Mauro Cozzani

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.

Decoy oligodeoxynucleotides targeting NF-kappaB transcription factors: induction of apoptosis in human primary osteoclasts

Proteins belonging to the nuclear factor kappaB (NF-kappaB) superfamily are involved in osteoclast formation, playing a very important role for both differentiation of osteoclast precursors and survival of mature osteoclasts. Several drugs used to fight bone loss in a variety of human pathologies, including osteoporosis, act by increasing the frequency of osteoclast apoptosis, since it was demonstrated that small changes in osteoclast apoptosis can result in large changes in bone formation. In this respect, targeting of NF-kappaB transcription factor could be of great interest. Among nonviral gene therapy strategies recently proposed to inhibit or even block NF-kappaB activity, the transcription factor decoy (TFD) should be taken in great consideration. The main issue of the present study was to examine the effects of decoy DNA/DNA molecules targeting NF-kappaB on apoptosis of human osteoclasts (OCs), with the aim to interfere with the pathway regulating osteoclast differentiation and programmed cell death. To this aim, we used a mixture of receptor activator of NF-kappaB ligand (RANKL), macrophage colony-stimulating factor (M-CSF) and parathyroid hormone (PTH) to prepare human OCs from peripheral blood cells. Then, transfection with the decoy molecules targeting NF-kappaB was performed. The results obtained demonstrate that in primary cells expressing typical osteoclast markers such as TRAP and MMP9, NF-kappaB decoy significantly stimulated apoptosis. Inhibition of IL-6 expression and induction of Caspase 3 were found in OCs treated with NF-kappaB DNA/DNA decoys. We consider these data as the basis for setting up experimental conditions allowing nonviral gene therapy of several bone disorders.

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.

Factors influencing the stability of miniscrews. A retrospective study on 300 miniscrews

The aim of this study was to investigate, over a period of approximately 3 years, the reactions to orthodontic loading of a type V titanium miniscrew. In this retrospective study, conducted in a private practice, the records of 300 miniscrews inserted in 132 consecutive patients (80 females, 60.6 percent) by the same surgeon were evaluated. The mean age of the patients was 23.2 years. Three types of miniscrews (type A: diameter 1.5 mm, length 9 mm; type B: diameter 1.5 mm, length 11 mm; and type C: diameter 1.3 mm, length 11 mm) were used. The clinical variables evaluated included the loading time and location of the miniscrew in relation to the gingiva and root. The success rates with different variables were compared using chi-square or Fishers exact test where appropriate. A cumulative survival rate of 81 percent (243/300) was found using Kaplan-Meier analysis, with an optimum success rate for the 1.3 mm wide miniscrew inserted in the attached gingiva, with immediate loading applied. Cox proportional hazard regression showed significant differences between success rate and the following parameters: gender, loading time, gingival or bone localization, and diameter of the miniscrews. Considering the clinically controllable parameters, and within the limits of this retrospective study, 1.3 mm diameter miniscrews inserted in attached gingiva and immediately loaded had the most favourable prognosis.

Condylar position and maxillary first premolar extraction

Condylar position in 17 patients whose Class II treatment (14 with edgewise appliances and 3 with Begg appliances) included extraction of the maxillary first premolars and in 17 control patients was compared by means of corrected tomography. The condyles in both groups were in an anterior position, and there were no statistical differences between the groups. In addition, no statistical correlation was found when the posttreatment bite depth, interincisal angle, and maxillary incisor inclination were correlated with condylar position. Thus, as determined in this study, condylar position was unrelated to treatment, bite depth, interincisal angle, and maxillary incisor inclination.

Comparison of different orthodontic devices for mandibular symphyseal distraction osteogenesis: A finite element study

INTRODUCTION In this study, we aimed to analyze the displacement field and the level of stability for a human mandible that had symphyseal distraction osteogenesis. The mandible was fitted with various orthodontic devices: tooth borne, bone borne, and hybrid. Three-dimensional nonlinear finite element analyses were performed to study differences between the nominal aperture of the device and the actual mandibular distraction. Furthermore, displacement fields of the mandibular arch evaluated with and without mastication forces were compared to determine the level of stability of each appliance. METHODS Computed tomography scan images of the mandible were processed to create the finite element model, which was completed by modeling the distraction device. Three cases were considered: the distraction device attached to the first molar and the first premolar (tooth borne), to the canine and basal bones (hybrid), or only to the basal bone (bone borne). The nominal aperture of each device was 2 mm. Mandibular displacements in the mastication phase were analyzed in the case of unilateral occlusion on the second premolar. RESULTS AND CONCLUSIONS Tooth-borne and hybrid devices allow orthodontists to better control the effective displacement transferred to the mandible by the distractor. Displacements of the mandibular arch were closer to the nominal aperture of the distractor than in the case of the bone-borne device. Hybrid devices were more stable under functional loads. However, parasitic rotations of the mandibular arms caused by mastication might counteract the benefits of distraction.

