Stefan Dačić

Ultrastructure of adhesive bond of composite to dentin

SUMMARY Ultrastructure of adhesive bond is a significant indicator of the efficiency of the bond between material and dental tissue. Bonding between composite and hard dental tissue is also most commonly assessed by measuring bonding strength or by absence of marginal gap along restoration interface. The aim of this investigation was to estimate ultrastructural features of the bond between composite materials and dentin after using two adhesive techniques. Twenty Class V cavities on extracted teeth were prepared and restored for scanning electron microscope (SEM) analysis of composite bonding to dentin. Adhesion was achieved by Adper Single Bond 2-ASB/3M ESPE or by Adper Easy One-AEO/3M ESPE. Photopolymerization of adhesives and composite material Filtek Ultimate FU/3M ESPE was performed using halogen light (Elipar Highlight 3M ESPE). After vertical sections through crown of teeth and composite restorations, surfaces of sections were treated with 37% phosphoric acid-60s and 2% NaOH-60s to remove the smear layer and obtain a better view of adhesive bond. SEM analysis of adhesive bond showed better micromorphological bonding of composite to dentin after etch and rinse adhesive technique (ASB/FU matherials) than after self-etch technique (AEO/FU materials). In etch and rinse technique, the ultrastructure of adhesive bond to dentin was composed of adhesive and hybrid layers, with resin processes in dentinal canals. In self-etch technique, apart from adhesive and hybrid layers, resin processes were rare or were not observed at all. Better ultastructural bonding of composite restoration to dentin was obtained with etch and rinse adhesive technique. Sažetak Ultrastruktura adhezivne veze je značajan pokazatelj efikasnosti pripoja materijala za zubna tkiva. Kvalitet veze kompozita za tvrda zubna tkiva takođe se procenjuje jačinom vezivanja ili odsustvom marginalne pukotine po obodu restauracija. Cilj ovog rada bio je da se proceni ultrastruktura veze kompozitnih materijala za dentin nakon primene dve adhezivne tehnike. Na ekstrahovanim zubima restaurisano je 20 kaviteta V klase za skenirajuću elektronsku mikroskopsku (SEM) analizu pripoja kompozita za dentin. Adhezija je obezbeđivana primenom Adper Single Bond2- ASB/3M ESPE, odnosno primenom Adper Easy One-AEO/3M ESPE. Svetlosna polimerizacija adheziva i kompozitnog materijala Filtek Ultimate-FU-/3M ESPE vršena je halogenim svetlom (Elipar Highlight 3M ESPE). Nakon vertikalnog presecanja krunica zuba kroz kompozitne restauracije i pripreme površine preseka (30% fosforna kiselina-30s i 2% NaOH-30s), vršena je SEM analiza adhezivne veze. Bolje mikromorfološko vezivanje kompozita za dentin SEM analiza adhezivne veze pokazala je kod adhezivne tehnike sa nagrizanjem i ispiranjem zubnih tkiva (ASB/FU materijali), u odnosu na tehniku samonagrizanja tkiva (AEO/FU materijali). Kod tehnike nagrizanja i ispiranja, ultrastruktura adhezivne veze za dentin sastojala se od hibridnog i adhezivnog sloja, kao i produžetaka smole u dentinskim kanalićima. Kod samonagrizajuće tehnike, pored adhezivnog i hibridnog sloja, retko su viđani ili uopšte nisu postojali produžeci smole u kanalićima. Bolju ultrastrukturu veze kompozita za dentin obezbedila je primena adhezivne tehnike sa nagrizanjem i ispiranjem tkiva.

