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PubMed2003

[The effect of Galla chinensis on the demineralization of enamel].

OBJECTIVE: To investigate the effect of Galla Chinensis with or without fluoride on demineralization of enamel. METHODS: Galla Chinensis with or without fluoride and acid buffer were used to treat the samples alternately and the treatment was repeated 8 times. Then the calcium of acid buffer was measured by American PE HTS 7000 plus and the specimens were observed with laser scanning confocal microscope. RESULTS: Compared with the calcium concentration of control group (deionized water or fluoride), the calcium concentration of all tested groups (except the 1 mg/ml group without fluoride) decreased significantly (P < 0.25). There was marked difference in total fluorescence (TF) and average fluorescence (AF) between the tested groups and control group (P < 0.05). As for the area of lesion, only groups without fluoride and the 4 mg/ml group containing fluoride decreased (P < 0.01). Confocal images showed that the zone of red area of tested groups was narrower than that of control group. CONCLUSION: Galla Chinensis can reinforce the resistance of enamel to acid, either with or without fluoride.

Dental Caries↗

PubMedDate not supplied

The effect of 10% carbamide peroxide bleaching material on microhardness of sound and demineralized enamel and dentin in situ.

This in situ study evaluated the microhardness of sound and demineralized enamel and dentin submitted to treatment with 10% carbamide peroxide for three weeks. A 10% carbamide peroxide bleaching agent--Opalescence/Ultradent (OPA)--was evaluated against a placebo agent (PLA). Two hundred and forty dental fragments--60 sound enamel fragments (SE), 60 demineralized enamel fragments (DE), 60 sound dentin fragments (SD) and 60 demineralized dentin fragments (DD)--were randomly fixed on the vestibular surface of the first superior molars and second superior premolars of 30 volunteers. The volunteers were divided into two groups that received bleaching or the placebo agent at different sequences and periods at a double blind 2 x 2 crossover study with a wash-out period of two weeks. Microhardness tests were performed on the enamel and dentin surface. The SE and DE submitted to treatment with OPA showed lower microhardness values than the SE and DE submitted to treatment with PLA. There were no statistical differences in microhardness values for SD and DD submitted to the treatment with OPA and PLA. The results suggest that treatment with 10% carbamide peroxide bleaching material for three weeks alters the enamel microhardness, although it does not seem to alter the dentin microhardness.

Adult↗

PubMed1997

The dentin substrate: structure and properties related to bonding.

OBJECTIVES: Dentin is a vital, hydrated composite material with structural components and properties that vary with location. These variations are reviewed along with alterations by physiological and pathological changes that allow classification into various forms of dentin. Structural characteristics and mechanical properties are reviewed and the limitations of our understanding of structure-property relationships for normal and modified forms of dentin are discussed with respect to their impact on dentin bonding. Recent progress in methods available to study dentin and its demineralization are emphasized with their promise to increase our understanding of dentin properties and structure. DATA SOURCES: Recent microstructural studies, focusing on scanning electron microscopy, atomic force microscopy and X-ray tomographic microscopy are included. A review of fundamental studies with emphasis on microstructurally sensitive methods, and prior reviews of basic mechanical properties are included with discussion of their correlation to composition and structure. STUDY SELECTION AND CONCLUSIONS: Emphasis in this work was placed on the major structural components of the tissue, including the collagen based organic matrix and its mineral reinforcement, the distribution of these components and their microstructural organization as related to mechanical properties and response to demineralization. Little information is included on biochemical and developmental studies or on non-collagenous proteins and other organic components for which limited understanding is available with respect to their role in structure-property relations and influence on bonding. In spite of the fact that the complexity of dentin precluded a comprehensive review, it is clear that local structural variations influence properties and impact nearly all preventive and restorative dental treatments. Much more work is needed in order to understand differences between vital and non-vital dentin, and dentin from extracted teeth. Although our knowledge is rudimentary in certain areas, increasingly sophisticated methods of studying dentin should provide the necessary information to model structure-property relations, optimize dentin bonding, and improve many aspects of preventive and restorative dentistry.

