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

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Abstract

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 2 kg, drilling speed of 1500 rpm, irrigation, standard artificial bone blocks, and the use of infrared thermography.

Introduction

Heat that is released during the preparation and insertion of implants could have consequences for the bone, and it has already been shown that the extent of the necrotic zone around the preparation site is proportional to the amount of heat generated.1 Repeated use causes drills to wear and reduces their efficiency, and the temperature increases each time a bur is used.2 Other variables may also affect their cutting ability and the amount of heat generated. Preparation of the site is a complex process and the shape, sharpness, and speed of the drill, applied axial load, and the density of the bone all have an effect.3, 4, 5, 6, 7

To our knowledge, the only review of this subject was published in 1999 by Tehemar who tried to identify all the factors that influence the amount of heat generated when bone is drilled.8 However, questions remain about the optimal design of the drill, the best type of irrigation, the degree of heat generated depending on the bone density, and the speed of the drill. Our aim was to find out whether these could now be answered.

Section snippets

Material and methods

We searched the MEDLINE/PubMed database for articles published between January 2000 and February 2014 using different combinations of the keywords implant and; heat or; temperature and; osteotomies or; drill. A total of 41 were found. After initial screening of titles and abstracts, the text was studied in more detail. Fourteen articles were excluded because they did not investigate preparation of the implant bed. Finally, 27 studies remained and were included in this review (Fig. 1).

Results

To assess the amount of heat generated in real time, thermocouples were used in 18 studies (Table 1) and infrared thermographs in 7 (Table 2). Three studies investigated immediate cell viability using immunohistochemical analysis (Table 3). Drill wear was the focus of 10 investigations.

Discussion

Direct comparison of the studies is difficult because of their different designs. This is attributed in part to the study model, the method used to measure the heat generated, or the variety of surgical tools used. For example, the axial load varied between 0.1 and 10 kg, even if it was not the aim of the investigation, and speeds varied between 500 and 2500 rpm.

Even the bone models, particularly the studies on porcine and bovine bone, must be questioned because they contain a lot of cancellous

Conclusion

Much research has been done on dental implants but less has been done on preparation of the implant site, and further studies are needed. To achieve better comparability and to maximise the translational potential of such research, we recommend the use of standard variables: an axial load of 2 kg, drilling speed of 1500 rpm, irrigation, standard artificial bone blocks, and the use of infrared thermography.

Conflict of interest

We have no conflicts of interest.

Sources of support: None.

Disclosure: The authors do not have any financial interests or commercial associations to disclose.

Ethics statement/confirmation of patient permission

This is a review about current literature without any patient contact. Consent for publication is not necessary.

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