Peri-implant Bone Area Research Articles

Stress Distribution within the Peri-Implant Bone for Different Implant Materials Obtained by Digital Image Correlation.

Stress distribution and its magnitude during loading heavily influence the osseointegration of dental implants. Currently, no high-resolution, three-dimensional method of directly measuring these biomechanical processes in the peri-implant bone is available. The aim of this study was to measure the influence of different implant materials on stress distribution in the peri-implant bone. Using the three-dimensional ARAMIS camera system, surface strain in the peri-implant bone area was compared under simulated masticatory forces of 300 N in axial and non-axial directions for titanium implants and zirconia implants. The investigated titanium implants led to a more homogeneous stress distribution than the investigated zirconia implants. Non-axial forces led to greater surface strain on the peri-implant bone than axial forces. Thus, the implant material, implant system, and direction of force could have a significant influence on biomechanical processes and osseointegration within the peri-implant bone.

Bone Quantification Around Chitosan-Coated Titanium Dental Implants: A Preliminary Study by Micro-CT Analysis in Jaw of a Canine Model.

Surface treatments of Ti in the dental implant industry are performed with the aim of in-creasing its bioactivity and osseointegration capacity. Chitosan (Cht) is a polysaccharide that has been proposed as a promising biomaterial in tissue engineering and bone regeneration, due to its ability to stimulate the recruitment and adhesion of osteogenic progenitor cells. The aim of our preliminary study was to evaluate, by micro-computed tomography (micro-CT), the osseointegration and bone formation around Cht-coated implants and to compare them with conventional surface-etched implants (SLA type). Four im-plants (8.5 mm length × 3.5 mm Ø) per hemiarch, were inserted into the jaws of five dogs, divided into two groups: chitosan-coated implant group (ChtG) and control group (CG). Twelve weeks after surgery, euthanasia was performed, and sectioned bone blocks were obtained and scanned by micro-CT and two bone parameters were measured: bone in contact with the implant surface (BCIS) and peri-implant bone area (PIBA). For BCIS and PIBA statistically significant values were obtained for the ChtG group with respect to CG (p = 0.005; p = 0.014 and p < 0.001 and p = 0.002, respectively). The results, despite the limitations, demonstrated the usefulness of chitosan coatings. However, studies with larger sample sizes and adequate experimental models would be necessary to confirm the results.

Computer-Guided Immediate Full-Arch Implant Reconstruction of the Mandible in Severe Periodontally Compromised Patients: Three-Dimensional Analysis of Bone Volume Changes.

Comprehensive rehabilitation in patients with severe periodontal destruction may require the use of dental implants. The primary aim of this study was to evaluate bone volume changes in periodontally compromised patients over a 12-month follow-up period after immediate full-arch implant reconstruction of the mandible. The secondary aim was to evaluate the repeatability of 3D bone volume change measurement methods around dental implants. The null hypothesis was that bone volume would decrease in the first year after delivery of the definitive prosthetic reconstruction. This retrospective study analyzed CBCT scans of 16 patients before and after computer-guided immediate full-arch implant reconstruction of the mandible. The bone volume change in the mandibular body and around the implants and the peri-implant bone area in coronal and axial cross sections were calculated. The average bone gain for the mandibular body was 3.3% ± 1.8%. The average bone volume increase in the peri-implant area was 23.2% ± 16.7%. The interobserver and intraobserver ICC values for 3D measurements were high (> 0.85). The null hypothesis was rejected. Both mandibular body and peri-implant surroundings undergo bone remodeling in the form of bone gain over 12 months after immediate implantation.

