Overcoming Esthetic, Functional, and Biomechanical Challenges With Assistance From Orthodontic Intrusion

When patients present with multiple problems that have accumulated over a lengthy number of years, it is important that clinicians conduct a thorough and analytical diagnosis and risk assessment. In the present case, a woman who had numerous congenitally missing teeth that had been replaced many years ago with traditional porcelain-fused-to-metal (PFM) bridges was at risk of experiencing structural failure. Among the structural compromises were severe wear in her mandibular anterior and broken porcelain on the lower bridges. In addition, she was dissatisfied with her smile due largely to a wide diastema. This case report describes how orthodontic intrusion was used as part of a six-phase treatment approach to enable a variety of esthetic, functional, and biomechanical challenges to be met.

A healthy 45-year-old woman presented with multiple esthetic, functional, and restorative concerns. She was unhappy with her smile, disliked the color and shape of her teeth, and wanted the diastema between her upper central incisors to be made smaller (Figure 1). The patient indicated her lower anterior teeth seemed worn down over the past several years (Figure 2) and some of her lower posterior crowns had chipped (Figure 3). She felt that too much of her gums showed above her maxillary posterior teeth, and she wanted implants where she had seven congenitally missing teeth that had been replaced at a young age with traditional PFM bridges (Figure 4). The patient related that local anesthesia had often been insufficient because her "nerves were intertwined" and that her fear level was high from having many dental visits as a young person.

There were no medical risks or medications that might influence treatment. The patient was a previous smoker but had quit many years ago. She reported having numerous dental visits with poor pain control for her seven congenitally missing teeth that had been restored with PFM bridges, continuing wear on her teeth, and smile appearance issues. The maxillary bridges were placed 20 years prior, and the lower bridges had been replaced once, 10 years ago. With the exception of the lower anterior wear, the patient noted no temporomandibular joint disorder or functional issues in recent years, though she expressed a vague memory of having some bite issues in her past.

Periodontal: All probing depths were 3 mm or less with very few sites of slight bleeding. There were no areas of recession, no mobility, and no mucogingival defects. The diagnosis was mild horizontal attachment loss (<3 mm), American Academy of Periodontology (AAP) 2 classification.

Risk: Low

Prognosis: Good

Biomechanical: With six full-coverage traditional PFM bridges placed many years ago, the abutment teeth had been extensively prepared. The upper right bridge abutments on tooth Nos. 3 and 5 as well as tooth No. 2 had been endodontically treated with post-and-core build-ups, further increasing the risk of structural failure. Aside from the bridges, teeth Nos. 15 and 18 presented with structural compromises due to large questionable restorations and increased risk for fracture. There were no carious lesions. While the patient was considered low risk for caries, many structural compromises and severe, active attrition (2 mm to 3 mm) were diagnosed.

Risk: High

Prognosis: Poor

Functional:The patient indicated no problems chewing or finding a comfortable bite in maximum intercuspation, but her lower anterior teeth were severely worn and she indicated that these teeth were actively changing. She reported no clenching, grinding, or other parafunctional habits. The upper anterior lingual surfaces of her bridges were rough and bulbous, and the lower anterior segment was super-erupted. The lower incisal areas of attrition appeared polished with sharp enamel edges, which confirmed that some excess friction still remained on the anterior teeth in her chewing envelope. The sequence of events in her dental history implied there must have been significant occlusal dysfunction during some period after her multiple bridges were placed, and the lower anterior teeth were subject to excessive forces from the bulky, rough upper anterior bridges. The broken porcelain on the lower bridges was indicative of those areas being involved in a previous period of occlusal dysfunction. These interpretations correlated with the patient's recall of a period of bite issues in her past. The diagnosis was a frictional chewing pattern.

Risk: Moderate

Prognosis: Fair

Dentofacial: During full smile the patient revealed part of the interdental papillae on the maxillary anterior teeth and full gingival display both above the maxillary bicuspids and on the mandibular anterior segment (Figure 4). While speaking the "shush" sound, her lower anterior gingiva was fully exposed due to compensatory super-eruption as the lower attrition had progressed.

Risk: High

Prognosis: Poor

A number of treatment goals were planned. First, biomechanical risk would be reduced by lessening the load per tooth using implant placement where permanent teeth were missing, except in the maxillary anterior segment. The risk for attrition on the lower anterior teeth would be decreased as well using orthodontics. Anterior esthetics would be improved through gingival recontouring and orthodontic repositioning, along with shade change, improved tooth form, and decreasing the diastema width. Dentofacial risk would be decreased by changing the gingival contours and levels on the lower anterior teeth orthodontically and by performing crown lengthening on the upper bicuspid areas. Functional risk would be reduced by orthodontically alleviating the patient's frictional chewing pattern, and equilibration would be performed after the restorations were done to help decrease the risk of functional pathology.

The goals of treatment also included restoring natural tooth length in the mandibular anterior teeth without unnecessary compromise to tooth structure.¹ Finally, the clinician wanted to ensure that the patient achieved adequate local anesthesia and would implement shorter appointments to accommodate her fears based on her history.

Teeth Nos. 22 through 27 were orthodontically intruded to eliminate the frictional chewing pattern, drive the gingival contours apically, and create adequate occlusal clearance to restore the lower anterior teeth to their ideal length.² Proper positioning of these lower teeth further presented the opportunity for conservative preparations. As a result, more enamel was available for adhesive protocols during cementation of the ceramic restorations.

