Skip Navigation



The European Journal of Orthodontics Advance Access published online on May 19, 2007
The European Journal of Orthodontics, doi:10.1093/ejo/cjm025
This Article
Right arrow Abstract Freely available
Right arrow FREE Full Text (PDF) Freely available
Right arrow All Versions of this Article:
29/3/304    most recent
cjm025v1
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Add to My Personal Archive
Right arrow Download to citation manager
Right arrowRequest Permissions
Google Scholar
Right arrow Articles by Faltermeier, A.
Right arrow Articles by Müßig, D.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Faltermeier, A.
Right arrow Articles by Müßig, D.
Social Bookmarking
Add to CiteULike   Add to Connotea   Add to Del.icio.us  
What's this?

© The Author 2007. Published by Oxford University Press on behalf of the European Orthodontics Society. All rights reserved. For permissions, please email: journals.permissions@oxfordjournals.org.

Influence of fibre and filler reinforcement of plastic brackets: an in vitro study

Andreas Faltermeier*, Martin Rosentritt**, Rupert Faltermeier*** and Dieter Müßig*

Departments of * Orthodontics
** Prosthetic Dentistry
*** Neurosurgery, University Medical Centre, Regensburg, Germany

Address for correspondence Dr A. Faltermeier, Department of Orthodontics, University Medical Centre, Franz-Josef-Strauss-Allee 11, D-93042 Regensburg, Germany, E-mail: andreas.faltermeier{at}klinik.uni-regensburg.de


   Summary
Top
 Summary
Introduction
 Materials and methods
 Results
 Discussion
 Conclusions
 References
 
In spite of their popularity in fulfilling aesthetic requirements, plastic brackets still present some disadvantages because of their low elastic modulus, decreased fracture toughness, and reduced wear resistance. Fibre-reinforced composites are well established in dentistry and consist of a polymer matrix in which reinforcing fibres are embedded. Stress is transferred from the polymer matrix to the fibres which present a high tensile strength. Hence, the mechanical properties of polymers could be improved.

The purpose of this study was to compare fracture strength, fracture toughness and flexural strength of an experimental fibre-reinforced bracket material, an SiO2 filler-reinforced bracket and an unfilled plastic bracket material (control group). Experimental brackets and specialized bars were manufactured. Tests were performed after thermal cycling (5°C/55°C) the samples in an artificial oral environment of a device to simulate mastication. Statistical evaluation was undertaken. The median, 25th and 75th percentiles were calculated and a Mann–Whitney U-test was performed.

In this study two findings were obvious. (1) Filler reinforcement of plastic brackets improved fracture strength and fracture toughness in comparison with the unfilled bracket material. (2) Glass fibre reinforcement of orthodontic bracket materials resulted in the greatest enhancement of the mechanical properties in comparison with the other test groups. Therefore, the application of glass fibres in plastic brackets is a successful method to enhance fracture strength.


   Introduction
Top
 Summary
 Introduction
Materials and methods
 Results
 Discussion
 Conclusions
 References
 
Orthodontic brackets bonded to enamel are responsible for transferring the force applied by the activated archwire to the tooth. Stainless steel is the material commonly used for manufacturing brackets. Nevertheless, the period of appliance wear is long and the demand for more aesthetic appliances has increased. Therefore, consequent research has resulted in the introduction of ceramic and plastic brackets which have an improved aesthetic appearance (Brantley and Eliades, 2001Go).

Polymer brackets were also established in response to reports of enamel damage during de-bonding of ceramic brackets and excessive wear of enamel surfaces on opposing teeth (Brantley and Eliades, 2001Go). However, in spite of their popularity in fulfilling aesthetic requirements, plastic brackets still present some disadvantages because of their low elastic modulus, decreased fracture toughness, and inability to withstand the torquing forces generated by rectangular wires (Arici and Regan, 1997Go). In addition, a plasticizing effect caused by water sorption of the polymeric structures has been described (Rantala et al., 2003Go; Göhring et al., 2005Go). Therefore, current research on reinforcement methods of plastic brackets has encompassed several areas, including reinforcement of the polymer by fillers (so-called ‘composites’) or fibres, or the use of metallic inserts on the bracket slot (Brantley and Eliades, 2001Go).

