Written by Richard Trushkowsky, DDS, FAGD, FADM, FICD Monday, 31 May 2004 19:00
Composite resins that are currently available can produce restorations that are highly aesthetic and long lasting. One classification of resin relies on the quantity and type of filler particles present. The size of the particles affects the quantity of filler particles that can be dissolved in the resin (loading), the polishability, and the wear rate of the material.1 Composite is classified generally into hybrids, microfills, packables, and flowables.1
Hybrids usually contain 2 types of filler particles. The first is ground glass with an average particle size of 1 µm or less (macrofiller); the second filler is a small quantity of dispersed silica with the average size of 0.04 µm (microfiller). Hybrids typically have 55% or greater volume filler loading. This imparts excellent handling, strength, wear, good surface polish, and moderate radiopacity.1
Microfills usually contain only microfiller particles in the dispersed phase. The average filler loading for most microfills is much lower than hybrids. The reduced loading makes the microfills softer than the hybrid composites, and most microfills are radiolucent. However, they handle well and have a low wear rate. Also, a high polish can be imparted to the material. They also possess a low elastic modulus, and in this author’s experience are useful in areas where more brittle material such as hybrids would not be suitable.1
More recently, universal microhybrid composite materials such as Venus (Heraeus Kulzer) have been introduced. It is the material used in the case report described in this article. The manufacturer has varied the refractive indices of the fillers and resin matrix, resulting in a material that demonstrates 3 distinct opacities that enable the restorative dentist to place a restoration that blends with the natural dentition.2 Venus is 61% filled by volume with ultrafine filler particles (0.7 µm) that include barium fluoride glass, characterized by a narrow particle size distribution and colloidal silica that ranges in size from 0.01 to 0.04 µm. Venus has a modulus of elasticity of 8,400 MPa, a flexural strength of 128 MPa, a compressive strength of 340 MPa, and an in vitro wear rate of 75 µm. The manufacturer claims that these properties permit its use for both anterior and posterior restorations.1,2
To achieve a truly natural polychromatic effect, stratification of various composite shades incorporated in an irregular placement is required.3 A 3-layer concept utilizes 2 composite shades to coincide with the optical properties of dentin and enamel. The opacious dentin shades are covered by a less chromogenic, more translucent enamel shade. These 2 shades are further overlaid with a more translucent incisal shade.4,5 Venus has 3 translucent shades: T1, a cool blue translucency; T2, a neutral translucency; and T3, a yellow translucency. The opacious dentin shades provide the chroma for the restoration.
Composite can be combined with fiber reinforcement to fabricate a splint to prevent motion or displacement of mobile teeth.6 Stabilization of mobile teeth provides masticatory comfort, occlusal stability, and sometimes improved aesthetics.6 Stabilization of severely periodontally involved teeth by a fiber-reinforced composite (FRC) may be indicated when a more definitive treatment plan is not feasible. Teeth with a reduced capacity to adapt may also pathologically migrate.7 Occlusal forces may accelerate attachment loss in progressive periodontitis. Trauma from occlusion may be a contributing or co-destructive factor in combination with an active inflammatory lesion.7
A FRC splint can be fabricated directly or indirectly. The advantage of a directly bonded splint is that it is a 1-visit procedure. However, connections between teeth can compromise the goal of achieving an aesthetic result.8,9 Change in the shape and appearance of the interproximal areas, incisal embrasures, and gingival spaces must be considered when placing the composite splint. The smile is directly affected by the appearance of teeth and the surrounding gingival tissues. The interproximal spaces have to be aesthetically modified by the splint so that they appear individually in the correct dimensions. Each tooth has to be individualized by shaping and contouring to avoid a block-like appearance of the tooth.
When a ribbon and composite are used for splinting, the ribbon should be placed in the tensile zone of the splint. Splinting teeth affects the 3-dimensional appearance of teeth. Connections have to be of adequate thickness to provide strength in function but not compromise appearance. The optimal placement of the connector should be in the incisal or middle third of the tooth.10
When 2 or more materials are combined, the resulting composite will have a combination of properties that neither component possesses individually. The properties will be intermediate between the 2 components.11 However, some components, especially toughness, can be significantly superior in the composite compared with either of the 2 materials. In fiber-reinforced polymers, the main function of fibers is generally to increase the stiffness and strength.11 The matrix acts to protect the fibers and fix their arrangement in a predetermined position that provides optimum reinforcement. The interface between the 2 components is important in transferring loads from the matrix to the fibers. The presence of poorly bonded fibers to which little load can be transferred is similar to having voids.11
A designer working with fiber laminates can take advantage of the anisotropy by careful selection of the material to match the predicted service stress direction(s). If a material is likely to be loaded in one direction, a unidirectional laminate will provide optimal reinforcement. The highest stiffness and strength are achieved using continuous fiber laminate.11 The important parameters responsible for the static strength of the FRC are impregnation of fibers with resins and the quantity of fibers in the polymerized matrix.11 The desirable properties for dental resin fiber reinforcement are strength, toughness, minimal water sorption, good optical qualities, biocompatibility, bondability, conformability, and manageability.11 The strength should be enough to support a significant load with minimal elastic distortion. This is the flexural strength or modulus of the material. The toughness of the material is also the resistance of the material to rapid crack propagation.
