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The Assessment of the Maximum Heat Production and Cooling Effectiveness of Three Different Drill Types (Conical vs. Cylindrical vs. Horizontal) during Implant Bed Preparation-An In Vitro Study

Authors:
  • This International Implant Foundation
  • Private Dental Practice

Abstract and Figures

The aim of this experimental study was to verify thermal diffusion differences, by measuring the maximum temperature achieved with different drill shapes. Synthetic bone blocks of type I density made from solid rigid polyurethane (PUR) foam were used to perform the drilling procedures. The experiment was conducted at three different rotation speeds: 800, 3000 and 5000 rpm. Conical drills (with and without an internal cooling hole) were compared with horizontal drills and disc drills. The temperature during drilling for implant bed preparation was estimated with the use of thermocouples and an infrared (IR) camera. The temperature during drilling with disc cutters for lateral basal implants did not exceed 33 ∘C and the temperature decreased in proportion to higher drill speed. The results indicate that the tested design is safe and will not cause bone overheating.
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applied
sciences
Article
The Assessment of the Maximum Heat Production and Cooling
Effectiveness of Three Different Drill Types (Conical vs.
Cylindrical vs. Horizontal) during Implant Bed
Preparation—An In Vitro Study
Stefan Ihde 1, Bartosz Dalewski 2and Łukasz Pałka 3, *


Citation: Ihde, S.; Dalewski, B.;
Pałka, Ł. The Assessment of the
Maximum Heat Production and
Cooling Effectiveness of Three
Different Drill Types (Conical vs.
Cylindrical vs. Horizontal) during
Implant Bed Preparation—An In
Vitro Study. Appl. Sci. 2021,11, 9961.
https://doi.org/10.3390/
app11219961
Academic Editor: Gabriele Cervino
Received: 27 September 2021
Accepted: 23 October 2021
Published: 25 October 2021
Publisher’s Note: MDPI stays neutral
with regard to jurisdictional claims in
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iations.
Copyright: © 2021 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
1Clinic for Maxillofacial Surgery, University of Belgrade, 11-000 Belgrade, Serbia; ihde1962@gmail.com
2Department of Dental Prosthetics, Pomeranian Medical University, 70-111 Szczecin, Poland;
bartosz.dalewski@pum.edu.pl
3Private Dental Practice, 68-200 ˙
Zary, Poland
*Correspondence: dr.lpalka@gmail.com
Abstract:
The aim of this experimental study was to verify thermal diffusion differences, by mea-
suring the maximum temperature achieved with different drill shapes. Synthetic bone blocks of
type I density made from solid rigid polyurethane (PUR) foam were used to perform the drilling
procedures. The experiment was conducted at three different rotation speeds: 800, 3000 and 5000 rpm.
Conical drills (with and without an internal cooling hole) were compared with horizontal drills and
disc drills. The temperature during drilling for implant bed preparation was estimated with the use
of thermocouples and an infrared (IR) camera. The temperature during drilling with disc cutters for
lateral basal implants did not exceed 33
C and the temperature decreased in proportion to higher
drill speed. The results indicate that the tested design is safe and will not cause bone overheating.
Keywords: conical drill; cylindrical drill; cutting disc; cortical bone; dental implants
1. Introduction
The impact the temperature has on the remodeling and healing processes of the bone
during implant site preparation has been extensively described in the literature [
1
]. The
shape of the drill, its design, fatigue, cooling technique, cooling material, the force applied
during drilling and the rotation speed have been considered crucial factors [
1
]. Different
temperature measuring tools have been used to analyze temperature changes including:
real time infrared thermography [
2
], type T thermocouples [
3
], type K thermocouples [
4
],
thermographic digital camera [
5
], digital thermometer [
6
], type K thermocouples and
digital thermometer [7].
Eriksson and Albrektsson [
8
] reported that the temperature generated by the drill
while preparing the implant site should not exceed 47
C for more than 1 min, as such
overheating causes irreversible osteonecrosis. Other reported factors influencing the overall
success of osseointegration are implant biocompatibility, design, surface, condition of the
host bed, surgical technique, and loading [9].
