Analysis Of Clinical Effects Of Three Gingival Retraction Methods By Using Digital Scanner

Objective:The present study was intended to compare the clinical effects of Ultrapak gingival retraction cords without drug,the Expasyl gingival retraction paste and semiconductor lasers and to provide a reference for suitable gingival retraction methods for fixed prostheses.30 mandibular and maxillary molars(except the third molars)were treated with the three gingival retreaction methods.The effective gingival retraction distance was measured and assessed on digital impressions.Methods:30 patients that underwent root canal treatment were indicated for fabrication of crowns.All patients received dental treatment in the VIP department of the Affiliated Stomatological Hospital of Nanchang University from June 2018 to April 2019.The patients were randomly divided into three groups according to the order of treatment.Ultrapak gingival retraction cords without drug,the Expasyl gingival retraction paste and semiconductor lasers were used for gingival retraction.The 3shape scanner was used to collect the digital models before and after gingival retraction.Digital models were overlapped and sectioned on the Geomagic Qualify 2013 software.Three-dimensional coordinates were created in long axis,buccal-lingual,and mesio-distal directions.In the buccal-lingual direction,planes were made parallel to the long axis of the teeth in the mesial 1/3,middle 1/3 and distal 1/3.The horizontal distance(W1,W2,W3)between the apexes of gingiva before and after gingival retraction was measured in the three planes.The mean values(?W)were calculated.Results:1.The mean retraction value in the Expasyl gingival retraction paste group was significantly greater than that in the Ultrapak gingival retraction cords without drug group(P<0.01).2.The mean retraction value in the semiconductor lasers group was significantly greater than that in the Ultrapak gingival retraction cords without drug gorup(P<0.01).3.The mean retraction value in the semiconductor lasers group had no difference compared to the Expasyl gingival retraction paste group(P>0.05).Conclusions:1.The Expasyl gingival retraction paste has better gingival retraction effects than Ultrapak gingival retraction cords without drug.2.Semiconductor lasers have better retraction effects than Ultrapak gingival retraction cords without drug.3.The Expasyl gingival retraction paste and semiconductor laser have no difference regarding to gingival retraction effects.4.All the three methods can achieve the minimum required retraction of 0.2mm for impression materials.