A pilot study of a modified radiographic technique for detecting early proximal cavities

Diagnosing the necessity of cavity preparation in demineralized proximal areas has been considered as a challenge in restorative treatment planning. The purpose of this study was to investigate the clinical performance of a modified radiographic technique for the detection of proximal cavities. The sample consisted of 44 proximal surfaces in 38 dental students. The patients had radiolucent proximal lesions restricted to the inner half of enamel or the outer third of dentine in bitewing radiographs, and there was doubt regarding the presence or absence of cavities in the approximal areas. The suspected surfaces were then examined by secondary bitewing radiographs which were taken after pressing radiopaque material into the proximal areas. Finally, orthodontic elastic separators were placed in the contact areas to provide enough space for direct visual and tactile examination, thus detecting any proximal cavity (reference standard). The sensitivity, specificity and accuracy of the modified bitewing radiography were calculated against the reference standard. Overall, 7 surfaces presented caries cavities according to the reference standard. All proximal radiolucencies observed in the inner half of enamel and 46% of those extended to the outer third of dentine were not cavitated when evaluated by direct visual and tactile examination. The sensitivity, specificity and accuracy of bitewing radiography with opaque material for detecting proximal cavities (n = 7) were 86, 100 and 98%, respectively. The tested radiographic technique displayed good validity in this pilot study for detecting proximal cavities in posterior teeth and should be further investigated.

In vitro effects of several surface preparation methods on shear bond strength of orthodontic brackets to caries-like lesions of enamel

AIM

The aim of this study was to evaluate the efficiency of several surface preparation methods for improving shear bond strength of brackets to demineralised enamel.

STUDY DESIGN

in vitro study. Eighty premolars were selected and divided into 5 groups. Group 1 served as the control, while the remaining 4 groups were immersed in a demineralising solution (pH 4.8) for 12 weeks. In groups 1 (control) and 2 (demineralised/control) conventional acid etching was used. In group 3, a solution of 5% sodium hypochlorite (NaOCl) was applied on enamel surface for one minute after acid etching. The brackets in group 4 were bonded with Transbond Plus self-etching primer, and group 5 underwent treatment with a 2% sodium fluoride (NaF) gel, which was applied on the enamel surface for 4 minutes before etching. Shear bond strength (SBS) and adhesive remnant index (ARI) were determined in all groups, and surface morphology was examined under scanning electron microscope (SEM).

RESULTS

The mean SBS of acid-etched demineralised enamel was significantly lower than that of acid-etched sound enamel (p<0.05). Treatment of caries-like lesions with 5% NaOCl or self-etching primer failed to improve the bond strength. After NaF treatment and acid etching of demineralised enamel, both type 1 and type 2 etching patterns were observed and the resulting SBS was comparable to that of sound enamel (p>0.05).

CONCLUSION

The application of 2% NaF on enamel caries before bracket bonding is an effective way for enhancing the bond strength.

Tensile properties of orthodontic elastomeric ligatures

CONTEXT

Tensile properties of elastomeric ligatures become important when efficiency of orthodontic appliances is considered.

AIMS

The aim of this study was to compare tensile strength, extension to tensile strength, toughness and modulus of elasticity of elastomeric ligatures in both the as--received condition and after 28 days of immersion in the simulated oral environment. Furthermore, the changes that occurred in tensile properties of each brand of ligatures after 28 days were evaluated.

SETTING AND DESIGN

Experimental-laboratory based.

MATERIALS AND METHODS

Elastomeric ligatures were obtained from different companies and their tensile properties were measured using Zwick testing machine in both the as-received condition and after 28 days of immersion in the simulated oral environment.

STATISTICAL ANALYSIS USED

The data were analyzed using independent sample t-tests, analysis of variance and Tukey tests.

RESULTS

After 28 days, all the ligatures experienced a significant decrease in tensile strength, extension to tensile strength and toughness ( P < 0.05), whereas modulus of elasticity increased in some groups and decreased in others. There were significant differences in tensile properties of different brands of ligatures in both conditions ( P < 0.05), with the exception of modulus of elasticity after 28 days.

CONCLUSIONS

The decrease in strength properties of elastomeric ligatures shows that they should be replaced at each appointment to reduce the risk of rupture. There are significant differences in tensile properties of different brands of ligatures, which should be considered during selection of these products.