Effect of temperature on the dental implant osseointegration development in low-density bone: an in vivo histological evaluation

Temperature Changes (ΔT) in Correlation with Number of Implant Osteotomy Preparations in Human Cadaver Tibiae, Comparing Osseodensification (OD) Burs in Clockwise (CW) versus Counterclockwise (CCW) Mode

(1) Background: OD burs are used in two different modes: (i) CW and (ii) CCW. The purpose of the study was to evaluate the ΔT during the preparation of implant osteotomies in a four-way interaction. (2) Methods: Three hundred and sixty osteotomies were prepared at 12 mm depth in human cadaver tibiae. The ΔT values were calculated similarly to the method used in two previous studies carried out by our group. Four different variables were evaluated for their effect on ΔT. (3) Results: A four-way interaction was observed in the CCW mode, allowing for 1000 RPM to have the least effect in both modes. However, in the CCW mode the use of 3.0 and 4.0 burs after 23 osteotomies showed a statistically significant increase in ΔT, and significant chatter, compared to the CW mode. In the CCW mode, the ΔT was increased significantly as the diameter of the burs increased in 800 and 1200 RPM. (4) Conclusions: The synergistic effect of drills' diameter, CCW mode, 800 and 1200 RPM, and bur usage (over 23 times) had a significant effect on ΔT, which exceeded 47 °C. One thousand (1000) RPM had the least effect in both modes. The 3.0 and 4.0 burs in the CCW mode drastically increased the temperature and produced significant chatter.

One-piece versus two-piece ceramic dental implants

In this narrative review, a structured comparison between one-piece and two-piece zirconia dental implants is highlighted. Ceramic dental implants have long ceased to be hype; on the contrary, they can offer a significant addition to the daily dental implant practice. Not only do their favourable aesthetics play a significant role, but their ability to work completely metal-free is of added value, particularly for patients with a proven allergy for Grade 5 titanium. Furthermore, the fact that peri-implantitis seems to appear only incidentally is an important supporting argument for their use as well. Whereas the original design of zirconia implants was formerly always of a one-piece/one-phase structure (the monobloc design), nowadays, two-piece/two-phase designs (the so-called hybrid concept) are also widely utilised to restore missing teeth. Both concepts have advantages and disadvantages, scientifically as well as clinically.For this paper, relevant articles from the recent scientific literature were selected from PubMed. The aim was to identify and summarise what has previously been published on one-piece versus two-piece ceramic implants. This article will compare the benefits and drawbacks of one-piece versus two-piece ceramic implants based on clinical- (design, different sizes, surgical protocol, prosthetics), scientific- (loading and eventual complications) and patient-related (costs and long-time perspectives) criteria.

The Effect of Dental Implant Drills Materials on Heat Generation in Osteotomy Sites: A Systematic Review

The aim of this review was to examine the impact of dental implant drill materials and wear profiles on heat generation in the osteotomy sites as reported in experimental studies and to critically appraise these studies. The research question was formulated based on predefined patient, intervention, comparison, and outcome (PICO) elements. A comprehensive electronic search was undertaken in Medline/PubMed Central, Science Direct, and Google Scholar, using predetermined keywords, followed by a manual search of the bibliography of the selected articles. The selection of the studies for the critical appraisal part of our study was based on the criteria used to assess the study designs such as study aims, outcome measure, clarity of method, sample selection, randomization, allocation concealment, sample attrition, bias, method of data analysis, and external validity. Increased heat generation was observed with both ceramic and metal drills; the heat generation was proportional to drills' wear. The literature was inconclusive regarding the association between drill material and heat generation. However, drill materials had a significant influence on the overall temperature increase during osteotomy. The noncoated drills showed a higher wear resistance, and it has been observed that using worn drills leads to more friction contact, reduced drill cutting efficiency, and increased heat generation. Eleven in vitro studies met the inclusion criteria, and showed a considerable methodological heterogeneity and confounding factors, including drill geometry, speed and load, depth and diameter, number of uses, irrigation protocol, study specimens, and the heat measuring device. Besides, most of the studies have a potential operator and assessor bias, and some have sponsorship bias. It is possible to conclude that the literature is not conclusive on the effect of drill materials on heat generation during osteotomy. Lack of standardization and uniformity in the study design, along with potential bias in the study methodology can be the reason for the heterogeneity of the results.

