Bone Overheating Research Articles

Ex vivo Evaluation of a New Drill System for Placement of Percutaneous Bone Conduction Devices.

The procedure for installation of a percutaneous bone-conducting device has undergone significant improvements since its introduction 40 years ago. Today, the linear incision technique with tissue preservation (LITT-P) and the minimally invasive procedure (MIPS) are the most commonly used approaches. In both these techniques, a gradual increase of the osteotomy using a three-step drilling sequence is utilized, as this approach can allow a stepwise deepening and widening of the osteotomy in the mastoid and can prevent bone overheating. A new minimally invasive procedure (MONO) has been developed that allows an osteotomy to be performed and enables complete removal of the bone volume in one single drill step for a 4 mm implant using a novel parabolic twist drill. Here, the feasibility of the MONO procedure was qualitatively and quantitatively evaluated in terms of the dura response to drill trauma in comparison with the outcomes achieved with guide drills used for the LITT-P and MIPS techniques. Fresh frozen temporal bone from a human cadaver was subjected to penetration by three drills beyond the base of the mastoid bone to different depths. The sites were evaluated, and the damage to and possible penetration of the dura were determined. The results showed that for a drill depth exceeding mastoid bone thickness by not more than 1 mm, damage to the dura was limited or nonexistent, whereas for a drill depth exceeding bone thickness by 2 mm, damage increased, or the dura was penetrated. There was a trend toward more damage and penetration for both the round burr and MIPS guide drill compared with the MONO drill bit. From this experimental ex vivo study, it can be concluded that if the dura is encountered, the MONO system is not more inclined to penetrate the dura than the conventional LITT-P and MIPS systems.

The Assessment of the Maximum Heat Production and Cooling Effectiveness of Three Different Drill Types (Conical vs. Cylindrical vs. Horizontal) during Implant Bed Preparation—An In Vitro Study

The aim of this experimental study was to verify thermal diffusion differences, by measuring the maximum temperature achieved with different drill shapes. Synthetic bone blocks of type I density made from solid rigid polyurethane (PUR) foam were used to perform the drilling procedures. The experiment was conducted at three different rotation speeds: 800, 3000 and 5000 rpm. Conical drills (with and without an internal cooling hole) were compared with horizontal drills and disc drills. The temperature during drilling for implant bed preparation was estimated with the use of thermocouples and an infrared (IR) camera. The temperature during drilling with disc cutters for lateral basal implants did not exceed 33 ∘C and the temperature decreased in proportion to higher drill speed. The results indicate that the tested design is safe and will not cause bone overheating.

Bone Temperature Variation Using a 3D-Printed Surgical Guide with Internal Irrigation

Bone overheating is a possible cause of implants early failure. When a surgical guide is used, the risk of heat injury is greater due to the reduced efficacy of the irrigation. The aim of this ex vivo study was to evaluate the effect of an additional built-in irrigation on bone temperature variation during implant osteotomy. Twelve bovine ribs were used. Cone beam computerized tomography (CBCT) was performed and a 3D-printed surgical guide with additional built-in irrigation tubes was produced for each rib. A total of 48 osteotomies were prepared, to compare the supplementary internal irrigation system (Group A) with external irrigation alone (Group B), no irrigation (Group C) and with free-hand surgery with external irrigation (Group D). Temperature was measured by three thermocouples placed at depths of 1.5, 7, and 12 mm. The largest temperature variation at each thermocouple showed median values of 3.0 °C, 1.9 °C, and 2.3 °C in Group 1; 2.3 °C, 1.7 °C, and 0.9 °C in Group 2; 3.2 °C, 1.6 °C, and 2.0 °C in Group 3; 2.0 °C, 2.0 °C, and 1.3 °C in Group 4, respectively. No differences were found among the four groups. In general, the highest temperature increase was observed with the use of the first drill (cortical perforator). Post-experimental CBCT revealed the presence of radiopaque material clogging the aperture of the internal irrigation channels. Additional internal irrigation was not found to significantly contribute to decrease bone temperature in this ex vivo setting.

