Double-blind study on materials testing with applied kinesiology.

Applied Kinesiology (AK) is a scientifically unproven method used in complementary medicine to recognize the (in)tolerance of dental materials. Test-retest reliability of AK was examined. The working hypothesis was the assumption that the reliability of AK would not exceed random chance. Two dentists qualified in AK examined 112 volunteers to determine individual (in)tolerance toward two dental composite materials. After the first examination, 31 subjects were excluded from further testing. At the end of the open test phase, 34 of 81 participants had been classified as "tolerant", and seven as "intolerant" to both materials. The remaining 40 individuals showed a combination of either tolerant (to material I)/intolerant (to material II), or the reverse (n = 20 each). Retrieval rate was tested under blind conditions. In 14 cases, the results of the open and blinded tests matched, whereas in 26 cases they did not (95% confidence interval, 21%-52%; p = 0.98). This outcome confirmed our working hypothesis.

Nanoleakage at the composite-dentin interface: a review.

The term "nanoleakage" was introduced to describe a specific type of leakage within the dentin margins of restorations. Nanoleakage appears as a consequence of the acid etching procedure allowing the penetration of oral and pulpal liquids such as acids into porosities within or adjacent to the hybrid layer. Nanoleakage is independent from microleakage. The amount of penetration depends on the type of bonding agent and on different parameters of the application technique (e.g. etching time, dentin moisture). Nanoleakage is much less extensive than microleakage and has probably no short-term clinical relevance. The long-term stability of the adhesive bond between dentin and restorative material, however, might be adversely affected. Nevertheless, based on the knowledge to date, acid etching prior to dentin bonding should be performed.

A clinical study to compare the efficacy of 2 electric toothbrushes in plaque removal.

OBJECTIVES: To compare the cleaning efficacy of a powered toothbrush with 3-dimensional brush head action (Braun Oral-B 3D Plaque Remover D15) and a high-speed "microtation" brush with an additional "microbrush-clip" (Rowenta Dentasonic MH921S). MATERIAL AND METHODS: 82 healthy subjects took part in the study. After a familiarization period of 8 days, the subjects abstained from all oral hygiene procedures for 48 h. After plaque was scored, the subjects brushed their teeth under supervision with the two brushes according to a split-mouth design. Immediately after brushing, subjects completed a questionnaire and plaque was scored again. RESULTS: The overall plaque scores were found to be significantly reduced from 3.05+/-0.60 to 1.96+/-0.63 by the D15 and from 3.02+/-0.58 to 2.24+/-0.64 by the Dentasonic (p<0.05). The proximal surface plaque scores were reduced from 3.20+/-0.63 to 2.17+/-0.69 by the D15 and from 3.17+/-0.60 to 2.44+/-0.69 by the Dentasonic. The relative plaque reduction was overall 36.6+/-12.2% for the D15 compared to 26.1+/-13.5% for the Dentasonic and at proximal surfaces, 33.1+/-12.3% and 23.2+/-13.0%, respectively. 75% of the subjects stated that they would prefer to keep the D15. CONCLUSIONS: Both brushes were able to remove a significant amount of plaque, but the D15 was significantly more effective compared to the Dentasonic. The additional "microbrush-clip" for the proximal embrasures failed to improve plaque removal from these tooth surfaces, compared to the D15 alone.

Influence of rubber-dam on the reconstruction of proximal contacts with adhesive tooth-colored restorations.

PURPOSE: To clinically measure the influence of rubber-dam on the proximal contact strength after its reconstruction with tooth-colored restorations. MATERIALS AND METHODS: The frictional forces during the removal of a metal strip from the proximal contact area were taken as measure for the proximal contact strengths of 46 restorations (35 ceramic inlays, 11 direct composite restorations). The teeth were separated with a rubber-dam and wedged thoroughly during the complete reconstruction procedure according to the multiple wedging technique. The proximal contact strengths were measured immediately before and immediately after removing the rubber-dam. RESULTS: The contact strengths were statistically significantly lower immediately after the removal of the rubber-dam (1.07+/-0.82N) compared to the situation with the rubber-dam (1.99+/-1.21N). The amount of the reduction after removing the rubber-dam was statistically significantly higher between the second premolar and the first molar (1.45+/-1.06N) compared to the contacts between the canines and the first premolar (0.32+/-0.44N) and the first and second premolar (0.59+/-0.77N). No influence of the restorative material, the use and localization of retainers, localization of the restoration, or number of teeth under the rubber-dam was detectable. CONCLUSION: Rubber-dam is recommended for adhesive restorations as it is helpful for achieving good adhesion between the tooth and restorative materials. Nevertheless, the application of rubber-dam seems to be a factor which complicates the reconstruction of adequate proximal contacts.

