Riccardo Nucera

Condylar volume and surface in Caucasian young adult subjects

BackgroundThere have been no quantitative standards for volumetric and surface measurements of the mandibular condyle in Caucasian population. However, the recently developed cone-beam computed tomography (CBCT) system allows measurement of these parameters with high accuracy.MethodsCBCT was used to measure the condylar volume, surface and the volume to surface ratio, called the Morphometric Index (MI), of 300 temporo-mandibular joints (TMJ) in 150 Caucasian young adult subjects, with varied malocclusions, without pain or dysfunction of TMJs.ResultsThe condylar volume was 691.26 ± 54.52 mm3 in males and 669.65 ± 58.80 mm3 in, and was significantly higher (p< 0.001) in the males. The same was observed for the condylar surface, although without statistical significance (406.02 ± 55.22 mm2 in males and 394.77 ± 60.73 mm2 in females).Furthermore, the condylar volume (693.61 ± 62.82 mm3 ) in the right TMJ was significantly higher than in the left (666.99 ± 48.67 mm3, p < 0.001) as was the condylar surface (411.24 ± 57.99 mm2 in the right TMJ and 389.41 ± 56.63 mm2 in the left TMJ; t = 3.29; p < 0.01). The MI is 1.72 ± 0.17 for the whole sample, with no significant difference between males and females or the right and left sides.ConclusionThese data from temporomandibular joints of patients without pain or clinical dysfunction might serve as examples of normal TMJs in the general population not seeking orthodontic care.

In vitro evaluation of the frictional forces between brackets and archwire with three passive self-ligating brackets.

The aim of this in vitro study was to evaluate the frictional forces between bracket and archwire that included three passive self-ligating brackets (Damon SL2 SDS). The brackets were individually bonded to a brass mount using a preformed 0.021 x 0.025 inch stainless steel wire jig in order to exclude adverse tipping or torsion. The central bracket was positioned 1 mm higher than the others, in order that the three brackets were vertically unaligned. Thirty-six similar set-ups including in total 108 brackets were investigated using the same wire: copper (nickel-titanium) 0.014 inches. A testing machine was designed and constructed to measure the frictional forces between the wire and the three-bracket set-up. Twelve set-ups were tested to measure kinetic frictional forces between the wire and unaligned passive self-ligating brackets used in the closed position. The frictional properties of two sets of 12 three-bracket set-ups (control) were tested and measured with an open slide and conventional ligation. A stainless steel ligature wire was used in the former, while elastomeric modules were employed in the latter. One-way analysis of variance showed a significant effect of ligation mode on the frictional properties of the three-bracket set-ups (P < 0.001). Post hoc pairwise comparison showed that the frictional forces arising from passive self-ligation were significantly lower (P < 0.01) than those resulting from elastic ligation. The same result was achieved when comparing self-ligation and metallic ligation (P < 0.01). No significant difference was found when comparing elastic and metallic ligation.

Rapid maxillary expansion in growing patients: Correspondence between 3-dimensional airway changes and polysomnography

OBJECTIVES The aim of the present prospective study was to investigate the effects of rapid maxillary expansion on the airway correlating airway volumes computed on cone beam computed tomography and polysomnography evaluation of oxygen saturation and apnea/hypopnea index. METHODS The study group comprised 14 caucasian patients (mean age 7.1 ± 0.6 years) undergone to rapid maxillary expansion with Haas type expander banded on second deciduous upper molars. Cone beam computed tomography scans and polysomnography exams were collected before placing the appliance (T0) and after 12 months (T1). Landmarks localization and airway semiautomatic segmentation on cone beam computed tomography scans allowed airway volume computing and measurements. RESULTS Increases of total airway volume, oxygen saturation and apnea/hypopnea index were statistically significant. No correlation was found among total airway volume, oxygen saturation and apnea/hypopnea index changes between the examined timepoints. CONCLUSIONS Computing airway volume on cone beam computed tomography allow to measure the amount of air that flows through nasal cavity, nasopharynx and oropharynx while oxygen saturation and apnea/hypopnea index could give information about functional parameters. In the present study all three variables investigated showed statistically significant differences between T0 and T1 but no correlation was found between increases of the different variables tested.

