Dry bonding: New perspectives for collagen hybridization

Advancements in dental adhesive technology have revolutionized dental treatments, invariably increasing the number and indications of restorative treatment options. Considering current techniques to bond to tooth tissue, dentin can be characterized as the most challenging mineralized dental substrate for successful long-lasting bonding. Resin-dentin bonding relies, partly or totally, on collagen hybridization to couple methacrylate-based resins to the underlying mineralized dentin. The aim of this study series was to revisit the dry-bonding approach by modifying the application protocol to effectively enable resin bonding to air-dried-etched dentin. Dentin pretreatments containing dimethyl sulfoxide (DMSO) in either ethanolic or aqueous solutions (50 % v/v) were tested to determine whether novel DMSO-dry bonding approaches could improve resin-dentin bonding. Mechanical and physical properties of DMSO-containing resins such as degree of conversion, elastic modulus, flexural strength, water sorption and solubility were evaluated. Resin-dentin interfaces were submitted to long-term microtensile testing, nanoleakage and micropermeability evaluation, in situ zymography and degree of conversion. Indirect assessment of enzymatic activity on DMSO-treated collagen was determined by dry mass loss, hydroxyproline quantification and elastic modulus. Gel zymography was used to determine the effect of DMSO pretreatments on MMP-2 and -9 activity. The wettability of air-dried DMSO-treated collagen by hydrophilic and hydrophobic resins was evaluated by contact angle measurements. This study series produced compelling evidence that DMSO-dry bonding constitutes a feasible alternative to reduce residual water from resin-dentin interfaces by broadening the moisture spectrum of demineralized dentin to substantially drier levels. Bonding methacrylate-based resins to extensively air-dried collagen greatly improved resindentinbonding following the DMSO-dry bonding approaches. Higher resin-dentin bond strength was accompanied by better hybrid layer formation with higher monomer conversion and reduced porosities, lower collagenolytic activity, enhanced dentin wettability and lower technique sensitivity. Altogether, such benefits contributed to more efficient collagen hybridization, addressing important issues in resin-dentin bonding with a single bonding protocol.Kuivasidostus: uusia näkökulmia kollageenin hybridisaatioon Sidostusteknologian kehitys on johtanut suuriin muutoksiin hammashoidossa, ja lisännyt merkittävästi korjaavan hoidon indikaatioita ja hoitotoimenpiteiden määrää. Nykyisillä sidostekniikoilla dentiini asettaa suuria haasteita sidoksen pitkäaikaiskestolle. Sidosaineen ja dentiinin liitos perustuu sidosaineen tunkeutumiseen dentiinin kollageeniverkoston sisään (ns. hybridisaatio), jonka kautta metakrylaattipohjaiset sidosaineet kiinnittyvät dentiiniin. Hybridisaatio on monimutkainen prosessi. Toimenpide täytyy suorittaa nopeasti kosteassa kudoksessa, ja sen tulisi kestää jopa vuosikymmeniä. Tämän tutkimussarjan tavoitteena oli tutkia sidostamista kuivaan kudokseen muokkaamalla protokollaa siten, että se onnistuisi ilmakuivattuun happokäsiteltyyn dentiiniin. Tutkimuksissa testattiin dentiinin esikäsittelyä dimetyylisulfoksidin (DMSO) etanoli- ja vesiseosten (50 til.-%) mahdollisia etuja, ja selvitettiin täysin uudenlaisen DMSO-kuivasidostuksen käyttöä sidoksen parantamisessa. Lisäksi selvitettiin DMSO:ta sisältävien sidosaineiden fyysisiä ja mekaanisia ominaisuuksia, kuten konversioastetta, kimmomoduulia, taivutuslujuutta, veden adsorptiota ja liukenemista. Vanhennettuja sidosrajapintoja tutkittiin mikrosidoslujuustestauksella, nanovuotoanalyysillä, mikropermeabiliteettitestauksella, in situ-zymografialla ja konversioasteanalyysillä. Entsyymien vaikutusta DMSO-käsiteltyyn dentiinikollageeniin tutkittiin epäsuorasti kuivapainomenetystä, hydroksiproliinin vapautumista ja kollageenin kimmomoduulia mittaamalla. Geelizymografialla määritettiin DMSO-esikäsittelyn vaikutusta MMP-2:n ja MMP-9:n aktiivisuuteen. Kuivatun DMSO-käsitellyn dentiinin kostutettavuutta tutkittiin kosketuskulmamittauksilla. Tutkimukset osoittivat DMSO-kuivasidostuksen olevan toteuttamiskelpoinen keino vähentää jäännösvettä sidosrajapinnassa mahdollistamalla sidostaminen kuivaan dentiiniin, ja se paransi sidosta merkittävästi. DMSO-kuivasidostaminen paransi dentiinin kostutettavuutta, hybridikerroksen laatua ja monomeerien konversiota, vähensi kollagenolyyttistä aktiivisuutta ja hybridikerroksen huokoisuutta, paransi välitöntä sidoslujuutta ja sen pysyvyyttä, ja vähensi käsittelyvirheiden riskiä. Kaiken kaikkiaan menetelmällä saavutettiin tehokkaampi dentiinikollageenin hybridisaatio vaikuttamalla useisiin sidostamisen kannalta merkittäviin tekijöihin

