Alveolar defects before and after surgically assisted rapid palatal expansion (SARPE): a CBCT assessment

ABSTRACT Introduction: Surgically Assisted Rapid Palatal Expansion (SARPE) promote maxillary expansion in skeletally mature patients. This technique is effective; however, some side effects are still unknown. Objectives: evaluate the presence of alveolar defects (dehiscences and fenestrations) in patients submitted to the SARPE. The null hypothesis tested was: SARPE does not influence the number of dehiscences and fenestrationss. Methods: A retrospective quasi-experiment study of a convenience sample of 279 maxillary teeth, in 29 patients evaluated with Cone Beam Computed Tomography (CBCT) at T1 (before SARPE), T2 (after expansion) and T3 (after retention), was performed. The examined teeth were: canines, first and second premolars, first and second molars. in axial, coronal, and cross-sectional views. The evaluations involved viewing slices from mesial to distal of the buccal roots. Results: All statistical analyses were performed using SAS 9.3 and SUDAAN softwares. Alpha used in the study was 0.05. Alveolar defects increased statistically from T1 (69.0%) to T2 (96.5%) and T3 (100%). Dehiscences increased 195% (Relative Risk 2.95) at the end of expansion (T2). After retention (T3), individuals were on average 4.34 times more likely to develop dehiscences (334% increase). Fenestrations did not increase from T1 to T2 (p = 0.0162, 7.9%) and decreased from T2 to T3 (p = 0.0259, 4.3%). Presence of fenestrations at T1 was a significant predictor for the development of dehiscences in T2 and T3. Dehiscences increased significantly in all teeth, except second molars. Conclusion: The null hypothesis was rejected. After SARPE the number of dehiscences increased and fenestrations decreased. Previous alveolar defects were predictor for dehiscences after SARPE.


INTRODUCTION
Fenestrations and dehiscences are found in patients without orthodontic treatment. 1 Many studies have examined the prevalence of alveolar defects during orthodontic treatment. [2][3][4][5][6] showed that there is more dehiscences in hyperdivergent than hypodivergent patients. However, there are conflicting results when the type of malocclusion (Class I or III) is evaluated. 6 In general, dehiscences are more frequent in the mandible and fenestrations in the maxilla. 1,6,7 Surgically Assisted Rapid Palatal Expansion (SARPE) is indicated for skeletally mature patients with severe maxillary transverse deficiency, with crowding, with a wide buccal corridor and failure of conventional maxillary expansion (RPE). 8 This surgical orthodontic treatment evolved from cuts in maxillary resistance areas to LeFort I osteotomy with or without pterygoid disjunction to decrease pressure against the teeth that would affect the cortical bone and prevent periodontal defects. 9,10 Orthodontic movements occur in the anchored teeth when the expander is activated after SARPE and can cause periodontal alterations in the bone. 5 The long-term risks of having these alveolar defects and the problems associated with their increase post-SARPE should be addressed. The question is: has this worked to reduce the number of bone defects with Romano FL, Sverzut CE, Trivellato AE, Saraiva MCP, Nguyen TT -Alveolar defects before and after surgically assisted rapid palatal expansion (SARPE): a CBCT assessment the modern techniques and appliances? There is no consensus regarding the best orthodontic appliance to be used with surgical procedure nor the surgical techniques. [9][10][11][12] Alterations promoted by SARPE have been evaluated in retrospective clinical studies using cephalometric radiographs, plaster models and CBCT imaging. 11,[13][14][15][16][17][18] However, the prevalence of fenestrations and dehiscences in patients that received SARPE still unknown.
Thus, the aim of this study was to evaluate the presence of alveolar defects (dehiscences and fenestrations) in patients submitted to the SARPE. The null hypothesis tested was that the SARPE does not influence the number of dehiscences and/or fenestrations.

MATERIAL AND METHODS
The inclusion and exclusion criteria are presented in Figure 1.    Quinelato, Rio Claro, Brazil).
Romano FL, Sverzut CE, Trivellato AE, Saraiva MCP, Nguyen TT -Alveolar defects before and after surgically assisted rapid palatal expansion (SARPE): a CBCT assessment 10 The osteotomy was performed following the intermaxillary suture and was completed using a chisel and mallet (Sverzut; Quinelato, Rio Claro, Brazil). After the fracture was made, the expansion screw was activated 2 mm (eight ¼ turns) then deactivated 1 mm to open a 1 mm diastema between the maxillary central incisors.
Seven days after surgery, the patients began to turn the screw with two 1/4 turns in the morning and two 1/4 turns at night.
Expansion was stopped when the palatal cusps of the maxillary molars occluded with the buccal cusps of the mandibular molars ( Fig 2B) and held in retention for six months. was classified as dehiscence ( Fig 4A). If the bone defect did not involve the alveolar crest, it was classified as fenestrations ( Fig 4B). 1,6,7 Evaluations were performed in dark room to improve the visualization of alveolar defects, 6    Alveolar defects increased to 96.5% at T 2 and 100% at T 3 . There was an 18.9% increase in the number of surfaces exhibiting dehiscences from T 1 to T 2 and 13.5% increase from T 2 to T 3 .
On the other hand, the number of surfaces with fenestrations decreased 3.6% from T 2 to T 3 . With treatment all teeth but second molars showed statistically significant increase in dehiscences development (p = 0.2263). The most affected teeth were first molars, followed by the first premolars (Table 1).
Romano FL, Sverzut CE, Trivellato AE, Saraiva MCP, Nguyen TT -Alveolar defects before and after surgically assisted rapid palatal expansion (SARPE): a CBCT assessment 16  defects. This is less than the data reported by Enhos et al. 7 (33.53%), however, their study included mandibular incisors, which shows a higher percentage of alveolar defects. 1,6,7 In this study, correlation among malocclusion, growth pattern with number of dehiscences and fenestrations was not evaluated.
Further studies are needed to test that hypothesis.
Periodontal evaluation in adult patients before orthodontic treatment is essential to determine alveolar morphology and to prevent undesirable effects. 6 19 It is possible that this bone decrease might be due to the tilting of maxillary bone. 20 In the present study, the prevalence of fenestrations decreased from T 2 to T 3 . This is because many fenestrations became dehiscences in T 2 or T 3 due to uncontrolled teeth tipping (Figs 4 and 5).  25 In this study, the activation followed the osteogenic distraction protocol that is widely used bt orthodontics and surgeons 26,27

CONCLUSION
The null hypothesis was rejected. Dehiscences increased and fenestrations decreased after SARPE. First molars and first premolars had the greater number of alveolar defects.