Erosive loss of tooth substance is dependent on enamel surface structure and presence of pellicle - An in vitro study.

OBJECTIVE: Aim of this in vitro study was to investigate erosive tooth loss in dependence of the enamel surface structure and presence of an acquired pellicle. METHODS: Enamel specimens from 19 bovine incisors (4 specimens/incisor) were allocated to four experimental groups (n = 19). The surfaces of half of the specimens were polished (two groups), while the other half was left native (two groups). Specimens of one polished and one native group were placed in pooled human saliva (30 min) for the formation of an acquired pellicle. Thereafter, all specimens were demineralized by superfusion with hydrochloric acid (17 min, pH 2.3) with collection of the superfluent. Erosive substance loss was determined by measuring the dissolved calcium content using a colorimetric assay with Arsenazo III reagent. Differences in erosive substance loss were statistically analyzed with respect to enamel surface and pellicle. A linear mixed effects model was fitted to the data and pairwise differences between groups were evaluated (significance level α= 0.05). RESULTS: Enamel surface structure (p < 0.001) and presence of pellicle (p = 0.01) had a significant effect on erosive substance loss. Polished surfaces with pellicle showed the lowest cumulative calcium release [nmol Ca/mm2] (means ± standard deviation: 48+/-5), followed by polished specimens without (51+/-9) and native specimens with pellicle (54+/-10). No significant differences were found between these groups. Highest cumulative calcium release was found for native specimens without pellicle (61+/-9; p < 0.05). CONCLUSIONS: Both enamel surface structure and the acquired pellicle are important determinants of the susceptibility to erosive tooth loss.

Change of erosive potential of apple and orange juice at different dilutions

The aim of this in vitro study was to investigate the change of erosive properties of apple and orange juice after dilution with tap water. Apple juice, orange juice and citric acid were assessed for pH and titratable acidity at different aqueous dilutions (100% ­ pure liquid, 60% ­ 3 : 2 mixing ratio, and 40% ­ 2 : 3 mixing ratio respectively). Thus, 72 bovine enamel specimens were distributed to 9 groups (n = 8 specimens per group), followed by 25 minutes of erosion by superfusion with the described test liquids according to group allocation. Erosive substance loss (µm) was determined profilometrically. The different substance losses within a dilution series were tested using the Wilcoxon rank sum test. The significance level was set to p ≤ 0.05. Erosive substance loss [µm] for 100% concentrations (median ± interquartile range) was highest for apple juice (5.7 ± 0.8), followed by citric acid (4.6 ± 0.4) and orange juice (1.5 ± 0.5). The dilution of apple juice (60%: 4.2 ± 0.7; 40%: 3.1 ± 0.5) and citric acid (60%: 3.7 ± 0.9; 40%: 2.8 ± 0.7) with tap water lead to a significant (p < 0.05) reduction of erosive potential in comparison to 100% concentrations. This effect was not consistent for orange juice, where significantly more substance loss was found for pure juice (100%) than for 60% diluted juice (60%: 1.1 ± 0.3, p < 0.05), but no significant difference was found between 100% and 40% (40%: 0.9 ± 0.6, p > 0.05), and 60% and 40%, respectively. In conclusion, dilution of apple juice with tap water led to a significant reduction of its erosive potential. For orange juice, the effect of dilution on the erosive substance loss was only limited.

Pure hydroxyapatite as a substitute for enamel in erosion experiments.

