Download to read offline
![ Mucosal topography is not static over 24 hrs
period.
There is difference between mucosal contours
just after raising in the morning and that exists
after 12 hrs in upright position [Stephen et. al
1966]
so all details achieved in the impression would
be altered by the time denture was completed.](https://image.slidesharecdn.com/impressionincd-250108044102-36814dd5/85/impression-techniques-in-complete-denture-70-320.jpg)
![Materials used are
Modelling compound sticks
Autopolymerising acrylic resins
Tissue conditioning materials [ modified resins]
Metallic pastes & elastomeric materials
Impression waxes](https://image.slidesharecdn.com/impressionincd-250108044102-36814dd5/85/impression-techniques-in-complete-denture-139-320.jpg)
impression techniques in complete denture
- 1.
- 3. Contents Introduction Definitions Historical review Impression theories Impression techniques Impression techniques in compromised situations Conclusion
- 4. Good impressionsare basic needs of a contented denture wearer. Impression making is the preliminary step in the construction of prosthesis The success of a prosthesis depends on the quality, accuracy and adequacy of the impression
- 5. According toSears, We do not TAKE impressions as we do on a mannequin : rather we MAKE impressions to accommodate the tissues with their varying degrees of displaceability and form.
- 6. To makean impression ,we measure with our eyes and figures the anatomic limits in the oral cavity and the impression material is shaped and molded into a negative likeness of supporting areas. The impressions should cover the maximum possible area –so force/mm sq reduces
- 7. Muscle attachments Not coveredCovered Denture Dislodgment and Ulceration Close to the ridge crest Then covered Patient trained to limit muscle movements
- 8. Accurate Preliminary impression GoodPreliminary cast Accurate custom tray Definitive impression Stable Record base Precise recording of maxillo-mandibular relations Stable , Retentive Dentures Patient and operator satisfaction
- 9. So itis unwise to disregard the importance of any step in the hope that the deficiencies will be rectified in the later steps
- 10. Historical review Before themiddle of 18th century ridges painted with dye and a block of ivory or bone was pressed on the ridge . Marked areas were scrapped away Waxes – As early as 1711,bees wax were the first used Plaster - 1844 by west cott ,Dwinelle Dunning Gutta percha - 1848,High working temprature,stifness
- 11. Modelling plastic- 1856 developed by Charles stens Hydrocolloid materials - 1925 First use of ZOE pastes by Ward & Kelly -1930 Alginate materials - 1940 Rubber & silicone materials – more recently
- 12. Definitions Impression :GPT-8 A Negativelikeness or copy in reverse of the surface of an object An imprint of the teeth and the teeth for the use in dentistry
- 13. According to Heartwell, Animpression is the negative form of the teeth and/or other tissues of the oral cavity , made in plastic material that becomes relatively hard or set while in contact with these tissues
- 14. Dental impression -GPT-8 A negative imprint of an oral structure used to produce a positive replica of the structure to be used as a permanent record or in the production of dental restoration or prosthesis
- 15. Complete denture impression Accordingto heartwell It is a negative registration of the entire denture bearing ,stabilizing and border seal areas present in the edentulous mouth
- 16. Preliminary impression: GPT-8 A negative likeness made for the purpose of the diagnosis , treatment planning or the fabrication of the tray Final impression: GPT-8 The impression that represents the completion of the registration of the surface or object. Sectional impression: A negative likeness that is made in sections
- 17. Impression technique Amethod and manner used in making negative likeness Impression tray A receptacle into which suitable impression material is placed to make a negative likeness A device that is used to carry confine and control impression material while making an impression
- 18. It shouldbe as complete as possible. It should be closely contacting the tissues. Borders in harmony with anatomic and physiologic limitations – Physiologic border molding
- 19. It shouldnot exert pressure. There should be no gross surface physical defects. The periphery of the impression should be in close contact with the resilient tissue at the height of the vestibule.
- 20. Three M’s ofsuccessful denture impressions Mold –Tray Method –Impression Technique Material Used
- 21. Impression Trays La Vereand Freda(1976) Stock Trays-Extension beyond 5mm beyond the external surface of the residual ridges Customized Trays-are Individualized Trays.
- 22. Requirements Rigid Retainshape Simple method of Construction Ease of modifying Smooth Edges
- 23. Materials Used Brass-Chromeplated Aluminium Polysterene Polycarbonate Nylon
- 24. Materials used formaking impression Primary impression a. Impression compound b. Alginate c. Waxes Final impression a. Impression plaster b. ZOE c. Agar d. Elastomers - regular, light body
- 25. Position of thepatient and the operator Seating of the Patient Upright- Occiput resting in the head rest. Gravity influences the position of the Tissues. Patient uses dentures while in upright position and hence tissues recorded in that position.
