A vertical overlap of about 2 to 4 millimeters between the upper and lower front teeth is generally considered a normal overbite. One study of people with well-aligned bites found a mean overbite of 2.45 mm, and clinicians commonly use the benchmark that the upper incisors should cover roughly one-third of the lower incisors’ visible height. Once that overlap exceeds about half the lower tooth height, most orthodontists classify it as a deep bite, which is where functional problems can begin.
What the Numbers Actually Mean
Overbite is measured as the vertical distance that the upper front teeth overlap the lower front teeth when your jaw is closed. It is not the same as overjet, which measures the horizontal gap between upper and lower incisors. The two get confused constantly, including in casual conversation and even on some dental websites, but they describe different dimensions of the bite. A person can have a normal overbite with an increased overjet, or vice versa.
In a study of a Brazilian sample with normal occlusion, the mean overbite was 2.45 mm, the mean overjet was 1.92 mm, and the interincisal angle averaged about 130 degrees.1Brazilian Dental Journal. Relationship between dental size and normal occlusion in Brazilian patients A separate study found that about two-thirds of its sample fell within the normal overbite range, with deep bite more common than open bite among those outside normal limits.2PMC. Analysis of the association between facial biotype, overbite and overjet in the permanent dentition The clinical definition of a deep overbite is a vertical overlap that exceeds half the height of the lower incisors, which in practice usually corresponds to something in the range of 4 mm or more depending on tooth size.3PubMed Central. Two middle-aged cases of deep overbite without molar support treated by orthognathic surgery
On the other end, if the upper and lower incisors do not overlap at all, or if the lower teeth bite in front of the uppers, the terminology shifts to open bite or anterior crossbite. So “normal” sits in a middle zone: enough vertical overlap to indicate proper jaw alignment, but not so much that the lower teeth are hidden behind or pressing into the gum tissue above.
How Overbite Changes from Baby Teeth to Adulthood
If you have a child whose front teeth seem to overlap a lot, it helps to know that overbite is not static. It shifts as the jaw grows and as primary teeth give way to permanent ones. In young children with primary teeth, overbite greater than 4 mm is fairly common but tends to decrease with age, likely because the continued eruption of primary molars adjusts the vertical dimension of the bite.4PubMed Central. Study of occlusal characteristics of primary dentition and the prevalence of maloclusion in 4 to 6 years old children in India
Once the permanent incisors come in, overbite tends to be somewhat greater than it was in the baby-tooth stage. This holds true even after accounting for the larger size of permanent incisors.5International Journal of Orthodontia and Oral Surgery. Various types of occlusion and amounts of overbite in normal and abnormal occlusion between two and twelve years That said, the direction of change from primary to permanent teeth is not always predictable. Some children see their overbite increase, while others see it decrease, and clinicians have found it difficult to forecast which way it will go based on the primary dentition alone.6PubMed. Occlusal changes from primary to permanent dentitions
Children with deep overbite often see their worst bite conditions during the mixed dentition phase, when both primary and permanent teeth are present. Research tracking these children has shown that overbite conditions can worsen during the prepubertal years but then improve on their own after puberty, which has practical implications for when treatment should start.7American Journal of Orthodontics and Dentofacial Orthopedics. Longitudinal growth changes in subjects with deepbite Jumping into aggressive treatment too early may mean correcting a problem that would have partially resolved with growth.
Why Humans Have Overbites at All
Most people assume that some degree of overbite is just how human teeth are meant to fit together. That is true now, but it was not always the case. Research published in Science found that for most of human history, adult teeth wore into an edge-to-edge bite: the upper and lower incisors met tip to tip, with no vertical overlap. The shift to the overbite that we now call “normal” appears to have happened after the Neolithic period, driven by changes in food-processing technology. Softer diets meant less incisal wear, which allowed the mild overbite of adolescence to persist into adulthood rather than flattening out.8PubMed. Human sound systems are shaped by post-Neolithic changes in bite configuration
This is more than a curiosity. The persistence of overbite and overjet in modern humans may have shaped the sounds we can produce. The researchers argued that the preservation of this bite configuration enabled the production of labiodental sounds like “f” and “v,” which are common in languages spoken by food-producing societies but rare in hunter-gatherer languages. So the 2 to 4 mm overlap we call “normal” is really a relatively recent development in human anatomy, made possible by how we prepare food.
What Causes an Excessive Overbite
When overbite goes beyond the normal range, the underlying cause is either skeletal, dental, or a combination. A skeletal deep bite involves a mismatch in how the upper and lower jaws grew, and the vertical growth component of the lower jaw plays a bigger role than rotational changes. Research has found that changes in the mandible’s vertical growth are roughly twice as influential as dental changes in the lower jaw, and about two and a half times as influential as anything happening in the upper jaw.9Dental, Oral and Craniofacial Research. Deep bite: A treatment planning decision support scheme A dental deep bite, by contrast, results from teeth themselves being in the wrong position: over-erupted upper or lower front teeth, or under-erupted back teeth that fail to prop the bite open sufficiently.
