Cephalometric Analysis

Prediction is only a goal and not a guarantee

Broadbent publishes two papers, which describes details of the technique that he devised to establish craniofacial measurements in normal children.For all this, Broadbent, with much justice, is considered the father of radiographic cephalometry.

In 1937

1937……

Helps in diagnosis.

Helps in classification of skeletal and dental abnormalities.

Helps in planning treatment of an individual.

Helps in evaluation of treatment results.

Helps in predicting growth related changes.

USES OF CONVENTIONAL CEPHALOMETRY

Conventional ceph

•A significant amount of external error.

•Manual data collection and processing.

•Lack of well defined outlines .

DISADVANTAGES

PHOTO CEPHALOMETRY

-Introduced by Thomas Hohl in 1978.-Photocephalometric planning was developed by Derek Henderson in the 1970s.

1970’s….

METHOD

-patient is made to assume natural head position with relaxed lips.

-radio opaque markers are placed on patients face and lat and A.P.

ceph are made.

-lateral and frontal photos are made in the same position.

-photo negatives are enlarged and super imposed on the

radiographic image.

-the projection of enlarged negative is put onto a photographic film

which produces a transparent photograph which can be

superimposed over cephalometric film

profile transparency showing the tracing of dental and skeletal structures

Lateral cephalometry

Prediction planning of the soft tissue changes following bimaxillary osteotomy using photocephalometry.

ADVANTAGES

-Quantitative information of the soft tissue.

-Direct measurements between the skeletal and soft

tissue landmarks.

-Changes in soft tissue can be compared pre and post op.

-Useful in serial growth studies.

DISADVANTAGES

-Difference in enlargement factors between photos and X-rays

with compromised accuracy.

-Complex procedure.

-Expensive.

DIGITAL CEPHALOMETRY

ADVANTAGES

Dose reduction

Image prediction

Reduced overall time

Measurements [Digital Calipers]

3-D Reconstruction

Contrast enhancement

Storage

Tele radiology

Environmental Friendly

COMPUTERIZED 2D PLANNING

WITH PREDICTED SOFT TISSUE

CHANGES FOLLOWING

ORTHOGNATHIC SURGERY……..

1980’S…..

SOFTWARE SYSTEMS FOR CEPHALOMETRIC ANALYSIS.

Rocky Mountain Orthodontics (RMO) was the first to provide the dental profession in the late 1960s with a computer-aided cephalometric diagnosis.

5 programs with largest market share.1. Dento Facial Planner plus (DFP), Windows 98 Platform

2. Dolphin Imaging (DI), Windows 98,2000,XP Platform

3. Quick Ceph System (QC), Macintosh Platform

4. Vista Dent (GAC), Windows XP Pro

5. Practice Works (OTP), WINDOWS -J.Dempsey Smith and Paul M. Thomas, AJO May 2004, vol125, issue 5.

IN A PATIENT WITH MANDIBULAR ADVANCEMENT….

Actual post op.

DFP prediction DI prediction QC prediction

GAC prediction OP prediction

IN PATIENT WITH MAXILLARY IMPACTION AND MANDIBULAR SETBACK…..

Actual post op.

DFP prediction

DI prediction

QC prediction GAC prediction

OP prediction

Inference from the study…..

1. Dento Facial Planner plus (DFP) were the clear favorites.

2. Dolphin Imaging (DI) and Quick Ceph System (QC) were

the next favorites.

3. Vista Dent (GAC) and Practice Works (OTP) were

consistently rated poor.

-J.Dempsey Smith and Paul M. Thomas, AJO May 2004, vol125, issue 5.

3D IMAGING

Many 3D techniques have been used in attempt to capture facial topography and to meet short comings of 2D methods . These include,

1. Morphoanalysis

2. LASER Scanning

3. 3D CT Scanning

4. 3D UltraSonoGraphy

5. 3D FacialMorphometry

6. Moire Topography

7. Contour Photography

8. Stereolithography

9. Streophotogrammetry

At Present……

STEREOLITHOGRAPHY

Brix et al introduced 3D model planning to maxillofacialsurgery

in 1985 using copy milling technique.

Stereolithography has replaced traditional CAD/CAM, in

making anatomical models.

Term Stereolithography / 3 Dimensional printing was coined by

CHARLES W.HULL in 1986.(patent)

First commercial stereolithographic prototype generator SLA-1

system was introduced at Autofact show in Detroit, Nov 1987.

Goals of 3D modeling for surgical application

1. To create accurate anatomical models.

2. To improve understanding of anatomical variation between

individuals.

