Enamel caries formation and lesion progression with a fluoride dentifrice and a calcium-phosphate containing fluoride dentifrice: a polarized light microscopic study

The effects of a fluoride dentifrice (Colgate Total) and a calcium-phosphate containing fluoride dentifrice (Enamelon) on caries-like enamel lesion formation and progression were evaluated in vitro. One quarter from each tooth (n = 12) was assigned to one of the study groups: 1) control group [artificial saliva only]; 2) Colgate Total; and 3) Enamelon. The dentifrices were applied to the enamel windows (3 minutes, 3 time per day for 14 days). Following treatment, enamel lesions were created with an acidified gel. After lesion initiation, sections were obtained for polarized light microscopy. To evaluate lesion progression, enamel windows with caries-like lesions in each test group were treated again for 14 days, returned to acidified gels for lesion progression, and then sections were obtained for polarized light microscopy. Mean lesion depths (polarized light, water imbibition) were as follows: 1) Lesion Initiation: Control 109 +/- 19 microns, Colgate Total 76 +/- 14 microns, Enamelon 63 +/- 17 microns; 2) First Lesion Progression: Control 164; +/- 24 microns, Colgate Total 124 +/- 22 microns, Enamelon 110 +/- 19 microns; 3) Second Lesion Progression: Control 235 +/- 23 microns; Colgate Total 172 +/- 27 microns, Enamelon 153 +/- 18 microns. Both Colgate Total and Enamelon enhanced the resistance of sound enamel and caries-like enamel lesions to a continuous in vitro cariogenic challenge when compared with matched controls (P < .05, ANOVA, DMR). Enamelon provided a further reduction in lesion depth for all periods when compared with Colgate Total (P > .05, ANOVA, DMR). Addition of bioavailable calcium and phosphate ions to a fluoride dentifrice may improve the ability of enamel to resist caries initiation and subsequent lesion progression.     

In vitro enamel caries formation: argon laser, light-emitting diode and APF treatment effect

PURPOSE: To evaluate argon laser irradiation (AL), light-emitting diode exposure (LED), and acidulated phosphate fluoride treatment (APF) in vitro effects on caries-like enamel caries formation. METHODS: Sound teeth (n = 18) were divided into four tooth quarters and coated with an acid-resistant varnish, leaving an enamel window exposed per tooth quarter. The tooth quarters were assigned to: (1) no treatment (control, mesiobuccal); (2) 1.23% APF (4 minutes, distolingual); (3) LED (Ultradent Ultra-Lume LED2 20 seconds, mesiolingual); and (4) AL (HGM Model 8, 11.5 J/cm2, 231 mW, 5mm beam size, 10 seconds, distobuccal). Following caries-like lesion formation (modified ten Cate solution), longitudinal sections (three per tooth quarter, 54 lesions per group) were obtained and evaluated for mean lesion depths (water imbibition, polarized light microscopy, ANOVA, DMR). RESULTS: Mean lesion depths were: 198 +/- 21 microm for controls; 186 +/- 17 microm for LED; 117 +/- 19 microm for AL; and 104 +/- 23 microm for APF. Lesion depths were statistically significantly decreased for AL (41%) and APF (47%) groups (P < 0.05), compared with controls. A slight lesion depth reduction for LED (6%) was present compared with controls; however this was not statistically significantly different (P > 0.05).     

Microleakage and bond strength of sealant to primary enamel comparing air abrasion and acid etch techniques

PURPOSE: The objective of this study was to compare the effect of air abrasion (KCP 2000), acid etching (37% phosphoric acid), and the combination of both procedures on the shear bond strength and microleakage of a light-cured pit-and-fissure sealant to the enamel of human primary molar teeth. METHODS: Noncarious extracted human primary molars were randomly divided into 4 groups in preparation for enamel bonding. The enamel surface was treated as follows for each group: (1) group 1 (control group); (2) group 2 (acid etch group); (3) group 3 (KCP [Kinetic Cavity Preparation System] group); and (4) group 4 (KCP and acid etch group). Delton, a light-cured pit-and-fissure sealant, was then applied to the occlusal surface after conditioning. The bonded specimens were maintained in distilled water at 37 degrees C+/-2 degrees C for 7 days, after which they were subjected to thermocycling followed by shear bond testing. Microleakage was determined by immersing the prepared teeth in 50% silver nitrate dye followed by sectioning and calculation of dye penetration. RESULTS: The mean shear bond strength of the KCP+acid etch group exhibited nearly 50% higher bond strength than the acid etch group (P<.01). In addition, specimens bonded to enamel conditioned only with acid etch exhibited bond strengths that were nearly twice that of those conditioned with the KCP system alone. No significant difference was noted between the air abrasion and control groups. CONCLUSIONS: In primary teeth, air abrasion combined with acid etching appears to provide the best conditions for enamel treatment prior to sealant placement.     