Fibre reinforcement is well established in dentistry and its use is gaining popularity (Behr et al., 2000Go; Bae et al., 2001Go; Grandini et al., 2005Go; Tirapelli et al., 2005Go). Fibre-reinforced composites (FRCs) consist of a polymer matrix in which reinforcing fibres are embedded. The reinforcing effect of fibres on polymers, due to stress transferring from the polymer matrix to the fibres has been confirmed (Hamza et al., 2004Go). Factors which influence the mechanical properties of FRCs include type and quantity of fibres, and orientation and impregnation of the fibres within the resin matrix. Different types of fibres such as carbon, polyethylene, and glass are available. In spite of the fact that carbon fibres raise the flexural strength of polymers, their unsightly black colour restricts their use (Yazdanie and Mahood, 1985Go; Hamza et al., 2004Go). The reinforcing effect of glass fibres is reported to be more effective than that of polyethylene fibres (Kolbeck et al., 2002Go). This could be attributed to adhesion problems between ultra-high modulus polyethylene fibres and the resin matrix (Vallittu, 1997Go; Hamza et al., 2004Go). In dentistry, FRCs are commonly used for denture reinforcement, periodontal splinting, resin-bonded metal-free prosthesis, and intracoronal pins and cores (Pereira et al., 2003Go). Uni-, bi-, and multidirectional fibre orientation is applied for reinforcement. Only when the direction of the highest strain is known can unidirectional fibre orientation be chosen.

Hence, it was decided to investigate the influence of a bidirectional glass fibre weave reinforcement with a Vectris Frame (Ivoclar-Vivadent, Schaan, Liechtenstein), which was embedded in an experimental polymeric bracket material in comparison with filler reinforcement.

The purpose of this study was to compare fracture strength, fracture toughness, and flexural strength of an experimental fibre-reinforced bracket material, an SiO2 filler-reinforced bracket material, and an unfilled plastic bracket material (control group). To simulate temperature changes and the moisture of saliva in the oral environment, all bracket materials were exposed to thermocycling (6000 x 5°C/55°C) in a device to simulate mastication before testing.


   Materials and methods
Top
 Summary
 Introduction
 Materials and methods
Results
 Discussion
 Conclusions
 References
 

Fracture strength of experimental brackets

Three different experimental bracket groups were produced. The first consisted of urethane dimethacrylate (UDMA) and the second was constructed of a bidirectional glass fibre weave of Vectris Frame (Ivoclar-Vivadent). Vectris Frame consists of pre-impregnated (prepreg) fibreglass/composite components with a fibre orientation of 90 degrees. The fibres were silica coated and embedded in a resin matrix. Frame prepregs with the dimensions of 2 x 2 x 0.3 mm were cut and embedded in an UDMA matrix in the bracket centre before polymerization. The third bracket group was manufactured of UDMA as a monomer matrix and functionally silane-treated SiO2 fillers. The filler level was 30 vol%. To obtain a homogenous mixture, the composite blend was mixed in a mixer device (Speed Mixer DAC 150FVZ, Hauschild Engineering, Hamm, Germany) for 60 seconds (1800 r.p.m.).

After preparation, the bracket polymers were carefully placed in a mould which was made of a silicone impression of an upper central incisor Brillant bracket (Forestadent, Pforzheim, Germany). The polymerization was carried out using a polymerization device (Targis-Power-Lichtofen, Ivoclar-Vivadent) for 25 minutes. After polymerization the brackets were taken out of the silicone mould and the surplus was removed with a scalpel. Ten brackets per group were produced.

