| [Objective] To measure the thicknesses of labial bone plates and labial gingiva at maxillary anterior teeth by using Core Bean Computer Tomography (CBCT), and to analyze the changing alveolar heights and widths before and after tooth extraction, and then to investigate the correlation between labial bone plates thickness and labial gingival thickness.[Method] Experiment A:According to a certain inclusion criteria,136 adults with complete dentition and centric occlusion were selected, and based on tooth position and gingival biotype, they were classified into different groups:from the perspective of tooth position, we got central incisor group, lateral incisor group and canine teeth group, each with 136 subjects (a total number of 272 teeth); from the perspective of gingival biotype, we had thin biotype group(52 subjects), average biotype group(48 subjects) and thick biotype group(36 subjects). After the image acquisition by NewTomVG CBCT imaging system, and combined with the scanned image of three-dimensional NNT-Viewer, labial bone plates thickness and labial gingival thickness on sagittal plane were measured respectively at 4mm,6mm and 8mm apical to Cemento-Enamel Junction (CEJ) at maxillary anterior teeth. With the help of SPSS22.0, relevant statistical analyses were conducted and the difference of P<0.05 could be taken to be of statistical significance.Experiment B:According to a certain inclusion criteria,58 adult patients with a missing upper central incisor and centric occlusion were selected, and based on the period of tooth loss, they were classified into 6-month group (Group A, with 21 subjects),6-to-12 months group (Group B, with 17 subjects), and 12-to-24 months group (Group C, with 10 subjects) and 24-to-36 months group (Group C, with 10 subjects). After the image acquisition by NewTomVG CBCT imaging system and combined with the scanned image of three-dimensional NNT-Viewer, taking the Cemento-Enamel Junction (CEJ) of uninjured central incisor as the reference point, alveolar widths of the missing, tooth and the tooth with the same name on the opposite side were measured respectively at 4mm,6mm and 8mm apical to Cemento-Enamel Junction (CEJ), meanwhile, their alveolar heights of buccal and palatal side as well as at the implantation site were also measured respectively. With the help of SPSS22.0, relevant statistical analyses were conducted and the difference of P<0.05 could be taken to be of statistical significance.(Results] 1. Experiment A:1. The differences of labial bone plates thickness at the same measurement point with the same tooth position but with different gingival biotypes were of statistical significance (P<0.01). At 4mm apical to CEJ, the labial bone plates thickness of thin biotype was generally thin, and among them, the bone plates thickness of canine teeth and thin biotype was the thinnest (0.33±0.08mm) at maxillary anterior teeth; the bone plates thickness at 8mm apical to CEJ was generally increased compared to that at 4mm and 6mm, and among them, the bone plates thickness of central incisor and thick biotype was the thickest at maxillary anterior teeth (1.10±0.22mm).2. The differences of labial bone plates thickness at the same measurement point of the same gingival biotype but with the different tooth positions were of statistical significance (P<0.01). At 4mm apical to CEJ, the labial bone plates thickness of canine teeth was generally thinner than that of central incisor and lateral incisor, and among them, the bone plates thickness of canine teeth and thin biotype was the thinnest (0.33±0.08mm) at maxillary anterior teeth; the bone plates thickness at 6mm apical to CEJ was generally increased compared to that at 4mm; and the bone plates thickness at 8mm apical to CEJ was generally increased compared to that at both 4mm and 6mm, and among them, the bone plates thickness of central incisor and thick biotype was the thickest at maxillary anterior teeth (1.10±0.22mm). At 4mm apical to CEJ, the gingival thickness of lateral incisor was generally thin; at 6mm apical to CEJ, the gingival thickness of lateral incisor and thin biotype was the thinnest (0.43±0.12mm) at maxillary anterior teeth; the gingival thickness at 8mm apical to CEJ was generally increased compared to that at 4mm and 6mm, and meanwhile, the gingival thickness of central incisor and thick biotype was the thickest at maxillary anterior teeth (1.01±0.38mm).3. During the Pearson correlation analysis of labial gingival thickness and labial bone plates thickness, in addition to the little correlation between labial gingival thickness and labial bone plates thickness of central incisor (r=0.123, P=0.227), lateral incisor (r=0.112, P=0.435) and canine teeth (r=0.138, P=0.331) at 8mm apical to CEJ, there was a slight correlation (r=0.2-0.4) between the two thicknesses in the result of other testing groups. Experiment 2:Experiment B:1. The measured