Periodontal diseases represent inflammatory conditions initiated by oral biofilms. From a clinical point of view, redness and swelling of the gingiva as well as increased pocket probing depths (PPD) with tendency to bleeding on probing (BoP) are common characteristics of patients suffering from periodontitis. Moreover, periodontitis may be recognized in radiographs by moderate to severe loss of alveolar bone.

Patients with stage IV periodontitis (Tonetti et al., 2018) are affected by the presence of severe periodontal lesions extending to the apical portion of the roots, resulting in tooth hypermobility, bite collapse, and drifting. In such cases, proper control of periodontitis and adequate orthodontic and prosthetic rehabilitation represent the only ways to restore masticatory function and reduce the risk of loss of the entire dentition.

Outcomes from studies in humans have indicated that elimination of the bacterial infection and institution of plaque control regimes result in almost all cases in periodontal health. This condition forms the basis for further corrections, including orthodontic therapy. This is corroborated by the fact that outcomes of experimental studies in dogs indicated that in biofilm‐free dentitions orthodontic tooth movement (i.e. tilting and bodily movements) neither jeopardized periodontal health nor induced loss of the attachment apparatus, even under reduced but healthy periodontal tissue conditions (Ericsson and Thilander, 1978; Polson et al., 1984). Apart from periodontal considerations leading to orthodontic treatment, the intervention path can be observed in the opposite direction in usual clinical practice.

Pathological tooth migration

Pathological tooth migration (PTM) is defined as tooth displacement that occurs as a consequence of periodontal disease. It often occurs in periodontal patients and represents one of the most obvious changes causing adult patients to seek orthodontic treatment as a first step. PTM commonly occurs in the anterior region, may affect one or more teeth, and often involves facial flaring, extrusion, rotations, over‐eruption, and diastema/spacing formation at teeth with alveolar bone loss. The position of a tooth is determined by an equilibrium that is the result of forces from the occlusion, the periodontium, and the pressure from soft tissues, including tongue, lips, and cheeks (Proffit, 1978). Typical forms of PTM are associated with an imbalance between the facial muscles and the tongue when the periodontal support is reduced, as the tongue pressure may be higher than the pressure from the facial muscles. The reported prevalence of PTM varies from 9.4% (Brunsvold et al., 1999) to 55.8% (Martinez‐Canut et al., 1997). Towfighi et al. (1997) reported a prevalence of 30% in patients with moderate and severe periodontitis. This is in line with Demetriou et al. (1991), who reported tooth migration in 36.9% of 330 periodontal patients.

The etiology of PTM is not yet fully elucidated, although several factors have been suggested as part of the causative pathway. The likelihood of tooth migration increased from 2.23‐ to 7.97‐fold when substantial bone loss and tooth loss had occurred and when gingival inflammation was present (Martinez‐Canut et al., 1997). This is in line with a study including 100 periodontitis patients, with an association observed between bone loss, increased probing depth, and PTM, although no correlation between parafunction such as clenching or bruxism and PTM was seen (Rathod et al., 2013).

The change in positioning of the center of resistance (CR) of the affected tooth, which becomes more apical as the alveolar bone height is reduced, and the pressure produced from the inflamed tissue within the periodontal pocket are also considered important. Costa et al. (2004) analyzed periodontal destruction in migrated and nonmigrated anterior teeth in 32 patients suffering from generalized chronic periodontitis. Facial flaring occurred most frequently (34.8%), followed by diastema formation. Extrusion was found in only 4.3% of this group of participants. Notably, severe bone loss (BL; 59%) and significant clinical attachment loss (CAL; 8.42 mm) were observed in extruded teeth, followed by teeth with facial flaring (45% BL and 6.07 mm CAL loss). Rotated and tilted teeth showed less bone reduction. Overall, migrated teeth exhibited greater BL and loss of CAL (40% BL and 5.1 mm) than nonmigrated teeth (31% BL and 4.1 mm; Costa et al., 2004). Other studies reported attachment loss of migrated teeth to be greater than for nonmigrated control teeth (4.79 ± 0.28 mm vs. 3.21 ± 0.18 mm, p <0.001; Towfighi et al., 1997). These results point to the fact that the destruction of periodontal tissue plays a significant role in PTM.

Development of severe PTM is often a major esthetic concern for patients and is central in decisions about dental and orthodontic treatment. Among patients undergoing periodontal therapy, the presence of PTM was the main reason for 9% of them, while 25% reported different esthetic problems (Brunsvold et al., 1999). Spontaneous correction after periodontal treatment can be expected in mild PTM (less than 1 mm). Orthodontic correction may be considered to treat more severe PTM and the existing malocclusion during the remission of active periodontitis. Traditionally, periodontal treatment is performed before the start of orthodontic treatment to safeguard movement of periodontally compromised teeth in noninflamed periodontal tissues. Interestingly, a recent randomized clinical trial did not show differences in periodontal status after orthodontic treatment between patients treated traditionally and in parallel with orthodontic treatment (Zasčiurinskienė et al., 2019).

Orthodontic correction of PTM helps to obtain optimal tooth alignment in the dental arches, well‐balanced occlusion, and normal tooth contacts. Improvement in the smile esthetics can be an important motivation for a patient with periodontitis to maintain the result of the combined periodontal and orthodontic treatment. During orthodontic treatment it is mandatory to carefully plan force levels and biomechanical set‐ups in view of the reduced bone support associated with the periodontally compromised dentition.

The increasing demand for combined periodontal and orthodontic treatment is obvious in a contemporary clinical therapeutical process. This highlights the need for a comprehensive assessment and tight collaboration between periodontists and orthodontists in a common treatment plan (Kloukos et al., 2022).

Treatment plan

A comprehensive treatment plan for patients diagnosed with stages I–IV periodontitis (Tonetti et al., 2018), including orthodontic problems such as tilting, malpositioning, and tooth migration, should include the following four steps (Sanz et al., 2020).

Goals of periodontal therapy

The following clinical parameters should be assessed at the end of active periodontal therapy:

• Reduction of periodontal tissue inflammation as measured by BoP. A full‐mouth mean BoP ≤25% should be achieved (Matuliene et al., 2008).
• Reduction in PPD measured in mm. Absence of residual pockets with PPD >5 mm should be achieved (Matuliene et al., 2008).
• Control of furcation involvement of multirooted teeth not exceeding degree I (Salvi et al., 2014).
• Absence of pain and discomfort.

Comprehensive periodontal examination