Measurements of volatile compound contents in resins using a moisture analyzer

Hashimoto M, Nagano F, Endo K, Ohno H. Measurements of volatile compound contents in resins using a moisture analyzer. Eur J Oral Sci 2010; 118: 94–99. © 2010 The Authors. Journal compilation © 2010 Eur J Oral Sci
The contents of volatile adhesive compounds, such as water, solvents, and residual unpolymerized monomers, affect the integrity and durability of adhesive bonding. However, there is no method available that can be used to rapidly assess the residual solvent or water contents of adhesive resins. This study examined the effectiveness of a digital moisture analyzer to measure the volatile compound contents of resins. Five self-etching adhesives and seven experimental light-cured resins prepared with different contents (0, 10, and 20% by weight) of water or solvents (acetone and ethanol) were examined in this study. The resins were prepared using different methods (with and without air blast or light-curing) to simulate the clinical conditions of adhesive application. Resin weight changes (% of weight loss) were determined as the residual volatile compound contents, using the moisture analyzer. After the measurements, the resin films were examined using a scanning electron microscope. The weight changes of the resins were found to depend on the amount of water or solvents evaporating from the resin. Water and solvents were evaporated by air blast or light-curing, but some of the water and solvents remained in the cured resin. The moisture analyzer is easy to operate and is a useful instrument for using to measure the residual volatile compound contents of adhesive resin.     

The relationship between dental anxiety and dental decay experience in antenatal mothers

Esa R, Savithri V, Humphris G, Freeman R. The relationship between dental anxiety and dental decay experience in antenatal mothers. Eur J Oral Sci 2010; 118: 59–65 . © 2010 The Authors. Journal compilation © 2010 Eur J Oral Sci
The aim of this study was to investigate the relationship between dental anxiety and dental decay experience among antenatal mothers attending Maternal and Child Health clinics in Malaysia. A cross-sectional study was conducted on a consecutive sample of 407 antenatal mothers in Seremban, Malaysia. The questionnaire consisted of participants' demographic profile and the Dental Fear Survey. The D_3cvMFS was employed as the outcome measure and was assessed by a single examiner (intraclass correlation = 0.98). A structural equation model was designed to inspect the relationship between dental anxiety and dental decay experience. The mean Dental Fear Survey score for all participants was 35.1 [95% confidence interval (34.0, 36.3)]. The mean D_3cvMFS score was 10.8 [95% confidence interval (9.5, 12.1)]. Participants from low socio-economic status groups had significantly higher D_3cvMFS counts than those from high socio-economic status groups. The path model with dental anxiety and socio-economic status as predictors of D_3cvMFS showed satisfactory fit. The correlation between dental anxiety and dental decay experience was 0.30 (standardized estimate), indicating a positive association. Socio-economic status was also statistically significantly associated with the D_3cvMFS count (β = 0.19). This study presented robust evidence for the significant relationship between dental anxiety and dental decay experience in antenatal mothers.     

Tooth agenesis patterns in bilateral cleft lip and palate

Bartzela TN, Carels CEL, Bronkhorst EM, Rønning E, Rizell S, Kuijpers-Jagtman AM. Tooth agenesis patterns in bilateral cleft lip and palate. Eur J Oral Sci 2010; 118: 47–52. © 2010 The Authors. Journal compilation © 2010 Eur J Oral Sci
Individuals with cleft lip and palate present significantly more dental anomalies, even outside the cleft area, than do individuals without clefts. Our aim was to evaluate the prevalence of tooth agenesis and patterns of hypodontia in a large sample of patients with complete bilateral cleft lip and palate (BCLP). Serial panoramic radiographs (the first radiograph was taken at 10.5–13.5 yr of age) of 240 patients with BCLP (172 male patients, 68 female patients) were examined. Third molars were not included in the evaluation. Agenesis of at least one tooth was present in 59.8% of patients. Upper laterals and upper and lower second premolars were missing most frequently. Using the tooth agenesis code (TAC), 52 different agenesis patterns were identified, of which simultaneous agenesis of 12, 22, 15, 25, 35, and 45 was the most frequent pattern. Nine of the 240 patients showed combined BCLP and oligodontia.     

