Comparison of a prepCheck-supported self-assessment concept with conventional faculty supervision in a pre-clinical simulation environment.

OBJECTIVES: This study aimed to evaluate the educational outcome of a digitally based self-assessment concept (prepCheck; DentsplySirona, Wals, Austria) for pre-clinical undergraduates in the context of a regular phantom-laboratory course. MATERIALS AND METHODS: A sample of 47 third-year dental students participated in the course. Students were randomly divided into a prepCheck-supervised (self-assessment) intervention group (IG; n = 24); conventionally supervised students constituted the control group (CG; n = 23). During the preparation of three-surface (MOD) class II amalgam cavities, each IG participant could analyse a superimposed 3D image of his/her preparation against the "master preparation" using the prepCheck software. In the CG, several course instructors performed the evaluations according to pre-defined assessment criteria. After completing the course, a mandatory (blinded) practical examination was taken by all course participants (both IG and CG students), and this assessment involved the preparation of a MOD amalgam cavity. Then, optical impressions by means of a CEREC-Omnicam were taken to digitalize all examination preparations, followed by surveying and assessing the latter using prepCheck. RESULTS: The statistical analysis of the digitalized samples (Mann-Whitney U test) revealed no significant differences between the cavity dimensions achieved in the IG and CG (P = .406). Additionally, the sum score of the degree of conformity with the "master preparation" (maximum permissible 10% of plus or minus deviation) was comparable in both groups (P = .259). CONCLUSION: The implemented interactive digitally based, self-assessment learning tool for undergraduates appears to be equivalent to the conventional form of supervision. Therefore, such digital learning tools could significantly address the ever-increasing student to faculty ratio.

Relationship of caries and fluorosis in adolescents from high- and low-fluoride areas in Iran.

OBJECTIVE: The main aim of the study was to investigate the association between water fluoride concentration and caries as well as fluorosis occurrence in adolescents in Iran. As a secondary aim we studied the relationship between caries and fluorosis occurrence. BASIC RESEARCH DESIGN: We examined 12-16 year-olds (n = 373) in Orumiyeh [0.3 mgF-/l, low-fluoride (LF)] and Pol Dasht [3.2 mgF-/l, high-fluoride (HF)] for caries-status [D3-Level, Pitts & Fyffe (DMFS)] and fluorosis prevalence [Thylstrup & Fejerskov index (TF)]. Children completed questionnaires about several sociodemographic and oral health related factors of the previous years. To adjust for confounding, we used log risk regression and estimated relative risks (RR) and 95% confidence intervals (CI). RESULTS: For 12-13 year-olds mean DMFS were 1.9 (sd 2.5) and 1.1 (2.2) in the LF and the HF-areas, respectively. Prevalence of aesthetically relevant fluorosis (TF > 2) was 1% (LF) and 87% (HF). Water fluoride concentration (adjusted for age and SES) was inversely associated with caries-status [RR: 0.7, (CI 0.6-0.8)]. RR for fluorosis was 17 (CI 8-33). In HF-area, caries scores were significantly higher for children with TF > or = 5 on upper central incisors compared with TF < or = 4 (p < 0.05 Mann-Whitney test). CONCLUSIONS: Caries prevalence in the examined areas in Iran is quite low. Above-optimal water fluoride concentration seems to be effective in reducing caries experience, but increases the occurrence of fluorosis. Severe fluorosis seems to be associated with higher caries occurrence in a high-fluoride area.

Influence of endodontic treatment, post insertion, and ceramic restoration on the fracture resistance of maxillary premolars.

