Article and Clinical Photos by Leendert Boksman, DDS, BSc, FADI, FICD and Robert C. Margeas, DDS

There is an ever-increasing body of dental research literature evaluating the use of fibers to reinforce the clinical performance of dental composites and acrylics. Teeth restored with fiber posts show a significantly higher resistance to fracture than titanium¹ and stainless steel posts.² Teeth restored with fiber posts are significantly stronger in static and fatigue fracture testing than teeth restored with metallic posts,³ resulting from an elastic modulus that more closely approaches dentin, producing less concentrated stress on the root.⁴ Similarly, custom fiberreinforced posts (Ribbond^® [Ribbond; Seattle, Wash.]) fabricated directly into the root canal space with composite show that polyethylene fiber-reinforced posts with composite cores demonstrate high survival rates and can be recommended for use.^5,6 Additionally, the insertion of Ribbond inside the cavity has a positive effect on fracture strength of endodontically treated molar teeth with MOD cavity preparation and cuspal fracture,⁷ as well as the ability to reinforce severely compromised teeth which have been endodontically treated.⁸

The use of fiber reinforcement has distinct advantages in traditional composite restorative techniques. The use of fiber under composite restorations can save the tooth structure by changing fracture lines if cusp failure should occur⁹ and significantly increases fracture strength of MOD composite restorations, especially if placed in a buccal to lingual direction.¹⁰ The fatigue strengths of particulate filler composite resins is 49-57 MPa, and those of fiber-reinforced composites is 90-209 MPa, with the strain of UHMWPE (ultra-high molecular weight polyethylene, i.e., Ribbond) being the highest.¹¹ Strain energy absorption can be increased 433 percent over unreinforced composite, with the leno-weave reinforced composite having the highest consistency due to the details of its architecture, which restricts fabric shearing and movement during placement.¹² Polyethylene reinforcing fiber, when used in combination with a flowable resin in high C-factor cavity preparations, results in stable bond strengths and an increase in the microtensile bond strength to the dentin floor.¹³ Another significant advantage of using fiber reinforcement in traditional Class II composite resins is the significant decrease in gingival microleakage.¹⁴

Strassler has written extensively on the benefits of fiber-reinforcing material with dental resins and has used fiber reinforcing in single-tooth replacement techniques,¹⁵ single visit, natural tooth pontic bridges¹⁶ and periodontal splinting with thin-high-modulus polyethylene ribbon.¹⁷ The high molecular weight polyethylene has a high wear resistance and high impact strength,¹⁸ with its plasma treatment resulting in chemical integration with composite resins.¹⁹ With a locked-stitched lenoweave, the fibers maintain their orientation when adapted to the tooth structure or integrated into temporization and do not unravel when cut.²⁰ The addition of fibers to provisional resins increases the fracture toughness and flexural strength,²¹ with the clinical implication of a reduced incidence of fixed provisional restoration failure²² due to enhanced fracture resistance.²³ Additional strengthening of the connector areas can be achieved through the use of a fiber-reinforcing material such as Ribbond^®-THM (Ribbond).²⁴ Polyethylene fiber-reinforced composite bridges can be considered as a permanent treatment due to their strength^25,26 with selection of appropriate fiber reinforcement and placement of the fibers allowing long-term clinical success.²⁷

CASE PRESENTATION

A 55-year-old patient presented to the practice with two failing upper centrals (Fig. 1). Tooth #8 had a vertical fracture and tooth #9 had a failing root canal treatment. Upon presentation of the various options to restore the area, the patient opted for placement of a 4-unit fixed bridge. The centrals were atraumatically extracted with minimal trauma to the soft tissues and alveolar process (Fig. 2). The lateral incisors were minimally prepared for the initial long-term temporization so that the gingival tissues would have an opportunity to stabilize.

Utilizing a previously fabricated polyvinyl siloxane matrix, an appropriate length of Ribbond-THM (thinner higher modulus) was cut to extend from lateral to lateral incisor (Fig. 3). The Ribbond-THM was wetted using unfilled bonding adhesive, the excess blotted off with a lint-free gauze and the saturated Ribbond was placed onto the lingual surface of the PVS matrix, followed by injection of Temptation^® (CLINICIAN'S CHOICE; New Milford, Conn.) (Fig. 4). A small amount of Temptation was also placed into the extraction sockets (Fig. 5), and the PVS matrix was seated intraorally (Fig. 6).

After polymerization was complete, the matrix was removed, and the temporary bridge was removed from the matrix (Fig. 7). To create the desired soft tissue emergence profile (ovate pontic form) for the final restoration, the temporary bridge was fabricated to extend 3 mm below the free margin of the gingival tissue. The over-extension was removed (Fig. 8), and both pontics were shaped and contoured to measure exactly 3 mm from the marked position of the free margin with flowable composite (Figs. 9, 10).

Initial shaping of the temporary bridge was followed by the application of Tempglaze^™ (CLINICIAN'S CHOICE), which was cured with a broad spectrum curing light for 30 seconds per unit (Fig. 11). The temporary was cemented with Cling2^® (CLINICIAN'S CHOICE), and all temporary cement was removed (Fig. 12). After 10 weeks, the soft tissue showed excellent tissue contours, which will allow for naturallooking emergence profiles for the #8 and #9 pontics (Fig. 13).

Three additional clinical cases are presented in photo format only, to show the type of tissue response that can be created with this technique (Figs. 14, 15, 16, 17, 18, 19).