Dental and Skeletal Changes in the Upper and Lower Jaws after Treatment with Schwarz Appliances Using Cone-Beam Computed Tomography

Abstract

Objective: The purpose of this research was to use cone-beam computed tomography (CBCT) images to evaluate dental and skeletal changes in upper and lower jaws after treatment with Schwarz appliances.Materials and Methods: 28 patients with Angle Class I molar relationships and crowding were randomly divided into two groups – 14 non-expanded and 14 expanded patients. 3D-Rugle CBCT software was used to measure various reference points before treatment (T0) and during the retention period of approximately 9 months after 6 to 12 month expansion (T1). Cephalometric and cast measurements were used to evaluate treatment in both groups. To test whether there were any significant differences between the control and treatment groups at T0 and T1, the Mann-Whitney U-test was used. Results: The dental arch (including tooth root apices) had expanded in the upper and lower jaws. Alveolar bone expansion of up to 2 mm apical to the cementoenamel junction (CEJ) was detected. The midpalatal sutures were separated in some cases and subsequent expansion was observed at the inner surface of the nasal cavity at the inferior turbinates. However,no significant (P > 0.05) difference was observed in the inter-width of the mandibular bodies, zygomatic bones, nasal cavity in the middle turbinate region, condylar heads, or antegonial notches. In mandibular and maxillary cast measurements, arch crowding and arch perimeter showed statistically significant changes in the expansion group. The mandibular width values demonstrated no significant changes as measured from a point 2 mm apical to the CEJ, whereas the maxillary width values demonstrated significant changes as measured from a point 2 mm apical to the CEJ. Conclusions: This study indicates that the Schwarz appliance primarily affects the dento-alveolar complex, while it has little effect on either the mandibular bodies, any associated structures including the maxillary midpalatal suture and the inter-width of the nasal cavity in the middle turbinate region. In addition, the center of rotation of the mandibular and maxillary first molar was observed apical to the root apex.

CBCT in orthodontics: assessment of treatment outcomes and indications for its use

“…69,71 Despite these limitations, CBCT has been used to discern the potential effects of treatment-or patient-specific variables on the integrity and morphology of bone around tooth roots in full-fixed appliance therapy and with both rapid and slow expansion. [72][73][74][75][76][77][78][79][80] Routine orthodontic therapy using full-fixed appliances is accompanied by significant changes in bone width even with small amounts of buccal movement of posterior teeth. 75,80 This finding raises the question of whether biologically compatible expansion is possible using specific combinations of fixed appliances and wires as claimed by some manufacturers.…”

“…76 Finally, slow palatal expansion using quadhelix or Schwarz appliances decrease and increase, respectively, buccal and lingual bone thicknesses. 73,[77][78][79] Bimaxillary protrusion in which orthodontic treatment aims to reduce the dentoalveloar prominence is an example of a patient plus treatment-specific variable that can contribute to compromised alveolar boundary resulting in dehiscences following incisor retraction. 81 Similarly, post-orthodontic increase in incisal proclination is known to be a risk factor for dehiscences.…”

The nance lingual arch: an auxiliary device in solving lower anterior crowding

“…Other appliances could also be use to contribute to lower anterior crowding correction, such as lip bumper (15,16) and Schwarz appliance (17,18). However, they are not recommended in some cases for being removable appliances, thus depending on patient compliance.…”

Comparison of estimated and actual changes in gap widths of expansion screws in plate appliances with 7- and 14-day activation

“…The patient must wear the appliance for several hours during the day and throughout the night [1, 3,6,8,9,10,11,13]. Shorter wearing periods, i.e., overnight only, are the exception [16,17,18]. Depending on the type of expansion screw, the gap may be opened between 0.2 and 0.4 mm by a 90° activation turn [6,9,15].…”

“…Das Weiterdrehen soll in der Regel 1-bis 2-mal/Woche [3,6,9,13] durchgeführt werden, seltener dagegen einmal zweiwöchent-lich [15], wobei der Patient seine Apparatur einige Stunden tagsüber und die ganze Nacht tragen sollte [1, 3,6,8,9,10,11,13]. Kürzere verordnete Tragezeiten, beispielsweise nur über Nacht, sind dagegen eher die Ausnahme [16,17,18]. Bei einer 90°-Drehung werden, je nach eingebauter Dehnschraube, Spaltverbreiterungen zwischen 0,2 und 0,4 mm in der Literatur angegeben [6,9,15].…”