• Component Description
• Eligible Sample
• Protocol and Procedure
• Quality Assurance & Quality Control
• Data Processing and Editing
• Analytic Notes
• References
• Codebook
  • SEQN - Respondent sequence number
  • FCX06DI - Fluorosis DI: #6
  • FCX07DI - Fluorosis DI: #7
  • FCX08DI - Fluorosis DI: #8
  • FCX09DI - Fluorosis DI: #9
  • FCX10DI - Fluorosis DI: #10
  • FCX11DI - Fluorosis DI: #11

National Health and Nutrition Examination Survey

2009-2010 Data Documentation, Codebook, and Frequencies

Fluorosis - Clinical (FLXCLN_F)

Data File: FLXCLN_F.xpt

First Published: March 2020

Last Revised: NA

Component Description

Dental fluorosis clinical assessment was included in the NHANES oral health examination to monitor fluorosis in the population for selected age groups. Fluoride exposure, from any source, during the period of tooth development (birth to 6 years) is associated with increased risk of developing dental (or enamel) fluorosis. Dental fluorosis is characterized by an increasing porosity or hypomineralization of the tooth enamel that leads to visual changes of the enamel that appear once a tooth erupts (Dean, 1934; Fejerskov et al., 1990). Most permanent teeth, except third molars, develop during the first 6-8 years of life. The severity of dental fluorosis depends on the dose and duration of fluoride ingestion during tooth development (Dean, 1942; Fejerskov et al., 1990).

In the United States, dental fluorosis is generally considered a cosmetic effect with no negative functional effect (Kaminsky et al., 1990; Fluoride Recommendation Work Group, 2001; US Department of Health and Human Services, 2015). The severe form of dental fluorosis, however, may have adverse dental effects because the pitting can compromise the protective function of the enamel and the affected area can break away (Clark and Slayton, 2014; Fejerskov et al., 1990; National Research Council, 2006; US Department of Health and Human Services, 2015). But the severe form is rare in the U.S. (Beltran-Aguilar et al., 2010; National Research Council, 2006).

Eligible Sample

A dental fluorosis clinical assessment was conducted on survey participants aged 6-19 years who received the Oral Health Examination (exam status code, OHDEXSTS, is complete or partial).

Protocol and Procedure

The dental fluorosis clinical assessment was conducted at the NHANES mobile examination center (MEC) by dental examiners, who were registered dental hygienists licensed in at least one U.S. state. The dental hygienists were trained by a licensed dentist with expertise in conducting dental surveys, following procedures similar to those used during NHANES 1999-2004. Similar training procedures were also used in NHANES 2011-2016.

A health technician entered examiner observations directly into a computerized data collection system at the MEC. Examiners used a dental mirror for the assessment. Teeth were not dried with air before assessment.

Unlike the dental clinical fluorosis assessment protocols used in 1999-2004 and 2011-2016, which examined all surfaces of all teeth except third molars, only the facial surfaces of fully erupted, permanent, maxillary anterior teeth (teeth number 6-11) were evaluated in NHANES 2009-2010. The dental fluorosis clinical assessment proceeded in a tooth by tooth manner, similar to the tooth count assessment, beginning with the maxillary right central incisor and proceeding posteriorly to the upper right cuspid. Then, the same sequence was repeated for the upper left side. The examiner observed the enamel condition of the corresponding bilateral tooth. For example, if initially examining tooth #6, then #11 is the examined bilateral tooth.

Each tooth was scored according to the Dean’s Fluorosis Index (DFI) and assigned one of the DFI disease severity categories (Table 1), based on the area of the tooth surface with visible fluorosis and presence of pitting: normal (DFI=0), questionable (5), very mild (1), mild (2), moderate (3), or severe (4) (Dean, 1934; Dean, 1942). Missing teeth, deciduous (primary) teeth, permanent teeth not fully erupted, and teeth in which more than one-half of the visible surface area was obscured by a restoration, caries, or orthodontic appliance were not assessed. These teeth were coded as 9 “cannot be assessed”. A tooth having a non-fluoride opacity was coded as 8. The NHANES Oral Health Examiners Manual provides detail on assessing a tooth for fluorosis.

