New Perspectives in Overcoming Bulk-Fill Composite Polymerization Shrinkage: The Impact of Curing Mode and Layering.

BACKGROUND: The purpose of this study was to investigate the effect of different light curing modes on the polymerization shrinkage of a bulk-fill composite and to evaluate the impact of two layering techniques on the cuspal deflection. METHODS: Nine different light curing modes were tested on bulk-fill composite samples in aluminum MOD cavities. Intensity, duration, and illumination distance were the factors that changed during the different curing modes. The digital image correlation method was used to visually represent the displacement of carbon particles on the materials' surface caused by shrinkage along both the horizontal and vertical axes. For simulating cuspal deflection, a separate protocol was used, with a bulk and horizontal layering technique. RESULTS: The results showed that the largest horizontal displacements were present in the soft start group (6.00 ± 0.82 µm) and in the X-tra power group (5.67 ± 1.21 µm). The smallest horizontal displacements were detected in normal curing modes (4.00 ± 1.58 µm; 4.00 ± 2.68 µm). The largest vertical displacements, at the bottom layer, were present in the normal curing mode group with a 20 s curing time (5.22 ± 1.56 µm), while the smallest vertical displacements were shown in the X-tra power group (2.89 ± 0.60 µm). The observed particle displacements showing the shrinkage of the composite were correlated with the curing mode. The bulk-fill group showed less cuspal deflection than the horizontal layering group did, but the difference was not statistically significant (p = 0.575). CONCLUSIONS: Within the limitations of this in vitro study, it can be concluded that lower intensities of curing lights (1200 mW/cm2) may perform better from the point of view of material shrinkage than high and extreme light intensities do. The pulse delay mode might be recommended in the case of bulk-fill materials. The number of layers did not significantly affect the cuspal deflection in the case of the studied composite.

Clinical bracket failure rates between different bonding techniques: a systematic review and meta-analysis.

BACKGROUND: Bracket failure increases the treatment time of orthodontic therapy and burdens patients with unnecessary costs, increased chair time, and possible new appointments. OBJECTIVE: To compare the bond failures of different orthodontic materials based on the results of available clinical studies. SEARCH METHODS: A systematic search of clinical trials was performed in the Cochrane, Embase, and Pubmed databases with no limitations. The list of investigated techniques contained conventional acid-etch primer (CM-AEP), self-etch primer (SEP), self-cure resin (SCR), and simple or resin-modified glass ionomer (RM-GIC) materials and procedures. SELECTION CRITERIA: Clinical studies reporting the failure rate of bonded brackets after using direct adhesive techniques on buccal sites of healthy teeth were included. DATA COLLECTION AND ANALYSIS: Bracket failure rates from eligible studies were extracted by two authors independently. Risk ratios (RRs) were pooled using the random-effects model with DerSimonian-Laird estimation. RESULTS: Thirty-four publications, involving 1221 patients, were included. Our meta-analysis revealed no significant difference in the risk of bracket failures between SEP and CM-AEP. After 6, 12, and 18 months of bonding, the values of RR were 1.04 [95% confidence interval (CI), 0.67-1.61], 1.37 (95% CI, 0.98-1.92), and 0.93 (95% CI, 0.72-1.20), respectively. At 18 months, bracket failure was 4.9 and 5.2% for SEP and CM-AEP, respectively. Heterogeneity was good or moderate (I2 < 42.2%). The results of RM-GIC at 12 months indicated a 57% lower risk of bracket failure using SCR as compared with RM-GIC (RR: 0.38; 95% CI, 0.24-0.61). At 18 months, bracket failures for SCR and RM-GIC were 15.8 and 36.6%, respectively (RR: 0.44; 95% CI, 0.37-0.52, I2 = 78.9%), demonstrating three to six times higher failure rate than in the case of etching primer applications. LIMITATIONS: A major limitation of the present work is that the included clinical trials, with no exceptions, showed variable levels of risk of bias. Another possible problem affecting the outcome is the difference between the clustering effects of the split mouth and the parallel group bracket allocation methods. CONCLUSIONS AND IMPLICATIONS: The results revealed no significant difference between SEP and CM-AEP up to 18 months after application. RM-GIC had much worse failure rates than acid-etching methods; additionally, the superiority of SCR over RM-GIC was evident, indicating strong clinical relevance. REGISTRATION: Prospero with CRD42020163362.

[Dental morphological and metric characteristics in contemporary and historical population of Târgu Mureș]. / Fogak morfológiai és metrikus jellegzetességeinek vizsgálata marosvásárhelyi középkori leleteken és a jelenkori helyi populáció körében.

INTRODUCTION: Teeth, as an integral part of human organism, are not exceptions from the physical anthropology changes caused by biological evolution and the way of living. Different stress factors and the natural selection are contributing to the emphasis of certain morphological characteristics. AIM: Comparison of dental metric characteristics and the presence of accessory tooth cusps between human remains from the Middle Ages and dental study models of today's patients. MATERIAL AND METHOD: Morphological characteristics of 132 teeth from 19 skulls and 694 teeth on dental models of 30 patients were examined. The mesiodistal, incisivocervical and buccolingual diameters of crowns were measured by a validated 2D image analysis method. Carabelli and talon cusps were also examined using a magnifying glass. RESULTS: Statistically significant differences between the size of the 14th-century and the present-day teeth were found in some of the teeth groups. In medieval artifacts, lateral teeth had smaller crown width than teeth measured in the contemporary population. The Carabelli cusps found in the archeological human remains belonged to grades 1 and 3 on Dahlberg scale (23.07%), while the Carabelli cusps observed in the contemporary group belonged to grades 3, 4, 5, 6 and 7 (50.90%). Talon cusp occurred only once in the contemporary group. CONCLUSION: In case of the contemporary teeth, the Carabelli cusps appeared in a more pronounced morphological form and with a higher frequency, which emphasizes the European origin of today's population. Orv Hetil. 2018; 159(30): 1235-1240.