Introduction
The purpose of this descriptive study was to use a carefully constructed, pilot-tested survey instrument to identify the most common orthodontic retainers and retention protocols prescribed in the United States as reported by active members of the American Association of Orthodontists.
Methods
We randomly selected 2000 active members, stratified by region of practice, for the study. Information gathered included, but was not limited to, the types of retainers prescribed in the maxillary and mandibular arches, duration of full-time and part-time wear, use of fixed retainers, appliances fabricated in office vs commercial laboratories, the number of debonds per year, and retention appointment schedules. The survey consisted of 20 questions. Data were gathered on a categorical scale and analyzed.
Results
We received 658 responses (32.9%) during a 12-week period. Maxillary Hawley retainers (58.2%) and mandibular fixed lingual retainers (40.2%) were the most commonly used. Most orthodontists prescribed less than 9 months of full-time wear of removable retainers and thereafter advised part-time, but lifetime wear. Most orthodontists (75.9%) did not instruct patients to have the fixed lingual retainers removed at a specific time. More orthodontists who prescribed Hawley retainers recommended longer full-time wear compared with clear thermoplastic retainers. The timing of scheduled retention appointments varied among clinicians and depended on the number of years in practice, the volume of patients debonded, and the type of prescribed retainer. The only regional difference associated with retainer design was the Northeast region, where mandibular fixed lingual retainers were used less frequently. Female orthodontists did not use mandibular fixed lingual retainers as often as their male counterparts.
Conclusions
Maxillary Hawley and mandibular fixed lingual retainers are most commonly used. This study is the first to describe retention protocols and the scheduling of retention appointments in the United States.
Retention of a patient’s corrected malocclusion is a vital component of successful orthodontic treatment. The degree of stability of each corrected malocclusion is unpredictable, and much effort is often required to maintain the final orthodontic position of the teeth. Teeth tend to move back to their pretreatment positions if they are not retained. Several retainer designs have evolved over time, with various retention protocols to minimize relapse. A few studies examined the relative effectiveness of these appliances. Because of the lack of scientific evidence, it appears that current recommendations are based largely on personal preference and nonscientific criteria. This has led to the use of various retainers and retention protocols.
Studies by Wong and Freer and Gottlieb et al have shed light on retainer designs and protocols. In 2004, Wong and Freer surveyed orthodontists in Australia and New Zealand to identify consistencies in retention procedures and found that the most commonly used retainers were maxillary invisible retainers and mandibular canine-to-canine bonded retainers. Orthodontists most commonly recommended a regular retention period of more than 2 years and defined permanent retention as “lifetime.” Gottlieb et al completed a 3-part comprehensive study intended to gather information on a range of orthodontic issues from diagnosis and treatment procedures to wires and softwares used. Their sample was recruited from orthodontists in the United States in 1986, 1990, and 1996. Hawley retainers declined in use from 1986 to 1996, whereas spring aligners, invisible retainers, and fixed bonded canine-to-canine retainers increased. Essix retainers were introduced by Sheridan et al in 1993 and were evaluated only in the 1996 study. The retainer of choice appeared to change during the 10-year period. Retention protocols were not evaluated in either study.
The purpose of this descriptive study was to use a carefully constructed and pilot-tested survey instrument to identify the most popular orthodontic retainer designs and retention protocols currently used in the United States as reported by active members of the American Association of Orthodontists (AAO). These results are not evidence for the “best practices in retention” and highlight only the most common practices in retention. As far as we are aware, this is the only study of its kind.
Material and methods
The procedures and protocol for this study were approved by the institutional review board at Case Western Reserve University in Cleveland, Ohio. After a critical review of the literature, we identified and noted commonly used retainer devices and protocols. To strengthen our initial survey instrument, 25 orthodontists from different regions of the United States were interviewed by telephone regarding the retention devices and protocols they commonly prescribed. A finite set of retention devices and protocols formed the backbone of our survey instrument. The preliminary survey was next pilot tested on 65 orthodontists at the meeting of the Cleveland Society of Orthodontists in October 2006. Their responses were analyzed to develop our final survey instrument and converted into the SNAP survey scanning module (Snap Surveys, Portsmouth, NH; Fig ). The final survey consisted of 20 questions: 4 to characterize our sample and 16 to help answer our question. Customized retention protocols that clinicians adopt for specific malocclusions (eg, impactions, deepbites, and so on) were not identified as a common practice in our pilot efforts and therefore were not part of the final survey instrument. The average time to complete the survey was 3 minutes. All orthodontists who responded to the Cleveland Society of Orthodontists’ survey were excluded from the final mailing.