Effects of orthopedic maxillary expansion on nasal cavity size in growing subjects: A low dose computer tomography clinical trial

OBJECTIVE The aim of this retrospective clinical trial was to evaluate the effects of rapid maxillary expansion on skeletal nasal cavity size in growing subjects by use of low dose computer tomography. METHODS Eight Caucasian children (three male; five female) with a mean age of 9.7 years (SD±1.41) were the final sample of this research that underwent palatal expansion as a first phase of orthodontic treatment. The maxillary expander was banded to the upper first molars and was activated according a rapid maxillary expansion protocol. Low-dose computer tomography examinations of maxilla and of the low portion of nasal cavity were performed before inserting the maxillary expander (T0) and at the end of retention (T1), 7 months later. A low-dose computer tomography protocol was applied during the exams. Image processing was achieved in 3 steps: reslicing; dental and skeletal measurements; skeletal nasal volume computing. A set of reproducible skeletal and dental landmarks were located in the coronal passing through the first upper right molar furcation. Using the landmarks, a set of transverse linear measurements were identified to estimate maximum nasal width and nasal floor width. To compute the nasal volume the lower portion of the nasal cavity was set as region of interest. Nasal volume was calculated using a set of coronal slices. In each coronal slice, the cortical bone of the nasal cavity was identified and selected with a segmentation technique. Dependent t-tests were used to evaluate changes due to expansion. For all tests, a significance level of P<0.05 was used. RESULTS Rapid maxillary expansion produced significant increases of linear transverse skeletal measurements, these increments were bigger in the lower portion of the nasal cavities: nasal floor width (+3.15 mm; SD ± 0.99), maximum nasal width (+2.47 mm; SD ± 0.99). Rapid maxillary expansion produced significant increment of the total nasal volume (+1.27 cm(3) ± SD 0.65). The anterior volume increase was 0.58 cm(3) while the posterior one was 0.69 cm(3). CONCLUSION In growing subjects RME is able to significantly enlarge the dimension of nasal cavity. The increment is bigger in the lower part of the nose and equally distributed between the anterior e the posterior part of the nasal cavity.

Load–deflection characteristics of superelastic and thermal nickel–titanium wires

The aim of this study was to investigate the mechanical properties of superelastic and thermal nickel-titanium (NiTi) archwires for correct selection of orthodontic wires. Seven different NiTi wires of two different sizes (0.014 and 0.016 inches), commonly used during the alignment phase, were tested. A three-point bending test was carried out to evaluate the load-deflection characteristics. The archwires were subjected to bending at a constant temperature of 37°C and deflections of 2 and 4 mm. Analysis of variance showed that thermal NiTi wires exerted significantly lower working forces than superelastic wires of the same size in all experimental tests (P < 0.05). Wire size had a significant effect on the forces produced: with an increase in archwire dimension, the released strength increased for both thermal and superelastic wires. Superelastic wires showed, at a deflection of 2 mm, narrow and steep hysteresis curves in comparison with the corresponding thermal wires, which presented a wide interval between loading and unloading forces. During unloading at 4 mm of deflection, all wires showed curves with a wider plateau when compared with 2 mm deflection. Such a difference for the superelastic wires was caused by the martensite stress induced at higher deformation levels. A comprehensive understanding of mechanical characteristics of orthodontic wires is essential and selection should be undertaken in accordance with the behaviour of the different wires. It is also necessary to take into account the biomechanics used. In low-friction mechanics, thermal NiTi wires are to be preferred to superelastic wires, during the alignment phase due to their lower working forces. In conventional straightwire mechanics, a low force archwire would be unable to overcome the resistance to sliding.

Airway compartments volume and oxygen saturation changes after rapid maxillary expansion: A longitudinal correlation study

OBJECTIVE To evaluate changes in airway volumes and respiratory performance in patients undergoing rapid maxillary expansion and determine whether any correlations exist between the morphological and respiratory functional modifications induced by rapid maxillary expansion and pretreatment airway stenosis. MATERIALS AND METHODS Fifteen patients (11 females and 4 males; mean age, 7.5 ± 0.3 years) were enrolled in the study. Each patient underwent cone beam computed tomography and polysomnography examination before rapid maxillary expansion and after the removal of the maxillary expander 12 months later. The airway regions were segmented and the volumes were computed. RESULTS The upper, middle, and lower airway volumes were significantly increased 2305 mm(3), 1144 mm(3), and 1915 mm(3), respectively. Similarly, oxygen saturation was increased (+5.3%) and the apnea/hypopnea index was improved (-4.2 events). All the observed modifications were statistically significant (P < .05). Baseline middle and lower airway volume showed a significant negative correlation with the oxygen saturation modification. CONCLUSIONS The results of this study showed that when rapid maxillary expansion is performed in subjects having posterior crossbite, oxygen saturation is improved. The improvement is greater in subjects having more reduced middle and lower airway volumes.

Influence of bracket-slot design on the forces released by superelastic nickel-titanium alignment wires in different deflection configurations.

