Mesh Diagram and Template Analysis / orthodontic courses by Indian dental academy

Mesh Diagram and Template analysis

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TEMPLATE ANALYSIS:History of Templates

In 1952, Baum devised a set of four template transparencies-that were designed to be laid directly on the cephalometric x-ray film for analysis after the method of Downs.

Higley 1956, developed cephalometric standards for children 4 to 8 years of age, proposed that celluloid transparencies be constructed for both sexes at each age level. The diagrams comprised two quadrilaterals formed by joining various craniofacial points, and outlining the maxillary first molar and the maxillary and mandibular incisors


In 1975, Johnston introduced a simplified method of generating long-term forecasts based on the addition of mean increments, using a printed grid upon which a tracing is superposed. He made no claims that predictions thus made are without error, but contended that they are not much worse than would be expected from an analysis of cephalometric error.

In 1975, Broadbent and Golden, produced a series of frontal and lateral cephalometric templates of individuals from 1 to 18 years of age to fulfill the need for a common yardstick or norm.

In 1977,Popovich and Thompson in a later study of 120 boys and 90 girls, developed a series of age, sex, and growth-type specific lateral templates- Craniofacial Templates. These investigators found that they were able to obtain a static evaluation, as well as a dynamic indication of anticipated future growth changes in individuals.


Ackerman 1979, used the material from the Michigan School Study1974 and the published material of Riolo and colleagues (Sexspecific template wth 13% enlargement) to construct a series of transparent templates for boys and girls in the different age groups. The templates were adjusted to "zero" magnification at the midsagittal plane to facilitate standardized diagnostic use with any cephalometric equipment


The Advantages of Templates to Lateral Head films:

1. They provide a simple system for rapid assessment of skeletal variables without mathematical calculation or measurement.

2. They make it easier to judge the outlines of the various skeletal and soft tissue components than points and planes do.

3. The degree of balance or imbalance and its location in the craniofacial complex can be demonstrated.

4. The various areas within the complex that are amenable to correction by conventional means can be readily identified.


5. Areas of disproportionate growth that may mitigate against a successful treatment result may be identified and taken into account in treatment.

6. Templates provide an indicator of general growth attainment of a child relative to his peers.

7. The effect of visually comparing superposed template and tracing provides an opportunity for a more complete understanding of the various craniofacial components.


The Analysis:

Analysis of template is based on a series of superimpositions of the template over a tracing of the patient being analyzed.

Classification:Based on:I.Age and sexspecific normative dataTemplates based on a study in the University of Michigan Elementary and Sec ondary School Growth Study

II.Visual comparison ( Rioloetal 1974)eg: Proportionate template


I.Age and sexspecific Templates:

Each template is, in effect, a compact set of oriented rulers graduated in years eg-(6 to 16 years), rather than in millimeters or degrees.

The necessity of deriving 2 templates- one for male and the other for female is necessary due to significant differences between growth timings of the two sexes

There is no list offered of the ways the templates should be used. It is, however, appropriate to provide a few general guidelines concerning the various kinds of superimposition


I.Cranial-Base Superimposition:

The patient's measurement and the norm are, in effect, oriented along SN or FH plane

FH plane should be given first consideration, because it is closer to the jaws and thus does not confound an evaluation of the size and position of the jaws with clinically irrelevant cranial base variation.


In some instances, the template will not even come close to fitting the face. In this instance, it may be necessary to use some other plane of superimposition

BaN

PMV

ANS-PNS


It is, however, important to emphasize once again that overall balance is sought, not a strict point-for-point match with the patient's age.

If the patient is 11 years old, but has a facial skeleton that generally matches the template points for, say, a child of 9 or even an adolescent of 14, nothing is amiss; However, if there is a mismatch (eg, cranial base and maxilla at 10 years of age and mandible at 6 or 7 years of age), there may well be a skeletal problem.

Regional superimposition then can be used to answer these questions by examining the size or position of the individual elements of the facial skeleton.


