Investigations into the use of an ultrasonic chisel to cut bone. Part 1: Forces applied by clinicians

Bone cutting processes and removal behaviors in orthopedic surgery with an ultrasonic orthopedic scalpel

Bone cutting is a common and important procedure in surgery. As a type of orthopedic instrument, ultrasonic orthopedic scalpels (UOSs) have been widely used due to their safety and convenience. Therefore, it is very important to have a deep understanding of the cutting process and the bone removal behavior of a UOS, to improve cutter design and complement the basic theory of the bone-cutting mechanism. However, few studies have focused on the characteristics of ultrasonic cutting. In this work, based on bone structure, the bone-cutting processes of a UOS were defined and the bone removal behavior in ultrasonic bone cutting was studied. In this study, it was believed that a direction of ultrasonic vibration different from that of the lamellar arrangement and collagen fibers would lead to different cutting characteristics. Based on this, the cutting modes were divided into four typical types. After examining and analyzing the crack propagation and chip formation of compact bone for the four cutting modes, the removal behaviors of ultrasonic bone cutting were defined. At the same time, the surface morphology indicated that there were significant differences in the surface damage for different cutting modes, which supported the idea that the bone removal behaviors were different for different modes. In addition, the force signals were analyzed and the results showed that there were differences in the cutting forces for different cutting modes. The static and dynamic components of the cutting forces were also analyzed. The study demonstrated the correlation between bone removal and the microscopic and submicroscopic structure of bone in ultrasonic cutting. These conclusions provided guidelines for analyzing bone tissue injuries caused by UOSs, improving the surgical process of bone cutting, optimizing the design of orthopedic instruments, and further complementing the basic theory of bone cutting.

Piezoelectric versus conventional techniques for orthognathic surgery: Systematic review and meta-analysis

PURPOSE

A systematic review and meta-analysis of the advantages and disadvantages of the piezo surgery comparing with conventional osteotomy in orthognathic surgery.

METHODS

We conducted this systemic review in accordance with the preferred reporting items for systematic reviews and meta-analysis (PRISMA) statement. We searched for relevant studies in the PubMed/MEDLINE, Embase databases, Lilacs, Scopus and Science Direct to identify prospective and retrospective studies, compare patient outcomes (intraoperative blood loss, operative time, neurosensory disturbance) after performing orthognathic surgery by conventional saw or piezo-electric device. According to pool individual results we used the mean difference (MD) with the 95% confidence interval (95% CI).

RESULTS

Among three studies that used conventional saw and three studies used piezo-electric device and nine studies used both techniques, the operative time required to perform orthognathic standard procedures was longer using piezo-electric device compared to conventional saw. The results showed that during using the conventional saw to perform orthognathic surgery the amount of the blood loss was higher than the amount while using piezo-electric device (MD -140.4 mL; P = 0.29). based on the studies that evaluated neurosensory disturbance, after 3 months and 6 months respectively, neurosensory disturbance was seen in 23.8% and 23.4% of patient who underwent conventional osteotomy versus 4.3% and 2.4% of the patients who underwent surgery in which piezo surgery was used. Our meta-analysis showed difference in neurosensory disturbance between piezo-surgery and conventional surgery at 3 months (MD -19.5; P = 0.11) and 6 months (MD -21; P = 0.5) postoperatively.

CONCLUSION

Piezo-electric device enabled lower blood loss and higher nerve integrity rates in outcomes according to the complications that associated with orthognathic surgery.

Osteotomy speed, heat development, and bone structure influence by various piezoelectric systems-an in vitro study

OBJECTIVES

The aim of this in vitro study was to evaluate osteotomy speed, heat development, and bone structure influence from osteotomies performed by various piezoelectric devices and insert tips. These devices and tips were compared among each other with regard to conventional rotatory and oscillating systems with special focus on the insert tip design and thickness.

MATERIAL AND METHODS

The osteotomies were conducted on porcine ribs utilizing 12 different insert tips (straight and angulated) and three conventional systems. After time and temperature measurements, histological analysis was carried out. Light microscopy was used to evaluate the roughness of the osteotomic surface and to search for indications of thermal bone necrosis. A special software analyzing tool was employed to determine cutting width (mm) and debris (%).

