TRIPASS XR تري باس

 

• It is a valuable aid in determining width, length and outline form of

the artificial teeth.

• It can also establish the algebraic proportion of the anterior teeth.

• Close-up photographs can give the interpupillary distance which

can be compared to the patient without teeth.

• Interpupillary distance helps in establishing the horizontal width of

the upper six anterior teeth.

Formula for calculating horizontal width is

Radiographs

Intraoral radiographs of natural teeth can provide information about

the size and form of the teeth to be replaced, despite the fact that

radiographs are slightly enlarged and distorted due to divergence of

the X-rays.

Extracted teeth

• Sometimes patients preserve the extracted teeth with them.

• Extracted teeth help in determining the shape, size and form of the

artificial teeth.

• However, colour cannot be determined with the extracted teeth.

Observing teeth of a close relative

• Close observation of the teeth of a close relative will give an idea

about the shade, shape and size of the teeth.

• Size, colour and arrangement of teeth of children can be effectively

used in selecting and arranging artificial teeth for their parents.

Evolution of anterior teeth selection

Selection of teeth is as old as dentistry itself. It involves the choices of

size, shade and outline form of the artificial teeth. The evolution of

various techniques used for anterior teeth selection is briefly

mentioned as follows:

Ivory age and early porcelain period: Teeth were selected mostly by the

dimensional measurement with slight consideration given to the

face form or other features.

J.W. White (1872): He gave the concept of correspondence and harmony.

He asserted the association of tooth form and colour with the

patient’s temperament.

W.R. Hall (1887): He gave the concept of typal form. Major basis of this

concept was the tooth labial surface curvatures, outline form and

neck width of the teeth. Minor basis was the relationship of the

labiolingual inclinations of the upper incisors with the facial profile.

Berry biometer ratio method (1906): This method is based on the concept

that the outline form of the inverted upper central incisor

approximated the outline form of the face. Berry found a correlation

between the tooth form and the face form. According to him, the

width of the central incisor is one-sixteenth of the width of the face

and one-twentieth of the length of the face.

Clapp’s tabular dimension table method (1912): This method is based on

selecting size of all the six anterior teeth arranged on the Bonwill

circle and the available interarch space.

Valderrama’s molar tooth basis (1913): According to this method, varying

measurement between combination of the cusp points indicated the

size of individual and overall tooth measurements.

B.J. Cigrande (1913): He used the outline of the fingernail to select the

outline form of upper central incisor.

Leon Williams typal form method (1914): This was interpreted by the

geometric pattern created by the outline form of the bony face

frame. He classified the teeth as square, square tapering, tapering

and ovoid forms. The upper central incisor was considered as the

model tooth form of the arch.

A. Nelson (1920): He gave the maxillary arch outline form technique

which assumed that the arch outline form was a valid method, as it

relates to the individual’s anatomy.

Wright’s photometric method (1936): It was based on using a photograph

of the patient with natural teeth and establishing the ratio by

comparative computation of the measurement of like areas of the

face and the photographs.

R.L. Myerson (1937): He gave a ‘multiple choice method’ which was

based on a need for characterization of teeth by time, wear, etc. and

varying the shade of teeth.

M.M. House (1939): He proposed the ‘House instrumental method’ of

projecting typal outline and profile silhouettes onto the face by

means of a telescopic projector instrument and silhouettes form

plates.

V.H. Sears (1941): He advocated the anthropometric cephalic index

method. This method was used to determine the width of the upper

central incisor by either dividing the transverse circumference of the

head by 13 or the bizygomatic width by 3.3. Also, the tooth length

should be in proportion to the face length.

Dentists’ Supply Company (1950): It gave the Bioform technique based on

geometric outline form of the face and the teeth, typal forms and the

3D harmony of the tooth and face forms. It is associated with the

tubular systems and the mould guide system.

Austenal Company (1951): It proposed ‘automatic instant selector guide’

which correlates form, size and appearance in such a manner that a

single reading is required to select an appropriate tooth mould

based on the dimension of the denture space and harmony of the

face and tooth form.

