( PDF ) Análise de metodologias de microdureza aplicadas a compósitos: é possível comparar resultados utilizando-se diferentes protocolos?

Download PDF

ads:

PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO GRANDE DO SUL

Análise de Metodologias de Microdureza aplicadas a Compósitos: é possível comparar

resultados utilizando-se diferentes protocolos?

Gustavo Frainer Barbosa –Doutorando em Odontologia, ênfase em Materiais Dentários

(PUCRS)

Orientador: Hugo Mitsuo Silva Oshima – Professor Doutor do Departamento de

Materiais Dentários (PUCRS)

Tese apresentada à Faculdade de

Odontologia da Pontifícia Universidade

Católica do Rio Grande do Sul como parte

dos requisitos para a obtenção do título de

Doutor.

Porto Alegre, Dezembro de 2010

ads:

Livros Grátis

http://www.livrosgratis.com.br

Milhares de livros grátis para download.

DEDICATÓRIA

Dedico este trabalho aos meus

dois grandes amores. À minha

esposa Raquel, companheira

inseparável de todos os

momentos, minha maior

incentivadora e minha maior

crítica. E ao meu filho Davi,

que com seu lindo sorriso me

incentiva e me mostra que,

parafraseando Fernando

Pessoa, “tudo vale a pena se a

alma não é pequena”.

ads:

AGRADECIMENTOS

Agradeço aos meus pais, eternos incentivadores, que me ensinaram que a

educação é a chave do crescimento.

Agradeço aos meus irmãos, que mesmo distantes estão sempre comigo.

Agradeço aos meus colegas de Doutorado, que muito me ajudaram nas minhas

novas descobertas e na minha evolução do saber.

Agradeço ao meu Orientador, Professor Dr. Hugo Mitsuo Silva Oshima, que me

incentivou a ingressar no Programa de Doutorado e que compreendeu as minhas

ausências, para que eu pudesse me dedicar a minha família, mas que, no entanto,

jamais duvidou da minha capacidade e que sempre teve a certeza de que chegaríamos

a um resultado final de qualidade.

Agradeço aos Professores do Programa de Doutorado por todas as trocas e

ensinamentos, em especial ao Professor Dr. Eduardo Gonçalves Mota por todo o seu

apoio e suporte técnico e à Professora Dra Rosemary Sadami Arai Shinkai que com

sua dedicação, incentivo e preocupação tornaram esta passagem um momento

inesquecível.

Agradeço ao amigo Regênio Mahfuz Herbstrith Segundo pelas trocas e

ensinamentos, pelo seu apoio incondicional, pelo seu incentivo diário e por sempre ter

um tempo para me ouvir.

Agradeço ao amigo e eterno Mestre Celso Gustavo Schwalm Lacroix pelo apoio,

pelos ensinamentos, pelo incentivo e pela confiança que sempre me depositou. Celso,

continuas sendo um exemplo de Profissional a ser seguido.

Agradeço ao amigo Tomas Geremia por seus ensinamentos, por seu apoio e por

sua sincera amizade.

Agradeço a amiga Luciene Petcov Machado por suas verdades sarcásticas que

muito me fizeram rir e refletir.

Sumário

DEDICATÓRIA ............................................................................................................................. 2

AGRADECIMENTOS ................................................................................................................... 3

1 Apresentação........................................................................................................................... 6

2 Artigo Submetido ao Journal of Applied Oral Science ........................................................ 10

3 Artigo Submetido à Operative Dentistry .............................................................................. 20

4 Discussão Geral .................................................................................................................... 26

5 Referências Bibliográficas Adicionais.................................................................................. 29

ANEXO 1 – Carta de aprovação da Comissão Científica e de Ética da Faculdade de Odontologia

da PUCRS ..................................................................................................................................... 30

ANEXO 2 – E-mail de confirmação de submissão de trabalho ao Journal of Applied Oral

Science .......................................................................................................................................... 32

ANEXO 3 – E-mail de confirmação de submissão de trabalho a Operative Dentistry ................ 33

1 Apresentação

A dureza é uma propriedade mecânica que pode ser conceituada como a

resistência que um material apresenta ao risco ou à formação de uma marca

permanente quando pressionado por outro material ou por marcadores padronizados

(Garcia, 2000).

Os valores de dureza apresentados por um determinado material possuem uma

dependência direta dos tipos de ligações atômicas, iônicas ou moleculares nele

existentes. Nos sólidos moleculares, como os plásticos, as forças de Van der Waals

atuam entre as moléculas e, por se tratarem de forças baixas, estes materiais são

considerados relativamente macios. Já nos sólidos metálicos e iônicos, como a

natureza das forças ligantes é mais intensa, esses materiais são mais duros, enquanto

os materiais de ligação covalente são, conhecidamente, os materiais de maior dureza

(Garcia, 2000).

No século XVIII, teve início a avaliação científica dessa propriedade dos

materiais, quando se convencionou, então, que a dureza de um material estava ligada

à capacidade que ele apresentava em arranhar outro material. Assim sendo, quanto

maior o risco provocado, mais duro era o material. A primeira escala de dureza foi

criada pelo mineralogista alemão Friedrich Mohs. Essa escala qualitativa atribui aos

materiais um número que indica a sua dureza, sendo o valor 1 atribuído ao talco e o

valor 10, valor máximo, ao diamante. A escala de Mohs é utilizada até os dias de hoje

como uma referência rápida quanto à dureza dos materiais (Blando, 2001).

Com a necessidade de qualificar e quantificar mais precisamente a dureza de

qualquer material, o desenvolvimento de pesquisas sobre o mecanismo dessa

propriedade nos materiais acarretou o surgimento de novas técnicas de medida. Dentre

as novas técnicas de medida de dureza, as mais difundidas e utilizadas até hoje

residem no método de identação (Blando, 2001).

O método identação, ou ensaio de dureza, consiste na aplicação de uma

pressão com uma ponta de penetração, a qual irá imprimir uma marca na superfície da

peça/material analisado. A medida da dureza será dada em função das características

da marca de impressão e da força aplicada. O primeiro ensaio de identação

padronizado e reconhecido industrialmente foi o ensaio de Brinell, proposto pelo

metalurgista sueco Johan August Brinell, por volta do ano de 1900. Posteriormente, em

1919, surgiu o teste de Rockwell, criado pelo metalurgista americano Stanley P.

Rockwell. Na década de 50, os estudos de Tabor permitiram avanços importantes para

os testes de dureza, ao relacionar a curva de descarga com propriedades plásticas e

elásticas dos materiais (Blando, 2001).

Os testes de microdureza surgiram, ainda na década de 50, da necessidade de

se utilizar cargas muito menores, porque os testes convencionais já não possuíam

cargas suficientemente baixas para medir somente a dureza de uma superfície tratada,

ou de um filme com espessura pequena (Blando, 2001). Atualmente os testes de

microdureza mais difundidos e utilizados são os métodos Vickers e Knoop. Ambos os

métodos são bem adequados para a medição de dureza em regiões pequenas e

selecionadas dos corpos de prova, sendo o método Knoop indicado para testar

materiais frágeis (Callister, 2002).