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.

Temperature Changes during Implant Osteotomy Preparations in Human Cadaver Tibiae Comparing MIS® Straight Drills with Densah® Burs

(1) Background: Several studies showed a sustained temperature of 47 °C or 50 °C for one minute resulted in vascular stasis and bone resorption with only limited bone regrowth over a 3-4-week healing period. The purpose of the present study was to evaluate the temperature changes (ΔΤ) that occur during the preparation of dental implant osteotomies using MIS^® straight drills versus Densah^® burs in a clockwise (cutting) drilling protocol. (2) Methods: Two hundred forty (240) osteotomies of two different systems' drills were prepared at 6 mm depth at 800, 1000, and 1200 revolutions per minute (RPM), in fresh, unembalmed tibiae, obtained by a female cadaver. ΔΤ was calculated by subtracting the baseline temperature on the tibial surface, from the maximum temperature-inside the osteotomy (ΔT = T_max - T_base). The variables were evaluated both for their individual and for their synergistic effect on ΔΤ with the use of one-, two-, three- and four-way interactions; (3) Results: An independent and a three-way interaction (drill design, drill width, and RPM) was found in all three RPM for the Densah^® burs and at 1000 RPM for the MIS^® straight drills. As Densah^® burs diameter increased, ΔΤ decreased. The aforementioned pattern was seen only at 1000 RPM for the MIS^® straight drills. The usage of drills 20 times more than the implant manufacturers' recommendation did not significantly affect the ΔΤ. A stereoscopic examination of the specimens confirmed the findings. (4) Conclusions: The independent and synergistic effect of drills' diameter, design and RPM had a significant effect on ΔΤ in human tibiae, which never exceeded the critical threshold of 47 °C.

Non-Destructive Removal of Dental Implant by Using the Cryogenic Method

Background and Objectives: The gold standard for a successful prosthetic approach is the osseointegration of an implant. However, this integration can be a problem in cases where the implant needs to be removed. Removing the implant with minimal damage to the surrounding tissues is important. Osteocytes cannot survive below −2 °C, but epithelial cells, fibroblasts, and other surrounding tissue cells can. Remodeling can be triggered by cryotherapy at temperatures that specifically affect osteocyte necrosis. In this study, we aimed to develop a method for reversing the osseointegration mechanism and for protecting the surrounding tissues by bone remodeling induced by CO2 cryotherapy. Materials and Methods: In this study, eight 2.8 mm diameter, one-piece mini implants were used in New Zealand rabbit tibias. Two control and six implants were tested in this study. After 2 months of osseointegration, a reverse torque force method was used to remove all osseointegrated implants at 5, 10, 20, and 30 Ncm. The osseointegration of the implants was proven by periotest measurements. Changes in bone tissue were examined in histological sections stained with toluidine blue after rabbit sacrifice. The number of lacunae with osteocyte, empty lacunae, and lacunae greater than 5 µm and the osteon number in a 10,000 µm2 area were calculated. Cryotherapy was applied to the test implants for 1 min, 2 min, and 5 min. Three implants were subjected to cryotherapy at −40 °C, and the other implants were subjected to cryotherapy at −80 °C. Results: Empty lacunae, filled osteocytes, lacunae >5 µm, and the osteon count around the implant applied at −40 °C were not significantly different from the control implants. The application of −40 °C for 1 min was found to cause minimal damage to the bone cells. The implants, which were applied for 1 min and 2 min, were successfully explanted on the 2nd day with the 5 Ncm reverse torque method. Test implants, which were applied cold for 5 min, were explanted on day 1. Tissue damage was detected in all test groups at −80 °C. Conclusions: The method of removing implants with cryotherapy was found to be successful in −40 °C freeze−thaw cycles applied three times for 1 min. To prove implant removal with cryotherapy, more implant trials should be conducted.

