Assessing Enamel Wear of Monolithic Ceramics With Micro-CT and Intra-oral Scanner.

OBJECTIVE: This in vitro study aimed to investigate enamel wear against 3 monolithic ceramics using 2 methods of measurement. METHODS: Three groups of standard flat monolithic ceramic specimens including zirconia-reinforced lithium silicate glass (Vita Suprinity, VITA Zahnfabrik), yttria-stabilised tetragonal zirconia (Lava Esthetic Zirconia), and lithium disilicate glass (IPS e.max Press, Ivoclar Vivadent) were prepared, with human enamel used as the control group. Each specimen was subjected to the 2-body wear test at 49 N for 250,000 cycles. Enamel antagonists were evaluated with micro-computed tomography (CT) and intra-oral scanner, allowing 3-dimensional images of vertical wear and volumetric loss of enamel antagonists to be calculated. One-way analysis of variance followed by Student-Newman-Keuls post hoc tests were used to examine the differences in vertical wear/volumetric loss amongst the groups. Paired t tests and intra-class correlations were used to compare vertical wear/volumetric loss between the micro-CT and intra-oral scanner groups. RESULTS: No significant difference in vertical wear was found amongst all groups. More volumetric loss was found in all test groups than in the control group (P < .001), but no significant difference was found amongst the test groups. There was a moderate positive correlation (r = 0.535, P = .033) between the vertical wear and volumetric loss. No significant difference between the 2 methods of measurement was found. CONCLUSIONS: Monolithic ceramics induce more enamel wear than natural teeth. Both micro-CT and intra-oral scanners can be used for measuring tooth wear with similar performance.

'Evaluation of the introduction of a dental virtual simulator on the performance of undergraduate dental students in the pre-clinical operative dentistry course'.

INTRODUCTION: Virtual reality-based platforms are becoming increasingly popular in education. The aim of this study was to evaluate the performance of undergraduate dental students with the introduction of the Moog Simodont dental trainer (VR) within the pre-clinical curriculum in the direct restoration module of the operative dentistry course using manual and digital methods. METHODS: Thirty-two randomly selected year 2 undergraduate students were divided into two groups: group 1, exposed to the Moog Simodont dental trainer (VR) and group 2, no exposure to VR. All students were then evaluated in carrying out a Class I preparation in a single-blinded fashion. All preparations were evaluated by three assessors using a traditional manual approach and a digital software. Statistical analysis of the data was performed using chi-square test (alpha = 0.05). RESULTS: The number of students who performed satisfactory preparations was more in group 1 (12/16), compared to group 2 (7/16). The percentage of satisfactory domains was significantly higher in group 1, compared to group 2, both in the manual evaluation (83.9% (94/112) and 59.8% (67/112) in groups 1 and 2, respectively) and in the digital evaluation (85.7% (96/112) and 55.4% (62/112) in groups 1 and 2, respectively) (P < .05). There was no significant difference between the manual and digital methods of evaluation with regard to the percentage of satisfactory or unsatisfactory preparations (P > .05). CONCLUSIONS: The use of the Moog Simodont dental trainer (VR) significantly improved the satisfactory performance of students. The virtual reality simulator may be a valuable adjunct in the undergraduate direct restorations course and for remedial student.

Human serum promotes Candida albicans biofilm growth and virulence gene expression on silicone biomaterial.

OBJECTIVES: Systemic candidal infections are a common problem in hospitalized patients due to central venous catheters fabricated using silicone biomaterial (SB). We therefore evaluated the effect of human serum on C. albicans biofilm morphology, growth, and the expression of virulence-related genes on SB in vitro. METHODS: We cultivated C. albicans SC5314 (wild-type strain, WT) and its derivative HLC54 (hyphal mutant, HM) for 48 h in various conditions, including the presence or absence of SB discs, and human serum. The growth of planktonic and biofilm cells of both strains was monitored at three time points by a tetrazolium salt reduction assay and by scanning electron microscopy. We also analyzed by RT-PCR its expression of the virulence-related genes ALS3, HWP1, EAP1, ECE1, SAP1 - SAP10, PLB1, PLB2, PLC and PLD. RESULTS: At each time point, planktonic cells of WT strain cultured in yeast nitrogen base displayed a much higher expression of EAP1 and HWP1, and a moderately higher ALS3 expression, than HM cells. In planktonic cells, expression of the ten SAP genes was higher in the WT strain initially, but were highly expressed in the HM strain by 48 h. Biofilm growth of both strains on SB was promoted in the presence of human serum than in its absence. Significant upregulation of ALS3, HWP1, EAP1, ECE1, SAP1, SAP4, SAP6 - SAP10, PLB1, PLB2 and PLC was observed for WT biofilms grown on serum-treated SB discs for at least one time point, compared with biofilms on serum-free SB discs. CONCLUSIONS: Human serum stimulates C. albicans biofilm growth on SB discs and upregulates the expression of virulence genes, particularly adhesion genes ALS3 and HWP1, and hydrolase-encoding genes SAP, PLB1 and PLB2. This response is likely to promote the colonization of this versatile pathogen within the human host.

Differences in dentofacial characteristics between southern versus northern Chinese adolescents.

AIM: To compare the dentofacial characteristics of southern and northern Chinese adolescents. METHODS: A southern Chinese sample comprised 70 males (Mean age 12.4 +/- 0.60 years) and 60 females (Mean age 12.5 +/- 0.4 years), and a northern Chinese sample consisted of 50 males (Mean age 12.8 +/- 1.8 years) and 50 females (Mean age 12.4 +/- 1.2 years). All subjects had a Class I molar relationship with no or minimal crowding, a well balanced cephalometric profile, and no history of orthodontic treatment. Patient cephalograms were traced and digitized and McNamara's analysis applied. RESULTS: A smaller midface and a shorter overall mandibular length were observed in southern Chinese, whereas significantly increased vertical dimension and a retrusive chin were noted in northern Chinese. Protrusive upper and lower incisors and a protrusive upper lip were found in southern Chinese. CONCLUSIONS: There were significant differences in dentofacial morphology between southern and northern Chinese adolescents. It is suggested that separate cephalometric norms be used for patients originating from different parts of China.

Assessment of maxillary position. Implant vs cephalometric methods.

OBJECTIVE: To compare changes in maxillary position assessed from a maxillary implant and three cephalometric methods based on linear measurements. METHODS: Series of tracings of the maxilla obtained around puberty from an implant study were analyzed. The displacement of the implant was used to determine the direction and amount of "actual" maxillary growth. Displacement of point A was measured according to three cephalometric methods. The values obtained from absolute, horizontal, and vertical displacement of point A by three cephalometric methods and by the implant method were compared. RESULTS: Results showed that estimation of displacement of the maxilla by three cephalometric methods (point A) was significantly larger than that of the implant method in all directions. The average difference in the horizontal plane was 0.7 mm, 1.2 mm, and 1.6 mm, respectively; the average difference in the vertical plane was 2.2 mm, 2.5 mm, and 3.6 mm, respectively. CONCLUSIONS: Estimations of changes in maxillary position by the implant method and by cephalometric methods were not proportional. All three cephalometric methods overestimated changes in the position of the maxilla.