The effect of tooth preparation on microleakage behavior

Many factors contribute to the microleakage of a restoration. One of the more important is the method of cavity preparation. This study compared the microleakage behavior of composite restorations placed in cavities prepared by different techniques. It also compared and correlated the microleakage data produced by an electrochemical vs a staining technique. Class V cavities were prepared in 48 premolars by four techniques: (1) tungsten carbide bur in a high-speed handpiece followed by acid etching; (2) air abrasion (27 microns Al2O3) followed by acid etching; (3) air abrasion (50 microns Al2O3) and (4) air abrasion (27 microns Al2O3), with n = 12 in each group. All teeth were restored with Prime and Bond 2.1 and Tetric Flow, then thermocycled between 5 degrees and 55 degrees C for 5000 cycles with a one minute dwell at each temperature. After thermocycling, a PVC-covered Cu wire was inserted apically into the pulp chamber of each tooth and sealed into position. Leakage was continuously followed by a conductimetric method for 75 days. The teeth then were immersed in 50% AgNO3 for two hours, rinsed in distilled water for 60 seconds, then placed in a rapid photographic developer solution for two hours, followed by rinsing and sectioning for microscopic examination. Electrochemical data were examined by ANOVA and Newman-Keuls multiple comparison tests, while Kruskal-Wallis and Rank Sum Difference tests were used on the staining evaluations. Spearman's rho test was used to correlate the two test techniques. Electrochemical data for cavities prepared with a bur or air abrasion followed by acid etching prior to restoration showed significantly less (p < or = 0.05) microleakage (mean leakage currents of 1.89 & 1.57 microA, respectively) than teeth prepared with air abrasion alone (mean leakage currents of 3.60 & 3.40 microA, respectively). Rank sum AgNO3 staining data (196 & 242 vs 371 & 368) supported these findings. The correlation between the electrochemical and staining data was significant (p < or = 0.05) for all four groups of test specimens.     

Fluoride-releasing sealant and caries-like enamel lesion formation in vitro

OBJECTIVE: The aim of this laboratory study was to evaluate the effects of a fluoride-releasing pit and fissure sealant (FS) and a conventional non-fluoride-containing pit and fissure sealant (CS) on caries-like lesion formation in enamel. DESIGN: Twelve extracted, macroscopically caries-free human molar teeth underwent fluoride-free prophylaxis and were sectioned into toothquarters. Cavity preparations were placed in buccal and lingual surfaces of the toothquarters, acid-etched and filled with sealant material (per the manufacturer's instructions) as follows: 1) mesiobuccal and mesiolingual quarters--FS (Fissurit-F, VocoChemie); and 2) distobuccal and distolingual quarters--CS (Fissurit, VocoChemie). Prior to caries formation in an acidified gel, the toothquarters were thermocycled (500 cycles) in artificial saliva. Sections were taken following caries initiation (6 week gel exposure) and caries progression (9 week gel exposure), and examined by polarized light microscopy to determine mean primary surface lesion depth and presence or absence of wall lesions. RESULTS: Mean surface lesion depths were significantly different between FS and CS groups following caries initiation (FS = 119 microns; CS = 157 microns, p < 0.05, paired t-test) and progression (FS = 169 microns; CS = 221 microns, p < 0.05, paired t-test). Wall lesions were reduced in FS (14% initiation; 25% progression) when compared with CS (19% initiation; 35% progression); however, this was not significantly different (p > 0.05, paired t-test). CONCLUSION: A pit and fissure sealant containing releasable fluoride provided a caries inhibiting effect with a significant reduction in lesion depth in the surface enamel adjacent to the fluoride-releasing sealant and a tendency toward reduction in the frequency of wall lesions. CLINICAL SIGNIFICANCE: Fluoride release by pit and fissure sealants may provide additional protection against caries formation in cuspal incline enamel and smooth surfaces adjacent to sealed pits and fissures, and act as a fluoride reservoir with long-term release of fluoride into the immediately adjacent oral environment.     

