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ePaper created 2015-11-17, 15:11:47 | version 1.38.0
66 Volume 1 | Issue 1/2015 Journal of Oral Science & Rehabilitation were used to define the global errors of the pro- cedureduetotheBooleanmethod,superimposi- tion,impressiontaking,gypsumcastingand3-D scanning. D a ta a n a lysi s Mean values and standard deviations were calculated for the 2-D data, while mean val- ues and standard deviations, as well as the 25th , 50th (median) and 75th percentiles, were calculated forthe 3-D data. Differences in the volumetric variation (Δ) between the implant and the contralateral sites were analyzed us- ing the Wilcoxon signed-rank test. The level of significance was set at α = 0.05. In case of normal distribution, a t-test was also per- formed. Results 2-D analysis Atthebuccalaspect(Table1),atendencytohigher horizontal resorption of the alveolar process was seeninthecentralregionswheretoothextraction wasperformedcomparedwiththemesialanddis- tal regions. Moreover, the resorption had a ten- dency to be higher at the coronal aspects com- pared with the apical. The horizontal resorption variedbetween3%and25%,dependingonthein- terception point from which it was analyzed, the highest variation being in the central/coronal re- gions,andthelowestbeingatthemesiodistal/api- cal regions. Similar results were observed at the lingual/palatal aspect (Table 2) and in the global horizontalvariation(Table3). Thevertical resorption ofthe alveolarprocess analyzed onthe sevenverticalcutting planeswas higher in the mesial and distal regions compared with the central regions at the buccal aspect. A tendencytohigherresorptionwasseeninthecen- tralregionsatthelingual/palatalaspect(Table4). 3-D analysis When the absolute values were taken into ac- count (Table 5), it was observed that the larger the ROI, the higherthevolume loss, with a pos- itive linear correlation between the two vari- ables(R2 = 0.9346;y= 0.126x).Thevolumeloss was 69.7 ± 39.1 mm3 and 74.3 ± 29.8 mm3 at the buccal and lingual/palatal aspects, respec- tively, and a global volume loss of 144.1 ± 61.2 mm3 was observed. The global volume loss in percentage was 12.7 ± 3.1%, showing a lower variability of the results between sites com- paredwiththeabsolutevalues(Table5).The loss was 5.9 ± 1.9% at the buccal and 6.8 ± 2.2% at the lingual/palatal aspects, the difference not being statistically significant. Small variations in volume at the control sites were also ob- served that represented the errors included in the 3-D analysis. Discussion 2-D analysis The2-Danalysisdemonstratedareductionofthe dimensions at boththe buccaland lingual/palatal aspects. However, the analysis of each intersec- tionpointandthecomparisonofallofthepatients were very demanding. Moreover, the variability per intersection point was very large, making drawingconclusionsusingthismethoddifficult.It is, of course, possible to select just one intersec- tion point and compare it with the lingual/palatal aspect orwiththat ofother patients. However,to perform a complete analysis ofthe phenomenon, 42 intersection points (such as those that com- posedthegrid)wereanalyzed. 2-D analysis offers advantages for investiga- tion of defect shape and for analysis of local de- fects. However, limits to consider include the use of2-Dnumberstoexpress3-Daspects,thelackof information aboutthe size ofthe area affected by the resorption, and the huge amount of data that must be recorded and that require a great deal of timetoanalyze. Moreover,greatvariabilityinresorptionexists, depending on where the volume loss is investi- gated. In the present study, a horizontal mean global volume loss of 3.8–43.9% in the analyzed area made it impossible to summarize the phe- nomenon with a unique number that expresses the volume loss. For the vertical loss in the 2-D analysis, the results have to be reported in mil- limeters, since it does not seemto be appropriate to report data in percentages because of the lack ofareferencedimension. 3-D analysis The3-Danalysisshowedthatshrinkageofthevol- ume of the alveolar process occurred at both the Volum etric 3 -D d igita l analysi s