El-Kholey et al. [
10
] suggested that the number of drills used during implant bed
preparation has no significant influence on the bone temperature increase following either
conventional or simplified drilling procedure. What is more, the drilling technique (con-
tinuous versus intermittent) did not cause rise in the temperature and subsequent bone
overheating (i.e., above 47
C) [
11
]. Nevertheless, there are some techniques which utilize
bone collected from the drill as a graft material and while applying them it is recommended
not to use cooling water and a decreased drilling speed [6].
Polyurethane (PUR) foam blocks have been commonly used in experimental studies
replacing cadaver or animal bone specimens [
4
,
7
,
12
17
]. According to Schim [
18
] and
Appl. Sci. 2021,11, 9961. https://doi.org/10.3390/app11219961 https://www.mdpi.com/journal/applsci
Appl. Sci. 2021,11, 9961 2 of 10
Horn [
19
] polyurethane foam is a good alternative for human cancellous bone as it dis-
plays similar mechanical properties and may be used as a medium for implant testing.
Horak et al. [
17
] conducted experimental studies to evaluate its mechanical properties
(temperature, strain and density) and reported that it is not only suitable for mechanical
investigations but also for investigations involving surgical instruments that generate heat.
Moreover, this type of foam meets the ASTM F-1839-08 “Standard Specification for Rigid
Polyurethane Foam for Use as a Standard Material for Testing Orthopaedic Devices and
Instruments” which makes it an ideal material for comparative testing of bone screws and
other medical devices and instruments.
The aim of the present
in vitro
study was to measure and verify the maximum tem-
perature of the drills used for placing crestal and lateral basal implants, with different
drill shapes. We hypothesized that disc cutters for lateral basal implants, regardless of
their design, would not exceed the temperature of 47
C and could be safely used while
preparing the implant bed site. Therefore we aimed to evaluate disc cutters safety protocol
in terms of maintaining non-hazardous bone temperature levels.
2. Materials and Methods
Polyurethane (PUR) foam blocks (Sawbones, Vashon Island, WA, USA) used in the
present studies simulate the clinical conditions encountered during implant bed prepara-
tion. Artificial bone blocks made from solid rigid polyurethane foam (Figure 1) are similar
to human D1 bone i.e., primarily dense cortical bone according to Misch’s classification [
20
]
and offer uniform and consistent physical properties that eliminate the variability encoun-
tered when testing with human cadaver bone. For this experiment foam blocks with a
thickness of 10 mm, a width of 15 mm, a length of 15 mm, and density of 0.64 g/cm
3
(40 pounds per cubic foot = 40 pcf) were used.
Appl. Sci. 2021, 11, x FOR PEER REVIEW 2 of 10
Polyurethane (PUR) foam blocks have been commonly used in experimental studies
replacing cadaver or animal bone specimens [4,7,12–17]. According to Schim [18] and
Horn [19] polyurethane foam is a good alternative for human cancellous bone as it dis-
plays similar mechanical properties and may be used as a medium for implant testing.
Horak et al. [17] conducted experimental studies to evaluate its mechanical properties
(temperature, strain and density) and reported that it is not only suitable for mechanical
investigations but also for investigations involving surgical instruments that generate
heat. Moreover, this type of foam meets the ASTM F-1839-08 “Standard Specification for
Rigid Polyurethane Foam for Use as a Standard Material for Testing Orthopaedic Devices
and Instruments” which makes it an ideal material for comparative testing of bone screws
and other medical devices and instruments.
The aim of the present in vitro study was to measure and verify the maximum tem-
perature of the drills used for placing crestal and lateral basal implants, with different drill
shapes. We hypothesized that disc cutters for lateral basal implants, regardless of their
design, would not exceed the temperature of 47 °C and could be safely used while pre-
paring the implant bed site. Therefore we aimed to evaluate disc cutters safety protocol in
terms of maintaining non-hazardous bone temperature levels.