The material should absorb a minimal amount of water, should be capable of being camouflaged within the composite, and should not cause any untoward biological response. The fiber should be capable of bonding chemically to the resin and minimizing debonding, and it should be capable of being shaped to conform to the geometry of the teeth and the dental arch. The rigidity and strength of the construction made from FRCs depend on the nature of the polymer and the type of fiber reinforcement, adequate impregnation of the fibers with resin, adhesion of the fibers to the matrix, the amount of fibers, the direction of the fibers, and the location of the fibers in the assembly.
Reinforcing fibers are difficult to impregnate with high-viscosity resins.11,12 If the impregnation is not effective due to the high viscosity or high volumetric shrinkage of the resin, the mechanical properties of the FRC will be less than ideal. Degradation of the fiber composite can occur if the fiber-matrix debonds as a result of circumferential cracking/opening along the outer surface of the fiber. Transverse fibers such as leno weave or triaxial braid restrict the growth of cracks since the cracks have to move around the fiber, thereby increasing the fracture toughness.13,14
Fiber reinforcement can be used to stabilize periodontally involved teeth. This can be done by the direct technique or an indirect technique. The direct technique requires fewer steps and can be done in one appointment. The advantages of the indirect technique are the following: (1) it is easier to place the materials needed since access is not limited; (2) there is no contamination by saliva while fabricating the splint; (3) an assistant or laboratory can fabricate the prosthesis; and (4) the composite can be more thoroughly cured. The direct technique is preferred for a periodontal splint.
The following case report describes the use of a microhybrid composite resin with fiber reinforcement to treat an older patient with periodontally involved teeth.
The patient, a 70-year-old male, presented with pain upon mastication involving teeth Nos. 25 and 26. He had a previously placed composite splint that had fractured, with recurrent decay on several teeth (Figure 1). Tooth No. 26 had class III mobility. The patient also had a full upper denture and was missing all the lower molars. The premolars had fractured cusps (Figure 2). An implant supported over denture was suggested as the best treatment option. However, the patient declined due to the expense, and he felt he was too old (although he was told this shouldn’t be a factor in his decision). The option he accepted was replacing the current splint with a fiber-reinforced composite and repairing the premolars with directly placed composites.
|Figure 1. Pre-operative labial view demonstrates the broken composite splint.||Figure 2. Pre-operative occlusal view illustrates the incisal anterior wear and posterior occlusal wear.|
All the remaining composite and decay were removed (Figure 3). A piece of dental floss (or a narrow strip of dead-soft material [tin foil]) can be placed over a model of the teeth or can be placed directly in the mouth to ascertain the length required. This piece is then placed over the fiber reinforcement selected and cut to the appropriate length. For this case, Ribbond THM and Triaxial were selected. Ribbond is an ultrahigh molecular weight polyethylene fiber that is cold gas oxygen plasma treated in order to promote an adequate bond of the resin to the fiber. Original Ribbond general purpose fiber reinforcement or Ribbond THM can be used. Ribbond THM has a higher flexural strength than regular Ribbond and is only 0.18 mm thick. Ribbond Triaxial is constructed of unidirectional fibers with braided fibers inserted between them. This provides greater strength than the leno weave because the fibers are relatively straight. Other materials that could have been used include Connect (Kerr/Sybron), Ever Stick (Stick Tech, Turku, Finland), and Splint-It (Pentron).
