Mouth Preparation- Lecture title : Mouth preparation - Lecture Date : 19-4-2012- Doctor: Qais George.

------------------------------------------------------------------------------------------- Our Lecture today is Mouth Preparation. Simply speaking it’s just like a patient receiving a surgical operation, you have to prepare the patient for the surgical operation.

For the metal framework RPD steps we have:In the Clinic- History & exam Primary Impressions, Mouth preparation, Final Impression.

Mouth Preparation:

The most important thing is that you make an appliance that’s relieving for the patient and that the patient could wear it and remove it as easy as possible. And you on your own create the most appropriate path of insertion and removal, and so facilitating the thing to you and to your patient. Because if the patient finds any difficulties in the rpd, he will not wear it, he’ll give it back to you, and it’ll be very difficult to correct it, because it’s made from cast materials.

We have objectives which is:-To return the mouth to optimum health and to eliminate any condition that would lead to failure of the prosthesis.

-It’s usually done after treatment planning, but should always precede secondary impression procedures and master cast formation.

Mouth Preparation Sequence:

-First of all we have, Oral surgical preparation.

-Periodontal therapy, to treat the tissue surrounding the tooth (bone, ligaments), to allow using the tooth as an abutment and make it fixed, otherwise we have to exclude it from our design.-Conditioning of abused teeth.-Occlusal adjustments.-Preparation of abutment teeth

(We’re going to concentrate on this in this lecture), Includes:

1) Conservative restoration of abutment teeth (might have caries, might be inclined… we have to fix this).

2) Preparation of guiding planes, for easier insertion and removal of the RPD.

3) Alteration of tooth contours, to adjust our desirable undercut areas, otherwise it’ll be useless, without any retentive means.

4) Rest seat preparation.

*Surgical intervention and Periodontal therapy, carried out FIRST, to allow for an adequate healing period before denture construction.*

First of all, we’re going to make our :

i.Oral Surgical Preparation .

-The important thing is, Extraction of non strategic, unrestorable weak tooth, that its presence may complicate the partial denture’s design.

-Removal of remaining roots, that are in close proximity to the tissue surface or that show evidence of pathosis.

-Elimination of bony spicules or knife-edged ridges in order to obtain good foundation for the denture. As you know our RPD is a hard material, the bone is also a hard material. The only resilience material in between is the soft tissue, which will be subjected to irritation from both, which will cause continuous trauma leading to inflammation then failure.

-Removal of interferences such as bony exostosis, enlarged tuberosities or tori that cannot be accommodated by modification of the denture design.

-Removal of hyperplastic tissues as fibrous tuberosities and flabby ridges that are not resolved by conservative-tissue conditioning program. Because they won’t withstand occlusal loading.

-Excision of abnormal soft tissue lesions such as cysts, polyps or papillomas.-Ridge augmentation (Increase the level of the ridge which is highly resorbed to make space for the metal framework and the other components of the RPD) and Vestibular extension may sometimes be required in severely resorbed ridges.

II. Periodontal Therapy:

The objective of periodontal therapy is to achieve and maintain a healthy periodontium for the remaining teeth, especially abutments.

Can be achieved by:

-Elimination of etiologic factors contributing to the disease, such as Calculus (esp. Upper 6’s Buccally and Lower anterior Lingually at the opening of the salivary glands), Traumatic Occlusion (due to buccally inclined molars), Overhanging margins of restorations, and Open contacts.

-Elimination and treatment of gingival inflammation and periodontal pockets.-Maintenance of oral hygiene through a plaque control regimen.

-Scaling and Root planning to remove plaque and calculus.

-Gingivectomy to eliminate suprabony pockets and to increase the length of the clinical crown to allow for the use of undercuts hidden by gingival tissue.

-Periodontal flap to correct deep periodontal pockets.

-Free gingival grafts to establish an adequate area of attached gingiva, especially on abutment teeth.

-Correction of occlusal trauma to prevent recurrence of periodontal disease. The main problem here is that the healing will be very difficult.

Patient should be followed up every 3-6 months for his periodentium, otherwise, we’re going to lose the abutments, and the end result will be Complete denture rather than Partial denture.

-Splinting of periodontally weakened teeth by temporary immobilization of teeth. Splinting: to support teeth that have minimum grade of mobility. Can be achieved by Inter-dental wiring or Splints, which may be either in the form of Acrylic or cast removable splints. Permanent splinting following Periodontal treatment is achieved by two or more cast restorations cemented on teeth. Done also by doing crown and attach wire especially on the palatal or lingual surfaces to support the mobile teeth (just like the ortho wires).

III. Conditioning of Abused Tissue

-Tissues covering edentulous areas may show signs of inflammation, burning sensation or distorted contours.

-Irritated or abused tissues in partially edentulous patients may arise due to poor oral hygiene, trauma from occlusion, an old ill-fitting denture, or due to continuous wearing of dentures.

-Irritation of the soft tissues may be in the form of Localized or Generalized inflammation, Denture Stomatitis, presence of soft displaceable tissues, Papillary Hyperplasia, or Epulis Fissuaratum.

