Franklin R. Tay David H. Pashley



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Water Movement Across Bonded Dentin – Too of a Good Thing
J Appl. Oral Sciences 2004; 12 (sp. Issue): 12-25.

Author:
Ricardo M. Carvalho*

Franklin R. Tay**

David H. Pashley***



*Department of Operative Dentistry, Endodontics and Dental Materials, Bauru School of Dentistry, University of Sao Paulo, Brazil; Member of the board editorial of the Journal Dental Research*
**Pediatric and Orthodontics, Faculty of Dentistry, University of Hong Kong, Prince Philip Dental Hospital, China**
***Department of Oral Biology and Maxillofacial Pathology, Medical College of Georgia, Augusta, GA, USA***

Commentary of abspathology



A B Schütz, Ph.D.
Dentist, Pharmacist, Master in Oral Pathology at the Federal University of Rio de Janeiro (UFRJ), Doctor in Oral Pathology at the Bauru School of Dentistry, University of Sao Paulo (FOB/USP), Brazil.  Address reprint request to Dr. Antonio Beltrao Schütz, José Bonifácio 2598/103, telephone: (055) 3221-6763, CEP: 97 015-450, Santa Maria, RS, Brazil.

Simplified dentin adhesives: the evolution in the technology of the adhesion

Years late, after to have had administrative problems with the Brazilian academic mean, intended to course post-doctoral study in the US. Because were more easily and fast to learn English than another language, and there was a position opened in the Oral Biology at the Kansas City University as well as interested me for chemistry, looked the Chairman of that Department, who, maybe for do not have scholarship of Brazilians Institutions of Research, or not to have Jew family name, require me TOEFL, TSE (score superior to 4 at one scale of 6), GRE (score superior to 6, at one scale of 7), and three letters of references of Brazilians professors, which was very difficulty for me require and obtain them, considering my disagree with relation to process of ingress of Professors at the Brazilian academic career that consider, in the great majority of the cases, to be fraudulent.

After controlling some inner feeling, looked Professor Odila Silva, at that time, Chairman of the Immunology and Microbiology Discipline, at the Bauru School of Dentistry, University of Sao Paulo (FOB/USP), who of immediate conceded me it. Unfortunately, did not have similar control to require others, dropping out the intention of studying in US.

As did not agree with the results of my first TOEFL test realized in 2001 at the Brazil-EUA cultural Institute (Londrina, Pr, Brazil), accusing it of being manipulated (manipulation of the sound), favoring Brazilians professors with scholarships given for the Brazilians institutions of research, and to difficulty for whom is not, or have not them, - as is my case - interested me for studying German; and after a fast auto-preparation, traveled to Germany.

But the attempt of coursing post-doctoral study in US was not lost because in addition to prepared me to TOEFL, GRE and TSE tests, I reviewed almost all American and Brazilian publication about Adhesive systems, inclusive suggesting, to the then American professor (Chairman Professor of Oral Biology at the Kansas University), the substitution of the acid attack of one of the Americans resins tested in that Department for citric acid, which afterward was utilized by the manufacture.

Then, my computer presented problem; during the time of the concert-time resolved to review that knowledge, when suddenly opened the J. Appl. Oral Sciences (Magazine of the post-graduation at the FOB/USP) of the Bauru School of Dentistry (where coursed my Ph.D. in Oral Pathology), reading the article wrote by Carvalho et al. (2004). At that time, returned to mind my doctoral study at the Bauru School of Dentistry at the Sao Paulo University (USP) because when passed near the Department of Dentistry at the FOB/USP listened voices almost imperceptibles to an audition not accurate direct to me in the attempt of conditioning me, such as three ex-students of that department made with the ex-chef of the Dentistry Department at the Federal University of Santa Maria (UFSM). He was too conditioned to obey that in an air travel to USA (American Airlines) ordered and he started to bite the flight stewardess, having stayed in prison for some time in Porto Rico. Ordered and he bit her. At that time time, confirmed itself what that there was affirmed about the Brazilian public service: “it is so conditioned for the oppose sites to the dictatorial military regime of 64 that if you order them to give the “tail” in the corner, will not be surprise if you to see the “ordinaries” (ordinários) or the “Colleague” (companheiros) with the trousers break down”. The same occur in relation to the scientific works. They believe in all that is talked, in all that is read and publish results absurd, without critical sense; enough the publisher to accept the work paid sent to publication. Then, resolved to read more accurately this article.

