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PubMed2005

Qualitative microanalysis of ions and ultrastructural changes in dentin exposed to laser irradiation and to metal salts solution.

BACKGROUND AND OBJECTIVES: This study evaluated the ultrastructural changes in dentin after treatment with the Nd:YAG laser and/or metal salt solutions and verified the presence of Sn++, Sr++, and F- in dentin structure. STUDY DESIGNS/MATERIALS AND METHODS: Sixty dentin disks were randomly divided into groups (n = 10): (I) control (no treatment), (II) Nd:YAG (1.5 W, 100 mJ, 15 Hz, 125 J/cm2), (III) 10% SnF2 aqueous solution for 30 minutes, (IV) Nd:YAG+10% SnF2 aqueous solution for 30 minutes, (V) 10% SrCl2 toothpaste for 30 minutes, (VI) Nd:YAG+10% SrCl2 toothpaste for 30 minutes. Then, all samples were prepared for scanning electron microscopy (SEM) and the samples from Groups I to IV for the energy dispersive X-ray microanalysis (EDX). RESULTS: SEM evaluation revealed occluded dentinal tubules and a dentin surface altered by the laser irradiation. The EDX microanalysis revealed Sn++ at a depth of 250 microm in Group IV and not deeper than 100 microm in Group III. In Group V, Sr++ was not deeper than 50 microm, but it could be detected at a depth of 500 microm in Group VI. F- was found only in Group IV. CONCLUSIONS: Ultrastructural changes caused by laser irradiation can increase dentin uptake of Sn++, Sr++, and F-.

Dentifrices↗
PubMed1997

Fluoride uptake in dentin with and without simulating dentinal fluid flow.

The aim of the present study was to compare fluoride uptake of dentin with and without simulating dentinal fluid flow. Eighty-five dentinal discs were prepared from retained human molars. Seventeen discs were used to assess baseline fluoride content (controls). Sixty-eight discs were evenly distributed among two experimental groups and were fixed for 24 h in a two-chamber device allowing for simulating dentinal fluid flow. Thirty-four samples were treated with dentifrice slurry containing a low fluoride concentration (Elmex, dilution 1:5); the remaining discs were treated with a solution of a high fluoride concentration (Elmex Fluid). For the perfused group, each of the 17 discs of the high and low concentration fluoride groups were constantly perfused during the experiment. The remaining fluoridated specimens were not perfused. All specimens were assayed for KOH-soluble fluoride and structurally bound fluoride. Structurally bound fluoride was determined in three successive layers of 20 microns each. Uptake of KOH-soluble fluoride was significantly higher in the specimens fluoridated with Elmex Fluid compared to the samples treated with the dentifrice slurry. The uptake of KOH-soluble fluoride was not influenced by perfusion of the dentinal discs. However, perfusion resulted in lower acquisition of structurally bound fluoride in the samples treated with the dentifrice slurry. After application of Elmex Fluid, no significant difference was found in the amount of structurally bound fluoride between the perfused specimens and non-perfused samples. It is suggested that further studies on fluoride uptake in dentin should use a model simulating outward dentinal fluid flow.

Analysis of Variance↗
PubMed1989

Evaluation of potassium oxalate as a cavity liner.

All dental restoratives exhibit some microleakage. Recent studies disclosed that oxalate salts were superior to Copalite varnish in reducing dentinal permeability, but inferior in reducing microleakage. This study compared the effectiveness of a potassium oxalate solution (DDS) with three other cavity liners (Copalite, Cavi-Line, Prisma Universal Bond) and a no-liner control in reducing microleakage under amalgam restorations. Under the conditions of this study, DDS solution was significantly effective in reducing microleakage under amalgam restorations.

Composite Resins↗
PubMed1992

An evaluation of smear layer with various desensitizing agents after tooth preparation.

