Abstract
Objectives
To determine the frequency of orthodontic emergencies and their impact on the treatment progress caused by delayed appointments due to the lockdown during the COVID-19 pandemic.
Materials and methods
Two hundred thirty-eight patients undergoing fixed orthodontic treatment participated in this cross-sectional study. A pre-structured questionnaire was divided into six parts (Part A-C comprised of orthodontic emergencies and Part D-F comprised of various adverse effects and impacts on treatment progress). Two specialist orthodontists performed clinical examinations to complete the questionnaire. The final data were expressed as frequency and percentage.
Results
Maximum number of patients reported four months after lockdown. Nearly half of the patients reported debonding of at least one of the brackets. Loosening of molar bands and debonding of second molar tubes were observed in 12.6% and 18.9% of patients, respectively. Ligation method failures were reported in 41.2% of the patients. Patients fitted with transpalatal arch/lingual arch skeletal anchorage showed a failure rate of 26.1% and 10%, respectively. Almost 29% of the patient complained of discomfort due to distal wire impingement. Undesired tooth movements were seen in almost 25% of patients. Alignment, space closure, and settling of occlusion were affected in 47.6%, 17.4%, and 35.7% of patients, respectively.
Conclusions
This study helps to determine various types of adverse effects that can occur due to delayed appointments. The study's outcomes suggest that clinicians should be prepared to deal with future pandemics or other causes that might lead to delayed appointments.
Keywords: COVID-19, Orthodontic emergencies, Questionnaire, Pandemic
1. Introduction
The coronavirus disease, commonly known as COVID-19 infection, has affected the entire world and impacted everyone, including medicine and dentistry. When very little was known about the contagious nature of COVID-19, many countries imposed nationwide or city-wise lockdowns/curfews to curb the menace of the spreading virus. In India too, a complete lockdown was in place for a period of three months (from March 24, 2020 to June 15, 2020). As human-to-human transmission was present mainly in a healthcare setting, only emergency hospital services were in place. Many institutions shut down routine outpatient services, leading to the reduction or suspension of dental services as well.1 In the specialty of orthodontics, this significantly impacted the follow-up of patients undergoing active orthodontic treatment.
Most patients were affected by the lack of access to orthodontic visits during the pandemic.2 Since the orthodontic appliance is prone to breakages and can lead to detrimental effects, patient compliance in follow-up appointments is one of the keys to successful orthodontic treatment. During the routine follow-up appointments, the ligation is changed, and necessary activations are carried out. Moreover, in certain types of appliances or mechanics, such as frictionless mechanics, it becomes mandatory for the patients not to miss follow-up visits as significant side effects can occur.
Missed or delayed appointments can significantly affect the patient's oral health and may lead to an overall increase in treatment duration.3 Additionally, patients' nonattendance results in a waste of resources and can seriously affect the productivity and efficiency of the dental care facility. It can also affect a patient's health, treatment length, and relationship with the orthodontist.3, 4, 5, 6 Due to the pandemic, more patients were compelled to miss their appointments. The primary aim of the present study was to determine the frequency of orthodontic emergencies and adverse events caused due to the pandemic. The secondary aim was to report the impact on the treatment progress caused by delayed appointments during the lockdown.
2. Materials and methods
This investigation was a single-centre cross-sectional study approved by the Institutional Ethical Committee (AIIMS/IEC/2020/3196). Data was collected from orthodontic patients undergoing treatment in the post-graduate orthodontic clinic, All India Institute of Medical Sciences, Jodhpur, India,after obtaining informed consent from the study participants. Inclusion criteria were: patients under active orthodontic treatment whose treatment commenced before the lockdown and healthy patients who could physically report for follow-up after the lockdown. The data was collected from 238 patients in different stages of fixed orthodontic treatment from June 2020 to March 2021 after the lifting of the lockdown, when routine orthodontic services were resumed in a phased manner. Data collection was done with the help of a pre-structured questionnaire developed in the English language. The questionnaire was piloted before the study's initiation with three orthodontic residents. Afterwards, the questionnaire was forward and backward-translated, followed by content and criterion validity tests, test-retest reliability, and internal consistency. It was validated to have good to excellent reliability.
