orthodontic anchorage is a basic procedure necessary for a successful treatment . for 
 this reason ,
clinicians seek to better understand various orthodontic devices , such as 
 headgear , transpalatal arch , lingual arch , and nance 's button .
these devices allow a 
 certain degree of movement of the anchorage unit and are dependent , to varying degrees , 
 on patient compliance . in severe cases or in cases of non - cooperative patients , 
 treatment could be compromised .
recently , skeletal anchorage has increased in popularity 
 due to the benefit of direct transfer of the point of anchorage from the teeth to the 
 skeleton . however , since 
 these mini - implants have been used in orthodontics , a small displacement during 
 treatment has been detected .
the mini - implant displacement allows contact between the 
 screw and the dental root , causing damage to the root or the periodontal ligament , 
 potentially leading to mobility or loss of the mini - implant .
unfortunately , there is not much information available on the displacement or adverse 
 effects of mini - implants .
recently , hsieh , et al . ( 2008 ) found that even endosseous titanium implants may not 
 necessarily serve as a rigid orthodontic anchorage at all force levels .
( 2004 ) investigated cephalometric 
 tracings and found a noteworthy extrusion and tipping forward of mini - implants after 
 en - masse retraction of anterior teeth . recently
, tomographic studies have evaluated the 
 position of mini - implants in both jaws , though without relating them to longitudinal 
 control . to the best of our knowledge ,
general dentistry and orthodontics constantly use radiographs with the main purpose of 
 assessing the validity of treatment methods . zanda ( 2007 ) described a new film holder for occlusal film that showed 
 effective reproducibility of occlusal radiographic images in dry skulls ( figure 1 ) , making it possible to take an occlusal 
 radiographic sequence at different times .
( 2005 ) used dry human skulls to analyze the reliability 
 in determining tooth position in posterior - anterior films .
using markers inserted in the 
 bands of molars and premolars from hyrax expanders allow identifying each one in each 
 side on posterior - anterior films .
occlusal x - ray film holder and skull positioned for standardized occlusal 
 radiograph the purpose of the present study was to evaluate the reliability and accuracy of a 
 radiographic analysis method for identifying the location of mini - implants inserted in 
 the posterior region of the maxilla in dry human skulls .
three human skulls were obtained from the anatomy department of the dental school of the 
 university center of maranho , brazil .
all skulls had preserved maxilla and mandible and 
 sufficient teeth on the posterior area of the maxilla for the successful placement of 
 mini - implants . the cortical bone condition and
the maxillary interadicular space were 
 evaluated using radiographic images between the second premolars and the first molars . 
 according to the same technical criteria used for patients ,
six self - drilling 
 mini - implants ( 1.6x1x7 mm ; osas , dewimed , tuttlingen , germany ) were placed between the 
 second premolars and the first molars at a 45 angle relative to the tooth 's long 
 axis .
once the study began , the main purpose was to test the reliability of different 
 operators for the proposed method in this research .
therefore , clinical operators with 
 various levels of professional experience were invited to take the occlusal radiographs . 

three operators were selected : an orthodontist , an implantodontist and an undergraduate 
 dental student .
each operator performed three occlusal radiographs taken at three 
 intervals of 15 days in each of the three skulls .
the set of three radiographs of each 
 skull was identified externally according to an identification number for the skull , the 
 operator and the time .
a total of 27 randomized occlusal radiographs were obtained using insight io-41 film 
 ( size 5.7 cm x 7.6 cm ; kodak ) with 1.5 s exposure time at 10 ma and 70 kv .
the occlusal 
 radiographs were taken with a correct alignment between the cylinder localizer from the 
 x - ray machine and the ring from the occlusal radiographic position self - drilling film . 

