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PubMed2004

Morphologic study of Nd:YAG laser usage in treatment of dentinal hypersensitivity.

Our previous in vitro study indicated that Nd:YAG laser irradiation on dentin could melt normal dentin surface and close the exposed dentinal tubule orifices without creating surface cracks. This study evaluated the morphologic changes of hypersensitive dentin after Nd:YAG laser irradiation. Thirty patients with clinically diagnosed cervical dentin hypersensitive teeth were treated with a Nd:YAG laser of 30 mJ intensity at 10 pulses per second for 2 min. An impression of the sensitive area was taken before and after laser treatment and then examined with a scanning electron microscope. The impression of the dentin surface after Nd:YAG laser treatment showed no protrusive rods, in contrast with the presence of numerous rods before laser irradiation. Because protrusive rods are a measure of open dentinal tubules, we interpret these data to support the hypothesis that Nd:YAG laser irradiation at specifications of 30 mJ, 10 pulses per second, and 2 min can be used to seal the exposed dentinal tubules.

Adolescent↗

PubMed1995

Resin bonding efficacy of Gluma 2000 to dentine of primary teeth: an in vitro study.

The aim of this study was to investigate (i) the effect of Gluma 2000 conditioning solution on the dentine of primary teeth, (ii) the penetration of Gluma 2000 adhesive resin into the etched dentine, (iii) the shear bond strength of a composite resin restorative material (Pekafill) bonded with Gluma 2000 to dentine, and (iv) the depth of penetration of adhesive resin into the etched dentine as a function of the conditioning time. Dentine surfaces conditioned for 15, 30, 60 and 120 seconds were examined by scanning electron microscopy. The smear layer was totally removed and, with the longer conditioning times, a fine crystalline precipitation, presumably calcium oxalate, was formed. After Gluma 2000 bonding of composite resin and dissolution of the teeth the resin interface showed excellent penetration into the etched dentine. Shear bond strengths of composite resin bonded with the adhesive resin were similar following conditioning for 15, 30, 60 and 120 seconds. Microphotographs of debonded specimens indicated that the mode of failure was cohesive within the resin. The depth of penetration of resin into etched dentine was determined by scanning electron microscopy, and a linear relationship was found between the thickness of the resin-impregnated layer and conditioning time. It was therefore concluded that depth of resin penetration and shear bond strength are not correlated. The study shows that the Gluma 2000 bonding system produces reliable adhesion of composite resin to dentine of primary teeth.

Acid Etching, Dental↗

PubMed1983

Dentine hypersensitivity--a review. Aetiology, symptoms and theories of pain production.

The exposure of cervical dentine has a multifactorial aetiology and pain may frequently be elicited by a number of stimuli. Management of the condition, dentine hypersensitivity, tends to be empirical because of the lack of knowledge concerning the mechanism of pain transmission through dentine. The pulpal changes associated with the condition and any modulating effect on symptoms are by no means clearly established. Evidence suggests that exposed dentine which is sensitive exhibits patent tubules. The question of how pain is initiated across the dentine has received considerable attention but still remains somewhat debatable. The literature reviewed indicates that, at most, nerve fibres only penetrate a limited distance along some dentinal tubules. The theories that either the odontoblasts and their processes act as dentinal receptors or the nerves in the pulp are the pain receptors, are discussed. Evidence for the stimulation of pulp nerve fibres by a hydrodynamic mechanism would appear the most likely mechanism. Nevertheless, whichever theory proves to be correct, occlusion of dentinal tubules would appear an essential prerequisite for an effective desensitising agent.

Dentin↗

PubMed1989

Human root caries: histopathology of initial lesions in cementum and dentin.

