Collagen degradation in endodontically treated teeth after clinical function.

Endodontically treated teeth restored with posts are susceptible to coronal leakage after long-term function. We hypothesize that demineralized collagen matrices (DCMs) created in dentin by acidic zinc phosphate cement within the dowel spaces degrade with time. Forty-two post-restored teeth were extracted after three periods of clinical service and were examined, by means of scanning and transmission electron microscopy, for the status of the DCMs. SEM revealed a progressive degradation of the DCMs, becoming less dense after 3 to 5 years, losing structural integrity after 6 to 9 years, and partially disappearing after 10 to 12 years. TEM revealed evidence of collagenolytic activity within the DCMs, with loss of cross-banding and unraveling into microfibrils, and gelatinolytic activity that resulted in disintegration of the microfibrils. Bacterial colonization and the release of bacterial enzymes and of host-derived matrix metalloproteinases may contribute to the degradation of collagen fibrils in root dentin after clinical function.

Bonding of all-porcelain crowns: structural characteristics of the substrate.

OBJECTIVES: The aim of this in vitro study was to evaluate the morphology of dentin in teeth prepared for single-unit all-porcelain crowns (SUAPC) in terms of tubule orientation, density and increase in surface area after etching. METHODS: Twenty anterior and 20 posterior teeth from adults were prepared 1mm below the cemento-enamel junction (CEJ) for SUAPC. The samples were divided into groups based on type of tooth (anterior or posterior) and bonding system employed. The teeth were processed for evaluation of morphology of the substrate, hybrid layer thickness and resin tag formation. The observations were subdivided according to location in the preparation and tubule density was calculated. RESULTS: The observations revealed the variability in tubule density and orientation in different areas within any one preparation. The morphology of the cervical margin was less predictable with the presence of cementum and an ill-defined cemento-dentinal junction. Statistically significant differences in the density of tubules were found depending on location. Groups 2, 3, 5 and 6 samples showed that the hybrid layer thickness and resin tag morphology depended on the density and direction of tubules. In those sectors with parallel and oblique tubule orientation and with a low density of tubules, the hybrid layer was significantly thinner than in areas with cross-sectioned tubules. SIGNIFICANCE: The cementum and the peripheral intertubular dentin surface area are likely to be responsible for the bond strength after acid etching of crown preparations, but not all areas exhibited equal responses to etching. In particular, the bonding substrate at the gingival margins may contribute little in terms of micromechanical retention.

Retrospective study of the clinical performance of fiber posts.

PURPOSE: To evaluate the clinical performance of C-Posts, AEstheti Posts and AEstheti Plus Posts after a period of clinical service ranging from 1-6 yrs. MATERIALS AND METHODS: 1,304 posts were included in the study: 840 Composiposts, 215 AEstheti posts and 249 AEstheti Plus posts were placed into endodontically treated teeth. Four combinations of bonding/luting materials were used. The patients were recalled every 6 months and clinical and radiographic examinations were completed. Endodontic and prosthodontic results were recorded. Actuarial Life Table statistical analysis and Mantel-Haenszel comparison of survival curve have been performed at 95% level of confidence. RESULTS: The 3.2% failure rate was due to two reasons: 25 posts debonded during removal of temporary restorations, and 16 teeth showed periapical lesions at the radiographic examination. No statistical significant differences were found among the four groups. The results of this retrospective study indicate that fiber posts in combination with bonding/luting materials can be routinely used.

Role of hybridization on marginal leakage and bond strength.

PURPOSE: To evaluate whether the hybrid layer significantly contributes to the seal of adhesive Class V restorations placed in vivo and to the bond strength obtained in vitro. MATERIALS AND METHODS: 20 periodontally severely compromised anterior teeth were selected for the leakage study. In each tooth, one round 3 mm wide V-shaped cavity with a maximum depth of 2 mm was prepared on the labial surface crossing the cementum-enamel junction. The sample teeth were randomly divided into two groups of ten samples each: in Group 1, Scotchbond Multi-Purpose Plus was applied in combination with Z-100 following the manufacturer's instructions. In Group 2 the bonding procedure was the same as in Group 1, except that after the phosphoric acid treatment, the cavities were treated with 5% NaOCl for 2 min. Following a period of clinical service of 60-90 days, the teeth were extracted and processed for the leakage test. RESULTS: At the enamel site, 30% of the samples of Group 1 and 70% of the samples of Group 2 showed dye penetration. At the dentin site, 50% of the samples of Group 1 showed leakage, while all the samples of Group 2 were severely infiltrated. Statistically significant differences between the groups both for the enamel sites (P < 0.05) and for dentin-cementum sites (P < 0.001) were found. Bond strength tests were performed on 2 mm thick dentin slides of tapered Class I cavities (n = 10 in each group). The mean bond strength value obtained from cavities treated without NaOCl was 15.23 (+/-1.40) MPa and with NaOCl treatment 20.52 (+/-1.70) MPa. Statistical analysis showed significant differences (P < 0.05) between the two groups. No hybrid layer was detected on the NaOCl-treated samples by scanning electron microscopy.

