Predictors of orthodontic treatment conclusion: A historical cohort study


The study investigated which patient and orthodontic treatment factors act as predictors for the conclusion of the ongoing treatment in a dental clinic of a specialization program in Orthodontics.


Data were collected from the records of patients treated from 1997 to 2015. Potential predictors for treatment conclusion were investigated: patient-related factors (PRFs) and treatment-related factors (TRFs). PRFs were sex, age, face balance, Angle malocclusion classification, open bite, denture, facial pattern, facial profile, buccal corridor, crossbite, maxillary deficiency, and sagittal mandibular behavior; and TRFs were therapeutic approaches, treatment modality, extractions, and Bolton discrepancy. The initial and final treatment dates were collected. Descriptive data analysis, univariate, and multivariate logistic regression were performed (5% significance).


Of the 903 records, 561 patients were included in the study. It was demonstrated that starting the treatment at a young age (PRF) and the presence of crossbite (TRF) are predictive factors for the treatment conclusion. A vertical facial pattern (dolichofacial or brachyfacial) and a greater number of extractions for orthodontic reasons may contribute positively to the conclusion of the treatment. The frequency of treatment inconclusion was higher during the first 2 years of treatment (more than 50% of the patients that initiated the treatment).


Young age at the beginning of treatment and the presence of crossbite malocclusion can increase the chance of treatment conclusion.


  • Patients who start treatment at a young age are more likely to complete treatment.

  • Patients with crossbite are more likely to complete treatment.

  • Patients who abandon treatment are most likely to do so during the first 2 years.

Orthodontic problems may be related to changes in craniofacial development and growth, which can result in crowded, inclined, or protruded teeth; a change in number, shape, and position of teeth; or soft orofacial tissues problems. These morphologic changes can lead to disturbances in the perimeter and length of the dental arches and result in a malocclusion, challenging the diagnosis, planning, and conclusion of orthodontic treatment. , In addition, orthodontic treatments are performed to improve esthetics and masticatory functions. In general, clinical criteria based on scientific evidence and professional experience are used to recommend such treatments without considering the patients’ expectations and opinions, which can lead to dissatisfaction and result in the treatment abandonment.

A high rate of treatment inconclusion is observed within the context of alterations in patient socioeconomic conditions, different orthodontic treatment approaches, an increased number of dental care professionals, and orthodontics’ specialization centers. Withdrawal (treatment interruption informing the dentist), abandonment (drop-off not informing the dentist) or transfer of the orthodontic treatment can have a negative impact on patients: the patient can remain unattended, persisting the orthodontic problem; or, in case of transference between professionals, the treatment plan and therapeutic approach can change, increasing the time required to conclude the treatment. In addition, the increase in service offers observed in recent years may contribute to patients’ mobility between professionals, institutions, dental offices, and clinics, increasing treatment inconclusion. To avoid the negative effects related to drop-offs, it is important to investigate whether patient-related factors (PRFs), such as sex, age, and morphologic characteristics; or treatment-related factors (TRFs): diagnosis and therapeutics approach (eg, dental extractions, interceptive approach in the mixed dentition, or corrective in the permanent denture) could contribute for the orthodontic treatment conclusion, even if some factors are not completely under the professional’s control.

The patient’s age at the beginning of the treatment can require different therapeutic approaches, which can influence the treatment outcomes, including occlusal function, esthetics, patient satisfaction, duration, and conclusion of the treatment. Nowadays, there is a high demand for orthodontic treatments, especially in adult patients with nonharmonious faces, such as those unbalanced vertically and transversely, crowded teeth and dental relationships functionally inadequate, such as crossbites. Contemporary orthodontics seeks to manage facial growth orthopedically; therefore, patients are recommended to start the treatment at a young age, in the deciduous and mixed denture, according to his malocclusion and degree of emotional maturity to undergo interceptive orthodontic treatment. ,

Therapeutic decisions in orthodontics (often related to personal preferences and experiences associated or not to scientific criteria) have instigated many discussions. , Over the last decades, the orthodontic specialty has experienced relevant technological changes, such as brackets bonded directly to the teeth, brackets with angulation, torque and rotation prescriptions, ceramic brackets, self-ligating brackets, shape memory and superelastic wires, and treatments with aligners, which generated tendencies for therapeutic decisions. Studies on the impact of different therapeutic approaches and factors associated with the orthodontic treatment or the patient on the treatment conclusion are quite scarce in the literature.