The questionnaire consisted of multiple-choice questions divided into six parts. Part A-C consisted of questions about orthodontic emergencies, such as loosening brackets and molar bands, breakages of anchorage systems, and archwire impingement.Part D-F comprised questions related to various adverse effects and impacts on treatment progress due to delayed appointments. In order to fill out the questionnaire, a clinical examination of all the patients enrolled in the study was performed by two specialist orthodontists wearing personal protective equipment. All the information was entered into the questionnaire simultaneously to prevent recall or opinion bias.
In order to assess the calculus index (CI), a special training session of one-hour duration was held for calibration of the examiners. After proper calibration, they were allowed to fill out the requisite questionnaire. Intraclass correlation coefficients used to evaluate inter-rater agreement for evaluation of CI for ten subjects were excellent (ICC value 0.97).
The calculus index was evaluated by measuring calculus scores from the surfaces of six index teeth divided by the surfaces evaluated.7 A score of 0.0–0.6 was considered good, whereas a 0.7–1.8 score was considered fair, and a score of 1.9–3.0 was considered poor. Debris score was not taken for evaluation as it may not represent the patient's long-term hygiene status.
Progress of the first stage of leveling and alignment was measured from contact point displacement (Little's Irregularity Index) as assessed from clinical photographs taken in the previous visit (before lockdown) and compared with the photographs of the current stage.8
Assessment of the progress of the second stage of space closure was measured clinically and compared with space present in the last visit before lockdown, as mentioned in the treatment records.
Assessment of progress in the third stage of settling occlusion was based on the clinical assessment of occlusion. The occlusion was considered settled if cusps of maxillary teeth lie within 2 mm of embrasures/groove of mandibular teeth with less than 2 mm distance between cusp and embrasure/groove on occluding the teeth.
2.1. Statistical analysis
Statistical analysis was performed by collecting data and analysing it with SPSS software (version 21.0, Armonk: NY). The data were expressed as a frequency and percentage.
3. Results
3.1. Demographic details (Table 1)
Table 1.
Demographic data.
| S No. | Variable | N (238) | Percentage |
|---|---|---|---|
| 1. | Gender | ||
| Male | 122 | 51.2 | |
| Female | 116 | 48.8 | |
| 2. | Age group | ||
| 10–20 years | 118 | 49.6 | |
| 20–30 years | 118 | 49.6 | |
| More than 30 years | 2 | 0.8 | |
| 3. | Malocclusion | ||
| Class I | 107 | 44.9 | |
| Class II | 119 | 50 | |
| Class III | 12 | 5.1 | |
| 4. | Patients under active treatment before lockdown | ||
|
238 | ||
|
120 | 50.4 | |
|
76 | 31.9 | |
|
42 | 17.7 | |
| 5. | Anchorage systems installed in the patients | ||
|
102 | 42.8 | |
|
96 | 40.3 | |
|
40 | 16.9 | |
| 6. | Delay in patient appointment from previous visit before lockdown | ||
| 3 months | 40 | 16.8 | |
| 4–6 months | 166 | 69.7 | |
| More than 6 months | 32 | 13.5 | |
| 7. | Residence of the patients | ||
| Residing locally | 179 | 75.2 | |
| Residing outside | 59 | 24.8 | |
| 8. | Difficulty in reporting for appointment | ||
| No | 197 | 82.8 | |
| Yes | 41 | 17.2 | |
The study group consisted of 238 patients who were undergoing fixed orthodontic treatment (122 males and 116 females), of which 118 patients were within the age group of 10–20 years (49.6%), 118 patients were within the age group of 20–30 years (49.6%), and two patients were older than 30 years (0.8%). 107 patients had Class I malocclusion (44.9%), 119 patients had Class II malocclusion (50%) and 12 patients had Class III malocclusion (5.1%).
The time delay between reporting for appointments after the lockdown was three months for 40 patients (16.8%), four to six months for 166 patients (69.7%), and more than six months for 32 patients (13.5%). Around 41 patients (17.2%) had difficulty reporting for the appointment. The majority of the patients were residing locally (75.2%).
3.2. Part A- Orthodontic emergencies-Fixed appliance component breakage and ligation system failure (Table 2)
Table 2.
