In Vivo Assessment of Astrocyte Reactivity in Patients with Progressive Supranuclear Palsy.

OBJECTIVE: Although astrocytic pathology is a pathological hallmark of progressive supranuclear palsy (PSP), its pathophysiological role remains unclear. This study aimed to assess astrocyte reactivity in vivo in patients with PSP. Furthermore, we investigated alterations in brain lactate levels and their relationship with astrocyte reactivity. METHODS: We included 30 patients with PSP-Richardson syndrome and 30 healthy controls; in patients, tau deposition was confirmed through 18F-florzolotau positron emission tomography. Myo-inositol, an astroglial marker, and lactate were quantified in the anterior cingulate cortex through magnetic resonance spectroscopy. We measured plasma biomarkers, including glial fibrillary acidic protein as another astrocytic marker. The anterior cingulate cortex was histologically assessed in postmortem samples of another 3 patients with PSP with comparable disease durations. RESULTS: The levels of myo-inositol and plasma glial fibrillary acidic protein were significantly higher in patients than those in healthy controls (p < 0.05); these increases were significantly associated with PSP rating scale and cognitive function scores (p < 0.05). The lactate level was high in patients, and correlated significantly with high myo-inositol levels. Histological analysis of the anterior cingulate cortex in patients revealed reactive astrocytes, despite mild tau deposition, and no marked synaptic loss. INTERPRETATION: We discovered high levels of astrocyte biomarkers in patients with PSP, suggesting astrocyte reactivity. The association between myo-inositol and lactate levels suggests a link between reactive astrocytes and brain energy metabolism changes. Our results indicate that astrocyte reactivity in the anterior cingulate cortex precedes pronounced tau pathology and neurodegenerative processes in that region, and affects brain function in PSP. ANN NEUROL 2024.

Cochlear Implantation in the Poorer-Hearing Ear Is a Reasonable Choice.

Choosing the optimal side for cochlear implantation (CI) remains a major challenge because of the lack of evidence. We investigated the choice of the surgery side for CI (i.e., the better- or poorer-hearing ear) in patients with asymmetric hearing. Audiological records of 74 adults with a unilateral hearing aid who had undergone surgery at Okayama University Hospital were reviewed. The definition of 'better-hearing ear' was the aided ear, and the unaided ear was considered the poorer-hearing ear. We performed a multiple regression analysis to identify potential predictors of speech recognition performance after unilateral CI in the patients. Fifty-two patients underwent CI in the poorer-hearing ear. The post-Ci bimodal hearing rate was far higher in the poorer-ear group (77.8% vs. 22.2%). A multivariate analysis revealed that prelingual hearing loss and the patient's age at CI significantly affected the speech recognition outcome (beta coefficients: 24.6 and -0.33, 95% confidence intervals [11.75-37.45] and [-0.58 to -0.09], respectively), but the CI surgery side did not (-6.76, [-14.92-1.39]). Unilateral CI in the poorer-hearing ear may therefore be a reasonable choice for adult patients with postlingual severe hearing loss, providing a greater opportunity for postoperative bimodal hearing.

Detailed clinical features and genotype-phenotype correlation in an OTOF-related hearing loss cohort in Japan.

