Recommendations for a safe restart of elective aerosol-generating oral surgery procedures following the COVID-19 pandemic outbreak: An Italian multicenter study.

Among healthcare workers, oral and maxillofacial surgeons are some of the most exposed to coronavirus disease (COVID-19). The aim of this retrospective study was to develop suggestions for continuing the work of oral and maxillofacial surgeons using a safe protocol for elective and urgent aerosol-generating procedures that could prevent the onset of new clusters. Based on the results obtained and a guidelines review of those Asian countries that had promptly managed the current pandemic, the following safety protocol was developed.

Implant Placement Following Crestal Sinus Lift with Sequential Drills and Osteotomes: Five Years after Final Loading Results from a Retrospective Study.

The aim of this retrospective study was to clinically evaluate the five-year outcomes of implants placed following a combined approach to the sinus, consisting of sequential drills and osteotomes. Medical records of patients with implants placed in combination with crestal sinus lift using sequential drills and osteotomes, with a residual alveolar bone crest between 4 to 8 mm, and a follow-up of at least five years after final loading, were evaluated. Outcomes were implant and prosthetic survival and success rates, any complication, and marginal bone loss. Data from 96 patients (53 women and 43 men; mean age 54.7 years; range 23-79 years) were collected. A total of 105 single implants were analyzed. After five years of function, two implants were lost and two prostheses failed. No major biological or prosthetic complications occurred. At the five-year examination, the marginal bone loss was 1.24 ± 0.28 mm. Within the limitations of this retrospective study it can be concluded that implants placed following a combined approach to the sinus consisting of sequential drills and osteotomes seem to be a viable option for the treatment of posterior atrophic edentulous maxilla.

Three-Year Retrospective Comparative Study between Implants with Same Body-Design but Different Crest Module Configurations.

Crest module can be defined as the portion of a two-piece implant designed to retain the prosthetic components and to allows the maintenance of the peri-implant tissues in the transition zone. AIM: To evaluate the three-year after loading clinical and radiographic data, collected from patients that received a prosthetic rehabilitation on conical connection implants with partial machined collar (PMC; CC Group) and same body-designed implants, with flat-to-flat connection and groovy neck design (FC Group). MATERIALS AND METHODS: A retrospective chart review of previously collected data, including documents, radiographs, and pictures of patients who received at least one implant-supported restoration on NobelReplace CC PMC or NobelReplace Tapered Groovy implants was performed. Patients with at least three years of follow-up after final loading were considered for this study. Outcomes measures were implant and prosthesis failures, any biological or technical complications, marginal bone loss. RESULTS: Eight-two patients (44 women, 38 men; average age 55.6) with 152 implants were selected and divided in two groups with 77 (CC group) and 75 (FC group), respectively. Three years after final loading, one implant in CC group failed (98.7% survival rate), while no implants failed in FC group (100% survival rate). One restoration failed in CC group (98.7% survival rate) with no restoration failing in the FC one (100% survival rate). Differences were not statistically significant (p = 1.0). Three years after final loading, mean marginal bone loss was 0.22 ± 0.06 mm (95% CI 0.2-0.24) in CC group and 0.62 ± 0.30 mm (95% CI 0.52-0.72) in FC group. The difference was statistically significant (0.40 ± 0.13 mm; 95% CI 0.3-0.5; p = 0.003). CONCLUSION: with the limitation of this retrospective comparative study, implants with conical connection and partial machined collar seem to achieve a trend of superior outcomes if compared with implants with flat connection and groovy collar design.

New protocol for in-house management of computer assisted orthognathic surgery.

The aim of this study was to evaluate retrospectively the accuracy of a protocol for completely in-house, computer-assisted, orthognathic surgery, generating resin printed intermediate surgical guides. A retrospective, observational study was made on a cohort of 15 patients treated consecutively from September 2017 to May 2019, who underwent bimaxillary orthognathic surgery planned with the same 3-dimensional program and whose surgical intermediate splints were obtained with the same all-in-house protocol. Virtual planned surgical movements were compared with the real surgical outcome. The differences were not significant for eight of the 12 variables considered. The p values, calculated with the Wilcoxon signed rank test, were evenly distributed and ranged from p=0.001 to p=0.820. Significant differences were reported in four measurements: angle between sella-nasion plane and a line connecting the incisal edge and the apex of the root of the most prominent incisor (U1-SN) (p=0.001), angle between Frankfort plane and a line connecting the incisal edge and the root apex of the most prominent upper incisor (p=0.008), dental midline discrepancies (p=0.006), and occlusal plane tilt (U1-FH) (p=0.001), basically due to intraoperative settings. The 3-dimensional resin printed surgical guides were shown to be a reliable alternative to the commercial ones and showed high rate of accuracy for most of the variables assessed. Four out of 12 of these showed significant errors, but two of them were only minimal discrepancies with no clinical implications.

