Occlusion and orthodontics by Almuzian

The ‘ideal’ occlusion described by orthodontists today is derived from the work published

by Angle (1900) and Andrews (1972, 1989).

It is generally assumed (Andrews, 1976; Roth, 1976) that an ideal static occlusal

relationship is compatible with an ideal functional occlusion, but this is not necessarily so

(Tipton and Rinchuse, 1991).

Ideal occlusion

It refer to an occlusion which has ideal static (Andrews six keys) and functional occlusal

relationship (mutually protected occlusion)

Malocclusion

It is any deviation from the physiologically acceptable contact of opposing dentition.

Occlusion

It is static contact between lower teeth with upper teeth.

Static Occlusion

it is the relationship between the maxillary and mandibular teeth when the teeth are brought

to maximum intercuspation.

Functional Occlusion

It is the occlusal contacts of the maxillary and mandibular teeth during function (speech,

mastication, and swallowing). Therefore, this type of occlusion should be free of

interferences in the non-working side. Three types of occlusion can be aimed at to be the

goal of functional occlusion after orthodontic treatment, which are:

1. Group function occlusion

2. Canine guidance occlusion.

3. Anterior/ Incisal guidance occlusion.

Intercuspal position (ICP)

It is the occlusal position with the teeth in maximum intercuspation (Synonymous with

centric occlusion).

Working Side

The side the mandible moves to-wards in lateral excursion.

Non-Working side

The side the mandible moves away from during lateral excursions.

Lateral excursions

Posterior teeth relationship is achieved by canine protected occlusion and group function

occlusion.

Terminal Hinge Axis (retruded/terminal arc of closure)

It is terminology often used to describe the intercondylar axis in CR. The condyles rotate

(hinge) on this axis during initial mandibular opening, approximately 25mm, before the

translation phase of TMJ movement occurs down the articular eminences

Retruded Contact Position (RCP)

The occlusal position when the condyle in the retruded axis position. Few millimetre

discrepancies between RCP and ICP are acceptable. Coincidence of ICP and RCP found in

22% of population only (Shefter and McFall, 1984)

Habitual closing movements

The ICP of the successive closure is the result of a conditioned reflex, generated by a

‘memory’ in the neuromuscular system, known as an engram. In some individuals, the

conditioned reflex makes manipulation of the condyles into the retruded axis position very

difficult to achieve. If tooth contact is prevented by using an anterior jig or bite plane for a

short period of time (approximately 10 minutes is usually adequate; Lucia, 1964) the

proprioceptive feedback leading to reflex closure in ICP is broken. The mandible can then

be more easily guided into the retruded axis position. (Short term deprogramming

manoveour)

Balanced occlusion

During the entire lateral movement posterior teeth on both the working side and the non-

working side are in contact. Present day thinking has completely dismissed this concept for

restoring the natural dentition, although it is still useful in complete denture construction.

Group Function

During the entire lateral movements the buccal cusps of the posterior teeth on the working

side are in contact. There are no tooth contacts on the non-working side.

Anterior/Incisal guidance

When the front teeth are placed together on their biting edges the posterior teeth should not

touch.

Canine protected Occlusion (canine guidance)

During the lateral excursion, contact occurs only between the upper and lower canine on

the working side. There is no contact between the teeth on the non-working side. The

canine tooth is the most appropriate tooth to guide the mandibular excursion. There are a

number of reasons why this might be so:

I.  The canine has a good crown/root ratio, capable of tolerating high occlusal forces;

II.  The canine root has a greater surface area than adjacent teeth, providing greater

proprioception;

III.  The shape of the palatal surface of the upper canine is concave and is suitable for guiding

lateral movements.

Andrews’s six keys of ideal occlusion:

Andrews (1972) have described the ideal occlusion in adults based on his study of 120

casts of non-orthodontics norms; compared to 1150 post-treatment study casts that were

presented at the American Association of Orthodontists. The six morphological

characteristics of optimal occlusion was the basis for the development of straight wire

appliance. It is worth mentioned that even these non orthodontic norm has a variable degree

of SD (up to 15 degree) however the occlusion stil considered optimal.

Andrews’s six keys are:

1. Molar relationship:

The distal surface of the distal marginal ridge of the upper first permenant molar contacts

and occludes with the mesial surface of the mesial marginal ridge of the lower second

molar.

The mesiobuccal cusp of the upper first permanent molar falls within the groove between

the mesial and middle cusps of the lower first permanent molar.

The mesiolingual cusp of the upper first molar seats in the central fossae of the lower first

molar.

