Historical Reflections on the Use of Internal Bleaching to Manage Discolored Teeth.

The process of internal bleaching of discolored teeth has been with us for well over 150 years, during which time both materials and procedures varied significantly. The etiology of tooth discoloration also reflected on a wide range of philosophies and causes, which lent itself to many trials and errors in management. Both success and failure characterized the achievements attained by our forefathers in managing this esthetic challenge, as years ago tooth extraction was often the first pathway chosen.

[Green tooth discoloration in a two-year-old boy]. / Groene tandverkleuring bij een peuter.

Green tooth discoloration can have several causes. From the patient history of the two-year-old with green tooth discoloration clear causal relationships can be identified. The pathological cause is an increase in bilirubin levels for an extended period of time. Determining the extent of tooth development in combination with the increase in bilirubin levels makes it possible to estimate the degree and pattern of green tooth discoloration. If the increase in bilirubin levels is short-lived, it is possible the permanent dentition will not be affected.

[Transient pink tooth discoloration during orthodontic treatment]. / Voorbijgaande roze coronale verkleuring van een gebitselement tijdens orthodontische behandeling.

A healthy adult male patient presented himself, 11 days after a fixed orthodontic appliance was placed, with a sudden pink discoloration of the dental crown of tooth 21. The emergency dentist on call diagnosed the discoloration as non-painful peri-apical periodontitis, partly on the basis of a radiograph, and recommended endodontic treatment of tooth 21. Prior to endodontic treatment, the patient was first seen by the orthodontist who had initiated treatment. Tooth 21 was investigated and reacted normally to percussion and palpation but did not react to the cold test. The patient was referred to an endodontist who made the likely diagnosis: 'Transient apical breakdown'. No endodontic treatment was carried out and the orthodontic treatment was not interrupted. Six weeks after the discoloration appeared, visible recovery was evident.

The Effect of Silver Diamine Fluoride in Preventing Caries in the Primary Dentition: A Systematic Review and Meta-Analysis.

OBJECTIVES: To investigate whether silver diamine fluoride (SDF) is effective in preventing new caries lesions in primary teeth when compared to placebo or active treatments. METHODS: Systematic review (CRD42016036963) of controlled clinical trials. Searches were performed in 9 electronic databases, 5 registers of ongoing trials, and reference lists of identified review articles. Two researchers carried out data extraction and quality appraisal independently. The primary outcome was the difference in caries increment (decayed, missing, and filled surfaces or teeth - dmfs or dmft) between SDF and control groups. These differences were pooled as weighted mean differences (WMD) and prevented fractions (PF). RESULTS: Searches yielded 2,366 unique records; 6 reports of 4 trials that randomized 1,118 and analyzed 915 participants were included. Two trials compared SDF to no treatment, 1 compared SDF to placebo and sodium fluoride varnish (FV), and 1 compared SDF to high-viscosity glass ionomer cement (GIC). All studies had at least 1 domain with unclear or high risk of bias. After 24 months of follow-up, in comparison to placebo, no treatment, and FV, SDF applications significantly reduced the development of new dentin caries lesions (placebo or no treatment: WMD = -1.15, PF = 77.5%; FV: WMD = -0.43, PF = 54.0%). GIC was more effective than SDF after 12 months of follow-up but the difference between them was not statistically significant (WMD, dmft: 0.34, PF: -6.09%). CONCLUSION: When applied to caries lesions in primary teeth, SDF compared to no treatment, placebo or FV appears to effectively prevent dental caries in the entire dentition. However, trials specifically designed to assess this outcome are needed.

Quality of life and stability of tooth color change at three months after dental bleaching.

