Slide 1

Introduction to Clinical Prosthodontics Slide 2 Clinic 1. History taking, examination, treatment planning, and Primary Impressions. Lab1. SM & custom trays. Clinic 2. Secondary/master/final impressions. Lab 2. Secondary/master/final casts & occlusal wax rims (record blocks) Clinic 3. Registration stage: 1. Aesthetics (maxillary wax rim) 2. Vertical (VD) & horizontal (RCP) relations. 3. Shade & Mould. Lab3. : Mounting teeth arrangement (setting) Clinic 4. Try in Repetition of previous visit. Post dam determination. Lab 4.: denture processing: flasking, dewaxing, packing, curing, deflasking, finishing and polishing. Clinic 5. Insertion Clinic 6. Review Slide 3 Clinic 1 Primary Impression-summary of the anatomical extent: Primary Impression-summary of the anatomical extent: Maxillary: Maxillary: Residual ridges, tuberosities and hamular notches, functional width and depth of the labial and buccal sulci, including frena. Residual ridges, tuberosities and hamular notches, functional width and depth of the labial and buccal sulci, including frena. Hard palate and its junction with the soft palate. Hard palate and its junction with the soft palate. Mandibular: Mandibular: Residual ridges and retromolar pads. Residual ridges and retromolar pads. Functional labial and buccal sulci (including frenal and external oblique ridges) Functional labial and buccal sulci (including frenal and external oblique ridges) Lingual sulci, lingual frenum, mylohyoid ridges and retromylohyoid areas. Lingual sulci, lingual frenum, mylohyoid ridges and retromylohyoid areas. Slide 4 Slide 5 Mucous membrane Mucosa: stratified squamus epithelium & connective tissue (lamina propria) Submucosa: connective tissues made of dens to loose areolar tissues If firmly attached: withstand pressure If loose, thin, traumatized, mobile, flappy: it wont be suitable to withstand pressure-not resilient. Masticatory mucosa (keratinized): hard palate, residual ridges, residual attachment gingiva. Slide 6 Hard palate Keratinized. Mid palatine suture: Submucosa is extremely thin- requires relief Horizontal portion of the Hard palate: 1 support for areas Rugae areas: set at an angle with the residual ridge- 2 support areas. Slide 7 The Palatal Gingival Vestige (remnants of the lingual gingival margin) It is the remains of the palatal gingiva. After tooth extraction the position of the vestige remains relatively constant, the same as the incisive papilla. This can be a very helpful pointer for posterior tooth positioning during denture construction Slide 8 Residual Ridges Residual Ridges Mucous membrane: Mucous membrane: keratinized keratinized firmly attached. firmly attached. Submucosa: devoid of glandular tissues. Dense collagenous fibers. Relatively thin, but sufficient to provide support for the denture base. Submucosa: devoid of glandular tissues. Dense collagenous fibers. Relatively thin, but sufficient to provide support for the denture base. Crest of the ridge: Crest of the ridge: Prone to resorption. Prone to resorption. 2 support area. 2 support area. Inclined facial surfaces Inclined facial surfaces Loses its firm attachment Loses its firm attachment Offers little support Offers little support Cannot withstand pressure Cannot withstand pressure Slide 9 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 Slide 10 Imaginary line. Usually 2mm in front of the fovea palatine Not the junction of the hard and soft palate- always on the soft palate. Submucosa Glandular tissues-because it is not supported by bone, it could be compressed and relocated with the impression to complete the palatal seal. Slide 11 Slide 12 Crest of the residual ridge Crest of the residual ridge Ridge is similar to that of the upper in healthy mouth. Ridge is similar to that of the upper in healthy mouth. Attachment varies considerably. In some people, the submucosa is loosely attached to the bone. Attachment varies considerably. In some people, the submucosa is loosely attached to the bone. When securely attached to the bone, the mucous membrane is capable of providing support for the denture. However, because underlying bone is cancelous, the crest of the residual ridge may be not favorable as a primary stress bearing area for the lower denture. When securely attached to the bone, the mucous membrane is capable of providing support for the denture. However, because underlying bone is cancelous, the crest of the residual ridge may be not favorable as a primary stress bearing area for the lower denture. Slide 