According to hydrodynamics, any agent blocking the dentinal tubules reduces the flow of fluids and diminishes hypersensitivity. The properties of the desensitizing agents that sponsor tubular occlusion and the barrier efficiency resulting from the interaction of the smear layer with test materials were examined with the scanning electron microscope and energy-dispersive x-ray microanalysis. Selected dentinal desensitizing was accomplished with burnishing procedures, cavity varnish, calcium hydroxide, and topical fluoride. Subjective evaluations were also recorded clinically after tooth preparation. This investigation indicated that the smear layer did not protect against zinc phosphate cement, and that cavity varnish prevented the formation of the smear plugs. The smear layer and plugs were basically composed of calcium and phosphorus, the major ingredients of dentin.

Adult↗
PubMed1995

Marginal seal and biocompatibility of a fourth-generation bonding agent.

OBJECTIVES: The pulpal reaction and the marginal sealing of in vivo restored samples using resin composite and Scotchbond Multi-Purpose adhesive system (3M Dental Products) were analyzed in this study. METHODS: Twelve Class I non-exposed cavity preparations were placed on premolars to be removed for orthodontic reasons. They were restored and observed at 7 d and 28 d. RESULTS: The examination of the resin-dentin interface under the scanning electron microscope (SEM) revealed: 1) a gap-free attachment between adhesive resin and dentinal surface in 80% of the areas studied, 2) penetration of resin tags into the dentinal tubules, and 3) formation of a 3-5 micrometer thick acid-resistant hybrid layer. Microfissures measuring about 10 micrometers were observed in only 20a% of the areas studied; these were located along the walls of the cavities, especially near the enamel in zones where there was a lower concentration of dentinal tubules. The histological analysis, carried out 7 d after preparation of the restoration, did not show any alteration of the pulp. After 4 wk, reparative dentin was produced in the pulpal areas corresponding to the restored cavities. SIGNIFICANCE: The quantity of newly formed dentin is correlated with the distance from the cavity to the pulp. The results indicate that acid-etching of vital dentin using 10% maleic acid does not impair pulpal healing in deep Class I cavities and that the Scotchbond Multi-Purpose adhesive system is able to preserve the morphological and biological integrity of the pulpo-dentinal complex.

Acid Etching, Dental↗
PubMed2005

Effect of desensitizing agents on the hydraulic conductance of human dentin subjected to different surface pre-treatments--an in vitro study.

OBJECTIVES: The aim of this study was to evaluate the variation of fluid filtration across dentin treated with different formulations of potassium oxalate gels and one gel of acidified sodium fluorophosphate, under five different pre-conditioned dentin surfaces. METHODS: The methodology used for the measurement of hydraulic conductance of dentin in the present study was based on the model suggested by Pashley, Stewart and Galloway [Arch Oral Biol 29 (1984)379]. Two hundred dentin discs 1 mm in thickness, obtained from human extracted third molars, were divided into 20 groups of ten specimens each. The groups corresponded to the following experimental materials: 3% potassium oxalate gel-pH 4; 6% potassium oxalate gel-pH 4; 3% potassium oxalate gel-pH 2.5 and 1.23% fluoride gel (APF gel)-pH 3.6-3.9, applied to dentin under the following surface conditions: air-dried, blot-dried, wet, EDTA air-dried; EDTA blot-dried. General MANOVA and post-hoc Duncan tests were performed on the data. RESULTS: Regardless of surface pre-treatment the 3% potassium oxalate gel-pH 2.5 produced the greatest reduction in dentinal filtration (p<0.05) even after citric acid challenge. In general, air-drying the dentin was the best surface pre-treatment (p<0.05). The interaction between the material and surface pre-treatment showed values of hydraulic conductance similar for most of the combinations, but the 3% potassium oxalate gel-pH 2.5 under wet conditions produced the largest reduction in hydraulic conductance. The APF gel produced the smallest reduction in hydraulic conductance when compared with the other materials, regardless of surface pre-treatment. SIGNIFICANCE: the potassium oxalate gels studied in this investigation have a great potential for tubule occlusion and, consequently, should be effective treatments of dentinal hypersensitivity, regardless of dentin wetness.

Acidulated Phosphate Fluoride↗
PubMed2004

In vitro study of dentin hypersensitivity treated by Nd:YAP laser and bioglass.

