Selective Grinding for Bilateral Balanced Complete Dentures: Flashcards
Which are the functional cusps in the mandibular and maxillary arch?
The Buccal cusps are the functional cusps for the Mandibular teeth:
- The (most mesial) buccal cusp of a mandibular tooth occludes with the mesial marginal ridge (MMR) of its corresponding tooth
- The distal buccal cusp of a mandibular molar tooth occludes in its central groove of its corresponding maxillary tooth
The lingual cusps are the functional cusps for the Maxillary teeth
- The (most distal) lingual cusp of a maxillary tooth occludes with the marginal ridge (DMR) of its corresponding mandibular tooth
SELECTIVE GRINDING:
OBJECTIVE:
The objective of selectively grinding complete dentures for balance is to eliminate premature tooth contacts (interferences) that prevent multiple, well-distributed points of contact between upper and lower teeth in the anterior and posterior areas on the right and left during working, balancing and protrusive occlusions.
SELECTIVE GRINDING:
STEP BY STEP:
- Remounting of casts and dentures
- Correct of the vertical processing errors
- Restore the centric occlusion
- Correct the balancing occlusion
- Correct the protrusive occlusion
- Polish the selectively ground denture teeth
- Mill-in the dentures
SELECTIVE GRINDING:
PREPARATION FOR REMOUNTING:
- Use a large “cutoff” disc to make retention cuts in the cast and immediately above the cast cuts in the mounting. Place these pairs of cuts in four areas: right buccal, left buccal, anterior and posterior. Make sure the bottom of the cast and all index keys are perfectly clean.
- Ensure there is total contact between the bottom of the cast and the mounting. Hold the cast and the mounting together in complete contact. Use dripping hot green or red modelling plastic to attach the cast to the mounting in the areas where the retention cuts are located.
- Do not cover the entire junction line. Leave some of the junction exposed to detect if the cast separates from mounting
SELECTIVE GRINDING:
ARTICULATOR SETTINGS:
First, check the articulator settings. Ensure the readings on the articulator are the same as when the denture teeth were set in wax
Also ensure that the condylar elements of the articulator are locked against the centric stops and the incisal guide pin is at the same setting as when the case was final waxed.
SELECTIVE GRINDING:
EQUIPMENT AND MATERIALS
- Double sided articulating paper (preferable)
- Hand piece or Lathe
- Mounted stones /
- Carbides
- Milling paste
SELECTIVE GRINDING:
CORRECTING THE VERTICAL PROCESSING ERROR:
- Evaluate the compensating curve
- All cusp tips of the denture should be on the compensating curve established in the waxed denture
- If a maxillary cusp tip is obviously protruding below the curve or a mandibular cusp tip is significantly above the curve, grind those cusp tips carefully to conform to the curve
- Also check for any wax flash that may compromise occlusal surfaces and remove carefully
- To eliminate interferences high spots, deflective contacts or prematurity’s they first have to be found
- The selective grinding process has strict rules
- These rules represent a precise orderly way of using articulating paper to identify prematurities and eliminate them
- The really gross interferences are seen as white spots surrounded by carbon rings
- This kind of mark shows a contact so heavy that the cusp has cut though the articulating paper
RESTORING THE CENTRIC OCCLUSION:
- For the next step remove the articulator paper markings with a cotton tip applicator moistened with monomer
- Place blue articulating paper on the right and left sides and tap the denture teeth together
- With the pin touching the table, there should be multiple, evenly distributed points of contact between maxillary and mandibular teeth
- The illustration shows all fossae and embrasures where stamp cups hit
- When correcting a vertical processing error (the pin is off the table), grind all these marks that appear in these places
CORRECTING THE WORKING AND BALANCING OCCLUSION:
Two paths of travel are possible when newly remounted dentures are moved into working and balancing relations
a) One is a path which the upper and lower teeth mesh best
b) The second is a path governed by the way articulator settings guide the upper member through lateral movements
* After waxing the dentures and subsequent processing the two paths should be the same
INTERFERENCE ON THE WORKING SIDE:
WORKING SIDE INTREFERENCE-> GRINDLINGUAL INCLINE OF BUCCAL CUSP OF UPPER BUCCAL INCLINE OF LINGUAL CUSP OF LOWER
INTERFERENCE ON THE BALANCING SIDE:
NON - WORKING SIDE INTREFERENCE-> GRIND BUCCAL INCLINE OF LINGUAL CUSP OF UPPER AND /OR LINGUAL INCLINE OF BUCCAL CUSP OF LOWER
SELECTIVE GRINDING
CORRECTING THE WORKING AND BALANCING OCCLUSION
— To correct the occlusion in eccentric positions follow these steps:
- Lock down the working side condyle and release the balancing side condyle
- Place red articulating paper on the right and left sides and move the articulator into a lateral excursion, being sure to incorporate side shift
- Grind premature spots and tracks
SELECTIVE GRINDING
CORRECTING THE WORKING AND BALANCING OCCLUSION
BULL Rule:
- On the working side, check for working side collisions between maxillary and mandibular anterior teeth that prevent posterior teeth from contacting
- If such anterior interference exists grind the facio-incisal surface of the offending lower anterior or the lingual surface of the maxillary anterior teeth
- Next follow the buccal of the upper and lingual of the lower (BULL) rule on the working side
- Grind red articulating paper marks found on the inclines or cusp tips associated with the buccal cusps of maxillary posterior teeth and lingual cusps of the mandibular posteriors
NOTE: The BULL rule only applies to the working side. Do not grind any other marks on the working side that are not a part of the rule.
SELECTIVE GRINDING:
CORRECTING THE WORKING AND BALANCING OCCLUSION:
Balancing site-rule?
Describe the scheme.
- On the balancing side, note that the only contacts possible occur between the buccal inclines of lingual cusps on maxillary teeth and the lingual inclines of buccal cusps of mandibular teeth
- The rule on the balancing side is to grind articulating paper marks found on inclines and cusp teeth associated with the buccal cusps of the mandibular teeth
- Disregard all other marks on balancing side
SELECTIVE GRINDING
CORRECTING THE WORKING AND BALANCING OCCLUSION
Start with a right lateral excursion then follow these steps:
- Lock down the right condylar element and release the left element
- Place the articulating paper between the maxillary and mandibular teeth on the right and left sides
- Move the articulator into a right lateral excursion – the right side becomes the working side
- Grind premature spots and tracks using Figure 1 as a guide. Disregard all other marks. Notice that the Figure conforms
- to the BULL and balancing side rules; that is buccal of the upper and lingual of the lower on the working side and buccal of the lower on the balancing side.
Continually repeat steps 2 through 4 above until a general contact pattern that resembles the figure develops on the working and balancing sides