Mutations in the OTOF gene are a common cause of hereditary hearing loss and the main cause of auditory neuropathy spectrum disorder (ANSD). Although it is reported that most of the patients with OTOF mutations have stable, congenital or prelingual onset severe-to-profound hearing loss, some patients show atypical clinical phenotypes, and the genotype-phenotype correlation in patients with OTOF mutations is not yet fully understood. In this study, we aimed to reveal detailed clinical characteristics of OTOF-related hearing loss patients and the genotype-phenotype correlation. Detailed clinical information was available for 64 patients in our database who were diagnosed with OTOF-related hearing loss. As reported previously, most of the patients (90.6%) showed a "typical" phenotype; prelingual and severe-to-profound hearing loss. Forty-seven patients (73.4%) underwent cochlear implantation surgery and showed successful outcomes; approximately 85-90% of the patients showed a hearing level of 20-39 dB with cochlear implant and a Categories of Auditory Performance (CAP) scale level 6 or better. Although truncating mutations and p.Arg1939Gln were clearly related to severe phenotype, almost half of the patients with one or more non-truncating mutations showed mild-to-moderate hearing loss. Notably, patients with p.His513Arg, p.Ile1573Thr and p.Glu1910Lys showed "true" auditory neuropathy-like clinical characteristics. In this study, we have clarified genotype-phenotype correlation and efficacy of cochlear implantation for OTOF-related hearing loss patients in the biggest cohort studied to date. We believe that the clinical characteristics and genotype-phenotype correlation found in this study will support preoperative counseling and appropriate intervention for OTOF-related hearing loss patients.

Exposure of female NZBWF1 mice to imiquimod-induced lupus nephritis at an early age via a unique mechanism that differed from spontaneous onset.

Systemic lupus erythematosus (SLE) is a chronic inflammatory and representative autoimmune disease. Extremely complicated and multifactorial interactions between various genetic factors and individual susceptibility to environmental factors are involved in the pathogenesis of SLE. Several studies have reported that mutation and activation of toll-like receptor (TLR) 7 are involved in the onset of autoimmunity, including SLE. Thus, we investigated the response of SLE-prone mice to continuous environmental factors, particularly TLR7 agonist exposure, and changes in their phenotypes. Female and male NZBWF1 (BWF1) mice were treated from 20 weeks of age with a TLR7 agonist, imiquimod (IMQ), 3 times weekly for up to 12 weeks. IMQ-exposed female BWF1 mice showed worsened lupus nephritis. However, autoantibody production was not enhanced in IMQ-exposed female BWF1 mice. The Th1 cytokine expression was upregulated in the kidney of IMQ-treated mice. In IMQ-exposed BWF1 mice, neutralization of IFN-γ suppressed early-phase lupus nephritis. Additionally, in male BWF1 mice IMQ exposure induced minor aggravation of lupus nephritis. These results suggest that the induction of aggravated lupus nephritis by TLR7 agonist exposure was related to the expression of IFN-γ via acute TLR7 signal-induced renal inflammation, and that the involvement of genetic factors associated with a predisposition to SLE is also essential. Thus, the activation of TLR7 signaling by exposure to environmental factors may upset the balance of factors that maintain SLE remission. We hypothesize that the inhibition of TLR7 signaling and IFN-γ signaling is effective for preventing the onset and flare and maintaining remission of lupus nephritis.

Metformin repositioning in rheumatoid arthritis.

OBJECTIVES: Metformin is a known therapeutic agent for diabetes. Recently, several reports suggested the possibility of improvement in autoimmune disease and malignancy conditions through the effect of metformin on the immune system. Although there have been reports on the therapeutic effects of metformin on mouse models of collagen-induced arthritis, simulating human rheumatoid arthritis (RA), the effect of metformin on human RA remains unknown. Therefore, we investigated the inhibitory effect of metformin on the pathogenesis of human RA in vitro. METHODS: Osteoclastogenesis was evaluated with or without metformin. through tartrate-resistant acid phosphatase staining, osteoclast-specific enzyme expression analysis, and a bone resorption assay. Human fibroblast-like synoviocyte MH7A cells were stimulated with TNF-α, and the expression of proinflammatory cytokines and protease and growth factor genes was evaluated with or without metformin. Metformin has been used to evaluate their potential modulatory effects on cells treated with TNF-α. Moreover, we examined angiogenesis by performing a tube formation assay using human umbilical vein endothelial cells (HUVECs) with or without metformin. RESULTS: Osteoclastogenesis was suppressed in the presence of metformin, and the expression of osteoclast-specific genes was reduced. The TNF-α-induced expression of inflammatory cytokines and protease and growth factor genes in MH7A cells was downregulated by metformin. Additionally, the induced formation of tubular networks in HUVECs was also disrupted following treatment with metformin. CONCLUSIONS: These results suggest that metformin might improve the pathogenesis of RA, including joint inflammation and destruction. Thus, metformin might be utilised as a potential therapeutic agent in the treatment of RA.

