A Thermal and Biological Analysis of Bone 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.

In Vitro Bioassay for Damage-Associated Molecular Patterns Arising from Injured Oral Cells

Gingival fibroblasts are a significant source of paracrine signals required to maintain periodontal homeostasis and to mediate pathological events linked to periodontitis and oral squamous cell carcinomas. Among the potential paracrine signals are stanniocalcin-1 (STC1), involved in oxidative stress and cellular survival; amphiregulin (AREG), a growth factor that mediates the cross-talk between immune cells and epithelial cells; chromosome 11 open reading frame 96 (C11orf96) with an unclear biologic function; and the inflammation-associated prostaglandin E synthase (PTGES). Gingival fibroblasts increasingly express these genes in response to bone allografts containing remnants of injured cells. Thus, the gene expression might be caused by the local release of damage-associated molecular patterns arising from injured cells. The aim of this study is consequently to use the established gene panel as a bioassay to measure the damage-associated activity of oral cell lysates. To this aim, we have exposed gingival fibroblasts to lysates prepared from the squamous carcinoma cell lines TR146 and HSC2, oral epithelial cells, and gingival fibroblasts. We report here that all lysates significantly increased the transcription of the entire gene panel, supported for STC1 at the protein level. Blocking TGF-β receptor 1 kinase with SB431542 only partially reduced the forced expression of STC1, AREG, and C11orf96. SB431542 even increased the PTGES expression. Together, these findings suggest that the damage signals originating from oral cells can change the paracrine activity of gingival fibroblasts. Moreover, the expression panel of genes can serve as a bioassay for testing the biocompatibility of materials for oral application.

Gingival Fibroblasts Are Sensitive to Oral Cell Lysates Indicated by Their IL11 Expression

Damaged cells that appear as a consequence of invasive dental procedures or in response to dental materials are supposed to release damage-associated signals. These damage-associated signals not only support tissue regeneration but might also contribute to unwanted fibrosis. The aim of this study was to identify a molecular target that reflects how fibroblasts respond to necrotic oral tissue cells. To simulate the cell damage, we prepared necrotic cell lysates by sonication of the osteocytic cell line IDG-SW3 and exposed them to gingival fibroblasts. RNAseq revealed a moderate increase in IL11 expression in the gingival fibroblasts, a pleiotropic cytokine involved in fibrosis and inflammation, and also in regeneration following trauma. Necrotic lysates of the human squamous carcinoma cell lines HSC2 and TR146, as well as of gingival fibroblasts, however, caused a robust increase in IL11 expression in the gingival fibroblasts. Consistently, immunoassay revealed significantly increased IL11 levels in the gingival fibroblasts when exposed to the respective lysates. Considering that IL11 is a TGF-β target gene, IL11 expression was partially blocked by SB431542, a TGF-β receptor type I kinase inhibitor. Moreover, lysates from the HSC2, TR146, and gingival fibroblasts caused a moderate smad2/3 nuclear translocation in the gingival fibroblasts. Taken together and based on IL11 expression, our findings show that fibroblasts are sensitive to damaged oral tissue cells.

The 3D Printing and Evaluation of Surgical Guides with an Incorporated Irrigation Channel for Dental Implant Placement

Dental implant insertion requires the preparation of the implant bed via surgical drilling. During this stage, irrigation is essential to avoid thermal damage to the surrounding bone. Surgical guides enhance the accuracy of the implant site preparation, but they mask the drilling site, hampering coolant delivery. A variety of designs are aimed at improving the coolant access to the target site. Using standard dental implant simulation software, this paper presents an in-house design and 3D printing workflow for building surgical guides that incorporate a coolant channel directed toward the entry point of the burr. The proposed design was evaluated in terms of the bone temperature elevations caused by drilling performed at 1500 rpm, under an axial load of 2 kg, and irrigation with 40 mL/min of saline solution at 25 °C. Temperature measurements were performed on porcine femoral pieces, in the middle of the cortical bone layer, at 1 mm from the edge of the osteotomy. The mean temperature rise was 3.2 °C for a cylindrical sleeve guide, 2.7 °C for a C-shaped open-sleeve guide, and 2.1 °C for the guide with an incorporated coolant channel. According to a one-way ANOVA, the differences between these means were marginally insignificant (p = 0.056). The individual values of the peak temperature change remained below the bone damage threshold (10 °C) in all cases. Remarkably, the distribution of the recorded temperatures was the narrowest for the guide with internal irrigation, suggesting that, besides the most effective cooling, it provides the most precise control of the intraosseous temperature. Further studies could test different design variants, experimental models (including live animals), and might involve computer simulations of the bone temperature field.

Oral squamous carcinoma cell lysates provoke exacerbated inflammatory response in gingival fibroblasts

OBJECTIVES

To study whether damaged epithelial cells and gingival fibroblast could affect the expression of inflammatory cytokines in healthy cells.

