Biomedical subjects

Thomas Attin

Publications and source records attributed to Thomas Attin.

At least 19 recordsLinked to original sources

PubMed2006

Protective effect of the in situ pellicle on dentin erosion - an ex vivo pilot study.

AIM: The acquired pellicle is well known as an anti-erosive proteinaceous layer on enamel, but its protective properties on dentin have not been investigated in detail until now. The aim of the present ex vivo study was to evaluate the erosive effects on pellicle coated dentin. METHODS: Bovine dentin slabs were exposed to the oral cavity of one subject for 120 min for in situ pellicle formation. Subsequently, the slabs were incubated with HCl (pH 2.3) in vitro for 5 min and erosive calcium-release was measured photometrically. In addition, the acid treated specimens were evaluated by transmission electron microscopy (TEM). Pellicle free samples served as controls. RESULTS: Calcium erosion from the pellicle coated dentin slabs amounted to 23.5+/-2.9 microg Ca/min (pellicle free samples: 32.2+/-4.2 microg Ca/min). The difference was statistically significant (p < or = 0.05). In pellicle coated as well as in uncoated dentin samples, TEM-evaluation showed a demineralised dentinal surface layer which thickness ranged between 3 and 6 microm. The pellicle itself was partially dissolved but not removed by hydrochloric acid treatment. CONCLUSION: The protective properties of the acquired pellicle against an erosive challenge of the dentinal surface are limited. The dentinal pellicle functions like an ion permeable network rather than a barrier.

Adult↗

PubMed2006

Influence of different restorative materials on lysozyme and amylase activity of the salivary pellicle in situ.

Lysozyme and amylase are the most abundant enzymatic components in the salivary pellicle. The purpose of the present study was to determine the influence of different substrata on amylase and lysozyme activity in salivary pellicles formed in situ. Slabs (5 mm diameter) of bovine dentine and enamel, of titanium, gold alloy, resin composite, PMMA, amalgam, and feldspar ceramic were fixed on the buccal sites of individual splints worn by six subjects for 30 min to allow pellicle formation. Thereafter, slabs were removed from the trays and rinsed with running water. Lysozyme activity was determined via lysis of Micrococcus lysodeicticus. Amylase activity was measured with a photometric method using 2-chloro-4-nitrophenyl-4-O-beta-D-galactopyranosylmaltotriosid (GalG2CNP) as substrate. Both pellicle enzymes were evaluated in the immobilized as well as in the desorbed state. Salivary enzyme activities were also measured. All investigated pellicles exhibited lysozyme and amylase activity. Great intraindividual and interindividual differences were observed. Over all samples, immobilized amylase activity amounted to 0.65 +/- 0.64 mU/cm2. Immobilized lysozyme activity was 5.04 +/- 1.55 U/cm2. There were no major effects of the substratum on pellicle-bound amylase and lysozyme activity. Immobilized and desorbed enzyme activities revealed a strong correlation (lysozyme: r = 0.700; amylase: r = 0.990). Salivary enzyme activities had only little impact on pellicle-bound enzyme activities. Amylase and lysozyme are incorporated in the acquired in situ pellicle on different solid surfaces in an active conformation. Dental material and enzyme activity in the saliva have only little impact on enzymatic activity in the pellicle in situ.

Adult↗

PubMed2006

External bleaching therapy with activation by heat, light or laser--a systematic review.

OBJECTIVE: External bleaching procedures utilizing highly concentrated 30-35% hydrogen peroxide solutions or hydrogen peroxide releasing agents can be used for tooth whitening. To enhance or accelerate the whitening process, heat-activation of the bleaching agent by light, heat or laser is described in the literature. The aim of the present review article was to summarize and discuss the available information concerning the efficacy, effects and side effects of activated bleaching procedures. SOURCES: Information from all original scientific full papers or reviews listed in PubMed or ISI Web of Science (search term: (bleaching OR brightening OR whitening OR colour) AND (light OR laser OR heat OR activation)) were included in the review. DATA: Existing literature reveals that activation of bleaching agents by heat, light or laser may have an adverse effect on pulpal tissue due to an increase of intra-pulpal temperature exceeding the critical value of 5.5 degrees C. Available studies do not allow for a final judgment whether tooth whitening can either be increased or accelerated by additional activation. CONCLUSION: Therefore, application of activated bleaching procedures should be critically assessed considering the physical, physiological and patho-physiological implications.

