Effect of 5% sodium hypochlorite or Tubulicid pretreatment in vivo on the marginal adaptation of dental adhesives and glass ionomer cements

The effect of pretreatment of dentin with a 5% sodium hypochlorite solution (NaOCl) or Tubulicid on the marginal adaptation of a glass ionomer cement (FUJI), a glass ionomer cement reinforced with silver particles (Ketac Silver) and 3 dentin adhesives (Clearfil, Dentin Bonding Agent and Scotch Bond) was tested in vivo. After a one month experimental period, the formation of gaps was measured from SEM photomicrographs. The sodium hypochlorite pretreated glass ionomer cement fillings showed gapfree margins, while the Tubulicid pretreated ones showed locally small gaps. When the 3 resinous dentin adhesives were used gaps were observed over the whole length of the dentinal margin with both techniques of pretreatment.     

Colonization of the human oral cavity by a Streptococcus mutans mutant producing increased bacteriocin

Streptococcus mutans strain JH1005 is a mutant that produces levels of bacteriocin activity three-fold-elevated than those produced by its parent, JH1001. A single infection regimen with JH1005 was found to result in persistent colonization of the teeth of all three adult subjects tested. This is a significant improvement over JH1001, which required multiple exposures in order to colonize the teeth of humans reliably. The levels of total cultivable bacteria and indigenous S. sanguis were not affected by JH1005 colonization. In two of the three subjects, total (indigenous plus JH1005) S. mutans levels were significantly decreased. The results provide additional support for the role of bacteriocin production as an ecological determinant in colonization by S. mutans. They also indicate that a practical regimen for infection by an effector strain might be achieved for use in the replacement therapy of dental caries.     

Shear bond strengths of resin adhesive cements to dentin and Ni-Cr-Be alloy.

Two adhesives, Super Bond and Panavia, were evaluated for shear bond strength to dentin. Twenty human teeth were used for each adhesive. Bonding sites were prepared in dentin (600 grit) and the adhesives applied according to the manufacturers' instructions. Bond strengths were determined with an Instron testing machine at 24 hours. Super Bond developed the strongest bond of 21.59 +/- 3.91 MPa. Panavia produced a lower bond strength of 2.68 +/- 1.45 MPa. Statistically, Super Bond was found to have a stronger bond than Panavia. The same two adhesives were applied to Ni-Cr-Be specimens and compared to Comspan. Twenty Rexillium III specimens were used for each adhesive at 24 hours and 20 for thermocycling. The metal specimens were ground flat (600 grit) and then air abraded with 50-micron aluminous oxide. The adhesives were applied to the metal surface in accordance with the manufacturers' instructions. One group was tested at 24 hours while the second group was tested after thermocycling (2,500 cycles at 6 degrees C to 60 degrees C). At 24 hours, Super Bond had a significantly stronger bond than the other materials. Comparison of the 24-hour to thermocycled bond strengths found Comspan had a significant increase in bond strength, Panavia had no significant change and Super Bond had a significant decrease in bond strength. After 2,500 thermocycles, Comspan, Panavia, and Super Bond were not significantly different in bond strength.     

Cephalometric analysis of maxillofacial morphology in unoperated cleft palate patients.

This study was designed to investigate maxillofacial morphology in adolescents and adults with unrepaired cleft palate, with or without cleft lip. Twenty-two Chinese patients with unilateral cleft lip and palate (the UCLP group), and 21 Chinese with cleft palate (the CP group) were cephalometrically evaluated and classified into the five ranges established from the means and standard deviations for matched normal Chinese populations. Many subjects in both UCLP and CP groups showed an intrinsic maxillary retrusion and a steeper mandible. The others had nearly normal maxillofacial morphology. The tendency for maxillary retrusion and a steeper mandible became increasingly remarkable with age. In the long axis of upper incisors in subjects with permanent dentition, there were no UCLP subjects with labial inclination, whereas three CP subjects exhibited labial inclination.     

Visual and profilometric wear measurements.

Wear of composites can be estimated by the degree of marginal discrepancy between the prepared cavity wall and the occlusal margins of composites. Such evaluations are done on casts by comparing and rating the marginal discrepancy with those on standard casts. We analyzed the reliability of this technique on metal and stone specimens. These specimens contained grooves of different width and depth. For the visual comparison we used stone casts of machined standards of known groove depth. We measured the depths of the metal specimens with a profilometer and made stone casts of these original specimens. Using the stone casts of the standards, five dentists estimated the unknown groove depths on the remaining stone casts. These estimates were done under standardized conditions and repeated by each dentist on five different occasions. The results showed that visual depth evaluations of die stone specimens underestimated the depths when compared with the values measured with a profilometer on the original metal models. One investigator gave significantly different (p less than 0.05) groove depth estimates at different occasions.     

