SECTIONEDITORS
The need of eccentric B. K. Motwani,
M.D.S.,*
and
balance A. B. Sidhaye,
during
mastication
M.D.S.**
Government Dental College and Hospital, Maharashtra, India A study of the masticatory performance of 30 patients with balancing contacts centric relation was compared with an equal number of patients with balancing contacts in both centric and eccentric relations. The study failed to show any significant difference between masticatory performance of the two groups. (J PROSTHET DENT 1990;64:689-90.)
M any prosthodontists
consider balanced occlusion in centric and eccentric relations to be essential for the successof complete dentures. However, some consider that only the balance in the centric relation is essentia1.l The controversy exists because there is no direct proof of the validity of balanced occlusion in eccentric relations during nonfunctional movements.2 Balanced occlusion may not be necessary for mastication; however, nonfunctional movements with balanced occlusion in an artificial denture could play a role in increasing masticatory efficiency. The present study was undertaken to determine the effect of balanced occlusion in centric and eccentric relations on masticatory efficiency in comparison with dentures with balanced occlusion only in centric relation.
MATERIAL
AND
METHODS
This study involved 80 patients who received complete dentures from the Department of Prosthetic Dentistry, Government Dental College and Hospital, Nagpur, India, from April to October 1985. All patients selected had previous denture experience. Dentures with nonanatomic teeth and patients with analomous jaw relations were deleted from the study. Patients were treated in the service clinic up to the final impression stage and were then transferred to the postgraduate clinic where they were categorized randomly into group A and group B. A total of 38 patients with records bearing even numbers were placed in group A and received dentures made on a Hanau model Hs articulator (Teledyne Hanau, Buffalo,
Submitted in partial fulfillment for the degree of M.D.S. (Prosthetic Dentistry) to the Nagpur University, Nagpur, India. *Assistant
Professor
in Prosthetic
Dentistry,
Surgery, Manipal, India. **Professor 10/l/22690
THEJOURNAL
of Prosthetic
Dentistry.
OF PROSTHETIC
DENTISTRY
College
of Dental
in
N.Y.). In this group, processing errors were eliminated in centric and eccentric jaw relations by remounting the dentures on the articulator, followed by selective grinding in the mouth.3 The remaining patients with records bearing odd numbers were placed in group B, and received dentures that were made on a mean value articulator. In this group of patients, processing errors were eliminated only in the centric relation by remounting the dentures on the mean value articulator and adjusting them later in the mouth.3 Patients in both groups were examined at the time of denture insertion. Correction of denture base extension and other adjustments were made when necessary. Each patient was recalled on the next day for adjustments and on subsequent days until he or she was comfortable, which usually took 3 to 5 days. On the fourteenth day, those patients who could eat comfortably with their dentures were recalled and the masticatory performance of 30 patients from each group was assessed by means of a masticatory performance test.4
RESULTS The investigations revealed that subjects in group A showed a mean masticatory performance value of 30.62 % , with a standard deviation of 2.53 % . Subjects in group B showed a mean masticatory performance value of 29.20%) with a standard deviation of 4.43 % . The difference in the mean value of masticatory performance was found to be statistically nonsignificant (Table I).
DISCUSSION Frechette5 compared the balanced and nonbalanced arrangement of teeth in artificial dentures by a device th.at recorded the distribution of masticatsry forces on tissues. The study measured the masticatory force applied in balanced occlusion and then the same dentures were nonbalanced by removing contacts. This method, however, was not valid. There are interfering cusps if the dentures are not
689
MOTWANI
Table
I. Mean masticatory performance values
Group
A+ Bt *Grout tGroup
A. Subiects B; Subjects
Mean masticatory performance value (%)
No. of subjects 30 30 with occlusion with occlusion
Standard
30.62 29.20 balanced balanced
in centric in centric
deviation (%)
as well as in eccentric relation only.
Degree freedom
t
2.53 4.43
balanced in an eccentric relation. Koita,G in a study of nine patients, prepared dentures on a simple hinge articulator. The occlusal errors were minimized by careful laboratory procedures. He tested the masticatory efficiency of the dentures 3 weeks after delivery, and subsequently used the same bases to prepare new dentures with balanced occlusion using an autopolymerizing acrylic resin. Before delivery, he remounted the dentures on an adjustable articulator for occlusal correction in both the centric and eccentric relation. Masticatory efficiency was tested 2 weeks after denture delivery. He concluded that there was a significant improvement in the masticatory performance when dentures were made in balanced occlusion on a semiadjustable articulator. The processing errors were minimized by remount procedures for the nonbalanced occlusions. He eliminated the discrepancies in centric as well as in eccentric occlusions in the balanced occlusions. However, the duration of denture wear before testing both types was not the same. The patients were already adapted to the bases when balanced occlusion was instituted. Therefore a comparison of the two types of occlusion was again not valid. Our study differs from the two studies mentioned in that it was done with two different groups of patients. Testing masticatory efficiency with two different occlusal patterns on the same patient sounds logical and scientific, provided each type is tested after the patient wears a denture for the same period of time. If one type is tested after the other, the test needs to be repeated in the reverse order to nullify the effect of the patient getting used to the denture. The number of days of wear and previous denture experience were controlled. The effect of other variables was minimized by selecting a large number of patients and by random placement in two groups. Our study shows that balanced occlusion in eccentric movements has no significant effect on masticatory performance. However, it should not be concluded from our study that
690
AND SIDHAYE
0.30
of
58
relation.
