Evaluation of dentin tubule occlusion after laser irradiation and desensitizing agent application

PURPOSE

To evaluate the effects of lasers (Nd:YAG and Er:YAG) and of topical desensitizing agents on dentin tubule occlusion by measuring real-time dentin fluid flow (DFF).

METHODS

32 molars were prepared with V-shape cavity at the cervical area, acid-etched, water rinsed, blotted dry, and treated with (1) Nd:YAG laser; (2) Er:YAG laser; (3) SuperSeal, a desensitizing agent; (4) ClinproXT, a resin-modified glass-ionomer (RMGI) varnish (n = 8 each). A real-time fluid flow measuring instrument (nano-Flow) was used to measure the DFF throughout the procedures. The DFF rates before and after the treatment were compared. Moreover, the surface topography of dentin tubules after each desensitizing method was examined using SEM.

RESULTS

DFF varied among the groups. The DFF rate was significantly reduced after laser irradiation/application of the desensitizing agents (P < 0.05). ClinproXT showed the greatest reduction of DFF rate (71.9%), followed by the SuperSeal (34.8%) and laser groups (P< 0.05). However, there was no significant difference between the Nd:YAG (24.1%) and Er:YAG (20.6%) groups (P > 0.05). In SEM images, narrowed dentin tubules were observed in both lased groups and SuperSeal group. In the ClinproXT group, the occluded dentin tubules by the RMGI covering were observed.

In vitro and in vivo evaluation of the effectiveness of three dentin desensitizing treatment regimens

PURPOSE

To evaluate the in vitro and in vivo effects of three treatment regimens on dentin permeability and reduction of dentin hypersensitivity (DH).

METHODS

The desensitization treatments were: Gluma Desensitizer PowerGel (GLU), MS Coat One (MSC), and dentin burnishing with fiber-resin burs (STB). A split-chamber device was used to determine the permeability of dentin slices cut from human molars in vitro. Fluid flow through dentin was recorded with a photochemical method after EDTA cleaning, albumin soaking and desensitization treatment (n = 10). 61 study participants with three severely hypersensitive teeth each were enrolled. Sensitivity was determined with an air stimulus before, immediately after treatment, and after 1, 3 and 6 months, using a verbal rating scale.

RESULTS

From the 61 study participants enrolled, 52 completed the trial. Permeability at baseline and after albumin soaking was not significantly different. All treatments produced reduced fluid flow through dentin (P > 0.05). All treatments reduced DH significantly (no or moderate sensitivity). Statistical results revealed significant differences among the treatments (P = 0.03). Mann-Whitney comparisons showed GLU, STB < MSC.

Bleaching technique effect on dentin permeability

PURPOSE

To evaluate the effect of bleaching techniques on dentin permeability. The hypothesis was that the bleaching agent associated or not to etching and/or energy source would be able to increase dentin permeability (conductance).

METHODS

Fifty 1 mm-thick disks of mid-coronal dentin were obtained from human third molars, which were mounted in a filtration chamber, allowing exposure of a standardized area of 0.282 mm2. All specimens were treated with 35% liquid phosphoric acid for 15 seconds to maximize dentin permeability. Then they were randomly allocated to five different conditions: C: placebo gel (negative control); HP: Whiteness HP Maxx (WM)-35% hydrogen peroxide; PA-HP: WM preceded by phosphoric acid etching for 15 seconds. HP-E: WM associated to a light source and PA-HP-E: WM preceded by phosphoric acid etching for 15 seconds and associated to a light source. The bleaching agent was applied for 10 minutes with intermediate agitation at 5 minutes. In the groups associated with a light source, it was activated for 30 seconds every 5 minutes. Afterwards, the permeability (Lp) was measured using the Flodec device. The data were collected and analyzed with one-way ANOVA and Tukey's test (P< 0.05).

RESULTS

Mean and standard deviation of Lp were: C = 1.92 (1.04); HP = 1.14 (0.29); PA-HP = 14.40 (8.62); HP-E = 4.18 (5.14); PA-HP-E = 27.32 (13.24). Data revealed that phosphoric acid etching could increase the dentin permeability, while the bleaching agent or light curing alone did not.