The impact of zero insertion torque on flapless immediate implant placement in the maxilla (5 years follow up clinical study)

Introduction: The achievement of good osseointegration in immediate implant placement can occur in the presence adequate primary stability. The insertion torque varies between cases depending on many factors. Aim: To assess clinically the impact of zero insertion torque on the survival of immediate implant placement in the maxilla for more than 5 years follow-up. Methods: A flapless immediate 2018 implants were in the maxilla in non-restorable single rooted teeth osteotomy site. The insertion torque of the implant was measured clinically by an integrated software. Results: The final insertion torque for 42 implants out of 2018 placed in fresh extraction sockets in the maxilla was zero (no primary stability). Their survival rate was 83.3%. Conclusions: The lack of certain conditions during immediate implant surgical installation and healing had the major effects on success. The loss of torque during immediate implant placement to zero may jeopardize the survival of the implants, but it may not be statistically significant with their failure and loss. The implant primary stability is not an absolute prerequisite to osseointegration; however, it may affect the implant survival rate.

A chair-side plasma treatment system for rapidly enhancing the surface hydrophilicity of titanium dental implants in clinical operations

PURPOSE

In order to promote osseointegration and shorten the healing time after dental implant operations, this study was conducted to develop a chair-side plasma treatment system in which Ti implants were used as a coaxial internal electrode to rapidly enhance their surface hydrophilicity.

METHODS

Surface hydrophilicity was evaluated by measurement of the water contact angle and the defined wetting time. Changes in temperature and chemical composition were analyzed using infrared thermal imaging and X-ray photoelectron spectroscopy (XPS), respectively. The biocompatibility of the treated implants was examined in an animal experiment.

RESULTS

A marked improvement of hydrophilicity was demonstrated by a decrease in the water contact angle of the treated implant to 0° and wetting of the whole surface within 3 s of water contact. The Ti implant hydrophilization mechanism was explained as a decrease in the degree of hydrocarbon contamination. The surface temperature of the treated implant was close to that of the human body, and good osseointegration was observed in the in vivo experiment.

CONCLUSION

The plasma treatment system developed here is a promising chair-side procedure for rapidly enhancing the surface hydrophilicity of Ti implants in clinical operations without any need to consider the degradation of hydrophilicity caused by long-term storage.

The limit of tolerable micromotion for implant osseointegration: a systematic review

Much research effort is being invested into the development of porous biomaterials that enhance implant osseointegration. Large micromotions at the bone-implant interface impair this osseointegration process, resulting in fibrous capsule formation and implant loosening. This systematic review compiled all the in vivo evidence available to establish if there is a universal limit of tolerable micromotion for implant osseointegration. The protocol was registered with the International Prospective Register for Systematic Reviews (ID: CRD42020196686). Pubmed, Scopus and Web of Knowledge databases were searched for studies containing terms relating to micromotion and osseointegration. The mean value of micromotion for implants that osseointegrated was 32% of the mean value for those that did not (112 ± 176 µm versus 349 ± 231 µm, p < 0.001). However, there was a large overlap in the data ranges with no universal limit apparent. Rather, many factors were found to combine to affect the overall outcome including loading time, the type of implant and the material being used. The tables provided in this review summarise these factors and will aid investigators in identifying the most relevant micromotion values for their biomaterial and implant development research.

Thermal exposure of implant osteotomies and its impact on osseointegration-A preclinical in vivo study

OBJECTIVES

Thermal and mechanical stresses during osteotomy preparation can impair implant osseointegration. This study investigated implant osseointegration following the measurement of temperature exposure during osteotomy drilling, varying drill design, sequence, and drill wear.

MATERIALS AND METHODS

36 tapered implants were placed in a mandibular minipig model after guided drilling of implant osteotomies using 4 different groups: (1) control drills with a conservative, sequential drilling sequence, (2) control drills using a shortened drill sequence (PF), (3) novel test drill displaying an optimized drill design and surface treatment, PF, and (4) aged test drill, PF. Intraosseous temperatures during drilling were measured using a temperature probe. BIC, fBIC, and tissue reactions were histomorphometrically derived after 2 and 8 weeks of healing.