PURPOSE: Intracoronary bleaching is a minimally invasive, alternative treatment that addresses aesthetic concerns related to non-vital teeth discoloration. However, to the best of our knowledge, no studies have assessed the psychosocial impacts of such procedures on patients' aesthetic perceptions. The aim of this study was to evaluate aesthetic perceptions and the psychosocial impact of patients up to 3 months after their teeth had been bleached with hydrogen peroxide (35%) and carbamide peroxide (37%) using the walking bleach technique. METHODS: The patients were randomly divided into two groups according to the bleaching agent used: G1 = hydrogen peroxide 35% (n = 25) and G2 = carbamide peroxide 37% (n = 25). Non-vital bleaching was performed in four sessions. Color was objectively (ΔE) and subjectively (ΔSGU) evaluated. Aesthetic perception and psychosocial factors were evaluated before, 1 week and 1 month after the bleaching using the Oral Health Impact Profile (OHIP) and Psychosocial Impact of Dental Aesthetics Questionnaire (PIDAQ) questionnaires. RESULTS: The color change (ΔE) values at 1 month were G1 = 16.80 ± 6.07 and G2 = 14.09 ± 4.83. These values remained stable until the third month after treatment (p > 0.05). There was a decrease in the values of OHIP-aesthetics and PIDAQ after treatment versus baseline (p < 0.05). This status was maintained through the third month after treatment. CONCLUSIONS: Both agents were highly effective and had a positive impact on the aesthetic perception and psychosocial impact of patients, values that also remained stable over time. Non-vital bleaching yields positive and stable impacts on aesthetic perception and psychosocial factors. ClinicalTrials.gov identifier NCT02718183.

Effect of Glutathione Bio-Molecule on Tooth Discoloration Associated with Silver Diammine Fluoride.

This study evaluated the effect of Glutathione (GSH) bio-molecule on the reduction of enamel and dentin discoloration after application of 38% silver diammine fluoride solution (SDF). One hundred and twenty bovine teeth specimens were used. The enamel and dentin specimens were divided into three groups: (1) SDF only (control); (2) SDF followed by application of a potassium iodide solution (KI); and (3) SDF mixed with 20% GSH. Half the specimens were exposed to light and the remainder kept in dark conditions (n = 10) Color changes were measured using a spectrophotometer at the following time intervals: before solution application (baseline) and immediately after application, then 3, 6, 24, 48, 72 h, and 7, 10 and 14 days. SEM/EDS analysis was performed on treated enamel and dentin. Statistical analysis was done using a repeated measures ANOVA test. The spectrophotometer results showed that the SDF group exhibited the greatest color changes under both light exposed and dark conditions, while SDF + GSH group was effective in decreasing the color changes in both light and dark conditions. The SDF + KI group showed an insignificant color changes over time. SEM/EDS analysis showed different patterns for the silver crystal formation in each group (SDF, SDF + GSH, and SDF + KI group). It was concluded GSH can effectively minimize color changes after application of SDF, especially on enamel and to a lesser extent on dentin.

Long-term follow-up of enamel color changes after treatment with fixed orthodontic appliances.

INTRODUCTION: The aim of this study was the long-term follow-up of enamel color changes observed in the middle third of buccal tooth surfaces after treatment with fixed orthodontic appliances. METHODS: The study included 120 maxillary central and lateral incisors and canines of 20 subjects who had fixed orthodontic treatment. The Spectro Shade Micro device (MHT, Verona, Italy) was used to evaluate the color changes of the teeth. Measurements were made from the middle third of the buccal surfaces of the teeth after fixed orthodontic treatment and in month 3, month 6, and year 1 of the retention phase. The Commission Internationale de l'Echairage L* a* b* system that expresses the color coordinates in L*, a*, and b* symbols was used to determine the tooth color, and ΔE values between the time periods were calculated. Repeated measurement analysis of variance was used in evaluating the color changes. RESULTS: The increases in ΔL values at 3 months, 6 months, and 1 year after treatment were statistically significant, whereas they were not statistically significant from months 3 to 6, month 3 to year 1, or month 6 to year 1. The decrease in Δa and the increase in Δb values were not statistically significant. ΔE values at all time periods were statistically significant within themselves, and the greatest change was observed 1 year after treatment. ΔE values were 1.52 to 3.57, and a visible but clinically acceptable color change occurred. CONCLUSIONS: In the first 3 months, there was a significant increase in the lightness of the tooth color.

The reproducibility of assessment of white spot lesions adjacent to orthodontic brackets, with a quantitative light induced fluorescence digital camera at different rotations of teeth - an in vitro study.