OBJECTIVES: An ideal material has yet to be discovered that can completely treat dentin hypersensitivity. However, if a highly biocompatible material such as bioglass, could be melted by laser irradiation to achieve better sealing depth for dentinal tubules, it may subsequently bond to dentin structures under a physiological environment and offer a prolonged therapeutic effect. METHODS: The authors used four types of energy parameters to melt the composition-modified bioglass. These four types were 30 Hz, 330 mJ/pulse (G+ mode), 30 Hz, 160 mJ/pulse (G- mode), 10 Hz, 400 mJ/pulse (D+ mode), and 10 Hz, 200 mJ/pulse (D- mode). The temperature elevation, occlusive depth of bioglass, and phase changes in the bioglass after laser irradiation were evaluated by means of scanning electron microscope (SEM), thermometer, and X-ray diffractometer (XRD). RESULTS: The occlusive depths of 2 and 10 microm in the dentinal tubules were achieved when the bioglass underwent 30 Hz, 160 mJ/pulse (G- mode) and 30 Hz, 330 mJ/pulse (G+ mode) of laser treatments, respectively. The bioglass experienced a temperature increase of less than 600 degrees C, and no phase transformation was observed after Nd:YAP laser irradiation. SIGNIFICANCE: The melting point of a composition-modified bioglass could be reduced and its use plus Nd:YAP laser have the potential in clinical use to treat dentin hypersensitivity.

Ceramics↗
PubMed2004

Resin bonding to cervical sclerotic dentin: a review.

Several reports have indicated that resin bond strengths to noncarious sclerotic cervical dentine are lower than bonds made to normal dentine. This is thought to be due to tubule occlusion by mineral salts, preventing resin tag formation. The purpose of this review was to critically examine what is known about the structure of this type of dentine. Recent transmission electron microscopy revealed that in addition to occlusion of the tubules by mineral crystals, many parts of wedge-shaped cervical lesions contain a hypermineralised surface that resists the etching action of both self-etching primers and phosphoric acid. This layer prevents hybridisation of the underlying sclerotic dentine. In addition, bacteria are often detected on top of the hypermineralised layer. Sometimes the bacteria were embedded in a partially mineralised matrix. Acidic conditioners and resins penetrate variable distances into these multilayered structures. Examination of both sides of the failed bonds revealed a wide variation in fracture patterns that involved all of these structures. Microtensile bond strengths to the occlusal, gingival and deepest portions of these wedge-shaped lesions were significantly lower than similar areas artificially prepared in normal teeth. When resin bonds to sclerotic dentine are extended to include peripheral sound dentine, their bond strengths are probably high enough to permit retention of class V restorations by adhesion, without additional retention.

Acid Etching, Dental↗
PubMed2002

The effect of pulpward pressure on the response to 50% lidocaine (lignocaine) applied to exposed dentine in cats.

The responses of intradental nerves can be blocked by 50% lidocaine applied to exposed, etched dentine. The aim here was to analyse electrophysiologically the contribution of pulpward pressure to the anaesthetic effect of lidocaine applied to exposed dentine. In 17 adult cats with intact lower canines, approximately 1mm of the coronal tip of the canine was removed and the exposed dentine acid-etched. Pulpward pressure was applied to the exposed dentine through a chamber fixed to the tip of the tooth. Cervical and coronal electrodes of silver wire and Ag/AgCl mixture were placed, the cervical 2mm from the gingival margin of the canine and the coronal into the coronal pulp chamber. The inferior alveolar nerve was surgically exposed and single pulpal nerve fibres responding to electrical stimulation of the canine were identified. The chamber was filled with 50% lidocaine solution, and 0 (atmospheric pressure), 1.3, 5.0 or 10.0 kPa pressure was applied to the chamber for 20 min. Orthodromic and antidromic action potentials were compared before and after the lidocaine application. When lidocaine was applied at 0, 1.3 or 5.0 kPa (n=5 each) for 20 min, all the orthodromic responses to cathodal electrical stimulation with the coronal electrode were blocked. Almost all orthodromic responses (12/15) remained unblocked when the cathodal electrical stimulation was applied with the cervical electrode. Applying 10.0 kPa pressure to the lidocaine solution blocked all the pulpal nerve responses (n=5) to both stimulation modes. The amplitude of the antidromic compound action potential was significantly decreased when the applied pressure was increased. These results suggest that increased pulpward pressure may effectively force anaesthetic solution more rapidly through the dentinal tubules into the pulp.

