Fiber Reinforced Composites in Dentistry

Click HERE to see the Clinical Article on FRC

Fiber Reinforced composite is also great for splinting of perio involved cases where you want to prolong retaining teeth. SEE THIS REPORT

1. Freudenthaler, J.W., G.K. Tischler, and C.J. Burstone, Bond strength of fiber-reinforced composite bars for orthodontic attachment. Am J Orthod Dentofacial Orthop, 2001. 120(6): p. 648-653.

Long fiber-reinforced composites (FRC) have been shown to have enhanced mechanical properties that allow their use in orthodontic applicances as bars that join teeth to form either anchorage or active units. This study was designed to determine if the bonding of an orthodontic attachment has sufficient strength to withstand loading during clinical use. The experimental model consisted of a hydroxyapatite stone that simulated enamel, FRC bars, and a bonded metal hook.

Three specimen types were compared:
(1) a metal hook-pad (the control),
(2) a woven FRC with a hook-pad, and
(3) a unidirectional FRC with a hook-pad.

Loads were applied both parallel and at 90 degrees to the tooth surface. Under no condition was the FRC pad combination weaker than the control pad. Under some loading conditions, the loads before failure were as much as 3 times greater than those for the control. The lowest strength was found with loads at 90 degrees to the tooth surface for all 3 types. Failure normally occurred in the FRC and rarely at the bracket or tooth interface. The excellent bonding of the orthodontic attachment to the FRC and the high strengths of the FRC attachment combination demonstrate the ability to form connecting bars between teeth for either anchorage or active segmental movements. These bars offer advantages in simplicity in treatment by reducing the need for some bands, attachments, or wires.

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2. Terry, D.A., P.T. Triolo, Jr., and E.J. Swift, Jr., Fabrication of direct fiber-reinforced posts: a structural design concept. J Esthet Restor Dent, 2001. 13(4): p. 228-40.
As the clinician continues the quest for optimal functional and esthetic success of a tooth-restorative complex, the current selection of restorative materials and techniques may prove overwhelming. Although no single system provides the ideal restorative solution for every clinical circumstance, understanding of general design criteria and the components for the various post and core systems available allow the clinician to appropriately select the method and materials compatible with the existing tooth structure and desired result.

This article provides a discussion of the various post and core systems, the methods and materials inherent in these systems, and general design principles. Using that basic information and clinical experience, the authors offer an alternative procedure for the rehabilitation of the intraradicular anatomy of the post-endodontic channel with a direct composite resin--the fiber-reinforced post and core system.

CLINICAL SIGNIFICANCE: Using improved restorative materials that stimulate the physical properties and other characteristics of natural teeth in combination with the proper design principles, the clinician can develop a tooth-restorative complex with optimal functional and esthetic results.As the clinician continues the quest for optimal functional and esthetic success of a tooth-restorative complex, the current selection of restorative materials and techniques may prove overwhelming.

Although no single system provides the ideal restorative solution for every clinical circumstance, understanding of general design criteria and the components for the various post and core systems available allow the clinician to appropriately select the method and materials compatible with the existing tooth structure and desired result. This article provides a discussion of the various post and core systems, the methods and materials inherent in these systems, and general design principles. Using that basic information and clinical experience, the authors offer an alternative procedure for the rehabilitation of the intraradicular anatomy of the post-endodontic channel with a direct composite resin--the fiber-reinforced post and core system.

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3. Ellakwa, A., et al., Influence of veneering composite composition on the efficacy of fiber- reinforced restorations (FRR). Oper Dent, 2001. 26(5): p. 467-75.
This study investigated the influence of fiber reinforcement on the flexural properties of four commercial (Artglass, Belleglass HP, Herculite XRV and Solidex) veneering composites (Series A) and two experimental composites (Series B&C). This study investigated how the composition of the veneering composites influenced the enhancement of strength and modulus produced by fiber reinforcement. The formulation of the experimental composites were varied by changing the filler load (Series B) or the resin matrix chemistry (Series C) to assess the effect these changes would have on the degree of reinforcement.

In Series A, the commercial veneering composites were reinforced by an Ultra-High-Molecular-Weight Polyethylene fiber (UHMW-PE/Connect) to evaluate flexural properties after 24 hours and six months. In Series B, experimental composites with the same organic matrix but with different filler loads (40% to 80% by weight) were also reinforced by Connect fiber to evaluate flexural properties. In Series C, experimental composites (Systems 1-4) with the same filler load (76.5% by weight) but with different organic matrix compositions were reinforced by Connect fiber to evaluate flexural properties. For Series B and C, flexural properties were evaluated after 24 hours water storage.

