radiographic evaluation of bone formation and density changes after mandibular third molar extraction: a 6 month follow up

background: there is a controversy about exact time of bone healing. the aim of this study was evaluation of bone formation and change of density after mandibular third molar extraction.     methods: radiographs were taken from 16 empty tooth sockets immediately after extraction of mandibular third molars and 2, 4 and 6 months later under similar condition. the radiographs were digitized and the density numbers of pixels were calculated. then, socket and neighbor regions were compared using photoshop software. three expert observers evaluated and compared the radiographs by the longitudinal radiographic assessment (lra) method. paired t-test and mcnemar test were used to analyze the data and investigate the inter-observer reliability, respectively. results: analysis of the quantitative digital subtraction radiography (qdsr) data indicated that the difference between the digital numbers of interest points and reference points has been decreased during the months 2, 4 and 6 but the difference between the month 4 and 6 was not significant. the alternative method indicated that the mean digital numbers in the socket within 0and 2 months period was less than 128 and within 4 and 6 months was more than 128. in evaluation of lra method, lamina dura started to change gradually in month 2 and it might disappear completely after 6 months. conclusion: both qdsr and lra methods can be used in evaluation of the rate of bone formation in the tooth socket but the former is more precise.