After thermocycling (5°C/55°C) the brackets were fractured with a Zwick universal testing machine 1446 (Zwick, Ulm, Germany). The load was axially applied at the bottom centre of the bracket pad. The crosshead speed chosen was v = 1 mm/minute.


Fracture toughness

For determination of fracture toughness, rectangular specimens (10 per group) with the dimensions of 36 x 8 x 4 mm (length x width x thickness) were manufactured. According to the bracket groups, three different bar groups were manufactured: the first consisted of UDMA; the second UDMA and a glass fibre weave [36 x 8 x 0.3 mm (length x width x thickness) Vectris Frame (Ivoclar-Vivadent)], embedded in the middle of the specimens (Figure 1); and the third group UDMA, reinforced with SiO2 fillers (filler level: 30 vol%). The Targis-Power-Lichtofen device (Ivoclar-Vivadent) was used for polymerization.


Figure 1
View larger version (9K):
[in this window]
[in a new window]
[Download PowerPoint slide]
  		Figure 1 Urethane dimethacrylate (UDMA) bars reinforced with a glass fibre weave in the centre.

 
The surface of the bars was ground with sand paper (grit 800). At the midspan of the specimens a 3-mm-deep and 0.5-mm-wide notch was prepared. This cut was extended to a notch of 0.2–0.5 mm in length using a razor blade device (Ivoclar-Vivadent). Before the tests were performed, all bars were thermocycled in a mastication device (5°C/55°C).

After preparation of the bars, a three-point bending test (Figure 2, support distance: 32 mm) was performed with the Zwick universal testing machine. The load was applied axially in the centre of the bars directly above the notch (v = 1 mm/minute).


Figure 2
View larger version (6K):
[in this window]
[in a new window]
[Download PowerPoint slide]
  		Figure 2 Three-point bending test for determining fracture toughness.

 
The fracture toughness (K1c) was determined according to the following formula (Williams and Cawood, 1990Go):

Formula

Formula

Formula
where S is the support distance, P the fracture load, B the width, H the height, and a the notch length.


Flexural strength

A silicone mould was manufactured with an inner dimension of 2 x 2 x 25 mm and three different groups of bars were produced: the first group consisted of UDMA; the second group of UDMA and a glass fibre weave of Vectris Frame (Ivoclar-Vivadent), which was embedded in the middle of the samples; and the third beam group was a composite, consisting of UDMA as a monomer matrix and SiO2 fillers (filler level: 30 vol%). The polymers were placed carefully in the mould and the polymerization was carried out using the Targis-Power-Lichtofen polymerization device (Ivoclar-Vivadent) for 25 minutes. Ten samples per polymer group were manufactured. All specimens were thermocycled at 5°C/55°C in a mastication device prior to testing.

The test was performed with a Zwick universal testing machine 1446. All beams were loaded to fracture using a three-point bending test following DIN 53452 (Hellerich et al., 1992Go). The support distance was 20 mm. The flexural strength ({sigma}) of the bars was determined using the following formula (Hellerich et al., 1992Go):

Formula
where F is the force, l the length, b the width, and h the height of the bars.


Artificial oral environment

Twenty-four hours after preparation, all brackets and bars were exposed to thermocycling to simulate the moisture of saliva and temperature changes in the oral environment. Therefore, all bracket groups were alternatively flooded every 2 minutes with warm (55°C) and cold (5°C) distilled water for 6000 cycles in a mastication device (Figure 3; Rosentritt et al., 1997Go).


Figure 3
View larger version (125K):
[in this window]
[in a new window]
[Download PowerPoint slide]
  		Figure 3 Artificial oral environment of a mastication device.

 

Statistics

Statistical analysis was undertaken using the Statistical Package for Social Sciences, version 12.0 (SPSS Inc., Chicago, Illinois, USA). Median, 25th and 75th percentiles were calculated. The Mann–Whitney U-test was performed. The level of significance was set to {alpha} = 0.05.