RESULTS

All piezoelectric tips created smooth cuts. Cutting widths in general were wider than the actual insert tip size with a tendency for narrow straight insert tips producing relatively wide osteotomies, whereas narrow angulated inserts produced relatively small osteotomies. None of the samples demonstrated distinct indication of necrosis. Overall, there was only a small amount of debris in all osteotomy gaps. Conventional rotatory saws were faster and created less heat compared to all tested piezoelectric systems. Straight tips proved faster osteotomy speed than angulated tips. Thin insert tips indicated to have a positive correlation to osteotomy time and performed faster than conventional microsaw. The average temperature rise was lower when using conventional systems, but critical exceeding temperatures were only observed in short-time exceptional cases. In general, temperature rise was less when using angulated inserts.

CONCLUSION

All tested tips are appropriate for bone surgery. Only small differences were found among the piezoelectric insert tips. Although conventional rotatory systems in general performed faster osteotomies, special designed and thin piezoelectric insert tips seem to have a positive influence on osteotomy speed. Ultimately, none of the tested devices or inserts combined all best features of speed, heat development, bone structure influence, and safety.

CLINICAL RELEVANCE

Narrow and straight piezoelectric insert tips demonstrated reduced osteotomy times. Nevertheless, a combination of conventional and piezoelectric systems in clinical practice might be the best way to work time-efficient, patient-oriented, and safe. The choice of instrument should be based on clinical experience of the user and should be evaluated individually depending on the case.

Evaluation of the lingual fracture patterns after bilateral sagittal split osteotomy according to Hunsuck/Epker modified by an additional inferior border osteotomy using a burr or ultrasonic device

This study was conducted to compare fracture patterns and operation times after sagittal split osteotomy (SSO) by Hunsuck/Epker approach, performed using a burr or ultrasonic device, with and without osteotomy modification. A total of 80 SSOs were performed in fresh human cadavers using a burr or ultrasonic device to investigate the influence of surgical instruments as well as an additional bone cut on the inferior border of the mandible in terms of lingual fracture patterns. The times required for osteotomy and sagittal split were measured, and postoperative cone beam computed tomography images of all splits were analyzed. Without an additional inferior osteotomy, preferred splits according to Hunsuck/Epker were achieved in 35% of cases (7/20) with the burr and 45% (9/20) with the ultrasonic instrument. The inferior modification resulted in a greater number of unwanted fracture patterns in both groups. There was no relationship between the split technique and the fracture pattern (P=0.7854). Statistically significant differences in osteotomy time were observed between burr osteotomy and modified burr osteotomy (P=0.006), as well as modified ultrasonic osteotomy (P<0.001), but not between burr and ultrasonic surgery both without the inferior cut (P=0.36). The bone cut on the inferior border did not improve split control, but rather increased the risk of unwanted fractures and extended the operation time.

Physics and Histologic Evaluation of Rotary, Ultrasonic, and Sonic Instruments

Rotary instruments (RIs) are the most commonly used to perform osteotomies in many fields of medicine. Owing to a new interest in performing a minimally invasive surgery, over last fifteen years new devices have been used in oral surgery such as ultrasonic instruments (UIs) and, lately, sonic instruments (SIs). Nowadays, bone preservation and regeneration are paramount in many clinical situations and, consequently, it is crucial to rely upon instruments, which cause the least tissue damage during the surgery. Concerning SIs, there is still few information about workload to be applied and related temperature increases; furthermore, there are no comparative in-vivo studies, which analyze the thermal and mechanical effects on bone. Thus, SIs have been compared with UIs and RIs in terms of heat generation, operating time, accuracy, and tissue damage. Decalcification and sectioning procedure resulted in no significant differences between the applied instruments in terms of bone damage. RIs resulted more efficient than UIs (P < 0.001), but demonstrated low accuracy (NRS 4.9), whereas SIs (P = 0.005) required more time to perform the osteotomy. The maximum temperature increase occurred in the ultrasonic group. Even though SI were the slowest, they have proved to be the most accurate (NRS 8.4) in comparison with UI (NRS 7.6) and RI (NRS 4.9). Within the limit of this study, sonic instruments could be considered a safe alternative to ultrasonic instruments.

