Etiology of Malocclusion_ Genral Factors Dr.Nabil Al-Zubair
Aetiology of Malocclusion General factors
EtiologyIs the science of investigation, study and demonstration the CAUSES of thedisease.
INTRODUCTION• Malocclusion is a developmental condition CAUSED in most cases by distortion of normal development and only a few cases caused by PATHOLOGY. • Although it is difficult to know the precise cause of most malocclusion BUT we do know in general what the possibilities are.
Multiple Factors• Occasionally a single specific cause is apparent e.g mandibular deficiency secondary to trauma to TMJ or characteristics malocclusion that occur in some genetic syndromes.• More often these problem result from complex interaction among multiple factors that influence growth and development
By the middle of 19th centurydifferent ideas was put forward to explainpossible causes of malocclusionHere are some of the earlier conceptson the aetiology of malocclusion; -Kingsley: the importance of inter- racial mixtures(marriage) -Talbot: the role of endocrine glands -Rogers: lip habit -Brash: theory of inheritance
Aetiology of Malocclusion Several attempts has been made to classify aetiology of malocclusion among which are;iii) Pre-eruptive abnormalities /Post eruptiveiv) Prenatal /Postnatalv) Determining / predisposing
Aetiology of Malocclusion GENERAL FACTORS LOCAL FACTORS • Congential absence of teeth • Anomalies of tooth size• They affect all or greater part of the • Anomalies of tooth shape occlusion. They include; • Abnormal labiel frenum (A) Abnormalities in skeletal relationship • Premature loss of deciduos teeth (B) Soft tissue factors • Supernumerary teeth • Abnormal resorption of deciduous teeth (C) Disproportion between tooth size and • Delayed eruption of permanent teeth ach length • Abnormal eruptive path • Ankylosis of deciduous teeth • Proximal caries • Improperly contoured restorations
GENERAL FACTORS They affect all or greater part of the occlusion. They include;(A) Abnormalities in skeletal relationship(B) Soft tissue factors(C) Disproportion between tooth size and ach length
ABNORMALTIES IN SKELETAL RELATIONSHIP • Refer to as skeletal factors• Include the following abnormalities; (i) Anterior-posterior mal -relationship (ii) VERTICAL MALRELATIONSHIP (iii) LATERAL MALRELATIONSHIP Result from: differential development of maxillae and mandible
Skeletal factors (i) Anterior-posterior mal relationship skeletal pattern Class II Malocclusion Maxillary protrusion MANDIBULAR RETROGNATHIA Class III Malocclusion Maxillary retrognathiaMANDIBULAR PROTRUSION
-it is HEREDITARY and ethnic in origin in most cases skeletal pattern
Class II Malocclusion Maxillary protrusionMandibular retrognathia Combination
Class III MalocclusionMaxillary retrognathiaMandibular protrusion Combination
Other possibilities are: differential development of maxillae and mandible Anterior-posterior mal relationshipa- Foetal intrauterine moulding; Pressure against mandible- if the head is excessively flex against the chest,- arm pressed against the face
b- Haematological e.g sickle cell anaemia patient can have Class IIskeletal pattern due to maxillary prognatism (Sickle cell gnathopathy)
c- Endocrine e.g hypothyrodism (Cretinism)-thereis reduce jaw growth as part of overall reductionin body growth
d- Disturbance in Embryonic development- TERATOGENS
Teratogens can disturb jaw growth if introduce at a time when the jaw is developingit can also lead to cleftlip and palate leading toclass III skeletal pattern
VERTICAL MALRELATIONSHIP There is (¹) excessive facial growth which increases the facial height and could cause skeletal open bite• Can result from mandibular prognatismdue to (²) hyperpituitarismAlso caused by (³) condylarhyperplasia
LATERAL MALRELATIONSHIPOccasionally dental bases is disproportional wide or narrow causing lingual or buccal cross bite of molars although the axial inclination of the teeth appear correct some of the causes of anterior-posterior malrelationship are also responsible for this abnormalities
GENERAL FACTORS(A) Abnormalities in skeletal relationship(B) Soft tissue factors(C) Disproportion between tooth size and These include muscles, lips, tongue and cheek ach length
(B) SOFT TISSUE FACTORThese include:- muscles,- lips,- tongue and- cheek This is a major factor in determining tooth position.
