Early Trabecular Bone Healing Around Titanium Implants: A Histologic Study in Rabbits

Osseointegration and osteoimmunology in implantology: assessment of the immune sustainability of dental implants using advanced sonographic diagnostics: research and case reports

OBJECTIVE

Bone marrow defects of the jaw (BMDJ) surrounding dental implants, in combination with impaired bone-to-implant contact (BIC), are difficult to detect in X-rays. This study evaluated BMDJ surrounding titanium (Ti-Impl) and ceramic (Cer-Impl) dental implants and incomplete BIC using a new trans-alveolar ultrasonography device (TAU) with numerical scaling for BIC.

METHODS

The titanium stimulation test (Ti-Stim) was used to detect immune overactivation in response to titanium. Bone density surrounding implants was measured using TAU. We also validated osteoimmune dysregulation.

RESULTS

TAU values showed reduced BIC and decreased osseointegration for Ti-Impl. Moreover, TAU values in the Cer-Impl group were more than twice those in the Ti-Impl cohort. The multiplex analysis of C-C motif chemokine 5 (CCL5, also known as RANTES) expression revealed a 20-fold increase in BMDJ surrounding Ti-Impl. Higher levels of CCL5 inflammation were present in the positive Ti-Stim group.

CONCLUSIONS

Our data indicate that Cer-Impl have an osteoimmune advantage over Ti-Impl. The key determinant for osteoimmune sustainability appears to be the absence of inflammation at the implant site. We therefore recommend the use of TAU to assess the implant site prior to implantation.

Infrared thermographic evaluation of rise in temperature with conventional versus trephine drills

Aim

To compare the rise in temperature using trephines over conventional ones during bone site preparation.

Setting and Design

An-vitro, evaluative study.

Materials and Methods

Twenty implant sites were prepared using pilot drill up to depth of 10 mm on bovine femoral bone. In first part, no irrigation was used. Five sites were prepared using conventional drill of 2.8 mm, and other five were prepared with help of trephine drills. On completion of each drill, infrared thermometer was used to measure temperature on both the drill tip and the shaft. The same procedure was repeated with bone immersed in saline.

Statistical Analysis Used

Student t test was used to evaluate the significance of difference.

Result

Study showed that the temperature rise at drill tip was significantly higher for trephine drill (52.98 ± 1.67 °C) than conventional drills (48.20 ± 0.67 °C), however the temperature difference in trephine and conventional drills was statistically insignificant.

Conclusion

The temperature increase was more distributed in conventional drills than trephine. Copious irrigation is thus mandatory for trephine drills. Intermittent drilling is preferred with conventional drills.

Implant functionalization with mesoporous silica: A promising antibacterial strategy, but does such an implant osseointegrate?

Objectives

New strategies for implant surface functionalization in the prevention of peri‐implantitis while not compromising osseointegration are currently explored. The aim of this in vivo study was to assess the osseointegration of a titanium‐silica composite implant, previously shown to enable controlled release of therapeutic concentrations of chlorhexidine, in the Göttingen mini‐pig oral model.

Material and Methods

Three implant groups were designed: macroporous titanium implants (Ti‐Porous); macroporous titanium implants infiltrated with mesoporous silica (Ti‐Porous + SiO₂); and conventional titanium implants (Ti‐control). Mandibular last premolar and first molar teeth were extracted bilaterally and implants were installed. After 1 month healing, the bone in contact with the implant and the bone regeneration in the peri‐implant gap was evaluated histomorphometrically.

Results

Bone‐to‐implant contact and peri‐implant bone volume for Ti‐Porous versus Ti‐Porous + SiO₂ implants did not differ significantly, but were significantly higher in the Ti‐Control group compared with Ti‐Porous + SiO₂ implants. Functionalization of titanium implants via infiltration of a SiO₂ phase into the titanium macropores does not seem to inhibit implant osseointegration. Yet, the importance of the implant macro‐design, in particular the screw thread design in a marginal gap implant surgery set‐up, was emphasized by the outstanding results of the Ti‐Control implant.

