Pre-Orthodontic Periodontal Considerations: Establishing a Rationale and Timeline for Periodontal Intervention

Introduction:
The proliferation of novel appliances in modern orthodontics, that are discreet or even completely undetectable, has encouraged a growing number of patients from adolescents to adults to seek out treatment. While referrals to an orthodontist are often made to address functional problems, esthetic reasons are an equal (if not more common) basis for addressing tooth malocclusions.¹ Multi-disciplinary treatments are often necessary to obtain a satisfying clinical result that improves appearance.² The goal of preventive periodontal surgery is to increase the health and soft tissue coverage around “at-risk” teeth before orthodontic treatment begins. This will ensure that there is adequate circulation to the hard and soft tissues to enable tooth movement without adverse long-term effects to the support of said teeth. While published literature often suggests that treating gingival recessions is easier and more predictable if carried out before it advances³, there are many instances where periodontal surgery during or after orthodontic treatment may be advantageous. Considerations such as the patient’s age, tolerance of dental procedures, development of the orofacial skeletal structures, depth of the vestibule and position of the teeth on their alveolar housing must all be weighed during the pre-orthodontic assessment. A gingival graft must be considered when buccal orthodontic movement of lower anterior teeth may lead to osseous dehiscence and subsequent gingival recession.⁴ If a pre-existing defect is diagnosed then gingival thickening procedures or grafting must be considered before orthodontic treatment begins. A periodontal diagnosis can be made only after a detailed and reproducible clinical examination (“charting”) has been performed. The results of this charting will lead directly to either initiating orthodontic treatment or to preliminary corrective treatment before initiating the orthodontic phase.

Protective Role of the Soft Tissue:
The definition of healthy soft tissues that surround both natural teeth and dental implants is composed of a zone of keratinized and attached gingiva (the “ZAG”) and elastic alveolar mucosa.⁵ These two tissues are clearly demarcated into clinically identifiable zones by the mucogingival junction (MGJ). The free gingiva begins at the gingival margin, which is normally located 1 to 3 mm coronal to the cemento-enamel junction (CEJ) and extends to the base of the gingival sulcus. The attached gingiva refers to the tissue that is firmly bound by Sharpey’s fibers to the cementum of the tooth and underlying bone and begins at the base of the gingival sulcus in health – or periodontal pocket in disease – and extends to the MGJ. The apical migration of the free gingival margin results in the exposure of root cementum which defines “gingival recession”.⁶ Root exposure may create painful tooth sensitivity that limits the patient’s function and/or behaviour. It may also be aesthetically unacceptable. More importantly, it is associated with concomitant bone loss whose clinical significance cannot be overlooked. Gingival recession results in persistent plaque accumulation, root caries, and cervical abrasion and erosion. Gingival recession is a common clinical finding that affects almost 90% of the North American population.⁷

In ideal conditions, and with optimal oral hygiene, gingival health can usually be maintained with as little as 1 or 2 mm of ZAG (referred to as minimal ZAG or “MZAG”).⁸ However, real world circumstances and behaviours often preclude those ideal conditions, and so soft-tissue grafting procedures are often indicated to establish and/or maintain health.⁸ Clinical situations in which grafting is indicated include the following:

• Chronically inflamed areas of MZAG or no ZAG where the alveolar mucosa prevents optimal plaque control.
• MZAG or no ZAG sites compromised by a frenum pull or shallow vestibule.
• Sites with evidence of advancing recession.
• Areas where planned orthodontic movement risk positioning the roots of a tooth/teeth prominently, thereby thinning the protective gingival covering.⁹
• Areas where planned orthodontic movement will tip a tooth/teeth tipped lingually, resulting in buccal displacement of the roots.
• Sites planned for restorative treatments where margins may extend subgingivally and impinge upon the biologic width.¹⁰
• In collaboration with denturists or when removable protheses are designed with clasps that risk irritating the marginal tissues.
• Areas where recession presents an aesthetic concern to the patient.
• Areas where root exposure has resulted in tooth sensitivity.
• Prophylactically, where any of the factors mentioned above should be considered to help reduce future complications.

