Conventional Drilling Research Articles

Fragmentation characteristics of abrasive particles for hard rock drilling with waterjet energy parameter

The use of abrasive waterjets (AWJs) for rock drilling offers advantages in urbanized areas, locations that are vulnerable to damage, and piling operations. However, the overall operational cost of AWJ systems remains high compared to that of conventional drilling methods, which constrains the long-term industrial application of AWJs. For instance, the abrasive costs account for over 60% of the total process cost, but the recycling of abrasives remaining after drilling could significantly reduce machining costs. In this study, the post-impact characteristics of abrasives were explored, aiming to enhance their recyclability. The physical properties and particle distribution of used abrasives vary depending on the jet energy, ultimately affecting their recyclability and recycling rate. The particle properties of used abrasives (particle size distribution, particle shape, and mean particle size) were compared under different waterjet energy variables (standoff distance (SOD) and water pressure) and test conditions (dry and underwater). Furthermore, the collision stages of the abrasive particles within a waterjet system were classified and analyzed. The results revealed that abrasive fragmentation predominantly occurred due to internal collisions within the mixing chamber. In addition, an attempt was made to optimize the waterjet parameters for an economical and efficient operation. The findings of this study could contribute to enhancing the cost-effectiveness of AWJ systems for rock drilling applications.

Multi‐objective optimization of ultrasonic vibration‐assisted drilling in carbon fiber reinforced polyetherketoneketone laminate

AbstractCarbon fiber reinforced polyetherketoneketone (CF/PEKK) possess excellent mechanical properties and also meet low‐carbon environmental standards, leading to their increasingly widespread application in recent years. To ensure the strength of mechanical connections, it is crucial to minimize drilling damage. This paper utilizes Ultrasonic Vibration‐Assisted Drilling (UVAD) to enhance hole‐making quality, comparing multiple drilling performance indicators with Conventional Drilling (CD), including thrust force, drilling temperature, delamination factor, and burr factor. The results demonstrate that UVAD significantly reduces thrust force and drilling temperature, decreases delamination and burring damage, and effectively improves hole quality. To further optimize processing parameters, the Non‐dominated Sorting Genetic Algorithm II (NSGA‐II) was used, targeting thrust force, Material removal rate (MRR), and delamination factor as optimization goals. The reliability of the model was verified through experimentations. This paper provides an effective technical approach for high‐quality drilling in CF/PEKK materials, offering significant practical application value for material processing in aerospace and other fields.Highlights The quality of CF/PEKK processed by CD and UVAD was compared. UVAD can effectively improve the quality of drilling. The drilling parameters were optimized by NSGA‐II. The reliability of the prediction model was verified by experiments.

P-36725719-1378 - Osseodensification versus conventional drills in diabetic patients: is implant stability affected?

P-36725719-1378 - Osseodensification versus conventional drills in diabetic patients: is implant stability affected?

Heat Generation and Pain Assessment in Piezosurgery Versus Conventional Drilling for Implant Placement: A Systematic Review.

The development of new technologies in implant dentistry has led to the introduction of piezosurgery, which utilizes ultrasonic vibrations for micrometric and selective bone cutting. It is hypothesized to reduce trauma to bone tissue, thereby potentially improving the healing process compared to traditional drilling methods. This systematic review examines the differences in heat generation and pain perception between piezosurgery and conventional drilling techniques for dental implant placement. An extensive review of literature was performed using various databases, includingPubMed via MEDLINE, EBSCO, and Google Scholar. Out of an initial pool of 2,279 articles, nine studies met the predefined inclusion criteria and were included in the final analysis following title and abstract screening and subsequent full-text evaluation. The quality of the selected studies was rigorously assessed using the Risk of Bias (RoB 2.0), Risk of Bias in Non-randomized Studies - of Interventions (ROBINS-I), and Quality Assessment Tool for In Vitro Studies (QUIN) tools. Data pertaining to thermal effects and postoperative pain associated with piezosurgery relative to conventional drilling protocols were collected. The results indicated a significant reduction in postoperative pain with piezosurgery; however, the technique was associated with higher intraoperative temperatures during osteotomy. These findings provide valuable insights into the potential benefits and limitations of piezosurgery in dental implant procedures.

