Pilot Hole Diameter Research Articles

Optimization of Pedicle Screw Parameters for Enhancing Implant Stability Based on Finite Element Analysis

ObjectiveTo improve the implant stability, the parameters including outer diameter, thread depth and pitch of pedicle screw were optimized by finite element analysis. MethodsThe insertion and pullout of pedicle screw were simulated by finite element analysis, and the precision of simulation was evaluated by comparing with mechanical tests. The influences of the parameters on the maximum insertion torque and maximum pullout force were analyzed by computational simulations including single-factor analysis and orthogonal experiment. ResultsThe simulation results agree with the mechanical tests. The influencing orders of the parameters on insertion torque and pullout force are both: outer diameter > pitch > thread depth. When the pilot hole diameter is 0.1 mm larger than the inner diameter of pedicle screw, the calculated Pearson correlation coefficient between the maximum insertion torque and maximum pullout force is r = 0.99. The optimized pedicle screw shows a maximum insertion torque of 485.16 N·mm and a maximum pullout force of 1726.33 N, which are 23.9% and 9.1% higher than those of standard screw, respectively. ConclusionsThe presently used models are feasible to evaluate the implant stability of pedicle screw. The maximum insertion torque and maximum pullout force of pedicle screw are highly correlated. The insertion torque and pullout force can be improved by increasing outer diameter and decreasing pitch. Beside the parameters of pedicle screw, the size of pedicle and bone mineral density are two considerable factors for a better implant stability.

Effect of Epoxy Resin Reinforcement on Screw Withdrawal Strength of Fiberboard and Particleboard Used in Furniture Industry

The study aimed to increase the screw withdrawal strength of medium density fiberboard and particleboard used in furniture strength by using epoxy resin in the screw pilot hole. Therefore, the effects of pilot hole diameters, screw diameter, and amount of epoxy resin on screw withdrawal strength of medium density fiberboard and particleboard from face and edge were investigated. According to TS EN 13446, 50 mm × 50 mm specimens were cut from commercial medium density fiberboard and particleboard boards. A static load was applied parallel to the screw direction. The screw withdrawal strength of medium density fiberboard was higher than the screw withdrawal strength of particleboard because of its density. Besides, the screw withdrawal strength of medium density fiberboard and particleboard samples with a 3.5 mm screw diameter was higher compared to those with a 4.5 mm screw diameter. A decrease in pilot hole diameter and an increase in the amount of epoxy resin provided higher screw withdrawal strength of materials. Using 20 % epoxy resin of the volume of the pilot hole resulted in two times better screw withdrawal strength values. The study showed that a higher amount of epoxy resin, smaller pilot hole diameter, and smaller screw diameter contribute to better screw withdrawal strength of both medium density fiberboard and particleboard from the face and edge.

Evaluation of the efficacy of modal analysis in predicting the pullout strength of fixation bone screws.

Pilot hole preparation has been shown to have an impact on the short and long-term stability of the screw fixation constructs. Investigation and comparison of two nondestructive modal analysis methods with conventional insertion torque (IT) and pullout tests in optimum pilot hole diameter detection. Twenty conical core titanium screws were embedded in high-density polyethylene blocks with different pilot hole diameters. The maximum IT was recorded for each screw during implantation. Then, two modal analysis methods including accelerometer (classical modal analysis [CMA]) and acoustic modal analysis (AMA) were carried out to measure the natural frequency (NF) of the bone-screw structure. Finally, stiffness (S), pullout force (Fult), displacement at Fult (dult) and energy dissipation (ED) were obtained from the destructive pullout test. The IT increased, as the pilot hole diameter decreased. The maximum value of IT was observed in the smallest pilot hole diameter. The same trend was found for the Fult and the first NF derived from both modal methods except for 5.5 mm pilot hole diameter. The natural NFs derived from CMA and AMA showed high correlations in different groups (R2=0.94) and did not deviate from y=x hypothesis in linear regression analysis. The Fult, dult, and ED were measured 4800 ± 172 N, 3.10 ± 0.08 mm and 14.23 ± 1.10N.mm, respectively. No significant change was observed in "S" between the groups. The highest Fult and first NF were obtained for the 5.5 mm pilot hole diameter. Both CMA and AMA were found to be reliable methods and can promote the undesirable contradiction between Fult and IT.

