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 Table of Contents  
ORIGINAL ARTICLE
Year : 2022  |  Volume : 29  |  Issue : 2  |  Page : 161-166

Are there associations between the occurrence of dental fluorosis and the experience of dentine hypersensitivity? A cross-sectional study


1 Department of Restorative Dentistry, University of Maiduguri Teaching Hospital, Maiduguri, Borno State, Nigeria
2 Department of Restorative Dentistry, Faculty of Dentistry, Bayero University, Kano, Nigeria
3 Department of Restorative Dentistry, Obafemi Awolowo University Teaching Hospital Complex, Ile Ife, Nigeria

Date of Submission08-Jan-2022
Date of Decision14-Mar-2022
Date of Acceptance23-Mar-2022
Date of Web Publication23-Apr-2022

Correspondence Address:
Paul Ikhodaro Idon
Department of Restorative Dentistry, University of Maiduguri Teaching Hospital, Maiduguri, Borno State
Nigeria
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/npmj.npmj_7_22

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  Abstract 


Objectives: Associations between the occurrence of dentine hypersensitivity (DH) and dental fluorosis (DF) have been suggested. Testing this association requires studies among populations with both conditions. This study aimed to determine the association between DF and the experience of DH among a population endemic for DF. Methods: This was a cross-sectional study conducted in 2021 over 6 months among 428 adult patients. Participants' demographics were collected, followed by verbal screening for DH and oral examinations. Clinical assessment for DH was carried out by tactile and evaporative methods. The presence and severity of DF were also assessed using the Thylstrup and Fejerskov Index. Data analysis included Chi-square and correlation statistics to assess the presence and strength of associations. Results: The overall prevalence of DH was 31.1%. A higher proportion (41.1%, P < 0.001) of participants with DF had DH than those without DF. The association between DH and DF was minimal but statistically significant (r = 0.174, P < 0.001). Among those with DF, the prevalence of DH was highest in participants with severe fluorosis (50%, P = 0.740). The proportion of sensitive teeth to the teeth examined was significantly higher (P < 0.0001) for participants with DF (289/4167, 6.9%) than participants without DF (267/6758, 4%). This proportion was also highest for severe DF (20/254, 7.9%, P = 0.572) than the mild and moderate forms. Conclusion: DH was more prevalent among individuals with DF. The prevalence of DH was not dependent on the severity of DF.

Keywords: Dental fluorosis, dentine hypersensitivity, endemic, endemic fluorosis, Nigeria


How to cite this article:
Idon PI, Ikusika OF, Sotunde OA, Ogundare TO. Are there associations between the occurrence of dental fluorosis and the experience of dentine hypersensitivity? A cross-sectional study. Niger Postgrad Med J 2022;29:161-6

How to cite this URL:
Idon PI, Ikusika OF, Sotunde OA, Ogundare TO. Are there associations between the occurrence of dental fluorosis and the experience of dentine hypersensitivity? A cross-sectional study. Niger Postgrad Med J [serial online] 2022 [cited 2022 May 22];29:161-6. Available from: https://www.npmj.org/text.asp?2022/29/2/161/343735




  Introduction Top


Dentine hypersensitivity (DH) is a relatively common patients presenting complaint or it may be discovered during intraoral examinations. It is usually associated with episodes of discomfort and pain, which may occur during normal daily activities such as eating, drinking or even breathing through the mouth. DH is also reported to be associated with psychological problems and reduced quality of life among patients.[1],[2],[3] The episodes of pain result from exaggerated response to stimulation of exposed dentin by external stimuli of chemical, thermal, tactile or osmotic origin.[4] These stimuli would not ordinarily give such responses in a healthy tooth.[4],[5] Tooth surface enamel loss and root exposure due to gingival recession are reported as the most common causes of DH.[6] Non-carious tooth wear lesions such as attrition, abrasion, erosion and abfraction result in loss of coronal enamel and/or root cementum and have been identified in the aetiology of DH.[6] The condition has also been identified among individuals with dental fluorosis (DF).[6],[7],[8]