Dentin surface treatment using a non‐thermal argon plasma brush for interfacial bonding improvement in composite restoration

Ritts AC, Li H, Yu Q, Xu C, Yao X, Hong L, Wang Y. Dentin surface treatment using a non‐thermal argon plasma brush for interfacial bonding improvement in composite restoration.
Eur J Oral Sci 2010; 118: 510–516. © 2010 Eur J Oral Sci The objective of this study was to investigate the treatment effects of non‐thermal atmospheric gas plasmas on dentin surfaces used for composite restoration. Extracted unerupted human third molars were prepared by removing the crowns and etching the exposed dentin surfaces with 35% phosphoric acid gel. The dentin surfaces were treated using a non‐thermal atmospheric argon plasma brush for various periods of time. The molecular changes of the dentin surfaces were analyzed using Fourier transform infrared spectrophotometry/attenuated total reflectance (FTIR/ATR), and an increase in the amount of carbonyl groups was detected on plasma‐treated dentin surfaces. Adper Single Bond Plus adhesive and Filtek Z250 dental composite were applied as directed. To evaluate the dentin/composite interfacial bonding, the teeth thus prepared were sectioned into micro‐bars and analyzed using tensile testing. Student–Newman–Keuls tests showed that the bonding strength of the composite restoration to peripheral dentin was significantly increased (by 64%) after 30 s of plasma treatment. However, the bonding strength to plasma‐treated inner dentin did not show any improvement. It was found that plasma treatment of the peripheral dentin surface for up to 100 s resulted in an increase in the interfacial bonding strength, while prolonged plasma treatment of dentin surfaces (e.g. 5 min) resulted in a decrease in the interfacial bonding strength.     

Mechanosensitivity of dental pulp stem cells is related to their osteogenic maturity

Kraft DCE, Bindslev DA, Melsen B, Abdallah BM, Kassem M, Klein-Nulend J. Mechanosensitivity of dental pulp stem cells is related to their osteogenic maturity. Eur J Oral Sci 2010; 118: 29–38. © 2010 The Authors. Journal compilation © 2010 Eur J Oral Sci
For engineering bone tissue, mechanosensitive cells are needed for bone (re)modelling. Local bone mass and architecture are affected by mechanical loading, which provokes a cellular response via loading-induced interstitial fluid flow. We studied whether human dental pulp-derived mesenchymal stem cells (PDSCs) portraying mature (PDSC-mature) or immature (PDSC-immature) bone cell characteristics are responsive to pulsating fluid flow (PFF) in vitro . We also assessed bone formation by PDSCs on hydroxyapatite-tricalcium phosphate granules after subcutaneous implantation in mice. Cultured PDSC-mature exhibited higher osteocalcin and alkaline phosphatase gene expression and activity than PDSC-immature. Pulsating fluid flow (PFF) stimulated nitric oxide production within 5 min by PDSC-mature but not by PDSC-immature. In PDSC-mature, PFF induced prostaglandin E₂ production, and cyclooxygenase 2 gene expression was higher than in PDSC-immature. Implantation of PDSC-mature resulted in more osteoid deposition and lamellar bone formation than PDSC-immature. We conclude that PDSCs with a mature osteogenic phenotype are more responsive to pulsating fluid shear stress than osteogenically immature PDSCs and produce more bone in vivo . These data suggest that PDSCs with a mature osteogenic phenotype might be preferable for bone tissue engineering to restore, for example, maxillofacial defects, because they might be able to perform mature bone cell-specific functions during bone adaptation to mechanical loading in vivo .     

Microtensile bond strength of a new silorane-based composite resin adhesive

Filtek LS is a new composite resin restorative system with a unique, low-shrinking, silorane-based monomer matrix. The current study was conducted to compare the durability of the bond to dentin of the new silorane-based bonding agent, Filtek Silorane System Adhesive, to the gold standard methacrylate-based bonding agent, Clearfil SE Bond. Extracted human molar teeth were sectioned to expose dentin. Either Filtek Silorane System Adhesive with Filtek LS composite or Clearfil SE Bond with Clearfil Majesty Posterior composite was applied to the dentin according to the manufacturer's instructions. The composites were placed incrementally and sectioned perpendicular to the composite-tooth interface to obtain rectangular beams. The beams were stored for 24 hours, 6 months, or 12 months in distilled water and stressed in tension in a universal testing machine. Data were analyzed with a two-way ANOVA/Tukey test. The 24-hour microtensile bond strengths were significantly greater than the 6- and 12-month bond strengths. Overall, there was no significant difference in the microtensile bond strength to dentin between the Filtek Silorane System Adhesive and the Clearfil SE Bond adhesive bonding agents. After one year of water storage, the new silorane-based composite resin bonding agent performed as well as the methacrylate-based composite resin bonding agent.     