13 Buccal shelf area The mucous membrane is more loosely attached and less keratinized than that covering the residual ridge. Although the mucous membrane may not be as suitable histological to provide support for the denture, the bone of the buccal shelf area is covered by a layer of cortical bone. This plus the fact that the shelf lies at right angle to the vertical occlusal forces, makes it the most suitable primary stress bearing area. Slide 14 The external oblique ridge does not govern the extension of the buccal flange because the resistance or lack of it varies widely. The buccal flange may extend to the external oblique ridge, up onto it or even over it depending on the location of the muco buccal fold. The bearing of the denture on muscle fiber of the buccinator would not be possible except for the fact that the fibers run parallel to the base, and,hence, its action is parallel to the border and not at right angle. Slide 15 The disto buccal border must converge rapidly to avoid the action of the masseter which is pushing inward the buccinator. Distal extension is limited by Ramus Buccinator Pterygo mandibular raph. Superior constrictor The sharpness of the boundaries of the retromolar fossa. (the denture should extend slightly to the lingual into the pearl shaped retro molar pad. Slide 16 The retro molar pad is a triangular soft pad of tissue. Its mucosa is composed of thin non keratinized epithelium. It submucosa contains Glandular tissues Fibers of the buccinator and superior constrictor Pterygo mandibular raph Fibers of the temporalis Because of theses structures, the denture base should only extend to one half to two third the retro molar pad. Slide 17 The retro molar pad: It is split into two sections. The anterior section is usually firm and fibrous. It is important for denture support and preventing distal denture displacement The mylohyoid ridge: Following the extraction of natural teeth and subsequent resorption, the mylohyoid ridge becomes more prominent. This can result in mucosal soreness beneath the denture bearing area over the mylohyoid ridge. Slide 18 Slide 19 Mylohyoid muscle Mylohyoid muscle It is a thin sheet of fibers and in a relaxed state will not resist the impression material. It is a thin sheet of fibers and in a relaxed state will not resist the impression material. Carrying the border under the mylohyoid cannot be tolerated. The contraction of this muscle will displace the denture. Carrying the border under the mylohyoid cannot be tolerated. The contraction of this muscle will displace the denture. Fortunately, the denture in the posterior area of the mylohyoid is beyond its attachment because the mucobuccal fold is not in this area. Fortunately, the denture in the posterior area of the mylohyoid is beyond its attachment because the mucobuccal fold is not in this area. In the retro mylohyoid fossa the border of the denture move back toward the body of the mandible producing the S curve of the lingual flange. In the retro mylohyoid fossa the border of the denture move back toward the body of the mandible producing the S curve of the lingual flange. In the anterior region, a depression, the pre mylohyoid fossa can be palpated and a corresponding prominence, the pre mylohyoid eminence seen on the impression In the anterior region, a depression, the pre mylohyoid fossa can be palpated and a corresponding prominence, the pre mylohyoid eminence seen on the impression Slide 20 Slide 21 Clinic 1 Making the Primary Impression Selection of the impression tray Selection of the impression tray impression trays are rigid containers used to carry the impression material into the mouth. They also support it while it sets or harden, and subsequently during removal from the mouth and when casts are poured. impression trays are rigid containers used to carry the impression material into the mouth. They also support it while it sets or harden, and subsequently during removal from the mouth and when casts are poured. Wide selection is available in metal or plastic. Wide selection is available in metal or plastic. Selection is based on: Selection is based on: Rigidity Rigidity The need to accommodate an appropriate amount of the impression material. The need to accommodate an appropriate amount of the impression material. The design or extent of the tray to the anatomical landmarks outlined previously. The design or extent of the tray to the anatomical landmarks outlined previously. Slide 22 Metal trays: Metal trays: Rigid