“…Several bioarchaeological investigations have also revealed increases in the frequency of periodontal disease with age in past populations (e.g., Costa, 1982;Kerr, 1991Kerr, , 1994Hillson, 1996;Oztunc et al, 2006). In some cases, the relationship between age and periodontal disease in modern populations is at least partly explained by behavioral factors, such as changes in oral hygiene or the increased use of medications that reduce salivary flow (Abdellatif and Burt, 1987;Sjögren and Nordström, 2000;Leal et al, 2010). However, some researchers have found that the significant relationship between age and periodontal disease persists when other factors, such as oral hygiene, are controlled for (Streckfus et al, 1999).…”