Introduction
Anterior open bite (AOB) continues to be a challenging malocclusion for orthodontists to treat and retain long-term. There is no consensus on which treatment modality is most successful. This study reports on the overall success rate of AOB orthodontic treatment in the adult population across the United States, as well as 4 major treatment modalities and other factors that may influence treatment success.
Methods
Practitioners and their adult patients with AOB were recruited through the National Dental Practice-Based Research Network. Patient dentofacial and demographic characteristics, practitioner demographic and practice characteristics, and factors relating to orthodontic treatment were reported. Treatment success was determined from posttreatment (T2) lateral cephalometric films and intraoral frontal photographs. Treatment was categorized into 4 main groups: aligners, fixed appliances, temporary anchorage devices (TADs), and orthognathic surgery. Extractions were also evaluated. Bivariate and multivariable models were used to investigate the association between treatment success and treatment modality, pretreatment (T1) dentofacial characteristics, patient and practitioner demographics, and practice characteristics, adjusting for clustering of patients within practice.
Results
A total of 254 patients, enrolled by 84 practitioners, contributed to T2 data for this study. There were 29 patients in the aligner group, 152 in fixed appliances, 20 in TADs, and 53 in surgery. A total of 49 patients underwent extractions of teeth other than third molars. Ninety-three percent finished treatment with a positive overbite on the T2 lateral cephalogram, and 84% finished with a positive vertical overlap of all incisors. The small number of aligners and TAD patients limited the ability to compare success rates in these groups. Patients treated with orthognathic surgery had a higher rate of success compared with those treated with fixed appliances only. Treatment success was also associated with academic practice setting, T1 mandibular plane angle ≤30°, no to mild T1 crowding, and treatment duration <30 months.
Conclusions
The overall success of orthodontic treatment in adult patients with AOB who participated in this study was very high. Orthognathic surgery was the only treatment modality that exhibited a statistically higher odds of successful outcomes. Some T1 dentofacial characteristics and treatment factors were associated with the successful closure of AOB.
Highlights
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There are a variety of orthodontic treatment methods used to treat anterior open bites.
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Overall success rates are very high for adult anterior open bite treatment.
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Orthognathic surgery exhibits a significant influence on treatment success rates.
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Several pretreatment dentofacial characteristics also influence treatment success.
Anterior open bite (AOB) is defined by a lack of vertical overlap between the incisal edges of the maxillary and mandibular teeth. The prevalence of AOB has been reported to range between 0.6% and 16.5%, varying by ethnic group, age, and stage of dentition. This malocclusion can have significant functional and psychological effects on patients. Patients with AOB may have difficulty incising food and enunciating certain phonemes, because of the altered tongue position on the incisors and the anterior hard palate. Furthermore, AOB development is often associated with unfavorable growth patterns, oral habits (ie, digit sucking and tongue posture), and nasopharyngeal airway obstructions. Because of its complex and multifactorial etiology, AOB continues to be 1 of the most challenging malocclusions for orthodontists to treat and retain successfully.
Patients with AOB can be treated using a variety of orthodontic treatment modalities. Standard edge-wise fixed appliances (FA) are commonly recommended for patients with AOB. FAs with extrusive mechanics for the anterior teeth can create an overlap between maxillary and mandibular incisors; however, this may lead to increased gingival display and is associated with a high potential for relapse. In some cases, practitioners may elect to treat patients with AOB with orthognathic surgery (SX), especially when a nongrowing, adult patient presents with an AOB that is of skeletal origin. Surgery may involve the maxilla, mandible, or both to skeletally correct the AOB.
In recent decades, the use of temporary anchorage devices (TADs) has become a popular nonsurgical technique for correcting AOB. Miniscrews or miniplates are used to provide anchorage for molar and premolar intrusion. Several case reports have shown TAD molar intrusion to be as successful as orthognathic surgery, suggesting a less invasive and less costly alternative to surgery.
