Changes in the size of dental arches in different variants of the course of the retention period of treatment in patients with anomalies in the maxillary canines position

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Introduction

According to epidemiological observations of domestic and foreign authors, in patients with completed growth of the maxillofacial skeleton, the frequency of anomalies in the position of teeth and closure of dental arches in different social groups varies from 25 to 89% [1; 2]. Anomalies in the position of the canines of the upper jaw in patients during the period of permanent bite occur with an approximate frequency of 31.7%, which is on average one third of the total number of dentofacial anomalies, and lead to the following morphofunctional changes in the orofacial complex: changes in the shape of the dental arches, dysfunction of the temporomandibular joint, changes in the profile of soft tissues of the face, etc. [3; 4].

The goal of orthodontic treatment is to normalize occlusal relationships, shape and size of dental arches. To solve the problems in young patients with anomalies of the position of the upper jaw canines, domestic and foreign authors have proposed a wide range of treatment methods [5; 6]. Despite the variety of orthodontic, orthopedic and combined treatment techniques, it is not possible to achieve a satisfactory clinical result in all clinical cases [7].

An unfavorable treatment outcome in patients with anomalies in t he position of the canines of the upper jaw during the period of permanent occlusion is determined not only by aesthetic, radiological and functional signs. One of the key factors determining the failure of orthodontic treatment is considered to be the lack of long-term stability of the result during the retention period, or relapse of the dentoalveolar anomaly [8; 9].

The aim of the study is to evaluate changes in the size of dental arches in patients with anomalies in the position of the upper jaw canines in long-term observation periods with different variants of the course of the retention period.

Materials and Methods

An open prospective clinical and instrumental study with elements of retrospective analysis was conducted. The study included 69 patients aged 18 to 45 years (mean age 24.1 ± 0.9 years) who had completed the active period of orthodontic treatment. The duration of observation of patients in the retention period ranged from 2 to 8 years (mean duration 3.57 ± 0.24 years).

Inclusion criteria for the study: patients aged 18 to 45 years (i.e., a group of young people); completed active period of orthodontic treatment, history of anomalies in the position of the crowns of the canines of the upper jaw (supra-, vestibular position, tortoanomaly, retention with vestibular position of the canine); observation period in the retention period of two years or more; viability of fixed wire retainers on both dental arches; availability of a complete set of medical documentation and informed consent for inclusion of the patient in the study.

Exclusion criteria for the study: periods of primary and mixed dentition; patient age over 45 or under 18 years; interrupted active period of orthodontic treatment; other dental anomalies in the anamnesis (e.g. palatal position of the canine / canines of the upper jaw, retention with palatal localization of the tooth, etc.); destructive changes or debonding of a fixed orthodontic retainer during the first two years of the retention period more than three times; incomplete set of medical documentation and / or patient refusal to participate in the study.

In the long-term observation periods of the retention period of orthodontic treatment, a number of patients showed clinically significant negative movement of teeth and their groups. According to this, two variants of the course of the retention period can be distinguished:

• favorable – the results of orthodontic treatment are stable and functionally satisfactory. In this case, there can be no tooth movement, may be insignificant and clinically undetectable;
• unfavorable – a relapse of anomalies in the position of the upper jaw canines (“true relapse”) or “relapse-like movement” of other teeth or their groups is determined, leading to a violation of the occlusion of the dental arches.

Depending on the course of the retention period, patients were divided into groups:

• Group 1 – individuals with an unfavorable course of the retention period (n = 22: 9 men and 13 women), the average age of individuals in the group was 23.8 ± 3.4 years;
• Group 2 – individuals with a favorable course of the retention period (n = 47: 19 men and 28 women), the average age of individuals in the group was 22.6 ± 1.9 years.

The analysis of biometric changes was carried out on the basis of measurements of transverse and sagittal dimensions of the dental arches in the area of the corresponding marker points on control and diagnostic models of the jaws of patients before and after orthodontic treatment and after two years from the beginning of the retention period.

For all indicators, the values of changes before and after orthodontic treatment and in the long-term observation periods in the retention period (D) were calculated.

The database was formed and processed using Microsoft Office (Microsoft Corp., USA), Microsoft Excel, Stata/MPv.13.0 for Windows (Stata Corp. LP, USA) and the online calculator medstatistic.ru. The initial quantitative data of both groups had a normal distribution according to the Kolmogorov-Smirnov criterion. For quantitative characteristics, the arithmetic mean (M) and standard error of the mean (m) were calculated. Fisher's F-test was used to assess the reliability of differences. The value p ˂ 0.05 was taken as the boundary level of statistical significance.