AIM: To investigate the effects of endodontic treatment, post placement and ceramic restoration type on the fracture resistance of premolars. METHODOLOGY: One hundred and twenty teeth maxillary premolars were allocated to four groups (A-D; n = 30). In group A, mesio-occlusal-distal-inlays with a buccal and palatal wall of 2 mm (MOD), in group B partial onlays with palatal cusp coverage and in group C total onlays with buccal and palatal cusp coverage were prepared. Group D served as untreated controls. Groups A-C were divided into three subgroups (n = 10): (i) teeth received solely the described preparations, (ii) teeth were root filled, (iii) teeth were root filled and quartz fibre posts were placed. Teeth were restored using Computer-assisted design/computer-assisted machining-ceramic-restorations and subjected to thermo-mechanical-loading; subsequently, the buccal cusp was loaded until fracture. RESULTS: Group D revealed significantly higher fracture resistance [mean (standard deviation)] [738 (272) N] compared to all other groups (P < 0.05; post hoc test Dunnett). For groups A-C, fracture resistance was significantly affected by the restoration type (P = 0.043) and endodontic treatment/post placement (P = 0.039; 2-way anova). Group A [380 (146) N] showed significantly lower fracture resistance compared to group B [470 (158) N] (P = 0.048; post hoc test Tukey). Compared to non-endodontically treated teeth [487 (120) N], root filled teeth revealed significantly lower fracture resistance [389 (171) N] (P = 0.031). CONCLUSION: The restoration of cavities with a remaining wall thickness of 2 mm using ceramic MOD-inlays is inferior with respect to the fracture resistance compared to partial onlay restorations. Root filled teeth without post placement show lower fracture resistance compared to non-endodontically treated teeth.

Evaluation of the remineralizing capacities of modified saliva substitutes in vitro.

OBJECTIVE: In this in vitro study the effects of various calcium and phosphate additions to a commercially available saliva substitute on remineralization of demineralised dentin were investigated. DESIGN: Bovine dentin specimens (n=70) were prepared. Before and after demineralisation (37 degrees C, pH 5.0, 5 days), one-quarter of each specimens surface was covered with nail varnish (control sound/demineralised tissue). Specimens were exposed either to original Saliva natura (SN 0) or to three modified versions (SN 1, SN 2 and SN 3) formulated with different degrees of saturation with respect to octacalciumphosphate (OCP) and dicalcium phosphate dihydrate (DCPD) for 2 and 5 weeks (37 degrees C). An aqueous solution (Buskes remineralizing solution) served as positive control (PC). Differences in mineral loss (deltadeltaZ) and lesion depth (deltaLD) before and after storage were evaluated from microradiographs. RESULTS: After both storage periods dentin specimens immersed in SN 0 revealed significantly higher mineral losses (indicated by deltadeltaZ) and higher lesion depths (indicated by deltaLD) compared to all other solutions (p<0.05; ANOVA). Specimens stored in SN 1 and 3 showed significantly higher mineral losses compared with PC (p<0.05). No differences could be observed between SN 2 and PC (p>0.05). Only SN 2 significantly remineralized from 2 to 5 weeks storage (p<0.05; t-test). CONCLUSIONS: An experimental Saliva natura solution (SN 2) with S(OCP)=2 and S(DCPD)=1.4 showed highest remineralizing capacity. Similar or better remineralization could not be achieved with slightly higher or lower saturated solutions.

[Modification of the mineralizing capacity of a saliva substitute (saliva natura) on enamel in vitro]. / Studie zu den Modifikationen der mineralisierenden Eigenschaften eines Speichelersatzmittels.

PURPOSE: This in vitro study investigated the effects of exposure to modified (with respect to calcium phosphate saturation) solutions of a commercial available saliva substitute (Saliva natura) on mineralization of enamel in vitro. METHODS: Bovine enamel specimens were prepared. Before and after demineralization (pH 4.95, 14 d, 37 degrees C), one-quarter of each specimen's surface was covered with nail varnish (control of sound/demineralized tissue). Specimens were exposed either to original Saliva natura [saturation with respect to octacalciumphosphate (S (OCP)): 0.03, pH 5.8] or to three lab-produced Saliva natura modifications (S (OCP): 1, 2, 3, pH 6.0) for two and five weeks (37 degrees C). An aqueous solution (S (OCP): 2.7, pH 7.0; Buskes remineralizing solution) served as positive control. Differences in mineral losses (DeltaDeltaZ) and lesion depths (DeltaLD) before and after storage were evaluated from microradiographs. RESULTS: After two weeks storage no differences among the solutions with regard to DeltaDeltaZ and DeltaDeltaLD could be observed (p>0.05; ANOVA). Five weeks storage in original Saliva natura resulted in significantly lower DeltaDeltaZ values compared to all other solutions (p<0.05). No differences with respect to DeltaDeltaZ among the modified solutions (S (OCP) 1, 2, 3; p>0.05) could be observed, whereas storage in the remineralizing solution resulted in higher DeltaDeltaZ values compared to all other solutions (p<0.05). For DeltaLD similar results could be revealed. However, no differences between the remineralizing solution and Saliva natura S (OCP) 2 could be shown (p>0.05). CONCLUSION: Saliva natura with an S (OCP) of 2 showed the highest remineralizing capacities. More pronounced remineralization could not be achieved with a higher S (OCP) of 3 under the conditions chosen.

