Effects of implant drill wear, irrigation, and drill materials on heat generation in osteotomy sites

The Effect of Dental Implant Drills Materials on Heat Generation in Osteotomy Sites: A Systematic Review

The aim of this review was to examine the impact of dental implant drill materials and wear profiles on heat generation in the osteotomy sites as reported in experimental studies and to critically appraise these studies. The research question was formulated based on predefined patient, intervention, comparison, and outcome (PICO) elements. A comprehensive electronic search was undertaken in Medline/PubMed Central, Science Direct, and Google Scholar, using predetermined keywords, followed by a manual search of the bibliography of the selected articles. The selection of the studies for the critical appraisal part of our study was based on the criteria used to assess the study designs such as study aims, outcome measure, clarity of method, sample selection, randomization, allocation concealment, sample attrition, bias, method of data analysis, and external validity. Increased heat generation was observed with both ceramic and metal drills; the heat generation was proportional to drills' wear. The literature was inconclusive regarding the association between drill material and heat generation. However, drill materials had a significant influence on the overall temperature increase during osteotomy. The noncoated drills showed a higher wear resistance, and it has been observed that using worn drills leads to more friction contact, reduced drill cutting efficiency, and increased heat generation. Eleven in vitro studies met the inclusion criteria, and showed a considerable methodological heterogeneity and confounding factors, including drill geometry, speed and load, depth and diameter, number of uses, irrigation protocol, study specimens, and the heat measuring device. Besides, most of the studies have a potential operator and assessor bias, and some have sponsorship bias. It is possible to conclude that the literature is not conclusive on the effect of drill materials on heat generation during osteotomy. Lack of standardization and uniformity in the study design, along with potential bias in the study methodology can be the reason for the heterogeneity of the results.

Comparison of the physical, thermal, and biological effects on implant bone site when using either zirconia or stainless-steel drill for implant bone site preparation

BACKGROUND/PURPOSE

Zirconia has been a popular material in dental implantology with good biocompatibility. But few research focused on its application in implant drills. This study aimed to investigate the physical, thermal, and biological effects on using the zirconia and stainless-steel drills for implant bone site preparation.

METHODS

We performed a series of experiments to evaluate the physical wearing properties of zirconia and stainless-steel drills of identical diameter and similar shape. During the implant site preparation thermal test, we subjected both drills onto a resin-embedded bone, utilizing a thermal couple device without irrigation. Moreover, we conducted a cell study by collecting bone cells in vivo while preparing the implant site with both tested drills. The cell activity was evaluated through cell proliferation colorimetric analysis (XTT) and alkaline phosphatase (ALP) activity measurements.

RESULTS

The zirconia drill outperforms the stainless-steel drill in terms of requiring less force, maintaining stability over repeated cutting tests, and generating lower temperatures during drilling (stainless-steel drill: 45.48 ± 1.31 °C; zirconia-coated drill: 32.98 ± 1.21 °C, P = 0.000247). Meanwhile, both types of drills show similar results in XTT colorimetric analysis and ALP activity test.

CONCLUSION

The thermal effect study is more favorable for using the zirconia drill than the stainless-steel drill for bone preparation. Cytological analysis indicate that the zirconia drill produces a similar impact on bone cells activity as the stainless-steel drill. Therefore, we conclude that the zirconia drills offer a good cutting effect similar to currently available stainless-steel drills in various aspects.

Steel drills versus zirconia drills on heat generation at the surgical site of dental implants: A systematic review and meta-analysis

Objective

The aim was to evaluate the difference in the heat generated between zirconia (Zr) and steel (SS) drills, during implant site preparation.

Material and methods

This systematic review followed the PRISMA methodology criteria and used the JBI Critical Assessment Guidelines for Quasi-Experimental Studies for quality assessment. The electronic search was conducted by using the PubMed/MEDLINE, Embase, and Cochrane Library databases to January 2023. The formulated population, intervention, comparison, outcome (PICO) question was "Do zirconia drills generate less heat than steel drills during implant site preparation?". The meta-analysis was based on an inverse variance (IV) method.

Results

This review included 10 studies in vitro that used zirconia drills compared to steel drills with or without coatings. The meta-analysis indicated a significant difference between Zr drills and SS drills, with a lower bone temperature variation with Zr drills.

Conclusions

Despite the limitations of this review, it was concluded that Zr drills had significantly less temperature variation than SS drills.

