Effects of ceramic thickness, ceramic translucency, and light transmission on light-cured bulk-fill resin composites as luting cement of lithium disilicate based-ceramics.

PURPOSE: To assess the effects of ceramic thickness, ceramic translucency, and light transmission on restorative composites used as luting cement for lithium disilicate-based ceramics. METHODS: Four luting types of cement were tested (n=8); a dual-cured resin cement (Multilink N), a light-cured conventional flowable composite (Tetric N-Flow), and two light-cured bulk-fill flowable composites (Tetric N-Flow Bulk Fill and X-tra base). The 20 s- or 40 s-light (1000 mW/cm2) was transmitted through 1- or 2-mm-thick high- or low-translucency (HT- or LT-) ceramic discs (IPS e.Max press) to reach the 1-mm-thick luting cement. Light transmitted to cement without ceramic served as a control. Vickers hardness number (VHN), flexural strength (FS), fractography, and degree of conversion (DC) were evaluated. One-way and multi-way analysis of variance was conducted to determine the effects of factors on VHN and FS. RESULTS: Ceramic thickness, light transmission time, and cement type significantly affected the VHN of the luting cement (P < .000). Only Multilink N (LT- and HT-1mm) and Tetric N-Flow (HT-1mm) reached 90% VHN of corresponding control by 20 s-light transmissions, but Tetric N-Flow exhibited lowest VHN and approximately 1/3-1/2 VHN of Multilink N (P < 0.05). X-tra base expressed superior physicochemical properties to Tetric N-Flow Bulk Fill (P < 0.05) and reached >90% VHN of control in all conditions with 40 s-light transmissions except for LT-2 mm. DC, FS, and fractography supported these findings. CONCLUSIONS: The light-cured bulk-fill composite served as a luting cement for lithium-disilicate-based ceramics in a product-dependent manner. Light transmission time is crucial to ensure sufficient luting cement polymerization.

Dental malformations associated with biallelic MMP20 mutations.

BACKGROUND: Matrix metallopeptidase 20 (MMP20) is an evolutionarily conserved protease that is essential for processing enamel matrix proteins during dental enamel formation. MMP20 mutations cause human autosomal recessive pigmented hypomaturation-type amelogenesis imperfecta (AI2A2; OMIM #612529). MMP20 is expressed in both odontoblasts and ameloblasts, but its function during dentinogenesis is unclear. METHODS: We characterized 10 AI kindreds with MMP20 defects, characterized human third molars and/or Mmp20-/- mice by histology, Backscattered Scanning Electron Microscopy (bSEM), µCT, and nanohardness testing. RESULTS: We identified six novel MMP20 disease-causing mutations. Four pathogenic variants were associated with exons encoding the MMP20 hemopexin-like (PEX) domain, suggesting a necessary regulatory function. Mutant human enamel hardness was softest (13% of normal) midway between the dentinoenamel junction (DEJ) and the enamel surface. bSEM and µCT analyses of the third molars revealed reduced mineral density in both enamel and dentin. Dentin close to the DEJ showed an average hardness number 62%-69% of control. Characterization of Mmp20-/- mouse dentin revealed a significant reduction in dentin thickness and mineral density and a transient increase in predentin thickness, indicating disturbances in dentin matrix secretion and mineralization. CONCLUSION: These results expand the spectrum of MMP20 disease-causing mutations and provide the first evidence for MMP20 function during dentin formation.

Biomechanical behavior of cavity design on teeth restored using ceramic inlays: An approach based on three-dimensional finite element analysis and ultrahigh-speed camera.

