Standardized and individualized vertical bitewing radiographs for a digital x-­‐ray system Det helsevitenskapelige fakultet Institutt for Klinisk Odontologi Content

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  Standardized and individualized vertical bitewing radiographs for a digital x-­‐ray system Det helsevitenskapelige fakultet Institutt for Klinisk Odontologi Content
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    "#$%&' ()&$*$ +%#,-#'-*.&- #,- *,-*/*-0#1*.&- /&'%*2#1 3*%&4*,5 '#-*65'#7)$ 86' # -*5*%#1 9:'#; $;$%&< +#'# =,&%%& >&,'*?$&,   @#<*11# A&-&'$&,   +*/ +%&88&,#??   B1*.#3&%) ()6,   +07&'/*$6'$C >#,$:A&%&' "D11&' E#7#% F*<2)#*2)#,# G61$%#- U NIVERSITETET I T ROMSØ   Det helsevitenskapelige fakultet Institutt for Klinisk Odontologi  " @6,%&,% 1   Abstract  ############################################################################################################################### $   2   Introduction  ######################################################################################################################## $   3   Background  ######################################################################################################################### %   3.1   Periodontal disease and infrabony lesions  ################################################################### %   3.2   Vertical bitewing versus apical radiographs  ################################################################ &   4   Materials and methods  ######################################################################################################## &   4.1   Modifying the holders  ################################################################################################## &   4.2   Taking radiographs with individualized and standardized film holders  ##################### "$   4.3   Measurements of distances and calculating angular errors  ######################################## "'   5   Results  ############################################################################################################################## "(   5.1   Impression materials  ################################################################################################## "(   5.2   Inter-examiner reliability of measurements  ############################################################### "&   5.3   Calculations of angles  ################################################################################################ ")   6   Discussion  ######################################################################################################################### $$   6.1   Main findings, short presentation of results  ############################################################### $$   6.2   Errors and solutions  ################################################################################################### $$   6.3   Previous work   ############################################################################################################ $%   6.4   Subtraction radiography  ############################################################################################# $&   6.5   Clinical relevance  ###################################################################################################### $*   6.6   Future developments  ################################################################################################## $)   7   Conclusion  ######################################################################################################################## $+   8   Acknowledgements  ########################################################################################################### $+   9 References  ####################################################################################################################### ',   Appendix  ################################################################################################################################# '$    $ 1   Abstract Intraoral radiographs are important tools for diagnosing, monitoring and evaluating the treatment of infrabony lesions. However, different beam angulations between exposures may give a wrong interpretation when evaluating them. A technique that is useful for monitoring bone loss and regeneration is the use of subtraction radiography. This technique is also very sensitive for changes in projection geometry, thus highly standardized radiographs are required. Previous attempts have been made to standardize and individualize vertical bitewing holders in conventional radiographs by Duckworth et al. (1983). The aim of the present study was to develop a similar system for digital radiographs that can be used on a routine basis with minimal effort in the clinic in the case of infrabony and furcational lesions. The radiographs were also tested for the subtraction technique. For this study, vertical bitewings with an aiming device were employed. Wire markers were incorporated into the holders to enable measurements of angular variations and an occlusal index was used for individualization. The radiographs were taken on phantom heads. In total, 2 sets of measurements on 36 exposures were compared. Radiographs with a difference in  projection geometry within 2 degrees were found to be acceptable for using the subtraction technique. 58% of the comparisons lie within this limit, both horizontally and vertically. It was concluded that by knowing which distances correspond to which degrees, the technique can easily be used in a clinical setting. 