Mean Lesion Depth Research Articles

Performance of a Novel Dual-Electrode Bipolar Radiofrequency Ablation Device a Chronic Porcine Study

: Over recent years, a variety of energy sources, including bipolar radiofrequency, have been used to replace the traditional incisions of the Cox-Maze procedure for the surgical treatment of atrial fibrillation (AF). The purpose of this study was to evaluate the safety and efficacy of a novel dual-electrode bipolar radiofrequency ablation device Synergy (Atricure, Inc., Cincinnati, OH USA) for AF in a chronic porcine model. : Six domestic pigs underwent a modified Cox-Maze IV procedure without cardiopulmonary bypass using the Synergy device. Animals survived for 30 days. Each pig then underwent induction of AF and was killed to remove the heart en bloc for histologic assessment. Each ablation line was dissected perpendicularly at 5-mm intervals to assess the lesion width, depth, and transmurality. : All animals survived the operation. Electrical isolation of the left atrial appendage and the pulmonary veins were documented by pacing acutely and at 30 days after the operation in all six animals. All animals failed to be induced in AF at 30 days. There was no gross evidence of intra-atrial thrombus formation or stricture of the pulmonary veins. All ablations (n = 209) examined were discrete, linear, and transmural, with a mean lesion width of 3.0 ± 0.7 mm and a mean lesion depth of 5.4 ± 3.3 mm. The mean ablation time was 16.3 ± 4.4 seconds, with a mean total energy delivery of 238 ± 170 J. : The Atricure Synergy was able to create reliable chronic transmural lesions of the modified Cox-Maze IV procedure on a porcine beating heart without cardiopulmonary bypass. The ablation lines were significantly wider when compared with its predecessor, the Isolator II.

A comparative evaluation of fluoridated and non-fluoridated mouthrinses using a 5-day cycling enamel erosion model

Objectives To assess the relative protective effect of commercial mouthrinses containing 0-450ppm fluoride on erosion progression in enamel using a simulated 5-day in vitro cycling model with concurrent monitoring of surface microhardness (SMH) and bulk tissue loss. Methods Specimens were randomly assigned to six treatment groups (n=6). The model mimicked morning and evening use with rinse times (30 or 60s) reflecting those prescribed on pack, interspersed with three cycles of demineralisation/remineralisation per simulated day. The latter comprised 1.0% citric acid monohydrate pH3.2 for 300s, with subsequent remineralisation in mucin-free artificial saliva pH7.0 for 120min. SMH was determined by Vickers microindentation and bulk tissue loss using white-light interferometry. Results From the end of day 1, fluoride-containing mouthrinses conferred statistically significant reductions in bulk tissue loss versus fluoride-free rinses (p<0.05), with lesion depth inversely proportional to fluoride concentration. From day 3, the mean lesion depth of specimens treated with the 450 ppm rinse were statistically significantly lower than all comparator treatment groups (p<0.05). Two distinct trends were apparent when comparing SMH changes in groups treated with fluoride-free versus fluoride-containing mouthrinses. In the latter, SMH levelled out over the final three simulated days in contrast to the former whose SMH continued to fall; differences were statistically significant at day 5 (p< 0.05). Conclusions Bulk tissue loss is inversely proportional to fluoride concentration in this cycling model. The plateau in SMH reflects stabilisation of mineral density as the study progresses and the number of fluoride binding sites and consequently uptake increases, in turn leading to enhanced lesion remineralisation.

Effect of Glass-ionomer Cement on the Progression of Proximal Caries

Although effective preventive strategies exist for pit and fissure caries, prevention of proximal caries remains a significant challenge. This split-mouth study was designed to investigate the effect of glass-ionomer cement (GIC) on the progression of initial proximal caries in posterior teeth, testing the hypothesis that local application of fluoride-releasing GIC would reduce this progression. GIC was applied to 41 pairs of posterior teeth after elastic band separation in 7- to 19-year-old individuals. Follow-up bitewing radiographs were taken at 6 and 12 months. Differences in Δ mean lesion depth at 6 and 12 months between test and control groups were significant (p < 0.05, p < 0.000). Lesions treated with GIC were more likely to remain in or regress to the outer half of enamel (OR = 6.3; 95%CI, 1.3-30.9). GIC provides an effective approach to the clinical management of incipient proximal caries.

