Effect of a 12‐methacryloyloxy‐dodecyl‐pyridinium‐bromide–containing adhesive with different post types on the long‐term bond strength to dentin

The use of matrix metalloproteinase (MMPs) inhibitors, such as 12‐methacryloyloxy‐dodecyl‐pyridinium‐bromide (MDPB), might improve the adhesion of glass‐fiber (GF) and polyfiber (PF) posts to root dentine. This study assessed the effect of an MDPB‐containing adhesive on the long‐term bond strength of GF or PF posts to bovine dentine. Bovine endodontically treated roots were randomly divided into six groups, according to the post type and adhesive system used, as follows: GF serrated post + MDBP‐free adhesive; GF serrated post + MDPB‐containing adhesive; GF smooth post + MDBP‐free adhesive; GF smooth post + MDPB‐containing adhesive; PF post + MDBP‐free adhesive; PF post + MDPB‐containing adhesive. Specimens were stored in water for 6 months, thermocycled (500 cycles wk^?1), and submitted to the pull‐out test and failure pattern analysis. The cement–dentin interface was evaluated using scanning electron microscopy. The pull‐out data were analyzed using anova and Tukey's test (α = 0.05). No significant interaction between the type of post and the adhesive system was found. Polyfiber posts showed lower bond strength than GF posts, whether serrated or smooth, and the bond strength of the serrated and smooth GF posts was not significantly different. Adhesive failures were predominant in all groups. The type of retainer influenced the bond strength, and MDPB‐containing adhesive did not improve the long‐term bond strength of posts to dentine.     

Three‐dimensional FEA of Effects of Two Dowel‐and‐Core Approaches and Effects of Canal Flaring on Stress Distribution in Endodontically Treated Teeth

Purpose: The aim of this 3D finite element analysis (FEA) was to assess stress distribution and levels in endodontically treated teeth restored with two dowel‐and‐core systems with differing root canal configurations. Materials and Methods: Four 3D finite element models of a laser‐digitalized maxillary central incisor embedded in alveolar bone were created. Internal morphology data and mechanical properties of the materials were obtained from the literature. Models included a (1) sound tooth (control) versus an endodontically treated maxillary central incisor with a crown ferrule preparation with two restorative approaches of a ceramic crown over a (2) gold alloy dowel‐and‐core or (3) glass‐fiber dowels with composite cores (4) the latter with a flared root canal. A 100 N static load was applied in the center of the palatal surface at a 45° angle, and the stress distribution pattern was analyzed using ANSYS^® software. Results: In Model 1 (control), maximum stresses occurred at the coronal third of the buccal (2.32 × 10⁷ Pa) and palatal aspects of dentin. The stress peak value of the model (2.45 × 10⁷ Pa) occurred on the palatal aspect of the enamel at the level of the cementoenamel junction. With the insertion of dowels with thin cement layers (Models 2 and 3), stress concentrations in radicular dentin decreased, while they increased in the dowel/cement/dentin interface. These models exhibited the greatest stress peak values in the incisal margin of the gold alloy core (18.9 × 10⁷ Pa) and in the cement layer (4.7 × 10⁷ Pa). In Model 4, stress peak value was observed in the porcelain crown (4.62 × 10⁷ Pa), and there was no stress concentration inside the cement layer. Conclusions: Within the limits of this study, the results suggest that the use of dowels and cements with mechanical properties similar to those of dentin, and an increased cement layer thickness, results in mechanical behavior similar to the physiological behavior of a sound tooth.     

Effect of Different Cements on the Biomechanical Behavior of Teeth Restored with Cast Dowel‐and‐Cores—In Vitro and FEA Analysis

Purpose: To test the hypothesis that the type of cement used for fixation of cast dowel‐and‐cores might influence fracture resistance, fracture mode, and stress distribution of single‐rooted teeth restored with this class of metallic dowels. Materials and Methods: The coronal portion was removed from 40 bovine incisors, leaving a 15 mm root. After endodontic treatment and standardized root canal relief at 10 mm, specimens were embedded in polystyrene resin, and the periodontal ligament was simulated with polyether impression material. The specimens were randomly divided into four groups (n = 10), and restored with Cu–Al cast dowel‐and‐cores cemented with one of four options: conventional glass ionomer cement (GI); resin‐modified glass ionomer cement (GR); dual‐cure resin cement (RC); or zinc‐phosphate cement (ZP). Sequentially, fracture resistance of the specimens was tested with a tangential load at a 135° angle with a 0.5 mm/min crosshead speed. Data were analyzed using one‐way analysis of variance (ANOVA) and the Fisher test. Two‐dimensional finite element analysis (2D‐FEA) was then performed with representative models of each group simulating a 100 μm cement layer. Results were analyzed based on von Mises stress distribution criteria. Results: The mean fracture resistance values were (in N): RC, 838.2 ± 135.9; GI, 772.4 ± 169.8; GR, 613.4 ± 157.5; ZP, 643.6 ± 106.7. FEA revealed that RC and GR presented lower stress values than ZP and GI. The higher stress concentration was coincident with more catastrophic failures, and consequently, with lower fracture resistance values. Conclusions: The type of cement influenced fracture resistance, failure mode, and stress distribution on teeth restored with cast dowel‐and‐cores.     