The Influence of Different Light Curing Modes on the Depth of Cure of the Composite Resin

Summary The aim of this study was to investigate the influence of different light curing modes on the depth of cure of the composite resin. The metal block with formed round holes served as a mold for the placement of the composite resin. The composite resin was cured with Penguin DB-685 lamp with four optional working modes: strong, low, gradually strong, and flashing. Unpolymerized part of the composite specimen was removed by scraping with a plastic spatula, and then each specimen was placed into the capsule with 1 ml of ethanol alcohol and mixed for 20 s in amalgamator. The length of the remaining composite specimen was measured with the digital caliper with a precision of 0.01 mm. The measured values were divided by 2 (according to ISO 4049 standard) and then statistically processed. Based on the measured lengths of the polymerized part of the composite specimens, the lowest average value of the depth of cure (2.75 ± 0.08 mm) was determined after polymerization with the low mode and the highest value was obtained (2.98 ± 0.08 mm) with strong polymerization mode. Statistically significant difference (p < 0.05) was determined between low polymerization mode and all other modes (strong, gradually strong and flashing mode). The observed statistically significant differences are not clinically important because all curing modes provided the necessary depth of cure, which is in accordance with the clinical recommendation of 2 mm thick composite layer.

Marginal adaptation of composite resins under two adhesive techniques.

In the present research, different adhesive techniques were used to set up fillings with composite resins. After the application of etch and rinse or self etch adhesive technique, marginal adaptation of composite fillings was estimated by the length of margins without gaps, and by the microretention of resin in enamel and dentin. The study material consisted of 40 extracted teeth. Twenty Class V cavities were treated with 35% phosphorous acid and restored after rinsing by Adper Single Bond 2 and Filtek Ultimate‐ASB/FU 3M ESPE composite system. The remaining 20 cavities were restored by Adper Easy One‐AEO/FU 3M ESPE composite system. Marginal adaptation of composite fillings was examined using a scanning electron microscope (SEM). The etch and rinse adhesive technique showed a significantly higher percentage of margin length without gaps (in enamel: 92.5%, in dentin: 57.3%), compared with the self‐etch technique with lower percentage of margin length without gaps, in enamel 70.4% (p < .001), and in dentin‐22.6% (p < .05). In the first technique, microretention was composed of adhesive and hybrid layers as well as resin tugs in interprismatic spaces of enamel, while the dentin microretention was composed of adhesive and hybrid layers with resin tugs in dentin canals. In the second technique, resin tugs were rarely seen and a microgap was dominant along the border of restoration margins. The SEM analysis showed a better marginal adaptation of composite resin to enamel and dentin with better microretention when the etch and rinse adhesive procedure was applied.

The Effect of Polymerization Technique on Marginal Index of Composite Fillings in Dentin

Summary Polymerization contraction of composite resins has been one of the most extensively studied phenomena in dentistry in recent years. Initial polymerization by low intensity light followed by polymerization high intensity light improves marginal adaptation of composite in tooth cavities. A number of studies have verified that less marginal leakage and lower marginal index (MI) exist in relation to standard polymerization (continuous high intensity light). The aim of the study was to quantittively evaluate the bond of composite materials to dentin and determine the MI values in dentin after the application of two techniques of light polymerization in two composite systems. Twenty V class cavities were restored on extracted teeth for scanning electron microscopic (SEM) analysis of composite to dentin junction. Adhesion to dentin was achieved using Adper Single Bond 2-ASB/3MESPE, that is, Adper Easy One-AEO/3MESPE. Light polymerization of composite materials Filtek Ultimate-FU/3MESPE was performed using standard halogen light (HIP) or soft start program (SOF). Marginal index of dentin was determined by measuring the length and width of marginal gap at the junction of composite filling to dentin, using scanning mirographies and Autodesk AutoCAD program. Two-way ANOVA test was used for statistical processing of the obtained results. Differences in MI index between different light polymerization techniques (HIP- 8,18 and SOF-7,12) were not statistically significant (p>0,05), while the differences between composite systems (ASB/FU- 3,67 i AEO/FU- 7,69) were statistically significant (p <0.05). The polymerization technique showed no significant effect on the composite to dentin junction. Lower MI dentin was established in composite system with the application of adhesive etch and rinse procedure in both polymerization techniques.

