16: Clear aligner orthodontic treatment of patients with periodontitis
Tommaso Castroflorio, Edoardo Mantovani, Kamy Malekian
Malocclusions related to periodontal disease
There is no direct influence between malocclusion and periodontal breakdown; however, quicker progression of periodontal disease is associated with occlusal discrepancies and is reduced by occlusal treatment.1,2 It has been demonstrated that in crowded areas plaque accumulation increases3 and, with respect to noncrowded areas, an increased number of periopathogenic species can be found.4 Furthermore, an altered topography of the gingiva and the alveolar bone is commonly found when teeth are crowded.5
There is a strict relationship between crowding and periodontitis because anterior teeth migration is enhanced by periodontal disease, leading to a further crowding in lower arch, which then hinders a proper periodontal health.6 Sanavi demonstrated that deep bite is directly related to periodontal breakdown due to soft tissue impingement on the upper and lower incisors (Fig. 16.1).7 Furthermore, multiple types of occlusal contacts have been associated with deeper probing depths: premature contacts in centric relation, posterior protrusive contacts, balancing contacts, combined working and balancing contacts, and length of slide between centric relation and centric occlusion.8 Another correlation was found in mesially inclined molars where the periodontal destruction was 10% greater than that found in normally inclined teeth.9
Orthodontic treatment in patients with periodontal disease
Orthodontics is needed in combination with periodontal and prosthodontic treatment to treat patients with a secondary malocclusion or in whom there is aggravation of an existing malocclusion related to periodontal disease.2 Despite the high number of published articles, there is still a lack of good evidence about many of the treatments, including orthodontics and periodontal therapy.10
The prevalence of pathologic tooth migration (PTM) among periodontal patients has been reported to range from 30.03% to 55.8%; periodontal bone loss appears to be the major factor in the etiology of PTM.11 In a recent study, Khorshidi et al. found that pathologic migration prevalence was 11.4% (35/314 patients); however, there was no pathologic migration in patients with mild chronic periodontitis. PTM prevalence is increased by the severity of periodontal disease, and no statistically significant difference between males and females was found.12
In early stages of PTM, spontaneous correction of migrated teeth sometimes occurs after periodontal therapy. When only a light degree of pathologic migration is considered, it has been hypothesized that this is due to wound contraction during healing (Fig. 16.2).13 Soft tissue forces of the tongue, cheeks, and lips are known to cause tooth movement and in some situations can cause PTM. The transseptal fibers play a key role in PTM by forming a chain from tooth to tooth and helping maintain contacts between teeth. If the continuity of the chain is weakened by periodontal disease, the balance of forces is upset, and displacement of the teeth can occur (Fig. 16.3).
Occlusal factors such as posterior bite collapse, shortened dental arches, occlusal interferences, and bruxism are connected to the etiology of PTM.
Patients with periodontal issues are commonly characterized by general flaring with spacing between the upper incisors, deepening of the bite (sometimes extrusion of a single tooth can occur), increased overjet, and crowding in the lower incisor region.14 Interposition of the lower lip behind the flared incisors can worsen the situation. An orthodontic treatment provided without a proper oral hygiene can result in iatrogenic damages: Moving a tooth into an infected infrabony defect can enhance the destruction of connective tissue.15 However, a combined ortho-perio treatment is efficient in the treatment of periodontitis and could effectively decrease the levels of inflammatory cytokines.16 Furthermore, the treatment should aim for the patient’s expectations and aesthetic goals.
Orthodontic treatment can allow the optimization of clinical situations17 such as:
Orthodontic treatment is indicated when the worsening of periodontal status can be promoted by tooth malposition such as:
Orthodontic treatment is mandatory when:
Diagnosis and treatment planning
Patient expectations
A very careful consideration of the patient’s chief complaint is due in order to clearly determine the patient’s needs and plan realistic treatment goals.18 These objectives generally should be economically, occlusally, periodontally, and restoratively realistic.17 The preliminary periodontal assessment is a fundamental screening process during which adherence to issues of home oral hygiene and regular appointment attendance is determined (Fig. 16.4).19
Multidisciplinary team
Since several skills and knowledge are needed to provide full treatment planning, in addition to a periodontist and an orthodontist, a restorative dentist, prosthodontist, and oral or maxillofacial surgeon can be involved. The importance of the team approach in achieving the best possible results in the management of adult orthodontic patients with bone loss cannot be overstated.20 In this phase, good communication between specialists is mandatory, and roundtable discussion is required to discuss complicated cases.21
Periodontal assessment
Main concept: orthodontic tooth movement without preexisting inflammation.
