Material and methods

Thirty growing skeletal Class III patients participated in this study according to the following inclusion criteria: they were 10 to 14 years of age at the start of treatment with a prepubertal stage of skeletal maturity according to the cervical vertebral maturation method. All had a skeletal Class III malocclusion because of a maxillary deficiency, an Angle Class III molar relationship, or an anterior crossbite without an anteroposterior functional shift. The patients and their parents were informed about the study, and the parents signed consent forms. In addition, an assent form was required for the children who participated in the study. The study was approved by the research ethical committees of the institutional review boards at Tanta University in Egypt and the University of Illinois at Chicago.

The patients were divided into 3 equal groups using a random number table. All patients were treated by the same operator (M.H.E).

• Group 1 (n = 10) included 6 boys and 4 girls with a mean age of 11.9 ± 1.3 years. They were treated with facemasks anchored with miniplates in the zygomatic buttress area of the maxilla (skeletally anchored facemask).

• Group 2 (n = 10) included 7 boys and 3 girls with a mean age of 12.24 ± 1 years. They were treated using Class III elastics extending from infrazygomatic miniplates in the maxilla to symphyseal miniplates in the mandible.

• Group 3 (n = 10) included 7 boys and 3 girls with a mean age of 11.7 ± 1.6 years. For the control group, records were taken before and after the observation period to distinguish treatment changes from growth changes. Then these patients started treatment.

For the facemask miniplate protocol, 2 anchor surgical miniplates (55-0851; Stryker Leibinger, Freiburg, Germany) were placed 1 at each zygomatic buttress area. Surgical miniplates were adapted and bent according to the anatomy of the zygomatic buttress in a curvilinear pattern according to the anatomic shape of the zygomatic buttress area and fixed with 3 self-tapping bone screws per side (2-mm diameter, 6-mm length; 50-20706; Stryker Leibinger). The distal end of the miniplate was exposed through the keratinized attached gingiva near the canine to prevent gingival irritation, and the end holes of the miniplates were cut to create hooks for elastics. Three weeks after the surgery, an orthopedic force of 400 to 500 g per side was applied by heavy extraoral elastics directed 30° downward and forward from the occlusal plane from the miniplates to the facemasks. The patients were asked to replace the elastics once each day. A removable maxillary biteplate covering the posterior occlusal surfaces was placed to eliminate occlusal interference in the incisor region until correction of the anterior crossbite was obtained ( Fig 1 ).

Facemask anchored with miniplates fixed in the zygomatic buttress.

For the Class III elastics and miniplate protocol, 4 straight miniplates (55-0851; Stryker Leibinger) were placed. In the maxilla, straight surgical miniplates, 25 mm or 6 holes in length, were adapted to the anatomy of the infrazygomatic buttress and fixed with 3 self-tapping bone screws per side (2-mm diameter, 6-mm length; 50-20706; Stryker Leibinger). In the mandible, straight miniplates of 21 mm or 5 holes in length were adapted to the bone anatomy inferiorly between the mandibular lateral incisors and canines and fixed with 2 or 3 self-tapping bone screws per side so that the upper screw was at the level of root apices. All mucoperiosteal flaps were secured and sutured, exposing the ends of the miniplates over the keratinized attached gingiva to prevent gingival irritation. The distal end holes of the miniplates were cut to create hooks for elastics.

Three weeks after the surgery, the miniplates were loaded with Class III elastics on each side to provide a force of approximately 250 g to each side. The patients were instructed to wear the elastics 24 hours per day. The elastics were replaced at least once each day. A removable biteplate covering the occlusal surface of maxillary teeth was placed to eliminate occlusal interference in the incisor region until correction of the anterior crossbite was obtained ( Fig 2 ).

Class III elastics extending from infrazygomatic miniplates in the maxilla to symphyseal miniplates in the mandible.

The decision to discontinue orthopedic treatment in groups 1 and 2 was made by the operator when the patients had 3 to 4 mm of positive anterior overjet.

For each patient, a lateral cephalogram and facial moulage were obtained before treatment (T1) and at the end of protraction therapy or the observation period (T2), All facial moulages were scanned with the Facial Insight 3D Scanner (Motion View Software, Chattanooga, Tenn). Hence, 3D photographs of all patients and controls were acquired. All subjects were in centric occlusion, with relaxed facial musculature and lips. The 3D photographs were imported in stereolithography binary file format (*.stl) into an advanced processing software package (Geomagic Control 14; Geomagic, Research Triangle Park, NC) for further analysis.