Comparison of the effects on dentin permeability of two commercially available sensitivity relief dentifrices

OBJECTIVE

The in vitro effects of two commercial sensitivity relief dentifrices, one containing 8.0% arginine, calcium carbonate, and 1450 ppm fluoride as sodium monofluorophosphate (MFP), and the other containing 8% strontium acetate and 1040 ppm fluoride as sodium fluoride, in occluding dentin tubules and reducing dentin fluid flow were compared in a blinded study using hydraulic conductance (Flodec).

METHODS

Human dentin segments were cut from extracted molars, mounted on acrylic blocks, etched, and connected to a Flodec to measure hydraulic conductance. Segments were divided into two groups (n = 6) and treated for one minute with either the arginine/calcium carbonate dentifrice or the strontium acetate dentifrice. The blocks were rinsed, connected to the Flodec, and the conductance was measured. Blocks were rinsed again and incubated in phosphate-buffered saline (PBS) for at least two hours before the next treatment. The cycle was repeated for a total of three treatments (one using a fingertip and the next two using a toothbrush). After the third treatment, the blocks were incubated in PBS overnight and conductance was re-measured. The two groups were further divided into three sets of two segments each, which were challenged for one minute with either 6% citric acid, orange juice, or grapefruit juice.

RESULTS

The hydraulic conductance study showed that the dentifrice containing 8.0% arginine, calcium carbonate, and 1450 ppm fluoride provided a significantly higher percentage reduction in fluid flow immediately after fingertip application, as well as after two brushing cycles, compared to the dentifrice containing 8% strontium acetate and 1040 ppm fluoride. After various acid challenges, the percentage reduction in fluid flow of dentin treated with the arginine/calcium carbonate dentifrice remained significantly higher than that of the strontium acetate dentifrice. These results are highly consistent with the results from an independent clinical study which showed that the arginine/calcium carbonate dentifrice provided dentin hypersensitivity relief immediately after direct topical application with a fingertip and massage for one minute per sensitive tooth, whereas the strontium acetate dentifrice did not.

CONCLUSION

Based on this in vitro hydraulic conductance study, the dentifrice containing 8.0% arginine, calcium carbonate, and 1450 ppm fluoride was significantly more effective in reducing fluid flow through dentin tubules as a result of occlusion than the dentifrice containing 8% strontium acetate and 1040 ppm fluoride. Further, the superior occlusion obtained with the arginine/calcium carbonate dentifrice was resistant to acid challenge.

Mechanism of action of a desensitizing fluoride toothpaste delivering calcium and phosphate ingredients in the treatment of dental hypersensitivity. Part III: Prevention of dye penetration through dentin vs a calcium- and phosphate-free control

It is generally accepted that the pain of dental hypersensitivity resulting from gum recession is from the movement of fluid within the exposed tubules of dentin, causing changes in pressure on the nerve within the pulpal cavity. One method of treating hypersensitivity is to occlude the tubules, preventing fluid movement. This article discusses the use of a dye penetration technique, which establishes this mechanism of action for a desensitizing fluoride toothpaste containing calcium and phosphate. Two groups of intact teeth were perfectly sealed with enamel paint. Windows 100-micro to 200-micro deep were opened on opposite sides of each tooth at the dentin-enamel junction and briefly etched using 20% polyacrylic acid. One batch of teeth was treated eight times for 30 mins each with a 1:3 slurry of the desensitizing toothpaste and another set with a similar slurry prepared from a calcium- and phosphate-free control. A 0.85% aqueous solution of acid red fuchsin dye was applied to each window and allowed to dry. After a brief rinse, the teeth were sectioned across the windows. Almost no dye penetration was seen in teeth treated with the desensitizing toothpaste; however, extensive penetration through the dentin was visible in the control-treated teeth. The differences in dye penetration for the two sets of teeth were significant by both subjective (P < .001) and objective (P < .01) measures. Tubule occlusion because of calcium and phosphate ions from the desensitizing toothpaste accounts for its tooth desensitizing efficacy.

Prevention of water contamination of ethanol-saturated dentin and hydrophobic hybrid layers

PURPOSE

This in vitro study evaluated the amount and distribution of outward fluid flow that occurred when an experimental etch-and-rinse hydrophobic adhesive was applied to ethanol-saturated dentin before and after oxalate pretreatment.

MATERIALS AND METHODS

Measurements of dentin permeability were performed under a constant pulpal pressure of 20 cm H2O in deep and middle dentin. A lucifer yellow solution was placed in the pulp chamber to determine the distribution of the water contamination of the hybrid layers.

