Laboratory assessment of the retentive potential of adhesive posts: a review.

OBJECTIVES: This review aimed at summarizing the laboratory evidence collected on the retentive ability of adhesive posts since their introduction in dentistry. DATA: Data were searched in articles published or in press in peer-review journals listed in MEDLINE. SOURCES: Papers were retrieved through PubMed. STUDY SELECTION: To collect the evidence of interest, the following search terms were used: bond* AND fiber post AND in vitro; lut* AND fiber post AND in vitro; push-out AND fiber post; pull-out AND fiber post; microtensile AND fiber post. "Related Links" were also considered and articles cited in the initially retrieved papers were included if relevant. No time limit was given to the query. CONCLUSIONS: Seventy relevant papers were reviewed. The retentive ability of adhesive posts has been tested with the microtensile technique, post-pull-out and push-out tests. If small-sized specimens are obtained, such as in microtensile and thin-slice push-out, stress uniformity is favoured, local differences in bonding conditions can be discerned, and the number of teeth needed for the test can be reduced. Although adhesion to intraradicular dentin is more challenging to achieve than bonding to crown tissues, the post-retention achieved with current luting systems and techniques is adequate to ensure the clinical success of adhesive post-retained restorations. To enhance the bond at the post-core and post-cement interfaces, several chemical pre-treatments of the post-surface have been tested with positive results. Self-adhesive resin cements, recently proposed to simplify the post-luting procedure, should be investigated further with regard to durability.

A clinical trial of Empress II porcelain inlays luted to vital teeth with a dual-curing adhesive system and a self-curing resin cement.

PURPOSE: The aim of the study was to clinically evaluate Empress II inlays cemented with a dual-curing bonding agent and a self-curing luting system. MATERIALS AND METHODS: Forty patients were selected to receive one Empress II inlay. Empress II is a heat-pressed glass ceramic containing lithium disilicate and lithium orthophosphate crystals, purported to provide higher stress resistance and improved strength. The restorations were placed between March and May 2000. Recalls were performed after 6, 12, 24, and 36 months. At the 3-year recall, 7 patients were lost to follow-up. Inlays were evaluated for postoperative sensitivity, marginal integrity, marginal leakage, color stability, surface staining, retention, and surface crazing (microcracks). RESULTS: At the 3-year recall, all the restorations were in place and only one showed postoperative sensitivity (at the first recall, 1 week after placement). Only 3 inlays showed slight marginal staining, and 4 inlays showed gaps, with little surface staining or microcracks. CONCLUSIONS: No inlay debonded or fractured during theobservation period. All the evaluated inlays were in place and acceptable.

In vitro evaluation of wall-to-wall adaptation of a self-adhesive resin cement used for luting gold and ceramic inlays.

PURPOSE: This in vitro study evaluated the wall-to-wall adaptation of a new self-adhesive resin-based cement (RelyX Unicem) in comparison with that of other cements when luting gold and porcelain inlays in standardized Class II cavities in extracted teeth. MATERIALS AND METHODS: In each experimental group (n = 10), a different combination of inlay and luting material was tested. Group 1: Porcelain Empress II (Ell) and RelyX Unicem (U); group 2: Ell and resin-based cement Variolink II in combination with primer and bonding Excite DSC; group 3: gold inlays (G) and U; group 4: G and Harvard zinc-oxy-phosphate cement; group 4: G and glass-ionomer cement Fuji Cem. After storage and thermocycling, microleakage testing was carried out and dye penetration was examined at the occlusal and cervical margins of each inlay. The differences in microleakage score were tested for statistical significance first comparing all groups, then pooling the groups for inlay material (Kruskal-Wallis nonparametric ANOVA and Mann-Whitney U test, p < 0.05). SEM observations of the tooth/cement/restoration interfaces were also made in each group. RESULTS: Harvard cement had the highest microleakage. The sealing ability exhibited by RelyX Unicem was satisfactory with both gold and porcelain inlays, and comparable to that of Fuji Cem and Variolink II. CONCLUSION: RelyX Unicem achieved an adequate seal on both enamel and dentin when used to lute in vitro gold and porcelain inlays.