All 3D photographs were acquired in a similar way and had the same orientation. The facial soft tissue changes after maxillary protraction were evaluated by superimposition of the T1 and T2 3D photographs for every patient by a surface-based registration, Maal et al concluded that surface-based registration is an accurate method to compare 3D photographs of the same subject at different times rather than reference frame-based registration.

For the initial register of T1 and T2 scans, 9 markers were used as references to superimpose the images: (1) left endocanthion, (2) left exocanthion, (3) right endocanthion, (4) right exocanthion, (5) soft tissue nasion, (6) left palpebrale superius, (7) left palpebrale inferius, (8) right palpebrale superius, and (9) right palpebrale inferius. The 3D photographs at T1 were set as fixed, and the T2 3D photographs were set as floating objects. For more refining of the superimpositions, the final register was made on the wide surface starting from right and left exocanthion and extending upward over all the forehead on the area that would not be influenced by the treatment. The T1 and T2 3D images were superimposed with the same coordinate system ( Fig 3 ). For the 3D analysis of each subject, the T1 face scan was set as a reference, and the T2 scan was set as the test, and then the 3D compare analysis was performed. The 3D compare analysis generated a 3D color-coded map that displayed the areas and magnitudes of changes in facial soft tissues between the T1 (reference) and T2 (test) scans ( Figs 4 and 5 ).

A, Points marked for initial approximate registration based on point landmarks for pretreatment and posttreatment face scans: 1 , right endocanthion; 2 , left endocanthion; 3 , right exocanthion; 4 , left exocanthion; 5 , soft tissue nasion; 6 , right palpebrale superius; 7 , left palpebrale superius; 8 , right palpebrale inferius; 9 , left palpebrale inferius. B, The final superimposition is made on the wide surface area starting from right and left exocanthions and extending upward over the forehead on the area that would not be influenced by the treatment.

Three-dimensional color-coded map displays the areas and magnitudes of changes in the facial soft tissues before and after bone-anchored maxillary protraction between the T1 and T2 scans; soft tissue landmarks selected to measure the magnitudes of deviation are right and left buccale point (Bc), right and left point of cheek (Ch), subnasale (Sn), labiale superius (Ls), labiale inferius (Li), soft tissue B-point (B’), soft tissue pogonion (Pg’), and soft tissue menton (Me’).

Three-dimensional color-coded map displays the areas and magnitudes of changes in the facial soft tissues of an untreated Class III patient at T1 and T2.

Soft tissue landmarks, including right and left buccale points, right and left points of the cheek, subnasale, labiale superius, labiale inferius, soft tissue B-point, soft tissue pogonion, and soft tissue menton, were defined using the Create Annotation function in the Geomagic Control 14 software. The Annotation function measured the magnitude of deviation between the T1 and T2 scans at the selected points corresponding to x-, y-, and z-axes (Dx, deviation in the transverse direction; Dy, deviation in the vertical direction; Dz, deviation in the anteroposterior direction) ( Fig 4 ). The magnitudes of deviations were analyzed statistically.

Cephalometric radiographs were obtained at T1 and T2 for all subjects to evaluate the amounts of maxillary advancement and the changes. Hence, the soft tissue changes were compared with actual skeletal movements. All cephalometric radiographs were scanned and analyzed by 1 investigator (M.H.E) using software (version 11.7; Dolphin Imaging and Management Solutions, Chatsworth, Calif). The analysis consisted of the following.

• 1.

  The reference system described by Tollaro et al constructed through 2 lines ( Fig 6 ):

  • Stable basicranial line, which extends from the most superior point of the anterior wall of sella turcica at the junction with tuberculum sellae (point T) and drawn tangent to lamina cribrosa of the ethmoid bone; these basicranial structures do not undergo remodeling after the age of 4 to 5 years ; and vertical T, a line constructed perpendicular to the stable basicranial line and passing through point T.

  

  Measurements based on stable basicranial line (SBL) and vertical T (VertT): 1 , Or-VertT; 2 , Ptm-VertT; 3 , A-VertT; 4 , A’-VertT; 5 , B-VertT; 6 , B’-VertT; 7 , Pg’-VertT.

• 2.

  Angular measures (SNA, SNB, ANB, SNO, SN-GoGn, SN-palatal plane, gonial angle, U1-palatal plane, L1-MP) ( Fig 7 ).

  

  Angular measurements (SNA, SNB, ANB, SNO, SN-GoGn, SN-palatal plane, gonial angle, U1-palatal plane, L1-MP).

• 3.

  Linear measures (A-Na Perp, Co-A, Co-Gn, U6-VRmx, overjet, overbite) ( Fig 8 ).

