1.Concepts and techniques of denture impression Vinay PavanKumar .K 1st year PG Student Dept of Prosthodontics AECS Maaruti dental college

2. Historical review Modified impression procedures Steps Theories Anatomical landmarks ObjectivesDefinitions Basic requirements Concepts and techniques of denture impression 3. There was no strong scientific evidence that different clinical situations require different combinations of materials and techniques for impressions The results of the review warrant serious consideration in prosthodontic teaching and clinical practice. Carlsson GE.etal What is the evidence base for the efficacies of different complete denture impression procedures? A critical review. journal of dentistry 41 (2013) 1723 MEDLINE/PubMed search + Cochrane Library 4. Impression A negative likeness or copy in reverse of the surface of an object; an imprint of the teeth and adjacent structures for use in dentistry Complete Denture Impression The negative registration of the entire denture bearing stabilizing and border seal areas of either the maxillae or mandible in a plastic material that becomes relatively hard or set while in contact with these tissues 5. Preliminary impression or primary impression A negative likeness made for the purpose of diagnosis, treatment planning or for the fabrication of a tray. Final impression The negative likeness made for the purpose of fabricating a prosthesis. 6. Historical review Before the middle of 18th century ridges painted with dye and a block of ivory or bone was pressed on the ridge . 1711 Matthias Gottfried Purman recorded the use of wax 1736 Phillip Pfaff used plaster casts to record maxillary- mandibular relations. 1844 Plaster of Paris first used as impression material 1848 Gutta Percha introduced 7. 1845-1899: concepts of atmospheric pressure, max extension of denture bearing area, equal distance of pressure, and adaptation of denture bearing tissues were stressed secondary wash impression started, plaster within the primary impression retention, stability , and comfort - anatomic considerations impression trays developed (mostly Brittannia metal), also non metal trays used 8. 1900-1929: Introduction of closed mouth impression technique. Border molding to capture the anatomy of the tissues (oral/perioral muscles) Placement of a posterior palatal seal (anatomic and mechanical), most texts recorded the termination of the posterior palatal seal as the vibrating line Introduced the concept of esthetics in impression 9. 1930-1940: Recognized the anatomy of denture bearing areas, and muscle physiology as related to impression procedures Emphasis on immediate denture techniques New materials-reversible hydrocolloids, ZOE Stressed the use of plaster for final impression procedures Introduction of the concept of mucostatics 10. 1950-1964: Introduction of rubber base and silicones Fisher R.D laid down six Fundamental Rules for Making Full Denture Impressions Appreciation for rationale of border molding and posterior palatal seal Use of modeling compound (preliminary impressions) Use of ZOE or plaster (secondary impressions) 11. 1965 present Two techniques were described sub atmospheric pressure (also called as vacustatic technique) and Flange technique A modified impression technique for hyperplastic alveolar ridges was described where surgical preparation was contraindicated Applied plaster impression technique for maxillary complete denture for combination syndrome Dynamic impression technique Dr. Joseph Massad introduced a technique of controlling the path of insertion thus minimizing the incidence of overextension 12. Basic Requirements Knowledge of facial &oral anatomy Knowledge of basic and reliable technique Knowledge and understanding of materials Skill and Patient management 13. Surface anatomy of lower face Rima oris Philtrum Vermilion zone Labial tubercle Labial commissure Modiolus Nasolabial groove Labiomental groove Labiomarginal sulcus 14. Structure of Oral Mucosa Epithelium Connective tissue - Lamina Propria. Submucosa to the underlying structure which may be bone or muscle 15. Thickness and consistency of submucosa - support denture The submucosa is firmly attached to the periosteum of the underlying bone of the residual ridge 16. Organization of the Oral Mucosa 3 types according to function: 1.Masticatory Mucosa:25% of total mucosa. 2.Lining Mucosa:60% of total mucosa 3.Specialized Mucosa:15% of total mucosa. 