Occlusion sheet # 7 - Mohammad Abukar

Occlusal Analysis
*This lecture is NOT included in the midterm exam

Occlusal analysis is an integral part of the examinations of the stomatognathic system (Dr. Maher will give lectures about TMJ and related muscles examination) and today we’ll talk about examination of occlusion and so we’ll conclude the whole stomatognathic system (which is TMJ, muscles and the teeth).
Clinical examination of occlusion includes extraoral and intraoral examinations.
Extraoral Examination: Examination of the stomatognathic system as a whole [TMJ and related structures (muscles and ligaments)].
Intraoral examination: Examination of the static and dynamic occlusal structures.
(We’ll discuss them soon in the sheet. Some inclines are considered dynamic because they become in contact during function. Static structures are the points on which centric occlusion takes place.)
In the previous lecture, we discussed interarch and intraarch static and dynamic relationship. In this lecture, we’ll add to this topic and will see the points of occlusion and the relationship and how we will transfer the information we obtained to the lab.
Examination includes:
1- Clinical study. (Examination of the patient)
2- Radiographs.
3- Study models. (The casts)
Extraoral Examination: We’ll talk about it briefly but we’ll study it in details later on:
- Palpation of the TMJ and related muscles (of mastication)
we’ll study the examination of each muscle in details later on.
- Study of the mandibular movements such as opening and mouth closing, mandible limitations in the jaw movement and the path of movement.
- Listen for sounds from TMJ (clicking and crepitus).
- In addition to these we also should take radiographs and study models.
Examination of TMJ includes:
Palpation: We let the patient set on the dental chair in the semi-reclined position and we palpate the TMJ and the related muscles in addition to listening by a special stethoscope that has two sides for the TMJ. The stethoscope is placed on the TMJ and we listen for sounds).
The sounds could be crepitus or clicking.
clicking = voice sounds like “tuck”
crepitus = rattling (خشخشة) which is continuous with movement.
Study of the mandibular movements: Opening and closure.. we notice the amount of opening and we notice if the path of opening is entirely in the center or if deviation to the right or the left takes place.
We notice if the amount of opening is normal (we know what the norms are = 40-60 mm). Also the right and left movements, protrusive and retrusive movements amounts should be in the range of the norms that we know.
Intraoral examination includes:
1- Dental examination (History, fillings, oral hygiene, extractions, ortho treatment) because all these affect occlusion.
2- Static occlusal structures.
3- Dynamic occlusal structures.
4- Arch organization.

1) Dental Examination and History:
- Study of the number and position of the teeth. Check teeth relation to one another whether it is correct or not, check if there are missing teeth and detect anomalies of tooth form and structure (e.g. the size of the teeth is abnormal and thus we should be knowing the anatomy so that we’ll know what is normal and what is not).
- Status of the teeth (hypo/hyper mineralization), caries or any other problems
- Pathologies of soft and hard tissues (caries, infections, if there is swelling and where it is etc.)
- The previously stated points are always done in the examination for the patient regardless of the problem he is facing.
2) Static occlusal structures: includes:
- Functional cusp tips, internal cusp ridges, marginal ridges of maxillary and mandibular teeth. We check the stability of the centric occlusion position (could the patient always close his mouth in the same point or not?) and the distribution of the occlusal stresses axially (we check the points of contact if they all are well-distributed on the teeth) and the masticatory function (whether the patient has problems during mastication or not).
- Check for mechanical tooth loss (abrasion, fracture in teeth.. next lecture we’ll see abrasion and fracture due to occlusal problems).
- Type of occlusion. Whether it is cusp to fossa, cusp to cusp or cusp to marginal ridge. We check if the contact is simultaneous, homogenous and equal in intensity bilaterally. This is detected by the articulating paper, we place the articulating paper (horseshoe-shaped) in the patient’s mouth, we ask him to bite and notice the points of occlusion if they are of same intensity and equal and if the distribution is on all the teeth because sometimes some teeth are not in contact with each other or the bite is on certain teeth more than other teeth.
- Occlusal morphology or tooth contact because this would affect occlusal stability, masticatory function and can cause closure interferences

