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PubMed2000

Differences in bonding to acid-etched or Er:YAG-laser-treated enamel and dentin surfaces.

STATEMENT OF PROBLEM: Er:YAG (erbium-doped yttrium aluminium garnet) lasers have been effective in the removal of dental tissues. It has been suggested that they are also useful for preparing dental surfaces for adhesion, but results to date have been controversial. PURPOSE: This study compared the tensile strength of bracket-tooth bonds obtained after preparation of the surface for adhesion (dentin or enamel) by conventional acid-etching or by Er:YAG laser etching and investigated microstructure of resin-tooth interfaces using the 2 procedures. MATERIAL AND METHODS: Eighty healthy human premolars were used. Brackets were cemented to acid-etched enamel, laser-etched enamel, acid-etched dentin, or laser-etched dentin (20 teeth per group). Dentin was previously exposed using a high-speed handpiece. Acid-etching was with 37% orthophosphoric acid (15 seconds for enamel, 5 seconds for dentin). Laser etching was with Er:YAG laser (four 200 mJ pulses per second for enamel; four 160 mJ pulses per second for dentin). Brackets were bonded with autocuring resin paste, having first applied a primer (dentin only) and then light-cured bonding resin. Tensile strength was determined with a universal testing machine. Data were analyzed with 2-way ANOVA and subsequent t test with Bonferroni correction. Fracture patterns were compared by the Wilcoxon test with Bonferroni correction. For SEM studies of the resin-tooth interface, a total of 12 premolars were used (3 for each tissue per treatment combination). RESULTS: Mean tensile bond strength for acid-etched enamel (14.05 +/- 5.03 MPa) was significantly higher (P<.05) than for laser-etched enamel (8.45 +/- 3.07 MPa), and significantly higher (P<.05) for acid-etched dentin (4.70 +/- 2.50 MPa) than laser-etched dentin (2.48 +/- 1.94 MPa). Bond failure after laser etching was due to microcohesive fracture of tooth tissue. SEM studies of both resin-enamel and resin-dentin interfaces indicated extensive subsurface fissuring after laser etching. CONCLUSION: Adhesion to dental hard tissues after Er:YAG laser etching is inferior to that obtained after conventional acid etching. Enamel and dentin surfaces prepared by Er:YAG laser etching show extensive subsurface fissuring that is unfavorable to adhesion.

Acid Etching, Dental↗

PubMed1993

A comparison of the dentine-removing characteristics of two endosonic units.

The purpose of this study was to compare the dentine-removing characteristics of size 25 K-files activated by the Cavi-Endo and Piezon-Endo units. The influence of power-setting, direction of file oscillation, interfacial force and operator-assisted movement were studied. Filing was performed on flat surfaces of dentine and impressions of the instrumented surfaces revealed characteristic patterns of dentine removal corresponding to the area of contact with the file which was quantified using a Reflex microscope. Differences in dentine removal as affected by the power output of the two systems were only apparent when the maximum power-setting on the Cavi-Endo was compared with the maximum recommended for root canal preparation on the Piezon-Endo. The Cavi-Endo removed significantly more dentine than the Piezon-Endo. When operator-assisted movement of the file was superimposed, both systems removed significantly more dentine than without assisted filing, However, the Piezon-Endo now removed significantly more dentine than the Cavi-Endo. This difference was more apparent when the file oscillated perpendicular to the dentine surface, compared with oscillation parallel to the substrate. An increase in the interfacial force from 30 g to 60 g resulted in a greater reduction in dentine removal by the Cavi-Endo compared with the Piezon-Endo. Thus, at a 30 g interfacial force there were insignificant differences between the endosonic units but at 60 g, the Piezon-Endo removed significantly more dentine than the Cavi-Endo. The dentine-removing characteristics of the two endosonic units tested are very different under certain conditions. These findings may have important clinical implications.

Dental Cavity Preparation↗

PubMed1995

A structural analysis of approximal enamel caries lesions and subjacent dentin reactions.

