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A histologic assessment of low-torque, ultrahigh-speed cutting technique
A histologic cutting
assessment
of low-torque,
ultrahigh-speed
technique
Alfred Schuchard, D.D.S.* University of California Scl~ool of Dentistry,
San Francisco,
Calif.
lh e pu 11 pa response to rotary cutting instruments is influenced by several factors: speed of the cutting instrument, type and size of the cutting instrument (bur or diamond), torque capability of the driving instrument, technique employed by the dentist, cooling armamentarium, and proximity to the pulp. At ultrahigh speeds, with the low-torque air turbines available, studies of rotational speed and torque indicated parameters of cutting speeds for most efficient removal of tooth structure with minimal frictional trauma.‘-” Excessive cutting pressure causes stalling, with large bites and inefficient frequency; while the reverse (low pressure) allows high rotational speed and minimal bite. Varying the bur or diamond size, bur design, and bur sharpness at compared torques can produce different cutting efficiencies with resultant varying frictional response.ls li, ; In other studies, torque capabilities of the turbines and the technique employed by the dentist were again related to cutting efficiency and frictional and vibratory responses resulting in varying pulpal responsesy-” It has been found that optimum operating technique, at ultrahigh speeds with low torque, allows efficient removal of tooth structure with short periods of instrument-tooth contact and less friction, in contrast to a technique utilizing high torque at ultrahigh and low speeds.“-I’; It has been documented that excessive heat can be transmitted to the dental pulp with resultant significant cellular damage.“-‘7 Maintenance of almost normal intrapulpal temperature can be accomplished by water or water-air spray or air and the aforementioned factors; however, the question of desiccation resulting from use of air as a coolant has not been resolved.“S-“a The clinical advantages and success of a flexible cooling armamentarium have been reported.l”, ‘(is 35 The action of any coolant at ultrahigh rotational speeds is one of cooling the entire coronal portion of the tooth.“’ Photographing at a rate of 250,000 frames per second, wherein a rotating bur and the spray can be observed in a portion of a *Professor
644
and Chairman,
Division
of Operative
Dentistry.
Volume Number
34 b
Fig. 1. One-hour normal. Remaining
Histologic
air-coolant specimen. Arrow points dentin (R.D.) = 0.5 mm. (Original
revolution, indicated that the air whirl at the site of the actual cut.‘O
created
assessment
of cutting
technique
to area of injury. Remainder magnification x40.)
by the rotating
bur precludes
645
of pulp
is
moisture
MATERIALS AND METHODS This continuing study involved 159 teeth. The cutting procedures were carried out principally by one dentist. However, specimens prepared by three other dentists are included. Contralateral, caries-free, asymptomatic premolars of individuals, 12 to 19 years of age, were used. All four quadrants were anesthetized with a local anesthetic, and the rubber dam was applied. Class II preparations were prepared with an air turbine, rotating at free-running speed of 250,000 r.p.m., and a No. 35 inverted cone bur. The preparations were cut deeper than normal, while attempting to avoid pulp exposure. In each subject, efforts were made to cut to similar depths. Two teeth in one subject were cut with an air-water spray of approximately 35 C.C. per minute, and the remaining two teeth were cut with the air stream emitted by the turbine handpiece. The completed preparations were sealed with a copal resin varnish and restored with amalgam. Teeth were surgically removed at periods of one hour and one, two, three, and four weeks. The apical thirds of the roots were removed with a fissure bur in an air turbine, and the specimens were fixed in 10 per cent buffered formalin. Decalcification was accomplished by immersing the teeth in a solution of 5 per cent nitric acid and 80 per cent alcohol. Specimens were imbedded in 50 per cent, low-viscosity nitrocellulose. Serial sections of 6 to 7 p were cut and stained with hematoxylin and eosin for examination. Sections showing the greatest pulpal response were selected for this report.
646
J. t’rosthet. December,
Schuchard
Fig. 2. Same specimen as in Fig. 1. Note which are centrally displaced. (Original Fig. 3. One-hour, magnification X400.)
Fig. 4. One-week normal. R.D. =
contralateral,
air-cooled 0.825 mm.
the separation magnification
air-water
of nuclei x40.)
from
spray specimen. R.D.
specimen. Arrow points to area (Original magnification ~40.)
