In this systematic review, the weighted prevalence of dental caries amongst cancer survivors were surprisingly highest in patients who only received chemotherapy compared to those who received radiotherapy or chemoradiotherapy. This discrepancy may be attributed to the distinct differences in the dental management of patients prior to radiotherapy versus those being prepared for chemotherapy. Patients undergoing head and neck radiotherapy are at life-long risk of developing osteoradionecrosis; subsequently, dental management protocols prior to radiation often entail aggressive approaches such as extractions. Another explanation for the unanticipated caries prevalence may be because the majority of the studies were carried out on children (12/19 studies) [14
], and a high proportion of the diagnoses in children was hematologic malignancies that were treated largely with curative chemotherapy. These children are ill for a long period of time and could have higher caries activity because of the need to frequently consume highly cariogenic dietary supplements for weight maintenance or are taking sucrose-rich medications. In addition, caregivers are often overwhelmed by their child's medical diagnosis and often neglect the oral health component. In contrast to the caries prevalence, the DMFT index is expectedly highest in patients who were post-radiation therapy compared to patients who were post-chemotherapy and healthy controls. The DMFT/S index is a means to obtain an estimation of dental disease in a population and is recommended by the World Health Organization (WHO) for the measurement of caries experience, thereby allowing for easy comparison among international studies [59
]. Despite the shortcomings of the DMFT/S index (e.g., failure to detect dental decay between posterior teeth surfaces due to the lack of dental radiographs, failure to distinguish the various reasons for missing teeth) and the suggestions by several authors to switch to alternative indices, the DMFT/S index is still the most widely utilized caries assessment tool presently [60
]. It would have been helpful to look at the caries activity trends longitudinally in this systematic review; however, it was not possible to compile this information due to the lack of specification, standardization, and/or wide ranges of time periods of DMFT data collection.
Similarly, attempts to describe periodontal health and periodontal disease beyond that of plaque and gingival indexes in cancer patients were difficult in this review. PI is a measure of oral hygiene that synthesizes both number of surfaces covered and the amount of hard and soft deposits on the teeth, and gingival index is a measurement of the amount of inflammation present in the gingival tissues. Although, there were other measurements of periodontal health such as oral health index-simplified (OHI-S), probing depth, clinical attachment loss, gingival recession, and bleeding index, each of these parameters were only reported in a single study and therefore could not be combined or compared with other studies to have any meaningful results. Other difficulties encountered include the various reports of outcome variables (raw data versus percentages) and the categorization of periodontal health without clear definition. The measurements of DMFT/S, PI, and GI are important clinical considerations for dental practitioners because they are predictive indicators for the determination of future disease [62
The majority of the intervention studies were carried out on patients who were post-head and neck radiotherapy, likely because these individuals are thought to be at a much higher risk for the development of dental caries compared to their post-chemotherapy counterparts. Expectedly, the use of fluoride products and chlorhexidine rinses are beneficial in reducing caries activity and levels of streptococcus mutans, respectively.
There continues to be a lack of clinical trials to evaluate the extent of dental disease associated with complications during cancer therapy, despite recommendations from the 1989 NIH consensus for more studies in this area [5
]. In this review, the weighted prevalence of an odontogenic infection during chemotherapy is approximately 6%. However, these studies had small sample sizes, did not report pre-existing oral conditions, and had varied styles of reporting results, making it tricky to draw conclusions. In addition, the pre-existing oral conditions in these patients were unknown. Despite the low prevalence of dental infections, there is some evidence in the literature that these infections may cause bloodstream bacteremia and become potentially life-threatening in immunosuppressed individuals. Based on this theoretical reasoning and indirect evidence, it appears reasonable to propose that all acute and potential sources of oral infections should be eradicated. Although, large prospective studies are required to definitively address this theoretical concern for oral infection.
Another area with poor evidence is the necessity for pre-cancer therapy dental clearance, and if required, the extent of disease that needs to be eradicated. However, conducting a prospective randomized controlled trial to evaluate eradicating all oral infections prior to patients undergoing cancer therapy versus no dental treatment may likely pose ethical concerns, especially if there is sufficient time for dental clearance. Eradicating acute dental problems versus eradicating both acute and chronic dental issues may be a more practical research design. At the time of this review, there was one cohort study that examined the viability of a minimal dental intervention clearance protocol in patients prior to chemotherapy. They found a 4% conversion rate of previously diagnosed chronic dental disease to acute inter-therapy pathology and a relative incidence of 10% conversion rate of acute conversion of previously diagnosed severe chronic periodontal disease [41
]. Based on their findings, the authors felt that patients with chronic dental pathology could proceed safely with chemotherapy, as the conversion rate to an acute condition was infrequent. Due to the distinct differences in the implications of the presence of dental disease in patients who are pre-chemotherapy versus those who are pre-radiotherapy, the results of this study cannot be extrapolated to patients undergoing radiotherapy. There are presently no studies that have investigated or assessed which dental treatment protocol may be the most superior and appropriate in patients undergoing radiotherapy.