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Influence of preparation features on retention and resistance. Part I: MOD onlays
FIXED PROSTHODONTICS SECTION
OPERATIVE DENTISTRY
l
EDITORS
GORDON WILLIAM
J. CHRISTENSEN SAMUEL E. GUYER LEFKOWITZ WILLIAM F. I’. MALONE
ROBERT C. SPROULL
Influence of preparation features on retention and resistance. Part I: MOD onlays Mitsuo Kishimoto, D.D.S., D.D.Sc.,* Herbert T. Shillingburg, and Manville G. Duncanson, Jr., D.D.S., Ph.D.*** The University
of Oklahoma,
College of Dentistry,
Oklahoma
City,
Jr., D.D.S.,**
Okla.
T
he mesial-occlusal-distal (MOD) onlay is a modification of the intracoronal inlay that has been in use as long as the precision casting technique.’ This restoration is recommended for protecting tooth structure, as compared to the standing cusps of MOD intracoronal preparations.2, 3 Inlays and onlays have been the subject of several studies focusing on stress concentration and the structural integrity of the restored tooth. The MOD box preparation was reported superior to the slice preparation in limiting stress.4Also, occlusal coverage in onlays reduced stress in the remaining tooth structure,5 as did the narrower isthmus width and minimal wall taper in inlay preparations.6 The effects of isthmus width and marginal ridge integrity on coronal fracture susceptibility were also demonstrated.’ The design of an MOD onlay preparation is dictated by the condition of the tooth. The isthmus usually follows caries in the central groove of the occlusal surface. Proximal boxes are often used to eradicate caries. The role of these features in providing retention and resistance has not been examined experimentally. The designs are placed empirically without knowing the advantage for the restoration. Several studies of preparation design have reported the theoretical basis of preparation geometry in retention and resistance.s“3 Mechanical analyses have examined the variables of taperI and the combination of surface area and preparation length in retention.15 The retention of complete veneer and partial veneer restora-
Supported in part by a grant from the Kerr Mfg. Co., Romulus, Mich.
*Formerly, Instructor, Department of Fixed Prosthodontics. **Professor and Chairman, Department of Fixed Prosthodontics. ***Associate Professor and Chairman, Department of Dental Materials.
0022-3913/83/010035+05$00.50/001983
The C. V. Mosby Co.
Fig. 1. MOD onlay preparation with proximal flares only.
Fig. 2. MOD onlay preparation proximal flares.
with
isthmus and
tions has been measured,16B ” and, more recently, the resistance and retention of complete veneer and partial veneer crowns have been reported.ls This study evaluates the variables of the proximal box, isthmus, and flares in relation to the retention and resistance of MOD onlays. Retention is that property of a cast restoration that resists removal along the path of insertion of the tooth preparation, while resistance prevents dislodgement of the restoration by forces directed in an apical or oblique direction.”
THE JOURNAL OF PROSTHETIC DENTISTRY
35
KISHIMOTO,
Fig. 3.
MOD
onlay
preparation
with
SHILLINGBURG,
AND
DUNCANSON
proximal
boxes.
Fig. 4. MOD onlay preparation proximal boxes.
Table I. Retention
with
isthmus and
Table II. Resistance forces of MOD onlay
forces of MOD onlay
(in pounds)
(in pounds) design
Mean
Proximal flares Isthmus and flares Boxes Boxes and isthmus
18.3 33 55.8 80.2
Preparation
Standard deviation 8.7 5.6 4.6 13.5
AND METHODS
Test dies were made for each of four variations of cavity preparation of an MOD onlay. These were (1) flares only (Fig. l), (2) isthmus and flares (Fig. 2), (3) two proximal boxes (Fig. 3), and (4) a classic MOD onlay preparation with an isthmus and two boxes (Fig. 4). Die fabrication, pattern fabrication, and the method of testing were done according to a technique previously described.ls A master die was fabricated from an Ivorine tooth (Columbia Dentoform Corp., New York, N.Y.), starting with occlusal reduction and proximal flares. The 36
Preparation
design
Mean
Proximal flares Isthmus and flares Boxes Boxes and isthmus
349 1,021 1,035 1,140
Standard deviation 92 103 50 55
n = 10.
n = 10.
