Ackerman Proffit 1969 2s3m56

American Journal of ORTHODONTICS Volume 56, Number

5, November,

ORIGINAL

1969

.ARTICLES

The characteristics of malocclusion: A modern approach to classification and diagnosis James Phkdelphia,

1. Ackerman, Pa.,

and

D.D.S.,* Lexington,

and

William

R. Proffit,

D.D.S.,

Ph.D.**

Icy.

W

hat me today call normal occlusion was described as early as the eighteenth century by John Hunter. Carabelli, in the mid-nineteenth century, was probably the first to describe in any systematic way abnormal relationships of the upper and lower dental arches. The edge-to-edge bite and overbite are actually derived from Carabelli’s system of classification. The term orthodontics (orthodontosie) was coined by Lefoulon of at approximately the same time as interest in these problems became widespread.l Even though several treatises on orthodontics had already been written by the beginning of the twentieth century, most notably the one by Norman Kingsley, these authors had no acceptable method for describing irregularities and abnormal relationships of the teeth and jaws. Edward II. Angle contributed the concept that if the mesiobuccal cusp of the maxillary first molar resbs in the buccal groove of the mandibular first molar, and if the rest of the teeth in the arch are aligned, ideal occlusion will result. Angle described three basic types of what he termed malocclusion, all of which represented deriations in an anteroposterior dimension.” The Angle classification was readily accepted by the dental profession, since it brought order out of what previously had been confusion regarding dental relationships. It was recognized almost immediately, however, that there were deficiencies in the Angle system. One of the most severe critics was Calvin Case, who pointed out that Angle’s method disregarded (in treatment planning as *Associate Medicine,

Professor University

**Associate Professor tistry, University of

and Chairman, of Pennsylvania. and Chairman, Kentucky.

Department Depart,ment

of

Orthodontic.s, of

Orthodontics,

School College

of

Dental of

Den-

443

well as classification) the relationship of the teeth to the face (t,hat is, thc~ profile). Another criticism by Case and others was that, although malocclusion was a three-dimensional problem, in thr Angle system only anteroposterior &vi character of certain m:i /. occlusions which have the same distomesial occlusion of the buecal t&h.” In 1912, in a report to the British Society for the Study of 0rthodon&s. Norman Bennet? suggested that malocclusions bc classified with regard to dcvi;Itions in the transverse dimension, the sagittal climc~nsion. and thr: vfkrticill dimension. This recommendation, rcjectod at the t,ime, was later realized in I irra \vork of Simon5 and the development of his system of gnathostatics. SinI relat,ed the teeth to the rest off the fact and cranium in all three dimensions 16 space. His approach, although somewhat complcs, clearly represented an ;1(1!.;ince. If it had not. been for the introduction cJf roentgmographic cephalotllet,rics in the 1930’s and 1940’s, bonathostat,ics probably would hart mad(. :I crcat,er impact on present-day orthodontics. With the advent of the latcra 1 c*(tphalogram, many of the relationships that could bc dct,ermined from gnathostatic casts could more easily be observed on the cephalomctric head film. Another early criticism of the Angle system was that it. merely described il~e relationship of the teeth and did not include a diagnosis. Simon.” l,nu& strom.F Hellma,n.7 and most, recently Horowitz and I-tixon” recognized the Ned 10 differentiate dentoalveolar and skeletal discrepancies and to evaluate tlicil’ relative contributions toward the creation of a malocclusion. These authors SUFxested that classification should include this t,ypcLof diagnosis atld point logicall; I 1)a treatment plan. Analogous

and

homologous

malocclusions

This difficulty becomes apparent when it is recognized that malocclusions having the same Angle classification may, indeed, be only ccnalogous malocclusions (having only the same occlusal relationships) and not necessarily homo7ogozcs (having all characteristics in common). Despite the informal additions to Angle’s system which most orthodontists use! there is a tendency to treat malocclusions of the same classification in a similar manner. Homologous malocclusions require similar treatment plans, whereas analogous malocclusions may require different treatment approaches. Some poor responses to treatment are undoubtedly related to this fault in diagnosis. Fig. 1 illustrates two nearly identical Angle Class II, Division 1 malocclusions in children of the same age. There are differences in skeletal proportions and in the relationships of the teeth to their respective jams, both of which affect the profile. Individual orthodontists may differ concerning treatment plans, but the two cases should not be treated c-xactly the same. These are analogous malocclusions.

