The effect of standoff distance and surface roughness on biofilm disruption using cavitation.

Effective biofilm removal from surfaces in the mouth is a clinical challenge. Cavitation bubbles generated around a dental ultrasonic scaler are being investigated as a method to remove biofilms effectively. It is not known how parameters such as surface roughness and instrument distance from biofilm affect the removal. We grew Strepotococcus sanguinis biofilms on coverslips and titanium discs with varying surface roughness (between 0.02-3.15 µm). Experimental studies were carried out for the biofilm removal using high speed imaging and image analysis to calculate the area of biofilm removed at varying ultrasonic scaler standoff distances from the biofilm. We found that surface roughness up to 2 µm does not adversely affect biofilm removal but a surface roughness of 3 µm caused less biofilm removal. The standoff distance also has different effects depending on the surface roughness but overall a distance of 1 mm is just as effective as a distance of 0.5 mm. The results show significant biofilm removal due to an ultrasonic scaler tip operating for only 2s versus 15-60s in previous studies. The technique developed for high speed imaging and image analysis of biofilm removal can be used to investigate physical biofilm disruption from biomaterial surfaces in other fields.

Enhanced bone healing around nanohydroxyapatite-coated polyetheretherketone implants: An experimental study in rabbit bone.

OBJECTIVE: To investigate the bone response to threaded polyetheretherketone (PEEK) implants coated with nanohydroxyapatite. MATERIALS AND METHODS: A total of 39 PEEK implants were coated with nanocrystalline hydroxyapatite and 39 uncoated implants were used as controls. The implant surface was characterized by optical interferometry and scanning electron microscope. The implants were inserted in the tibia and femur of 13 rabbits. After 6 weeks of healing, quantitative and qualitative analyses were performed. RESULTS: The test implants showed significantly higher removal torque test values compared with the control group. Histomorphometric evaluation demonstrated higher bone-to-implant contact for the test implants; however, there were no differences in bone area between the groups. Qualitative histological analyses demonstrated inflammatory cellular reactions in close vicinity of both implant surfaces. A two-cell layer of foreign body giant cells was observed irrespective of sample type. CONCLUSION: Our findings demonstrate that implants with a threaded design render good stability to PEEK in both coated and uncoated implants. Nanohydroxyapatite-coated PEEK implants demonstrated improved bone formation compared with uncoated controls.

An in vitro comparison of possibly bioactive titanium implant surfaces.

The aim of the study was to compare Ca and P formation (CaP) and subsequent bone cell response of a blasted and four different possibly bioactive commercially pure (cp) titanium surfaces; 1. Fluoride etched (Fluoride), 2. Alkali-heat treated (AH), 3. Magnesium ion incorporated anodized (TiMgO), and 4. Nano HA coated and heat treated (nano HA) in vitro. Furthermore, to evaluate the significance of the SBF formed CaP coat on bone cell response. The surfaces were characterized by Optical Interferometry, Scanning Electron Microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS). CaP formation was evaluated after 12, 24 and 72 h in simulated body fluid (SBF). Primary human mandibular osteoblast-like cells were cultured on the various surfaces subjected to SBF for 72 h. Cellular attachment, differentiation (osteocalcin) and protein production (TGF-beta(1)) was evaluated after 3 h and 10 days respectively. Despite different morphological appearances, the roughness of the differently modified surfaces was similar. The possibly bioactive surfaces gave rise to an earlier CaP formation than the blasted surface, however, after 72 h the blasted surface demonstrated increased CaP formation compared to the possibly bioactive surfaces. Subsequent bone cell attachment was correlated to neither surface roughness nor the amount of formed CaP after SBF treatment. In contrast, osteocalcin and TGF-beta(1) production were largely correlated to the amount of CaP formed on the surfaces. However, bone response (cell attachment, osteocalcin and TGF-F production) on the blasted controls were similar or increased compared to the SBF treated fluoridated, AH and TiMgO surface.

Precipitation of calcium phosphate in the presence of albumin on titanium implants with four different possibly bioactive surface preparations. An in vitro study.

