PHYSIOPATHOLOGY OF OCCLUSION IN CHILDREN

PHYSIOPATHOLOGY OF OCCLUSION IN CHILDREN

INTRODUCTION

The term occlusion is generally used to refer to the simple contact relationship of dental occlusal surfaces but the concept of occlusion must include the whole of the relationships:

*Functional

*dysfunctional

*Parafunctional    

DEFINITION OF OCCLUSION: 

• The word ”  occlusion  ” comes from the Latin  occludere,
  • an expression meaning “to close”.
• In medicine, the same term refers to
  • the bringing together of the edges of a natural opening, 
  • eyelid occlusion or eye closure.
• In dentistry: this term also refers to:
  •  closing the dental arches 
  • that the different functional movements during which the maxillary and mandibular teeth come into contact. .(at least one point)

• According to Posselt : “Static relation of contacts between antagonistic teeth”.
• According to Batarec : “It is a state defined by one or more contacts between antagonistic teeth.”

DETERMINANTS OF OCCLUSION: 

Correspond to the elements that direct the mandible to a given position. Three in number:

• Neuro-muscular determinants.
• Posterior determinants: ATM.
• Anterior determinants: the dental arches.

   a: reminder of the anatomy and role of the masticatory muscles:

1. The elevator muscles:

The temporal, the masseter, the internal pterygoid.

2. The mandibular depressor muscles  :

The external pterygoid                 

The suprahyoid muscles. The digastric. 

                                                               The mylohyoid.

                                                               The geniohyoid

3. muscle action:

ELEVATORS               protractor: masseter, internal pterygoid

                                           Retractor: temporal

PROTRACTOR DEPRESSORS: external pterygoid

                                       Retractors: digastric, mylohyoid, geniohyoid

• Protrusion  : is ensured by: the synchronous contraction of the right and left external pterygoids.

Lowering of the mandible will be limited by: internal pterygoid and the anterior part of the temporals

• Mandible retrusion : Contraction of the middle and posterior temporal bundles.
• Laterality :

• Working side  : Contraction of the posterior and middle temporal bundles.
• Non-working side  : Contraction of the external pterygoid, internal pterygoid and the anterior fibers of the temporal.

     b: posterior determinants: ATM

• The condyle  : prominent projection above a narrowed part called the neck of the condyle. 

Only the anterior part of the condyle is articular 

• The meniscus  : The mandibular condyle and the temporal condyle are separated by the meniscus which is a biconcave fibrous disc and has two faces: 

• -a face >which comes to be applied on the convexity of the condyle of the temporal. 
• -a face < which is applied to the anterior convexity of the mandibular condyle.
• Means of union  : The joint capsule comprises

• – long superficial fibers that run from the temporal to the mandible
• -deep short fibers which are either temporomandibular or menisco-mandibular.
• Synovial membranes  :   There are two synovial membranes: 

• -synovial > or suprameniscal
• -synovial <or submeniscal.

PHYSIOPATHOLOGY OF OCCLUSION IN CHILDREN

the role of ATM

• Movable joint allows opening and closing movements of the mandible.
• Plays an important role in the amount and direction of condylar and mandibular growth

c: _anterior dental determinants 

• The incisor-canine group and the cuspid teeth (PM and M)
• guides the mandible in ICM and during mandibular movements
• Horizontal and vertical overjet: the overjet and overbite of the anterior teeth which determines the incisal trajectory: which is the sliding of the FV of the I< on the FP of the I>.

NORMOCCLUSION  

• Normocclusion  

• is the reference model 
• defining ideal static and kinematic occlusal relationships. 
• This model is almost never found naturally.
• functional occlusion : 

• close to Normocclusion 
• without mandibular deviation,
•  the timing with respect to the characteristics of the PIM and
•  interference-free guidance.

NORMAL STATIC OCCLUSION:

• The maxillary teeth cover the mandibular teeth. 
• The implantation of the teeth is not vertical.
• There is an external (vestibular) orientation of the maxillary posterior teeth and an internal (palatal or lingual) orientation of the mandibular teeth.

In the sagittal direction  : 

• Lower teeth mesial position of 1/2 cusp
• Incisor overjet 2.5mm 
• The teeth are organized around the 1st upper molar

PHYSIOPATHOLOGY OF OCCLUSION IN CHILDREN

• According to Angle  : the key to occlusion is the relative position of the first molars. 
• In normal occlusion,
  • the mesiovestibular cusp of the upper first molar 
  • is received in the vestibular groove of the first lower molar 

In mixed dentition the classification changes since we must take into consideration the LEE WAY or drift space gain generated by the replacement of IV and V 

This phenomenon causes that when the temporary teeth are lost there is a slight surplus of space available in the dental arch in the posterior region.