OBJECTIVES: The study evaluated the suitability of pure crystalline hydroxyapatite (HA) as a substitute for human (H) and bovine (B) enamel in erosion experiments. METHODS: Human and bovine enamel and hydroxyapatite specimens (n = 18 each) were submitted to demineralisation by HCl at pH values of 3.0, 2.6 and 2.0 (1.0, 2.5, and 10 mmol/l concentration). Specimens were eroded in a superfusion chamber for 7 min (flow rate: 1 µl/s). Multiple fluid samples were taken per specimen throughout the exposure period. The dissolved calcium content was measured using a colorimetric assay with Arsenazo III reagent, to serve as surrogate for erosive substance loss. Additionally, erosive tissue loss was quantified by profilometry. Differences in erosive substance loss were assessed by the Kruskal-Wallis and Conover's posthoc test. RESULTS: Good agreement in erosive substance loss between HA and human specimens was found at pH 2.6, as no statistically significant difference and considerable overlap of their respective interquartile ranges was observed. At pH 2.0 and 3.0, a statistically significant difference between HA and human and bovine enamel was determined. HA consistently tended to have lower mean dissolution rates, with a maximum deviation from human enamel of -16% at pH 3. It displayed lower specimen variability with an average coefficient of variation of 17%, compared to 25% (H) and 25% (B), respectively. CONCLUSIONS: Crystalline hydroxyapatite may not be suitable for full substitution of biologic enamel in erosion experiments focusing on absolute measurement values, but is useful for establishing consistent relative trends between erosive agents due to biosimilar erosion behavior and lower experimental variability. This is especially true for preliminary studies where approval for use of biological samples is restricted. CLINICAL SIGNIFICANCE: Crystalline hydroxyapatite is a useful substitute of human or bovine enamel in experiments studying chemical aspects of dental erosion.

Comparison of Profilometric and Microindentation Analyses for Determining the Impact of Saliva on the Abrasion of Initially Eroded Enamel.

The aim of this in vitro study was to investigate the impact of saliva on the abrasion of eroded enamel using two measuring methods. A total of 80 bovine enamel specimens from 20 bovine incisors were allocated to four experimental groups (n = 20 specimens per group). After baseline surface microhardness (SMH) measurements and profilometry all specimens were subjected to erosion (2 min, 1% citric acid, pH: 3.6, 37°C). SMH was determined again, and the depths of the Knoop indentations were calculated. Thereafter, specimens were incubated in human saliva (group 1 - no incubation/control, group 2 - 0.5 h, group 3 - 1 h, group 4 - 2 h) before toothbrush abrasion was performed. After final SMH measurements and profilometry, indentations were remeasured, and surface loss was calculated. SMH did not return to baseline values regardless of the length of saliva incubation. Further, an irreversible substance loss was observed for all specimens. With the indentation method, significantly (p < 0.05) more substance loss was found for controls (least square means ± standard error of 198 ± 19 nm) than for groups 2-4 (110 ± 10, 114 ± 11, and 105 ± 14 nm). Profilometric assessment showed significantly more substance loss for controls (122 ± 8 nm) than for group 4 (106 ± 5 nm). Intraclass correlation for interrater reliability between measurement methods was low (0.21, CI: 0.1-0.3), indicating poor agreement. Exposure of eroded enamel to saliva for up to 2 h could not re-establish the original SMH. The amount of measured substance loss depended on the measurement method applied.

Assessment of peri-implant defects at titanium and zirconium dioxide implants by means of periapical radiographs and cone beam computed tomography: An in-vitro examination.

OBJECTIVE: To test the accuracy of measurement of interproximal peri-implant bone defects at titanium (Ti) and zirconium dioxide (ZrO2 ) implants by digital periapical radiography (PR) and cone beam computed tomography (CBCT). MATERIAL AND METHODS: A total of 18 models, each containing one Ti and one ZrO2 implant, were cast in dental stone. Six models each were allocated to following defect groups: A-no peri-implant defect, B-1 mm width defect, C-1.5 mm width defect. The defect width was measured with a digital sliding caliper. Subsequently, the models were scanned by means of PR and CBCT. Three examiners assessed the defect width on PR and CBCT. Wilcoxon signed-rank test and Wilcoxon rank sum test were applied to detect differences between imaging techniques and implant types. RESULTS: For PR, the deviation of the defect width measurement (mm) for groups A, B, and C amounted to 0.01 ± 0.03, -0.02 ± 0.06, and -0.00 ± 0.04 at Ti and 0.05 ± 0.02, 0.01 ± 0.03, and 0.09 ± 0.03 at ZrO2 implants. The corresponding values (mm) for CBCT reached 0.10 ± 0.11, 0.26 ± 0.05, and 0.24 ± 0.08 at Ti and 1.07 ± 0.06, 0.64 ± 0.37, and 0.54 ± 0.17 at ZrO2 implants. Except for Ti with defect A, measurements in PR were significantly more accurate in comparison to CBCT (p ≤ 0.05). Both methods generally yielded more accurate measurements for Ti than for ZrO2 . CONCLUSIONS: The assessment of interproximal peri-implant defect width at Ti and ZrO2 implants was more accurate in PR in comparison to CBCT. Measurements in CBCT always led to an overestimation of the defect width, reaching clinical relevance for ZrO2 implants.

