Rationale

1. Teeth are loaded about 20 minutes daily 

2. Average physiologic anterior resting space is 4mm +/-1 (agonist/antagonist balance) 

3. MAPA averages 2mm of thickness at cuspid discluding elements 

4. MAPA engages on patient’s lower cuspids during bruxing etc. Passive (no contact) otherwise 

5. When the MAPA is engaged (parafunctional activity, etc.), The bicuspids and molars have no PDL stimulation, the temporal muscles are all but shut down .

• Masseter and medial pterygoid muscle function reduced by over 70% by decreasing leverage. Contact is far away from fulcrum and force (condyles and muscles) 

• Bilateral balanced cuspid contact in protrusion. Ideally 4mm in protrusion and lateral runs 

• Flat, or nearly so, the cuspid discluding elements prevent isometric forces to lateral pterygoid movements similar to skates on ice 

• Teeth and condyles can reach their “home” or neutral zone by removing posterior dental contact. This also relaxes muscles.

• Prevents sinus bones from being loaded or flexed 

• Compression on nerves and vessels reduced throughout face and TMJs 

See below the drawing showing lower cuspid contacting the MAPA

Comparison with other Anterior Bite Guards

1. All other anterior loaded bite guards whether segmental or fully covered, load on incisors. 

2. The freeway space is often violated. This is especially true in posteriorly loaded appliances when the material is too thick. The normal agonist/antagonist resting of muscles are then changed. Muscle spindle fibers and Golgi tendon bodies try to maintain muscle length or modify muscles over time by establishing a new muscle memory. This can lead to tooth intrusion. 

3. Bruxing is a parafunctional activity. Forces placed on teeth or bite guards are very mild in the awake state compared to sleep. Inhibitory reflexes that are present during awake time are mostly absent during sleep. Parafunctional activity can inflict far greater forces and for a much longer period during sleep. Therefore, bite guard wear is most critical during sleep. No bite guard, anterior or posterior, should be worn continuously for more than two months. 

4. Loading on incisors whose roots are somewhat conical and small can cause intrusion during hard bruxism when inhibitory reflexes during sleep are absent. The premaxilla bone can even be moved (anterior open bites, etc. can occur). Cuspid loading is far more resistant to movement.

5. Loading on large and long “cuspid roots” which are in very dense bone is far safer. Additionally, you have the dense PDL protective feedback from the cuspids that help prevent trauma via the muscles. Not so much with incisors.