2. Materials and Methods
Polyurethane (PUR) foam blocks (Sawbones, Vashon Island, WA, USA) used in the
present studies simulate the clinical conditions encountered during implant bed prepara-
tion. Artificial bone blocks made from solid rigid polyurethane foam (Figure 1) are similar
to human D1 bone i.e., primarily dense cortical bone according to Misch’s classification
[20] and offer uniform and consistent physical properties that eliminate the variability
encountered when testing with human cadaver bone. For this experiment foam blocks
with a thickness of 10 mm, a width of 15 mm, a length of 15 mm, and density of 0.64 g/cm
3
(40 pounds per cubic foot = 40 pcf) were used.
Figure 1. The polyurethane (PUR) block used for drills testing.
The experiment was carried out with eight different drills from the same manufac-
turer (Ihde Dental, Gommiswald, Switzerland), i.e.:
Group 1: Conical drills with (drill 1) and without (drill 2) a hole for standard implants
with conical core.
Group 2: Cylindrical drills Ø 2.0 mm (drill 3), Ø 2.5 mm (drill 4) and with cutting disc
Ø7 mm (drill 5).
Group 3: Cutting discs Ø8 mm (drill 6), Ø9 mm (drill 7) and Ø10 mm (drill 8) as pre-
sented in Figure 2.
Figure 1. The polyurethane (PUR) block used for drills testing.
The experiment was carried out with eight different drills from the same manufacturer
(Ihde Dental, Gommiswald, Switzerland), i.e.:
Group 1: Conical drills with (drill 1) and without (drill 2) a hole for standard implants
with conical core.
Group 2: Cylindrical drills Ø 2.0 mm (drill 3), Ø 2.5 mm (drill 4) and with cutting disc
Ø7 mm (drill 5).
Group 3: Cutting discs Ø8 mm (drill 6), Ø9 mm (drill 7) and Ø10 mm (drill 8) as
presented in Figure 2.
Appl. Sci. 2021,11, 9961 3 of 10
Appl. Sci. 2021, 11, x FOR PEER REVIEW 3 of 10
Drill 1
conical drill
without a hole
Drill 2
conical
drill with
a hole
Drill 3
cylindrical
drill Ø2.5
mm
Drill 4
cylindrical
drill Ø2
mm
Drill 5
cylindrical
drill with a
cutting disc
Ø7 mm
Drill 6
cutting disc
Ø8 mm
Drill 7
cutting disc
Ø9 mm
Drill 8
cutting disc
Ø10 mm
Figure 2. Specific drills for the experimental investigation.
The experimental setup, as shown in Figure 3, consisted of the surgical drilling
machine (Implantmed, W&H, Bürmoos, Austria) fixed in a three- axis movement CNC
machine. A PUR block with thermocouples to detect the temperature changes inside the
foam was fixed on a table in the same horizontal axis as the surgical drilling machine
(drills 1 and 2) and in the same drilling direction. An IR camera (FLIR T1020, FLIR
Systems, Wilsonville, OR, USA) was mounted in front of the PUR block to record the
temperature at the cutting edge of the experimental drills while perforating the PUR
block.
Figure 3. Experimental setup: 1—Infrared (IR) camera with PC connection; 2—PUR block with
installed thermocouples connection to PC; 3—measured drill; 4—W&H surgical drilling machine;
5—drilling machine fixation and three axis movement; 6 and 7—PC for drill movement controlling
and recording data from IR camera and thermocouples.
Figure 2. Specific drills for the experimental investigation.
The experimental setup, as shown in Figure 3, consisted of the surgical drilling
machine (Implantmed, W&H, Bürmoos, Austria) fixed in a three- axis movement CNC
machine. A PUR block with thermocouples to detect the temperature changes inside the
foam was fixed on a table in the same horizontal axis as the surgical drilling machine
(
drills 1 and 2
) and in the same drilling direction. An IR camera (FLIR T1020, FLIR Systems,
Wilsonville, OR, USA) was mounted in front of the PUR block to record the temperature at
the cutting edge of the experimental drills while perforating the PUR block.
