Now Reading
The value of cone beam computed tomography imaging in surgically assisted rapid palatal expansion: a systematic review of the literature

The value of cone beam computed tomography imaging in surgically assisted rapid palatal expansion: a systematic review of the literature



International Journal of Oral & Maxillofacial Surgery, 2017-07-01, Volume 46, Issue 7, Pages 827-838, Copyright © 2017 International Association of Oral and Maxillofacial Surgeons


Abstract

This study aimed to evaluate the reliability of cone-beam computed tomography (CBCT) imaging of the maxillary structures and the postoperative dentoskeletal, nasal airway, periodontal, and facial soft tissue changes after surgically assisted rapid palatal expansion (SARPE). A systematic review of the literature on CBCT analysis of SARPE was performed. The PubMed, Embase, and Cochrane Library databases were searched. Nine articles were included, involving a total of 228 patients. The general trend was tooth-borne distraction with pterygomaxillary dysjunction. A systematic increase in all transverse dimensions at the dentoalveolar and dental levels, as well as a certain degree of tipping and extrusion of the anchorage teeth and tipping of the skeletal segments, was detected. Soft tissue findings reflected the underlying dentoalveolar changes. A decrease in the buccal alveolar bone thickness and alveolar crest level occurred. Results confirm that CBCT is an accurate and reliable method to assess anatomical changes after SARPE. Although this systematic review provides valuable preliminary information about the effects of SARPE, results should be interpreted with caution due to the low level of evidence of the publications, great heterogeneity among study groups regarding outcome variables and surgical–orthodontic protocols, and lack of long-term data.

Surgically assisted rapid palatal expansion (SARPE) is the procedure of choice to manage severe transverse maxillary deficiencies in adult patients. It has been reported to improve stability compared to non-surgical rapid palatal expansion (RPE). Indeed, SARPE releases bone structures that are resistant to expansion forces. There is no consensus regarding the areas of major resistance to maxillary expansion and the number of osteotomies required to obtain a parallel opening of the midpalatal suture, but some authors relate pterygomaxillary dysjunction to a parallel expansion.

The majority of studies evaluating the transverse skeletal effects of maxillary expansion have been based on conventional cephalometric analysis using postero-anterior radiographs, occlusal views, or dental casts. The inherent limitations of all planar two-dimensional (2D) projections, such as magnification, distortion, and difficulties in landmark identification and superimposition of the anatomical structures, result in images with low accuracy and reliability and explain why these methods have been open to some criticism. With the introduction of three-dimensional (3D) imaging modalities, a more detailed and accurate evaluation of the dentoskeletal structures has become feasible compared with conventional 2D radiographs. In particular, several studies have now analysed the efficacy of SARPE using cone beam computed tomography (CBCT). Its high potential for evaluating the maxillary structures has been confirmed, mainly due to its advantages of good resolution and accuracy (only about 2% magnification), precision, non-invasiveness, lower effective radiation dose, and shorter acquisition times (60 s).

Within this context, the purpose of the present study was to conduct a systematic review of the literature on CBCT imaging and analysis of maxillary changes after SARPE in order to investigate the reliability of CBCT for maxillary analysis and to study changes in the midpalatal suture, skeletal and dental changes, changes in the nasal cavity, periodontal effects, and soft tissue facial changes.

Materials and methods

This systematic review focused on non-growing, non-syndromic human patients with skeletal maxillary transverse deficiencies treated with SARPE and studied with CBCT. The variables studied (dentoskeletal, midpalatal, nasal, periodontal, and soft tissue changes) were compared before and after treatment. Case reports, case series with a sample of n < 10, oral communications, posters, and theses were excluded.

The PICOS principle (participants, intervention, comparisons, outcomes, and study design) was followed.

Search strategy

A systematic review of the literature on SARPE and analysis with CBCT was performed. An electronic search in the PubMed (National Library of Medicine, NCBI), Cochrane Library, and Embase databases was performed in January 2015 and subsequently updated in July 2016. Table 1 shows the key words used to build the search strategy. The electronic search was completed by a manual search of the reference lists of selected publications.