The adhesion between prefabricated FRC posts and composite resin cores: microtensile bond strength with and without post-silanization.

OBJECTIVES: Aim of the study was to measure the adhesion between two types of translucent prefabricated FRC posts (FRC Postec, Ivoclar-Vivadent, FRC; Light-Post, RTD, LP), and two types of flowable composites used as core materials (UnifilFlow, GC, UF; Tetric Flow, Ivoclar-Vivadent, TF), with or without the application of a silane (Monobond-S, Ivoclar-Vivadent, S) on the post surface. METHODS: The experimental groups were: 1.1 FRC+UF; 1.2 FRC+S+UF; 1.3 FRC+TF; 1.4 FRC+S+TF: 2.1 LP+UF; 2.2 LP+S+UF; 2.3 LP+TF; 1.4 LP+S+TF. The bond strength at the interface between post and core was measured with the microtensile non-trimming technique. Thirty to thirty-five beam-shaped specimens per group were obtained from cylinders of core material, which had been built up around the post by progressively adding small increments of composite resin. Each specimen was loaded in tension until failure at either one of the two post-core interfaces present in each stick. The differences in interfacial bond strength among the groups were tested for statistical significance with the two-way ANOVA. RESULTS: The measured bond strengths in MPa were: [table: see text]. The statistical analysis revealed that post-silanization had a significant effect on adhesion (p<0.05). With any combination of post and core materials tested, the application of a silane onto the post surface prior to building up the core significantly increased the post-core bond strength. SIGNIFICANCE: For improved adhesion at the interface between prefabricated FRC posts and composite resin cores, post-silanization is advisable.

Density of dentinal tubules affects the tensile strength of root dentin.

OBJECTIVES: The aim of this study is to count the dentinal tubules in the coronal and middle-apical third of root dentin of teeth extracted due to the progression of periodontal disease, and to compare the Ultimate Tensile Strength (UTS) of the same areas. The research hypothesis was that root dentin areas with different densities of dentinal tubules would also show different UTS values. METHODS: From 10 caries free maxillary central, lateral incisors and canines, extracted for periodontal reasons from three patients, cylindrical specimens approximately 10 mm long were prepared parallel to the long axis of the root and then divided into two parts using a low speed diamond saw one from the coronal third of the root, (Group 1) and one from the middle-apical third of the root (Group 2). The density of the dentinal tubules of the specimens of the two groups was measured by means of a scanning electron microscope and the UTS of the specimens was measured by a microtensile test. One way ANOVA was used to assess the effect of specimen location (coronal specimens vs. middle-apical specimens) on UTS. The differences in the density of dentinal tubules between coronal and middle-apical specimens were also subjected to statistical analysis using one-way ANOVA. RESULTS: UTS values of middle-apical specimens were found to be significantly (p < 0.05) higher than those of coronal specimens. The results of the one-way analysis of variance showed that the number of dentinal tubules of the samples from the coronal part of the root groups was significantly higher than that of samples from the middle-apical part (p < 0.05). SIGNIFICANCE: These results suggest that high values of tensile strength of the dentin are associated with low densities of dentinal tubules and that apical areas of root dentin are more resistant to tension than coronal ones.

Bonding to worn or fractured incisal edges: shear bond strength of new adhesive systems.

OBJECTIVES: Resin composites can be proposed for the restoration of incisal edges. If a progressive wear or an old fracture is responsible for the loss of the incisal edge, the bonding substrate is likely to be sclerotic dentin, surrounded by enamel. The purpose of the study was to measure under laboratory conditions, the shear bond strength of three adhesive systems to the enamel and dentin exposed on the edge of incisors as a result of a long-time wear or an old fracture. METHOD AND MATERIALS: Thirty extracted human incisors were selected. The teeth had to exhibit some exposed dentin on their edges, a result of old fractures or wear. The 30 specimens were randomly divided into three groups. In each group, a different adhesive system was tested for the ability to efficiently bond a resin composite restoration to the dental substrate. A three-step system (Scotchbond Multipurpose Plus), a one-bottle adhesive (Scotchbond 1), and a self-etching adhesive (Prompt-L-Pop) were compared. The shear bond strength of the restored samples was measured under a loading machine. The pattern of failure that each sample underwent as a result of loading was assessed under a stereomicroscope. RESULTS: The highest values of bond strength were yielded by Scotchbond Multipurpose Plus (28.14 MPa), followed by Scotchbond 1 (16.15 MPa), and Prompt-L-Pop (9.26 MPa). These differences were statistically significant (P < .05). The most frequent pattern of failure was the combined adhesive-cohesive in resin fracture. CONCLUSION: Adhesive systems involving phosphoric acid etching of the substrate were more dependable than a self-etch adhesive when bonding a resin composite restoration to worn or fractured incisal edges.