Pre-orthodontic Periodontal Evaluation:
Periodontal examination and diagnosis are critical first steps in the pre-orthodontic work-up prior to initiating treatment. This prerequisite is even more apparent when the patient has completed skeletal growth, as in adult orthodontics. The periodontal examination aims to identify two main categories of potential pathology:

1. Active inflammatory or infectious periodontitis: such as gingivitis and periodontitis, which must be treated thoroughly before and throughout orthodontic treatment.
2. Deficient supportive periodontal tissues: during the pre-treatment evaluation, these conditions must be differentiated into either osseous, soft tissue or a combination both types of deficiencies.

Each type of defect and their individual characteristics will influence the orthodontic plan. For example, horizontal bone loss compromises the osseous support of the affected teeth and will subsequently demand reduced orthodontic forces based on the crown-to-root ratios and the apical migration of their points of rotation. Horizontal osseous deficiencies around multirooted teeth may not be easy to diagnosis, and so a thorough clinical examination with advanced three-dimensional imaging might be necessary reduce the risk of overlooking them. However, even with additional diagnostic testing, bone defects such as fenestrations and dehiscences can still be missed. These will ultimately affect the results of the orthodontic treatment.¹¹ It cannot be stressed enough that a comprehensive consultation that addresses these realities must be part of the informed consent process.

Soft tissue deficiencies are evaluated based on three components:

1. The thickness of the gingiva.
2. The amount of ZAG.
3. The presence/severity of any gingival recessions.

The first component is categorized between patients presenting a thick periodontal biotype and those with a thin periodontal biotype.¹² With the recent 2017 American Academy of Periodontology World Workshop on Disease Classification, biotypes are now described by their gingival “phenotypes”.⁵ Appreciating the gingival phenotype will help the clinician predict how fast recession or attachment loss may occur. Employing gingival phenotype as a prognostic indicator for further gingival recession/attachment loss is a skill that clinicians learn over time with clinical experience.

Phenotype integrates the following components of the mucogingival complex in arriving at a classification:

• The gingival thickness (GT).
• Keratinized tissue width (KTW).
• Gingival morphotype (GM)
• Bone morphotype (BM)
• Tooth dimension.

Utilizing these parameters, three categories¹³ emerge:

1. Thin scalloped phenotype: teeth will present with a narrow ZAG, translucent and delicate gingiva superimposed on a relatively thin alveolar bony housing. Light tension applied to the lips and/or cheeks will often cause blanching of the gingiva thereby exposed fine blood vessels and root prominences. These teeth are usually associated with narrow triangular crowns with a buccal profile that is more subtly convex and with interproximal contacts that are proximal to the incisive edge.
2. Thick flat phenotype: teeth will present with a broad ZAG demonstrating thick fibrotic gingiva and a comparatively thick alveolar bony housing. The coronal tooth morphology tends to be square with increased cervical convexity and a proximal contact that is located more apically.
3. Thick scalloped phenotype: teeth will present with a narrow coronal band of thick fibrotic gingiva and a pronounced gingival scallop. This phenotype is a hybrid of the two phenotypes described above with the coronal aspect having characteristics consistent with a thick phenotype and the apical aspect having mucogingival characteristics that are more like a thin phenotype.

The amount of ZAG is easily measured in millimeters with a periodontal probe. When it measures less than 3 mm, it is typically insufficient to maintain periodontal health around natural teeth or dental implants manifesting itself with characteristic inflammation.

Finally, gingival recession results when the marginal tissue migrates apical to the cementoenamel junction (CEJ), exposing the root surface. Recession is measured from the CEJ to the coronal tissue margin. In addition, it is important to measure and monitor the width of attached gingiva, which can be determined by measuring the distance from the coronal margin of the gingiva to the mucogingival junction (MGJ) and subtracting the sulcular probing depth. At times, especially if the gingiva is thin, it can be challenging to identify the MGJ. Gently rolling the mucosa with an instrument such as a periodontal probe can be helpful in locating the apical extent of the attached gingiva. The position of frenum attachments should also be noted as part of the mucogingival evaluation. A frenum attachment at or near the gingival margin may contribute to recession. Gingival recessions are identified according to the classification system described by Miller in 1985⁶ and divided into 4 categories:

