Saturday, August 24, 2013
RETRIEVEL OF DENTURE, CORRECTION OF OCCLUSAL DISCREPANCIES,FINISHING AND POLISHING PROCEDURES.
Retrievel of denture, correction of occlusal
Discrepancies,finishing and polishing Procedures.
Ø Review of Literature
Ø Deflasking procedure
Ø Problems cause during Deflasking
Ø Causes for dimensional changes in complete denture during processing
Ø Lab remounting procedure
Ø Correction of Occlusal discrepancies by selective grinding
Ø Advantages of selecting grinding
Ø Removal of denture from cast
Ø Finishing of complete denture
Ø Polishing of complete denture
Ø Summary & conclusion
Successful fabrication of complete dentures requires a combination of sound clinical as well as laboratory procedures. Clinical procedures however accurate are not of much use if the laboratory procedures are not properly carried out from the pouring of casts to retrieval of denture & finishing & Polishing of dentures all go a long way in the success of the prosthesis.
Carelessness in the final stages of denture fabrication such as during retrieval of dentures from the flasks, failure to correct the Occlusal discrepancies induced as a result of processing & inadequate finishing & polishing will result in dentures which are far below the result that could have been achieved if a little more time & efforts would have been invested in the final stages. This seminar deals with these steps in the making of a denture which are generally given least importance but if properly done, greatly enhance the comfort function & esthetics of the final prosthesis.
Review of the Literature:
1. Nikazad s Javing 1973 : Described a method the top half of molds for processing dentures were made in the top half of the flask. This technique speeds up the removal of processed dentures from their molds and reduces the possibility of fracturing either the denture base or the teeth.
2. Majid Bissasu 1998 : Described a easy procedure to facilitate the removal of the palatal and lingual portions of flasking stone. So it reduces the hazards of denture base fracture or deformation during Deflasking of the processed denture. Advantage of this procedure is it reduces the flasking and Deflasking time.
3. Than-E-Holf 1977 : Conducted a study that incited that numerous benefits from remounting dentures to correct occlusion and recon touring the tissue side of the bases at the time of insertion. He showed that post insertion complaints were decreased by remounting procedures.
4. Garrent D Barrett 1985 : Described a reprocible split cast technique for accurate demounting and remounting of a Pre – or post processing complete denture master cast without stress or fracture.
5. Sigmund 1953 : Conducted a study on investing changes during flasking may lead to malocclusion in complete duve. There is sufficient evidence to indicate that there is some shifting of the teeth during the investing procedure & described methods to reduce this shifting.
6. Robert C. Wesley 1973 : Conducted study in 50 patient regarding posterior tooth contact and pin opening during processing changes in complete denture it was found that there was a definite shift of the tooth contacts to the more posterior teeth after processing but that the amount of pin opening did not seems to be related to the number of location of the tooth contacts.
7. William A walker, Donal C Kramer and Rager Marcev 1978 : Described a detailed step – by – step procedure for finishing and polishing denture based produce highly polished surfaces free from all imperfection.
8. Mutahhar Ulusay, Nuron Ulusoy, Keveser Aydin 1986 : Evaluated polishing techniques of surface roughness of acrylic resin. 9 methods of grinding & polishing heat cute resins were evaluated. They found that the best surface finish was obtained when abrasive stones coarse medium fine abrasive discs rotating felt come and rotating soft brush C chalk powder were used progressively.
Definition for Deflasking:
Definition of Remounting:
Any method used to relate restorations to an articulator for analysis and for to assist in development of a plane for occlusal equilibration or reshaping.
Definition of Selective Grinding:
The intentional alteration of the occlusal surfaces of teeth to change their form .
Definition of finishing:
It is process to put a final coat or surface on, the retirement of form prior to polishing.
Definition of Polishing:
The act of process of making a denture or casting smooth and glossy.
Deflasking: When Deflasking complete dentures it is best to use a Deflasker which allows retrieval from the flask without damage to the dentures or flask. Deflasking with a hammer can damage. The flask and results in unnecessary breakage of the dentures.
