OF ARTIFICIAL TEETH FOR COMPLETELY SELECTION OF ARTIFICIAL TEETH FOR COMPLETELY EDENTULOUS PATIENTS Prof.Dr. Ahlam El-Sharkawy Head of prosthodontic departement Pharos University in Alexandria

Introduction The anterior teeth are primarily selected to satisfy the esthetic requirement , where as the posterior teeth are primarily selected to satisfy the functional requirements . The anterior teeth are composed of six maxillary and six mandibular teeth.

OBJECTIVES FOR TOOTH SELECTION TO CONSTRUCT THE COMPLETE DENTURE THAT………… 1. FUNCTION WELL EFFICIENT FOR MASTICATION. 2. ALLOW PATIENT TO SPEAK NORMALLY. 3. ESTHETICALLY PLEASING. 4. PRESERVE TISSUE STRUCTURES OF THE GNATHODYNAMIC SYSTEM 5. SHOULD MAINTAIN THE VERTICAL DIMENSION

Selection of anterior teeth

Anterior teeth selection Guides for the anterior teeth selection Pre-extraction guides Study cast Photographs Radiographs Extracted teeth Old denture.

If the pre-extraction records are not available systematic procedure can be followed to select the teeth which will harmonize with the patient’s facial characteristics

Maxillary anterior teeth Selection Size Shape (Form) Shade (color).

Selection of size Width Length.

Width of the anterior teeth

a. Bizygomatic distance The average width of the maxillary central incisor is estimated to be 1:16 of the bizygomatic width Bizygomatic width the distance between the cheek bones measured just in front of the ears.

a. Bizygomatic distance The combined width of the six maxillary anteriors is about one third the bizygomatic width.

b. The width of the nose An estimation of the position of cusp tip of the upper natural canine can be found by extending parallel lines from the lateral surface of the ala of the nose onto the labial surface of the upper occlusion rim.

c. Corners of the mouth The distance measured between the two commisures (angles of the mouth ) will represent the width of the upper six anteriors from the distal surface of the canine to the distal surface of the other canine.

Corners of the Mouth Mark corners at rest (#7 wax spatula) Position of distal of the canines

Length The necks of the upper anterior teeth overlap the anterior ridge by 2-3 mm cervically, and the incisive edges of the centrals must show below the relaxed lip by 2-3 mm in a young person and less than half that amount in an elderly patient.

Amount of tooth shown About 2 mm of teeth are shown when lip is relaxed.

High Lip Line Highest point of upper lip when smiling Cervical necks lie at or above this line If shorter teeth are selected, esthetics compromised

Guidelines for Setting Anterior Teeth High Lip Line Corner of Mouth Angulation is as important as midline

FORM OF THE ANTERIOR TEETH . The guides for selecting the form of anterior teeth : 1- Shape of the face. 2- Shape of the arch.

1-The shape of the face . According to Leon Williams classification the human face has been classified into Three types Square Tapering Ovoid

SQUARE , OVOID , TAPERING FORMS

The shape of the maxillary central incisor coincides with the inverted form of the face

Selection of the form Shape of the face. It was claimed that the shape of the upper central incisor bears a definite relationship to the shape of the face. Thus if one of these teeth is enlarged and the incisal edge placed above the brows with the neck of the tooth on the chin, then the outline of the tooth would nearly coincide with that of the face.

SQUARE Facial form - the width of the forehead, zygomatic arch and mandibular angle is equal. Profile - straight and flat ala area Incisal form - mesial and distal lines are almost parallel till the length of 2/3rd from incisal edge.

ovoid Facial form - width of zygomatic arch is wider than the distance of forehead. Profile - ovoid ala area Incisal form - mesial and distal lines are curved.

Tapering Facial form - the width becomes narrow from forehead towards the zygomatic arch and mandibular angle. Profile - curved or flat Incisal form - mesial and distal lines become narrow from incisal edge to cervical end.

Selection of the form 2-Shape of the arch.

Patient’s sex and age: A cuboidal tooth form is required for the males A spheroidal form for the females. Teeth for males should have a less convexity than for females. The incisal edge of older patient is flat to resemble attrition of natural teeth.

Dentogenic concept (SPA) Sex, personality, age are the factors which will determine the form of the anterior teeth

Personality The dentist should select and arrange teeth so that it improves the patient’s personality. The patient can be vigorous ore delicat. More squarish and large teeth are selected for vigorous people

Feminine MUSCULINE Prominent teeth Smaller teeth Large sized teeth Square arch form Square labial surface Square incisal edges and corners Darker shade Flat smiling line Canine – cervical area is more visible and prominent Feminine Smaller teeth Round corners Curved contours & arch form Curved labial surface Round incisal edges and corners Delicate appearance Curved smiling line Canine – mesial 3rd only seen

Age Younger people Older people Lighter shade More incisal translucency Minimal wear of incisal edge Curved smiling line Pointed canines Older people Darker shade Less incisal translucency increased wear of incisal edges Flat smiling line Loss of tips of canine

Check Shade Against the Patients Face Check shade of existing denture Ask if patient wants same shade or change Allow patient to view shade against lip with mirror Obtain patient approval

Patients age – With age, darker, while lighter teeth are suitable for young patients. Patients complexion—light teeth for fair skin, blue eyes, dark teeth usually for dark skin and black eyes.

The anterior teeth from the lightest to the darkest Upper central incisor The upper lateral The lower central and lateral The upper and lower canines are the darker.

II-Selection of posterior teeth

1-Size of posterior denture teeth a-Length: This is determined by the amount of denture space available between the upper and lower ridges.

b-Width From distal of canine to the tuberosity in the maxillary denture, and to the retromolar periphery of the lower denture. The teeth with a narrower buccolingual width than the natural teeth are selected.