Humans↗

PubMed2006

Volumetry of human molars with flat panel-based volume CT in vitro.

The flat panel-based volume computed tomography (fpVCT) is a new CT device applicable for experimental, three-dimensional evaluation of teeth at a resolution of about 150 microm in the high contrast region. The aim of this study was to investigate whether fpVCT was suitable for quantification of the volumes of dental hard tissues and the root canal system to establish a new method for morphological studies. Fifty-two extracted third molars (maxillary: 31, mandibular: 21) were examined with a prototype of an fpVCT using a volumetry algorithm at different levels according to the radiographic density of enamel and dentine. Volumetry of the root canal system was performed after "region growing segmentation": starting from a voxel in the centre of the root canal, this algorithm searches voxels of same density in the surrounding. The volumetry of the root canal system was stopped by the investigator at the apical constriction. Results showed that dentine, enamel and root canal system could be well distinguished in three-dimensional images. Volumetry yielded the following data (cm(3), mean+/-SD): dentine 0.438+/-0.111, enamel 0.227+/-0.051, root canal system 0.052+/-0.017 and total volume 0.753+/-0.159. In conclusion, the fpVCT is appropriate for non-destructive volumetry of large numbers of teeth in experimental laboratory studies.

Absorptiometry, Photon↗

PubMed2006

Review on fluoride-releasing restorative materials--fluoride release and uptake characteristics, antibacterial activity and influence on caries formation.

OBJECTIVES: The purpose of this article was to review the fluoride release and recharge capabilities, and antibacterial properties, of fluoride-releasing dental restoratives, and discuss the current status concerning the prevention or inhibition of caries development and progression. METHODS: Information from original scientific full papers or reviews listed in PubMed (search term: fluoride release AND (restorative OR glass-ionomer OR compomer OR polyacid-modified composite resin OR composite OR amalgam)), published from 1980 to 2004, was included in the review. Papers dealing with endodontic or orthodontic topics were not taken into consideration. Clinical studies concerning secondary caries development were only included when performed in split-mouth design with an observation period of at least three years. RESULTS: Fluoride-containing dental materials show clear differences in the fluoride release and uptake characteristics. Short- and long-term fluoride releases from restoratives are related to their matrices, setting mechanisms and fluoride content and depend on several environmental conditions. Fluoride-releasing materials may act as a fluoride reservoir and may increase the fluoride level in saliva, plaque and dental hard tissues. However, clinical studies exhibited conflicting data as to whether or not these materials significantly prevent or inhibit secondary caries and affect the growth of caries-associated bacteria compared to non-fluoridated restoratives. SIGNIFICANCE: Fluoride release and uptake characteristics depend on the matrices, fillers and fluoride content as well as on the setting mechanisms and environmental conditions of the restoratives. Fluoride-releasing materials, predominantly glass-ionomers and compomers, did show cariostatic properties and may affect bacterial metabolism under simulated cariogenic conditions in vitro. However, it is not proven by prospective clinical studies whether the incidence of secondary caries can be significantly reduced by the fluoride release of restorative materials.

Cariostatic Agents↗

PubMed2006

Effect of bleaching on subsurface micro-hardness of composite and a polyacid modified composite.