II.Regional Superimposition : The template is placed over the cephalogram or a tracing of the cephalogram, and the pair of points that define the measurement is compared with the template scales at symmetric ages eg, 6 and 6, 8 and 8, 10 and 10, etc) until a match is achieved

1.Cranial base length

Anterior PosteriorTotal

Register on S, read age at N Register at S, read age at Ba Ba to N at symmetric ages


Facial height:

Upper anterior Upper posterior lower anterior Anterior Posterior

ANS to N, or S-N, or FH PNS to S, or S-N, or FH ANS to GnN to GnS toGo


Maxillary size

LengthEffective length

PNS to ANS or point AAr to point A

Mandibular size

Ramus height Body length Overall "Effective" length

Ar to GoGo to Gn, Pog, or point B Ar to Gn, Pog, or point BAr to Gn


Dental position:

Maxillarydentition

Orient on palatal plane, register at A, read molar position at upper contact-point dots (M) and incisor position at 1 /1

Mandibular dentition

Orient on mandibular plane (Go-Gn), register at point B, estimate molar position by interpolation at lower terminal planes (M) and incisor position at 1 /1Dental

extrusion:

Maxillary

Palatal plane registered at A to Downs occlusal plane (DOP ,M or 1/1

Mandibular Mandibular plane (Go-Gn) registered at B to DOP or 1/1


II.Proportionate Template Analysis( Visual comparison):

The proportionate template is based on the principle of the visual comparison of lateral cephalometric .tracings with average normal tracings.

Measurements of body proportions will be used to illustratethe philosophy of this template. Average mans height is 5feet 9 inches and so templates are madeIn relation to this body height.

It may be argued, however, that a single template cannot be used for all individuals because of variations in body height


To accommodate variations in skull size, four templates were designed:

i)The average template that was developed by averaging "geometrically the dimensions of the sample.

ii)The large template was intended for larger than-average persons

iii)small template for persons with smaller-than-average craniums and jaws. iv) In addition, an extra-large template was designed for considerably larger-than-average individuals


Separate templates for men and women are unnecessary because the basic skeletal assembly patterns of men and women are so similar that they can be combined.

The main differences between men and woman are large Frontal sinuses, supraorbital ridges and noses, as well as the more prominent chin found in men.

While there is some sexual dimorphism in the craniofacial structures, a single representative proportionate template may be used for both men and women.


Application of the Proportionate template: The following approaches to superimposing the template on the tracing are recommended.

Method 1:

The mid-S-J point of the template is superimposed on that of the tracing, and the template is adjusted to the point where the Ba-N lines on the template and the tracing are parallel to each other. At this time, the anterior and posterior cranial base lengths are checked by superimposing S-N and Ba-S, respectively.


If either cranial base length is grossly deficient or excessive, the mid-S-J point superpositioning is disregarded .

Method 2:

Here both the Ba-N lines are superimposed and the S-J lines will be parallel to each other.

The template is then raised or lowered, keeping the Ba-N lines parallel until both of the mid S-J points are equidistant from either of the Ba-N lines. In other words, the mid-S-J points should be level with each other relative to the Ba-N line.

In attempting to identify location and extent of craniofacial disproportions, methods 1 and 2 will generally suffice.


Method 3:

Some individuals, whom neither of these methods is entirely satisfactory. In these cases, the template may have to be superimposed using other

reference points or planes.By moving the tempIate over the tracing, various abnormal bony

craniofaciaI elements can be identified and compared.

The tracing should then be interpreted by systematically observing the following dental and skeletal relationships and proportions:

1. The relative spatial position of maxilla and mandible.

Check whether the maxilla and mandible are anteroposteriorly protrusive or retrusive, and note the relative vertical position of this jaw to the template.

Note whether the mandibular plane approximates that of the template. State whether the steepness is mild, moderate, or severe.

Determining the relative spatial position will immediately provide an indication of which jaw(s) is at fault, its relative position to the cranium, and the extent of jaw dysplasia.


Measure the distance between the incisal edge of the upper teeth and the lower border of the upper lip. Judge the distance clinically and cephalometrically with the lips at rest. On the average, the lip embrasure is 2 to 3 mm above the incisal edge of the maxillary incisors.

For soft tissues:

Lips-comment on thickness, competence, and strain

Nose-comment on size and shape of root, body, and tip

Chin-comment on thickness, prominence, and deficiency.

2.Maxilla .

Measure length along the palatal plane (ANS-PNS) from Ptm to point A. State the degree of deficiency that exists: mild, moderate, or severe.

Measure incisor height from the palatal plane to the incisal tip. State whether the incisor height is excessive or deficient and to what extent.


Determine whether the axial incisor inclination approximates that of the template. Determine whether the incisors are too upright or too labially inclined.

Measure molar height from the palatal plane to the occlusal surface of the maxillary first molar. Determine whether the molar height is satisfactoy., excessive, or deficient.

3.Mandible

Determine whether the body length

Normal, deficient or Excessive

To determine this, superimpose the mandibular planes of the template and tracing and register on pogonion.

Confirm the observation by moving the template along the mandibular plane of the tracing and register on gonion.


