Sensitivity of resonance frequency analysis method to assess implant stability

The aim of this human cadaver study was to determine the correlation between bone quality and implant stability parameters, and the relationship between resonance frequency value and peri-implant bone loss. Thirty-two implants were placed into four human cadaver mandibles. The bone density of the implant recipient site was determined using computerized tomography (CT) in Hounsfield units (HU). The peak insertion torque values were recorded. The resonance frequency (RF) measurements were performed immediately following implant insertion and also after one, two and three turns of the implant in a counterclockwise direction, representing peri-implant bone loss. The mean bone density, insertion torque and RFA values of all implants were 152 +/- 264 HU, 41.7 +/- 6 Ncm and 69.7 +/- 9 ISQ. Statistically significant correlations were found between bone density and insertion torque values, bone density and ISQ values, and insertion torque and ISQ values. A significant influence of the peri-implant bone loss on ISQ value was also observed. The findings from this study illustrate significant correlation between bone density and implant stability parameters, and a linear relationship between peri-implant bone levels and resonance frequency value.     

Biomechanical aspects of primary implant stability: a human cadaver study

Background: The quality of bone is an important factor in the successful implant treatment, and it is evident that higher implant failure is more likely in poor quality of bone. The primary stability of oral implants related to resistance to micromotion during healing is influenced by bone quality, surgical technique, and implant design.
Purposes: The aims of this biomechanical study were to explore the effect of bone quality on initial intraosseous stability of implants, and to determine the correlations between the bone quality and implant stability parameters.
Materials and Methods: Twenty-four implants (Neoss Ltd., Mölnlycke, Sweden) were placed into anterior and posterior regions of three human cadaver mandibles. The bone densities of implant recipient sites were preoperatively determined using computerized tomography (CT) in Hounsfield unit (HU). The maximum insertion torque values were recorded, and primary implant stability measurements were noninvasively performed by means of resonance frequency analysis (RFA).
Results: The bone density values ranged from −267 HU to 553 HU. It was found that mean bone density, insertion torque, and RFA values were 113 ± 270 HU, 41.9 ± 5 Ncm, and 70 ± 7 implant stability quotient (ISQ), respectively. Statistically significant correlations were found between bone density and insertion torque values ( r  = 0.690, p  < .001); bone density and ISQ values ( r  = 0.557, p  < .05); and insertion torque and ISQ values ( r  = 0.853, p  < .001).
Conclusion: CT is a useful tool to assess bone quantity and quality in implant recipient sites, and bone density has a prevailing effect on implant stability at placement.     

Bone density assessments of dental implant sites: 3. Bone quality evaluation during osteotomy and implant placement

PURPOSE: In previous publications of this series of studies on human cadaver jaws, bone densities were assessed and compared using subjective evaluation, conventional computed tomography (CT), and cone-beam computed tomography (CBCT). The aim of this study was to compare subjective bone quality during osteotomy and implant insertion resistance torque to noninvasive subjective and objective radiographic bone density assessments. MATERIALS AND METHODS: Forty-two designated implant sites were selected. Self-tapping implants were inserted into these sites. The operator subjectively rated the bone density during the osteotomy procedure. Resistance torque was recorded during insertion of the implants. RESULTS: Subjective drilling resistance was modestly correlated to subjective radiographic density evaluation (Lekholm and Zarb; Spearman's rho of 0.53, P < .001). Subjective drilling resistance compared to the bone density in Hounsfield units (HU) obtained using CT and CBCT showed correlation coefficients of 0.61 and 0.59, respectively (P < .001). Significant overlap of density values was found for adjacent drilling ratings. On average, a difference in bone density of 180 HU was required to identify differences between drilling resistance groups. Comparisons of 2 implant insertion resistance torque variables (highest reading and regression slope of available readings) with CT and CBCT HU showed correlation coefficients of 0.61 to 0.63 (P < .01). CONCLUSION: Insertion torque resistance was modestly correlated with objective CT and CBCT measurements of bone density. The merit of these assessments of cadavers awaits clinical study.     