   Results
Top
 Summary
 Introduction
 Materials and methods
 Results
Discussion
 Conclusions
 References
 
A significant increase of fracture strength (P = 0.012) was found when reinforcing UDMA brackets with a glass fibre weave (Figure 4a, Table 1). The glass fibre-reinforced brackets showed a distinct enhancement of fracture strength in comparison with the unfilled UDMA brackets. The unfilled UDMA brackets showed a median fracture strength value of 317 N (Table 2).


Figure 4
View larger version (12K):
[in this window]
[in a new window]
[Download PowerPoint slide]
  		Figure 4 Fracture strength (a), fracture toughness (K1c) (b), and flexural strength (c) of experimental polymer brackets (median, 25th and 75th percentiles, minimum, and maximum).

 

View this table:
[in this window]
[in a new window]

  		Table 1 Statistical analysis (Mann–Whitney U-test and P values) of mechanical properties of experimental brackets.

 

View this table:
[in this window]
[in a new window]

  		Table 2 Median values and standard deviations of the mechanical properties of the experimental brackets.

 
A small, but significant (P = 0.022), improvement in fracture toughness was observed when SiO2 filler-reinforced brackets were compared with unfilled UDMA brackets (Figure 4b, Table 1). However, fracture toughness of the glass fibre-reinforced brackets almost tripled in comparison with the unfilled and filled polymer brackets.

A median value of 130 N/mm2 was observed, when the flexural strength of glass fibre-reinforced brackets was examined (Table 2). No significant increase in flexural strength was found, when UDMA brackets were compared with filler-reinforced brackets. The flexural strength of glass fibre-reinforced brackets showed a significant improvement in comparison with the unfilled and filled brackets (Figure 4c, Table 1).


   Discussion
Top
 Summary
 Introduction
 Materials and methods
 Results
 Discussion
Conclusions
 References
 
Aesthetics should be one of the most central properties of dental materials. For that reason greater attention has been paid to tooth-coloured brackets, especially in adult treatment. Nevertheless, in the oral cavity orthodontic appliances are subjected to cyclic mechanical and thermal loading in a wet environment during treatment. Thus, in this study an artificial oral environment was chosen to simulate temperature changes in a damp milieu in vitro. Fracture toughness, fracture strength, and flexural strength were tested. Fracture toughness is described as the ability of a material to resist crack propagation, whereas fracture strength is the stress at which the material fractures. The flexural strength test is able to compare the load-bearing capacity of different materials under flexure. According to Pereira et al. (2003)Go, the flexural strength test deserves particular attention, because it measures tension and compression acting together, simulating clinical conditions.

In this investigation UDMA was chosen as the polymer matrix, because it reveals increased tensile properties, low viscosity, and faster and more complete conversion (Asmussen and Phillips, 1998Go; Göhring et al., 2005Go). These factors may influence the mechanical properties of the experimental brackets and the embedding quality of the used bidirectional glass fibres and SiO2 fillers. A large amount of literature is available concerning fibre reinforcement and fibre content of FRCs (Drummond et al., 2004Go; Narva et al., 2004Go; Kanie et al., 2005Go; Lassila et al., 2005Go). Nevertheless, Behr et al. (2000)Go demonstrated that a higher fibre content does not necessarily lead to higher flexural strength. They stated that not only the fibre content but also the bond between the polymer matrix and fibres and the composition of the matrix influence the mechanical properties of FRCs.

In orthodontics FRCs have been successfully used as fixed orthodontic retainers or for temporary tooth splinting in periodontally compromised patients (Karaman et al., 2002Go). FRCs have also been used as experimental orthodontic wires (Huang et al., 2003Go) and space maintainers (Kargul et al., 2003Go). However, Kirzioglu and Erturk (2004)Go reported that FRC space maintainers could be accepted as successful appliances only for short periods. They stated that prolonged use of this material for retention in orthodontic patients must be evaluated in long-term studies.

