Search PubMed⌕ Search

Biomedical subjects

W Geurtsen

Publications and source records attributed to W Geurtsen.

At least 19 recordsLinked to original sources
PubMed2002

Effect of TEGDMA on the intracellular glutathione concentration of human gingival fibroblasts.

Previous studies revealed that primarily small and relatively hydrophilic comonomers, such as TEGDMA, leach out of resin-based restorative materials into aqueous media. Subsequently, these compounds may cause detrimental reactions with intracellular metabolic systems. The present experiments attempted to elucidate the interactions of TEGDMA with the important intracellular reducing agent glutathione (GSH). The influence of various concentrations of TEGDMA (0.5-7.5 mM) on viability and intracellular GSH concentration of primary human gingival fibroblasts was determined by means of a fluorescence assay (monobromobimane) performed in microtiter plates. Cells were treated with TEDGMA between 2 and 24 h. The incubation of fibroblasts with TEGDMA even at subtoxic concentrations quickly decreased the intracellular glutathione level to 30-50% of controls within the first 2-6 hours. However, no simultaneous adverse effect on cell viability was found. Longer incubation periods up to 24 h caused a regulatory reincrease at TEGDMA concentrations <or= 2.5 mM, whereas higher concentrations resulted in a continuous depletion of glutathione concentration concomitant with a significant decrease of cell viability. Because glutathione plays an important role in protection and detoxification processes as well in the regulation of cell death, the early and extensive depletion of the intracellular glutathione pool due to TEGDMA may significantly contribute to the cytotoxic potency of this compound.

Cell Survival↗
PubMed2002

Chemical-biological interactions of NaF with three different cell lines and the caries pathogen Streptococcus sobrinus.

Fluoride is used in dentistry as a prophylactic agent to reduce caries rates due to the demineralization/remineralization effect and its influence on the metabolism of cariogenic bacteria. The purpose of this study was to evaluate the cytotoxic effects of sodium fluoride (NaF) on three different cell lines and the antibacterial potency on Streptococcus sobrinus. Cell lines were treated with various concentrations of NaF ranging from 0.039 mM to 10 mM for 24 h. For microbial assays, concentrations of NaF between 0.03 mM and 10 mM were added to liquid cultures of bacteria. Our results showed that immortalized human keratinocytes (HaCaT) and human osteogenic sarcoma cells (SAOS-2) were similarly affected by concentrations up to 2.5 mM. However, cell growth of HaCaT was slightly more inhibited at 2.5 mM of NaF than SAOS-2. At concentrations between 0.62 mM and 10 mM, 3T3 mouse fibroblast cells reacted more sensitively than HaCaT and SAOS-2 to NaF. The 3T3 cells did not survive in the presence of 10 mM NaF. NaF caused no significant effect on all tested cells at concentrations of < or = 0.31 mM. NaF at 0.039 mM and 0.06 mM did not affect growth of S. sobrinus. At concentrations of 0.125 mM and 0.5 mM, growth was slightly reduced. The proliferation of S. sobrinus significantly decreased at 1 mM and 2 mM NaF. S. sobrinus survived at 4 mM, revealing a delayed log phase with a decreased proliferation. No viable S. sobrinus cells were detected at concentrations of > or = 8 mM NaF. Data analysis revealed that overall treatment effects were highly significant (P<0.05, analysis of variance, Tukey's difference test). This study indicates that cytotoxic effects due to NaF significantly vary in dependence upon the applied cell line. The toxicity of NaF approached 50% (TC50) at concentrations of 6 mM for HaCaT, 2.3 mM for 3T3 cells, and 7.5 mM for SAOS-2. Additionally, NaF revealed antimicrobial effects only at concentrations that are significantly higher than oral fluoride concentrations.

3T3 Cells↗
PubMed2002

Culture of primary human gingival fibroblasts on biodegradable membranes.