Appl. Sci. 2021, 11, x FOR PEER REVIEW 3 of 10
Drill 1
conical drill
without a hole
Drill 2
conical
drill with
a hole
Drill 3
cylindrical
drill Ø2.5
mm
Drill 4
cylindrical
drill Ø2
mm
Drill 5
cylindrical
drill with a
cutting disc
Ø7 mm
Drill 6
cutting disc
Ø8 mm
Drill 7
cutting disc
Ø9 mm
Drill 8
cutting disc
Ø10 mm
Figure 2. Specific drills for the experimental investigation.
The experimental setup, as shown in Figure 3, consisted of the surgical drilling
machine (Implantmed, W&H, Bürmoos, Austria) fixed in a three- axis movement CNC
machine. A PUR block with thermocouples to detect the temperature changes inside the
foam was fixed on a table in the same horizontal axis as the surgical drilling machine
(drills 1 and 2) and in the same drilling direction. An IR camera (FLIR T1020, FLIR
Systems, Wilsonville, OR, USA) was mounted in front of the PUR block to record the
temperature at the cutting edge of the experimental drills while perforating the PUR
block.
Figure 3. Experimental setup: 1—Infrared (IR) camera with PC connection; 2—PUR block with
installed thermocouples connection to PC; 3—measured drill; 4—W&H surgical drilling machine;
5—drilling machine fixation and three axis movement; 6 and 7—PC for drill movement controlling
and recording data from IR camera and thermocouples.
Figure 3.
Experimental setup: 1—Infrared (IR) camera with PC connection; 2—PUR block with
installed thermocouples connection to PC; 3—measured drill; 4—W&H surgical drilling machine;
5—drilling machine fixation and three axis movement; 6 and 7—PC for drill movement controlling
and recording data from IR camera and thermocouples.
Appl. Sci. 2021,11, 9961 4 of 10
In this study, a load of 2 kg was applied, in accordance with the procedures described
by Misir et al. [
21
]. For the cutting disc measurement, drills 3, 4, 5, 6, 7 and 8 were installed
in the vertical axis with the rotary function of the CNC machine, as shown in Figure 4.
In front of the PUR block the FLIR T1020HD thermal camera was mounted to record the
temperature in the cutting edge while drilling [
18
]. The experiment was done at three
different rotational speeds of 800, 3000 and 5000 rpm. Each measurement combination of
the drill type and rpm was performed only with cooling, for which the surgical drilling
machine cooling system was used with water as a cooling medium. Cooling water was
showered on the drill or cutting disc while performing experiment. Three holes were
drilled with each drill to test the samples of the polyurethane foam.
Appl. Sci. 2021, 11, x FOR PEER REVIEW 4 of 10
In this study, a load of 2 kg was applied, in accordance with the procedures described
by Misir et al. [21]. For the cutting disc measurement, drills 3, 4, 5, 6, 7 and 8 were installed
in the vertical axis with the rotary function of the CNC machine, as shown in Figure 4. In
front of the PUR block the FLIR T1020HD thermal camera was mounted to record the
temperature in the cutting edge while drilling [18]. The experiment was done at three
different rotational speeds of 800, 3000 and 5000 rpm. Each measurement combination of
the drill type and rpm was performed only with cooling, for which the surgical drilling
machine cooling system was used with water as a cooling medium. Cooling water was
showered on the drill or cutting disc while performing experiment. Three holes were
drilled with each drill to test the samples of the polyurethane foam.
Figure 4. An experimental setup: 1—IR camera with connection to PC 2—PUR block; 3vertical axis of CNC machine
with rotary function; 4—measured drill (cutting disc); 5—CNC machine with three axis movement; 6 and 7—PC for drill
movement controlling and recording data from IR camera.
Drills 1 and 2 were used in horizontal axis 2 mm/30 mm/min axial movement of a
drill (drilling) and then the load was reduced by moving the drill 1 mm back (with an
axial movement of a drill 500 mm/min). Using this interrupted drilling technique it was
possible to drill through the PUR block. According to some researchers one of the benefits
of this type of interrupted drilling protocol is lower heat production [22]. Interrupted
drilling protocol 5 mm/min was also used for drills 3, 4, 5, 6, 7 and 8 (drilling was 2 mm
by 5 mm/min and then 1 mm back by 500 mm/min).
