LAVEREETAL
teeth selected will be longer for both men and women. On the other hand, the majority of the teeth selected will be within 1 mm of both the length and width of the natural tooth dimensions. An interesting sidelight of this project resulted when face forms were determined by use of the tooth indicator (Table II).
Contributing authors Daniel M. Castagna, DDS, Stafford J. Duhn, DDS, Benjamin E. Dooley, DMD, Anthony R. Maniscalco, DDS, Susan J. Protzel, DDS, Dennis D. Shinbori, DDS, Craig S. Yarborough, DDS, Gerald W. Holloway, CDT, University of the Pacific, School of
Dentistry, Removable Prosthodontics Department.
Reprint requests to: ARTHUR M. LAVERE, DDS SCHOOL OF DENTISTRY UNIVERSITY OF THE PACIFIC 2155 WEBSTER ST. SAN FRANCISCO, CA 94115
Laboratory teeth Sheldon Winkler, Jason KwokC
wear DDS,a
investigation George
E. Monasky,
of resin posterior DDS,
MSP,b
denture
and
Temple University, Schoolof Dentistry, Philadelphia, Pa. This investigation compared the wear resistance of three “improved” resin posterior denture tooth formulations with two conventional products on a mechanical toothbrush abrasion machine. The ability of the teeth to resist this type of abrasion was evaluated by determination of the weight loss during 339 hours of brushing with firm nylon bristle toothbrushes. All brands exhibited negligible loss, with the conventional brands performing better than the “improved” formulations. (J PROSTHET DENT 1992;67:812-4.)
R
esin teeth were introduced in the early 1930s and are used today in the fabrication of a majority of removable prostheses. Among the advantages claimed for resin teeth, as opposed to porcelain teeth, are a more natural appearance, less breakage, a reduction of clicking, a better bond between the teeth and the resin base, and the ease of grinding, recontouring, and repo1ishing.l A major disadvantage of resin teeth is the rapid wear of posterior tooth surfaces. While the wear resistance of acrylic resin teeth has improved since their introduction to the profession, the possibility exists that the wear factor can unfavorably affect the occlusal vertical dimension and tooth relationships, causing stresseson the oral mucosa and underlying bone and adversely influencing esthetics.
Partially supported by Grant No. 07.535RU from the Ben Franklin Partnership Program of the Commonwealth of Pennsylvania. BProfeasor,Department of Prosthodontics. bProfesaor,Department of Prosthodontics. “Dental student, researchassistant. 10/l/36563
812
An investigation of the abrasion characteristics of anatomic acrylic resin denture teeth produced by three different manufacturers (Dentsply International, York, Pa., Myerson Tooth Corp., Cambridge, Mass., and Lactona Corp., Morris Plains, N.J.) found small but clinically insignificant differences among the brands tested. The investigators concluded that the selection of teeth should be based on personal preference and esthetic considerations rather than on assumed differences in wear rates.2 In an attempt to “provide all the ease of adjustment and patient adaptability usually associated with plastic” while providing increased wear resistance,3 a major artificial tooth manufacturer developed a new tooth material (Trubyte Bioform IPN, Dentsply International, York, Pa.). These teeth were said to minimize the disadvantages of acrylic resin teeth and enhance certain of their desirable qualities.* The new tooth material was composed of an unfilled, highly cross-linked, interpenetrating polymer network. Interpenetrating polymer networks are structures formed when a polymer is cross-linked into a three-dimensional network occupied by a second cross-linked polymer. The
JUNE1992
VOLUME67
NUMBER6
Fig. 1. Mechanical toothbrushing
cross-linked networks coexist in the same space, physically trapped within each other, and cannot be disassociated without rupture of the chemical bonds. This interpenetrating network structure is claimed to produce enhanced physical properties in resin teeth.5 Two additional resin tooth formulations, also claimed to possessincreased wear resistance, were introduced by other toothmanufacturers (Orthosit-PE, Ivoclar, Schaan, Liechtenstein, and Verilux, Universal Dental, Montgomeryville, Pa.). Favorable reports on each of these products have appeared in recent years.5-s
MATERIALS
AND
METHODS
This investigation compared the wear resistance of the three “improved” commercial products against conventional resin teeth (Bioform, Dentsply International, York, Pa., and Nuform, Universal Dental, Montgomeryville, Pa.) on a toothbrush abrasion machine. It must be emphasized that the method employed measures only the abrasion resistance under the specific conditions of this test. It is not necessarily indicative of resistance to other types of abrasion, such as occluding tooth surfaces, parafunctional activities, and diet. Blocks of posterior teeth were brushed in a motor-driven mechanical toothbrushing machine of the type used in testing the abrasive qualities of dentifrices (Fig. 1). This machine is equipped with six brush holders so that six blocks of posterior teeth can be tested simultaneously. The ability of the various brands to resist this type of abrasion
THE
JOURNAL
OF PROSTHETIC
DENTISTRY
machine with control box.