Selection of anterior teeth

Complete denture is considered aesthetic when the teeth and the

denture base are in harmony with the surrounding facial structures.

Lack of harmony gives an unaesthetic look which may be due to

selection of incorrect size, shape or colour of the teeth or even

improper orientation of the occlusal plane. Therefore, selection of

artificial teeth requires thorough knowledge and skills.

Selection of anterior teeth is primarily based on satisfying the

aesthetic need of the patient. The three important factors on which the

anterior teeth selection is usually based are as follows:

(i) Size of the teeth

(ii) Form of the teeth

(iii) Colour of the teeth

Size of the teeth

The size of the teeth selected for a particular patient should be in

accordance to the size of his/her face and head. Usually, larger people

have larger teeth and vice versa but there can be variations where

larger people may have smaller teeth and smaller ones may have

larger. There are a number of methods, as discussed below, by which

sizes of anterior teeth are selected.

Based on size of the face

The facebow is used to measure the bizygomatic width of the face.

Sears anthropometric cephalic index

The mesiodistal width of the maxillary central incisor is measured by

measuring the circumference of the head and dividing by 13.

Berry biometric index

The length of the face is measured by taking two arbitrary points, one

at the hairline and the other at lower edge of the most prominent part

of the chin.

Pound’s formula

The same values were also observed by M.M. House and J.L. Loop.

Trubyte tooth indicator is also used to determine the size of the

maxillary central incisors.

Golden proportion

B. Levin advocated that the perceived mesiodistal width of the

maxillary anterior teeth lies in the golden proportion of 1.681:1 when

viewed from the front (i.e. central incisors are 1.681 times broader

than the lateral incisor). He suggested the use of this proportion to

select and arrange anterior teeth to achieve maximum aesthetics (Fig.

7-1).

FIGURE 7-1 Existence of golden proportion between the

elements of anterior maxillary teeth.

Size of the maxillary arch

The distance measured between the crest of the incisive papilla and

the hamular notch on one side and between the two hamular notches

gives the approximate width of all anterior and posterior teeth (Fig. 7-

2).

FIGURE 7-2 Measurement between incisive papilla and

hamular notch.

The measurements may not be always correct because factors such

as amount of bone loss, spacing and tooth rotation may influence the

size of anterior teeth.

Distance between the canine eminences

The distance between distal of one canine eminence to the other

eminence is measured with the help of flexible plastic ruler which

indicates the combined mesiodistal width of maxillary anterior teeth.

The measurement is always done labial to anterior border of the

incisive papilla.

Alternately, a well-contoured maxillary rim is placed in the

patient’s mouth and the corners of the mouth are marked on the rim.

Distance between these two markings gives the approximate width of

maxillary anterior teeth.

Jaw relations

The available interarch space greatly influences the height, width and

position of the anterior teeth selected. When the available space is

more, longer teeth will be more aesthetically acceptable than smaller

ones.

Contour of residual ridge

• Artificial teeth should be placed along the contour of the residual

ridge that existed when the natural teeth were present.

• Knowledge of the resorption pattern of both maxilla and mandible

will aid in accurate visualization of the original contour.

• Resorption of the maxillae in the anterior segment is in the vertical

and palatal direction and posteriorly it is in the vertical and medial

direction.

• Resorption of the mandible in the anterior segment is in the vertical

and lingual direction and posteriorly it is in the vertical and slightly

lingual direction.

• As resorption occurs, the maxillary arch becomes smaller and the

mandibular arch becomes larger.

Vertical distance between the ridges

• The length of teeth is determined by the amount of available interarch

space.

• Longer teeth are used, if adequate space is available to eliminate the

visualization of the denture base.

• Teeth are more attractive in appearance than the denture base.

• Denture base can be characterized or personalized to give more

natural appearance.

Lip support

• When lips are relaxed and apart, the labial surface of the maxillary

anterior teeth supports the upper lips.

• Usually, the incisal edges extend inferior to or slightly below the lip

margins.

• When teeth are in occlusion and the lips are together, the labial

incisal one-third of the maxillary anterior teeth supports the

superior border of the lower lip.

