Enamel spurs projecting from the cemento-enamel junction into the furcation as well as small islands and droplets of enamel deposited on furcational root surfaces are characteristic morphological features of human maxillary and mandibular molars. The furrows and recesses created by these structures form pathways for bacterial invasion and predispose for local periodontitis. Furthermore, the furcations are often covered by thick central cementum ridges, with steplike or tongue-like deepenings around enamel droplets. In the cementum, there is a variable number of small and large openings, representing either cementum-inherent channels or large open connections between pulp chamber and furcation. These structures offer ample opportunities for uncontrollable bacterial retention and colonisation, and the possibility for pulpal infections to spread into the furcation. The literature covering these issues is summarized.