Genipin and insulin combined treatment improves implant osseointegration in type 2 diabetic rats

BackgroundType 2 diabetes mellitus (T2DM) has a harmful effect on the stability and osseointegration of dental implants. T2DM induces mitochondrial damage by inhibiting AMPK signaling, resulting in oxidative stress and poor osteogenesis in the peri-implant bone area. Genipin is a major component of gardenia fruits with strong antioxidant, anti-inflammation, and antidiabetic actions, and it also can activate mitochondrial quality control via the AMPK pathway. The purpose of this study was to investigate the effects of genipin and insulin treatment on implant osseointegration in T2DM rats and explore the underlying mechanisms.MethodsStreptozotocin-induced diabetic rats received implant surgery in their femurs and were then assigned to five groups that were subjected to different treatments for three months: control group, T2DM group, insulin-treated T2DM group (10 IU/kg), genipin-treated T2DM group (50 mg/kg), and the genipin and insulin combination-treated T2DM group. Then, we regularly assessed the weight and glucose levels of the animals. Rats were euthanized at 3 months after the implantation procedure, and the femora were harvested for microscopic computerized tomography analysis, biomechanical tests, and different histomorphometric assessment.ResultsThe results indicated that the highest blood glucose and oxidative stress levels were measured for the T2DM group, resulting in the poorest osseointegration. The combination-treated T2DM group mitigated hyperglycemia and normalized, reactivated AMPK signaling, and alleviated oxidative stress as well as reversed the negative effect of osseointegration. There were beneficial changes observed in the T2DM-genipin and T2DM-insulin groups, but these were less in comparison to the combination treatment group.ConclusionOur study suggests that treatment with genipin in combination with insulin could be an effective method for promoting implant osseointegration in T2DM rats, which may be related to AMPK signaling.

Mechanical Stress Analysis of Different Configurations of the All-on-4 Concept in Atrophic Mandible: A 3D Finite Element Study.

This study evaluated the mechanical behavior of different configurations of the All-on-4 treatment concept designed with straight short (6-mm-length), straight standard (11-mm-length), or tilted standard (30-degree angled; 11-mm-length) posterior implants. The All-on-4 configurations were performed in atrophic mandible models and consisted of anterior straight standard and posterior tilted standard implants (H1 model), anterior straight standard and posterior straight short implants (H2 model), and anterior and posterior straight standard implants (H3 model). Three oblique forces of 100 N were simulated in the posterior region of the prosthetic bar. The values of stress were obtained for the ductile materials using the von Mises equivalent stress (σvm) criteria. The stress peaks in the peri-implant bone crest were measured by the maximum (σmax) and minimum (σmin) principal stresses. The two-way analysis of variance (two-way ANOVA) and Tukey post hoc tests determined significant differences (P < .01) of stress values among the ductile materials (implant and prosthetic components). The use of tilted standard posterior implants (H1 model) showed the lowest values of σmax and σmin in the posterior region of the peri-implant bone area. On the other hand, the use of straight short (H2 model) or straight standard (H3 model) posterior implants significantly reduced the von Mises mean stresses in the bar screws, abutments, and abutment screws (P < .01). The higher odds of technical failures (screw fracture/loosening) may be expected when the All-on-4 configuration is performed with tilted standard posterior implants. Also, peri-implant bone overload may occur when the All-on-4 design is performed with straight short or straight standard posterior implants in atrophic mandibles.

In silico evaluation of the stress fields on the cortical bone surrounding dental implants: Comparing root-analogue and screwed implants

Tooth loss is a problem that affects both old and young people. It may be caused by several conditions, such as poor oral hygiene, lifestyle choices or even diseases like periodontal disease, tooth grinding or diabetes. Nowadays, replacing a missing tooth by an implant is a very common process. However, many limitations regarding the actual strategies can be enumerated. Conventional screwed implants tend to induce high levels of stress in the peri-implant bone area, leading to bone loss, bacterial bio-film formation, and subsequent implant failure. In this sense, root-analogue dental implants are becoming promising solutions for immediate implantation due to their minimally invasive nature, improved bone stress distribution and because they do not require bone drilling, sinus lift, bone augmentation nor other traumatic procedures.The aim of this study was to analyse and compare, by means of FEA, the stress fields of peri-implant bone around root-analogue and screwed conventional zirconia implants. For that purpose, one root-analogue implant, one root-analogue implant with flaps, two conventional implants (with different threads) and a replica of a natural tooth were modelled. COMSOL was used to perform the analysis and implants were subjected to two simultaneous loads: 100 N axially and 100 N oblique (45°). Resultsrevealed that root-analogue implants, namely with flaps, should be considered as promising alternatives for dental implant solutions since they promote a better stress distribution in the cortical bone when compared with conventional implants.

