Antonio Gracco

Quantitative cone-beam computed tomography evaluation of palatal bone thickness for orthodontic miniscrew placement

INTRODUCTION The purpose of this study was to evaluate the 3-dimensional thickness of the palate to determine the best location to place miniscrews. METHODS We selected digital volumetric tomographs from 162 healthy subjects, aged 10 to 44 years (80 male, 82 female). The sample was divided into 3 groups. Group A included 52 subjects (ages, 10-15 years; 28 boys, 24 girls); group B included 38 subjects (ages, 15-20 years; 18 males, 20 females), and group C had 72 subjects (age, 20-44 years; 34 men, 38 women). Ninety-degree paracoronal views of the palatal region at 4, 8, 16, and 24 mm posterior to the incisive foramen were reconstructed, and bone height was measured laterally from the midline in each reconstruction at 0-, 3-, and 6-mm increments to describe the topography of the palate. Measurements of palatal height in 27 of the 162 patients were made by 2 different investigators. Method error was calculated according to the Dahlberg formula (S(2) = Sigmad(2)/2n), and systematic error was evaluated with the dependent Student t test, with P <0.05 considered significant. RESULTS The thickest bone (4-8 mm) was found in the anterior part of the palate, at the suture and in the paramedian areas, but the posterior region, despite its reduced thickness, is also suitable for miniscrews. The Kruskal-Wallis test showed no significant differences between the groups in the various palatal sections (median suture, 3 and 6 mm to the right and left of the suture) except between groups A and C in the 16-mm paracoronal section at 6 mm to the right and left of the suture. There were no statistically significant differences due to sex or between the right and left sides of the palate. CONCLUSIONS The anterior region is the thickest part of the palate, but the bone thickness in the posterior region is also suitable for screws of appropriate diameter and length.

Numerical/experimental analysis of the stress field around miniscrews for orthodontic anchorage.

The aims of this study were to analyse the stress distribution developing around an orthodontic miniscrew (OM) inserted into the maxilla and to determine the stress field changes for different screw lengths and for different levels of osseointegration occurring at the bone/screw interface. An integrated experimental/numerical approach was adopted. Using the photoelastic technique, the stress field arising in the bone after screw insertion and the application of the initial orthodontic load was assessed. The finite element (FE) method was used to determine the stress acting in the bony tissue after a given time following screw application, when, for the viscoelastic relaxation effects, the only stress field remaining was that due to the application of the orthodontic load. Different levels of osseointegration were hypothesized. Photoelastic analyses showed that stress distribution does not change significantly for moderate initial orthodontic loads. From the FE simulations, it was found that critical conditions occur for screws 14 mm long with an orthodontic load of 2 N. The optimal screw length seems to be 9 mm. For such a dimension, small stress values were found as well as low risk of lesion to the anatomical structures.

Computed tomography evaluation of mandibular incisor bony support in untreated patients

INTRODUCTION In this study, we aimed to verify, via computed volumetric tomography, a correlation between the morphology of the mandibular symphysis and the various facial types. METHODS From a sample of 148 digital volumetric tomographs, the subjects were classified as either short face (25 subjects), normal face (27 subjects), or long face (28 subjects) according to the average values of their Frankfort-mandibular plane angle. The 80 healthy subjects were between 12 and 40 years of age. Tomography was carried out using NewTom 3G volume scanner (QRsr1, Verona, Italy). The following parameters were measured on the sections corresponding to the 4 mandibular incisors: height, thickness, and area of the entire symphysis; height, thickness, and area of the cancellous bone of the symphysis; distance of the vestibular and lingual cortices from the apices of the 4 incisors; and possible inclination of each mandibular incisor, expressed in degrees. The F test or analysis of variance (ANOVA) and the Tukey HSD Test were subsequently used. RESULTS The total thickness of the symphysis was greater in the short-face subjects than in the long-face subjects. No statistically significant differences in the total and cancellous areas of the symphysis were found between the 3 facial types. In all 3 groups, the total and cancellous heights and areas were greater at the central incisors than at the lateral incisors. CONCLUSIONS There is a statistically significant relationship between facial type and the total thickness of the mandibular symphysis.

