Posterior teeth angulation in non-extraction and extraction treatment of anterior open-bite patients

This study was approved by the Ethics in Research Committee of Bauru Dental School, University of São Paulo, Brazil.

The study comprised 60 open-bite treated patients of both sexes, selected from the files of the Orthodontic Department at Bauru Dental School, University of São Paulo, divided into two groups: Group 1 consisted of 30 (12 male; 18 female) patients treated with non-extraction, with mean pre- and posttreatment ages of 15.26 (SD = 3.99) and 17.73 (SD = 4.16) years, respectively, and an initial mean open bite of 1.47 mm. Ten patients presented with Class I, 18 with Class II, and 2 with Class III malocclusions. Ten patients underwent maxillary expansion either with hyrax or Haas appliances to correct posterior crossbites or to provide space in the maxillary arch [25, 26]. Group 2 included 30 patients (11 male; 19 female), treated with extractions, with mean pre- and posttreatment ages of 14.03 (SD = 2.70) and 16.53 (SD = 3.12) years, respectively, with an initial mean open bite of 1.93 mm. Fourteen patients presented with Class I, 15 with Class II, and 1 with Class III malocclusions. Twenty-seven were treated with four first premolar extractions, 2 were treated with two first maxillary premolar extractions, and 1 was treated with two first mandibular premolar extractions. Seven underwent maxillary expansion either with hyrax or Haas appliances to correct posterior crossbites or to provide space in the maxillary arch. The main selection criterion was that the patients should present initially an anterior open bite clinically greater than or equal to 1 mm (Fig. 1). Additional criteria were the presence of all maxillary and mandibular teeth up to the first molars and that the patients had been treated non-extraction and with extractions with Edgewise appliances.

In the non-extraction group, treatment was conducted with the standard Edgewise technique, which is characterized by the use of 0.022 × 0.028-in. conventional brackets. For leveling and alignment, the usual wire sequence begins with a 0.015-in. twist-flex or a 0.016-in. nickel-titanium wire, followed by 0.016, 0.018, and 0.020-in. stainless steel round wires. Vertical anterior elastics to correct the open bite usually began to be used when at least an 0.018-in. stainless steel round archwire was inserted. The elastics were used until a positive overbite was obtained. Detailing of tooth position and the finishing procedures were accomplished by either 0.019 × 0.025-in. or 0.021 × 0.025-in. rectangular wires and 0.018-in. round wires, respectively. No additional auxiliaries were used to control the vertical dimension. After the active treatment period, a Hawley retainer was used in the maxillary arch and a bonded canine-to-canine retainer in the mandibular arch. Myofunctional therapy was recommended to correct tongue posture and function, when necessary. The mean treatment time was 2.46 years.

In the extraction group, the appliances used were similar to the non-extraction group. After the extractions, if there were anterior crowding, the canines were initially retracted until the anterior teeth could be aligned. Thereafter, leveling and alignment progressed as in the non-extraction group until a rectangular wire was inserted. Vertical anterior intermaxillary elastics were usually used after insertion of a 0.018-in. round stainless steel archwire. The elastics were used until a positive overbite was obtained. Maxillary and mandibular anterior retraction were performed on the rectangular archwires with elastic chains. Anchorage reinforcement was provided with an extraoral headgear in the maxillary and a lip bumper in the mandibular arch, when necessary. The retention procedures were similar to the non-extraction group. Myofunctional therapy was recommended to correct tongue posture and function, when necessary. The mean treatment time was also 2.49 years.

Two lateral cephalometric headfilms were obtained from each patient at the pre- (T1) and posttreatment (T2) stages. The cephalometric tracings and landmark identifications were performed on acetate paper by a single investigator (M.R.) and then digitized with a DT-11 digitizer (Houston Instruments, Austin, TX). In total, 128 landmarks were identified and 30 measurements were performed (Table 1 and Figs. 2, 3, 4, and 5). These data were stored in a computer and analyzed with Dentofacial Planner 7.0 (Dentofacial Planner Software, Toronto, Ontario, Canada), which corrected the image magnification factors of the groups. The magnification factors varied from 6 to 10.94%, because the radiographs were taken on different X-ray machines.

Maxillomandibular relationship
SNA (°)	SN to NA angle
SNB (°)	SN to NB angle
ANB (°)	NA to NB angle
Growth pattern
SN.PP (°)	SN to palatal plane angle
SN.GoGn (°)	SN to Go–Gn angle
PP.MP (°)	Angle between palatal plane(ANS/PNS) and mandibular plane(Go/Gn)
FMA (°)	Frankfurt horizontal to mandibular plane angle
Gonial angle (°)	Ar–Go to Go–Gn angle
LAFH (mm)	Lower anterior face height: distance from ANS to menton
Dental relationship
Overbite (mm)	Distance between the maxillary and mandibular incisor borders.
Maxillary teeth mesio-distal angulations
Mx4.BOP (°)	Long axis (apex to tip) of maxillary 1st premolar to bisected occlusal plane (BOP)
Mx5.BOP (°)	Long axis (apex to tip) of maxillary 2nd premolar to bisected occlusal plane (BOP)
Mx6.BOP (°)	Long axis (furcation to center of the crown) of maxillary 1st molar to bisected occlusal plane (BOP)
Mx7.BOP(°)	Long axis (furcation to center of the crown) of maxillary 2nd molar to bisected occlusal plane (BOP)
Mx4.PP (°)	Long axis (apex to tip) of maxillary 1st premolar to palatal plane(ANS–PNS)
Mx5.PP (°)	Long axis (apex to tip) of maxillary 2nd premolar to palatal plane (ANS–PNS)
Mx6.PP (°)	Long axis (furcation to center of the crown) of maxillary 1st molar to palatal plane (ANS–PNS)
Mx7.PP (°)	Long axis (furcation to center of the crown) of maxillary 2nd molar to palatal plane (ANS–PNS)
Mandibular teeth mesio-distal angulations
Md4.BOP (°)	Long axis (apex to tip) of mandibular 1st premolar to bisected occlusal plane (BOP)
Md5.BOP (°)	Long axis (apex to tip) of mandibular 2nd premolar to bisected occlusal plane (BOP)
Md6.BOP (°)	Long axis (furcation to center of the crown) of mandibular 1st molar to bisected occlusal plane (BOP)
Md7.BOP (°)	Long axis (furcation to center of the crown) of mandibular 2nd molar to bisected occlusal plane(BOP)
Md4.MP (°)	Long axis (apex to tip) of mandibular 1st premolar to mandibular plane (Go–Gn)
Md5.MP (°)	Long axis (apex to tip) of mandibular 2nd premolar to mandibular plane (Go–Gn)
Md6.MP (°)	Long axis (furcation to center of the crown) of mandibular 1st molar to mandibular plane (Go–Gn)
Md7.MP (°)	Long axis (furcation to center of the crown) of mandibular 2nd molar to mandibular plane (Go–Gn)
Interdental angulations
Mx4.Md4 (°)	Long axis (apex to tip) of maxillary and mandibular 1st premolars
Mx5.Md5 (°)	Long axis (apex to tip) of maxillary and mandibular 2nd premolars
Mx6.Md6 (°)	Long axis (furcation to center of the crown) of maxillary and mandibular 1st molars
Mx7.Md7 (°)	Long axis (furcation to center of the crown) of maxillary and mandibular 2nd molars

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