Bunny teeth is a colloquial term for upper front teeth that stick out noticeably beyond the lower teeth, giving the smile a rabbit-like appearance. In dental terms, the condition involves prominent or protruding maxillary central incisors, often accompanied by what orthodontists call increased overjet, meaning the horizontal gap between the upper and lower front teeth is larger than normal. The causes range from childhood habits and tongue posture to inherited jaw structure, and while the look is sometimes considered charming, significant protrusion can create real problems with biting, speaking, and vulnerability to injury.
What Exactly Makes Teeth Look Like “Bunny Teeth”
The defining feature is forward positioning of the two upper central incisors relative to the lower teeth. In a typical bite, the upper front teeth sit just slightly ahead of the lower ones, with a horizontal overlap of roughly two to four millimeters. When that gap grows well beyond that range, the upper teeth become visually dominant, especially when smiling or when the lips are relaxed. In more pronounced cases, the teeth may angle outward (a tilt dentists call labial inclination) rather than simply sitting farther forward. A case report of severe protrusion documented maxillary overgrowth with pronounced labial inclination of the incisors, significant enough to cause gum recession on the palatal side and require surgical correction.1Hindawi / Case Reports in Dentistry. Maxillary Protrusion with Severe Overjet Treated by Maxillary Anterior Alveolar Osteotomy That is the extreme end of the spectrum, but it illustrates the anatomy involved: the teeth themselves, the bone that holds them, and how far forward both sit relative to the rest of the face.
The appearance is sometimes confused with an overbite, but the two are different measurements. Overbite describes vertical overlap: how much the upper front teeth cover the lower ones from top to bottom. Overjet describes horizontal distance: how far the upper teeth jut out in front of the lower ones. Bunny teeth are primarily an overjet issue, though the two often coexist. A person can have deep overbite without any visible protrusion, or they can have dramatic forward protrusion with relatively little vertical overlap.
Childhood Habits That Push Teeth Forward
One of the most well-documented causes of protruding upper incisors is prolonged thumb or finger sucking. The pressure of the thumb against the back of the upper front teeth, repeated thousands of times over months or years, gradually pushes them forward while simultaneously pressing the lower front teeth inward. A study examining sucking habits and dental alignment in young children found that daily thumb or digit sucking lasting more than a year was associated with a significantly increased overjet, as well as higher rates of certain bite misalignments and anterior open bite.2PubMed Central. The association between nutritive, non-nutritive sucking habits and primary dental occlusion The key factor is duration. Brief thumb sucking in infancy rarely causes lasting changes, but the habit persisting past age three or four, when permanent teeth are beginning to develop beneath the gums, raises the risk substantially.
Pacifier use follows a similar pattern, applying outward pressure on the upper arch. However, thumb sucking tends to produce more pronounced effects because the thumb is harder, applies force to a more focused area, and the habit often continues longer than pacifier use.
Tongue Thrust and Mouth Breathing
A less obvious but persistent cause is tongue thrust swallowing, a pattern where the tongue pushes firmly against or between the front teeth during every swallow. Most people swallow hundreds of times a day, and each swallow generates real force. When that force is directed forward against the upper incisors rather than upward against the palate, it can gradually push the teeth outward over time. A review of tongue thrust described it as a retained infantile swallow pattern that, when it persists into later childhood, leads to protruded teeth among other problems.3PubMed Central. Orofacial Myofunctional Therapy in Tongue Thrust Habit: A Narrative Review Research comparing dental features in people with and without tongue thrust found that overjet was significantly greater in the tongue-thrusting group.4PubMed Central. Effect of Tongue Thrust Swallowing on Position of Anterior Teeth
Mouth breathing contributes through a related mechanism. When someone habitually breathes through the mouth rather than the nose, the tongue drops to the floor of the mouth instead of resting against the palate. This removes the gentle outward pressure the tongue normally exerts on the upper jaw, allowing the upper arch to narrow. Meanwhile, the cheeks press inward unopposed. The net result can be a narrow upper jaw with teeth that flare forward. Researchers have documented that mouth breathing, tongue thrust swallowing, and abnormal resting tongue posture can all deform the bony structures of the jaw over time through the constant low-level forces they exert.5The Bulletin of Tokyo Dental College. Malocclusion Associated with Abnormal Posture
The Role of Genetics and Jaw Structure
Not all bunny teeth are caused by habits. The size relationship between the upper and lower jaws is largely inherited, and when the upper jaw grows proportionally larger or sits farther forward than the lower jaw, the upper teeth end up protruding even without any environmental push. This skeletal component is sometimes the dominant factor, especially in cases where protruding teeth show up in families across generations.