17. The Masticatory mucosa covers the crest of the ridge The residual attached gingiva firmly adherent to the supporting bone Hard palate It is characterized by a well defined keratinized layer on its outermost surface subject to changes in thickness The specialized mucosa covers the dorsal surface of the tongue. This mucosal covering is keratinized 18. The Lining mucosa - nonkeratinized layer Vestibular spaces Alveolingual sulcus Soft palate Ventral surface of the tongue Unattached gingiva found on slopes of residual ridge. 19. Anatomical landmarks Relief areas Stress bearing areas or supporting areas Peripheral areas or limiting areas 20. Anatomical landmarks in Maxilla Limiting structures: Labial frenum Labial vestibule Buccal frenum Buccal vestibule Hamular notch Posterior palatal seal area 21. Supporting structures Primary stress bearing areas : Hard palate Posterolateral slopes of the residual alveolar ridge Secondary stress bearing areas : Rugae Maxillary tuberosity Relief areas Incisive papilla Cuspid eminence Mid palatine raphae Fovea palatine 22. Limiting structures Labial frenum A fold of mucous membrane at the median line. No muscle attachment v shaped notch should be recorded during impression making Excessive relief weakens denture base 23. Labial vestibule Extends from one buccal frenum to the other on the labial side . The major muscle in this area is Orbicularis oris Impression - sufficient support to the upper lip The labial flange of the impression -sufficient height No interference of the labial flange with the action of lip in function. 24. Buccal Frenum Dividing line between the labial and buccal vestibules. It may be a single fold, or double fold. Broad and fan shaped It has the attachment of following muscles Levator anguli oris Orbicularis oris Buccinators 25. Buccal Vestibule Extends from the buccal frenum anteriorly to the hamular notch posteriorly. The size of the buccal vestibule varies: contraction of the buccinators position of mandible amount of bone loss in the maxilla. The ramus and the coronoid process of the mandible masseter 26. Hamular notch Depression between maxillary tuberosity and the hamulus of the medial pterygoid plate. Distolateral border of the denture base rests in the hamular notch Soft area of loose areolar tissue 27. Posterior palatal seal Soft tissues at or along the junction of hard and soft palate on which pressure within the physiological limits of the tissues can be applied by denture to aid in the retention of the denture Marks the beginning of motion in the soft palate when an individual says ah extends from one hamular notch to other This region contains glandular tissue 28. Aids in retention by maintaining contact with soft palate Reduces the tendency of gag reflex Prevents food accumulation between the soft palate and the denture base Compensate for polymerisation shrinkage 29. Supporting structures Hard palate Foundation of hard palate Ultimate support Submucosa of antero lateral part - adipose tissue Postrolateral part - glandular tissue Horizontal portion of hard palate lateral to midline act as primary stress bearing area 30. Residual ridge Shape and size of alveolar ridges change : natural teeth are removed Mucous membrane is firmly attached to the periosteum Important area of support. Bone undergoes resorption - secondary stress bearing area. Removing the dentures from the mouth for 6 to 8 hrs a day, allows keratinization 31. Rugae In the area of the rugae, palate is set at an angle to the residual ridge and is thinly covered by soft tissue. irregularly shaped rolls of soft tissues. should not be distorted in an impression technique: since rebounding tissue tends to unseat the denture. 32. Maxillary tuberosity Bulbous extension of the residual ridge in the 2nd and 3rd molar region terminating in hamular notch. Enlargement can be fibrous or bony Excess tissue : prevent proper location of the occlusal plane and may interfere with the lower denture 33. Relief areas Mid Palatine Raphe Median palatine raphae extends from incisive papilla to distal end of hard palate Thin mucosal covering with less submucosa non-resilient Adequate relief should be given to avoid trauma from denture base 34. Incisive papilla Elevation of soft tissue over the incisive foramen or nasopalatine canal Burning sensation, parasthesia and pain - relief is necessary 35. Fovea Palatinae Bilateral indentations near the midline of palate formed by coalescence of several mucous gland ducts. Aids in determining vibrating line. 36. Anatomical landmarks in mandible Limiting structures Labial frenum Labial vestibule Lingual frenum Buccal frenum Buccal vestibule Alveolo lingual sulcus Retromolar pad Pterygomandibular raphe 37. Supporting