a complk
inary test of the replicability analysis system L. Harvey, DDS, MA,a A. Hatch, DDS, MSC
John
W. Osborne,
DDS,
MS,b and
University of Colorado School of Dentistry, Denver, Colo. A system for computerized occlusal analysis was tested in a laboratory. The investigation focused on the ability of the system to replicate results when sensors were used five times under a series of three levels of load that were applied to the occlusion. Also compared were the effects of zero mm immediate side shift and 0.2 mm immediate side shift on the research model. Results showed that there were both statistically significant differences (p 5 0.05 level) and nonsignificant differences scattered among the data derived from both articulator treatments. (J ~PROSTHET DENY 1992;67:697-700,)
computerized system (T-Scan System, Tekscan, Inc., Boston, Mass.) for analyzing occlusion has been described.i A component of the system is the sensor (Figs. 1 and Z), which receives the interocclusal forces and transmits information to a computer that contains special software. Sensors are intended to be used a number of times with each patient. The purpose of this pilot project was to measure the ability of the system to repeat results when diverse known levels of relative force were applied to a sensor. The effects of zero immediate side shift (ISS) to 0.2 mm ISS on the research model used were also compared.
MATERIAL
AND METHODS
Two hundred sensors were randomly sorted into two equal groups. For the project, 10 sensors were selected from each group. The manufacturer’s instructions were followed for use of tbe sensors and the computer. For this study, one use of a sensor was defined as the placement of a sensor between the occlusal surfaces of mounted diagnostic casts, the application of a series of three levels of load--& 25, and 35 kg-by a press, and the recording of the appropriate data. One set of Denar No. 118 Goldberg premounted epoxy casts were attached to a Denar Mark 11 articulator (Denar, Anaheim, Calif.). One investigator fully equilibrated the casts. He used occlusion registration strips (Artus Corp.,
This study wassupported by Basic Researchin Science grant No. 079. aProfessorof Restorative Dentistry and Acting Clinical Director. %ofessor of Restorative Dentistry and Director of Clinical Research. CAssoeiate Professor of Dentistry Dentistry. 1011/355BP
THEJOURNAL
OF PROSTHETIC
and Chairman of Operative
DENTISTRY
Englewood, NJ.) and articulating ribbon (Denar) to indicate occlusal contacts. The articulator was clamped onto the frame of a No. 2 Greenerd Arbor press (Press and Machine Co, Nashua, N.H.) with a Dillon force gauge (Dillon & Co., Van Nuys, Calif.) so that known loads could be applied to the articulator by way of the central stud bolt that holds the upper mounting ring and cast to the articulator (Fig 3). For part I of the project, the articulator was set with 0 mm ISS and was locked into the centric relation position by the centric latch. Each new sensor was locked into the T-Scan handle and centered in the interocclusal position with the h,andle slightly elevated. The 3-D Force Snapshot mode was selected. One investigator slowly pulled downward on the arm of the press with an average speed of 8 seconds/5 kg and stopped at 15 kg, 25 kg, and 35 kg consecutively so that the second operator could store the data in the computer, initiate a 2-D mode permanent computer printout, and count the number of 3-D contact force columns at each level of applied force. After each use, the T-Scan handle was removed so that the sensor could be straightened in the bite fork. The sensor was replaced between the teeth The same experimental procedures were repeated five times with each of the first group of 10 sensors. For part two of the project, each condylar element of the articulator was set with 0.2 mm ISS on each side (for a totaI of 0.4 mm) and the centric latch was released. The procedure followed part one of the project except that the upper member was held in the centric relation position. The second group of 10 sensors were used to collect the data. Statview 512-t (Abacus Concepts, Berkeley, Calif.), a software program for Macintosh computers, was used to analyze the data and produce graphics of the mean8 and
standard deviations. The software also computed a factor analysis for the nonparametric data. A level ofp 5 .05 was selected to be the level of significance.
697
NATZVEY,
I
SYSTEM
OSBORNE,
AND
HATCH
UNIT
COMPUTER MOTHERi3OARO
CONTROL BUTTONS
Fig.
