Surgical management remains a mainstay of modern cancer treatment, including for HNSCC. While removal of simple, early stage tumors may result in minimal side effects, surgical treatment of more advanced stage lesions can produce numerous esthetic, functional, and psychological sequelae. Potential impacts of surgery on oral function include difficulty tasting, speaking, chewing, and swallowing, whereas the excision of mucosal surfaces, loss in soft tissue volume, and removal of bone may result in substantial esthetic deformities [18]. Maxillofacial prosthodontics is an essential component of oral rehabilitation in patients with oral cancer undergoing surgical management.

The primary goals of maxillofacial prosthodontics are to restore oral function, improve facial esthetics, and enhance quality of life [19]. For example, maxillofacial prosthodontists fabricate various appliances, such as obturators, partial bridges, etc., to support ongoing cancer treatment and for patients following surgical procedures [20]. By utilizing computed tomography imaging, medical modeling technology, and virtual surgical planning (VSP), maxillofacial prosthodontists are able to accurately pre-plan the prosthetic and dental rehabilitation of patients undergoing complex surgical reconstruction [21, 22]. Undoubtedly, the maxillofacial prosthodontist is an essential member of the cancer team and plays a vital role in achieving optimal treatment outcomes for cancer patients.

Radiotherapy remains one of the primary treatment modalities for both localized and late-stage cancers. Further, various randomized control trials have demonstrated a superior tumor response to radiotherapy and concurrent chemotherapy, rather than radiotherapy alone, for numerous advanced tumors including HNCs [23–25]. The side effects and toxicities related to radiotherapy, however, have the potential to impart a substantial amount of morbidity and worsen quality of life for many patients. Despite recent advances in radiotherapy technique and delivery, many of the dental and oral complications related to head and neck radiation, such as oral mucositis, salivary gland dysfunction, radiation caries, and osteoradionecrosis, are still largely prevalent among this cancer population.

Chemotherapeutic agents comprise a vast group of chemicals designed to halt the growth of cancer cells, either through inducing apoptosis or preventing their replication. These agents produce their toxic effects by targeting rapidly proliferating cells, such as the basal cells of the mucosal layer as well as the acinar and ductal cells of the salivary glands [53]. The oral side effects of chemotherapy are relatively common and may include OM, candidiasis and other oral infections (including bacterial, viral, and fungal infections), xerostomia, oral bleeding, and potentially periodontal disease [53, 54]. Although concomitant chemotherapy often produces OM, the concomitant use of targeted agents may further alter mucositis risk, severity, and course [55, 56].

Hematopoietic stem cell transplantation (HSCT), on the other hand, involves the transplantation of healthy hematopoietic stem cells to patients with dysfunctional or depleted bone marrow for the treatment of various cancers, immune-deficiency syndromes, and hemoglobinopathies [57]. HSCT carries the risk of numerous acute and chronic complications that may impact the oral cavity, such as OM, oral candidiasis, herpes simplex virus (HSV) recrudescence, and graft-vs.-host disease (GVHD).

Medication-related osteonecrosis of the jaw (MRONJ) is a potentially debilitating condition characterized by non-healing exposed bone in patients who have used either antiresorptive or antiangiogenic agents [64, 65]. High-dose regimens of antiresorptive medications, like bisphosphonates and receptor activator of nuclear factor kappa B ligand (RANKL) inhibitors (e.g., denosumab), are frequently used to prevent skeletal-related adverse events in adults with malignancies involving bone [66]. Although the pathophysiology of MRONJ has been greatly debated, most hypotheses suggest the role of altered bone remodeling, oversuppression of bone resorption, and angiogenesis inhibition as key mechanisms resulting in this disease process [67].

Dentists and other oral healthcare specialists play a vital role in preventing or minimizing a patient's risk of developing MRONJ. Dental assessments and the provision of prophylactic dental care prior to initiation of antiangiogenic or antiresorptive therapy have been shown to decrease a patient's chances of developing MRONJ [68]. In patients with MRONJ, treatment is divided into either conservative (such as maintaining optimal oral hygiene, eliminating soft and hard tissue disease, antibiotic therapy, and the use of antibacterial mouthwashes) or surgical management [68]. Although the success rate of surgical treatment for MRONJ has proven to be high [69], the side effects of these invasive resections have the potential to impart a substantial amount of morbidity.