structures Buccal shelf Residual alveolar ridge Relief areas Mylohyoid ridge Mental foramen Genial tubercles Torus mandibularis 38. Limiting structure Labial frenum Shorter and wider than the maxillary frenum. Band of fibrous connective tissue similar : to maxilla. Incisive and orbicularis oris influence this frenum. Unlike in maxilla, this frenum is active 39. Buccal Frenum Usually in the area of 1st pre molar. The oral activities in these area are horizontal as well as vertical (ex. Grinning and puckering) thus needing wider clearance. Muscle acting in this region are Buccinators Depressor anguli oris Orbicularis oris 40. Labial Vestibule Extends between the two buccal frenum Mentalis muscle is an active muscle in this region Length and thickness of the labial flange of denture occupying this space is crucial in influencing lip support and retention Impression will be narrowest in the anterior labial region 41. Retromolar pad Pear shaped triangular soft pad of tissue Bounded by: Buccinator Superior constrictor muscle Pterygomandibular raphe Terminal part of tendon of temporalis 42. Alveololingual sulcus Between lingual frenum to retromylohyoid curtain and divided into three regions Anterior region Lingual frenum to mylohyoid ridge. Premylohyoid fossa- premylohyoid eminence in impression. 43. Middle region From pre-mylohyoid fossa to the distal end of the mylohyoid ridge. Lingual flange extends away from the ridge- tongue rests on the top of flange and aids in stabilizing the lower denture. 44. Posterior region The flange deviates towards the ridge into the retromylohyoid fossa. Proper recording gives typical S form of the lingual flange. 45. Buccal shelf area The area between the mandibular buccal frenum and the anterior edge of the masseter is known as the buccal shelf. It is bounded medially by the crest of the residual ridge anteriorly by the buccal frenum , laterally by the external oblique line and distally by retromolar pad. 46. Crest of the Mandibular Ridge Covered by the fibrous connective tissue Underlying bone is of cancellous type without a cortical bony plate covering . The fibrous connective tissue is favorable for resisting the externally applied forces, such as the denture. 47. Objectives of impression making PRESS P - Preservation of the alveolar ridges. R - Retention E - Esthetics. S - Stability. S - Support. - Carl O. Boucher in 1944 48. Preservation of the alveolar ridges M.M. De Vans dictum It is more important to preserve what already exists than to replace what is missing. Not to use heavy pressure Covering as much of the supporting areas as possible - minimize the possibility of soft tissue abuse and bone resorption. 49. Retention Retention of a denture is that quality inherent in the dental prosthesis acting to resist the forces of dislodgment along the path of placement It depends upon factors that produce attachment of the denture to the mucosa. Resists the adhesiveness of foods, the force of gravity and the forces associated with the opening of the jaws 50. Factors affecting retention of dentures Anatomical factors Physiological factors Physical factors Mechanical factors Muscular factors 51. Anatomical factors Physiological factors Saliva and its quality Size of denture bearing area - Retentive force is directly proportional to the area covered. Quality of the denture bearing area 52. Physical factors Adhesion Cohesion Interfacial surface tension Capillarity and capillary attraction Atmospheric pressure and peripheral seal 53. Mechanical factors Retentive springs Undercuts Magnetic forces Denture adhesive Suction chambers and suction discs Muscular factors The muscles apply supplementary retentive forces on the denture. It is most effective in the neutral zone. 54. Oral and facial musculature provides supplementary retentive forces Denture bases must be properly extended to cover the maximum area possible The occlusal plane must be at the correct level The arch form of the teeth must be in the neutral zone 55. Stability The quality of a dental prosthesis to be firm, steady or constant, to resist displacement by functional horizontal or rotational stresses Relationship of the denture base to the underlying bone 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. 56. To be stable a denture requires Good retention No interfering occlusion Proper tooth arrangement Proper form and contour of the polished surfaces Proper orientation of the occlusal plane Good control and coordination of the patient's musculature. 