Research on Medium density fiberboard (MDF) behavior against screw axial withdrawal: Impact of density and operational variables

Screw joint is a prevalent connection method in furniture, buildings, and structures, which plays an essential role in the integrity and durability of a wooden structure. Considering such benefits, the impact of core and face layers density, screw direction, pilot hole diameter, screw type, and water immersion on screw axial withdrawal resistance of medium density fiberboard (MDF) were investigated in this paper. The results showed that screw withdrawal resistance (SWR) of MDF panels in surface and edge directions were raised as density increased. The surface SWR was found to be higher than the corresponding ones in the edge direction. Besides, fine thread drywall displayed higher SWR than coarse thread drywall in both directions, due to more thread embedded. Results revealed that SWR was more affected by pilot hole diameter than panel density. Moreover, the best SWR was observed when the pilot hole was set close to the root diameter of the screw. The treatment of water soaking of MDF samples for 2 h negatively affected the SWR. Therefore, the edge SWR was more affected by water immersion. In addition, failure modes of screw withdrawal included sheet-shaped fracture of face layer along with protrusion of core fibers by pulling out the screw from surface and edge directions, respectively. This study suggests that a reliable connection can be made by selecting the proper screw and adjusting an accurate pilot hole even in a lighter product that is installed in humid conditions.

Determination of the strength performance of table frames

The objective of this study was to investigate relation of diameter of pilot hole and screw, and machining accuracy on withdrawal strengths of the screws and durability of the dining tables. For this purpose, fasteners and material types on the failure loads of dining table corner joints have been analyzed experimentally and statistically. Double ended thread bolts with different drilling regimes have been used as fastener types. Parallel investigation of rigidity and durability of tables, according to the current EN norms, and withdrawal capacities in accordance with the procedures described in ISO 9087 was performed. According to the results, it is concluded that the diameter of the drilled hole significantly influences the value of the withdrawal strengths of the screws. By analyzing the effect of drilling diameter on rigidity of tables, a statistically significant difference was determined. As the drilling diameter increases, the rigidity of the examined dining tables decreases

Investigation of Influence of Pilot Hole on Thread Mill Processes Based on Monitoring Results with a Wireless Monitoring Holder System

In this study, we focused on screw cutting with a thread mill tool based on helical interpolation motion and proposed a novel monitoring method to achieve a high accuracy of screw cutting with a wireless holder system. In the present report, we investigated the influence of pilot hole diameter on the accuracy of machining the screw for three kinds of steel materials, which were JIS S50C (200 HV2 hardness), JIS SKD61 (400 HV2 hardness) and JIS SKD61 (600 HV2 hardness) steels., based on measured cutting force from the wireless holder system. As a result, the proposed monitoring method is effective to estimate the processes and to improve the accuracy of machining screws from various work materials using helical interpolation motion of a thread mill tool.

Evaluation of Cortical Bone Microdamage and Primary Stability of Orthodontic Miniscrew Using a Human Bone Analogue.

Orthodontic miniscrews have gained popularity; however, they have some drawbacks, including screw loosening that results from bone resorption caused by excess microdamage created during screw insertion. Pilot hole preparation through the cortical bone is considered beneficial to avoid such microdamage, while an overly large pilot hole impairs primary stability. Hence, we used a human bone analogue to evaluate the microdamage and primary stability to estimate the optimal pilot hole size that would minimize the screw loosening risk. Ti6Al4V orthodontic miniscrews and 1.0-mm-thick synthetic cortical bone pieces were prepared. Various compressive loads were applied in indentation tests to test pieces’ surfaces, and the microdamaged areas were confirmed as stress-whitening zones. Screw insertion tests were performed in which a miniscrew was inserted into the test pieces’ pilot hole with a diameter of 0.7–1.2 mm in 0.1-mm intervals, and the stress-whitening area was measured. The insertion and removal torque were also measured to evaluate primary stability. The stress-whitening areas of the 1.0–1.2 mm pilot hole diameter groups were significantly smaller than those of the other groups (p < 0.05), whereas the 0.9 and 1.0 mm pilot hole diameter groups showed higher primary stability than other groups. In conclusion, the bone analogue could be utilized to evaluate microdamage in cortical bones and the primary stability of miniscrews.