Platform switching versus regular platform single implants: 5-year post-loading results from a randomised controlled trial.

PURPOSE: To compare the clinical and radiographic outcomes of platform switching (PS) and regular platform (RP) implants. MATERIALS AND METHODS: This study was designed as a randomised controlled split-mouth trial. Eighteen patients, with bilaterally missing single premolars or molars to be restored with implant-supported single crowns, were consecutively enrolled. Implant sites were randomly assigned to be treated according to the PS concept (PS group), or with matching implant-abutment diameters (RP group). A total of 36 implants were placed in healed bone, with an insertion torque between 35 and 45 Ncm, according to a one-stage protocol. All the implants were loaded with a screw-retained provisional crown 3 months after implant insertion. Definitive screw-retained single crowns were delivered 2 months later. Outcome measures were implant and prosthetic survival rates, biological and prosthetic complications, marginal bone level (MBL) changes, pocket probing depth (PPD) and bleeding on probing (BOP). Clinical data were collected at implant placement (baseline), implant loading (3 months later) and at 9, 36 and 60 months after loading. RESULTS: One patient dropped out after 4 years of follow-up. No implant failed and no prosthetic complications were recorded during the study period. One patient experienced mucosal inflammation with positive BOP (RP group) after 3 months and three patients had bilateral peri-implant mucosal inflammation with positive BOP at 6, 24 and 36 months, respectively. No other biological complications were recorded up to 60 months of follow-up. There were no statistically significant differences between groups for complications (3/18 versus 4/18; P = 1.0). Nine months after loading the mean MBL was 0.93 ± 0.26 mm (95% CI 0.81 to 1.05) for RP implants and 0.84 ± 0.23 mm (95% CI 0.73 to 0.95) for PS implants. No statistically significant difference was observed between the groups (P = 0.18). Thirty-six months after loading, the mean MBL was 1.09 ± 0.31 mm (95% CI 0.95 to 1.24) in the RP group and 1.06 ± 0.24 mm (95% CI 0.94 to 1.17) in the PS group, with no statistically significant difference between groups (P = 0.70). Sixty months after loading the mean MBL was 1.24 ± 0.39 mm (95% CI 1.05 to 1.43) in the RP group and 1.20 ± 0.21 mm (95% CI 1.01 to 1.39) in the PS group, with no statistically significant difference between the groups (P = 0.85). The mean PPD was 2.58 ± 0.58 mm (95% CI 2.32 to 2.84) in the RP group and 2.40 ± 0.72 mm (95% CI 2.21 to 2.59) in the PS group at 60 months follow-up, with no statistically significant difference between the groups (P = 0.49). The mean BOP was 0.90 ± 0.88 (95% CI 0.58 to 1.22) in the RP group and 0.93 ± 0.97 (95% CI 0.51 to 1.35) in the PS group at 60 months of follow-up, with no statistically significant difference between the groups (P = 0.85). CONCLUSIONS: Implants restored according to the PS concept and matching implant-abutment diameters showed comparable clinical and radiographic results up to 5 years after loading.

Effectiveness of Calcium Phosphate Desensitising Agents in Dental Hypersensitivity Over 24 Weeks of Clinical Evaluation.