Repair and regeneration of periodontal tissues by tissue engineering is dependent on the use of biodegradable polymer scaffolds which serve as a carrier for cells or bioactive substances. There is a need to understand how a specific biomaterial may influence gene expression. The aim of this investigation was to develop and to optimize an in vitro technique for the adherance and proliferation of primary human gingivaL cells on implantable and biodegradable matrices. Square pieces of Bio-Gide matrix (BG) and slices of Ethisorb tamponade (ET) were coated with poly-L-lactide. The stability of coated and uncoated scaffolds was investigated by incubation in standard culture medium. Various concentrations of the cells were seeded onto coated and uncoated polymer matrices in tissue culture dishes without shaking ("static seeding") or continuous shaking ("agitated seeding"). Cultures were grown for 4 week and were then evaluated by light and scanning electron microscopy. After a culture period of 10 d, BG-carriers showed a delicate consistency which made histological processing difficult. Cells were grown only sparsely in coated and non-coated BG-scaffolds. Contrary. ET-specimens were stable during a 4 week culture period. After "static seeding" a significantly higher number of cells resulted in comparison to those in "agitated" cultures. The cells were evenly distributed throughout the ET-carriers and produced extracellular matrix compounds as well. Furthermore, the examination with RT-PCR (reverse transcription-polymerase chain reaction) revealed that the cells synthesized and secreted type I collagen, and expressed genes implicated in transducing bone morphogenetic protein (BMP) signals. Messenger RNAs for BMP-2, -4, -7, the BMP type I receptors Act R-1 (alk 2, activin-like kinase receptor), BMPR-IA (alk 3), -IB (alk 6), and the type II receptor BMPR-II were detected. These data reveal that static seeding favors the adherence and proliferation of primary gingival cells on polyglactin matrices. This system may serve as a valuable tool for periodontal tissue engineering.

Activin Receptors, Type I↗
PubMed2002

Identification of second canals in the mesiobuccal root of maxillary first and second molars using magnifying loupes or an operating microscope.

Various authors have investigated the frequency of second canals (MB2) in the mesiobuccal roots of maxillary molars, predominantly first molars. Further, it has been reported that the percentage of MB2 canals that are treated during routine endodontic therapy is much lower than the number of second canals identified in vitro. It was the purpose of this study to investigate whether the use of an operating microscope may improve the diagnosis of MB2 canals in mesiobuccal roots of maxillary molars. The canal orifices of 100 maxillary first and second molars (50 of each) were initially inspected by Examiner 1 using individually-adapted x2 magnifying loupes. Subsequently, all teeth were examined by a second investigator using an operating microscope (OPM) with x8 magnification. Finally, the mesiobuccal roots of all teeth were separated. Then, the sections were analysed histologically and by SEM. The histological investigation revealed a total number of 63 MB2 canals, 39 in first, and 24 in second molars. Only 26 (41.3%) of those canals were identified using magnifying loupes, whereas 59 (93.7%) were found by means of an operating microscope.

Dental Equipment↗
PubMed2001

Long-term effects of four extraction media on the fluoride release from four polyacid-modified composite resins (compomers) and one resin-modified glass-ionomer cement.

It was the aim of the present experiments to evaluate the fluoride leaching of four compomers and one resin-modified glass-ionomer cement (gic) into aqueous media over a 1-year period. Various extraction/equilibrium solutions were applied to simulate important intraoral parameters. Specimens of Dyract, Compoglass F, F2000, one experimental compomer, and the resin-modified gic Fuji II LC were stored for 366 days in distilled water (I), acidic medium (pH 4.2) (II), neutral medium (pH 7.0) (III), or solution III supplemented with 1.6 u/mL porcine liver esterase (IV). Equilibrium media were changed and fluoride concentration was measured every 48 h (first 30 d), thereafter each week (twice), then every 14 d (three times), and finally every 28 d up to a total period of 1 year. Data were statistically analyzed for significant differences by means of Scheffe' tests (p < 0.05). The gic and the compomers leached significantly more fluoride into the acidic solution in the initial phase compared to the other media (p < 0.05). Cumulative fluoride release from all materials (except experimental compomer) was elevated because of esterase activity (p <0.05). Measurable but low quantities of fluoride were segregated into all media during the 1-year period. But no significantly different long-term fluoride release into the various media from the investigated materials was found. The data indicate that plaque-associated organic acids or salivary hydrolases may increase initial fluoride release from resin-modified gics or compomers in the oral cavity. Because long-term fluoride release from all materials decreased to low concentrations within a 30-day period, their caries preventive effect remains questionable.

