Jaw movements analysis. Part 1: Electrognathographic Replicator
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[[|Italian]]Jaw movements analysis. Part 1: Electrognathographic Replicator
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 , 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 . The discussion introduces two recording approaches:
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.
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 . Misrepresenting these dynamics leads to occlusal discrepancies that compromise masticatory efficiency and patient comfort.
The transverse hinge axis () represents the axis around which the mandible rotates during initial mouth opening. Accurately localizing 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.
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:
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.
Accurate localization of 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:
Increased muscular strain. 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
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 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 () and sagittal () axes, providing a comprehensive framework for understanding mandibular kinematics in clinical practice.
(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.)