 

Table 1. Dean’s Fluorosis Index (DFI) criteria and scoring on the NHANES dental fluorosis clinical assessment

NHANES DFI Value	Fluorosis Severity Level	Description
0	Normal	No fluorosis detected
1	Very mild	Opaque, paperwhite areas involving less than ¼ of the tooth surface
2	Mild	Opaque, paperwhite areas involving ¼ to less than ½ of the tooth surface
3	Moderate	Opaque paperwhite areas involving ½ or more of the tooth surface
4	Severe	Discrete or confluent pitting in involved areas
5	Questionable	Slight aberration of normal enamel appearance, including white flecks
8	Non-fluoride opacity	Coded if non-fluoride opacity
9	Cannot be assessed	Coded if the tooth was missing, not fully erupted, one-half or more of the tooth was replaced with a restoration, covered with orthodontic band, or destroyed by caries.

Quality Assurance & Quality Control

The specific quality assurance and quality control (QA/QC) practices for the dental fluorosis clinical assessment are documented in detail in the NHANES Oral Health Examiners Manual.

All dental examiners received an initial training that consisted of lecture, practice simulations, and standardization sessions using projected images. Following initial training, examiners received field training at the MEC consisting of more practice simulations, standardizations, and calibration sessions with NHANES survey participants.

During data collection, the reference examiner visited each dental examiner 2-3 times a year to conduct a random number of replicate examinations during each visit. The reference examiner determined if retraining and future monitoring of the dental examiner was needed. The reference examiner also conducted an annual retraining session for all dental examiners to reinforce existing protocols and to introduce protocol updates as needed.

Since 1999, data for the oral health examination have been recorded directly onto a computerized data collection system at the MEC. The system is integrated centrally and allows for ongoing monitoring of much of the data. As part of the quality control practice, all data are reviewed systematically for logical inconsistencies. Before data release, the collected data are further reviewed.

Data Processing and Editing

The data files are produced with the teeth numbered using the Universal or ADA Dental Numbering System for teeth numbers 6-11.

Analytic Notes

NHANES is the only survey providing national estimates on dental fluorosis. Two-year estimates of fluorosis prevalence by DFI category demonstrated variability within and across multiple-year time periods. To assess the data quality of the clinical dental fluorosis examination, a review was conducted on the NHANES 1999-2004 and 2011-2016 data. The report is available at the NCHS website (National Center for Health Statistics and National Center for Chronic Disease Prevention and Health Promotion, 2019). The 2009-2010 data were not included in this evaluation report because of key differences with fluorosis assessment in 2009-2010 compared with the other years: dental hygienists conducted the assessment and only the facial surfaces of the maxillary anterior teeth were evaluated. However, the findings and the quality assessment principles used in this report should be strongly considered when determining whether these data are appropriate for the user’s analytic objectives, including studies of prevalence and trends.

DATA EVALUATION OF 2009-2010 FLUOROSIS CLINICAL ASSESSMENT DATA

As described previously in the review of the 1999-2004 and 2011-2016 clinical dental fluorosis examination data report, several QA processes were implemented to evaluate these data. These QA processes were applied to the 2009-2010 data along with additional evaluations of rater variability and reliability. Below are summaries of the findings that were assessed on the final data.

For these analyses, each participant was assigned a dental fluorosis severity value based on the lesser of the two most affected tooth-level DFI values among the six upper anterior teeth. For all analyses, tooth-level DFI value of cannot be assessed (code 9) and non-fluoride opacity (code 8) were recoded to missing. The questionable category, which was recorded during data collection as 5, was recoded to 0.5. This is consistent with Dean’s assignment of values, and reflects a questionable value falling between normal and very mild, in terms of severity. Only youth with at least two teeth with a non-missing DFI value (i.e., 0, 0.5, 1, 2, 3, or 4) were assigned a person-level DFI and included in further analyses.