Posterior Tooth Selection Buccolingual size can affect the tongue space smaller teeth if tongue space is limited

Posterior teeth selection Posterior teeth should have a small bucco-lingual width to keep forces on the supporting structure to a minimum. The mesiodistal measurements of the upper posterior teeth is taken from the distal surface of the canine to the prominence of the tuberosity. The lower posterior teeth should not extend posterior to the mesial border of the retromolar pad.

2-Form of the occlusal surface (Mould or shape) Cusp angle :the angle made by the slope of the cusp with the cusp plane

Cusp Height : The perpendicular distance between the tip of the cusp and its base plane

Anatomic Teeth (10°, 20°, 30°, 40°) 10° 20° 30°

Cusped Teeth (Anatomic teeth) have 30-35 cusp angle Indicated when there is a well defined ridge and normal jaw relations.

Advantages of anatomic teeth 1. Esthetically acceptable 2. More efficient in cutting of food, thereby reducing forces that are directed to the supporting structures during masticatory movement. 3. They can be arranged in balances occlusion

Disadvantages of anatomic teeth 1. It is mandatory to use an adjustable articulator. 2. Eccentric records must be done for articulator adjustments 3. Clinical remount is essential to adjust the occlusion after denture settling. 4. Balanced occlusion lost when settling occurs. 5. More horizontal forces during functions. 6. Frequent relining, Fast bone resorption

Flat or Inverted Cusped Teeth Have zero cusp angle with grooves to aid mastication

Non-Anatomic Teeth (0°, Rational, Monoline, etc.) Jaw size discrepancies (Class III) Severe ridge resorption Poorer esthetics, due to lack of cuspal inclines

Indications of flat plane teeth 1-In class II and III jaw relations. 2- patients with temporomandibular joint disorders. 3-In case of atrophic alveolar ridge. 4-In the presence of hyper mobile gingival tissues (flabby ridge).

Disadvantages of flat plane teeth a) Reduced masticatory efficiency. b) Poor appearance. c) Food may become packed into the depression of teeth. d) It is very difficult to obtain balance. .

3-shade (color) The same shade as the canines should normally be used one or two shades darker.

Tooth material Artificial teeth for complete denture are either acrylic teeth or porcelain teeth

Denture Tooth Material Porcelain teeth less common now Acrylic easier to set and adjust

Comparison between acrylic and porcelain teeth 1-Hardness and abrasion resistance: Porcelain teeth are harder and more resistant to wear.

2-Aesthetics the appearance of porcelain teeth had a better reputation than the acrylic teeth. The porcelain teeth will not have stains, while acrylic teeth can be stained

3-Retenion to denture base The bonding of porcelain teeth to the denture base is purely mechanical. This by pins on anterior teeth and holes in posteriors Retention of acrylic teeth to denture base is chemical.

4-Thermal expansion The coefficient of thermal expansion of porcelain is much lower than acrylic resin which my results in cracking of acrylic base. The coefficient thermal expansion of acrylic teeth is the same as acrylic denture base.

5-Adjustment Porcelain is more difficult to grind and difficult to polish Acrylic can be ground and easily polished.

6-Density Acrylic teeth are lighter in weight

7-Impact strength The impact strength of acrylic teeth is greater than that of porcelain. So acrylics may be used in cases of close anterior occlusion.

8-In service Acrylic teeth transmit less force to the mucosa. On contact with the opposing teeth, acrylic teeth are less noisy. While With Porcelain teeth, clicking occurs on contact with the opposing teeth.

Acrylic teeth are used in the following situations 1. Limited inter-arch distance 2. Maxillary single denture against natural dentition. 3. Maxillary single denture opposing partial denture 4. Opposing natural teeth with gold occlusal surfaces

Denture Tooth Material Acrylic New acrylics wear better Improved translucency with layers More resilient - Less breakage Chemically bonds to base Quieter Easier to set/adjust Gum sticks Porcelain Less wear More translucent Brittle - fracture easily Don’t bond to base (stain, fall out) Difficult to set, adjust

Porcelain teeth - Wear is clinically insignificant over a long period of time - No significant loss vertical dimension - Difficult to grind and fit into a close inter-ridge space - Cause dangerous abrasion to opposing gold crown and natural teeth. - Have a sharp impact sound - Will not bond to the base material except with mechanical means. The anterior porcelain teeth have pins at the back, while the posteriors have holes.

Acrylic resin teeth - Wear is clinically significant - Loss of occlusal vertical dimension due to wear. - Occlusal surface is altered by wear. - Do not chip, and have softer impact sounds - Easy to adjust and polish - Easy to grind into close inter ridge space - Will bond to base material by chemical union. - Minimal wear to opposing natural teeth and gold crowns. This is a definite indication for their use

The following facts are true for nearly all natural teeth: The neck of the tooth has a more pronounced color than the incisive edge. The incisive edge if not worn, is more translucent than the body of the tooth and is usually of a bluish shade (composed entirely of enamel) The upper central incisors are lightest teeth in the mouth followed by the laterals and canines. Posterior teeth are usually uniform in color. Teeth darken slightly with age.

Advantages of non anatomic teeth 1. Comfortable 2. The allow greater range of movements which is necessary in patients with mal-related jaws (as those with Para functional jaw habits ). 3. Non anatomic teeth exerts less horizontal or torquing forces, so they are used with flat ridge cases. 4. Centric record only is needed.

Non-Anatomic Teeth No overbite Normal overjet (1-2mm)