All the samples were prepared in a mold 2 mm x 2 mm x 25 mm and stored in distilled water at 37 degrees C until they were ready for flexural testing in an Instron Universal Testing Machine using a crosshead speed of 1 mm/minute. The results showed no significant differences in the flexural strength (FS) between any of the commercial reinforced composites in Series A. The flexural modulus (FM) of the fiber-reinforced Belleglass HP group was significantly higher than for Artglass and Solidex.

Water storage for six months had no significant (p>0.05) effect on the flexural strength of three of the four reinforced veneering composites. The flexural strength for Artglass was significantly reduced (p0.05) by six-month water storage. In Series B, however, increasing the amount of filler loading improved the flexural modulus of the reinforced experimental composite but had no effect on its flexural strength. In Series C, changing the organic matrix formulation had no affect on flexural strength but affected the flexural modulus of the reinforced experimental composite.

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4. Rosentritt, M., et al., In vitro repair of three-unit fiber-reinforced composite FPDs. Int J Prosthodont, 2001. 14(4): p. 344-9.

PURPOSE: Clinical damage, such as the fracture or abrasion of composite veneers, may cause the loss of a fixed partial denture (FPD). Intraoral methods may help in repairing and therefore lengthening the life span of the restoration. The aim of this in vitro study was to evaluate an intraoral method of repairing fractured FPDs made of two different fiber-reinforced composite framework systems.

MATERIALS AND METHODS: Shear bond strengths of a composite between two different fiber- reinforced composite frameworks were determined after five different mechanical surface treatments. A silicate-silane coating intraoral air- abrading system provided the most reliable bond strength values and was therefore used for treatment for the following veneer repair. The repair of 24 three-unit posterior FPDs was performed using a restorative composite resin. All FPDs were examined after simulating clinical service using thermocycling and mechanical loading. Fracture forces were determined for original FPDs and for FPDs after simulated intraoral repair.

RESULTS: The fracture strength of all original FPDs was about 900 N. After repair, a maximum decrease in strength of about 15% was determined. FPDs that were extremely damaged by cutting the framework showed the lowest results, with values of about 450 N.

CONCLUSION: The repair of the fractured veneer of fiber-reinforced composite FPDs provided good results and therefore may lengthen the life span of damaged FPDs. The repair of the fractured frameworks showed good results but can only be recommended for limited temporary use.

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5. Krasteva, K., Clinical application of a fiber-reinforced post system. J Endod, 2001. 27(2): p. 132-3.
The tooth structure of an endodontically treated tooth was restored with a core on a post, both prefabricated with fiber-reinforced polymer- ceramic material (Sculpture/FibreKor) and subsequently with a metal- free crown.

The tooth restoration is described in detail. It includes root canal preparation, polyvinyl siloxane impression taking, laboratory fabrication of the core on the post, adhesive cementation of the post-and-core system in the root canal, fabrication and cementation of the restorations, adjustment, and finishing. The success of this metal-free system is based on its increased flexural and tensile strength. Its application is safe, effective, and reliable. The high- quality aesthetics of the restorations is due to the translucency of the post-and-core material.

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6. Bacakova, L., et al., Polishing and coating carbon fiber-reinforced carbon composites with a carbon-titanium layer enhances adhesion and growth of osteoblast-like MG63 cells and vascular smooth muscle cells in vitro. J Biomed Mater Res, 2001. 54(4): p. 567-78.
Carbon fiber-reinforced carbon composites (CFRC) are considered to be promising materials for orthopedic and dental surgery. Their mechanical properties can be tailored to be similar to those of bone, and their chemical composition (close to pure carbon) promises that they will be tolerated well by the surrounding tissue.

In this study, CFRC composites were fabricated from phenolic resin and unidirectionally oriented Torayca carbon fibers by carbonization (1000 degrees C) and graphitization (2500 degrees C). The material then was cut with a diamond saw into sheets of 8 x 10 x 3 mm, and the upper surface was polished by colloidal SiO2 and/or covered with a carbon-titanium (C:Ti) layer (3.3 microm) using the plasma-enhanced physical vapor deposition method.

Three different kinds of modified samples were prepared: polished only, covered only, and polished + covered. Untreated samples served as a control. The surface roughness of these samples, measured by a Talysurf profilometer, decreased significantly after polishing but usually did not decrease after coating with a C:Ti layer. On all three modified surfaces, human osteoblast-like cells of the MG63 line and rat vascular smooth muscle cells (both cultured in a Dulbecco's minimum essential medium with 10% fetal bovine serum) adhered at higher numbers (by 21-87% on day 1 after seeding) and exhibited a shorter population doubling time (by 13-40%). On day 4 after seeding, these cells attained higher population densities (by 61-378%), volume (by 18-37%), and protein content (by 16-120%).

