Temperature threshold levels for heat-induced bone tissue injury: a vital-microscopic study in the rabbit

Minimally invasive management of vital teeth requiring root canal therapy

The present study aimed to investigate the possible use of a non-instrumentation technique including blue light irradiation for root canal cleaning. Extracted human single rooted teeth were selected. Nine different groups included distilled water, NaOCl, intra-canal heated NaOCl, and NaOCl + EDTA irrigation after either instrumentation or non-instrumentation, and a laser application group following non-instrumentation technique. The chemical assessment of the root canal dentine was evaluated using energy dispersive spectroscopy (EDS) and Fourier transform infrared (FT-IR) spectroscopy. Surface microstructural analyses were performed by using scanning electron microscopy (SEM). The antimicrobial efficacy of different preparation techniques was evaluated using microbial tests. Light application didn't change the calcium/phosphorus, carbonate/phosphate and amide I/phosphate ratios of the root canal dentin. The root canal dentin preserved its original chemistry and microstructure after light application. The instrumentation decreased the carbonate/phosphate and amide I/phosphate ratios of the root canal dentin regardless of the irrigation solution or technique (p < 0.05). The application of light could not provide antibacterial efficacy to match the NaOCl irrigation. The NaOCl irrigation both in the non-instrumentation and instrumentation groups significantly reduced the number of bacteria (p < 0.05). The use of minimally invasive root canal preparation techniques where the root canal is not instrumented and is disinfected by light followed by obturation with a hydraulic cement sealer reduced the microbial load and preserved the dentin thus may be an attractive treatment option for management of vital teeth needing root canal therapy.

In vitro evaluation of temperature change on the root surface after the removal of root canal filling

This study aimed to compare the temperature changes occurring on the root surfaces after the removal of root canal filling with two different root canal sealers by two different reciprocating files. Sixty extracted teeth with a single root and canal were used in this study. After chemomechanical preparation, the root canals in the experimental groups were filled with gutta-percha and AH Plus or CeraSeal, while those of the control groups were filled with gutta-percha only. Resiproc or WaveOne Gold were used for the removal of the root canal filling. Temperature changes in the middle and apical third of the root surface were recorded by a thermal camera at different time intervals. Among the groups using the same sealer, the temperature rise observed on the root surface at the end of 90 s in the Resiproc groups was found to be significantly higher than that of the WaveOne Gold groups.

The Use of 810 and 1064 nm Lasers on Dental Implants: In Vitro Analysis of Temperature, Surface Alterations, and Biological Behavior in Human Gingival Fibroblasts

Objective: The primary objective of this study was to evaluate the safety of 810 and 1064 nm laser treatment on dental implants. Background: Peri-implantitis is a challenge for clinicians and researchers. Methods: A pig mandible model was used to evaluate temperature increases during laser irradiation. Surface alterations on processed pure titanium discs were analyzed via scanning electron microscopy and measurement of surface contact angles. Processed titanium discs were cocultured in vitro with human gingival fibroblasts; subsequently, cell proliferation was measured. Results: The maximum temperature and time to reach each threshold were comparable. No surface alterations were detected after 810 nm laser irradiation, whereas surface cracks were observed after 1064 nm laser irradiation under the parameter setting of 31.84 W/cm2. Compared with unaltered processed pure titanium discs, the proliferation of human gingival fibroblasts was significantly greater on altered processed pure titanium discs. Conclusions: The use of either 810 or 1064 nm laser treatments may increase the risk of thermal damage in terms of increased temperature if the parameter setting is not warranted. In addition, the use of 1064 nm laser treatment could lead to changes in pure titanium discs that do not negatively affect cell proliferation. Further investigations of laser-assisted therapy are necessary to improve guidelines concerning the treatment of peri-implantitis. Clinical trial registration number: 2021-P2-098-01.

In vitro mechanical analysis of X-shaped femoroplasty with polymethyl methacrylate boundary a fall on the greater trochanter. Injury 2023;54 Suppl 6:110747. [PMID: 38143120 DOI: 10.1016/j.injury.2023.04.034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

To evaluate with mechanical testing (MT) using synthetic femurs, an X-shaped femoroplasty technique with polymethyl methacrylate (PMMA), analyzing the results applied to the prophylaxis of proximal femur (PF) fractures caused by low-energy trauma. MT was performed simulating a fall on the greater trochanter, using fifteen Sawbones™ models. They were divided into three experimental groups (n = 5): control (DP) group, drilled without augmentation (DWA) group, and X-shaped augmentation (DX) group. Maximum load, stiffness, absorbed energy and displacement were analyzed primarily in all groups; and secondarily then, morphology and fracture type were verified in all groups while PMMA volume, temperature and time polymerization were analyzed only in the DX group. The MT results obtained for synthetic models respectively in the DP, DWA, and DX groups were: mean maximum load (5562.0 ± 464.8) N, (4798.0 ± 121.2) N, and (7132.0 ± 206.9) N; mean stiffness values (673 ± 64.34) N/mm, (636 ± 8.7) N/mm, and (738 ± 17.13) N/mm, and mean absorbed energy values (36,203 ± 3819) N.mm, (27,617 ± 3011) N.mm, (44,762 ± 3219) N.mm; mean displacement values (13.6 ± 1.45) N, (11.1 ± 0.5) N, and (13.2 ± 0.69) N. The mean volume, temperature reached during filling in the DX group were 9.8 mL, 42.54ºC with 1' 56" of polymerization. The fracture types were similar between the DP and DWA groups, affecting the trochanteric region, as distinctly to those in the DX group, which were restricted to the femoral neck. The values obtained in MT showed statistical significance when analyzed by one-way ANOVA (5%) for maximum load, stiffness, and absorbed energy between groups. In conclusion, X-shaped PMMA augmentation presents a protective biomechanical characteristic against PF fractures generated in synthetic models by boundary a fall on the greater trochanter.

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.

Thermal Effects of 445-nm Diode Laser Irradiation on Titanium and Ceramic Implants

This study aimed to evaluate temperature changes in titanium and ceramic implants after using a 445-nm diode laser under different in vitro conditions. Titanium (Ti) and ceramic (Zr) dental implants were placed into a bone analog, and an intrabony defect was created at each implant. A 445-nm diode laser was used to irradiate the defects for 30 seconds, noncontact, at 2 W in continuous wave (c.w.) and pulsed mode. The experiment was done at room temperature (21.0 ± 1°C) and in a water bath (37.0 ± 1°C). Two thermocouple probes were used to record real-time temperature changes (°C) at the coronal part of the implant (Tc) and the apex (Ta). The temperature was recorded at time 0 (To) and after 30 seconds of irradiation (Tf). The average temperature change was calculated, and a descriptive analysis was conducted (P < .05). The Ti implant resulted in the highest ΔT values coronally (29.6°C) and apically (6.7°C) using continuous wave at 21°C. The Zr implant increased to 26.4°C coronally and 5.2°C apically. In the water bath, the coronal portion of the Ti and Zr implants rose to 14.2°C and 14.01°C, respectively, using continuous waves. The ΔT values for Ti were 11.9°C coronally and 1.7°C apically when placed in a water bath using pulsed mode. The lowest ΔT occurred on the Zr implant with ΔTc and ΔTa of 4.8°C and 0.78°C, respectively. Under in vitro conditions, the 445-nm diode laser in pulsed mode seems to be safe for use on ceramic implants and should be used with caution on titanium implants.

