Why You Should Keep A Gap Between Upper and Lower Teeth

Why You Should Keep A Gap Between Upper and Lower Teeth

Have you heard the word “TCH”, Teeth Contact Habit? TCH is the habit that your upper and lower teeth are lightly touched whenever your face is resting. This is very common and considered a bad habit to cause excess tension in the facial muscles.

You should keep a tiny space or gap between the upper and lower teeth whenever your face is resting. The opposite bad habit of this is called, TCH, Teeth Contact Habit. By the way, I used to say TCH as a bad example, but some people misunderstood that you are supposed to keep the teeth touching lightly, so stopped saying the word “TCH” much.

The gap should be 1-3mm between them. That's the ideal. You want to keep the gap whenever your face is resting, functioning (e.g. eating), or expressing emotion (e.g. smiling), except chewing. Chewing is the only time that your teeth can touch because the main purpose of the teeth is to break down the food into pieces so you can swallow. That's why the teeth exist. 

By the way, every time I talk about this gap story, some people comment, “Wait, Dr. Mew said “Butterfly Bite”. So let me introduce his latest opinion later because I asked him a couple of weeks ago. 

Anyway, please note that whenever your upper and lower teeth are touching, light pressured tension is being caused there, and the tension accumulates to overdeveloped masseter muscles and jaw pain because the pressure exists for a long time.

The other example symptoms are: a wider face, asymmetrical face, and/or grinding habit while sleeping. I am not a psychologist or anything, so cannot help you reduce mental stress in your life, but you can at least try to not cause physical stress by keeping the tiny gap there. When you have physical stress, it can worsen your mental stress too. 

Another underlooked side effect of Teeth Contact Habit is to cause jowls or saggy face, because when the masseter muscles overdevelop, they tend to grow downward, which results in pulling the skin down. If you are in your 20's or younger, you probably won’t notice. They just become bigger, and your face becomes wider because the other muscles are still working fine to lift up the face. But if you are 30’s or older, the compensated muscles are not as strong as before, and the muscles around the masseter muscles move downward, which pulls the skin down.

I don’t mean that the young don’t have to care about the gap though. In fact, the earlier you master this good gap habit, the easier it is to continue. So if you are young, you should take it seriously. If you are mature, you should take it even more seriously, because you might have developed the wrong habit (TCH) for a long time.

3 tips to keep a tiny gap between upper and lower teeth whenever except chewing.

#1 Tip: Mewing Tongue Posture® whenever your face is resting

If you don’t know what Mewing is, be sure to check our Mewing 101. You want to imagine that the tongue is slightly lifting up the maxilla (upper jaw) and the upper teeth to create the gap. You should not press up hard. You should always do soft mewing vs hard mewing. Check the video to understand the difference if you don’t know it.

Anyway, instead of dropping the jaw down to create the space, please lift up the upper to create the gap. because the more you use the downward mentalis muscle (the red chin area: overworking muscle), the saggier and longer your face becomes. With age, our faces become longer, because of this reason.

Also, as you can see below, when the upper and lower teeth are touched, the space in the Temporomandibular Joint becomes smaller and tighter, which leads to pain. When there is enough space between the teeth, the TMJ space is loose enough not to feel pain.

Image depicting the 'Teeth Contact Habit', illustrating the common practice of teeth touching and its potential impact on dental and facial health.So forget about the area below the lower lip. Don’t try to activate any muscles there. You should always be activating the face above the upper lip. That includes cheeks, which are sleeping muscles (blue areas in our anatomy).
Personally, I recently noticed that when I mew, I feel like it's easier to nose-breathe. Does anyone feel the same? Please let me know. As an experiment, try to UNmew on purpose and nose breath at the same. Then Mew and nose breathe. Do you feel the difference? Keep your mouth closed during the experiment. Don’t you feel it’s easier to breathe from the nose when you are mewing?

I'm not a breathing expert, but I've been focusing on nose breathing now because we have just launched Sleep Tape™. Since I started nasal breathing even while exercising, I have noticed a big difference in my endurance. I run outside and try to keep my mouth shut all the time. If I have to mouth breathe, I stop running. By the way, of course, my skin is covered up against the sun exposure though. Anyway, when I run, I make sure that I keep my mouth shut and nose breathe all the time. 

It's hard at the beginning. It was hard, but now I got used to it. And I realized my endurance is so much improved. I'm so surprised at myself in fact. When I work out Lesmills Body Combat cardio exercise, I’ve noticed a big improvement in my endurance. I've been doing this Body Combat since in my early 20s for about 20 years, so I can tell the difference objectively.