The histopathology of human root caries was examined in extracted teeth by different optical methods. The present part of the study details the sequential stages of initial caries in both cementum and peripheral dentin. Significant differences are shown between the mechanisms operating on the various dental hard tissues during development of caries. Histologically distinguishable reaction patterns depended on both the degree of the cariogenic challenge and the respective structural features of cementum and peripheral dentin. Earliest lesions, histologically visible as small clefts traversing cementum and extending into peripheral dentin, were clinically not detectable. Cementum was stepwise destroyed until peripheral dentin became exposed. The exposed peripheral dentin was sclerosed and tubule-free. Demineralization of dentin preceded the degradation of the organic matrix. Frequently, a hypermineralized layer occurred in both cementum and exposed dentin. Its localization was not identical with the anatomical surface. Initial penetration of bacteria into peripheral dentin occurred along small clefts. Breakdown of the organic matrix was the final step in the destructive phase of the carious process.

Aged↗

PubMed1993

The structure of dentin surfaces exposed for bond strength measurements.

The structure of dentin on three different levels, near enamel, central, and deep dentin, was examined. The solid area available for bonding was studied in a scanning electron microscope (JSM 840) connected to a computer-assisted image analysis instrument (IBAS 2). The number of tubule openings per unit area (frequency) and the area percentages of these tubule openings were recorded. Three dentin disks were obtained from both buccally and occlusally located dentin of a single tooth (third molars were used), and the two deeper levels were each 1.25 mm deeper than the level above. The disks showed an increasing number of tubules with an increasing diameter the deeper into the dentin they were cut. Disks from the occlusal part of the tooth showed, in general, a higher number and area percentage of tubule openings than the corresponding disks from the buccal part. The variation across each disk was also larger for disks from the occlusal part than from the buccal part of the tooth. This variation increased with increasing depth of dentin. The most solid dentin with the lowest variation was found in superficial disks of buccally located dentin.

Dental Bonding↗

PubMed1993

Assessment by nano-indentation of the hardness and elasticity of the resin-dentin bonding area.

The hardness and Young's modulus of the successive layers across a resin-dentin bonding area were determined by nano-indentation for four commercially-available dentin adhesive systems, of which two were also applied with a different conditioning agent. With a computer-controlled nano-indentation technique, minute triangular indentations were made within a small area of a few micrometers' diameter at a load of a few milli-Newtons. The load and displacement of the indenter were continuously monitored during the loading-unloading sequence, so hardness and Young's modulus could be computed as a function of the indenter geometry and the applied load. The hardness of the resin-dentin interdiffusion zone was significantly lower than that of unaltered dentin. A gradient of moduli of elasticity was observed from the rather stiff dentin over a more elastic resin-dentin interdiffusion zone and adhesive resin layer to the restorative composite. That gradient was more substantial in those systems that produced relatively thick adhesive resin layers or supplementally provided a filled low-viscosity resin as an intermediate layer between the adhesive resin and the bulk restorative composite. Such an elastic bonding area might have a strain capacity sufficient to relieve stresses between the shrinking composite restoration and the rigid dentin substrate, thereby improving the conservation of the dentin bond and, as a consequence, the marginal integrity and retention of the restoration.

Composite Resins↗

PubMed2001

Dentin regeneration in vital pulp therapy: design principles.

The nature and specificity of the mechanisms by which the amputated dentin-pulp interface is therapeutically healed determine the properties of the barrier at this site and play a critical role in the outcome of vital pulp therapy. Healing of the dentin-pulp complex proceeds either by natural repair-which results in defensive hard-tissue formation, or therapeutically regulated dentin regeneration, which aims to reconstitute the normal tissue architecture at the pulp periphery. Progress in biomedical research opens new directions for the design of biologically effective pulp therapies. Application of biocompatible and biodegradable carrier vehicles for local delivery of signaling molecules in pulp-capping situations showed induction of fibrodentin/reparative dentin formation, but often at the expense of underlying pulp tissue. An alternative pre-clinical model aiming to reconstitute normal tissue architecture directly at the dentin-pulp interface should be designed on the basis of the direct induction of odontoblast-like cell differentiation and reparative dentin formation at the pulp-capping material interface. Experimental data clearly showed that pulpal cells can differentiate directly into odontoblast-like cells in association with specific extracellular matrices (dentinal or fibrodentinal matrix) or TGF beta 1-containing artificial substrates. Dentin-induced dentinogenesis can be used as a master plan for the achievement of new therapeutic opportunities. In the present study, several short-term experimental studies on dog teeth for potential direct induction of odontoblast-like cell differentiation at the surface of rhTGF beta 1-containing artificial substrates (Millipore filters, hydroxyapatite granules, calcium hydroxide, pure titanium) failed to induce any specific reparative dentinogenic effects.