Fig. 5. Same specimen as Fig. 4 showing hemorrhage, predentin. (Original magnification x400.)
the cytoplasmic
=
of injury.
odontoblastic
0.625
processes
mm. (Original
Remainder
degeneration,
Dent. 1975
of pulp
is
and irregular
FINDINGS The typical one-hour response to a preparation cut at ultrahigh speed using air coolant was disorientation and damage to the odontoblastic nuclei with separation from their cytoplasmic processes (Fig. 1) . The nuclei appeared more rounded than the typical oval shape in unaffected areas, with displacement pulpally (Fig. 2). The remainder of the pulp appeared normal. The contralateral specimen (Fig. 31 prepared cvith water spray showed essentially the same response as the tooth prepared with air coolant.
Volumr Number
34 6
Fig. 6. One-week, contralateral, nuclei and interrupted predentin
Histologic
air-water formation.
Fig. 7. Two-week air-cooled specimen (Original magnification X400.)
spray R.D.
showing
assessment
specimen = 0.87 organization
of
cutting
technique
647
showing disoriented odontoblastic mm. (Original magnification x64.) and
repair.
R.D.
=
0.94
mm.
A representative one-week response to an air coolant (Fig. 4) showed an area of hemorrhage and, proceeding apically, degeneration and disorientation of the nuclei. The irregular pattern of the predentin illustrates interruption of odontoblastic activity, and the absence of predentin deposition is attributable to the cellular injury. At greater resolution (Fig. 5)) the absence of odontoblastic nuclei is notable. The contralateral specimen prepared with water spray is shown in Fig. 6. The response, while not as severe as that with the air-coolant specimen, was comparable. Note that the preparation was not cut as deep as the air-cooled specimen. A two-week response to air-coolant cavity preparation is one of organization and repair in an otherwise normal pulp (Fig. 7). The area of early injury, characterized by disruption and disorientation of the odontoblastic nuclei, with resultant faulty and irregular production of predentin, now shows deposition. Observe the increased vascularity in the predentin area. Fig. 8 shows the contralateral response to air-water spray, which is comparable to that of the air-cooled specimen, although there was evidence of a mild inflammatory infiltrate below the repair area. The deeper penetration of the cavity preparation possibly accounted for the greater inflammatory response. The three-week air-coolant specimens (Fig. 9) and contralateral air-water spray specimens (Fig. 10) again indicated comparable recovery. While the depth of preparation was similar to that in other specimens, the over-all response was milder, demonstrating varying physiologic responses that can occur in different individuals. Four-week specimens cooled by air and air-water spray were comparable, showing well-developed areas of repair (Figs. 11 and 12). The remainder of the pulps in the dry specimens appeared to be normal.
64%
J. Prosthet. December,
Schuchard
Fig. 8. Two-week,
contralateral, magnification x65.)
(Original
Fig. 9. Three-week tion
air-cooled
specimen.
spray Recovery
specimen area.
showing R.D.
=
0.65
repair. mm.
R.D.
=
(Original
0.565
mm.
magnifica-
~64.)
Fig. 10. Three-week, mm.
air-water
Dent. 1975
(Original
contralateral, magnification X400.)
air-water
spray
specimen.
Recovery
area.
R.D.
=
0.395
DISCUSSION Earlier studies have demonstrated that, when cutting at ultrahigh speeds, intrapulpal temperature can be controlled by air-water spray or air and an atraumatic cutting technique. This study, involving contralateral teeth in individuals, indicates insignificant differences in pulpal response to wet and dry cutting. With an adequate coolant, cutting of virgin enamel produces very little pulpal response.3” However, cutting into dentin will produce a significant response. The result of altering
Volume Number
34 6
Histologic
assessment
of
cutting
technique
649
Fig. 11. Four-week air-cooled specimen showing reparative dentin. R.D. = 0.41 mm. (Original magnification x65.) Fig. 12. Four-week, contralateral, air-water spray specimen showing reparative dentin. R.D. = 0.48 mm. (Original magnification x400.)
vital hard or soft tissue is the rupturing of cell cytoplasm, producing an environment unstable for the physiologic processes of odontoblast nuclei. Structural changes occurred within the body of the nuclei which caused the process of protein denaturation.37 The scanning electron microscope study by BrHnnstrGm and Garberoglio38 showed that dentinal tubules containing cytoplasmic processes travel in irregular fashion one-fourth the length of the dentin from the pulp. The study indicated globule-like structures in the distal aspect of the tubules and postulated the presence of interstitial fluids in the tubules. Considering this, cavity depth and the number of cytoplasmic processes altered vary the response to the cutting procedure. As the remaining dentin thickness decreased, pulpal responses increased inversely.3Q, 4o Caries involving the dentin initiates a defense response within the vital hard and soft tissues of the tooth. The typical inflammatory response is in a physiologic range and is reversible until the process encroaches upon the pulp. Remaining dentin ranging from 0.8 to 1.1 mm. has been reported before the occurrence of pathologic changes.“> 42 Restorative procedures and their related heat, desiccation, and vibration have the potential for varying the pulp response when cutting unaffected tooth structure. Minimizing the accumulative pulpal trauma is possible by understanding the capabilities of the rotary equipment for efficient and effective removal of tooth structure. Conservative cavity design and the use of the rotary instruments in an intermittent “painting operation” to accepted depths are also integral parts of an atraumatic operating technique.