RESULTS

The distribution of fluorescence in dentin specimens that were not pretreated with oxalate revealed that the dye permeated around the resin tags and filled the hybrid layer. Dentin specimens pretreated with oxalate prior to resin bonding, showed 80% to 83% less (p < 0.05) water contamination compared to controls. The dentin permeability results obtained before and after oxalate pretreatment showed that oxalate decreased dentin permeability by 98% (p < 0.05) compared to acid-etched controls. This prevented outward fluid movement during bonding, resulting in better resin sealing of dentin due to the formation of a double seal of resin tags over calcium oxalate crystals in the tubules.

CONCLUSION

Outward dentinal fluid flow may contaminate hybrid layers during adhesive bonding procedures. Pretreatment of acid-etched dentin with 3% oxalic acid prior to bonding procedures can prevent outward fluid flow during bonding and water contamination of the hydrophobic hybrid layers.

A breakthrough therapy for dentin hypersensitivity: how dental products containing 8% arginine and calcium carbonate work to deliver effective relief of sensitive teeth

OBJECTIVE

These studies have utilized a range of state-of-the-art surface techniques to gain insight into the mechanism of action of a new technology for dentin hypersensitivity relief based upon arginine and calcium carbonate and, in particular, to address important questions regarding the nature and extent of dentin tubule occlusion.

METHODS

Confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM), and atomic force microscopy (AFM) have been used to assess tubule occlusion. Energy dispersive x-ray (EDX) and electron spectroscopy for chemical analysis (ESCA) have been used to identify the composition of the dentin plug. CLSM has also been used to compare the mechanism of action of the toothpaste and the desensitizing prophylaxis paste, to address whether both the arginine and the calcium carbonate components are essential to occlusion, to identify the location of the arginine within the occluded dentin, and to demonstrate resistance of the occlusion to acid challenge. Hydraulic conductance has been used to assess the effectiveness of the arginine-calcium carbonate technology in arresting dentin fluid movement, to evaluate the effects of pulpal pressure on the robustness of the occlusion, and to confirm the resistance of the occlusion to an acid challenge.

RESULTS

The CLSM, SEM, and AFM studies demonstrate that the arginine-calcium carbonate technology is highly effective in rapidly and completely occluding dentin tubules. The EDX and ESCA studies show that the dentin surface deposit and occluded tubule plug contain high levels of calcium and phosphate, as well as carbonate. CLSM has confirmed that the toothpaste and the desensitizing prophylaxis paste have the same mechanism of action, that the arginine and calcium carbonate components are both essential to the effectiveness of these products, and that the arginine becomes incorporated into the dentin plug. The hydraulic conductance studies demonstrate that the occlusion provided by the arginine-calcium carbonate technology results in highly significant reductions in dentin fluid flow, and that the tubule plug is resistant to normal pulpal pressure and acid challenge.

CONCLUSION

A breakthrough technology based upon arginine and calcium carbonate provides clinically proven benefits with respect to rapid and lasting relief of dentin hypersensitivity. It is unique in that two of its key components, arginine and calcium, are found naturally in saliva, and that the arginine and calcium carbonate work together to accelerate the natural mechanisms of occlusion to deposit a dentin-like mineral, containing calcium and phosphate, within the dentin tubules and in a protective layer on the dentin surface.

Dentin hypersensitivity: from diagnosis to a breakthrough therapy for everyday sensitivity relief