These results were more pronounced in VSMC than in MG63 cells and in both groups of C:Ti-covered samples than in the polished only samples. The release of carbon particles from the CFRC composites was significantly decreased--by 8 times in the polished only, 24 times in the covered only, and 42 times in the polished + covered samples. These results show that both polishing and carbon- titanium covering significantly improve the biocompatibility of CFRC composites in vitro, especially when these two modifications are combined.

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7. Tanner, J., P.K. Vallittu, and E. Soderling, Effect of water storage of E-glass fiber-reinforced composite on adhesion of Streptococcus mutans. Biomaterials, 2001. 22(12): p. 1613-8.
This study investigated the effect of water storage of fiber-reinforced composite on the adhesion of Streptococcus mutans (S. mutans) and its ability to stay adhered and multiply on the FRC.

The materials (E-glass fibers and denture base polymer) were stored in water for 14 or 30 days or left dry. Water contact angles of the materials before and after water storage were determined. Test specimens, with or without parotid saliva or serum pellicle, were incubated in a suspension of S. mutans allowing initial adhesion to occur. Bacterial adhesion and multiplication was studied using scanning electron microscopy. Contact angles of both materials were significantly reduced after water storage indicating an increase in surface free energy.

When studied without a surface pellicle, water storage significantly increased adhesion of S. mutans to both glass and polymer. Saliva coating of the materials resulted in higher degree of adhesion to glass fibers in comparison with polymer and after 14 days water storage glass bound over twice as much S. mutans cells than the polymer matrix. Bacterial growth and biofilm formation occurred equally on both materials.

RESULTS: The results of this in vitro study suggest that in order to avoid the possible increase in S. mutans adhesion, the reinforcing glass fibers should be covered with the matrix polymer of the composite.

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8. Rifkin, R. and E.A. McLaren, Restoring vertical dimension and facial harmony with the conservative use of fiber-reinforced composite resin. Pract Proced Aesthet Dent, 2001. 13(3): p. 233-7.

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9. Behr, M., et al., Comparison of three types of fiber-reinforced composite molar crowns on their fracture resistance and marginal adaptation. J Dent, 2001. 29(3): p. 187-96.
Three types of fiber-reinforced composite (FRC) molar crowns were tested on their fracture resistance and marginal adaptation under simulated oral stress conditions. Two glass fiber systems, one processed with a vacuum/pressure system, the other by manual fiber adaptation, and a polyethylene fiber system were evaluated. Every group consisted of 12 crowns.All crowns were luted adhesively on human molars and exposed to thermal cycling and mechanical loading (TCML: 6000x5 degrees C/55 degrees C; 1.2x10(6)x50N; 1.66Hz).

The marginal adaptation was evaluated through dye-penetration and analyzed semi-quantitatively with a scanning electron microscope. The fracture resistance was measured using a Zwick universal testing machine.The highest fracture resistance was observed on the glass-fiber systems (FibreKor/Sculpture 1875N+/-596; Vectris/Targis 1726+/-542), though statistically, the polyethylene system (belleGlass/Connect 1388+/-620) was not significantly weaker.

All systems exceeded the fracture resistance required to withstand the maximum masticatory forces expected in the molar region. The marginal adaptation generally had a tendency towards larger gaps after TCML. The crown/composite-cement bond deteriorated significantly after TCML with the manual fiber adaptation and the polyethylene fiber system. The cement/tooth bond strength depended on which composite-cement/dentin-adhesive system was used.

CONCLUSION: The fracture resistance of molar crowns made of glass-fiber reinforced composite was higher than those of polyethylene fiber-reinforced composite crowns. However, there was no statistically significant difference. The marginal adaptation seems to depend on the fiber systems and composite-cement/dentin adhesive system used.

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10. Behr, M., et al., Glass fiber-reinforced abutments for dental implants. A pilot study. Clin Oral Implants Res, 2001. 12(2): p. 174-8.
Titanium abutments in dental implants shine through all-ceramic crowns and therefore limit excellent esthetic results. Prototypes of tooth- colored fiber-reinforced abutments were investigated to avoid the shining-through effect.

In vitro, the fracture strength was determined after thermal cycling and mechanical loading of all-ceramic single crowns and four-unit bridges made of a fiber-reinforced composite. The suprastructures were adhesively fixed onto fiber-reinforced implant abutments and compared with those fixed on standard titanium abutments. The median of the fracture strength of the titanium-supported all- ceramic crowns was significantly higher than the median of crowns fixed onto the prototypes. But this value was still more than twice as high as the maximum loading force under oral conditions.