MATERIALS AND METHODS

Cell suspensions were submitted to different treatments to obtain the lysates: no treatment (supernatant control), sonication, and freeze/thawing. All treatments were centrifuged, and the supernatants of the lysates were used for experimentation. Cell viability assays, RT-qPCR of IL1, IL6 and IL8, IL6 immunoassay, and immunofluorescence of NF-kB p65 were applied to verify the inflammatory crosstalk of damaged cells over healthy plated cells. Furthermore, titanium discs and collagen membranes were treated with lysates and checked for IL8 expression by RT-qPCR.

RESULTS

Lysates obtained upon sonication or freeze/thawing of oral squamous carcinoma cell lines provoked a robust increase in the expression of IL1, IL6, and IL8 by gingival fibroblasts, which was confirmed by IL6 immunoassays. Lysates obtained from the gingival fibroblasts failed to increase the expression of inflammatory cytokines in oral squamous carcinoma cells. Additionally, oral squamous carcinoma cell lysates caused the activation of the NF-kB signalling cascade in gingival fibroblasts as indicated by the phosphorylation and nuclear translocation of p65. Finally, oral squamous carcinoma cell lysates adhered to the titanium and collagen membrane surfaces and increased IL8 expression by gingival fibroblasts growing in these materials.

CONCLUSIONS

Injured oral epithelial cells can release factors that incite gingival fibroblasts to become pro-inflammatory.

CLINICAL RELEVANCE

Injuries affecting the oral mucosa generate epithelial fragments that may reach the underlying connective tissue and provoke inflammation. These injuries are routinely caused by mastication, sonication for teeth cleaning, teeth preparation, prostheses maladaptation, and implant drilling.

A neural network framework for immediate temperature prediction of surgical hand-held drilling

BACKGROUND AND OBJECTIVE

Heat generation and associated temperature rise in surgical drilling can cause irreversible tissue damage. It is nearly impossible to provide immediate temperature prediction for a hand-held drilling process since both feed rate and motion vary with time. The objective of this study is to present and test a framework for immediate bone drilling temperature visualization based on a neural network (NN) model and a linear time-invariant (LTI) model.

METHODS

In this study, the finite element analysis (FEA) model is used as the ground truth. The NN model is used to predict the location-dependent thermal responses of FEA, while LTI is used to superimpose these responses based on the location history of the heat source. The use of LTI can eliminate the uncertainty of the unlimited possibility in the time domain. To test the framework, two three-dimensional drilling cases are studied, one with a constant drilling feed and straight path and the other with a varying feed and a varying path.

RESULTS

The NN model using U-net architecture can achieve the predicted correlation of over 97% with only 1% of the total number of data points. Using the framework with U-net and LTI, both case studies show good agreement in temporal and spatial temperature distributions with the ground truth. The average error near the drilling path is less than 10%. Discrepancies are mainly found near the heat source and the regions near the removed material.

CONCLUSIONS

An FEA surrogate model for rapid and accurate prediction of 3D temperature during arbitrary bone drilling is successfully made. The overall error is less than 5% on average in the two case studies. Future improvements include strategies for training data selection and data formating.

Design modification of surgical drill bit for final osteotomy site preparation towards improved bone-implant contact

Implant stability significantly impacts accelerated osseointegration, leading to faster patient recovery. Both primary and secondary stability necessitates superior bone-implant contact influenced by the surgical tool required to prepare the final osteotomy site. Besides, excessive shearing and frictional forces generate heat causing local tissue necrosis. Hence, surgical procedure necessitates proper irrigation with water to minimize heat generation. Notably, the water irrigation system removes bone chips and osseous coagulums, which may help accelerate osseointegration and improve bone-implant contact. The inferior bone-implant contact and thermal necrosis at the osteotomy site are primarily responsible for poor osseointegration and eventual failure. Therefore, optimizing tool geometry is key to minimizing shear force, heat generation, and necrosis during final osteotomy site preparation. The present study explores modified drilling tool geometry, especially cutting edge for osteotomy site preparation. The mathematical modeling is used to find out ideal cutting-edge geometry that facilitates drilling under relatively less operational force (0.55-5.24 N) and torque (98.8-154.5 N-mm) with a significant reduction (28.78%-30.87%) in heat generation. Twenty-three conceivable designs were obtained using the mathematical model; however, only three have shown promising results in static structural FEM platforms. These drill bits are designed for the final drilling operation and need to be carried out during the final osteotomy site preparation.

Osseointegration in relation to drilling speed in the preparation of dental implants sites: A systematic review

STATEMENT OF PROBLEM

The drilling speed used for preparing dental implants may affect bone-implant contact (BIC), implant stability quotient (ISQ), and bone area fraction occupancy (BAFO). Different rotational speeds and the presence or absence of irrigation during site preparation have been investigated, but an established protocol for achieving the best osseointegration results is lacking.

PURPOSE

The purpose of this systematic review was to investigate the influence of drill rotational speed on bone drilling for dental implant placement and its relationship with osseointegration.