Influence of tissue characteristics at margins on leakage of Class II indirect porcelain restorations.

PURPOSE: To evaluate the sealing ability of Class II porcelain inlays with margins placed in cementum-dentin and enamel, luted by two new different cementing materials. MATERIALS AND METHODS: Thirty extracted molars, free from caries and restorations, were selected. The sample cavities were prepared in a standardized manner and then were divided in three groups (n = 10) at random. Group 1: The cervical margin was located 1 mm below the CEJ and the inlays were luted with EBS Multi (Espe) bonding system in combination with Compolute 1.0 Aplicap (CLA 1.0, Espe) experimental resin cement. Group 2: The cervical margin was placed 1 mm below the CEJ and Syntac bonding system (Vivadent) and Variolink II resin cement (Vivadent) were used. Group 3: The cervical margin was placed 0.5 mm above the CEJ and the same materials selected for Group 1 were used. IPS-Empress (Ivoclar) inlays were made following manufacturer's instructions. After luting procedures and 2500 thermal cycles (5 degrees and 55 degrees C), the samples were processed and evaluated for marginal leakage at cervical and occlusal site. Samples of Group 3 were first sectioned in the center of the restorations as in Group 1 and 2 and scored (Group 3A) and then two other cuts were made along the buccal and lingual areas (Group 3B) and also scored. After scoring dye penetration of Group 1 and 2 samples, half of the sections were randomly selected to evaluate: (1) resin cement thickness, (2) Hybrid layer formation at the interface between adhesive material and dental substrate and (3) to observe the morphology of the Class II cavity margins. The leakage data were statistically evaluated with the Mann-Whitney U test (P < 0.5). RESULTS: Statistically significant differences were found between Groups 3A and 3B at the occlusal site, and not at the cervical site. Samples of Group 1 showed a cement thickness of 92 microns, and 68 microns in Group 2. Hybrid layer and resin tag formation was evident in Group 1. In Group 2 samples, the hybrid layer formation was less evident and thinner than in Group 1. At cervical margins, an outer layer, not identifiable as sound dentin, of 200-300 microns thick, was noted. This layer was present in all three groups between outer margin and sound dentin. The margins located both cervically and axially in enamel mainly showed prisms cut along their long axis and a low level of structured etch pattern.

In vitro leakage of resin-bonded all-porcelain crowns.

PURPOSE: The purpose of this study was to evaluate the sealing ability of single-unit all-porcelain crowns with margins placed in cementum-dentin and luted with two different cementing materials. MATERIALS AND METHODS: Twenty extracted molars, free of caries and restorations, were selected. The sample abutments were prepared in a standardized manner and then divided in two groups (n = 10) at random. Group 1: The cervical margin was located 1 mm below the CEJ and the crowns were luted with EBS Multi (Espe) bonding system in combination with Compolute 1.0 Aplicap (CLA 1.0, Espe) experimental resin cement. Group 2: The cervical margin was placed 1 mm below the CEJ, and Syntac bonding system (Vivadent) and Variolink II resin cement (Vivadent) were used. IPS-Empress (Ivoclar) crowns were made following manufacturer's instructions. After luting procedures and 2,500 thermal cycles (5 degrees and 55 degrees C), the samples were processed and evaluated for marginal leakage at the cervical site. After scoring dye penetration in group 1 and 2 samples, half of the sections were randomly selected in order to evaluate 1) resin cement thickness and 2) hybrid layer formation at the interface between adhesive material and dental substrate. The leakage data were statistically evaluated with the Kruskal-Wallis non-parametric analysis of variance (ANOVA) by ranks with Bonferroni alpha adjustment (p < 0.05). RESULTS: Sixty percent of the group 1 samples and 80% of group 2 showed leakage. In group 1, the dye penetration was often limited to the cervical margin site, while in group 2, it mainly extended to the axial walls. Statistically significant differences between samples of the two groups were not found. Samples of group 1 showed a cement thickness of 82 microns, while 75 microns was found in group 2. A hybrid layer and resin tag formation were evident in group 1. In group 2 samples, the hybrid layer formation was less evident and thinner than in group 1. CONCLUSIONS: The two adhesive systems performed similarly. The cervical margins of single-unit all-porcelain crowns must be considered as one of the weakest areas of this type of esthetic restoration.

