The mechanical mixer improved elastic recovery and compressive strength of the alginate impression materials tested and had no effect on strain in compression and tear energy. A mechanical mixer facilitates the mixing of alginate impression materials and improves some mechanical properties.

IntroductionPeripheral giant cell granuloma and peripheral ossifying fibroma are clinicopathologically distinct gingival lesions. Both are included in clinical differential diagnoses of common benign and reactive gingival epulides in humans. It is often impossible to make a clinical distinction between the two entities, thereby making definitive diagnosis dependent on histopathologic features. While our search of the English literature revealed several reports of peripheral giant cell granuloma with ‘bone formation’, we were unable to identify any reports of hybrid peripheral ossifying fibroma-peripheral giant cell granulomas.Case presentationWe report a case of a 44-year-old Caucasian man presenting with a three-month history of swelling of his right posterior mandible, related to an area of previous dental implant restoration. A clinical examination revealed modest extraoral facial swelling of his right posterior mandible, while an intraoral examination showed a 45×25×15mm sessile, lobular soft tissue mass of the right posterior mandibular gingiva. The mucosal covering of the lesion exhibited focal surface ulceration. A panoramic radiograph showed two implants at the vicinity of the lesion with no other significant findings. An excisional biopsy of the lesion followed by histopathologic examination of the biopsy specimen revealed salient and distinctive features of peripheral giant cell granuloma and of peripheral ossifying fibroma, estimated at near equal proportions. This raises the possibility of a hybrid odontogenic lesion.ConclusionThe presentation of this lesion, with areas of peripheral giant cell granuloma along with a distinct area of extensive osseous formation and stroma reminiscent of a peripheral ossifying fibroma, justifies consideration of this as a possible hybrid lesion. Although the biologic behavior of a combined lesion is not anticipated to deviate significantly from that of either of the single entities, this case resurrects an enduring debate as to whether peripheral giant cell granuloma and peripheral ossifying fibroma are simply parts of a disease spectrum, or whether some of these lesions represent true hybrid lesions. It is therefore recommended that more cases with histopathologic features similar to the lesion in our case be reported in the literature to further elucidate the histogenesis of these lesions.

Purpose To evaluate the wear resistance of a recently developed three‐dimensional (3D) printed denture teeth resin compared to three commercially available prefabricated denture teeth. Materials and Methods A total of 88 maxillary first molar denture teeth were evaluated: C (Classic; Dentsply Sirona, York, PA), DCL (SR Postaris DCL; Ivoclar Vivadent, Schaan, Liechtenstein), IPN (Portrait IPN; Dentsply Sirona, York, PA), and F (Denture Teeth A2 Resin 1 L; Formlabs, Somerville, MA). The 3D printed denture tooth specimens were fabricated from a methacrylate‐based photopolymerizing resin using stereolithography (SLA). Denture teeth were subjected to a three‐body wear test with a poly(methylmethacrylate) (PMMA) abrasive slurry. A Leinfelder‐style four station wear apparatus with custom bullet‐shaped milled zirconia styli was utilized with a load force of 36–40 N at 1.7 Hz for 200,000 cycles. Maximum depth of wear was measured using a lab grade scanner and analyzing software program. Data were analyzed using a one‐way ANOVA followed by the Tukey's Multiple Comparisons post hoc test (α = 0.05). Results A statistically significant difference in depth of wear was found between denture tooth materials (p < 0.001). The mean vertical depth of wear for the 3D printed denture teeth (0.016 ± 0.010 mm) was statistically significantly less than the prefabricated denture teeth. The highly cross‐linked denture teeth, DCL (0.036 ± 0.011 mm) and IPN (0.035 ± 0.014 mm), exhibited statistically significantly less wear than the conventional acrylic denture teeth. The conventional acrylic denture teeth demonstrated the greatest wear (0.058 ± 0.014 mm). No significant difference in depth of wear was found between DCL and IPN (p > 0.001). Conclusions Denture tooth material significantly influences the depth of wear. The 3D printed denture teeth demonstrated superior wear resistance compared to the commercially available prefabricated denture teeth when opposed to zirconia. Denture teeth fabricated with SLA technology may have a promising future in prosthetic dentistry.

The aim of this study was to examine the impact of psychomotor operative video demonstrations on irst-year dental students who are performing speciic procedures for the irst time in a preclinical setting. The class was randomly divided into two groups, and three restorative procedures were selected. On the date on which each procedure was to be performed in the preclinical laboratory for the irst time, one group (experimental, n=50) was shown a technique video for that speciic procedure immediately before commencing the exercise; the control cohort (n=50) did not view the video. Technical performance on procedures was evaluated by students and two calibrated and blinded examiners. The students' perceptions of the experience were also collected in a survey. All irst-year students participated in the study, for a 100% response rate. A Mann-Whitney U test did not show any group differences in technical performance (mean values on preparation: 77.1 vs. 77.8; amalgam: 82.7 vs. 82.8; composite: 79.7 vs. 78.0). A Spearman rho test revealed a signiicantly higher correlation in 13 out of 25 evaluation categories between student self-assessment and blinded examiner assessment for the experimental group. A chi-square test of questionnaire responses revealed a positive student perception of administering these videos for the preparation (X 2 =4.8, p<0.03), the amalgam restoration (X 2 =12.4, p<0.001), and the composite restoration (X 2 =11.3, p<0.001). The psychomotor video demonstrations did not immediately improve student performance on preclinical operative procedures, but they were well received by students and augmented self-assessment ability. These indings suggest that videos can be a useful teaching aid in a preclinical environment, especially regarding comprehension of concepts.

BackgroundThe purpose of this study was to compare the shear bond strengths of two color-change adhesives with a commonly used conventional light-cure adhesive while using a self-etching primer, and to compare any changes in shear bond strengths over time.MethodsOne hundred and eighty extracted bovine incisors were randomly divided into nine groups of 20 teeth each. The teeth were prepared with a self-etching primer (Transbond™ Plus) Metal lower incisor brackets were bonded directly to each tooth with two different color-change adhesives (TransbondPlus and Grēngloo™) and a control (Transbond XT). The teeth were debonded at three different time points (15 minutes, 24 hours, 1 week) using an Instron at 1.0 mm/min. The teeth that were to be debonded at 24 hours and 1 week were stored in distilled water at 37°C to simulate the oral environment. The data were analyzed by two-way analysis of variance and with Fisher’s protected least-significant difference multiple comparisons test at the P < 0.05 level of significance. Adhesive remnant index (ARI) scores were calculated for each debonded tooth.ResultsTransbond Plus at 1 week had the highest mean shear bond strength (14.7 mPa). Grēngloo tested at 24 hours had the lowest mean shear bond strength (11.3 mPa). The mean shear bond strengths for the remaining seven groups had a range of 12–14.5 mPa. Grēngloo had >80% samples presenting with an ARI score of 1 at all times. Interestingly, both Transbond groups had ARI scores of 3 in more than 50% of their samples.ConclusionTime had no significant effect on the mean shear bond strength of Transbond XT, Grēngloo, or Transbond Plus adhesive.