Expansion treatment using Invisalign®: Periodontal health status and maxillary buccal bone changes. A clinical and tomographic evaluation

The aim of this study was to evaluate changes in periodontal status and maxillary buccal bone by considering clinical and tomographic parameters during the first year of orthodontic expansion with Invisalign® aligners. Upper first (1PM) and upper second (2PM) premolars of 19 patients with orthodontic expansion requirement treated with Invisalign® aligners were evaluated. Plaque index (PI), gingival index (GI), probing pocket depth (PPD), clinical attachment level (CAL) and cone beam tomographic (CBCT) records were collected at 76 sites before starting treatment (T0) and at 12 months (T1). Bone height was measured from cementoenamel junction (CEJ) to the crest cortical bone (CC). Bone thickness was measured at two levels: 4 mm (CEJ+4) and 6 mm (CEJ+6) apical to the CEJ. A descriptive analysis was made of the variations of bone thickness and height in a series of cases. The average expansion was 1.93 mm for 1PM and 167 mm for 2PM. Arithmetic mean of distance CEJ-CC in 1PM was 3.05 mm at T0, and remained at 3.05 mm at T1. Arithmetic mean of distance CEJ-CC in 2PM was 2.06 mm at T0 and 2.31 at T1. Post-expansion, most of the analyzed sites (86%) exhibited a bone thickness of ≥0.5 mm. The greatest variations between T0 and T1 were observed at the level of 1PM CEJ+ 4 and 2PM CEJ+ 6. The minimal changes in the clinical records (GI, PI, PPD and CAL) between T0 and T1 were compatible with the maintenance of gingivalperiodontal health. Invisalign® for expansion movements did not produce substantial changes in the evaluated periodontal clinical parameters or in the bone measurements. Removable appliances reduce plaque retentive factors and favor adequate oral hygiene.

Surface wear of resin composites used for Invisalign® attachments

Orthodontic treatments with Invisalign® require the use of attachments, which are composite resin buttons attached to tooth surfaces. Attachments constitute one of the most powerful tools for improving the efficiency of orthodontic tooth movement. The main purpose of this study was to evaluate surface wear over six months in two resin composites (Filtek Z350 XT, 3MESPE and Amelogen Plus TW, Ultradent Products Inc. ) used for making Invisalign® attachments. These composites were selected for their esthetic and mechanical properties. Forty attachments were bonded to the buccal surface of maxillary teeth. Materials were randomized and assigned in a double blind manner. Impressions were taken of the attachments using a preestablished technique immediately after bonding and following 6 months of clinical use. The impressions were examined by Scanning Electron Microscopy (SEM) at 12-fold magnification to identify changes in surface texture and attachment shape. Data were analyzed using Mann-Whitney's test on the overall ranking of detected changes in those variables. Statistically significant differences (P<0. 001) were found for surface wear, with greater changes in Amelogen Plus. Attachment shape did not change significantly in either material (P>0. 05). According to the results of this study, the alteration of the attachment surface during the first six months of treatment depends on the composite used, while attachment shape does not appear to be affected, so the clinical performance of the materials evaluated could be considered acceptable.