Conclusions

Next‐generation implants made of macroporous Ti infiltrated with mesoporous SiO₂ do not seem to compromise the osseointegration process. Such implant functionalization may be promising for the prevention and treatment of peri‐implantitis given the evidenced potential of mesoporous SiO₂ for controlled drug release.

In Vitro Study on Bone Heating during Drilling of the Implant Site: Material, Design and Wear of the Surgical Drill

OBJECTIVE

An in vitro study was made to compare mean thermal variation according to the material, design and wear of the surgical drills used during dental implant site preparation.

MATERIAL AND METHODS

Three study groups (stainless steel drills with straight blades; diamond-like carbon-coated drills with straight blades; and diamond-like carbon-coated drills with twisted blades) were tested to compare material, design and wear of the surgical drill in terms of overall mean values (complete sequence of drills) and specific mean values (each drill separately). The groups comprised four drills: initial, pilot, progressive and final drill. Implant site configuration was performed through an intermittent and gradual drilling technique without irrigation at 800 rpm in standardized synthetic blocks. Maximum axial loading of two kilograms was controlled by an automatic press. Each surgical drill was submitted to 50 drillings and was sterilized every five uses. A thermographic camera analyzed the mean thermal changes. The software-controlled automatic press kept systematic drilling, axial loading and operational speed constant without any human intervention. Student's t-test, ANOVA and multiple linear regression models were performed. The level of significance was 5% (p = 0.05).

RESULTS

The overall mean comparison between the stainless steel and diamond-like carbon-coated materials showed no statistically significant differences (p > 0.05), though specific mean comparison showed statistically significant differences between the drills of the different groups (p < 0.05). The twisted blades exhibited less overall and specific mean thermal variation than straight blades for the progressive and final drills (p < 0.01). In addition, the initial and pilot drills showed a greater mean thermal change than the progressive and final drills. The mean thermal variation was seen to increase during the 50 drillings.

CONCLUSIONS

Within the limitations of this study, it can be concluded that the drill material did not significantly influence the overall mean thermal variation except for the pilot drill. The drill design affected overall and specific mean thermal variation since the twisted blades heated less than the straight blades. The initial and pilot drills increased the specific mean thermal variation with respect to the progressive and final drills. In addition, all drills in each group produced a gradual increase in mean temperature during the 50 drillings.

Infrared Thermographic Evaluation of Temperature Modifications Induced during Implant Site Preparation with Steel vs. Zirconia Implant Drill

Background: The heat produced during implant site osteotomy can potentially interfere with and influence the osseointegration process of a dental implant. The objective of this in vitro investigation was to measure the temperature changes during simulated osteotomies in bovine rib bone. The measurements were made at the apical area of the osteotomies with steel implant drills compared to zirconia implant drills. Methods: Steel cylindrical drills (2 mm) and zirconia cylindrical drills (2 mm) were evaluated in vitro using bovine rib bone for a total of five groups based on the number of osteotomies performed with each drill: 10, 20, 40, 90, or 120 osteotomies. Bone and apical drill temperatures were measured by means of infrared thermography. The drilling time for each osteotomy was measured for each preparation. Results: Statistically significant differences were found in the temperature measurements in the bone and apical portion of the drills between the study groups (p < 0.05). A statistically significant difference was observed for drilling time preparation between steel cylindrical drill (2 mm) and zirconia cylindrical drills (2 mm) (p < 0.01). Conclusions: The drill material has an impact on the temperature changes that occur at its apical portion during bone preparation for implant placement.

Targeted Drug Delivery from Titanium Implants: A Review of Challenges and Approaches