Fig. 2. Posterior resin denture teeth mounted in die stone in metal compartment.
was evaluated by determination of the weight loss during the brushing period. Die stone molds (Vel-Mix, Kerr Manufacturing Co., Romulus, Mich.) for six sets (three maxillary right and three mandibular right) of each sample of posterior teeth to be tested were fabricated (Fig. 2) to fit into the six compartments of the mechanical brushing machine. Before weighing the teeth, gross debris was carefully removed followed by 15 minutes in an ultrasonic cleaner with an all-purpose cleaning solution. The teeth were then rinsed in distilled water before being placed in a desiccator for 24 hours. The teeth were weighed with an electronic analytic balance (model ER-180A, A & D Co., Ltd., Tokyo, Japan). Extreme care was taken to adjust the position of the
813
WINKLER,
Table
I.
AND
KWOK
Weight loss (% ) of resin teeth after 339 hours of brushing (mean values f standard deviations) Teeth
Bioform Bioform IPN Nuform Orthosit-PE Verilux
First 0.37 0.59 0.40 0.60 0.77
premolar f f f f f
0.17 0.16 0.20 0.08 0.07
Second 0.54 0.55 0.36 0.70 0.77
teeth so that 4 mm of the occlusal portion of each tooth would protrude in a level horizontal plane above the die stone mold. The teeth were selected with an attempt to equalize the size of the occlusal tables and the angulation of the cusps among the molds to be tested. The brushing heads, containing three-row 0.010 inch diameter firm nylon bristle toothbrushes (Lactona Corp., Montgomeryville, Pa.), applied a constant load of approximately 154 gm. A brushing time of 339 hours was used. The teeth were also weighed at 113 and 226 hours, but these weighings showed negligible weight loss. At the end of each brushing period before weighing, the teeth were removed from their molds and carefully cleaned as they were at the start of the investigation. The alignment of the brushes was checked before turning on the machine and several other times during each day to assure that the entire occlusal surfaces of the four teeth in each compartment were being evenly brushed. The machine was set to produce 70 strokes each minute. RESULTS The greatest resistance to toothbrush abrasion was exhibited by the conventional resin teeth followed by the three brands of teeth with claimed increased wear resistance characteristics (Table I). However, weight loss was less than 1% in all samples over an extended period of time and can be considered clinically insignificant. DISCUSSION All of the teeth tested exhibited excellent wear resistance to toothbrush abrasion, with the very minimal weight loss being clinically insignifcant. A brushing time of 200 minutes on the mechanical brushing machine has been calculated to be comparable to 4 to 6 years of normal hand brushing.g* lo Considering that the teeth were subjected to 339 hours of brushing and exhibited negligible loss, the wear resistance of all of the teeth tested can be said to be outstanding.