Argon laser curing of fluoride-releasing pit and fissure sealant: in vitro caries development

The purpose of this study was to compare the effect of argon laser polymerization of a visible-light-cured, fluoride-releasing pit and fissure sealant on caries development in vitro. A total of twelve caries-free premolar and molar teeth was selected, and underwent a fluoride-free prophylaxis and soft tissue debridement. Cavity preparations were placed in buccal and lingual surfaces. Lingual cavity preparations were filled with the fluoride-releasing sealant (UltraSealXTplus, Ultradent) and visible light cured per the manufacturer's recommendation. Buccal preparations were filled with the fluoride-releasing sealant and argon laser cured (231 mW, 12 J/cm2 for 10 seconds). Following sealant placement, the teeth were sectioned into buccal and lingual halves. An acid-resistant varnish was placed leaving a 1 mm rim of exposed surface enamel adjacent to the sealant. The specimens were then thermocycled in synthetic saliva (500 cycles, 5 to 50 degrees C). In vitro caries lesions were formed (2.2 mM Ca, 2.2 mM PO4, 50 mM acetic acid, 5 ppm fluoride, pH 3.95). Longitudinal sections (five sections per tooth half) were obtained and evaluated by polarized light microscopy for mean outer surface lesion depths and frequency of wall lesions. Mean primary surface (outer) lesion depth was significantly decreased (ANOVA, DMR, P < .05) for the fluoride-releasing sealant with argon laser polymerization (152 +/- 16 um) when compared with visible light curing (211 +/- 23 um). Likewise, wall lesion frequency was substantially reduced for the argon laser polymerized sealants (17 percent) when compared with that for the visible light polymerized sealants (24 percent, ANOVA, DMR, P < .05). Argon laser polymerization of a fluoride-releasing pit and fissure sealant improved caries resistance markedly in the surface enamel adjacent to the sealant material. Argon laser curing enhanced the caries protective ability of the sealant along the enamel-resin cavosurface, as noted by a decrease in wall lesion frequency. Argon laser polymerization provides further caries protection against a cariogenic challenge over that afforded by fluoride-releasing sealants. Caries development around a sealant material may be hampered by the combination of fluoride release from the sealant and argon laser polymerization.     

In vitro caries formation in primary tooth enamel: role of argon laser irradiation and remineralizing solution treatment

BACKGROUND: The authors evaluated the effects of argon laser (AL) diation and remineralizing solution (RS) treatment alone and in combination on carieslike lesion formation in primary tooth enamel in an in vitro study. MATERIALS AND METHODS: The authors divided 10 caries free primary tooth enamel surfaces into four segments and assigned them to one of four treatment groups: no treatment control, AL irradiation alone at 13.5 joules per square centimeters (0.270 watts, 5-millimeter beam, 10 seconds), RS treatment alone for two minutes and AL irradiation before RS treatment. The authors created in vitro caries using a modified ten Cate solution. They evaluated longitudinal sections (three per tooth segment, 30 per treatment group) for mean lesion depth. RESULTS: After lesion formation, mean lesion depths (+/- standard deviation) were 179 +/- 16 micrometers for the no treatment controls, 137 +/- 19 microm for AL irradiation alone, 87 +/- 9 microm for RS treatment alone and 68 +/- 12 microm for AL irradiation before RS treatment. All treatment groups had mean lesion depths that were significantly less than those for the matched no-treatment control group (analysis of variance [ANOVA], Duncan multiple range [DMR] test, P < .05). AL irradiation before RS treatment significantly reduced lesion depth compared with AL irradiation alone or RS treatment alone (ANOVA, DMR test, P < .05). CONCLUSIONS: The maximum reduction in lesion depth in primary tooth enamel was achieved when the RS--which contained calcium, phosphate and fluoride in a carbopol base--was combined with AL irradiation. CLINICAL IMPLICATIONS: It would appear that to improve clinical caries resistance to enamel dissolution, AL irradiation before RS treatment could be used.     

