Articulators used in dentistry . pptx...

Detail description of articulators and its uses

1. Articulators S P Mathivathani

2. Articulator may be defined as a mechanical device that represents the temporomandibular joints and jaw members to which maxillary and mandibular casts may be attached to simulate jaw movements.

3. FROM 1700 To 1800: FROM 1801 To 1900: FROM 1901 TO 1950: HISTORY and EVOLUTION:

4. FUNCTIONS: Hold the maxillary and mandibular casts in a determined fixed relationship. Mounting of dental casts for diagnosis treatment planning and patient presentation. Simulate the jaw movements like opening and closing. Fabrication of occlusal surfaces for dental restorations. Arrangement of artificial teeth for complete and removable partial dentures.

5. MINIMAL REQUIREMENTS: They are necessary for the fabrication of complete dentures to the patients centric position. They are: It must accurately maintain the correct horizontal and vertical relationship of the patient’s casts. The casts should be easily removable and attachable to the articulator without loosing their correct horizontal and vertical relationship.

6. iii. The articulator should have an incisal guide pin with a positive stop, that is adjustable and can be calibrated. The articulator should be able to open and close in a hinge like fashion. The articulator should accept a face-bow transfer utilizing an anterior reference point. The construction should be accurate, rigid and of non corrosive material.

7. LIMITATIONS: Metal, plastic articulators show errors in tooling. It does not exactly simulate the intraborder and functional movements of the mandible. Errors in jaw relation procedure are reproduced as errors in the denture occlusion. Articulators do not have any provision to indicate or correct these errors.

8. CLASSIFICATION OF ARTICULATORS: Based on theories of occlusion Based on position of condylar elements Based on ability to simulate jaw movements Based on the adjustability of the articulator

9. 1) BASED ON THEORIES OF OCCLUSION:

10. BASED ON THEORIES OF OCCLUSION: 1) BONWILL THEORY ARTICULATORS: WGA Bonwill (1858) Known as theory of equilateral triangle. Bonwill’s articulator Allows lateral movements & permit movements only in horizontal plane.

11. Theory of equilateral triangle: Acc. to which distance between the condyles and the distance between condyles and the midpoint of the mandibular incisors (incisal point) is equal, with sides of 4”. Teeth move in relation to each other as guided by the incisal and condylar guidances; the articulator is designed such that these fall within the equilateral triangle.

12. 2) CONICAL THEORY ARTICULATORS: R.E. Hall (1918) Adjustable 3D anatomic articulator. Lower teeth move over the surface of the upper teeth as over the surface of a cone generating an angle of 45° with the central axis.

13. RE Hall’s Experimental Conical Theory Type Articulator

14. 3) SPHERICAL THEORY ARTICULATORS: G. S. Monson (1916) Lower teeth move over the surface of the upper teeth as over a surface of sphere with a diameter of 8” with its center located in the region of glabella .

15. MAXILLOMANDIBULAR INSTRUMENT

16. DISADVANTAGES OF ARTICULATORS BASED ON THEORIES OF OCCLUSION: Based on theoretical concepts. No provision for variations from the theoretical relationships that occur in different persons.

17. 2) Based on position of condylar elements: Ar-con term coined by Bergstrom. Ar: Articulator; Con: Condyle. Condylar analogues: mandibular element Condylar fossa/guidance: maxillary element Condylar analogues: maxillary element Condylar fossa/guidance: mandibular element

18. As condyles move in the articulator similar to natural glenoid fossa, visualization and understanding of condylar movements is better in arcon articulators. There seems to be no other advantage with regard to accuracy of movement or superiority in clinical evaluation of complete dentures when compared to nonarcon articulators.