BACKGROUND: Calcium phosphate-based compounds are used to treat dental hypersensitivity (DH). Their long-term clinical behaviour needs further research. This study compared the 24-week effectiveness of Teethmate Desensitizer (TD), a pure tetracalcium phosphate (TTCP) and dicalcium phosphate dihydrate (DCPD) powder/water, to that of Dentin Desensitizer (DD), and Bite & White ExSense (BWE), both of calcium phosphate crystallites. METHODS: A total of 105 subjects were selected. A random table was utilised to form three groups of 35 subjects. DH was evaluated using the evaporative sensitivity, tactile sensitivity tests, and the visual analogue scale (VAS) of pain. Response was recorded before the application of the materials (Pre-1), immediately after (Post-0), at 1 week (Post-1), 4 weeks (Post-2), 12 weeks (Post-3) and 24 weeks (Post-4). The non-parametric distribution was assessed with the Shapiro-Wilk statistical test. Intra-group differences for the six time points were evaluated with the Friedman statistical test and the Kruskal-Wallis test. RESULTS: All the materials decreased DH after 24 weeks in comparison to Pre-1. However, the TTCP/DCPD cement showed the greatest statistical efficiency. CONCLUSIONS: The significant decrease of VAS scores produced by TD in the long term suggest the material as the most reliable in the clinical relief of DH.

Sinus augmentation grafting with anorganic bovine bone versus 50% autologous bone mixed with 50% anorganic bovine bone: 5 years after loading results from a randomised controlled trial.

PURPOSE: To compare the outcomes of implants inserted in maxillary sinuses augmented with 100% anorganic bovine bone (ABB) grafts versus mixed with 50% ABB and 50% autologous bone graft using a lateral window approach. MATERIALS AND METHODS: This study was designed as a randomised controlled trial of parallel groups. Patients in need of an implant-supported prosthesis in maxillary posterior areas, with a residual alveolar bone height ranging between 0 and 4 mm, were recruited for lateral sinus grafting and implant placement. Patients were randomly allocated to receive two different graft materials according to a parallel group design: group A was grafted with 50% ABB and 50% autogenous bone; group B was grafted with 100% ABB. After 7 months, tapered implants were inserted with an insertion torque between 20 and 45 Ncm. Three months later implants were loaded with screw-retained temporary crowns. Definitive crowns were delivered after 3 months. Outcome measures were implant and prosthesis survival rates, complications, radiographic marginal bone-level changes, probing pocket depths (PPDs) and bleeding on probing (BOP). Clinical data were collected at definitive prosthesis delivery, and 1, 2 and 5 years after definitive loading. RESULTS: Thirty-two consecutive patients were treated with 32 sinus elevation procedures (16 group A, 16 group B). A total of 46 implants were inserted. One patient (with two implants) dropped out in group A, and two patients (with three implants) dropped out in group B. No implant/crown failed by the end of the study. Three complications (one sinus membrane perforation and two chipping of the ceramic) were observed in three patients in group A, versus none in group B (relative risk was 0.81; 95% CI 0.64-1.03; P = 0.225). At the 2-year follow-up, the mean marginal bone loss was 1.18 ± 0.50 mm (95% CI 0.95-1.45 mm) in group A and 1.28 ± 0.48 mm (95% CI 0.97-1.43 mm) in group B, with no statistically significant differences between the two groups (difference 0.11 ± 0.22 mm; 95% CI -0.06-0.16 mm; P = 0.586). At the 5-year follow-up, the mean marginal bone loss was 1.37 ± 0.48 mm (95% CI 1.13-1.86 mm) in group A and 1.42 ± 0.48 mm (95% CI 1.17-1.90 mm) in group B (difference 0.15 ± 0.08 mm; 95% CI 0.10-0.22 mm; P = 0.426). At the 2-year follow-up, the mean PPD value was 2.70 ± 0.39 mm for group A and 2.54 ± 0.66 mm for group B, with no statistically significant difference between groups (difference 0.17 ± 0.39 mm; 95% CI 0.06-0.32 mm; P = 0.456). At the 5-year follow-up, the mean PPD value was 3.20 ± 0.44 mm for group A and 3.32 ± 0.49 mm for group B (difference 0.12 ± 0.43 mm; 95% CI 0.02-0.22 mm; P = 0.672). At the 2-year follow-up, the mean BOP value was 1.21 ± 0.79 for group A and 1.28 ± 0.68 for group B (difference 0.06 ± 0.49; 95% CI -0.23-0.25; P = 0.297), and at the 5-year follow-up, the mean BOP value was 1.77 ± 0.62 for group A and 1.91 ± 0.48 for group B (difference: 0.14 ± 0.51; 95% CI -0.05-0.33; P = 0.492). CONCLUSIONS: Within the limitations of this study, the present data confirm similar clinical outcomes of implants inserted in sinuses grafted with ABB versus implants inserted in sinuses grafted with mixed 50% ABB and 50% autologous bone.

