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PubMed1998

Radiographic and histologic analysis of cemented double tapered femoral stems.

The macroscopic, radiographic, and histologic features of the prosthesis-cement and cementbone interfaces and adjacent bone were studied in 21 cemented hemiarthroplasties in sheep that had lived until sacrifice at 9 months. The features were compared with those immediately after implantation of the stem in the contralateral femur. The femoral stem was a double taper that was either polished collarless, matte collarless, or matte collared. There was no prosthesis to cement debonding or cement to bone radiolucent line immediately after implantation, and there was excellent interdigitation at the cement-bone interface. After 9 months there was no evidence of prosthesis to cement debonding and no stem with definite loosening. At 9 months after implantation there was evidence of bone remodeling with new bone filling what were presumed to be gaps at the cement-bone interface from immediately after implantation. Radiolucent lines at the cement-bone interface were found to represent trabeculation of the cortical bone rather than the presence of a complete fibrous interface, which was not seen. There was no difference between stem types. Sheep have been shown to be useful in a model of cemented hip arthroplasty and, although no differences were seen between stem types at 9 months after implantation, long term differences cannot be excluded.

Animals↗
PubMed1999

Comparative micromotion of fully and proximally cemented femoral stems.

This investigation studied the differences of in vitro micromotion between two stem designs. The two stem types investigated were a proximally cemented stem with distal press fit and a fully cemented stem. After initial micromotion testing to 2250 N in simulated single leg stance and stair climb, six of each stem type were loaded dynamically for 1 million cycles at 950 N at 1 Hz. Micromotion studies were repeated. The two stem types had similar micromotion. For the single leg stance, fully cemented implant motion averaged (+/- 95% confidence) 18 +/- 8 microns toggle, 41 +/- 5 microns axial, and 59 +/- 22 microns rotation. Proximally cemented implant motion averaged 20 +/- 6 microns toggle, 42 +/- 6 microns axial, and 31 +/- 15 microns rotation. For the simulated stair climb, fully cemented implant motion averaged 24 +/- 10 microns toggle, 45 +/- 8 microns axial, and 92 +/- 32 microns rotation. Proximally cemented implant motion averaged 19 +/- 10 microns toggle, 42 +/- 9 microns axial, and 87 +/- 53 microns rotation. For both loading conditions, there were no significant differences measurable between the two systems. After dynamic testing of the fully cemented implants, there were no significant changes in the micromotion of either the toggle or the rotation, but an average of 18 microns increase of axial motion was measured in the fully cemented stem. For the proximally cemented implants, there were no significant changes after dynamic testing. This differences was not considered clinically significant because roentgen stereophotogrammetric analysis studies have shown that more than 4 mm of migration is required before clinical symptoms manifest. The protocol developed in this study may help provide a screening process to determine the stability of femoral stem designs before these devices are used clinically.

Adult↗
PubMed2001

The clinical significance of vacuum mixing bone cement.

This controlled study compared the strength and porosity of 48 polymethylmethacrylate cement-implant constructs prepared with open bowl versus vacuum mix technique. Forty-eight blast finished stainless steel rods of 13 mm diameter were implanted with centralizers into 17-mm inner diameter tubes that had been retrograde filled with polymethylmethacrylate cement. The eight cement preparations used were open bowl and vacuum mixed Simplex, Osteobond, Zimmer Dough Type, or Palacos R. Six replications of each condition were performed. The tubes were maintained at 37 degrees C. Each tube was cut transversely into five segments. The center three segments were used for data analysis: pushout strength, cycles to failure, and interface porosity analysis. Rod pushout data showed there was no significant difference between open bowl and vacuum mixed samples when all cement brands were combined. Mean sheer force for Palacos R vacuum mixed samples was greater than open bowl (634+/-47 versus 423+/-171), whereas the force for the Zimmer Dough Type cement open bowl was greater than that of the vacuum mixed samples (901+/-71 versus 705 +/-82). Cycles to failure data did not show significant differences when open bowl and vacuum mixed samples were compared when cements were analyzed individually or combined. Image analysis of cement-implant interfaces showed that vacuum mixing reduced void area significantly compared with open bowl mixing in the Palacos R and Osteobond preparations. Vacuum mixing does not appear to reduce cement prosthesis interface porosity or improve its mechanical properties in all cements.

