The necessity of a molar depends on its type and location. Molars are the large, flat teeth at the back of the mouth, primarily designed for grinding food. Because these teeth are fundamental to the mechanics of eating, the decision to remove a damaged or painful molar can be confusing. Understanding the unique function of molars and how different types contribute to oral health is the first step in determining their necessity.
The Role of Molars in Oral Function
Molars perform the majority of the heavy work involved in the initial stages of digestion. These large teeth have broad, flat surfaces (cusps) specifically shaped to crush and grind food into a manageable consistency for swallowing. Approximately 90% of the entire chewing process, known as mastication, takes place in the molar region.
The forces generated by the jaw muscles are concentrated on these back teeth, creating a powerful grinding action. The average maximum bite force in the molar area can reach 400 to 500 Newtons (about 90 to 112 pounds of force). This mechanical power is necessary to process tough or fibrous foods.
Molars also act as the structural “backstops” of the dental arch, maintaining the correct relationship between the upper and lower jaws, a concept called occlusion. Proper occlusion is maintained by the consistent contact between the molars, which helps distribute tremendous bite forces evenly across the jawbone. This alignment affects chewing comfort and the health of the jaw joints.
Distinguishing Between Molar Types
The necessity of a molar varies considerably based on its position in the mouth. Adults typically have up to 12 molars, divided into first, second, and third molars, with three on each side of the upper and lower jaws. Each type contributes differently to the overall stability and function of the bite.
The first and second molars are the workhorses of the mouth and are considered essential for function. The first molars are often the first permanent teeth to erupt and are positioned to take the brunt of the chewing forces. Their broad roots and strong position make them crucial for maintaining the vertical height of the face and the stability of the dental arch. Losing a first or second molar almost always requires professional replacement to prevent long-term complications.
The third molars, commonly called wisdom teeth, are the most posterior teeth and are often the least necessary. They are the last teeth to emerge, typically between the ages of 17 and 25. Wisdom teeth are the most common molars to be removed because they frequently become impacted, erupt only partially, or cause crowding. If a third molar is removed and the first and second molars are healthy and properly aligned, replacement is rarely necessary, as the bite remains stable without them.
Immediate and Long-Term Effects of Molar Loss
If a functional molar (a first or second molar) is lost and not replaced, a series of negative changes can occur over time. One immediate effect is the loss of support for adjacent teeth.
The teeth next to the empty space often begin to shift or tilt into the gap, disrupting the alignment of the dental arch. This shifting creates spaces between other teeth, making them harder to clean and increasing the risk of decay and periodontal disease.
A second consequence involves the opposing tooth, the molar directly above or below the missing one. Without its partner to stop its movement during biting, this opposing tooth can begin to move out of the jawbone, a process called super-eruption. This movement changes the bite relationship, causing uneven wear on other teeth and potentially leading to jaw joint discomfort. The change in position also exposes the tooth root, increasing its susceptibility to damage and sensitivity.
Over the long term, the absence of the molar root leads to alveolar bone loss in the jaw. The root of a tooth provides mechanical stimulation to the surrounding bone tissue, which keeps the bone dense and healthy. Once the tooth is gone, this stimulation ceases, and the jawbone begins to resorb, or shrink. The loss of bone density can negatively impact the integrity of surrounding teeth and complicate any future efforts to replace the missing tooth.
Options for Replacing a Missing Molar
For a missing first or second molar, replacement is generally recommended to restore function and prevent the issues associated with tooth loss. The two primary options are dental implants and fixed bridges. Both solutions aim to restore chewing ability and maintain the proper alignment of the bite.
Dental implants are widely considered the gold standard for tooth replacement because they mimic the structure of a natural tooth. An implant involves surgically placing a titanium post into the jawbone, which acts as a replacement root and prevents bone loss by stimulating the tissue. Once the post integrates with the bone, a custom-made crown is attached, providing a stable, independent, and long-lasting replacement.
A fixed bridge offers an alternative solution that can be completed more quickly than an implant. This restoration consists of an artificial tooth suspended between two crowns. The crowns are cemented onto the healthy adjacent teeth, which serve as anchors for the replacement tooth. While a bridge restores function, it requires the modification of those healthy teeth and does not provide the necessary stimulation to prevent jawbone loss beneath the missing tooth.