Rigid Provided in a wider range of sizes. Provided in a wider range of sizes. Needed to be cleaned and sterilized before reuse. Needed to be cleaned and sterilized before reuse. Plastic trays are intended to be disposable Plastic trays are intended to be disposable Impression materials: Impression materials: Alginate Alginate Compound Compound Rubber Rubber Check that the tray is not over extended or under extended. Then load the impression material and make the mandibular impression standing in front of the patient. For the maxillary impression, the clinician should be positioned behind the patient. As this affords more control over the upper tray and also allow the patients head to be leaned forward should they experienced nausea during the impression procedure. Check that the tray is not over extended or under extended. Then load the impression material and make the mandibular impression standing in front of the patient. For the maxillary impression, the clinician should be positioned behind the patient. As this affords more control over the upper tray and also allow the patients head to be leaned forward should they experienced nausea during the impression procedure. Slide 23 Slide 24 Inadequate final impression: contact clinician to discuss possible risks of proceeding with the case Inadequate final impression: contact clinician to discuss possible risks of proceeding with the case Model fractures upon removal from impression. Model fractures upon removal from impression. Large positive or negative defects, or flaws in critical areas. Large positive or negative defects, or flaws in critical areas. Poor surface quality of the model due to water/saliva/blood contamination or improper mixing of gypsum, showing a powdery, friable surface. Loss of or damage to critical areas during model trimming (examples: retromolar pad, hamular notch and muscle attachments). Loss of or damage to critical areas during model trimming (examples: retromolar pad, hamular notch and muscle attachments). Slide 25 Lab 1 Producing Casts & Special Trays Ensure that impressions have been decontaminated prior to dispatch to the lab. Preparing the primary cast: Principally used to provide bases on which customized special trays are constructed. Also useful for planning treatment, for example for outlining the potential supporting areas of the denture. Cast are made in Plaster of Paris ( hemihydrate of calcium sulphate) & Stone (- hemihydrate of calcium sulphate). Pour using 50:50 mixture of plaster of Paris/ dental stone (vacuum mixed) under vibration. Make the base at least 10mm thick to be sufficiently robust to survive subsequent handling. Slide 26 Powder/liquid ratio Thin mix: longer setting time, poor surface hardening, setting expansion is low, easier to pour. Thick mix: the opposite. Spatulation time: time taken to mix the powder & liquid into creamy consistency.(30-60 sec.) Increasing the spatulation time: Rapid set. Decreases surface hardness. Increases the setting expansion. Temperature: water temp. up to 40 c decreases setting, above 40 c increases setting. Chemical additives. E.g. Borax increases setting time. Slide 27 Read the prescription before beginning all procedures. Box master model impressions- Diagnostic casts do not require boxing. Measure dental stone and water according to manufacturer's directions. Add powder to water rather than water to powder. For best results, vacuum mixing is recommended. Do not invert impressions to develop a base until the stone reaches initial set. Slide 28 Master casts Base thickness must be 1/2-inch (13 mm) minimum for strength. This is measured from the deepest part of the palate on the upper (Figure 1c) or the "floor of the mouth" on the lower (Figure 1d). Slide 29 After trimming, the base of the model must be parallel to the residual ridge (figures 1e and 1f). The base must be indexed for mounting and remounting. Two methods are shown here. Other techniques are acceptable as long as the index allows accurate remounting of the model. Slide 30 The depth of the buccal sulcus is approximately 1-1.5- mm below the land area. Positive defects (bubbles), if any, must be in non-vital areas and small enough to be easily removed (1-mm diameter or less as a guide). Negative defects (voids), if any, should be small and in non-critical areas. These should be filled with stone to blend with the surrounding anatomy. The master cast must include all anatomical surfaces in the final impression. Slide 31 Special Trays Material: Should be safe to handle, compatible with biological tissues & impression material, sufficiently rigid to preclude distortion. Examples: Self-cured or light-cured acrylic resin Peripheral extension: Cover the entire denture-bearing area within the anatomical limits previously described. 