DF is a developmental defect of enamel which occurs due to excessive fluoride intake during amelogenesis. It is mostly identifiable on permanent teeth where it is associated with multiple changes to subsurface enamel. These changes range from small white opaque flakes on tooth surfaces to pits and grooves and varying degrees of post-eruption staining. DF can cause varying degrees of post-eruptive enamel breakdown depending on its severity. The enamel defects are attributed to hypomineralisation which is a feature of the disease process.[9],[10],[11]

High-fluoride concentration negatively affects the secretion and maturation phase of amelogenesis leading to the formation of hypomineralised, porous enamel at the sub-surface layer extending towards the enamel–dentine junction.[11],[12],[13] The enamel produced in a high fluoride environment is 'soft' and easily chips off exposing the dentine.[13] Studies have shown that hypomineralised teeth are frequently associated with severe hypersensitivity.[12],[14] Vieira et al.[13] in 2006 reported the presence of larger dentinal tubules in dentine with higher fluoride concentrations compared with normal dentine. This could be a second reason for the occurrence of hypersensitivity in teeth with DF, the first being the loss of hypomineralised enamel over time.

A plethora of evidence from the literature have linked the occurrence and prevalence of DH to various aetiological factors.[2],[4],[6] The association between fluorosed enamel and DH may be more apparent when populations endemic for DF are studied. There are available studies, though limited in number among populations endemic for DF, that have reported the prevalence of DH and its association with DF.[7],[8] The prevalence of DH was reported by Tonguc et al.[7] to be significantly higher in a population endemic for DF when compared to another population.

There is presently no study to assess this association in any of the fluorosis endemic regions of Nigeria. DF is endemic in the location for the present study with reported fluoride content in water as high as 4.6 mg/l[15],[16] and prevalence of DF of 30.2%.[3] A separate study in the same location had also reported a significant proportion of diagnosed DH in individuals with DF.[6] The study however was only among participants diagnosed with DH. The lack of comparison of those findings with figures from individuals without DF stimulated our desire to conduct this study. Therefore, to further illuminate the association between DH and DF, this study aimed to determine the association between the loss of hypomineralised enamel in individuals with DF and their experience of DH in Maiduguri, an area endemic for fluorosis. We hypothesise that the presence of DF affects individuals' experience of DH.


  Methods Top


Ethical consideration

The protocol for this study was reviewed and approved by the Research and Ethics Committee of the University of Maiduguri Teaching Hospital (UMTH/REC/21/785), Maiduguri in January 2021. The study was conducted in accordance with relevant ethical principles as stated by the World Medical Association Declaration of Helsinki (version 2013 Brazil).[17]

Study design

This was a cross-sectional study conducted over a 6-month (June to December) period among adult patients at the hospital in 2021 and we followed the recommendations provided in the STROBE guidelines[18] for the conduct of observational studies.

Setting

The study was conducted in oral diagnosis and restorative clinics of UMTH, Maiduguri, Nigeria. The dental clinics of the hospital are the largest of its type in the Northeast of the country and attend to a major proportion of the dental patients in Maiduguri Metropolis and surrounding states. Maiduguri is the capital of Borno State, and like other specific locations in the Northeast of Nigeria, it is endemic for DF.[3],[19] Maiduguri is located on latitude 11° 50´ North and longitude 13° 9' East. The area lies on a vast sedimentary basin with an average elevation of 300 m above sea level within the Nigerian section of the Chad Basin sedimentary formation.[16],[20] The major source of water for the Maiduguri Water Treatment Plant are the rivers on Bama Hills and Lake Alau.[16] The major source of drinking water however is from groundwater sources of wells and boreholes of varying depths,[3] which taps from the water-bearing zones of the upper, middle and lower aquifers.[21],[22] Fluoride concentrations are highest in these sources to as much as 4.6[15] and 5.6 mg/L.[23],[24] DF is most common among residents who use these sources of drinking water compared to those who use surface water (rivers) sources.[3]

Participants

The minimum required sample size for the study was 154 as determined by the sample size formula (n = z2p (1 − p/d2)[25] for cross-sectional studies, using prevalence (11.28%) of participants with DF that had DH in a similar previous study.[8]



where,

n = sample size

z = standard normal deviation = 1.96

p = proportion of prevalence = 0.1128 (11.28%)

d = absolute error of precision = 0.05

therefore,



n = 153.8 ≈ 154

Participants were dental patients attending the clinics during the study period who were invited and recruited to participate. They consisted of adult patients who consented to participate in the study, and had not undergone periodontal treatment or vital bleaching procedures in the past 3 months, and not on orthodontic appliances. Teeth with clinical attachment loss greater than 2 mm, crown restorations or used as abutments for fixed or removable prosthesis, cracked teeth, teeth with extensive or defective restorations, non-carious cervical lesions, erosion, attrition, extensive caries and suspected pulpitis were excluded from the study.

