“SELECTION AND ARRANGEMENT OF ANTERIOR TEETH FOR PREDICTABLE ESTHETICS AND FUNCTION IN COMPLETE DENTURE PROSTHESIS

CONTENTS

1. INTRODUCTION 2. HISTORY

3. FACTORS CONSIDERED FOR DESIRED ESTHETICS FOR CONVENTIONAL COMPLETE DENTURE PROSTHESIS

4. SELECTION OF ANTERIOR TEETH

5. ANTERIOR TOOTH ARRANGEMENT AND PLACEMENT

6. PRINCIPLES OF TEETH ARRANGEMENT FOR ANTERIOR TEETH

7. GUIDELINES FOR TEETH ARRANGEMENT AND PLACEMENT FOR ANTERIOR TEETH

8. EVALUATION OF ESTHETICS

9. CONCLUSION

10. BIBLIOGRAPHY

INTRODUCTION

Esthetically and functionally acceptable complete dentures should not differ from natural teeth. Therefore, the selection and arrangement of artificial teeth is an important concern in complete denture construction. Several factors have been proposed as aids for artificial tooth selection and arrangement and numerous methods have been devised for evaluation of reliable esthetic factors in determining artificial tooth form and dimensions.

Denture esthetics is defined as “the cosmetic effect produced by dental prosthesis which affects the desirable beauty, attractiveness, character and dignity of the individual.” The subject of esthetics, however, has always been a grey area in dentistry. It is not a totally scientific and objective description, nor is it hundred percent an art form. Denture esthetics is a blending or combination of the art form and the science of prosthodontics. As such it is not possible to establish firm scientific rules, or laws of esthetics. However, it is possible to postulate a set of guidelines that, if adhered to, will result in esthetically pleasing complete denture that are also functional.

HISTORY

The first theory ever introduced for artificial anterior teeth selection was the temperamental theory. Afterwards, Williams (1914) suggested that a correlation existed between the upside-down facial profile and the shape of the upper central incisors. Forty years back Frush and Fisher introduced the dentogenic theory on the basis of sex, personality and age of each individual. Lowery and Nelson proposed that a close relationship existed between the face, tooth and tooth arch form. However, recent studies were able to confirm the relationship neither between the face form and the shape of upper central incisor nor between palatal shape and the form of upper central incisor.
Boucher stated that "a study that would search for a relationship between the upper cuspids and the rugae might be worth the effort."Allen first suggested relating the rugae to the position of the teeth. Wood and Kraus' described fleshy landmarks on the surface of the palate that could be used for orientation and measurement of tooth position. Peavy and Kendrick" described these landmarks in relation to changes in tooth position. Moore contended that the anteriormost rugae generally pointed to the center of the maxillary canine and that the incisive papilla lay directly between the central incisors. The rugae and the incisive papilla were selected as landmarks because they remain in the edentulous mouth.
Width-to-length ratio and tooth-to-tooth width ratio of the maxillary anterior teeth have been considered as important factors for dental esthetics and harmonic teeth arrangement. Unfortunately, only few guidelines describe maxillary anterior teeth proportions. The Golden Proportion was described by Levin who proposed that dental esthetics could be achieved when central-to-lateral and lateral-to-canine width ratios were in the Golden Proportion (62 %). However, Preston and Rosenstiel were not able to confirm the existence of the Golden Proportion in natural dentition. Brisman proposed that the optimal width-to-length ratio for the maxillary central incisor should be 75 %, while Wolfart, Sterret and Magne suggested the ratio up to 85 %.
Currently, there is no universally accepted single esthetic factor that can be used reliably to aid artificial tooth selection and a need exists for improved training and guidance on artificial tooth selection and arrangement. Therefore, further studies seem to be necessary either to confirm or disapprove some contradictory results from other studies.