MATERIAL
Fig. 5. A, Die is inserted into assembled mold filled with acrylic. B, U-bolt is then removed and split mold disassembled to retrieve die and pattern.
flares were made to an extension that simulated the finishing flares normally placed on the proximal box of an MOD onlay preparation. They did not resemble the extent or depth of the proximal reduction recommended in the “slice cut” preparation. At this time and after each succeeding alteration in the master die, a silicone mold was made and filled with acrylic resin (Duralay, Reliance Mfg. Co., Chicago, Ill.) of thin consistency. A steel bolt 0.25 inch in diameter was embedded in each acrylic pattern. The die patterns were invested in a phosphate-bonded investment (Ceramigold, Whip-Mix Corp., Louisville, Ky.) and cast JANUARY
1983
VOLUME
49
NUMBER
1
MOD
ONLAYS
EFFECT OF PREPARATION FEATURES ON RETENTION OF M.O.D. ONLAYS
80
FEATURES
Fig. 6. Chain is attached to loop on casting to test on Instron retention by tensile removal (arrow) machine.
Fig. 8. Retention values are shown for each of four preparation designs tested (p i .Ol). EFFECT OF PREPARATION FEATURES ON RESISTANCE OF M.O.D. ONLAYS 1200
8
900
8 Ysj l-0 zz ;$
600
25 -1% a
300
34s t i? IL 0
I FEATURES
Fig. 9. Resistance values are shown for each of four preparation designs tested (p < .Ol). Fig. 7. Stylus is directed against ball bearing on occlusal surface of casting to test resistance against compressive force (arrow). Prop prevents damage to die during testing. in a nickel-chrome alloy (Gemini II, Kerr Mfg. Co., Romulus, Mich.). Patterns for onlays were fabricated of acrylic resin in a two-piece split mold made of nickel-chrome alloy and held together with a U-bolt (Fig. 5). Each pattern had a fossa on the buccal incline of the lingual cusp to accommodate a steel ball bearing to which resistance THE JOURNAL
OF PROSTHETIC
DENTISTRY
forces were applied. A 12-gauge round wax form was bent and attached to the marginal ridge areas to produce a U-shaped sprue that was left on the casting for retention testing (tensile removal). The patterns were invested in a gypsum-bonded investment (BeautyCast, Whip-Mix Corp.) and cast in a Type III gold alloy (Firmilay, J. F. Jelenko & Co., New Rochelle, N.Y.). Castings were cemented to their respective dies with zinc phosphate cement under 11 pounds seating pressure for 10 minutes, as described by Jorgensen.20 The 37
KISHIMOTO,
dies with cemented restorations were stored in 100% humidity for 24 hours before testing. The onlays were tested first for retention by applying tensile forces to the sprue on an Instron testing machine (Instron Corp., Canton, Mass.), using a crosshead speed of 0.05 inch per minute (Fig. 6). After removal, the restorations and dies were pickled in hydrochloric acid, cleaned in an ultrasonic bath for 10 minutes, and dipped in acetone. The U-shaped sprues were removed to accommodate resistance testing. The onlays were recemented and placed on the Instron machine at an angle of 45 degrees. Compressive forces were applied through a tapered stylus attached to the load cell of the Instron against a steel ball bearing in the fossa on the occlusal surface of the casting (Fig. 7). The same crosshead speed was used. Retention and resistance tests were conducted with 10 restorations for’each of the four preparation dies. RESULTS Means and standard deviations were computed for the retention and resistance values obtained from the preparation designs. The means and standard deviations for retentive forces are shown in Table I and those for resistance in Table II. Duncan’s New Multiple Range Test was done at the 1% significance level to analyze the forces of retention and resistance (Figs. 8 and 9). There were significant differences in retention forces among the four preparation designs. The classic design with an isthmus and two boxes showed the highest value, while a preparation with proximal flares only showed the lowest value. The MOD onlay with isthmus and two boxes also exhibited the highest resistance, while the preparation with only proximal flares displayed the lowest resistance. There was no significant difference in resistance between the preparation with two boxes and the preparation with an isthmus only. DISCUSSION The preparation with occlusal reduction and flares only was tested to provide a base line for the evaluation of the other design features. Because of the small surface area covered, retention was minimal. Retention increased progressively with the addition of each feature. The boxes were more retentive than the isthmus, and the combination of the two was more retentive than the boxes alone. This result is logical since the geometry becomes more complex and the surface area with the retentive features increases. The results, however, show differences that were not demonstrated in a previous study.” 38
SHILLINGBURG,
AND
DUNCANSON
The resistance produced by the baseline preparation with only occlusal reduction and flares was probably attributable to the inclined planes of the occlusal surface. The isthmus and proximal boxes were nearly equal in providing resistance of the MOD onlay preparation. Combining them produced a significant increase in resistance. It should be noted, however, that the increase was nowhere near the sum of the resistance developed by each individually. Rather, the increase in resistance found when the isthmus and boxes were used together was in the magnitude of 10% over either feature used alone. SUMMARY Four variations of an MOD onlay preparation were studied for retention and resistance. Boxes were more effective than an isthmus in increasing retention value. The combination of boxes and isthmus showed the highest retention. The combination of boxes and isthmus also exhibited the highest resistance. There was no difference in resistance between boxes and the isthmus. The illustrations were done by Mr. Robert Shackleford of the Graphic and Media Department of the University of Oklahoma Health Sciences Center.
