Evaluation of the Accuracy of Measurements Made on Images Taken From the Mouth for Dental Arches
Condition: Malocclusion
MeSH terms: Malocclusion
Study type: Observational

Summary: 
      The general trend in the orthodontic practice is to become digital in many aspects. Since
      1980s, digital photographs have been available and they play a principal role in the
      orthodontic practice for documentation and diagnosis purposes. Now photographs have an
      important role in teaching, scientific research and medical examination.

      Successful orthodontic treatment is based on a comprehensive diagnosis and treatment
      planning. A few of the fundamental factors in the diagnosis are the spacing condition, tooth
      size, arch form and dimensions, as well as the tooth-arch discrepancies. Intraoral
      photographs' major role is to enable orthodontists to document and analyze the occlusal
      relationships as well as the dental and soft-tissue features in order to arrive at a good
      diagnosis and an appropriate treatment plan.

      In 1975, Robert Little developed Little's irregularity index (LII). The index was proposed to
      assess teeth irregularity, crowding, relapse, and alignment of anterior teeth as it measured
      the linear displacements in the horizontal plane between contact points of anterior teeth,
      ignoring vertical displacement, from mesial surface of one canine to the contra-lateral one.
      The sum of the 5 liner measurements of displacements was the LII score. The higher the index
      value, the more severe irregularity of the teeth was. LII has been originally developed for
      mandibular incisors to study relapse; however, researchers have used it to assess upper and
      lower incisors irregularity

      Tooth-size-arch-length discrepancy (TSALD) is widely used on study models to assess the level
      of harmony between tooth size and the supporting basal bone. Bolton analysis is another
      important measurement used to identify disharmony between maxillary and mandibular tooth size
      which is considered an important factor to ensure the success of orthodontic treatment. With
      the application of the suggested formulas, the overall ratio should be 91.3% (±1.91) and the
      partial (anterior) ratio should be 77.2% (±1.65).

      The validity and reliability of performing the above mentioned analyses on images taken of
      the dental arches have not been evaluated yet in the literature. This is the aim of the
      current project.
    

Detailed description: 
      Assessment of the LII scores, TSALD, Bolton analysis has been performed by the majority of
      previous studies using plaster models and calipers in a direct manner. Others have measured
      previous variables indirectly using 2-dimensional and 3-dimensional (3D) methods. 2D methods
      have included 2D scans of plaster models or 2D images of the occlusal views. The obtained
      images have been then analyzed either manually or on-screen using dedicated software. 3D
      methods have included digital models and have been used by several researchers. Although the
      wealth of knowledge 3D methods provide, they require the use of 3D imaging techniques with
      the resultant additional costs, time and labor.

      Many studies have used 2D digital images of poured plaster models to perform software-based
      measurements of tooth movement during active treatment but these studies have not reported
      the accuracy and reproducibility of their methods. Dental impressions have been required to
      obtain proper study models. This procedure is a time- and labor-consuming for the
      orthodontist and could be exhausting to the patient. When braces are fitted, impression
      taking becomes a difficult task and if several impressions are required in the context of a
      research project, this would impose additional burden to patients and researchers. Therefore,
      taking intra-oral images of dental arches instead of impressions seems to be a very
      convenient alternative.

      Validity and reliability of measurements made on photographs of study models have been
      evaluated in previous reports. However, it seems to be that there is only one paper in the
      literature with the aim of validating the use of intra-oral images of the dental arches for
      performing dental measurement. They found that the analysis of LII was valid. However, the
      practicability of their suggested method of imaging was questionable and their evaluation was
      only confined to the LII, which is not the only variable that is used in our ordinary plaster
      model analysis.

      Therefore, the primary aim of the current work were to evaluate the validity and reliability
      of measurements made directly on intraoral photographs compared to those made on poured
      plaster models in the assessment of the LII, TSALD, and Bolton ratios. As a secondary aim,
      the comparisons were also accomplished with those measurements made on photographs taken of
      the corresponding poured plaster models .
    

Intervention name(s): Plaster models; Digital Images of the dental arches; Digital images of models
Intervention type(s): Diagnostic Test; Diagnostic Test; Diagnostic Test
Intervention description(s): The impressions taken of the dental arches will be poured with hard gypsum in order to make use of the models for taking measurements. These measurements will be considered the gold standard.; The dental arches will be captured using a dedicated camera in order to be used for measuring the outcomes.; The poured dental models will be captured using a dedicated camera in order to be used for measuring the outcomes.
Other intervention name(s): Study models; Study casts; Poured study models; Intra-oral images
Observational model: Other
Time perspective: Cross-Sectional
Sampling method: Probability Sample
Study population: 
        Patients with different levels of malocclusion
      
Keywords: Validity; Reliability; Reproducibility; Intra-oral images; Plaster models; Digital images; Little's index of irregularity; Bolton's analysis; Tooth-size-arch-length-discrepancy