Exposures for orthodonticsExtrusionsSoft and hard tissue correctionImplant site development
The adjunctive relationship between orthodontics and periodontics is both complex and symbiotic. Both specialties rely on each other’s principals and expertise to accomplish their respective goals. Advances in material science and technical developments have changed the outlook on how we treat patients and what is clinically possible. The interactions of the two have led to a series of proposed goals and guidelines that can be realized . They include:
Improved cleansability by reduction of crowding
Vertical positioning changes to reduce osseous resective needs
Alignment of maxillary gingival margins to avoid surgery
Forced eruption for traumatic fractures
Embrasure change to regain papillary form
Improved spacing for dental implants
13.2 Patient Evaluation
Of paramount importance, prior to performing any procedure, is the formulation of a proper diagnosis. The medical and dental histories must be carefully reviewed for any needed precautions or contraindications that may influence treatment planning. Diagnosis should be based on clinical findings and confirmed radiographically. Marked technological improvements in radiography have had a significant impact on the accuracy of analysis. Most procedures require simple imaging techniques. These include roentgenograms and orthopantomograms. For more complex procedures such as exposure of impacted teeth, the use of cone beam computed tomography (CBCT) is essential . This affords the clinician the ability to accurately determine the position of the impaction in three dimensions. Until the advent of this tool, the guesswork of periapical radiographs using Clark’s rule (tube-shift technique or SLOB rule) was always present . Intraoperatively, procedural progress in many areas may be determined by either periapical or CBCT analysis, depending on the situation.
13.3 Exposures of Impacted Teeth
Of historical interest is the evolution of exposures of impacted teeth. Until the development of direct bonding of orthodontic devices, practitioners were limited in their abilities to move impacted teeth. An example of this was the use of wire ligation [4, 5]. The ligature was placed around the cervical neck of the tooth and then attached to the orthodontic appliance. Control of mechanics was haphazard. The use of dental adhesives beginning in the mid-twentieth century changed that dramatically . Multiple generations and advances in etching and adhesive materials have improved our abilities to accurately bond teeth. As a result, mechanics have been made more predictable. A variety of devices are now available for bonding to an impacted tooth. These include buttons, cleats, chains (single and double) in a multiplicity of varieties, and direct bond brackets. The most prevalent impacted tooth, aside from third molars, is the maxillary canine. A number of theories have been proposed as to the cause of impactions. These may be localized or generalized and range from tooth size to arch discrepancies or even idiopathic in nature, etc. Specific causes include endocrine and febrile diseases and irradiation. Buccal impactions are usually attributed to inadequate arch space or vertical developmental position. Palatals, according to the guidance theory, are caused by local predisposing factors which interfere with the path of eruption. Genetics is also a significant cause . These have been cited in the literature as occurring in about 1–5% of cases [8, 9]. They are more prevalent in the Caucasian population and occur in the palate about 85% of the time . The female predilection of occurrence is about 2:1 with bilateral incidence occurring in 8% of individuals [7, 11].
13.3.1 Canine Exposures
Because of differences in accessibility, buccal and palatal exposures must be approached differently. Though canines located on the buccal would seemingly be easier to expose, careful diagnosis of their relative position is essential. For those located close to the bony crest and having little cortical plate, a simple gingivectomy, removal of the thin plate of the bone and follicle, may suffice. This is provided that there is adequate keratinized tissue and a bracket can be placed. Important in management of these and all related procedures is the sufficient exposure of the crown of the tooth. Incumbent on the surgeon is the knowledge of intended mechanics to bring the tooth into proper alignment. For those teeth located coronal to or at the mucogingival junction, a pedicle flap with apical positioning is indicated. This is provided that there is adequate vestibular depth (Fig. 13.1). Both of these scenarios require a single intervention. The gingival flap is positioned apical to the bracket. Ligation can be done directly with the orthodontic appliance. In cases where the impaction in question is located beyond the possibility of apical flap positioning, a two-step approach is required. The crown of the tooth is bonded to a chain, a wire (attached to the chain) is extended through the edge of the incision, and the tooth is brought into position through the flap. Subsequently, keratinized tissue may be augmented to the cervical area of the previously impacted tooth if necessary. The patient must be informed of this possibility at the initial stage of planning.