Influence of Multiple Used Implant Drills on Their Cutting Performance and Fracture Resistance

This study aimed to analyze the influence of multiple uses of zirconia implant drills on their cutting performance and bending strength. The hypothesis was that drill usage and sterilization cycles would not affect drilling time or flexural strength. Sixty zirconia twist drills from Z-Systems were used to drill in the angulus mandibulae region of fresh porcine jaws. The drills were divided into four groups based on the cycle count, and the drilling time was measured. Bending strength tests were conducted using a universal testing machine, and statistical analysis was performed using ANOVA tests. The results showed that drilling times followed a normal distribution, and significant differences were observed in drilling times between group 1 and the other groups for the pilot drill. However, no significant differences were found for ø3.75 mm and ø4.25 mm drills, and drilling times also varied significantly among different drill diameters, regardless of the cycle count. Flexural strength did not significantly differ among drill diameters or sterilization cycles. Overall, using and sterilizing zirconia implant drills had no significant impact on drilling time or flexural strength. Nevertheless, drilling times did vary depending on the diameter of the drill. These findings provide valuable insights into the performance and durability of zirconia implant drills, contributing to the optimization of dental implant procedures.

Osseointegration in relation to drilling speed in the preparation of dental implants sites: A systematic review

STATEMENT OF PROBLEM

The drilling speed used for preparing dental implants may affect bone-implant contact (BIC), implant stability quotient (ISQ), and bone area fraction occupancy (BAFO). Different rotational speeds and the presence or absence of irrigation during site preparation have been investigated, but an established protocol for achieving the best osseointegration results is lacking.

PURPOSE

The purpose of this systematic review was to investigate the influence of drill rotational speed on bone drilling for dental implant placement and its relationship with osseointegration.

MATERIAL AND METHODS

This review included the preferred reporting items for systematic reviews and meta-analyses (PRISMA) and was registered in the international prospective register of systematic reviews (PROSPERO) database. Electronic searches were performed in the MEDLINE (PubMed), Scopus, Science Direct, and Embase databases. The risk of bias was analyzed by using the systematic review center for laboratory animal experimentation (SYRCLE).

RESULTS

A total of 1282 articles were found, and after removing duplicates and applying the eligibility criteria to in vivo articles on animals that addressed drilling speed and its relationship to osseointegration, 8 articles were selected for analysis. Of these, 5 articles showed no statistical differences, and 3 others showed significantly better osseointegration results by analyzing the parameters of BIC, BAFO, ISQs, and pull-out forces (PoFs). In all selected articles, high-speed drilling was performed with irrigation.

CONCLUSIONS

Although drilling speed seems to affect bone perforation, no definitive protocol was found in the literature consulted. The results vary depending on the combination of different factors, including bone type, irrigation, and drilling speed.

Wearing Effect of Implant Steel Drills and Tappers for the Preparation of the Bone Osteotomies: An Infrared Thermal Analysis and Energy Dispersive Spectroscopy-Scanning Electron Microscopy (EDS-SEM) Study

Background: The thermal effect correlated with implant osteotomy could produce significant effects on the healing process and fixture osseointegration. The aim of the present investigation was to assess the heat generation and surface wearing of dental implant drills and manual tappers during simulated osteotomies on animal ribs. Methods: Steel drills (20 units per type) and tappers (20 units per type) were evaluated for a total of 30 osteotomies. The infrared thermal analysis was performed at the first and thirtieth osteotomy. The surface alteration and wearing was assessed by energy dispersive spectroscopy–scanning electron microscopy (EDS-SEM) prior to and after use. Conclusions: The drill material produced a non-significant temperature change during bone osteotomy. Lower heating was reported for manual tappers in favor of a manual osteotomy instead rotary instruments.

Temperature Changes during Implant Osteotomy Preparations in Human Cadaver Tibiae Comparing MIS® Straight Drills with Densah® Burs