Comparison between piezoelectric surgery and conventional saw in sagittal split osteotomies: a systematic review

A systematic review of the advantages and disadvantages of piezoelectric surgery in comparison with conventional saws for sagittal split osteotomy (SSO) was performed. Relevant studies published in the last 10 years were identified through a search of the PubMed/MEDLINE, Science Direct, and Embase databases and assessed against predetermined eligibility criteria. The initial search resulted in 1736 articles. After applying the inclusion and exclusion criteria, 12 articles remained. A total of 799 patients with an average age of 27.5 years underwent SSO performed using a saw or ultrasonic device. Results showed that it took longer to perform the osteotomies using an ultrasonic device than using a conventional saw. At ≥6 months of follow-up, neurosensory disturbance was seen in 4.7% of patients who underwent piezoelectric surgery versus 61.6% of patients who underwent surgery in which a conventional saw was used. It was found that the use of piezoelectric surgery in SSO leads to the best outcome regarding neurosensory disturbance when compared to conventional saws (P=0.04) at ≥6 months of follow-up. Further studies are required for the evaluation of the other clinical parameters assessed.

A novel technique for micro-hole forming on skull with the assistance of ultrasonic vibration

Micro-hole opening on skull is technically challenging and is hard to realize by micro-drilling. Low-stiffness of the drill bit is a serious drawback in micro-drilling. To deal with this problem, a novel ultrasonic vibration assisted micro-hole forming technique has been developed. Tip geometry and vibration amplitude are two key factors affecting the performance of this hole forming technique. To investigate their effects, experiment was carried out with 300μm diameter tools of three different tip geometries at three different vibration amplitudes. Hole forming performance was evaluated by the required thrust force, dimensional accuracy, exit burr and micro-structure of bone tissue around the generated hole. Based on the findings from current study, the 60° conically tipped tool helps generate a micro-hole of better quality at a smaller thrust force, and it is more suitable for hole forming than the 120° conically tipped tool and the blunt tipped tool. As for the vibration amplitude, when a larger amplitude is used, a micro-hole of better quality and higher dimensional accuracy can be formed at a smaller thrust force. Findings from this study would lay a technical foundation for accurately generating a high-quality micro-hole on skull, which enables minimally invasive insertion of a microelectrode into brain for neural activity measuring.

Piezoelectric Bone Surgery: A Review of the Literature and Potential Applications in Veterinary Oromaxillofacial Surgery

Piezoelectric bone surgery is a recent and innovative technology, permitting a selective cut of mineralized tissue while sparing soft tissue. Similar to a dental scaler, a high frequency vibration, in the range of 25-35 kHz, is transmitted to a metallic tip. However, the power of the piezosurgical instrument is three to six times higher than that of a dental scaler. The major advantages of this technology include high precision, a design that increases ease of curvilinear osteotomy, less trauma to soft tissue, preservation of neurological and vascular structures, reduced hemorrhage, minimal thermal damage to the bone, as well as overall improvement of healing. The handpiece of the instrument is equipped with a sterile irrigation system and light-emitting diode (LED) light, which improves visibility and overall safety. Piezoelectric surgery is particularly useful when performing delicate bone procedures such as periodontal or endodontic surgery. It is also indicated when performing more invasive bone surgery such as maxillectomy, mandibulectomy, and condylectomy, where preservation of neurovascular structures is important. Piezoelectric instruments are different from rotary instrumentation or oscillating saws, they require light pressure with constant motion of the tip. Training is required to master the technique.

Understanding nonlinear vibration behaviours in high-power ultrasonic surgical devices

Ultrasonic surgical devices are increasingly used in oral, craniofacial and maxillofacial surgery to cut mineralized tissue, offering the surgeon high accuracy with minimal risk to nerve and vessel tissue. Power ultrasonic devices operate in resonance, requiring their length to be a half-wavelength or multiple-half-wavelength. For bone surgery, devices based on a half-wavelength have seen considerable success, but longer multiple-half-wavelength endoscopic devices have recently been proposed to widen the range of surgeries. To provide context for these developments, some examples of surgical procedures and the associated designs of ultrasonic cutting tips are presented. However, multiple-half-wavelength components, typical of endoscopic devices, have greater potential to exhibit nonlinear dynamic behaviours that have a highly detrimental effect on device performance. Through experimental characterization of the dynamic behaviour of endoscopic devices, it is demonstrated how geometrical features influence nonlinear dynamic responses. Period doubling, a known route to chaotic behaviour, is shown to be significantly influenced by the cutting tip shape, whereas the cutting tip has only a limited effect on Duffing-like responses, particularly the shape of the hysteresis curve, which is important for device stability. These findings underpin design, aiming to pave the way for a new generation of ultrasonic endoscopic surgical devices.