Uma vez que a Odontologia não é uma ciência ímpar, isolada dentro de um

contexto, a utilização destes métodos está presente na constante construção e

evolução do conhecimento odontológico e, conseqüentemente, no desenvolvimento de

novos materiais e aprimoramento dos materiais já existentes e utilizados no dia a dia

do Cirurgião Dentista.

Neste sentido, as resinas compostas têm sido constantemente testadas e

analisadas através de ensaios mecânicos in vitro. Dentre os inúmeros ensaios

mecânicos possíveis de serem realizados, o ensaio de microdureza possui especial

destaque, pois é definido como um teste simples para determinar a resistência do

material após submetê-lo a edentações (Polydorou et al., 2007; Nayif et al., 2007). Para

Mota et al. (2006), a microdureza de um material define sua capacidade de resistir ao

desgaste, principalmente, em regiões de áreas funcionais. Poskus et al. (2004), Correr

et al. (2005) e Tango et al. (2007), também destacam que os testes de dureza são

comumente usados para indicar o grau de conversão nas reações de polimerizações.

Para Poskus et al. (2004), existe uma correlação entre os valores de dureza e o

grau de conversão dos monômeros após a polimerização. Sendo assim, diversos

fatores externos podem influenciar no resultado dos testes de microdureza e,

consequentemente, no resultado final da restauração, tais como distância da fonte de

luz (Rode et al., 2007), o tempo de polimerização das resinas, a densidade de energia

(Tango et al., 2007). Fatores internos também podem influenciar os resultados obtidos,

podemos citar como exemplo a composição (Nayif et al., 2007), a cor e a opacidade da

resina (Correr et al., 2005).

No entanto, possíveis fatores relacionados diretamente aos métodos de

microdureza não estão descritos na literatura como sendo passíveis de influenciar nos

resultados obtidos. Nos trabalhos que utilizam ensaios mecânicos de microdureza não

é possível observar padronização nem na carga aplicada sobre as amostras, nem no

tempo que esta carga atua sobre a amostra. Também não há padronização quanto ao

tipo de teste de microdureza (Vickers ou Knoop) a ser empregado. Isto pode ser

observado em alguns trabalhos científicos descritos no quadro 1.

Portanto, o objetivo deste estudo é comparar os resultados obtidos em testes de

microdureza, sobre uma resina composta, quando utilizados diferentes protocolos, e

avaliar a possibilidade de se fazer analogias com base nos resultados obtidos.

Quadro 1: Diversificação das variáveis empregadas em testes de microdureza apresentados em artigos

científicos.

Artigo Força Tempo Ensaio

Hahnel S, Henrich A, Bürgers R, Handel G, Rosentritt M. Investigation of

Mechanical Properties of Modern Dental Composites After Artificial

Aging for One Year. Oper Dent. 2010; 30(4): 412-419.

500g 60seg Vickers

Komori PCP, Paula AB, Martin AA, Tango RN, Sinhoreti MAC, Correr-

Sobrinho L. Effect of Light Energy Density on Conversion Degree and

Hardness of Dual-cured Resin Cement. Oper Dent. 2010; 30(5): 120-

124.

50g 15seg Knoop

Camargo EJ, Moreschi E, Baseggio W, Cury JA, Pascotto RC. Composite

depth of cure using four Polymerization techniques. J Appl Oral Sci.

2009; 17(5):446-50.

25g 5seg Knoop

Fleming GJP, Awan M, Cooper PR, Sloan AJ. The potential of a resin-

composite to be cured to a 4mm depth. Sloan. Dental Materials 24

(2008) 522–529.

500g 15seg Vickers

Aguiar FH, e Oliveria TR, Lima DA, Ambrosano G, Lovadino JR.

Microhardness of different thicknesses of resin composite

polymerized by conventional photocuring at different distances. Gen

Dent. 2008 Mar-Apr;56 (2):144-8.

25g 10seg Knoop

Hannig C, Duong S, Becker K, Brunner E, Attin T. Effect of bleaching on

subsurface micro-hardness of composite and a polyacid modified

composite. Dent Mater. 2007; 23: 198–203.

2N - Knoop

David JR, Gomes OM, Gomes JC, Loguercio AD, Reis A. Effect of

exposure time on curing efficiency of polymerizing units equipped

with light-emitting diodes. Journal of Oral Science, Vol. 49, No.1, 19-

24,2007.

50g 30seg Vickers

Aguiar FHB, Braceiro A, Lima DA, Ambrosano GMB, Lovadino JR. Effect

of Light Curing Modes and Light Curing Time on the Microhardness

of a Hybrid Composite Resin. The Journal of Contemporary Dental

Practice, Volume 8, No. 6, September 1, 2007.

25g 10seg Knoop

Polydorou O, Mönting JS, Hellwig E, Auschill TM. Effect of in-office tooth

bleaching on the microhardness of six dental esthetic restorative

materials. Dental Materials 23 (2007) 153–158.

50g 30seg Knoop

Yazici AR, Kugel G, Gül G. The Knoop Hardness of a Composite Resin

Polymerized with Different Curing Lights and Different Modes. The

Journal of Contemporary Dental Practice, Volume 8, No. 2, February 1,

2007.

500g 15seg Knoop

Nayif MM, Nakajima M, Aksornmuang J, Ikeda M, Tagami J. Effect of

adhesion to cavity walls on the mechanical properties of resin

composites. Dent Mater. 2008; 24: 83–89.

50g 15seg Knoop

Tango RN, Sinhoreti MAC, Correr AB, Sobrinho LC, Consani RLX. Effect

of Veneering Materials and Curing Methods on Resin Cement Knoop

Hardness. Braz Dent J. 2007; 18(3): 235-239.

50g 15seg Knoop

Brandt WC, Moraes RR, Sobrinho LC, Sinhoreti MAC, Consani S. Effect

of different photo-activation methods on push out force, hardness

and cross-link density of resin composite restorations. Dent Mater.

2008; 24: 846-850.

50g 15seg Knoop

Rode KM, Kawano Y, Turbino ML. Evaluation of Curing Light Distance

on Resin Composite Microhardness and Polymerization. Oper Dent.

2007; 32-6: 571-578.

50g 45seg Vickers

Mota EG, Oshima HMS, LHB, Pires LAG, Rosa RS. Evaluation of

diametral tensile strength and knoop microhardness of five

nanofilled composites in dentin and enamel shades. Stomatologija.

2006; 8:67-9.

100g 15seg Knoop

Correr AB, Sinhoreti MAC, Sobrinho LC, Tango RN, Schneider LFJ,

Consani S. Effect of the Increase of Energy Density on Knoop

Hardness of Dental Composites Light-Cured by Conventional QTH,

LED and Xenon Plasma Arc. Braz Dent J. 2005; 16(3): 218-224.

50g 15seg Knoop

Poskus LT, Placido E, Cardoso PEC. Influence of placement

techniques on Vickers and Knoop hardness of class II composite

resin restorations. Dent Mater. 2004; 20: 726–732.