Investigation of the effects of heat treatment and hot isostatic pressing on micro-drilling of Ti6Al4V alloy fabricated by laser powder bed fusion

In this study, micro-drilling performance of laser powder bed fusion (LPBF) Ti6Al4V alloy with heat treatment (HT) and hot isostatic pressing (HIP) post-processing conditions was investigated and compared to wrought material. The tests were performed at two spindle rotational speeds (5000 and 10000 rev/min) and a feed per tooth (4 μm/tooth) under dry and minimum quantity lubrication (MQL) conditions using conventional drilling (CD) and peck drilling (PD) strategies. Micro-drilling performance was evaluated in terms of thrust force, surface roughness, subsurface microstructure and microhardness, burr formation, and tool wear. The test results showed that LPBF-HT and LPBF-HIP Ti6Al4V alloys exhibited different micro-drilling performances than the wrought material due to their different microstructural and mechanical properties. The LPBF-HIP Ti6Al4V characterized by higher strength and lamellar microstructure with higher β phase fraction (33.2%) led to higher thrust force, lower surface quality and higher burr height. On the other hand, the wrought Ti6Al4V with higher ductility, lower hardness, and lower β phase fraction (16.3%) showed lower thrust forces, surface roughness, and burr height. Notably, employing MQL conditions with the PD strategy provided good surface quality and reduced burr formation. A higher degree of tool wear was obtained in micro-drilling of LPBF-HIP Ti6Al4V. The major wear types were adhesion, BUE, and flank wear. Besides, chippings were observed in micro-drilling of LPBF-HT and LPBF-HIP Ti6Al4V.

Research and Tests on the Technology of Releasing and Fishing Stuck Throttles Under Pressure

Abstract In order to solve the problem of gas well shutdown caused by fishing failure due to stuck throttles, and to avoid situations such as the inability to lift the pipe string and high cost of handling stuck throttles, the basic structures of the slip-type throttles were analyzed. And based on the actual situation on site, it was determined that the deformation of the slip mechanism was the main cause of the throttles getting stuck. And combined with conventional bridge plug drilling and grinding, coiled tubing fishing, and steel wire fishing techniques, the technology of grinding and milling under pressure to release and fishing stuck throttles was studied. Theoretical analysis has been conducted on the feasibility of using coiled tubing mill to break the slip mechanism of the stuck throttles, including mill torque, construction displacement, drilling pressure, etc. At the same time, the technical principle and operation process of gas lift fishing throttles were introduced. Two three-packer string wells were successfully tested in the field. After the stuck throttles were milled and unblocked by the coiled tubing, the stuck throttles of Φ73.0 mm tubing were successfully salvaged, one of which was fished by gas lift. The average construction time is less than 2.5 days. The research results show that the technology of grinding and milling with pressure to release and fishing stuck throttles is safe and efficient, providing a new technical means for dealing with stuck throttles and has good promotion and application value.

Multi response optimization of process parameters in titanium alloy minimum quantity lubrication drilling operation

Abstract This work investigates the application of minimal quantity lubrication (MQL) in the drilling process, where a combination of liquid and air creates an aerosol in the form of a fine mist. This protective layer decreases friction and tool wear, hence improving overall efficiency. The study examines the conventional Gulfcut oil blend drilling technique to enhance drilling performance on the titanium alloy Ti-6Al-4V under MQL circumstances. The key drilling parameters, namely spindle speed (N), feed rate (F), and point angle (D), were analyzed using a Taguchi L16 orthogonal array. The experimental inquiry aimed to identify the most favorable conditions that lead to the least amount of torque (TQ), thrust force (TF), and surface roughness (SR). An Analysis of Variance (ANOVA) was used to examine the impact of control factors on drilling performance. The optimized drilling parameters led to a reduction in torque, thrust force, and surface roughness by 12.88%, 21.29%, and 25.76%, respectively. Furthermore, microstructure analysis demonstrated that the Gulfcut lubricant plays a pivotal role in reducing grain size during drilling. This research provides valuable insights into optimizing drilling conditions for titanium alloy using a conventional Gulfcut oil blend with MQL, aiming to reduce torque, thrust force, and surface roughness.