RESULTS

Compared to control drills (1) or (2), test drills (3) resulted in significantly lower maximum temperatures ((35.4 (CI 30.2-40.5)°C vs. (46.5 (CI 41.0-52.0)°C, p = .0021)) and shorter drill times ((4.5 (CI 1.6-7.3)sec vs. 10.3 (7.3-13.4)sec). Lower osteotomy temperature values and shorter drill times corroborated with significantly higher BIC after 2 and 8 weeks healing for the test (3) compared to control groups (2) (2 weeks: (44.9 (CI 34.1-55. 7)% vs. (31.3 (CI 20.5-42.2)%, p = <.0001 and 8 weeks: (73.7 ( CI 64.2-83.2)% vs. (66.2 (CI 57.0-75.4)%, p = <.0455).

CONCLUSION

The improved osseointegration of implants placed after osteotomy preparation with novel test drills using a shortened drill sequence compared to standard drills and conventional drill protocols might be attributed to more favorable thermal profiles and less mechanical stress exerted on the bone surrounding the implant osteotomy.

Implant removal using thermal necrosis-an in vitro pilot study

OBJECTIVES

The purpose of this pilot porcine cadaver study was to evaluate the feasible temperature thresholds, which affect osteocyte viability and bone matrix in a preclinical setup, assessing the potential of thermal necrosis for implant removal for further in vivo investigations.

MATERIALS AND METHODS

After implant bed preparation in the upper and lower jaw, temperature effects on the bone were determined, using two tempering pistons with integrated thermocouples. To evaluate threshold temperature and time intervals leading to bone necrosis, one piston generated warm temperatures at 49 to 56 °C for 10 s and the other generated cold temperatures at 5 to 1 °C for 30 s. Effects were assessed by a semi-quantitative, histomorphometrical scoring system, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM).

RESULTS

The bone matrix was significantly degenerated starting at 51 °C for 10 s and 5 °C for 30 s. The osteocyte condition indicated significant bone damage beginning at cold temperatures of 2 °C. Temperature inputs starting at 53 °C led to decalcification and swollen mitochondria, which lost the structure of their inner cristae.

CONCLUSIONS

This study identified temperatures and durations, in both heat and cold, so that the number of samples may be kept low in further studies regarding temperature-induced bone necrosis. Levels of 51 °C for 10 s and 5 °C for 30 s have presented significant matrix degeneration.

CLINICAL RELEVANCE

Temperature thresholds, potentially leading to thermo-explantation of dental implants and other osseointegrated devices, were identified.

Temperature Threshold Values of Bone Necrosis for Thermo-Explantation of Dental Implants-A Systematic Review on Preclinical In Vivo Research

PURPOSE

Very high or low temperatures will lead to bone damage. The objective of this review was to analyze threshold values for thermal bone necrosis.

METHODS

Histological animal studies evaluating thermal effects on bone necrosis were selected via electronic and hand searches in English and German language journals until 1 November 2019. The outcome measures were temperature-exposure intervals and laser settings effecting bone damage. Furthermore, investigated parameters were the bone-to-implant contact ratios (BIC) and infrabony pockets around dental implants after thermal treatment. For quality assessment of studies, the CAMARADES study quality checklist was applied.

RESULTS

A total of 455 animals in 25 animal studies were included for data extraction after screening of 45 titles from 957 selected titles of the MEDLINE (PubMed), The Cochrane Library, Embase and Web of Science search. The threshold values for bone necrosis ranged between 47 °C and 55 °C for 1 min. A threshold value for cryoinsult and laser treatment has not yet been defined. However, temperatures in the vicinity of 3.5 °C produce a histologically proven effect on the bone and in the surrounding tissue. At 50 °C for 1 min, BIC values significantly decreased and infrabony pockets increased. Bone quality had an influence on the outcome, as cancellous bone suffered higher bone damage from thermal treatment compared to cortical bone.