Efficacy of a novel bipolar radiofrequency ablation device on the beating heart for atrial fibrillation ablation: A long-term porcine study

Over recent years, a variety of energy sources have been used to replace the traditional incisions of the Cox maze procedure for the surgical treatment of atrial fibrillation. This study evaluated the safety and efficacy of a new bipolar radiofrequency ablation device for atrial ablation in a long-term porcine model. Six pigs underwent a Cox maze IV procedure on a beating heart off cardiopulmonary bypass using the AtriCure Isolator II bipolar ablation device (AtriCure, Inc, Cincinnati, Ohio). In addition, 6 pigs underwent median sternotomy and pericardiotomy alone to serve as a control group. All animals were allowed to survive for 30 days. Each pig underwent induction of atrial fibrillation and was then humanely killed to remove the heart en bloc for histologic assessment. Magnetic resonance imaging scans were also obtained preoperatively and postoperatively to assess atrial and ventricular function, pulmonary vein anatomy, valve function, and coronary artery patency. All animals survived the operation. Electrical isolation of the left atrial appendage and the pulmonary veins was documented by pacing acutely and at 30 days in all animals. No animal that underwent the Cox maze IV procedure was able to be induced into atrial fibrillation at 30 days postoperatively, compared with all the sham animals. All 257 ablations examined were discrete, linear, and transmural, with a mean lesion width of 2.2 +/- 1.1 mm and a mean lesion depth of 5.3 +/- 3.0 mm. The AtriCure Isolator II device was able to create reliable long-term transmural lesions of the modified Cox maze procedure on a beating heart without cardiopulmonary bypass 100% of the time. There were no discernible effects on ventricular or valvular function.

Comparing two quantitative methods for studying remineralization of artificial caries

Objectives To compare the detection of changes before and after remineralization of artificial enamel and dentin caries by microCT scanning, polarized light microscopy (PLM) and transverse microradiography (TMR). Methods Fourteen extracted premolars were cut into tooth blocks and painted with an acid-resistant varnish leaving one enamel and one dentin surface exposed. The tooth blocks were immersed into demineralizing solution for 4 days to produce artificial caries-like lesions and scanned by microCT. Then the 14 tooth blocks were randomly allocated into two groups. Seven tooth blocks in Group I were cut longitudinally through the exposed surface into 100–150 μm thick sections and microradiographs were taken. The other seven tooth blocks in Group II were left intact. All the tooth blocks and sections were then immersed into remineralizing solution for 5 days. PLM and TMR of the tooth sections in Group I were taken again. Depth of the lesion on the TMR was measured. Tooth blocks in Group II were scanned by microCT. Results Mean lesion depth in Group I reduced by 13.0% and 8.2% after remineralization for enamel and dentin, respectively (paired t-test, P < 0.001). In Group II, linear attenuation coefficient (LAC) of the region of interest (ROI) increased by 11.1% and 23.8% after remineralization for enamel and dentin lesions, respectively (paired t-test, P < 0.001). Conclusion Both microCT and microradiography are able to detect a change of similar magnitude in the artificial caries lesions after remineralization. MicroCT may be used to substitute TMR and PLM in in vitro studies about caries.

