Lateral alveolar ridge augmentation using an equine-derived collagen-containing bone block: A prospective case series.

OBJECTIVES: To assess the clinical performance of an equine-derived collagen-containing bone block (CXBB) for lateral alveolar ridge augmentation and staged implant placement. MATERIAL AND METHODS: A total of n = 16 patients (16 implants) had received a modified surgical protocol for lateral ridge augmentation using a size-adapted rigidly fixed CXBB and contour augmentation. After 26 weeks of submerged healing, the primary endpoint was defined as the final ridge width (RW26) sufficient to place an adequately dimensioned titanium implant at the respective sites. Secondary outcomes included the gain in ridge width (RWg) and the need for secondary grafting. Clinical outcomes (bleeding on probing-BOP, probing depth-PD, and mucosal recession-MR) were assessed at implant loading and after a median observation period of 12.3 months. RESULTS: In all patients (n = 16) investigated, RW26 allowed for a successful placement of an adequately dimensioned titanium implant at respective sites exhibiting mean RWg values of 5.09 ± 1.07 mm. A soft tissue dehiscence was noted in one patient (6.3%), and a secondary grafting was needed in two patients (12.5%) The changes in mean BOP, PD, and MR values at V9 amounted to 10.23 ± 30.11%, 0.14 ± 0.80 mm, and -0.01 ± 0.04 mm, respectively. CONCLUSIONS: CXBB may represent a feasible approach for lateral alveolar ridge augmentation and two-stage implant placement.

Comparison of a polyethylene glycol membrane and a collagen membrane for the treatment of bone dehiscence defects at bone level implants-A prospective, randomized, controlled, multicenter clinical trial.

OBJECTIVES: The aim of the present randomized, controlled clinical multicenter trial was to compare a polyethylene glycol (PEG) and a native collagen membrane (BG) for simultaneous guided bone regeneration at bony dehiscence-type defects around bone level titanium implants. MATERIAL AND METHODS: The study enrolled 117 patients requiring implant treatment in the posterior maxilla or mandible with expected buccal bony dehiscence-type defects at the placed titanium implants. According to a parallel groups design, defects were filled with a synthetic bone filler and randomly assigned to either PEG or BG membrane. As primary parameter, the relative vertical bone fill was assessed at baseline and at re-entry after 6 months of healing. As secondary parameters, the marginal bone level (MBL) was assessed radiographically and soft tissue conditions were recorded up to 18 months postloading. RESULTS: Both groups showed comparable vertical bone fill revealing a relative change in defect height of 59.7% (PEG) and 64.4% (BG). The absolute mean reduction in defect size was 2.5 mm in the PEG group and 3.2 mm in the BG group. Although both groups revealed a statistically significant mean defect reduction (p < .001), a comparison between the two groups did not show statistical significances. The non-inferiority test with inferiority limit of -5% could not be rejected, based on the 90% confidence interval of the differences of the two means with lower limit -15.4%. After 18 months, an MBL increase of 0.45 ± 0.43 mm in the PEG group and 0.41 ± 0.81 mm in the BG group was detected (p < .001). Soft tissue complications were observed in both groups without showing statistical significance. CONCLUSIONS: Both membranes supported bone regeneration at dehiscence-type defects and obtained vertical bone fill with a relative change in defect height of 59.7% (PEG) and 64.4% (BG); however, the non-inferiority of PEG could not be shown.

Influence of autoclavation on the efficacy of extracted tooth roots used for vertical alveolar ridge augmentation.

