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PubMed1993

Comparative SEM and TEM examination of the ultrastructure of the resin-dentin interdiffusion zone.

The resin-dentin interdiffusion zone produced by a dentin-adhesive system that removes the smear layer and concurrently decalcifies superficial dentin was morphologically examined by both scanning and transmission electron microscopy. Cross-sectioned resin-bonded dentin discs were etched with an argon-ion beam to make the resin-dentin interface observable by SEM. For the TEM examination, the sections were partly decalcified by an aqueous EDTA solution to facilitate ultramicrotomy and to disclose the ultrastructure of the interdiffusion zone. Both SEM and TEM confirmed the presence of the resin-dentin interdiffusion zone as the junction between the deep unaltered dentin structure and the restorative resin. Within the interdiffusion zone, three sublayers with characteristic ultrastructure and staining were identified by TEM. An upper diffuse black layer contained few structural features. Underneath, partially-altered collagen fibrils were closely packed, mostly running parallel with the interface and perpendicular to the dentinal tubules. Their outline was electron-dense, forming tunnel-like structures. At the base of the upper layer, several stained projections were found to bulge out into the underlying collagen network and appeared to be confined by obstructive, parallel-running collagen fibrils. Finally, the third dense layer, containing hydroxyapatite crystals, demarcated the superficially demineralized dentin layer from the deeper unaltered dentin. Resin diffusion into the decalcified dentin surface layer was evident, but diminished with depth, presumably reducing deeper resin impregnation into the interfibrillar spaces. The citric acid dentin-pretreatment probably caused denaturation of the superficial collagen fibrils. Its decalcifying effect gradually weakened with depth, leaving behind hydroxyapatite crystals at the base of the interdiffusion zone.(ABSTRACT TRUNCATED AT 250 WORDS)

Acid Etching, Dental↗

PubMedDate not supplied

Short-term dentin bridging of mechanically-exposed pulps capped with adhesive resin systems.

Dentin bridging of 150 mechanically exposed monkey pulps to two adhesive resins [BondWell LC (BW); Clearfil Liner Bond II (LB)] and a calcium hydroxide cement [Dycal (DY)] were histopathologically evaluated at 3, 7, 14, 30, and 60 days after operation (n = 10). The dentin bridge structure was three-dimensionally reconstructed from serial sections using a computer-aided reconstruction system. At three and seven days, in all pulps, no necrotic tissue and slight inflammatory cell infiltration was observed just below the exposure site. At 14 days, spindle-shaped fibroblast cells could be detected at the wound surface. All dentin chips showed reparative dentin deposition along the periphery of the wound surface. From this stage, the formation of secondary dentin from the pulpal wall at the periphery of the exposed area was recognized in all pulps. At 30 days, initial signs of dentin bridging were observed at the wound surface with a well-organized layer of odontoblastoid cells. The exposed area became occluded with a dentin bridge as the observation period increased. Group DY showed significantly higher incidence of dentin bridging than other groups at 30 days (p < 0.05). However, no significant difference of dentin bridge formation was found between Group DY and Groups BW and LB at 60 days. Bacterial penetration along the cavity walls and pulp tissue could not be detected in all groups. Histopathological observations and three-dimensional image analysis suggested that dentin bridge formation may occur following three patterns: (1) formed from the periphery of the residual dentin chip at the wound surface within 14 days, (2) formed within 14 days from the periphery of the cavity floor and with formation of reparative dentin by stimulation during the cavity preparation, and (3) formed from the wound surface within 30 days after exposure.

Animals↗

PubMed2002

Shear bond strengths to coronal and pulp chamber floor dentin.