OBJECTIVE: To investigate the influence of different bleaching techniques on subsurface physical properties of composite and polyacid modified composite tested via determination of micro-hardness. METHODS: Specimens of Tetric Flow, Tetric EvoCeram and Compoglass were light cured (2.5mm thickness) and stored in artificial saliva for 2 weeks (n=12/group). The samples were only removed for application of the following bleaching agents in a humid atmosphere: Either Vivastyle (1h/d), Whitestrips (30min/d), sodium-perborate-water mixture (once for 72h), Simply White (1h/d), or Opalescence XtraBoost (1st and 5th day for 15min) were applied on the surfaces of the samples. Untreated specimens served as negative controls, samples treated with ethyl alcohol for 1h acted as positive controls. After the bleaching period, samples were cross-sectioned and the micro-hardness (Knoop) of different subsurface levels (0.1mm-2.0mm) was determined. RESULTS: All bleaching techniques significantly reduced the Knoop-hardness of the restoratives compared to untreated controls. Thereby, bleaching significantly affected not only superficial but also the deep layers of the specimens: in superficial layers (0.1mm, 0.2mm) lowest micro-hardness values amounted to 69.5% and 76.3% of the respective untreated controls (Compoglass/Vivastyle). In deeper subsurface levels, the lowest hardness was observed with Opalescence/Tetric EvoCeram (0.3mm: 78.3%; 0.4mm: 80%; 0.5mm: 80.5%; 1.0mm: 84.2%; 2.0mm: 84.4%). SIGNIFICANCE: Bleaching with the tested bleaching agents softens the adhesive restorative materials examined. Due to the fact that subsurface layers are also affected, polishing of the surface may not suffice for re-establishing the physical properties of the surface of the fillings.

Borates↗

PubMed2006

Influence of carbamide peroxide on enamel fluoride uptake.

OBJECTIVE: Aim of the study was to evaluate the influence of carbamide peroxide (CP) on enamel fluoride uptake by comparing enamel fluoride uptake from a 1% amine fluoride (AmF) gel with the fluoride acquisition from a 10% carbamide peroxide agent supplemented with 1% AmF. MATERIALS AND METHODS: Three enamel cylinders (4mm in diameter) were prepared from the buccal surfaces of 60 bovine incisors. One sample of each tooth was used for determination of baseline fluoride content of the respective tooth. The two remaining samples were allocated to the experimental series 1 or 2, respectively. Each series consisted of five experimental groups (A-E, n=12) and differed with respect to the length of the treatment period with the gels (A-D). The experimentally designed gels (pH 5.5) used in the study were as follows: A (10% CP), B (10% CP, 1% F(-) as AmF), C (1% F(-) as AmF), D (no CP, no F(-)) and were formulated on the same basis. The enamel samples were covered for 4h with the respective gel at 37 degrees C and were then transferred to artificial saliva for 20 h (series 1). The samples of group E served as controls and were not treated with a gel. In series 2, treatment with the gels and storage in saliva was conducted seven times. Finally, the samples were assessed for KOH-soluble and structurally bound fluoride. RESULTS: Only the enamel samples treated with the fluoridated bleaching gel (group B) and with the amine fluoride gel (group C) exhibited significant fluoride acquisition. Thereby, both gels showed significantly lower uptake in series 1 as compared to series 2. Both KOH-soluble and structurally bound fluoride acquisition was significantly higher in group C than in group B. CONCLUSION: Treatment with a carbamide peroxide gel supplemented with amine fluoride causes less fluoride acquisition in enamel than a pure amine fluoride gel. Under the conditions of the study, it is assumed that carbamide peroxide seems to influence enamel fluoride uptake.

Amines↗

PubMed2006

Methods for assessment of dental erosion.

Various assessment techniques have been applied to evaluate the loss of dental hard tissue and the surface-softened zone in enamel induced by erosive challenges. In this chapter, the most frequently adopted techniques for analyzing the erosively altered dental hard tissues are reviewed, such as profilometry, microradiography, scanning electron microscopy, atom force microscopy, nano- and microhardness tests and iodide permeability test. Moreover, methods for chemical analysis of minerals dissolved from dental hard tissue are discussed. It becomes evident that the complex nature of erosive mineral loss and dissolution might not be comprehended by a single technique, but needs application of different approaches for full understanding.

Fluorescence↗

PubMed2006

Antimicrobial effectiveness of a highly concentrated chlorhexidine varnish treatment in teenagers with fixed orthodontic appliances.