Apatites↗

PubMed2006

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.

Animals↗

PubMed2005

In vitro antibacterial effects of the dentin primer of Clearfil Protect Bond.

OBJECTIVES: This study aimed to investigate the antibacterial effects of the dentin primer of a commercially available self-etching adhesive system, Clearfil Protect Bond, which contains antibacterial monomer 12-methacryloyloxydodecylpyridinium bromide (MDPB). METHODS: Inhibitory effects against Streptococcus mutans, Lactobacillus casei, or Actinomyces naeslundii were examined by an agar-disc diffusion method using the Clearfil Protect Bond primer containing 5% MDPB and an acidic adhesion-promoting monomer MDP, the primer only with MDP, and the primer with 1% cetylpyridinium chloride. The minimum inhibitory/bactericidal concentrations (MIC/MBC) of each primer for the three bacterial species were determined by serial microdilution assays. For testing the bactericidal effects seen in dentin, the primer was applied to demineralized dentin blocks in which S. mutans had been impregnated, and numbers of viable bacteria were counted. RESULTS: For all three bacteria, the sizes of the inhibition zones produced by Clearfil Protect Bond primer were significantly greater than for the other primers (p<0.05, ANOVA and Scheffe's F-test). The MIC/MBC values of Clearfil Protect Bond primer were less than those of the primer without MDPB, and comparable to those of the primer containing cetylpyridinium chloride. No bacterial recovery was obtained after application of Clearfil Protect Bond primer to the bacteria-impregnated dentin, although the primer without MDPB showed some bactericidal effect. SIGNIFICANCE: Clearfil Protect Bond primer has strong antibacterial activity based upon MDPB against S. mutans, L. casei and A. naeslundii, and the capability to disinfect cavities containing residual bacteria.

Acid Etching, Dental↗

PubMed2006

Transversal wavelength-independent microradiography, a method for monitoring caries lesions over time, validated with transversal microradiography.

This paper describes a microradiographic method for measuring mineral concentration in a transversal geometry with thick (< or =3.2 mm) sections: transversal wavelength-independent microradiography (T-WIM). It was tested on bovine enamel and dentin samples in vitro, and the results were validated with those of transversal microradiography (TMR). 48 enamel and 48 dentin samples (3.2 x 3.2 x 1.5 mm) were embedded in acrylic resin, randomly divided into six groups of 8 dentin or 8 enamel samples, and demineralized for 0 (sound control), 1, 2, 3, 4, or 5 weeks. For T-WIM, samples were imaged on film with polychromatic 40-kV Cu X-rays with an Al (0.25 mm)/Ni (0.02 mm) filter together with an aluminium/zinc step wedge. TMR slices (about 80 mum for enamel and about 130 mum for dentine) were subsequently cut from the centre of the samples and subjected to TMR. Microradiographs from both methods were digitized and image analysis software was used to calculate lesion depth and mineral loss. The relations between T-WIM and TMR results for mineral loss (DeltaZ) and lesion depth were nearly linear (r > or = 0.96) for both enamel and dentin. The slopes of the regression lines were between 0.99 and 1.02 except for DeltaZ in dentine, which was 0.89. It was concluded that T-WIM is a suitable method for TMR on thick samples.

Animals↗

PubMed1991

[Incipient cariogenic demineralization of human enamel].

