牙本质表面状态对粘结界面影响的激光扫描共聚焦显微镜研究

目的 :研究不同表面状态下形成的牙本质湿粘结界面的异同。方法 :以RhodamineB为荧光剂 ,用激光扫描共聚焦显微镜 (LSCM)分别观察干燥或湿润粘结时形成的牙本质粘结界面的异同。结果 :湿粘结时 5种粘结系统在牙本质粘结界面都有良好的渗透。以丙酮为溶剂的粘结系统干燥粘结时形成的混合层的厚度有明显的降低 ,牙本质小管中树脂突较细 ,中断现象增多 ,长度缩短。结论 :干燥粘结时 5种粘结剂在牙本质表面的渗透性减弱。     

Penetration of bonding resins into fibre-reinforced composite posts: a confocal microscopic study

AIM: To compare the penetration of two different bonding resins applied for different contact times, on glass reinforced-reinforced composite root canal posts showing an interpenetrating polymer network (IPN) or cross-linked polymer matrix. The research hypothesis was that the bonding resins were equally able to penetrate into the IPN post whereas less penetration was evident into the cross-linked post. In addition, the prolonged contact time of the bonding resin on the surface of post was assumed to increase the resin penetration. METHODOLOGY: A total of 36 posts, comprising 18 IPN posts (everStick Post) and 18 cross-linked posts (C Post Millennium) were divided into 12 groups of three posts. All posts had a diameter of 1.2 mm. Both bonding resins (Scotchbond Multi Purpose Plus and Stick Resin) were labelled with Rhodamine B for determination of the resin penetration into the post. After contact times of 1, 30 and 300 s the bonding resins were light cured for 60 s. Penetration of bonding resins into three sections of each post was measured by confocal scanning light microscope. The influences of post and type of adhesive resin on resin diffusion into the polymer matrix of the post were assessed by nonparametric methods. RESULTS: For C Post Millennium and for 1 s contact time, no penetration of bonding resins into the polymer matrix of posts occurred in any section of any post. For the everStick Post, penetration was always noted after 300 s contact (mean 22.8 microm) and nearly always after 30 s contact (mean 3.5 microm), with very little difference between the two adhesives. The degree of penetration into everStick Posts was invariably greater after 300 s contact than after 30 s (P < 0.001). Both sets of results were highly significantly greater than the zero penetration recorded using C Post Millennium or 1 s contact time (P < 0.001). CONCLUSIONS: The ability of bonding resins to penetrate into everStick Post with IPN polymer matrix may give the opportunity to establish a good link between fibre-reinforced composite posts, luting cements and composite cores.     

Dye leakage and SEM study of roots obturated with Thermafill and dentin bonding agent.

The apical seal of roots obturated with a dentin bonding agent and Thermafill with and without the use of sodium hypochlorite as an irrigating solution was compared by a dye leakage test. Roots obturated with Thermafill and a zinc oxide eugenol sealer were used as controls. Thirty-eight roots were prepared chemomechanically and divided into three experimental groups. The teeth of group 1 were filled with Thermafill and the dentin bonding agent using sodium hypochlorite as the irrigant. The teeth of group 2 were filled in the same way, but saline solution was used as the irrigant. Before the root canal was filled the smear layer was removed from the root canal walls of both groups by rinsing the root canal with a 17% EDTA solution. The teeth of group 3 were filled with Thermafill and a zinc oxide eugenol sealer. The teeth were immersed in 2% methylene blue solution. The root fillings of groups 1 and 2 leaked significantly more than those of group 3. The resin-dentin-guttapercha interface of group 1 was observed by scanning electron microscopy and showed a typical hybrid layer. An intimate contact between resin and dentin was present in group 2, but a resin-dentin interdiffusion zone was only occasionally observed. The use of dental adhesives and the hybrid layer formation did not improve the seal of Thermafill root canal fillings.     

