Lyn smadi &Hind alabbadi

Dr. Iyad

21

24/3/2015Our website: jude20111.wordpress.com

University of JordanFaculty of Dentistry

Fourth year – 2nd semester 2014-2015

Orthodontics

Lecture No.

Date:

Doctor:

Done by:

Sheet Slides

Hand Out

Price& dateof printing:

Designed by: Hind Alabbadi

Lyn & Hind Ortho Sheet No8 Date 24/3/2015

Dear colleges It's a dry sheet , study it well and we’ll be more than happy to answer any questions you might have,

1st 6 pages was written by LYN and the last 6 pages by HIND .

Note: you should know the definitions of points and landmarks on cephalometric radiograph.

Introduction: part of assessing the patient is to take investigations. The most important investigations are radiographs and study models.

There are different kinds of radiographs, and we’re going to focus on cephalometry. Cephalometry will give standardized and reproducible form of lateral skull views.

(You need to know the standardization, u need to determine the magnification. The seating and the position of the patient is very important. )

There are 2 types of cephalometry:

- Anteroposterior cephalometric radiograph and Lateral cephalometric radiograph.

In Standardized anteroposterior:

- The patient is seated properly and the magnification is known and specified.- Usually it needs advanced measurements and analysis.- Mainly used for symmetrical per asymmetry purposes, especially in facial deformities (facial asymmetry)

and hemifacial microstomia. Problems in the transverse plane.

In lateral skull views we are covering the anteroposterior and vertical dimensions. Any problems arising in transverse we should take PA (posteroanterior caphalometric radiograph). PA has basic points that should be sited: midline, symmetrical points and make specific measurements.

** if we want to take cephalogram for a pt, we should benefit from and there should be a good reason to take it. It is considered malpractice to take cephalogram for every single patient coming for orthodontic treatment.

** First of all, you should do clinical examination, which is very important. You examine the pt and then determine if you need radiographs, and if you need radiographs you need to determine what type. Not all of the patients need radiographs, most of the patients might need OPGs.

** The idea of taking standardized radiographs is to do measurements. It’s basically to help you in diagnosis. We need to do a proper tracing in order to help us in, mainly, diagnosis.

** Remember the concept of ALARA: as low as reasonably achievable. Nowadays, there are new technologies and other types of X-rays, so you need to wait and determine if you really need to do those new types of X-rays. Out of the new technologies is the cone beam, which is a very powerful diagnostic tool and the radiation is slightly less than cephalometry so you can consider it, if it was to offset the disadvantages of conventional X-rays. But it’s not acceptable to take all types of X-rays. so if a patient has impacted canine why to take OPG, occlusal and periapical while we can do a single cone beam to take the information we need, and in this case cone beam will be better as a diagnostic tool and radiation exposure will be less if we calculate it for the previously mentioned radiographs. But it’s not acceptable in this case to take OPG, occlusal radiographs and a cone beam.

In facial asymmetry, some dentists take 3D-CT scan, which will expose the patient to a very high radiation, it’s very helpful but with very high radiation. But when you want to make measurements it’s useless, so anything you want to utilize you need to justify.

Lyn & Hind Ortho Sheet No8 Date 24/3/2015

** cone beam is very powerful and very accurate in the presentation of the actual craniofacial structures. It will give 3D image of the object. OPG, Cephalometrics are 2D.

** ADVANTAGES of 3D X-ray over 2D: (the dr was talking about cone beam)

- 3D representation of dental and craniofacial structures. - Visualization from different angles and perspectives.- No magnification errors or projection artifacts. - Management of superimpositions.- Digital imaging and communications format. To ease communication with the patient; to let the patient see

the X-ray and explain what the patient needs to know. - Generation of data for diagnosis, modeling and manufacturing. If you can capture 3D accurate data, you can

transfer it to a 3D printer; so you can print the mandible, the maxilla or part of the jaw. - Radiation exposure within a similar range of other dental radiographic & lower than that of medical CT

devices. In dental cone beam, we are only exposing the area of interest to the radiation. Also the sensors in cone beam are very powerful so you don’t need to use high dose of radiation. In other dental radiographs we might need more than one type of radiographs (E.g. occlusal and OPG) that can be substituted with a single cone beam.