OBJECTIVES: To assess the influence of autoclavation on the efficacy of extracted tooth roots (TR) used for vertical alveolar ridge augmentation and two-stage osseointegration. MATERIAL AND METHODS: Maxillary premolars were randomly assigned to either autoclavation (TR-A) or were left untreated (TR-C) and used as block grafts for vertical alveolar ridge augmentation in both lower quadrants (n = 4 beagle dogs). At 12 weeks, titanium implants were inserted and left to heal for 3 weeks. Histological analyses considered vertical bone gain (BD-BC), augmented area (AA) and bone-to-implant contact (BIC) at vestibular (v) and oral (o) aspects. RESULTS: Both TR-C and TR-A (exposures n = 3) grafts were associated with a replacement resorption and marked vertical bone gain. Median BD-BC (TR-C: 1.45 [v] to 1.62 mm [o] versus TR-A: 0.97 [v] to 1.79 mm [o]) and AA (TR-C: 0.64 [v] to 2.36 mm2 [o] versus TR-A: 0.22 [v] to 2.36 mm2 [o]) values were comparable in both groups. V BIC (TR-C: 49.32 [v] to 52.97% [o] versus TR-A: 25.34 [v] to 46.11% [o]) values were significantly higher in the TR-C group. CONCLUSIONS: Both TR-C and TR-A grafts equally supported vertical alveolar ridge augmentation; however, osseointegration was partially facilitated in the TR-C group.

Can implants move in bone? A longitudinal in vivo micro-CT analysis of implants under constant forces in rat vertebrae.

OBJECTIVES: Whereas stationary stability of implants has been postulated for decades, recent studies suggested a phenomenon termed implant migration. This describes a change in position of implants as a reaction to applied forces. The present study aims at employing image registration of in vivo micro-CT scans from different time points and to assess (a) if migration of continuously loaded implants is possible and (b) migration correlates with the force magnitude. MATERIAL AND METHODS: Two customized machined implants were placed in the dorsal portion of caudal vertebrae in n = 61 rats and exposed to standardized forces (0.5 N, 1.0 N, and 1.5 N) applied through a flat nickel-titanium contraction spring, or no forces (control). Micro-CT scans were performed at 0, 1, 2, 4, 6, and 8 weeks after surgery. The baseline image was registered with the forthcoming scans. Implant migration was measured as the Euclidean distance between implant tips. Bone remodeling was assessed between the baseline and the forthcoming scans. RESULTS: The findings confirmed a positional change of the implants at 2 and 8 weeks of healing, and a linear association between applied force and velocity of movement (anterior implant: χ2  = 12.12, df = 3, and p = .007 and posterior implant: χ2  = 20.35, df = 3, and p < .001). Bone apposition was observed around the implants and accompanied by formation of load-bearing trabeculae and a general cortical thickening close and also distant to the implants. CONCLUSION: The present analysis confirmed that implants can migrate in bone. The applied forces seemed to stimulate bone thickening, which could explain why implants migrate without affecting stability.

Microstructural volumetric analysis of lateral ridge augmentation using differently conditioned tooth roots.

OBJECTIVES: Previous research revealed that autogenous tooth roots may be biologically equivalent to conventional bone grafts for lateral ridge augmentation. However, these analyses were limited to two dimensions, whereas healing is a volumetric process. The present study aimed at volumetrically assessing the microstructure following lateral ridge augmentation using extracted tooth roots. MATERIAL AND METHODS: The roots of differently conditioned maxillary premolars (i.e., healthy: PM-C; endodontically treated: PM-E; ligature-induced periodontitis: PM-P) and retromolar cortical autogenous bone (AB) blocks were used for lateral ridge augmentation at chronic-type defects in the lower quadrants of n = 16 foxhounds. At 12 weeks, titanium implants were inserted and left to heal for another 3 weeks. Tissue biopsies were scanned using microcomputed tomography (µCT), and volumes of interest were separated at the buccal and oral aspects to measure bone volume per tissue volume (BV/TV), trabecular thickness (Tb.Th), trabecular separation (Tb.Sp), and connectivity density (Conn.D). RESULTS: All groups investigated revealed comparable BV/TV, Tb.Th, Tb.Sp, and Conn.D values at either the augmented buccal or pristine oral aspects, respectively. A gradual but heterogeneous replacement of grafts was observed in all groups, but residual PM fragments were particularly noted in PM-C and PM-P groups. CONCLUSIONS: Differently conditioned PM and AB grafts were associated with a comparable bone microstructure within the grafted area. The duration of replacement resorption may vary considerably among the subjects. CLINICAL RELEVANCE: Autogenous tooth roots may serve as potential alternative to AB for localized alveolar ridge augmentation.

