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Mandibular rest position: a reliable position influenced by head support and body posture
E M Tingey1, P H Buschang, G S Throckmorton
1Department of Orthodontics, Baylor College of Dentistry, Texas A&M University System Health Science Center, 3302 Gaston Ave., Dallas, TX 75246, USA.
Summary
Mandibular rest position involves significant movement of incisors, molars, and condyles. Head and body posture influence these movements, indicating complex jaw dynamics beyond simple opening rotation.
Area of Science:
- Dentistry
- Biomechanics
- Human Anatomy
Background:
- Understanding mandibular rest position is crucial for diagnosing and treating various dental and temporomandibular joint (TMJ) disorders.
- Previous research has not fully elucidated the relationship between incisor, molar, and condyle positions in the mandibular rest position across different body postures.
Purpose of the Study:
- To investigate the relationship between incisor, molar, and condyle positions in the mandibular rest position.
- To determine how these positions change with varying head and body postures.
Main Methods:
- A prospective study involving 24 healthy adult males with Class I occlusion.
- Optoelectric tracking of 5 landmarks (lower incisor, bilateral condyles, and molars) from maximum intercuspation to four distinct rest positions.
- Rest positions were established using minimal electromyographic and verbal cues in upright supported, upright unsupported, supine supported, and supine unsupported conditions.
Main Results:
- Significant movements (P <.01) of incisors, molars, and condyles were observed across all four rest positions.
- Slight but significant differences in molar and condyle movement were noted between supported and unsupported upright postures.
- Distinct mandibular movement patterns emerged between upright (posterior rotation) and supine (anterior rotation) positions.
Conclusions:
- Mandibular rest position is not a simple opening rotation from the intercuspal position.
- Head support and body posture significantly influence the pattern of mandibular movement during rest position establishment.