2. Crown Angulation (Tip)

In normally occluded teeth the gingival portion of the long axis of each crown is distal to

the occlusal portion of that axis. The degree of tip varies with each tooth type.

3. Crown Inclination (Torque)

Crown inclination is the angle between a line that is perpendicular to the occlusal plane,

and a line tangent to the middle of the labial or buccal clinical crown.

Anterior crowns: In upper incisors, the occlusal portion of the crown’s labial surface is

labial to the gingival portion.

Upper posterior crowns: Lingual crown inclination is slightly more pronounced in the

molars than in the cuspids and bicuspids.

Lower posterior crowns: Lingual inclination progressively increases from the cuspids

through molars.

4. Rotations

Teeth should be free of undesirable rotations. If rotated, a molar or bicuspid occupies more

space than normally (a condition un-receptive of normal occlusion). A rotated incisor can

occupy less space than normal.

5. Contact points (Spacing)

In the absence of such abnormalities as genuine tooth-size discrepancies, contact points

should be tight.

6. Curve of Spee:

A flat occlusal plane should be a treatment goal. Measured from the most occlusally

prominent-cusp of the lower second molar to the lower central incisor, no curve was deeper

than 1.5mm in the non-orthodontics norms.

Roth mentioned that for a functional occlusion we need (Roth 6 keys of functional

occlusion)

1. ICP coincide with RCP

2. Cuspal guidance or Canine guidance (the decision to provide cuspal or canine guidance

depend on the FMPA. In high angle case, group function is the aim and opposite in low

angle case. Di Pietro 1977).

3. Incisor guidance

4. Upper teeth overlap lower

5. Biting along the LA of the teeth

The six identified characteristics were deemed to be realistic treatment objectives for

more than 90% of the patients accepted by North American orthodontists and for white

people only

Another problem lies in the dynamics of wire bending effects. For example, as you place

torque in the anterior part of the archwire you negate tip by a ratio of four-to-one (wagon

Wheel effect)

Bennett and McLaughlin Seventh Key:

A seventh key was added by Bennett and McLaughlin (1993) which is correct tooth size;

i.e. no tooth-size discrepancies.

Importance of functional tooth contacts

It has frequently been proposed that the following problems can result from certain patterns

of functional tooth contact.

1. Mandibular dysfunction, egermark-erikson et al (1983)show no evidence

2. Bruxism, Egermark-Erikson et al (1983)show no evidence

3. Periodontal disease, there is very little work to support it except the work by Ericsson,

Thilander and Lindhe 1978) on beagle dogs with experimental periodontitis which done on

animal and can not rely on it.

4. Instability of tooth position, Roth claims that but there is no evidence.

Types of articulators in orthodontics

1. Hinge 'articulators' should be considered a cast holding instrument rather than a true

articulator. does not permit lateral movements.

2. Plane Line and Average Value articulators permit both vertical and horizontal movements

but do not address finer movements of the TMJs. The horizontal movements are based on

average angles which are usually 30 (for condylar guidance, 15( for incisal guidance and an

intercondylar distance of 110mm)

3. Semi-adjustable articulators can accept a facebow (see below) and can be adjusted in the

vertical, sagittal and horizontal planes to approximate lateral and protrusive mandibular

movements.

ARCON - ARticulator CONdyle. The condylar ball is on the lower arm and the articular

fossa is on the upper arm (e.g. Denar).

Non-ARCON - The condyles are on the upper arm (e.g. Dentatus).

4. Fully-adjustable articulators aim to provide more adjustments and a greater degree of

accuracy. They require pantographic tracings, which attempt to record border movements

of the mandible, and the articulator is adjusted to simulate these movements. These

instruments are expensive, time-consuming and rely on excellent laboratory support to

ensure the degree of accuracy is maintained.

The use of articulator in orthodontics by Clark 2001

There are few indications for the use of articulator-mounted casts in orthodontics.

Their use is advocated in the following circumstances:

1. Where a significant discrepancy (>2 mm) exists between RCP and ICP.

2. Multiple missing teeth.

3. Orthognathic cases.

4. Although the evidence for occlusal parameters in the aetiology of TMD is equivocal, the

articulator-mounting of study models pre-orthodontic treatment and pre-debond in

individuals with TMD is recommended. This will enable the clinician to ensure that

occlusal interferences are eliminated prior to debond and a record retained of the funcional

occlusal relationships for medico-legal purposes.