Evaluation of Postoperative Effects of Using Ozonated Water as an Irrigant on Soft and Hard Tissues Surrounding Dental Implants: A Randomized Controlled Clinical Trial.

Aim To evaluate the short-term and long-term postoperative effects of ozonated water when used as an irrigant in terms of postoperative pain, healing, and implant stability when compared to normal saline irrigation during implant surgery, both carried out using conventional drilling protocol. Methods A total of 34 implants were placed in 17 patients, two implants in each patient, one implant using normal saline as an irrigant and another one using ozonated water as an irrigant during the surgical procedure of implant site osteotomy. Postoperative pain was assessed after 48 hours of the surgical procedure using the visual analog scale (VAS). Soft tissue healing was assessed after eight days using the tissue healing index. Osseointegration was checked by measuring the primary stability at the moment of implant placement and comparing it to the secondary stability measured three months after the implant placement. These stability values (ISQ) were obtained using resonance frequency analysis (RFA). Results The VAS scores for the control group (Group A) after 48 hours were 71.76±5.57 and for the experimental group (Group B) after 48 hours were 47.64±5.33 so mean values in the experimentalgroup were significantly lower as compared to that in the control group (p<0.001). The mean healing index score for the control group (Group A) was 3.35±0.49 and the mean healing index score for the experimental group (Group B) was 4.64±0.49 so the mean values of tissue healing index in the experimental group were significantly higher as compared to that in the control group (p<0.001). The increase in stability value over the period of three months is 5.83 ISQ in the control group while the increase in stability value over the period of three months is 7.06 ISQ in the experimental group. The difference although not statistically significantshows a slight increase in stability in the experimental group as compared to that of the control group. Conclusion Ozone water irrigation at implant site osteotomy reduced postoperative pain and accelerated the tissue wound healing but the significant effect on osseointegration could not be determined.

Unlocking implant success: the impact of surgical techniques on primary stability in the posterior maxilla.

The study conducted by Olmedo-Gaya et al. aimed to investigate the effects of various surgical techniques on the initial stability of implants placed in the posterior maxilla through a randomized controlled clinical trial. The study compared insertion torque (IT) and implant stability quotients (ISQ) among implants placed using under preparation, expanders, and standard surgical instrumentation. The study enrolled 108 patients, each receiving one implant in the posterior maxilla region. Patients were distributed into three groups: group 1 (n = 36) with the under preparation technique, group 2 (n = 36) using the expander technique, and group 3 (n = 36) with conventional drilling. IT was measured using a torque indicator, while ISQ was recorded through resonance frequency analysis immediately post-surgery. The ISQ values were analyzed in relation to the patient's bone quality, categorized into types II, III, and IV. ISQ values varied significantly with bone quality, being highest in type II (76.65) and type III (73.60), and lowest in type IV (67.34) bone, with a significant difference (p < 0.0001). The conventional drilling technique yielded lower ISQ values (69.31) compared to under preparation (74.29) and expander techniques (73.99), with statistical significance (p = 0.008 and p = 0.005, respectively). Surgical technique significantly influences primary stability in low-quality bone. Conventional drilling results in lower ISQ values, suggesting that alternative techniques such as under preparation or expanders should be used in low-quality bone to achieve better primary stability. For implants in low-quality bone, replacing the conventional drilling technique with under preparation or expander techniques can enhance primary stability.

