|Year : 2019 | Volume
| Issue : 3 | Page : 350-354
An In-vitro study on thermal changes during implant drilling with different irrigation volumes
U Mercan1, M Sumer2, OA Kaya3, I Keskiner4, DG Meral1, O Erdogan1
1 Department of Oral and Maxillofacial Surgery, Okan University, Faculty of Dentistry, Istanbul, Turkey
2 Department of Oral and Maxillofacial Surgery, Ondokuz Mayis University, Faculty of Dentistry, Samsun, Turkey
3 Department of Oral and Maxillofacial Surgery, Kaya, Dental Oral and Dental Health Clinic, Izmir, Turkey
4 Department of Periodontology, Ondokuz Mayis University, Faculty of Dentistry, Samsun, Turkey
|Date of Acceptance||22-Nov-2018|
|Date of Web Publication||6-Mar-2019|
Dr. U Mercan
Department of Oral and Maxillofacial Surgery, Faculty of Dentistry, Okan University, Gulbahar Mh. Oya Sok. No: 23/A, Mecidiyekoy – Sisli, Istanbul 34394
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Objective: Irrigation with saline is one of the essential methods for reducing the heat generated during dental implant osteotomy. High irrigation volume impairs visibility of the surgical field, thus complicates the surgery. In this study, we aimed to determine the optimal irrigation volume for heat reduction during dental implant drilling. Materials and Methods: Thirty-two implant osteotomies were prepared on four fresh cow ribs. Heat generated during the final implant drilling was measured both with infrared thermography and thermocouple method. Initial and maximum temperatures were measured at four different irrigation volumes; 32, 44, 56, and 68 ml/min. Results: Both measurement methods showed that the amount of temperature rise is associated with the irrigation volume during implant drilling. There is no further decrease in temperature rise above irrigation volume of 56 ml/min. Conclusion: Saline irrigation with 56 ml/min provides sufficient heat reduction during dental implant drilling and higher irrigation volumes are not necessary.
Keywords: Heat, implant osteotomy, infrared, saline irrigation
|How to cite this article:|
Mercan U, Sumer M, Kaya O A, Keskiner I, Meral D G, Erdogan O. An In-vitro study on thermal changes during implant drilling with different irrigation volumes. Niger J Clin Pract 2019;22:350-4
|How to cite this URL:|
Mercan U, Sumer M, Kaya O A, Keskiner I, Meral D G, Erdogan O. An In-vitro study on thermal changes during implant drilling with different irrigation volumes. Niger J Clin Pract [serial online] 2019 [cited 2019 Mar 25];22:350-4. Available from: http://www.njcponline.com/text.asp?2019/22/3/350/253460
| Introduction|| |
One of the most common complications of dental implant treatment is bone loss around the implant collar, which may develop at the early or later phases of implant osseointegration. Overheating of the implant osteotomy during drilling may be a contributing factor to bone loss at early healing period. Excessive temperature caused by implant drilling would result in tissue necrosis, thereby jeopardize bone healing around dental implant. Generally, temperature above 50°C is considered to induce thermonecrosis. The amount of heat during implant site preparation can be reduced by different measures. These include lowering drilling speed, using sharp and single-use drills, using copious saline irrigation, cooling the saline solution, changing drill characteristics, and changing the drilling sequence. Saline irrigation is one of the essential measures for reducing temperature rise during drilling. The irrigation volume should be sufficient enough to reduce heat without impairing the visibility of the surgical field. The aim of this in-vitro study was to determine minimum irrigation volume, which provides sufficient heat reduction during implant drilling.