CONCLUSION

No clear threshold value for bone necrosis is available according to the current literature for warm and cold stimuli. More in-depth and clinical studies are required to provide further insights in assessing the potential of thermal necrosis for implant removal.

Radiographic bone level around particular laser-treated dental implants: 1 to 6 years multicenter retrospective study

Purpose

The aim of the present retrospective study was to evaluate clinical and radiological outcomes, in terms of implant survival rate, marginal bone loss, and peri-implantitis incidence, of a titanium implants with an innovative laser-treated surface.

Materials and methods

A total of 502 dental implants were inserted in four dental practices (Udine, Arezzo, Frascati, Roma) between 2008 and 2013. All inserted implants had laser-modified surface characterized by a series of 20-μm-diameter holes (7–10 μm deep) every 10 μm (Synthegra®, Geass srl, Italy). The minimum follow-up period was set at 1 year after the final restoration. Radiographs were taken after implant insertion (T0), at time of loading (T1), and during the follow-up period (last recall, T2). Marginal bone loss and peri-implant disease incidence were recorded.

Results

A total of 502 implants with a maximum follow-up period of 6 years were monitored. The mean differential between T0 and T2 was 0.05 ± 1.08 mm at the mesial aspect and 0.08 ± 1.11 mm at the distal with a mean follow-up period of 35.76 ± 18.05 months. After being in function for 1 to 6 years, implants reported varying behavior: 8.8% of sites did not show any radiographic changes and 38.5% of sites showed bone resorption. The bone appeared to have been growing coronally in 50.7% of the sites measured.

Conclusion

Implants showed a maintenance of marginal bone levels over time, and in many cases, it seems that laser-modified implant surface could promote a bone growth. The low peri-implant disease incidence recorded could be attributed to the laser titanium surface features that seem to prevent bacterial colonization. Future randomized and controlled studies are needed to confirm the results of the present multi-centrical retrospective analysis.

Temperatures generated during implant site preparation with conventional drilling versus single-drill method: an ex-vivo human mandible study

BACKGROUND

Bone overheating during osteotomy is a potential cause of necrosis and consequent failure of dental implant osseointegration. The aim of this study is to identify any differences between conventional osteotomy with drills of increasing size and the use of a single drill in terms of the temperature increase in the bone during implant site preparation.

METHODS

Thirty-eight implant sites were prepared in ex vivo human mandibles, 19 using the conventional method with drills of increasing diameter (group A) and 19 using a single-drill method (group B), with no irrigation in either procedure. An infrared thermometer was used to measure the temperature difference (T°) induced by the drills at each site. Student's t-test (with P<0.05) was used to compare the temperature increase induced by the last drill in group A, and by the single drill in group B.

RESULTS

The mean ΔT° in group A was 0.64 °C, while in group B it was 1.47 °C. The difference between the temperatures obtained in the two groups was statistically significant (P=0.0073).

CONCLUSIONS

In statistical terms, the two methods differ significantly in the temperature increase induced by the drilling procedure, but this difference is clinically irrelevant.

Using 445 nm and 970 nm Lasers on Dental Implants-An In Vitro Study on Change in Temperature and Surface Alterations

The aim of this study was to evaluate the safety of using a 445 nm laser on dental implants by comparing it with a laser with 970 nm wavelength. Two models, a pig mandible and glass ionomer cement, were used to evaluate the temperature increase in dental implants during laser irradiation with both wavelengths. Temperature was measured every second at four different places on the dental implants. Different power settings, effects of water cooling, distance of the laser fibre to the dental implant and continuous comparison to a pulsed laser beam were tested. Surface alterations on titanium discs after laser irradiation for 4 min at 2.0 W, were analysed in a scanning electron microscope (SEM). The maximum temperature and time to reach each of the thresholds were comparable between the 445 nm and 970 nm lasers. Neither the 445 nm nor the 970 nm wavelength showed any signs of surface alterations on the titanium discs. Using a 445 nm laser on dental implants is as safe as using a 970 nm laser, in terms of temperature increase and surface alterations. Applying a generous amount of cooling water and irradiating in short intervals is important when using lasers on dental implants.

