Evaluation of gingival displacement, bleeding and ease of application for polytetrafluoroethylene (PTFE) and conventional retraction cord - a clinical trial

OBJECTIVE

Conventional use of retraction cord in soft tissue management is effective only when the non-resilient nature of material does not jeopardize gingival health. Therefore this study aims to clinically evaluate the gingival displacement, ease of application and bleeding from polytetrafluoroethylene (PTFE) retraction cord.

PATIENTS AND METHODS

This study is a single-center, parallel-group, randomized controlled clinical trial (1:1). Sixty patients indicated for full coverage metal-ceramic restoration for first molars were enrolled and randomly allocated to experimental (PTFE Cord) and control (conventional plain retraction cord) groups. After crown preparation and isolation, a pre-displacement impression was made. Assigned gingival displacement material was applied for 5 minutes, followed by post-displacement impression. Casts were prepared and used for assessment of mean horizontal gingival displacement by measuring displacement using a stereomicroscope (20 x). Post-displacement gingival bleeding and ease of application were also assessed clinically. t-test and Chi-square tests were used for statistical assessment of gingival displacement, gingival bleeding and ease of application.

RESULTS

Gingival displacement, bleeding and ease of application were similar among study groups (p > 0.05). Mean gingival displacement in the experimental group was 197.1 µm, and 167.7 µm in the control group. Bleeding was observed in 30% and 20% of cases of experimental and control group, respectively. Ease of application was 'difficult' in 53.3% and 43.3% of cases of experimental and control group, respectively. Non-impregnated gingival retraction cord and PTFE cord displayed similar outcomes of gingival displacement, ease of placement and bleeding after cord removal.

CONCLUSIONS

Post-displacement bleeding and discomfort for PTFE cord placement suggest that this technique needs improvement. Therefore further studies are warranted to improve and investigate the physical and biological response to PTFE retraction cord.

Implant abutment disinfection using plasma of argon and 0.2% and chlorhexidine gel applications immediately before prosthesis delivery: clinical and radiographic status at 5-years of follow-up

OBJECTIVE

The purpose of this five-year follow-up study was to investigate the clinical and radiologic status of implants that had undergone abutment disinfection immediately prior to prosthetic loading (PL) using plasma of argon (PA) or 0.2% chlorhexidine (CHX) gel.

PATIENTS AND METHODS

Sixty patients who had had an implant-supported prosthesis fitted at least five years previously were recruited for this study. In groups 1, 2, and 3, implant abutment disinfection was performed using PA, 0.2% CHX, and a vapor protocol, respectively. Modified plaque index (mPI), modified bleeding index (mBI), probing depth (PD), and mesial and distal crestal bone loss (CBL) were measured. A questionnaire on routine oral hygiene, smoking habits, and systemic health status was also administered. Sample size estimation was performed, and group comparisons were made. Probability values less than 0.05 were considered statistically significant.

RESULTS

Group 1, 2, and 3 included 20 (20 implants) patients each. At five-year's follow-up, there was no difference in mBI, mPI, and PD in all groups. There was no significant difference in peri-implant CBL in all patients. None of the patients were immunosuppressed or had periodontal disease, and or had used nicotinic products within the past five years. Toothbrushing twice daily was reported by at least 90% of individuals in all groups. Flossing of interproximal spaces once daily was reported by at minimum 60% of individuals in all groups.

CONCLUSIONS

Disinfection of implant abutments directly before PL can be performed using AP, or 0.2% CHX gel.

Effect of Framework's Manufacturing Technique on Screw's Preload of Implant Supported Prosthesis

Background

Implant supported prosthesis is a common treatment modality. Nowadays, new manufacturing techniques are available to fabricate them.

Aims

To evaluate the effect of different manufacturing techniques of implant supported frameworks (ISF) on the preload of abutment's screws.

Materials and Methods

A mandibular edentulous acrylic model with four dental implants temporarily stabilized in the interforaminal area was used. One ISF was fabricated using the conventional technique; implants were removed from the model and reassembled into the framework; this framework served as the passively fitting framework (PF). Three additional frameworks were constructed: conventional cast framework (CF), milled framework (MF) and 3D-printed framework (3D-PF). The gap between the frameworks and the neck of the implants were recorded in microns using a digital microscope. A tightening torque (TT) of 35 N·cm was applied to all the four abutments' screws and the screw's preload was recorded using two methods, by strain gauges (SGs) that were attached to the neck of each implant and fed into a stain book in microstrain (μɛ) and by removal torque (RT) using a digital torque meter.

Results

The frameworks' gap means from the lowest to the highest were PF, CF, 3D-PF, and MF. The RT was significantly lower than the TT in all frameworks (P ≤ 0.05). One-way analysis of variance (ANOVA) revealed that the PF had the lowest RT, while the CF and the 3DPF both had the highest RT, and those differences were found to be statistically significantly (P ≤ 0.05). When preload of the frameworks was recorded by SGs, one-way ANOVA revealed that PF had the highest preload value, while both 3D-PF and MF had the lowest preload values, those differences were also found to be statistically significant (P ≤ 0.05).

Conclusion

The fabrication of implant-supported frameworks using milling or selective laser melting computer aided design/computer-aided manufacturing technologies did not necessarily enhance the screw's preload. This lack of enhancement could be attributed to the great amount of marginal gap in the frameworks fabricated by both techniques.