Early childhood caries and associated determinants: a cross-sectional study on Italian preschool children.

OBJECTIVES: This study evaluates the influence of several determinants on the presence of early childhood caries (ECC) in preschool children living in northern Sardinia, Italy. These determinants include the educational level and occupational status of the parents as a proxy for the socioeconomical level (SES) and behavioral factors (dietary and oral hygiene). METHODS: An observational cross-sectional study was designed with a dental examination and a standardized questionnaire. Five hundred forty-four subjects (260 girls and 284 boys) were enrolled and categorized into two age groups: 359 children were aged 18-47 months and 185 children were aged 48-60 months. RESULTS: The total caries prevalence was 15.99%. Caries risk increased with lower parents' educational level (P = 0.01), increased number of siblings (P < 0.01), the use of bottle feeding (P = 0.02), and the use of a sweetened baby's pacifier at night (P = 0.01). In robust multivariate analysis, a high parental educational level played a protective role on the presence of caries lesion [odds ratio (OR) = 0.51, 95% confidence interval (CI) 0.34-0.78]; the mother's being employed had a positive statistically significant association with the child having decayed, missing, filled tooth surfaces = 0 (OR = 0.64, 95% CI 0.23-0.97). The presence of more than one sibling in the family was associated with caries (OR = 1.70, 95% CI 1.20-2.40). CONCLUSION: ECC prevalence evaluated was similar to other western countries, and SES and behavioral habits influence the development of ECC.

Oral characteristics of trisomy 8 and monosomy 18: a case report.

Several reports described various mosaic chromosomal syndromes characterized by alterations originated by either an excess or deficit in the number of chromosomes. A case of mosaic trisomy 8 and monosomy 18 with significant involvement of the oral cavity is described, both in terms of general medicine and from a dental-oral perspective, and the treatment plan was planned and discussed.Regular follow-up visits enabled to verify significant improvement in all parameters of the patient's oral health, which urged us to press on with our quest to protect the right to health of patients affected by disabilities.

Differences in oral health among Italian adolescents related to the type of secondary school attended.

PURPOSE: The aim of the present study was to evaluate the possible interaction between the type of secondary school attended, oral clinical data and self-perceived oral health (SPOH) behaviour among Italian adolescents. MATERIALS AND METHODS: A total of 913 adolescents living in Milan (Italy), attending two different types of secondary schools, grammar and technical secondary schools, were examined regarding dental caries and gingival conditions. Oral health behaviour data were collected using an anonymous questionnaire. The presence of caries was recorded using the decayed missed filled tooth (DMFT) index, gingival conditions with community periodontal index (CPI) following World Health Organization recommendations. Stepwise logistic regression was applied to determine whether the type of school attended was associated with the clinical outcome variables and subjects' SPOH and with oral health or lifestyle behaviour. RESULTS: The prevalence of caries was 59.8% (95% CI = 41.3 to 76.8); a third of participants showed a CPI = 0, whereas 34.9% had bleeding at probing and 37.9% had calculus. Caries distribution was significantly related to the type of school attended in each score of the DMFT categorisation (P < 0.01). Experience of tooth discomfort was claimed by 23.6% of subjects from grammar schools and 35.3% from technical schools (P < 0.01). In males, CPI > or = 1 was associated with the type of school, OR = 1.6 (95% CI = 1.1 to 2.5), the highest DMFT score and experience of self-perceived tooth discomfort, OR = 1.6 (95% CI = 1.2 to 2.0) and OR = 1.2 (95% CI = 1.4 to 2.6), respectively. In females, only CPI > or = 1 and highest DMFT score were associated with the type of school, OR = 2.1 (95% CI = 1.3 to 3.3) and OR = 1.6 (95% CI = 1.2 to 2.0), respectively. CONCLUSIONS: The type of school is a sensitive indicator of oral health status among adolescents.

Diagnostic evaluation of serial sections of labial salivary gland biopsies in Sjögren's syndrome.

