Prostho sheet # 15 - Eman Al-momani

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Prostho sheet # 15 - Eman Al-momani

Post by Shadi Jarrar on 25/1/2011, 6:19 am

بسم الله الرحمن الرحيم

note : this sheet contains several images.. download the file in order to see them.
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Selective Grinding and Milling

Selective grinding is defined as “modification of the occlusal forms of the teeth by grinding at selected places to improve function”. From the manual

Today’s lecture is about selective grinding and milling then we are going to talk about finishing and polishing of complete dentures, delivering the denture then review appointment.
Just a quick review about last lecture,
we talked about sources of occlusion errors and there were plenty of sources for the occlusion of the final denture to be compromised, that’s why we said we’re going to do laboratory remount, were you remount the denture using new master casts,
then do selective grinding, By doing the following sequence of steps:
 Restore the vertical dimension.
 Refine centric occlusion.
 Perfect working and balancing occlusion.
 Correct protrusive occlusion.
< Always keep in mind that the incisal pin should be touching the incisal guidance table >
Selective grinding will be done using articulating papers of different thicknesses, the one that you will be using is “65µm” in thickness, the articulating paper has certain color on each side. one side is blue, the other is red. You have to use one side for a certain movement and the other side for another movement -for example- Use red articulating paper for making centric occlusion and blue articulating paper for eccentric movements. You must write the colors that you have used for each movement in order not to forget. Then you have to use proper instrument to compleat your work, you need stainless steel burs and acrylic burs (like the ones you used before but smaller).
Restoring the vertical dimensions
“A lateral shift of a tooth or a tooth shifted to produce a high cusp can increase the vertical dimension.”
If the pin is not touching the incisal table that means that one or more of the teeth has moved from its place and the vertical dimension has increased, so what to do is that we can reduce the interfering cusp or we can deepen the opposing fossa.
concentrate –if you can- on deepening the opposing fossa not the cusp itself, but if the cusp was high in every movement then we can reduce the cusps’ height, and that is done by reducing the inclines not the tips of the cusps in order not to lose their function.
Note: If you see that, the cusps are high during centric occlusion then you have to deepen the opposing fossa but if you see that the cusps are high during every movement then you can reduce the inclines’ height of the interfering cusp(s).
In centric occlusion, the occlusion that we need is to have all of the supporting cusps (lower buccal, upper palatal) meet there opposing central fossa, i.e. lower buccal cusps should meet the central fossa of the opposing upper teeth and the upper palatal cusps should meet the central fossa of the opposing lower teeth. Moreover, there should be no occlusion on the anterior teeth.
So to obtain even contact in centric occlusion:
 Lock the upper arm of the articulator in centric relation. Check the occlusion by opening and closing the articulator, and lightly tapping the teeth together on red articulating paper.

 Loosen the locks on the condylar elements and move the denture in eccentric movements. Using blue articulating paper between the teeth.

Now, the cusp which has one color means that it is high in centric occlusion only, so you can deepen the opposing fossa, but the cusp which has two colors demarks that its’ high in centric and eccentric movements so you have to reduce the cusp itself. The cusp might be a supporting cusp so you have to be careful while reducing its height, by reducing the incline or the cusp itself.
At the end of the procedure - in centric occlusion- you should have even contact on all the posterior teeth, but not on the anterior teeth.


Now as you can see, we have a space between the upper and lower posterior teeth.


We’ll use a horse-shoe articulating paper (not like the type in the picture) so you can check occlusion on both sides at the same time.


Now if you look here you can see that we have a contact on the palatal cusp of the second premolar, and that is not the even contact that we are searching for. We need the contact to be on all of the palatal cusps. So deepen the opposing fossa as we said before to restore the correct even contact.

Adjust the working relation:
After we have obtained the even contact in centric occlusion, we are going to adjust the working relation; right movement, left movement and then protrusive movement.
Loosen the centric locks and use blue articulating paper.
As a rule in selective grinding, the supporting cusps are not ground. These are the maxillary palatal cusps and the mandibular buccal cusps, because they are essential to maintain the recorded vertical dimension. However, we can reduce the upper buccal or the lower lingual cusps this is called the B.U.L.L. Rule. (Buccal of Upper, Lingual of Lower), so always on the working side the cusps that we trim are buccal of upper and lingual of lower.
Now In the BULL’s rule, reduce the lingual inclines of the upper buccal cusp not the buccal inclines of the buccal cusps because they are visible so they effect esthetics also they are not the ones which are involved with the sliding movement,
as for the lower lingual reduce the buccal inclines of the cusps because they are the ones which make the shift in the lateral movement.
On the balancing side the upper palatal and the lower buccal (supporting cusps) should be touching, so if any interference exists reduce the lingual slope of the lower buccal cusp, The buccal cusp is a centric holding cusp so grind carefully and do not reduce the cusp tip.