OBJECTIVE: To evaluate the recolonization pattern of Mutans streptococci (ms) on densely colonized teeth with fixed orthodontic appliances after treatment with a highly concentrated (36%) chlorhexidine varnish. MATERIALS AND METHODS: Healthy subjects (n = 19) with fixed orthodontic appliances and high bacterial ms counts in saliva were recruited. In order to establish a baseline registration, plaque adjacent to brackets was sampled and cultivated on Dentocult strips. Following professional tooth cleaning, chlorhexidine varnish was applied on all teeth for 8 minutes. The degree of recolonization with ms was assessed 2 weeks after varnish application in plaque around the brackets. For statistical analysis, the data were subjected to a repeated measures design. RESULTS: After 2 weeks, ms counts were reduced as compared to baseline values. However, the reduction only weakly met statistical significance (P = .049). CONCLUSIONS: The application of a highly concentrated chlorhexidine varnish in patients with fixed orthodontic appliances does not result in a distinct reduction of ms numbers 2 weeks after treatment.

Adolescent↗

PubMed2006

Shear bond strength of repaired adhesive filling materials using different repair procedures.

PURPOSE: Matrices of adhesive restorative materials and repair procedures may both influence bond strength of repaired adhesive materials. This study examined the bond strength of adhesive filling materials to mature adhesive materials after pretreatment with Co-Jet, Monobond S, and Silibond. MATERIALS AND METHODS: A hybrid composite (Tetric Ceram), a polyacid-modified composite resin (Dyract), and an ormocer (Definite) and their corresponding bonding agents were tested in combination with the repair systems. Restorative materials were placed in molds and polymerized. In group A (control), homologous materials were applied on the polymerized surface directly. In group B, homologous filling materials were placed onto the respective material with the corresponding bonding agent. In group C, adhesive repair filling material was applied after solely pretreating with the repair systems. In group D, the restorative material was applied after pretreatment with the repair systems and application of the corresponding bonding agent. Each subgroup consisted of 20 specimens. The shear bond strength of the samples was measured in a universal testing machine according to the test procedure ISO 10477. RESULTS: The significantly best bond strength of repair filling material on Tetric was achieved by pretreating with Co-Jet followed by application of the corresponding bonding agent (25.5 +/- 5.4 MPa, p < 0.05). A single application of the bonding agent or use of Monobond with bonding agent also yielded bond strengths of 20 MPa or more on Tetric. For Dyract or Definite, bond strengths of 15.5 +/- 5.3 MPa or less were achieved with the different repair procedures. CONCLUSION: Successful pretreatment of hybrid composites for repair can be achieved by application of Co-Jet followed by the corresponding bonding material, whereas sufficient repair of ormocers and polyacid-modified resin composites is limited.

Acrylic Resins↗

PubMed2006

[In vitro cytotoxicity of different self-etching dental adhesive systems].

The study evaluated the cytotoxicity of five self-etching dentin adhesive systems applied on dentin specimens of different thicknesses. The test materials (A: Adper Prompt-L-Pop, B: Xeno II, C: Clearfil SE Bond, D: One up Bond F, E: Resulcin Aqua Prime & Monobond) and a positive control (35% H202) were applied on 1.0, 1.5 and 2.5 mm thick bovine dentin specimens (each subgroup n = 5) in a dentin barrier test device. The experiments were performed with perfusion (2 ml/h) of the pulpal part of the chamber. The eluates were obtained before (baseline) and 15, 30, 45, 60 and 120 min after application of the adhesives and pipetted onto L-929 fibroblasts. Cytotoxicity of the materials was determined in relation to the baseline value using the MTT assay and statistical analysis was performed by ANOVA. After 15 min perfusion, test materials B-E applied on 1.0 mm and B and E applied on 1.5 mm dentin specimens exhibited cytotoxic potential. However, after 30 min perfusion none of the adhesives showed any toxicity. Cytotoxicity decreased with increasing thickness of the dentin slices and was lower for Adper Prompt-L-Pop compared to adhesives B-E. Self-etching adhesive systems might exhibit cytotoxic potential when applied on dentin of less than 1.5 mm thickness. However, cytotoxicity of the materials decreased with increasing dentin thickness and increasing duration of perfusion.

