Premolar teeth are a distinct type of tooth in the human mouth, positioned between the pointed canine teeth and the broader molars. These teeth are found in both the upper and lower jaws, serving a transitional role in chewing. Humans typically possess eight premolars in total, with two located in each of the four quadrants. They are a permanent part of adult dentition, contributing to overall oral function.
Location and Structure
The first premolar is the fourth tooth from the midline in each quadrant, directly behind the canine. This placement distinguishes it from the second premolar, which is the fifth tooth. The maxillary (upper) first premolar commonly has two cusps: a buccal (cheek side) and a lingual (tongue side), with the buccal cusp typically longer. It frequently has two roots (one buccal, one lingual), though a single, wide root can occur in about 40% of cases. Its occlusal (biting) surface often appears ovoid or hexagonal, characterized by a central developmental groove and a mesial marginal groove that crosses the mesial marginal ridge.
The mandibular (lower) first premolar generally has a single root. Its crown features a large, well-developed buccal cusp and a smaller lingual cusp, which may resemble a cingulum. The occlusal surface is comparatively small, and its mesial central developmental groove can extend onto the lingual surface. These distinct anatomical characteristics help differentiate the first premolars from the single-cusped canines and the multi-cusped molars.
Role in Chewing
First premolars play a specific role in mastication, acting as an intermediary between the tearing function of the canines and the grinding capabilities of the molars. Their unique shape, with two cusps, allows them to perform both tearing and initial grinding.
These teeth crush and shear food into smaller, more manageable pieces. This preliminary breakdown prepares food for the more extensive grinding by molars further back in the mouth. The mechanical reduction of food size by the first premolars is an initial stage of digestion, facilitating easier swallowing and nutrient absorption.
Development and Eruption
Permanent first premolar teeth emerge as replacements for the deciduous (“baby”) first molars. Their development begins early, with calcification appearing around 1.5 years of age, and enamel completion by about 5 to 6 years.
Eruption of the permanent first premolars typically occurs between 10 and 11 years for upper teeth and 10 to 12 years for lower teeth. While individual eruption times can vary, this process generally follows a predictable sequence as part of the transition from primary to permanent dentition. By adolescence, most individuals will have their full complement of permanent premolars.
Common Dental Considerations
First premolar teeth can be susceptible to cavities, partly due to their position and anatomical grooves, which can trap food particles and plaque. Maintaining consistent oral hygiene, including regular brushing and flossing, is important to prevent decay. Dental professionals often provide guidance on proper techniques to access these teeth.
These teeth are frequently involved in orthodontic treatment, particularly when space is needed to correct crowded teeth or to retract anterior teeth. Orthodontists may recommend extracting one or more first premolars to create about 7 millimeters of space per quadrant. This space is then used to align other teeth, improving overall bite and appearance. While less common than wisdom teeth, first premolars can also experience developmental anomalies or impaction (failure to erupt properly). Addressing such issues often involves dental intervention to ensure proper oral health and function.