Animals↗

PubMed2000

Dental unit waterline antimicrobial agents' effect on dentin bond strength.

BACKGROUND: In response to concerns of bacterial biofilm colonization of dental unit waterlines, a wide range of commercial intermittent and continuous chemical treatments for dental unit waterlines have been developed and marketed. There has been little research on the possible effect of continuous chemical treatment regimens on dentin-bonding agents. The authors evaluate the effect of four proposed antimicrobial agents used in dental unit waterlines on dentin bond strength. METHODS: The authors used a fifth-generation dentin-bonding agent to bond composite cylinders to molar dentin surfaces. They then used selected antimicrobial agents as rinsing agents after conditioning. The composite cylinders were shear tested, and their fracture strengths were compared statistically. RESULTS: All proposed antimicrobial agents reduced dentin bond strength. Proposed waterline treatment regimens of a diluted mouthrinse and chlorhexidine significantly reduced dentin bond strength compared with sodium hypochlorite and citric acid regimens. CONCLUSION: Dental professionals should be aware of potential interactions between dental unit waterline antimicrobial agents and dentin-bonding agents. Further research in this area is warranted, as the clinical implications are uncertain at this time. CLINICAL IMPLICATIONS: Dental unit waterline antimicrobial agents may adversely affect dentin bonding strength.

Adhesives↗

PubMed1998

Effectiveness of simplified dentin bonding systems.

The effectiveness of newly developed commercial dentin bonding systems (SB, MB II and KB) was evaluated by measuring the contraction gap width of a resin composite restored into a cylindrical dentin cavity prepared in an extracted human molar and by measuring the tensile bond strength to the flat dentin surface. In addition, calcium loss during dentin conditioning was analyzed using electron microanalyses. An experimental dentin bonding system composed of EDTA conditioning, GM solution priming and a bonding agent containing 10-MDP was employed as a control in which it was presumed that contraction gap formation was prevented completely. However, gap formation was observed using the three commercial simplified dentin bonding systems. SEM observation showed that the gap was formed between the resin composite and the top surface of the dentin cavity wall indicating that the fracture occurred at the adhesive interface, but never inside the dentin nor inside the resin composite.

Calcium↗

PubMed1999

Adhesion of a new commercial self-etching/self-priming bonding resin to human caries-infected dentin.

We have examined the adhesive properties of a new commercial self-etching/self-priming bonding resin (Unifil Bond, UB) to normal and caries-infected dentin of human extracted molars using scanning electron microscopy (SEM) and a micto-tensile bonding strength (MTBS) test. In this study, 7 human extracted molars with moderate occlusal caries were used, and flat surfaces including occlusal dentin caries were prepared from the teeth. After the application of UB to the surfaces, a composite resin was built up, and subjected to the measurement of MTBS and SEM observation of the interfacial morphology between UB and dentin. The MTBS of UB to normal dentin was 33.4 MPa, but that to caries-infected dentin was 11.0 MPa. There was a significant difference between the MTBS to normal and carious dentin. SEM observation revealed that the typical hybrid layer was not formed in caries-infected dentin. These results suggested that resin infiltration into caries-infected dentin was not sufficient to allow perfect sealing of the restoration.

Acid Etching, Dental↗

PubMed1999

Unprotected protein at the dentin-adhesive interface.

