Influence of dental chair backrest inclination on the registration of the mandibular position.
BACKGROUND
Varying the inclination of the dental chair backrest might alter the distribution of occlusal contact points.


OBJECTIVE
The purpose of this study was to identify the influence of backrest inclination on the registration of the mandibular position.


METHODS
Ten participants aged between 18 and 30 years with a complete permanent dentition, uncompromised motor function, no tooth mobility, and no temporomandibular disorders were selected. To register interocclusal contacts, an autopolymerizing methylmethacrylate device was adapted to the maxillary anterior teeth and a composite resin increment was added to the mandibular central incisors. Contacts were registered with the following variations in the inclination of the dental chair backrest: 90 degrees, 120 degrees, and 180 degrees. A standardized digital photograph was made of each mark in each backrest position, and the images were superimposed to measure the distances in registration from 90 to 120 and from 90 to 180 degrees. Data were analyzed with the Student paired t test (α=.05).


RESULTS
When the chair was inclined from the 90-degree to the 120-degree position, the mandible was repositioned posteriorly by a mean of 0.67 mm, but the difference was not statistically significant. When the chair was inclined from the 90-degree to the 180-degree position, however, the mandible was repositioned posteriorly by a statistically significant mean of 1.41 mm.


CONCLUSIONS
Mandibular position is influenced by increasing inclination, and this influence was statistically significant at a 180-degree incline.
Private practice, São Paulo, Brazil.
Mariana Freire
MF
Coelho
Professor, Department of Restorative Dentistry, São Paulo State University "Júlio de Mesquita Filho" (UNESP), São José dos Campos, Brazil.
Bruno das Neves
Bd
Cavalcanti
Professor, Department of Dentistry, University of Taubaté (UNITAU), Taubaté, Brazil.
Ana Christina
AC
Claro Neves
Doctoral student, Department of Bioscience and Oral Diagnosis, São Paulo State University "Júlio de Mesquita Filho" (UNESP), São José dos Campos, Brazil.
Renata Pilli
RP
Jóias
Full Professor, Department of Dental Materials and Prosthodontics, São Paulo State University "Júlio de Mesquita Filho" (UNESP), São José dos Campos, Brazil. Electronic address: sigmarrode@uol.com.br.
Sigmar de Mello
Sde M
Rode
D000293:Adolescent; D000328:Adult; D003766:Dental Occlusion; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007574:Jaw Relation Record / Q000379:methods*; D008334:Mandible / Q000033:anatomy & histology*; D010781:Photography; D055815:Young Adult