Performance Evaluation of Solvent Assisted-Steam Injection Processes with Asphaltene Insoluble Solvents

Adding solvents to steam flooding processes during bitumen production can reduce the water and natural gas usage but may create a new unique set of problems. Most solvents are toxic and are prohibited to be used on sites. Most importantly, since the solvent-bitumen-steam interactions are not well understood, solvent-steam coinjection into bitumen reservoirs may lead to produce lower quality oil. Because of the high asphaltene content of bitumen reservoirs and the presence of clays in the reservoir, the quality of the produced oil is determined mainly by the interaction of solvents with these elements. These interactions can be detrimental on the performance of the steam processes by enhancing the asphaltene precipitation which can plug the reservoir pores and/or by forming emulsions in produced oil which may require additional surface facilities to separate water-in-oil emulsions at the surface due to asphaltene-water interactions. This study will investigate the solvent-asphaltene-clay-steam interactions that occur during solvent-steam injection into high asphaltene content bitumen reservoirs. Two solvents were used: n-hexane (E1 and E4) and a commercial solvent (CS) (E2 and E5). Five experiments were run: two miscible floodings (E1 and E2), one steam flooding (E3) and two SA-SF (E4 and E5). The performances of the solvents were evaluated according to the oil production and the produced oil quality, the asphaltene clay content, viscosity and emulsions of this oil. During miscible flooding, E1 (n-hexane flooding) performed only slightly better than E2 (commercial solvent flooding). The quality of produced oil, however, was vastly different due to the asphaltene and clay content. The commercial solvent is composed of heavy dearomatized hydrocarbons ranging from C11 to C16, and therefore is more prone to carrying asphaltenes. During E3, E4, and E5, in which steam was used, the differences were made even clearer. Although E5 had a better recovery than steam alone (E3), the oil quality was very poor, containing high amounts of asphaltene and clay. However, for E4 where steam and n-C6 were injected more clay was observed than E5 in which steam and commercial solvent (CS) were injected. E5 also produced less oil than E4; the heavier weight of the CS keeps it at a liquid state even at steam temperatures, limiting its coverage of the rock. The high asphaltene content of the produced oil also caused severe emulsions problems, as the asphaltene and clays present deposited in the water oil interface and stabilized the water droplets. From these results, the use of heavy hydrocarbon solvents is not recommended for SA-SF processes into high asphaltene content reservoirs, as their interactions with the bitumen, reservoir and steam are detrimental to not only the recovery factor, but also the quality of the oil