Determine whether the ramus height (Ar to Go) is within the average range and indicate to what extent it is excessive or deficient. Correlate this measurement with the steepness of the mandibular plane.

Determine the degree of gonial angle:

average, mildly, moderately, or severely acute or obtuse.

Measure incisor height from menton to the incisor tip: state normal, excessive, or deficient

For incisor inclination, superimpose on the mandibular plane registering on menton. Determine the extent (if any) of relative retrusion or labial inclination of the lower incisors.

Measure molar height from the palatal plane to the occlusal surface of the mandibular first molar. Check whether the molar height is satisfactory, deficient, or excessive.


4.Upper/Lower Facial Height:

Determine upper facial height (N-ANS) as excessive or deficient.

Determine lower facial height (ANS-menton) as excessive or deficient.

Determine disproportion as none, mild, moderate, or severe.

5.Vertical Dimensions of Dentition For maxillary and mandibular incisors and molars ,

Superimpose the template on the occlusal plane of the tracing and check the molar and the incisor heights. Determine whether the molar and incisor heights are normal, excessive, or deficient.


Proportionate templates have been shown to be useful, particularly in orthognathic surgical procedures,for visually determining the extent and location of vertical and anteroposterior dysplasias from lateral headfilm.

Before finalizing a treatment plan involving surgery, final measurements should always be made on dental casts and not be obtained from tracings alone.

Templates thus provide a visual appraisal of cephalometric tracing and, therefore, are simple yet deceptively sophisticated. Templates exhibit the rare virtue of demanding the active participation of the clinician. WhereasConventional numeric analyses permits the clinician (or perhaps more often an assistant) to go through the motions of recording a list of uninterpreted numbers With practice and a mod icum of perseverance, use of templates can become an almost indispensable diagnostic aid.


MESH DIAGRAM ANALYSIS

In 1939,Lucien de Coster, of Belgium, advocated transformation of a mesh coordinate for analysis of radiographs in norma lateralis of orthodontic patients.

In 1948 at the Eorsyth Dental Center it was used graphically to convey the essential aspects of facial development for orthodontic diagnosis

Experience with this method of cephalometric analysis has resulted in an appreciation of proportions and relationships among facial components, particularly because sagittal and vertical variations or dysplasias in facial development, including the soft tissue profile, are registered simultaneously.

Originally,Total facial height was used as the vertical reference(scaling factor) for construction of the mesh diagram and face depth. length of anterior skull base -- Horizontal scaling factor www.indiandentalacademy.com

But since lower face height is more affected than upper face height in individuals with malocclusion, the latter distance adopted subsequently as the vertical scaling factor for tbe mesh diagram.

Landmarks: I. Soft tissue landmarks: glabella, nasion, pronasale (tip of the nose), subnasale ( attachment of upper lip to the nasal septum ) labrale superius (most prominent point of the upper lip), stomion (contact point of upper and lower lips), labrale inferius (most prominent point of lower lip), supramentale (sulcus labiomentalis), pogonion (the most prominent point on the chin).


Mesh diagram Landmarks:


II.Hard tissue Landmarks:

Symphysis mentalis : point B, pogonion, menton, the most dorsal point on the symphysis mentalis to depict its greatest thickness, and a point on the lingual surface where the symphysis converges around the mandibular incisors

Breadth of the Ramus:a point on the concave anterior contour just above the 0cclusal plane of the teeth and a point along the posterior contour of the ramus

Thickness of the neck of the condyle:obtained hy marking the intersection between the anterior and posterior contours of the condylar neck and the caudad (infe rior) surface of the clivus (posterior skull base


The maxillary area, Reveals a triangular area.A)Its posterior (dorsal) limit represents the deepest point on the anterior aspect of the pterygomaxillary fissure that separates the dorsal (posterior) aspect of the maxilla from the left and right pterygoid processes. B)The highest point of the triangle represents the dorsal limit of the orbital wall in the infratemporal fossa C)Third point of the triangle represents the lower (caudad) limit of the zygomatic process. The functional occlusal plane was drawn to best estimate as a line through the cusps of maxillary and mandibular posterior tooth crowns.

Inclination of maxillary and mandibular central incisors :incisal margins of the maxillary and mandibu lar central incisors to somewhere along the root or the pulp canal


Construction of the Mesh Diagram: The mesh diagram is constructed by first drawing a core rectangle, by drawing a vertical through nasion, parallel to the extracranial reference line and two horizontal lines perpendicular to this vertical, one at nasion and the second through the anterior nasal spine (ANS). The fourth line is drawn parallel to the vertical at a distance from nasion equal to (NS)] By dividing the sides of the core grid rectangle into two equal parts, the distances are obtained for drawing additional horizontal and vertical grid lines to complete the mesh diagram. The face is thereby inscribed in a rectilinear coordinate system composed of 24 small rectangles“The X coordinate– were scaled to anterior cranial base length y coordinate---to the upper face height.