Effects of Protective Measures against COVID-19 on Auditory Communication for People with Hearing Loss.

WHO has recommended various measures to combat the COVID-19 pandemic, including mask-wearing and physical distancing. However, these changes impair communication for individuals with hearing loss. We investigated the changes in auditory communication associated with COVID-19 measures in 269 patients (male: 45.7%, female: 54.3%, median age: 54 y.o.). Most patients with hearing loss had difficulty engaging in auditory communication with people wearing masks, especially in noisy surroundings or with physical distanc-ing. These difficulties were noticeable in patients with severe hearing loss. Developing communication support strategies for people with hearing loss is an urgent need while COVID-19 measures are in place.

Genetic Counseling of a Hearing-impaired Patient with Multiple Genetic Mutations.

Since April 2012, genetic testing for congenital hearing loss is covered by the public health insurance in Japan. Recent (since August 2015) developments in next-generation sequencing technology have enabled the detection of 154 mutations in 19 genes. Genetic testing provides valuable information on hearing phenotype, prognosis, and prediction of associated symptoms. We report a hearing-impaired patient in whom multiple genetic mutations were detected. This patient carries two missense mutations in GJB2 (p.G45E, p.Y136X), as well as a mitochondrial mutation (7445A>G). Since the number of genes detectable by genetic testing has increased, the diagnosis of hearing loss can be made with greater accuracy. However, it is often difficult to clinically understand and interpret the genotype information, especially when multiple gene variants are detected in one patient or family. Genetic counseling plays an important part in the intervention for or follow-up of such patients. Genotypic and phenotypic information of other family members is necessary, so that both the patient and the family can understand and accept the results of genetic testing.

Comparison of incidence of hyponatremia between intranasal and oral desmopressin in patients with central diabetes insipidus.

Central diabetes insipidus (CDI), which is characterized by polyuria and polydipsia, is caused by a deficiency of the antidiuretic hormone arginine vasopressin (AVP). While CDI is treated with desmopressin, an analogue of AVP, the intranasal formulation is inconvenient and CDI patients reportedly prefer the oral formulation to the intranasal one. In Japan, intranasal desmopressin had been the only formulation for the treatment of CDI until 2012, when the desmopressin orally disintegrating tablet (ODT) was approved for treatment. In this study we analyzed 26 patients with CDI in whom intranasal desmopressin was switched to desmopressin ODT. The mean daily dose of intranasal desmopressin was 10 ± 8 µg/day, and that of desmopressin ODT was 142 ± 59 µg/day. The mean serum sodium levels were 140 ± 5 mmol/L and 140 ± 3 mmol/L with intranasal desmopressin and desmopressin ODT, respectively, and there were no significant differences between these values. The frequency of hyponatremia (<135 mmol/L) with intranasal desmopressin was 11.7% and that with desmopressin ODT was 7.6%, while the frequency of hyponatremia (<130 mmol/L) with intranasal desmopressin was 4.2% and that with desmopressin ODT was 1.3%. Statistical analyses revealed that incidence of hyponatremia was significantly decreased after the switch to desmopressin ODT. Thus, it is suggested that water balance is better controlled with desmopressin ODT than with intranasal desmopressin in patients with CDI.

[Assessment of hearing aid outcome using CADL].