Improving C1 Pedicle Screw Placement for Atlantoaxial Instability with Ultrasonic Bone Burr Assistance

This study aims to evaluate the safety and efficacy of the ultrasonic bone burr (UBB) in facilitating C1 pedicle screw placement for atlantoaxial instability (AAI) treatment, compared to the conventional high-speed drill (HSD) technique. A retrospective analysis was conducted on patients undergoing posterior screw-rod fixation for AAI between December 2017 and July 2023. The patients were divided into two groups based on the tools used for screw placement: UBB and HSD. Data on surgical duration, estimated blood loss, spinal cord and arterial injury incidence, screw placement accuracy, neurological status measured by the Japanese Orthopedic Association (JOA) score and fusion rates, were collected and analyzed. 13 patients received C1 pedicle screw placement via UBB facilitation, while 8 were treated using the HSD approach. The UBB group showed a significant reduction in blood loss and operation time compared to the HSD group (P=0.002 and P<0.001, respectively). No spinal cord or arterial injuries occurred in either group. Optimal screw placement was confirmed in all UBB cases versus 87.5% in the HSD group (P=0.139). Both groups demonstrated significant improvements in JOA scores with no inter-group difference. The fusion rate was 100% in the UBB group and 87.5% in the HSD group, not statistically different (P=0.381). UBB is a viable alternative for C1 pedicle screw placement, associated with reduced blood loss and shorter operation time, while achieving comparable clinical outcomes to the conventional HSD method. Nevertheless, further research with a larger sample size is needed.

Energy Evolution Characteristics and Hydraulic Fracturing Roof Cutting Technology for Hard Roof Working Face during Initial Mining: A Case Study

In the process of mining, a large area of hard roof will be exposed above a goaf and may suddenly break. This can easily induce rock burst and has a significant impact on production safety. In this study, based on the engineering background of the hard roof of the 2102 working face in the Balasu coal mine, the spatial and temporal characteristics of the strain energy of the roof during the initial mining process were explored in depth. Based on a theoretical calculation, it is proposed that hydraulic fracturing should be carried out in the medium-grained sandstone layer that is 4.8–22.43 m above the roof, and that the effective fracturing section in the horizontal direction should be within 30.8 m of the cutting hole of the working face. The elastic strain energy fish model was established in FLAC3D to analyze the strain energy accumulation of the roof during the initial mining process. The simulation and elastic strain energy results show that, as the working face advances to 70–80 m, the hard roof undergoes significant bending deformation. The energy gradient increases with the rapid accumulation of strain energy to a peak value of 140.54 kJ/m3. If the first weighting occurs at this moment in time, the sudden fracture of the roof will be accompanied by the release of elastic energy, which will induce rock burst. Therefore, it is necessary to implement roof cutting and pressure relief before reaching the critical step of 77 m. To this end, the comprehensive hydraulic fracturing technology of ‘conventional short drilling + directional long drilling’ is proposed. A field test shows that the hydraulic fracturing technology effectively weakens the integrity of the rock layer. The first weighting interval is 55 m, and it continues until the end of the pressure at the 70 m position. The roof collapses well, and the mining safety is improved. This study provides an important reference for hard roof control.

Application of Nanofibrous Clay Minerals in Water-Based Drilling Fluids: Principles, Methods, and Challenges

Nanofibrous clay minerals, specifically palygorskite (Pal) and sepiolite (Sep), have been becoming a new generation of rheological additives for drilling fluid systems due to their unique nanostructure, high performance, environmentally benign nature, and cost-effectiveness. These nanoclay minerals exhibit excellent colloidal and rheological properties in aqueous systems, even in saline and high-temperature environments. Although Pal and Sep have been employed as auxiliary rheological additives in a few cases to enhance the salt resistance of conventional water-based drilling fluids (WBDFs), these two clay minerals have not yet been used on a large scale due to a lack of understanding of their structures and properties, as well as the control of their performance. This paper presents a comprehensive review of the clay mineralogy, colloidal chemistry, rheological behaviors, and filtration properties of nanofibrous clay minerals in WBDFs, with critical comments. It also discusses the challenges and prospects for further research. This review provides new insights into fundamental and applied studies of nanofibrous clay minerals and helps promote the large-scale application of nanofibrous clay products in drilling fluids.