This paper provides an overview of the current knowledge of diagnosis, epidemiology, etiology, and clinical management of dentin hypersensitivity. It summarizes technical approaches to relieve sensitivity in professional and home-use products, with emphasis on the clinical evidence for the efficacy of desensitizing toothpaste, and introduces a new innovative dentifrice technology containing 8% arginine, calcium carbonate, and 1450 ppm fluoride. Dentin hypersensitivity is characterized by short, sharp pain arising from exposed dentin in response to external stimuli which cannot be ascribed to any other form of dental defect or disease. The hydrodynamic theory proposes that pain-producing stimuli cause a change in dentin fluid flow that activates intra-dental nerve fibers, via a mechanoreceptor response, to cause pain. To be hypersensitive, dentin must be exposed and dentin tubules must be open to external stimuli and patent at the pulp. Gingival recession is the primary cause of dentin exposure, and a major predisposing factor for dentin hypersensitivity. Dentin hypersensitivity is a prevalent condition. It has been reported to afflict 15-20% of the adult population, typically 20 to 50-year-olds, with peak incidence between 30 and 39 years. Some studies have reported higher prevalence levels of up to 57%. The incidence of dentin hypersensitivity is expected to rise with changing diets, and as caries and periodontal disease prevention result in improved oral health status, and retention and functionality of the dentition. Treatments to relieve dentin hypersensitivity are based on interruption of the neural response to pain stimuli or occlusion of open tubules to block the hydrodynamic mechanism. Effective and robust dentin occlusion offers the greatest prospect for instant and lasting relief of dentin hypersensitivity. In particular, materials which can coat exposed dentin surfaces, in addition to plugging and sealing open dentin tubules, offer the intriguing prospect of strengthening dentin and rendering it less susceptible to predisposing factors, while concurrently reducing dentin hypersensitivity. Clinical studies have shown that a new toothpaste containing 8% arginine, calcium carbonate, and 1450 ppm fluoride as sodium monofluorophosphate offers significantly increased efficacy in reducing sensitivity, compared to a market-leading toothpaste containing 2% potassium ion. Mechanism of action studies have shown that this technology physically seals dentin tubules with a plug that contains arginine, calcium carbonate, and phosphate. This plug, which is resistant to normal pulpal pressures and to acid challenge, effectively reduces dentin fluid flow and, thereby, reduces sensitivity.

Effects of a combined application of potassium oxalate gel/adhesive agent on dentin permeability in vitro

PURPOSE

To test the effects of sequential application of potassium oxalate gel/adhesive agent on in vitro dentin permeability.

MATERIALS AND METHODS

Full crown preparations were made in extracted human molars to expose deep coronal dentin. The roots and pulp were removed and the resulting crown segments were connected to a special device (Flodec) to permit the measurement of the permeability of the specimens before and after treatments. Minimum and maximum permeability were recorded after smear layer and phosphoric acid treatment. A new smear layer was created and the permeability measured after the crowns were bonded with Single Bond (3M ESPE), One-Up Bond F (Tokuyama), and AdheSE (Ivoclar Vivadent), either according to manufacturer's instructions or after treating the acid-etched dentin with a 3 wt% potassium oxalate gel. The results were expressed as a percentage of maximum permeability values. Impressions and epoxy resin replicas from the crown segments were produced for SEM examination.

RESULTS

None of the adhesives were able to eliminate the fluid flow through dentin. Two-way ANOVA revealed that the application of potassium oxalate prior to the bonding procedures was the most effective technique in reducingthe dentin permeability (p < 0.05), regardless of the adhesive used. SEM micrographs showed that transudation of dentinal fluid could be identified on the surfaces of all replicas.

CONCLUSION

The use of potassium oxalate gel was effective in reducing the permeability of bonded dentin.

Single-bottle adhesives behave as permeable membranes after polymerisation. II. Differential permeability reduction with an oxalate desensitiser

OBJECTIVES

This study examined the changes in hydraulic conductance and ultrastructure of dentine bonded with simplified etch-and-rinse adhesives to oxalate desensitiser pre-treated acid-etched dentine.

METHODS

Human dentine disks were acid-etched, treated with an oxalate desensitiser (BisBlock, Bisco), and bonded with One-Step (OS), Single Bond (SB), OptiBond Solo Plus (OB) or Prime and Bond NT (PB). Similar disks from each group were acid-etched, and bonded without oxalate pre-treatment. Hydraulic conductance of the specimens was measured at 20 cm of water pressure and analysed with nonparametric statistical methods. Epoxy resin replicas of the smear layer-covered dentine and bonded dentine were examined with SEM for the extent of fluid transudation. Specimens bonded under perfusion were examined with TEM after tracer immersion.

RESULTS

OB and PB exhibited a highly significant reversal of the reduced hydraulic conductance obtained with BisBlock on unbonded acid-etched dentine. Profuse water transudation across the bonded dentine was observed from the replicas. Adhesive interfaces were covered with spherical globules that interfered with dentine hybridization. Conversely, no significant difference in hydraulic conductance was observed in SB, between Bisblock pre-treated, unbonded and bonded acid-etched dentine. Significantly lower hydraulic conductance was shown on application of OS to Bisblock-treated acid-etched dentine. Water transudation was sparse, interfering surface globular structures were absent, and only angular subsurface crystals were seen in the dentinal tubules.