Acid Etching, Dental↗

PubMed2005

Effect of topical fluoride application on toothbrushing abrasion of resin composites.

OBJECTIVES: This in vitro study assesses toothbrushing abrasion of a microfill (Heliomolar Radioopaque) and a hybrid composite (Herculite XRV) after application of two acidic fluoride agents. METHODS: Thirty-six specimens of each resin composite were fabricated, ground flat and polished. Subsequently the 36 samples of each material were evenly assigned to three groups. In the first group, samples were treated with the fluoride varnish Bifluorid 12 (5.5% F, pH 5.6), in the second group with Elmex Fluid (1.25% F, pH 4.3). In the third group, specimens remained unfluoridated (controls). After 8h, the samples were subjected to toothbrushing abrasion (2000 brushing strokes, load: 250 g) in an abrasive slurry. Fluoridation and brushing abrasion were repeated twice. Afterwards, abrasion of the materials was quantitatively determined with a laser profilometer and statistically analyzed (ANOVA). RESULTS AND SIGNIFICANCE: With Herculite both, Bifluorid 12 (P = 0.0001) and Elmex Fluid (P = 0.0001) led to a significant increase of brushing abrasion compared to the non-fluoridated group. However, no significant difference was observed between the two fluoridation regimes. Heliomolar showed a tendency towards higher abrasion after treatment with Elmex Fluid compared to Bifluorid 12 (P = 0.0496) and the non-fluoridated group (P = 0.0496), whereas treatment with Bifluorid 12 yielded no significant difference compared to the non-fluoridated Heliomolar specimens. Fluoridation of Herculite resulted in a 106-121% increase of abrasion, whereas Heliomolar only showed an increase by 5-30%. Application of the acidic fluoride products used led to an increase in toothbrushing abrasion of the tested composite restorative materials. However, clinical long-term studies are needed to determine the effect of topical fluoride regimes on resin composite materials.

Acrylic Resins↗

PubMed2005

Lysozyme activity in the initially formed in situ pellicle.

UNLABELLED: Lysozyme is one of the most abundant enzymatic components in the salivary pellicle. The purpose of the present in situ study was to determine if and to which extent lysozyme immobilised in pellicles exposes enzymatic activity. Influence of different oral sites and pellicle formation time on enzyme activity was also evaluated. Bovine enamel slabs (5mm diameter) were fixed on buccal and oral sites of individual trays worn by six subjects for 3 and 30 min on different days. After pellicle formation, slabs were removed from the trays and rinsed with running water. Afterwards, pellicle-bound lysozyme activity was determined via lysis of Micrococcus lysodeicticus photometrically in two steps. In a first step, lysozyme was desorbed in phosphate buffer and dissolved activity was measured. In a second step, slabs were incubated in phosphate buffer with the substrate and remaining immobilised activity was determined. All investigated pellicles exhibited lysozyme activity. Great intra- and inter-individual differences were observed. Mean desorbed activity of 3 min-pellicles amounted to 26.06+/-17.81 U/cm(2) (30 min; 26.79+/-17.48). The remaining immobilised activity was 13.54+/-11.42 for 3 min-pellicles and 16.08+/-12.81 for 30 min-pellicles. Pellicle derived lysozyme showed a Michaelis type kinetic. CONCLUSION: In situ pellicle exposes lysozyme activity even after a 3 min formation period. Exposed enzyme activity is neither influenced by pellicle formation time nor by the site of pellicle formation. It shows great inter- and intra-individual differences.

Adsorption↗

PubMed2005

Fluoride uptake and resistance to further demineralisation of demineralised enamel after application of differently concentrated acidulated sodium fluoride gels.