Influence of Multiple Used Implant Drills on Their Cutting Performance and Fracture Resistance

This study aimed to analyze the influence of multiple uses of zirconia implant drills on their cutting performance and bending strength. The hypothesis was that drill usage and sterilization cycles would not affect drilling time or flexural strength. Sixty zirconia twist drills from Z-Systems were used to drill in the angulus mandibulae region of fresh porcine jaws. The drills were divided into four groups based on the cycle count, and the drilling time was measured. Bending strength tests were conducted using a universal testing machine, and statistical analysis was performed using ANOVA tests. The results showed that drilling times followed a normal distribution, and significant differences were observed in drilling times between group 1 and the other groups for the pilot drill. However, no significant differences were found for ø3.75 mm and ø4.25 mm drills, and drilling times also varied significantly among different drill diameters, regardless of the cycle count. Flexural strength did not significantly differ among drill diameters or sterilization cycles. Overall, using and sterilizing zirconia implant drills had no significant impact on drilling time or flexural strength. Nevertheless, drilling times did vary depending on the diameter of the drill. These findings provide valuable insights into the performance and durability of zirconia implant drills, contributing to the optimization of dental implant procedures.

New strategy for osseodensification during osteotomy in low-density bone: an in vitro experimental study

The goal of this in vitro study was to evaluate and propose a new strategy for osseodensification technique using a drill counterclockwise to densification of bone of low density. Synthetic bone blocks of two different low densities (type III and IV) were used for the tests. The conventional drilling group (CD group) used Turbo-drill in a clockwise direction, and the osseodensification group (OD group) applied Turbo-drill in a counterclockwise direction. The applied tests were: (i) measurement of the temperature variation (ΔT) and (ii) measurement of the torque during the osteotomies, comparing the new strategy with the conventional drilling. Both groups were tested without (condition c1) and with (condition c2) irrigation, generating four subgroups: CDc1, CDc2, ODc1, and ODc2. Twenty osteotomies were made for each subgroup with a thermocouple positioned intra-bone (1 mm distant from the osteotomy) to measure the temperature produced. Other 20 samples/group were used to measure the torque value during each osteotomy in both synthetic bone density blocks. The mean of the ΔT during the osteotomies in type III bone was: 6.8 ± 1.26 °C for the CDc1 group, 9.5 ± 1.84 °C for the ODc1, 1.5 ± 1.35 °C for the CDc2, and 4.5 ± 1.43 °C for ODc2. Whereas, in the type IV bone, the ΔT was: 5.2 ± 1.30 °C for the CDc1 group, 7.0 ± 1.99 °C for the ODc1, 0.9 ± 1.05 °C for the CDc2, and 2.7 ± 1.30 °C for ODc2. The maximum torque during the osteotomies was: 8.8 ± 0.97 Ncm for CD samples and 11.6 ± 1.08 Ncm for OD samples in the type III bone; and 5.9 ± 0.99 Ncm for CD samples and 9.6 ± 1.29 Ncm for OD samples in the type IV bone. Statistical differences between the groups were detected in tests and conditions analyzed (p < 0.05). Using the drill counterclockwise for osseodensification in low-density bone generated a significantly greater torque of a drill than in CD and temperature variation during osteotomies. However, the temperature range displayed by the OD group was below critical levels that can cause damage to bone tissue.

Effect of 940 nm diode laser irradiation and dentin bonding agent on permeability of furcation area in primary molars

Purpose

Multiple accessory canals make furcation area of primary molars the most common port of entry of bacterial endotoxins to periradicular area. Reduction in permeability can improve prognosis of these teeth. Therefore, this study was designed to compare the effect of 940 nm diode laser and dentin bonding agent on the dye penetration of furcation area in primary molars.

Material and Methods

Thirty teeth were divided into three groups, that is, Group 1 (control group), Group 2 (dentin bonding agent applied over floor of pulp chamber), and Group 3 (diode laser irradiated over floor of pulp chamber). The samples were prepared and seven from each group were tested by dye penetration and three were sent for scanning electron microscopy. Rise in temperature in the perifurcal area was also recorded at the time of laser irradiation. Dunn's pair-wise comparison analysis was used for the analysis for the difference in dye penetration among the group.

Results

: The maximum rise in temperature recorded postirradiation was 6.90C. Dye penetration was significantly reduced in Group 2 Dentin bonding group (DBG) as compared to control group (P = 0.0025). Reduction in permeability was observed in Group 3 Laser group (LG) but this was not statistically significant (P = 0.197). Scanning electron microscope revealed open dentinal tubules in Group 1. There were no open dentinal tubules in Group 2, while Group 3 had sealed dentinal tubules with glass-like surface over the region.

Conclusion

Dentin bonding agent led to substantial decrease in dye penetration of furcation area of primary molars. This method should be evaluated clinically to improve successful pulpectomy procedures of primary molars.

External Root Surface Temperature Control with 1,1,1,2-Tetrafluoroethane Intracanal Cryotherapy during Thermoplastic Obturation: An In Vitro Study

AIM

The aim of this in vitro study was to determine the effectiveness of 1,1,1,2-tetrafluoroethane (TFE) intracanal cryotherapy for external root surface temperature control during thermoplastic obturation.

MATERIALS AND METHODS

Thirty extracted adult single-rooted mandibular incisors were selected for this study. Endodontic shaping was performed until size X3 Protaper Next Rotary endodontic file. The teeth were divided into three groups: Group I-Control group wherein conventional irrigation was done using physiologic saline stored at room temperature, Group II-Irrigational Cryotherapy group using physiologic saline at 2.5°C, and Group III-Intracanal TFE cryotherapy group with intracanal refrigerant TFE application. Temperatures were recorded in the apical 3 mm before and after completion of each intervention and post thermoplastic obturation using a noncontact digital laser infrared thermometer.

RESULTS

Intracanal cryotherapy with TFE resulted in a mean decrease of 9.27°C compared with conventional irrigation that exhibited in a mean decrease of 2.13°C. Also, in intracanal cryotherapy group with TFE application, compared with the baseline (24.50°C), no significant differences were observed post obturation (24.61°C) with high-temperature-injectable gutta percha technique indicating good control of temperature rise on the external root surface.

CONCLUSION

Intracanal cryotherapy with refrigerant TFE was highly effective in controlling temperature rise on the external root surface during injectable thermoplastic obturation technique.

CLINICAL SIGNIFICANCE

Minimizing deleterious effects due to high temperatures generated during the thermoplastic obturation is critical. Clinically feasible measures to reduce the transmission of heat generated during thermoplastic obturation have been searched since long. In this regard, intracanal cryotherapy with TFE can be effectively used to control the rise of temperature on the external root surface when employing thermoplastic obturation technique.

