Rehabilitation of a Head and Neck Cancer Survivor With a Functionally and Biomechanically Challenged Dentition

A 58-year-old female patient presented desiring a more appealing smile with whiter teeth (Figure 1 through Figure 3). She reported that since undergoing radiation therapy approximately 18 years ago her teeth had become gray, thin, and translucent and were gradually becoming shorter in length. In addition, many posterior teeth had received facio-gingival fillings that were stained and failing and looked unattractive to her (Figure 4). Systematic diagnosis would reveal significant biomechanical and functional issues related to her chief complaints and create challenging decisions for the clinician.

The patient was a nonsmoker who did not drink alcohol and was an otherwise healthy individual who had undergone radiation therapy at age 40 for stage II squamous cell carcinoma of the larynx. Although she had avoided surgery and chemotherapy, symptoms of xerostomia persisted and her dentition suffered as a result. She had no allergies, and the only prescribed medication she was taking was levothyroxine, 50 mg daily, which she had been taking for about 7 years. No medical consultation was done.

Her previous dentist had made fluoride trays for her to wear throughout her 8 weeks of radiation therapy; however, she no longer wore the trays 17 years post remission and was still experiencing xerostomia. She reported occasional clicking and popping of the temporomandibular joints, wearing and thinning of the anterior teeth, and difficulty closing her teeth together without first shifting her lower jaw backwards. Otherwise, she reported many facio-gingival fillings that had been placed to cover areas where enamel had been lost and root surfaces exposed.

Periodontal: The patient had been seen twice yearly for prophylaxis appointments and recall examinations for as long as she could remember. She had mostly mild gingival recession, but in areas of abrasion in the mandibular posterior recession was more significant. No bleeding on probing existed, and all pocket depths were 2 mm to 3 mm. Additionally, there was no loss of crestal cortication, and bone levels were normal, within 2 mm of cementoenamel junction (Figure 5). The periodontal diagnosis was American Academy of Periodontology (AAP) stage 1, grade A.¹

Risk: Low
Prognosis: Excellent

Biomechanical: No active carious lesions were present. There were acceptable occlusal amalgam restorations on teeth Nos. 2 and 15, a failing amalgam restoration on tooth No. 31, and one failing interproximal amalgam on tooth No. 30. The facio-gingival surfaces of teeth Nos. 3 through 14, 19 through 23, and 27 through 30 were covered with failing Class 5 restorations placed 6 to 8 years ago. These restorations had been placed to protect against what the author believed was initially abfraction (often referred to as noncarious cervical lesions [NCCLs]) due to function, followed by ongoing erosion and abrasion. The loss of tooth structure on the facio-gingival surfaces was moderate to severe and appeared multifactorial. Additionally, the patient had erosive pitting lesions on the cusp tips of her posterior teeth. Mild to moderate attrition was seen throughout her dentition; however, the maxillary lingual and mandibular facial surfaces of the anterior teeth revealed moderate to severe attrition, up to 1.5 mm.

Risk: High
Prognosis: Poor

Functional: The patient had a normal range of opening. Attrition was evident on most of her dentition, ranging from 0.5 mm to 1.5 mm; it was greater on the palatal surfaces of the maxillary anterior teeth and the facio-incisal surfaces of the mandibular anterior teeth. The patient reported occasional clicking and popping of the temporomandibular joints with no symptoms otherwise; her load test and immobilization test were normal, signifying no joint concerns. She had noticed "wearing" of the incisal edges of the anterior teeth and difficulty closing her teeth together without retruding her lower jaw. Her symptoms and occlusal analysis led to a working diagnosis of a constricted chewing pattern.²

Risk: Moderate
Prognosis: Fair

Dentofacial: The patient revealed a low smile line; only the papillae of the maxillary anterior teeth showed in her full smile. The incisal edges of her maxillary teeth were hidden behind her lower lip in repose. The patient reported that her previous dentist smoothed the edges of her anterior teeth so they would not show the wear as much. Her mandibular incisors were moderately crowded and she had never been orthodontically treated.

Risk: Low
Prognosis: Good

The primary goals of the case were to improve esthetics of all teeth; restore the surfaces of lost enamel; correct the mandibular crowding and restore the flat, worn edges of the mandibular teeth; and provide the patient, as she put it, "the smile I used to have." The patient preferred long-term solutions rather than, for example, the 6- to 8-year duration of her Class 5 composite restorations.

Based on the functional diagnosis of a constricted chewing pattern, it was determined that the wear facets on the anterior teeth were a result of excess contact and friction on those surfaces (maxillary lingual and mandibular facial surfaces) during normal chewing cycles. To fulfill the esthetic, functional, and biomechanical goals, namely restoring lost tooth surfaces and correcting functional envelope to spare any additional tooth loss, normal dimensions and position of the anterior teeth would be required, and the chewing envelope would need to be accommodated without causing excess friction on the teeth.