Volume Number

Fig.

56 5

1. Clinical

malocclusions required.

Characteristics

records are

of

analagous

apparently but

similar not

Angle

homologous.

Class

II,

Different

of malocclusion

Division treatment

1 malocclusions. procedures

445

The are

Fig.

2.

cant

of the

A

complex

Angle

occlusal

plane

Class relative

I malocclusion.

The

to the

plane.

Frankfort

casts

are

trimmed

to

represent

the

Volume Yumber

56 5

C%ara.cteristics of malocclusion

447

referred to o’rthodontists include an anteroposterior problem. (In surveys of large population groups, this is less common) .g For many years, orthodontists have extended the Angle classification, in a nonstandard and nonsystematic way. To quote Simon5 : “If one asks an experienced orthodontist : ‘How do you treat Class I (Angle) ?’ he usually replies with the question: ‘Which kind of malocclusion do you really mean?’ ” Fig. 2 illustrates an Angle Class I malocclusion which obviously would require further description. We believe that the criticisms leveled at the Angle system are valid and must be overcome. In this article, we propose a classification scheme for malocclusions in which five characteristics and their interrelationships are assessed. We are suggesting not that the Angle system be discarded but, rather, that it be enhanced systematically. It is interesting that ours is a synthesis of two schemes, the Angle classification and the Venn diagram, both of which were proposed late in the nineteenth century by Angle and Vcnn. A complex of interrelated variables, as encountered in malocclusion, may be represented most conveniently through the use of sets. Venn proposed this representation in 1880, and it has become prominent in symbolic logic for computer use. The set theory deals with collections or groups of entities, rather than with single entities, and it represents the relationships between these groups by graphic patterns.lO A Venn diagram offers a visual demonstration of interaction or overlap among parts of a complex structure. A collection or group in this system is defined as a set, and all elements contained in a set have some common property. The interrelationships of two sets, X and Y, are illustrated in Fig. 3. Our representation of malocclusion, using a modified Venn diagram, is

1

Fig. 3. The interrelationships of two sets (X have no overlapping qualities. Both sets are ence represented by the box which encloses qualities in the area of overlap. In C all Y’s subset. D shows that elements of the universe

and Y). X and Y in A represent sets which contained in a universe or frame of referthem. In B the sets X and Y share common have qualities of X. Y in this case is called a are contained in sets X and Y.

Ant.

J. Orthodontics November1969

shown in Fig. 4. In our scheme a set is defined on the basis of morphologic devi ations from the idea.1. With regard to the dentition itself, the standard is ideal alignment into arch form and ideal interdigitation. If the teeth are perfectI). aligned in both arches, by definition ideal occlusion will occur when the mesicrlingual CUSpS Of tllcl maxillary first, I~lola7X red in the ct~tltld fOSSil(‘ Of tilt, ~nandibular first molars, 1)rovidetl the curves of Spec are harmonious ant1 thcgr.cL is no tooth-size discrctl)~lll(.\-.ll This, 01’ course, is the original Angle cotlcdel)l l’rofile ideals may vary, depending upon ethnic and racial differences. by

Classification

Common teeth within

groups

to all dentitions is the degree of alignment and symmetry of tlie t,hc dental arches. We represent this as the universe (Group 1)

,/

/

.’

‘_

._ ‘j

‘_’

‘1\

/’

Fig.

defined

4.

Representation on the basis

of malocclusion of morphologic

using deviations.

a modified (See text.)