Resin-dentin interfaces of endodontically-treated restored teeth.

PURPOSE: To compare by confocal and scanning electron microscopy the post-resin-dentin interfaces of endodontically-treated teeth which had been restored with dentin-bonding systems and composite and needed to be extracted after 6 months to 6 years of clinical service. MATERIALS AND METHODS: Sixteen single rooted teeth showing proximal lesions penetrating the pulp chamber were included in the investigation and divided into two groups. Group 1 teeth were endodontically-treated, restored with carbon fiber posts and resin-based composite. Group 2 teeth were treated in the same way and covered with porcelain fused-to-metal crowns. RESULTS: Two thirds of the observed interfaces showed resin penetration of the root dentin in the middle and coronal third of the post space preparation, while only one third of the interface showed resin infiltration in the apical third of the post space preparation. Debonding of the adhesive from the resin infiltrated dentin area and debonding of the composite cement from the adhesive were the most frequently observed failure modes and were observed in one third of the observed interfaces. There was no difference between the post-resin-dentin interfaces of teeth covered and teeth not covered with porcelain-fused to metal crowns. Teeth extracted after longer periods of clinical service showed more abundant areas of debonding of the adhesive from the resin-dentin interdiffusion zone. The presence of bacteria in resin infiltrated dentin tubules was observed in two specimens.

Three-year clinical comparison of survival of endodontically treated teeth restored with either full cast coverage or with direct composite restoration.

STATEMENT OF PROBLEM: Little information exists regarding the outcome of crown build-ups on endodontically treated teeth restored with metal-ceramic crowns or with only a direct-placed composite. PURPOSE: The aim of this study was to evaluate the clinical success rate of endodontically treated premolars restored with fiber posts and direct composite restorations and compare that treatment with a similar treatment of full-coverage with metal-ceramic crowns. MATERIAL AND METHODS: Subjects included in this study had one maxillary or mandibular premolar for which endodontic treatment and crown build up was indicated and met specific inclusion/exclusion criteria. Only premolars with Class II carious lesions and preserved cusp structure were included. Subjects were randomly assigned to 1 of the following 2 experimental groups: (1) teeth endodontically treated and restored with adhesive techniques and composite or (2) teeth endodontically treated, restored with adhesive techniques and composite, and then restored with full-coverage metal-ceramic crowns. Sixty teeth were included in the first group and 57 in the second. All restorations were performed by one operator. Causes of failure were categorized as root fracture, post fracture, post decementation, clinical and/or radiographic evidence of marginal gap between tooth and restoration, and clinical and/or radiographic evidence of secondary caries contiguous with restoration margins. Subjects were examined for the listed clinical and radiographic causes of failure by 2 calibrated examiners at intervals of 1, 2, and 3 years. Exact 95% confidence intervals for the difference between the 2 experimental groups were calculated. RESULTS: At the 1-year recall, no failures were reported. The only failure modes observed at 2 and 3 years were decementations of posts and clinical and/or radiographic evidence of marginal gap between tooth and restoration. There was no difference in the failure frequencies of the 2 groups (95% confidence interval, -17.5 to 12.6). There was no difference between the number of failures caused by post decementations and the presence of marginal gaps observed in the 2 groups (95% confidence intervals, -9.7 to 16.2 and -17.8 to 9.27). CONCLUSION: Within the limitations of this study, the results upheld the research hypothesis that the clinical success rates of endodontically treated premolars restored with fiber posts and direct composite restorations after 3 years of service were equivalent to a similar treatment of full coverage with metal-ceramic crowns.