3. Results
The data obtained from the experiments are presented in Table 1 and Figure 5. The
results of the investigation showed that drill 1 without a hole (with increasing groove
helix) generated the temperature of 38.4 °C at the speed of 800 rpm with cooling. When
the speed increased the heat production increased accordingly, but the maximum values
were still acceptable (T
3000
max = 61.5 °C and T
5000
max = 63.8 °C).
Table 1. The maximum temperature detected on the thermocouple for conical drills and cutting
discs during three revolutions. Version with cooling.
Drill Numbe
r
Type Revolutions (rpm) Maximum Temperature (°C)
1 conical
800 38.4
3000 61.5
5000 63.8
2 conical
800 N/A
3000 75.4
5000 65.5
Figure 4.
An experimental setup: 1—IR camera with connection to PC 2—PUR block; 3—vertical axis of CNC machine
with rotary function; 4—measured drill (cutting disc); 5—CNC machine with three axis movement; 6 and 7—PC for drill
movement controlling and recording data from IR camera.
Drills 1 and 2 were used in horizontal axis 2 mm/30 mm/min axial movement of
a drill (drilling) and then the load was reduced by moving the drill 1 mm back (with an
axial movement of a drill 500 mm/min). Using this interrupted drilling technique it was
possible to drill through the PUR block. According to some researchers one of the benefits
of this type of interrupted drilling protocol is lower heat production [
22
]. Interrupted
drilling protocol 5 mm/min was also used for drills 3, 4, 5, 6, 7 and 8 (drilling was 2 mm
by 5 mm/min and then 1 mm back by 500 mm/min).
3. Results
The data obtained from the experiments are presented in Table 1and Figure 5. The
results of the investigation showed that drill 1 without a hole (with increasing groove helix)
generated the temperature of 38.4
C at the speed of 800 rpm with cooling. When the speed
increased the heat production increased accordingly, but the maximum values were still
acceptable (T3000max = 61.5 C and T5000 max = 63.8 C).
On the other hand, drill 2 with a hole showed that even if the interrupted drilling
protocol was used, the temperatures were higher than those produced by drill 1. The maxi-
mum temperatures generated by the drill were T
5000
max = 75.4
C,
T3000max = 65.5 C
and
at the speed of 800 rpm the drill was completely blocked inside the PUR foam interrupting
the experiment (Figure 6).
Appl. Sci. 2021,11, 9961 5 of 10
Table 1.
The maximum temperature detected on the thermocouple for conical drills and cutting discs
during three revolutions. Version with cooling.
Drill Number Type Revolutions (rpm) Maximum
Temperature (C)
1conical
800 38.4
3000 61.5
5000 63.8
2conical
800 N/A
3000 75.4
5000 65.5
6cutting disc
800 27.4
3000 27.3
5000 26.5
7cutting disc
800 33.4
3000 29.5
5000 28.3
8cutting disc
800 33.2
3000 29.4
5000 28.3
Appl. Sci. 2021, 11, x FOR PEER REVIEW 5 of 10
7 cutting disc
800 33.4
3000 29.5
5000 28.3
8 cutting disc
800 33.2
3000 29.4
5000 28.3
Figure 5. The maximum temperature detected on the thermocouple for conical drills and cutting discs during three revo-
lutions. Version with cooling.
On the other hand, drill 2 with a hole showed that even if the interrupted drilling
protocol was used, the temperatures were higher than those produced by drill 1. The max-
imum temperatures generated by the drill were T
5000
max = 75.4 °C, T
3000
max = 65.5 °C and
at the speed of 800 rpm the drill was completely blocked inside the PUR foam interrupting
the experiment (Figure 6).
Figure 6. The experiment with conical drill #2 was interrupted when it got blocked in the PUR foam
at the speed of 800 rpm.
0
10
20
30
40
50
60
70
80
800 rpm 3000 rpm 5000 rpm
maximum detected temperature (°C)
drill # 1 drill #2 drill #6 drill #7 drill #8
Figure 5.
The maximum temperature detected on the thermocouple for conical drills and cutting discs during three
revolutions. Version with cooling.
Appl. Sci. 2021,11, 9961 6 of 10
Figure 6.
