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Muchitsch, AP; Winsauer, H; Wendl, B; Pichelmayer, M; Kuljuh, E; Navysany, MT; Muchitsch, M.
Effects of a hinged expansion screw for median mandibular distraction treatment on the lower first molars regarding tooth inclination and intermolar transverse distance.
J Orofac Orthop. 2014; 75(1):25-35 Doi: 10.1007/s00056-013-0191-7
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Führende Autor*innen der Med Uni Graz
Muchitsch Alfred Peter
Co-Autor*innen der Med Uni Graz
Pichelmayer Margit
Wendl Brigitte

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The goal of this study was to assess the extent to which median mandibular distraction via a cemented and screw-retained full-coverage splint appliance employing a hinged expansion screw causes inclination changes in the lower first molars and widens the dental arch. Our study included 17 patients (12 females and 5 males; average age 16 years and 3 months) who presented with transverse space deficits and pronounced dental crowding. Baseline and final mandibular casts reflecting the situations before and after 6 weeks of median distraction therapy were created, scanned, and matched via their coordinate systems. Perpendiculars were drawn at the geometric centers between the cusp tips of teeth 36 and 46 and projected against the frontal plane. The intersection angles yielded single-tooth and total inclination values for both molars, and the difference between the intermolar distances measured at the geometric centers of both teeth provided the amount of transverse expansion. An intraclass correlation coefficient (ICC) of >0.99 was obtained in a series of three measurements. After distraction treatment, the total inclination values between teeth 36 and 46 changed by +2.93 ± 9.14°. The corresponding single-tooth inclinations changed by +0.68 ± 6.32° and -2.25 ± 4.33°, respectively. Both molars underwent similar degrees of buccal or lingual tipping. Compared to a mean expansion of +6.9 ± 1.83 mm at the distraction screw, a distance increase of only +3.77 ± 1.27 mm along the transversal connecting teeth 36 and 46 was recorded. Pearson's correlation coefficient was 0.336 between total tipping and intermolar expansion (p=0.187) and -0.426 between total tipping and patient age (p=0.088). Expansion amounts were approximately twice as long at the expansion screw as between the first molars. This V-shaped expansion pattern was due to the hinged connections between each expansion screw and the full-coverage splints. The buccal and lingual tipping of molars measured may be due to varying heights of the posterior alveolar ridge during mixed dentition or to anatomy-related differences in the expansion-screw position. In all cases we observed a mainly parallel opening of the distraction gap on the vertical plane.
Find related publications in this database (using NLM MeSH Indexing)
Adolescent -
Adult -
Bone Screws -
Child -
Dental Prosthesis Design -
Female -
Humans -
Male -
Malocclusion - pathology
Malocclusion - therapy
Mandible - pathology
Mandible - surgery
Mandibular Advancement - instrumentation
Mandibular Advancement - methods
Models, Anatomic -
Molar - pathology
Molar - surgery
Osteogenesis, Distraction - instrumentation
Osteogenesis, Distraction - methods
Palatal Expansion Technique - instrumentation
Tooth Movement Techniques - instrumentation
Tooth Movement Techniques - methods
Treatment Outcome -
Young Adult -

Find related publications in this database (Keywords)
Median mandibular distraction
Inclination of mandibular first molars
Expansion of mandibular first molars
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