In vitro evaluation of fluoride products in the development of carious lesions in deciduous teeth

The purpose of this study was to evaluate the effect of the application of fluoride products on the development of enamel caries in deciduous teeth. A total of 108 deciduous teeth were chosen for the study. Acid-resistant varnish was applied on the teeth, leaving only one area of 5 mm x 1 mm of dental enamel exposed. The teeth were allocated randomly to one of the following groups: 1) control - toothpaste without fluoride; 2) 1.23% fluoride gel; 3) Duraflur fluoride varnish; 4) Duraphat fluoride varnish; 5) Fluorniz fluoride varnish; 6) Fluorphat fluoride varnish; 7) varnish with Duofluorid; 8) 12% silver fluoride diamine (Cariestop); 9) children's fluoride toothpaste (500 ppm). The tested products were applied on the teeth according to the manufacturer's recommendations and the teeth were stored in a moist environment for 24 hours. Each group of teeth was then subjected to a pH cycling model for 14 days, after which the teeth were cut through the center for an analysis of the depth of the carious lesion by polarized light microscopy. Comparisons were made between the treatments and the control group. The mean lesion depth values were 318 microm +/- 39 (control), 213 microm +/- 27 (fluoride gel), 203 microm +/- 34 (Duraflur), 133 microm +/- 25 (Duraphat), 207 microm +/- 27 (Fluor-niz), 212 microm +/- 27 (Fluorphat), 210 +/- 28 (Duofluorid), 146 +/- 31 (Cariestop) and 228 +/- 24 (fluoride toothpaste). None of the products used here was able to completely prevent the formation of lesions. The highest cariostatic effect was achieved by fluoride varnish Duraphat and the lowest by the fluoride toothpaste.

Methods for calculating the severity of demineralization on tooth surfaces from PS-OCT scans.

Several studies have demonstrated that polarization sensitive optical coherence tomography (PS-OCT) can be used to nondestructively measure the severity of subsurface demineralization in enamel and dentin. The reflectivity in the polarization state orthogonal to the initial linear polarization incident on the tissue is low at sound tissues interfaces and high in demineralized areas that strongly scatter and depolarize the light. The purpose of this study was to develop improved algorithms for assessing the depth and severity of demineralization from PS-OCT scans for use with 2D and 3D tomographic images. Subsurface caries-like lesions of increasing depth and severity were produced in adjoining windows on ten bovine enamel samples by exposure to demineralization over periods of 1 to 4 days. Each sample also had a sound window to be used as a control. PS-OCT scans were acquired for each sample and analyzed using various methods to calculate the lesion depth and area. Algorithms were developed and used to automatically detect the lesion depth and area, and calculate the volume for improved assessment of lesion severity. Both fixed-depth and automatic edge-finding algorithms were able to detect significant differences between each of the days and sound enamel. The lesion depth and mineral loss were also measured with polarized light microscopy and transverse microradiography after sectioning the teeth. Mean lesion depths ranged from 40 to 100 μm. This demonstrates the edge-finding algorithm can be used to automatically determine the depth and severity of early lesions for the rapid analysis of PS-OCT images.

Effect of fluoride varnish on enamel demineralization around brackets: An in-vivo study

Even with advances in materials and techniques, demineralization around brackets during orthodontic treatment continues to be a problem. The purpose of this in-vivo study was to evaluate the effect of a fluoride varnish on enamel demineralization adjacent to bonded brackets. Fifteen patients who needed at least 2 premolars extracted for orthodontic reasons were selected. In each patient, 1 premolar was considered the test tooth, and the other was the control. Brackets were bonded, and T-loops were engaged on all premolars, but only the test teeth received fluoride varnish. The premolars were extracted after 85 to 95 days, and buccolingual sections 50 to 70 microm in thickness were evaluated with polarized light microscopy. The mean depth of demineralization in each lesion was measured 3 times on photographs by an operator blinded to the groups (intraclass correlation of the 3 measurements was 0.988). The mean lesion depths were 57.0 +/- 5.5 microm in the test group and 94.3 +/- 6.7 microm in the control group. There was significant reduction (approximately 40%) in depth of demineralization in the test group (P <.001). Fluoride varnish can be beneficial as a preventive adjunct in reducing demineralization adjacent to brackets.