** new devices have the ability to take OPG, ceph and cone beam. (3 in one)

** when taking cone beam for example, it will capture 3D image of hard tissues. But to superimpose the soft tissues on the actual 3D of hard tissues we have 2 techniques; you can use photos which is not realistic because photos are 2D, so it’s not so accurate since it has some magnifications and distortion (magnification is not controlled and high distortion). Another technique which is more accurate, a device to take 3D image of the face and soft tissues i.e. sterophotogrammetry.

** Stereophotogrammetry: using an imaging videos or cameras to give 3D data of the soft tissues of the face. And then superimposition of this 3D image of soft tissues on an actual 3D of hard tissues. So integration of soft and hard tissues. This is easily manipulated and we don’t have to do measurements, we can superimpose it on preexisting data.

**cone beam is not very powerful to detect problems in airway passages. Since they are soft tissues and cone beam capture images for hard tissues. However, there are specific software that can give us volume of airway passages from a cone beam image.

**The use of CBCT imaging for the assessment of the airway can provide clinically useful information in orthodontics. Airway volume and respiratory function are highly relevant to the orthodontic specialty. Studies have confirmed that airway problems are significantly related to different types of malocclusion and that nasal obstruction is a major aetiological factor for dentofacial anomalies.

** cephalometric analysis: the process of evaluating skeletal, dental and soft tissue relationships of a patient, by comparing measurements with population norms. (Norms came from radiographic studies that were held in different places in the world, there are longitudinal and cross sectional studies to give us the norms. Every population has its own norms, so we can’t take Negros norms and take it as our norms because of racial differences. Dr. Ahmad Hamdan made a study and measure the norms of Jordanian population on cephalograms.

** tracing of cephalograms:

- Manual: to identify points - Digitization: on screen on special software you should locate points using the mouse, and the software will

give you the lines and the angles. In the past, there was a digitizer (similar to scanner) in which you put the

Lyn & Hind Ortho Sheet No8 Date 24/3/2015

ceph X-ray as a hard copy on the digitizer and you locate the points using electronic pin or instrument. Nowadays, everything is digital and you will do everything on screen using the mouse.

(Nothing showed that digitization is better or manual is better)

- You should determine the validity: which depends on: a) Film qualityb) Reproducibility of points: to be reliable c) experience

** Dolphin and quick ceph are examples of softwares that are used to digitize cephalometric radiographs. But the problem with them that they depend on certain norms, so if you want to use them you should make sure to input the norms of the population you are working at. You will locate the points, the software will give you the lines and angles, and you will interpret the numbers the software giving you.

** You should always examine any X-ray systematically. Usually it’s easy to begin with upper right for example and to scan it. You shouldn’t focus only on the main cause you’ve taken the radiograph for. Train your eye to scan the whole radiograph and you should be able to spot any problem.

** It’s very important to be able to interpret the cephalometric radiograph after doing the tracing. And you should scan the whole radiograph systematically, and to be able to spot any abnormalities in the pituitary and other structures (sinuses for example). Many problems you might discover accidently.

** Why we use cephalograms: we use them for different purposes but the main purpose is diagnosis, we can use it to determine the best treatment option to consider, also for prediction and for research.

** No substitute for a thorough clinical assessment. Radiographs should aid in the assessment of the pt. Sometimes, we know the patient has skeletal class 2 from clinical examination, and we take ceph why? To know why the patient has this problem and the magnitude of the problem.

In Growth of the craniofacial, there are five components:

- cranium- mandibular and maxillary bony structures- Alveolar part carrying the dentition.- maxillary and mandibular dentition

Any problem arising in the craniofacial will be a combination of these factors.

