[Comparison of shear bond strength of orthodontic brackets bonded with Core Max II and Transbond XT in fluorosed teeth and evaluation of enamel damage after debonding]

Orthodontic bracket bonding may encounter difficulties in fluorosed teeth. The aims of this study were to compare the shear bond strength [SBS] of brackets bonded to fluorosed teeth with Core Max II and Transbond XT and to assess the enamel damage after debonding. In this in-vitro study, 60 fluorosed [TFI=4 and 5] and non-fluorosed teeth were divided into two subgroups. The standard edgewise metallic brackets were bonded to the teeth with Transbond XT in the first and third groups, and with Core Max II in the remaining groups. After bonding, the SBS of the brackets was tested with a universal testing machine. The obtained data were analyzed by two-way ANOVA, post-hoc [LSD], Kruskal-Wallis, Wilcoxon, and paired samples tests. Fluorosis significantly reduced SBS [P =0.041]. Core Max II significantly increased SBS [P =0.040]. Teeth in group 4 [fluorosis and Transbond XT] had the lowest SBS [13.44 +/- 1.69 MPa]; group 2 [fluorosis and Core Max II] showed the highest enamel damage. Core Max II is a good adhesive for orthodontic bracket bonding in fluorosed teeth but conservative debonding methods should be necessarily applied to decrease enamel damage

[Prediction of the mesiodistal size of unerupted canines and premolars in an Iranian population in Shiraz in comparison to Moyers' table]

The determination of the tooth size-arch size relationship [space analysis] is an important factor for diagnosis and treatment planning in the mixed dentition. It is essential to use this analysis before eruption of the canines, first and second premolars. This study produced linear regression equations for an Iranian population. Study models of 276 subjects [138 males and 138 females] were selected from pretreatment patients' records of Orthodontic Department of Dental School and private offices in Shiraz. The greatest mesiodistal diameters of all teeth on each model were obtained except the second and third molar by digital caliper with 0.01mm accuracy. Finally, regression equations [Y=a+bx] were formulated to be used clinically for the estimation of mesiodistal width of permanent unerupted canines and premolars. SPSS software and Wilcoxon Signed Ranks test were used to analyze the date. The coefficients of determination [r[2]] of the regressions ranged between 0.17 and 0.47 and were higher for females than males, and also mandible than maxilla. It found significant difference between the prediction of this study and Moyers' prediction. The equations derived in this study were Y=11.71+0.43x and Y=8.22+0.57x for maxilla and mandible respectively. At the other hand, the 85% level was a more accurate determination than the commonly used 75% confidence level likewise. Moyers' prediction tables were found to under-estimate tooth size summation compared with the present investigation

[Effect of premolars extraction on Bolton overall ratio in an Iranian population]

Tooth size discrepancies [Bolton ratio] affect the best possible esthetic and functional results at the end of treatment. The extraction decision is the most critical decision when planning treatment, and the premolars are the most common teeth in this decision. The purpose of this study was to compare the effect of different patterns of premolar extraction on tooth size discrepancy at the end of orthodontic treatments. This cross-sectional study was carried out on 200 study models of the patients [145 females and 55 males] who were selected through available selective sampling method. The greatest mesiodistal width of all teeth were measured except for the second and third molars. The measuring was done by a digital caliper with 0.01mm accuracy. According to calculated Bolton overall ratios, the patients' casts were divided into three groups: NB [Normal Bolton], DB [Decreased Bolton], and IB [Increased Bolton]. This classification was based on the overall Bolton normal values plus or minus one standard deviation. The Bolton overall ratios of each group were measured before and after hypothetical extractions of different four premolars. The data was analyzed using one way ANOVA, and the paired t-test was used for comparing the ratios between males and females. The results showed that there was no significant difference between males and females in Bolton overall ratios. Significant differences were found between overall ratios for different combinations of premolar extraction before and after extractions. The Bolton overall ratios showed to be smaller after premolar extractions in each group. After premolar extractions, some patients in the NB and IB groups were transferred to the DB, and NB group respectively. According to the results of this study four premolars extraction causes a decrease in Bolton overall ratio and in some patients, increased overall ratios could be corrected to normal values after removal of second mandibular premolars

[Evaluation of the precision of panoramic radiography in dimensional measurements and mandibular steepness in relation to lateral cephalomerty]

Lateral cephalornetry is mostly used when cephalometric measurements are made from radiographs. However, because of the superimposed images appearing on the lateral cephalograms, reliable measuring of the individual angles [for example Gonial angle] becomes very difficult. How reliable the cephalometric measurements are when determined from an orthopantomogram is the purpose of this study. In the first stage of this descriptive analytical study, five different measurements [Gonial angle, FMA, Condyle height, Ramus height and Body length of the mandible] were studied on two dry skulls. The same measurements were made on the panoramic images of these dry skulls and then compared with these measurements in lateral cephalometirc radiography. In the second stage of this study, the same measurements were studied on the panoramic and lateral cephalornetry of 101 subjects [52 females and 49 males, mean age of 16]. Then the measurements were compared in different growth patterns. For data analysis, the pearson correlation coefficient was used. In comparison of actual measurements obtained from dry skulls and panoramic radiographic measurements, it was revealed that all the five measurements [except length of the body of the mandible] in panoramic radiographs were close to actual degrees in dry skulls. Correlation tests showed the hightest correlation between panoramic and cephalometric radiographs in gonial angle [r=0.89, P<0.001] whereas the least correlation was seen in the length of mandibular body. In different growth patterns, it was seen that gonial angle and ramus height showed the highest correlation between the two radiographs. The ability to determine growth direction from the orthopantomogram will be useful because majority of dentists request an OPG for patients during routine dental examination