The presence of hearing impairment deteriorates patients' quality of life by affecting their daily-life communication. Several self-report assessments are available to evaluate the subjective outcome of hearing aids, however, the procedures to evaluate the impairment of communication induced by hearing impairment has not been well established. A PC-recorded audio file prepared to evaluate the communication ability of hearing aid users, by extracting fifteen spoken language items from the Communication ADL Test: sp-CADL. A before and after study was performed among the hearing aid users who were attending Okayama University Hospital to evaluate the improvement in each of the 15 sp-CADL scores. Twenty-one adults were included in this study whose age ranged from 22 to 83 years old (mean: 56.7 years old). The total and individual scores of the sp-CADL improved significantly after the use of the hearing aids (p < 0.05). The total sp-CADL score of the patients with hearing aids showed a good correlation with the best scores of the speech discrimination test measured before wearing hearing aids.

[The age at which the grade of Special Child Dependent's Allowance Act can be judged in the case of deaf children].

The spread of neonatal hearing screening has made the identification of hearing loss in early childhood possible, and most of the children with hearing loss are diagnosed and provided with early intervention within several months after their birth. However, they have to wait to receive the Special Child Dependent's Allowance until their hearing levels are evaluated with audiometers. Under the Special Child Dependent's Allowance Act now in force, a delay of several years occurs for those children before they can receive the allowance after diagnosis. We retrospectively reviewed hearing test results of children who had not reacted at 90dBnHL bilaterally in ABR within 12 months after birth, and examined when those results were certain enough to determine their allowance eligibility. We found that the eligibility in children with hearing loss alone could be determined at 1 year of age; as for children who had other disorders, since it was mostly difficult to test them with an audiometer, the diagnosis of hearing loss must always be made carefully but it was also possible to determine the eligibility for the allowance at 1 year of age.

Optimal time of starting tocilizumab in acute phase of adult-onset Still's disease and comparison of its efficacy with that of methotrexate: a case series and a review of the literature.

Adult-onset still's disease is a rare condition that is generally treated by glucocorticoids. Importantly, due to the limited established treatments, glucocorticoid-refractory cases are particularly difficult to treat. Between December 2009 and August 2022, nine patients with adult-onset Still's disease were treated with tocilizumab (tocilizumab group). The therapeutic efficacy and safety of tocilizumab initiation in the acute phase were evaluated in cases of initial onset and recurrence. We also compared the efficacy of tocilizumab with that of methotrexate (methotrexate group, n = 13), which has been the drug of choice for adjunctive therapy. Tocilizumab demonstrated the expected efficacy in all four patients who received it at relapse and in three of the five patients who received it at the initial onset. However, two patients developed macrophage activation syndrome following treatment. A comparison of treatment effects between the methotrexate and tocilizumab groups revealed that the ferritin and C-reactive protein levels, severity score, and glucocorticoid doses decreased over time in both groups; nonetheless, the tocilizumab group experienced a more stable effect. Tocilizumab is undoubtedly a valuable treatment option for adult-onset Still's disease, especially when administered at relapse. This suggests that it shows both high safety and good efficacy. Nevertheless, a larger sample size is required to validate the efficacy and safety of tocilizumab compared with those of the existing alternatives. Key Points • We examined the significance of TCZ in terms of therapeutic efficacy, reduction in glucocorticoid usage, and safety in patients with AOSD. • We compared the therapeutic efficacy of TCZ with that of MTX, which is often used to treat glucocorticoid-resistant AOSD. • TCZ is undoubtedly a valuable treatment option for AOSD, especially when administered at relapse, suggesting both high safety and good efficacy.

Investigation of the effects of Bipolar Radiofrequency Energy on the Structural Morphology of Dental Plaque.