REFERENCES 1. Black, G. V.: Operative Dentistry: The Technical Procedures in Filling Teeth, ~012. Chicago, 1908, Medico-Dental Publishing Co., p 174. 2. Ingraham, R.: The application of sound biomechanical principles in the design of inlay, amalgam, and gold foil restorations. J Am Dent Assoc 40~402, 1950. 3. Shillingburg, H. T., and Fisher, D. W;: The MOD onlay-A rational approach to a restorative problem, New Mex Dent J !21:12, 1970. 4. Craig, R. G., El-Ebrashi, M. K., Le Peak, P. J., and Peyton, F. A.: Experimental stress analysis of dental restorations. Part I: Two-dimensional photoelastic stress analysis of crowns. J PROSTHET DENT 17~292, 1967. 5. Fisher, D. W., Caputo, A. A., Shillingburg, H. T., and Duncanson, M. G.: Photoelastic analysis of inlay and onlay preparations. J PROSTHET DENT 33:47, 1975. 6. Farah, J. W., Dennison, J. B., and Powers; J. M.: Effects of design on stress distribution of intracoronal gold restorations. J Am Dent Assoc 941151, 1977. 7. Mondelli, J,, Steagall, L., Ishikiriama, A., Navarro, M. F. L., and Soares, F. B.: Fracture strength of human teeth with cavity preparations. J PROSTHET DENT 43~419, 1980. 8. Smyd, E. S.: Advanced thought in indirect inlay and fixed bridge fabrication. Part I. J Am Dent Assoc 31:759, 1944. 9. Smyd, E. S.: Advanced thought in indirect inlay and fixed bridge fabrication. Part II. J Am Dent Assoc 31:913, 1944. 10. Rosenstiel, E.: The retention of inlays and crowns as a function of geometrical form. Br Dent J 103:388, 1957. 11. Guyer, S. E.: Multiple preparations for fixed prosthodontics. J PROSTHET DENT 23~529, 1970.
12. Gilboe, D. B., and Teteruck, W. R.: Fundamentals of extra-
JANUARY
1983
VOLUME
49
NUMBER
1
MOD ONLAYS
13.
14.
15.
16. 17.
coronal tooth preparation: Part I: Retention and resistance form. J PROSTHETDENT 32:651, 1974. Hegdahl, T., and Silness, J.: Preparation areas resisting displacement of artificial crowns. J Oral Rehabil 4~201, 1977. Jorgensen, K. D.: The relationship between retention and convergence angle in cemented veneer crowns. Acta Odontol Stand 13:35, 1955. Kaufman, E. G., Coelho, D. H., and Laurence, C.: Factors influencing the retention of cemented gold castings. J PROS‘WHETDENT 11:487, 1961. Lorey, R. E., and Myers, G. E.: The retentive qualities of bridge retainers. J Am Dent .4ssoc 76:568, 1968. Reisbick, M. H., and Shillingburg, H. T.: Elect of preparation geometry on retention and resistance of cast gold restorations. Calif Dent Assoc J 3:51, 1975.
