Optimization of steroid injection intervals for prevention of stricture after esophageal endoscopic submucosal dissection: A randomized controlled trial

BACKGROUND

Esophageal endoscopic submucosal dissection enables en bloc resection of large superficial esophageal cancer; however, this procedure may induce severe stricture. Intralesional steroid injection is an effective treatment for prevention of stricture after endoscopic resection; however, there have been no studies assessing the duration of such treatment. The aim of this study was to reduce treatment duration and to evaluate the effectiveness of weekly and biweekly steroid injections in preventing esophageal stricture after endoscopic resection.

PATIENTS METHOD

We performed a randomized controlled trial comparing patients receiving weekly or biweekly intralesional triamcinolone injections. Patients with a mucosal defect greater than 75% (3/4) of the luminal circumference after esophageal endoscopic submucosal dissection for superficial esophageal cancers were enrolled. The primary endpoint was the duration of steroid injection treatment.

RESULTS

The median duration of treatment was 37.0 days in the weekly group and 34.2 days in the biweekly group (P = 0.059). Among patients with a mucosal defect larger than 50 mm, there was a significant difference in the median duration of treatment between the weekly and biweekly groups (42.5 days vs 29.0 days, P = 0.013).

CONCLUSION

Biweekly steroid injection of triamcinolone reduces treatment duration, particularly in those with mucosal defects larger than 50 mm. (Acta gastro-enterol. belg., 2016, 79, 315-320).

Development of an RPD CAD system with finite element stress analysis

The structural design of removable partial dentures (RPDs) is critical for preventing distortion of the prosthesis, protecting abutment teeth and residual ridges as well as for high masticatory performance. The aim of this study was to clarify the feasibility and utility of a computer-aided designing (CAD) system with finite element analysis (FEA) for molar teeth arrangement in unilateral distal extension base RPDs. The shapes of artificial teeth and residual ridge were measured and converted into point group data. Solid models were created from surface-modelled point group data in a 3D surface CAD format. An occlusal rim was created on the residual ridge mucosa and the occlusal rim - residual ridge mucosa model with FEA function was created. Stress distribution on the residual ridge mucosa was compared by changing the loading point. The artificial teeth were then arranged in locations with the lowest amount of stress. After building an artificial teeth - saddle - residual ridge mucosa model, stress distribution in the residual ridge mucosa was re-evaluated by simulating occlusal force. On the occlusal rim - residual ridge mucosa model, stress was reduced when the loading point was located around the buccal shelf where functional cusps of artificial teeth were charted. It was confirmed that stress distribution in the residual ridge mucosa was equalized on the artificial teeth - saddle - residual ridge mucosa model. This system might be clinically useful tool for designing RPDs if FEA-guided designing of retainers and connectors can be added.

Bending rigidity of composite resin coating clasps

The purpose of this study is to examine the bending profiles of composite resin coating cast clasps. The cobalt-chromium alloy cast clasps were made using tapered wax pattern. Silane coupling method (Silicoater MD, Kulzer Co.) was used to attach composite resin to metal surface. The breakage and the bending rigidity of composite resin coating clasps were evaluated. Results were as follows: 1) After the repeated bending test to the tips of clasp arm at 10,000 times in 0.25 mm deflection, neither crack on composite resin surface nor separation at resin/metal interface was observed in any specimen. 2) There was no significant difference in the bending rigidity of clasp arms between before and after composite resin coating. From these results, it was demonstrated that the composite resin coating cast clasp was available in clinical cases and coating with composite resin had little influence on the bending rigidity of clasp arms. Therefore, it was suggested that our clasp designing and fabricating system to control the bending rigidity of clasp arms could be applied to composite resin coating clasps.

Influence of dimensional factors and heat treatment on permanent deformation of wrought wire clasps

The purpose of this study is to examine the fatigue profiles of wrought wire clasps during the clinical use. Cobalt-chromium-nickel alloy wires were bent into circular beams, which dimensions and fabrication methods were similar to the clinical cases. Deflections of 0.5 mm in a normal direction were applied 10,000 times to the tips of clasp arm and permanent deformations were measured. The following results were obtained. 1) The clasp arms with larger cross sectional diameter, shorter length and smaller radius of curvature showed larger amounts of permanent deformation. 2) The amounts of permanent deformation of the clasp arm remarkably decreased by electric resistance soldering and decreased further more by heat treatment at 500 degrees C for 10 minutes after soldering regardless of the number of deflection. From the results of this study, it was concluded that dimensional factors and heat treatment influenced the permanent deformation of the wrought wire clasps remarkably. Therefore, considering these factors, wrought wire clasps could be designed to reduce permanent deformation.

Effects of heat treatment on mechanical properties of base metal wrought wire clasps

The purpose of this study is to determine the effects of heat treatment and soldering on the change of shape and mechanical properties of cobalt-chromium-nickel alloy wrought wire clasps. The change of distance between the tips of the clasp arm was measured and mechanical properties were examined using the bending test. The following results were obtained. 1) By heat treatment at 500-700 degrees C for 10 minutes, bending rigidity and deflection at the proportional limit of the clasp arm increased significantly (p < 0.01), while permanent deformation after the bending test decreased considerably (p < 0.01). Concerning the deformation of clasp arms by heating, the distance between clasp tips increased remarkably above 500 degrees C (p < 0.01). 2) These mechanical properties of clasp arms were improved both by electric resistance soldering with silver solder and by heat treatment at 500 degrees C for 10 minutes after soldering. From these results, it was concluded that electric resistance soldering and adequate heat treatment were very effective to improve the mechanical properties of the clasp arm, especially to increase the deflection at the proportional limit and reduce the permanent deformation.