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Temperature rise in teeth developed by rotating instruments
JUNE 1955
V O L U M E 50 • N UM BER 6
OF T f/F A M ER/CA tf D EJVTAl ASSOCIAT/OW
Temperature rise in teeth developed by rotating instruments
F. A. Peyton, D .Sc., A nn A rbor, M ich.
Recently various rotating instruments used to cut tooth tissue have been suffi ciently refined and improved so that many dentists are now employing rotating speeds with these instruments which pre viously were considered impractical. For many years speeds of 4,000 to 6,000 rpm were considered standard; now speeds of 10,000 to 15,000 rpm are being used routinely, with some operators employing instrument speeds of 20,000 to 30,000 rpm. Associated with increased operating speeds has been the accepted use of cool ants applied to the tooth during the cutting operation. The desirability of coolants of various types1’2 applied in different manners3,4 has been suggested for several years. Some studies have been reported of the temperature rise to be expected in the cutting instrument5 and tooth6-9 when different rotating instru ments are employed. In general, these studies have been confined to relatively slow speeds of rotation. 629
PURPOSE AND M ETHOD OF STU DY
The purpose of the investigation reported herein was to determine the temperature rise in the tooth when steel burs, carbide burs, and diamond instruments of similar dimensions were rotated at speeds over
P ro fe s s o r o f d e n t is t r y , U n iv e r s ity o f M ic h ig a n S c h o o l o f D e n t is tr y . 1. S h e r m a n , J . A . T h e v a p o r s p r a y m e th o d f o r c o n t r o l o f p a in . J . C a n a d . D . A . 13:11 J a n . 1947. 2 . L ie b e r , L e o n . T h e r m a l c o n t r o l a p p a r a t u s f o r d e n t a l d r i l l i n g . J . A . D . A . 3 3 :1 1 1 7 S e p t . I , 1946. 3 . K i l l i le a , J . F. A i r - c o n d i t i o n e d h a n d p ie c e . J . A . D . A . 3 2 :9 6 6 , A u g . I, 1945. 4 . T h o m a s , B. O . A . E ffe c tiv e n e s s o f c h i ll e d b u r s in e l i m i n a t i n g p a in . J . D . R es. 30:361 Aug. 1941. 5 . H u d s o n , D . C . , a n d S w e e n e y , W. T . T e m p e r a tu r e s d e v e lo p e d in r o t a t in g d e n t a l c u t t i n g in s tr u m e n ts . J.A. D .A . 4 8 :1 2 7 F e b . 1954. 6. P e y to n , F . A . , a n d V a u g h n , R. C . T h e r m a l c h a n g e s d e v e lo p e d d u r in g t h e c u t t i n g o f t o o t h tis s u e . F o r t. R e v . C h ic a g o D . S o c . 2 0 :9 D e c . 15, 1950. 7 . P e y to n , F. A . , a n d H e n r y , E. E . P r o b le m s o f c a v it y p r e p a r a t io n w it h m o d e r n in s tr u m e n ts . N e w Y o r k D . J . 2 2 :1 4 7 A p r i l 1952. 8 . H e n s c h e l, C . J ; H e a t im p a c t o f r e v o lv in g in s tr u m e n ts o n v i t a l d e n t in t u b u le s . J . D . R es. 22:3 23 A u g . 1943. 9 . W a ls h , J . P., a n d S y m m o n s , H . F . C o m p a r is o n o f t h e h e a t p r o d u c t io n a n d m e c h a n ic a l e f f ic i e n c y o f d i a m o n d in s tr u m e n ts , s to n e s , a n d b u rs a t 3,0 0 0 a n d 60,0 00 r p m . N e w Z e a la n d D . J . 4 5 :2 8 J a n . 1949.
