Role Of Different Radiographic Techniques In Orthodontics

                                                    

 

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Contents :

1-    Introduction                                                                                              

2-    SELECTION CRITERIA FOR THE USE OF RADIOGRAPHS IN    ORTHODONTIC

3-    Classification of orthodontic radiograph

·        Intra-oral radiograph

a)   Periapical radiographs (I.O.P.A)

b)   Bitewing radiographs

c)    Occlusal radiographs.

 

·        Extra-oral radiograph

a)   Panoramic

b)   Lateral Cephalometric

c)   Hand Wrist radiograph

 

4-    Another classification :

·        2D Radiographs

 

·        3D Radiographs

 

5-    Reference

 .................................................

1-    Introduction

 

 Wilhelm conrad roentgen discovered X-rays in 1895, Radiographs are essential in orthodontic diagnosis, Two kinds of radiograph required for orthodontic diagnosis:

                  I.            Those taken to provide information regarding the condition of teeth ,the periodontium and the bony structures

               II.             Assessment of the malocclusion in relation to the facial skeletal structure.

 

 

1. 2-    SELECTION CRITERIA FOR THE USE OF RADIOGRAPHS IN    ORTHODONTIC

 

For treatment planning it is frequently necessary to be able to
assess accurately the relationships of the teeth to the jaws, and
the jaws to the rest of the facial skeleton.
In addition, radiographs may be used in the presence of clinical
indicators to assess treatment progress and growth changes.

Additional information may be required from radiographs
when a clinical examination suggests the presence of an
abnormality, or when interceptive and active orthodontic
treatment is being considered

 

Uses of radiographs in orthodontics:

·        To asses general development of dentition ,presence absence and state of eruption of the teeth.

·        Detection of any pathologies associated with the teeth and jaws.

·         To determine the number, size and shape of the teeth.

·        To determine the extent of root resorption of deciduous teeth and root formation of permanent teeth.       

·        To study the character of alveolar bone.

·        Valuable aid in cranio-dentofacial analysis.

·        For the calculation of total tooth material[mesiodistal dimension of permanent teeth.

·        To confirm the axial inclination of the roots of teeth

·        Diagnosis of facial asymmetry

·        Detection of  skeletal maturity cervical vertebrae maturation hand-wrist radiograph dental maturity.

                    

3-Classification of orthodontic radiograph

·        Intra-oral radiograph :

a)   Periapical radiographs (I.O.P.A)

 

- These can be taken to determine the presence and position of unerupted teeth, the presence or absence of apical disease or root form

- When canines are ectopically positioned, periapical views can form part of a parallax technique and, in certain cases, allow assessment of resorption of lateral incisor roots. Other periapical views may also be indicated when a clinical examination, a panoramic radiograph, or a treatment history, necessitates further investigation

Advantage of IOPA:

• Ø Low radiation dose
• Ø Possible to obtain localized views of the area of interest.
• Ø They offer excellent clarity of teeth and their supporting structures.

 

Disadvantage of IOPA :

• Ø Assessment of entire dentition requires too many radiographs.
• Ø Children may not allow placement of intraoral film
• Ø Cannot be used in patients having high gag reflex and trismus

b)   Bitewing radiographs

 

-         Bitewing radiographs are used primarily to record the coronal portion of the maxillary and mandibular posterior dentition along with their supporting stuctures..

 

Used To detect:

• Ø Interproximal caries in early stage of development.
• Ø Secondary caries below restorations.
• Ø Height and contour of interdental alveolar bone.
• Ø Calculus deposits in interproximal areas.
• Ø Over hanging proximal restorations

c)    Occlusal radiographs.