- 26. If the Headbent Backwards Suprahyoid & Infrahyoid Muscles get tensed Swallowing difficult Obstruction of airway
- 27. Maxillary arch impression. Theoperator stands behind and to the right side of patient . The left side is bought around from the back to the left side of the patient . The left hand side is used to retract the lip . The right is used to position the tray in themouth
- 28. Mandibular arch impression. The patientis in the upright position. The operator stands facing the patient to the front and right side of the patient.
- 29. Instruct patient theprocedures prior to impression making Ease of procedures Reduce anxiety Protect patients clothing Mouth wash before and after Small Napkin/Paper Towel provided Sterilization Protocol “Universal Precautions”
- 30. A goodimpression must aid to fulfill Muller Devan’s dictum(1952): “The preservation of that, which remains and not the meticulous replacement of what is lost”
- 31. (1) Preservation ofalveolar ridges. Impression techniques covering maximum supporting areas and using pressures within physiological limits of the tissue. Pressure in the impression technique is reflected as pressure in the denture base and results in soft tissue damage and bone resorption.
- 32. (2) Retention Retention ofa denture is its resistance to removal in a direction opposite to that of its insertion. Retention resists the adhesiveness of foods, the force of gravity and the forces associated with the opening of the jaws
- 33. The factors ofretention are: Physical - adhesion, cohesion, atmospheric pressure, interfacial surface tension etc. Physiological – oral and facial musculature Mechanical – undercuts.
- 34. Henry A Collet(1965) -Primary retention depends upon close adaptation to the tissues and it is proportional to the area covered.
- 35. (3) Stability -relationship of the denture base to the underlying bone. The stability of a denture is its ability to remain securely in place when it is subjected to horizontal movements. Attained by more intimate contact of labial and buccal flanges with the labial and buccal slopes and of the lingual flanges with the lingual slopes of the ridge.
- 36. Retention isthe only factor of stability that is directly related to the impression-making phase. It is absolutely essential because all other factors of stability are either ineffective or minimal if retention is lacking. Boucher – “stability requires maximum use of all bony foundation where the tissues are firmly attached to the bone”.
- 37. (4) Support – Denturesupport is the resistance to vertical forces of mastication and to occlusal or other forces applied in a direction towards the basal seat
- 38. Maxillary and Mandibularbasal bones and their covering of the mucosal tissue. Enhanced by selective placement of pressures that are in harmony with the resiliency of the tissues that make up the basal seat.
- 39. 5) Esthetics – Developmentof the labial and buccal borders, so that they are not only retentive but also support the lips.
- 40. Extent of Impressions Maxillary Residual ridges ,Tuberosities and Hamular Notches Functional width and depth of Labial and Buccal Sulci including freni Hard palate and Its junction with soft palate
- 41. Mandibular Impression Residualridges and retromolar pads Functional labial and Buccal sulci Frena + External Oblique ridge Lingual sulci , Lingual Freni, Mylohyoid ridge , retro mylohyiod area
- 42. According toDe Van ,the difficulty in making edentulous impression is due to varying tissue displacibility Because of these variations impressions must selectively place pressure on the mucous membrane and the bones- compatible with the histological tolerance And hence the origin of theories
- 43. According tolevin:Techniques can be classified into 4 categories 1.Amount of Pressure used …Mucocompressive ,Mucostatic and Selective pressure 2.Open and Closed 3.Hand manipulations or Functional movement 4.Type of Tray
- 45. Amount of pressureused- Based on theories of impression Pressure-Mucocompressive Technique by Greene brother Minimal Pressure Technique-Page Selective Pressure Technique- Boucher
- 46. Based on thetechnique Open mouth technique Closed mouth technique Also Hand manipulations Functional movements
- 47. Based on thetype of the tray Stock tray impression Custom tray impression Based on the purpose of impression on the purpose of impression Diagnostic impression Primary impression Secondary impression
- 48. Amount of pressureused 1.DEFINITE PRESSURE / MUCOCOMPRESSIVE/Mucodisplaciv e theory By GREEN IN 1896 The main objective was to attain better retention of the denture & this is achieved by positive peripheral seal.
- 49. Displacing thesoft tissues while making impression will result in better distribution of occlusal forces to the basal seat. It is logical to make impressions that would press the tissues in the same manner as chewing forces, thus ensuring contact during chewing.
