Detectability of residual Epiphany and gutta-percha after root canal retreatment using a dental operating microscope and radiographs - an ex vivo study

AIM

To compare the detectability of residual Epiphany and gutta-percha after root canal retreatment using a dental operating microscope and radiographic examination with the residual area measured after rendering the roots transparent.

METHODOLOGY

Sixty extracted single-rooted maxillary central incisor teeth were enlarged to apical size 40. Thirty canals were filled using vertically compacted Epiphany, the remainder were filled with vertically compacted gutta-percha and AH Plus sealer. After re-instrumentation to apical size 50, radiographs of the roots were taken in buccolingual and mesiodistal direction. Residual filling material was categorized by three observers using the radiographs and a dental operating microscope. The area of remaining material that was made visible by radiographs was measured with the aid of a computer image analysis programme. After clearing the roots, areas of residual filling material on the root canal wall were measured using a microscope.

RESULTS

Computer image analysis of the radiographs showed significantly smaller areas of remaining gutta-percha and Epiphany compared with the analysis of the transparent teeth that revealed only one absolutely clean root (Epiphany). Especially in the gutta-percha group, the scores determined by the observers using radiographic examination gave an over-optimistic impression of cleanliness compared with the scores determined by the visualization through the microscope.

CONCLUSION

Especially for remaining gutta-percha, the operating microscopes provided better detection of residual root filling material in retreated maxillary incisor teeth.

Two-year evaluation of a new nano-ceramic restorative material

The purpose of this prospective study was to evaluate the clinical performance of a new restorative material (Ceram.X) in combination with a new primer-adhesive (K-0127). One operator placed two Class I or II restorations in molars of 43 patients. One molar was restored with Ceram.X/K-0127, the other one with Tetric Ceram/Syntac Classic. At baseline, after 1 and 2 years, the restorations were evaluated by one evaluator using modified Ryge's criteria. After 2 years, 31 patients were examined. One Ceram.X-restoration had to be removed for root canal treatment due to pulpitis. Thus, failure rate of Ceram.X was 3.2% and of Tetric Ceram, 0%. In both groups, no sensitivity, no recurrent caries, and no changes in surface texture were recorded after 2 years. One restoration in each group showed slight changes in color stability (score B). Marginal discoloration (score B) was found concerning three Ceram.X-restorations (10.0%) and two Tetric Ceram-restoration (6.5%). Marginal integrity was score B for four Ceram.X-restorations (13.3%) and for four Tetric Ceram-restorations (12.9%). No statistically significant differences were found (p>0.05). After 2 years of clinical service, 96.8% of Ceram.X/K-0127 and 100% of Tetric Ceram/Syntac Classic restorations were in place and performed clinically well.

Effects of Irradiation on in situ Remineralization of Human and Bovine Enamel Demineralized in vitro

The objective of this study was to evaluate the effects of irradiation and surface condition on in situ remineralization of demineralized human and bovine enamel. Specimens (n=96) obtained from 24 human molars and 24 bovine incisors were prepared. The surfaces of half of the specimens were abraded while the others remained natural. Each of the 12 human and bovine abraded and sound specimens was irradiated fractionally up to 46.5 Gy (3.1 Gy/day, 5 days/week), while the remaining samples were not irradiated. Prior to and following the demineralization (pH 5.0; 14 days) all specimens were partly covered with nail varnish (control). After in vitro demineralization 2 irradiated and 2 nonirradiated specimens were inserted into both buccal aspects of 12 intraoral appliances, which were worn by 12 persons for a period of 6 weeks. All samples were brushed twice a day with a fluoride-containing toothpaste. Mineral analyses revealed a significant influence on mineral loss (DeltaZdemin), mineral gain (DeltaDeltaZ), lesion depth (LDdemin), and lesion depth reduction (DeltaLD) of the variables 'material' and 'irradiation' (p<0.05; ANOVA). Reciprocal interactions could be observed between these two variables for DeltaZdemin, DeltaDeltaZ, and LDdemin, due to significantly reduced values found for the irradiated, abraded bovine specimens compared to the nonirradiated ones (p<0.05; Bonferroni post hoc test). It can be concluded that neither irradiation nor abrasion influenced in vitro demineralization or in situ remineralization of the human specimens, whereas abrasion hampered demineralization in irradiated, bovine specimens.

Oral Hygiene Products and Acidic Medicines

Acidic or EDTA-containing oral hygiene products and acidic medicines have the potential to soften dental hard tissues. The low pH of oral care products increases the chemical stability of some fluoride compounds, favors the incorporation of fluoride ions in the lattice of hydroxyapatite and the precipitation of calcium fluoride on the tooth surface. This layer has some protective effect against an erosive attack. However, when the pH is too low or when no fluoride is present these protecting effects are replaced by direct softening of the tooth surface. Xerostomia or oral dryness can occur as a consequence of medication such as tranquilizers, anti-histamines, anti-emetics and anti-parkinsonian medicaments or of salivary gland dysfunction e.g. due to radiotherapy of the oral cavity and the head and neck region. Above all, these patients should be aware of the potential demineralization effects of oral hygiene products with low pH and high titratable acids. Acetyl salicylic acid taken regularly in the form of multiple chewable tablets or in the form of headache powder as well chewing hydrochloric acids tablets for treatment of stomach disorders can cause erosion. There is most probably no direct association between asthmatic drugs and erosion on the population level. Consumers, patients and health professionals should be aware of the potential of tooth damage not only by oral hygiene products and salivary substitutes but also by chewable and effervescent tablets. Additionally, it can be assumed that patients suffering from xerostomia should be aware of the potential effects of oral hygiene products with low pH and high titratable acids.

Profilometric and Microradiographic Studies on the Effects of Toothpaste and Acidic Gel Abrasivity on Sound and Demineralized Bovine Dental Enamel

The objective of this study was to assess the abrasive effects of toothpastes and acidic F gels on sound and demineralized enamel. Pairs of enamel specimens were cut from bovine incisors, embedded in epoxy resin and polished. An artificial subsurface lesion of 80-90 microm depth was created in one specimen from each pair. The samples were covered with adhesive tape, thereby exposing the enamel for abrasivity testing. All samples were divided into six groups of 15 and brushed with a slurry (1:3) of F gel or toothpaste and human saliva. Brushing with water (control) or with slurry was carried out (16,000 strokes) using a medium toothbrush (load 275 g) mounted in a brushing machine. Abrasion was evaluated using laser profilometry, and was about 50% less on sound than on demineralized enamel (p < 0.001). In the latter, brushing with water (0.09 +/- 0.03 microm) or with fluoride-free gel (0.08 +/- 0.03 microm) resulted in negligible wear. With a medium-abrasive paste (1.76 +/- 0.85 microm) and an acidic F gel (2.48 +/- 0.72 microm), brushing abrasion was significantly greater (p < 0.001) than with a low-abrasive paste (0.84 +/- 0.38 microm). The greatest wear (16.6 +/- 10.8 microm) was observed with high-abrasive paste (p < 0.001), and here transversal microradiography revealed a complete loss of the pseudointact surface after brushing. In vitro formed caries-like lesions can be abraded (by toothbrushing) more easily than sound enamel; hence, initial white spot lesions should preferably be brushed with oral hygiene products of low abrasivity.

