Overbite, Underbite, Crossbite: How Bites Go Wrong

What are the main types of bite problems?

Malocclusion is the umbrella term for teeth and jaws that do not meet the way they are designed to, and it breaks down into a short list of named patterns. Most describe the relationship between the upper and lower front teeth when the back teeth are closed; the rest describe how the teeth fit within their own row.

A small amount of overlap and protrusion is normal — upper front teeth are supposed to sit slightly ahead of and over the lowers. The label applies when the pattern is pronounced enough to affect function, wear, hygiene, or appearance, and real mouths usually combine patterns: crowding with a deep bite, or an overjet with a single tooth in crossbite.

How orthodontists classify bites

Orthodontists organize all of this with the Angle classification, which sorts bites into three classes by how the first molars — the anchor teeth of the bite — meet front-to-back. It is the shorthand on referral notes and treatment plans, so it is worth being able to read.

Class I means the molars meet in the normal relationship. The jaws line up, but the teeth themselves may still crowd, space, rotate, or cross — most malocclusion lives here. Class II means the upper teeth and jaw sit relatively forward of the lowers; overjet and deep bites are its common faces. Class III means the lower jaw sits relatively forward, producing the underbite pattern.

The classification carries a useful distinction inside it: whether a bite problem is dental (the teeth are misplaced in normally matched jaws) or skeletal (the jaws themselves are mismatched in size or position). Dental problems are generally the more straightforward to treat, because moving teeth is orthodontics' core skill. Skeletal patterns — a genuinely forward lower jaw, a truly narrow upper jaw — respond best when growth can still be guided, which is a large part of why timing matters so much in children, and why the same bite can be a simpler case at nine than at nineteen.

The front-to-back problems: overbite, overjet, and underbite

Overbite, overjet, and underbite are all descriptions of the same axis — how far the upper front teeth sit over, ahead of, or behind the lowers — and they are the patterns people most often notice in the mirror. They are also commonly conflated: overbite is vertical (how far the uppers reach down over the lowers), overjet is horizontal (how far they angle out), and the two often travel together.

A pronounced deep bite does more than look a certain way. Lower front teeth can strike the roof of the mouth behind the upper teeth, and the front teeth take chewing forces they are not shaped for, which accelerates edge wear — wear that compounds in anyone who also grinds at night, one reason dentists bring up night guards for grinding when they see flattened front edges. Significant overjet carries a blunter, well-known risk in children: front teeth that protrude are simply more exposed to injury in falls and sports.

Underbite is the rarer and more structural pattern of the three — more often skeletal, tied to jaw growth, and more likely to affect biting into food and speech sounds. Its correction depends heavily on age and severity, ranging from growth guidance in children to surgery in some adult skeletal cases; a dedicated guide covers how an underbite gets fixed across those scenarios.

The crosswise and vertical problems: crossbite, open bite, crowding

Crossbite and open bite describe the other two axes a bite can miss on — side-to-side and vertical — and crowding and spacing describe the row itself. They draw less attention than a protruding front tooth, but the functional stakes are often higher.

Crossbite puts individual teeth on the wrong side of their opposing row: a back tooth biting inside the lower row, or a front tooth closing behind the lowers. Because the teeth still have to meet somewhere, the jaw often learns to shift sideways or forward to find a comfortable closure — and a bite that only works with the jaw displaced puts asymmetric load on teeth, gums, and jaw joints. A single tooth in traumatic crossbite can take enough concentrated force to damage its own gum support over time.

Open bite leaves the front teeth unable to meet, which shows up functionally: biting into a sandwich or an apple with the front teeth becomes difficult, and some speech sounds are affected. In children, a persistent open bite often has a mechanical cause worth finding — prolonged thumb-sucking or a tongue-thrust swallowing pattern — because correcting the bite without addressing the habit invites relapse.

Crowding is the most common reason people seek straightening: teeth without room rotate and overlap, creating surfaces a brush struggles to reach. Spacing is its mirror image. Both are usually dental rather than skeletal, which is why they respond well to conventional orthodontics at nearly any age.

Does a bad bite actually need treatment?

Not always — and an honest page says so. Plenty of imperfect bites function fine for a lifetime, and treating a bite that neither hurts function nor bothers its owner is a choice, not a necessity. The real question is whether the bite is doing damage or is likely to: concentrated wear on particular teeth, teeth so crowded they cannot be kept clean, a jaw that must shift to close, difficulty biting or chewing, speech effects, or front teeth exposed to injury.

Those functional consequences are the useful dividing line between orthodontics as healthcare and orthodontics as cosmetics — and a companion guide digs into when to treat a bad bite versus when watching is reasonable. It is a genuine spectrum: a mild deep bite with no wear can be left alone for decades, while a traumatic crossbite in a teenager is a problem compounding annually.

