## 4 Discussion  
The rationale for evaluating whether sites with GR and a thin phenotype should be augmented either prior or after OT, depends on meticulous assessment of risk factors associated with GR, clinical and imaging evaluation, and selection of the optimal soft tissue augmentation technique. In our study, a third of the periodontitis/oral surgeons surveyed reported that they receive referrals from orthodontists before orthodontic treatment, whereas almost 40% of orthodontists indicated that they refer patients for soft tissue augmentation before OT. The majority of the evaluated dentists agreed that the ideal timing of soft tissue augmentation depends on each specific case. Both groups of surveyed dentists considered \"planned tooth movement\" as the most important factor determining clinical  
Figure 8: Biplot graph of the MCA of the answers to question 5. Figure 9: Biplot graph of the multiple correspondence analysis of the answers to question 6.  
decision-making. The impact of orthodontic treatment on the periodontal status has been studied widely. The majority of researchers indicate that dental arch expansion and the proclination of incisors pose a higher risk for bone dehiscence and, consequently, gingival recession [12; 13; 14; 15; 16]. In a recent study, when the tooth inclination of the upper and lower incisors increased labially during OT, the GR after OT increased by approximately 0.2 mm per \(1^{\circ}\)[13]. The problem also relates to growing patients, even though the potential of osseous tissue to remodel itself is regarded to be high in this group. A study based on a CBCT examination revealed that in young patients, the frequency of dehiscence after orthodontic treatment increased from 27% to 50% [16] which poses a threat in terms of the development of GR in the future. Retrolcination of the lower incisors led to a reduction in GR in most studies [17; 18]. However, the gingival papillae receded following orthodontic treatment, especially in the lower anterior tooth area in patients treated with premolar extraction [19]. On the basis of previous studies, it can be concluded that both teeth proclination and retroclination in patients with a thin phenotype can lead to alterations of the gingival margin. It has been reported that, for every 1 mm increase in GR, a successive increase of 0.98 mm in buccal bone dehiscence will be present [20]. The key issue is the position of the root in the alveolar bone. Orthodontic movement of the root toward the center of the alveolar envelope reduces the dimensions of GR and improves the prognosis for surgical procedures [21]. In these cases, the surgery (recession coverage with coronally advanced flap or connective tissue graft) should be planned after OT. If the plan for OT involves arch expansion or dislocation of the roots toward the margin of the bone envelope, soft tissue augmentation prior to OT ought to be considered. In reality, the majority of orthodontic movements are complex and involve both translation, inclination, and movements in the direction of the centre of the alveolar bone or in the opposite direction. Having said that, the safest approach might be to consider soft tissue augmentation before OT. This approach is in accordance with the answers by the participants in our study, who indicated that the optimal timing of soft tissue augmentation depends on the clinical situation (51% of periodontitis/oral surgeons' answers and 45% of orthodontists' answers) and the most important factor that determines the timing of the surgery is \"planned tooth movement\" (46% and 33%, respectively). The consensus from the American Academy of Periodontology clearly indicates that all root coverage procedures presented in the literature may significantly improve the clinical parameters [22; 23].