Xerostomia, which generally worsens with age,³ needed to be taken into account in the patient's long-term dental treatment plan, especially in light of her past radiotherapy. One consideration was whether or not coronal and root surfaces would become increasingly susceptible to caries over time. Another issue to consider was whether caries management protocols would be sufficient to maintain tooth structure or whether another treatment method should be implemented to lower her risk of future biomechanical concerns.

Providing the patient conservative dental care options while offering definitive long-term solutions proved to be complex. Several options were contemplated:

1. Orthodontic therapy could be utilized to uncouple the constricted chewing pattern,⁴ but this would not address the NCCLs on many facial surfaces nor improve the moderate to severe attrition on the maxillary anterior teeth. Adhesive restorations, or "bonding," could be used to cover those surfaces, however adhesive protocols on dentin and root surfaces would be a compromise and only a short-term solution. More importantly, the patient was not willing to consider wearing orthodontic braces.

2. Adhesive, minimally invasive veneers were considered with or without orthodontic therapy. This approach would have been possible for use on the patient's anterior teeth as there was adequate enamel for adhesion, but only if the constricted chewing pattern was corrected. Orthodontia could correct the constricted chewing pattern, but the facial, Class 5 lesions would not have long-term restorations.

3. A third option involved the use of full-coverage, cohesively retained restorations on teeth with inadequate enamel (Nos. 3 through 14, 19 through 21, and 28 through 30) and feldspathic veneers where there was adequate enamel for adhesion (Nos. 22 through 27),⁵ along with straightening of the crowded mandibular anterior teeth with limited orthodontic therapy, ie, aligner therapy. This approach would allow for long-term restoration of all Class 5 surfaces as well as occlusal pitting and thin enamel with cohesively retained crowns while providing a method to open the occlusal vertical dimension (OVD). Moreover, it would let margins be placed at or below the gingival margins to help resist future bacterial damage due to ongoing and, likely, increasing xerostomia during the patient's lifetime.

The third option satisfied the greatest number of long-term benefits, including the patient's functional, biomechanical, and esthetic needs. The use of full-coverage crowns, of course, would increase biomechanical risk due to the removal of tooth structure that might otherwise have been saved and would mean that the patient would need full coverage for the rest of her life. The patient was made aware of the risks and benefits expected from each treatment option and, in consultation with the clinician and after careful consideration, chose the third option.

Phase 1: Deprogramming

The patient was fitted with a bowless Kois deprogrammer, which she wore for 2 weeks.² While wearing the device she reported greater freedom of movement, and her symptoms of joint clicking disappeared. Load and immobilization tests were repeated with no abnormal results. Once she was deprogrammed, a centric relation record was taken and a Kois dentofacial analyzer was used to mount the casts on an articulator. The first point of contact was on the mesio-palatal surface of tooth No. 11, which confirmed the working diagnosis of a constricted chewing pattern.²

Phase 2: Spring Aligner

Although the patient refused full orthodontia, she agreed to wear a spring aligner (Inman Aligner^™, inmanaligner.com) for a short period of time for the purposes of moving the mandibular incisors posteriorly, assisting in decreasing the constricted chewing pattern, and straightening the mandibular incisors to an extent. A total of 2.5 mm interproximal reduction (ie, 0.5 mm over five teeth, as per the digital workup from the aligner manufacturer) was completed on the mandibular incisors with the use of an interproximal reduction kit (Komet IPR kit, Komet USA, kometusa.com).The patient then wore the Inman Aligner for 5 weeks.⁶ She requested that some characteristics of natural overlap be maintained in her final smile, so the Inman appliance therapy was stopped short of ideal arch form.

Phase 3: Maxillary Preparations and Temporization

Because OVD was to be increased and the restorations were to be delivered one arch at a time, a polyvinylsiloxane (PVS) matrix made from the wax-up of the mandibular arch was transferred to the mandibular teeth utilizing esthetic provisional material (Luxatemp^® Automix Plus, DMG America, dmg-america.com) (Figure 6). This would provide ideal occlusion for the new maxillary provisionals and final crowns.

The maxillary teeth were prepared according to the wax-up using PVS reduction guides. Provisional restorations were fabricated with shade B1 Luxatemp and cemented into place in four three-unit splints using temporary cement (Figure 7). After 4 weeks the patient felt comfortable with her new bite at the increased vertical dimension. A PVS impression was made for the prepared maxillary arch (Figure 8), and porcelain-fused-to-metal (PFM) crowns, fabricated with a high-noble metal due to its greater bond strength to porcelain,⁷ were produced for teeth Nos. 3 through 14. Circumferential porcelain margins were utilized to achieve ideal optical properties.⁸ Crowns were cemented with a self-adhesive universal resin cement (RelyX^™ Unicem, 3M Oral Care, 3m.com).

