Degree of conversion of three fissure sealants cured by different light curing units using micro-Raman spectroscopy

Background/purpose: Monomer to polymer conversion is important for optimal mechanical properties and resistance to biodegradation of resin-based materials. Incomplete conversion of fissure sealants may account for lower retention and fracture resistance as well as elution of leachable components. The objective of this study was to determine the degree of conversion (DC) of three fissure sealants cured using a conventional quartz-tungsten halogen (QTH) or a high power light-emitting diode (LED) light-curing unit using micro-Raman spectroscopy. Materials and methods: Delton Opaque and Helioseal Opaque and Helioseal Clear were applied to 60 noncarious permanent molars and cured with the QTH or the LED. Micro-Raman spectra were obtained from the top and the bottom surface of each sample. Three-way analysis of variance (alpha = 0.05) was used for data analysis. Results: Top surface DC values were significantly higher than bottom surface in each material irrespective of the light-curing unit (P lt 0.05). LED produced significantly higher DC values than the QTH with all three materials (P lt 0.05). Helioseal Opaque showed significantly lower DC values than Helioseal Clear (P lt 0.05). DC values for Delton and Helioseal Clear were comparable (P > 0.05). Conclusion: Higher DC is achieved with the LED with less exposure time compared with the conventional QTH at top and bottom surfaces of the three fissure sealants, although a lower conversion may be expected in opaque materials

Uticaj kompozita s malom kontrakcijom i konvencionalnih kompozita na postoperacionu osetljivost zuba

Introduction. Postoperative sensitivity in restorative dentistry can be related to preparation trauma, dentin adhesives' ability to seal open dentinal tubules, deformation of restorations under occlusal stresses and microleakage. Objective. The study assessed possible reduction in postoperative sensitivity with low shrinkage compared to conventional composites using different bonding agents and the influence of the operator skill on the incidence of postoperative sensitivity. Methods. Nine hundred and sixty permanent premolars and molars with primary carious lesions from patients 21 to 40 years old were used. Cavities 2 to 3 mm deep and with margins in enamel were prepared by four operators. Two operators had five years (A and B) and two had over 20 years (C and D) of clinical experience. Teeth were divided into eight groups each contained 120 restorations: (1) Els®+James-2 (original formula), (2) Els®+James-2 (new formula), (3) Els®+Excite, (4) InTenSe®+James-2 (original formula), (5) InTenSe®+James-2 (new formula), (6) InTenSe®+Excite, (7) Tetric Ceram®+Excite, and (8) Point 4®+OptiBond Solo Plus. At 14 days postoperatively, two independent operators, who did not take part in the clinical procedure, assessed postoperative teeth sensitivity using special questionnaires. Data were analyzed using non-parametric chi-square, Mann-Whitney and ANOVA tests. Results. Group 8 showed significantly higher score than the other groups. Less postoperative sensitivity was reported with two low-shrinkage composites (groups 2, 3, and 5) but with no significant difference. There was no statistical difference between groups 1, 2, 3, 4, 5, 6 and 7. Operator A had the highest postoperative sensitivity score compared to the other three. Conclusion. Conventional composite material Point 4® with its bonding agent caused significantly more postoperative sensitivity than low shrinkage composites combined with different adhesives. Operator skill influenced the incidence of postoperative sensitivity.Uvod. Posle postavljanja kompozitnih ispuna može da se javi postoperaciona osetljivost izazvana preparacionom traumom, sposobnošću adhezivnog sistema da hermetički zatvori dentinske kanaliće, deformacijom pod okluzalnim opterećenjem ili prodorom bakterijskih toksina. Cilj rada. Cilj istraživanja je bio da se ispita da li je osetljivost zuba manja kod kompozita s malom kontrakcijom u poređenju s konvencionalnim kompozitima i odgovarajućim adhezivnim sistemima, kao i uticaj veštine stomatologa na incidenciju postoperacione osetljivosti zuba. Metode rada. Na 960 premolara i molara stalne denticije s primarnim karijesom, pacijenata starosti od 21 godine do 40 godina, preparisani su kaviteti dubine 2-3 mm s rubovima u gleđi. Čitavu proceduru su obavila četiri specijalista stomatologije, od kojih su dva imala pet (A i B), a druga dva više od 20 godina kliničkog iskustva (C i D). Zubi su svrstani u osam grupa od po 120 uzoraka prema korišćenom kompozitnom i adhezivnom sistemu: 1) Els®+James-2; 2) Els®+James-2 (nova formula); 3) Els®+Excite; 4) InTenSe®+James-2; 5) InTenSe®+James-2 (nova formula); 6) InTenSe®+Excite; 7) Tetric Ceram®+Excite; i 8) Point 4®+OptiBond Solo Plus. Dve nedelje posle intervencije dva nezavisna stomatologa (koja nisu učestvovala u kliničkoj proceduri) ocenjivala su posebnim upitnicima postoperacionu osetljivost zuba. Podaci su analizirani neparametrijskim c2, Man-Vitnijevim (Mann-Whitney) i ANOVA testom. Rezultati. U osmoj grupi utvrđena je statistički značajno češća postoperaciona osetljivost nego u ostalim grupama zuba. Nije bilo statistički značajne razlike između grupa 1, 2, 3, 4, 5, 6 i 7. Kompoziti sa nižom polimerizacionom kontrakcijom izazvali su manju postoperacionu ostetljivost, ali bez statističke značajnosti razlika (grupe 2, 3 i 5). Kod stomatologa A javljala se statistički značajno češće postoperaciona osetljivost nego kod ostala tri. Zaključak. Tip kompozitnog materijala s odgovarajućim adhezivnim sistemom i spretnost stomatologa utiču na učestalost pojave osetljivosti zuba posle restauracija srednje dubokih kaviteta II klase