Analysis of Variance↗
PubMed2001

Femoral stem insertion generates high bone cement pressurization.

Adequate bone cement pressurization is critical in obtaining optimal femoral cement mantles during total hip arthroplasty. Pressurization can be generated during insertion of the femoral stem into the cement-filled canal. This may be clinically useful in augmenting conventional cement gun pressurization. Two factors, which were expected to influence the amount of insertion-induced pressurization, are the cement's cure state (viscosity) at the time of insertion and the femoral stem profile. This study evaluated the effect of these factors on cement pressurization during stem insertion. Femoral stems were inserted at a controlled rate into a reusable, simulated femoral canal. Intramedullary pressures were monitored at four locations along the canal's medial midline. The intrusion factor quantity, which accounts for pressure magnitude, duration of pressurization, and cement viscosity, was developed to quantify pressurization. Stem insertion into late cure stage (high viscosity) cement resulted in significantly higher intramedullary pressures (as much as 187% higher) and intrusion factors (as much as 43% higher) as compared with early stage (low viscosity) cement. The highest pressures and intrusion factors were found in the distal canal. A tapered stem profile resulted in significantly higher pressures (as much as 65%) and higher intrusion factors (as much as 63%) than a straight stem.

Arthroplasty, Replacement, Hip↗
PubMed2002

Use of injectable calcium phosphate cement for fracture fixation: a review.

Injectable osteoconductive calcium phosphate cements have been introduced as an adjunct to internal fixation for treating selected fractures. These cements harden without producing much heat, develop compressive strength, and are remodeled slowly in vivo. The main purpose of the cement is to fill voids in metaphyseal bone, thereby reducing the need for bone graft, but cements also may improve the holding strength around metal devices in osteoporotic bone. Several bioactive cements are being developed. One of these cements, Skeletal Repair System, is available in Europe and has been approved by the United States Food and Drug Administration for use in selected distal radius fractures. Cadaveric studies have shown that using Skeletal Repair System cement with conventional metal fixation in certain fractures of the distal radius, tibial plateau, proximal femur, and calcaneus can produce better stability, stiffness, and strength than metal fixation alone. Early clinical results have shown reduced time to full weightbearing when cement has been used for augmentation of tibial plateau and calcaneal fractures, more rapid gain of strength and range of motion when used in distal radius fractures, and improved stability in certain hip fractures. Bioactive cements in general also may prove useful in vertebroplasty.

Animals↗
PubMed2004

Augmentation of pedicle screw fixation strength using an injectable calcium phosphate cement as a function of injection timing and method.

STUDY DESIGN: Axial pullout tests using fresh cadaveric thoracolumbar vertebral bodies. OBJECTIVES: To evaluate the effect of a new injectable calcium phosphate cement on the axial pullout strength of both revised and augmented pedicle screws in comparison with polymethyl methacrylate and in terms of injection method. SUMMARY OF BACKGROUND DATA: Failure of pedicle screws by loosening and back out remains a significant clinical problem and is of particular concern for patients with low bone quality. Polymethyl methacrylate was shown to significantly improve the screw pullout strength. However, polymethyl methacrylate is known to have a high polymerization temperature, which may damage surrounding tissues, and a short handling time, and it lacks long-term biocompatibility. Bone mineral cements such as calcium phosphate have a longer working time, very low thermal effect, and are biodegradable as well as having good mechanical strength. Recently, new calcium phosphate cement with improved infiltration properties for better injectability has been introduced, but its performance in augmenting the pedicle screw fixation has not been tested yet. METHODS: The bone mineral densities of 52 vertebral bodies (T11-L5) were measured using dual-energy x-ray absorptiometry. In each vertebral body, a 6.5-mm-diameter and 45 +/- 5-mm-long pedicle screw was inserted into either the right or left pedicle, representing an initial intact implantation. These intact screws were pulled axially until failure at 10 mm/min. Following failure of the intact pedicle, 3.0 cc of cement was injected into the failed screw hole, representing a revision case, and the prepared screw hole in the contralateral intact pedicle representing an augmentation case. The cement was injected either to the distal tip of the screw hole (calcium phosphate-1 group, n = 19) or along the entire length of the screw hole (calcium phosphate-2 group, n = 20), and the screws were inserted. The cement was then allowed to cure for 24 hours at room temperature before both screws were pulled to failure. In 13 specimens, polymethyl methacrylate was injected along the entire length of the screw hole (polymethyl methacrylate group). Kruskal-Wallis and Mann-Whitney tests were used to compare the screw pullout strengths for study groups, whereas linear relationships between variables were assessed with scatter plots and Spearman correlation coefficients with a significance level of 0.05. RESULTS: Mean bone mineral densities of all groups were similar. A significant positive correlation was seen between bone mineral density and intact pullout strength. In revision, the pullout strength of calcium phosphate-1 was similar to that of intact, whereas the pullout strength of calcium phosphate-2 and polymethyl methacrylate was significantly greater than that of intact. In augmentation, all 3 injection methods significantly improved the pullout strength over intact. Injection of the calcium phosphate cement along the entire screw length was found to produce significantly higher pullout strengths than injection only at the distal tip of the screw in revision case. Injection of polymethyl methacrylate produced significantly higher pullout strengths than the injection of calcium phosphate by either method in both revision and augmentation. CONCLUSION: Results of this study demonstrate that the new calcium phosphate cement can improve the axial pullout strength of revised and augmented pedicle screws when injected along the entire length of the screw. This suggests that the injection method may be crucial for revision of failed pedicle screws. Considering inherent properties more favorable for in vivo application, such as nonexothermal polymerization and longer working time, and significant improvement in pullout strength, the new calcium phosphate cement may be a good alternative to polymethyl methacrylate for the augmentation of pedicle screw fixation.