The present study examines the correlation between caries lesions in enamel and the corresponding dentin reactions in proximal tooth surfaces with lesions ranging from enamel lesions to cavitations without dentin exposure. Using quantitative imbibition technique, the highest degree of tissue porosity, irrespective of lesion activity, was always noted along a Central-Traverse (CT), which followed the direction of the rods from the deepest point of penetration to the surface. The conical shape of approximal enamel lesions can thus be seen as the result of systematic variations in porosity along the rods determined by the specific interproximal environment. The initial dentin reaction, related to the enamel lesion approaching the enamel-dentin junction (EDJ), was seen as a local dentin translucency where the CT crossed the EDJ. Results from histomorphometric analyses revealed that, when the enamel lesions reached the EDJ, brownish discoloration in the dentin never exceeded the histologic contact area between the enamel lesion and the EDJ. In relation to the less advanced parts of the individual enamel lesion, the dentin responded with formation of translucent dentin. These reactions did not occur beyond an area determined by lines in the direction of the rods from the peripheral part of the enamel lesion towards the EDJ. The results did not support the view that dentin caries spreads along the enamel-dentin junction. The peripheral dentin translucency is therefore generated by stimuli transmitted along the rods of the less advanced parts of the enamel lesions.

Adolescent↗

PubMed1991

Adhesion to bovine dentin--surface characterization.

X-ray photo-electron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS) were used to characterize the dentin surface, to determine the effects of different pre-conditioning procedures on the elemental composition of the dentin surface, and to investigate the interaction between dentin and a dentin bonding agent (ScotchBond) by studying the changes in the elemental composition of dentin as a result of the interaction. Scanning electron microscopy (SEM) was used to characterize sample surface morphology, which was then correlated with surface elemental composition. The results showed that: (a) the elemental composition of the smear layer was similar to that of the underlying dentin; (b) cleaning with hydrogen-peroxide did not produce any modification in the elemental composition of the dentin surface; and (c) acid-etching led to an almost complete demineralization of the dentin, leaving behind an organic-rich surface. The results suggest that bonding systems that use acid-etching as a pre-conditioning procedure should be based on agents able to interact with the organic components of dentin, since bonding agents that rely on a chelation-to-calcium reaction are unlikely to be successful. The investigation of the interaction between the bonding agent and dentin led to a postulated adhesive-bonding reaction mechanism and suggested a partially cohesive failure in the bonding agent during fracturing of a dentin-bonding-agent-bonded assembly.

Acid Etching, Dental↗

PubMed1995

Cytotoxic interactive effects of dentin bonding components on mouse fibroblasts.

Previous studies have shown a wide range of pulpal reactions to dentin bonding systems and a poor correlation between in vitro and in vivo toxicity of dentin bonding agents. Because dentin bonding agents are composed of multiple components which may diffuse through dentin, we hypothesized that these components may cause cytotoxicity through interactive (synergistic) effects. We investigated the cytotoxicities of four dentin bonding components--HEMA, Bis-GMA, TEGDMA, and UDMA--and interactive effects for three binary combinations of the dentin bonding components--HEMA and Bis-GMA, Bis-GMA and TEGDMA, and TEGDMA and UDMA. Cytotoxicities to Balb/c 3T3 mouse fibroblasts were measured by the MTT assay. Concentrations which caused 50% toxicity compared with controls (TC50 values) were compared, and the interactive effects were determined by evaluation of the differences between observed and expected MTT activities of the cells. The ranks of toxicity of the dentin bonding components in terms of TC50 values were as follows: Bis-GMA > UDMA > TEGDMA >>> HEMA (least toxic) after 24- and 72-hour exposures. As binary combinations, the three combinations of dentin bonding components interacted in three ways--synergism, additivism, and antagonism--which were influenced by the concentrations of both components. The longer period of exposure resulted in a significant increase in the cytotoxicity of the dentin bonding components and combinations. The findings indicate that both exposure time and the interactions between the dentin bonding components may be important parameters in determining the cytotoxicity of dentin bonding agents in vivo.

3T3 Cells↗

PubMed1979

Innervation of different parts of the predentin and dentin in young human premolars.

The innervation of the predentin and inner part of the mineralized dentin was studied at the ultrastructural level in ten premolars. Each tooth was divided into fifteen different parts, each containing odontoblasts, predentin and dentin. It was found that the innervation in the coronal dentin was more compact than in the root dentin. Within the coronal dentin itself, the most densely innervated area was the dentin covering the pulp horns. No nerves were identified more than 100 microns from the pulp-dentinal border. No nervous structures were found in the mineralized dentin of the root. Nervous structures which seemed to have no connection with the odontoblastic processes were frequently observed in the predentin of the root. Signs of degeneration of the nervous structures of the predentin of the root was also a common finding. The observation that the intradentinal nerves were confined to the predentin and the most pulpal part of the dentin supports the theory that surface stimulation on dentin has an indirect effect on the nerves activated by movements in the liquid of the dentinal tubules.