each operator took the occlusal radiograph for each of the skulls with the occlusal 
 films inserted in the zanda ( 2007 ) 
 film holder and fit the film in more number of posterior teeth of the maxilla .
all radiographs and a ruler with same lateral size were digitized using a scanner 
 ( be@rpaw 2400ta plus , scanner a4 ) ( figure 2 ) .
the 
 radiographs were measured using macbiophotonics imagej software originally applied in 
 biologic researches for microscopic image capture .
after the mini - implant positions , the points were defined and 
 measured using a cartesian coordinate system ( figure 
 3 ) .
the cartesian system was composed by the following measures : occlusal radiographs with mini - implants placed occlusal radiographs and measurements line a : a straight line traced over the maximum number point of the midpalatal suture ;   line b : a line perpendicular to the intersection of line a at the virtual point 
 representative of the incisive foramen ; distance xd : for the mini - implant on the right side , the minimum distance from the head 
 of the mini - implant to line a ; distance yd : for the mini - implant on the right side , the minimum distance from the head 
 of the mini - implant to line b ; distance x ' d : for the mini - implant on the right side , the minimum distance from the tip 
 of the mini - implant to line a ; distance y ' d : for the mini - implant on the right side , the minimum distance from the tip 
 of the mini - implant to line b ; distance xe : for the mini - implant on the left side , the minimum distance from the head 
 of the mini - implant to line a ; distance ye : for the mini - implant on the left side , the minimum distance from the head 
 of the mini - implant to line b ; distance x ' e : for the mini - implant on the left side , the minimum distance from the tip 
 of the mini - implant to line a ; distance y ' e : for the mini - implant on the left side , the minimum distance from the tip 
 of the mini - implant to line b. the means and standard deviations of the distances on each side were calculated 
 considering the operator and the skull ( table 
 1 ) .
the intra - operator reliability for the measurements was estimated using the 
 interclass correlation coefficient ( icc ) .
analysis of variance ( anova ) was used to test 
 the effect of different image times and different operators . mean and standard deviation ( sd ) for each measurement and operator ( op )
statistical analysis indicated a significantly high , positive correlation between the 
 maxillary occlusal radiography taken by the different operators ( table 2 ) .
intra - operator reliability for mini - implant measurements expressed as interclass 
 correlation coefficient ( icc ) ( n=3 ) the icc test verified the measurements of each variable made by each operator on each 
 skull that localize the head and the tip of the mini - implant ( x , y , x ' and y ' ) . 

intra - operator correlations were above 0.87 for all the operators and each of the skulls 
 ( table 2 ) .
this value seems to indicate a 
 similar variation , indicating an excellent reproducibility through a positive and high 
 correlation . in terms of the effect of time
, the operator and its interactions showed no 
 statistically significant differences in any of the variables analyzed by anova ( table 3 ) .
the goal of the present study was to test the reliability and accuracy of the 
 radiographic occlusal position developed by zanda ( 2007 ) used as a device to verify the stability of 
 posteroanteriorly and lateromedially positioned orthodontic mini - implants .
the 
 hypothesis was that this method can be used as a replicate for maxillary occlusal 
 radiographs for location of mini - implant placement in the posterior region of the 
 maxilla . since the introduction of the cephalostat as a standard for taking cephalometric 
 radiographs ,
the cephalostat has been traditionally used to determine the direction and 
 amount of skeletal and dental changes .
several devices have also been developed and 
 improved with longitudinal research in orthodontic patients .
some studies have reported 
 that film holders and markers of anatomic structures contribute to the improvement in 
 radiographic images . also creating more information about the position of structures 
 during orthodontic treatments .
based on these presumptions , our study 
 used a model of an occlusal x - ray film holder to obtain the most uniform radiographic 
 series . additionally , the selected anatomic structures used as references to determinate 
 the measurements were chosen because they are known to be stable during treatment .
this study showed that the use of the occlusal x - ray film holder is sufficiently 
 accurate for investigations of mini - implant stability and an alternative to 
 cephalometric analyses for determinate mini - implant displacement .
furthermore , the 
 numerical information on the displacement of the mini - implants can be correlated with 
 the amount of dental movement determined by the retraction .
( 2004 ) reported that mini - implants do 
 not remain stable at forces higher than 400 g. these findings suggest that studies are 
 necessary to quantify mini - implant displacement caused by treatment , especially by means 
 of the innumerable variables related to the use of this transitional anchorage 
 device .
our findings show that future clinical studies will be able to evaluate the direction of 
 the displacement of the mini - implants .
also , different types of this skeletal anchorage 
 device could be compared considering the thickness , the design and the length with the 
 suffered displacement .
computed tomography ( ct ) scans are not routinely used to improve the quality of 
 craniofacial measurements in orthodontics .
the present data prove that the method 
 presented here is valid and can be performed at a much lower cost compared to ct .
this 
 means that clinicians and researchers can better understand this innovative modality of 
 anchorage using an easily attainable and low - cost material .
another important benefit of 
 this method is a lower exposure of patients to radiation to detect the stability of the 
 mini - implants .
we believe that clinical studies on this topic are very important for 
 further acknowledgment of transitory anchorage device .
however , there is a great deal of 
 responsibility in deciding to prescribe radiographs , especially ct scans ; it is 
 complicated and depends on the effects on the orthodontic therapy management .
human skulls were used for safety reasons due to the potential exposure of patients to 
 ionizing radiation .
the adopted model simulates similar conditions used for patients , 
 with a reduced x - ray exposure time . 