100g 15seg Knoop

Neves AD, Discacciati JAC, Oréfice RL, Jansen WC. Correlation

between degree of conversion, microhardness and inorganic content

in composites. Pesqui Odontol Bras. 2002; 16 (4): 349-354.

200g 15seg Vickers

2 Artigo Submetido ao Journal of Applied Oral Science

Analysis of microhardness methodologies applied to composites: is it possible to

compare results using different protocols?

Objective: To evaluate correlation between load and dwell time in composite resin

microhardness tests, using Vickers and Knoop mechanic test methods.

Materials and Methods: Resin Grandio (Voco, Cuxhaven, Germany), shade A2, was used to

make the samples. Ninety (90) samples were made on a six-(6)-mm-diameter by three-(3)-mm-

deep polytetrafluorethylene matrix, where two equidistant increments were each photocured for

20s by the LED device (Celalux, Voco, Cuxhaven, Germany, with 800 mW/cm

). The samples

were randomly divided into three groups according to the load factor. Groups I, II and III

received loads at 50g, 100g and 500g respectively. These groups were divided into nine

subgroups according to the deal time (15s, 30s, 45s). Then, the light exposed surface of each

composite resin sample was divided into two hemispheres. Each sample side received three

indentations, totaling 540 indentations with Shimadzu HMV tester (Shimadzu, Kyoto, Japan).

The Vickers (VHN) and Knoop (KHN) results were submitted to a two-way ANOVA with fixed

factors (load and dwell time), and to the post-hoc Tukey multiple comparison test at α = 0.05.

Results: Significant differences were recorded between groups for each methodology, Vickers

and Knoop (p<0.001). Among the Vickers (VHN) tested samples, the average recorded ranged

from 164.94 (50g for 45s) to 210.33 (100g for 45s). Knoop microhardness (KHN) ranged from

128.92 (500g 45s) to 184.26 (100g 15s). For both methodologies, both load and dwell time were

statistically significant (p<0.001), this way showing that different loads and dwell time influence

the microhardness of resins.

Conclusion: This study demonstrated that correlating both Vickers and Knoop microhardness

test results is not recommended, and similar protocols must be applied to allow comparisons

among the different studies that use the same kind of test.

Key Words: Methods. Hardness. Composite resins.

INTRODUCTION

Mechanical tests are commonly used to check-up and improve several classes of dental

materials. One of such commonly used tests on dentistry research is the hardness test.

Hardness can be defined as the resistance of a material to indentation

. Moreover, hardness is

related to the material strength, its proportional limit and its ability to abrade or to be abraded by

opposing dental structures/materials

Development of materials, such as composite resins, filled with smaller particles, has

been increasingly using microhardness testers that use less than 1 Kgf during the indentation.

Historically, Vickers and Knoop microhardness tests have been used by the majority of

investigators for testing hardness of this kind of material

3-5,7,8,10,12-17,19,21,22,24,26

. This can be

explained by the fact that such test is a simple and reliable method

to show the strength of

materials through their resistance to indentation.

Although microhardness tests are widely used tests, the measured hardness depends

on test load and dwell times

. However, there is no standardization neither on the load applied

value, nor on the time of load application on the composite sample. Also, correlations between

Vickers and Knoop microhardness tests are commonly carried out, but no work to date has

related that possibility and there may be no correlation in hardness values when different

indenter shapes are compared

Thus, the aim of this in vitro study was to correlate time and load of each kind of

microhardness test (Vickers / Knoop) on a composite resin and then show, with the obtained

results, if comparison between these two different microhardness tests is possible.

MATERIALS AND METHODS

A commercially available nanohybrid composite resin (Grandio, Voco, Cuxhaven,

Germany, Lot 732242), shade A2, was used to prepare 90 samples. These samples were

made using a PTFE (polytetrafluorethylene) 6 mm diameter and 3 mm high double entry mold.

The PTFE mold was placed on a glass plate and the composite resin was inserted in two 2-mm-

thick-maximum increments. To achieve a smooth surface on the last increment, a polyester strip

was used on the increment and pressed by means of a glass plate. Each increment was

photocured using a LED device (Celalux, Voco, Cuxhaven, Germany, with 800 mW/cm

) during

20s. The light source power was checked with a radiometer (Demetron, Kerr, Orange, CA, EUA)

every five exposures.

The samples were stored in a recipient with distilled water for 24h and protected from

light at 37 °C in a culture stove (model 002 CB, Fanem Ltda, São Paulo, SP, Brazil). Afterwards,

the samples were randomly divided into three groups according to the load factor. Groups I, II

and III received loads at 50g, 100g and 500g respectively. These groups were divided into nine

subgroups according to the deal time (15s, 30s, 45s) as shown on Table 1.

Then, the light exposed surface of each composite resin sample was divided into two

hemispheres. Each sample side received three indentations, totaling 540 indentations with

Shimadzu HMV tester (Shimadzu, Kyoto, Japan). The Vickers (VHN) and Knoop (KHN) results

were submitted to a two-way ANOVA with fixed factors (load and dwell time), and to the post-

hoc Tukey multiple comparison test at α = 0.05.

RESULTS

Significant differences were recorded between groups for each methodology, Vickers

and Knoop (p<0.001). Among the Vickers (VHN) tested samples, the average recorded ranged

from 164.94 (50g for 45s) to 210.33 (100g for 45s). Knoop microhardness (KHN) ranged from

128.92 (500g 45s) to 184.26 (100g 15s). Multiple comparisons are presented on Tables 2, 3, 4

and on Graphs 1, 2. For both methodologies, both load and dwell time were statistically

significant (p<0.001).

DISCUSSION

The Vickers and Knoop hardness tests have been used for analysis of composite resin

conversion degree in several studies

5,7,9,15,19

. These studies advocate that higher obtained

values, through microhardness tests, correspond to higher composite resin conversion degree,

obtained by photo-polymerization

7,19

. Recent studies have used different dwell times and

different load values to analyze this conversion. However, a direct analogy cannot be drawn,

because there are significant differences between these methods and between the variables

used

. Some of these existing variables are a result of internal factors (such as filler, particle

size, polymeric matrix), and of external factors (such as distance from the light power source,

time of composite resin polymerization, energy density, composition, shade and resin composite

opacity) that may influence on the microhardness tests.

Another existing variable is the type of light power source. Different light units result in

conversion value variations

6,7,15,18,19,20,23

, what can be explained by the existing characteristics

of each light source, such as light bulb type, number and disposition plus power and heat

produced inside the light source units. In a specific study

, three different light power sources

(LED, PAC and quartz-tungsten-halogen light) were used on two different composite resins. The

hardness obtained from the composites photocured by PAC source was statistically lower when

compared with the composites photocured by LED or by the halogen light. But there is no

difference between these two last light sources, independently from the resin increment

thickness. Regarding dwell time, it was observed that the increase in time exposure increased

Knoop hardeness values in the composite resin when LED or PAC was used. As to the halogen

light, the increase in dwell time did not influence the Knoop hardness values, but these values

decreased as the resin increment thickness increased. Besides this, it was demonstrated that

the composite resin increment size can modify the polymerization degree

. According to Aguiar,

et al.