- 50. Technique A preliminaryimpression is made in impression compound A special tray is constructed with its periphery 1/8th inch shorter than denture outline. With this tray another impression with compound is taken.
- 51. Occlusion rimsare made and the height of the bite adjusted against a similar bite-rim on the lower ridge. Relief areas - median raphe is softened and the impression is again inserted in the mouth and is held under biting pressure for one or two minutes.
- 52. Peripheral muscletrimming is done by asking the patient to give various cheek and lip movements as in swallowing, eating & talking. Posterior palatal seal is obtained by swallowing movements of the patient, under biting pressure.
- 53. Modified techniques (1) compoundis removed from metal tray and is used as a tray. (2) special trays are made out of sheet metal or cast in metal.
- 54. Disadvantages Displaced tissues,attempts to return to its normal unstrained position and so will move the denture out of its intended position, resulting in deflective occlusal contacts.
- 55. Dentures willfit well during mastication only a short period, but will not be as closely adapted to the tissues, when the patient is at rest. Tissues so distorted tend to rebound.
- 56. Advocates -werenot always able to obtain desired pressure, but tend to create excessive pressure. This often resulted in good initial retention but eventual cut off of blood supply, tissue breakdown & bone resorption. Thus the retention obtained is transient & harmful.
- 57. This techniquedoes not allow for adequate muscle trimming of the periphery. So impressions are over extended and must be arbitrarily trimmed
- 58. According toKawabe’s Indication for Mucocompressive Technique Ridge Shape –Flat Mucosa Thickness-Uneven Bone Surface-Smooth This technique does not allow for adequate muscle trimming of periphery , so impression are overextended and must be arbitrarily trimmed
- 59. “Mucostatic¨ wascoined by Dr. Carrol W. Jones, This principle was proposed by Mr. Harry L. Page, an engineer, 1938. Mucostatic was presented as a principle not a technique
- 60. It followsthe law of hydrostatics A "mucostatic impression" “Absolute accurate negative replica of the ridge tissues in their normal passive form”.
- 61. PAGE states“ interfacial surface tension operates by virtue of a thin fluid film between two intimately contacted objects” Major factor in the retention of the denture.
- 62. Addison (1944)“atmospheric pressure have nothing to do with denture retention as it’s always present and we adapt to it, exerting a physiological force equal to the pressure of the atmosphere
- 63. Mr. Page in1946, he stated that “All soft tissues are chiefly fluid, since 80% or more of the tissues are composed of water and so behave in a continued state Pascal’s law – “Pressure on a confined liquid will be transmitted equally throughout the liquid in all directions.”
- 64. Since thesoft tissues are confined under a denture, any pressure applied will be transmitted undiminished in all directions. So, when denture base maintains perfect contact with the tissues, retention is achieved without difficulty. The depth, detail and outline form of flange has no retentive value.
- 65. Dentures madeform mucostatic impressions will have a better prognosis than those made from mucocompressive impressions which will subject osseous tissues to continuous stress.
- 66. Mucostatic school “Soft tissueshould be registered in unstrained rest position – any other position will compel tissue to regain its rest position- leading to dislodgment of the denture.”
- 67. Wilson’s rule ofdenture coverage remains valid as when first presented in 1920. “All foundation area possible should be covered so long as the base does no interfere with normal muscle function”.
- 68. According tothis concept interfacial surface tension, the only major force in denture retention acts best when the surfaces are displaced at right angles to each other. The force is diminished as it approaches a parallel plane.
- 69. Merits Minimizes pressurewhile making impressions & thereby maintaining tissues in healthy conditions It is useful in sharp & flabby ridges.
- 70. Mucosal topographyis not static over 24 hrs period. There is difference between mucosal contours just after raising in the morning and that exists after 12 hrs in upright position [Stephen et. al 1966] so all details achieved in the impression would be altered by the time denture was completed.
- 71. Care takento obtain minute details of mucosal surface is worthless due to dimensional changes that occur in impression material and cast Factors of retention like atmospheric pressure & orofacial musculature was completely avoided.
- 72. It overlooked thefundamental rules laid by FISH that Denture should extend maximum with in the functional limits, Periphery should rest in soft tissue at every given point , There must neither be under extension nor over extension.
- 73. Short flangesaffect stability and retention. It is difficult to get an impression with out even a thin film of saliva. Since stress from these dentures will not be distributed as broadly over the basal seal, tissue health and retention may be compromised.
