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1. SELECTIVE GRINDING IN COMPLETE DENTURE
INTRODUCTION: -
Occlusal harmony in complete denture is necessary if the dentures
are to be comfortable, to function efficiently, and to preserve the
supporting structures. It is difficult to see occlusal discrepancies
intraorally with complete denture. The resiliency of the supporting soft
tissues and displaceability of the tissues in varying degrees tend to
disguise premature occlusal contacts. The tissues permit the dentures to
shift; as a result, after the first interceptive occlusal contact the remaining
teeth appear to make satisfactory contacts. The eye cannot be relied upon
to observe occlusal discrepancies, and the patient cannot be depended
upon to diagnosed occlusal faults. It is the responsibility of the dentist to
find and correct these occlusal discrepancies and permit the patient to
depart free of occlusal disharmony. Occlusal faults can be determined by
obtaining and interocclusal record from the patient and remounting the
dentures on an articulator. These faults can be corrected by careful
selective grinding procedures. Remounting of the dentures on the
articulators and selective sliding procedures should be carried out at the
time of placement of the dentures.
DEFINITION: -
Selective gliding is defined as the, “intentional alteration of the occlusal
surfaces of the teeth to change their form.”
-- Glossary of the Prosthodontic terms 1999.

2. Teeth are altered by selective grinding to make simultaneous cusp tip to
cusp tip contact on both sides of the arch when the jaws are in left or a
right lateral position, balanced occlusion in a static eccentric position
exists. When the mandible is in a straight protruded relation with the
maxilla and the posterior teeth are altered to make cusp contacts at the
same time to anterior teeth make incisal edges contact balanced occlusion
protrusion exists.
REVIEW OF LITERATURES: -
Schuyler, Friedrich and Vaeghan in 1935 observed the disturbances
in occlusal relationship and opening of the bite of full dentures made of
acrylic resin, even when the flask was completely closed during
processing.
Osborne and Taylor in 1941 have noted the disturbance and
attributed it to over packing and the accompanying displacement of teeth
in the mold. It was felt, however, that these changes were caused in part
by the volumetric change of acrylic resin during polymerization. They
used the following method to estimate the amount of change in occlusal
relationship -
The top of the incisal guide pin was flush with the top of the
articulator at the time the cases were waxed. The distance that the pin
dropped in order to make contact with the incisal guide plane when the
finished dentures were placed in centric position on the articulator gave a
rough means of comparison of the amount of disturbance of occlusal
relationship in each case.

3. Avoiding remounting the dentures on articulator and selective
grinding leads to,
1) A deformation of underlying soft tissues,
2) Discomfort, and
3) Destruction of the underlying supporting bone. Later occlusal
errors may be concealed and impossible to locate and correct
because of distorted and swollen tissues.
CAUSES OF OCCLUSAL DISHARMONY: -
1) Incorrect registration of retruded contact position (RCP)
2) Irregularities in setting the teeth.
3) Tooth movement when flasking and packing
4) Incomplete flask closure.
1) Incorrect registration of retruded contact position (RCP)
This is probably the most common cause of error in the occlusion of
finished dentures. During registration considerable care is taken to obtain
a correct vertical dimension and the physiological fully retruded position
of the mandible, but often, when brought together, the record blocks exert
uneven pressure on their respective supporting alveolar ridges, and this
condition passes unnoticed. On finishing the denture the teeth are found
to occlude only in the area where the premature contact of the occlusal
rims occurred the remainder of the teeth being slightly out of degree of
contact. The degree of separation will be related the degree of premature
contact occurring between the rims.
Another fault causing errors in the occlusion of the finished dentures
results from slight movement of record blocks on the ridges during
registration due to their imperfect fit and inadequate retention. All these

4. errors can usually be lessened by using an accurately fitting acrylic base
in preference to a shellac base which invariably warps slightly.
2) Irregularities in setting the teeth
When setting up teeth the technician is unlikely to produce a
perfectly even contact in retruded, protruded and lateral occlusions. Some
teeth will be in good occlusion while others will be slightly out of
occlusion, thus producing areas of heavy pressure. This cannot happen
when the teeth are held firmly in the final denture base material and
results in premature tooth contacts in the occlusion and articulation of the
finished dentures
3) 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 if such teeth are not
correctly repositioned they will cause occlusal irregularities. Repositioned
they will cause occlusal are not correctly repositioned they will cause
occlusal irregularities. When packing acrylic dough, teeth may be driven
into the investing plaster, particularly when packing follows soon after
flasking and the plaster has a low crushing strength. Raped closure of the
flask in the bench press will add to the hazard. Injection moulding
techniques for packing acrylic are an obvious improvement.
4) Incomplete flask closure
Such an occurrence not only causes an increase of vertical dimension
because of the alteration in tooth / cast relationship but also result in
derangement of the occlusion which usually necessitates the total remake
of the denture.
Remounting dentures with check records --

