Bisco: The “U-Beam” Bridge Richard Lin, Jr., DMD
Clinical Affairs Manager, Bisco

I have the opportunity to evaluate many new products at Bisco, and I am so excited about the U-Beam™ Bridge that I wanted to share this case study. I believe the U-Beam reinforcement system, created for indirect composite bridges, results in highly aesthetic restorations, which are not only strong and pleasing to the eye, but also conservative and beneficial for our patients. It’s the latest product that will advance our dental community by revolutionizing indirect restorations. I want to share my experience regarding this product and its minimally invasive procedure with you so that you may use it when the clinical situation arises.

A 27-year-old male presented with #19 missing due to previous extraction. #18 had an occlusal amalgam with evidence of incipient mesial caries. #20 was a virgin tooth (Fig. 1). The patient wanted to fill the space at #19, but was opposed to an implant because he was uncomfortable with surgery. Since #20 was unrestored, we made the conservative decision to forego placement of a three-unit bridge with conventional crown abutments. A U-Beam supported composite bridge with inlay abutments was the more desirable choice of restorations.

I began by administering local anesthetic via a mandibular Gow-Gates block and buccal infiltration. I used 1.8 cc of Septocaine (articaine hydrochloride 4%, 1:100,000 epinephrine), followed by 1.8 cc of Lidocaine (2% HCl, 1:100,000 epinephrine). Removal of the amalgam in #18 was achieved with Bisco’s Diamond Amalgam Remover (N-813014). Upon exploration and excavation, the mesial “incipient caries” resulted in moderate caries that required a large proximal box. I incorporated a gingival floor depth of at least 2.0 mm as measured from the external margin of the tooth to the axial-gingival line angle, a buccal-lingual width of at least 4.2 mm, and a vertical measurement from the gingival floor to the occlusal surface of at least 2.5 mm. The preparation was accomplished by using Bisco’s N-845KR025 Diamond bur. This bur is ideal for cutting the proximal box since its diameter is 2.0 mm and corresponds with the gingival floor depth requirement. Proper preparation for the U-Beam was verified with the larger 4.0 mm end of the U-Beam Gauge (Fig. 2). I kept the prep for #20 conservative to preserve sound tooth structure (Fig. 3). Since #20 is a smaller tooth, the proximal box dimensions were kept the same as for the molar, with the exception that the buccal-lingual width was 3.0 mm. The final prep form is accomplished using Bisco’s N-845KR025 Diamond bur. The proximal box preparation was verified by using the smaller 3.0 mm end of the U-Beam Gauge (Fig. 4). An impression was made using Twinz™ VPS Xtra-Lite Body on the preps and the Twinz VPS Heavy Body in the impression tray. The case was sent to a Tescera Certified Lab, which can be found at www.bisco.com. I placed temporary inlays in the prepped areas and cemented them in place with Temp Bond (Kerr).

Bisco, one of the dental industry’s most respected manufacturers, has developed an innovative, metal-free indirect composite bridge named the U-Beam Bridge. Tescera™ ATL (Fig. 5) an indirect composite, is the result of a long history of placing composites under pressure. In the early years of ATL development, nitrogen gases were used to create pressure, and regular air became the standard in 2002. The Tescera unit utilizes 60 psi of air and pressurizes the indirect composite in the Light Cup to eliminate porosities prior to light curing. This procedure is applied during each incremental layer as the lab technician builds up the dentin, enamel, and incisal portions of the restoration. Following the sequences of light cup cycles, the final step is to place the restoration in the Heat Cup for final polymerization using pressure and a heat curing cycle, under water, in an oxygen-free environment. The result is a strong, porosity free, highly aesthetic composite restoration that is wear resistant and is used for inlays, onlays, crowns, and bridges.

Bisco incorporated the Tescera technology in the development of the U-Beam posterior three-unit bridges. Prior to Bisco’s U-Beam, lab technicians used fiber mesh or ribbons to fabricate three-unit bridges, which failed due to the flexible nature of the fiber mesh/ribbons.

The U-Beam incorporates the concept of two vertical “I” beams, proven effective in commercial building construction, to support the buccal and lingual cusp areas for cuspal support while connecting gingivally, thus giving the “U” configuration. The beam is constructed of unidirectional pretensed quartz fibers bound together into a single matrix.

The U-Beam fits into the proximal boxes of the abutment inlay/onlay preparations and is given additional support when a fiber-reinforced rod is placed and bonded in the hollow center of the “U” with Tesceraflo composite (Fig. 6). This configuration gives unparalleled strength to an indirect composite bridge. Tests show it takes only 100 MPa to break a 4x4x25mm block of indirect composite with ribbon/mesh reinforcement, where a force of more than 200 MPa is needed to break the same sized block supported with a U-Beam and rod system.

The patient returns for cementation, upon receipt of the U-Beam Bridge from the lab (Fig. 7 and 8). After local anesthesia, (mandibular Gow-Gates block of 1.8 cc Septocaine (articaine hydrochloride 4%, 1:100,000 epinephrine) and 1.8 cc Lidocaine (2% HCl, 1:100,000 epinephrine), the temporaries and residual temporary cements were removed and the U-Beam bridge was placed. After verifying the fit, I sandblasted the internal surfaces of the inlay abutments, etched with Uni-EtchÆ, a 32% phosphoric acid to clean off the surfaces, and applied two coats of adhesive, One-StepÆ Plus. I used a gentle stream of air to evaporate the solvent from the One-Step Plus and light-cured each surface for 10 seconds. The abutment teeth were etched with Uni-Etch 32% phosphoric acid, rinsed thoroughly with water and dried. I applied an oxalate dentin desensitizer, BisBlock™, onto the dentin surfaces for 30 seconds to eliminate potential dentinal sensitivity, rinsed, and left the surface moist for wet bonding. Two coats of One-Step Plus were applied and air dried, followed by 10 seconds of light-curing. Duo-Link™ dual-cured cement was dispensed directly into the preparations to bond the U-Beam bridge. The U-Beam bridge was seated and spot tacked for two seconds using a Power Probe with Bisco’s VIP™ junior halogen curing light. This held the U-Beam Bridge in place while the excess cement is removed with brushes. A final light-cure of 40 seconds per surface with an 11 mm light probe completed the bonding process. Occlusion was checked with no adjustments. The occlusal surfaces of the abutments were etched with phosphoric acid and BisCover™ Liquid Polish was applied, air-thinned, and light-cured with the halogen light for 30 seconds to seal the margins and give a high gloss finish to the teeth and restoration (Fig. 9).

Dr. Richard Lin, Jr. received his BSC degree in Commerce from the University of Louisville in 1973 after completing his first two years in Chemistry at Purdue University. He worked for five years before entering dental school at the University Of Louisville, School Of Dentistry in 1978. He graduated in 1982 with his DMD degree and established his private practice in Virginia with emphasis on cosmetic dentistry. After practicing for 14 years in Virginia, Dr. Lin sold his practice and moved to the Chicago-land area to practice with several colleagues. He has enhanced his dental knowledge through a multitude of CE courses and has successfully treated many full mouth rehabilitations. Dr. Lin left his associate position after eight years and joined Bisco in May, 2004, as the Clinical Affairs Manager. You may contact Dr. Lin at (847) 534-6012 or rlin@bisco.com.