Data collection

Before examination, every participant was asked if they experience pain or shocking sensation while taking cold, hot, acidic, sour food or drinks or while brushing their teeth. Facial/buccal surfaces of all the teeth were assessed for fluorosis using the Thylstrup and Fejerskov Index (TFI)[26] to produce a maximum of 28 scores. Except for participants with TFI score of zero, a mean score (> 0 ≤ 9) was derived to classify the severity for each participant by dividing the sum of the individual tooth scores by the number of teeth scored. Participants' scores were thereafter grouped into four classes: TFI = 0, TFI > 0–3, TFI 4–6 and TFI 7–9, as absent DF, mild, moderate and severe DF, respectively.

Every tooth, except those that did not meet the inclusion criteria, was examined for DH using tactile and/or thermal/evaporative stimuli. Teeth were isolated with cotton wool rolls and an explorer tip was used to scratch the tooth surfaces. Where the response to tactile stimulation was negative, sensitivity to air-blast was tested approximately 10 min after the tactile test. The examiner's gloved fingers isolated the immediate adjacent teeth mesial and distal to the test tooth as a blast of air was delivered perpendicular to the tooth surface from a three-way dental air syringe, placed 1cm away, at a pressure of 55–65 psi. This was done to the buccal and lingual cervical areas, occlusal surfaces and areas of exposed dentin for 1 s. DH was defined as being present where there was discomfort, shocking sensation or pain on the application of either of the two stimuli. All examinations were performed under natural light after drying the teeth with gauze by a trained and pre-calibrated examiner. Pre-testing to determine intra-examiner agreement gave kappa values of 0.97 and 0.94 for DF and DH, respectively.

Statistical analysis

The IBM SPSS software for Mackintosh (IBM Corp., Version 21.0. Armonk, NY, USA: IBM Corp.) was used to analyse retrieved data. Descriptive statistics generated frequencies and proportions for qualitative variables. Quantitative variables were presented in means and standard deviations. The Chi-square test and the z test for proportions were used to examine the bivariate associations between participants' demographics and the presence of DH and DF. It was also used to test associations between the number of sensitive teeth and the presence and severity of DF. Pearson's correlation was utilised to examine the strength of these associations. Comparisons of mean age and mean number of teeth by participants' variables were made with independent samples t-test and one-way ANOVA test. The level of statistical significance was set at P < 0.05 (two-sided).


  Results Top


Four hundred and seventy-six patients attended the clinics during the study period and 428 (response rate = 98.6%) agreed to participate. Their ages ranged from 18 to 74 years with a mean (standard deviation) of 33.3 (11.2). Majority (61.7%) were <34-year-old, and 38.6% were female. One hundred and forty-two (33.2%) participants gave a positive answer to having sensitivity on taking different drinks and food or from toothbrushing during normal daily life. On examination, however, only 133 (31.1%) of these participants were confirmed to have DH. Twenty-seven (19%) participants with DH were on home treatment with a desensitising toothpaste, while only 3 (2.1%) had received in-office treatment.

