fatemeh gorjizadeh

The aim of this study was to assess the detection of some hard- and soft-tissue cephalometric landmarks when using a thyroid lead shield.

Two study groups were designed, and each group consisted of 50 cephalograms: the first group was without thyroid shield cephalograms and the second group consisted of cephalograms taken using a lead thyroid shield. An observer blinded about the aim of the study was appointed to identify 12 landmarks on the lateral cephalograms.

Out of 12 of landmarks, 3 landmarks had a significant relationship with the thyroid shield group. Landmarks of cervical point, second and third vertebrae were not detected in 20%, 30%, and 66% of cases, respectively.

Two hard-tissue landmarks (second and third vertebrae) and one soft-tissue landmark (cervical point) were masked by the thyroid shield when preparing a cephalogram.

Application of zirconia in dentistry has increased due to its good properties. Since zirconia is not possible to be etched, evaluation of the other methods of surface treatment is important.
The aim of this study was to evaluate zirconia surfaces treated by different output powers of Er: YAG laser and sandblasting technique by scanning electron microscope (SEM).
15 specimens were prepared of 3Y-TZP ceramic material. After polishing of all the samples, divided into 5 groups; control group, 1.5 W Er: YAG laser irradiated group, 2.5W Er: YAG laser irradiated group, 3.5 W Er: YAG laser irradiated and sandblasted group. Then SEM image of each group were prepared and analyzed.
The SEM images of study groups showed there is no significant difference between control group and laser groups at × 3000, but at the more magnifications (× 15000 and × 60000), with increasing laser power, surface roughness and deformation of crystals increases. SEM of Sandblasted group showed a change in surface texture with the formation of microretentive grooves and deformation of zirconia crystals shape.
By increasing the Er: YAG laser power on zirconia ceramics, the surface roughness increases but not impressive. Application of sandblasting technique on zirconia provides greater surface roughness than Er: YAG laser treatment. 1.5 W (150 mJ) Er: YAG laser radiation has no significant effect on surface morphology of zirconia but 2.5 W (250 mJ) and 3.5 W (350 mJ) outputs, change the surface morphology.

The aim of this study was to evaluate the effect of conventional and high-power light emitting diode (LED) light curing units on shear bond strength (SBS) of metal and ceramic brackets to tooth surface.
Forty sound bovine maxillary central incisors were used for the study. The teeth were divided into four groups (n=10). Teeth surfaces were etched with 37% phosphoric acid for 20 seconds. After applying a uniform layer of adhesive primer on the etched enamel, composite was placed on the base of brackets. The samples were light cured according to the manufacturer’s instructions and thermocycled. The SBS was measured. The failure mode was scored using the adhesive remnant index (ARI).
The mean SBS of samples in groups A (high-power LED, metal bracket), B (high-power LED, ceramic bracket), C (conventional LED, metal bracket) and D (conventional LED, ceramic bracket) was 23.1±3.69, 10.7±2.06, 24.92±6.37 and 10.74±3.18MPa, respectively. The interaction effect of type of LED unit (high-power/conventional) and bracket type on SBS was not statistically significant (P=0.483). In general, type of LED unit did not affect SBS. Type of bracket significantly affected SBS (P The obtained SBS is the same for both bracket types by use of high-power and conventional LED light curing units. Regardless of the type of LED unit, SBS of ceramic brackets was significantly lower than that of metal brackets.

Application of zirconia ceramics has increased. Since the commonly used surface treatment for porcelain, i.e. acid etching is not efficient for zirconia surfaces, evaluation of other surface treatment methods for zirconia is important. The aim of this study was to compare the shear bond strength (SBS) of metal brackets to zirconia treated with different powers of Er:YAG laser, sandblasting and silane.
In this experimental study, five blocks of 3 mol% yttria stabilized tetragonal zirconia ceramics (3Y-TZP-A) were cut into small cubes. After the sintering process, 72 samples were assigned to six groups (n=12). The first group did not receive any surface treatment. The second, third and fourth groups were irradiated with Er:YAG laser with 1.5 W (150 mJ), 2.5 W (250 mJ) and 3 W (300 mJ) powers, respectively in a long pulse mode for 20 seconds. The samples in the fifth group were sandblasted. The sixth group samples were silanized. After bonding of brackets to the samples, they were stored in distilled water, thermocycled and their SBS was measured by a universal testing machine. Mode of failure was assessed by a stereomicroscope.
The SBS of brackets to zirconia in groups one to six was 0.31±0.23, 0.51±0.14, 1.11 ±0.40, 3.32±1.52, 9.5±2.99 and 3.88±2.20 MPa, respectively. ANOVA revealed a significant difference among the six groups. Tamhane’s test showed that the SBS in group five was significantly higher than that in the other groups. Bond failure occurred at the adhesive/zirconia interface in all groups.
Surface treatment of zirconia with sandblasting provided appropriate bond strength of brackets for clinical applications. But, Er:YAG laser and silane did not create sufficient SBS to zirconia surfaces.

