Head and neck radiotherapy effects on the dental pulp vitality and response to sensitivity tests: A systematic review with meta-analysis

Background Experimental studies are controversial regarding the effects of radiotherapy for head and neck cancer (HNC) on the dental pulp. Therefore, a systematic review of clinical studies is necessary to investigate whether alterations in pulp status occur. Objectives To evaluate the evidence on radiotherapy for HNC and pulp status. Methods A systematic search of articles published until November 2021 was performed in the MEDLINE/PubMed, Cochrane Library, Web of Science (All Databases), Scopus, EMBASE, and Open Grey databases. The eligibility criteria were based on the PICOS strategy, as follows: (P) vital teeth of adult patients with intraoral and/or oropharyngeal cancer; (I) radiotherapy; (C) control group or values of the same tooth before radiotherapy (basal values); (O) pulpal status after radiotherapy; and (S) clinical studies. The Cochrane Risk of Bias in Nonrandomized Studies of Interventions tool was used to assess the quality of the included studies. Meta-analyses were performed using fixed and random effects. The overall quality of evidence was assessed through the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) tool. Results Six studies were included for qualitative analysis. Five were classified as serious risk of bias and one as moderate risk of bias. Four studies reported altered pulp responses to cold thermal tests after radiotherapy initiation. Meta-analyses were performed using three included studies. From these, all were included in the meta-analysis for pulp response values to cold sensitivity test immediately after radiotherapy initiation (risk ratio: 0.00 [CI: 0.00, 0.02], p I-2 = 0%); and two in the meta-analysis for pulp response values to cold sensitivity test after 4-5 months of radiotherapy (risk ratio: 0.01 [CI: 0.00. 0.06], p I-2 = 0%). Two reported progressively higher readings to pulp response in the electrical test after radiotherapy initiation (mean difference: -11.46 [-13.09, -9.84], p I-2 = 68%). Two studies demonstrated a pulp oxygen saturation (SpO(2)) decrease at the end of radiotherapy; and an increase after 4-6 months of radiotherapy beginning. And other demonstrated normal dental pulp SpO(2) 4-6 years after treatment. GRADE analysis presented a moderate certainty of evidence. Discussion This review verified that radiotherapy for HNC causes significant alterations on the dental pulp responses, but does not seem to induce pulp necrosis. Significant limitations regarding controlling for confounding factors, classification of interventions, and measurement of outcomes were verified, evidencing the need for well-designed studies. Conclusions This systematic review demonstrated that radiotherapy for HNC induced significant changes in the pulp response with moderate quality of evidence. Such altered responses cannot determine pulp status accurately.