Evaluation of Peri-Implant Bone Grafting Around Surface-Porous Dental Implants: An In Vivo Study in a Goat Model.

Dental implants with surface-porous designs have been recently developed. Clinically, peri-implant bone grafting is expected to promote early osseointegration and bone ingrowth when applied with surface-porous dental implants in challenging conditions. The aim of this study was to comparatively analyze peri-implant bone healing around solid implants and surface-porous implants with and without peri-implant bone grafting, using biomechanical and histomorphometrical assessment in a goat iliac bone model. A total of 36 implants (4.1 mm wide, 11.5 mm long) divided into three groups, solid titanium implant (STI; n = 12), porous titanium implants (PTI; n = 12) and PTI with peri-implant bone grafting using biphasic calcium phosphate granules (PTI + BCP; n = 12), were placed bilaterally in the iliac crests of six goats. The goats were sacrificed seven weeks post-operatively and then subjected to biomechanical (n = 6 per group) and histomorphometrical (n = 6 per group) assessment. The biomechanical assessment revealed no significant differences between the three types of implants. Although the peri-implant bone-area (PIBA%) measured by histomorphometry (STI: 8.63 ± 3.93%, PTI: 9.89 ± 3.69%, PTI + BCP: 9.28 ± 2.61%) was similar for the three experimental groups, the percentage of new bone growth area (BGA%) inside the porous implant portion was significantly higher (p < 0.05) in the PTI group (10.67 ± 4.61%) compared to the PTI + BCP group (6.50 ± 6.53%). These data demonstrate that peri-implant bone grafting around surface-porous dental implants does not significantly accelerate early osseointegration and bone ingrowth.

Three-Dimensional Finite Element Analysis of Stress Distribution in Zirconia and Titanium Dental Implants.

Zirconia has been presented as an alternative biomaterial to titanium, commercially presented as a single-body implant and/or as an abutment, demonstrating clinically biocompatible favorable results in white and rose esthetics. However, the number of long-term in vivo studies and mechanical tests evaluating the response of stress distribution compared with titanium implants is still limited. The aim of the study was to compare the principal peak stresses in the peri-implant bone around titanium and zirconia implants using the finite element method. Four groups of 3-dimensional models were constructed for the tests: G1, external hexagon titanium implant with a zirconia abutment; G2, zirconia implant with a zirconia abutment; G3, single-body titanium implant; and G4, single-body zirconia implant. Axial and oblique loads of 100 N at 45° were simulated in the prosthetic crown. The bone results showed that the peak stresses decreased by 12% in zirconia implants with 2 parts for axial load and 30% for the oblique load. In single-body implants, the peak stresses decreased 12% in the axial load and 34% in the oblique load when a zirconia implant was used compared with a titanium implant. Although the stress values in megapascals are similar, it can be concluded that the zirconia implants decrease the stress peaks at the peri-implant bone area around the implant platform when compared with titanium implants.

Influence of Implant Position in Implant-Assisted Removable Partial Denture: A Three-Dimensional Finite Element Analysis.

To determine the ideal position of a dental implant to assist a posterior extended partial removable dental prosthesis (PRDP), through stress values, displacement values, and deformation of periodontal ligament (PDL). A finite element analysis of different implant positions was analyzed using a 3D mandible model from a human patient. Test models were created: model A (implant in second molar area), model B (implant in the first molar area), and model C (implant in premolar area). A control model without implant support was also created. Overall displacement values, von Mises stress distribution maps, and nonlinear deformations were evaluated. Some differences could be observed between test models. The introduction of an implant in the edentulous area, unlike a conventional removable partial denture without implant support, decreases stress values in the biological structures such as: mandible, tooth, soft tissue, and PDL. Placing the implant in the first molar area resulted in improved displacement values, and reduced maximum stress values at the peri-implant bone area, metal structure, and implant were observed. Within the limitations of this study we can conclude that placing the implant in the position of the first molar improves biomechanical behavior of implant-assisted PRDPs.