Temperatures generated during implant site preparation with conventional drilling versus single-drill method: an ex-vivo human mandible study

Bone overheating during osteotomy is a potential cause of necrosis and consequent failure of dental implant osseointegration. The aim of this study is to identify any differences between conventional osteotomy with drills of increasing size and the use of a single drill in terms of the temperature increase in the bone during implant site preparation. Thirty-eight implant sites were prepared in ex vivo human mandibles, 19 using the conventional method with drills of increasing diameter (group A) and 19 using a single-drill method (group B), with no irrigation in either procedure. An infrared thermometer was used to measure the temperature difference (T°) induced by the drills at each site. Student's t-test (with P<0.05) was used to compare the temperature increase induced by the last drill in group A, and by the single drill in group B. The mean ΔT° in group A was 0.64 °C, while in group B it was 1.47 °C. The difference between the temperatures obtained in the two groups was statistically significant (P=0.0073). In statistical terms, the two methods differ significantly in the temperature increase induced by the drilling procedure, but this difference is clinically irrelevant.

Uncovering dental implants using a new thermo-optically powered (TOP) technology with tissue air-cooling.

Uncovering implants with lasers, while bloodless, has been associated with a risk of implant and bone overheating. The present study evaluated the effect of using a new generation of high-power diode lasers on the temperature of a dental implant and the surrounding tissues using an in vitro model. The implant temperature was measured at three locations using micro thermocouples. Collateral thermal damage of uncovered soft tissues was evaluated using NTBC stain. Implant temperature rise during and collateral thermal soft-tissue damage following implant uncovering with and without tissue air-cooling was studied using both the classic operational mode and the new thermo-optically powered (TOP) technology. For the classic surgical mode using a cork-initiated tip and constant laser power set at 3.4 W, the maximum temperature rise in the coronal and apical parts of the implant was 23.2 ± 4.1°С and 9.5 ± 1.8°С, respectively, while 1.5 ± 0.5 mm of collateral thermal damage of the soft tissue surrounding the implant model occurred. Using the TOP surgical tip with constant laser power reduced implant overheating by 30%; collateral thermal soft-tissue damage was 0.8 ± 0.2 mm. Using the TOP surgical mode with a tip temperature setting of 800°C and air-cooling reduced the implant temperature rise by more than 300%, and only 0.2 ± 0.1 mm of collateral thermal soft-tissue damage occurred, typical for optimized CO2 laser surgery. Furthermore, use of the new generation diode technology (TOP surgical mode) appeared to reduce the time required for implant uncovering by a factor of two, compared to the standard surgical mode. Use of the new generation diode technology (TOP surgical mode) may significantly reduce overheating of dental implants during uncovering and seems to be safer for the adjacent soft and hard tissues. Use of such diode lasers with air-cooling can radically reduce the rise in implant temperatures (by more than three times), potentially making this technology safe and effective for implant uncovering.

HIFU scattering by the ribs: constrained optimisation with a complex surface impedance boundary condition

High intensity focused ultrasound (HIFU) enables highly localised, non-invasive tissue ablation and its efficacy has been demonstrated in the treatment of a range of cancers, including those of the kidney, prostate and breast. HIFU offers the ability to treat deep-seated tumours locally, and potentially bears fewer side effects than more established treatment modalities such as resection, chemotherapy and ionising radiation. There remains however a number of significant challenges which currently hinder its widespread clinical application. One of these challenges is the need to transmit sufficient energy through the ribcage to ablate tissue at the required foci whilst minimising the formation of side lobes and sparing healthy tissue. Ribs both absorb and reflect ultrasound strongly. This sometimes results in overheating of bone and overlying tissue during treatment, leading to skin burns. Successful treatment of a patient with tumours in the upper abdomen therefore requires a thorough understanding of the way acoustic and thermal energy is deposited. Previously, a boundary element (BE) approach based on a Generalised Minimal Residual (GMRES) implementation of the Burton-Miller formulation was developed to predict the field of a multi-element HIFU array scattered by human ribs, the topology of which was obtained from CT scan data [1]. Dissipative mechanisms inside the propagating medium have since been implemented, together with a complex surface impedance condition at the surface of the ribs. A reformulation of the boundary element equations as a constrained optimisation problem was carried out to determine the complex surface velocities of a multi-element HIFU array which generated the acoustic pressure field that best fitted a required acoustic pressure distribution in a least-squares sense. This was done whilst ensuring that an acoustic dose rate parameter at the surface of the ribs was kept below a specified threshold. The methodology was tested at an excitation frequency of 1 MHz on a spherical multi-element array in the presence of anatomical ribs.