Three-dimensional computed tomographic evaluation of bilateral sagittal split osteotomy lingual fracture line and le fort I pterygomaxillary separation in orthognathic surgery using cadaver heads: ultrasonic osteotome versus conventional saw

PURPOSE

The purpose of this study was to observe the quality of the fracture line on the lingual side of the mandible after sagittal split osteotomy and the quality of pterygomaxillary separation after Le Fort I osteotomy using the BoneScalpel ultrasonic osteotome.

MATERIALS AND METHODS

Bimaxillary procedures, according to the standard protocol, were performed using 10 fresh cadaver heads. The ultrasonic osteotome was used in the study group, and a reciprocating saw was used in the control group. Three-dimensional reconstructions of postoperative computed tomographic scans were obtained. The lingual ramus fracture pattern and the pterygomaxillary separation pattern were observed, classified, and compared. Postoperative dissections of the skulls were performed to assess the integrity of the infra-alveolar nerve and the descending palatine artery.

RESULTS

No significant differences were found in the cutting time of bone between the BoneScalpel and the sagittal saw. Of the sagittal split osteotomies in the study group, 90% showed a good pattern (vertical pattern of fracture line extending to the inferior border of the mandible running behind the mandibular canal) compared with 50% of the sagittal split osteotomies in the control group. Ideal separation of the pterygoid plates without fractures was observed in 80% of the Le Fort I osteotomies in the study group compared with 50% of the osteotomies in the control group. High-level fractures occurred in 30% of cases in the control group compared with none in the study group. The integrities of the infra-alveolar nerve and the descending palatine artery were preserved in all cases.

CONCLUSION

Use of the ultrasonic BoneScalpel did not require more time than the conventional method. An improved pattern of lingual fracture lines in mandibular sagittal split osteotomy procedures and the pattern of pterygomaxillary separation in Le Fort I osteotomy procedures were observed.

Analysis of forces in conventional and ultrasonically assisted plane cutting of cortical bone

Bone cutting is a well accepted but technically demanding surgical procedure in orthopaedics. A level of tool penetration force during cutting of bones has been the prime concern to surgeons, since it can produce unnecessary mechanical damage to surrounding tissues. Research in this area has been undertaken for many decades to find ways to minimise the cutting force. Cutting of bone with ultrasonic tools is a relatively new technique replacing conventional procedures in neuro-, dental and orthopaedic surgeries, due to its precision and safety. In this article, the level of forces produced during a chisel-like tool penetration in a fresh cortical bone is studied. The obtained force data are analysed for both conventional cutting and ultrasonically assisted cutting. Through a series of experiments, it was demonstrated that the depth of cut and parameters of ultrasonic oscillations affected the level of cutting force, the former being the main factor in both types of cutting. It was found that the tool penetration force was decreased with an increase in the ultrasonic frequency or amplitude and was not affected by the cutting speed. The rise in bone temperature was measured and was found to be insensitive to the level of cutting speed within the range used in this study.

Characterisation of bone following ultrasonic cutting

OBJECTIVES

Ultrasonic surgery is an increasingly popular technique for cutting bone, but little research has investigated how the ultrasonic tip oscillations may affect the cuts they produce in bone. The aim of this investigation was to evaluate the oscillation and cutting characteristics of an ultrasonic surgical device.

MATERIALS AND METHODS

A Piezosurgery 3 (Mectron, Carasco, Italy) ultrasonic cutting system was utilised with an OP3 style tip. The system was operated with the tip in contact with porcine bone samples (loads of 50 to 200 g) mounted at 45° to the vertical insert tip and with a water flow of 57 ml/min. Tip oscillation amplitude was determined using scanning laser vibrometry. Bone surfaces defects were characterised using laser profilometry and scanning electron microscopy.

RESULTS

A positive relationship was observed between the magnitude of tip oscillations and the dimensions of defects cut into the bone surface. Overloading the tip led to a reduction in oscillation and hence in the defect produced. A contact load of 150 g provided the greatest depth of cut. Defects produced in the bone came from two clear phases of cutting.

CONCLUSIONS

The structure of the bone was found to be an important factor in the cut characteristics following piezosurgery.

CLINICAL RELEVANCE

Cutting of bone with ultrasonics is influenced by the load applied and the setting used. Care must be used to prevent the tip from sliding over the bone at low loadings.

