Gingival Retraction with 980-nm Diode Laser Compared to Double-Cord Technique: An In vitro Study

In fixed prosthodontics, the need for gingival retraction prior to impression plays a fundamental role in ensuring the reproduction of anatomical details in the preparation using traditional impression materials or Intraoral Scanner (IOS) light beams. The recent introduction of laser in dentistry has opened new therapeutic options in the displacement of the gingival margin.

This study aimed to compare the efficacy of a 980 nm diode laser with the double gingival retraction cord technique to obtain a longitudinal and vertical displacement of the gingival margin.

Four bovine mandibles were used as the experimental model (n=32 teeth). Sixteen teeth were randomly assigned to the laser group (group A), and the other 16 to the retraction cord group (group B). For each group, the initial status was considered the corresponding control group. After tooth preparation, in both groups, a conventional impression was taken with Polyvinyl Siloxane (PVS). Successively, the gingival margins were displaced by using a 980nm-diode laser for group A, and by means of two retraction cords for group B. After the retraction process, a new impression was taken with the same polyvinyl siloxane. The amount of horizontal and vertical gingival displacement (HD, VD) was measured by an image analyzer. Tukey’s, Student’s t-test, and One-way ANOVA test were employed.

There was a statistically significant difference (P<0.001) found in both methods compared to the corresponding control groups. A statistically significant difference (P<0.05) between the means of laser vertical displacement and the cord vertical displacement was observed. Conversely, no statistically significant difference was observed when the laser horizontal displacement and cord longitudinal displacement were compared (P>0.05).

The gingival displacement obtained by means of a 980 nm diode laser has been found to be similar to the displacement obtained with the double-cord technique. However, the double-cord technique provided a better vertical displacement. The findings suggest that the 980 nm diode laser may represent a valuable alternative in the displacement of the gingival margin.