When Single-Tooth Dentistry Falls Short

A 72-year-old male was referred by a local oral maxillofacial surgeon to have a single implant restored in the area of tooth No. 29. The patient had a long history of caries, single-tooth restorations, and multiple extractions despite being on a regular recare schedule. Implants had been placed in his lower arch by two different surgeons when teeth were lost. His medical history required significant consideration regarding the diagnosis, treatment planning, and execution of his dental care and future needs.

The patient reported an extensive medical history that would present challenges for dental treatment and his long-term oral health success. He indicated the following conditions: Guillain-Barre syndrome, limited scleroderma, rheumatoid arthritis (RA), GERD, Crohn's disease, pulmonary sarcoidosis, and a history of basal cell carcinoma. Oral manifestations of Guillain-Barre syndrome may include lingering difficulty with chewing, swallowing, or speech; scleroderma effects can include xerostomia, difficulty opening, swallowing, and speaking, as well as pseudoankylosis of the temporomandibular joint (TMJ); rheumatoid arthritis has been associated with greater incidence of periodontal disease, decreased salivary rates, and poorer oral hygiene¹; GERD is associated with decreased oral pH, erosion of tooth structure, and increased caries risk²; complications with Crohn's disease can include aphthous ulcers, lip swelling, xerostomia, mucogingivitis, cheilitis, and salivary duct abscess or inflammation; sarcoidosis, rarely, may cause swelling of mucosa, gingivitis, and ulcers.

Many of the patient's prescribed medications were associated with xerostomia and gastric issues, such as: azathioprine, an immunosuppressive drug used for rheumatoid arthritis that can cause nausea and vomiting; diphenoxylate-atropine, which is used for irritable bowel syndrome and may cause nausea, vomiting, and dry mouth; and mesalamine DR, which is used for ulcerative colitis and may also cause vomiting.

When completing the dental history form, the patient indicated recent caries, dry mouth, past difficulty with dental treatment, and changes to his teeth due to chipping or wear. He also mentioned some difficulty speaking and limited opening for dental treatment, which was primarily attributed to scleroderma.

The periodontal examination revealed no areas of bleeding on probing, with minor (<2 mm) horizontal bone loss on teeth Nos. 4, 5, 19, and 22 through 25. Less than 1 mm of recession was documented on teeth Nos. 11 and 19. All probing depths were less than 3 mm except teeth Nos. 19 (buccal, 4 mm) and 22 through 24 (mesial, distal, 4 mm). With the diagnosis of Stage 1, Grade A, with localized areas of Stage 2 (teeth Nos. 19 and 22 through 24), the dentist determined that the treatment risk was low and the prognosis good.

However, the biomechanical examination indicated a poor prognosis associated with high risk. The number and the extent of carious lesions, medical conditions, and medications were important considerations in determining the restorability of the patient's remaining teeth. Tooth No. 3 was deemed hopeless as there was a failing crown and composite patch in the furcation as well as a periapical lesion. Tooth No. 4 was structurally very compromised with a guarded prognosis and probable endodontic needs. Tooth No. 12 had extensive undermining caries and a hopeless prognosis.

The lower dentition presented several teeth that, in a low-caries-risk environment, might have been restored. For example, teeth Nos. 19, 21, 22, 25, and 26 could have been addressed with full-coverage crowns and endodontic therapy. Teeth Nos. 27 and 28 could have full-coverage restorations; however, Nos. 23 and 24 were hopeless due to recurrent caries. In discussing options with the patient and considering all of his autoimmune issues, dry mouth, and medications, there was a high likelihood of recurrent decay in the future despite removing the current caries and implementing a strong caries management program.² The patient was given the option and elected to remove the remaining teeth on the mandibular arch, have an additional implant in the area of tooth No. 27, and utilize the existing implants for a screw-retained fixed prosthesis.

In terms of function, the patient had limited range of motion, most likely due to the limited scleroderma. He had no pain, joint sounds, or difficulty chewing, and the joints accepted loads without discomfort. While the patient reported no functional issues, some fremitus was noted on maxillary anterior teeth. Wear was found on mandibular facial surfaces of the incisors and a diastema had appeared between teeth Nos. 8 and 9 over an unknown period of time. The dentist recognized that, over the years of tooth loss and replacement, the anterior teeth may have become constricted. As the mandibular dentition was to be fully replaced, the occlusal vertical dimension could be opened to remove the chewing pattern constriction (Figure 1 through Figure 3). While the risk was deemed moderate, the overall prognosis was considered good.

Similarly, a dentofacial analysis identified that the patient had a low lip line and did not reveal any gingival display during a full smile (Figure 4).