How soft tissues could be A cause for malocclusion?
• The effects are as follows; (i) Muscle dysfunction e.g Bell palsy-The facial muscleaffect the growth ofthe jaw in two ways; -The formation of bone at the point of muscle attachment depend on the activity of the muscle -Growth of soft tissue carry the jaw downward and forward
(ii) Short lips-leads to proclination of anteriors, increase overjet and occasionally open bite(iii)Hyperactive mentalis muscle (iv) Cheek/lip defect-causes displacement or proclination of the teeth to the affected (v)Tongue-e,g regions Macroglossia Extra-oral Muscles Intra-oral Muscles
How soft tissues could be A cause for malocclusion? غير كفء The presence of incompetent lips failure of the lower lip to control the position of the upper incisorsCompetent lips incompetent lips
غير كفءThe lips may be incompetent due to many reasons 1. Increased LFH 2. Mandibular retrognathia 3. Short upper lip 4. Incisor protrusion
What does Soft Tissue Dysfunction Do? ٍ َ ِ َ ْ َ ٍ ْ َ ُ َّ إِنا كل َّ شيء خلَقناهُ بقدَ ر
What does Soft Tissue Dysfunction Do?The Gothic Arch The Roman Arch
When the tongue rests in the roof of the mouth the teeth erupt around the tongue forming a normal shaped and sized jaw. The tongue is the scaffold for the upper jaw
All of these children will have an underdeveloped upper jaw.Those children who breath through the mouth or have the lips apart at rest willnot have the tongue in the roof of the mouth.
Aetiology of Malocclusion GENERAL FACTORS (A) Abnormalities in (B) Soft tissue factorsskeletal relationship (C) Disproportion between tooth size and ach length
(C)TOOTH SIZE AND ARCH LENGTH DISPROPORTION• Basically HEREDITARY in origin DISPROPORTION• Patient inherit small arch from one parent and large tooth size from other parent leading to crowding • Or a combination of large arch and small tooth size resulting in spacing
Aetiology of Malocclusion ClassificationMcCoy and Shepard (1956) a) Direct(determining) b) Indirected (predisposing)Salzman a) Prenatal b) PostnatalT.C white (1976 ) - Dental base abnormalities - Pre-eruptive abnormalities(large frenum, tooth germ position) - Post eruptive abnormalities(swallowing habit, suckling, premature loss of deciduous teeth)Moyers (1972) a)Heredity b)Developmetal Defects c)Trauma d) Physical agents e) Habits f) Diseases g)malnutritionGraber - General (extrinsic) factors - Local (intrinsic) factorsWilliam Proffit (2005) (i) specific causes (ii) Genetic influences (iii) Environmental influences
Hereditary is significant in determining the following characteristics:• Tooth size• Arch length and width• Height of the palatal vault• Crowding or spacing• Overbite and overjet• Position and configuration of muscles• Tongue size and shape• Character of the oral mucosa
Heredity also plays a role in:• Congenital deformities• Facial asymmetry• Size and position of the jaws• Oligodontia and anodontia• Supernumerary teeth• Variations in tooth shape
II. Congenital defects The following examples could be considered the most common congenital causes of malocclusion:• Clefts of the lip and palate• Cerebral Palsy closure of sutures of the skull• Crouzons syndrome• Cleido-Cranial Dysostosis• Cranial Synostosis
Cleft lip and Palate:! A congenital defect showing GENETIC INFLUENCEfrom one third to one half of all cleft palate childrenhas a familial history of this deformity.The following characteristic features ofmalocclusion are always concurrent withcongenital cleft lip and palate:a) Anterior cross-biteb) Bilateral or unilateral posterior crossbitec) Malpositioning and rotation of the maxillary incisorsd) Deflect the teeth from their normal eruptive path.