CONCLUSIONS

Convective water fluxes through dentine may be reduced by applying Bisblock to acid-etched dentine before bonding with One-Step or Single Bond. However, reducing adhesive permeability with the use of oxalate desensitiser is not applicable to low acidity adhesives such as OptiBond Solo Plus and Prime and Bond NT.

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.

In vitro dentine permeability: the relative effect of a dentine bonding agent on crown preparations

OBJECTIVE

The aim of this study was to determine whether a dentine bonding agent (DBA) had an effect in reducing fluid filtration under cemented provisional crowns.

METHODS

Crown preparations on 34 premolars, randomly allocated to two equal-sized test and control groups, were assessed for dentine permeability by a fluid filtration technique. In the test group, prepared crowns were acid-etched and then treated with a DBA (Prime & Bond NT). In the control group, no such DBA was applied. Provisional crowns were cemented on both groups of teeth using non-eugenol zinc oxide cement. Fluid filtration rates were measured repeatedly after crown preparation, at cementation, 1 h, 1 day, 1 week and 3 weeks following crown cementation for both groups. Filtration rates were also measured after acid-etching and dentine bonding for the test group.

RESULTS

There was insufficient evidence to suggest any statistically significant differences either between the two groups or, on average, across the five time points in each group in terms of the relative percentage of fluid filtration.

CONCLUSION

The DBA used did not seal dentinal tubules any more than did the smear layer and provisional crowns luted with a non-eugenol ZnO cement.

2000 Judson C. Hickey Scientific Writing Award. Effect of impression materials on hybridized dentin

STATEMENT OF PROBLEM

Tooth sensitivity after crown preparation is not an uncommon complication. For dentin bonding agents to be effective in preventing postoperative sensitivity, they must remain intact throughout the fixed prosthodontic procedures.

PURPOSE

This study evaluated, by analyzing the change in dentin permeability, whether a dentin bonding agent was removed from the surface of prepared teeth in the process of making an impression.

MATERIAL AND METHODS

Eighty extracted human molars were cut horizontally apical to the cemento-enamel junction and horizontally through the middle of the clinical crown. The specimens were prepared to measure dentin permeability (fluid flow rate, Lp). The specimens (n = 40) were randomly assigned to either the primer-only group (PO) or the primer + adhesive group (PA). Five different impression materials were tested: vinyl polysiloxane, polyether, polysulfide, irreversible hydrocolloid, and reversible hydrocolloid. Dentinal permeability was measured after smear layer removal (control, etched Lp = ELp), after coating the dentin with either PO or PA (coated Lp = CLp), and again after making an impression (impression Lp = ILp). A 1-way ANOVA of differences, followed by a Student-Newman-Keuls test (alpha=.05), was performed to compare the ELp, CLp, and ILp values.

RESULTS

A statistically significant difference was found between the CLp and ELp for all 5 impression materials in both groups (PO and PA). No difference was found between the CLp and ILp values for any of the impression materials. No significant differences were found between any of the 5 impression materials or either of the dentin surface treatments (PO or PA) when measuring the CLp and ILp.

CONCLUSION

The dentin bonding agent had a significant effect in decreasing the Lp of the treated specimens. None of the impression materials significantly affected the measured CLp. There was no significant difference between the PO or PA (CLp) values.

Self-contamination of deep dentin by dentin fluid

PURPOSE

To compare, with the use of a resin replica technique, surface features of deep, acid-conditioned dentin from vital human molars that were anesthetized with an anesthetic: Group 1: without a vasoconstrictor (Mepivacaine 3%), and Group 2: containing a vasoconstrictor (Lidocaine 2% with 1:80,000 epinephrine).

MATERIALS AND METHODS

10 Class I cavities with dentin caries were included in each group. Following complete caries removal, a total-etch technique was performed with 32% phosphoric acid (Uni-Etch) for 15 s. After rinsing, each cavity was air-dried for 1 s, then a slow setting vinyl polysiloxane (President) impression was taken. As a control, impressions were taken from three additional cavities in teeth that were anesthetized with Mepivacaine 3% but not acid etched. A TEM-grade epoxy resin was used to prepare replicas from the impressions. Polymerized replicas were coated with gold and examined with a scanning electron microscope.

RESULTS

In Group 1, fluid was visible leaving tubular orifices in all replicas. In addition, three were covered with a smooth, amorphous film that was different from the granular appearance of the smear layer in the control cavities. In Group 2, patent tubular orifices without fluid were observed in all specimens. Odontoblast process-like structures were seen from some dentin tubules.