The objective of this study was to analyse fluoride uptake and microhardness alteration of carious-like demineralised enamel after application of differently concentrated acidulated sodium fluoride gels and to determine the effect of fluoridation on enamel resistance against subsequent demineralisation. Artificial caries-like lesions of bovine enamel specimens were treated with sodium fluoride gels of different concentration (group A: 1.25%, group B: 0.62%, group C: 0.31%, group D: 0.15%; n=20 each group) for 5 min and stored in artificial saliva for 24 h. This cycle was carried out three times. Subsequently, KOH-soluble and structurally bound fluoride (determined at depths of 30, 60, and 90 microm) were analysed. In the second part of the study, for each 12 enamel specimens surface microhardness was determined before and after demineralisation, after fluoridation with the differently concentrated gels A-D, and after a second demineralisation. With all groups uptake of KOH-soluble and structurally bound fluoride resulted in higher levels than baseline content. Statistical analysis revealed significant differences between fluoride uptake among the groups, with highest uptake for the 1.25% gel and lowest for the 0.15% gel. Moreover, with all gels highest uptake was observed in the outermost enamel layer (P<0.05). Microhardness values after second demineralisation increased with increased concentration of the applied sodium fluoride gel. Increasing concentration of the applied gel implies better protection of the enamel specimens against subsequent demineralisation (P<0.05). It is concluded that differently concentrated acidulated sodium fluoride gels resulted in concentration-related significant uptake of fluoride in carious-like demineralised enamel, leading to a better demineralisation protection with increasing fluoride concentration in the gel.

Acidulated Phosphate Fluoride↗

PubMed2005

Erosive effects of different acids on bovine enamel: release of calcium and phosphate in vitro.

The present study intended to investigate minimal erosive effects of different acids on enamel during short time incubation via determination of calcium and phosphate dissolution. Bovine enamel specimens were eroded for 1-5 min with eight different acids of pH 2, 2.3 and 3 (citric (CA), maleic (MA), lactic (LA), tartaric (TA), phosphoric (PA), oxalic (OA), acetic (AA) and hydrochloric acid (HCl)). Calcium (Ca) and phosphate (P) release were determined photometrically using arsenazo III (calcium) and malachite green (phosphate) as substrates. Each subgroup contained eight enamel specimens. Amount of titratable acid was determined for all acidic solutions. MA, LA, TA, AA and HCl caused linear release of Ca and P, PA of Ca, CA of P. For CA, MA, LA, TA, AA, PA and HCl mineral loss was shown to be pH-dependent. Ca dissolution varied between 28.6+/-4.4 (LA, pH 2) and 2.4+/-0.7 nmol mm(-2)min(-1) (HCl, pH 3), P dissolution ranged between 17.2+/-2.6 (LA, pH 2) and 1.4+/-0.4 nmol mm(-2)min(-1) (HCl, pH 3). LA was one of the most erosive acids. AA was very erosive at pH 3. HCl and MA were shown to have the lowest erosive effects. There was only a weak correlation (r=0.28) between P and Ca release and the amount of titratable acid. The method of the present study allows investigation of minimal erosive effects via direct determination of P and Ca dissolution. During short time exposition at constant pH level, erosive effects mainly depend on pH and type of acid but not on amount of titratable acid.

Acetic Acid↗

PubMed2005

Fracture resistance of endodontically treated maxillary premolars restored with CAD/CAM ceramic inlays.