SEM Evaluation of Thermal Effects Produced by a 445 nm Laser on Implant Surfaces

The aim of this in vitro study was to evaluate thermal effects on implant surfaces using a 445 nm diode laser (Eltech K-Laser Srl, Treviso, Italy) with different power settings and irradiation modalities. Fifteen new implants (Straumann, Basel, Switzerland) were irradiated to evaluate surface alteration. Each implant was divided into two zones: the anterior and posterior areas. The anterior coronal areas were irradiated with a distance of 1 mm between the optical fiber and the implant; the anterior apical ones were irradiated with the fiber in contact with the implant. Instead, the posterior surfaces of all of the implants were not irradiated and used as control surfaces. The protocol comprised two cycles of laser irradiation, lasting 30 s each, with a one-minute pause between them. Different power settings were tested: a 0.5 W pulsed beam (T-on 25 ms; T-off 25 ms), a 2 W continuous beam and a 3 W continuous beam. Lastly, through a scanning electron microscopy (SEM) analysis, dental implants' surfaces were evaluated to investigate surface alterations. No surface alterations were detected using a 0.5 W laser beam with a pulsed mode at a distance of 1 mm. Using powers of irradiation of 2 W and 3 W with a continuous mode at 1 mm from the implant caused damage on the titanium surfaces. After the irradiation protocol was changed to using the fiber in contact with the implant, the surface alterations increased highly compared to the non-contact irradiation modality. The SEM results suggest that a power of irradiation of 0.5 W with a pulsed laser light emission mode, using an inactivated optical fiber placed 1 mm away from the implant, could be used in the treatment of peri-implantitis, since no implant surface alterations were detected.

Cauterization of Narrow Root Canals Untouched by Instruments by High-Frequency Current

The mechanical removal of bacteria is fundamental to the treatment of infected root canals, but complete sterilization of biofilms tends not to extend to uninstrumented areas. However, during electrical conduction to a root canal filled with a conductor, the higher impedance where the root canal is narrower generates Joule heat that may result in a large temperature increase and sterilization. The effect of a high-frequency electric current on the wall of a simulated narrow root canal was investigated by scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS). Simulated root canals, 0.1 mm in diameter, were prepared in dentine blocks. The root canal wall was treated with Plank-Rychlo solution for 5 min to create a decalcified layer. The simulated root canal was filled with either saline or NaClO, and 150 or 225 V at 520 kHz was applied for 0 s, 1 s, or 5 s. As the conduction time increased, and when the saline was replaced with NaClO, the proportion with a flat decalcified surface decreased, dentinal tubules and a lava-like morphology were significantly more evident on SEM (p < 0.01), and EDS showed significant decreases in carbon and oxygen and increases in calcium (p < 0.01). It was concluded that filling uninstrumented root canals with NaClO and using electrical conduction for 5 s could incinerate and eliminate the organic material of the root canal wall. The application of high-frequency electric current may lead to the cure of many cases of persistent apical periodontitis.

Evaluation of Change in Radiographic Fractal Dimension around Dental Implants Placed with Low-Speed Drilling and Standard Drilling Protocols

Osseointegration is a process that depends on a multitude of factors, including the type of drilling, whether biological or conventional. Objective: Establish box-counting dimension values for radiological images in patients with implants placed with both drilling methods. Material and method: The sample included 129 implants corresponding to 50 patients. A double-blind study of data collection was carried out with the subsequent analysis of the fractal dimension as a comparative value of the state of the trabecular architecture. Results: We found no significant differences (p ≥ 0.05) between the two study groups comparing both drilling techniques. The values for the conventional drilling technique are 0.24 ± 0.07 and for biological drilling: 0.19 ± 0.11 with a p-value of 0.767. Conclusions: The drilling technique does not influence the success of the procedure and the osseointegration process.

Results of thermal osteonecrosis for implant removal on electron microscopy, implant stability, and radiographic parameters - a rat study

BACKGROUND

This rat study aimed to evaluate the feasibility of temperature thresholds that affect peri-implant bone cells and morphology and the potential usefulness of thermal necrosis for inducing implant removal for a subsequent in vivo pig study.

METHODS

On one side, rat tibiae were thermally treated before implant insertion. The contralateral side was used as the control group without tempering. Temperatures of 4 °C, 3 °C, 2 °C, 48 °C, 49 °C, and 50 °C were evaluated with a tempering time of 1 min. Energy-dispersive X-ray spectroscopy (EDX) and transmission electron microscopy (TEM) analyses were performed.

RESULTS

The EDX analysis revealed significant increases in element weights at 50 °C (e.g., calcium, phosphate, sodium, and sulfur; p < 0.01). The results of the TEM analysis showed that at all the applied cold and warm temperatures, signs of cell damage were observed, including vacuolization, shrinkage, and detachment from the surrounding bone matrix. Some cells became necrotic, leaving the lacunae empty.

CONCLUSIONS

Temperature of 50 °C led to irreversible cell death. The degree of damage was more significant at 50 °C and 2 °C than at 48 °C and 5 °C. Although this was a preliminary study, from the results, we identified that a temperature of 50 °C at a time interval of 60 min can lower the number of samples in a further study of thermo-explantation. Thus, the subsequent planned in vivo study in pigs, which will consider osseointegrated implants, is feasible.

Thermal properties of polymethyl methacrylate vary depending on brand and type

Polymethyl methacrylate (PMMA) is commonly used in orthopedic surgery and has several applications, most often for fixation of arthroplasty components. While its overall safety and tolerance are well described, less is known regarding the thermal properties of PMMA as it sets from a liquid to solid state, as well as the potential for osseous thermal necrosis. This study addresses potential variations in the setting time and maximum temperature of PMMA formulations in common use and explores the potential clinical implications of this variability. Seven commercially available formulations of PMMA that varied by brand and/or viscosity were obtained and prepared according to manufacturer's instructions. Peak temperature and duration were measured in controlled settings for each type and compared to previously described thresholds for thermal bone necrosis. Depuy SmartSet (HV), Zimmer Palacos R (HV), and Zimmer Palacos (LV) exceeded the 56°C threshold reported to potentially induce immediate osseous thermal necrosis. Additionally, Biomet Cobalt (MV) and Stryker Simplex P (MV) had lower peak temperatures but exceeded thermal necrosis thresholds due to curing duration. The lowest peak temperature was observed for Smith & Nephew Versabond (MV), which was significantly lower than all types except Depuy SmartSet (MV). Setting time was not significantly different among groups. There are significant differences in the thermal properties of PMMA formulations in current use. Selection of specific PMMA formulations represents an additional route of procedural optimization depending on the needs of the treating surgeon.