57. Support The resistance to vertical forces of mastication and to occlusal or other forces applied in a direction toward the basal seat. Enhanced by selective placement of pressures that are in harmony with the resiliency of the tissues that make up the basal seat. 58. Areas of support are divided into Areas of support Primary Maxillary: Posterior ridges and flat areas of the palate Mandibular: Buccal shelf, posterior ridges Reason: These are the areas that are at right angles to the occlusal forces and usually do not resorb easily Secondary Maxillary: Anterior ridge and all ridge slopes. Mandibular: Anterior ridge and all ridge slopes. Reason: These are the areas that are greater than at right angles to occlusal forces or are parallel to them; also the areas of edentulous ridge that are at right angles to occlusal forces but tend to resorb under load. Slight All vestibular areas that provide very little support but are needed for the very important peripheral seal 59. Esthetics Thickness of the denture flanges Thicker denture flanges are preferred in long- term edentulous patients - labial fullness. Impression should perfectly reproduce the width and height of the entire sulcus for the proper fabrication of the flanges. 60. Classification of impressions A. Based on the theories of impression. Pressure theory- Mucocompressive Minimal pressure- Mucostatic Selective pressure 61. B. Based on the position of the mouth while making the impression. Open mouth Closed mouth C. Based on the method of manipulation for border molding. Hand manipulation Functional movements 62. Pressure theory :Mucocompressive Definite pressure The assumption that denture retention is tested most severely during mastication, many dentists formerly considered it essential for the tissue to remain in contact with the denture during chewing Greene in 1896 Records the oral tissues in a functional and displaced form Materials used - impression compound, waxes and soft liners. Dentures made by this technique tend to get displaced due to the tissue rebound at rest 63. Technique Primary impression - impression compound Special tray - base plate. Second Impression - impression compound Bite rims with uniform occlusal surfaces are then made. Areas to be relieved are softened and the impression is inserted in mouth and held under biting pressure for one or two minutes. Borders are molded by asking the patient to perform functional movements. 64. Advantages Better retention and support Disadvantages Excess pressure - increase alveolar bone resorption. Excess pressure on peripheral tissues and the palate - transient ischaemia. Tissue rebound when the tissue resume their normal resting state. Pressure on sharp bony ridges - pain 65. Minimal pressure theory : Mucostatic or non pressure or passive technique Page gave the concept of mucostatic based on Pascals law Mucostatic Dr. Carrol W. Jones Retention is mainly due to interfacial surface tension. The mucostatic technique results in a denture, which is closely adapted to the mucosa of the denture-bearing area but has poor peripheral seal. 66. Technique A compound impression is made. A baseplate wax space is adapted. A special tray is adapted over the wax spacer. Spacer is removed and an impression is made with a free flowing material with little pressure. Escape holes are made for relief. 67. Disadvantages Shorter flanges prevent the wider distribution of masticatory stresses. Reduced coverage Lack of border molding : reducing retention Lack of border seal: food to slip beneath the denture. Advantage High regard for tissue health and preservation : better prognosis 68. Short denture borders are readily accessible to the tongue which might provoke some irritation. Shorter flanges may reduce support for the face which can affect esthetics. The shorter flange would mean less lateral stability. Patients with poor residual ridges and reduced areas of attached gingiva were difficult to treat 69. Selective pressure theory Combines the principles of both pressure and minimal pressure techniques Tissue preservation + mechanical factor of achieving retention with minimum pressure, which is within the physiologic limits of tissue tolerance 70. Philosophy of the 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 71. Boucher divided basal seat area into different zones according to capacity to withstand masticatory loads without undergoing resorption. Primary stress bearing area Relief areas Secondary stress bearing area 72. Advantages Technique considers the physiologic functions of the tissues of the basal seat, and therefore appears more sound and appealing. Disadvantages Some feel that it is impossible to record areas with varying pressure. Since some areas are still recorded under functional load, the denture still faces the potential danger of rebounding and loosing retention 73. Open-mouth Impressions Impressions are made with the tray that is held by the dentist Advantage Preferred because the operator can see whether muscle trimming is done properly 74. Closed-mouth Impressions Supporting tissues are recorded in a functional relationship Wax occlusion rims that are made on preliminary casts. Border molding and the final impressions are completed McMillan - tongue movements are more forceful when teeth are together. 