OBJECTIVES: To investigate the effects of radiofrequency (RF) energy, applied through a power toothbrush, on the structural morphology of dental plaque and its bacteria components. Previous studies showed that a toothbrush powered by RF (ToothWave) effectively reduces extrinsic tooth stains, plaque, and calculus. However, the mechanism by which it reduces dental plaque deposits is not fully established. MATERIALS AND METHODS: Multispecies plaques at sampling time points of 24, 48, and 72 hours were treated with the application of RF using ToothWave with the toothbrush bristles 1 mm above the plaque surface. Groups that underwent the same protocol but without RF treatment served as paired controls. Confocal laser scanning microscope (CLSM) was used to determine cell viability at each time point. Plaque morphology and bacteria ultrastructure were viewed using scanning electron microscope (SEM) and transmission electron microscope (TEM), respectively. STATISTICAL ANALYSIS: Data were analyzed statistically using analysis of variance (ANOVA) and Bonferroni post-tests. RESULTS: At each time, RF treatment significantly (p < 0.05) reduced the viable cells in plaque and caused a substantial disruption of plaque morphology, while the untreated plaque had intact morphology. Cells in treated plaques showed disrupted cell walls, cytoplasmic material, huge vacuoles, and heterogeneity in electron density, while these organelles remained intact in untreated plaques. CONCLUSION: The application of RF via a power toothbrush can disrupt plaque morphology and kill bacteria. These effects were enhanced by the combined application of RF and toothpaste.

Caries preventing efficacy of new Isomalt-containing mouthrinse formulations: a microbial study.

OBJECTIVES: The effectiveness of an Isomalt-containing mouthrinse to prevent caries development was investigated. METHODS: Human enamel blocks were randomly assigned to five groups (n = 30/group): De-ionized distilled water (DDW), and mouthrinse containing either (IFC) 1% Isomalt, 225 ppm fluoride, and 0.05% cetylpyridinium chloride (CPC), (IF) 1% Isomalt and 225ppm fluoride, (FC) 225 ppm fluoride and 0.05% CPC or (F) 225 ppm fluoride. During 7-day demineralization in a Microbial Caries Model, mouthrinses were applied once daily for 1 min. Demineralization was assessed using Surface Microhardness testing for percentage change in SMH (%ΔSMH) and Transverse Microradiography for mineral loss (ΔZ). Data analysis (α = 0.05) used paired t-test (Intra-group comparison using SMH) and ANOVA/Tukey's for inter-group comparisons (%ΔSMH and ΔZ). RESULTS: With SMH, relative to sound enamel baseline, demineralization was significant (P < 0.001) in all groups, except in IFC. Intergroup comparison with %ΔSMH showed significantly (p < 0.001) greater demineralization in DDW compared to other groups, and in IF, FC, and F compared to IFC (P < 0.001). With ΔZ, relative to DDW, all groups significantly (p < 0.0001) inhibited demineralization at varying percentages. CONCLUSIONS: Mouthrinse containing Isomalt, fluoride, and CPC inhibited demineralization amidst cariogenic biofilm; thus, highlighting its potential as a more effective caries control tool than mouthrinse with only fluoride.

Exploration of tumor size measurement methods in preoperative breast cancer assessment using whole-body silicon photomultiplier PET: feasibility and first results.

PURPOSE: Whole-body silicon photomultiplier positron emission tomography (WB SiPM PET) could be used to diagnose breast cancer spread before lumpectomy. We aimed to investigate the method of measuring the tumor size by WB SiPM PET as a basis for diagnosing breast cancer spread in the breast. MATERIALS AND METHODS: We retrospectively reviewed 35 breast cancer lesions in 32 patients who underwent WB SiPM PET/CT in the prone position as preoperative breast cancer examinations from September 2020 to March 2022. In all cases, a 20-mm spherical VOI was placed in the normal mammary gland to measure the mean standardised uptake value (SUVmean) and the standard deviation (SD) of 18F-fluorodeoxyglucose (FDG) uptake. We prepared four types of candidates (SUVmean + 2 SD, SUVmean + 3 SD, 1.5 SUVmean + 2 SD, 1.5 SUVmean + 3 SD) for thresholds for delineating tumor contours on PET images. On the semiautomatic viewer soft, the maximum tumor sizes were measured at each of the four thresholds and compared with the pathological tumor sizes, including the extensive intraductal component (EIC). RESULTS: The lesion detection sensitivity was 97% for WB SiPM PET. PET detected 34 lesions, excluding 4-mm ductal carcinomas in situ (DCIS). PET measurements at the '1.5 SUVmean + 2 SD' threshold demonstrated values closest to the pathological tumor sizes, including EIC. Moreover, '1.5 SUVmean + 2 SD' had the highest concordance (63%). CONCLUSIONS: The study demonstrated that among various PET thresholds, the '1.5 SUVmean + 2 SD' threshold exhibited the best performance. However, even with this threshold, the concordance rate was limited to only 63%.