Temperature Changes and SEM Effects of Three Different Implants-Abutment Connection during Debridement with Er:YAG Laser: An Ex Vivo Study

The study aimed to evaluate a temperature increase in, and damage to, titanium implants during flapless laser debridement. The study analyzed 15 implants with various implant–abutment connections: a two-piece implant (n = 4) with a screw abutment (IA—Implant–Abutment) and a one-piece implant with a ball type fixture (BTF, n = 4) or fix type fixture (FTF, n = 4). The implants were placed in porcine mandibles 2 mm over a bone crest to imitate a peri-implantitis. The implants were debrided in contact mode for 60 s with a Er:YAG laser at fluence of 9.95 J/cm² (G1 group: 50 mJ/30 Hz); 19.89 J/cm² (G2 group: 100 mJ/30 Hz); 39.79 J/cm² (G3 group: 200 mJ/30 Hz), or a scaler with a ceramic tip (G4 control group: 4 W/20 Hz). The temperature was measured with thermocouples at implant and abutment levels. The damage in the titanium surface (n = 3, non-irradiated implants from each type) was assessed using SEM (Scanning Electron Microscopy). The temperature increase at the implant level for the laser was higher at IA in contrast with FTF and BTF. (p < 0.05) The temperature change at the abutment level was lower for the scaler in contrast to Er:YAG laser at FTF. (p < 0.0002) Er:YAG laser didn’t increase the temperature by 10 °C at 100 mJ/30 Hz and 50 mJ/30 Hz. Based on SEM analysis, cracks occurred on the surface of two-piece implants and were more pronounced. Cracks and the melting of the titanium surface of two-piece implants cleaned with Er:YAG laser at 100 or 200 mJ were observed. The specimens treated with the ultrasonic scaler with a plastic curette showed the remaining dark debris on the titanium surface. We recommend using Er:YAG laser at 50 mJ/30 Hz during flapless implants debridement.

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.

Comparison of wear and temperature of zirconia and tungsten carbide tools in drilling bone: in vitro and finite element analysis

Drilling is extensively used in operations on bones and dental implants, and yet poses a considerable challenge because it can damage cells as well as cause mechanical and thermal stresses to the bone. The goal of this study was to assess the temperature changes and instrument wear using both zirconium dioxide (ZrO₂) ceramics and tungsten carbide (WC) tools using a 3-dimensional finite element analysis (FEA) of bone drilling. The wear of conical burrs made from ZrO₂ and tungsten carbide was measured using scanning electron microscopy (SEM) and image processing software. Temperature was measured by an infrared thermometer. As well as 3-dimensional FEA, the temperature and wear of the burrs was predicted with the aid of the Johnson-Cook model for bone material properties. Comparison between the ZrO₂ and WC burrs using SEM showed that the ZrO₂ burr was less worn than the WC burr (p = 0.044) and there was significant difference in temperature between the two (p = 0.020). We conclude that ZrO₂ tools are a suitable alternative to WC, particularly in superficial drilling with coolant, as they wear less than the WC tools. The results of the FEA successfully predicted the variation in temperature and the wear on the tools.

A bone preservation protocol that enables evaluation of osseointegration of implants with micro- and nanotextured surfaces

Development of surface treatments has enabled secure attachment of dental implants in less than 1 month. Consequently, it is necessary to characterize accurately the osseointegration of the implant surface in the region of the bone-implant contact (BIC). We developed a method for sample preparation that preserves both bone and BIC to permit analysis of the contact interface. We prepared eight nanotextured implants and implanted them in rabbit tibias. After healing for 30 days, outcomes were analyzed using both our bone preservation protocol and routine decalcification followed by preparation of histological sections stained by hematoxylin and eosin (H & E). Pull-out tests for implant osseointegration were performed after healing. Non-implanted samples of rabbit mandible were used as a control for assessing organic and mineralized bone characteristics and bone structure. Our bone preservation protocol enabled evaluation of many of the same bone characteristics as histological sections stained with H & E. Our protocol enables analysis of implant samples, implant surfaces and osseointegration without risk of BIC damage.