Adjust protrusive relations
We all know that while doing the protrusive movement the upper incisal edges should slide on the buccal surface of the lower incisors until they meet edge to edge, and the posterior teeth should be in contact.
the Christianson’s phenomena is only applied on natural dentate patients not denture wearing patients OK! , that’s why the posterior teeth should be in contact during the protrusive movement in denture wearing patients.
Sooo when adjusting protrusive relations you have to keep in mind that there will be no space between the posterior teeth when the anterior teeth are at contact.
Now if the anterior teeth are touching and the posterior teeth are not, that means the anterior teeth are high and they should be reduced by grinding the labial surface of the lower anterior and the palatal surface of the upper anteriors until you achieve contact between the posterior teeth,
If heavy posterior contact exists with no anterior contact, reduce the distal inclines of the maxillary cusps and the mesial inclines of the mandibular cusps.


Here on the working side, we should have a complete contact and obviously, we don’t so we have to reduce the interfering cusps.


Here on the balancing side, we should see a contact between the functional cusps but apparently, we don’t, so we need to adjust it.
As we have explained before you do your selective grinding till you achieve good contact. Sometimes it’s hard to get all of the balancing contacts (between the supporting cusps) achieved on the balancing side, in this case you can have some of the balancing contacts touching and its better to have them between the molars, that means if you don’t have balancing contacts on the premolars it’s ok as far as you’ve got them on molars.
The same is done for the other balancing and working sides.

To summarize up, achieving good occlusion demands the following:
 Supporting cusps should be in there maximum intercuspation (in centric relation).
 On the working side, upper and lower buccul cusps should be touching, so does the upper and lower lingual cusps.
 As for the balancing side, supporting cusps should be touching.

Milling
Milling is defined as “the process of refining or perfecting the occlusion of removable partial or complete dentures by placing abrasives between their occluding surfaces while the dentures make contact in the various excursions on the articulator”.
From the manual

After you are satisfied with your occlusion, the second step is to smoothen the teeth’s surfaces as they have became rough during the grinding step, in order to have smooth gliding from centric to eccentric movements.
This step is done by using Carborundum paste, place the material between the occlusal surfaces and then move the articulator through all the excursive movements.
When milling is completed, remove all traces of carborundum by washing it off. The ground surfaces of the teeth must be polished after that.

After the selective grinding and milling are completed, an occlusal index is made to preserve the face-bow mounting if a clinical remount is necessary.

Finishing and Polishing
First remove the master cast by using a plaster saw, it’s a very difficult process especially if there were sever under cuts, then any excess acrylic material is removed by polishing the denture.
Polishing is done using tungsten carbide burs, then use stones for smoothening the lingual surface, and for cleaning excess materials between the teeth use small burs, then we do polishing using polishing past and special polishing instruments, polish all the surfaces including the palatal (fitting) surface, until you get the final look of the denture.
Then you can –by using small round burs- make stipples to let the denture look more natural. This step actually depends on the patents request if he wants it or not.
Delivering and Adjusting Complete Dentures.
Now it’s time to deliver the dentures to the patient, of course delivering the denture is not just placing the denture in the patients mouth but also adjusting it in his/her mouth,
Adjustments include extra oral, intraoral and occlusion.
Denture Evaluation:
 Dentist’s evaluation.
 Patient’s evaluation.
 Friend’s evaluation.
If the patient has had a previous denture, he/she should remove it for at least 12-24 hours. to relief the tissues which were compressed.
So many errors are expected and the sources of them are:
 Errors made by the dentist.
 Errors made at the laboratory.
 Inherent deficiencies in the materials.
 Biological factors.
Before inserting the denture inside the patients’ mouth inspect the extra oral errors, for example: Smooth any sharp areas, Inspect for specules with gauze by passing it over the denture, Blend angular changes on periphery with the art portion of the denture.

