Journal of Dental Research

Epigenetic modifications occur in response to environmental changes and play a fundamental role in gene expression following environmental stimuli. Major epigenetic events include methylation and acetylation of histones and regulatory factors, DNA methylation, and small non-coding RNAs. Diet, pollution, infections, and other environmental factors have profound effects on epigenetic modifications and trigger susceptibility to diseases. Despite a growing body of literature addressing the role of the environment on gene expression, very little is known about the epigenetic pathways involved in the modulation of inflammatory and anti-inflammatory genes. This review summarizes the current knowledge about epigenetic control mechanisms during the inflammatory response.

Accurate assessment of mineral density (MD) provides information critical to the understanding of mineralization processes of calcified tissues, including bones and teeth. High-resolution three-dimensional assessment of the MD of teeth has been demonstrated by relatively inaccessible synchrotron radiation microcomputed tomography (SRµCT). While conventional desktop µCT (CµCT) technology is widely available, polychromatic source and cone-shaped beam geometry confound MD assessment. Recently, considerable attention has been given to optimizing quantitative data from CµCT systems with polychromatic x-ray sources. In this review, we focus on the approaches that minimize inaccuracies arising from beam hardening, in particular, beam filtration during the scan, beam-hardening correction during reconstruction, and mineral density calibration. Filtration along with lowest possible source voltage results in a narrow and near-single-peak spectrum, favoring high contrast and minimal beam-hardening artifacts. More effective beam monochromatization approaches are described. We also examine the significance of beam-hardening correction in determining the accuracy of mineral density estimation. In addition, standards for the calibration of reconstructed grey-scale attenuation values against MD, including K₂PHO₄ liquid phantom, and polymer-hydroxyapatite (HA) and solid hydroxyapatite (HA) phantoms, are discussed.

The suppression of pain during surgical interventions has been a major achievement for humankind. Chronologically, in 1842, William E. Clarke, a chemist in Rochester (NY), provided Elijah Pope with ether for the purposes of tooth extraction. In 1844, in Boston, G.Q. Colton and the dentist Horace Wells used nitrous oxide as an anesthetic for tooth extraction. On the 16th of October, 1846, the American dentist William T.G. Morton became a pioneer within the medical community with respect to anesthesia by inhalation when he used ether as an anesthetic at the Massachusetts General Hospital. In 1847, the Scot James Young Simpson began to use chloroform as an anesthetic for obstetrics in Edinburgh. These events gave rise to several disputes among their users (who are not very well-known today), who strove to claim that they had been the discoverers of surgical anesthesia, with a view to obtaining a series of patents and state sinecures. This article attempts to clarify certain discrepancies about the authorship of surgical anesthesia. The evidence suggests that surgical anesthesia first began to be applied in the field of dentistry.

The efficacy of the local application of recombinant human fibroblast growth factor-2 (FGF-2) in periodontal regeneration has been investigated. In this study, a randomized, double-blind, placebo-controlled clinical trial was conducted in 253 adult patients with periodontitis. Modified Widman periodontal surgery was performed, during which 200 µL of the investigational formulation containing 0% (vehicle alone), 0.2%, 0.3%, or 0.4% FGF-2 was administered to 2- or 3-walled vertical bone defects. Each dose of FGF-2 showed significant superiority over vehicle alone (p < 0.01) for the percentage of bone fill at 36 wks after administration, and the percentage peaked in the 0.3% FGF-2 group. No significant differences among groups were observed in clinical attachment regained, scoring approximately 2 mm. No clinical safety problems, including an abnormal increase in alveolar bone or ankylosis, were identified. These results strongly suggest that topical application of FGF-2 can be efficacious in the regeneration of human periodontal tissue that has been destroyed by periodontitis.

