DEVELOPING ANALOGUE SUBTITUTE FOR THE MAXILLARY DENTURE BEARING AREA

Dr Muhammad Rizwan Memon FCPS

Assistant Professor

Mucous membrane Residual Ridge Incisive papilla Rugae area Mid palatine raphe Hard palate Soft palate Tuberosity Zygomatic process Torus palatinus

Serves as cushion between the denture base and supporting bone

Composed of mucosa and submucosa Submucosa is formed by connective tissue that varies in

thickness, contain glandular, fat or muscle cells Mucosa is formed by stratified squamous epithelium,

kertatinized Mucosa covering hard palate, crest of residual ridges is

classified as masticatory mucosa In healthy mouth submucosa is firmly attached to

periosteum of underling bone, if it is loosely attached , inflamed or edematus will be displacable and

will affect the stability and support of denture and if thin will be easily traumatized

Hard Palate:

Two maxillary and one palatine bone provide support to the maxillary denture base

At medial palatal suture mucosa is extremely thin, that may need to be relieved to avoid trauma from denture base

Posterolateral part of hard palate provide primary support ]primary stress beaing area}, in area of rugae palate is an angle and is thinly covered by soft tissues provides secondary support

Residual ridges continuously resorbed throughout life after extraction of teeth

Bone is subject to resorption which limits its potential for support, so counted as secondary stress bearing area

At peripheral area mucosa is loosely attached, unable to withstand masticatorty forces, however it contributes to border seal

Incisive foramen:

Located beneath the incisive papilla

Location of incisive papilla gives indication about amount of ridge resorption

Denture base should be relieved at incisive papilla as nerves and blood vessels passes through the foramen

Maxillary Tuberosity:

After extraction of mandibular teeth maxillary teeth overerupt causing hanging of tuberosity

These enlargements often are fibrous or bony

Difficult to develop proper occlusal plane therefore need surgical removal

Sharp, Spiny Processes:

These are frequently present on maxillary and palatine bones without any problem

With resorption of residual ridges they can irritate soft tissues between them and denture base

Sharp, spiny overhanging edge on greater palatine foramen may irritate the covering soft tissues

Denture base should be relieved from these areas

Torus Palatinus:

Found in 20% of population

Should be relieved from denture base to avoid trauma of thin covering mucosa

Labial frenum Buccal frenum Labial vestibule

• From buccal frenum to buccal frenum

Buccal vestibule From buccal frenum to hamular

notch

Hamular notch Fovea palatinae vibrating lines

From hamular notch hamular notch

Labial notch in the labial frenum must be wide and deep enough

Labial vestibular mucosa is classified as lining mucosa.

Lips, cheeks, alveololingual sulcus, soft palat, ventral surface of tongue and unattached gingiva on slopes of ridges are also covered with lining mucosa

Lining mucosa is not keratinized and freely movable

Tone of Orbicularis Oris muscle depends upon the support derived from the position of teeth and thickness of labial flange

Orbicularis oris pulls buccal frenum forward and buccinator backward so it requires more clearance than labial frenum

Buccal vestibule:

Size and shape of distal end of the buccal flange must be adjusted to ramus, coronoid process of mandible and masseter muscle

Width of buccal vesibule is reduced by opening and moving of mandible on opposite side and on heavy closing pressure masseter muscle contracts and reduce width of buccal vestibule

Due to resorption of ridge, root of Zygoma located opposite the 1st molar region become more noticeable, requiring relief of denture to avoid soreness of thinly covering mucosa

Hamular notches forms distal limit of buccal vestibule, contains thick submucosal layer that can be easily displaced helping in achieving posterior palatal seal

Imaginary line present on soft palate and marks the beginning of motion when patient says “Ah” extend from one hamular notch to other

Distal end of denture extend at least to the vibrating line

During wide opening of mouth pterygomandibular raphe is pulled forward, if denture base extend too far in to hamular notch, mucous membrane covering raphe will be traumatized

Two orifices one each side of the midline.

