Influence of adhesive application duration on dentin bond strength of single-application bonding systems

This study examined the relationship between the bond agent application duration and the dentin bond strength of several single-application bonding systems. The restorative material/ bonding systems used were Reactmer, with its single-application bonding system Reactmer Bond (RB, Shofu Inc, Kyoto, Japan); Palfique Estelite, with its single-application bonding system One-Up Bond F (OU, Tokuyama Co, Tokyo, Japan) and F2000 Compomer, with its bonding system Primer/Adhesive in Clicker (F2,3M Dental Products, St Paul, MN 55144, USA). Bovine mandibular incisors were mounted in self-curing resin and wet ground with #600 SiC to expose labial dentin. Adhesives were applied for 5, 10, 20, 30 and 60 seconds, and restorative materials were condensed into a Teflon mold (04 x 2 mm) on the dentin and light activated. Fifteen samples per test group were stored in 37 degrees C water for 24 hours, then shear tested at a crosshead speed of 1.0 mm/min. One-way ANOVA followed by Duncan test (p = 0.05) was done. SEM observations of the treated dentin surface were also conducted. The dentin bond strength ranged from 6.9 +/- 2.4 to 11.2 +/- 2.8 MPa for RB, 8.9 +/- 2.2 to 12.2 +/- 1.9 MPa for OU, and 7.8 +/- 3.1 to 11.4 +/- 2.6 MPa for F2. No significant differences were found among the 10-60 second application duration groups for the systems used. From the SEM observations, demineralization of the dentin surface was more pronounced with longer application duration. The data suggest that the duration of single-application bonding systems was not a crucial factor for determining dentin bond strength, even though morphological changes were observed on the dentin surface.     

Optical scattering power for characterization of mineral loss

Mineral loss in early caries cannot be measured without invasive procedures. To quantify mineral loss without sectioning the tooth, one must determine the optical scattering of the enamel. Using enamel white-spot lesions, we hypothesize that the optical scattering power (Sp) of the demineralized enamel would provide a quantitative estimate of mineral loss. Enamel slabs were demineralized to produce artificial white spots. The data were acquired by means of a Charge-Coupled Device (CCD) camera and image-processing software. For the purpose of comparison, mineral loss (deltaZ) of the demineralized samples was determined by the use of a microhardness approach after the samples were sectioned. The scattering power correlated well with deltaZ (r2 = 0.82). In contrast, simple reflectance of the demineralized samples correlated poorly with deltaZ (r2 = 0.22). The validity of using scattering power to measure demineralization has been confirmed by a three-dimensional Monte Carlo Simulation.     

Effect of five staining solutions on the colour stability of two acrylics and three composite resins based provisional restorations

The effect of coffee, tea, coca-cola, orange-juice and red wine on the colour stability of acrylic and composite based provisional materials were evaluated. Two acrylic resins and three composite resins were studied. 48 standardized specimens for each provisional material were prepared. Each group was divided into 6 subgroups. Specimens from each group were immersed in staining solutions at room temperature for 30 days. Red wine and tea caused the most significant colour changes and orange juice showed the least significant colour changes. deltaE of all of the provisional restorations materials was changed after the immersion in all of the staining solutions during the experimental process.     

Correlation of noncarious cervical lesion size and occlusal wear in a single adult over a 14-year time span

STATEMENT OF PROBLEM: Noncarious cervical lesions are described as having a multifactorial cause, with occlusal trauma and toothbrush abrasion frequently mentioned as major factors. Finite element modeling studies have demonstrated a relocalization of occlusal stresses to the cervical area due to flexure of the crown. This may cause microcracking, especially under tensile stresses, that will lead to a loss of enamel and dentin in the cervical region. Clinical confirmation of an occlusal cause for noncarious cervical lesions has been difficult to obtain. PURPOSE: This study investigated whether occlusal wear was correlated with an increase in the size of noncarious cervical lesions. MATERIAL AND METHODS: Loss of contour at occlusal and cervical sites on 3 teeth of a single individual was measured using digital and visualization techniques at 3 time intervals over a 14-year time span. The 1983 baseline casts and 1991, 1994, and 1997 clinical impressions of a single adult patient with existing noncarious cervical lesions were replicated in epoxy. Surfaces of all replicas were digitized with a contact digitizing system. Sequential digitized surfaces were fit together and analyzed using AnSur-NT surface analysis software. Clinical losses of surface contour by volume and depth of the left mandibular first molar and first and second premolars were recorded. RESULTS: Nine measurements of cervical volume loss (range 0.9 to 11.5 mm(3)) and 9 corresponding measurements of occlusal volume loss (range 0.39 to 7.79 mm(3)) were made. The correlation between occlusal and cervical volume loss was strong (r(2)=0.98) and significant (P<.0001). CONCLUSION: For the single adult patient in this study, there was a direct correlation between occlusal wear and the growth of noncarious cervical lesions.     

A case of tumoural calcinosis in the temporomandibular joint associated with systemic sclerosis

Systemic sclerosis (SSc) is a relatively rare condition characterized by the excessive production and deposition of collagen within tissue. This condition is thought to be immunologically mediated and, in addition to its notorious cutaneous manifestations, often involves multiple organs. A case is presented of systemic sclerosis associated with extensive tumoural calcinosis in the temporomandibular joint. There has been no evidence of recurrence or complications during approximately 2 years of follow up, but long-term follow up is essential.     

The exacerbation of depression,hostility, and social anxiety in the course of Internet addiction among adolescents: A prospective study

Background

In adolescent populations worldwide, Internet addiction is prevalent and is often comorbid with depression, hostility, and social anxiety of adolescents. This study aimed at evaluating the exacerbation of depression, hostility, and social anxiety in the course of getting addiction to Internet or remitting from Internet addiction among adolescents.

Method

This study recruited 2293 adolescents in grade 7 to assess their depression, hostility, social anxiety and Internet addiction. The same assessments were repeated one year later. The incidence group was defined as subjects classified as non-addicted in the first assessment and as addicted in the second assessment. The remission group was defined as subjects classified as addicted in the first assessment and as non-addicted in the second assessment.

Results

The incidence group exhibited increased depression and hostility more than the non-addiction group and the effect of on depression was stronger among adolescent girls. Further, the remission group showed decreased depression, hostility, and social anxiety more than the persistent addiction group.

Conclusions

Depression and hostility worsen in the addiction process for the Internet among adolescents. Intervention of Internet addiction should be provided to prevent its negative effect on mental health. Depression, hostility, and social anxiety decreased in the process of remission. It suggested that the negative consequences could be reversed if Internet addiction could be remitted within a short duration.