Orthodontic diagnosis

DIAGNOSTIC AIDS

Diagnostic aids include the use of:

1. Study models2. Orthopantomography3. Cephalometries4. Other views: hand wrist and periapical radiographs5. Photography6. 3D Imaging

Orthopantomographs:

Exactly after Second World War, Paatero of Finland tumed to body section

radiography or tomography (laminagraphy) for better radiographic visualization of

craniofacial structures.It is possible to obtain radiographic image of a particular area, or

a layer within 3 dimensional subjects by carefully synchronizing the movement of the

source of radiation and the film. With both the x-ray beam source and the film casseette

rotating, everything else is thrown out of focus except the precise level of structures of

interest. The parts that in focus will appear in sharp details; while, the intervening

structures are blurred out.

The benefits in brief:

*-Razor-sharp real-time images, no film processing, no scanning, no readouts.

*-Environmental protection, no darkroom no chemicals

*-Radiation dose reduction ranging from 50%(panoramic)to 70%( cephalometric)

*-Within 2 minutes it appears on the monitor & ready to be analyzed or stored on p.c.or

you can send it throw E-MaiL p.c.

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رؤوف. دطعمة

Several advantages from the OPG can be obtained:

1- Comfort, since no film will be inserted inside the patient mouth. And the total time

needed not exceed 1-1.2 min to perform the x-ray.

2- It is more easy for the operator when he has uncoopertive patients, children patient

with gagging reflex & trismus = lockjaw.

3- Least total radiation " 5.06 rad " in comparison with periapical x-ray.

Disadvantages:

1- It cannot give precise information on periodontal membrane.

Note: the intraoral radiograph provides more accurate information about the

periodontal ligament.

2- The lower incisors region is not properly reproduced due to some overlapping as a

result of shifting in the axis of rotation.

3 - Additionally the inclination of the lower incisors is usually slanted with the crown

mesially inclined.

Uses of OPG:

1- For growth & development studies: Delayed tooth eruption, abnormality in eruption

path, abnormal resorption, supernumerary teeth, cysts, congenitally absent teeth,

ankylosis, prolong retention, density of the bone, axial inclination, inadequate space of

the clinical entities that concerning to the general practitioner or orthodontist. & distant

from apices to mandibular plane.

2- The tempromandibular joint: the OPG provides a sharp & accurate profile view of the

condyle & the articular eminence or the articulm fosse itself.

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3- Sinuses & mastoid region: the importance of maxillary sinuses is very recognized by

orthodontist since a reduced sinuses size related to mouth breather & collapse of

maxillary segments.

4- Mandibular morphology: the OPG gives a clear picture about the bony mass of the

mandible, the extent of the alveolar bone, height & width of the ramous. "All of these

information are important in regards of orthodontic treatment" good survey for the

teeth present & absent is clear in addition to the presence of any supernumerary teeth

or any pathology.

5- Space adequacy: the OPG of grate benefit during the serial extraction procedure

which require the removal of some deciduous teeth followed by some permanent teeth

(usually the fours) and this require knowledge about the stages of root formation of the

teeth.

6- Investigation of facial asymmetries and swelling.

7- Suspected fractures of mandible and maxilla.

Study models

Dental casts for orthodontic purposes are usually trimmed, so that the bases

assumed in a symmetrical shape & then they are polished. This trimming will aid to

detect the asymmetry within the dental arches & to analyze arch form. The trimmed &

polished study model is acceptable for presentation to the patient. The study model

provide a good help to examine the teeth from facial and lingual aspect during

articulation, In addition to the possibility of the space analysis on the study model & the

size selection of the orthodontic bands.

Finally: the study model used for modulation due to treatment & the explanation of that

for the patient or parents.

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In fixed appliance therapy: the study model can be used to form and bend the arch wire,

which will fit exactly to the arch form of the patient.

Steps of fabrication study model:

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Space analysis (Carey's analysis)

The arch length-tooth material discrepancy is the main cause for most

malocclusions. This discrepancy can be calculated with the help of Carey's analysis. This

analysis is usually done in the lower arch. The same analysis when carried out in the

upper arch is called as arch perimeter analysis.

Methodology

Determination of arch length: The arch length is measured anterior to the first

permanent molar using a soft brass wire. The wire is placed touching the mesial aspect

of lower first permanent molar, then passed along the buccal cusps of premolars, incisal

edges of the anteriors and finally continued the same way up to the mesial of the first

molar of the contralateral side. The brass wire should be passed along the cingulum of

anterior teeth if anteriors are proclined and along the labial surface if anteriors are

retroclined. The mesiodistal width of teeth anterior to the first molars are measured and

summed up as the Total tooth material. The difference between the arch length and the

actual measured tooth material gives the discrepancy.

Interpretation

The amount of discrepancy between arch length and tooth material is calculated.

If the arch length discrepancy is:

• 0 to 2.5 mm-Proximal stripping can be carried out to reduce the minimal tooth

material excess.

• 2.5 to 5 mm-Extraction of 2nd premolar is indicated

• Greater than 5 mm-Extraction of first premolar is usually required.

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INTRAORAL RADIOGRAPHS

The intraoral radiographs are the easiest to take for most orthodontic patients.

The most frequently used views include:

A. Intraoral periapical radiographs

B. Bitewing radiographs

C. Occlusal radiographs

A. Intraoral Periapical RadiographsThey are ideal for the detection of anomalies related to changes in tooth

structure and/ or the lamina dura and/ or the periapical region. They are ideal for

localized views in relatively small areas of interest because of the excellent clarity that

they allow.