The aim of the present study was to compare the nucleating behaviour on four types of bioactive surfaces by using the simulated body fluid (SBF) model with the presence albumin. Titanium discs were blasted (B) and then prepared by alkali and heat treatment (AH), anodic oxidation (AO), fluoridation (F), or hydroxyapatite coating (HA). The discs were immersed in SBF with 4.5 mg/ml albumin for 3 days, 1, 2, 3 and 4 weeks and analysed with scanning electron microscopy/energy dispersive X-ray analysis (SEM/EDX) and X-ray photoelectron spectroscopy (XPS). Topographic surface characterisation was performed with a contact stylus profilometer. The results demonstrated that the bioactive surfaces initiated an enhanced calcium phosphate (CaP) formation and a more rapid increase of protein content was present on the bioactive surfaces compared to the blasted control surface. The observation was present on all bioactive surfaces. The fact that there was a difference between the bioactive surfaces and the blasted control surface with respect to precipitation of CaP and protein content on the surfaces support the fact that there may be biochemical advantages in vivo by using a bioactive surface.

Increased bone contact to a calcium-incorporated oxidized commercially pure titanium implant: an in-vivo study in rabbits.

The aim of this study was to evaluate the bone response to an oxidized titanium implant (Ox) and a calcium-incorporated oxidized titanium implant (Ca). A blasted titanium implant (Bl) was used as control. The implants were topographically characterized using an optical interferometer and placed: one in each distal femoral metaphysis and two in each proximal tibial metaphysis in rabbits. The rabbits were killed 12 weeks after implant insertion, and the implants and their surrounding tissues were removed en bloc for histomorphometrical evaluations. Topographical evaluation revealed three different surfaces: average height deviation (S(a), microm) values for Ca:Ox:Bl implants were 0.3:0.6:0.9, developed surface area ratios (%) 17:44:31, number of summits per microm(2) 208:136:118, and core fluid retention index values 1.33:1.33:1.38. The mean percentages of bone contact to the implants placed in the tibia (Ca:Ox:Bl) were 47:30:34 and to the implants placed in the femur (Ca:Ox) 32:20. The mean percentages of surrounding bone area for the implants placed in the tibia were 40:47:37 and for the implants placed in the femur 43:46. A significant increase in bone contact was found for smooth (S(a) <0.5 microm) but more densely peaked calcium-incorporated oxidized implants when compared to slightly rougher (S(a)=0.5-1.0 microm) oxidized or blasted implants.

Early bone formation in human bone grafts treated with platelet-rich plasma: preliminary histomorphometric results.

The aim of this study was to evaluate the effect of platelet-rich plasma (PRP) on early and late bone healing after autogenous maxillary sinus grafting. Eleven patients were subjected to sinus augmentation with particulated autogenous bone bilaterally with the addition of PRP in one side. Platelet counts in baseline whole blood and PRP were registered. Biopsies were taken in the grafted bone of the sinus area with trephine at 3 months (nine patients) and simultaneously a micro-implant was installed in the same region. The micro-implants with surrounding bone were retrieved by biopsy at 6 months (seven patients). Undecalcified cut and ground sections were histomorphometrically analysed. Quantification of new and old bone in all biopsies was performed. The results of this histological study showed that significantly more new bone was formed at PRP-treated sites compared to controls after 3 months of healing. After 6 months, this effect could no longer be observed. This is in accordance with previous studies showing that PRP has a rather low regenerative capacity but may influence the early phase of bone healing. The additional value of PRP in autogenous bone grafts in the maxillary sinus is questionable.

Improved bone ingrowth and fixation with a thin calcium phosphate coating intended for complete resorption.

Bonit is claimed to be a resorbable electrochemically deposited calcium phosphate coating consisting mainly of brushite, which is a hydroxyapatite precursor. This study involved a comparison of Ti6Al4V screw-shaped implants with and without a 15 +/- 5 microm Bonit coating in rabbit tibia and femur, after 6 and 12 weeks of insertion. The biomechanical removal torque test showed significantly increased values for the coated implants after 12 weeks (p < 0.05) but not after 6 weeks of integration. Higher bone-implant contact was found for the coated implants in the tibia after 6 weeks and for both tibial and femoral screws after 12 weeks (p < 0.05). There was no difference in the inflammatory reaction around the implants, and possible grains of the coating could be detected after 6 weeks, but not after 12 weeks of follow-up. This unloaded short-term study has shown promising results for the easily applicable and resorbable coat (Bonit) compared to uncoated titanium-alloy implants.

Enamel matrix derivative and titanium implants.