OBJECTIVE To evaluate how different bracket-slot design characteristics affect the forces released by superelastic nickel-titanium (NiTi) alignment wires at different amounts of wire deflection. MATERIALS AND METHODS A three-bracket bending and a classic-three point bending testing apparatus were used to investigate the load-deflection properties of one superelastic 0.014-inch NiTi alignment wire in different experimental conditions. The selected NiTi archwire was tested in association with three bracket systems: (1) conventional twin brackets with a 0.018-inch slot, (2) a self-ligating bracket with a 0.018-inch slot, and (3) a self-ligating bracket with a 0.022-inch slot. Wire specimens were deflected at 2 mm and 4 mm. RESULTS Use of a 0.018-inch slot bracket system, in comparison with use of a 0.022-inch system, increases the force exerted by the superelastic NiTi wires at a 2-mm deflection. Use of a self-ligating bracket system increases the force released by NiTi wires in comparison with the conventional ligated bracket system. NiTi wires deflected to a different maximum deflection (2 mm and 4 mm) release different forces at the same unloading data point (1.5 mm). CONCLUSION Bracket design, type of experimental test, and amount of wire deflection significantly affected the amount of forces released by superelastic NiTi wires (P<.05). This phenomenon offers clinicians the possibility to manipulate the wires load during alignment.

In vitro evaluation of resistance to sliding in self- ligating and conventional bracket systems during dental alignment

Objective To investigate the resistance to sliding (RS) in self-ligating and conventional ligation bracket systems at 5 different second-order bracket angulations by using low-stiffness alignment wires in a 3-bracket experimental model and to verify the performance of the main RS components in both systems when these wires are used. Methods Interactive self-ligating brackets with closed and open slides were used for the self-ligating (SL) and conventional ligation (CL) groups, respectively; elastomeric ligatures (1 mm inner diameter) were used in the latter system. The alignment wire used was 0.014 inch heat-activated NiTi (austenitic finish temperature set at 36℃ by the manufacturer). A custom-made testing machine was used to measure frictional resistance. Tests were repeated 5 times at every angulation simulated. All data were analyzed statistically. Results The RS increased significantly with increasing angulation in both SL and CL groups (p < 0.0001). However, the RS values were significantly higher at every angulation (p < 0.0001) in the CL group. Conclusions Despite the relevance of the binding phenomenon, ligation forces predominantly affect the RS when low-stiffness alignment wires are used.

Low-dose protocol of the spiral CT in orthodontics: comparative evaluation of entrance skin dose with traditional X-ray techniques

BackgroundThe aim of this study was to evaluate the amount of radiation doses absorbed by soft tissues (entrance skin dose) with a low-dose spiral computed tomography (CT) protocol compared to conventional X-ray techniques commonly used in orthodontics.MethodsThe amount of skin dose has been evaluated using a tissue-equivalent head-neck radiotherapy humanoid phantom with thermoluminescent dosimeters placed at the level of eye lens, parotid glands, and thyroid glands. CT images have been taken using a Sensation 16 Siemens CT scan and a low-dose protocol (15 mAs, 1 pitch, 2.5 mGy (CTDIvol), 80 kV, 1-mm slice thickness).ResultsThe difference in image quality between traditional X-ray techniques and low-dose spiral CT was statistically significant (P < 0.05). The difference in mean absorbed dose instead was not statistically significant.ConclusionsOur protocol allows a more accurate orthodontic diagnosis without an increase of radiological risk for the patients in comparison to traditional X-ray techniques.

Analysis of the characteristics of slot design affecting resistance to sliding during active archwire configurations

BackgroundDuring orthodontic treatment, a low resistance to slide (RS) is desirable when sliding mechanics are used. Many studies showed that several variables affect the RS at the bracket-wire interface; among these, the design of the bracket slot has not been deeply investigated yet. This study aimed to clarify the effect of different slot designs on the RS expressed by five types of low-friction brackets in vertical and horizontal active configurations of the wire.MethodsFive low-friction brackets (Damon SL II, Ormco, Orange, CA, USA; In-Ovation, GAC International, Bohemia, NY, USA; Quick, Forestadent, Pforzheim, Germany; Time 2, AO, Sheboygan, WI, USA; Synergy, RMO, Denver, CO, USA) coupled with an 0.014-in NiTi thermal wire (Therma-Lite, AO) were tested in two three-bracket experimental models simulating vertical and horizontal bracket displacements. A custom-made machine was used to measure frictional resistance with tests repeated on ten occasions for each bracket-wire combination. Design characteristics such as the mesio-distal slot width, slot depth, and presence of chamfered edges at the extremities of the slot were evaluated on SEM images (SUPRA, Carl Zeiss, Oberkochen, Germany) and analyzed in relation to the data of RS recorded.ResultsTime 2 was found to show the higher frictional forces (1.50 and 1.35 N) in both experimental models (p < 0.05), while Quick and Synergy brackets showed the lower frictional values in the vertical (0.66 N) and in the horizontal (0.68 N) bracket displacements, respectively. With vertically displaced brackets, the increased mesio-distal slot width and the presence of clear angle at mesial and distal slot edges increase the values of RS. With brackets horizontally displaced, the RS expressed by the wire is influenced simultaneously by the depth of the slot, the mesio-distal slot width, and the presence of clear angle at the extremities of the slot base, the clip, or the slide.ConclusionIn order to select the proper low-friction bracket system, clinicians should consider specific characteristics of slot design apart from the wire engaging method.