The experiment with conical drill #2 was interrupted when it got blocked in the PUR foam
at the speed of 800 rpm.
Drills 3 and 4, which are usually used to cut material in radial direction, had been
moving 5 mm/min towards a PUR block. In this case, it was shown that this experimental
setup with interrupted drilling protocol, cooling and drill speed of 3000 rpm was not
suitable for making the hole in the radial direction of the PUR foam as drill #3 fractured
and the experiment with drill #4 was stopped so that the drill would not break (Figure 7).
Appl. Sci. 2021, 11, x FOR PEER REVIEW 6 of 10
Figure 6. The experiment with conical drill #2 was interrupted when it got blocked in the PUR foam
at the speed of 800 rpm.
Drills 3 and 4, which are usually used to cut material in radial direction, had been
moving 5 mm/min towards a PUR block. In this case, it was shown that this experimental
setup with interrupted drilling protocol, cooling and drill speed of 3000 rpm was not
suitable for making the hole in the radial direction of the PUR foam as drill #3 fractured
and the experiment with drill #4 was stopped so that the drill would not break (Figure 7).
Figure 7. On the left, fractured drill 3 and on the left drill 4.
For drills with cutting discs (5, 6, 7, 8) a similar experimental setup as for drills 3 and
4 was used, as shown in Figure 3. It could have been observed that the disc-drill was self-
carrying cooling medium into the depth of the slot (Figure 8).
Drill 5 cut the PUR foam very easily but with the vertical part, which was in this case
made for radial cutting. The vertical part of this drill that is used for making the slot, did
not manage to cut the PUR foam with the 5 mm/min cutting movement and 3000 rpm
rotational speed. The drill 5 then bent and the experiment was stopped so as not to destroy
the drill.
Figure 7. On the left, fractured drill 3 and on the left drill 4.
For drills with cutting discs (5, 6, 7, 8) a similar experimental setup as for drills 3
and 4 was used, as shown in Figure 3. It could have been observed that the disc-drill was
self-carrying cooling medium into the depth of the slot (Figure 8).
Appl. Sci. 2021, 11, x FOR PEER REVIEW 6 of 10
Figure 6. The experiment with conical drill #2 was interrupted when it got blocked in the PUR foam
at the speed of 800 rpm.
Drills 3 and 4, which are usually used to cut material in radial direction, had been
moving 5 mm/min towards a PUR block. In this case, it was shown that this experimental
setup with interrupted drilling protocol, cooling and drill speed of 3000 rpm was not
suitable for making the hole in the radial direction of the PUR foam as drill #3 fractured
and the experiment with drill #4 was stopped so that the drill would not break (Figure 7).
Figure 7. On the left, fractured drill 3 and on the left drill 4.
For drills with cutting discs (5, 6, 7, 8) a similar experimental setup as for drills 3 and
4 was used, as shown in Figure 3. It could have been observed that the disc-drill was self-
carrying cooling medium into the depth of the slot (Figure 8).
Drill 5 cut the PUR foam very easily but with the vertical part, which was in this case
made for radial cutting. The vertical part of this drill that is used for making the slot, did
not manage to cut the PUR foam with the 5 mm/min cutting movement and 3000 rpm
rotational speed. The drill 5 then bent and the experiment was stopped so as not to destroy
the drill.
Figure 8.
On the left, cutting disc carrying cooling medium into the depth of the slot. On the right,
drill 5 bent at 3000 rpm.
Drill 5 cut the PUR foam very easily but with the vertical part, which was in this case
made for radial cutting. The vertical part of this drill that is used for making the slot, did
not manage to cut the PUR foam with the 5 mm/min cutting movement and 3000 rpm
rotational speed. The drill 5 then bent and the experiment was stopped so as not to destroy
the drill.
Appl. Sci. 2021,11, 9961 7 of 10
For cutting discs 6, 7, and 8 the vertical slots with 2.7 mm thickness were first milled
as shown in Figure 9a (drills number 7 and 8), and then horizontal slots were made by the
cutting discs (Figure 9b). The horizontal slots were made by interrupted drilling protocol
and with 5 mm/min horizontal cutting speed.