Piezoelectric vs. conventional implant site preparation: ex vivo implant primary stability

OBJECTIVES

This study aims to determine differences in primary stability between implants placed in cortical bone following Piezoelectric or conventional site preparation, as assessed by resonance frequency analysis (RFA) and reverse torque testing (RTT).

MATERIAL AND METHODS

Four fresh bovine ribs were acquired and surgical guides fabricated with five sites per rib (n = 20), for proper site preparation. Implant sites were prepared via conventional drilling technique as per manufacturer's instruction (Implantium) or via Piezoelectric (Mectron) implant site preparation using the Implant Prep kit. Twenty 10 mm long, 3.6 mm diameter Implantium implants were placed with 35 Ncm torque; 10 implants per preparation method. RFA was assessed via the Osstell Mentor. Five values were taken per implant. All implants where subjected to a reverse torque in increasing increments of 5 until 50 Ncm force was reached.

RESULTS

The five RFA values per site were averaged and plotted by placement technique. A paired t-test statistical analysis was run. The average RFA values showed no statistical significance between the 10 test (RFA = 69.04 ± 5.11) and 10 control (RFA = 70.94 ± 6.41) sites (P > 0.05). All implants in both groups withstood RTT up to 50 Ncm force without movement and thus showed no statistical differences.

CONCLUSION

Results of this ex vivo study imply that the Piezoelectric implant site preparation affords similar primary implant stability in comparison to conventional rotary instrumentation in cortical bone.

High power, low frequency ultrasound: meniscal tissue interaction and ablation characteristics

This study evaluates high power low frequency ultrasound transmitted via a flat vibrating probe tip as an alternative technology for meniscal debridement in the bovine knee. An experimental force controlled testing rig was constructed using a 20 kHz ultrasonic probe suspended vertically from a load cell. Effect of variation in amplitude of distal tip displacement (242-494 μm peak-peak) settings and force (2.5-4.5 N) on tissue removal rate (TRR) and penetration rate (PR) for 52 bovine meniscus samples was analyzed. Temperature elevation in residual meniscus was measured by embedded thermocouples and histologic analysis. As amplitude or force increases, there is a linear increase in TRR (Mean: 0.9 to 11.2 mg/s) and PR (Mean: 0.08 to 0.73 mm/s). Maximum mean temperatures of 84.6°C and 52.3°C were recorded in residual tissue at 2 mm and 4 mm from the ultrasound probe-tissue interface. There is an inverse relationship between both amplitude and force, and temperature elevation, with higher settings resulting in less thermal damage.

Enhancing oral implantology with power ultrasonics

Oral implantology is the branch of dentistry focused on the reconstruction of missing teeth and their supporting structures with natural or synthetic substitutes. Conventional instruments used during oral implantation exhibit severe operational limitations, especially in the presence of limited surgical access, anatomically delicate bone structures, and proximity to soft tissues, because of the high risk of injury. This paper illustrates the design and performance characteristics of two novel ultrasonic devices developed to improve the implantation process. The working frequency of both systems is in the 25 to 26 kHz range and the acoustic power is modulated in line with the specific operations. The first tuned device presented in this work relies on a planar vibration at its tip to drill holes in bone. The second exploits a longitudinal-flexural composite vibration mode which facilitates the insertion of dental implants into the jawbone. The vibration characteristics of the proposed systems are investigated using finite element (FE) models subsequently validated by experimental modal analysis (EMA). Ultimately, the operational benefits of the investigated devices are supported by clinical evidence.

Influence of the power level of an ultra-sonic system on dental cavity preparation

The aim of this study was to evaluate the shape of dental cavities made with the CVDentus system using different ultrasound power levels. One standard cavity was made on the buccal aspect of 15 bovine incisors with a CVDentus cylindrical bur (82142). The sample was divided into three groups: G1-ultrasound with power II; G2-ultrasound with power III; and G3-ultrasound with power IV. A standardizing device was used to obtain standardized preparations and ultrasound was applied during one minute in each dental preparation. The cavities were sectioned in the middle, allowing observation of the cavity's profile with a magnifying glass, and width and depth measurement using the Leica Qwin program. The Kruskal-Wallis (p<0.05) and Dunn statistical analyses demonstrated differences between the dental cavity shapes when powers III and IV were used. However, the cavities that were made with power III presented dimensions similar to those of the bur used for preparation. We concluded that the power recommended by the manufacturer (III) is the most adequate for use with the CVDentus system.