Influence of two dentin bonding systems on the demineralization of the root surface

It has been assumed that dentin adhesives can prevent root surface caries. The aim of this study was to determine the caries-protective effect of two different dentin bonding systems on the demineralization of root surfaces in vitro. The root surfaces of 60 freshly extracted caries-free human molars were thoroughly cleaned and polished, thereby removing the cementum. The teeth were then coated with acid-resistant nail varnish, exposing two rectangular windows of 6 mm2 each. One window served as an untreated control, while the other window was treated with a dentin bonding system. The specimens were distributed among the following experimental groups--Group 1: Syntac, Heliobond (no air thinning); Group 2: Syntac, Heliobond (as recommended); Group 3: Syntac, without Heliobond; Group 4: Prime & Bond 2.0 (no air drying); Group 5: Prime & Bond 2.0 (as recommended); Group 6: Prime & Bond 2.0 (dentin pretreated with 36% phosphoric acid). Subsequently, all specimens were demineralized for 6 days with acidified gel (HEC, pH 4.8, 37 degrees C). From each tooth, three dentinal slabs were cut perpendicular to the polished surface of the windows. The slabs were ground to a thickness of 80 microns and imbibed with water. The depth of the respective demineralized areas was determined using a polarized light microscope. All control specimens exhibited lesions with a mean depth of 67 microns. In Groups 2, 3, and 5 the lesion depth was reduced significantly, while in Groups 1, 4, and 6 no lesions could be detected. It was concluded that the demineralization of the root surface can be impeded by application of the dentin adhesives tested.     

Tubule-occluding effect of desensitizing laser treatment on prepared dentin surfaces: an environmental SEM study

PURPOSE: The purpose of this in vitro study was to demonstrate the dentinal tubule-occluding effect of desensitizing laser treatment on dentin surfaces using environmental scanning electron microscopy (E-SEM). MATERIALS AND METHODS: Ground dentin surfaces were divided into 5 areas. Each area received a different mode of laser irradiation (low potency [LP] versus high potency [HP] and short time [ST] versus long time [LT]). Lased dentin surfaces were viewed and graded under E-SEM at x5000 magnification. RESULTS: The tubule closure rates of 4 different irradiation modes were as follows: LP/LT (74%) > HP/ST (70%) > LP/ST (51%) > HP/LT (46%) > control (6%). CONCLUSION: It was demonstrated that desensitizing laser application was an efficient treatment option for the occlusion of dentinal tubule apertures.     

Dye leakage and SEM study of roots obturated with Thermafill and dentin bonding agent

Abstract— The apical seal of roots obturated with a dentin bonding agent and Thermafill with and without the use of sodium hypo-chlorite as an irrigating solution was compared by a dye leakage test. Roots obturated with Thermafill and a zinc oxide eugenol sealer were used as controls. Thirty-eight roots were prepared chemomech-anically and divided into three experimental groups. The teeth of group 1 were filled with Thermafill and the dentin bonding agent using sodium hypochlorite as the irrigant. The teeth of group 2 were filled in the same way, but saline solution was used as the irrigant. Before the root canal was filled the smear layer was removed from the root canal walls of both groups by rinsing the root canal with a 17% EDTA solution. The teeth of group 3 were filled with Thermafill and a zinc oxide eugenol sealer. The teeth were immersed in 2% methylene blue solution. The root fillings of groups 1 and 2 leaked significantly more than those of group 3. The resin-dentin-guttaper-cha interface of group 1 was observed by scanning electron microscopy and showed a typical hybrid layer. An intimate contact between resin and dentin was present in group 2, but a resin-dentin inter-diffusion zone was only occasionally observed. The use of dental adhesives and the hybrid layer formation did not improve the seal of Thermafill root canal Wings.     