Periodontitis is characterized by microbially associated, host-mediated inflammation that results in loss of periodontal attachment. The bacterial biofilm formation initiates gingival inflammation and promotes tissue breakdown (Tables 16.1 and 16.2).22
Table 16.1
| DISEASE SEVERITY AND COMPLEXITY OF MANAGEMENT | |||||
| Stage I: Initial Periodontitis | Stage II: Moderate Periodontitis | Stage III: Severe Periodontitis With Potential for Additional Tooth Loss | Stage IV: Advanced Periodontitis With Extensive Tooth Loss and Potential for Loss of Dentition | ||
| Evidence or risk of rapid progression, anticipated treatment response, and effects on systemic health | Grade A | Individual Stage and Grade Assignment | |||
| Grade B | |||||
| Grade C | |||||
Table 16.2
| PERIODONTITIS STAGE | Stage I | Stage II | Stage III | Stage IV | |
|---|---|---|---|---|---|
| Severity | Interdental CAL at site of greatest loss | 1–2 mm | 3–4 mm | ≥5 mm | ≥5 mm |
| Radiographic bone loss | Coronal third (<15%) | Coronal third (15%–33%) | Extending to mid-third of root and beyond | Extending to mid-third of root and beyond | |
| Tooth loss | No tooth loss due to periodontitis | Tooth loss due to periodontitis ≤4 teeth | Tooth loss due to periodontitis of ≥5 teeth | ||
| Complexity | Local | Maximum probing ≤4 mm | Maximum probing depth ≤5 mm | In addition to stage II complexity: | In addition to stage III complexity: |
| Mostly horizontal bone loss | Mostly horizontal bone loss | Probing depth ≥6 mm | Need for complex rehabilitation due to: | ||
| Vertical bone loss ≥3 mm | Masticatory dysfunction | ||||
| Furcation involvement class II and III | Secondary occlusal trauma (tooth mobility ≥2) | ||||
| Moderate ridge defect | Severe ridge defect | ||||
| Bite collapse, drifting, flaring | |||||
| <20 remaining teeth (10 opposing pairs) | |||||
| Extent and Distribution | Add to stage as descriptor | For each stage, describe extent as localized (<30% of teeth involved), generalized, or molar/incisor patter | |||
The primary goal is to eliminate periodontal disease and stabilize the dentition. The clinical and radiologic assessments of the periodontal situation are mandatory before treatment planning. Assessment also enables the identification of recessions, horizontal bone loss, and lesions such as crater defects (one-, two-, and three-wall defects and furcation defects).
Limiting factors are:
Prior to orthodontic treatment, the following can be performed:
It is mandatory that the orthodontist and periodontist discuss the management of periodontal issues and plan the correction.23
Patients with a malocclusion may present with preexisting mucogingival problems or fragile periodontal support that is susceptible to attachment loss during or after orthodontic treatment (Fig. 16.5).24 A proper amount of attached gingiva is needed to dissipate the mechanical trauma induced by mastication and tooth brushing. If teeth are inside the alveolar ridge, predictable soft tissue grafting procedures such as the subepithelial connective tissue graft (SCTG) and the free gingival graft (FGG) may be performed prior to tooth movement to prevent gingival recession.25
In a systematic review, Kloukos et al. investigated the indication and timing of soft tissue augmentation in orthodontic patients. No randomized controlled trial was identified, and only limited data were available.26 Furthermore, osseous defects cannot allow many adult patients to clean teeth adequately and require correction prior to or during orthodontic therapy. These osseous defects include interproximal craters; one-, two-, and three-wall defects; furcation defects; and horizontal defects. Interproximal craters are two-wall defects, where attachment loss occurs on the mesial and distal surfaces of the adjacent roots and the remaining walls are the buccal and lingual ones. Orthodontic movement cannot improve interproximal craters; if the crater is mild to moderate, then resective surgery and bone recontouring should be executed.
In one-wall defects, there has been destruction of three of the four interproximal walls, leaving one wall remaining. These defects are difficult for a periodontist to manage because resection could be too destructive and regeneration is inappropriate. Orthodontic eruption of the tooth can eliminate the defect associated with occlusal reduction.27
Three-wall defects must be treated prior to orthodontics with regenerative therapy.28 A provisional splinting of the teeth undergoing periodontal surgery is needed to provide stabilization. Roccuzzo et al. demonstrated that the enamel matrix derivative (EMD) alone and in association with various grafts give the best results for the treatment of intrabony defects, with improvements in terms of clinical attachment level (CAL) gain and pocket depth (PD) reduction. In this study, the orthodontic treatment was initiated 8 to 12 months after guided tissue regeneration (GTR) procedures and aimed at correcting malposition, creating contact points, and providing nontraumatic occlusion.29
Since the fibroblastic and osteoblastic turnover is necessary to heal the defect before moving the adjacent teeth, the timing of orthodontic treatment after regenerative therapy is still debated.30–32 Sanz et al. recommended waiting to begin orthodontic therapy until at least 6 months after the completion of periodontal regenerative therapy to carry out the movement in fully healed sites.33
Furcation defects are typically divided into three classifications: class 1, 2, or 3. Class 1 furcation defects are usually monitored during orthodontic therapy. Class 2 and 3 furcation defects should be treated by the periodontist before the orthodontic treatment to allow a proper hygiene. Sometimes, if the periodontal health of adjacent teeth can be maintained, hopeless teeth are used during orthodontic treatment to provide anchorage and occlusal function for the patient.