In Vertical and anteroposterior problems we need to determine where the problem is and what’s causing this problem and this is the purpose of cephalogram. So you need to analyse it as:

- Cranium to the maxillary part - Cranium to the mandible - The Maxilla and the mandible as one structure to the cranium- Upper to lower dentition - Mandibular bone and supporting dentition to the cranium - Maxilla to the mandible

Lyn & Hind Ortho Sheet No8 Date 24/3/2015

The ideal relationships of the facial and dental components can be represented as shown in A. Cephalometric analysis can distinguish and clarify the differing dental and skeletal contributions to malocclusions that present identical dental relationships. A Class II division 1 malocclusion, for example, could be produced by (B) protrusion of the maxillary teeth although the jaw relationship was normal, (C) mandibular deficiency with the teeth of both arches normally related to the jaw, (D) downward-backward rotation of the mandible produced by excessive vertical growth of the maxilla, or a number of other possibilities. The objective of cephalometric analysis is to visualize the contribution of skeletal and dental relationships to the malocclusion in this way, not to generate a table of numbers that are estimators of relationships. Measurements and other analytic procedures are a means to the end of understanding dental and skeletal relationships for an individual patient, not ends in themselves.

** to sum up

The cephalometric radiographs could be used to evaluate dentofacial proportions and clarify the anatomic basis for a malocclusion. The orthodontist needs to know how the major functional components of the face (cranial base, jaws, teeth) are related to each other. Any malocclusion is the result of an interaction between jaw position and the position the teeth assume as they erupt, which is affected by the jaw relationships. For this reason, apparently similar malocclusions as evaluated from the dental occlusions may turn out to be quite different when evaluated more completely. Although careful observation of the face can provide this information, cephalometric analysis allows greater precision.

Lyn & Hind Ortho Sheet No8 Date 24/3/2015

Example :

Class 3 related to skeletal problem (growth of the mandible)

Class 3 related to dental problem

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

1-Skeletal AP (vertical )

2 -Dental factor : A- relation to skeletal bases. B-each other

3 -Soft tissue (profile , tongue position )

Skeletal pattern : A-P or Anterio-posterior

1-ANB: SNA & SNB angle 2- Wits analysis.

SNA

-For assess of A-P position of maxilla with regards to the cranial base.

-mean 81 ± 3 ( i.e. normal range from 78 to 84, beyond this standard deviation it consider abnormal )

SNB

-For assess of A-P position of mandible with regards to the cranial base .

-mean 78 ± 3

ANB angle :

-Compares the relationship between max and man with cranial base, gives an indication of skeletal pattern :

2-4Class 1

>4Class2

<2Class3

If you have a case with ANB angle = 5 , so class 2 , but is it max protrusion or man retrusion problem or both ? you should measure the SNA and SNB to know that.

Lyn & Hind Ortho Sheet No8 Date 24/3/2015

Limitations of SNA,SNB & ANB : We assumes that cranial base( SN) is reliable for comparison, however it may has a problem instead of having a problem on max or man .

How to know if the SN line is incorrect? We do something called Eatman conversion

Eatman conversion (Eatman correction) :

-To correct for discrepancies in SNA only not SNB because N point movement has a bigger effect on SNA than SNB.

-provides that SN-mx p (SN-maxillary plane) is within range (8 ± 3 ) & SNA is not 81 ( i.e. not normal)

-The Rule: For every degree the SNA is more than 81, subtract 0.5 from ANB for each degree increase in SNA and vice versa .

Examples:

SNA = 83 so more than the normal by 2 , we correct the ANB by decrease its angle by 1 (1\2 2 =1) .

SNA = 79 so less than normal by 2 , we correct the ANB by increase its angle by 1 (1\2 2 =1).

Wits Analysis :

-A.Jacobson

-designed to avoid the limitations of ANB angle as an indicator of AP jaw discrepancy

As illustrated here :

-compares relationship of max and man with functional occlusal plane.

-It's based on a projection of points A and B to the functional occlusal plane ,

along with the linear differences between theses points is measured .

-Note that the Functional occlusal plane being used rather than an occlusal plane.