MATERIAL AND METHODS

This review included the preferred reporting items for systematic reviews and meta-analyses (PRISMA) and was registered in the international prospective register of systematic reviews (PROSPERO) database. Electronic searches were performed in the MEDLINE (PubMed), Scopus, Science Direct, and Embase databases. The risk of bias was analyzed by using the systematic review center for laboratory animal experimentation (SYRCLE).

RESULTS

A total of 1282 articles were found, and after removing duplicates and applying the eligibility criteria to in vivo articles on animals that addressed drilling speed and its relationship to osseointegration, 8 articles were selected for analysis. Of these, 5 articles showed no statistical differences, and 3 others showed significantly better osseointegration results by analyzing the parameters of BIC, BAFO, ISQs, and pull-out forces (PoFs). In all selected articles, high-speed drilling was performed with irrigation.

CONCLUSIONS

Although drilling speed seems to affect bone perforation, no definitive protocol was found in the literature consulted. The results vary depending on the combination of different factors, including bone type, irrigation, and drilling speed.

Quantification and comparison of the regional acceleratory phenomenon in bone following piezosurgery or bur osteotomy: A pilot study in rats

BACKGROUND/OBJECTIVE

The Regional Acceleratory Phenomenon (RAP) can be induced surgically via decortication (selective cortical penetrations) of bone to accelerate orthodontic tooth movement. Few studies have compared the impact and efficiency of different decortication methods to induce the RAP. The aim of this study was to determine if there is a significant difference in the intensity of the RAP induced by a surgical defect created either using a piezoelectric knife or a rotary bur.

METHODS

Twenty-two Sprague-Dawley rats were divided into two treatment groups (each n = 8) and a control group (n = 6). The treatment groups were subjected to transcortical penetrations (TP) of the right tibia using either a piezoelectric knife (PTP) or a rotary bur (BTP). The right tibias of the control group animals had reflection of tissues (SHAM) and the left legs were kept for comparison (INTACT). The animals were killed at 7 and 14 days after the operation in an equally distributed manner. Microcomputed tomography images were obtained and analyzed utilizing artificial intelligence for bone cortical porosity (Ct.Po) locally and regionally.

RESULTS/CONCLUSION

Regionally, TP using a PTP induced significantly (p < .05, Kruskal-Wallis test) more Ct.Po than BTP or INTACT for both the 7- and 14-day time points. PTP was not found to induce significantly more Ct.Po than SHAM at any time point. However, PTP induced significantly more Ct.Po than the INTACT group for each time point, while SHAM did not. The local analysis did not reveal any relevant significant differences between groups.

Clinical effects of conventional and underprepared drilling preparation of the implant site based on bone density: A systematic review and meta-regression

PURPOSE

There is no clinical consensus to determine the right balance between underpreparation and marginal bone level changes. The purpose of this systematic review and meta-regression was to investigate the influence of the type of drilling preparation of the implant site in relation to the bone mineral density on the clinical success, expressed in terms of the MBL and implant failure rate.

STUDY SELECTION

A thorough search was performed using the digital databases MEDLINE PubMed, EMBASE, and Cochrane Central Register of Controlled Trials by entering research lines or various combinations of free words. The main keywords used were "dental implants", "bone density", and "torque".

RESULTS

The mean bone resorption in the conventional preparation group was -0.43 (± 0.28) mm, whereas it was -0.80 (± 0.37) mm in the underprepared group. For the D1/D2/D3 bone group, the slope was significantly different from zero and linearity; the D4 bone group slope was not significantly different from zero and was almost parallel, although it was significantly different from linearity. The box and whiskers plot shows that the MBL in underprepared sites tended to be significantly higher with a higher variation than that in conventionally prepared sites.

CONCLUSIONS

Within its limits, our meta-regression analysis showed that MBL is influenced by the type of drilling preparation and bone mineral density. In particular, a lower MBL was observed in the D1 bone with conventional preparation than with underpreparation. Moreover, a greater implant-to-osteotomy site mismatch was positively associated with greater MBLs in the bone densities of D1/D2/D3.

Impact of local predisposing/precipitating factors and systemic drivers on peri‐implant diseases

BACKGROUND

Strong evidence suggests the infectious nature of peri-implant diseases occurring in susceptible hosts. Epidemiological reports, though, indicate that peri-implantitis is a site-specific entity. Hence, the significance of local factors that may predispose/precipitate plaque accumulation and the impact of systemic drivers that alter the immune response are relevant in the prevention and management of peri-implant disorders.

PURPOSE

The purpose of the present review is to shed light on the significance of local and systemic factors on peri-implant diseases, making special emphasis on the associations with peri-implantitis.

METHODS

The biologic plausibility and supporting evidence aiming at providing a concluding remark were explored in the recent scientific literature for local predisposing/precipitating factors and systemic drivers related to peri-implant diseases.