Appl. Sci. 2021, 11, x FOR PEER REVIEW 7 of 10
Figure 8. On the left, cutting disc carrying cooling medium into the depth of the slot. On the right,
drill 5 bent at 3000 rpm.
For cutting discs 6, 7, and 8 the vertical slots with 2.7 mm thickness were first milled
as shown in Figure 9a (drills number 7 and 8), and then horizontal slots were made by the
cutting discs (Figure 9b). The horizontal slots were made by interrupted drilling protocol
and with 5 mm/min horizontal cutting speed.
(a)
(b)
Figure 9. (a). Vertical, 2.7 mm- thick slot for cutting discs. (b). Horizontal and vertical slot from
cutting disc #6 in PUR foam.
Experiments with drills 6, 7, and 8 were made with cooling, interrupted drilling
protocol and the maximum measured temperature did not exceed 30 °C (Table 1, Figure
2).
The results obtained for axial conical drills (drills 1 and 2) with the interrupted
drilling protocol and cooling were similar to the results after drilling at one time
(uninterrupted drilling protocol), i.e., the produced heat was about 10–15% lower. With
increased rotation speed, the maximum temperatures measured by IR camera increased
for both tested drills. The drill without a hole provided better results than the drill with a
hole (2) even if the cooling medium was flowing through the drill’s hole.
Experiments with drills number 3 and 4 showed that the experimental setup with
interrupted drilling, cooling and the drill speed of 3000 rpm was not suitable for making
the slot in the radial direction in the PUR foam. Drill 3 fractured and the experiment with
drill 4 was stopped so that the drill would not break. Experiments with drills 6, 7, and 8
were made with cooling, interrupted drilling protocol and the maximum measured
temperature was below 30 °C.
4. Discussion
While preparing implant bed various factors need to be taken into consideration,
including the drills shape, drilling technique, cooling material and drilling speed and
torque, as well as the implant system used [23–26]. In some systems there is a tendency to
minimize the number of drills to simplify the procedure and lower the overall costs
[27,28]. In other systems, a large number of drills allows for safe and precise bed
preparation in risky recipients [29]. As far as the heat production is concerned, Watanabe
et al. [30] reported that maximum heat temperature without irrigation was higher than
that with irrigation, which contradicts our observations, whereas Gehrke et al. [23]
suggested that the double irrigation technique produced a significantly smaller increase
Figure 9.
(
a
). Vertical, 2.7 mm- thick slot for cutting discs. (
b
). Horizontal and vertical slot from
cutting disc #6 in PUR foam.
Experiments with drills 6, 7, and 8 were made with cooling, interrupted drilling
protocol and the maximum measured temperature did not exceed 30
C (Table 1, Figure 2).
The results obtained for axial conical drills (drills 1 and 2) with the interrupted drilling
protocol and cooling were similar to the results after drilling at one time (uninterrupted
drilling protocol), i.e., the produced heat was about 10–15% lower. With increased rotation
speed, the maximum temperatures measured by IR camera increased for both tested drills.
The drill without a hole provided better results than the drill with a hole (2) even if the
cooling medium was flowing through the drill’s hole.
Experiments with drills number 3 and 4 showed that the experimental setup with
interrupted drilling, cooling and the drill speed of 3000 rpm was not suitable for making
the slot in the radial direction in the PUR foam. Drill 3 fractured and the experiment
with drill 4 was stopped so that the drill would not break. Experiments with drills 6, 7,
and 8 were made with cooling, interrupted drilling protocol and the maximum measured
temperature was below 30 C.
4. Discussion
While preparing implant bed various factors need to be taken into consideration,
including the drill’s shape, drilling technique, cooling material and drilling speed and
torque, as well as the implant system used [
23
26
]. In some systems there is a tendency to
minimize the number of drills to simplify the procedure and lower the overall costs [
27
,
28
].
