Effects of low-level laser therapy and orthodontic tooth movement on dental pulps in rats.
OBJECTIVE
To describe the microscopic pulpal reactions resulting from orthodontically induced tooth movement associated with low-level laser therapy (LLLT) in rats.


METHODS
Forty-five young male Wistar rats were randomly assigned to three groups. In group I (n = 20), the maxillary right first molars were submitted to orthodontic movement with placement of a coil spring. In group II (n = 20), the teeth were submitted to orthodontic movement plus LLLT at 4 seconds per point (buccal, palatal, and mesial) with a GaAlAs diode laser source (830 nm, 100 mW, 18 J/cm(2)). Group III (n = 5) served as a control (no orthodontic movement or LLLT). Groups I and II were divided into four subgroups according to the time elapsed between the start of tooth movement and sacrifice (12 hours, 24 hours, 3 days, and 7 days).


RESULTS
Up until the 3-day period, the specimens in group I presented a thicker odontoblastic layer, no cell-free zone of Weil, pulp core with differentiated mesenchymal and defense cells, and a high concentration of blood vessels. In group II, at the 12- and 24-hour time points, the odontoblastic layer was disorganized and the cell-free zone of Weil was absent, presenting undifferentiated cells, intensive vascularization with congested capillaries, and scarce defense cells in the cell-rich zone. In groups I and II, pulpal responses to the stimuli were more intense in the area underneath the region of application of the force or force/laser.


CONCLUSIONS
The orthodontic-induced tooth movement and LLLT association showed reversible hyperemia as a tissue response to the stimulus. LLLT leads to a faster repair of the pulpal tissue due to orthodontic movement.
Department of Pediatric Dentistry and Orthodontics, Division of Orthodontics, State University of Rio de Janeiro, Rio de Janeiro, Brazil. labiramia@yahoo.com.br
Luciana Baptista Pereira
LB
Abi-Ramia
Andrea Sasso
AS
Stuani
Adriana Sasso
AS
Stuani
Maria Bernadete Sasso
MB
Stuani
Alvaro de Moraes
Ade M
Mendes
D000818:Animals; D002196:Capillaries / Q000473:pathology; D002467:Cell Nucleus / Q000473:pathology; D002843:Chromatin / Q000473:pathology; D003593:Cytoplasm / Q000473:pathology; D003782:Dental Pulp / Q000098:blood supply / Q000473:pathology* / Q000528:radiation effects; D004912:Erythrocytes / Q000473:pathology; D005347:Fibroblasts / Q000473:pathology; D006940:Hyperemia / Q000473:pathology; D054023:Lasers, Semiconductor; D028022:Low-Level Light Therapy; D008297:Male; D008648:Mesoderm / Q000473:pathology; D008963:Molar / Q000473:pathology / Q000528:radiation effects; D009804:Odontoblasts / Q000473:pathology; D009969:Orthodontic Wires; D011897:Random Allocation; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors; D014087:Tooth Movement Techniques / Q000295:instrumentation
D002843:Chromatin