RESULTS

Local predisposing factors such as soft tissue characteristics, implant position and prosthetic design proved being strongly associated with the occurrence of peri-implant diseases. Hard tissue characteristics, however, failed to demonstrate having a direct association with peri-implant diseases. Robust data points toward the strong link between residual sub-mucosal cement and peri-implant diseases, while limited data suggests the impact of residual sub-mucosal floss and peri-implantitis. Systemic drivers/habits such as hyperglycemia and smoking showed a strong negative impact on peri-implantitis. However, there is insufficient evidence to claim for any link between metabolic syndrome, atherosclerotic cardiovascular disease, and obesity and peri-implant diseases.

CONCLUSION

Local predisposing/precipitating factors and systemic drivers may increase the risk of peri-implant diseases. Therefore, comprehensive anamnesis of the patients, educational/motivational programs and exhaustive prosthetically-driven treatment planning must be fostered aiming at reducing the rate of biological complications in implant dentistry.

Damaged Mesenchymal Cells Dampen the Inflammatory Response of Macrophages and the Formation of Osteoclasts

Damage to mesenchymal cells occurs by dental implant drills as a consequence of shear forces and heat generation. However, how the damaged mesenchymal cells can affect the polarization of macrophages and their differentiation into osteoclastogenesis is not fully understood. To simulate cell damage, we exposed suspended ST2 murine bone marrow stromal cells to freeze/thawing or sonication cycles, followed by centrifugation. We then evaluated the lysates for their capacity to modulate lipopolysaccharide-induced macrophage polarization and RANKL-MCSF-TGF-β-induced osteoclastogenesis. We report that lysates of ST2, particularly when sonicated, greatly diminished the expression of inflammatory IL6 and COX2 as well as moderately increased arginase 1 in primary macrophages. That was confirmed by lysates obtained from the osteocytic cell line IDG-SW3. Moreover, the ST2 lysate lowered the phosphorylation of p65 and p38 as well as the nuclear translocation of p65. We further show herein that lysates of damaged ST2 reduced the formation of osteoclast-like cells characterized by their multinuclearity and the expression of tartrate-resistant phosphatase and cathepsin K. Taken together, our data suggest that thermal and mechanical damage of mesenchymal cells causes the release of as-yet-to-be-defined molecules that dampen an inflammatory response and the formation of osteoclasts in vitro.

An Osteotomy Tool That Preserves Bone Viability: Evaluation in Preclinical and Clinical Settings

The main objectives of this work were to assess the efficiency, ease-of-use, and general performance of a novel osseoshaping tool based on first-user clinical experiences and to compare these observations with preclinical data generated in rodents using a miniaturized version of the instrument. All patients selected for the surgery presented challenging clinical conditions in terms of the quality and/or quantity of the available bone. The presented data were collected during the implant placement of 15 implants in 7 patients, and included implant recipient site (bone quality and quantity) and ridge evaluation, intra-operative handling of the novel instrument, and the evaluation of subsequent implant insertion. The instrument was easy to handle and was applied without any complications during the surgical procedure. Its use obviated the need for multiple drills and enabled adequate insertion torque in all cases. This biologically driven innovation in implant site preparation shows improvements in preserving vital anatomical and cellular structures as well as simplifying the surgical protocol with excellent ease-of-use and handling properties.

Multiscale analysis of craniomaxillofacial bone repair: A preclinical mini pig study

BACKGROUND

The rate of reparative osteogenesis controls when an implant is sufficiently stable as to allow functional loading. Using a mini pig model, the rate of reparative osteogenesis in two types of implant sites e.g., an osteotomy versus a fresh extraction socket were compared.

METHODS

Eight adult mini pigs were used for the study. In Phase I, three premolars were extracted on one side of the oral cavity; 12 weeks later, in Phase II, osteotomies were produced in healed extraction sites, and contralateral premolars were extracted. Animals were sacrificed 1, 5, and 12 weeks after Phase II. Bone repair and remodeling were evaluated using quantitative micro-computed tomographic imaging, histology, and histochemical assays coupled with quantitative dynamic histomorphometry.

RESULTS

One week after surgery, extraction sockets and osteotomy sites exhibited similar patterns of new bone deposition. Five weeks after surgery, mineral apposition rates were elevated at the injury sites relative to intact bone. Twelve weeks after surgery, the density of new bone in both injury sites was equivalent to intact bone but quantitative dynamic histomorphometry and cellular activity assays demonstrated bone remodeling was still underway.

CONCLUSION(S)

The mechanisms and rates of reparative osteogenesis were equivalent between fresh extraction sockets and osteotomies. The volume of new bone required to fill a socket, however, was significantly greater than the volume required to fill an osteotomy. These data provide a framework for estimating the rate of reparative osteogenesis and the time to loading of implants placed in healed sites versus fresh extraction sockets. This article is protected by copyright. All rights reserved.