Procedures for Deflasking of complete denture :
1. Remove the Lid from the flask containing the bench cooled denture.
2. Place the flask bottom side up in the Deflasker and tighten the thumb screw until it contacts the bottom plate.
3. Place the pry bars through the slots in the side of the Deflasker and engage. The slots in the flask between both halves of the flask.
4. Press down on the engaged pry bars first and then pry up these movements readily separate the flask from the stone enclosed denture.
5. Place a Knife-blade in contact with the junction between the stone cap and the rest of the stone enclosing the denture. Tap the back of the knife blade with a plastic mallet to separate the stone cap and to expose the cusp tips and incisal edges of the denture teeth.
6. Use care in separating the stone cap from dentures with acrylic teeth.
7. With a saw and a spiral blade, cut through the stone that encloses. The denture opposite the central incisor teeth take care to avoiding sawing into teeth or denture blast.
8. Place more saw cuts at the distobuccal corners of the flasked denture. So that the stone enclosing the denture has three cuts.
9. Place a knife in the anterior saw cut and pry gently to separate the stone from the buccal and anterior flanges of the denture.
10. Place a knife in the posterior cut, and pry laterally to separate any posterior section of stone may have adhered to the buccal flange of the denture.
11. Remove stone from the palate or tongue area of the mandibular dentures by first relieving the stone adjacent to lingual surfaces of the denture teeth with a knife take care to avoid cutting teeth or denture base.
12. After reliving the stone adjacent to the lingual surfaces of the denture teeth, gently pry the stone in the lingual area of the denture or the palate of the maxillary denture, and lift it away from the denture.
13. Make more cuts lingual to the heel area of the mandibular dentures if necessary.
14. Remove the denture from the investing stone except where it encloses the cast.
15. Protect the teeth with the hand and with a plastic mallet carefully tap away the stone enclosing the cast. Exercise care to avoid damaging the teeth by striking them with the mallet.
16. Use a tooth brush to clean out the index groove on the base of the cast. This cleansing makes if possible to position the cast accurately on the mounting stone for correction.
17. After retrieval from the stone the dentures are ready for remounting on the articulator.
1. Breaking of the denture
2. Breaking of the cast
3. Breaking of the both cast and denture.
4. Denture base or denture teeth broken during Deflasking as result of using a hammer to tap stone from the flask.
Attention to the details of flasking to eliminate under cuts, proper use of tinfoil substitute, and careful Deflasking procedures minimize breakage of dentures and facilitate raid retrieval.
Causes for dimensional change in denture during processing.
1. Polymerization shrinkage.
2. Processing stresses.
3. Incorrect registration of centric occlusion.
4. Irregularities in setting teeth.
5. Tooth movement when flasking and packing.
6. Incomplete flask closure.
7. Wear in moving parts of articulators.
Polymerization shrinkage: When methyl methacrylate monomer is polymerized to form poly (Methyl Metharcylate), the density of the mass changes from 0.94 to 1.19 g/cm. This change in density results in volumetric shrinkage of 21%. When a conventional heat activated resin is mixed at the suggested powder Liquid ratio, about one third of resultant mass is liquid. Consequently the volumetric shrinkage exhibited by the polymerized mass should be approximately 7%. In addition to volumetric shrinkage, one also must consider the effect of linear shrinkage. Linear shrinkage exerts significant effects on denture base adaptation and cuspal interdigitation. By convention, linear shrinkage values are determined by measuring the distance between two predetermined reference points, in the second molar region of a completed tooth arrangement. After polymerization of the denture base resin and removal of prosthesis from the master cast the distance between prepolymerization and post polymerization measurements is recorded as linear shrinkage the greater the linear shrinkage the greater the discrepancy observed in the initial fit of a denture. Based on a projected volumetric shrinkage of 7%, an acrylic resin denture base should exhibit a linear shrinkage of approximately 2%. In reality linear shrinkage generally is observed to be less than 1%.
Examination of the polymerization process indicates that thermal shrinkage of resin is primarily responsible for the linear shrinkage phenomenon in heat activated systems. During initial stages of cooling process the resin remain relatively soft. Therefore the pressure maintained on the flask assembly causes the resin to contract at approximately the same rate as the surrounding dental stone.
