Let’s be blunt—size matters when it comes to mouthguards.

Too small, and it won't decompress your jaw.
Too big, and you'll end up tossing it in a drawer.
The right size? That’s the key to unlocking cranial expansion, reducing jaw pain, and rewiring your entire posture system from the bite up.

In this guide, I’ll walk you through how to choose the perfect Reviv size—whether you’re dealing with TMJ, bruxism, posture collapse, or just want your brain to stop screaming.

1. Why Mouthguard Sizing Isn’t One-Size-Fits-All

Most off-the-shelf guards pretend we all have the same face, jaw, and dental arch.

Wrong.

Your:

• Dental width
  
  
• Facial shape
  
  
• Tongue posture
  
  
• Breathing style
  

All affect what size and shape guard works for you.

2. The Two Core Reviv Models: Reviv One vs Reviv Two

Before we talk size, let’s talk type.

Reviv One

• Soft rubber
  
  
• Great for sleep
  
  
• Thicker = faster decompression
  

Reviv Two

• Firmer material
  
  
• Better for day use
  
  
• Slimmer, more stable long-term
  

👉 Explore both: Reviv Mouthguard Collection

 

3. The Reviv Size Chart (Quick Reference)

Need help choosing? Start with Reviv One Medium. It fits 70% of users.

4. Small Mouth? Here’s What You Need to Know

If your mouth feels crowded easily:

• Choose Reviv One Small
  
  
• Avoid excessive bulk—less is more
  
  
• Focus on night-time decompression only
  

Note: Children under 12 should not use Reviv unless approved.

5. Medium Fit: The "Most People" Option

Medium is the Goldilocks zone.

Good for:

• Average dental arches
  
  
• First-time users
  
  
• Both day and night wear
  

Start here unless you know you have a small or wide jaw.

6. Large Fit: When to Size Up

Signs you need a large guard:

• You have wide molars or cheek tension
  
  
• Smaller guards feel like they “pop out”
  
  
• You breathe best with more bite separation
  

Choose Reviv Two Large for daytime structure and durability.

7. What If You’re Between Sizes?

Start with the smaller size.

Why?

• It’s easier to remold and test
  
  
• Too big = no stability, poor suction
  
  
• You can always size up later
  

 

8. How to Measure Your Mouth at Home

Try this:

• Take a selfie with teeth slightly apart
  
  
• Look at your arch width and teeth spacing
  
  
• Compare to product photo of Reviv guard
  
  
• If you see overhang on sides → size down
  

This isn't scientific—but it works.

 

9. Sizing for Women vs. Men: What’s the Difference?

Jaw structure, not gender.

But trends:

• Many women prefer Reviv One Small or Medium
  
  
• Most men fit Reviv One Medium or Reviv Two Medium/Large
  

👉 Fit it right: Step-by-Step Fitting Guide

10. Sizing for Teens and Young Adults

If under 18:

• Use Reviv One Small
  
  
• Monitor for growth changes
  
  
• Refit every 3–6 months
  

Do not use Reviv if child still has baby teeth.

11. Day Fit vs Night Fit: Does Size Change?

Yes.

Night Fit:

• You can tolerate more bulk
  
  
• Prioritize decompression over speech
  

Day Fit:

• Needs to be slimmer
  
  
• Choose Reviv Two in Medium or Large
  

12. Signs Your Guard Is the Wrong Size

Watch for:

• Slipping during sleep
  
  
• Excess saliva
  
  
• Jaw tension worsening
  
  
• You hate wearing it
  

If you don’t love it—it’s the wrong size or fit.

 

13. Mouth Shape Types and What Fits Them

Narrow arches → Reviv One Small
Square jaws → Reviv Two Medium or Large
Overbite/underbite → Try softer material for adaptation
Asymmetry → Go soft first, then firm once decompressed

14. Guard Size Affects Cranial Pressure (Yes, Really)

More space = more decompression.

But too much height too fast = headaches.

Start with the minimum effective size, then progress.

15. Guard Not Staying in? Here's Why

Likely causes:

• Wrong size
  
  
• Poor boil-and-bite fit
  
  
• You bit too hard (locked it)
  

👉 Refit guide: How to Fit Reviv Mouthguard

16. Do You Need Multiple Sizes?

Some users buy:

• Reviv One for night
  
  
• Reviv Two for day
  

Especially if posture or performance is a goal.

 

17. Travel-Sized Option: Which One Packs Best?

Reviv One is the most compact and easiest to carry.

If you travel often, grab a backup in your ideal size.
 👉 Read: Travelers: How to Fit and Clean on the Road

18. What If My Face or Bite Changes Over Time?

It will. That’s the point.

Reviv users often:

• Increase arch width
  
  
• Improve jaw alignment
  
  
• Need to size up after 6–12 months
  

Re-measure and re-fit every few months.

19. Still Unsure? Start with This

If confused:

• Pick Reviv One Medium
  
  
• Mold it gently
  
  
• Test for 3–5 nights
  

Adjust from there.

20. Long-Term Plan: Match Guard Size to Jaw Growth

Your jaw will adapt. So should your guard.

We recommend:

• Replacing every 9–12 months
  
  
• Sizing up as needed
  
  
• Tracking comfort over time
  

This isn’t a one-off product. It’s a tool for structural transformation.

FAQs

1. What if I order the wrong size?
You can exchange or repurchase once you identify your proper fit. Most users start with Medium.

2. Can I cut or trim the guard if it’s too big?
We don’t recommend cutting. It affects the stability. Size down instead.

3. How do I know if it’s too small?
If it doesn’t stay in or causes gum discomfort, you may need to size up.

4. What size do most people order?
Reviv One Medium or Reviv Two Medium.

5. Can I wear a large if I have a small mouth?
Only if you're experienced with guards and need greater height. Otherwise, stick with proper sizing.

6. Can children use Reviv?
Not recommended under age 12. Always monitor growth and dental development.

7. How do I know when to size up?
If your arches expand and the current guard feels loose or ineffective, it's time to scale.

8. Can I use the same size for both models?
Generally, yes. But some users prefer a size smaller in Reviv One for tighter night fit.

9. How does size affect decompression?
Larger guards often offer more decompression—but too much too fast can trigger tension. Start conservatively.

10. Should I consult a dentist?
 Reviv is designed to be self-fit. But if in doubt, consult a dentist—ideally one trained in TMJ or cranial biomechanics.

Conclusion

Choosing the right Reviv mouthguard size isn’t cosmetic—it’s structural.

Your size determines:

• How well your jaw decompresses
  
  
• How fast your posture improves
  
  
• How long you stick with the process
  

The wrong size locks dysfunction in.
The right one unlocks everything.

Pick the size that fits. Then let Reviv do its work.

👉 Choose your Reviv guard here and get started tonight