Treatment of Class II malocclusion with 2-maxillary premolar extractions: Monthly vs biweekly appointments, which is more efficient?

Introduction

This study compared whether there is a difference in treatment time (TT) and efficiency when appointments are held once a month or at 2-week intervals in patients with Class II malocclusion treated with 2-premolar extractions

Methods

The patients of this retrospective sample were treated with the same orthodontic mechanics and divided into 2 groups according to frequencies of orthodontic appointments. Group 1 consisted of 18 patients (10 males, 8 females), with an initial mean age of 14.38 ± 1.38 years and appointments once a month. Group 2 consisted of 19 patients (9 males, 10 females), with an initial mean age of 14.12 ± 1.38 years and biweekly appointments. Edgewise fixed appliances with a slot size of 0.022 × 0.028 mm were used, and the anterior teeth were retracted en-masse with a rectangular wire and elastic chains. The Peer Assessment Rating and Objective Grading System indexes were measured in the dental models at the beginning and the end of treatment. Efficiency was assessed by dividing the percentage of improvement of each occlusal index concerning the multiplication of TT and the number of appointments.

Results

Both groups presented similar Peer Assessment Rating and Objective Grading System indexes at the end of treatment. Groups 1 and 2 presented different TTs (28.06 and 22.05 months, respectively); however, there were no differences regarding the efficiency of both protocols.

Conclusions

Patients with Class II malocclusion treated with 2-maxillary premolars had significantly shorter treatment times when seen on biweekly appointments than those with monthly appointments; however, there was no difference in efficiency between protocols.

Highlights

•

Treatment time (TT) and efficiency were compared in patients treated once a month or at 2-week intervals.
•

The Peer Assessment Rating and Objective Grading System indexes were used.
•

Efficiency was assessed considering the occlusal index, TT, and number of appointments.
•

TT was shorter in the group seen on a biweekly frequency.
•

There was no intergroup difference regarding treatment efficiency.

Class II malocclusion treatment is a challenge faced by orthodontists. Although there are several treatment possibilities, their selection depends on factors such as malocclusion severity (skeletal or dental), the patient’s esthetic assumptions, and adherence. Furthermore, an estimate of the total TT and whether the treatment will be efficient is essential, both from a clinical point of view and the financial costs involved. ^,

In 1988, Alger did not find significant differences between longer (6 weeks) and shorter (4 weeks) orthodontic appointments, claiming that it may not be necessary to follow up with patients every 3 or 4 weeks. It was suggested that 6-week appointment intervals are satisfactory and produce TTs within the accepted limits with fewer patient visits. Nonetheless, it is not certain that in terms of the duration of orthodontic treatment, it may be more important to keep treatment short rather than longer appointment intervals. ^, A previous study observed that the average time between appointments could be associated with increased treatment duration and that extractions may not affect treatment time.

Overall, the appointments must be organized in an optimized way with the biological response to the applied forces, given the periodontal condition of the patient. It has been proved that continuous forces offer a greater risk to root resorption than intermittent forces. ^, Regarding the en-masse retractions, the forces promoted by closed springs would be more harmful than elastics. Even with weekly consultations, ^, no significant problems concerning the loss of periodontal support or significant root resorption were reported. ^, In addition, the elastics used to assist tooth movement lose their force significantly in the first days of use, which may also suggest weekly consultations in some patients. ^,

At the end of orthodontic treatment, it is important to have therapeutic goals. Objective criteria are often used to evaluate the results and stability of orthodontic treatment. In this context, the Peer Assessment Rating (PAR) index and the American Board of Orthodontics (ABO) Objective Grading System (OGS) are 2 of the most used indexes. ^, The PAR index assesses pretreatment and posttreatment dental models, comprising 11 criteria. The greater the average percentage reduction in the PAR score, the greater the completion obtained by the orthodontic treatment. ^, The OGS is a more robust method of outcomes, which evaluates posttreatment dental models according to 8 different components: alignment, marginal ridges, buccolingual slope, occlusal relationships, occlusal contacts, overjet, interproximal contacts, and root angulation. For measurements, a metal gauge is used.

Considering the overall clinical importance of treatment efficiency, this study aimed to compare the treatment time (TT) and treatment efficiency index (TEI) using PAR and OGS indexes in patients with Class II malocclusion treated biweekly or once a month (4-5 weeks) appointments. The null hypothesis conserved no differences in Class II TT and efficiency between the 2 treatment protocols.

Material and methods

This retrospective study was approved by the Ethics in Research Committee at the University of São Paulo. All patients involved in this investigation provided written informed consent.

Orthodontic treatments were performed by graduate students at the Orthodontic Program under the supervision of the clinical instructors to ensure uniformity in the protocols and mechanics used.

Based on a previous study, a sample size calculation was performed to detect a minimum difference of 6.0 months for TT considering a standard deviation of 6.31. An α error of 5% and a β of 20% were considered. Thus, a minimum of 36 patients was needed.

The sample was selected from the orthodontic records of patients treated in the Orthodontic Department at the University of São Paulo between 2008 and 2013. All records were organized in a crescent order. The available files were consecutively evaluated after this order until the minimum number of patients was selected on the basis of the sample size calculation. Hence, sample selection was interrupted when the necessary number of patients was obtained.

