Assessment of the effect of the use of laser light or dantrolene on facial muscle under occlusal wear: a Raman spectroscopic study in a rodent model.
OBJECTIVE
The aim of the present study was to use Raman spectroscopy to measure levels of CaPi in muscles under occlusal wear and treated with laser phototherapy (LPT) or muscle-relaxant therapy or both on rodents.


BACKGROUND
The etiology of temporomandibular disorders is multifactorial. Malocclusion may influence the masticatory muscles, causing fatigue. A major type of fatigue is the metabolic, caused by the increased accumulation of metabolites such as inorganic phosphate. Raman spectroscopy allows nondestructive analysis of the biochemical composition of tissues.


METHODS
The 30 male Wistar rats were randomly divided into three groups: occlusal wear (G-1), occlusal wear + LPT (G-2), and occlusal wear + muscle relaxant (G-3). Ten untreated animals were used for baseline data. Under intraperitoneal general anesthesia, animals of groups 1, 2, and 3 had unilateral amputation of molar cusps to simulate an occlusal-wear situation. The masseter muscle of G-2 received LPT (lambda830 nm, 4 J/cm(2), 40 mW, phi approximately 2 mm) after the procedure and repeated every other day for 14-30 days. Animals of G-3 were treated with a daily injection of dantrolene (2.5 mg/kg in 0.5 ml of H(2)O) beginning 24 h after cusp removal. Animals were killed with an overdose of general anesthetics at days 14 and 30 after cusps removal, and the ipsilateral masseter muscle was excised and divided into two parts. One part was routinely processed and underwent histologic analysis; the other was kept in liquid nitrogen for Raman spectroscopy. The mean value of the intensity of the peak 958 per centimeter was determined.


RESULTS
No morphologic changes were seen. Raman analysis showed significantly less Raman intensity in the laser group at 30 days (p < 0.01).


CONCLUSIONS
Occlusal wear did not caused morphologic alterations in the masseter muscle but resulted in changes of the levels of CaP(i) that were less compromising when the laser light was used.
Lisboa
Márcio V
MV
Center of Biophotonics, School of Dentistry, Federal University of Bahia, Salvador, Brazil.
Lopes
Cibelle B
CB
Rocha
Rick
R
Ramos
Tais Andrade
TA
de Abreu
Igor D N
ID
Cangussu
Maria Cristina T
MC
Pinheiro
Antonio L B
AL
dos Santos
Jean N
JN
D000818:Animals; D002118:Calcium / Q000378:metabolism; D003620:Dantrolene / Q000494:pharmacology*; D004195:Disease Models, Animal; D005152:Facial Muscles / Q000187:drug effects* / Q000503:physiopathology / Q000528:radiation effects*; D028022:Low-Level Light Therapy; D008297:Male; D008406:Masseter Muscle / Q000187:drug effects* / Q000503:physiopathology / Q000528:radiation effects*; D009125:Muscle Relaxants, Central / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D013059:Spectrum Analysis, Raman; D019217:Tooth Attrition / Q000503:physiopathology / Q000628:therapy*
D009125:Muscle Relaxants, Central; D003620:Dantrolene; D002118:Calcium