T. R. Pitt Ford

Physical and chemical properties of a new root-end filling material.

This study determined the chemical composition, pH, and radiopacity of mineral trioxide aggregate (MTA), and also compared the setting time, compressive strength, and solubility of this material with those of amalgam, Super-EBA, and Intermediate Restorative Material (IRM). X-ray energy dispersive spectrometer in conjunction with the scanning electron microscope were used to determine the composition of MTA, and the pH value of MTA was assessed with a pH meter using a temperature-compensated electrode. The radiopacity of MTA was determined according to the method described by the International Organization for Standardization. The setting time and compressive strength of these materials were determined according to methods recommended by the British Standards Institution. The degree of solubility of the materials was assessed according to modified American Dental Association specifications. The results showed that the main molecules present in MTA are calcium and phosphorous ions. In addition, MTA has a pH of 10.2 initially, which rises to 12.5 three hours after mixing. MTA is more radiopaque than Super-EBA and IRM. Amalgam had the shortest setting time (4 min) and MTA the longest (2 h 45 min). At 24 h MTA had the lowest compressive strength (40 MPa) among the materials, but it increased after 21 days to 67 MPa. Finally, except for IRM, none of the materials tested showed any solubility under the conditions of this study.

Mineral trioxide aggregate stimulates a biological response in human osteoblasts

We report a novel material that appears to stimulate cytokine production in human osteoblasts and allow good adherence of the cells to the material. We have examined cultured osteoblasts (MG-63) in the presence of mineral trioxide aggregate (MTA) as set in moist conditions; secondly, we examined the behavior of these MG-63 cells with respect to cytokine and osteocalcin production and alkaline phosphatase activity. Standard ELISA assays were used for assessment of interleukin (IL)-1 alpha, IL-1 beta, IL-6, macrophage colony stimulating factor (M-CSF), and osteocalcin. Furthermore the levels of alkaline phosphatase were measured to establish the level of differentiation of the cells. Cells without MTA served as controls. Cells also were grown in the presence of polymethylmethacrylate (PMA), the commonly used orthopedic cement. In all dishes cells were seen adhering to the base and MTA at 6 h and had increased to confluence at 144 h. IL-1 alpha (175.1 +/- 32.6 pg/mL), IL-1 beta (154.0 +/- 26.7 pg/mL), and IL-6 (214.7 +/- 21.8 pg/mL) were raised when the cells were grown in the presence of MTA at 144 h, with raised values at all time intervals. M-CSF appeared to be unaffected although the overall value was high (7,045.0 +/- 89.5 pg/mL). In contrast, cells grown in the absence of MTA produced negligible amounts of these cytokines (< pg/mL) as did those cells grown in the presence of PMA. Osteocalcin production increased when cells were grown on MTA from 3.8 +/- 0.87 ng/mL to 19.7 +/- 2.8 ng/mL. No osteocalcin could be detected with PMA. Cells in contact with MTA also appeared to have levels of alkaline phosphatase similar to those reported elsewhere (4.3 +/- 0.21 mumol/mg protein/min). No cells could be found attached to PMA and so no alkaline phosphatase activity could be measured.

Osteoblast biocompatibility of mineral trioxide aggregate

This study investigated the biocompatibility of variants of mineral trioxide aggregate (MTA), by culturing human MG63 osteosarcoma cells in the presence of materials, observing cytomorphology and cell growth, and then assaying cytokine expression from the cells. Reference materials were employed. Cell growth was quantified by preparing samples (n = 6) at 2, 4 and 7 days, for viewing by scanning electron microscopy and then scoring the amount of material that was covered by healthy cells. Subsequently, samples of culture media were tested using ELISA assays for expression of Interleukin (IL)-1alpha, IL-6, IL-8, IL-11 and macrophage colony stimulating factor (M-CSF). These assays were compared with controls where no material was present, and where media and fetal calf serum had not been exposed to cells. Results showed good cell growth on MTA. Expression of IL-6 from cells was only evident in the presence of MTA and Interpore 200. Interleukin-8 was expressed in high concentrations only in the presence of MTA. There was no evidence of expression of IL-1alpha or IL-11 with any material. Production of M-CSF was high for all materials. It appears that the variants of MTA are biocompatible and suitable for use in clinical trials.

An evaluation of accelerated Portland cement as a restorative material

Biocompatibility of two variants of accelerated Portland cement (APC) were investigated in vitro by observing the cytomorphology of SaOS-2 osteosarcoma cells in the presence of test materials and the effect of these materials on the expression of markers of bone remodelling. Glass ionomer cement (GIC), mineral trioxide aggregate (MTA) and unmodified Portland cement (RC) were used for comparison. A direct contact assay was undertaken in four samples of each test material, collected at 12, 24, 48 and 72 h. Cell morphology was observed using scanning electron microscopy (SEM) and scored. Culture media were collected for cytokine quantification using enzyme-linked immunosorbent assay (ELISA). On SEM evaluation, healthy SaOS-2 cells were found adhering onto the surfaces of APC variant, RC and MTA. In contrast, rounded and dying cells were observed on GIC. Using ELISA, levels of interleukin (IL)-1beta, IL-6, IL-18 and OC were significantly higher in APC variants compared with controls and GIC (p<0.01), but these levels of cytokines were not statistically significant compared with MTA. The results of this study provide evidence that both APC variants are non-toxic and may have potential to promote bone healing. Further development of APC is indicated to produce a viable dental restorative material and possibly a material for orthopaedic