BACKGROUND: A quantitative light-induced fluorescence digital (QLF-D) camera is able to assess demineralizations adjacent to orthodontic brackets. Rotations of teeth during and the presence of the orthodontic appliances may influence the longitudinal follow-up of such lesions over time. METHODS: Brackets were bonded on extracted teeth: 54 incisors and 31 canines. Demineralizations were formed in vitro directly cervical of the bracket. Images were captured using a QLF-D camera mounted on an optical bench, equipped with a goniometer on a turntable. The teeth were placed in the goniometer simulating buccolingual rotation (0°, 10°, 20°), the turn-table was used for mesiodistal rotations (0°, 10°, 20°). Standardized QLF-D images were made before (with and without a wire) and after debonding at combinations of aforementioned angles of rotation. The image after debonding at 0° buccolingual and 0° mesiodistal rotation served as a control. RESULTS: The presence of a bracket resulted in a significantly higher fluorescence loss, yet a smaller lesion area (p < 0.05) in comparison to the control. A significant higher fluorescence loss was seen for rotations towards lingual relative to the 0° buccolingual and 0° mesiodistal rotation, while the effect was less explicit towards buccal. CONCLUSIONS: Fluorescence loss and lesion size are influenced by the angle of rotation under which the demineralization is photographed. The full extent of demineralizations is only apparent after debonding when photographed at rotations of 0° mesiodistal and up to 20° buccal. Precaution must be taken into account assessing demineralizations of patients undergoing treatment with fixed appliances when using a QLF-D camera.

[Staining effect of bovine incisors in vitro by tea solutions].

OBJECTIVE: To determine the optimum staining condition of tea solutions on bovine incisors in vitro, by comparing the color stability of tooth surface of different concentrations of tea solutions and methods on bovine incisors in vitro. METHODS: Twenty bovine incisors with color surface A1 were chosen, then randomly divided into 4 groups (n=10). Group 1: soaked with 2% tea solution continuously for 6 days; group 2: soaked with 2% tea solution for 6 days, but changed fresh tea solution everyday; group 3: soaked with 1% tea solution continuously for 6 days; group 4: soaked with 1% tea solution for 6 days but fresh tea solution changed every day. After 6 days of staining, the surface color (Δ E value) of all the samples were measured with crystal eye. After brushing 30 times with toothbrushes, the color of bovine incisors were measured again. Then the samples were soaked in artificial saliva at 37 ° C, and Δ E value was measured for 14 days. RESULTS: After staining for 6 days, the Δ E values of the 2% tea solution groups were better than those of the 1% groups (20.21 vs. 16.44, 24.09 vs. 19.22, P<0.05); the groups with the same tea solution concentration, a better result was observed for the group soaked with daily fresh tea solution than for the group that experienced continuous staining (24.09 vs. 20.21, 19.22 vs. 16.44, P<0.05). Groups 1 and 2 were selected for subsequent brushing experiments. The color of both groups became lighter after brushing, and a better result was observed for the continuous staining group than for the group stained in daily fresh solution (3.06 vs. 9.51, P<0.05). The samples with better coloring effect soaked with 2% tea solution continuously for 6 days were put into artificial saliva for 14 days. There was not any significant change in coloring at the end of the first two days (1.51 vs. 1.51, P>0.05), and the color was visibly lighter after the third day (1.51 vs. 5.89, P<0.05), and no further significant change was observed until the 14th day (5.81 vs.5.89, P>0.05), which was darker coloring than that of the pre-staining group. CONCLUSION: Continuous staining on bovine incisors with 2% tea solution with subsequent soaking in artificial saliva resulted in consistent coloring from day 3 to day 14, and this method could be used as an ideal model for teeth staining in vitro.

A preliminary study on the relationship between iron and black extrinsic tooth stain in children.

Black extrinsic tooth stain, which has long troubled many people, is common among children and influences the aesthetics of teeth. The pigment was proposed to be a black insoluble ferric compound, but this is controversial. To determine whether iron exists in black stain, we collected 10 samples of black stain and 10 samples of plaque separately from children with and without black stain using sterile titanium implant curettes, and analysed the samples by inductively coupled plasma-mass spectrometry. Iron was present in both black stain and plaque, with concentrations ranging from 76·12 to 1116·88 µg g-1 . The contents of iron in black stain were significantly higher than in plaque. Because bacteria may be involved in the aetiology of black stain, we assessed the functional genes of bacteria in black stain based on 16S rRNA gene sequencing results obtained using Phylogenetic Investigation of Communities by Reconstruction of Unobserved States. Of 253 Kyoto Encyclopedia of Gene and Genomes (KEGG) pathways tested, 56 differed in abundance between samples from children with and without black stain. Genera altered in black stain were related to many of the pathways. Some KEGG Orthology groups showed differences between black stain and plaque of control group were found to be related to iron. SIGNIFICANCE AND IMPACT OF THE STUDY: In this study, we have confirmed the existence of iron in black extrinsic tooth stain by ICP-MS. It was the first time the functional genes of bacteria in black stain were accessed and the genes associated with iron were found. These findings provided clues on the research of aetiology of black stain, which troubled millions of children. It also revealed the association between metabolic pathway of microbiota and oral phenomenon.

