The effect of pregnancy on orthodontic tooth movement in rats

Consideration of hormonal changes for orthodontic treatment during pregnancy and lactation - a review

Hormonal changes in pregnant and lactating women significantly affect bone metabolism and overall stress levels, positioning them as a unique group within the orthodontic population. Fluctuations in estrogen, progesterone, prolactin, and other hormones are closely linked to bone remodeling and the periodontal tissue's response to inflammation caused by dental plaque. Hormones such as thyrotropin, leptin, and melatonin also play crucial roles in pregnancy and bone remodeling, with potential implications for orthodontic tooth movement. Additionally, adverse personal behaviors and changes in dietary habits worsen periodontal conditions and complicate periodontal maintenance during orthodontic treatment. Notably, applying orthodontic force during pregnancy and lactation may trigger stress responses in the endocrine system, altering hormone levels. However, these changes do not appear to adversely affect the mother or fetus. This review comprehensively examines the interaction between hormone levels and orthodontic tooth movement in pregnant and lactating women, offering insights to guide clinical practice.

Orthodontic treatment during pregnancy, lactation, and postmenopausal period: a questionnaire development

This study aimed to develop and validate a self-administered questionnaire in Brazilian Portuguese to verify the level of knowledge of orthodontists in the care of pregnant, lactating, and postmenopausal women, named "Considerations on Orthodontic Treatment during Pregnancy, Lactation, and Postmenopausal Periods." The development and validation of the questionnaire consisted of the following steps: a) item generation; b) item reduction; c) questionnaire design; and d) validity and reliability tests in a cross-sectional study with 258 orthodontists working in the field from different Brazilian states. A total of 60 orthodontists participated in test-retest over a mean period of 45 days. The preliminary questionnaire consisted of a total of 60 questions. After item reduction, 40 questions were selected for the final version of the questionnaire, with eight questions about pregnant women; six about lactating women; 18 about postmenopausal women, and eight about general knowledge in dentistry. Each item had three response options in the Likert scale format. Face and content validity analysis, reliability assessment through internal consistency (Cronbach's alpha and McDonald's omega), and test-retest reliability through the intraclass correlation coefficient (ICC) and Spearman's correlation coefficient were performed. Face and content validity indicated that the questionnaire was considered valid, objective, and easily understandable. The questionnaire had good internal consistency (Cronbach's alpha = 0.77; McDonald's omega = 0.78) and good test-retest reliability (ICC = 0.71; Spearman's correlation coefficient = 0.51). The questionnaire was considered valid and reliable to assess the level of knowledge of orthodontists in the care of pregnant, lactating, and postmenopausal women.

The risk of osteonecrosis of the jaw and adverse outcomes in patients using antiresorptive drugs undergoing orthodontic treatment: A systematic review

Objectives

Medication-related osteonecrosis of the jaw (MRONJ) is rare. It is a serious adverse effect of certain drugs, of which bisphosphonates (BPs) are the most widely known. The aim of this systematic review was to analyze all published evidence for the reported adverse outcomes as a result of orthodontic treatment in patients undergoing antiresorptive therapy.

Data

All types of studies involving patients undergoing orthodontic treatment and treated with antiresorptive drugs were considered. A meta-analysis was not conducted due to the high amount of variability and heterogeneity in the reporting and presentation of data among the studies meeting the inclusion criteria.

Sources

A systematic search was performed using 4 databases (PubMed, MEDLINE, EMBASE and CINAHL).

Study selection

Seven studies matched the inclusion criteria for this review, reporting a total of 29 patients. MRONJ was only reported in 1 patient. The adverse outcomes following orthodontic treatment included difficulty achieving root parallelism (n = 4), difficulty achieving complete space closure (n = 3), exaggerated tooth mobility post-debond (n = 2), increased duration of orthodontic treatment beyond expected completion (n = 1), sclerotic alveolar bone changes seen on post-op radiographic images (n = 2), and an increased amount of root resorption (n = 1).