additionally , the anatomic structures used to obtain all measurement tracings are easily 
 identified , as well as their presence in the same plane and height as the indicated 
 inserted mini - implant in the posterior maxillary area .
, we believe that the selected areas are not influenced by 
 soft tissue thickness and do not compromise the visualization of the anatomic structures 
 used and the installed mini - implants . the number of dry skulls used in this type of study has revealed variations in other 
 studies .
the number of 
 skulls used in the present study was sufficient to verify the influence of individual 
 anatomic variations in the statistical analysis .
it should be noted that we opted for a 
 research design that did not evaluate the anatomic aspects in relation to accuracy and 
 reliability .
the aim of the 
 study was to analyze operator 's reproducibility on separate occasions .
the intraclass 
 correlation proved that , with the skull change and , consequently , the occurrence of 
 anatomic variations , a high and significant correlation was found among the different 
 measurements of each skull .
the agreement in the operators ' measurements ( table 3 ) shows that this method is useful for research and for 
 clinical evaluation . for clinical use
, it is indicated to attach the film to the film 
 holder ( figure 1 ) and after adaption inside of the 
 mouth , ask for the patient to occlude . only with the dental occlusion is possible to 
 achieve stability to use this intraoral radiographic technique .
zanda ( 2007 ) found variations in the 
 reliability of measurements far from the occlusal plane , whereas the present study 
 showed no statistically significant differences .
in the present study , this 
 reproducibility was found because the mini - implants and the anatomic structures used the 
 same plane into the maxilla , both are at the same tall of palatal plane .
variables 
 describing the position of the head and the tip of the mini - implant were in the same 
 plane .
also , the midpalatal suture was chosen as a reliable reference for the 
 determination of a measurement for each variable .
it should be mentioned that the method 
 presented here only identifies mini - implant localization on the posterior region of the 
 maxilla .
this implies that , in future studies , an additional use for this method in 
 another site of the maxilla or mandible may be the identification of a more reliable 
 anatomic structure for each studied region .
the results of the present study demonstrate that this radiographic method was highly 
 reproducible among operators and accurate for the identification of measurements . also , 
 no differences were observed based on the time and the operator using this method .
these 
 results support the use of this standardized method for occlusal radiographs for 
 mini - implant identification on the posterior maxilla .
 objectivethe purpose of this study was to evaluate the reliability and accuracy of a 
 radiographic analysis method for the location of mini - implants inserted in the 
 posterior region of the maxilla . 
 material and methodstwo self - drilling mini - implants were installed between the second premolar and the 
 first molar on the right side and left side in three dry skulls . 
 three operators 
 performed three occlusal radiographs , using an occlusal x - ray film holder , at 
 three different times in each of the three skulls . 
 resultsthe interclass correlation coefficient showed a significantly high , positive 
 correlation ( p<0.05 ) , indicating an excellent reliability between operators . 
 
 the analysis of variance showed no significant differences in time and among the 
 operators . 
 conclusionbased of these findings , it may be concluded that this methodology can be used by 
 several operators in longitudinal clinical studies on orthodontic mini - implants at 
 the anterior - posterior and lateral - medial locations or longitudinal 
 displacement . 