Biomedical subjects

A Wennerberg

Publications and source records attributed to A Wennerberg.

At least 37 records · Page 2Linked to original sources

PubMed2000

Re-establishment of the atomic composition and the oxide structure of contaminated titanium surfaces by means of carbon dioxide laser and hydrogen peroxide: an in vitro study.

BACKGROUND: In clinical situations with peri-implant bone resorption, re-integration of the exposed implant surface is sometimes preferable, which requires a clean surface. Previous investigations have shown that cleaning of contaminated titanium surfaces using chemical and abrasive methods is difficult. PURPOSE: The aim of this investigation was to evaluate the efficacy of different combinations of chemical and physical methods (citric acid, hydrogen peroxide, and carbon dioxide [CO2] laser irradiation) for removal of contaminants and subsequent reconstruction of the surface oxide of intraorally contaminated titanium foils. MATERIALS AND METHODS: Commercially pure titanium foils (99.6%, 5 x 5 mm in size) were contaminated by placement on dentures in volunteering patients, simulating a peri-implantitis situation. The contaminated foils and clean control foils were treated by seven and six combinations of citric acid, hydrogen peroxide, and CO2 laser irradiation, respectively. The effect of the cleaning procedures was evaluated by x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). RESULTS: The initial elemental composition of the contaminated foils was 70% carbon (C), 20% oxygen (O), 10% nitrogen (N), and only traces of titanium (Ti) (< 1%). One treatment proved to be more effective than the others: irradiations by 5-second cycles of superpulsed CO2 laser at a power of 7 W, 10-millisecond pulse width, and with an 80-Hz frequency on a wet surface, followed by repeated application of supersaturated citric acid for 30 seconds, each time followed by rinsing with ultrapure water until all tissue remnants had been removed. Finally, hydrogen peroxide of 10-mM concentration was added to the implant surface and evaporated by CO2 laser at the same settings. This treatment protocol resulted in 10% Ti, 45% O, 41% C, and 2 to 3% N, a composition comparable to that of unused foils: 9% Ti, 40% O, 48% C, and traces of N and chlorine (CI). X-ray photoelectron spectroscopy profiles showed that the thickness of the surface oxide was restored and even augmented with this protocol for treatment of contaminated titanium. CONCLUSION: A combination of citric acid, hydrogen peroxide, and CO2 laser irradiation seems to be effective for cleaning and reestablishment of the atomic composition and oxide structure of contaminated titanium surfaces.

Carbon↗

PubMed1999

Surface characterization, protein adsorption, and initial cell-surface reactions on glutathione and 3-mercapto-1,2,-propanediol immobilized to gold.

Monolayers of glutathione (GSH) and 3-mercapto-1,2-propanediol (MG) on gold were tested for their bioreactivity by assessing the degree of inflammatory reaction as manifested by the adherence and activation of platelets and white blood cells (wbc) after exposure to blood ex vivo. Surface composition was characterized by XPS, and noncontact optical profilometry was used to determine surface roughness. The thickness and composition of the adsorbed protein layers were measured by ellipsometry/antibody techniques in vitro. Cell adhesion and activation were quantified by acridine orange staining, fluorescein-diacetate staining, and by specific antibodies against cell membrane antigens. Distinct differences among the surfaces were observed relative to the amounts and composition of adsorbed plasma proteins and the adhesion and activation of platelets (CD62P-exposure) and wbc (CD11b/CD18-exposure). GSH surfaces, which adsorbed the least amount of plasma protein, caused the least adherence and activation of platelets (CD62P), followed by the highest activation of wbc (CD11b/18). The MG surfaces caused a rapid recruitment and activation of platelets (CD62P), followed by a lower activation of wbc (CD11b/18). Thus it appears that measurements of the initial adsorption of plasma protein from anticoagulated plasma and of the adhesion and activation of platelets after 8 min of exposure to whole blood cannot be used to predict accurately the adhesion and activation behavior of inflammatory cells after longer periods (2 h) of exposure on different surfaces.

Adsorption↗

PubMed1999

Surface corrosion of dental ceramics in vitro.