In other systems, a large number of drills allows for safe and precise bed preparation
in risky recipients [
29
]. As far as the heat production is concerned, Watanabe et al. [
30
]
reported that maximum heat temperature without irrigation was higher than that with
irrigation, which contradicts our observations, whereas Gehrke et al. [
23
] suggested that the
double irrigation technique produced a significantly smaller increase in the temperature
in the cortical bone during both continuous and intermittent drilling movement. It is
worth highlighting that while using disc drills the temperature decreased in proportion to
the increasing drilling speed, which, so far, has not been described in the literature. This
may have some clinical implications as disk implants are used in cranio-facial surgery for
epithesis anchorage in auricular and orbital regions [
31
,
32
]. Since in these regions there
Appl. Sci. 2021,11, 9961 8 of 10
is a close vicinity of anatomical structures and the bone often undergoes irradiation, high
temperature during bed preparation may be undesirable.
Gaspar et al. [
25
] showed that the effects of the bone preparation by low speed drilling
(50 rpm) without irrigation and conventional drilling (800 rpm) with irrigation are similar,
which means that both drilling techniques are successful in keeping bone cells alive. In our
study, one drill fractured during drilling and the experiment with drill 4 was stopped so
that the drill would not break. It might have been due to the fact that the PUR foam is
harder than the real bone of the mandible, or cylindrical part of these drills were not sharp
enough for radial drill cutting. In our opinion the radial movement 5 mm/min is very slow
to be performed in clinical environment while drilling into the patient’s bone.
In this study, the drill without a hole (1) provided better results than the drill with
a hole (2) even if the cooling medium was flowing throughout the hole. These results
confirm findings presented by Strbac et al. [
15
] for twist drills with 2 mm diameter and
10 mm drilling depth. They reported the lowest temperature change of 20.45
C for external
irrigation in comparison with internal irrigation where the temperature rose to 28.30
C. We
have concluded that the amount of metal-mass in the drill helps to absorb and distribute
the heat better than the through-and-through irrigation of the cutting part of the drill.
There are also numerous articles regarding the importance and differences between
simplified and conventional drilling techniques in regards to their numbers, which show
that the outcome on the bone is the same [
10
]. Jimbo et al. [
33
] evaluated the combined
effect of drilling sequence and implant diameter. It turned out that the simplified tech-
nique did not influence bone formation. What is more, studies conducted by El-Kholey
and Elkomy [
34
] showed that a simplified drilling technique generates as much heat as
the conventional one. To prove their hypothesis they used 80 implants with 2 different
diameters placed in bovine ribs.
Guazi et al. [
35
] tested implants placed in sites prepared with a simplified protocol
with one drill and multiple conventional drilling steps. Their results showed that both
drilling techniques are successful, but single-bur technique was less time consuming and
caused less pain. Additionally, Sarendranath et al. [
36
] compared simplified protocols
with conventional ones in terms of biological response. The authors concluded that the
simplified procedure provides biological outcomes comparable to those achieved following
the conventional one. El-Kholey et al. [
10
] evaluated 120 implant site preparations with
three different diameters following simplified and conventional drilling procedures and
measured the bone temperature using K-type thermocouple and a sensitive thermometer
before and after each drill was used. They concluded that there was no significant difference
in temperature increase when implants were prepared by either of methods.
5. Conclusions
Basing on the above results, we may conclude that since the temperature during
drilling with disc cutters for lateral basal implants did not exceed 33
C and, what is more,
it decreased in proportion to higher drill speed, this design is safe and will not cause bone
overheating. Thus, a high drilling speed with irrigation for disc cutters seems to be safe
protocol for lateral basal implant osteotomy site preparation.
Author Contributions: Conceptualization, S.I. and Ł.P.; methodology, S.I.; software, S.I.; validation,
S.I., Ł.P. and B.D.; formal analysis, Ł.P.; investigation, S.I.; resources, S.I.; data curation, B.D.; writing—
original draft preparation, Ł.P.; writing—review and editing, S.I., Ł.P. and B.D.; supervision, Ł.P. All
authors have read and agreed to the published version of the manuscript.
Funding: This research received no external funding.
Institutional Review Board Statement: Not applicable.
Informed Consent Statement: Not applicable.
Data Availability Statement: Data are available upon request from the corresponding author.
Conflicts of Interest: The authors declare no conflict of interest.
Appl. Sci. 2021,11, 9961 9 of 10
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