Association between incisor positions and amount of interdental stripping in patients undergoing orthodontic treatment

Introduction

The study aimed to investigate the effect of a nonextraction treatment approach with interdental stripping (IDS) on the dentofacial structures in patients with dental and skeletal Class I, II, and III malocclusions.

Methods

A total of 60 patients with mild-to-moderate crowding of the teeth and nonsevere skeletal malocclusion were included and divided into 3 groups: Class I, Class II, and Class III groups (n = 20 per group). In all patients, nonextraction orthodontic treatment was administered, and those who underwent IDS at the jaw quadrants as needed were evaluated. For pretreatment and posttreatment evaluation, lateral cephalometric radiography and 3-dimensional dental model scans were acquired for each patient. For statistical analysis, paired-samples t test and 1-way analysis of variance with Tukey post-hoc test were used for parametric variables, whereas the Wilcoxon paired signed rank test and Kruskal-Wallis test with Dunn post-hoc test were used for nonparametric variables.

Results

An increase in the maxillary incisor angle was observed in patients with Class I and Class III malocclusions, whereas a decrease was observed in patients with a Class II malocclusion ( P < 0.05). Mandibular incisor angles were significantly increased in the Class II malocclusion group ( P < 0.05) but unchanged in the other groups. IDS was more frequently applied to the posterior aspect of the maxilla and mandible in patients with a Class II malocclusion than in patients with other malocclusion types, and the amount of IDS at the anterior aspect of the mandible was significantly higher in the Class III group.

Conclusions

Combined nonextraction orthodontic treatment and IDS yielded successful treatment outcomes. IDS application was localized to different jaw regions according to the different malocclusion types.

Graphical abstract

Highlights

  • We examined interdental stripping (IDS) needs of nonextraction patients.

  • The rate and location of IDS varied according to the type of malocclusion.

  • Patients with Class II malocclusion needed more IDS for posterior teeth than anterior teeth.

  • Patients with Class II malocclusion need IDS mostly in the mandibular anterior teeth.

  • IDS applied to maxillary incisors was negatively correlated with incisor position.

Various orthodontic treatments have been developed to achieve a good facial profile and occlusion. Treatment of borderline patients of a nonsevere skeletal malocclusion and mild-to-moderate crowding without adverse effects is a challenge, and in these patients, orthodontists face difficulty in making a decision between an extraction or nonextraction treatment approach for prevention of poor stability and protrusive profile. Some reports indicated that nonextraction treatment was not associated with significant problems in terms of stability; nevertheless, only a few studies evaluating the effect of nonextraction orthodontic treatment on dentofacial structures under different classification types of malocclusion are reported in the literature.

The use of nonextraction orthodontic treatment options such as various expansion or nonexpansion, stripping, distalization, and surgical or nonsurgical methods in a wide range of indications is gaining popularity among patients and many orthodontists. Many methods for gaining space during the procedure of orthodontic treatment and dental alignment are available, of which, stripping called interdental stripping (IDS), is widely used by many clinicians and researchers. , Previous studies recommended IDS as an option for tooth extraction and reported that it could contribute to stability after orthodontic treatment in borderline patients. , , IDS achieves preservation of the transverse arch width without marked change in the anterior tooth position, self-alignment of crowding, and decrease in both treatment time and chair time , , ; therefore, it is generally used for the elimination of black triangles after orthodontic treatment, adjustment of the tooth shape, fixing discrepancies of the Bolton ratio and tooth size, treatment of borderline patients, and increasing stability. , , , In addition, although IDS is a potential risk factor for caries development, reports have indicated that preventive procedures and patient motivation can overcome the associated risk.

We conducted a retrospective study to clarify the effectiveness of treatment in patients with borderline dental and skeletal Class I, II, and III malocclusions. The study aimed to determine the location of the jaw region and incisor positions in patients with Class I, II, and III malocclusions with mild-to-moderate crowding and nonsevere skeletal discrepancies who underwent nonextraction treatment.