[Table 1] summarises the demographics and the distribution of DH and DF among the participants. DF (63.7%) and DH (51.1%) were highest among participants <34 years old. Chi-squared analysis showed that age was associated with the presence of DF (P < 0.001) and DH (P = 0.008), while gender was associated only with DF, higher in females. No association was noted between gender and DH (P = 0.061). These associations were tested with Pearson's correlation and showed a weak but positive correlation between age and DF (r = 0.137, P = 0.005), and weak but negative with DH (r = −0.157, P = 0.001). Correlation was also weak and negative for gender and DF (r = −0.169, P = 0.000).
Table 1: Demographics and distribution of dentine hypersensitivity and dental fluorosis among the participants by age and gender

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[Table 2] shows the distribution of sensitive teeth and the prevalence of DH among the participants. The overall prevalence of DH among the participants was 31.1%. The presence of DH was associated with DF. A higher proportion (69/168, 41.1%, P < 0.001) of participants with DF had DH than those without DF. Pearson's correlation statistics showed the association between DH and DF to be negligible, positive and significant (r = 0.174, P < 0.001). A total of 10,925 teeth were examined for DH, while 2106 teeth were excluded from the study as they did not meet the inclusion criteria. Following Chi-square analysis, the proportion of sensitive teeth to the teeth examined was significantly higher (χ2 = 44.735, P < 0.0001) for participants with DF (289/4167, 6.9%) than participants without DF (267/6758, 4%). The mean sensitive teeth were only marginally higher for participants with DF and not significant.
Table 2: Distribution of participants with fluorosis, dentine hypersensitivity and number of sensitive teeth

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The characteristics of participants with DH (n = 133), with or without DF are shown in [Table 3]. The Chi-square test showed a significant association between DH and gender among the participants with or without DF (P = 0.017). There were more females than males (38/31; female:male = 1.22:1) with DF that had DH, found to be significant with the z test for proportions (z = 19.095, P < 0.01) [Table 3]. This relationship was reversed (42/22; female:male = 1:1.91) for participants without DF, also significant with the z test for proportions (z = 10.792, P < 0.01). The mean age was significantly (P < 0.001) lower for participants with fluorosis who had DH.
Table 3: Characteristics of participants with dentine hypersensitivity (n=133)

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[Table 4] presents the prevalence, distribution and comparisons of DH among participants with DF based on the severity of fluorosis. Chi-square tests showed that the prevalence of DH was highest for participants with severe DF, though not statistically significant (P = 0.740). The proportion of sensitive teeth to the number of teeth examined was also highest for this group (20/254, 7.9%, P = 0.572), but not statistically significant. No significant difference was observed in the mean number of sensitive teeth (P = 0.768) following One-way ANOVA analysis.
Table 4: Distribution of participants and hypersensitive teeth by the severity of dental fluorosis (n=168)

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  Discussion Top


The major contribution of this study was in the description of the presence of DH and differences in its occurrence among groups of individuals with and without DF using a sample of dental patients in a region endemic for DF. Confirming what has been reported in the literature,[27],[28] the prevalence of DH based on self-perception or questionnaire produces over-estimations as the perceived sensitivity could be due to other causes. An exaggeration of 6.3% was noted in the present study after examination to confirm the self-perceived DH. Also consistent with the general consensus, the prevalence of DH was associated with age.[4],[27],[28] Our findings showed that the prevalence of DH decreased with age. This confirms previous reports, that is, its reduction with increasing age known to be related to natural desensitisation from secondary dentine deposits and tubular sclerosis.[28] Adding to the numerous controversial reports,[29],[30],[31],[32] gender showed no association with DH in this study. The general report however remains that it is commoner among females,[33] probably because they are more sensitive to pain and indulge more in acidic diets.[34]

Although gender and age were associated with DF, higher in the younger adults and females, the reason in this study could be the greater desire for better aesthetics among these two groups.[3] Similar[35] and contrasting[8] findings have been reported in other endemic and non-endemic regions around the globe for age. The controversial reports about the association between DF, gender and age may ultimately be due to population differences, or age and gender differences of clinic attenders in clinic-based studies.

The present study showed that the majority of patients with DH had DF. The prevalence of DH was significantly higher among those with DF, as well as a slightly higher mean number of sensitive teeth per patient. There is very scarce information in the literature to compare our findings with. However, Zhang et al.[8] reported a lower prevalence of DH among individuals with mild DF than those without clinical features of DF in an area endemic for the condition.[8] They however noted that the number of participants without DF was too small to allow for statistical analysis, and the prevalence of DH was much lower in this fluorosis endemic region compared to the other non-fluorosis-endemic regions in China. This was explained as probably due to continuous remineralisation of the tooth tissue from exposure to fluoride with subsequent occlusion of the dentinal tubules, which would reduce hydrodynamic transmission and sensitivity.[8] This explanation for their findings however contradicts reports from studies that have shown dentine fluoride concentrations to affect crystal size, with higher fluoride concentrations, resulting in less tooth mineralisation.[13],[36] The mineralisation is indirectly proportional to the severity of DF and dentine tubule size, which translates to the higher tendency for sensitivity. Furthermore, the population studied by Zhang et al.[8] had only the mild form of DF.

