In vitro Comparison of the Efficiency of Celluloid and Metallic Matrices in Proximal Restorations with a Bulk Polymer-based Biomaterial

The purpose of the study was the comparison of the contact tightness of the restored proximal area of lateral teeth with celluloid and metallic matrices and a bulk polymer-based biomaterial using an original in vitro assessing method.In 300 plastic right upper molars, mesial and distal vertical boxes (4 mm width in all directions) were prepared. 150 teeth were restored using circumferential celluloid bands and the rest were restored with sectional metallic saddle bands with the same thickness. The mesial/distal contact tightness was measured, before preparations and after restorations using dental floss and an original system consisting in a dynamometer connected to the model fixed on a plate that could slide gravitationally on vertical metallic rails actioned by a mass of 850 g attached with a string. The passing through force was recorded. For the mesial surfaces, the force varied from 4.782 � 0.014 N (sound) to 5.086 � 0.011 N (restored) (p [ 0.05) for circumferential celluloid matrix while for the sectional metallic matrix, the values varied from 4.787 � 0.016 N (sound) to 5.596 � 0.01 N (restored) (p [ 0.05). For the distal surfaces, the force varied from 5.589 � 0.01 N (sound) to 4.777 � 0.011 N (restored) (p [ 0.05) for circumferential celluloid matrix while, for the sectional metallic matrix, the values varied from 5.586 � 0.012 N (sound) to 5.793 � 0.015 N (restored) (p [ 0.05). Comparing to the sound surfaces, the bulk polymer-based material with high consistency and the circumferential celluloid matrices generated poorer distal and slightly stronger mesial contact area tightness while the sectional metallic ones drove to stronger mesial and distal contacts. However, the celluloid bands are often preferred because they allow the photopolymerization process and permit a good visual control during most of the steps of the working protocol.