Effects of masticatory loading on bone remodeling around teeth vs. implants: insights from a preclinical model

OBJECTIVES

Teeth connect to bone via a periodontal ligament whereas implants connect to bone directly. Consequently, masticatory loads are distributed differently to periodontal versus peri-implant bone. Our objective was to determine how masticatory loading of an implant versus a tooth affected peri-implant versus periodontal bone remodeling. Our hypothesis was that strains produced by functional loading of an implant would be elevated compared to the strains around teeth, and that this would stimulate a greater degree of bone turnover around implants versus in periodontal bone.

MATERIALS AND METHODS

Sixty skeletally mature mice were divided into two groups. In the Implant group, maxillary first molars (mxM1) were extracted, and after socket healing, titanium alloy implants were positioned sub-occlusally. After osseointegration, implants were exposed, resin crowns were placed, and masticatory loading was initiated. In a Control group the dentition was left intact. Responses of peri-implant and periodontal bone were measured using micro-CT, histology, bone remodeling assays, and quantitative histomorphometry while bone strains were estimated using finite element (FE) analyses.

CONCLUSIONS

When a submerged osseointegrated implant is exposed to masticatory forces peri-implant strains are elevated, and peri-implant bone undergoes significant remodeling that culminates in new bone accrual. The accumulation of new bone functions to reduce both peri-implant strains and bone remodeling activities, equivalent to those observed around the intact dentition.

Evaluation of potential tissue heating during percutaneous drill-assisted bone sampling in an in vivo porcine study

BACKGROUND

Minimally invasive, battery-powered drilling systems have become the preferred tool for obtaining representative samples from bone lesions. However, the heat generated during battery-powered bone drilling for bone biopsies has not yet been sufficiently investigated. Thermal necrosis can occur if the bone temperature exceeds a critical threshold for a certain period of time.

PURPOSE

To investigate heat production as a function of femur temperature during and after battery-powered percutaneous bone drilling in a porcine in vivo model.

METHODS

We performed 16 femur drillings in 13 domestic pigs with an average age of 22 weeks and an average body temperature of 39.7 °C, using a battery-powered drilling system and an intraosseous temperature monitoring device. The standardized duration of the drilling procedure was 20 s. The bone core specimens obtained were embedded in 4% formalin, stained with haematoxylin and eosin (H&E) and sent for pathological analysis of tissue quality and signs of thermal damage.

RESULTS

No significant changes in the pigs' local temperature were observed after bone drilling with a battery-powered drill device. Across all measurements, the median change in temperature between the initial measurement and the temperature measured after drilling (at 20 s) was 0.1 °C. Histological examination of the bone core specimens revealed no signs of mechanical or thermal damage.

CONCLUSION

Overall, this preliminary study shows that battery-powered, drill-assisted harvesting of bone core specimens does not appear to cause mechanical or thermal damage.

Thermal and physical damage in skull base drilling using gas cooling modes: FEM simulation and experimental evaluation

BACKGROUND

Skull base drilling, as a high-risk process, is one of the most important techniques of skull base surgeries.

METHODS

The temperature, thrust force, and torque were calculated using finite element method (FEM) simulation under two conventional cooling models, and internal and external CO₂ cooling modes at four rotational speeds (1000-4000 rpm). The temperatures at the bottom and on the surface of the drilling site were measured experimentally using a thermometer and a thermographic camera, respectively. The results were then compared with FEM results.

RESULTS

The efficiency rates of CO₂ coolants in reducing the maximum temperature, thrust force, and torque were at least 5.0-11.2%, 16.5-33.8%, and 6.9-11.3% higher than conventional cooling modes, respectively. The experimental results indicated that, in contrast to the maximum temperature, temperature durability was 72.7-107.3% higher in the conventional cooling modes than the cooling modes with external CO₂ coolant systems. The cracks and surface defects were less in the CO₂ coolants than the other cooling modes. The maximum temperature after the second and third drillings increased by 17.7 and 26.8%, compared to the first drilling in the conventional cooling modes. On the other hand, the repeated drillings had no impact on the temperature in the CO₂ cooling modes.

CONCLUSION

Skull base drilling with a rotational speed of 2000 rpm in the cooling mode of an external CO₂ coolant, even for repeated drillings, can lead to a skull drilling process with minimum risk of drill bit breakage and thermal and physical damage.

Different grinding speeds affect induced regeneration capacity of human treated dentin matrix