650
Schuchard
J, Prorthet. Dccembcr.
Dent. 1975
References 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.
11. 12. 13. 13. 1.5. 16. 17. 18.
19. 20. 21. 22. 23. 24. 25.
Semmelman, J. O., Kulp, P. R., and Kurlandsik, C.: Cutting Studies of Turbine Speed, J. Dent. Res. 40: 404-410, 1961. Schuchard, A., and Watkins, E. C.: Comparative Efficiency of Rotary Cutting Instrumerits, J. PROSTHET. DENT. 15: 908-923, 1965. Watkins, E. C.: The Cutting Effectiveness of Rotary Instruments in a Turbine Handpiece, J. PROSTHET. DENT. 24: 181-184, 1970. Greener, E. H., and Lindenmeyer, R. S.: Bur Geometry and Its Relationship to Cutting, J. Dent. Res. 47: 87-97, 1968. Ingraham, R., and Hartley, J.: High Speed Technique Evaluated, Dental Times, Sept. 15, 1968. Schuchard, A., and Watkins, E. C.: Cutting Effectiveness of Tungsten Carbide Burs and Diamond Points at Ultra-High Rotational Speeds, J. PROSTHET. DEIVT. 18: 58-65, 1967. Coeyman, C. A., and Wolford, R. E.: Cutting Effectiveness of Dental Burs With Varying Number of Flutes, Int. i\ssoc. Dent. Res. Abst. No. 357, March, 1969. Holden, G. P.: Some Observing on the Vibratory Phenomena Associated With High Speed Air Turbines and Their Transmission to Living Tissue, Br. Dent. J. 113: 265-275, 1962. Schuchard, A.: Surface Temperature Response by Use of Air Coolant in Restorative Procedures, J. Am. Dent. Assoc. 75: 1188-l 193, 1967. Schuchard, A., and Watkins, E. C.: Thermal and Histological Response to High Speed and Ultra High Speed Cutting in Tooth Structure, J. Am. Dent. Assoc. 71: 1451-1458, 1965. Zack, L., and Cohen, G.: Thermogenesis in Operative Techniques, J. PROSTHET. DEKT. 12: 977-984, 1962. Schuchard, .4., and Watkins, E. C.: Temperature Response to Increased Rotational Speeds, J. PROSTIIET. DEKT. 11: 313-317, 1961. Hartnett, J. E., and Smith, W. F.: The Production of Heat in the Dental Pulp by the Cse of an Air Turbine. J, Am. Dent. Assoc. 63: 210-214, 1961. Bhaskar, S. A., and Lilly, C. E.: Intra-Pulpal Temperature During Cavity Preparation, J. Dent. Res. 44: 644-647, 1965. Carlton, M. L., Jr., Bouschor, C. F., and Dorman, H. L.: External Heat Transfer to the Dental Pulp, Int. Assoc. Dent. Res. 41: 37, 1963. (Abst.) Schuchard, A.: Action of Water Coolants With Ultra-High Rotational Speeds, J. PROSTNET. DEXT. 12: 559-565, 1962. James, J. E., Schour, I., and Spence, J. M.: Response of the Human Dental PuIp to GuttaPercha and Cavity Preparation, J. Am. Dent. Assoc. 49: 639-650, 1954. Lisanti. J. F., and Zander. H. A.: Thermal Injury to Normal Dog Teeth: In Vivo Measltrements of Pulp Temperature Increases and Their Effect on the Pulp, J, Dent. Res. 31: 548-558, 1952. Langeland, K.: Tissue Changes in the Dental Pulp: An Experimental Histological Study, Odontol. Tidskr. 65: 239-385, 1957. Nyborg, H., and BrHnnstrGm, M.: Pulp Reaction to Heat, J. PROSTHET. DENT. 19: 605612, 1968. Langeland, K.: Pulp Reaction to Cavity Preparation and to Burns in the Dentin: A Preliminary Report, Odontol. Tidskr. 68: 463-470, 1960. Langeland, K., and Langeland, L. K.: Cutting Procedures With Minimized Trauma, J. .4m. Dent. Assoc. 76: 991-1005, 1968. Pestle, I-1. H., Lefkowitz, W., and McConnell, D.: Pulp Response to Heat, J. Dent. Res. 38: 740, 1959. (Abst.) Lefkowitz, W., Robinson, H. B. G., and Pestle, H. H.: Pulp Response to Cavity Preparation, J. PROSTHET. DENT. 8: 315-324, 1958. Swerdlow, H., and Stanley, H. R., Jr.: Reaction of the Human Dental Pulp to Cavity Preparation: Results Produced by Eight Different Operative Grinding Techniques, J. Am. Dent. Assoc. 58: 49-59, 1959.