PURPOSE: To evaluate the bond strengths of two different types of resin bonding systems to coronal dentin and dentin of the pulp chamber floor. MATERIALS AND METHODS: 20 extracted human molars were sectioned into three regions; superficial coronal dentin, deep coronal dentin and floor of pulp chamber dentin. The dentin surface of each region was bonded with Single Bond or Clearfil Liner Bond 2V. A core build-up light-cured resin composite, Clearfil Photocore, was placed and light-cured for 40 seconds. After storage in 37 degrees C water for 24 hours, shear bond strengths were measured using a single plane shear test assembly at a crosshead speed of 2.0 mm/minute. Morphological changes of the conditioned dentin and hybrid layer formation were observed by SEM. RESULTS: For Single Bond, the bond strengths to superficial dentin were within anticipated bounds (23 MPa), whereas the bond strengths to deep dentin (15 MPa) and floor of pulp chamber dentin (13 MPa) were significantly lower (P < 0.05). For Clearfil Liner Bond 2V, higher bond strengths (approximately 30 MPa) were obtained for each region. The data were analyzed by one- and two-way ANOVA, and Fisher's PLSD (P < 0.05). The appearance of the conditioned dentin varied according to dentin region and conditioner. For Single Bond, thick hybrid layers (3-4 microm) were observed, while thin hybrid layers (less than 0.5 microm) were observed in Clearfil Liner Bond 2V for all regions.

Analysis of Variance↗

PubMed2003

Sealing properties of a self-etching primer system to normal caries-affected and caries-infected dentin.

PURPOSE: To compare the ability of an experimental antibacterial self-etching primer adhesive system to seal exposure sites in normal, caries-affected and caries-infected human dentin. METHODS: 30 extracted human third molars were used within 1 month of extraction. 10 intact normal teeth comprised the normal group. 20 teeth with occlusal caries that radiographically extended halfway to the pulp were excavated using caries-detector solution (CDS) and a #4 round carbide bur in a slowspeed handpiece. Half of those teeth were fully excavated free of CDS-stained material without exposing the pulp, and were designated as the caries-affected dentin group. The remaining 10 teeth were excavated as close to the pulp as possible without obtaining an exposure, but whose dentin continued to stain red with CDS; this group was designated as the caries-infected dentin group. The remaining dentin thickness in all of the specimens in the other two groups was then reduced to the same extent as the caries-infected group. Direct exposures of the pulp chamber were made with a 1/4 round bur in the normal dentin or a 25 gauge needle in the other two groups. After measuring the fluid flow through the exposure, the sites were then sealed with an experimental antibacterial fluoride-containing self-etching primer adhesive systems (ABF). Fluid conductance was remeasured every week for 16 weeks. RESULTS: The fluid conductance through the exposure fell 99% in all groups following resin sealing. The seals of normal and caries-affected dentin remained relatively stable over the 16 weeks, while the seals of caries-infected dentin gradually deteriorated, reaching significance at 8 weeks. TEM examination revealed very thin (ca. 0.5 mm) hybrid layers in normal dentin, 3-4 microm thick hybrid layers in caries-affected dentin and 40 microm thick hybrid layers in caries-infected dentin. The tubules of caries-infected dentin were enlarged and filled with bacteria. Resin tags passed around these bacteria in the top 20-40 microm thereby encapsulating them in resin.

Acid Etching, Dental↗

PubMedDate not supplied

Bonding to sound vs caries-affected dentin using photo- and dual-cure adhesives.

This study aimed to evaluate the microtensile bond strength (microTBS) of photo- and dual-cure adhesives to sound and caries-affected dentin using total- and self-etch techniques. Human third molars with occlusal caries were prepared as previously described by Nakajima and others (1995). Dentin surfaces were bonded with Optibond Solo Plus (Kerr; photo-cure adhesive) or Optibond Solo Plus + Dual-cure activator (Kerr; dual-cure adhesive) with total- and self-etch technique. Clearfil AP-X (Kuraray) was used for composite buildups. Following storage in distilled water at 37 degrees C for 24 hours, the teeth were sectioned into 0.7-mm thick slices to obtain sound and caries-affected dentin slabs, then trimmed to form hour glass shapes with a 1 mm2 cross-sectional area. The specimens were subjected to microtensile testing using EZ-test (Shimadzu) at 1 mm/minute. Data were analyzed using three-way ANOVA and Student's t-Test (p<0.05). Bond strengths to sound dentin with photo- and dual-cure adhesives using total- and self-etch techniques were significantly higher than those to caries-affected dentin. Dual-cure adhesive significantly decreased bond strengths both to sound and caries-affected dentin. The total-etch technique showed no beneficial effect on caries-affected dentin compared with the self-etch technique. Scanning electron microscopic observation of the resin-dentin interfaces revealed that hybrid layers in caries-affected dentin were thicker than those observed in sound dentin with photo- and dual-cure adhesives. Resin infiltration into dentinal tubules of caries-affected dentin was hampered by the presence of mineral deposits.