814
MONASKY,
premolar
First
molar
f ” + + *
0.28 0.60 0.45 0.56 0.83
+ f 2 f k
0.31 0.16 0.17 0.21 0.15
Second
0.18 0.15 0.08 0.07 0.14
molar
0.29 zk 0.16 0.65 f 0.08 0.51 It 0.14 0.60 + 0.10 0.71 + 0.24
However, it should be stressed that the ability of the posterior tooth forms to resist abrasion was tested only under one condition, and other types of wear could produce significantly different results. SUMMARY Laboratory testing of three brands of newly formulated resin posterior teeth with claimed increased wear qualities and two brands of conventional teeth showed that the conventional formulations possessedgreater wear resistance to toothbrush abrasion. The weight loss of all of the teeth tested was negligible (clinically insignificant), however, and did not indicate the superiority of any one brand or formulation over another. Toothbrush abrasion need not be a factor to be considered in the selection of a posterior tooth mold for the brands tested. REFERENCES 1. Dentists’ desk reference: Materials, instruments and equipment. 2nd ed. Chicago: American Dental Association, 1983:177-g. 2. Khan Z, Morris JC, van Fraunhofer JA. Wear of anatomic acrylic resin denture teeth. J PROSTHET DENT 1985,53:550-l. 3. Trubyte Bioform IPN product brochure 38063, Dentsply International, York, Pa., 1990. 4. Smith RA. Research aspects of a new tooth material. Student Clinicians Am Dent Assoc J 1981;1:22. 5. Ogle RE, David L-J, Ortman HR. Clinical wear study of a new tooth material. Part II. J PROSTHET DENT 19&5;54:67-75. 6. Michl RJ. Isosit-a new dental material. Quintessence Int 197&&l-5. 7. van Fraunhofer JA, Razavi R, Khan 2. Wear characteristics of highstrength denture teeth. J PROSTHET DENT 198&59:173-5. 8. de Gee AJ, Werner A, Davidson CL. Abrasion of several artificial prostheses-elements. Amsterdam, The Netherlands; Department of Clinical Materials Science, University of Amsterdam, 1989. 9. Phillips RW, Swartz ML. Effects of diameter of nylon bristles on enamel surface. J Am Dent Assoc 1953;47:20-6. 10. Kafalias MC, Swartz ML, Phillips RW. Physical properties of selected dental resins. Part I. J PROSTHET DENT 1963;13:1087-107.
Reprint requeststo: DR. SHELDON WINKLER TEMPLE UNIVERSITY SCHOOL OF DENTISTRY PHILADELPHIA, PA 19140
JUNE
1992
VOLUME
67
NUMBER
6
teeth selected will be longer for both men and women. On the other hand, the majority of the teeth selected will be within 1 mm of both the length and width of the natural tooth dimensions. An interesting sidelight of this project resulted when face forms were determined by use of the tooth indicator (Table II).
Contributing authors Daniel M. Castagna, DDS, Stafford J. Duhn, DDS, Benjamin E. Dooley, DMD, Anthony R. Maniscalco, DDS, Susan J. Protzel, DDS, Dennis D. Shinbori, DDS, Craig S. Yarborough, DDS, Gerald W. Holloway, CDT, University of the Pacific, School of
Dentistry, Removable Prosthodontics Department.
Reprint requests to: ARTHUR M. LAVERE, DDS SCHOOL OF DENTISTRY UNIVERSITY OF THE PACIFIC 2155 WEBSTER ST. SAN FRANCISCO, CA 94115
Laboratory teeth Sheldon Winkler, Jason KwokC
wear DDS,a
investigation George
E. Monasky,
of resin posterior DDS,
MSP,b
denture
and
Temple University, Schoolof Dentistry, Philadelphia, Pa. This investigation compared the wear resistance of three “improved” resin posterior denture tooth formulations with two conventional products on a mechanical toothbrush abrasion machine. The ability of the teeth to resist this type of abrasion was evaluated by determination of the weight loss during 339 hours of brushing with firm nylon bristle toothbrushes. All brands exhibited negligible loss, with the conventional brands performing better than the “improved” formulations. (J PROSTHET DENT 1992;67:812-4.)
R
esin teeth were introduced in the early 1930s and are used today in the fabrication of a majority of removable prostheses. Among the advantages claimed for resin teeth, as opposed to porcelain teeth, are a more natural appearance, less breakage, a reduction of clicking, a better bond between the teeth and the resin base, and the ease of grinding, recontouring, and repo1ishing.l A major disadvantage of resin teeth is the rapid wear of posterior tooth surfaces. While the wear resistance of acrylic resin teeth has improved since their introduction to the profession, the possibility exists that the wear factor can unfavorably affect the occlusal vertical dimension and tooth relationships, causing stresseson the oral mucosa and underlying bone and adversely influencing esthetics.