Titanium implants are considered the gold standard of treatment for dental and orthopedic applications. Biocompatibility, low elasticity, and corrosion resistance are some of the key properties of these metallic implants. Nonetheless, a long-term clinical failure of implants may occur due to inadequate osseointegration. Poor osseointegration induces mobility, inflammation, increased bone resorption, and osteolysis; hence, it may result in painful revision surgeries. Topographical modifications, improvement in hydrophilicity, and the development of controlled-release drug-loading systems have shown to improve cellular adhesion, proliferation, and differentiation. Surface modifications, along with drug coating, undoubtedly demonstrate better osseointegration, especially in challenged degenerative conditions, such as osteoporosis, osteoarthritis, and osteogenesis imperfecta. Anabolic bone-acting drugs, such as parathyroid hormone peptides, simvastatin, prostaglandin-EP4-receptor antagonist, vitamin D, strontium ranelate, and anti-catabolic bone-acting drugs, such as calcitonin, bisphosphonates, and selective estrogen receptor modulators, expedite the process of osseointegration. In addition, various proteins, peptides, and growth factors may accessorize the idea of localized therapy. Loading these substances on modified titanium surfaces is achieved commonly by mechanisms such as direct coating, adsorption, and incorporating in biodegradable polymers. The primary approach toward the optimum drug loading is a critical trade-off between factors preventing release of a drug immediately and those allowing slow and sustained release. Recent advances broaden the understanding of the efficacy of adsorption, hydrogel coating, and electrospinning layer-by-layer coating facilitated by differential charge on metallic surface. This review discusses the existing approaches and challenges for the development of stable and sustained drug delivery systems on titanium implants, which would promote faster and superior osseointegration.

Bone healing response in cyclically loaded implants: Comparing zero, one, and two loading sessions per day

When bone implants are loaded, they are inevitably subjected to displacement relative to bone. Such micro-motion generates stress/strain states at the interface that can cause beneficial or detrimental sequels. The objective of this study is to better understand the mechanobiology of bone healing at the tissue-implant interface during repeated loading. Machined screw shaped Ti implants were placed in rat tibiae in a hole slightly bigger than the implant diameter. Implants were held stable by a specially-designed bone plate that permits controlled loading. Three loading regimens were applied, (a) zero loading, (b) one daily loading session of 60 cycles with an axial force of 1.5 N/cycle for 7 days, and (c) two such daily sessions with the same axial force also for 7 days. Finite element analysis was used to characterize the mechanobiological conditions produced by the loading sessions. After 7 days, the implants with surrounding interfacial tissue were harvested and processed for histological, histomorphometric and DNA microarray analyses. Histomorphometric analyses revealed that the group subjected to repeated loading sessions exhibited a significant decrease in bone-implant contact and increase in bone-implant distance, as compared to unloaded implants and those subjected to only one loading session. Gene expression profiles differed during osseointegration between all groups mainly with respect to inflammatory and unidentified gene categories. The results indicate that increasing the daily cyclic loading of implants induces deleterious changes in the bone healing response, most likely due to the accumulation of tissue damage and associated inflammatory reaction at the bone-implant interface.

Effects of mechanical repetitive load on bone quality around implants in rat maxillae

Greater understanding and acceptance of the new concept "bone quality", which was proposed by the National Institutes of Health and is based on bone cells and collagen fibers, are required. The novel protein Semaphorin3A (Sema3A) is associated with osteoprotection by regulating bone cells. The aims of this study were to investigate the effects of mechanical loads on Sema3A production and bone quality based on bone cells and collagen fibers around implants in rat maxillae. Grade IV-titanium threaded implants were placed at 4 weeks post-extraction in maxillary first molars. Implants received mechanical loads (10 N, 3 Hz for 1800 cycles, 2 days/week) for 5 weeks from 3 weeks post-implant placement to minimize the effects of wound healing processes by implant placement. Bone structures, bone mineral density (BMD), Sema3A production and bone quality based on bone cells and collagen fibers were analyzed using microcomputed tomography, histomorphometry, immunohistomorphometry, polarized light microscopy and birefringence measurement system inside of the first and second thread (designated as thread A and B, respectively), as mechanical stresses are concentrated and differently distributed on the first two threads from the implant neck. Mechanical load significantly increased BMD, but not bone volume around implants. Inside thread B, but not thread A, mechanical load significantly accelerated Sema3A production with increased number of osteoblasts and osteocytes, and enhanced production of both type I and III collagen. Moreover, mechanical load also significantly induced preferential alignment of collagen fibers in the lower flank of thread B. These data demonstrate that mechanical load has different effects on Sema3A production and bone quality based on bone cells and collagen fibers between the inside threads of A and B. Mechanical load-induced Sema3A production may be differentially regulated by the type of bone structure or distinct stress distribution, resulting in control of bone quality around implants in jaw bones.

