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

Jaw movements analysis. Part 1: Electrognathographic Replicator (view source)

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-== {{main menu}} ==
+{{main menu}}
-{{ArtBy|||autore=Gianni Frisardi|autore2=Flavio Frisardi}}
+{{ArtBy| | autore = Gianni Frisardi | autore2 = Flavio Frisardi }}
-[[File:Electrognathograph.jpg|left|frameless|311x311px|'''Figure 2:''' Comparison of original (A) and modified (B) Sirognathograph outputs for mandibular reflexes.]]
+[[File:Epoc-0040 copia.jpg|left|frameless|350x350px]]
-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.
+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.
-Electrognathographic devices like the Sirognathograph exhibit two major limitations:
+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:
-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.
+Paraocclusal clutch: Avoids vertical interferences, preserving natural occlusal relationships.
+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.
-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.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.
+Impact of Mislocalized tHA:
+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.
-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.
+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 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:
+Simulations and Mathematical Modeling
+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:
-Neurological Disorders: Differential diagnosis of conditions like Parkinson's disease and amyotrophic lateral sclerosis.
+A 10 mm mislocalization in tHA results in a vertical cuspal error of 0.87 mm with 5° inclined cusps.
+Flat cusps show negligible error under similar conditions, highlighting the influence of cusp morphology on occlusal dynamics.
-Masticatory Function Analysis: Improved data accuracy for research into complex mandibular movements. 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.
+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:
-{{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.}}
+Increased muscular strain.
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+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.
-[[Category:Jaw movements]] [[Category:TMD Diagnosis]]
+==Conclusions==
+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.
+Challenges in Clinical Integration
+Despite their potential, kinematic tools face barriers to widespread adoption, including:
+High costs of advanced diagnostic systems.
+The need for specialized training to interpret kinematic data.
+Perceived complexity of integrating these tools into routine practice.
+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.
+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.
+{{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.}}