The orthodontist must evaluate the horizontal bone loss because there is an alteration of crown/root ratios. If horizontal bone loss has occurred in only one area, reduction of crown length will avoid the creation of bony defects between adjacent teeth after leveling.
During orthodontic treatment, the following can be performed:
After orthodontic treatment, the following can be performed:
Orthodontic assessment: Determination of final occlusion
Dental history in adult patients should not be overlooked and, along with restorative requirements, is a key factor in determining the final occlusion. A specific evaluation of parafunctional habits, temporomandibular disorders, cracked teeth, and wear facets is mandatory (Table 16.3). Particular focus is on the following:
Table 16.3
| Issues | Goals |
|---|---|
| Crowding | Alignment |
| Flaring | Closure of diastemas and retraction, intrusion |
| Black triangles | Reshaping by interproximal reduction, retraction, intrusion |
| Bone peaks and gingival margins need leveling | Intrusion/extrusion |
| Removal of occlusal interference | Retraction and intrusion, selective grinding |
| Worn/lost teeth | Prosthetic rehabilitation/space closure |
| Prevention of relapse | Retention |
Considerations
Every orthodontic tooth movement beyond the cortical plate should be avoided. Gingival recessions can be related to excessive expansions and movements outside the alveolar bone housing (i.e., when an alveolar bone dehiscence has been created) (Fig. 16.6).34 Vanarsdall suggested that patients with a transverse skeletal maxillomandibular discrepancy greater than 5 mm are susceptible to recessions, especially if palatal expansion is needed.35 With the introduction of three-dimensional (3D) imaging in orthodontics, a diagnosis in three planes of space can be obtained with relative ease and minimal radiation.36
In a recent study on adolescent patients, an evaluation using cone-beam computed tomography (CBCT) scans before and after orthodontic alignment stated that bone thickness (BT) decreased and height from the cementoenamel junction to the alveolar crest (BH) increased significantly for the incisors and mesiobuccal root of the first molars. Arch dimensions generally increased together with tipping, and expansion related to alignment resulted in horizontal and vertical bone loss at the incisors and mesiobuccal root of the first molars. Thinner BTs and more severe crowding before treatment increased the risk for buccal bone loss.37 As extraction may worsen the soft tissue profile, especially in adult patients, protraction of the lower incisors is an alternative dealing with cases of lower crowding or increased overjet. A beneficial effect on the soft tissue profile through smoothing of the mentolabial sulcus can be achieved, but the optimal position of the lower incisors is still not clear.
No association between proclination and gingival recession has been found by Artun and Grobéty,38 while others consider lower incisor proclination a risk.39 Diedrich40 stated that the specific anatomy must be taken into consideration, such as the gingival health and the force system.
The morphology of mandibular anterior alveolus differs in hypodivergent, hyperdivergent, and norm divergent patients, but the evaluation of symphysis morphology on cephalometric radiographs might not be a solid method aimed at predicting gingival recession in the anterior region of the mandible. The relationship between periodontal status of mandibular incisors and selected cephalometric parameters has recently been investigated: the width of keratinized gingiva (WKT) was found to correlate with ANB, WITS, and symphysis length, while gingival thickness (GT) was associated with WITS and symphysis length. Both WKT and GT are regarded as significant risk factors for gingival recession.