(2007), the polymerization method is a determinant factor and the manufacturer’s

recommended time for polymerizing a composite resin is not enough for an “ideal

polymerization”.

For these reasons, this study used the same light source (LED), at the same distance,

with the same polymerization time (20s) and same dwell time on all samples. Since 2-mm-thick-

maximum increments were used for each polymerization, the thickness variant of the increment

did not act in this study, this way satisfying the works by David, et al.

(2007), Aguiar, et al.

(2007). Following preparation, the samples were tested for Knoop and Vickers loads with

different dwell times. Significant non-linear differences among them were noted, demonstrating

that different loads and dwell times influence the resin microhardness, according to what

Shahdad et al.

(2007) have stated, that is, the variation of hardness with load is a well-known

artifact of traditional hardness testing and is often known as the indentation size effect.

In this way, the strong correlation that some studies claim to exist between wear

resistance and hardness, as it is shown at Abe, et al.

. (2001) in their study, in which they found

a strong correlation between wear resistance and Knoop hardness of the materials tested, may

not exist. Other studies have either completely ruled it out or suggested a limited correlation

between the hardness and wear resistance

1,11,25

. This correlation between wear resistance and

hardness can only be possible if the same testing protocol is applied, and the obtained results

are compared to different polymerization time.

To Shahdad et al.

. (2007) Vickers and Knoop hardness tests seem to be the preferred

choice of test among majority of the investigators. However, the comparisons could be

inappropriate, because there is a great deal of variability among the tests that have been

performed. And besides, these tests have a specific limitation that is the microscopic

measurements of hardness indentations after the indenter is removed. These measurements

can be affected by some factors, like as, the limitation in resolution of the optical system, the

perception of the operator and the elastic recovery of the material

Therefore, for the hardness test analysis to be faithful to both Knoop and Vickers, a

universal rule for future studies is needed, with equal dwell time and load values. This way, the

odds of loyalty of further studies will be greater. Moreover, direct comparisons between the two

different types of mechanical test, cited above, are not viable as show by the majority of the

obtained results where VHN are greater than KHN. Thus, we see that past studies ‘could not

have made comparisons' among different times and loads, because there are differences

between the tests and, consequently, in their results, making any comparative statement

unworkable.

CONCLUSION

This study demonstrated that correlating both, Vickers and Knoop, microhardness test

results is not recommended, and similar protocols must be applied to allow comparisons among

the different studies that use the same kind of test.

REFERENCES

1- Abe Y, Sato Y, Taji T, Akagawa Y, Lambrechts P, Vanherle G. An in vitro wear study

of posterior denture tooth materials on human enamel. J Oral Rehabil. 2001; 28: 407–

12.

2- Abe Y, Sato Y, Akagawa Y, Ohkawa S. An in vitro study of high-strength resin

posterior denture tooth wear. Int J Prosthodont. 1997; 10: 28–34.

3- Aguirar FH, e Oliveria TR, Lima DA, Ambrosano G, Lovadino JR. Microhardness of

different thicknesses of resin composite polymerized by conventional photocuring at

different distances. Gen Dent. 2008 Mar-Apr; 56 (2):144-8.

4- Aguiar FHB, Braceiro A, Lima DA, Ambrosano GMB, Lovadino JR. Effect of Light

Curing Modes and Light Curing Time on the Microhardness of a Hybrid Composite

Resin. J Contemp Dent Pract. 2007; V.8, No. 6, Sep 1.

5- Brandt WC, Moraes RR, Sobrinho LC, Sinhoreti MAC, Consani S. Effect of different

photo-activation methods on push out force, hardness and cross-link density of resin

composite restorations. Dent Mater. 2008; 24: 846-850.

6- Camargo EJ, Moreschi E, Baseggio W, Cury JA, Pascotto RC. Composite Depth of

Cure Using Four Polymerization Techniques. J Appl Oral Sci. 2009; 17(5): 446-50.

7- Correr AB, Sinhoreti MAC, Sobrinho LC, Tango RN, Schneider LFJ, Consani S. Effect

of the Increase of Energy Density on Knoop Hardness of Dental Composites Light-

Cured by Conventional QTH, LED and Xenon Plasma Arc. Braz Dent J. 2005; 16(3):

218-224.

8- David JR, Gomes OM, Gomes JC, Loguercio AD, Reis A. Effect of exposure time on

curing efficiency of polymerizing units equipped with light-emitting diodes. J Oral Sci.

2007; V.49, No.1:19-24.

9- Emami N, Sjödahl M, Söderholm KJM. How filler properties, filler fraction, sample

thickness and light source affect light attenuation in particulate filled resin

composites. Dent Mater. 2005; 21: 721–730.

10- Fleming GJP, Awan M, Cooper PR, Sloan AJ. The potential of a resin-composite to

be cured to a 4mm depth. Dent Mater. 2008; 24: 522–529.

11- Harrison A, Huggett R, Handley RW. A correlation between abrasion resistance and

other properties of some acrylic resins used in dentistry. J Biomed Mater Res. 1979;

13: 23–34.

12- Krishnan VK, Yamuna V. Effect of initiator concentration, exposure time and

particle size of the filler upon mechanical properties of a light-curing radiopaque

dental composite. J Oral Rehabil. 1998; 25: 747–751.

13- Mota EG, Oshima HMS, LHB, Pires LAG, Rosa RS. Evaluation of diametral tensile

strength and knoop microhardness of five nanofilled composites in dentin and

enamel shades. Stomatologija. 2006; 8:67-9.

14- Nayif MM, Nakajima M, Aksornmuang J, Ikeda M, Tagami J. Effect of adhesion to

cavity walls on the mechanical properties of resin composites. Dent Mater. 2008; 24:

83–89.

15- Neves AD, Discacciati JAC, Oréfice RL, Jansen WC. Correlation between degree of

conversion, microhardness and inorganic content in composites. Pesqui Odontol Bras.

2002; 16 (4): 349-354.

16- Polydorou O, Mönting JS, Hellwig E, Auschill TM. Effect of in-office tooth bleaching

on the microhardness of six dental esthetic restorative materials. Dent Mater. 2007; 23:

153–158.

17- Poskus LT, Placido E, Cardoso PEC. Influence of placement techniques on Vickers

and Knoop hardness of class II composite resin restorations. Dent Mater. 2004; 20:

726–732.

18- Retamoso LB, Onofre NML, Hann L, Marchioro EM. Effect of light-curing units in

shear bond strength of metallic brackets: an in vitro study. J Appl Oral Sci. 2010;

18(1):68-74.

19- Rode KM, Kawano Y, Turbino ML. Evaluation of Curing Light Distance on Resin

Composite Microhardness and Polymerization. Oper Dent. 2007; 32-6: 571-578.

20- Santos MJMC, Passos SP, Encarnação MOL, Santos Junior GC, Bottino MA.

Hardening of a dual-cure resin cement using QTH and LED curing units. J Appl Oral

Sci. 2010; 18(2):110-5.