75. Advantage Saving of time Disadvantage Appointment time may fatiguing the dentist and patient Tendency for overextensions Problem of limited space between the tuberosity and pear shaped pad No control over the amount of pressure during the final impressions Soft tissues displaced- rebound bone resoption 76. Dynamic impression technique Cagna et al, The neutral zone revisited: From historical concepts to modern application, J Prosthet Dent 2009;101:405-412 77. Steps in impression making Examination and conditioning of the patient and the mouth. Seating of the patient Selection of impression material Selection of the impression tray Selection of impression technique Making the preliminary impression Constructing the primary cast Fabricating the custom tray Border molding Making the final impression 78. Examination and conditioning of the patient and the mouth Inflammation of the mucosa Distortion of denture-foundation tissues Excessive amounts of hyperplastic tissue Insufficient space between the upper and lower ridges 79. Impression material Classification Elastic 1. Reversible hydrocolloid 2. Irreversible hydrocolloid 3. Rubber impression materials a. Polyether b. Silicone Non-elastic 1. Gypsum products 2. Metallic oxide pastes 3. Impression compound 80. Based on Prosthodontic use Preliminary impression materials : Impression compound Alginate Final impression materials: Plaster of paris, zinc oxide-eugenol paste, irreversible hydrocolloid, silicone, polysulfide rubber, polyether, tissue-conditioning material 81. SELECTION OF THE IMPRESSION TRAY A device that is used to carry, confine, and control impression material while making an impression (GPT-8). Classification of impression trays Bases on whether they are prefabricated or individualized Stock trays Custom trays 82. Depending on the presence or absence of holes or perforations Perforated Non-perforated Depending on whether they are meant for dentate or edentate individuals Dentulous trays Edentulous trays Combination trays 83. Seating of the patient Position of the operator for maxillary impression Position of the operator for mandibular impression 84. Preliminary impression making :Maxillary Practice positioning of the tray Labial frenum - guide. Anterior fingers - 1st molar region Adhesive - silicone putty material or alginate Impression compound Posterior part of tray- contact with tissues 85. Border moulding Labial and buccal vestibules Coronoid process Impression poured - stone 86. Primary impression : Mandibular Posterior extent of tray retromolar pad Tray loaded with material and catered over the ridge with tongue slightly raised Alternating pressure on molar region with index finger Functional movements done to get the border limit 87. Constructing the custom tray Outline for the wax spacer is drawn on the cast Posterior palatal seal area on the cast is not covered with the wax spacer maxilla Buccal shelf not covered - mandible Baseplate wax approximately 1 mm in thickness is placed on the cast Self-curing acrylic resin tray material - uniformly adapted over the cast Tray thickness - 2 to 3 mm Resin handle is attached in the anterior region of the tray 88. Spacer design Roy Mac Gregor recommends placement of a sheet of metal foil in the region of incisive papilla and mid palatine raphae 89. Neill recommends adaptation of 0.9 mm casing wax all over except PPS area Boucher recommends placement of 1 mm base plate wax on the cast except PPS area 90. Morrow, Rudd, Rhoads recommends to block out undercut areas with wax ,adapt full wax spacer 2 mm short of resin special tray border all over & placement of 3 tissue stops equidistant from each other Sharry recommended Base plate wax adapted over whole area, four stops 2mm width cut from wax : cuspid and molar region- extend from palatal aspect of ridge : mucobuccal fold 91. Border molding Border molding is the process by which the shape of the borders of the tray is made to