An in vitro evaluation of selective demineralised enamel removal using bio-active glass air abrasion

Unnecessary over-preparation of carious enamel often occurs clinically during operative caries management. The working hypothesis to be investigated in this study is the potential for bio-active glass air abrasion to remove selectively only demineralised enamel in artificial enamel lesions when compared to equivalent alumina air abrasion, so potentially minimising cavity over-preparation. Bisected artificial, paired smooth surface enamel lesions on ethics-approved, extracted sound human molars were created and subsequently air abraded with 27 μm alumina (n = 19) and bio-active glass (n = 19). The difference between pre-operative lesion boundary and post-operative cavity margin was calculated following optical confocal fluorescent assessment of the lesion boundary. Data indicated mean% over-preparation (sound enamel removal) of 176% with alumina and 15.2% for bio-active glass (p = 0.005). Bio-active glass abrasion removed completely the demineralised enamel from artificial lesions with clinically insignificant over-preparation of sound tissue, indicating technique selectivity towards grossly demineralised enamel. Alumina air abrasion resulted in substantial enamel removal in both sound and demineralised tissues indicating the operator selectivity required to use the techniques effectively in clinical practice.     

Lesions in vitro associated with a Fl-containing amalgam and a stannous fluoride solution

Secondary caries is one of the most important factors leading to replacement of amalgam restorations. This investigation compared the anticariogenic effect of a fluoride-containing amalgam, a stannous fluoride application in the cavity prior to restoration with conventional amalgam, and the combination of the fluoride treatment with the well-recognized technique of cavity varnishing. Class 5 cavities were prepared in the middle third of both buccal and lingual surfaces of 20 extracted premolars. Conventional amalgam was inserted in 10 cavities (control group). Fluoride-containing amalgam was inserted in 10 cavities (second group). The third group received a treatment of 8% SnF2 and the fourth group received the SnF2 and a cavity varnish application before insertion of the conventional amalgam. After 15 weeks in an acid-gel for caries-like lesion formation, the teeth were sectioned longitudinally and examined with polarized light. The results showed that both fluoride-containing amalgam and conventional amalgam with prior treatment of the cavity with the stannous fluoride solution and varnish had an inhibitory effect on the development of artificial cavity wall caries in vitro.     

Influence of posteruptive age of enamel on its susceptibility to artificial caries

Epidemiologic studies and caries experiments with animals have suggested that caries susceptibility of teeth decreases with age. Observations on the changes in the dental tissues and their environment with age have pointed out that a process commonly referred to as 'posteruptive maturation' of the dental enamel may be responsible. To test this assumption 10 unerupted third molars and 56 erupted human premolar teeth of various posteruptive ages were subjected for 130 days to an acid gel for caries-like lesion formation in vitro. Sections of the teeth were examined with polarized light and 'contour maps' were drawn with the approximate porosity of the lesions. The results were: unerupted = 833 microns (+/- 261); erupted of posteruptive age 0-3 years = 561 microns (+/- 150), 4-10 years = 470 microns (+/- 136), 11-30 years = 459 microns (+/- 192) and over 30 years = 297 microns (+/- 89). These findings show a decrease in the susceptibility of enamel to artificial caries with increasing age, which was especially marked at and shortly after eruption. This may be explained by a completion of mineralization of the outer enamel at about eruption, by a maturation process of the outer enamel posteruptively and by a reduction in the permeability of enamel occurring through to old age. The fluoride content of the mid-coronal buccal surface enamel under study was found to decrease posteruptively with age, therefore not accounting for the decreasing caries susceptibility.     

Does bonding to dentin reduce microleakage of composite restorations?