18. Potts, R. G., Shillingburg, H. T., and Duncanson, M. G.: Retention and resistance of preparations for cast restorations. J PROSTHETDENT 43:303, 1980. 19. Shillingburg, H. T., Hobo, S., and Whitsett, I,. D.: Fundamentals of Fixed Prosthodontics, ed 2. Chicago, 1981, Quintessence Publishing Co., Inc., p 79. 20. Jorgensen, K. D. Factors affecting the lilm thickness of zinc phosphate cements. Acta Odontol Stand 18:479, 1960.
Keflrzntrequt31s tot DR. HERBERT T. SHILLINGBURG, JR UNIVERSITYOF OKLAHOMA COLLEGEOF DENTISTRY P.O. Box 26901 OKLAHOhlA CITY, OK 73190
ARTICLES TO APPEAR IN FUTURE ISSUES Procompetition
health policies and the future of prosthodontics
H. L. Bailit, D.M.D.,
Ph.D., and J. E. Grasso, D.D.S., M.S.
Staining of composite and microfilled Robert L. Cooley, D.M.D.,
resin with stannous fluoride
MS., and Wayne W. Barkmeier, D.D.S., M.S.
Autogenous bone grafts for atrophic edentulous mandibles: A review of twenty patients Thomas A. Curtis, D.D.S., and William R. Ware, D.D.S.
Dense apatite ceramic (DA0 Harry W. Den&en,
implant systems: A preliminary
report
D.D.S., Ph.D., Hein A. Veldhuis, D.D.S., and Bob V. Rejda, Ph.D.
Internal derangements of the temporomandibular M. Franklin Dolwick, D.M.D.,
The dysgnathogenic
joint: Fact or fiction?
Ph.D., Richard W. Katzberg, M.D., and Clyde A. Helms, M.D.
distress syndrome
Gerald Dufour, D.D.S.
Complications
of head and neck radiation therapy and their management
R. L. Engelmeier, D.M.D.,
and G. E. King, D.D.S.
Surgical template fabrication for immediate dentures John B. Farmer, D.M.D.
A tongue-shielding
radiation stent
Terance J. Fleming, D.D.S., and Steven C. Rambach, D.D.S.
Clinical evaluation of two hundred patients with temporomandibular joint syndrome Harold Gelb, D.M.D.,
and Ira Bernstein, D.M.D.
THE JOURNAL OF PROSTHETIC DENTISTRY
39
OPERATIVE DENTISTRY
l
EDITORS
GORDON WILLIAM
J. CHRISTENSEN SAMUEL E. GUYER LEFKOWITZ WILLIAM F. I’. MALONE
ROBERT C. SPROULL
Influence of preparation features on retention and resistance. Part I: MOD onlays Mitsuo Kishimoto, D.D.S., D.D.Sc.,* Herbert T. Shillingburg, and Manville G. Duncanson, Jr., D.D.S., Ph.D.*** The University
of Oklahoma,
College of Dentistry,
Oklahoma
City,
Jr., D.D.S.,**
Okla.
T
he mesial-occlusal-distal (MOD) onlay is a modification of the intracoronal inlay that has been in use as long as the precision casting technique.’ This restoration is recommended for protecting tooth structure, as compared to the standing cusps of MOD intracoronal preparations.2, 3 Inlays and onlays have been the subject of several studies focusing on stress concentration and the structural integrity of the restored tooth. The MOD box preparation was reported superior to the slice preparation in limiting stress.4Also, occlusal coverage in onlays reduced stress in the remaining tooth structure,5 as did the narrower isthmus width and minimal wall taper in inlay preparations.6 The effects of isthmus width and marginal ridge integrity on coronal fracture susceptibility were also demonstrated.’ The design of an MOD onlay preparation is dictated by the condition of the tooth. The isthmus usually follows caries in the central groove of the occlusal surface. Proximal boxes are often used to eradicate caries. The role of these features in providing retention and resistance has not been examined experimentally. The designs are placed empirically without knowing the advantage for the restoration. Several studies of preparation design have reported the theoretical basis of preparation geometry in retention and resistance.s“3 Mechanical analyses have examined the variables of taperI and the combination of surface area and preparation length in retention.15 The retention of complete veneer and partial veneer restora-
Supported in part by a grant from the Kerr Mfg. Co., Romulus, Mich.
*Formerly, Instructor, Department of Fixed Prosthodontics. **Professor and Chairman, Department of Fixed Prosthodontics. ***Associate Professor and Chairman, Department of Dental Materials.