An in vitro investigation of penetration depth of dentine bonding agents into carious dentine

The aim of the present in vitro study was to determine the penetration depth of dentine bonding agents into carious dentine as a possible strategy in caries treatment of deep lesions. Forty-eight extracted carious teeth were used for the experiments and divided in four groups. In a split-tooth design, one half of each tooth was treated without caries excavation, and the second half after caries excavation. In group 1 the teeth were treated with Prime & Bond 2.0 without phosphoric acid etching, and in group 2 with phosphoric acid etching. In group 3, the teeth were treated with All-Bond 2 without phosphoric acid etching, and in group 4 with phosphoric acid etching. Bonding agents were marked with an orange dye prior to application. The composition of the bonding agents had no significant influence on penetration depths. The mean thickness of the outer, necrotic caries zone in unexcavated specimens was 117 microm (+/-126). Bonding agents penetrated significantly deeper into unexcavated carious dentine (mean 124 +/- 76 microm) compared with excavated dentine (11 +/- 14 microm) and sound dentine (3 +/- 4 microm). Acid etching significantly reduced the thickness of the outer caries zone, and the penetration depth of the bonding agents into unexcavated carious specimens by approximately 50%, and increased it into sound dentine. The results indicate that dentine bonding agents could completely penetrate the unexcavated outer carious dentine in 90% of specimens. Further studies are required to determine whether further caries activity is arrested after treatment with dentine bonding procedures.

Individual vitality pattern of in situ dental biofilms at different locations in the oral cavity

The aim of the study was to examine the three-dimensional vitality structure of dental biofilms grown simultaneously at different locations in the oral cavity over a 48-hour period. Eight healthy volunteers wore special acrylic appliances. On each buccal side of the upper and the lower jaw three glass slabs were inserted, allowing for growth of a biofilm mimicking approximal plaque. After 48 h, the specimens were removed and biofilms were stained using two fluorescent dyes which selectively stain vital bacteria green and dead bacteria red. Under the confocal laser scanning microscope optical sections of 1 microm throughout the biofilm were made. To assess the vitality values (proportion of vital bacteria) of the whole biofilm as well as the vitality distribution in the different plaque sections an image analysis program was used. Plaque from the different locations revealed mean vitality values between 64.4 and 75.7% in the upper jaw and between 64.3 and 76.8% in the lower jaw, which were not statistically different. However, a great variation of the vitality values for the different layers and among the 8 subjects was found. Nevertheless, the analysis of the data of each single volunteer revealed a very similar vitality pattern in all twelve locations.

Systemic versus Topical Fluoride

The actual mechanism of fluoride action is still a subject of debate. A dogma has existed for many decades, that fluoride has to be ingested and acts mainly pre-eruptively. However, recent studies concerning the systemic effect of fluoride supplementation concluded that the caries-preventive effect of fluoride is almost exclusively posteruptive. Moreover, epidemiologists have cast doubt on the validity of the 'old' studies dealing with fluoride use. The concept of the posteruptive fluoride effect is supported by in vitro and in situ investigations demonstrating that the mode of action of fluoride can be attributed mainly to its influence on de- and remineralization kinetics of dental hard tissues. Therefore, topical fluoride application (e.g. in the form of fluoridated dentifrices) should be encouraged. There are still important questions open that need to be answered despite existing knowledge about the caries-preventive effect of fluoride.

Influence of buffering effects of dentifrices and fluoride gels on abrasion on eroded dentine

OBJECTIVE

Evaluation of abrasion resistance of eroded and non-eroded dentine brushed with experimental dentifrices and gels of varying buffering capacities.

DESIGN

One hundred and twenty human dentine specimens were distributed among six groups (A-F) according to the different buffering capacities of experimental toothpastes and gels. The dentifrices (pH: 4.5) and gels (pH: 4.5) differed in fluoride content, RDA-value and buffer capacity (given as mg KOH needed for neutralisation): (A) 0.125%F, RDA: 77, 6mg KOH; (B) 0.125%F, RDA: 125, 24mg KOH; (C) 0.125%F, RDA: 129, 12mg KOH; (D) 0%F, RDA: 81, 1.55mg KOH; (E) 1.25%F, RDA: 21, 8.5mg KOH; (F) 0.125%F, RDA: 7, 3.11mg KOH. Ten specimens were cycled through three alternating demineralisations (1% citric acid, 5min) and remineralisations (artificial saliva, 1min) including brushing abrasion in an automatic brushing machine (2 x 2000 strokes). Ten samples of each group were not eroded, but only brushed.

RESULTS

After three cycles, loss of dentine was determined by profilometry (mean +/- S.D. [microm]). Eroded samples: (A) 37.12+/-4.95; (B) 48.67+/-4.77; (C) 39.88+/-3.76; (D) 32.92+/-2.67; (E) 3.65+/-1.35; (F) 6.47+/-1.31. Uneroded samples: (A) 30.78+/-6.47; (B) 37.84+/-7.75; (C) 30.07+/-3.05; (D) 26.93+/-2.30; (E) 1.76+/-0.94; (F) 0.51+/-0.18. Analysis of variance revealed significantly higher abrasion values for the eroded compared to the non-eroded samples (P<or=0.05). Dentifrices with same pH-value, fluoride content and similar RDA-values but a higher buffering capacity exhibited significantly more abrasion than toothpastes with lower buffering capacity. Highly-concentrated fluoride gel with higher buffering capacity lead to less abrasion values compared to the gel with low fluoride concentration and low buffering capacity.

CONCLUSION

Toothbrushing abrasion behaviour of eroded dentine may be influenced by the fluoride content, RDA-value and buffering capacity of the applied dentifrice or gel.

Impact of the intraoral location on the rate of biofilm growth

The aims of the present study were: a) to assess the impact of the intraoral location on the rate of biofilm growth, and b) to establish an in vivo biofilm model to examine intraoral biofilm growth. Eight healthy volunteers wore acrylic splints with 15 glass slabs each in the upper and lower jaws to build up plaque. After 48 h, the specimens were removed and stained using the vital fluorescence technique. Biofilm thickness was evaluated by confocal laser scanning microscopy (CLSM). The mean plaque thickness amounted to 77.6 +/- 29.1 microm on the buccal sites of the upper jaw and 71.9 +/- 26.3 microm on the buccal sites of lower jaw. On the palatal site a biofilm of 52.1 +/- 26.2 microm thickness was grown, which was significantly less compared with the other locations evaluated (p < 0.001). The results demonstrate that the in situ biofilm thickness on the buccal sites was similar irrespective of the location in the oral cavity. The new splint system described may be a useful tool for further standardised experimental studies regarding influences on growth and structure of intraoral biofilms.

Effect of mineral supplements to citric acid on enamel erosion

The aim of this study was to evaluate the effect of mineral supplements to citric acid (1%; pH 2.21) on enamel erosion under controlled conditions in an artificial mouth. From each of 156 bovine incisors one polished enamel sample was prepared. The samples were divided among 13 experimental groups (n=12). In group 1 citric acid only was used (control). In groups 2-10 either calcium, phosphate or fluoride in various low concentrations was admixed to the citric acid. In groups 11-13 the citric acid was supplemented with a mixture of calcium, phosphate and fluoride. For demineralisation the specimens were rinsed with the respective solution for 1 min, immediately followed by a remineralisation period with artificial saliva (1 min). The specimens were cycled through this alternating procedure five times followed by rinsing for 8 h with artificial saliva. The de- and remineralisation cycle was repeated three times for each specimen interrupted by the 8 h-remineralisation periods. Before and after the experiments, the specimens were examined using microhardness testing (Knoop hardness) and laser profilometry. Hardness loss and enamel dissolution was significantly higher for the controls as compared to the remaining groups. Significantly lowest hardness loss for all groups was recorded for group 12 with admixture of calcium, phosphate and fluoride to citric acid. The significantly highest enamel loss was recorded for the controls compared to all other samples. Groups 3 and 4 revealed significantly lower and higher tissue loss compared to the remaining groups (2-13), respectively. The other groups did not differ significantly from each other. Modification of citric acid with calcium, phosphate and fluoride exerts a significant protective potential with respect to dental erosion. However, with the low concentrations applied enamel dissolution could not be completely prevented.