3) Dynamic occlusal structures: includes:
- Incisal border of mandibular incisors, cusps of canines (involved during lateral excursion), lingual surfaces of maxillary anterior teeth (involved in protrusive movements), guiding mandibular movements, masticatory function and functional healthy anterior guidance.
- All these are taken into consideration in the dynamic occlusal analysis.
What is the importance of dynamic occlusal analysis?
- Changes in static structures would influence occlusal stability while changes in the dynamic structures would result in functional occlusal interferences (their influence is seen during function) while static structures will affect the stability of the teeth
 consequent problems in the stomatognathic system (any problem in occlusion affects the teeth, the joints and the muscles because all of them they work as a system).
4) Arch organization (inter/intraarch relationship):
The Dr. said “Interarch” while in the slide it was “Intra”.. Actually, after reading it seemed to me that both terms are applicable.
- Observation of the arch organization such as rotation, the position of the teeth, drifting of the teeth, etc. When we start our clinical courses we may notice rotation in the 2nd premolars of some patients so that they will be twisted (The buccal cusp is facing the mesial side instead of being toward the buccal). Such situations cause interferences. Another thing we may face is drifting of the teeth (Where there is an extracted tooth, migration may take place towards the mesial mainly but sometimes, to a lesser extent, towards the distal. Drifting can cause occlusal interferences
- All these abnormalities could result in change of the relationship with the opposing arch and thus they could cause occlusal interferences.
- Observation of the teeth in the sagittal and frontal plane (Curve of (von) spee and the curve of Wilson) and this is important so that the movement during function will be without interferences..
• While examining arch organization we check:
A- Examination of the maximum intercuspation position.
B- Examination of the displacement between centric occlusion and centric relation.
C- Examination of the anterior guidance.
D- Examination of the vertical dimension of occlusion.
All these terms are now familiar for you. We’ll repeat them in relation to the occlusal analysis.



A) Examination of the maximum intercuspation position:
• Stability of the centric occlusion is maintained by simultaneous, homogenous contact on all the teeth. How do we examine it? by the articulating paper.
• There should be a rapid closure of the mandible from the open position to maximum intercuspation. Opening and closure should be done always the without any interferences or side movements, should be regular and reproducible. The opening and closure should be always on the same path and the same intensity.
• Palpation of muscles of elevation during closure (looking for asynchronism and asymmetry). We examine the muscles that make closure of the mandible (i.e. the elevators of the mandible = temporalis, masseter and medial pterygoid). We palpate these muslces and check the intensity (is there a muslce that has force or contraction more than another during closure or not because this would indicate something that we’ll study later on.
• Palpation of the teeth once closure occurs. We put our finger on the buccal surface of the teeth and we ask the patient to close his teeth, the teeth should not move once they become in contact with each other, if movement occurs, this is what we call fremitus.
• Fremitus is occlusal trauma on the teeth causing their mobility due to occlusal trauma.. usually it is high contact.
B) Displacement between centric occlusion and centric relation.
• We know that centric occlusion is the maximum intercuspation between teeth while centric relation is a ligamentous position when the condylar head is in the foremost uppermost (anterior superior position in the glinoid fossa)  okay some people say posterior superior.. till now no one knows where the condyle exactly is in the centric relation but nowadays books use the foremost uppermost position in the glinoid fossa.
• We measure the anteroposterior and the lateral aspects of the shift (displacement) by asking the patient to close into the centric occlusion and we mark a point on the mandibular incisor showing where the maxillary incisor comes in contact.. e.g. the midline.. we mark the midline. Then, we ask the patient to go into centric relation (Dr. Suzan taught us how to let the patient be back to the centric relation) and then we mark again and we measure the distance between the two points horizontally, mesiodistally and vertically.
• The existence of a lateral component is indicative of a problem. There should be no lateral component in the centric relation.. If there is a lateral component, there will be a problem in the centering of the mandible (the patient doesn’t know where his centric relation exactly is  it is not reproducible).
• A displacement magnitude more than 2 mm is usually associated with signs and symptoms. We said that centric occlusion and centric relation coincide in only 10% of the patients while in 90% there is 1-2 mm only. If it is more than 2 mm there is a problem and if there is a lateral component then there is also a problem.