(1) Background: Several studies showed a sustained temperature of 47 °C or 50 °C for one minute resulted in vascular stasis and bone resorption with only limited bone regrowth over a 3-4-week healing period. The purpose of the present study was to evaluate the temperature changes (ΔΤ) that occur during the preparation of dental implant osteotomies using MIS^® straight drills versus Densah^® burs in a clockwise (cutting) drilling protocol. (2) Methods: Two hundred forty (240) osteotomies of two different systems' drills were prepared at 6 mm depth at 800, 1000, and 1200 revolutions per minute (RPM), in fresh, unembalmed tibiae, obtained by a female cadaver. ΔΤ was calculated by subtracting the baseline temperature on the tibial surface, from the maximum temperature-inside the osteotomy (ΔT = T_max - T_base). The variables were evaluated both for their individual and for their synergistic effect on ΔΤ with the use of one-, two-, three- and four-way interactions; (3) Results: An independent and a three-way interaction (drill design, drill width, and RPM) was found in all three RPM for the Densah^® burs and at 1000 RPM for the MIS^® straight drills. As Densah^® burs diameter increased, ΔΤ decreased. The aforementioned pattern was seen only at 1000 RPM for the MIS^® straight drills. The usage of drills 20 times more than the implant manufacturers' recommendation did not significantly affect the ΔΤ. A stereoscopic examination of the specimens confirmed the findings. (4) Conclusions: The independent and synergistic effect of drills' diameter, design and RPM had a significant effect on ΔΤ in human tibiae, which never exceeded the critical threshold of 47 °C.

The effects of multiple drilling of a bone with the same drill bit: thermal and force analysis

Repeated use of the same drill bit during drilling wears off the cutting edges, which can lead to a significant increase in heat as a result of friction, which is harmful to a bone above 55 °C. Few previous studies have examined the effects of using the same drill bit several times, on temperature. The objective of this study was to determine the effect of each drilling on temperature and force. 72 trials were performed. A total of 24 stainless steel drill bits of ∅3.2 mm were used to drill bovine bone samples. Each drill bit was used at least 3 times. T thermocouples were used to measure temperatures during each drilling test. Possible correlations of cutting parameters were studied. Tests were performed on a test rig measuring forces and temperatures during drilling. Effects of spindle speed (N), feed rate (V_f), and several trials (E) on temperature and forces were measured. Images of the drill bits were analyzed by digital microscopy before and after the drilling series for signs of wear. Temperatures increased significantly from E₁ to E₃. They decreased moderately with V_f. The best cutting conditions were at N = 200 rpm for V_f = 60 mm/min and N = 100 rpm for V_f = 30 mm/min drilling. At N > 200 rpm, they were very high. Temperature rise is significantly related to number of drilling (E), spindle speed (N), and inversely to feed rate (V_f). Analysis of images by digital microscopy confirmed drill bits wearing off, following the number of trials.

3D printed implant surgical guides with internally routed irrigation for temperature reduction during osteotomy preparation: A pilot study

OBJECTIVE

The purpose of this study was to test a novel through-the-guide means of irrigation in an in-vitro bovine bone model and to explore the method clinical applicability.

MATERIALS AND METHODS

Surgical guides were designed to fit over five fresh bovine samples. Control osteotomy sites were compared to experimental sites irrigated through a 3D printed surgical guide with customized channels that direct the coolant toward the interface of the alveolar crest and drill. Temperature was measured during surgery with thermocouples located at 3 and 6 mm from the crestal height of the bone, and with an infrared thermal camera taking direct temperature readings from a window cut into axial wall at 9 mm from the crestal height of the ridge.

RESULTS

Incorporation of routed irrigation significantly decreased heat generation, keeping temperature consistently below 47°C. A clinical case illustrates the method applicability using standard implant planning software, 3D printing technology, and regular implant armamentarium.

CONCLUSIONS

The in-vitro analysis shows that this method mitigates temperature increase caused by static surgical guide irrigation blockade at the osteotomy site. This technique can be incorporated in the surgical guide design using commercially available software and 3D printing technology and has immediate applications in practice.

CLINICAL SIGNIFICANCE

The in-vitro analysis shows that this method can significantly mitigate the temperature increase caused by static surgical guide irrigation blockade at the osteotomy site. This technique also has the advantage that it can be incorporated in the digital surgical guide design using commercially available software and 3D printing technology. The method has immediate applications in practice, and especially in the treatment of edentulism in esthetic zone where use of guided surgery for implant placement is crucial in obtaining consistent results.

Effect of low-speed drilling without irrigation on osseointegration: an experimental study in dogs

OBJECTIVE

To study the early phases of osseointegration at implants installed in sites prepared with either high rotational speed with irrigation or low rotational speed without irrigation.

MATERIAL AND METHODS

After 3 months from tooth extraction, two implants were installed in one side of the mandible of twelve dogs. The osteotomies were prepared either at 60 rpm without irrigation or at 750 rpm with refrigeration. Biopsies were obtained after 4 and 8 weeks of healing, six animals each period for histological analyses.