32 teeth (12 premolars and 20 molars) were studied under light microscopy, polarized microscopy, transparence light microscopy and scanning electron microscopy. These teeth presented changes in colour in their free and proximal surface as well as close to pits and fissures. As an extra diagnostic test the PAS reaction was used to assess descalcifying processes in both light and transparence microscopy. Polarized light was used to assess normal enamel. Scanning electron microscopy corroborated the lesions produced in the enamel surface in the form of micropores. PAS reaction diagnosed decalcifying processes in yellow, brown and brownish stains. White staims not always were PAS-positive and when they reacted in the same manner as other positive stains, with the immersion technique. This penetrated 40-60 umtrs. and in some areas in relation to lamellae they reached dentin. Light, polarized and scanning electron microscopy showed the presence of micropores in the external surface of enamel in PAS-positive cases. The possibility of a modified PAS technique to use in clinical practice is discussed. It is concluded that PAS relation is useful as "ex situ" test to detect the first signs of mineral salt loss at the enamel surface. More research is needed to transfer these results to clinical practice.

Bicuspid↗

PubMed1999

In situ fluoride retention in enamel and dentine after the use of an amine fluoride dentifrice and amine fluoride/sodium fluoride mouthrinse.

The aim of this in situ investigation was to study the effect of an amine fluoride/sodium fluoride mouthrinse (total F = 250 ppm) in addition to an amine fluoride dentifrice (F = 1,250 ppm) on the amount of acquired fluoride in enamel and dentine. In the partial prosthesis of 12 participants a combined specimen of slightly demineralized enamel and dentine was placed. During two consecutive experiments, each lasting 3 weeks, the participants used an amine fluoride dentifrice alone or in combination with a fluoride mouthrinse. After the in situ period the specimens were retrieved and both the enamel and the dentine specimens were analysed for the amount of KOH-soluble fluoride and structurally bound fluoride. The results showed a significant increase in both KOH-soluble and structurally bound fluoride in enamel and dentine when a fluoride mouthrinse was used. Whether the rinsing procedure was performed immediately after toothbrushing or with a delay of 2 h did not influence the results. Furthermore it was shown that dentine acquired substantially more fluoride than enamel during the experimental period. The results indicate that a fluoride mouthrinse used in addition to a fluoride dentifrice may have a beneficial effect on the protection of enamel and dentine against caries.

Adsorption↗

PubMed2006

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.

Animals↗

PubMed2003

Treatment of root caries lesions with chlorhexidine-containing varnishes and dentin sealants.

PURPOSE: To evaluate the effects of chlorhexidine-containing varnishes and dentin sealants on the progress of demineralization, cariogenic bacteria and clinical appearance of root caries lesions. METHODS: 68 lesions in 22 adult patients, with a mean age of 51.3 +/- 13.8 years were enrolled in this study. After the removal of soft, infected dentin, all lesions were randomly sealed with (1.) Cervitec, used as control (CE), (2.) EC 40 (EC), (3.) Prime and Bond NT (PB) or (4.) Seal & Protect (SP). Clinical appearance, laser fluorescence diagnosis (DIAGNOdent) and bacteriological status were recorded at intervals of 1 and 3 months. RESULTS: Regarding alteration of surface texture and color of the lesions, differences between the groups were not detected. Application of EC resulted in suppressed MS counts after 3 months (P < 0.05). Initial lower MS counts were observed in the CE group (P = 0.053). Laser fluorescence values increased in the chlorhexidine groups (CE = 27.9 +/- 17.5, EC = 28.3 +/- 26.0) but remained stable in the sealant groups (PB = 15.1 +/- 22.0, SP = 10.2 +/- 7.3), (P < 0.05).

Adult↗

PubMed1992

Solubilization of dentin matrix collagen in situ.

The effects of the oral environment on dentin matrix collagen were studied. In the partial prostheses of 12 participants, two completely demineralized dentin specimens were mounted covered by a Dacron gauze. After an experimental period of seven weeks, the specimens were transferred to a trypsin-containing buffer for determination of the amount of denatured collagen. Subsequently, the specimens were incubated with a bacterial collagenase for assessment of the amount of collagen. After the intra-oral exposure, there was a collagen loss varying between 1 and 47 wt%. This variation might be due to differences in proteolytic activity of the colonizing microflora. After exposure to the oral environment, only about 0.5 wt% of the available collagen was trypsin-degradable. This indicates a rapid solubilization of the denatured collagen from the specimens into the oral cavity. A separate group of specimens was examined by light microscopy and transmission electron microscopy. Various degrees of breakdown could be discerned. Some experimental specimens showed loss of surface integrity and tubules heavily infected with different types of micro-organisms. The lumens of the tubules were enlarged, sometimes creating caverns as a result of the loss of the intertubular collagenous matrix.