Effects of pilot hole diameter and depth on screw driving torques in plywood

Factors affecting screw driving torques in plywood were investigated in this work. The factors were number of layers (7 and 9), pilot hole diameter (3.0 and 3.5 mm), pilot hole depth (60 and 80% of the thickness of specimen), and thickness of the metal plate (7.5 and 10 mm). Screw driving torques were studied in oriented strandboard, medium-density fiberboard, particleboard, and some wood-plastic composites. There is no such information about screw driving torques in plywood (PW). Therefore, this study focused on the plywood made of aspen (Populus tremula L.). The mean seating torque (SET) values ranged from 0.31 to 0.69 N∙m, whereas mean stripping torque (STT) values ranged from 0.50 to 4.7 N∙m. The ratios of STT/SET were between 2 and 5 in PW with seven layers, whereas the ratios were between 4 and 7 in PW with nine layers. The results indicated that the four main effects of SET and STT were statistically significant with p-values of ˂ 0.0001.

Influence of pilot hole diameter in cancellous screw fixation in a reduced density animal bone model

BackgroundScrew fixation in osteoporotic bone is clinically challenging. Screw failure rates are growing due to an increasing prevalence of osteoporosis. To address this, biomechanical models are needed to recreate the bone clinically encountered alongside the development of new operative techniques. The first aim of this study was to test whether the use of a smaller than recommended pilot-hole diameter improved pull-out strength for cancellous screws, with the second aim to create a model of low-density porcine bone for biomechanical testing. MethodsThirty porcine tibiae were cut into transverse metaphyseal sections of 20 mm thickness. Bone density was altered using 0.15 M Hydrochloric acid, and measured and pre- and post-demineralisation using HRμCT. Seventy-two screw areas were randomised to either 2.5 mm or 1.5 mm pilot holes and to either be normal or reduced density. Maximum axial pull-out strength was measured. FindingsDemineralisation reduced bone density by 12% (p < 0.0001) and 11% (p < 0.0001) for 2.5 mm and 1.5 mm pilot hole diameters respectively. Pull-out strength reduced by 50% (p = 0.0001) and 44% (p < 0.0001) following demineralisation for both 2.5 mm and 1.5 mm pilot hole diameters. Pull-out strength increased by 51% (p = 0.0008) when inserting screws into 1.5 mm pilot holes in low density bone, and by 28% (p = 0.027) in normal bone. InterpretationPorcine bone can be demineralised to model low density cancellous bone. This novel model showed that pullout force is significantly reduced in lower density screw holes, but that this reduction can be mitigated by reducing pilot hole diameter for cancellous screws.

Effects of Countersink Hole on Driving Torques of Screw in Joints Constructed of Medium Density Fiberboard

Aim of study: The aim of this study was to investigate the effect of&#x0D; countersink along with some other factors affecting screw driving torques in&#x0D; joints made of medium density fiberboard (MDF). There is limited research has&#x0D; been done in the field of screw driving torques in wood based composites. In&#x0D; all of these studies, the specimen consisted of a single wood-based composite&#x0D; material and metal plate which was used for the consistency of the screw&#x0D; driving data. However, in this study, the screw driving torques were obtained&#x0D; by the specimens consisted of two MDF testing blocks jointed by a screw.&#x0D; &#x0D; Material and Method: In general, there were two main screw driving&#x0D; torques; seating torque (SET) and stripping torque (STT). The MDF testing&#x0D; blocks had dimension of 150 mm long × 75 mm wide and two different thicknesses&#x0D; were used. For upper testing block, 8-mm-thick MDF and for lower testing block,&#x0D; 18-mm-thick MDF were used. Torques measurements were obtained by an adjustable&#x0D; torque screwdriver. Factors were embedded screw orientation (face-to-face and face-to-side),&#x0D; pilot-hole diameter (2.5 and 3.0 mm), pilot-hole depth (12 and 16 mm) and&#x0D; countersink type (with and without countersink).&#x0D; &#x0D; Main results: The results of statistical analysis indicated that the&#x0D; four-way interaction among the embedded screw orientation, screw length,&#x0D; countersink type and pilot-hole diameter was significant on the mean SET and&#x0D; STT in the MDF joints.&#x0D; &#x0D; Highlights: This study will help MDF manufacturers to understand&#x0D; the screw performance of their products in terms of screw driving torques.

