The choice of storage medium for preserving traumatically avulsed teeth is important for the success of future replantation. The objectives of this study were to evaluate the effectiveness of six different media: culture medium, alpha minimal essential medium (alpha-MEM), milk, Hank's balanced salt solution (HBSS), ViaSpan and conditioned medium (CM) to preserve cultured periodontal ligament fibroblasts (PDLF). Periodontal ligament fibroblasts were obtained from explants of human healthy extracted teeth. Plates with confluent PDLF were soaked in the various media for 2, 8 and 24 h at 4 degrees C. A control group was incubated with culture medium at 37 degrees C. After incubation, cell viability was determined by trypan blue exclusion test. Viable cells were then analyzed for mitogenic (with thymidine) and clonogenic capacity (by culturing one cell/well). Storage of PDLF up to 24 h decreased their vitality by only 2%-14%. Vitality of the PDLF after 2, 8 and 24 h was highest when stored in milk or HBSS (91%-97%) and lowest when stored in ViaSpan or CM (82%-93%). PDLF stored for 2-8 h in various media had a mitogenic capacity comparable to the control. However, increasing the storage period to 24 h decreased the mitogenicity of the cells by 3%-39%. The highest mitogenicity was found in PDLF stored in milk or HBSS and the lowest in CM or ViaSpan. The clonogenic capacity of the cells dropped by 38%-71% after 24 h and was the best indicator of the deteriorating effect of long storage. Milk and HBSS were the most effective in preserving the clonogenic capacity. Nevertheless, reduction in the viability, mitogenicity or clonogenic capacity was statistically significant in nearly all the tested media only after 24 h of incubation. In conclusion, HBSS and milk were the most effective media for preserving the viability, mitogenicity and clonogenic capacity after storage for up to 24 h at 4 degrees C.

Kaufman AY, Keila S, Yoshpe M. Accuracy of a new apex locator: an in vitro study. International Endodontic Journal , 35 , 186-192, 2002. Aim The purpose of this study was to test in an in vitro model the accuracy of a Bingo 1020 electronic apex locator, to compare the results to those of a well known apex locator, Root ZX, as well as to those of the radiographic method of tooth length determination. Methodology A total of 120 extracted teeth, preserved in Thymol solution and kept refrigerated, was used for the study. The experiment was performed on singlerooted teeth and on one-root canal, chosen randomly, in multirooted teeth. The teeth were randomly divided into 12 groups of 10 teeth each. After access preparation, the actual length (AL) was measured. The teeth were embedded in an alginate model specially developed for testing apex locators. Electronic tooth length measurements (EL) were carried out prior to root canal preparation using the two electronic apex locators (EAL) -Root ZX and Bingo 1020; three measurements were taken and an average computed. After the third measurement, the file was left in the root canal and a periapical radiograph was taken. The radiographic length (RL) was recorded by measuring the file length from the coronal reference point to the tip of the file. Each root canal was then prepared to a no. 40 K-file diameter using a standardized technique; saline was used for irrigation. Upon comple-

Emdogain (EMD), a formulation of Enamel Matrix Proteins (EMP), is used clinically for periodontal regeneration, where it stimulates cementum formation and promotes gingival healing. In this study, we investigated the in vitro effects of EMD on rat bone marrow stromal cells (BMSC) and gingival fibroblasts (GF). EMD (at 25 micro g/mL) increased the osteogenic capacity of bone marrow, as evidenced by approximately three-fold increase in BMSC cell number and approximately two-fold increase in alkaline phosphatase (ALP) activity and mineralized nodule formation. The presence of EMD in the initial stages (first 48 hrs) of the culture was crucial for this effect. In contrast, EMD did not induce osteoblastic differentiation of GF (evidenced by lack of mineralization or ALP activity) but increased up to two-fold both their number and the amount of matrix produced. These in vitro data on BMSC and GF could explain the promotive effect of EMD on bone formation and connective tissue regeneration, respectively.

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Prostaglandin E 2 (PGE 2 ) has been shown to exert a bone anabolic effect in young and adult rats. In this study we tested whether it possesses a similar effect on bone formation and bone mass in aging rats. Fifteen-month-old rats were injected daily with either PGE 2 at 5 mg/kg or vehicle for 14 days. PGE 2 treatment stimulated the rate of cancellous bone formation (a 5·5-fold increase in bone formation rate), measured by the incorporation of calcein into bone-forming surfaces at the tibial proximal metaphysis. This effect resulted in increased cancellous bone area (+54%) at the same site. Since PGE 2 treatment resulted in a much higher proportion of bone surface undergoing bone formation and thus lined with osteoblasts, we tested the hypothesis that PGE 2 stimulates osteoblast differentiation from bone marrow precursor cells both in vivo and in vitro. We found that ex vivo cultures of bone marrow stromal cells from rats injected for 2 weeks with PGE 2 at 5 mg/kg per day yielded more (4-fold) mineralized nodules and exhibited a greater (by 30-40%) alkaline phosphatase activity compared with cultures from vehicle-injected rats, attesting to a stimulation of osteoblastic differentiation by PGE 2 .We also compared the osteogenic capacity of bone marrow from aging (15-month-old) versus young (5-week-old) rats and its regulation by PGE 2 in vitro. Bone marrow stromal cell cultures from aging rats exhibited a greatly diminished osteogenic capacity, reflected in reduced nodule formation (6% of young animals) and lower alkaline phosphatase activity (60% of young animals). However, these parameters could be stimulated in both groups of animals by incubation with 10-100 nM PGE 2 . The magnitude of this stimulation was greater in cultures from aging rats (+550% vs +70% in nodule formation of aging compared with young rats).In conclusion, we demonstrate here that PGE 2 exerts a bone anabolic effect in aging rats, similar to the effect we and others have reported in young, growing rats. The PGE 2 -stimulated bone formation, which augments bone mass, most likely results from recruitment of osteoblasts from their bone marrow stromal precursors.