As cooling proceeds, the soft resin approaches its glass transition temperature (Tg). The Tg lies with in a thermal range in which the polymerized resin passes from a soft, rubbery state to a rigid, glassy state. Hence, cooling the denture base resin beyond the Tg. Yields, a rigid mass. In turn this rigid mass contracts at a rate different from the surrounding dental stone. The shrinkage occurring below Tg is thermal in nature and varies according to the composition the resin.
To illustrate the effect of thermal shrinkage, consider the following example. The Tg for poly (Methylmethacrylate) is approximately 1050C room temperature is 200C. The generally accepted value for linear co-efficient of thermal expansion for poly (methyl methacrylate) is 81 x 10-6 per degrees centigrade therefore as the denture base resin is cooled from the Tg. To room temperature it undergoes linear shrinkage that may be expressed as.
L T = (81 x 10-6/0C) (1050C - 200C) (100%) = 0.69%
2. Processing Stresses : When ever a natural dimensional change is inhibited, the affected material contains stresses. If stresses are relaxed, a resultant distortion or warpage of the material may occur. This principal has important reminification in the fabrication of denture bases, because stresses invariably are induced during processing.
Stress also are produced as the result of thermal shrinkage as a polymerized resin is cooled below its Tg. The resin becomes relatively rigid. Further cooling yields thermal shrinkage. A denture base resin generally is encased in a rigid investing medium, such as dental stone, during this process. Because denture base resins and dental stones contract at markedly different rates, a contraction differential is established. Hence a disparity in contraction rates also yields stresses with in the resin. Additional factors that may contribute to processing stresses with in resin. Additional factors that may contribute to processing stresses include improper mixing and handling of the resin and poorly controlled heating and cooling of the flask assembly.
The release of stresses yields dimensional changes that a cumulative in nature. Fortunately, these dimensional changes are quite small total dimensional changes occurring as a result of processing and service are in the range of 0.1 to 0.2 mm (as measured from Second molar to Second molar). Therefore it is doubtful such changes would be clinically significant and they detectable by patient.
3. Incorrect Registration of Centric occlusion: This is probably the most common cause of error in the occlusion of finished dentures when registering the position of centric occlusion considerable care is taken to obtain a correct vertical dimension and physiological fully retruded position of the mandible, but often the record rims when brought together exert uneven pressure on their respective supporting alveolar ridges. This is due to premature contacts of the record rims on side of the mouth in Second molar region. This causes uneven compression of mucosa supporting the record blocks and often displaces them from ridges.
Another fault causing errors in the occlusion of the finished dentures results from slight movement of record blocks on the ridges during centric registration due to their imperfect fit and inadequate retention.
Another error of occlusion may result from the manner in which the models and record blocks are set in the articulator. The models may not be placed accurately in the blocks or the articulator may not handled with due care when the models are being attached with plaster.
4. Irregularities in setting the teeth :
The technician when setting up teeth is unlikely to produce a perfectly even contact in centric and lateral occlusions. Some teeth will be in good occlusion whilst others will be slightly out of occlusion, thus producing areas of heavy pressure. In waxing up following the setting of teeth it is possible for them to more slightly due to the contraction of the wax on cooling, causing irregularities in the articulation and occlusion of complete dentures.
5. Tooth movement when flasking and packing :
Movement of the teeth may occur at the time of boiling out the wax trial base after the dentures have been flasked and it such teeth are not correctly repositioned they will cause minor Occlusal irregularities. Also, when packing, teeth may be driven into the enveloping plaster, particularly when packing follows soon after investing and the plaster is in the ‘green state’. The possibility of such an error occurring is increased when the methyl methacrylate is used in a slightly advanced stage of dough, and when the posterior teeth have been ground to fit close to the ridge. Rapid closure of the flask in the piets will add to the hazard.
6. Incomplete flask closure :
This causes not only, an increase of vertical dimension but also results in an upset of balanced occlusion.
7. Articulator wear :
All articulators are subject to wear and the older and more worn the articulator the greater will be the errors in occlusion and articulation. Every piece of mechanical apparatus exhibits some play in its moving parts and when this becomes easily detectable the bearing should be replaced.