Targeted therapies, which target specific genes and proteins involved in the growth and survival of cancer cells, and immunotherapies, which stimulate a patient's own immune system to combat cancer, are quickly becoming central pillars of cancer treatment. Although the introduction of targeted therapies and immunotherapies have revolutionized treatment for numerous types of malignancies, they have also produced novel side effects known as immune-related adverse events (irAE). While these adverse events have been observed in nearly all parts of the body, their impact on the oral cavity is notable [70].

Obtaining dental clearance is an essential step prior to the initiation of cancer treatment, particularly for patients to be exposed to radiation to the head and neck. The rationale for dental screening prior to cancer therapy derives from numerous studies linking an increased incidence of intra-therapy complications, such as acute dental infections, with poor oral health [79–81].

A complete oral evaluation prior to the initiation of cancer treatment should elucidate the following information: presence of a dental home, date of last dental visit, recognition of past and current dental problems, an oral/dental evidence-based risk assessment such as CAMBRA (caries management by risk assessment), and an evaluation of past and current medication use.

Additionally, the patient should receive oral prophylaxis including professional hygiene therapy as well as eliminate any existing low-grade infections and possible sources of trauma (e.g., trauma from denture or fixed orthodontic appliances) [82]. The National Institute for Dental and Craniofacial Research recommends that elective surgical procedures be postponed until the cessation of cancer therapy, while invasive procedures be completed at least 14 days prior to the initiation of head and/or neck radiation and 7–10 days prior to myelosuppressive chemotherapy [83]. Finally, patients should be educated in proper oral hygiene techniques for the prevention of future dental caries and oral disease that may impact cancer treatment.

The increased risk of acute oral complications resulting from radiation and/or chemotherapy highlights the importance of continued proper oral hygiene practices and maintenance. Patients should continue to use the modified Bass brushing method with fluoride toothpaste at least two times per day [84], floss one time per day, avoid the use of alcoholic mouthwashes, and remain on a regular hygiene recall schedule with their dentist. The use of removable appliances and prostheses, especially those with the potential to cause hard and soft tissue damage, should be limited. Stimulation of salivary production in those patients demonstrating hyposalivation can be achieved either through the use of sugar-free lozenges or gums (e.g., xylitol) [85, 86].

It is crucial that dentists and other oral healthcare specialists maintain communication with the oncologist throughout the duration of cancer therapy and obtain proper consultation with the oncologist prior to any dental procedures, including prophylaxis. A blood sample should be obtained from patients undergoing chemotherapy roughly 24 h prior to any invasive oral surgical procedures and postponed when the following are present: platelet counts <75,000/mm³; abnormal clotting factors present; and/or absolute neutrophil count of <1,000/mm³ [83].

Following the completion of cancer therapy, patients should remain on a regular recall schedule as recommended by their dentist and continue practicing proper oral hygiene including the use of fluoride toothpaste and varnish. In patients at higher risk for dental caries (especially post-allogeneic HSCT/GVHD) as well as those with a history of oral malignancy (such as OSCC), a more intensive and frequent recall schedule may be necessary. Further, a patient's hematologic status, such as the resolution of immunosuppression and/or thrombocytopenia following the cessation of cancer therapy, should be assessed prior to dental treatment. Furthermore, the dentist should update the patient's medication list and assess for any anti-resorptive and/or anti-angiogenic medications used throughout the duration of cancer treatment.

Finally, childhood cancer therapy has the potential to result in numerous dental, craniofacial, and soft tissue complications. Children are particularly susceptible to the long-term effects of cancer therapy as treatment typically occurs during the most active stage of growth and organ development [87]. For example, these patients are at an increased risk for dental caries, abnormalities in tooth morphology and composition, hyposalivation, maxillary and mandibular growth disturbances, and temporomandibular dysfunction (TMD) [88, 89]. As such, pediatric and general dentists should be aware of these potential complications and monitor for any abnormal deviations in craniofacial and/or dental growth and development [83].