacron within 24 hours at 37ᵒC with 5% CO2. For control, HUVEC cultured in the standard growth medium, were used. In the presence of PMS, MTS was reduced by mitochondrial dehydrogenases of endothelial cells to formazan staining blue. Supernatant of cell cultures was evaluated by photocolorimetric method on Stat Fax 3200 analyzer (microplate reader) of Awareness technology Inc. Palm City Fl. (USA).&#x0D; Results. The lowest mean values were noted in Dacron group 0.21 (0.20-0.22) optical density units, the highest values were noted in the control group 0.36 (0.35-0.38); parameters in PTFE group were 0.35 (0.33-0.36). In comparison of the groups statistically significant differences were found between the control group and Dacron group (р0.001), control and PTFE group (р=0.037), Dacron and PTFE (р0.001). Incubation with Dacron led to suppression of metabolic activity of cells by 41.7% as compared to the control group (р0.001). Metabolic activity of cells exposed to PTFE, approached that of the control group, that is, it corresponded to the optimal conditions of culturing of endothelial cells in vitro.&#x0D; Conclusion. In comparison with polyethylene-terephthalate (Dacron), polytetrafluoro-ethylene (PTFE) showed the least suppression of metabolic activity of endothelial cells in vitro.

Long-term results of polytetrafluoroethylene versus saphenous vein repair of degenerative carotid artery aneurysm

ObjectiveTo compare the results of polytetrafluoroethylene (PTFE) and great saphenous vein (GSV) bypass after resection of a degenerative aneurysm of the carotid artery. MethodsFrom January 1994 to November 2017, 37 patients (27 men) with a mean age of 58 years (range, 39-82 years) with a degenerative aneurysm of the carotid artery (median diameter, 28 mm; range, 19-42 mm), underwent resection of the aneurysm followed by a bypass with either a GSV (n = 10) or a PTFE prosthesis (n = 27). Although 31 patients were asymptomatic, 6 patients were symptomatic: transient ischemic attack (n = 4), minor stroke (n = 1), and compression of the hypoglossal nerve (n = 1). The preoperative workup included duplex ultrasound examination of the arteries to the head, and angiography or computed tomography angiography. All patients were operated under general anesthesia and six were intubated through the nose. Sixteen patients were monitored through transcutaneous oximetry. No shunt was used in this series. In 10 patients receiving a PTFE graft, the external carotid artery was implanted in the prosthesis. Mean follow-up was 16.9 ± 2 years (95% confidence interval, 14.5-19.3 years). Primary end points were the 30-day combined stroke/death rate, graft infection, late graft patency, and late stroke-free survival. Secondary end points were cranial nerve injury and length of postoperative hospital stay. ResultsPostoperative mortality was nil in both groups. One postoperative stroke was observed in the PTFE group, whereas none occurred in the GSV group (P = .84). No graft infection was observed in either group. At 10 years, survival in the GSV group was 80 ± 12%, and survival in the PTFE group was 76 ± 8% (log-rank [Mantel-Cox], P = .85). In the GSV group, graft patency at 7 and 10 years was 85 ± 13%. In the PTFE group B, graft patency was 100% (log-rank [Mantel-Cox], P = .12). No late stroke was observed. Two transient cranial nerve injuries were observed in the GSV group (20%) and two in the PTFE group (8%) (P = .97). Length of hospital stay was comparable in both groups (GSV group, 6 days; PTFE group, 5 days; P = .12). ConclusionsThis study suggests that, after resection of a degenerative aneurysm of the carotid artery, bypass with a PTFE prosthesis gives comparable results to those obtained with the GSV. We recommend sparing the GSV and instead using a PTFE prosthesis in patients with a degenerative aneurysm of the carotid artery.

Effects of salivary pH on coating durability of two different aesthetic archwire coatings under a simulated intraoral environment

ObjectivesThis study compared the effects of normal salivary pH, and acidic pH found in patients with poor oral hygiene, on the durability of aesthetic archwire coated with epoxy resin and polytetrafluoroethylene (PTFE). MethodsThe posterior parts of the archwires were sectioned into 20 mm segments (N = 102) and divided among six groups. Four groups were treated with different pH levels and two served as controls. The specimens were immersed in individual test tubes containing 10 ml of artificial saliva adjusted to a pH of 6.75 or 3.5. The tubes were sealed and stored in a 37 °C water bath for 28 days. After 28 days, the specimens were ligated to brackets embedded in an acrylic block and subjected to mechanical stress using an electronic toothbrush for 210 s. The specimens were photographed, and images were measured for coating loss using AutoCAD® software. Surface morphology was observed using a scanning electron microscope (SEM). ResultsSignificant coating loss (p < 0.001) was found in the epoxy resin groups, regardless of pH value, but not in the PTFE groups. The acidic pH caused epoxy resin layer coating loss by twice as much as normal pH. SEM revealed existing manufacturing defects on the as-received epoxy resin coating, whereas the retrieved epoxy resin demonstrated rupture, roughness, and coating loss in multiple locations. SignificanceEpoxy resin coatings demonstrate poor durability in acidic environments. This condition is worsened by the existing manufacturing defects found on as-received archwires. Hence, archwires coated with epoxy resin are not recommended in patients with poor oral hygiene.

Flexor tendon repair with a polytetrafluoroethylene (PTFE) suture material.

There is a consensus that after a flexor tendon repair an aggressive rehabilitation protocol with early active motion can improve functional outcome, provided that the combination of material and suturing technique can meet the higher biomechanic demands. Bearing this in mind we evaluated a polytetrafluoroethylene (PTFE) suture (SERAMON®, Serag-Wiessner) as a possible material for flexor tendon repair. 40 flexor tendons were harvested from fresh cadaveric upper extremities. 3-0 and 5-0 strands were used both in the polypropylene (PPL) as well as in the PTFE group. In the first phase of the study, we evaluated knotting properties and mechanical characteristics of the suture materials themselves. In the second phase, a 2-strand Kirchmayr-Kessler suture technique was applied for a core suture of a flexor tendon (n = 16). In the third phase, we performed a tendon repair including an epitendinous running suture with 5-0 PPL or 5-0 PTFE material (n = 22). One way ANOVA tests were performed. The linear loading strength of single strand knotted PPL 3-0 was 19.87 ± 0.59N. The linear loading strength of knotted PTFE 3-0 was 32.47 ± 1.67N. For PPL 3-0 maximum linear strength was achieved with five knots, for PTFE 3-0 with eight knots. When a Kirchmayr-Kessler core-only repair was performed, then in the PPL group the loading strength of the repaired tendon was 30.74 ± 9.77N. In the PTFE group the loading strength was 23.74 ± 5.6N (p = 0.10). However, all repairs in the PTFE group failed due to cheese wiring. When a Kirchmayr-Kessler core and epitendinous repair technique was used, then in the PPL group the loading strength of the repaired tendon was 49.90 ± 16.05N. In the PTFE group the loading strength was 73.41 ± 19.81N (p = 0.006). PTFE demonstrates superior strength properties in comparison to PPL for flexor tendon repairs. However, standard 2 strand techniques have proved inadequate to bear the higher biomechanic demands.