A genome-wide association study identifies an association between variants in EFCAB4B gene and periodontal disease in an Italian isolated population.

BACKGROUND AND OBJECTIVE: Periodontitis in one of the most prevalent dental diseases. Despite numerous studies have investigated its aetiopathogenetic factors, few works have focused on its genetic predisposition and most of them took into account only candidate genes. Therefore, we conducted a Genome Wide Association Study in an Italian isolated population aimed at uncovering genetic variants that predispose to this disorder. METHODS: Diagnosis of chronic periodontitis was made following the criteria of the American Academy of Periodontology. Patients with chronic periodontitis were grouped into different categories: slight, severe, localized and generalized. A control group composed by people without signs of periodontitis or gingivitis was defined. DNA was genotyped using 370k Illumina chips. Linear mixed model regression was used to test the association between each single nucleotide polymorphism (SNP) (independent variable) and the periodontitis status (dependent variable), controlling for confounders sex, age and smoking. The genomic kinship matrix was also used as random effect. RESULTS: Four SNPs on the gene EFCAB4B resulted significantly associated to localized periodontitis (P < 5 × 10-8 ), with the best hit on the rs242016 SNP (P = 1.5 × 10-8 ). CONCLUSION: We have identified a novel significant association between the EFCAB4B gene and localized periodontitis. These results open a new perspective in the understanding of genetic factors contributing to this common disorder.

Caries and Innate Immunity: DEFB1 Gene Polymorphisms and Caries Susceptibility in Genetic Isolates from North-Eastern Italy.

BACKGROUND: The DEFB1 gene, encoding for the constitutively expressed human ß-defensin 1 (hBD1) antimicrobial peptide is a potential candidate when studying genetic susceptibility to caries. DEFB1 genetic variations have been reported as contributing to hBD1 production impairment, leading to a greater susceptibility to be infected by oral pathogens, also leading to periodontitis. METHODS: We analysed 5 DEFB1 polymorphisms, namely 3 functional single-nucleotide polymorphisms (SNPs) at the 5'-untranslated region (UTR), -52G>A (rs1799946), -44C>G (rs1800972), and -20G>A (rs11362), 2 SNPs at the 3'-UTR, c*5G>A (rs1047031) and c*87A>G (rs1800971) SNP located in potential miRNA binding sites, looking for possible correlations with the risk to develop caries in 654 adult subjects from isolated populations of north-eastern Italy. Dental caries prevalence was evaluated with the DMFT (decayed, missing, filled teeth) index, calculated after an accurate oral examination. DEFB1 SNP genotyping was performed with an Illumina 370k high-density SNP array. RESULTS: Two DEFB1 SNPs were significantly associated with the DMFT index: the strongest association emerged from rs11362 SNP (p = 0.008). In particular G/G homozygous individuals showed a higher DMFT index compared to both G/A heterozygous and A/A homozygous individuals; rs1799946 SNP was also significantly associated with DMFT (p = 0.030), and individuals homozygous for the T allele had a higher DMFT value compared to heterozygous C/T and homozygous C/C individuals. CONCLUSIONS: Our study replicated, on a larger number of individuals, previous findings showing the association between two 5'-UTR SNPs in the DEFB1 gene and DMFT, suggesting that these polymorphisms could be considered as potential markers for assessing the risk to develop caries.

Contraction stress, elastic modulus, and degree of conversion of three flowable composites.

The aim of this study was to measure the contraction stress of three flowable resin composites and to correlate the stress with the elastic modulus and the degree of conversion. One low-shrinkage (Venus Diamond Flow) and two conventional (Tetric EvoFlow and X-Flow) flowable composites were polymerized for 40s with a light-emitting diode (LED) curing unit. Contraction force was continuously recorded for 300s using a stress-analyser, and stress values were calculated at 40s and at 300s. The maximum stress rate was also calculated for each specimen. The elastic modulus of each composite was assayed using a biaxial flexural test, and degree of conversion was analysed with Raman spectroscopy. X-Flow exhibited higher stress values than the other tested materials. Venus Diamond Flow showed the lowest stress values at 40s and at 300s, and the lowest maximum stress rate. Stress values were correlated with elastic modulus but not with degree of conversion, which was comparable among all tested materials.

The effect of ageing on the elastic modulus and degree of conversion of two multistep adhesive systems.

During the curing reaction, the monomers of dentine bonding systems should cross-link sufficiently to strengthen an adhesive so that it is clinically reliable. This study evaluated how different storage conditions (air vs. water storage) affect the elastic modulus (E-modulus) and degree of conversion (DC) of a three-step etch-and-rinse adhesive and a two-step self-etch adhesive. The biaxial flexural test and Raman microscopy were performed on resin disks made from the bonding agents Adper Scotchbond Multi-Purpose (SBMP; 3M ESPE) and Clearfil Protect Bond (CPB; Kuraray). The measurements were repeated after storage in either air or water for 15 and 30 min and for 1, 24, and 72 h. At time 0, the E-modulus was not affected by the adhesive system, whilst the degree of cure of CPB was higher than that of SBMP. Air storage increased the E-modulus at each ageing interval. Storage in water increased the E-modulus until it reached a maximum at 24 h, after which it decreased significantly at 72 h. No linear correlation between the percentage DC and E-modulus of the two adhesives was found when stored in water. The results of this study indicate that the mechanical properties and polymerization kinetics of SBMP and CPB are affected by storage time and medium.