Temperature-dependent erosivity of drinks in a model simulating oral fluid dynamics.

OBJECTIVES: Aim of this investigation was to study the temperature-dependent in vitro enamel erosion of five acidic drinks and citric acid under controlled conditions in an artificial mouth. METHODS: The erosive potential of Orange juice, Coca-Cola Zero, Sprite Zero, two fruit teas and citric acid (control) was investigated on bovine enamel specimens at temperatures between 5 °C and 55 °C. The pH values and total calcium content of all test drinks were determined. Specimens were immersed into an artificial mouth to imitate physiological oral conditions for 60 h. Cyclic de- and re-mineralization was performed, imitating the intake of six drinks in six h followed by a six-hour remineralization phase, where only artificial saliva ran over the specimens. Total erosive enamel loss was determined by contact profilometry. Differences in substance loss at different temperatures were tested for statistical significance (p-values ≤ 0.05) by means of ANOVA. RESULTS: Rising liquid temperature did not result in a considerable change of pH. Highest substance loss was observed for citric acid (33.6 ±â€¯6 µm to 38.7 ±â€¯6 µm), while only little erosion was induced by fruit tea (0.8 ±â€¯1 µm to 5.9 ±â€¯1 µm). Rising liquid temperature did not result in significantly increased substance loss for citric acid, orange juice and Coca-Cola Zero. Sprite Zero and both fruit teas, however, caused significantly (p < 0.001) more enamel loss at elevated temperature. CONCLUSIONS: Not all investigated drinks showed a temperature-induced change in erosivity. CLINICAL SIGNIFICANCE: For some erosive beverages it can be recommended to keep the consummation temperature as low as possible to decrease the risk of erosive tooth substance loss.

Location of unaccessible implant surface areas during debridement in simulated peri-implantitis therapy.

BACKGROUND: An in vitro model for peri-implantitis treatment was used to identify areas that are clinically difficult to clean by analyzing the pattern of residual stain after debridement with commonly employed instruments. METHODS: Original data from two previous publications, which simulated surgical (SA) and non-surgical (NSA) implant debridement on two different implant systems respectively, were reanalyzed regarding the localization pattern of residual stains after instrumentation. Two blinded examiners evaluated standardized photographs of 360 initially ink-stained dental implants, which were cleaned at variable defect angulations (30, 60, or 90°), using different instrument types (Gracey curette, ultrasonic scaler or air powder abrasive device) and treatment approaches (SA or NSA). Predefined implant surface areas were graded for residual stain using scores ranging from one (stain-covered) to six (clean). Score differences between respective implant areas were tested for significance by pairwise comparisons using Wilcoxon-rank-sum-tests with a significance level α = 5%. RESULTS: Best scores were found at the machined surface areas (SA: 5.58 ± 0.43, NSA: 4.76 ± 1.09), followed by the tips of the threads (SA: 4.29 ± 0.44, NSA: 4.43 ± 0.61), and areas between threads (SA: 3.79 ± 0.89, NSA: 2.42 ± 1.11). Apically facing threads were most difficult to clean (SA: 1.70 ± 0.92, NSA: 2.42 ± 1.11). Here, air powder abrasives provided the best results. CONCLUSION: Machined surfaces at the implant shoulder were well accessible and showed least amounts of residual stain. Apically facing thread surfaces constituted the area with most residual stain regardless of treatment approach.

Cleaning Efficacy of Manual Toothbrushes Around Brackets - A Pilot Randomised Control Trial.