The objective of this study was to evaluate possible structural surface changes in different dental ceramic materials in a provocative corrosive environment in vitro. On the basis of compositional and microstructural differences, seven dental ceramic materials were selected for the test. After sintering and autoglazing, the surface roughness of the specimens was evaluated by confocal laser profilometry. A specially designed specimen holder made it possible to locate the same surface area before and after contact with the corrosive solution. The surface topography was additionally analysed using scanning electron microscopy. All the ceramic materials displayed evidence of surface structural changes on the exposed surfaces, but to varying degrees. Traditional leucite-containing feldspathic porcelains displayed an increase in surface roughness compared with baseline conditions when kept in 4% acetic acid at 80 degrees C for 18 h. Micro-crystalline and non-crystalline ceramic materials, on the other hand, demonstrated a smoother surface or just a minor increase in surface roughness. Whether or not the smoother post-corrosion appearance of certain ceramic materials is indicative of a true increase in corrosion resistance or is merely the result of an uniformly progressive corrosive process will be the object of future studies.

Ceramics↗

PubMed1999

The influence of Carisolv on enamel and dentine surface topography.

The purpose of the present study was to investigate the surface topography of healthy enamel and dentine before and after application of a new chemomechanical system for caries removal, Carisolv. The same surfaces were investigated with respect to the influence of phosphoric acid, plus carious dentine after removal with either Carisolv or burrs. One-hundred freshly extracted teeth were used. Surface topography was measured in two different ways in order to characterize the surfaces at different levels of resolution, atomic force microscopy (AFM) and a contact stylus profilometer. Somewhat conflicting data were obtained with the two measuring techniques. When surfaces were investigated over a small area (AFM), healthy enamel seemed unaffected by Carisolv, while healthy dentine became smoother. Etching enamel with phosphoric acid resulted in a rougher surface, while no effect was detected on etched healthy dentine. Caries removal using Carisolv resulted in a smoother surface compared with conventional caries removal. When the surfaces were monitored with the contact profilometer, no effect of Carisolv could be detected on healthy enamel or dentine. Phosphoric acid etching, in contrast, increased the surface roughness of both enamel and dentine. When compared with conventional caries removal technique, caries removal with Carisolv did increase the surface roughness.

Acid Etching, Dental↗

PubMed1999

In vitro dentin pretreatment: surface roughness and adhesive shear bond strength.

The aim was to define the morphology and roughness of dentin from different tooth areas after various pretreatments to identify the effect of hybrid layer, resin tags, and mineralised dentin surface on shear bond strength. Thirty-eight extracted molars were used, each providing two sections of cervical (c) and lateral (l) dentin. Five pretreatments were performed: A) 0.2% EDTA; B) abrasion with Al2O3 particles, 0.2% EDTA; C) 10% H3PO4; D) 10% H3PO4 and immersion in a collagenase solution; E) control: no treatment. Z100 composite resin cylinders were bonded to the specimens with All Bond 2 bonding resin and tested for shear bond strength. Twelve other specimens from each group were analysed with an optical profilometer and an atomic force microscope, and four were further examined by scanning electron microscopy (SEM). Mean shear strength values in MPa were: Ac: 8.36 +/- 4.23; Al: 8.77 +/- 3.68; Bc: 6.05 +/- 3.62; Bl: 8.39 +/- 4.60; Cc: 6.87 +/- 3.45; Cl: 9.00 +/- 5.62; Dc: 13.30 +/- 5.45; Dl: 8.44 +/- 4.47; Ec: 4.10 +/- 1.54; El: 6.09 +/- 4.34. No statistically significant difference for cervical versus lateral dentin was found within treatments except for group D. Treatments performed on lateral dentin did not differ significantly. In cervical dentin, A differed from E; C from E; and D from A, B, C and E. An increased surface roughness was found in group D. Shear bond strength to dentin did not seem to depend on a hybrid layer formation, but on the direct contact of the adhesive with the mineralised dentinal surface and partly on the orientation of the dentinal tubules.

Acid Etching, Dental↗

PubMed1999

Influence of surface roughness of barrier walls on guided bone augmentation: experimental study in rabbits.