Split-cast procedure for remounting the complete denture master cast
Accurate remounting of the detached complete denture master cast to its mounted articulated base is essential to maintain the original articulated interarch and occlusal relationship. Inaccurate remounting will result in occlusal discrepancies. In this technique describes a reproducible split-cast technique for accurate demounting and remounting of a pre-or past processing complete denture master cast without unwarranted stress or fracture.
1. Require the master cast from the boxed final impression boxing will preserve the appropriate morphologic border contours and master cast base thickness.
2. Finish the base of master cast with a fine model trimmer wheel.
3. Cut two posterior and one anterior index grooves into the master cast base. After refinement apply a thin coating of petroleum Jelly to each index groove with a cotton pellet. It is not necessary to lubricate the entire base.
4. Using Jaw relation records, mount the moist master cast in the articulator using fast setting plaster. When the plaster sets, smooth and refine the mounted master cast an articulated base so that a crisp demarcation interface exists between the cast and plaster base.
5. Remove the master cast and its articulated base from the articulator. Fill a standard mixing bow 1 with near boiling water (minimum temperature of 1800F) to a level approximately 1 inch greater than the height of the articulated base.
6. Place the articulated base with the mounted master cast into the hot water and adjust the water level to a point 2 to 4 mm above the interface. Leave the mounted master cast in water for 10 seconds or until the cast and base separate. The sudden temperature change and expansion of the base plaster causes separation. Do not completely immerse the mounted master cast.
7. When remounting the cast wet the entire articulated plaster base and only the base portion of the master cast. Fit the plaster base and base portion of master cast together, and allow them to dry. A perfect readaptation of the master cast and articulated base will result.
8. Cut parallel horizontal grooves on the lateral surface to secure the master cast to the articulated base. After the surfaces are moistened, apply a thin mix of plaster into grooves and extended over both the cast and base. Smooth and position the remounted cast and its base on the articulator.
1. After remounting the dentures in the articulator check the relationship of the incisal guide pin to the incisal guide table. After the incisal guide pin does not contact the incisal guide table because of changes during processing a processing error of 1 mm though not insignificant, is correctable. However, an error of more than 1 mm which often requires considerable reduction on the Occlusal surfaces of the denture teeth to regain the vertical dimension of occlusion is undesirable.
2. Check contacts between the heel of mandibular dentures and the tuberosity region of maxillary dentures to make certain that the increase in vertical dimension is not result of an overly thick denture base resin in these areas.
3. Place articulating paper between the teeth and gently tap the articulator together to indicate defective occlusal contacts.
4. Adjust these contacts with a stone bur, if the teeth are porcelain or if the teeth are resin, continue to adjust the occlusion in the centric relation position and in the eccentric positions, according to the rules of selective grinding. Do not adjust the cusps in centric relation position unless they are high not only in the centric relation position, but also in the right-and left lateral and protrusive positions. Generally, reduction results in grinding of the fossae rather than the cusp tips. When adjusting the working position, adjust the buccal cusps of the upper teeth and the lingual cusps of the mandibular teeth to eliminate defective contacts. On the non working, or balancing side defective contacts are usually on centric holding cusps and grinding requires a compromise we prefer to grind the inclines of the maxillary lingual cusps rather than the buccal cusps of the mandibular dentures.
5. Move the articulators into a working position and examine the relationship of the working cusps, mark the defective contacts with articulating paper and examine the resulting pattern. Eliminate defective contacts on porcelain teeth by adjusting the buccal cusps of the maxillary lingual teeth and the lingual cusps of the mandibular teeth with a stone.
6. Examine the balancing contacts in a similar manner and adjust the lingual cusps of the maxillary teeth or the buccal cusps of the mandibular teeth to corrective defective contacts.
7. After completing the selective grinding, move the articulator into the various positions, and check the occlusion into the various positions, with tissue paper strips. Now the incisal guide pin should contact the incisal guide table and there by indicate reestablishment of the original vertical dimension of occlusion. Do not complete definitive polishing of the Occlusal surfaces of the teeth at this time because the dentist usually remounts the dentures on the day of insertion.