FACTORS CONSIDERED FOR DESIRED ESTHETICS FOR CONVENTIONAL COMPLETE DENTURE PROSTHESIS

The subject of esthetic should be examined from three points of view. These are:- (i) The biological-physiological (ii) The biomechanical (iii) Psychological view point

BIOLOGICAL-PHISIOLOGICAL:-

It is necessary to have an understanding of facial musculature, normal facial appearance, and the physiological limits, or parameters, within which esthetic compromises are to be made. A proper impression procedure is necessary to provide the dentist with a final maxillary cast that has an accurate representation of the labial vestibule and all the other remaining structures. This is to be followed by the fabrication of a maxillary recording base that fits the cast as closely as possible so that the trial base does not stand too far away from the cast. When excessive relief of the cast for blocking out the labial undercut is utilized in fabricating the trial base, it tends to push the lip at the height of the vestibule. This tends to distort the appearance of the maxillary lip, foreshortening it and making it bulge. This may lead to the choice of shorter tooth, or placement of maxillary centrals too high. The result will be that when the denture is complete and the final denture base is closely adapted to tissue, the maxillary anterior teeth will show less than originally intended by the dentist. This is because the properly contoured labial flange will not cause the lip to bulge, and the lip will suddenly appear to have lengthened. The dentist should also have a visual concept of the cause-and-effect relationship. For example, if an edentulous patient has a tight, drawn, purse-stringed appearance of the lips, then proper support with a fully formed occlusal rim, and lip support by the labial two thirds of the artificial teeth, should evert the vermilion of the lip. This would afford a much more important in females, because of the use of lipstick which accentuates the thickness or fullness of the lips. As the patient become older, there are natural lines on the face that tend to deepen and to accentuated. Since the majority of edentulous patients are found within the older age group, it is to be remembered that there is a loss of elasticity of the facial musculature. There is a tendency to want to “plump out” the face with additional thickness of denture base material. This is usually counterproductive unless the musculature is almost totally flaccid otherwise, the musculature tends to act to loosen the denture, or the facial appearance becomes strained. Another approach to removing facial wrinkles is to increase the vertical dimension. This approach is fraught with the greatest of dangers and must be used with caution. It is true that the facial appearance will be better, but the ability to function, patient comfort, and the long range health of the residual alveolar ridges will frequently be adversely affected. It may also cause a “clicking sound” during speech. Indeed, the actual process of trail placement of the maxillary anterior teeth, and the function of the maxillary and mandibular anteriors during the production of speech, afford one of the best guidelines for creating and monitoring an adequate interocclusal distance, or freeway space. If it is necessary to place maxillary anterior somewhat lower for esthetic reasons, then the following procedure should be followed:- 1. The lower anterior should be placed lower in order to maintain an adequate interarch space. This will usually also necessitate a lowering of the occlusal plane posteriorly. This will have the effect of placing the teeth closer to the mandibular ridge, which should aid in lending stability to the mandibular denture. 2. The maxillary teeth should moved slightly more anteriorly at the incisal edges so that there will be sufficient clearance in protrusion. Tilting the incisal edges of the mandibular incisors lingually should be avoided. According to Muyskems “ for every 1mm the incisal edges of the mandibular anterior teeth are posterior to their normal arrangement, the tongue is deprived of approximately 100mm cubic space in which to function.”

BIOMECHANICAL:-

There are certain mechanical limitations in the placement of anterior teeth that must be taken into account. A primary question about placement that is always asked is “on the ridge?” or “how far off the ridge?” A general answer is that we should place the anterior teeth as closely in relation to the residual ridges as were the original natural teeth. Fish states, “in the upper jaw, there is no exception to the rule of replacing the natural teeth by setting the artificial ones in exactly the same relation to the body of the maxillae unless the patient’s appearance will be improved by some slight modification.” However, Fish also says, “the proper position for the teeth is not necessarily on the ridge or outside the ridge but at a point where the tongue and cheek pressures balance.”

PSYCHOLOGICAL:-

Esthetics concerns itself with more than just oral or facial appearance. The patient’s self-image is also an important factor. A patient’s perception of his or her appearance may result in a broad smile (if it is positive self evaluation) or a tight-lipped, small controlled smile. In the latter case, the patient’s own doubts and dissatisfaction about his or her appearance result in the patient conveying these feelings to others. A patient with a poor self-image, may appear gloomy, unsure, hesitant, questioning, reticent and introverted. A patient with a more positive feeling tends to smile more broadly. The smile is important because it is really the frame that enhances the picture, the picture being the dentures. Indeed, camper’s line may be thought of as a psychological plane of orientation. In the case of a vain person, or a person who appears happy the plane tends to rise; however, in a person who is depressed or discouraged, it may slant downward. The position of the plane of orientation or occlusal plane, established by the dentist, has, to a certain extent, an effect in determining the appearance of patient’s psychological state. For example by effecting downward slant to the plane posteriorly an observer may gain a negative impression of the patient’s emotional or psychological state. Thus, in this case, the dentures would detract from, rather than enhance the appearance of a patient who may, in reality, be a very happy person. “It must be constantly borne in mind that the incisal line, the occlusal plane and the vertical dimension are determined by the dynamics of function and not by any particular static relationship.”

