Incisor and mandibular movement during retrusion P.L. Foglio-Bonda a, * , G. Migliaretti b , F. Cavallo b , V. Rocchetti a , C. Bodin c a Dental Clinic University of Eastern Piedmont, Novara, Italy b Department of Public Health, Statistical Unit, University of Turin, Italy c Dental School University of Brescia, Italy Accepted 16 January 2006 Introduction Human mastication, respiration, speech, swallow- ing and suckling are directed by the jaw muscle tensions, the temporo-mandibular joints (TMJs), the ligaments and by the occlusal dental contacts. Mastication is commonly assessed by recording movements of the mandibular incisors because the condyles and incisors are part of the same rigid bony system. Opening, 1 protrusion and lateratru- sion 2 are often used to determine the jaw function but the retrusive mandibular movement is rarely considered in the study of the human oro-facial Archives of Oral Biology (2006) 51, 581—586 www.intl.elsevierhealth.com/journals/arob KEYWORDS Retrusion; Mandibular movements; Jaw kinematics; Mastication; Human Summary Human mastication, respiration, speech, swallowing and suckling are directed by the jaw muscle activites, the temporo-mandibular joints, the ligaments and by the occlusal dental contacts. Mastication is usually assessed by border move- ments of the mandibular incisors. While the border movements of opening, protrusion and lateratrusion are often used to determine the mandibular functions, the movement of retrusion is rarely considered in the study of the human oro-facial functions. Our purpose was to evaluate the mandibular movement of retrusion in a population that did not present any symptoms nor clinical signs of temporo-mandibular disorders. The study was performed on 117 males and 121 females (age range: 17.7—65.2 years; mean age: 31.1 years) using electrognathographic registrations (Sirognatograph * , Siemens, Benshein, Germany). Every patient was instructed and trained before recording. The measurements were calculated on the sagittal plane registrations. The results showed that the mandibular movement of retrusion was present in 233 out of the 238 studied subjects (97.9%) whatever was the dental class, the age or the sex. The width range was between 0.3 and 5.4 mm and the mean value was 1.75  0.91 mm. The inferential analysis performed by a 3-way ANOVA model demon- strated no significant difference in retrusion value by dental class, gender or age. The most frequent numerical value was 1.5 mm, observed in 16 subjects (6.7% of the studied population). These results suggest that, in order to respect the physiological characteristics, more attention is needed in performing dental treatments. # 2006 Elsevier Ltd. All rights reserved. * Corresponding author. Tel.: +39 3213734874; fax: +39 3213734843. E-mail addresses: odonto@maggioreosp.novara.it, fbonda@med.unipmn.it (P.L. Foglio-Bonda). 0003–9969/$ — see front matter # 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.archoralbio.2006.01.005