This study evaluated the effect of adhesive application only to enamel on the marginal microleakage of composite resin restorations performed with different adhesive systems. Standardized cylinder-shaped cavities were prepared on the buccal surface of eighty bovine incisors. Two etch-and-rinse (Adper Scotchbond Multi-purpose [3M ESPE, St. Paul, MN USA] and Adper Single Bond 2 [3M ESPE]) and two self-etching (Clearfil SE Bond [Kuraray, Osaka, Japan] and Adper Prompt [3M ESPE]) adhesive systems were evaluated. The adhesives were applied only to enamel or to both dentin and enamel. After adhesive light-activation, the cavities were restored with composite resin. The samples were coated with two layers of nail polish, except an area of 1-mm wide around of the restoration, and immersed in a methylene blue solution. Afterwards, the specimens were ground in order to obtain powder which was immersed in absolute alcohol. The solutions were centrifuged and the supernatant was analyzed using an absorbance spectrophotometer. Linear regression was used to estimate the dye concentration. Data were analyzed using ANOVA and Tukey's tests (alpha = 0.05). The etch-and-rinse adhesives showed lower microleakage means compared to those of the self-etching adhesives. Adper Prompt presented higher microleakage means. There was no difference between the modes of application of the adhesive on the cavity for all adhesive systems, except for Clearfil SE Bond. This showed lower microleakage when applied to the whole cavity. Bonding to dentin may not reduce microleakage of composite restorations.     

Demineralization of Er:YAG and Er,Cr:YSGG laser-prepared enamel cavities in vitro

The aim of the present study was to establish whether cavity preparation by means of an erbium laser with efficient water cooling is capable of reducing the susceptibility of the prepared dental enamel to demineralization and thus of achieving a potential caries-protective effect in the region of cavity margins. To this end, cavities limited to the enamel were prepared in the crowns of 10 teeth each using an Er:YAG (lambda = 2,940 nm) and an Er,Cr:YSGG laser (lambda = 2,780 nm). A control cavity prepared conventionally with a diamond drill in the same occlusal zone was assigned to each of these cavities. The specimens were then subjected to a pH-cycling caries model. Analysis was performed by quantitatively measuring the demineralization front under a polarized-light microscope. The results of the study showed that enamel cavities prepared with the erbium lasers used display a statistically significant acceleration of demineralization compared to conventionally prepared cavities (p < 0.01). The Er:YAG laser cavities revealed demineralization to a depth of 133.9 (SD 25.7) microm, while the value observed with the Er,Cr:YSGG laser was 133.8 (SD 25.8) microm. The depth of demineralization in the control groups was only 77.4 (SD 13.8) microm and 79.3 (SD 37.6) microm. No difference could be found between the two lasers (p = 0.98). Based on these in vitro tests, it cannot be assumed that use of the erbium laser for cavity preparation offers any advantages in terms of resistance to secondary caries in clinical practice.     

Occlusal caries formation in vitro: comparison of resin-modified glass ionomer with fluoride-releasing sealant

The purpose of this laboratory study was to evaluate caries-like lesion formation in occlusal enamel adjacent to a light-cured resin-modified glass ionomer utilized as a pit and fissure sealant and a conventional light-cured, fluoride-releasing sealant. Fluoride-free prophylaxis was done on occlusal surfaces of 12 caries-free mandibular molar teeth that had not been exposed to the oral cavity. Occlusal surface morphology was examined by SEM on the uncoated specimens. Each tooth was then sectioned into 2 portions buccolingually, producing mesial and distal tooth halve. Occlusal surfaces of mesial tooth halves were prepared for an experimental light-cured resin-modified glass ionomer (RMG) sealant (PH-SE II, ESPE), and for comparison, a light-cured fluoride-releasing pit and fissure (PFS) sealant (Helioseal F, Ivoclar) was placed on occlusal surfaces of the corresponding distal tooth halves. The sealed occlusal surfaces were examined uncoated by SEM to compare RMG and PFS adaptation. After thermocycling in artificial saliva, caries-like lesions were formed in the occlusal surfaces adjacent to RMG and PFS. Longitudinal sections were taken for comparison of lesion formation adjacent to RMG and PFS. Mean lesion depths in occlusal surfaces were 64 +/- 17 mm for RMG, and 116 +/- 27 mm for PFS (p < 0.05, paired t-test). Occlusal lesions terminated at the point where bonding occurred between the occlusal enamel and RMG or PFS. SEM surface topography demonstrated adequate adaptation of the materials with obliteration of the typical pit and fissure surface morphology by both RMG and PFS. While both the resin-modified glass ionomer and fluoride-releasing sealant materials protected the pit and fissure enamel from caries development, the resin-modified glass ionomer reduced the extent of caries involvement in the adjacent unsealed occlusal incline enamel, when compared with the resin sealant.     