Research into the genetic architecture of anterior tooth shape and size in Australian twins has shown that traits of front teeth are substantially heritable, with genetic correlations between corresponding teeth on the left and right sides being high, and about a third of permanent tooth trait pairs showing evidence of shared genetic influence.6Elsevier (Archives of Oral Biology). The genetic architecture of anterior tooth morphology in a longitudinal sample of Australian twins and families This means the size, shape, and angulation of your front teeth are influenced by the same genes that shaped your parents’ teeth. If both your parents had relatively large upper incisors set in a slightly forward upper jaw, you are more likely to inherit a similar pattern.
Certain medical conditions can also affect jaw growth in ways that exaggerate the protrusion. In children with juvenile idiopathic arthritis affecting the jaw joint, inflammation can suppress growth of the lower jaw while the upper jaw develops normally, creating a mismatch. Up to 70% of these patients with jaw joint involvement show some form of craniofacial growth disturbance, often resulting in a small, set-back lower jaw and prominent upper teeth.7ScienceDirect. Craniofacial growth and dento-alveolar development in juvenile idiopathic arthritis patients While this is an uncommon cause, it illustrates how the skeletal relationship between upper and lower jaws can drive tooth prominence independent of habits.
When Two Teeth Develop as One
Occasionally, bunny teeth look unusual not because of protrusion but because one or both upper central incisors are abnormally large. This can happen when two tooth buds fuse during development, creating a single extra-wide tooth. Dental fusion and a related anomaly called gemination are among the more common developmental dental anomalies in children.8PubMed Central. Fusion or Gemination? Diagnosis and Management in Primary Teeth: A Report of Two Cases In one documented case, an upper central incisor had fused with a supernumerary (extra) tooth, producing a visibly oversized front tooth with two separate roots visible on X-ray.9PubMed Central. Fused upper central incisors: management of two clinical cases A child with one normal-sized and one fused, oversized central incisor can look very much like a cartoon bunny, with the exaggerated tooth drawing immediate attention. These cases are managed differently from simple protrusion, sometimes requiring reshaping, veneers, or extraction and replacement depending on how the fused roots affect function.
The Lip Factor
Something people rarely consider is the role lips play in keeping teeth in position. The lips apply gentle, continuous inward pressure on the front teeth. In a person with competent lip closure, meaning the lips meet comfortably at rest without strain, this pressure helps counterbalance the outward push of the tongue from behind. But when the lips are short or habitually apart (a condition called lip incompetence), that restraining pressure is reduced, and the teeth are freer to drift forward.
This relationship works in both directions: protruding teeth make it harder for the lips to close, and incomplete lip closure allows teeth to protrude further. A study of children with incompetent lips found that treatment with an oral screen, a device that sits behind the lips and encourages them to close, led to backward tilting of proclined upper incisors and a measurable decrease in overjet within a year.10Elsevier / American Journal of Orthodontics. Effect of oral screen treatment on dentition, lip morphology, and function in children with incompetent lips The takeaway is that soft tissue balance matters. The teeth sit in an equilibrium between the tongue pushing outward and the lips and cheeks pushing inward. Disrupt either side, and the teeth shift.