Dental intrinsic green pigmentation from primary to mixed dentition: clinical and histological findings.

AIM: The aim of this report is to present a case of a child with green pigmentation of the primary dentition caused by bilirubin elevation due to choleostasis during neonatal life, and the 5-year follow-up. CASE REPORT: The case presented initially with bands of green pigmentation of all primary teeth in a pattern that followed the time of their calcification, with those formed earlier being more severely affected. Fading of the green pigmentation was detected during the follow-up, while erupted lower permanent incisors were normal. Histological findings of an exfoliated primary incisor showed a green line at the enamel-dentine junction with the external surface of the dentine showing a band of variable width and irregularly arranged tubules. CONCLUSION: Bilirubin green pigmentation of primary teeth follows a chronological pattern and its intensity fades with time. Overlying enamel in affected areas may appear thinner.

The effect of immediate and delayed polishing on the color stability of a composite resin.

Polishing techniques are known to enhance the longevity and appearance of composite resin restorations. However, the influence of the timing of polishing on the final results of a restoration is not well documented. The aim of this study was to determine the effect of immediate and delayed polishing on the color stability of a composite resin. Sixty composite resin specimens were fabricated and randomly divided into 2 groups according to immersion solutions: group 1, deionized water (control); and group 2, coffee (as staining solution). The groups were further divided according to polishing time periods (immediate, 1 day, 7 days, 14 days, and 21 days). The polishing was performed by 1 calibrated operator using a sequence of aluminum oxide discs with different granulations. Color measurements were assessed at baseline and after a 48-hour immersion in the assigned medium by a reflection spectrophotometer, according to CIE L*a*b* parameters. The data were submitted to an analysis of variance (ANOVA) and the post hoc Tukey test at a significance level of 0.05. The ANOVA showed that the immersion solutions had a statistically significant difference (α = 0.05) on color stability. The composite resin color stability was not influenced by the timing of polishing, and all subgroups showed clinically unacceptable discoloration after exposure to coffee. Thus, with regard to color stability, the timing of final polishing may be established according to the preferences of the clinician.

Effect of bleaching on color stability and roughness of composite resins aged in staining beverage.

Composite resin properties can be affected by contact with gel during bleaching procedures; however, there is no consensus about the effect of this contact on resin susceptibility to color change. This study aimed to evaluate staining susceptibility and surface roughness changes in 2 composite resins (Filtek Z250 XT and Filtek Z350 XT) after application of bleaching peroxides and storage in different media. Forty-two disc-shaped specimens of each composite were made, polished, and divided into 3 groups according to treatment type (35% hydrogen peroxide, 16% carbamide peroxide, or deionized water as a control group). These groups were subdivided into 2 groups according to immersion media (n = 7): deionized water or red wine. Color and average roughness (Ra) measurements were taken 24 hours after specimen preparation (T0), immediately after bleaching procedures (T1), and immediately after aging (staining; T2). Statistical analyses were performed using 2-way analyses of variance for repeated measurements and the Tukey test (P < 0.05). Bleaching resulted in minimal color change (ΔE* < 1) in all groups. Filtek Z350 XT specimens presented greater mean values of color change. The Ra values did not increase significantly after bleaching procedures or aging (staining) in all groups. Thus, bleaching agents did not significantly change the color or roughness of the composite resins used in this study.

Staining Beverages and Cigarette Smoke on Composite Resin and Human Tooth Fluorescence by Direct Spectrometry.

