DEVELOPING ANALOGUE SUBTITUTE FOR THE MAXILLARY DENTURE BEARING AREA. Dr Muhammad Rizwan Memon FCPS Assistant Professor

Transcription

1 DEVELOPING ANALOGUE SUBTITUTE FOR THE MAXILLARY DENTURE BEARING AREA Dr Muhammad Rizwan Memon FCPS Assistant Professor

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

3 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

4 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

5 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

6 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

7 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

8 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

9 Torus Palatinus: Found in 20% of population Should be relieved from denture base to avoid trauma of thin covering mucosa

10 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

11 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

12 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 1 st 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

13 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

14 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

15 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

16 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

17 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

18 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

19 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:

20 Tray Selection 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

21 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

22 Primary Impression Making (Alginate)

23 In Old denture wearer, we relined their old denture with tissue conditioner and use it as primary impression

24 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

25 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)

26 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

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

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

29 If overextended trim it and if underextended, the length is corrected by addition of Modeling compound

30 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

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32 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

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36 Objectives: To confirm the correct recording of the periphery Apply petroleum jelly Mix and apply ZoE paste on the borders perform all the movements as for initial periphery record Look for over and under extensions and

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38 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

39 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)

40 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

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42 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

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