Material and methods

The study was approved by Erciyes University Clinical Researches Ethics Committee, Kayseri, Turkey (Approval no. 2019/857). The sample size was determined by power analysis with G∗Power software (version 3.1.3; Franz Faul University, Kiel, Germany): twenty patients were required for more than 95% power to detect significant differences with an effect size of 0.85 at a significance level of α = 0.05. A total of 60 patients with nonsevere skeletal and dental Class I, II, and III malocclusions who underwent nonextraction treatment on the basis of minimal-moderate dental arch crowding, good facial profile, and acceptable dentofacial relationships at the Department of Orthodontics, Faculty of Dentistry, Erciyes University, were randomly selected. The patients were divided into 3 groups (each, 20 patients) as follows: Class I, 11 female patients and 9 male patients with a mean age of 15.82 ± 1.54 years and 16.00 ± 3.04 years, respectively; Class II, 12 female patients and 8 male patients with a mean age of 14.47 ± 2.10 years and 14.80 ± 1.64 years, respectively; Class III, 12 females and 8 male patients with a mean age of 14.64 ± 1.36 years and 15.00 ± 1.73 years, respectively. The selection criteria were as follows: (1) balanced facial profile and minimum-moderate dental arch crowding (Class I: maxillary arch, 2.29 ± 1.25; mandibular arch, 1.73 ± 1.75; Class II: maxillary arch, 2.18 ± 1.51; mandibular arch, 1.66 ± 1.00; Class III, maxillary arch, 2.07 ± 1.11; mandibular arch, 1.82 ± 0.94; Table I ); (2) borderline skeletal and dental Class I, II and III malocclusions; (3) no narrowing of the maxillary or mandibular dental arch and congenitally or secondary missing tooth; (4) no restorative treatment performed, and no wear on the mesial and distal sides of any teeth; and (5) good quality models and lateral cephalometric radiographs at pretreatment and posttreatment in the malocclusion groups.

Table I
Distribution of patients according to the malocclusion groups
Groups n Age, y Treatment duration, y Mean age, n Initial crowding, mm
Female Male Maxillary arch Mandibular arch
Class I 20 15.91 ± 2.27 1.26 ± 0.85 15.82 ± 1.54 (11) 16.00 ± 3.04 (9) 2.29 ± 1.25 1.73 ± 1.75
Class II 20 14.55 ± 1.96 1.89 ± 0.92 14.47 ± 2.10 (12) 14.80 ± 1.64 (8) 2.18 ± 1.51 1.66 ± 1.00
Class III 20 14.78 ± 1.48 2.01 ± 1.12 14.64 ± 1.36 (12) 15.00 ± 1.73 (8) 2.07 ± 1.11 1.82 ± 0.94
Total 60 15.09 ± 2.00 1.68 ± 0.98 14.92 ± 1.80 (35) 15.38 ± 2.33 (25) 2.18 ± 1.28 1.74 ± 1.27

Note. Data was given mean ± standard deviation.

Orthodontic treatment was performed using Roth prescription brackets with 0.018-in slot (Mini Master; American Orthodontics, Sheboygan, Wis). After transition to the rectangular stainless-steel wire phase, the residual amount of crowding and dental relationships was resolved by IDS with single-sided diamond discs (Galaxy IDS Diamond Discs; OrthoTechnology, Lutz, Fla) mounted on a handpiece with smooth enamel surfaces. , Subsequently, in each tooth treatment, a wooden wedge was placed between the target tooth and adjacent tooth, and polishing was carried out with diamond finishing burs and medium and extra-thin polishing discs (Sof-Lex, 3M Dental Products, St Paul, Minn). The IDS quantities were measured during the treatment using stripping thickness gauges (ContacEZ IPR Thickness Gauge; OSE Company, Inc, Gaithersburg, Md). Topical fluoride gel was applied after each IDS, and the patient was advised on oral hygiene practice with toothpaste and mouth rinse containing fluoride. In each malocclusion group, IDS was performed to obtain appropriate dentofacial relationships and resolve the need for interdigitation. Over application was avoided by careful evaluation of the dental interactions at each follow-visit. In addition to IDS, Class II elastics were applied in the Class II group, whereas Class III elastics were applied in the Class III group. All patients were provided instructions on oral hygiene and use of intermaxillary elastic at each visit; at the end of the treatment course, no diastemas or crowding was observed, while good alignment of the interdigitation dental arches and Class I canine and molar relationship was attained.