Adult↗

PubMed1993

Notes on the dissolution of human dental enamel in dilute acid solutions at high solid/solution ratio.

The aim of the present study was to elucidate the nature of the relationship between enamel apatite and lesion fluid during demineralization. Powdered enamel in samples of 1.0 g was suspended in 3 ml of 10, 30, 50, or 70 mmol/l HCl under gentle agitation for up to 24 h at 20 degrees C. After 20 min and 24 h, pH and the concentrations of calcium and phosphate were determined and the degree of saturation with respect to various calcium phosphates calculated. The experiments were replicated 15 times using the same enamel samples. Twenty minutes after the start of dissolution, both pH and concentrations of calcium and phosphate had increased, and the solution became supersaturated with respect to hydroxyapatite, and in some runs also with respect to brushite. During the subsequent 23 h and 40 min, pH continued to increase, despite the supersaturation with respect to apatite, whilst the concentrations of calcium and phosphate decreased due to formation of apatite and, occasionally, brushite mineral. The data indicated that release of carbonate from enamel and its conversion to H2CO3 caused the increase in pH and thus, played a major role in the dissolution-reprecipitation process.

Calcium↗

PubMed2003

Viscoelastic properties of demineralized dentin matrix.

OBJECTIVES: To evaluate the viscoelastic properties of demineralized dentin matrix. Stress-relaxation studies were done on matrices in tension and strain elongation or creep studies were done in both tension and compression. METHODS: Mid-coronal dentin disks were prepared from extracted unerupted human third molars. Disks were 0.5 mm thick for stress-relaxation or tensile creep experiments and 0.2-0.3 mm thick for compressive creep studies. 'I' beam specimens were prepared from dentin disks and the middle region was demineralized in 0.5 M EDTA (pH 7) for 4 days. The specimens were held in miniature friction grips in water and pulled at 100 micro m s(-1) to strains of 5, 10, 15 or 20% and then held for 10 min to follow the decay of stress over time. Creep was determined on demineralized dentin immersed in water in tension and in compression. Compressive creep was measured using an LVDT contact probe with loads of 0.02-0.5 N. Strain data were converted to compliance-time curves (strain/stress) and expressed as total compliance (J(t)), instantaneous elastic compliance (J(o)), retarded elastic compliance (J(R)) and viscous response (t/eta) or creep. RESULTS: The dentin matrix exhibits both stress-relaxation and creep behavior. Stress-relaxation and tensile creep were independent of strain but compressive creep rates were inversely related to compressive strain. Creep values were about 10% at low compressive strains, but fell progressively to 1% at high strains. Compliance-time curves fell with stress and came closer together. However, tensile creep was about 3% regardless of the strain. SIGNIFICANCE: The dentin matrix exhibits viscoelastic properties, but is not linearly viscoelastic. The relatively high creep rates of the matrix under low compressive loads may cause viscous deformations in poorly infiltrated hybrid layers in resin-bonded teeth under function.

Analysis of Variance↗

PubMed1996

Protection of bovine enamel and dentine by chlorhexidine and fluoride varnishes in a bacterial demineralization model.

