DEVELOPMENT_OF_OCCLUSION part 1

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DEVELOPMENT OF OCCLUSION:

DEVELOPMENT OF OCCLUSION DEVELOPMENT OF OCCLUSION Dr. Chetana Bindrani 1 st Yr M.D.S

Definition of Occlusion (origin:16th Century, Latin:oocludere= to close,shut or stop up) :

Definition of Occlusion (origin:16 th Century, Latin:oocludere = to close,shut or stop up) Angle : Normal relation of the occlusal inclined planes of teeth when jaws are closed Gregory : Changing inter-relationship of the opposing surfaces of maxillary & mandibular teeth which occurs during the movements of mandible and the terminal full contact of the maxillary and mandibulare dental arches.

Slide 3:

Foster : Relationship between all components of masticatory system in normal function,dysfunction and parafunction . IDEAL OCCLUSION Ideal occlusion is a hypothetical formula,which does not and cannot exist in man. Ideal tooth form necessiates an unbiemished heredity, an optimum favourable environment and a devlopemental history devoid of any accident,diseases or occurrence,which would modify the inherent growth plan.

Maxwell Ideal Occlusion Prerequisites (1948):

Maxwell Ideal Occlusion Prerequisites (1948) 1- Normally developed coronal contour of properly cordinated M-D & B-L dimensions 2- Normally developed tooth, ossesous , muscular and other anatomic structures 3- A definite geometric and anatomic ,individual & collective relationship of dentition 4- A definite geometric and anatomic relationship of the dentition ,cranium and mandible.

Andrew’s Six Keys of Occlusion (1970):

Andrew’s Six Keys of Occlusion (1970) Molar inter arch relationship. Mesio -distal crown angulation . Labio -lingual crown inclination. Absence of rotation. Tight contacts. Curve of spee .

General Factors :

General Factors Skeletal Factors It includes : Jaw realtion to cranial bone Can exist in all 3 planes- Sagittal , Vertical & lateral. Jaw relation to each otherCan exist in all 3 planes Sagittal : Skeletal Class 1:Ideal antero -posterior relationship Skeletal Class 2: Lower jaw positioned back w.r.t class 1. Skeletal Class 3: Lower jaw positioned forward w.r.t class1 Alveolar bone to basal bone

Slide 8:

Muscle Factors Buccinator Mechanism Tongue position Posture of lips Deviant swallowing pattern/Tongue Thrusting Swallowing

EQUILIBRIUM THEORY:

EQUILIBRIUM THEORY Weinstein et al in 1952- Equilibrium theory of tooth position. William Profitt in 1977- Equilibrium theory revisited. Definition of Equlibrium . FOUR MAJOR PRIMARY FACTORS: INTRINSIC FORCES BY TONGUE AND LIPS EXTRINSIC FORCES: HABITS AND APPLIANCES FORCES FROM DENTAL OCCLUSION FORCES FROM PERIODONTAL MEMBRANE A DISTINCTION BE MADE BETWEEN THE AMOUN T AND DURATION OF FORCE

NORMAL INTRA ORAL & EXTRA ORAL PRESSURE:

NORMAL INTRA ORAL & EXTRA ORAL PRESSURE

EQUILIBRIUM THEORY:

EQUILIBRIUM THEORY

Slide 13:

WALLEN, JDR 1974: Vertically directed pressures during swallowing are less in patients with anterior open bite than in patients with normal vertical relationship. Normal = 280 gms /cm2 Increased values recorded upto 630 gms /cm2 It is the relatively high position of the incisors that keeps the tongue from contacting them so quite often

Slide 14:

Dental Factors Discrepancy in jaw size and teeth dimensions manifested as lack of space in primary dentition & crowding in secondary dentition Etiology of dental crowding Evolutionary trend towards a diminution in size of jaws without corresponding reduction in tooth sizes ,Theory supported by Moose Et Al(1968) Dietary Factors: Modern diet needs less chewing and hence less stimulation to jaw growth Present population represents a mixture of people with different backgrounds and physical characteristics leading to skeletal and dental disharmonies Occlusal Contacts Proximal Contacts

Localized Factors :

Localized Factors Aberrant developmental position of individual teeth Presence of supernumerary teeth Developmental Hypodontia Labial Frenum Oral habits.

