Influence of two masticating conditions on assessment of movement path stability

The effect of mandibular movement on temporomandibular joint morphology while eating French fries

BACKGROUND

The preferred masticatory side was reported to be almost always the same as the affected side of the temporomandibular disorder. Unbalanced alterations of temporomandibular joint morphology were found to be associated with unilaterally masticatory habits. The aim of this study was to investigate the effect of the mandibular movement on the remodeling of temporomandibular joint during eating French fries using a 3D motion capture system.

METHODS

Twelve volunteers with non-maxillofacial deformity and a healthy temporomandibular joint were recruited. The 3D models of the mandible and the maxilla were reconstructed according to computed tomography. The subjects were asked to eat French fries by unilaterally mastication, which was recorded by a 3D motion capture system. The trajectories of the incisors and the condyles and the condylar acceleration during unilateral mastication were analyzed.

RESULTS

During incisal biting, there was no significant difference in the condylar trajectories between the left and right sides (P > 0.05). During unilateral mastication, the average displacement and acceleration of the masticatory condyles were significantly lower than those of the non-masticatory condyles (P < 0.05). The trajectory angles of the masticatory condyles were significantly steeper than those of the non-masticatory condyle (P < 0.05). During swallowing, there was no obvious movement of the mandible.

CONCLUSIONS

Between both temporomandibular joints, unilateral mastication resulted in significant differences in the regions of the condylar movement within the articular fossa, and then caused different compressive regions of the temporomandibular joints. Thus, unilateral mastication might result in a significantly different pattern of temporomandibular joint remodeling between the two sides.

Reproducibility of the Obtained Centric Relation Records in Patients with Disc Displacement with Reduction

Objective

The aim of this study was to investigate reproducibility of the position of centric relation in patients with disc displacement with reduction.

Materials and methods

The test group included 30 subjects, diagnosed with disc displacement with reduction in right, left or both joints. The control group included 12 individuals with no signs and symptoms of temporomandibular disorders. Using chin point guidance with a jig, centric relation record was made three times by every participant, in a single session. Left and right condylar position for each centric relation record was determined and recorded using the electronic ultrasonic measuring device. The data were transferred to the computer, processed and analyzed. Condylar distances between centric relation records were measured (anteroposterior, vertical, transversal and linear values), and the data were statistically analyzed using the t and the F tests.

Results

No statically significant difference was found between the test and the control groups. Two thirds of study participants demonstrated condylar position of the repeated centric relation recording within the area of 0.3 mm in diameter. For more than 90% of participants that area was within 0.4 mm.

Conclusions

There is no difference in reproducibility of the centric relation between patients with disc displacement with reduction and healthy temporomandibular joint individuals (p>0.05). When doing centric relation record on a patient with disc displacement with reduction there is no need for previous splint therapy and standard precautions are acceptable. The obtained results must be interpreted within the experimental group, and not projected on the other groups of temporomandibular disorders.

Short-Term Crossover Study on the Effect of Orthogonalized Deep-Grooved Posterior Artificial Teeth on the Masticatory Efficiency of Complete Denture Wearers

Background:

Mastication has been regarded to play an important role in achieving quality daily life for the elderly. On the occlusal surface of posterior artificial teeth, parallel grooves of 1 mm depth and 1 mm width with an inter-groove distance of 2 mm have been found to significantly improve masticatory efficiency on a mechanical simulator.

Materials and Methods:

In the present study, the effect of the grooved design on masticatory efficiency in edentulous subjects using a short-term crossover trial was evaluated. Six edentulous participants, 1 male and 5 females, were assigned into two groups. One received duplicated complete dentures with grooved molars first, and the other received duplicated complete dentures with conventional molars first. The design of the teeth was crossover after evaluating masticatory efficiency. Raw carrot, raw lettuce and mixed foodstuffs were used to evaluate masticatory efficiency. Subjects were instructed to masticate 20 strokes and arbitrary strokes until they felt like swallowing.

Results:

The number of masticatory strokes taken was significantly smaller using the grooved design (p<.05). Masticatory efficiency analysis revealed that the grooved design achieved significantly higher masticatory efficiency at 20 masticatory strokes for raw carrot and mixed foodstuffs (p<.05).

Conclusion:

Results show that compared with conventional lingualized occlusion, the grooved design accomplishes higher masticatory efficiency in vivo. Considering the distinction of this design that it can be applied to any existing denture occlusion, the design might help improve the dietary life of the elderly.

Markerless three-dimensional tracking of masticatory movement

Conventional methods for measuring mandibular movement are expensive and require headgear and a marker attached to the mandibular incisors. These make assessment of normal chewing difficult. The aim of the present study was to test the validity of a markerless three-dimensional system for tracking masticatory movement by comparing it with a conventional method using an incisal marker. The study investigated 100 chewing cycles in 10 participants. The jaw tracking system consisted of a camera capable of recording depth and red, green, and blue data simultaneously, a laptop computer, and data analysis software. Depth data for each participant's face, tracked in real time, produced a computed 3D mask. The most prominent point of the soft tissue under the lip was defined as the chin point. A dental clasp cemented to the labial surface of the mandibular incisors was defined as the incisal point. The movement of these two measuring points was simultaneously recorded during mastication of chewing gum for 20s. To conduct the same analysis on each cycle from the two measuring points, all cycles were normalized by dividing by the corresponding vertical displacement because of their size variation. The findings showed excellent intramethod correlation for normalized horizontal displacement at every level (>0.9; except for 2 out of 19 levels; 0.896 and 0.898), and a lack of proportional bias. These findings suggest a correlation between the chewing cycles from two measuring points, the incisor and the chin, further suggesting the feasibility of a markerless system for tracking masticatory movement.

Myofunctional orofacial examination: comparative analysis in young adults with and without complaints

PURPOSE

To verify myofunctional orofacial characteristics in young adults and to compare data on individuals with and without myofunctional complaints, aiming to identify the main myofunctional problems and differentiating them from characteristics that are common for this population, as well as to list items for myofunctional evaluation in this population.

METHODS

Cross-sectional study with 85 adult participants, aged between 19 and 39 years, selected through consecutive sampling at the Department of Speech, Language and Hearing Sciences of Universidade Veiga de Almeida. The participants were divided into two groups: G1 (comprising 50 individuals referred for orofacial myofunctional disorders) and G2 (comprising 35 volunteers without complaints). Descriptive evaluation of craniofacial structures of hard and soft tissues, kinesiology and mandible range of motion and functional patterns of breathing, chewing, and swallowing was applied. Three expert Speech-Language pathologists assessed all participants. Statistical analysis was done using χ2-test, Student's t-test, or Mann-Whitney test. The reliability level was 99%.

RESULTS

A predominance of Angle Class I pattern of occlusions for G2 (p<0.0001) was found. G1 showed (p<0.0001) mandible movements with deviations and joint noises, amplitude reduction in lateral and protrusive movements, unilateral chewing, nonexpected muscle contraction, temporomandibular joint noises, swallowing with excessive contraction of the orbicularis oris muscle, loud noise, and residues (p=0.006).

CONCLUSION

The main myofunctional orofacial alterations in young adults with complaints refer to changes of the mandibular movements and patterns of chewing or of swallowing, reflecting the main items of the clinical evaluation. Many items of assessment and characterization do not differ between the groups, and these should be analyzed regarding their relevance.