The primary stability of two dental implant systems in low-density bone

Primary stability in low-density bone is crucial for the long-term success of implants. Tapered implants have shown particularly favourable properties under such conditions. The aim of this study was to compare the primary stability of tapered titanium and novel cylindrical zirconia dental implant systems in low-density bone. Fifty implants (25 tapered, 25 cylindrical) were placed in the anterior maxillary bone of cadavers meeting the criteria of low-density bone. The maximum insertion (ITV) and removal (RTV) torque values were recorded, and the implant stability quotients (ISQ) determined. To establish the isolated influence of cancellous bone on primary stability, the implantation procedure was performed in standardized low-density polyurethane foam bone blocks (cancellous bone model) using the same procedure. The primary stability parameters of both implant types showed significant positive correlations with bone density (Hounsfield units) and cortical thickness. In the cadaver, the cylindrical zirconia implants showed a significantly higher mean ISQ when compared to the tapered titanium implants (50.58 vs 37.26; P < 0.001). Pearson analysis showed significant positive correlations between ITV and ISQ (P = 0.016) and between RTV and ISQ (P = 0.035) for the cylindrical zirconia implants; no such correlations were observed for the tapered titanium implants. Within the limitations of this study, the results indicate that cylindrical zirconia implants represent a comparable viable treatment option to tapered titanium implants in terms of primary implant stability in low-density human bone.     

Analysis of bone stress and primary stability of a dental implant using strain and torque measurements

IntroductionThe consensus among researchers is that early failure of dental implants is due to the lack of primary stability and compressive stress on the peri-implant bone that exceeds the physiological tolerance.ObjectiveThe objective of this work is to propose a new methodology to quantify bone stress during dental implant insertion and to correlate it with primary stability.Materials and MethodsTitanium dental implants with a diameter of 3.75 mm were inserted in a 3.35 mm hole of a synthetic bone of polyurethane (PU) foam with a density of 20 PCF (0.32 g/cm³). During insertion, the insertion torque was measured with a digital torque meter and the bone strain was measured with strain gages located at 2, 4, 6, 8, and 10 mm from the coronal region.ResultsThe tests showed that the compressive strain is maximum in the third coronal region and decreases in the apical direction. The data also showed that there is a relationship between strain, insertion torque, and the primary stability of dental implants.ConclusionThe stress and strain on the bone progressively decreased from the coronal to the apical third. The maximum compressive stress (0.42 MPa) during insertion of the implant did not exceed bone strength. Insertion of 3.75 mm implants in type D2 bone with a 3.35 mm hole provides adequate primary stability without excessive compression of the bone.Clinical SignificanceFor the implant-bone combination used in the present study, the compressive stress generated during implant insertion did not exceed the physiological limit of cortical and medullary bone to the point of impairing osseointegration.     

Evaluation of Primary Stability of Self‐Tapping and Non‐Self‐Tapping Dental Implants. A 12‐Week Clinical Study

Purpose: The aim of this study was to investigate the relationship between surgical techniques and implant macro‐design (self‐tapping/non‐self‐tapping) for the optimization of implant stability in the low‐density bone present in the posterior maxilla using resonance frequency analysis (RFA). Materials and Methods: A total of 102 implants were studied. Fifty‐six self‐tapping BlueSkyBredent® (Bredent GmbH&Co.Kg®, Senden, Germany) and 56 non‐self‐tapping Standard Plus Straumann® (Institut Straumann AG®, Waldenburg, Switzerland) were placed in the posterior segment of the maxilla. Implants of both types were placed in sites prepared with either lateral bone‐condensing or with bone‐drilling techniques. Implant stability measurements were performed using RFA immediately after implant placement and weekly during a 12‐week follow‐up period. Results: Both types of implants placed after bone condensing achieved significantly higher stability immediately after surgery, as well as during the entire 12‐week observation period compared with those placed following bone drilling. After bone condensation, there were no significant differences in primary stability or in implant stability after the first week between both implant types. From 2 to 12 postoperative weeks, significantly higher stability was shown by self‐tapping implants. After bone drilling, self‐tapping implants achieved significantly higher stability than non‐self‐tapping implants during the entire follow‐up period. Conclusions: The outcomes of the present study indicate that bone drilling is not an effective technique for improving implant stability and, following this technique, the use of self‐tapping implants is highly recommended. Implant stability optimization in the soft bone can be achieved by lateral bone‐condensing technique, regardless of implant macro‐design.     

