Republication: Conservative Management of Skeletal Class II Malocclusion with Gummy Smile, Deep Bite, and a Palatally Impacted Maxillary Canine

Skeletal

• Class II relationship due to the maxillary protrusion and relative mandibular retrusion (SNA 85°, SNB 78°, ANB 7°)

• High mandibular plane angle (SN-MP 39°, FMA 32°).

Dental

• Class II molar relationships: near full cusp bilaterally (6 mm)

• Overjet of 7.5 mm

• 100% impinging deepbite

• Retrusive upper incisors (U1 to NA 1 mm) with decreased axial inclination (U1 to SN 96°)

• Increased axial inclination the lower incisors (L1 to MP 102°).

Facial

• Convex profile (15.5°)

• Protrusive lips (2 mm/2 mm to the E-line)

• Hyperactive mentalis with the lips closed.

The American Board of Orthodontics (ABO) Discrepancy Index (DI)^[1] was 38 points as shown in the subsequent worksheet in worksheet 1 (p12) at the end of this report.

First option

Extract three teeth (retained URc, impacted UR3, and UL4). Move the UR4 into the UR3 position. Disadvantages for this treatment option include compromised dental esthetics and ipsilateral loss of canine guidance.

Second option

Extract two teeth (retained URc and impacted UR3), followed by prosthetic restoration with a fixed partial denture or an implant-supported prosthesis. The disadvantages for this approach include cost, loss of tooth structure for conventional prosthesis, implant failure if bone fixtures are used, and a potential compromise in both esthetics and function with either prosthetic option.

Third option

Extract the retained URc and align the dentition with a fixed passive self-ligating (PSL) appliance. Expose the impacted UR3 with an open window technique. Allow the impaction to erupt spontaneously,^[2] and then align the entire arch with full fixed orthodontics. Place maxillary anterior miniscrews to intrude the upper incisors for correction of the deep bite. Install maxillary posterior bone screws bilaterally in the infrazygomatic crests (IZC) to provide anchorage for retraction of the entire maxillary dentition. The perceived disadvantages for this option include increased treatment time and potential root resorption of UR2. After weighing the pros and cons, the patient preferred the least invasive, most conservative approach (Option 3) despite the treatment risks. On completion of active treatment, a gingivectomy is indicated on the labial surface of the maxillary anterior segment. Assuming there is adequate biologic width of the gingival attachment, as defined later in this report, a gingivectomy with a diode laser is indicated to increase the crown length of the dentition in the maxillary anterior segment (the esthetic zone).

Palatally impacted maxillary canines

After third molars, maxillary canines are the second most commonly impacted teeth, affecting approximately 2% of the population.^[4] Two-thirds of maxillary canine impactions are palatal, and the remaining third are transalveolar or labial to the roots of the adjacent teeth.^[5,6] The etiology for the location of palatally impacted maxillary canines is unknown;^[7] however, both guidance and genetic theories have been proposed.^[8,9] The guidance theory holds that the lateral incisor root serves as a guide for canine eruption, so a missing lateral incisor or deformed root interferes with the normal path of eruption. The genetic theory proposes an inherent predisposition to palatally impacted maxillary canines.^[10] There are multiple sequelae associated with canine impactions including: (1) migration of adjacent teeth, (2) internal or external root resorption of the impaction and/or adjacent teeth, (3) cyst formation, (4) infection, and (5) referred pain.^[11]

The maxillary canines are important keystones for optimal dental esthetics and function,^[12] so their proper eruption and alignment are a high priority. Proper diagnosis is critical for efficient surgical and orthodontic management of eruption anomalies. CBCT is a precise method for three-dimensional (3D) localization of an unerupted canine.^[13] Without 3D imaging, it is difficult to plan an efficient and relatively atraumatic uncovering of an impaction. CBCT imaging is also useful for planning the orthodontic mechanics to recover the canine and align it in the arch.

There are two methods for managing palatal impactions – preventative and surgical.^[5,14] Prevention with interceptive treatment is preferable if the problem is diagnosed at an early age. This approach for an unerupted maxillary canine involves extracting the deciduous canine, and then, orthodontically opening the space between the maxillary permanent lateral incisor and the primary first molar or permanent first premolar. Ericson and Kurol^[5] reported that removing the maxillary deciduous canine before 11 years of age has a differential effect on the normal eruption of the succedaneous canine. If the radiographic image of the canine crown is located distal to the midline of the lateral incisor root, 91% of the potentially impacted canines erupt normally [Figure 20]. However, the success rate decreases to 64% if the canine crown is located mesial to the midline of the lateral incisor root. Timely extraction of the deciduous canine is very effective for enhancing the eruptive potential of a canine, with a deviated path of eruption; however, the space opening must be carefully managed to avoid root resorption if the unerupted canine is near the roots of the adjacent lateral incisors and/or premolars.^[15]