Table 1
Primary and secondary key words used for the systematic literature search.
Primary key words Secondary key words
1. SARPE 1. Cone-beam
2. Surgically assisted rapid palatal expansion 2. Conebeam (MeSH)
3. SARME 3. CBCT
4. Surgically assisted rapid maxillary expansion 4. CB-CT
5. Palate surgery (MeSH) 5. Digital volume tomography
6. Maxilla surgery (MeSH) 6. CVT
7. Osteogenesis distraction (MeSH) 7. Compact computed tomography
8. Palatal expansion technique (MeSH) 8. Compact CT
9. Compact volume tomography
10. Volumetric computed tomography
11. Volumetric CT
12. Ortho cubic
13. Flat panel
14. 3 dimensional evaluation
15. Three dimensional evaluation
MeSH, medical subject heading term.

Study selection and quality assessment

The search strategy was performed independently by two investigators (ICP, MPG). First, all titles obtained in the electronic search were screened. When the title did not contain sufficient information for exclusion, the paper was selected for abstract evaluation; the abstracts of all potentially relevant papers were reviewed based on the study inclusion criteria. The papers were obtained in full when they appeared to fulfil the inclusion criteria the also when the abstract did not contain sufficient information for exclusion. Full-text articles were analysed for final inclusion. If there was a discrepancy in results between the two investigators, a consensus decision was taken; when an article was rejected, the reason was noted. Cohen’s kappa coefficient (κ) was used to measure inter-rater agreement for title and abstract selection. The electronic search was completed by a manual search of the reference lists of selected publications with the same selection strategy as described above. The methodological quality of the studies was assessed independently by the same two investigators. The materials and methods, results, and discussion sections were analysed based on the Cochrane Collaboration tool for assessing the risk of bias.

Results

Search results

The initial electronic search yielded 134 references in PubMed, 26 in Embase, and eight in Cochrane Library ( n = 168). Eleven additional studies were identified by manual search ( n = 179). After duplicate removal, 152 potentially relevant references were assessed. The full papers of 13 references were analysed in detail. Application of the inclusion criteria led to the exclusion of six more articles, and two more references were added in an update performed in July 2016. Finally, nine articles were found to be clinically or technically relevant to the subject of the study and were included in this systematic review. A QUORUM flow diagram giving an overview of the selection process is presented in Fig. 1 . The articles were categorized according to their emphasis, as shown in Table 2 .

QUORUM flow diagram of the article selection process.
Fig. 1
QUORUM flow diagram of the article selection process.

Table 2
Classification of relevant papers that were analysed in detail in this study.
Category Number of papers References
1. Accuracy and reliability of CBCT imaging of the maxillary structures 5 Gauthier et al. 2011
Nada et al. 2012
Nada et al. 2013
Sygouros et al. 2014
Zandi et al. 2014
2. Changes in midpalatal suture 1 Salgueiro et al. 2015
3. Maxillary skeletal and dental changes 6 Nada et al. 2012
Nada et al. 2013
Nada et al. 2013
Sygouros et al. 2014
Zandi et al. 2014
Kayalar et al. 2016
4. Nasal changes/upper airway changes 3 Nada et al. 2013
Pereira-Filho et al. 2014
Zandi et al. 2014
5. Periodontal changes 3 Gauthier et al. 2011
Sygouros et al. 2014
Kayalar et al. 2016
6. Soft tissue facial changes 3 Nada et al. 2012
Nada et al. 2013
Nada et al. 2013
7. Effects of bone-borne and tooth-borne devices 4 Nada et al. 2012
Nada et al. 2013
Nada et al. 2013
Zandi et al. 2014
8. Dental and skeletal changes with and without pterygomaxillary dysjunction 1 Sygouros et al. 2014
9. Effects of tooth-borne and hybrid devices 1 Kayalar et al. 2016
CBCT, cone beam computed tomography.

Types of studies

Out of the nine papers included in this systematic review, three were case series, four were cohort studies, and two were randomized clinical trials. Eight studies were prospective and one was retrospective. Three (33.3%) were performed by the same study group. Table 3 shows the characteristics of the studies included.