In an in vitro demineralization model, the protective effect of two chlorhexidine varnishes, Cervitec (1% w/w chlorhexidine diacetate and 1% w/w thymol) and EC40 (40% w/w chlorhexidine diacetate), was compared with that of Fluor Protector, a varnish containing 0.1% w/w F. The demineralization model comprised an acidogenic Streptococcus mutans suspension in agarose placed on enamel or dentine specimens. The experiments extended over three serial 22-hour demineralization periods with fresh S. mutans suspensions for each period. To determine whether the varnishes released enough demineralization-inhibiting compounds, approximately 10 microliters of the varnishes was applied adjacent to the enamel and dentine specimens just before the first application of the S. mutans suspensions and left during the serial experiments (release study). In a separate series of experiments, the effect of the pretreatment of the enamal and dentine specimens with the various varnishes was tested (pretreatment study). In the release study the protective effect for enamel decreased in the order: EC40 = Fluor Protector >> Cervitec = no treatment. For dentine this order was: EC40 >> Fluor Protector = Cervitec > no treatment. In the pretreatment study, the enamel specimens were best protected by Fluor Protector (Fluor Protector >> Cervitec = EC40 > no treatment), while the dentine specimens were best protected by the chlorhexidine treatments (Cervitec = EC40 > Fluor Protector > no treatment). A 1:1 mixture of Cervitec and Fluor Protector was as effective as the most effective component alone. It is concluded that a varnish containing both fluoride and chlorhexidine may be useful, since it could give optimal protection to both enamel and dentine.

Animals↗

PubMed2004

Tensile strength and microhardness of treated human dentin.

OBJECTIVES: To determine the ultimate tensile strength and Knoop hardness of mineralized, EDTA-treated, sodium hypochlorite (NaOCl)-treated, EDTA-treated resin-infiltrated, and NaOCl-treated resin-infiltrated dentin. METHODS: Dumbell-shaped specimens with a cross-sectional area of 0.5 mm2 were prepared from the crowns of extracted human third molars. Specimens were randomly assigned to the following experimental groups: (1) mineralized dentin; (2) 0.5 M EDTA-demineralized dentin, pH 7/5 days; (3) 5% NaOCl-deproteinized dentin/2 days; (4) EDTA-treated, Single Bond resin-infiltrated dentin; (5) NaOCl-treated, Single Bond resin-infiltrated dentin. All specimens were tested in tension in a Vitrodyne testing machine at 0.6 mm/min. Knoop microhardness was measured on the fractured edges of specimens in groups 1, 3, 4, and 5. Results were analyzed by ANOVA and SNK tests (p < 0.05). RESULTS: Both EDTA and NaOCl treatments caused significant reductions in the tensile strength and microhardness of mineralized dentin (p < 0.05) with the largest reductions observed after NaOCl treatment (p < 0.05) Resin infiltration of treated dentin resulted in moderate increase of its tensile strength and microhardness, however, the original mineralized values were not recovered (p < 0.05). SIGNIFICANCE: Whenever dentin surfaces are treated with EDTA or NaOCl prior to a clinical bonding procedure, clinicians must be aware that a weak layer may be present at the interface, which may lead to premature failures of resin/dentin bonds.

Analysis of Variance↗

PubMed1992

Reduction of intra-oral demineralization of enamel after single exposures to sodium fluoride.

Studies demonstrated the effects of single rinses with low concentrations of NaF on the intra-oral demineralization of enamel. Blocks of bovine enamel were covered with Streptococcus mutans IB1600, mounted in palatal appliances, and worn in the mouths of volunteers for specified times. Subjects rinsed with solutions of NaF, with or without sucrose. Demineralization was determined as changes in iodide penetrability (delta Ip) of the enamel, while the pH and F of the streptococcal plaque, and enamel F, were determined with ion-specific electrodes. Delta Ip was reduced by about 80% (from 14.5 +/- 2.7 to 2.8 +/- 2.3 units) when 250 micrograms F/mL was added to the sucrose rinse. Corresponding plaque pH's were 4.1 +/- 0.5 and 4.2 +/- 0.3, consistent with a lack of effect on bacterial acidogenesis. Protection against mineral loss was concentration-dependent. Administration of sucrose at different times after NaF revealed that the effect of F persisted for at least 60 min. Analyses of plaque F demonstrated an initial elevation and concentration within the cells, followed by a drop to stable, baseline values. Enamel F increased slowly to almost 500 micrograms/g enamel after 105 min. The protective effect of F appeared to be manifested in two stages, the first related to a high plaque F and the second to F that became incorporated into the enamel. Analysis of the data suggested that F was transferred from plaque to enamel during the experimental period.