Volume Number
26. 27. 28. 29. 30. 31. 32. 33. 34. 35.
36. 37. 38. 39. 40. 41. 42.
34 6
Histologic
assessment
of
cutting
technique
651
Zach, L., and Cohen, G.: Pulp Response to Externally Applied Heat, Oral Surg. 19: 515530, 1965. Heithersay, G. S., and Brinnstrom, M.: Observations on Heat Transmission Experiments With Dentin. I. Laboratory Study, J. Dent. Res. 42: 1140-1145, 1963. Brannstrom, M.: Dentinal and Pulpal Response. II. Application of an Air Stream to Exposed Dentin. Short Observation Period, Acta Odontol. Stand. 18: 17-28, 1960. Cotton, W. R.: Pulp Response to an Air Stream Directed Into Human Cavity Preparation, Oral Surg. 24: 78-88, 1967. Schuchard, A.: Pulpal Response at 160,000 r.p.m. Using Air Coolant, J. Calif. Dent. Assoc. 38: 26-31, 1962. Schuchard, A., and Watkins, E. C.: Pulpal Response at Conventional and Ultra High Speeds Using Air Coolant, J. So. Calif. Dent. Assoc. 31: 391-395, 1963. Cotton, W. R.: Pulpal Response to Cavity Drying, J. Dent. Child. 38: 85-92, 1971. Hamilton, I. A., and Kramer, I.: Cavity Preparation With and Without Waterspray, Br. Dent. J. 123: 281-285, 1967. Dachi, S. F., and Stigers, W. R.: Pulpal Effect of Water and Air Coolants Used in High Speed Cavity Preparations, J. Am. Dent. Assoc. 76: 95-98, 1968. Bouschor, C. F., and Matthews, J. L.: A Four Year Clinical Study of Teeth Restored After Preparation With an Air Turbine Handpiece With an Air Coolant, J. PROSTHET. DENT. 16: 306-309, 1966. Schuchard, A., and Reed, 0. M.: Pulpal Response to Pin Placement, J. PROSTHET. DENT. 29: 292-300, 1973. Searls, J. C.: Light and Electron Microscope Evaluation of Changes Involved in Odontoblasts of the Rat Incisor by the High Speed Drill, J. Dent. Res. 46: 1344-1355, 1967. Brlnnstrijm, M., and Garberoglio, R.: The Dentinal Tubules and the Odontoblast Processes: A Scanning Electron Microscopic Study, Acta Odontol. Stand. 30: 291-311, 1972. Tylman, S., Spence, J. M., Weiss, M. B., and Massler, M.: Pulpal Response Under Extracoronal and Intracoronal Preparations, J. Dent. Res. 37: 984, 1958. (Abst.) Stanley, J. R., Jr.: Traumatic Capacity of High Speed and Ultra Sonic Dental Instrumentation, J. Am. Dent. Assoc. 63: 749-766, 1961. Reeves, R., and Stanley, H. R.: The Relationship of Bacterial Penetration and Pulpal Pathosis in Carious Teeth, Oral Surg. 22: 59-65, 1966. Shovelton, D. S.: A Study of Deep Carious Dentine, Int. Dent. J. 18: 392-405, 1968. UNIVERSITY
OF CALIFORNIA
SCHOOL OF DENTISTRY SAN FRANCISCO, CALIF.
ARTICLES Muscle-formed J. F. Walsh,
94143
TO APPEAR IN FUTURE ISSUES complete
mandibular
F.D.S.,
R.C.P.S.(Glas.),
B.D.S.,
A method for the control of Jay F. Watson, D.D.S., and Robert Temporomandibular Lawrence A. Weinberg,
joint D.D.S.,
dentures and T. Walsh,
galvanism B. Wolcott,
function M.S.
and
M.B.I.S.T.
