Effects of crown movement on periodontal biotype: a digital analysis

Dimensional changes of the gingival tissues induced by clear aligners and fixed orthodontic appliances: A retrospective study

OBJECTIVE

The aim of this study was to evaluate gingival tissue adaption induced by orthodontic tooth movement, in terms of clinical crown height (i.e., attachment loss), and thickness of the keratinized gingiva at the margin level.

METHODS

Pre- and post-treatment intraoral models/scans of 100 orthodontically treated patients (50 treated with clear aligners and 50 treated with fixed appliance) were acquired. Models were digitally scanned. Each couple of pre- and post-treatment scans were superimposed using the Compare© software (Medit spa, Seoul, Republic of Korea) taking the same reference landmarks in all cases, that were the palatal rugae for the upper arch, and the labial median frenulum for the lower arch. Only teeth that had undergone vestibulo-palatal (or vice versa) movement, greater than 1 mm were included in the analyses. The change from pre-treatment to post-treatment, in the clinical crown height and thickness of the keratinized gingiva at the margin level were digitally measured and compared between the two groups. Statistical analysis included paired t-tests, and unpaired t-tests with significance set at p<0.05.

RESULTS

There was a statistically significant change in clinical crown height and gingival thickness in both groups. However, a clinically relevant attachment loss was found only within the fixed appliance group. Whereas, regarding the change in gingival thickness, there was no clinically relevant changes between the two groups.

CONCLUSIONS

Orthodontic tooth movement with fixed appliance is associated to a clinically relevant attachment loss. Clear aligners seem to be associated with a more discrete attachment loss than the one observed with fixed appliances.

CLINICAL RELEVANCE

Orthodontists should pay attention and monitoring the clinical crown height (i.e., attachment loss) during orthodontic movement, mostly when using fixed appliances.

The Influence of Orthodontic Treatment on Periodontal Health between Challenge and Synergy: A Narrative Review

By correctly repositioning teeth, orthodontic therapy improves both the function and appearance of an occlusion. The relationship between teeth and the tissues that surround and support them significantly influences these alterations. With ever more adults seeking orthodontic care, orthodontists are increasingly seeing patients with periodontal issues. Concerns about the patient's appearance, such as uneven gingival margins or functional issues caused by inflammatory periodontal diseases, should be accounted for when designing orthodontic treatment plans. Furthermore, orthodontics may increase the chances of saving and recovering a degraded dentition in cases of severe periodontitis. Today, general dentists, dontists, and orthodontists play integrative roles that enable them to achieve the best possible results for their patients. This review will improve the results of interdisciplinary treatments and increase cooperation between dental specialists by drawing attention to the essential connection between orthodontics and periodontics in regular clinical practice.

Assessment of physiological posterior-tooth displacement under habitual occlusal force by intraoral scanning using implant-supported crowns as the reference

STATEMENT OF PROBLEM

Studies that have used digital methods to quantitatively evaluate physiological tooth displacement under occlusal force are sparse.

PURPOSE

The purpose of this clinical study was to measure physiological posterior tooth displacement under occlusal force by intraoral scanning and reverse engineering technology by using implants as the reference.

MATERIAL AND METHODS

A total of 14 participants received 15 implant-supported single mandibular first molar crowns. The surface data of maxillary and mandibular posterior teeth (U1 and L1) and the buccal occlusal data in the maximum intercuspal position (MIP) with habitual occlusal force were obtained by using an intraoral scanner (TRIOS 3, v20.1.2). The U1 and L1 data were segmented into single teeth, which were then aligned to the buccal occlusal data by using the "best-fit alignment" command to build the data under occlusal force (U2 and L2). U1 and L1 data were compared with U2 and L2 data to calculate the centroid and functional cusp vertex displacements and the long axis deflections of the second premolars and second molars, taking the first molar as the reference. The medians, and first quartile (Q₁), third quartile (Q₃) of the above data were reported, and the Shapiro-Wilk and Wilcoxon tests were used to analyze the differences (α=.05).