Adult↗

PubMed1997

Does assessment of microbial composition of plaque/saliva allow for diagnosis of disease activity of individuals?

Microbiological tests are limited in their applicability in the assessment of caries activity and in caries prediction. They can be effective in group of persons with high or low caries experience. The reasons for the limitation of microbiological tests rests with unique characteristics of the microflora and local environments of the oral cavity, which will modify the cariogenicity of plaque in an individual. Thus, high numbers of S. mutans may be associated with the development of a lesion at a site, while a second susceptible site with high levels of this organism in the same subject will remain caries free. This paper identifies some aspects of oral bacteria which can contribute to the unique nature of the microflora associated with plaque in an individual. Firstly, the range of bacteria potentially involved in caries has widened and now includes, for example, 'low pH' non-mutans streptococci. The presence of such organisms in plaque in an individual may influence early enamel demineralization. Most significantly, Streptococcus mutans, Streptococcus mitis and Actinomyces naeslundii have been shown to be comprise many distinct clones, with different distribution among subjects. Little is known of the impact of clonal diversity on caries activity but in some bacterial diseases particular clones are associated with virulence. Therefore, possession of a particular clone or clones by an individual could be related to caries activity. Also, the extent of clonal diversity may reflect the nature of the oral environment. Recent studies suggest that cells are released from biofilms, during adherence and growth, i.e. the early phases of development. Thus, determination of the numbers of a given species in non-stimulated saliva may indicate whether it is actively growing in plaque. Microbiological tests on the oral flora should perhaps be used to monitor the status of the oral cavity, after establishing a norm for the individual patient. Research on species and clonal diversity of oral bacteria among human populations; diversity and its role in the caries process; and the liberation of biofilm cells could provide data to allow better appreciation and evaluation of the results of microbiological testing.

Actinomyces↗

PubMed1996

Demineralization of dentine grooves in vitro.

Caries mainly occurs at retention sites for plaque such as pits, fissures, margins of restorations and interproximal sites. An in vitro model was developed to investigate dentine caries in narrow gaps. Forty bovine coronal dentine discs were covered with bonding agent. In 20 discs, two grooves, 200 and 340 mu m wide and 500 mu m deep, were sawn to mimic fissures. In the 20 other discs, a 1-mm-wide groove was made and, after polyester sheets were placed against both walls, filled with composite. After curing of the composite and removal of the sheets, grooves of 22 mu m remained at the borders of the restoration. All grooves were exposed to 8% methylcellulose gel 0.1 M lactic acid at pH 4.8 for 1 week. Demineralization was determined by microradiography of sections sawn out of the center of the discs. The walls of the grooves showed subsurface lesions, which decreased in size towards the base of the grooves. The average mineral losses (vol % x mu m) at the entrance of the 22-, 200- and 340-mu m-wide grooves were 1,112 (SD 370), 1,277 (293) and 1,277 (255), halfway down the groove 218 (150), 659 (244) and 797 (207) and at the base of the groove 140 (88), 285 (145) and 504 (205), respectively. Analysis of variance and Tukey's B test showed that the average mineral losses from grooves of different width and from sites at different depth were all significantly different at p<0.05 level, but not for the mineral losses from the entrance of the two wider grooves and from the two lower sites in the narrowest groove. The reduced mineral loss in the two narrower groove widths is assumed to be caused by the more limited inward diffusion of acids and outward diffusion of mineral ions through the methylcellulose gel.

Analysis of Variance↗