| Materials and Methods|| |
The study specimens consisted of four similar fresh cow ribs, which were selected from a local butcher shop. Ethical protocol is not required for this research. Specimens with the same cortical layer thickness (3 mm) and compatible with type II bone according to the Lekholm and Zarb  classification were selected to provide uniform experimental conditions. Eight implant sockets were prepared on each specimen and a total of 32 sockets were created. Drilling procedures were undertaken with the use of a conventional dental implant hand piece (SG20, NSK, NSK, Tochigi, Japan) that was attached to a physiodispenser (Surgic AP, NSK, Tochigi, Japan) at 1200 rpm/50 N cm speed. The drills used in the study were from a commercially available dental implant system (Nobel Parallel Conical Connection; Nobel Biocare, Gothenburg, Sweden). All experiments were performed in a climate-controlled room. The room temperature was set to 24°C. There was no direct ventilation on the working station. The specimens, saline solutions, and the working equipment were brought to the room 2 h before the experiments. The drilling protocol that was recommended by the manufacturer for creating an implant bed with 13 mm length and 4.3 mm width was applied. The distance between the centers of each implant socket was 10 mm. Specimens were divided into four groups according to the different external irrigation levels during the final drilling. The irrigation volumes were set to four different levels; first saline level: 32 ml/min, second saline level: 44 ml/min, third saline level: 56 ml/min, and fourth saline level: 68 ml/min. The temperature measurements were performed during the final drilling with both infrared thermography (IR) (Optris LS LT, Optris, Berlin, Germany) and thermocouple (TC) (model 5SRTC-TT-K-36, Omega Engineering, Manchester, UK) method. The IR thermometer had double and cross-laser for exact spot-size marking. It was stably placed at 16-mm distance from the marking point, which was made with 1-mm size roller pen on the bone surface near the implant socket [Figure 1]. For TC measurements, two TCs were inserted into 1-mm3-sized holes, which were prepared at 1 mm distance and at 3 mm depth from the margins of the implant site surface [Figure 2]. TCs were read by a four-channel, handheld data logger thermometer (model HH147, Omega Engineering, Manchester, UK). The mean values of two TC readings were registered as TC measurements. Constant, real-time temperature readings by both methods allowed determining the initial and maximum temperatures during the drilling. The differences between the initial and maximum measurements of the thermometers at different saline levels were labeled as “temperature increase” and used for comparisons. The procedures were applied by the same surgeon.
|Figure 1: Measurements were performed during the final drilling with both infrared (IR) thermography and thermocouple. L1 (light 1), PC (Computer)|
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|Figure 2: The view of the final drilled implant sites and thermocouples inserted holes on the bone|
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The methodology of the study was reviewed by an independent statistician. The statistical analysis was performed with SPSS 22.0 software (SPSS Inc., Chicago, IL, USA). Normal distribution of the data was assessed by the Shapiro–Wilk test and it was found that the data were normally distributed. The one-way ANOVA test was used to compare the groups and the Tukey Honest Significant Difference (HDS) test was used to determine the group that caused the difference. The paired sample t-test was used to evaluate repeated measures. Significance was assessed at P < 0.05 level.
| Results|| |
The results of TC and IR temperature measurements were given in [Table 1] and [Table 2]. According to both TC and IR measurements, the initial temperatures were not significantly different among four saline levels (P > 0.05). Maximum TC temperatures recorded during the drilling were significantly different among the groups (P: 0.001). Similarly, maximum IR temperatures were significantly different among the groups (P: 0.001). When the heat generated during drilling taken into consideration, TC measurements demonstrated statistically significant difference between the mean values of the temperature increases in four different saline levels (P: 0.001). The mean temperature increase at first saline level was significantly higher than the third and fourth saline levels (P: 0.004 and 0.003). The temperature increase at second saline level was significantly higher than third (P: 0.002) and fourth saline (P: 0.007) levels. There was no significant difference in temperature increase between the first and the second saline levels (P > 0.05). There was no significant difference in temperature increase between the third and fourth saline levels (P > 0.05). The IR measurements showed similar results with TC measurements and there was a statistically significant difference between the mean values of the temperature increase in four different saline levels (P: 0.001). The temperature increase at first saline level was significantly higher than second, third, and fourth saline levels (P: 0.016, 0.004, and 0.003, respectively). The temperature increase at second saline level was significantly higher than third (P: 0.005) and fourth saline (P: 0.005) levels. There was no significant difference in temperature increase between the third and fourth saline levels (P > 0.05).
|Table 1: Results of thermocouple (TC) measurements at different irrigation levels|
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|Table 2: Results of infrared (IR) measurements at different irrigation levels|
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| Discussion|| |
Heat generation has been considered one of the key factors associated with the outcomes of dental implant surgery. Eriksson and Albrektsson  showed that critical threshold temperature of over 47°C maintained for 1 min causes irreversible bone damage.
Several factors influence the amount of temperature rise during drilling. The amount of saline irrigation is one of most important factors among these. Although high irrigation volume would keep the temperature within desirable limits, it may impair the visibility of the implant drill and surgical area. The visibility of the drill is important for the surgeon as the markings on dental implant drill define the depth of the drill. In this study, we aimed to determine the sufficient irrigation volume for dental implant drilling. The results of this in-vitro study demonstrated that the temperature generated during the drilling decreases with higher saline irrigation volumes. However, no further temperature decrease occurs above irrigation volume 56 ml/min.