[ new index [micro angle] for evaluating sagittal jaw relationship in comparison with beta angle; a cephalometric study]

In Orthodontic diagnosis and treatment planning one of the most important issue is an accurate anteroposterior measurement of jaw relationship. The most commonly used angular and linear measurements that have been proposed, such as ANB angle and Wit's appraisal can be inaccurate and misleading due to their dependence on various factors. This study was aimed at establishing a new cephalometric measurement, named the micro angle, to assess the sagittal jaw relationship with accuracy and reproducibility. The micro angle uses 3 skeletal landmarks, point A, point B and a perpendicular line from point A to the mandibular plan. One hundred and fifteen pretreatment cephalometric radiographs of orthodontic patients [mean age 16 +/- 2 years] were selected on the basic of inclusion criteria according to their skeletal and profile patterns. The patients compromised of 30 class I, 45 class II and 40 class III skeletal relationships and profile pattern, the mean and standard deviation for the new angel [micro] and the previous reported angle [beta] were evaluated. One way analysis of variance [ANOVA] and the Newman-Keuls test were used for data analysis as well as, dermination of the new angle's specifity and sensitivity comparing with beta angle. The results obtained showed that a patient with a micro angle between 16.1 degree and 23.9 degree can be considered to have a class I skeletal pattern. A more acute micro angle is an indication of a class II skeletal pattern and a more obtuse micro angle indicates a class III skeletal pattern. The new angle [micro angle] has an acceptable specificity and sensitivity in determining the anteroposterior relation of jaws and thus can be used for assessing the type and severity of jaw discrepancies, besides the other diagnostic parameters

[Use of panoramic radiographs in localization of maxillary impacted canines]

In spite of low prevalence of maxillary canine impaction in population [1%-3%], its occurrence in orthodontic patients is nearly high sometimes reaching 23.5%. The exact determination of impacted canine location is of high importance for better access as well as correct force application. The purpose of this study was to determine the impacted maxillary canines location by orthopantomograph using Chaushu's method in comparison with their real location which were determined by surgical exposure of the teeth. Sixty eight panoramic radiographs of patients with either unilateral or bilateral maxillary canine impaction were evaluated using Chaushu's method. The available selected patients [14 males, 54 females] were treated orthodontically by force eruption of canines after surgical exposure. The mean age of the patients was 17 years. The largest mesiodistal width of 82 impacted canines as well as central incisors of the same side and also the contralateral side erupted canines were measured and evaluated using Chanchu's technique for determining canineincisor and canine-canine indexes [CII, CCI]. Also these ratios were evaluated and compared for different horizontal and vertical positions of impacted canines. The mean of CII for palatally and bucally impacted canines were found to be 1.17 and 1.07 respectively which was statistically significant. Considering their vertical positions, it was revealed that CII was valid only in coronally positioned situation. In case of unilateral impaction, the CCI did not show to be statistically significant for buccal or palatal side. Evaluating the relation of impacted canine crown to the lateral incisor's root, it was found that the palatally impacted canines were located more mesially than bucally impacted ones. Although panoramic radiography could show the buccal or palatal position of the impacted canines in coronally impaction situations, but due to the effect of their vertical position and also maxillary apical form on the radiographic magnification, use of other complementary radiographs for exact determination of impacted canine location seems to be necessary

Tooth size in cleft lip and or palate patients in comparison with normal individuals in Shiraz

The most common major defect of the lip and palate is clefting. Clefting occurs due to failure of fusion between embryologic structures. Tooth size abnormalities are common in these patients. This study was performed to determine the tooth size in cleft lip and or patients and compare with normal individual. This study was carried out on 51 pretreatment orthodontic records of the cleft lip and or palate patients and compared with 276 normal individuals. These subjects were in acceptable age for determination of the mesiodistal width of the teeth. The greatest mesiodistal width of all permanent teeth on each model was obtained except the second and third molars. The measuring was done by digital calliper with 0.01 mm accuracy. The collected data were analyzed by SPSS software and t. test. This study showed that there was no asymmetry in tooth size between cleft and normal sides of the maxillary arch. The upper teeth in cleft patients were smaller than the upper teeth in normal patients and there was a significant difference. The lateral incisor and first premolar in females and the central incisor, second premolar and first molar in males were smaller in the cleft patients than normal groups in the mandibular arch. We concluded that: 1] tooth size of the maxillary arch in cleft patients was smaller than non-cleft subjects. 2] There was no significant difference between cleft and non-cleft sides in tooth size. 3] Tooth size in mandibular arch of cleft patients was affected less than maxillary arch