Acid Etching, Dental↗

PubMed1995

Interfacial morphology and strength of bonds made to superficial versus deep dentin.

PURPOSE: To evaluate the interfacial morphology (SEM) of two bonding systems to superficial and deep dentin using a reverse-sandwich technique, coupled with measurement of micro-tensile bond strengths (MTBS). MATERIALS AND METHODDS: Superficial and deep dentin disks were prepared from the same tooth in freshly-extracted human third molars. All-Bond 2 (total etch versus no etch) or Imperva Bond (total etch versus no etch) were applied to superficial versus deep dentin surfaces and the two disks were bonded together into a reverse-sandwich configuration. RESULTS: SEM revealed that All-Bond 2 and Imperva Bond applied under total etch conditions formed thicker resin-infiltrated layers (4-8 micrometers) on deep dentin than on superficial dentin (2-4 micrometers), and that All-Bond 2 and Imperva Bond applied to unetched dentin formed very thin resin-infiltrated layers (less than 0.5 micrometers) on both dentin substrates. MTBS of All-Bond 2 and Imperva Bond were more than 20 MPa irrespective of dentin depth and were not significantly different. Without acid etching, the MTBS of both systems to deep dentin was significantly lower than to superficial dentin. These results suggested that for the total-etch systems, dentin depth affected the thickness of the resin-infiltrated layer, but the thickness of the resin-infiltrated layer had no significant relationship with MBTS. The present data also indicated that the acid-etch technique could prevent the decrease of bond strength seen in deep dentin in the absence of etching.

Acid Etching, Dental↗

PubMed2001

The use of oxalate to reduce dentin permeability under adhesive restorations.

PURPOSE: To test a novel approach to reducing dentin permeability that localizes occlusion of dentin tubules by calcium oxalate crystals to the subsurface without lowering resin bond strengths to oxalate-treated dentin surfaces. MATERIALS AND METHODS: Flat dentin surfaces of extracted human third molars were etched with a mass fraction of 32% phosphoric acid (Bisco) for 15 s and rinsed. Half of the surface was treated with a potassium oxalate gel (mass fraction of 3% monopotassium monohydrogen oxalate) for 2 mins. The entire surface was then moist bonded with either One Step (OS) or Scotchbond Multi-Purpose (SB) adhesive systems. A resin-based composite (Z-100) buildup was made over the entire surface. After storage for 24 hrs in distilled water, the teeth were longitudinally sectioned to separate the oxalate-treated half from the untreated (control) half. Each half was serially sectioned into several 0.7 mm thick slabs which were then trimmed to an hour-glass shape to reduce the bonded area to approximately 0.8 mm2 and tested in tension. Pre- and post-treatment hydraulic conductance (Lp) of dentin was determined using dentin discs with a standard protocol. SEM images were obtained to examine the effects of treatment both on the dentin surface and along the tubules beneath the surface. The bonded interface was also examined by SEM. RESULTS: Treating etched dentin discs with the oxalate gel caused significant reduction of the Lp of dentin (80% reduction, P < 0.05). There were no statistically significant differences between bond strengths of oxalate-treated and untreated surfaces for either adhesive system. OS resulted in a bond strength of 25.8 +/- 9.2 MPa to untreated and 27.8 +/- 8.9 MPa to oxalate treated surfaces (P > 0.05). SB showed bond strengths of 22.9 +/- 7.9 MPa and 22.9 +/- 9.6 MPa to untreated and treated surfaces, respectively (P > 0.05). SEM images showed that the application of potassium oxalate gel on etched dentin resulted in the formation of crystals inside the tubules rather than on the surface. Examination of the bonded interfaces demonstrated that the crystal formation inside the tubules did not compromise the formation of a typical hybrid layer on the top of dentin surfaces. Resin monomers penetrated into the tubules filling the spaces around the crystals forming resin tags with a jagged-like feature.