Influence of olive oil emulsions on dentin demineralization in vitro

The effect of two different concentrations of olive oil emulsions on development of artificial caries-like dentin lesions under severe demineralizing conditions was investigated. Bovine dentin samples (n = 180) were ground flat, polished, divided into four groups, and subjected to three demineralization cycles per day. Samples were stored in one of the following solutions for 5 min prior to demineralization in a buffer solution (pH 5): Group 1: 50% oil emulsion (olive oil and distilled water); group 2: 5% oil emulsion; group 3: distilled water; and group 4: 1,500 ppm sodium fluoride. Daily up to 9 days, lesion depth (ld) and mineral loss (deltaZ) were determined by means of microradiography and analyzed by ANOVA and Tukey's studentized range test (p < or = 0.05). Lesion depth increased with time for all groups. Mineral loss increased in groups 1-3. A small but significant decrease in mineral loss was observed following treatment with lipid emulsions as compared to treatment with distilled water, but fluoride treatment was considerably more effective. Mean mineral loss (means +/- SD in vol% x microm) averaged over the study period was 4,368 +/- 1,599, 4,536 +/- 1,823, 4,849 +/- 1,798, and 789 +/- 177 for group 1, 2, 3, and 4, respectively. Ratio (deltaZ/ld) remained constant around 30 vol% for groups 1-3, but decreased for group 4. In conclusion, externally provided lipids have the potential to reduce dentin demineralization in vitro.

Fluoride uptake, retention, and remineralization efficacy of a highly concentrated fluoride solution on enamel lesions in situ

Repeated topical application of concentrated fluorides is known to reduce caries. Little is known about fluoride retention and remineralization in incipient caries lesions following a single application. We investigated fluoride and the remineralization kinetics of a single application of elmex fluid (GABA International AG, Münchenstein, Switzerland; 10,000 ppm F) in initial enamel lesions. In this double-blind, placebo-controlled, randomized, crossover in situ study that conformed to good clinical practice, volunteers received intra-oral removable appliances carrying demineralized enamel samples after application of elmex fluid or placebo. After 5 min, 1, 2, 3, and 4 weeks in situ, KOH-soluble fluoride (KOHF), structurally bound fluoride (SBF), mineral gain, and lesion depth reduction were measured. Elmex fluid promoted higher KOHF and SBF at all times, decreased KOHF with time, increased SBF up to 3 weeks, and registered a higher mineral gain than placebo. Volunteers with higher stimulated salivary flow rates had lower fluoride uptake, but higher mineral gain. In conclusion, a single application of highly concentrated fluoride solution increases remineralization.

Erosive potential of oral care products

Seven oral care products and orange juice as a positive control were tested for the erosive potential by immersing each enamel specimen (10 per group) into solutions of the various products for 10 and 20 min. Before and after the experiment Knoop surface hardness (SMH) was measured. The enamel microstructure before and after immersion was assessed by scanning electron microscopy and confocal laser scanning microscopy. Orange juice produced the most marked losses of hardness after 10 and 20 min. Among the dental hygiene products only the fluoride-free toothpaste produced a significant reduction of hardness after 10 as well as after 20 min. With the exception of Elmex gel, all tested oral care products led to a significant (p < 0.05) increase of enamel hardness. The results of the hardness measurements corresponded with the microstructure findings. It may, therefore, be concluded that the tested fluoride-containing oral care products do not exhibit any erosive potential, which could be picked up with the methodologies under study.

Chemomechanical caries removal: a comprehensive review of the literature

Compared to the past, caries removal has become more efficient, however inherent fundamental drawbacks of the drilling approach have remained: unpleasantness to patients, need for local anesthesia, and potential adverse effects to the pulp due to heat and pressure. Chemomechanical caries removal, introduced almost three decades ago, was claimed to be a non-invasive alternative for the removal of carious dentine. In essence, the technique involved applying a solution onto the decayed dentinal tissue, allowing it to soften it, and, finally, scraping it off with blunt hand instruments. The partially degraded collagen in carious dentine was chlorinated by chemomechanical caries removal solutions. This chlorination affected the secondary and/or quaternary structure of collagen, by disrupting hydrogen bonding. Carious material removal was thus facilitated. The purpose of this paper is to perform a comprehensive review of the literature regarding chemomechanical caries removal, including the most recently available product, the initial reports on which warrant renewed interest in the approach.

What Is the Optimum Fluoride Concentration Needed for the Remineralization Process?

In vitro experiments could demonstrate that only negligible amounts of fluoride are necessary to promote remineralization of incipient caries lesions. From the clinical point of view, there is evidence that only under certain circumstances is a stabilization of the surface zone of an incipient caries lesion the true mechanism of action of topically applied fluorides. However, an optimum universally valid fluoride concentration needed for this process cannot be defined.

Influence of resin cement viscosity on microleakage of ceramic inlays

OBJECTIVES

The aim of the present investigation was to evaluate the effect of the different viscosities of two resin luting cements on microleakage of ceramic inlays at dentinal margins. The effect of the width of the space between inlay and tooth, on the quality of the marginal seal was also investigated.

METHODS

Mesial and distal class V cavities were prepared in 48 extracted third molars. The incisal margins of the cavities were in enamel and the cervical margins in dentin. Subsequently, Empress inlays with different cervical margin gap dimensions were fabricated. The mean cervical gap dimensions in the respective groups were as follows: group 1 (27 microm); group 2 (232 microm); group 3 (406 microm). Half the inlays in each group (16) were cemented with a low viscous resin luting cement, and half (16) with a highly viscous resin luting cement. The teeth were subjected to occlusal loading with synchronized thermal cycling in a masticatory simulator. Then, the specimens were immersed in basic fuchsin solution, and dye penetration along the cavity walls was measured. In addition, marginal adaptation was analyzed in the SEM at baseline and after loading, using a replica technique.

RESULTS

With regard to dye penetration at dentinal margins, the highly viscous cement performed statistically significantly better at dentin/composite margins than the low viscous cement (p=0.0158). These findings are supported by SEM analysis.

SIGNIFICANCE

It is assumed that polymerization stress within the luting cement could not be completely compensated for by larger luting spaces. Highly viscous luting cements are recommended for cementing class V inlays in larger luting spaces.

Clinical evaluation of chemomechanical caries removal in primary molars and its acceptance by patients

The purpose of this study was to evaluate the clinical efficiency and patient acceptance of the chemomechanical caries removal agent Carisolvtrade mark in deciduous teeth. Contralateral primary molars of sixteen 7- to 9-year-old patients (32 teeth) were treated with the air-motor and with Carisolv, respectively. Patients replied to a pre- and a postoperative questionnaire. Complete caries removal (CCR) was accomplished in all air-motor sessions. It was not achieved within the time limit of 15 min in 6 (37.5%) Carisolv sessions. Air-motor CCR time ranged between 6 and 18 s (mean: 11.81 s ). Carisolv CCR time, where accomplished within 15 min, ranged between 6 min 46 s and 13 min 57 s (mean: 6 min 51 s). Preoperatively, the majority of the children reported disliking the drilling, and that they would visit the dentist more often and prefer sitting in the chair longer if they could avoid it. Postoperatively, the majority of the children reported disliking the taste of Carisolv, estimated Carisolv to have taken longer, would not recommend it to their friends, and preferred the air-motor. In conclusion, Carisolv, although a step forward in terms of solution volume required, is not in a position to replace rotary instruments for caries removal: it did not remove decay completely in one third of our sample; it was much slower than the air-motor; it had a chlorine taste/odor our patients disliked.