Action Potentials↗
PubMedDate not supplied

Effects of pulsatile versus non-pulsatile pulpal pressure simulations on diffusional transport across human dentine in vitro.

The influence of a simulated pulsatile pulpal pressure on the diffusion of NaCl through slices of human dentine (n = 12) was evaluated in vitro. The average hydraulic conductance of the slices of dentine was 0.0131 +/- 0.0031 microliter/cm2 per min per cmH2O(x +/- SD). A 1 mol/l NaCl solution was placed on one side of the slices of dentine and deionized water on the other side. The time needed to reach a steady state and the quantity of NaCl that diffused through the slice were successively measured on the same slice of dentine, under three conditions: without pressure simulation, with a static pressure of 1.5 kPa, and with a pulsatile pressure varying from 1.2 to 1.8 kPa. The pressure was applied to the deionized water. When a static pressure was applied, the time required to reach a steady state increased from 24 to 30 h. When a pulsatile pressure was applied the time required to reach a steady state decreased from 24 to 12 h. No statistically significant difference was found between the quantity of NaCl that had diffused when the steady state was reached.

Analysis of Variance↗
PubMed1997

Low versus high pressure for in vitro determination of hydraulic conductance of human dentine.

The purpose of this study was to evaluate the effect of applied pressure and measurement time on the in vitro measurement of hydraulic conductance of human dentine. Dentine slices were prepared from 50 third molars. Water was forced through the slices under a constant hydrostatic pressure. Five pressures were tested: 1.3 kPa (n = 10), 13.3 kPa (n = 10), 26.6 kPa (n = 10), 40 kPa (n = 10) and 53.3 kPa (n = 10). The volume that went through the slices was recorded every 10 min for 3 h. The volume, the fluid flow rate and the hydraulic conductance under the five pressures were compared. The volume increased with time and pressure. The fluid flow and hydraulic conductance decreased with time under 13.3, 26.6 and 40 kPa, but remained constant under 1.3 and 53.3 kPa. Used of a low pressure (1.3 kPa) may permit water to pass through dentinal tubules without disturbing intratubular contents. Medium pressures (13.3, 26.6, 40 kPa) seemed to disturb tubule contents progressively, resulting in decreased fluid flow and therefore a decreased hydraulic conductance with time. Under these pressures, the calculated values of hydraulic conductance may be unreliable because they are time-dependent. High pressure (53.3 kPa) seemed to pack the tubule contents against intratubular resistances immediately, resulting in low fluid flows and low hydraulic conductances.

Analysis of Variance↗
PubMed1994

Dental pain evoked by hydrostatic pressures applied to exposed dentin in man: a test of the hydrodynamic theory of dentin sensitivity.

The hydrodynamic theory of dentin sensitivity holds that pain is evoked by stimuli producing minute shifts in tubule fluid. In human volunteers hydrostatic pressures were applied to prepared dentinal cavities. The subjects reported the magnitude and quality of their sensations of pain by means of an intermodal matching technique in combination with verbal descriptors. No pain could be elicited when the smear layer was present. After removal of this layer, pressure stimuli of either direction evoked sharp pain. Rapid changes in pressure induced higher pain intensities than slow changes, indicating that the dental A-delta system is dynamic and gradient dependent. These results provide support for the hydrodynamic theory of dentin sensitivity and also lend credence to the notion that the movement of fluid across dentin induces a selective activation of the A-delta nerves in healthy pulps which is highly correlated with a sensation of sharp and/or shooting pain.

Acid Etching, Dental↗
PubMed1995

Microleakage through dentin after crown cementation.