balanced occlusion is not necessary for the total successof the complete denture treatment. It is possible that with interfering contacts in eccentric positions, the patient might subconsiously avoid premature contacts by not making lateral movements of the mandible. Further investigation is necessary to determine if the chewing pattern is different in the two types of occlusion and, if so, whether the difference has any effect on the stomatognathic system.
SUMMARY A study of the masticatory performance of 30 patients with balancing contacts in centric relation was compared with the masticatory performance of an equal number of patients with balancing contacts in both centric and eccentric relations. The study failed to show any significant difference between the masticatory performance of the two groups. REFERENCES 1. Heartweh
2. 3. 4. 5.
CM, Rahn AO. Syllabus of complete dentures. 3rd ed. Philadelphiaz Lea & Fehiger, 1980:217. Hickey JC, Zarb GA. Boucher’s prosthodontic treatment for edentulous patients. 8th ed. St Louis: CV Mosby Co, 1980:419,473. Sidhaye AB, Master SB. RtRcacy of remount procedures using masticatory performance tests. J PROSTHET DENT 1979;41:129-33. Manly RS, Braley LC. Masticatory performance and efficiency. J Dent Res 1950;29:448-62. Frechette AR. Comparison of balanced and nonbalanced occlusion of artificial denture based upon distribution of masticatory force. J PROS-
THET DENT 1955;5:301-10.
6. Koita AK. A scientific study to investigate improvement in masticatory function by balanced occlusion on complete artificial dentures [Thesis]. Bombay: University of Bombay, 1975. Reprint
requests
to:
DR. A. B. SIDHAYE GOVEZNMENT DENTAL AIJRANGAFW 431001 MAIMA~IHTFIA, INDIA
COLLF,GE AND HOSPITAL
DECEMBER
1990
VOLUME
64
NUMBER
6
The need of eccentric B. K. Motwani,
M.D.S.,*
and
balance A. B. Sidhaye,
during
mastication
M.D.S.**
Government Dental College and Hospital, Maharashtra, India A study of the masticatory performance of 30 patients with balancing contacts centric relation was compared with an equal number of patients with balancing contacts in both centric and eccentric relations. The study failed to show any significant difference between masticatory performance of the two groups. (J PROSTHET DENT 1990;64:689-90.)
M any prosthodontists
consider balanced occlusion in centric and eccentric relations to be essential for the successof complete dentures. However, some consider that only the balance in the centric relation is essentia1.l The controversy exists because there is no direct proof of the validity of balanced occlusion in eccentric relations during nonfunctional movements.2 Balanced occlusion may not be necessary for mastication; however, nonfunctional movements with balanced occlusion in an artificial denture could play a role in increasing masticatory efficiency. The present study was undertaken to determine the effect of balanced occlusion in centric and eccentric relations on masticatory efficiency in comparison with dentures with balanced occlusion only in centric relation.
MATERIAL
AND
METHODS
This study involved 80 patients who received complete dentures from the Department of Prosthetic Dentistry, Government Dental College and Hospital, Nagpur, India, from April to October 1985. All patients selected had previous denture experience. Dentures with nonanatomic teeth and patients with analomous jaw relations were deleted from the study. Patients were treated in the service clinic up to the final impression stage and were then transferred to the postgraduate clinic where they were categorized randomly into group A and group B. A total of 38 patients with records bearing even numbers were placed in group A and received dentures made on a Hanau model Hs articulator (Teledyne Hanau, Buffalo,
Submitted in partial fulfillment for the degree of M.D.S. (Prosthetic Dentistry) to the Nagpur University, Nagpur, India. *Assistant
Professor
in Prosthetic
Dentistry,
Surgery, Manipal, India. **Professor 10/l/22690
THEJOURNAL
of Prosthetic
Dentistry.