Clear aligner therapy (ALN) is another recently-developed alternative to traditional FA for AOB. The thickness of the plastic on the occlusal surfaces, in combination with the forces of mastication, is believed to produce an intrusive force on the posterior dentition, which may aid with AOB closure. , Although several case studies have demonstrated successful AOB correction, molar intrusion has not been confirmed. ,
Extractions of premolars, and in some cases molars, may be recommended for AOB correction, especially in the presence of crowding. Premolar extractions are used to create space for greater incisor retraction and uprighting to close the AOB through what is often referred to as the “drawbridge” effect. , Posterior extractions allow molars to move anteriorly (“wedge effect”), resulting in a closing rotation of the mandible. ,
Although there are a variety of orthodontic treatment modalities used to correct AOB in adults, there is still no consensus on what method(s) are most successful. , A better understanding of the success rates for these treatments, as well as other factors that may influence treatment outcome, would greatly aid clinicians in the management of these patients. The purpose of this large observational prospective cohort study, conducted under the auspices of the National Dental Practice-Based Research Network (PBRN), was to explore treatment recommendations, outcomes, and stability of adult patients with AOB. This publication reports on the overall success rate of AOB treatment and explores how treatment success varies with treatment modality, pretreatment (T1) dentofacial characteristics, and patient and practitioner demographic and practice characteristics.
Material and methods
Dental providers and their adult patients with AOB were recruited from 6 regions of the National Dental PBRN (West, Midwest, Southwest, South Central, South Atlantic, and Northeast). Institutional Review Board (IRB) approval was obtained from the University of Alabama at Birmingham IRB (acting as the Central IRB), the Kaiser Permanente IRB (for the Western region), and the University of Rochester Research Subjects Review Board (for the Northeastern region). In addition, institutional IRB approval was obtained at individual academic settings when required. Practitioners and patients were compensated for their participation in this study. As members of the National Dental PBRN, the practitioners completed a T1 questionnaire that elicited information on their training and practices.
Inclusion criteria for practitioners were as follows: (1) orthodontist or dentist who routinely performs orthodontic treatment, (2) estimates to recruit 3 to 8 adult patients in active treatment for AOB, and expects to have treatment completed within 24 months of enrollment into the study, (3) routinely takes cephalometric radiographs (cephalogram) before and after treatment, (4) able to upload deidentified cephalogram and digital intraoral frontal photographs to a central data repository, (5) affirms that the practice can devote sufficient time in patient scheduling to allow recording of all data required for the study, and (6) does not anticipate retiring, selling the practice, or moving during the study.
Inclusion criteria for patients were as follows: (1) aged at least 18 years at the time of enrollment; (2) must have an AOB, which is defined as at least 1 incisor that does not have vertical overlap with teeth in the opposing arch. The remaining incisors may have minimal incisor overlap, but none can contact teeth in the opposing arch; (3) must be in active treatment for AOB, and expect to have treatment completed within 24 months of enrollment into the study; and (4) must have an initial cephalogram (taken before the beginning of treatment). A cephalogram created from a cone-beam computerized tomography scan is acceptable.
Exclusion criteria for patients were as follows: (1) clefts, craniofacial conditions or syndromes; (2) significant physical, mental, or medical conditions that would affect treatment compliance, cooperation, or outcome; (3) expects to move before the completion of the study; and (4) initial treatment plans estimated to be more than 36 months.
T1 questionnaires were completed by practitioners and patients at the enrollment visit to obtain information about patient characteristics, T1 diagnosis, and recommended/accepted treatment. Once active treatment was complete, posttreatment (T2) questionnaires were completed by practitioners and their patients to obtain information about treatment methods used. All study forms can be accessed at https://www.nationaldentalpbrn.org/study-results/#1589299528044-b9cab599-914e .
T1 and T2 lateral cephalometric images were collected. These images were traced using Dolphin Imaging & Management Solutions software (version 11.0; Dolphin Imaging and Management Solutions, Chatsworth, Calif), and measurements were generated using an automated, custom analysis. Cephalometric landmarks, summarized in Figure 1 , were first identified by 1 examiner and reviewed by the second examiner (L.S.T. and S.A.F.). Disagreements in landmark identification were resolved using the consensus between the 2 examiners, with a third examiner (K.W.C.) consulting if the 2 examiners could not reach a consensus.