2mm short of the sulcus to allow for border molding. Handles: Should be formed to avoid encroaching on the surrounding tissues. Slide 32 Space for impression material: Should accommodate the optimum thickness of the chosen impression material Irreversible Hydrocolloid: 3mm. Zinc oxide-eugenol : close fitting Poly vinyl siloxanes: depending on the viscosity Polyethers : 2-3mm Polysulphides: 2-3mm. Perforations?? Trays for complete dentures are requested without perforations so that peripheral seal can be estimated. Slide 33 If no specific instructions are provided, fabricate tray to the following standard: Outline the tray 1-2 mm short of the mucobuccal reflection for both upper and lower models. This will allow room for border moulding material and save time for the clinician. The tray must extend to the depth of the hamular notches on the upper and should cover the retromolar pads on the lower. The lingual extension on the lower should stop at the mylohyoid line in the posterior and at the junction with the floor of the mouth in the anterior section. Slide 34 Place relief material such as baseplate wax to the outlined area and cut out three tissue stops. Avoid placing a tissue stop over the incisive papilla. Slide 35 The maxillary tray is made with 1 mm wax spacer and ends short of the final tray extensions. On the maxilla, wax must not cover the posterior palatal seal area. The mandibular tray is made with no spacer(close fit) Tray is well adapted to the model with no voids. Tray must be of uniform thickness. Thickness must be sufficient in strength to prevent distortion or breakage in use. The required thickness will vary with the material used. In general, acrylic resin and similar materials (such as light cure resins) should be approximately 2 mm thick, and 1 mm short of the mucobuccal fold to allow for border moulding. The handle must be placed in the anterior so that it does not interfere with placement of tray or border moulding procedures. The handle may be placed approximately where the wax rim or anterior teeth would be positioned on a baseplate. Unless specified otherwise by the clinician, the tray borders should be between 1 to 2 mm short of the mucobuccal reflection. Slide 36 Custom Trays - Quality Failures Border extensions significantly longer or shorter than standard. Tray not stable (flexible) due to insufficient thickness. Tray cracked or damaged. Improper handle position (interferes with border moulding or insertion). Sharp and/or rough edges, which may irritate the patient. Slide 37 Clinic 2 Definitive (secondary) Impression Slide 38 Classification: Elasticity Slide 39 Lab 2 Base plates & Wax rims Master/secondary cast (poured in stone) Base plate: Self-cured or light- cured acrylic resin. Wax rim (review lecture: Base plates & Waxrims/3 rd year course) Slide 40 Clinic 3 Registration Stage Before complete dentures are constructed, the dentist with the aid of the technician, must build a pro-forma or template of the intended denture using-usually- wax rims. Before complete dentures are constructed, the dentist with the aid of the technician, must build a pro-forma or template of the intended denture using-usually- wax rims. According to glossary of prosthodontic terms the registration is a record made of the desired maxillomandibular relationship and is used to relate casts on the articulator According to glossary of prosthodontic terms the registration is a record made of the desired maxillomandibular relationship and is used to relate casts on the articulator Maxillomandibular relationship is a relationship of the maxilla to the mandible; any one of the infinite relationships of the mandible to the maxilla Maxillomandibular relationship is a relationship of the maxilla to the mandible; any one of the infinite relationships of the mandible to the maxilla In simple terms: the registration stage is 3-dimensional prescription whereby the template of the intended denture is prescribed and fashioned clinically before being dispatched to the laboratory for placement of the teeth on the trial denture. In simple terms: the registration stage is 3-dimensional prescription whereby the template of the intended denture is prescribed and fashioned clinically