| Abstract|| |
Background: Implant success and survival rate ranges from 93% to 97%; however, failures are not very uncommon. These failures can be caused due to a variety of reasons out of which increased heat during drilling of osteotomies is a major contributor.Aim: The aim of this study was to develop a new generation diamond-coated drill and compare the thermal changes between commercially available drills and the experimental diamond coated drill during implant site preparation in artificial bone. Material and Methods: Three types of drills were selected for the study; Group A (Carbide), Group B (Stainless Steel), and Group C (Experimental). A total of 60 implant site preparations were performed with all the drills in artificial bone using a surgical unit linked to a testing device, in order to standardize implant drilling procedures. Bone temperature variations were recorded when drilling at a depth of 10 mm. A constant irrigation of 50 ml/minute and drilling speed of 800 r.p.m. was maintained. Results: The mean temperature of Group A, Group B, and Group C was 35.57°C, 36.83°C and 34.23°C, respectively. The results were assessed and statistically analyzed using ANOVA test and post hoc Bonferroni test. Statistically significant higher temperatures were obtained with stainless steel drill and carbide drill when compared with the experimental diamond coated drill. (P = 0.000). Conclusions: Diamond coated osteotomy drills have shown promising results in reducing heat generation at the osteotomy. Further studies need to be conducted to maximize the potential use of diamond as components of drills in implant dentistry.
Keywords: Bone drilling, diamond, heat generation, implant drills, thermal osseonecrosis
|How to cite this article:|
Wadkar PP, Khalap S, Shetty D, Gupta A, Shetty A, Dharmadhikari S. A novel, new generation drill coating for osteotomy site preparation. Indian J Dent Res 2019;30:767-71
|How to cite this URL:|
Wadkar PP, Khalap S, Shetty D, Gupta A, Shetty A, Dharmadhikari S. A novel, new generation drill coating for osteotomy site preparation. Indian J Dent Res [serial online] 2019 [cited 2020 Aug 5];30:767-71. Available from: http://www.ijdr.in/text.asp?2019/30/5/767/273439
| Introduction|| |
Implant success and failure are dynamic time linked conditions and predictability of implants with sustainable long-term function and esthetics is a challenge. Implant success and survival depends largely on the primary healing capability of alveolar bone following surgery and the establishment of osseointegration. Along with mechanical damage to the bone because of drilling procedures, there is a concomitant temperature rise in the bone adjacent to the implant site. Hyperemia, fibrosis, osteocyte degeneration, potentially increased osteoclastic activity, and necrosis are some of the complications due to thermal damage which consequently determine the implant survival.,,, Utmost care must be taken during implant bed preparation to ensure minimal change in temperature.
It has been determined that the upper threshold for bone survival during implant site preparation ranges between 44°C and 47°C, when drilling time was kept below 1 minute, The regenerative capacity of the bone was practically nonexistent at 50°C., Bone necrosis is induced if bone is exposed to temperature around 90°C even for few seconds., Most of the energy used in cutting process is dissipated into heat even if a precise drilling technique is used.,, Necrosis of the surrounding cells will always occur because of the frictional heat generated at the time of the surgery, thereby representing a significant risk for failed bone integration.
Literature has reported various techniques to reduce the amount of frictional heat generated during osteotomy preparation. Some of these are the use of sharp drills at slow rotational speeds,, use of graded series of drill sizes rather than one large drill, intermittent drilling rather than continuous drilling, drills with more efficient cutting design, and use of internal and/or external irrigation., The amount of force exerted while drilling determines the amount of wear on the drills. However, the intrinsic properties of the drill play a crucial role to ensure minimal heat generation.,,,,
Artificial bones are now widely used for research in implantology because of their favorable properties.,,,,,, Currently, implant drills are made of stainless steel alloys, stainless steel coated with titanium nitride, tungsten carbide and zirconia based ceramics. In spite of all the available drill materials and their widespread use there is still scope to reduce heat generation during drilling. Allsobrook et al. reported that tungsten carbide drills produced less heat than stainless steel drills. Oliveira et al. reported that stainless steel drills produced higher heat than zirconia based drills while Pires and colleagues reported no difference between stainless steel and alumina toughened zirconia drills. Diamond is one of the hardest and most wear resistant material known today to mankind. Its use as a drill for implantology has been limited due to the difficulties in bonding to the substrate. Various authors have been involved in the development of diamond coating technologies for potential use as drilling tools. This in vitro study uses an experimental diamond coated drill as a potential tool for osteotomy preparation and compares it with commercially available drills by studying temperature changes during osteotomy preparation.
| Materials and Methods|| |
Solid rigid polyurethane blocks (Sawbone®, Pacific Research Laboratories, Inc., Washington, USA) were used in this study to simulate the physical properties of human bone accurately. The use of artificial bones in implant related research has become popular due to their consistency and ready availability. A customized block of 20 pounds per cubic foot (pcf) trabecular bone; with 2 mm thick 30 pcf cortical bone was used in the study to simulate mandibular bone. Digital thermometer DS18B20 (Maxim, Sunnyvale, California) was used to measure the temperature rise during drilling procedures. It had an operating temperature range of -55°C to + 125°C and was accurate to ±0.5°C with a response time of 3 seconds. Four digital thermometer sensors and a data logger which showed the mean temperature of the four sensors were used to record temperature. Holes were drilled using a carbide bur to a depth of 10mm in the solid rigid polyurethane block to place the sensors [Figure 1]. Sensors were placed 2 mm away from the proposed osteotomy site to ensure no damage occurred during osteotomy site preparation. An average value of the four sensors was taken as the final reading. Condensation silicone (Speedex, Coltène/Whaledent AG, Switzerland) was placed over the holes to act as a sealant and to prevent any irrigation fluid from entering the holes, which could affect the temperature readings directly or damage the sensors. The drills used in this study were divided into 3 groups; Group A (Carbide), Group B (Stainless Steel), and Group C (Diamond coated) [Figure 2]. The drills used were a 2.0 mm diameter carbide coated drill (Group A) (Myriad, Equinox Medical Technologies B.V, Holland); 2.0 mm diameter stainless steel drill (Group B)(Uniti, Equinox Medical Technologies B.V, Holland) and an Experimental diamond coated drill was developed by coating a 2.0 mm diameter stainless steel drill (Uniti, Equinox Medical Technologies B.V, Holland)(Group C). For the experimental drill, the stainless steel drill was coated with diamond particles using electroplating process. For this, the part of the drill which was not to be plated was masked using a self-adhesive tape. The parts requiring plating were left exposed. The prepared drill was placed in nickel plating bath in an appropriate jig. The drill was connected electrically and the jig was filled with diamond particles. After a pre-determined period, the particles were bonded to the drill. Afterwards the drill was removed from its jig and placed in the nickel bath to complete the particle bonding process. After completion of the entire process the diameter of the drill had increased by 10 μm.
