Dental implications of transoral robotic surgery (TORS) in the management of head and neck cancer

Transoral robotic surgery (TORS)

The advent of transoral robotic surgery (TORS) signified a turning point for the treatment of oropharyngeal cancers and selected supraglottic and hypopharyngeal cancers. TORS is defined as surgery performed through the oral cavity by robotic arms controlled by a surgeon using a computer-enhanced system. In 2005, TORS was first used for excision of an epiglottic vallecular cyst.⁴ Subsequently in the following year, TORS was described in the literature for effective surgical management of tonsillar carcinoma.⁵ Since then, TORS has been used in the UK as a minimally invasive surgical alternative for resection of a variety of benign and malignant lesions of the oropharynx, larynx and hypopharynx.^6,7

The most commonly used TORS system in the UK is the da Vinci Surgical System (Intuitive Surgical Inc, Sunnyvale, CA, USA).⁸ This system consists of three main components: a patient-side cart consisting of arms mounted with an endoscope and surgical instruments (Figure 1), a surgeon console with master controllers (Figure 2), and a vision cart that provides a high-definition view of the operative site. The da Vinci system tracks the surgeon's controller movements at the console and actively translates the large movements into microscopic motions of the instrument tips inside the patient's oral cavity. It also features tremor filtration, thus enhancing accuracy of tissue manipulation. The endoscope arm has two integrated cameras with magnification ability, providing the surgeon with a three-dimensional perspective of the internal structures. The other articulating arms consist of stabilized patented EndoWrist instruments offering a wide range of motions, up to 7° of freedom. The instruments with EndoWrist technology consist of graspers, needle drivers, and various energy instruments designed to provide surgeons with natural dexterity while operating through small incisions. This robotic set-up effectively removes the line of site limitations imposed by standard transoral approaches, and allows surgical manipulations that are more delicate and precise than those that can be achieved through conventional open approaches. As a result, there is significantly reduced surgical morbidity, better preservation of swallowing function, improved cosmetic outcomes and reduced length of hospitalization following surgery.^9,10 In some cases, adjuvant post-operative radiotherapy or chemotherapy could either be avoided or reduced.¹¹

Dental implications of TORS

Introducing relatively large robotic arms into a confined space of the oral cavity puts the intra-oral structures of a patient's mouth at risk of traumatic injuries. Despite the defining feature of TORS being its transoral approach, there are few studies exploring the post-operative complications affecting the hard and soft tissues of the oral cavity.¹²

Surgical site exposure for TORS is obtained through the routine use of a mouth gag. A Crowe-Davis mouth gag (Figure 3a) is often used for base of tongue and tonsillar procedures, while the FK-WO Laryngo-Pharyngoscope retractor system (Figure 3b) is used for exposing the larynx and hypopharynx. The mouth gag is secured onto a region of the patient's teeth or directly onto the alveolar ridges in an edentulous patient, essentially ‘jacking’ open the jaws to facilitate access of the instrument arms into the surgical site. The significant forces exerted onto these areas can result in increased mobility of periodontally involved teeth, inadvertent tooth extractions, damage of restorations or mucosal and tongue lacerations (Figure 4). The surgeon may protect the teeth with gauze swabs or silicone guards attached to the mouth gag (Figure 5).

Haptic feedback remains a major limitation for robot-assisted surgery. As the surgeon no longer manipulates the instruments directly, the ability to sense interactive forces of the instruments with the surroundings is impaired. This lack of natural force-feedback risks collision of the instrument arms with adjacent oral structures and culminating in inadvertent injuries to the teeth and mucosa.¹³ A patient's awareness about potential dental complications should form part of the consent process prior to any TORS procedure.

Role of the dentist

The Royal College of Surgeons of England has published a guidance document detailing the pathway of dental care that is recommended for oncology patients receiving radiotherapy, chemotherapy and/or bone marrow transplantation.^14,15 In the authors' opinion, this guideline can be adopted by and tailored for those undergoing TORS.

Prior to commencement of any TORS procedures, the patient should undergo a full dental assessment with comprehensive evaluation of the dentition and its surrounding supporting periodontium. Patients with active periodontal disease or lone-standing teeth (Figure 6) should be cautioned about risks of increase in tooth mobility and potential tooth loss, whereas those with a heavily restored dentition should be aware of the risks of displacement or breakages of restorations. Root-treated anterior teeth restored with posts and crowns are particularly at risk. Even before the surgery, consideration should be given to extracting teeth at high risk of avulsion.

At this stage of the initial assessment, impressions can also be taken in order to construct a well-fitted customized thermoplastic mouthguard (Figure 7). The use of thermoplastic mouthguards has been proposed to reduce the risk of intra-operative dental injuries.^15,16 A mouthguard offers good protection for the teeth and oral mucosa. Apart from being an obvious physical barrier, it allows even load distribution across the dentition, and directs any applied forces parallel down the axis of the teeth, reducing the risk of tooth fracture.

Conclusion

Integrated multidisciplinary care is fundamental in the management of head and neck cancer in order to improve treatment outcomes and patients' quality of life. In this regard, the dental considerations for TORS should not be overlooked. Given that TORS is now being used increasingly in the UK, the dental profession undoubtedly should also have a basic understanding of this modern surgical technique. Surgeons, as well as dentists, must be aware of the potential dental complications that can arise and understand ways to mitigate these risks.