Hard tissue alterations after socket preservation: an experimental study in the beagle dog

Objectives: The aim of the following experimental study was to assess bone changes in the horizontal and vertical dimension when using different socket preservation procedures. Material and methods: In five beagle dogs the distal roots of the 3rd and 4th premolar were extracted without elevation of a mucoperiosteal flap and the following treatments were assigned: Tx 1: The extraction socket was filled with BioOss Collagen (R) (Geistlich Biomaterials, Wolhusen, Switzerland) and interrupted sutures were applied. Tx 2: The extraction socket was filled with BioOss Collagen (R) (Geistlich Biomaterials, Wolhusen, Switzerland) and a free gingival graft was sutured to cover the socket. Tx 3: The extraction socket was left with its blood clot and interrupted sututes were applied. Four month after surgery the dogs were sacrificed and from each extraction site two histological sections were selected for histometric analysis. The following parameters were evaluated: (1) the vertical dimension was determined by placing a horizontal line on the lingual bone wall. Then, the distance from this line to the buccal bone wall was measured. (2) The horizontal dimension was assessed at three different areas measured from the top of the lingual crest: 1 mm (Value 1), 3 mm (Value 3) and 5 mm (Value 5). Results: The mean vertical loss of the buccal bone plate for the Tx 1 group was 2.8 +/- 0.2 mm. The Tx 2 group showed vertical loss of 3.3 +/- 0.2 mm. The Tx 3 group demonstrated 3.2 +/- 0.2 mm of mean vertical loss. The horizontal dimension of the alveolar process was 4.4 +/- 0.3/6.1 +/- 0.2/7.2 +/- 0.1 mm at the three different levels for the Tx 1 group. The Tx 2 group depicted bone dimensions of 4.8 +/- 0.2/6.0 +/- 0.2/7.1 +/- 0.1 mm. The horizontal dimension of the Tx 3 group was 3.7 +/- 0.3/6.2 +/- 0.2/7.0 +/- 0.1 mm. When the results from the horizontal measurements were tested with the analysis of variance (ANOVA), a clear significance could be found in particular for Value 1 mm between the test groups Tx 1 and Tx 2 and the control group (Tx 3) (P<0.001). Furthermore the mean of treatment 1 (Tx 1) was slightly significantly lower than of treatment 2 (Tx 2) (P<0.05). Conclusion: The findings from the present study disclose that incorporation of BioOss Collagen (R) into the extraction socket has only limited impact on the subsequent biologic process with particular respect to the buccal bone plate. The horizontal measurement of the alveolar ridge depicted that the loss of the buccal bone plate was replaced to a certain amount by newly generated bone guided by the BioOss Collagen (R) scaffold. It seems that the mechanical stability provided by BioOss Collagen (R) and furthermore by a free gingival graft could act as a placeholder preventing the soft tissue from collapsing.