Individual variation in the position of facial landmarks and teeth implied that the facial configurations of the subjects studied differed markedly in the degree of prognathism and in facial shape.

So contour ellipses were used to illustrate variations.The amount and direction of this variation in the location of a given landmark were reflected in the lengths of the major and minor axes of the corresponding ellipses.

No variance was found at Nasion (horizontal) and ANS (vertical) as they served to scale the coordinates of the grid

The major and minor axes of the ellipses were longest for landmarks at greatest distance from the origin of the coordinate system (nasion). As variances of the landmarks were expressed in proportion to upper face height and face depth


To determine the need for separate age norms of children at various ages, a mesh diagram analysis was undertaken on the purely longitudinal sample of male and female twin pairs Moorreess 1991

Although the size of the mesh rectangles at 8 and 16 years varied, anatomic landmarks in the mesh coordinate system at 8 years of age, when plotted in the mesh coordinate system of the same individuals at 16 years, showed that the location of landmarks at both ages was remarkably close


Procedure for Mesh Distortion:

The mesh coordinates are subsequently distorted to display differences in the proportionate location of each landmark in the individual`s mesh.

This objective is accomplished by two steps: 1. By locating the median proportionate position of each landmark in its respective grid rectangle of the patient's mesh diagram Eg:the mean location of gonion within its small grid rectangle is horizontaly at 14% from the anterior vertical line and vertically at 27% from the upper horizontal line.

Deviation of the patient's gonion from its median location is represented by an arrow that depicts the displacement factor.


2. Distorting the grid lines of the specific small mesh rectangle to reflect the deviation of each landmark from its normal proportional location.

Due to variations in landmarks, the sides of some rectangles will be elongated while others will be shortened, indicating the sites of facial disproportion or disharmony .

~ After the location of all landmarks has been evaluated, distortions are drawn through the points marked on the tracing for various landmarks.

These distortions are smoothed and thereby constitute trend lines revealing the differences in the individual's facial pattern with respect to the norm.


When the mesh is drawn on the tracing of the lateral cephalogram of an individual patient, it is important to compare first the size of the individual's small individual rectangles with the size of the small rectangles of the norm

If the height is smaller (the length being the same as that on the norm), the face is short in comparison to its depth

If the hcight is greater, the face is longer.

The same reasoning pertains to the length of the small rectangles.

If the length is greater (the height being the same as that on the norm) the face is deep,

If the length is shorter, the face is shallow


Distortion of the vertical grid lines:

This first vertical line is distorted only for soft-tissue landmarks: glabella, soft-tissue nasion, the tip of the nose, subnasale, labrale superior, stomion (if the lips are closed), labrale inferior, supramentale, and soft-tissue pogonion.

Soft-tissue nasion may be unreliable because it is often compressed by the headrest of the cephalostat during careless positioning of the patient in the cephalostat

The Second vertical line is distorted for the bony landmarks of the anterior part of the face: glabella, ANS, point A, incisal edges of the maxillary and mandibular central incisors, pointB, pogonion, and gnathion.


Distortion Qf vertical 4 is determined by: articu lare, basion, and gonion, but not sella turcica, in as much as the distance nasion-sella turcica determines the location of line 4.

Distortion of vertical 5 follows the distortions of vertical 4, since the distortion of vertical 5 is based on the position of the same landmarks.

Vertical grid line 3 is distorted last because it is influenced by the distortions of vertical 2 and vertical 4

1 2 3 4 5A

B

C

D

E

F

G


The horizontal grid lines distortions They are represented by lines A to G.

The first and second horizontal lines (A and B) are distorted only for the vertical location of sella turcica.

The third line (C) is distorted for the tip of the nose, articulare, and basion.

Line D is distorted for the tip of the nose, the posterior nasal spine, articulare, and basion. It will always pass through the anterior nasal spine, because this landmark is used for .scaling the mesh diagram

Line E is distorted for stomion (if the lips are closed), the incisal edge of the maxillary central incisors, and the incisal edge of the mandibular cen tral incisors

Line F is distorted for gnathion and gonion

Line G will parallel the distortion of line F.www.indiandentalacademy.com

Utilization Of the Mesh Diagram Method:

1.Mesh diagram analysis of a patient with a mesognathic face, everted but potentially competent lips, and overjet of maxillary incisors. Transformations of horizontal grid lines indicate a slightly long anterior face height and short posterior face height as well as a short ramus due to caudad position of the condyle and cephalad position of gonion.