Lysyl oxidase (lox) gene deficiency affects osteoblastic phenotype.

Lysyl oxidase (LOX) catalyzes cross-linking of elastin and collagen, which is essential for the structural integrity and function of bone tissue. The present study examined the role of Lox gene deficiency for the osteoblast phenotype in primary calvarial osteoblasts from E18.5 Lox knockout (Lox ( -/- )) and wild type (wt) (C57BL/6) mice. Next to Lox gene depletion, mRNA expression of Lox isoforms, LOXL1-4, was significantly downregulated in Lox ( -/- ) bone tissue. A significant decrease of DNA synthesis of Lox ( -/- ) osteoblasts compared to wt was found. Early stages of osteoblastic apoptosis studied by annexin-V binding as well as later stages of DNA fragmentation were not affected. However, mineral nodule formation and osteoblastic differentiation were markedly decreased, as revealed by significant downregulation of osteoblastic markers, type I collagen, bone sialoprotein, and Runx2/Cbfa1.

Ex vivo study on root canal instrumentation of two rotary nickel-titanium systems in comparison to stainless steel hand instruments.

AIM: To investigate instrumentation time, working safety and the shaping ability of two rotary nickel-titanium (NiTi) systems (Alpha System and ProTaper Universal) in comparison to stainless steel hand instruments. METHODOLOGY: A total of 45 mesial root canals of extracted human mandibular molars were selected. On the basis of the degree of curvature the matched teeth were allocated randomly into three groups of 15 teeth each. In group 1 root canals were prepared to size 30 using a standardized manual preparation technique; in group 2 and 3 rotary NiTi instruments were used following the manufacturers' instructions. Instrumentation time and procedural errors were recorded. With the aid of pre- and postoperative radiographs, apical straightening of the canal curvature was determined. Photographs of the coronal, middle and apical cross-sections of the pre- and postoperative canals were taken, and superimposed using a standard software. Based on these composite images the portion of uninstrumented canal walls was evaluated. RESULTS: Active instrumentation time of the Alpha System was significantly reduced compared with ProTaper Universal and hand instrumentation (P < 0.05; anova). No instrument fractures occurred in any of the groups. The Alpha System revealed significantly less apical straightening compared with the other instruments (P < 0.05; Mann-Whitney U test). In the apical cross-sections Alpha System resulted in significantly less uninstrumented canal walls compared with stainless steel files (P < 0.05; chi-squared test). CONCLUSION: Despite the demonstrated differences between the systems, an apical straightening effect could not be prevented; areas of uninstrumented root canal wall were left in all regions using the various systems.

Effect of carboxymethylcellulose-based saliva substitutes on predemineralised dentin evaluated by microradiography.

OBJECTIVE: This study investigated the effect of six lab-produced saliva substitutes based on carboxymethylcellulose (CMC) differing in octacalciumphosphate saturations (OCP-s) on mineralisation of bovine dentin in vitro. DESIGN: Dentin specimens were prepared (n=234); prior to and after demineralisation (37 degrees C; pH 5.0; 7 d), one-third of each specimen surface was covered with nail varnish (control of sound dentin). Subsequently, specimens (n=13) were exposed to either one of the six CMC-based solutions (OCP-s: 0, 0.5, 1, 2, 4, and 8) at pH 6.5 or to Glandosane for 5 and 10 weeks (37 degrees C). Two aqueous solutions (OCP-s: 0 and 1) served as controls. After storage, thin sections were prepared and mineral loss was calculated by transversal microradiography. RESULTS: After both storage periods specimens immersed in Glandosane revealed a significantly increased mineral loss compared to all other solutions (p<0.05; Bonferroni post hoc test). Control solution with OCP-s=1 induced a significant remineralisation (p<0.05; adjusted paired t-test). Only after 5 weeks exposure to the CMC-based solution with an OCP-s=2 a significant remineralisation compared to baseline (p<0.05) as well as a significantly increased mineral gain of the surface area compared to higher saturated solutions (p<0.05; Bonferroni post hoc test) could be observed. CONCLUSIONS: CMC seems to hamper dentin remineralisation, although after 5 weeks a mineral gain could be induced with slightly supersaturated CMC-solutions with respect to OCP.