Semiautomatic device for in vitro/ experimental bone perforation in dental implant research

PurposeThe present study presents a semiautomatic device developed to perform in vitro experiments using surgical drills for assisting dental implant research. It was built to perform tests independent of human direct contact, and contains an adjustable toolholder for engaging different types of implant contra angle hand pieces, in which different drills can be adapted. The researcher is able to make a range of adjustments on the machine, such as controlling the drilling force and depth.Materials and methodsThe device was tested on samples of both synthetic and natural bone with type I density, and a sequence of drills selected to perform the perforations. Drilling time and perforation force exerted during drilling were evaluated, as both parameters are required to be standardized.ResultsIt was observed that the drilling performed using the device was uniform using both types of bone, although the drilling time for the synthetic bone was higher. All perforations were exactly on the spot previously determined, and without variations in drill angulations. The perforation force was higher for the lance pilot drill for both bone types, and the natural bone required a higher axial force than the synthetic bone.ConclusionThus, we consider this device trustable to perform standardized analysis and provide accurate results. It can be used for tests performed in universities and companies that develop dental implant materials and products.     

Fresh‐frozen vs. embalmed bone: is it possible to use formalin‐fixed human bone for biomechanical experiments on implants?

Purpose: As formalin is an extremely reactive electrophilic chemical that reacts with tissues, the purpose of this study was to explore whether formalin fixation could potentially alter the mechanical properties of bone tissue and have an effect on the primary stability measurements of implants.
Material and methods: ∅3.3 × 8 mm, ∅4.1 × 8 mm, and ∅4.8 × 8 mm implants were placed on sockets prepared into the anterior surface of the radius of two fresh-frozen human cadavers. The insertion torque of each implant was quantified using a strain-gauged torque-wrench connected to a data acquisition system at a sample rate of 10 KHz, and resonance frequency analysis measurements were also undertaken for each implant. The cadavers were then subjected to embalment with 10% formalin for 3 months, and the same experiments were undertaken on the contra lateral radius of the cadavers.
Results: The insertion torques before and after chemical fixation were similar for ∅3.3 mm ( P >0.05), and higher values were obtained for ∅4.1 mm and ∅4.8 mm implants after chemical fixation ( P <0.05). The resonance frequency analysis values before and after chemical fixation were similar for all implants ( P >0.05).
Conclusions: Implants have higher insertion torque values in formalin-fixed bone than fresh-frozen human bone, but similar implant stability quotients in both cases. The insertion torque technique can detect the difference between formalin-fixed and fresh-frozen human bone, but resonance frequency analysis cannot.     

Adapted preparation technique for screw-type implants: explorative in vitro pilot study in a porcine bone model