Geometric Parameters Influence on the Screw Withdrawal Strength of Coir Agglomerates

ABSTRACT This study aims to evaluate the screw withdrawal behavior of agglomerated panels fabricated with coir fibers and a polyurethane resin as binder. Based on design of experiments, an analysis was conducted to understand and describe the withdrawal behavior by evaluating the main parameters that affect panel/screw interaction. Using Box–Behnken method, the maximum withdrawal strength was predicted by a second-degree response model with good approximation. The model presented the optimum combination of the main parameters that govern panel/screw interaction, namely: screw nominal diameter, pilot hole diameter and screw depth of penetration. The latter showed the greatest contribution to withdrawal strength.

EFFECTS OF PILOT HOLE DIAMETER ON SCREW-DRIVING TORQUES IN MEDIUM DENSITY FIBERBOARD

ABSTRACT This study investigated the effects of pilot-hole diameter in medium density fiberboard (MDF) on the characterization of screw-driving torques. The factors investigated were the embedded screw orientation and pilot hole diameter. Based on the curves obtained from screw-driving process, the measurements of the seating torque (SET) and stripping torque (STT) were obtained. The results of statistical analysis indicated that the SET and STT values in MDF were significantly affected by the pilot hole diameter. In the case of driving screws into the side of MDF material, the mean SET ranged from 0.37 to 1.23 N∙m and STT values ranged from 1.18 to 2.68 N∙m whereas for the face specimens, the mean SET ranged from 0.57 to 1.56 N∙m and STT values ranged from 2.89 to 5.41 N∙m.

Effect of pilot hole on biomechanical and in vivo pedicle screw–bone interface

To experimentally study the influence of pilot hole diameter (smaller than or equal to the internal (core) diameter of the screw) on biomechanical (insertion torque and pullout strength) and histomorphometric parameters of screw-bone interface in the acute phase and 8 weeks after pedicle screw insertion. Fifteen sheep were operated upon and pedicle screws inserted in the L1-L3 pedicles bilaterally. The pilot hole was smaller (2.0 mm) than the internal diameter (core) of the screw on the left side pedicle and equal (2.8 mm) to the internal diameter (core) of the screw on the right side pedicle. Ten animals were sacrificed immediately (five animals were assigned to pullout strength tests and five animals were used for histomorphometric bone-screw interface evaluation). Five animals were sacrificed 8 weeks after pedicle screw insertion for histomorphometric bone-screw interface evaluation. The insertion torque and pullout strength were significantly greater in pedicle screws inserted into pilot holes smaller than internal (core) diameter of the screw. Histomorphometric evaluation of bone-screw interface showed that the percentage of bone-implant contact, the area of bone inside the screw thread and the area of bone outside the screw thread were significantly higher for pilot holes smaller than the internal (core) diameter of the screw immediately after insertion and after 8 weeks. A pilot diameter smaller than the internal (core) diameter of the screw improved the insertion torque and pullout strength immediately after screw insertion as well the pedicle screw-bone interface contact immediately and 8 weeks after screw placement in sheep with good bone mineral density.

Effect of sequential hole enlargement on cortical bone temperature during drilling of 6.2-mm-diameter transcortical holes in the third metacarpal bones of horse cadavers

To compare the bone temperature and final hole dimensions associated with sequential overdrilling (SO) and single 6.2-mm drill bit (S6.2DB) methods used to create transcortical holes in the third metacarpal bones (MCIIIs) of horse cadavers. 60 MCIIIs from 30 horse cadavers. In phase 1, hole diameter, tap insertion torque, peak bone temperature, and postdrilling bit temperature for 6.2-mm-diameter holes drilled in the lateral or medial cortical region of 12 MCIIIs via each of three 2-bit SO methods with a single pilot hole (diameter, 3.2, 4.5, or 5.5 mm) and the S6.2DB method were compared. In phase 2, 6.2-mm-diameter transcortical holes were drilled via a 2-bit SO method (selected from phase 1), a 4-bit SO method, or a S6.2DB method at 1 of 3 locations in 48 MCIIIs; peak bone temperature during drilling, drill bit temperature immediately following drilling, and total drilling time were recorded for comparison. Hole diameter or tap insertion torque did not differ among phase 1 groups. Mean ± SD maximum bone temperature increases at the cis and trans cortices were significantly less for the 4-bit SO method (3.64 ± 2.01°C and 8.58 ± 3.82°C, respectively), compared with the S6.2DB method (12.00 ± 7.07°C and 13.19 ± 7.41°C, respectively). Mean drilling time was significantly longer (142.9 ± 37.8 seconds) for the 4-bit SO method, compared with the S6.2DB method (49.7 ± 24.3 seconds). Compared with a S6.2DB method, use of a 4-bit SO method to drill transcortical holes in cadaveric equine MCIIIs resulted in smaller bone temperature increases without affecting hole accuracy.