This space can represent nearly 2 mm per arch in the upper jaw and 3.5 mm in the mandible. This may seem minimal but this space can be critical to promote optimal eruption of permanent teeth.

If space is “used” well, problems with eruption and tooth alignment may be less than if space is “lost” when adjacent teeth migrate or drift unfavorably.

It can be:

• rectilinear or straight 
• A mesial march prefigures cl I or cl III
• A Distal March foreshadows cl. II.

PHYSIOPATHOLOGY OF OCCLUSION IN CHILDREN

In the transverse direction

• Upper arch circumscribes lower arch (1/2 cusp)
• Lower vestibular cusp tip in upper intercuspal groove
• Coincidence of inter-incisal points

In the vertical direction

• 2.5mm overlap
• Incisor less than 1 mm from the occlusal plane

DYNAMIC OCCLUSION:

MANDIBULAR POSITIONS: we have 3 positions

1. THE RC CENTERED RELATIONSHIP:

It is a mandibular-cranial relationship independent of the teeth.

This is the most posterior, unforced position of the mandible,

 The condyles occupy a high and symmetrical position in the glenoid cavities

Position from which all lateral movements are still possible

2. OCCLUSION POSITION IN PIM 

The mandibular closed position where the dental arches have the maximum number of contact points or surfaces is called the maximum intercuspation position or MIP. 

 In PIM, relationships are established between the occlusal surfaces of the teeth and more precisely between the cusps, the pits and the marginal ridges.

PHYSIOPATHOLOGY OF OCCLUSION IN CHILDREN

3. RESTING POSITION: R

Conditioned by the balance of the facial muscles of the head and neck:

 minimal tonic contraction to counterbalance the force of gravity.

MANDIBULAR MOVEMENTS:

• The protrusion movement: 

    This is the path that the mandible takes when the lower incisors 

slide on the palatal surfaces of the upper incisors, from the position 

maximum intercuspidation PIM to end to end which is the position 

of PP protrusion. hence the notion of INCISIVE GUIDE: its length and its slope depend on two parameters: the overlap and the overhang

• The movement of laterality.

The path taken by the mandible when the lower teeth slide laterally on the internal faces of the vestibular cusps of the maxillary teeth and, more particularly, on the palatal face of the upper canine.

The surfaces on which the lower support cusps slide are called ”  guide surfaces.”

PHYSIOPATHOLOGY OF OCCLUSION IN CHILDREN

• Posterior determinants  :

CT: pure rotation of the condyles according to the BENNET movement = this is the displacement of the condyle outwards 

CNT: movement of the condyle downwards and forwards and inwards

• Previous determinants:

CT: canine function or group

CNT: no contact.

PHYSIOPATHOLOGY OF OCCLUSION IN CHILDREN

Functional occlusion  : occlusion is said to be functional when we have:

• Canine protection with CNT disocclusion
• There should be no interference from the non-working side.
• There should be no interference with the posterior teeth when the mandible is in incisal protrusive contact. 
• Uniform contact of the incisal edges in propulsion.
• The anterior teeth do not touch when there is maximum intercuspation.
• Maximum intercuspidation of the teeth when the mandible is in centric relation.

A good occlusion allows:

• -to perform closing and lateral movements without interference.
• -to have a distribution of forces on each of the teeth taken individually especially in

• the PIM 
• During extrusion contacts,
•  during swallowing movement which is repeated on the order of 1000 times / 24 h.

• to allow adequate muscle function.
• to have a normal condyle-glenoid cavity relationship.
• to have an appropriate inter-arch distance

• Interferences: Are obstacles to the functional movements of the mandible
• Premature contact: 

• Tooth contact that occurs before the maximum intercuspation position 
• modifying the usual path of the mandible 

MALOCCLUSIONS:

• Functional malocclusion 

• = convenience occlusion : Different from Normocclusion, 
• it allows oral functions, despite the presence of occlusion anomalies, 
• without generating structural damage or functional impotence. 
•  Pathogenic malocclusion 

• is characterized by one or more occlusion anomalies, 
• exceeding the adaptive potential of the subject. 
• It can trigger, maintain or contribute to the appearance of structural damage and/or functional disorders of the masticatory system.

