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PubMed1994

Extended fissure sealants: an adjunctive aid in the prevention of demineralization around orthodontic bands.

Banding of molars is still the attachment mode of choice to the majority of clinical orthodontists. One of the acknowledged hazards of orthodontic treatment continues to be the presence of clinically detectable areas of enamel demineralization following the removal of orthodontic appliances. Factors that contribute to this demineralization include inaccurate adaptation of the bands and breakdown of the seal as a consequence of the inadequate bonding strength of the cements and their solubility in oral fluids. Traditional cleaning methods limit adequate plaque control to those areas gingival and incisal to the cemented bands. The iatrogenically created defective band-tooth interface areas pose particular problems, because the ingress of food particles and bacterial plaque make these areas prone to demineralization. A technique is introduced whereby fissure sealant is extended to cover the entire occlusal perimeter, effectively sealing the band-tooth circumferential interface. This technique represents an additional method of prophylaxis against the demineralization that can accompany orthodontic intervention.

Adolescent↗

PubMed2006

Real-time atomic force microscopy of root dentine during demineralization when subjected to chelating agents.

AIM: To explore the potential of atomic force microscopy (AFM) for the examination of changes to dentine surfaces during demineralization and evaluate qualitatively the effect of EDTA, EDTAC and citric acid. METHODOLOGY: Nine canine teeth were sectioned transversely at the cemento-enamel junction, and the crowns discarded. Subsequently, each root was embedded in an epoxy cylinder and discs approximately 5 mm thick were cut. A standard metallographic procedure was then used to prepare the surfaces for observation. From the central portion of these samples, two specimens were symmetrically prepared per tooth so that a total number of 18 samples was produced. To allow the use of a liquid cell during AFM, the samples were embedded in silicone rubber and were then randomly divided into three groups, as follows: group 1: 17% EDTA (pH 7.7), group 2: 17% EDTAC (pH 7.7) and group 3: 10% citric acid (pH 1.4). Topographical images were acquired during the demineralization process, allowing real-time observation of the dentine surface. Two operators assigned scores to the AFM images using a double-blind method. anova analysis with random effects (P < 0.05) was used to compare the results. RESULTS: The average scores were 6.13 +/- 0.35 for EDTAC, 7.36 +/- 0.23 for EDTA and 14.55 +/- 1.21 for citric acid. Citric acid was statistically different from EDTA and EDTAC while EDTA and EDTAC were not statistically different. CONCLUSIONS: The most effective demineralizing substance was citric acid. The methodology developed for real-time observation of dentine surfaces is a valuable method to evaluate demineralization.

Chelating Agents↗

PubMed2005

The ability of 1.23% acidulated phosphate fluoride gel to inhibit simulated endogenous erosion in tooth roots.

BACKGROUND: Endogenous dental erosion is that produced by contact of gastric acids with tooth structure. It may affect exposed root cementum/dentine as well as coronal enamel, causing marked loss of mineral. The aim of this study was to determine whether 1.23 per cent acidulated phosphate fluoride gel, if applied to the surface cementum at certain intervals during an erosive acid challenge, could provide any protection against demineralization. MATERIALS AND METHODS: Roots of preserved extracted human teeth were painted with a water and acid resistant varnish, leaving two windows (3x1mm) of exposed dentine. These were placed in a solution containing 0.06MHCl and 2.2mMCaHPO4, which has been shown to simulate gastric acid when it meets the tooth surface. The roots were placed in the erosive solution unprotected (controls), or subject to APF application for four minutes prior to and every 10, 30 or 120 minutes during the erosive challenge. Roots were removed at either 6 or 12 hours, washed thoroughly and cut into 120microm thick sections. Depths of demineralization were measured using an optical graticule under polarized light microscopy. RESULTS: A high level of protection was provided when the roots were coated with APF gel every 10 or 30 minutes. CONCLUSIONS: APF gel will partially inhibit endogenous erosion of roots for up to 30 minutes if applied, for example, the night before a morning reflux episode. This should be considered along with other erosion control or reduction procedures for patients suffering from the effects of endogenous erosion.

Acidulated Phosphate Fluoride↗

PubMed2005

Effects of salicylic-lactic acid conditioner on the shear bond strength of brackets and enamel surfaces.