Conclusions

The high amount of heterogeneity and limited evidence precluded a valid interpretation and analysis of the results through pooling of data. Additional data with sufficient quality, a reduction of bias, and a greater prospective cohort of patients is crucial to assess adverse effects, mechanisms of action, and associated risk factors in at-risk patients.

Clinical significance

Based on the limited evidence available in the literature, it is unclear whether orthodontic treatment alone can precipitate MRONJ. However, antiresorptive drug therapy may be associated with a sub-optimal treatment outcome.

The effects of calcitonin on post-orthodontic relapse in rats

Objectives

To determine the effects of systematic calcitonin administration on post‐orthodontic relapse in rat model.

Material and methods

This experimental animal model involved 36 male Wister rats. The maxillary right first molars were moved mesially, using a modified orthodontic appliance delivered 50 gm, for 14 days, retained for 4 days and left to relapse for 10 days. The study group was divided into three subgroups in which a single injection of calcitonin (20 IU/Kg), three injections of calcitonin (20 IU/Kg), each every other day, and normal saline were administered subcutaneously after orthodontic tooth movement has finished. The relapse ratio, histomorphometric analysis including osteoblasts, osteoclasts numbers and bone area and immunohistochemical analysis including the expression of receptor activator of nuclear factor kappa Β (RANK), receptor activator of nuclear factor kappa Β ligand (RANKL) and osteoprotegerin (OPG) were measured and assessed.

Results

The relapse ratio was significantly reduced in the three‐dose calcitonin group (28%) compared to the single dose calcitonin group (34%) and the control group (46%). This was accompanied by a nonsignificant increase in osteoblasts number and bone area in three‐dose calcitonin group and a nonsignificant reduction in osteoclast number. However, the immune histochemical expression of RANK, RANKL and OPG did not show statistically significant difference at the end of relapse period.

Conclusions

Systemic administration of three doses of calcitonin may minimize the relapse ratio in experimentally moved rat molars.

Does the rate of orthodontic tooth movement change during pregnancy and lactation? A systematic review of the evidence from animal studies

Background

The changes in bone homeostasis observed during pregnancy and lactation could result in alterations in the rate of orthodontic tooth movement, but research in human subjects presents significant ethical and practical limitations. Our aim was to compare the amount of orthodontic tooth movement between pregnant/lactating or not animals.

Methods

We searched without restrictions 8 databases and performed hand searching until July 2019 (PubMed, Central, Cochrane Database of Systematic Reviews, SCOPUS, Web of Science, Arab World Research Source, ClinicalTrials.gov, ProQuest Dissertations and Theses Global). We searched for studies comparing quantitatively the amount of orthodontic tooth movement between pregnant/lactating or not animals. Following retrieval and selection of studies, the collection of related data was performed and the risk of bias was assessed using the SYRCLE’s Risk of Bias Tool. Exploratory synthesis was carried out using the random effects model.

Results

Four studies were finally identified raising no specific concerns regarding bias. One study showed that lactation increased the rate of tooth movement by 50 % [p < 0.05]. Although an overall increase was noted in the pregnancy group as well, it did not reach statistical significance [3 studies, Weighted Mean Difference: 0.10; 95% Confidence Interval: − 0.04 - 0.24; p = 0.165].

Conclusions

The metabolic changes occurring during pregnancy and lactation may have an impact on the rate of tooth movement in animals. Although these animal experimental results should be approached cautiously, it could be safe practice to consider the impact of these physiological changes in the clinical setting.

Registration

PROSPERO (CRD42018118003).

