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^® (Geistlich Biomaterials, Wolhusen, Switzerland) and interrupted sutures were applied.: Tx 2: The extraction socket was filled with BioOss Collagen^® (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^® 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^® scaffold. It seems that the mechanical stability provided by BioOss Collagen^® and furthermore by a free gingival graft could act as a placeholder preventing the soft tissue from collapsing.     

Hard tissue alterations after socket preservation with additional buccal overbuilding: a study in the beagle dog

Objectives: The aim of this study was to histometrically assess alterations of the ridge following socket preservation alone and socket preservation with additional buccal overbuilding.
Material and Methods: In five beagle dogs four extraction sites were randomly subjected to one of the following treatments:
Tx 1: The socket was filled with BioOss Collagen^® and covered with a free gingival graft from the palate.
Tx 2: The buccal bone plate was augmented using the GBR-technique, the socket was filled with BioOss Collagen^® and covered with a free gingival graft.
Tx 3: The buccal bone plate was forced into a buccal direction using a manual bone spreader. The socket was filled with BioOss Collagen^® and covered with a free gingival graft from the palate.
Tx 4: The socket was filled with BioOss Collagen^® and a combined free gingival/connective tissue graft was used to cover the socket and for buccal tissue augmentation.
For each experimental site, two histological sections were subjected to histometric analysis and evaluated for (i) vertical bone dimensions and (ii) horizontal bone dimensions.
Results: All treatment groups showed horizontal and vertical bone loss. The mean vertical bone loss of the buccal bone plate was significantly lower in Tx 4 than in the other groups, while no statistical significant differences could be detected among the groups in the horizontal dimension.
Conclusion: Overbuilding the buccal aspect in combination with socket preservation does not seem to be a suitable technique to compensate for the alterations after tooth extraction.     

Ridge alterations following tooth extraction with and without flap elevation: an experimental study in the dog

Background: Different approaches were advocated to preserve or improve the dimension and contour of the ridge following tooth extraction. In some of studies, socket 'flapless extraction' apparently had a successful outcome.
Aim: The objective of the present experiment was to compare hard tissue healing following tooth extraction with or without the prior elevation of mucosal full-thickness flaps.
Material and methods: Five mongrel dogs were used. The two second mandibular premolars (₂P₂) were hemi-sected. The mesial roots were retained. By random selection the distal root in one side was removed after the elevation of full-thickness flaps while on the contralateral side, root extraction was performed in a flapless procedure. The soft tissue wound was closed with interrupted sutures. After 6 months of healing, the dogs were euthanized and biopsies were sampled. From each experimental site, four ground sections – two from the mesial root and two from the healed socket – were prepared, stained and examined in the microscope.
Results: The data showed that the removal of a single tooth (root) during healing caused a marked change in the edentulous ridge. In the apical and middle portions of the socket site minor dimensional alterations occurred while in the coronal portion of the ridge the reduction of the hard tissue volume was substantial. Similar amounts of hard tissue loss occurred during healing irrespective of the procedure used to remove the tooth was, i.e. flapless or following flap elevation.
Conclusion: Tooth loss (extraction) resulted in marked alterations of the ridge. The size of the alveolar process was reduced. The procedure used for tooth extraction – flapless or following flap elevation – apparently did not influence the more long-term outcome of healing.     

Early healing of implants placed into fresh extraction sockets: an experimental study in the beagle dog. II: ridge alterations

Aims: To describe the early phases of healing at the alveolar ridge around dental implants placed into fresh extraction sockets and to study whether (i) the dimension of the socket and (ii) a new implant surface nano-topography may have any influence.
Materials and Methods: Sixteen beagle dogs received 64 test (new surface) and control implants randomly placed at the distal socket of 3P3 and 4P4. The implant shoulder was levelled with the marginal buccal bone crest. Animals were sacrificed at 4 h, 1, 2, 4 and 8 weeks for histological examination.
Results: Bone loss occurred at the buccal crest between the 4-h and 1-week healing intervals, being more pronounced at the third premolar site [vertical bone loss between day 0 and 8 weeks 1.1 (0.5) mm]. The corresponding loss at the fourth premolar site was 0.3 (0.5) mm. Test sites containing implants with discrete crystalline deposition nano-particles' surface exhibited less buccal bone resorption than control sites at 8 weeks.
Conclusion: Dimensions of the socket influenced the process of wound healing of implants placed into fresh extraction sockets, with more bone loss in the narrower sockets; however, the implant surface nano-topography seemed to have a limited effect in the healing of this implant surgical protocol.     