The final study sample included 37 patients (19 males, 18 females). Patients were evaluated according to the frequency of orthodontic appointments. According to the objectives of this study, the inclusion criteria were: Class II malocclusion Division 1 or 2, presence of all permanent teeth up to the first molars, absence of dental anomalies of number or shape, and no history of orthodontic treatment.

Group 1 consisted of 18 patients (10 males, 8 females) treated at appointments once a month. Their initial mean age was 14.38 ± 1.38 years. Group 2 consisted of 19 patients (9 males, 10 females) treated with biweekly appointments. Their initial mean age was 14.12 ± 1.38 years. Conventional Edgewise fixed appliances with 0.022 × 0.028-in were used in the patients. A usual wire sequence of an initial 0.015-in Twist-Flex or 0.016-in nickel-titanium was followed by 0.016, 0.018, 0.020, and 0.018 × 0.025-in stainless steel archwires. Accentuated and reversed curves of Spee in the maxillary and mandibular arches, respectively, were used for deepbite correction.

In the mentioned groups, anterior teeth were retracted en-masse, with elastic chains from the anterior hook to the hook of the maxillary first molars combined with rectangular wires. An extraoral headgear was used to reinforce anchorage when necessary. Class II intermaxillary latex elastics with a magnitude from 200 to 250 g of force were used for treatment completion. Both groups finished with acceptable occlusions, normal overbite and overjet, Class I canine relationships, and no posterior crossbites. The retention protocol consisted of a Hawley plate in the maxillary arch for a mean period of 1 year and a mandibular fixed retainer bonded on mandibular canines.

The initial age and sex of each treated patient were obtained through the analysis of their files, which included orthodontics records as well as initial and final dental models, also having their initial therapeutic plan consulted regarding the proposed treatment protocol. The records of therapeutic procedures were evaluated regarding the pretreatment and final dates of treatment, frequency, number of appointments, and the final treatment report. Patient cooperation was also observed in the records. The initial and final dental study models were selected on the basis of the inclusion criteria. Damaged dental models were excluded from the sample.

The PAR index was measured according to DeGuzman et al. Thus, the evaluation consisted of 5 criteria: alignment, overjet, overbite, midline, and posterior occlusion, measured at the beginning (I-PAR) and the end of orthodontic treatment (F-PAR). The amount of occlusal improvement was obtained by subtracting the F-PAR value from the I-PAR (DifPAR). This variation in the occlusal index expressed as a percentage was called the percentage of PAR reduction (PcPAR). A total of 74 pairs of models were measured at pretreatment and posttreatment. A digital caliper (FWP, Maub, Polland) was used to perform the measurements.

The ABO recommends using the OGS to measure the quality of treatment completion. The OGS uses 7 criteria measured on dental models: alignment, marginal ridges, buccolingual inclinations, overjet, occlusal contacts, occlusal relationships, interproximal contacts, and 1 measure in the panoramic radiograph, the roots angulation. The metal ruler recommended by the ABO (ABO Measurement Meter, St Louis, Mo) was used to evaluate models. Each deviation from normality >0.5 mm was recorded. Similarly to the PAR index, the greater the sum of the criteria, the greater the severity of the malocclusion. ^, OGS was also measured before treatment (I-OGS) and at the end of treatment (F-OGS), as well as its variation, DifOGS, and PcOGS. To evaluate TEI, the following formula was applied:

TEI = PcPAR/TT × number of appointments (NA). In this way, it was possible to evaluate the 3 fundamental variables for TEI, which are directly proportional to PcPAR and inversely proportional to TT and NA.

The same examiner (D.L.T.) reevaluated the PAR and OGS indexes after a 4-week interval, using dental models of 15 randomly selected patients. Random and systematic errors were calculated according to Dahlberg’s formula and with dependent t tests, respectively, at P <0.05.

Statistical analysis

This study focused on a descriptive analysis. Therefore, qualitative variables were presented in absolute values and percentages, and quantitative variables were described with means and standard deviations.

The group characteristics regarding sex, malocclusion severity, type of Class II, NAs, emergency visits, and missed appointments were presented in Table I . Descriptive data related to the patient’s age, occlusal indexes, TT, and treatment efficiency were included in Table II .

Table I

Descriptive data results of intergroup comparability regarding sex, Class II malocclusion severity, type of Class II malocclusion, NAs, emergency visits, and missed appointments

Variables	G1 (monthly), n = 18	G2 (biweekly), n = 19
Sex
Females	8 (44.4)	10 (52.6)
Males	10 (55.6)	9 (47.4)
Severity
One half cusp	2 (11.1)	2 (10.5)
Three fourths cusp	4 (22.2)	1 (5.3)
Full cusp	12 (66.7)	16 (84.2)
Type of malocclusion
Division 1	15 (83.3)	12 (63.2)
Division 2	3 (16.7)	7 (36.8)
NAs	29.5 (5.2)	40.9 (6.4)
Emergency visits	3.05 (1.3)	3.67 (1.3)
Missed appointments	1.05 (1.1)	0.94 (1.3)