Human-treated dentin matrix (hTDM) is a biomaterial scaffold, which can induce implant cells to differentiate into odontoblasts and then form neo-dentin. However, hTDM with long storage or prepared by high-speed handpiece would not to form neo-dentin. In this research, we developed two fresh hTDM with different grinding speeds, which were low-speed hTDM (LTDM) with maximum speed of 500 rpm and high-speed hTDM (HTDM) with a speed of 3,80,000 rpm. Here, we aim to understand whether there were induced regeneration capacity differences between LTDM and HTDM. Scanning electron microscope showed that DFCs grew well on both materials, but the morphology of DFCs and the extracellular matrix was different. Especially, the secreted extracellular matrixes on the inner surface of LTDM were regular morphology and ordered arrangement around the dentin tubules. The transcription-quantitative polymerase chain reaction (qRT-PCR), western blot and immunofluorescence assay showed that the dentin markers DSPP and DMP-1 were about 2× greater in DFCs induced by LTDM than by HTDM, and osteogenic marker BSP was about 2× greater in DFCs induced by HTDM than by LTDM. Histological examinations of the harvested grafts observed the formation of neo-tissue were different, and there were neo-dentin formed on the inner surface of LTDM and neo-cementum formed on the outer surface of HTDM. In summary, it found that the induction abilities of LTDM and HTDM are different, and the dentin matrix is directional. This study lays a necessary foundation for searching the key factors of dentin regeneration in future.

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

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

Accuracy of guided biopsy of the jawbone in a clinical setting: A retrospective analysis

The aim of this study was to investigate the accuracy of a previously described technique for guided biopsy of osseous pathologies of the jawbone in a clinical setting. The data sets of patients who had undergone guided biopsy procedures were retrospectively examined for accuracy. Digital planning of the biopsies and manufacturing of the tooth-supported drilling template were performed with superimposed cone beam computed tomography and intraoral scans using implant planning software. After a trephine biopsy was taken using the template, the postoperative low-dose cone beam computed tomography was analyzed for accuracy using the planning software with the corresponding (digitally-planned) biopsy cylinder. The mean angular deviation was 4.35 ± 2.5°. The mean depth deviation was -1.40 ± 1.41 mm. Guided biopsy seems to be an alternative to a conventional approach for minimally invasive and highly accurate jawbone biopsy.

Evaluation of Different Osteotomy Drilling Speed Protocols on Cortical Bone Temperature, Implant Stability and Bone Healing: An Experimental Animal Study

The aim of this study was to measure the effect of drilling speed on heat generation in the cortical bone, on primary and secondary implant stability of implants and on early and late bone healing with micro-computed tomography (micro-CT). Sixty implants were placed in the iliac crest of six sheep in order to form 5 different drilling protocols: 50rpm without saline cooling, and 400rpm, 800rpm, 1200rpm and 2000rpm with saline cooling.  Simultaneous cortical bone temperature and primary stability at the time of placement; secondary stability and the ratio between relative bone and tissue volume (BV/TV) in 2D and 3D in micro-CT analysis were evaluated after 4 and 8 weeks. The 50rpm group had the highest cortical bone temperature and the longest operation duration with the highest primary stability. Slightly higher values of secondary stability (T2) and subsequent 2D and 3D BV/TV values were found in 1200 rpm with irrigation at 8 weeks. All groups had sufficient ISQ values at 8 weeks for loading although the micro-CT analysis showed varying percentages of bone tissue around implants. The influence of drill speed for implant osteotomy and its irrigation is minimal when it comes to changes in temperature of the cortical bone, primary and secondary implant stability and BV/TV.

Effects of the technique and drill design used during the osteotomy on the thermal and histological stimulation

The objective of our in vivo study was to compare the effects of the osteotomy on the thermal alterations, the bone healing and count of polymorphonuclear cells, comparing the drill design (cylindrical or conical) using continuous or intermittent movement. Twelve rabbits were used, which were made four osteotomies (n = 2 per tibia) to simulate the surgical drilling sequence for the installation of a dental implant at 8 mm of length and regular diameter. Four groups were proposed: group G1, cylindrical drill with continuous movement; group G2, cylindrical drill with intermittent movement; group G3, conical drill with continuous movement; and, group G4, conical drill with intermittent movement. Thermal mean variation was 6.91 ± 1.4 °C in group 1, 4.30 ± 1.3 °C in group 2, 2.78 ± 0.6 °C in group 3, and 2.77 ± 0.7 °C in group 4. Whereas the mean area of new bone formation was 1.00 ± 0.3 mm² in group 1, 1.48 ± 0.3 mm² in group 2, 2.20 ± 0.4 mm² in group 3, and 2.43 ± 0.4 mm²in group 4. The mean count of polymorphonuclear cells, in the group 1 was 62.4 ± 5.9 cells, group 2 was 50.7 ± 4.2 cells, group 3 was 44.4 ± 3.7 cells, and group 4 was 42.4 ± 3.7 cells. The conical drill sequence produced a significantly smaller increase in temperature during both techniques (continuous and intermittent), more effective new bone formation and a smaller number of polymorphonuclear cells. During the osteotomy for the installation of implants, the professional must take to consider the drill design to perform a less traumatic surgical technique, which can improve and facilitate the healing of peri-implant tissues.

A novel system exploits bone debris for implant osseointegration

BACKGROUND

Bone debris generated during site preparation is generally evacuated with irrigation; here, we evaluated whether retention of this autologous material improved the rate of peri-implant bone formation.

