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Occlosion & Jaw Relation Registration

Sondos Harbieh &

Baraa'h Alsalamt

Khalid Al-Hamad

27-10-2013

Occlusion - Occlusion is Relation of the of the maxillary and mandibular teeth when in functional contact during activity of the mandible. - Terminal Hinge Axis is an imaginary line goes horizontally between the condyles during rotation . Another definition for the occlusion from the slide : - An integral part within the stemato-gnathic system (SGS) (SGS: Teeth, TMJ, muscles, Periodontium. ) that relates teeth, not only to other teeth, but the other components of the SGS during normal function, Para function and Dysfunction.

RCP , ICP and centric relation RCP : retruded contact position ICP : inter-cuspal position - Centric Relation: The Maxillomandibular relationship in which the condyles articulate with thinnest avascular portion of their respective disks ( in centric relation you are talking about the maxilla and the mandible and the condition of the condyle )

- While the retruded contact position you are referring to the contact of the teeth (from the the slide : the initial tooth contact upon closure when the condyles have purely rotated whilst in their most superior unrestrained position in the glenoid fossae.) - and inter-cuspal position is the complete intercuspation of teeth regardless

of the condyle position (Centric Occlusion) -the inter-cuspal position is the habitual position that the patient will come with with his natural teeth when patient come to you need a restoration , crown or etc you must plan in what position your future restoration will be in (in its existing occlusion which is the inter-cuspal position or you want to change the position to the centric relation or to the retruded contact position ) - In 90% of the population, ICP is 1-2mm anterior to RCP

Here in this picture you can see the maximum interdigitation in the inter-cuspal position while if the mandible moves backward a little bit you can see that there

is a contact ( cusp to cusp contact ) which is not comfortable to the patient so that is why the patient will move forward for maximum interdigitation So the mandible will go a little bit backward but because the way the teeth are matching the patient will not occlude in this position he will use the habitual position which is the inter-cuspal position **So what will happen when the teeth are lost ? the inter-cuspul position is not exist now , because the inter-cuspal position is only exist because of teeth and now the only existing position is the centric relation because it is a boundary position it is not controlled by the way the teeth meet -You don`t want to lose your all teeth to lose your inter-cuspal position . Sometimes when there is a key contact between two teeth ( usually between the second molars ) we call it holding contact that hold your current intercuspal position , if you lose that contact the patient will get into a new inter-cuspal position

The significance of the inter-cuspal position - It’s the position in which vertical occlusal forces are most effectively borne by the periodontium with teeth likely to be loaded axially. - It’s the end point of the chewing cycle. - In every day practice, this is the position in which restorations are made and the position you must work with Because it is easier and practical and you don`t use retruded contact position (RCP) unless you have to , And that is happen when you lose your inter- cuspal position , for example in complete denture there is no teeth and there is no inter-cuspal position ( it`s lost) … Some times also in fixed restorations ( bridges ) we icrease the vertical dimension so the teeth will no longer meet and the ICP is lost again and we use instead the RCP . So when your existing position is lost you have to go with another position ( a boundary position ,a reproducible position ) which is the RCP ..

- FOR EXAMPLE : When patient occlude in RCP it will be uncomfortable to him , (we will call it the holding contact deserving the inter-cuspul position ) but every time he occlude in this contact he will avoid it and go to the ICP and develop a memory for that . So usually patient know where to close and go directly into ICP … Slide 10

-If you are preparing a tooth ( a single crown ) , the contact in the ICP position will be lost and the patient will develop a new ICP so you prepare the tooth and the patient come back again, you remove your temporary crown the patient will come occluding in that tooth because the mandible moved to a new ICP Slide 11 From the examples You must know that to lose the ICP you don`t need to lose all the teeth , you can only lose a contact which is a holding contact and you will lose the existing intercuspal position

TO SUMMARIZE : -The inter-cuspal position is the easy position for you the patient come with it and it is for every day practice -You always use the inter-cuspal position unless you can’t use it any more ( in increasing vertical dimension , when losing all teeth ,when cutting all the teeth ) you switch to the RCP .

Mandibular movement :

When the mandible moves, teeth slide over each other. This partly determined by: - the Shape of the teeth( anterior guidance) - Anatomical constraints of the TMJ (Posterior guidance). - Both ( the teeth and TMJ) should be in harmony.