PURPOSE: To test the cleaning efficacy of different manual toothbrushes in orthodontic patients in a single-blind randomised clinical trial. The brushes tested were selected based on previous in vitro tests. MATERIALS AND METHODS: Thirty-five regular orthodontic patients with a minimum of six bonded brackets on the maxillary anterior teeth were randomly assigned to three experimental groups: staged (2-level) (Candida Parodin, 12 patients) and V-shaped (Oral-B Ortho, 12 patients) toothbrush head designs were compared in a two-phase study to planar control brushes (Paro M 43, 11 patients). First, all participants were advised to brush their teeth twice daily for 2 min for 3 weeks. Prior to the start and at the end of the study, the gingival index was assessed to evaluate the level of oral hygiene. Afterwards, cleaning efficacy was assessed planimetrically by disclosing the respective teeth after two days of not performing any oral hygiene measures. RESULTS: Of the initial 35 participants, two did not attend after 3 weeks and had to be excluded. After 3 weeks, the control (5 out of 180 sites or -2.8% with GI ≥ 2) and staged groups (16 out of 216 sites or 7.5% with GI ≥ 2) showed minor improvement in the oral hygiene level. In contrast, the V-shaped group (29 out of 198 sites or 14.6 % with GI ≥ 2) showed a statistically significant improvement of the oral hygiene level. Planimetric evaluation, however, showed no superior cleaning efficacy of any of the tested head designs. CONCLUSIONS: The use of V-shaped and staged toothbrush head designs might be beneficial in patients with inadequate oral hygiene undergoing orthodontic treatment with a fixed appliance. Further large-scale investigations are, however, necessary to validate the presented results.

In vitro cleaning potential of three implant debridement methods. Simulation of the non-surgical approach.

OBJECTIVES: To assess the cleaning potential of commonly used implant debridement methods, simulating non-surgical peri-implantitis therapy in vitro. MATERIALS AND METHODS: One-hundred-and-eighty dental implants were ink-stained and mounted in combined soft and hard tissue models, representing peri-implantitis defects with angulations of 30, 60, and 90° covered by a custom-made artificial mucosa. Implants were treated by a dental school graduate and a board-certified periodontist for 120 s with following instruments: Gracey curette, ultrasonic scaler, and an air powder abrasive device with a nozzle for sub-mucosal use utilizing glycine powder. All procedures were repeated 10 times for each instrumentation and defect morphology respectively. Images of the implant surface were taken. Areas with color remnants were planimetrically determined and their cumulative surface area was calculated. Results were tested for statistical differences using two-way anova and Bonferroni correction. Micro-morphologic surface changes were analyzed on scanning electron microscope (SEM) images. RESULTS: The areas of uncleaned surfaces (%, mean ± standard deviations) for curettes, ultrasonic tips, and air abrasion accounted for 74.70 ± 4.89%, 66.95 ± 8.69% and 33.87 ± 12.59% respectively. The air powder abrasive device showed significantly better results for all defect angulations (P < 0.0001). SEM evaluation displayed considerable surface alterations after instrumentation with Gracey curettes and ultrasonic devices, whereas glycine powder did not result in any surface alterations. CONCLUSION: A complete surface cleaning could not be achieved regardless of the instrumentation method applied. The air powder abrasive device showed a superior cleaning potential for all defect angulations with better results at wide defects.

The in Vitro Antimicrobial Efficacy of PDT against Periodontopathogenic Bacteria.

Periodontitis, an inflammatory disease, is caused by biofilms with a mixed microbial etiology and involves the progressive destruction of the tooth-supporting tissues. A rising number of studies investigate the clinical potential of photodynamic therapy (PDT) as an adjunct during active therapy. The aim of the present review was to evaluate the available literature for the in vitro antimicrobial efficacy of photodynamic therapy focusing on the periodontopathogenic bacteria Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis and Fusobacterium nucleatum. The focused question was: "Is it possible to decrease (at least 3 log steps or 99.9%) or even eliminate bacterial growth by photodynamic therapy in vitro when compared to untreated control groups or control groups treated by placebo?" In general, PDT resulted in a substantial reduction of surviving bacteria. However, not all studies showed the desired reduction or elimination. The ranges of log10-reduction were 0.38 (58%) to a complete eradication (100%) for P. gingivalis, 0.21 (39%) to 100% for A. actinomycetemcomitans and 0.3 (50%) to 100% for F. nucleatum. In conclusion, further and particularly more comparable studies are needed to evaluate if PDT can be clinically successful as an adjuvant in periodontal therapy.