OBJECTIVE: With dental bonding systems that require acid etching of dentin, inadequate adhesive penetration can leave exposed collagen at the dentin-adhesive interface. The exposed collagen could be degraded by bacterial proteases, compromising the integrity of the dentin-adhesive bond and, ultimately, the restoration. The purpose of this study was to develop a nondestructive staining technique to identify exposed collagenous protein at the dentin-adhesive interface. METHOD AND MATERIALS: The following adhesives were placed, according to manufacturer's instructions, on dentin cut from 15 human third molars: Scotchbond Multi-Purpose, Scotchbond Multi-Purpose Plus, and 3M Single Bond. Light microscopic sections of native dentin-adhesive interfaces of each tooth were cut and stained with Goldner's trichrome. This reagent stained exposed protein in the sections a distinct red-orange. RESULTS: Exposed protein was identified at the dentin-adhesive interface with each of the adhesives. Corollary scanning electron microscopic examination confirmed the presence of exposed protein, i.e., protein that was removed by sodium hypochlorite, at the interface. Sites of exposed protein that were clearly identified in the light microscopic sections were obscured in the transmission electron microscopic sections. CONCLUSION: In vitro identification of inadequacies in the dentin-adhesive bond is the first step in determining sites that may be vulnerable to premature breakdown under clinical conditions.

Azo Compounds↗

PubMedDate not supplied

Bond strength of composite to dentin treated by air abrasion.

This study compared the bond strength of composite to dentin produced by an air-abrasive dentin pretreatment and acid etch only. Two hundred sixty extracted human molars were randomly divided into 13 groups (n = 20). An occlusal dentin surface with a defined smear layer was exposed. Dentin was conditioned either with 37% H3PO4 for 20 seconds, or an air-abrasion unit (KCP 1000, ADT) was used with 120 and 160 psi pressure and two different particle sizes, 50 and 27 microns. A combination of both treatments beginning with air abrasion was tested as well as dentin specimens without pretreatment. The dentin adhesive Syntac Single-Component was applied under dry and moist conditions. Composite cylinders with a bond diameter of 2.5 mm were bonded in two increments to the teeth. Specimens were stored for 24 hours at 37 degrees C in distilled water and then thermo-cycled for 1000 cycles (5/55 degrees C). Shear bond strength was tested using a Universal Testing Machine at 0.5 mm/min cross-head speed. Means and standard deviations in MPa were calculated. Analysis of variance and Bonferroni pairwise comparison tests were performed. Lowest bond strengths were obtained in specimens without conditioning the dentin. Air-abraded specimens showed a significantly higher bond strength than the before-mentioned groups. The comparison for acid-etched groups and air-abraded specimens revealed higher values for the abraded groups. Air abrasion with 160 psi pressure produced a significantly higher bond strength than 120 psi. There was no significant difference between the 27 and 50 microns particles. Air abrasion in combination with a self-priming bonding agent produced bond strength on dentin at least comparable to conditioning with 37% H3PO4.

Acid Etching, Dental↗

PubMedDate not supplied

Influence of the direction of tubules on bond strength to dentin.

This study investigated the influence of the direction of dentinal tubules on resin-dentin tensile bond strength (mu TBS) using four commercially available bonding systems and observed the resin-dentin interfaces with an SEM. The dentin bonding systems used in this study were Clearfil Liner Bond II (LB, Kuraray), Imperva Fluoro Bond (FB, Shofu), Single Bond (SB, 3M) and One-Step (OS, BISCO). Thirty-six extracted caries-free human molars were used for micro tensile bond testing and eight additional teeth were used for scanning electron microscopy (SEM). The teeth were divided into two groups according to the direction of the dentinal tubules at the resin-dentin interface: a perpendicular group, in which the occlusal enamel was removed perpendicular to the long axis of the tooth, and a parallel group, in which the mesial half of the tooth was removed parallel to the long axis of the tooth, and the coronal dentin surface was used for bonding. After the flat dentin surfaces were polished with #600 silicon carbide paper, each surface was treated with one of the four adhesive systems according to the manufacturer's recommendation, then covered with resin composite (Clearfil AP-X, Kuraray) to provide sufficient bulk for micro-tensile bond testing. After 24 hours in 37 degrees C water, the resin-bonded teeth were serially sliced perpendicular to the adhesive surface, the adhesive interface trimmed to a cross sectional area of 1 mm2 and subjected to tensile forces at a crosshead speed of 1 mm/min. Statistical analysis of the tensile bond strengths were performed using two-way ANOVA and Fisher's PLSD test at 95% level of confidence. The tensile bond strength of the group with tubules parallel to the bonded interface was higher than that of tubules cut perpendicularly. This tendency reached statistical significance using SB and OS.

