Presentation on theme: "SELECTION AND ARRANGEMENT OF ARTIFICIAL TEETH IN COMPLETELY EDENTULOUS PATIENTS."— Presentation transcript:
SELECTION AND ARRANGEMENT OF ARTIFICIAL TEETH IN COMPLETELY EDENTULOUS PATIENTS
Short Learning Objectives Anterior teeth selection Posterior teeth selection Arrangement of Teeth
INTRODUCTION The selection of artificial teeth for edentulous patients requires a knowledge and understanding of a number of physical and biologic factors that are directly related to each patient. Careful examination of the faces and teeth of people with natural teeth will develop a sense of dentofacial harmony that is the objective of tooth selection and esthetics. There must be harmony of color, form, size, and arrangement of teeth
Anterior tooth selection The factors of shade selection are:- 1. Age. 2. Sex. 3. Complexion. 4. Patient -preference
METHODS USING PRE-EXTRACTION GUIDES It includes- Diagnostic casts, Photographs, Radiographs, Extracted teeth
Anterior tooth selection Factors to be considered for selection of anterior teeth: A. Shade (color) B. Size C. Form
METHODS USING ANTHROPOLOGICAL MEASUREMENTS- These methods measures certain anatomical dimensions and derive the size of teeth using certain formula-
Circumference of the head Width of the upper CI= bi-zygomatic width Total Width of the upper anterior = Total Width of the lower anterior =---- Width of the upper anteriors 5
METHODS USING ANATOMIC LANDMARKS Seven anatomic entities are used as guides to selection of anterior teeth for size: 1.Size of the face 2.Size of the maxillary arch 3.Incisal papilla and the cuspid eminence or the Buccal Frenum 4.Maxillomandibular relations 5.The contour of the residual ridges 6.The vertical distance between the ridges 7.The lips
Resorption Pattern in maxilla and Mandible
THE VERTICAL DISTANCE BETWEEN THE RIDGES: – The length of the teeth is determined by the available space between the existing ridges. THE LIPS – When the teeth are in occlusion and the lips are together, the labial incisal third of the maxillary anterior teeth supports the superior border of the lower lip – In speech the incisal edges of the maxillary anterior teeth contact the lower lip at the junction of the moist and dry surfaces of the vermilion border. – It is best demonstrated when the letter F, as in fifty five is pronounced
FORM OF ANTERIOR TEETH:- The form and outline of the anterior teeth can be determined using the following factors: 1.Shape of the patient’s face or facial form 2.Patient’s profile 3.Dentogenic concept
Typal form theory: Leon Williams (1917) According to this, the shape of the teeth should be inverse of the shape of the face. Teeth form can be- square, ovoid and tapering
Dentogenic concept Dentogenics is the art, practice and technique of creating the illusion of natural teeth in artificial dentures and is based on the elementary factor influenced by sex, personality and age of the patient. It was first described by Frush and Fisher.
Dentogenic concept: Sex: – In female, the incisal angles are more rounded and the teeth have lesser angulation while in males, the incisal angles are rounded to a lesser degree. – The incisal edge of the CI is parallel to the lips and the laterals are above the occlusal plane in males But in females it follows curve of the lower lip (CI & LI) – The distal surface of CI are rotated posteriorly for females, LI overlapping CI. – Reverse in males, providing masculine features.
Dentogenic concept: Age: – separated into young, middle or elderly. – Due to decrese in muscle tone, sagging of the cheeks and the lower lips occur. To prevent cheek biting, horizontal overlap of the posterior teeth can be increase. – Inter occlusal distance reduces with age. Hence, mandibular teeth are more visible than the maxillary teeth. – In old patients the teeth tend to have square form due to attrition, round features disappears and line angle quite prominent in those patients.
Dentogenic concept: Age: – Old patient have gingival recession, & can be reproduced in the dentures – The color of the teeth also changes with age. Personality: – It seems reasonable that a large vigorous type of persons have teeth of a size and form with prominent markings, different from those of a delicate appearing patient.