Attenuation of radiation‐ and chemoradiation‐induced mucositis using gamma‐d‐glutamyl‐l‐tryptophan (SCV‐07)

Oral Diseases (2010) 16 , 655–660 Objective: To evaluate the efficacy of a novel immunomodulating peptide (SCV‐07) in attenuating the course of radiation‐induced mucositis in an established animal model of oral mucositis (OM). Material and Methods: In three separate experiments, golden Syrian hamsters received either an acute radiation challenge to the buccal mucosa of eight fractionated doses of 7.5 Gy of radiation over a 2‐week‐period, or a combination of acute radiation and cisplatin. In each experiment, animals were treated with varying doses or schedules of SCV‐07 or placebo. OM was scored in a blinded fashion using digital images obtained during the experimental period. Results: We found that SCV‐07 reduced the severity and duration of both acute and fractionated radiation‐induced OM. Similarly, when radiation and chemotherapy were used to induce OM, treatment with SCV‐07 significantly reduced the duration of ulcerative OM. The therapeutic benefit was dependent on both dose and schedule of administration. Conclusion: Taken together, we found SCV‐07 was able to modify the duration and severity of oral mucositis and was dependent on schedule and dose.     

Insulin‐like growth factor‐binding protein‐2 and ‐3 in gingival crevicular fluid

Takenouchi Y, Ohshima M, Yamaguchi Y, Nishida T, Senda N, Idesawa M, Otsuka K, Ito K. Insulin‐like growth factor‐binding protein‐2 and ‐3 in gingival crevicular fluid. J Periodont Res 2010; 45: 803–808. © 2010 John Wiley & Sons A/S Background and Objective: Insulin‐like growth factor‐binding proteins (IGFBPs) are crucial regulators of insulin‐like growth factor (IGF). They enhance or inhibit IGF functions, but also exhibit IGF‐independent effects. In a previous study, we detected, qualitatively, IGFBP‐2 and ‐3 in gingival crevicular fluid using a cytokine antibody array. Here we extended these results using an ELISA to determine the concentrations of IGFBP‐2 and ‐3 in gingival crevicular fluid. In addition, we explored whether the expression of IGFBP‐2 and IGFBP‐3 correlates with periodontal disease severity. Material and Methods: Gingival crevicular fluid samples from 92 sites of 12 patients affected with periodontal disease and from 100 sites of 19 healthy volunteers, were collected, divided into two groups and analyzed by ELISA for IGFBP‐2 and ‐3 expression. The potential correlation among probing depth, gingival index and the concentrations of IGFBP‐2 and ‐3 was analyzed. Results: Positive correlations were observed between the concentration of IGFBP‐2 and probing depth and gingival index, but not for IGFBP‐3. The IGFBP‐2 concentrations at bleeding on probing‐positive sites and at sites with a probing depth of ≥ 4 mm were higher than at bleeding on probing‐negative sites and at sites with a probing depth of ≤ 3 mm. Conclusion: These results indicate that IGFBP‐2 is a potential novel marker for periodontal disease progression. As IGFBP‐2 modulates bone metabolism and cell migration, IGFBP‐2 in the gingival crevicular fluid may reflect periodontal disease activity.     

The effect of different posts on fracture strength of roots with vertical fracture and re‐attached fragments

Summary The aim of this in vitro study was to test the effect of different post systems on fracture strength of roots with re‐attached fragments. Root canals of eighty extracted single‐rooted human teeth were instrumented (ProFile) and randomly divided into two groups. The roots in the first group were vertically cracked, and the fragments were re‐attached using Super Bond C&B (Sun Medical, Tokya, Japan). The roots in the second group were kept sound. Obturation of the roots was performed with MetaSEAL (Sun Medical) and gutta‐percha. Post spaces were prepared, and the roots were restored with one of the followings: UniCore (Ultradent), Everstick (Stick Tech), Ribbond (Ribbond), ParaPost (Coltene/Whaledent) (n = 10). Four mm high build‐ups were created (Clearfil DC Bond Core; Kuraray, Tokyo, Japan). Compressive loading of the samples was performed after 24 h (1 mm min^?1). Mean load necessary to fracture each sample was recorded (Newton) and statistically analysed (One‐way anova , t‐tests). ParaPost showed the highest fracture strength among the roots with re‐attached fragments (P < 0.05). UniCore and ParaPost systems showed similar fracture strength in the sound roots (P > 0.05). Re‐attached fragments significantly reduced the fracture strength of roots in UniCore group (P = 0.000). Ribbond post showed mostly repairable fractures. Metal post (ParaPost) showed the highest fracture strength in the roots with re‐attached fragments; however, fracture pattern was 41% non‐repairable. Re‐attached fragments significantly reduced the fracture strength of the roots in UniCore group. Prefabricated posts showed similar fracture strength in the sound roots. Customized post systems EverStick and Ribbond showed mostly repairable failure after loading in sound roots or roots with re‐attached fragments.