8. Recheck the occlusion on the articulator in the centric relation position using articulator paper, and evaluate the pattern of contacts. Equalize the contacts on the right and left sides to assure a uniform distribution.
Correction of Occlusal discrepancies by selective grinding:
In order to produce a satisfactory result it is important to carry out the selective grinding systematically to ensure that.
1. Vertical dimension is maintained.
2. An even distribution of occlusal stress is obtained in centric occlusion.
3. An even distribution of stress is maintained in lateral positions.
The vertical dimension is controlled by the lower buccal cusps and the upper palatal cusps and their opposing fossae there fore it is essential that these zones must receive careful consideration when establishing centric and lateral occlusion.
Grinding into centric occlusion:
Place thin blue articulating paper on the Occlusal of the lower teeth and close the articulator for with sufficient pressure to record just the first contact areas. Observe the prominent cusp or cusps and decide whether the cusp or its opposing fossa should be ground by checking this cusp in its lateral working position and then its balancing position. If the offending cusp makes premature contact in both centric and lateral working positions then the cusp and not the fossa should be ground to produce even centric occlusion. When, however, a cusp producing premature contact in the centric position does not cause premature contact when in working and balancing positions then the fossa is ground to accommodate the cusp. (The lateral contacts can be marked with red articulating paper for purposes of differentiate on this principle is followed until an even centric occlusion is obtained through out the dentition.
Grinding in for Lateral excursions:
To enhance the retention and stability of the dentures and to reduce the stress applied to the Alveolar ridges of the mandible moves laterally, it is most important to provide a free sliding lateral articulation and elimination of cusp lock.
Red articulating paper is placed between the occlusal surface of the teeth and the dentures moved with light pressure from centric occlusion into right lateral occlusion. If the upper and lower buccal cusps make premature contact and balancing side is out of occlusion then the upper buccal cusp is ground as the lower buccal cusp is required to maintain vertical dimension and even pressure in centric occlusion when the lower lingual and upper palatal cusps occlude prematurely in this lateral position the lower lingual cusp is ground to produce balance of both sides of the denture. The upper palatal cusp is required for the maintenance of vertical dimension in centric occlusion. The grinding of the buccal upper and lingual lower cusps to produce balance in lateral movements is often referred to as grinding to the “Bull” rule.
Should the balancing side exhibit premature occlusion between the lower buccal cusp and the palatal upper cusp it will be necessary to grind the palatal upper cusp and not the lower buccal cusp since this cups is required to maintain vertical dimension and even pressure is centric occlusion and contact in the working lateral position.
The procedure having been completed for the right lateral position it is then repeated for the left lateral excursion having established a free lateral sliding movement of the occlusion of the protrusive contacts is studied.
Correction of contacts in protrusion:
As we are dealing with an artificial dentition, and are not concerned with the possible over eruption of teeth as may occur with a natural dentition. Most of the grinding for correction of premature contacts of incisal edges of anterior teeth, when in protrusive occlusion, can be carried out at the expense of the lower incisors. A limited amount of grinding lower of the upper anterior teeth to simulate attrition, related to the patient’s age, can enhance the appearance of the dentures.
Perfecting Articulation with Grinding-in paste:
The main correction of occlusal irregularities must be carried out with small mounted abrasive stones in a hand-piece so that the vertical dimension is kept under control. The amount of adjustment made with grinding-in paste must be small as this will reduce all occluding surfaces and if excessive will result in loss of vertical dimension. A paste of course grit carborundum powder mixed one with Vaseline or tooth paste is used first. Followed by one of fine grit carborundum to smooth the previously ground tooth surfaces and produce a perfectly even occlusion.
Reduction of sharp edges of Ground teeth:
On completion of all grinding, sharp edges present buccally and lingually must be rounded to prevent tongue and cheek irritation rubber wheels, water of Air stone, and finally pumice paste used with polishing brushes will produce a smooth finish.
Advantages of Remounting and Selective grinding:
The Patient remount method is to remount the dentures on articulators.