In vitro cleaning potential of three different implant debridement methods.

OBJECTIVES: To assess the cleaning potential of three different instrumentation methods commonly used for implant surface decontamination in vitro, using a bone defect-simulating model. MATERIALS AND METHODS: Dental implants were stained with indelible ink and mounted in resin models, which represented standardized peri-implantitis defects with different bone defect angulations (30, 60 and 90°). Cleaning procedures were performed by either an experienced dental hygienist or a 2nd-year postgraduate student. The treatment was repeated 20 times for each instrumentation, that is, with a Gracey curette, an ultrasonic device and an air powder abrasive device (PAD) with glycine powder. After each run, implants were removed and images were taken to detect color remnants in order to measure planimetrically the cumulative uncleaned surface area. SEM images were taken to assess micromorphologic surface changes (magnification 10,000 ×). Results were tested for statistical differences using two-way ANOVA and Bonferroni correction. RESULTS: The areas of uncleaned surfaces (%, mean ± standard deviations) for curettes, ultrasonic tips, and airflow accounted for 24.1 ± 4.8%, 18.5 ± 3.8%, and 11.3 ± 5.4%, respectively. These results were statistically significantly different (P < 0.0001). The cleaning potential of the airflow device increased with wider defects. SEM evaluation displayed distinct surface alterations after instrumentation with steel tips, whereas glycine powder instrumentation had only a minute effect on the surface topography. CONCLUSION: Within the limitations of the present in vitro model, airflow devices using glycine powders seem to constitute an efficient therapeutic option for the debridement of implants in peri-implantitis defects. Still, some uncleaned areas remained. In wide defects, differences between instruments are more accentuated.

Retrospective evaluation of CAD/CAM cantilever reconstructions to restore compromised posterior teeth: a preliminary report.

PURPOSE: To describe the survival, clinical rating, and patient satisfaction of monolithic computer-aided design/computer-assisted manufacture (CAD/CAM) ceramic single unit cantilever crowns placed on hemisected molars and premolars after a follow-up of at least 12 months. MATERIALS AND METHODS: Sixteen consecutive patients (mean age, 56.8 years) with 16 restored two-unit cantilever crowns (5 premolars and 11 hemisected molar abutments) were reevaluated after an observation period of at least 12 months. Tooth mobility, plaque and bleeding scores, and pocket probing depths were assessed on both the restored and contralateral untreated teeth. Patient satisfaction was evaluated using a visual analog scale. RESULTS: The mean observation time was 25.7 ± 13.1 months. All restorations were in situ, and no significant biologic differences were observed between the treated and contralateral teeth. Clinical evaluation showed good performance, and patient satisfaction was recorded as excellent. CONCLUSION: The use of CAD/CAM ceramic single-unit cantilever crowns may be regarded as a conservative and cost-effective treatment modality with high patient acceptance in carefully selected patients.

Labial soft tissue volume evaluation of different techniques for ridge preservation after tooth extraction: a randomized controlled clinical trial.

OBJECTIVE: To volumetrically evaluate soft tissue changes of different ridge preservation techniques compared to spontaneous healing 6 months after tooth extraction. MATERIALS AND METHODS: In each of 40 patients, one single-rooted tooth was extracted and four treatment modalities were randomly assigned to the following groups (n = 10 each): A) ß-tricalcium-phosphate-particles with a polylactid coating (ß-TCP), B) demineralized bovine bone mineral with 10% collagen covered with a collagen matrix (DBBM-C/CM), C) DBBM with 10% collagen covered with an autogenous soft tissue punch graft (DBBM-C/PG), D) spontaneous healing (control). Impressions were obtained before extraction and 6 months later, casts were digitized and volumetric changes at the buccal soft tissues were determined. One-way anova was performed and pair-wise Wilcoxon rank sum test with Bonferroni-Holm method was applied for comparison of differences between two groups. RESULTS: After 6 months, horizontal contour changes accounted for -1.7 ± 0.7 mm (A), -1.2 ± 0.5 mm (B), -1.2 ± 0.7 mm (C) and -1.8 ± 0.8 mm (D). None of the group comparisons reached statistical significance. CONCLUSIONS: Six months after tooth extraction all groups revealed a horizontal volume change in the buccal soft tissue contour. Application of DBBM-C/CM or DBBM-C/PG reduced the amount of volume resorption compared to ß-TCP or spontaneous healing without reaching statistically significant difference.