1. Schematic view of T-scan system.
level of load showed no significant differences among the five uses for 15 kg zero mm ISS, 35 kg zero mm ISS, and 35 kg 0.2 mm ISS. There were significant differences, among the five uses for 15 kg 0.2 mm ISS, 25 kg 0.2 mm and 25 kg zero mm ISS, and a 3 x 5 section of load and uses data showed significant differences between the three levels of load for both articulator ISS treatments. DISCUSSION
Fig,
2. Schematic of intraoral sensor.
RESULTS There were significant differences among and between some of the sensors, uses, and levels of force and not between other uses and levels of force. An examination of the data (Figs. 4 through 6) graphically shows a composite of the mean, standard deviation error bars of the 10 sensors used in each group of 0 mm and 0.2 mm at 15 kg, 25 kg, and 35 kg levels of load. To illustrate the variability of the data, an examination of the 0 mm ISS data showed: the first use at 15 kg of load had a mean of 3.4 occlusal contacts with a standard deviation of 2.43 and a range of 4, with a minimum of 1 and a maximum of 5 contacts. This data was quite different from the opposite end of the 0 mm ISS data, which showed: the fifth use at 35 kg of load, a mean of 6.2 occlusal contacts and a standard deviation of 2.44 contacts, a range of 4 with a minimum of 6 and a maximum of 10 occlusal contacts. Factor analysis of each 5 x 10 slice of the data at each 698
It is believed that the occlusal contacts that can be identified at the lowest levels of biting force are of the most interest to the dentist. The first interceptive occlusal contact(s) have to be correctly identified so that the correct assumptions can be made about the relationship of the occlusion and mandibular position before deciding on the appropriate treatment.’ Treatment hypotheses might then range from grinding and polishing one minor interceptive tooth contact, discovered in an excursive mandibular movement, to splint (bite plane) therapy followed by an occlusal equilibration. Therefore, indicators of occlusal and incisal contacts must be valid and reliable at low levels of applied force and must be repeatable. For example, if a dentist adjusts an occlusal prematurity, one cannot assume that the prematurity was eliminated simply because of one effort to grind and polish. An earlier study measured the ability of the computerized occlusal analyzer to repeat results with one known interceptive occlusal contact.3 That report showed that the tests of that particular sample of sensors produced both reliable and valid results, through only two uses, when required to detect one known interceptive occlusal contact. The system for computerized occlusal analysis was tested in the laboratory to eliminate some variables and control other variables of mandibular movement and occlusion. As Gibbs et a1.4pointed out, the mandible is capable of moving with six degrees of motion. If all of the variables produced by six degrees of motion had been added to the research model and recorded, the analysis of MAY
1992
VOLUME
67
NUMBER
6
COMPUTERIZED
QCCLUSAL
ANALYSIS
Fig. 5. Shows column mean bars with standard deviations of five replications that compared data from (odd xnumbered) 8 mm and (even x-numbered) 0.2 mm ISS under 25 kg of load.
Fig. 3. Articulator secured to Greenerd press containing Dillon gauge for applying a known load to articulator.
Fig. 4. Shws column mean bars with standard deviations of five replications that compared data from (odd X-numbered) 0 mm and (even X-numbered) 0.2 mm ISS under 15 kg of load.
the data would have become extremely complex. We were primarily interested in the ability of the system to repeat results with a limited number of variables, This research report did not attempt to correlate the loTHE
JOURNAL
OF PRC9STHETlC
DENTISTRY
Fig. 6. Shows column mean bars with standard deviations of five replications that compared data from (odd xnumbered) 0 mm and (even x-numbered) 0.2 mm ISS under 35 kg of load.
cation or size of the occlusal contacts reported by the computerized system with the occlusal contacts indicated by shim stock and articulating ribbon. This will be the next phase of the research, which will also be done in the laboratory. There were fewer contacts at lighter occluding forces than heavier forces, in agreement with Riise’G’ observations regarding other recording and marking media. The differences may be (I) within the quality and design of the sensors, as suggested by the width of tbe standard deviations; (2) in the variables inherent in recording static versus dynamic occlusal contacts as when the ISS was added; (3) perhaps the increase in the number of contacts, showing that shim stock and articulating ribbon did not, discriminate satisfactorily among the occlusal contacts when the occlusal equilibration was done; or (4) a combination of the above possibilities or other unknowns. The occluding forces acting on the sensors were considered relative forces. The range of forces selected for this project were regarded as within the normal range of chewing forces generated by some patients”.il and the range of 699
HAWVEY,
OSBORKE,
AND HATCH
forces through which some patients pass as they progress to greater masticatory forces. Tine color video display and software programming of the system were impressive and a step in the right direction. Dentists need to be able to analyze occlusion objectively. It was fascinating to watch initial occlusal or incisal contact(s) appear in computer-generated color 3-D movies and to seeforce column(s) suddenly arise at a contact, lengthen, and disappear as mandibular movement progressed.
