Intraosseous Heat Production and Preparation Efficiency of Surgical Tungsten Carbide Round Drills: The Effect of Coronectomy on Drill Wear

Temperature variations during bone removal procedures similar to third molar extraction using different instruments

Bone removal is commonly used in the extraction of third molars and the heat generated during the process can interfere with the repair of bone. The aim of this study was to evaluate the temperature variation presented in bone removal performed with a high-speed turbine (400000 rpm), implant motor with straight piece (100000 rpm), low-speed micromotor (20000 rpm) and piezoelectric saw (30 kHz) in pig mandibles. For this, bone removal was carried out around 20 posterior teeth, under constant saline solution irrigation with a syringe and needle. In addition, the time required to perform bone removal was recorded. The results indicated a mean (SD) temperature variation of 0.96 °C (0.6 °C) for the high-speed turbine, 1.38 °C (0.5 °C) with the implant motor, 2.22 °C (0.7 °C) for the low-speed micromotor and 2.90 °C (1.3 °C) for the piezoelectric saw. The conventional variance was calculated discounting the variation of time used for bone removal around the teeth. There was a statistically significant difference in temperature variation between the high-speed turbine vs the micromotor (p = 0.009) and the high speed micromotor vs the piezoelectric saw (p = 0.04). We conclude that there is a statistically significant difference in temperature variation between the instruments used in oral and maxillofacial surgery, with higher rotation speeds resulting in the lowest temperature variations and a reduced surgical time.

Breakage and displacement of the high-speed hand-piece bur during impacted mandibular third molar extraction: three cases

Background

The high-speed hand-piece bur is one of the methods to perform tooth sectioning during the minimally traumatic extraction of impacted mandibular third molars. During tooth sectioning, the breakage of the bur might take place when it is improperly used. Three cases of the breakage and displacement of a high-speed hand-piece bur during extraction are reported, aiming to remind dental surgeons of this complication.

Case presentation

The bur fragment in case 1 was embedded in the mandibular bone under the previously removed crown of tooth 48 and distal to tooth 47. The bur fragment in case 2 was embedded in the lingual edge of the socket and partly beneath the mucosa on the lingual side. The position of the bur fragment in case 3 was similar to that of case 1 but was completely embedded in the spongious bone. The three cases were performed by first-year residents, and all of the bur fragments were successfully removed by attending doctors after accurately locating them by radiological examination.

Conclusions

In order to avoid breakage of the high-speed hand-piece bur, the number of uses of the bur should be monitored and the integrity and state of the bur should be carefully checked. Moreover, light pressure with little lateral force should be used during tooth sectioning. If bur breakage and displacement occur, the retrieval protocol should be determined based on the imaging findings and conducted as soon as possible to avoid serious consequences.

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.

Influence of bone density, screw size and surgical procedure on orthodontic mini-implant placement - part A: temperature development

The aim of this in vitro study was to determine the influence of bone density, orthodontic mini-implant (OMI) size, and the surgical procedure on temperature increase during implant site osteotomy and placement. OMIs of different sizes (2.0×7, 2.3×7, 2.0×11, and 2.3×11mm) were placed in artificial bone blocks of different densities (D1-D4). Optionally, the drilling and insertion angle was 90° or 60° to the bone surface. A total of 640 OMIs were inserted, and predrilling was performed in 320 cases. All insertions were done without irrigation with an axial load of 20N, which resulted in 64 groups. Temperature measurements were performed during implant site preparation and placement using Type-K-thermocouples. Mean temperature increase differed for OMI osteotomy between 1.38°C and 8.75°C and placement between 3.8°C and 18.74°C, respectively. Critical thermal increase was especially reached during placement using long implants. Increasing bone density and implant size (diameter <length) correlated with thermal increase. Predrilling and angulated implant placement resulted in less heat development. Critical temperature behaviour in high-density bone could be partially responsible for the high failure rates of OMI placement in the lower jaw. The influence of the implant size on temperature development should be considered when selecting an OMI.

The influence of the chosen in vitro bone simulation model on intraosseous temperatures and drilling times

There is no consensus about the most suitable in vitro simulating material investigating heat generation during bone preparation. The aim was to compare heat increases and drilling times of bone removals in different bone simulating materials and to compare them to fresh human cadaver bone. A cavity was drilled in the following samples: (1) bovine rib; (2) pig rib; (3) 20 PCF (lb/ft³) polyurethane (PU) block with 3 mm (50 PCF) cortical layer; (4) 20PCF PU without cortical; (5) 30 PCF PU with 2 mm (40 PCF) cortical; (6) 30 PCF PU with 1 mm (40 PCF) cortical; (7) 30PCF PU without cortical; (8) poly-methyl-methacrylate (PMMA); (9) fresh human cadaver rib. Data were analyzed with ANOVA followed by Tukey’s post hoc tests. P < 0.05 was considered significant. Highest heat increases and slowest drilling times were found in bovine ribs (p < 0.001). Regarding temperatures, human ribs were comparable to the pig rib and to PUs having cortical layers. Considering drilling times, the human rib was only comparable to the 20 PCF PU with 3 mm cortical and to 30 PCF PU without cortical. By the tested in vitro bone removals, only the 20 PCF PU with 3 mm cortical was able to simulate human ribs, considering both temperature increases and drilling times.