SELECTION OF ANTERIOR TEETH.

Esthetics play major role in selection of anterior teeth. Artificial teeth are manufactured in a variety of shapes, sizes and colors. Teeth are manufactured in molds. All the teeth from a particular mold will have the same size and shape. The shade vary depending on the color of the material packed into the mold. Different patients require different shapes, size and color of artificial teeth. Therefore one must know the various criteria in order to select the right mold for the patient from the huge variety that are available. SELECTION CRITERIA FOR ANTERIOR TEETH:-

* Selection of tooth size * Selection of tooth shape and form * Selection of tooth color * Selection of tooth material

Selection of tooth size:- Size has 3 dimensions; a) Height (occlusogingival) b) Width (mesiodistal) c) Thickness (faciolingual) The thickness is less significant for teeth selection. The tooth size should be appropriate to the size of the face and sex of the patient.

The following methods are used as guide to select size of teeth.

(I) Pre-extraction guides: Pre-extraction guides when present are very useful in the selection of artificial teeth. These include: (i) Diagnostic casts (ii) Photographs (iii) Radiographs (iv) Extracted teeth (v) Old dentures

(i) Diagnostic casts:- Diagnostic casts of the patient’s natural or restored teeth prior to extraction of the remaining teeth are the most reliable guides in the selection of size and form, but the shade of the teeth cannot be determined. (ii) Photographs:- Their usefulness can vary depending on the extent the teeth are visible. They may provide information on width of the teeth and form (rarely on color). By measuring and comparing a known distance on the patient’s face and in the photograph, the teeth width can be calculated. (iii) Radiographs:- They can supply useful information about the size and form. However, we must compensate for the slight enlargement and distortion inherent in radiographs. (iv) Extracted teeth:- Sometimes patient’s may possess extracted teeth. They are excellent guides on size and form (though not on color). (v) Old dentures:- These are sometimes useful, especially if they are immediate dentures. However old dentures must always be reassessed, as the original selection might not have been the best one.

(II) Post-extraction methods: If the patient is edentulous and wearing complete dentures, examine the patient with the dentures he presently wears, paying attention to the following:- (i) Do the teeth appear lost in the face (too small or set too far in)? (ii) Do the teeth appear too small, regular and set like a picket fence? (iii) Are the teeth set too high, and are they almost lost from view during speaking and smiling? (iv) Are the teeth overbearing, too large, out of proportion in their length and breadth to the size and dimension of the face and head? (v) Do the maxillary teeth show in smiling, and the mandibular teeth during speech?

All these observations should be used in arriving at a determination of which teeth should be selected for the trial denture. On the basis of the teeth the patient is wearing, determine whether to choose teeth that are larger or smaller, longer or shorter, wider or narrower, flatter or having a more curved labial surface.

Many authors suggest using the measurement of the bizygomatic width and dividing the measurement by 16 to arrive at an estimate of the width of the maxillary central incisor. A face-bow may be utilized to obtain this measurement. This measurement may be divided by 3.3 to arrive at the approximate width of the six anterior teeth arranged on the curve of the properly contoured occlusal rim.

Pound evaluates tooth width by “measuring the distance from zygoma to zygoma, one to one and one half inches back to the lateral corner of the eyes.” Length is a measure of the distance from the hairline to the lower edge of the bone to the chin with the face at rest. These measurements are by 16, and indicate the length and width of the central incisor.

Pound’s formula:- Width of maxillary central incisor = Bi-zygomatic width 16

Selection of teeth shape and form:-

Form refers primarily to the outline of anything and shape is the quality of the thing that depends on the relative position of all points composing its outline.
The shape of the teeth is an important consideration in denture esthetics. The dentist must select a tooth form that is in harmony with the face as well as personality of the patient. Tooth form is probably more difficult to decide upon than tooth size, especially when there are absolutely no pre-extraction guides.