To attain statistical significance, 370 responses were required. This was based on approximately 10,000 active members of the AAO, a 95% CI, and a ± 5% sampling error. Similar to the US Census Bureau, orthodontists were subdivided into 4 regions: (1) Northeast (Conn, Mass, Me, NH, NJ, NY, Pa, RI, and Vt), (2) South (Ala, Ark, Del, DC, Fla, Ga, Ky, La, Md, Miss, NC, Okla, SC, Tenn, Tex, Va, and WVa), (3) Midwest (Iowa, Ill, Ind, Kan, Mich, Minn, Mo, Neb, ND, Ohio, SD, and Wis), and (4) West (Alaska, Ariz, Calif, Colo, Hawaii, Idaho, Mont, Nev, NM, Ore, Utah, Wash, and Wyo).
To have an equal number of respondents from each region, 400 respondents—100 from each region—were needed. With an expected 20% response rate, 2000 orthodontists, 500 from each region, received the surveys with addressed, prestamped return envelopes. A table of random numbers was used to select a stratified, random sample of 2000 active orthodontists from the 2005 AAO directory. We excluded affiliate, associate, honorary, international, and retired orthodontists. Twelve weeks later, the responses were scanned by 1 operator (E.H.) into SNAP for statistical analyses. Each scanned survey was compared with the hard copy for accuracy. Responses that did not scan properly because of notations or corrections were assessed and manually corrected. The number of responses corrected was recorded. The data were then exported into SPSS software (SPSS, Chicago, Ill) for statistical analyses.
Statistical analysis
Frequencies, percentages, and chi-square tests were used to analyze the data. Responses to questions were further subgrouped based on the frequencies. The most popular maxillary retainers were collapsed into 3 groups: clear, Hawley, and other. Likewise, the most popular mandibular retainers were collapsed into 5 groups: clear, Hawley, spring aligners, fixed, and other. Cross-tabulation tables and chi-square tests were used to detect differences between the independent variables (questions 1-4) and dependent variables (questions 5-20), and differences between types of retainers (questions 5 and 9) and the prescribed protocols (questions 6-8, 10-12, 16-20) associated with each retainer. Significance for all chi-square tests was predetermined at P <0.05.
Results
We received 658 (32.9%) completed surveys of the 2000 that were mailed. There were 13,160 questions scanned by the SNAP scanning module and 190 scanning mistakes manually corrected, representing 1.44% of responses.
Table I describes the sample characteristics (questions 1-4) and provides the region of practice, sex, number of years practiced, and number of debonds in 2006.
| Variables | n | % |
|---|---|---|
| Question 1. Regions | ||
| Northeast | 144 | 21.9% |
| South | 164 | 24.9% |
| Midwest | 196 | 29.8% |
| West | 149 | 22.6% |
| Question 2. Sex | ||
| Male | 568 | 86.7% |
| Female | 87 | 13.3% |
| Question 3. Years practiced | ||
| 0-5 years | 26 | 4.0% |
| 6-15 years | 169 | 25.8% |
| 16-25 years | 203 | 30.9% |
| >25 years | 258 | 39.3% |
| Question 3. Years practiced (collapsed) | ||
| 0-15 years | 195 | 29.7% |
| 16-25 years | 203 | 30.9% |
| >25 years | 258 | 39.3% |
| Question 4. Debonds | ||
| <150 | 202 | 31.2% |
| 150-300 | 310 | 47.8% |
| >300 | 136 | 21.0% |
Table II is a summary of surveyed retainer and retention protocol variables (questions 5-15); it represents the collapsed data.