  

  Linear measurements (A-Na Perp, Co-A, Co-Gn, U6-VRmx, overjet, overbite).

To assess the reliability of the measurements on the face scans and cephalometric radiographs, 10 patients were randomly selected, and all measurements were repeated 3 weeks after the initial measurements by the same operator.

As a measure of reliability, intraclass correlation coefficients were computed to investigate the reliability of the method used by the investigators. An intraclass correlation coefficient of approximately 0.99 and a 95% confidence interval ranging from 0.678 to 0.999 for all variables in this study indicate very good reliability of the method we used.

Results

There were no statistically significant differences between the 3 groups at T1 for ages and the analyzed cephalometric parameters ( Table I ). There were significant active treatment effects in the changes between T1 and T2 in groups 1 and 2. The changes from T1 to T2 in the 3 groups are shown in Table II .

Table II

Descriptive statistics for changes (T2-T1) and comparison by ANOVA and Bonferroni post hoc tests for multiple comparisons

	Parameter	Group 1		Group 2		Group 3		ANOVA	Post hoc test
		MP + FM		MP + CI III elastics		Control
		Mean	SD	Mean	SD	Mean	SD	P	Groups 1-2	Groups 1-3	Groups 2-3
	Treatment period (mo)	8	1.33	8.9	2.33	9.4	1.77	NS		NS	NS
Anteroposterior relationship	Or-VertT (mm)	3.03	1.77	3.88	1.7	0.61	0.54	‡	NS	†	‡
	Ptm-VertT (mm)	2.1	0.9	2.73	0.58	0.49	0.41	‡	NS	‡	‡
	A-VertT (mm)	4.87	1.56	5.81	1.23	1.18	0.6	‡	NS	‡	‡
	B-VertT (mm)	−1.45	0.32	−0.67	0.35	1.67	0.45	‡	‡	‡	‡
	Pg-VertT (mm)	−1.55	0.35	−0.65	0.09	1.94	0.09	‡	‡	‡	‡
	SNA (°)	4.78	1.14	5.65	0.83	0.44	0.49	‡	NS	‡	‡
	SNB (°)	−1.21	0.85	−0.39	0.59	0.89	0.7	‡	*	‡	†
	ANB (°)	5.99	1.54	6.04	1.16	0.82	0.68	‡	NS	‡	‡
	SNO (°)	2.78	0.74	3.29	1.15	0.29	0.39	‡	NS	‡	‡
	(A-Na Perp) (mm)	5.55	2.45	6.07	1.29	−0.73	0.6	‡	NS	‡	‡
	(Co-A) (mm)	4.8	1.29	5.74	1.2	1.21	2.26	‡	NS	‡	‡
	(Co-Gn) (mm)	0.95	0.25	1.74	0.37	2.12	3.34	NS	NS	NS	NS
	Wits appraisal (mm)	7.01	2.34	7.32	1.28	−1.03	1.1	‡	NS	‡	‡
Vertical relationship	LAFH (ANS-Me) (mm)	2.94	1.68	1	0.18	1.9	1.86	*	*	NS	NS
	SN – GoGn (°)	2.03	0.76	−0.98	0.51	−0.53	0.76	‡	‡	‡	NS
	SN-palatal plane (°)	−0.65	0.24	−0.7	0.86	−0.61	1.17	NS	NS	NS	NS
	Gonial angle (Ar-Go-Me) (°)	−3.2	0.61	−4.18	0.49	−0.26	0.61	‡	NS	‡	‡
	U1-palatal plane (°)	0.25	0.37	0.14	0.44	0.59	0.98	NS	NS	NS	NS
	IMPA (L1-MP) (°)	−2.56	1.76	1.1	0.18	0.42	0.22	‡	‡	‡	NS
Dental relationship	U6-VRmx (mm)	0.14	0.31	0.119	0.06	0.28	0.13	NS	NS	NS	NS
	Overbite (mm)	−1.48	1.52	−0.65	0.71	0.82	1.05	‡	NS	‡	*
	Overjet (mm)	7.13	1.25	7.11	1.59	−0.57	0.56	‡	NS	‡	‡
Soft tissue relationship	A′-VertT (mm)	5.24	1.98	6.75	2.61	1.22	0.48	‡	NS	‡	‡
	B′-VertT (mm)	−1.125	1.12	−0.48	0.62	1.69	6.44	*	NS	‡	NS
	Pg’-VertT (mm)	−1.08	0.87	−0.72	0.62	1.83	0.2	‡	NS	‡	‡

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