Objective: The aim of this study was to quantify the effect of adapted preparation on the insertion torque of self‐tapping implants in cancellous bone. In adapted preparation, bone condensation – and thus, insertion torque – is controlled by changing the diameter of the drilling. Material and methods: After preparation of cancellous porcine vertebral bone with drills of 2.85, 3, 3.15 or 3.35 mm final diameters, Brånemark sytem^® Mk III implants (3.75 × 11.5 mm) were inserted in 141 sites. During implantation, the insertion torque was recorded. Prior to implant insertion, bone mineralization (bone mineral density (BMD)) was measured with dental quantative computed tomography. The BMD values measured at the implant position were correlated with insertion torque for varying bone condensation. Results: Based on the average torque recorded during implant insertion into the pre‐drilled canals with a diameter of 3 mm, torque increased by approximately 17% on reducing the diameter of the drill by 5% (to 2.85 mm). On increasing the diameter of the osteotomy to 3.15 mm (5%) or 3.35 mm (12%), torque values decreased by approximately 21% and 50%, respectively. Conclusion: The results demonstrate a correlation between primary stability (average insertion torque) and the diameter of the implant bed on using a screw‐shaped implant. Thus, using an individualized bone mineralization‐dependent drilling technique, optimized torque values could be achieved in all tested bone qualities with BMDs ranging from 330 to 500 mg/cm³. The results indicate that using a bone‐dependent drilling technique, higher torque values can also be achieved in poor bone using an individualized drilling resulting in higher bone condensation. As immediate function is dependent on primary stability (high insertion torque), this indicates that primary stability can be increased using a modified drilling technique in lesser mineralized bone.     

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.     

Alveolar segmental "sandwich" osteotomies for posterior edentulous mandibular sites for dental implants.

PURPOSE: The purpose of this retrospective study was to evaluate crestal stability of alveolar augmentation using an interpositional bone graft for dental implant restorations. PATIENTS AND METHODS: Eight patients with 10 graft sites were followed from 1 to 4 years with panographic evaluation to determine if dimension changes of the alveolar graft sites had occurred. RESULTS: Ten graft sites showed stability and maintenance of alveolar form and osseointegration of restored dental implants. Very little loss of crestal height was observed; 20 of 22 implants placed remained stable at follow-up. CONCLUSION: The interpositional alveolar bone graft appears to be a viable alternative to block grafting or guided bone regeneration.     

Influence of surgical technique and surface roughness on the primary stability of an implant in artificial bone with different cortical thickness: a laboratory study

Objective: The aim of this biomechanical study was to assess the interrelated effect of both surface roughness and surgical technique on the primary stability of dental implants. Material and methods: For the experiment, 160 screw‐designed implants (Biocomp^®), with either a machined or an etched surface topography, were inserted into polyurethane foam blocks (Sawbones^®). As an equivalent of trabecular bone, a density of 0.48 g/cm³ was chosen. To mimic the cortical layer, on top of these blocks short‐fibre‐filled epoxy sheets were attached with a thickness varying from 0 to 2.5 mm. The implant sites were prepared using either a press‐fit or an undersized technique. To measure the primary stability of the implant, both the insertion and the removal torques were scored. Results: Independent of the surgical technique used, both implant types showed an increased insertion and removal torque values with increasing cortical thickness, although >2 mm cortical layer no further increase in insertion torque was observed. In the models with only trabecular bone (without cortical layer) and with a 1 mm cortical layer, both implant types showed a statistically higher insertion and removal torque values for undersized compared with the press‐fit technique. In addition, etched implants showed a statistically higher insertion and removal torque mean values compared with machined implants. In the models with 2 and 2.5 mm cortical layers, with respect to the insertion torque values, no effect of either implantation technique or implant surface topography could be observed. Conclusion: The placement of etched implants in synthetic bone models using an undersized preparation technique resulted in enhanced primary implant stability. A correlation was found between the primary stability and the cortical thickness. However, at or above a cortical thickness of 2 mm, the effect of both an undersized surgical approach, as also the presence of a roughened (etched) implant surface, had no extra effect. Besides the mechanical aspects, the biological effect of undersized drilling, i.e. the bone response on the extra insertion torque forces should also be elucidated. Therefore, additional in vivo studies are needed. To cite this article:
Tabassum A, Meijer GJ, Wolke JGC, Jansen JA. Influence of surgical technique and surface roughness on the primary stability of an implant in artificial bone with different cortical thickness: a laboratory study.
Clin. Oral Impl. Res. 21 , 2010; 213–220.
doi: 10.1111/j.1600‐0501.2009.01823.x     