Slide 17:

Over Bite > 6mm 6.6% Open Bite > 2mm 2.5% EXISTENCE OF RACIAL VARIATION From Kelly et al, university of carolina , 1977

Slide 18:

Talbot Edward angle Mathew cryer Lischer & Paul Milo Hellman Broadbent Development of Concepts of Occlusion

Classification of Developemnt Occlusion:

Classification of Developemnt Occlusion Hellman 1929 1- Before eruption of primary teeth, Before completion of primary occlusion 2- Completion of primary occlusion Eruption phase of permanent 1 st molars/incisors 3- Eruption of 1 st molars incisors completed Exchange phase of lateral teeth Eruption phase of permanent second molar 4- Eruption of 2 nd molar completed Eruption phase of permanent 3 rd molar 5- Eruption phase of permanent 3 rd molar completed.

Slide 20:

Classification Post-Natal Development of Occlusion Van Der Linden – 1972 Birth to complete primary dentition First inter-transitional period First transitional period Second inter-transitional period Second transitional period Adult dentition

Slide 21:

Barnetts table 1978 Stages Age Characteristics First 3 Primary Dentition Second 6 Eruption of 1 st permanent molars Third 6-9 Exchange of Incisors Fourth 9-12 Exchange of Lateral Teeth(lateral canine,premolar ) Fifth 12 Eruption of 2 nd Molars

Slide 22:

1 st stage Guides 2nd Stage 1st stage Guides 3 rd stage 2 nd & 3 rd stage Guides 4 th stage 2 nd stages Guides 5 th stage

Slide 23:

For convenience purpose Pre-dental Relationship The decidous dentition The mixed dentition The permanent dentition

Predental Period:

Predental Period Birth to complete eruption of primary dentiton

Slide 25:

Gumpads are alveolar arches at the time of birth Maxillary gum pad is horse shoe shaped. Ashley-Montagu classified into 4 shapes: Long, Moderatly Broad, Very Broad & Excessively Broad. Mandibular ridge is “U” shaped Gumpads develop in 2 equal parts,a labio - buccal and a lingual portion by DENTAL GROOVE, labio - buccal part is differentiated first and grows more rapidly and gets divided into 10 segments by TRANSVERSE GROOVES.Lingual part differentiates later and remains relatively smooth.

Slide 27:

Ten segments correspond to a deciduous tooth sac LINGUAL GINGIVAL GROOVE :which separates ridge from the palate and defines inner alveolar margin. It is equivalent to adult gingivo -palatine groove. The transverse groove between canine and first deciduous molar crypt is important in assessing the relationship of 2 pads. This groove is referred to as LATERAL SULCUS. Central and canine segments are equal in size and well demarcated and are seperated from less distinct and occasionally lingually positioned lateral incisors segments by 2 shallow grooves.

Slide 28:

1 st molar segment is largest and is limited anteriorly by lateral labial frenum . 2 nd molar segment merges with the dental groove an is harder to recognize. Labial frenum is continuous with the incisive papilla in 25% of newborns, attachment varies. Sites of primary tooth eruption Anteriorly ----> Labio-buccal portion. 1 st molar- ---> partly labiobuccal , partly lingual. 2nd molar---> completely lingual.

Mandibular Gumpad:

Mandibular Gumpad It is divided by gingival & dental groves into medial lingual & lateral labiobuccal portions The Mandibular arch is U-shaped or rectangular in form, it can be divided into anterior & 2 lateral parts Anterior Part = 4 incisors segments = broad & everted in front 2 Lateral parts = 4 Molar Segments = Narrow edge & Elevated above Anterior Part Grooves are not as pronounced as in Maxilla Gumpad is hard and firm as in Maxilla except for anterior everted part which is depressible

Relationship of Gumpads:

Relationship of Gumpads At rest gumpads are seperated by tongue and protrudes over the lower gum pad to lie immediately behind lower lip Upper gum pad is wider than lower and when two are approximated, there is complete overjet all around the lower gumpad Lateral sulcus of lower is usually posterior to that of upper Contact is seen in the first deciduous molar region Madibular Gumpads is distal to maxillary 2.7 mm in males & 2.5 mm in females.