Injury Risk and Speech Effects
Bunny teeth are not just a cosmetic issue. Teeth that stick out past the protective cover of the lips are more exposed to the world, and they are more likely to get hit. Research has found that prominent upper front teeth, classified as Class II Division 1 in orthodontic terms, affect roughly a quarter of twelve-year-olds in the UK, and early treatment with appliances that correct the protrusion reduced the incidence of new dental trauma compared to delaying treatment. In the group that waited, 30% experienced new trauma to the front teeth, compared to 19% among those treated early.11Cochrane Database of Systematic Reviews. Orthodontic treatment for prominent upper front teeth (Class II malocclusion) in children and adolescents That is a meaningful difference, especially considering that a fractured or knocked-out permanent incisor is a lifelong dental problem.
Separately, research into malocclusion and dental injuries in preschoolers found that both crowding and increased overjet were associated with a higher occurrence of dental trauma, though the strength of that association depended on what other bite features were present.12PubMed. Association between occlusal characteristics and the occurrence of dental trauma in preschool children: a case-control study
Speech can also be affected. Producing certain sounds, particularly “s” and “z,” requires the tongue to make precise contact near the upper front teeth with a specific amount of space between the teeth. When the overjet is large or the bite is open, that precision is harder to achieve. Research on the relationship between incisor position and speech found that a correct “s” sound is more difficult to produce when overjet is increased or overbite is decreased.13European Journal of Orthodontics. Articulatory disorders in speech as related to the position of the incisors Many children naturally compensate, and a mild protrusion might never cause noticeable speech difficulty. But in more pronounced cases, a slight lisp or whistling quality on sibilant sounds is common enough that speech therapists routinely screen for dental alignment.
Social and Emotional Impact
For children and teenagers, protruding front teeth can become a target. A study of orthodontic patients found that being bullied was significantly associated with increased overjet, increased overbite, and a high need for orthodontic treatment. Participants who were bullied reported lower self-esteem across multiple domains, including social competence, physical appearance, and general self-worth, along with greater emotional and social impact from their oral condition.14PubMed. Bullying in orthodontic patients and its relationship to malocclusion, self-esteem and oral health-related quality of life
A systematic review looking at the relationship between malocclusion and bullying across multiple studies confirmed that extreme overjet, defined at thresholds of greater than four, six, or nine millimeters depending on the study, along with deep overbite and visible spacing or missing teeth, showed the strongest connections to bullying experiences.15PubMed Central. Is there a relationship between malocclusion and bullying? A systematic review The evidence here is not that protruding teeth cause psychological harm in some mechanistic way; rather, visible dental differences make children a more frequent target for teasing, and the repeated social stress of that teasing affects how they feel about themselves. This is one of the reasons orthodontic treatment for significant overjet is often considered more than cosmetic, and why many dental insurance plans cover it when the protrusion crosses a clinical threshold.
Treatment Options
How bunny teeth are corrected depends on whether the problem is mainly dental (the teeth themselves are angled wrong) or skeletal (the jaws are mismatched in size or position). Most cases in children and adolescents involve some combination of both, and the age at which treatment starts matters.
For younger children whose jaws are still growing, functional appliances like the Twin Block or Herbst device are commonly used. These work by redirecting jaw growth, encouraging the lower jaw to grow forward while restraining the upper jaw, effectively closing the gap. The Cochrane review of treatment for prominent upper front teeth found moderate-quality evidence that early intervention with these appliances reduced trauma risk compared to waiting, as noted above. The trade-off is that early treatment means a longer overall period in some form of appliance, and some children may still need braces later for final alignment.
For adolescents and adults who have finished growing, conventional braces or clear aligners can retract the upper front teeth into a more normal position, often by extracting premolars to create space. In severe cases where the jaw discrepancy is too large for braces alone, surgical correction becomes an option. The case report mentioned earlier described a maxillary anterior alveolar osteotomy, a procedure that surgically repositions the bone segment holding the front teeth, used when orthodontics alone would not adequately correct the protrusion.1Hindawi / Case Reports in Dentistry. Maxillary Protrusion with Severe Overjet Treated by Maxillary Anterior Alveolar Osteotomy
For habit-related protrusion in young children, addressing the habit itself is sometimes enough. Orofacial myofunctional therapy, exercises that retrain tongue posture and swallowing patterns, can help correct tongue thrust.3PubMed Central. Orofacial Myofunctional Therapy in Tongue Thrust Habit: A Narrative Review Oral screens can address lip incompetence.10Elsevier / American Journal of Orthodontics. Effect of oral screen treatment on dentition, lip morphology, and function in children with incompetent lips And simply stopping thumb sucking before the permanent incisors fully erupt sometimes allows the teeth to settle back on their own, though this depends on how much bone remodeling has already occurred.