Non-compliance maxillary molar distalizing appliances: an overview of the last decade

OBJECTIVES To perform a literature review focusing on the use of non-compliance intraoral appliances for molar distalization therapy. MATERIALS AND METHODS A literature search ranged from January 1999 to December 2009 in order to describe dento-alveolar changes and skeletal vertical modifications following the use of conventional anchorage intraoral distalizing appliances. The quality of the retrieved studies was ranked on a 12-points scale, from low to high quality. RESULTS A total of 214 articles were found and only 24 were considered eligible for the critical examination. Maxillary first molar distalization ranged from 6.4mm to 0.5mm with a concomitant distal tipping from 18.5° to bodily distalization. A smaller amount of distal movement and a greater amount of crown tipping can be noted at second molars. Premolar anchorage loss and incisor proclination represent an unavoidable side-effect and ranged from 4.33 mm to 0.73 mm and from 13.7° to 0.6° respectively. Skeletal vertical modifications were noted. Increase in vertical facial dimension ranged from 1.5° to -1.8° and lower anterior facial height ranged from an increase of 3.2 to a decrease of 0.6 mm. The assessment of study quality showed that 19 studies were of low quality, 3 of medium quality and 2 of medium-high quality. CONCLUSIONS Maxillary molar distalization can be effectively performed with the use of noncompliance intraoral appliances. As a consequence, premolar anchorage loss, incisor proclination and a slight increase in vertical facial dimension can occur. Because of the lack of high-quality studies the findings of this review should be carefully interpreted.

Unusual Extraction Treatment in Class II division 1 Using C-Orthodontic Mini-Implants

This paper describes the treatment of a female patient, aged 23 years and 5 months, with a Class II division 1 malocclusion, who showed severe anterior protrusion and lower anterior crowding. Specially-designed orthodontic mini-implants were placed bilaterally in the interdental space between both the upper and the lower posterior teeth. Both lower first molars showed severe apical lesions. Therefore, the treatment plan consisted of extraction of both upper first premolars and lower first molars, en masse retraction of the upper six anterior teeth, lower anterior alignment, and protraction of all the lower molars. C-implants(R) were used as substitutes for maxillary posterior anchorage teeth during anterior retraction and as hooks for mandibular molar protraction. The correct overbite and overjet were obtained by intruding and retracting the upper six anterior teeth into their proper positions. The dentition was detailed using conventional orthodontic appliances. The upper C-implants contributed to an improvement in facial balance, and the lower C-implants made it possible to protract the lower second and third molars with less effect on the axis of the lower anterior teeth. The active treatment period was 29 months and the patients teeth continued to be stable 11 months after debonding.

Arch width changes with a rapid maxillary expansion appliance anchored to the primary teeth.

OBJECTIVE To examine the dimensional changes after rapid maxillary expansion (RME) carried out in the transitional dentition with the primary teeth as anchorage. MATERIALS AND METHODS Group A was composed of 31 consecutive transitional dentition patients with posterior quadrant crossbites treated with a Haas-type RME appliance anchored on the maxillary primary molars and canines. No treatment was administered after palatal expansion. Study models were made before RME (T1), at appliance removal (T2), and at least 1 year after appliance removal (T3). A control sample of 60 individuals with posterior quadrant crossbites who had had no orthodontic treatment was categorized into group B (30 individuals with an average age comparable with the treated patients at T2) and group C (30 individuals with an average age comparable with the treated patients at T3). RESULTS Permanent molar crossbites were corrected at T2, and this correction was maintained at T3 in all patients. The mean permanent maxillary intermolar width was 42.6 +/- 2.3 mm at T1, 46.7 +/- 1.9 mm at T2 (P < .01), and 46.3 +/- 1.8 mm at T3 (P < .01) in group A; 42.9 +/- 2.7 mm (P < .01) in group B; and 44.4 +/- 3.0 (P < .01) in group C. Premolar and canine widths were slightly wider than the control at T3. CONCLUSION To avoid undesirable treatment-induced effects on maxillary permanent molars, a stable transverse correction could be achieved with the RME appliance anchored on the primary teeth.

Dental arch changes following rapid maxillary expansion.

The purpose of this research was to evaluate changes in upper arch dimension and form following rapid maxillary expansion (RME) using a modified Haas appliance in the primary dentition. The sample comprised 49 children [17 males, 32 females, mean age 7 years 5 months, standard deviation (SD) 1 year 1 month] with a crossbite or maxillary crowding. Twenty patients had a normal SN-GoGn angle (7 males, 13 females, mean 33.25 degrees, SD 2.10), three were low angle (1 male, 2 females, mean 27.67 degrees, SD 2.31), and 22 were high angle (8 males, 14 females, mean 39.95 degrees, SD 3.15). The vertical dimensions of four patients could not be measured, due to the unavailability of radiographs. Expansion was undertaken to either correct a crossbite or treat maxillary crowding. The upper dental casts were analysed using a computerized system: before treatment (T1), at appliance removal (T2), and 2 years 4 months after appliance removal (T3). Using bootstrap statistical analysis applied to distance ratio values [Euclidean distance matrix analysis (EDMA)], it was found that 48 patients showed a change in arch form. In 40.82 per cent (n = 20, group A), the arch form changed from T1 to T2, T1 to T3, and T2 to T3. In 32.65 per cent (n = 16, group B), it varied from T1 to T2 but relapsed at T3 to the form of T1. For 24.5 per cent (n = 12, group C), it changed from T1 to T2 but maintained the same form at T3. The favourable characteristics for obtaining expansion, identified by logistic regression analysis, were being male, of an immature stage of dental development (lateral incisor not fully erupted) and the presence of a lateral crossbite. Intercanine and intermolar widths, arch length, and the distance between the interincisive point and the line joining the canines (depth of the intercanine arch) at the different time points were analysed using a two-tailed t-test (P < 0.05). For the whole group, the increase in intercanine and intermolar width and in the depth of the intercanine arch was significant. Comparison between groups A, B, and C was undertaken using an analysis of variance, but there was no significant difference between the groups. This modified type of Haas appliance was able to increase the transverse dimension of the maxillary dental arch in the mixed dentition. The most appropriate timing for treatment appears to be before the eruption of the permanent lateral incisors.