Caries process on occlusal surfaces: evolving evidence and understanding

Management of the caries process on occlusal surfaces of permanent molars has proven a major challenge. The onset of caries on these surfaces takes place soon after their eruption, and the permanent first molars, followed by the second molars, remain the sites in the dentition which show the highest caries prevalence. This paper is structured in the form of questions and answers in which traditional concepts of caries susceptibility of occlusal surfaces are appraised and confronted with the current evidence. Then, research studies examining the role of biological determinants on the development and arrest of occlusal caries in young permanent teeth are discussed. Finally, the contribution of these studies in terms of developing the available scientific evidence and our understanding of the caries process on occlusal surfaces is analyzed. The current evidence does not support the concept that the early onset and high prevalence of occlusal caries in young permanent teeth are due to a particularly low inherent resistance of the occlusal surface or due to the presence of inaccessible fissure-like structures on these surfaces. Evidence is provided to show that the most influential biological determinants of the development and arrest of occlusal caries are thick plaque accumulation on the groove-fossa system and the stage of tooth eruption limiting mechanical oral function. Consequently, active occlusal lesions are significantly more prevalent in erupting than in fully erupted teeth. The major contribution of this review is to provide updated knowledge about the biological principles determining the development and arrest of caries on occlusal surfaces of erupting teeth.