BACKGROUND: By using the guided tissue regeneration concept it is possible to augment bone, beyond the skeletal envelope, provided certain biologic, surgical, and barrier-related demands are met. Among barrier-related factors of importance are the surface properties. PURPOSE: The aim of this study was to evaluate whether different surface roughness of the barrier wall influences the amount and morphology of augmented bone in a secluded space, using a titanium cylinder as barrier device placed on the rabbit skull. MATERIALS AND METHODS: Cylinders of commercially pure titanium were fabricated by machining, using a turning tool. The inner cylinder wall was either left untreated or grit-blasted with titanium dioxide to increase surface roughness. The topographic profile of the inner surface of two cylinders (1 turned and 1 grit-blasted) was measured in vitro to achieve a numeric characterization of each type of surface topography. Two cylinders, one with grit-blasted and one with turned inner walls, were surgically placed and secured to the skull bone of each of eight rabbits. The plate of the cortical bone, facing the experimental area framed by the cylinder wall was removed, and care was taken to ensure total blood fill of the cylinders. After 3 months, the animals were sacrificed to obtain histology for histomorphometry. RESULTS: The relative volume of augmented tissue in the grit-blasted cylinders (77.9 +/- 10.5%) did not differ significantly from that in the turned cylinders (73.4 +/- 5.5%, p = .118), neither did the volume of mineralized bone (20.1 +/- 8.2% vs. 22.1 +/- 7.2%, p = .064). The trabecular density of the augmented bone was higher close to the walls of both the turned and the grit-blasted cylinders compared to the overall trabecular density within the cylinders, but no significant difference between the two groups. However, the area of mineralized bone in direct contact with the inner surface of the titanium cylinder was significantly larger in the grit-blasted (33.9 +/- 13.3%) compared to the turned cylinders (12.0 +/- 8.5%, p = .01). CONCLUSIONS: The use of titanium barriers with a grit-blasted inner surface compared to barriers with a turned surface resulted in the formation of similar amounts of bone beyond the skeletal envelope of the rabbit skull. However, a larger area of augmented mineralized bone was found in direct contact with the inner surface of the grit-blasted cylinders.

Animals↗

PubMed1999

Complications in partially edentulous implant patients: a 5-year retrospective follow-up study of 133 patients supplied with unilateral maxillary prostheses.

BACKGROUND: Numerous studies have reported successful outcomes for restoration of fully edentulous patients with Brånemark implants. However, some studies indicate more mechanical problems in restored partially edentulous situations. PURPOSE: The objective was to study patients with potential risk for mechanical complications after implant treatment. MATERIALS AND METHODS: Patients were retrospectively evaluated 5 years after implant treatment in upper jaw Appelgate-Kennedy Class II situations. Altogether 422 implants ad modum Brånemark were installed in 137 consecutively treated patients. One hundred thirty-three prostheses were placed and followed-up for 5 years, according to routine clinical protocols. RESULTS: The overall 5-year implant cumulative survival rate (CSR) was 94.0%. The corresponding CSR for loaded implants and prostheses was 97.7% and 98.4%, respectively, and the overall marginal bone loss was 0.8 mm (+/- 0.6 mm) after 5 years. Sixteen abutment screws fractured in seven patients (5%) and 17 prostheses (13%) presented loose abutment or gold screws during the follow-up period. Significantly more problems were reported in association with prostheses that included the canine (p < .05), and significantly more gold screws were working loose when only two implants were supporting the frameworks (p < .01). CONCLUSIONS: Upper jaw implant treatment in unilateral free-end situations seems to involve more mechanical problems than other implant treatment groups when only two implants can be installed and when the canine tooth is missing. However, most of these complications are easily adjusted, and the clinical survival of implants and prostheses is the same for these groups compared to other groups of partially edentulous implant patients.

Adult↗

PubMed1999

Atomic force microscopic study of commercially available implant abutments.

BACKGROUND: Clinical studies have reported a correlation between the surface roughness of implant abutments and the rate of supragingival and subgingival plaque formation. In order to maintain periimplant health, it is important to understand the relationship between abutment surface characteristics and plaque formation. PURPOSE: The aim of this study was to use high image resolution imaging techniques for analysis of implant abutment surface topography. MATERIALS AND METHODS: Five commercially available implant abutments (Brånemark, Nobel Biocide, AB, Goteborg, Sweden, Astra, Astra Tech AB, Mondal, Sweden, IMZ, Friatec AG, Mannheim, Germany, Steri-Oss, Denar Corp, Anaheim, Calif, USA, and POI, Kyocera Corp, Kyoto, Japan) were visually and quantitatively characterized using an atomic force microscope. RESULTS: Statistical analysis by analysis of variance and Fishers's Protected Least Significant Differences showed significant differences (p < .05) between arithmetic mean deviation values of surface relative to the center plane (Sa). Power spectral density analysis also was effective as a spacing parameter. Sectional profiles measured the exact length, depth, or height of the specific features on the images. CONCLUSIONS: Within the limits of this study, the Brånemark, Astra and IMZ abutments displayed turning marks in x direction from the procedure. The Steri-Oss abutment showed smoothest surface among the five abutments tested.

