Regional alterations in fiber type distribution, capillary density, and blood flow after lower jaw sagittal advancement in pig masticatory muscles.
Muscular remodeling is known to be a prerequisite for permanent correction of mandibular-maxillary malocclusion. The objective of this study was to clarify if an increase in type I fiber number is accompanied by an increased capillary density and improved muscular blood flow. Juvenile pigs received build-ups on the molars, which induced a protrusion of 7.6 + 1.5 mm. After 4 weeks of treatment, chronic lower jaw protrusion induced a marked muscle blood flow increase in the anterior and medial regions of the superficial part of the masseter and in the medial pterygoid muscle (P < 0.05). Furthermore, an increase in capillary density and in the amount of type I fibers was found in all regions of masticatory muscles with an increased muscle blood flow (P < 0.05). Finally, the capillary-to-fiber ratio increased (P < 0.05). Muscle blood flow and capillary density showed a strong linear correlation (r = 0.89, P < 0.01). These changes suggest a complex muscle adaptation for long-term, fatigue-resistant activity during the early corrective period of mandibular-maxillary malocclusion treatment.
Gedrange
T
T
Department of Orthodontics, Technical University, Dresden, Germany.
Walter
B
B
Tetzlaff
I
I
Kasper
M
M
Schubert
H
H
Harzer
W
W
Bauer
R
R
D000818:Animals; D002196:Capillaries / Q000502:physiology; D007150:Immunohistochemistry; D019186:Mandibular Advancement; D008410:Masticatory Muscles / Q000033:anatomy & histology* / Q000098:blood supply*; D018656:Muscle Fibers, Fast-Twitch / Q000502:physiology; D018657:Muscle Fibers, Slow-Twitch / Q000502:physiology; D018919:Neovascularization, Physiologic; D012039:Regional Blood Flow; D013552:Swine