• When patient says ‘fifty-five’, the incisal edges of the maxillary

anterior teeth contact the lower lip at the junction of the moist and

dry surfaces of the vermillion border (Fig. 7-3).

• Properly contoured maxillary rim will aid in determining the length

of the teeth.

FIGURE 7-3 Incisal edges of upper anterior teeth contact

lower lip as the patient speaks ‘fifty-five’.

Form of the teeth

On the basis of facial form

The anterior teeth selected should harmonize with the facial form, i.e.

the frame in which the selected teeth has to be placed. J. Leon Williams

(1914) classified maxillary anterior teeth on the basis of typal form. He

classified the facial form as follows:

(i) Square

(ii) Tapering

(iii) Square tapering

(iv) Ovoid

Later, House and Loop classified teeth considering the mesiodistal,

incisogingival and facial outline form of the tooth. They classified

three pure typal forms and their five possible combinations (Fig. 7-4).

(i) Square

(ii) Tapering

(iii) Ovoid

FIGURE 7-4 Form of teeth selected on the basis of facial

form: (A) square; (B) ovoid; (C) tapering.

The combinations were square–tapering, reverse–tapering, ovoid–

square, ovoid–tapering and ovoid–reverse–tapering.

On the basis of facial profile

The labial surface of the teeth selected should harmonize not only

with the facial form but also with the facial profile of the patient. The

general facial profiles are as follows (Fig. 7-5):

(i) Convex

(ii) Concave

(iii) Straight

FIGURE 7-5 Teeth selected on the basis of facial profile.

The frontal surface of the teeth should appear flat or convex

depending on the profile of the patient when viewed from the side.

On the basis of colour or shade of the anterior

teeth

• The colours recognized by the human eye are the effect of certain

wavelength of light on the retina.

• During shade selection, it is observed that yellow is more dominant

in the gingival third and grey is more dominant in the incisal third.

• Colour has four qualities, namely, hue, chroma, value and

transparency.

• Hue: It is the basic colour of the spectrum.

• Chroma (saturation): It is the amount of colour per

unit area of an object. It is synonymous with the

intensity of the basic colour.

• Value (brilliance): It refers to lightness and darkness

of an object.

• Transparency: It is the property of an object that

permits the passage of light through it.

• E.B. Clarke (1933) established that shade possesses three dimensions,

namely, cervical, incisal and transitional shade in the middle third

of the tooth.

• Generally, cervical area has more chroma and incisal area is more

translucent in the anterior teeth.

• Also, there is transition of shade from the central incisors to the

canines.

• The canines are less translucent, more opaque and have more

chroma than the central incisors.

• Shade selection also depends on sex, personality and age (SPA).

• Factors influencing shade selection with age are secondary dentin,

abrasion and stains.

• Colour of the face is the basic guide to the colour of the teeth.

While selecting the shade or colour, observations are made in the

following three positions:

(i) Outside the mouth along the side of the nose

(ii) Under the lips with only the incisal edges exposed

(iii) Under the lips with the cervical end exposed when the patient

opens mouth widely

Prerequisites for Shade Selection

• Shade tabs should be moistened.

• North (white) light is ideal for shade selection.

• Light should not be focused for more than few seconds.

• Blue-coloured object is viewed in between.

• Shade is also confirmed at the distance of 6–8 feet.

• The dentist should position himself/herself such that the teeth to be

viewed should be in a plane perpendicular to the plane of his/her

vision and the patient should be in upright position.

• Teeth are always viewed from different angles so that shadows do

not influence the shade.

• There should be harmony between the colour of the teeth and colour

of skin, hair and eyes.

Composition of material of anterior teeth

• Artificial teeth are made of either porcelain or acrylic resin.

• Porcelain teeth are usually vacuum fired and are denser.

• Porcelain teeth are difficult to wear but retain their polish.

• Porcelain is attached to the acrylic denture base by mechanical

means (usually by gold pins) (Fig. 7-6).

• Acrylic teeth have less strength than porcelain teeth.

• Acrylic teeth wear faster than porcelain teeth.

• Acrylic teeth bond to the acrylic denture base by chemical means.

• Acrylic teeth can be easily grinded as compared with porcelain

teeth.