Phase 4: Mandibular Preparations and Seating

For the mandibular anterior teeth (Nos. 22 through 27), because they had healthy intact enamel and there were no existing Class 5 composite restorations, feldspathic porcelain veneers, which offer natural esthetics, were fabricated. For molar No. 19 and premolars Nos. 20 and 21, PFM crowns were indicated due to significant recession and root exposure, especially after removal of failing composite. Tooth No. 31 received a direct composite restoration. A photograph of the mandibular arch partially prepared is provided in Figure 9.

After fabrication, the crowns were inserted and occlusion was verified. Rubber dam isolation was carried out to individually seat the veneers utilizing an adhesive cementation protocol with a total-etch technique using a translucent cement (Variolink^® Esthetic LC, Ivoclar Vivadent, ivoclarvivadent.com) (Figure 10). Posterior PFM crowns, again fabricated with a high-noble metal because of its bond strength to porcelain, were cemented using a cohesive protocol with self-adhesive universal resin cement (RelyX Unicem).

Radiographs were taken to ensure full seating of the restorations was obtained and that no residual cement was left. Final photographs were taken 1 week after seating of the mandibular restorations (Figure 11 through Figure 14).

The patient was asked to fill out the functional dental history several weeks after her new smile was in place. She reported that she no longer felt like she had to shift her lower jaw and squeeze her teeth into position and was very happy with the appearance of her smile.

Xerostomia is the most common side effect of radiation therapy for head and neck cancer patients; it is a result of the loss or decreased function of the salivary glands, predominantly the submandibular glands.^9,10 In the present case, the patient suffered from the symptoms of xerostomia, likely due to hyposalivation as a result of decreased salivary function from the destruction of glands from radiation therapy; however, no testing was done to objectively quantify the salivary flow rate.Xerostomia is a significant risk factor for many dental issues, especially as patients age and take more medications. It is estimated that 30% of the population over age 65 has symptoms of xerostomia. A careful medical history should be taken for these patients at all initial and recall appointments. Also, medications should be noted along with their potential side effects, including xerostomia. As patients get older, the bacteria profile of their biofilm favors root decay, causing bacteria such as lactobacillus and actinomyces.¹¹ Careful consideration must be given to the type of restoration, the coverage near the gingiva, and the patient's home care habits and regimen so these types of bacteria can be avoided.

In this case, managing the patient's biomechanical, or structural, risk was, in effect, a trade-off and was carefully contemplated. On the one hand, biomechanical risk was decreased by the replacement of the many old, existing, failing composites with long-term cohesively retained restorations. However, biomechanical risk also was increased with the removal of tooth structure needed to accommodate PFM restorations.

To keep her mouth moist and stimulate salivary flow, the patient was advised to, on a daily basis, use a water-based lubricant throughout the day, carry a water bottle and sip water periodically, and chew xylitol gum. She was prescribed a 5000 ppm dentifrice to use twice daily. The patient slept at night with a humidifier and was advised to continue to do so. Biomechanically, the overall prognosis has remained fair due to her ongoing risk of xerostomia.

The patient's functional risk was mitigated by the limited orthodontics in the mandibular anterior dentition and the increase in OVD. Together these modalities allowed for a normal envelope of function where equal, bilateral, and simultaneous posterior occlusion resulted along with no frictional interferences on the surfaces of the anterior restorations during function. A comfortable "home" position was created where the patient no longer felt the need to retrude the mandible and squeeze her teeth to make them occlude. After completion of treatment, her diagnosis was acceptable function with a good prognosis.

Dentofacial risk was largely unchanged from her old smile to her new smile. The addition of 1 mm to 2 mm of incisal edge length as well as a wider buccal corridor aided in the appearance of a fuller, more natural smile. The soft tissue from preoperative to the postoperative stage remained largely unchanged, with a healthy gingival appearance exhibited at both stages.

A systematic approach to this rehabilitation was utilized in order to account for all risks before treatment began. The patient was clearly informed of the risks and the treatment needed to achieve her desired goals. The patient also was made aware of her ongoing risk due to xerostomia from her radiation therapy. At the time of this writing, she is happy with her smile and the comfort of her new bite and regrets not having committed to treatment sooner.

The author thanks Peter Pizzi, MDT, CDT, and his team at Pizzi Dental Studio Inc. for the laboratory work in this case and his mentorship.

Dane M. Avondoglio, DMD
Private Practice, Mason, Ohio