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Figure 20

Illustration of the concept proposed by Ericsson and Kurol (1988) for prevention of maxillary permanent canine impaction by the timely extraction of the retained deciduous canine (outline dotted in white) and space opening if needed to accommodate the erupting canine. The probable success of the procedure depends on the sagittal position of the unerupted canine relative to the midline of the maxillary canine in a two-dimensional radiograph

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If prevention is not feasible, or the procedure fails to prevent the impaction, the most desirable approach is surgical exposure of the canine in combination with orthodontic treatment.^[14] This type of interdisciplinary treatment requires careful communication between the orthodontist, surgeon, and patient. Kokich^[2] described several advantages of preorthodontic uncovering and spontaneous eruption of the palatally impacted canine, when compared to the closed eruption technique. Removing the relatively thick palatal mucosa and bone covering the impacted canine allows for more predictable spontaneous eruption. However, in young adult patients, the passive pre-orthodontic eruption process requires almost a year, and the procedure is less predictable in adolescent patients.^[14]

For the present patient, miniscrew-guided eruption of the impacted canine was performed in conjunction with surgical uncovering and orthodontic treatment [Figure 21]. After exposing the impacted canine using a simplified open-window technique, the previously impacted tooth extruded 2-3 mm in 2 months. A miniscrew was placed on the labial surface for anchorage to guide the movement of the canine into the arch-form. As palatal impactions are moved facially, gingival accumulation on the labial surface is common and may result in an unesthetic short clinical crown. The excess gingival tissue is easily removed with a diode laser before bracket placement.^[16]

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Figure 21

The progression for the recovery and alignment of the palatally impacted right maxillary canine is shown in a series of occlusal photographs taken at monthly intervals from the start of treatment at zero months to completion of the initial alignment at 16 months

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Efficient management of impacted maxillary canines requires a proper diagnosis and thorough understanding of anchorage demands for proper alignment. Becker et al.^[17] analyzed a sample of 37 impacted maxillary canines and found that the most common reasons for failure to recover an impaction were related to two diagnostic deficiencies: (1) inaccurate assessment of the location and orientation of the impaction, and (2) failure to understand the anchorage demands for proper alignment.^[17] For the present patient, the CBCT image was used to plan the surgical uncovering and miniscrew anchorage. This approach resulted in ideal functional and esthetic alignment without periodontal or esthetic compromise.

Gummy smile

The ideal amount of gingival display when smiling is around 1–2 mm.^[18] Excessive maxillary gingival exposure is commonly referred to as “gummy smile.” The problem may be generalized or localized and has multiple etiologies.^[19,20] Extraoral factors include as follows: (1) short and/or hypermobile upper lip, (2) maxillary anterior dentoalveolar extrusion, and (3) vertical maxillary excess. Intraoral manifestations include gingival hypertrophy and altered passive eruption (APE).

APE occurs when the gums do not physiologically recede following active tooth eruption. Coslet’s^[21] classification of APE is based on the width of attached keratinized gingiva and the location of the osseous crest in relation to the CEJ. There are four classifications of APE: Type I Subgroup A, Type I Subgroup B, Type II Subgroup A, and Type II Subgroup B. In all four groups, the free gingival margin is located occlusal to the CEJ. Classification of APE is helpful in determining subsequent treatment,^[22] and a summary can be shown in Table 2.

Table 2 Coslet’s classification for altered passive eruption relates to the zone of keratinized gingiva and the osseous crest relative to the cementoenamel junction. The mucogingival junction is marked by the black-dotted line. The mucogingival junction is noted by a dotted line. Types I and II reflect the width of attached gingiva, and gingiva. Subtypes A and B are defined by the cementoenamel junction relative to crestal bone height dimension

	Type I-A	Type I-B	Type II-A	Type II-B
Zone of attached keratinized gingiva	Adequate	Adequate	Inadequate	Inadequate
Osseous crest in relation to the CEJ	Osseous crest is 2-3 mm apical to the CEJ	Osseous crest is at the CEJ	Osseous crest is 2-3 mm apical to the CEJ	Osseous crest is at the CEJ
Treatment	Gingivectomy	Gingivectomy + osseous surgery	Apically positioned flap	Apically positioned flap + osseous surgery

CEJ – Cementoenamel junction

APE-related, short clinical crowns were diagnosed as the etiology of the current patient’s gummy smile. Measuring gingival sulcus depth and bone sounding under local anesthesia to determine the level of crestal bone are important diagnostic tools for determining if a gingivectomy is indicated to correct gummy smile.^[23] The present patient exhibited an adequate zone of attached gingiva, and the bone sounding depth was found to be 5 mm. Based on Coslet’s^[21] classification [Table 2] of APE, the patient was classified as Type I-A (excessive gingival width), and a diode laser gingivectomy was deemed an appropriate treatment to enhance dental esthetics by increasing crown lengths in the anterior segment.

