A novel filling technique for packable composite resin in Class II restorations

Microleakage in class II restorations: open vs closed centripetal build-up technique

PURPOSE

This study evaluated whether a Class II restoration in a flowable resin composite has to be placed prior to (open-sandwich technique) or after (closed-sandwich technique) construction of the interproximal wall in the centripetal build-up technique in order to reduce microleakage.

METHODS AND MATERIALS

Thirty non-carious molars were selected and randomly divided into two groups (n = 15). A standardized Class H preparation was made with the cervical margin 1 mm below the cementum-enamel junction. In Group 1, flowable resin composite was applied as a 1 mm base, remaining exposed at the cervical margin. In Group 2, the hybrid resin composite was applied to the interproximal wall, followed by a layer of flowable composite on the pulpal floor, away from the margins. The restorations were then subjected to 500 thermal cycles, each with a dwell time of 20 seconds at 5 degrees C and 55 degrees C. Adaptation at the cervical margin was evaluated by dye penetration and SEM analysis using the replica technique. The data were statistically analyzed using the Mann-Whitney U-test (p < 0.05).

RESULTS

The centripetal open-sandwich technique led to significantly lower dye penetration than the centripetal closed-sandwich technique (p < 0.001).

CONCLUSION

Flowable resin composite placed under hybrid resin composites in Group 1 provided better marginal adaptation and fewer voids. However, neither Group 1 nor Group 2 was able to completely prevent microleakage.

Resin composite contours

When placing posterior composite resin restorations, clinicians often struggle to achieve good contacts. Frequently contacts that are successful are only confined to the occlusal aspect of the proximal wall. A clinical technique is discussed which achieves the correct contour as well as tight contacts. The technique is also minimally invasive and highly aesthetic.

Clinically relevant issues related to preheating composites

STATEMENT OF THE PROBLEM

Issues regarding the use of composite preheating need to be investigated so that the clinician will better understand the variables associated with this method.

PURPOSE

To examine the multiple aspects of use of a commercial composite preheating device (Calset, AdDent Inc., Danbury, CT, USA).

MATERIALS AND METHODS

Temperature values of three heating units and composite compules were obtained using a K-type thermocouple and were recorded digitally in real time. The following parameters were measured: maximum heater and composite temperature and its stability upon storage, composite temperature change when removed from the heater and injected, the effect of delivery system on ejected composite temperature, and the effect of repeated and extended preheating on composite monomer conversion (using infrared spectroscopy). Monomer conversion was measured after repeated composite cycling (from room temperature [RT] to 60 degrees C, 10x) or extended preheating (24 hours at 60 degrees C), and values were compared with composite maintained at RT (control group). Among test parameters, data (N=5 for each parameter) were analyzed using Student's t-test, analysis of variance, and the Tukey-Kramer post-hoc test where appropriate (alpha=0.05).

RESULTS/CONCLUSIONS

Two of the three tested units achieved the stated preset temperatures. Composite attained temperature values close to the heating unit. Composite temperature drop upon removal from the heater was dramatic: within 2 minutes a 50% temperature drop was noted. Heating the compule while preloaded in the syringe provided higher delivery temperatures than heating the compule separately (p < 0.00). Optimum results were achieved when preheated composite was dispensed and used as quickly as possible. Neither repeated nor extended preheating of composite significantly affected monomer conversion.

CLINICAL SIGNIFICANCE

Preheating composite has potential benefits, but should be used with knowledge of its limitations. Reheating of unused composite does not affect its degree of conversion, thus decreasing material waste. Heating of the composite preloaded in the delivery syringe enhances the temperature of extruded composite.