Animals↗
PubMed2001

Immunohistological and morphometric analysis of inflammatory cells in rapidly progressive periodontitis and adult periodontitis.

The purpose of this study was to localize, characterize, and quantify in situ the inflammatory cells in the gingival connective tissue prior and subsequent to the initial therapy of ten patients with rapidly progressive periodontitis (RPP) and five patients with adult periodontitis (AP). Using immunohistological techniques, the amount of T lymphocytes, alphabeta-T lymphocytes, gammadelta-T lymphocytes, B lymphocytes, and plasma cells was determined at the beginning of the periodontal therapy (baseline) and at the time of periodontal surgery. Furthermore, the distribution of collagen types I, III, V, and VI was investigated using transmission electron microscopy. At baseline, patients with RPP revealed much higher numbers of inflammatory cells than patients with AP. During initial therapy of patients with RPP, the amount of T cells, alphabeta-T cells, and gammadelta-T cells was reduced significantly (P<0.05). Biopsies of patients with AP revealed a statistically significant reduction of all cell types, except alphabeta-T cells and gammadelta-T cells in the deep connective tissue. The transmission electron microscopy of biopsies from patients with RPP and AP with severe inflammation taken at baseline revealed that collagen types I and III were destroyed nearly completely in areas with leukocyte infiltration, whereas collagen types V and VI revealed a more pronounced labeling reaction. The results revealed that, during initial therapy, the amount of inflammatory cells was reduced significantly more in biopsies of patients with AP than in patients with RPP. At baseline, the inflamed gingival tissue consists mainly of collagen types V and VI in areas with infiltrates of inflammatory cells.

Adult↗
PubMed2001

Effects of various storage media on surface hardness and structure of four polyacid-modified composite resins ("compomers").

It was the purpose of this study to determine surface microhardness and structure of four poly-acid modified composite resins ("compomers") after 1-year storage in water and various solutions. Specimens of the compomers Dyract (DY), Compoglass F (CG), an experimental compomer (EC), and of F2000 (F) were stored at 37 degrees C for 1 year in distilled water, acidic buffer (pH 4.2), neutral buffer (pH 7.0), and neutral buffer supplemented with 1.6 u/ml porcine liver esterase. Then the specimens were kept dry for 3 days further. Continuously dry-stored samples (37 degrees C) served as controls. Surface microhardness (Vickers) was read at baseline (prior to wet storage), after 24 h and 144 h, then every 30 days up to 1 year and after the further 3 days of dry storage. Surface roughness (Ra) was determined at baseline, after 3, 6, 9, and 12 months and, finally, after the further 3 days. In addition, randomly selected control and experimental specimens were investigated by SEM. Data were statistically analyzed by a three-factor ANOVA using Scheffé tests (P<0.05). Vickers hardness of all experimental samples dropped significantly due to wet storage (P<0.000) during the first month. However, the type of storage medium did not influence microhardness significantly. Surface roughness was not altered by wet storage except for compomer F, which revealed pronounced surface cracks in the SEM. Altogether, our findings point out that surface microhardness and structure of the investigated compomers were not significantly deteriorated by the tested intraoral conditions, such as humidity, pH-fluctuation, or the action of hydrolytic salivary enzymes.

Acids↗
PubMed2001

Biocompatibility of root canal filling materials.