The purpose of this study was to evaluate the effects of salicylic-lactic (SL) acid conditioner on the shear bond strength of brackets. Fluoride releasing (Light-bond) and non-fluoride releasing (Enlight) composite adhesives were used after conditioning with 0.22% salicylic + 9% lactic acid or 34% phosphoric acid. Composite adhesives were light cured with either a halogen light curing (HLC) unit for 30-50 s or a plasma arc curing (PAC) unit for 4 s. The shear bond strength was measured with an Instron. Failure modes of debonded brackets were identified based on adhesive remnants on the bracket and tooth. Salicylic-lactic acid conditioning was found to provide adequate shear bond strength. Groups conditioned with SL acid were debonded mainly at the enamel-resin interface and comparatively clean enamel surface after debonding was observed than those conditioned with phosphoric acid. Using confocal laser scanning microscopic examinations, it was found that demineralization patterns between SL acid and phosphoric acid conditioned groups were not different when the same adhesive was used. The SL acid conditioner did not reduce the demineralization. Light-bond adhesive showed less demineralization than Enlight adhesive. The PAC unit can be recommended as an alterative to the HLC unit because it significantly reduces the irradiation time.

Acid Etching, Dental↗

PubMed1986

Development of a three-dimensional extracellular matrix synthesized by human diploid fibroblasts in vitro.

Development and maturation of an extracellular matrix, synthesized by human gingival fibroblasts, have been studied microscopically. Pairs of demineralized, fibronectin-coated slices of human tooth root, 300 micron thick, were placed on confluent cell layers, defining a 0.5 mm wide space. The cultures were grown under standard conditions with ascorbic acid (50 micrograms ml-1) added daily. At various times up to 13 weeks, the cultures were fixed and the samples prepared for light and electron microscopy. Cells from the monolayer became attached to, and migrated up, the vertical root surface and, during the time studied, completely filled the space between the root slices with an extracellular matrix. A close association was seen between the cell membrane and collagen fibres in the demineralized surface initially. A thin layer of fibrillar material was deposited between the cell and the vertical surface, and eventually an extracellular matrix surrounding the cells and attaching to the root surface was present. Samples fixed in the presence of Ruthenium Red showed intense staining of the fibrillar material, indicating the presence of anionic molecules. Additional cells migrated onto the newly synthesized matrix and up the root surface. Growth of the fibrillar networks on either side, horizontally and vertically, continued and, eventually, an extracellular matrix attaching to the vertical surfaces completely filled the previously empty space. Immunocytochemical staining showed that the matrix contained hyaluronic acid, chondroitin sulphate, dermatan sulphate and fibronectin at this time. Collagen fibres were observed at 6 weeks, and at later times collagen types I, III and V were the primary matrix components. The fibroblasts attaching to the root slice and those present at the edge of the matrix had an elongated, polar form. The cells within the matrix frequently showed a stellate appearance with numerous extended processes, in contact with fibrillar material or collagen fibres. Fibroblast processes were at later times seen to enclose bundles of collagen fibres and to mediate cell-to-cell contact, occasionally via desmosome-like structures. The structure and composition of the matrix and the appearance and apparent behaviour of the cells were similar to that observed in the healing wound. This system thus could provide a model for studying various aspects of regeneration of extracellular matrix.

Collagen↗

PubMed2001

Reversal of primary root caries using a dentifrice with a high fluoride content.

Root caries is a widespread problem and can be quite serious in older populations. The restoration of root carious lesions is often difficult. Compared to enamel caries, there has been limited research into the pharmaceutical management of primary root caries lesions (PRCLs), and many of these studies have been carried out in vitro, with limited numbers of clinical trials. Fluoride is presently a cornerstone in dentifrice formulations for cost-effective and anticaries therapy. It is generally accepted that fluoride ions promote remineralization of tooth substances and reduce the rate of demineralization. The use of a dentifrice with a high fluoride content may be considered to reverse PRCLs, since more fluoride is required for the remineralization of roots than for enamel. This paper reviews the effects of dentifrices with high fluoride contents on the management of root caries.

Adult↗

PubMed1996

Biochemical comparison of plaque fluid on tooth and acrylic surfaces during a sucrose challenge.

