growth of the face and dental arches

Growth of the Face and Dental Arches

The Dentofacial pattern can be easily and accurately assessed at chair side. In clinical terms pertinent growth issues are discussed in relation to how growth changes the pattern of the face, occlusion, and dental arches. Knowledge of pattern appraisal and growth can be integrated in coming to efficacious clinical decisions about a young patient.

THE NATURE OF GROWTH

Growth refers to an increase in anatomic size. Threeparameters commonly used in growth literature to

assesscraniofacial size increase are magnitude, velocity, anddirection. Magnitude refers to the linear dimensionoverall or the dimension of a part. Direction means

thevector of size increase as might be described on a

three dimensional coordinate system. Velocity is defined as the amount of change per unit of time

Size increase is typically illustrated in one of two ways:

1. cumulative or distance curve: is when growth is measured periodically and measurements are plotted as percentages of total .

2. Incremental human growth curve :is rapid accelerating prenatal growth, rapid decelerating postnatal growth for the first 2 or 3 years, and a period of relatively slow incremental growth during childhood followed by growth acceleration for 2 or 3 years during pubertal adolescence.

Cumulative (distance) growth curve.

Incremental growth curve illustrating growth stages

Development :

BASIC CONCEPTS OF HUMAN GROWTH

1. Growth disposition is similar for all healthy individuals:

Healthy individuals go through growth stages that are the same for everyone, according to Valadian and Porter.' The prenatal period, from conception to birth, averages 40 weeks in length. Infancy includes the first 2 years of life after birth, and childhood ranges from 2 to 10 years for girls and 2 to 12 years for boys. The length of adolescence is the same for both sexes but comprises different years, 10 to 18 years for females and 12 to 20 years for males.

2. Different body parts increase in length at different rates:

From birth to adulthood, the head increases about

twice in length, the trunk about three times, the arms

about four times, and the legs about five times.

Different parts of the body grow at different times and at different rates.

3. The overall potential for growth is determined primarily byintrinsic or genetic factors

. Genetic endowment is the main determinant of growth potential. Intrinsic factors are also those conditions and events that occur from conception to birth. Maternal nutrition or disease can modify child development before birth. Some tissues.

4. The extent to which an individual attains his or her potential for growth is determined predominately by extrinsic or environmental factors

Extrinsic factors include all postnatal environmental conditions, such as nutrition, illness, exercise, and climate. Environmental factors of particular interest to the dental clinician are oral habits, pathology, caries, premature loss of teeth, and metabolic disease. In the absence of detrimental extrinsic

factors, the dentofacial complex will tend to attain its

maximum potential in growth.

CRANIOFACIAL GROWTH PRINCIPLES:

1.The basic tissue types and functioning spaces that comprise the head and face are subject to growth timing differences.

Neural tissue has attained about 60% to 70% of adult size by birth and its growth is about 95% completed by middle childhood.

Muscle tissue is only 40% to 45% of its adult size by birth, and its growth is approximately 70% completed by 7 years of age. The size of cranio-facial lymphoid tissue (tonsils and adenoids) is about 125% of adult size at 5 years of age and decreases gradually to adulthood

2. Growth of primary cartilage and functioning spaces has adirecting influence on cranio-facial pattern change

primary cartilage is genetically predisposed, acts during growth as an autonomous tissue, and is able to directly influence the craniofacial pattern.

By middle childhood, most primary cartilage is replaced by bone in a process called

Endochondral Bone Formation.

3. Mandibular condylar cartilage, craniofacial sutures, and appositional-resorptive bone change facilitate pattern growth of the head and face

During craniofacial growth, the mandible is repositioned continuously to its best functional advantage. Reposturing alters the anatomic position of condyle to glenoid fossa. Compensatory growth of secondary condylar cartilage is one mechanism that facilitates maintenance of mandibular position.

4. Growth of the head and face tends to demonstrate relative equivalency.

1.Different parts of the craniofacial complex grow at different times:

Different parts of the face experience differences in growth timing as well.

By birth, the cranial height dimension has attained about 70% of its adult status; cranial width, 65%; and cranial length or depth, 60% In contrast, only 40% of facial height and 45% of facial length (depth) has been achieved by birth. Face width (i.e., bizygomatic and bigonial), on the other hand, has attained about 60% of adult stature. Growth in face width actually falls between the classic neural and general somatic growth curves.

BASIC CONCEPTS OF CRANIOFACIAL GROWTH

2. Differences in growth size, direction, velocity, and timing are observed among individuals.

Generally, females mature 2 years earlier than males.

Males tend to grow larger in size than

females.

3. The heads and faces of no two humans are exactly the same.

CRANIOFACIAL PATTERN

There are two methods commonly used in dentistry gather information about craniofacial pattern.

1.One method is to examine the patient physically at chair side. Information collected in this fashion is based on criteria contrived and established in the practitioner's mind.

2.The second method is to analyze dental records. Historically, cephalometric analysis has been a particularly useful tool for collecting objective information about craniofacial patterns.

IDEAL PARADIGMS FOR DENTOFACIAL PATTERN

The words ideal paradigm mean "perfect example."

