Polymerization time compatibility index of polyvinyl siloxane impression materials with conventional and experimental gingival margin displacement agents

[Laboratory evaluation of retraction cords properties]

The aim of the study was the investigation of the effect of two factors on the diameter changings of different types of retraction cords. Using an optical microscope MBS-10 (x10) the diameter of the different retraction cords was measured. The measurement also was performed after tension and after wetting cords with distilled water. The cords diameter decreased after their tension and increased after wetting. The degree of diameter changes depends on the kind of cords weaving. Braided cords "00" and "1" sizes diameter after it tension decreased at 31% and 37%, knitted cords under tension changed the diameter at 53% and 48%, correspondingly. Cords features after wetting also varied. Wetting of the braided cords with distilled water did not lead to significant diameter changes while wetting of knitted cords increases their diameter at 13% (00) and 15% (1).

Preimpression troughing with the diode laser: A preliminary study

STATEMENT OF PROBLEM

The mechanical-chemical technique and the use of a laser are methods for displacing the gingiva to make an accurate impression of the preparation for a complete crown. The tissue needs to be displaced and the hemorrhage controlled to capture the prepared finishing line in the impression. The degree of undesirable gingival recession after these displacement techniques is unknown.

PURPOSE

The purpose of this pilot clinical study was to clinically monitor and compare the regeneration of the gingival tissue by using 2 methods of gingival displacement in the same participant: the mechanical-chemical technique with double cords impregnated with aluminum chloride and the 810 nm diode laser (Odyssey; Ivoclar Vivadent AG).

MATERIAL AND METHODS

A total of 6 participants needing 2 crowns on natural teeth were included in this study. At the first visit, the teeth were prepared with a 0.5-mm subgingival finishing line and interim crowns were fabricated. One of the teeth was randomly assigned to the double cord technique with 2 (# 000 and # 1) impregnated 5% aluminum chloride cords and the other to the 810 nm diode laser. An adjacent tooth served as a control. A device was made that would function as a fixed reference point for the measurements at different time intervals. A notch was created on the device to position the digital ruler between the occlusal notch and the free gingival margin to measure the distances. The measurements were recorded for each patient before displacement of the gingiva and at the time of cementation of the definitive crowns. The patients were followed at 1 week, 3 weeks, and 8 weeks after cementation of the definitive crowns.

RESULTS

The amount of recession with the cord impregnated with aluminum chloride was 0.26 mm 8 weeks after cementation of the definitive crowns with a range between 0.00 mm and 0.72 mm. The diode laser showed an average recession of 0.27 mm with a range between 0.01 mm and 0.68 mm.

CONCLUSIONS

This study found an average loss of gingival height of 0.26 mm for the double cord technique and 0.27 mm for the laser. The amount of recession was considered not clinically significant.