0022-3913/83/010035+05$00.50/001983
The C. V. Mosby Co.
Fig. 1. MOD onlay preparation with proximal flares only.
Fig. 2. MOD onlay preparation proximal flares.
with
isthmus and
tions has been measured,16B ” and, more recently, the resistance and retention of complete veneer and partial veneer crowns have been reported.ls This study evaluates the variables of the proximal box, isthmus, and flares in relation to the retention and resistance of MOD onlays. Retention is that property of a cast restoration that resists removal along the path of insertion of the tooth preparation, while resistance prevents dislodgement of the restoration by forces directed in an apical or oblique direction.”
THE JOURNAL OF PROSTHETIC DENTISTRY
35
KISHIMOTO,
Fig. 3.
MOD
onlay
preparation
with
SHILLINGBURG,
AND
DUNCANSON
proximal
boxes.
Fig. 4. MOD onlay preparation proximal boxes.
Table I. Retention
with
isthmus and
Table II. Resistance forces of MOD onlay
forces of MOD onlay
(in pounds)
(in pounds) design
Mean
Proximal flares Isthmus and flares Boxes Boxes and isthmus
18.3 33 55.8 80.2
Preparation
Standard deviation 8.7 5.6 4.6 13.5
AND METHODS
Test dies were made for each of four variations of cavity preparation of an MOD onlay. These were (1) flares only (Fig. l), (2) isthmus and flares (Fig. 2), (3) two proximal boxes (Fig. 3), and (4) a classic MOD onlay preparation with an isthmus and two boxes (Fig. 4). Die fabrication, pattern fabrication, and the method of testing were done according to a technique previously described.ls A master die was fabricated from an Ivorine tooth (Columbia Dentoform Corp., New York, N.Y.), starting with occlusal reduction and proximal flares. The 36
Preparation
design
Mean
Proximal flares Isthmus and flares Boxes Boxes and isthmus
349 1,021 1,035 1,140
Standard deviation 92 103 50 55
n = 10.
n = 10.
MATERIAL
Fig. 5. A, Die is inserted into assembled mold filled with acrylic. B, U-bolt is then removed and split mold disassembled to retrieve die and pattern.
flares were made to an extension that simulated the finishing flares normally placed on the proximal box of an MOD onlay preparation. They did not resemble the extent or depth of the proximal reduction recommended in the “slice cut” preparation. At this time and after each succeeding alteration in the master die, a silicone mold was made and filled with acrylic resin (Duralay, Reliance Mfg. Co., Chicago, Ill.) of thin consistency. A steel bolt 0.25 inch in diameter was embedded in each acrylic pattern. The die patterns were invested in a phosphate-bonded investment (Ceramigold, Whip-Mix Corp., Louisville, Ky.) and cast JANUARY
1983
VOLUME
49
NUMBER
1
MOD
ONLAYS
EFFECT OF PREPARATION FEATURES ON RETENTION OF M.O.D. ONLAYS
80
FEATURES
Fig. 6. Chain is attached to loop on casting to test on Instron retention by tensile removal (arrow) machine.