Upper Incisor Position and Bony Support in Untreated Patients as Seen on CBCT

OBJECTIVE To test the null hypothesis that there are no correlations between the morphology of the upper jaw, the position of the upper incisors, and facial type. MATERIALS AND METHODS From a sample of 191 patients, the FMA angle was used to select 20 short face type, 20 norm face type, and 20 long face type patients, aged 12 to 40 years. Using cone-beam computed tomography (CBCT), tomography was carried out on sagittal sections corresponding to the four upper incisors. Some parameters defining the dentoskeletal relationships, the alveolar thickness, the alveolar height, and the dental movement were measured. The measurements were processed using analysis of variance and Tukeys test. RESULTS At the upper central incisors, short face type patients presented a greater alveolar bone thickness than long face type patients. In short face type and norm face type subjects the root apex of the upper incisors was farther away from the lingual cortex than in the long face type patients. At the central incisors the alveolar thickness was greater and the lingual cortex was higher with respect to the lateral incisors in all three facial types. CONCLUSION At the upper incisors, facial type is statistically significantly correlated with both alveolar bone thickness and distance between the root apex and lingual cortex.

Long-term stability of alveolar bone grafts in cleft palate patients

INTRODUCTION Many authors have examined the surgical bone treatment of cleft palate patients, but no study has emphasized the role of orthodontic therapy. The aims of this study were to evaluate the long-term stability of bone grafts when using an orthodontic-surgical protocol, to determine the success of bone grafts in minor vs severe clefts, and to develop a qualitative method for assessing the success of bone grafting. METHODS Forty-nine patients were included in this study. Occlusal x-rays were taken before (T0), immediately after (T1), and at least 1 year after bone grafting (T2). Two radiographic parameters were analyzed adjacent to the cleft side: the vertical bone level (Bergland scale) and the horizontal bone level (Witherow-derived scale). RESULTS The bone graft success at T2 was 91.84% (95% confidence interval, 84.55-96.41). The severity of the cleft before grafting was not statistically correlated with success at T2 (P <0.05). The concordance rate between Bergland and Witherow values was 87.07% (95% confidence interval, 82.69-90.69). The variables analyzed (sex, age, type of cleft, lateral incisor agenesis) were not statistically correlated (P <0.05) with the stability of bone graft. Based on the results, the only factor involved in the stability of the graft seems to be dental age at the time of bone grafting and the orthodontic therapy before and after grafting. CONCLUSIONS It seems appropriate to recommend early application of a surgical-orthodontic protocol to treat cleft lip and palate patients, prevent postoperative bone resorption, and guarantee correct positioning of the teeth.

Palatal Volume Following Rapid Maxillary Expansion in Mixed Dentition

OBJECTIVE To evaluate volumetric variations in the palate following rapid expansion, both immediately after treatment and over time. MATERIALS AND METHODS The sample was composed of 30 patients in early mixed dentition treated with a Haas-type device cemented onto the primary second molars. The mean age of the patients upon commencement of expansion was 7 years and 6 months (standard deviation [SD], 12 months). Measurement of palatal volume was conducted via 3D acquisition of plaster models using laser scanning before treatment (T1), upon device removal (T2), and 2.6 years afterward (T3). RESULTS The volume of the palate increased in a statistically significant fashion from T1 to T2 and from T1 to T3, and it decreased in a nonsignificant fashion from T2 to T3. CONCLUSIONS Palatal volume significantly increases with rapid maxillary expansion (RME) treatment with insignificant relapse. The use of virtual 3D models with the aid of Apposite software permits evaluation of the morphologic and volumetric changes induced by orthodontic treatment.

Optimal Palatal Configuration for Miniscrew Applications

OBJECTIVE To test the hypothesis that palatal bone is not able to support titanium miniscrews (11 mm in length and 2 mm in diameter) when subjected to forces normally generated during orthodontic treatment. MATERIALS AND METHODS The miniscrew-palatal bone system was modeled and analyzed using the commercial finite element method software ANSYS Multiphysics 10.0; tests were done in both a state of total osseointegration and in the absence of it. Calculations were carried out in both cases in configurations where the miniscrew was inserted into two different palatal regions: in the first it was anchored in one layer of cortical bone and in the underlying trabecular bone; in the second, two layers of cortical bone and the trabecular bone in between were involved. Two different loads were taken into account, 240 gf and 480 gf, both of which are within the normal range for orthodontic treatment, and applied to the miniscrew heads. RESULTS The results demonstrated that the miniscrew inserted into the palate can be anchored to bone and loaded within normal orthodontic force range without exceeding the stress levels that lead to bone fracture. The osseointegrated system was characterized by a lower level of stress than the nonosseointegrated one, but anchorage within the second layer of cortical bone markedly reduced the stress on the trabecular bone, thereby improving the stability of the implant, also in the absence of osseointegration. CONCLUSIONS The hypothesis is rejected. Miniscrews loaded within the normal orthodontic force range do not exceed the stress levels that lead to bone fracture.

