Abstract: Objective To apply digital analysis to compare the clinical gingival retraction effects, including gingival pain degree, sulcus width (SW) and gingival recession (GR), between diode laser method and single cord method. Methods A total of 52 teeth were selected from 42 patients who needed fixed partial denture restoration. They were randomly divided into two groups, diode laser gingival retraction group and single cord gingival retraction group. Twentysix normal teeth were selected as blank control group. VRS digital pain grading method was used to evaluate the pain degree of the two gingival retraction methods, and 3shape scanner was chosen to rebuild digital models before and after gingival retraction at the time point of 0 week, 1st week and 6th week. Finally, the acquired data was input into geomagic qualify 2014 software to compare the gingival effects SW, GR0, GR1 and GR6 before and after gingival displacement. Results The pain level of the diode laser group was lower than that of the single cord group (P<0.05); the SW of diode laser group (buccal (0.394 2±0.087 3)mm, palatal (0.397 4±0.086 8)mm) was greater than the single cord group (buccal (0.322 8±0.057 3) mm, palatal side (0.306 0±0.050 6)mm) (P<0.05); the GR0 (0.342 5±0.027 9)mm, GR1 (0.162 5±0.056 9)mm, and GR6 (0.239 3±0.020 6)mm of the diode laser group were larger than those of the single cord group, GR0 (0.273 0±0.018 7)mm, GR1 (0.145 9±0.030 8)mm, GR6 (0.162 5±0.015 9)mm (P<0.05). Conclusion The diode laser method can lead to lower pain degree. Both two methods can achieve ideal sulcus width, but permanent gingival recession will be caused. The amount of gingival recession after diode laser gingival retraction is larger. Therefore, it is recommended to use single cord method for patients with thick gums, while for patients sensitive to pain, laser method could also be considered.

Key words: single cord gingival retraction, diode laser, width of gingival sulcus, gingival recession