Table 2.

Summary of Study Characteristics and Results of the Included Studies (TPA Only)^a

Study	Sample		Retraction Method	Other Anchorage Group Type	Material of TPA Used
	TPA Group	Other Group
Zablocki et al. (2008)2	N = 30; 11 M, 13.1 ± 1.7 years; 19 F, 13.2 ± 2 years	N = 30; 11 M, 12.9 ± 2 years; 19 F, 14.1 ± 3.3 years	18 × 25 preangulated Roth appliance and continuous arch wire	No TPA anchorage	Soldered Goshgarian TPA
Feldmann and Bondemark (2008)4
(a)	N = 30; 15 M, 15 F; 14.4 ± 1.65 years	N = 30; 15 M, 15 F; 14 ± 1.53 years	Space closure with 0.22-inch slot size and continuous light forces, space closure was carried with active tie-backs using 0.019 × 0.025 SS space closure arch wire	Subperiosteal Onplant	(2.00 × 1.00 mm) SS bar soldered to the maxillary first molar, with 2 mm of space between bar and palate
(b)		N = 30 ; 15 M, 15 F; 14 ± 1.53 years		Orthosystem anchorage
(c)		N = 30; 15 M, 15 F; 14 ± 1.72 years		Headgear
Wilmes et al. (2009)32	N = 10, 20.9 years	N = 10, 20.9 years	Not reported	One mini-implant + TPA (0.8 mm)
Liu et al. (2009)10	N = 17; 3 M, 14 F; 19.71 ± 3.06 years	N = 17; 3 M, 14 F; 21.65 ± 4.49 years	Sliding mechanics and en masse retraction of anterior teeth with power chain and SS ligatures	Mini-screws	Not reported
Liu et al. (2009)33	N = 23; 4 M, 19 F; 17.8 ± 4.3 years	N = 19; 3 M, 16 F; 20.2 ± 5.5 years	Sliding technique	Mini-screws	Not reported
Basha et al. (2010)34	N = 7, 16 ± 1.41 years	N = 7, 17.36 ± 1.35 years	En masse sliding retraction on 0.019 × 0.025 wires	Mini-implants	Not reported
Sharma et al. (2012)12	N = 15; 10 F, 20 M; 17.4 years	N = 15; 10 F, 20 M; 17.4 years	Canine retraction only using 9-mm nitinol closed coil spring of length 9 mm	Mini-screws	0.9-mm SS wire soldered to the palatal surface of molar bands
Gökçe et al. (2012)35	N = 9; 5 F, 4 M; 15.9 years	N = 9; 5 F, 4 M; 16.7 years	Canine distalization; closed coil spring with a force of 100 g	Mini-screws	0.9-mm-diameter SS wire was soldered to palatal/lingual region of the molar bands
Al-Sibaie et al. (2014)13	N = 28; 16 F, 12 M; 22.34 ± 4.56 years	N = 28; 19 F, 9 M; 22.34 ± 4.56 years	TPA group: two-step retraction with class II division 1 in mini-implant: sliding en masse retraction of upper anterior teeth	Mini-implant	Passive TPA soldered to U6 bands, 0.9-mm SS, coffin loop centered to the midpalatal line about 1–2 mm distant from palatal surface

^aAP, anteroposterior; A-OLp position f the maxillary base; DUM-V, the vertical distance between the distal upper molar point and rotated SN plane; F, female; FH, Franfort horizontal; Is-OLp, position of maxillary incisor; M, male; Ms-OLp, position of maxillary molar; NS, nonsignificant; OLp, occlusal line perpendicular; PTV, pterygoid vertical plane; SS, stainless steel; TPA, transpalatal arch; U1, maxillary central incisor; U6, maxillary first molar; UIT-V, the vertical distance between the upper incisal tip and the rotated SN plane (SN′); Y, line perpendicular to Frankfort horizontal pass through sella.

^bMesial molar movement is a calculated as percentage of the molar movement provided in the article.