Influence of off-axis loading of an anterior maxillary implant: a 3-dimensional finite element analysis

PURPOSE: To evaluate the influence of the stress/strain distribution in bone around an anterior maxillary implant using 2 types of bone and under 3 different loads. MATERIALS AND METHODS: A premaxillary finite element model featuring an implant and its superstructure was created. Six different testing conditions incorporating 2 types of cancellous bone (high density and low density) under 3 different loading angles (0, 30, and 60 degrees) relative to the long axis of the implant were applied in order to investigate resultant stress/strain distribution. RESULTS: The maximum equivalent stress/strain increased linearly with the increase of loading angle. For each 30-degree increase in loading angle, the maximum equivalent stress in cortical bone increased, on average, 3 to 4 times compared with that of the applied axial load. In addition to loading angle, bone quality also influenced resultant stress distribution. For the low-density bone model, a substantial strain in the cancellous bone was found not only near the implant neck but also at the implant apex. CONCLUSION: To achieve a favorable prognosis under off-axis loading of an anterior maxillary implant, careful case selection for appropriate bone quality and precise occlusal adjustment should be attempted to optimally direct occlusal force toward the long axis of the implant.     

An improved impact technique for monitoring percutaneous implant integrity

PURPOSE: The purpose of this study was to investigate the validity of the current Periotest system when measuring implant systems and to present a new system to monitor implant interface integrity. MATERIALS AND METHODS: The new system records an impact accelerometer signal and utilizes software for data analysis to determine the resonance frequency of an implant-abutment system. The new system uses the handpiece from the Periotest to acquire an impact signal but makes no use of the rest of the device. Tests were completed to determine the repeatability of the new system along with the effects clinical variables such as abutment torque, angulation of the handpiece, striking height, and distance handpiece is held from the abutment have on the measurement results. Accuracy of the current Periotest method as well as the new system was independently evaluated through the use of an abutment with a strain gauge attached. RESULTS: The new system for impact testing is shown to have greater accuracy than that of the Periotest device. Additionally, the effects of handpiece distance from abutment and torque (when above 15 Ncm) were found to be negligible while angulation of the handpiece and striking height affected the resonance frequency of the new system. CONCLUSION: The results of the in vitro testing indicate that greater resolution and accuracy can be achieved from an impact test that utilizes a clinical measurement protocol and independent analysis of the impact accelerometer signal.     

Influence of defect depth on resonance frequency analysis and insertion torque values for implants placed in fresh extraction sockets: a human cadaver study

Background: Clinical studies show promising outcomes with implants inserted at the time of extraction. However, this often results in an initial bone defect at the marginal region which preferably should heal for an optimal function. Therefore, monitoring of these implants is vital.
Purposes: The aims of this study were to determine the initial stability of implants placed into fresh extraction sockets, and to explore the correlations between the peri-implant bone levels and implant stability parameters.
Materials and Methods: Six human cadaver mandibles including all natural teeth were selected for this study. All natural teeth were gently extracted, and 84 implants were immediately placed into fresh extraction sockets with five different implant depths. The maximum insertion torque values were recorded, and primary implant stability measurements were performed by means of resonance frequency analysis (RFA). The vertical distance between implant/abutment junction and the first bone–implant contact was recorded using a periodontal probe.
Results: It was found that the insertion torque and RFA were 28.9 ± 7 Ncm and 65.6 ± 9 implant stability quotient (ISQ), respectively, for 420 measurements from all 84 implants. Statistically significant correlation was found between insertion torque and ISQ values ( r  = 0.86; p  < .001) for all implants. Both insertion torque and ISQ values dramatically decreased when the amount of peri-implant vertical bone defect increased.
Conclusion: The results of this study demonstrated a linear relationship between peri-implant vertical bone defect depth and RFA value. It is proposed that the RFA method is sensitive to detect changes of the marginal bone level and may be used to monitor healing of peri-implant bone defects.     