Gliding capacity of different dental flosses.

BACKGROUND: One of the major concerns with the use of dental floss is the passage of the proximal contact, which might be influenced by the material characteristics of the floss. The aim of this study was to compare the gliding capacities of different flosses with major differences in structure and experimental behavior in vivo. METHODS: In a clinical, single-blind, crossover study of 27 subjects, the forces necessary for passing all 14 proximal contacts between the first premolars were measured using 2 polytetrafluoroethylene (PTFE)-based flosses, 2 nylon-based flosses, and 1 nylon-based tape. The flosses were fixed in a special holder with strain gauges, which allowed registration of the maximum forces at insertion into and removal from the interdental area. RESULTS: In most contacts, the PTFE flosses needed less force compared to the nylon flosses. The range between the flosses was higher in the mandible compared to the maxilla and increased from the mesially located contacts to the more distally located contacts. The nylon tape required higher forces at insertion for all maxillary contacts. All other flosses proved to be equivalent at these contacts. CONCLUSIONS: PTFE flosses are superior to nylon flosses in terms of passing stronger proximal contacts in both directions. Due to gliding differences between different types of floss, the selection of a floss has the potential of compensating intra- and interindividual variation in contact strengths.

The effect of NaOCl dentin treatment on nanoleakage formation.

The term "nanoleakage" has been introduced to explain a penetration pathway within hybrid layers of the dentin-composite junction in the absence of gap formation. This phenomenon is argued in the literature to be a risk factor for the quality of the dentin bonding. NaOCl is a well-known agent used to remove collagen layers that are exposed after acid etching. The purpose of this study was to determine the influence of an NaOCl treatment of dentin to the formation of nanoleakage. Class V cavities were prepared in 40 human molars with the cervical margins located in dentin. After etching with phosphoric acid, 20 samples were treated with 10% NaOCl for 60 s, and 20 samples were used as control. Composite restorations were placed using two different bonding systems. The specimen were exposed in silver nitrate solution and then in developer. After embedding, the teeth were sectioned, dried, coated with gold, and analyzed by SEM. For all the specimen in the control group, backscatter images indicated a silver penetration within the hybrid layer. There was no penetration of silver detectable in the teeth that were treated with NaOCl. We conclude that the removal of the collagen layer by using NaOCl avoids the formation of nanoleakages with the materials tested.

Comparison of the safety and efficacy of an oscillating/rotating battery-powered toothbrush and a standard manual toothbrush.