In 2009-2010, 67.3% of youth aged 6-11 years and 90.6% of youth aged 12-19 years had at least two upper anterior teeth with a non-missing DFI value. The percentages of missing DFI value are similar to other survey cycles for youth 6-11 years (Table 2). Comparing to youth aged 6-11 years, youth aged 12-19 years had a lower percentage of missing DFI value. This is consistent with data from other survey cycles as well. However, youth aged 12-19 years in 2009-2010 had slightly higher percentage with missing DFI scoring, compared to youth aged 12-19 years from 2011-2016 cycles.

Table 2. Number (unweighted) of participants in the clinical dental fluorosis analysis of six upper anterior teeth, by fluorosis scoring status and age group for youth aged 6-19 years, NHANES 2009-2016

	2009-2010		2011-2012		2013-2014		2015-2016
Dean’s Fluorosis Scoring Status	n	%	n	%	n	%	n	%
Study participants ages, 6-11 years
Missing due to no dataa	19	1.6	37	2.9	25	1.9	9	0.7
Missing due to 8s & 9sb	380	31.1	352	27.7	441	33.6	425	33.3
Non-missingc	823	67.3	883	69.4	846	64.5	843	66.0
Total	1222	100.0	1272	100.0	1312	100.0	1277	100.0
Study participants ages, 12-19 years
Missing due to no dataa	44	3.4	47	3.8	27	1.9	10	0.8
Missing due to 8s & 9sb	79	6.0	17	1.4	25	1.8	29	2.3
Non-missingc	1187	90.6	1166	94.8	1339	96.3	1231	96.9
Total	1310	100.0	1230	100.0	1391	100.0	1270	100.0

^a: Participants did not receive the fluorosis assessment thus with no fluorosis score data available in any of the six upper anterior teeth.
^b: Participants with no valid fluorosis score assigned because at least 5 out of their six upper anterior teeth were coded as “8 (nonfluoride opacities)” or “9 (cannot be assessed)” during the fluorosis assessment.
^c: Participants with a Dean’s Fluorosis Index score of 0, 0.5, 1, 2, 3, or 4 in at least two of their six upper anterior teeth.

Inter-Examiner Reliability: Evaluation of Gold Standard Examinations from 2009-2010

In 2009-2010, gold standard examinations were conducted by a reference examiner on 3.7% (n=76) of participants aged 6-19 years who completed the dental fluorosis assessment. Complete data for analysis (i.e., at least two upper anterior teeth with valid DFI values from both examiner and reference) were available for 72 participants. To assess inter-examiner reliability, we calculated percent agreement and kappa statistics comparing person-level DFI values computed by the reference examiner and the dental examiner for the same participant. In addition, weighted kappa statistics were computed using different weighting schemes to describe various levels of disagreement between dental examiner and reference examiner on the DFI scale (i.e., difference in one category, two categories, etc.). Survey examination weights were not used in these analyses.

The unweighted kappa (Cohen et al. 1960) assigns a weight of 1 for perfect agreement (e.g., examiner DFI = 1 and reference DFI =1) and 0 for no agreement (e.g., examiner DFI = 1 and reference DFI =2); Custom #1 weights assigned 1 for perfect agreement, 0.667 for 1 category difference, 0.333 for a 2 category difference, and 0 for a difference of more than 2 categories; Custom #2 (based on Kumar et al., 2000) assigned 1 for perfect agreement, 0.5 for 1 category difference, and 0 for all others; the other two weighting schemes were based on Cicchetti and Allison (1971) and Fleiss and Cohen (1973). Qualitative interpretation of numeric kappa statistic value ranges are: less than chance agreement (<0), slight agreement (0.00-0.20), fair agreement (0.21-0.40), moderate agreement (0.41-0.60), substantial agreement (0.61-0.80), and almost perfect (0.81-0.99) (Landis and Koch, 1977). Kappa <0.60 may also be used as a general indicator of inadequate agreement among raters (McHugh, 2012).