AIM: The aim of present study was to evaluate if an enamel matrix derivative (Emdogain) may enhance bone formation and osseointegration of titanium implants, using a well-documented rabbit model. MATERIAL AND METHODS: Thirty-six threaded commercially pure titanium (cp.ti.) implants were inserted in six New Zealand white rabbits. One implant was placed in each femur and two in each tibia. Prior to implant insertion approximately 0.5 mL of Emdogain (EMD) (test) or the vehicle gel (PGA: propylene glycol alginate) (control) was injected into the surgically prepared implant site. The follow-up time was 6 weeks. Biomechanical evaluations by resonance frequency analysis (RFA) and removal torque measurements (RTQ) were performed. Histomorphometrical quantifications were made on ground sections by measurements of the percentage of bone-to-metal contact, bone area inside the threads as well as outside the threads (mirror image). Bone lengths along the implant surface were also measured and used for shear strength calculations. RESULTS: The results demonstrated no beneficial effects from the EMD treatment on bone formation around titanium implants in any of the tested parameters. Significant differences were demonstrated with removal torque test and shear force calculations for the control implants. No other parameter demonstrated a statistically significant difference. CONCLUSION: The results of the present study may indicate that EMD does not contribute to bone formation around titanium implants. This observation may indicate that the bone formation that occurs after EMD treatment in periodontal defects is the result of functional adaptation. However, further research is required to evaluate the effect of EMD treatment on bone formation.

Titanium implants and BMP-7 in bone: an experimental model in the rabbit.

This study evaluates the effect of rhBMP-7/OP-1 on the osseointegration of commercially pure titanium implants in an experimental implant model in rabbits. Threaded titanium implants with two transverse parallel canals were inserted in the femur and tibia of rabbits. The canals were filled with, 10 microg of BMP-7/collagen carrier, pure collagen carrier or were left empty as a control. The stiffness of the implant fixation was evaluated by Resonance Frequency Analysis (RFA) at baseline and four weeks postoperatively. Percentage of bone ingrowth in the canals was measured on microradiographs. Histomorphometry along the threaded part of the implants was performed on 15 microm thin sections. The results from the RFA demonstrated a higher mean value for the BMP-7 treated implants in the tibia than the carrier treated implants but not compared to the control implants. The control implants in the tibia demonstrated more bone ingrowth in the upper canal than to the carrier or the BMP-7 treated implants. Apart from these differences there were no significant effects of BMP. In this study BMP-7 did not contribute to any substantially improved bone anchorage of titanium implants.

Systemically administered human growth hormone improves initial implant stability: an experimental study in the rabbit.

PURPOSE: This study was an investigation to determine whether human growth hormone (hGH) continuously administered to rabbits may improve implant integration in bone. MATERIALS AND METHODS: Thirty-two commercially pure titanium (c.p. Ti) implants were inserted in the tibiae of 16 rabbits. Human growth hormone (0.3 U/kg/d) or sodium chloride (NaCl) was administered by subcutaneous pumps. Insulin-like growth factor-1 (IGF-1) levels in blood were measured. Two biomechanical tests were performed: (1) every second week resonance frequency analysis (RFA) was used to investigate implant stability or stiffness at the interface and, after 8 weeks of follow-up, (2) removal torque (a measure of implant integration and stability) was registered. Further evaluation was performed by dual energy x-ray analysis (DEXA), to evaluate bone mineral density, and histomorphometric analysis of tissue-to-implant integration on undecalcified cut and ground sections. RESULTS: A difference in implant stability was detected with the RFA technique after 2 weeks and 8 weeks in favor of the hGH-treated rabbits. No significant differences were detected with removal torque, DEXA, and histomorphometric measurements. The blood test demonstrated antibody development in the rabbits treated with hGH after 4 weeks. CONCLUSION: Growth hormone has an initial beneficial effect on implant integration; however, owing to rapid antibody formation, this study did not demonstrate whether this effect remains in the long term.

Parathyroid hormone (1-34) receptor-binding and second-messenger response in rat incisor odontoblasts.

Even though indirect evidence indicates that PTH exerts an anabolic effect on dentinogenesis, the existence of PTH receptors and any second-messenger response in odontoblasts have not been demonstrated. The aim of this study was to investigate whether rat incisor odontoblasts express PTH receptors, and to identify which second messenger pathway the hormone may activate. Odontoblasts were dissected from rat incisors. Amino-terminal (1-34) fragment rat PTH [rPTH(1-34)] conjugated to fluorescein isothiocyanate visualized receptor sites on the cell surface. Upon incubation of odontoblasts with rPTH(1-34), cAMP formation was increased. However, no fluctuations in intracellular calcium activity were observed upon rPTH(1-34) stimulation when using Fura-2 as a Ca2+ probe. In long-time incubations, stimulation with PTH(1-34) upregulated APase activity. The results demonstrate that rPTH(1-34) evokes an anabolic response in dentinogenically active odontoblasts, and that this may be mediated through the protein kinase A/cAMP pathway, whereas no indications for Ca2+ as a second messenger were evident.