Slide 31:

Mer Clinch Clinch’s classification of Gumpad Relationship Type 1 70% Madibular arch is slightly lingual to maxillary arch in incisor & molar regions Type 2 27% Mandibular arch slightly distal in molar region but definitely distal in anterior region Type 3 3% Mandibular arch was definitely distal in both molar and incisor region

Primary Dentition:

Primary Dentition The eruption of primary teeth begins at about 6 months after birth and all the primary teeth are erupted by 2 and half years. However the roots of second molar are incomplete. Therefore establishment of primary dentition takes place at about 3 yrs of age until 6 years of age when 1 st permanent tooth begins to erupt.

Certain Features:

Certain Features Spacing of Incisor Teeth Anthropoid Spaces Vertical Positioning of Incisor teeth Distal surfaces of upper and lower 2 nd molars on the same vertical plane Spaced Dentition Deep Bite U-Shaped upper and lower arches No curve of spee Slight overjet Slight or no Crowding

Crowding is rare in primary dentition:

Crowding is rare in primary dentition Intrabony Position of Primary Tooth buds develop at a common Level Intra – alveolar space adjustmnents Absence of bone overlays Primary tooth buds are situated for optimal eruption.

OVERBITE & overjet:

OVERBITE & overjet The vertical labial overlap of the maxillary incisors over the mandibular incisors with the teeth in centric occlusion is termed as overbite. At 3 yrs of age, there is excessive overbite, frequently retognathic tendency of mandible. The horizontal overlap pf the maxillary incisors with teeth in centric occlusion is termed as overjet . At 2 years, the overjet is on average 4 mm, with a range of 2-6mm.

Slide 36:

The overjet & overbite exhibits a steady decrease up to the age of 5 years, where an edge-to-edge incisor relationship is common. This is due to following reasons: Attrition of the teeth, Emergence of splanchnocranium from beneath the neurocranium . Lengthening of the ramus & downward & forward growth of the mandible,

Slide 37:

PHYSIOLOGICAL BITE OPENING : According to Schwartz there are 3 periods of physiological raising of the bite, With the eruption of first permanent molar at the age of 6. With the eruption of second permanent molar at the age of 12 With the eruption of third permanent molar at the age of 18.

Spacing in Primary Teeth:

Spacing in Primary Teeth First described by Dellabarre in year 1819 ‘Physiological’ spaces Khorkhous and Norman ‘Developmental’ spaces Fraber in 1962 Type 1 Continuously Spaced Type 2 Continuously Closed Spacing is variable. Any spaces between molars close at the time of eruption of 1 st permanent molarwhereas spacing between incisors persist until the teeth are replaced

Slide 39:

According to Bishara et al, generalized spacing Maxillary = 0 – 10mm ( avg 5 mm) Mandible = 0 – 6mm ( avg 3mm) Prediction of Degree of Crowding Lighton BC Deciduous Permanent (Crowding) Crowding 10 in 10 No Spaces 7 in 10 Spaces below 3mm 5 in 10 Spaces 3-6 mm 2 in 10 Over 6 mm No Crowding

Slide 40:

Namba 1981 Jaws Amount of Spacing In Primary dentition Cases with Good alignment of Incisor Teeth (Perm) Maxilla > 6mm 86 3-6 mm 67 < 3mm 37 Mandible > 4.5 mm 100 2- 4.5 mm 68 < 2mm 40

Slide 41:

Prevalence of Spacing (%) in primary dental arch [ONO, 1960] Types of Spacing Maxillary (%) Mandibular (%) Primate Spaces 15.3 10.3 Development Spaces 8.3 11.4 Primate & Developmental Spaces 69.4 53.6 Closed Spaces 7 24.7

PRIMATE SPACES:

PRIMATE SPACES

Primate Spaces:

Primate Spaces Baume 1940 Simian Gap Primate Spacing Bokya 1968 Anthropoid Spacing Foster and Hamilton 1969 1998, IJPD Alexander and Prabhu conducted a study on 1026, 3-4 yr old S outh Indian children Presence of Physio and primate spacing 75% Devoid of Spaces 3% Not a result of Functional adaptation but inherent pattern Present at time of eruption of deciduous cuspids Interlocking of Deciduous Canines SIEPEL 1946 Avg Primate Space U=0.85mm L=0.72mm

Significance of primate spaces:

Significance of primate spaces Spaced primary arches produce more favorable alignment of permanent incisors Presence of mandibular primate space is conducive of proper molar occlusion by means of an easy mesial shift of mandibular molars (prim) into the primate space The mean increase in the intercanine width brought about by the lateral and frontal alveolar growth is lesser in spaced arches than non spaced arches where there is no extra space for the erupting permanent incisors Width of permanent incisors is greater than their deciduous counterparts, primate spaces helps to accommodate wider teeth

First intertransitional period:

First intertransitional period From establishment of primary dentition to initiation of mixed dentition period (3-6 yrs)

terminologies:

terminologies ARCH LENGTH BI-CANINE ARCH WIDTH BI-MOLAR ARCH WIDTH

Slide 47:

Length of deciduous Arches 89% of maxillary arches remain unchanged 83% of mandibular arches remain unchanged A slight decrease of length was noted in rest cases. No increase in length observed Cause: Mesial Migration of deciduous 2 nd Molar just after eruption Development of proximal caries.

Slide 48:

Intercanine and Intermolar Width Only minor changes in transverse dimensions observed Increment of 0.5 mm in less than 20% of cases Similar results by Lewis (450 cases) and Goldstein (540 cases) Type 2 cases were narrower than Type 1 Physiological Spacing Clinch Not a single case in which spacing developed after full eruption of all Deciduous teeth There is no increase in space in type 1 No development of spaces in Type 2 No adequate expansion or extension of arches between 3-5 yrs.

Slide 49:

Antero-posterior relationship Relationship of opposing deciduous canines as well as the position of distal surfaces of upper and lower 2 nd M remain unchanged through the period of completed deciduous detention Vertical Growth of alveolar process to make allowance for “ successional dentition” Lewis: Do not misinterpret attrition of upper deciduous anteriors as increase in alveolar height Sagittal growth of jaws as described by Sicher , produced retromolar areas which develop posteriorly to the arches to make allowance for accessional teeth

Primary Molar Relationships:

Primary Molar Relationships Flush terminal/Vertical plane: Distal surface of upper and lower teeth are in straight plane. Mesial Step: Distal Surfaces of lower molar is more mesial than that of upper. Distal Step: Distal surface of prim second molar lies distal to that of upper.

Slide 51:

Flush plane type Mesial step type Distal step type The three types of terminal planes The mesiodistal relationship of upper and lower second molars can be classified into three types 1. Flush terminal plane type 2. Mesial step type 3. Distal step type. BAUME 1950

Slide 52:

Bishara et al- Changes in Molar relationship between deciduous and permanent dentition J. Orthodontic Dento Facial Orthopeadic , 1988 DS 95% (23 sides) all progressed to either have a class 2 tendency or full class 2 molar relationship F.T/ V.T = 29.4% (71 sides) 56.3% Class 1 43.7% Class 2

Slide 54:

Greater the Mesial step, greater probability of Molar relationship to develop Class 3. More Favorable Molar relationship in primary dentition lessens the chance for a class 2 occlusion developing in the permanent dentition but does not prevent it ! Thus some cases from M.S develop into class 2 but in smaller percentage Incidence of Class 3 increased as magnitude of Mesial Step increased. 1% -- > 19% Conclusion: It is necessary to periodically evaluate the changes in Occlusal relationships