Timeframe of socket cortication after tooth extraction: A retrospective radiographic study

Objectives

To assess the timeframe between tooth extraction and radiographically detectable socket cortication in humans.

Methods

Two hundred and fifty patients with a CT scan ≤36 months after tooth extraction were included. First, three orthoradial multiplanar reconstruction slices, representing the major part of the extraction socket, were scored regarding the degree of bone healing as (i) healed, that is, complete/continuous cortication of the socket entrance, or (ii) non‐healed. Thereafter, based on the results of all three slices, the stage of cortication of the extraction socket, as one unit, was classified as (i) non‐corticated, that is, all three slices judged as non‐healed, (ii) partially corticated, that is, 1 or 2 slices judged as non‐healed, or (iii) completely corticated, that is, all three slices judged as healed. The possible effect of several independent parameters, that is, age, gender, timeframe between tooth extraction and CT scan, tooth type, extent of radiographic bone loss of the extracted tooth, tooth‐gap type, smoking status, presence of any systemic disease, and medication intake, on cortication status was statistically evaluated.

Results

Three to 6 months after tooth extraction, 27% of the sockets were judged as non‐corticated and 53% were judged as partially corticated. After 9–12 months, >80% of the sockets were corticated, while some incompletely corticated sockets were detected up to 15 months after extraction. Each additional month after tooth extraction contributed significantly to a higher likelihood of a more advanced stage of cortication, while radiographic bone loss ≥75% significantly prolonged cortication time; no other independent variable had a significant effect.

Conclusions

The results indicate a considerably long timeframe until complete cortication of an extraction socket, that is, 3–6 months after tooth extraction 3 of 4 sockets were still not completely corticated, and only after 9–12 months, complete cortication was observed in about 80% of the sockets.     

Vertical and horizontal ridge alterations after tooth extraction in the dog: flap vs. flapless surgery

Objective: To compare ridge alterations after flap and flapless tooth extraction in the vertical and horizontal dimension in the dog model. Material and methods: This study was carried out on five Beagle dogs. Four extractions were performed in the lower jaw of each dog (two per side. Pm3, Pm4). At the time of tooth extraction, flap surgery was performed on one side (control group). On the contra‐lateral side, a flapless extraction was performed (test group). Mesial sockets were left untreated on both sides. After 3 months of healing, the dogs were sacrificed and prepared for histological analysis. Results: Ten samples were evaluated on each group. The vertical difference in height between the buccal and lingual crest was 1.48 mm for the flap, and 1.22 mm for the flapless group. The horizontal dimension of the ridge was 4.41 mm (at 1 mm from the crest), 5.72 mm (at 3 mm from the crest) and 6.67 mm (at 5 mm form the crest) in the flap group. In the flapless group, the measurements were 4.5, 5.58 mm and 6.44 at 1, 3 and 5 mm from the crest, respectively. Conclusion: Evaluating ridge alterations in the vertical and horizontal dimension after 3 months of healing following tooth extraction, results for the flap and the flapless group were very similar. To cite this article:
Blanco J, Mareque S, Liñares A, Muñoz F. Vertical and horizontal ridge alterations after tooth extraction in the dog: flap vs. flapless surgery.
Clin. Oral Impl. Res. 22 , 2011; 1255–1258.
doi: 10.1111/j.1600‐0501.2010.02097.x     

Immediate loading after implant placement following tooth extraction up-regulates cellular activity in the dog mandible

Objectives: The aim of this study was to investigate cellular activity of the cervical portion of peri‐implant tissue due to immediate loading after implant placement following tooth extraction from the dog mandible, in terms of morphological, immunohistochemical and molecular characteristics. Material and methods: A sand‐blasted implant was inserted into the root septum bone of each extraction socket and was connected to a superstructure made from resin and then covered with an expanded polytetrafluoroethylene membrane. Implants without the superstructure were used as the non‐loading control group. Animals were sacrificed 1–3 weeks later and specimens were observed using light microscopy and mRNA levels were analyzed by real‐time polymerase chain reaction. Results: The new bone formation ratio in the loading group at 3 weeks was significantly higher than in the non‐loading group. Alkaline phosphatase (ALP)‐positive cells were observed in tissues around the implant surface in both groups at each of the time periods. More osteocalcin (OCN)‐positive cells were observed in the non‐loading group than in the loading group at 2 weeks. The expression of ALP mRNA in the loading group was significantly up‐regulated compared with the non‐loading group (P<0.05). The expression of OCN mRNA in the loading group was significantly up‐regulated compared with the non‐loading group at 2 weeks (P<0.05). Conclusion: These results suggest that immediate loading after implant placement following tooth extraction osteogenic affects cellular activity of cervical portion of peri‐implant tissue. To cite this article:
Sato R, Matsuzaka K, Kokubu E, Inoue T. Immediate loading after implant placement following tooth extraction up‐regulates cellular activity in the dog mandible.
Clin. Oral Impl. Res. xx , 2011; 000–000.
doi: 10.1111/j.1600‐0501.2010.02118.x     

