Centric slide, bite force and muscle tenderness changes over 6 months following fixed orthodontic treatment.
OBJECTIVE
The postorthodontic change of the masticatory muscles was evaluated using three parameters: maximal voluntary bite force (MVBF), slide in centric (difference between maximal intercuspation and retruded contact position), and muscle sensitivity to palpation.


METHODS
MVBF was measured with a custom-made rubber tube bite force device, centric slide with a digital caliper, and sensitivity to palpation of the masseter and temporalis muscles (scale 0-3) during application of standardized digital force (10 N). Data were collected at four time points: T0, before bracket removal; T1, immediately after bracket removal; T2, after 3 months of retention; and T3, after 6 months of retention. Patients (n = 41; 22 females, 19 males; mean age 17.4 +/- 5.4 years) were examined from T0 to T1 and from T1 to T2. Of these, 28 (15 females, 13 males) were followed at T3.


RESULTS
Immediately after bracket removal (T0 to T1), MVBF increased significantly by 15%. Another significant increase (15.5%) was found 3 months posttreatment (T1-T2), and almost no increase (2%) at 6 months (T2-T3). The slide in centric remained within normal values during the three time points. A decline in sensitivity to palpation from T1 to T3 was found for both masseter and temporalis muscles.


CONCLUSIONS
Neuromuscular adaptability begins within several minutes after bracket removal. A second stage of muscular adaptation occurs within 3 months of retention. These findings suggest that muscular adjustment occurs within a short period after orthodontic treatment.
Winocur
Ephraim
E
Department of Oral Rehabilitation, The Maurice and Gabriela Goldschleger School of Dental Medicine, Tel Aviv University, Israel. winocur@post.tau.ac.il
Davidov
Itschack
I
Gazit
Esther
E
Brosh
Tamar
T
Vardimon
Alexander D
AD
D000222:Adaptation, Physiological; D000293:Adolescent; D000704:Analysis of Variance; D001732:Bite Force; D002138:Calibration; D003768:Dental Occlusion, Centric; D005260:Female; D006801:Humans; D008297:Male; D008406:Masseter Muscle / Q000502:physiology*; D053581:Muscle Strength Dynamometer; D009971:Orthodontics, Corrective; D013703:Temporal Muscle / Q000502:physiology*; D013997:Time Factors