Titanium implant functionalization with phosphate-containing polymers may favour in vivo osseointegration.

AIM: Osseointegration of titanium implants is predictable, but can be improved via surface functionalization. MATERIALS AND METHODS: One hundred and twenty implants were installed in parietal bone of 12 domestic pigs and left to heal for 1 or 3 months. Five groups were defined according surface treatments: immersion in water (H2 O), 10% polyphosphoric acid (PPA10), 1% phosphorylated pullulan (PPL1), 10% phosphorylated pullulan (PPL10) or 10% phosphorylated pullulan + 1 µg bone morphogenetic protein-2 (PPL10 BMP). As primary outcome, implant osseointegration was evaluated by quantitative histology, namely peri-implant bone formation (B/T in %) and bone-to-implant contact (BIC in %) for each healing period. The Wilcoxon signed-rank test and Mann-Whitney U-test with α = 0.05 were performed. RESULTS: PPL10 and PPA10 groups showed significantly higher B/T and BIC results than the control (H2 O) group at 1-month (p < .05). No significant difference was found between PPL1 and H2 O or between PPL10 BMP and H2 O, irrespective of healing time (1 or 3 months) or investigated parameter (B/T and BIC; p > .05). After 3 months, no experimental group showed a significant difference compared to the control group (H2 O) for both investigated parameters (B/T and BIC; p > .05). CONCLUSION: Functionalizing titanium implants with inorganic or organic phosphate-containing polymers at 10 wt% concentration may stimulate peri-implant bone formation and implant osseointegration at early healing times.

Effect of insertion torque on titanium implant osseointegration: an animal experimental study.

OBJECTIVE: To evaluate the effect of implant insertion torque on the peri-implant bone healing and implant osseointegration. MATERIAL AND METHODS: Bilaterally in the tibia of five adult New Zealand white rabbits, 20 implants were installed, subdivided into four groups, corresponding to two insertion torque conditions (low, < 10 Ncm vs. high > 50 Ncm) and 2 experimental periods (2 weeks vs. 4 weeks of healing). The implant insertion torque was determined by the surgical drill diameter relative to the implant diameter. Implant osseointegration was evaluated by quantitative histology (bone-to-implant contact with host bone [BIC-host], with neoformed bone [BIC-de novo], with both bone types [BIC-total], and peri-implant bone [BA/TA]). Every response was modelled over time using GEE (general estimation equation) with an unstructured variance-covariance matrix to correct for dependency between the measurements from one animal. The statistical significance level of α = 0.05 was applied. RESULTS: Significantly, more BIC-host and BIC-total were recorded for H implants compared with L implants after 2 week of healing (P = 0.010 and P = 0.0001, respectively). However, this result was no longer found for the extended healing period. Furthermore, BIC-total significantly increased over time for L implants (P < 0.00001). In contrast, the significant increase in BA/TA over time was found for H implants (P < 0.01). Finally, H insertion torque led to an increased BA/TA after 4 week of healing (P < 0.02) compared with the L insertion protocol. CONCLUSION: L insertion torque implants installed in the rabbit tibial bone osseointegrate with considerable de novo bone formation. This bone neoformation enables L implants to catch up, already during the early osseointegration stage, the initial inferior amount BIC contact compared with that of H implants. A negative impact of the created strain environment accompanying H insertion torque implant installation on the biological process of osseointegration could not be observed, at least not at tissue level.

Three-year clinical performance of a HEMA-free one-step self-etch adhesive in non-carious cervical lesions.