Reverse Total Shoulder Arthroplasty with a Cementless and Metaphyseal Stem Fixation Is a Viable Option for the Treatment of Proximal Humeral Fractures with Calcar Involvement

BACKGROUND

The purpose of the study was to evaluate the suitability of reverse total shoulder arthroplasty (RTSA) with a cementless and metaphyseal stem fixation as a treatment for complex proximal humeral fractures (PHFs) with a calcar fragment when this may be fixed with a steel wire cerclage. Clinical and radiographic outcomes were compared with the same RTSA for PHFs without a calcar fragment at a minimum of five-year follow-up.

METHODS

A retrospective analysis was performed on acute PHFs "with a medial calcar fragment" (group A) and "without a calcar fragment" (group B) treated with a RTSA and cementless metaphyseal stem fixation.

RESULTS

At an average follow-up of 6.7 years (5-7.8 years), no statistical difference was observed comparing group A (18 patients) to group B (50 patients) for active anterior elevation (141 ± 15° vs. 145 ± 10°, p = 0.67), active external rotation ER1 (49 ± 15° vs. 53 ± 13°, p = 0.55), and active internal rotation (5 ± 2 vs. 6 ± 2, p = 0.97). Similarly, a comparison of ASES score (89.2 ± 10 vs. 91.6 ± 9, p = 0.23) and Simple Shoulder Test score (91.1 ± 11 vs. 90.4 ± 10, p = 0.49) revealed no significant difference.

CONCLUSION

RTSA with a cementless and metaphyseal stem fixation represents a safe and feasible treatment for complex PHFs with a medial calcar fragment when this may be fixed with a steel wire cerclage.

Does the Periprosthetic Fracture Pattern Depend on the Stem Fixation Method in Total Hip Arthroplasty?

Background

Management of periprosthetic femoral fractures (PFFs) is reportedly challenging. Different patterns of PFFs would occur based on whether stem fixation was primarily cemented or cementless and whether these patterns would be associated with clinical outcomes, such as subsidence, fracture union, and complications, after stem revision.

Methods

A retrospective comparative study was performed, involving 52 PFF patients treated with tapered fluted modular stems (TFMSs). In the 52 patients with Vancouver B2 or B3, including 21 cemented stems and 31 cementless stems, fracture patterns and bone stock were analyzed. Clinical outcomes after revision surgery using the TFMSs were compared between the two groups.

Results

Transverse or short oblique type PFFs occurred around the cemented stem with loosening at the bone-cement interface. The Paprosky type III femoral deficiency and Vancouver type B3 fracture were observed more frequently in the cemented stem group. Otherwise, spiral fractures occurred more frequently in the cementless group (p < 0.001). Excessive subsidence of > 5 mm was observed more frequently in the cemented stem group (p < 0.001). The re-revision rates were higher in the cemented group than in the cementless group (p = 0.047).

Conclusions

In our study, it was found that the patterns of transverse or oblique PFFs were more frequently produced with cemented stems, while long spiral fractures were more frequent with cementless stems. Stem subsidence and reoperation related to complications were more common in patients with PFFs around cemented stems than those with PFFs around cementless stems.

Bone cutting efficiency and heat generation using a traditional fluted Burr and a novel fluteless resurfacing tool

BACKGROUND

Powered instrumentation is often used for bone preparation and/or removal in many orthopaedic procedures but does risk thermogenesis. This study compares biomechanical properties of a fluted burr and a novel fluteless resurfacing tool.

METHODS

Twenty cadaveric metatarsals were tested with four predetermined cutting forces to evaluate heat generation and cutting rate for the fluted burr and fluteless resurfacing tool over 40 s or until a depth of 4 mm was reached. Cutting rate was calculated from displacement transducer data. Heat generation was measured by thermocouples placed in the bone adjacent to the burring site. Assuming a body temperature of 37 °C, a 10 °C increase in heat was used as the threshold of inducing osteonecrosis.

FINDINGS

At 1.0 N and 1.7 N, the thermal osteonecrosis threshold was reached at comparable times between burrs, while the bone removed by the resurfacing tool was on average five times greater than fluted burr at 1.0 N and over twice as great at 1.7 N. Statistical analysis of these common cutting forces showed the resurfacing tool had significantly higher cutting rates (P < 0.01). As a result, the fluted burr produced higher temperatures for the same amount of bone removal (P < 0.01).

INTERPRETATION

In a cadaveric study, the fluteless resurfacing tool demonstrated higher bone cutting rates and lower heat generation for the same amount of bone removed than a traditional fluted burr.

Dental implant surface morphology, chemical composition, and topography following double wavelength (2780/940 nm) laser irradiation. An in vitro study

OBJECTIVE

The aim of this in vitro study was to evaluate morphology alterations, chemical composition, and topography of moderately rough dental implants following double-wavelength laser irradiation.

MATERIAL AND METHODS

Commercial-grade titanium dental implants representing different surface characteristics (Osseospeed [OS], TiUnite [TiU], and Roxolid SLActive [RS]) were used. Laser irradiation was performed using a computer-controlled robotic device with calibrated energy/power settings and deionized water spray. Micro-, nano-morphology surface alterations, chemical composition, and surface topography (S_a , S_ds , S_dr ) in the test group (laser plus water), control group A (water only), and control group B (no treatment) were analyzed using scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX), and white light laser profilometer (Interferometry).

RESULTS

SEM-evaluation revealed minor between-group differences in micro- and nano-morphology within each implant system. Significant overall differences in surface element content were observed between the test and control group B for all implant systems (p < .05). For the test compared with control group B, statistically significantly higher oxygen content was detected for OS and RS (p < .05), a corresponding significant difference was detected for carbon for TiU (p < .05). For RS, a significantly lower content of titanium and zirconium was detected within the test group (p < .05). A significant difference in topography between test and control group B was observed for OS (S_a : p = .039 and S_dr : p = .041) with the highest roughness value for control group B.

CONCLUSIONS

Altered chemical composition and surface topography were observed for all implant surfaces compared with untreated control following double wavelength laser irradiation. A clinical evaluation of the impact of the altered surface composition following double wavelength laser irradiation on the ability to reosseointegrate appears warranted.

Influence of relative positions of the heat carrier and lateral canal opening on gutta-percha obturation of lateral canals in a three-dimensional-printed model

Background/purpose

Effective filling of the lateral canals is of great significance in successful root canal treatment, but it is generally being challenging. This study aimed to evaluate the influence of relative positions of the heat carrier and lateral canal opening on gutta-percha obturation of lateral canals in a three-dimensional (3D)-printed model.

Materials and methods

Thermal conductivity and real-time temperature transmission of gutta-percha were investigated using laser flash and thermal infrared analyses. 3D-printed root canal models with lateral canals at 1, 3, and 5 mm from the apex were fabricated, and different relative positions of the heat carrier were tested. The obturation process was recorded on video, and the obturation depth of the lateral canals was observed using X-ray micro-computed tomography.