PURPOSE: To compare the cleaning efficacy of a battery-powered toothbrush with an oscillating/rotating action (Dr. Best Powerclean) and a standard flat-trimmed manual toothbrush (Elmex super 39) in a single-blind, cross-over clinical study. MATERIALS AND METHODS: 78 healthy subjects took part in the study. Subjects were asked to abstain from all oral hygiene procedures for 48 hours, after which hard and soft oral tissues were examined. Plaque was then scored using the Turesky modification of the Quigley-Hein Index, and subjects were instructed to brush their teeth for a total time of 1 minute with either one or the other brush, according to a predetermined randomization schedule. Immediately after brushing, plaque was scored again and hard and soft tissues were re-examined. All plaque scoring was carried out by the same investigator who was blind with respect to the brushes used. Subjects were instructed to continue with their usual oral care routine throughout the study period. They were scheduled to return after 12-14 days, having again abstained from all oral hygiene for 48 hours prior to the visit, in order to repeat the evaluation sequence but brushing with the alternative brush. Prior to analysis of the results, data from the two phases of the study were combined. RESULTS: Both toothbrushes were found to be safe as used in the study. Using the non-parametric Wilcoxon test for paired samples, whole mouth plaque scores were found to be reduced significantly from 2.04 +/- 0.60 to 1.57 +/- 0.51 by the Powerclean toothbrush (P < 0.001), and from 1.99 +/- 0.65 to 1.27 +/- 0.52 by the manual toothbrush (P < 0.001). At approximal surfaces, the plaque scores were also significantly reduced from 2.14 +/- 0.0.59 to 1.69 +/- 0.50 for the Powerclean (P < 0.001), and from 2.08 +/- 0.64 to 1.40 +/- 0.57 for the manual toothbrush (P < 0.001). A comparison of the two brushes revealed that the manual toothbrush removed significantly more plaque than the Powerclean, both for the whole mouth and approximal surfaces (P < 0.001). The Powerclean reduced whole mouth plaque by 23.2 +/- 11.5% compared to 37.8 +/- 14.0% for the manual toothbrush and approximal plaque by 20.9 +/- 10.6% and 34.9 +/- 14.0%, respectively. It is concluded that the Dr. Best Powerclean toothbrush is not as effective as a standard flat-trimmed manual toothbrush.

Clinical evaluation of the efficacy of a battery-powered toothbrush. results from two independent studies.

PURPOSE: To compare the clinical efficacy with respect to plaque removal of a battery-operated power toothbrush (Dr. Johns Spin Brush Classic) with two manual toothbrushes, a standard ADA flat trim reference brush and the Oral-B CrossAction toothbrush. MATERIALS AND METHODS: Efficacy was evaluated in two independent studies using a randomized, single-use, cross-over design. Healthy adult subjects from a general population brushed their teeth for a timed 1 min and plaque was scored before and after brushing was completed. In Study 1 (Spin Brush vs. ADA toothbrush), plaque was scored using the modified Quigley and Hein Plaque Index, while in Study 2 (Spin Brush vs. CrossAction) plaque was scored using the Modified Navy Plaque Index. In addition, a hard and soft tissue examination was carried out before and after brushing to allow evaluation of safety. RESULTS: In Study 1, both the ADA toothbrush and the Spin Brush significantly reduced levels of whole mouth and approximal plaque (P < 0.0005); however, the Spin Brush was not significantly more effective than the manual brush. Relative plaque reduction for the whole mouth was 35.6 +/- 16.0% for the Spin Brush compared to 38.9 +/- 14.9% for the manual toothbrush (P < 0.047), and, for the approximal surfaces, 32.7 +/- 14.6% and 36.3 +/- 13.7%, respectively (P = 0.024). In Study 2, both toothbrushes significantly reduced plaque levels (P < 0.0001), but, as for Study 1, the CrossAction manual toothbrush was more effective than the Spin Brush. For whole mouth, marginal and approximal sites, respectively, the Spin Brush reduced plaque by 54.3%, 43.5% and 62.0%, compared with 58.6%, 47.5% and 67.1% for the CrossAction toothbrush. The difference in favor of the CrossAction brush was statistically significant (P < 0.0005) for all areas.

Effect of intrapulpal pressure simulation in vitro on shear bond strengths and hybrid layer formation.