INTRODUCTION: This study evaluated the fluorescence intensity (FI) of different brands of composite resins (CRs) and compare those values with the FI of human tooth, under the action of cigarette smoke (CI), coffee (CA), and soft drink (CO), measured by direct spectrometry. MATERIALS AND METHODS: A total of 30 specimens of each brand (Filtek Z350, Esthet-X, Amelogen, Durafill) were made. Others 30 tooth specimens (3 mm/diameter) were obtained from human molars using a trephine bur. The specimens were randomly divided into three groups (n = 10), according to substances: CI, CA, CO. The FI was directly measured using an optic fiber associated with a spectrometer and was measured at baseline and after staining. Data were submitted to Kruskal-Wallis, Dunnett, and Dunn tests. RESULTS: Staining influenced FI mean values among CRs and between those with human tooth. Z showed the closest FI mean values of tooth after staining. CONCLUSION: Staining beverages and cigarette smoke negatively influenced on FI of CR and human tooth. CLINICAL SIGNIFICANCE: The study shows darkening treatments influenced on the fluorescent property of the dental tissues and restorative materials according to the direct spectrometry analysis.

Natural reversal of tooth discoloration and pulpal response to testing following removal of a miniscrew implant for orthodontic anchorage: a case report.

AIM: To highlight the reversal of signs suggesting pulpal necrosis following removal of a mini-implant without endodontic intervention. SUMMARY: A 23-year-old woman presented with a class III malocclusion, with crowded and malformed teeth and excessive gingival display. During orthodontic treatment, a Tomas orthodontic miniscrew was placed between the root apices of the maxillary central incisors. This was carried out by an orthodontic specialist who had treated more than 700 patients (with more than 2000 mini-implants) over the past 9 years. After 2 weeks of treatment, the right maxillary central incisor discoloured and did not respond to electrical pulp tests (EPT) but was sensitive to endo-ice. The miniscrew was removed under local anaesthesia. Teeth 11 and 21 were fixed with ligation wire, and glass-ionomer cement (GIC) was added to the occlusal surfaces of the first and second maxillary molars to heighten the occlusion and disclude the maxillary anterior teeth. After 4 months, the colour and pulp reactions to EPT and endo-ice of tooth 11 returned to normal. Because the use of a miniscrew had appeared to damage the pulp, subsequent a conservative orthodontic treatment using, traditional 'J' hooks was used and achieved satisfactory results. After 23 months of orthodontic treatment, the treatment was complete and a 15-month follow-up showed a successful outcome.

Dental patients' perceptions and motivation in smoking cessation activities.

OBJECTIVE: The aim of the present study was to investigate smokers' perceptions of and motivation for smoking cessation activities in dentistry. MATERIALS AND METHODS PATIENTS: who smoked were consecutively recruited from general as well as specialist dental care clinics in Sweden. After a dental visit the patients completed a questionnaire about self-perceived oral health, smoking habits, motivation, reasons to quit and not to quit smoking, support to quit, smoking cessation activities and questions about smoking asked by dentists and dental hygienists. RESULTS: The sample consisted of 167 adult patients (≥ 20 years) who smoked daily. During the last 6 months, 81% of the patients had experienced oral health problems. The most common complaints were discolourations of the teeth, periodontal problems and dry mouth (38%, 36% and 33%, respectively). Improved general health was a major reason to quit smoking (89%). It was also stated that it was important to avoid oral health problems. 71% of the patients preferred to quit by themselves and 16% wanted support from dentistry. High motivation to quit smoking was reported by 20%. Occurrence of periodontitis during the last 6 months was significantly associated with being highly motivated to stop smoking (OR = 3.0, 95% CI = 1.03-8.55). CONCLUSIONS: This study revealed that, although it was important to quit smoking to avoid oral health problems, the patients were not aware that tobacco cessation activities can be performed in dentistry. Periodontal problems seem to be the most motivating factor among the patients who were highly motivated to stop smoking.

The post-traumatic colour change of primary incisors: a colourimetric and longitudinal study.