In this investigation two findings were apparent. (1) Filler reinforcement of plastic brackets improved fracture toughness and fracture strength in comparison with unfilled brackets. (2) Glass fibre weave reinforcement of orthodontic brackets demonstrated the greatest mechanical properties of the tested samples. The explanation for these findings is that stress is transferred from the polymer matrix to the fibres which present a high tensile strength (Nohrstrom et al., 2000Go; Hamza et al., 2004Go).

In the present study the glass fibre weaves were positioned in the central part of the specimens. Göhring et al. (2005)Go found a significant reinforcing effect of flexural strength when the fibre weaves were located on the tension but not on the compression side of the samples. However, the direction of forces on brackets caused by the activated archwire, food, and opposing teeth during mastication is multidirectional. Because of the complex structure of orthodontic brackets and the unpredictable forces on brackets, the glass fibre weaves in this study were placed in the centre of the brackets and bars.

Several investigations have demonstrated that reinforcement of the polymeric structure with fibres and fillers is able to increase the mechanical properties (Jaarda et al., 1996Go; Condon and Ferracane, 1997Go; Drummond et al., 2004Go; Göhring et al., 2005Go; Kanie et al., 2005Go; Lassila et al., 2005Go). However, during cyclic temperature loading, interfacial stress between polymer matrix and fillers or fibres can occur, because of different thermal expansion coefficients (Göhring et al., 2005Go). Chai et al. (2005)Go found that water immersion affected the flexural strengths of different FRCs. In agreement with others (Vallittu et al., 1998Go; Vallittu, 2000Go; Tanner et al., 2001Go), Lassila et al. (2002)Go the decrease in flexural properties of FRCs after water immersion was mainly caused by the plasticizing effect of the water. Water molecules are able to penetrate into the spaces between polymer chains. As a result, water molecules push the polymer chains further apart and cause, after a sufficient period of time, an expansion in a wet environment. This results in a decline of the secondary chemical bonding forces (van der Waals forces) between the polymer chains (Rantala et al., 2003Go). Therefore, the mechanical properties, e.g. flexural strength and fracture toughness of plastic brackets, are reduced. Exposed fibres and voids in the structure of the FRC lead to another problem during water exposure in the oral environment. By means of capillary forces water could be absorbed (Rantala et al., 2003Go). As a result, water saturation of the brackets could be hastened. Poorly impregnated fibres could accelerate this progress. Nevertheless, Meric et al. (2005)Go reported that silica glass fibres showed sufficient qualities in aqueous environments, such as the oral environment. Consequently, fibreglass reinforcement, which is able to withstand the moisture of saliva in the oral cavity, seems to be a method to improve the mechanical properties of orthodontic brackets.


   Conclusions
Top
 Summary
 Introduction
 Materials and methods
 Results
 Discussion
 Conclusions
References
 
Reinforcement with fillers or fibres is able to improve the mechanical properties of polymeric brackets. The application of glass fibre weaves in plastic brackets has the podential to enhance fracture strength.


   References
Top
 Summary
 Introduction
 Materials and methods
 Results
 Discussion
 Conclusions
 References
 

    Arici S, Regan D. Alternatives to ceramic brackets: the tensile bond strength of two aesthetic brackets compared ex-vivo with stainless steel foil-mesh bracket bases. British Journal of Orthodontics (1997) 24:133–137.[Abstract]

    Asmussen E, Phillips RW. Influence of UEDMA, BisGMA and TEGDMA on selected mechanical properties of experimental resin composites. Dental Materials (1998) 14:51–56.[CrossRef][Web of Science][Medline]

    Bae JM, et al. The flexural properties of fiber-reinforced composite with light-polymerized polymer matrix. International Journal of Prosthodontics (2001) 14:33–39.[Web of Science][Medline]

    Behr M, Rosentritt M, Lang R, Handel G. Flexural properties of fiber reinforced composite using a vacuum/pressure or a manual adaptation manufacturing process. Journal of Dentistry (2000) 28:509–514.[CrossRef][Web of Science][Medline]

    Brantley WA, Eliades T. Orthodontic materials: scientific and clinical aspects (2001) Stuttgart, Germany: Thieme.