Drilling of bone: Effect of drill bit geometries on thermal osteonecrosis risk regions

Bone-drilling operation necessitates an accurate and efficient surgical drill bit to minimize thermal damage to the bone. This article provides a methodology for predicting the bone temperature elevation during surgical bone drilling and to gain a better understanding on the influences of the point angle, helix angle and web thickness of the drill bit. The proposed approach utilized the normalized Cockroft-Latham damage criterion to predict material cracking in the drilling process. Drilling simulation software DEFORM-3D is used to approximate the bone temperature elevation corresponding to different drill bit geometries. To validate the simulation results, bone temperature elevations were evaluated by comparison with ex vivo bone-drilling process using bovine femurs. The computational results fit well with the ex vivo experiments with respect to different drill geometries. All the investigated drill bit geometries significantly affect bone temperature rise. It is discovered that the thermal osteonecrosis risk regions could be reduced with a point angle of 110° to 140°, a helix angle of 5° to 30° and a web thickness of 5% to 40%. The drilling simulation could accurately estimate the maximum bone temperature elevation for various surgical drill bit point angles, web thickness and helix angles. Looking into the future, this work will lead to the research and redesign of the optimum surgical drill bit to minimize thermal insult during bone-drilling surgeries.

Recommended Drilling Parameters of Tungsten Carbide Round Drills for the Most Optimal Bone Removals in Oral Surgery

Background

High temperatures during drilling can cause thermal osteonecrosis and abnormal wound healing. According to our best knowledge, a widely accepted recommendation for optimal drilling parameters in routine oral surgery bone removals does not exist.

Purpose

Our aim was to investigate the correlations of different drilling parameters, including axial load and revolution speed on drilling temperatures and preparation times.

Materials and Methods

Standard, 5 mm deep cavities were drilled in 20 PCF (lb/ft³) dens polyurethane blocks with 3 mm (50PCF) cortical layer using new and worn, 3.1mm in diameter tungsten carbide round drills. Worn drills were used in 50 impacted third molar operations before. Axial loads of 3N, 10N, and 25N and speeds of 4.000-8.000-16.000-40.000 revolutions per minute (rpm) were tested. Temperature differences of drilling parameters were calculated by 1-way ANOVA, followed by Tukey's HSD post hoc tests. Time differences and differences among “optimal” and “suboptimal” groups (with the cut-off value of 3°C and 3s) were estimated by Kruskal-Wallis test with pairwise comparisons. P<0.05 was considered significant.

Results

The highest mean temperatures with new and worn drills were 4.64±0.53°C and 6.89±1.16°C, while drilling times varied between 0.16±0.02s and 22.77±5.45s. A 3°C and 3s cut-off value classified drillings significantly to (1) optimal [3N and 8000-16000-40000 rpm or 10N and 4000-8000-16000-40000 rpm] or suboptimal due to (2) high temperatures or (3) long preparation times. Using worn drills, the following parameters should be avoided: 3N with 4.000-8.000 rpm, 10N with 40000 rpm, and 25N at any revolutions.

Discussion

The study extensively mapped the drilling temperatures and preparation times of tungsten carbide round drills. Temperatures did not exceed 10°C during drillings with maximal amount of cooling, as well as the drilling parameters, which kept temperatures and preparation times in the most optimal range which were clearly established.

Tooth sectioning for coronectomy: how to perform?

OBJECTIVES

The aim of this study was to determine the increase in heat production, preparation time, and cutting surface quality of conventional, high-speed rotating instruments and piezoelectric preparation for coronectomy procedures.

MATERIALS AND METHODS

One hundred intact extracted molars were sectioned horizontally, sub-totally, 1 mm under the cemento-enamel line with five methods: (1) tungsten carbide torpedo (TcT), (2) round (TcR) drills using a conventional speed surgical straight handpiece (< 40,000 min^-1), (3) tungsten carbide fissure (TcF), (4) diamond torpedo (DT) drills using a surgical high-speed, contra-angle handpiece (~ 120,000 min^-1), or (5) a saw-like piezoelectric tip (PT). Temperatures, preparation times, and cutting surface irregularities were registered and the differences were analyzed with ANOVA, Tukey's HSD post hoc test (temperature, time) and with chi-square test (irregular surface).

RESULTS

Rotating instruments produced a maximal temperature increase of less than 1 °C. TcF produced the least heat (ΔT = - 3.92 °C to the baseline), while PT produced significantly the highest temperature increases (ΔT = 12.38 °C, p < 0.001). Tungsten carbide drills were the fastest for coronectomy (from 55.9 to 64.3 s), while DT (169.7 s) while PT (146.8 s) were significantly slower. TcT and TcR drills produced an irregular root surface more frequently.

CONCLUSIONS

During coronectomy, rotating instruments produced entirely acceptable heat, while PT produced unacceptable temperatures. Tungsten carbide drills performed coronectomies effectively, but the diamond torpedo and PT seemed clinically questionable. Considering heat, speed, and the cutting surface quality simultaneously, TcF in a surgical high-speed handpiece seems to be the best choice for coronectomy.

CLINICAL RELEVANCE

The correct insert can significantly reduce excessive heat and operation time during coronectomy procedures.