Arrange teeth according to personality
MATERIALS OF TEETH:- There are two main types: 1. Porcelain, 2. Acrylic Porcelain teeth: - vacuum fired and air fired. The vacuum is better because they are harder and have luster. Generally porcelain teeth are preferred particularly for young person because they look more vital, very smooth and difficult to abrade.
MATERIALS OF ANTERIOR TEETH:- Acrylic teeth: They are made from acrylic resin, indicated when there is insufficient inter-occlusal distance, and grinding becomes necessary, also in situation where there are opposing natural teeth, partial denture and gold bridge. They are inferior when they are compared with porcelain because they can not maintain luster for long time and abraded easily.
MATERIALS OF ANTERIOR TEETH ACRYLIC TEETH : 1- Not brittle, but poor abrasion resistance. 2- Esthetic very good. 3- Chemical bonding with denture base. 4- Easily ground and polish. 5- Transmit fewer forces to the mucosa. 6- No clicking on contact. 7- Thermal expansion same as acrylic denture base. PORCELAIN TEETH : 1- Brittle, more resistance to abrasion 2- Excellent (does not stain). 3- Mechanical bonding by pins or undercuts holes. 4- Difficult to grind and polish. 5- More forces to the mucosa. 6- Clicking on contact. 7- Much lower than acrylic causes stresses in acrylic denture base. 23
Posterior tooth selection Posterior teeth are selected for color, buccolingual width, mesiodistal length, vertical height (occluso-gingival length) and occlusal form. 1- Shade (color): - should be harmonized to the shade of anterior teeth, maxillary first premolars are sometimes used for esthetic more than function, so it's advisable to select premolar teeth with lighter color than the other posterior teeth, but not lighter than anterior teeth. Generally the shades of posterior teeth are slightly darker than anterior teeth.
2-Bucco-lingual width:- - should be slightly narrower than natural teeth to decrease occlusal surfaces which direct less stress during function to supporting tissue, and also enhance the development of the correct form of polished surfaces of the denture. 3- Mesio-distal width: -Narrower than natural ones. -should be equal to the distance between canine line and anterior border of maxillary tuberosity for upper teeth. For lower teeth should be equal to distance between canine line and anterior border of retro molar pad area.
4- The occluso-gingival height - Controlled by the available inter-arch distance. The length of the maxillary first premolar should be comparable to that of maxillary canine to have the proper esthetic effect. The height of posterior teeth usually divided into long, short, medium. Long posterior teeth are generally more esthetic in appearance than are shorter teeth.
5- Occlusal form: Selecting the tooth to be used is based on the concept of occlusion to be developed, the philosophy of occlusion to be fulfilled, and the accomplishment approached. It is given in the table below.
28 SELECTION COMPARISION OF DENTURE TOOTH MOLDS AND OCCLUSAL CONCEPTS TOOTH MOLDOCCLUSAL CONCEPTADVANTAGEDISADVANTAGE 20 or 30- degree cusp teeth Centric jaw record, face bow, protrusive records to semi- adjustable. Set upper anterior and posterior teeth, then lowers to cross-arch contact or “balanced-occlusion” Reported slightly more efficient in chewing tests Posteriors appears more natural Most time and complexity of records Limitations of anterior tooth positions Restriction of posterior tooth positions to that allowed by Cuspal anatomy Monoplane 0- degree Centric jaw record only Simple articulator Set 12 anterior teeth with Overjet but no overbite Set lower teeth in flat plane to middle of retromolar pad Set upper to match; no attempt on contact on excursions Simplest of all recordings Simplest articulators Quick arrangement of teeth Wide range of posterior tooth positions possible No lateral stresses on mucosa with parafunction Easier for patients with uncoordinated closures Flat premolars may appears less esthetic Reported as less aesthetics Anterior esthetics need more Overjet and no overbite
29 SELECTION COMPARISION OF DENTURE TOOTH MOLDS AND OCCLUSAL CONCEPTS TOOTH MOLDOCCLUSAL CONCEPTADVANTAGEDISADVANTAGE Flat teeth with compensating curve or second molar ramp Centric jaw record Semi-adjustable articulator Anterior teeth with Overjet and slight overbite Posterior set to contact on at least 1 point on non-working or balancing side Simple to set up; allows for more esthetic overlap of anterior teeth The posterior point contact maintain denture base stability on excursion or parafunction Slightly more laboratory set up Premolars appear flat if visible Combination or “lingualized” occlusion Centric jaw record Monoplane lower posterior teeth set to retromolar pad Anatomic upper posterior teeth set with only lingual, not buccal cusp touching Upper premolars appear natural Some range of posterior tooth position allowed Reported slightly better chewing than monoplane Some grinding needed to create upper cusp tip/lower fossa contacts
Arrangement Of Anterior Teeth It is important that the artificial anterior teeth are placed in the same antero-posterior position and at the same length as natural teeth to provide adequate esthetics and phonetics.