New dimensions in endodontic imaging: part 1. Conventional and alternative radiographic systems

Conventional radiographs used for the management of endodontic problems yield limited information because of the two-dimensional nature of images produced, geometric distortion and anatomical noise. These factors often act in combination. This review paper assesses the limitations of periapical radiographs and seeks to clarify three-dimensional imaging techniques that have been suggested as adjuncts to conventional radiographs. These include tuned aperture computed tomography, magnetic resonance imaging, ultrasound, computed tomography and cone beam computed tomography (CBCT). Of these techniques, CBCT appears to be an effective and safe way to overcome some of the problems associated with conventional radiographs.

Detection of periapical bone defects in human jaws using cone beam computed tomography and intraoral radiography

AIM To compare the diagnostic accuracy of intraoral digital periapical radiography with that of cone beam computed tomography (CBCT) for the detection of artificial periapical bone defects in dry human jaws. METHODOLOGY Small and large artificial periapical lesions were prepared in the periapical region of the distal root of six molar teeth in human mandibles. Scans and radiographs were taken with a charged couple device (CCD) digital radiography system and a CBCT scanner before and after each periapical lesion had been created. Sensitivity, specificity, positive predictive values, negative predictive values and Receiver Operator Characteristic (ROC) curves as well as the reproducibility of each technique were determined. RESULTS The overall sensitivity was 0.248 and 1.0 for intraoral radiography and CBCT respectively, i.e. these techniques correctly identified periapical lesions in 24.8% and 100% of cases, respectively. Both imaging techniques had specificity values of 1.0. The ROC Az values were 0.791 and 1.000 for intraoral radiography and CBCT, respectively. CONCLUSIONS With intraoral radiography, external factors (i.e. anatomical noise and poor irradiation geometry), which are not in the clinicians control, hinder the detection of periapical lesions. CBCT removes these external factors. In addition, it allows the clinician to select the most relevant views of the area of interest resulting in improved detection of the presence and absence of artificial periapical lesions.

Prophylactic treatment of dens evaginatus using mineral trioxide aggregate.

Two case reports with dens evaginatus are presented. Each patient had one tooth affected. There was a prominent tubercle on the occlusal surface of the mandibular second premolar. Under local anesthesia and rubber dam isolation a partial pulpotomy was conducted and mineral trioxide aggregate was placed. After 6 months the teeth were removed as part of planned orthodontic treatment. Histological examination of these teeth showed an apparent continuous dentin bridge formation in both teeth, and the pulps were free of inflammation. These cases show that mineral trioxide aggregate can be used as an alternative to existing materials in the proplylactic treatment of dens evaginatus.

Effect of super-EBA as a root end filling on healing after replantation

The effect of Super-EBA cement as a root-end filling placed in teeth before replantation was examined in eight molar roots in monkeys. After extraction, root ends were resected, the canals contaminated with oral bacteria, root-end cavities prepared, and fillings of Super-EBA placed before replantation. After 8 wk, the jaws were removed and prepared for histological examination. The tissue response to Super-EBA was very mild, with only a few inflammatory cells being observed at the root end of 3 of the 8 roots filled. Previous work showed a similarly mild response to Intermediate Restorative Material and a very much more severe response to amalgam. It is concluded that the tissue response to Super-EBA as a root-end filling is acceptable and considerably more favorable than that to amalgam.

Effect of IRM root end fillings on healing after replantation

The effect of IRM as a root end filling placed in teeth prior to replantation was examined in 21 molar teeth in monkeys. After extraction, root ends were resected, the canals contaminated with oral bacteria, root end cavities prepared, and fillings of IRM or amalgam placed prior to replantation. After 8 wk the jaws were removed and prepared for histological examination. Bacteria were demonstrated in only 9 of 15 teeth filled with IRM; 18 of the roots (60%) were associated with inflammation, which was only moderate or severe around 5 (17%), and extended > 0.1 mm around only 2 roots. In contrast, of the 6 teeth filled with amalgam, all contained bacteria in the root canals and 11 roots were associated with moderate or severe inflammation, which around 8 roots extended > 0.5 mm. The difference in severity of inflammation for the two materials was statistically significant (p < 0.001). The tissue response to root end fillings of IRM in replanted teeth was less severe and less extensive than that to amalgam.

The radiographic detection of periapical lesions in dogs.

The study investigated the correlation between the radiographic and histologic examinations of periapical lesions in dogs. The roots of four dogs were examined 3 months after root fillings had been placed and those of two dogs 1 year after placement of root fillings. Overall, as the extent of inflammation increased so did the size of the radiographic lesions, but there was some disagreement between methods, particularly in the detection of normal apices. The examination of radiographs could not be regarded as a substitute for histologic examination.