Why Modern Humans Have More Dental Crowding
There is an evolutionary angle to tooth prominence that rarely comes up in conversations about braces. Our ancestors ate diets that required far more chewing force than modern processed food: raw plants, tough meat, fibrous roots. That heavy chewing wore teeth down significantly over a lifetime, and jaws that could accommodate large teeth were a survival advantage. The theory, supported by anthropological research, is that the tooth-jaw size mismatch common in modern populations exists because our diets softened faster than our genetics could adapt. Teeth remain sized for a demanding ancestral diet, while jaws, which develop partly in response to chewing forces during childhood, often end up smaller because they are not subjected to those forces.16American Journal of Orthodontics. The adaptive value of dental crowding: A consideration of the biologic basis of malocclusion
This does not directly explain bunny teeth in the overjet sense, since crowding and protrusion are different problems. But it provides context for why so many people need orthodontic treatment at all. The human mouth is, in a sense, still calibrated for a lifestyle we stopped living thousands of years ago. Smaller jaws with teeth that are still relatively large create conditions where crowding, impaction, and malalignment are almost the default rather than the exception.
How Smile Perception Varies Across Cultures
Whether protruding front teeth bother someone depends partly on where they live and what their culture considers attractive. In some East Asian countries, slightly prominent canine teeth (called “yaeba” in Japan) have been considered endearing, and some people have even sought cosmetic dental work to add the look. Bunny teeth, while different from yaeba, fall into a similar gray zone: mildly protruding front teeth are sometimes seen as youthful or approachable rather than as a defect.
Cross-cultural research on smile characteristics found significant differences in smile satisfaction between Latvian and Uzbek young adults, with Uzbek participants reporting notably higher satisfaction with their smile appearance despite differences in smile type and the number of teeth displayed.17Dove Press / PubMed Central. Cross-Cultural Analysis of Smile Characteristics, Perception, and Satisfaction Among Latvian and Uzbek Young Adults: A Comparative Study While this study did not focus specifically on protrusion, it underscores that dental satisfaction is culturally mediated. What motivates one person to seek orthodontic treatment might not register as a concern for someone from a different background. The line between a charming quirk and a problem worth fixing is drawn differently depending on aesthetic norms, access to orthodontic care, and how much social pressure exists around dental appearance in a given community.
Why Rabbit Incisors Are Not Like Human Ones
The comparison to rabbits is more than just visual. Actual rabbit teeth and human teeth work on fundamentally different systems. Rabbit incisors grow continuously throughout the animal’s life. They are open-rooted, meaning the base of the tooth never closes off, and new enamel and dentin are constantly deposited. Research on rabbit teeth has shown that the continuously erupting incisor has enamel on its front surface and cementum on its back surface, more like a root on one side and a crown on the other, a structure completely unlike any human tooth.18PubMed. Demonstration of enamel matrix proteins on root-analogue surfaces of rabbit permanent incisor teeth Rabbits keep their incisors worn to a functional length by gnawing; if a rabbit loses an opposing tooth or stops wearing them down, the incisors can overgrow dramatically, curving into spirals that prevent the animal from eating.
Human teeth, by contrast, erupt once, reach their final length, and stop. The “bunny” comparison is purely about the visual impression of two big front teeth dominating the smile. The biology behind it could not be more different. A rabbit’s prominent incisors are a core feature of its feeding strategy, evolved over millions of years for gnawing bark and fibrous vegetation. A human’s prominent incisors are typically a mismatch between jaw size, tooth size, and the soft-tissue forces shaping both during development.