Results of in vitro and in vivo studies clearly indicate that some endodontic sealers may cause local and systemic adverse effects. Though occasionally contradictory data has been reported from various authors, it may be concluded that zinc-oxide-eugenol sealers possess a marked cytotoxic and tissue-irritating potency. Most Ca(OH)2-based materials, however, were biocompatible. Genotoxic effects have been observed with sealers releasing paraformaldehyde or containing mutagenic substances, such as bisphenol-A-diglycidyl-ether or its derivatives. It cannot be excluded that these materials may pose a systemic risk because formaldehyde is rapidly distributed systemically following its application into the pulp cavity. Furthermore an increasing number of cases with an aspergillosis of the maxillary sinus have been observed which were mainly caused by zinc-releasing endodontic sealers. Overall, it is recommended that for endodontic practice, sealers that have been found to be biocompatible in a "mixed bag" of various in vitro and in vivo tests, be selected. From this point of view, ZnOE-sealers should no longer be used for root canal fillings. This recommendation applies also to sealers containing paraformaldehyde or generating this substance during their setting reaction. More experimental and clinical studies are necessary to elucidate whether new materials, such as mineral trioxide aggregate (MTA) or calcium phosphate cement, will be biocompatible alternatives in the future.

Animals↗
PubMed2001

Metabolic effects of dental resin components in vitro detected by NMR spectroscopy.

Earlier studies have shown that the comonomer triethyleneglycol-dimethacrylate (TEGDMA) and the photostabilizer 2-hydroxy-4-methoxybenzophenone (HMBP) are cytotoxic and inhibit cell growth. It was the aim of this study to elucidate the underlying metabolic effects of TEGDMA and HMBP on immortal contact-inhibited Swiss albino mouse embryo cells (3T3 fibroblasts) by nuclear magnetic resonance (NMR) spectroscopy. Cell extracts and culture media were analyzed by NMR spectroscopy for metabolic changes after incubation for 24 hours with ED20-concentrations of TEGDMA and HMBP. TEGDMA could be detected in all fractions (cytosol, lipid fractions, and culture media) of 3T3 cells, while HMBP was found only in the lipid fraction accumulated at a maximum rate (51 nmol/mg DNA) compared with TEGDMA (27 nmol/mg DNA). TEGDMA increased the concentration of phosphomonoesters to 180+/-36% and decreased the phosphodiesters to 65+/-5% of controls (control = 100%). Thus, the turnover of phospholipids was enhanced, whereas content and composition of phospholipids of membranes did not alter markedly. Additionally, TEGDMA changed the metabolic state of cells, indicated by slight decreases of nucleoside triphosphates and an increase in the ratio of nucleoside diphosphates to nucleoside triphosphates, while HMBP had no effect. The most remarkable effect of TEGDMA was a nearly complete decline of the intracellular glutathione levels. Analysis of our data shows that NMR spectroscopy of cell-material interactions may reveal metabolic effects of organic test substances which are not detectable by standard in vitro assays. The comonomer TEGDMA affected the metabolism of the cells on different levels, while HMBP accumulated in the lipid fraction and induced significantly fewer effects on cell metabolism.

3T3 Cells↗
PubMed2001

Effects of mechanical force on primary human fibroblasts derived from the gingiva and the periodontal ligament.

Previous experiments have shown that mechanical stress may alter the interactions between cells and extracellular matrix (ECM). The purpose of our study was to investigate the effects of mechanical load on metabolism and ECM expression of primary human periodontal cells. The influence of gravitational force on proliferation, lactate dehydrogenase (LDH) release, and tenascin expression of gingival (HGF) and periodontal ligament fibroblasts (HPDL), as well as their adhesion to various extracellular matrix (ECM) components, was determined. Cells were centrifuged in microplates or flat tubes for 16 hrs at 217 g. Neither an enhanced release of LDH nor an alteration of cell proliferation could be detected after centrifugation. However, the attachment of loaded gingival and periodontal ligament fibroblasts to all tested ECM components significantly decreased in comparison with controls (Wilcoxon-Mann-Whitney test; HGF, p < 0.05; HPDL, p < 0.01). Tenascin expression of mechanically stressed fibroblasts significantly increased in comparison with controls (p < 0.01).