REFERENCES 1. Manees, WL, BenjaminM, Podoloff R..Computerized ccclusal analysis:
CONCLUSPONS
6. Brekhns PJ, Armstrong WD, Simon WJ. Stimulation of the muscles of mastication. J Dent Res 1941;20:87. 7. Gibbs CH, Mahan PE, Mauderli A, Lundeen HC, Walsh EM. Limits of human bite strength. J PROSTHETDENT 1986;56:22G-9. 8. Gibbs CH, Maban PE, Lundeen HC, et al. Occ!usal forces during chewing: influence on biting strength and food consistency. J PROSTHET DENT 1981:46:561-7. 9. Brudevold F. A basic study of the chewing forces of a denture wearer. J Am Dent Assoc 1951;43:45. 10. Lundgren D, Laurel1 L. Occlusal force pattern during chewing and biting in dentitions restored with fixed bridges of cross-arch extension J Oral Rehabil 1986;13:57. 11. Anderson DJ. Measurement of stress in mastication. II. J Dent Res 1956:X&71.
For the batches of sensors sampled and tested, there were unpredictable variations with significant differences and nonsignificant differences scattered among the uses, levels of force, and articulator ISS treatments.
The ability of a system for computerized occlusal analysis to replicate results was tested by comparing two sets of occlusal data generated by an articulator in a laboratory. The articulator was first set with 0 mm and subsequently adjusted with 0.2 mm immediate side shift. Ten randomly selected sensors were used in each of the two groups. A series of three different levels of load were applied to each sensor and data were collected through five replications. The results showed considerable variations among the test conditions.
700
a new technology. Quintessence Int 1987;18:287-92. 2. Troest T. Diagnosing minute deflective occlusd contacts. d PROSTHET DENT 1964;14:71.
3. Harvey WL, Hatch RA, Osborne JW. Computerized occlusal analysis: an evaluation of the sensors. J PROSTHETDENT 1991;65:89-92. 4. Gibbs CH, Messerman T, Reswick JB. Functional movements of the mandible. J PROSTHETDENT 1971;26:604. 5. Riise C. A clinical study of the number of occlusai tooth contacts in the intercuspal position at light and hard pressure in adults. J Oral Rehabil 1982:9:469.
Reprint requests to: DR. WAYNE L. HARVEY
UCHSC UNIVERSITYOF COLORADO SCHOOL OF DEYTISTRY Box C-284 4200 E NINTH AVENUE DENVER, CO 80262
inary test of the replicability analysis system L. Harvey, DDS, MA,a A. Hatch, DDS, MSC
John
W. Osborne,
DDS,
MS,b and
University of Colorado School of Dentistry, Denver, Colo. A system for computerized occlusal analysis was tested in a laboratory. The investigation focused on the ability of the system to replicate results when sensors were used five times under a series of three levels of load that were applied to the occlusion. Also compared were the effects of zero mm immediate side shift and 0.2 mm immediate side shift on the research model. Results showed that there were both statistically significant differences (p 5 0.05 level) and nonsignificant differences scattered among the data derived from both articulator treatments. (J ~PROSTHET DENY 1992;67:697-700,)
computerized system (T-Scan System, Tekscan, Inc., Boston, Mass.) for analyzing occlusion has been described.i A component of the system is the sensor (Figs. 1 and Z), which receives the interocclusal forces and transmits information to a computer that contains special software. Sensors are intended to be used a number of times with each patient. The purpose of this pilot project was to measure the ability of the system to repeat results when diverse known levels of relative force were applied to a sensor. The effects of zero immediate side shift (ISS) to 0.2 mm ISS on the research model used were also compared.