Order of Adjustments:
We start to adjust the fitting surface by evaluating it using Pressure Indicating Paste, then the Peripheries with also Pressure Indicating Paste (one side at a time), then you adjust the occlusion with articulating paper and clinical remount, finally you adjust esthetics, phonetics and also you should take into consideration your patient concerns.
Insert the Maxillary Denture First and ask the patient if he’s comfortable with it, if there are certain areas that the patient can locate at this stage you have to take them into consideration. Check if the denture is fully seated and check the adaptation of the denture base.

(We usually use Pressure Indicating Paste), Dry the denture up, place a thin coat with a stiff brush and leave some streaks in paste.

(A thin coat with some streaks like this)




reflect the cheaques then place the denture, - “be careful” the denture should not touch the tissues of the oral cavity because it will remove the PIP that you have put- seat the denture properly then remove it out of the oral cavity, then read the PIP.

Reading the PIP:
Ther are some areas wich will look like one of these cases:
 Burn through areas (No paste left):it means that there is an excessive pressure and that area should be relieved.
 Paste remaining with no streaks: Acceptable or normal contact.
 Streaks remaining: No tissue contact and other areas need to be relieved.

You have to be careful while reliving some areas, like the maxillary tuberosity, because it always has an undercut and that’s for improving retention to prevent unseating of the denture while functioning. So use care in retentive areas like hamular notch and tuberosity undercuts; they look like burn through but may not require adjustment.
Relieving pressure spots is done by using large acrylic burs.
Repeat until the denture is fully seated, and relatively uniform contact is achieved ( minimal streaks and no gross burn through ).
After adjusting the fitting surface you have to adjust the extensions by placing PIP on the periphery on one side and check if the PIP has been erased, that means that there is an over extension. So trim it, then re-apply the PIP and repeat the process until you get the desired results, then do this step on the other side.
There are some areas that need special attention like Frenal Areas; frequently they need to be adjusted by using fissure burs.
Also you have to use the PIP on polished surfaces to see if the borders are thick or if there is an over support in these surfaces, (you have to keep in mind that close to the teeth you did root prominences on purpose so you keep them and don’t trim them);


To make it more clear take a look at these pictures:


Root prominences=> should be kept without trimming.


Thick peripheries => should be trimmed.



Also we adjust the palate, as we said the palate should be very thin, so if you apply the PIP and it was removed you have to trim away the excess thickness; because it will affect phonetics and the comfort of your patient.
Then check retention for the upper denture by pulling it down and anteriorly if you find resistance then there is good retention,
(Retention: is the resistance to vertical movement away from the tissue)
(Support: is the resistance to vertical movements towards the tissues)
now if you want to check retention in the posterior part of the denture, then put your fingers behind the canines palataly and try to flip the denture, if you feel resistance then that means that there is good retention, but if it moves from its place then that means retention is compromised, (maybe the post dam was not carved good!).
Over extension of the flanges are checked by asking the patient to open and close his mouth, if the denture drops that indicates over extension. As for the posterior overextensions (beyond the vibrating line) , adjust using an indelible marker, by drawing the vibrating line intraoraly, it will print on the fitting surface of the denture when you place the denture in your patients mouth, then trim the excess material.
Repeat for the Mandibular Denture; if you want to check retention anteriorly try to pull it anterioly, and if you want to check the retention posteriorly place your fingers on the anterior teeth and push down
if the posterior part goes up  bad retention 
but if it stays in its place  good retention 
Occlusal Analysis:
Place both dentures in their places, ask the patient to close his mouth on a cotton roll placed between the posterior teeth bilaterally for a minute to simulate compression of the tissues, after that ask the patient to close in centric relation, check “visually” the occlusion, then check by using articulating papers. if you have gross occlusal errors you have to adjust them orally then do clinical remount.
One of the common occlusal errors at the time of insertion is to have an anterior open bite that means that we have an interference in the posterior teeth and we have to adjust it using articulating paper as we said before.
Occlusal adjustment intraoraly is a very exhausting step because the patient is not used to wear dentures, besides there is saliva which interfers your work, and it’s so annoying for the patient to be asked to open and close his mouth, so the best thing you can do is to deal with this step extraoraly, by doing clinical remount.
Clinical Remount.