Aged↗
PubMed2004

Practical applications of antibiotic-loaded bone cement for treatment of infected joint replacements.

The use of antibiotic-loaded bone cement is an accepted treatment method for infected joint arthroplasties. It is helpful to separate the use of antibiotic-loaded bone cement as a method of prophylaxis as compared with the treatment of an established infection. A low dose of antibiotic-loaded bone cement (< or = 1 g of antibiotic per batch of cement) should be used for prophylaxis, and high-dose antibiotic-loaded bone cement (> 1 g antibiotic per batch of cement) is indicated for treatment. The only commercially available antibiotic-loaded bone cement products are low dose, with the use of tobramycin or gentamicin as an antibiotic selection. High-dose antibiotic-loaded bone cement requires hand mixing by the surgeon to facilitate the use of high dosages and choices of multiple antibiotics. Treatment of infected hip and knee arthroplasties with high-dose antibiotic-loaded bone cement is aided by the use of spacers of various shapes and sizes. These spacers, whether they are static or articulating (mobile), are meant to provide local delivery of antibiotics, stabilization of soft tissues, facilitation of an easier reimplantation, and improved clinical outcomes.

Anti-Bacterial Agents↗
PubMed2006

Intradiscal cement leak following percutaneous vertebroplasty.

STUDY DESIGN: A retrospective study to detect patients with cement leakage into the disc space following vertebroplasty. OBJECTIVE: To determine the frequency, causes, and clinical significance of cement leakage into the disc space. SUMMARY OF BACKGROUND DATA: Much has been written about cement leakage into the epidural space following vertebroplasty but only little about intradiscal leakage. METHODS: A total of 66 patients with 1 cemented osteoporotic, fractured vertebra between T5 and L5 were followed for at least 2 years. Two of the senior authors (Y.M. and A.P.) evaluated independently cement leakage into the disc space, possible causes were investigated, and the clinical results were evaluated according to patient self-assessment. RESULTS: Detected in 27 patients, cement leakage into the disc space did not negatively affect patient satisfaction with the procedure. In 7 of these patients, leakage occurred through an intravertebral vacuum cleft and, in 8, through a perforation of the endplate created by the needle tip. In only 2 patients was cement found to cross the height of the vertebral body and leak into the contralateral disc. CONCLUSIONS: Apart from iatrogenic endplate perforation, cement extravasation into the disc space was always found to occur through the fractured endplate or a vacuum cleft. Placing the needle tip far from the fractured endplate and using more solid cement appear to decrease the risk of leakage.

Aged↗
PubMed1993

Light-cured glass ionomer cement as a retrograde root seal.