Results

Gutta-percha showed low thermal conductivity of 1.07 W/(m·K), and heating increased the temperature of gutta-percha above 60 °C only within 1 mm beyond the heat carrier tip. For lateral canals at 1 and 3 mm from the apex, gutta-percha penetrated further with deeper penetration of the heat carrier (P < 0.05). For 5-mm lateral canals, the heat carrier was always at apical level and the gutta-percha obturation depth was more at 2 mm apically than at 3 or 4 mm (P < 0.05).

Conclusion

Gutta-percha is a poor thermal conductor. The position of the heat carrier in relation to the lateral canal opening affects obturation depth. Only when the heat carrier reaches or passes the lateral canal opening can gutta-percha penetrate a lateral canal.

Comparison of heat production and bone architecture changes in the implant site preparation with compressive osteotomes, osseodensification technique, piezoelectric devices, and standard drills: an ex vivo study on porcine ribs

This study aimed at investigating differences in heat generation and bone architecture following four different implant site preparation techniques: compressive osteotomes, conventional drills, osseodensification (OD mode with osseodensification drills), and piezoelectric systems. Porcine rib bones were used as a model for implant surgery. Thermocouples were employed to measure temperature changes, and micro-CT to assess the bone architecture. The primary stability and insertion torque values of the implants placed in the differently prepared sites were assessed. The temperature changes were higher with Piezo. The average primary stability using the ISQ scale was the greatest for drills (76.17 ± 0.90) and the lowest for osteotomes (71.50 ± 11.09). Insertion torque was significantly higher with the osseodensification method (71.67 ± 7.99 Ncm) in comparison to drills, osteotomes, and piezo. Osteotomes showed the highest bone to implant contact percentage (39.83 ± 3.14%) and average trabecular number (2.02 ± 0.21 per mm), while drills exhibited the lowest (30.73 ± 1.65%; 1.37 ± 0.34 per mm). Total implant site bone volume was the highest with osseodensification (37.26 ± 4.13mm³) and the lowest for osteotomes (33.84 ± 3.84mm³). Statistical analysis showed a high primary stability and decrease in temperature during implant site preparation with osseodensification technique. The results support the use of osseodensification technique for implant site preparation.

Does Saline Irrigation at Different Temperatures Affect Pain, Edema, and Trismus After Impacted Third Molar Surgery: A Clinical Trial

PURPOSE

Lower impacted third molar surgery is a very common oral-maxillofacial surgical procedure, which has complications such as facial swelling, pain, and trismus. This clinical trial aimed to compare the intensity of postoperative morbidity (pain, facial swelling, and trismus) following the third molar surgery performed using saline irrigation at different temperatures (4 °C, 10 °C, or 25 °C).

MATERIALS AND METHODS

This double-blind, single-center, split-mouth, randomized prospective clinical trial was conducted among 48 systemically and periodontally healthy patients who had bilaterally asymptomatic mandibular third molars. Patients were randomly allocated into 2 groups (n = 24) according to the temperature of the saline used. In each patient, one impacted third molar was determined as the test group (4 °C or 10 °C saline irrigation) and the other impacted third molar as the control group (25 °C saline irrigation). Trismus and swelling were evaluated on the 1^st, 3^rd, and 7^th days postoperatively. Pain perception by visual analog scale (VAS) and the total number of analgesics taken during the 7 postoperative days were recorded. Data were analyzed using the Shapiro-Wilk test, the chi-square test, one-way analysis of variance, Duncan test, the Kruskal-Wallis test, the Dunn test, and the Friedman test (P < .05).

RESULTS

Forty-eight patients (28 females, 20 males) with a mean age of 24.6 ± 3.8 years were included in the study. The duration of operations was similar. VAS values of test groups [test group 1 (4 °C): 4.0, test group 1 (10 °C): 8.0] and the number of analgesics taken [test group 1 (4 °C): 0, test group 1 (10°) C): 3] were significantly lower (P < .001) than control groups (VAS, control group 1: 13.0, control group 2: 15.5, number of analgesic taken, control group 1: 5.5, control group 2: 4.0). Significant differences were found between the test groups in VAS values and the number of analgesics taken (P < .001). Also, the lowest trismus and facial swelling values were detected in the 4 °C test group at all time points (P < .001).

CONCLUSION

In the impacted third molar surgery, the use of cooled saline irrigation during bone removal may be a simple, inexpensive, and effective method for reducing early postoperative complaints.

Effect of thermal osteonecrosis around implants in the rat tibia: numerical and histomorphometric results in context of implant removal

The purpose of this rat study was to explore the feasibility of in vivo temperature thresholds affecting bone contact at the implant surface. Based on these data, thermal necrosis should be used for implant removal in the subsequent in vivo study. Rat tibiae of 48 animals at one site were randomly treated with heat or cold before implant insertion. Temperatures of 4 °C, 3 °C, 2 °C, 48 °C, 49 °C and 50 °C for a tempering time of 1 min were evaluated. Numerical simulations of the heat source-implant-bone system were carried out. Effects were assessed by histomorphometrical measurements. The results showed that the selected method of direct tempering using a tempering pin was suitable for maintaining a uniform layer around the pin. Starting at warm temperatures of 48 °C and rising to 50 °C, the BIC ratio revealed declining values and a significant difference was observed when comparing 50 °C to the control group (p = 0.03). However, there were no significant variations within the cold temperatures. This study pinpointed temperature discovered that could lead to the thermo-explantation and so that the number of samples used in future studies on temperature-induced bone necrosis can be reduced to a minimum. Significant BIC value reduction was seen at a temperature of 50 °C for 1 min.

Erbium laser-assisted ceramic debonding: a scoping review

PURPOSE

Removal of ceramic restorations and appliances can be time consuming, invasive, and inconvenient. Erbium lasers offer an alternative noninvasive method for debonding of ceramic appliances. This paper aims to provide a comprehensive review of current literature on the effectiveness of erbium lasers for removal of ceramic restorations and appliances from natural teeth and dental implants.

METHODS

A comprehensive search of 7 databases, including Medline (Ovid), Embase, Dentistry and Oral Sciences Source (DOSS), Web of Science, Cochrane Library, and ProQuest Dissertations and Theses was performed. The inclusion and exclusion criteria were agreed prior to the literature search. Two reviewers independently screened the title and abstract. A third reviewer then broke the tie, if any. The selected articles then underwent full text review and the data was extracted.

RESULTS

The search identified 4117 unique articles published through June 10, 2021. Studies were assessed and categorized based on the type of restoration/appliance, type of abutment, type of laser, laser settings, efficacy of debonding, and pulpal temperature rise. Thirty-eight full-text articles were reviewed for inclusion. Time for ceramic debonding varies depending on the type of restorations and materials. Removal of zirconia crowns from teeth and implant abutments requires a longer period of time compared to lithium disilicate crowns. Temperature increases were reported as 5.5 degrees or less. Laser setting and laser type affect the debonding time and the increase in temperature. Examinations of debonded ceramics demonstrated no known structural damages resulting from laser applications.