Analysis of Variance↗

PubMed2004

mRNA expression and protein localization of dentin matrix protein 1 during dental root formation.

Dentin matrix protein 1 (DMP1) is an acidic phosphoprotein. DMP1 was initially detected in dentin and later in other mineralized tissues including cementum and bone, but the DMP1 expression pattern in tooth is still controversial. To determine the precise localization of DMP1 messenger RNA (mRNA) and the protein in the tooth, we performed in situ hybridization and immunohistochemical analyses using rat molars and incisors during various stages of root formation. During root dentin formation of molars, DMP1 mRNA was detected in root odontoblasts in parallel with mineralization of the dentin. However, the level of DMP1 mRNA expression in root odontoblasts decreased near the coronal part and was absent in coronal odontoblasts. DMP1 protein was localized along dentinal tubules and their branches in mineralized root dentin, and the distribution of DMP1 shifted from the end of dentinal tubules to the base of the tubules as dentin formation progressed. During the formation of the acellular cementum, DMP1 mRNA was detected in cementoblasts lining the acellular cementum where its protein was localized. During the formation of the cellular cementum, DMP1 mRNA was detected in cementocytes embedded in the cellular cementum but not in cementoblasts, and its protein was localized in the pericellular cementum of cementocytes including their processes. During dentin formation of incisors, DMP1 mRNA was detected in odontoblasts on the cementum-related dentin, where its protein was localized along dentinal tubules near the mineralization front. The localization of DMP1 mRNA and protein in dentin and cementum was related to their mineralization, suggesting that one of the functions of DMP1 may be involved in the mineralization of dentin and cementum during root formation.

Animals↗

PubMed1996

Effects of hexafluorosilicate on the precipitate composition and dentine tubule occlusion by calcium phosphate.

OBJECTIVES: To improve the calcium phosphate precipitation (CPP) method for the occlusion of dentine tubules with calcium phosphate, the addition of calcium hexafluorosilicate (CaSiF6) to CPP solution was evaluated in vitro with respect to its occluding capacity and the composition of the precipitate. METHODS: The occlusion of dentine tubules was evaluated by SEM observations and by measurements of dentine permeability. The composition of the precipitate was determined by measuring the calcium to phosphorus (Ca/P) ratio of the precipitate in dentine tubules by energy dispersive X-ray spectroscopy (EDS). RESULTS: The addition of CaSiF6 to the CPP solution resulted in an increase of the Ca/P ratio in the precipitate not only on the dentine surface but also inside the dentine tubules; indicating that the precipitate became more apatitic in nature. The addition of CaSiF6 had no effect on occluding capacity in terms of measurements of dentine permeability or SEM observations. Dentine permeability decreased to approximately 4% of pretreatment values and the dentine tubules were occluded for approximately 10-15 microns from the dentine surface. CONCLUSION: It is concluded that the addition of CaSiF6 to CPP solution was desirable, since it provided a more apatitic precipitate in the dentine tubules, not only on the dentine surface but also inside the tubules, and there were no drawbacks with respect to its occluding capacity.

Apatites↗

PubMed2001

Dentin wetting by four adhesive systems.