1. It reduces patient participation.
2. It permits the dentist to see better what he is doing.
3. It provides a stable working foundation; bases are not shifting on resilient tissues.
4. The absence of salvia makes possible more accurate markings the articulating paper or tape.
5. Corrections can be made away from the patient, thus preventing occasional objections when patients see their dentures being ground.
Removing Dentures from Cast:
After correction of processing error and construction of a face-bow index if requires, the dentures are ready for removal from the cast and finishing and polishing.
Procedure for removing dentures from cast:
1. Using a cast trimmer, thin the casts with the dentures seated on them, but avoid trimming the denture base.
2. Remove the stone from the denture in small sections. Use a bur or a saw judiciously in removing the stone in sections without damaging the dentures.
3. A shell blaster also is useful in removing stone from the interior of the denture.
4. A pneumatic chisel aids in removing stone from the denture however, Great care is essential to prevent damage to the denture. Particularly to the denture teeth. Do not attempt to pry the denture from the cast because it can result in fracturing the denture. After removal from the cast, the dentures are ready for finishing and polishing.
Various abrasives that are used for finishing and polishing Procedures of Complete denture
Abrasives are rough gritty and wear producing particles .abrasive is a substance which is used to remove excess material by cutting. Substance used to grind objects in order to give them desired size, shape or finish.
Pumice: A substance of volcanic origin consisting chiefly of complex silicates of aluminum, potassium and sodium occurring as a very light, hard, porous grayish powder. It is used as a polishing agent. The effect will be depending on particle size. It is used for smoothening of denture base and polishing teeth in mouth.
Chalk: Chalk is calcium carbonate prepared by a precipitation method. There are various grades of physical forms of calcium carbonate available for different polishing technique. It is used for polishing denture base.
Sand: Sand particles consist of small grains of Silica (SiO2) it is formed by the decomposition of sand stones due to various effect of weather.
Types are: Pit Sand, River Sand, Sea Sand.
Sand should contain sharp, angular and durable grains. It is used in the form of sand paper.
Finishing & Polishing instrument.
1. Finishing burs: It should at least 12 fluted, however some of them are 40 fluted. They may be made up of stainless steel or tungsten carbide. They wont cut the restorative materials, but only removes excesses creating a smoother surface.
2. Paper carried abrasives: These are usually sand cuttle garnet or baron carbide. Guide to paper disc or strips the paper disc should be attached to mandrel.
3. Brushes: They will be available in different forms like wheels, cylinders, cones.
4. Rubber: Plain rubber ended rotary tools are essential for any polishing procedures. They will be available in different shape. E.g.: Cups, Wheel, cones.
5. Cloth: Cloth carried on a metal wheel is used in final stages of polishing, either with or without a polishing medium.
6. Felt: Different shape of felt is wheel, cone and cylinders usually with polishing agents.
Polishing the Complete Denture:
Two methods of polishing complete dentures will be presented.
Method used for Polishing of the Complete Denture.
1. After taking the complete denture from the cast use a shell blaster to remove any stone that adheres to the denture take care to avoid burning the surface of the acrylic resin shell blasting.
2. Trim the flash from the complete denture with an arbor band or a large bur mounted on a laboratory lathe.
3. Finish the frenum attachments with a small carbide bur to create the desired freedom.
4. With a chisel carefully remove stone adhering to the gingival margins. Make a chisel by grinding a broken Instrument to form sharp triangular edges which facilitate the removal of stone from the gingival margin.
5. Check the interior of the denture carefully with a finger. Locate any modules of acrylic resin and remove them with a round bur.
6. Complete the relief for the frenum attachment by using No. 558 or a No. 771 bur to do the final finishing and to open the frenum attachment.
7. Finish the lingual border area of the mandibular complete denture with a hand piece-mounted small carbide bur. Frequently a standard size arbor band is too large for this area.
8. Thin the palate if necessary take care to avoid producing grooves when using an arbor band. A large lathe-mounted Laboratory bur also is useful for these procedures.
9. Pumice the dentures with a prepared rag wheel.
Preparing rag wheel: Special preparation of a rag wheel makes it more effective for pumicing and polishing. The procedure described also conditions used rag wheels by giving them the flexibility and flutiness necessary to achieve a smooth finish.