Soon after the introduction of porcelain anterior teeth it was realized that there was some relationship between the shape of the edentulous upper arch and the upper teeth. For example, a ‘V’ shaped arch is associated with incisors which are narrower at the neck than at the incisal edges; a square-like arch with almost parallel-sided incisors; and a round arch with ovoid teeth. (Fig.)

To date, no universally reliable method of determining tooth form has been found. The Williams classification (1914) is the most universally accepted method of determining anterior tooth form.
The theory of matching teeth to face forms, which have generally square, tapering, or ovoid characteristics, was advanced by J. Leon Williams (1914).

Classification of Williams

The classification of Leon Williams though not scientifically correct, is undoubtedly the simplest and most useful guide yet suggested, with the added advantage that most manufacturers of artificial teeth have adopted it for their products. He claimed that the shape of the upper central incisors bears a definite relationship to the shape of the face. Thus, if one of these teeth were enlarged, and the incisal edge placed above the brows with the neck of the tooth on the chin, then the outline nearly coincide with that of the face. (fig. a). He classified the form of the human face, for simplicity into three types: square, tapering and ovoid. Each type merging into the others without any clear line of demarcation. In order to determine to what type an individual belongs the clinician imagines two lines, one on either side of the face, running about 2.5cm infront of the tragus of the ear and through the angle of the jaw. If these lines are almost parallel, the type is square; if they converge towards the chin, the type is tapering; and if they diverge at the chin, the type is ovoid. (fig. b)

Fig. a

Fig. b

FORM OF ANTERIOR TEETH

The form of the face and the form of natural teeth are so varied that it would be impossible to develop a system of geometric figures that would be adequate for all individuals. In nature the most pleasing appearing sights or objects are those whose form is in harmony with the surrounding environment. A lack of harmony presents a contrast, and a marked contrast is not always pleasing. Artificial teeth will not present a pleasing appearance if they draw attention away from the surrounding environment. The form of a tooth should conform to the contour of the face as considered from the labial, mesial, distal and incisal aspects. The general outline of the tooth should conform to the general outline of the face when viewed from the frontal aspect. A tooth viewed from the mesial or distal should conform to the contour of the profile. The geometric figures- square, tapering, ovoid and combinations thereof serve as a starting point in selecting the tooth form as it is viewed from the frontal aspect. (fig. A).

The TRUBYTE tooth indicator may be used in one of two ways to establish the facial form. a. Place the tooth indicator on the patient’s face, allowing the nose to come through the central triangle. Centre the pupils of the eye in the eyes slots and hold the indicator with its centre lines coinciding with the median line of the face. The form of the face will be best observe by noting the particular characteristic of each form as it appears in comparison with the vertical lines of the indicator. In the square form the sides of the face will approximately follow the vertical lines of the indicator. In the square tapering form, the upper third of the lower two thirds will taper inward. In tapering faces, the side of the face from the forehead to the angle of the jaw will taper at an inward diagonal. Ovoid faces will be best determined by examination of the curved outline of the face against the straight vertical of the tooth indicator. (fig. A ) b. To determine the facial profile, observe the relative straightness or curvature of the profile. Check three points; the forehead, the base of the nose, and the point of the chin. If these three points are in line, the profile is straight. If the points of the forehead and of the chin are recessive, the profile is curved. (fig. B )

In addition, it was suggested that the labial curvature of the teeth be in harmony with frontal curvature of the face. Sharry states, “this approach to the problem, although scientifically unsound, was used by many tooth manufacturers and is, perhaps, the basis of tooth selection most often used today.

The form or shape of the teeth differs in males and females. The difference in the shape of the anterior teeth in males and females are:- * In females the incisal angles are more rounded and the teeth have a lesser angulations. In males, the incisal angles are rounded to a lesser degree and the teeth are more angular * The incisal edge of the central incisors is parallel to the lips and the laterals are above the occlusal plane in males. But the incisal edges of the central and lateral incisors follow the curve of the lower lip in females. * The mesial surface of the lateral incisors are rotated anteriorly in relation to the centrals in females. * In males the incisal end of the laterals are hidden by the centrals. This makes the canine very prominent in males. * Females on smiling expose more anterior teeth hence, the premolar should be arranged based on esthetics for females.