Part A- Orthodontic emergencies -Fixed appliance component breakage and Ligation system failure.
| S No. | Variable | N | Percentage |
|---|---|---|---|
| 1. | How many debonding of brackets were present? (n = 238) | ||
| No debonding | 127 | 53.4 | |
| 1-3 bracket debonding | 99 | 41.6 | |
| 4-6 bracket debonding | 10 | 4.2 | |
| More than 6 bracket debonding | 2 | 0.8 | |
| 2. | How many molar bands were loosening? (n = 238) | ||
| No loosening | 208 | 87.4 | |
| 1 band loosened | 21 | 8.8 | |
| 2 bands loosened | 5 | 2.1 | |
| ≥3 bands loosened | 4 | 1.7 | |
| 3. | How many second molar tubes were debonded? (n = 238) | ||
| No debonding | 193 | 81.1 | |
| In one quadrant | 35 | 14.7 | |
| In two quadrants | 5 | 2.1 | |
| In three quadrants | 4 | 1.7 | |
| In four quadrants | 1 | 0.4 | |
| 4. | What was the frequency of ligation system failure? (n = 238) | ||
| No failure of ligation system | 140 | 58.8 | |
| Modules Dislodged | 74 | 31.1 | |
| Ligature wire breakage | 10 | 4.2 | |
| Both modules and ligature wire loosened | 13 | 5.5 | |
| Self-ligation bracket door broken | 1 | 0.4 | |
Out of a total of 238 patients undergoing fixed orthodontic treatment, debonding of brackets was observed in 111 patients (46.6%), out of which 99 patients (41.6%) had one to three brackets debonded, ten patients (4.2%) had four to six brackets debonded, and two patients (0.8%) had more than six brackets debonded.
First molar band loosening or breakage was observed in 30 patients (13.6%), out of which 21 patients (8.8%) had one band loosened, five patients (2.1%) had two bands loosened, and four patients (1.7%) had three or more of their bands loosened.
Debonding of the second molar buccal tube was observed in 45 patients (19.9%), out of which 35 patients (14.7%) had one buccal tube debonded, five patients (2.1%) had two buccal tubes debonded, four patients (1.7%) had three buccal tubes debonded and one patient (0.4%) had all four buccal tubes debonded.
Ligation system failure was noted in 98 patients (41.2%). Ligature modules were dislodged in 74 patients (31.1%), while ligature wire was broken in 10 patients (4.2%). Combined ligature modules dislodgement and ligature wire breakages were observed in 13 patients (5.5%), and in one patient, self-ligation bracket door was broken (0.4%).
3.3. Part B- Orthodontic emergencies-Anchorage system breakage (Table 3)
Table 3.
Part B- Orthodontic emergencies -Anchorage system breakage.
| Variable | N (136) | Percentage | |
|---|---|---|---|
| 1. | Was TPA/Lingual Arch intact? (n = 96) | ||
| Intact | 71 | 73.9 | |
| Loosened/broken | 25 | 26.1 | |
| 2. | Was Mini Screw Implant/SAS intact? (n = 40) | ||
| Intact | 36 | 90 | |
| Skeletal anchorage failure | 4 | 10 | |
Of 238 patients, 96 were fitted with transpalatal arch(TPA) or lingual arch, and 40 had mini-implants for anchorage. Out of 96 patients, TPA/lingual arch breakage or loosening was observed in 25 patients (26.1%). Among patients having mini-implant or skeletal anchorage plates, four patients (10%) reported loosening of the skeletal anchorage system.
3.4. Part C- Orthodontic emergencies- Archwire impingement (Table 4)
Table 4.
Part C- Orthodontic emergencies-Archwire impingement.
| S No | Variable | N | Percentage |
|---|---|---|---|
| 1. | Did patients experience distal archwire impingement? (n = 238) | ||
| No | 169 | 71 | |
| Yes | 69 | 29 | |
| Yes (n = 69) | |||
| In one quadrant | 54 | 78.3 | |
| In equal to or more than or two quadrants | 15 | 21.7 | |
| 2. | Did patients do any self-relief measure to relieve discomfort due to distal archwire impingement? (n = 69) | ||
| No | 51 | 73.9 | |
| Yes | 18 | 26.1 | |
| 3. | Did patients visit a private practitioner for emergency relief due to archwire impingement? (n = 69) | ||
| No | 57 | 82.6 | |
| Yes | 12 | 17.4 | |
Distal archwire impingement was observed in 69 patients (29%). Fifty-four patients (78.3%) had impingement seen in one quadrant and 15 patients (21.7%) had impingement in two or more quadrants. Around 18 patients (26.1%) sought self-relief to relieve the discomfort due to archwire impingement. Twelve patients (17.4%) had to visit the nearest private practitioner for emergency relief.
