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Difference between revisions of "Jaw movements analysis. Part 1: Electrognathographic Replicator"
Jaw movements analysis. Part 1: Electrognathographic Replicator (view source)
Revision as of 23:27, 15 July 2024
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===Sampling Frequency Limit=== | ===Sampling Frequency Limit=== | ||
Recent studies conducted on subjects with temporomandibular dysfunction have shown that the amplitude of the mandibular reflex is reduced on the ipsilateral side of the deviation<ref>Cruccu G, Frisardi G, Van de Stenbergher: Side asymmetry of the jaw jerk in craniomandibular dysfunction. Arch Oral Biol 1992; 4: 257-262.</ref>. The sampling performed by the Sirognathograph is insufficient to obtain a more detailed evaluation of the relationship between the mandible's position and the mandibular reflex evoked by the chin tap with a trigger hammer. As seen in figure 2a, no deflection of the mandible downward is noted at the time of the chin tap, and in any case, the mandible begins its displacement after the onset of the muscle action potential. This is because for sampling at 50 Hz, the device acquires 1 point every 20 ms when the mandibular reflex has already ended. The chin tap can therefore be considered an impulsive act, requiring a faster sampling frequency. | Recent studies conducted on subjects with temporomandibular dysfunction have shown that the amplitude of the mandibular reflex is reduced on the ipsilateral side of the deviation<ref>Cruccu G, Frisardi G, Van de Stenbergher: Side asymmetry of the jaw jerk in craniomandibular dysfunction. Arch Oral Biol 1992; 4: 257-262.</ref>. The sampling performed by the Sirognathograph is insufficient to obtain a more detailed evaluation of the relationship between the mandible's position and the mandibular reflex evoked by the chin tap with a trigger hammer. As seen in figure 2a, no deflection of the mandible downward is noted at the time of the chin tap, and in any case, the mandible begins its displacement after the onset of the muscle action potential. This is because for sampling at 50 Hz, the device acquires 1 point every 20 ms when the mandibular reflex has already ended. The chin tap can therefore be considered an impulsive act, requiring a faster sampling frequency. | ||
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<gallery widths="350" heights="282" perrow="2" mode="slideshow"> | <gallery widths="350" heights="282" perrow="2" mode="slideshow"> | ||
File:Sirignathograph e jaw jerk 1.jpg|'''Figure 2a:''' The upper trace represents the neuromotor response of the jaw jerk, while the lower trace shows mandibular displacement along the Z-axis. Note that the mandible erroneously displaces vertically after the activation of masseter motor units. | File:Sirignathograph e jaw jerk 1.jpg|'''Figure 2a:''' The upper trace represents the neuromotor response of the jaw jerk, while the lower trace shows mandibular displacement along the Z-axis. Note that the mandible erroneously displaces vertically after the activation of masseter motor units. | ||
File:Siro e jaw jerk 2.jpg|'''Figure 2b:''' The same trace as figure 2a after modifying the Sirognathograph hardware. Increasing the sampling frequency allowed the real spatial position of the mandible to be detected. | File:Siro e jaw jerk 2.jpg|'''Figure 2b:''' The same trace as figure 2a after modifying the Sirognathograph hardware. Increasing the sampling frequency allowed the real spatial position of the mandible to be detected. | ||
</gallery> | </gallery> | ||
</Center> | |||
A thorough analysis of the electrical circuit showed that, without making drastic changes, the SF can be increased up to a maximum of 500 Hz. Indeed, for the 20 ms period (SF = 50 Hz), the Sirognathograph completes the sampling cycle in about 3 ms and remains inactive for the remaining 17 ms. Therefore, by reducing the sampling cycle to 2 ms, the SF can be increased tenfold (500 Hz). This is possible because the latency time (0.75 ms) and saturation time (2.5 ms) have a tolerance of + 50%. Therefore, to increase the SF, some changes to the electrical circuit were necessary. | A thorough analysis of the electrical circuit showed that, without making drastic changes, the SF can be increased up to a maximum of 500 Hz. Indeed, for the 20 ms period (SF = 50 Hz), the Sirognathograph completes the sampling cycle in about 3 ms and remains inactive for the remaining 17 ms. Therefore, by reducing the sampling cycle to 2 ms, the SF can be increased tenfold (500 Hz). This is possible because the latency time (0.75 ms) and saturation time (2.5 ms) have a tolerance of + 50%. Therefore, to increase the SF, some changes to the electrical circuit were necessary. | ||