Influence of delayed placement of composites over cured adhesives on dentin bond strength of single-application self-etch systems

This study examined the relationship between delay in composite placement over cured adhesives and the dentin bond strength of several single-application self-etch adhesive systems. The adhesive system/resin composite combinations used were: Adper Prompt L-Pop/Filtek Z250 (AP), AQ Bond Plus/Metafil C (AQ), Fluoro Bond Shake One/Beautifil (FB), G-Bond/Solare (GB), One-Up Bond F Plus/Palfique Estelite (OF), Xeno IICF Bond/Xeno CF (XE). Bovine mandibular incisors were mounted in self-curing resin and wet ground with #600 SiC to expose labial dentin. The adhesives were applied according to each manufacturer's instructions, and resin pastes were condensed into a mold (?4x2 mm) immediately, and 1, 2, 5 and 10 minutes after light irradiation of the adhesives. Ten 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/minute. One-way ANOVA followed by Tukey's HSD test (alpha = 0.05) was done. SEM observations of the dentin surface after the tests were also conducted. Dentin bond strength ranged from 9.5 +/- 2.2 to 14.0 +/- 2.4 MPa for AP, 7.3 +/- 2.2 to 12.2 +/- 3.1 MPa for AQ, 10.0 +/- 3.5 to 16.3 +/- 2.4 MPa for FB, 11.4 +/- 1.5 to 16.3 +/- 1.2 MPa for GB, 14.2 +/- 3.4 to 15.1 +/- 3.0 MPa for OF and 11.5 +/- 2.4 to 15.9 +/- 2.2 MPa for XE. Except for OF, no significant differences were found among the 2 to 10 minute delayed placement groups for the systems used. Significant lower bond strengths were obtained for the immediate placement groups except for OF. From SEM observations, cohesive failure of the dentin surface was more pronounced with the longer delay in placement. The data suggest that delayed composite placement over the cured adhesives are suggested for optimum dentin bond strength of single-application self-etch adhesive systems.     

Influence of environmental conditions on dentin bond strengths of one-application adhesive systems

Resin composites are considered susceptible to environmental conditions that might affect bond strength. This study investigated the influence of relative humidity and temperature on the dentin bond strength of newly developed one-application adhesive systems. Bonding systems employed in this study were five commercial one-application adhesive systems. Labial surfaces of bovine incisors were ground wet on 600-grit SiC paper. The teeth were transferred to a controlled temperature and humidity chamber and the specimens were prepared in six different environmental conditions, A) 25 +/- 0.5 degrees C, 50 +/- 5% RH, B) 25 +/- 0.5 degrees C, 80 +/- 5% RH, C) 25 +/- 0.5 degrees C, 95 +/- 5% RH, D) 37 +/- 0.5 degrees C, 50 +/- 5% RH, E) 37 +/- 0.5 degrees C, 80 +/- 5% RH, F) 37 +/- 0.5 degrees C, 95 +/- 5% RH. The dentin surfaces were treated according to each manufacturer's instructions. Resin composites of each bonding system were condensed into a mold and light irradiated. After storage in 37 degrees C water for 24 hours, 10 specimens per group were tested in a shear mode in a testing machine at a crosshead speed of 1.0 mm/minute. Statistical analysis was carried out with one-way ANOVA followed by Duncan's multiple range tests at a p-value of 0.05. The dentin bond strengths of one-application adhesive systems decreased with increasing RH. These data suggest that the relative high humidity in the oral environment needs consideration in developing clinical procedures for management of these one-application adhesive systems.     

Toothpaste detergents: a potential source of oral soft tissue damage?

Abstract: Objectives: Toothpastes are thought to be of benefit to cleaning teeth but may also have the potential for soft tissue damage at least on the cellular level by inclusion of detergents in their formulation. The aim of this study was to observe the in vitro response of oral mucosa like cells to toothpaste detergents. Methods: TERT‐1 keratinocytes were exposed to varying concentrations of the detergents Adinol, Sodium Lauryl Sulphate, Tego Betain and Pluronic as well as PBS and culture medium. After 2‐min exposure, cells were washed and incubated in fresh medium for 24 h. Cell death was then spectrophotmetrically measured using an MTT assay. Results: Except for Pluronic, cell viability was markedly reduced for all detergents at all increasing concentrations when compared to the positive medium control. Cells treated with Pluronic were stimulated compared to medium alone. Conclusions: These in vitro data suggest that some detergents may have the potential to cause soft tissue damage in the mouth. Although in vivo, saliva may neutralize such effects. The results for Pluronic suggest a possible oxidative stress response that bears further study.     