Fluoride release from light-curing restorative materials

PURPOSE

To measure the in vitro fluoride release from three polyacid-modified resin-based composites (Dyract AP, Compoglass F, F2000) and one resin-modified glass-ionomer cement (Vitremer VLC) for 28 days in two different buffer solutions.

MATERIAL AND METHODS

30 cylindrical specimens of each material were prepared. Subsequently, 15 samples of each material were stored in neutral (pH 6.8) and acidic (pH 4.0) buffer solution (5 mL), respectively. After 4, 8, 12 hrs and 1, 2, 4, 8, 14 days, respectively, the samples were transferred into new solutions. The fluoride content was determined with a fluoride sensitive electrode. Data were analyzed with ANOVA, followed by closed-test-procedure based on Kruskal-Wallis.

RESULTS

Compared to the neutral solution, all materials showed a significantly higher release of fluoride in acidic environment within the 28-day period (P < 0.001, ANOVA). In acidic buffer solution Vitremer VLC and Compoglass F showed a significantly higher fluoride release than F2000 and Dyract AP (P < 0.001, closed-test-procedure). In neutral solution Dyract AP showed the significantly lowest release (P < 0.001, closed-test-procedure). Fluoride release from the materials tested is higher in an acidic environment than in a neutral environment.

An in vitro assessment of the strength of porcelain veneers dependent on tooth preparation

The treatment of teeth using veneer restorations combines aesthetic and functional improvements with a low destructive technique. Different kinds of tooth preparation techniques are described in the literature for this kind of restoration. This in vitro study aimed to examine the influence of the incisal preparation on the loadability of teeth restored with porcelain laminate veneers. Thirty-six selected mandibular incisors were randomly assigned to three groups with 12 teeth per group. In the first group, only the facial surface was prepared. In the second group, the preparation included a rounded incisal edge and a distinct chamfer lingually. The third group served as an unprepared control. Empress(R) veneers were then fabricated and cemented with a low viscous luting composite material. After 120 days storage in Ringer's solution, the specimens were loaded incisally to the point of failure. Statistical analysis of the results showed significant differences between the series (P=0.0103). Group 2 (with preparation of the incisal edge) exhibited the lowest fracture resistance (466+/-99 N) (N, mean forces). When prepared only facially, the teeth restored with Empress veneers reached the strength of unprepared teeth. Compared with the biting force described for incisors in the literature, the in vitro loadability reached in this investigation seems to jusitify the clinical use of both preparation designs tested.

Brushing abrasion of luting cements under neutral and acidic conditions

Four resin based materials (Compolute Aplicap, ESPE; Variolink Ultra, Vivadent; C&B Metabond, Parkell and Panavia 21, Kuraray), two carboxylate cements (Poly-F Plus, Dentsply DeTrey and Durelon Maxicap, ESPE), two glass-ionomer cements (Fuji I, GC and Ketac-Cem Aplicap, ESPE), one resin-modified glass ionomer cement (Vitremer, 3M) one polyacid-modified resin composite (Dyract Cem, Dentsply DeTrey) and one zinc phosphate cement (Harvard, Richter & Hoffmann) were investigated according to their brushing resistance after storage in neutral and acidic buffer solutions. For this purpose 24 cylindrical acrylic molds were each filled with the materials. After hardening, the samples were stored for seven days in 100% relative humidity and at 37 degrees C. Subsequently, they were ground flat and polished. Then each specimen was covered with an adhesive tape leaving a 4 mm wide window on the cement surface. Twelve samples of each material were stored for 24 hours in a buffer solution with a pH of 6.8. The remaining 12 samples were placed in a buffer with a pH of 3.0. All specimens were then subjected to a three media brushing abrasion (2,000 strokes) in an automatic brushing machine. Storage and brushing were performed three times. After 6,000 brushing strokes per specimen, the tape was removed. Brushing abrasion was measured with a computerized laser profilometer and statistically analyzed with ANOVA and Tukey's Standardized Range Test (p < or = 0.05). The highest brushing abrasion was found for the two carboxylate cements. The lowest brushing abrasion was found for one resin based material, Compolute Aplicap. With the exception of three resin-based materials, a lower pH led to a higher brushing abrasion.

Brushing abrasion of eroded dentin after application of sodium fluoride solutions

The aim of the present in vitro study was to evaluate the influence of sodium fluoride solutions on brushing abrasion of eroded dentin. Dentin specimens were prepared from 60 bovine incisors. The specimens were embedded in acrylic resin, ground flat, polished and subsequently covered with tape exposing an area of 1.8 mm x 10.0 mm in the center of the exposed dentin. The samples were alternatingly stored in a demineralizing solution (5 min) and a remineralizing solution (1 min) for 5 times. The erosive soft drink Sprite light(R) served as a demineralizing solution and artificial saliva was used as a remineralizing solution. Prior to storage in artificial saliva 15 specimens were each treated for 1 min with 250 and 2,000 ppm fluoride solution, respectively. Fifteen specimens were treated with distilled water instead of the fluoride solution (= eroded controls). The remaining samples were neither eroded with the soft drink nor fluoridated (= uneroded controls). After each immersion in artificial saliva the specimens were submitted to abrasion in a toothbrushing machine. After 5 demineralization-remineralization brushing cycles the total amount of tooth wear due to erosion and subsequent abrasion was profilometrically evaluated. Statistical analysis revealed the significantly lowest wear in the uneroded controls and the highest amount of abrasion in the eroded controls. Application of the fluoride solutions increased the wear resistance of the eroded dentin specimens, showing significantly better protection by the high-concentration compared to the low-concentration solution. The susceptibility to abrasion of the eroded dentin specimens treated with the high-concentration fluoride solution did not differ significantly from the uneroded dentin samples. It is concluded that application of 2,000 ppm sodium fluoride solutions immediately before toothbrushing significantly reduces abrasion of eroded dentin in vitro.

Influence of acidified fluoride gel on abrasion resistance of eroded enamel

The objective of the study was to evaluate the abrasion resistance of eroded enamel brushed with an acidified fluoride gel. Each enamel specimen was prepared from one of 64 bovine incisors. The specimens were embedded in acrylic resin, ground flat, polished and subsequently covered with a tape exposing an area of 1.8x10.0 mm in the center of the enamel specimens. The samples were alternatingly stored in a demineralizing solution (5 min) and a remineralizing solution (1min) four times. An acidic soft drink (Sprite Light(R)) served as a demineralizing solution and artificial saliva was used as a remineralizing solution. After each remineralization the specimens were brushed in an automatic brushing machine (2,000 strokes, 2.5 N load) and subsequently stored again in saliva (1 min). A mixture of artificial saliva (5 ml) with a gel (1 ml) based on the formulation of Elmex(R) gelée (Wybert, Lörrach, Germany) served as an abrasive slurry. Thirty seconds after brushing, the slurry was removed from the specimens by rinsing with destilled water. For each of 16 specimens the following gels (A-D) were used: gels A (pH 7.0) and B (pH 4.5) were unfluoridated; gels C (pH 7.0) and D (Elmex gelée; pH 4.5) contained 1.25% F-. After two cycles the specimens were kept in the saliva for 8 h. Finally the tape was removed and the abrasion was determined profilometrically. The following values (mean +/- SD) were obtained and statistically analyzed by analysis of variance and Wilcoxon two-sample tests (p</=0.01): gel A, 0.96+/-0.24 microm; B, 1.58+/-0.32 microm; C, 0. 71+/-0.23 microm; D, 0.25+/-0.08 microm. The differences between all experimental groups were statistically significant. It is assumed that treatment of enamel erosions with an acidified fluoride gel results in a higher abrasion resistance compared to gels which are either unfluoridated or neutral.

