Introduction: Guidelines for routine antibiotic prophylaxis (AP) before dental procedures to prevent periprosthetic joint infection (PJI) have been hampered by the lack of prospective clinical trials. Objectives: To apply value-of-information (VOI) analysis to quantify the value of conducting further clinical research to reduce decision uncertainty regarding the cost-effectiveness of AP strategies for dental patients undergoing total knee arthroplasty (TKA). Methods: An updated decision model and probabilistic sensitivity analysis (PSA) evaluated the cost-effectiveness of AP and decision uncertainty for 3 AP strategies: no AP, 2-y AP, and lifetime AP. VOI analyses estimated the value and cost of conducting a randomized controlled trial (RCT) or observational study. We used a linear regression meta-modeling approach to calculate the population expected value of partial perfect information and a Gaussian approximation to calculate population expected value of sample information, and we subtracted the cost for research to obtain the expected net benefit of sampling (ENBS). We determined the optimal trial sample sizes that maximized ENBS. Results: Using a willingness-to-pay threshold of $100,000 per quality-adjusted life-year, the PSA found that a no-AP strategy had the highest expected net benefit, with a 60% probability of being cost-effective, and 2-y AP had a 37% probability. The optimal sample size for an RCT to determine AP efficacy and dental-related PJI risk would require approximately 421 patients per arm with an estimated cost of $14.7 million. The optimal sample size for an observational study to inform quality-of-life parameters would require 2,211 patients with an estimated cost of $1.2 million. The 2 trial designs had an ENBS of approximately $25 to $26 million. Conclusion: Given the uncertainties associated with AP guidelines for dental patients after TKA, we conclude there is value in conducting further research to inform the risk of PJI, effectiveness of AP, and quality-of-life values. Knowledge Transfer Statement: The results of this value-of-information analysis demonstrate that there is substantial uncertainty around clinical, health status, and economic parameters that may influence the antibiotic prophylaxis guidance for dental patients with total knee arthroplasty. The analysis supports the contention that conducting additional clinical research to reduce decision uncertainty is worth pursuing and will inform the antibiotic prophylaxis debate for clinicians and dental patients with prosthetic joints.