A light-cured ionomer cement was investigated as a retrograde root seal, without a retrograde cavity. This was compared with the material used in a retrograde cavity, and with a conventional glass ionomer cement, as a seal. The adaptation and sealing ability of the test materials were assessed using a confocal optical microscope with a fluorescent dye. The root canals of 40 extracted human single-rooted teeth were prepared and filled with gutta-percha and sealer. All the teeth were subsequently apicected, then divided into four equal groups. In one group, a retrograde cavity was prepared, and the light-cured glass ionomer cement was placed as a retrograde root filling. No retrograde cavities were prepared in the three remaining groups. The light-cured glass ionomer cement was applied directly onto the apicected root face. Two different thicknesses of light-cured glass ionomer cement were tested, a thin layer (approximately 1 mm) in one group, and a thicker layer (> 1 mm) in another group. A conventional glass ionomer cement was used in the last group, and applied directly onto the root face in a single thickness (approximately 1 mm). In the group where the light-cured glass ionomer cement was used in a retrograde cavity, the material was often well adapted to one cavity wall, but gaps were found on the opposite wall. The light-cured and conventional glass ionomer cement retrograde root seals were well adapted to the root face, regardless of the thickness of material used. The thinly applied (approximately 1 mm) light-cured glass ionomer cement retrograde root seals permitted the least leakage.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed1976

In vitro attachment of Streptococcus sanguis to dental crown and bridge cements.

The ability of a common dental plaque bacterium, Streptococcus sanguis, to adhere to dental crown and bridge cements in vitro was investigated. Cylindrical blocks of five different commercial brands of cement, with and without acquired pellicles, were indubated with buffer suspensions of S. sanguis for 1 h. Attached bacteria were counted under the microscope. S. sanguis had particularly high affinity for uncoated resin cement. In contrast, the carboxylate cement tested was a poor substrate for the adherence of this bacterium. The other cement types (zinc phosphate, zinc oxide and silico-phosphate) had intermediary qualities as adhering surfaces. The presence of an acquired pellicle, obtained by pretreatment with saliva, influenced the initial adherence of bacteria to cement in vitro. On the resin cement a salivary pellicle strongly suppressed the bacterial adhesion. For the zinc phosphate, zinc oxide and silico-phosphate cements a pellicle slightly enhanced the attachment of S. sanguis. On the carboxylate cement only few organisms attached also after pretreatment with saliva.

Cell Count↗
PubMed2006

Injectable PLGA microsphere/calcium phosphate cements: physical properties and degradation characteristics.

Calcium phosphate (CaP) cements show an excellent biocompatibility and often have a high mechanical strength, but in general degrade relatively slow. To increase degradation rates, macropores can be introduced into the cement, e.g., by the inclusion of biodegradable microspheres into the cement. The aim of this research is to develop an injectable PLGA microsphere/CaP cement with sufficient setting/cohesive properties and good mechanical and physical properties. PLGA microspheres were prepared using a water-in-oil-in-water double-emulsion technique. The CaP-cement used was Calcibon, a commercially available hydroxyapatite-based cement. 10:90 and 20:80 dry wt% PLGA microsphere/CaP cylindrical scaffolds were prepared as well as microporous cement (reference material). Injectability, setting time, cohesive properties and porosity were determined. Also, a 12-week degradation study in PBS (37 degree C) was performed. Results showed that injectability decreased with an increase in PLGA microsphere content. Initial and final setting time of the PLGA/CaP samples was higher than the microporous sample. Porosity of the different formulations was 40.8% (microporous), 60.2% (10:90) and 69.3% (20:80). The degradation study showed distinct mass loss and a pH decrease of the surrounding medium starting from week 6 with the 10:90 and 20:80 formulations, indicating PLGA erosion. Compression strength of the PLGA microsphere/CaP samples decreased siginificantly in time, the microporous sample remained constant. After 12 weeks both PLGA/CaP samples showed a structure of spherical micropores and had a compressive strength of 12.2 MPa (10:90) and 4.3 MPa (20:80). Signs of cement degradation were also found with the 20:80 formulation. In conclusion, all physical parameters were well within workable ranges with both 10:90 and 20:80 PLGA microsphere/CaP cements. After 12 weeks the PLGA was totally degraded and a highly porous, but strong scaffold remained.

Biocompatible Materials↗
PubMed2004

Nanocrystalline tetracalcium phosphate cement.

