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Difference between revisions of "Transverse Hinge Axis"
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'''Abstract:''' This chapter addresses the disconnection between clinicians and the bioengineering aspects of diagnostic tools, focusing on kinematic replicators like the Sirognathograph and Kinesiograph K7. These devices, widely used for analyzing mandibular movements, lose three angular degrees of freedom, undermining their ability to accurately represent the complexity of mandibular dynamics. The chapter critiques the Research Diagnostic Criteria (RDC) for dismissing the clinical value of these tools due to perceived low validity. However, the clinical and biomechanical importance of accurately determining the transverse hinge axis (tHA) and its associated rototranslational movements is highlighted, showing that errors in tHA localization can significantly affect dental occlusion and prosthetic rehabilitation. | |||
The discussion introduces a comparison between two approaches: the paraocclusal clutch, which avoids vertical interference, and the occlusal clutch, which can cause discrepancies in occlusal recordings. Through practical examples and mathematical simulations, the chapter demonstrates how even slight mislocalizations of the tHA—particularly in scenarios involving inclined dental cusps—can result in substantial occlusal errors, compromising masticatory efficiency and patient comfort. | |||
The article concludes that, contrary to RDC claims, kinematic tools play a crucial role in enhancing the accuracy of dental treatments. It emphasizes the need for further integration of advanced diagnostic tools in clinical practice to ensure precise prosthetic rehabilitation and optimal patient outcomes. | |||
==Scientific Philosophy and Clinical Implications== | ==Scientific Philosophy and Clinical Implications== | ||
In the previous chapter, "[[Jaw_movements_analysis._Part_1:_Electrognathographic_Replicator]]", the disconnection between clinicians and the bioengineering foundations of diagnostic tools such as kinematic replicators was highlighted. This disconnect is particularly evident with outdated instruments like the Sirognathograph and the Kinesiograph K7,<ref>C. Martín et al. "Kinesiographic study of the mandible in young patients with unilateral posterior crossbite." Am J Orthod Dentofacial Orthop. 2000 Nov.</ref> common clinical tools that, despite widespread use, fail to faithfully reproduce the three-dimensional movements of the mandible. These instruments have a significant limitation: they lose three angular degrees of freedom, two of which could theoretically be recovered, while one, related to the <math>Y</math> axis, remains undefinable. This poses a broader problem, namely the risk that technological innovation, driven by industrial cycles, creates tools that do not fully reflect the complexity of biophysical reality. It would therefore be desirable for professionals to collaborate with research centers to critically evaluate these devices before their use. Adopting technology solely based on the manufacturer's reputation has led to the phenomenon of the Research Diagnostic Criteria "RDC," which was created to eliminate methods and tools with low clinical validity. This chapter will explore the concept of the "Hinge Axis" <math>HA</math>, an extensively studied and debated topic that continues to raise questions regarding its actual clinical and diagnostic usefulness. The determination of the hinge axis was traditionally performed using methods initially described by McCollum,<ref name="McCollum19602">B.B. McCollum. "The mandibular hinge axis and a method of locating it." J Prosthet Dent. 1960;10:428–435.</ref><ref name="McCollum19392">B.B. McCollum. "Fundamentals Involved in Prescribing Restorative Dental Remedies." Dent Items Interest. 1939;61:522–535, 641–648, 724–736, 852, 863, 942–950.</ref> and subsequently perfected over the years.<ref name="Lauritzen19612">A.G. Lauritzen, L.W. Wolford. "Hinge axis location on an experimental basis." J Prosthet Dent. 1961;11:1059–1067.</ref><ref name="Lauritzen19702">A.G. Lauritzen. Arbeitsanleitung für die Lauritzen Technik. Manual 6, Post Graduate Course 1970. (According to Bosman).</ref><ref name="Lauritzen19742">A.G. Lauritzen. Atlas of occlusal analysis. Colorado Springs: HAH Publications, 1974:95–105.</ref> This method, known as the "kinematic pantographic method,"<ref name="Bosman19742">A.E. Bosman. Hinge axis determination of the mandible. Leiden: Stafleu & Tholen, 1974.</ref> uses the length of the mandibular opening segment as a key parameter, providing generally acceptable accuracy, though not free from errors. | In the previous chapter, "[[Jaw_movements_analysis._Part_1:_Electrognathographic_Replicator]]", the disconnection between clinicians and the bioengineering foundations of diagnostic tools such as kinematic replicators was highlighted. This disconnect is particularly evident with outdated instruments like the Sirognathograph and the Kinesiograph K7,<ref>C. Martín et al. "Kinesiographic study of the mandible in young patients with unilateral posterior crossbite." Am J Orthod Dentofacial Orthop. 2000 Nov.</ref> common clinical tools that, despite widespread use, fail to faithfully reproduce the three-dimensional movements of the mandible. These instruments have a significant limitation: they lose three angular degrees of freedom, two of which could theoretically be recovered, while one, related to the <math>Y</math> axis, remains undefinable. This poses a broader problem, namely the risk that technological innovation, driven by industrial cycles, creates tools that do not fully reflect the complexity of biophysical reality. It would therefore be desirable for professionals to collaborate with research centers to critically evaluate these devices before their use. Adopting technology solely based on the manufacturer's reputation has led to the phenomenon of the Research Diagnostic Criteria "RDC," which was created to eliminate methods and tools with low clinical validity. This chapter will explore the concept of the "Hinge Axis" <math>HA</math>, an extensively studied and debated topic that continues to raise questions regarding its actual clinical and diagnostic usefulness. The determination of the hinge axis was traditionally performed using methods initially described by McCollum,<ref name="McCollum19602">B.B. McCollum. "The mandibular hinge axis and a method of locating it." J Prosthet Dent. 1960;10:428–435.</ref><ref name="McCollum19392">B.B. McCollum. "Fundamentals Involved in Prescribing Restorative Dental Remedies." Dent Items Interest. 1939;61:522–535, 641–648, 724–736, 852, 863, 942–950.</ref> and subsequently perfected over the years.<ref name="Lauritzen19612">A.G. Lauritzen, L.W. Wolford. "Hinge axis location on an experimental basis." J Prosthet Dent. 1961;11:1059–1067.</ref><ref name="Lauritzen19702">A.G. Lauritzen. Arbeitsanleitung für die Lauritzen Technik. Manual 6, Post Graduate Course 1970. (According to Bosman).</ref><ref name="Lauritzen19742">A.G. Lauritzen. Atlas of occlusal analysis. Colorado Springs: HAH Publications, 1974:95–105.</ref> This method, known as the "kinematic pantographic method,"<ref name="Bosman19742">A.E. Bosman. Hinge axis determination of the mandible. Leiden: Stafleu & Tholen, 1974.</ref> uses the length of the mandibular opening segment as a key parameter, providing generally acceptable accuracy, though not free from errors. | ||