It has been proved that, there's craniofacial asymmetry but much of this skeletal asymmetries are clinically ignorable. This asymmetry may exist in teeth size arranged in right and left sides of human mouth too. Orthodontists should pay attention to bilateral tooth asymmetry in treatment planning stage.
This study was conducted to demonstrate whether the difference between size of left and right side teeth is actual.
A total of 200 plaster dental molds were used which were collected from a private practice in Tehran. A caliper with accuracy of 0.01 mm was used for measuring teeth and most teeth were measured twice and the average value was considered as the teeth size. In all cases, the Vernier calipers jaws were moved along the teeth longitudinal axis and the biggest width was measured in the contact point area.
In average 83.16% of left and right teeth in upper jaw and 83.66% of left and right teeth in the lower jaw were not symmetrical and teeth in the upper and lower jaws were completely similar 16.84% and 16.34%, respectively.
The result of the study showed that nearly 83% of teeth in maxilla and mandible are asymmetric in mesiodistal width. Mandibular second molar and canine showed the highest and lowest bilateral asymmetry respectively.

tooth transposition is a rare condition especially in the mandibular arch. Management of this condition is so hard, complicated and unknown for most of the clinicians.
Case report: In this report we describe a case of orthodontic management of a partial mandibular left lateral incisor and canine transposition. We used a modified lingual arch appliance for initial correction of tooth transposition, more detailing was achieved by fix treatment.
Early detection of this anomaly is very important. Providing panoramic radiography to assess the developing dentition during the age of 6 to 8 years is an apropos forethought.

Prediction of the mesio-distal width of the unerupted premolars and canine is an important point to the practitioner. The main goal of this study was to find the relationship of the teeth size to be used when needed in treatments planning. 200 plaster casts including 5600 teeth were measured and studies. A caliper with accuracy of 0.1 mm was used for measuring teeth and most teeth were measured twice and the average value was considered as the teeth size. In all cases, the vernier calipers jaws were moved along the teeth longitudinal axis and the biggest width was measured in the contact point area. Tables of mesiodistal widths of the permanent teeth and some equations were prepared. The measurement difference varied from 0 to 0.04 mm. the average value of difference was 0.016 mm with SD of 0.02 mm. All teeth in male are bigger than those in female and this different is most evident in canine teeth, especially the lower jaw canine teeth. At the end of this study an equation was found which was used to measure the total value of mesiodistal width of canine and premolar teeth of upper and lower jaws in a simple and exact way.

Hemifacial macrosomia (HFM) is the second most common facial congenital anomaly. Deficiency of hard and soft tissue on one side of the face is its obvious clinical finding, which can cause facial asymmetry. Hemifacial microsomia is described in three grades of severity, although grade II has two subgroups (mild and severe). Many anomalies can be misdiagnosed with different grades of Hemifacial microsomia, e.g. Treacher Collins syndrome, traumatic postnatal deformity, Goldenhar syndrome, hemi mandibular elongation, Parry-Romberg syndrome, juvenile rheumatoid arthritis, Nager acrofacial dysostosis syndrome, post axial acrofacial dysostosis, muscle dysfunction, branchio-oto-renal syndrome and Maxillofacial dysostosis. The first step to treating patients with HFM, is an accurate diagnosis. Decision making for treatment planning of patients with HFM, is highly dependent on the severity of the deformity and patients age. In mild grades of the anomaly, functional therapy can improve facial and occlusal symmetry when they are young, but in more severe grades, imposition of orthopedic treatment, may be undesirable and waste of time. Early surgical interventions to encourage the growth in the affected condyle may be helpful in severe cases; however, consultation with the surgeon is advised to determine the patients who need early surgery. Distraction osteogenesis is a controversial treatment modality, which still needs more long-term studies.