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

Revision as of 22:49, 25 November 2024

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Jaw movements analysis. Part 1: Electrognathographic Replicator

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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 }}
+{{ArtBy|||autore=Gianni Frisardi|autore2=Flavio Frisardi}}
-[[File:Epoc-0040 copia.jpg|left|frameless|350x350px]]
-The analysis begins by revisiting the disconnect between clinical practice and the bioengineering principles underlying diagnostic tools. Devices like the Sirognathograph and Kinesiograph K7 were developed to measure mandibular movements, but their inability to account for angular dynamics introduces significant inaccuracies. This shortcoming limits their ability to replicate the complexity of mandibular kinematics, particularly in relation to <math>_tHA</math>, a critical axis for prosthetic and functional evaluations. Despite the RDC's exclusion of these tools, their clinical significance in capturing precise mandibular movements warrants a detailed reassessment. By understanding the mechanics of mandibular dynamics, clinicians can address occlusal errors and improve rehabilitation outcomes.
-The RDC dismissed kinematic replicators due to perceived low validity in diagnosing Temporomandibular Disorders (TMDs). However, this chapter argues that these tools remain invaluable in capturing the subtleties of mandibular movements, particularly rototranslational dynamics around <math>_tHA</math>. The discussion introduces two recording approaches:
+[[File:Electrognathograph.jpg|left|frameless|363x363px]]
+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.
-Paraocclusal clutch: Avoids vertical interferences, preserving natural occlusal relationships.
+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.
-Occlusal clutch: Can introduce vertical discrepancies, leading to inaccuracies in occlusal recordings.
-Through simulations and clinical case studies, the analysis highlights how tHA mislocalization impacts occlusal errors, particularly in patients with inclined dental cusps. These findings underline the necessity of integrating advanced kinematic tools into clinical workflows to enhance diagnostic precision and treatment outcomes.
-Impact of Mislocalized tHA:
+'''Sampling Frequency'''
-With flat dental cusps and a mandibular opening of 0 mm, cuspal errors are negligible.
-With a 3 mm mandibular opening, errors range from 0 mm (exact localization) to 1 mm (mislocalization of 10 mm).
-Inclined cusps introduce significant errors even at 0 mm opening, with vertical cuspal errors reaching 0.87 mm for a 10 mm mislocalization.
-Rototranslational Dynamics:
-Mandibular movements involve a combination of rotation and translation, particularly around <math>_tHA</math>. Misrepresenting these dynamics leads to occlusal discrepancies that compromise masticatory efficiency and patient comfort.
-The transverse hinge axis (<math>_tHA</math>) represents the axis around which the mandible rotates during initial mouth opening. Accurately localizing <math>_tHA</math> is essential for aligning occlusal surfaces and ensuring functional harmony. However, even minor errors in its determination can lead to significant clinical repercussions, particularly in patients with complex occlusal morphologies.
+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).
-Simulations and Mathematical Modeling
+'''Loss of Rotational Degrees of Freedom'''
-The chapter presents mathematical simulations to illustrate the effects of tHA mislocalization on occlusal recordings. Using a mandibular opening of 15 mm as a reference, the radius of movement was calculated based on the average Bonwill triangle (90.7 mm). The analysis revealed that even small variations in tHA localization produce angular discrepancies, particularly when dental cusps are inclined. For example:
-A 10 mm mislocalization in tHA results in a vertical cuspal error of 0.87 mm with 5° inclined cusps.
+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.
-Flat cusps show negligible error under similar conditions, highlighting the influence of cusp morphology on occlusal dynamics.
-Accurate localization of <math>_tHA</math> is critical for ensuring the success of prosthetic treatments. Mislocalization not only affects the alignment of occlusal surfaces but also disrupts the balance of masticatory forces, leading to:
+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.
-Increased muscular strain.
+'''Enhancing the Sirognathograph requires:'''
-Accelerated wear of prosthetic materials.
-Reduced patient comfort and satisfaction.
-The chapter emphasizes that incorporating advanced diagnostic tools, such as the SICAT JMT and Zebris JMA systems, can significantly improve the accuracy of tHA localization, mitigating these risks.
-==Conclusions==
+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.
-The RDC's exclusion of kinematic replicators from clinical practice raises concerns about the loss of critical diagnostic capabilities. While these tools may have limitations, their ability to capture detailed mandibular dynamics makes them indispensable for certain clinical applications. The simulations presented in this chapter underscore the importance of understanding mandibular kinematics, particularly in the context of prosthetic rehabilitation.
+'''Clinical Implications'''
-Challenges in Clinical Integration
+The loss of rotational data not only compromises diagnostic accuracy but also affects rehabilitative outcomes. For example:
-Despite their potential, kinematic tools face barriers to widespread adoption, including:
-High costs of advanced diagnostic systems.
+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.
-The need for specialized training to interpret kinematic data.
+Misdiagnosis of TMDs: The inability to differentiate between linear and angular displacements may lead to false positives in patients presenting with asymptomatic jaw deviations.
-Perceived complexity of integrating these tools into routine practice.
+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.
-However, these challenges are outweighed by the benefits of improved diagnostic precision and treatment outcomes. The chapter advocates for continued research and development to address these barriers and promote the adoption of kinematic tools in clinical workflows.
-This chapter demonstrates that mandibular kinematic replicators, despite their limitations, play a crucial role in enhancing the accuracy of prosthetic rehabilitation. By accurately localizing <math>_tHA</math> and understanding rototranslational dynamics, clinicians can minimize occlusal errors and optimize masticatory efficiency. The findings challenge the RDC's dismissal of these tools, highlighting their importance in achieving precise and effective dental treatments.
+'''Conclusions'''
-Future chapters will expand on the vertical (<math>_aHA</math>) and sagittal (<math>_cHA</math>) axes, providing a comprehensive framework for understanding mandibular kinematics in clinical practice.
+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.
-{{q2|But is understanding <math>_tHA</math> dynamics enough?|No, the mandibular kinematic phenomenon requires a comprehensive understanding of all six degrees of freedom. These include the vertical and sagittal axes, topics that will be addressed in upcoming chapters.|This debate extends beyond the RDC to the fundamentals of science itself, which emphasizes 'Masticatory Efficiency' as the key metric for evaluating mandibular function.}}