Cell Adhesion↗
PubMed2001

Molar fracture resistance after adhesive restoration with ceramic inlays or resin-based composites.

PURPOSE: To determine the fracture resistance of teeth, following treatment with various types of adhesive restorations. MATERIALS AND METHODS: 5 0 caries-free, extracted human molars were randomly divided into five groups consisting of 10 molars each. MOD cavities were prepared in 40 molars with a width in the facio-lingual direction of 50% of the intercuspal distances. The cavities were filled with the following materials: Cerec or IPS Empress ceramic inlays, Arabesk or Charisma F resin-based composite (RBC) restorations. The control group consisted of 10 sound, non-restored molars. All 50 teeth were loaded occlusally until fracture using a tensile testing machine. The statistical analysis included ANOVA, Kolmogorov-Smimov-test, Scheffé test, and boxplots. RESULTS: There was no significant difference (P > 0.05) between the mean values of the sound teeth (2,102 N) and the teeth with the Cerec ceramic inlays (2,139 N). However, both groups demonstrated a significant difference (P < 0.05) when compared with the teeth with IPS Empress ceramic inlays (1,459 N) and Arabesk RBC restorations (1459 N). No significant differences were found between the last two groups. Molars restored with Charisma F composite restorations (1,562 N) revealed no significant difference when compared with all other groups including controls (P > 0.05). A stabilization of molars is possible by means of an adhesive restoration in the form of an "internal splinting" regardless of the restorative material used.

Acrylates↗
PubMed2000

Effects of BisGMA and TEGDMA on proliferation, migration, and tenascin expression of human fibroblasts and keratinocytes.

Previous studies have documented a marked cytotoxic potency of BisGMA and TEGDMA. The purpose of this investigation was to determine if these substances also affect proliferation, migration, and tenascin expression of primary human gingival fibroblasts (HGF) and immortalized human keratinocytes (HaCaT). These parameters play an important role in healing wounds. HGF and HaCaT cultures were incubated with TEGDMA and BisGMA. Cell proliferation (BrdU-assay) and migration (Boyden method) were determined 24 h after incubation. Tenascin expression was investigated four and seven days after treatment. Results were statistically evaluated by ANOVA using the Wilcoxon-Mann-Whitney test (p < 0.05). Proliferation of both cell types was significantly inhibited at concentrations > or = 0.25 mM (TEGDMA) or > or = 0.01 mM (BisGMA). Migration of HaCaT was significantly increased after incubation with BisGMA for 24 h. TEGDMA did not alter migration of HGF and HaCaT. In addition, TEGDMA had no effect on tenascin expression of both cell cultures. After 4 days of incubation, BisGMA (at a concentration of 0.01 mM) significantly reduced tenascin production of HaCaT cultures related to cell number. However, 7 days after treatment, BisGMA significantly increased tenascin expression of HGF and HaCaT cultures. Altogether, our results indicate that BisGMA can affect migration of keratinocytes and alters the expression of the extracellular matrix component tenascin. Thus, BisGMA may significantly influence the healing of injured oral tissues.

Antimetabolites↗
PubMed2000

Compatibility of resorbable and nonresorbable guided tissue regeneration membranes in cultures of primary human periodontal ligament fibroblasts and human osteoblast-like cells.