Among the skeletal factors most strongly associated with deep bite, the gonial angle (the angle at the back corner of the jaw), the ratio of front to back face height, the ramus length, and the overall basal angle of the jaws stand out. On the dental side, an increased curve of Spee, which describes the arc formed by the biting surfaces of the teeth from front to back, and insufficient eruption of the lower first molars are prominent contributors.10PubMed Central. Skeletal and dentoalveolar features in patients with deep overbite malocclusion This distinction matters because it directly influences what kind of treatment will work. You cannot fix a skeletal mismatch with braces alone if the problem is fundamentally about jaw shape.
Childhood Habits That Influence Overbite
Sucking habits in early childhood can shift the developing bite in several directions. Children who used a pacifier daily for more than a year were more likely to develop a reduced overbite or open bite, meaning the habit pushed the front teeth apart vertically rather than deepening the overlap. In contrast, thumb or finger sucking for more than a year was associated with increased overjet and a Class II bite relationship, meaning the upper teeth were pushed forward relative to the lowers.11PubMed Central. The association between nutritive, non-nutritive sucking habits and primary dental occlusion Randomized trial data has also linked pacifier use beyond 12 months to a substantially higher rate of posterior crossbite.12European Journal of Orthodontics. The effect of early childhood non-nutritive sucking behavior including pacifiers on malocclusion: a randomized controlled trial
So sucking habits do not uniformly cause deep overbite. They can push the bite in either direction depending on the type of habit and how long it lasts. The common parental fear that a pacifier will give a child a deep bite is often backwards: pacifiers are more strongly linked to open bites and crossbites than to deep overbites.
When a Deep Overbite Becomes a Health Problem
Many adults live with overbites of 4 or 5 mm without symptoms or complications. The concern is not about crossing a bright-line millimeter threshold but about whether the deep overlap is causing specific functional problems. The most commonly cited complications are soft tissue trauma (where the lower incisors bite into the gum behind the upper front teeth), accelerated tooth wear, and reduced space between the arches for restorative dental work like crowns or bridges.3PubMed Central. Two middle-aged cases of deep overbite without molar support treated by orthognathic surgery
Research has found a significant link between deep bite and dental attrition, the gradual wearing down of tooth surfaces from repetitive contact.13PubMed Central. The Prevalence of Temporomandibular Disorders and Dental Attrition Levels in Patients with Posterior Crossbite and/or Deep Bite: A Preliminary Prospective Study Over decades, this wear can thin the enamel on the lower incisors and the palatal surfaces of the upper incisors, making those teeth more vulnerable to sensitivity and fracture.
The relationship between deep bite and jaw joint problems is more contested but still noteworthy. One study found that headaches, muscle disorders, disc displacement, and other temporomandibular joint issues occurred significantly more often in people with deep bites, with the combination of deep bite and retroclined (tilted backward) upper incisors posing the highest risk.14European Journal of Orthodontics. Temporomandibular disorders and psychological status in adult patients with a deep bite Other researchers have described deep bite as one of several factors that may contribute to biomechanical changes in the jaw joints, though it is rarely considered a sole cause of TMD.15PubMed Central. A novel posterior occlusal splint improves symptoms and prognosis of coexisting temporomandibular disorders and deep bite: a retrospective study
There is also a periodontal angle. Deep traumatic overbites, where the lower incisors repeatedly contact the gum tissue behind the upper front teeth, have been associated with unusual periodontal lesions, particularly when oral hygiene is poor.16British Dental Journal. Periodontal lesions associated with deep traumatic overbite When the lower front teeth repeatedly traumatize the palatal gingiva, the tissue can recede or form pockets that trap bacteria. Treating these lesions is challenging because the underlying bite problem tends to reintroduce the trauma even after the gum tissue heals.17European Journal of General Dentistry. A critical review of the management of deep overbite complicated by periodontal diseases
An Unexpected Finding About Speech
One complication that people rarely associate with overbite is speech. A study of schoolchildren in mixed dentition found that deep overbite was actually protective against speech distortion, reducing the likelihood by more than half compared to children without deep bite.18PubMed Central. Association between malocclusion, tongue position and speech distortion in mixed-dentition schoolchildren: an epidemiological study That result ran counter to what most people would expect, since a deeper overlap changes the space available for the tongue. The researchers speculated that the increased vertical overlap may help stabilize the tongue position for certain sounds. Posterior crossbite, on the other hand, was associated with more speech distortion. This is a reminder that not every aspect of a deep bite is harmful; some features of the bite pattern can be functionally neutral or even advantageous in specific contexts.
How a Deep Bite Gets Treated
If your overbite is in the normal range and causing no symptoms, there is no clinical reason to treat it. Treatment decisions revolve around deep bites that are causing tissue damage, significant tooth wear, jaw pain, or functional problems, or that are likely to cause them as the bite continues to develop.
