Mounting Occlusal Rims On Articulator Introduction
Mounting is done to position wax occlusal rims and casts on articulator and fix them in particular position. This chapter demonstrates simple method to mount casts on mean value articulator.
Table of Contents
Armamentarium
Maxillary and mandibular occlusion rims with casts.
- Mean value articulator
- Dental plaster
- Rubber bowl and plaster mixing spatula
- Wax knife
- Modeling clay
- Thread
- Petroleum jelly.
Read and Learn More: Preclinical Prosthodontics Notes
Step 1:
Indexing should be done on the base of the master cast using any of the indexing method (groove indexing or notch indexing). Midline is marked on both the occlusal rims taking labial frenum (on the cast) as reference. Maxillary and mandibular rims are placed together in such a way that maxillary rim overlaps the mandibular rim labially by 2 mm. Midline of maxillary and mandibular rims should coincide with each other.
Note: Horizontal overlapping of mandibular rim by maxillary rim is essential to achieve overjet in teeth arrangement.
Step 2:
The rims are sealed together to maintain the horizontal overlapping. Sealing is done in molar area by marking cross by hot wax knife. This sealing will prevent movement of hot wax rims during mounting procedures and maintains them in specific position.
The rims are sealed at specific position. The interface of two rims is occlusal plane. In the articulator, anterior reference point is central pin and posterior reference is provided by posterior reference rod. Central pin and posterior reference rod form the plane of articulator (or plane of orientation).
While mounting, the occlusal plane should coincide with articulator plane (or plane of orientation). A thread tied on posterior reference rod can be used to verify position of occlusion rim. Modeling clay is placed on mounting ring of lower member of articulator. The sealed rims are placed on the clay accordingly that the central pin is in midline and it is at the level of occlusal plane (between maxillary and mandibular rims).
The position of rims is adjusted in such a way that the occlusal plane (on wax rim) matches with the articulator plane. The thread can be used for checking the match of twoplanes.
Note: Before adjusting the rims on articulator, make sure that the central pin is fully seated in its position. Check the matching of two planes at eye level.
Step 3:
Apply thin coat of petroleum jelly in index (grooves or V shaped notches).
Step 4:
Mix dental plaster in homogeneous and creamy consistency using rubber bowl and spatula. Pour mixed plaster in grooves or notches made on base of the maxillary cast using wax knife.
Step 5:
Pour remaining mixed plaster on the whole base of the maxillary cast. Apply plaster on mounting ring also. Close upper member of articulator. Allow plaster to fill the spaces provided in mounting ring. Remove excess plaster coming out from mounting ring and make it parallel to upper surface of mounting ring.
Note: Plaster used for mounting should be creamy in consistence. If it is not creamy and free flowing then during closing the upper member, pressure will be exerted on casts and this may change position of rims which leads to discrepancy of planes.
Step 6:
Try to shape mounting plaster according to the shape of cast. Add or remove plaster as needed. Use flat metal strip like plaster mixing spatula or wax knife for shaping the plaster. Shape mounting plaster according to periphery of cast (according to shape of base of the cast).
Step 7:
Use wet cotton or finger to smooth the mounting plaster and allow it to set.
Step 8:
Once upper mounting plaster is set, turn the articulator upside down for mounting mandibular cast. Open the articulator slowly and remove the clay.
Step 9:
Apply thin coat of petroleum jelly on index on the base of mandibular cast. Wet the cast base with water before applying plaster on the base.
Step 10:
Mix plaster and pour index first and then pour remaining plaster on base. Apply some plaster on mounting ring also.
Step 11:
Close the lower member and follow the procedures performed during mounting of maxillary cast. Shape the mounting plaster according to shape of cast contour Smoothen the plaster using wet cotton. Use dry cotton to clean the articulator. Maxillary and mandibular casts mounted on mean value articulator.
Note: Never wash articulator under tap water to clean it. This may expand mounting plaster which results in increase of vertical dimension of occlusion. If plaster expands, the vertical pin will not be in contact with anterior guide table. Extend the midline and canine lines on mounting plaster. Write name, age, sex, of the patient or roll no, and name.
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