Fluoride uptake by enamel and dentin from bonding agents and composite resins: a comparative study

The present study was performed to compare the amount of in vitro fluoride uptake by enamel and dentin from fluoridated bonding agent with non-fluoridated composite (Group I), non-fluoridated bonding agent with fluoridated composite (Group II) and fluoridated bonding agent with fluoridated composite resin (Group III). Sixty extracted premolars were selected and divided into three groups of 20 teeth each. Restorative materials were applied according to manufacturer's instructions into standard windows created in the teeth, cured and placed in de-ionised water for three months. The fluoride content of successive acid etch biopsy was determined by specific ion-electrode analysis. Although significant amount of fluoride uptake occurred in all the test groups, fluoride uptake was found to be highly significant in dentin when compared to enamel in Group, I, II and III (P<0.001). The fluoride uptake was greater by both enamel and dentin in Group III ie fluoridated bonding agent with fluoridated composite resin.     

Nanoleakage patterns of four dentin bonding systems.

OBJECTIVES: The purpose of this study was to evaluate the nanoleakage patterns of four dentin bonding systems. METHODS: The dentin bonding systems used in this study were: Single Bond, One Coat Bond, Prime & Bond NT/Non Rinse Conditioner (NRC), and PermaQuik. Flat occlusal dentin surfaces from extracted human molars were finished with wet 600-grit silicon carbide paper, and bonded with one of the dentin bonding systems. After 24 h storage at 37 degrees C in water, margins were finished with polishing discs and the surrounding tooth surfaces coated with nail varnish. The samples were immersed in a 50% (w/v) solution of silver nitrate for 24 h, and exposed to photodeveloping solution for 8 h. The samples were cut longitudinally, polished, and mounted on stubs, carbon coated and observed in a Field Emission-SEM using backscattered electron mode. RESULTS: Different nanoleakage patterns were observed with the different adhesive systems. However, accumulations of silver particles were often noted at the base of the hybrid layer for all materials. Single Bond and One Coat Bond demonstrated uptake of silver particles both within the hybrid layer and the adhesive resin. Prime & Bond NT/NRC showed silver staining throughout almost the entire thickness of the hybrid layer. The leakage pattern of PermaQuik revealed loose silver deposition within the hybrid layer. The composition of each adhesive system may play a role in forming the different leakage patterns. SIGNIFICANCE: The current dentin bonding systems used in this study do not achieve perfect sealing at the restoration/dentin interface, which may influence the durability of the bond to dentin.     

Diffusion of medicaments within root canal dentin. A scanning electron microscopic study

Root canals of 21 maxillary human teeth were enlarged with reamers and flushed alternatively with sodium hypochlorite and hydrogen peroxide. After its mechanical preparation, root canals were dressed with camphorated paramonochloropherol and/or formocresol delivered by paper points. All three medicaments crystallize both on dentin walls and inside dentinal tubules. The clinical implications of these findings are discussed.     

The optimum combination of dentin bonding systems.

The efficacy of dentin bonding systems composed of a commercial or an experimental dentin cleanser, a dentin primer, and an intermediate resin was examined by measurement of the wall-to-wall polymerization contraction gap. Light-activated composites in a cylindrical dentin cavity were prepared in exposed dentin of the proximal surface of the extracted human premolar. The combination of a dentin cleanser of neutralized 0.5 mol/L EDTA, a dentin primer of 35% hydroxyethyl methacrylate (HEMA) or 35% HEMA containing 5% glutaraldehyde and a commercial intermediate resin (Clearfil New Bond, Kuraray Co., Osaka, Japan; Pyrofil Light Bond, Sankin Co., Osaka, Japan) was effective in compensating for the contraction stress of a light-activated composite and for obtaining marginal integrity between the composite and the dentin cavity wall.     

Antibacterial activity of fifth-generation dentin bonding systems.