Analysis of Variance↗

PubMed2000

Effect of smear layers on the bonding of a self-etching primer to dentin.

PURPOSE: The objective of this work was to evaluate the effect of the absence and presence of smear layers on bonds made to dentin using a self-etching primer system, Clearfil SE Bond. MATERIALS AND METHODS: Dentin surfaces with different smear layer thickness were created from mid-coronal sound dentin in extracted, human third molars. The control group was cryofractured to create a bonding surface that was devoid of a smear layer. The experimental teeth were ground with wet 60-, 180- or 600-grit SiC paper. They were bonded using SE Bond, followed by resin composite buildups. After 1 day, bonded specimens were sectioned into multiple 1- x 1-mm beams. Microtensile bond strengths were determined and the results analyzed with ANOVA and the Student Neuman Keuls test. Fractographic study of cross sections of failed interfaces from the dentin side of representative beams was performed using both SEM and TEM. RESULTS: SE Bond produced high bond strengths (ca 50 MPa) to both smear layer-free and smear layer-covered dentin. SEM examination was inadequate to define the exact nature of interfacial failures. TEM observations demonstrated a thin (ca 400 to 500 nm) hybrid layer in the fractured dentin and thicker (ca 1 to 4 microns) hybrid layers on smear layer-covered dentin. This included a thick, hybridized smear layer and a thin, underlying true hybrid layer in the intact dentin. Separation of the two hybrid layers was not evident in interfacial failures. CONCLUSION: Self-etching primers create thin hybrid layers that incorporate the smear layer. This study shows that formation of true hybrid layers occurs irrespective of smear layer thickness and that both hybrid layers may function as a unit during loading without separation. identification of secondary cracks from TEM fractographic analysis exemplifies the complex reaction to tensile stresses in multilayered joint systems that comprise materials of variable compliance.

Acid Etching, Dental↗

PubMed2000

Recent developments in dentin bonding.

Hybridization of the dentin with resin by monomer interdiffusion has been identified as the basic bonding mechanism resulting in an intimate interlocking of the cured resin with the dentin. Today, growing efforts are made to simplify and shorten the bonding procedures, e.g. by combining the functions of primer and adhesive. Ultrastructural investigations using high-resolution optical technology provided exciting insight into the interactions of bonding systems and dentin. It became clear, that the maintenance or recovery of microporosities in the dentin is most important for optimal hybridization. This can be achieved by the moist bonding technique, which is mandatory in acetone-based systems. The observation that certain bonding systems are able to bond to dentin depleted from the demineralized collagen network raised the question of whether the collagen-resin interdiffusion zone really represents a prerequisite for successful bonding to dentin. The use of strongly acidic primer monomers introduced the concept of "self-etching" primers not only to dentin but also to enamel, which eliminates the necessity of a separate conditioning step. Clinical investigations are necessary to evaluate the potential of recently developed all-in-one products which combine the functions of conditioner, primer, and adhesive. With improvements in dentin bonding and the development of new resins that exhibit little or no shrinkage upon polymerization, even greater applications for adhesive technology will be found in dentistry.

Acetone↗

PubMedDate not supplied

Influence of adhesive application duration on dentin bond strength of single-application bonding systems.