Coalescence of several mucous glands - always located in the soft palate. They act as collecting ducts for a group of minor palatine salivary glands

Vibrating Line is usually 2mm in front of the fovea palatine

1. Examination & conditioning of pt: 2. Selection of impression material 3. Selection of impression tray 4. Seating of pt: 5. Making the preliminary impression 6. Constructing the primary cast 7. Fabrication of primary tray 8. Border molding 9. Diagnostic impression 10. Final impression

Oral tissues must be healthy before recording impressions

Patients leave their denture out of mouth for at least 24 hours before recording impression to resolve inflammation

If patients object, then dentures must be relined with tissue conditioner

Impressions that record the tissues with minimum displacement are described as Mucostatic

Impressions that record the tissues with displacement are described as Mucodisplacing

Choice of selecting material is based on oral conditions, skill of operator and concept of functions of tissues surrounding the denture

Preliminary impression materials (select material that have relatively high viscosity to compensate for deficiencies of tray)

▪ Silicone putty (flow beyond the tray to compensate for under extension of tray, because of its elastic nature record undercuts easily but can not be added to if any part is deficient)

▪ Irreversible hydrocolloid (records details accurately but poured cast immediately to avoid dimensional changes)

▪ Impression compound ( flow beyond the tray to compensate for under extension of tray, non elastic does not record undercuts easily but can be added to if any part is deficient)

▪ The material of choice is high viscosity alginate

BASED ON METHOD OF FABRICATION:

Stock trays Custom made trays Individualized trays BASED ON PRESENCE OR ABSENCE

OF HOLES: Plane or non perforated trays Perforated trays Based on material: Plastic trays Metal trays Based on dental status use to make

trays: Trays for dentate or partially dentate pt: Trays for edentulous pt:

Objective is to obtain slightly over extended impression around the borders

Tray should be moistened with water before trying it in mouth so as to reduce the friction with lips and oral mucosa

Sides of properly fitted tray should avoid direct contact with the buccal and labial surfaces of teeth by approximately ¼ inch/5mm

Maxillary tray should extend to include the hamular notches

For alginate impression, under extension of tray is modified with boxing wax

Tray Selection

Chair position for maxillary impression:

Seat the pt: in an upright position Pt: Jaw should be at or below the operator elbow level Operator stand behind the pt: Grape the pt: head around the left hand & retract the lip.

Right hand is used to insert & seat the tray in pt: mouth.

Instructions

Sit quietly and relax

Breath through nose

Not to swallow during impression making

Primary Impression Making (Alginate)

In Old denture wearer, we relined their

old denture with tissue conditioner and

use it as primary impression

1mm thick baseplate wax is placed on cast within outlined border except poster palatal seal area

Tissue stoppers should be placed

Wax spacer will not be used if metallic oxide impression paste is used

Custom tray should be 2 to 3 mm thick with stepped handle

DEFINITION:

“The shaping of the border areas of an impression tray by functional or manual manipulation of the tissues adjacent to the borders to duplicate the contour & size of the vestibule” (GPT 2005)

Improves the stability of the prosthesis. Shape the impression borders & allows the

muscle to function in harmony with the dentures.

Improves the retention by producing the

peripheral seal

1. Modeling compound sticks 2. Auto-polymerizing acrylic resins 3. Tissue conditioners 4. Polyether impression paste 5. Impression waxes

Flanges of custom tray should be reduced 2mm short of reflections to create space for border molding material

If overextended trim it and if underextended, the length is

corrected by addition of Modeling compound

Two ways; 1. In one step (Reduce no of insertion of tray and

chances of errors created in one step affect another contour)

2. Segment by segment

No hard & fast rule May follow Uni or Bilateral approach Can built anterior &/ or posterior portion first The maxillary impressions are made in six

segments

Objectives:

To confirm the correct recording of the periphery

Apply petroleum jelly Mix and apply ZoE paste on the borders and

perform all the movements as for initial periphery record

Look for over and under extensions

0.5 mm of border molding material is removed to create space for final impression material

Spacer wax if present is removed from inside the tray

Atleast 3 escape holes should be placed inside tray to provide relief for impression material to not displace tissues

Final impression materials:

Plaster of paris (not user friendly)

Metallic oxide paste (Rigid on setting, used only when no any bony undercuts, used in close fitting tray, not used in patients with dry mouth)

Poly ether and Silicone impression materials (used in spaced custom tray when bony undercuts are present)

Alginate (used in spaced custom tray when bony undercuts are present in low viscosity)

Mix the material in proper ratio on the glass slab and paint a thin layer on whole surface of tray including the periphery

Seat first anterior then posterior After one minute border mold (first anterior then

posterior) Remove after 3-4 minutes Inspect the Impression

The procedure for preserving functional depth and width of sulcus is called Beading and Boxing

Strip of beading wax is attached 2 to 3 mm below the border all around

A thin sheet about 10 to 15 mm of hight is then attached outside the beading strip

Hard plaster is then poured in boxed impression and allowed to set