Long-term assessment of psychologic outcomes of orthognathic surgery.

PURPOSE: This long-term study of post-orthognathic surgery patients aimed at assessing perceptions of problems with physical and psychologic functioning, self-concept, body image, and satisfaction with the surgical outcome based on subjective evaluations. In addition, the patient's perception of self-concept, body image, and function was compared with the perception of pretreatment patients and controls with no treatment need. Patients and Methods: One hundred seventeen patients who underwent orthognathic surgery 10 to 14 years earlier and participated in a psychologic study 10 years earlier received questionnaires that were composed of 4 instruments designed to assess these factors. A sample of 92 persons representing a population without treatment need and 39 patients requesting treatment for a malocclusion served as control groups. RESULTS: The findings of this study support the hypothesis that improvement in appearance brought about by orthognathic surgery is associated with improvement in psychosocial adjustment. Orthognathic surgery resulted in subjective estimation of function, appearance, health, and interpersonal relationships that was higher than that among pretreatment and no-treatment control groups. The level of body image and self-esteem approximated but did not reach that of a nonpatient population. CONCLUSIONS: In view of the current psychologic and social environment, patients should be offered the appropriate treatment to correct a disfigurement if it is subjectively perceived by them as a handicap, in part to improve the psychologic outcome.     

Bacteriology of human gingivitis

The subgingival bacterial floras of naturally occurring gingivitis in adults and children were characterized and compared with the floras of other periodontal conditions previously studied. The composition of the gingivitis floras was found to be distinct from that of floras associated with health or with moderate, severe, or juvenile periodontitis. There were no major differences between the floras of naturally-occurring gingivitis and the floras of the human experimental gingivitis model. Data indicated that the flora of healthy sites within a mouth is influenced by the number of inflamed sites, which argues against independence of sites bacteriologically. Proportions of ten bacterial species increased in both gingivitis and periodontitis, as compared with health, in both adults and children. These species were found in both affected and unaffected sites of people with gingivitis. The numbers of five other cultivable species and the "large treponeme", which was not cultivated, increased in gingivitis and periodontitis of adults only. Significant differences in non-spirochetal floras between children and adults were not found, although they were in the experimental gingivitis model studied previously. Cultivable spirochetes did differ between children and adults. Children had fewer samples positive for spirochetes, and children's positive samples contained greater proportions of T. socranskii subsp. paredis. Some species that predominate in periodontitis, but which are absent from healthy gingivae, were found as a small percentage of the flora in gingivitis. This suggests that increased serum and blood in the gingival crevice encourage species that relate to periodontitis.     

An in vitro evaluation of the contents of root canals obturated with gutta percha and AH-26 sealer or Resilon and Epiphany sealer

The purpose of this study was to compare the contents of root canals obturated with gutta percha and AH-26 sealer (Dentsply, Tulsa, OK) to canals obturated with the Resilon and Epiphany (Pentron, Wallingford, CT) system. Canal contents were assessed by determining the percentage of canal space occupied by core material, sealer, voids, and debris. Forty extracted human maxillary anterior teeth were instrumented, and the teeth were randomly assigned to either the gutta percha/AH 26 group or the Epiphany/Resilon group. Canals were obturated, and the teeth were subsequently embedded in resin and sectioned horizontally at 2, 4, and 6 mm from the anatomic apex. Sections were photographed by using a low vacuum scanning electron microscope. Image-J (Wayne Rasband; National Institute of Health, Bethesda, MD) software was used to quantify the proportion of core material, sealer, voids, and debris in each canal. Percentages and statistical comparisons for each method were compared. There were no significant differences found among the two groups in terms of the percentage of core (p = 0.9), sealer (p = 0.58), debris (p = 0.999), or voids (p = 1.00). Additionally, there were no differences in the percentage of core material, sealer, debris, or voids at any of the examined levels (2, 4, or 6 mm).     

The effects of viscoelastic parameters on residual stress development in a zirconia/glass bilayer dental ceramic.

