Hinge and Mean value articulator

for BDS student

1. HINGE & MEAN VALUE ARTICULATOR BY- RESHA GHOSH , FINAL YEAR GROUP- C, ROLL NO.- 33

2. DEFINITION :- Articulator may be defined as a mechanical device that represent the temporomandibular joint and jaw members to which maxillary and mandibular casts may be attached to simulate jaw movement.

3. PURPOSE :- To hold the maxillary and mandibular casts in a determined fixed relationship Mounting of dental casts for diagnosis treatment planning and patient presentation. To simulate the jaw movement like opening and closing. Fabrication of occlusal surfaces for dental restoration. Arrangement of artificial teeth for complete and removable partial denture.

4. ADVANTAGES :- Properly mounted casts allow the operator to better visualize the patients occlusion, especially from lingual view. Patient cooperation is not a factor when using an articulator. once appropriate interocclusal records are obtained from the patient. reduces the chair time, patient appointment time. The refinement of complete denture occlusion in the mouth is extremely difficult because of shifting denture bases and resiliency of the supporting tissue. Inter occlusal records can be obtained and complete denture occlusion can be refined outside the mouth on an articulator. More procedures can be delegated to auxillary personnel when utilizing an articulator for development of patients occlusion. The patients saliva, tongue, and cheeks are not factors when using an articulator .

5. CLASSIFICATION OF ARTICULATOR :- Several basis of classification of articulator were proposed, some of them are as follows . – Based on the instruments function . – Based on theories of occlusion . – Based on the type of inter occlusal record used . – Based on the adjustabililty of the articulator

6. BASED ON INSTRUMENT FUNCTION:- Ability to simulate the jaw movement • At the international prosthodontic workshop on complete denture occlusion at the University of Michigan in 1972, the articulators classified based on – instrument capability , – intent , – recording procedure, – record acceptance. • Class I : Hinge Type • Class II : Arbitrary – type A, type B, type C • Class III : Average -type A, type B • Class IV : Special – type A, type B

7. CLASS 1 simple articulator (Simple holding instruments) capable of accepting a single static registration. • Only Vertical motion possible. • positive stops and locks at the mounted position • Use in cases where a tentative jaw relation is done • for crown and bridge, and operative instruments • Example : Slab articulator, Hinge joint articulator (J.B. GARIOT), Barn door articulator .

8. HINGE ARTICULATOR :- Designed by J B Gariot in 1805. Consist of a simple hinge with a screw in the posterior region contracting the upper member to serve as a vertical stop. Barn door hinge: these are articulators that gave a vertical stop.

9. MEAN VALUE ARTICULATOR Class 2 Nonadjustable Articulator 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.

10. COMPONENT PARTS Upper member Condylar shaft & slot with spring Lower member Two additional pins for orientation & support Two vertical arms on either side,hold the upper& lower members together. Incisal adjustment screw Incisal pin Midincisal pin Incisal pin table Fig : Mean value articulator

11. Why is a mean value articulator called so? -Because it has 3 fixed mean values • intercondylar distance- 10 to 11cm • condylar guidance- 30 degrees incline • incisal guidance- 9-12degrees

12. Design The condylar shaft represents the glenoid fossa The condylar slots are angulated at a 30º incline & have a spring mechanism,which helps to push the condylar rod into position. The incisal pin which rests on the incisal table,maintains the vertical height & separation between the upper and lower members. The mid incisal pin helps in the orientation of maxillary anterior teeth according to the midline & the occlusal plane.

13. Articulation procedure- The occlusal rim fused with the centric record are placed over the respective casts. A thread is suspended all around the articulator, running anteriorly across the midincisal pin to the point where the posterior horizontal pin meets the vertical rod. This thread line must coincide with the occlusal plane.

14. - wax blocks are stabilized on t he lower member- one anteriorly & two posteriorly and the occlusal rim with casts is placed over the wax blocks. - The height of the wax is increased or reduced as required , such that the reference plane of the thread coincides with the occlusal plane & the incisal pin meets the incisal table.

15. The upper member is swung open. Plaster is mixed &placed over the cast & the upper member is then gently closed , till the incisal pin touches the the incisal table. Excess is removed. Once the plaster is set, the articulator is now reversed. The lower member is swung open & the wax blocks are removed . The space between lower cast & lower member is adequately filled with plaster . Excess is removed and finished.

16. THANK YOU