2   Introduction Periodontal disease is a common condition characterized by loss of the supportive apparatus of teeth including the alveolar bone (Armitage 2000). In more advanced forms a common feature is the presence of infrabony lesions (Papapanou and Tonetti 2000). These lesions have been described as angular or vertical bone loss. They seem to increase the risk of progression of the disease if appropriate treatment is not given (Papapanou and Wennström 1991). Intraoral radiographs are very important tools in diagnosing, monitoring and evaluating the treatment of infrabony lesions (Jeffcoat et  ' al. 2000). Highly standardized intraoral radiographs are required for documentation of treatment results of advanced periodontitis, including bone gain in infrabony lesions. Sources of error when comparing consecutive radiographs include projection geometry, distortion of films and contrast/brightness due to varying exposures to the x-ray source (Hausmann et al. 1991). One challenge in utilizing intraoral radiographs is that the central ray angulation differs slightly from each projection, and may give a wrong interpretation when evaluating them (Hausmann et al. 1989). When taking intraoral images, there will always be some discrepancy in the angle and distance  between the primary image and the follow-up. This is inevitable unless one has something to aid in the taking of the radiograph, ensuring similar projection angles on the primary and the follow up pictures. Furthermore, understanding the difficulty of attaining this similarity, it is wise to have a tool for calculating any discrepancy and taking this into account when evaluating the difference between two exposures taken at different times. Achieving such a system will make it possible to monitor bone regeneration after periodontal treatment, and also follow the progression of an ongoing disease, comparing intraoral radiographs taken before and after treatment. A technique for monitoring bone loss and regeneration is subtraction radiography (Gröndahl et al. 1983, Kulczyk et al. 2006). The technique was introduced by Gröndahl in 1983 and has been shown to be more sensitive to detect smaller radiographic changes on serial radiographs than conventional analysis, but it is very sensitive to changes in projection geometry (Hausmann et al. 1991). Studies have shown that the level of standardization of the projection geometry greatly influences the performance of the subtraction radiography (Schulz et al. 1991, Hausmann et al. 1985). In bitewing images, the beam is oriented at right angles to the long axis of the teeth, compared to periapicals in the same area, thus providing less distortion. With  periapicals it is often difficult to attain the same 90-degree angulation because of the  palate and the floor of the mouth hindering parallel placement of the film with the teeth (Hausmann et al. 1989, Polson and Reed 1984). One can cover a greater area in the apical direction with a vertical bitewing compared to a horizontal, thus capturing the full depth of a potential infrabony lesion. Based on this knowledge vertical  bitewings were used in this study. Previously, attempts have been made, in conventional radiography, to reduce the problem to vertical and horizontal angles  between subsequent exposures by using vertical bitewing films which avoid film distortion, aluminium or copper step wedges for brightness/contrast correction, and  % individualization of the film holder with resin or silicon tooth impressions while taking the image (Duckworth et al. 1983). Attempts have also been made for the direct technique in the digital system (Muratore et al. 2001). The aim of the present study was to develop a similar system for digital intraoral radiographs that can be used on a routine basis with minimal effort in the clinic in cases of infrabony and furcational lesions, and also to decide a threshold for angular variation in projection geometry in order to use the subtraction technique. This was done by adapting and modifying the technique developed by Duckworth et al. (1983) for an indirect digital radiographic system, using vertical bitewing film holders with alignment rings. The film holders were individualized in addition to making markers on the holders so as to  be able to calculate any discrepancy. By taking several images with the same holders one could then check the reproducibility of the holders, as well as calculate the difference in beam angulation between the primary image and the follow-ups. 3   Background 3.1   Periodontal disease and infrabony lesions Periodontal diseases include a range of pathological conditions from mild  periodontitis to severe periodontitis. Gingivitis is always the precursor, but does not necessarily lead to periodontitis. Today we cannot distinguish a potentially  progressing form of gingivitis from a stable form (Kesic et al. 2010). It is therefore of utmost importance to discover signs of destructive periodontal disease at an early stage, or to predict the risk for further destruction after treatment. Both gingivitis and  periodontitis are graded from mild to severe according to the severity of the condition (Amercian Academy of Periodontology 1999). The etiological factors of periodontal disease are complex, but there is broad agreement of bacteria within the biofilm  playing an important role in the development of periodontitis (Kesic et al. 2010). Even though the etiology is complex, the aim of treatment is mechanic removal of  biofilm and calculus to both prevent and treat the disease. Periodontal pockets are usually characterized by probing depths of at least 4 mm and loss of clinical  periodontal attachment. If the bottom of the pocket is located apically to the alveolar
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