A standard millimetric ruler in the cephalostat was used to calibrate millimetric measurements. When a ruler was present in only 1 of a patient’s cephalograms (either T1 or T2), the sella-nasion distance of the lateral cephalogram with the ruler present was used to calibrate the cephalogram without the ruler (n = 13). When a ruler was not present on both a patient’s T1 and T2 cephalograms (n = 14), a standard distance for nasion-menton, based on published norms, was used to calibrate the T1 cephalogram. , The T2 lateral cephalogram was then calibrated using the sella-nasion distance of the T1 lateral cephalogram, as described above.
T1 and T2 intraoral frontal photographs were deidentified and forwarded to the research team at the University of Washington. The Photographic Open Bite Severity Index (POSI) was developed to score the severity of the patient’s T1 AOB and final result using the pre- and T2 intraoral frontal photographs. Seven categories were developed on the basis of the number and type of teeth with vertical overlap ( Fig 2 ): (0) all 4 incisors with positive overlap; (1) 1 or 2 maxillary lateral incisors without vertical overlap (but both maxillary central incisors have vertical overlap); (2) 1 maxillary central incisor without vertical overlap (the other maxillary central has vertical overlap); (3) 2 maxillary central incisors without vertical overlap (at least 1 maxillary lateral has vertical overlap); (4) all 4 maxillary incisors without vertical overlap; (5) all anterior teeth, including canines, without overlap; and (6) all anterior teeth, including canines, plus at least 1 premolar without vertical overlap.
Each image was rated independently by the same 2 examiners, and the scores were compared. Disagreements in ratings were resolved using the consensus between the examiners, with a third examiner consulting if the two could not reach a consensus.
To calculate intra- and interrater reliability, 10 cephalometric images, and 20 intraoral frontal images were randomly selected. Cephalometric landmarks were identified, and frontal photographic images were rated by each evaluator and repeated 1 month later. Both inter- and intrarater reliability were excellent as determined using intraclass correlations. For the cephalometric analysis, the mean interrater reliability was 97%, and the mean intrarater reliability was 98%. For the POSI, the interrater mean percent agreement was 92.5%, and the mean kappa was 95.5%. The intrarater mean percent agreement was 97%, and the mean kappa was 98.5%.
Statistical analysis
Treatment success was defined using the following outcomes measures: (1) cephalometric analysis: lateral cephalometric radiographs were used to evaluate treatment success—defined by positive overbite at T2. The most anterior central incisors were measured; and (2) POSI: intraoral frontal photographs were used to evaluate treatment success—defined by a score of 0 (all 4 incisors with positive overlap) at T2.
Success rates were calculated for the following variables to identify potential factors related to successful AOB treatment: (1) treatment modality (ALN, FA, TAD, SX, and extractions), (2) patient T1 dentofacial characteristics, (3) treatment duration, (4) patient, demographic characteristics, and (5) practitioner demographic and practice characteristics.
Treatment was ascertained on the basis of the T1 and T2 questionnaires, with the latter enquiring about any changes in the treatment plan that were implemented after the enrollment time. In cases in which there were inconsistencies in reported treatment, clinical records were reviewed to confirm treatment.
Four mutually exclusive treatment categories were identified for investigation: (1) ALNs with no FA, TADs, or SX; (2) FA with no TADs, or SX; (3) TAD with no SX; and (4) orthognathic surgery (SX).
The treatment groups represent an increasing ability to manage complex malocclusions and an increasing level of invasiveness. Patients with treatment from multiple categories were categorized into the more invasive treatment category. For example, a patient treated with both aligners and FA was placed in the FA group. Almost all patients in the TADs or SX groups also underwent FA. Extractions of a premolar or anterior teeth were also identified, which could be performed in combination with any of the treatment groups listed above.
Patient T1 dentofacial characteristics were reported at enrollment, and cephalometric values were obtained from T1 cephalograms. Dentofacial characteristics identified for examination included profile, molar classification, maxillary and mandibular crowding, posterior crossbite, facial pattern, habits, and missing teeth. T1 cephalometric values evaluated included: ANB (°), mandibular plane angle (Mp-SN) (°), IMPA (°), and overbite (mm).
The duration of active orthodontic treatment was calculated as the time from appliance placement to appliance removal, on the basis of information from the T1 and T2 questionnaires, respectively. Patient characteristics included age, gender, race, insurance coverage, education level, and previous orthodontic treatment. Practitioner characteristics included, specialization, country of dental school, age when enrolled in dental network, gender, race and ethnicity, years since graduation from dental school, geographic region of practice, and practice type.
