Deflasking , Remounting and Occlusal Adjustment Dr.Mohammad Al Sayed 16/3/2008 Deflasking of the dentures :A-Removing the mold after processing the acrylic resin denture the flask is cooled slowly . to room temperature remove the lid of the flask by prying .with a knife
.place the flask in an ejector press using minimum pressure eject the . mold from the flask :B-Removing the denture and cast remove the stone cap ( the third layer ) by gently prying it off to expose the occlusal . surfaces and incisal edges of the teeth with a plaster saw make 4 cuts, 2 in canine . region and 2 in the posterior region with the plaster knife gently pry the sectioned plaster away from the facial surface of the
. teeth after removing the outer sections of stone from the denture , trim the stone away from the lingual surfaces of the teeth before attempting to remove the inner section of . plaster and stone this procedure will a-prevent breaking the teeth b-prevent lifting the denture from the cast
During deflasking: be careful to preserve thecast, also do not left or remove the denture from the casts .Clean the denture and cast from plaster Remove any stone or bubbles from the exposed acrylic resin and from the .occlusal surfaces of the teeth Remove any particles of stone from the- .base of the cast and index grooves Using a stiff brush , soap and water clean the denture and cast before starting the laboratory remount
Laboratory remount procedure :and selective grinding Objective: to correct errors in the occlusion due to slight changes in the position of the teeth that may have occurred during waxing, packing and processing. To obtain a smooth even contact of the teeth in centric and .eccentric positions During flasking and processing changes in the occlusion may occur due to
several possible causes called :processing errors Dimensional changes in the wax after setting up of the.1 teeth. This should be very slight if the occlusion of .the wax-up was carefully examined before flasking The heat cured acrylic resin expands and contracts .2 during the curing procedure. It expands as the polymerizing temperature is reached then starts to contract (polymerization shrinkage) .Then as it . cools to room temperature it contracts again The total effect of this dimensional change is a slight
shrinkage which may change the position of the . teeth The expansion of the investing material during the .3 . processing . The pressure of the flask press.4 In order to correct these errors, the* dentures are returned to the articulator after deflasking.The casts are repositioned on the original plaster mountings using the key (index) in the base of the cast. The casts are
attached to the plaster mountings by sticky .wax The condylar elements of the articulator are* locked in the centric relation and the articulator is closed. If the incisal pin does not touch the incisal guide table the occlusal vertical dimension has been changed and .must be re-established Occlusal adjustment: (Selective grinding) The sequence of steps should be as :follows
.Restore the vertical dimension. 1 .Refine centric occlusion. 2 Perfect working and balancing. 3 .occlusion .Correct protrusive occlusion. 4 Selective grinding is carried out using* articulating paper to mark the area of .premature contacts :Procedure Adjust the articulator to the proper. 1 . setting Use red articulating paper for making
centric occlusion and blue articulating paper for the eccentric . movements Grind the teeth with small green or. 2 .diamond stones :Restore the vertical dimension. 3 A lateral shift of a tooth or a tooth shifted to produce a high cusp can increase the vertical .dimension
Do not grind the cusp tips unless it is high in every excursion, but rather reduce the fossa .or inclined plane of the cusp .Error: high cusp grind the fossa Error: Lateral shift, buccal shift or lingual shift grind the cusp inclines Obtain even contact in centric.4 :occlusion a. Lock the upper arm of the articulator in centric relation. Check the occlusion by opening and closing the articulator, and lightly tapping the
. teeth together on red articulating paper b. Loosen the locks on the condylar elements and .move the denture in eccentric movements .Using blue articulating paper between the teeth If the cusp is high in centric occlusion only deepen . the fossa If the cusp is high in both centric and eccentric . position reduce the cusp Reduce the teeth until the incisal pin touches the
incisal guide table and uniform contact exists on all posterior teeth. Anterior teeth should not touch in .centric occlusion :Adjust the working relation. 5 .Loosen the centric locks and use blue articulating paper As a rule in selective grinding the centric holding cusps are not ground. These are : the maxillary lingual . cusps and the mandibular buccal cusps These cusps are essential to maintain the recorded . vertical dimension If interferences exists in the working side reduce either .the upper buccal cusps or the lower lingual cusps
This is called B.U.L.L. Rule In the bull rule reduce the lingual inclines of the upper buccal cusp and the buccal inclines of the lower lingual .cusps :Adjust the balancing relation. 6 Rule : If interference exists on the balancing side reduce the lingual slope of the lower buccal cusp. The lingual buccal cusp is a centric holding cusp so grind carefully and .do not reduce the cusp tip
:Adjust protrusive relation. 7 a. If the anterior teeth have heavy contact with no contact on the posterior teeth grind the labial surface of the lower anterior and the palatal surface .of the upper anteriors b. If heavy posterior contact exists with no anterior contact reduce the distal
inclines of the maxillary cusps and the mesial inclines of . the mandibular cusps :Carborundum paste milling. 8 The articulator is moved through all the excursive movements using carborundum paste to smooth the various gliding surface of the teeth. Milling must be done lightly to prevent losing balancing contacts .which might decrease the vertical dimension a. Move the articulator into right lateral, left lateral .and protrusive movements
.b. Move the articulator in a circular movement . Use light strokes do not force or press When milling is completed remove all. 9 .traces of carborundum The ground surfaces of the teeth must be. 10 polished when grinding has been . completed
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