Scattering of high-intensity focused ultrasound by the ribs: Constrained optimization with a complex surface impedance boundary condition

One of the challenges of trans-rib high-intensity focused ultrasound (HIFU) treatment is the need to transmit sufficient energy through the ribcage to ablate tissue whilst minimizing the formation of side lobes, and sparing healthy tissue. Ribs strongly absorb and reflect ultrasound. This may result in overheating of bone and overlying tissue during treatment, leading to skin burns. Successful treatment of a patient with tumors of the liver or the pancreas therefore requires a thorough understanding of the way acoustic and thermal energy is deposited. A boundary element approach was developed to predict the field of a multi-element HIFU array scattered by human ribs in 3D. This forward model has been reformulated as a constrained least squares optimization problem where the velocity of each individual element on the array is an optimization variable. A locally reacting complex surface impedance condition at the surface of the ribs has been implemented. The methodology has been tested at an excitation frequency of 1 MHz on a spherical section multi-element array and a total of six array-rib configurations have been investigated. The results were compared against other focusing and rib-sparing approaches, demonstrating the efficacy and flexibility of the constrained optimization approach.

Towards the optimisation of acoustic fields for ablative therapies of tumours in the upper abdomen

The efficacy of high intensity focused ultrasound (HIFU) for the non-invasive treatment of cancer has been demonstrated for a range of different cancers including those of the liver, kidney, prostate and breast. As a non-invasive focused therapy, HIFU offers considerable advantages over other techniques such as chemotherapy and surgical resection, in terms of its non-invasiveness and low risk of harmful side effects. There is, however, a number of significant challenges which currently hinder its widespread clinical application. One of these challenges is the need to transmit sufficient energy through the ribcage to induce tissue necrosis at the required foci whilst minimising the formation of side lobes and sparing healthy tissue. Ribs both absorb and reflect ultrasound strongly. As such, a common side effect of focusing ultrasound in regions located behind the rib cage is the overheating of bone and surrounding tissue, which can lead to skin burns. Successful treatment of a patient with tumours in the upper abdomen therefore requires a thorough understanding of the way acoustic and thermal energy are deposited. This is likely to rely on a treatment planning procedure in which optimal source velocity distributions are obtained so as to maximise a dose quantity at the treatment sites, whilst ensuring that this quantity does not exceed a specified threshold at other field locations, particularly on the surface of the ribs. Previously, a boundary element approach based on a Generalised Minimal Residual (GMRES) implementation of the Burton-Miller formulation was developed to predict the field of a multi-element HIFU array scattered by human ribs, the topology of which was obtained from CT scan data [1]. This work describes the reformulation of the boundary element equations as a least-squares minimisation problem with non-linear constraints. The methodology was subsequently tested at an excitation frequency of 100 kHz on a spherical multi-element array in the presence of a perfectly rigid cylindrical scatterer with hemi-spherical end-caps. Reduction of side lobes in the exterior domain and of acoustic pressure magnitudes on the surface of the cylinder were achieved whilst preserving a local maximum in the focal region.

Design and performance study of an orthopaedic surgery robotized module for automatic bone drilling

Many orthopaedic operations involve drilling and tapping before the insertion of screws into a bone. This drilling is usually performed manually, thus introducing many problems. These include attaining a specific drilling accuracy, preventing blood vessels from breaking, and minimizing drill oscillations that would widen the hole. Bone overheating is the most important problem. To avoid such problems and reduce the subjective factor, automated drilling is recommended. Because numerous parameters influence the drilling process, this study examined some experimental methods. These concerned the experimental identification of technical drilling parameters, including the bone resistance force and temperature in the drilling process. During the drilling process, the following parameters were monitored: time, linear velocity, angular velocity, resistance force, penetration depth, and temperature. Specific drilling effects were revealed during the experiments. The accuracy was improved at the starting point of the drilling, and the error for the entire process was less than 0.2 mm. The temperature deviations were kept within tolerable limits. The results of various experiments with different drilling velocities, drill bit diameters, and penetration depths are presented in tables, as well as the curves of the resistance force and temperature with respect to time. Real-time digital indications of the progress of the drilling process are shown. Automatic bone drilling could entirely solve the problems that usually arise during manual drilling. An experimental setup was designed to identify bone drilling parameters such as the resistance force arising from variable bone density, appropriate mechanical drilling torque, linear speed of the drill, and electromechanical characteristics of the motors, drives, and corresponding controllers. Automatic drilling guarantees greater safety for the patient. Moreover, the robot presented is user-friendly because it is simple to set robot tasks, and process data are collected in real time.