Effect of a fluoridated food item on enamel in situ.

After the consumption of food items prepared with fluoridated salt elevated fluoride concentrations can be observed in saliva, whereby enamel mineralization is supposed to be positively affected. The aim of this double-blind (with respect to fluoride), placebo-controlled, randomized, cross-over study was to evaluate the effects of the consumption of either a fluoridated (effect) or a placebo food item on the mineral content of sound and pre-demineralized human enamel in situ. During both phases of the study 8 enamel specimens in each of 10 intraoral appliances were positioned, either recessed or flush with the acrylic surface. One of the flanges was brushed twice daily with fluoride-free toothpaste prior to the storage of the appliance in sucrose solution. The subjects were asked to refrain from other sources of fluorides except for the consumption of either a highly fluoride-containing (0.5 mg) or a placebo cookie (3 times daily) during the respective study phase. Mineral content and lesion depth were measured in the enamel specimens and fluoride concentrations in saliva and urine. Significantly increased urinary and salivary (immediately after food consumption) fluoride concentrations compared to baseline were observed during the effect phase. In the absence of fluorides more pronounced demineralization was observed, especially for the recessed specimens of both surface conditions. Brushing was shown to inhibit demineralization, particularly during the placebo phase. In conclusion, fluorides added to food items seem to be efficacious to inhibit enamel demineralization in plaque-covered enamel but might be less effective if oral hygiene is adequate.

Resin infiltration of natural caries lesions.

Infiltration of non-cavitated caries lesions with light-curing resins could lead to an arrest of lesion progression. The aim of this study was to evaluate the penetration of a conventional adhesive into natural enamel caries after pre-treatment with two different etching gels in vitro. Extracted human molars and premolars showing proximal white-spot lesions were cut across the lesions perpendicular to the surface. Corresponding lesion halves were etched for 120 sec with either 37% phosphoric acid gel (H(3)PO(4)) or 15% hydrochloric acid gel (HCl), and subsequently infiltrated with an adhesive. Specimens were observed by confocal microscopy. Mean penetration depths (SD) in the HCl group [58 (37) microm] were significantly increased compared with those of the H(3)PO(4) group [18 (11) microm] (p < 0.001; Wilcoxon). It can be concluded that etching with 15% hydrochloric acid gel is more suitable than 37% phosphoric acid gel as a pre-treatment for caries lesions intended to be infiltrated.

In vitro study assessing apical leakage of sealer-only backfills in root canals of primary teeth.

AIM: To assess the sealing ability of zinc oxide-eugenol (ZOE), Apexit, and Sealapex used as sealer-only backfills in root canals of primary teeth using the high-pressure replica technique. METHODOLOGY: Two hundred and seventy root canals of deciduous molars as well as primary anterior teeth were randomly assigned to three groups (n=90). Root canals were prepared to size 35 and filled with either zinc oxide-eugenol (ZOE), Apexit, or Sealapex using a lentulo filler. Twenty-four hours after setting of the materials the roots were nail-varnished (except for the apical tip), and half of the specimens (n=45) were penetrated by a coloured (rhodamine B) epoxy resin. The resin was infiltated into the pores and cavities of the teeth in a high-pressure vessel. The remaining groups (n=45) were stored in 100% humidity, and infiltration of the resin followed after 40d. Apical leakage was assessed by means of a grinding technique using eight steps of 0.5mm each. RESULTS: ZOE and Apexit failed to seal the root canals in both subgroups. This was significantly different from the root canals filled with Sealapex where in both subgroups some 30% of the specimens revealed a tight seal up to a distance of 2.9mm of the apex. CONCLUSIONS: Under the conditions of this study it can be concluded that Sealapex shows less leakage than ZOE and Apexit. With regard to the three materials tested, Sealapex should be a viable alternative for sealer-only obturation of pulpectomized primary teeth. The high-pressure replica technique seems to be suitable for assessing leakage of root canal filling materials.