| Variable | n | % |
|---|---|---|
| Question 5. Maxillary arch retainer | ||
| Clear thermoplastic | 199 | 30.4% |
| Hawley | 381 | 58.2% |
| Other | 75 | 11.5% |
| Question 6. Maxillary retainer period of full-time wear | ||
| Yes | 515 | 81.5% |
| No | 117 | 18.5% |
| Question 7. Maxillary retainer full-time wear | ||
| <3 months | 147 | 28.3% |
| 3-9 months | 279 | 53.7% |
| >9 months | 94 | 18.1% |
| Question 8. Maxillary retainer part-time wear | ||
| About 16 hours/day | 64 | 12.0% |
| About 8 hours/day | 358 | 66.9% |
| Other | 113 | 21.1% |
| Question 9. Mandibular arch retainer | ||
| Clear thermoplastic | 119 | 18.2% |
| Hawley | 184 | 28.1% |
| Spring aligner | 58 | 8.9% |
| Fixed lingual | 263 | 40.2% |
| Other | 30 | 4.6% |
| Question 10. Mandibular retainer period of full-time wear | ||
| Yes | 312 | 80.4% |
| No | 76 | 19.6% |
| Question 11. Mandibular retainer full-time wear | ||
| <3 months | 91 | 29.3% |
| 3-9 months | 166 | 53.4% |
| >9 months | 54 | 17.4% |
| Question 12. Mandibular retainer part-time wear | ||
| About 16 hours/day | 41 | 12.6% |
| About 8 hours/day | 217 | 66.6% |
| Other | 68 | 20.9% |
| Question 13. Instruct to stop wearing removable retainers | ||
| No, wear retainers forever | 501 | 84.2% |
| Yes, <2 years after debond | 30 | 5.0% |
| Yes, 5 years after debond | 26 | 4.4% |
| Yes, after third molars are extracted | 38 | 6.4% |
| Question 14. Instruct to have fixed retainers removed | ||
| Yes | 138 | 24.1% |
| No | 435 | 75.9% |
| Question 15. When do you instruct to have fixed lingual retainer removed? | ||
| <2 years after debonding | 11 | 8.3% |
| 2-5 years after debonding | 38 | 28.6% |
| >5 years after debonding | 40 | 30.1% |
| After third molars are extracted | 44 | 33.1% |
Table III summarizes retention appointment schedules (questions 16-20).
| Variable | n | % |
|---|---|---|
| Question 16. First appointment after debonding | ||
| <4 weeks after debonding | 126 | 19.2% |
| 1-2 months after debonding | 429 | 65.4% |
| >2 months after debonding | 100 | 15.2% |
| No retention appointment; patient dismissed | 1 | 0.2% |
| Question 17. Second appointment after debonding | ||
| <3 months after the first appointment | 160 | 24.3% |
| 3-5 months after the first appointment | 314 | 47.7% |
| ≥6 months or greater after the first appointment | 171 | 26.0% |
| No second appointment; patient dismissed | 13 | 2.0% |
| Questions 18. Third appointment after debonding | ||
| <6 months after the second appointment | 212 | 32.9% |
| 6-11 months after the second appointment | 326 | 50.6% |
| ≥1 year after the second appointment | 81 | 12.6% |
| No third appointment; patient dismissed | 25 | 3.9% |
| Question 19. Fourth appointment after debonding | ||
| <6 months after the third appointment | 97 | 15.7% |
| 6-11 months after the third appointment | 258 | 41.7% |
| ≥1 year after the third appointment | 165 | 26.7% |
| No fourth appointment; patient dismissed | 98 | 15.9% |
| Question 20. Fifth appointment after debonding | ||
| <6 months after the fourth appointment | 51 | 9.9% |
| 6-11 months after the fourth appointment | 170 | 32.9% |
| ≥1 year after the fourth appointment | 171 | 33.1% |
| No fifth appointment; patient dismissed | 125 | 24.2% |
Table IV illustrates the statistically significant differences among the 4 characteristic variables of orthodontists (questions 1-4), the types of retainers most commonly prescribed (questions 5 and 9), and the surveyed retainer and retention protocol variables (questions 5-20).