OBJECTIVES: To evaluate the dentin wetting by four adhesive systems and to relate the wetting properties with the adhesive efficiency. METHODS: Scotch Bond Multipurpose Plus (3M), Syntac Single-Component (Vivadent), One-Step (Bisco) and Heliobond (Vivadent) were used. The substrate was superficial and deep human dentin. Roughness and water contact angle were measured before and after acid etching. Dentin wetting by resins was studied by contact angle measurements as a function of time to evaluate the spreading time. The shear bond strength was evaluated following a single plane method, and the microleakage was evaluated in Class V cavities. RESULTS: Acid etching increased dentin roughness and wettability and no differences were found between acids tested. Dentin wetting and roughness was higher on deep dentin. Dentin wetting and shear bond strength of resins was similar except for Heliobond that displayed the lowest value. Microleakage was higher on the gingival wall, and the leaking was lowest for Scotch Bond Multipurpose Plus, and maximum for Heliobond. The spreading time exceeded 30s with water-based and hydrophobic adhesives, and was lower with an acetone-based adhesive. Dentin depth had some influence on contact angle and shear bond strength: contact angles obtained with SBMP and One-Step were higher on superficial dentin, and shear bond strength for One-Step was higher on superficial dentin. Dentin wetting by resins could be correlated to shear bond strength and microleakage. SIGNIFICANCE: Dentin acid etching with different conditioners promotes similar roughness and wetting changes. On a similar substrate, the adhesion depends on the chemical and wetting characteristics of resins.

Acid Etching, Dental↗

PubMed2003

Microtensile bond strength of total-etch and self-etching adhesives to caries-affected dentine.

OBJECTIVES: To evaluate the microtensile bond strength of total-etch or self-etch adhesives to caries-affected versus normal dentine, and to correlate these bond strengths with DIAGNOdent laser fluorescence and Knoop microhardness (KH) measurements of the substrates. METHODS: Extracted carious human molars were ground to expose flat surfaces where the caries lesion was surrounded by normal dentine. Surfaces were bonded with either Prime & Bond NT, Scotchbond 1, Clearfil SE Bond or Prompt L-Pop, according to manufacturers' recommendations. A crown was built up using resin composite (Tetric Ceram). After storage in water (37 degrees C, 24 h), teeth were vertically serially sectioned into 0.7 mm thick slabs and trimmed to yield 1 mm(2) test area that contained either caries-affected or normal dentine. Samples were tested in tension in an Instron machine at 1 mm/min. The quality of the dentine just beneath each fractured specimen was measured by laser fluorescence and KH. RESULTS: Total-etch adhesives yielded higher bond strengths than self-etching systems. Significantly lower results were obtained with Prompt L-Pop. All the adhesives attained higher strengths in normal than in caries-affected dentine, but the differences were only significant for Prime & Bond NT and Clearfil SE Bond. Higher laser fluorescence values and lower KH (p<0.001) were recorded in caries-affected dentine compared to normal dentine. CONCLUSIONS: The total-etch adhesives evaluated produced higher bond strengths to normal and caries-affected dentine than self-etching systems. Laser fluorescence measurements discriminated caries-affected dentine from normal dentine, and were strongly correlated with KH. However, laser fluorescence and KH did not permit high correlations with resin-dentine bond strengths in caries-affected dentine.

Acid Etching, Dental↗

PubMed2002

Cervical tooth wear and sensitivity: erosion, softening and rehardening of dentine; effects of pH, time and ultrasonication.