D.D.S. its
effect
on
concepts
of
occlusion
assessment
of low-torque,
ultrahigh-speed
technique
Alfred Schuchard, D.D.S.* University of California Scl~ool of Dentistry,
San Francisco,
Calif.
lh e pu 11 pa response to rotary cutting instruments is influenced by several factors: speed of the cutting instrument, type and size of the cutting instrument (bur or diamond), torque capability of the driving instrument, technique employed by the dentist, cooling armamentarium, and proximity to the pulp. At ultrahigh speeds, with the low-torque air turbines available, studies of rotational speed and torque indicated parameters of cutting speeds for most efficient removal of tooth structure with minimal frictional trauma.‘-” Excessive cutting pressure causes stalling, with large bites and inefficient frequency; while the reverse (low pressure) allows high rotational speed and minimal bite. Varying the bur or diamond size, bur design, and bur sharpness at compared torques can produce different cutting efficiencies with resultant varying frictional response.ls li, ; In other studies, torque capabilities of the turbines and the technique employed by the dentist were again related to cutting efficiency and frictional and vibratory responses resulting in varying pulpal responsesy-” It has been found that optimum operating technique, at ultrahigh speeds with low torque, allows efficient removal of tooth structure with short periods of instrument-tooth contact and less friction, in contrast to a technique utilizing high torque at ultrahigh and low speeds.“-I’; It has been documented that excessive heat can be transmitted to the dental pulp with resultant significant cellular damage.“-‘7 Maintenance of almost normal intrapulpal temperature can be accomplished by water or water-air spray or air and the aforementioned factors; however, the question of desiccation resulting from use of air as a coolant has not been resolved.“S-“a The clinical advantages and success of a flexible cooling armamentarium have been reported.l”, ‘(is 35 The action of any coolant at ultrahigh rotational speeds is one of cooling the entire coronal portion of the tooth.“’ Photographing at a rate of 250,000 frames per second, wherein a rotating bur and the spray can be observed in a portion of a *Professor
644
and Chairman,
Division
of Operative
Dentistry.
Volume Number
34 b
Fig. 1. One-hour normal. Remaining
Histologic
air-coolant specimen. Arrow points dentin (R.D.) = 0.5 mm. (Original
revolution, indicated that the air whirl at the site of the actual cut.‘O
created
assessment
of cutting
technique
to area of injury. Remainder magnification x40.)
by the rotating
bur precludes
645
of pulp
is
moisture
MATERIALS AND METHODS This continuing study involved 159 teeth. The cutting procedures were carried out principally by one dentist. However, specimens prepared by three other dentists are included. Contralateral, caries-free, asymptomatic premolars of individuals, 12 to 19 years of age, were used. All four quadrants were anesthetized with a local anesthetic, and the rubber dam was applied. Class II preparations were prepared with an air turbine, rotating at free-running speed of 250,000 r.p.m., and a No. 35 inverted cone bur. The preparations were cut deeper than normal, while attempting to avoid pulp exposure. In each subject, efforts were made to cut to similar depths. Two teeth in one subject were cut with an air-water spray of approximately 35 C.C. per minute, and the remaining two teeth were cut with the air stream emitted by the turbine handpiece. The completed preparations were sealed with a copal resin varnish and restored with amalgam. Teeth were surgically removed at periods of one hour and one, two, three, and four weeks. The apical thirds of the roots were removed with a fissure bur in an air turbine, and the specimens were fixed in 10 per cent buffered formalin. Decalcification was accomplished by immersing the teeth in a solution of 5 per cent nitric acid and 80 per cent alcohol. Specimens were imbedded in 50 per cent, low-viscosity nitrocellulose. Serial sections of 6 to 7 p were cut and stained with hematoxylin and eosin for examination. Sections showing the greatest pulpal response were selected for this report.
646
J. t’rosthet. December,
Schuchard
Fig. 2. Same specimen as in Fig. 1. Note which are centrally displaced. (Original Fig. 3. One-hour, magnification X400.)
Fig. 4. One-week normal. R.D. =
contralateral,
air-cooled 0.825 mm.
the separation magnification
air-water
of nuclei x40.)
from
spray specimen. R.D.
specimen. Arrow points to area (Original magnification ~40.)