5. It can be appreciated that even with care on the part of dentist and
technician errors may occur which influence the finical occlusion and
articulation of finished dentures. In some instances these errors may
corrected by careful use of marking paper or tape at the chair side, but
such correction is often proved false when check records are taken for
confirmation. It is far satisfactory, and often less time-consuming
clinically, to register the retruded contact position of the finished denture
with check record, mount the finished dentures on an adjustable
articulator and then refine the occlusion either at the chair side or in the
laboratory.
OBJECTIVES OF CORRECTING OCCLUSAL DISHARMONY : -
The objectives as stated by Schuyler in 1935 are,
1) Maximum distribution of stress in centric maxillo-mandibular
relation.
2) Retention of the maxillo-mandibular opening.
3) Harmony of guiding inclines, which distributes eccentric occlusal
stresses.
4) Reduction of the incline of guiding tooth surfaces, that occlusal
stresses may be more favorably applied to the supporting tissues.
5) Retention of sharpness of cutting cusps.
6) Increase in food exits.
7) Decrease in contact surfaces.
It must be remembered that the occlusion of the natural dentition
and the occlusion of the complete denture may differ in many respects, to
the advantages and convenience of the dentures. For instance, a denture is

6. a unit of 14 teeth fastened rigidly together, while natural teeth are
anchored independently of each other. The natural teeth must be
considered individually for occlusion, while the 14 teeth can be treated as
one whole unit. We can have balanced occlusion in complete denture
with some teeth out of contact or some inclines out of contact. The
dentures would be balanced as far as 3 – point contact is concerned if
only the cuspids and second molars worked in harmony.
ELIMINATING OCCLUSAL ERRORS IN ANATOMIC TEETH: -
Articulating paper of minimum thickness is used for marking the
actual contacts of the teeth. Paper is interposed between the teeth and
marking are obtained by tapping the teeth together. This can be done on
both sides at the same time.
Grinding is done with mounted chayes stones no. 16, 11, 05. The
marking process and the grinding are repeated until practically all the
teeth contact in Centric Occlusion. During this grinding procedure, the
incisal pin is relieved of contacts on the incisal guidance table to allow
for the slight reduction in Vertical Dimension that must necessarily take
place. After centric deflective occlusal contacts have been removed the
pin is placed in contact with the incisal table and is kept in contact
through the remainder of the grinding procedure.

7. I] TYPES OF OCCLUSAL ERROR IN CENTRIC OCCLUSION
AND THEIR CORRECTION: -
3 types of occlusal errors can exist in Centric Occlusion, and each
can be corrected by specific grinding for that error.
1) Any pair of opposing teeth can be too long and hold the other teeth
out of contact.
Correction: - The fossae of the teeth are deepened by grinding so
the teeth will in effect, telescope into each other. The cusps are not
shortened.
2) The upper and lower teeth can be too nearly end to end.
Correction: - For correction of this error grinding in such a way as
to move the upper cusp inclines bucally and the lower cusp
inclines lingually. In the process the central fossae are made
broader, the lingual cusp of the upper tooth is made more narrow
when it is ground from the lingual side, and the buccal cusp of the
lower tooth is made more narrow when it is ground from the
buccal side. The cusps are not shortened
3) The upper teeth can be too far buccal in relation to the lower teeth.
Correction: - The lingual cusp of the upper tooth is made more
narrow by broadening the central fossa, and the buccal cusp of the
lower teeth is moved buccally by broadening the central fossa.

8. In effect, the upper lingual cusps is moved lingually and the
lower buccal cusp is moved buccaly so the tooth telescope into each
other. Cusps are not shortened.
II] TYPES OF WORKING SIDE OCCLUSAL ERRORS AND
THEIR CORRECTION: -
6 types of errors can exist in the occlusal contacts on the working
side. Each of these will cause other teeth to be hold out of contact in
working occlusion, and each requires selective grinding of specific cusp
inclines for its elimination.
1) Both the upper buccal cusp and the lower lingual cusp are too long.
Correction: - The length of the cusps is reduced by grinding to
change the incline extending from the central fossa to the cusp tip.
The central fossa is not made deeper, but the upper buccal cusps
and the lower lingual cusps are made shorter so the other teeth will
touch in that position.
2) The buccal cusps make contact but the lingucal cusps do not.
Correction: - Buccal cusps of the upper teeth are ground from the
central fossa to the cusps tip to shorten the cusp and change the
lingual incline of the cusps so it will be less steep.