Past concepts that the pulp does not become infected until an actual carious exposure takes place have been challenged. The antibacterial effects of the dentin bonding systems Single Bond, Prime&Bond NT, and Excite were evaluated using the bacteria Streptococcus mutans ATCC 25175, Streptococcus intermedius, Lactobacillus acidophilus, Prevotella oris, Prevotella bivia, Prevotella denticola, Porphyromonas gingivalis, Porphyromonas endodontalis, and Clostridium ramosum with a disk diffusion method. Chlorhexidine (0.2%) was used as a positive control. After incubation zones of inhibited bacterial growth were measured. Prime&Bond NT showed growth inhibition for all bacterial strains. Lactobacillus acidophilus and Streptococcus mutans were remarkably resistant to Single Bond, whereas EX produced no inhibitory effect on Porphyromonas endodontalis, although the adhesive produced the maximum halo inhibition to Streptococcus mutans (15+/-1 mm), showing an antibacterial effect closest to chlorhexidine. The variety of results obtained in this study suggest that antibacterial properties of current dentin adhesives may depend on components that are originally incorporated to promote adhesion.     

Improving bond strength through acid etching of dentin and bonding to wet dentin surfaces.

A bonding system using moisture on the tooth surface can be an enormous benefit as obtaining dentin dryness in the mouth is nearly impossible. The author describes a system that bonds to both wet and dry surfaces.     

SEM evaluation of resin-carious dentin interfaces formed by two dentin adhesive systems.

OBJECTIVES: We investigated the influence of dentin tubule direction and identifiable zone of carious dentin on the microstructure and the thickness of the hybrid-like layer (HL) formed by self-etch and etch-rinse adhesive systems. METHODS: An etch-rinse and a self-etching adhesive were bonded to dentin carious zones divided into groups with parallel or perpendicular orientation relative to the dentin tubules at the resin-carious dentin interface (N=5/variable). Bonds were prepared to each of the four zones of carious dentin apparent after staining with Caries Detector: pink, light pink, transparent and apparently normal; six non-carious third molars were controls. The microstructure and thickness of the HL were determined by SEM and compared using three-way ANOVA and Tukey's multiple comparisons (p<0.05). RESULTS: Etch-rinse controls gave thicker HLs than self-etching systems; orientation did not affect thickness for the self-etch system. Perpendicular orientations gave thicker HLs than parallel for the pink zone bonded with the etch-rinse system. For both adhesives, HL thickness in the pink zone was significantly greater than in light pink for the perpendicular group, but no significant differences were found among other variables. HL microstructure was more granular and rougher for the etch-rinse than for the self-etching system. Pores and cracks were obvious in the more demineralized zones. Resin tags were shorter and irregular in the transparent zone and often were completely absent in the outer demineralized zones (pink, light pink). SIGNIFICANCE: Microstructure of bonded interfaces varies markedly depending on adhesive system, tubule orientation and carious zone.     

SEM study of a self-etching primer adhesive system used for dentin bonding in primary and permanent teeth

PURPOSE: The purpose of this study was to evaluate the interfacial micromorphology of direct esthetic restorations bonded to primary or permanent tooth dentin with a self-etching primer adhesive system. METHODS: Superficial dentin at the occlusal surface of 15 primary and 15 permanent molars was exposed with a carbide bur. Prompt-L-Pop was applied in one half of each surface. A control bonding system, Single Bond or Vitremer Primer, was used in the other half Teeth were restored either with a composite resin (Filtek Z250), a compomer (Hytac), or a resin-modified glass ionomer (Vitremer). Twenty-five scanning electron microscope fields from 5 teeth were evaluated blindly by two investigators for each condition. RESULTS: In this study, a significant difference in quality of the interfacial seal was not observed when restorations performed in primary teeth were compared to restorations in permanent teeth. Interfacial gaps were observed in most restorations bonded with Prompt-L-Pop and restored with Filtek Z250 (9/10), Hytac (9/10), or Vitremer (5/10). No interfacial gaps were observed in teeth bonded with Single Bond and restored with Filtek Z250 (0/10) or Hytac (0/10), while all teeth bonded with Vitremer Primer and restored with Vitremer presented gaps (10/10). To understand the reason for the interfacial gaps observed with Prompt-L-Pop, we examined if this system generated a hybrid layer at the dentin/restorative material interface. All surfaces bonded with Single Bond and restored with Filtek Z250 or Hytac presented a visible hybrid layer. In contrast, 0/10 (Z250) and only 3/10 (Hytac) restorations bonded with Prompt-L-Pop showed signs of a hybrid layer. CONCLUSION: The self-etching primer adhesive system Prompt-L-Pop failed to generate sealed interfaces consistently between the dentin of primary and permanent teeth and the composite resin or the compomer evaluated in this study.     