Experimental study on ultrasonic vibration‐assisted drilling performance of carbon fiber polyetherketoneketone laminate

AbstractParts made from carbon fiber reinforced polyetherketoneketone (CF/PEKK) primarily use mechanical connections during assembly, where the quality of hole processing directly impacts the connection strength. However, defects like delamination, burrs, and fiber pull‐out frequently occur during drilling. While existing research focuses on optimizing conventional drilling (CD) and helical milling (HM), ultrasonic vibration‐assisted drilling (UVAD) shows superior performance in reducing thrust force and defects. This study experimentally evaluates the hole‐making performance of CF/PEKK using the UVAD method. It examines the effects of ultrasonic vibration on thrust force, drilling temperature, processing damage, chip morphology, and surface microstructure, and discusses the damage suppression mechanism. The results show that the UVAD method significantly reduces thrust force and drilling temperature compared to the CD method, with similar trends in delamination and burr damage. This study demonstrates that using the UVAD method for drilling CF/PEKK laminates effectively reduces thrust force, drilling temperature, and machining damage, thereby significantly improving processing quality. The material removal mechanism of UVAD was analyzed, offering substantial insights and practical guidance for the efficient drilling of CF/PEKK laminates.Highlights The drilling performance of CF/PEKK was studied. The drilling quality of UVAD and CD is compared by experiments. UVAD has a lower thrust force and drilling temperature. UVAD can reduce machining damage and improve machining quality.

Reservoir Potential Evaluation of the Middle Paleocene Lockhart Limestone of the Kohat Basin, Pakistan: Petrophysical Analyses

The Lockhart Limestone is evaluated for its reservoir potential by utilizing wireline logs of Shakardara-01well from Kohat Basin, Pakistan. The analyses showed 28.03% average volume of shale (Vsh), 25.57% average neutron porosity (NPHI), 3.31% average effective porosity (PHIE), 76% average water saturation (Sw), and 24.10% average hydrocarbon saturation (Sh) of the Lockhart Limestone in Shakardara-01 well. Based on variation in petrophysical character, the reservoir units of the Lockhart Limestone are divided into three zones i.e., zone-1, zone-2 and zone-3. Out of these zones, zone-1 and zone-2 possess a poor reservoir potential for hydrocarbons as reflected by very low effective porosity (1.40 and 2.02% respectively) and hydrocarbon saturation (15 and 5.20%), while zone-3 has a moderate reservoir potential due to its moderate effective porosity (6.50%) and hydrocarbon saturation (52%) respectively. Overall, the average effective porosity of 3.31% and hydrocarbon saturation of 24.10% as well as 28.03% volume of shale indicated poor reservoir potential of the Lockhart Limestone. Lithologically, this formation is dominated by limestone and shale interbeds in the Shakardara-01 well. Cross-plots of the petrophysical parameters versus depth showed that the Lockhart Limestone is a poor to tight reservoir in Shakardara-01 well and can hardly produce hydrocarbons under conventional drilling conditions.

Antimicrobial Efficacy of Chemomechanical Carie Removal Agents-A Systematic Integrative Review.

Dental caries is the most common oral disease in the world. When treatable, the drilling method continues to be used. This technique has its disadvantages because it is invasive and nonspecific. Chemomechanical carious tissue removal agents (CCRAs) such as Carisolv™ or Papacarie® are non-invasive products that allow for the specific elimination of infected dentin. On the other hand, cariogenic bacteria are largely responsible for the initiation and development of lesions. The aim is to analyze whether CCRAs have a relevant antimicrobial effect on cariogenic bacteria. A bibliographic search strategy was carried out in online databases using PRISMA 2020. The evaluation of the antibacterial efficacy of CCRAs was carried out through the analysis of the reduction in CFUs of cariogenic bacteria, and the presence of bacterial deposits, TVC, SVC and LVC by comparison with conventional drilling methods. The results showed that the percentage of reduction in TVC, SVC and LVC for each agent is mostly high, but not significantly different from mechanical methods. The best results were found with CCRAs when compared to polymeric drills. The results also showed that there is a lack of methodological standardization. CCRAs have been shown to have a relevant antimicrobial effect on cariogenic bacteria; however, more studies need to be carried out using standardized methodologies.