The purpose of this study was (a) to evaluate the cytocompatibility of three resorbable and nonresorbable membranes in fibroblast and osteoblast-like cell cultures and (b) to observe the growth of those cells on the various barriers by scanning electron microscopy (SEM). Primary human periodontal ligament fibroblasts (HPLF) and human osteoblast-like cells (SAOS-2) were incubated with nonresorbable polytetrafluoroethylene (ePTFE) barriers and resorbable polylactic acid as well as collagen membranes. Cytotoxic effects were determined by XTT (mitochondrial metabolic activity) and sulforhodamine B assays (cellular protein content). In addition, HPLF and SAOS-2 grown for 21 days on the investigated barriers were evaluated by SEM. Data were analyzed statistically by ANOVA using the Wilcoxon-Mann-Whitney test (P < 0.05). No changes were established in the periodontal ligament fibroblasts and human osteoblast-like cells after incubation with the collagen membrane. Cytotoxic effects, however, were induced by the polylactic acid barrier which slightly inhibited cell metabolism of the periodontal fibroblasts (XTT: 90.1% +/- 3.6 of control value). Moderate cytotoxic reactions were caused by the nonresorbable ePTFE membrane in HPLF-cultures (XTT: 82.7% +/- 3.5) and osteoblast-like cell monolayers (XTT: 80.0% +/- 0.6%). Mitochondrial activity in both cell cultures was significantly reduced by ePTFE barriers in comparison to non-incubated control cells (P = 0.028). SEM analysis of cell behavior on barriers demonstrated the differences between these materials: collagen barriers were densely populated with HPLF and SAOS-2, whereas only few or no cells were seen to adhere to the ePTFE and polylactic acid membranes. Our findings indicate that the collagen barrier investigated is very cytocompatible and may be integrated into connective tissue well. On the contrary, the ePTFE and polylactic acid membranes induced slight to moderate cytotoxic reactions which may reduce cellular adhesion. Thus, gap formation between the barrier surface and the connective tissue may be promoted which may facilitate epithelial downgrowth and microbial accumulation. Consequently, these effects may reduce the potential gain in periodontal attachment.

Absorbable Implants↗
PubMed2000

Infection of primary human gingival fibroblasts by Porphyromonas gingivalis and Prevotella intermedia.

Adhesion and penetration of clinical isolates of Porphyromonas gingivalis and Prevotella intermedia in human gingival fibroblast monolayers were studied by transmission electron microscopy (TEM). Fibroblasts were cultured from biopsies of human healthy gingiva. Porphyromonas gingivalis and Prevotella intermedia were isolated from patients with periodontitis. Fibroblasts were incubated with microorganisms in an antibiotic-free medium for 24 h. Then cultures were washed to remove nonadherent bacteria. Consecutively, infected cultures were grown for another 24 h. Thereafter, the treated monolayers were prepared for TEM investigations. Internalized Porphyromonas gingivalis and Prevotella intermedia were visible after 24 h of incubation. Prevotella intermedia showed only division in cytoplasm of fibroblasts after 24 h and 48 h incubations. Infected fibroblasts revealed various morphological alterations such as extensive vacuolization and breakdown of mitochondria. These findings demonstrate that Porphyromonas gingivalis and Prevotella intermedia may invade human gingival fibroblasts and thus may damage these cells directly or due to the release of microbial cytotoxic components.

Adult↗
PubMed2000

Comparison of the number and diameter of dentinal tubules in human and bovine dentine by scanning electron microscopic investigation.

Detailed information on dentine structure is essential for interpreting data from investigations on dentine-adhesive materials. The purpose here was to compare the number and diameter of dentinal tubules at similarly prepared surfaces of bovine permanent central incisors and human deciduous and third molars. In bovine teeth, crowns and roots were used; in human samples only the crowns were investigated. Tubule density in the middle layer was higher in bovine root (BR) dentine (number of tubules per mm(2)+/-SD: 23, 760+/-2453) than in human deciduous (HD) (18,243+/-3845), human permanent (HP) (18,781+/-5855), and bovine coronal (BC) (17, 310+/-2140) dentine. The corresponding values for the deep layer were 23,738+/-4457 (BR), 24,162+/-5338 (HD), 21,343+/-7290 (HP), and 20,980+/-4198 (BC). No significant differences were found for the number of dentinal tubules in bovine coronal dentine compared to the dentine of human deciduous and permanent molars. The mean diameter of bovine dentinal tubules was slightly, but not significantly, higher than in human dentine (middle layer/deep layer+/-SD): BC, 2. 85 microm+/-0.18/3.50 microm+/-0.33; BR, 3.10 microm+/-0.33/3.23 microm+/-0.30; HD, 2.55 microm+/-0.16/2.82 microm+/-0.28; HP, 2.65 microm+/-0.19/2.90 microm+/-0.22. These findings demonstrate that corresponding coronal dentine layers of human deciduous and permanent molars, and of bovine central incisors, are not significantly different in their number of tubules per mm(2) and their tubule diameter, whereas tubule density in bovine root dentine is significantly higher. These results suggest that provided standardized preparations are used, bovine incisor crown dentine is a suitable substitute for human molar dentine in adhesion studies.