Venn

diagram

in which

sets

are

Volume .l’umber

56 5

Characteristics

of malocclusion

449

Many malocclusions affect the profile. For this reason, profile is represented as, a major set (Group 2) within the universe. Lateral (transverse), anteroposterior (sagittal) , and vertical deviations and their interrelationships (Groups 3 to 9) are represented by three interlocking subsets within the profile set. This scheme allows any malocclusion to be sufficiently described by five or fewer characteristics. This classification system can most easily be described by outlining the method of application. For the sake of simplicity in describing the system, we will assume that complete diagnostic records (casts, facial photographs, and radiographs, including a cephalometric head film) are available. Classification may be made, however, by careful observation of the patient’s occlusion and facial appearance. It is generally agreed that in ideal occlusion the maximum intercuspal (centric occlusion) and the unstrained retruded position of the mandible (centric relation) should approximately coincide. In this classification, if there is a shift of more than 1 to 2 mm. between the point of initial tooth in terminal hinge closure and maximum intercuspation, the point of initial should be used. Step 1 in the classification procedure is an analysis of the alignment and symmetry of the teeth in the dental arches (interproxima.1 relationships). Alignment is the key word of Group 1; among the possibilities are ideal, crowding (arch-length deficiency), spacing, and mutilated. Irregularities of individual teeth are described, if desired, by the method of Lischer,5 namely, the use of the suffix -ver.sioll to describe the direction of individual tooth malalignments. Ideal occlusion, plus many (but by no means all) Angle Class I malocclusions, would fall into our Group 1. In Step 2 one views the patient’s profile. This can be done most accurately from a good profile or silhouette photograph. In the profile view, it should be noted whether the face is anteriorly divergent (mandible prominent) or posteriorly divergent (mandible recessive) I2 and whether the lips are convex (prominent), straight, or concave relative to the nose and chin. The “divergence” is most often related to the facial skeleton ; lip position is strongly influenced by the teeth. Lip and mouth posture should also be considered in the evaluation. In Step 3 the dental arches are viewed with regard to lateral dimensions (transverse plane), and the buccolingual relationships of the posterior teeth are noted. The term type is used to describe the various kin.ds of cross-bite. A judgment is also made as to whether the problem is basically dentoalveolar or skeletal or due to a combination of the two. There is, of course, a continuous range from problems which are entirely skeletal to those which are entirely dental. Most cases have components of both, with one or the other predominating. Thus, a bilateral pal&al cross-bite would be a type of malocclusion. If this were due entirely to constriction of maxillary development, it would be a skeletal problem. A similar constriction of the maxillary dental arch alone would be dentoalveolar in nature. As a general rule, maxillary or mandibular is used to indicate where the problem is. In Step 4 the patient and dental arches are viewed in the anteroposterior

Fig.

5.

five

characteristics.

This

complex

Group

9

malocclusion

can

be

sufficiently

described

by

reference

to

Volume Number

56 5

Charncte~risfics of malocclusion

451

dimension (sagittal plane). In this dimension, the Angle classification system is utilized and is merely supplemented by stating whether a deviation is skeletal, dentoalveolar, or a combination. This information can be derived from observing the patient or more accurately from a cephalometric head film. In Step 5 the patient and the dentition are viewed with regard to the vertical dimension. Rite depth is used to describe the vertical relationships. The possibilities are anterior open-bite, anterior deep-bite, posterior open-bite, or posterior collapsed bite. To determine whether this is on a skeletal, dentoalveolar, or combined basis, a chalometric analysis may be particularly helpfu1.13-15 Examples

of

group

classification

As one can see from Fig. 4, this approach defines nine groups of malocclusions. The complexity of the orthodontic problem increases with the group number. Thus, a G-roup 9 malocclusion is the most complex in that there is an alignment problem, a problem in profile, and problems in the lateral, vertical, and anteroposterior dimensions as well. Such a malocclusion (Fig. 5) would be classified and sufficiently described (which constitutes diagnosis) as follows : GROUP

9

Alignment: Both arches crowded Profile: Posteriorly divergent, convex Type: Maxillary palatal cross-bite, bilateral, skeletal and dental Class: Class I, excessive overjet, dental; Class II, skeletal Bite depth: Open-bite, skeletal Jt can be seen that Case A in Fig. 1 is a : GROUP

-I

Aligwaent: Ideal Profile: Posterior divergent, convex Class: Class II, Division 1, skeletal Since all other characteristics are normal, no further description is needed. The logic of the system specifies this case well enough that its records could be approximated from this description alone. Similarly, another a.ctnal case (Fig. 6) would be classified and described as follows : GROUP

2

Alignment: Ideal Profile: Convex This case (the classic Class I bimaxillary protrusion) is sufficiently described without further qualification. Again, the logic of the system uniquely specifies this case. The case presented in Fig. 2 can be seen to have problems of alignment and symmetry and deviations laterally and anteroposteriorly but not vertically. It, therefore, should be classified as follows: GROUP 6 Alignnze?l.t: Both arches crowded, midline deviation profile: Posteriorly divergent, convex Type: Maxillary palatal cross-bite of the premolars, bilateral, dental

Aln. J. Orthodontzcs RTovember 1969

Fig.