Adolescent↗

PubMed2001

Effect of different conditioning protocols on adhesion of a GIC to dentin.

PURPOSE: This study examined the ultrastructure and microtensile bond strength (microTBS) of a restorative glass-ionomer cement (GIC; Dentsply) to sound dentin that was conditioned with various techniques. MATERIALS AND METHODS: Dentin surfaces from extracted human third molars were abraded with 180-grit SiC paper. Five groups of three teeth each were prepared: C - no acid pretreatment (control); P - 10% polyacrylic acid (PAA) for 10 s, no rinsing; R - 10% PAA for 20 s, rinsed; K - 25% PAA for 25 s, rinsed; and H -32% phosphoric acid for 15 s, rinsed. TEM was performed on a bonded specimen from each group, using unstained, undemineralized sections. GIC buildups were made on the remaining teeth, and after storage at 100% humidity for 24 h, the teeth were sectioned for microTBS and SEM evaluation. RESULTS: TEM revealed the presence of a structure known as the intermediate layer in all groups. This layer contains metallic salts contributed by both the GIC and dentin. In group C, this layer was restricted to the smear layer. In groups P and R, intermediate layers could be found above partially demineralized zones within the intertubular dentin. In groups conditioned with more aggressive protocols (K and H), the intermediate layers shifted downward to reside within the superficial portions of completely demineralized collagen. Group C had statistically lower microTBS (p < 0.05), while the other groups were not significantly different from each other. SEM revealed adhesive failures along the dentin surface in group C and mixed failures in the other groups. CONCLUSION: The lower microTBS observed in the control group reflects the weakness of the smear layer attachment to dentin. The higher microTBS in the other groups probably represent the cohesive strength of GIC under tension, rather than its true adhesive strength to dentin. Acid pretreatment dissolves the smear layer, creates a zone of partially demineralized dentin, and allows the PAA to interact with dentin via the intermediate layer. Overly aggressive conditioning renders the dentinal tubules patent, and leaves deeper demineralized dentin that does not form part of the intermediate layer.

Acid Etching, Dental↗

PubMed2003

Effects of chloramines and sodium hypochlorite on carious dentin.

In chemo-mechanical caries removal procedures, chloramines are typically used for chemical softening of carious dentin. However, the specific effect of chloramines to be compared to sodium hypochlorite has not been sufficiently clarified. In present study, the effect of chloramines used in the Carisolv-system on carious dentin mechanical properties and morphology were investigated, using Vickers hardness test and scanning electron microscopy (SEM). Sections of permanent teeth with dentin caries were treated with chloramines, prepared by mixing amino acids (glutamic acid, lysine, and leucine) with sodium hypochlorite or with sodium hypochlorite alone or with purified water. There was a tendency that the application of the sodium hypochlorite solution softened the sound dentin and/or inner layer of carious dentin more than the application of the chloramines solution did. In SEM observations, the application of chloramines resulted in opening dentinal tubules in the outer layer of carious dentin: Occluded dentinal tubules were seen after sodium hypochlorite application. There is a possibility that the amino acids in the Carisolv-system decrease the aggressive effect of sodium hypochlorite on sound dentin and/or inner layer of carious dentin and also would enhance the disrupting effect on degenerated collagen in carious dentin outer layer.

Cariostatic Agents↗

PubMed1990

[SEM investigations on the human sclerosed dentinal tubules].

Sclerotic changes of dentinal tubules appeared in the dentin beneath the carious, attrition and abrasion lesions and in the transparent root dentin were investigated using the scanning electron microscopy. 1) Shape of crystal-like substances appeared in the dentinal tubules could not be closely related to kinds of dentin destruction. 2) In the dentinal tubules beneath the carious lesions, cuboidal or rhomboid-shaped, short rod-like, long rod-like, plate-like and droplet-like crystals were mainly observed. Combination of cuboidal or rhomboid-shaped and short rod-like crystals or that of long rod-like and plate-like crystals were most frequently observed. 3) In the dentinal tubules beneath attrition and abrasion lesions, cuboidal or rhomboid-shaped, short rod-like and droplet-like crystals were mainly observed, however, the size of cuboidal or rhomboid-shaped crystal was usually smaller than that observed beneath carious lesion and they deposited compactly within the tubules. 4) In the sclerosed dentinal tubules in the transparent root dentin, compact deposition of rhomboid-shaped and irregular sand-like crystals were usually observed. Size of rhomboid-shaped crystal is smaller than that observed beneath carious lesion. The deposit of sand-like crystal in the tubules was easily discriminated from the matrix of peritubular dentin. 5) In any case, the kinds of crystals and pattern of deposition were not necessarily same between the neighboring tubules. However, in a tubule, they were almost same in shape and mode of deposition throughout the entire length of tubule from the outer side to the pulpal side. These facts seem to indicate that mineral deposition within the tubule due to sclerosis is performed under individual condition. 6) Finding showing biological control of mineral deposition within the dentinal tubules by the odontoblasts could not be observed.