Descriptive statistics were performed on the patient and practitioner sample.
Overall success rates were calculated on the basis of the following outcome measures: (1) positive overbite (mm) on T2 lateral cephalogram, and (2) T2 POSI = 0—indicating positive overlap of all anterior teeth.
Because the cephalometric overbite measurements were only based on the most anterior central incisors, the POSI—which assesses the vertical position of all incisors—was used in most analyses.
Success rates for treatment modality, patient T1 dentofacial characteristics and cephalometric measures, treatment duration, patient demographic characteristics, and practitioner demographic and practice characteristics were obtained. Bivariate analyses were preliminarily performed to identify factors with statistically significant differences in treatment success. The clustering of patients within practitioners was adjusted for by using a generalized estimating equation. This clustering was implemented using PROC GENMOD in SAS (version 9.4, SAS Institute Inc, Cary, NC) with the CORR = EXCH option.
Multivariable predictive models were developed to identify predictors for treatment success, defined as POSI = 0. Specifically, the differences between success rates for different treatment categories (ie, SX vs no SX, SX vs FA, TADs vs FA, ALN vs FA) were explored. The predictive models were developed by entering all variables with P <0.10 after adjusting for the clustering of patients within practices. Backward elimination was performed until all characteristics had a P <0.10. Treatment category, extractions, and initial overbite (mm) were retained in the final reduced models regardless of the significance level because of clinical importance. SAS software was used to perform all statistical analyses.
Results
A total of 91 practitioners and 347 patients and were recruited for this study from October 2015 to June 2016. Data on T2 were collected from 84 practitioners and 260 patients through December 2018. Six patients had insufficient data for analyses, leaving a total of 254. The remainder of the practitioners and patients either withdrew from the study (24) or did not complete treatment within the study period (63). In addition, 24 patients were missing T2 cephalometric data, leaving a total of 230 patients for cephalometric analysis. Patients missing T2 intraoral images (22) were excluded from the POSI analysis, resulting in a total of 232 patients for POSI analysis.
The mean age of the practitioner sample was 48.8 years (standard deviation [SD], 9.8 years; range, 31-66 years), and 73% were male. The mean age of the patient sample was 32.1 years (SD, 11.9 years; range, 18-71 years), 75% were female, and 42% of the patients had prior orthodontic treatment. Details of practitioner and patient demographic characteristics are summarized in Tables I and II .
| n | % | |
|---|---|---|
| Status | ||
| Orthodontist | 82 | 98 |
| General practitioner | 2 | 2 |
| Sex | ||
| Male | 61 | 73 |
| Female | 23 | 27 |
| Age, y | ||
| <45 | 32 | 38 |
| 45-54 | 24 | 29 |
| 55-64 | 23 | 27 |
| ≥65 | 5 | 6 |
| Race and ethnicity, n = 83 | ||
| White | 52 | 63 |
| Asian | 19 | 23 |
| Multiracial | 2 | 2 |
| Hispanic | 10 | 12 |
| Geographic region of practice | ||
| West | 34 | 41 |
| Midwest | 8 | 10 |
| Southwest | 16 | 19 |
| South Central | 6 | 7 |
| South Atlantic | 9 | 11 |
| Northeast | 11 | 13 |
| n | % | |
|---|---|---|
| Sex, n = 253 | ||
| Male | 64 | 25 |
| Female | 189 | 75 |
| Age, y, n = 253 | ||
| 18-20 | 43 | 17 |
| 21-30 | 106 | 42 |
| 31-40 | 58 | 23 |
| ≥41 | 46 | 18 |
| Race and ethnicity, n = 253 | ||
| White | 146 | 58 |
| Black | 23 | 9 |
| Asian | 24 | 9 |
| Multiracial | 8 | 3 |
| Hispanic | 52 | 21 |
| Previous orthodontic treatment, n = 253 | ||
| Yes | 106 | 42 |
| No | 147 | 58 |
| Insurance coverage, n = 254 | ||
| No dental or medical insurance | 54 | 21 |
| Dental insurance does not cover orthodontics | 64 | 25 |
| Dental insurance covers orthodontics | 74 | 29 |
| Insurance covers orthognathic surgery | 62 | 24 |
| Highest level of education, n = 253 | ||
| High school graduate or less | 45 | 18 |
| Some college or associate degree | 79 | 31 |
| Bachelor’s degree | 84 | 33 |
| Graduate degree | 45 | 18 |
The mean T1 overbite measured from the lateral cephalograms was −2.3 mm (SD, 2.1; range, −12.9 mm to 1.1 mm). All patients did not have a vertical overlap of at least 1 incisor (POSI >0), and no incisors had contact with opposing teeth. Sixty-five percent (n = 151) exhibited no vertical overlap of all 4 incisors (POSI ≥4).