METHODS

In 25 rats, a miniature implant system composed of an osseo-shaping tool and a tri-oval-shaped implant was compared against a conventional drill and round implant system. A split-mouth design was used, and fresh extraction sockets served as implant sites. Histology/histomorphometry, immunohistochemistry, and microcomputed tomography (μCT) imaging were performed immediately after implant placement, and on post-surgery days 3, 7, 14, and 28.

RESULTS

Compared with a conventional drill design, the osseo-shaping tool produced a textured osteotomy surface and viable bone debris that was retained in the peri-implant environment. Proliferating osteoprogenitor cells, identified by PCNA and Runx2 expression, contributed to faster peri-implant bone formation. Although all implants osseointegrated, sites prepared with the osseo-shaping tool showed evidence of new peri-implant bone sooner than controls.

CONCLUSION

Bone debris produced by an osseo-shaping tool directly contributed to faster peri-implant bone formation and implant osseointegration.

Surgical Drill Bit Design and Thermomechanical Damage in Bone Drilling: A Review

As drilling generates substantial bone thermomechanical damage due to inappropriate cutting tool selection, researchers have proposed various approaches to mitigate this problem. Among these, improving the drill bit design is one of the most feasible and economical solutions. The theory and applications in drill design have been progressing, and research has been published in various fields. However, pieces of information on drill design are dispersed, and no comprehensive review paper focusing on this topic. Systemizing this information is crucial and, therefore, the impetus of this review. Here, we review not only the state-of-the-art in drill bit designs-advances in surgical drill bit design-but also the influences of each drill bit geometries on bone damage. Also, this work provides future directions for this topic and guidelines for designing an improved surgical drill bit. The information in this paper would be useful as a one-stop document for clinicians, engineers, and researchers who require information related to the tool design in bone drilling surgery.

Effects of condensation and compressive strain on implant primary stability: A longitudinal, in vivo, multiscale study in mice

Aims

Surgeons and most engineers believe that bone compaction improves implant primary stability without causing undue damage to the bone itself. In this study, we developed a murine distal femoral implant model and tested this dogma.

Methods

Each mouse received two femoral implants, one placed into a site prepared by drilling and the other into the contralateral site prepared by drilling followed by stepwise condensation.

Results

Condensation significantly increased peri-implant bone density but it also produced higher strains at the interface between the bone and implant, which led to significantly more bone microdamage. Despite increased peri-implant bone density, condensation did not improve implant primary stability as measured by an in vivo lateral stability test. Ultimately, the condensed bone underwent resorption, which delayed the onset of new bone formation around the implant.

Conclusion

Collectively, these multiscale analyses demonstrate that condensation does not positively contribute to implant stability or to new peri-implant bone formation.

Cite this article:Bone Joint Res. 2020;9(2):60–70.

Comprehensive analysis on orthopedic drilling: A state-of-the-art review

Bone drilling is a well-known internal fixation procedure to drill a hole, fixing the bone fragments to reduce the susceptibility of permanent paralysis. The success of bone drilling is evaluated based on the extent of osteonecrosis in terms of heat generation, tissue damage, quality of hole, and drilling forces. The appropriate control of cutting conditions, drill geometric parameters, and bone-specific parameters offer bone drilling a viable solution through conventional and non-conventional drilling techniques. The majority of the published research work considers only limited parameters and tries to optimize the drilling parameters and performance measures. However, bone drilling involves numerous conventional and non-conventional drilling parameters and technologies. In order to develop a better understanding of all the studied parameters and performance measures, there is a dire need to develop a framework. The key objective of this review study is to establish a hierarchy of the framework by collecting almost all the parameters studied until now and addressed the relationship between parameters and performance measures to diminish the controversies in the published literature. Therefore, this framework is novel in nature, organizing all the parameters, performance measures, logical comparisons, and limitations of studies. This holistic review can help medical surgeons and design engineers to understand the complicated relationship among parameters and performance measures associated with this state-of-art technologies. Also, modeling, simulations, and optimization techniques are included to explore the application of such techniques in recent advancements in orthopedic drilling.

Single-drill implant induces bone corticalization during submerged healing: an in vivo pilot study

Purpose

The aim of the present paper is to evaluate a simplified implant site preparation technique to preserve bone bulk and enhance osseointegration using a new conical self-tapping implant in cancellous bone.

Materials and methods

Ten Expander® 3.8 × 10 mm implants (NoDrill®, Milano, Italy) were inserted in the right side (test group) of sheep’s iliac crest using only the pilot drill 1.8 mm in diameter. Ten 3.8 × 10 mm Dynamix® implants (Cortex, Shlomi, Israel) were inserted in the right side (control group) of the same animals following the drilling protocol provided by the manufacturer. Histological, histomorphometric, and biomechanical analyses were performed after 2 months.

Results

Implants that belonged to the test group showed a %BIC of 70.91 ± 7.95 while the control group implants had a %BIC value of 49.33 ± 10.73. The %BV was 41.83 ± 6.30 in the test group and 29.61 ± 5.05 in the control group. These differences were statistically significant. A phenomenon of osseocorticalization, characterized by more bone volume percentage around implant area than in the neighboring areas, caused by implant threads geometry, was evident in the test group.