Despite the fact that one-step adhesives are currently used routinely in clinical practice, long-term studies on their clinical performance are scarce. The objective of this randomized controlled clinical trial was to test the hypothesis that a 2-hydroxyethyl methacrylate (HEMA)-free one-step self-etch adhesive performs worse than a conventional multistep etch-and-rinse adhesive. Two-hundred and seventy-six non-carious cervical lesions in 52 patients were restored with a micro-hybrid composite (Gradia Direct; GC). These restorations were bonded in random order either with the HEMA-free one-step adhesive G-Bond (GC) or with the 'gold-standard' (control) three-step adhesive Optibond FL (Kerr). The restorations were evaluated after 6, 12, 24, and 36 months of clinical service regarding retention, marginal adaptation, microleakage, caries occurrence, and sensitivity. After a medium-long period of 3 yr, similar success in clinical performance was observed for the simplified all-in-one adhesive and the conventional three-step adhesive. However, the one-step adhesive exhibited significantly more incisal marginal defects and discolorations. Whereas marginal degradation appeared to arrest for the multistep etch-and-rinse adhesive after 12 months, the enamel margins of the restorations bonded with the one-step self-etch adhesive continued to deteriorate. These incisal marginal defects were, however, small and could easily be removed by polishing. For both adhesives, large and sclerosed lesions appeared to be at higher risk of retention loss.

The importance of adhesive area delimitation in a microshear bond strength experimental design.

PURPOSE: The purpose of this study was to assess the influence of adhesive area delimitation on the microshear bond strength of different adhesives to dentin. MATERIALS AND METHODS: Eighteen bovine incisors were sectioned and the exposed dentin surfaces were prepared with 600-grit SiC paper. These teeth were randomly divided into three groups, according to the adhesive to be applied: two-step etch-and-rinse Adper Single Bond 2 (3M ESPE), two-step self-etching Clearfil SE Bond (Kuraray), and one-step Clearfil S3 Bond (Kuraray). On each dentin surface, 4 samples were built up with the composite resin Z100 (3M ESPE); on 2 of these, a suggested area delimitation technique was employed. After 24 h of storage in water at 37°C, samples were subjected to the microshear bond strength test, and the failure modes were evaluated under optical and scanning electron microscopes. The obtained results were statistical analyzed using two-way ANOVA and Tukey's test. RESULTS: Groups without area delimitation presented significantly higher bond strength results (p < 0.05) and a higher incidence of cohesive failures. In these groups, fractures tended to occur beyond the limits of the actual adhesive area, while the area restriction technique succeeded in avoiding this phenomenon. The three adhesives performed similarly when area delimitation was employed (p > 0.05), but Clearfil S3 Bond showed significantly higher bond strength results when no area delimitation was taken into account (p < 0.05). CONCLUSION: The extension of the adhesive area beyond the limits of the composite cylinder may play an important role in the results of microshear bond strength tests, while the suggested area delimitation technique may lead to less questionable outcomes.

Influence of dentin cavity surface finishing on micro-tensile bond strength of adhesives.

UNLABELLED: The current trend toward minimal-invasive dentistry has introduced innovative techniques for cavity preparation. Chemical vapor deposition (CVD) and laser-irradiation technology have been employed as an alternative to the common use of regular burs in high-speed turbines. OBJECTIVES: The purpose of this study was to assess the influence of alternative techniques for cavity preparation on the bonding effectiveness of different adhesives to dentin, and to evaluate the morphological characteristics of dentin prepared with those techniques. METHODS: One etch&rinse adhesive (OptiBond FL, Kerr) and three self-etch systems (Adper Prompt L-Pop, 3M ESPE; Clearfil SE Bond, Kuraray; Clearfil S3 Bond, Kuraray) were applied on dentin prepared with a regular bur in a turbine, with a CVD bur in a turbine, with a CVD tip in ultrasound and with an Er,Cr:YSGG laser. The micro-tensile bond strength (microTBS) was determined after storage in water for 24h at 37 degrees C, and morphological evaluation was performed by means of field-emission-gun scanning electron microscopy (Feg-SEM). RESULTS: Feg-SEM evaluation revealed different morphological features on the dentin surface after the usage of both the conventional and alternative techniques for cavity preparation, more specifically regarding smear-layer thickness and surface roughness. CVD bur-cut, CVD ultra-sonoabraded and laser-irradiated dentin resulted in lower microTBSs than conventionally bur-cut dentin, irrespective of the adhesive employed. SIGNIFICANCE: The techniques, such as CVD diamond-bur cutting, CVD diamond ultra-sonoabrasion and laser-irradiation, used for cavity preparation may affect the bonding effectiveness of adhesives to dentin, irrespective of their acidity or approach.

Influence of notch geometry and interface on stress concentration and distribution in micro-tensile bond strength specimens.