Results and Discussion

In both observation groups, morphometric changes in the dental arches during orthodontic treatment were expressed in the expansion of the dental arches, most pronounced in the premolar region, and the lengthening of the dental arches, most pronounced in the upper jaw. There were no significant changes in the transverse dimensions in the upper canine region (Table 1). It should be noted that, despite the uniform “geometric trend”, the degree of transformation of the dental arches differed between the groups. Significant differences were determined in relation to the magnitude of expansion in the area of the first premolars of the upper jaw (5.00 ± 0.52 mm in the 1st group, 3.20 ± 0.37 mm in the 2nd group), canines of the upper (2.12 ± 0.35 mm in the 1st group, 0.88 ± 0.38 mm in the 2nd group) and lower jaws (0.60 ± 0.36 mm in the 1st group and 1.59 ± 0.40 mm in the 2nd group), the magnitude of elongation of the frontal section of the upper (2.45 ± 0.49 mm in the 1st group and 1.24 ± 0.37 mm in the 2nd group) and lower (1.70 ± 0.39 mm in the 1st group and 0.61 ± 0.30 mm in 2nd group) of dental arches. Also, reliable differences were found in the difference in the lengths of the dental arches (in the 1st group 1.58 ± 0.16 mm, in the 2nd – 2.22 ± 0.24 mm).

 

Table 1

Changes in the parameters of teeth and dental arches during orthodontic treatment in patients with anomalies of the upper jaw canines

Estimated parameter, mm	1st Group, n = 22	2nd Group, n = 47
D 1.3–2.3	2.12 ± 0.35	0.88 ± 0.38*
D 1.4–2.4	5.00 ± 0.52	3.20 ± 0.37*
D 1.6–2.6	2.14 ± 0.56	1.81 ± 0.26
D 3.3–4.3	0.60 ± 0.36	1.59 ± 0.40*
D 3.4–4.4	2.45 ± 0.36	2.25 ± 0.32
D 3.6–4.6	1.98 ± 0.52	1.51 ± 0.43
D l	2.45 ± 0.49	1.24 ± 0.37*
D l ’	1.70 ± 0.39	0.61 ± 0.30*
l – l ’	1.58 ± 0.16	2.22 ± 0.24*

Note: * – significant difference between the parameters in groups 1 and 2 (p < 0.05).

 

In the long-term observation periods in the retention period, “true relapse”, consisting of a partial return of the upper jaw canines to their original position, was determined in 21.2 % of cases (n = 15). "Relapse-like movement" of teeth, consisting of spontaneous movement of other teeth and change in the occlusion of dental arches, was detected in 28.9 % of patients (n = 20). Isolated "true relapse" was recorded in 2 cases (2.9 %), isolated "relapse-like movement" of teeth – in 7 cases (10.1 %), in the remaining cases, spontaneous movement of canines was combined with a change in the position of other teeth, the formation of anomalies of dental arches and occlusion.

In patients of the 1st and 2nd observation groups, in the retention period of orthodontic treatment, reduction changes in the transverse dimensions of the dental arches in the area of the canines of the upper jaw, as well as premolars and molars of both jaws were recorded (Table 2). Despite the general morphogeometric pattern of changes in the dental arches, a reliable difference in the values of biometric indicators was determined in patients in each observation group.

 

Table 2

Changes in transverse parameters of dental arches in the retention period of orthodontic treatment in patients with anomalies of the upper jaw canines in long-term observation periods

Estimated parameter, mm	Group 1, n = 22	Group 2, n = 47
D 1.3–2.3	–1.38 ± 0.27	–0.30 ± 0.20*
D 1.4–2.4	–3.25 ± 0.52	–1.27 ± 0.12*
D 1.6–2.6	–1.50 ± 0.74	–0.83 ± 0.15
D 3.3–4.3	0.29 ± 0.78	–0.85 ± 0.14
D 3.4–4.4	–1.12 ± 0.48	–0.89 ± 0.16
D 3.6–4.6	–0.82 ± 0.43	–0.55 ± 0.44

Note: * – significant difference between the parameters in groups 1 and 2 (p < 0.05).

