Background:
The aim of this study was to investigate the relationship between serum levels of vitamin D and calcium and the severity of gingival disease in patients with end-stage renal disease undergoing dialysis.

Material and methods:
In this case-control study, 43 patients diagnosed with chronic kidney disease undergoing dialysis were evaluated for probing pocket depth, clinical attachment loss, gingival index, bleeding on probing and plaque index. Then, they were divided into the case group with gingival disease and the control group without gingival disease. Serum levels of vitamin D and calcium were also determined. Data were analyzed using stata11 software using chi-square test and independent t-test with a significance level of 0.05 and a 95% confidence level.

Results:
The difference between the mean serum levels of vitamin D in the case and control groups was 33.66, which was statistically significant (P-value <0.001). The difference between the mean serum calcium levels in the case and control groups was 0.85, which was statistically significant (P-value> 0.001). There was no statistically significant relationship between the mean age and the body mass index between the case and the control groups (P-value = 0.13 and P-value = 0.39, respectively). There was no significant difference between the two groups in terms of gender (P-value = 0.43).

Conclusions:
Serum levels of vitamin D and calcium were lower in dialysis patients with gingival disease than in patients on dialysis without gingival disease, also no significant relationship was observed between age, sex and body mass index with gingival disease in dialysis patients.