Evaluation of First Molar Inclinations and Transverse Arch Width in Individuals With Posterior Crossbite
Condition: Crossbite (Anterior) (Posterior); Dental Malocclusion; Maxillary Anomaly
MeSH terms: Malocclusion
Study type: Observational

Summary: 
      This study aims to evaluate and compare the inclination of the lower and upper permanent
      first molars and the transversal width of the lower and upper jaws in individuals of
      different age groups to evaluate whether the existing anomaly at different ages in
      individuals with a bilateral posterior crossbite. For this reason, first molar tooth
      inclination and lower and upper jaw transversal width will be evaluated in adolescent and
      post-adolescent individuals with a bilateral posterior crossbite.
    

Detailed description: 
      The maxillary dental arch covers the mandibular arch in every space like a box cover in
      normal occlusion. The transversal disappearance of this relationship is called a crossbite.
      If this deformity occurs between posterior group teeth, it is defined as a posterior
      crossbite. In other words, in posterior crossbite, while the teeth are in centric occlusion,
      the vestibule tubercles of the upper posterior teeth come into contact with the central fossa
      of the lower posterior teeth. This occlusal discrepancy may concern only one tooth, or it may
      involve multiple teeth or all teeth. A posterior crossbite can be observed unilaterally or
      bilaterally and is usually caused by insufficient width of the upper jaw compared to the
      lower jaw.

      Crossbite; stated that it is a term used for the abnormal buccal, labial, or lingual
      relations of the lower and upper jaw teeth or tooth groups when the lower and upper dental
      arches are in the closing state. Crossbite is divided into two groups as anterior and
      posterior crossbite according to the region in the mouth. Anterior crossbite indicates
      malocclusion of the jaws and/or dental arches in the sagittal direction, while posterior
      crossbite indicates malocclusion in the transversal direction. Posterior crossbite is defined
      as the contact of the buccal tubercles of the posterior maxillary teeth with the lingual
      tubercles of the opposite mandibular teeth. This anomaly can be seen unilaterally or
      bilaterally and may involve one or more teeth. In addition, although the canines were
      anterior teeth before, these teeth were included in the posterior region while expressing
      posterior crossbite. A posterior crossbite can be seen in the primary, mixed, and permanent
      dentition period.

      Posteroanterior (PA) cephalograms are the most readily available and reliable diagnostic tool
      for the radiological identification and evaluation of transversal irregularities.
      Traditionally, orthodontists have focused on two-dimensional lateral cephalograms; however,
      treatment is done in all three planes. A planar assessment of the transverse space cannot be
      made unless the PA cephalogram is analyzed. Typically, standard PA cephalograms were not used
      as part of routine diagnostic recordings. However, PA radiographs should be added as an
      additional recording material in individuals with a posterior crossbite.

      Digital radiographs and digital photographs are becoming the norm in orthodontic records.
      Recent developments also include electronic working models. Because the medical and dental
      anamnesis, digital photos, radiographs, and all treatment notes were in digital format have
      become desirable to obtain digital study models. Dental cast models have a long and proven
      history in orthodontics. It has become the "gold standard" in orthodontics with many
      advantages, from cast models that can be mounted on an articulator for a three-dimensional
      study, from routine dental examination to ease of manufacture, cheapness, and ease of
      measurement. Digital operating models offer advantages that include storage and reassessment,
      ease of cross-transmission, and possibly equal or better diagnostic capabilities. In
      addition, linear dental anatomical measurements were obtained from plaster and digital
      models, while Bolton analysis was performed on the cast and digital models.

      At the beginning of the treatment, dental plaster models obtained from the lower and upper
      jaw dimensions will be scanned with a three-dimensional model scanning device (3 Shape R700
      3D Scanner, 3 Shape A/S, Copenhagen, Denmark). Scanned models will be analyzed with the
      3Shape Orthoanalyzer program (3Shape A/S, Copenhagen, Denmark). A point will be placed on the
      distal, facial, mesial, and lingual surfaces of each tooth, from the right first permanent
      molar to the left first permanent molar in the same arch. These points will be chosen by the
      rules established by Moyers et al. and Brust and McNamara to determine the geometric center
      of each tooth, the tooth center. This point provides a broader arc width measurement because
      it will eliminate the effect of tooth rotation. After cast rotation, the first molars' facial
      and lingual cusp crests will be selected to assess molar tooth tilt and angulation. An
      inclination below 180 degrees indicates that the molars are inclined buccally, while values
      above 180 degrees indicate that these teeth are inclined lingually.

      Dental arch width measurements will be measured between the following teeth: permanent
      canines, first premolars, second premolars, and permanent first molars. Arch width will be
      evaluated with two sets of measurements: the distance from the lingual point of the selected
      tooth to the similar point on its antimere and between the centroid and antimer of a tooth.

      The arch depth shall be measured as the distance from the midpoint between the facial
      surfaces of the central incisors to the tangent line to the mesial surfaces of the first
      permanent molars. Arch circumference will be determined by summing the segments between the
      points of contact from the mesial surface of the first permanent molar to the mesial surface
      of the opposite first permanent molar.
    

Intervention name(s): Dental model analysis
Intervention type(s): Other
Intervention description(s): No interventional treatment intervention will be made for individuals. Digital dental models taken for orthodontic recording will be examined.
Observational model: Cohort
Time perspective: Retrospective
Sampling method: Probability Sample
Study population: 
        Individuals with and without posterior crossbite who applied for orthodontic treatment
      
Biospecimen description: 
      Data of cast plaster model scans of the lower and upper jaws obtained from individuals for
      routine treatment procedures were obtained and stored digitally.
    
Keywords: posterior crossbite; dental model analysis; molar inclination; dental arch parameter