BACKGROUND: Cervical dentine wear is commonly observed and may be associated with dentine hypersensitivity. Erosion is thought to play a part in both conditions but compared to enamel has been little studied in dentine. AIM: The aims of these studies in vitro were to: (i) determine the effects of citric acid on dentine at different pH values and over time; (ii) measure the depth of dentine demineralisation or softening using ultrasonication; (iii) determine whether softened dentine can be remineralised or rehardened using artificial saliva. METHODS: Groups of flat dentine specimens prepared from unerupted human third molar teeth were: (a) exposed to citric acid at pH 3.2 for periods up to 4 h with mineral water as control; (b) exposed to citric acid at pH 2.54, 3.2, 4.5, 5.5 and 6.0 for 2 h and then subjected to ultrasonication stepwise up to 480 s; (c) exposed to citric acid at pH 2.54, 3.2, and 4.5, placed into artificial saliva for 24 h and then subjected to ultrasonication as in (b). Loss of dentine was measured by profilometry, after, each phase of erosion, ultrasonication and immersion in artificial saliva. RESULTS: Depth of erosion significantly increased non-linearly with time and significantly decreased with increasing pH. Ultrasonication had minimal albeit significant effects on control specimens. Removal of softened dentine increased with ultrasonication time. Depth of softening significantly increased with increasing erosion time to 2 h, plateauing at 2 microm. Depth of softening increased to 2 microm from pH 2.54 to pH 3.2 and decreased at higher pH values thereafter. 24 h in artificial saliva provided no protection to the soften zone against ultrasonicaion. Citric acid at all pH values and exposure times removed the dentine smear layer to expose tubules. Ultrasonication did not remove the smear layer on control specimens but removed all deposits formed after exposure to artificial saliva. CONCLUSION: It is concluded that dentine is susceptible to erosion even at relatively high pH, the tubule system is readily exposed and dentine, unlike enamel, shows little propensity to remineralise.

Analysis of Variance↗

PubMed2002

Effect of irrigation solutions on dentin bonding agents and restorative shear bond strength.

STATEMENT OF PROBLEM: The presence of irrigation solution prior to the application of dentin bonding agents may be one source of contamination and may adversely affect bond strength. PURPOSE: The purpose of this in vitro investigation was to evaluate the effect of irrigation solutions of different purity levels on the shear bond strength of a hybrid composite to dentin. MATERIAL AND METHODS: Forty extracted, intact human molars were hand-scaled. All soft tissue was removed, and the teeth were stored in room-temperature tap water for 1 week. Subsequently, each tooth was embedded in autopolymerizing acrylic resin with the coronal portion exposed. After complete polymerization of the resin, the dentin surfaces were exposed, and the crown was cut longitudinally on all 4 sides to produce flat dentin surfaces for bonding. The prepared specimens were assigned to 4 groups of irrigation solutions: tap water (control), sterile water, 0.9% NaCl irrigation solution, and filtered water. Within each irrigation group were 4 dentin bonding agent subgroups: Prime & Bond NT, One-Step, Single Bond Adhesive, and OptiBond Solo. The dentin surfaces (n = 10 per irrigation/bonding agent pair) were etched with 37% phosphoric acid, rinsed with the assigned irrigation solution for 15 seconds, and then dried. Plastic cylinders (3 mm long x 3 mm inner diameter) were filled with a hybrid composite (Herculite XRV) and bonded to the dentin. Specimens were loaded in a universal testing machine, and shear force was applied to the base of the composite cylinders, parallel to the dentin surfaces, at a crosshead speed of 0.05 in/min until fracture. Failure loads were recorded. Bond strength data were compared with analysis of variance (P<.05). Post-hoc comparisons of means were performed with t tests and P values adjusted for multiple comparisons (Bonferroni method). RESULTS: Tap water irrigation (control) produced no significant difference in bond strengths for all dentin bonding agents tested. When other irrigation solutions were used, One-Step consistently produced significantly lower bond strengths than other dentin bonding agents (P<.05). No preferential choice of irrigation solution could be made for Prime & Bond or Single Bond Adhesive. However, when One-Step or Solo was used, irrigation with normal saline significantly reduced bond strengths (P<.05). CONCLUSION: Within the limitations of this study, the bond strength to dentin of a hybrid composite irrigated with different solutions was dependent on the dentin bonding agent used.

Acid Etching, Dental↗

PubMed2006

Short- and long-term in vitro study of the bonding of eight commercial adhesives to normal and deproteinized dentin.