conform accurately to the contours of the buccal and labial vestibules Manipulation of the border tissues, against a moldable impression material Borders of the tray are molded to a form that will be in harmony with the physiological action of the limiting anatomical structures 92. Border molding may be carried out in sections either recording one part of the border at a time or recording all parts of the borders simultaneously. Recording all of the borders simultaneously has two general advantages: The number of insertions of tray is reduced. Developing all borders simultaneously avoids propagation of errors caused by a mistake in one section affecting the borders contours in another. 93. Custom tray fabrication 94. Border moulding Sectional Recording all borders simultaneously 95. Final impression 96. Boxing impressions and making casts Enclosure of an impression by building up vertical walls- desired size, base of cast, preserve details of impression 97. Final cast 98. Displaceable (flabby) anterior maxillary ridge The extent of the displaceable tissue is drawn on the impression surface. This area, and the equivalent area of the tray, are then removed, using a scalpel and acrylic bur Use a low-viscosity material and paint or syringe these onto the displaceable tissue to record them in a minimally- displaced position. 99. Fibrous posterior mandibular ridge McCord.JF ,Grant.AA ,Impression making, BDJ, 2000 ;188: 9, pp 484 92 100. Flat (atrophic) mandibular ridge covered with atrophic mucosa McCord and Tyson described this technique The impression medium here is an admix of 3 parts by weight of (red) impression compound to 7 parts by weight of greenstick; the admix is created. McCord.JF ,Grant.AA ,Impression making, BDJ, 2000 ;188: 9, pp 484 92 101. Technique for Impressing Class IV Mandibular Edentulous Ridge Chandrasekharan et al, A Technique for Impressing the Severely Resorbed Mandibular Edentulous Ridge, Journal of Prosthodontics, 2012; 21: 215218 102. Review of literature Study evaluated changes in impression pressure produced by different types of relief space and escape holes in the impression tray for making an impression of a simulated maxillary edentulous arch For making impressions of an edentulous maxilla, the data suggest that a tray with an escape hole 1.0 mm or larger or a spacer thickness of base plate wax (1.40 mm) be used. Komiyama O et al, Effects of relief space and escape holes on pressure characteristics of maxillary edentulous impressions, J Prosthet Dent 2004;91:570-6 103. Goodacre et al, CAD/CAM fabricated complete dentures: concepts and clinical methods of obtaining required morphological data, J Prosthet Dent 2012;107:34-46 104. Infante et al, Fabricating complete dentures with CAD/CAM technology, J Prosthet Dent 2014 105. CONCLUSION Ideal impression must be in the mind of the dentist before it is in his hand. He must literally make the impression rather than take it - M.M. De van 106. References Zarb G, Hobkirk JA, Eckert SE, Jacob RF, editors. Prosthodontic treatment for edentulous patients. 13th ed. St. Louis: Elsevier Mosby; 2013 pp 161-179 Sheldon Winkler, Essentials of complete Denture prosthodontics, 2nd edition,2012, AITBS Publishers, India, pp 88-105 Sharry .J.J, Complete denture Prosthodontics, 3rd edition, Mc Graw Hill company, pp 191-210. 107. Rudd and Morrow, Dental lab procedures, Complete dentures, 2nd edition, 1986, Mosby Publications, USA, Pp 9 - 89 Nair KC, A primer on complete denture fabrication, 1st edition, 2013, Ahuja publication, India Pp 67-77 Zimmer I.D. and Sherman, H. An analysis of the development of complete denture impression techniques. J Prosthet dent 46: 242-249, 1981. Komiyama O et al, Effects of relief space and escape holes on pressure characteristics of maxillary edentulous impressions, J Prosthet Dent 2004;91:570-6 108. McCord.JF ,Grant.AA ,Impression making, BDJ, 2000 ;188: 9, pp 484 92 Rao.S etal, A Systematic Review of Impression Technique for Conventional Complete Denture, J Indian Prosthodont Soc (Apr-June 2010) 10(2):105111 Chandrasekharan.NK et al, A Technique for Impressing the Severely Resorbed Mandibular Edentulous Ridge, Journal of Prosthodontics, 2012; 21: 215218 109. Goodacre et al, CAD/CAM fabricated complete dentures: concepts and clinical methods of obtaining required morphological data, J Prosthet Dent 2012;107:34-46 Infante et al, Fabricating complete dentures with CAD/CAM technology,J Prosthet Dent 2014 Dwivedi A, Vyas R, Theories of impression making and their rationale in complete denture prosthodontics. J Orafac Res 2013;3(1):34-37