-         Occlusal Radiographs Indicated when a requirement to visualize a relatively large segment of a dental arch, including the palate or floor of the mouth

Uses of occlusal radiographs:

• Ø To precisely locate roots, supernumerary, unerupted and impacted teeth.
• Ø To localize foreign bodies in the jaws and stones in the ducts of salivary glands.
• Ø To evaluate the integrity of the anterior, medial and lateral outline of the maxillary sinus.
• Ø In providing information relative to the location, nature, extent and displacement of fractures of maxilla and mandible.
• Ø To determine the medial and lateral extent of pathoses and detect their presence in the palate

•   Extra-oral radiograph

a)   Panoramic

 

-         Panoramic Radiography: Pantomography or Rotational radiography, Radiographic procedure that produces a single image of the facial structures, including both maxillary and mandibular arches and their supporting structures

 

Advantages of OPG:

• Ø Broad anatomic region imaged.v
• Ø Relatively low patient radiation dose.
• Ø Relative convenience, ease and speed with which the procedure may be performed.
• Ø Performed on patient who are unable to open the mouth.
• Ø Inter-operator variation is minimal

 

Disadvantage of OPG:

• Ø Specialized equipment is required.
• Ø The cost is two to four times that of intraoral X-ray machine.
• Ø Geometric distortion, Magnifications and Overlapping of structures.
• Ø Objects whose recognition may be important for the interpretation may be situated outside the plane of focus called the focal trough.

Indications of OPG:

• Ø Evaluation of trauma, third molars ,extensive or unique pathoses.
• Ø Tooth development in mixed dentition analysis.
• Ø Developmental anomalies.
• Ø Broad coverage of the jaws is desirable.

Contra indications of OPG:

• Ø Panoramic films are not suitable for diagnostic examination requiring high image resolution

a)   Lateral Cephalometric

 

-         Cephalometric images may be used to aid diagnosis and
treatment planning and when appropriate provide a baseline
for monitoring progress .

-         The images must be analyzed to obtain the maximum clinical information. In malocclusions where the incisor relationship does not require significant change such radiographs are unlikely to be required.  

-         Patients who may require lateral cephalometry include those
with a skeletal discrepancy when functional appliances or fixed
appliances are to be used for labio-lingual movement of
the incisors.

 

Indications of Cephalometric radiograph :

• Ø In orthodontic diagnosis and treatment planning.
• Ø Assessment of horizontal/vertical skeletal relationship, incisor position/inclination, soft tissue profile
• Ø Helps in classification of skeletal and dental abnormalities.
• Ø Helps in evaluation of treatment results.
• Ø Post-functional to assess skeletal/dental relationship Plan retention and monitor post retention phase .
• Ø Helps in predicting growth related changes.
• Ø Research purpose

 

Limitations of cephalometric radiograph :

• Ø Individual variability
• Ø Ethnic variability
• Ø Gender variability

 

Types of cephalometric analysis used in orthodontics: 

• Ø Down’s(1948)
• Ø Wylie(1947,1952)
• Ø Rediel(1952)
• Ø Steiner’s(1953)
• Ø Tweed’s(1954)
• Ø Sassouni(1955)
• Ø Bjork (1961)
• Ø Eastman(1970)
• Ø Jaraback(1972)
• Ø  Harvold(1974)
• Ø Wits(1975) ž Ricketts(1979)
• Ø Pancherz(1982)
• Ø McNamara’s(1983)
• Ø Holdaway(soft tissue)1983
• Ø Bass(aesthetic)1991

Cervical Vertebral Maturation Method :

                 c)Hand Wrist radiograph

-         Hand Wrist Radiographs: Assessment of the skeletal age is often made with the help of a hand radiograph which can be considered the Biological clock.

-         Hand wrist region is made up of numerous small bones. These bone show a predictable and scheduled pattern of appearance, ossification and union from birth to maturity. Hence, this region is one of the most suited to study growth

 

 Indication Of Hand Wrist Radiographs:

• Ø In patients who exhibit major discrepancy between dental and chronologic age.
• Ø Determination of skeletal maturity status prior to treatment of skeletal malocclusion.
• Ø To assess the skeletal age in a patient whose growth is affected by infections, neoplastic or traumatic conditions.
• Ø Help to predict future skeletal maturation rate and status.
• Ø To predict the pubertal growth spurt.