- 74. Minimal-pressure dentures gives inadequatesupport to the face. As the denture would be small in a patient with a severely resorbed maxillary ridge, it would be necessary to position the teeth over the crest of the ridge. Thus supporters of this theory failed to realize, the biology of the tissues as an important criterion.
- 75. Advantage Minimizespressure while making impression and thereby maintaining tissues in healthy condition. Avoidance of continous osseous stress as in case of Mucocompressive technique
- 76. Disdvantage Lessretention because of Less ridge coverage and Border seal Reduced coverage,,..so no distribution of Forces over the Basal seat area Acccording Fish: the form of the mucostatic denture minimized the retentive role of the musculature The lack of Border seal also permits the food to slip beneath the denture The shorter flanges may reduce support for the face which can affect the aesthetics Very difficult to treat the patient with poor residual ridge(Resorbed)
- 77. Indication Accordingto Kawabe Ridge shape-U shape Mucosa thickness-even Surface of the alveolar Bone-Smooth
- 78. Advocated byBoucher, It combines the principles of both pressure and minimal pressure techniques.
- 79. Indication Accordingto Kawabe Ridge shape-V shape Mucosa thickness-Flabby Surface of the alveolar Bone-Rough Sharp
- 80. The philosophy ofthe selective pressure technique Certain areas of the maxilla and mandible, are by nature better adapted for withstanding extra loads from the forces of mastication. These tissues can be recorded under slight placement of pressure while other tissues must be recorded at rest.
- 81. Primary stress bearingareas of the Maxilla : crest of alveolar ridge and horizontal plate of palatine bone, Mandible: is the buccal shelf area. Secondary stress bearing areas of Maxilla : rugae area and all ridge slopes Mandible : retromolar pad area, and all ridge slopes
- 82. The retromolarpad area is an area of support and so if the denture is not extended over this area, a typical boat-shaped resorption is caused in the area.
- 83. RELIEF AREAS Maxilla-Incisive papilla, midpalatine suture, tori. Mandible- Crest of the residual ridge.
- 84. Since thistechnique is based on principle of regarding both the biological as well as the physical factors concerning impression procedure, it is widely preferred in the cases of well-formed healthy ridges.
- 85. Roy MacGregor recommends placement of a sheet of metal foil in the region of incisive papilla and mid palatine raphae,
- 86. Neill recommendsadaptation of 0.9 mm casing wax all over except PPS area
- 87. Heartwell two techniquesfor achieving selective pressure for maxillary impressions 1) By scraping compound primary impression 2) By fabrication of custom tray with 5 relief holes
- 88. Boucher recommendsplacement of one mm base plate wax on the cast except PPS area
- 89. Morrow, Rudd,Rhoads recommends to block out undercut areas with wax and then adapt a full wax spacer two mm short of the resin special tray border all over & placement of three tissue stops (4´4 mm) equidistant from each other
- 90. Halperin recommendsthe 'Philosophy of the custom impression tray with peripheral relief'. slopes of the ridges are considered to be the primary stress bearing areas and therefore these areas are functionally loaded with compound during making of the final impression.
- 91. there isno need to make a wash secondary impression as he considers the tray surface and the border-moulded areas as the final impression surface
- 93. (1) Cannotbe used in flabby ridge cases (2) Opponents of this technique feel that it is impossible to record some areas with different pressure from that applied to other areas.
- 94.
- 95. The patient’smouth is partly open and the tray is held by the dentist. Advantage Operator can see whether muscle trimming is done properly.
- 96. The rationale-The supporting tissues are recorded in a functional relationship. The functional movements include talking, sucking, swallowing and eating. Vertical Dimension is established before making the impression.
- 97. Jaw relationeither tentative or Final is usually also completed at this time First material-Impression compound Second material-Flow at mouth temprature Recentely soft liner has been advocated
- 98. Thus according toStanley P. Freeman, amount of tissue compression is like that in function. Advantages: 1. Interference of tray-handles and operator’s fingers is eliminated.
- 99. 2.Time savingby obtaining the jaw relation and the posibility of Border moulding without interferance of Tray handle and operators fingers Mac milllan stated that these impression technique are the only ones capable of adequately trimming the lingual borders of the lower This is based on the belief that tongue movements are more forceful when the teeth are together than when the mouth is opened and tongue is protruded
- 100. Disadvantages: Appointment timefatiguing of the dentist and patient. Tendency for over extension and under extension. Release of pressure of occlusion may cause rebounding of denture Contraindicated in presence of considerable amount of movable tissue.
- 101. The contourof the denture borders may be obtained by the dentist with use of manual manipulations of the lips and cheeks within functional limits. Patient’s tongue movements record the lingual borders.