Effects of additional teaching of final-year dental students on their radiographic diagnosis of caries

The aim of this study was to evaluate whether the skills of final-year dental students in the diagnostic interpretation of bitewing radiographs could be improved by additional didactic instruction. 6 consecutive classes of students in the same stage of education (last semester in the Department of Operative Dentistry) took part in the investigation from 1995 to 1998. At the beginning of each semester, the same in vivo made bitewing radiograph was demonstrated in a separate radiology revision lecture and interpreted with the students. The intensification of the training in the diagnosis of bitewing radiographs was made when the 4th class of students started. At the end of each semester, each student of the 6 consecutive classes was asked to evaluate the same bitewing radiograph, which had been demonstrated at the start of the semester. The students were not told that they had already diagnosed from this radiograph before. The results of the radiographic diagnosis were then analyzed using an evaluation system paying special attention to the treatment decision. True positive and true negative diagnoses were scored as correct and false positives and false negatives as incorrect. There was no significant difference (ANOVA) in the ability to diagnose from bitewing radiographs between the groups of students who received, and those who did not receive, additional training. The benefits of this type of additional instruction in the last semester in the Department of Operative Dentistry seem only to be important in some individual cases.

Effect of different luting procedures on the seating of ceramic inlays

This in vitro study evaluated the effect of different luting procedures on the proper seating of ceramic inlays and on the marginal seal through microleakage testing. Sixty mesial-, occlusal-, distal- (MOD) cavities were prepared in third molars, and distributed among four groups. In the control group 1, the cavity surface was treated with dentin and enamel bonding agents; ceramic inlays were placed into the cavity and light cured. In group 2, the dentin and enamel bonding agents were cured prior to the placing of the inlays, and following the insertion. In group 3, the inlays were luted without enamel bonding. In group 4, the inlays were cemented using a one-bottle bonding and two times light curing. The groups with only one time light curing at the end of the luting process exhibited the smallest luting space following cementation. The smallest dye penetration values were obtained for the two groups with separate light curing of the dentin bonding agent. Reducing the film thickness of polymerized dentin bonding agents, i.e. by changing the composition of the bonding agents, could facilitate proper seating of ceramic inlays together with a better marginal seal.

Use of variable remineralization periods to improve the abrasion resistance of previously eroded enamel

The objective of the study was to evaluate the period of remineralization needed to re-establish the resistance of eroded enamel against brushing abrasion. Enamel specimens were prepared from 84 polished bovine incisors. The samples were evenly distributed among 7 groups (A-G) and submitted to ten alternating de- and remineralization cycles which included abrasion by toothbrushing. Demineralization was accomplished by immersing the specimens in the erosive soft drink Sprite Light((R)) for 1 min. Remineralization was performed by storing the samples in artificial saliva for either 0 min (A), 10 min (B), 60 min (C) or 240 min (D). After each remineralization, the specimens were brushed in an automatic brushing machine. Group E (erosion and 240 min remineralization, but no brushing) group F (erosion, but no remineralization and no brushing), and group G (brushing, but no erosion and no remineralization) served as controls. After performing the cycles, loss of enamel was determined by profilometry. The following values (mean +/- SD) were obtained and statistically analyzed (p<0.05): group A (5.16+/-1.26 microm), B (2.47+/-0.68 microm), C (1.72+/-0.75 microm), D (1.11+/-0.42 microm), E (0.81+/-0. 23 microm), F (1.04+/-0.31 microm), G (0.22+/-0.15 microm). Only the differences between groups D, E, and F were statistically not significant. Under the chosen in vitro conditions, it is concluded that abrasion resistance of eroded enamel continuously increases with remineralization time. However, even after a period of 1 h of remineralization, abrasion of previously eroded enamel is increased

Root lesions in a group of 50-60 year-old Germans related to clinical and social factors

From a preventive point of view collection of data concerning carious and non-carious cervical tooth defects is definitely important. Consequently, the prevalence and distribution of different root lesions were studied and correlated with behavioral and biological factors in 50- to 60-year-old German individuals (n = 298). Additionally, the data were correlated with characteristics concerning oral health and known risk factors such as gender, educational level, and presence of plaque. An interview included questions on sociodemographic and socioeconomic characteristics, dental and general health status, and various behavioral parameters. During clinical examination data concerning coronal and root lesions, restorations, probing depth, gingival bleeding, and dental plaque were obtained. The participants represented a social middle class population with a high awareness of dental health. Obviously, for the participants, known risk factors for root decay such as gender, educational level and plaque index were of minor importance. Factors correlating with root caries were: (a) number of missing teeth, (b) probing depth, (c) smoking habit, (d) regular dental attendance and (e) the reason for the last dental treatment. Additionally, the prevalence of non cariogenic lesions, primarily resulting from increased but wrongly performed oral self care, seems gradually to relieve carious root destruction.

Influence of two dentin bonding systems on the demineralization of the root surface

It has been assumed that dentin adhesives can prevent root surface caries. The aim of this study was to determine the caries-protective effect of two different dentin bonding systems on the demineralization of root surfaces in vitro. The root surfaces of 60 freshly extracted caries-free human molars were thoroughly cleaned and polished, thereby removing the cementum. The teeth were then coated with acid-resistant nail varnish, exposing two rectangular windows of 6 mm2 each. One window served as an untreated control, while the other window was treated with a dentin bonding system. The specimens were distributed among the following experimental groups--Group 1: Syntac, Heliobond (no air thinning); Group 2: Syntac, Heliobond (as recommended); Group 3: Syntac, without Heliobond; Group 4: Prime & Bond 2.0 (no air drying); Group 5: Prime & Bond 2.0 (as recommended); Group 6: Prime & Bond 2.0 (dentin pretreated with 36% phosphoric acid). Subsequently, all specimens were demineralized for 6 days with acidified gel (HEC, pH 4.8, 37 degrees C). From each tooth, three dentinal slabs were cut perpendicular to the polished surface of the windows. The slabs were ground to a thickness of 80 microns and imbibed with water. The depth of the respective demineralized areas was determined using a polarized light microscope. All control specimens exhibited lesions with a mean depth of 67 microns. In Groups 2, 3, and 5 the lesion depth was reduced significantly, while in Groups 1, 4, and 6 no lesions could be detected. It was concluded that the demineralization of the root surface can be impeded by application of the dentin adhesives tested.