Morphometric Analysis of the Upper Premolars

Summary Morphological and anatomical characteristics of the tooth are of great importance for clinical dentistry. These aspects of the tooth can be better conceptualized from the perspective of external and internal morphology of dental crowns and roots. The aim of this study was to determine the average total length of the upper first and second premolars, the average length of crowns, the average length of roots and to determine the most common number of the roots and root canals of these teeth. We used 41 first and 48 second extracted upper premolars.The length of these teeth was measured by a digital micrometer. The number of roots was determined visually, and each tooth was longitudinally dissected across the vestibular-palatal plane for determining the number of root canals. The average total length of the upper first premolars was 22.5 mm, the average crown length was 8.8 mm, the mean root length was 13.7 mm. The upper first premolars usually have two roots in 53.7% and two root canals in 82.9%. The average total length of the upper second premolars was 22.5 mm. The average crown length was 8.4 mm and the mean root length was 14.1 mm. The upper second premolars usually have one root in 89.6% and one root canal in 79.2%. The determined average values of the length of these teeth and the length of their crowns and roots were similar to the values of the same population reported by other authors.

Morphological Variations of the Cemento-Enamel Junction in Permanent Dentition / Morfološke varijacije cementno gleđnog spoja kod zuba stalne denticije

Abstract Cemento-enamel junction (CEJ) is an important anatomical structure of the tooth, which is located in the cervical part of the tooth between the crown and root, or at the contact point between the enamel which overlaps the tooth crown and cementum overlapping the root dentin. There are four possible relationships between two tissues that make the CEJ such as: the cement overlaps the enamel; the enamel overlaps the cement; the enamel and cement abut each other with no overlap; the enamel and cement are not in contact. The aim of this study was to determine the relationship between the enamel and cement which make the CEJ in different types of permanent teeth. The material consisted of 30 permanent teeth with intact CEJ. Staining of CEJ was carried out using the methylene blue. After staining, the tooth was washed under the running water and drying at room temperature. Each tooth was longitudinally cut in the vestibular-oral direction. Observation of CEJ was done with Leica light microscope and images were obtained using a Nikon camera. The results indicated that the most common form of CEJ between the cement and enamel in the region of CEJ was that cement and enamel abutted without overlap (36.7%), followed by the cement overlapping the enamel (33.3%), and the cases when a gap between the cement and enamel (16.7%) was present, and when the enamel overlaped the cement (13.3%). Because of the morphological diversity of CEJ, careful performing of dental interventions in the region of tooth neck is necessary because they may change the morphology of this region, induce the pathological processes and hypersensitivity of teeth. Sažetak Cementno gleđni spoj (cemento-enamel junction - CEJ) predstavlja važnu anatomsku strukturu koja se nalazi u vratnom delu zuba na mestu dodira gleđi koja prekriva dentin krunice i cementa koji prekriva dentin korena zuba. Četiri moguće veze izmeđi dva mineralizova tkiva koja čine CEJ opisuju se na sledeći način: cement prekriva gleđ, gleđ prekriva cement, gleđ i cement se dodiruju linijski i gleđ i cement se ne dodiruju. Cilj ovog istraživanja bio je da se utvrdi međuodnos gleđi i cementa u nivou CEJ kod različitih vrsta stalnih zuba. Materijal je činilo 30 stalnih zuba sa očuvanim CEJ. Za bojenje tkiva u nivou CEJ korišćena je metilen plava. Nakon bojenja, vršeno je ispiranje zuba pod mlazom vode i sušenje na sobnoj temperaturi. Svaki zub je uzdužno presecan u vestibularno-oralnom pravcu. Posmatranje CEJ je sprovedeno svetlosnim mikroskopom Leica na uvećanju x10, a fotografisanje korišćenjem Nikon kamere. Rezultati ove studije su pokazali da je najzastupljeniji odnos tkiva u nivou CEJ dodir gleđi i cementa u 36,7% slučajeva. Cement je prekrivao gleđ u 33,3%; gleđ i cement se nisu dodirivali u 16,7% i gleđ je prekrivala cement u 13,3% slučaja. Zbog morfološke raznolikosti CEJ neophodno je pažljivo izvođenje različitih stomatoloških intervencija u vratnom regionu zuba, jer u suprotnom može doći do promene njene morfologije, pojave patoloških procesa i pojačane osetljivosti zuba.