These tissues are usually treated by: -Elimination of the factor causing tissue irritation.-Using mouth wash preferably Saline Solution.

-Tissue massaging using a soft tooth brush.-Tissue rest (tissue will not be subjected to load).-Tissue conditioning material (Soft reline material) could be used for patients with old dentures. We’re going to put a pushing material on the tissue surface of the denture to relieve the pressure on the soft tissue.

-Denture Stomatitis may require additional treatment with antifungal agent (e.g. Nystatin) when infection with Candida Albicans is evident.-Hypertrophied or Hyperplastic tissue growth in the form of Palatal Papillary Hyperplasia or Epulis Fissuratum may either completely resolve or may only shrink in size after treatment.

-Although surgical removal of unresolved tissues causes scar formation, surgery may sometimes be indicated if these tissues interfere with the design and placement of the denture.

We have to create a healthy environment that can receive our RPD.Sometimes we need the 2 steps mentioned above (Surgical and Periodontal treatments), sometimes we don’t need them, so we just begin with the 3rd step (Conditioning).

IV. Occlusal Modification

-Adjusting the occlusion of natural teeth is preformed to establish simultaneous occlusal contact and harmonious cuspal relation.-Occlusal equilibrium should be carried out first on a duplicate the diagnostic cast and then performed in the patient’s mouth.-It’s usually achieved by Selective Grinding or by Recontouring or placing a Surveyed Crown on offending teeth.

Objectives :

-Eliminate Premature contact resulting from Over-eruption of teeth.-Eliminate deflective occlusal contact to establish harmony between Centric occlusion and centric relation.-Obtain simultaneous contact in eccentric positions.-Establish an even occlusal plane.

End of Part (1)

Done by:Fadi Omar Massarwa

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Part # 2 Done by : Saleh Al-Naimi -------------------------------------------------------------------------------

IV. Occlusal modification ( continue )

Here in Occlusal modification we might Have :

1- Supra-eruption.

and it means The extent of treatment depends on the severity of occlusal plane irregularity.

Examples :

_ Slightly over-erupted molar teeth may require simple reduction

_ If over-eruption is accompanied by migration of the maxillary tuberosity, correction may either require the use of a the metal denture base instead of a thick acrylic base or surgical reduction of the tuberosity if the position of the maxillary sinus allows.

Sometimes the maxillary sinus is too big that we cannot reduce the bone , it means we are going to penetrate the sinus , once the maxillary sinus is penetrated it will cause chronic inflammation & chronic headache to the patient

2- Infra – occlusion.

It’s better to correct than supra occlusion ( supra-eruption)

It means Lengthen the clinical crowns of teeth that are in infra-occlusion by placement of cast overlays or crowns. Main purpose is to Elevate them to reach the corrected Occlusion

Sometimes we can do :

- Extractions : of severely malposed or over erupted teeth

As we can see in this picture , there is no interocclusal distance , and its very important to detect these malforemed teeth while Examination

. its mostly due to the patient’s neglection of his teeth once the patient do multiple extractions and he don’t replace the missing teeth he will end up with Irregularities such us : supraeruption and this will impair the occlusal plane of Course ..

- In such cases we should correct these teeth to Adjust our occlusal plane and get an ideal contact

RPD Treatment Planning

Occlusal relationship must be evaluated with mounted diagnostic casts to study the following:

_ Vertical Dimension of Occlusion (existing VDO assessment)_ Occlusal plane_ Amount of interocclusal space .. Very important thing _ Horizontal and vertical relationship of anterior teeth_ Centric occlusal contacts_ Occlusal eccentric schemes (anterior guidance, group function)

Above factors play a critical role designing a removable partial denture.

Once you take your cast on the Articulator you have to study And recognize these steps in order not to suffer while constructing the RPD

Preparation Of Abutment Teeth

- Abutment teeth supporting removable partial dentures especially distal extension partial dentures are subjected to distal tipping, rotation and horizontal movement.

- Every effort should thus be made to preserve and protect abutments from destruction.

And this is Achieved by proper treatment planning and adequate abutment preparation .

- Abutment teeth should also be adequately prepared to provide support, stability, reciprocation and retention for the partial denture.

Preparation of the abutment teeth is preferably carried out first on a duplicate of the diagnostic cast and then performed in the patient's mouth.

- Abutments are grouped according to the extent of preparation required into:

1- Abutments Require Minor Modifications , these are sound

2- Abutments requiring conservative direct restorations or indirect cast inlay/onlay preparation . And these Abutments Exhibit Extensive carious lesions

3- Abutments requiring indirect surveyed crown restoration, And this one to correct Long Access of the teeth we cannot remove, because its important in Our Design .

