Material and Methods

Series II

Five groups of three unit bridges (n = 5/group) coded A to E were prepared from Artglass dental composite with or without Connect fiber reinforcement and tested to failure.

Group A:  1.5mm square bar of Artglass.	Group B:  1.0mm vertical bar of connect ribbon between the abutement teeth.	Group C:  1.0mm horizontal bar of connect ribbon between abutement teeth.

Group D:  Artglass resin bar verically sandwiched between connect ribbon.	Group E:  1.5mm square bar of Artglass wrapped with connect ribbon over pontic area.

Preparation of the Bridges:  A three-unit bridge (23 mm in length) from lower 2^nd premolar to lower 2^nd molar replacing the lower 1^st molar (6.5 mm length, 5.5-mm height, and 8.5-mm width) was prepared on a typodont model.  Crown preparations on the two abutments incorporated a distal recess on the premolar and a mesial one on the molar (1.5-mm in width and depth).  Before construction of the bridge, a vacuform pull down matrix was prepared to better standardize the exterior outer form of the bridge.  Then the prepared model was duplicated using Agar-Agar impression material.  This allowed bridges to be prepared on a standard preparation. By using the same pull-down, the outer form of the bridges were also duplicated in an improved-standardized fashion (Figure 2a).

Figure 2a.  A photograph showing the model and the “pulldown” (arrow) designed for this study.

Group A:  Bridges completely fabricated from Artglass resin.

Artglass resin (dentine translucent shade) was adapted to the two abutment dies to form 1 mm thick copings.  The recess areas were covered with a very thin layer of resin to ensure the fabricated resin bar would seat passively into place.  The copings were light-cured for 20 second intervals.  The distance between the distal recess in the premolar coping and the mesial recess in the molar coping was measured.

Artglass resin was formed into a 1.5 mm square bar to the length required to span across the pontic area and to overlay the floor of the recessed areas in the copings.  The resin bar was light-cured for 20 seconds.  The cured bar was placed into the recess areas on a thin wash of Revolution 2 resin (Kerr). The bar was gently seated into place and light-cured for 20 second intervals at each end of the bar.  Additional Revolution 2 resin increments were added as necessary to complete the seal between bar and copings.  Each increment was light-cured for 20 seconds.  A transparent addition-cured clear silicone putty (Memosil CD putty -Heraeus Kulzer) template matrix of an ideally contoured bridge was used to aid bridge construction.  The mesial or distal internal surface of the matrix was partially filled with Artglass resin.  This was located over the bridge substructure on the sectional cast.  The resin was light-cured for 20 second intervals through the clear matrix.  The matrix was removed and additional resin added as required until the bridge was complete.  The bridge was removed from the dies and trimmed using fine tungsten carbide points to clearly define marginal fit and inter-proximal contact areas.

The bridge was polymerized off the dies for 180 seconds in a Unixs laboratory light-curing unit (Kulzer, Germany).

The bridge was glazed with unfilled resin being applied as a thin coating, then light-cured.

Group B:  Bridges fabricated in Artglass resin with a vertically placed bar fabricated from Connect (Belle de St. Claire) between the abutment teeth.

Construction of the bridges in Group B was as for A except as follows:  Connect by Belle de St. Claire was used to form the bar.  The 1 mm wide reinforcement ribbon was cut to the required length to span across the pontic area and to overlay the recessed floor areas in the copings.  The reinforcement ribbon was carefully impregnated with Kerr unfilled resin.  When the ribbon became transparent in appearance, indicating saturation by unfilled resin, the ends of the vertically placed fiber bar in the pontic area were twisted to the horizontal position to lie flat in the coping recesses.  The shaped ribbon was light-cured for 20 second intervals along its entire length.  The cured ribbon bar was seated into the recess areas on a thin wash of Revolution 2 resin (Kerr) and bridge construction was completed as for Group A.

Group C:  Bridges fabricated in Artglass resin with a horizontal bar placed between the abutment teeth.

Construction of bridges in group C was the same as for group B except for the following:  The cured ribbon bar was horizontally placed in to the recess areas on a thin wash of Revolution 2 resin (Kerr).

Group D:  Bridges were fabricated in Artglass resin with a vertical bar sandwiched in between Connect reinforcement ribbon.  This was attached along the sides of the bar and wrapped around the copings on the abutment teeth.

Artglass resin was adapted to the two abutment dies to form thin 1 mm copings.  The recess areas were covered in a thin layer of resin.

The distance between the distal side on the premolar coping and the mesial side on the molar coping was measured.  Artglass resin was formed into a 2 mm depth by .5 mm wide bar to the length required to span across the pontic area and lie against the interproximal sides of the two-formed copings.  The resin bar was light-cured for 20 seconds.  The cured bar was made to fit intimately against the two inter-proximal surfaces of the copings.  A minute increment of Revolution 2 resin (Kerr) was placed at each end and light-cured for 20 second intervals.  Additional Revolution 2 resin increments were added as necessary to complete the seal between bar and copings.  Each extra increment was light-cured for 20 seconds.  Connect (Belle de St. Claire) fiber was wrapped around the copings and bar.  The 1 mm wide reinforcement ribbon was cut to the required length and wrapped around the circumference of the two copings and either side of the resin vertical bar that initiated the pontic area.  The reinforcement ribbon was carefully placed against the buccal side of a coping and attached with a minute amount of Revolution 2 resin (Kerr), then the next length of ribbon was impregnated by a small amount of Kerr unfilled resin.  Attachment to the copings and pontic bar was undertaken in incremental stages to ensure the ribbon laid intimately against the side of the coping or pontic bar.  At each attachment site, when the ribbon had become transparent in appearance, it was immediately light-cured for 20 seconds.  The encircling reinforcement ribbon was finished beyond the connection area between pontic and retainer.  Otherwise the bridges were constructed as for group A.

Group E:  Bridges fabricated in Artglass resin with a horizontal bar placed between the abutment teeth that had 50 mm length of Connect reinforcement ribbon wrapped around the pontic bar.

Fabrication of the bridges in this group was similar to group A except for the following:  A 50 mm length of Connect reinforcement ribbon was wrapped around the pontic bar in such a fashion as not to impinge on the ends of the bar that would rest passively on the recess areas in the two copings.  The 50 mm length of ribbon was attached to the bar with a minute amount of unfilled resin and light-cured.  The ribbon was then saturated in unfilled resin; when the ribbon appeared transparent, it was wrapped tightly around the central area of the pontic bar and light cured for 20 second sessions around the entire circumference of the bar.  The cured ribbon bar was placed in to the recess areas on a thin wash of Revolution 2 resin (Kerr) and bridge construction was completed as for group A.

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Citation Number: Vol. 5, No. 4, Page 005