Prostaglandin E2 and interleukin-1 levels in smokeless tobacco-induced oral mucosal lesions

Inflammatory mediators released as a result of smokeless tobacco (ST)-induced irritation may play a role in the development of oral mucosal lesions at habitual tobacco placement sites in ST users. The present study examined levels of interleukin-1 (IL-1) and prostaglandin E2 (PGE2) in ST-induced mucosal lesions and compared these to mediator levels in clinically normal mucosa. Soft tissue biopsies were obtained from white mucosal lesions at habitual placement sites and normal alveolar mucosal tissue at non-placement sites in 18 ST users. Fifteen non-tobacco using subjects also provided normal alveolar mucosal biopsies. IL-1 and PGE2 were recovered from the specimens, and mediator levels were determined by enzyme immunoassay. Prostaglandin E2 levels (pg/mg) were lower in both regions in the ST subjects, but values did not vary significantly between the regions with 2.77±0.72 and 2.86±0.99 at placement and non-placement sites, respectively, in ST users and 7.31±3.84 in non-tobacco users. Both IL-1α and IL-lβ (pg/mg) were significantly (p < 0.0I) elevated in ST lesions (IL-lã=25.56±4.00; IL-1β=7.76±1.68) compared to either non-placement sites in ST users (IL-lα=14.64±2.65; IL-lβ=1.63±0.72) or non-tobacco users (IL-lα=12.84±2.60; IL-lβ=2.04±0.75). In view of IL-l's role in keratinocyte proliferation and its inflammatory effects, this cytokine may contribute to mucosal and gingival alterations observed in ST users.     

A Comparison of an Accelerated Technique for Casting Post-and-Core Restorations With Conventional Techniques

Purpose This project compares an accelerated technique for the casting of post-and-core restorations with four traditional techniques. The accelerated technique uses two phosphate-bonded investments and the traditional techniques use a gypsum- and a phosphate-bonded investment. The study measures and compares the differences between the seating of the casting and the seating of the acrylic resin pattern. The effects of the techniques on the fit of castings with and without a ferrule are also compared. Materials and Methods Six groups of 10 castings were made from plastic patterns formed on a stainless steel test die. A different investment and/or burnout method was used for each group. Each group had two subgroups: ferruled and nonferruled. The fit of the plastic patterns was measured at two time intervals after forming, 2 weeks and 3 months. The patterns were invested immediately after the 3-month measurement, and the difference in fit of the castings was calculated. An ANOVA and Tuckey-Kramer test were done to determine the statistical validity. Results The seating of the patterns after 3 months of storage was consistently worse than the 2-week measurements of fit. The ferrule and nonferrule patterns were not statistically different in seating. Measurement of the castings showed that the ferruled castings seated significantly worse than the nonferrule castings. The difference in the seating of the castings as compared with the patterns was considered clinically unacceptable, showing a range of 0.301 mm to 0.528 mm. The nonferrule castings showed a significant difference in seating among groups. The difference ranged from - 0.099 mm to 0.322 mm. Conclusions The castings of the ferrule subgroups were considered clinically unacceptable and were not analyzed for significance. Among the nonferrule castings, the group using a gypsum investment and conventional technique for investing and burnout but no ring liner showed the best seating. The accelerated technique was intermediate in seating with a difference of 0.148 mm from the seating of the patterns. This group was significantly different from the two best groups but not from the remaining three groups.     

The effectiveness of the Titan-S sonic scaler versus curettes in the removal of subgingival calculus. A human surgical evaluation

This study evaluated clinically the effectiveness of hand versus sonic subgingival scaling and root planing in the removal of calculus by visually examining the root surface at the time of periodontal flap surgery. Consideration was given to the method of instrumentation, probing depth, number of roots, and type of tooth surface. Eleven patients with moderate to advanced periodontal disease were evaluated. Four subjects were scaled and root planed with the Titan-S only, four with curettes only, and three with the Titan-S + curettes. At reevaluation 3 to 6 weeks after scaling and root planing, the decision to perform periodontal flap surgery was made based upon probing depth, bleeding upon probing, previous access to the root surface, furcation involvement, and the patient's level of oral hygiene. A full thickness mucoperiosteal flap was elevated to gain access to the root surface and measure the distance from the cementoenamel junction to the residual calculus. A total of 690 surfaces were evaluated surgically. The percentage of surfaces with residual calculus for each method of instrumentation was: Titan-S only (31.9%), curettes only (26.8%), and Titan-S + curettes (16.9%). Overall, 15.7% of the surfaces probing 0 to 3 mm, 29.3% of the surfaces probing 4 to 5 mm, and 44.4% of the surfaces probing 6 to 12 mm had residual calculus.(ABSTRACT TRUNCATED AT 250 WORDS)