C) Examination of the anterior guidance.
• There should be a harmonious anterior guidance on incisors and laterals too. We ask the patient to make a protrusive movement after we put an articulating paper on his anterior teeth and we mark the path the mandible takes on the maxillary anterior teeth on the lingual surfaces of maxillary anterior teeth.. it should be harmonious in intensity on centrals and lateral incisors.
D) Examination of the vertical dimension of occlusion.
• Vertical dimension of occlusion is the lower facial height when the teeth are in contact with each other. It changes with age. It may be reduced with ageing because of flaccidity in the muscles along with wearing in the teeth while the other part (upper) of the face remains as it is with no changes.
• Loss of the vertical dimension of occlusion could result either from pathological loss of tooth structure and/or migration of the teeth. This could cause problems from an esthetic point of view because the angles of the mouth become unsupported and drop to the side. Plus nose and chin would move more forward and this is typical in the elderly. Neuromuscular problems may also occur because the teeth would travel a longer distance to close to each other from the vertical dimension at rest and this would cause neuromuscular problems.

Parafunctional habits:
Habits including infantile swallowing, nail, lip, tongue and pen biting.
What is infantile swallowing?
When babies swallow, till a certain age, they usually push their tongue between the maxilla and the mandible because the tongue will be moving forward. The tongue hasn’t gone back yet (I think to the pharynx as there is a pharyngeal part of the tongue). So, most of it will be in the mouth. And this is the infantile type of swallowing (The tongue comes between the maxilla and the mandible).
Some people maintain this with life so when they swallow they tend to push the tongue between the teeth and this would cause proclination of the teeth because there is an abnormal force from the tongue on the teeth. It is abnormal because when we swallow, we close the mouth anteriorly and the teeth together and so there will be a seal for swallowing.. they provide this seal by the tongue not through the lips and the contact of teeth with each other.
Nail biting is also a parafunctional habit. Lip and tongue biting can also have an influence on the occlusal stability and function. Nail and pen biting could result in changes in the tooth morphology or position.
Playing the wind instruments (e.g. flute) is also a parafunctional habit.
Also eating lots of nuts can be considered as a parafunctional because it affects teeth morphology. Nuts don’t cause an abnormal tooth position.


Occlusal analysis: Use of articulator


A part of the examination is making a cast for the patient. We take bite for the patient (by “normal” wax, green stick, compound or aluwax). Also we can use polyvinyl selxane which is a rubber material similar to that of impression for crown and bridge we also put it on teeth.. and we articulate the casts with each other. We also use face-bow because if we want to have the accurate relationship we should position the mandible to be related to the condyles on the articulator as it is in the patient’s mouth. Otherwise, in the centric we won’t have a problem but if we want to simulate the movements we’ll find that we should’ve used face-bow.
So, the use of articulators is a complementary step to confirm our clinical observations.. we examined the patient clinically.. sometimes we have certain things that may affect the examination such as: cheek, tongue and saliva that may erase the marks of the articulating paper so we better use the articulator..
Also it can add information because it is sometimes easier to locate occlusal contacts on the casts because there is no saliva erasing the marks + it is independent of soft tissue interferences + the advantage that we could rotate the articulator and see the relationship from the lingual side. So, if the reproduction of the casts is good and the bite is talking properly, there will be a greater benefit from using the articulator.
We also use articulators for occlusal equilibration (selective grinding). Any type of occlusal modification should be done on the articulator systematically before any irreversible changes are done in the patient’s mouth. So, articulators are also diagnostic of the treatment because if I started on the patient’s mouth directly, I may find interference and we removed it from patient mouth.. when we recheck occlusion we may find that we created a new interference!
You shouldn’t start occlusal modification in the patient mouth before seeing the result on the articulator and for this we need accurate study models taken in alginate (usually alginate doesn’t give us accurate study models.. if we want something very accurate we have to use polyvinyl selxane) and then mount it on a semi-adjustable articulator as a minimum plus the use of facebow registration in the centric relation jaw position. Hinge-articulators are not enough for occlusal equilibration or selective grinding.




Criteria of functional occlusion
What are the optimum criteria that we always look for in the patient?
1- Minimal shift between centric relation and centric occlusion.
2- Harmonious vertical dimension of occlusion.
3- Stable contacts in maximum intercuspation position with multiple bilateral, homogenous and simultaneous contacts on maximum number of posterior teeth NOT anteriors and in the last lecture we said why.
4- Functional anterior guidance free of posterior interferences.
















*Done by: Mohammad Abukar
*Occlusion lec. # 7
*Date of the lec. : 20.3.2011
*Dr. Yara Oweis