Micro-Raman spectroscopic analysis of the degree of conversion of composite resins containing different initiators cured by polywave or monowave LED units

Objectives: To determine the degree of conversion (DC) over 48 h post-curing of resin mixtures containing trimethylbenzoyl-diphenylphosphine oxide (TPO) initiator cured by a polywave or a monowave LED light-curing unit (LCU). Methods: In resin mixtures based on equal weight percent (wt%) of BisGMA and TEGDMA the following initiators were added: 0.2 wt% camphorquinone (CQ) + 0.8 wt% ethyl-4-dimethylaminobenzoate (EDMAB) (Group 1); 1 wt% TPO (Group 2) and 0.1 wt% CQ + 0.4 wt% EDMAB + 0.5 wt% TPO (Group 3). Half of the samples in each group (n = 5) were cured using a polywave (bluephase (R) G2, Ivoclar Vivadent) or a monowave LED LCU (bluephase (R), Ivoclar Vivadent). The DC was measured using micro-Raman spectroscopy within 5 min and then 1, 3, 6, 24 and 48 h post-irradiation. The data were analysed using general linear model and two-way ANOVA for the factors 'time', 'material', 'surface' and 'LCU' at alpha = 0.05. Results: The initial DC values obtained upon light curing remained similar over a 48 h period. bluephase (R) G2 produced the highest DC in Group 2 followed by Group 3, and Group 1. bluephase (R) resulted in the highest DC in Group 1, followed by Group 2 and Group 3 (p lt 0.05). Conclusions: Unfilled resin materials containing both TPO- and CQ-amine initiators are effectively cured using bluephase (R) G2. Resin mixture with the same wt% of initiators is better cured when TPO is the only initiator, compared to CQ-amine only or combined TPO and CQ-amine system. After initial light cure, no additional conversion of uncured monomers was detected in an unfilled resin material over 48 h at 37 degrees C

Remaining Unreacted Methacrylate Groups in Resin-Based Composite With Respect to Sample Preparation and Storing Conditions Using Micro-Raman Spectroscopy

