Intraosseous heat generation during sonic, ultrasonic and conventional osteotomy

https://doi.org/10.1016/j.jcms.2015.05.018Get rights and content

Abstract

Objectives

To assess heat generation in osteotomies during application of sonic and ultrasonic saws compared to conventional bur.

Methods

Two glass-fiber isolated nickel–chromium thermocouples, connected to a recording device, were inserted into fresh bovine rib bone blocks and kept in 20 ± 0.5 °C water at determined depths of 1.5 mm (cortical layer) and 7 mm (cancellous layer) and 1.0 mm away from the planned osteotomy site. Handpieces, angulated 24–32°, were mounted in a vertical drill stand, and standardized weights were attached to their tops to exert loads of 5, 8, 15 and 20 N. Irrigation volumes of 20, 50 and 80 ml/min were used for each load. Ten repetitions were conducted using new tips each time for each test condition. The Mann–Whitney-U test was used for statistical analysis (p < 0.05).

Results

Both ultrasonic and sonic osteotomies were associated with significantly lower heat generation than conventional osteotomy (p < 0.01). Sonic osteotomy showed non-significantly lower heat generation than ultrasonic osteotomy. Generated heat never exceeded the critical limit of 47 °C in any system. Variation of load had no effect on heat generation in both bone layers for all tested systems. An increased irrigation volume resulted in lower temperatures in both cortical and cancellous bone layers during all tested osteotomies.

Conclusion

Although none of the systems under the conditions of the present study resulted in critical heat generation, the application of ultrasonic and sonic osteotomy systems was associated with lower heat generation compared to the conventional saw osteotomy. Copious irrigation seems to play a critical role in preventing heat generation in the osteotomy site.

Introduction

Unintended damage to delicate anatomic structures is considered as the main disadvantage of conventional osteotomy systems (Schlee et al., 2006, Vercellotti et al., 2001, Vercellotti, 2004). To overcome this problem, ultrasonic osteotomy systems have recently been introduced to craniomaxillofacial (CMF) surgery (Papadimitriou et al., 2012, Heinemann et al., 2012, Schmidt et al., 2013). The development of the piezo-osteotomy armamentarium has provided the dentomaxillofacial surgery profession with the appropriate technology for operations in the vicinity of vulnerable structures, namely nerves, blood vessels and the Schneiderian membrane (Siervo et al., 2004, Nordera et al., 2007, Stübinger et al., 2008). Piezo-osteotomy applies micro vibrations of 60–200 μms−1 at 24–29 kHz. Vibrations within this range of frequency and up to a limit of 50 kHz will cut through the inelastic mineralized tissue, leaving the elastic structures unharmed (Vercellotti et al., 2001, Vercellotti, 2004, Stübinger et al., 2005). To cut bone while minimizing the risk of damage to soft tissues, osteotomies use ultrasound at relatively low frequencies (20–36 kHz). In some cases, ultrasound may be modulated at low frequency (30 Hz or lower) to avoid overheating and bone compaction (Vercellotti et al., 2001) or at even lower sonic frequencies (16 Hz–20 kHz) (Heinemann et al., 2012). Although a higher level of safety and fewer iatrogenic defects have been consistently reported for ultrasonic osteotomy systems, some concerns still remain about the osteotomy speed and heat generation (Rashad et al., 2011, Rashad et al., 2013).

Most recently, sonic osteotomy systems with maximum sound frequencies of 6 kHz have been developed and are useful for several procedures, such as tooth extraction, alveolar bone augmentation or sinus floor elevation (Geminiani et al., 2011, Papadimitriou et al., 2012, Geminiani et al., 2013). However, the application of sonic osteotomy for oral surgery is based on a series of clinical reports only, and very few histological or in vitro studies have been conducted. Although fewer adverse events for these new sonic osteotomy systems were reported, demonstrating the main advantage over the traditional oscillating saw (Heinemann et al., 2012, Geminiani et al., 2013, Weitz et al., 2014), the major concern remains that a longer time is needed for bone cuts (Viganò et al., 2014).

During osteotomy, a certain degree of bone necrosis occurs regardless of any action taken to prevent it. From a functional point of view, this necrosis is a significant risk for bone healing (Eriksson et al., 1984). Several studies have demonstrated that a temperature increase above 47 °C might affect vital bone its regeneration (Eriksson and Albrektsson, 1983, Sharawy et al., 2002, Chacon et al., 2006). As already mentioned, sonic and ultrasonic osteotomies are generally described to be significantly more time consuming than those with conventional saws and burs (Rashad et al., 2015). According to Sener et al. (2009), heat induction is directly proportional to the time of exposure to frictional forces during conventional drilling. Abouzgia and Symington (1996) demonstrated that an increase in heat induction is associated with a longer duration of preparation. The limited availability of evidence in recent literature indicates the need for further research in this field to keep pace with the development of this relatively new technology. A direct comparison of available osteotomy systems concerning heat induction is still missing. Hence the null hypothesis states no difference in heat generation with application of various osteotomy systems. The aim of the present study was to compare conventional bur, ultrasonic and sonic osteotomy systems in standardized in vitro preparations in terms of heat generation under different irrigation volumes and osteotomy loads.

Section snippets

Bone

One hundred and twenty fresh bovine ribs were used in the present study due to their similarities to the human jaw in terms of bone density and the ratio between cortical and cancellous bone (Rashad et al., 2011, Rashad et al., 2013).

Osteotomy systems

Three osteotomy saw systems (Fig. 1) with different specifications (Table 1) were used as follows:

  • Conventional: Kavo Intrasurg 1000® (Kavo Dental GmbH, Biberach/Riß, Germany); Lindemann bur H254E/Gebr. Brasseler GmbH & Co. KG, Komet, Lemgo, Germany)

  • Sonic: Kavo

Heat generation

All temperature measurements showed increased values both in cortical (Table 2) and in cancellous (Table 3) bone. The highest temperature increase was detected during conventional osteotomy. Both ultrasonic and sonic osteotomies were associated with significantly lower heat induction than bur osteotomy (p < 0.05, Table 4). Sonic osteotomy showed non-significantly lower heat induction than ultrasonic osteotomy. However, under all conditions, the detected values never exceeded the critical limit

Discussion

The present study suggested that both ultrasonic and sonic osteotomies induce significantly lower heat compared to bur osteotomy. The sonic saw generated the lowest heat increase, although the difference was not statistically significant when compared to ultrasonic osteotomies. All the average values, however, remained below 47 °C for all the studied systems. Even absolute values did not excced the critical threshold while in several of the conventional osteotomies with high load and low

Conclusion

Sonic and ultrasonic osteotomies are advantageous in comparison to conventional bur osteotomies with regard to heat development. The critical role of irrigation volume in preventing harmful heat induction is highlighted.

Funding source

None.

Conflict of interest statement

The authors declare no conflict of interest.

Acknowledgments

None.

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