Effect of pilot hole diameter and tapping on insertion torque and axial pullout strength of 4.0-mm cancellous bone screws

To evaluate the effects of pilot hole diameter and tapping on insertion torque and axial pullout strength of 4.0-mm cancellous bone screws in a synthetic canine cancellous bone substitute. 75 synthetic cancellous bone blocks (15 blocks/group). For groups 1 through 5, screw size-pilot hole diameter combinations were 3.5-2.5 mm (cortical screws), 4.0-2.5 mm, 4.0-2.5 mm, 4.0-2.0 mm, and 4.0-2.0 mm, respectively. Holes were tapped in groups 1, 2, and 4 only (tap diameter, 3.5, 4.0, and 4.0 mm, respectively). One 70-mm-long screw was inserted into each block; in a servohydraulic materials testing machine, the screw was extracted (rate, 5 mm/min) until failure. Mean group values of maximum insertion torque, axial pullout strength, yield strength, and stiffness were determined. Mean maximum insertion torque differed significantly among the 5 groups; the group 5 value was greatest, followed by group 3, 4, 2, and 1 values. Group 3, 4, and 5 axial pullout strengths were similar and significantly greater than the group 2 value; all values were significantly greater than that for group 1. Group 5 and 4 yield strengths were similar and significantly greater than the group 3, 2, and 1 values. Stiffness in group 3 was similar to group 4 and 2 values but significantly greater than the group 5 value; all values were significantly greater than that for group 1. These synthetic cancellous bone model findings suggested that tapping a 2.0-mm-diameter pilot hole when placing a 4.0-mm screw is the optimal insertion technique.

Lateral resistance of joints made with various screws in commercial wood plastic composites

In this study, the effects of screw diameter, pilot hole diameter, end distance, thickness of side and main members, loading speed and screw type on the lateral resistance of screw joints in commercial wood plastic composites were investigated and also compared with those calculated using the European Yield Model (EYM). The results have shown that for a given diameter of screw, increase in end distance, thickness of joint members, pilot hole diameter and loading speed, increases lateral resistance of the joint. Comparing screw effect it was found that lateral resistances of joints made with various screws did not have significant differences. The results have also shown that the accuracy of EYM prediction of lateral resistance for the joints fractured in mode I s is better than those fractured in modes III s or V.

Investigation on withdrawal resistance of various screws in face and edge of wood–plastic composite panel

Withdrawal resistances of screws driven into commercial wood–plastic composite (WPC) panels in both face and edge directions have been measured and the results have been compared with those of conventional medium density fiberboard (MDF) and particleboard. Three types of screws namely; sheet metal screw (gauge #4, 8, 10, 14), wood screw (gauge #8) and drywall screw (gauge #8) were used. The results have indicated that withdrawal resistances of screws in WPC panels in both directions increase as screw diameter, loading rate and penetration depth increase. Similar increases were observed when pilot holes diameter were increased close to the root diameter of the screws. Beyond this limit, increasing the pilot hole diameter up to the nominal diameter of the screws, significantly reduced withdrawal resistance. No significant differences were observed between different types of screw. Face and edge withdrawal resistances of screws in WPC panels were higher as compared with those of MDF and particleboard panels.