Calcium hydroxide cements can lack long-term stability and achieve sustained release by matrix-controlled diffusion of hydroxyl ions. Tetracalcium phosphate (TTCP) hydrolyzes slowly to form calcium hydroxide and a thin insoluble apatite layer that prevents further reaction. In this study, mechanical amorphization was used to create a setting calcium-hydroxide-releasing cement from TTCP. The effect of high-energy ball milling of TTCP on the mechanical properties of the cement was investigated. X-ray diffraction data were used to determine the phase composition of the set cements. An accelerated in vitro test compared pH of water after prolonged boiling of nanocrystalline TTCP cements and a calcium salicylate material. As milling time increased, cement compressive strength and degree of conversion increased. Hydroxyl ion release from the cement was comparable with that from a calcium salicylate material. This new cement system offers the antimicrobial potential of calcium salicylate materials combined with the long-term stability of insoluble apatite cements.

Anti-Bacterial Agents↗
PubMed2004

A novel test method for evaluation of the abrasive wear behaviour of total hip stems at the interface between implant surface and bone cement.

After total hip replacement, some cemented titanium stems show above-average early loosening rates. Increased release of wear particles and resulting reaction of the peri-prosthetic tissue were considered responsible. The objective was to develop a test method for analysing the abrasive wear behaviour of cemented stems and for generating wear particles at the interface with the bone cement. By means of the novel test device, cemented hip stems with different designs, surface topographies and material compositions using various bone cements could be investigated. Before testing, the cemented stems were disconnected from the cement mantle to simulate the situation of stem loosening (debonding). Subsequently, constant radial contact pressures were applied on to the stem surface by a force-controlled hydraulic cylinder. Oscillating micromotions of the stem (+/- 250 microm; 3 x 10(6)cycles; 5 Hz) were carried out at the cement interface initiating the wear process. The usability of the method was demonstrated by testing geometrically identical Ti-6A1-7Nb and Co-28Cr-6Mo hip stems (n= 12) with definite rough and smooth surfaces, combined with commercially available bone cement containing zirconium oxide particles. Under identical frictional conditions with the rough shot-blasted stems, clearly more wear particles were generated than with the smooth stems, whereas the material composition of the hip stems had less impact on the wear behaviour.

Biocompatible Materials↗
PubMed1993

Pressurization of bone cement under standard, flanged and custom acetabular components for total hip replacement.

Custom acetabular components are proposed to achieve uniform cement mantles, even in irregular acetabula presented at revision, in order to enhance fixation. One aim of developing custom components was to permit pressurization of bone cement by the components at insertion and maintain the pressure during polymerization. A model acetabulum was set up for the insertion of standard, flanged and custom components under constant force. Cement pressure was measured at the floor of the acetabulum by means of a piezoelectric diaphragm transducer. Polythene tubes were inserted in the model acetabular walls to estimate penetration of cement into cancellous bone. Insertion of the standard and flanged components caused cement pressures up to 106 kPa which decayed to less than 21 kPa as cement escaped at the rim and the components came into contact with the acetabulum. The custom component maintained a pressure of over 60 kPa during polymerization from an initial pressure of 105 kPa and examination of cement mantles on removal showed no evidence of contact. The custom component also showed enhanced penetration of cement, especially around the rim of the acetabulum. It is concluded that the custom component design achieves higher cement pressures and that better fixation will result.

Bone Cements↗
PubMed1994

The prevalence of femoral osteolysis associated with components inserted with or without cement in total hip replacements. A retrospective matched-pair series.

The prevalence of femoral osteolysis in hips in which a femoral component had been inserted without cement was compared with that in hips with a cemented component, in a retrospective matched-pair study of the results of primary total hip arthroplasties; all patients had received the same type of acetabular component. Forty-one hips in thirty-nine patients who had a Harris-Galante porous-coated total hip prosthesis without cement were matched by age, sex, weight, duration of follow-up, and diagnosis with forty-one hips in thirty-eight patients who had a hybrid total hip reconstruction; the hybrid reconstruction consisted of the same acetabular component and a Precoat femoral component inserted with a so-called third-generation cementing technique. All of the operations were done by the same surgeon, who used the same operative approach and the same course of postoperative rehabilitation. All of the patients were followed for at least four years (mean, six years). Osteolysis developed in twelve (29 percent) of the hips that had a femoral component without cement compared with none of the hips that had a cemented component (p < 0.0002). At the latest follow-up examination, none of the femoral components that had been inserted with cement were loose and none had been revised, while eight (20 percent) of the femoral components that had been inserted without cement were loose and five (12 per cent) had been revised. This retrospective matched-pair study controlled for many of the variables associated with a comparison of the rates of femoral osteolysis in separate series of femoral components fixed with and without cement.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Patterns of osteolysis around total hip components inserted with and without cement.