Suppurative Inflammation and Local Tissue Destruction Reduce the Penetration of Cefuroxime to Infected Bone Implant Cavities

Treatment of post-traumatic and implant-associated osteomyelitis (IAO) includes surgical debridement, removal of implants and long-term antibiotic therapy. The success of antibiotic therapy relies not only on activity towards the infecting pathogen, but also on sufficient penetration of the target site. The aim of the present study was to characterize the local pathological changes associated with reduced penetration of cefuroxime to infected bone implant cavities. Previously, reduced penetration of systemically administrated cefuroxime was demonstrated in the implant cavity of 10 pigs with Staphylococcus aureus IAO present for 5 days. In the present study, a comprehensive histopathological characterization of the peri-implant bone tissue was performed and correlated with the reduced penetration of cefuroxime. In two pigs, the levels of oxygen, pyruvate and lactate was estimated in the implant cavity. A peri-implant pathological bone area (PIBA) developed with a width of 1.2 up to 3.8mm. PIBAs included: (1) suppuration, resulting in destruction of the implant cavity contour, and (2) a non-vascular zone of primarily necrotic bone tissue. A strong negative correlation was seen between PIBA width and cefuroxime area under the concentration time curves (AUC[0-last]) and peak concentration of cefuroxime (Cmax). All metabolic measurements demonstrated hypoxia. In conclusion, subacute suppurative bone inflammation with local tissue destruction can result in decreased penetration of antibiotics and insufficient oxygen supply.

Effect of a local, one time, low-dose injection of zoledronic acid on titanium implant osseointegration in ovariectomized rats

IntroductionLocal application of bisphosphonates has been proven to be safer than systemic administration to promote implant fixation. The objective of this study was to introduce such a simple, convenient and efficient method to enhance titanium (Ti) implant osseointegration in ovariectomized (OVX) rats.Material and methodsTwenty female Sprague-Dawley rats sequentially underwent bilateral ovariectomy and tibia implantation, and injection of 30 µg/implant zoledronic acid (ZOL) at the site of implantation was performed. At the end of the study, the tibiae, mandibles, femurs and vertebrae were harvested for dual energy X-ray absorptiometry, histology and micro-computed tomography examination.ResultsOvariectomized rats showed poor bone density, bone mass and trabecular microstructure. OVX + ZOL rats were characterized by significantly improved peri-implant bone area (1.72-fold), bone contact (2.30-fold), bone mineral density (1.57-fold) and bone mineral content (1.67-fold), as well as moderately increased bone volume to total volume ratio (1.34-fold), percentage osteointegration (1.54-fold), connectivity density (1.45-fold), and trabecular number (1.43-fold), but decreased trabecular separation (57.69%) when compared with the control levels (p < 0.05). No histological signs of jaw osteonecrosis were observed in the rats treated with ZOL, and there was no significant difference between the OVX group and OVX + ZOL group in the bone mass of the mandible, femur and 5th lumbar vertebra (p > 0.05). In addition, the overproduction of osteoporosis-induced advanced glycation end-products (AGEs) was completely prevented by local treatment with 30 µg/implant ZOL.ConclusionsA local, one time, low-dose injection of ZOL at the site of implantation is able to promote the osseointegration of Ti implants following postmenopausal osteoporosis, and this action may be partly mediated by inhibition of the osteoporosis-induced AGE overproduction in the bone marrow.

Osseointegration of titanium implants with SLAffinity treatment: a histological and biomechanical study in miniature pigs.