Timing matters. A systematic review concluded that orthodontic treatment for deep bite started in late mixed dentition or early permanent dentition produced better results and greater long-term stability than treatment started in the early mixed-dentition phase.19PubMed. Orthodontic treatment of deep bite in mixed dentition and/or early permanent dentition: What about stability? – A systematic review This aligns with the growth data showing that overbite often improves naturally after puberty; waiting allows the clinician to distinguish a deep bite that will self-correct from one that needs intervention.7American Journal of Orthodontics and Dentofacial Orthopedics. Longitudinal growth changes in subjects with deepbite
For dental deep bites, the standard approach involves either intruding the over-erupted front teeth or extruding the under-erupted back teeth to level the curve of Spee. Traditional fixed braces remain the workhorse, but clear aligners have become increasingly popular. A comparison of Invisalign and conventional braces in adults with severe deep overbite found both were effective, with aligners potentially preferred for patients with high-angle facial patterns.20PubMed. Comparison of clinical outcomes between Invisalign and conventional fixed appliance therapies in adult patients with severe deep overbite treated with nonextraction However, a systematic review cautioned that clear aligners handle mild to moderate dental deep bites well but remain uncertain for skeletal cases. A common issue is that the planned correction in the digital treatment setup often overshoots what the aligners actually achieve, meaning overcorrection or refinement trays are frequently needed.21PubMed. Effectiveness and accuracy of clear aligners in treatment of deep bite: a systematic review
For skeletal deep bites in adults where the jaw relationship itself is the problem, orthodontics alone may not be sufficient, and orthognathic surgery can be indicated. These are the most complex cases, often involving patients who have already lost posterior teeth that would normally maintain the vertical dimension of the bite.
Does the Correction Last
Relapse is a legitimate concern with deep bite treatment. The good news is that long-term data suggests corrections hold up reasonably well. In a study tracking 30 treated patients against 32 untreated controls over the long term, the treated group showed a mean relapse of only 0.8 mm. The untreated group actually experienced bite opening of 0.7 mm over the same period, meaning the gap between treated and untreated outcomes narrowed somewhat but remained favorable for the treated group.22European Journal of Orthodontics. Long-term follow-up of orthodontically treated deep bite patients
A larger study found that only about 10% of treated deep bite patients relapsed to an overlap of 50% or more of the lower incisor height, and even in those cases, the amount of overbite increase was small. Among patients who still had a deep bite at follow-up, gingival contact and palatal impingement were more common in patients who had not been compliant with treatment than in patients who experienced true relapse, suggesting that incomplete correction is a bigger practical problem than genuine relapse of a fully corrected bite.23European Journal of Orthodontics. Stability and relapse after orthodontic treatment of deep bite cases—a long-term follow-up study
How Overbite Changes as You Age
Even without treatment, overbite does not stay constant throughout life. A longitudinal study that followed people with normal occlusion from age 13 to age 60 found a gradual reduction in overbite of about 1.4 mm over that span. About half of that decrease happened between ages 13 and 17, likely driven by continued jaw growth and the eruption of second and third molars. The remaining decrease, roughly 0.6 mm, occurred between ages 17 and 60 and may reflect late mandibular growth and the natural wearing down of the incisal edges over decades of use. Men showed slightly more reduction than women, probably because of both greater late jaw growth and more pronounced incisal wear.24Dental Press Journal of Orthodontics. Normal occlusion in maturational life process
Interestingly, some other bite measurements barely change with age at all. A separate longitudinal study of untreated adults found that overbite, overjet, and molar relationship remained largely age-invariant over the period studied.25PubMed. A longitudinal study of arch size and form in untreated adults The apparent tension between these findings probably reflects the different time windows and sample characteristics involved. The takeaway is that overbite shifts slowly and modestly in adulthood, trending slightly downward, but you should not expect a deep bite to resolve on its own once you are past your growth years.
How Self-Perception Factors In
One aspect that orthodontists weigh but rarely discuss in detail with patients is the psychological dimension. Research on adolescents has found that how people perceive their own smile has a stronger effect on self-esteem than any objective measure of malocclusion. Adolescents who rated their own smile positively had meaningfully higher self-esteem scores than those who rated it poorly, regardless of clinical severity.26PubMed. Impact of severity of malocclusion and self-perceived smile and dental aesthetics on self-esteem among adolescents Among specific types of malocclusion, spacing of the front teeth, crowding, and increased overjet were most closely associated with low self-esteem, while deep overbite per se did not rank among the top offenders on that list.27PubMed Central. Effect of malocclusion on the self-esteem of adolescents
This makes sense when you think about what is visible. A deep overbite, unless extreme, mostly affects how the teeth meet rather than how the smile looks from the outside. Spacing, crowding, and protruding upper teeth are more immediately visible to others and to the person in the mirror. So if you are concerned about a deep bite purely for cosmetic reasons, it is worth honestly evaluating whether it is actually visible when you smile or talk. Many people with overbites of 5 or 6 mm look perfectly fine to everyone around them. The clinical question is whether the bite is causing damage, not whether it photographs well.