Table 3
Overview of the studies included.
First author, year of publication Origin Study design Sample size and distribution Mean age at time of surgery (range), years Distraction device Latency period (days) Distraction rate PD GA Same surgical procedure/same surgeon CBCT time points Scanning parameters Aim of the study
Kayalar 2016 Turkey/Germany Prosp., RCT 20
(9 M/11 F)
19.37 ± 4.18
(18–35)
Hyrax/hybrid device NR 0.5 mm/d Yes Yes Yes/yes T0: before SARPE
T1: 14 d later
T2: 6 m later
Scanora 3D (0.24-mm voxel size, 14.5 cm FOV) To compare the dental, skeletal, and periodontal effects of TB and TB/hybrid appliances in SARME
Salgueiro 2015 Brazil Prosp., CS 14
(5 M/9 F)
25.3
Type I: 23.9
Type II: 33.5
Hyrax/Haas 5 0.5 mm/d Yes Yes NR/yes T0: before SARPE
T1: 15 d later
T2: 60 d later
T3: 180 d later
i-CAT device To evaluate the opening pattern and bone neoformation process at the midpalatal suture
Pereira-Filho 2014 Brazil Prosp., CS 15
(6 M/9 F)
30.2 ± 7.4 Hyrax 7 0.75 mm/d Yes NR NR/NR T0: before SARPE
T1: after expansion
T2: 6 m later
i-CAT device (22 × 16 FOV) To evaluate upper airway changes
Sygouros 2014 Greece/Turkey Retrosp., cohort 20
(4 M/16 F)
10 −PD
10 +PD
−PD: 19.2
+PD: 18.4
Hyrax 3 0.5 mm/d −PD group
+PD group
NR Yes/NR T0: before SARPE
T1: 3–6 m later
NR To evaluate and compare skeletal, dental, dentoalveolar, and periodontal changes with and without PD
Zandi 2014 Iran Prosp., RCT 28
(9 M/19 F)
13 TB
15 BB
TB: 20.3 (15–27)
BB: 19.4 (15–23)
Hyrax/TPD 7 0.5–0.6 mm/d Yes NR Yes/yes T0: before SARPE
T1: 4 m later
Newton device (0.4-mm voxel size, 12 cm FOV) To evaluate and compare skeletal and dental changes using TB and BB devices
Nada 2013 Netherlands/Egypt Prosp., cohort 40
(13 M/27 F)
25 TB
15 BB
TB: 25.4 ± 9
BB: 30 ± 10
Hyrax/TPD 7 1 mm/d Yes Yes NR/yes T0: before SARPE
T1: 22 m later
i-CAT device (0.4-mm voxel size, 22 × 16 cm FOV) To assess and compare soft tissue facial changes using TB and BB distractors
Nada 2013 Netherlands/Egypt Prosp., cohort 32
(11 M/21 F)
19 TB
13 BB
TB: 24.2 ± 7
BB: 31.9 ± 10
Hyrax/TPD 7 1 mm/d Yes Yes Yes/yes T0: before SARPE
T1: 22 m later
i-CAT device (0.4-mm voxel size, 22 × 16 cm FOV) To assess the effects of BB and TB on the volumes of the nose and nasal airway
Nada 2012 Netherlands/Egypt/Czech Republic Prosp., cohort 45
(17 M/28 F)
28 TB
17 BB
TB: 24.5 ± 9
BB: 29.4 ± 10
Hyrax/TPD 7 1 mm/d Yes Yes Yes/yes T0: before SARPE
T1: 22 m later
i-CAT device (0.4-mm voxel size, 22 × 16 cm FOV) To evaluate the long-term effects of TB and BB devices
Gauthier 2011 Canada Prosp., CS 14
(5 M/9 F)
23.0 ± 1.9
(16.4–39.7)
Hyrax NR NR Yes NR NR/yes T0: before SARPE
T1: 6 m later
i-CAT device (0.2-mm voxel size, 22 × 16 cm FOV) To evaluate the periodontal effects of SARPE
BB, bone-borne; CBCT, cone beam computed tomography; CS, case series; d, days; F, female; FOV, field of view; GA, general anaesthesia; m, months; M, male; NR, not reported; PD, pterygomaxillary dysjunction; −PD, without pterygomaxillary dysjunction; +PD, with pterygomaxillary dysjunction; Prosp., prospective; RCT, randomized clinical trial; Retrosp., retrospective; SAPME, surgically assisted rapid maxillary expansion; SARPE; surgically assisted rapid palatal expansion; TB, tooth-borne; TPD, transpalatal distractor.

Methodological quality

The Cochrane Collaboration tool for assessing the risk of bias could not be applied in this systematic review. Consequently, the Newcastle–Ottawa scale (NOS) for assessing the quality of non-randomized studies was used ( Table 4 ).

