26 Chapter 2 All the other clinical variables (ordinal data) were analysed via Wilcoxon signed rank tests (for within-group differences) and a Mann-Whitney U test (for between-group differences). Implant and overdenture survival rate differences between the groups were calculated using a Log Rank test. A p-value of less than 0.05 was considered statistically significant. Pairwise deletion was used for missing data and between-group comparisons. List-wise deletion was used for missing data and within-group comparisons. All the analyses were performed with the SPSS 23.0 software (SPSS, Inc., Chicago, IL, USA). 2.3 RESULTS Patient Characteristics The solitary attachment group’s mean age was 60.1 years (+- 8.6, range 37.5-75.0) and the bar group’s was 63.8 years (+- 5.4, range 53.0 – 72.6). Gender distribution was equal in both groups (13 male, 12 female). During the follow-up period, four participants deceased (one in the solitary attachment group, three in the bar group), two participants moved without leaving an address (one in each group) and one participant (bar group) was too ill to attend the 5-year follow-up. Consequently, 23 solitary attachment group participants and 20 bar group participants were available for the 5-year evaluation (Fig. 2.1). Table 2.1 | Mean values and standard deviations (SD) of the marginal bone level change in mm for the solitary attachment and bar attachment groups, and the frequency distribution of the marginal bone level change 1 and 5 years after overdenture placement. 1 year after prosthesis placement 5 years after prosthesis placement Solitary attachment (n = 23) Bar attachment (n = 24) p-value Solitary attachment (n = 23) Bar attachment (n = 20) p-value Mean mm (SD) -0.58 (0.71) -0.31 (0.47) p = 0.002a -1.41 (1.38) -0.99 (0.96) p = 0.024a 0 to -0.5 mm 55.9% 71.4% 29.5% 42.7% >0.5 to -1.0 mm 17.2% 18.4% 18.2% 15.9% >-1.0 to -1.5 mm 17.2% 6.1% 18.2% 17.1% >-1.5 to -2.0 mm 6.5% 3.1% 11.4% 6.1% > -2.0 to -2.5 mm 1.1% 1.0% 1.1% 8.5% > -2.5 to -3.0 mm 1.1% 0.0% 5.7% 4.9% > -3 mm 1.1% 0.0% 15.9% 4.9% a Differences between the study groups were tested with the independent Student’s t-test.
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