630 • THE JO U R N A L O F THE A M E R IC A N DEN TA L A S S O C IA T IO N
10,000 rpm to cut tooth tissue, with the application of a water spray, air, or no coolant to the tooth during the cutting operation. Freshly extracted teeth were used and rotating speeds of between ap proximately 10,000 and 30,000 rpm were employed. The tests were conducted in a manner similar to those described in a previous report.6 Essentially, a thermo couple was inserted to the dentinoenamel junction in the tooth, and tissue was then cut away until the thermocouple was ex posed. Intermittent cutting action was employed with a two second cut followed by a one second rest. The temperature was recorded at the instant of thermo couple exposure, and was considered to approximate closely the temperature de veloped in the tooth adjacent to the area. Three types of cutting instruments were employed in this study—steel and carbide burs of the inverted cone type, no. 37, and inverted cone diamond points, no. 39. The product of one manufacturer was selected for each type of instrument. The temperature developed by these cut ting instruments was determined when both a one-half pound and a one pound force was applied to the handpiece. Cool ants were applied in the form of either an air stream, or an atomized air-water spray mixture, directed on the cutting instrument.
240
200
U J
5 »20 uj
a.
5 40 INT
00
5
10
15
20
25
30
R O T A T IN G SPE E D ( R.P.M. * 1 0 0 0 )
Fig. 1 • T e m p e r a tu r e rise w h en no c o o la n t, air or a ir-w a ter spray m ix tu re was a p p lied to to o th d u rin g cu ttin g o p era tio n
OBSERVATIONS
Figure 1 shows the temperature rise at speeds up to 30,000 rpm when no. 37 steel burs were used at one-half pound pressure to cut tooth tissue, with water spray or air coolants applied, or with no coolant employed. Each recorded value on the graph represents an average of five or more individual measurements. The broken portion of the curves on the left represent values obtained in a pre vious study7 when the same instrument was studied at slower speeds of rotation. It is important to keep in mind that all of the results obtained from this study represent the temperature rise above the normal operating condition, such as room temperature or mouth temperature. The results in Figure 1 show that when no coolant is applied there is a uniform rise in the temperature developed in the tooth with an increase in operating speed. Inasmuch as the temperature developed in the tooth is accepted as being the chief source of discomfort and tooth damage with rotating instruments, it can be seen that only at very low speeds of operation is the temperature sufficiently low to avoid damage when no coolant is em ployed. Of the two coolants studied, the water spray was most effective, giving a temperature rise of only approximately 15°F. when the steel bur was used at a half pound pressure and 30,000 rpm. The values shown in Figure 2 represent the results obtained with steel burs when employed under the same conditions as described for Figure 1, except that a pres sure of one pound was applied. From these values it can be seen that the water spray coolant is effective in keeping the temperature rise in the tooth to less than 20°F., even when heavy pressure and high speeds are employed. Air directed into the cavity during the cutting opera tion has some beneficial cooling effect as shown by results in both Figures 1 and 2. The shape of the curve (labeled no coolant) is of no importance in Figure 2.
PEYTON . . . V O L U M E 50, J U N E 1955 • 631
*3 7
S TEEL
1LB
Pr
»
BU 1
e s s u r e
!
y
A
/
/
/
A R B ID E 8 JR
37
1/2 L B . PRESSURE
NO C 00LAN r
s '
NO COOLA IT o
' /
AIR COOLA
/ AIR COOLA W A T E R (S P ? A r i COOL
______
W ATER fSP AY) COOLA JT
NT
-------R O T A T IN G
____________
^
R O TA TING SPEEO ( R.P.M. x 1 0 0 0 )
S P E E D (R.P.M. * IO O O )
F ig. 2 • T e m p e r a tu r e rise in to o th w h en bur was o p e r a te d u n d er co n d itio n s sim ilar to th ose in F ig u re 1, e x c e p t g r ea ter p ressu re was a p p lied
F ig. 3 • E ffe c t o f coola n ts on tem p er a tu r e rise in to o th w h en ca rb id e bur was e m p lo y e d w ith ligh t p ressu re at various sp eed s
Less uniform results were obtained from individual measurements when the heavy pressure was applied with no cool ant. Therefore, the average values are probably less accurate than those ob tained when coolants or less pressure were applied. The dulling action on the burs was pronounced when the one pound pressure was employed at high speeds of rotation with no coolant. In general, the temperature rise shown in Figure 2 was consistently higher for all conditions than the rise shown in Figure 1 when a half pound pressure was ap plied. At speeds of more than 10,000 rpm, a force of only a half pound or less should be applied to the handpiece for most favorable operating conditions. Figure 3 shows the average tempera ture rise obtained at different speeds of rotation when a no. 37 carbide bur was used with a half pound pressure applied to the handpiece. When no coolant was employed, the temperature rise was slightly less with carbide burs than with steel burs, as is indicated by a comparison with values shown in Figure 1. When either air or water spray coolants were employed, the temperature rise was al most the same for carbide as for steel burs.