[In vitro analysis of an new saliva substitute (Saliva natura) on enamel and dentin]. / In-vitro-Studie zur Untersuchung eines neuen Speichelersatzmittels (Saliva natura) auf Schmelz und Dentin.

BACKGROUND: Hyposalivation is an important chronic side effect of radiotherapy in the head and neck area, and patients often alleviate their symptoms using saliva substitutes. The aim of this study was to evaluate the effects of two commercially available saliva substitutes (Saliva natura and Glandosane) on the mineral loss of bovine enamel and dentin in vitro. An aqueous remineralization solution served as control. METHODS: Each 45 bovine enamel and dentin specimens were prepared. Prior to (control of sound dentin) and after (control of demineralized dentin) demineralization (37 degrees C; enamel: pH 4.95; 14 d; dentin: pH 5.0; 7 d) one third of each specimens surface was covered with nail varnish. Subsequently, the specimens (n = 15) were exposed to Glandosane and Saliva natura as well as a remineralization solution for 14 days (37 degrees C). Specimens were examined using transversal microradiography. RESULTS: Compared to Saliva natura and the reminerlization solution, Glandosane induced both significantly increased mineral losses as well as lesion depths of the enamel specimens (p < 0.05; ANOVA, Bonferroni). After exposure of the dentin specimens to Saliva natura a significantly increased mineral loss could be observed (p < 0.001), whereas no differences in mineral loss could be observed for the enamel specimens (p = 0.078; t-test). CONCLUSIONS: Within the limitations of an in vitro study it can be concluded that Glandosane revealed a demineralizing potential on bovine enamel as well as on dentin and should not be recommended for dentate patients. Since Saliva natura has a demineralizing effect on dentin, a further improvement regarding the remineralizing capacity would be desirable.

Surface layer erosion of natural caries lesions with phosphoric and hydrochloric acid gels in preparation for resin infiltration.

The infiltration of proximal enamel lesions with low-viscosity light curing resins could be a viable approach to stop lesion progression. However, penetration of sealant might be hampered by the comparatively highly mineralized surface layers of natural lesions. Therefore, the aim of this study was to compare the efficacy of three different etching gels in removing the surface layer in various etching times. Extracted human molars and premolars showing proximal white spot lesions were cut across the demineralized areas. Ninety-six lesions expected from visual examination to be confined to the outer enamel (C1) were selected. The cut surface and half of each lesion were varnished, thus serving as control. Subsequently, the lesions were etched with either phosphoric (37%) or hydrochloric (5 or 15%) acid gel for 30-120 s (n = 8/group). Specimens were examined using confocal microscopy and transversal microradiography. Surface layer reduction was significantly increased in lesions etched with 15% HCl gel for 90 and 120 s compared to those etched with H(3)PO(4) gel for 30-120 s (p < 0.05). No significant differences regarding the depths of erosion in the lesions compared to sound enamel could be observed (p > 0.05). An effective reduction in the surface layer of natural enamel caries can be achieved by etching with 15% hydrochloric acid gel for 90-120 s.

Effects of luting agent and thermocycling on bond strengths to root canal dentine.

AIM: To investigate the effects of luting agent and thermocycling on bond strengths to root canal dentine. METHODOLOGY: Extracted maxillary canines (n =144) were root filled and divided into six groups of 24 teeth each. Fibre posts (FRC Postec) were inserted using six luting agents: Panavia F, Multilink, Variolink II, PermaFlo DC, RelyX Unicem and Clearfil Core. Each root was sliced into six discs (thickness 1 mm) representing the coronal, middle and apical part of the root canal. Push-out tests were performed 24 h after post insertion (n = 12) as well as after thermocycling (5000x; 5-55 degrees C, 30 s) (n = 12). Statistical analysis was conducted using analysis of variance (anova) followed by post-hoc comparisons (Tukey-B). The influence of thermocycling on bond strengths was investigated for each material and region separately using t-tests. RESULTS: The bond strengths were significantly affected by the luting agent (P < 0.001), the root position (P = 0.003) and thermocycling (P < 0.001; three-way anova). RelyX had significantly higher bond strengths compared with all other materials (P < 0.05; Tukey-B). The apical region of the root canal had significantly higher bond strengths compared with the middle and coronal region (P < 0.05; Tukey-B). After thermocycling for RelyX a significant increase in bond strengths was detected for the middle and apical region (P < 0.01; t-test, Bonferroni factor 18). CONCLUSIONS: Bond strengths were affected significantly by luting agent and root position. RelyX had higher bond strengths compared with other materials. The apical region of the canals was characterized by significantly higher bond strengths.