MATERIAL
AND METHODS
Two hundred sensors were randomly sorted into two equal groups. For the project, 10 sensors were selected from each group. The manufacturer’s instructions were followed for use of tbe sensors and the computer. For this study, one use of a sensor was defined as the placement of a sensor between the occlusal surfaces of mounted diagnostic casts, the application of a series of three levels of load--& 25, and 35 kg-by a press, and the recording of the appropriate data. One set of Denar No. 118 Goldberg premounted epoxy casts were attached to a Denar Mark 11 articulator (Denar, Anaheim, Calif.). One investigator fully equilibrated the casts. He used occlusion registration strips (Artus Corp.,
This study wassupported by Basic Researchin Science grant No. 079. aProfessorof Restorative Dentistry and Acting Clinical Director. %ofessor of Restorative Dentistry and Director of Clinical Research. CAssoeiate Professor of Dentistry Dentistry. 1011/355BP
THEJOURNAL
OF PROSTHETIC
and Chairman of Operative
DENTISTRY
Englewood, NJ.) and articulating ribbon (Denar) to indicate occlusal contacts. The articulator was clamped onto the frame of a No. 2 Greenerd Arbor press (Press and Machine Co, Nashua, N.H.) with a Dillon force gauge (Dillon & Co., Van Nuys, Calif.) so that known loads could be applied to the articulator by way of the central stud bolt that holds the upper mounting ring and cast to the articulator (Fig 3). For part I of the project, the articulator was set with 0 mm ISS and was locked into the centric relation position by the centric latch. Each new sensor was locked into the T-Scan handle and centered in the interocclusal position with the h,andle slightly elevated. The 3-D Force Snapshot mode was selected. One investigator slowly pulled downward on the arm of the press with an average speed of 8 seconds/5 kg and stopped at 15 kg, 25 kg, and 35 kg consecutively so that the second operator could store the data in the computer, initiate a 2-D mode permanent computer printout, and count the number of 3-D contact force columns at each level of applied force. After each use, the T-Scan handle was removed so that the sensor could be straightened in the bite fork. The sensor was replaced between the teeth The same experimental procedures were repeated five times with each of the first group of 10 sensors. For part two of the project, each condylar element of the articulator was set with 0.2 mm ISS on each side (for a totaI of 0.4 mm) and the centric latch was released. The procedure followed part one of the project except that the upper member was held in the centric relation position. The second group of 10 sensors were used to collect the data. Statview 512-t (Abacus Concepts, Berkeley, Calif.), a software program for Macintosh computers, was used to analyze the data and produce graphics of the mean8 and
standard deviations. The software also computed a factor analysis for the nonparametric data. A level ofp 5 .05 was selected to be the level of significance.
697
NATZVEY,
I
SYSTEM
OSBORNE,
AND
HATCH
UNIT
COMPUTER MOTHERi3OARO
CONTROL BUTTONS
Fig.
1. Schematic view of T-scan system.
level of load showed no significant differences among the five uses for 15 kg zero mm ISS, 35 kg zero mm ISS, and 35 kg 0.2 mm ISS. There were significant differences, among the five uses for 15 kg 0.2 mm ISS, 25 kg 0.2 mm and 25 kg zero mm ISS, and a 3 x 5 section of load and uses data showed significant differences between the three levels of load for both articulator ISS treatments. DISCUSSION
Fig,
2. Schematic of intraoral sensor.
RESULTS There were significant differences among and between some of the sensors, uses, and levels of force and not between other uses and levels of force. An examination of the data (Figs. 4 through 6) graphically shows a composite of the mean, standard deviation error bars of the 10 sensors used in each group of 0 mm and 0.2 mm at 15 kg, 25 kg, and 35 kg levels of load. To illustrate the variability of the data, an examination of the 0 mm ISS data showed: the first use at 15 kg of load had a mean of 3.4 occlusal contacts with a standard deviation of 2.43 and a range of 4, with a minimum of 1 and a maximum of 5 contacts. This data was quite different from the opposite end of the 0 mm ISS data, which showed: the fifth use at 35 kg of load, a mean of 6.2 occlusal contacts and a standard deviation of 2.44 contacts, a range of 4 with a minimum of 6 and a maximum of 10 occlusal contacts. Factor analysis of each 5 x 10 slice of the data at each 698
It is believed that the occlusal contacts that can be identified at the lowest levels of biting force are of the most interest to the dentist. The first interceptive occlusal contact(s) have to be correctly identified so that the correct assumptions can be made about the relationship of the occlusion and mandibular position before deciding on the appropriate treatment.’ Treatment hypotheses might then range from grinding and polishing one minor interceptive tooth contact, discovered in an excursive mandibular movement, to splint (bite plane) therapy followed by an occlusal equilibration. Therefore, indicators of occlusal and incisal contacts must be valid and reliable at low levels of applied force and must be repeatable. For example, if a dentist adjusts an occlusal prematurity, one cannot assume that the prematurity was eliminated simply because of one effort to grind and polish. An earlier study measured the ability of the computerized occlusal analyzer to repeat results with one known interceptive occlusal contact.3 That report showed that the tests of that particular sample of sensors produced both reliable and valid results, through only two uses, when required to detect one known interceptive occlusal contact. The system for computerized occlusal analysis was tested in the laboratory to eliminate some variables and control other variables of mandibular movement and occlusion. As Gibbs et a1.4pointed out, the mandible is capable of moving with six degrees of motion. If all of the variables produced by six degrees of motion had been added to the research model and recorded, the analysis of MAY
1992
VOLUME
67
NUMBER
6
COMPUTERIZED
QCCLUSAL
ANALYSIS
Fig. 5. Shows column mean bars with standard deviations of five replications that compared data from (odd xnumbered) 8 mm and (even x-numbered) 0.2 mm ISS under 25 kg of load.