In Vitro Protection Against Dental Erosion Afforded by Commercially Available, Calcium-Fortified 100 Percent Juices

Calcium in acidic beverages can decrease a person's risk of experiencing dental erosion. The authors compared the pHs and titratable acidities of commercially available calcium-fortified and unfortified 100 percent juices, and enamel and root surface lesion depths after they were exposed to different juices. The authors measured the pH and titratable acidity of calcium-fortified and unfortified 100 percent juices. They exposed enamel and root surfaces to different 100 percent juices for 25 hours and measured lesion depths. They used the Spearman rank correlation test and the two-sample t test to identify associations between the juices' properties and lesion depths and to compare lesion depths between fortified and unfortified juices. The authors found that fortifying apple, orange and grapefruit juices with calcium prevented enamel erosion and decreased root surface erosion (P < .01). They also found that fortifying white grape juice with calcium decreased enamel erosion (P < .001) but not root surface erosion. They observed that mean lesion depths were greater in root surfaces than in enamel surfaces after exposure to unfortified orange juice and all fortified juices (P < .001). Calcium concentrations in commercially available, calcium-fortified 100 percent juices are sufficient to decrease and prevent erosion associated with extended exposure to a beverage. People at risk of experiencing erosion could decrease their erosion risk by consuming calcium-fortified juices.

Potential inhibition of demineralization in vitro by fluoride-releasing sealants

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. 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. 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. ProSeal provided increased demineralization inhibition compared with a conventional sealant containing no fluoride, but less than that shown by a glass ionomer sealant. ProSeal's physical properties and cariostatic effects may allow for applications beyond traditional sealant use.

The Effects of Three Different Pastes on Enamel Caries Formation and Lesion Depth Progression-An In Vitro Study

ABSTRACT Prevention of initiation and interruption in progression of early lesions are the desirable modes of caries management. Fluoride dentifrices and casein phosphopeptides are known to inhibit demineralization and enhance remineralization. The present study was conducted with the objective to investigate the effects of fluoridated dentifrice, non-fluoridated dentifrice and casein phosphopeptide amorphous calcium phosphate paste on enamel caries formation and lesion depth progression.228 tooth sections derived from extracted human permanent molars.were used The study was carried out in 3 phases where in each phase the enamel sections were treated for 14 days twice a day for 3 minutes with respective agents, followed by acid demineralization using 0.05 M acetic acid resulting in lesions. The depths of the lesions were measured using stereomicroscope. The mean lesion depths of three test groups were compared with each other as well as with control group at the end of each phase. Comparison of mean lesion depths of different groups was carried out using analysis of variance (ANOVA) and student's unpaired-t-test. The fluoridated dentifrice group had significantly lesser mean lesion depth than control group in all the three phases (P&lt;0.05). In second phase, non-fluoridated dentifrice and CPP-ACP paste groups had significantly lesser mean lesion depths than control groups (P&lt;0.05). The study demonstrated that twice a day application of fluoridated dentifrice provides substantial protective effect against lesion formation and lesion depth progression. The study could not demonstrate any additional ability of CPP-ACP paste in reducing lesions depth progression and effect was similar to non-fluoridated dentifrice group.

Laser-Fluoride Effect on Root Demineralization

Although the individual cariostatic effects of laser and fluoride have been shown, the combined effect of CO(2) laser and fluoride on root demineralization remains uncertain and was the main aim of this study. By using a pH-cycling system and Polarized Light Microscopy, we demonstrated the synergistic effect of fluoride combined with CO(2) laser treatment on reducing root demineralization. The mean lesion depths (in microm) for each group were 160 +/- 14 (Control), 113 +/- 8 (Laser treatment alone), 111 +/- 6 (Fluoride treatment alone), and 25 +/- 7 (Fluoride followed by laser treatment). A significant laser-enhanced fluoride uptake, characterized by the ToF-SIMS analysis, was revealed by the 37% and 400% increments in loosely and firmly bound fluorides (both p < 0.002) in laser-irradiated areas, compared with the non-irradiated controls. In conclusion, there is a significant synergistic effect of combined CO(2) laser and fluoride treatment on the inhibition of root demineralization, possibly due to laser-enhanced fluoride uptake in the root.