Partially supported by Grant No. 07.535RU from the Ben Franklin Partnership Program of the Commonwealth of Pennsylvania. BProfeasor,Department of Prosthodontics. bProfesaor,Department of Prosthodontics. “Dental student, researchassistant. 10/l/36563
812
An investigation of the abrasion characteristics of anatomic acrylic resin denture teeth produced by three different manufacturers (Dentsply International, York, Pa., Myerson Tooth Corp., Cambridge, Mass., and Lactona Corp., Morris Plains, N.J.) found small but clinically insignificant differences among the brands tested. The investigators concluded that the selection of teeth should be based on personal preference and esthetic considerations rather than on assumed differences in wear rates.2 In an attempt to “provide all the ease of adjustment and patient adaptability usually associated with plastic” while providing increased wear resistance,3 a major artificial tooth manufacturer developed a new tooth material (Trubyte Bioform IPN, Dentsply International, York, Pa.). These teeth were said to minimize the disadvantages of acrylic resin teeth and enhance certain of their desirable qualities.* The new tooth material was composed of an unfilled, highly cross-linked, interpenetrating polymer network. Interpenetrating polymer networks are structures formed when a polymer is cross-linked into a three-dimensional network occupied by a second cross-linked polymer. The
JUNE1992
VOLUME67
NUMBER6
Fig. 1. Mechanical toothbrushing
cross-linked networks coexist in the same space, physically trapped within each other, and cannot be disassociated without rupture of the chemical bonds. This interpenetrating network structure is claimed to produce enhanced physical properties in resin teeth.5 Two additional resin tooth formulations, also claimed to possessincreased wear resistance, were introduced by other toothmanufacturers (Orthosit-PE, Ivoclar, Schaan, Liechtenstein, and Verilux, Universal Dental, Montgomeryville, Pa.). Favorable reports on each of these products have appeared in recent years.5-s
MATERIALS
AND
METHODS
This investigation compared the wear resistance of the three “improved” commercial products against conventional resin teeth (Bioform, Dentsply International, York, Pa., and Nuform, Universal Dental, Montgomeryville, Pa.) on a toothbrush abrasion machine. It must be emphasized that the method employed measures only the abrasion resistance under the specific conditions of this test. It is not necessarily indicative of resistance to other types of abrasion, such as occluding tooth surfaces, parafunctional activities, and diet. Blocks of posterior teeth were brushed in a motor-driven mechanical toothbrushing machine of the type used in testing the abrasive qualities of dentifrices (Fig. 1). This machine is equipped with six brush holders so that six blocks of posterior teeth can be tested simultaneously. The ability of the various brands to resist this type of abrasion
THE
JOURNAL
OF PROSTHETIC
DENTISTRY
machine with control box.
Fig. 2. Posterior resin denture teeth mounted in die stone in metal compartment.
was evaluated by determination of the weight loss during the brushing period. Die stone molds (Vel-Mix, Kerr Manufacturing Co., Romulus, Mich.) for six sets (three maxillary right and three mandibular right) of each sample of posterior teeth to be tested were fabricated (Fig. 2) to fit into the six compartments of the mechanical brushing machine. Before weighing the teeth, gross debris was carefully removed followed by 15 minutes in an ultrasonic cleaner with an all-purpose cleaning solution. The teeth were then rinsed in distilled water before being placed in a desiccator for 24 hours. The teeth were weighed with an electronic analytic balance (model ER-180A, A & D Co., Ltd., Tokyo, Japan). Extreme care was taken to adjust the position of the
813
WINKLER,
Table
I.