OBJECTIVE: The aims of this study were to investigate the influence of deproteinization of dentin on the shear bond strength (SBS) mediated by eight dentin adhesives, and to evaluate the long-term durability of the SBSs. The hypotheses were that deproteinization of dentin would not affect the capacity for adherence, and that in contrast to the SBSs to collagen-rich surfaces, the SBSs to deproteinized surfaces would be stable during a 1-year period of storage in water. MATERIAL AND METHODS: Ground surfaces of human dentin were either rinsed with water (normal dentin) or treated with sodium hypochlorite (deproteinized dentin). The dentin surfaces were analyzed by Fourier transform-infrared spectroscopy (FT-IR) using horizontal attenuated total reflectance (HATR). In addition, the SBS to normal and deproteinized dentin treated with the adhesives was measured after 24 h or 1 year of storage in water. RESULTS: The IR absorption peaks at approximately 1,640, 1,560, and 1,240 cm(-1) were assigned to the collagen matrix and peaks at about 1,000 cm(-1) were assigned to the phosphate group in hydroxyapatite. From the relative magnitude of the peaks, it was determined that the utilized deproteinization method was effective. Furthermore, the normal dentin group showed SBS values ranging from 10 to 39 MPa and the deproteinized dentin group showed SBS values ranging from 13 to 30 MPa. CONCLUSIONS: According to the statistical analysis, the results only partly supported the hypotheses: it was found that the influence on bond strength of deproteinization of dentin surfaces and the effect of 1 year of storage in water depended on the composition of the dentin adhesive.

Acid Etching, Dental↗

PubMed2003

Efficacy of a resin coating on bond strengths of resin cement to dentin.

PURPOSE: The aims of this study were to (1) evaluate the effect of a resin coating consisting of a dentin bonding system and a flowable resin composite on the microtensile bond strength (micro-TBS) of a resin cement to dentin in indirect composite restorations and (2) compare the bond strengths of direct and indirect composite restorations. MATERIALS AND METHOD: Occlusal surfaces of human premolars were ground to obtain flat dentin surfaces and were divided into seven groups. For indirect restorations, the dentin surfaces of the experimental groups were bonded with a dentin bonding system (DBS), Clearfil SE Bond (SE) or Single Bond (SB) with and without a flowable resin composite, Protect Liner F (PLF), temporized for one day and cemented with a resin cement (Panavia F) according to the manufacturer's instructions. The dentin surfaces of the control group were temporized without prior treatment, and indirect composite (Estenia) was bonded with Panavia F. For the direct restorations, either SE or SB was applied to the dentin surface and the entire surface was built up with direct composite (Clearfil AP-X). After 24 hours in water storage, micro-TBS was measured at a crosshead speed of 1 mm/min. The data were analyzed with one-way analysis of variance and Fisher's protected least significant difference test (p < .05). RESULTS: The original bond strength of the resin cement (Panavia F) to dentin significantly improved with the use of a resin coating technique in indirect restorations (p < .05). The combination of DBS + PLF showed significantly higher bond strengths compared with the single use of DBS. The combination of SE + PLF as a resin coating provided the highest bond strengths in indirect restorations (p < .05). However, the best bond strengths were observed when SE and SB were used for direct composite restorations (p < .05). CONCLUSIONS: The application of a resin coating consisting of a dentin bonding system and a flowable resin composite on the dentin following cavity preparation significantly improved the micro-TBS of the resin cement Panavia F to dentin in indirect restorations. However, the bond strengths of indirect composite restorations were significantly lower than those of direct composite restorations even with the resin coating technique. CLINICAL SIGNIFICANCE: Indirect composite restorations may require a resin coating to improve the bonding performance of the resin cement Panavia F to dentin. However, adhesive systems with direct composite restorations still provide superior bond strengths compared with indirect restorations.

Analysis of Variance↗

PubMed2001

Study of dentinal tubule architecture of permanent upper premolars: evaluation by SEM.