PURPOSE: To test the hypothesis that simulation of an intrapulpal pressure during the application of dentin bonding systems influences hybrid layer formation in vitro. MATERIALS AND METHODS: 180 teeth and three different bonding agents were used for shear bond strength measurements and for confocal laser scanning microscopy studies on the dentin-composite interface. The bonding agents (30 teeth each material) were applied without (90 teeth, Group A) and with intrapulpal pressure simulation of 34 cm H20 with water (90 teeth, Group B). 45 specimens from each group were sheared in a testing machine, and 45 teeth from each group were used for CLSM studies after labeling the primer components of the bonding agents with a fluorescent dye. RESULTS: After simulation of pulpal pressure the bond strengths decreased significantly in all groups (Syntac [without/with]: 16.0 +/- 4.5/8.0 +/- 3.7, P= 0.001; Gluma: 13.3 +/- 4.6/8.4 +/- 4.4, P= 0.008; Prime & Bond NT: 14.8 +/- 5.8/8.7 +/- 5.7, P= 0.007; n = 15 each; U-tests). There were no significant differences between the hybrid layer thickness without/with simulation of pulpal pressure (Syntac: 3.6 +/- 0.6/4.1 + 1.2, P= 0.35; Gluma: 3.5 +/- 0.6/3.7 + 0.9, P= 0.49; Prime & Bond NT: 3.5 +/- 0.9/3.8 + 0.8, P= 0.44; n = 15 each; U-tests). In the case of simulation of an intrapulpal pressure, CLSM examination revealed a distinctly shallower penetration of the adhesives into dentin compared to the samples treated without intrapulpal pressure.

Factors influencing proximal dental contact strengths.

The aim of this study was to systematically measure proximal contact strength in complete natural dentitions of 30 adults (25.3 +/- 3.0 years of age), and to analyze its relationship to tooth type, tooth location, chewing effort and time of day variation. The contact strengths were measured dynamically during removal of a calibrated 0.05-mm-thick metal strip between the proximal contacts of adjacent teeth. Proximal contact strengths were lower in the maxilla (2.51 +/- 1.36 N) compared to the mandible (4.26 +/- 1.88 N). Within the jaws, the lowest proximal contact strength was measured between canine and first premolar (2.91 +/- 1.79 N) and the highest between second premolar and first molar (3.73 +/- 1.95 N). Chewing increased the proximal contact strength within the maxilla (before: 2.51 +/- 1.36 N, after: 3.02 +/- 1.45 N) but it remained unchanged in the mandible (before: 4.26 +/- 1.88 N, after: 4.22 +/- 1.85 N). The proximal contact strength increased significantly from morning (3.39 +/- 1.86 N) to noon (3.61 +/- 1.77 N), and then decreased in the afternoon (3.43 +/- 1.60 N). It was concluded that proximal contact strength can be significantly influenced by location, tooth type, chewing and time of day variation. Based on the differences in distribution due to the effect of chewing and time of day, it is speculated that proximal contact strength is a physiological entity of multifactorial origin.

The nanoleakage phenomenon: influence of different dentin bonding agents, thermocycling and etching time.

"Nanoleakage" takes place within the hybrid layer zone of the dentin-composite interface in spaces not occupied by polymerized resin. The purpose of this study was to quantify the amount of nanoleakage in specimens treated with one of six different bonding agents. For one agent, different etching times were used, and for two agents results after thermocycling were obtained. Standardized class V cavities were prepared in 165 extracted human molars with cervical margins located in dentin. After placement of the composite using bonding agents, the teeth were stored in a 1% rhodamin-B-isothiocyanate solution for 24 h at 20 degrees C, embedded in methacrylate, and sectioned parallel to the long axis of the tooth. A confocal laser scanning microscope was used to visualize a layer 10 microm below the prepared surface of the section. The lengths of the penetrated pathways were measured, representing the amount of nanoleakage. In all materials tested, penetration pathways appeared within the hybrid layer in absence of gap formation. Penetration lengths of the tested materials were in a range from 69 +/- 24 microm to 469 +/- 333 microm. Thermocycling had no statistically significant influence, and etching for 15 s resulted in statistically significantly shorter penetration compared to longer etching.

Enamel hypoplasia of primary teeth in chronic renal failure.

Chronic renal failure (CRF) in the first years of life is associated with developmental defects of enamel in the permanent dentition. We investigated if CRF also affects the primary (deciduous) dentition. Thirty-one children with CRF on conservative treatment (n = 12) or on renal replacement therapy (n = 19) underwent dental inspection. In addition, 18 CRF children provided an exfoliated deciduous tooth for microscopic examination. Enamel defects were detected in a total of 12 children (31%), either clinically or microscopically. Of the 7 children affected clinically, 6 (19% of all examined) presented localized hypoplasia of the primary canines, which was found only in 3% of healthy control children: 1 patient had generalized pitted enamel hypoplasia. By microscopy, 5 of 10 primary canines examined showed enamel hypoplasia localized exclusively in enamel formed after birth. The "birth line," a visible structure within the primary enamel, was always present, which excludes a prenatal onset of the defects. Of the 12 patients with an enamel defect, 9 had a documented onset of CRF within the first 7 weeks of life. We conclude that renal disease leading to CRF may affect enamel formation of primary teeth in early postnatal life, resulting in lesions different from those observed in the secondary dentition.