Analysis of Variance↗

PubMed1998

Quantitative and qualitative investigations of surface enlarged titanium and titanium alloy implants.

Screw shaped implants of commercially pure (c.p.) titanium and titanium-6aluminum-4vanadium (Ti6A14V) were blasted with particles of TiO2 of mean sizes of 25 microns (Group I) and 75 microns (Group II) and inserted in rabbit bone for 3 months. The surface roughness of the implants was examined and quantified with an optical scanning 3-dimensional instrument (TopScan 3D system), revealing the two alloy surfaces in each group had similar surface roughness. Biomechanical (removal torque) tests showed the c.p. titanium implants to be significantly more stable in the bone bed than those of Ti6A14V. In Group I, the c.p. titanium implants demonstrated a mean removal torque of 38 N cm while the Ti6A14V demonstrated a mean removal torque of 27 N cm (P = 0.004). Group II implants revealed a mean removal torque of 70 N cm for the c.p. ti and 50 N cm for the alloy samples (P = 0.003). The removal torque values were converted to shear forces/strengths by three calculation methods, based on (a) the entire length of the implant surface in the cortical region, (b) the thickness of the cortical bone measured in close vicinity to the thread peaks and (c) the bone-metal contact length measured on the non-unscrewed neighbouring implants. Group I: (a) the c.p. ti implants revealed a mean shear force of 4 vs a mean of 3 N/mm2 for the alloy samples. Shear strengths based on (b); were 8 for c.p. ti vs 6 N/mm2 for the alloy. The mean shear strength/force if calculated according to (c) revealed 23 for c.p. ti vs 18 N/mm2 for the alloy. Corresponding numbers for Group II; (a) c.p. ti 8 compared to 6 N/mm2 for the alloy, (b) c.p. ti demonstrated a mean value of 17 vs 11 N/mm2 for the alloy. According to method (c); c.p. ti had a mean shear strength of 26 vs 22 N/mm2 for the alloy samples. Histomorphometrical comparisons were performed on 10 microns thick undecalcified ground sections in the light microscope. In both Group I and Group II, the calculations of the mean bone-to-metal contact demonstrated more bone in contact to the c.p. titanium implants than to the Ti6A14V ones. Whereas comparisons of the bone volume inside the threads demonstrated slightly higher bone volumes around the alloy samples, no statistically significant difference was obtained between the two materials histomorphometrically.

Alloys↗

PubMed1998

A histomorphometric evaluation of screw-shaped implants each prepared with two surface roughnesses.

Four different surface modifications were designed. Forty screw-shaped implants were divided into 4 groups, 10 screws in each. Every screw was prepared with 2 different surface topographies. The surface topography was measured with a confocal laser scanning profilometer and the surface roughness was characterized using 1 height, 1 spatial and 1 hybrid descriptive parameter. After 12 weeks in rabbit bone all screws were histomorphometrically evaluated. Blasted surfaces demonstrated more bone in contact to implant surface compared with turned surfaces. Most bone in close contact to implant surface was found for a surface blasted with 75 microns sized particles, numerically characterized with an average height deviation (Sa) of 1.4 microns, an average wavelength (Scx) of 11.6 microns and a developed surface area ratio (Sdr) of 1.5.

Aluminum Oxide↗

PubMed1998

Attachment and proliferation of human oral fibroblasts to titanium surfaces blasted with TiO2 particles. A scanning electron microscopic and histomorphometric analysis.