Facebows

A facebow is an instrument which records and allows the transfer of the relationship of the

terminal hinge intercondylar axis and the maxillary dentition from the patient to the

articulator.

The procedure permits a more accurate simulation of lateral and protrusive mandibular

movements

The facebow method is specific to the articulator system. For the more commonly used

Denar system, the posterior reference point is the external auditory meatus (in the region of

the inter-condylar axis) whilst the anterior reference point is 42mm vertically above the

incisal edge of the right lateral incisor

Inter-occlusal Record (IR)

1. ICP

Injectable silicones (Jet-Bite, BluMouse)

Conventional wax-bites.

2. CR

This position, also known as 'pre-centric', is recorded to assess the first contact for the re-

organised approach for restorative dentistry

To obtain the pre-centric record a jig is made to hold the teeth apart and stabilise the jaws

whilst the IR material hardens.

How to achieve dynamic occlusion?

A. Di Pietro, 1977, investigated the frequency of naturally occurring patterns of occlusion.

He found canine guidance truly exists in only 35% of normal occlusions, and these always

have low Frankfort/Mandibular plane angles and flat occlusal planes.

Group function is more frequent, and becomes progressively more posterior as the cant of

the occlusal plane increases.

B. The decision whether to aim for canine guidance or group function should thus be based on

evaluating the probability of finishing a case to a low angle, flat occlusal plane dento-facial

pattern.

In forward growth rotation, canine guidance is the aim,

a posterior rotation will favour group function.

C. Correct bracket height, giving good levelling of the arches with adequately stiff finishing

wires will enable smooth intercuspal contacts to be achieved.

D. Consistent arch forms, with particular attention to final co-ordination will also ensure that

the arches fit together on closure.

E. The clinician must develop the ability to assess centric relation correctly and treat to that

position, eliminating any mandibular shift that may be present initially.

The 6Elements Orthodontic Philosophy by Andrews

ELEMENT I

Optimal Tooth and Arch Characteristics

An arch is optimal when: the roots are centered over basal bone, the crowns are inclined so

the teeth can interface and function optimally, the Curve of Spee is between 0 and 2.5 mm,

the contact areas abut, and skeletal maxillary width is in harmony with skeletal mandibular

width (Element III).

ELEMENT II

Optimal Anteroposterior (AP) Jaw Positions

The AP position of the maxilla is optimal when the FA points of Element I maxillary

incisors are on the Goal Anterior Limit Line (GALL). Mandibular AP position is optimal

when it is in centric relation, the incisors are Element I and they interface optimally with

Element I incisors in an optimal maxilla.

ELEMENT III

Optimal Jaw Widths

Mandibular width is naturally optimal for most individuals. Maxillary width is optimal

when the distance (X’ mm) between the mesio-lingual cusp tips of Element I maxillary rst

molars is equal to the distance (X mm) between the central fossae of the Element I

mandibular rst molars.

ELEMENT IV

Optimal Jaw Heights

Jaw heights are optimal when: the tooth positions are Element I, the middle anterior, lower

anterior, and posterior face heights are equal, the maxillary incisors’ FA points are level

with the lower border of the upper lip in repose, and the occlusal plane is in harmony with

function and esthetics.

ELEMENT V

Optimal Chin Prominence

Chin prominence is measured independently AP of jaw position. Assuming normal

soft tissue thickness, chin prominence is optimal when pogonion point matches the

prominence of the FA points of Element I mandibular incisors.

ELEMENT VI

Optimal Occlusion

Optimal occlusion involves: the Six Keys

to Optimal Occlusion*, Element I teeth

and arches, and the Element II, III, and IV jaw positions. Collectively, these are the

characteristics of an esthetic, functional, and healthy occlusion.

OCCLUSION and MALOCCLUSION

Written by Mohammed Almuzian

CONTENTS

1. Introduction

2. Normal and Ideal Occlusion

2.1 Reasons for Classification

2.2 Historical review of Angle’s Classification

2.3 Weakness of Angle’s Classification system

2.4 Additions to Angle’s system of Classification and

other classification systems

3.0 Classification in Primary Dentition

4.0 Modern Concepts of Classification and

Treatment goals

5.0 Conclusions

6.0 References

1.0 Introduction

It is logical to create orderliness out of chaos and to simplify all things

disorganised and complex. In orthodontics, we are dealing with biological variations and

malocclusions are not so easily sorted and classified. It is not surprising then, that Angle’s

classification, although universally accepted for the last 100 years is not without its many

shortcomings. Classification itself is not diagnosis. No two Class II malocclusion are

similar .It is no wonder that orthodontics cannot be practiced primarily by any set of rules,

however cleverly devised. The following discussion will touch on normal and ideal

occlusion, the reasons for classification, a brief historical review of Angle’s classification,

additions to Angle’s classification, types of classification systems and modern concepts on

classifications.