• Class I: Exposure of root dentin present with the free gingival margin resting coronal to the mucogingival junction. There is no evidence of any interproximal soft tissue loss. The recession is superimposed on healthy periodontium.
• Class II: Exposure of root dentin present with the free gingival margin resting at or apical to the mucogingival junction. There is no evidence of any interproximal soft tissue loss.
• Class III: Exposure of root dentin present with the free gingival margin resting coronal to the mucogingival junction. There is concomitant loss of interproximal soft tissue (papillae). The recession is superimposed on healthy periodontium.
• Class IV: Exposure of root dentin present with the free gingival margin resting at or apical to the mucogingival junction. There is concomitant loss of interproximal soft tissue (papillae).

Additional Considerations:

1. Patient Behavior: The patient is routinely controlling plaque without inflicting trauma excessive brushing and damaging flossing technique. If control of gingival inflammation cannot be satisfied and verified over a period of several months, withholding periodontal and/or orthodontic treatment should be considered.
2. Subjective Observations: The presence of sensitivity at the site of the recessions, or if an esthetics problem is caused by the recessions.

In all cases, it is preferable to perform periodontal intervention prior to the initiation of the orthodontic phase of treatment. This sequence aims to mitigate the worsening or creation of a new gingival defect. Periodontal treatments that augment the ZAG originate from the 1950’s when Friedman defined mucogingival defects and described denudation and pushback procedures for their correction.¹⁴ In 1963, Bjorn described the first free gingival graft.¹⁵ In that study, free gingival grafts were used to gain keratinized attached gingiva by deepening the vestibule. This technique was first introduced to North America in 1964.¹⁶

Current Corrective Treatments:
Mucogingival defects can now be corrected by several techniques, including:

1. Laterally or coronally advanced pedicle grafts.
2. Coronally advanced flaps alone or in conjunction with barrier membranes or enamel matrix proteins. This category of techniques also includes “tunnelling” approach (or its well-publicized trademarked counterpart “the Pinhole Technique”).
3. Free gingival grafts.
4. Subepithelial connective tissue autografts and allografts.

Each technique has its indications, advantages, and limitations. However, the amount of root coverage that can be achieved through periodontal plastic surgery can be predicted based upon Miller’s classification of marginal tissue recession.³ Successful treatment is benchmarked against the ideal healing results of (a) complete root coverage; (b) the sulcus depth is 2 mm or less, and (3) there is no bleeding on probing.

Conclusion:
In treatment planning, the clinician must initially define factors influencing patient selection for treatment. This initial assessment and conversation with the patient is essential so that the patient’s expectation can be set at a reasonable level in regard to the complexity of the problem, the difficulties that may be encountered during the corrective procedure and the anticipated clinical outcome. Once the etiologic factors have been identified, it is important to educate the patient and provide instruction in any corrective behavior indicated. In addition to informing patients of their responsibility, they should be given the treatment options and alternatives with expected outcomes. The consequences of no treatment should be explained so that patients can make informed decisions about their treatment. A recent long term study demonstrated that 83% of sites receiving gingival augmentation maintained a reduction in recession for up to 35 years and 48% of untreated sites had an increase in recession.¹⁷ This study showed that thin biotypes remain more stable over time if grafting procedures are performed to thicken the tissue as compared to thin biotypes; however, highly motivated patients can prevent the development/progression of gingival recession and inflammation for more than 20 years. Like many dental and periodontal problems, early identification will generally result in a simple correction with a predictable outcome. Clinicians are encouraged to train their dental team members, and their patients, to identify recession, the associated symptoms, and patient complaints, as well as both surgical and nonsurgical solutions for correcting these problems. To do so will result in a more effective periodontal screening and maintenance program that will result in better patient care and orthodontic outcomes.

Oral Health welcomes this original article.

References

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About the Author

Dr. Yair Lenga received his DDS and Masters of Periodontology degrees from the University of Toronto and completed his dental residency at Mount Sinai Hospital. He currently works full-time in his private practice, Lenga Perio in midtown Toronto.