21- Shahdad SA, McCabe JF, Bull S, Rusby S, Wassell RW. Hardness measured with

traditional Vickers and Martens hardness methods. Dent Mater. 2007; 23: 1079–1085.

22- Tango RN, Sinhoreti MAC, Correr AB, Sobrinho LC, Consani RLX. Effect of Veneering

Materials and Curing Methods on Resin Cement Knoop Hardness. Braz Dent J. 2007;

18(3): 235-239.

23- Thomé T, Steagall Jr. W, Tachibana A, Braga SRM, Turbino ML. Influence of the

distance of the curing light source and composite shade on hardness of two

composites. J Appl Oral Sci. 2007; 15(6):486-91.

24- Yazici AR, Kugel G, Gül G. The Knoop Hardness of a Composite Resin Polymerized

with Different Curing Lights and Different Modes. J Contemp Dent Pract. 2007; V.8, No.

2, Feb 1.

25- Wassell RW, McCabe JF, Walls AW. Subsurface deformation associated with

hardness measurements of composites. Dent Mater. 1992; 8:218–23.

26- Whitman DJ, McKinney JE, Hinman RW, Hesby RA, Pelleu Jr GB. In vitro wear rates

of three types of commercial denture tooth materials. J Prosthet Dent. 1987; 57:243–6.

Table 1: The random division has created 9 groups.

Table 2: Means comparison for all groups.

50g 100g 500g

VHN KHN VHN KHN VHN KHN

15s

179.32

168.13

202.04

184.25

181,58

140.77

30s

185.74

149.87

197.20

179.13

193.76

139.40

45s

164.94

180.33

210.33

148.09

186.56

128.92

n =90

LOAD

DWELL TIME

LOAD I

(50 g)

LOAD II

(100 g)

DWELL TIME I

(15 s)

n = 10

Knoop / Vickers

n = 10

Knoop / Vickers

DWELL TIME II

(30 s)

n = 10

Knoop / Vickers

n = 10

Knoop / Vickers

DWELL TIME III

(45 s)

n = 10

Knoop / Vickers

n = 10

Knoop / Vickers

LOAD III

(500 g)

n = 10

Knoop / Vickers

n = 10

Knoop / Vickers

n = 10

Knoop / Vickers

Table 3: Means for Vickers groups in homogeneous subsets are displayed.

Tukey HSD

Subset for alpha = .05

GROUP N

1 2 3

45s50g 30 164,9467

15s50g 30 179,3233 179,3233

15s500g 30 181,5867 181,5867

30s50g 30 185,7433 185,7433 185,7433

45s500g 30 186,5667 186,5667 186,5667

30s500g 30 193,7667 193,7667

30s100g 30

197,2000 197,2000

15s100g 30

202,0467 202,0467

45s100g 30

210,3333

Sig.

,282

,220

,136

Table 4: Means for Knoop groups in homogeneous subsets are displayed.

Tukey HSD

Subset for alpha = .05

GROUP N

1 2 3

45s500g 30 128,9200

30s500g 30 139,4067

15s500g 30 140,7767 140,7767

45s100g 30 148,0900 148,0900

30s50g 30 149,8700 149,8700

15s50g 30

168,1333 168,1333

30s100g 30

179,1333

45s50g 30

180,3333

15s100g 30

184,2667

Sig.

,350

,070

,708

Graph 1: Means and outliers in Vickers Microhardness results.

Graph 2: Means and outliers in Knoop Microhardness results.

3 Artigo Submetido à Operative Dentistry

Analysis of Knoop microhardness test: is it possible to make an analogy between

conversion degree and the obtained results using different protocols?

Objective: To correlate time and load on Knoop microhardness test over a composite resin and

to show, with the obtained results, whether composite resin conversion degree comparison is

possible through the tests.

Materials and Methods: Resin Grandio (Voco, Cuxhaven, Germany), shade A2, was used to

make the samples. Ninety (90) samples were made on a six-(6)-mm-diameter by three-(3)-mm-

deep polytetrafluorethylene matrix, where two equidistant increments were each photocured for

20s by the LED device (Celalux, Voco, Cuxhaven, Germany, with 800 mW/cm

). The samples

were randomly divided into three groups according to the load factor. Groups I, II and III

received loads at 50g, 100g and 500g respectively. These groups were divided into nine

subgroups according to the deal time (15s, 30s, 45s). Each sample received three indentations,

totaling 270 indentations with Shimadzu HMV tester (Shimadzu, Kyoto, Japan). The Knoop

(KHN) results were submitted to a two-way ANOVA with fixed factors (load and dwell time), and

to the post-hoc Tukey multiple comparison test at α = 0.05.

Results: Significant differences were recorded between groups. Among the Knoop

microhardness (KHN) tested samples, the average recorded ranged from 128.92 (500g 45s) to

184.26 (100g 15s). For this methodology, both load and dwell time were statistically significant

(p<0.001), this way showing that different loads and dwell time influence the microhardness of

resins.

Conclusion: This study demonstrated that Knoop microhardness test results is not

recommended for composite resin conversion degree comparisons, and similar protocols should

be applied to allow this kind of correlation.

Running (short) title: Analysis of Knoop microhardness test

INTRODUCTION

Composite resins are widely used in restorative dentistry. Patients’ constant demands

for esthetic associated with the enhancement of mechanical properties have brought important

improvements to composite resins, and as a result, this restorative material has been given

universal applicability. On the posterior restorations, for example, the material is constantly

under masticatory stresses. So, composite resins with good mechanical properties should be

selected for that purpose.

Thus, in order to check up the mechanical properties of this class of restorative materials,

mechanic tests have been commonly used, being the so-called hardness tests one of them.

Such test is a simple and reliable method to reflect the strength of a given material through its

resistance to indentation. Several studies have used the Knoop microhardness test for analysis

of the composite resin conversion degree.

2,3,4,5,6

These studies advocate that higher obtained

values, through microhardness tests, correspond to higher composite resin conversion degree,

obtained by photo-polymerization.

3,6

However, although correlations between Knoop microhardness tests are commonly

performed to compare the composite resin conversion degree, there has not been any work to

date that has reported such possibility. Also, the measured hardness depends on load and dwell

times test,

but there is no standardization neither on the load applied value, nor on the time of

load application over the composite resin sample in the published studies.

Therefore, the aim of this in vitro study was to correlate time and load on Knoop

microhardness test over a composite resin and to show whether an analogy between the

composite resin conversion degree and the obtained results is possible.

MATERIALS AND METHODS

A commercially available nanohybrid composite resin (Grandio, Voco, Cuxhaven,

Germany, Lot 732242), shade A2, was used to prepare 90 samples. These samples were

made using a PTFE (polytetrafluorethylene) 6 mm diameter and 3 mm high double entry mold.

The PTFE mold was placed on a glass plate and the composite resin was inserted in two 2-mm-

thick-maximum increments. To achieve a smooth surface on the last increment, a polyester strip

was used on the increment and pressed by means of a glass plate. Each increment was

photocured using a LED device (Celalux, Voco, Cuxhaven, Germany, with 800 mW/cm

) during

20s. The light source power was checked with a radiometer (Demetron, Kerr, Orange, CA, EUA)

every five exposures.