Diabetes is associated with a high prevalence of periodontal disease, but little is known about the effects of periodontal disease on incident diabetes. In total, 5848 non-diabetic individuals aged 30-59 yrs who completed a health examination were analyzed in this study. They were divided into three categories: no pathological pockets, moderate periodontitis, or severe periodontitis. Incident diabetes was defined as newly diagnosed cases with fasting plasma glucose > 125 mg/dL. Cox proportional hazards models estimated the effect of periodontitis on incident diabetes during a seven-year follow-up period. Moderate and severe periodontitis was significantly associated with an increased risk of diabetes in unadjusted analyses, but the magnitude of the association decreased after full adjustment [hazard ratio (HR) = 1.00, 95% confidence interval (95% CI) = 0.77-1.30 and HR = 1.28, 95% CI = 0.89-1.86, respectively]. Our findings do not indicate an apparent association between periodontitis and incident diabetes, although there was a tendency for increased risk.

We hypothesized that tobacco smoke induces alterations to the 3-OH fatty acids present in lipid A in a manner consistent with a microflora of reduced inflammatory potential. Whole saliva samples and full-mouth clinical periodontal recordings were obtained from persons with (22 smokers; 15 non-smokers) and without (14 smokers; 15 non-smokers) chronic periodontitis. Clear differences in the contributions of multiple saturated 3-OH fatty acid species were noted in the group with disease compared with healthy individuals. Increases in the long-chain fatty acids associated with anaerobic bacterial periodontopathogens, particularly 3-OH-C_i17.0 (146.7%, relative to controls), were apparent. Significant reductions in the 3-OH fatty acids associated with the consensus (high potency) enteric LPS structure (3-OH-C_12.0 and 3-OH-C_14.0; 33.3% and 15.8% reduction, respectively) were noted in smokers compared with non-smokers with chronic periodontitis. Thus, smoking is associated with specific structural alterations to the lipid-A-derived 3-OH fatty acid profile in saliva that are consistent with an oral microflora of reduced inflammatory potential. These findings provide much-needed mechanistic insight into the established clinical conundrum of increased infection with periodontal pathogens but reduced clinical inflammation in smokers.

Mandibular prognathism is a common dentofacial phenotype with a substantial genetic component; however, few susceptibility loci have been mapped. Ethnicity is a risk factor for mandibular prognathism, and a relatively high prevalence is observed in Asian populations. The hypothesis of this study suggested that a specific locus for mandibular prognathism exists in the Han Chinese population. So, the authors studied a Han Chinese pedigree in which mandibular prognathism was inherited (11 affected, 10 unaffected) in an autosomal dominant pattern. A genomewide linkage scan was performed with the Illumina Linkage-12 DNA Analysis Kit. Multipoint parametric and nonparametric linkage analyses were performed with MERLIN 1.01. A susceptibility locus was identified on chromosome 14q24.3-31.2, with a nonparametric linkage score of 11.341 (empirical P = .020) and a logarithm of the odds score of 2.032 (empirical P = .008). Haplotype analysis refined the candidate locus to a 10.62-cM interval (72.42 to 83.14 cM; 74.57 to 84.66 Mb) between rs1468507 and rs7141857. Within this interval, the candidate functional genes are TGFB3 and LTBP2. In conclusion, the authors detected a suggestive linkage for mandibular prognathism in a Han Chinese pedigree, and this finding can be combined with previous studies to further understand the genetic basis of mandibular prognathism.

Dental agenesis is either syndromic or non-syndromic. Here, we describe a familial case with Carvajal/Naxos syndrome associating woolly hair, palmoplantar keratoderma, and biventricular dilated cardiomyopathy. In addition to these signs, all three affected family members had hypo/oligodontia ranging from absence of the lower left second molar to 15 missing teeth, the typical pattern of oligodontia being absent 2nd premolars and absent 2nd and 3rd molars. Mutation screening in the desmoplakin gene (DSP) revealed a de novo missense mutation (c.1790 C>T, p.Ser597Leu) changing a serine residue conserved in all vertebrates. In addition, this variation was absent from 100 control DNA samples. There were no mutations in the plakoglobin gene. This familial case report and two other previous reports demonstrate that autosomal-dominant mutations in the DSP gene are associated with hypo/oligodontia in the setting of Carvajal/Naxos syndrome. This study suggests that dentists discovering oligo/hypodontia should screen for woolly hair and palmoplantar keratoderma because of the probable cardiac involvement with an inherent high risk of severe cardiomyopathy. In addition, this study reveals the role of desmosomes in the development of teeth and suggests that other genes encoding proteins of the desmosome could be involved in oligo/hypodontia.