Methods Of Assessing Skeletal Age:

Ø Bjork ,Grave and Brown method

Ø Fishman’s skeletal maturity indicatorsv

Ø Hagg and Taranger method

Ø Atlas method by Greulich and Pyle

1-    Another classification :

·        2D Radiographs

 

·        3D Radiographs

 

-         3-dimensional (3D) Imaging is one of the most important tools for orthodontists to evaluate and record size and form of craniofacial structures , Orthodontists routinely use 2-dimensional (2D) static imaging techniques to record the craniofacial anatomy, but deepness of structures cannot be obtained and localized with 2D imaging.
So goals of (3D) techniques are to replicate or describe the anatomic and physiological facts exactly and to display the three-dimensional (3D) anatomy precisely

Methods of current medicine is possibly 3D imaging techniques
giving detailed and problem-oriented information about soft
and hard tissues such as :

1- Computerized Tomography (CT)
2- Cone Beam Computerized Tomography (CBCT)
3- Micro Computerized Tomography (MCT)
4- 3D laser scanning
5- structured light technique
6- sterophotogrametry or 3D surface imaging systems (3dMD)
7- 3D facial morphometry (3DFM)
8- Tuned-Aperture Computed Tomography (TACT)
10- Magnetic Resonance Imaging (MRI

accordingly these are the most popular methods of 3D imaging
helpful in assessment and studying of facial growth :

1-Computerized Tomography (CT) :

-         Technique: The patient is usually scanned in the axial plane
sections taken in succession by a beam ; the desired image appears when these sections combined on computer . the sectioned imagies ranges from 64 to 128.

 Advantages:

Ø In this technique, due to the sectioning of tissues,
organs are not superposed on each other , so it helps in assessment of normal growth pattern and detecting of : craniofacial deformaties

Ø Orofacial trauma and fractures 

Ø TMJ ankylosis or fractures

Ø Differences in airway volumes after rapid palatal expansion , examination of the maxillary sinus.

Disadvantages:

Ø Expensive,

Ø very high dose of radiation

Ø Not available in every hospital

Ø In addition, CT data is insufficient compared
with other soft-tissue imaging techniques.

2-Cone Beam Computerized Tomography (CBCT) :

 

-          technique : Craniofacial CBCT devices are designed to overcome some of the limitations of conventional CT scanning devices.

-         There are a lot of differences among the CBCT devices including patient positioning, scan time, resolution, radiation dose, and clinical ease of use of crosssectional area.

Advantages:

• Ø it allows 3D(volumetric) data with very low
  
• radiation dose at one time ,
• radiation dose at one time ,
• Ø CBCT allows re-alignment of 2-dimensional
  
• images in coronal-sagittal- oblique and various incline planes
• images in coronal-sagittal- oblique and various incline planes
• Ø Determination of normal and abnormal craniofacial anatomy,
• Ø Determination of 3D maxillo-mandibular relationship during facial growth.

Disadvantages:

Ø The main factor of weakness in image quality is
image artifacts , The actual color of the skin and soft tissue images cannot be determined

3-sterophotogrametry or 3D surface imaging systems (3dMD) :

 

-         Technique: Stereophotogrammetry includes photographing a 3D object from 2 different coplanar planes in order to acquire a 3D reconstruction of the images ,This method has proven to be very effective in the face display.

Advantages:

 

Ø recorded the changes that occur on the face of the
patients during growth ,

Ø have developed a stereophotorammetric
system that presents the 3D coordinates of any chosen facial landmarks

   Disadvantages:

 

Ø Due to tissue reflections, hair and eyebrows
intervention, change of posture between the different views and movements during imaging decrease the probability of obtaining the most accurate facial images.

Ø  In addition, since laser or light cannot
penetrate to excessively curved and reflective surfaces, certain structures, such as the eyes and ears, cannot give a good image.

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