library(magrittr)
library(kableExtra)
tab2 <- data.frame(Gender = c("Male", "Female", "Total"),
                   Healthy = character(3),
                   Gingivitis = character(3),
                   Perio = character(3),
                   Total = character(3))
kable(tab2) %>%
  kable_styling(bootstrap_options = c("striped", "hover")) %>%
  add_header_above(c(" " = 1, "Periodontal Status" = 3, " " = 1))