A – type I with mesial step terminal plane B -- TYPE I WITH A STRAIGHT TERMINAL PLANE:

A – type I with mesial step terminal plane B -- TYPE I WITH A STRAIGHT TERMINAL PLANE A B

MESIAL MIGRATION OF 1st PERMANENT MOLAR:

MESIAL MIGRATION OF 1 st PERMANENT MOLAR

TYPE II WITH A STRAIGHT TERMINAL PLANE:

TYPE II WITH A STRAIGHT TERMINAL PLANE

TYPE II (mandible) TYPE I (maxilla) WITH A DISTAL TERMINAL PLANE:

TYPE II (mandible) TYPE I (maxilla) WITH A DISTAL TERMINAL PLANE

INFLUENCE OF FORCED MASTICATION:

INFLUENCE OF FORCED MASTICATION

3 MECHANISMS OF NORMAL OCCLUSAL ADJUSTMENT:

3 MECHANISMS OF NORMAL OCCLUSAL ADJUSTMENT Direct occurrence of mesial step. Early mesial shift effecting a closure of primate spaces. Late mesial shift on shedding of deciduous molars, characteristic feature of humans.

VANDER LINDEN’S CONCEPT OF APICAL AREA (1978):

VANDER LINDEN’S CONCEPT OF APICAL AREA (1978)

Slide 62:

The apical area in an INFANT is comprised of the region that contains forming parts of the deciduous and permanent teeth In THE DECIDUOUS DENTITION, the apical area is constituted of the region in which apices of deciduous can be located and the forming parts of the permanent teeth are situated. In THE MIXED DENTITION, the apical area consists of the region, where the roots of the deciduous and permanent teeth can be located and forming parts of the non erupted are situated In THE PERMANENT DENTITION, the apical area is the region where the apices of the fully formed teeth are located

Slide 63:

Apical area is further divided into: ANTERIOR MIDDLE POSTERIOR Between the mesial surfaces of forming parts of permanent canines and those of apices after the eruption is completed. Between Anterior part and Mesial Surface of the forming part of the 1 st permanent Molar Situated dorsally to the middle section and includes maxillary tuberosity and lingual tuberosity in Mandible

ANTERIOR SECTION OF APICAL AREA IN MANDIBLE:

ANTERIOR SECTION OF APICAL AREA IN MANDIBLE Small Medium Large

M MMMMmmmmm :

M MMMMmmmmm

Slide 66:

MANDIBULAR INCISOR TRANSITION PATTERN A, B, C

ANTERIOR SECTION OF APICAL AREA IN MAXILLA:

ANTERIOR SECTION OF APICAL AREA IN MAXILLA Small Medium Large

Slide 69:

MAXILLARY INCISOR TRANSITION PATTERN A, B, C

INCISOR LIABILITY:

INCISOR LIABILITY Incisor liability term coined by Warren Mayne 1968. The combined sum of the M-D width of the 4 permanent incisors is > that of the primary incisors. According to BLACK, 1969 Maxilla = 7.6mm Mandible = 6mm This is just one reason why American Association of ORTHODONTICS recommends the first visit to orthodontist at 7 YEARS of age. According to MOORREES & CHADHA, 1965 Maxilla = 7.42mm Mandible = 5.14mm

Slide 71:

Jaw Arch Tooth MesioDistal Diameter (mm) Total (mm) Permanent Centrals 9 18 Permanent Laterals 6.4 12.8 Maxillary Total Width 30.8 Deciduous Centrals 6.5 13 Deciduous Laterals 5.1 10.2 Total Width 23.2 Liability ( Mayne ) -7.6 Permanent Centrals 5.4 10.8 Permanent Laterals 5.9 11.8 Mandibular Total Width Deciduous Centrals 4.2 8.4 Deciduous Laterals 4.1 8.2 Total Width 16.6 Liability ( Mayne ) -6

Slide 72:

In the mandibular arch however, when the lateral erupt, there is an average 1.6 mm less spaces available for the 4 mandibular incisors than would required for perfectly aligning them.