Effect of various Ca2+/PO4(3-) concentrations of linseed-based saliva substitutes on enamel in vitro.

Remineralization might be hampered by various polymers used in saliva substitutes. Thus, the present study evaluated the effects of various calcium and phosphate concentrations of linseed-based solutions on the mineral loss of pre-demineralized bovine enamel in vitro. A commercially available saliva substitute (Salinum) based on linseed was tested as well. Enamel specimens were prepared from bovine incisors and embedded in epoxy resin. One-third of each sample was covered with nail varnish (control of sound enamel). After demineralization (37 degrees Celsius; pH 5.0; 14 days) another third of the samples was nail-varnished again. Subsequently, the specimens (n = 10) were exposed to 12 linseed-based solutions (Ca(2+) addition 0-2 mM; PO4(3-) addition 0-3.2 mM) at pH 5.5 and 6.5 as well as to Salinum) for 14 days (37 degrees Celsius). The differences in mineral loss between the values prior to and after the storage in the various solutions were evaluated from microradiographs of thin sections (100 mum). The general linear model revealed a significant dependency for the mineral loss on 'calcium' (P = 0.003), but not on 'pH' (P = 0.397) and 'phosphate' (P = 0.094). Salinum) induced a significant greater mineral loss compared with equivalently saturated solutions (P < 0.05; anova, Bonferroni). The solution with the highest calcium and phosphate concentration showed the greatest mineral gain (P = 0.033; paired t-test). The addition of calcium and phosphate seems to have a positive effect on the remineralizing qualities of linseed-based saliva substitutes.

Influence of calcium phosphates added to mucin-based saliva substitutes on bovine dentin.

OBJECTIVES: Remineralization of dentin by mucin-containing saliva substitutes might be inhibited by sialic acids bound to mucin, which are known to complex calcium. Thus, the aim of this investigation was to evaluate the effects of various mucin-containing solutions, differing in calcium phosphate concentrations, to be used as saliva substitutes on demineralized bovine dentin in vitro. METHOD AND MATERIALS: Bovine specimens (153) were embedded in epoxy resin, polished (4,000 grit), and partly covered with nail varnish (control of sound dentin). After demineralization for 14 days (pH 5.5), the specimens (n = 9) were exposed to 14 mucin-based solutions (30 g/L) at 2 different pH values (5.5 or 6.5) and differing in saturation with respect to apatites. Two fluoride-free solutions and the commercially available saliva substitute Saliva Orthana(Orthana, Kastrup) served as controls. Differences in mineral loss (deltadeltaZ) and lesion depth (deltaLD) between the values prior to and after storage in the various solutions were evaluated from microradiographs of thin sections (100 microm). RESULTS: The general linear model revealed an almost significant dependency on calcium for deltadeltaZ (P = .050) and a significant dependency on calcium for deltaLD (P = .037). pH influenced deltadeltaZ significantly (P < .001), whereas deltaLD was not influenced significantly (P = .169). Neither deltadeltaZ (P = .475) nor deltaLD (P = .703) were influenced significantly by phosphate. CONCLUSION: Even with low concentrations of calcium and phosphates, mucin-based saliva substitutes are capable of inhibiting demineralization of bovine dentin, whereas with solutions supersaturated with respect to apatites, a remineralizing effect could be observed.

Microradiographic study on the effects of mucin-based solutions used as saliva substitutes on demineralised bovine enamel in vitro.