RESULTS

After 4 weeks of healing, new bone percentage in contact with the implant surface (BIC%) was 46.6 ± 7.3% and 43.1 ± 6.8% at the low- and high-speed sites, respectively (p = 0.345). After 8 weeks of healing, the fractions increased to 60.0 ± 11.1% and 60.2 ± 6.2%, respectively (p = 0.753).

CONCLUSIONS

Implants installed in sites prepared using either low-rotational drilling without irrigation or high speed with irrigation presented similar amounts of osseointegration.

Low-speed drilling without irrigation versus conventional drilling for dental implant osteotomy preparation: a systematic review

PURPOSE

This paper aims to review the evidence comparing low-speed drilling without irrigation versus conventional drilling for dental implant osteotomy preparation.

MATERIALS AND METHODS

A systematic review was carried out based on the PRISMA statement. Four databases and gray literature were searched up to November 2020. In vitro, animal, and clinical studies were included. The variables were temperature change, drilling time, quantity of harvested bone, osteotomy precision, marginal bone loss, implant success rate, osseointegration, and the histomorphologic characteristics and cellularity of the osteotomy and of the harvested bone. Different tools for the assessment of bias were applied for each study design.

RESULTS

A total of 626 articles were identified, of which 13 were included. Both low-speed drilling without irrigation (test group) and conventional drilling (control group) maintained temperatures below the critical temperature of 47 °C. The test group yielded a greater quantity and more beneficial cellular and histomorphologic properties of harvested bone, with a longer drilling time and greater osteotomy precision (p < 0.05). No significant results were obtained regarding drill wear, osseointegration, marginal bone loss, implant success rate, and histomorphology of the dental implant osteotomy (p > 0.05). The results, in particular on the osteotomy precision and quantity of harvested bone chips, should be interpreted with caution because outcomes are based in only one in vitro study.

CONCLUSIONS

Low-speed drilling without irrigation seems to be comparable to conventional drilling in preparing dental implant osteotomies. In some situations, low-speed drilling without irrigation might offer advantages over conventional drilling. The results should be interpreted with caution due to the low percentage of clinical human studies. Accordingly, more clinical studies are needed to improve the scientific evidence on this topic.

CLINICAL RELEVANCE

The low-speed drilling without irrigation is a valid technique for dental implant osteotomy preparation. Its higher quantity and quality of harvested autologous bone might be particularly beneficial in cases of dental implant placement with minor simultaneous bone regeneration.

Thermal effects of various drill materials during implant site preparation-Ceramic vs. stainless steel drills: A comparative in vitro study in a standardised bovine bone model

OBJECTIVES

The aim of this study was to evaluate thermal effects of ceramic and metal implant drills during implant site preparation using a standardised bovine model.

MATERIAL AND METHODS

A total of 320 automated intermittent osteotomies of 10- and 16-mm drilling depths were performed using zirconium dioxide-based and stainless steel drills. Various drill diameters (2.0/ 2.2, 2.8, 3.5, 4.2 mm ∅) and different cooling methods (without/ with external saline irrigation) were investigated at room temperature (21 ± 1°C). Temperature changes were recorded in real time using two custom-built multichannel thermoprobes in 1- and 2-mm distance to the osteotomy site. For comparisons, a linear mixed model was estimated.

RESULTS

Comparing thermal effects, significantly lower temperatures could be detected with steel-based drills in various drill diameters, regardless of drilling depth or irrigation method. Recorded temperatures for metal drills of all diameters and drilling depths using external irrigation were below the defined critical temperature threshold of 47°C, whereas ceramic drills of smaller diameters reached or exceeded the harmful temperature threshold at 16-mm drilling depths, regardless of whether irrigation was applied or not. The results of this study suggest that the highest temperature changes were not found at the deepest point of the osteotomy site but were observed at subcortical and deeper layers of bone, depending on drill material, drill diameter, drilling depth and irrigation method.

CONCLUSIONS

This standardised investigation revealed drill material and geometry to have a substantial impact on heat generation, as well as external irrigation, drilling depth and drill diameter.