No statistical difference was found between four-unit bridges made by fiber-reinforced composite inserted onto titanium abutments and those inserted onto fiber-reinforced abutments. Fiber-reinforced abutment prototypes for dental implants avoided the shining-through effect associated with metal abutments. Their load-bearing capacity after in vitro stress simulation was higher than the maximum oral loading force. With some improvements, the fiber-reinforced implant abutments are therefore a promising alternative to titanium abutments.

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11. Meiers, J.C. and M.A. Freilich, Conservative anterior tooth replacement using fiber-reinforced composite. Oper Dent, 2000. 25(3): p. 239-43.

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12. Trushkowsky, R.D., Esthetic posterior tooth replacement using a fiber reinforced bridge. Compend Contin Educ Dent, 2000. 21(1): p. 80-4.

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13. Shuman, I.E., Replacement of a tooth with a fiber-reinforced direct bonded restoration. Gen Dent, 2000. 48(3): p. 314-8.
Today's methods and materials for tooth replacement are multiple and varied. Modern materials now allow for highly conservative abutment preparations that can retain bonded single tooth replacement fixed prostheses. A case report is presented in which fiber reinforced with composite resin was used for placement of a three-unit fixed long-term provisional restoration, providing fracture resistance while achieving an esthetically pleasing, durable restoration.

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14. Giordano, R., 2nd, Fiber reinforced composite resin systems. Gen Dent, 2000. 48(3): p. 244-9.
The Targis/Vectris and Sculpture/FibreKor systems were devised to create a translucent maximally reinforced resin framework for fabrication of crowns, bridges, inlays, and onlays. These materials are esthetic, have translucency similar to castable glass-ceramics such as OPC and Empress, and have fits that are reported to be acceptable in clinical and laboratory trials. These restorations rely on proper bonding to the remaining tooth structure; therefore, careful attention to detail must be paid to this part of the procedure.

Cementation procedures should involve silane treatment of the cleaned abraded internal restoration surface, application of bonding agent to the restoration as well as the etched/primed tooth, and finally use of a composite resin. Each manufacturer has a recommended system which has been tested for success with its resin system. These fiber reinforced resins are somewhat different than classical composites, so not all cementation systems will necessarily work with them.

Polishing of the restoration can be accomplished using diamond or alumina impregnated rubber wheels followed by diamond paste. The glass fibers can pose a health risk. They are small enough to be inhaled and deposited in the lungs, resulting in a silicosis-type problem. Therefore, if fibers are exposed and ground on, it is extremely important to wear a mask. Also, the fibers can be a skin irritant, so gloves also should be worn.

If the fibers become exposed intraorally, they can cause gingival inflammation and may attract plaque. The fibers should be covered with additional composite resin. If this cannot be accomplished, the restoration should be replaced. The bulk of these restorations are formed using a particulate filled resin, similar in structure to conventional composite resins. Therefore, concerns as to wear resistance, color stability, excessive expansion/contraction, and sensitivity remain until these materials are proven in long-term clinical trials. They do hold the promise of minimizing tooth reduction and may be particularly useful in preserving sound tooth structure. Although not the primary intended use, an excellent application is long- term temporization, such as for patients requiring full mouth rehabilitation.

The belleGlass/Connect, Ribbond, and GlasSpan materials rely on nonimpregnated polyethylene fibers which have mechanical properties inferior to Vectris and FibreKor. These fibers may be used to greater success as splinting materials, in provisional restorations, and in repair of complete and partial removable dentures.

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15. Vallittu, P.K. and C. Sevelius, Resin-bonded, glass fiber-reinforced composite fixed partial dentures: a clinical study. J Prosthet Dent, 2000. 84(4): p. 413-8.

STATEMENT OF PROBLEM: Resin-bonded, glass fiber-reinforced composite fixed partial dentures (FPDs) have been under development for some time. There is a lack of data regarding the clinical usefulness of such prostheses.

PURPOSE: The clinical performance of 31 resin-bonded, glass fiber-reinforced composite fixed partial dentures was evaluated in a preliminary study. MATERIAL AND METHODS: The prostheses were made to replace 1 to 3 missing maxillary or mandibular teeth in each of 31 patients. The prostheses had a framework made of continuous unidirectional E-glass fibers with multiphase polymer matrix and light- polymerized particulate composite resin veneering. The prostheses were examined after 6-month periods for up to 24 months (mean follow-up time was 14 months). Partial or total debonding of the prostheses or the framework fracture was considered a treatment failure.

