This report aimed to describe an effective biomechanics to control the upper incisors inclination during the
correction of gummy smile with bimaxillary proclinations. A 14-year-old female presented with a Class II
division I incisor relationship complicated with bimaxillary proclination on a Class 2 skeletal base. The lips
were incompetent, showing 7 mm of upper incisors at rest and 5mm maxillary gingival display on smiling
with normal upper lip length. Treatment involved extraction of all first permanent premolars followed by
upper and lower fixed appliances. Intrusion of the upper incisors with controlled labial crown torque was
accomplished with mini-implant anchorage placed bilaterally on the infrazygomatic crests with the retraction
forces above the centre of resistance using 0.019x0.025-in stainless steel archwire in 0.022-in slot. The
0.019x0.025-in stainless steel archwire in 0.022-in slot provided the vertical play to favour lingual crown
tipping despite having forces above the centre of resistance for concurrent anterior segment intrusion.
To determine the number of cases that are at risk of poor stability in terms of arch width changes following fixed appliances treatment at the Orthodontic Unit, Klinik Pergigian Cahaya Suria, Kuala Lumpur. In a retrospective audit, 101 pre- and post-treatment lower study casts were selected from cases completed in the year 2015 at the Orthodontic Unit, Klinik Pergigian Cahaya Suria, Kuala Lumpur. Samples were measured using a universal caliper by a single calibrated operator. Samples was categorised as extraction or non-extraction types. Arch width changes was determined using paired T-test. The recommended limit was 0mm for inter-canine width, 2 mm for inter-first premolar width and 3mm for inter-second premolar and inter-molar width. Differences were considered “within limits”, if the changes were within the recommended limit ±0.25mm (for possible marginal measurement error) and “expanded”, if above the range for within limits. 42.6% were non-extraction while 57.4% were extraction cases. In the non-extraction group, 52.2% cases had expanded inter-canine widths, followed by inter-first and second premolars (27.9%) and interfirst molar (20.9%) widths. Arch width changes for the inter-first and second premolars and inter-molars widths were statistically significantly different (p<0.05) but bot clinically significant. In the extraction group, 67.2% had expanded inter-canine widths, followed by inter-first premolar (64.3%), inter-second premolar (9.1%) and inter-first molar (5.2%) widths. The inter-canine (M=1.43; SD=2.71, p<0.05) and inter-first premolar (M=2.87; SD=2.61, p<0.05) widths statistically and clinically significant expansion but the inter-second premolar and molar were significantly contracted (p<0.05). The number of cases with expanded arch widths was high regardless of the extraction type.
Keywords: Arch width expansion, stability