Measurement of ridge alterations following tooth removal: a radiographic study in humans

Objective: The aim of this study was a radiographic mesiodistal analysis of the shape of the bone crest 3 months after tooth removal. Material and methods: One hundred single tooth extractions were performed on 100 patients because of orthodontic or prosthetic causes. Bite blocks were used for two radiographs: one on the day of extraction and the other after healing of the socket, 3 months later. These X‐rays were used to determine: (1) the most apical distance of alveolar ridge resorption, with baseline as the line between bone‐to‐teeth contact (the greatest distance in bone resorption height) and (2) the mesiodistal distance (MDD) and mesial and distal angles arising after bone tissue modeling. Results: Significant differences (P<0.05) emerged between the MDDs of multiple‐ [8 mm, 95% confidence interval (CI): 6.09, 9.90] and single‐root teeth (5.60 mm, 95% CI: 4.80, 6.50). However, mesial or distal angles or the most apical distance of alveolar ridge resorption did not differ (mean distance in height=4.32 mm, 95% CI: 3.85, 4.78; mean angle=24°). Conclusions: In this study, the post‐extraction mesiodistal bone distance between teeth adjacent to the edentulous ridge depends on the size of the edentulous space. Nevertheless, the distance does not affect the distance in bone loss height. The distance of bone resorption height reaches a balance at the midpoint, which we consider indicative of stable healing. This resorption process must be considered when placing dental implants in fresh extraction sockets, especially in aesthetic sites, because the implant surfaces could be exposed after 3 months. To cite this article:
Moya‐Villaescusa MJ, Sánchez‐Pérez A. Measurement of ridge alterations following tooth removal: a radiographic study in humans.
Clin. Oral Impl. Res. 21 , 2010; 237–242.
doi: 10.1111/j.1600‐0501.2009.01831.x     

Early healing of implants placed into fresh extraction sockets: an experimental study in the beagle dog. De novo bone formation

Objectives: Describe the early phases of tissue integration in implants placed into fresh extraction sockets and test whether a new implant surface nano‐topography (DCD nano‐particles, Nanotite^?) promotes early osseointegration when compared with minimally rough surface implants (DAE, Osseotite^®). Material and Methods: Sixteen beagle dogs received 64 test and control implants randomly installed into the distal socket of ₃P₃ and ₄P₄. Histomorphometric analysis of bone to implant contact (BIC) and bone area was performed at 4 h, 1, 2, 4 and 8 weeks. Results: Wound healing initiated with a coagulum that was substituted by a provisional matrix at 1 week. Bone formation started concomitant to a marked bone resorption. At 2 weeks, woven bone formation was evident and gradually remodelled into lamellar bone at 4 and 8 weeks. BIC increased similarly throughout the study in both groups with a tendency to higher percentages for the test devices at 2 and 4 weeks. The influence of the DCD nano‐particles was more evident at the fourth premolar site. Conclusion: Osseointegration occurred similarly at both implant groups, although the socket dimension appeared to influence bone healing. It is suggested that the enhanced nano‐topography has a limited effect in the immediate implant surgical protocol.     

Evaluation of alveolar process resorption after tooth extraction using the socket shield technique without immediate installation of implants: a randomised controlled clinical trial

Our aim was to evaluate resorption of the alveolar ridge using the socket shield technique (SST) without immediate placement of dental implants. This randomised controlled clinical trial included 27 patients: 14 maxillary non-molar teeth were partially extracted using the SST (test group) and 13 were extracted using a minimally traumatic extraction approach (control group). Alterations in height and thickness of the alveolar ridge were evaluated by cone beam computed tomograms taken immediately after, and 100 days after, surgery. Minor resorption was observed in the height of the buccal and palatal plates, without intergroup difference (p ≥ 0.10). The test group showed significantly better preservation of the buccal-to-palatal crest dimension (p ≤ 0.05). In the control group, preservation of buccal plate thickness was significantly greater (p ≤ 0.05), but intragroup vertical resorption of the buccal plate and reduction in the buccal-to-palatal crest distance were greater (p ≤ 0.05). The SST without the immediate placement of implants showed greater preservation of the buccal-to-palatal crest dimension and lower preservation of buccal wall thickness compared with minimally traumatic extraction. In addition, it provided superior maintenance of the baseline buccal wall height. The modified SST is a promising approach, but factors that interfere with the results should be investigated.     