Time course of peri-implant bone regeneration around loaded and unloaded implants in a rat model

The time-course of cancellous bone regeneration surrounding mechanically loaded implants affects implant fixation, and is relevant to determining optimal rehabilitation protocols following orthopaedic surgeries. We investigated the influence of controlled mechanical loading of titanium-coated polyether-ether ketone (PEEK) implants on osseointegration using time-lapsed, non-invasive, in vivo micro-computed tomography (micro-CT) scans. Implants were inserted into proximal tibial metaphyses of both limbs of eight female Sprague-Dawley rats. External cyclic loading (60 or 100 μm displacement, 1 Hz, 60 s) was applied every other day for 14 days to one implant in each rat, while implants in contralateral limbs served as the unloaded controls. Hind limbs were imaged with high-resolution micro-CT (12.5 μm voxel size) at 2, 5, 9, and 12 days post-surgery. Trabecular changes over time were detected by 3D image registration allowing for measurements of bone-formation rate (BFR) and bone-resorption rate (BRR). At day 9, mean %BV/TV for loaded and unloaded limbs were 35.5 ± 10.0% and 37.2 ± 10.0%, respectively, and demonstrated significant increases in bone volume compared to day 2. BRR increased significantly after day 9. No significant differences between bone volumes, BFR, and BRR were detected due to implant loading. Although not reaching significance (p = 0.16), an average 119% increase in pull-out strength was measured in the loaded implants. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:997-1006, 2017.

Monitoring the Changes of Material Properties at Bone-Implant Interface during the Healing Process In Vivo: A Viscoelastic Investigation

The aim of this study was to monitor the changes of viscoelastic properties at bone-implant interface via resonance frequency analysis (RFA) and the Periotest device during the healing process in an experimental rabbit model. Twenty-four dental implants were inserted into the femoral condyles of rabbits. The animals were sacrificed immediately after implant installation or on day 14, 28, or 56 after surgery. Viscoelastic properties at bone-implant interface were evaluated by measuring the implant stability quotient (ISQ) using RFA and by measuring the Periotest values (PTVs) using the Periotest device. The bone/implant specimens were evaluated histopathologically and histomorphometrically to determine the degree of osseointegration (BIC%). The BIC% values at different time points were then compared with the corresponding ISQ values and PTVs. The mean ISQ value increased gradually and reached 81 ± 1.7 on day 56, whereas the mean PTV decreased over time, finally reaching −0.7 ± 0.5 on day 56. Significant correlations were found between ISQ and BIC% (r = 0.701, p < 0.001), PTV and BIC% (r = −0.637, p < 0.05), and ISQ and PTV (r = −0.68, p < 0.05). These results show that there is a positive correlation between implant stability parameters and peri-implant-bone healing, indicating that the RFA and Periotest are useful for measuring changes of viscoelastic properties at bone-implant interface and are reliable for indirectly predicting the degree of osseointegration.

A comparative study of the bone contact to zirconium and titanium implants after 8 weeks of implantation in rabbit femoral condyles

Zirconium (Zr) has been found to have comparable characteristics to titanium with a favorable modulus of elasticity. In addition, the release of Zr-ions of a Zr implant is supposed to further increase the bone-to-implant response. Therefore, the objective of this study is to compare the bone contact to Zr and Ti implants in the femoral trabecular bone of rabbits. In addition, implants provided with a hydroxyapatite (HA) coating were included, as such a coating was proven before to enhance the secondary implant stability. A total of 32 implants consisting of 16 Zr (8 HA coated) and 16 Ti (8 HA coated) implants were installed in the femoral condyle of 16 rabbits. After 8 weeks of healing the femoral condyles including the implants were retrieved and studied histologically. The bone-to-implant contact (BIC) percentage was assessed and analyzed statistically. The BIC values of the uncoated Zr and Ti implants showed comparable BIC values (45.1 ± 14.8 vs. 45.5 ± 13.1). The BIC percentage was slightly higher for HA coated Zr and Ti implants (60.3 ± 17.1, 59.8 ± 16.4, respectively) compared to uncoated, but statistical testing indicated that this difference was not significant. It can be concluded that Zr and Ti implants show a comparable bone-implant contact after 8 weeks of implantation in the currently used rabbit model. In addition, the deposition of a sputtered HA coating on both Zr and Ti implants did not further improve their bone integration.