Selection of tooth color:-

Color is another important quality for the selection of artificial teeth and like the size and shape it has to be selected by the dentist and approved by the patient.

Properties of color:- Color is recognized by the human eye when a light of a particular wavelength is reflected off an object. A color can be described under four parameters:- (i) Hue (ii) Saturation or chroma (iii) Brilliance or value (iv) Translucency

(i) Hue: - It denotes a specific color produced by a specific wavelength of light. It should be in harmony with the patient’s skin color or else it will produce an artificial look for the denture. (ii) Saturation or chroma:- It is the amount of color per unit area of an object. In other words, it denotes the intensity of the color. Objects with highly saturated colors lack depth. (iii) Brilliance or value:- It denotes the lightness or darkness of an object. It is actually the dilution of the color with either black or white to produce darker or lighter shades respectively. In people with light skin color, teeth with lighter shades should be chosen on vice-versa. (iv) Translucency:- It is the property of the object to partially allow passage of light through it. Enamel has high brilliance and translucency, hence, artificial teeth should also show the same properties for a natural appearance.

Color of natural teeth:- Most natural teeth have the same hue which is basically yellow. However, the chroma and value can vary with age, race, position in the arch, intrinsic and extrinsic staining etc. Teeth get progressively darker with age. Young teeth have larger pulp chambers. The red color of the pulp effects the color of the tooth. As the tooth ages there is deposition of secondary dentine making the tooth more saturated and opaque. All the teeth do not have same color. The color varies from tooth to tooth. Studies have confirmed that the canines are darker than the incisors.

Pre-extraction guides:-

Photographs of teeth can give an idea of color variation within the tooth, stains and other defects which is useful if the patient wishes to be duplicated. Some patients may present old extracted teeth. Extracted teeth changes color with time. They lighten with time. They cannot be relied upon for the exact shade. However, they might provide information on stains and other features that the patient might want replicated. Although scientifically no correlation has been proven, skin color is more commonly used to select tooth color. The tooth color should not be too conspicuous on the face. This would attract attention to the teeth. The tooth color should be in harmony with the face color. Fair skinned individuals can be given lighter shades.

Techniques of color selection:- A shade guide is used to select the color. The color is selected in three positions:- 1. Outside the mouth along the side of the nose. 2. Beneath the lips with only incisal edge showing. 3. Beneath the lips with only the cervical third covered and most of the teeth exposed.

The first step establishes the basic color. The second step simulates the tooth exposure when the mouth is relaxed. The third reveals the tooth as in a smile. The color selection should be done in bright daylight, preferably near a source of natural light like a window. Bright makeup or lipstick may distract during color selection and must be removed. Color selection must be made as quickly as possible, prolonging the process might fatigue and confuse the eyes.

Selection of tooth material:-

The most commonly used material for artificial teeth is acrylic resin primarily because of their low cost and ease of use. The other choice is porcelain teeth. They are more esthetic and durable, but they are technically more difficult to use. A combination of acrylic and porcelain teeth may also be used.

Material for artificial teeth:- Based on the material used different teeth may be selected; 1. Acrylic teeth 2. Porcelain teeth 3. Porcelain acrylic combination scheme 4. Acrylic teeth with amalgam inserts 5. Acrylic teeth with cast gold occlusal surface

Acrylic resin teeth:- Acrylic is perhaps the most widely used tooth material for complete dentures. The modern acrylic teeth available are cross-linked to improve strength and hardness. Advantages of acrylic teeth:- 1. Inexpensive and easily available 2. Easy to grind and adjust especially in small inter-ridge spaces. 3. Absorbs occlusal stresses. 4. Does not wear opposing natural teeth and gold crowns 5. Bonds chemically to denture resin. 6. Softer impact sound. Disadvantages of acrylic teeth:- 1. Wears easily 2. Vertical dimension may be lost because of wear. 3. Stains and discolors with time. 4. Loss of comminuting efficiency with time.

Porcelain teeth:- Porcelain teeth do not bond chemically to the denture base rather they are mechanically retained to the base material with the help of pins or channel within the teeth. Acrylic enters these channels and locks it mechanically to the denture base.