Numerous studies have evaluated characteristics of saline irrigation on temperature rise during implant drilling. The temperature rise can be reduced by using additional internal irrigation through a hole inside the drill. However using these relatively expensive internal irrigation systems, it was found unjustifiable as the osseous cooling provided by internal irrigation was not clinically significant. Another alteration in irrigation method is using cooled irrigation solution during drilling. Sener et al. compared temperature change without using irrigation and using saline solution at 10 and 25°C. The authors made the temperature measurements with thermoresistors, which were placed at depths of 3, 7, and 12 mm. They found that using cold irrigation solution is effective in reducing the heat during drilling and it may be applied in dense bone such as mandibular anterior region. To our best knowledge, there is only one study available in English literature, which evaluated effects of irrigation volume on heat generation during implant drilling. This study by Sindel et al. was an in-vitro study conducted on the sheep mandibles. They prepared the implant osteotomies with three irrigation amounts; no irrigation, irrigation volume 12 ml/min, and irrigation volume of 30 ml/min. The study demonstrated that the temperature rise in no-irrigation group was significantly higher than 12 and 30 ml/min groups, whereas no statistically significant difference was found between 12 and 30 ml/min irrigation groups. These results conflict with the results of our study as there was significant reduction in thermal change with irrigation volumes higher than 32 ml/min in our study. Our study suggests that 56 ml/min is the threshold irrigation volume that provides constant cooling for dental implant drilling. TC method and IR are two of the most commonly used methods for evaluating thermal changes during drilling. TC method is a direct method, which uses heat-sensitive probes connected to thermometers or computers. With TC method, it is possible to measure temperature changes at deeper locations. IR is an indirect and noninvasive method, which is based on the study of energy emitted by electromagnetic radiation. Although it is considered more accurate than the TC method, it could hide the temperature measurements in deeper layers of the implant site preparation. However, both methods are considered reliable methods for thermal evaluation of implant drilling., In the present study, we used both methods to determine temperature rise during implant drilling. Two methods were in accordance with each other and demonstrated similar changes in temperature with different irrigation volumes. We did not make comparisons between the results of two measurement methods as it was beyond the scope of this study.
There are two differences of our study from the other studies. The first difference is that we made temperature measurements only at the crestal part of the implant osteotomy. Two previous studies showed that more heat is generated at the superficial part of the implant cavity compared to deeper parts., Sumer et al. compared the heat at the different depths of the implant osteotomy and they showed the heat generated at 3 mm depth was significantly higher than other groups. According to the result of the study of Sumer et al., we tried to evaluate generated heat in 3 mm depth of the bone. In addition, the implant neck is more vulnerable to bone loss compared to deeper parts of implant cavity. Therefore, the neck part of the implant body is more critical as far as thermal damage is taken into consideration. In this study, we focused on the thermal changes at the implant neck rather than the deeper part of the osteotomy.
The second difference of our study is that we made the temperature measurements only during final drilling but not during pilot and first two twist drillings. For implant placement, bone could be drilled in a single procedure or in gradual steps. According to the sequential preparation procedure, each drilling step removes a quantity of bone from implant osteotomy site. Necrotic zone around the preparation site may be removed by next bigger drill. The heat generation by the final drill may be important to define the relation between implant and contact surface of the bone., Strbac et al. showed that independent from irrigation, 2 mm diameter twist drill causes significantly higher heat generation than 3.5, 4.3, and 5 mm diameter sequential drills. In the present study, the final drill with a diameter of 4.3 mm was preferred for the evaluation of the heat generation.
One weakness of our study is that the force applied to the bone with the hand piece was not automated and a surgeon made the drillings. Force/Pressure applied during the drilling is one of the factors that affects the heat generation. In the previous in-vitro studies, different techniques have been used to standardize the forces during osteotomy for heat evaluation.,,, In present in-vitro study, we tried to simulate the clinical operation conditions for implant site preparation. For the simulation of clinical operation condition, the implant site was prepared without using a standardized device to apply axial load. The implant beds were prepared by same surgeon for the consistency of the results.
In conclusion, the results of this in vitro suggest that amount of temperature rise is associated with the irrigation volume during implant drilling. There is no further decrease in temperature rise above irrigation volume of 56 ml/min and higher irrigation volume is not necessary during final implant drilling.
This in-vitro study was performed at Ondokuz Mayis University, Faculty of Dentistry; authors of the study are grateful to Ondokuz Mayis University for their scientific help. We thank Ebru Osmanoglu Akyol, PhD, for statistical review and analysis.
Financial support and sponsorship
Conflict of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2]
[Table 1], [Table 2]