Remineralization Potential of a Fluoridated Carbamide Peroxide Whitening Gel

Little knowledge exists regarding the potential remineralizing benefits of adding fluoride to carbamide peroxide-based whitening gels. The aim of this project was to evaluate whether a whitening system with fluoride will remineralize previously demineralized enamel. Twenty-four extracted teeth were sectioned into quadrants labeled A to D. Tooth quadrants in groups A, B, and D were demineralized with a lactic acid, methyl-cellulose gel system to mimic incipient carious lesions. Group C was neither demineralized nor treated. Group D was demineralized, but not treated with a whitening gel. Groups A and B were exposed to one of two commercially prepared 10% carbamide peroxide whitening gels: one that was fluoride free (group A) and one that contained fluoride (0.463%NaF) (group B). Remineralization was evaluated histologically and analyzed statistically using paired t tests accepting p < 0.05 as significant. Shade comparisons showed equal whitening efficacy of both gel A and B. Paired t tests show a significant reduction in lesion depth after treatment with the fluoride containing gel (B: mean lesion depth = 100 microm; p < 0.01), while there was no difference for the gel lacking fluoride (A: mean lesion depth = 110 microm). Under the conditions of this study, the addition of fluoride to a tooth whitening system does not affect the gel's whitening efficacy. The addition of fluoride could provide remineralization properties to the gel. As tooth whitening therapies continue to grow and evolve, a strong focus should rest on improving these materials in ways that will provide ever greater patient benefits. Coupling the esthetic benefits of whitening with the preventive benefits of fluoride is a natural step in this direction. Therapuetic quantities of fluoride can impact remineralization properties of commercially available tooth whitening gels without altering whitening properties.

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

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. 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. 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). 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. It would appear that to improve clinical caries resistance to enamel dissolution, AL irradiation before RS treatment could be used.

An in vitro microbial-based model for studying caries-preventive agents

Objective. The aim of the study was to develop an in vitro microbial-based caries model to test potentially caries-preventive agents. Material and methods. In this model, cariogenic Streptococcus mutans biofilms are grown on tooth samples within a reaction chamber hermetically surrounded by a bacteria-tight glove box allowing the manipulation of specimens during operation. The specimens were mounted in two rows on the inner and outer rims of a specimen turntable passing several inlet pipes transporting all necessary media. Using 64 lower incisors in 4 experiments, a 10 ppm NaF solution and an experimental potentially caries-preventive glycan solution were tested compared to a water control. The mean lesion depth was determined by confocal laser scanning microscopy. Results. The depths of the caries-like lesions showed no statistically significant difference irrespective of whether the specimens were mounted on the inner or outer rim of the specimen turntable. As expected, the NaF solution inhibited the development of caries-like lesions almost completely. The experimental glycan solution revealed a statistically significantly lower demineralization depth compared to the control and a significantly higher depth compared to the NaF group. The system could be operated over a period of more than 9 weeks without unintentional contamination and the manipulation of the tooth specimens could be accomplished. Conclusions. In conclusion, our in vitro system is suitable for testing potential caries-preventive agents in a reproducible way by using whole tooth samples and offers full access together with the possibility of manipulating the specimens during operation.