Ultrasonic osteotomy as a new technique in craniomaxillofacial surgery

Ultrasound osteotomy is a new surgical technique used in dentistry to section hard tissues without damaging adjacent soft tissues. It was hypothesized that this could also be useful in craniofacial and orthognathic surgery. An ultrasonic device was employed in the following craniofacial surgical procedures: 144 Le Fort I osteotomies, 140 palatal expansions after Le Fort I osteotomies and 140 bilateral sagittal osteotomies; 2 Le Fort III osteotomies for treatment of Crouzon syndrome in two patients; 12 cases of unicortical calvarial bone grafting; removal of superior orbital roof in 25 cases of craniofaciostenosis; removal of external wall of the orbit in 10 cases of orbital cavity tumour; removal of anterior and posterior walls of the frontal sinuses in four cases of orbital cavity tumour. Integrity of soft tissues and surgical time were evaluated. Functional results were good without any soft-tissue damage being observed, but the overall operative time was increased. Ultrasound osteotomy is a new technical procedure that is advantageous for bone cutting in multiple situations, with minimal to no damage in adjacent soft tissues such as brain, palatal mucosa and the inferior alveolar nerve.

Piezoelectric osteotomy: a new technique for bone surgery-advantages in craniofacial surgery

INTRODUCTION

Ultrasonic bone cutting is a new surgical technique used in dentistry to section hard tissues without damaging adjacent soft tissues. We hypothesized that such a device could also be useful in craniofacial surgery, particularly during the removal of the superior orbital roof during craniofaciostenosis surgery.

MATERIALS AND METHODS

An ultrasonic device was employed in different craniofacial surgical procedures: 1. to remove the superior orbital roof in 30 cases of craniofaciostenosis, 2. to perform a Le Fort III osteotomy for the treatment of Crouzon syndrome in two patients, 3. to cut the parietal and frontal bone in 30 cases of craniofaciostenosis. The integrity of soft tissues and surgical time was evaluated.

RESULTS

Functional results were good without any soft tissue damage appreciated. The overall operative time, however, was increased.

CONCLUSIONS

Piezosurgery is a new technical procedure, which can be advantageous for bone cutting in multiple situations with minimal to no damage in adjacent soft tissues.

Qu’est-ce que la Piezosurgery®? Intérêten chirurgie craniomaxillofaciale. Àpropos de deux ans d'expérience

INTRODUCTION

Piezosurgery is a new surgical technique used in dentistry to section hard tissues without damaging adjacent soft tissues. We hypothesized that such a device could also be useful in craniofacial and orthognathic surgery.

MATERIAL AND METHOD

An ultrasonic device (Mectron) was employed in different craniofacial surgical procedures: a) to perform 144 Le Fort I osteotomies, 140 palatal expansions after Le Fort I osteotomies, and 134 bilateral sagittal osteotomies; b) to perform a Le Fort III osteotomy for treatment of Crouzon syndrome in 2 patients; c) to perform 5 segmental osteotomies and 3 osteotomies of the inferior edge of the mandible for facial asymmetry; d) to perform 12 cases of unicortical calvarial bone grafting; e) to remove the superior orbital roof in 20 cases of craniofaciostenosis and the frontal bone in 5 cases; f) to remove the external wall of the orbit or the anterior and posterior wall of the frontal sinuses in 10 cases of orbital cavity tumors; g) to approach the skull base through the frontal sinuses in 4 cases. Integrity of soft tissues and surgical time were evaluated.

RESULTS

Analysis of the results showed that Piezosurgery: a) allows very precise cutting; b) avoids bone cutting using an osteotome; c) spares soft tissue such as brain, dura-mater, palatal mucosa, and the inferior alveolar nerve; d) increases the time of bone cutting but not the overall operative time because of the absence of soft tissue protection.

DISCUSSION

Piezosurgery is a new technical procedure, which can be advantageous for bone cutting in many situations, sparing adjacent soft tissues such as brain, palatal mucosa, and the inferior alveolar nerve from any damage. The device's lack of power appears to be a minor problem compared with the advantages.