(iii) ENDOCRINE DISTURBANCE Thyroid affect ERUPTION Parathyroid (Calcium metabolism) affect CALCIFICATIONHYPOTHYROIDISMeffects: Hyperparathyroidism• abnormal resorption pattern Bone is replaced by fibrous tissue giving the• Delayed eruption ground glass appearance acceleration of• Retained deciduous teeth skeletal ossification Effects:Hyperthyroidism • early eruption of both deciduouseffect: &permanent teeth•acceleration of skeletal ossification • Loss of lamina dura, and cortical bone•early eruption of both deciduous (teeth loss)&permanent teeth
DISTURBANCE OF NORMAL FUNCTION Nasal Breathing Mouth Breathing Normal Swallow Abnormal Tongue Thrust SwallowAbnormal Habits . Thumb and Finger Sucking : - Lip-sucking and Lip-biting - Finger Nail Biting
Abnormal Habits a. Sucking Habits:i. Thumb and Finger Sucking :* Causse:i. Improper or inadequate nursing.i i . Insecurity or attention getting mechanism.iii. Habit during eruption of teeth.iv. Feeling of hunger.v. Feeling of personal in adequacyvi. A simple learn habit with no underlyingneurosis.
PhasesThumb sucking habit could be divided into 3 phases: (a) Phase I: Normal Subclinically Significant Thumb-Sucking: From birth to 3 years. (b) Phase II: Clinically Significant Thumb- Sucking: From 3- 7 years عسير (c) Phase III :Intractable Thumb- Sucking: after 7 years
Clinical Features of Prolonged Active Thumb-Sucking:i. Finger habit opens mouth beyondpostural resting position. The thumbfinger exerts a labial and a depressingvector on the maxilla incisors as well aslingual and depressing vector on themandibular incisors .The resulted malocclusion may be- labial tipping of upper incisors,- lingual tipping and flattening of lower incisors and- severe ANTERIOR OPEN BITE.
ii ANTERIOR OPEN BITE resulted from thumb sucking is characteristic round well circumbeded open bite "fish mouth appearance". The anterior open bite Resulted from excessive eruption of posterior teeth alonginterference with the normal eruption of with separation of the jaws and alteration ofupper and lower incisors. vertical equilibrium of the posterior teeth
The anterior open bite tongue thrustiii. Anterior tongue thrust swallow:It become for the tongue to thrust forwardduring swallowing in order to affect ananterior seal.
iv. Maxillary constriction due to:! Negative pressure within the mouth fromsucking action.! Disturbance of horizontal equilibrium: whenthe thumb is placed between teeth, the tonguemust be lowered with lack of tongue pressureson the lingual surfaces of the upper posteriorteeth.! Increase of cheek pressure:because of the buccinator stretching along withmouth opening and its active contraction duringthe active sucking action
v. High vault palate with narrow nasal flooroccurred secondarily to the maxillaryconstriction and to the upward pressure fromthe finger against the anterior part of thepalate. vi. The finger itself may show the effect of habits. A callus or virus infection may be formed due to sucking. ! From all the above the persistent thumb sucking habit is capable of producing a picture of class II division 1 malocclusion.
Factors that Affecting the Degree of Damage to Teeth and Investing Tissue:1) Frequency of habit during the day. Themore frequency the more the damage.2) Duration of habit: Duration of habitbeyond early childhood. The more durationthe more the damage.3) Intensity of habit: passive insertion offinger in mouth with no muscle activity is lessharmful than active sucking with contractionof perioral musculature. 4) Position of digit
b)- Lip-sucking and Lip-bitingWhen the lower lip is repeatedly heldbeneath the maxillary anterior teeth, theresult is:! Labioversion of maxillary anterior teeth.• Open bite.• Lingoversion of mandibular anterior teeth.