The purpose of this study was to determine the effect of c.p. titanium surfaces blasted with TiO2 particles on the biological responses of human gingival fibroblasts (HGF). Fibroblast morphology and attachment were investigated on turned (control) titanium surfaces and those blasted with 45 microns (standard), 45-63 microns, and 63-90 microns TiO2 particles. The specimens were analyzed using a confocal laser scanner and SEM. The cell profile areas were measured using a semiautomatic interactive image analyser. The figures were expressed as percent of attachment. The turned samples had the smoothest surfaces and the roughest were those blasted with 63-90 microns. All TiO2 blasted specimens had homogeneous surfaces. Cells appeared to flatten, spread and form cellular bridges with the adjacent cells. Fibroblasts on the turned titanium surfaces appeared to follow the direction of the fine irregularities on the surface but tended to spread haphazardly on the blasted surfaces. The attachment assays showed no significant difference in the percentage of fibroblast cell attachment on the standard surfaces compared to the turned surfaces. Both surfaces blasted with 45-63 microns or 63-90 microns had significantly (P < 0.05) lower percentages of cell attachment than the control. The surfaces blasted with 63-90 microns particles had the lowest rate of cell attachment. A significant correlation (P < 0.01) was found between the degree of particle size and attachment of fibroblasts after 1-72 h. It is concluded that surface micro-texture influences the attachment and growth of HGF: surfaces blasted with 45 microns TiO2 do not inhibit fibroblast attachment and smooth or finely grooved surfaces could be conducive to cellular attachment.

Air Abrasion, Dental↗

PubMed1998

Surface structure of retrieved ICLH femoral cups.

We characterized the surface structure of 21 retrieved femoral ICLH cups, as an indirect measure of surface damage, with an optical scanner specially developed for surface roughness measurements. 3 unused cups were measured and served as controls. The mean insertion time was 10 (5-15) years. 5 areas on each cup were measured, 1 on the top and 4 at the edge. The mean value of 3 different, commonly used, surface roughness parameters was calculated for the edge measurements. We found no correlation between the surface topography and clinical patient data such as age, body-weight, head-shaft angle, implantation time and wear of the polyethylene socket.

Aged↗

PubMed1997

Bone tissue reactions to an electrophoretically applied calcium phosphate coating.

Oral implants of a threaded design, calcium phosphate (CaP)-coated using an electrophoretic deposition technique, were compared to uncoated commercially pure (c.p.) titanium control in an animal study with 4 weeks and 6 months of follow-up, respectively. The 3D surface roughness of a CaP-coated implant was about three times greater than that of an uncoated control. Histomorphometric analyses of the direct bone-implant contact demonstrated a short-term advantage to the CaP-coated implants, whereas no significant difference to the uncoated titanium was found after 6 months. Comparison of the amount of bone inside or outside the threads showed similar values for test and control after 4 weeks. Significantly higher amounts of bone outside the uncoated c.p. titanium implants were measured after the long-term follow-up.

Animals↗

PubMed1997

Surface characterization and biological evaluation of spark-eroded surfaces.

Forty commercially pure titanium implants were prepared with a spark-eroding process in order to create highly increased surface roughnesses. Two degrees of roughness were achieved by altering the applied current. Surface topographical characterization was performed with SEM and an optical profilometer. The surface composition and oxide layer were investigated using Auger scanning microscopy. In the present study, there was a large difference between the stipulated and measured surface roughness, indicating the need for a careful surface characterization in each new study. After 12 wk in rabbit bone, no statistically significant difference was found with respect to peak removal torque and histomorphometric analyses. The results from the present study provide no support for further increase of the surface roughness than that possible to achieve with a blasting technique.

Journal Article↗

PubMed1996

Torque and histomorphometric evaluation of c.p. titanium screws blasted with 25- and 75-microns-sized particles of Al2O3.

A comparison was made between screw-shaped c.p. titanium implants blasted with either 25- or 75-microns particles of Al2O3. The implant surfaces were investigated with respect to topography and composition before implantation in rabbit bone. Grit blasting with 25- or 75-microns particles produced two different surface roughnesses, but no significant difference in the surface composition for the two surfaces. After 12 weeks insertion time in the rabbit tibia and femur, a higher removal torque and more bone-to-metal contact was found for the implants blasted with 75-microns particles compared with the 25-microns-blasted ones.

Aluminum Oxide↗

PubMed1996

Experimental study of turned and grit-blasted screw-shaped implants with special emphasis on effects of blasting material and surface topography.