Laser and mechanical micro-drilling for aerospace applications

Traditional laser percussion drilling encounters challenges related to poor geometry and thermal defects. At the same time, mechanical micro-drilling while generating high-quality holes, faces issues such as premature drill breakage and difficulty drilling at acute angles. This review paper introduces a novel approach to micro-drilling Inconel 718 alloy sheets at acute angles by combining sequential laser and mechanical drilling. The study showcases the feasibility and fundamental characteristics of this innovative technique. Results indicate that the sequential laser-mechanical micro-drilling approach mitigates the drawbacks associated with laser-drilled holes, leading to reduced burr size, decreased machining time, and increased tool life when compared to conventional mechanical drilling methods. This advancement holds promise for enhancing precision and efficiency in aerospace applications, paving the way for improved manufacturing processes in the aerospace industry.

Clinical Outcome Success of Silver-Modified Atraumatic Restorative Treatment (SMART) in Treating Children with Dental Caries in Primary Teeth: A Systematic Review

Abstract Objective: A novel approach called silver-modified atraumatic restorative therapy (SMART) integrates glass ionomer cement (GIC) restorations with silver diamine fluoride (SDF). This new method combines the ability of GIC to seal the tooth and sever the nutrition that bacteria require to proliferate, with the bactericidal power of SDF. The purpose of this review is to evaluate and compare the available data regarding the efficacy of the SMART approach in treating children's carious primary teeth. Materials and Methods: The earliest date accessible up until February 15, 2024, was thoroughly searched in databases including Scopus, PubMed, Cochrane, Science Direct, Lilacs, Science Direct, Web of Science, and Google Scholar. The review only comprised randomized controlled trials. The PICO strategy (P: Children with dental caries in primary teeth; I: SMART; C: Conventional drill and fill method or atraumatic restorative treatment [ART] therapy; O: Clinical success) was adopted. Risk of bias assessment and quality of evidence were assessed using the RoB-2 tool and GRADE tool, respectively. Results: Four full-text publications that met the eligibility criteria underwent additional processing for data extraction and qualitative analysis. In three studies, no difference was found in the clinical performance of SMART and conventional drill and fill/ART therapy, whereas in one study, the clinical performance of SMART was found to be better than the conventional ART therapy. Conclusion: SMART and conventional drill and fill/ART techniques have comparable clinical performance for carious primary teeth of children. SMART can be used to treat asymptomatic deep carious lesions as well as apprehensive children. However, the cost-effectiveness of SMART restorations needs to be investigated in a variety of demographics.

Experimental study on shale-breaking of special-shaped cutter PDC bit

To enhance the drilling efficiency and extend the service life of PDC (Polycrystalline Diamond Composite) bits in shale formations, this study delves into the rock-breaking mechanisms of special-shaped cutters through a comprehensive experimental approach. This involves optimizing the cutter designs, conducting laboratory experiment and field testing. Among the various cutter geometries considered, concave, axe, planar, and triangular cutters are chosen as the focal points for unit rock-breaking experiments. These tests aim to assess their cutting loads and cutting specific energy to gain a deeper understanding of their performance characteristics. Based on experimental, the debris characteristics are analyzed. Based on the understanding of the shale-breaking characteristics of special-shaped cutters, field testing is performed using a novel PDC bit with a special-shaped cutter. Compared with planar cutters, the concave cutter and the triangular cutter generate lower cutting loads and cutting specific energy. Under identical conditions, the average cutting force and cutting specific energy of concave cutter at different cutting depths are reduced by 16.1% and 19.6% Specifically, the concave cutter generates the largest debris when operated under similar conditions, which is beneficial for increasing rock-breaking efficiency. Laboratory experiment indicate that compared to conventional drill bits, the novel drill bit experiences an increase in torque of approximately 9.8% with increasing WOB (weight on bit). Under high WOB, the ROP (rate of penetration) increases by about 75.4%, while the mechanical specific energy decreases by nearly 40%. Additionally, the novel bit vibration characteristics remain superior to conventional drill bits. Field testing shows that the average ROP of the novel bit and total footage drilled increase by up to 13.3% and 27.2%, respectively, in comparison with those for the conventional bit. The research results are helpful to speed up the efficiency of shale gas drilling.