All dental models were scanned with a 3-dimensional (3D) model scanning device (3 Shape R700 3D Scanner; 3 Shape A/S, Copenhagen, Denmark) and submitted for analysis with Orthoanalyzer software (3 Shape A/S) ( Fig 1 ). The mesiodistal crown diameter was defined as the largest interdental distance between the mesial and distal contact points ( Fig 2 ) according to the method of Jensen et al. Bolton analysis was performed for the values obtained in individual teeth. To calculate the tooth sizes, mesiodistal dimensions of the anterior (from the distal side of the canine on 1 side to the distal side of the canine on the other side) and posterior (from the distal side of the first molar tooth on 1 side to the distal side of the first molar tooth on the other side) teeth were measured on the dental models acquired before and after treatment. However, the amount of anterior stripping was determined by the difference in the teeth sizes between the distal faces of the right and left canine teeth before and after treatment. The amount of posterior stripping was determined by subtracting the size difference of the anterior teeth from that of all teeth. Data on the number of patients in each group, sex, mean age, duration of treatment, and initial crowding amounts are shown in Table I . Lateral cephalometric radiographs were acquired digitally with an x-ray device (OP300; Instrumentarium Dental, Tuusula, Finland) according to the manufacturer’s instruction. On lateral cephalometric radiographs acquired before and after treatment, the distances and angles at the sagittal view ( Table II ) were evaluated with Dolphin Imaging software (version 11.0; Dolphin Imaging and Management Solutions, Chatsworth, Calif) ( Fig 3 ).

Fig 1
A, Application of a 3D scanning device in which 3D scans of the models are acquired at the beginning and end of the treatment. B-D , 3D scans of the dental models at the right profile, left profile, and frontal views.

Fig 2
A and B , Mesiodistal size of each tooth in the maxilla and mandible was measured individually on the 3D dental model.

Table II
Measurements performed on the lateral cephalometry radiographs acquired during the study period
Cephalometric measurements Abbreviations Descriptions
Sagittal values
SNA (°) Angle formed between sella, nasion, and A-point The position of the maxilla relative to the cranial base is determined.
SNB (°) Angle formed between sella, nasion, and B-point The position of the mandibula relative to the cranial base is determined.
ANB (°) Angle formed between A-point, nasion, and B-point It is used to determine the relationship between the maxilla and mandibula.
Incisor position values
U1/SN (°) Angle formed between maxillary incisor long axis and sella-nasion line The relationship between the maxillary incisors and the head base is determined.
U1/PP (°) Angle formed between maxillary incisor long axis and palatal plane (anterior nasal spine-posterior nasal spine) The relationship between the maxillary incisors and the palatal plane is determined.
U1-NA (mm) Perpendicular distance from the tip of the maxillary incisor to the plane between points N and A The position of the maxillary incisors relative to the NA line (protrusive, normal, retrusive) is determined.
U1/NA (°) Angle formed by the intersection of the maxillary incisor long axis to the plane between points N and A The angle (proclined, normal, retroclined) between the NA line of the maxillary incisors is determined.
L1-APog (mm) Distance between mandibular incisor incisal tip and A-pogonion line The position of the mandibular incisors according to the line between Pogonion and point A (protrusive, normal, retrusive) is determined.
IMPA (°) Angle formed between mandibular incisor long axis and mandibular plane (Gonion-Menton) The angle of the mandibular incisors relative to the mandibular plane (proclined, normal, retroclined) is determined.
L1-NB (mm) Perpendicular distance from the tip of the mandibular incisor to the plane between points N and B The position of the mandibular incisors relative to the NB line (protrusive, normal, retrusive) is determined.
L1/NB (°) Angle formed by the intersection of the mandibular incisor axis to the plane between points N and B The angle (proclined, normal, retroclined) between the NB line of the mandibular incisors is determined.

Fig 3
The values of angle and distance used for lateral cephalometric analysis are shown in different colors. S, sella; N, nasion; PNS, posterior nasal spine; ANS, anterior nasal spine; A, A-point; B, B-point, Pog, pogonion; Go, gonion; Me, menton; Gn, gnathion.

Statistical analysis

SPSS (version 24.0; SPSS Inc, Chicago, Ill) software was used for statistical analysis. The Shapiro-Wilks test was used to test the normality of the obtained data. Paired-samples t test and Wilcoxon paired signed rank test were used for comparisons between before and after treatment. One-way analysis of variance and Tukey tests were used for parametric variables, and Kruskal-Wallis and Dunn’s tests were used for nonparametric variables for the assessment of malocclusion type, Bolton ratio, and association of IDS amount among the groups. In addition, the Spearman correlation coefficient was used for correlation analysis to determine the relationship between IDS amounts and incisor positions. A P value of <0.05 was considered statistically significant.