Fig. 5. Same specimen as Fig. 4 showing hemorrhage, predentin. (Original magnification x400.)
the cytoplasmic
=
of injury.
odontoblastic
0.625
processes
mm. (Original
Remainder
degeneration,
Dent. 1975
of pulp
is
and irregular
FINDINGS The typical one-hour response to a preparation cut at ultrahigh speed using air coolant was disorientation and damage to the odontoblastic nuclei with separation from their cytoplasmic processes (Fig. 1) . The nuclei appeared more rounded than the typical oval shape in unaffected areas, with displacement pulpally (Fig. 2). The remainder of the pulp appeared normal. The contralateral specimen (Fig. 31 prepared cvith water spray showed essentially the same response as the tooth prepared with air coolant.
Volumr Number
34 6
Fig. 6. One-week, contralateral, nuclei and interrupted predentin
Histologic
air-water formation.
Fig. 7. Two-week air-cooled specimen (Original magnification X400.)
spray R.D.
showing
assessment
specimen = 0.87 organization
of
cutting
technique
647
showing disoriented odontoblastic mm. (Original magnification x64.) and
repair.
R.D.
=
0.94
mm.
A representative one-week response to an air coolant (Fig. 4) showed an area of hemorrhage and, proceeding apically, degeneration and disorientation of the nuclei. The irregular pattern of the predentin illustrates interruption of odontoblastic activity, and the absence of predentin deposition is attributable to the cellular injury. At greater resolution (Fig. 5)) the absence of odontoblastic nuclei is notable. The contralateral specimen prepared with water spray is shown in Fig. 6. The response, while not as severe as that with the air-coolant specimen, was comparable. Note that the preparation was not cut as deep as the air-cooled specimen. A two-week response to air-coolant cavity preparation is one of organization and repair in an otherwise normal pulp (Fig. 7). The area of early injury, characterized by disruption and disorientation of the odontoblastic nuclei, with resultant faulty and irregular production of predentin, now shows deposition. Observe the increased vascularity in the predentin area. Fig. 8 shows the contralateral response to air-water spray, which is comparable to that of the air-cooled specimen, although there was evidence of a mild inflammatory infiltrate below the repair area. The deeper penetration of the cavity preparation possibly accounted for the greater inflammatory response. The three-week air-coolant specimens (Fig. 9) and contralateral air-water spray specimens (Fig. 10) again indicated comparable recovery. While the depth of preparation was similar to that in other specimens, the over-all response was milder, demonstrating varying physiologic responses that can occur in different individuals. Four-week specimens cooled by air and air-water spray were comparable, showing well-developed areas of repair (Figs. 11 and 12). The remainder of the pulps in the dry specimens appeared to be normal.
64%
J. Prosthet. December,
Schuchard
Fig. 8. Two-week,
contralateral, magnification x65.)
(Original
Fig. 9. Three-week tion
air-cooled
specimen.
spray Recovery
specimen area.
showing R.D.
=
0.65
repair. mm.
R.D.
=
(Original
0.565
mm.
magnifica-
~64.)
Fig. 10. Three-week, mm.
air-water
Dent. 1975
(Original
contralateral, magnification X400.)
air-water
spray
specimen.
Recovery
area.
R.D.
=
0.395
DISCUSSION Earlier studies have demonstrated that, when cutting at ultrahigh speeds, intrapulpal temperature can be controlled by air-water spray or air and an atraumatic cutting technique. This study, involving contralateral teeth in individuals, indicates insignificant differences in pulpal response to wet and dry cutting. With an adequate coolant, cutting of virgin enamel produces very little pulpal response.3” However, cutting into dentin will produce a significant response. The result of altering
Volume Number
34 6
Histologic
assessment
of
cutting
technique
649
Fig. 11. Four-week air-cooled specimen showing reparative dentin. R.D. = 0.41 mm. (Original magnification x65.) Fig. 12. Four-week, contralateral, air-water spray specimen showing reparative dentin. R.D. = 0.48 mm. (Original magnification x400.)
vital hard or soft tissue is the rupturing of cell cytoplasm, producing an environment unstable for the physiologic processes of odontoblast nuclei. Structural changes occurred within the body of the nuclei which caused the process of protein denaturation.37 The scanning electron microscope study by BrHnnstrGm and Garberoglio38 showed that dentinal tubules containing cytoplasmic processes travel in irregular fashion one-fourth the length of the dentin from the pulp. The study indicated globule-like structures in the distal aspect of the tubules and postulated the presence of interstitial fluids in the tubules. Considering this, cavity depth and the number of cytoplasmic processes altered vary the response to the cutting procedure. As the remaining dentin thickness decreased, pulpal responses increased inversely.3Q, 4o Caries involving the dentin initiates a defense response within the vital hard and soft tissues of the tooth. The typical inflammatory response is in a physiologic range and is reversible until the process encroaches upon the pulp. Remaining dentin ranging from 0.8 to 1.1 mm. has been reported before the occurrence of pathologic changes.“> 42 Restorative procedures and their related heat, desiccation, and vibration have the potential for varying the pulp response when cutting unaffected tooth structure. Minimizing the accumulative pulpal trauma is possible by understanding the capabilities of the rotary equipment for efficient and effective removal of tooth structure. Conservative cavity design and the use of the rotary instruments in an intermittent “painting operation” to accepted depths are also integral parts of an atraumatic operating technique.