Insufficient irrigation induces peri‐implant bone resorption: an in vivo histologic analysis in sheep

To measure in vivo impact of dense bone overheating on implant osseointegration and peri-implant bone resorption comparing different bur irrigation methods vs. no irrigation. Twenty TI-bone implants were inserted in the inferior edge of mandibles of sheep. Different cooling procedures were used in each group: no irrigation (group A), only internal bur irrigation (group B), both internal and external irrigation (group C), and external irrigation (group D). The histomorphometric parameters calculated for each implant were as follows: %cortical bone-implant contact (%CBIC) and %cortical bone volume (%CBV). Friedman's test was applied to test the statistical differences. In group A, we found a huge resorption of cortical bone with %CBIC and %CBV values extremely low. Groups B and C showed mean %CBIC and %BV values higher than other groups The mean %CBV value was significantly different when comparing group B and group C vs. group A (P < 0.05). Significant differences in %CBIC were found also between group C and group A (P < 0.05). Thermal injury, due to insufficient irrigation, of hard bone caused massive resorption of the cortical bone and implant failure. Drilling procedures on hard bone need an adequate cooling supply because the bone matrix overheating may induce complete resorption of dense bone around implants. Internal-external irrigation and only internal irrigation showed to be more efficient than other types of cooling methods in preventing bone resorption around implants.

The optimization of acoustic fields for ablative therapies of tumours in the upper abdomen

High intensity focused ultrasound (HIFU) enables highly localized, non-invasive tissue ablation and its efficacy has been demonstrated in the treatment of a range of cancers, including those of the kidney, prostate and breast. HIFU offers the ability to treat deep-seated tumours locally, and potentially bears fewer side effects than more invasive treatment modalities such as resection, chemotherapy and ionizing radiation. There remains however a number of significant challenges which currently hinder its widespread clinical application. One of these challenges is the need to transmit sufficient energy through the ribcage to ablate tissue at the required foci whilst minimizing the formation of side lobes and sparing healthy tissue. Ribs both absorb and reflect ultrasound strongly. This sometimes results in overheating of bone and overlying tissue during treatment, leading to skin burns. Successful treatment of a patient with tumours in the upper abdomen therefore requires a thorough understanding of the way acoustic and thermal energy is deposited. Previously, a boundary element approach based on a Generalized Minimal Residual (GMRES) implementation of the Burton–Miller formulation was developed to predict the field of a multi-element HIFU array scattered by human ribs, the topology of which was obtained from CT scan data (Gélat et al 2011 Phys. Med. Biol. 56 5553–81). The present paper describes the reformulation of the boundary element equations as a least-squares minimization problem with nonlinear constraints. The methodology has subsequently been tested at an excitation frequency of 1 MHz on a spherical multi-element array in the presence of ribs. A single array–rib geometry was investigated on which a 50% reduction in the maximum acoustic pressure magnitude on the surface of the ribs was achieved with only a 4% reduction in the peak focal pressure compared to the spherical focusing case. This method was then compared with a binarized apodization approach based on ray tracing and against the decomposition of the time-reversal operator (DORT). In both cases, the constrained optimization provided a superior ratio of focal peak pressure to maximum pressure magnitude on the surface of the ribs.

Implant periapical lesion: Diagnosis and treatment

The implant periapical lesion is the infectious-inflammatory process of the tissues surrounding the implant apex. It may be caused by different factors: contamination of the implant surface, overheating of bone during drilling, preparation of a longer implant bed than the implant itself, and pre-existing bone disease. Diagnosis is achieved by studying the presence of symptoms and signs such us pain, swelling, suppuration or fistula; in the radiograph an implant periapical radiolucency may appear. A diagnostic classification is proposed to establish the stage of the lesion, and determine the best treatment option accordingly. The following stages are distinguished: acute apical periimplantitis (non-suppurated and suppurated) and subcacute (or suppurated-fistulized) apical periimplantitis. The most adequate treatment of this pathology in the acute stage and in the subacute stage if there is no loss of implant stability is apical surgery. In the subacute stage, if there is implant mobility, the extraction of the implant is necessary. Key words:Implant periapical lesion, apical periimplantitis, retrograde periimplantitis.