Our findings of a higher prevalence of DH among individuals with DF compared to those without DF are similar to those from previous studies among patients in Isparta[7] and India.[34] The exposure of the dentine, patency, diameter and number per unit area of dentinal tubules are important determinants of the presence of DH. The higher occurrence of DH in people with fluorosis may be due to the effect of fluorosis on dentine. Vieira et al.[13] demonstrated that dentine affected by fluorosis had reduced crystal growth and wider dentinal tubules compared to normal dentine.[29] As the fluoride content decreases mineralisation rate, it produces a hypo-mineralised dentine and may explain the wider dentinal tubules.[13],[37] Based on the hydrodynamic theory,[38] this dentine when exposed would more likely transmit impulses with resultant sensitivity. Furthermore, higher concentrations of dentine fluoride are related to a greater number of these wide dentine tubules per unit area of the dentine surface. Furthermore, teeth with higher fluoride concentrations are stiffer (higher modulus of elasticity), and more likely to lose their enamel coverings under masticatory function exposing the dentine.[13] Kour and Vandana[34] reported significant correlations between the severity of fluorosis and the severity of DH measured on the verbal rating scale after pain stimulation. Although not significant, this may explain why our results show the highest prevalence of DH based on the DF severity groups to be among patients with TFI range of 7–9. This may also explain the significantly higher mean number of sensitive teeth among participants with DF, but the severity of the DF does not appear to affect it.

The role of neurogenic inflammation in the occurrence of DH has been suggested.[39],[40],[41] This has been related to the possible role of plaque, which has been found to be associated with teeth exhibiting DH.[34] Findings showing that fluorotic teeth had significantly higher plaque index than non-fluorotic teeth, probably due to enamel defects, could support the secondary role of plaque in addition to the changes in the dentine of fluorosed teeth for the presence of DH. This was however not assessed in the present study.

The differences in the prevalence of DH between the genders were significant for the fluorotic and non-fluorotic groups, with the females being more affected in the fluorotic group than the males. Higher prevalence among females was also reported in similar studies among individuals with fluorosis but with no statistical significance.[7],[8],[34] The possible reason for this could be the usual higher oral hygiene awareness and practices among females, in this case, adding to the higher tendency for DH in addition to the DF. The mean age for those affected by DH was significantly lower for the fluorotic group. This is contrary to findings by Tonguc et al.[7] with no significant difference between the two groups but consistent with findings of Kour and Vandana.[34] Fluorotic teeth may suffer from enamel breakdown after eruption due to increased porosity, especially in the severe forms, pre-disposing them to DH earlier than in non-fluorotic teeth. Furthermore, these teeth are likely to have wider dentinal tubules that pre-disposes them to DH. This earlier onset of DH may eventually become dampened by ageing due to secondary dentine formation and sclerosis.

This study is limited by the relative lack of data on DH among individuals with DF in the literature for comparison and discussion of the results. The findings of the present study were thus discussed only in relation to the three available fluorosis-endemic population studies,[7],[8],[34] and two others on apatite crystal and dentinal tubule size in fluorotic dentine.[13],[36]


  Conclusion Top


We found that DH was significantly more prevalent among individuals with DF than those without DF. Prevalence of DH was not dependent on the severity of DF among individuals with the condition. The findings from this study may be used to suggest that further epidemiological studies be conducted among fluorosis endemic populations to examine their experience of DH to comprehensively understand how DF affects the occurrence of DH. A better understanding of this relationship is important in establishing DF as part of the aetiology of DH. This affords better planning of prevention and treatment among populations endemic for DF.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Tables

  [Table 1], [Table 2], [Table 3], [Table 4]



 

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