Interfacial micromorphology and tensile bond strength of dentin bonding systems after NaOCl treatment.

PURPOSE: The objective of this study was to test the hypothesis that NaOCl treatment of acid-etched dentin would not lower the tensile bond strength of adhesive resins, but would eliminate the hybrid layer. MATERIALS AND METHODS: One hundred twenty teeth and three different bonding agents were used for SEM- and CLSM-visualization of the dentin-composite interface and for bond strength measurements. After etching with phosphoric acid, 75 dentin samples were pretreated with 10% NaOCl. The other 75 samples were etched only with phosphoric acid and were kept as controls. Composite was bonded to the pretreated surfaces with a bonding resin. RESULTS: NaOCl-treated samples: hybrid layers were not visible, but resin tags and resin penetration through lateral branches of tubules were prominent. Layers of unfilled resin were not apparent for Gluma CPS and Prime & Bond 2.1. Hypochlorite treatment of acid-etched dentin resulted in reduced bond strengths for specimens bonded with Syntac and Gluma CPS, but such treatment increased bond strength for Prime & Bond 2.1 bonded specimens. CONCLUSION: The removal of the collagen layer with NaOCl can enhance or decrease bond strengths, depending on the bonding agent used.

Mercury vapor release from dental amalgam after laser treatment.

The aim of this in vitro study was to determine whether the treatment of amalgam with different lasers leads to an increased release of mercury (Hg) vapor. In the case of CO2-lasers in pulse and continuous-wave mode, there was no effect visible on the amalgam surface and no Hg vapor could be detected. Using an Nd:YAG, Er:YAG or Nd:YLF laser, crater formation could be observed on the amalgam surfaces. With the solid state lasers tested, however, the Hg vapor measurements taken indicated that pulses applied to amalgam cause a substantially increased release of Hg vapor. This vapor may contribute to the patient's total mercury exposure.

Influence of different etching times on hybrid layer formation and tensile bond strength.

PURPOSE: To correlate the thickness of the dentin/resin hybrid layer and the influence of different etching times to the composite resin tensile bond strength. MATERIALS AND METHODS: 775 human molars were prepared by removing the occlusal cusps to expose middle dentin using a microtome saw. Five commercially available dentin bonding agents were applied according to the manufacturers' instructions. Only the etching times were varied. For confocal laser scanning microscopy (CLSM) measurements, 325 teeth were used and the etching times were varied (not etched, 15, 30, 60 or 120 seconds). The primer components or self-priming adhesive, respectively, were fluorescence-labeled by rhodamine B isothiocyanate. In each case, the prepared surfaces were then covered by a layer of composite resin, sectioned and examined using a CLSM in fluorescent mode. The extension of hybrid layers was quantified by measuring the distances between the dentin-composite junction to a visible boundary. For the tensile bond strength measurements (Zwick testing machine), 450 molars were prepared, using different dentin etching times (not etched, 15, 30, 60, 120 and 180 seconds). RESULTS: A hybrid layer was found in all etched teeth. The CLSM data gave evidence for an exponent-function relationship between the periods of etching and the thickness of the hybrid layer. The highest tensile bond strengths were achieved after 15 s of etching, followed by 30 s and 60 s. Under these etching conditions and irrespective of the bonding agent, bond strengths were significantly higher (P < or = 0.05) than without etching or after 120 and 180 s of etching. There was no linear correlation between the thickness of the hybrid layer and the bond strength.

Dentinal adhesion and histomorphology of two dentinal bonding agents under the influence of eugenol.