Conclusion

This surgical protocol allows to insert an innovative fixture geometry in low-density bone using only a pilot drill. This technique demonstrated many clinical and histological advantages with respect to standard implant drilling procedures and classical implant geometry.

Heat Generation at the Implant-Bone Interface by Insertion of Ceramic and Titanium Implants

PURPOSE

The aim of this study is to record material- and surface-dependent heat dissipation during the process of inserting implants into native animal bone.

MATERIALS AND METHODS

Implants made of titanium and zirconium that were identical in macrodesign were inserted under controlled conditions into a bovine rib tempered to 37 °C. The resulting surface temperature was measured on two bone windows by an infrared camera. The results of the six experimental groups, ceramic machined (1), sandblasted (2), and sandblasted and acid-etched surfaces (3) versus titanium implants with the corresponding surfaces (4, 5, and 6) were statistically tested.

RESULTS

The average temperature increase, 3 mm subcrestally at ceramic implants, differed with high statistical significance (p = 7.163 × 10^-9, resulting from group-adjusted linear mixed-effects model) from titanium. The surface texture of ceramic implants shows a statistical difference between group 3 (15.44 ± 3.63 °C) and group 1 (19.94 ± 3.28 °C) or group 2 (19.39 ± 5.73 °C) surfaces. Within the titanium implants, the temperature changes were similar for all surfaces.

CONCLUSION

Within the limits of an in vitro study, the high temperature rises at ceramic versus titanium implants should be limited by a very slow insertion velocity.

Intraosseous Temperature Change during Installation of Dental Implants with Two Different Surfaces and Different Drilling Protocols: An In Vivo Study in Sheep

Background: The intraosseous temperature during implant installation has never been evaluated in an in vivo controlled setup. The aims were to investigate the influence of a drilling protocol and implant surface on the intraosseous temperature during implant installation, to evaluate the influence of temperature increase on osseointegration and to calculate the heat distribution in cortical bone. Methods: Forty Brånemark implants were installed into the metatarsal bone of Finnish Dorset crossbred sheep according to two different drilling protocols (undersized/non-undersized) and two surfaces (moderately rough/turned). The intraosseous temperature was recorded, and Finite Element Model (FEM) was generated to understand the thermal behavior. Non-decalcified histology was carried out after five weeks of healing. The following osseointegration parameters were calculated: Bone-to-implant contact (BIC), Bone Area Fraction Occupancy (BAFO), and Bone Area Fraction Occupancy up to 1.5 mm (BA1.5). A multiple regression model was used to identify the influencing variables on the histomorphometric parameters. Results: The temperature was affected by the drilling protocol, while no influence was demonstrated by the implant surface. BIC was positively influenced by the undersized drilling protocol and rough surface, BAFO was negatively influenced by the temperature rise, and BA1.5 was negatively influenced by the undersized drilling protocol. FEM showed that the temperature at the implant interface might exceed the limit for bone necrosis. Conclusion: The intraosseous temperature is greatly increased by an undersized drilling protocol but not from the implant surface. The temperature increase negatively affects the bone healing in the proximity of the implant. The undersized drilling protocol for Brånemark implant systems increases the amount of bone at the interface, but it negatively impacts the bone far from the implant.

Understanding Peri-Implantitis as a Plaque-Associated and Site-Specific Entity: On the Local Predisposing Factors

The prevalence of implant biological complications has grown enormously over the last decade, in concordance with the impact of biofilm and its byproducts upon disease development. Deleterious habits and systemic conditions have been regarded as risk factors for peri-implantitis. However, little is known about the influence of local confounders upon the onset and progression of the disease. The present narrative review therefore describes the emerging local predisposing factors that place dental implants/patients at risk of developing peri-implantitis. A review is also made of the triggering factors capable of inducing peri-implantitis and of the accelerating factors capable of interfering with the progression of the disease.

A Novel Osteotomy Preparation Technique to Preserve Implant Site Viability and Enhance Osteogenesis

The preservation of bone viability at an osteotomy site is a critical variable for subsequent implant osseointegration. Recent biomechanical studies evaluating the consequences of site preparation led us to rethink the design of bone-cutting drills, especially those intended for implant site preparation. We present here a novel drill design that is designed to efficiently cut bone at a very low rotational velocity, obviating the need for irrigation as a coolant. The low-speed cutting produces little heat and, consequently, osteocyte viability is maintained. The lack of irrigation, coupled with the unique design of the cutting flutes, channels into the osteotomy autologous bone chips and osseous coagulum that have inherent osteogenic potential. Collectively, these features result in robust, new bone formation at rates significantly faster than those observed with conventional drilling protocols. These preclinical data have practical implications for the clinical preparation of osteotomies and alveolar bone reconstructive surgeries.