Several studies have reported Oral Squamous Cell Carcinoma (OSCC) association with etiological factors, such as smoking and alcohol. The aim of the present study was to establish whether the methylenetetrahydrofolate reductase (MTHFR) C677T genotype and a high alcohol intake, solely or in interaction, have an impact on the oral cancer risk, DNA methylation, or multiple methylation of tumor-related genes. MTHFR C677T genetic polymorphism was determined by the PCR/RFLP method, and DNA methylation was assessed by nested methylation-specific PCR. The risk for multiple methylation was significantly increased in heavy-drinking patients with the TT genotype, compared with CC and CT patients (OR = 10.873; 95% CI, 1.134-104.24). Multiple methylation was significantly associated with tumor stage (p = 0.018), and showed a trend of association with the presence of nodal metastases (p = 0.058). A significant association was found between TT genotype and methylation status of the RASSF1A gene in OSCC patients (p = 0.012). Heavy-drinking individuals with the TT genotype showed increased oral cancer risk compared with the CC genotype (OR = 3.601; 95% CI, 1.036-12.513), and compared with the CC and CT genotypes (OR = 4.288; 95% CI, 1.325-13.877). Our study suggested gene-environment interactions between high alcohol intake and the MTHFR 677TT genotype for elevated oral cancer risk, with a significant impact on multiple methylation of cancer-related genes.

Mastication as a mild but life-long exercise has been examined as a possibility for maintaining brain function in the elderly. Little is known, however, about the cerebral circulatory response during masticatory movement. The aim of this study was to develop a monitoring system for circulation dynamics during masticatory movement and to apply this system to the study of cerebral autoregulation. Cerebral blood flow, heart rate, and arterial blood pressure were simultaneously recorded, and changes in these circulatory systems were quantitatively evaluated in 38 young healthy volunteers. Transfer function analysis was also performed on blood pressure and cerebral blood flow for investigation of cerebral autoregulation during gum chewing. Although increases in cerebral blood flow, mean blood pressure, and heart rate suggested the activation of cerebral and systemic circulation during gum chewing, increased cerebral circulation was independent of systemic circulation. Our results suggest that cerebral autoregulation is well maintained during jaw movements.

Because dentin is more caries-susceptible than enamel, its demineralization may be more influenced by additional fluoride (F). We hypothesized that a combination of professional F, applied as acidulated phosphate F (APF), and use of 1100-ppm-F dentifrice would provide additional protection for dentin compared with 1100-ppm-F alone. Twelve adult volunteers wore palatal appliances containing root dentin slabs, which were subjected, during 4 experimental phases of 7 days each, to biofilm accumulation and sucrose exposure 8x/day. The volunteers were randomly assigned to the following treatments: placebo dentifrice (PD), 1100-ppm-F dentifrice (FD), APF + PD, and APF+FD. APF gel (1.23% F) was applied to the slabs once at the beginning of the experimental phase, and the dentifrices were used 3x/day. APF and FD increased F concentration in biofilm fluid and reduced root dentin demineralization, presenting an additive effect. Analysis of the data suggests that the combination of APF gel application and daily regular use of 1100-ppm-F dentifrice may provide additional protection against root caries compared with the dentifrice alone.

Inability of chemical phosphorylation of sodium trimetaphosphate to induce intrafibrillar mineralization of type I collagen may be due to the failure to incorporate a biomimetic analog to stabilize amorphous calcium phosphates (ACP) as nanoprecursors. This study investigated adsorption/desorption characteristics of hydrolyzed and pH-adjusted sodium trimetaphosphate (HPA-Na₃P₃O₉) to collagen. Based on those results, a 5-minute treatment time with 2.8 wt% HPA-Na₃P₃O₉ was used in a single-layer reconstituted collagen model to confirm that both the ACP-stabilization analog and matrix phosphoprotein analog must be present for intrafibrillar mineralization. The results of that model were further validated by complete remineralization of phosphoric-acid-etched dentin treated with the matrix phosphoprotein analog and lined with a remineralizing lining composite, and with the ACP-stabilization analog supplied in simulated body fluid. An understanding of the basic processes involved in intrafibrillar mineralization of reconstituted collagen fibrils facilitates the design of novel tissue engineering materials for hard tissue repair and regeneration.