Results

It should be noted that there is no statistically significant difference between each group in terms of initial crowding amounts. For the relationships between the first and repeat measurements after 4 weeks by the same investigator (T.O) in 10 patients randomly selected from each group, the intraclass correlation coefficient was 0.987 for the length measurements, 0.954 for the distance measurements, and 0.915 for the angle measurements, which indicated high reliability of the repeat measurement values.

Pretreatment and posttreatment comparisons are shown in Tables III and IV . The angle formed between the sella, nasion, and A-point (SNA); the angle formed between the sella, nasion, and B-point (SNB); the angle formed between A-point, nasion, and B-point (ANB), and the angle formed between maxillary incisor long axis and sella-nasion line (U1-SN) were not significantly different in all 3 groups ( Table III ). The angle formed between the maxillary incisor long axis and palatal plane (U1/PP) was significantly increased in Class I and Class III groups, whereas it was significantly decreased in the Class II group ( P < 0.05). U1-NA was significantly decreased in the Class II group, but it was significantly increased in the Class III group. The angle formed by the intersection of the maxillary incisor long axis to the plane between the nasion and A-point (U1/NA) was significantly increased in both Class I and Class III groups, whereas it was decreased in the Class II group, although without significance ( Table III ). The variables of the mandibular incisors were not significantly different in Class I and Class III groups, whereas it was significantly increased in the Class II group. The tooth sizes at pretreatment and posttreatment were similar ( Table IV ).

Table III
Comparison of sagittal and incisor measurements between T0 and T1 in patients with Class I, Class II, and Class III malocclusion groups
Variables Timepoint Class I Class II Class III
Mean ± SD P value Mean ± SD P value Mean ± SD P value
Sagittal values
SNA (°) T0 81.98 ± 5.21 0.887 81.03 ± 3.14 0.461 78.46 ± 4.22 0.740
T1 81.73 ± 5.85 81.84 ± 3.67 79.98 ± 5.16
SNB (°) T0 79.94 ± 5.42 0.873 75.69 ± 3.00 0.626 80.76 ± 3.58 0.701
T1 79.66 ± 5.61 76.35 ± 4.44 80.29 ± 4.53
ANB (°) T0 2.05 ± 3.40 0.614 4.62 ± 2.18 0.745 −0.23 ± 1.78 0.874
T1 1.53 ± 3.13 3.49 ± 1.77 −0.41 ± 1.96
Maxillary incisor values
U1/SN (°) T0 108.12 ± 5.91 0.204 106.09 ± 6.52 0.509 106.12 ± 7.44 0.801
T1 110.92 ± 7.64 107.67 ± 8.40 106.82 ± 9.05
U1/PP (°) T0 113.79 ± 6.05 0.007 113.06 ± 5.15 0.022 115.29 ± 6.68 0.008
T1 117.94 ± 7.52 109.48 ± 5.29 120.60 ± 6.52
U1-NA (mm) T0 4.40 ± 2.23 NS 4.59 ± 2.26 0.046 5.87 ± 2.59 0.016
T1 5.26 ± 2.44 3.54 ± 1.80 9.31 ± 4.71
U1/NA (°) T0 24.22 ± 5.39 0.049 24.33 ± 4.91 NS 27.51 ± 6.87 0.034
T1 27.38 ± 6.97 23.59 ± 5.37 32.86 ± 8.96
Mandibular incisor values
L1-APog T0 4.29 ± 6.94 NS 1.77 ± 2.69 <0.001 3.69 ± 2.87 NS
T1 3.37 ± 2.04 3.60 ± 3.10 3.32 ± 2.12
IMPA (°) T0 88.92 ± 7.19 NS 91.29 ± 6.80 0.003 87.96 ± 8.23 NS
T1 85.62 ± 19.31 96.37 ± 7.08 87.70 ± 4.76
L1-NB (mm) T0 9.49 ± 21.37 NS 3.93 ± 1.61 <0.001 4.13 ± 1.63 NS
T1 5.64 ± 2.49 6.56 ± 2.57 4.14 ± 1.44
L1/NB (°) T0 24.71 ± 6.53 NS 23.09 ± 5.05 <0.001 24.57 ± 7.47 NS
T1 25.02 ± 6.13 29.49 ± 5.54 23.65 ± 4.85
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Jun 12, 2021 | Posted by in Orthodontics | Comments Off on Association between incisor positions and amount of interdental stripping in patients undergoing orthodontic treatment
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