The working side vs the non working side

- You don’t say balancing side in dentate patient but in complete denture you may use this term - The working side is the side where the mandible is headed ( when you move the mandible to the right then the working side is the right and the nonworking side will be the other side ) When the mandible moves , teeth meets and slide over each other and this will be controlled by canine guiding occlusion . the canine will control the way the mandible will move and the way the teeth will separate , because the canines the upper and lower in the working side are only teeth contacting so the shape of these teeth ( the buccal of the lower and the palatal of the upper will dictate the movement of the mandible on the working side) , other teeth should be out of occlusion in dentate patient this is the canine protecting occlusion the canine is carring the load and all the other teeth is out of occlusion - it could be a group function not only the canines function , other teeth will participate which are the premolars ( so canine and premolars are contacting and other teeth are not contacting ) , so now we call it group function not canine guidance or combination … initially group function at the beginning of the movement canines and premolars are contacting but then the canines will pick up the movement and will separate the teeth out of occlusion

Anterior guidance

When patient pushes his mandible forward the movement will be controlled by different factors the factors are

- the shape of the lower - the way the upper and the lower anterior teeth contact

- it’s the effect of the contact between the incisal edges of the lower teeth against the palatal surfaces of the upper teeth on mandibular movement. -If you have steep incisal guidance you will have increase separation of the posterior teeth like in class 2 division 2 -Also the anterior guidance will be controlled by condyle guidance which is the way the condyle moves on the fossa but this is some thing you can’t change , The anterior guidance will affect directly your work ( you might be doing a crown on anterior teeth or you have to develop an anterior guidance in natural teeth to separate the posterior teeth ) when the mandible is moving forward posterior teeth should be out of occlusion ( in complete denture you shouldn’t do that ,when edentulous patient is moving his mandible forward the posterior teeth should be in contact ) there is a difference between occlusion in dentate patient and in edentulous patient . -The anterior guidance is protective , is protecting the posterior teeth , the mandible moves forward and downward so posterior teeth upper and lower will be out of contact ( in dentate patient ) -The anterior guidance should be comfortable to the patient - Smooth guidance, that is , there are no mandibular deflection. -Acceptable aesthetics & in term of phonetics. -Minimal movement of guidance teeth ( we don`t want over load on anterior teeth so you have to select the proper teeth and avoid weakened or periodontally involved teeth or teeth with post or crown ) Because the anterior teeth are guiding the movement of the mandible the best thing is that this teeth should be strong enough to carry the load so if there are teeth weakened periodontally or restorative you have to avoid them and select another teeth to carry the load . - they should provide posterior disocclusion ( posterior teeth should be out of occlusion )

-And if you are placing crowns and the anterior teeth , if they keep fracturing then there is something wrong in the load with these anterior teeth.

Occlusal registrations for CD- clinical steps

this patient here is edentulous and we finally managed the secondary casts, after taking a primary impression, fabricating a custom tray and taking the final impression. to get a good copy for the edentulous patient's ridges. so in the next step in the third visit is aims to create the shape of the complete denture we want to make. if your impression are accurate you will be sure that the fitting surface of the CD will be accurate enough, but how about the polished surface (the occlosal surface). How could we register the dimensions between upper and lower casts as they are in the patient mouth, because there is no teeth in the mouth the vertical dimensions in dentate patient will be controlled by the existing teeth when he closes his mouth. but if there is no teeth the patient can close the mandible all the way up. vertical dimension registration : we want the casts molded on the articulator, to estimate the patient with a certain vertical opening to provide space for the dentures. horizontal relation : between the lower and upper jaws (RCP). we can make that using wax rims, wax is easy to handle you can add to it , use a wax knife to decrease it, building the dentures on wax , register the RCP (the centric relation) and determine the vertical dimension Centric relation : a boundary relation which the patient can reproduce even without having his teeth, we can use wax to register it in the patient's mouth then move to the articulator and copy it to our dentures to fit in the patient's mouth. HOW can we register vertical and horizontal relations?

starting with the upper rim ,because it is wax you can simply add or decrease it changing it's dimensions.

◄ determine incisal show : how much you want

your patient to show teeth (0mm, 1mm or 2mm).

◄ using the fox plane device: it gives the

direction of the wax inclination . make the level of the wax parallel to the inter pupillary line anteriorly, and to the camper's line posteriorly. Camper's line : imaginary line between the inferior border of the ala of the nose to the tragus of the ear, usually the tip of the tragus. ** fox's plane IS NOT a face bow , one of the common mistakes made by students in exams.

◄ It should give good support to the upper lip ,

we build it up esthetically.