We reviewed the radiographs of 137 patients (137 hips) who had been managed with a total hip arthroplasty, with insertion of an extensively porous-coated femoral component without cement, because of osteoarthrosis or avascular necrosis. A porous-coated acetabular component had been inserted with cement in sixty-three of these patients (Group A) and without cement in seventy-four patients (Group B). The radiographs were examined for osteolysis, either directly adjacent to the joint or at locations remote from the joint. The mean duration of follow-up was 105 months (range, fifty-four to 142 months). The rate of osteolysis of the acetabulum in the unrevised hips in which the acetabular component had been inserted with cement was 37 per cent (nineteen of fifty-one). The osteolysis was most frequently of the linear type, a pattern that was associated with a high prevalence of loosening in the hips that had a cemented cup (30 per cent [nineteen of sixty-three]). The rate of acetabular osteolysis (18 per cent [thirteen of seventy-one]) in the patients who had a cup that had not been inserted with cement and that had not been revised was not as high as that associated with the surviving cups that had been inserted with cement (p < 0.05). The osteolysis associated with the cups that had not been inserted with cement was localized and expansile, and it was not associated with loosening of the component. However, it produced more loss of bone than did the linear pattern of osteolysis around the cemented cups.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetabulum↗
PubMed2002

Comparison of total hip arthroplasty performed with and without cement : a randomized trial.

BACKGROUND: This study was designed to compare the fixation of a Mallory-Head total hip prosthesis with and without cement. METHODS: Two hundred and fifty patients with osteoarthritis of the hip were randomized to receive a Mallory-Head total hip prosthesis designed for insertion with cement or the same prosthesis designed for insertion without cement. Neither the patient nor the outcomes assessor was aware of the type of prosthesis. Outcomes were assessed with respect to mortality, revision arthroplasty, health-related quality of life (evaluated with the Harris hip score, Merle d'Aubign and Postel hip score, McMaster-Toronto Arthritis Patient Preference Disability Questionnaire (MACTAR), Western Ontario and McMaster University Osteoarthritis Index (WOMAC), and the time trade-off technique), and the six-minute-walk test. Patients were seen at three, six, and twelve months and yearly thereafter. RESULTS: The prosthesis was inserted with cement in 124 patients and without cement in 126 patients. The mean age of the patients was sixty-four years, 48% were female, and the mean duration of follow-up was 6.3 years. There were thirteen revisions in the group that had fixation with cement and six in the group that had fixation without cement (p = 0.11), and more femoral components were revised in the group that had fixation with cement (twelve versus one; p = 0.002). All health-related quality-of-life measures improved postoperatively in both groups. CONCLUSIONS: In this randomized trial, the group that had the cemented Mallory-Head hip prostheses required more revisions of the femoral component than did the group with the cementless Mallory-Head prostheses, which was perhaps related to the titanium-alloy femoral stem. Our findings are specific to the implants evaluated in this study.

Aged↗
PubMed1981

Two-hour bacterial colonization of dental luting cements in vivo.

Test specimens of zinc phosphate, polycarboxylate, zinc oxide-EBA, silico-phosphate and resin cements were carried in the mouth for 2 hours. The bacteria adhering to the cement specimens were quantified after culture on selective and non-selective, solid media. Significantly fewer bacteria could be recovered from the EBA cement than from the other cement types. All cement specimens, as well as samples from tooth surfaces, showed selective enrichment of Actinomyces viscosus compared with the proportion of this organism in saliva. The silicophosphate and particularly the polycarboxylate cement were poor substrates for the adhesion of Streptococcus mutans. Scanning electron micrographs revealed heavy accumulations of coccoid and filamentous organisms on zinc phosphate cement surfaces. Fewer bacteria, mainly cocci, were seen on the polycarboxylate and silico-phosphate cements, whereas the micrographs of the EBA and resin cement surfaces were difficult to interpret.

Actinomyces↗