Fig. 8. Retention values are shown for each of four preparation designs tested (p i .Ol). EFFECT OF PREPARATION FEATURES ON RESISTANCE OF M.O.D. ONLAYS 1200
8
900
8 Ysj l-0 zz ;$
600
25 -1% a
300
34s t i? IL 0
I FEATURES
Fig. 9. Resistance values are shown for each of four preparation designs tested (p < .Ol). Fig. 7. Stylus is directed against ball bearing on occlusal surface of casting to test resistance against compressive force (arrow). Prop prevents damage to die during testing. in a nickel-chrome alloy (Gemini II, Kerr Mfg. Co., Romulus, Mich.). Patterns for onlays were fabricated of acrylic resin in a two-piece split mold made of nickel-chrome alloy and held together with a U-bolt (Fig. 5). Each pattern had a fossa on the buccal incline of the lingual cusp to accommodate a steel ball bearing to which resistance THE JOURNAL
OF PROSTHETIC
DENTISTRY
forces were applied. A 12-gauge round wax form was bent and attached to the marginal ridge areas to produce a U-shaped sprue that was left on the casting for retention testing (tensile removal). The patterns were invested in a gypsum-bonded investment (BeautyCast, Whip-Mix Corp.) and cast in a Type III gold alloy (Firmilay, J. F. Jelenko & Co., New Rochelle, N.Y.). Castings were cemented to their respective dies with zinc phosphate cement under 11 pounds seating pressure for 10 minutes, as described by Jorgensen.20 The 37
KISHIMOTO,
dies with cemented restorations were stored in 100% humidity for 24 hours before testing. The onlays were tested first for retention by applying tensile forces to the sprue on an Instron testing machine (Instron Corp., Canton, Mass.), using a crosshead speed of 0.05 inch per minute (Fig. 6). After removal, the restorations and dies were pickled in hydrochloric acid, cleaned in an ultrasonic bath for 10 minutes, and dipped in acetone. The U-shaped sprues were removed to accommodate resistance testing. The onlays were recemented and placed on the Instron machine at an angle of 45 degrees. Compressive forces were applied through a tapered stylus attached to the load cell of the Instron against a steel ball bearing in the fossa on the occlusal surface of the casting (Fig. 7). The same crosshead speed was used. Retention and resistance tests were conducted with 10 restorations for’each of the four preparation dies. RESULTS Means and standard deviations were computed for the retention and resistance values obtained from the preparation designs. The means and standard deviations for retentive forces are shown in Table I and those for resistance in Table II. Duncan’s New Multiple Range Test was done at the 1% significance level to analyze the forces of retention and resistance (Figs. 8 and 9). There were significant differences in retention forces among the four preparation designs. The classic design with an isthmus and two boxes showed the highest value, while a preparation with proximal flares only showed the lowest value. The MOD onlay with isthmus and two boxes also exhibited the highest resistance, while the preparation with only proximal flares displayed the lowest resistance. There was no significant difference in resistance between the preparation with two boxes and the preparation with an isthmus only. DISCUSSION The preparation with occlusal reduction and flares only was tested to provide a base line for the evaluation of the other design features. Because of the small surface area covered, retention was minimal. Retention increased progressively with the addition of each feature. The boxes were more retentive than the isthmus, and the combination of the two was more retentive than the boxes alone. This result is logical since the geometry becomes more complex and the surface area with the retentive features increases. The results, however, show differences that were not demonstrated in a previous study.” 38
SHILLINGBURG,
AND
DUNCANSON
The resistance produced by the baseline preparation with only occlusal reduction and flares was probably attributable to the inclined planes of the occlusal surface. The isthmus and proximal boxes were nearly equal in providing resistance of the MOD onlay preparation. Combining them produced a significant increase in resistance. It should be noted, however, that the increase was nowhere near the sum of the resistance developed by each individually. Rather, the increase in resistance found when the isthmus and boxes were used together was in the magnitude of 10% over either feature used alone. SUMMARY Four variations of an MOD onlay preparation were studied for retention and resistance. Boxes were more effective than an isthmus in increasing retention value. The combination of boxes and isthmus showed the highest retention. The combination of boxes and isthmus also exhibited the highest resistance. There was no difference in resistance between boxes and the isthmus. The illustrations were done by Mr. Robert Shackleford of the Graphic and Media Department of the University of Oklahoma Health Sciences Center.
REFERENCES 1. Black, G. V.: Operative Dentistry: The Technical Procedures in Filling Teeth, ~012. Chicago, 1908, Medico-Dental Publishing Co., p 174. 2. Ingraham, R.: The application of sound biomechanical principles in the design of inlay, amalgam, and gold foil restorations. J Am Dent Assoc 40~402, 1950. 3. Shillingburg, H. T., and Fisher, D. W;: The MOD onlay-A rational approach to a restorative problem, New Mex Dent J !21:12, 1970. 4. Craig, R. G., El-Ebrashi, M. K., Le Peak, P. J., and Peyton, F. A.: Experimental stress analysis of dental restorations. Part I: Two-dimensional photoelastic stress analysis of crowns. J PROSTHET DENT 17~292, 1967. 5. Fisher, D. W., Caputo, A. A., Shillingburg, H. T., and Duncanson, M. G.: Photoelastic analysis of inlay and onlay preparations. J PROSTHET DENT 33:47, 1975. 6. Farah, J. W., Dennison, J. B., and Powers; J. M.: Effects of design on stress distribution of intracoronal gold restorations. J Am Dent Assoc 941151, 1977. 7. Mondelli, J,, Steagall, L., Ishikiriama, A., Navarro, M. F. L., and Soares, F. B.: Fracture strength of human teeth with cavity preparations. J PROSTHET DENT 43~419, 1980. 8. Smyd, E. S.: Advanced thought in indirect inlay and fixed bridge fabrication. Part I. J Am Dent Assoc 31:759, 1944. 9. Smyd, E. S.: Advanced thought in indirect inlay and fixed bridge fabrication. Part II. J Am Dent Assoc 31:913, 1944. 10. Rosenstiel, E.: The retention of inlays and crowns as a function of geometrical form. Br Dent J 103:388, 1957. 11. Guyer, S. E.: Multiple preparations for fixed prosthodontics. J PROSTHET DENT 23~529, 1970.
