Split-mouth clinical trial evaluating pain perception in orthodontic patients using four types of separators: An in vivo study

INTRODUCTION

Orthodontic treatment often begins with the placement of separators to create interproximal space for band placement. These separators, while essential, are often associated with varying degrees of pain and discomfort, which can influence patient compliance and satisfaction. Understanding the extent of pain associated with different types of separators is crucial for improving patient experience and tailoring pain management strategies. The extent of separation depends on the magnitude of the force, its duration, and the adaptability of the periodontal ligament. The extent and severity of pain experienced by patients vary based on individual pain threshold, the magnitude and duration of force applied, and psychological factors.^[1] Separation is a procedure done in orthodontic treatment that involves forcing or wedging teeth apart, generally for a week, to gently loosen the tight interproximal contacts between teeth to provide space for the fitting of orthodontic bands.^[2] Understanding the impact of separator selection on both treatment efficiency and patient comfort is essential in orthodontic practice. The ideal separator should give rapid and good separation without causing the patient discomfort or pain, thereby making the fitting of the band to the tooth.^[3]

The history of orthodontic separation dates back to the early 20^th century, with Angle first advocating the use of brass wire ligatures to achieve space creation.^[4] Several types of separators are commonly used, including elastomeric rings, spring separators, and brass wire separators. Several types of separators are commonly used, including elastomeric rings, spring separators, brass wire, and kesling separators. Each type differs in force application, duration of effectiveness, and comfort. Studies such as those by Asiry et al.^[5] and Eslamian et al.^[6] reported that peak pain typically occurs within 24 hours after separator placement, with rigid separators often causing greater discomfort than flexible ones.

Each type differs in force application, duration of effectiveness, and comfort. Despite their clinical utility, a systematic evaluation of pain perception caused by these separators in vivo is lacking in the literature. Hence, the present study was conducted to evaluate pain perception using different types of orthodontic separators, with a focus on patients’ perception of pain and discomfort.

MATERIAL AND METHODS

The study is a non-randomized, split-mouth clinical trial conducted in vivo to evaluate pain perception associated with four different types of orthodontic separators placed in different quadrants of the same patient. This study was approved by the Institutional Health Ethical Committee and Institutional Research and Development Committee of Saraswati Dental College and Hospital, Lucknow.

The study was conducted on 54 participants seeking fixed orthodontic treatment, aged between 17 and 28 years, with no previous history of orthodontic treatment. The study design and participant flow are illustrated in Figure 1. The study included participants who met the following inclusion criteria: Absence of systemic illness, willingness to participate, no prior history of orthodontic treatment, fully erupted permanent first and second molars and second premolars, no caries or restorations on the proximal surfaces of these teeth, and good gingival and periodontal health. Exclusion criteria included the presence of systemic disease, poor oral hygiene, and any signs of gingival or periodontal pathology.

Close

Figure 1:

Consort-style flowchart showing participant enrollment, allocation of quadrants to the four separator groups, follow-up, and analysis.

Export to PPT

Out of 97 participants who fulfilled and willing the inclusion criteria given below, only 54 participants who gave their consent to participate in the study were selected. The sample size was calculated using G power software (version 3.1), keeping the standard values of alpha error at 0.05 and power of the study at 90% and effect size at 0.25, and the minimum sample size of the study is 52.

Statistical analysis was performed using the statistical package for the social sciences software version 26.0 statistical analysis software. Descriptive statistics, including mean and standard deviation, were used to summarize pain perception scores for each separator group at 4 hours, 24 hours, and on the 5^th day. One-way analysis of variance (ANOVA) was applied to compare mean pain scores among the four groups. Where statistically significant differences were found, tukey’s honestly significant difference post hoc test was used for pairwise comparisons. P < 0.05 was considered statistically significant.

Each participant’s mouth was divided into four quadrants, with each type of separator placed in a fixed, non-randomized order to maintain consistency. Group allocation for the four separators in different quadrants is summarized in Table 1. All separators were placed simultaneously during the same clinical appointment to standardize the timing of force application. Participants were guided on how to independently assess pain in each quadrant by gently biting or pressing the specific area, aided by a quadrant-specific chart to localize discomfort. Figures 2 and 3 illustrate the placement of kesling and elastomeric separators in the maxillary right and left quadrants, respectively, and brass wire and kansal separators in the mandibular left and right quadrants, respectively. Pain perception was measured using the numerical pain rating scale (NPRS), a validated patient-reported scale ranging from 0 (no pain) to 10 (worst possible pain). Participants recorded their pain scores for each quadrant at 4 hours, 24 hours, and on the 5^th day after separator placement. A follow-up visit was scheduled on the ^6th day to remove the separators, which were kept for 5 days as peak pain occurs around day 2 and reduces after day 3, ensuring optimal space creation with minimal discomfort. All data related to pain perception and discomfort were documented on a standardized data sheet.