19. 3) Based on ability to simulate jaw movements: II a II b II c III a IV b IV a III b

20. CLASS I: Single static registration Vertical movement CLASS II: Vertical movement Horizontal movement (protrusive and lateral) CLASS III: Vertical movement Horizontal movement (protrusive and lateral) Facebow transfer (But only part of condylar- movement simulated) CLASS IV: Vertical movement Horizontal movement (protrusive and lateral) Facebow transfer Adjustable intercondylar distance

21. 3) Based on ability to simulate jaw movements: At the International Prosthodontic Workshop on complete denture occlusion at the University of Michigan in 1972. Based on instrument’s capability, intent, recording procedure and record acceptance. Most widely used classification .

22. Class I (Hinge Type): Most simplest articulators; capable of accepting a single static registration. Only Vertical motion possible.

23. Common example: Slab articulator

24. Other examples : Barn door articulator, Gysi Simplex, Hinge joint articulator (J.B. GARIOT),

25. Class II (Arbitrary Type): These articulator permits horizontal and vertical movements but they do not orient the movement to TMJ a face-bow.

26. Type A: Eccentric motion is unrelated to patient motion. Permit limited eccentric motion based on averages. Eg: Mean value articulator

27. Type B: --Limited eccentric movement based on arbitrary theory of motion Eg: Monson’s articulator -Spherical Theory Articulator Hall’s articulator -Conical Theory Articulator

28. TYPE C: --Permit limited eccentric motion based on engraved records obtained from the patient. Ex: House’s articulator by M. M. House (1920) , Gnathic Relator

29. FUNCTIONAL METHOD: NEEDLE-HOUSE METHOD: Occlusal rims are fabricated from impression compound. Four metal balls or styli are embedded in the canine and molar areas of the maxillary occlusal rim. The occlusal rims are inserted and the patient is asked to perform various functional and excursive movements of the mandible with the styli contacting the lower rim. The styli makes three-dimensional diamond-shaped tracings, which can be transferred to the House articulator.

30. Three-dimensional diamond-shaped tracings

31. Class III: Permit horizontal and vertical movements. They do accept facebow transfer. Do not allow total customization of the condylar pathways. They simulate condylar pathways by using average or mechanical equivalents for the whole or part of the condylar motion.

32. TYPE A: Accept only protrusive record, lateral condylar inclination is determined by formula Eg: Hanau wide-vue, Dentatus TYPE B: Accept both protrusive and some lateral records Eg: Hanau Kinoscope, Ney articulator, Panadent.

33. HANAU ARTICULATOR DENTATUS ARTICULATOR

34. NEY ARTICULATOR PANADENT ARTICULATOR

35. CLASS IV: Accept 3 dimensional dynamic registrations; Allow for orientation of casts to TMJ and simulation of mandibular movements Simulate all mandibular movements; fully adjustable articulators. Accept facebow transfer. Arcon type with adjustable intercondylar distance.

36. BASED ON CONDYLAR RECORDINGS: Condylar pathways are engraved by patient (Stereographic recording) TYPE IV A TYPE IV B Condylar pathways are obtained using 3 dimensional tracings (Pantographic recordings)

37. TYPE IV A: Record mandibular movement in 3 planes. Engraving, milling, or burnishing the recording medium by means of styli, teeth. Instrument used is termed stereograph and recording is called Stereographic record. Eg: TMJ articulator given by Kenneth Swanson in 1965. Intraoral registration of jaw movements is by studs on autopolymerising resin, similar to Needle House method.

38. TYPE IV B: Pantograph is the instrument used to record in one or more planes, paths of mandibular movements and to provide information on the programming of an articulator. Tracing is called Pantographic tracing, or Pantogram.

39. Tracings obtained are similar to gothic arch tracing, but are obtained in all three planes. Six styli and tracing tables are attached by means of facebows and clutches to maxilla and mandible. They can also be available in electronic form.