Degree of conversion and interfacial nanoleakage expression of three one-step self-etch adhesives.

Suboptimally polymerized monomers may be responsible for the reduced material properties of simplified adhesives and their inherent bonded interface instability. This study was performed to determine the degree of cure within the hybrid layers produced by three one-step self-etch adhesives in situ using Raman microspectroscopy and to investigate nanoleakage expression. Dentin disks were bonded with AdheSE One, Adper Prompt L-Pop, or iBond. Composite layers of 2-mm thickness were built up in bulk on the polymerized adhesive surfaces and then the adhesive-dentin interfaces were exposed to a micro-Raman beam. Adhesive penetration was calculated using the relative intensities of bands associated with mineral and adhesive, and the degree of conversion (DC) was evaluated. Interfacial nanoleakage expression was evaluated on the same specimens. The DC values for the tested adhesives were found to increase in the following order: AdheSE One (48 +/- 16%) < Adper Prompt L-Pop (83 +/- 2%) = iBond (90 +/- 6%; P < 0.05). AdheSE One showed greater nanoleakage expression than iBond or Adper Prompt L-Pop. Increased nanoleakage expression was associated with AdheSE One that showed the lowest DC. This suggests that a low DC may affect the quality and the long-term stability of the adhesive interface owing to the elution of unreacted monomers forming a porous and highly permeable hybrid layer.

Degree of conversion of resin blends in relation to ethanol content and hydrophilicity.

OBJECTIVES: To evaluate the degree of conversion of five experimental adhesive systems in relation to their hydrophilicity. The resin blends ranged from hydrophobic to hydrophilic and were tested as neat bonding agents, or solvated with increasing percentages of ethanol. The hypothesis tested was that extent of polymerization of resin blends is affected by resin hydrophilicity, solvent concentrations or time of polymerization. METHODS: Five light-curing versions of neat experimental resin blends were submitted to investigation: (1) 70% E-BisADM, 28.75% TEGDMA; (2) 70% BisGMA, 28.7% TEGDMA; (3) 70% BisGMA, 28.7% HEMA; (4) 40% BisGMA, 30% TCDM, and 28.75% TEGDMA; (5) 40% BisGMA, 30% BisMP, and 28.75% HEMA. All blends included 1% EDMAB and 0.25% CQ. Ethanol in different weight percentages (A: 0%, B: 30%, C: 50%, D: 70% and E: 90%) was added to these resin blends simulating different formulation of adhesives. A differential scanning calorimeter was used to measure the degree of conversion of resin blends as a function of resin hydrophilicity, solvent concentration and time of curing. Data were analyzed with three-way ANOVA and Tukey's post hoc test. RESULTS: Exotherms showed that degree of conversion was influenced by the hydrophilicity of the blends resin (p<.05), percentage of ethanol dilution (p<.05) and time of curing (p<.05). 30% ethanol dilution increased degree of conversion compared to neat compounds irrespective to resin type and curing time, showing the highest degree of conversion values of the study design. SIGNIFICANCE: This study supports the hypothesis that high ethanol percentages (>50mass%) may compromise extent of polymerization kinetics of dental adhesives.

Degree of conversion of Filtek Silorane Adhesive System and Clearfil SE Bond within the hybrid and adhesive layer: an in situ Raman analysis.

OBJECTIVES: To examine the degree of conversion (DC) of the adhesive interfaces created by Filtek Silorane Adhesive and Clearfil SE Bond using micro-Raman spectroscopy. METHODS: The adhesives were applied on human dentin in accordance with manufacturer's instructions. Specimens were cut to expose the bonded interfaces to the micro-Raman beam (Ranishaw InVia; laser wl 785 nm). Raman spectra were collected along the dentin/self-etching primer/adhesive interface at 1 microm intervals. The relative intensities of bands associated with mineral (P-O functional group at 960 cm(-1)) and adhesive (C-C-O group at 605 cm(-1)) components within the bonded interface were used to detect monomer penetration into the dentin matrix and to calculate the degree of conversion (C=C at 1640 cm(-1) as reaction peak, C-C-O at 605 cm(-1) as reference peak). Data were statistically analyzed with two-way ANOVA. RESULTS: DC of Filtek Silorane Adhesive was 69+/-7% in the adhesive layer, increasing (p<0.05) to 93+/-5% in the primer and 92+/-9% in the hybrid layer. Clearfil SE Bond showed a DC of 83+/-3% in the hybrid and 85+/-3% in the adhesive layer. Thus, Filtek Silorane Adhesive showed a higher DC than Clearfil SE Bond in the hybrid layer (p<0.05), but a lower DC in the adhesive (p<0.05). SIGNIFICANCE: As high DC is a fundamental pre-requisite for the stability of the bond over time, this study supports the hypothesis that optimal stability of Filtek Silorane Adhesive can be obtained. However, further research is needed to investigate the mechanical properties of the hybrid layer created by Filtek Silorane Adhesive and its long-term stability.