Intraosseous Heat Generation During Osteotomy Performed Freehand and Through Template With an Integrated Metal Guide Sleeve: An In Vitro Study

OBJECTIVE

To investigate drill wear and consequent intraosseous temperature elevation during freehand and guided bone drilling, with attention to the effect of metal-on-metal contact during guided drilling.

MATERIALS AND METHODS

Osteotomies were performed on bovine ribs, with 2.0 mm diameter stainless steel drill bits of the SMART Guide System, under 3 sterilization protocols, at 800, 1200, 1500, and 2000 rpm. Sterilization was performed after every 3 drilling. Temperature was measured after every 30 drilling.

RESULTS

The studied contributing factors had a cumulative effect, and each contributed significantly to temperature elevation. Whether guide use led to a near-necrotic (47°C) temperature increment depended largely on the applied sterilization protocol.

CONCLUSION

The metal sleeve is a significant contributing factor to heat generation during guided osteotomy, but its effect can be offset by keeping the other studied factors under control.

Schneiderian Membrane Perforation Rate and Increase in Bone Temperature During Maxillary Sinus Floor Elevation by Means of Er: YAG Laser-An Animal Study in Pigs

PURPOSE

To assess the time of preparation, bone temperature increase, and the Schneiderian membrane perforation rate during maxillary sinus floor elevation.

MATERIALS AND METHODS

The research included 30 maxillary sinuses (n = 30) of a pig, divided into 2 groups (n = 15). The lateral bony windows were created using Er:YAG laser (200 mJ, 15 Hz, energy density: 25.48 J/cm) and a diamond bur (control). The membrane was elevated using laser (50 mJ, 50 Hz) and hand instruments. The bone temperature was measured by K-type thermocouple.

RESULTS

Significantly lower rates of the Schneiderian membrane perforation were found in the laser group (6.67%) compared with the bur (33%) (P < 0.05). The significant higher increase in temperature (mean 7.6°C) was found in the experimental group as compared with the control group (mean 2°C) (P = 0.0000033). The average time necessary for the laser bony window osteotomy was 10 minutes and 37 seconds, whereas using the bur required middling 5 minutes and 50 seconds (P = 0.000283).

CONCLUSION

The application of Er:YAG laser may significantly reduce the risk of iatrogenic perforation of the Schneiderian membrane and does not cause an irreversible thermal damage in a pig model.

Effects of Osteotomy Lengths on the Temperature Rise of the Crestal Bone During Implant Site Preparation

AIM

To compare temperatures of the crestal bone during implant site preparation for different osteotomy lengths and implant systems.

METHODS

Bovine ribs were used to simulate the cortical bone of the human mandible. Three different implant systems were tested: Astra Tech, Ankylos, and XiVE. Six drills per system were performed, meaning each drilling set was used for 2 drills per 3 osteotomy lengths (8, 12, and 16 mm). Drilling force, drilling speed, drilling length, and temperature were recorded.

RESULTS

Differences in the maximum temperature of the crestal bone during the first drilling for various osteotomy lengths (P = 0.021) and all implant systems (P = 0.013) were observed. A similar result was showed during the second drilling; osteotomy lengths (P = 0.014) and drilling systems (P = 0.003). Second drillings showed lower temperatures of the crestal bone with statistical differences on all measurements (P < 0.001). Astra Tech and Ankylos implant systems showed similar performance; XiVE had lower temperature and higher temperature differences between osteotomy lengths.

CONCLUSIONS

Different drilling lengths contributed to the variation in temperature regardless of the implant system. Longer drills and osteotomies induced higher temperatures on the crestal bone. The maximum temperature difference between the shortest and the longest osteotomy was under 1°C. Temperature above 47°C that could cause bone necrosis was not recorded at any time. The XiVE system showed the best performance.