Unweighted kappa values for the three dental examiners who conducted fluorosis assessments in 2009-2010 ranged from 0.48 to 0.65 (Table 3). When considering the results across all four weighting schemes, the agreement between the dental examiners and reference examiner ranged from 0.26 through 0.92. These reliability statistics would be considered fair to almost perfect agreement based on the Landis and Koch interpretation of kappa values. When McHugh’s requirement of a kappa value of at least 0.60 for adequate agreement is applied, the majority of the kappa values indicate adequate agreement (i.e., 11 out of 15 kappa values computed for 3 examiners were at or above 0.60).

In general, the percent agreement and kappa statistics between dental examiners and reference examiner in 2009-2010 are comparable to those in 1999-2004 and 2011-2016 cycles, based on assessments using only 6 upper anterior teeth (Table 3). As mentioned in the above Protocol and Procedure session, the NHANES 2009-2010 fluorosis clinical assessments were conducted by dental hygienists. This is different from the NHANES 1999-2004 and 2011-2016 protocol, in which the assessments were conducted by dentists. However, similar training procedures were used throughout these time periods for both dentists in 1999-2004 and 2011-2016, as well as dental hygienists in 2009-2010. Results from the kappa statistics supported the comparability between the two type of examiners. Although given the current state dental practice law, dental hygienists are usually not allowed to diagnose dental fluorosis. Data users should take the additional training and the surveillance nature of NHANES into account.

Table 3. Percent agreement and kappa statistics on person-level Dean’s Fluorosis Index values assigned by dental examiner and reference examiner based on assessments of six upper anterior teeth for participants aged 6-19 years with available gold standard observations: National Health and Nutrition Examination Survey, 1999-2004, 2009-2010, and 2011-2016

Survey Cycle and Examiner	n	Agreement (%)	Unweighted kappa	Weighted Cicchetti-Allison	Weighted Fleiss-Cohen	Weighted Custom #1	Weighted Custom #2
1999-2004
A	60	68.33	0.40	0.44	0.51	0.45	0.43
B	50	74.00	0.64	0.78	0.88	0.74	0.71
C	44	75.00	0.44	0.57	0.68	0.60	0.58
D	91	78.02	0.65	0.79	0.91	0.77	0.75
E	36	80.56	0.68	0.72	0.76	0.76	0.75
2009-2010
F	22	81.8	0.65	0.81	0.92	0.81	0.77
G	27	66.7	0.48	0.61	0.72	0.60	0.56
H	23	80.8	0.62	0.53	0.26	0.68	0.71
2011-2016
I	56	71.43	0.55	0.71	0.85	0.72	0.68
J	21	80.95	0.52	0.66	0.78	0.63	0.59
K	49	48.98	0.30	0.40	0.52	0.35	0.34
L	18	44.44	0.24	0.48	0.73	0.40	0.34

NOTE: All kappa statistics were computed using the following Dean’s Fluorosis Index values: 0 = Normal, 0.5 = Questionable (recoded from collected value of 5), 1 = Very mild; 2 = Mild, 3 = Moderate, 4 = Severe. All values of 8 (non-fluoride opacity) and 9 (could not assess) were set to missing.

Prevalence of Dental Fluorosis Severity of Six Anterior Teeth Among Youth

Weighted 2-year and 6-year estimates of dental fluorosis severity were computed on children 6-19 years (the common age range across all years) who had at least 2 upper anterior teeth with a non-missing DFI value (1999-2004, n=9,395; 2009-2010, n=2,010, 2011-2016, n=7,158). Examination sample weights were used in these analyses.