In situ evaluation of a new silorane-based composite resin's bioadhesion properties

Objectives

The aim of the present study was to compare, in situ, the initial dental plaque formation on a recently developed silorane-based composite resin, Filtek Silorane, and on a widely used methacrylate-based composite resin, Synergy D6, and to relate possible differences to surface free energy, hydrophobicity and type of organic matrix.

Methods

Discs of Filtek Silorane and Synergy D6 were prepared and polished equally in order to attain the same surface roughness. Water, formamide and 1-bromonaphthalene contact angles were determined and the surface free energy and the hydrophobicity of the materials calculated. Two discs of each material were mounted in individual oral splints and exposed to the oral cavity of 20 participants for 4 h. After this period the microbial adhesion to both materials’ surface was measured by two different approaches, the DAPI staining and the plate count. Statistical analysis was performed using non-parametric tests.

Results

The surface roughness (R_a parameter) was similar between the two materials and lower than 0.2 μm. Mean water and formamide contact angles were significantly higher for Filtek Silorane, which presented significantly lower surface free energy and greater degree of hydrophobicity in comparison to Synergy D6. The bioadhesion potential evaluated by either DAPI staining or plate count did not differ between the two materials.

Significance

In contrast to previous in vitro studies, the present in situ study found no statistically significant differences with respect to bacterial adhesion between Filtek Silorane and Synergy D6, despite the differences found for surface free energy and hydrophobicity.     

Dentin treatment effects on the bonding performance of self-adhesive resin cements

Mazzitelli C, Monticelli F, Toledano M, Ferrari M, Osorio R. Dentin treatment effects on the bonding performance of self-adhesive resin cements. Eur J Oral Sci 2010; 118: 80–86. © 2010 The Authors. Journal compilation © 2010 Eur J Oral Sci
The effects of dentin surface treatments on the microtensile bond strengths and on the interfacial characteristics of self-adhesive resin cements were investigated. Flat dentin surfaces were obtained from human molars and were treated as follows: (i) no treatment of dentin; (ii) 0.1 M EDTA scrubbed for 60 s; or (iii) 10% polyacrylic acid applied for 30 s. Three self-adhesive cements were used to lute composite overlays on deep-coronal dentin surfaces in the presence of simulated pulpal pressure (15 cm of H₂O). Bonded specimens were cut into beams 1 mm thick and stressed in tension until failure. Fractured sticks were examined under a scanning electron microscope. Additional specimens were stained with Masson's trichrome and observed under light microscopy for interfacial evaluations. The bond strength to dentin of the hydrophobic and solvent-free cement (RelyX Unicem) was unaffected by the tested dentin treatments. The bond strength of the 2-hydroxyethyl methacrylate (HEMA)-based cement (Bis-Cem) decreased after treatment of dentin with EDTA and/or polyacrylic acid. The hydrophilic and water-containing cement (G-Cem) attained a higher bond strength when luted on polyacrylic acid-conditioned dentin. In conclusion, smear layer removal, opening of dentinal tubules, and the water content of dentin differently influence the bond strengths and the interfacial characteristics of self-adhesive cement–dentin interfaces.     

Two year clinical evaluation of a low-shrink resin composite material in UK general dental practices

Objective

A novel resin composite system, Filtek Silorane (3M ESPE) with reduced polymerization shrinkage has recently been introduced. The resin contains an oxygen-containing ring molecule (‘oxirane’) and cures via a cationic ring-opening reaction rather than a linear chain reaction associated with conventional methacrylates and results in a volumetric shrinkage of ∼1%. The purpose of this study was to review the literature on a recently introduced resin composite material, Filtek Silorane, and evaluate the clinical outcome of restorations formed in this material.

Methods

Filtek Silorane restorations were placed where indicated in loadbearing situations in the posterior teeth of patients attending five UK dental practices. These were evaluated, after two years, using modified USPHS criteria.