مثالللتوضيح

Lyn & Hind Ortho Sheet No8 Date 24/3/2015

Skeletal pattern : Vertical

-Max to man relationship , we do it clinically by measure the Frankfurt mandibular plane angle, it could be normal , increased or decreased.

1-MMPA maxillary mandibular plane angle : mean 27 ± 4 degree .

We measure it in cephalogram which will be more accurate

2-Facial proportion : mean 55% ± 2%

Lower face height to the total face height .

The dr. showed us pic of reduced lower facial height (deep overbite) and to know if the cause was dental problem or skeletal we look for MMPA

Other patient presented with anterior open bite and to know if the cause was dental problem or skeletal we look for cephalogram!

Dental factors:

A-Relationship of incisors to skeletal bases :

1-Upper incisors to max plane angle. Mean 109 ± 6

To see incisor inclination which could be retroclined, proclined or normally inclined

To know the reason of increased overjet , is it skeletal or dental? If the upper incisor were normally inclined so it's not dental problem so then we go to check if it is skeletal

Lyn & Hind Ortho Sheet No8 Date 24/3/2015

2-Lower incisors to man plane angle. Mean 93 ± 6

3 -A-pogonion (A-pog) : The line from A to pogonion

The best esthetic results were obtained when the lower incisors edges lie anterior to A-pog line .

B-Relationship to each other : Upper incisors to lower incisors.

For example in case of sever class 2 dev 1 but with normal overjet ,How do you explain that?

It'a all about dentoalveolar compensation and if we want to do surgical correction of man , 1st we need to reposition the incisors to their normal position and that's known as Decompensation

1-Interincisal angle (which determine upper and lower incisors ): 133± 10

It's mainly for stability and it's our Tx target not diagnosis , the pt must has incisal stop , you can't get a proper stable relationship if you don't have this normal angle.

2-Lower incisor edge to Upper incisor centroid distance.

Centroid is a point at the root of incisor (almost midpoint ) and at which the rotation movement occurs .

This relation associated with overbite depth, If the vertical projection of lower incisor

become anterior to the Centroid this is indication of stable overbite .

Soft tissue analysis:

-mainly for diagnosis and Tx planning prior to oral surgery.. (we rely on the soft tissue profile to do surgical correction )

-Should be supplementing to clinical examination.

Lyn & Hind Ortho Sheet No8 Date 24/3/2015

Note: it's difficult to relax the muscle of the pt's face so we don't relay very much on soft tissue analysis.

1-E line. ( esthetic line ) : a line from tip of the nose to the tip of the chin and you determine the position of upper lip to lower lip , normally to be behind the E-line.

2-Holdaway line: soft tissue pogonon with the upper lip and intercepting the nose, we see upper lip position which normally at that line!

Table ( Eastman Analysis )

-Interpretation of the numbers to produce cephalometric report , look for the skeletal, dental and soft tissue .

Prescription:

1-Tx methods ( what's the best Tx option)

2-Growth modification

3-Comoflage ( by clinical examination)

4-orthognathic surgery ( is it dental or skeletal problem )

Type of tooth movement :

1-Removable appliance.

2-Fixed appliance.

Lyn & Hind Ortho Sheet No8 Date 24/3/2015

Prognosis Tracing :

-gives a clue of the result of upper removable appliance Tx of class 2 problem .

-if the Tx will be stable and esthetically pleasing or not.

-we look for 2 angles:

lowest acceptable upper incisor to max plane is 98 degree ( if <98 we can't do URA )

Highest acceptable inter incisal angle which = 150 degree.

Visual Tx objective ( VTO)

-For the prognosis of the TX in case of fixed appliance.

-Based upon movement of lower incisors to A-pog line.

Lower incisor edge-centroid relationships

-good for overbite stability.

-normally it's anterior at the end of the Tx.

Superimposition:

-To monitor the Tx progress and compare the changes before and after .

-To know the changes which occur because of the growth or the TX.

- By looking to a stable structure for e.g sella of the cranial base after age of 6 and inferior alveolar nerve in the man

Prediction. ___

Research .___

Good luck

Lyn & Hind Ortho Sheet No8 Date 24/3/2015