In 2009-2010, 31.7% (SE=2.9) of youth 6-19 years were estimated to have very mild fluorosis, 19.3% (SE=3.0) mild, 1;6% (SE=0.2) moderate, and 0.4% (SE=0.1) severe (Table 4).

Variability in the prevalence of different dental fluorosis severity levels was seen in the 2-year and six-year estimates across time periods. The 2-year estimated percentage of youth 6-19 years with very mild fluorosis was ranged from 15.7% to 31.7%, and ranged from 2.2% to 19.3% for mild, 0.6% to 5.9% for moderate, and 0.0% to 0.8% for severe fluorosis. The six-year estimates from 1999-2004 and 2011-2016 were 18.0% and 23.2% for very mild, 3.4% and 8.5% for mild, 1.4% and 3.8% for moderate, and 0.2% and 0.3% for severe fluorosis (Table 4), respectively. The observed variability may be partially explained by youth missing teeth that could not be assessed. The eruption patterns of children are such that the permanent central incisors may be present and assessed; whereas, the other permanent teeth may not be fully erupted yet, especially among youth aged 6-11 years.

Assessing the percentage of dental fluorosis using the six anterior teeth has certain limitations (Akinkugbe et al., 2014; Medina-Solis et al., 2008). Comparing to estimates that use 28 teeth, prevalence could be underestimated and estimates less stable when only six teeth were used. The limitations of six teeth are further compounded when using the DFI for defining fluorosis since two assessed teeth are a requirement and youth aged 6-11 years are less likely to have 2 fully erupted permanent teeth for assessment. As shown in above Table 2, only 67.3% of youth 6-11 years in the 2009-2010 sample satisfied this requirement. While these facial surfaces are easily accessible to direct visual inspection, using the upper six-anterior teeth may underestimate the prevalence and severity of fluorosis because late forming teeth are not included in the estimates. For instance, prior study has indicated that the lack of second permanent premolars and molars in the assessment could explain the lower prevalence of fluorosis observed among youth 6-11 years compared to youth aged 12-15 years (Beltran-Aguilar et al., 2005). In addition, previous studies also suggested that the prevalence and severity of dental fluorosis may vary by birth cohort (Beltran-Aguilar et al., 2002; Beltran-Aguilar et al., 2005). Therefore, estimated changes over time should consider to be age-adjusted or limit the number of years included in the age group for the analysis.

Table 4. Percentage (weighted) dental fluorosis severity levels, based on person-level Dean’s Fluorosis Index of six anterior teeth, among youth 6-19 years: National Health and Nutrition Examination Surveys 1999-2004, 2009-2010, and 2011-2016

Survey years	n	Overall		1=Very Mild		2=Mild		3=Moderate		4=Severe
		PCT	SE	PCT	SE	PCT	SE	PCT	SE	PCT	SE
2009-2010	2010	53.0	4.4	31.7	2.9	19.3	3.0	1.6	0.2	0.4	0.1
1999-2000	2925	26.0	4.6	18.6	3.3	4.4	0.7	2.7	0.8	0.2	0.1
2001-2002	3061	18.6	2.5	15.5	2.2	2.2	0.4	0.8	0.2	0.1	0.0
2003-2004	2816	24.6	2.1	20.1	2.0	3.6	0.4	0.6	0.2	0.2	0.2
1999-2004	8802	23.0	1.8	18.0	1.4	3.4	0.3	1.4	0.3	0.2	0.1
2011-2012	2049	35.3	3.1	21.0	2.6	7.7	0.8	5.9	0.8	0.8	0.3
2013-2014	2185	51.4	5.8	31.4	3.7	15.0	3.3	4.9	1.3	0.1	0.1
2015-2016	2074	21.1	3.7	17.3	3.0	3.0	0.8	0.8	0.3	0.0	0.0
2011-2016	6308	35.9	2.6	23.2	1.8	8.5	1.2	3.8	0.5	0.3	0.1