Three-dimensional defect evaluation of air polishing on extracted human roots.

BACKGROUND: Root surfaces experience continuous abrasive instrumentation during lifelong periodontal maintenance. Periodontists need both effective and minimally abrasive debridement techniques. Air polishing devices might, therefore, constitute a good alternative to mechanical instrumentation. Because little is known of the three-dimensional shape and volume of the abrasion caused by different powders, it is the aim of the study to investigate the three-dimensional extent of these defects. METHODS: Cementum-covered roots of 20 extracted human premolars were coated with resin caps, leaving four areas with identical diameter open for instrumentation using bicarbonate powder and glycine powder. Treatment times were 5 and 10 seconds in a first interval and 10 seconds in a second interval. Maximum settings were chosen for power and lavage. The teeth were scanned using microcomputed tomography initially and after every treatment interval. Differences in volume and defect depths were calculated by superimposition of the scans and tested for significance (Wilcoxon test, P <0.001). RESULTS: Defect volumes (in mm(3)) presented in medians (interquartile ranges) for the bicarbonate powder after 5, 10, 15, and 20 seconds, respectively, were 0.16 (0.11), 0.28 (0.16), 0.32 (0.18), and 0.41 (0.28), and for glycine powder, 0.00 (0.02), 0.01 (0.05), 0.03 (0.11), and 0.06 (0.1). For each time period, abrasion caused by glycine was significantly lower (five- to 20-fold) compared to defects caused by bicarbonate. CONCLUSIONS: In patients with exposed root surfaces, cleaning with bicarbonate powder cannot be recommended. Less abrasive glycine powder, however, demonstrated non-critical substance loss.

Povidone-iodine gel and solution as adjunct to ultrasonic debridement in nonsurgical periodontitis treatment: an RCT pilot study.

OBJECTIVES: Polyvinylpyrrolidone-iodine (PVP-iodine or povidone- iodine) enhances the treatment outcomes of initial periodontal treatment but the degree of benefit varies in the literature. A main reason might be the concentration of the dosage form and its contact time with the periodontal tissues. In this randomized pilot study the effect of repeated subgingival application of PVP-iodine during scaling and root planing (SRP) was assessed. Changes of clinical parameters and microbiotic taxa after 3 months were analyzed. METHOD AND MATERIALS: In a split-mouth design 12 patients with generalized, severe periodontitis were treated with SRP combined with subgingival application of either PVP-iodine or water. Test and control sides were isolated with a special rubber dam technique. Irrigations were reapplied during SRP. Periodontal probing depth (PD) and recessions were documented before treatment and after 3 months. Samples of subgingival bacteria before SRP and after 1 week, 1 month, and 3 months were analyzed. RESULTS: Three months after SRP, changes for PD and recession in deep pockets were significantly higher in the PVP-iodine group (P = .012 and .044 respectively). The number of these pockets was reduced from 73 at baseline to 8 in the test and 19 in the control group. In both groups, bacterial taxa were reduced after 1 week. One month after SRP only taxa of Porphyromonas gingivalis in the PVP-iodine group were lower than at baseline. After 3 months, all taxa regained baseline values. CONCLUSION: PVP-iodine reapplied frequently during SRP might enhance pocket depth reduction in initially deep pockets.

In vitro evaluation of the erosive potential of viscosity-modified soft acidic drinks on enamel.