Electrochemical oxidation following sandblasting and acid-etching (SLA) treatment has received interest as a surface modification procedure for titanium (Ti) implants (denoted as an SLAffinity surface); however, little information is available on its impacts on the in vivo performance of SLAffinity-Ti implants. The present study evaluated the osseointegration and biomechanical bone-tissue response to SLAffinity-Ti implants with micro- and nanoporous oxide layers. The interaction between blood and the tested implants was examined. In total, 144 implants with the following surfaces were used: a standard machined (M-Ti), an SLA-Ti, and an SLAffinity-Ti surface. For each animal, four implants (one M-Ti, one SLA-Ti, and two SLAffinity-Ti) were inserted into the mandibular canine-premolar area for histomorphometric observations and another four implants were inserted into the flat surface on the anteromedial aspect of the rear tibia for removal torque (RT) tests. After 2, 4, and 8weeks of implantation, histomorphometric and RT tests were conducted. Interactions between blood and implants were better for implants with the SLAffinity-Ti surface. RT tests showed a significant improvement in fixation strength for SLAffinity-Ti implants (84.5 ± 8.7N-cm) after 8weeks compared to M-Ti (62.95 ± 11.5N-cm) and SLAffinity-Ti (76.1 ± 6.6N-cm) implants. A histological evaluation showed that osseous integration had occurred with all implants after 8weeks. SLAffinity-Ti implants exhibited 28.5 ± 6.2% bone-to-implant contact (BIC) at 2weeks and 84.3 ± 8.1% at 8weeks. M-Ti implants exhibited BIC levels of 17.0 ± 5.4 and 76.5 ± 6.3%, whereas SLA-Ti implants exhibited BIC levels of 28.5 ± 6.2 and 81.1 ± 8.4% at corresponding time intervals. In terms of the peri-implant bone area (BA), values for SLAffinity-Ti implants ranged from 29.5 ± 4.1 to 88.3 ± 3.0%. For M-Ti implants, values ranged from 20.3 ± 5.5 to 81.7 ± 4.2%. For SLA-Ti implants, values ranged from 23.0 ± 3.5 to 84.0 ± 3.6%. Electrochemical oxidation increased the oxide layers and improved the blood interaction with SLAffinity-Ti implants, resulting in significantly higher bone apposition with the SLAffinity-Ti implants after 2 and 8weeks of healing. An increase in resistance for the RT of SLAffinity-Ti implants over the 8-week healing period was also observed. The use of SLAffinity-Ti implants has potential for improvement of early osseointegration.

The Effect of Parathyroid Hormone on Osseointegration in Insulin-Treated Diabetic Rats.

Uncontrolled diabetes mellitus is associated with impaired osseointegration. Diabetic individuals might benefit from bone anabolic therapies. Intermittent administration of 1-34 parathyroid hormone (PTH) stimulates bone formation in rodent models. However, this anabolic effect fails in diabetic rats. Whether the anabolic effect of PTH can be achieved in insulin-controlled diabetic rats has not been investigated yet. After diabetes induction with streptozotocin in 40 female Wistar rats, the animals were randomly divided into 4 groups: diabetes, diabetes plus PTH, insulin-treated diabetes, and insulin-treated diabetes plus PTH. After 1 week, miniscrews were inserted in the tibiae. Osmotic pumps with insulin or saline solution were implanted. Animals received 60 mg/kg PTH or saline solution. Histomorphometric analysis was performed. In diabetic rats, no changes of medullary periimplant bone area or bone-to-implant contacts (BICs) were achieved with or without treatment with PTH. However, also animals treated with insulin failed to response significantly to PTH regarding bone area (7.4 ± 4.1% and 8.1 ± 4.1%) and BICs (33.7 ± 16.9% and 49.9 ± 11.9%). These results demonstrate that the metabolic characteristics of the diabetic rats produced a condition unable to respond to PTH treatment, even when hyperglycemia was controlled with insulin.