Biological Evaluation of Implant Drill Made from Zirconium Dioxide

Purpose

Zirconia is a good candidate material in the dental field. In this study, we evaluated biological responses against a zirconia drill using a bone cavity healing model.

Materials and Methods

Zirconia drills, stainless steel drills, and the drilled bone surface were observed by scanning electron microscopy (SEM), before and after cavity preparation. For the bone cavity healing model, the upper first and second molars of Wistar rats were extracted. After 4 weeks, cavities were prepared with zirconia drills on the left side. As a control, a stainless steel drill was used on the right side. At 3, 7, and 14 days after surgery, micro‐CT images were taken. Samples were prepared for histological staining.

Results

SEM images revealed that zirconia drills maintained sharpness even after 30 drilling procedures. The bone surface was smoother with the zirconia drill. Micro‐CT images showed faster and earlier bone healing in the zirconia drill cavity. On H‐E staining, at 7 days, the zirconia drill defect had a smaller blank lacunae area. At 14 days, the zirconia drill defect was filled with newly formed bone.

Conclusions

The zirconia drill induces less damage during cavity preparation and is advantageous for bone healing. (197 words)

Early tissue responses to zoledronate, locally delivered by bone screw, into a compromised cancellous bone site: a pilot study

Background

In fracture treatment, adequate fixation of implants is crucial to long-term clinical performance. Bisphosphonates (BP), potent inhibitors of osteoclastic bone resorption, are known to increase peri-implant bone mass and accelerate primary fixation. However, adverse effects are associated with systemic use of BPs. Thus, Zoledronic acid (ZOL) a potent BP was loaded on bone screws and evaluated in a local delivery model. Whilst mid- to long-term effects are already reported, early cellular events occurring at the implant/bone interface are not well described. The present study investigated early tissue responses to ZOL locally delivered, by bone screw, into a compromised cancellous bone site.

Methods

ZOL was immobilized on fibrinogen coated titanium screws. Using a bilateral approach, ZOL loaded test and non-loaded control screws were implanted into femoral condyle bone defects, created by an overdrilling technique. Histological analyses of the local tissue effects such as new bone formation and osteointegration were performed at days 1, 5 and 10.

Results

Histological evaluation of the five day ZOL group, demonstrated a higher osseous differentiation trend. At ten days an early influx of mesenchymal and osteoprogenitor cells was seen and a higher level of cellular proliferation and differentiation (p < 5%). In the ZOL group bone-to-screw contact and bone volume values within the defect tended to increase. Local drug release did not induce any adverse cellular effects.

Conclusion

This study indicates that local ZOL delivery into a compromised cancellous bone site actively supports peri-implant osteogenesis, positively affecting mesenchymal cells, at earlier time points than previously reported in the literature.

Ultrastructural characterization of the implant interface response to loading

Dynamic loading can affect the bone surrounding implants. For ultrastructural exploration of the peri-implant tissue response to dynamic loading, titanium implants were installed in rat tibiae, in which one implant was loaded while the contralateral served as the unloaded control. The loaded implants received stimulation either within 24 hrs after implantation (immediate loading) or after a 28-day healing period (delayed loading) for 4, 7, 14, 21, or 28 days. The samples were processed for histology and gene expression quantification. Compared with the unloaded control, bone-to-implant contact increased significantly by immediate loading for 28 days (p < .05), but not in case of delayed loading. No effect of loading was observed on the bone formation in the implant thread areas, on the blood vessel area, and on endosteal callus formation. Loading during healing (immediate) for 7 days induced, relative to the unloaded control, a 2.3-fold increase of Runx2 in peri-implant cortical bone (p < .01) without a change in the RANKL/Opg ratio. Loading after healing (delayed) for 7 days up-regulated Runx2 (4.3-fold, p < .01) as well as Opg (22.3-fold, p < .05) compared with the unloaded control, resulting in a significantly decreased RANKL/Opg ratio. These results indicate a stimulating effect of dynamic loading on implant osseointegration when applied during the healing phase. In addition, gene expression analyses revealed molecular adaptations favoring bone formation and, at the same time, affecting bone remodeling.