In vivo vs in vitro anticariogenic behavior of glass-ionomer and resin composite restorative materials.

OBJECTIVE: To evaluate the in vivo vs the in vitro anticariogenic potential of glass-ionomer and resin composite restoratives, utilizing a standardized interfacial gap model. METHODS: (a) In vitro study. Box shaped cavities were prepared at the buccal surfaces of extracted premolars limited to enamel. The incisal cavity walls received no treatment and were covered with 40 microm-thick metal spacers. The cavities were restored with a glass-ionomer (Ketac-Fil, n=8) and a fluoride-free resin composite (Scotchbond MP Plus/Z100, n=8). After 4 weeks immersion in an acidic gel (pH 4), thin sections were produced and examined under polarized-light microscopy.(b) In vivo study. Four low caries activity volunteers, with first four premolars, each planned to be extracted for orthodontic reasons, participated in the study. Cavities were prepared as before and filled contralaterally per patient with glass-ionomer (n=8) and resin composite (n=8). After 6 months in vivo, the teeth were extracted, sectioned and investigated by polarized-light microscopy, Raman microspectroscopy and SEM-EDS X-ray microanalysis. Unpaired t-test (lesion dimensions) and one-way ANOVA and Newman-Keuls tests (Ca, P wt%, Ca/P ratios) were used to identify statistically significant differences in lesion analysis (alpha=0.05). RESULTS: (a) In vitro study. All restorations developed lesions at incisal and cervical margins. At gap-free regions glass-ionomers showed reduced lesion dimensions compared to those of composites (p<0.05). At regions with gaps, no significant differences were found in lesion depth between the restorative groups tested. Lesion length was increased in composite, and decreased in glass-ionomer, whereas lesion depth in both restorative groups was increased in comparison to gap-free regions (p<0.05).(b) In vivo study. No lesions were observed at gap-free regions. At gap regions, 75.5% of glass-ionomer and 62.5% of composite restorations developed lesions. The lesion dimensions were significantly greater in glass-ionomer (p<0.05). A reduction in PO4(3-), CO3(2-), Ca and P was found in lesions compared to intact tissues. No F was detected and no CaF2 lattice vibrations were found at the enamel margins facing the gap adjacent to glass-ionomers. SIGNIFICANCE: In the presence of a standardized interfacial gap, no preventive effect was exerted in vivo from the glass-ionomer to protect the adjacent enamel wall from secondary caries attack. The lack of any correlation between the in vivo and in vitro models tested implies that artificial caries experiments have a negligible clinical relevance in predicting the in vivo effect.     

Microleakage in conservative cavities varying the preparation method and surface treatment

Objective

To assess microleakage in conservative class V cavities prepared with aluminum-oxide air abrasion or turbine and restored with self-etching or etch-and-rinse adhesive systems.

Material and Methods

Forty premolars were randomly assigned to 4 groups (I and II: air abrasion; III and IV: turbine) and class V cavities were prepared on the buccal surfaces. Conditioning approaches were: groups I/III - 37% phosphoric acid; groups II/IV -self-priming etchant (Tyrian-SPe). Cavities were restored with One Step Plus/Filtek Z250. After finishing, specimens were thermocycled, immersed in 50% silver nitrate, and serially sectioned. Microleakage at the occlusal and cervical interfaces was measured in mm and calculated by a software. Data were subjected to ANOVA and Tukey’s test (α=0.05).

Results

Forty premolars were randomly assigned to 4 groups (I and II: air abrasion; III and IV: turbine) and class V cavities were prepared on the buccal surfaces. Conditioning approaches were: groups I/III - 37% phosphoric acid; groups II/IV -self-priming etchant (Tyrian-SPe). Cavities were restored with One Step Plus/Filtek Z250. After finishing, specimens were thermocycled, immersed in 50% silver nitrate, and serially sectioned. Microleakage at the occlusal and cervical interfaces was measured in mm and calculated by a software. Data were subjected to ANOVA and Tukey’s test (α=0.05).

Conclusion

Marginal seal of cavities prepared with aluminum-oxide air abrasion was different from that of conventionally prepared cavities, and the etch-and-rinse system promoted higher marginal seal at both enamel and dentin margins.     