Imaging α-synuclein pathologies in animal models and patients with Parkinson's and related diseases.

Deposition of α-synuclein fibrils is implicated in Parkinson's disease (PD) and dementia with Lewy bodies (DLB), while in vivo detection of α-synuclein pathologies in these illnesses has been challenging. Here, we have developed a small-molecule ligand, C05-05, for visualizing α-synuclein deposits in the brains of living subjects. In vivo optical and positron emission tomography (PET) imaging of mouse and marmoset models demonstrated that C05-05 captured a dynamic propagation of fibrillogenesis along neural pathways, followed by disruptions of these structures. High-affinity binding of 18F-C05-05 to α-synuclein aggregates in human brain tissues was also proven by in vitro assays. Notably, PET-detectable 18F-C05-05 signals were intensified in the midbrains of PD and DLB patients as compared with healthy controls, providing the first demonstration of visualizing α-synuclein pathologies in these illnesses. Collectively, we propose a new imaging technology offering neuropathology-based translational assessments of PD and allied disorders toward diagnostic and therapeutic research and development.

A 68-year-old phenotypically male patient with 21-hydroxylase deficiency and concomitant adrenocortical neoplasm producing testosterone and cortisol.

The steroidogenic enzyme 21-hydroxylase is necessary for the synthesis of both glucocorticoids and mineralocorticoids. 21-hydroxylase is a cytochrome P-450 enzyme and is encoded by the gene CYP21A2. Here we report a 68-year-old phenotypically 'male' but genetically female patient with 21-hydroxylase deficiency (21OHD) and the concomitant virilizing adrenocortical carcinoma. This patient grew up as a male and has not encountered any episodes of adrenal insufficiency without glucocorticoid replacement in his lifetime. A chromosome test at admission, however, identified the 46, XX karyotype, and serum 17-hydroxyprogesterone and urine pregnanetriolone and 11ß-hydroxyandrostendione were all elevated, consistent with 21OHD. Moreover, serum testosterone was 1.90 ng/ml, much higher than the female standard levels, and serum cortisol was 5.7 µg/ml, slightly lower than standard levels. Genetic analysis identified the patient as a heterozygote of the two pathogenic mutations in the CYP21A2 gene: IVS2-13C(A)>G and R356W. Magnetic resonance imaging (MRI) revealed the presence of left adrenal tumor measuring 6 cm, which was subsequently diagnosed as adrenocortical carcinoma based on the criteria of Weiss. Immunohistochemical analysis of the tumor specimens revealed the expression of various enzymes involved in testosterone production, including 3ß-hydroxysteroid dehydrogenase, 17α-hydroxylase/17,20-lyase, and 17ß-hydroxysteroid dehydrogenase. Importantly, the expression of immunoreactive 21-hydroxylase was detected in these tumor cells. The levels of adrenal tumor-derived steroid metabolites were all markedly decreased following the surgery. This is the first report on a virilized 21OHD patient associated with the adrenocortical tumor that produces testosterone. Moreover, the concomitant adrenocortical tumor may ameliorate adrenocortical insufficiency by producing cortisol.

A case of breast cancer: Suppression of lactation-related FDG uptake 2 days after cabergoline administration.