    Chai J, Takahashi Y, Hisama K, Shimizu H. Effect of water storage on the flexural properties of three glass fiber-reinforced composites. International Journal of Prosthodontics (2005) 18:28–33.[Web of Science][Medline]

    Condon JR, Ferracane JL. In-vitro wear of composite with varied cure, filler level, and filler treatment. Journal of Dental Research (1997) 76:1405–1411.[Abstract/Free Full Text]

    Drummond J, Lin L, Miescke KJ. Evaluation of fracture toughness of a fiber containing dental composite after flexural fatigue. Dental Materials (2004) 20:591–599.[CrossRef][Web of Science][Medline]

    Göhring T N, Gallo L, Lüthy H. Effect of water storage, thermocycling, the incorporation and site of placement of glass-fibers on the flexural strength of veneering composite. Dental Materials (2005) 21:761–772.[CrossRef][Web of Science][Medline]

    Grandini S, Goracci C, Monticelli F, Tay FR, Ferrari M. Fatigue resistance and structural characteristics of fiber posts: three-point bending test and SEM evaluation. Dental Materials (2005) 21:75–82.[CrossRef][Web of Science][Medline]

    Hamza TA, Rosenstiel SF, Elhosary MM, Ibraheem RM. The effect of fiber reinforcement on the fracture toughness and flexural strength of provisional restorative resins. Journal of Prosthetic Dentistry (2004) 91:258–264.[CrossRef][Web of Science][Medline]

    Hellerich W, Harsch G, Haenle S. Biegeversuch DIN 53452. In: Werkstofführer Kunststoffe—Eigenschaften, Prüfungen, Kennwerte (1992) 6th edn. Munich: Thieme. 197–210.

    Huang ZM, et al. Fabrication of a new composite orthodontic archwire and validation by a bridging micromechanics model. Biomaterials (2003) 24:2941–2953.[CrossRef][Web of Science][Medline]

    Jaarda MJ, Wang RF, Lang BR. A regression analysis of filler particle content to predict composite wear. Journal of Prosthetic Dentistry (1996) 77:57–67.[Web of Science]

    Kanie T, Arikawa H, Fujii K, Ban S. Deformation and flexural properties of denture base polymer reinforced with glass fiber sheet. Dental Materials (2005) 24:297–303.[Web of Science]

    Karaman AI, Kir N, Belli S. Four applications of reinforced polyethylene fiber material in orthodontic practice. American Journal of Orthodontics and Dentofacial Orthopedics (2002) 121:650–654.[CrossRef][Web of Science][Medline]

    Kargul B, Caglar E, Kabalay U. Glass fiber reinforced composite resin space maintainer: case reports. Journal of Dentistry for Children (2003) 70:258–261.

    Kirzioglu Z, Erturk MS. Success of fiber material space maintainer. Journal of Dentistry for Children (2004) 71:158–162.

    Kolbeck C, Rosentritt M, Behr M, Lang R. In-vitro study of fractures strength and marginal adaption of polyethylene-fibre-reinforced composite versus glass fibre-reinforced composite fixed partial dentures. Journal of Oral Rehabilitation (2002) 29:668–674.[CrossRef][Web of Science][Medline]

    Lassila LV, Nohrstrom T, Vallittu PK. The influence of short-term water storage on the flexural strength of unidirectional glass fiber-reinforced composites. Biomaterials (2002) 23:2221–2229.[CrossRef][Web of Science][Medline]