A Novel in vitro Microbial-Based Model for Studying Caries Formation – Development and Initial Testing

We report on the development and the initial testing of a new microbial-based caries model. Specimens were fixed on a rotating mount within a reaction chamber hermetically surrounded by a sterilised glove box. A cariogenic environment was obtained by inoculation with Streptococcus mutans (ATCC 25175) combined with a continuously repeating supply of sucrose solution, trypticase soy broth and artificial saliva applied by dripping. Twenty-five caries-free upper premolars were used. The mesial parts of the occlusal fissures had been sealed with a resin-based fissure sealant (test group 1). To produce marginal gaps, the distal parts had been moistened with saliva before resin application (test group 2). Five teeth served as control and were exposed to all fluids under sterile conditions before being removed from the system after 7 days. Test specimens were infected with S. mutans and were incubated for another 14 days. No unintentional contamination occurred during the 3-week period of operation. Demineralizations were evaluated by using confocal laser scanning microscopy. Only the test specimens showed clearly visible signs of biofilm formation and caries-like lesions. The mean primary lesion depth did not differ significantly between test groups. Wall lesion depths and surface areas of demineralizations underneath the fissure sealants were significantly higher in test group 2. Thus, our model allows the simultaneous production of primary and secondary caries-like enamel lesions in a considerable number of specimens and facilitates the possibility to manipulate and transfer them without necessarily terminating the experiment, opening new possibilities for in vitro caries research.

Gold‐Tip Electrodes—A New “Deep Lesion” Technology for Catheter Ablation? In Vitro Comparison of a Gold Alloy Versus Platinum–Iridium Tip Electrode Ablation Catheter

Gold-tip electrodes. Radiofrequency (RF) catheter ablation is widely used to induce focal myocardial necrosis using the effect of resistive heating through high-frequency current delivery. It is current standard to limit the target tissue-electrode interface temperature to a maximum of 60-70 degrees C to avoid char formation. Gold (Au) exhibits a thermal conductivity of nearly four times greater than platinum (Pt-Ir) (3.17 W/cm Kelvin vs 0.716 W/cm Kelvin), it was therefore hypothesized that RF ablation using a gold electrode would create broader and deeper lesions as a result of a better heat conduction from the tissue-electrode interface and additional cooling of the gold electrode by "heat loss" to the intracardiac blood. Both mechanisms would allow applying more RF power to the tissue before the electrode-tissue interface temperature limit is reached. To test this hypothesis, we performed in vitro isolated liver and pig heart investigations comparing lesion depths of a new Au-alloy-tip electrode to standard Pt-Ir electrode material. Mean lesion depth in liver tissue for Pt-Ir was 4.33+/-0.45 mm (n=60) whereas Au electrode was able to achieve significantly deeper lesions (5.86+/-0.37 mm [n=60; P<0.001]). The mean power delivered using Pt-Ir was 6.95+/-2.41 W whereas Au tip electrode delivered 9.64+/-3.78 W indicating a statistically significant difference (P<0.05). In vitro pig heart tissue Au ablation (n=20) increased significantly the lesion depth (Au: 4.85+/-1.01 mm, Pt-Ir: 2.96+/-0.81 mm, n=20; P<0.001). Au tip electrode again applied significantly more power (P<0.001). Gold-tip electrode catheters were able to induce deeper lesions using RF ablation in vitro as compared to Pt-Ir tip electrode material. In liver and in pig heart tissue, the increase in lesion depth was associated with a significant increase in the average power applied with the gold electrode at the same level of electrode-tissue temperature as compared to platinum material.

The efficacy of a fluoride varnish in reducing enamel demineralization adjacent to orthodontic brackets: an in vitro study