2.0 Normal and ideal occlusion

To classify malocclusion, one must have a concept of normal occlusion.

Normal occlusion is not synonymous with ideal occlusion. “Normal” implies a range

around a mean or average, whereas “ideal” represents a hypothetical concept or goal.

Therefore, a “normal” occlusion would be one with all teeth present and occluding in a

stable and pleasing manner but with variations in position within acceptable normal range.

Normal occlusion, conceived to represent 100% perfection, was a myth( Katz, 1990).

2.1 Reasons for classification

Why do we need to classify? It is done for traditional reasons, for ease of

reference, for purposes of comparison, and for ease in self communication (Moyers1988).

It is part of the diagnostic and treatment planning procedure. It summarizes diagnostic data

and implies a treatment plan. Furthermore it reduces and condenses the data base of clinical

information to a list of the patient’s problems ( Proffit, 2000).

Strang (1950) defined classification as a process of analysing cases of malocclusion for the

purpose of segregating them into a small number of groups; these groups are characterised

by certain specific and fundamental variations from normal occlusion of teeth. These

variations, in turn, become influential and deciding factors in determining the correct plan

of treatment.

According to Katz (1990), classification is a vital element in the diagnosis of a

malocclusion and in treatment planning. It also facilitates communication between

professionals since it provides dentists with a common descriptive language.

2.2 Historical review of Angle’s Classification

Edward Angle published his “Classification of Malocclusion” in 1899 in the

periodical, Dental Cosmos. He utilised the presumed constancy of the position of the

maxillary first molar to develop a morphologic standard for classification. He

supplemented the information presented in this article in the publication in 1900 of the

sixth edition of his book, Treatment of the Teeth and Fractures of the Maxillae. However,

there are some obvious and pertinent differences in the information presented in these two

publications and the information contained in the 1907, seventh edition of his book,

Treatment of Malocclusion of the Teeth.

In 1900, Angle considered the maxillary permanent first molars and maxillary permanent

canines important teeth from which to judge the mesio-distal interarch relationship of the

dental arches, but he believed all the teeth were to be taken into consideration when

determining the classification of cases.

Angle described in minute detail each contacting cusp incline to prove his point that in

ideal occlusion every tooth ( except the lower centrals and upper third molars) should have

two antagonists (fig 1.).Therefore, even if the mesiobuccal cusp of the upper first molar

fitting perfectly into the lower molar buccal groove, the patient does not possess proper

occlusion; unless the upper first molar also has a mesial crown tilt that allows the distal

incline of the distal cusp of the upper first molar to occlude with the mesial incline of the

mesial cusp of the lower second molar

An occlusion where the first molars classically fit the criteria of the upper mesiobuccal

cusp to lower buccal groove , but the premolars and canine contact only one opponent tooth

each, would be considered Class I by Angle( fig.2). However, Angle would not have

considered the occlusion as “ideal” occlusion.

Fig

Fig. 1. Angle’s prototype ideal occlusion. All teeth (except the lower centrals and upper

third molars) have two antagonists. Note proper mesial tilt of the upper first molars.

Mesio-lingual cusp of first maxillary molar must sit in central lingual fossa of lower first

molar.

. 2. Traditional Angle Class I molar

(mesiobuccal cusp in lower molar

groove).

However, teeth have only one

antagonist.

In his 1900,sixth edition text, Angle defined Class II malocclusion as an abnormal

mesiodistal relation of jaws and dental arches in which all mandibular teeth occlude distally

to normal by the width of one bicuspid. Class III malocclusion was defined as an abnormal

relation in which the mandibular teeth are positioned mesial to normal by the width of one

bicuspid ( Class I would have a range of approximately 14mm; if the premolar is assumed

to be of 7.5mm in width).

However, in 1907, and in his seventh edition work, he made a significant modification in

the definition of Class II and Class III malocclusions. Angle altered the amount of

deviation from ideal Class I to either Class II or Class III malocclusion from “width of a

bicuspid” to “deviation from ideal of more than one-half the width of one cusp”.( Class I

now has a range of 7mm ). He mentioned that, one must consider, first, the mesio-distal

relations of the jaws and dental arches, as indicated by the relation of the lower first molars

with the upper first molars- the keys to occlusion; and second, the positions of the

individual teeth, carefully noting their relations to the line of occlusion.