The samples were stored in a recipient with distilled water for 24h and protected from

light at 37 °C in a culture stove (model 002 CB, Fanem Ltda, São Paulo, SP, Brazil). Afterwards,

samples were randomly divided into 9 groups according to load (50, 100 or 500g) and dwell

time (15, 30 or 45s) as shown on Table 1.

Each light exposed surface sample side received three indentations, totaling 270

indentations with Shimadzu HMV tester (Shimadzu, Kyoto, Japan). The Knoop (KHN) results

were submitted to a two-way ANOVA with fixed factors (load and dwell time), and to the post-

hoc Tukey multiple comparison test at α = 0.05.

RESULTS

Significant differences were recorded between groups. Among the Knoop microhardness

(KHN) tested samples, the average recorded ranged from 128.92 (500g 45s) to 184.26 (100g

15s). For this methodology, both load and dwell time were statistically significant (p<0.001), this

way showing that different loads and dwell time influence the microhardness of resins. Multiple

comparisons are presented on Tables 1 and 2.

DISCUSSION

The Knoop microhardness test has been shown as one of the best methods for testing

the hardness of composite resins

, and hardness has been shown to be an indirect measure of

the degree of conversion.

Over the last few years, several studies related to the degree of

conversion and mechanical properties of composite resins have been developed.

These

studies advocate that the radiant exposure generated by the light source can influence the

degree of conversion of composite resins and thereby influence their mechanical properties.

So, higher obtained values through microhardness tests correspond to higher composite resin

conversion degree, obtained by photo-polymerization.

3,6

Recent studies have used different dwell times and different load values to analyze this

conversion on several composite resin brands. However, a direct analogy cannot be drawn,

because there are significant differences between these methods and between the variables

used.

Besides, since the microhardness value is greatly influenced by some variables, a cross-

comparison between the different brands is limited.

Some of these existing variables are a

result of internal factors (such as filler, particle size, polymeric matrix), and of external factors

(such as distance from the light power source, time of composite resin polymerization, energy

density, composition, shade and resin composite opacity) that may influence on the

microhardness tests.

Another existing variable is the type of light power source. Different light units result in

conversion value variations

3,5,6,11,12,13,14

, what can be explained by the existing characteristics of

each light source, such as light bulb type, number and disposition plus power and heat

produced inside the light source units. The polymerization method is a determinant factor, but

the manufacturer’s recommended time for polymerizing a composite resin is not enough for an

“ideal polymerization”.

Besides this, it was demonstrated that the composite resin increment

size can modify the polymerization degree.

For these reasons, this study used the same light source (LED), at the same distance,

with the same polymerization time (20s) and same dwell time on all samples. Since 2-mm-thick-

maximum increments were used for each polymerization, the thickness variant of the increment

did not act in this study. Following preparation, the samples were tested for Knoop loads with

different dwell times. Significant non-linear differences among them were noted, demonstrating

that different loads and dwell times influence the resin microhardness.

The variation of hardness

with load is a well-known artifact of traditional hardness testing and is often known as the

indentation size effect.

In this way, the strong correlation that some studies claim to exist between conversion

degree and hardness may not exist. Other studies have either completely ruled it out or

suggested a limited correlation between the hardness and wear resistance

16,17,18

. This

correlation between wear resistance and hardness can only be possible if the same testing

protocol is applied, and the obtained results are compared to different polymerization time.

Although Knoop hardness tests seem to be the preferred choice of test among the

majority of the investigators, the comparisons could be inappropriate, because the hardness

values were often greater at the center of the specimens.

And besides, these tests have a

specific limitation that is the microscopic measurements of hardness indentations after the

indenter is removed. These measurements can be affected by some factors such as the

limitation in resolution of the optical system, the perception of the operator and the elastic

recovery of the material.

Therefore, for the Knoop microhardness test analysis to be faithful, a universal rule for

future studies is needed, with equal dwell time and load values. This way, the odds of loyalty of

further studies will be greater. Moreover, direct comparisons between hardness and composite

resin conversion degree, are not viable. Thus, we see that past studies ‘could not have made

analogies between conversion degree and Knoop microhardness tests' among different times

and loads, because there are differences between the tests and, consequently, in their results,

making any comparative statement unworkable.

CONCLUSION

This study demonstrated that Knoop microhardness test results are not recommended to

composite resin conversion degree comparisons, and similar protocols should be applied to

allow this kind of correlation.

REFERENCES

1. Silva EM, Poskus LT & Guimarães JGA (2008) Influence of Light-polymerization Modes

on the Degree of Conversion and Mechanical Properties of Resin Composites: A

Comparative Analysis Between a Hybrid and a Nanofilled Composite Operative

Dentistry, 33 (3) 287-293.

2. Brandt WC, Moraes RR, Sobrinho LC, Sinhoreti MAC & Consani S (2008) Effect of

different photo-activation methods on push out force, hardness and cross-link density

of resin composite restorations Dental Materials 24 846-850.

3. Correr AB, Sinhoreti MAC, Sobrinho LC, Tango RN & Schneider LFJ, Consani S (2005)

Effect of the Increase of Energy Density on Knoop Hardness of Dental Composites

Light-Cured by Conventional QTH, LED and Xenon Plasma Arc Brazilian Dental

Journal 16 (3) 218-224.

4. Emami N, Sjödahl M & Söderholm KJM (2005) How filler properties, filler fraction,

sample thickness and light source affect light attenuation in particulate filled resin

composites Dental Materials 21 721–730.

5. Neves AD, Discacciati JAC, Oréfice RL & Jansen WC (2002) Correlation between

degree of conversion, microhardness and inorganic content in composites Pesquisa

Odontológica Brasileira 16 (4) 349-354.

6. Rode KM, Kawano Y & Turbino ML (2007) Evaluation of Curing Light Distance on Resin

Composite Microhardness and Polymerization Operative Dentistry 32 (6) 571-578.

7. Shahdad SA, McCabe JF, Bull S, Rusby S & Wassell RW (2007) Hardness measured

with traditional Vickers and Martens hardness methods Dental Materials 23 1079–

1085.

8. Price RBT, Fahey J & Felix CM (2010) Knoop Microhardness Mapping Used to Compare

the Efficacy of LED, QTH and PAC Curing Lights Operative Dentistry 35 (1) 58-68.

9. Pollington S, Kahakachchi N & van Noort R (2009) The Influence of Plastic Light Cure

Sheaths on the Hardness of Resin Composite Operative Dentistry 34 (6) 741-745.

10. Yan YL, Kim YK, Kim K-H & Kwon T-Y (2010) Changes in Degree of Conversion and

Microhardness of Dental Resin Cements Operative Dentistry 35 (2) 203-210.

11. Camargo EJ, Moreschi E, Baseggio W, Cury JA & Pascotto RC (2009) Composite

Depth of Cure Using Four Polymerization Techniques. Journal of Applied Oral Science

17(5) 446-450.

12. Retamoso LB, Onofre NML, Hann L & Marchioro EM (2010) Effect of light-curing units

in shear bond strength of metallic brackets: an in vitro study Journal of Applied Oral

Science 18 (1) 68-74.