To test the hypothesis that fluoride varnish is effective in reducing demineralization (white spot) lesions adjacent to bonded orthodontic brackets. Two similar samples of extracted bovine incisors, with bonded orthodontic brackets, were separated into an experimental group (fluoride varnish was applied) and control group (no fluoride varnish) to examine the preventive effects of fluoride varnish. The dental clinic of the State University of Maringá--UEM (Maringá, Paraná, Brazil). Thirty-eight extracted bovine incisors with bonded orthodontic brackets. Fluoride varnish was applied topically to half of the sample of extracted bovine teeth. No varnish was applied to the other half. The depths of enamel demineralization (white spot) lesions were measured from polarized light microscopy images using image analysis software. The teeth in both the experimental and control groups had been exposed to a cariogenic environment twice a day for 35 days. Those teeth that had been treated with two applications of fluoride varnish (one at the outset and another 15 days later) demonstrated about 38% less mean lesion depth than teeth where no varnish had been applied. Orthodontists may wish to consider the application of fluoride varnish during fixed orthodontic therapy to help reduce the development of enamel white spot lesions.

In vitro effects of pulsed holmium laser energy on canine uroliths and porcine cadaveric urethra.

To assess the effect of holmium laser energy on canine uroliths and porcine urethra. Uroliths of known composition and fresh cadaveric urethra were exposed to holmium laser energy. Urolith fragmentation times and depth of urethral lesions were determined. Overall mean fragmentation time was 11.8 +/- 8.01 seconds. Magnesium ammonium phosphate (MAP) and urate uroliths had significantly shorter fragmentation times compared to other uroliths. Fragmentation time of MAP uroliths irradiated with 1.2 J/pulse was significantly longer than the fragmentation time of MAP uroliths irradiated with 0.3 J/pulse. Overall mean lesion depth for urethral specimens treated with 90 degrees contact mode irradiation was significantly greater than overall mean lesion depth for specimens treated with 30 degrees non-contact mode. Holmium laser energy effectively fragmented canine uroliths and caused minimal urethral damage in vitro. Dogs with urolithiasis may represent a useful animal model for developing human lithotripsy procedures.

Effect of fluoride varnish on demineralization adjacent to brackets bonded with RMGI cement

Far too often a less-than-optimal esthetic result occurs after orthodontic treatment due to demineralization of enamel adjacent to fixed orthodontic appliances in patients with inadequate oral hygiene. In vitro studies have shown that a resin-modified glass ionomer (RMGI) cement and a fluoride varnish might help clinicians combat this problem. The purpose of this study was to evaluate, in vitro, the effect of a fluoride-releasing cavity varnish on inhibition of enamel demineralization adjacent to orthodontic brackets bonded with RMGI and composite resin cements. Brackets were bonded to 48 extracted human third molars. Half were bonded with a composite resin (Transbond, 3M Unitek, Monrovia, Calif) and half with an RMGI (Fuji Ortho LC, GC America, Alsip, Ill). Each group was further divided into 2, with half receiving an application of fluoride-releasing varnish (Duraflor, Pharmascience, Montreal, Québec, Canada). The samples were cycled in an artificial caries solution for an hour twice daily for 31 days. After each caries challenge, the teeth were brushed with a soft toothbrush to simulate normal mechanical wear of the varnish. The loss of fluoride varnish was timed. Teeth were sectioned longitudinally and photographed under polarized light microscopy. Mean lesion depth was measured, and analysis of variance (ANOVA) (P ≤.0001) and the Duncan multiple range test (P ≤.05) indicated significant differences among the groups. Teeth bonded with composite resin showed a 35% reduction in mean lesion depth when fluoride varnish was applied. Teeth bonded with RMGI cement showed no significant differences in lesion depth between varnish and nonvarnish groups. Both RMGI groups had 50% smaller mean lesion depths when compared with the composite resin group without fluoride varnish. Samples bonded with RMGI cement illustrated a wedge effect, with lesion depth shallower near the bracket. A chi-square test showed that the fluoride varnish was lost significantly faster in samples bonded with Fuji Ortho LC (P =.013). Although the fluoride varnish could not prevent demineralization, it appears to be beneficial in reducing lesion formation. Clinicians should consider applying fluoride varnish on areas of enamel that exhibit demineralization or are at risk of demineralization in patients with poor oral hygiene. (Am J Orthod Dentofacial Orthop 2002;122:125-34)