Table 4
Newcastle–Ottawa quality assessment scale (NOS): range from 0 to 9.
First author, year of publication Study type Sample and distribution NOS results
Kayalar 2016 Prospective, RCT 20 (9 male, 11 female) Not applicable
Salgueiro 2015 Prospective, case series 14 (5 male, 9 female) Not applicable
Pereira-Filho 2014 Prospective, case series 15 (6 male, 9 female) Not applicable
Sygouros 2014 Retrospective, cohort 20 (4 male, 16 female)
(10–PD, 10 +PD)
7
Zandi 2014 Prospective, RCT 28 (9 male, 19 female)
(13 TB, 15 BB)
Not applicable
Nada 2013 Prospective, cohort 40 (13 male, 27 female)
(25 TB, 15 BB)
8
Nada 2013 Prospective, cohort 32 (11 male, 21 female)
(19 TB, 13 BB)
8
Nada 2012 Prospective, cohort 45 (17 male, 28 female)
(28 TB, 17 BB)
8
Gauthier 2011 Prospective, case series 14 (5 male, 9 female) Not applicable
BB, bone-borne; −PD, without pterygomaxillary dysjunction; +PD, with pterygomaxillary dysjunction; RCT, randomized clinical trial; TB, tooth-borne.

Regarding reporting bias, only two papers reported information about the mean screw opening during SARPE. The correlation between screw opening and maxillary opening was not a variable studied in any of the papers analysed. Two studies reported intraoperative screw activation. Overcorrection was performed by three study groups. One study compared postoperative results between cases in which pterygomaxillary dysjunction was performed and cases in which it was not. The duration of the surgical intervention was reported in one article only. Orthodontic management was assessed in three publications. Four out of the nine papers provided detailed information about the timing of orthodontic treatment following the completion of active distraction. Only one paper reported postoperative complications. The use of specific postoperative instructions or medication was reported in only one study.

Patients

A total of 228 patients managed with SARPE were reported in the nine selected articles. The sample size ranged from 14 patients to 45 patients, and the patients ranged in age from 15 years to 41.9 years, with a mean age at the time of surgery of 24.3 years. Of the total sample, 149 were female (66.5%) and 75 were male (33.5%).

The protocols of eight studies were approved by medical ethics committees. Only one paper failed to specify this aspect. Patient informed consent was specifically reported in seven papers, while two articles omitted this information.

Taking into account the type of distraction device, a tooth-borne distractor (TB) was used in 162 patients (69.3%), whereas a bone-borne distractor (BB) was used in 60 patients (26.3%) and a hybrid device was used in the remaining 10 (4.4%). Pterygomaxillary dysjunction (+PD) was reported in 218 patients (95.6%); no pterygomaxillary dysjunction (−PD) was performed in the remaining 10 (4.4%).

A TB device was used in 158 patients (69.3%). A BB device was used in 60 patients (26.3%) and a hybrid device in the remaining 10 (4.4%).

CBCT images

Table 3 summarizes the CBCT protocols and scanning parameters used in the different studies. In three studies, measurements were performed by one observer who was not directly involved in the treatment and who was blinded to the type of treatment. In another study, all measurements were performed by a blinded examiner (resident in orthodontics) under the supervision of an oral and maxillofacial radiologist. Two observers, blinded to the type of treatment, were involved in another study. One paper reported that measurements were made by a single examiner and another that measurements were made by two operators, with no further information on blinding, and the remaining articles did not describe the examiner conditions.

Parameters were calculated twice at a 2-week, 4-week, or 8-week interval. In particular, measurements were taken twice within a 2-week interval for the right teeth at T0 to establish intra-examiner reliability, and 16 and 11 randomly selected CBCT scans were measured twice with a 2-week interval. The remaining articles did not provide such details.

Expansion devices

Table 3 summarizes the distractor devices used in the selected articles. One of the TB device study groups reported a mean screw opening of 9.82 mm (range 7.5–12.0 mm). Another paper reported 7.8 ± 2.8 mm for the TB group and 7.3 ± 2.0 mm for the BB group. The remaining articles did not specify this parameter. The correlation between screw opening and maxillary opening was not a variable studied in any of the articles analysed.

Surgical intervention and expansion protocol

Surgical specifications of the selected articles are summarized in Table 3 . Regarding the specific expansion protocol, one study specified screw activation of 2 mm intraoperatively and another reported screw activation until a diastema of 1 mm was shown. Only one study performed activation–latency cycles: the screw was activated for 7 days followed by no activation for the next 7 days. The clinical aim of expansion was referred to as the dimension at which the palatal cusps of the maxillary teeth touched the buccal cusps of the lower dentition, or simply as the dimension at which “adequate expansion was achieved”. Overcorrection was performed in two studies: one aimed for an overexpansion of 2–3 mm on either side, and the other for a slight overcorrection of the crossbite. The remaining articles did not specify these parameters.