Aspartate-serine-serine (DSS) repeats are abundant in naturally occurring proteins that are critical for tooth formation. We recently developed octuplet repeats of aspartate-serine-serine (8DSS) peptides to promote the nucleation of calcium phosphate carbonate from free ions. In this paper, we report a possible role of 8DSS in promoting mineral deposition onto human enamel. Human enamel specimens were demineralized, exposed briefly to 8DSS solution, and then exposed to simulated body fluid that favors mineral deposition. At various stages of treatment, nano-mechanical behaviors, namely, hardness and elastic modulus, were determined by nano-indentation. Nano-indentation results showed that 8DSS treatment effectively improved the mechanical and elastic properties of demineralized enamel. The values of hardness and elastic modulus for the 8DSS-treated enamel were significantly higher than those of surfaces without 8DSS treatment. Furthermore, 8DSS peptides promoted the uniform deposition of nano-crystalline calcium phosphate carbonate over demineralized enamel surfaces and reduced surface roughness of demineralized enamel.

Hybrid-layer degradation occurs because of acidic properties of currently used adhesive systems. Titanium tetrafluoride couples with tooth surface, and titanium compounds are not substituted. Caffeic acid phenethyl esther inhibits endogenous matrix metalloproteinases that cause hybrid-layer degradation. It was hypothesized that titanium tetrafluoride and caffeic acid phenethyl esther application on exposed dentine surfaces before adhesive applications would inhibit nanoleakage and hybrid-layer degradation without compromising the bond strength of the adhesives. In ultracut thin sections, human dentine–chemical agent–adhesive composite interfaces were observed under transmission electron microscope with complementary scanning electron microscopy. Microtensile bond strength tests were also accomplished. Titanium tetrafluoride and titanium tetrafluoride + caffeic acid phenethyl esther applications decreased bond strength values. Caffeic acid phenethyl esther showed decreased silver nitrate penetration for cements based on Bisphenol glycydilmethacrylate and methyl methacrylate, whereas cement based on 4-methacryloyloxyethyl trimellitate anhydride methyl methacrylate showed almost no infiltration. Caffeic acid phenethyl esther application before cementation could inhibit nanoleakage and biodegradation of the hybrid layer.

Although effective preventive strategies exist for pit and fissure caries, prevention of proximal caries remains a significant challenge. This split-mouth study was designed to investigate the effect of glass-ionomer cement (GIC) on the progression of initial proximal caries in posterior teeth, testing the hypothesis that local application of fluoride-releasing GIC would reduce this progression. GIC was applied to 41 pairs of posterior teeth after elastic band separation in 7- to 19-year-old individuals. Follow-up bitewing radiographs were taken at 6 and 12 months. Differences in Δ mean lesion depth at 6 and 12 months between test and control groups were significant (p < 0.05, p < 0.000). Lesions treated with GIC were more likely to remain in or regress to the outer half of enamel (OR = 6.3; 95%CI, 1.3-30.9). GIC provides an effective approach to the clinical management of incipient proximal caries.

This study tested the hypothesis that all-ceramic core-veneer system crown reliability is improved by modification of the core design. We modeled a tooth preparation by reducing the height of proximal walls by 1.5 mm and the occlusal surface by 2.0 mm. The CAD-based tooth preparation was replicated and positioned in a dental articulator for core and veneer fabrication. Standard (0.5 mm uniform thickness) and modified (2.5 mm height lingual and proximal cervical areas) core designs were produced, followed by the application of veneer porcelain for a total thickness of 1.5 mm. The crowns were cemented to 30-day-aged composite dies and were either single-load-to-failure or step-stress-accelerated fatigue-tested. Use of level probability plots showed significantly higher reliability for the modified core design group. The fatigue fracture modes were veneer chipping not exposing the core for the standard group, and exposing the veneer core interface for the modified group.