They are recommended for:

1. Adult cases with periodontal disease

2. Evaluation of the dental health of the deciduous and/or permanent teeth periapically

3. Detection of pathologic conditions in the early stage especially dental caries

4. Assessment of traumatized teeth after an injury (especially root fractures)

5. Calculation of the total space analysis

6. Detection of root resorption, before during and after treatment.

B. Bitewing Radiographs

Bitewing radiographs are used primarily to record the coronal portion of the

upper and the lower posterior dentition. They are used for:

• The detection of proximal caries

• The study of interdental bone height

• The detection of secondary caries under restorations

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•The detection of overhanging margins of proximal restorations.

C. Intraoral Occlusal Radiographs

They are useful in localization of impacted teeth or for the study of the labio-

lingual position of the root apices in the anterior segments of the upper and the lower

dentition.

FACIAL PHOTOGRAPHS

Facial photographs are the easiest to store, occupy the least amount of space and

provide immense information to the clinician as well as the patient. Photographs can be:

• Extraoral photographs

• Intraoral photographs

Extraoral Photographs

Extraoral photographs are considered essential records and should be taken before

starting treatment and after completion of treatment. The information provided by

these photographs is valuable to the orthodontist and patient.

Uses of extraoral photographs

1. Evaluation of craniofacial relationships and proportions before and after treatment

2. Assessment of soft tissue profile

3. Detection and recording muscle imbalances

4. Detecting and recording facial asymmetry

5. Identifying patients

The requirements for extraoral photographs include:

1. High quality and standardized facial photographs taken in natural head position

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2. Patients head oriented accurately in all three planes of space and in FH plane

3. Background free of distractions

4. Quality lightening revealing facial contours with no shadows in the background

5. Ears exposed for purpose of orientation

6. Eyes open and looking straight ahead with glasses removed

The views taken regularly for patients include:

1. Frontal facial with lips relaxed

2. Facial profile with lips relaxed

3. Three-quarter view, smiling

4. Frontal facial smiling.

For facial deformity cases or cases likely to undergo orthognathic correction, further

views are required:

1. Frontal facial in maximum intercuspal position, lips sealed

2. Left and right, facial profile in maximum intercuspation, lips sealed

3. Left and right, facial profile, lips relaxed

4. Left and right three-quarter view, smiling

5. Bird view from above the patient (by standing behind and above the patient)

Intraoral Photographs

These views are used in:

1. Recording the structure and color of enamel

2. Patient motivation

3. Assessing and recording health or disease of the teeth and soft tissue structures

4. Monitoring of treatment progress

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5. Studying of relationships before, immediately following and several years after

treatment, to improve treatment planning

The requirements for intraoral photographs include:

1. High quality and standardized intraoral color prints

2. Photographs should be oriented accurately in all three planes of the space

3. Free of distractions - retractors, labels etc.

4. Quality lightening revealing anatomical contours and free of shadows

5. Tongue should be retracted posteriorly

6. Free of saliva and/or bubbles

7. Clean dentition

The views include:

1. One frontal photograph in maximum intercuspation

2. Two lateral views-right and left

3. Two occlusal views-upper and lower

3D IMAGING

Except for a few structures of interest which lie in the midsagittal plane, it is

difficult to make accurate measurements using cephalograms. Conventional facial

photos too lose depth information by projecting images of structures at different

heights upon a single plane. Moreover, the dental cast (a three dimensional

representation of oral tissues) must be integrated into facial images.

Conventional computed tomography (CT) imaging involves' the use of rotating X-ray

equipment, combined with a digital computer, to obtain images of the body. Using CT

imaging, cross-sectional images of body organs and tissues can be produced.

Their use in orthodontic treatment has been limited due to the following reasons:

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1. The dose of ionizing radiation has been high

2. Economically costly

3. Slices of relatively thick

4. Distortions are produced if CT scans are done with orthodontic appliances in place

Cone beam computed tomography (CBCT)

CBCT is a faster, more compact version of traditional CT with a lower dose of

radiation. Through the use of a cone-shaped X-ray beam, the size of the scanner,

radiation dosage and time needed for scanning are all dramatically reduced.

The 3D views produced may be useful in certain orthodontic cases:

1. Accurate location of impacted teeth and a more accurate assessment of any

associated pathology, particularly resorption of adjacent teeth.

2. Assessment of alveolar bone coverage

3. Assessment of alveolar bone height and volume {which may be relevant in potential

implant cases)

4. Study the placement of microimplants (used to provide anchorage)

5. TMJ or airway analysis

CBCT allows the acquisition of detailed 3D images of the face in high resolution. Using

this virtual 3D information, computer-aided surgery (CAS) software allows surgical

planning and simulation which offers a number of possibilities:

1. A more detailed vision of the anatomy of the patient in three dimensions.

2. The data from CBCT can be combined with the data captured from 3D facial camera

systems. This allows the clinicians to see the relationship of the soft tissues with the

underlying hard tissues. Virtual surgery can then be undertaken on this 3D model and

the effect on the overlying soft tissues assessed.

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3. Virtual surgery will allow the surgeon to calculate the most appropriate and safest

osteotomy lines in advance of the operation.

4. This virtual setup can be used to manufacture positioning splints and construct

customized fixation plates. Although the radiation dose is considerably smaller than

conventional CT scanning, the dose is still higher than for the conventional radiographs.

Therefore, CBCT should therefore only be used when conventional radiography has

failed to give or is very unlikely to give, the necessary diagnostic information. Other 3D

imaging techniques are also being developed for use in orthodontics such as optical

laser scanning and stereo-photogrammetry.

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