Adolescent↗
PubMed2000

Biocompatibility of resin-modified filling materials.

Increasing numbers of resin-based dental restorations have been placed over the past decade. During this same period, the public interest in the local and especially systemic adverse effects caused by dental materials has increased significantly. It has been found that each resin-based material releases several components into the oral environment. In particular, the comonomer, triethyleneglycol di-methacrylate (TEGDMA), and the 'hydrophilic' monomer, 2-hydroxy-ethyl-methacrylate (HEMA), are leached out from various composite resins and 'adhesive' materials (e.g., resin-modified glass-ionomer cements [GICs] and dentin adhesives) in considerable amounts during the first 24 hours after polymerization. Numerous unbound resin components may leach into saliva during the initial phase after polymerization, and later, due to degradation or erosion of the resinous restoration. Those substances may be systemically distributed and could potentially cause adverse systemic effects in patients. In addition, absorption of organic substances from unpolymerized material, through unprotected skin, due to manual contact may pose a special risk for dental personnel. This is borne out by the increasing numbers of dental nurses, technicians, and dentists who present with allergic reactions to one or more resin components, like HEMA, glutaraldehyde, ethyleneglycol di-methacrylate (EGDMA), and dibenzoyl peroxide (DPO). However, it must be emphasized that, except for conventional composite resins, data reported on the release of substances from resin-based materials are scarce. There is very little reliable information with respect to the biological interactions between resin components and various tissues. Those interactions may be either protective, like absorption to dentin, or detrimental, e.g., inflammatory reactions of soft tissues. Microbial effects have also been observed which may contribute indirectly to caries and irritation of the pulp. Therefore, it is critical, both for our patients and for the profession, that the biological effects of resin-based filling materials be clarified in the near future.

Animals↗
PubMed2000

Placement of the preparation line and periodontal health--a prospective 2-year clinical study.

The aim of this prospective clinical 2-year study was to determine whether the placement of the proximal margins of crowns within the zone of the biologic width results in periodontal alterations. In 41 patients, 116 prepared teeth as well as 82 unrestored, healthy contralateral teeth were examined. The following indices were determined before as well as 3, 6, 12, and 24 months after preparation: hygiene index, papillary bleeding index (PBI), and probing depth. After preparation, the distance between the restoration margins and the alveolar crest was measured with a modified periodontal probe on both proximal aspects of each tooth. These values were classified into 3 groups: I = < or = 1 mm between crown margin and alveolar crest, II = 1 to 2 mm, and III = > 2 mm. In addition, radiographs were taken directly after cementation of each restoration and after 12 and 24 months. The hygiene index did not significantly vary during the investigation, but PBI increased in all groups. The highest PBI increase was found in group I; in this group, the most significant increase was found between 3 and 6 months after preparation. The mean probing depth only increased in group I during the first 3 months after preparation on the mesial aspects. Only minor changes were found on the distal aspects of the teeth in group I and on all aspects in groups II and III. No alterations of the bone levels were diagnosed on the radiographs. These results indicate that the location of the restoration margins within the zone of the biologic width may impair the periodontal health of restored teeth.

Adult↗