Sialic acids and proteins bound to mucins are known to form complexes with calcium, and this mechanism may hamper the remineralization of calcium-containing mucin-based saliva substitutes. Thus, the aim of this investigation was to evaluate the effects of adding various concentrations of calcium phosphate to self-made mucin-containing solutions on demineralised bovine enamel in vitro. Bovine specimens were prepared, embedded in epoxy resin, and polished to 4000 grit. Subsequently, the surfaces of the specimens were partially covered with nail varnish, thus serving as a control of sound enamel, and demineralised (37 degrees C; pH 5.0) for 14 (19 groups; n=10) or 28 days (three groups; n=9). After demineralization, the specimens were exposed to mucin-based solutions (30 g/l) with various saturations with respect to apatites containing 0.1 mM NaF, CaCl(2) (0-20 mM) and KH(2)PO(4) (0-52 mM) at two different pH values (5.5 or 6.5). A fluoride-free solution and the commercially available saliva substitute Saliva Orthana (Orthana, Kastrup, Copenhagen Denmark) served as controls. The differences in mineral loss (DeltaDeltaZ) between the values prior to (DeltaZ(Demin)) and after storage (DeltaZ(Effect)) in the various solutions were evaluated from microradiographs of thin sections (100 microm). The general linear model revealed a significant dependency of DeltaDeltaZ for calcium (P=0.006), but not for phosphate (P=0.081) or pH (P=0.114). DeltaZ(Effect) was only significantly reduced compared with DeltaZ(Demin) in the group with the highest saturation with respect to hydroxyapatite (P<0.05; t-test). In conclusion, mucin-based saliva substitutes with an adequate composition are able to remineralize bovine enamel in vitro.

Progression of sealed initial bovine enamel lesions under demineralizing conditions in vitro.

The use of sealants for the infiltration of proximal enamel lesions could be a promising alternative to the common strategies of remineralization and operative treatment. The aim of the present study was to compare the progression of sealed initial enamel lesions after exposure to a demineralizing solution in vitro. In each of 54 bovine enamel specimens three subsurface lesions were created. Two of the lesions were etched with phosphoric acid and sealed with either a fissure sealant or with various adhesives (1-5) for 15 s or 30 s, respectively, whereas one lesion remained as the untreated control. Subsequently, half of each specimen was covered with nail varnish (baseline) and the other half was reexposed to a demineralizing solution for 14 days (experimental). The specimens were cut perpendicularly to the surface, infiltrated with a low-viscosity fluorescent resin and observed with a confocal laser scanning microscope (CLSM). For lesions sealed with the fissure sealant and adhesives 1-3, the progression of lesion depth (0-31 microm) was significantly decreased (p<0.01; paired t test) compared with the untreated control (57 microm). For the fissure sealant and adhesives 1 and 3 extended penetration times (30 s) resulted in significantly reduced lesion progression compared to 15 s. It can be concluded that filling of the pores in initial enamel lesions with the fissure sealant and adhesives 1-3 can inhibit further demineralization in vitro.

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.

Caries and fluorosis in 6- and 9-year-old children residing in three communities in Iran.

OBJECTIVES: The aim of this study was to investigate the caries and fluorosis prevalence among 6- and 9-year-old students in three communities in Iran with varying urbanization and fluoride in piped water. METHODS: Data were obtained from 523 dental examinations of 6- and 9-year olds in an upper middle class district in Teheran (T) (0.3 mg F/l), the city of Semnan (S) (1.3 mg F/l), and the village Dibaj (D) (0.2 mg F/l). RESULTS: Children in the naturally fluoridated town showed slightly higher dmfs/dfs (SD) values for both 6-year olds [S: 9.1 (9.2), T: 7.2 (7.4), D: 7.1 (6.1)] and 9-year olds [S: 6.0 (6.2), T: 4.4 (4.2), D: 5.0 (4.7)], whereas the mean dmft/dft values as well as the numbers of caries-free children were comparable. A lower prevalence of dental restorations was reported for both Semnan and Dibaj compared with Teheran. A higher prevalence of fluorosis [Tooth Surface Index of Dental Fluorosis (TSIF) 3-7] was observed in the naturally fluoridated town compared with the low-fluoridated communities. CONCLUSIONS: The ingestion of naturally fluoridated water (1.3 mg F/l) seemed to have a negligible effect on caries prevalence, but resulted in higher prevalence of dental fluorosis. It is emphasized that the study population was not adjusted for socioeconomic status, availability of dental care nor for exposures to other sources of fluoride. Nevertheless, it can be concluded that caries prevalence in Iran is quite low compared with that in other countries in the Middle East and that the elevated fluoride levels in the drinking water in Semnan may contribute to the development of mild to severe fluorosis.