The class is usually 45 minutes. I used to be tired and couldn’t move around like a rabbit in the last 10 minutes, but now I can, and I often am the only one who is jumping around without exhaustion out of 30 people in the studio. Sometimes, there is another rabbit in addition to me. I checked how the person was breathing. Sure thing, he was nose-breathing. I didn't ask him, but due to my occupational habit, I check people’s face habits often. I made sure that his mouth was closed all the time.

In summary, keeping a good Face Posture® such as Mewing Tongue Posture®, a gap between upper and lower teeth, and a tiny smile helps improve not just your aesthetic look, but also your performance. 

#2 Tip: Body Posture

In order to keep good oral posture, it is critical to keep good body posture too. In other words, it is very hard to keep a gap between the upper and lower teeth when your body posture is bad because the upper jaw is hanging down toward the lower teeth.

For example, when the body posture is hunched over, isn’t it easier to touch the teeth aka Teeth Contact Habit? I can try to maintain the gap if I’m conscious but if not, my teeth would be probably touching.

So I realized, if my head is above my butt, I can easily nose breathe, and I can easily keep space. Try it out. You can also mew with bad body posture. Isn’t it hard to nose breathe?

When the body is hunching over, the airway is obstructed, so isn't it harder to keep the space?  But if you keep your head above your butt, and keep mewing, I can easily keep the gap. 

By the way, I asked Dr. Mew about “Butterfly Bite” which he might often mention in the past, because every time I mentioned this gap story, some people were confused. 

A couple of weeks ago, I asked him and he said that the reason why he said the molar and the back teeth should be touching each other whenever the face is resting is because modern faces are deteriorating compared to ancient faces ages ago. Older faces were stronger, and body posture was better too, due to a lot of physical labor and harder food to chew. But nowadays, so many lifestyles changed. We sit at desks all the time, hunching over to check phones for so many hours, eating soft foods, etc. So our facial structures have changed, which may result in TCH, Teeth Contact Habit.

That is what he means, and I believe that if you can try to keep the gap, you should. My face is deteriorating, but I can keep the space, so I should. So is yours if you can. 

If you ask any Japanese dentists or medical professionals, they all say that we should keep the gap between the upper and lower teeth. They learn the importance of space at dental school, so this gap rule is more well-known than Tongue Posture®.

If you see this photo of me when I was 31 years old, you can see that my face is much wider. At that time I was grinding, my teeth were touched, and my tongue was down. 

Photograph of Koko Hayashi before adopting the Mewing Tongue Posture®, providing a visual reference for the initial facial structure prior to the technique.

I'm currently 44 years old, and at that time I didn't know anything about Mewing, the teeth gap, or those Face Posture® tips, although I was doing Face Yoga. My body weight stays the same, so it’s not fat that was making the face fuller, but overworking muscles especially masseter muscles (The red on the cheek in anatomy.). I wasn’t using Sleep Tape™ at that time either, so although I was doing nasal breathing, my mouth was slightly open while sleeping, which means the chin muscle was overworking in bed too. 

#3 Tip: Swallow without TCH

In general, the less touching, the better. The more TCH, the more aging for the face. This principle applies to swallowing too.

Let's drink something and when you swallow, I don't want you to click the teeth (Upper and lower teeth are touching.). Unless you are conscious, your teeth might be touching every time you swallow.

Until I learned this principle in 2022, I think I was clicking every time I swallowed, which is very bad, because I drink water all day long.

Please let me know if the teeth are touching or not when you swallow in YouTube’s comments. 

The trick not to clicking when you swallow is to keep good body posture and make sure you are doing the 3 tongue movements that I often talk about. If you don’t what the 3 are, check the How to Drink video. Be careful with your neck tension too. You don’t want to move the other muscles than tongue and throat so much. If the other muscles are moving, that means you are depending on the other muscles too much, instead of relying on the core muscles for the face: The tongue.

I noticed that when my body posture is bad, it’s easy to click my teeth when I swallow. In other words, when my body posture is good, I don’t have to click them. Keep your head above your butt, and feel like your tongue is lifting up the palette to keep space between the upper and lower teeth when you swallow.

There are more tips for better drinking habits so if you are interested, be sure to check the video out.


#1 Tip: Mewing Tongue Posture® whenever your face is resting

#2 Tip: Body Posture

#3 Tip: Swallow without TCH

Let’s be conscious of the gap every time you swallow. It is such a tiny habit, but it can add up because we swallow so many times every single day!

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