Primary stability evaluation of different morse cone implants in low-density artificial bone blocks: A comparison between high-and low-speed drilling

This study aimed to evaluate various biomechanical parameters associated with the primary stability of Maestro and Due Cone implants placed in low-density artificial bones, prepared using high-speed drilling with irrigation and low-speed drilling without irrigation. The insertion torque (IT), removal torque (RT), and implant stability quotient (ISQ) values were recorded for Maestro and Due Cone implants placed in low-density polyurethane blocks (10 and 20 pounds per cubic foot (PCF) with and without a cortical layer) prepared using high-speed and low-speed with or without irrigation using a saline solution, respectively. A three-way ANOVA model and Tukey's post-hoc test were conducted, presenting data as means and standard deviations. P-values equal to or less than 0.05 were considered statistically significant. No statistically significant differences in IT, RT, and ISQ between drilling speeds were observed. However, Maestro implants exhibited lower IT and RT values after high- and low-speed drilling across almost all polyurethane blocks, significantly evident in the 20 PCF density block for IT and in the 20 PCF density block with the cortical layer for the RT with low-speed drilling (IT: 47.33 ± 10.02 Ncm and 16.00 ± 12.49 Ncm for Due Cone and Maestro implants, respectively, with p < 0.01; RT: 44.67 ± 22.81 Ncm and 20.01 ± 4.36 Ncm for Due Cone and Maestro implants, respectively, with p < 0.05) and among the same implant types inserted in different bone densities. Additionally, the study found that for all bone densities and drilling speeds, both implants registered ISQ values exceeding 60, except for the lowest-density polyurethane block. Overall, it can be inferred that low-speed drilling without irrigation achieved biomechanical parameters similar to conventional drilling with both implant types, even with lower IT values in the case of Maestro implants. These findings suggest a promising potential use of low-speed drilling without irrigation in specific clinical scenarios, particularly when focusing on preparation depth or when ensuring proper irrigation is challenging.

Assessing wire EDM as a novel approach for CFRP drilling: performance and thermal analysis across lay-up configurations

Conventional drilling of carbon fibre–reinforced plastic (CFRP) presents significant challenges due to the material’s abrasive nature and anisotropic properties, leading to tool wear, delamination, and surface damage. To address these challenges, this study pioneers the use of wire electrical discharge machining (WEDM) to evaluate the drilling performance of thick CFRP lay-up configurations mainly unidirectional and multidirectional, marking the first application of WEDM for CFRP drilling. The study evaluates material removal rate (MRR), delamination factor (DF), and surface damage while employing an analytical solution to estimate surface temperature and heat conduction in the laminates. An eight-full factorial experimental design was employed, involving variations in ignition current (3 A and 5 A) and pulse-off time (4 µs and 8 µs). The findings revealed that the multidirectional lay-up achieved an MRR of 2.85 mm3/min, significantly outperforming the unidirectional lay-up’s MRR of 0.95 mm3/min, representing a 300% increase at 5 A and 4 µs. However, the increase in discharge energy led to surface damage such as delamination, frayed fibres, and irregular circularity, especially evident in the unidirectional lay-up. For delamination, the multidirectional lay-up had the highest top DF of 1.4 at 5 A and 6 µs, while the unidirectional lay-up achieved the peak bottom DF of 1.24 at the same levels. While none of the parameters significantly affected the responses, the current exhibited the highest contribution ratios. Analytical predictions of the thermal distribution indicated a 45-µm delamination length at the laminate surface and depth, aligning closely with experimental predictions of 30–50 µm.