OBJECTIVES: Describe stress distribution and compare stress concentration factor (K(t)) for homogeneous micro-specimens with different notch geometries and stick-shaped homogeneous and bimaterial specimens by means of finite element (FE) analysis. METHODS: Axisymmetric models were created for homogeneous specimens with different notches and for stick-shaped homogeneous and bimaterial specimens. FE mesh was refined at areas of expected stress concentration and boundary conditions included an applied tensile stress in the axial direction. Linear elastic analysis was used. RESULTS: For hourglass homogeneous specimens, K(t) equaled 1.32 and 1.12 for a notch radius of 0.6mm and 3.3mm, respectively. A non-uniform axial (sigma(zz)) stress distribution was found in the notch cross-section, with values at the outer edge being 78% and 25% larger than at the center. In addition, a triaxial stress state was generated. Stick-shaped and dumbbell homogeneous specimens presented K(t)=1 and a uniform, uniaxial stress distribution along the entire cross-section. Shear stresses were zero for all homogeneous specimens. When an adhesive interface was added to the stick-shaped specimen, an area of localized axial stress concentration (K(t)=1.55) was detected at the bimaterial joint near the outer edge. Normal stresses sigma(rr) and sigma(thetatheta) and shear stress tau(zr) were also non-zero at the free-edge. CONCLUSIONS: Dumbbell or stick-shaped specimens are favored for muTBS testing, as they do not present stress concentrations due to geometry. However, dissimilar mechanical properties of joint components will lead to stress concentrations and non-uniform multi-axial stresses, although to a lesser extent.

Effect of low-shrinking composite on the bonding effectiveness of two adhesives in occlusal Class-I cavities.

The purpose of this study was to evaluate if a low-shrinking composite can improve the bonding effectiveness of adhesives in highly constrained conditions. A low-shrinking composite ('els-extra low shrinkage', Saremco) was bonded in standardized occlusal Class-I cavities using a three-step ('cmf', Saremco) and a two-step etch-and-rinse adhesive ('XP Bond', Dentsply). Both adhesives were also combined with a conventional composite ('Z100', 3M ESPE). Half of the restored cavities were exposed to 20,000 thermo-cycles. 3-way ANOVA revealed a significant effect for the factors 'adhesive' and 'composite' (both p<0.0001), but not for 'thermo-cycling' (p=0.994). Significantly higher bond strengths were recorded for the low-shrinking composite than for the control composite, using either of the adhesives. The low-shrinking composite in combination with the three-step etch-and-rinse adhesive performed best in the high C-factor Class-I cavity. The two-step etch-and-rinse adhesive suffered strongly from polymerization-shrinkage stress, which could be partially restored by using the low-shrinking composite.

Micro-tensile bond strength and interfacial characterization of an adhesive bonded to dentin prepared by contemporary caries-excavation techniques.

OBJECTIVES: To evaluate the micro-tensile bond strength (µTBS) and interfacial characteristics of adhesive-dentin bonds produced after caries-removal with contemporary techniques. METHODS: Carious molars were cut at the base of the fissure, exposing 'sound' and 'carious' dentin at different spots. After caries-excavation, a composite was bonded using a 2-step self-etch adhesive. The µTBS was measured and the mode of fracture analyzed using a stereomicroscope and imaged by Feg-SEM, while additional non-fractured specimens were histologically analyzed after Masson's trichrome staining in order to identify potentially incompletely resin-enveloped collagen. RESULTS: µTBS to residual caries-excavated dentin was lower than to sound dentin. The different caries-removing techniques had a significant effect on the µTBS. Er:YAG laser guided by a LIF-feedback system (Kavo) resulted in the lowest µTBS (26.8% lower than to 'sound' dentin) and a distinct layer of incompletely resin-enveloped collagen at the interface. Although different degrees of collagen exposure were seen for other caries-removing techniques, such as a thick layer for CeraBur (Komet-Brasseler), some unprotected collagen areas for Cariex (Kavo), or completely resin-enveloped collagen for a tungsten-carbide-bur (Komet), the µTBS appeared not directly affected (10%, 16.6%, and 15.3% lower than to 'sound' dentin, respectively). Carisolv (MediTeam) resulted in the highest µTBS (only 1% reduction compared to that to 'sound' dentin), followed by the tungsten-carbide-bur aided by Caries Detector (Kuraray) (4.8% reduction). Enzymatic caries excavation using the experimental SFC-VIII (3M-ESPE) aided by a disposable plastic instrument resulted in a 19.4% reduction in µTBS as compared to that to 'sound' dentin. SIGNIFICANCE: The dentin bonding receptiveness depends to a large extent on the caries-excavation method employed.