Calcinosis↗

PubMed1989

Dentin: a dynamic substrate--a review.

The structure of dentin is unusual in that the number and size of its tubules changes as one moves from the periphery toward the pulp chamber. Near the pulp, the tubules are very close together and the water content of this deep dentin is high. Near the enamel, the tubules are far apart, occupying less than 1% of the surface area. When enamel or dentin is cut, the surface becomes covered by an adherent layer of cutting debris called the smear layer. Its composition presumably reflects the composition of the underlying dentin. It is only about 1 micron thick but its presence modifies the function of the dentin a great deal. It lowers dentin permeability and therefore can be regarded as protective. However, it masks the underlying dentin and hence interferes with attempts to bond dental materials directly to dentin. If it is removed, the dentin becomes much more permeable and fluid shifts across the open tubules can cause sensitivity in vivo. As smear layers are very acid-labile, they often dissolve in oral fluids. Several attempts have been made to replace smear layers with acid resistant structures that accomplish the same function. Smear layer structure is being studied by using both scanning electron microscopy as well as electronic particle sizing equipment. The close adaptation of dental materials to smear layers and to underlying dentin is currently an area of very active research. Removal of smear layers increases adaptation and bonding strength but may increase the incidence of pulpal inflammation if the bonding is not uniform or permanent. The dynamics of dentin are just beginning to be understood.

Dental Restoration, Permanent↗

PubMed2006

Oxalate-containing phytocomplexes as dentine desensitisers: an in vitro study.

It is known that pulpal fluid movement through dentinal tubules causes dentinal hypersensitivity and that pain can be reduced by decreasing the fluid flow. The aim of this study was to evaluate dentinal permeability and morphology after a single exposure to experimental phytocomplex substances containing oxalates. The treatments tested were experimental pastes, gels and solutions of phytocomplexes (extracted from rhubarb, spinach and mint), an experimental paste containing 5% potassium oxalate, and two commercial toothpastes recommended for dentinal hypersensitivity (Elmex and Sensodyne). Dentine discs from human third molars were used in this study. Each sample was brushed for 3 min with each treatment in order to test reductions in dentinal permeability. Each treated sample was challenged with orthophosphoric acid for 90 s to determine changes in dentinal permeability and the sensitivity of treatments to acid challenge. Scanning electron microscopy was used to analyse the samples. This study found that spinach and rhubarb phytocomplex treatments reduced dentinal permeability by occluding dentinal tubules through formation of calcium oxalate crystals. These results indicate that phytocomplexes extracted from rhubarb and spinach, used in different formulations, should be effective for topical treatment of dentinal hypersensitivity.

Amines↗

PubMed1994

Self-etching dentin primers containing phenyl-P.

The dentin bonding efficacies of two commercial dentin bonding systems and experimental self-etching dentin primers composed of methacryloxyethyl hydrogen phenyl phosphate (Phenyl-P) and either hydroxyethyl methacrylate (HEMA) or glyceryl methacrylate (GM,2,3-dihydroxypropyl methacrylate) were examined. The wall-to-wall polymerization contraction gap width of a commercial light-activated resin composite in a cylindrical dentin cavity and the tensile bond strength to a flat dentin surface were measured. Changes in dentin hardness were determined by Micro Vickers Hardness measurement, and an SEM observation was performed after priming. Formation of a contraction gap was completely prevented by the application of Phenyl-P diluted in HEMA or GM solution combined with a commercial dentin bonding agent, although gap formation was evident in nearly half of the specimens with both commercial dentin bonding systems. The mean tensile bond strengths of the tested groups varied from 16.3 to 20.7 MPa, and there were no significant differences between groups. Based on the measurement of Micro Vickers Hardness and SEM observation after priming, a slight reduction in dentin hardness was observed. However, this reduction in dentin hardness due to self-etching priming did not significantly correlate with either contraction gap width or tensile bond strength.