Diode laser

Gingivectomy and labial frenectomy

It is important to have a good understanding of biologic width before a gingivectomy procedure.^[24,25] Some symptoms of biologic width violation include persistent gingival inflammation, recurrent pocket depths, and tissue recession.^[24] Biologic width is a term that was coined by Cohen^[23] and is defined as the combined heights of the connective tissue attachment and epithelial attachment. In 1961, Gargiulo et al.^[26] reported the average connective tissue height was 1.07 mm, and the average epithelial attachment was 0.97 mm, leading to an average biologic width of 2.04 mm. The average depth of the facial gingival sulcus was 0.69 mm, thus the average total gingival height above the bone was found to be approximately 2.73 mm [Figure 22]. Kois^[27] rounded this value up to 3 mm and called it the biologic zone [Figure 22]. Maintaining a biologic zone of 3 mm is an important factor in maintaining a healthy dentogingival complex.

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Figure 22

A diagram of the periodontal attachment to a tooth illustrates the concept of biologic width: sulcus depth + width of the epithelial attachment + connective tissue attachment of collagen fibers directly into cementum occlusal to the alveolar bone crest. The total width of the biologic zone is ∼3 mm

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For the present patient, the 3 mm reserved for maintaining the biologic zone was subtracted from the 5 mm bone sounding depth, revealing 2 mm of gingival width could be safely removed with laser gingivectomy.^[28] As an additional procedure, the area of attachment for an impinging maxillary midline frenum was also removed with the diode laser, and the wound healed by secondary intention.

The word “LASER” is an acronym which stands for Light Amplification by Stimulated Emission of Radiation. Dental devices are generally classified as superficial and deep penetrating lasers.^[29] Diode lasers deeply penetrate the tissue and are well absorbed by hemoglobin, thereby producing a layer of coagulation within the soft tissues (hemostasis) that controls bleeding. Diode lasers are usually preferred for dental soft-tissue revision because of their precise cutting and coagulation ability. For orthodontic gingival hypertrophy, diode laser gingivectomy is reported to provide earlier healing and greater improvement in gingival health compared to scalpel surgery.^[30,31] Pre- and post-treatment comparison of gingival exposure when smiling is documented in Figure 23.

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Figure 23

Pretreatment (left) and posttreatment (right) lower facial photographs. The upper two views are a comparison of full smile before and after treatment. The lower two photos area similar comparison with the lips closed

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Posterior and anterior bite turbos

For the present patient, the use of posterior BTs opened the bite to permit the correction of buccal crossbite for the upper left premolars. The subsequent anterior BTs were installed on the lingual surfaces on the maxillary central incisors for correction of her deep bite. Because of the large overjet, anterior BTs were bonded more gingivally. BTs should not be used on endodontically treated teeth because the latter are more susceptible to fracture. Upright or lingually tipped maxillary incisors may require a correction in the axial inclination before installing BTs. Anterior BTs serve as vertical stops in occlusion at the desired vertical dimension of occlusion (VDO). Spontaneous eruption of the posterior dentition to the desired occlusal plane, consistent with the treatment VDO, was the primary mechanism for overbite correction. However, the vertical load associated with anterior BTs may result in intrusion of the upper and lower incisors.^[32-34]

Class II elastics

Class II elastics tend to retract the maxillary arch and extrude the maxillary anterior segment while rotating the plane of occlusion posteriorly (clockwise). The lower dentition compensates by posterior rotation of the mandible, opening of the VDO, extrusion of the posterior teeth, and increased axial inclination of the incisors. With respect to anterior dental segments, Class II elastics produce two predictable side effects: uprighting of the maxillary incisors and flaring of the mandibular incisors.^[35] To resist the incisal tipping effects of Class II elastics, higher torque brackets are indicated in the maxillary anterior and lower torque brackets are prescribed for the mandibular anterior.^[36,37] However, for the present patient, standard torque brackets were placed in both arches. This approach worked well for the lower arch because L1 to SN° improved from 102° to 97°. Unfortunately, the expected flaring effect of the intrusive force, anchored by the maxillary anterior miniscrews [Figure 12], was inadequate to counteract the side effects of the Class II elastics, so the axial inclination the upper incisors decreased (U1 to SN° from 96° to 90°). In retrospect, this problem was preventable as follows: (1) use higher torque brackets on the maxillary incisors, (2) progress to larger rectangular archwires to more completely express torque [Table 3], and/or (3) place palatal root torque in the anterior segment of the maxillary rectangular archwire.

Table 3 Archwire sequence chart summarizes the sequential mechanics over the course of active treatment

Inadequate torque control of the maxillary incisors prevented the complete correction of the Class II posterior segments [Figure 15]. This problem resulted in the deduction of 10 additional points on the CRE score. The patient was adequately treated to ABO standards as evidenced by an overall CRE score of 25; however, if there was adequate overjet for a complete Class II correction, the score would have been a truly outstanding 15.