RESULTS: Two prostheses debonded during the follow-up period; 1 debonding was related to improper occlusal adjustment and the other to unknown reasons. Kaplan-Meier survival probability at 24 months was 93%. No framework fractures were observed.

CONCLUSION: The results of this preliminary study suggest that the resin-bonded, glass fiber-reinforced FPDs may be an alternative for resin-bonded FPDs with a cast metal framework.

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16. Duncan, J.P., M.A. Freilich, and C.J. Latvis, Fiber-reinforced composite framework for implant-supported overdentures. J Prosthet Dent, 2000. 84(2): p. 200-4.
This article presents a new method for fabricating a framework for an implant-supported overdenture using unidirectional fiber-reinforced composite. This procedure eliminates the need for a traditional metal alloy framework. The fiber-reinforced composite framework has the advantages of lower cost, less time and materials needed during fabrication, minimal potential for toxicity to the technician and patient, and a more esthetic metal-free final result.

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17. Hughes, T.E. and H.E. Strassler, Minimizing excessive composite resin when fabricating fiber-reinforced splints. J Am Dent Assoc, 2000. 131(7): p. 977-9.

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18. Tanner, J., P.K. Vallittu, and E. Soderling, Adherence of Streptococcus mutans to an E-glass fiber-reinforced composite and conventional restorative materials used in prosthetic dentistry. J Biomed Mater Res, 2000. 49(2): p. 250-6.
The adherence of Streptococcus mutans to E-glass used in fiber- reinforced composites, denture base polymer, and four other restoratives was investigated. The materials were studied with and without a parotid saliva and serum pellicle. Specimens of the studied materials (E-glass, denture base polymer, titanium, cobalt-chromium alloy, gold alloy, and grained feldspar ceramic) were incubated in a suspension of S. mutans, allowing initial adhesion to occur.

The degree of bacterial adhesion was studied using scanning electron microscopy (SEM). The studied uncoated materials showed rather similar adhesion of S. mutans. Saliva coating resulted in a decrease of adherence to all materials except glass. With a saliva pellicle E-glass showed the strongest ability to bind S. mutans, and it differed significantly from the other studied materials.

Serum coating markedly decreased adhesion to all materials, and only minor differences among the studied materials were observed. The results of this study suggest that the studied restoratives are rather similar with respect to S. mutans adhesion and that a saliva pellicle may promote adhesion of S. mutans to glass fibers.

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19. Winters, K.L., Using a fiber-reinforced ceromer for fixed restorations. Dent Today, 1999. 18(6): p. 70-3.

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20. Lopez, L.A., A metal-free fiber-reinforced replacement of a fractured tooth--a case report. Pract Periodontics Aesthet Dent, 1999. 11(4): p. 508-10, 512, 517.

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21. Gohring, T.N., W.H. Mormann, and F. Lutz, Clinical and scanning electron microscopic evaluation of fiber- reinforced inlay fixed partial dentures: preliminary results after one year. J Prosthet Dent, 1999. 82(6): p. 662-8.

STATEMENT OF PROBLEM: Restorative dentistry searches for nonmetal reinforcement of esthetic fixed partial dentures (FPDs).

PURPOSE: This clinical study evaluated conservative fiber-reinforced composite FPDs bonded to inlay abutments. MATERIAL AND METHODS: Twenty fiber- reinforced composite inlay FPDs were made for 15 patients. Restorations were manufactured with the Targis Vectris glass-fiber-reinforced composite system and a simplified laboratory technique. The 20 bonded inlay FPDs were examined clinically and by SEM after 1 year.

RESULTS: All 20 FPDs were intact at the 1-year examination. There were no signs of fracture, surface defects, or excessive wear with SEM. SEM marginal analysis exhibited 91.6% +/- 5% excellent margins at the tooth-luting composite interface and 86. 1% +/- 8% excellent margins at luting composite/restoration interface.

CONCLUSION: On the basis of the results of this descriptive study, bonded glass-fiber-reinforced composite inlay FPDs were considered clinically successful at the 1- year examination.

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22. Arbogast, K.B. and S.S. Margulies, A fiber-reinforced composite model of the viscoelastic behavior of the brainstem in shear. J Biomech, 1999. 32(8): p. 865-70.
Brainstem trauma occurs frequently in severe head injury, often resulting in fatal lesions due to importance of brainstem in crucial neural functions. Structurally, the brainstem is composed of bundles of axonal fibers distinctly oriented in a longitudinal direction surrounded by an extracellular matrix.