In the rabbit tibia, commercially pure titanium implants blasted with 25-microns Al2O3 and TiO2 particles respectively were inserted and studied with respect to removal torque and histomorphometry. In the rabbit femur, as-machined implants and implants blasted with 75-microns Al2O3 particles were histomorphometrically compared. Before implant insertion, the differently produced surface topographies were characterized numerically and visually. The tibial implants blasted with different materials and the same sized (25 microns) blasting particles demonstrated similar results. Comparing implants blasted with 75-microns Al2O3 particles to as-machined implants, the blasted specimens exhibited a statistically significant higher bone-to-metal contact after 12 weeks in the rabbit bone.

Aluminum Oxide↗

PubMed1996

Characterizing three-dimensional topography of engineering and biomaterial surfaces by confocal laser scanning and stylus techniques.

Three-dimensional measurements of surface topography were performed using a confocal laser scanner and a contact stylus instrument. Three surfaces known to be difficult to evaluate were chosen to be measured on the same area with the two instruments. The measurements from the optical and the contact stylus profilometer were compared with each other and with measurements obtained from high-resolution atomic force microscopy, which served as a reference instrument. Six implants manufactured from commonly used biomaterials were also measured on the same part of the implant, but not on the same area, with the optical and the contact profilometer in order to simulate the measurements that would be performed when different laboratories measure similarly treated surfaces. The numerical and visual differences achieved when measuring the same area with the two instruments investigated were compared. In general, we found an underestimation of the surface features with the contact stylus measurement and an overestimation with the confocal scanner. The stylus readings are mainly influenced by the radius of the stylus tip, the pressure of the stylus tip on the surface, and the hardness of the material. The optical profilometer has a tendency for creating spikes when surfaces with deep slopes are measured. For relatively soft metallic biomaterials, we found that using the optical instrument is the most appropriate method for surface roughness characterization, particularly when screw-shaped implants are analysed, whereas the stylus is preferred when larger areas with substantial slopes within the surface structure are to be evaluated.

Biocompatible Materials↗

PubMed1996

Ductular reaction after submassive necrosis in humans. Special emphasis on analysis of ductular hepatocytes.

The ductular reaction to acute submassive necrosis was studied in human livers removed at the time of orthotopic liver transplantation. Single, double, and triple immunohistochemical labeling in combination with morphometry was used to analyze the phenotype and proliferative and apoptotic rates of various epithelial cell compartments. These were divided on the basis of immunohistochemistry and morphology into three subtypes: 1) CK19+/AE1+ mature bile duct epithelium, 2) HEP-PAR+ mature hepatocytes (HEPs), and 3) CK19+/AE1+ ductular hepatocyte (DH) cells lying at the interface between the portal tract connective tissue and the hepatic lobules. Cycling cells were defined as those showing Ki-67+ (MIB-1) nuclear labeling. Apoptotic cells were identified with in situ labeling using the terminal deoxynucleotidyl transferase-mediated dUTP-digoxigenin nick end labeling assay. Special emphasis was placed on DHs that appeared at the interface between the portal tracts and hepatic lobules. During the recovery phase from submassive hepatic necrosis, subtraction of the rate of cell death from the proliferative index shows that all of the epithelial compartments experience a net increase in the number of cells. The highest proliferation rate occurs in the DHs, which is significantly (P < 0.0001) higher than the proliferation rate seen in either the HEP or bile duct epithelium compartments. Immunohistochemical analysis of the highly proliferative DH compartment shows it to be a heterogeneous population with unique phenotypic features. Like epithelial cells in the ductal plate of fetal liver and cholangiocarcinomas, DHs are positioned on a laminin-rich matrix and focally express vimentin and Lewis(x) and show up-regulation of bcl-2 and type IV collagenase. However, unlike ductal plate cells, DHs are CD34 and alpha-fetoprotein negative. Although a subpopulation of DHs share phenotypic features with mature bile duct epithelium (AE1/cytokeratin 19 and type IV collagenase positive) or HEP (HEP-PAR, albumin, and alpha-1-antitrypsin positive), they are also clearly separate from both populations; DHs are negative or only weakly stain for glutathione-S-transferase-pi and are type IV collagenase positive. Moreover, occasional DHs also co-expressed HEP-PAR or alpha-1-antitrypsin and AE1, indicative of both hepatocyte and ductular differentiation. These findings suggest that DHs seen in human livers after submassive necrosis may represent a transient amplifying population arising from a progenitor population located in or near the canals of Herring. In addition, injured hepatocytes can express cytokeratin 19 and AE1, which normally are biliary intermediate filaments.

Adult↗