Radiographic evaluation
Absolute values of the alveolar bone widths (AWs) and their changes in time (ΔAW) were shown in Table
1. The site of the implant, i.e., bicuspid versus molar, had been checked to test the influence of the variance in the alveolar width change between the two groups with regard to this confounding factor. On the other side, the Friedman tests did not reveal any significant influence on the changes between the genders (Table
1).
Table 1
Median and interquartile range \( \overset{\sim }{m} \)(iqr) of the alveolar bone width at baseline 1 (pre-extraction) and baseline 2 (before delayed dental implant placement) and after 10 years for sites with porcine bone graft (A) and collagen sponge (B)
| Overall sites |
A | 30 | 10.9(2.3) | 8.4(2.1) | 9.4(1.6) | − 2.7(0.9) | + 1.3(1.1) | − 1.3(1.6) | < 0.0001 | < 0.0001 | < 0.0001 |
B | 24 | 10.6(2.0) | 7.1(1.1) | 9.0(1.5) | − 3.9(1.4) | + 1.8(1.1) | − 2.2(1.6) | < 0.0001 | < 0.0001 | < 0.0001 |
Intergroup analysis (p value*) | | 0.8616 | 0.0032 | 0.1296 | < 0.0001 | 0.0688 | 0.0863 | | | |
Effect of site (p value^) | | < 0.0001 | < 0.0001 | 0.0099 | 0.0176 | 0.6093 | 0.0086 | | | |
Effect of gender (p value^) | | 0.0442 | 0.0102 | 0.0448 | 0.7096 | 0.8234 | 0.8236 | | | |
| Premolar |
A | 16 | 9.8(0.7) | 7.1(1.3) | 9.1(1.4) | − 2.8(1.0) | + 1.5(1.5) | − 1.3(1.7) | 0.0004 | 0.0004 | 0.0004 |
B | 13 | 10.2(0.8) | 6.7(0.7) | 8.3(1.4) | − 3.3(1.1) | + 1.7(1.4) | − 1.5(1.5) | 0.0002 | 0.0002 | 0.0002 |
Intergroup analysis (p value*) | | 0.5524 | 0.1349 | 0.2816 | 0.0562 | 0.8434 | 0.2190 | | | |
| Molar |
A | 14 | 12.1(0.3) | 9.1(0.9) | 9.9(1.8) | − 2.7(0.5) | + 1.0(1.7) | − 1.8(2.0) | 0.0001 | 0.0001 | 0.0234 |
B | 11 | 12.1(0.6) | 7.5(1.6) | 9.4(1.2) | − 4.6(0.6) | + 1.9(0.7) | − 2.7(1.1) | 0.0009 | 0.0009 | 0.0009 |
Intergroup analysis (p value*) | | 1 | 0.0005 | 0.2743 | < 0.0001 | 0.0061 | 0.2972 | | | |
| Premolar vs molar |
A (p value*) | | < 0.0001 | < 0.0001 | 0.0209 | 0.06772 | 0.0612 | 0.0843 | | | |
B (p value*) | | < 0.0001 | 0.0594 | 0.0395 | 0.0003 | 0.3102 | 0.0137 | | | |
The intragroup analyses suggested that significant width reductions of the alveolar processes were observed in both groups from baseline 1 to baseline 2, that is about 2/3 months after the alveolar ridge preservation and before the dental implant placement, with a loss ranging between − 2.7 and − 4.6 mm. This proved that, at least in the molar region, the alveolar ridge preservation technique with low absorption material should fulfill its purposes exactly matching the expectations of the clinician.
The radiological outcome of the alveolar ridge expansion procedure, measured from baseline 2 to 10 years, showed a significant increase in the alveolar width in both groups (A and B) and sites (bicuspid and molar); in fact, significant increases in width (ranging from + 1.0 mm to + 1.9 mm with p values ≤ 0.0009) were still visible after a decade.
Cross-group analyses suggested that loss in the alveolar width was higher in group B than in group A at least until the second surgery, i.e., alveolar ridge expansion (2/3 months after) for both implant sites.
Changes in alveolar width, albeit not significant in the premolar sites, ranged from 9.8(0.7) to 7.1(1.3) mm and from 10.2(0.8) to 6.7(0.7) mm for group A and B, respectively; on the contrary, they significantly changed from 12.1(0.3) to 9.1(0.9) mm and from 12.1(0.6) to 7.5(1.6) mm for group A and B, respectively, in the molar site.
Again, changes in the molar area indicated that alveolar ridge expansion led to an overall and statistically significant higher increase (p = 0.0061) in group B, + 1.9 (0.7 mm, than that reported in group A, + 1.0(1.7) mm. Furthermore, the remodeling process after tooth avulsion and before dental implant placement (2/3 months after ridge preservation) demonstrated that the premolar regions behaved significantly different (with p = 0.0003) when compared to the molar ones, even if for the extraction sockets filled with collagen sponges.
Finally, no significant differences were registered at 10-year follow-up between the two procedures and between the two implant sites (Table
1).
Overall radiologic outcomes (from baseline 1- to 10-year survey) calculated summing over time the changes in alveolar width after both surgeries (ARP and ARS) showed no significant differences between the group A and B.
The outcomes regarding the buccal contours demonstrated that few implants in group B (2 out of 24 placed in sockets preserved with collagen alone) had no complete buccal bone coverage, as visible in the CBCT images and segmentations. Moreover, the analysis of the distribution of the data (Table
2) demonstrated that group A showed significantly worst results over the long term than group B (Fisher’s exact test
p value = 0.0005).
Table 2
Distribution about maintenance of the buccal bone plate at 10 years of follow-up for the porcine bone graft group (A) and collagen sponge group (B)