OBJECTIVE: The objective of this in vitro study was to investigate the effect of viscosity-modified soft acidic drinks on enamel erosion. MATERIALS AND METHODS: A total of 108 bovine enamel samples (∅ = 3 mm) were embedded in acrylic resin and allocated into six groups (n = 18). Soft acidic drinks (orange juice, Coca-Cola, Sprite) were used both in their regular forms and at a kinetic viscositiy of 5 mm(2)/s, which was adjusted by adding hydroxypropyl cellulose. All solutions were pumped over the enamel surface from a reservoir with a drop rate of 3 ml/min. Each specimen was eroded for 10 min at 20 °C. Erosion of enamel surfaces was measured using profilometry. Data were analyzed using independent t tests and one-way ANOVAs (p < 0.05). RESULTS: Enamel loss was significantly higher for the regular (Coca-Cola, 5.60 ± 1.04 µm; Sprite, 5.49 ± 0.94 µm; orange juice, 1.35 ± 0.4 µm) than for the viscosity-modified drinks (Coca-Cola, 4.90 ± 0.34 µm; Sprite, 4.46 ± 0.39 µm; orange juice, 1.10 ± 0.22 µm). CONCLUSION: For both regular and viscosity-modified forms, Coca-Cola and Sprite caused higher enamel loss than orange juice. Increasing the viscosity of acidic soft drinks to 5 mm(2)/s reduced enamel erosion by 12.6-18.7 %. CLINICAL RELEVANCE: The erosive potential of soft acidic drinks is not only dependent on various chemical properties but also on the viscosity of the acidic solution and can be reduced by viscosity modification.

Expression of embryonic stem cell markers and osteogenic differentiation potential in cells derived from periodontal granulation tissue.

The aim of this study was to identify if cells obtained from periodontal granulation tissue possess embryonic stem cell properties and osteogenic capacities in vitro. Periodontal granulation tissue was removed from one furcation and one infrabony defect (FGTC/IGTC-furcation/infrabony defect derived granulation tissue cells) of six patients. The extracted tissues were treated with collagenase/dispase solution, cultured and passaged twice, while a fraction of them was bacteriologically analyzed. Upon reaching confluence, total RNA was extracted, followed by cDNA synthesis and real-time PCR analysis. Gene expression levels of collagen type I, alkaline phosphatase (ALP), and the embryonic stem cell markers Nanog, Oct-4, Rex-1 and Sox-2 were measured, calibrated against the housekeeping gene GAPDH. Further, osteogenic differentiation was induced. Mineralized matrix formation was confirmed by von Kossa staining, and ALP activity was measured colorimetrically. The total bacterial load amounted to 9.4 ± 14.6 × 10(6) counts/mg of tissue for IGTC, and 11.1 ± 6.1 × 10(6) counts/of tissue for FGTC. Among the embryonic stem cell markers (FGTC/IGTC), Nanog was most highly expressed (3.48 ± 1.2/5.85 ± 5.7), followed by Oct-4 (1.79 ± 0.69/2.85 ± 2.5), Sox-2 (0.66 ± 0.3/1.26 ± 1.4) and Rex-1 (0.06 ± 0.0/0.04 ± 0.0). The osteogenic differentiation process was positive in both FGTC and IGTC, judged by increased von Kossa staining, and elevated ALP activity and gene expression. This study provides evidence that infected periodontal granulation tissue harbors cells expressing embryonic stem cell markers, and exhibiting osteogenic capacities when in culture in vitro.

Infected periodontal granulation tissue contains cells expressing embryonic stem cell markers. A pilot study.