1. Place the rag wheel on a spiral chuck, run the lathe at low speed, and use a knife to cut the threads holding the rag wheel plies together. Hold the knife firmly while cutting the threads.
2. Stop the lathe, separate the plies of the rag wheel and make certain to cut the thread completely.
3. With the rag wheel on the spiral cheek rotate the lathe low speed and hold a stainless steel plaster spatula against the rag wheel to remove the cut threads and make the wheel fluffy.
4. Single the strayed threads with a lighted match to make the wheel uniform. Place a metal pan beneath the wheel, and have the lathe and any suction device in the non operating position. Have a bowl of water available to douse the wheel if it flares.
5. After placing the rag wheel in water, return it to the lathe and start the lathe at low speed. Rotate the singed wheel against the stainless steel spatula again to fluff it and remove any remaining threads.
6. Modified rag wheel is ready for use.
1. Make slurry of fine flour of pumice with water, using copious amounts to the slurry, wet the rag wheel and polish the denture at low speed more the denture throughout the polishing to prevent formation of plane surface. Use a brush or prophy cup with slurry to polish areas less accessible to the rag wheel.
2. Polish the palate and areas of the denture not readily accessible to the rag wheel by using a prophy cup or a Dixon brush with slurry of flour of pumice smooth the denture in this manner because a larger polishing instrument would obliterate anatomic details. After completing the pumicing wash the denture thoroughly in water, dry it and examine it for scratches. It any scratches are visible on the pumiced surface. Repeat the pumicing and post pone the high polishing until after removing all scratches.
3. Stipple the denture with a No. 200 finishing bur Rotate this bur slowly in a hand piece and hold it in light contact with the surface of the denture to be stippled that is, the area of the attached gingiva. Use light random circular movement of the bur against the resin surface to produce an egg shell or stippled, effect that breaks up light reflections and corrects minor imperfections in the resin.
4. Go over the stippled area lightly with a rubber prophy cup and slurry of flour of pumice.
5. Put a high shine on the denture with No. 341 Tigeleam or prepared chalk slurry and a modified rag wheel. Do not use this rag wheel with any other polishing material. Examine the denture carefully for scratches and polish out any missed previously. Take care when polishing or pumicing the denture to keep from abrading anatomic details of the plastic teeth.
6. Brush the denture with green soap to remove all traces of polishing material, and examine the denture carefully rinse the denture in water, and store it in a plastic container of water until needed.
Method II for Polishing the complete denture
1. Remove the denture from the cast.
2. Remove the stone that adheres to the gingival margin area of the denture with bard-parker handle and a No. 25 blade. Trim away excess flash with a Laboratory Lathe-mounted carbide bur place the denture in an ultrasonic cleanser containing a solution for removal of gypsum products. Adjust for frenum clearance with No. 558 bur mounted in a Laboratory Lathe.
3. Use a rubber point mounted on a mandrel and a dental lathe to remove scratches from the denture base in areas in accessible to the larger pumice wheel. Pumice the denture using flour of pumice or fine pumice mixed with water and a modified rag wheel as described previously.
4. Polish areas between the teeth with a bristle brush and pumice slurry.
5. Put the initial high shine on the denture with a soft rag wheel and prepared chalk mixed with water.
6. Put the final high shine on the denture with a soft chalmois wheel and gold rouge.
7. Stipple the denture with a straight hand piece No. 4 round bur bent slightly to rotate eccentrically.
8. Place the bur in a lathe and with the lathe running at slow speed; stipple the surface of the denture base in a random motion. Apply a high polish to the dentures again, scrub them with soap and water and place them in a container of water until ready for use by the dentist.
Acrylic resin teeth are polished by the same method as the denture base material. A rubber prophy cup and fine pumice or flour of pumice is used to restore the surface luster of acrylic teeth after modification. A high luster is restored to the surface of these teeth with a soft rag wheel and a high-shine material, such rouge or prepared chalk slurry. Care should be taken when polishing resin teeth to avoid removing too much material from the Occlusal surfaces and thereby, effecting the occlusion. One disadvantage of using plastic teeth by inadvertent contact between teeth and polishing wheel.