AND
KWOK
Weight loss (% ) of resin teeth after 339 hours of brushing (mean values f standard deviations) Teeth
Bioform Bioform IPN Nuform Orthosit-PE Verilux
First 0.37 0.59 0.40 0.60 0.77
premolar f f f f f
0.17 0.16 0.20 0.08 0.07
Second 0.54 0.55 0.36 0.70 0.77
teeth so that 4 mm of the occlusal portion of each tooth would protrude in a level horizontal plane above the die stone mold. The teeth were selected with an attempt to equalize the size of the occlusal tables and the angulation of the cusps among the molds to be tested. The brushing heads, containing three-row 0.010 inch diameter firm nylon bristle toothbrushes (Lactona Corp., Montgomeryville, Pa.), applied a constant load of approximately 154 gm. A brushing time of 339 hours was used. The teeth were also weighed at 113 and 226 hours, but these weighings showed negligible weight loss. At the end of each brushing period before weighing, the teeth were removed from their molds and carefully cleaned as they were at the start of the investigation. The alignment of the brushes was checked before turning on the machine and several other times during each day to assure that the entire occlusal surfaces of the four teeth in each compartment were being evenly brushed. The machine was set to produce 70 strokes each minute. RESULTS The greatest resistance to toothbrush abrasion was exhibited by the conventional resin teeth followed by the three brands of teeth with claimed increased wear resistance characteristics (Table I). However, weight loss was less than 1% in all samples over an extended period of time and can be considered clinically insignificant. DISCUSSION All of the teeth tested exhibited excellent wear resistance to toothbrush abrasion, with the very minimal weight loss being clinically insignifcant. A brushing time of 200 minutes on the mechanical brushing machine has been calculated to be comparable to 4 to 6 years of normal hand brushing.g* lo Considering that the teeth were subjected to 339 hours of brushing and exhibited negligible loss, the wear resistance of all of the teeth tested can be said to be outstanding.
814
MONASKY,
premolar
First
molar
f ” + + *
0.28 0.60 0.45 0.56 0.83
+ f 2 f k
0.31 0.16 0.17 0.21 0.15
Second
0.18 0.15 0.08 0.07 0.14
molar
0.29 zk 0.16 0.65 f 0.08 0.51 It 0.14 0.60 + 0.10 0.71 + 0.24
However, it should be stressed that the ability of the posterior tooth forms to resist abrasion was tested only under one condition, and other types of wear could produce significantly different results. SUMMARY Laboratory testing of three brands of newly formulated resin posterior teeth with claimed increased wear qualities and two brands of conventional teeth showed that the conventional formulations possessedgreater wear resistance to toothbrush abrasion. The weight loss of all of the teeth tested was negligible (clinically insignificant), however, and did not indicate the superiority of any one brand or formulation over another. Toothbrush abrasion need not be a factor to be considered in the selection of a posterior tooth mold for the brands tested. REFERENCES 1. Dentists’ desk reference: Materials, instruments and equipment. 2nd ed. Chicago: American Dental Association, 1983:177-g. 2. Khan Z, Morris JC, van Fraunhofer JA. Wear of anatomic acrylic resin denture teeth. J PROSTHET DENT 1985,53:550-l. 3. Trubyte Bioform IPN product brochure 38063, Dentsply International, York, Pa., 1990. 4. Smith RA. Research aspects of a new tooth material. Student Clinicians Am Dent Assoc J 1981;1:22. 5. Ogle RE, David L-J, Ortman HR. Clinical wear study of a new tooth material. Part II. J PROSTHET DENT 19&5;54:67-75. 6. Michl RJ. Isosit-a new dental material. Quintessence Int 197&&l-5. 7. van Fraunhofer JA, Razavi R, Khan 2. Wear characteristics of highstrength denture teeth. J PROSTHET DENT 198&59:173-5. 8. de Gee AJ, Werner A, Davidson CL. Abrasion of several artificial prostheses-elements. Amsterdam, The Netherlands; Department of Clinical Materials Science, University of Amsterdam, 1989. 9. Phillips RW, Swartz ML. Effects of diameter of nylon bristles on enamel surface. J Am Dent Assoc 1953;47:20-6. 10. Kafalias MC, Swartz ML, Phillips RW. Physical properties of selected dental resins. Part I. J PROSTHET DENT 1963;13:1087-107.
Reprint requeststo: DR. SHELDON WINKLER TEMPLE UNIVERSITY SCHOOL OF DENTISTRY PHILADELPHIA, PA 19140
JUNE
1992
VOLUME
67
NUMBER
6