Comparing the Temperature Effect of Dedicated Minimally Invasive Motor System to the Discontinuous Use of Rotatory Burrs in the Correction of Hallux Valgus

The purpose of this study was to compare 2 motor systems for percutaneous osteotomy. The study consisted of 2 stages. In the first stage, bone temperatures during osteotomy using burrs or saw was measured using a thermal camera. In the second stage, the tissue and burr temperature elevation during surgery in 80 consecutive patients (96 feet) with hallux valgus undergoing distal first metatarsal and phalangeal osteotomies (hallux and in 61/96 feet lesser digits) were measured. The burr osteotomy procedure included the use of irrigated 2- or 4.1 mm rotary wedge burrs in discontinuous cutting bursts of less than 20 seconds. Tissue surface temperature was measured with a thermal camera. The temperature generated during the procedure was found to be significantly associated with the burr diameter used but was not affected by the type of motor. At the 6-week visit, thickness of the soft tissues over the first metatarsal head was similar in both groups. Temperature control using a noninvasive thermal camera is recommended to prevent tissue damage associated with heat generated during the use of rotary burrs. A dedicated low-speed high-torque system does not seem to be necessary and standard orthopaedic equipment can be used.Levels of Evidence: Level II: Comparative prospectively collected series.

Surgical Drill Bit Design and Thermomechanical Damage in Bone Drilling: A Review

As drilling generates substantial bone thermomechanical damage due to inappropriate cutting tool selection, researchers have proposed various approaches to mitigate this problem. Among these, improving the drill bit design is one of the most feasible and economical solutions. The theory and applications in drill design have been progressing, and research has been published in various fields. However, pieces of information on drill design are dispersed, and no comprehensive review paper focusing on this topic. Systemizing this information is crucial and, therefore, the impetus of this review. Here, we review not only the state-of-the-art in drill bit designs-advances in surgical drill bit design-but also the influences of each drill bit geometries on bone damage. Also, this work provides future directions for this topic and guidelines for designing an improved surgical drill bit. The information in this paper would be useful as a one-stop document for clinicians, engineers, and researchers who require information related to the tool design in bone drilling surgery.

In Vitro Study on Bone Heating during Drilling of the Implant Site: Material, Design and Wear of the Surgical Drill

OBJECTIVE

An in vitro study was made to compare mean thermal variation according to the material, design and wear of the surgical drills used during dental implant site preparation.

MATERIAL AND METHODS

Three study groups (stainless steel drills with straight blades; diamond-like carbon-coated drills with straight blades; and diamond-like carbon-coated drills with twisted blades) were tested to compare material, design and wear of the surgical drill in terms of overall mean values (complete sequence of drills) and specific mean values (each drill separately). The groups comprised four drills: initial, pilot, progressive and final drill. Implant site configuration was performed through an intermittent and gradual drilling technique without irrigation at 800 rpm in standardized synthetic blocks. Maximum axial loading of two kilograms was controlled by an automatic press. Each surgical drill was submitted to 50 drillings and was sterilized every five uses. A thermographic camera analyzed the mean thermal changes. The software-controlled automatic press kept systematic drilling, axial loading and operational speed constant without any human intervention. Student's t-test, ANOVA and multiple linear regression models were performed. The level of significance was 5% (p = 0.05).

RESULTS

The overall mean comparison between the stainless steel and diamond-like carbon-coated materials showed no statistically significant differences (p > 0.05), though specific mean comparison showed statistically significant differences between the drills of the different groups (p < 0.05). The twisted blades exhibited less overall and specific mean thermal variation than straight blades for the progressive and final drills (p < 0.01). In addition, the initial and pilot drills showed a greater mean thermal change than the progressive and final drills. The mean thermal variation was seen to increase during the 50 drillings.

CONCLUSIONS

Within the limitations of this study, it can be concluded that the drill material did not significantly influence the overall mean thermal variation except for the pilot drill. The drill design affected overall and specific mean thermal variation since the twisted blades heated less than the straight blades. The initial and pilot drills increased the specific mean thermal variation with respect to the progressive and final drills. In addition, all drills in each group produced a gradual increase in mean temperature during the 50 drillings.

Experimental investigation on the effect of drill quality on the performance of bone drilling

Bone drilling is a well-known process in operative fracture treatment and reconstructive surgery. The cutting ability of the drill is lost when used for multiple times. In this study, the effect of different levels of drill wear on bone temperature, drilling force, torque, delamination around the drilling region and surface roughness of the hole was investigated using a series of experiments. Experimental results demonstrated that the wear of the drill is strongly related to the drilling force, torque, temperature and surface roughness of the drilled hole. Statistical analysis was performed to find the effect of various factors on multiple response variables in the bone drilling process. The favorable conditions for bone drilling are obtained when feed rate, drill speed and the roughness of the cutting edge of the drill were fixed at 30 mm, 2000 rpm and up to 2 mm, respectively. Further, analysis of variance (ANOVA) was performed to determine the factor with a significant impact on the response variables. F-test and p-value indicated that the feed rate had the highest effect on grey relational grade followed by the roughness of the drill. This study suggests that the sharp drill along with controlled drilling speed and feed rate may be used for safe and efficient surgical drilling in bone.

