Selection of Artificial Teeth 2024 PDF

Selection of Artificial Teeth  Terminology Cusp angle The angle made by the average slope of a cusp with the cusp plane measured mesio-distal or bucco-lingual Cusp height The perpendicular distance between the tip of a cusp and its base plane Selection of anterior teeth  Objective:...

Selection of Artificial Teeth  Terminology Cusp angle The angle made by the average slope of a cusp with the cusp plane measured mesio-distal or bucco-lingual Cusp height The perpendicular distance between the tip of a cusp and its base plane Selection of anterior teeth  Objective: To restore the natural appearance of the face by replacing missing natural teeth with artificial teeth.  Factors that are considered in selection of anterior teeth I- Shade (color) of the teeth For the selection of the color of the anterior teeth a shade guide is used Factors affecting the selection of a tooth shade 1- Age of the patient - Darker with age as the pulp chamber becomes opaque with age - With abrasion of teeth a- loss of the translucency of enamel b- dentine picks up stains from oral fluids, food and tobacco 2- Patient’s complexion - Color of the face: light teeth for light skin and blue eyes, dark teeth for dark skin and eyes 3- Patients’ personal approval Dr. Wafaa Ibrahim Characteristics of natural teeth - The neck of the tooth has a more pronounced color than the incisive edge - The incisive edge : more translucent than the body - The lightest teeth in the mouth: centralslateralscanines II- Tooth Shape (Form) Factors affecting the selection of the shape of the teeth 1- Shape of the arch - The shape of the teeth should be in harmony with the shape of the arch (square, tapered and ovoid) 2- Shape of the face - The shape of the upper central incisors should be in harmony with the shape of the inverted form of the face. The incisive edge above the brows. The neck of the tooth  the chin How to determine the type of face? Two lines are drawn on either sides of the face 2.5 cm in front of the tragus of the ear through the angle of the jaws  If parallel square  If converge toward the chin ovoid or tapering 3- Effect of gender & age on tooth form Males usually have sharper line angles compared to females Old patients have a rather straight incisal edge to simulate the effect of attrition Dr. Wafaa Ibrahim III- Size of the teeth The size of the teeth comprises their width and length Factors to be considered in the selection of tooth size A- BL width  Phonetics B- MD width  Esthetics C- Length  Esthetics a- Width: Width of the six maxillary anteriors is slightly less than one third of the bizygomatic width which is the distance between the cheek bones measured just in front of the ears. The width of the natural central incisor is approximately 1/16 the bizygomatic width of the patient’s face A vertical line extending along the lateral surface of the ala often will pass through the middle of the natural upper canine Distance between the 2 commisures (angle of the mouth) = MD width of the six anterior teeth The incisive edges of the centrals must show 2-3 mm in a young person and less than half that amount in old age Dr. Wafaa Ibrahim b- Length - Determined by the high lip line. - The amount of upper teeth shown below the upper lip depends on: 1- Length of the upper lip (short or long lip) 2- Mobility of the upper lip 3- Age of the patient - The incisive edges of the centrals must show 2-3 mm in a young person and less than half that amount in old age - Length of face/Width of face=Length of the tooth/Width of the tooth - In large interridge space  use longer teeth to eliminate the display of the denture base. Size of anterior teeth depends on 1- Pre-extraction records Photographs Radiographs Previous dental prosthesis Pre-extraction casts and shade determination. Extracted teeth 2- Proper contoured occlusal rims 3- High lip line 4- Arch form and size Selection of posterior teeth a- Shade - Shade is the same as anterior teeth b- Size Mesio-distal width Dr. Wafaa Ibrahim  Mesio-distal width in the mandibular arch: use a ruler to mark the crest of the mandibular ridge from the base of the retromolar pad to the canine area Mesio-distal width in the maxillary arch: use a ruler to mark the crest of the maxillary ridge till the beginning of the maxillary tuberosity. Bucco-lingual width Should have a small bucco-lingual width to decrease the forces on the supporting structures and are more efficient. Occluso-gingival height (long-medium-short)  Depends on the inter ridge distance C- Occlusal form The posterior teeth are classified into: 1- Anatomic form - Anatomic form has cusps grooves and inclined planes - Example: Cusp angle with 33° - Usually used for young healthy patients with normal relations and well developed ridges 2- Non anatomic form - Cuspless or flat teeth (less cutting efficiency) - Non-anatomic forms are used in the following conditions  Cross-bite ridge relation  T.M.J. disturbance  Hysterical patients with neuromuscular in-coordination  Advanced ridge resorption  Flabby ridges Dr. Wafaa Ibrahim 3- Semi-anatomic form - Are hybrid between anatomic and non-anatomic teeth (have low cusps and occlusal carvings) to improve the cutting efficiency. - Example: Cusp angle of 20° Tooth material Artificial teeth may be made of: -Acrylic resin - Porcelain - Metal - Combination between acrylic resin and metal Porcelain teeth They need mechanical means of retention pins for anterior teeth and diatoric holes for posterior teeth Dr. Wafaa Ibrahim Dr. Wafaa Ibrahim