June 15, 2022
The pulp is the soft tissue present within the tooth that contains the blood vessels and nerves. It is protected by hard tissue layers called the dentin and the enamel. The pulp is located in the coronal (crown) portion of the tooth and also in the roots. The part of the pulp present in the coronal area is called the pulp chamber. The extension of the pulp chamber into the root or roots (in case of multi-rooted teeth) are called pulp canals.
The pulp chamber is not a typical cubical structure. The ends of its roof project two horn-like structures that extend into the cuspal areas of the tooth. The cusps are the hilly projections seen on the tooth. These pulpal extensions into the cusps are called pulp horns. The number of pulp horns in a tooth depend on the type of the tooth. The number of pulp horns can range from one to five.
Compared to permanent teeth, pulp horns in the deciduous teeth are located much higher. This is because of the shorter height of the crown due to a shorter dentinal area. Hence, in children, cavities can progress rapidly as the pulp is inflamed much quicker.
A part of the pulp horns extend into the dentin as well. As stated before the pulp houses the nerves in the tooth that caries the stimulus of pain. These nerves enter the tooth from the apex of the root and later branch upwards. There are different types of nerves within the pulp. The ones that terminate at the pulp horn are called A-delta fibres.
The A-delta fibres conduct pain at a faster rate. It senses the short, sharp and pricking pain. The stimuli of pain is usually triggered by the movement of a fluid in the dentinal region. This movement of fluid occurs as a result of imbalance in the pressure of pH caused by the invasion of microbes on the tooth. This in turn can be due to consumption of sweet foods, mechanical trauma to the tooth or cold stimuli.
When the patient presents with a complain of sharp shooting pain in the tooth, the dental surgeon takes a radiograph to confirm the extent of the decay. The pulp horn appears black on the radiograph and the pulp horn can be appreciated as a spicule originating from the pulp in the line of the cusp. While the enamel and dentin appear white, the decayed portion appears black. On the radiograph, in most cases, the decayed portion involves the pulp horn too.
In order to check the health of the tooth, an electric pulp tester is used. This device stimulates the A-delta fibres and a threshold level is set to see how early or late the tooth responds to the electrical stimulus. This test cannot be done in primary or deciduous teeth because of the less amount of A-delta fibres in milk teeth compared to permanent teeth.
Carious attack on the pulp horn usually hints at a treatment modality that involves removal of the coronal portion of the pulp only or in some more severe cases, removal of the entire pulp from the roots. Following the removal and disinfection of the pulp from the canals, the tooth is reinforced with filling materials. This pulp therapy is called root canal treatment.
In cases where only the coronal portion of the pulp is amputed and the pulp in the roots is deemed healthy, then the tooth is layered with a pulp protective material and restored accordingly. This technique is called pulpotomy.
In some cases, while removing the carious portions of the tooth, the dentist may expose the pulp horn. However, the bleeding from this portion can be controlled and the pulp horn and its surrounding tissues can be covered by materials like Mineral Trioxide Aggregate or Biodentin which restrict any further complications. This procedure is called direct pulp capping. The success of this procedure in milk teeth is less compared to adult teeth.
Pulp horns usually recede with age. The constant force of mastication on the teeth over the years initiates the formation of another layer of dentin called the secondary dentin. This dentin covers the pulp horns in the process. Thus, with time, the pulp chamber is flattened due to the recession of the pulp horns.
Pulp horns play a sensory, and at the same time a protective role in the normal functioning of the tooth. They are one of the important diagnostic considerations that substantiates future treatment plan.