Bimaxillary proclination is a common malocclusion in the South Indian population, characterised by protrusive upper and lower incisors with a prominent dentoalveolar component. Treatment often involves extraction of the first premolars followed by retraction of the anterior teeth. While sagittal correction is the primary treatment objective, control over vertical dental changes is equally important to ensure favourable facial aesthetics and long-term occlusal stability.

In orthodontics, conventional anchorage refers to the use of teeth themselves as resistance units to prevent unwanted movement, without the aid of specialised devices such as temporary anchorage systems (TADs). Tooth movement during retraction is frequently accompanied by vertical side effects, including molar extrusion and incisor

intrusion or extrusion, which can influence the vertical dimension of the face. These changes are typically managed using biomechanical strategies such as mild reverse curves in archwires during retraction phase, tip-back bends, anchor bends, or inclusion of second molars—without resorting to skeletal anchorage. However, the effectiveness of these conventional approaches in controlling vertical dental movements, particularly in specific ethnic populations, remains under-investigated.

Vertical control becomes especially critical during space closure following premolar extractions, as the vertical positioning of molars and incisors can significantly influence facial harmony, occlusal function, and post-treatment stability. While anchorage mechanics play a pivotal role in guiding tooth movement, there is a paucity of data on how conventional anchorage systems affect vertical changes in non-growing patients, especially within the South Indian demographic.

Proffit et al. highlighted that unregulated molar extrusion could increase the mandibular plane angle, leading to clockwise mandibular rotation and undesirable vertical facial changes (1). Similarly, Bishara et al. underscored the importance of maintaining molar vertical position to preserve facial balance, particularly in patients predisposed to vertical growth patterns (2). On the anterior front, the vertical movement of incisors has a direct impact on smile esthetics and soft tissue profile. While intrusion can reduce excessive gingival display and enhance lip competence, uncontrolled extrusion may yield suboptimal esthetic outcomes. Kuroda et al. reported that skeletal anchorage allows for superior vertical control of incisors; however, findings from studies using conventional mechanics have been inconsistent, often depending on the specific biomechanical approach employed (3).

Ethnic variations in craniofacial morphology further complicate treatment planning. South Indian individuals typically exhibit a tendency toward bimaxillary proclination and reduced anterior facial height compared to Caucasian norms. Ajith et al. emphasized the necessity for population-specific standards in orthodontic diagnosis and treatment planning to improve outcome predictability (4). Consequently, data derived from Western populations may not fully apply to South Indian cohorts.

Despite extensive research on skeletal anchorage, studies focusing on vertical dental changes with conventional anchorage—particularly in South Indian populations—remain scarce. Given the unique craniofacial characteristics of this group, there is a need to explore whether traditional anchorage mechanics offer sufficient vertical control during anterior retraction.

This prospective clinical study aims to systematically evaluate the vertical displacement of molars and incisors during anterior retraction using conventional anchorage in South Indian patients with bimaxillary proclination, and to assess the adequacy of these methods in maintaining vertical control throughout treatment.

Aims and objectives

Aim:

To evaluate the vertical positional changes of molars and incisors during anterior retraction following premolar extraction using conventional anchorage—without the use of additional anchorage reinforcements—in a South Indian cohort.

Objectives:

To quantify vertical changes in the upper molars, upper incisors, lower molars, and lower incisors relative to stable cephalometric reference planes during anterior retraction.

Study Design and Sample:

This was a prospective clinical study involving 35 patients (23 female, 12 male) diagnosed with bimaxillary proclination. All patients were selected from a single orthodontic facility in South India (Department of Orthodontics, Government Dental College, Alappuzha, Kerala) and were treated by the same clinician to maintain consistency in the treatment protocol. This study was funded by State Board of Medical Research under Directorate of Medical Education, Kerala.

Inclusion criteria:

• Age between 16 and 25 years
• Full permanent dentition (excluding third molars)
• Class I skeletal base with bimaxillary dental proclination
• No prior orthodontic treatment
• Average mandibular plane angle inclination (SN-MP)
• All pre-treatment and post-treatment cephalograms taken from the same machine in the standard position by the same operator.
• Good quality pre-treatment and post-treatment lateral cephalograms.

Exclusion criteria:

• Systemic disease
• Evidence of bone loss
• Current periodontal disease.

Treatment Protocol:

Pre-treatment radiographs and full set photographs were taken initially. All 35 patients underwent extraction of all first premolars. Anterior retraction was carried out using conventional anchorage methods. No special anchorage reinforcements like transpalatal arches or palatal buttons were used.

Fixed mechanotherapy was carried out using a 0.022” slot MBT prescription appliance. The leveling and alignment phase was completed using nickel-titanium (NiTi) archwires, progressing from 0.014” round to 0.019” × 0.025” rectangular dimensions. During the retraction phase, 0.019” × 0.025” stainless steel archwires served as working wires. Retraction forces were applied using elastomeric chains placed on these rectangular stainless steel archwires.