Acid Etching, Dental↗

PubMed1995

Effects of fluoride on the calcium phosphate precipitation method for dentinal tubule occlusion.

Use of the calcium phosphate precipitation (CPP) method makes possible the occlusion of dentinal tubules to approximately 10 to 15 microns from the dentinal surface, and thus shows good potential for the treatment of dentin hypersensitivity. The precipitate formed in the dentinal tubules by the CPP method is, however, not apatite [HAP; Ca10(PO4)6(OH)2], a component of tooth and bone, but dicalcium phosphate dihydrate (DCPD; CaHPO4.2H2O). Since fluoride enhances the conversion of DCPD to HAP, we evaluated the effects of fluoride on the texture of the precipitate formed by the CPP method and on its capacity to occlude dentinal tubules in this in vitro study. CPP solution (1.0 mol/L CaHPO4.2H2O dissolved in 2.0 mol/L H3PO4) was applied to a dentin disk and was subsequently neutralized with a post-treatment solution (1 mol/L NaOH, from 0 to 0.1 mol/L NaF). Scanning electron microscopy revealed that the precipitate occluded dentinal tubules to a depth of approximately 10 to 15 microns from the dentinal surface, regardless of the NaF concentration (from 0 to 0.1 mol/L) in the post-treatment solution. Also, dentin permeability was reduced to 15% by the CPP treatment regardless of the NaF concentration. The Ca/P molar ratio of the precipitate, measured by x-ray micro-analysis, was higher (1.25 +/- 0.04) in the presence of NaF than in its absence (1.03 +/- 0.01). For further identification of the precipitate formed in the dentinal tubules, the same procedure was used in glass tubes (diameter, 1 mm), so that a larger amount of precipitate would be obtained.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium Phosphates↗

PubMed1996

Dynamics of the pulpo-dentin complex.

Dentin has a relatively high water content due to its tubular structure. Once dentin is exposed, this intratubular water is free to move in response to thermal, osmotic, evaporative, or tactile stimuli. Fluid shifts across dentin are thought to cause sufficient shear forces on odontoblasts, nerve endings, nearby fibroblasts, and blood vessels to cause significant mechanical irritation, disruption, or damage, depending on the magnitude of the fluid shift. Even in the absence of fluid shifts, the water-filled tubules provide diffusion channels for noxious (i.e., bacterial products) substances which diffuse inward toward the pulp, where they can activate the immune system, provide chemotactic stimuli, cytokine production, and produce pain and pulpal inflammation. Viewed from this perspective, dentin is a poor barrier to external irritants. However, pulpal tissues react to these challenges by increasing the activity of nerves, blood vessels, the immune system, and interstitial fluid turnover, to make the exposed dentin less permeable either physiologically, via increased outward fluid flow, or microscopically, by lining tubules with proteins, mineral deposits, or tertiary dentin, thereby enhancing the barrier properties of dentin, and providing additional protection to pulpal tissues. These reactions involve dentin and pulp, both in the initiation of the processes and in their resolution. These responses of the dental pulp to irritation of dentin demonstrate the dynamic nature of the pulpo-dentin complex.

Bacterial Toxins↗

PubMed2002

Invasion of dentinal tubules by oral bacteria.

Bacterial invasion of dentinal tubules commonly occurs when dentin is exposed following a breach in the integrity of the overlying enamel or cementum. Bacterial products diffuse through the dentinal tubule toward the pulp and evoke inflammatory changes in the pulpo-dentin complex. These may eliminate the bacterial insult and block the route of infection. Unchecked, invasion results in pulpitis and pulp necrosis, infection of the root canal system, and periapical disease. While several hundred bacterial species are known to inhabit the oral cavity, a relatively small and select group of bacteria is involved in the invasion of dentinal tubules and subsequent infection of the root canal space. Gram-positive organisms dominate the tubule microflora in both carious and non-carious dentin. The relatively high numbers of obligate anaerobes present-such as Eubacterium spp., Propionibacterium spp., Bifidobacterium spp., Peptostreptococcus micros, and Veillonella spp.-suggest that the environment favors growth of these bacteria. Gram-negative obligate anaerobic rods, e.g., Porphyromonas spp., are less frequently recovered. Streptococci are among the most commonly identified bacteria that invade dentin. Recent evidence suggests that streptococci may recognize components present within dentinal tubules, such as collagen type I, which stimulate bacterial adhesion and intra-tubular growth. Specific interactions of other oral bacteria with invading streptococci may then facilitate the invasion of dentin by select bacterial groupings. An understanding the mechanisms involved in dentinal tubule invasion by bacteria should allow for the development of new control strategies, such as inhibitory compounds incorporated into oral health care products or dental materials, which would assist in the practice of endodontics.

