Objectives: This study aims to compare the curve of Spee in human permanent healthy dentitions in two age groups to the disclusion in the premolar and molar region during protrusion. Materials and Methods: Sixty subjects were chosen and equally divided into two age groups of 18-25 years and 35-44 years. The left side of the mandibular dental casts was photographed using a digital camera to measure the curve of Spee. The canine cusp, mesiobuccal cusp of the first molar and the distal cusp of the second molar were marked and joined to form an arc. Using AUTOCAD software, the radius for this arc was obtained. A protrusive interocclusal record was made using rigid bite registration material to measure the amount of posterior disclusion during edge to edge protrusion. A dial gauge with an accuracy of 1/100 of a millimeter was used to measure the distance between the cusp tip indentations at the region of the buccal cusp of the mandibular 2nd premolar and distobuccal cusp of mandibular 1st molar. The results obtained were statistically analyzed. Results: The radius of curve of Spee increased nonsignificantly with age. The mean disclusion values measured in premolar and molar region showed a nonsignificant decrease with age. Conclusion: As age advances, there is a flattening of the curve of Spee and a concurrent reduction in the disclusion values during protrusion.
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