# The Impact of Orthodontic Treatment on Pre-Existing Gingival Recessions: A Retrospective Study
## 4 Discussion
The incomplete healing of GRs in mandibular incisors which was found in the present study may be explained by the fact that the labial alveolar bone is anatomically very thin already before OT, and may predispose the development of dehiscences after orthodontic movement of these teeth [38]. The percentage of improved GRs in the present study was largest on maxillary canines (84.6%), which is in contrast to the results of [PERSON] et al. (2014), where GRs worsened after orthodontic treatment [26]. That could be influenced by the negative torque, usual in Roth prescription brackets, sometimes leading to a significant labial movement of the canine root. In the present study, all patients were treated with maxillary canine torque of 0\({}^{\circ}\) or +7\({}^{\circ}\). Careful bracket torque selection for teeth with GR's, bearing in mind the position of the root in the alveolus, could have influenced our results. However, this is only a speculation, as the present study had a retrospective design. As the study patients had different malocclusions, we found it essential to analyze patient-related factors, which could have influenced GR change. Pre-treatment overbite had an impact on GR change: patients with reduced overbite had a tendency for GR worsening in comparison to normal/deep overbite cases, where improvement of GR was found. The results are in line with the results by [PERSON] et al. (2007), where an average improvement of 2 mm in GRs was observed in maxillary incisors [36]. The sample consisted mainly patients with traumatic deep bite. Therefore, a significant improvement in GR was related to the elimination of the causative factor--mechanical load. Based on the results of the present study and earlier studies, it may be expected that the treatment of deep overbite may favor the improvement of GR. [PERSON] et al. (2012) also found that patients with hypoydivergent vertical growth pattern (deep bite) have a lower prevalence of dehiscence than those with a normo-divergent or hyper-divergent (open bite) growth pattern [39]. GR improvement in the present study was similar in both pre-treatment increased and decreased overjet at the patient level and tooth level. However, in the study by [PERSON] et al. (2014) authors found that decreasing incisor proclamation had positive effect on the improvement of GR. Later studies by [PERSON] et al. (2015) and [PERSON] et al. (2017) did not find such an association, suggesting that correction of increased overjet does not influence GR change [40,41]. Gingival biotype at patient level did not result in significantly different GR change; however, at tooth level, a smaller improvement was found in teeth with thin biotype. Some authors suggest that GRs are less likely to improve after OT in cases with thin biotype [42]. However, in the study by [PERSON] et al. (2014), no association between GR change and gingival biotype was reported suggesting that gingival thickness is not the most critical factor [26]. The sagittal dental relationship has also been found to influence GR change. The literature mostly describes Angle class III cases as risk factors to GR worsening after OT, mainly due to retroclination of lower incisors to camouflage malocclusion [32]. [PERSON] et al. observed that Class III patients with excessive dental compensations had more than three times as many teeth with labial GRs after OT in comparison to patients with Class I or Class II [43]. The results of the present study support these findings: no significant GR improvement was found in Angle III patients. Patients with a Class III relationship had 2.6-times less chance for GR improvement than those with Class I or II. This observation can be explained by the anatomically thin buccal cortical plate, and the presence of dehiscences and fenestrations in the mandibular incisor region found in all types of untreated sagittal malocclusions [38].