RESIDUAL ALVEOLAR RIDGE In patient with long edentulous period, much bone could have been lost from the residual alveolar ridge. In this situation, artificial teeth should not be placed against the ridge As a general rule: the longer the natural teeth have been out the farther the artificial teeth should be from the ridge The teeth should be placed closer to the residual ridge when there is less shrinkage and farther from ridge when there has been more resorption
Arch Form And Shape
RELATIONSHIP TO INCISIVE PAPILLA Incisive papilla is a guide to anterior tooth position because it has a constant relationship to the natural CI. A line marking the centre of the incisive papilla on the cast is extended forward onto the labial surface of the cast and CI are set on either side of this line. However in few cases, where facial mid line doesn’t coincide with papilla, better to take facial midline as guide. Incisive papilla is also a guide to the antero-posterior position of the teeth. Labial surfaces of the CI are usually 8-10 mm in front of the papilla
Horizontal overlap (over jet) and Vertical overlap (over bite):
Arrangement Of The posterior Teeth Standardized parameters 1. Curve of Wilson' as transversal compensating curve. 2. Curve of Spee' as sagittal compensating curve. 3.Optimum intercuspation of the antagonists.
Curve of Wilson Curve of Spee
Common errors in arrangement of teeth. 1.Lack of rotation of anterior teeth to give a narrower effect. 2.Setting mandibular anterior teeth too forward in order to meet maxillary teeth. 3.Failure to make the canine the turning point of the arch. 4.Setting mandibular 1st premolar to the buccal side of the canines. 5.Setting the mandibular posterior teeth too far to the lingual side in the 2nd molar region which cause tongue interference and mandibular denture displacement 6.Failure to establish the occlusal plane at the proper level and inclination. 7.Establishing the occlusal plane by an arbitrary line on the face.
Take Home Message….. Teeth selection should be in harmony in color, shape and size with the patient’s face, sex and age for a successful fabrication of complete denture prosthesis. Teeth should be positioned in harmony with intraoral and circumoral muscle activity and adjusted so that they occlude and articulate evenly. Several different prosthetic tooth molds have been produced, and each has some purported advantages. In the absence of a clear advantage, tooth molds, selected should be esthetically pleasing and have a simple procedure to set up.
MCQs 1.Dentogenic concept was given by- a.Boucher b.Frush and fisher c.Rudd d.Winkler
2. Distance of labial surfaces of the central incisors from incisive papilla is- a.5-7mm b.6-8mm c.8-10mm d.10-12mm
3. Total width of upper anterior as compared to bizygomatic width is- a.½ b.1/3 c.¼ d.1/5
4. Antero-posterior compensating curve is provided by- a.Curve of Wilson b.Curve of Monson c.Curve of spee d.Curve of Berry
5. Total Width of lower anterior as compared to upper anterior is a.2/3 b.¾ c.4/5 d.5/6