Macheamento do orifício piloto: análise mecânica na vértebra de carneiro e no modelo de osso artificial

OBJETIVO: Avaliar a influencia do macheamento do orificio piloto associado as outras variaveis como o seu diâmetro em relacao ao diâmetro interno do parafuso e o modo de preparo no torque de insercao, na resistencia ao arrancamento dos parafusos utilizados para a fixacao anterior da coluna cervical. METODO: Vinte corpos de prova de poliuretana e 30 vertebras toracicas (T1-T5) foram testadas. Em cada corpo de prova foram realizados quatro orificios, sendo dois com diâmetro de 2,0mm e dois com 2,5mm. Esses orificios foram confeccionados com broca ou sonda, de acordo com o grupo experimental. O macheamento do orificio piloto era ou nao realizado, dividindo desse modo o grupo experimental em subgrupos iguais. Foram formados oito grupos experimentais (quatro utilizando poliuretana e quatro utilizando vertebras de carneiro). Parafusos corticais com 3,5mm de diâmetro externo e 14mm de comprimento foram inseridos nos orificios piloto. O torque de insercao foi mensurado durante a implantacao dos parafusos e, em seguida, foram realizados ensaios mecânicos de arrancamento em maquina universal de testes Emic®, softwareTesc 3.13, celula de carga de 1.000N, velocidade de aplicacao de forca de 0,2mm/min, pre-carga de 5N e tempo de acomodacao de 10 segundos. A propriedade avaliada nos ensaios mecânicos foi a forca maxima de arrancamento. RESULTADOS E CONCLUSAO: O macheamento do orificio piloto reduziu significativamente o torque de insercao e a forca de arrancamento dos parafusos em todos os grupos experimentais.

TAPPING PILOT HOLE: MECHANICAL ANALYSIS OF SHEEP VERTEBRA AND THE ARTIFICIAL BONE MODEL

Objective: To determine the effect of pilot hole tapping, together with other variables such as pilot hole diameter, in relation to inner screw diameter and preparation method, on the insertion torque and pullout resistance of the screws used for anterior fixation of the cervical spine. Method: Twenty polyurethane test bodies and 30 thoracic vertebrae (T1-T5) were tested. Four holes were drilled into each test body: two of them with a diameter of 2.0 mm and two with a diameter of 2.5 mm. The holes were drilled using a bit or probe, according to the experimental group. Each experimental group was divided into two equal subgroups, with and without pilot hole tapping. In all, there were eight experimental groups: four using polyurethane specimens and four using sheep vertebrae. Cortical screws of 3.5 mm in outer diameter and 14 mm in length were inserted into the pilot holes. The insertion torque was measured during screw implantation and mechanical pullout tests were then performed using an Emic® universal testing machine, with the Tesc 3.13 software, load cells of 1000 N, force application rate of 0.2 mm/min, preloading of 5 N and accommodation time of 10 seconds. The property evaluated in the mechanical tests was the maximum pullout force. Results and Conclusion: Pilot hole tapping significantly decreased the insertion torque and pullout force of the screws in all the experimental groups.

The Influence of the Insertion Technique on the Pullout Force of Pedicle Screws

The pullout strength of a typical pedicle screw was evaluated experimentally for different screw insertion techniques. OBJECTIVE.: To conclude whether the self-tapping insertion technique is indeed the optimum one for self-tapping screws, with respect to the pullout strength. It is reported in the literature that the size of the pilot-hole significantly influences the pullout strength of a self-tapping screw. In addition it is accepted that an optimum value of the diameter of the pilot-hole exists. For non self-tapping screw insertion it is reported that undertapping of the pilot-hole can increase its pullout strength. Finally it is known that in some cases orthopedic surgeons open the threaded holes, using another screw instead of a tap. A typical commercial self-tapping pedicle screw was inserted into blocks of Solid Rigid Polyurethane Foam (simulating osteoporotic cancellous bone), following different insertion techniques. The pullout force was measured according to the ASTM-F543-02 standard. The screw was inserted into previously prepared holes of different sizes, either threaded or cylindrical, to conclude whether an optimum size of the pilot-hole exists and whether tapping can increase the pullout strength. The case where the tapping is performed using another screw was also studied. For screw insertion with tapping, decreasing the outer radius of the threaded hole from 1.00 to 0.87 of the screw's outer radius increased the pullout force 9%. For insertion without tapping, decreasing the pilot-hole's diameter from 0.87 to 0.47 of the screw's outer diameter increased its pullout force 75%. Finally, tapping using another screw instead of a tap, gave results similar to those of conventional tapping. Undertapping of a pilot-hole either using a tap or another screw can increase the pullout strength of self-tapping pedicle screws.