12. Gilboe, D. B., and Teteruck, W. R.: Fundamentals of extra-
JANUARY
1983
VOLUME
49
NUMBER
1
MOD ONLAYS
13.
14.
15.
16. 17.
coronal tooth preparation: Part I: Retention and resistance form. J PROSTHETDENT 32:651, 1974. Hegdahl, T., and Silness, J.: Preparation areas resisting displacement of artificial crowns. J Oral Rehabil 4~201, 1977. Jorgensen, K. D.: The relationship between retention and convergence angle in cemented veneer crowns. Acta Odontol Stand 13:35, 1955. Kaufman, E. G., Coelho, D. H., and Laurence, C.: Factors influencing the retention of cemented gold castings. J PROS‘WHETDENT 11:487, 1961. Lorey, R. E., and Myers, G. E.: The retentive qualities of bridge retainers. J Am Dent .4ssoc 76:568, 1968. Reisbick, M. H., and Shillingburg, H. T.: Elect of preparation geometry on retention and resistance of cast gold restorations. Calif Dent Assoc J 3:51, 1975.
18. Potts, R. G., Shillingburg, H. T., and Duncanson, M. G.: Retention and resistance of preparations for cast restorations. J PROSTHETDENT 43:303, 1980. 19. Shillingburg, H. T., Hobo, S., and Whitsett, I,. D.: Fundamentals of Fixed Prosthodontics, ed 2. Chicago, 1981, Quintessence Publishing Co., Inc., p 79. 20. Jorgensen, K. D. Factors affecting the lilm thickness of zinc phosphate cements. Acta Odontol Stand 18:479, 1960.
Keflrzntrequt31s tot DR. HERBERT T. SHILLINGBURG, JR UNIVERSITYOF OKLAHOMA COLLEGEOF DENTISTRY P.O. Box 26901 OKLAHOhlA CITY, OK 73190
ARTICLES TO APPEAR IN FUTURE ISSUES Procompetition
health policies and the future of prosthodontics
H. L. Bailit, D.M.D.,
Ph.D., and J. E. Grasso, D.D.S., M.S.
Staining of composite and microfilled Robert L. Cooley, D.M.D.,
resin with stannous fluoride
MS., and Wayne W. Barkmeier, D.D.S., M.S.
Autogenous bone grafts for atrophic edentulous mandibles: A review of twenty patients Thomas A. Curtis, D.D.S., and William R. Ware, D.D.S.
Dense apatite ceramic (DA0 Harry W. Den&en,
implant systems: A preliminary
report
D.D.S., Ph.D., Hein A. Veldhuis, D.D.S., and Bob V. Rejda, Ph.D.
Internal derangements of the temporomandibular M. Franklin Dolwick, D.M.D.,
The dysgnathogenic
joint: Fact or fiction?
Ph.D., Richard W. Katzberg, M.D., and Clyde A. Helms, M.D.
distress syndrome
Gerald Dufour, D.D.S.
Complications
of head and neck radiation therapy and their management
R. L. Engelmeier, D.M.D.,
and G. E. King, D.D.S.
Surgical template fabrication for immediate dentures John B. Farmer, D.M.D.
A tongue-shielding
radiation stent
Terance J. Fleming, D.D.S., and Steven C. Rambach, D.D.S.
Clinical evaluation of two hundred patients with temporomandibular joint syndrome Harold Gelb, D.M.D.,
and Ira Bernstein, D.M.D.
THE JOURNAL OF PROSTHETIC DENTISTRY
39