The mean T2 overbite measured from the lateral cephalograms was 1.3 mm (SD, 1.1 mm; range, −5.6 mm to 3.7 mm). Ninety-three percent of patients (n = 215) had a positive overbite measured on the T2 lateral cephalogram. Eighty-four percent (n = 194) of the patients exhibited positive vertical overlap of all anterior teeth at the end of treatment (POSI = 0). A summary of T1 and T2 POSI scores are presented in Table III . Two-thirds of our sample was classified as having a long-faced skeletal pattern on the basis of the vertical morphologic classification system.
| POSI at T1 | POSI at T2 | |||||||
|---|---|---|---|---|---|---|---|---|
| No. of patients | 0 | 1 | 2 | 3 | 4 | 5 | 6 | |
| 1 | 35 | 33 | 2 | 0 | 0 | 0 | 0 | 0 |
| 2 | 34 | 27 | 7 | 0 | 0 | 0 | 0 | 0 |
| 3 | 12 | 9 | 1 | 0 | 1 | 1 | 0 | 0 |
| 4 | 85 | 70 | 11 | 2 | 1 | 1 | 0 | 0 |
| 5 | 13 | 9 | 4 | 0 | 0 | 0 | 0 | 0 |
| 6 | 53 | 46 | 2 | 1 | 0 | 0 | 2 | 2 |
| Total | 232 | 194 | 27 | 3 | 2 | 2 | 2 | 2 |
Eleven percent of patients were treated with aligners only, 60% with FA only (no TADs or SX), 8% with TADs (no SX), and 21% with SX. Most of the TAD and SX patients also underwent FA therapy. Despite a recommendation rate of 37% for SX, only 21% of patients who completed treatment had surgery. Treatment is summarized in Table IV .
| Final treatment category | n | % | Extractions | |
|---|---|---|---|---|
| No | Yes | |||
| Aligners only | 29 | 11 | 29 | 0 |
| Fixed (no TADs or surgery) | 152 | 60 | 111 | 41 |
| TADs (no surgery) | 20 | 8 | 17 | 3 |
| Surgery | 53 | 21 | 48 | 5 |
| POSI at T2 = 0 | ||||
| Treatment duration (months) | n | % | n = 190 | % |
| <17 | 52 | 23 | 45 | 86 |
| 17-22 | 52 | 23 | 44 | 85 |
| 23-29 | 70 | 31 | 63 | 90 |
| >30 | 54 | 24 | 38 | 70 |
Patients in the TADs and surgery treatment groups exhibited slightly higher success rates compared with those treated with aligners or with FA only, but these differences were not statistically significant when comparing all 4 groups in a single model ( Table V ).
| All | POSI = 0 | Extractions | POSI = 0 | No extractions | POSI = 0 | |||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| n = 232 | n = 194 | % | P | n = 45 | n = 34 | % | P | n = 187 | n = 160 | % | P | |
| Final treatment category ∗ | 0.3 | NE | 0.4 | |||||||||
| Aligners only | 26 | 21 | 81 | 0 | 0 | Undefined | 26 | 21 | 81 | |||
| Fixed (no TADs or surgery) | 141 | 114 | 81 | 37 | 27 | 73 | 104 | 87 | 84 | |||
| TADs (no surgery) | 19 | 17 | 89 | 3 | 2 | 67 | 16 | 15 | 94 | |||
| Surgery | 46 | 42 | 91 | 5 | 5 | 100 | 41 | 37 | 90 | |||
| Extractions | 0.2 | |||||||||||
| No | 187 | 160 | 86 | |||||||||
| Yes | 45 | 34 | 76 | |||||||||
| OR = 0.5 | ||||||||||||
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