The commonly practiced removal of granulation tissue during periodontal surgery, aiming to eliminate infection and optimize healing conditions, may also remove progenitor stem cells that could otherwise support periodontal regeneration. The present study aimed to investigate if cells with embryonic stem cell properties are present in periodontal granulation tissue. During the course of flap surgery inflammatory granulation tissue was obtained from four patients and five periodontal defects. Tissues were processed in a collagenase/dispase solution to release the cells. Part of the resulting suspension was processed for bacteriological analysis (IAI PadoTest 4.5), whereas the remaining cell suspension was cultured and passaged once. Upon reaching confluence, total RNA was extracted, followed by cDNA synthesis. PCR was then performed (SYBR Green-based protocols) to measure gene expression levels of Collagen type I, and embryonic stem cell markers Nanog, Oct4, Rex-1 and Sox2. Results are expressed as 2⁻Δ(Ct) values of the target gene, calibrated against a house-keeping gene (GAPDH). A high total bacterial load up to 20.6 ± 11.0×10(6) counts/mg of tissue was found. Collagen type I was strongly expressed, confirming the predominance of mesenchymal/fibroblastic cells. Among the studied embryonic stem cells markers, Nanog was most highly expressed (2.3 ± 1.2), followed by Oct4 (1.1 ± 0.5), Rex-1 (0.6 ± 0.2) and Sox2 (0.3 ± 0.2). This is the first study that demonstrates the presence of cells expressing embryonic stem cell markers among infected granulation tissue. This knowledge needs to be considered when devising future strategies to improve periodontal wound healing and regeneration.

In vitro evaluation of the oxidation efficacy of transgingival photodynamic therapy.

OBJECTIVE: To evaluate the capability of soft laser light to penetrate blood, serum, gingival connective tissue and pure collagen type I. MATERIALS AND METHODS: A 1:1 mixture of methylene blue (MB) and diphenylisobenzofuran (DPBF) was irradiated for 60 s with a diode laser (670 nm, 0.3 W) through blood, serum, gingival connective tissue and collagen type I (2 mm transillumination thickness). The oxidation of DPBF by MB was determined spectrophotometrically by measuring the optical density (oD) at 410 nm. The absorption spectra of DPBF/MB irradiated through MB (1%) and strawberry red solution (3%) served as control. RESULTS: The mean oD of non-irradiated DPBF/MB was 1.98 ± 0.04. Irradiation through MB showed no oxidation of DPBF (1.98 ± 0.02; p > 0.05), while interposition of strawberry red and serum resulted in almost complete oxidation of DPBF (0.13 ± 0.09, 0.06 ± 0.03; p ≤ 0.0001). Irradiation through gingiva and collagen reduced the oxidation of DPBF significantly (1.0 ± 0.04, 0.7 ± 0.04; p ≤ 0.0001), accounting for 50% to 35% of the non-irradiated DPBF/MB solution. CONCLUSION: Red light from a diode laser can penetrate blood and gingival tissues. However, light absorption for collagen and connective tissue can hamper the oxidation process.

Cleaning potential of glycine air-flow application in an in vitro peri-implantitis model.

OBJECTIVES: The study aimed to assess the accessibility of a glycine powder blasting device to implant surfaces in models imitating different peri-implantitis defects. The null hypothesis was that the device allows for complete surface decontamination in all defect types. MATERIALS AND METHODS: Eighteen implants were dip-coated and placed in resin blocks with different defect morphologies. Vertical bone angulations of 90°, 60°, 30° and 15° were chosen and the implants were treated for 10 s using an air-flow device employing glycine powder. Once removed, photographs from the implants were taken in three directions: perpendicularly (90°) to the implant axis and with an angulation of 60° and 120°, the latter ones to assess the coronal and apical thread areas. The area with residual color represented areas, which were not accessible to the powder. This area was planimetrically assessed. Medians and inter-quartile ranges (IQR) of the percentage of uncleaned surfaces were calculated and nonparametric paired and unpaired statistical analyses were performed. RESULTS: The median percentages (IQR in brackets) of uncleaned areas in the 90°, 60°, 30° and 15° defects were of 3%(A) (6), 8%(A) (4), 24%(B) (8), and 51%(C) (13), respectively (different superscript capital letters represent statistically significant differences; P < 0.0001). The upper aspects of the threads (coronal faces) were significantly better cleaned than the lower ones (P < 0.001). This finding was more pronounced in narrower defects. CONCLUSION: Although a complete surface decontamination could not be performed in any of the defects, the biggest part of the surface could be cleaned in the larger defects. Especially in narrow defects and under the threads, residually stained areas remain on the implant surfaces.