Dentinal tubules are the means by which the pulp and mineralised tissues surrounding the dentine (enamel and cementum) communicate. Through these tubules external agents can damage the pulp and subsequently the periodontal ligament. Given the importance of dentinal tubules, the authors evaluated the numerical density, shape, and individual surface area of tubule openings and the percentage of dentine occupied by these. Eight permanent upper premolars were studied using scanning electron microscopy (SEM). In the crown, the external surface of the dentine was evaluated at the dentino-enamel junction and the internal surface at the pulp chamber wall. At the cervical, middle and apical thirds of the root, the external surface was evaluated at the cemento-dentinal junction and the internal surface at the root canal wall. The results showed that numerical density of tubule openings is significantly greater (p < 0.05) at the cervical third of the dentine, at its junction with the cementum and at the pulpal chamber wall, with respect to other areas evaluated. The individual surface area of each opening varied from 5.72 microns 2 in the dentine of the pulpal chamber wall to 0.97 micron 2 in the dentine of the apical third of the root canal wall. The percentage of area occupied by the dentinal tubules per mm2 of dentine was significantly higher (p < 0.01) at the internal dentinal surface as compared to the external. The shape of the tubule openings was found to be circular in the crown and became more irregular as the apical third of the root was approached.

Adolescent↗

PubMed2006

Dentin-pulp complex responses to carious lesions.

To understand the molecular events underlying the dentin-pulp complex responses to carious progression, we systematically analyzed tissue morphology and dentin matrix protein distribution in non-carious teeth and in teeth with enamel and dentin caries. Dentin matrix proteins analyzed included collagen type I, phosphophoryn (PP) and dentin sialoprotein (DSP), all of which play decisive roles in the dentin mineralization process. Human non-carious and carious third molar teeth were freshly collected, demineralized, and processed for hematoxylin and eosin staining. The ABC-peroxidase method was used for immunohistochemical staining of collagen type I, PP and DSP proteins using specific antibodies. In situ hybridization was also performed. In contrast to elongated odontoblasts in non-carious teeth, odontoblasts subjacent to dentin caries were cuboidal and fewer in number. The predentin zone was also dramatically reduced in teeth with dentin caries. The staining intensity for collagen type I, PP and DSP in the dentin-pulp complex increased progressively from non-carious teeth, to teeth with enamel and dentin caries. In situ hybridization studies showed DSP-PP mRNA expression in odontoblasts and dental pulp that was consistent with our immunohistochemical results. These results suggest that carious lesions stimulate the dentin-pulp complex to actively synthesize collagen type I, PP and DSP proteins. This response to carious lesions is likely to provide a basis for reparative and/or reactionary dentin formation.

Animals↗

PubMed1995

Scanning transmission electron microscopy/energy-dispersive spectroscopy analysis of the dentin adhesive interface using a labeled 2-hydroxyethylmethacrylate analogue.

In an attempt to compare the morphology of the dentin adhesive interface and the wetting and penetration of the adhesive in relation to the dentin surface, we studied four dentin adhesive systems using scanning transmission electron microscopy (STEM) and energy-dispersive spectroscopy (EDS). 2-Hydroxyethylmethacrylate (HEMA), a monomer common to many commercial dentin adhesive systems, was altered to produce a thiolated analogue (HETMA). Sulfur, traceable by EDS and STEM, was substituted for the oxygen atom in the backbone of the HEMA molecule. The resulting analogue, with solubility parameters and other wetting and physical properties very similar to those of HEMA, was applied to four sets of tooth specimens, each pre-treated with a different primer or etchant. Three separate pre-treatments--nitric acid, maleic acid, and citric acid/ferric chloride--created a demineralized zone approximately 1 to 3 microns thick at the dentin surface. The HETMA was found to permeate freely into this zone when either of the latter two pre-treatments was used. However, the band of dentin that was demineralized by the nitric acid pre-treatment appeared impermeable to the HETMA. The fourth pre-treatment, an alcohol-based solution including the phosphorus acid ester PENTA and HEMA, modified the smear layer of the tooth slightly and did not appear to demineralize the dentin. HETMA applied to the specimens pre-treated with PENTA and HEMA was clearly in intimate contact with the dentin or modified smear layer; however, it did not penetrate or diffuse into these areas. It did flow into the dentinal tubules, as was also evident with each of the other systems. It was concluded that the acid pre-treatment of the dentin greatly influenced the wetting behavior of the dentin adhesive and thus could substantially affect the resultant bond strength of the dentin adhesive systems.

Acid Etching, Dental↗