Rehabilitation of the maxillary arch after bone graft using immediate loading with implant-supported fixed restoration

Moderate and controlled loading environments support or enhance osteogenesis, and, consequently, a high degree of bone-to-implant contact can be acquired. This is because when osteoprogenitor cells are exposed to limited physical deformation, their differentiation into osteoblasts is enhanced. Then, some range of microstrain is considered advantageous for bone ingrowth and osseointegration. The primary stability has been considered one of the main clinical means of controlling micromotion between the implant and the forming interfacial tissue, which helps to establish the proper mechanical environment for osteogenesis. Based on the biological aspects of immediate loading (IL), the objective of this study is to present a clinical case of maxillary arch rehabilitation using immediate loading with implant-supported fixed restoration after bone graft. Ten dental implants were placed in the maxilla 6 months after the autogenous bone graft, removed from the mandible (bilateral oblique line and chin), followed by the installation of an immediate-load fixed cross-arch implant-supported restoration because primary stability was reached for 8 implants. In addition, instructions about masticatory function and how it is related to interfacial micromotion were addressed and emphasized to the patient. The reasons for the IL were further avoidance of an interim healing phase, a potential reduction in the number of clinical interventions for the patient, and aesthetic reasons. After monitoring the rehabilitation for 8 years, the authors can conclude that maxillary IL can be performed followed by a well-established treatment planning based on computed tomography, providing immediate esthetics and function to the patient even when autogenous bone graft was previously performed in the maxilla.

Influence of immediate and early loading on bone metabolic activity around dental implants in rat tibiae

OBJECTIVES

The aim of this study was to examine the influence of immediate and early loading on dynamic changes in bone metabolism around dental implants using bone scintigraphy.

MATERIAL AND METHODS

Two titanium implants were inserted in the right tibiae of 21 rats. Closed coil springs with 4.0-N loads were applied parallel to the upper portion of the implants for 35 days. According to the load application timing, rats were divided into three groups: immediate loading (IL) group, early loading 1 day after implant insertion (1-D early loading [EL]) group, and loading 3 days after implant insertion (3-D EL) group. Rats were intravenously injected with technetium-99 m-methylene diphosphonate (Tc99 m-MDP) (74 MBq/rat) and scanned by bone scintigraphy at 1, 4, 7, 11, 14, 21, 28, and 35 days after load application. The ratio of accumulation of Tc99 m-MDP around the implants to that of a reference site (uptake ratio) was calculated to evaluate bone metabolism.

RESULTS

In every group, the uptake ratio increased until 7 days after load application and then gradually decreased. It was significantly higher than baseline at 4, 7, 11, and 14 days (P < 0.001). The uptake ratio in the 1-D EL and 3-D EL groups were significantly higher than that in the control group and also that in the IL group (P < 0.001).

CONCLUSIONS

Bone metabolism initially increased and then gradually decreased to baseline despite differences in load timing. Increases in bone metabolic activity differed according to load application timing; the later the load application, the more enhanced the bone metabolism.

Early healing events around titanium implant devices with different surface microtopography: a pilot study in an in vivo rabbit model

In the present pilot study, the authors morphologically investigated sandblasted, acid-etched surfaces (SLA) at very early experimental times. The tested devices were titanium plate-like implants with flattened wide lateral sides and jagged narrow sides. Because of these implant shape and placement site, the device gained a firm mechanical stability but the largest portion of the implant surface lacked direct contact with host bone and faced a wide peri-implant space rich in marrow tissue, intentionally created in order to study the interfacial interaction between metal surface and biological microenvironment. The insertion of titanium devices into the proximal tibia elicited a sequence of healing events. Newly formed bone proceeded through an early distance osteogenesis, common to both surfaces, and a delayed contact osteogenesis which seemed to follow different patterns at the two surfaces. In fact, SLA devices showed a more osteoconductive behavior retaining a less dense blood clot, which might be earlier and more easily replaced, and leading to a surface-conditioning layer which promotes osteogenic cell differentiation and appositional new bone deposition at the titanium surface. This model system is expected to provide a starting point for further investigations which clarify the early cellular and biomolecular events occurring at the metal surface.