The resin-bonded cast post core: technical preparation and cementation protocols.

Post and core restorations have been widely utilized in the reconstruction of endodontically treated teeth. This study compares the traditional cast post core with the bonded type, and reviews the restoration of devitalized teeth without imposing frictional forces within the root canal walls. Clinical and laboratory aspects are discussed, with emphasis on the cementing procedure. Several resin cements are evaluated and compared to traditional zinc oxide phosphate cement techniques; microleakage test results are presented. The learning objective of this article is to outline the clinical indications, advantages, disadvantages, and the clinical techniques employed for resin-bonded cast post core restoration. A case of an endodontically treated maxillary left central incisor following a direct trauma is used to illustrate the procedure of resin-bonded post core placement. Biocompatibility of the cast post core is confirmed by a radiograph 2 years postoperatively.

Shear bond strength of four dentinal adhesives applied in vivo and in vitro.

OBJECTIVES: The purpose of this study was to determine whether dentine bonding performed under clinical conditions is as reliable as laboratory bonding. METHODS: Freshly cut dentine was used in vivo or in vitro as a substrate for the bonding of various adhesive systems. Bond strength was measured in shear loading. RESULTS: Clearfil Liner Bond, Optibond and All Bond 2 showed better results when applied in vivo than in vitro. Scotchbond Multipurpose showed the opposite effect but the bond strength was, for both conditions, superior to the other three products. Only All Bond 2 presented statistically significant differences in bond strength between in vivo and in vitro applied bonding. CONCLUSIONS: The results indicate that, with the new hydrophilic dentine bonding systems, in vitro application does not lead to substantially different results when compared with, in vivo application.

Micromorphologic relationship between resin and dentin in Class II restorations: an in vivo and in vitro investigation by scanning electron microscopy.

The wetting property of dentinal bonding systems may play an important role in the mechanism of adhesion to dentin. Some studies have observed that tags penetrate 100 microns or more in nonvital teeth and less than 10 microns in vital teeth. This investigation was designed to evaluate the micromorphologic relationship between in vivo and in vitro dentin after application of two new dentinal bonding systems in Class II restorations. Class II cavities were restored in vitro and in vivo with Gluma 2000 adhesive and Pekafill hybrid resin or Scotchbond Multi-purpose adhesive and Z100 composite resin. After dissolution of dental structures, the restorations were observed with a scanning electron microscope. No morphologic differences were found between in vivo and in vitro specimens with either of the new dentinal adhesive systems tested. Short resin tags were often found in vivo, particularly at the cavity walls. Only a few areas in vivo had deep resin tags (longer than 100 microns) and these were always at the cavity floor.

[New research on endodontic carbon-fiber posts]. / Nuove ricerche sui perni endocanalari in fibra di carbonio.

The authors present their clinical experience with fibre-carbon posts, which has been carried on for more than 4 years, supporting it with studies made in European and U.S.A. Universities, specially regarding the mechanical resistance and retention of those posts. Tests show luting procedures as the critical and improvable point. No real retention increase results using Sealbond and Flexi-Flow composite cements; failure always occurs at cement-post junction. Using a special fibre-carbon post, named Composipost Retentive, which presents circumferential grooves, very superior retention is obtained. Using 5 types of composite cement (Sticky Post, Flexi-Flow, Sealbond, Super Bond and All Bond II), we reach a very high retention. Super Bond and All Bond II specially show a tensile strength over 120 kg measured with Instrom machine. Those two composite cements massively penetrate in dentinal tubules, giving best results in cement-root channel interface.

In vivo evaluation of glass-ionomer cement adhesion to dentin.

Class V cavities were prepared in 20 vital teeth and 10 extracted teeth. For all the restorations, glass-ionomer cement was used as a liner at the base of the cavity. The cavity was then restored with a microfilled composite resin. After the extraction of the vital teeth, all specimens were sectioned and tested for marginal microinfiltration of 2% methylene blue dye. The teeth restored in vivo showed no signs of infiltration between the dentin and the glass-ionomer liner. The dye penetrated between the liner and the composite resin in five in vivo restorations. The in vitro restorations dye was present between the dentin and the liner. Examination of replicas under the scanning electron microscope revealed no gaps between the glass-ionomer cement and the dentin in the in vivo specimens, while gaps of various sizes were present in the in vitro replicas. Glass-ionomer cement was able to bond to dentin when used as a liner in vital teeth but not when used in extracted teeth. This can be attributed to the presence of a partially humid environment in vivo that favors the application process. In vitro, specimens are to a large extent dehydrated.

Marginal adaptation of crowns: a scanning electron microscopic investigation.