Occlusal errors may be removed by making corrections while the dentures are in the patient’s mouth or by making new maxillomandibular relation records and replacing the dentures on an articulator. The later method is more accurate because the dentures are seated on rigid bases, the errors are more easily seen and soft tissues and saliva do not interfere with selective grinding. Extra information from the manual
Clinical remount is recommended because selective grinding intraoraly is difficult due to many factors including:
 Shifting of the denture bases.
 Tissue distortion.
 Eccentric closures by the patient.
 Presence of saliva.
 Lack of visibility.
 Time consuming.
 Psychological factor  the patient will feel that there is something wrong with the denture when you keep asking him/her to open/close his/her mouth several times.
Now if we want to remount the dentures we want the master casts, but as you know we’ve broken them, so how can we solve the problem !!!
We make new casts  but this time we don’t need to have a proper fitting surface,
“be careful” place wet cotton rolls in the undercuts because if the plaster goes inside them it will be difficult to remove it.
Now by using the occlusal index, which we made previously, seat the maxillary denture, and then pour the remount plaster onto the denture.
Record Centric Relation
Use small amount of bite registration material made of silicon, place it between the occlusal surfaces and ask the patient to close on it, we don’t need the patient to close until there is perforation in the bite registration material, because if there is a high point the patient will bite on it first then a shift will happen to achieve maximum intercuspation so this way if a shift happens with a maximum intercuspation we can’t recognize which cusp is interfering with proper occlusion, so what you have to do is to ask the patient to close slowly until the first tooth touches then the patient should stop closing and that’s the position that you will be doing (the centric relation).
Mount the lower denture according to this occlusal relationship and start identifying which tooth is causing interference, then fix the occlusion you can use again the bite registration material, or some other types of materials like aluwax (aluminum reinforced wax),
place the aluwax on top of the occlusal surface then put it in hot water to soften it, then insert the denture inside the patients mouth and ask him/her to close until the first teeth touch then he/she should stop and according to the record we place it between the upper and lower teeth and turn the articulator upside down then mount the lower denture.
Ensure that no debris are under the dentures that interfere with the centric position after mounting,
here you can do an extra step you can bring a piece of wax or bite registration paste and put it between the anterior teeth then ask the patient to bite edge to edge with his lower anterior teeth 4 to 6 mm in protrusion, then you can put this protrusive record on the articulator and if the condylar inclination which we made at the beginning matches the protrusive record then the protrusive relation is correct.
Then do selective grinding using articulating papers with different thicknesses, you can start with thicker articulating paper and then finish with a thinner one, you don’t need an 8µ articulating paper - as it is written in the slide - because occlusion of complete dentures does not necessarily have to be accurate.
Ensure:
 No anterior contacts in Centric Occlusion.
 Uniform simultaneous in bilateral centric contacts.
 Smooth excursive movements; ensure good selective grinding.
Balanced Occlusion
You have to ensure:
 That Balancing contacts are present.
 That Balancing contacts are not heavier than working contacts.
 And there should be 2-4 mm (the free way space) between the teeth.

Phonetics
Phonetics are highly dependent on the occlusion of teeth and setting of the teeth as we took before.
‘F’ sound: is pronounced when the maxillary incisors touch the lower lip.
‘S’ sound: is pronounced when the incisors are close together, and it depends on the free way space; if there were no free way space then it’ll be pronounced as ‘sh’.
You have to know that phonetics are not adjusted at this stage, because it just needs adaptation from the patient to the denture, so you can leave it to the post-insertion appointment to be adjusted.
Then check esthetics and approval of the patient to the denture, and tell the patient that is this is the last chance to criticize the shape, color, and size of the teeth.
After you do the adjustment, you have to do polishing using deferent types and sizes of stones, then for the final polish use felt cloth wheel (which is disposable).
Give the patient instructions about the dentures, its preferable to give him/here written instructions about how to deal with the denture while doing Mastication and how to speak with it, and finally how to provide care to it.

OK…now after you give the dentures to the patient you should expect problems in the first week, so you tell the patient to come back in another appointment after 2 or 3 weeks for the post-insertion stage, and don’t forget to tell the patient that you will face some problems in your first week, so this appointment is important to solve any displeasure you find in the denture.
If you don’t tell the patient that he’ll face some problems with his denture then the patient will think that the denture is not good and you’ll end up in losing a patients confidence with you.
(بمعنى ان المريض سوف ينعتك بالطبيب الغير ماهر لأنه وجد الطقم غير مريح)
So at the time of post insertion or post fitting of the dentures there are certain problems that we’ll take them in details in the 4th year “ISA” because this is basically a clinical step but here is an overview:
Diagnose the problem using PIP, articulating paper, or indelible marker.
Take your time while diagnosis because patients are frequently wrong in exactly locating the source of their problem, so look and think.
Ask the patient some questions:
 Where do you feel the pain?
 When do you feel it? Is it upon chewing only or upon insertion?
 How long the pain lasts?
 Anything makes it better or worse!?
Have the patient demonstrate the problem.
Actually there are limited number of problems (if you have followed the steps correctly and if you did the needed adjustments at the insertion stage);
The problems are usually:
 From the denture base.
 Occlusion.
 Interferences; especially at protrusive movement.
 Retention.
 Vertical dimension.
 Allergies and infections.
 Tooth position.