Indications:- 1. When sufficient inter-ridge space is available. 2. Well formed ridges 3. When superior esthetics is required

Advantages:- 1. Very esthetic 2. Does not stain or discolor easily 3. Does not wear easily 4. Maintains vertical dimension for years 5. Maintains masticating/comminuting efficiency for years. 6. Can be reused through rebasing

Disadvantages:- 1. Clicking sound on impact 2. Difficult to grind and adjust 3. Requires adequate inter-ridge distance 4. Abrades or chips opposing natural teeth 5. Abrades opposing gold crowns 6. Does not form a chemical bond to the denture base 7. Being brittle, it may chip off or fracture occasionally

ANTERIOR TOOTH ARRANGEMENT AND PLACEMENT

Payne states, “set the teeth where they grew.” (Fig.1) shows the pattern of alveolar resorption that takes place in the anterior region. With this as a guide, it is possible to more closely place the artificial tooth in approximately the position that it was in the patient’s natural dentition.

Fig. 1

The use of phonetics as a guide also aids in the placement of the maxillary anteriors. The incisal edges should be positioned so that the ‘f’, ‘v’, and ‘ph’ sounds can be correctly pronounced. (Fig.2)

Fig. 2

The ‘s’, ‘z’ and ‘c’ sounds are an aid in determining proper tooth placement and the interrelationship of phonetics and vertical dimension (fig.3). If the occlusal dimension is too great, the teeth will come together prematurely, and they will ‘click’. Thus, have the patient count 61-67, and observe whether the anterior teeth come in contact during connected speech while pronouncing the ‘s’ sound. If the teeth contact, the vertical dimension is too great and there is insufficient interocclusal distance.

Fig. 3

It is also necessary to pay attention to the horizontal and vertical occlusal relationship (Fig.4). The vertical and horizontal overlap of the anterior teeth are to be correlated with the type of posterior occlusion that is chosen for an individual case.

Fig. 4

Schiffman has shown that the maxillary incisors fall approximately 8-10mm anterior to the point of intersection of a line that bisects the midline of the palate perpendicularly through the incisive papilla. (Fig.5). This perpendicular bisecting line also extends outward approximately through the midline of the maxillary canines. The labial incisal angle of the incisors should be placed so that the lip is supported by the plane of the labial two thirds of the surface of the incisors. (Fig.6)

Fig. 5

Fig. 6

Consideration must also be given to choosing a first maxillary premolar that is of sufficient occlusogingival length so that there will not be an obvious display of denture base material upon smiling, or for patients with a high lip line. In a sense, the first premolar can be considered an anterior teeth from esthetic viewpoint.

PRINCIPLES OF TEETH ARRANGEMENT

Each tooth is attached/luted/sealed to the occlusal rim based on the following principles.

MAXILLARY CENTRAL INCISORS: (a) The long axis of the tooth is parallel to the vertical axis when viewed from the front. (b) The long axis of the tooth is sloping labially when viewed from the side. (c) The incisal edge of the tooth evenly contacts the occlusal plane.

MAXILLARY LATERAL INCISORS: (a) The long axis of the teeth is tilted towards the middle when viewed from the front. (b) The long axis of the tooth is sloping labially when viewed from the side. The inclination of the slope is greater than that of the central incisor. (c) The incisal edge is 2mm above the level of the occlusal plane and the edge is tilted towards the midline.

MAXILLARY CANINE: (a) The long axis of the tooth is parallel to the vertical axis when viewed from the front. A mild mesial tilt is supposed to improve its esthetics (b) The long axis of the tooth is parallel to the vertical axis when viewed from the side. (c) The cuspal tip of the canine touches the plane of occlusion. (d) The cervical third of the canine should be more prominent than the cuspal third.

MANDIBULAR CENTRAL INCISOR: (a) The long axis of the tooth is parallel to the vertical axis when viewed from the front. (b) The long axis of the tooth slopes slightly labially when viewed from the side. (c) The incisal edge of the tooth should be 2mm above the plane of occlusion.

MANDIBULAR LATERAL INCISOR: (a) The long axis of the tooth is parallel to the vertical axis when viewed from the front. (b) The long axis of the tooth slopes slightly labially when viewed from the side but not so steeply as the central incisor. (c) The incisal edge of the tooth should be 2mm above the plane of occlusion.