Prevalence of incidental maxillary sinus findings in Italian orthodontic patients: a retrospective cone-beam computed tomography study

Objectives To determine the prevalence of incidental maxillary sinus findings in a large sample of orthodontic patients by cone-beam computed tomography (CBCT) with a wide field of view and assess the relationships of such abnormalities with age and gender. Methods Five hundred thirteen CBCT scans obtained for orthodontic diagnosis and treatment planning in a Northern Italian population (N = 513; 292 female and 221 male subjects; 1,026 maxillary sinuses) were studied. The frequencies of pseudocysts and mucosal thickening of the maxillary sinus were recorded. Logistic regression analysis was used to determine the influence of age and gender on these abnormalities. Results Pseudocysts were detected in 52 patients (10.1%) and 59 sinuses (5.75%). Mucosal thickening was observed in 206 patients (40.1%) and 258 sinuses (25.1%). Gender and age were significantly associated with pseudocysts (p = 0.027) and mucosal thickening (p < 0.001), respectively. Conclusions Half of the orthodontic patients had incidental maxillary sinus findings. Men were more likely to show pseudocysts, and older patients (aged 41 - 60 years) were more likely to show mucosal thickening.

Factors associated with the efficacy of mandibular advancing device treatment in adult OSA patients

The aim of this study was to evaluate the anthropometric, demographic, occlusal and cephalometric characteristics of a group of adult obstructive sleep apnea (OSA) patients treated with mandibular advancement devices (MADs) and to determine the factors associated with treatment efficacy. Twenty-three consecutive patients with mild to severe OSA (polysomnographically diagnosed [T0]) were recruited for this prospective study; they were treated with a Silensor(®) appliance, and a polysomnographic exam with the MAD in situ was performed 2 to 3 months later (T1) to evaluate MADs efficacy. Based on apnea-hypopnea index (AHI) differences between the T0 and T1 values, patients were classified into two groups: completely recovered and not completely recovered patients. The differences in anthropometric, demographic, occlusal and cephalometric parameters between the two groups were analyzed, and significant parameters verified. The sample showed these prevalent characteristics: deep bite, crossbite, tooth wear, dental and skeletal Class II, mesofacial mandibular vertical growth pattern, low position of the hyoid bone, longer soft palate length. The transverse diameters of upper maxilla had the greatest impact on T0 AHI. The factors associated with MAD efficacy were: age under 55 years, distance between the hyoid bone and the mandibular plane (H-MP) less than 20 mm, divergence of mandibular vertical growth pattern (SN^MP) less than 29°.

Effects of thread shape on the pullout strength of miniscrews.

INTRODUCTION The aim of this study was to determine the effects of variations in thread shape on the axial pullout strength of orthodontic miniscrews. METHODS A total of 35 miniscrews, 7 of each design being considered, were tested by performing pullout tests on a synthetic bone support. We used self-tapping and self-drilling miniscrews having a diameter of 2 mm and a thread shaft length of 12 mm (the longest and the largest supplied by the manufacturer). A buttress reverse thread shape served as the control design and was tested against 4 experimental designs, each manufactured with a modification in thread shape while maintaining all other characteristics. The experimental groups had the following thread designs: buttress, 75° joint profile, rounded, and trapezoidal. RESULTS The control group with a buttress reverse thread shape had consistently higher pullout strength values than did the other designs. A statistically significant reduction in pullout force was found between the buttress reverse and the buttress thread miniscrews. CONCLUSIONS Thread design influenced the resistance to pullout of the orthodontic miniscrews. The buttress reverse thread shape provided the greatest pullout strength.