Difference between revisions of "Jaw movements analysis. Part 1: Electrognathographic Replicator"

Latest revision as of 11:29, 26 November 2024

Jaw movements analysis. Part 1: Electrognathographic Replicator

Article by Gianni Frisardi · Flavio Frisardi

The Sirognathograph and related tools were once widely used to record mandibular movements for diagnosing TMDs. However, the RDC eliminated these devices, citing low validity in accurately diagnosing TMDs. Studies by Lund et al. demonstrated that such devices lacked sensitivity and specificity, often leading to false-positive diagnoses. Yet, their inability to capture complex rotational kinematics is due more to engineering limitations than inherent diagnostic flaws.

For instance, the Sirognathograph employs Hall effect sensors to capture linear displacements but fails to record angular rotations along critical axes like the sagittal and frontal planes. This loss of three angular degrees of freedom undermines its ability to fully represent the 6 degrees of freedom required for accurate mandibular modeling. Figure 1 illustrates this fundamental limitation.

Sampling Frequency: The Sirognathograph's sampling frequency of 50 Hz is insufficient for recording rapid or impulsive mandibular movements, such as those during a jaw jerk reflex or a meniscal click. As shown in prior research, the mandible’s displacement during these events occurs faster than the system's capacity to register. Modifying the device to increase the frequency to 500 Hz, as achieved in later prototypes, allowed the detection of mechanical latencies and improved spatial resolution of jaw movements (Figure 2).

Loss of Rotational Degrees of Freedom: The Sirognathograph only captures linear displacements along the X, Y, and Z axes but ignores the rotational components. During a mandibular opening or protrusion, simultaneous rotations and translations occur, especially at the working condyle. However, the mixing and inversion of sensor data suppresses angular information, leading to inaccuracies in reconstructing mandibular dynamics.

For instance, the angular displacement of 4.1° observed during mandibular opening is lost due to these engineering constraints. Without this data, clinicians cannot accurately calculate angular velocities, crucial for diagnosing specific TMDs or planning prosthetic rehabilitations.

Enhancing the Sirognathograph requires:: Increasing Sampling Frequency: Modifications to the circuit increased the sampling rate from 50 Hz to 500 Hz, improving temporal resolution for impulsive actions like the jaw jerk. Isolating Angular Data: Avoiding the summation and inversion of sensor outputs preserves angular displacements and allows better differentiation of rotational and translational movements. Redesigning Sensor Arrays: Positioning additional sensors along different axes could theoretically restore lost rotational degrees of freedom.

Clinical Implications: The loss of rotational data not only compromises diagnostic accuracy but also affects rehabilitative outcomes. For example:

Cuspal Errors in Prosthetics: Incorrect hinge axis localization due to missing angular data can result in errors in cusp alignment during prosthetic rehabilitation, affecting masticatory efficiency. Misdiagnosis of TMDs: The inability to differentiate between linear and angular displacements may lead to false positives in patients presenting with asymptomatic jaw deviations. However, the Sirognathograph's capacity to analyze linear displacements remains valuable for assessing orofacial pain in neurological disorders. Studies show alterations in mandibular kinematics in conditions like Parkinson's disease, where deviations in speed, trajectory, and rhythm of movement are prominent markers.

Conclusions: While the Sirognathograph is unsuitable for TMD diagnosis due to its engineering flaws, dismissing its potential in other clinical domains would be premature. Its application in differential diagnoses of neurological orofacial conditions remains promising. Future research should focus on redesigning diagnostic tools to better accommodate the complex kinematics of mandibular movements, ensuring precision in both diagnosis and treatment planning.