40. 4) BASED ON THE ADJUSTABILITY: NON-ADJUSTABLE FULLY-ADJUSTABLE SEMI-ADJUSTABLE CENTRIC RECORD PROTRUSIVE RECORD CENTRIC RECORD PROTRUSIVE RECORD FACE BOW TRANSFER CENTRIC RECORD PROTRUSIVE RECORD FACE BOW TRANSFER LATERAL RECORDS INTERCONDYLAR DISTANCE RECORD

41. MOST COMMONLY USED ARTICULATORS:

42. MEAN VALUE ARTICULATOR

43. MEAN VALUE ARTICULATOR: So called because it has 3 fixed mean values : intercondylar distance: 100–110mm { 4 inches } condylar guidance: 33 degrees incisal guidance: 9-12 degrees

44. USES: Used if occlusal contacts are to be oriented in centric occlusion only. It can open and close in a fixed horizontal axis and has a fixed incisal table and condylar path. It is also called three-point articulator.

45. CLASSIFICATION OF ARTICULATOR: Based on theories of occlusion Based on position of condylar elements Based on ability to simulate jaw movements Based on the adjustability of the articulator BASED ON BONWILL’S EQUILATERAL TRIANGLE THEORY NON-ARCON ARTICULATOR CLASS II TYPE A ARTICULATOR NON-ADJUSTABLE ARTICULATOR

46. COMPONENT PARTS: (a) Upper member (b) Condylar shaft and slot with springs (c) Lower member (d) Two additional pins for orientation and support (e) The two vertical arms on either side

47. COMPONENT PARTS: (f) Incisal adjustment screw (g) Incisal pin (h) Mid-incisal pin ( i ) Incisal pin table

48. UPPER MEMBER: Triangular frame Two Condylar elements Vertical Rod with a thumb screw.

49. LOWER MEMBER: L-Shaped frame with horizontal and vertical arm. Horizontal arm is triangular and its apex contains incisal guide table. Vertical arm is rectangular containing condylar guidance slot at upper portion.

50. INCISAL GUIDE TABLE: very short cylinder, concave upper surface. VERTICAL ROD OR INCISAL PIN: keep fixed distance between the upper & lower member at anterior end. pointed tip - rest on the center

51. INCISAL GUIDE PIN: anterior reference point. The incisal edge of the maxillary incisors at the mid line of the occlusal rim should touch the tip of incisal pin during articulation.

52. CONDYLAR GUIDANCE: Represented by a slot (condylar track) Condylar element of upper member passes through this track. A spring is mounted within this track to establish the condylar element

53. SUPPORT ARM: ORIENTATION ARM:

54. MOUNTING PROCEDURE:

55. MOUNTING PROCEDURE:

56. ARTICULATOR CARE AND MAINTENANCE

57. CLEANING: Use a mild soap and water solution with the aid of a brush to dissolve accumulations of wax Then air dry and lubricate. DO NOT use strong detergents, alkalies , gasoline or naphthalene as cleaning agents.

58. LUBRICATION: Lubricate the working and bearing components with a thin film of sewing machine or high speed handpiece type oil. Wipe off excess oil to prevent accumulations of dust or grit. A thin coating of petroleum jelly must be applied to all Articulator surfaces that will be contacted by the gypsum mounting material.

59. STORAGE: Store the articulator in a clean, dry atmosphere free of plaster and carborundum dust; away from acids, alkalies or corrosive medicaments.

60. RECENT ADVANCES: Virtual Articulators are also called as `SOFTWARE articulators`. They comprises of virtual condylar and incisal guide planes.

61. Guide planes can be measured precisely using jaw motion analyser or average values are set in the program like average value articulator The Virtual Articulators are able to design prostheses kinematically. They are capable of simulating human mandibular movements by moving digitalized occlusal surfaces against each other and enabling correction of digitalized occlusal surfaces to produce smooth and collision-free movements. Presently Virtual Articulator is supporting mechanical articulator in better visualizing of the occlusion, in near future they replaces mechanical articulators.

62. CONCLUSION: “It must be recognized that the person operating the instrument is more important than the instrument. If dentists understand articulators and their deficiencies, they can compensate for their inherent inadequacies.”

63. The choice of articulator depends upon such factors as: (a) intended use, (b) availability of equipment, (c) patient's occlusion, (d) skill of the technician, (e) skill of the operator, (f) expense.

64. Thank you