3.5. Part D- Adverse effects-Impact on oral hygiene (Table 5)
Table 5.
Part D- Adverse effects -Impact on oral hygiene.
| Variable | N (238) | Percentage |
|---|---|---|
| Calculus Index | ||
| Good (0.0–0.6) | 76 | 31.9 |
| Fair (0.7–1.8) | 141 | 59.3 |
| Poor (1.9–3.0) | 21 | 8.8 |
Long-term oral hygiene of the patients was noted using Calculus Index. Seventy-six patients (31.9%) had good oral hygiene with a score of 0–0.6, 141 patients (59.3%) had fair scores of 0.7–1.8, whereas only 21 patients (8.8%) had poor oral hygiene with a score of 1.9–3.0.
3.6. Part E- Adverse effects- Arch form changes and undesired tooth movement (Table 6)
Table 6.
Part E- Adverse effects – Arch form changes and undesired tooth movement.
| S No | Variable | N | Percentage |
|---|---|---|---|
| 1. | Did you observe any undesirable changes in arch form in either arch? (n = 238) | ||
| No change | 222 | 93.2 | |
| Expansion of arch form | 8 | 3.4 | |
| Constriction of arch form | 5 | 2.1 | |
| Skewing of arch form | 3 | 1.3 | |
| 2. | Were there any undesired tooth movements seen? (n = 238) | ||
| No undesired movements | 177 | 74.4 | |
| Rotations | 17 | 7.1 | |
| Extrusions | 9 | 3.9 | |
| Intrusions | 3 | 1.3 | |
| Space opening | 6 | 2.5 | |
| Relapse of corrected teeth | 23 | 9.7 | |
| Side effects due to overuse of inter-maxillary elastics | 3 | 1.1 | |
Of 238 patients, arch form changes were observed in 16 patients (6.8%). Of these 16 patients, eight patients (3.4%) had the expansion of arch form, five patients (2.1%) had constriction of arch form, and in 3 patients (1.3%), arch-skewing was seen.
Out of 238 patients, undesired tooth movement was observed in 61 patients (25.6%). Rotation, extrusion, and intrusion were observed in 17 (7.1%), 9 (3.9%), and 3 (1.3%) patients, respectively. Space opening was observed in 6 patients (2.5%), while relapse of corrected teeth was seen in 23 patients (9.7%). Three patients (1.1%) reported side effects of overusing inter-maxillary elastics leading to Class III tendency, buccal crossbite, and canine extrusion.
3.7. Part F- Adverse effects- Effect on treatment progress in three stages of fixed orthodontic treatment (Table 7)
Table 7.
Part F- Adverse effects -Effect on treatment progress in three stages of fixed orthodontic treatment.
| S No. | Stage and category of treatment | N (238) | Percentage |
|---|---|---|---|
| 1. | Stage I- Leveling and alignment (n = 120) | ||
| Progressed | 62 | 52.4 | |
| Maintain | 41 | 32.7 | |
| Retreat | 17 | 14.9 | |
| 2. | Stage II-Space closure (n = 76) | ||
| Progressed | 23 | 30.3 | |
| Maintain | 41 | 53.9 | |
| Retreat | 12 | 15.8 | |
| 3. | Stage III- Settling of occlusion (n = 42) | ||
| Progressed | 27 | 64.3 | |
| Maintain | 15 | 35.7 | |
| Retreat | 0 | 0 | |
Out of 238 undergoing fixed orthodontic treatment, 120 (50.4%) were in leveling and alignment stage, 76 patients (31.9%) were in the retraction phase of fixed orthodontic treatment, and 42 patients (17.7%) were in the settling of occlusion phase of the treatment.
Among the patients in leveling and alignment phase, alleviation of crowding was seen in 62 patients (52.4%), no change was seen in 41 patients (32.7%), and worsening of alignment i.e., retreatment was required in 17 patients (14.9%).
For patients undergoing retraction and space closure, 23 patients (30.3%) showed progress in space closure, 41 patients (53.9%) showed no closure of space, and retreatment for space closure was seen in 12 patients (15.8%).
Among 42 patients in the third stage, 27 patients showed improvement in settling of occlusion (64.3%) whereas, 15 patients (35.7%) failed to show any progress in settling of occlusion.