STATEMENT OF PROBLEM: Endodontically treated posterior teeth are more likely to fracture compared to posterior teeth with vital pulps. Reinforcement with an extracoronal restoration that covers the cusps is the most commonly recommended method for reducing the risk of fracture. It is not known whether bonded intracoronal restorations without cuspal coverage will reduce the risk of fracture. PURPOSE: The aim of this in vitro study was to investigate whether reinforcement of endodontically treated premolars with MOD preparations could be achieved by insertion of bonded CAD/CAM ceramic inlays. MATERIAL AND METHODS: Forty-five extracted maxillary premolars were equally distributed among 3 groups (END, CER, CTR). In group END (n=15), root canals were enlarged with a rotary NiTi system and obturated with heat-softened gutta-percha around a plastic carrier (Thermafil). After filling of the endodontic access cavities with autopolymerizing composite resin (Luxacore), standardized MOD cavity preparations were made and CAD/CAM ceramic inlays (CEREC) were fabricated and then bonded to the teeth with composite resin (Tetric) and an adhesive system (Syntac Classic). In group CER (n=15), teeth without endodontic treatment were restored with bonded inlays (CEREC). Sound premolars served as controls (group CTR, n=15). Teeth were then thermal cycled (1445 cycles, dwell time: 30 seconds, 5 degrees /55 degrees C). An eccentric load was applied on the buccal incline of the palatal cusp in a universal testing machine until cusp fracture (N). Fracture load was evaluated with the Mann-Whitney test, and type of fracture, with a chi-square analysis (alpha=.05). The type of fracture was determined by visual inspection: type I - supragingival fracture within the palatal cusp; type II - fracture below cemento-enamel junction of palatal cusp; and type III - fracture of palatal cusp and central portion of the tooth exposing the root canal cavity. RESULTS: No significant difference was found among the 3 groups with respect to load required for fracture. Mean fracture load +/- SD was recorded as follows: 291.6 +/- 113.7 N for group END, 363.2 +/- 140.3 N for group CER, and 296.5 +/- 170.5 N for group CTR. Regarding fracture modes, significantly more teeth from group END exhibited fractures of type III and II compared with control specimens. CONCLUSION: Teeth restored with bonded CAD/CAM ceramic inlays (CEREC) fractured with a significantly higher number of severe fractures compared to the control group.

Bicuspid↗

PubMed2005

Enzymes in the acquired enamel pellicle.

The acquired pellicle is a biofilm, free of bacteria, covering oral hard and soft tissues. It is composed of mucins, glycoproteins and proteins, among which are several enzymes. This review summarizes the present state of research on enzymes and their functions in the dental pellicle. Theoretically, all enzymes present in the oral cavity could be incorporated into the pellicle, but apparently enzymes are adsorbed selectively onto dental surfaces. There is clear evidence that enzymes are structural elements of the pellicle. Thereby they exhibit antibacterial properties but also facilitate bacterial colonization of dental hard tissues. Moreover, the immobilized enzymes are involved in modification and in homeostasis of the salivary pellicle. It has been demonstrated that amylase, lysozyme, carbonic anhydrases, glucosyltransferases and fructosyltransferase are immobilized in an active conformation in the pellicle layer formed in vivo. Other enzymes, such as peroxidase or transglutaminase, have been investigated in experimental pellicles. Despite the depicted impact of enzymes on the formation and function of pellicle, broader knowledge on their properties in the in vivo-formed pellicle is required. This might be beneficial in the development of new preventive and diagnostic strategies.

Adsorption↗

PubMed2005

Subsurface microhardness of enamel and dentin after different external bleaching procedures.

PURPOSE: To evaluate the influence of various bleaching systems on subsurface microhardness of enamel and dentin. METHODS: 60 bovine crowns were distributed among seven groups (A: Opalescence Xtra Boost, B: Opalescence Quick, C: Rapid White, D: Whitestrips, E: Opalescence 10%, F: Opalescence PF 15%). The crowns were sectioned and baseline hardness (Knoop) of enamel and dentin was assessed on the sectioned surface at various distances from the enamel surface. The sectioned surface was covered with wax and the enamel was treated for 10 days with the bleaching agents A-F according to manufacturers' instructions. Bleaching with C-F was conducted each day (C: twice per day for 10 minutes, D: twice per day for 30 minutes, E: 8 hours, F: 4 hours), systems A-B were applied on first and fifth days (A: twice for 10 minutes, B: 1 hour). Finally, hardness was re-assessed. Data were statistically analyzed to compare baseline hardness and final hardness in the respective groups (P< 0.05). RESULTS: Analysis showed that in Group C, hardness was significantly reduced in both enamel and dentin. In the remaining groups, significant reduction of hardness was observed up to the following depths [microm] in enamel; A: 250, B: 700, D: 300, E: 150, F: 150. In these groups no significant hardness changes were recorded in subsurface dentin.

Animals↗