| ObjectiveCBCT measurement before implanting surgery has become a routine preoperative method. For reducing operating complications of dental implanting in posterior zone of upper jaw, by measuring the length of the implant on CBCT image and actual length of the implant, the distance between the alveolar crest and the bottom of the maxillary sinus (sinus-ridge length) was calculated, therefore to find a proper measurement for clinical use.MethodsFrom 2009 July to 2011 March,21 patients with CBCT examination, who met the shooting conditions, were chosen from 88 patients accepted dental implant operation in posterior zone of upper jaw in the Department of Oral Implantology, General Hospital of Chinese People's Armed Police Forces. A unified standard of CBCT examination was taken before and after surgery. The data were saved as DICOM format. By using NNTViewer software, the lengths of the upper left central incisor before and after operation were compared to verify the error of measurement conditions firstly. Then the total length of the implant (the length of the implant with healing cap fully screwed in) was measured again, the value was compared with the total length of the actual implant to get the rate of magnification. Eventually to get the right length of sinus-ridge distance. All data were analyzed using statistical package SPSS17.0. Measurement data expressed as "mean±standard deviation". Results21 patients (13 males, 8 females) aged 58.8±8.8 years (36-76 years old) were included in this study. Distribution of missing teeth in upper jaw: first premolar in 2 cases (9.5%), second premolar 3 (14.3%), first molar 11 cases (52.8%), the second molar in 5 cases (23.8%).1. Three maxillofacial surgeons took part in the measurement according to the same program and standards before and after surgery for 21 patients. The measurements were repeated 2 weeks later. The results were independent sample test. There was no significant difference among the groups. (surgeon1:t=-0.982, P=0.338>0.05; surgeon2:t=-1.506,P=0.148>0.05; surgeon3:t=-0.081,P=0.936>0.05).2. Comparison between the actual length of the implant and the results of CBCT image measurement: the total length of the actual implant, the total length of the implant on CBCT images after surgery, the sinus-ridge height, the angle of the implant axis were measured. The mean values were calculated with student's test. It was found that CBCT value was greater than the actual length of the implant. The difference was significant(t=-15.123, P=0.000)。3. Sinus-ridge height measurement: In the posterior zone of upper jaw, the implant axis angle ranged between 98.5o and 121.3o with an average of 109.99o±8.18o. The magnification rate was within 8.71%±2.65%.Conclusions1. The three-dimensional anatomical structure of posterior zone of upper jaw could be directly showed by CBCT. The individual differences could be neglected.2. In the experiment, the amplification error of CBCT aroused mainly from the angle of posterior zone of upper jaw and the volume effect during image processing.3. It was found in the study that if the tilt angle of alveolar crest of posterior zone of upper jaw was measured before implant surgery, one can clearly calculate the actual height of alveolar bone, and then select the appropriate implant and reduce the risk of implant wear sinus. |
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