The aim of this study was to measure degree of conversion (DC) of resin-based composites (RBCs) using micro-Raman spectroscopy followed by different sample preparation procedures and storing conditions. Ninety samples of Tetric EvoCeram (Ivoclar Vivadent, Schaan, Liechtenstein) were prepared in standardized molds and cured with a high powered LED light-curing unit, bluephase (R)) (Ivoclar Vivadent, Schaan, Liechtenstein) for 20 s. Samples were allocated to eight groups. DC of groups I and 2 was recorded without or after polishing. DC in groups 3 and 4 was recorded from vertically sectioned samples versus "split" samples. DC in groups 5-8 was recorded after storing samples at room temperature and humidity, in 90 +/- 2% humidity at 37 +/- 1 degrees C, distilled water at 37 +/- 1 degrees C or buffered incubation medium (BIM) at 37 +/- 1 degrees C for 24 h. Mean values of DC in polished and unpolished samples were 63.6% (+/- 3.2%) and 54.7% (+/- 5.2%), respectively (p lt 0.0001). There was no significant difference in DC after sample-sectioning (p > 0.05). Significantly higher DC values were obtained after storing samples in BIM (76.8% +/- 2.1%) than in distilled water (59.7% +/- 5.7%), extreme humidity (60.3% +/- 3.9%) or in room conditions (63.6% +/- 3.2%) (P lt 0.001). DC of an RBC measured by micro-Raman spectroscopy may be affected by differences in sample preparation and storing conditions, making it difficult to extrapolate data from in vitro studies into clinically relevant information

Optimizing the concentration of 2,4,6-trimethylbenzoyldiphenylphosphine oxide initiator in composite resins in relation to monomer conversion

The aim of this study was to optimize the concentration of 2,4,6-trimethylbenzoyldiphenylphosphine oxide (Lucirin (R) TPO) in unfilled and filled composite resins in relation to the degree of conversion (DC). Increasing concentrations of Lucirin (R) TPO between 0.05-4.97 wt% were added to equimolar mixtures of Bis-GMA/TEGDMA. Filled resins contained 75 wt% fillers. Standardized samples were cured using a polywave LED light-curing unit (bluephase (R) G2, Ivoclar Vivadent). Increased initiator concentrations increased logarithmically the DC of unfilled and filled resins. The DC of unfilled resins was in the range of 73-91% at the top and 63-81% at the bottom surfaces and that of filled resins was in the range of 53-81% at the top and 47-70% at the bottom surfaces. The DC in unfilled and filled resins reached a plateau at 1.08 wt% and 1.50 wt% Lucirin (R) TPO, respectively. Fillers significantly reduced conversion but had no effect on the logarithmic relationship between initiator concentration and the DC

Quantitative micro-Raman assessment of dentine demineralization, adhesive penetration, and degree of conversion of three dentine bonding systems

Unreacted monomers in adhesive systems may cause a reduction in material properties, an increase in the long-term instability of the restoration, and pulpal irritation. The degree of dentine demineralization, adhesive penetration, and the degree of conversion (DC) across the dentine-adhesive interface of self-etch adhesives were measured using micro-Raman spectroscopy. Two-step, self-etch AdheSE, one-step self-etch AdheSE One, and etch-and-rinse Excite (control) (Ivoclar Vivadent AG, Schaan, Liechtenstein) were studied. Nine human molars were allocated to three groups and a flat dentine surface was prepared. A smear layer was produced by grinding dentine with 600-grit silicone-carbide discs under water. After application and polymerization of the adhesive, teeth were sectioned to produce four 1-mm-thick slices per tooth for micro-Raman spectroscopy. There were statistically significant differences in the depth of dentine demineralization between all adhesives. The depth and degree of demineralization decreased in the order: Excite > AdheSE > AdheSE One. The mean +/- standard deviation (SD) values for DC within the adhesive layer were 85.2 +/- 2.9% (Excite), 81.4 +/- 4.2% (AdheSE), and 54.3 +/- 10.1% (AdheSE One), and within the hybrid layer were 55.2 +/- 22.5% (Excite), 65.1 +/- 16.9% (AdheSE), and 42.0 +/- 16.2% (AdheSE One). All systems showed a discrepancy between dentine demineralization and adhesive penetration. A significant amount of unreacted monomers were associated with all systems but particularly with the etch-and-rinse system