Assessment of correlation between computerized tomography values of the bone and cutting torque values at implant placement: a clinical study

PURPOSE: The relationship between computerized tomography (CT) values of bone surrounding endosseous implants and the cutting torque values required for self-tapping during implant placement was examined for the purpose of predicting the initial stability (bone quality) during implant placement by presurgical CT scan examinations and determining whether it can be quantified. MATERIALS AND METHODS: The study sample consisted of 13 subjects with 56 implants. Sites for implant placement were determined based on CT data using implant planning software. The average CT values of the bone surrounding the simulated implants were calculated by the software. Using a stereolithographic drill guide, implants were placed at the locations indicated by the protocol. The cutting torque values required for self-tapping were measured during implant placement. The resulting CT values and cutting torque values were analyzed statistically for correlation. RESULTS: The correlation was considered significant at a level of .01 or less, and the correlation coefficient was 0.77. DISCUSSION: There was a strong correlation between CT values and cutting torque values in the clinical cases evaluated. These results indicate that it may be possible to predict and quantify initial implant stability and bone quality from presurgical CT diagnosis and implant simulation. CONCLUSION: Presurgical CT examination may be an effective technique for predicting initial stability of the implant and bone quality.     

The Effects of Cortical Bone Thickness and Trabecular Bone Strength on Noninvasive Measures of the Implant Primary Stability Using Synthetic Bone Models

Purpose: This study investigated how the primary stability of a dental implant as measured by the insertion torque value (ITV), Periotest value (PTV), and implant stability quotient (ISQ) is affected by varying thicknesses of cortical bone and strengths of trabecular bone using synthetic bone models. Materials and Methods: Four synthetic cortical shells (with thicknesses of 0, 1, 2, and 3 mm) were attached to four cellular rigid polyurethane foams (with elastic moduli of 137, 47.5, 23, and 12.4 MPa) and one open‐cell rigid polyurethane foam which mimic the osteoporotic bone (with an elastic modulus 6.5 MPa), to represent the jawbones with various cortical bone thicknesses and strengths of trabecular bone. A total of 60 bone specimens accompanied with implants was examined by a torque meter, Osstell resonance frequency analyzer, and Periotest electronic device. All data were statistically analyzed by two‐way analysis of variance. In addition, second‐order nonlinear regression was utilized to assess the correlations of the primary implant stability with the four cortex thicknesses and five strengths of trabecular bone. Results: ITV, ISQ, and PTV differed significantly (p < .05) and were strongly correlated with the thickness of cortical bone (R² > 0.9) and the elastic modulus of trabecular bone (R² = 0.74–0.99). Conclusions: The initial stability at the time of implant placement is influenced by both the cortical bone thickness and the strength of trabecular bone; however, these factors are mostly nonlinearly correlated with ITV, PTV, and ISQ. Using ITV and PTV seems more suitable for identifying the primary implant stability in osteoporotic bone with a thin cortex.     

种植体即刻负载临床疗效观察

目的：种植体即刻负载技术有益于缩短种植手术与修复的“等待期”,及时满足患者的美观和咀嚼要求,进一步扩大种植义齿临床适应症,本文旨在探讨该技术的适应症、操作技巧,评价其远期临床疗效。方法：CDIC种植体植入23例牙缺失患者,共植入49枚种植体,术后一周内完成上部结构修复,经检测种植体动度、GI及有无种植体周围炎、口腔全景片等指标,评价临床成功率。结果：随访1-6年,23例患者中,仅一例患者的一枚植体松动、脱落,其余种植体均获临床成功,临床成功率为97.96％。结论：即刻负载修复病例的选择应为牙槽嵴丰满之中青年患者,种植体周围应有足够的骨壁包绕,以增加种植体初期稳定性。从黏骨膜瓣环切至种植体窝洞预备,都应贯彻“宁小勿大”原则,增加种植体的嵌合能力。一期法、非翻瓣式手术有利于软组织愈合,减少种植体周围炎发生机率。前牙即刻加载修复时,多枚种植体的连冠（T-T）修复优于单枚种植体修复,后牙即刻加载适用于2颗以上的种植体支持式固定修复,可以分散殆力,增加稳定性。     