The Effect of Low-Level Laser Therapy on the Acceleration of Orthodontic Tooth Movement

In clinical practice, low-level laser therapy (LLLT) is widely used. The main aim of this review is to assess the effectiveness of LLLT in accelerating tooth movement in human subjects. The PRISMA checklist was utilized as a guideline to carry out this systematic review. The electronic databases were searched from Google Scholar (2014-2018) and PubMed, and comprehensive research on this topic was also manually conducted. Therefore, 77 articles randomized clinical trials (RCTs) or controlled clinical trials (CCTs) were selected. After screening studies, consequently, eleven trials met the inclusion criteria. Eight out of 11 studies showed LLLT has a significant impact on the acceleration of orthodontic tooth movement, and there was no statistically significant difference in the rate of tooth movement between the laser group and the control group in the two remaining studies. Furthermore, five out of 11 articles showed that LLLT has no adverse effects. Although we have some degree of understanding from a cellular point of view to LLLT effects, we still do not know whether these cellular level changes have any effect on the clinical acceleration of orthodontic tooth movement. The results are inconclusive and cannot be generalized to the public community; therefore, well-structured studies are required.

Effect of combined oral contraceptives on orthodontic tooth movement in a female rat model

Background

To investigate the effect of combined oral contraceptives (COC) on orthodontic tooth movement (OTM) and periodontal remodelling in a female rat model.

Methods

A total of 80 three-month-old female, Sprague-Dawley rats were randomly divided into experimental and control groups. The maxillary first molars were moved mesially using nickel-titanium coil springs (50 g force). The experimental group (N = 40) ingested 1.5 ml COC (Marvelon, 0.12 mg/d, N.V. Organon, Oss, The Netherlands) daily. The control group (N = 40) ingested 1.5 ml saline (0.9% sodium chloride) daily. After 7, 14, 21 and 28 days of force application, 10 rats in each group were euthanased and a vernier calliper was used to measure the orthodontic movement of the first molar. Root resorption at pressure areas was assessed by H and E staining. Micro-CT was used to detect alveolar bone mineral density.

Results and conclusion

The amount of OTM in the experimental group (0.46 ± 0.16 mm) was significantly less than in the control group (0.85 ± 0.25 mm; p = 0.003) during the 28 days of observation. There were significantly smaller (p = 0.002) root resorption lacunae in the experimental group (111710 ± 4037 pixels) compared with the control group (204962 ± 21318 pixels) after 28 days. There was no statistically significant difference in the bone mineral density between the experimental and control groups throughout the study period (p > 0.05 at each time point). The short-term administration of COC may retard tooth movement and reduce the level of root resorption during OTM in female rats.

The Effect of Ovariectomy and Orchiectomy on Orthodontic Tooth Movement and Root Resorption in Wistar Rats

STATEMENT OF THE PROBLEM

Root resorption (RR) after orthodontic tooth movement (OTM) is known as a multifactorial complication of orthodontic treatments. Hormonal deficiencies and their effect on bone turnover are reported to have influences on the rate of tooth movement and root resorption.

PURPOSE

This study was designed to evaluate the effect of female and male steroid sex hormones on tooth movement and root resorption.

MATERIALS AND METHOD

Orthodontic appliances were placed on the right maxillary first molars of 10 ovariectomized female and 10 orchiectomized male Wistar rats as experimental groups and 10 female and 10 male healthy Wistar rats as control groups. NiTi closed-coil springs (9mm, Medium, 011"×.030", Ortho Technology(®); Tampa, Florida) were placed between the right incisors and the first right maxillary molars to induce tipping movement in the first molars with the application of a 60g force. After 21 days, the rats were sacrificed and tooth movement was measured by using a digital caliper (Guanglu, China). Orthodontic induced root resorption (OIRR) was assessed by histomorphometric analysis after hematoxylin and eosin staining of sections of the mesial root.

RESULTS

The rate of tooth movement was significantly higher in all female rats, with the root resorption being lower in the experimental group. The rate of tooth movement in experimental male rats was significantly higher than the control group (p= 0.001) and the rate of root resorption was significantly lower in the experimental group (p= 0.001).

CONCLUSION

It seems that alterations in plasma levels of estrogen, progesterone, and testosterone hormones can influence the rate of OTM and RR. The acceleration in tooth movement increased OTM and decreased RR.