before being dispatched to the laboratory for placement of the teeth on the trial denture. Slide 41 Unless the clinician has cast the definitive impression and has scored the master cast to define the postdam, the rim will not exhibit a clinically meaningful seal. Unless the clinician has cast the definitive impression and has scored the master cast to define the postdam, the rim will not exhibit a clinically meaningful seal. After immersing the rim in proper disinfectant material, ensure that the rim is well adapted. Alternating finger pressure on both sides of each rim should not elicit rocking. After immersing the rim in proper disinfectant material, ensure that the rim is well adapted. Alternating finger pressure on both sides of each rim should not elicit rocking. Start with the upper rim- insert it and then ensure that the infra-nasal tissues are harmonious with the soft tissues of the middle third of the face. Failure to do so may affect the form and length of the upper lip. Start with the upper rim- insert it and then ensure that the infra-nasal tissues are harmonious with the soft tissues of the middle third of the face. Failure to do so may affect the form and length of the upper lip. Confirm that the upper lip is adequately supported. This should result in restoration of the vermilion border. Confirm that the upper lip is adequately supported. This should result in restoration of the vermilion border. Determine the level of the incisal point relative to the resting upper lip. Some text books recommend 2mm below the resting upper lip level. Younger patients with class II div I may require more(2-4mm) and older patient ( over 70) may require the incisal level at the level of the resting lip or 1mm above it. Determine the level of the incisal point relative to the resting upper lip. Some text books recommend 2mm below the resting upper lip level. Younger patients with class II div I may require more(2-4mm) and older patient ( over 70) may require the incisal level at the level of the resting lip or 1mm above it. Slide 42 The antero-posterior location of the incisal point can be determined by asking the patient to say a word containing a fricative consonant, e.g. fish. The incisal point should correspond to the vermilion border of the lower lip. The antero-posterior location of the incisal point can be determined by asking the patient to say a word containing a fricative consonant, e.g. fish. The incisal point should correspond to the vermilion border of the lower lip. Determining the maxillary anterior & posterior plan: Determining the maxillary anterior & posterior plan: The plan of the six anterior should be parallel to the inter-pupillary line. Use a foxs occlusal plane guide. The plan of the six anterior should be parallel to the inter-pupillary line. Use a foxs occlusal plane guide. The posterior plan should be made parallel to ala- tragus line The posterior plan should be made parallel to ala- tragus line The tips of the maxillary canines can be determined by extending a dental floss from the inner canthus of the eye through the lateral border of alar cartilage into the rim. The tips of the maxillary canines can be determined by extending a dental floss from the inner canthus of the eye through the lateral border of alar cartilage into the rim. Using the mark on the rim corresponding to the canine tips, reduce the inferior borders of the posterior rims by 3-5 to create the buccal corridors. Using the mark on the rim corresponding to the canine tips, reduce the inferior borders of the posterior rims by 3-5 to create the buccal corridors. The customization of the upper rim is finished by scribing The customization of the upper rim is finished by scribing Centre line. Centre line. High smile line High smile line Canine points Canine points The above technique of customizing the upper rim is the one used at the Dental Health centre-the one to be used by dental student. Another technique to customize the upper rim is Swissedent technique (review lecture on wax rims /3 rd year). The above technique of customizing the upper rim is the one used at the Dental Health centre-the one to be used by dental student. Another technique to customize the upper rim is Swissedent technique (review lecture on wax rims /3 rd year). Face bow transfer : depending on the case, the clinician may consider it necessary to use a face-bow to transfer the relationship of the upper rim to an arbitrary hinge axis. although it may not be strictly necessary to