How is space shortage measured?
The difference between the arch length the teeth need to stand in a neat line and the arch length the jaw actually provides is called the space shortage. It is calculated by measuring the total width of the teeth, the length of the dental arch, and the angle of the front teeth. This is why there is no single answer for everyone to the question, “Can’t we do it without extraction?”
| Space shortage | General direction |
|---|---|
| About 4mm or less | Space is often created without extraction |
| About 5–8mm | Combine non-extraction methods or consider extraction as well |
| About 9–10mm or more | Many recommend extraction |
In the past, extraction was often recommended once the shortage exceeded just 4–6mm, but these days shortages of around 8mm are sometimes resolved without extraction using mini-screws and similar tools. These numbers are only a reference; the face and the condition of the bone have to be looked at together.
How is space created without extraction?
- Moving the molars back: a small screw (an orthodontic mini-screw) is placed in the jawbone and force is applied to move the dental arch backward. The further they move, the longer it takes
- Arch expansion: the arch is widened sideways. In adults, a screw in the palate bone is sometimes added for reinforcement, and in some cases about 5–7mm of space can be expected
- Interproximal reduction: the enamel where teeth touch is trimmed very thinly to make space. Across 7 contact points, around 2mm can sometimes be gained (interproximal reduction)
Each method has limits. If teeth are pushed too far without extraction, the jawbone (alveolar bone) can’t support them, the teeth move outside the bone, and the gums recede. Not extracting isn’t always the way to protect your teeth.
If my mouth protrudes, do teeth have to be extracted?
Not necessarily, but if the mouth protrudes a lot, there is a limit to how far it can be brought back without extraction. Looking at the relationship between the lips, nose and chin in profile, we compare your current mouth, how much change you want, and the expected look after extraction. Changes in appearance are judged by the patient’s satisfaction, so the clinical team doesn’t decide alone.
The bite also plays a role. In a deep bite, where the upper teeth cover the lower teeth deeply, non-extraction is often favorable; in an open bite, where the upper and lower front teeth don’t meet, extraction is often favorable. These are only general tendencies, so we don’t draw conclusions before looking inside the mouth.
Is extraction a disadvantage if my lips are thin?
It can be. When the front teeth move back after extraction, the lips also look slightly further back. People with thick or average lips often don’t notice much difference, but those whose lips are naturally thin can easily feel that their mouth looks sunken even with a small change. In such cases, we choose non-extraction or reduce the number of teeth extracted.
Some say the philtrum looks longer, but in many cases it doesn’t actually get longer — it just looks that way as the lips move back. We plan in detail how far the front teeth move back and how much of the front teeth shows when you smile.
How we do it at Wonjin Dental
The reason I give you the numbers first is to pin down the shortage, not to suggest extraction based on that number alone. I look at where the mouth sits, whether the lips are thin, and how the upper and lower teeth close, all together.
We explain the space shortage, the position of the mouth, and the harmony of the lips and face in one sitting, and we extract or don’t extract only after you are convinced. An orthodontic diagnosis is ₩100,000 (as of September 2026), and the costs of full and partial orthodontics can be found in all fees.
Frequently asked questions
Does extraction orthodontics take longer than non-extraction?
It often takes longer because there is a step to close the extraction space. However, non-extraction also takes longer if the molars are moved back a lot, so in the end the amount of movement determines the timeline.
Which teeth are usually extracted for orthodontics?
The small molars (premolars) are commonly extracted. It depends on where space is needed and the condition of the teeth.
Can I have orthodontics with only my wisdom teeth removed?
Removing wisdom teeth alone doesn’t create space for the front teeth. However, in a plan that moves the molars back, the wisdom teeth are sometimes removed first.
Won’t the extraction space open up again?
If you don’t wear a retainer after the space is closed, it can open up or teeth can rotate. The retention period after orthodontics is important.