| Variables | Q1 | Q2 | Q3 | Q4 | Q5 | Q9 |
|---|---|---|---|---|---|---|
| Q1 | χ 2 = 4.081 P value = 0.253 |
χ 2 = 9.922 P value = 0.357 |
χ 2 = 14.405 P value = 0.025 ∗ |
χ 2 = 6.330 P value = 0.387 |
χ 2 = 22.312 P value = 0.034 ∗ |
|
| Q2 | χ 2 = 4.081 P value = 0.253 |
χ 2 = 49.130 P value = 0.000 ∗ |
χ 2 = 16.726 P value = 0.000 ∗ |
χ 2 = 1.010 P value = 0.603 |
χ 2 = 19.966 P value = 0.001 ∗ |
|
| Q3 | χ 2 = 9.922 P value = 0.357 |
χ 2 = 49.130 P value = 0.000 ∗ |
χ 2 = 4.833 P value = 0.565 |
χ 2 = 1.043 P value = 0.903 |
χ 2 = 6.173 P value = 0.628 |
|
| Q4 | χ 2 = 14.405 P value = 0.025 ∗ |
χ 2 = 16.726 P value = 0.000 ∗ |
χ 2 = 4.833 P value = 0.565 |
χ 2 = 6.188 P value = 0.186 |
χ 2 = 13.090 P value = 0.109 |
|
| Q5 | χ 2 = 6.330 P value = 0.387 |
χ 2 = 1.010 P value = 0.603 |
χ 2 = 1.043 P value = 0.903 |
χ 2 = 6.188 P value = 0.186 |
χ 2 = 473.881 P value = 0.000 ∗ |
|
| Q6 | χ 2 = 0.059 P value = 0.996 |
χ 2 = 5.328 P value = 0.021 ∗ |
χ 2 = 0.977 P value = 0.614 |
χ 2 = 3.679 P value = 0.159 |
χ 2 = 27.307 P value = 0.000 ∗ |
|
| Q7 | χ 2 = 4.104 P value = 0.663 |
χ 2 = 0.168 P value = 0.919 |
χ 2 = 16.182 P value = 0.003 ∗ |
χ 2 = 3.300 P value = 0.509 |
χ 2 = 72.013 P value = 0.000 ∗ |
|
| Q8 | χ 2 = 5.347 P value = 0.500 |
χ 2 = 3.468 P value = 0.177 |
χ 2 = 6.694 P value = 0.153 |
χ 2 = 6.246 P value = 0.181 |
χ 2 = 3.196 P value = 0.525 |
|
| Q9 | χ 2 = 22.312 P value = 0.034 ∗ |
χ 2 = 19.966 P value = 0.001 ∗ |
χ 2 = 6.173 P value = 0.628 |
χ 2 = 13.090 P value = 0.109 |
χ 2 = 473.881 P value = 0.000 ∗ |
|
| Q10 | χ 2 = 3.660 P value = 0.301 |
χ 2 = 3.933 P value = 0.047 ∗ |
χ 2 = 3.562 P value = 0.168 |
χ 2 = 2.108 P value = 0.349 |
χ 2 = 17.496 P value = 0.001 ∗ |
|
| Q11 | χ 2 = 0.199 P value = 1.000 |
χ 2 = 1.766 P value = 0.414 |
χ 2 = 17.442 P value = 0.002 ∗ |
χ 2 = 9.533 P value = 0.049 ∗ |
χ 2 = 58.612 P value = 0.000 ∗ |
|
| Q12 | χ 2 = 4.022 P value = 0.674 |
χ 2 = 0.270 P value = 0.874 |
χ 2 = 4.235 P value = 0.375 |
χ 2 = 8.614 P value = 0.071 |
χ 2 = 5.309 P value = 0.505 |
|
| Q13 | χ 2 = 14.704 P value = 0.099 |
χ 2 = 1.906 P value = 0.592 |
χ 2 = 23.934 P value = 0.001 ∗ |
χ 2 = 1.303 P value = 0.972 |
||
| Q14 | χ 2 = 5.543 P value = 0.136 |
χ 2 = 4.743 P value = 0.018 ∗ |
χ 2 = 14.382 P value = 0.001 ∗ |
χ 2 = 2.074 P value = 0.355 |
||
| Q15 | χ 2 = 10.530 P value = 0.309 |
χ 2 = 5.929 P value = 0.115 |
χ 2 = 3.786 P value = 0.706 |
χ 2 = 5.832 P value = 0.422 |
||
| Q16 | χ 2 = 8.196 P value = 0.515 |
χ 2 = 2.399 P value = 0.494 |
χ 2 = 13.121 P value = 0.041 ∗ |
χ 2 = 34.053 P value = 0.000 ∗ |
χ 2 = 15.750 P value = 0.015 ∗ |
χ 2 = 11.514 P value = 0.485 |
| Q17 | χ 2 = 12.396 P value = 0.192 |
χ 2 = 8.590 P value = 0.035 ∗ |
χ 2 = 14.197 P value = 0.028 ∗ |
χ 2 = 40.447 P value = 0.000 ∗ |
χ 2 = 10.531 P value = 0.104 ∗ |
χ 2 = 19.621 P value = 0.075 |
| Q18 | χ 2 = 8.762 P value = 0.460 |
χ 2 = 3.688 P value = 0.297 |
χ 2 = 8.137 P value = 0.228 |
χ 2 = 47.286 P value = 0.000 ∗ |
χ 2 = 19.404 P value = 0.004 ∗ |
χ 2 = 19.277 P value = 0.082 |
| Q19 | χ 2 = 12.548 P value = 0.184 |
χ 2 = 5.692 P value = 0.128 |
χ 2 = 8.563 P value = 0.200 |
χ 2 = 14.103 P value = 0.029 ∗ |
χ 2 = 16.221 P value = 0.013 ∗ |
χ 2 = 15.523 P value = 0.214 |
| Q20 | χ 2 = 3.637 P value = 0.934 |
χ 2 = 4.249 P value = 0.236 |
χ 2 = 13.537 P value = 0.035 ∗ |
χ 2 = 14.907 P value = 0.021 ∗ |
χ 2 = 17.810 P value = 0.007 ∗ |
χ 2 = 24.676 P value = 0.016 ∗ |
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