- 102. The dentureborders may also be formed by having the patient make “Functions” or ”Physiological” movements such as swallowing, sucking, grinning, licking. Etc.
- 103. ‘DYNAMIC IMPRESSION‘ Chase andTryde et al. Functional or physiological method of making impressions
- 104. TECHNIQUE Impression materialsthat continue to flow over an extended period of time such as tissue conditioners or wax. This material is placed in the patient’s transitional denture and the patient normal activities molds the borders
- 105. Disadvantages Cannot beused routinely Not all patients truly move the impression materials as needed, some may use extreme movement ,others less
- 106. Type of impressionTrayBased on the type of the tray Stock tray impression: Good impression can be obtained only if the rides are good…Difficult if the ridges are poorer ..severely resorbed Custom tray impression Always better
- 107. Natural dentitionlies in this zone, and this is where the artificial teeth should be positioned. This area of minimal conflict may be located by using the neutral zone technique.
- 115. Techniques aremodified in compromised conditions to achieve as much retention and stability as possible within limits.
- 116. Hyperactive gagreflex compromise the quality of treatment As Conny D.J stated the patients problem whether iatrogenic, physiologic, psychological, anatomic or organic disturbances are identified and treated before making the impression.
- 117. Prosthodontic Management– excess thickness, over extensions or improper post dam is corrected. Impression materials with shorter setting time can be used.
- 118. Limited opening ofmouth following Radical surgery Sequelae to facial burns Scleroderma
- 119. Walter describeda technique with the use of sectional stock trays. Impressions of one side of the jaw was made one at a time and the two halves were joined and cast was poured Cura etal., describes the technique to fabricate the maxillary and mandibular sectional trays and folding maxillary complete denture for the limited mouth opening.
- 124. A flabbyridge is one, which becomes displaceable due to fibrous tissue deposition. Most frequently seen in the upper anterior region. Usually occurs when natural teeth oppose an edentulous ridge. A flabby ridge causes instability of the denture.
- 125. Methods to overcomethis problem SURGERY This involves removal of the fibrous tissue to leave a firm ridge.
- 126. A primaryimpression is taken in alginate loaded in a stock tray. The impression is then poured and a special tray is constructed on the model. The special tray is close fitting and has a hole or "window" over the area corresponding to the flabby ridge. An impression is taken in impression paste (mucodisplacive).
- 127. Once thishas set it is left in place and impression plaster (mucostatic) is painted over the flabby ridge and allowed to set and removed as one impression. The impression is removed as one, cast and the denture constructed on the resulting model.
- 128. In suchsituations ,lack of ideal amount of supporting structures decreases and the encroachment of the surrounding mobile tissues into the denture border reduces both stability and retention
- 129. Lott andLevin advocated -making impressions of the soft structures of the mouth adjacent to the buccal ,lingual ,labial and palatal surfaces and incorporating the resulting extensions or flanges in the denture Patient is asked to forcefully perform functions of swallowing etc to give a border extensions which cover maximum surface area
- 130. Tryde in1965 used the dynamic impression method on the same principle to obtain the sublingual flange
- 131. This sublingualflange extension increases the tissue surface without interfering with the functions of mastication , deglutition and phonation The active incorporating of tongue activity also stabilizes the denture
- 132. Conclusion Impression visitsprovide us with the opportunity to confirm the Diagnosis and determine the degree of Patient Compliance Flawed impressions account for the majority of the Denture problems
- 133. Though thereare many techniques/ procedures available for the dentist to make a ideal impression, the procedures followed should be based on sound biological principles depending on patients oral and systemic conditions
- 137. Border moldingis the shaping of the peripheries of an impression material by the manipulation or action of the tissues adjacent to the borders of the impression .
- 138. ◦ SINGLE STEPOR SIMULTANEOUS BORDER MOULDING ◦ INCREMENTAL OR SECTIONAL BORDER MOULDING
- 139. Materials used are Modelling compound sticks Autopolymerising acrylic resins Tissue conditioning materials [ modified resins] Metallic pastes & elastomeric materials Impression waxes
- 140. In theupper tray, escape holes (1-2mm in diameter) spaced 1cm apart is placed along the median palatine raphe, beginning at the incisive fossa and ending just anterior to the PPS area. In the lower tray, escape holes spaced ½ inch apart are placed along the crest of the ridge.
- 141. Fibrous (unemployed)posterior mandibular ridge: Flat (atrophic) mandibular ridge covered with atrophic mucosa:
Editor's Notes
- #54 abc