Close

Figure 2:

Intraoral photograph showing kesling separator placed in the maxillary right side and elastomeric separator placed in the maxillary left side.

Export to PPT

Close

Figure 3:

Intraoral photograph showing a brass wire placed on the mandibular left side and a kansal separator placed on the mandibular right side.

Export to PPT

RESULTS

Table 2 reveals a comparative evaluation of pain perception scores recorded using the NPRS for the four separator groups: kesling (group I), elastomeric (group II), brass wire (group III), and kansal (group IV) at 4 hours, 24 hours, and on the 5^th day following separator placement. At 4 hours, pain perception was highest in the kansal separator group and lowest in the kesling separator group. A similar pattern was observed on the 5^th day, with kansal separators continuing to show the highest pain scores and kesling the least. At 24 hours, the kansal separator again recorded the highest mean pain score, while the elastomeric separator group reported the lowest. Statistical analysis using one-way ANOVA revealed a significant difference in pain perception scores among the four groups at 4 hours (P = 0.028) and on the 5^th day (P = 0.012). However, no statistically significant difference was observed at 24 hours (P = 0.152). Post hoc comparisons further confirmed that the pain associated with kansal separators was significantly greater than with kesling and elastomeric separators at the significant time points.

DISCUSSION

In this study, kansal separators produced the highest pain levels across all time points, while kesling separators were the most comfortable. Elastomeric separators resulted in moderate discomfort. Significant differences at 4 hours and day 5 indicate that the separator type directly affects the pain experience, while the non-significant variation at 24 hours likely reflects individual pain adaptation.

These findings align with those of Shivaprasad et al.,^[3] who reported better tolerance with kesling separators after adjustment. The declining pain trend supports prior studies, which note peak discomfort within the first 24 hours. Consistent with Hoffman, brass wire separators caused soft-tissue irritation; however, Hoffman found elastomeric separators to be the most painful, unlike our results, where kansal separators ranked highest.^[4]

Overall, rigid separators can induce more discomfort and may be less suitable for patients with sensitive skin. The split-mouth design minimized individual variability, strengthening internal comparisons. Clinically, kesling or elastomeric separators may be preferred in pain-sensitive patients to enhance comfort and compliance.

The findings of this study confirm that separator type significantly impacts pain perception. kesling separators consistently caused the least discomfort, in agreement with Kumar et al., who also noted reduced pain by day 5.^[7] In contrast, kansal separators were the most painful throughout, likely due to their rigidity and force application.

The observed pain peak between 4 and 24 hours, followed by a gradual decline, is consistent with the findings of Asiry et al. and Eslamian et al., reinforcing the transient nature of separator-induced discomfort.^[5,6]

Although early differences in pain were not statistically significant, the consistent trend of greater pain with rigid separators supports findings by Tripathi et al., Sabuncuoglu et al. who emphasized better patient tolerance with kesling separators.^[8,9]

The significant difference observed at 24 hours highlights the impact of separator design during initial adjustment. In addition, findings from Oshomoji et al. suggest that higher separation force may correlate with increased discomfort, potentially explaining the consistent pain associated with kansal separators in our study.^[10] Additionally, findings from Oshomoji et al. and Manandhar P suggest that higher separation force may correlate with increased discomfort.^[10,11]

The intra-subject split-mouth design used here minimized individual variability, enhancing the reliability of comparisons. The use of the NPRS scale, validated by Iwasaki et al. and Polat and Karaman, ensured accurate and consistent pain reporting across quadrants.^[12,13]

A key strength of this study is its intra-subject (split-mouth) design, wherein each participant received all four separator types in different quadrants. This approach minimized inter-individual variability and enhanced internal validity. The use of the NPRS, a validated and reliable tool, further ensured consistency in pain assessment.

However, certain limitations should be acknowledged. The relatively small sample size may affect the generalizability of results. Pain perception, being subjective, can vary with psychological state, individual pain thresholds, and unmonitored analgesic use, all of which were not controlled. Additionally, the study did not evaluate separator efficiency or dislodgement, both of which may impact pain perception. The short follow-up period may have also overlooked delayed discomfort.

These findings emphasize the need to prioritize patient comfort in orthodontic care. kesling separators, being better tolerated, are well-suited for pediatric or pain-sensitive patients. In contrast, kansal and brass wire separators, though effective, may cause more discomfort and should be used with caution. Future studies should explore separator efficiency, consider psychological factors, and include broader samples to support more personalized and comfortable treatment choices.

CONCLUSION

This study demonstrates that separator type significantly affects pain perception, with rigid separators causing more discomfort, especially in the early hours, and flexible ones like kesling being better tolerated. Pain levels declined over time, reflecting patient adaptation. NPRS shows more consistent and statistically significant differentiation between separator types. These findings highlight the importance of selecting separators that balance clinical effectiveness with patient comfort, promoting better compliance and individualized orthodontic care.