OBJECTIVES: Sjögren's syndrome is a chronic inflammatory disease. The detection of chronic inflammatory infiltrates containing >50 lymphocytes (lymphocytic focus) per 4 mm2 tissue in minor salivary gland biopsies is a diagnostic parameter of the disease. The aim of the study was to examine if an increase in the tissue area of a single minor labial salivary gland biopsy through serial histological sections in patients affected by primary Sjögren's syndrome could facilitate the detection of the diagnostic focus score (grades >1 or >2). METHODS: We observed 24 labial salivary gland biopsies from patients affected by primary Sjögren's syndrome, diagnosed according to the clinical-laboratory criteria proposed by the American-European Consensus Group. The analysis was carried out on sections (n= 72) obtained at three different levels at 200 micrometers from one another. The serial sections regarding the 3 levels were reviewed by the same oral pathologist, who detected both the total number of foci, and their surface, calculating a cumulative focus score. RESULTS: No significant correlation was found between the number of lobules per histological section and the focus score (Pearson correlation 0.363, p= 0.01). No significant variation in focus score distribution was identified in the three serial histological levels at 200 micrometers from one another. From the comparison between the number of lobules observed and the focus score grade, no direct proportionality between the amount of parenchyma analyzed and the focus score was found. CONCLUSIONS: The focus score remained unchanged in the serial sections at different depths.

Diagnostic evaluation of serial sections of labial salivary gland biopsies in Sjögren’s syndrome

No disponible

Objectives: Sjögren’s syndrome is a chronic inflammatory disease. The detection of chronic inflammatory infiltrates containing >50 lymphocytes (lymphocytic focus) per 4 mm2 tissue in minor salivary gland biopsies is a diagnostic parameter of the disease. The aim of the study was to examine if an increase in the tissue area of a single minor labial salivary gland biopsy through serial histological sections in patients affected by primary Sjögren’s syndrome could facilitate thedetection of the diagnostic focus score (grades >1 or >2).Methods: We observed 24 labial salivary gland biopsies from patients affected by primary Sjögren’s syndrome, diagnosed according to the clinical-laboratory criteria proposed by the American-European Consensus Group.The analysis was carried out on sections (n= 72) obtained at three different levels at 200 micrometers from one another.The serial sections regarding the 3 levels were reviewed by the same oral pathologist, who detected both the total number of foci, and their surface, calculating a cumulative focus score.Results: No significant correlation was found between the number of lobules per histological section and the focus score (Pearson correlation 0.363, p= 0.01). No significant variation in focus score distribution was identified in the three serial histologicallevels at 200 micrometers from one another. From the comparison between the number of lobules observed and the focus score grade, no direct proportionality between the amount of parenchyma analyzed and the focus score was found.Conclusions: The focus score remained unchanged in the serial sections at different depths (AU)

Histology and stability study of cortical bone graft influence on titanium implants.

OBJECTIVE: The mechanisms for integrating titanium implants in recipient bone are still not well defined, and it is not known whether the process of bone formation around implants inserted into grafts is the same as that described for titanium implants in nongrafted cortical bone. This study compared the histology, stability, and osseointegration of titanium implants inserted in cortical bone with and without a simultaneous autologous cortical bone graft in an experimental animal model. METHODS: Thirty titanium implants were inserted in 3 sheep. Half of the implants were inserted to fix the graft to the recipient bone, and the remainder were inserted in the distal part of the tibial metaphysis as controls. The animals were humanely killed at 2, 6, and 8 months after surgery. A stability test (unscrewing torque) was performed immediately on 12 fresh specimens (6 grafted implants and 6 control implants). The remaining unscrewed implants, both grafted and not grafted, were subjected to histomorphometric analysis. RESULTS: After osseointegration, the unscrewing force exceeded the fracture limit of the titanium fixtures in both the grafted samples and controls, demonstrating their optimal stability but failing to demonstrate an improvement in the grafted bone. Histomorphometric analysis demonstrated newly formed tissue that extended from the contact area inside the graft, beginning at 6 months. At 8 months, the implant threads in the graft were surrounded by a large amount of newly formed bone mixed with necrotic fragments. CONCLUSIONS: Our results show that onlay cortical grafts on cortical bone enhance the osteogenic potential of the host bone, ensuring solid, viable bone tissue support that results in a high rate of integration of the titanium fixtures. The loading forces affect the bone-healing process after implant insertion; bone matrix was deposited unequally, being greater proximally (90% versus 40%), which is perpendicular to the maximal load tension lines when the sheep are standing. This implies that in the human jaw, where the tension lines parallel the axis of the implants, the implants can play an important role in guiding new bone formation during osseointegration.