4. Discussion
In our centre, routine orthodontic services were resumed in a phased manner after three months of complete lockdown. More than fifteen percent of the patients found it challenging to come for appointments for various reasons such as lack of transportation, change of residence, restricted movement in highly affected COVID-19 areas, different government rules in different areas, and, more predominantly, the fear of contracting the viral infection. A minimum delay of three months in all three stages of orthodontic treatment was noted, thusaffecting the overall duration. A retrospective study by Xiang et al.9 showed that a treatment delay was caused by lockdown in 98.6% patients with an average delay of approximately nine weeks. This observation is in accordance with the study of Haeger et al.,3 where the effect of missed appointments was analysed, and the average length of treatment was 18.3 months. However, the treatment period dropped to 17.3 months if there were no missed appointments, yet it increased to 20 months for patients who missed one or more appointments. Beckwith et al.10 also showed that for every missed return visit, there was an increase of 1.09 months.
It has been reported that only 32.3% of patients experienced various orthodontic emergencies due to delayed appointments; however, every missed/delayed appointment doubled the risk of occurrence of orthodontic emergencies.9 Orthodontic emergencies may also increase anxiety levels.11 During the lockdown period, an effort was made to resolve the problems related to fixed appliances via telephonic or video consultations without necessitating a clinic visit.
Bracket debonding, archwire ligation failure, and distal segment archwire impingement were the most common complaint reported by orthodontic patients. Almost forty-five percent of the patients reported some sort of breakage in brackets. Two patients reported more than six debonded brackets, and nearly two percent had three or more molar bands loosened. These breakages can significantly affect the orthodontic treatment duration as re-alignment of many teeth will demand downgrading to the lighter alignment wires. A previous study reported that patients with loose or broken brackets averaged 2.8 more months in treatment and 1.5 more visits than those with no loose brackets. Patients with repositioned brackets averaged 5.5 more months and 3.7 more visits than those without repositioning. Every loose bracket added 1.21 months and 0.77 appointments. The first repositioned brackets significantly added 2.78 months and 1.94 appointments to treatment.3 Loosening of the brackets or bondable buccal tubes was also among the most common cause of an emergency visit in orthodontic treatment in a previous study.12 A previous study by Miao et al.13 also reported debonding of brackets in 50% of patients undergoing fixed appliance therapy post-lockdown however, the number of debonded brackets and molar band loosening were not reported.
In the present study, 30% of the patients experienced dislodgement of modules, whereas just 4.2% experienced loosening of ligature wire. Ligature ties may provide more secure ligation over the long term than modules. It offers additional advantages like less plaque and food accumulation.14 TPA or lingual arch was broken in 26.1% of the patients. None of the patients were able to remove the appliance on its own. Previous studies have reported TPA breakage and cementation failure of approximately 2% and 30%, respectively, and more commonly with large-diameter wires.15,16 Overall, skeletal anchorage systems were found to be relatively stable in most patients (90%). The success rate of mini-implants and mini-plates reported to be 90% and 98.6%, respectively.17, 18, 19
Discomfort due to distal archwire impingement was reported by 29% of the patients. This aspect can significantly affect soft-tissue health and masticatory efficiency. In a previous study, distal archwire impingement was found to be the most commonly reported orthodontic emergency, followed by debonding or loosening of brackets.20
Patients were contacted via telemedicine and relief measures such as chewing gums or applying candle wax (whenever orthodontic wax was unavailable) to protect them from sharp-edges caused by ligature wires, brackets, or hooks. In extreme cases, careful use of nail clippers or any home tool to cut impinging sharp wires was also advised.21 Few patients had to visit a general dentist to provide optimum relief solutions. Therefore, it is recommended to check for archwire ends before dismissing the patient on every visit.