After a fast reading, verifying the organization of the text, its grammatical correction, and the quality of the figures, thought: “this is thing of the first world.” However, after a more accurately reading, maybe, for having stayed distant of the reading of this theme, confess that had difficulty for understanding its structure. Salve better judgment, I did not identify a structure that might classified it as an research report, or of a review article, considering that important articles realized in other Americans Universities were not reviewed. What that liked to be the principal objective, “evidence of water movement across material-dentin interface associated with the use of the dentin adhesives RMGIC and GICs,” there was yet been illustrated and discussed by Pashley and other colleagues in specific articles. However, Carvalho et al. (2004) promote us the excellent collectanea of the Pashley’s hypotheses. Of new, only the enthusiastic hypothesis, “in the environmental SET micrograph of unfractured spherical body in Fuji VII is not a dehydratation artifact (fig.22),” having as basis the ingenuous conclusion that the spherical bodies do not contain polimerisable resin component, but that the spherical bodies contain air. Meanwhile, as affirmed Yiu et al. (2004), the spherical bodies, when fractured, reveals the original eggshell-like characteristics, caused by water, probably, evaporated from the fractured shell. In other words, were artifacts caused for dehydration.

Was also difficult to identify the difference between the spherical bodies presented in the fig. 22 and those presented in figs. 10, 11 e 12. Is interesting to observe that all these blisters are intact, not turning possible to evidence rupture or cracks in the “flood-gate” blisters.

Also, did not understand the difference between artifactual cracks observed inside the polyakenolate matrix and “water tree”, because there is difference between the pattern of distribution of “water tree,” and the water trees that are formed as a result of absorption and deterioration of the insulation polymer around underground electrical cables (fig. 17). While in the latter there is a uniform distribution of cracks, in the former are concentrate in the center, justly where there is greater resistance to the cut, and a greater concentration of artifactual cracks. Besides, the simple identification of the presence of cracks is not sufficient to establish a continuity solution with extern surface. They may until same to increase the elasticity such as occur in the sole of a shoe.

In the vision that the blisters were identified, in a greater number, in simplified dentin adhesives, which might indicate points of the “flood-gate” from water that draw off gradually through “water trees” or artifactual cracks, in spite of agreeing with the hypothesis of Carvalho et al. (2004) that spherical bodies or dehydratation artifact, identified in GI-based materials, might serve to deflect or blunt any cracks that attempt propagate themselves throughout the matrix, disagree that the blisters of “flood-gate”, identified at great number in simplified dentin adhesives, might result in the weakening of the adhesive-composite interface. They must be seen as an advance in the technology of these materials, because may indicate points of obliteration of the dentinal tube under greater fluid pressure before of the complete polymerization of the adhesive, which for its initial elasticity acquire the form of blister similar what of a balloon in the extremity of a tube under outflow of water, whose flood may be detained according to the augment of the elasticity of the adhesive until the dehydratation artifact, and not as the simple diffusion of water throughout of the adhesive. This process must be interpreted as static or of physical contention and not as a dynamic process of diffusion of blisters water across a semi-permeable (polymerized adhesive layers) layer. Due to the polymerization process not to be uniform and the mechanic resistance as well as the elastic modulus of the polymer to increase with time; the attempt of diffusion of water only occur in regions of greater fluid pressure, and in local of increased exothermic reaction, where a appreciable mechanical resistance was not obtained during the firsts 24 hours. Therefore, must not be interpreted as lack of adhesion of the simplified dentin adhesives, but as a mean of promoting the increase of the surface of contact between two solid surfaces that may also actuate as a region of attenuation of the stress, as a buffer or as a “pillow”, such as glicoaminoglicans inside extra-cellular matrix, because of the significantly high elasticity of the adhesive in these regions.

The greater contribution in the Carvalho et al. (2004) study was to reproduce the fig.10, but that was not sufficiently valorized for him and his colleagues, because it promote to the manufactures the indication that a simplified dentin adhesives may still be better developed, objecting the better utilization of the smear layer and smear plug, as a additional layer for better obtaining adhesion, such as is produced for some self etchting primers that retain smear plugs within the tubules create superior dentin sealing (Hashimoto; Ito; Tay; Sviziero et al., 2004).

Therefore, the enthusiastic professor Carvalho and your group of research that excuse me; is very difficult to accept some of the interpretation and conclusions of the results of this valorized study, however, controversial in some points, but defended with force and enthusiasm by the expert professor at the FOB/USP and his colleagues.



References

Tay F, Carvalho RM, Pashley DH (2004) Water movement across bonded dentin – too much of a good thing. J Appl. Oral Sci 12 (sp. Issue): 12-25.

Yiu CKY, Tay FR, King NM, Pashley DH et al. (2004) Interation of glass-ionomer cements with Moist Dentin. J Dent Res 83: 283-289.

Hashimoto M, Ito S, Tay FR, Sviziero et al. (2004) Fluid movement across the Resin-dentin interface during and after boding. Dentin. J Dent Res 83: 283-289.


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