Hemisection in the Age of Dental Implants: A Case Report

Due to the long-term negative sequelae that present secondary to loss of posterior teeth, practitioners have adopted many options for the treatment of extensively decayed molars and premolars.¹ The most common treatment options for the loss of mandibular teeth had long been restricted to toothborne fixed and removable prosthetics.² The advent of dental implants as a common treatment modality has since provided a predictable option for the treatment of these nonrestorable molars and premolars. While reliable, dental implants may be cost-prohibitive for some patients, require unique medical and dental management, and patients might be reluctant to accept treatment due to fear surrounding a surgical procedure.^3,4

Because dental implants may not be well-suited for every case, practitioners need to be cognizant of other potential options for treating the loss of posterior teeth. Hemisection represents a form of conservative dentistry that aims to retain as much of the original tooth structure as possible.⁵ This procedure has several indications from an endodontic, prosthodontic, and periodontal perspective. Carnevale et al most notably pioneered the hemisection procedure, establishing a 93% survival rate based on 3-, 5-, and 10-year follow-up examinations. He went on to establish a technique that involved a trifold combination of endodontic intervention, periodontal treatment, and prosthodontic assessment for long-term success.^6,7 Many other researchers have since elaborated on these three phases of hemisection to provide better understanding of the sequential treatment planning of the procedure as well as the etiology of disease origin.^8,9 Several have gone as far as to directly compare the efficacy and longevity of single crowns on tooth-resected molars to that of implant restorations, finding their long-term prognosis to be similar, further making a case for both hemisection and root resection.^8,10 Modern research suggests that the success of root resection and single-tooth crown placement is as high as 85%, indicating that proper adherence to this technique has, for the most part, stood the test of time in the era of dental implants.^10,11

Three phases of hemisection have since been identified in recent years. First, the tooth must be endodontically treated, because if a root canal cannot be performed or an endodontic failure occurs, then the hemisection is contraindicated immediately. Prevalence of accessory canals, pulpal necrosis, and periodontal furcation involvement in the form of furcal bone loss or decay is an indication of hemisection.⁸ Periodontal surgery is then performed to eliminate any furcal defects while simultaneously creating an environment that fosters maintenance and long-term hygiene to ensure a positive long-term outcome. Adequate periodontal support between the roots of the teeth is necessary as well, as minimal intraradicular bone is also a contraindication. Without the recontouring for ideal periodontal health as well as preoperative periodontal assessment, the patient will likely be unable to maintain the area hygienically and the teeth will consequentially fail.⁹

Restoratively, if the tooth is a terminal abutment in a fixed or removable partial prosthesis and its conservation is necessary for the longevity of a restoration in that area, hemisection becomes a unique restorative option.^11-13 Several challenges, however, must be considered from a prosthodontic perspective. When preparing a hemisected tooth, one must consider root diameter changes given the decrease in furcal trunk diameter and overall remaining tooth structure; the preparations will have a smaller, thinner preparation resulting in a restoration that has a greater taper from the occlusal-gingival direction. This will require great attention to the preparation of the most gingival portion of the teeth to avoid overcontoured restorative margins, which can potentially lead to deleterious periodontal outcomes or weakening of the remaining tooth structure and subsequent failure. It is, therefore, important to be mindful of the gingival architecture during the prosthodontic preparation phase to optimally produce a cleansable, well-fitting restoration.^14-17

The following case presentation examines a tooth that posed both periodontal and restorative challenges in a medically compromised patient. The purpose of this case report is to present a novel form of hemisection, an alternative and conservative means of preserving tooth structure and occlusal equilibrium in a compromised patient. The case demonstrates a unique method of treatment for when dental implants or traditional restorative techniques are not an option to establish posterior support.

The patient, a 68-year-old man with a history of posterior tooth loss, presented for routine recall prophylaxis. He had teeth extracted posteriorly at various times throughout his life, often receiving dental implant treatment, as seen in his full-mouth x-ray series (Figure 1). The patient's medical history became increasingly complicated over time due to chronic glucocorticoid use to treat an autoimmune disease. Many implants began to fail as he aged and his quality of bone declined. His reliance on warfarin due to his long-standing atrial fibrillation also began to introduce surgical complications.