To enhance anchorage control, mild reverse curves were incorporated into the archwires during the retraction phase. These curves were intended to induce slight distal tipping of the posterior anchor teeth and to counteract the extrusive moments on molars typically associated with retraction mechanics.

All patients were over 16 years of age at the start of treatment; therefore, the influence of residual growth on vertical facial height and mandibular plane angle (FMA) was presumed to be clinically insignificant. Post-treatment lateral cephalometric radiographs were obtained immediately following the removal of fixed appliances.

Parameters Measured:

Lateral cephalograms were taken at two stages: T1 – Pre-treatment

T2 – post-treatment immediately after appliance removal

The following vertical parameters were measured using a stable cranial base reference line (Upper teeth to palatal plane; lower teeth to mandibular plane):

• Upper molar height (U6-palatal plane)
• Lower molar height (L6-mandibular plane)
• Upper incisor height (U1-palatal plane)
• Lower incisor height (U1-mandibular plane)

All measurements were made by the same operator using digital cephalometric software to minimise inter- observer error. A calibration check was done by repeating measurements on 10 random cephalograms after two weeks.

Statistical Analysis:

The data collected was entered into a spreadsheet and analyzed using IBM SPSS statistics version 25. Mean and standard deviations were used to summarize the data. Normality was checked using Shapiro Wilk tests. All variables except upper incisor height (Baseline and post treatment) were normally distributed. The baseline and post treatment values for normally distributed variables were compared using paired t test. Wilcoxon signed rank test was used for comparing baseline and post treatment values of upper incisor height. P values <0.05 were considered statistically significant.

Comparison of Vertical Dental Measurements at Baseline and Post-Treatment

All values are in millimeters. Statistical tests used: Paired t-test (*), Wilcoxon signed-rank test (#).

The values of upper molar height and upper incisor height showed a statistically significant increase following treatment (Table 1 and Figure 1). Though lower molar height showed a slight increase following treatment, the change was not statistically significant. Similarly though lower incisor height showed a slight decrease following treatment , the change was not statistically significant (Table 1).

Figure 1. Box whisker plot illustrating the mean vertical changes in the upper molars (UMH), lower molars (LMH), upper incisors (UIH) and lower incisors (LIH).

This study aimed to evaluate skeletal vertical changes during anterior retraction using conventional anchorage in South Indian patients with bimaxillary proclination. Vertical changes in the position of molars and incisors were measured to assess the extent of extrusion or intrusion following space closure with premolar extractions.

The results indicated modest vertical changes, with mean differences typically between 0.5 mm and 1.5 mm. Although a subset of patients experienced clinically significant vertical changes (≥1 mm), these were not substantial enough to adversely affect facial proportions. This suggests that conventional anchorage methods, when properly applied with appropriate biomechanical control, can provide sufficient vertical stability during retraction.

Mild extrusion, particularly of the anterior teeth, has been well-documented in extraction mechanics. Kim et al.

(5) observed increased lower anterior facial height in patients treated with conventional anchorage, especially in hyperdivergent cases. Our study used conventional anchorage method of reverse curves in stainless steel arch wires during retraction phase, which may have limited such effects.

These findings align with those of Upadhyay et al. (6), who demonstrated that while skeletal anchorage devices like miniscrews offer superior vertical control, conventional anchorage can still be effective when managed skillfully. Park and Kwon (7) also emphasized that vertical effects depend more on force direction and mechanics than anchorage type, with two-step retraction techniques showing better vertical control than en-masse retraction with tipping forces.

The variability in the results (particularly in molar movement) suggests that individual patient characteristics or treatment specifics (e.g., anchorage type, force application) could influence outcomes.

Importantly, this study provides data specific to the South Indian population, which has a high prevalence of bimaxillary proclination. Sridharan et al. (8) found that this group often presents with increased incisor proclination and vertical facial proportions compared to Western norms. Our results help establish region-specific evidence that conventional mechanics can be adapted to achieve satisfactory vertical control in this population.

One limitation of this study is the absence of a comparative group using skeletal anchorage methods, which restricts the ability to directly evaluate the relative effectiveness of conventional anchorage in controlling vertical dental changes.

This clinical study evaluated vertical dental changes during anterior retraction using conventional anchorage in South Indian patients with bimaxillary proclination. The results demonstrated that vertical changes in molars and incisors were generally modest and within clinically acceptable limits. Despite the absence of skeletal anchorage, effective vertical control was achieved through proper biomechanical planning and the use of anchorage reinforcement appliances.

These findings support the viability of conventional anchorage in managing both sagittal and vertical dimensions during extraction-based treatment in patients with bimaxillary proclination. Furthermore, this study contributes population-specific data relevant to the South Indian demographic, where such evidence remains limited.

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