A perfect example can, on the other hand, be a powerful diagnostic and treatment-planning tool. The patient's facial pattern can be compared with criteria for idealness, the differences noted, and hence a problem list constructed.

GROWTH AND FACIAL PATTERN

CONSISTENCY IN PATTERN MATURATION

Following birth, the face increases in size to a greater extent than does the calvaria. Bell, Proffit, and White propose that, by adulthood, the ideal face should be equally proportioned in forehead, midface, and lower face heights.

Graphic illustration of facial profile flattening from6 years of age (solid line) to 18 years of age (broken line)

IDEAL FRONTAL FACIAL PATTERN

The ideal frontal facial pattern for a 7-year-old child might include the following criteria:

1. Right and left face halves are symmetrical. 2. Glabella (midpoint between eyebrows) to sub-

nasale (point where columella merges with upper lip) equals subnasale to menton (inferior aspect of chin).

3. Subnasale to lower border of upper lip represents one third the distance from subnasale to menton.

4. Upper central incisor edge is 2 mm inferior to lower border of upper lip.

5. Alar base width equals inner canthal width.

IDEAL FACIAL PROFILE PATTERN

The ideal profile pattern for a 7-year-old child might include the following criteria:

1. Chin 5 mm behind FHP 2. Most anterior aspect of lower lip on FHP 3. Most anterior aspect of upper lip 5 mm

ahead of FHP 4. Nasolabial angle of 100 degrees 5. No more than 2 mm lip separation when

relaxed

Ideal facial and profile pattern:

MAINTENANCE OF OVERALL PATTERN

At chair side, disharmony between the maxilla and the

mandible can be simply and readily identified. A list of

differences can be formulated by comparing the patient's facial measurements with the criteria of an ideal face.

The differences serve as a patient problem list. Adding

average growth change to the pattern presented by the individual will give an estimate of how facial patterns will look at a later age.

This growth scheme is known as a mean-change-expansion

scheme

It to be the most useful to predict the effects of growth on facial pattern.

The mean-change-expansion scheme is useful for evaluation of almost all patients routinely seen in the dental office.

According to Graber and Swain" modification of the dentofacial complex occurs by the following means:

1. Condylar growth (secondary cartilage growth) 2. Glenoid fossa adaptation (apposition-resorption

bone growth) 3. Elimination of functional retrusion 4. More favorable mandibular growth direction 5. Withholding of downward and forward maxillary

arch movement (apposition-resorption bone growth) 6. Differential upward and forward eruption of lower

buccal segment (apposition-resorption bone growth) 7. Orthopedic movement of maxilla and upper

dentition (maxillary suture system growth)

FACIAL GROWTH EMULATES GENERAL SOMATIC GROWTH

The adolescent growth spurt is characterized by increased growth velocity at about 10 to 12 years of age for girls and 12 to 14 years of age for boys. The maximum velocity or peak height velocity of growth is attained approximately 2 years after pubertal onset.

GROWTH AND PATTERN OF OCCLUSION

Usually, no teeth are clinically visible at birth. Leighton

has shown that the upper anterior gum pad (intercuspid

width) is typically wider than the lower anterior pad,

and the upper anterior gum pad protrudes (overjet)

about 5 mm relative to the lower anterior gum pad."

The upper anterior gum pad usually overlaps (overbite)

the lower anterior pad by about 0.5 mm. In the first 6

months of postnatal life, there is marked palatal width

increase, and the overjet decreases rapidly.

PRIMARY DENTITION TERMINUS

By 3 years of age, the occlusion of 20 primary teeth is usually established. The relationship of the distal terminal planes of opposing second primary molar teeth can be classified into one of three categories A flush terminal plane (flush terminus) means that the anterior-posterior positions of the distal surfaces of opposing primary second molars are in the same vertical plane.

A mesial-step terminus is defined as a lower second primary molar terminal plane that is mesial to the maxillary primary terminus. Distal-step terminal plane is descriptive of the situation in which the mandibular second primary molar terminus is distal to the upper second primary molar terminus.

Graphic illustration of permanent first molar occlusion development. Outlined crown images represent three terminal plane relationships of primary second molars at about 5 years of age. Darkened images represent various permanent first molar relationships at initial occluding contact ( about 61/2 years of age) and at full occlusion contact (about 12 years of age).

OPPOSING FIRST MOLARS AT INITIAL CONTACT:

A class I relationship means that the mesialbuccal (m-b) cusp of the upper permanent molar contacts at or very near the buccal groove of the lower permanent first molar. This occurs approximately 55% of the time. An end-on relationship means that m-b cusps of both molars oppose one another. The incidence of this situation is about 25%.