This study examined the relationship between the bond agent application duration and the dentin bond strength of several single-application bonding systems. The restorative material/ bonding systems used were Reactmer, with its single-application bonding system Reactmer Bond (RB, Shofu Inc, Kyoto, Japan); Palfique Estelite, with its single-application bonding system One-Up Bond F (OU, Tokuyama Co, Tokyo, Japan) and F2000 Compomer, with its bonding system Primer/Adhesive in Clicker (F2,3M Dental Products, St Paul, MN 55144, USA). Bovine mandibular incisors were mounted in self-curing resin and wet ground with #600 SiC to expose labial dentin. Adhesives were applied for 5, 10, 20, 30 and 60 seconds, and restorative materials were condensed into a Teflon mold (04 x 2 mm) on the dentin and light activated. Fifteen samples per test group were stored in 37 degrees C water for 24 hours, then shear tested at a crosshead speed of 1.0 mm/min. One-way ANOVA followed by Duncan test (p = 0.05) was done. SEM observations of the treated dentin surface were also conducted. The dentin bond strength ranged from 6.9 +/- 2.4 to 11.2 +/- 2.8 MPa for RB, 8.9 +/- 2.2 to 12.2 +/- 1.9 MPa for OU, and 7.8 +/- 3.1 to 11.4 +/- 2.6 MPa for F2. No significant differences were found among the 10-60 second application duration groups for the systems used. From the SEM observations, demineralization of the dentin surface was more pronounced with longer application duration. The data suggest that the duration of single-application bonding systems was not a crucial factor for determining dentin bond strength, even though morphological changes were observed on the dentin surface.

Adhesiveness↗

PubMedDate not supplied

Dentin sealers' effect on the diameter of pulpal microvessels: a comparative vitalmicroscopic study.

After crown preparation, exposed and untreated dentinal tubules can result in bacterial penetration into pulp. Treating the exposed dentin involves closing the tubules. Dentin sealers are often applied on a very thin dentin layer that covers the pulp chamber. In these cases, the sealers may have some effect on local micro-circulation through dentin. This study examined the acute effects of different dentin sealers on the vascular-diameter of pulpal vessels measured by vitalmicroscopic technique in rats. Gluma Desensitizer in Group 1 (n = 10), Seal & Protect with acid etching in Group 2 (n = 10) and Seal & Protect without acid etching in Group 3 (n = 10) were applied on a very thin layer of dentin in the left lower incisor of male Sprague-Dawley rats weighing 336 +/- 93SE/g. Saline served as the untreated control. After one-hour equilibration time, changes in vessel diameter were recorded with a digital camera connected to a microscope at baseline and at 5, 15, 30 and 60 minutes after the investigated materials were administered on dentin. The results were evaluated by ANOVA. In each group, diameter changes were averaged (compared to the baseline diameters) and standard errors of the mean were calculated for each examined time. The results suggest that Gluma Desensitizer caused the most severe pulpal vessel-diameter changes, followed by Seal & Protect with acid etching, while the least change was recorded in Seal & Protect without acid etching.

Acid Etching, Dental↗

PubMedDate not supplied

[Sclerotic dentin: aetio-pathogenetic hypotheses].

The situation with regard to current knowledge concerning dentinal sclerosis is examined. SEM and TEM examination of specimens of sclerotic dentin showed changes in diameter and tubular content leading to various degrees of obstruction of the lumen. There is agreement that this is due to the neo-apposition of peri-tubular dentin associated with intra-tubular deposition of crystals of Whitelockite, although the debate is still open on how such deposition may come about. Sclerotic casts are created in the tubules that may completely occlude the lumen or present a central cavity. In general these casts are surrounded by a thin fissure that has been variously interpreted. Many agree that sclerotic dentin has an increased mineral component, but without clarifying whether this is only a quantitative increase or whether it is also due to hyper-mineralisation of pre-existing dentin. An examination of the literature reveals numerous hypotheses surrounding the genesis of sclerotic dentin: some say it is due to passive phenomena of dissolution and precipitation whereas others suggest active involvement of the odontoblastic processes and the pulp. Since no studies have confirmed or confuted these theses, we may continue to think of dentinal sclerosis as a multifactorial event, due both to an increase in the thickness of peri-tubular dentin and to intra-tubular precipitation of calcium salts associated with mineralisation of the organic structures present in the lumen.

Calcium Phosphates↗