Background: Hyperfunction of the muscles of the upper lip is considered as the most common cause of excessive gingival display (EGD). The aim of this study was to demonstrate the effectiveness of botulinum toxin (BT) injection as a conservative treatment for EGD due to muscular hyperfunction and to compare the outcome of 2 injection methods. Material and methods: This study included 40 participants who were randomly assigned into 2 groups of 20 each, The first group received 2.5IU BT injection at 1 point per side (2-points group), while the second group received a total of 5 IU of BT at 2 points per side (4-points group). The outcome variables were the reduction in the central and lateral gingival display expressed as the difference between the pre- and post-injection measurements and the degree of satisfaction of the participants. The follow up visits were at 2- and 12-weeks postinjection. The study variables were statistically analyzed and probability values of <0.05 were considered significant. Results: There was a significant improvement (P < 0.0001) in both groups throughout the follow up period, but the improvement achieved by 4-points group was significantly better than that of the 2-points group with respect to the gingival display and the degree of satisfaction (P < 0.0001). Conclusions: Botulinum toxin injection represents a safe and less invasive modality for treatment of EGD, the 4-points method results in better outcome in terms of clinical measurements and degree of satisfaction over the 2-points method.