Most studies on marginal adaptation have been performed in vitro; only a few studies have investigated in vivo marginal adaptation and microleakage of crowns. In this study, gold crowns were prepared and cemented on abutments, and their marginal discrepancies were analyzed by scanning electron microscopy according to the impression-replica and cross-section methods. Three observers measured the marginal discrepancies of each crown. Interobserver variance of accuracy was 10 microns by the impression-replica and 15 microns by the cross-section method. The mean values were 124.16 microns by the impression-replica and 129.79 microns by the cross-section method. The two methods tested showed similar results.

Morphologic aspects of the resin-dentin interdiffusion zone with five different dentin adhesive systems tested in vivo.

The new generation of enamel dentin adhesive materials provides removal of the smear layer, inducing structural changes in the dentinal surface and creating a retentive interdiffusion zone or hybrid layer between the two substrates. Some studies have demonstrated hybrid layer formation in in vitro samples, but few articles have described it in in vivo specimens. The hybrid layer forms in peritubular and intertubular treated dentin and improves adhesion between tooth surface and adhesive resins. This in vivo study investigated the formation of a hybrid layer by use of five different enamel dentin adhesive systems. The dentin adhesives systems were tested on flat dentin preparations made on vestibular surfaces of periodontally compromised teeth. The sample teeth were extracted immediately after the resin was cured. Half of the samples were used to visualize the hybrid layer and the other half to observe the morphology of the resin tags by use of scanning electron microscopy. All the tested products formed a hybrid layer. In many areas of samples of Gluma 2000, Scotchbond Multipurpose, All Bond 2, and Super Bond D Liner systems, characteristic reverse cone-shaped tags were visible. Resin tags produced by Clearfil Liner Bond adhesive were narrower at the apertures of tubules than those of the other four adhesive materials. Morphology of the hybrid layer and of the resin tags of these samples were similar to in vitro samples observed in other studies.

Adaptability and microleakage of indirect resin inlays: an in vivo investigation.

The purpose of this in vivo study was to evaluate the microleakage of indirect composite resin inlays and to determine the thickness of composite resin luting material. Twenty periodontally involved posterior teeth scheduled for extraction were selected and Class II cavities were prepared. Ten cavities had gingival margins placed in enamel above the cementoenamel junction, and the other 10 were placed in dentin below the cementoenamel junction. Six months after cementation, the teeth were extracted and analyzed. The leakage was higher in inlays with gingival margins in dentin than in inlays with gingival margins in enamel. The cement thickness was between 15 and 40 microm, a clinically acceptable range.

Electron spin resonance studies of dental composites: effects of irradiation time, decay over time, pulverization, and temperature variations.

Polymerization induced by UV-VIS light of composite dental materials produces a solid matrix within which terminal radicals of non-polymerized monomers remain trapped. Electron Spin Resonance (ESR) allowed three different types of radicals to be identified. The analysis of ten normally available commercial products gave information on: (1) the propagation of the conversion reaction as a result of exposure to light; (2) the time necessary for the decay of each type of radical; and (3) the variations with temperature and the effects of shattering on the materials under study. The presence of inorganic filling material slowed the process of polymerization, while it accelerated the decay of radicals. It was suggested that the nature of these processes depended on the composition of the base resin materials, whereas it did not depend on the sizes of the filler particles. Moreover, the complete propagation of the conversion reaction needed a period of light exposure greater than that currently suggested by the manufacturers. The structural stability and the resistance of the composites were confirmed by both the long period of decay and the high temperatures needed to overcome the potential barrier for starting the radical decay process. Finally, the composite shattering investigation indicated that particles removed by surface abrasion experience rapid radical decay, thus reducing the possibility of harmful effects on internal organs.

Cement thickness and microleakage under metal-ceramic restorations with a facial butted margin: an in vivo investigation.

Ten metal-ceramic restorations with buccal porcelain butt margins and palatal metal beveled margins were fabricated for periodontally hopeless teeth. After cementation, the experimental crowns remained in the oral environment for 3 to 6 months; the teeth were then extracted and used for microscopic and microleakage evaluation. All ten crowns showed at least a small amount of microleakage, but adaptation of beveled margins proved to be superior to that of shoulder porcelain margins.

A new dentinal bonding agent and microfilled resin system: a 2-year clinical report.

The purpose of this investigation was to study the clinical results obtained with the Gluma dentinal bonding system and Pekalux microfilled composite resin. Sixty esthetic restorations were placed by three different operators. Two years of clinical observation revealed good results. Alpha scores were given to 50 restorations for marginal integrity, 52 for color stability, and 54 for anatomic form. Bravo scores were given to eight restorations for marginal integrity, six for color stability, and four for anatomic form. Only two restorations had to be replaced.