FIGURE 7-6 Porcelain teeth attached to acrylic resin by pins

or diatoric holes: (A) Pins embedded in porcelain teeth; (B)

diatoric hole.

Porcelain teeth versus acrylic resin teeth

Posterior tooth form can be made of a variety of materials. Porcelain

and acrylic resin teeth are most commonly used for manufacturing

denture teeth. Differences between porcelain teeth and acrylic resin

teeth are given in Table 7-1.

Table 7-1

DIFFERENCES BETWEEN PORCELAIN AND ACRYLIC RESIN

TEETH

Porcelain Teeth Acrylic Resin Teeth

More aesthetic than acrylic resin teeth Less aesthetic

More resistant to wear Least resistant to wear which is

clinically significant

Retained on the denture base by mechanical interlocking; diatoric

holes can be placed into teeth into which the denture base resin flows

Chemically adhere to the denture

base

Teeth are brittle and clicking sound is produced on contact with the

opposing teeth

Have softer impact sound

Resistant to staining but may show marginal staining Tend to stain more rapidly

Require greater interarch distance because they cannot be grounded as

thin in the ridge lap area as acrylic teeth without destroying the

diatoric channels which are the only means of retention to the denture

base

They can be grounded to thin

sections and polished and also can

be placed in decreased interarch

distance

Shape and form are maintained during trimming Shape and form cannot be

maintained during trimming

Ground porcelain surface should be highly polished to reduce friction

and prevent chipping

Self-adjusting and self-polishing

Wear does not cause much change in the vertical dimension Wear results in loss of vertical

dimension

Only type of denture teeth that allows the denture to be rebased

because they can be grounded and polished and can maintain shape

for years

This is not possible in case of

acrylic resin teeth

Can cause abrasion to opposing gold crowns and the natural teeth Causes less abrasion to the

opposing gold crowns and the

natural teeth

Squint test

Squint test is useful in evaluating the shade of the teeth with the

complexion of the face. In this method, the clinician partially closes

the eyelids to reduce the amount of light. The clinician then compares

the prospective colours of the artificial teeth held along the face of the

patient. The colour that fades first from the view is the one that is least

conspicuous in comparison with the colour of the face. Such a colour

is selected for artificial teeth of a complete denture patient.

Dentogenic concept

It is defined as the art, practice and technique of creating an illusion of

natural teeth in artificial dentures and is based on the elementary

factors suggested by the sex, personality, age (SPA) of the patient.

Dentogenic restoration is designed to enhance the natural

appearance of the individual.

J.P. Frush and D.R. Fisher (1956) proposed the dentogenic concept in

selecting artificial teeth based on SPA. Their concept was based on the

work of William Zech, a Swiss sculptor, who applied ‘sculpture’ in

denture and helped to achieve the effect of sex identity. They

advocated that in order to achieve complete harmony in an individual

patient, the influence of the above-mentioned factors along with the

cosmetic factor should be considered. The arrangement of the teeth is

influenced by the following factors:

• Age

• Sex

• Personality

• Cosmetic factor

• Artistic reflection

Sex

Sex of the individual influences the arrangement of the artificial teeth.

The individual contours and arrangement of the teeth are different for

men and women.

Tooth form varies with the sex of the individual (Figs 7-7 and 7-8).

Male Female

Squareness of arch denotes masculine

dentition

Roundness of the arch form denotes feminine dentition

Masculine tooth forms are generally square Feminine tooth forms are usually ovoid

In men, the incisal edges are more angular The incisal edges of the anterior teeth are more rounded

Incisal edges of maxillary anterior teeth are

parallel to the lips

Incisal edges of the maxillary anterior teeth in women

follow the curve of lower lip

Distal surface of central incisors is usually not

rotated

Distal surface of the central incisors is usually rotated in

posterior direction

Lateral incisors are almost at the same level as

central incisors and impart quality of hardness

Lateral incisors are narrower and shorter than central

incisors and impart quality of softness

The mesial surface of the lateral incisors is

posterior to the distolabial surface of the

central incisors

The mesial surface of the lateral incisors is often in anterior