2.A retrusive mandible, cephalad position of gonion and steep mandibular plane, shown by the grid transformations of a patient with Class II, division 1 maloc clusion. The soft-tissue profile likewise indicates a retrusive mandible, pouting lips, and a stub nose.


3.Mesh diagram analysis of a patient with a Class III type of malocclusion resulting from marked mandibular prognathism.

The transformations of horizontal grid lines indicate the cephalad position of sella turcica, articulare, and basion, as well as to a lesser degree, gonion. The displacement vector for gonion also has a ventral component.


Mesh diagram analysis of a patient with open bite in a Class III type of malocclusion.

The transformations of vertical grid lines indicate marked mandibular pro gnathism and proclined mandibular incisors as well as the dorsal position of basion.

The distorted horizontal grid lines reveal the caudad dysplasia of the anterior aspect of the mandible resulting in long lower face height.


Mesh diagram used in the Norma Frontalis:

Kaplin 1985, pursued the use of the Cartesian coordinate system oriented on a facial midline through the crista galli, for studying radiographs in norma frontalis as in norma sagittalis.

The basic grid of this coordinate system is composed of the midline and parallel to it another vertical line through the right or left zygoma, as well as two horizontal lines also perpendicular to the midline (one through the crista galli at its intersection with the sphenoid and the other through ANS).


This core grid serves to construct a coordinate sys tem of 24 rectangles based on half the length of the horizontal and vertical dimensions of the core grid

The distortions of differences in the proportionate location of landmarks are entered unilaterally, the other side serving for reference

Shortness of right ramus compared to left

midline deviation of mandibular incisors, chin; condyle, and ramus in both horizontal and vertical direction www.indiandentalacademy.com

Computerized Mesh Diagram Analysis

The remarkable advances in the

state-of-the-art personal computers, digitizing and plotting equipment, as well as their relatively low cost make computerized grid distortion an attractive alternative to hand distortions.

Itconsiders the upper and lower face separately

Treatment changes in the facial profile and under lying hard tissue structures are demonstrated by superimposing the initial and posttreatment cephalograms on the anterior cranial base.


…….. Pretreatment

_____ postreatment


To assess the effectiveness of this treatment, the posttreatment cephalometric tracing was superimposed with the indiyidualized norm and registered on pronasale while the vertical references were kept parallel .

Results showed that the treatment outcome was remarkably close to the patient's computer-generated individual norm.

The computerized mesh diagram is a departure from all other computerized cephalometric analyses in that it is less time-consuming because facial land marks are not digitized. Moreover, the use of the individualized norm is flexible because the patient's tracing can be manipulated over the norm in as many ways as necessary to formulate treatment alternatives before deciding on the final treatment plan www.indiandentalacademy.com

The mesh method should gain recognition because a computerized program is now available that generates an individualized norm for a patient by simply entering the values of facial depth and height. Patients with severe facial dysmorphologic features are particularly suited for a proportional analysis with the mesh diagram when surgical correction of facial deformities and malocclusions is required. The mesh diagram, contributes to treatment planning and thus the treatment outcome by recognizing and respecting the individuality of each patient


References: 1.. Jacobson A. The proportionate template as a diagnostic aid. AmJ Orthod 1979;75:156-172. 2. Jacobson A. Orthognathic diagnosis using the proportional template. Oral Surg 1980;38:820. . 3.Jacobson A, Kirkpatrick M. Proportionate templates for orthodontic diagnosis in children. J Clin Orthod 1983;17:180. 4.HarrisJE,Johnston L, Moyers RE. A cephalometric template: Its construction and clinical significance. Amj Orthod 1963; 49:249.


5.Johnston LE Jr. Template Analysis. J Clin Orthod 1987;21:585-90.

6. Moorrees CFA. Normal variation and its bearing on the use of cephalometric radiographs in orthodontic diagnosis AmJ Orthod 1953;39:942-950.

7. Moorrees CFA, van Venrooij ME, Lebret LML, GlatkyCB, Kent RLJr, Reed RB. New norms for the meshdiagram analysis. AmJ Orthod 1976;69:57-71

8.Alexandre Jacobson: Radiographic Cephalometry,1995

9.William Proffit: Contemporary Orthodontics:3rd edition, 2000


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Mesh Diagram and Template Analysis / orthodontic courses by Indian dental academy

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