Results

A total of 100 restorations, of mean age 25.7 months, in 64 patients, were examined, comprised of 30 Class I and 70 Class II. All restorations were found to be present and intact, there was no secondary caries. Ninety-seven per cent of the restorations were rated optimal for anatomic form, 84% were rated optimal for marginal integrity, 77% were rated optimal for marginal discoloration, 99% were rated optimal for color match, and 93%% of the restorations were rated optimal for surface quality. No restoration was awarded a “fail” grade. No staining of the restoration surfaces was recorded and no patients complained of post-operative sensitivity.

Significance

It is concluded that, within the limitations of the study, the two year assessment of 100 restorations placed in Filtek Silorane has indicated satisfactory clinical performance.     

Partially erupted third molars as a potential source of infection in patients receiving peripheral stem cell transplantation for malignant diseases: a retrospective study

Öhman D, Björk Y, Bratel J, Kristiansson C, Johansson P, Johansson J-E, Brune M, Hasséus B. Partially erupted third molars as a potential source of infection in patients receiving peripheral stem cell transplantation for malignant diseases: a retrospective study. Eur J Oral Sci 2010; 118: 53–58. © 2010 The Authors. Journal compilation © 2010 Eur J Oral Sci
Forty-four patients with malignant diseases for which they received peripheral stem cell transplant therapy (PSCT) were retrospectively studied regarding local and systemic infection originating from around partially erupted third molars (PEMs). Twenty-two patients had one or more PEMs, while 22 patients had none. Data were retrieved from medical and dental records. Systemic and local signs of infection and treatment were assessed. We recorded the number of transplanted CD34⁺ blood stem cells, days with white blood cell counts < 0.5 × 10⁹ l⁻¹, days until engraftment, maximum level of C-reactive protein (CRP), days with fever, positive blood cultures, days taking antibiotics, days drinking < 0.5 l, days of total parenteral nutrition, days receiving intravenously administered analgesics, and number of admission days. No statistically significant difference was detected between patients with PEMs and those without PEMs regarding any of the studied parameters. Of patients with PEMs, 36% (8 of 22) developed local infections around PEMs during the PSCT period. The study indicates that PEMs pose no significant risk of causing systemic infection in patients receiving PSCT for malignant diseases but increase the risk of developing a local infection, justifying close supervision and early treatment in cases of local infection during PSCT treatment.     

Effects of age condition on the distribution and integrity of inorganic fillers in dental resin composites

Objectives

The aim of this study is to evaluate the distribution of the filler size along with the zeta potential, and the integrity of silane-bonded filler surface in different types of restorative dental composites as a function of the material age condition.

Materials and methods

Filtek P60 (hybrid composite), Filtek Z250 (small-particle filled composite), Filtek Z350XT (nanofilled composite), and Filtek Silorane (silorane composite) (3M ESPE) were tested at different stage condition (i.e., fresh/new, aged, and expired). Composites were submitted to an accelerated aging protocol (Arrhenius model). Specimens were obtained by first diluting each composite specimen in ethanol and then dispersed in potassium chloride solution (0.001 mol%). Composite fillers were characterized for their zeta potential, mean particle size, size distribution, via poly-dispersion dynamic light scattering. The integrity of the silane-bonded surface of the fillers was characterized by FTIR.

Results

The material age influenced significantly the outcomes; Zeta potential, filler characteristics, and silane integrity varied both after aging and expiration. Silorane presented the broadest filler distribution and lowest zeta potential. Nanofilled and silorane composites exhibited decreased peak intensities in the FTIR analysis, indicating a deficiency of the silane integrity after aging or expiry time.

Conclusion

Regardless to the material condition, the hybrid and the small-particle-filled composites were more stable overtime as no significant alteration in filler size distribution, diameter, and zeta potential occurred. A deficiency in the silane integrity in the nanofilled and silorane composites seems to be affected by the material stage condition.

Clinical significance

The materials conditions tested in this study influenced the filler size distribution, the zeta potential, and integrity of the silane adsorbed on fillers in the nanofilled and silorane composites. Thus, this may result in a decrease of the clinical performance of aforementioned composites, in particular, if these are used after inappropriate storage conditions.

     

Siloranes in dental composites.