Implant Periapical Lesions: Etiology and Treatment Options

Implant failures due to apical pathology are conditions that have not been extensively studied nor reported in the literature. The implant periapical lesion (IPAL) has different symptoms, and several etiologies have been proposed in the literature. This article reviews cases of IPAL reported in peer-reviewed journals and presents possible treatment options. Analysis of the data collected was performed based on diagnosis, cause of extraction of the natural tooth, location, period of implant placement, implant surface, and treatment approach. Even the data presented in this review are based on few reported cases the etiology of these lesions seems to be multifactorial or with an unknown origin. Contamination of the implant surface, bone overheating during surgery, excessive torquing of the implant, poor bone quality, perforation or thinning of the cortical bone, premature or excessive load over the fixture, fracture of the bone inside the hollow portion of the hollow implant, and an implant placement in an infected maxillary sinus have been discussed. In general, areas around endodontically compromised teeth should be carefully analyzed prior to implant placement to prevent implant failures.

Robotized System for Automation of the Drilling in the Orthopedic Surgery. Control Algorithms and Experimental Results

Many orthopedic operations involve drilling and tapping before the insertion of screws into bone. Usually the drilling is executed by hand which brings lots of problems. The accuracy of the drilling, the possibility of braking the blood vessels after the rear hole, the oscillations widening the hole diameter – there are some of examples for that. But the bone overheating is the most important problem. To avoid these problems and reduce the subjective factor the automation drilling is recommended. In the work the automatic drilling module is presented as well as the experimental setup design for establishment the drilling process technical parameters and especially the bone resistant force measurement. The obtained results are shown and the corresponding conclusions are done.

Inflammatory Implant Periapical Lesion: Etiology, Diagnosis, and Treatment—Presentation of 7 Cases

To investigate implant periapical lesions, and to describe their treatment. The hypothesis of this evaluation is that implant periapical lesions are disorders of the area surrounding the apex of a dental implant, and that their etiology can be multifactorial (ie, vascular impairment, vascular ischemia, overheating of bone during drilling, and implant surface contamination). The diagnosis is based on the clinical manifestations and x-ray findings. The x-ray findings usually involve a periapical radiotransparency. Seven patients with implant periapical lesions (3 in the upper jaw, and 4 in the mandible) after implant placement are described. All patients reported pain, and 3 suffered from inflammation. Upon percussion, the 3 nonsubmerged implants produced a dull sound, with no mobility. A panoramic x-ray study showed periapical transparencies around 5 implants, whereas in 1 case, computed tomography showed a maxillary sinus reaction. The diagnosis was acute apical peri-implantitis (nonsuppurative in 2 cases, and suppurative in 5 cases). The clinical manifestations did not subside with antibiotics. In all cases, treatment consisted of implant periapical surgery, after which the symptoms disappeared. The radiotransparencies showed progressive resolution. The possibility of implant periapical lesions must be taken into account. A rapid diagnosis should be established to treat the lesions at an early stage, hence preventing the need for implant extraction.

Microscopical features in retrieved human Branemark implants: a report of 19 cases

Synopsis The authors present a histologic analysis of 19 Branemark titanium implants retrieved for different causes: four implants were removed for abutment fracture, one for dental nerve dysesthesia, two for bone overheating, two for peri-implantitis, nine for mobility, one for unknown causes. In the implants removed for fracture a high bone-implant contact percentage was present (71.83±4.96%) with compact, mature bone at the interface. The picture of the failure due to bone overheating was characteristic with the presence of bone sequestra and of a gap between implant and bone filled by lymphocytes and plasma cells: many bacteria surrounded the necrotic bone and no newly regenerated bone was present. In peri-implantitis an inflammatory infiltrate was observed in the peri-implant tissues: a dense fibrous connective tissue was present around implants failed for mobility. The microscopical picture is certainly extremely important in identifying the causal determinants of an implant failure.

A histologic evaluation of eight cases of failed dental implants: is bone overheating the most probable cause?

Biomechanical overloading has been stated to be, overall, the major cause of implant failures. Very important can be, however, in the etiopathogenesis of early implant failure, the overheating of the surgical site. The authors present eight cases of implant loss most probably due to bone overheating, even if other causes cannot be excluded. The microscopical picture, in all cases, was composed by the same features: 1. presence of bone sequestra; 2. no regeneration of the peri-implant bone; 3. presence of an inflammatory infiltrate in the gap between bone and implant; 4. no organization of the peri-implant bone clot; 5. presence of a compact and mature bone around the implant; 6. presence of bacteria around the implant and the necrotic bone.