CONCLUSIONS

Erbium lasers are effective noninvasive tools to remove all ceramic restorations/appliances from natural teeth and implant abutments without causing harm to abutments. Laser-assisted debonding should be considered as a viable alternative to rotary instrumentation for ceramic crowns; however, clinical studies of erbium-assisted ceramic retrieval are needed.

The accuracy of using guided endodontics in access cavity preparation and the temperature changes of root surface: An in vitro study

Background

Guided endodontics is a successful technique that has been gradually applied to endodontic therapy in recent years without being affected by the operator’s experience. However, the guided bur produces excessive heat during continuous rotation and friction with root canal walls, it is not clear whether the degree of temperature increase may lead to the periodontal ligament and alveolar bone damage.

Methods

A total of 58 teeth were used, of which 40 teeth were not grouped, all used to evaluate the accuracy. 40 single-rooted premolars were scanned using CBCT and an intra-oral scanner, and 3D-printed guided plates were made with the pre-designed access. A custom-made guided bur was used to prepare the access cavities. The postoperative CBCT data and pre-designed pathways were matched to evaluate the deviation between the planned and virtual paths. The other 18 teeth were randomly divided into three groups (ET20 and ProTaper F3 as the control group, guided endodontics as the test group), with 6 teeth in each group. The temperature changes on the root surfaces were inspected with a thermocouple thermometer.

Results

The average deviation on the tip and the base of the bur was 0.30 mm and 0.28 mm (mesial/distal), and 0.28 mm and 0.25 mm (buccal/lingual). The average angle deviation was 3.62°. The mean root surface temperature rise of the guided endodontics group was the lowest (5.07 °C) (P < 0.05).

Conclusions

The access cavity preparation performed with guided endodontics has feasible accuracy and low-temperature rise on the root surfaces. Due to the limitations of the study, whether it has high reliability and safety in clinical applications needs to be further studied in vivo.

Heat Generation During Initial Osteotomy for Implant Site Preparation: An In Vitro Measurement Study

Introduction

Controlling temperature generation during implant site preparation is important to prevent implant early failure.

Aim

The present in vitro study aimed at measuring temperature variation generated during the initial osteotomy using both rotatory and piezo-surgical inserts.

Methods

Nine groups were defined according to drill and insert type, cooling volume (mL/min) and cooling temperature. A total of 315 implant site preparations were performed in an artificial bone sample and the temperature was measured using an infrared camera. Drills’ wear was assessed using scanning electron microscopy at baseline and after 10 and 35 utilizations.

Results

Piezo-surgical insert groups determined a temperature increase that was significantly higher than the one generated by rotatory drills groups (p < 0.001). When considering rotatory drills groups a temperature ≥ 40 °C was never recorded.

Conclusion

Lower saline temperature implied a significant temperature decrease (p < 0.001), while the increase in cooling volume did not imply a temperature decrease. The scanning electron microscopy analysis of the drills demonstrated that little drill wear occurred up to 35 utilization times.

Ultrasonic bone cement removal efficiency in total joint arthroplasty revision: A computer tomographic-based cadaver study

Polymethylmethacrylate (PMMA) removal during septic total joint arthroplasty revision is associated with a high fracture and perforation risk. Ultrasonic cement removal is considered a bone-preserving technique. Currently, there is still a lack of sound data on efficacy as it is difficult to detect smaller residues with reasonable technical effort. However, incomplete removal is associated with the risk of biofilm coverage of the residue. Therefore, the study aimed to investigate the efficiency of ultrasonic-based PMMA removal in a human cadaver model. The femoral components of a total hip and a total knee prosthesis were implanted in two cadaver femoral canals by 3rd generation cement fixation technique. Implants were then removed. Cement mantle extraction was performed with the OSCAR-3-System ultrasonic system (Orthofix®). Quantitative analysis of cement residues was carried out with dual-energy and microcomputer tomography. With a 20 µm resolution, in vitro microcomputer tomography visualized tiniest PMMA residues. For clinical use, dual-energy computer tomography tissue decomposition with 0.75 mm resolution is suitable. With ultrasound, more than 99% of PMMA was removed. Seven hundred thirty-four residues with a mean volume of 0.40 ± 4.95 mm³ were identified with only 4 exceeding 1 cm in length in at least one axis. Ultrasonic cement removal of PMMA was almost complete and can therefore be considered a highly effective technique. For the first time, PMMA residues in the sub-millimetre range were detected by computer tomography. Clinical implications of the small remaining PMMA fraction on the eradication rate of periprosthetic joint infection warrants further investigations.

Comparison of Maximum Heat Generation during Implant Site Preparation between Single and Gradual Drilling Protocols in Artificial D1 Bone Blocks: An In Vitro Study

Aim

Two protocols for implant site preparation have been demonstrated in the literature: conventional gradual drilling and single drilling.

Objectives

The purpose of this study is to assess the maximum temperature changes reached during and after implant site preparation of 4.2 implant diameter using the gradual drilling protocol and single drilling protocol. Material and Methods. The artificial bone block samples (#1522-23; Sawbones, Malmö, Sweden) with the density of d1 were divided into two groups. Twelve implant site preparations were performed with the use of only one drill in group A, and the same number of preparations was performed using five gradual drills in group B. The drilling speed was set for each group at 1500 rpm with the use of external irrigation with a constant of 50 ml/min at room temperature (25 ± 1°C). The maximum temperature changes were measured using an infrared camera (Fluke Ti55, USA). The data were gathered and analyzed using Student's t-test for independent samples.

Results

With the 95% confidence intervals (CIs) for the means of ∆T between groups A and B, group B showed a statistically significant higher temperature change (∆T) than group A.

Conclusions

The current outcomes propose that the single drilling protocol, while preparing a bed for a 4.25 mm dental implant in d1 artificial bone blocks, generates less heat than the conventional gradual drilling protocol.

Effects of a simplified drilling protocol at 50 rpm on heat generation under water-free conditions: an in vitro study

PURPOSE

In recent years, guided implant surgery has been widely used for the convenience of patients and surgeons. Further streamlining the surgical procedure would make implant surgery more convenient. Low-speed water-free conditions are often used in guided implant surgery. Therefore, in this study, we attempted to confirm once again whether drilling was safe at a low speed without water. The main purpose of this study was to evaluate whether a simplified drilling protocol that omits some intermediate steps in the drilling process was safe from the viewpoint of heat generation.

METHODS

D1 density artificial bone blocks were drilled under 50 rpm, 10 N·cm water-free conditions, and the surface temperature was measured using a digital infrared camera. First, drilling was performed with the sequential drilling method, which is the most widely used technique. Second, for each drill diameter, the temperature change was measured while performing simplified drilling with omission of the previous 1, 2, or 3 steps.

RESULTS

In sequential drilling, the heat generated during drilling at all diameters was less than the critical temperature of osteonecrosis (47°C) except for the ⌀2 drill. Statistical significance was observed in all groups when comparing sequential and simplified drilling in the ⌀3.2, ⌀3.8, and ⌀4.3 drills (P<0.001). However, in the simplified drilling procedures, the temperature was below the osteonecrosis threshold temperature (47°C) except for the ⌀4.3 drill with the omission of the previous 3 steps (⌀3.0, ⌀3.2, and ⌀3.8).

