March 22, 2021
The posterior teeth (teeth at the back) are mainly used to break and crush down the food we eat while chewing. A hallmark of a posterior teeth is the fact that they have rounded protuberances on the chewing surface called cusps. Apart from helping in breakdown of the food, cusps play an important role in ensuring a proper bite as the upper and lower teeth occlude together. Depending on the type of tooth, there can be two, three, four or five cusps present.
In 1842, George Carabelli, a Hungarian, described an extra cusp that was present on the permanent first maxillary molar. This cusp is found behind the mesiolingual (towards the midline, facing the palate) cusp. It was thus named, the Cusp of Carabelli. There is no exact cause behind the formation of this cusp. Genetic factors and overactivity of the cells responsible for the formation of teeth are likely to play a role in the development of this cusp. In rare instances, the Cusp of Carabelli can be seen in milk teeth. If present, they are seen more often on the upper primary second molar.
Cusp of Carabelli usually does not have any particular function. All it does is broaden the chewing surface, thereby increasing the width of the tooth. In most cases, this cusp flattens or wears out with increasing age. There are patients who might feel Cusp of Carabelli as a hindrance in the bite or who feel their food gets lodged more often in the region of that cusp. The former can be resolved by a dentist as he or she can trim down the cusp. The issue of food lodgement can be a matter of concern as this can cause the tooth to decay which can lead to a tooth infection. In such a case, the tooth can be restored with a suitable cement after the removal of debris. The dentist ensures that the tooth is contoured after cementation such that the food does not lodge again in the region of the Cusp of Carabelli.
The Cusp of Carabelli is found on a tooth that is one of the sturdiest in the oral cavity. The permanent first maxillary molar has three roots that firmly position the tooth in the socket. As a result, this tooth is often used as an anchorage when other teeth need to be moved to correct the bite in developing dentition. Anchorage is taken by fabricating a ring of stainless steel around the tooth to which other wire components of an appliance are soldered. The presence of Cusp of Carabelli makes it difficult for the dentist to place the ring around the tooth. As a result, the cusp might need to be trimmed as convenient.
Even though Cusp of Carabelli does not have any function of its own, it is said that it is involved in compensatory mechanisms that maintain the harmony of the oral cavity. In order to ensure better bite, the Cusp of Carabelli's size would be more to meet the cusps of the lower molars. Then there are certain hypothesis that suggest that larger the crown of a tooth, more complex is its structure. Hence, based on this, the prevalence of Cusp of Carabelli is higher in bigger teeth.
The Cusp of Carabelli is often looked as an extension of the dentin (hard tissue layer under the enamel) of the mesiolingual cusp and it has often been reported that it has a pulp horn of its own. A pulp horn is the highest portion of the pulp, the soft tissue component of the tooth that houses its blood vessels and nerves. In cases where a Cusp of Carabelli has its own pulp horn, a patient might feel sensitivity and pain in case the cusp has a deep cavity.
In forensic dentistry, the Cusp of Carabelli can be used for identification purpose. This cusp is more prevalent in Caucasian, Europeans and South Asian populations compared to Mongoloids and Americans. Males and females equally display this trait.
Cusp of Carabelli has been studied as an important dental anthropological factor in the skulls of apes, Neanderthals and ancient humans. The evolutionary patterns are still studied extensively in order to theorize the importance of this cusp.