Potential inhibition of demineralization in vitro by fluoride-releasing sealants

BACKGROUND: The incorporation of fluoride into sealants has been viewed as a viable way to prevent pit-and-fissure caries by potential inhibition of demineralization through the release of fluoride to enamel. The authors conducted a study to examine the effect of a recently introduced fluoride-releasing sealant (ProSeal, Reliance Orthodontic Products, Itasca, Ill.) on enamel demineralization in an in vitro artificial caries system. METHODS: The authors randomly assigned 45 extracted human third molars to three treatment groups receiving either conventional sealant without fluoride (Group 1), fluoride-releasing sealant (Group 2) or glass ionomer sealant with high fluoride release (Group 3). They placed cavity preparations on the buccal surfaces of the molars and filled them with the assigned material. They placed acid-resistant varnish on the specimens' enamel surfaces to within 1 millimeter of the sealant, leaving a 1-mm rim of sound enamel available for in vitro enamel caries formation. They thermocycled the teeth (500 cycles) in artificial saliva. They subjected the teeth to an in vitro artificial caries challenge for six weeks to produce caries-like lesions in enamel adjacent to the sealant materials. The authors took longitudinal sections from each tooth, immersed them in water and examined them via polarized light microscopy to determine wall lesion frequencies. RESULTS: The mean (+/- standard deviation) lesion depths were 232 +/- 17 micrometers for Group 1, 144 +/- 21 mum for Group 2 and 128 +/- 15 mum for Group 3. The wall lesion frequency was 12 percent for Group 1 and 7 percent for both Groups 2 and 3. There was a significant difference (P < .05) among the fluoride-releasing materials versus the nonfluoride-releasing material. This study indicates that the new fluoride-releasing sealant substantially reduces the amount of enamel demineralization adjacent to the material. CONCLUSION: ProSeal provided increased demineralization inhibition compared with a conventional sealant containing no fluoride, but less than that shown by a glass ionomer sealant. CLINICAL IMPLICATIONS: ProSeal's physical properties and cariostatic effects may allow for applications beyond traditional sealant use.     

Removal of enamel caries with an air abrasion powder

This study compared the efficiency of air abrasion on enamel caries with selective enamel powder (SEP) or with alumina powder and a negative and positive control group. Ninety-three extracted molars with non-cavitated incipient enamel lesions were selected. After embedding the roots in resin, each lesion was sectioned perpendicular to the surface and photographed. Each lesion was classified microscopically as having or not having dentin involvement. The lesions were distributed into four groups with an equal number of enamel caries with or without dentin involvement. Each group was treated differently: Group 1 had SEP abrasion, Group 2 had alumina abrasion, Group 3 had sodium bicarbonate abrasion (negative control) and Group 4 had bur treatment (positive control). The surface was rephotographed after treatment. Superimposition of the photographs identified areas of "correct-excavation," "under-excavation" and "over-excavation." There were no statistical differences between lesions treated with or without dentin involvement for Groups 2 through 4. However, in the SEP group, all measured areas were significantly influenced by dentin involvement. In pairwise comparisons, no statistical differences were found between the alumina and bur groups. The SEP group, however, showed statistically significant differences for each area compared to the alumina group in enamel caries without dentin involvement. SEP performed as well as alumina and bur in lesions with dentin involvement. SEP is different in its ablative properties toward caries with dentin involvement or no dentin involvement. In terms of dental treatment, SEP seems to have a diagnostic potential for enamel lesions before operative intervention in patients with high caries risk.     

Lasers in dentistry 3. The use of lasers for the prevention of dental caries

Studies in our laboratories have demonstrated that specifically chosen CO2 laser treatment of dental enamel can markedly inhibit subsequent caries-like progression compared to controls in a laboratory model. Optimum caries inhibition in enamel appears to be achieved by pretreatments that produce surface temperatures in the range of 800-1200 degrees C. For clinical application the surface enamel heating must not lead to consequent pulp chamber temperature rises of > 4 degrees C. To meet these conditions a pulsed laser is required with a sufficiently high absorption coefficient (wavelength = 9.3 or 9.6 microns), pulse duration of 5-100 microseconds, 10-25 pulses per spot, repetition rate of 10-30 pulses per second, and low but effective fluence (approximately 1-5 J/cm2/pulse). A human intra-oral study has confirmed inhibition of caries progression in the human mouth. The clinical potential is good for caries preventive treatments by specific carbon dioxide laser conditions.     