OBJECTIVE: The purpose of this study was to compare the product profile of a Silorane based composite which polymerizes by a cationic ring opening process with the product profile of different methacrylate based restoratives. METHODS: Four methacrylate based materials Filtek Z250, Filtek P60,Tetric ceram, Spectrum TPH and a Silorane based material were investigated with regard to their compressive strength, flexural strength, E-Modulus and ambient light stability. The data were analyzed by 1-way ANOVA and 2 sample t test (p<0.05). Shrinkage data were determined by the Archimedes method and the bonded disk method. The reactivity of the Silorane and Tetric ceram were derived from the time resolved shrinkage behaviour and the development of the E-Modulus over time. RESULTS: The Silorane Composite revealed with 0.94 vol% (bonded disk method) and 0.99 vol% (Archimedes method) the lowest polymerization shrinkage among all tested composites. Its reactivity was comparable to the reactivity of Tetric Ceram. However, the ambient light stability of >10 min for Silorane was higher than the ambient light reactivity of the other tested methacrylates (55-90 s). SIGNIFICANCE: The ring opening chemistry of the Siloranes enables at the first time shrinkage values lower than 1 vol% and mechanical parameters as E-Modulus and flexural strength comparable to those of clinically well accepted methacrylate based composites.     

N-Desmethylclozapine exerts dual and opposite effects on salivary secretion in the rat

Ekström J, Godoy T, Riva A. N -Desmethylclozapine exerts dual and opposite effects on salivary secretion in the rat. Eur J Oral Sci 2010; 118: 1–8. © 2010 The Authors. Journal compilation © 2010 Eur J Oral Sci
N -Desmethylclozapine is a major metabolite of the atypical antipsychotic drug clozapine, used in the treatment of therapy-resistant schizophrenia. Patients under clozapine treatment report a troublesome sialorrhea. Recent experiments show clozapine to exert mixed agonist/antagonist actions on salivary secretion in rats. The present study was performed to define the secretory role of N -desmethylclozapine and to compare it with that of its parent compound. N -Desmethylclozapine evoked secretion by acting directly on the muscarinic acetylcholine M1-receptors of 'silent' duct-cannulated parotid and submandibular glands of the anaesthetized rat. In chronic surgically denervated glands, the secretory response was enlarged. The methacholine-evoked secretion, as well as the parasympathetic nerve-evoked secretion, were reduced by N -desmethylclozapine and involved blockade of M3-receptors, while the sympathetic nerve-evoked response was reduced, involving blockade of α₍₁₎-adrenergic receptors. Synergistic interactions between N -desmethylclozapine and the β-adrenergic receptor agonist, isoprenaline, occurred. Compared with clozapine, the excitatory efficacy of N -desmethylclozapine was higher and the inhibitory efficacy was lower (parasympathetic activity) or about the same (sympathetic activity). Theoretically, in humans treated with clozapine, an increase in the N -desmethylclozapine : clozapine ratio would contribute to salivation during the night and at rest, and, furthermore, the magnitude of the reduction in the reflexly elicited secretion is likely to diminish.     

A confocal micro-endoscopic investigation of the relationship between the microhardness of carious dentine and its autofluorescence

Banerjee A, Cook R, Kellow S, Shah K, Festy F, Sherriff M, Watson T. A confocal micro-endoscopic investigation of the relationship between the microhardness of carious dentine and its autofluorescence. Eur J Oral Sci 2010; 118: 75–79. © 2010 The Authors. Journal compilation © 2010 Eur J Oral Sci
This study aimed to investigate the null hypothesis that there is no relationship between the microhardness of carious dentine and its native autofluorescence (AF). Six extracted, carious molars were sectioned through natural lesions in the mesio-distal longitudinal plane. The Knoop microhardness (Knoop hardness number, KHN) of the cut surfaces of each sample was recorded at regular intervals through sound and carious dentine. Confocal fibre-optic micro-endoscopic (CFOME) examination of the carious dentine and the sound dentine was carried out at the same intervals using the Cellvizio system (600 μm wide, flat-end probe) with an excitation wavelength of 488 nm. The blindly collected numerical data were analysed using the original microhardness KHN. The data analysis indicated that the autofluorescence signals increased significantly when the microhardness of dentine dropped below 25 KHN. Therefore, the null hypothesis was disproved, and it was concluded from this investigation that the autofluorescent signal intensity recorded using CFOME could produce an objective and reproducible correlation to the microhardness of carious dentine. Confocal fibre-optic micro-endoscopic examination could have clinical potential as a technology to help delineate the carious dentine that might be excavated in a clinical procedure in vivo .     

