A person’s “bite,” or dental occlusion, describes how the upper and lower teeth meet when the mouth is closed. Understanding what a normal bite looks like is important because any deviation from this standard can affect chewing, speaking, and the health of the jaw joints.
Defining the Ideal Bite Relationship
The standard for a normal bite in dentistry is termed Angle’s Class I Occlusion, which describes a harmonious relationship between the upper and lower teeth. This ideal alignment is characterized by precise vertical and horizontal overlaps of the front teeth, as well as specific contact points for the back teeth.
When viewed from the front, the upper teeth should gently cover the lower teeth, both vertically and horizontally. The optimal vertical overlap, known as overbite, is typically where the upper incisors cover about 20 to 30% of the lower incisors. A slight horizontal overlap, or overjet, means the upper front teeth sit just 1 to 2 millimeters in front of the lower front teeth. The center line between the two upper front teeth should align perfectly with the center line of the two lower front teeth.
The relationship of the back teeth is precise. Specifically, the prominent, pointed cusp on the cheek-side of the upper first molar should fit neatly into the central groove of the lower first molar. Moving forward, the tip of the upper canine tooth should align to fit between the lower canine and the lower first premolar.
This precise tooth-to-tooth arrangement ensures that the entire upper arch is slightly wider than the lower arch, allowing all upper teeth to fit just outside the lower teeth. When the teeth are properly aligned, they form a smooth, continuous curve without any gaps or overlapping, which helps distribute the forces of biting and chewing evenly.
Functional Roles of Proper Alignment
Proper alignment allows the upper and lower teeth to shear and grind food evenly, which is the first step in the digestive process. When the bite is balanced, food is broken down more thoroughly, which promotes better nutrient absorption.
A balanced bite also plays a significant role in protecting the teeth from excessive wear. When the alignment is correct, the pressure from biting and grinding is distributed uniformly across all teeth, preventing any single tooth or group of teeth from receiving disproportionate force. This prevents the excessive wearing down of enamel that can occur with uneven contact points over time.
The position of the teeth also influences speech articulation and the health of the jaw joint. The teeth and the jaw structure provide the necessary boundaries for the tongue to form specific sounds, such as ‘s’ and ‘th’ sounds. Furthermore, a correct bite ensures that the forces of the jaw muscles are directed through the teeth and joints in a way that minimizes stress on the temporomandibular joint (TMJ).
Common Types of Bite Deviations
When the upper and lower teeth do not meet in the harmonious Class I relationship, the condition is called a malocclusion. The most common deviations involve issues with the vertical or horizontal overlap of the front teeth. In an overbite, often called a deep bite, the upper front teeth cover too much of the lower front teeth, sometimes concealing the lower teeth almost entirely when the mouth is closed.
Conversely, an underbite occurs when the lower jaw protrudes, causing the lower front teeth to sit in front of the upper front teeth. Another common deviation is an open bite, where the upper and lower front teeth (or sometimes the back teeth) do not touch at all when the jaw is closed, leaving a visible gap.
A crossbite is a misalignment where one or more upper teeth fit inside the lower teeth. This can occur with the front teeth (anterior crossbite) or the back teeth (posterior crossbite). Beyond the arch-to-arch relationships, deviations also include crowding, where there is not enough space in the jaw for all teeth, causing them to overlap or twist. Spacing, the opposite condition, involves excessive gaps between the teeth.