Values in Figure 4 represent the tem perature rise that can be expected from a no. 37 carbide bur when one pound is applied to the handpiece. The greater force during cutting caused some increase in temperature rise when no coolant was used, but with water spray and air cool ants, the temperature rise was not greatly different from that observed with the carbide bur when operated at either the half or one pound pressure. The temperature rise obtained when a no. 39 diamond was employed with a half
# 37 C I
& RBI0E 6 IR
L B . P 3ESSURE
^ .
— ■o
NO COOLA T
9/
n
y
3 o-
—
—
___________
_
W ATER fSP JAY) COOI-A IT
R O T A T IN G SPEEO (R .P .M . X 1 0 0 0 )
F ig. 4 • T e m p e r a tu r e rise in to o th p r o d u c e d b y c a rb id e bu r o p e r a te d at d ifferen t sp eed s w ith o n e p o u n d p ressu re a n d d ifferen t coola n ts
632 • TH E J O U R N A L O F T H E A M E R IC A N D EN T A L A S S O C IA T IO N
R O T A T IN G
S P E E D (R.P.M.
X
1000)
R O T A T IN G S P E E D (R .P M . * 1 0 0 0 )
F ig. 5 • T e m p e r a tu r e rise d e v e lo p e d by d ia m on d p o in t o p e r a te d at va riou s sp eed s w ith a half p o u n d pressu re and variou s coola n ts
F ig. 6 • I n flu e n c e o f o n e p o u n d p ressu re on d ia m on d p o in t o p e r a te d at variou s sp eed s w ith n o c o o la n t, air o r a ir-w a ter spra y a p p lied
pound pressure is shown in Figure 5. These values were uniformly lower than those obtained with either carbide or steel burs, regardless of whether tested with water spray or air coolants or without a coolant being applied. A temperature rise of only approximately 15° F. was observed at 30,000 rpm when this dia mond instrument was operated with a water spray applied. An increase in pressure to one pound on the no. 39 diamond caused some in crease in the temperature rise observed (Fig. 6). When a water spray was ap plied, the temperature that developed in the tooth was not excessive even at speeds of over 30,000 rpm. For some unknown reason it appeared that air coolant alone applied to the diamond was not as effec tive at a one pound pressure and speeds of more than 15,000 rpm as it was on steel and carbide burs.
when cut with steel burs, carbide burs and diamond instruments operated at speeds up to approximately 30,000 rpm. Study was made of the effect of air and water spray as coolants in comparison with no coolant, and, in addition, the effect of a half pound and one pound force on the handpiece was observed. In general, the diamond instrument showed less temperature rise than was shown by the burs under all comparable conditions of study. The carbide bur gen erally caused a little less temperature rise in the tooth than the steel bur. Results indicate that a coolant is essential when operating rotating instruments at speeds of 10,000 rpm or above, and of the two coolants studied, the water spray is the most effective. When the water spray was employed, there appeared to be no dam age to the tooth from overheating at any speed of rotation of the instruments stud ied. Further studies would be desirable to determine the temperature rise devel oped by other rotating instruments such as disks, wheels or other burs with the same and other coolants applied.
