Transverse maxillary deficiency is frequently observed in patients who seek orthodontic treatment and is often characterized by unilateral or bilateral crossbite as well as anterior crowding. There are different treatment approaches, depending on the skeletal maturity, the amount of desired expansion, and the presence of a concomitant sagittal or vertical problem.

In skeletally immature patients, rapid orthopedic palatal expansion (RPE) is a common method of treatment. However, as the patient matures and circummaxillary sutures offer more and more resistance to expansion, this procedure produces predominantly dentoalveolar expansion and may cause periodontal complications.

In skeletally mature patients, the deficiency can be corrected by segmental LeFort I osteotomy or surgically assisted rapid palatal expansion (SARPE). When compared with RPE, SARPE is believed to limit the amount of tooth movement from dentoalveolar expansion, as it eliminates the sutural resistance to expansion and therefore produces few periodontal side effects. Nevertheless, forces delivered by the expander still produce areas of compression in the periodontal ligament, which could lead to alveolar bone resorption and possible changes at the attachment level.

Some studies have evaluated periodontal effects of orthopedic RPE, yet limited information exists concerning SARPE. The protocols used in past studies have been highly variable: clinical measurements, radiographic measurements, and measurements on models and/or pictures. To date, no study has employed complete clinical and 3D radiographic evaluation of posterior teeth as well as central incisors. Only 2 published studies used tomography, which is known to provide better quantitative 3D images of osseous changes. Developed 2 decades ago, cone-beam computerized tomography (CBCT) is a multiplanar imaging technique that allows visualization of slices as well as 3D reconstructions like medical CT scanning does, with a better resolution and a far lower ionizing radiation dose.

The purpose of this prospective and comparative clinical study was to evaluate the periodontal effects of SARPE by means of a complete clinical evaluation and a CBCT evaluation. The working hypothesis was that SARPE has no detrimental effect on the periodontium.

Material and methods

This study was approved by the ethics committee of the Hôpital du Sacré-Coeur de Montréal. The sample included 14 patients (5 males, 9 females), with a mean age of 23.0 years ± 1.9 years (range: 16.4 to 39.7 years). Subjects were selected from among the patients who sought orthodontic treatment at the Faculté de médecine dentaire, Université de Montréal. The inclusion criteria were severe transverse maxillary deficiency (> 7 mm) ; advanced skeletal maturity as assessed by chronological age, cervical vertebral maturation, and sexual secondary characteristics; no missing maxillary teeth (except lateral incisors); good general health; good periodontal health; good oral hygiene; nonsmoking status during the study period; and acceptance and signature of the consent form. The only exclusion criterion was any health problem that presented a contraindication to the surgery. Pretreatment and treatment characteristics of the sample are presented in Tables I and II .

Table I

Sample pretreatment characteristics

	Sex	Age	Dental characteristics				Skeletal characteristics
			Molar Relation		OJ	OB	SNA	SNB	ANB	FMA
			Right	Left
1	M	17.9 years	II (6)	II (5)	10.0	7.0	82.0	76.0	6.0	28.0
2	F	16.9 years	I	II (5)	4.0	3.0	78.0	79.0	−1.0	27.0
3	M	25.3 years	III (1)	III (3.5)	1.0	−1.0	82.5	81.0	1.5	29.0
4	F	16.9 years	I	II (4.5)	3.0	2.0	82.5	77.0	5.5	34.0
5	F	26.7 years	I	I	0.5	0.5	84.0	82.5	1.5	35.0
6	F	39.7 years	I	II (3)	3.0	2.0	77.5	73.0	4.5	32.0
7	F	20.4 years	II (3)	II (3)	6.5	6.0	85.0	76.5	8.5	31.0
8	M	20.7 years	I	I	5.0	0.0	86.0	78.5	7.5	33.0
9	F	27.1 years	II (3.5)	II (3)	1.5	7.5	81.5	73.0	8.5	35.0
10	M	18.2 years	II (4.5)	II (2)	2.5	2.5	77.5	76.0	1.5	28.0
11	F	16.4 years	I	I	3.0	4.0	81.5	78.5	3.0	22.0
12	F	25.2 years	II (5.5)	I	3.0	4.0	78.5	76.0	2.5	19.0
13	F	34.11 years	II (4)	II (7)	6.5	0.0	79.0	74.0	5.0	41.0
14	M	17.4 years	III (5)	III (5)	0.0	0.0	83.5	86.5	–3.0	24.0

 

Table II

Sample treatment characteristics

	Screw	Extraction		Surgery
	Expansion	Without	With	One maxilla	Two maxillae
1	7.50	X		X
2	10.25	X
3	9.75	X
4	9.00		X
5	10.50	X
6	10.00	X
7	9.00	X
8	11.50	X
9	10.50	X
10	9.00		X
11	9.00		X
12	8.25		X
13	11.25		X		X
14	12.00	X		X

 

All orthodontic clinical manipulations were performed by C.G. (resident in orthodontics) and supervised by A.P. (orthodontist). All patients were treated using a Hyrax-type expander, which was bonded to both first and second premolars as well as first molars with a metal extension on the mesial-occusal surface of the second molar to prevent supraeruption during the expansion and retention. The mean expansion was 9.82 mm (7.5 to 12.0 mm). All had a 1-year retention period (4 months with the Hyrax-type appliance and 8 months with a Hawley-type appliance) before fixed orthodontic treatment began. All surgeries were performed by the same oral and maxillofacial surgeon (N.P.). The surgery included osteotomies of the lateral walls of the maxilla, midpalatal suture, and pterygoid plates, as well as release of the nasal septum.

At this time, 2 time points were considered: T0 (initial) and T1 (6 months after expansion) for all patients. A periodontal chart was completed at each time point by a periodontist (R.V.). The collected data included probing depth, width of keratinized tissue, attachment level using the enamocemental junction, gingival recession, tooth mobility, bleeding on probing, and assessment of the furcations.

A CBCT (i-CAT, Imaging Sciences International, Hatfield, Pa) was taken at each time point, and scanning parameters were a visualization field of 22 cm (enlarged field), an acquiring time of 22 seconds, and a voxel size of 0.2 mm. During image acquisition, subjects were seated with the head stabilized, occlusal plane parallel to the floor, and teeth in maximal intercuspidation. The Digital Imaging and Communications in Medicine (DICOM) images were assessed with Dolphin 3D software, 10.5 version (Dolphin Imaging and Management Solutions, Chatsworth, Calif). All measurements were done by a blinded examiner (O.Q., resident in orthodontics, under the supervision of M.P. (oral and maxillofacial radiologist). The following parameters were recorded: buccal alveolar bone thickness (BABT) ( Fig 1 ), palatal alveolar bone thickness (PABT) ( Fig 2 ), buccal alveolar crest level (BACL) ( Fig 3 ), and interproximal alveolar crest level (IACL) ( Fig 4 ). From an axial section parallel to the occlusal plane ( Fig 5 ), a curved planar reconstruction was made in which the imaging plane passed through the center of each maxillary tooth. A serial transplanar reconstruction was then made, giving 0.2-mm-thick and 0.5-mm-spaced orthogonal slices. The first 3 parameters were evaluated on slices that passed through each cusp, from the canine to the second molar on both sides. Palatal and buccal bone thicknesses were measured at a level 2 mm apical to the furcation of the right first molar. The fourth parameter was measured on a coronal slice passing through the long axis of each central incisor.

Radiographic image showing BABT.

Radiographic image showing PABT.

Radiographic image showing BACL.

Radiographic image showing IACL.

Images showing curved planar reconstruction and serial transplanar reconstruction made from an axial section