In details:
If the problem was from the Denture Base;
The problem will mostly be because of Impingements, specules, sharp edges. Diagnose them using PIP. (Now is the proper time to use the PIP).


You have to be careful while examining, cause sometimes the problem comes from occlusion, so you have to ask the patient when he feels the pain, if he/she feels it while chewing then you should expect that there is a premature contact between the teeth at one side that brings heavy occlusion at that side, in this case you should adjust the tooth not the base.


if the problem was from occlusion;
The patient will complain from a pain that lasts throughout the day, so you’ll know it’s because of the continuous chewing  there is an occlusion problem!
Usually it’s difficult to locate the error intraorally so you have to do clinical remount.

Retention Problems;
If the patient came back unsatisfied with his/her dentures because they drop while eating or swallowing,
then the most common problem will be  the flanges are over-extended. so adjust them using PIP,(put the PIP on the borders of the denture then do functional movements, see if the PIP is burned through in certain areas; it means that there is an over-extension so trim it).
Sometimes the retention problem comes from short flanges, we adjust them by elongating the flanges (we’re not gonna talk about it now, wait till next year  ).

Occlusal Vertical Dimension (OVD) problems,
If it was Excessive then the patient will have generalized pain and fatigue in his muscles.
If there was “an Insufficient vertical dimension” or an “excessive free way space”, the denture will lose its efficiency during chewing. The patient will feel that he/she is taking time while bringing his/her teeth into occlusion, so he’ll lose power in chewing.

Allergies and Infections,
- uncommon.
- if there was an allergy, it will be accompanied by generalized inflammation.
There are also hygienic problems  the patient comes with a sore throat.

Tooth Position problems,
It results in:
 Instability.
 difficulty in chewing, (at this stage it’s difficult to adjust it so you have to trim the teeth and re-set them on the dentures).
 Esthetic, phonetic problems (change position of the teeth).

Most Common Areas Requiring Adjustments,
In the maxillary denture:
 The hamular notch.
 Buccal areas around the tuberosities.
 Labial frenumrequires relief
 Base of zygomatic arch.
 Mid line raphe.
In the mandibular denture:
 Area of lingual (and sometimes labial) frenum, if overextented  it may cause ulcer or dislodgment.
 Buccal shelf area, remember it’s a primary area for retention, if excessive pressure is exerted then ulceration may happen.
 Retromylohyoid overextensions: the denture moves during swallowing.
Phonetic problems,
You have to wait and allow time for adaptation, sometimes you need to add soft wax to the palate to increase its thickness it, check if it improves the phonetics then add acrylic.



By that, you will have a perfect complete denture, which is ready to be worn by the patient. So the patient will be happy, You will be happy, and every one will be happy, seee!!! We make people happy. :p








Good luck every one

Done by: Eman Hashem Al-momani.
Sheet #13
3rd lec. for Dr.nadia.


Last edited by Shadi Jarrar on 27/1/2011, 1:29 am; edited 1 time in total
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Shadi Jarrar
مشرف عام

عدد المساهمات : 997
النشاط : 12
تاريخ التسجيل : 2009-08-28
العمر : 26
الموقع : Amman-Jordan

http://jude.my-rpg.com

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Re: Prostho sheet # 15 - Eman Al-momani

Post by Mohammad Bustani on 27/1/2011, 1:06 am

its no 15 .. 13 was abt festooning and written by hanan :D
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Mohammad Bustani

عدد المساهمات : 14
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تاريخ التسجيل : 2009-09-06
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Re: Prostho sheet # 15 - Eman Al-momani

Post by Shadi Jarrar on 27/1/2011, 1:31 am

أنا عدلتها .. بس هو بالشيت مكتوب 13 .. يمكن خطأ

شكرا على كل حال محمد
:)
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Shadi Jarrar
مشرف عام

عدد المساهمات : 997
النشاط : 12
تاريخ التسجيل : 2009-08-28
العمر : 26
الموقع : Amman-Jordan

http://jude.my-rpg.com

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Re: Prostho sheet # 15 - Eman Al-momani

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