Effect of toothbrushing on fluoride release of polyacid-modified composite resins

The aim of the study was to evaluate the fluoride release of polyacid-modified composite resins (Dyr-act, Compoglass) submitted to brushing abrasion. Twenty samples were taken from each material and stored in a buffer solution (pH 4.0) for 12 days. Each day, the samples were transferred to a fresh solution. Ten samples of each material were brushed in an automatic tooth-brushing machine (250 strokes, 260-g load) every fourth day. The remaining samples were not subjected to brushing. Fluoride content of the solutions was measured with a fluoride sensitive electrode after the addition of TISAB. Statistical analysis demonstrated significant differences between the two materials with regard to cumulative fluoride release within the 12 days of the experiment. However, no difference was observed between the fluoride release of the brushed samples compared to the unbrushed specimens. This was true for both, the cumulative fluoride release and its release on the day following brushing. It is assumed that regular brushing of the tested materials did not influence their release of fluoride and that brushing of polyacid-modified composite resins does not lead to maintaining their initially high level of fluoride release.

Fluoride release/uptake of polyacid-modified resin composites (compomers) in neutral and acidic buffer solutions

The aim of the present study was to evaluate the fluoride uptake/release of polyacid-modified resin composites (compomers) in neutral and acidic buffer solutions. Two compomers (Dyract and Compoglass) were tested and the conventional glass-ionomer cement (GIC) Vivaglass Base served as a control. Forty specimens were fabricated from each of the respective materials. Twenty of these specimens were placed in artificial saliva and the other 20 specimens in a fluoridated dentifrice slurry for 5 min. Then, 10 fluoridated and 10 non-fluoridated specimens were immersed in a neutral buffer solution (pH 6.8), and the other specimens were immersed in an acidic solution (pH 4.0). After 1, 2, 3, 4, and 5 days the samples were again placed in either a fluoridated dentifrice slurry or saliva for 5 min, after which time they were transferred to fresh buffer solutions. The fluoride content of the solutions was assessed with a fluoride sensitive electrode. Fluoride release from all the materials decreased continuously during the experiment, with a significantly higher release in the acidic solution compared to the neutral buffer solution. Fluoridation did not result in an increased fluoride release for the compomers. However, the conventional GIC revealed a significantly higher fluoride release after fluoridation. It is concluded that Dyract and Compoglass can not be replenished with fluoride, irrespective of the pH value of the environment.

Dental status of schoolchildren from a rural community in Cameroon

This study assessed the dental health status of children in a rural community in Cameroon. The investigation was carried out in 1996 on a total of 403 pupils aged between 5-17 years. The children were divided into 3 age groups, (I-III): I: 5-8 years (n = 157), II: 9-12 years (n = 191), II: 13-17 years (n = 55). The teeth were examined for dmft/DMFT, CPI, opacities and treatment needs. 22.6 per cent of the pupils were caries free, and the following mean dmft/DMFT-values were obtained: Age group I, dmft: 2.26 + 2.84, DMFT: 0.85 + 1.39. Group II, dmft: 0.60 + 1.35, DMFT: 2.76 + 2.74. Group III, dmft: 0.05 + 0.22; DMFT: 5.12 + 3.04. Opacities or other enamel disorders were observed in 16.9 per cent of the children. 68.7 per cent of them needed invasive dental treatment and 61.3 per cent required restorative treatment only. 7.4 per cent needed extractions and 25.6 per cent required prevention/sealant care as sole measure. 6.6 per cent of the children showed CPI-grade 0. The majority scored CPI-grade 1 (37.7 per cent) and grade 2 (49.9 per cent). The reported data suggest that improved dental health mindedness and availability of oral health care services are required in order to reduce oral health diseases.

Correlation of transversal microradiography and microhardness on in situ-induced demineralization in irradiated and nonirradiated human dental enamel

The objective was to evaluate whether a correlation exists between microhardness (MH) and transversal microradiographical (TMR) data for in situ-induced caries lesions in irradiated and nonirradiated human enamel. Enamel specimens were prepared from the lingual and buccal surfaces of 20 freshly extracted, caries-free third molars. The surfaces were polished (4000 grit). Either the lingual or the buccal specimen of each tooth was irradiated with 60 Gy; the other sample was not irradiated. Two irradiated and two nonirradiated specimens were inserted into both buccal aspects of each of five intraoral mandibular appliances. The appliances were worn by five persons for 6 weeks day and night. One side was brushed daily with a fluoride-free toothpaste; on the other side, dental plaque was allowed to grow. Individual oral hygiene was performed without any fluorides. During meals, the appliance was stored in 10% sucrose solution. Then the enamel specimens were cut perpendicular to their oral surface. The cut surface was polished (4000 grit) and the Knoop hardness number (KHN) was measured across the lesions, at 25, 50 and 75 microm from the oral surface. After MH testing the samples were polished again, thereby reducing the surface by about 10 microm. Subsequently, the slabs were ground to a thickness of 90 microm, and studied by means of TMR. Mineral loss was calculated with dedicated software at the locations corresponding to the MH testing. A total of 120 paired data was submitted to linear-regression analysis. Neither MH nor TMR showed significant differences between irradiated and nonirradiated enamel lesions. A linear relation was found between square root of KHN and the mineral volume percent. In naturally induced caries lesions, MH values can be converted to mineral volume percent using the equation [21.19 + 3.66 x square root of KHN]. This equation fits the data with a reliable correlation coefficient (r2=0.915).

Evaluation of the apical seal of root canal fillings with different methods

The purpose of the study was to compare dye penetration methods conducted passively, under negative pressure, or under high pressure conditions. Ninety human maxillary incisors were instrumented and obturated with either the lateral condensation or single cone technique. India ink was used as a dye for passive and negative pressure (60 Torr) penetration methods. For dye penetration under high pressure conditions (200 MPa), a colored epoxy resin was used. Apical leakage was linearly measured evaluating both the root surface that showed the highest degree of penetration and all four surfaces of each root. The results revealed no significant difference between passive and negative pressure penetration methods. The amount of apical leakage obtained using dye penetration under high pressure conditions was significantly lower. Lateral condensation and single cone techniques yielded similar sealing abilities. It is concluded that there is no need to use negative pressure for evaluating the sealing ability of root canal fillings in vitro.

Clinical evaluation of a hybrid composite and a polyacid-modified composite resin in Class-II restorations in deciduous molars

The aim of this prospective study, conducted in a dental practice was to evaluate the success rate of a hybrid composite material (TPH-Spectrum; Dentsply DeTrey, Konstanz, Germany) and a polyacid-modified composite resin (Compoglass; Vivadent, Schaan, Liechtenstein) in Class II restorations in primary molars after 1 year. A total of 190 restorations (96 with TPH-Spectrum and 94 with Compoglass) were inserted in 52 children. TPH-Spectrum was applied using the total etching technique, whereas Compoglass was inserted without acid etching prior to application of the bonding adhesive. The restorations were assessed according to the Ryge criteria, directly after placement and after 1 year. After 12 months, 6.4% of the Compoglass and 3.1% of the TPH-Spectrum restorations were clinically unacceptable and had to be renewed. The fillings with Compoglass revealed a tendency to lower evaluation scores with respect to color matching, cavosurface discoloration, anatomic form, margin integrity and caries assessment than the restorations with TPH-Spectrum. However, these differences were statistically not significant. The results of the present investigation show that, at least for a period of 1 year, both the hybrid composite TPH-Spectrum and the polyacid-modified composite resin Compoglass are suitable materials for restoration of deciduous molars. However, owing to the fewer treatment steps required for application of a polyacid-modified composite resin, this type of material may be more favorable for restoring primary molars.

