The purpose of this study was to determine the ability of long shelf-life milk to serve as a temporary storage medium for the maintenance of periodontal ligament (PDL) cell viability on avulsed teeth. PDL cells were plated onto 24-well culture plates and allowed to attach for 24 h. Minimal Essential Medium was replaced with regular pasteurized milk (refrigerated milk), long shelf-life milk (Parmalat), or Save-A-Tooth. Tap water served as the negative control, and Minimal Essential Medium served as the positive control. The tissue culture plates were incubated at 37 degrees C for 1, 2, 4, or 8 h. Cell viability was determined using a cell proliferation assay (CellTiter 96 AQ Assay) and absorbance read at 490 nm. ANOVA indicated that all media performed significantly better than tap water at all time periods. At 8 h, PDL cell viability in regular pasteurized milk and long shelf-life milk were significantly greater than in Save-A-Tooth (p < or = 0.001). There was no significant difference between regular pasteurized milk and long shelf-life milk at any time period. These results suggest that long shelf-life milk, which has the advantage of not requiring refrigeration, is as effective a storage medium for avulsed teeth as regular pasteurized milk and more effective than Save-A-Tooth.

The purpose of this study was to test the feasibility of adapting a new microtensile testing technique to measure resin cement bond strengths to the cervical, middle, and apical thirds of root canals. Post spaces were created in extracted human teeth, and the roots were ground flat on one side to expose the canal and permit ideal placement of one of two resin cements (Panavia 21 or C&B Metabond). After 48 h of storage, serial 1-mm-thick cross-sections were cut to create 6-10 specimens per root. The first three specimens were from the cervical third, the next three were from the middle third, and the last three were from the apical third of the root. Each 1 x 1 x 8 mm specimen was pulled to failure in a miniature testing machine. The results indicated that both resin cements produced high bond strengths (12-23 MPa), and that bond strengths to the apical third were significantly higher (p < 0.05) than to the cervical or middle third with either cement. This new method shows promise for evaluating resin bond strengths within root canals.

The anatomy of third molars has been described as unpredictable. However restorative, prosthetic, and orthodontic considerations often require endodontic treatment of third molars in order for them to be retained as functional components of the dental arch. The purpose of this study was to investigate and characterize the anatomy of maxillary and mandibular third molars. One hundred fifty maxillary and 150 mandibular extracted third molars were vacuum-injected with dye, decalcified, and made transparent. The anatomy of the root canal system was then recorded. Seventeen percent of mandibular molars had one root (40% of which contained two canals), 77% had two roots, 5% had three roots, and 1% had four roots. Teeth with two roots exhibited highly variable canal morphology, containing from one to six canals, including 2.2% that were "C-shaped." Fifteen percent of maxillary molars had one root, 32% had two roots, 45% had three roots, and 7% had four roots. Teeth with one root demonstrated the most unusual morphology, with the number of canals varying from one to six. An in vivo study of the canal morphology of treated third molars is suggested to provide the practitioner with an understanding of the clinical implications of third molar root anatomy.

The purpose of this study was to determine the efficacy of several milk substitutes compared to whole milk in maintaining the viability of human periodontal ligament (PDL) cells on avulsed teeth. PDL cells were obtained from freshly extracted, healthy third molars and cultured in Eagle's minimal essential media (EMEM). The cells were plated onto 24-well culture plates and allowed to attach for 24 h. EMEM was replaced with refrigerated whole milk (positive control), reconstituted powdered milk, evaporated milk, or one of two baby formulas (Similac or Enfamil). Tap water served as the negative control. Tissue culture plates were incubated with the experimental media at 37 degrees C for 1, 2, 4, or 8 h. Cell viability was determined by a cell proliferation assay (CellTiter 96 AQ Assay), with absorbance read at 450 nM. A two-way ANOVA (p < 0.001) indicated that at 1 h there was no difference in the effect on PDL cell viability between any of the materials and whole milk. At 2 h, Enfamil and Similac performed significantly better than whole milk, whereas evaporated milk performed worse. At 4 h, Enfamil performed better than whole milk, whereas all other milk substitutes performed worse. At 8 h, all substitutes performed worse than whole milk. These results suggest that Enfamil, which is supplied in powder form that does not require special storage and has a shelf life of 18 months, is a more effective storage medium for avulsed teeth than pasteurized milk for at least 4 h.