Clinical guide · For dental professionals
What the published evidence says about soft, hard/soft and hard acrylic occlusal guards, and how patient factors map to each material.
Strength of evidence reflects the published studies, most of which are small.
| Patient factor | Material most supported | Evidence |
|---|---|---|
| Heavy sleep bruxism or strong clenching; goal is lower muscle activity | Processed acrylic hard splint | Weak [1][3]; a 2024 meta-analysis found no material difference [2] |
| Protecting worn teeth, restorations or implants | Processed acrylic hard splint | Moderate for material wear (lab) [15][16]; expert opinion for clinical protection |
| Patients who wear through softer appliances | Processed acrylic hard splint | Moderate (lab wear) [15][16] |
| Moderate grinding or clenching; comfort matters for adherence | Hard/Soft (dual laminate) | Material properties and expert opinion; no dedicated clinical trials |
| Mild grinding or clenching; patient intolerant of rigid appliances | Soft splint | Weak–moderate [4][6] |
| Short-term TMD or myofascial pain | Soft or hard, similar results | Moderate [6][7][8] |
| Joint sounds or disc displacement | Hard acrylic; avoid fully soft | Weak [9] |
| Chronic TMD pain (over 3 months) | Self-care and physical or behavioural therapy first; splint optional | Guideline [24] |
| Snoring or suspected sleep apnea | Screen or refer before any flat-plane appliance | Weak [21][22][23] |
| Children or mixed dentition | Not routine; if used, soft and closely monitored | Weak [12][13][25] |
Comfort, short-term use
Evidence: Matched hard splints for short-term TMD pain in a 200-patient RCT [6] and outperformed them at 4 months in one trial [7]. Lowered maximum bite force and improved sleep-quality scores over 2 months [4].
Cautions: Raised night-time masseter activity in 5 of 10 patients [1]; increased joint vibration [9]; highest wear and roughness of common splint materials in chewing simulation [15].
Comfort with a hard occlusal surface
Evidence: No dedicated clinical trials of hard/EVA laminates. The design combines a harder occlusal layer, which wears less than EVA in laboratory tests [15][17], with a soft inner layer for fit and comfort. In one trial a dual-laminate of a different construction (PETG with a TPU inner layer) performed like hard acrylic on joint vibration [9].
Cautions: Less adjustable than processed acrylic; a soft inner layer may allow slight tooth movement, so confirm fit at follow-up.
Stability and durability
Evidence: Lowered night-time masseter activity in 8 of 10 patients [1]; largest EMG reduction among hard, soft and semi-soft in a 3-month trial [3]; PMMA is harder than PETG/TPU [17] and wears less than EVA [15][16]. Occlusal contacts can be adjusted chairside.
Cautions: Firmer feel; some patients need time to adapt. 3 mm and 6 mm thicknesses showed no EMG difference [14].
In some patients. In a 10-patient crossover study the soft splint raised night-time masseter activity in 5 patients, while the hard splint lowered it in 8 [1]. A 2024 meta-analysis found no overall difference between materials, with low to very low certainty [2].
In laboratory chewing simulation, EVA showed the most wear and roughness, while PMMA and polycarbonate wore least [15]. A systematic review of in-vitro studies found thermoformed materials wear most [16].
For short-term pain, yes in most trials: a 200-patient RCT found no difference between a hard flat-plane splint, a soft splint and self-care alone at 12 months [6].
A flat-plane splint that does not advance the mandible increased the apnea–hypopnea index by more than 50% in 5 of 10 patients with sleep apnea in one study [21]. Screen for snoring and sleep apnea first.
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