Angle summarized the classification as follows:

Class I. Arches in normal mesio-distal relations

Class II. Lower arch distal to normal in its relation to the upper arch

Division 1. Bilaterally distal, protruding upper incisors

Subdivision. Unilaterally distal, protruding upper incisors.

Division 2. Bilaterally distal, retruding upper incisors.

Subdivision. Unilaterally distal, retruding upper incisors.

Class III. Lower arch mesial to normal in its relation to upper arch.

Subdivision. Unilaterally mesial.

=

2.3 Weakness of Angle’s classification system

1) Although it is an adequate classification of antero-posterior relationships , it did not

include information about the transverse and vertical planes.

2) It did not consider the profile of the patient i.e the relationship of the teeth to the face

3) It contained no information as to which jaw was at fault; Angle assumed that it was

always the mandible, which was not the case and was misleading if the skeletal

proportions did not match the occlusal relationships.

4) It cannot differentiate between analogous ( having only the same occlusal relationships)

and homologous ( having all characteristics in common ) malocclusions.

5) It does not indicate the complexity and severity of the problem.

6) Cephalometrics have demonstrated that the upper first molar and canine can assume a

range of possible positions compared to the facial skeleton

7) It does not address the dynamic situation of the first molars during the transitional phase

of the late mixed primary dentition.

8) It does not address the malocclusion in primary teeth.

2.4 Additions to Angle’s system of classification and other classification systems

The deficiencies in the original Angle system led to a series of informal

additions at an early stage. Gradually, Angle’s classification numbers were extended to

refer to four distinct but related characteristics: the classification of malocclusion, as in the

original plan; the molar relationship; the skeletal jaw relationship; and the pattern of

growth.( Proffit, 1993).

CLASS I CLASS II CLASS III

Molar and Jaw Relationship Molar and Jaw Relationship Molar and Jaw

Relationship

Dental Malocclusion Skeletal and/or Dental Skeletal and/or Dental

(Crowding, etc) Malocclusion

Malocclusion

The basis of the Angle classification was the relationship of the first molar teeth and the

alignment (or the lack of it ) of the teeth relative to the line of occlusion. It therefore has

four groups:

Normal occlusion Normal ( Class I ) molar relationship, teeth on line of

occlusion

Class I malocclusion Normal ( Class I ) molar relationship, teeth crowded, rotated

etc.

Class II malocclusion Lower molar distal to upper molar, relationship of other

teeth to line of occlusion not specified

Class III malocclusion Lower molar mesial to upper, relationship of other teeth to

line of occlusion not specified.

In the United Kingdom, the labio-lingual incisor relationship is also classified as

Class I “Normal” incisor overjet and the lower incisors occluding on the incisal

third of the upper incisors

Class II Increased in overjet, the lower incisors occluding on the cingulum of

the Division 1 upper incisors or distally into the palatal tissue

Class II Deep overbite and minimal overjet

Divvision 2

Class III Three or all mandibular incisors occluding labially to maxillary incisors

In the 1930s, the German orthodontist Simon proposed a new system of

classification based on a specific recording of the vertical orientation of the jaws to the

cranium by what Simon called “gnathostatic” casts. He tried to relate the dentition to the

cranium in three dimensions of space: the median sagittal plane ( using the midpalatal

raphe) at right angles to the Frankfurt horizontal plane , at right angle to the orbital

plane.However, this system is cumbersome and little used in practice.

In 1938, Strang described his seven process of case study for classification. His emphasis

was on the position of the mandible and its superimposed dentures in relation to cranial

anatomy in determining correct classification.These processes include assessing :

1) A study of the inclined plane relationship

2) A study of the axial inclination of each dental unit

3) A frontal analysis of midline deviations and condylar positions

4) Rotations of buccal teeth, especially the maxillary molars

5) Consideration of lost teeth, unerupted , missing and supernumerary teeth

6) A study of frontal and profile photographs

7) A study of profile cephalograms

His directions required mentally repositioning the first molars to their “proper” location

using determinations such as axial positions of other teeth, especially the canines

Ricketts and others ( late 1960) designed a computerised cephalometric analysis that

classified malocclusions from a cephalometric radiograph rather than from casts. The

distance along the occlusal plane between the distal surfaces of the mandibular and

maxillary molars were used as criteria in the classification. In Class I, the mandibular molar

is 3mm forward, in Class II, the maxillary molar is forward or even, and in Class III, the

mandibular molar is more than 6mm forward.