We hypothesize that the oriented structure and architecture of the brainstem dictates this mechanical response and results in its selective vulnerability in rotational loading. In order to understand the relationship between the biologic architecture and the mechanical response and provide further insight into the high vulnerability of this region, a structural and mathematical model was created.

A fiber-reinforced composite model composed of viscoelastic fibers surrounded by a viscoelastic matrix was used to relate the biological architecture of the brainstem to its anisotropic mechanical response. Relevant model parameters measured include the brainstem's composite complex moduli and relative fraction of matrix and fiber. The model predicted that the fiber component is three times stiffer and more viscous than the matrix. The fiber modulus predictions were compared with experimental tissue measurements.

The optic nerve, a bundle of tightly packed longitudinally arranged myelinated fibers with little matrix, served as a surrogate for the brainstem fiber component. Model predictions agreed with experimental measures, offering a validation of the model. This approach provided an understanding of the relationship between the specific biologic architecture of the brainstem and the anisotropic mechanical response and allowed insight into reasons for the selective vulnerability of this region in rotational head injury.

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23. Gohring, T.N., I. Krejci, and F. Lutz, [Resin-bonded inlay bridges made of glass-fiber-reinforced composites. A step-by-step description of their clinical use]. Schweiz Monatsschr Zahnmed, 1999. 109(4): p. 368-84.

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24. Waltimo, T., et al., Adherence of Candida albicans to the surface of polymethylmethacrylate-- E glass fiber composite used in dentures. Int J Prosthodont, 1999. 12(1): p. 83-6.

PURPOSE: The use of reinforcing fibers in dentures has raised concerns about possible increased adherence of yeasts to the surface. The aim of this in vitro study was to compare the adherence of Candida albicans to the surface of denture-base polymer and to E-glass fibers.

MATERIALS AND METHODS: Test specimens were made from an autopolymerized denture- base resin (Palapress) reinforced with preimpregnated unidirectional E- glass fibers, which were exposed at the surface. The test specimens were pretreated with parotid saliva and incubated without agitation in standardized yeast suspensions (10(8) colony-forming units per mL) in phosphate-buffered saline at 37 degrees C for 1 hour. The test specimens were then washed to remove nonadherent cells. After being air dried, they were sputter coated with gold-palladium for scanning electron microscopy (SEM). To compare the adherence to different surfaces, the number of yeast cells found either on the polymer matrix or on the glass fibers was counted from SEM fields (170 microns x 120 microns, 600 x) of randomly selected areas.

RESULTS: The mean density of yeast cell found on the surface of the polymer matrix was significantly higher (P 0.001) than that on the surface of glass fibers. The number of adherent yeast cells found at the interface between the fibers and polymer matrix was high.

CONCLUSION: The adherence of C albicans to E-glass fibers was lower than to polymer matrix in the denture composite. If fibers are exposed only during polishing of the composite, the reinforcing material appears not to increase the adherence of this common oral yeast. However, areas with permanently exposed fibers may provide mechanical retention for yeast cells at the interface of the components.

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25. Goldberg, A.J. and M.A. Freilich, An innovative pre-impregnated glass fiber for reinforcing composites. Dent Clin North Am, 1999. 43(1): p. 127-33, vi-vii.
This article summarizes the development of pre-impregnated, fiber- reinforced composites. Previous efforts with various reinforcement materials for splinting are cited. The benefits of pre-impregnation are explained. The clinical procedure for placing a fiber-reinforced composite splint is described.

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26. Rudo, D.N. and V.M. Karbhari, Physical behaviors of fiber reinforcement as applied to tooth stabilization. Dent Clin North Am, 1999. 43(1): p. 7-35, v.
This article presents an understanding of the mechanical response of polymer matrix composite materials that are reinforced with fibers that have high levels of failure strain. Also discussed are the basic principles for the use of the materials and techniques to optimize the clinical success for the applications in which these fibers are used to restore and maintain form and function to the masticatory structures.

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27. Freilich, M.A., et al., Preimpregnated, fiber-reinforced prostheses. Part I. Basic rationale and complete-coverage and intracoronal fixed partial denture designs. Quintessence Int, 1998. 29(11): p. 689-96.
This is the first of two articles describing the development and use of a continuous fiber-reinforced composite as a framework for the fabrication of fixed partial dentures and splints. The chemical composition and physical structure of the fiber-reinforced composite, along with the progression and development of a variety of fiber- reinforced composite materials, are discussed. Criteria for case selection, tooth preparation, and the clinical and laboratory procedures required for partial- or complete-coverage fixed partial denture fabrication and delivery are described.