In a recent study, no higher occurrence of gingival recession in cases of pronounced proclination of lower incisors without violating the osseous envelope of the alveolar process has been found. It can be speculated that if the gingiva maintains appropriate thickness, it is more resistant and less affected by tension from large proclination.41 In a retrospective study, Melsen found that gingival recession on mandibular incisors was not significantly increased during orthodontic treatment. Thin gingival biotype, visual plaque, and inflammation are useful predictors of gingival recession.42
Teeth can be moved with their surrounding periodontium when careful attention is paid to local anatomy and periodontal health. Furthermore, tooth movement with or through bone can be provided using different force systems.43 When an optimal oral hygiene has been achieved, it is possible to apply orthodontic forces, even if the periodontal tissue has reduced connective tissue attachment and alveolar bone height.44,45 Traditional fixed orthodontic appliances induce microbial changes toward periodontopathogenic anaerobic bacteria because of the increased plaque accumulation.46 These effects are normalized after removal of orthodontic appliances without lasting detrimental effects, but in some patients there is a significant risk for irreversible periodontal destruction.47 Thus the use of clear aligners that promote a better periodontal health when compared to fixed appliances48–50 may be the optimal choice in patients with periodontal involvement. With clear aligners, it is possible for good control of oral hygiene throughout treatment, while the first months with fixed appliances are always difficult to manage.51
The forces and moments generated by aligners of the Invisalign system are always within the range of orthodontic forces.52 The forces and couples delivered by aligners are determined by the shape of the crown and the type and amount of displacement of the particular tooth and therefore the contacts between tooth and the inner surface of the appliance. Tipping movement is predictable with thermoplastic appliances, but difficulties about root control have been reported.53
Since the gingival margin of the aligner is elastic, it is not surprising that an aligner would have difficulty controlling the forces applied in this region. The introduction of Power Ridges demonstrates that when a torque correction of about 10 degrees is required, torque loss is negligible. The force couple generated by a thermoplastic aligner torquing an upper incisor consists of a tipping force near the gingival margin and a resulting force produced by movement of the tooth against the opposite inner surface of the appliance, near the incisal edge.54 The undesirable mesial movement of first molar compensation requires programmed forward mesial root rotation, in effect producing crown tipback rotation.55
In an in vitro study, Simon et al.56 investigated the influence of auxiliaries, such as attachments and Power Ridges, on performing root movements of upper central incisor torque. A loss of torque up to 50% must be considered; however, it must be noted that the efficacy of fixed orthodontic appliances does not reach 100% either. Conventional orthodontic brackets and wires do not completely fill the bracket slots so that the wire is able to twist, leading to a loss of moment known as torque play. The loss of torque between an arch of 0.019 × 0.025 in. section (usual size for the final stages of orthodontic treatment) and a 0.022 × 0.028 in. slot is about 10 degrees.
A more recent study stated that Invisalign is able to achieve predicted tooth positions with high accuracy in nonextraction cases.57 Lombardo et al.58 stated that some tooth movements can be achieved with aligners more easily than others. In particular, vestibulolingual tipping and rotation reached 72.9% and 66.8% of the prescribed movement, respectively. In a retrospective study, Sfondrini et al.59 found no differences between aligners and brackets about buccolingual inclination control on upper incisors. These studies led to different conclusions probably because of the development and improvements in materials, technologies, and treatment protocols. Several factors are involved in determining successful tooth movement: the attachment’s shape and position, the aligner’s material and thickness, the amount of activation present in each aligner, and the techniques used for the production of the aligners.60
Treatment outcomes depend also on the patient’s characteristics, bone density and morphology, crown and root morphology of teeth, as well as on factors related to the clinician such as the accuracy in performing the requested amount of interproximal reduction (IPR), which is usually underestimated.
The plastic foil used for the fabrication is thinned out by thermoforming at the gingival edge of the aligners, thus representing the area where they are less rigid. Furthermore, to avoid loss of anchorage, simultaneous movement of multiple teeth should not be performed.
Planning clear aligner therapy (CAT) with virtual setup software facilitates choosing an appropriate number of anchor teeth and the proper sequence of tooth movement to minimize the risk of anchorage loss.61 However, an aligner alone cannot provide proper anchorage control, especially in situations in which tooth morphology is not favorable (i.e., small clinical crowns, reduced undercuts). To overcome clear aligner limitations, the development of effective attachments (rectangular and vertical), for both anchorage management and better root control, is increasing. The use of conventional bulk-fill resins for the attachment creation leads to a higher precision.62
The 3D planning, especially when associated with CBCT data, can allow a proper control; moreover, the velocity of movements can be selectively slow (0.12 mm/20 g/14 days). A CBCT examination is useful to evaluate the spatial position of the teeth within bone. They may be positioned off-axis and present radiographically with fenestrations and dehiscences.24 Anticipated orthodontic treatment can improve tooth position in the bone so that mucogingival deficiencies can be subsequently reevaluated (Fig. 16.7).63
In periodontal patients there is interproximal bone loss, and the periodontal objectives are more valuable than the occlusal ones. The role of the orthodontist should be leveling the bone peaks. The marginal ridges are not always helpful for positioning the posterior teeth. If they are worn or abraded, it is more important to find the best position to facilitate restoration.
Tooth shape is another factor with great importance in treatment planning. In the majority of patients, we find three main tooth shapes: rectangular, triangular, and barrel-shaped teeth. Especially when the crown has a triangular shape, the distance between the bone crest and the contact point is relatively large, and the interproximal papilla tends to be absent. Tarnow demonstrated that the papilla is present in 100% of cases when the distance from the contact point to the interdental bone crest is 5 mm or less.64 Since adults have narrower pulp chambers, IPR can be performed and black triangles closed (Fig. 16.8).
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