2009-2010 DATA QUALITY ASSESSMENT SUMMARY

There are potential sources of error in the measurement of fluorosis in general, and specifically in sample surveys, such as NHANES. While these potential sources of error exist, the inter-examiner reliability statistics and variability of prevalence of different dental fluorosis severity are seen across the cycles of dental fluorosis clinical assessments (i.e., 1999-2004, 2009-2010, and 2011-2016). Additionally, it is important to note the limitations of assessing only six permanent upper anterior teeth rather than 28 among youth who may have a higher proportion of missing or primary teeth and the implication of this when using the lesser of two DFI values to define dental fluorosis.

For general information on analyzing NHANES data and the use of examination sample weights refer to the NHANES Analytic Guidelines and the on-line NHANES Tutorial.

References

• Akinkugbe A, Iafolla T, Chattopadhyay A, Garcia I, Adams A, Kingman A. The role of partial recording protocols in reporting prevalence and severity of dental fluorosis. Community Dent Oral Epidemiol 42(6):563-71. 2014.
• Beltrán-Aguilar ED, Griffin SO, Lockwood SA. Prevalence and trends in enamel fluorosis in the United States from the 1930s to the 1980s. J Am Dent Assoc. 2002 Feb;133(2):157-65
• Beltran-Aguilar ED, Barker L, Dye BA. Prevalence and severity of dental fluorosis in the United States, 1999–2004. NCHS Data Brief, no 53. Hyattsville, MD: National Center for Health Statistics. 2010.
• Beltran-Aguilar ED, Barker LK, Canto MK, et al. Surveillance for Dental Caries, Dental Sealants, Tooth Retention, Edentulism, and Enamel Fluorosis; United States, 1988-1994 and 1999-2002. MMWR Surveill Summ 2005;54(03);1-44.
• Clark MB, Slayton RL. Fluoride Use in Caries Prevention in the Primary Care Setting. Pediatrics 2014;134(3):626–33.
• Dean HT. Classification of mottled enamel diagnosis. J Am Dent Assoc 21(8):1421–6. 1934.
• Dean HT. The investigation of psychological effects by the epidemiological method. Fluorine and Dental Health 19:23–33. 1942.
• Fejerskov O, Manji F, Baelum V. The nature and mechanisms of dental fluorosis in man. J Dent Res 69 Spec No:692–700. 1990.
• Fluoride Recommendations Work Group. Recommendations for using fluoride to prevent and control dental caries in the United States. MMWR Recomm Rep 50(RR–14):1–42. 2001.
• Kaminsky LS, Mahoney MC, Leach J, Melius J, Miller MJ. Fluoride: Benefits and risks of exposure. Crit Rev Oral Biol Med 1(4):261–81. 1990.
• Medina-Solis CE, Pontigo-Loyola AP, Maupome G, Lamadrid-Figueroa H, Loyola-Rodríguez JP, Hernández-Romano J, Villalobos-Rodelo JJ, de Lourdes Marquez-Corona M. Dental fluorosis prevalence and severity using Dean's index based on six teeth and on 28 teeth. Clin Oral Investig. 12(3):197-202. 2008.
• National Center for Health Statistics, National Center for Chronic Disease Prevention and Health Promotion. Data quality evaluation of the dental fluorosis clinical assessment data from the National Health and Nutrition Examination Survey: 1999-2004 and 2011-2016. National Center for Health Statistics. Vital Health Stat 2(183). 2019. https://www.cdc.gov/nchs/data/series/sr_02/sr02_183-508.pdf.
• National Research Council. Health effects of ingested fluoride. Washington, DC: National Academies Press. 2006.
• U.S. Department of Health and Human Services Federal Panel on Community Water Fluoridation. U.S. Public Health Service recommendation for fluoride concentration in drinking water for the prevention of dental caries. Public Health Rep 130(4):318–31. 2015.

Codebook and Frequencies