Marginal integrity of low-shrinking versus methacrylate-based composite: effect of different one-step self-etch adhesives

The aim of the study was to evaluate the influence of composite type and adhesive system on the quality of marginal adaptation in standardized Class V cavities before and after thermo-mechanical loading (TML). The cavities were restored using different combinations of three adhesive systems [(Silorane System Adhesive (SSA), Clearfil S³ Bond (S3), G-Bond (G-B)] and two resin composite materials (Filtek Silorane, Clearfil AP-X). Six groups (n = 10): Group A (SSA-Primer + SSA-Bond, Filtek Silorane), Group B (SSA-Primer + SSA-Bond, Clearfil AP-X), Group C (S3 + SSA-Bond, Filtek Silorane), Group D (S3 + SSA-Bond, Clearfil AP-X), Group E (G-B + SSA-Bond, Filtek Silorane) and Group F (G-B + SSA-Bond, Clearfil AP-X) were defined. Marginal adaptation was assessed on replicas in the SEM at 200 × magnification before and after TML (3000 × 5–55 °C, 1.2 10⁶ × 49 N; 1.7 Hz) under simulated dentinal fluid. The highest scores of continuous margins (%CM) were observed in the group F (G-B + SSA-Bond, Clearfil AP-X: before loading 96.4 (±3.2)/after loading 90.8 (±7.0)). A significant effect of adhesive system, composite type and loading interval was observed on the results (p < 0.05). Significantly lower scores of %CM were observed for silorane-based composite (Filtek Silorane) after TML in comparison with methacrylate-based composite (Clearfil AP-X) considering total marginal length (p < 0.05). For both Filtek Silorane and Clearfil AP-X, G-Bond performed significantly better than SSA-Primer and Clearfil S³ Bond (p < 0.05). For all combinations of one-step self-etch adhesives and SSA-Bond resin coating, silorane-based low-shrinking composite exhibited inferior marginal adaptation than did the methacrylate-based composite.     

Satisfaction with teeth and life-course predictors: a prospective study of a Swedish 1942 birth cohort

Ekbäck G, Nodrehaug-Åstrøm A, Klock K, Ordell S, Unell L. Satisfaction with teeth and life-course predictors: a prospective study of a Swedish 1942 birth cohort. Eur J Oral Sci 2010; 118: 66–74. © 2010 The Authors. Journal compilation © 2010 Eur J Oral Sci
This study aimed to assess the stability or change in satisfaction with teeth among Swedish adults between the ages of 50 and 65 yr, and to identify the impact of socio-demographics and of clinical and subjective oral health indicators on participants' satisfaction with teeth during that period. Self-administered standardized questionnaires were used as part of a longitudinal study. In 1992, 1997, 2002, and 2007 all residents (born in 1942) of two Swedish counties were invited to participate in the study. A total of 63% women and 66% men reported being satisfied with their teeth between 50 and 65 yr of age. The corresponding figures, with respect to dissatisfaction, were 7% and 6% respectively. Generalized estimated equation models revealed a decline in the odds of being satisfied with advancing age, which was particularly important in subjects with lower education, tooth loss, and smokers. Consolidation in oral health perceptions starts before age 50, suggesting early intervention before that age. Promotion of a healthy adult lifestyle and improved access to quality oral healthcare might increase the likelihood of people being satisfied with their teeth throughout the third age-period in both genders.     

Ultrastructural localization of salivary mucins MUC5B and MUC7 in human labial glands