9. 3) The lingual cusps make contact but the buccal cusps do not.
Correction: - The lower lingual cusps are shortened by changing
the buccal incline of the lower lingual cusp so it is not as steep.
Upper lingual cusp is not shortened and the central fossa is not
made deeper.
4) Upper buccal or lingual cusps are mesial to their intercuspative
positions. This error may occur along positions. This error may
occur along with any of the 3 above listed.
Correction: - Grinding is done so the mesial inclines of the upper
buccal cusps are moved distally when the cusps are narrowed and
the distal inclines of the lower cusps are moved forward. The same
cuspal inclination is maintained in this procedure.
5) Upper buccal or lingual cusps are distal to their inter cusping
positions. This error may occur along with the bucco-lingual errors.
Correction: - Grinding is dome from the distal of the upper cusps
and from the mesial of the lower cusps.
6) Teeth on the working side may not contact.
Cause of this error is excessive contact on the balancing side.

10. III] TYPE OF BALANCING - SIDE ERRORS AND THEIR
CORRECTION: -
There are 2 types of balancing side errors –
1) Balancing – side contact is so heavy that the working side teeth
are held out of contact
Correction: - Paths are ground through the buccal cusps of the
lower teeth to reduce the incline of the part of the cusp that is
preventing the teeth on the working side from contacting.
No grinding is done from the lingual cusps that may be
involved in this contact.
2) There is no contact on the balancing side.
Correction: - Shorten the buccal cusps of the upper teeth and
the lingual cusps of the lower teeth on the working side. In this
process, the lingual inclines of the buccal cusps of upper teeth
and buccal incline of lingual cusps of lower teeth are made less
step. No grinding is done on central fossae.

11. ELIMINATING OCCLUSAL ERRORS IN NON ANATOMIC
TEETH :-
An Interocclusal Centric Relation record is made in a bite registration
material with the opposing teeth just out of contact. Dentures are mounted
on articulators and the following procedures are undertaken.
1) After being detected by articulating paper between the teeth,
gross premature contact in Centric Relation are removed by
grinding. Same procedures are used to locate and remove all
occlusal interferences lateral and protrussive movements. The
grinding is done that appear to have been ripped or elongated in
processing. In Centric Occlusion no grinding is done on the
distobuccal portion of the lower second molar. All balancing-
side grinding is done on the lingual position of the occlusal
surfaces of the upper second molar.
2) Abrasive paste is placed on the teeth on the articulator. These
teeth are milled when the upper member of the articulator
moves in and out of protrusive and right and left lateral
excursions. When the teeth slide smoothly through all
excursions, the dentures are removed from the articulators and
washed. Seldom is any correction necessary to attain a
bilaterally balanced occlusion.
3) Spot grinding is done to correct any small discrepancies in
Centric Relation that remain after the grinding with abrasive
paste. The dentist adjust them after identifying the discrepancies
with articulating paper – using a light tapping motion with the

12. articulator and grinding the marks to ensure even occlusal
contact in Centric Occlusion.
SUMMARY AND CONCLUSION :
Selective grinding in complete denture Prosthodontics is an important
laboratory procedure which is carried out by remounting of the dentures
after processing is completed. This remounting may either be laboratory
remount or patient remount.
Inspite of carrying out each step in denture construction very carefully
it is seen that in the end when the dentures are remounting there is an
occlusal prematurities or interferences may be needed.

13. REFERENCES
1. I George, Charles, Judson: Boucher’s Prosthodontic Treatment for
edentulous Patients. U.S.A. 1997, Mosby Company, ed 10; 500-503.
2. Charles Heartwell: Syllabus of Complete Denture. U.S.A. 1992, ed 4;
394-406.
3. Merrell Swenson: Complete Dentures. U.S.A. 1959, Mosby Company,
ed 4: 273-294.
4. Holt J : Research on remounting procedures.
J Prosthet Dent 1977, 38:388.
5. Moore P : Indicate pastes - Their behavior and use.
J Prosthe Dent 1979, 41:258.