Abstract
ObjectivesTo three-dimensionally evaluate deviations of full-arch intraoral (IO) scans from reference desktop scans in terms of translations and rotations of individual teeth and different types of (mal)occlusion.Materials and methodsThree resin model pairs reflecting different tooth (mal)positions were mounted in the phantom head of a dental simulation unit and scanned by three dentists and three non-graduate investigators using a confocal laser IO scanner (Trios 3®). The tooth-crown surfaces of the IO scans and reference scans were superimposed by means of best-fit alignment. A novel method comprising the measurement of individual tooth positions was used to determine the deviations of each tooth in the six degrees of freedom, i.e., in terms of 3D translation and rotation. Deviations between IO and reference scans, among tooth-(mal)position models, and between dentists and non-graduate investigators were analyzed using linear mixed-effects models.ResultsThe overall translational deviations of individual teeth on the IO scans were 76, 32, and 58 µm in the lingual, mesial, and intrusive directions, respectively, resulting in a total displacement of 114 µm. Corresponding rotational deviations were 0.58° buccal tipping, 0.04° mesial tipping, and 0.14° distorotation leading to a combined rotation of 0.78°. These deviations were the smallest for the dental arches with anterior crowding, followed by those with spacing and those with good alignment (p < 0.05). Results were independent of the operator’s level of education.ConclusionsCompared to reference desktop scans, individual teeth on full-arch IO scans showed high trueness with total translational and rotational deviations < 115 µm and < 0.80°, respectively.Clinical relevanceAvailable confocal laser IO scanners appear sufficiently accurate for diagnostic and therapeutic orthodontic applications. Results indicate that full-arch IO scanning can be delegated to non-graduate dental staff members.
Highlights
The development of chairside intraoral (IO) scanners started with techniques for scanning small arch segments for single-tooth restorations [1]
IO scanners generate dental-arch models by combining 3D images of small dental-arch segments to create a full-arch image. This requires the superimposition of overlapping segmental surfaces, which can lead to inaccuracies in the positions of small segments and individual teeth
Other studies evaluated the trueness of IO scans by measuring metric distances between corresponding model surface points [19,20,21,22,23,24,25]
Summary
The development of chairside intraoral (IO) scanners started with techniques for scanning small arch segments for single-tooth restorations [1]. Deviations from defined landmarks on crowns have been used to compare IO scans with desktop scans These studies address clinical questions concerning the effects of the following: operator’s experience [7, 11], scanning strategy [4, 12, 13], tooth malpositions [4], and arch width [5]. It must be noted that the abovementioned approaches are unable to specify the deviation of single teeth in all six degrees of freedom, i.e., in terms of 3D translation and rotation [14] This is important, because deviations of individual teeth and tooth movements are usually described in such terms—in the field of orthodontics, for example. These terms of description could be useful for evaluating virtual dental arch models
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