dentistry Dominic Thorncroft

Dental Morphology Of Permanent Premolars

The term premolar is used to denote any tooth in the permanent dentition of mammals that replaces a primary molar.

There are 8 premolars – 4 in the maxillary arch and 4 in the mandibular arch. They can be identified by the International Numbering System using the formula of Viohla as teeth 14, 15, 24, 25 for maxillary premolars and 34, 35, 44, 45 for mandibular premolars.

Functions: The premolars function with the molars in the mastication of food and in maintaining the vertical dimension of the face. They assist the canines in shearing and cutting food morsels. All premolars support the corners of the mouth and cheeks from sagging, which is more visible in older people.

Fillings in premolars should be aesthetic, especially on mesio-occlusal surfaces of upper first premolars in patients with a wide smile and a high lip line.

dentistry Dominic Thorncroft

Dental Morphology Of The Mandibular Central Incisor

The surface of the crown is nearly smooth. The crown is very narrow with respect to its length. The mesioincisal and distoincisal angles are nearly right angles, or only a little rounded.

N.B. This tooth is so symmetrical that it is quite difficult to tell left from right unless on models or in the mouth.

Both mesial and distal contact points are in the incisal third, almost level with the incisal edge. This phenomenon is unique to mandibular central incisors. The root is very narrow mesiodistally, but wide faciolingually. The lingual surface is smooth and shallow, without any grooves, accessory ridges or pits.

The labiolingual dimension is greater than the mesiodistal dimension. This is quite different from the measurements of the maxillary incisors and an important mark to distinguish mandibular incisors from maxillary incisors.