Toothbrushing abrasion of polyacid-modified composites in neutral and acidic buffer solutions

STATEMENT OF PROBLEM

Polyacid-modified composites are recommended for use in lesions that are subjected to toothbrushing abrasion and acidic challenges, such as cervical lesions. There is little information whether these materials are able to withstand degradation due to erosive attacks and toothbrushing abrasion.

PURPOSE

This study evaluated the resistance of polyacid-modified composites against toothbrushing abrasion under acidic and neutral conditions.

METHODS

Forty specimens fabricated of each of two polyacid-modified composites (Dyract, Compoglass) were investigated. For each composite group, 20 specimens were placed in a neutral solution (pH: 6.8) and 20 specimens were placed in an acidic solution (pH: 3.0) for 24 hours. All specimens were brushed in an automatic toothbrushing machine, then subjected to storage in the respective buffer solution (8 hours), followed by brushing three times. Abrasion was determined profilometrically.

RESULTS

For both materials, abrasion in the acidic environment was significantly higher compared with neutral conditions. Thus, Compoglass composite demonstrated a lower abrasion resistance than Dyract composite.

CONCLUSION

The abrasion resistance of the investigated materials was reduced under acidic conditions.

Marginal leakage in class II-restorations after use of ceramic-inserts luted with different materials

The efficiency of using prefabricated ceramic inlays to prevent microleakage has been discussed in different investigations. The purpose of this study was to evaluate the marginal microleakage of a new glass ceramic inlay system in combination with two different composite luting materials and one polyacid-modified composite, respectively. Standardized class II cavities (n = 60) were filled with (1) Empress inlays fixed with a highly viscous luting composite as a control group, and with glass ceramic inlays (Cerana) in combination with (2) a highly viscous luting composite, (3) a low-viscous luting composite and (4) a polyacid-modified composite, respectively. After thermocycling the marginal quality was analysed with scanning electron microscopy, and the dye penetration along the cavity walls was measured. The use of the Cerana inlays with a polyacid-modified composite resin did not reveal a good marginal adaptation. However, the combination of the Cerana and the Empress inlays with the highly viscous composite exhibited a comparable marginal fit. Within the limitations of an in vitro study it is concluded that the combination of the new glass ceramic inlays with a polyacid-modified composite cannot be recommended for clinical use.

Irradiation effects on microhardness of fluoridated and non-fluoridated bovine dentin

The objective of this study was to evaluate the effects of irradiation on microhardness of dentin. Dentin blocks from the cervical region of bovine incisors were treated as follows: (1) no irradiation; (2) irradiation of specimens up to 60 Gy (2 Gy/day, 5 days/week); (3) no irradiation, but fluoridation of specimens for 5 min/d; (4) irradiation of specimens and daily fluoridation. Knoop hardness number (KHN) of the control specimens was 62.63+/-14.75 (mean+/-SD). This was significantly different from the irradiated dentin samples (8.74+/-2.59 KHN). Hardness of the fluoridated dentin specimens was 11.19+/-1.95 KHN in the non-irradiated group and 10.03+/-2.76 KHN in the irradiated groups, respectively. Within the limitations of an in vitro study, it is concluded that dentin is severely affected by irradiation. This could be an explanation for the frequently observed side-effects of irradiation like loss of enamel, gap formation at the amelodentinal junction, and caries of the cervical region. Fluoridation with acidic gels decreases microhardness of dentin surface, and does not prevent softening due to radiation, when saliva is absent.

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.

In vivo study on the effectiveness of a lacquer containing CaF2/NaF in treating dentine hypersensitivity

The purpose of this double-blind study was to evaluate the effectiveness of a commercially available fluoride lacquer (Bifluorid 12) containing CaF2 (6%) and NaF (6%) in reducing dentine hypersensitivity. A fluoride lacquer containing only NaF (6%) served as a control. Twenty-five adult patients complaining about at least two hypersensitive teeth participated in this study. In each patient and at each appointment, one tooth was treated with Bifluorid 12, while the other was treated with the control substance. Sensitivity levels were determined before and after the application of each lacquer at baseline as well as at 1, 2 and 3 weeks after the start of study. The final evaluation of hypersensitivity was performed at 4 weeks, and follow-ups were undertaken at 6 and 12 months. A reproducible air blast stimulus and a visual analogue scale were used for evaluation. Results demonstrated a distinct reduction of hypersensitivity after 1, 2 and 3 weeks in the Bifluorid 12 group. Initially, no obvious effects could be observed in the control group. However, a clear alleviation could be observed after 2 and 3 weeks with the control. After 4 weeks, the overall sensitivity scores were comparably low, without any significant differences between the two fluoride lacquers. In both groups, the effects of treatment were seen over the 12-month observation period. Bifluorid 12 was considered at least comparable to the control. It is concluded from this study that Bifluorid 12 is effective in the initial reduction of dentine hypersensitivity. The combination of CaF2/NaF can be recommended for clinical use.

Initial tensile bond strength of resin-modified glass ionomers and polyacid-modified resins on perfused primary dentin

The objective of this study was to evaluate the initial tensile bond strength of a resin-modified glass ionomer (Photac-Fil) and two polyacid-modified composite resins (Compoglass, Dyract) to primary dentin. A hybrid composite resin (Tetric) and two chemical cured glass ionomers (BaseLine, Hi-Dense) served as controls. Ninety caries-free dentinal discs were ground flat and perfused with Ringer's solution. Dentinal surfaces were conditioned (except for Base Line). From each material, fifteen standardized specimens were attached to the dentin. Light-curing of the respective materials followed (1 min), and adhesion was tested with a universal testing machine 15 min after application. The highest initial bond strength was observed with Tetric (5.17 MPa). Closed test procedure (Kruskal-Wallis) showed significant differences between all materials (P < 0.05), except for Compoglass (1.82 MPa) vs. Dyract (2.35 MPa), and BaseLine (0.37 MPa) vs. Photac-Fil (0.42 MPa). The condensable glass ionomer Hi-Dense revealed a mean tensile bond strength of 0.79 MPa. Adhesion of (polyacid-modified) composite resins is superior to the other tested glass ionomer materials, when applied to perfused primary dentin.

Effect of fluoride treatment on remineralization of bleached enamel

The objective of the study was to evaluate the remineralizing capacity of different fluoride treatments on dental enamel bleached with carbamide peroxide (Opalescence). Sixty bovine enamel slabs were subjected to four cycles comprising bleaching (12 h) and remineralization in artificial saliva (8 h). The samples were evenly distributed among four groups (A-D). During the first hour of the remineralization period the specimens in Group A were covered with a fluoride varnish (Duraphat; 2.23% F-). In group B the enamel slabs were stored in a fluoride solution (0.2% F- as NaF) for 1 min prior to remineralization. Group C did not receive a fluoride treatment, and group D (control) was stored in distilled water instead of bleaching. Microhardness (VHN) was evaluated before the experiments and after the second and fourth cycle, respectively. Final hardness was calculated as percentage of the initial hardness. Analysis of variance was applied to the data followed by pairwise comparisons with corrected level of significance (P < 0.01). Hardness decreased significantly in groups A-C compared to the control group (D). The bleached and unfluoridated specimens (group C) showed a significantly higher hardness loss compared to the fluoridated specimens, whereas no significant difference was observed between the two fluoridated groups. It is concluded that remineralization of bleached enamel is improved by application of highly concentrated fluorides.