Infrared Thermographic Evaluation of Temperature Modifications Induced during Implant Site Preparation with Steel vs. Zirconia Implant Drill

Background: The heat produced during implant site osteotomy can potentially interfere with and influence the osseointegration process of a dental implant. The objective of this in vitro investigation was to measure the temperature changes during simulated osteotomies in bovine rib bone. The measurements were made at the apical area of the osteotomies with steel implant drills compared to zirconia implant drills. Methods: Steel cylindrical drills (2 mm) and zirconia cylindrical drills (2 mm) were evaluated in vitro using bovine rib bone for a total of five groups based on the number of osteotomies performed with each drill: 10, 20, 40, 90, or 120 osteotomies. Bone and apical drill temperatures were measured by means of infrared thermography. The drilling time for each osteotomy was measured for each preparation. Results: Statistically significant differences were found in the temperature measurements in the bone and apical portion of the drills between the study groups (p < 0.05). A statistically significant difference was observed for drilling time preparation between steel cylindrical drill (2 mm) and zirconia cylindrical drills (2 mm) (p < 0.01). Conclusions: The drill material has an impact on the temperature changes that occur at its apical portion during bone preparation for implant placement.

An experimental comparative study of drilling efficiency and temperature elevation with unmodified and modified medical drills in pig tibia bone

Background

There are no medical drill specifications capable of achieving bone drilling in a short time under low-thrust and low-speed drilling. Gekkou-drill® is an industrial drill that enables drilling with low cutting resistance by its characteristic point design. Our aims were to develop Gekkou-modified drills by processing to the points of currently available medical drills and to verify whether these modified drills enable less invasive drilling procedure for bone tissue in thermal exposure compared with unmodified medical drills.

Materials and methods

Two commercially available 3.2-mm drills were compared before and after Gekkou modification. Drilling of pig tibias was performed at speeds of 300, 800, and 1,500 rpm and a uniform thrust force of 10 N. Temperature at the entry point for bone drilling was measured using a digital thermometer system. The feed rates were calculated using cortical thickness and monitoring data of the digital force gauge.

Results

Two unmodified drills could not penetrate the cortical bone on the near side at 300 rpm, even after 5 min of drilling. The maximum temperatures with modified drills were 54.6 °C and 46.2 °C at 300 rpm. At medium to high speeds, those were statistically significantly lower than with unmodified drills (58.5 °C vs. 90.5 °C at 800 rpm, 62.6 °C vs. 80.8 °C and 73.9 °C vs. 104.6 °C at 1,500 rpm). The feed rates for modified drills were 4.9–6.9 times as high as unmodified drills at 800 rpm, and 3.4 to 4.5 times at 1,500 rpm. On the other hand, the feed rates of modified drills at 300 rpm were equal to or higher than those of unmodified drills at 1500 rpm.

Conclusion

Gekkou-modified drills clearly suppressed the temperature rise and increased the feed rate compared with conventional drills. Furthermore, it was notable that these modified drills had higher performance even at conditions of low thrust and low speed.

Comparative Analysis of the Chemical Composition and Microstructure Conformation Between Different Dental Implant Bone Drills

Background: Hardness is considered an important parameter for evaluating the clinical performance of dental implant bone drills. It is connected to the chemical composition, microstructure conformation and manufacture of the surgical drills. Methods: Microstructure of five dental implant drills using scanning electronic microscopy (SEM) integrated with energy dispersive X-ray spectrometry. Vickers microhardness was measured using a CV 2000 microhardness tester with an indentation force of 500 g. Results: Composition of the implant drills was typical of martensitic stainless steel (MSS). The drills contained 13%–17% of Cr; Mo, Si and Mn were present as minor ligands. The examined bone drills showed different external surface conformation and hardness in relation to the different industrial production processes. A rougher external surface and a higher hardness value are characteristics of the surgical bone drills produced by hot forming; the implant drills produced by machining showed mailing lines on their external surface and a lower hardness. Conclusions: Different compositions and treatments were used by the manufacturers to improve the hardness of the external layer of the dental implant drills making them prone to a diverse heat generation during the implant site preparation.