BACKGROUND: Tooth colour change after trauma has been described subjectively as ranging from yellow/pink to grey/black. AIM: To investigate the longitudinal colourimetric change of post-traumatic discoloured primary incisor using an intraoral colourimeter. DESIGN: A total of 34 primary incisors from 15 boys and eight girls were studied. The mean post-injury day during clinic visits (SD) and number of visit was 205.4 (194.8) and 3.9 (2.0). CIE L* (lightness), a* (green-red) and b* (blue-yellow) of the maxillary primary incisors were measured at every visit. The colour difference (ΔE*ab ) was calculated between the traumatized tooth and the control. Scatter graphs were made depicting the colour change of discoloured teeth and the ΔE*ab over time. RESULTS: Mean CIE L*, a* and b* of the unaffected control were 80.8 (2.29), 0.9 (0.77) and 13.1 (2.67), respectively. L* gradually decreased to 70.7 (on day 71), then slowly recovered. a* increased to 3.7 (day 29) and decreased slowly. b* only demonstrated a small change that was within the control range during the follow-up. ΔE*ab increased to 9.58 (day 56) and decreased slowly. CONCLUSION: The earlier recovery of a* was followed by the recovery of L*. During the post-traumatic period, ΔE*ab failed to reach the clinically acceptable threshold.

Adverse effects of orthodontic treatments.

Orthodontic therapy, like any other medical intervention, in addition to its benefits carries the risk of potential complications and is associated with adverse effects-including periodontal problems, external root resorptions, pulpal changes, enamel damages (demineralization, discoloration, attrition), temporomandibular disorders, infective endocarditis, soft tissue damages, discomfort, pain and the risk of either aspiration or indigestion of medical instruments and appliances. Usually these effects are multifactorial in origin- most often a result of interactions between the patient, the dental practitioner and the technical aspects of the appliances or techniques. With preventive measurements and care, most of these complications can be either limited or completely avoided. Therefore, every dental practitioner must be fully aware of these effects and associated risk factors in order to maximize the treatment outcome. The present review aims to summarize these effects of orthodontic therapies, and provide a detailed description of factors and preventive measures, in order to minimize these damages.

Long-term clinical and radiographic follow up of subluxated and intruded maxillary primary anterior teeth.

AIMS: This study aimed to determine the kinds of sequelae resulting from intrusive luxation and subluxative injuries in primary anterior teeth as well as the timing of such sequelae. MATERIALS AND METHODS: In this longitudinal retrospective study, data were collected from dental records and radiographs of patients with traumatic dental injury (TDI) treated at the Centre for the Study and Treatment of Dental Trauma in Primary Dentition (Pelotas, RS, Brazil). Fifty-two children, with seventy intruded teeth, and 76 children, with 99 subluxated teeth, met the inclusion criteria. Sequelae, such as crown discoloration, fistula, pulp canal obliteration (PCO), inflammatory root resorption (IRR), and internal root resorption, were investigated. The data on the sequelae were distributed into eight follow-up periods: 0-30 days, 31-90 days, 91-180 days, 181-365 days, 1-2 years, 2-3 years, 3-4 years, and >4 years. RESULTS: The sample comprised 99 subluxation cases and 70 intruded teeth. Crown discoloration was the most prevalent sequelae. Among the subluxated teeth, <50% of IRR, fistula, crown discoloration, and PCO occurred within 180 days after TDI; however, the sequelae were also diagnosed after longer periods. Majority of sequelae of intrusion were diagnosed within the 181-365 days and 1-2 years periods but were also observed after more than 4 years of follow up. CONCLUSIONS: For both intrusion and subluxation, trauma sequelae were diagnosed even after the 3-4 years of follow-up.

Teeth whitening versus the influence of extrinsic factors on teeth stains.

The improvement of teeth colour is the effect of using whitening toothpastes, professional removal of dental deposits, pulpless teeth and vital teeth whitening. The aim of the study was evaluation of various methods of teeth whitening in relation to sex and age of the investigated as well as the extrinsic factors causing teeth stains such as cigarette smoking, consumption of coffee and tea. Questionnaire survey was conducted in the group of 204 patients, reporting for a dental treatment at the Chair and Department of Conservative Dentistry with Endodontics of the Medical University of Lublin as well as private dental practice in Lublin. Questionnaire survey was elaborated for the needs of the planned investigation and included questions concerning, among others, socio-demographic data of the investigated, methods of teeth whitening, cigarette smoking, consumption of coffee and tea. Statistic analysis was performed with the use of descriptive statistics, Chi2 test, Mann-Whitney test. The values of p < 0.05 were considered statistically essential. Women used whitening toothpastes more frequently in comparison with men (χ2 = 7.96, p < 0.01). People who declared drinking at least one coffee cup used whitening toothpastes more frequently in comparison with the people drinking coffee occasionally and those who didn't drink it (χ2 = 9.99, p < χ0.05).