“Buck teeth” is the common term for a dental condition where the upper front teeth noticeably protrude beyond the lower front teeth. Clinically, this is known as an increased overjet, a characteristic of a Class II malocclusion. This misalignment is extremely common, affecting an estimated 15 to 20% of children and adolescents globally. The underlying causes are often complex, rarely resulting from a single factor but arising from a combination of anatomical, developmental, and environmental influences.
Inherited Skeletal Structure
The foundational structure of the facial bones plays a significant role in determining tooth position, and these hereditary factors are often the most important underlying causes of a pronounced overjet. The relationship between the upper jaw (maxilla) and the lower jaw (mandible) establishes the skeletal framework for the bite.
A discrepancy in the size or position of these two bones is a primary contributor to buck teeth. One common pattern is mandibular retrognathism, where the lower jaw is underdeveloped or positioned too far backward. Alternatively, the upper jaw may be overdeveloped or positioned too far forward, a condition known as maxillary prognathism.
Genetic influences govern the overall size, shape, and growth pattern of the jaws, meaning these traits often run in families. Specific genes and chromosomal locations have been linked to jaw development, suggesting a genetic predisposition for certain skeletal patterns.
Environmental Habits and Pressure
Consistent external pressures exerted on the developing teeth and jaw, often stemming from habitual behaviors, primarily affect the alignment of the teeth within the bone rather than the underlying skeletal structure itself. The three most common habits that alter dental position are prolonged thumb or finger sucking, habitual tongue thrusting, and chronic mouth breathing.
Prolonged thumb or finger sucking, especially if continued past the age of three or four, puts direct, forceful pressure on the upper front teeth. This force pushes the incisors forward and often tips them outward, increasing the horizontal overjet. The sucking motion also causes the muscles in the cheeks to press inward, which can narrow the upper dental arch and exacerbate the protrusion.
Tongue thrusting occurs when the tongue protrudes between the front teeth during swallowing or speaking. The repetitive pressure from the tongue pushing against the back of the upper incisors acts as a constant orthodontic force. While a tongue thrust is a normal infantile swallow pattern, its persistence into childhood can maintain or worsen an existing protrusion.
Chronic mouth breathing alters the natural resting position of the tongue. When the mouth is consistently open for breathing, the tongue often rests low in the floor of the mouth instead of against the palate. The absence of the tongue’s natural pressure on the upper jaw can prevent the maxilla from developing its full width, resulting in a narrow upper arch and a forward tilting of the upper teeth.
Dental Development and Spacing Issues
Protrusion can also originate from factors related specifically to the teeth themselves and their eruption patterns, independent of major skeletal size discrepancies. One common factor is a tooth-to-jaw size discrepancy, where a mismatch exists between the size of the teeth and the jawbone. If teeth are large relative to jaw size, the resulting crowding can push the front teeth outward.
The timing of the loss of primary (baby) teeth is a key developmental factor. Premature loss can allow neighboring permanent teeth to drift into the open space, disrupting the intended path of the permanent incisors. Conversely, a delayed loss of primary teeth can force the permanent teeth to erupt in an abnormal position.
The presence of supernumerary teeth, which are extra teeth that develop beyond the normal count, can also contribute to alignment issues. These extra teeth can physically obstruct the eruption of the permanent incisors or create crowding that forces the incisors into a protrusive position. Conversely, congenitally missing teeth can create large gaps that allow the remaining teeth to drift.