Infrared Thermographic Evaluation of Temperature Modifications Induced during Implant Site Preparation with Cylindrical versus Conical Drills

Background: A few studies have investigated the influence of drilling on bone healing. Many factors have been reported to influence temperature rise during surgical preparation for implant placement: drill geometry, drilling depth, sharpness of the cutting tool, drilling speed, pressure applied to the drill, use of graduated versus one‐step drilling, intermittent versus continuous drilling, and use or not of irrigation. Purpose: The objective of this study was to quantify the temperature changes in cortical bone and at the apical portion of the drills during implant site preparation with a cylindrical implant drill versus a conical implant drill. Materials and Methods: Two implant drill systems were evaluated in vitro using bovine femoral cortical bone. The two implant drill systems evaluated in this study were system A (a cylindrical drill with triple twist drills) (Bone System, Milano, Italy) and system B (a conical drill with quadruple twist drills) (Bone System). Site preparation began, and the temperature of the cortical bone and at the apical portion of the drill was measured by the infrared thermography. Results: The mean temperature produced in the cortical bone during implant preparation was 31.2 ± 0.5°C for the cylindrical drills and 29.1 ± 0.6°C for the conical drill. The mean temperature produced in the apical portion of the drill during implant site preparation was 32.1 ± 0.7°C for the cylindrical drill system and 29.6 ± 0.6°C for the conical drill. Statistically significant differences were found in the temperature measurements in the cortical bone in the two groups (p < .05). A statistically significant difference was observed for the temperature measurements in the apical portion of the drill in the two groups (p < .005). Discussion: The model system used in this work was able to evaluate the temperature in the cortical bone and in the apical portion of the drills; the temperature modifications in the apical portion of the drill seemed to be correlated to the drill geometry. The results of the present study showed that drill geometry seems to be an important factor in heat generation during implant site preparation. Conclusion: The drill geometry could explain the increased temperature in the apical portion of the drill.     

Short Communication: Use of a Diagnostic Software to Predict Bone Density and Implant Stability in Preoperative CTs

Background: Computerized tomographs (CTs) are commonly used for presurgical planning of dental implant placement. It is possible that implant stability can be predicted based on quantitative measurements of bone density at planned implants sites with the use of diagnostic software. Purpose: The aim was to evaluate if there is a correlation between bone density measurements in specific implant positions in preoperative CTs and insertion torque (IT) and implant stability measurements when placing the implants. Materials and Methods: The study comprised of four patients in whom presurgical CTs had been used to plan implant treatment. A total of 26 implants (Neoss, Harrogate, UK) were placed in the totally edentulous maxilla (n = 3) or mandible (n = 1). IT was measured during implant insertion and the torque/time curves examined for mean IT (newton‐centimeters) over the total curve. The stability of implants was measured with resonance frequency analysis. The positions of the implants were extracted from a postoperative CT to the preoperative one. Bone density was measured with a dedicated software (3Diagnosys? 3.0, 3Diemme, Cantù, Italy) in virtual hollow probes, indicating the bone volume within 1 mm from each implant surface. The Spearman Rank correlation test was used to find possible correlations. Results: Statistically significant correlations were found between mean bone density, mean IT, and implant stability measurements. Conclusions: This pilot study showed a correlation between bone density, as measured in Hounsfield units in preoperative CTs, and IT and implant stability measurements at the surgical placement of the implants. The findings support the idea that integration of bone density measurements in implant probes in preoperative CTs using treatment‐planning software may be a useful feature to predict implant stability and to avoid failures.