RESULTS

Under occlusal force, the median (Q₁, Q₃) centroid displacements of posterior teeth ranged from 61 (52, 101) μm to 146 (80, 186) μm; the functional cusp vertex displacements ranged from 82 (62, 117) μm to 146 (98, 189) μm, and the long axis deflections ranged from 0.45 (0.25, 0.87) degrees to 1.03 (0.52, 1.41) degrees. Mandibular second premolars displaced lingually, mesially, and apically; mandibular second molars displaced distally and apically; and maxillary second premolars and second molars displaced lingually and apically.

CONCLUSIONS

A digital method taking implant-supported single crowns as the reference was used to demonstrate physiological posterior-tooth displacement under habitual occlusal force.

Immune System Acts on Orthodontic Tooth Movement: Cellular and Molecular Mechanisms

Orthodontic tooth movement (OTM) is a tissue remodeling process based on orthodontic force loading. Compressed periodontal tissues have a complicated aseptic inflammatory cascade, which are considered the initial factor of alveolar bone remodeling. Since skeletal and immune systems shared a wide variety of molecules, osteoimmunology has been generally accepted as an interdisciplinary field to investigate their interactions. Unsurprisingly, OTM is considered a good mirror of osteoimmunology since it involves immune reaction and bone remolding. In fact, besides bone remodeling, OTM involves cementum resorption, soft tissue remodeling, orthodontic pain, and relapse, all correlated with immune cells and/or immunologically active substance. The aim of this paper is to review the interaction of immune system with orthodontic tooth movement, which helps gain insights into mechanisms of OTM and search novel method to short treatment period and control complications.

Effects of Rigid and Nonrigid Connections between the Miniscrew and Anchorage Tooth on Dynamics, Efficacy, and Adverse Effects of Maxillary Second Molar Protraction: A Finite Element Analysis

Introduction

Direct, rigid indirect, and nonrigid indirect absolute anchorages using temporary anchorage devices (TADs, mini-implants/miniscrews) can provide promising opportunities for challenging, yet common, orthodontic tooth movements such as molar protraction. Rigid rectangular wire and ligature wire are the most common methods of attaching a tooth to a miniscrew in indirect anchorages. We aimed to provide a comparison of the rigidity of the connecting wire in terms of stress on the miniscrew, the anchorage loss, and the risk of root resorption using finite element analysis (FEA).

Methods

The maxillary right second molar was protracted into the proximal space at a 150 g load (1) using direct absolute anchorage with a tapered miniscrew implanted between the premolar roots and using indirect absolute anchorage with the second premolar reinforced by the miniscrew through (2) a rigid stainless steel (SS) wire or (3) a nonrigid SS ligature wire (4) at different elastic moduli. Stresses and displacements of 4 models' elements were measured. The risk of external root resorption was evaluated.

Results

Connecting the tooth to the miniscrew using rigid full-size wire (model 2) compared to ligature (model 3) can give better control of the anchorage (using the ligature wire, the anchorage loss is 1.5 times larger than the rectangular wire) and may reduce the risk of root resorption of the anchorage unit. However, the risk of miniscrew failure increases with a rigid connection, although it is still lower than with direct anchorage. The miniscrew stress when using a ligature is approximately 30% of the rigid model using the rectangular wire. The miniscrew stress using the rectangular wire is approximately 82.4% of the miniscrew stress in the direct model. Parametric analysis shows that the higher the elastic modulus of the miniscrew-tooth connecting wire in the indirect anchorage, the less the anchorage loss/palatal rotation of the premolars/and the risk of root resorption of the anchorage teeth and instead the stress on the miniscrew increases.

Conclusions

Direct anchorage (followed by rigid indirect anchorage but not nonrigid) might be recommended when the premolars should not be moved or premolar root resorption is a concern. Miniscrew loosening risk might be the highest in direct anchorage and lowest in nonrigid indirect anchorage (which might be recommended for poor bone densities).