SUM M ARY
Investigations have been made of the temperature that developed in teeth
V O L U M E 50 • N UM BER 6
OF T f/F A M ER/CA tf D EJVTAl ASSOCIAT/OW
Temperature rise in teeth developed by rotating instruments
F. A. Peyton, D .Sc., A nn A rbor, M ich.
Recently various rotating instruments used to cut tooth tissue have been suffi ciently refined and improved so that many dentists are now employing rotating speeds with these instruments which pre viously were considered impractical. For many years speeds of 4,000 to 6,000 rpm were considered standard; now speeds of 10,000 to 15,000 rpm are being used routinely, with some operators employing instrument speeds of 20,000 to 30,000 rpm. Associated with increased operating speeds has been the accepted use of cool ants applied to the tooth during the cutting operation. The desirability of coolants of various types1’2 applied in different manners3,4 has been suggested for several years. Some studies have been reported of the temperature rise to be expected in the cutting instrument5 and tooth6-9 when different rotating instru ments are employed. In general, these studies have been confined to relatively slow speeds of rotation. 629
PURPOSE AND M ETHOD OF STU DY
The purpose of the investigation reported herein was to determine the temperature rise in the tooth when steel burs, carbide burs, and diamond instruments of similar dimensions were rotated at speeds over
P ro fe s s o r o f d e n t is t r y , U n iv e r s ity o f M ic h ig a n S c h o o l o f D e n t is tr y . 1. S h e r m a n , J . A . T h e v a p o r s p r a y m e th o d f o r c o n t r o l o f p a in . J . C a n a d . D . A . 13:11 J a n . 1947. 2 . L ie b e r , L e o n . T h e r m a l c o n t r o l a p p a r a t u s f o r d e n t a l d r i l l i n g . J . A . D . A . 3 3 :1 1 1 7 S e p t . I , 1946. 3 . K i l l i le a , J . F. A i r - c o n d i t i o n e d h a n d p ie c e . J . A . D . A . 3 2 :9 6 6 , A u g . I, 1945. 4 . T h o m a s , B. O . A . E ffe c tiv e n e s s o f c h i ll e d b u r s in e l i m i n a t i n g p a in . J . D . R es. 30:361 Aug. 1941. 5 . H u d s o n , D . C . , a n d S w e e n e y , W. T . T e m p e r a tu r e s d e v e lo p e d in r o t a t in g d e n t a l c u t t i n g in s tr u m e n ts . J.A. D .A . 4 8 :1 2 7 F e b . 1954. 6. P e y to n , F . A . , a n d V a u g h n , R. C . T h e r m a l c h a n g e s d e v e lo p e d d u r in g t h e c u t t i n g o f t o o t h tis s u e . F o r t. R e v . C h ic a g o D . S o c . 2 0 :9 D e c . 15, 1950. 7 . P e y to n , F. A . , a n d H e n r y , E. E . P r o b le m s o f c a v it y p r e p a r a t io n w it h m o d e r n in s tr u m e n ts . N e w Y o r k D . J . 2 2 :1 4 7 A p r i l 1952. 8 . H e n s c h e l, C . J ; H e a t im p a c t o f r e v o lv in g in s tr u m e n ts o n v i t a l d e n t in t u b u le s . J . D . R es. 22:3 23 A u g . 1943. 9 . W a ls h , J . P., a n d S y m m o n s , H . F . C o m p a r is o n o f t h e h e a t p r o d u c t io n a n d m e c h a n ic a l e f f ic i e n c y o f d i a m o n d in s tr u m e n ts , s to n e s , a n d b u rs a t 3,0 0 0 a n d 60,0 00 r p m . N e w Z e a la n d D . J . 4 5 :2 8 J a n . 1949.