The teeth were cleaned with flour of pumice (a clean, medium-grit diamond bur can also be used) to roughen the enamel. Aluminum oxide finishing strips can be used to clean interproximal areas and remove any debris that may interfere with bonding. The teeth were etched 15 seconds on enamel and 10 seconds on dentin with 37% phosphoric acid, then rinsed until all color was removed. Excess water can be removed with a high-speed vacuum, then blotted to keep the exposed dentin moist. Gluma Comfort Bond + Desensitizer (Heraeus Kulzer) was placed with a microbrush and lightly scrubbed onto all the etched surfaces, air-dried, then light-cured. I Bond (Heraeus Kulzer) or similar adhesives can also be used to minimize any sensitivity. Venus (Heraeus Kulzer) was selected as the composite material. Alternatives include Filtek Supreme (3M ESPE), Esthet-X (DENTSPLY Caulk), Four Seasons (Ivoclar Vivadent), Point 4 (Kerr), Miris (Colténe/Whaledent), Vitalescence (Ultradent), Gradia Direct (GC America), and Simile (Pentron).
Venus has 23 shades in 3 opacities. The superficial layer is the semi-translucent enamel shade, and the deepest layer is the opacious dentin shade. The shades needed were selected using the shade guide provided. This shade guide is fabricated from the material itself. Each tab inserts into a plastic holder. The back of the holder has the formula of enamel and dentin shades that were used to create the tab. A more opaque resin was used interproximally and to build up the incisal edge on the lingual aspect. This served to block shadow from the back of the mouth. The labial was overlaid with several enamel shades, and the final enamel was a more translucent shade. Brown and gold effect colors can be placed interproximally to lend more definition. A thin layer of the lightest shade of translucent incisal composite resin was placed in a ribbon at the level of the contact area from the distal of tooth No. 22 to the distal of tooth No. 27.
The Ribbond was wetted with a light coating of unfilled bonding adhesive. It may now be handled in the same manner as composite resin. The excess unfilled bonding adhesive was blotted using lint-free gauze. Ribbond was adapted to the teeth and compressed through the composite layer so that it touched the teeth. Once the Ribbond was compressed through the composite resin, an interproximal carver was used to tuck it interproximally so that it adapted to the contour of the teeth (Figure 4). Ribbond’s minimal memory makes this easier to accomplish. This manageability is a result of the cross-link, lock-stitch leno weave. This weave helps prevent slippage of the fibers in the resin. This will also aid in preventing mobile teeth from moving away from the splint.
|Figure 3. The old composite is removed, and flaring and spacing are revealed.||Figure 4. Ribbond is embedded into composite placed on the lingual of the lower anterior teeth and adapted to the contour, then pressed interproximally.|
Once the Ribbond was adapted, excess composite resin was removed to minimize finishing and polishing, then the composite was feathered at the gingival and incisal borders to avoid an abrupt edge. The composite was now light-cured from the labial and lingual. Each tooth was cured individually for 20 to 40 seconds, depending on the light source. A thinner strip of Ribbond was wrapped circumferentially at the wider embrasures to reinforce these areas (Figure 5). The opaque shade was now used interproximally to prevent shine-through of shadow from the back of the mouth (Figure 6). Gingival embrasures were maintained by contouring and/or using wedges. Incisal embrasures should also be carved. The composite should be rounded and indented interproximally to maintain the individuality of the teeth.
The composite was again light-cured. The labial veneers were initiated by placing a darker gingival shade, feathering toward the occlusal, and light-curing. The next lighter shade selected was used to cover the remaining labial surface. The final translucent enamel layer was placed. Durafill can be placed instead if a higher polish is desired and if there is more chance of staining. A camel-hair brush can be used to contour the material. FlowLine (Heraeus Kulzer) composite was placed over the lingual composite, smoothed with a brush, and light-cured (Figure 7). This provides a smooth surface that usually requires no polishing.
A flame-shaped finishing bur was used to remove any interproximal excess.
Sof-Lex (3M ESPE) polishing discs were used on the labial, and Epitex (GC) was used interproximally. A variety of diamond impregnated points and discs (Pogo, DENTSPLY/Caulk) can be used to develop anatomy and contour further. A medium rough diamond can create texture on the surface to help diffract light. A diamond or aluminum oxide polishing paste can be used to create a glossy but textured surface.
|Figure 5. Narrower pieces of Ribbond are wrapped circumferentially around the previously placed horizontal piece of Ribbond to give added support in the wider interproximal areas.||Figure 6. Composite is placed interproximally to cover the Ribbond and to reestablish correct embrasure space and contour.|
|Figure 7. Flowable composite is placed over the lingual adapted Ribbond, and a brush is used to smooth the surface. The composite is light-cured.|
The premolars were then restored. The teeth were etched for 15 seconds on the enamel and 10 seconds on the dentin. Several coats of Gluma Comfort Bond + Desensitizer were scrubbed lightly on all the etched surfaces, air-dried, then light- cured. The opacious dentin layer was placed next. Cusps and fossae were shaped with a P-11 (Ivoclar Vivadent) and an interproximal carver, then light-cured. The final last 0.5 mm of semi-translucent composite represented the enamel layer. Cusps and fossae were maintained and marginal ridges developed. Occlusion was verified, and finishing with egg- and flame-shaped finishing burs was initiated. Rubber points and discs create a smooth surface. A diamond polishing paste gives a final luster.
