Date of Award

5-2011

Document Type

Thesis

Degree Name

Master of Dental Science (MDS)

Program

Prosthodontics

Research Advisor

David R. Cagna, D.M.D., M.S.

Committee

Swati Ahuja, B.D.S., M.D.S. Robert L. Brandt, D.D.S., M.S. Vinay Jain, B.D.S., M.S., M.D.S. Mark Scarbecz, Ph.D.

Keywords

Articulator, Interchangeability, Calibration, Eccentric, Excursion, Tolerance

Abstract

Background: Dental articulation is a method of approximating the patient's mandibular motion in order to allow for analysis of dental relations and fabrication of appliances. The most prevalent method used in teaching institutions is the semi-adjustable articulator. Several of these instruments claim interchangeability without loss of clinical accuracy and studies have supported this claim. No studies to date have assessed the interchangeability of the articulators in any relation other than hinge axis closure. Assessment of the accuracy of interchangeability of calibrated articulators will inform the profession of this parameter of articulation and allow for informed decisions on whether or not to rely on interchangeability in analysis and fabrication.

Objectives: To examine the ability of an operator to set condylar inclination repeatedly on a semi-adjustable articulator. To assess the utility of a new measurement jig to assess the calibration status of articulators and to measure sample of instruments repeatability in hinge axis closure and then in measured lateral excursion to assess eccentric interchangeability.

Method: 78 Unused Whip Mix 2240 and 71, 1 year-old Whip Mix 2240 semi-adjustable articulators were placed in a custom made measurement jig following calibration. Condylar inclination was evaluated with a digital angle meter and gauge blocks were utilized as reference points to measure the position (X and Y axes) of the test gauge and a height meter was used to measure the vertical (Z axis) in hinge axis closure position and in a measured lateral excursion.

Results: The data suggests that: (1) A single operator was able to program the horizontal condylar inclination of the Whip Mix 2240 with 95% confidence within one degree of his target value. (2) A prescribed lateral movement on a series of new articulators was able to position a specific measurement point (maxillary first bicuspid facial cusp tip) in the same spatial location within tolerance reported for hinge axis closure of calibrated instruments. (3) A prescribed lateral movement on a series of used articulators positions a specific measurement point (maxillary first bicuspid facial cusp tip) in the same spatial location within tolerance reported for hinge axis closure of calibrated instruments (4) 88.5% of 1 year‑old instruments verified as interchangeable with the 2245 check gauge. (5) A calibrated Whip Mix 2240 can be eccentrically positioned with 95% confidence within +/‑ 0.2mm vertically and +/‑ 0.1mm horizontally.

DOI

10.21007/etd.cghs.2011.0141

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