This study investigated the relationship between type of luting cement for artificial crowns and microleakage through dentinal tubules. Standardized preparations were made on intact human premolars, and crowns were made in a base metal alloy using conventional techniques. The castings were randomly assigned to the following luting agent groups: zinc phosphate (ZP), polycarboxylate (PC), glass ionomer (GI), phosphate ester composite resin (GMA/PE), and a composite resin with a NPG-GMA dentin bonding agent (GMA/NPG). Then they were cemented in a standardized manner. The specimens were artificially aged, stained, sectioned, and microleakage occurred through dentinal tubules toward the pulp measured. The rank in order from least to most (best to worst) leakage was GMA/NPG, GI, GMA/PE, PC, and ZP. Material GMA/NPG recorded significantly less leakage than all other materials. Therefore, the results of this study suggest that material GMA/NPG may reduce pulpal sensitivity and pathosis.

Analysis of Variance↗
PubMed1996

Transient effects of low-energy CO2 laser irradiation on dentinal impedance: implications for treatment of hypersensitive teeth.

This study evaluated the effect of CO2 laser irradiation on dentinal impedance by passing known cyclic potentials across dentinal wafers mounted as a window in an electrolytic cell and measuring the resulting electrical impedance. Wafers were equilibrated in 0.1 M of KCl. The wafer specimens were irradiated with a CO2 laser (12 W, 0.1 ms, energy density 1.25 J/cm2). The time for impedance equilibration after irradiation was compared with equilibration after mounting. Mounted samples required 48 h to approach equilibrium in the electrolyte. After laser irradiation, impedance of previously equilibrated samples also required 48 h to equilibrate. This, along with exponential curve fitting, confirmed that laser treatment reintroduced a transient alteration in impedance. Equilibration time after irradiation and the mounting were similar. Dentin desociation apparently caused this transient impedance. Energy dispersive X-ray analysis confirmed the disappearance of K+Cl- after irradiation. Therefore, laser irradiation may cause dentinal desociation, yielding temporary clinical relief of dentinal hypersensitivity until rehydration occurs.

Carbon Dioxide↗
PubMed1998

Effects of CO2 laser in treatment of cervical dentinal hypersensitivity.

The effectiveness of CO2 laser therapy in the reduction and elimination of dentinal hypersensitivity in vivo and its thermal effects on tooth surfaces in vitro were investigated. Twenty-three patients with 91 sensitive teeth participated in this study and were followed for 3 months. The parameters used with CO2 laser were 1 W in a continuous wave mode and irradiation time ranging from 5 to 10 s. Hypersensitivity was assessed by thermal stimulus (a blast of air from a dental syringe). Thermal effects were measured by thermography using 10 extracted human teeth. After laser treatment, all patients were immediately free from sensitive pain. Over 3 months, the CO2 laser treatment reduced dentinal hypersensitivity to air stimulus by 50%. All teeth remained vital with no adverse effects. Thermography revealed no temperature increase on irradiated tooth surfaces subjected to water coolant. These results show that the CO2 laser is useful in the treatment of cervical dentinal hypersensitivity without thermal damage to pulp.

Adult↗
PubMed1999

The combined occluding effect of sodium fluoride varnish and Nd:YAG laser irradiation on human dentinal tubules.

Various methods and materials used in the treatment of dentin hypersensitivity are thought to achieve a therapeutic benefit by tubule occlusion. The aim of the present study was to evaluate the combined occluding effect of sodium fluoride varnish and Nd:YAG laser irradiation on human dentinal tubules. Thirty-six dentin specimens with exposed dentinal tubule orifices were used in this study. The samples were randomly divided into four groups. Groups A, B, and C were varnished by sodium fluoride, whereas group D served as a control. Then, group C was lased by 30 mJ of Nd:YAG laser, 10 pulses/s for 2 min by light painting. Three hours later, groups B and C were brushed by an electrical toothbrush for 30 min. Under SEM observation, the control group showed numerous exposed dentinal tubule orifices, and the sodium fluoride varnished specimens showed closure of exposed dentinal tubule orifices. After electrical toothbrushing, most of the sodium fluoride varnish was brushed away, except in the specimens that were irradiated by Nd:YAG laser. Over 90% of the dentinal tubule orifices were occluded by sodium fluoride varnish combined with Nd:YAG laser irradiation.

Combined Modality Therapy↗