In vitro enamel caries formation and orthodontic bonding agents

PURPOSE: To examine, in vitro, the caries-like lesion formation in enamel adjacent to fluoride-releasing orthodontic bonding agents using polarized light microscopic techniques. METHODS: 40 human extracted permanent third molars with sound enamel smooth surfaces were divided into two treatment groups: Light Bond group, a fluoride-releasing filled resin orthodontic bonding agent (n=20); and Pro Seal group, an orthodontic bonding agent with glass-ionomer (n=20). Prior to bonding agent placement on the buccal surfaces, acid-resistant varnish was applied to the molar teeth leaving a 2 mm (occlusal-cervical direction) by 5 mm (mesial-distal direction) exposed sound enamel window on the buccal surfaces of each molar tooth. The exposed window had the assigned orthodontic bonding agent applied, according to the manufacturer's instructions. With each specimen, a 1 mm (occlusal-cervical direction) by 5 mm (mesiodistal direction) sound enamel window was exposed by selectively removing the acid-resistant varnish on the opposing lingual or palatal surface with each molar tooth, and serving as a matched internal control with each molar. The molar teeth were then sectioned into buccal and lingual/palatal tooth halves. Acid-resistant varnish was applied to the cut surfaces. Each group underwent synthetic saliva rinsing for 2 weeks prior to in vitro caries formation using a modified ten Cate solution over a 2-week lesion initiation period. Longitudinal sections (three per treatment and control groups) were taken for polarized light study. The remaining tooth portions were exposed to synthetic saliva rinsing for 1 week and then exposed to the in vitro caries solution for an additional 1-week period to allow for lesion progression within the exposed enamel windows (progression 1 period). Longitudinal sections (three per treatment and control groups) were taken at the end of lesion progression 1 for polarized light study. After lesion progression 1, the remaining tooth portions were exposed to synthetic saliva rinsing for 1 week and then exposed to the in vitro caries solution for 1 week to allow for additional lesion progression within the exposed enamel windows (progression 2 period). Longitudinal sections (three per treatment and control groups) were taken at the end of lesion progression 2 for polarized light study. All longitudinal sections from the treatment and control groups at all three time periods (lesion initiation, progression 1 and progression 2) were imbibed with water and examined with polarized light microscopy to determine lesion depths and evaluate the enamel-resin interface. Mean (SD) lesion depths were determined and compared (ANOVA, t-test). RESULTS: Following lesion initiation, lesion progression 1 and lesion progression 2 periods, both treatment groups exhibited significant reductions in mean lesion depth when compared with the matched no treatment control group (P< 0.05). The Pro Seal group exhibited statistically significant reductions in mean lesion depths when compared with those for the Light Bond group at lesion initiation, lesion progression 1 and lesion progression 2 periods (P< 0.05, ANOVA, t-test). Both orthodontic bonding agents showed intact and intimate enamel-bonding agent interfaces with no lesion formation within the underlying bonded enamel. Caries-like lesions were only present in the exposed enamel windows adjacent to the orthodontic bonding agents.     

Inhibition of demineralization in vitro around fluoride releasing materials

Replacement of restorations because of secondary caries is a continuing problem in restorative dentistry. This investigation assessed the capacity of fluoride-releasing restorative materials to resist caries in vitro when used in roots. Class 5 cavities were prepared in buccal and lingual surfaces of 30 extracted premolars and restored with one of three polyacid modified resin composites (F-2000, Hytac and Compoglass F), a resin modified glass-ionomer cement (Fuji II LC) a conventional glass ionomer (Ketac-Fil), and a resin composite (Z-100). After 5 weeks in an acid gel for caries-like lesion formation, the teeth were sectioned longitudinally and examined with polarized light. The results showed that restoration of caries with polyacid modified resin composites and resin modified glass ionomer cements may be of great importance in the prevention of secondary caries around the restorations in roots. Clinical Relevance Light cured fluoride-releasing restorations may inhibit caries-like lesions. Inhibition of demineralization in vitro around fluoride releasing materials.