Occlusion
- ppDefinition of occlusion:
– According to Chaput: it is a static state obtained by the contact relationships between the dental occlusal surfaces, whatever the mandibular positions.
– According to Glickman: the term occlusion concerns tooth contact relationships resulting from neuromuscular control of the masticatory system.
- Occlusal morphology:
- The occlusal table
- Marginal ridges
- Central pits
- Support cusps: these are pyramidal eminences which articulate in PIM with the marginal ridges and the central fossae; these are the stops intended to maintain the DVO.
– 1st mandibular group: vestibular cusps of the PM and M
– 2nd mandibular group: occlusal edge of the incisors and canines
– 3rd maxillary group: palatal cusps of the PM and M
- Guide cusps: these are:
– The maxillary vestibular cusps of the PM and M
– The mandibular lingual cusps of the PM and M
– The palatal surfaces of the maxillary incisors and canines
- Reference positions and different types of occlusion:
3.1. Reference position:
a- Posture position:
It is defined as the resting position of the mandible, it can be considered as a reference position specific to each individual; it is in this position that mandibular movements begin and end.
When the muscles relax after the function, the posture position is resumed.
In this position, the teeth are not in contact. The distance between the occlusal faces is equal to 1-2mm, this is the “free space of inocclusion”
b- The centered relation:
This is a cranial mandible relationship independent of the teeth. It is the most posterior, symmetrical, unforced position of the mandible, the condyles occupy a high and retracted position in their glenoid cavities, a position from which all lateral movements are possible.
In this position, the mandible can perform a pure rotation movement by a virtual axis passing through each of the condyles. At the end of the closing movement in centric relation, the teeth come into contact; this is the RC contact position.
c- The PIM:
This is the mandibular closing position where the dental arches present the maximum number of contact points or contact surfaces.
In PIM, precise relationships are established between the occlusal surfaces of the teeth and more precisely between the cusps, the pits and the marginal ridges which must be examined.
3.2. The different types of occlusion:
a- Ideal occlusion:
Ramfjord speaks of ideal occlusion when all parts of the masticatory system exist in harmony to achieve optimal functional capacity and health.
It refers to an aesthetic and anatomical ideal.
– Stable and harmonious occlusion ratio both in RC and in the field from RC to centric occlusion.
– Equal ease in bilateral movements in deduction and propulsion.
– DV allows a resting position with adequate free space for occlusion.
– Normal orientation of occlusal forces for tooth stability.
b- Occlusion of convenience :
The notion of “normal” usually implies the absence of pathology and characterizes a biological system that functions within physiological limits.
Therefore, the concept of occlusion of convenience implies the function within physiological limits, a certain capacity of adaptation and the absence of identifiable pathological manifestations. It is a satisfactory acquired balance due to the compensations, which are established progressively:
– On the one hand, between the different mobile connections of the masticatory system.
– On the other hand, the periodontium has adapted through bone and cement remodeling.
So there is a functional adaptation of tissue structures.
c- Traumatic occlusion:
According to Stillman, this is a situation where bringing the jaws into close contact with each other results in damage to the supporting structures of the teeth.
d- Other concepts of occlusion:
- Balanced occlusion:
In balanced occlusion, there is simultaneous contact between the right and left posterior segments of the arch during lateral movements of the mandible, as well as simultaneous contact between the anterior segment of the arch during protrusive movements of the mandible.
Considered at one time as an ideal type of functional relationship, balanced occlusion is rarely encountered in the natural dentition.
Balanced dental contacts carry a risk of periodontal injury, which presupposes the benefits of apparent balance that could be provided by creating bilateral balance through occlusal adjustment using prosthetic restorations.
- Hinge axis occlusion: (gnathological theory)
It is based on the principle that the RC and the RC arc represent the functional aspects of occlusion. It assumes that the functional movements of the mandible begin with the condyles in RC and that the execution movements are functional such that the factors that govern the mandibular movements determine the occlusal morphology of the teeth.
- Static study of occlusion:
4.1. Intra-arcade arrangement:
a- Sagittal plane:
“The SPEE curve”: it refers to the anteroposterior curve of the occlusal surfaces, it begins at the top of the lower canine and follows the top of the vestibular cusps of the PM and M. The teeth must be arranged following this curve with superior concavity.
During an examination, it is important to check its regularity; an overly marked “SPEE curve” whose harmony is destroyed by dental migrations, causes occlusal obstacles disrupting functional movements.
b- Frontal plane: “Wilson curve”
The teeth are arranged in a curve with superior concavity, it is an imaginary line passing through the top of the cusps of the molars on each side of the arch.
c- Horizontal plane:
Due to the relative equivalence of the vestibulo-lingual dimensions of the occlusal areas of the same arch, it is possible to deduce the existence of substantially parallel curves:
– Primary cusp curves
– Secondary cusp curves
– Coalescence furrow curves
4.2. Inter-arcade arrangement:
The study of inter-arch relationships implies the existence of an asymptomatic clinical situation. The teeth must be able to meet freely without any pathology.
a- In the sagittal direction:
Each tooth comes into contact with 2 opposing teeth, with the exception of the upper 3rd molars and lower central incisors.
● Anterior sector: over jet of 1 to 2mm
● Canine sector: Angle canine class
● Molar sector: Angle molar class
b- In the transverse direction:
The mandibular arch is entirely circumscribed by the upper arch.
● Anterior sector: coincidence of the upper and lower inter-incisal points in relation to the mid-sagittal line.
● Canine sector: canine overhang
● Molar sector: meshing (cusp/pit ratio) the meshing between the pits or marginal ridges with the supporting cusps creates the occlusion stops.
c- In the vertical direction:
● Anterior sector: over bite of 1 to 2mm
● Canine sector: the upper canine covers the lower canine
● Molar sector: the upper molar covers the lower molar
- Conclusion :
We will emphasize that the various elements that make up the masticatory system constitute an anatomophysiological unit and are connected in a common place “the occlusion”.
It is essential that every practitioner respects the integrity of any unit in all therapeutic acts ; a single poorly adjusted crown can cause occlusal disturbances; a single extracted tooth that is not replaced can cause the disruption of an entire set of teeth.
The seemingly smallest intervention can disrupt the balance of oral health.
Occlusion
Wisdom teeth can cause infections if not removed.
Dental crowns restore the function and appearance of damaged teeth.
Swollen gums are often a sign of periodontal disease.
Orthodontic treatments can be performed at any age.
Composite fillings are discreet and durable.
Composite fillings are discreet and durable.
Interdental brushes effectively clean tight spaces.
Visiting the dentist every six months prevents dental problems.