13. Santos MJMC, Passos SP, Encarnação MOL, Santos Junior GC & Bottino MA (2010)

Hardening of a dual-cure resin cement using QTH and LED curing units Journal

Applied Oral Science 18 (2) 110-115.

14. Thomé T, Steagall Jr. W, Tachibana A, Braga SRM & Turbino ML (2007) Influence of

the distance of the curing light source and composite shade on hardness of two

composites Journal of Applied Oral Science 15 (6) 486-491.

15. Aguiar FHB, Braceiro A, Lima DA, Ambrosano GMB & Lovadino JR (2007) Effect of

Light Curing Modes and Light Curing Time on the Microhardness of a Hybrid

Composite Resin Journal of Contemporary Dental Practice 8 (6) September 1.

16. Abe Y, Sato Y, Akagawa Y & Ohkawa S (1997) An in vitro study of high-strength resin

posterior denture tooth wear International Journal of Prosthodontics 10 28–34.

17. Harrison A, Huggett R & Handley RW (1979) A correlation between abrasion

resistance and other properties of some acrylic resins used in dentistry Journal of

Biomedical Materials Research 13 23–34.

18. Whitman DJ, McKinney JE, Hinman RW, Hesby RA & Pelleu Jr GB (1987) In vitro

wear rates of three types of commercial denture tooth materials Journal of Prosthetic

Dentistry 57 243–246.

Table 1: Means comparison for all groups.

50g 100g 500g

15s

30s

45s

KHN

168.13

149.87

180.33

KHN

184.25

179.13

148.09

KHN

140.77

139.40

128.92

Table 2: Means for Knoop groups in homogeneous subsets are displayed.

Tukey HSD

Subset for alpha = .05

GROUP N

1 2 3

45s500g 30 128,9200

30s500g 30 139,4067

15s500g 30 140,7767 140,7767

45s100g 30 148,0900 148,0900

30s50g 30 149,8700 149,8700

15s50g 30

168,1333 168,1333

30s100g 30

179,1333

45s50g 30

180,3333

15s100g 30

184,2667

Sig.

,350

,070

,708

4 Discussão Geral

Os métodos de ensaio mecânico Vickers e Knoop têm sido utilizados para

avaliar as propriedades mecânicas dos materiais em diversos estudos. Na odontologia

a utilização destes testes é muito comum, sendo a resina composta um dos materiais

de uso odontológico que, frequentemente, recebe este tipo de análise. Uma

propriedade mecânica constantemente avaliada neste material é o grau de conversão

obtido com a fotoativação. Quanto maior for o tempo de fotoativação maior será o grau

de conversão alcançado. Desta forma, através dos resultados obtidos, é feita uma

analogia que cria uma relação direta entre o valor encontrado e o grau de conversão da

resina composta. Assim sendo, quanto maior forem os valores obtidos através dos

testes de microdureza, maior será, portanto, o grau de conversão alcançado com a

fotoativação das resinas compostas. Estudos recentes utilizaram diferentes tempos de

aplicação e diferentes valores de carga para avaliar esta conversão, como pode ser

verificado através dos trabalhos citados nos artigos apresentados e, também, através

da Tabela 1, presente na apresentação deste trabalho. Porém, existem diferenças

significativas entre estes estudos e entre as variáveis utilizadas que impossibilitam uma

analogia direta dos seus resultados. Um exemplo destas diferenças e/ou variáveis

existentes é a presença de fatores internos presentes em uma resina composta, tais

como, o tipo de carga, o tamanho da partícula e a matriz polimérica, que podem

influenciar os resultados alcançados. Segundo Yan et al. (2010), o valor de

microdureza é fortemente influenciado por fatores, tais como a carga das partículas que

compõe o compósito e, por este motivo, comparações entre diferentes marcas

comerciais são limitadas. Conforme Hahnel et al. (2010), existe um número

considerável de materiais compósitos no que tange o tipo de partícula empregada.

Todavia, diferenças entre estes materiais referentes ao tipo do sistema monomérico, ao

tipo de composição das partículas e ao tipo de união química das partículas matriciais

podem contabilizar performances mecânicas diferentes e podem ocasionar diferenças

na resistência dos materiais à degradação química e mecânica.

Existem, também, fatores externos, tais como a distância da fonte de luz, o

tempo de polimerização das resinas, a densidade de energia, a composição, a cor e

opacidade da resina que também podem influenciar nos testes de microdureza.

Para Fróes-Salgado et al. (2009), quando a distância entre o compósito e a fonte

de luz aumenta uma severa atenuação da luz é observada. Segundo Neves et al.

(2002) as diferentes unidades de luz resultam em variações nos valores de conversão,

por apresentarem diferenças em suas características, como tipo, número e disposicão

das lâmpadas, potência e calor gerado no interior dos aparelhos. Aguiar et al. (2007)

relataram que o método de polimerização é um fator determinante e que o tempo

recomendado pelo fabricante dos compósitos resinosos são insuficientes para uma

“ideal polimerização”. Para Correr et al. (2005) que analisaram diferentes fontes de luz

(LED, PAC, e Luz Halógena) em duas resinas diferentes, a dureza dos compósitos

fotoativados por PAC foi estatisticamente inferior em relação aos compósitos

fotoativados com luz halógena ou LED, que por sua vez, não se diferenciaram entre si,

independente da profundidade. Já em relação ao tempo de exposição, constatou-se

que o aumento do tempo produziu compósitos com maiores valores de dureza Knoop

quando se utilizou LED ou PAC. Para Luz Halógena o aumento de tempo de exposição

não influenciou os valores de dureza e que os valores de dureza Knoop diminuíram

com o aumento da profundidade. Além disto, Aguiar et al. (2007) constataram que o

tamanho do incremento de resina também pode modificar o grau de polimerização, o

que vai ao encontro do que é afirmado por Camargo et al. (2009) e por Pollington et al.

(2009), que preconizam que o incremento de resina possua no máximo 2mm de

espessura.

Por essas razões o presente estudo utilizou a mesma fonte de luz (LED), com a

mesma distância, com o mesmo tempo de polimerização (20s) e com o mesmo tempo

de aplicação de carga sobre todas as amostras. Assim como, foram realizados

incrementos com no máximo 2mm para cada fotoativação, para que esta variante não

atuasse neste trabalho, indo, desta forma, ao encontro dos trabalhos de Correr et al.

(2005), David et al. (2007), Aguiar et al. (2007). Após a confecção das amostras, estas

foram submetidas aos testes Knoop e Vickers com diferentes tempos e cargas

constatando-se diferenças significativas e não lineares entre os resultados obtidos,

demonstrando, assim, que diferentes cargas e tempos influenciam na microdureza das

resinas, contrariando Shahdad et al. (2007) que afirmam que a microdureza independe

da carga.