650
Schuchard
J, Prorthet. Dccembcr.
Dent. 1975
References 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.
11. 12. 13. 13. 1.5. 16. 17. 18.
19. 20. 21. 22. 23. 24. 25.
Semmelman, J. O., Kulp, P. R., and Kurlandsik, C.: Cutting Studies of Turbine Speed, J. Dent. Res. 40: 404-410, 1961. Schuchard, A., and Watkins, E. C.: Comparative Efficiency of Rotary Cutting Instrumerits, J. PROSTHET. DENT. 15: 908-923, 1965. Watkins, E. C.: The Cutting Effectiveness of Rotary Instruments in a Turbine Handpiece, J. PROSTHET. DENT. 24: 181-184, 1970. Greener, E. H., and Lindenmeyer, R. S.: Bur Geometry and Its Relationship to Cutting, J. Dent. Res. 47: 87-97, 1968. Ingraham, R., and Hartley, J.: High Speed Technique Evaluated, Dental Times, Sept. 15, 1968. Schuchard, A., and Watkins, E. C.: Cutting Effectiveness of Tungsten Carbide Burs and Diamond Points at Ultra-High Rotational Speeds, J. PROSTHET. DEIVT. 18: 58-65, 1967. Coeyman, C. A., and Wolford, R. E.: Cutting Effectiveness of Dental Burs With Varying Number of Flutes, Int. i\ssoc. Dent. Res. Abst. No. 357, March, 1969. Holden, G. P.: Some Observing on the Vibratory Phenomena Associated With High Speed Air Turbines and Their Transmission to Living Tissue, Br. Dent. J. 113: 265-275, 1962. Schuchard, A.: Surface Temperature Response by Use of Air Coolant in Restorative Procedures, J. Am. Dent. Assoc. 75: 1188-l 193, 1967. Schuchard, A., and Watkins, E. C.: Thermal and Histological Response to High Speed and Ultra High Speed Cutting in Tooth Structure, J. Am. Dent. Assoc. 71: 1451-1458, 1965. Zack, L., and Cohen, G.: Thermogenesis in Operative Techniques, J. PROSTHET. DEKT. 12: 977-984, 1962. Schuchard, .4., and Watkins, E. C.: Temperature Response to Increased Rotational Speeds, J. PROSTIIET. DEKT. 11: 313-317, 1961. Hartnett, J. E., and Smith, W. F.: The Production of Heat in the Dental Pulp by the Cse of an Air Turbine. J, Am. Dent. Assoc. 63: 210-214, 1961. Bhaskar, S. A., and Lilly, C. E.: Intra-Pulpal Temperature During Cavity Preparation, J. Dent. Res. 44: 644-647, 1965. Carlton, M. L., Jr., Bouschor, C. F., and Dorman, H. L.: External Heat Transfer to the Dental Pulp, Int. Assoc. Dent. Res. 41: 37, 1963. (Abst.) Schuchard, A.: Action of Water Coolants With Ultra-High Rotational Speeds, J. PROSTNET. DEXT. 12: 559-565, 1962. James, J. E., Schour, I., and Spence, J. M.: Response of the Human Dental PuIp to GuttaPercha and Cavity Preparation, J. Am. Dent. Assoc. 49: 639-650, 1954. Lisanti. J. F., and Zander. H. A.: Thermal Injury to Normal Dog Teeth: In Vivo Measltrements of Pulp Temperature Increases and Their Effect on the Pulp, J, Dent. Res. 31: 548-558, 1952. Langeland, K.: Tissue Changes in the Dental Pulp: An Experimental Histological Study, Odontol. Tidskr. 65: 239-385, 1957. Nyborg, H., and BrHnnstrGm, M.: Pulp Reaction to Heat, J. PROSTHET. DENT. 19: 605612, 1968. Langeland, K.: Pulp Reaction to Cavity Preparation and to Burns in the Dentin: A Preliminary Report, Odontol. Tidskr. 68: 463-470, 1960. Langeland, K., and Langeland, L. K.: Cutting Procedures With Minimized Trauma, J. .4m. Dent. Assoc. 76: 991-1005, 1968. Pestle, I-1. H., Lefkowitz, W., and McConnell, D.: Pulp Response to Heat, J. Dent. Res. 38: 740, 1959. (Abst.) Lefkowitz, W., Robinson, H. B. G., and Pestle, H. H.: Pulp Response to Cavity Preparation, J. PROSTHET. DENT. 8: 315-324, 1958. Swerdlow, H., and Stanley, H. R., Jr.: Reaction of the Human Dental Pulp to Cavity Preparation: Results Produced by Eight Different Operative Grinding Techniques, J. Am. Dent. Assoc. 58: 49-59, 1959.
