Baseline Bruxism & Masseter Overload
Sleep grinding drives repeated, forceful masseter contractions all night long.
- ~13%: Adults with bruxism (general population estimate)
- ~20–40: Nightly clench episodes (per hour of sleep)
- ~250 psi: Peak bite force (during grinding episode)
- Progressive: Untreated tooth wear (enamel loss over years)
What happens during sleep bruxism
Jaw muscles clench and grind teeth involuntarily during sleep cycles.
Why the masseter takes the strain
The masseter is the primary closing muscle, absorbing most clench force.
Downstream effects if untreated
Chronic overload causes tooth wear, jaw soreness, and muscle enlargement.
Night Guard — Occlusal Splint Therapy
A custom plastic splint cushions bite force and shields tooth surfaces.
- Hard acrylic: Guard material (or dual-laminate)
- Nightly: Wear pattern (during sleep only)
- High: Tooth-wear protection (while worn consistently)
- Minimal: Muscle activity change (clenching still occurs)
How a night guard works
A molded splint sits between arches, spreading and cushioning bite force.
What it protects
Guards shield enamel and restorations from direct grinding contact.
What it does not change
Underlying muscle activity and clenching habit largely continue unchanged.
Muscle-Relaxing Injection Into the Masseter
A routine outpatient injection gradually relaxes an overactive jaw muscle.
- Outpatient: Procedure setting (brief in-office visit)
- 1–2 wks: Onset of effect (gradual muscle relaxation)
- ~3–4 mo: Duration of effect (per treatment cycle)
- Noticeable: Muscle bulk reduction (over following weeks)
What the injection does
It temporarily reduces the muscle's ability to contract forcefully.
Typical treatment course
A few injection points into the masseter, repeated periodically as needed.
What it does not address
It does not correct any underlying bite or occlusal contact issue.
Comparative Effect — Guard vs Injection
Each option addresses a different part of the bruxism problem.
- High: Guard: tooth protection (direct mechanical barrier)
- Unchanged: Guard: muscle activity (clenching persists beneath)
- Reduced: Injection: muscle activity (over several weeks)
- Low: Injection: tooth protection (no occlusal barrier added)
Mechanical protection pathway
The guard absorbs force at the tooth surface, sparing enamel directly.
Muscle-relaxation pathway
The injection lowers muscle contraction strength and bulk gradually.
Neither is a complete fix alone
Combining both addresses teeth and muscle for broader relief.
Clinical Outcome & Treatment Selection
Night guards remain standard first-line; injections suit select cases.
- Night guard: First-line approach (standard of care)
- Selective: Injection candidacy (hypertrophy or discomfort)
- Common: Combined use (guard plus injection)
- Periodic review: Follow-up (reassess fit and effect)
Why the guard stays first-line
It is simple, low-risk, and directly protects tooth structure nightly.
When injection is considered
Reserved for visible muscle enlargement or persistent jaw discomfort.
Combined management
Many patients use a guard alongside periodic injection therapy.