Animals↗

PubMedDate not supplied

Effect of cutting instruments on permeability and morphology of the dentin surface.

There are major differences in morphological detail after cutting the dentin surface among the methods commonly used to prepare dental cavities. The purpose of this study was to compare dentin permeability and the morphology of the dentin surfaces prepared with diamond and carbide steel burs after etching with 6% citric acid. Twenty-four freshly extracted human third molars were sectioned, mounted on plexiglass, and connected to the dentin-permeability measuring apparatus. The permeability of dentin was measured by fluid filtration and expressed as hydraulic conductance. There were two study groups of 12 teeth. Each tooth had one occlusal cavity preparation prepared but utilized three depths: the original was prepared just into the dentin, the second 0.5 mm deeper than the first, and the third 0.5 mm deeper than the second. One group had the first cavity prepared with a diamond, the second deepened using a steel bur, then the third depth was made by use of the diamond. The other group had the first cavity preparation prepared with a steel bur, deepened 0.5 mm again using a diamond, then deepened again using a steel bur. Dentin permeability was measured after cavity preparation, then after 2 minutes of acid etching. Analysis of variance and Duncan's multiple range test were used to establish whether differences were significant at the 0.05 confidence level. Prepared and acid-etched surfaces were characterized using a scanning electron microscope to identify any differences between the two groups. After acid etching with 6% citric acid, the permeability of dentin cavities prepared with diamond burs was significantly less than the permeability of cavities prepared with carbide steel burs. After etching, there were differences in the appearance of the dentin surfaces prepared with diamonds and steel burs. Dentin bonding agents may have their effectiveness reduced when placed following cavity preparation by use of a diamond.

Dental Bonding↗

PubMed1999

Calcium phosphates produced by physical methods in the treatment of dentin hypersensitivity.

BACKGROUND: The aim of this paper is to study the properties of innovative materials based on defective calcium phosphates produced by physical methods in the therapy of dentin hypersensitivity. METHODS: In particular, the effects of gels, aqueous solutions and toothpastes containing the above mentioned materials on dentinal permeability measured as dentin hydraulic conductance have been studied. The calcium phosphates have been characterized by X-ray powder diffraction (Rietveld analysis) and Fourier transform infra-red analysis. In addition, scanning electron microscopy has been performed to study the surface of dentin and enamel after treatment with the phosphates. In particular sound occlusal dentin, sound cervical dentin, carious occlusal dentin, sound buccal enamel and carious buccal enamel have been observed. RESULTS: The results have shown that these biocompatible materials can be produced with chemical and physical characteristics very similar to dentin and/or enamel. By forming a protective layer inside and outside the dentin tubuli, the calcium phosphates significantly reduce the dentinal hypersensitivity. CONCLUSIONS: These phosphates seem to be a promising material for clinical application.

Calcium Phosphates↗

PubMed2002

Influence of NaOCl deproteinization on shear bond strength in function of dentin depth.

PURPOSE: To determine the influence of NaOCl application on shear bond strengths (SBS) to superficial and deep dentin, using Prime & Bond 2.1. MATERIALS AND METHODS: Superficial and deep dentin was exposed in 40 extracted third molars by sectioning the occlusal surface immediately under the enamel-dentin junction or close to the pulp chamber. After polishing the dentin disks (600-grit SiC), they were assigned to two groups: (1) 36% orthophosphoric acid for 15 seconds, or (2): 36% orthophosphoric acid for 15 seconds followed by 5% sodium hypochlorite (NaOCl) for 2 minutes. The dentin adhesive was applied as per manufacturer's instructions, followed by TPH resin-based composite. The specimens were stored in water for 24 hours at 37 degrees C and thermocycled x500 and SBS were determined. Data were statistically analyzed with ANOVA and Student's t-test. RESULTS: For acid-etched specimens, superficial dentin resulted in statistically higher mean SBS than deep dentin. After NaOCl application, deep and superficial dentin resulted in statistically similar mean SBS. Collagen removal did not affect mean SBS on superficial dentin, while SBS values on deep dentin were increased.

Acetone↗