In vivo tissue response to ultrasound assisted application of biodegradable pins into cortical and cancellous bone structures: a histological and densitometric analysis in rabbits

In orthopaedic traumatology biodegradable pins are increasingly used for fixation of small bone fragments. In the present study, the ultrasound-assisted anchoring technique (SonicFusion technique), a osteosynthesis method being recently introduced in cranial applications, in which ultrasonic energy is used to insert and anchor polymer pins in bone, was compared with the conventional pin application procedure. The aim of the present study was to assess the short and long term thermal impact of two different ultrasonic energy levels on different bone structures in the distal medial femur of rabbits. The treatment groups consisted of customized polylactide pins applied at a low and a high energy level, the Reference Control and a Negative Control. The thermal effect on bone tissues was evaluated by means of qualitative and semi-quantitative histology and micro-computerized tomography. Five days following surgery, all implant sites showed no tissue damage but normal signs of early ongoing tissue repair. Enhancing the energy level by about 30% had no significant impact on the tissue response. At 4 weeks after surgery test sites covered by ultrasound-aided implantation showed a significantly enhanced bone/implant contact as compared to pins applied by conventional application. In conclusion, the ultrasound assisted anchoring technique not only did not impair bone regeneration, but even improved implant integration.

Influence of a zirconia sandblasting treated surface on peri-implant bone healing: An experimental study in sheep

A sandblasting process with round zirconia (ZrO(2)) particles might be an alternative surface treatment to enhance the osseointegration of titanium dental implants. Our previous study on sheep compared smooth surface titanium implants (control) with implant surfaces sandblasted with two different granulations of ZrO(2). As the sandblasted surfaces proved superior, the present study further compared the ZrO(2) surface implant with other surface treatments currently employed: machined titanium (control), titanium oxide plasma sprayed (TPS) and alumina sandblasted (Al-SL) at different times after insertion (2, 4 and 12weeks). Twelve sheep were divided into three groups of four animals each and underwent implant insertion in tibia cortical bone under general anaesthesia. The implants with surrounding tissues were subjected to histology, histomorphometry, scanning electron microscopy and microhardness tests. The experimentation indicated that at 2weeks Zr-SL implants had the highest significant bone ingrowth (p<0.05) compared to the other implant surfaces, and a microhardness of newly formed bone inside the threads significantly higher than that of Ti. The present work shows that the ZrO(2) treatment produces better results in peri-implant newly formed bone than Ti and TPS processing, whereas its performance is similar to the Al-SL surface treatment.

Effects of bur wear during implant site preparation: an in vitro study

BACKGROUND

Few studies have investigated the influence of drilling on bone healing. After the drilling of bone and placement of dental implants a sequence begins of cellular and molecular events which represents a combined response of wound healing. The bone healing around dental implants is a complex phenomenon and influences the proliferation and differentiation of pre-osteoblasts into osteoblasts, together with the activation of periosteal and endosteal lining cells, and initiates the production and mineralization of osteoid matrix followed by the organization of the bone-implant interface. The objective of this study is to quantify the temperature changes in cortical bone and marrow spaces during implant site preparation in bovine rib bone. A total 10 harvested bovine ribs and 6 10.5 x 3.5 new drills for implant insertion with external irrigation (Bone System, Milano, Italy) were used in this study. The implant sites were prepared with 10 mm long drills at 500 rpm under abundant external irrigation with saline solution at 37 degrees C. Each drill was used for 10, 30, 60, 90 and 120 implant site preparations; each drill was then observed under SEM for evaluation of the damage of the cutting edge after 10, 30, 60, 90 and 120 preparations. There was an higher and statistically significant increase in the temperature in the cortical bone; this increase in temperature increases with the number of the times of drill use. The drill wear seemed to play a major role in heat production and could explain the observed increased temperature of the bone.