 

Thus, in patients with signs of relapse of the anomaly, the magnitude of the reduction of the transverse dimensions of the dental arches is greater in the area of the upper canines (–1.38 ± 0.27 mm in the 1st group, –0.30 ± 0.20 mm in the 2nd group) and upper premolars (–3.25 ± 0.52 mm in the 1st group, –1.27 ± 0.12 mm in the 2nd group). It should be noted that in patients of the 1st group, in the long-term observation periods, there are practically no signs of narrowing of the dental arch in the area of the canines of the lower jaw (0.29 ± 0.78 mm in the 1st group, -0.85 ± 0.14 mm in the 2nd group).

The figure demonstrates that with recurrent changes in the shape of the dental arches in the lateral sections, the final values of the absolute increases in transverse parameters in the 1st and 2nd observation groups in the long-term observation periods have practically no differences.

 

Fig. Typical oscillations of transverse parameters of dental arches in the retention period of orthodontic treatment of patients with anomalies of the upper jaw canines:a – Δ1.3–2.3; b – Δ3.3–4.3; c – Δ1.4–2.4; d – Δ3.4–4.4; e – Δ1.6–2.6; f – Δ3.6–4.6

 

Analysis of changes in the sagittal parameters of the dental arches in the retention period in remote observation periods in patients with anomalies in the position of the canines of the upper jaw revealed a typical reaction of the shape of the dental arch to a decrease in the transverse parameters in the form of an elongation of the frontal section. This phenomenon was determined in both observation groups (Table 3).

 

Table 3

Changes in the sagittal parameters of dental arches in the retention period of orthodontic treatment in patients with anomalies of the upper jaw canines in long-term observation periods

Estimated parameter, mm	1st Group, n = 22		2nd Group, n = 47
	True relapse, n = 15	Relapse-like movement, n = 20
D l	0.95 ± 0.32	2.44 ± 0.16	0.66 ± 0.25
Dl ’	0.50 ± 0.19	1.53 ± 0.24	0.51 ± 0.19
l – l ’	1.50 ± 0.24	0.68 ± 0.36	2.05 ± 0.21*

Note: * – significant difference between the indicators in groups 1 and 2 (p < 0.05).

 

In patients with relapse of the anomaly, the degree of increase in the length of the frontal sections of the dental arches correlated mainly with the form of relapse. In the case of a “true relapse”, the increase in the length of the upper dental arch was 0.95 ± 0.32 mm, and the lower one was 0.50 ± 0.19 mm, which indicates that the decrease in the transverse dimensions of the dental arches was balanced by a negative change in the position of the canines of the upper jaw (rotation, displacement in the vertical and/ or sagittal planes). Against the background of changes in the position of other teeth (i.e. incisors and premolars) during the "relapse-like movement", the position of the upper canines remains practically unchanged, and an increase in the length of the upper dental arch by 2.44 ± 0.16 mm and the lower by 1.53 ± 0.24 mm is determined. This indicates that compensation for the space deficit occurs mainly due to an increase in the protrusion of the incisors, which leads to a decrease in the disproportion of the lengths of the frontal sections (up to 0.7 mm) and a violation of the closure of the incisors.

In individuals with stable orthodontic treatment results, the reduction of transverse dimensions of the dental arch amounted to 0.30 ± 0.20 to 1.27 ± 0.12 mm, depending on the topography, which led to an increase in the length of the frontal section of the upper dental arch by 0.66 ± 0.25 mm, and the lower one by 0.51 ± 0.19 mm. The physiological value of the difference in the lengths of the frontal sections of the dental arches was stable and amounted to 2.05 ± 0.21 mm. Thus, the determined changes in the transverse and sagittal dimensions of the dental arches within individually acceptable intervals determined the constancy of the clinical picture and the stability of the result of orthodontic treatment.

Conclusions

In long-term observation periods (two years from the beginning of the retention period of orthodontic treatment and later), patients with anomalies in the position of the canines of the upper jaw show a change in the metric parameters of the dental arches, which causes a recurrent change in their shape in the lateral sections. At the same time, the final values ​​of the absolute increases of the transverse parameters both in the case of a stable result of orthodontic treatment and in the presence of a relapse of the anomaly have virtually no differences.

About the authors

D. A. Rusanova

E.A. Vagner Perm State Medical University

Author for correspondence.
Email: rurusanovs@gmail.com
ORCID iD: 0000-0002-1321-4871

Postgraduate Student of the Department of Childhood Dentistry and Orthodontics

Russian Federation, Perm

P. V. Ishmurzin

E.A. Vagner Perm State Medical University

Email: rurusanovs@gmail.com
ORCID iD: 0000-0003-2344-1266

DSc (Medicine), Associate Professor of the Department of Childhood Dentistry and Orthodontics

Russian Federation, Perm

References

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