Effect of amalgam fillings on the mercury concentration in human amniotic fluid.

BACKGROUND: Methyl mercury (MeHg) and metallic Hg are well known as neurotoxic agents. Dental amalgam contributes significantly to elemental Hg vapour exposure in the general population. There is little information about Hg concentration in human amniotic fluid (AF) of pregnant women and its potential toxic effect on the fetuses. OBJECTIVE: Primary to assess the relationship between the presence of detectable mercury (Hg) concentration in human AF, number and surface areas of amalgam fillings of pregnant women; secondary to analyse their obstetric history and perinatal complications. METHODS: Seventy-two pregnant women took part in this prospective study. One dentist recorded the dental status, presence, number and surface areas of amalgam fillings. Total Hg concentration in AF was determined in digested samples using automatic cold vapour atomic absorption equipment. The detection limit of Hg in AF, determined from blank readings, was 0.08 ng/ml. To estimate the dependence of the explanatory variables (such as number and surface areas of amalgam fillings, fish consumption, presence of liver or neurological diseases and smoking habits) on mercury concentration several linear regression models were built up. Stepwise logistic regression procedures were running on total sample and on patients with at least one amalgam filling (Positive Filling group = PF). Principal component analysis (PCA) provided two factors, which explained for more the 60% of the variance among the variables. RESULTS: The overall mean Hg concentration in AF among all patients was 0.37+/-0.49 ng/ml. Nineteen (26.4%) women had a Hg concentration <0.08 ng/ml (Hg negative group). In 53 (73.6%) patients, with a concentration > or = 0.08 ng/ml (Hg positive group), the mean value of Hg was 0.49+/-0.52 ng/ml. The average number of amalgam fillings was 2.26 +/- 3.19 in the Hg negative group and 5.32+/-3.03 in the Hg positive group (ANOVA one-way p=0.04). A dependence of mercury concentration on number of amalgam fillings (p=0.03), surface area of the amalgam fillings (p=0.04) and fish consumption (p=0.04) was observed but not at a significant level. In stepwise logistic procedure the number of amalgam fillings gave a contribution to the model (p=0.04), although null value was included in the confidence intervals. We observed no statistically significant differences (chi2 test) among the patients with a Hg concentration <0.08 ng/ml (n=19) and those with a concentration > or = 0.08 (n=53) with regard to obstetric history and perinatal complications. CONCLUSIONS: Number and surface areas of amalgam fillings influenced positively Hg concentration in AF but not at a significant level. Moreover Hg levels detected in AF were low and no adverse outcomes were observed through pregnancies and in the newborns.

In vivo enamel fluoride uptake after use of fluoride products.

PURPOSE: To evaluate fluoride uptake in enamel after use of products containing different fluoride components of distinct oral hygiene regimen in vivo. METHODS: 84 healthy subjects (24 females and 60 males aged 19-26 years, mean 22.2) recruited from the students attending the courses of the Medical Faculty of the University of Sassari, Italy, were randomly assigned to one of four treatments groups: A: treated with a dentifrice containing sodium monofluorophosphate (1250 ppm F-); B: treated with dentifrice with 1250 ppm F- from AmF; C: treated with an AmF toothpaste (1250 ppm F-) and a mouth rinse with 250 ppm F- from AmF; or D: treated with a NaMFP toothpaste (1250 ppm F-) plus 1250 ppm NaMFP varnish. Acid-etched enamel microbiopsies on the vestibular surface of the first maxillary premolar were collected at baseline (to), after 20 days of test product use (t1) and after 24 hours without treatment (t2). Fluoride concentration was measured using an ion-specific electrode. All measurements were made in triplicate and analyzed statistically using two-way factorial ANOVA for independent samples standard weighted-means analysis. RESULTS: The fluoride uptake in the enamel shows a considerable variation between the groups. Significant differences were found both within all products in terms of fluoride concentration in enamel for (P < 0.0001 for two-way ANOVA, and later Tukey HSD test). After 20 days of treatment, the group using AmF toothpaste plus AmF mouthrinse had a higher fluoride uptake than the groups using either of the other products (P < 0.05). In conclusion, all products lead to an appreciable amount of fluoride uptake in enamel; AmF products led to higher concentrations. The concentration of fluoride accumulated during treatment phase remained high after 24 hours following the cessation of use.