Palatal impactions should be approached using a full-thickness mucoperiosteal flap (Figs. 13.2 and 13.3) with adequate extension for access and hemostasis. This is particularly critical with impactions that are extensively covered by bone. It is imperative that a dry field be obtained in order to effect a proper bond of a chain to the tooth. Local anesthetics with a vasoconstrictor, hemostatic agents, and careful handling of the flap are normally adequate. If untoward position of the tooth makes adhesion of a bond unfeasible on either the buccal or lingual of the crown, lateral aspects must be used until the eruptive sequence allows bonding in a more appropriate area. The crown is gently manipulated with an elevator, or similar instrument, to evaluate patency of the periodontal ligament. The entire occlusal aspect must be free of bony encumbrance to insure its ability to be moved. Studies have not shown a difference in outcomes between open and closed techniques in which the crown is either exposed or unexposed postoperatively . If the operator chooses the former, exposure will be determined by the position of the crown in relation to the edge of the reflected flap. That distance dictates either removal of marginal tissue or creation of a stoma in the tissue for exit of the chain attachment to the appliance.
13.3.2 Other Impaction Exposures
Impactions of other teeth may occur individually or coincidental with others (Fig. 13.4). Similar principles apply to their exposure as well. On occasion, teeth close to the surface of the gingiva with an unimpeded exit path may erupt with the simple removal of occlusal tissue. Many times, trauma to an area may prevent eruption of a succedaneous tooth, and the simple removal of tissue is the only procedure needed (Fig. 13.5).
Complications including postoperative bleeding and infection should be managed appropriately and expeditiously. Careful surgical and bonding techniques reduce the potential for debonding of either a bracket or chain. When it does happen, further procedures are indicated. Patients need to be informed of the potential problems prior to intervention, not after the fact.
13.4 Mucogingival Therapy in Orthodontics
Tooth eruption activity dictates a significant portion of the gingival biotype. The position of teeth with regard to the dentoalveolar process also plays an important role in the dimension of that phenotype . The effect of orthodontic movement on the periodontium is controversial . Several authors state that well-aligned teeth with optimal occlusal relations will provide a physiologic process of auto-cleansing. This allows for plaque removal with well-managed plaque control when there are closed contacts [15, 16]. Current bias concerns itself with augmentation of soft tissue in thin biotypes. The rationale is that of prevention of future mucogingival recession [15, 17, 18]. Accordingly, a wide and thick keratinized attachment apparatus is therefore critical to resist orthodontic forces, especially in arch expansion. In addition, it resists functional and physiologic trauma. A more conservative approach is one of careful observation and monitoring on the part of the orthodontist and general practitioner for signs of change. Should they occur, action to remedy the problem should be considered. These include inflammation of the gingival marginal tissue as well as progressive recession. A significant number of procedures are available to augment soft tissue. Location and anatomy of the site should be given consideration as to the appropriate modality. Soft tissue augmentation is discussed in the chapters by Chambrone et al., Zadeh et al., and Wong in this volume.
13.4.1 Free Soft Tissue Autografts
Current assumptions state the need for 2 mm of keratinized tissue in individual with thin phenotypes [15, 19, 20]. Tooth movements to the facial (expansion) and extrusion are most likely to incur negative alterations in the mucogingival complex, thus increasing the risk of dehiscence or recession [13, 21–24]. Soft tissue autografts are believed to be the gold standard as a surgical option by which thin areas devoid of keratinized tissue can be augmented. This is the most reliable option for tissue gain [22, 25–28]. A recipient site is prepared, and donor tissue is usually taken from the surface of the hard palate. This tissue is typically characterized by a superficial layer of epithelium with the underlying layer being connective tissue in nature. Widths range from.8 mm to 1.6 mm in dimension . Although active tooth movement may proceed during surgical intervention, if the need for grafting is advisable prior to therapy, grafting should be considered beforehand to avoid exacerbation of the condition . The decision to graft is based not only on the amount of keratinized tissue present but also the frenum and vestibular position. Expected outcomes of this therapy include a thickened band of keratinized tissue, able to resist abrasion, reduction of frenum pull, if present, and increased vestibular depth (Fig. 13.6). This provides the patient better auto-cleansing and better access for personal oral hygiene. Alternative materials can be substituted for autografts and include allografts, xenografts, and synthetic materials. These may be used in conjunction with biologics to produce similar outcomes in regard to the gain in keratinized tissue. They afford the benefit of the elimination of a donor site, thus decreasing morbidity and surgical donor time [30, 31]. Randomized controlled trials and clinical control for long-term findings are needed to provide proof of greater efficacy of one technique over another.