Synergistic effects of bisphosphonate and calcium phosphate nanoparticles on peri-implant bone responses in osteoporotic rats

The prevalence of osteoporosis will increase within the next decades due to the aging world population, which can affect the bone healing response to dental and orthopedic implants. Consequently, local drug targeting of peri-implant bone has been proposed as a strategy for the enhancement of bone-implant integration in osteoporotic conditions. In the present study, an established in-vivo femoral condyle implantation model in osteoporotic and healthy bone is used to analyze the osteogenic capacity of titanium implants coated with bisphosphonate (BP)-loaded calcium phosphate nanoparticles (nCaP) under compromised medical conditions. After 4 weeks of implantation, peri-implant bone volume (%BV; by μCT) and bone area (%BA; by histomorphometry) were significantly increased within a distance of 500 μm from implant surfaces functionalized with BP compared to control implants in osteoporotic and healthy conditions. Interestingly, the deposition of nCaP/BP coatings onto implant surfaces increased both peri-implant bone contact (%BIC) and volume (%BV) compared to the deposition of nCaP or BP coatings individually, in osteoporotic and healthy conditions. The results of real-time PCR revealed similar osteogenic gene expression levels to all implant surfaces at 4-weeks post-implantation. In conclusion, simultaneous targeting of bone formation (by nCaP) and bone resorption (by BP) using nCaP/BP surface coatings represents an effective strategy for synergistically improvement of bone-implant integration, especially in osteoporotic conditions.

Zirconia Implants with Laser Surface Treatment: Peri-Implant Bone Response and Enhancement of Osseointegration

The aim of this study was to prepare zirconia implants with laser-modified surfaces and to evaluate peri-implant tissue response and osseointegration in an animal study. The experimental zirconia implants received one of the following surface treatments and were placed in the tibiae of SD rats: vertical irradiation with a fiber laser (vertical fiber laser), horizontal irradiation with a fiber laser (horizontal fiber laser), vertical irradiation with a Neodymium-doped yttrium orthovanadate (YVO4) laser (vertical YVO4 laser), and horizontal irradiation with a YVO4 laser (horizontal YVO4 laser). The control implants were smooth surfaced. Tibiae with implant bodies were collected 28 days after implant placement, and removal torque values were measured. Tissue sections were prepared for light microscopy, and the bone-implant contact (BIC) ratio and the peri-implant bone area (BA) were measured. The vertical fiber-laser implants had a mean BIC that was significantly higher than other implants. The mean BIC of the vertical fiber-laser implants was approximately 4.2 folds of the value of the control implants on the cortical bone side and approximately 2.7 folds of the value of the control implants on the bone marrow side. The mean BA was significantly higher in the vertical YVO4-laser implants. The vertical fiber-laser implants had a mean torque removal value that was approximately 2.4 folds of the value of the control implants and approximately double of the value of the vertical or horizontal YVO4-laser implants. The horizontal fiber-laser implants had a mean removal torque value that was approximately double of the value of the control implants and approximately 1.7 folds of the value of the vertical or horizontal YVO4-laser implants (p<0.05). Both types of lasers were useful in implant surface treatment to enhance osseointegration of zirconia implants.

Osseointegration of biochemically modified implants in an osteoporosis rodent model