Volume Number
26. 27. 28. 29. 30. 31. 32. 33. 34. 35.
36. 37. 38. 39. 40. 41. 42.
34 6
Histologic
assessment
of
cutting
technique
651
Zach, L., and Cohen, G.: Pulp Response to Externally Applied Heat, Oral Surg. 19: 515530, 1965. Heithersay, G. S., and Brinnstrom, M.: Observations on Heat Transmission Experiments With Dentin. I. Laboratory Study, J. Dent. Res. 42: 1140-1145, 1963. Brannstrom, M.: Dentinal and Pulpal Response. II. Application of an Air Stream to Exposed Dentin. Short Observation Period, Acta Odontol. Stand. 18: 17-28, 1960. Cotton, W. R.: Pulp Response to an Air Stream Directed Into Human Cavity Preparation, Oral Surg. 24: 78-88, 1967. Schuchard, A.: Pulpal Response at 160,000 r.p.m. Using Air Coolant, J. Calif. Dent. Assoc. 38: 26-31, 1962. Schuchard, A., and Watkins, E. C.: Pulpal Response at Conventional and Ultra High Speeds Using Air Coolant, J. So. Calif. Dent. Assoc. 31: 391-395, 1963. Cotton, W. R.: Pulpal Response to Cavity Drying, J. Dent. Child. 38: 85-92, 1971. Hamilton, I. A., and Kramer, I.: Cavity Preparation With and Without Waterspray, Br. Dent. J. 123: 281-285, 1967. Dachi, S. F., and Stigers, W. R.: Pulpal Effect of Water and Air Coolants Used in High Speed Cavity Preparations, J. Am. Dent. Assoc. 76: 95-98, 1968. Bouschor, C. F., and Matthews, J. L.: A Four Year Clinical Study of Teeth Restored After Preparation With an Air Turbine Handpiece With an Air Coolant, J. PROSTHET. DENT. 16: 306-309, 1966. Schuchard, A., and Reed, 0. M.: Pulpal Response to Pin Placement, J. PROSTHET. DENT. 29: 292-300, 1973. Searls, J. C.: Light and Electron Microscope Evaluation of Changes Involved in Odontoblasts of the Rat Incisor by the High Speed Drill, J. Dent. Res. 46: 1344-1355, 1967. Brlnnstrijm, M., and Garberoglio, R.: The Dentinal Tubules and the Odontoblast Processes: A Scanning Electron Microscopic Study, Acta Odontol. Stand. 30: 291-311, 1972. Tylman, S., Spence, J. M., Weiss, M. B., and Massler, M.: Pulpal Response Under Extracoronal and Intracoronal Preparations, J. Dent. Res. 37: 984, 1958. (Abst.) Stanley, J. R., Jr.: Traumatic Capacity of High Speed and Ultra Sonic Dental Instrumentation, J. Am. Dent. Assoc. 63: 749-766, 1961. Reeves, R., and Stanley, H. R.: The Relationship of Bacterial Penetration and Pulpal Pathosis in Carious Teeth, Oral Surg. 22: 59-65, 1966. Shovelton, D. S.: A Study of Deep Carious Dentine, Int. Dent. J. 18: 392-405, 1968. UNIVERSITY
OF CALIFORNIA
SCHOOL OF DENTISTRY SAN FRANCISCO, CALIF.
ARTICLES Muscle-formed J. F. Walsh,
94143
TO APPEAR IN FUTURE ISSUES complete
mandibular
F.D.S.,
R.C.P.S.(Glas.),
B.D.S.,
A method for the control of Jay F. Watson, D.D.S., and Robert Temporomandibular Lawrence A. Weinberg,
joint D.D.S.,
dentures and T. Walsh,
galvanism B. Wolcott,
function M.S.
and
M.B.I.S.T.
D.D.S. its
effect
on
concepts
of
occlusion