CLASSIFICATION OF MALOCCLUSIONS

Types (overall structural framework )	Skeletal	Sagittal: Ballard classification (class I, II, III) Vertical: normodivergent, hypodivergent, hyperdivergent Transverse: asymmetry (basicranial asymmetry, laterognathia, etc.)
	Dental	Sagittal : Angle classification (class 1, class 2, class 3)  Vertical : open bite, overbite (excessive overlap)  Transverse : exoclusion, reverse occlusion
Occlusal anomalies (occlusal clash dysfunction)	Wedging anomalies : dental and mandibular stabilization anomaly in OIM Centering anomalies ( decentering): mandibular position anomaly in OIM Guidance anomalies : direction anomaly towards OIM
Occlusion categories (pathogenic incidence)	Normocclusion Functional occlusion  Functional malocclusion  Pathogenic malocclusion

Pathological occlusion is defined by signs of imbalance 

• at the dental level: wear, cracks, 
• at the periodontal level.
• and cracking and noises at the ATM level 

Harmful forces:

Relevant to a pathological occlusion, they can determine lesions which fall within the framework of what is commonly called occlusal trauma.

Occlusal trauma:

This is a diagnosis that cannot be clinical, it is radiological, it is a lesion that occurs at the level of the periodontal tissue following a traumatic occlusion, it can be responsible for dental ankylosis.

The term occlusal trauma defines the local lesion related to harmful forces, in this case we can say that the occlusion is traumatic since it determines a lesion.

On the one hand : occlusal trauma is not limited to forces coming from opposing teeth, it extends to all harmful forces whether they are specific to our organism or exogenous (muscle tics, habits)

And that these are exerted on the occlusal face or on any face of it.

On the other hand : given the adaptive power of the periodontium and other components of the masticatory system, an occlusion outside the usual morphological norms (pronounced overbite) is not necessarily traumatic.   

 We can describe two situations:

– a traumatic occlusion : potentially traumatic. 

– a traumatic occlusion : really traumatic.

The nature of the forces exerted must be taken into consideration: strong, weak, continuous, as well as the influence of the frequencies of the forces, and the duration, intensity and direction of the force.

ETIOLOGIES OF MALOCCLUSIONS  :

Most malocclusions are mainly caused by:

Hereditary or genetic This is why we often encounter similar problems among members of the same family. By:

• Incorrect implantation of teeth during their eruption into the oral cavity 
• Lack of space causing dental crowding (overlapping, rotations) 
• or excess space between teeth, extra or missing teeth 
• and imbalances between the shape and size of the jaws. 

Acquired   or external elements (environment) such as for example:

• Dysfunction

• Abnormal swallowing : Poor position of the tongue at rest or during swallowing
• Obstructive airway  problems causing chronic mouth breathing. This can affect jaw development and tooth position

• Parafunction: Chronic habits of sucking fingers on an object that can exert enough force for a long enough period of time to move teeth that will have a detrimental influence on tooth positioning.
• Premature loss of primary teeth through caries or permanent loss through extractions performed over the years can cause the other teeth to shift and contribute to the development of malocclusions.
• A trauma, accident or blow to the face that could cause teeth to move.
• Treatment of caries  : It happens that the occlusion is modified during dental care creating a (prematurity). An amalgam which fills a carious tooth can modify the relationships with the opposing teeth and create an imbalance. 
• The position of the teeth and jaw affects the occlusion. Missing, misaligned, crowded or protruding teeth are the cause of malocclusion.

DIAGNOSIS:

On the periodontal level: we will look in particular

• small accumulations of tartar under the gums, 
• tooth mobility.
• vertical or angular  bone destruction

On the neuromuscular level : we will look for

• muscle and joint pain 
• weakened function of the masseters.
• a muscle spasm.
• ATM disorders.

On the occlusal plane : we will look for 

• traumatic contacts: interferences and prematurities. 
• dental malpositions.
• poor fillings

All of these constitute occlusal disharmonies which can cause destruction of periodontal tissues, dental mobility and deviation of the path of the mandible.

CONSEQUENCES OF OCCLUSAL IMBALANCE

The most commonly observed disorders associated with malocclusions:

•  Aesthetic problems : affecting dental harmony and smile.
•   Chewing and speaking disorders 
• Joint problems (pain, discomfort, cracking, hypersensitivity of certain teeth, meniscus disorders). In the long term given a SADAM
• Dental problems: Enamel and dentin abrasion, Sclerosis and pulp calcification, Fractures, cracks, Mobility and Migration
• Posture problems and musculoskeletal disorders : including scoliosis 

CONCLUSION

Strict application of the rules of dental occlusion is the very basis of dentistry because it ensures comfort for the patient, it keeps the mandible in balance so as to avoid the appearance of temporomandibular dysfunction.

PHYSIOPATHOLOGY OF OCCLUSION IN CHILDREN

  Cracked teeth can be healed with modern techniques.
Gum disease can be prevented with proper brushing.
Dental implants integrate with the bone for a long-lasting solution.
Yellowed teeth can be brightened with professional whitening.
Dental X-rays reveal problems that are invisible to the naked eye.
Sensitive teeth benefit from specific toothpastes.
A diet low in sugar protects against cavities.
 

PHYSIOPATHOLOGY OF OCCLUSION IN CHILDREN