Previous studies have investigated variations in dental plaque fluid composition within a single mouth after a sucrose exposure. The purpose of this study was to determine a potential source of calcium and phosphorus in plaque by comparing the pH, calcium and phosphorus concentrations in plaque fluid obtained from an acrylic appliance with samples taken from supragingival tooth surfaces within the same individual after a sucrose challenge. Separate plaque samples from 14 individuals were collected from an acrylic appliance or tooth surfaces within same individual before and 15 min after a 20% sucrose rinse. Each plaque sample was centrifuged and nanolitre samples of plaque fluid were analysed for pH with a pH microelectrode, for total calcium concentration by atomic absorption in a graphite furnace, and for phosphorus concentration by spectrophotometry. There was an increase in the calcium and phosphorus concentration in the plaque after the sucrose challenge and a significant increase in calcium and phosphorus concentrations in the plaque taken from the teeth compared to the acrylic surfaces. The results indicate that the increased total calcium and phosphorus in plaque during a sucrose challenge is probably derived from the demineralization of enamel or extracellular demineralized components.

Acrylic Resins↗

PubMedDate not supplied

The effect of whitening agents on caries susceptibility of human enamel.

This in vitro study evaluated whether the treatment of human enamel with whitening agents containing different concentrations of carbamide or hydrogen peroxide changes the susceptibility of enamel to caries. Twenty-four sound human incisors were selected for this study. For each tooth, the crown was sectioned into two halves in the cervical-incisal direction. One half of the sectioned tooth was treated and the other half was used as a control specimen. Each half was randomly divided into three treatment groups (eight two-halves/group). The whitening agents were 10% carbamide peroxide, 20% carbamide peroxide with fluoride and 35% hydrogen peroxide. Following pretreatment, the specimens were demineralized for four days in an in vitro microbial caries model and then analyzed using a confocal laser scanning microscope (CLSM). Results showed that there were no significant differences between the treated and controlled specimens for teeth treated with 10% carbamide peroxide or 35% hydrogen peroxide. However, specimens treated with 20% carbamide peroxide with FP (0.11% fluoride and potassium nitrate) were less susceptible to caries than their controls at p < or = 0.05. In conclusion, application of bleaching agents does not increase the caries susceptibility of human enamel.

Carbamide Peroxide↗

PubMed2001

In vitro evaluation of different remineralization periods in improving the resistance of previously eroded bovine dentine against tooth-brushing abrasion.

One dentine specimen was prepared from each of 90 bovine incisors. The samples were then evenly distributed among nine groups (A-I) and submitted to 10 alternating de- and re-mineralization cycles, including abrasion by tooth brushing. Each cycle started with a demineralization using the erosive soft drink Sprite Light for 1 min, followed by storing the samples in pooled human saliva for a total of 240 min. The specimens were removed from the saliva at different intervals (group A, 0 min; B, 15 min; C, 30 min; D, 45 min; E, 60 min; F, 90 min; G, 120 min) and brushed in an automatic brushing machine. Groups H (erosion, but no brushing) and I (no erosion, but brushing), which were also stored in saliva for 240 min, served as controls. After these cycles, loss of dentine was determined by profilometry, producing the following values (mean+/-S.D.), which were analysed statistically (P< or = 0.05): group A (5.03+/-1.49 microm), B (4.44+/-1.09 microm), C (4.91+/-0.95 microm), D (5.47+/-1.52 microm), E (5.29+/-1.45 microm), F (4.76+/-0.74 microm), G (5.16+/-0.71 microm), H (2.61+/-1.31), I (1.11+/-0.39). Groups A-G had no significant differences, but they showed a significantly greater loss of dentine than groups H and I. It is concluded that the abrasion resistance of eroded bovine dentine is still decreased after a remineralization period of 120 min.

Analysis of Variance↗

PubMedDate not supplied

Initial in situ secondary caries formation: effect of various fluoride-containing restorative materials.

This study evaluated the effects of various restorative materials (Ariston pHc; Dyract; Vitremer; Tetric Ceram; Compoglass F, F2000; Hytac and Ketac Molar) on initial secondary caries formation in situ. Eighty-eight enamel slabs from sound human molars were sterilized (ethylene dioxide) and embedded in epoxy resin. Standardized tooth preparations were filled with the various restorative materials according to manufacturers' recommendations. One specimen from each group was inserted into one of two buccal aspects of an intraoral appliance worn by 11 volunteers for four weeks, day and night. Oral hygiene was performed without additional fluoride application. During meals and oral hygiene procedures, the appliances were stored in sucrose solution (10%). After in situ exposure, the samples were prepared for microradiographic assessment. Mineral content and lesion depth were evaluated by a dedicated software package (TMR 1.24). Lesion depth and mineral loss of the carious lesions close to Ariston pHc was significantly lower when compared to distant parts of the same lesions (p < 0.05; t-test, Bonferroni-Holm correction). All other materials containing fluoride showed no caries protective effect on surrounding enamel (p > 0.05; t-test, Bonferroni-Holm correction). A hydroxyl-, calcium- and fluoride-containing restorative material hampers demineralization next to the restoration, whereas, fluoride release of various fluoride-containing restorative materials does not affect demineralization of adjacent enamel in situ.