Comparison of wear and temperature of zirconia and tungsten carbide tools in drilling bone: in vitro and finite element analysis

Drilling is extensively used in operations on bones and dental implants, and yet poses a considerable challenge because it can damage cells as well as cause mechanical and thermal stresses to the bone. The goal of this study was to assess the temperature changes and instrument wear using both zirconium dioxide (ZrO₂) ceramics and tungsten carbide (WC) tools using a 3-dimensional finite element analysis (FEA) of bone drilling. The wear of conical burrs made from ZrO₂ and tungsten carbide was measured using scanning electron microscopy (SEM) and image processing software. Temperature was measured by an infrared thermometer. As well as 3-dimensional FEA, the temperature and wear of the burrs was predicted with the aid of the Johnson-Cook model for bone material properties. Comparison between the ZrO₂ and WC burrs using SEM showed that the ZrO₂ burr was less worn than the WC burr (p = 0.044) and there was significant difference in temperature between the two (p = 0.020). We conclude that ZrO₂ tools are a suitable alternative to WC, particularly in superficial drilling with coolant, as they wear less than the WC tools. The results of the FEA successfully predicted the variation in temperature and the wear on the tools.

Healing at sites prepared using different drilling protocols. An experimental study in the tibiae of sheep

The aim of the experiment was to study the healing at implants installed in site prepared in bone type 1 using different rotation speeds and cooling strategies. The tibiae of twelve sheep were used as experimental sites. Two implant sites were prepared in each tibia using drills either at a high or a mixed speed under irrigation. At the mixed-speed sites, 60 rpm without irrigation were applied for the last drill, the countersink and during implant installation. Biopsies representing the healing after 1, 2, and 6 weeks were obtained and ground sections were prepared. At the histological analyses, after 1 week of healing, no new bone was found at both high- and mixed-speed sites. After 2 weeks of healing, small amounts of newly formed bone were observed in the cortical layer, reaching percentages of 3.6±3.0% at the mixed-speed sites, and of 2.2±1.5% at the high-speed sites. An irrelevant quantity of new bone was seen in the marrow compartments of a few specimens. After 6 weeks of healing, new bone was found in higher quantity, reaching in the cortical compartment 66.9±6.8% and 67.3±17.7% at the mixed- and high-speed sites, respectively. The respective percentages in the marrow compartment were 23.2±13.0% and 30.6±29.2%. No statistically significant differences between high- and mixed-speed groups were found. It was concluded that the use of the last drill and the installation of the implant with or without irrigation yielded similar bone healing and osseointegration.

Clinical Influence of Micromorphological Structure of Dental Implant Bone Drills

Background

Considerations about heat generation, wear, and corrosion due to some macrostructural bur components (e.g., cutting lips, rake angle, flute, and helix angle) have been widely reported. However, little is known about how the microstructural components of the implant drill surface can influence the implant drill lifetime and clinical performance.

Aim

To investigate accurately the surface morphology of surgical bone drill, by means of multivariate and multidimensional statistical analysis, in order to assess roughness parameters able to predict the evolution of tribological phenomena linked to heat development, wear, and corrosion occurring in clinical use.

Materials and Methods

The surfaces of implant drills approximately 2.0mm in diameter made by five manufacturers were examined by means of confocal microscope with white light laser interferometry, obtaining several surface roughness parameters. Statistical multivariate analysis based on discriminant analysis showed, for each cut-off, the parameters which discriminate the manufacturers.

Results

The microstructural parameters used by discriminant analysis evidenced several differences in terms of drill surface roughness between the five manufacturers.

Conclusions

The observed surface roughness difference of drills is able to predict a different durability and clinical performance especially in heat generation and wear onset.

Improved Dental Implant Drill Durability and Performance Using Heat and Wear Resistant Protective Coatings

The dental implant drilling procedure is an essential step for implant surgery, and frictional heat in bone during drilling is a key factor affecting the success of an implant. The aim of this study was to increase the dental implant drill lifetime and performance by using heat- and wear-resistant protective coatings to decrease the alveolar bone temperature caused by the dental implant drilling procedure. Commercially obtained stainless steel drills were coated with titanium aluminum nitride, diamond-like carbon, titanium boron nitride, and boron nitride coatings via magnetron-sputter deposition. Drilling was performed on bovine femoral cortical bone under the conditions mimicking clinical practice. Tests were performed under water-assisted cooling and under the conditions when no cooling was applied. Coated drill performances and durabilities were compared with those of three commonly used commercial drills with surfaces made from zirconia, black diamond. and stainless steel. Protective coatings with boron nitride, titanium boron nitride, and diamond-like carbon have significantly improved drill performance and durability. In particular, boron nitride-coated drills have performed within safe bone temperature limits for 50 drillings even when no cooling is applied. Titanium aluminium nitride coated drills did not show any improvement over commercially obtained stainless steel drills. Surface modification using heat- and wear-resistant coatings is an easy and highly effective way to improve implant drill performance and durability, which can improve the surgical procedure and the postsurgical healing period. The noteworthy success of different types of coatings is novel and likely to be applicable to various other medical systems.