Mouth Preparation for RPD framework

Objectives :

obtain parallel guiding surfaces to achieve positive rests to remove excessive undercut//lower the height

ofcontour Sometimes we tend to lower the height of contour To Achieve Esthetics , because we don’t want the retentive Arm of the clasp to show .

to create desired undercut for retention

Preparation of abutment teeth in any of the previous groups should be carried out in a planned sequence:

1- Conservative restoration of abutment teeth.2. Preparation of guiding planes.3. Alteration of tooth contours.4. Rest seat preparation.

(1) Conservative Treatment of Abutment Teeth.

a) Carious lesions in abutment teeth should be conservatively treated and restored with either properly condensed amalgam or preferably castinlay restorations

b) Pulpal exposures are endodonticaly treated and the tooth is preferably protected by cast crown restoration (“surveyed crown”).

Endonditcally treated teeth should not be Subjected to load ,because its Brittle and subjected to breakage of crown . so We have to Crown it or what we call it (. (التلبسية

c) Construction of cast crowns (“surveyed crowns”) either full crowns ( the whole crown will be Covered ) OR veneered crowns ( Only the buccal or facial Surfaced will be covered )

This Procedure for : preservation and protection of weak abutments & patients exhibiting bad oral hygiene.

Surveyed Cast Crowns as RPD Abutments

When Does One Choose to Fabricate a Crown to Serve as a Removable Partial Denture Abutment?

When correction of unacceptable tooth contours cannot be achieved through enamel modification alone leading to significant it means we prepare the tooth by using Straight fissure burs , if it cannot be done We have to crown the tooth

Dentine Exposure Caries & sensitivity

To restore a badly broken down clinical crown ( picture slides 8 ) To reestablish a proper occlusal plane (i.e. supra-erupted teeth ) To provide proper rests, especially with anterior teeth and

adequate retentive undercuts for direct retainers I-bar, C clasp) when inadequate contours exist.

Here the doctor started to read the slides Which are not included in the Exam so please if you want to have An idea about it .. Go back to pages (8,9,10,11)

(2) Guide Planes

Guide planes are prepared on the proximal or lingual surfaces of teeth, so that they are made parallel to each other and to the path of appliance insertion

The ideal guiding plane is 2 to 4 mm in occlusogingival height.

However, in distal extension partial dentures the required height is 1.5 to 2 mm to permit slight movement of the framework thus releasing the denture from the guiding plane and decreasing torque on abutments

Guiding planes are also prepared on the lingual surfaces of teeth to

provide maximum resistance to lateral stresses

As you can see in this picture ( from 2-4 ) is the guiding plane, so when you prepare it you have to Follow the Anatomy of the tooth ( as represented with the arrows ) using straight diamond fissure bur . you never make straight cut to the tooth

These stars represent the position of our guiding planes ( Goes up & Down ) in vertical movement which is the most appropriate path of insertion and removal

Guide Plane PreparationThese lines should be parallel to each other (The darkish areas next to the lines should be removed and polished)

(3) Alteration Of Tooth Contours

The crown contour of abutment teeth may require modification by contouring the enamel (enameloplasty) but without dentinal exposure.

And it’s indicated in the following Cases:

(1)Excessive tooth contours where the height of contour should be lowered for proper positioning of the clasp arms in order to:

Permit for the proper location of the retentive clasp

Locate the reciprocal clasp arm in the proper position

Allow for an easy and more direct placement of the retentive clasp arm by modifying the proximal side.

(2)Moderate grinding of the incisal or occlusal surface may be required to achieve proper occlusion

(3)To create or modify retentive undercut areas in such cases like improperly located or an insufficient undercut we tend to do :

[DIMPLE UNDERCUTS] : A dimple or a hole is prepared in the gingival third of the tooth. Mainly done for the Retentive Arm

(4) eliminate sharp edges and angles resulting from attrition or abrasion

(5) Modification of the lingual surfaces of lower teeth to facilitate insertion of mandibular major connectors .

Contor of RPD Abutment Example of promoting Esthetics by modifying the Contour of RPD Abutment : As you can see in this picture the survey line has changed By using Parallel sided bur

Example of Promoting Esthetics by modifying the Contour of RP

(4) Rest Seat Preparation

Here the doctor started to pick few points and talked about it :

Burs used for rest seat preparation :

1- Diamonds & Medium round carbide For Occlusal Rest Seats

2- Long, medium diameter cylindrical bur or diamond For Cingulum Rest Seats & Guiding Planes .

Types Of Rests :

- Occlusal Rests

- Cingulum (Lingual) Rests

- Incisal Rests Small Vshaped notch, Located 1.5 to 2.0 mm from the proximal incisal angle of the tooth.

- Embrasure Rests : back-to-back” occlusal rests

Here the preparation is TOO LOW

Here the preparation is TOO HIGH

Composite Bonded Cingulum Rests Flat emergence profile Pumice, rinse, etch, bond using rubber

dam Ensure cervical composite well

adapted

Part (2) Done by : Saleh Al-Naimi

Thanks everyone who participated in the Trip, You have made it Very special =]And Also not to forget Our Group Team work.. Allah ya36ekom Alf 3afye Good Luck in your Exams colleagues !!