This study examined the influence of eugenol on the dentinal adhesion of an enamel-dentin bonding agent that removes the smear layer (total-etch technique) and a system that partially dissolves the smear layer (self-conditioning adhesive system). The tensile bond strength was measured on flat, dentinal surfaces after application and removal of pure eugenol for 15 minutes and a eugenol-containing temporary luting agent for 24 hours. In addition, the resin-dentin interface was evaluated with confocal laser scanning microscopy. Dentinal adhesion was found to be significantly reduced after the application of eugenol when a dentin bonding agent that dissolves the smear layer was used. Under confocal laser scanning microscopy, the resin-dentin interdiffusion zone of both adhesive was found to be changed, not only after application of eugenol but also after application of a eugenol-containing temporary luting agent.

Applications of confocal laser scanning microscopy to dental bonding.

The introduction of confocal laser scanning microscopy (CLSM) has provided a valuable new technique for the visualization of bonding structures such as a hybrid layer in dentin (Watson, 1989, 1991). In the case of seven commercially-available dentin bonding systems, it could be demonstrated that the CLSM renders considerably more detailed information than the SEM because of its non-destructive nature and because of the possibility of a distinction between components of bonding agents. With most of the bonding systems, measurements of the thickness of the hybrid layer could be carried out when the primer component was labeled with rhodamine B. It was found that this thickness is significantly increased by increases in etching time and only slightly decreased by increases in the drying time of the dentin and of the primer. When rhodamine B was used for dye penetration tests on four different dentin bonding systems, a leakage within the demineralized zone in the dentin was found in each of the specimens. This structure appears similar to that which Sano et al. (1995) called "nanoleakage". The amount of nanoleakage could not be measured by this method. In the case of enamel or ceramic bonding, a penetration zone was found which corresponded to the etching patterns found in enamel and ceramics, respectively. We conclude that CLSM can offer a wealth of new information about bonding morphology and, therefore, should be used in addition to conventional methods so that the maximum information can be obtained.

Progression of dental demineralization with and without modified tunnel restorations in vitro.

This study evaluated the caries-inhibitory effects of a glass-ionomer cement restoration. As a model to assess these effects, a Ketac-Fil restoration was placed beneath the mesial or distal enamel layer in 14 extracted human molars by means of access from the occlusal fossa. The teeth were insulated in all but two areas on the approximal surfaces. The prepared teeth were mounted on a hollow cylinder and a localized progressing demineralization of the approximal surfaces was induced by storage of the samples in an acidified gel. Immediately before and 14, 21, 28, 35, and 42 days after initiation of demineralization, standardized radiographs were obtained to assess the progression of demineralization. On each radiograph, the demineralized lesions were assessed by measurement of the coronoapical extension (CA) and the central depth (CD). At 28, 35, and 42 days after initiation of the demineralization, the CD of the lesions of the glass-ionomer cement group was revealed to be statistically significantly smaller than the lesions of the control group (no tunnel restoration) (P < 0.1). A multiple linear regression analysis identified CA and time as factors correlated to CD positively and the glass-ionomer restoration as a factor related to CD negatively (P < 0.001). It seems that modified tunnel restorations utilizing glass-ionomer cement inhibit progression of dental demineralization in vitro.

Experimental investigation of the shear strengths of teeth in the region of the dentinoenamel junction.

The shear strengths of human incisors, canines, premolars, and molars and bovine incisors in the region of the dentinoenamel junction were tested. The median shear strength of all human teeth, 38.99 MPa, was not significantly different from that of bovine teeth, 37.40 MPa. Among the groups of human teeth, the highest median shear strength was obtained from mandibular premolars (46.15 MPa), and the lowest from mandibular canines (32.63 MPa). Physical treatments (cooling or drying) led to a significant reduction in shear strengths. A similar effect was found after exposure to amino butyrate (a caries-removing agent) but not after exposure to sodium hypochlorite (used in endodontic treatment). In all investigated groups of teeth, the fracture areas were mainly in dentin and never exactly at the dentinoenamel junction; indicating that the cohesion of dentin, not the adhesion between dentin and enamel, is the limiting factor in the shear strength.