With the inconclusion of the treatment, orthodontic problems could remain and have a negative impact on patients’ oral health and quality of life. , , To identify clinical aspects that could avoid treatment drop-offs, this study investigated PRFs and TRFs as predictors for the conclusion of the orthodontic treatment using the clinical records of a Lato Sensu Specialization Program in Orthodontics. The hypothesis tested was that patient-related and treatment-related variables do not influence the conclusion of the treatment.

Material and methods

A historical cohort study of aggregated data (retrospective cohort) of patients’ clinical records was performed. The study investigated factors potentially related to the outcome: conclusion of the orthodontic treatment.

Clinical records of the Lato Sensu Specialization Program in Orthodontics, Dentistry School, University of Passo Fundo, located in Passo Fundo, in the North region of Rio Grande do Sul, Brazil.

The population of this study was composed of patients who started treatment at the Lato Sensu Specialization Program in Orthodontics, Dentistry School, University of Passo Fundo, located in Passo Fundo, in the North region of Rio Grande do Sul, Brazil from 1997 to 2015. Patients with complete records were considered eligible: medical history and orthodontic files (panoramic radiography, lateral teleradiography, extra and intraoral photographs). Sociodemographic data, diagnosis, planning, and evolution of the orthodontic treatment were collected by a single operator. A reduced number of patients who initiated treatment during the deciduous dentition (n = 6) and mandibular prognathism not associated with transverse and sagittal maxillary deficiency (n = 5) was observed in the study. Therefore, these patients were excluded from the study of subsequent analysis.

The outcome investigated was the conclusion of orthodontic treatment.

Patient-related (PRFs) and treatment-related (TRFs) potential predictive factors for the conclusion of the orthodontic treatment were investigated:

(1) PRFs: (a) Demographic characteristics: sex and age. (b) Orthodontic diagnosis: face (balanced or not); malocclusion (Angle Class I, II, and III); open bite (absent or present); mixed or permanent denture; facial profile (straight, convex, or concave), buccal corridor (wide or with filling), absence or presence of crossbite (anterior, posterior, and anterior and posterior) or edge-to-edge relationship of the incisors, maxillary deficiency (with or without), and mandibular sagittal behavior (with or without deficiency) were recorded and coded.

(2) TRFs: (a) Therapeutic approaches used (brackets and/or accessory devices, rapid maxillary expansion (RME), reverse traction of the maxilla associated with RME and associated removable devices) treatment protocols with permanent tooth extractions (with the extraction of up to 2 teeth, with the extraction of 3 or more teeth) presence or absence of dental size discrepancy (Bolton discrepancy), whether or not the treatment was completed. (b) Treatment modalities (interceptive, corrective, and interceptive and corrective).

In addition, it was observed that the number of patients starting orthodontic treatment decreased over the years. Therefore, the influence of the starting year on the outcome (treatment conclusion) was also analyzed. Thus, the years were divided into 3 groups, with an approximate number of patients: first tercile (1997-2000: representing 41.9% of the total participants), second tercile (2001-2006: 33%), and third tercile (2007-2015: 25.1%).

Statistical analysis

A descriptive analysis was performed to determine the relative and absolute frequencies of the predictor variables and outcome (orthodontic treatment conclusion).