630 • THE JO U R N A L O F THE A M E R IC A N DEN TA L A S S O C IA T IO N
10,000 rpm to cut tooth tissue, with the application of a water spray, air, or no coolant to the tooth during the cutting operation. Freshly extracted teeth were used and rotating speeds of between ap proximately 10,000 and 30,000 rpm were employed. The tests were conducted in a manner similar to those described in a previous report.6 Essentially, a thermo couple was inserted to the dentinoenamel junction in the tooth, and tissue was then cut away until the thermocouple was ex posed. Intermittent cutting action was employed with a two second cut followed by a one second rest. The temperature was recorded at the instant of thermo couple exposure, and was considered to approximate closely the temperature de veloped in the tooth adjacent to the area. Three types of cutting instruments were employed in this study—steel and carbide burs of the inverted cone type, no. 37, and inverted cone diamond points, no. 39. The product of one manufacturer was selected for each type of instrument. The temperature developed by these cut ting instruments was determined when both a one-half pound and a one pound force was applied to the handpiece. Cool ants were applied in the form of either an air stream, or an atomized air-water spray mixture, directed on the cutting instrument.
240
200
U J
5 »20 uj
a.
5 40 INT
00
5
10
15
20
25
30
R O T A T IN G SPE E D ( R.P.M. * 1 0 0 0 )
Fig. 1 • T e m p e r a tu r e rise w h en no c o o la n t, air or a ir-w a ter spray m ix tu re was a p p lied to to o th d u rin g cu ttin g o p era tio n
OBSERVATIONS
Figure 1 shows the temperature rise at speeds up to 30,000 rpm when no. 37 steel burs were used at one-half pound pressure to cut tooth tissue, with water spray or air coolants applied, or with no coolant employed. Each recorded value on the graph represents an average of five or more individual measurements. The broken portion of the curves on the left represent values obtained in a pre vious study7 when the same instrument was studied at slower speeds of rotation. It is important to keep in mind that all of the results obtained from this study represent the temperature rise above the normal operating condition, such as room temperature or mouth temperature. The results in Figure 1 show that when no coolant is applied there is a uniform rise in the temperature developed in the tooth with an increase in operating speed. Inasmuch as the temperature developed in the tooth is accepted as being the chief source of discomfort and tooth damage with rotating instruments, it can be seen that only at very low speeds of operation is the temperature sufficiently low to avoid damage when no coolant is em ployed. Of the two coolants studied, the water spray was most effective, giving a temperature rise of only approximately 15°F. when the steel bur was used at a half pound pressure and 30,000 rpm. The values shown in Figure 2 represent the results obtained with steel burs when employed under the same conditions as described for Figure 1, except that a pres sure of one pound was applied. From these values it can be seen that the water spray coolant is effective in keeping the temperature rise in the tooth to less than 20°F., even when heavy pressure and high speeds are employed. Air directed into the cavity during the cutting opera tion has some beneficial cooling effect as shown by results in both Figures 1 and 2. The shape of the curve (labeled no coolant) is of no importance in Figure 2.
PEYTON . . . V O L U M E 50, J U N E 1955 • 631
*3 7
S TEEL
1LB
Pr
»
BU 1
e s s u r e
!
y
A
/
/
/
A R B ID E 8 JR
37
1/2 L B . PRESSURE
NO C 00LAN r
s '
NO COOLA IT o
' /
AIR COOLA
/ AIR COOLA W A T E R (S P ? A r i COOL
______
W ATER fSP AY) COOLA JT
NT
-------R O T A T IN G
____________
^
R O TA TING SPEEO ( R.P.M. x 1 0 0 0 )
S P E E D (R.P.M. * IO O O )
F ig. 2 • T e m p e r a tu r e rise in to o th w h en bur was o p e r a te d u n d er co n d itio n s sim ilar to th ose in F ig u re 1, e x c e p t g r ea ter p ressu re was a p p lied
F ig. 3 • E ffe c t o f coola n ts on tem p er a tu r e rise in to o th w h en ca rb id e bur was e m p lo y e d w ith ligh t p ressu re at various sp eed s
Less uniform results were obtained from individual measurements when the heavy pressure was applied with no cool ant. Therefore, the average values are probably less accurate than those ob tained when coolants or less pressure were applied. The dulling action on the burs was pronounced when the one pound pressure was employed at high speeds of rotation with no coolant. In general, the temperature rise shown in Figure 2 was consistently higher for all conditions than the rise shown in Figure 1 when a half pound pressure was ap plied. At speeds of more than 10,000 rpm, a force of only a half pound or less should be applied to the handpiece for most favorable operating conditions. Figure 3 shows the average tempera ture rise obtained at different speeds of rotation when a no. 37 carbide bur was used with a half pound pressure applied to the handpiece. When no coolant was employed, the temperature rise was slightly less with carbide burs than with steel burs, as is indicated by a comparison with values shown in Figure 1. When either air or water spray coolants were employed, the temperature rise was al most the same for carbide as for steel burs.