alveolar widths for the missing upper central incisor and the uninjured central incisor were as follows:The alveolar widths for Group A at 4mm,6mm and 8mm apical to CEJ in edentulous area were measured as 4.10±0.56mm,6.35±0.47mm and7.74±0.27mm respectively, while the measured alveolar widths for Group B were 3.28±0.47mm,5.24±0.68mm and 6.71±0.50mm respectively, the measured alveolar widths for Group C were 2.87±0.4mm, 4.76±0.51mm and 6.34±0.36mm respectively, and the measured values for Group D were 2.72±0.4mm,4.61±0.6mm and 5.86±0.69mm respectively, which demonstrated that there was statistical significance in the differences between the alveolar widths in edentulous area and of the uninjured tooth with the same name on the opposite side (P<0.05). The alveolar width decreased when getting closer to the gingival margin, and as time passed by, the alveolar width of the missing upper central incisor became gradually narrower. The D-value between the alveolar widths in edentulous area and of the uninjured tooth with the same name on the opposite side in Group A and the differences between Group A and the results of the other groups were statistically significant (P<0.01); the differences of the D-value between the alveolar heights in edentulous area and of the uninjured tooth with the same name on the opposite side in Group B, C and D were also obvious and were statistically significant (P<0.01); however, there was no statistical significance in the D-value between t the alveolar widths in edentulous area and of the uninjured tooth with the same name on the opposite side in Group C and Group D (P>0.05).2. The alveolar heights of the missing upper central incisor and uninjured central incisor in buccal and palatal side as well as at the implantation site were measured as follows:The alveolar heights in edentulous area in Group A were measured as 18.71±1.45mm,20.5±1.58mm and 20.5±1.42mm respectively, and the alveolar heights in edentulous area in Group B were measured as 17.3±1.44mm, 19.44±1.58mm and 19.49±1.61mm respectively, while measured values in Group C and Group D were 17.08±1.02mm,18.78±2.23mm,18.29±1.7mm and 16.89±1.89mm, 18.42±2.16mm,18.64±1.61mm respectively; compared with the measured values of the uninjured tooth with the same name on the opposite side, the alveolar heights in buccal and palatal side as well as at the implantation site in edentulous area were obviously decreasing, and the differences were statistically significant (B<0.05), and as passed by, the alveolar heights of the missing upper central incisor became gradually smaller. The D-value between the alveolar heights in edentulous area and of the uninjured tooth with the same name on the opposite side in Group A and the differences between Group A and the results of the other groups were statistically significant (P<0.01); there was no statistical significance for the differences of the D-value between the alveolar heights in edentulous area and of the uninjured tooth with the same name on the opposite side in Group B, C and D (P>0.05); and there was no statistical difference for the D-value between the alveolar heights in edentulous area and of the uninjured tooth with the same name on the opposite side in Group C and Group D (P>0.05).[Conclusion] 1.At the same measurement point and with the same tooth position but of different gingival biotypes, labial bone plates thicknesses at maxillary anterior teeth are different, the labial bone plates thickness of thin biotype are the thinnest, while the labial bone plates thickness of thick biotype are the thickest.2.At maxillary anterior teeth, the labial gingival thicknesses of the same gingival biotype and at the same measurement point but with different tooth position are different, and among them, the labial gingival thickness of central incisor is the thickest, while the labial gingival thickness of lateral incisor is the thinnest, and the canine teeth has a moderate labial gingival thickness; At maxillary anterior teeth, the labial bone plates thicknesses of the same gingival biotype and at the same measurement point but with different tooth position are different, and among them, the labial bone plates thickness of central incisor is the thickest, while the labial gingival thickness of lateral incisor is the thinnest.3.At 4mm and 6mm apical to CEJ at maxillary anterior teeth, there is a slight correlation between the labial gingival thickness and labial bone plates thickness, while at 8mm apical to CEJ, there is no correlation between the two.4.After a period of 6 moths of a missing central incisor, the resorption for the width and height of alveolar bone is the most obvious, and the alveolar bone loss is more obvious in labial bone plates and around gingival margin; after one year of the tooth loss, the resorption for alveolar bone becomes gradually steady and smooth. |
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