The measurement of mandibular movement permits a subjectspecific dynamic analysis (1) and is useful for the diagnosis of oral disorders and for designing the functional occlusal surfaces of dental prostheses (2). Furthermore, mandibular movement data can be utilized to evaluate the outcomes between before and after prosthodontic treatments and can be critical to predict the prognosis of oral rehabilitation (3, 4). A threedimensional (3D) mandibular movement device is ideal for tracking the condylar and incisal inclination movements. These devices include the magnetometry (Mandibular kinesiograph) and optoelectronic tracking systems (Sirognathograph) (5, 6) , and the Gnathohexagraph (Gnathohexagraph III, JM-2000, GC, Tokyo, Japan) , which is an optoelectronic jawtracking system with 6 degrees of freedom. These devices can measure mandibular movements during mastication using cameras to track the spatial position of lightemitting diodes (7). However, these devices are often not available in clinics because of its high cost in general, (8) , and complex to handle in daily clinical practice. Therefore, a simple, acceptable, and reliable device to measure mandibular movement is needed by clinicians. The anterior deprogramming device (ADD) , also known as the Lucia Jig, comprises an individually fabricated anterior guide table, which allows for mandibular Correspondence to:
The vertical dimension of occlusion (VDO) must be correctly estimated when fabricating complete dentures to achieve efficient mastication and swallowing. The comfortable zone (CZ) method for VDO estimation is based on trichotomous subjective response.However, the difference in comfort level within and out of the CZ still needs to be determined. Therefore, this study aimed to examine the differences in subjective comfort on a 100mm visual analog scale (VAS) when raising or lowering the VDO and to assess the relationship among the responses to the CZ method.Eight edentulous patients (five men and three women, with a mean age of 78.5±7.6 years) were recruited. The VAS score was obtained two times at the most comfortable position (MCP) and when it was raised from +1 to +7 mm (7VDO) . The VAS score was also obtained when the MCP was lowered from -1 to -3 mm (3VDO) . Oneway analysis of variance and Bonferroni's multiple comparison test were performed to analyze the differences in VAS scores at 11 VDOs.The VAS score significantly decreased when the VDO was raised by +3 mm from the MCP (p = 0.009) and continued to decrease in +4 (p = 0.001) , +5, +6, and +7 mm (p < 0.001, respectively) . In addition, it significantly decreased when the VDO was lowered by -2 mm from the MCP (p = 0.048) . The results suggest that VDO estimates may be appropriate between -1 and +2 mm from the MCP when fabricating new complete dentures.
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