The patient had maintained his oral health for several years until furcal decay was noted on tooth No. 18 at his recall examination (Figure 2), and upon the removal of the original fixed partial prosthesis the extent of the decay was fully appreciated (Figure 3). The patient had failure of implants at sites Nos. 19 and 20. Given his medical history as well as his history of failed dental implants, the patient was reluctant to attempt any type of implant surgical intervention and wanted to explore possible treatment alternatives. Thus, it was decided to restore the mandibular left side with a fixed partial prosthesis with abutment teeth at Nos. 18 and 20.

With the patient hesitant to receive dental implants and opposed to removable appliances, various fixed prosthodontic options were discussed. After clinical examination of the location of the decay (Figure 3), the patient was given the option of endodontics followed by hemisection of tooth No. 18, wherein the furcal decay would be removed but both remaining roots would be retained as terminal abutments on a four-unit fixed partial prosthesis. While this treatment modality was unorthodox, the patient ultimately consented to it.

Decay was initially removed and root canal therapy (RCT) was completed on tooth No. 18. As was evident in the radiograph (Figure 4) tooth No. 18 presented with C-shaped mesial and distal roots, which appeared as two single canals. Using advanced microscopy aided by an apex locator, the apex of the distal root had clinically terminated 2 mm to 3 mm shorter than the  radiographic apex. After completion of RCT using the WaveOne Gold system (Dentsply Sirona, dentsplysirona.com), a core buildup was placed using a combination of flowable and packable composite. The No. 18 hemisection was then accomplished, and each individual retained root was prepared as if it were a premolar tooth, in the expectation of acting like a single-unit abutment crown. Crown lengthening was then performed in the interseptal bone between the retained roots of tooth No. 18. A full-thickness flap was elevated and the soft tissue debrided between the roots, and an end-cutting bur was used to carefully remove 2 mm to 3 mm of interseptal bone (Figure 5).

A final impression using an intraoral scanner (TRIOS, 3Shape, 3shape.com) was taken and the model was 3D printed while a porcelain-fused-to-metal (PFM) fixed partial prosthesis was fabricated for the patient (Figure 6 and Figure 7). The PFM prosthesis was ultimately inserted and luted with a zinc-phosphate cement providing clinical adequacy (Figure 8), and an otherwise hopeless dental situation was salvaged with the use of a unique treatment modality. A final panoramic radiograph is shown in Figure 9.

Although implant dentistry may have been the ideal treatment plan yielding the longest, optimal prognosis in this case, the hemisection treatment provided the patient with a fixed partial prosthesis that considered his prognostically poor situation and has thus far provided occlusal stability for the past 3 years.In patients in whom the use of removable prosthetics is not preferable and implant dentistry is unrealistic, this treatment may serve as an alternative to meet patient wishes. This form of treatment should be especially considered given that research suggests hemisected teeth have an average success rate of 87% to 90%.^9,18,19 Of paramount importance is the emphasis on frequent recall, home care, and overall oral hygiene. While the tooth and prosthesis are contoured in a way to facilitate oral hygiene, it is ultimately the patient's responsibility to perform rigorous hygiene, most importantly at the hemisection of the crown. Using a combination of interdental brushes, water flosser, and floss threaders, clearing debris from the hemisection point is critical for maintenance. Without consistent recalls and in-office and out-of-office maintenance, the hemisection treatment will fail secondary to continued decay in the former furcal area.

Equally important, however, is the management of expectations as research further suggests that the long-term prognosis of the hemisection treatment will not be that of a stable, single terminal abutment tooth.⁹ Moreover, while the patient in this case was given very specific oral hygiene instruction for maintenance of a very unique hemisection, given the difficulty of this task, it should be noted that poorly maintained home care may lead to a poor long-term prognosis of the fixed partial prosthesis.

Hemisection has proven to be a valuable procedure in the dentist's toolbox, one that can help to provide an alternative to more costly and invasive surgical treatment. In the presence of mitigating factors like a complicated medical history or unfavorable anatomy, unique restorative steps may need to be taken. Practitioners must differentiate true odontogenic failures from opportunities for restorative creativity. Hemisection, thus, provides an additional novel option in the restorative arsenal.

Ross Teicher, DDS
Clinical Associate Professor, Department of Cariology and Comprehensive Care, New York University College of Dentistry, New York, New York

Marc Henschel, DDS
Associate Professor of Clinical Community Oral Health, University of Pennsylvania School of Dental Medicine, Philadelphia, Pennsylvania

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