Early healing of implants placed into fresh extraction sockets: an experimental study in the beagle dog. III: soft tissue findings

Aim: To describe histologically the early phases of soft tissue healing to implants placed into fresh extraction sockets. Materials and Methods: In 16 beagle dogs, 64 3.25‐mm‐wide cylindrical screw implants were inserted into the distal sockets of the third and fourth lower premolars using a one‐stage trans‐mucosal healing protocol. Biopsies were then taken at 1, 2, 4 and 8 weeks and prepared for histological examination. Results: One‐week specimens showed a junctional epithelium and an underlying loose connective tissue rich in inflammatory cells. At 2 weeks, signs of epithelial proliferation and a more organized connective tissue were observed. At 4 and 8 weeks, inflammation was absent; the epithelium appeared mature and in close contact with the surface of the healing abutment or the implant. The connective tissue was dense in an area close to the implant surface and the fibres were aligned parallel to the implant surface. The soft tissue dimensions at 8 weeks were approximately 5 mm, including about 3–3.5 mm of epithelium and 1–1.5 mm of connective tissue. Conclusion: Soft tissue healing to implants placed in fresh extraction sockets may result in a longer epithelial interface than implants placed in a healed ridge.     

Effect of a xenograft on early bone formation in extraction sockets: an experimental study in dog

Aim: The aim of this study was to study the effect on early bone formation resulting from the placement of a xenograft in the fresh extraction socket in dogs.
Material and methods: Five beagle dogs were used. The distal roots of the third and fourth mandibular premolars were removed. In one quadrant, a graft consisting of Bio-Oss^® Collagen was placed in the fresh extraction wound, while the corresponding premolar sites in the contra-lateral jaw quadrant were left non-grafted. After 2 weeks of healing, the dogs were perfused with a fixative, the mandibles removed, the experimental sites dissected, demineralized, sectioned in the mesio-distal plane and stained in hematoxyline–eosine.
Results: The central portion of the non-grafted sockets was occupied by a provisional matrix comprised of densely packed connective tissue fibers and mesenchymal cells. Apical and lateral to the provisional matrix, newly formed woven bone was found to occupy most of the sockets. In the apical part of the grafted sockets , no particles of the xenograft could be observed but newly formed bone was present in this portion of the experimental site. In addition, limited numbers of woven bone trabeculae occurred along the lateral socket walls. The central and marginal segments of the grafted sockets, however, were occupied by a non-mineralized connective tissue that enclosed Bio-Oss^® particles that frequently were coated by multinucleated cells.
Conclusions: The placement of Bio-Oss^® Collagen in the fresh extraction wound obviously delayed socket healing. Thus, after 2 weeks of tissue repair, only minute amounts of newly formed bone occurred in the apical and lateral borders of the grafted sockets, while large amounts of woven bone had formed in most parts of the non-grafted sites.     

Dimensional ridge alterations following immediate implant placement in molar extraction sites: a six-month prospective cohort study with surgical re-entry

Aim: To assess dimensional ridge alterations following immediate implant placement in molar extraction sites.
Material and methods: Twelve subjects received 12 immediate transmucosal implants in molar extraction sites. Peri-implant defects were treated according to the principles of Guided Bone Regeneration by means of a deproteinized bone substitute and a bioresorbable collagen membrane. Changes in vertical (IS-BD, CREST-BD) and horizontal distances (EC-I, IC-I) of alveolar bony walls to the bottom of the defects (BD) and to the implant surfaces (I) were compared between implant placement and surgical re-entry at 6 months.
Results: The implant survival rate at 6 months was 100%. Statistically significant differences ( P <0.01) were observed in the mean changes in vertical distances IS-BD and CREST-BD between baseline and re-entry. At re-entry, all peri-implant marginal defects assessed from the internal socket wall to the implant surface (IC-I) were healed. The residual combined thickness of the buccal wall with the newly formed peri-implant bone at sites with an initial thickness of 1 mm was statistically significantly smaller ( P <0.05) compared with that of sites with an initial buccal thickness of 2 mm (2.50 ± 0.76 vs. 4±0 mm).
Conclusions: The marginal defects around immediate implants placed in molar extraction sites were completely filled after 6 months of healing through de novo bone formation. Bone resorption was observed from the external aspects of the buccal and oral socket walls. Dimensional changes of the external socket walls were mostly pronounced at the buccal aspects.