use a face- bow in all cases, there is no valid objection to their use in the prescription of complete denture. Face bow transfer : depending on the case, the clinician may consider it necessary to use a face-bow to transfer the relationship of the upper rim to an arbitrary hinge axis. although it may not be strictly necessary to use a face- bow in all cases, there is no valid objection to their use in the prescription of complete denture. Slide 43 Clinic 3 Slide 44 Slide 45 Relating the mandible to the maxilla Relating the mandible to the maxilla This 3-dimensional: This 3-dimensional: Vertical (vertical dimension) Vertical (vertical dimension) Sagital ( antero-posterior) Sagital ( antero-posterior) Coronal (left right) Coronal (left right) Vertical: Vertical: Resting Vertical Dimension (RVD) Resting Vertical Dimension (RVD) Occlusal Vertical Dimension (OVD) Occlusal Vertical Dimension (OVD) Affect tolerance and appearance Affect tolerance and appearance Free way space (RVD-OVD) Free way space (RVD-OVD) Slide 46 RVD measurement: RVD measurement: Select to measuring points in the midline of the face-one relate to the nose and one to the chin. These points must be on sites with minimal influence from the muscles. Select to measuring points in the midline of the face-one relate to the nose and one to the chin. These points must be on sites with minimal influence from the muscles. Ask the patient to moisten his or her lip and bring them into light contact, then ask the patient to swallow and relax his jaws Ask the patient to moisten his or her lip and bring them into light contact, then ask the patient to swallow and relax his jaws This is verified by asking the patient to say the word M while the measurement is made. This is verified by asking the patient to say the word M while the measurement is made. Attention should be made to unwanted skin movement. Use Willis gouge or any other device-ruler- to measure the distance between the two reference points. This the RVD. Attention should be made to unwanted skin movement. Use Willis gouge or any other device-ruler- to measure the distance between the two reference points. This the RVD. The maxillary & mandibular rims are then inserted-after the upper rim has been moulded- and the lower rim is reduced in height- usually; or added to if under sized) until it contacts the upper rim evenly at a vertical dimension of occlusion some 2-4mm less than RVD The maxillary & mandibular rims are then inserted-after the upper rim has been moulded- and the lower rim is reduced in height- usually; or added to if under sized) until it contacts the upper rim evenly at a vertical dimension of occlusion some 2-4mm less than RVD Slide 47 methods of determining vertical dimension -1. Boos: Bimeter (an oral meter that measures pressure) -2. Silverman: closest speaking space- looked at bicuspid area -3. Pound: phonetics and esthetics -4. Lytle: neuromuscular perception -5. Pleasure: pleasure points (tip of nose and chin) Slide 48 Sagittal (antero-posterior) Retruded Contact Position (RCP) Retruded Contact Position (RCP) Reporduciple Reporduciple Several techniques: Several techniques: Squash bite Squash bite Wax rims Wax rims Intra-oral tracing Intra-oral tracing This visit is finished by This visit is finished by selecting the shade and mould. selecting the shade and mould. determining the post dam area. determining the post dam area. Slide 49 Selection of the mould & shade Slide 50 Facebow transfer of the maxillary rim Slide 51 Slide 52 Facebow transfer Slide 53 Slide 54 Lab 3 Mounting. (indexing) Setting the teeth using the shade & mould selected by the dentist. Wax up and contouring. (hands out summarizing this laboratory procedures will be given) Slide 55 Clinic 4 try-in visit Verify the appearance. Verify the appearance. Verify the occlusal requirements. Verify the occlusal requirements. Examine speech Examine speech ( Please review lecture : try-in /3 rd year) Slide 56 Lab 4 Flasking, Packing and finishing Packing & processing of the denture: 1.Removal of wax 2.Replacing the wax mould with PMMA (hands- out summarizing this laboratory procedures will be given) Slide 57 Clinic 5 Fit /Delivery Mirror those of the trial stage except hopefully the patient is taking the dentures home. Mirror those of the trial stage except hopefully the patient is taking the dentures home. (review lecture on denture insertion/ 3 rd year) Arrange review visits for your patient as needed. Arrange review visits for your patient as needed.