The present study examined the impact of implant surface modifications on osseointegration in an osteoporotic rodent model. Sandblasted, acid-etched titanium implants were either used directly (control) or were further modified by surface conditioning with NaOH or by coating with one of the following active agents: collagen/chondroitin sulphate, simvastatin, or zoledronic acid. Control and modified implants were inserted into the proximal tibia of aged ovariectomised (OVX) osteoporotic rats (n=32/group). In addition, aged oestrogen competent animals received either control or NaOH conditioned implants. Animals were sacrificed 2 and 4 weeks post-implantation. The excised tibiae were utilised for biomechanical and morphometric readouts (n=8/group/readout). Biomechanical testing revealed at both time points dramatically reduced osseointegration in the tibia of oestrogen deprived osteoporotic animals compared to intact controls irrespective of NaOH exposure. Consistently, histomorphometric and microCT analyses demonstrated diminished bone-implant contact (BIC), peri-implant bone area (BA), bone volume/tissue volume (BV/TV) and bone-mineral density (BMD) in OVX animals. Surface coating with collagen/chondroitin sulphate had no detectable impact on osseointegration. Interestingly, statin coating resulted in a transient increase in BIC 2 weeks post-implantation; which, however, did not correspond to improvement of biomechanical readouts. Local exposure to zoledronic acid increased BIC, BA, BV/TV and BMD at 4 weeks. Yet this translated only into a non-significant improvement of biomechanical properties. In conclusion, this study presents a rodent model mimicking severely osteoporotic bone. Contrary to the other bioactive agents, locally released zoledronic acid had a positive impact on osseointegration albeit to a lesser extent than reported in less challenging models.

Impact of immediate loading on early bone healing at two‐piece implants placed in fresh extraction sockets: an experimental study in the beagle dog

To study early bone healing of immediately loaded implants placed in fresh extraction sockets versus immediate implants without occlusal loading in the dog. A total of 48 implants were placed in the distal sockets of Pm3 and Pm4 in the lower jaw of 12 Beagle dogs immediately after tooth extraction. In the control group, no loading was applied. In the test group, an immediate loading restoration with occlusal contacts was performed. Dogs were sacrificed at 2, 4 and 8weeks for histological analysis. At the end of the study, there was a 100% implant and prosthesis survival. Similar results for test and control groups were observed for bone-to-implant contact (%) and peri-implant bone area. Inter-thread bone area tended to decrease in the control and increase in the test. With respect to ridge alterations, bone resorption was more pronounced on the buccal aspect and was observed in both groups. Immediate loading did not impair early stages of bone healing and crestal bone modelling at two-piece implants in fresh extraction sockets in the beagle dog; however, bone resorption occurred in all specimens in both groups.

In vivo evaluation of bioactive glass‐based coatings on dental implants in a dog implantation model

Although titanium is commonly used as a favorable bone implant material due to its mechanical properties, its bioactive and osteoconductive capacity is relatively low. Calcium phosphate ceramics, predominantly hydroxyapatite (HA), have been frequently used for coating purposes to improve the bioactive properties. In view of the suggested osteopromotive capacity of bioactive glasses (BGs), this study aimed to evaluate the effect of BG incorporation into HA coatings on implant performance in terms of bone contact and bone area. A total of 48 screw-type titanium implants with magnetron sputter coatings containing different ratios of HA and BG (HA, HABGLow, and HABGHigh; n = 8) were placed into the mandible of 16 Beagle dogs. After 4 and 12 weeks, their performance was evaluated histologically and histomorphometrically. Peri-implant bone area percentage (BA%) was determined in three zones (inner, 0-500 μm; middle, 500-1000 μm; and outer, 1000-1500 μm). Additionally, bone-to-implant contact (BIC%) and first bone-implant contact (1st BIC) were assessed for each sample. After 4 weeks, bone-to-implant contact for the HA- and HABGLow-coated groups was significantly higher (P < 0.05) than for the HABGHigh coatings. Mean values for overall BA% showed comparable values for both the HABGLow (58.3%)- and HABGHigh (56.3%)-coated groups. Data suggest that the relative BA around the HA-coated implants (67.8%) was higher, although this was only significant compared to the HABGHigh group. After 12 weeks, all three groups showed similar bone-to-implant contact and no differences in BA were found. The incorporation of BG into HA sputter coatings did not enhance the performance of a dental implant in implantations sites with good bone quality and quantity. On the contrary, coatings containing high concentrations of BG resulted in inferior performance during the early postimplantation healing phase.