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-== {{main menu}} ==
+{{Main menu}}
 {{ArtBy|||autore=Gianni Frisardi|autore2=Flavio Frisardi}}
-'''Abstract:'''
+[[File:Electrognathograph.jpg|left|frameless|363x363px]]
-This chapter critically evaluates the diagnostic utility of electrognathographic devices such as the Sirognathograph in Temporomandibular Disorders (TMDs). The limitations of these instruments, including their inability to accurately capture rotational movements and inadequate sampling frequencies, are highlighted. Although the Research Diagnostic Criteria (RDC) excluded such tools due to their low clinical validity, this chapter explores their potential relevance in differential diagnosis for neurological disorders associated with orofacial pain. A proposal for modifying the hardware of these devices to improve functionality is also presented. Finally, the discussion transitions to the analysis of the Condylar Hinge Axis, a key element in mandibular kinematics, which will be elaborated upon in subsequent chapters.
+The Sirognathograph and related tools were once widely used to record mandibular movements for diagnosing TMDs. However, the RDC eliminated these devices, citing low validity in accurately diagnosing TMDs. Studies by Lund et al. demonstrated that such devices lacked sensitivity and specificity, often leading to false-positive diagnoses. Yet, their inability to capture complex rotational kinematics is due more to engineering limitations than inherent diagnostic flaws.
-== Introduction ==
+For instance, the Sirognathograph employs Hall effect sensors to capture linear displacements but fails to record angular rotations along critical axes like the sagittal and frontal planes. This loss of three angular degrees of freedom undermines its ability to fully represent the 6 degrees of freedom required for accurate mandibular modeling. Figure 1 illustrates this fundamental limitation.
-The historical context traces back to the 1990s when researchers like Lund and Feine critiqued the diagnostic accuracy of jaw-tracking devices. These critiques prompted the development of the RDC, which sought to establish standardized criteria for TMD diagnosis by eliminating unvalidated instrumental methods. Jaw movement replicators, such as the Sirognathograph, were dismissed due to their low sensitivity and specificity in measuring mandibular kinematics. However, this chapter reconsiders their diagnostic potential and technical limitations.
+'''Sampling Frequency:''' The Sirognathograph's sampling frequency of 50 Hz is insufficient for recording rapid or impulsive mandibular movements, such as those during a jaw jerk reflex or a meniscal click. As shown in prior research, the mandible’s displacement during these events occurs faster than the system's capacity to register. Modifying the device to increase the frequency to 500 Hz, as achieved in later prototypes, allowed the detection of mechanical latencies and improved spatial resolution of jaw movements (Figure 2).
-== Limitations of Current Electrognathographic Devices ==
+'''Loss of Rotational Degrees of Freedom:''' The Sirognathograph only captures linear displacements along the X, Y, and Z axes but ignores the rotational components. During a mandibular opening or protrusion, simultaneous rotations and translations occur, especially at the working condyle. However, the mixing and inversion of sensor data suppresses angular information, leading to inaccuracies in reconstructing mandibular dynamics.
-=== Key Technical Challenges === Electrognathographic devices like the Sirognathograph exhibit two major limitations:
+For instance, the angular displacement of 4.1° observed during mandibular opening is lost due to these engineering constraints. Without this data, clinicians cannot accurately calculate angular velocities, crucial for diagnosing specific TMDs or planning prosthetic rehabilitations.
-Sampling Frequency: The 50 Hz frequency fails to capture high-speed movements such as mandibular reflexes or meniscal clicks, resulting in data loss during rapid kinematic events.
+'''Enhancing the Sirognathograph requires::''' Increasing Sampling Frequency: Modifications to the circuit increased the sampling rate from 50 Hz to 500 Hz, improving temporal resolution for impulsive actions like the jaw jerk.
-Degrees of Freedom: These devices measure only linear displacements along the Cartesian axes (<math>X</math>, <math>Y</math>, <math>Z</math>), excluding angular data critical for accurate kinematic analysis.
+Isolating Angular Data: Avoiding the summation and inversion of sensor outputs preserves angular displacements and allows better differentiation of rotational and translational movements.
-=== Proposed Modifications === To address these issues, modifications include increasing the sampling frequency to 500 Hz and enhancing hardware to capture angular movements. These adjustments significantly improve the instrument's capacity to analyze mandibular reflexes and detailed jaw movements.
+Redesigning Sensor Arrays: Positioning additional sensors along different axes could theoretically restore lost rotational degrees of freedom.
-<gallery mode="slideshow" widths="350" heights="280"> File:Electrognathograph.jpg|'''Figure 1:''' Schematic representation of the Sirognathograph hardware. File:Sirignathograph and jaw jerk.jpg|'''Figure 2:''' Comparison of original (A) and modified (B) Sirognathograph outputs for mandibular reflexes. </gallery>
+'''Clinical Implications:''' The loss of rotational data not only compromises diagnostic accuracy but also affects rehabilitative outcomes. For example:
-== Implications for Clinical and Differential Diagnosis ==
-Despite its limitations, the Sirognathograph retains potential utility in differentiating orofacial pain related to neurological conditions, such as Parkinson's disease and dystonias. These disorders manifest as alterations in mandibular movement speed, rhythm, and range, which may be detectable through enhanced electrognathographic devices.
+Cuspal Errors in Prosthetics: Incorrect hinge axis localization due to missing angular data can result in errors in cusp alignment during prosthetic rehabilitation, affecting masticatory efficiency.
+Misdiagnosis of TMDs: The inability to differentiate between linear and angular displacements may lead to false positives in patients presenting with asymptomatic jaw deviations.
+However, the Sirognathograph's capacity to analyze linear displacements remains valuable for assessing orofacial pain in neurological disorders. Studies show alterations in mandibular kinematics in conditions like Parkinson's disease, where deviations in speed, trajectory, and rhythm of movement are prominent markers.
-== Discussion ==
+'''Conclusions:''' While the Sirognathograph is unsuitable for TMD diagnosis due to its engineering flaws, dismissing its potential in other clinical domains would be premature. Its application in differential diagnoses of neurological orofacial conditions remains promising. Future research should focus on redesigning diagnostic tools to better accommodate the complex kinematics of mandibular movements, ensuring precision in both diagnosis and treatment planning.{{Login or request Member account}}
-The clinical and engineering limitations of the Sirognathograph and similar devices have led to their exclusion from primary TMD diagnosis. However, their modified versions may find relevance in the following areas:
-Neurological Disorders: Differential diagnosis of conditions like Parkinson's disease and amyotrophic lateral sclerosis.
-Masticatory Function Analysis: Improved data accuracy for research into complex mandibular movements.
-== Conclusions ==
-While the RDC's exclusion of electrognathographic devices for TMD diagnosis is justified, their potential for differential diagnosis in orofacial pain disorders remains underexplored. Further research should focus on refining these tools to align with clinical needs, especially in addressing the kinematic complexities of mandibular movements. In the next chapter, the role of the Condylar Hinge Axis in mandibular kinematics will be critically examined to assess its clinical utility.
-{{q2|Would you eliminate electrognathographs from clinical TMD diagnosis?|Yes, but I would retain them for differential diagnosis in neurological pathologies overlapping with orofacial pain.}}
-[[Category:Jaw movements]] [[Category:TMD Diagnosis]]