We present a case of a 35-year-old woman with breast cancer in lactation 3 months after childbirth, in which a lactation inhibitor was useful for 18F-FDG PET/CT examination. Via ultrasonography and biopsy with histopathology, we diagnosed the lesion in the upper region of the left breast as invasive ductal carcinoma. She stopped breastfeeding and was administered cabergoline to suppress lactation. Two days after the administration, 18F-FDG PET/CT revealed segmental uptake (10 cm in diameter) and no lactation-related uptakes. Dynamic MRI also revealed a segmental enhancement of the same size as 18F-FDG PET/CT. The lactation inhibitor was useful to delineate the extent of the lesion during the 18F-FDG PET/CT examination.

Evaluation of a novel caries detecting oral rinse.

AIM: LumiCare™ Caries Detection Rinse (LC Rinse), a starch-based rinse, illuminates active initial caries (positive response) using dental curing light, thus augmenting the dentist's visual examination. This clinical study investigated if active caries as assessed by the International Caries Detection and Assessment System (ICDAS) were more likely to have positive LC Rinse response than sound surfaces and inactive caries. METHODS: 25 subjects participated in the study. Caries was assessed on selected teeth and the entire dentition, firstly using ICDAS and then by fluorescence evaluation after LC Rinse application. Data were statistically analyzed using Diagnostic Odds Ratio (OR) and Chi-square test X2 (α = 0.05). Sensitivity (Se), specificity (Sp), and Diagnostic accuracy (DA) were calculated. RESULTS: With selected teeth, active caries were 638.6 times (60.05 with full dentition) more likely to have positive LC Rinse response than sound surfaces and inactive caries combined (X2, p < 0.01) and 191.67 times (18.35 with full dentition) than inactive lesions only (X2, p < 0.01). With combined sound surfaces and inactive caries, Se, Sp, and DA of LC Rinse assessment were 0.94, 0.98, and 0.96 respectively. CONCLUSIONS: LC Rinse can distinguish between active caries, inactive caries and hypomineralization, and can augment caries detection with high sensitivity, specificity, and diagnostic accuracy.

Morphological and Elemental Evaluation of Investigative Mouthwashes to Repair Acid-Eroded Tooth Surface.

Purpose: Erosive tooth wear (ETW) is characterized by subsurface demineralization and tooth substance loss with crater formation. Remineralization of subsurface demineralization has previously been demonstrated; however, repair of the eroded surface is still under investigation. This study investigated the effectiveness of mouthwashes containing hydrolyzed wheat protein (HWP) in repairing ETW through promotion of organized crystal growth. Methods: Enamel Erosion was created on 210 enamel blocks by 10-minute demineralization in 1% Citric Acid (pH 3.5). Then, blocks were randomly assigned to seven groups (30/group); (A) 0.2% HWP, B) 1% HWP, (C) 2% HWP, (D) 1% HWP + 0.05% NaF, (E) Listerine™ mouthwash, (F) 0.02% NaF Crest™ Pro-health mouthwash and (G) artificial saliva (AS) only. Groups were subjected to daily pH-cycling consisting of one 5-minute erosive challenge with citric acid, three 1-minute mouthwash treatment periods, and then storage in AS for the rest of the time for 28 days. Treatment effects were assessed using SEM-EDX. Statistical analysis was by ANOVA and Tukey's multiple comparison. Results: In groups exposed to HWP-containing mouthwashes, there was growth of fiber-like crystals that increased in packing density in a dose-dependent manner (0.2%, 1%, 2%) on the eroded enamel surfaces, with increased calcium and phosphate contents on the treated surfaces. The non-HWP-containing groups had the eroded surfaces covered by structureless deposit layer firmly attached to the surface. Conclusion: Treating eroded enamel surface with HWP-containing mouthwash resulted in repair of the damaged tissue by formation of a protective layer of crystal deposits within and on the eroded enamel tissue.