The incisor liability can be compensated by: :

The incisor liability can be compensated by: 1) Interdental spacing in the primary incisor region The physiologic spaces that exist in the primary dentition are important factors in allowing relatively large permanent incisors. This is about 3.8 mm in maxilla and 2.7 mm in mandible.

Slide 74:

2) Increase in intercanine width : During the exchange of incisors the obvious change in the dental arch can be observed. That is intercanine width increases markedly at the time of eruption of mandibular and maxillary lateral incisors. INTERCANINE WIDTH OF DECIDUOUS DENTITION MAXILLA : 28.8mm MANDIBLE : 22.3 mm

Slide 75:

INTERCANINE WIDTH AFTER ERUPTION OF PERMANENT INCISORS MAXILLA : 31 mm MANDIBLE : 24 mm

Slide 76:

INTERCANINE WIDTH AFTER ERUPTION ALL PERMAMNENT INCISORS MAXILLA : 32 mm MANDIBLE : 25.5 mm

Slide 77:

SEXUAL DIMORPHISM IN INTERCANINE WIDTH More width is gained in the boys then the girls. Therefore girls have greater liability to have incisor crowding, especially mandibular incisor crowding. Moorrees CFA, Chadha JM: Normal variation in dental development, JDR, 1965

Slide 78:

According to Moorrees CFA and Chadha J.M (1959) by the time the lateral incisors have completed their eruption the intercanine width increases by about 3 mm in each arch. Furthermore, in the maxilla the intercanine width increases by another 1.5 mm when the canines erupt. Is this really growth? CLINICAL IMPLICATIONS :

Slide 79:

3) Increase of Anterior Length in the Dental Arch : Increase in the length of the dental arch in A-P dimension will also provide space for the larger permanent incisor to be accommodated. It is necessary for permanent incisors to erupt more labially to obtain necessary added space. Actually the permanent incisors move at about 2.2 mm labially in maxilla, and 1.3 mm in mandible from the location of the primary incisors. CLINICAL IMPLICATIONS:

Slide 80:

4) Change of Axial Inclination of Incisors : Primary teeth are generally very upright but permanent teeth tend to incline to the labial or buccal surface. The interincisal angle between the maxillary and mandibular C.I. is about 150 o in the primary dentition and in permanent dentition is about 123 o This makes the permanent dental arch circumference wider. This is another advantageous condition for the arrangement of the large permanent incisors. This contributes to 1-2 mm of additional space

REFERENCES (BOOKS):

REFERENCES (BOOKS) VAN DER LINDEN – DEVELOPMENT OF OCCLUSION William R. Profitt – contemporary orthodontics Thomas M. Graber – Current orthodontic concepts and techniques White & Gardner – Book of orthodontics. Robert E. Moyers – handbook of orthodontics Sameer Bishara – Textbook of orthodontics McDonald – Text book of dentistry for children and adolescence. Jimmy Pinkham - Infancy through adolescence Mathewson – Sidney Finn –

Cross references:

Cross references Louis J. Baume Occlusion : I. the Biogenetic Course of the Deciduous Dentition Physiological Tooth Migration and its Significance for the Development Occlusion : II. The Biogenesis of Accessional Dentition Physiological Tooth Migration and its Significance for the Development Occlusion : III. the Biogenesis of the Successional Dentition Physiological Tooth Migration and its Significance for the Development Occlusion : IV. The Biogenesis of Overbite Physiological Tooth Migration and its Significance for the Development Transition in human dentition, monograph no 13 , craniofacial gerowth series, Van der Linden , the university of michigan , U.S.A, 1982 Early Caniofacial development Age changes in the occlusal pattern of deciduous dentition, Ram S. Nanda 1973 Eqilibrium theory REVISITED : Factors influencing tooth position, William R Profitt , 1977