The effect of polyelectrolyte multilayer coated titanium alloy surfaces on implant anchorage in rats

Advances have been achieved in the design and biomechanical performance of orthopedic implants in the last decades. These include anatomically shaped and angle-stable implants for fracture fixation or improved biomaterials (e.g. ultra-high-molecular-weight polyethylene) in total joint arthroplasty. Future modifications need to address the biological function of implant surfaces. Functionalized surfaces can promote or reduce osseointegration, avoid implant-related infections or reduce osteoporotic bone loss. To this end, polyelectrolyte multilayer structures have been developed as functional coatings and intensively tested in vitro previously. Nevertheless, only a few studies address the effect of polyelectrolyte multilayer coatings of biomaterials in vivo. The aim of the present work is to evaluate the effect of polyelectrolyte coatings of titanium alloy implants on implant anchorage in an animal model. We test the hypotheses that (1) polyelectrolyte multilayers have an effect on osseointegration in vivo; (2) multilayers of chitosan/hyaluronic acid decrease osteoblast proliferation compared to native titanium alloy, and hence reduce osseointegration; (3) multilayers of chitosan/gelatine increase osteoblast proliferation compared to native titanium alloy, hence enhance osseointegration. Polyelectrolyte multilayers on titanium alloy implants were fabricated by a layer-by-layer self-assembly process. Titanium alloy (Ti) implants were alternately dipped into gelatine (Gel), hyaluronic acid (HA) and chitosan (Chi) solutions, thus assembling a Chi/Gel and a Chi/HA coating with a terminating layer of Gel or HA, respectively. A rat tibial model with bilateral placement of titanium alloy implants was employed to analyze the bones’ response to polyelectrolyte surfaces in vivo. 48 rats were randomly assigned to three groups of implants: (1) native titanium alloy (control), (2) Chi/Gel and (3) Chi/HA coating. Mechanical fixation, peri-implant bone area and bone contact were evaluated by pull-out tests and histology at 3 and 8weeks. Shear strength at 8weeks was statistically significantly increased (p<0.05) in both Chi/Gel and Chi/HA groups compared to the titanium alloy control. No statistically significant difference (p>0.05) in bone contact or bone area was found between all groups. No decrease of osseointegration of Chi/HA-coated implants compared to non-coated implants was found. The results of polyelectrolyte coatings in a rat model showed that the Chi/Gel and Chi/HA coatings have a positive effect on mechanical implant anchorage in normal bone.

Topical Application of Melatonin and Growth Hormone Accelerates Bone Healing around Dental Implants in Dogs

Growth hormone (GH) and melatonin belong to the group of growth factors. These substances have been proposed to improve and accelerate osseous healing using topical applications. The aim of this study was to evaluate the effect of the topical administration of GH and melatonin on osseointegration of dental implants in Beagle dogs 2, 5, and 8 weeks after their insertion. Twelve adult Beagle dogs and 48 implants were used in the study. The maxillary and mandibular premolars and molars were extracted. Each mandible received cylindrical screw implants of 3.25 mm in diameter and 10 mm in length. Prior to implanting, 4 IU of recombinant human GH and 1.2 mg of lyophilized powdered melatonin was applied to one osteotomy at each side of the mandible. None was applied at the control sites. The implants were retrieved at 2, 5, and 8 weeks for light microscopic examination, energy-dispersive x-ray microanalysis, and histomorphometric measurements in ground sections. At week 2, BIC was significantly higher in the melatonin-growth hormone group than in the implant control one (34.20 vs 25.05%; p = .010). The M-GH group also increased significantly the peri-implant bone area (64.72 vs 53.20%; p = .038) and interthread bone area (35.62 vs 25.08%; p = .02). At weeks 5 and 8, BIC and bone density around implants were similar to both groups. Significant differences were detected in bone neoformation at 8 weeks in ML-GH group (9.04 vs 7.53%; p = .05). Regarding the mineral composition, in ML-GH group increments in concentrations of phosphorus (10.70 vs 10.34; p = .013) were observed at 2 weeks and of magnesium (0.29 vs 0.25; p = .019) 5 weeks after implantation. The present study confirms that GH and melatonin synergistically enhance new bone formation around titanium implants in early stages of healing.