The distraction device was left in place after the desired expansion had been achieved for a retention period of 3 months, 4 months, or 6 months. Two articles did not report this variable. At the end of the consolidation period, some authors installed a transpalatal arch on the first molars. In one study, a Hawley-type appliance was fitted for 8 months. The remaining articles did not report the use of any post-expansion stabilization devices. Orthodontic treatment was initiated 8–10 weeks after the end of active distraction, or after the 6-month retention period. The remaining articles did not specify when orthodontic treatment was started. Orthodontic management was performed by a single orthodontist in one study and by several in another. The remaining articles did not specify this point.

Complications

Only one paper reported complications after SARPE. These included mild extrusion of a premolar, oedema, and haematoma.

The use of specific postoperative instructions or medication was reported in only one study.

Reported inclusion/exclusion criteria for SARPE

With regard to inclusion criteria, a general inclusion criterion was adult age with skeletal maturity and a concomitant transverse maxillary deficiency. The size of the deficiency was required to be greater than 7 mm in one study, greater than 5 mm in another, and was left unspecified in the other seven studies included in this systematic review.

Additional inclusion criteria were good general health, good periodontal health, no missing maxillary teeth (except lateral incisors), non-smoking status during the study period, and signature on the consent form.

All patients included in this systematic review were evaluated radiologically with CBCT ( Table 3 ).

With regard to exclusion criteria, according to the papers included in this systematic review, patients were excluded from SARPE if the following conditions were present: developmental maxillofacial deformities or craniofacial anomalies that could alter the effects of expansion, systemic disease, prior maxillary trauma or previous surgery, absence of more than four teeth in the posterior maxillary arch, radiological signs of fluid accumulation in the maxillary sinuses, age under 18 years, absence of maxillary first molars, previous periodontal disease, previous orthodontic treatment, and genetic disease. For one study group, the exclusion criteria were summarized as any health problem that contraindicated surgery. Methodologically, one study excluded patients who were missing the required set of CBCT scans and another excluded patients whose lips were not at rest during CBCT scan acquisition.

Reliability of CBCT imaging of the maxillary structures

The reliability of CBCT for the diagnosis of transverse maxillary deficiency and for the postoperative evaluation of SARPE was assessed with the analysis of reported correlation coefficients. Globally, intra-examiner reliability ranged from 0.550 to 0.996. Individually, values ranged from 0.966 to 0.996, 0.70 to 0.96, and 0.55 to 0.98. One paper gave a single value of 0.93, and another reported that the intra-class correlation coefficient showed that all measurements could be repeated with an insignificant error not affecting the results. Four articles did not specify this parameter. Only one paper reported the inter-observer correlation coefficient, which ranged between 0.60 and 0.95.

Changes in the midpalatal suture

Radiographic analysis (CBCT) of postoperative changes in the midpalatal suture was performed in one selected study only ( Table 5 ). The authors reported a type I opening pattern of the midpalatal suture (opening from the anterior to the posterior nasal spine) in 85.7% of the patients, while a type II opening (opening from the anterior nasal spine to the transverse palatal suture) was observed in the remaining 14.2%. They related the opening pattern to the patient’s age: older individuals showed a tendency to a V-shaped opening. Bone density values after 180 days of retention were smaller than those of the preoperative period, and it was concluded that a retention period of more than 6 months is necessary.

Table 5
Overview of studies included in the systematic review: skeletal, dentoalveolar, and dental changes, nasal changes, periodontal changes, facial soft tissue changes, and midpalatal suture changes.
First author/year CBCT T1/T2 Skeletal, dentoalveolar, and dental changes Nasal changes Periodontal changes Facial soft tissue changes Midpalatal suture changes
Kayalar 2016 T1: 14 d
T2: 6 m
  • Less anterior dental expansion in the hybrid devices group than in the TB group

  • Posterior dental expansion was comparable in the two groups

  • The first molars tipped buccally more in the TB group, but moved upright during the retention period

  • The mean skeletal maxillary widening was found to be similar in the two groups, with a V-shaped pattern

  • Hybrid devices produced less tipping and reduced tooth resorption compared to TB expanders

NR
  • A decrease in the BABT

  • Neither the hybrid nor the TB distractor involved any risk of periodontal damage to the molars

  • Hybrid devices produced less bone resorption than TB expanders

NR NR
Salgueiro 2015 T1: 15 d
T2: 60 d
T3: 180 d
NR NR NR NR
  • Type I opening pattern: 85.7%