A univariate regression analysis was performed to determine the most relevant predictive factor, and those showing P ≤0.25 were included in a multivariate model. Then, the influence of the selected PRFs and TRFs on the conclusion of the orthodontic treatment was analyzed using multivariate regression, with a significance of 5%. In the multivariate analysis, factors that demonstrated a very low correlation to the outcome were subtracted from the final model: sex, age at the beginning of the treatment, face balance, crossbite extraction protocol, and year of treatment start. The prevalence ratios and confidence intervals were obtained. Data were analyzed using STATA 14 (Statistics/Data Analysis, College Station, Tex).


From a total of 903 patients records, data from 561 were included in the study. Patients have from 5 to 56 years old, with a mean of 14 years. The average treatment time varied between 5 and 190 months, with an average of 47 months.

The data collected from each patient are presented in Table I , which shows a greater number of female participants (56.1% of the included patients), having permanent (50.4%) or mixed (49.6%) denture, dolichofacial pattern (52.4%), convex facial profile (60.8%), broad (59.5%) buccal corridor, with a balanced face (92.7%), with a maxillary deficiency (61.5%), but not mandibular deficiency (80.4%), mostly having Class II malocclusion (56%), with no crossbite (73.6%) or open bite (88.6%). The Bolton analysis consists of measuring the discrepancy between the size of maxillary and mandibular teeth: the sum of the mesiodistal width of the 12 mandibular teeth is divided by the sum of the maxillary teeth. The overall ratio of 91.3% is considered an optimum interarch relationship. Different ratios are called Bolton discrepancy and were present in 62.6% of the participants. Regarding the treatment, most of the patients were submitted to corrective treatment modality (67.6%), using brackets (43.5%) or RME; 44%), and an extraction protocol of ≤2 teeth (75.9%).

Table I
Distribution of patients according to PRF and TRF characteristics and conclusion of treatment
Characteristics Concluded Did not conclude
n % n %
Total 377 67.2 184 32.8
Male 158 64.2 88 35.8
Female 219 69.4 96 30.6
Permanent 199 70.3 84 29.7
Mixed 178 64.0 100 36.0
Facial pattern
Mesofacial 122 66.0 63 34.0
Brachyfacial 56 68.3 26 31.7
Dolichofacial 199 67.7 95 32.3
Face profile
Straight 129 71.7 51 28.3
Convex 221 64.8 120 35.2
Concave 27 67.5 13 32.5
Buccal corridor
Filled 157 69.2 70 30.8
Broad 220 65.9 114 34.1
Face balance
Balanced 343 66.0 177 34.0
Unbalanced 34 82.9 7 17.1
Maxillary deficiency
Without deficiency 148 68.5 68 31.5
With deficiency 229 66.4 116 33.6
Mandibular deficiency
Without deficiency 303 67.2 148 32.8
With deficiency 74 67.3 36 32.7
Angle classification
Class I malocclusion 116 73.0 43 27.0
Class II malocclusion 207 65.5 107 34.5
Class III malocclusion 54 63.5 31 36.5
Absence 278 67.2 135 32.8
Anterior and/or posterior 89 72.4 34 27.6
Edge-to-edge 10 41.7 14 58.3
Open bite
Absence 334 67.2 163 32.8
Presence 43 67.1 21 32.9
Treatment modality
Corrective 262 69.1 117 30.8
Interceptive and corrective 89 67.0 44 33.0
Interceptive 26 53.1 23 46.9
Therapy instituted
Brackets 174 71.3 70 28.7
RME 159 64.4 88 35.6
RME and RT 35 67.3 17 32.7
Removable appliance and associated 9 50.0 9 50.0
Extraction protocol
≤2 teeth 276 64.8 150 35.2
≥3 teeth 101 74.8 34 25.2
Discrepancy of Bolton
Absence 234 66.7 117 33.3
Presence 143 68.0 67 32.0
Year of treatment start
First tercile: 1997-2000 175 74.5 60 25.5
Second tercile: 2001-2006 117 63.2 68 36.8
Third tercile: 2007-2015 85 60.3 56 39.7
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Feb 28, 2021 | Posted by in Orthodontics | Comments Off on Predictors of orthodontic treatment conclusion: A historical cohort study
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