The Baropodometer
On 1996, it was introduced the Electronic Baropodometer (Diagnostic Support S.r.l. Via Dora 1 - 00198 Roma, Italy) (Figure 1), a patented modular platform, with the possibility to connect several modules together, obtaining a full length up to cm 240 (7,90 ft). This system allows the analysis of the walk in a natural way. The acquisitions are based detecting each cm square of the plantar surface contact. On 2006 it was introduced an advanced version of the modular technology based on an high resolution platform, realizing the modularity beyond that length also in width. This new system (Electronic Baropodometer MultiSensor) (Figure 1) uses four sensors each cm square and is available with a width of 40 cm (15,75 in) or 80 cm (31,50 in) and a length up to 320 cm (1,50 ft). While integrating optical devices and foot pressure platform, the system is named D.B.I.S. Digital Biometry Images Scanning (including hardware and software).
The sample
Thirty Caucasian adult females were enrolled in the study after signing an informed consent form. They were selected as asymptomatic subjects for TMDs, assessed according to the American Academy of Orofacial Pain [8]. This group was partly formed by the same subjects of the control group investigated in a previous cited study from the same group [1], but in that study they were investigated in different conditions: only with two symmetric cotton rolls between dental arches. In this new study we add some findings observed when other test conditions were investigated. We add new data concerning the conditions in which the subjects are put with only one cotton roll positioned in the right or in the left sides of dental arches. The use of only one cotton roll, instead of two symmetric cotton rolls (as in the previous study), causes an asymmetric imbalance of the occlusion caused by the shift of the mandible versus one side or another when only a cotton roll is inserted between dental arches. When two symmetric cotton rolls are inserted, no shift of the mandible is observed.
In this study, these subjects without TMD's symptoms were investigated not in usual conditions, but after an experimentally induced imbalance of occlusion, given by a unilateral cotton roll placed in the right or the left sides. The condition "in habitual occlusion" was used as control.
The variables
The platform was the Electronic Baropodometer MultiSensor system, D.B.I.S. (Digital Biometry Images Scanning) (Diagnostic Support S.r.l. Via Dora 1 - 00198 Roma, Italy) (Figure 1).
The position of the load cells could not be modified to adapt to different foot shapes. However, the differences in foot shapes among the subjects were never indicated as a limit for the study of the loading in the orthopaedic literature, and it is why we adopted this method in this investigation [9].
The variables investigated in this study were: the load surface (expressed in mm2), the loading pressure (expressed in gr/cm2) and the loading (expressed in percentage for the two sides) on the feet during locomotion in habitual occlusion and with an unilateral cotton roll interposed between dental arches in the right or in the left sides.
Posturographic recordings were performed with subjects walking on the platform and always making two walks, involving firstly the right foot and finally the left foot.
Three different conditions were enrolled during the walking posturography: i) cotton roll between the dental arches only in the left side; ii) cotton roll between the dental arches only in the right side; iii) habitual occlusion.
The experimentally induced imbalance of occlusion was performed with an unilateral cotton roll midly crushed between the dental arches in one side; in this condition the subject was asked to swallow [10]. The condition in habitual occlusion was used as control condition.
For each condition, the mean pressure during walking (gr/cm2) on the theoretical barycentre, the percentage of loading on the left and the right feet and the loading surface (mm2) on the right and the left feet, were recorded as posturographic parameters. The theoretical barycentre was considered as the point whose projection on the ground falls in the middle of the connecting segment between the barycentre of the right and left limbs [10].
Data analysis
The Statistical Package for Social Sciences programme (SPSS® Inc., Chicago, Illinois, USA) was used to perform the data analysis. Each data set was tested for normality using the Skewness test and the Kurtosis test. Through these analyses, parametric methods were used for the hypothesis testing. For each variable, a one way ANOVA was performed to evaluate the existence of significant differences among the three different experimental conditions. Subsequently, and when appropriate, pairwise comparisons, between the experimental conditions were performed by a Tukey HSD and a Bonferroni test. A p value less than 0.05 was accepted for rejection of the null hypothesis.