OBJECTIVES: The aim of this study was to test the hypothesis that the residual stresses in a zirconia-based bilayer dental composite system can be tailored through heat treatment above and below the glass transition temperature of glass veneers. METHODS: Ceramic bilayer disc specimens were prepared from a zirconia core and a glass veneer. Each bilayer ceramic group was heat treated 40 degrees C below, 20 degrees C and 40 degrees C above and at the glass transition temperature of the glass veneer, and cooled using a fast or a slow cooling rate. Specimens were tested for flexure strength using a biaxial bending fixture. Residual stresses were calculated using a fracture mechanics approach. RESULTS: Heat treatments produced significant differences (p < or =0.05) between the mean flexural strengths of the heat treatment groups when the specimens were cooled using a fast cooling rate. However, there was not a significant difference (p >0.05) between the mean flexural strengths of the heat treatment groups when a slow cooling rate was used. Fractures initiated from the veneer surfaces of the specimens. SIGNIFICANCE: Heat treatment above and below the glass transition temperature of the veneer layer, and the cooling rate have a significant effect on the flexural strength of the bilayer ceramic laminates. The existence of residual compressive stress is the most likely reason for the observed strength increases. Residual stresses can be modified using the elastic-viscoelastic relaxation behavior of a glass veneer.     

In vivo evaluation of an oral health toothpaste with 0.1% vitamin E acetate and 0.5% sunflower oil (with vitamin F)

Objectives : To measure the delivery of active ingredients of a new oral health toothpaste with zinc citrate trihydrate/triclosan and containing α‐tocopherol acetate (vitamin E) and sunflower oil (vitamin F) and compare its anti‐plaque/anti‐ginigvitis efficacy to that of a clinically proven control toothpaste. Methods : The new toothpaste contained 0.1% vitamin E acetate (α‐tocopherol acetate) and 0.5% sunflower oil as a source for vitamin F (linoleic acid). It also included an anti‐caries agent (0.32% sodium fluoride) and a proven gum‐health active system (0.3% triclosan and 0.75% zinc citrate trihydrate). Three studies were carried out. In study 1 (n=45) the bio‐availability of zinc and triclosan was measured in plaque 12h after brushing with the test toothpaste. In study 2 (n=93) the effect of the test toothpaste on plaque and gingival condition was investigated over three weeks in a randomised, parallel, double‐blind, controlled design. The control toothpaste was a fluoride toothpaste containing 0.3% triclosan. Healthy adult volunteers with GI>1.0 were enrolled and given a full mouth scale and polish. Plaque levels (Modified Quigley and Hein Index) and gingival condition (Gingival Index) were assessed at baseline and after three weeks. Study 3 (n=93) lasted for nine weeks. Subjects did not receive a full mouth scale and polish at baseline but the study was otherwise identical to study 2. Results : In study 1, no triclosan was detected in baseline plaque samples; mean triclosan concentration in plaque 12h after last brushing with the test toothpaste was 5.78μg/g (std=4.74); the mean zinc concentration rose from 15.2μg/g zinc ion in baseline plaque samples to 84.3μg/g zinc ion (p>0.0001) in samples taken 12h after brushing. In study 2, mean plaque and gingival indices were significantly reduced in both test and control group after three weeks compared to baseline; there was no significant difference between the test and control group after three weeks. In study 3, mean plaque and gingival indices were significantly reduced in both test and control group after three and nine weeks compared to baseline; there was no significant difference between the test and control group after three and nine weeks. Conclusion : The delivery of zinc and triclosan from a new oral health toothpaste containing zinc citrate trihydrate and triclosan was unaffected by the addition of α‐tocopherol acetate (vitamin E) and sunflower oil (vitamin F). The new toothpaste was effective in reducing plaque levels and improving gingival conditions to the same degree as a clinically proven positive control. Regular oral hygiene with this toothpaste is therefore beneficial for maintaining healthy and strong gums.     

The effect of tooth preparation design on the breaking strength of Dicor crowns: 2

Six maxillary first premolar tooth preparation designs for all-ceramic restorations were tested for their effect on the strength of Dicor crowns. Ten crowns were fabricated for each preparation design, and the breaking strengths were measured. Three finish line designs (1.2-mm shoulder with sharp axiogingival line angle, 1.2-mm chamfer, and 0.8-mm chamfer) and two total occlusal convergence angles (5 degrees and 15 degrees) were tested. All preparations possessed 2.0 mm of occlusal reduction. The average breaking strengths of the 10 Dicor crowns were compared to those of 10 metal ceramic control restorations. The three groups of restorations fabricated for preparations with 5 degrees of occlusal convergence were significantly weaker than those made for preparations with 15 degrees of convergence. The metal ceramic restorations were significantly stronger (247.45 kg) than the strongest Dicor crowns (56.2 kg).