|Figure 2: Drills used in the study (Group A-carbide, Group B-Stainless Steel, Group C-Diamond Coated)|
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As the design of the three drills was the same, a direct comparison could be drawn between them. A total of sixty osteotomies were prepared, twenty osteotomies with each drill [Figure 3]. In order to reduce any bias, osteotomies were randomly prepared in different locations of the block. The drilling protocol was carried out at a speed of 800 rpm and at a constant irrigation of 50 ml/min of isotonic saline solution at room temperature. All the osteotomies were prepared till a depth of 10 mm [Figure 4]. For each drill, a dynamic recording of the temperature change during the osteotomy preparation was done and the results were subjected to statistical analysis. A one-way ANOVA test and post hoc Bonferroni test were carried out.
|Figure 3: Prepared final osteotomies surrounded by the holes for temperature sensors|
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| Results|| |
The change in temperature due to the drilling procedure was recorded by the digital thermometer. The results from drilling of osteotomies with all the three drills were taken into consideration and statistically analyzed. The mean temperature of Group A (Carbide), Group B (Stainless steel), and Group C (Experimental) was 35.57°C, 36.83°C, and 34.23°C respectively [Table 1]. One-way ANOVA revealed statistically significant differences for the groups (F = 31.03 and P = 0.0). Post hoc Bonferroni test indicated a significant difference between Group A and Group B (P = 0.001), Group A and Group C (P = 0.000), and Group B and Group C (P = 0.000) [Table 2].
| Discussion|| |
Artificial bones have been used for research in implantology in various previous studies.,,,,,, Identical size, accurate morphology and low variability in density and strength are some of the advantages of these bone replicas. These features make them preferable to cadaver bone, which has high variation in its density. The effect of blood supply on heat dissipation cannot be put into perspective in this in-vitro study.
This experimental setup utilized four sensors. Previous studies,,, reported in literature have used one or two temperature sensors. Such an experimental setup is prone to error because exact dissipation of heat into surrounding bone cannot be calculated. The same problem does not exist when four sensors are used. Also, any error in parallelism of the mounting holes or the osteotomy preparation, will not give an erroneous temperature reading because a mean of the four sensors is taken.
Diamond is one of the hardest and most wear resistant materials known to man; making it a viable option for various applications in the drilling industry. Direct deposition of diamond onto steel was hampered until a few decades ago because of the following difficulties: (a) the catalytic effect of iron in the preferential nucleation of graphite; (b) at the usually applied deposition temperature there is solubility of atomic carbon in steel; and (c) during cooling after deposition large thermal stresses are generated due to the large mismatch in the thermal expansion coefficients of diamond and steel. Use of an interlayer system between the steel substrate and the diamond coating provides a solution to the problem. Ideally, this layer structure should (1) avoid surface diffusion of iron, (2) allow for diamond nucleation, and growth on top of this surface, (3) supply a good bonding to both the diamond layer and the steel substrate, and (4) deal with the thermal stresses generated during cooling.
The thermal conductivity of the drill material plays an important role in the dissipation of heat from the osteotomy site. Greater the thermal conductivity greater amount of heat in absorbed by the drill itself and lesser amount of heat is dissipated in the surrounding bone. Thermal conductivity of carbide, stainless steel, and diamond are 84.02 W/(m.k), 16.3W/(m.k), 2200 W/(m.k), respectively. This might be the possible explanation for less heat generation by diamond coated drills as compared to the other drills. It can also be attributed to a higher resistance to wear of diamond. The standard deviation observed with the use of the diamond coated drill was significantly less than that of the other drills [Table 1]. This indicates that the drills can be used more number of times as compared to the other drills investigated.
Diamond although an excellent abrasive material, is still difficult to coat upon other substrates. This is because of the slow rate of deposition and requirement of expensive machinery, making it difficult to manufacture drills on a large scale. However, the results of this study indicate that diamond coated drills significantly reduce temperature rise while creating implant osteotomies thus opening new spheres of areas of research and development.
| Conclusion|| |
The success of endosteal implants depend on their ability to undergo uneventful primary healing. Critical precursors to healing are minimum thermal and mechanical damage to bone during implant bed preparation. Diamond coated osteotomy drills have shown promising results in reducing heat generation at the osteotomy. However, this is just an initial step in developing a new drill coating and further studies need to be conducted to maximize the potential use of diamonds as components of drills in implant dentistry.
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Conflicts of interest
There are no conflicts of interest.
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Dr. Pooja P Wadkar
201, Blossoms, Off Sir M.V Road, Opp Vishal Hall, Andheri East, Mumbai - 400 069, Maharashtra
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2]