Overall oral hygiene was found to be satisfactory for most orthodontic patients, which might be due to oral hygiene instructions at beginning of the treatment and reinforcing the same during the telephonic consultation during the lockdown. Lack of good oral health can lead to plaque accumulation, gingivitis, and tooth decay which can prolong or may lead to discontinuation of orthodontic treatment.22
Changes in the arch form were observed in 17% of the patients. Due to delayed appointment schedules, undesired tooth movement was primarily observed in rotations, extrusion, space opening, and non-relieving or worsening of crowding in a small number of patients. One of the reasons for such undesired tooth movement could be the dislodgement of elastic modules and broken ligature wires. Overexpression of inter-maxillary elastics also occurred in patients where edge-to-edge and Class III tendency was observed in one of them. The deleterious effects of inter-maxillary elastics have already been previously established.23, 24, 25
The data from the present study showed that the progress of nearly half of the patients in all three stages of orthodontic treatment was adversely affected by delayed appointments. More than half of the patients undergoing leveling and alignment showed improvement, whereas the rest showed no change or worsening of the crowding. A similar response was seen in patients undergoing retraction and space closure. Nearly Thirty-six percent of patients showed no change in the third stage of occlusal settling which may cause further prolongation of treatment. Xiang et al.9 observed that orthodontic emergencies impacted the progress of stage three the most, which may increase the overall treatment duration. One reason that can be attributed is frequent breakage of the fixed appliance or activation or ligation failure. Therefore, it can be concluded that the delay in appointments may affect the overall progress of the treatment in patients undergoing fixed orthodontic treatment.
5. Limitations
This study provides data on missed or delayed appointments and their implications on all aspects of orthodontic treatment from a public-funded tertiary-referral outpatient orthodontic clinic. However, the increased cost of orthodontic treatment associated with the increased number of appointments could not be analysed. The current study is based on single-centre study therefore the results of this study may be limited in external validity. Patient's perception to various orthodontic emergencies could also not be assessed due to limited contact with the patients. Nevertheless, this study's findings on the detrimental effect of missed appointments provide insight into getting prepared or taking adequate preventive measures in the event of anticipated missed or delayed appointments for whatsoever reasons.
6. Conclusions
The results of the present study show that:
-
•
The most common type of orthodontic emergency was debonding of one or more brackets.
-
•
Distal archwire impingement was the most common cause of discomfort.
-
•
The lockdown impacted progress in all three stages of fixed orthodontic treatment, with the second stage affected the most.
Source of funding
None.
Ethical approval
Ethical approval was obtained from the Institutional Ethics Committee, AIIMS Jodhpur (AIIMS/IEC/2020/3196), Rajasthan, India.
Declaration of competing interest
None.
Contributor Information
Vinay Kumar Chugh, Email: drvinaychd@yahoo.com.
Navleen Kaur Bhatia, Email: drnavleenbhatia@gmail.com.
Pravin Kumar, Email: pravinkumar5@hotmail.com.
Ankita Chugh, Email: ankitamody@gmail.com.
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References
- 1.Infection Prevention and Control during Health Care when Novel Coronavirus (nCoV) Infection Is Suspected. World Health Organization. WHO/2019-nCoV/IPC/2020.3.
- 2.Shenoi S.B., Deshpande S., Jatti R. Impact of COVID-19 Lockdown on patients undergoing orthodontic treatment: a questionnaire study. J Indian Orthod Soc. 2020;54(3):195–202. doi: 10.1177/0301574220942233. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 3.Haeger R.S., Colberg R.T. Effects of missed appointments and bracket failures on treatment efficiency and office productivity. J Clin Orthod. 2007;41(8):433–437. [PubMed] [Google Scholar]
- 4.Lin C.K. Behavior-associated self-report items in patients' charts as predictors of dental appointment avoidance. J Dent Educ. 2009;73(2):218–224. [PubMed] [Google Scholar]
- 5.Patel P., Forbes M., Gibson J. The reduction of broken appointments in general dental practice. Prim Dent Care. 2000;7(4):141–144. doi: 10.1308/135576100322578889. [DOI] [PubMed] [Google Scholar]