A technique for finishing and polishing denture bases William A Welker, D.D.S., M.S.D., Donal C Kramer, D.D.S., M.S. and Roger W. Mercer USAF Medical center, wright wright patterson AFB, Ohto.
A common complaint of denture wearers is that they are unable to keep their dentures clean and free from stains. This results from improper home care by the patient or improper finishing of the art portion of the denture. T alleurate this common complaint patients should receive explicit instructions in home care, and dentures should be finished and polished so that they are free ali surface,scratches and imperfections.
When the dentures are poorly finished food debris will not be trapped on the surface, thus preventing objectionable odor, and taste and an unsightly appearance.
The following technique proven successful in producing blemish-free dentures:
Materials and Method:
1. Deflask the dentures and remove the resin flash from the borders.
2. Use chisels to remove excess acrylic resin or stone from around the necks of the teeth. The chisels should include one with a right bevel, one with left bevel, one with a fine point. They are easily made from old dental hand Instrument.
3. Smooth the interproximal spaces, papillae and rugae area with a soft bristly brush and flour of pumice large brushes and rag wheels destroy the anatomy and should not be used.
4. Polish the cervical surface of each artificial tooth with a rubber polishing cup. This will produce smooth surface at the junction of the tooth and acrylic resin. A region most difficult for patients to keep clean.
5. Remove scratches from the borders with a large rag wheel and pumice.
6. Lightly buff the remainder of the denture base with a rag wheel and pumice. Light pressure will not destroy the anatomy or the tinting of the denture base.
7. Rinse the denture in water to remove the pumice thoroughly dry, and inspect for remaining imperfections. It imperfections are visible, repeat the rag wheel and pumice procedure.
8. Hard-to-reach regions such as the curve of the palate. The rugae area and the lingual surfaces of lower incisors and canines, are smoothed with midget rubber points. Followed by pumice applied on a small cotton point made by winding cotton on a suitable used bur.
9. Wash the dentures thoroughly with soap and water, dry and inspect the base material under magnification. All denture surfaces, with the exception of the basal seat area should present a smooth egg shell texture tree of imperfection. If not the previous steps must be repeated.
10. Apply Ti-gloss to a new rag wheel and lightly buff the denture surface.
11. Wash and dry the denture and again inspect it for imperfection small, hard-to-reach imperfections are now removed with the rubber points and cotton points using Ti-gloss.
12. Use Ti-gleem on a rag wheel with a light buffing action to produce on final high shine.
Dentures bases finished by this technique will produce highly polished surfaces free from all imperfections. The denture bases will remain free of stains and odors with normal home care.
Summary & Conclusion :
Method of Retrieval of denture, correction of occlusal discrepancies finishing & Polishing procedures are discussed in this seminar. These are the end procedures before the denture is finally deserved to the patient. A little extra effort & time are required for these & there is not excuse, Which will justly a compromise in these final steps. This procedure will enhance the comfort, function & esthetics of the denture which is the final aim every prosthesis is fabricated for.
After the index grooves or notches are cleaned the dentures and casts are seated to the mounting stone with sticky wax. After remounting of denture and casts, occlusal discrepancies caused during processing.
Every dentist who treats patients with complete dentures is probably aware that the planned contact relationship of apposing. Posterior teeth are not the same in the processed dentures as it was before the dentures were processed. Correction of Occlusal discrepancies should be accomplished at the appointment for the initial placement of the dentures.
There are two main factors in the production of Occlusal discrepancies in the processed denture.
1. A change in the relationship of a tooth or teeth to the master cast during processing procedures.
2. Warp age of the denture base through release of inherent strains when the denture is separated from the cat upon which it was processed. In the first instance the tooth may change its relationship to the master cast as a result of investing procedures (exothermic reaction of investing stone causing an expansion of wax).
3. Cure less packing of acrylic resin in the molds.
4. Improper closure of the flask halves.
Several methods of processing procedures have been suggested to minimize the risk of causing such change.