Thread shape factor: evaluation of three different orthodontic miniscrews stability.

The thread shape factor (TSF) to evaluate the relationships between geometrical characteristics and mechanical properties of the temporary anchorage devices (TADs) has recently been introduced. This in vitro experimental study evaluated in 30 different tests with three TADs: ORTHOImplant (1.8 mm diameter and 10 mm length; 3M Unitek), Tomas (1.6 mm diameter and 10 mm length; Dentaurum), and Orthoeasy (1.7 mm diameter and 10 mm length; Forestadent). Scanning electron microscopy images were acquired for each TAD to measure the TSF; afterwards, the maximum insertion torque (MIT) was evaluated and thereafter pull-out tests on two differently designed organic bone analogs were carried out using a testing machine with a crosshead speed of 2 mm/minute being applied. One-way analysis of variance with group as factor was performed. Post hoc multiple comparisons Bonferroni test was used. Rank-transformed data were used when asymmetry of data was shown. To assess correlation between characteristics, load, and MIT, Spearman's rank correlation coefficient was used. A P-value of 0.05 was considered statistically significant. Significant direct correlations were found between TSF and depth and both load and MIT. Particularly, a correlation of 0.90 (P < 0.001) was found between depth and MIT for 2.2 mm cortical thickness. The authors conclude that MIT and maximum load values of pull-out test are statistically related to depth of the thread of the screw and to TSF.

Tooth developmental anomalies in severe combined immunodeficiency disease and juvenile myelomonocytic leukemia: common clinical features and treatment outcomes.

AIM: Human Severe Combined Immunodeficiency (SCID) is a prenatal disorder of T lymphocyte development that depends on the expression of numerous genes. Juvenile myelomonocytic leukemia (JMML), previously known as juvenile chronic myeloid leukemia (JCML), is a rare, myelodysplastic/myeloproliferative disease typically presenting in early childhood. CASE REPORTS: Two cases are described of immunodeficiency disorders, both treated with chemotherapeutic drugs (Busulfan plus cyclophosphamide) before bone marrow transplantation. After treatment, these two different cases showed several similar oral lesions: microdontia, root alterations, numerous tooth ageneses, incomplete calcification, enamel hypoplasia, premature apexification and hypodontia. Both subjects underwent dental and orthodontic treatment. The first phase comprised orthopaedic treatment using a removable appliance (Interim-G®) followed by rapid palatal expansion; in the second phase patients underwent tooth extraction and were treated using fixed appliances for 19 and 26 months, respectively (mean 2 years) to obtain final alignment and maximum intercuspation. In the third and final phase, reconstruction of malformed teeth was completed, and implant-supported protheses were applied. CONCLUSION: The difficulties of managing and treating these diseases are discussed, with particular focus on tooth anomalies and malocclusion disorders. Collaboration between dentist and paediatrician in dealing with patients with a variety of oral lesions and tooth anomalies is important in order to prevent any other possible tooth lesions and ensure correct jaw development.

Decontamination of root canals with the gallium-aluminum-arsenide laser: an in vitro study.

OBJECTIVES: In this in vitro study, we investigated the bactericidal effects on root canals of 810-nm diode laser irradiation, alone or combined with sodium hypochlorite and citric acid irrigation. MATERIALS AND METHODS: One hundred sixteen single-rooted human teeth extracted for periodontal reasons were randomly divided into four experimental groups. The canal of each tooth was prepared with a conventional step-back technique and a pure culture of vancomycin-resistant Enterococcus faecalis grown in brain heart infusion broth was used to contaminate the root canal. The specimens were incubated at 37 degrees C for 15 d in a test tube filled with agar, adding fresh bacterial suspension every 48 h, and sent them for microbiological analysis and bacterial count. Subsequently they were divided into four groups: in group A, 29 teeth were irrigated with 2 mL of 10% citric acid solution; in group B, 29 teeth were irrigated with 2 mL 5.25% sodium hypochlorite (NaOCl) solution; in group C, 29 teeth were irradiated with 810-nm laser energy via a 200-microm optic fiber at 2.5 W power in pulsed mode (10 msec on and 10 msec off) for 5 sec; and in group D, 29 teeth were irrigated with NaOCl, irradiated with the laser, then irrigated with citric acid, and irradiated with the laser, followed again by NaOCl irrigation and laser irradiation. All the samples were again sent for microbiological analysis and bacterial count. RESULTS: Group A had a bactericidal effect of 0.041 log mean CFU, that of group B was 3.381 log mean CFU, and that of group C was 1.459 log mean CFU, whereas group D showed the best results, with a bactericidal effect of 7.178 log mean CFU. CONCLUSIONS: The use of NaOCl, citric acid, and diode laser energy together have a synergistic effect, increasing treatment efficacy and leading to significantly better decontamination of the root canal.

Effects of Nd: YAG laser irradiation on the root canal wall dentin of human teeth: a SEM study.

The purpose of this study was to observe the morphological and histological changes on the root canal walls after Nd:YAG laser application. Twenty vital, recently extracted single-rooted human teeth were used for this study. Root canals were cleaned and shaped by a conventional step-back technique--by means of k files up to a 20 k-file type at working length--and subsequently shaped by Ni-Ti root-canal rotary instrumentation up to 30/06 and irrigated with 2.5% hypochlorite solution. Ten teeth (control group) were left unlased, while the other ten teeth were irradiated with Nd:YAG laser by means of a 320 microns fibre inserted in the root canal at 1 mm from the apex with a power of 1.5 Watt and a frequency of 15 pps for five seconds in retraction with rotating movements. The control specimen showed debris and smear layer on the root canal surface obscuring the dentin tubules. The root canal walls irradiated with Nd:YAG laser showed a clear glazed surface, some open dentinal tubules and some surface craters with cracks. Such results confirm that smear layer and debris are removable with Nd:YAG laser, however clearing all root canal walls is still difficult and, if the energy level and duration of application are inadequate, a certain degree of thermal damage and morphological changes in dentin structure are observable.