- 6.Reekie D., Devlin H., Worthington H. The prevention of failed appointments in general dental practice. Br Dent J. 1997;182(4):139–143. doi: 10.1038/sj.bdj.4809325. [DOI] [PubMed] [Google Scholar]
- 7.Greene J.C., Vermillion J.R. The simplified oral hygiene index. J Am Dent Assoc. 1964;68:7–13. doi: 10.14219/jada.archive.1964.0034. [DOI] [PubMed] [Google Scholar]
- 8.Almasoud N., Bearn D. Little's irregularity index: photographic assessment vs study model assessment. Am J Orthod Dentofacial Orthop. 2010;138(6):787–794. doi: 10.1016/j.ajodo.2009.01.031. [DOI] [PubMed] [Google Scholar]
- 9.Xiang J., Xin Y., Wang R., et al. Appointment impact and orthodontic emergency occurrence during the coronavirus disease 2019 pandemic: a retrospective study. Am J Orthod Dentofacial Orthop. 2022;161(1):e12–e19. doi: 10.1016/j.ajodo.2020.12.016. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 10.Beckwith F.R., Ackerman R.J., Cobb C.M., Tira D.E. An evaluation of factors affecting the duration of orthodontic treatment. Am J Orthod Dentofacial Orthop. 1999;115(4):439–447. doi: 10.1016/s0889-5406(99)70265-9. [DOI] [PubMed] [Google Scholar]
- 11.Quan S., Guo Y., Zhou J., et al. Orthodontic emergencies and mental state of Chinese orthodontic patients during the COVID-19 pandemic. BMC Oral Health. 2021;21(1):477. doi: 10.1186/s12903-021-01834-3. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 12.Gyawali R., Pokharel P.R., Giri J. Emergency appointments in orthodontics. APOS Trends Orthod. 2019;9(1):40–43. [Google Scholar]
- 13.Miao Z., Zhang H., Han Y., Wang L., Wang S. Orthodontic care in orthodontic patients during the COVID-2019 pandemic: emergency, emergency response and orthodontic treatment preference. BMC Oral Health. 2023;23(1):364. doi: 10.1186/s12903-023-03066-z. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 14.Pellegrini P., Sauerwein R., Finlayson T., et al. Plaque retention by self-ligating vs elastomeric orthodontic brackets: quantitative comparison of oral bacteria and detection with adenosine triphosphate-driven bioluminescence. Am J Orthod Dentofacial Orthop. 2009;135(4):426–427. doi: 10.1016/j.ajodo.2008.12.002. [DOI] [PubMed] [Google Scholar]
- 15.Moore T.R., Kennedy D.B. Bilateral space maintainers: a 7-year retrospective study from private practice. Pediatr Dent. 2006;28(6):499–505. [PubMed] [Google Scholar]
- 16.Fathian M., Kennedy D.B., Nouri M.R. Laboratory-made space maintainers: a 7-year retrospective study from private pediatric dental practice. Pediatr Dent. 2007;29(6):500–506. [PubMed] [Google Scholar]
- 17.Lam R., Goonewardene M.S., Allan B.P., Sugawara J. Success rates of a skeletal anchorage system in orthodontics: a retrospective analysis. Angle Orthod. 2018;88(1):27–34. doi: 10.2319/060617-375.1. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 18.Topouzelis N., Tsaousoglou P. Clinical factors correlated with the success rate of miniscrews in orthodontic treatment. Int J Oral Sci. 2012;4(1):38–44. doi: 10.1038/ijos.2012.1. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 19.Jing Z., Wu Y., Jiang W., et al. Factors affecting the clinical success rate of miniscrew implants for orthodontic treatment. Int J Oral Maxillofac Implants. 2016;31(4):835–841. doi: 10.11607/jomi.4197. [DOI] [PubMed] [Google Scholar]
- 20.Turkistani K.A. Impact of delayed orthodontic care during COVID-19 pandemic: emergency, disability, and pain. J World Fed Orthod. 2020;9(3):106–111. doi: 10.1016/j.ejwf.2020.07.004. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 21.Mote N., Dhanjani V., Toshniwal N., Pallan K., Rathod R. COVID-19 and progressive orthodontics. J Indian Orthod Soc. 2020;54(4):347–351. doi: 10.1177/0301574220957539. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 22.Krishnan V., Ambili R., Davidovitch Z., Murphy N.C. Gingiva and orthodontic treatment. Semin Orthod. 2007;13(4):257–271. [Google Scholar]
- 23.Ellen E.K., Schneider B.J., Sellke T. A comparative study of anchorage in bioprogressive versus standard edgewise treatment in Class II correction with intermaxillary elastic force. Am J Orthod Dentofacial Orthop. 1998;114(4):430–436. doi: 10.1016/s0889-5406(98)70189-1. [DOI] [PubMed] [Google Scholar]
- 24.Buchner H.J. Maintaining mandibular anchorage in Class II, division 1 treatment. Angle Orthod. 1949;19(4):231–249. [Google Scholar]
- 25.Bien S.M. Analysis of the components of force used to effect distal movement of teeth. Am J Orthod. 1951;37(7):514–520. doi: 10.1016/0002-9416(51)90071-1. [DOI] [PubMed] [Google Scholar]