3. Provide working model for pre operative surgical

simulation.

4. To improve patient education.

5. To manufacture custom implantable devices.

6. Maintain cost effectiveness.

Step 1:- Utilize accurate imaging modality to obtain anatomical data,

viz CT/MRI.

Step2:- Design the prototype using CAD.

Step3:- Build the prototype with stereolithography.

STEPS IN PRODUCING AN ACCURATE 3D PROTOTYPE

APPLICATIONS OF STEREOLITHOGRAPY

•Craniofacial surgeries

•Distraction osteogenesis

•Trauma

•Dental implant surgery

•ORTHOGNATHIC SURGERY

•TMJ surgery

•Reconstruction / Augmentation

LIMITATIONS OF STEREOLITHOGRAPHY

Main limitation is the cost factor.Higher radiation dose to which the patient is exposed.Time consuming.

Study by Erickson et al about opinion of surgeons on stereolithography,In 92% cases there was improvement in planning.73% surgeons used models to educate the people.77% surgeons believed using Stereolithography models saved opreration room time.73% surgeons referred to models during surgery to visualize the approach. -Erickson et al ‘An opinion survey of reported benefits from the use of stereolithographic models’ JOMS 1999; 57, 1040-1043.

The imaging modalities needed to create a patient model are,

1. MAXILLOFACIAL CT,

2. STEREOPHOTOGRAMMETRY IMAGE OF THE

FACE, AND

3. LASER-SCANNED MODEL OF THE DENTITION.

MAXILLOFACIAL CT

An interactive software

tool can manipulate the raw

CT DICOM data.

The maxillofacial skeleton

data segmented (isolated),

and 3D skeletal model

rendered for visualization.

PRINCIPLE OF STEREOPHOTOGRAMMETRY

There are two geometric strategies for measuring in three

dimensions. They are

1. Orthogonal measurement-CT scans to 3D

2. Measurement by triangulation-Stereophotogrammetry

Systems that measure by triangulation analogize the geometry of mammalian stereoscopic vision.

Stereophotogrammetry, first suggested for use in dentistry by Mannsbach in 1922. The earliest clinical use of stereophotogrammetry was reported by Thalmann - Degan in 1944

FACIAL IMAGE ACQUISITION

I FACIAL IMAGE ACQUISITION

A standard stereo camera set-up is used to capture the facial image pairs. Digitally controlled slide projectors are used to flash separate random texture and structured light patterns onto the subject's face. Using digitally controlled switching between cameras and projectors, the time between capture is less than one second.

The reconstructed

representation of the face can

be rotated on a standard

computer monitor and the 3D

coordinates of any visible point

can be captured by pointing and

clicking with a standard mouse

or other similar device

LASER-SCANNED MODEL OF THE DENTITION

FINAL OUTPUT

OCCLUSAL SPLINTS THROUGH CAD/CAM

STEPS IN SPLINT FABRICATION

•Neither CT or CBCT provided accurate enough images of the patient’s dental structure.

• So the dental casts were scanned usingan optical 3D laser with a resolution of 20micron, to visualize the 3D models via surface rendering.

• This gives precise details of the shapeand size of the patient’s teeth.

•3D treatment plan was sent to the CAD/CAM Centre so that stereolithographic surgical splints could be manufactured.

Computer aided occlusal wafers…..

Intermediate splint using CAD Final splint using CA D

Data acquisitionMorphometric & orthodontic

• Clinical Examination• Imaging (3D CT)• Dental Arches Plaster Casts

Data Integration• 3D Cephalometry• Surgeon’s Experience

Surgical Planning•Type of Osteotomy (Maxillary and/or mandibular)•Quantitative displacement for bone repositioning

Surgical Simulation• Bone segmentation according to surgical procedure• Real time mobilization of bone segments with 6 degrees of freedom•Prediction of facial soft tissue adaptations according to underlying bone repositioning

Surgery• Transfer of plan•Guidance for bone reposition

splint using CA D/CAM

THE FUTURE…

Provides the surgeons with a 3D visualization at the tip of surgical instruments.

Navigation surgery

Require a sophisticated system which consists of a stereo pair of infra red cameras which track and record the 3D orientation of a surgical instrument within the field of vision.

Use of a standard occlusal surgical wafer may then not be required as the positioning of the osteotomy segment is guided by the recorded change in the 3D coordinates of certain landmarks from the preoperative to the pre-planned position.

The past is a source of knowledge and future is a source of hope.To love the past implies a faith in the future.

Thanking you……