Effects of Osteotomy Lengths on the Temperature Rise of the Crestal Bone During Implant Site Preparation

AIM

To compare temperatures of the crestal bone during implant site preparation for different osteotomy lengths and implant systems.

METHODS

Bovine ribs were used to simulate the cortical bone of the human mandible. Three different implant systems were tested: Astra Tech, Ankylos, and XiVE. Six drills per system were performed, meaning each drilling set was used for 2 drills per 3 osteotomy lengths (8, 12, and 16 mm). Drilling force, drilling speed, drilling length, and temperature were recorded.

RESULTS

Differences in the maximum temperature of the crestal bone during the first drilling for various osteotomy lengths (P = 0.021) and all implant systems (P = 0.013) were observed. A similar result was showed during the second drilling; osteotomy lengths (P = 0.014) and drilling systems (P = 0.003). Second drillings showed lower temperatures of the crestal bone with statistical differences on all measurements (P < 0.001). Astra Tech and Ankylos implant systems showed similar performance; XiVE had lower temperature and higher temperature differences between osteotomy lengths.

CONCLUSIONS

Different drilling lengths contributed to the variation in temperature regardless of the implant system. Longer drills and osteotomies induced higher temperatures on the crestal bone. The maximum temperature difference between the shortest and the longest osteotomy was under 1°C. Temperature above 47°C that could cause bone necrosis was not recorded at any time. The XiVE system showed the best performance.

The effects of irrigation volume to the heat generation during implant surgery

Background

To evaluate the effects of the amount of irrigation on heat generated during implant site preparation.

Material and Methods

Ten freshly dissected sheep mandibles were sectioned into 30 equal bone blocks and transferred into a heat-controlled water tank. Implant socket preparations were performed with four consecutive drills. Temperature measurements were performed with a thermocouple inserted into the bone immediately before the preparation and after the drilling using three different physiologic saline irrigation set-ups: 1- No irrigation, 2- 12 ml/min and 3- 30 ml/min irrigation volume. The temperature differences between three different irrigation set-ups for implant drills 1, 2, 3 and 4, and the temperature differences between the drills for three different irrigation set-ups were separately compared.

Results

The temperature difference of no irrigation group was significantly higher than 12 ml/min and 30 ml/min groups for all four drills (p<0.05), whereas no statistically significant difference was found between 12 ml/min and 30 ml/min irrigation groups. (P >0.05) The temperature difference of drill 1 is significantly higher than drills 2, 3 and 4 for no irrigation group. (P <0.05) The temperature differences of drill 1, 2 and 3 were significantly higher than the temperature difference of drill 4 for 12 ml/min irrigation group. (p<0.05).

Conclusions

The heat generated during drilling is not directly proportional to the coolant volume. Given that certain amount of irrigation is applied, implant sites can be prepared safely without the need for additional irrigation, which may result in reduced visibility of the surgical site and therefore a suboptimal surgery.

Key words:Dental implants, irrigation, heat generation, drilling.

Heat generation and drill wear during dental implant site preparation: systematic review

To identify factors that minimise damage during the drilling of sites for dental implants, we reviewed published papers on the amount of heat that is generated. We systematically searched English language studies published between January 2000 and February 2014 on MEDLINE/PubMed and found 41 articles, of which 27 related to an increase in temperature during preparation of the site. We found only basic research with a low level of evidence. Most of the studies were in vitro, and osteotomies were usually made in non-vital bone from cows or pigs. To measure heat in real time, thermocouples were used in 18 studies and infrared thermographs in 7. Three studies reported the use of immunohistochemical analysis to investigate immediate viability of cells. The highest temperature measured was 64.4°C and the lowest 28.4°C. Drill wear was reported after preparation of 50 sites, and there was a significant increase in temperature and a small change in the physiological balance of the proteins in the bone cells. Differences in the study designs meant that meta-analysis was not appropriate. For future work, we recommend the use of standard variables: an axial load of 2kg, drilling speed of 1500rpm, irrigation, standard artificial bone blocks, and the use of infrared thermography.