Optimization of the concentration of photo-initiator in a one-step self-etch adhesive.

OBJECTIVES: The objective of this study was to determine the optimal concentration of photo-initiator (camphorquinone) in an experimental one-step self-etch adhesive and to investigate the role of the photo-initiator. METHODS: Seven experimental one-step adhesives with a varying amount of camphorquinone ranging from 0 to 5.25wt% were prepared. Their micro-tensile bond strength to enamel and dentin was determined. In addition, the bond strength was also determined when the adhesive was not light-cured prior to the application of the composite. SEM and TEM were used for further evaluation of the resultant interfacial ultrastructure. RESULTS: The bond strength to enamel was not influenced by the amount of photo-initiator, whereas the bond strength to dentin dropped significantly when concentrations below 0.35wt% camphorquinone were used. Besides phase-separation droplets, electron microscopy revealed the presence of many small droplets at the bottom of the adhesive layer when the adhesive contained no or only a low concentration of initiator, or when the adhesive was not light-cured. SIGNIFICANCE: Since polymerization is severely hampered by oxygen inhibition in thin layers, one-step self-etch adhesives depend greatly on the polymerization of the first layer of lining composite to achieve their ultimate mechanical strength. Consequently, the bond strength to enamel is not influenced by the amount of photo-initiator, but on dentin, bond strength is compromised by droplets, probably due to water absorption, and additionally by the negative effect of water on polymerization and by continuing demineralization of unpolymerized acidic monomers. Overall, it was found that minimally 0.7wt% camphorquinone was needed.

Bonding effectiveness of two contemporary self-etch adhesives to enamel and dentin.

OBJECTIVES: Among contemporary adhesives, self-etch adhesives have been adopted by general practitioners for routine adhesive restorative purposes, mainly because of their ease of use. However, many versions that differ for their clinical application procedure, pH, number of components, etc., are currently available on the market. The purpose of this study was to determine the bonding effectiveness of two new self-etch adhesives (Adper Easy Bond and Adper ScotchBond SE, 3M ESPE) to enamel and dentin using a micro-tensile bond strength (microTBS) protocol and to characterise the interfacial ultra-structure at enamel and dentin using transmission electron microscopy (TEM). METHODS: The adhesives were applied onto coronal human enamel and dentin surfaces and built up with the micro-hybrid resin composite Z100 (3M ESPE). The 'gold-standard' two-step self-etch adhesive Clearfil SE Bond (Kuraray) served as control. Specimens were sectioned to sticks and trimmed at the interface to a cylindrical hour-glass shape ('trimmed' micro-specimens). Non-demineralized and demineralized TEM sections through the adhesive-dentin/enamel interface were prepared by ultra-microtomy. RESULTS: The microTBS of the two self-etch adhesives to enamel was statistically significantly lower than that of the control. To dentin, the microTBS of Adper Easy Bond was significantly lower than that of Adper ScotchBond SE and the control. TEM showed a tight interface to enamel for all three self-etch adhesives. A relatively thick, completely demineralized and acid-resistant hybrid layer was formed at dentin by Adper ScotchBond SE, whereas the interaction of Adper Easy Bond was much shallower, and comparable to that of so-called 'ultra-mild' self-etch adhesives. Some degree of spot- and cluster-like nano-leakage was observed for both adhesives, but did not differ in extent and form from that observed for the control. CONCLUSIONS: Although the new two self-etch adhesives revealed a tight interaction at both enamel and dentin, their bond strength to both tooth tissues was generally lower than that of the control adhesive. Nevertheless, their bonding effectiveness appears in line with other simplified self-etch adhesives.