Overbite vs Underbite: What Is the Difference?

When it comes to bite alignment, two of the most commonly searched terms are overbite and underbite. Many people notice something different about how their teeth meet, or they may have been told at a dental appointment that their bite is worth monitoring. Understanding what these terms actually mean — and how they differ from a normal bite or a crossbite — can help you feel more informed before any professional conversation.

This article explains overbite vs underbite clearly and honestly, exploring how each presents, how they compare with a normal bite, how bite differences may appear from the side profile, and when it may be worth having a bite assessed by a dental professional at a dentists in wimpole street london.

Before comparing overbite and underbite, it helps to understand what dental occlusion means. Occlusion simply refers to how the upper and lower teeth meet when the jaws come together. Current UK clinical understanding recognises that bite relationships exist on a spectrum — very few people have a perfectly textbook bite, and significant variation is common.

In an ideal or normal bite, the upper front teeth sit slightly in front of the lower front teeth, with a small vertical overlap — typically around 1–2mm — and the back teeth interlock comfortably. The upper arch is slightly wider than the lower, meaning the upper teeth sit just outside the lower teeth on both sides. This arrangement generally supports comfortable chewing, speech and jaw function.

When the relationship between the upper and lower teeth falls outside this range, it is referred to as a malocclusion — literally meaning "bad bite." Overbite and underbite are two distinct types of malocclusion, as is crossbite, which is covered later in this article.

An overbite describes a situation where the upper front teeth overlap the lower front teeth by a greater-than-typical vertical distance. This is sometimes called a deep bite when the overlap is more pronounced.

A small degree of vertical overlap is entirely normal and expected. It is only when the overlap becomes more significant — where the upper teeth cover a substantial portion of the lower front teeth, or in more pronounced cases, where the upper teeth almost entirely cover the lower teeth — that it may be considered clinically notable.

In some cases, a deep overbite can cause the lower front teeth to bite into the roof of the mouth (the palate), which may affect gum tissue and tooth wear over time. However, the degree to which this happens varies considerably between individuals.

From a side profile, a more pronounced overbite can sometimes give the appearance of the upper jaw projecting further forward relative to the lower jaw. In some individuals, the chin may appear to recede slightly. However, facial appearance depends on many factors beyond tooth position alone — including jaw bone structure, soft tissue, and individual anatomy — so it is important not to draw firm conclusions about facial appearance from tooth position in isolation.

An underbite — also referred to as a Class III malocclusion or prognathic jaw in clinical settings — occurs when the lower front teeth sit in front of the upper front teeth when the jaws are closed. This is the reverse of the normal tooth relationship.

Underbites are generally less common than overbites in the UK population. They can range from mild, where only a small number of front teeth are affected, to more pronounced, where the lower jaw protrudes noticeably in front of the upper jaw. In some cases, the underlying jaw relationship (skeletal relationship) is the primary factor; in others, it may be mainly a dental (tooth position) issue.

When viewed from the side, a more pronounced underbite can sometimes give the appearance of the lower jaw sitting forward relative to the upper jaw and the overall face. The chin may appear more prominent. Again, the degree to which this is visually apparent varies significantly between individuals, and many people with mild underbites have little noticeable difference in facial appearance.

The table below summarises key differences across bite types. It is intended as a general educational guide only and does not reflect every possible clinical situation.

This table is for general educational purposes. Individual presentations vary considerably.

A crossbite is a further distinct type of malocclusion that is sometimes confused with an overbite or underbite, but refers to something different. Where an overbite and underbite describe primarily a front-to-back or vertical relationship between the upper and lower front teeth, a crossbite describes a situation where one or more upper teeth sit inside (rather than outside) the lower teeth.

Crossbites can occur at the front of the mouth (anterior crossbite) or at the sides (posterior crossbite). In a posterior crossbite, for example, some of the upper back teeth may sit on the inside of the lower back teeth, which is the reverse of the normal arrangement.

Crossbites are considered a separate category of malocclusion and are assessed differently. Like overbites and underbites, the significance of a crossbite depends on the individual situation, including the number of teeth affected, jaw position, and whether there are any functional concerns. If you are exploring aligner-based correction, you may also find this useful: can Invisalign fix overbite.