OF PROSTHETIC
DENTISTRY
College
of Dental
in
N.Y.). In this group, processing errors were eliminated in centric and eccentric jaw relations by remounting the dentures on the articulator, followed by selective grinding in the mouth.3 The remaining patients with records bearing odd numbers were placed in group B, and received dentures that were made on a mean value articulator. In this group of patients, processing errors were eliminated only in the centric relation by remounting the dentures on the mean value articulator and adjusting them later in the mouth.3 Patients in both groups were examined at the time of denture insertion. Correction of denture base extension and other adjustments were made when necessary. Each patient was recalled on the next day for adjustments and on subsequent days until he or she was comfortable, which usually took 3 to 5 days. On the fourteenth day, those patients who could eat comfortably with their dentures were recalled and the masticatory performance of 30 patients from each group was assessed by means of a masticatory performance test.4
RESULTS The investigations revealed that subjects in group A showed a mean masticatory performance value of 30.62 % , with a standard deviation of 2.53 % . Subjects in group B showed a mean masticatory performance value of 29.20%) with a standard deviation of 4.43 % . The difference in the mean value of masticatory performance was found to be statistically nonsignificant (Table I).
DISCUSSION Frechette5 compared the balanced and nonbalanced arrangement of teeth in artificial dentures by a device th.at recorded the distribution of masticatsry forces on tissues. The study measured the masticatory force applied in balanced occlusion and then the same dentures were nonbalanced by removing contacts. This method, however, was not valid. There are interfering cusps if the dentures are not
689
MOTWANI
Table
I. Mean masticatory performance values
Group
A+ Bt *Grout tGroup
A. Subiects B; Subjects
Mean masticatory performance value (%)
No. of subjects 30 30 with occlusion with occlusion
Standard
30.62 29.20 balanced balanced
in centric in centric
deviation (%)
as well as in eccentric relation only.
Degree freedom
t
2.53 4.43
balanced in an eccentric relation. Koita,G in a study of nine patients, prepared dentures on a simple hinge articulator. The occlusal errors were minimized by careful laboratory procedures. He tested the masticatory efficiency of the dentures 3 weeks after delivery, and subsequently used the same bases to prepare new dentures with balanced occlusion using an autopolymerizing acrylic resin. Before delivery, he remounted the dentures on an adjustable articulator for occlusal correction in both the centric and eccentric relation. Masticatory efficiency was tested 2 weeks after denture delivery. He concluded that there was a significant improvement in the masticatory performance when dentures were made in balanced occlusion on a semiadjustable articulator. The processing errors were minimized by remount procedures for the nonbalanced occlusions. He eliminated the discrepancies in centric as well as in eccentric occlusions in the balanced occlusions. However, the duration of denture wear before testing both types was not the same. The patients were already adapted to the bases when balanced occlusion was instituted. Therefore a comparison of the two types of occlusion was again not valid. Our study differs from the two studies mentioned in that it was done with two different groups of patients. Testing masticatory efficiency with two different occlusal patterns on the same patient sounds logical and scientific, provided each type is tested after the patient wears a denture for the same period of time. If one type is tested after the other, the test needs to be repeated in the reverse order to nullify the effect of the patient getting used to the denture. The number of days of wear and previous denture experience were controlled. The effect of other variables was minimized by selecting a large number of patients and by random placement in two groups. Our study shows that balanced occlusion in eccentric movements has no significant effect on masticatory performance. However, it should not be concluded from our study that
690
AND SIDHAYE
0.30
of
58
relation.
balanced occlusion is not necessary for the total successof the complete denture treatment. It is possible that with interfering contacts in eccentric positions, the patient might subconsiously avoid premature contacts by not making lateral movements of the mandible. Further investigation is necessary to determine if the chewing pattern is different in the two types of occlusion and, if so, whether the difference has any effect on the stomatognathic system.
SUMMARY A study of the masticatory performance of 30 patients with balancing contacts in centric relation was compared with the masticatory performance of an equal number of patients with balancing contacts in both centric and eccentric relations. The study failed to show any significant difference between the masticatory performance of the two groups. REFERENCES 1. Heartweh
2. 3. 4. 5.
CM, Rahn AO. Syllabus of complete dentures. 3rd ed. Philadelphiaz Lea & Fehiger, 1980:217. Hickey JC, Zarb GA. Boucher’s prosthodontic treatment for edentulous patients. 8th ed. St Louis: CV Mosby Co, 1980:419,473. Sidhaye AB, Master SB. RtRcacy of remount procedures using masticatory performance tests. J PROSTHET DENT 1979;41:129-33. Manly RS, Braley LC. Masticatory performance and efficiency. J Dent Res 1950;29:448-62. Frechette AR. Comparison of balanced and nonbalanced occlusion of artificial denture based upon distribution of masticatory force. J PROS-
THET DENT 1955;5:301-10.
6. Koita AK. A scientific study to investigate improvement in masticatory function by balanced occlusion on complete artificial dentures [Thesis]. Bombay: University of Bombay, 1975. Reprint
requests
to:
DR. A. B. SIDHAYE GOVEZNMENT DENTAL AIJRANGAFW 431001 MAIMA~IHTFIA, INDIA
COLLF,GE AND HOSPITAL
DECEMBER
1990
VOLUME
64
NUMBER
6