The primary goals for treatment were to manage the structural and biomechanical risk (caries) and restore acceptable function for this patient. Hopeless teeth would be extracted and the existing implants on the mandibular arch would be utilized for an implant-supported fixed restoration. Implants would be placed at site Nos. 3, 4, 12, and 14 to restore function to the maxillary dentition and at site No. 27 to provide additional support for the mandibular fixed restoration. The patient would be placed on a caries management protocol including recare visits every 4 months with fluoride varnish application, CTx5 treatment rinse (CariFree), and CTx4 gel 5000 (CariFree).^3,4

In the first phase of treatment, teeth Nos. 3, 4, 12, 19, and 21 through 28 were removed. Crowns on implant Nos. 18, 20, and 30 were removed and healing abutments were placed to help support a mandibular immediate complete denture, which had been fabricated to utilize during healing of the extraction sites (Figure 5). A locator abutment was placed on implant No. 29 for added retention to the mandibular immediate complete denture (Figure 6). A maxillary immediate partial denture was used for the maxillary healing phase. Soft relines were provided to aid in patient comfort. During this phase, tooth No. 6 required endodontic treatment due to a periapical lesion and pulpal necrosis.

In the next treatment phase, lithium disilicate (IPS e.max, Ivoclar Vivadent) crowns were placed on teeth Nos. 5, 6, 11, and 13 due to structural compromises and recurrent decay. Margins on these crowns were intentionally placed 0.5- to 1.0-mm subgingivally on the premise of reducing caries susceptibility on these teeth; however, there are studies that question the value of subgingival margins.⁵ During this period, while the lower immediate complete denture was in function, and because the latter had increased the patient's occlusal vertical dimension (Figure 7 and Figure 8), the constricted chewing pattern was relieved. The dentist also noted that the diastema between teeth Nos. 8 and 9 had gradually closed.

Four months after his teeth had been removed, the patient was seen by an otolaryngologist for bleeding while coughing. He was subsequently diagnosed with oral-pharyngeal cancer—Stage 2 SCC p16 + of the left posterior base of tongue.⁶ The referring oral and maxillofacial surgeon advised against the implants that had been planned for teeth Nos. 3, 4, 12, 14, and 27 due to radiation therapy and the risk of osteoradionecrosis.

For the last stage of treatment, after healing of the extraction sites, the decision was made to proceed with a lower fixed restoration minus the addition of the implant in the area of tooth No. 27. Though not ideal, it was felt that the four existing implants would provide adequate support (Figure 5). Impressions of the lower implants proved to be quite challenging due to the patient's very limited opening and the non-parallel angulations of the implants. Typically, an open-tray impression with pick-up copings has been shown to render the greatest accuracy⁷; however, in this case, doing so was impossible due to the patient's limited opening and tissue fragility (Figure 9). A closed-tray impression was ultimately successful and a milled titanium bar was fitted and utilized with nanohybrid composite for a fixed, screw-retained mandibular restoration. For the mandibular restoration, the laboratory created a copy scan of the immediate complete denture, and then created a milling file for a titanium bar and a copy of the teeth. The two parts were milled separately, with the teeth made from hybrid nano-ceramic (Crystal Ultra, Digital Dental). After the two components were fitted and bonded, the gingival area was covered with composite (Gradia, GC America Inc.), and the final product was polished and glazed for delivery (Figure 10 through Figure 13).

Considering the advice from the referring oral and maxillofacial surgeon, a maxillary removable partial denture (RPD) was fabricated rather than risking the potential of osteoradionecrosis (Figure 14). The lithium disilicate crowns on teeth Nos. 5 and 13 had already been seated, and rest preparations and guide planes were created intraorally with a handpiece to accommodate the maxillary RPD.

This patient presented a challenging medical and dental history that directly impacted his dentition. Xerostomia, limited range of motion in the TMJ, and medication side effects contributed to his high caries rate and tooth loss. Implants were placed by two different surgeons at different times and with two different implant systems. More confounding, they were placed at different depths and different angles, making the restorative phase very difficult. Xerostomia made the option of a removable complete lower denture a poor choice for patient comfort and function. In fact, during the healing phase, the existing immediate complete denture rested upon the healing abutments and the locator, which helped minimize tissue irritation and discomfort. The screw-retained fixed mandibular arch restoration was successfully delivered and functions well; the patient is satisfied. The maxillary RPD was a compromise; however, the patient remains relatively comfortable as the remaining dentition provides reasonable stability (Figure 14 through Figure 16). As a result of the oral-pharyngeal cancer radiation therapy, salivary gland function has decreased further, and the patient is being closely monitored for any new caries activity.

There are times when single-tooth dentistry is appropriate, but when the biological system is failing, a larger perspective is crucial. An accurate history, diagnosis, and good risk assessment will result in a more predictable outcome for patients. Today, patients may have an array of clinical providers and varied treatment systems. This can be challenging for the restorative dentist to decode in order to provide the correct armamentarium to manage treatment. Working effectively and collaboratively with the entire dental team is essential to the best possible treatment for all patients (Figure 17 and Figure 18).

The author would like to thank Claudio Bucceri, CDT, for laboratory consultation and fabrication, and Matthew Falkenstein, DDS, for his willing counsel.

Bryan Nakagawa, DMD
Private Practice
Salem, Oregon