CONCLUSIONS

In general, drilling under low-speed, water-free conditions has shown stable results in terms of heat generation. Simplified drilling showed statistically significantly greater heat generation than sequential drilling. However, most of the diameters and omitted steps seem to be clinically acceptable, so it will be useful if an appropriate selection is made according to the patient's clinical condition.

Comparative Analysis of Temperature Variation with Three Continuous Wave Obturation Systems in Endodontics: An In Vitro Study

The aim of this study was to assess temperature changes with different continuous wave obturation systems when downpacking to 2 mm and 4 mm from the apical foramen in an open system not simulating the surrounding biological structures at body temperature. Sixty single-rooted teeth were divided into three groups: (A) Dia-Duo® (DiaDent Group International, Cheongju-si, Korea), (B) Elements Free® (Kerr Corporation, Orange, CA, USA) and (C) Calamus® (Dentsply Sirona, Ballaigues, Switzerland). The root canals were instrumented with Protaper Gold (Dentsply Sirona, Ballaigues, Switzerland) to size F2 (25.08). The root canals were filled by a continuous wave using an AH Plus® sealer (Dentsply Sirona). Temperatures during the obturation procedure were measured by a thermal imaging camera (Testo 875-1®) perpendicular to a vice where the teeth were held at −2 mm and −4 mm from the apical foramen. Comparisons were made by applying Student’s t-test and ANOVA (p = 0.05). The continuous wave technique at −2 mm with the Dia-Duo system® emitted average temperatures of 37.3 °C, Elements Free® emitted 39.85 °C and Calamus® emitted 40.16 °C. At −4 mm, the Dia-Duo system® emitted average temperatures of 34.81 °C, Elements Free® emitted 33.73 °C and Calamus® emitted 32.91 °C. There were significant differences between continuous waves at −2 mm and at −4 mm (p < 0.05). Dia-Duo® was the only system that did not present significant differences between the two lengths (p = 0.197). Regarding the heat emitted, the best system was Elements Free®, since, at −2 mm, it emitted the highest temperature without going above 47 °C. The Dia-Duo® system had lower temperatures. It could be concluded that not all systems transmit the same temperature to the apex and, therefore, to the periapical tissues. The surrounding conditions, such as temperature and humidity, have not been considered in this study.

Breakage and displacement of the high-speed hand-piece bur during impacted mandibular third molar extraction: three cases

Background

The high-speed hand-piece bur is one of the methods to perform tooth sectioning during the minimally traumatic extraction of impacted mandibular third molars. During tooth sectioning, the breakage of the bur might take place when it is improperly used. Three cases of the breakage and displacement of a high-speed hand-piece bur during extraction are reported, aiming to remind dental surgeons of this complication.

Case presentation

The bur fragment in case 1 was embedded in the mandibular bone under the previously removed crown of tooth 48 and distal to tooth 47. The bur fragment in case 2 was embedded in the lingual edge of the socket and partly beneath the mucosa on the lingual side. The position of the bur fragment in case 3 was similar to that of case 1 but was completely embedded in the spongious bone. The three cases were performed by first-year residents, and all of the bur fragments were successfully removed by attending doctors after accurately locating them by radiological examination.

Conclusions

In order to avoid breakage of the high-speed hand-piece bur, the number of uses of the bur should be monitored and the integrity and state of the bur should be carefully checked. Moreover, light pressure with little lateral force should be used during tooth sectioning. If bur breakage and displacement occur, the retrieval protocol should be determined based on the imaging findings and conducted as soon as possible to avoid serious consequences.

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.

Does implant placement using a minimally invasive technique increase early failures among trainees at an academic center?

PURPOSE

This study aims to identify whether dental implants placed using a flapless technique have a higher early failure rate, defined as failure within 6 months of placement, compared to implants placed with flap elevation when a surgical guide is not used.

METHODS

A retrospective cohort study was conducted to evaluate implants placed with either flapless (FL) or mucoperiosteal flap (MF) surgery between 2006 and 2012 at the Philadelphia VA Medical Center (PVAMC). Implant status after FL or MF surgery was assessed using dental encounter and radiographs at subsequent follow-up appointments to assess for early implant failures within 6 months of implant placement.

RESULTS

The FL technique was used to place 89 implants in 38 subjects, while the MF technique was used to place 381 implants in 139 subjects. Early failure occurred in 37 implants, of which 13 occurred in the FL group and 24 occurred in the MF group. FL surgery was found to be associated with a 265% increase in early implant failure (OR 2.653; 95% CL 1.287-5.469) and was statistically significant (p = 0.0064). Residents were over 200% more likely to have an early implant failure when using the FL technique (OR 2.314; 95% CL 1.112-4.816), CONCLUSIONS: Analysis revealed flapless implant placement was associated with higher early implant failure rates. In addition, early failures were more likely to occur when residents placed an implant using the flapless technique. While FL surgery can result in long-term success, it is a more technique-sensitive approach that requires greater clinical skill and stricter case selection to perform.

Temperature Changes during Implant Osteotomy Preparations in Fresh Human Cadaver Tibiae, Comparing Straight with Tapered Drills

The success of osseointegration depends on many factors. With temperatures beyond a 47 °C threshold over 1 min, bone survival may be impaired. The purpose of the study was to evaluate, in fresh human cadaver tibiae, the temperature changes during osteotomy preparations using two straight and two tapered implant systems’ drills, external irrigation, and varying revolutions per minute (RPM). The tibiae from a fresh female cadaver were harvested bilaterally. Two tapered and two straight design drills were assessed. Two-hundred and forty osteotomies were prepared at 6 mm depth following the drill sequence of the manufacturers’ protocol for each drilling speed. Difference in temperature (ΔΤ) was calculated by subtracting the baseline from the maximum temperature (ΔT = T_max − T_base). Drill design and drill diameter, as independent variables or synergistically, had a significant effect on ΔΤ. Tapered drills: As the drill diameter increased, ΔΤ increased at all RPM. Straight drills: As the drill diameter increased, ΔΤ remained constant or slightly decreased at all RPM. Drill diameter and design had a significant effect on ΔΤ in human tibiae, which never exceeded the critical threshold of 47 °C. Tapered drills caused significantly greater heat production compared to straight drills.