Fig. 3. Articulator secured to Greenerd press containing Dillon gauge for applying a known load to articulator.
Fig. 4. Shws column mean bars with standard deviations of five replications that compared data from (odd X-numbered) 0 mm and (even X-numbered) 0.2 mm ISS under 15 kg of load.
the data would have become extremely complex. We were primarily interested in the ability of the system to repeat results with a limited number of variables, This research report did not attempt to correlate the loTHE
JOURNAL
OF PRC9STHETlC
DENTISTRY
Fig. 6. Shows column mean bars with standard deviations of five replications that compared data from (odd xnumbered) 0 mm and (even x-numbered) 0.2 mm ISS under 35 kg of load.
cation or size of the occlusal contacts reported by the computerized system with the occlusal contacts indicated by shim stock and articulating ribbon. This will be the next phase of the research, which will also be done in the laboratory. There were fewer contacts at lighter occluding forces than heavier forces, in agreement with Riise’G’ observations regarding other recording and marking media. The differences may be (I) within the quality and design of the sensors, as suggested by the width of tbe standard deviations; (2) in the variables inherent in recording static versus dynamic occlusal contacts as when the ISS was added; (3) perhaps the increase in the number of contacts, showing that shim stock and articulating ribbon did not, discriminate satisfactorily among the occlusal contacts when the occlusal equilibration was done; or (4) a combination of the above possibilities or other unknowns. The occluding forces acting on the sensors were considered relative forces. The range of forces selected for this project were regarded as within the normal range of chewing forces generated by some patients”.il and the range of 699
HAWVEY,
OSBORKE,
AND HATCH
forces through which some patients pass as they progress to greater masticatory forces. Tine color video display and software programming of the system were impressive and a step in the right direction. Dentists need to be able to analyze occlusion objectively. It was fascinating to watch initial occlusal or incisal contact(s) appear in computer-generated color 3-D movies and to seeforce column(s) suddenly arise at a contact, lengthen, and disappear as mandibular movement progressed.
REFERENCES 1. Manees, WL, BenjaminM, Podoloff R..Computerized ccclusal analysis:
CONCLUSPONS
6. Brekhns PJ, Armstrong WD, Simon WJ. Stimulation of the muscles of mastication. J Dent Res 1941;20:87. 7. Gibbs CH, Mahan PE, Mauderli A, Lundeen HC, Walsh EM. Limits of human bite strength. J PROSTHETDENT 1986;56:22G-9. 8. Gibbs CH, Maban PE, Lundeen HC, et al. Occ!usal forces during chewing: influence on biting strength and food consistency. J PROSTHET DENT 1981:46:561-7. 9. Brudevold F. A basic study of the chewing forces of a denture wearer. J Am Dent Assoc 1951;43:45. 10. Lundgren D, Laurel1 L. Occlusal force pattern during chewing and biting in dentitions restored with fixed bridges of cross-arch extension J Oral Rehabil 1986;13:57. 11. Anderson DJ. Measurement of stress in mastication. II. J Dent Res 1956:X&71.
For the batches of sensors sampled and tested, there were unpredictable variations with significant differences and nonsignificant differences scattered among the uses, levels of force, and articulator ISS treatments.
The ability of a system for computerized occlusal analysis to replicate results was tested by comparing two sets of occlusal data generated by an articulator in a laboratory. The articulator was first set with 0 mm and subsequently adjusted with 0.2 mm immediate side shift. Ten randomly selected sensors were used in each of the two groups. A series of three different levels of load were applied to each sensor and data were collected through five replications. The results showed considerable variations among the test conditions.
700
a new technology. Quintessence Int 1987;18:287-92. 2. Troest T. Diagnosing minute deflective occlusd contacts. d PROSTHET DENT 1964;14:71.
3. Harvey WL, Hatch RA, Osborne JW. Computerized occlusal analysis: an evaluation of the sensors. J PROSTHETDENT 1991;65:89-92. 4. Gibbs CH, Messerman T, Reswick JB. Functional movements of the mandible. J PROSTHETDENT 1971;26:604. 5. Riise C. A clinical study of the number of occlusai tooth contacts in the intercuspal position at light and hard pressure in adults. J Oral Rehabil 1982:9:469.
Reprint requests to: DR. WAYNE L. HARVEY
UCHSC UNIVERSITYOF COLORADO SCHOOL OF DEYTISTRY Box C-284 4200 E NINTH AVENUE DENVER, CO 80262