MANDIBULAR CANINE: (a) The long axis of the tooth is very slightly tilted lingually when viewed from the front (b) The long axis of the tooth slopes slightly mesially when viewed from the side (c) The canine tip is slightly more than above 2mm above the occlusal plane. (d)

GUIDELINES FOR TOOTH ARRANGEMENT AND PLACEMENT FOR ANTERIOR TEETH

Frontal view: (a) Parallel to the interpupillary line (b) Incisal edge of maxillary incisors: 1-2mm below maxillary lip at rest (c) No bulging should be evident under the nostrils (d) Philtrum should be restored if possible (e) Full vermilion border of lip should be seen (f) “Smile line”(maxillary incisal edges) should follow the line of the lower lip on smiling

Sagittal view: (a) Upper lip should be everted and not fallen in (b) Tooth support of the lip is by two third of the incisal labial surface of the anteriors.

Horizontal view: (a) Central incisors should be 8-10mm anterior to the midpoint of the incisive papilla (b) Canines are on a line drawn perpendicular to the midline of the palate, through the centre of the incisive papilla.

EVALUATION OF ESTHETICS

The evaluation of esthetics is very important as this is probably one of the foremost criteria of acceptance by the patient. All the esthetic adjustments and attraction made during the various stages of denture construction are once again evaluated. This includes evaluation of the lips and mouth and the teeth. (a) Evaluation of lip support and fullness: The patient is viewed from the front and from the side with the lips draped normally over the denture. Under extension, overextension, excess flange thickness, increased vertical dimension and improper tooth positioning can cause facial changes. Some of the signs a dentist should look for are:- * signs of facial strain * excess fullness of the lips * inadequate lip support * does the patient have a ‘cotton roll under the lip appearance’? * are the angles of the mouth turned downward? * Is the philtrum obliterated? * Inadequate visibility of the vermilion borders of the lip. * Inadequate support of the cheeks * Does the chin look too close to the nose? Excess flange thickness can obliterate the philtrum giving a typical cotton roll under the lip appearance. In this case, the flanges may be thinned by trimming. Signs of strain on the face- if the patient is straining to close his lips, the vertical dimension could be excessive. An increase vertical dimension could be corrected to some extend by returning it to the articulator and selectively grinding the teeth. Signs of reduced vertical dimension of occlusion- include wrinkling of the lips, chin looks too close to the nose and a downward curve of the corners of the mouth. Excessive fullness of the lips can be because the teeth are placed too far forward. Inadequate lip support can be because the teeth are placed too lingually. The vermilion border of the lips look too thin and subdued. (b) Evaluation of the teeth:
Tooth size, color and position are once again assessed, tooth visibility is checked when the patient talks and smiles. The buccal corridor is assessed. The curvature of the teeth in relation of the curvature of the smile is assessed.

CONCLUSION

The alteration of appearance is a normal consequence of aging. Tissues atrophy, the folds and creases of the face become exaggerated. The loss of teeth intensifies the change. The muscles are no longer properly supported, which results in abnormal facial expressions. The loss of the residual ridge alters total face height and may give the appearance of prognathism. The selection of the proper mold and shade of denture teeth is but one part of denture esthetics. Compensating the lost of alveolar bone, correctly positioning anterior teeth for tissue support and re-establishing the correct vertical dimension of occlusion, in combination with proper tooth selection creates good entire esthetics. Proper contour and normal physiologic movement of the muscles enhances an esthetic denture, whereas improper support is severely detract from it. Even though denture construction requires a step by step progression, these steps cannot be isolated but rather must be integrated to produce an optimal result. Aesthetic is of supreme importance to a patient and where this is the case, the operator must be prepared to devote extra time and care to this part of denture construction.

BIBLIOGRAPHY 1. Sheldon Winkler: Essentials of complete denture prosthodontics, second editon, 2004. 2. Zarb. Bolender: Prosthodontic treatment for edentulous patients, twelfth edition, 2004. 3. John Joy Manappallil : Complete denture prosthodontics, first edition, 2006. 4. Charles M. Heartwell, Arthur O. Rahn : Syllabus of complete dentures, fourth edition, 1992. 5. A. Roy Macgregor : Clinical dental prosthetics, third edition, 1994.