A class II relationship, occurring 19% of the time, is one in which an upper m-b cusp is anterior to the lower m-b cusp. Class III represents the situation in which an upper m-b cusp is distal to the lower buccal groove. This occurs in only 1% of the population

1% Class III

49% Class I (ms) 27% Class I 59% Class I

37% Flush 49% End-on

14% Class II ids) 23% Class II

3% Class III

39% Class II

IDEAL STATIC OCCLUSION PATTERN

Criteria for ideal dental occlusion for a 7-year-old child might include the following:

Class I molar and canine interdigitation 2-mm anterior and posterior overjet 2mm anterior overbite Coincident dental midlines

GROWTH AND DENTAL ARCH PATTERN

The crowns of primary teeth begin calcification between 3 and 4 months prenatally.5' The calcification of mandibular teeth usually precedes that of the maxillary dentition; the central incisors typically show first evidence of calcification and the second molars last.

Boys typically begin calcification before girls. The first primary tooth to erupt is the central

incisor at about 71/2 months, and the last to erupt is the second primary molar at about 2'/2 years. Closure of root apex occurs at 3 years for the second primary molar

The usual sequence of primary dentition eruption is:

A-B-D-C-E Calcification of the permanent teeth does

not begin until after birth.S1 The first permanent molar is the first to show evidence of calcification, which takes place during the second postnatal month. The third molar is the last to begin calcification, which occurs at about 9 years.

Average dimensional dental arch changes from age 6 to 18 years for maxillary and mandibular arches are as follows:

Lower Arch Arch width: Bicanine: 3-mm increase

Bimolar: 2-mm increase Arch length: 1-mm decrease because of up -righting

of incisors Arch circumference: Decrease of 4 mm

Upper Arch

Arch width: Bicanine: 5-mm increase

Bimolar: 4-mm increase

Arch length: Slight decrease because of up- righting of incisors

Arch circumference: Increase of 1 mm

IDEAL DENTAL ARCH PATTERN

For the dental arch, the ideal pattern for a 7-year-old child might meet the following criteria:

1. Tight proximal contacts 2. No rotations 3. Specific buccal-lingual axial inclinations 4. Specific mesial-distal axial inclinations 5. Even marginal ridges vertically 6. Flat occlusal plane 7. Excess (positive) leeway space

TOOTH SIZE/ARCH SIZE RATIO AS PATTERNDETERMINANT distal tooth size is determined primarily by

genetic factors. Dental size is expressed through X-linked

inheritance, and racial differences are known. The upper lateral incisor shows the most variability in tooth size.

The clinical crowns of all permanent teeth, except for

the third molar, are completely formed by middle childhood

COMPUTATION OF TOOTH SIZE/ARCH SIZE

BALANCEThe analysis involves the following steps: 1. Measure the combined width of the lower

lateraland central incisors on one side. 2. Measure directly from the radiograph the

crownsizes of the unerupted 4-5 on the same side. 3. Add together the incisor and the premolar

sizes. 4. Refer to the prediction chart to determine the

sizes of the unerupted 3-4-5

COMPENSATIONS IN DENTAL ARCHDEVELOPMENT

Several means are available for creating dental arch space. They includethe following:

1. Move molars distally. 2. Decrease the mesial-distal dimension of

the teeth present in the arch. 3. Increase the buccal-lingual axial

inclination of theincisors. 4. Reduce the number of teeth in the arch by

extraction

For each millimeter of excessive occlusal curve, 1 mm of

arch length space is required."s To upright labially inclined incisors, arch length

space is also required. In contrast, more arch length is created when

retroclinedincisors are proclined through therapy; the length of

thearch is increased by repositioning the incisal edges

froma lingual to a more labial position.

MAINTENANCE OF OVERALL PATTERN

Dental arch space excess (1 to 2 mm) is a relatively ideal situation. Clinically, little intervention is usually required because mesial drifting of the permanent teeth often results in little or no crowding or residual spacing. Space excess exceeding 3 to 4 mm, however, can lead to dental arch problems. For example, congenital absence of one or more teeth can leave so much arch space that mesial drifting cannot compensate. Decisions favoring retention of primary teeth as long as possible, extraction

Space deficiencies less than -2 mm can usually be managed with a lower lingual holding arch. Arch space deficiencies of -3 to -6 mm should be scrutinized carefully.

Typically, a space-regaining lower lingual arch or arch length expansion treatment measure is indicated.

Arches with deficiencies in excess of -6 mm are candidates for aggressive space-regaining techniques, dental arch expansion treatment, or one of a number of serial extraction sequences.

EFFECT OF ENVIRONMENTAL FACTORS ON DENTAL ARCH PATTERN

hood. Dental arch status is subject to the ravaging effects of environmental factors that include early loss of primary teeth, interproximal caries, pathology, ankylosis of primary teeth, oral habits, trauma, and early eruption of permanent second molars.

The environmental factors most commonly affecting dental arch status are probably caries and premature loss of primary teeth.

1. E loss had the most deleterious effect on dental arch length. 2. Early posterior primary loss resulted in 2- to 4-mm space

closure per quadrant in both arches. 3. Space loss was age related in the upper but not in the lower

arch. 4. Upper D loss typically resulted in blocked-out cuspids; upper

E loss usually led to an impacted second permanent premolar. 5. The greatest space loss was caused by mesial molar

movement. 6. More space was lost in the first year after premature tooth

loss than in successive years. 7. No recovery of space was demonstrated during growth in the

upper arch, and little was found in the lower arch.

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