This study evaluated 51 patients after one year.  Half the patients were taking Vitamin D ≥ 400 IU per day and Calcium ≥ 1000 mg/day. It found Calcium and Vitamin D had a modest positive effect on periodontal (gum) health.  Vitamin D supplementation may reduce gingival inflammation and bone loss. 

More details here: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3472001/

Garcia MN, Hildebolt CF, Miley DD, Dixon DA, Couture RA, Spearie CL, Langenwalter EM, Shannon WD, Deych E, Mueller C, Civitelli R. One-year effects of vitamin D and calcium supplementation on chronic periodontitis. J Periodontol. 2011 Jan;82(1):25-32. doi: 10.1902/jop.2010.100207. Epub 2010 Sep 1. PMID: 20809866; PMCID: PMC3472001.