The canines are also used, in Class I, the maxillary canine cusp tip is 2mm distal to the

mandibular canine cusp tip, in Class II, the maxillary canine cusp tip is 1mm or more

forward, and in Class III, the maxillary cusp tip is more than 5mm distal to the mandibular

cusp.

In 1969, Ackerman and Proffit proposed a new classification scheme that combines five

descriptive characteristics for malocclusions : alignment in occlusal view, profile and soft

tissue, transverse plane deviations ( crossbites ), sagittal plane deviations( antero-posterior)

using Angle’s classification, and vertical problems of bite depth. The five characateristics

can each be found alone or in overlapping combination for a total of nine classification

groups.

3.0 Classification in Primary Dentition

Primary molars are classified by the relationship of the distal surface of the

lower second molar relative to the distal surface of the upper second molar. Canines are

classified by the relationship of their long axes ( Wei, 1988).

Mesial step primary molar; distal surface of the lower second molar is mesial to the distal

surface of the upper second molar. Canines are Class I; long axis of the upper canine

occludes in embrasure distal to lower canine.

Flush terminal plane; distal surfaces of upper and lower second molars and flush. Canines

are classified as end-to-end because their long axes are aligned

Distal step primary molar and Class II canine relationship; distal surface of lower second

molar is distal to the upper molar and the upper canine occludes in the embrasure mesial to

the lower canine

Mesial step molar, but the upper canine occludes farther distal than the embrasure distal to

the lower canine ; this is called a Class III canine relationship.

Proffit 2000

4.0 Modern concepts of classification and treatment goals

Remember Angle’s classification of Class I is a range. Unfortunately, many

orthodontist use Class I as a goal of successful treatment. Katz (1992) proposed a premolar

derived classification.

Class I The most anterior upper premolar fits exactly into the embrasure created by the distal

contact of the most anterior lower premolar.

When this relationship is achieved, the canines will relate correctly, as will the incisors.

Molar relation is not a major concerned. This classification will work when teeth are

extracted in only one arch. If no premolar exist in a quadrant, then the center axis of the

upper canine crown should be used as a reference to the distal contact of the lower canine.

This modified classification can also be quantified and lend it to computerisation.

For the mixed dentition, the center axis of the upper first decidous molar should split the

embrasure between both lower decidous molars. In the event that an upper first decidous

molar is lost, a line drawn through the centre axis of the edentulous space should bisect the

embrasure between the two lower deciduous molars.

5.0 Conclusion

Edward Angle’s classification of malocclusion, although with many

shortcomings as described has stood the test of time because it is easy to understand and

apply. It has become the established language of communication between orthodontist and

also accepted by the legal profession. Numerous other classifications has evolved to make

up for the weakness of the Angle’s Classification. In current practise, extraction is common

and the attainment of Class I molars is sometime not possible or desired. A modified Class

I classification has been proposed and described. Classification in the mixed dentition has

also been addressed. Most classifications are static and not truly inclusive eg. no

consideration of the temporomandibular articulations. As clinicians, we must remember

that classification is not diagnosis, it is only an aid in grouping of cases of similar

appearance for ease of communication and discussion. Each individual case should be

treated on its own merit and strict adherence to a “Classification oriented goal” is not

always desired.

6.0 References:

Angle E. Treatment of malocclusion of the teeth and fractures of maxillae.

Angle system.7th ed. Philadelphia: SS White Manufacturing ,1907

44-59

Katz M.I. et al. The 100 year dilemma: what is a normal occlusion, and how is

malocclusion classified? Quintessence Int. 1990:21:407-414.

Katz M.I. Angle classification revisited 1: Is current use reliable. Am. J.

Orthod. Dentofac. Orthop. 1992:102:173-179

Katz M.I. Angle classification revisited 2: A modified Angle classification.

Am. J. Orthod. Dentofac. Orthop. 1992:102:277-284

Moyers R.E. Handbook of Orthodontics 4th ed. Year Book Medical Publishers

Inc. 1988: 183-195

Proffit W. Contemporary Orthodontics 2nd ed. Mosby Year Book Inc. 1993:

175-182

Rinchuse D. and Ambiguities of Angle’s classification. Angle Orthod.1989: 59:295-

Rinchuse D. 298.

Strang R.H.W. A text-book of Orthodontia. 3rd ed. Philadelphia: Lea & Feibiger,

1950:79-106

Wei S.H.Y. Pediatric Dentistry , total patient care. 1st ed. Philadelphia: Lea &

Feibiger, 1988: 431