Ceramic fracture and debonding are the primary failures that follow ceramic inlay and can lead to stress and tooth fracture. In this study, we examined two designs-concave and flat-of the gingival cavity bottom for tooth cavities restored using ceramic inlays. We investigated the biomechanical behavior of ceramic inlay-restored teeth (concave and flat) through three-dimensional finite element analysis (FEA) and experimentally validated the results using an ultrahigh-speed camera. We conducted in vitro real-time recording of the deformation of a restored tooth during loading using an ultrahigh-speed camera. This technique enables further image registration to observe deformation variation and vector fields. The deformation vector fields revealed that the concave design moved the deformation toward the buccal side of the cavity bottom, whereas the flat design moved it toward the palatal side. These findings correlated with the FEA results, which indicated that the concave design constrained stress in the dentin cavity and relieved palatal stress. Our results suggest that incorporating a concave design in cavity preparation can improve the fracture resistance of ceramic inlay-restored teeth, preventing unrestorable fractures. The current study is the first to utilize an ultrahigh-speed camera in dental biomechanics, and such cameras are useful for nondestructive and dynamic analysis. STATEMENT OF SIGNIFICANCE: First utilize ultrahigh-speed cameras in dental biomechanics analysis. Tooth fracture videos captured by ultrahigh-speed camera helps us learn fracture mechanics in between tooth cavity design and ceramic inlay. Concave design leads to stress in safer areas that causes a less damaging fracture. Minimal invasive preparation by concave design strengthens tooth fracture resistance. Non-destructive data from ultrahigh-speed cameras combined with FEA can get more insight into how the stress and strain derived in biomaterials.

Restoring Large Defect of Posterior Tooth by Indirect Composite Technique: A Case Report.

Advances in adhesive dentistry have led to increased use of indirect restorations. In some situations, indirect composite techniques are more advantageous than direct composite filling techniques, such as establishing proper occlusal and interproximal anatomy, reducing polymerization shrinkage stress, and promoting the degree of conversion. This article presents a case about restoring the lower right first molar with extensive loss of tooth structure by the composite onlay to achieve a proper anatomic form and rehabilitate chewing function. This one-year clinical case encourages clinicians to manage large decay of posterior tooth conservatively. The given functional and esthetic outcomes demonstrate the promising applicability of the indirect composite technique.

Reply to Alizadeh's Letter to the Editor Re: Lu, P.Y. et al., Nutrients 2017, 9, 38.

n/a.

Dietary Patterns and Pancreatic Cancer Risk: A Meta-Analysis.

A number of studies have examined the associations between dietary patterns and pancreatic cancer risk, but the findings have been inconclusive. Herein, we conducted this meta-analysis to assess the associations between dietary patterns and the risk of pancreatic cancer. MEDLINE (provided by the National Library of Medicine) and EBSCO (Elton B. Stephens Company) databases were searched for relevant articles published up to May 2016 that identified common dietary patterns. Thirty-two studies met the inclusion criteria and were finally included in this meta-analysis. A reduced risk of pancreatic cancer was shown for the highest compared with the lowest categories of healthy patterns (odds ratio, OR = 0.86; 95% confidence interval, CI: 0.77-0.95; p = 0.004) and light-moderate drinking patterns (OR = 0.90; 95% CI: 0.83-0.98; p = 0.02). There was evidence of an increased risk for pancreatic cancer in the highest compared with the lowest categories of western-type pattern (OR = 1.24; 95% CI: 1.06-1.45; p = 0.008) and heavy drinking pattern (OR = 1.29; 95% CI: 1.10-1.48; p = 0.002). The results of this meta-analysis demonstrate that healthy and light-moderate drinking patterns may decrease the risk of pancreatic cancer, whereas western-type and heavy drinking patterns may increase the risk of pancreatic cancer. Additional prospective studies are needed to confirm these findings.

[A rare case of Silver-Russell syndrome in adult and literature review].

Silver-Russell syndrome (SRS) is a rare genetic disorder with non-specific manifestations and severity, so that the clinical diagnosis of SRS remains difficult. We reported a 23-year-old female patient with SRS characterized with short body stature, asymmetry, obesity, fifth finger clinodactyly and dislocation of hip. The patient had a past history of lengthening operation on the right lower limb at the age of 10. Chromosome analysis revealed (46, XX). The patient was admitted due to severe asymmetry in low extremities caused by right-side obesity. After successful orthopedic surgery in the right hips and thighs the symptoms of patient were relieved.

Organocatalyzed Michael-Henry reactions: enantioselective synthesis of cyclopentanecarbaldehydes via the dienamine organocatalysis of a succinaldehyde surrogate.

Asymmetric formal [3+2] cycloadditions of 4-hydroxybut-2-enal, a succinaldehyde surrogate, and nitroalkenes with an organocatalyst provided cyclopentanecarbaldehydes containing four consecutive stereogenic centers with excellent enantioselectivities.