Habits Lower lip suckingProclination of theupper incisors Retroclination of the lower incisors It is important that habits are stopped before treatment is commenced
C)- Abnormal Swallowing/ Tongue Thrust Habit Protrusion of the tongue against or between the anterior dentition and excessive circum-oral activity during deglutition. Innate behavior Universal infant oral behavior for children under the age of 6 years.
d)-Finger Nail Biting* Incidence:- Is absent under the age of 3 years.- There is rapid increase at 6 years of age.-- The habit should not be accepted as aprimary symptom of maladjustment.Crowding rotation and attrition of the incisaledges of incisors especially the mandibularincisors. This malocclusion is due to theuntoward pressures introduced during nailbiting. غير مرغوب فيه
e)- Mouth Breathing* Types of Mouth Breathing: • Pathological mouth breathing • Habitual mouth breathing • Habitual mouth breathing, by removal of the cause and clearing of nasal passages, patient still breath from his mouth as a habit
* Causes and Types of Mouth Breathing:• Pathological mouth breathing, one of thefollowing may result into obstruction of thenasal air passage:! Large adenoids.! Diseased tonsil e.g. tonsillitis.! Hypertrophy of nasal turbinate.! Nasal deformity e.g. deflected nasal septum.! Hypertrophy of lymphoid tissue inthe nasopharynx.! High fever.
* Characteristic Features of Malocclusion: Mouth Breathing:1. Narrow V-shape maxilla with high arched2. Protruded maxilla withprotrusion ofupper anterior teeth3. Broad mandible4. Retroclination of the lowerincisors5. Increase over-jet6. Posterior cross-bite7. Gingival and periodontaldisease
Skeletal factors Genetic Soft tissue factorsAetiology OF malocclusion Enviromental Dental factors Prenatal factors Natal factors Postnatal factors Teratogenesis Trauma to the condylar region Traumatic injury to the mandible TMJ Irradiation Intra-uterine fetal posture Infectious conditions such as rheumatoid arthritis Abnormal function such as oral respiration, abnormal swallowing Habits such as thumb sucking prevent normal muscle activity
Environmental FactorsPostnatal• Birth injuries• TMJ injuries• Accidents, fractures• Avulsion or displacement of teeth
منظور المعاصرةEtiology in Contemporary Perspective
• Mendelian developed a different• Edward Angle & his view which was that malocclusion is contemporaries influenced the primarily the result of inherited dentofacial proportions which may finding that malocclusion is a be altered by developmental disease of civilization . variations, trauma ,or altered function.
Etiology of Crowding and Malalignment :1. Disproportion b/w jaw & tooth size.2. Environmental factors.3. Mouth breathing alter the tongue- lip/cheek equilibrium.4. Hereditary factors.
Etiology of Skeletal Problems:-Skeletal orthodontic problems Causes of skeletal problems: resulting from malposition or 1. Inherited patterns. malformation of the jaws rather 2. Defects in embryologic than irregularity of the teeth development & genetic syndromes (rare). 3. Trauma (common cause). 4. Functional influences.
Egs :-1. Class II malocclusion havetendency toward (retrognathicmandible) due to heredity.The more sever the case isprobably due to hereditary &environmental effects.
2. . Mandibular prognathism or Class III malocclusion There is a definite familial & racial tendencyIt is caused by:1. Excessive mandibular growth due to constant distraction of the condyle from the fossa .2. Large tongue3. Respiratory needs .4. Pharyngeal dimensions.5. Hereditary factors (major cause).6. Functional mandibular shifts (affect teeth more than jaws).
3. Open bite can be due to :• Sucking habit .• Tongue posture accompany nasal obstruction.• Excessive eruption of posterior teeth.• Hereditary factors.
Conclusion• Whatever the malocclusion is itwill be always stable a/f growth hasbeen completed.• Malocclusion ,after all is adevelopmental problem.