Correlation of microhardness and wear in differently eroded bovine dental enamel

The purpose of the study was to compare the microhardness data of differently eroded enamel surfaces with the wear caused by toothbrushing. Sixty bovine enamel specimens were polished and prepared for microhardness determination. The polished surfaces were covered with tape except for a 1.3 x 10.0 mm window. Fifteen specimens each were stored in an erosive beverage (Sprite Light) for either 1, 5 or 15 min. Each specimen was immersed in 10 ml of the beverage. The remaining 15 specimens were not eroded. Interferometrical analysis revealed that substance loss after 15 min of erosion was negligibly low (about 75 mm). In all specimens Vickers microhardness determinations were conducted on eroded (= final hardness) and non-eroded (= initial hardness) enamel surfaces. The specimens were subsequently submitted to toothbrushing abrasion using a slurry consisting of 1 g non-fluoridated dentifrice in 5 ml artificial saliva. The total amount of tooth wear due to erosion and subsequent abrasion was profilometrically evaluated. Statistical analysis revealed a significant decrease in hardness and a significant increase in wear with increasing time of storage in the erosive beverage. Overall regression analysis yielded a statistically significant correlation between both initial and final hardness and the amount of tooth wear. The correlation of abrasion and final hardness could be described by a quadratic mathematical function. It is concluded that the susceptibility of eroded enamel to toothbrushing abrasion can be correlated with Vickers microhardness values, thereby suggesting an overproportionate increase of abrasion with decreasing hardness values.

Microscopic studies of accessory canals in primary molar furcations

The purpose of this study was to evaluate the incidence of accessory canals in the furcation region of human primary second molars. Forty freshly extracted teeth were radectomized and furcations were separated. The severed pulp chamber floors were decalcified and dehydrated. Paraffin embedding followed and cross-cut serial sections were taken from the specimens. Microscopic examination of each section followed. Sixteen out of twenty (80 percent) of the maxillary and fifteen out of twenty (75 percent) of the mandibular primary second molars demonstrated accessory foramina in the furcation area. 17.3 percent of the accessory foramina were found in the pulp chamber floor and 82. 7 percent were observed interradicular, close to the periodontal ligament. Thirty percent of the primary second molars demonstrated accessory canals, running from the pulp chamber to the periodontal ligament. Within the limitations of a microscopic investigation it is assumed that accessory furcation canals might be responsible for interradicular bone pathology in case of pulpal inflammation or necrosis.

Diffusion behavior of eugenol from zinc oxide-eugenol mixtures through human and bovine dentin in vitro

The objective of this in vitro study was to evaluate the long-term diffusion behavior of eugenol from different zinc oxide-eugenol mixtures through thin dentin layers. In 24 freshly extracted, caries-free human teeth standardized cavities were prepared exhibiting a dentin surface area of 7 mm2. The remaining thickness of the dentin close to the pulp chamber amounted to at least 0.2 mm. In a second experiment standardized dentin disks (0.2 mm thick) were prepared from 24 bovine incisors. The disks were embedded in epoxy resin, thus exposing a resin-free, standardized area of 7 mm2. Specimens from both experiments were inserted into a screw cap of a vial. Cp-Cap, Temp Bond, and two zinc oxide-eugenol mixtures (P/L ratios of 10:1 and 2:1) were applied to each of six specimens from both experiments. The opposing surface was in contact with 1 ml of Ringer solution. After 1 day, 7 days, and 21 days respectively, the amount of penetrated eugenol was determined with High-Performance Liquid Chromatography (HPLC). In both experiments we found a persistent release and diffusion of eugenol, irrespective of the applied material. However, for the second experiment, we saw more pronounced diffusion rates. Furthermore, the materials showed significant differences, particularly for low versus high P/L ratios.

Influence of enamel conditioning on bond strength of resin-modified glass ionomer restorative materials and polyacid-modified composites

This study evaluated enamel bond strength of restorative materials containing both glass ionomer and composite components. Three resin-modified glass ionomer restorative materials (Fuji II LC, Vitremer, Photac-Fil), three polyacid-modified composites (VariGlass VLC, Dyract, Ionosit Fil), a hybrid composite (blend-a-lux) and a chemical-cured glass-ionomer cement (ChemFil Superior) were tested for enamel tensile bond strength with and without conditioning of the tooth surfaces. Tensile bond strength was determined for five specimens each of conditioned and unconditioned bovine teeth. Specimen conditioning was performed as recommended by the manufacturers. The tensile bond strength was tested with a universal testing machine. Except for the enamel bond strength of ChemFil Superior, all materials showed greater adhesion to conditioned tooth surfaces than to unconditioned specimens. Enamel bond strengths of the polyacid-modified composites applied after a phosphoric acid etching technique (Ionosit Fit, Dyract, VariGlass) were greater compared with the materials applied after surface conditioning with polyacrylic acid-containing agents. No significant difference was observed between the hybrid composite and the tested materials attached with the phosphoric acid etching technique. To improve adhesion of the tested materials to enamel, following the manufacturer's instructions about tooth surface conditioning is recommended. Superior bond strength to enamel was obtained for polyacid-modified composites, which are attached with the phosphoric acid etching technique and thereby resemble the adhesion patterns of composites.

Properties of resin-modified glass-ionomer restorative materials and two polyacid-modified resin composite materials

The objective of the study was to evaluate the physical properties of four resin-modified glass-ionomer cements (Fuji II LC, Ionosit Fil, Vitremer, Photac-Fil) and two polyacid-modified resin composite materials (Dyract and Variglass VLC)). They were compared with a hybrid resin composite (blend-a-lux) and a chemically cured glass-ionomer cement (ChemFil Superior). The compressive strength, flexural strength, modulus of elasticity, and surface microhardness of the resin-modified glass-ionomer materials and the polyacid-modified resin-composite materials were inferior to those of the hybrid resin composite and similar to those of the conventional glass-ionomer cement. The hybrid resin composite exhibited the lowest resistance to wear caused by brushing. Some of the materials showed a marked decrease in hardness at depths exceeding 2.0 mm. Generally, the strength properties of the tested resin-modified glass-ionomer materials and the polyacid-modified resin composite materials were inferior to those of the hybrid resin composite.

Influence of dentin conditioning on bond strength of light-cured ionomer restorative materials and polyacid-modified composite resins

The purpose of the study was to evaluate the dentin bond strength of restorative materials containing both glass ionomer and composite resin components. Three resin-modified glass ionomer restorative materials (Fuji II LC, Photac-Fil, Vitremer), three polyacid-modified composite resins (Dyract, Ionosit Fil, VariGlass VLC), a hybrid composite (blend-a-lux) and a chemical-cured glass ionomer cement (ChemFil Superior) were investigated for dentin tensile bond strength with and without conditioning of the tooth surfaces. For each material, tensile bond strength was determined using five conditioned and five unconditioned bovine tooth specimens. Conditioning of the specimens was performed according to the manufacturers' instructions. The tensile bond strength was tested with a universal testing machine. Statistical analysis was performed with analysis of variance, the Scheffe's-test and the Student's t-test. All materials showed higher adhesion to conditioned dentin than to unconditioned specimens. Except for Photac-Fil, the bond strength to conditioned dentin of all resin-modified glass ionomer restorative materials and polyacid-modified composite resins was higher as compared to the chemical-cured glass ionomer and the hybrid composite. However, these differences were not statistically significant. All polyacid-modified composite resins resulted in higher bond strengths to conditioned dentin as compared to the resin-modified glass ionomer restorative materials. These differences were statistically significant only for VariGlass VLC as compared to Photac-Fil. In order to improve adhesion of the tested materials to dentin it is highly recommended to follow the manufacturers' instructions concerning dentin conditioning.