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28. Meiers, J.C., et al., Preimpregnated, fiber-reinforced prostheses. Part II. Direct applications: splints and fixed partial dentures. Quintessence Int, 1998. 29(12): p. 761-8.
This article is the second in a series that describes the development, physical properties, and clinical applications of fiber-reinforced composite materials. The development of fiber-reinforced composite technology has opened new avenues for fabricating direct tooth replacements and splints that are esthetic and simple in design and execution and have the potential for excellent durability. Splinting techniques for hypermobile dentitions or postorthodontic retention and the replacement of anterior and posterior teeth using a groove preparation, a denture tooth, and a fiber-reinforced composite framework will be described.

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29. Belvedere, P.C., Single-sitting, fiber-reinforced fixed bridges for the missing lateral or central incisors in adolescent patients. Dent Clin North Am, 1998. 42(4): p. 665-82, ix.
Many materials, methods, and techniques for the reinforcing of composites to bond a pontic onto abutment teeth have been tried and promoted. In this article, the author examines the use of fiber reinforcement in fixed bridges, describing the various steps performed by the dentist during the procedure.

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30. Vallittu, P.K., Compositional and weave pattern analyses of glass fibers in dental polymer fiber composites. J Prosthodont, 1998. 7(3): p. 170-6.

PURPOSE: This study compared weave patterns and glass compositions of five glass fiber materials found in commercial fiber-reinforced dental composites.

MATERIALS AND METHODS: A scanning electron microscope (SEM) was used to investigate the woven structure of five glass fiber products, and an energy-dispersive x-ray spectrometer (SEM/EDS) was used to determine the elemental composition of these glass fibers in the bulk and at the surface of the fiber. Five fibers of each product were analyzed.

RESULTS: The fiber products were either unidirectional rovings or bidirectional weaves. More precisely, the woven structures were linen weave, twill weave, or twill weave ribbon. SEM/EDS analysis revealed that the composition of the glass fibers was typical for E (electrical)-glass fibers with one exception. One product intended for use in fixed prosthodontics included unidirectional fibers with a composition consistent with a modified high-tensile-strength R-glass. Boron oxide found on the surface of glass fibers would likely contribute to an increased potential for corrosion of fiber-reinforced composite. CONCLUSIONS: The predominant fiber composition in these products is E-glass. Because the degree of hydrolytic stability of polymer-fiber composites over time may lead to material failure in permanent restorations, this property should be investigated further.

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31. Lopez, L.A., Restoration without compromise: using a fiber-reinforced polyceramic composite system to replace missing teeth. Dent Today, 1998. 17(4): p. 96-9.

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32. Kettunen, J., et al., The effect of an intramedullary carbon-fiber-reinforced liquid crystalline polymer implant on bone: an experimental study on rabbits. J Biomed Mater Res, 1998. 42(3): p. 407-11.
A novel composite material with an ultra-high strength and a low elastic modulus called carbon-fiber-reinforced liquid crystalline polymer (LCP/CF) has been developed. We studied the effects of an intramedullary LCP/CF rod on bone in rabbits.

A LCP/CF rod of 3.2 mm in diameter and 50 mm in length was introduced into the intramedullary canal of the right femur in ten rabbits weighing an average of 3.6 (3.1- 4.2) kg. The follow-up intervals were 3 and 52 weeks. No signs of deformity or osteopenia were seen in the operated femurs in the radiographic, histological, and histomorphometric studies.

Histologically, the implant was enclosed by cancellous bone in the metaphyseal area and by a thin cancellous bone cuff in medullary cavity. Bone was able to grow in direct contact with the LCP/CF rod. No signs of degradation of the implants or of adverse tissue reaction were seen. The intramedullary LCP/CF rod had no harmful effects on bone in rabbits. The biocompatibility of the LCP/CF appeared to be good.

This novel composite material demonstrates properties that may be useful in orthopedic applications.

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33. Freilich, M.A., et al., Development and clinical applications of a light-polymerized fiber- reinforced composite. J Prosthet Dent, 1998. 80(3): p. 311-8.

STATEMENT OF PROBLEM: After 0 years of intermittent reports in the literature, the use of fiber reinforcement is just now experiencing rapid expansion in dentistry.

PURPOSE: This article describes the development and use of a continuous, unidirectional fiber reinforced composite as a framework for the fabrication of fixed prostheses. METHODS: By using various matrix materials and fibers, a number of fiber-reinforced composite formulations were evaluated with the goal of creating a system with optimized mechanical properties and handling characteristics. Fiber-reinforced composite based on a light polymerized BIS-GMA matrix has been used clinically to make 2-phase prostheses comprised of an internal glass fiber-reinforced composite substructure covered by a particulate composite. The clinical and laboratory procedures required for the fabrication and use of reinforced composite fixed prostheses are described for laboratory- fabricated complete or partial coverage fixed prosthesis and chairside prosthesis.