Upon completion of the orthodontic intrusion (Figure 5) teeth Nos. 22 through 27 were built up with direct composite to restore proper tooth length and position and to provide a visual mock-up for the patient.³ The mock-up would later be replaced with ceramic restorations.

Implants (SLActive^®, Strauman, straumann.com) were placed at missing tooth site Nos. 19, 29, and 30. After osseous integration, custom abutments were fabricated and provisional crowns were cemented with resin cement (RelyX^™ Unicem, 3M ESPE, 3m.com) in order to stage treatment over an extended period of time, as per the patient's wishes for emotional and financial reasons, and maintain occlusal and positional stability.

Implants on teeth Nos. 7 and 10 were considered; however, the patient refused orthodontic brackets on the maxilla, and there was inadequate interdental space in those sites as she presented (Figure 6). Instead, the patient was given the option of having new bridges fabricated, which she chose. Connective tissue grafts were placed at site Nos. 7 and 10 to provide adequate tissue for ovate pontic site development. Provisional bridges, tooth Nos. 6X8 and 9X11, were cemented with RelyX Unicem, with ovate pontics extended 3 mm apical to the facial free gingival margin.

The tissues were allowed to heal and mature for 6 months. After healing, two three-unit lithium-disilicate (e.max^®, Ivoclar Vivadent, ivoclarvivadent.com) bridges were placed on tooth Nos. 6X8 and 9X11 for esthetic final restorations.

Implants (SLActive) were placed at site Nos. 4 and 13. At the same time, esthetic crown lengthening was performed on the adjacent teeth in order to move the gingival margins more apically.⁴ The crown abutments on Nos. 3, 5, 12, and 14 were provisionalized, and after osseous integration provisional crowns were placed on the No. 4 and 13 abutments to allow healing. After 6 months to allot for tissue healing and maturation, lithium-disilicate (e.max) crowns were placed on teeth Nos. 3 through 5 and 12 through 14.

The mandibular posterior teeth that had been provisionalized, Nos. 19 through 21 and 28 through 31, were readied for lithium-disilicate (e.max) crowns and cemented with RelyX Unicem. Occlusal equilibration was then performed using a Kois deprogrammer for bilateral, equal-intensity, simultaneous posterior contacts.⁵

The lower anterior incisal composites were removed, and teeth Nos. 22 through 25 and 27 were prepared for lithium-disilicate (e.max) veneers. Tooth No. 26 had very little remaining enamel and required full coverage, thus it would be cemented with a cohesive protocol while the other teeth would be treated using an adhesive protocol. The canines were verified to have light occlusal contacts and the incisors were slightly out of contact. Finally, the patient was seated upright and asked to chew on 200-µm blue articulating paper (Bausch Articulating Papers, Inc, bauschdental.com). No streaks appeared on upper incisors confirming that the contours of the occluding surface would not interfere with her chewing envelope.

The treatment was staged over 6 years due in part to the patient wanting to keep appointments short and stretch out payments. The patient's periodontal risk remained low. Biomechanically, as the posterior bridges were replaced by single-unit implants and crowns, liability for failure due to forces of mastication on bridge abutments was mitigated to some extent. Removing the bridges eliminated the risk of having these three- or four-unit restorations fail due to a single tooth failure. Functional risk was mitigated by moving the lower anterior teeth out of their frictional position and utilizing a Kois deprogrammer to equilibrate the final restorations. Finally, dentofacial concerns were successfully addressed with crown lengthening and orthodontics by decreasing the gingival display and harmonizing that which remained.

A comparison of the occlusal maxillary condition preoperatively versus postoperatively can be seen in Figure 7 and Figure 8, while the same can be seen for the mandibular in Figure 3 and Figure 9.

The patient was extremely happy with the results of her treatment. Her goals of having whiter teeth, accomplished through use of a whiter porcelain than her original PFM crowns, improved tooth form, and less gingival showing in several areas, along with a smaller midline diastema, were all met (Figure 10 through Figure 12). Her local anesthesia was carefully administered and shorter appointments over a somewhat protracted period of time were successfully utilized to provide a positive experience for the patient.⁶

To help ensure longevity of the treatment outcome, follow-up protocols are at 6-month recall. No splints were made for the patient because there were no parafunctional habits. At the time of this writing, teeth Nos. 15 and 18 remain in need of treatment with full-coverage restorations.

This case report offers an example of how orthodontic intrusion can be utilized to enable clinicians to meet esthetic, functional, and biomechanical challenges. A six-phase approach was used that combined a variety of treatments, including implant placement, gingival recontouring, orthodontic repositioning, and crown lengthening, to attain a successful outcome. A Kois deprogrammer was used for equilibration of the final restorations. An analytical approach to diagnostics, risk assessment, and prognosis helped provide a patient who had dental anxiety from many previous unpleasant dental visits a comfortable, positive experience.

The author would like to thank Zori Rabinovitz, DMD, for the implant surgery and placement in this case, Chun-Yu Yogi Chen, DMD, for the orthodontic care, and Alexander Dental Studio, Inc in Milford, Massachusetts, for the laboratory support.

Mia W. Fitzgerald, DMD, FAGD
Private Practice, Sudbury, Massachusetts