6. This

malocclusion

can

be sufficiently

described

by two

characteristics.

Class: Class I, anterior cross-bite of ma.xillary right lateral incisor. dental One can see from these examples that the type, class, or bite depth is not indicated if it is found to be normal. As stated earlier, ideal occlusion with good facial esthetics is classified as follows : GROUP

1

Alignment: Summary

and

Ideal

conclusions

This method of classification based on five descriptive characteristics and defining nine groups of malocclusions overcomes the major weaknesses of the Angle system. Specifically, arch-length problems, w&h or without an influence

Volume Number

56 5

Chamcteristics

of malocclusion

453

on the profile, are recognized ; the influence of the dentition on the profile is taken into ; all three planes of space, not just the sagittal plane, are taken into consideration; the differentiation between dental and skeletal problems is made at the appropriate level ; and diagnosis is inherent in the classification. An additional advantage is that the logical approach used in constructing the classification is similar to that employed for preparing computer programs. This means that this new system should lend itself well to surveys and to other uses where data processing by computers is desired. Quantification and assessment of severity of malocclusion (as in determination of the presence of handicapping malocclusion) still requires a numerical scale which can be easily d&d to our system. We would like to avoid the implication made so often in the past that accurate classification, diagnosis, and treatment planning are the only important aspects of orthodontic evaluation. In the long run, etiology is a key factor, for if the cause of a malocclusion cannot be altered or eliminated during treatment, the treatment result may not be stable. Ideally, etiology should be included in a classification scheme, but the present state of our knowledge still does not permit this. Similarly, the view of occlusion taken in this classification in part remains the “static” view traditional in orthodontics. A dynamic analysis of tooth s in functional mandibular movements should already be part of orthodontic evaluation, particularly after the completion of orthodontic tooth movement. Occlusal of the teeth, in the final analysis, is the major criterion for assessment of occlusion. We believe that this particular scheme can enhance communication between orthodontists. It can also serve as an aid in logical treatment planning and should be particularly helpful as a teaching tool. Finally, the computer compatibility of this classification will make it u,seful for automated data retrieval and processing. REFERENCES

1. Weinberger, B. W.: Historical resume of the evolution and growth of orthodontics. In Anderson, G. M.: Practical orthodontics, ed. 8, St. Louis, 1955, The C. V. Mosbp Company. 2. Angle, E. H.: Classification of malocclusion, Dental Cosmos 41: 245-264, 350-357, 1899. 3. Case, C. 8.: Techniques and principles of dental orthopedia, (reprint of 1921 edition), New York, 1963, Leo Bruder, pp. 16-18. 4. Bennett, N. G.: Report of the Committtee on Orthodontic Classification, Oral Health 2: 321-327, 1912. 5. Simon, P. W.: Fundamental principles of a systematic diagnosis of dental anomalies (translated by B. E. Lischer), Boston, 1926, Stratford Co., p. 320. 6. Lundstrom, A. F.: Malocclusion of the teeth regarded as a problem in connection with the apical base, Svensk tandl. tdskr. 16: 147-296, 1923. 7. Hellman, M. : Diagnosis in orthodontia and the method I use in practice, Angle Orthodontist 13: 3-14, 1944. 8. Horowitz, S., and Hixon, E. H.: The nature of orthodontic diagnosis, St. Louis, 1966, The C. V. Mosby Company. 9. Zwemer, J. D., and Young, W. D.: Summary of studies on the prevalence of malocclusion. In Proffit, W. R., and Norton, L. A. (editors) : Education for Orthodontics in General Practice, Lexington, 1966, University of Kentucky. 10. Feinstein, A. R.: Boolean algebra and clinical taxonomy, New England J. Med. 269: 929-938, 1963.

Orthodontists pursue

are a

position

of

chanical

violence,

comparable L. G.: 1912.)

not

vicarious latitude with

The

value

in

accord

course and to the of

of

longitude,

eradicate perfect teeth

with

the

idea

development all

then the

correlation in the

design

that

until expect,

evidences

by of

of

parts

of

the

the

the

dentition

teeth the

in unrestricted American

be

reached

institution

perverted

face,

may

have

of

growth,

some

and

permitted an form obtain

development. Orthodontist

to

uncertain of

(Singleton, 3:

me-

a result 204-211,