RESULTS: Although additional clinical experience is needed, fiber-reinforced composite materials can be used to make metal-free prostheses with excellent esthetic qualities.

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34. Vallittu, P.K., I.E. Ruyter, and K. Ekstrand, Effect of water storage on the flexural properties of E-glass and silica fiber acrylic resin composite. Int J Prosthodont, 1998. 11(4): p. 340-50.

PURPOSE: The aim of this study was to determine the effect of water on the flexural properties of fiber-reinforced denture base polymers. MATERIALS AND METHODS: Continuous woven silanized electrical glass, or E-glass, fibers and woven silica fibers were used to reinforce heat- cured and autopolymerized denture base polymers. Fibers were oriented at a 45-degree angle to the long axis of the test specimens. Control specimens were unreinforced. Dry test specimens and those stored in water for up to 48 weeks were tested with a three-point loading apparatus. The surfaces of the fibers of the test specimens stored dry or 48 weeks in water were analyzed with a scanning electron microscope to evaluate the degree of adhesion between fibers and polymer matrix.

RESULTS: The ultimate transverse strength of unreinforced and reinforced denture base polymers decreased during 48 weeks' storage in water (P 0.05, one-way analysis of variance, n = 5), and most of this reduction occurred during the first 4 weeks of storage in water. The flexural modulus of the unreinforced test specimens decreased significantly (P 0.001), whereas there was less, if any, change in the flexural modulus of the fiber-reinforced test specimens. Scanning electron microscopic examination revealed no differences in adhesion of E-glass fibers to the polymer matrix when the specimens stored in water were compared with those stored by. Reduced adhesion between the silica fibers and matrix was observed after 48 weeks' storage in water.

CONCLUSION: The results of this study suggest that the ultimate transverse strength of the E-glass fiber-reinforced test specimens decreased 14% and that of the silica fiber-reinforced test specimens decreased 36% after 48 weeks of storage in water.

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35. Trinkner, T.F. and M. Roberts, Aesthetic restoration with full-coverage porcelain veneers and a Ceromer/fiber-reinforced composite framework: a case report. Pract Periodontics Aesthet Dent, 1998. 10(5): p. 547-54; quiz 556.
Due to the recent evolution of dental materials and procedures, the restoration of a particular clinical condition can be accomplished by various alternatives. While the use of integrated treatment modalities permit the restoration team to utilize the benefits of each material simultaneously, it requires the development of a comprehensive preoperative treatment plan to address the specific concerns of each region or material utilized. This article describes the use of a multidisciplinary approach to restore proper occlusion, function, and aesthetics in a patient with worn dentition.

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36. Blitz, N., Adaptation of a fiber-reinforced restorative system to the rehabilitation of endodontically treated teeth. Pract Periodontics Aesthet Dent, 1998. 10(2): p. 191-3.

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37. Rosentritt, M., et al., Intraoral repair of fiber-reinforced composite fixed partial dentures. J Prosthet Dent, 1998. 79(4): p. 393-8.
STATEMENT OF THE PROBLEM: Fractured composite facings may result in replacement of a fixed partial denture unless a reliable intraoral repair method can be provided.

PURPOSE: This in vitro study tested the quality of an intraoral repair method for fractured facings of fixed partial dentures made of a fiber-reinforced composite system. MATERIAL AND METHODS: Shear bond strengths of a light-curing composite to a fiber-reinforced composite material were determined after different mechanical surface treatments. Aluminum oxide air abrading provided the most reliable bond strength values and therefore was used as a pretreatment for the facing repair of three-unit posterior fixed partial dentures. Facing repair was performed with the tested light- curing hybrid composite. Facing fracture strengths of repaired and original fixed partial dentures were determined after thermocycling and mechanical loading.

RESULTS: Median facing fracture strength of the original fixed partial dentures was 1450 N after a simulated clinical service of 5 years. Facing fracture strengths of the repaired fixed partial dentures were significantly lower compared with the control group after an additional simulated 2-year interval. However, the median fracture force was still 1000 N. CONCLUSIONS: The facing repair of a fiber-reinforced fixed partial denture with a hybrid composite in combination with aluminum oxide air-abrading pretreatment and silanization provided sufficient fracture strength. Therefore the replacement of the complete restoration may be avoided.

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