The periodontal pathogen Tannerella forsythia possesses a glycosylated S-layer as an outermost cell decoration. While the S-layer provides a selection advantage to the bacterium in the natural habitat, its virulence potential remains to be investigated. In the present study, the immune responses of human macrophages and gingival fibroblasts upon stimulation with wild-type T. forsythia and an S-layer-deficient mutant were investigated. The mRNA expression levels of the pro-inflammatory mediators IL-1β, TNF-α, and IL-8 were analyzed by qPCR, and the production of the corresponding cytokines was investigated by ELISA. The S-layer-deficient T. forsythia mutant induced significantly higher levels of pro-inflammatory mediators compared with wild-type T. forsythia, especially at the early phase of response. Analysis of these data suggests that the S-layer of T. forsythia is an important virulence factor that attenuates the host immune response to this pathogen by evading the bacterium’s recognition by the innate immune system. Abbreviations: DMSO, dimethylsulfoxide; FBS, fetal bovine serum; GAPDH, glycerinaldehyde-3-phosphate-dehydrogenase; HGFs, human gingival fibroblasts; LPS, lipopolysaccharide; MEM, minimal essential medium; MTT, 3,4,5-dimethylthiazol-2-yl-2,5-diphenyl tetrazolium bromide; OD, optical density; PBS, phosphate-buffered saline; qPCR, quantitative polymerase chain-reaction; SD, standard deviation; Tannerella forsythia ATCC 43037, Tf wt; Tannerella forsythia ATCC 43037 S-layer mutant, Tf ΔtfsAB.

There is increasing interest in the development of new in vitro tissue models. In this study, a tissue model of periodontal ligament (PDL) was established by 3-D-culturing human PDL cells in a thin sheet of porous poly (lactic-co-glycolic acid) scaffold. Growth of the model was evidenced by MTT assay and various microscopies. After being subjected to static compression of 5 ~ 35 g/cm² for 6 hrs, the RANKL mRNA expression was significantly up-regulated by force ≥ 25 g/cm² in the model. After being subjected to static compression of 25 g/cm² for 6 ~ 72 hrs, the mRNA expression of PTHrP, IL-11, IL-8, and FGF-2, potential osteoclastogenesis inducers, was significantly up-regulated in the model, which was further verified by the compression of human PDL in vivo. However, when human gingival fibroblasts were substituted for PDL cells in the model, almost no osteoclastogenesis inducers were up-regulated by compression. This tissue model can serve as an effective tool for the study of PDL mechanoresponse. Abbreviations: periodontal ligament, PDL; periodontal ligament cells, PDLCs; poly (lactic-co-glycolic acid), PLGA; orthodontic tooth movement, OTM; extracellular matrix, ECM.

Prostaglandin E₂ (PGE₂) plays important roles in the bone resorption of inflammatory diseases such as rheumatoid arthritis and periodontitis via specific prostaglandin receptors (i.e., EP1-EP4). In this study, the authors examined whether Prevotella intermedia regulates PGE₂ production and EP expression in human periodontal ligament fibroblasts (hPDLs); they also explored the potential signaling pathways involved in PGE₂ production. P. intermedia induced PGE₂ production and cyclooxygenase-2 (COX-2) expression in a dose- and time-dependent manner. Indomethacin and NS-398 completely abrogated the P. intermedia–induced PGE₂ production without modulating COX-2 expression. Specific inhibitors of extracellular signal-regulated kinase, c-Jun N-terminal kinase, p38, phosphatidylinositol 3-kinase, and protein kinase C—but not c-AMP and protein kinase A—significantly attenuated the P. intermedia–induced COX-2 and PGE₂ expression. P. intermedia reduced EP1 expression in a concentration- and time-dependent manner. The results indicate that the COX-2-dependent induction of PGE₂ by P. intermedia in hPDLs is mediated by multiple signaling pathways.