Accuracy of three types of digital guides for crown lengthening surgery: An in vitro study

The guided protocols always yield a higher accuracy than freehand surgery. However, the accuracy of digital guides for crown lengthening surgery (CLS) is unknown. The purpose of this study was to evaluate the trueness of 3 types of digital guides for CLS. Twenty individually designed maxillary models were divided into 4 groups according to surgical guides: type I (T1), type II (T2), type III (T3), and free-hand. T1 comprised a planed gingival margin at the tissue level. T2 included both the planed gingival margin and alveolar crest at the tissue level. T3 consisted of a planed gingival margin at the tissue level and an alveolar crest at the bone level. CLS was performed under the indication of the guides. Trueness of the guides was evaluated through the deviation of the gingival zenith and alveolar crest height. The control group had higher vertical and horizontal distance deviations of gingival zenith compared to the 3 digital guide groups (P < 0.001). There were no significant differences among the 3 test groups in terms of gingival zenith deviations (P > 0.05). With regard to height deviation of alveolar crest, the control and T1 groups were higher than T2 group (P < 0.001), while T3 group had the lowest deviations among the 4 groups (P < 0.001). The digital guides assisted CLS procedures are more accurate than free-hand method. The trueness of type III guide was better than type I and type II.