Oral health problems in general are not cosmetic in their consequences — by one industry-foundation estimate, US adults miss more than 243 million hours of work or school each year over them 1Ref 1CareQuest Institute for Oral Health (2023).US Adults Miss 243 Million Hours of Work or School Annually Due to Oral Health Problems.US adults miss more than 243 million hours of work or school annually due to oral-health problems, per CareQuest's estimate.. Bite problems earn treatment when they sit on that functional side of the line: when correcting the bite protects teeth, gums, or joints from a trajectory of damage, rather than only changing a photograph.

Bite problems in children: why age seven matters

Children get screened for bite problems earlier than most parents expect — the professional recommendation is an orthodontic check by around age seven, when enough permanent teeth have arrived for the bite's trajectory to be readable. Early evaluation exists to identify developing problems sooner, and in some cases to head off more invasive or costly treatment later 2Ref 2American Association of Orthodontists (2024).Early Orthodontic Care at Age 7: A Path to Cost-Effective Treatment.Early orthodontic evaluation around age seven may identify developing problems sooner and in some cases avoid more invasive or costly treatment later..

The logic is growth. A skeletal pattern — a narrow upper jaw producing a crossbite, a jaw-growth mismatch producing an underbite — is most treatable while the jaws are still growing and can be guided. The same problem discovered after growth has finished may require longer treatment, extractions, or surgery to achieve what a growth-phase intervention might have managed simply. An early visit does not mean early braces; most children evaluated at seven are simply monitored, and the common outcome is a plan for when treatment would be worthwhile, if ever.

For parents watching at home, the observable cues are the patterns this page has already named: front teeth that protrude noticeably or never touch, a lower jaw that slides sideways on closing, pronounced crowding as permanent teeth arrive, or a thumb or pacifier habit persisting well into school age. A separate guide collects the signs of a bite problem parents tend to notice first and what each one means.

How bad bites get corrected — and a caution on mail-order aligners

Correction is matched to the type and the age. Crowding, spacing, and rotations — the dental problems — are the home territory of braces and aligners; the types of braces differ more in appearance and mechanics than in what they can ultimately achieve. Skeletal patterns recruit growth-guidance appliances in children, and in some adult cases jaw surgery combined with orthodontics. Habit-driven open bites start with the habit. And every path ends the same way: teeth hold their new positions only with retention, so it is fair to ask early how much do retainers cost, because retainers are part of the treatment, not an accessory.

One route deserves specific caution: direct-to-consumer aligners sold without in-person exams. A study of the FDA's MAUDE device database catalogued the adverse events reported with these products — among them tooth mobility, newly created open bites, gum recession, and pain 3Ref 3Kunkel T, et al. (2023).Adverse Events Related to Direct-To-Consumer Sequential Aligners - A Study of the MAUDE Database.Adverse events reported to the FDA MAUDE database for direct-to-consumer sequential aligners include tooth mobility, open bite, gum recession, and pain; the reports document harm types, not national incidence rates.. Those reports cannot say how often harm occurs, but they document what it looks like when it does. The pattern is not mysterious: moving teeth without imaging the roots and bone, checking gum health first, and monitoring along the way removes exactly the safeguards that catch problems early. Anyone noticing recession during any aligner treatment has reason to pause and be examined — a separate guide covers gum recession causes and what can be done about it.

Bite correction is one of dentistry's slowest purchases — typically many months to a few years — which makes the diagnosis, not the appliance, the thing worth paying for. Two opinions on a complex bite are routine, and a plan that names the bite type, the mechanism, and the retention strategy is the mark of a plan worth trusting.

What treating a bite problem costs, in outline

Orthodontic pricing deserves real numbers, and those live in dedicated cost guides for braces, aligners, and retainers — the per-option figures vary too much by region, complexity, and provider to summarize honestly in one paragraph. What belongs here is the structure: cost scales with how much movement is needed and for how long, skeletal problems cost more than dental ones, adult treatment often costs more than the same movement in a growing child, and retention adds a real, recurring line item after the visible treatment ends.

Insurance behaves differently here than for most dental care. Orthodontic benefits, where they exist at all, are commonly a separate lifetime allowance rather than part of the annual maximum, and coverage rules differ across plan types — the difference between a dental PPO, a DHMO, and a discount or membership plan changes what "covered" even means, so the plan-type definitions are worth understanding before comparing quotes 4Ref 4American Dental Association (2024).Types of Dental Plans.Dental PPO, DHMO, and discount or membership plans work differently, along with terms like deductible, coinsurance, and annual maximum..

The practical sequence: get the diagnosis and written plan first, then a pre-treatment estimate showing what the plan will actually contribute, then compare options against the same plan. The early-evaluation point from the pediatric section doubles as the cost strategy — problems identified while growth can help are, in some cases, the cheaper versions of themselves 2Ref 2American Association of Orthodontists (2024).Early Orthodontic Care at Age 7: A Path to Cost-Effective Treatment.Early orthodontic evaluation around age seven may identify developing problems sooner and in some cases avoid more invasive or costly treatment later..