Abstract
Masticatory efficiency may be impaired in individuals with dentofacial deformities. The objective of the present study was to determine the condition of masticatory efficiency in individuals with dentofacial deformities. 30 patients with class II (DG-II) and 35 patients with class III (DG-III) dentofacial deformity participated in the study, all had an indication for orthognathic surgery. 30 volunteers (CG) with no alterations of facial morphology or dental occlusion and with no signs or symptoms of temporomandibular joint dysfunction also participated. Masticatory efficiency was analysed using a bead system (colorimetric method). Each individual chewed 4 beads, one at a time, over 20 s measured with a chronometer. The groups were compared in terms of masticatory efficiency using analysis of variance (ANOVA), with the level of significance set at P < 0.05. Masticatory efficiency was significantly greater in CG ( P < 0.05) than in DG-II and DG-III in all chewing tasks tested, with no significant difference between DG-II and DG-III ( P > 0.05). It was observed that the presence of class II and class III dentofacial deformity affected masticatory efficiency compared to CG, although there was no difference between DG-II and DG-III.
Unfavourable skeletal relations and impaired occlusion lead to impaired mastication in individuals with dentofacial deformities. Difficulty in mastication is one of the main complaints of adults with dentofacial deformities, who usually seek orthosurgical treatment due to aesthetic and functional problems.
Masticatory efficiency can be defined as the ability to triturate a certain portion of food within a determined period of time and can be quantified as the individual ability to fragment natural or artificial foods. It is influenced by occlusal contacts, signs and symptoms of temporomandibular dysfunction, malocclusion, bite force, number of functional teeth, body size, texture of the material used to evaluate it, and oral sensorimotor function.
Individuals with severe malocclusions have lower masticatory efficiency than individuals with no malocclusal changes. The reason for this reduced masticatory efficiency in these individuals is not fully understood. Most of the studies cited in the literature use the sieve method to assess masticatory efficiency. This is difficult to use clinically because it involves a slow and complex analysis, with loss of sensitivity and reproducibility since it involves the loss of chewed material by swallowing or by dissolution with saliva.
The bead system proposed for the assessment of masticatory efficiency is effective because it costs little, involves no dissolution with saliva, suffers no variations, and there are no losses during evaluation. It is also precise and rapid and its physical properties are constant and reproducible in a reliable manner.
The objective of the present study was to determine whether the presence of class II and class III facial deformity influences masticatory efficiency.
Materials and methods
The study was approved by the Research Ethics Committee of the University Hospital, Faculty of Medicine of Ribeirão Preto, University of São Paulo (HCFMRP-USP), protocol n° 11463/2006, and all subjects gave written informed consent to participate.
The study sample consisted of 95 individuals and the control group included 30 volunteers (12 men and 18 women; mean age 24 years). The deformity group (DG) consisted of 65 volunteers who attended the Craniomaxillofacial Surgery Outpatient Clinic of the Integrated Centre for the Study of Facial Deformities (CIEDEF) of HCFMRP-USP. Thirty of these patients (9 men and 21 women; mean age 25 years) had a diagnosis of class II dentofacial deformity (DG-II) characterized by mandibular retrognathism and/or excess maxillary growth, and 35 (18 men and 17 women; mean age 24 years) had a diagnosis of class III dentoskeletal deformity (DG-III) characterized by mandibular prognathism and/or maxillary deficiency, with the mandible being more anteriorized in relation to the maxilla.
The control group consisted of volunteers with natural dentition, with no alterations of facial morphology or dental occlusion, with no complaints of signs or symptoms of temporomandibular joint dysfunction, and without missing teeth, except for the third molars.
DG-II and DG-III consisted of patients with an indication for surgical correction of the deformity, regardless of occlusal or skeletal changes in the vertical and/or transverse direction. All patients were supposed to be undergoing orthodontic treatment with fixed braces on the upper and lower teeth, regardless of the phase of treatment. The patients were supposed to have no more than one missing tooth on the same side of the arcade, with or without an interdental space due to a tooth extraction for orthodontic or dental treatment or to early losses.
Individuals with central or peripheral neurological disorders, who had suffered traumatic injuries in the head and neck region, and individuals wearing full or partial dentures were excluded from the study. There were no restrictions regarding the race or social level of the participants.
An examination of the oral cavity was performed in each participant to determine the pattern of dental occlusion, the occurrence of missing teeth, and the use of orthodontic braces.
Masticatory efficiency was assessed by the colorimetric method, consisting of a bead system ( Fig. 1 ). All participants were instructed to sit straight in a comfortable chair with feet resting on the floor. Before the evaluation, each participant received a mint-flavoured sugarless chewing gum tablet (Trident ® ) to remove the resting neuromuscular memory and to achieve habitual mastication as much as possible. The participant chewed the gum for 30 s measured by the researcher with a Kenko ® digital chronometer, model KK-2808.
After a 3 min interval, the participant was asked to chew a total of 4 beads, one at a time for 20 s each, measured by the researcher with a chronometer, with a 3 min interval between beads. Two beads were chewed in the habitual manner, characterizing habitual mastication 1 and habitual mastication 2, and the other two were chewed unilaterally, one on the right side and the other on the left side.
The beads were identified and the triturated content was placed in a beaker, dissolved in 5 ml water and constantly stirred for approximately 30 s. The solution was filtered and its staining intensity was measured with a spectrophotometer (Beckman DU-640), which measured staining as absorbance (nm), later transformed to fuchsin concentration (μg/ml).
Statistical analysis
Data concerning the masticatory efficiency of CG, DG-II and DG-III were analysed statistically by analysis of variance (ANOVA), with the level of significance set at P < 0.05.
The model used is based on the assumption that its residues have normal distribution, with 0 mean and constant variance. In cases in which this assumption was not valid, the response variable was log and square root transformed. The analyses were carried out with the aid of the SAS 9.0 software, version 9 (Cary, NC, USA).
Results
Mean masticatory efficiency was higher in CG (habitual chewing 1 = 2.50 ± 1.01, habitual chewing 2 = 2.57 ± 1.02, right chewing = 2.59 ± 0.94, left chewing = 2.67 ± 1.01) than in DG-II (habitual chewing 1 = 0.81 ± 0.30, habitual chewing 2 = 0.84 ± 0.36, right chewing = 1.03 ± 0.80, left chewing = 0.94 ± 0.42) and DG-III (habitual chewing 1 = 0.63 ± 0.37, habitual chewing 2 = 0.73 ± 0.39, right chewing = 0.73 ± 0.47, left chewing = 0.75 ± 0.42) for all masticatory tasks tested ( P < 0.05), with no significant difference being observed between DG-II and DG-III ( P > 0.05). The results are presented in Fig. 2 .
Results
Mean masticatory efficiency was higher in CG (habitual chewing 1 = 2.50 ± 1.01, habitual chewing 2 = 2.57 ± 1.02, right chewing = 2.59 ± 0.94, left chewing = 2.67 ± 1.01) than in DG-II (habitual chewing 1 = 0.81 ± 0.30, habitual chewing 2 = 0.84 ± 0.36, right chewing = 1.03 ± 0.80, left chewing = 0.94 ± 0.42) and DG-III (habitual chewing 1 = 0.63 ± 0.37, habitual chewing 2 = 0.73 ± 0.39, right chewing = 0.73 ± 0.47, left chewing = 0.75 ± 0.42) for all masticatory tasks tested ( P < 0.05), with no significant difference being observed between DG-II and DG-III ( P > 0.05). The results are presented in Fig. 2 .