  • Type II opening pattern: 14.2%

  • Older individuals showed a tendency to a V-shaped opening

  • The bone density values after 180 d of retention were smaller than those of the preoperative period

Pereira-Filho 2014 T1: after expansion
T2: 6 m
NR
  • A significant increase in the smallest transverse section area of the nasal airway at T1 and a tendency to relapse at T2

  • Maxillary expansion, 6 m after SARPE, does not result in a significant improvement in the airway dimensions (area and volume)

NR NR NR
Sygouros 2014 T1:3–6 month
  • Buccal tipping of all posterior teeth but not of the canines

  • Vestibular tipping of the alveolar crest, more in the −PD group; differences not statistically significant

  • An increase in all transverse measurements at the dentoalveolar and dental levels, with more alveolar bending and more buccal tipping in the −PD group

  • A true skeletal anterior expansion, no posterior expansion, and a constriction in the middle area (in the −PD group)

  • No statistically significant differences between −PD and +PD groups

NR
  • A decrease in the BABT and BACL

  • A greater decrease in the premolar area in the −PD group

NR NR
Zandi 2014 T1: 4 m
  • In the coronal plane, a V-shaped expansion with more widening at the dental arch than in the palatal bone

  • Postero-anteriorly, a parallel expansion

  • Comparable dental and skeletal changes between TB and BB groups

  • A small increase in the nasal floor width without differences between TB and BB groups

NR NR NR
Nada 2013 T1: 22 m
  • Posterior alveolar expansion and anterior alveolar retropositioning, without statistically significant differences between TB and BB groups

  • Increased retro-inclination of the upper incisors, with no differences between groups

NR NR
  • Posterior retropositioning of the upper lip and increased projection of the cheek area, with no statistically significant differences between TB and BB groups

NR
Nada 2013 T1: 22 m
  • An expansion at the level of the root apices of the first molars, without statistically significant differences between TB and BB groups

  • An increase in nasal airway volume 2 years after SARPE, with no statistically significant differences between TB and BB groups

NR
  • Nasal alar width increased; differences between TB and BB groups were not statistically significant

NR
Nada 2012 T1: 22 m
  • Expansion at the level of the root apices of premolars and molars, without statistically significant differences between TB and BB groups

  • Posterior alveolar expansion and anterior alveolar retropositioning, without statistically significant differences between TB and BB groups

NR NR
  • Posterior retropositioning of the upper lip and increased projection of the cheek area, with no statistically significant differences between TB and BB groups

NR
Gauthier 2011 T1: 6 m NR NR
  • A decrease in the BABT and BACL

  • An increase in the PABT

  • A tendency towards a decrease in the IACL on the mesial aspect of the central incisors

NR NR
BABT, buccal alveolar bone thickness; BACL, buccal alveolar crest level; BB, bone-borne; CBCT, cone beam computed tomography; d, days; IACL, interproximal alveolar crest level; m, months; NR, not reported; PABT, palatal alveolar bone thickness; −PD, without pterygomaxillary dysjunction; +PD, with pterygomaxillary dysjunction; SARPE; surgically assisted rapid palatal expansion; TB, tooth-borne.

Skeletal and dental changes

Immediately postoperative

Radiographic analysis (CBCT) of the immediate maxillary dental and skeletal changes was not reported in any of the selected articles.

After retention

Radiographic analysis (CBCT) of the maxillary dental and skeletal changes after retention was performed by three study groups ( Table 5 ). One of them reported a V-shaped expansion of the dentoskeletal structures in the coronal plane and greater widening of the dental arch (range 6.53–7.23 mm) than of the palatal bone (range 3.92–4.33 mm), with comparable dental and skeletal changes between TB and BB devices. Postero-anteriorly, parallel expansion of the dental arch and palatal bone was observed. In another study group, an increase in all transverse measurements at the dentoalveolar and dental levels and a true anterior skeletal expansion were detected, although the posterior aspect of the maxilla showed no expansion. The −PD group exhibited a constriction in the middle area and more pronounced buccal alveolar bending and buccal tipping, but without statistical significance. The final article found significantly less anterior dental expansion in the hybrid devices group than in the TB group, and posterior dental expansion was comparable in the two groups. The first molars tipped buccally to a greater extent in the TB group, but moved upright during the retention phase. Mean skeletal maxillary widening was found to be similar in the two groups, with a V-shaped pattern.

You're Reading a Preview

Become a DentistryKey membership for Full access and enjoy Unlimited articles

Become membership

If you are a member. Log in here