Portanto, para que a análise dos testes de microdureza seja fiel, tanto para o

ensaio de microdureza Knoop, quanto para o ensaio de microdureza Vickers,

necessita-se de uma regra universal para os futuros estudos e se faz necessário um

protocolo de testagem com tempo e carga únicos e iguais, porque, desta maneira, as

chances de fidelidade dos futuros estudos serão maiores. Além disto, possíveis

comparações diretas entre os dois diferentes tipos de ensaio mecânico, citados

anteriormente, se mostraram inviáveis. Variações significativas e não lineares também

foram encontradas quando os dois tipos de ensaio foram comparados. Os valores

encontrados para os testes realizados com a metodologia Vickers foram, na quase

totalidade das vezes, maiores que os valores encontrados quando utilizada a

metodologia Knoop. . Desta forma, analogias e comparações entre estes dois tipos de

ensaio mecânico devem ser evitados. Assim sendo, podemos perceber que os estudos

passados “não poderiam fazer comparações” quando utilizados tempos e cargas

diferentes, pois existem diferenças entre os testes realizados e, consequentemente, em

seus resultados, ficando, desta forma, qualquer afirmação comparativa inviável de ser

realizada.

5 Referências Bibliográficas Adicionais

1-BLANDO, Eduardo. Estudo de técnicas de indentação dinâmica para avaliação

de materiais na região de nano e microdureza. 2001, 172 f. Dissertação (Mestrado

em Engenharia) - Faculdade de Engenharia, Pontifícia Universidade Católica do Rio

Grande do Sul, Porto Alegre , 2001.

2-CALLISTER, William D. Ciência e engenharia de materiais: uma introdução. 5. ed.

Rio de Janeiro : LTC, c2002. 589 p.

3-CAMARGO EJ, MORESCHI E, BASEGGIO W, CURY JA, PASCOTTO RC.

Composite depth of cure using four Polymerization techniques. Journal of Applied

Oral Science. 2009; 17(5):446-50.

4-FRÓES-SALGADO NRG, PFEIFER CSC, FRANCCI CE, KAWANO Y. Influence of

Photoactivation Protocol and Light Guide Distance on Conversion and Microleakage of

Composite Restorations. Operative Dentistry. 2009; 34(4): 408-414.

5-GARCIA, Amauri. Ensaios dos materiais. Rio de Janeiro : LTC, c2000. 247 p.

6-HAHNEL S, HENRICH A, BÜRGERS R, HANDEL G, ROSENTRITT M. Investigation

of Mechanical Properties of Modern Dental Composites After Artificial Aging for One

Year. Operative Dentistry. 2010; 35(4): 412-419.

7-HANNIG C, DUONG S, BECKER K, BRUNNER E, ATTIN T. Effect of bleaching on

subsurface micro-hardness of composite and a polyacid modified composite. Dental

Materials. 2007; 23: 198–203.

8-KOMORI PCP, PAULA AB, MARTIN AA, TANGO RN, SINHORETI MAC, CORRER-

SOBRINHO L. Effect of Light Energy Density on Conversion Degree and Hardness of

Dual-cured Resin Cement. Operative Dentistry. 2010; 30(5): 120-124.

ANEXO 1 – Carta de aprovação da Comissão Científica e de

Ética da Faculdade de Odontologia da PUCRS

ANEXO 2 – E-mail de confirmação de submissão de trabalho

ao Journal of Applied Oral Science

[JAOS] JAOS-1901 Submission Acknowledgement

Quinta-feira, 16 de Setembro de 2010 13:48

De:

"Carlos F. Santos" <jaos@usp.br>

Adicionar remetente à lista de contatos

Para:

"Gustavo Frainer Barbosa" <gfraibar@yahoo.com.br>

Dear Dr. Gustavo Frainer Barbosa,

Thank you for submitting the manuscript, "JAOS-1901 - Analysis of

microhardness methodologies applied to composites: is it possible to

compare results using different protocols?" to Journal of Applied Oral

Science. With the online journal management system that we are using, you

will be able to track its progress through the editorial process by

logging

in to the journal web site:

Manuscript URL:

http://submission.scielo.br/index.php/jaos/author/submission/40525

Username: gfraibar

If you have any questions, please contact me. Thank you for considering

this journal as a venue for your work.

Yours sincerely,

_____________________________________________________

Carlos F. Santos, DDS, MSc, PhD, Associate Professor

Editor-in-Chief

Journal of Applied Oral Science

http://www.scielo.br/jaos

ANEXO 3 – E-mail de confirmação de submissão de trabalho

a Operative Dentistry

6 10-319-L Manuscript received - Operative Dentistry

Terça-feira, 26 de Outubro de 2010 13:59

De:

"editor@jopdent.org" <editor@jopdent.org>

Adicionar remetente à lista de contatos

Para:

gfraibar@yahoo.com.br

Cc:

hoshima@terra.com.br, ed_mota@terra.com.br, [email protected]om.br,

lucian[email protected]r, marcelfarret@yahoo.com.br

Dear Mr. Barbosa,

On October 26, 2010, I received your manuscript entitled "Analysis of Knoop microhardness test: is it

possible to make an analogy between conversion degree and the obtained results using different

protocols?" by Gustavo Barbosa, Hugo Oshima, Eduardo Gonçalves, Ana Maria Spohr, Luciana Hirakata,

and Marcel Farret.

Your manuscript has been assigned the Paper #: 10-319-L.

You may check on the status of this manuscript by visiting your author home page

at http://jopdent.allentrack.net.

Thank you for submitting your work to Operative Dentistry.

Sincerely,

Kevin Matis

Editorial Assistant

Operative Dentistry

Livros Grátis
( http://www.livrosgratis.com.br )
 
Milhares de Livros para Download:
 
Baixar livros de Administração
Baixar livros de Agronomia
Baixar livros de Arquitetura
Baixar livros de Artes
Baixar livros de Astronomia
Baixar livros de Biologia Geral
Baixar livros de Ciência da Computação
Baixar livros de Ciência da Informação
Baixar livros de Ciência Política
Baixar livros de Ciências da Saúde
Baixar livros de Comunicação
Baixar livros do Conselho Nacional de Educação - CNE
Baixar livros de Defesa civil
Baixar livros de Direito
Baixar livros de Direitos humanos
Baixar livros de Economia
Baixar livros de Economia Doméstica
Baixar livros de Educação
Baixar livros de Educação - Trânsito
Baixar livros de Educação Física
Baixar livros de Engenharia Aeroespacial
Baixar livros de Farmácia
Baixar livros de Filosofia
Baixar livros de Física
Baixar livros de Geociências
Baixar livros de Geografia
Baixar livros de História
Baixar livros de Línguas

Baixar livros de Literatura
Baixar livros de Literatura de Cordel
Baixar livros de Literatura Infantil
Baixar livros de Matemática
Baixar livros de Medicina
Baixar livros de Medicina Veterinária
Baixar livros de Meio Ambiente
Baixar livros de Meteorologia
Baixar Monografias e TCC
Baixar livros Multidisciplinar
Baixar livros de Música
Baixar livros de Psicologia
Baixar livros de Química
Baixar livros de Saúde Coletiva
Baixar livros de Serviço Social
Baixar livros de Sociologia
Baixar livros de Teologia
Baixar livros de Trabalho
Baixar livros de Turismo
 
 