Piras M, Hand AR, Tore G, Ledda GP, Piludu M. Ultrastructural localization of salivary mucins MUC5B and MUC7 in human labial glands. Eur J Oral Sci 2010; 118: 14–18. © 2010 The Authors. Journal compilation © 2010 Eur J Oral Sci
As a result of their presence throughout the mouth in the submucosa or between muscle fibers, minor salivary glands secrete directly and continuously into the oral cavity, providing mucosal surfaces with highly glycosylated proteins that are active in bacterial aggregation and in oral tissue lubrication. In this study, we investigated the ultrastructural localization of the MUC5B and MUC7 mucins in human labial glands by means of a postembedding immunogold technique. Thin sections of normal human labial glands, obtained during surgery, were incubated with polyclonal antibodies to human salivary mucins MUC5B and MUC7, and then with gold-labeled secondary antibodies. Specific MUC5B reactivity was found in the secretory granules of mucous cells of all glands examined, and was associated with the luminal membrane of duct cells. MUC7 labeling was observed in the granules of both mucous and seromucous secretory cells of the glandular parenchyma. Quantitative analyses demonstrated that seromucous granules have higher immunogold labeling densities for MUC7 than mucous granules. Our immunohistochemical data extend the results of previous light microscopic studies of MUC5B and MUC7 localizations, pointing out the significant contribution of human labial glands in the secretion process of these two mucins.     

Finite element and Weibull analyses to estimate failure risks in the ceramic endocrown and classical crown for endodontically treated maxillary premolar

Lin C-L, Chang Y-H, Chang C-Y, Pai C-A, Huang S-F. Finite element and Weibull analyses to estimate failure risks in the ceramic endocrown and classical crown for endodontically treated maxillary premolar. Eur J Oral Sci 2010; 118: 87–93. © 2010 The Authors. Journal compilation © 2010 Eur J Oral Sci
The present study evaluated the failure risks of an endodontically treated premolar with severely damaged coronal hard tissue and restored with either a computer-aided design/computer-aided manufacturing (CAD/CAM) ceramic endocrown or a classical crown configuration. Two, three-dimensional finite element maxillary premolar models were designed with endodontic treatment and restored with either a chairside economic reconstruction of esthetic ceramic (CEREC) ceramic endocrown or a classical crown. The Weibull function was incorporated with finite element analysis to calculate the long-term failure probability relative to different load conditions. Additionally, an in vitro fatigue-load fracture experiment was performed to validate the numerical simulation results. The results indicated that the stress values on the dentin and luting cement for the endocrown restoration were lower than those for the crown configuration. Weibull analysis revealed that the individual failure probability in the endocrown dentin and luting cement diminished more than those for the crown restoration. While the overall failure probabilities for the endocrown and the classical crown were similar, fatigue fracture testing revealed that the endocrown restoration had higher fracture resistance than the classical crown configuration (1,446 vs. 1,163 MPa). This investigation implies that the endocrown can be considered as a conservative, aesthetic, and clinically feasible restorative approach for endodontically treated maxillary premolars.     

Photoelastic determination of polymerization shrinkage stress in low-shrinkage resin composites

Low-shrinkage resin composites are in the focus of research in posterior resin composite restoratives. The aim of the study was to examine the polymerization shrinkage stress of new composites (Venus Diamond/ Heraeus Kulzer; SDR/DENTSPLY) and an experimental low-shrinkage resin composite (Ormocer/VOCO) in comparison to established low-shrinkage resin composites (Filtek Silorane/ 3M ESPE; els/Saremco; Filtek Supreme XT/3M ESPE; Clearfil Majesty Posterior/Kuraray). Cylindrical cavities (? 4 mm) in Araldit-B epoxy resin plates (40×40×4 mm) were pretreated with the Rocatec system to ensure bonding of the resin composites. The resin composite specimens (n = 10) were exposed to light for 60 s with a QTH curing device (Translux energy, Heraeus Kulzer, Germany). The samples were stored dark and dry (23 °C). Polymeri-zation shrinkage stress data (MPa) 4 min and 24 h post exposure were calculated based on the diameter of the first-order isochromatic rings, obtained from the Araldit plates. The statistical analysis of the obtained data was carried out with the Wilcoxon test (p = 0.05). After 24 h, the following mean stress values and standard deviations were obtained: Venus Diamond 3.4 ± 0.27 MPa; SDR 3.3 ± 0.26 MPa; exp. Ormocer 4.0 ± 0.18 MPa; Filtek Silorane 2.8 ± 0.19 MPa; els 2.5 ± 0.09 MPa; Filtek Supreme XT 6.0 ± 0.20 MPa; and Clearfil Majesty Posterior 5.6 ± 0.15 MPa. For all materials, higher polymerization stress values were recorded after 24 h. All differences in the shrinkage data obtained after 24 h were statistically significant (p < 0.05) except Venus Diamond/SDR. Venus Diamond, els and SDR showed shrinkage data closer to that of Filtek Silorane.