Evaluation of different rotary devices on bone repair in rabbits

In oral surgery, the quality of bone repair may be influenced by several factors that can increase the morbidity of the procedure. The type of equipment used for ostectomy can directly affect bone healing. The aim of this study was to evaluate bone repair of mandible bone defects prepared in rabbits using three different rotary devices. Fifteen New Zealand rabbits were randomly assigned to 3 groups (n=5) according to type of rotary device used to create bone defects: I - pneumatic low-speed rotation engine, II - pneumatic high-speed rotation engine, and III - electric low-speed rotation engine. The anatomic pieces were surgically obtained after 2, 7 and 30 days and submitted to histological and morphometric analysis. The morphometric results were expressed as the total area of bone remodeling matrix using an image analysis system. Increases in the bone remodeling matrix were noticed with time along the course of the experiment. No statistically significant differences (p>0.05) were observed among the groups at the three sacrificing time points considering the total area of bone mineralized matrix, although the histological analysis showed a slightly advanced bone repair in group III compared to the other two groups. The findings of the present study suggest that the type of rotary device used in oral and maxillofacial surgery does not interfere with the bone repair process.

Inferior Alveolar Nerve Transposition—An In Vitro Comparison Between Piezosurgery and Conventional Bur Use

An in vitro comparison between a new ultrasound-based piezoelectric device and a conventional bur was performed for lateralization or transposition of the inferior alveolar nerve to evaluate the effects on soft and hard tissue. Transposition of the inferior alveolar nerve was performed in the cadaver mandibles of 10 sheep: the left nerve was uncovered with a saline-cooled diamond-coated spherical bur (2000 rpm), and the right nerve was uncovered with the piezoelectric device mounted with a spherical diamond tip. The surface, the zone of bone defect, and the nerve were examined by light microscopy and laser microscopy. Bone treated with the rotary bur showed significantly smoother surfaces and shallower defect zones (50 microm) in comparison with the piezoelectric device (150 microm). Lesions of the epineurium and an increased amount of bone particles were found in the lesions prepared with the piezoelectric device. In vitro preparation with the piezoelectric device was more invasive to the bone than was a conventional diamond bur. Touching the inferior alveolar nerve resulted in roughening of the epineurium without affecting deeper structures. The degree of injury was lower than when using the conventional rotary bur.

Identification of milling parameters for manual cutting of bicortical bone structures

Within the framework of the development of a new neurosurgical robot system, parameters of conventional manual neurosurgical bone milling had to be determined. These results were used as a reference for the design and validation of the robotic versus manual milling task. Bovine scapulae were used for the tests because their bicortical structure is similar to the bone structure of the skull. The exercise was to cut defined geometries that had been registered on the bone prior to the start of the milling operation. The geometries had to be milled with a depth of 3 mm, which corresponded to the radius of the ball of the cutter. Different parameters like tool position, rotary speed, temperature, forces and time were registered. Eleven experienced neurosurgeons with practical experience of 80-1200 skull operations participated in this study. First results show a large variation in depth along the line. The lateral deviation was up to 5 mm, the depth error up to 2.5 mm, the tool temperature was 22 degrees C to 65 degrees C, and rotary speed varied from 15,000 to 80,000 rpm. Registered forces had maxima of 16 N in the feed direction and 21 N normal to the surface; average forces were approximately 1-2 N.

Investigations into the use of an ultrasonic chisel to cut bone. Part 2: Cutting ability

OBJECTIVES

Ultrasound may offer a possible alternative to rotary instruments for removing bone. This study was undertaken to analyse in vitro the various factors that influence the cutting of bone by an ultrasonic chisel.

STUDY DESIGN

A block of bovine femur was moved in a longitudinal direction under a stationary ultrasonic chisel. The force and depth of the cut was recorded for cutting rates of 28-112 mm/min and with increasing rake angles of 0 to +20 degrees. The pressure exerted by the chisel was recorded for different cutting rates.

RESULTS

When the cutting rate increases there is a corresponding increase in the downward force which is followed by a decrease in the force at rates greater than 56 mm/min. The depth of the cut increases up to a rate of 56 mm/min after which it decreases. Both the longitudinal and downward forces do not change when the rake angle changes from 0 to +10 degrees. The downward force decreases when the rake angle increases from +10 to +20 degrees.

CONCLUSIONS

The bone is cut slowly with the ultrasonic chisel, but this would assist in precision. Where such an instrument is used for cutting bone the clinicians should be aware that both low forces and cutting rates are required, and the instrument should be held at a low rake angle.