A microhybrid composite that is available in a variety of shades, opacities, and translucencies can be utilized for both anterior and posterior restorations. Composite combined with appropriate fiber reinforcement can be used in a variety of ways, such as a periodontal splint. Ribbond is translucent and practically colorless so that its fibers virtually disappear in the composite resin. In 2 visits, the patient described in this case had his teeth restored to function and aesthetics with minimal expense (Figures 8 to 10). The splint and posterior restorations are easily repaired if chipped or broken. Periodontal heath can be maintained by the patient using interproximal brushes as well as 3-month recalls. The patient still has the option of more definitive procedures if he desires.
|Figure 8. Anterior view open bite demonstrates individual tooth contour and embrasure reestablished.||Figure 9. Patient in habitual occlusion demonstrates improved aesthetics.|
|Figure 10. Occlusal view reveals posterior anatomy restored to the premolars and incisal anterior edges restored.|
1. Technical Bulletin, Heraeus Kulzer. 2002.
2. Browning GC. USAF Dental Investigation Service. Detachment 1, USAF School of Aerospace Medicine, Great Lakes, Il 60088. Venus Color Adaptive Matrix Restorative April 2003 Project 02-033
3. Terry DA. Color matching with composite resin: a synchronized shade comparison. Pract Proced Aesthet Dent. 2003;15(7):515-521.
4. Terry DA. Dimensions of color: creating high-diffusion layers with composite resin. Compend Contin Educ Dent. 2003;24(suppl 2):3-13.
5. Blank JT. Simplified techniques for the placement of stratified polychromatic anterior and posterior direct composite restorations. Compend Contin Educ Dent. 2003;24(suppl 2):19-25.
6. Serio FG. Clinical rationale for tooth stabilization and splinting. Dent Clin North Am. 1999;43(1):1-6.
7. Serio FG, Hawley CE. Periodontal trauma and mobility. Dent Clin North Am. 1999;43(1):37-44.
8. Strassler HE, Garber DA. Anterior esthetic considerations when splinting teeth. Dent Clin North Am. 1999;43(1):167-178.
9. Rappelli G, Putignano A. Tooth splinting with fiber-reinforced composite materials: achieving predictable aesthetics. Pract Proced Aesthet Dent. 2002;14(6):495-500.
10. Strassler HE, Haeri A, Gultz JP. New-generation bonded reinforcing materials for anterior periodontal tooth stabilization and splinting. Dent Clin North Am. 1999;43(1):105-126.
11. Vallittu PK. Strength and interfacial adhesion of FRC-tooth system. In: Vallittu PK, ed. The Second International Symposium on Fibre-Reinforced Plastics in Dentistry. Turku, Finland: University of Turku, Institute of Dentistry; 2002:3-28. Paper 1.
12. Freilich MA, Meiers JC, Duncan JP, et al. Fiber-Reinforced Composites in Clinical Dentistry. Carol Stream, Ill: Quintessence Pub Co; 2000.
13. Karbhari VM, Rudo DN, Strassler HE. Society for Biomaterials Annual Meeting, Reno, Nev, 2003, Poster 529 Continuous Fiber-Reinforced Composites for Dentistry Symposium The Development and Clinical Use of a Leno Woven UHMWPE Ribbon In Dentistry. Designing Fiber Reinforcements That survive in The Real World of the Damaging Oral Environment
14. Rudo DN, Karbhari VM. Physical behaviors of fiber reinforcement as applied to tooth stabilization. Dent Clin North Am. 1999;43(1):7-35.
Dr. Trushkowsky maintains a private practice in Staten Island, NY, emphazing aesthetic and restorative dentistry. He is a fellow in the Academy of General Dentistry, the Pierre Fauchard Academy, the Academy of Dental Materials, and the American and International College of Dentists. He is a member of the American Prosthodontic Society, the Academy of Osseointegration, and the American Academy of Cosmetic Dentistry. He is online with Dental Quest and is on the editorial board of Contemporary Esthetics and Restorative Practice. He is an evaluator for many leading manufacturers and CRA and is a senior consultant to the Dental Advisor.
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