Values in Figure 4 represent the tem perature rise that can be expected from a no. 37 carbide bur when one pound is applied to the handpiece. The greater force during cutting caused some increase in temperature rise when no coolant was used, but with water spray and air cool ants, the temperature rise was not greatly different from that observed with the carbide bur when operated at either the half or one pound pressure. The temperature rise obtained when a no. 39 diamond was employed with a half
# 37 C I
& RBI0E 6 IR
L B . P 3ESSURE
^ .
— ■o
NO COOLA T
9/
n
y
3 o-
—
—
___________
_
W ATER fSP JAY) COOI-A IT
R O T A T IN G SPEEO (R .P .M . X 1 0 0 0 )
F ig. 4 • T e m p e r a tu r e rise in to o th p r o d u c e d b y c a rb id e bu r o p e r a te d at d ifferen t sp eed s w ith o n e p o u n d p ressu re a n d d ifferen t coola n ts
632 • TH E J O U R N A L O F T H E A M E R IC A N D EN T A L A S S O C IA T IO N
R O T A T IN G
S P E E D (R.P.M.
X
1000)
R O T A T IN G S P E E D (R .P M . * 1 0 0 0 )
F ig. 5 • T e m p e r a tu r e rise d e v e lo p e d by d ia m on d p o in t o p e r a te d at va riou s sp eed s w ith a half p o u n d pressu re and variou s coola n ts
F ig. 6 • I n flu e n c e o f o n e p o u n d p ressu re on d ia m on d p o in t o p e r a te d at variou s sp eed s w ith n o c o o la n t, air o r a ir-w a ter spra y a p p lied
pound pressure is shown in Figure 5. These values were uniformly lower than those obtained with either carbide or steel burs, regardless of whether tested with water spray or air coolants or without a coolant being applied. A temperature rise of only approximately 15° F. was observed at 30,000 rpm when this dia mond instrument was operated with a water spray applied. An increase in pressure to one pound on the no. 39 diamond caused some in crease in the temperature rise observed (Fig. 6). When a water spray was ap plied, the temperature that developed in the tooth was not excessive even at speeds of over 30,000 rpm. For some unknown reason it appeared that air coolant alone applied to the diamond was not as effec tive at a one pound pressure and speeds of more than 15,000 rpm as it was on steel and carbide burs.
when cut with steel burs, carbide burs and diamond instruments operated at speeds up to approximately 30,000 rpm. Study was made of the effect of air and water spray as coolants in comparison with no coolant, and, in addition, the effect of a half pound and one pound force on the handpiece was observed. In general, the diamond instrument showed less temperature rise than was shown by the burs under all comparable conditions of study. The carbide bur gen erally caused a little less temperature rise in the tooth than the steel bur. Results indicate that a coolant is essential when operating rotating instruments at speeds of 10,000 rpm or above, and of the two coolants studied, the water spray is the most effective. When the water spray was employed, there appeared to be no dam age to the tooth from overheating at any speed of rotation of the instruments stud ied. Further studies would be desirable to determine the temperature rise devel oped by other rotating instruments such as disks, wheels or other burs with the same and other coolants applied.
SUM M ARY
Investigations have been made of the temperature that developed in teeth