Orthodontists and dentists often describe bite relationships in terms of skeletal classification (how the upper and lower jaw bones relate to each other) and dental classification (how the teeth themselves sit regardless of jaw position). These are not always the same thing — it is possible to have a dental overbite without a significant skeletal jaw discrepancy, and vice versa.

Understanding this distinction matters because it influences how a bite is assessed and what factors a dental professional might consider. For example, a mild overbite with no functional issues and a healthy jaw relationship may simply require monitoring. A more pronounced jaw discrepancy may involve different considerations entirely, including whether clear aligners are appropriate.

Current orthodontic guidance in the UK, informed by bodies such as the British Orthodontic Society, emphasises that clinical assessment should always account for the individual's overall oral health, jaw relationship, tooth position, age and specific concerns — rather than applying a one-size-fits-all approach.

It is natural to wonder whether bite differences may influence how the face looks — particularly when viewed from the side. The honest answer is: it depends.

In more pronounced cases, both overbites and underbites can sometimes be associated with differences in how the lower face appears in profile. However, facial appearance is determined by a combination of factors including bone structure, soft tissue, muscle tone, and genetics — not tooth position alone. Many people with overbites or underbites have no noticeable difference in facial appearance, particularly when the bite difference is mild.

It is important to note that bite assessment should be grounded in functional and oral health considerations. Facial appearance is a sensitive area, and any discussion of cosmetic concerns should happen within a professional, supportive clinical conversation — not as a reason to feel self-conscious about bite alignment.

This is one of the most commonly asked questions when comparing these two bite types — and it does not have a universal answer.

Whether an overbite or underbite is more clinically significant depends on several individual factors:

• The degree of the bite difference — mild variations are very common and may require no intervention

• The jaw relationship — whether the difference is primarily dental or involves the underlying jaw bones

• Functional effects — such as difficulty chewing, tooth wear, or jaw discomfort

• Tooth and gum health — whether bite position is contributing to enamel wear or gum problems

• Age and dental development — particularly relevant in younger patients where growth may still be a factor

• Individual symptoms and concerns — including any discomfort, speech considerations, or functional difficulties

Neither bite type is inherently "worse" for every person. A mild overbite may have no clinical significance, while a more pronounced underbite may require assessment — and the reverse is equally possible. Severity is assessed individually, and the NICE and NHS emphasis on clinical assessment reflects this.

Bite alignment is routinely assessed as part of a standard NHS or private dental check-up. Your dentist will look at how your teeth meet and whether there are any signs of concern, such as unusual tooth wear, jaw discomfort, or difficulty biting and chewing.

Situations where it may be worth discussing your bite with a dental professional include:

• Noticeable difficulty biting or chewing certain foods

• Jaw discomfort, clicking or aching

• Visible or progressive tooth wear

• Concerns about gum health related to how the teeth meet

• Self-consciousness about bite or appearance that you would like professional guidance on

• A child whose bite is developing in a way that prompts questions

It is worth noting that not every overbite, underbite or crossbite requires treatment. Many bite variations are monitored over time without any active intervention. Any decision about whether orthodontic assessment or treatment is appropriate is highly individual and would be discussed in detail with a qualified dental professional, often during a dental check-up.

• Does your dentist check your bite as part of your routine appointments, and have you had the chance to ask questions about it?

• If you have noticed something about your bite — such as uneven wear or occasional jaw discomfort — is it something you have raised with a dental professional?

• Are you researching this topic out of general curiosity, or do you have specific concerns you would like to discuss with a clinician?

These are genuinely useful questions to hold in mind when considering whether professional advice may be helpful.

If the answers point to practical concerns — chewing, comfort, or wear — it can be sensible to schedule your appointment for an in-person bite assessment.

This article is for educational information only and does not replace professional dental assessment or advice. Bite differences vary by individual and require in-person examination to determine relevance and treatment need. Nothing here is a diagnosis, guaranteed outcome, or personalised treatment recommendation. If you are concerned about your bite, seek advice from a qualified dental professional.

Written Date: 25 September 2026 | Next Review Date: 25 September 2027