◄ place the midline, canine line, smile line

and reassure the occlusal plane conformance with the inter pupillary line and camper's line. by that your wax rim which representing the upper denture is DONE :D smile line midline Canine line

IMPORTANT NOTE: These three pictures are for the same patient, they are different from each other by the orientation of the occlusal plane. viewed from the dead center give a straight line , from above curved down and from below curved up. so you have to be aware about your position because it will affect your work. You have to look from dead center don't look from the side or from above you have to be straight ahead to make sure that your occlosal rim is parallel to the inter pupillary line. How much we show from the teeth below the lip, it differ between males and females, females tend to show more from the teeth. female : maxillary central incisors 3.40 mm and mandibular central incisors 0.49 mm. while males : max. central incisors: 1.91 mm and mand. central incisors : 1.23 mm. and with increasing age we tend to show less from the upper teeth and more of the lower teeth. how can i use that; if my patient is about 60 year old i make my incisal rims up to the level of the lip. also you have to discuss it with the patient. when you want to determine the Vertical dimension use non mobile dots .

Methods for determining occlusal vertical dimension:

◄ preextraction records

◄using old casts of the

patient's mouth when he was edentulous.

◄ preextraction

measurements in his file.

◄ Ridge relations

usually a good vertical dimension can be achieved when the ridges are almost parallel to each other.

◄ measurements of old dentures

◄ Niswonger technique: we determine the interocclusal rest space ( the free

way space) the commonest technique when the patient comes to our clinic without anything to help us, we have to create that vertical dimension then we use the rest of stuff here. the space between the ridges at occlusion and at rest. then place the upper and lower wax rim to meet to gather in the patient's mouth, and measure the Vertical dimension (e.g. it is 40 mm) then get the mandible into resting position (relaxing position) the mandible should drop a little bit to get (e.ge 44mm) new vertical dimension. by this we get the difference between those two readings which is 44 mm at rest - 40 mm at occlusion = 4 mm is the inter occlusal space. which means when the patient is relaxing there is around 4 mm of space between the upper and lower rims of the complete denture. if that space is around 3 mm then your vertical dimension at occlusion is correct.

◄ phonetics : asking the patient to pronounce certain letters

◄ esthatics : bring the upper and lower rims to the standers, the lower rim

does not be higher than the corners of the mouth, that usually conforms for good occlusion.

◄ Tactile perciption

◄ Bite force

to be honest the is no one technique that gives you dead right vertical dimension, you have to use combinations of these things. How to get the Rest vertical dimension? ask the patient to pronounce the litter M and relax , or drink some water and relax again, or open wide and tap on the cheek and ask him to close until the lips parley touch. these will help to get the patient into resting position. Resting position means that : the mandible is resting there with minimal contractual activity, the muscles are not contracting, by this we will get the bigger vertical dimension at rest which we just said an ex. 44 mm. then when we place the wax rims in ask the patient to close and measure the vertical dimension at occlusion, which should be less than the VDR (vertical dimension at rest) by around 3 mm , which is the Niswonger technique. you can use instruments and place dots to check the difference. Mistake : in some cases during practice in DTC you may end up with wax rims dimensions that their VDO bigger than VDR! which means you have to reduce from the wax rims. until the VDO is smaller than VDR by around 3 mm.

Video 1: how to get the patient's mandible into resting position.

to check that ur vertical dimensions are correct.

Video 2 : Adjusting vertical dimension to obtain the required free way space. a patient putting the wax rims with increased VD and he is trying to talk

saying Mississippi, because there is no space the patient can't talk. then the dentist adjusted the lower rim to increase the space between the rims to the proper space and then patient could talk again.

so u can use the measurements and check again with phonetics and go to tactile sensation with the general esthetics to the patient and you can come to the conclusion that : yes my vertical dimension is correct or I have to adjust it , increasing or decreasing it.

You have to know that VD

is not measured by micrometers, if your VDO was 40 or 41 or 42 it doesn't need to be accurate by micrometers you have to give the patient an area of a good VD there is a correct area that the patient can stand with it , so it is a range or an area of FWS (free way space) you could increase or decrease it a little bit without affecting the function wanted from the denture. and the patent being fine.

But if it is too much increased or decreased then your patent will be affected , that's why no one technique will give you an exact VD wanted it gives you an indication. also it is not very accurate because:

- tissues are mobile. - esthetics perceptions of

esthetics differ from one dentist to another

- the general comfort of the patient himself

-phonetics usually the patient is a new edentulous when you just put the rims in , a lot of saliva is secreted it is not comfortable normally he will not pronounce some words properly even if your VD is correct.

so each technique has a divorce by itself but if you use combination of these techniques you will end up by providing the patient an acceptable VD.

this is a good video to take a look at:

https://www.youtube.com/watch?v=Q1xoWm0Ts_A&feature=youtube_gdata_player Done by : Sondos Harbieh Baraa'h Alsalamat