Thermal Load and Heat Transfer in Dental Titanium Implants: An Ex Vivo-Based Exact Analytical/Numerical Solution to the ‘Heat Equation’

Introduction: Heat is a kinetic process whereby energy flows from between two systems, hot-to-cold objects. In oro-dental implantology, conductive heat transfer/(or thermal stress) is a complex physical phenomenon to analyze and consider in treatment planning. Hence, ample research has attempted to measure heat-production to avoid over-heating during bone-cutting and drilling for titanium (Ti) implant-site preparation and insertion, thereby preventing/minimizing early (as well as delayed) implant-related complications and failure. Objective: Given the low bone–thermal conductivity whereby heat generated by osteotomies is not effectively dissipated and tends to remain within the surrounding tissue (peri-implant), increasing the possibility of thermal-injury, this work attempts to obtain an exact analytical solution of the heat equation under exponential thermal-stress, modeling transient heat transfer and temperature changes in Ti implants (fixtures) upon hot-liquid oral intake. Materials and Methods: We, via an ex vivo-based model, investigated the impact of the (a) material, (b) location point along implant length, and (c) exposure time of the thermal load on localized temperature changes. Results: Despite its simplicity, the presented solution contains all the physics and reproduces the key features obtained in previous numerical analyses studies. To the best of our knowledge, this is the first introduction of the intrinsic time, a “proper” time that characterizes the geometry of the dental implant fixture, where we show, mathematically and graphically, how the interplay between “proper” time and exposure time influences temperature changes in Ti implants, under the suitable initial and boundary conditions. This fills the current gap in the literature by obtaining a simplified yet exact analytical solution, assuming an exponential thermal load model relevant to cold/hot beverage or food intake. Conclusions: This work aspires to accurately complement the overall clinical diagnostic and treatment plan for enhanced bone–implant interface, implant stability, and success rates, whether for immediate or delayed loading strategies.

Effect of a neodymium-doped yttrium aluminium garnet laser on the physicochemical properties of contaminated titanium surfaces and macrophage polarization

AIM(S)

The objective of this study was to evaluate the changes in the physical and chemical properties of titanium surfaces contaminated by a Nd:YAG laser with different levels of energy and the regulation of macrophage polarization.

MATERIALS AND METHODS

The titanium specimens were divided into four groups. The blank control group consisted of the above-mentioned contaminated titanium specimens, and the conditioned control group consisted of sandblasted and acid-etched (SLA) titanium surfaces. The blank control and condition control groups were sealed and preserved in a sterile dark box. There were two experimental groups treated with the Nd:YAG laser-one with 0.5 W and the second with 1.0 W. Surface characteristics were evaluated using scanning electron microscopy, surface profilometry, and contact angle assays. The macrophage viability and proliferation of mouse RAW246.7 were analysed, and the macrophage surface markers, macrophage cytokines, and inflammatory and anti-inflammatory genes were expressed.

RESULTS

The Nd:YAG laser increased the hydrophilicity and roughness of the titanium surface after decontamination. Fewer RAW264.7 cells were observed on the titanium surface after Nd:YAG decontamination than on the contaminated titanium surface expressing the M1-type macrophage marker CCR7, whereas more cells were observed after decontamination than on the contaminated titanium surface expressing the M2-type macrophage marker CD206. Following Nd:YAG laser treatment, the secretion of the inflammatory cytokines IL-1β and TNF-α by RAW264.7 cells on the titanium surface was decreased, whereas the secretion of the anti-inflammatory cytokines IL-4 and IL-10 was increased. RAW264.7 cells cultured for 3 days on the titanium surface after Nd:YAG decontamination treatment expressed significantly reduced levels of the inflammation-related genes IL-1β, TNF-α, IL-6 and iNOS. The expression of the anti-inflammatory genes Arg-1, IL-4, IL-10 and TGF-β by RAW264.7 cells was significantly up-regulated after 3 days of incubation on the titanium surface after Nd:YAG decontamination treatment.

CONCLUSION(S)

The Nd:YAG laser increased the hydrophilicity and roughness of the titanium surface after decontamination, and this change inhibited M1-type macrophage polarization and promoted M2-type macrophage polarization.

The effects of multiple drilling of a bone with the same drill bit: thermal and force analysis

Repeated use of the same drill bit during drilling wears off the cutting edges, which can lead to a significant increase in heat as a result of friction, which is harmful to a bone above 55 °C. Few previous studies have examined the effects of using the same drill bit several times, on temperature. The objective of this study was to determine the effect of each drilling on temperature and force. 72 trials were performed. A total of 24 stainless steel drill bits of ∅3.2 mm were used to drill bovine bone samples. Each drill bit was used at least 3 times. T thermocouples were used to measure temperatures during each drilling test. Possible correlations of cutting parameters were studied. Tests were performed on a test rig measuring forces and temperatures during drilling. Effects of spindle speed (N), feed rate (V_f), and several trials (E) on temperature and forces were measured. Images of the drill bits were analyzed by digital microscopy before and after the drilling series for signs of wear. Temperatures increased significantly from E₁ to E₃. They decreased moderately with V_f. The best cutting conditions were at N = 200 rpm for V_f = 60 mm/min and N = 100 rpm for V_f = 30 mm/min drilling. At N > 200 rpm, they were very high. Temperature rise is significantly related to number of drilling (E), spindle speed (N), and inversely to feed rate (V_f). Analysis of images by digital microscopy confirmed drill bits wearing off, following the number of trials.

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.

Zygomatic approach with single-piece implants: A technical note

Single piece zygomatic implant, or a remote anchorage implant, is an effective tool for the rehabilitation of the atrophic/resected jaws with least postoperative complications such as screw loosening, screw fractures, bone loss, mucositis, and peri implantitis. The aim of this paper was to summarize a technique for the use of a zygomatic approach for single piece implants. We used the key-words 'single piece implants" and the search revealed 700 papers in the PubMed database. After screening through the abstracts, we selected 50 articles that we finally reviewed. Zygomatic fixtures avoid the grafting procedures and cantilever situation, restoration of atrophic or postablative jaws are completed with immediate loading. It is advisable placement of zygomatic implant flapless with surgical guide, but the author believes more on the tactile perception and when the splint is at mucosal or bone level, a small change in orientation will lead the dramatic error in desired angulation leading to unwanted complication.

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 Effect of Operatory Room Temperature, Surgical Drill Diameter, and Temperature of Irrigants at Different Depths of Implant Site Preparation - Thermographic Analysis on Goat Mandible

Background:

Drilling of the implant site results in transient rise in temperature of the surrounding bone disrupting the bone healing process and implant stability. Overproduction of heat due to various factors at osteotomy site needs to be controlled as it hampers the final outcome of the procedure.

Purpose:

The purpose of this study was to evaluate various factors related to implant drills responsible for heat generation and temperature rise during osteotomy.

Materials and Methods:

A total of 64 bone specimens with dimensions of 15 mm × 15 mm were obtained from goat mandibles and were equally divided into Groups A and B with operating room temperature maintained at 25°C and 30°C, respectively. Osteotomies were performed using drills with diameters (4.2 mm and 5.6 mm) at various drilling depths (10 mm and 13 mm) with external saline irrigation temperatures (4°C and 25°C). Temperature change was recorded by laser thermometer.

Results:

The surgical drill depths, diameters, and room temperatures made no differences in temperatures at implant drilling sites whereas the temperatures of the irrigants provide sufficient heat control during drilling.

Conclusion:

Cooled saline provides beneficial effects in controlling the temperatures of osteotomy sites as compared to saline used at room temperature during implant site preparation.