    Lassila LV, Tezvergil A, Lahdenpera M, Alander P, Shinya A, Vallittu PK. Evaluation of some properties of two fiber-reinforced composite materials. Acta Odontologica Scandinavica (2005) 63:196–204.[Web of Science][Medline]

    Meric G, Dahl JE, Ruyter IE. Physicochemical evaluation of silica-glass fiber reinforced polymers for prosthodontic applications. European Journal of Oral Science (2005) 113:258–264.[CrossRef]

    Narva KK, Lassila LVJ, Vallittu PK. Fatigue resistance and stiffness of glass fiber-reinforced urethane dimethacrylate composite. Journal of Prosthetic Dentistry (2004) 91:158–163.[CrossRef][Web of Science][Medline]

    Nohrstrom TJ, Vallittu PK, Yli-Urpo A. The effect of placement and quantity of glass fibers on the fracture resistance of interim fixed partial dentures. International Journal of Prosthodontics (2000) 13:72–78.[Web of Science][Medline]

    Pereira CL, Demarco FF, Cenci MS, Osinaga PWR, Piovesan EM. Flexural strength of composites: influence of polyethylene fiber reinforcement and type of composite. Clinical Oral Investigations (2003) 7:116–119.[CrossRef][Medline]

    Rantala LI, Lastumäki TM, Peltomäki T, Vallittu PK. Fatigue resistance of removable orthodontic appliance reinforced with glass fibre weave. Journal of Oral Rehabilitation (2003) 30:501–506.[CrossRef][Web of Science][Medline]

    Rosentritt M, Leibrock A, Lang R, Behr M, Scharnagl P, Handel G. Gerät zur Simulation des Kauorgans (Regensburger Kausimulator). Materialprüfung (1997) 39:77–80.

    Tanner J, Vallittu PK, Soderling E. Effect of water storage of E-glass fiber-reinforced composite on adhesion of Streptococcus mutans. Biomaterials (2001) 22:1613–1618.[CrossRef][Web of Science][Medline]

    Tirapelli C, Ravagnani C, Panzeri FC, Panzeri H. Fiber-reinforced composites: effect of fiber position, fiber framework, and wetting agent on flexural strength. International Journal of Prosthodontics (2005) 18:201–212.[Web of Science][Medline]

    Vallittu PK. Ultra–high-modulus polyethylene ribbon as reinforcement for denture polymethyl methacrylate: a short communication. Dental Materials (1997) 13:381–382.[CrossRef][Web of Science][Medline]

    Vallittu PK. Effect of 180-week water storage on the flexural properties of E-glass and silica fiber acrylic resin composite. International Journal of Prosthodontics (2000) 13:334–339.[Web of Science][Medline]

    Vallittu PK, Ruyter IE, Ekstrand K. Effect of water storage on the flexural properties of E-glass and silica fiber acrylic resin composite. International Journal of Prosthodontics (1998) 11:340–350.[Web of Science][Medline]

    Williams JG, Cawood MJ. European group on fracture: Kc and Gc methods for polymers. Polymer Testing (1990) 9:15–26.[CrossRef][Web of Science]

    Yazdanie N, Mahood M. Carbon fiber acrylic resin composite: an investigation of transverse strength. Journal of Prosthetic Dentistry (1985) 54:543–547.[CrossRef][Web of Science][Medline]


Add to CiteULike CiteULike   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us    What's this?



This Article
Right arrow Abstract Freely available
Right arrow FREE Full Text (PDF) Freely available
Right arrow All Versions of this Article:
29/3/304    most recent
cjm025v1
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Add to My Personal Archive
Right arrow Download to citation manager
Right arrowRequest Permissions
Google Scholar
Right arrow Articles by Faltermeier, A.
Right arrow Articles by Müßig, D.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Faltermeier, A.
Right arrow Articles by Müßig, D.
Social Bookmarking
Add to CiteULike   Add to Connotea   Add to Del.icio.us  
What's this?