Effect of solvents on bonding to root canal dentin

The long-term success of resin cementation of post/cores is likely increased with improvement in resin-root canal dentin bonding. The adverse effect of some irrigation constituents (NaOCl, H2O2) or medications (eugenol) on the bond strengths of resins to dentin have been reported. The purpose of this in vitro study was to evaluate the effect of two gutta-percha solvents (chloroform versus halothane) on microtensile bond strength to root canal dentin. Thirty, extracted, human, single-rooted teeth were instrumented to a #70 file and randomly divided into 3 groups of 10 each. The root canals were treated with water, chloroform, or halothane for 60 s. All root canals were obturated using C&B Metabond. After 24 h of storage in distilled water, serial 1-mm-thick cross-sections were cut and trimmed. Microtensile bond strength to apical, middle, and coronal root canal dentin were measured using an Instron machine. Using pooled data, the results indicated that water-treated roots had significantly higher resin-dentin bond strengths compared with chloroform or halothane treatment groups (control: 23.9 MPa; chloroform: 18.3 MPa; halothane: 17 MPa; p < 0.05). Gutta-percha solvents have an adverse effect on bond strengths of adhesive cements to root canal dentin.     

Effects of ultrasonic root end preparation on resected root surfaces: SEM evaluation

OBJECTIVE: The purpose of this study was to investigate the in vitro effect of ultrasonic retrotips on root end surfaces. STUDY DESIGN: Root end resection was performed on 45 single-root teeth endodontically treated after extraction. Setting the ultrasonic device at full power, a retrograde cavity was made by a stainless steel tip in 9 specimens (SS-FP). In another 9 samples a diamond tip was used (D-FP). Setting the intensity of the ultrasonic device at half power, 9 specimens were treated using stainless steel tips (SS-HP) and 9 using diamond tip (D-HP). Nine teeth were only apically resected and used as controls. Histologic serial sections were examined by scanning electron microsope to assess the number of root-face cracking, the marginal quality, and the crack type. RESULTS: No significant difference between diamond and stainless steel groups was found at a given power setting. Significant differences were found between SS-FP and SS-HP group for both the number of cracks and the marginal quality.     

Effects of Nd: YAG laser irradiation on the root canal wall dentin of human teeth: a SEM study

The purpose of this study was to observe the morphological and histological changes on the root canal walls after Nd:YAG laser application. Twenty vital, recently extracted single-rooted human teeth were used for this study. Root canals were cleaned and shaped by a conventional step-back technique--by means of k files up to a 20 k-file type at working length--and subsequently shaped by Ni-Ti root-canal rotary instrumentation up to 30/06 and irrigated with 2.5% hypochlorite solution. Ten teeth (control group) were left unlased, while the other ten teeth were irradiated with Nd:YAG laser by means of a 320 microns fibre inserted in the root canal at 1 mm from the apex with a power of 1.5 Watt and a frequency of 15 pps for five seconds in retraction with rotating movements. The control specimen showed debris and smear layer on the root canal surface obscuring the dentin tubules. The root canal walls irradiated with Nd:YAG laser showed a clear glazed surface, some open dentinal tubules and some surface craters with cracks. Such results confirm that smear layer and debris are removable with Nd:YAG laser, however clearing all root canal walls is still difficult and, if the energy level and duration of application are inadequate, a certain degree of thermal damage and morphological changes in dentin structure are observable.