Adult↗

PubMed2006

Caries susceptibility of human fluorosed enamel and dentine.

OBJECTIVE: Objective of our laboratory study was to determine the impact of dental fluorosis severity on the formation of caries in the human enamel and dentine. MATERIALS AND METHODS: Thirty-three human molars were grouped according to modified Thylstrup-Fejerskov index (TFI) into normal (N, TFI 0), mild fluorosis (ML, TFI 1-3) and moderate fluorosis (MD, TFI 4-6). Three mesio-distal sections were made in corono-apical axis of the tooth, giving enamel and dentine samples. They were embedded in an epoxy resin, and polished. Half of the polished surface was covered with an acid resistant varnish and immersed in standard acidified buffer solution (pH 4.5) for 48 h to create artificial caries lesions. They were treated with 5% NaOCl for 45 min and sectioned longitudinally along the center into two halves. Cut surfaces were polished and observed under a confocal laser scanning microscope for depth of demineralization. Morphology of the demineralized zones was observed under a field emission scanning electron microscope (FE-SEM). Data were analyzed using one-way ANOVA and Sheffe test (p=0.05). RESULTS: Statistically significant difference in depth of demineralization was found between N and MD groups (p=0.046) in the enamel, and between N and ML (p=0.002), N and MD (p<0.001), ML and MD (p=0.029) in dentine. FE-SEM observation of the normal enamel showed direct dissolution with large fissures. Spongy appearance of intertubular dentine gradually disappeared from N to MD. CONCLUSIONS: Moderately fluorosed enamel showed a significant caries resistance. In contrast, mild and moderately fluorosed dentine was significantly caries susceptible in vitro.

Adult↗

PubMed1984

Histomorphometric evaluation of the dimensional changes in rat-incisor tissues following histological processing and embedding in paraffin wax and glycol methacrylate.

A three-dimensional reconstruction of undemineralized and paraffin wax- or or glycol methacrylate-embedded demineralized rat incisors was made using a computerized histomorphometry. Compared to the undemineralized ground sections, the two demineralizing and embedding procedures grossly distorted the tooth sections. In general, embedding in wax caused shrinkage and in methacrylate caused swelling. Direction and magnitude of the deformation varied in the different tissues of the tooth and its surrounding structures. The distortion was influenced by the ratio between the soft and hard tissues at different cross-sectional levels of the tooth.

Animals↗

PubMed1986

Dissolution and precipitation reactions in human tooth enamel under weak acid conditions.

Slices of enamel were demineralized in weak acid solutions at pH 5. The solutions were analysed for Ca, P, Na and Mg. A substantial increase of the Ca/P ratio in the solution after about 6 h of demineralization was ascribed to brushite formation. The ratios of liberated Ca/Na, P/Na, Ca/Mg and P/Mg were always lower than the correspondent ratios in sound enamel. It was concluded that precipitation of brushite, and a preferential dissolution of Na and Mg compounds from the enamel both play a role in the dissolution-precipitation reactions in dental enamel during acid attack.

Acids↗

PubMed2002

[Determination of Ca2+ content in human enamel by electroprobe after polypeptide tooth paste usage].

OBJECTIVE: The purpose of this study was to investigate the capability of polypeptide tooth paste for remineralization of human enamel. METHODS: 8 enamel slabs,which were taken from extracted tooth for orthodontics reason, were immersed in artificial cariogenic solution for 0.5h. Then,the slabs were treated by tooth paste with polypeptide and tooth paste without polypeptide for 5 min. After tooth paste were washed away by warm water, the slabs were immersed in artificial saliva. The experiment were carried out twice per day for 15 days. Two slabs were taken from test group(treated by tooth paste with polypeptide) and control group (treated by tooth paste without polypeptide) on the twelfth day and fifteenth day, respectively. The Ca(2+) content in enamel slabs were determined by electroprobe and analyzed by image process. RESULTS: The content of Ca(2+) in test group was higher than that in control group significantly. CONCLUSION: The polypeptide tooth paste has certain capability of inhibiting demineralization for human enamel.

