Is it normal for the upper teeth to not cover the lower teeth?

Dec 02, 2022 Source: Cainiu Health

Dr. Zhang Liwen

Introduction

The upper teeth normally overlap the labial surface of the lower teeth by no more than one-third of the crown, which is considered a normal overbite and overjet relationship. When the upper teeth fail to cover the lower teeth properly, it may indicate deep overbite or excessive overjet, both of which are abnormal occlusal relationships. These conditions can affect dental aesthetics and proper bite function. Over time, they may lead to excessive tooth wear and temporomandibular joint disorders, posing certain health risks.

It is generally not normal when the upper teeth cannot cover the lower teeth.

Under normal circumstances, the upper teeth should overlap the outer surface of the lower tooth crowns by no more than the top one-third, which is considered a normal overbite and overjet relationship. However, if the upper teeth fail to cover the lower teeth—such as when the incisal edge of the upper teeth bites too deeply behind the lower teeth, exceeding 2–3 mm—it may indicate deep overbite. Conversely, if the upper teeth protrude beyond the lower teeth by more than 2–3 mm, it is referred to as excessive overjet. Both conditions represent abnormal occlusion. Such malocclusions not only affect dental aesthetics but may also impair chewing function. Over time, they can lead to excessive tooth wear and temporomandibular joint disorders, posing certain health risks.

When the upper teeth fail to cover the lower teeth properly, patients are advised to promptly visit the orthodontic department of a hospital for evaluation. Based on the specific condition, an appropriate treatment plan can be developed, and orthodontic appliances may be recommended when necessary to restore a normal bite relationship.

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Is it normal for the upper teeth to cover the lower teeth when the mouth is closed?

Under normal circumstances, it is common and perfectly normal for the upper teeth to overlap the lower teeth when the mouth is closed. This biting pattern is a very common chewing motion and typically does not cause any problems. The way the upper teeth overlap the lower teeth when closing the mouth is known as a normal occlusal relationship, representing the optimal alignment of teeth and jaws. When we chew food, the upper and lower teeth fit together closely to effectively grind food into smaller pieces.

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What does it mean when the lower teeth overlap the upper teeth?

When the lower teeth cover the upper teeth, it is called "underbite," commonly referring to anterior crossbite malocclusion. This condition may result from congenital disorders, respiratory diseases, systemic diseases, or other causes. In addition to these factors, genetic inheritance may also contribute to the development of an underbite. If this condition affects a patient's normal daily life, they can seek medical treatment at a hospital for correction.

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What is the maxillary nerve?

The maxillary nerve is a branch of the trigeminal nerve. It transmits sensory and pain information from the upper teeth, jaw, nasal mucosa, tongue, and parts of the face to the central nervous system. The maxillary nerve originates in the gums, runs along the midfacial region, passes through the upper jaw and nasal cavity, and terminates in the upper lip and cheek. It conveys sensory signals to the brain and contributes to the control of chewing movements.