English Abstract↗

PubMed2004

Deletion of gtfC of Streptococcus mutans has no influence on the composition of a mixed-species in vitro biofilm model of supragingival plaque.

Glucosyltransferases from Streptococcus mutans are thought to play an important role in bacterial adherence to the tooth surface. The goal of the present study was to determine the effect of the deletion of the gtfC gene, which encodes a glucosyltransferase that catalyses primarily the formation of insoluble glucan (mutan), on colonization of S. mutans in a mixed-species biofilm model of supragingival plaque. A gtfC deletion mutant of S. mutans UA159 grew poorly in biofilms on a polystyrene surface in Todd-Hewitt medium containing sucrose, but biofilm formation in the semi-defined fluid universal medium (FUM) was not affected. The S. mutans gtfC mutant colonized with the same efficiency as the wild-type strain when grown together with five other species in a mixed-species biofilm on hydroxyapatite in a mixture of FUM and saliva with pulses of sucrose and showed the same ability to demineralize enamel in vitro. Colonization of mutant and wild-type strains was also equal in an association experiment in specific-pathogen-free rats. However, the gtfC mutant gave rise to more dentinal fissure lesions and smooth surface caries than the wild-type strain; this could be caused by a change in diffusion properties as a result of to the lack of mutan.

Animals↗

PubMed1987

Biochemical and scanning electron microscope study of lipids chloroform-methanol extracted from unerupted and erupted human tooth enamel.

Almost twice as much fatty acid was extracted without demineralization from the mature enamel of erupted teeth treated with 2:1 chloroform-methanol as from the enamel of unerupted teeth (32.64 micrograms/g versus 15.60 micrograms/g). Palmitic C16:0, stearic C18:0, oleic C18:1 omega 9 and linoleic acids C18:2 omega 6 were the chief fatty acids detected by gas-liquid chromatography. The percentage of free fatty acids and diglycerides was larger in unerupted than erupted teeth, whereas that of triglycerides, phosphatidylethanolamine and phosphatidylcholine was larger in erupted teeth. These changes may be due to bacteria and other contaminants (saliva and pellicle). The large amounts of free fatty acids, diglycerides, cholesterol and phospholipids as intrinsic components were probably due to the persistence of membrane remnants entombed during enamel formation, as indicated by the visualization of holes and by the increase in the size and number of focal holes after lipid-solvent interaction with the enamel surface. These defects always occurred in rods and never in inter-rod material. Other minute defects, including empty-widened intercrystal spaces, were also observed inside some rods.

Adolescent↗

PubMed1989

The interrelationship between the root surface and alveolar bone of the replanted avulsed tooth after etching.

It has been suggested that removal of the damaged nonvital periodontal ligament (PDL) may result in slower destruction of tooth substance following replantation of teeth. It has also been suggested that citric acid conditioning of surgically exposed dentin may enhance connective tissue attachment on root surfaces. The aim of this study was to examine the interrelationship between the acid etched root surface of the replanted tooth and the alveolar bone. Forty-five available anterior teeth from six monkeys were divided into 3 groups in this experiment. All teeth were extracted and dried for 2 hrs. In the first group the teeth were replanted immediately after endodontic therapy. The teeth in the second group were replanted after immersion in 10% sodium hypochlorite and subsequently irrigation with normal saline. In the third group, the cementum and necrotic PDL were removed by grinding the root surfaces which were then treated with citric acid (PH = 1) for 3 minutes followed by normal saline irrigation. All teeth were replanted without splinting and were subjected to histological examination at 12 week post-replantation. Close apposition of collagen fibrils of the new connective tissue to the exposed root surface was observed in most cases in the second and third group, although bony ankylosis and inflammatory root resorptions were also found in some areas. Teeth in the first group, the control experiment, had much more replacement and inflammatory resorptions. Then the result suggested that demineralization with citric acid on the denuded avulsed tooth prior to replantation may decrease the chance of replacement resorption and result in fibrous adhesion to the alveolar bone.

Adhesiveness↗

PubMed1983

Diffusion in mammalian tooth enamel in relation to the caries process.

For the rate of demineralization of enamel during caries, three physicochemical processes are of importance: the diffusion into and out of the enamel, the dissolution of mineral and the complexation of ions. The interpretation of diffusion experiments in conjunction with artificial caries experiments and computer simulations is described. In the caries process, relevant diffusion coefficients of small ions and molecules are of the order of magnitude 10(-9)--10(-7) cm2 s-1.

Animals↗