Performance and safety of collagenated xenogeneic bone block for lateral alveolar ridge augmentation and staged implant placement. A monocenter, prospective single-arm clinical study.

OBJECTIVES: To assess the clinical safety and performance of collagenated xenogeneic bone block (CXBB) for lateral alveolar ridge augmentation and two-stage implant placement. MATERIAL & METHODS: In ten patients exhibiting a single-tooth gap, the surgical procedure included the preparation of mucoperiosteal flaps, a rigid fixation of CXBB (Geistlich Bio-Graft® ) using an osteosynthesis screw, and contour augmentation. After 24 weeks of submerged healing, the primary endpoint was defined as the final ridge width sufficient to place an adequately dimensioned titanium implant at the respective sites. Secondary outcomes included, for example, the gain in ridge width (mm). Clinical parameters (e.g., bleeding on probing - BOP, probing depth - PD, mucosal recession - MR) were assessed immediately after the cementation of the crown and at the final visit. RESULTS: At 24 weeks, implant placement could be achieved in 8 of 10 patients exhibiting a mean gain in ridge width (mean ± SD) of 3.88 ± 1.75 mm. Histological analysis has pointed to a homogeneous osseous organization of CXBB. The changes of mean BOP, PD, and MR values at the final visit amounted to 16.62 ± 32.02%, 0.04 ± 0.21 mm, and -0.04 ± 0.12 mm, respectively. CONCLUSIONS: CXBB may be successfully used to support lateral alveolar ridge augmentation and two-stage implant placement.

Biomechanical, micro-computed tomographic and immunohistochemical analysis of early osseous integration at titanium implants placed following lateral ridge augmentation using extracted tooth roots.

OBJECTIVES: To assess biomechanical, micro-computed tomographic (micro CT) and immunohistochemical characteristics of early osseous integration at titanium implants placed following lateral ridge augmentation using autogenous extracted tooth roots. MATERIAL & METHODS: The roots of healthy maxillary premolars (PM) and retromolar cortical autogenous bone (AB) blocks were used for lateral ridge augmentation at chronic-type defects in the lower quadrants of n = 16 foxhounds. At 12 weeks, titanium implants were inserted and left to heal for another 3 weeks. Osteocalcin (OC) antigen reactivity, removal torque values (RT) and the bone volume per tissue volume (micro CT- BV/TV) along the implants were assessed. RESULTS: Median OC (PM: 6.71 vs. AB: 2.73%), RT (PM: 61.97 vs. AB: 44.8 Ncm) and BV/TV (PM: 0.34 vs. AB: 0.21) values were comparable in both PM and AB groups. CONCLUSIONS: PM and AB grafted sites equally supported the early stages of osseointegration.

Bone tissue response to experimental zirconia implants.

OBJECTIVES: This study seeks to assess the bone tissue response at experimental zirconia implants in comparison with titanium implants by means of descriptive histology and histomorphometry in a dog model. MATERIALS AND METHODS: Experimental zirconia implants with three different surface roughnesses (Z1 < Z2 < Z3) and conventional sandblasted large grit and acid-etched titanium implants were inserted bilaterally in the lower jaws of nine beagle dogs. Tissue biopsies were obtained after 3 and 14 days and 10 weeks of transmucosal healing. The tissue response was investigated by assessing new, old, and total bone-to-implant contact (nBIC, oBIC, and tBIC). RESULTS: After 3 days, histological specimens of all groups showed an intimate contact between the implant threads and pristine bone (tBIC: Ti 42.3 % > Z2 30.1 % > Z3 28.9 % > Z1 25.1 %, p > 0.05, unpaired t test, respectively). A provisional matrix was evident at all implant surfaces. At 14 days, percentages of BIC increased in all groups (tBIC: Ti 62.1 % > Z3 69.2 % < Z2 44.4 % > Z1 42.3 %; nBIC: Z3 58.9 % > Ti 52.2 % > Z2 35.1 % > Z1 32.5 %). Two implants, one of group Z1 and one of group Z2, were lost. At 10 weeks, 13 of 18 zirconia implants were lost, equally distributed between all three surface modifications. The remaining implants revealed increased BIC values (tBIC: Z3 69.5 % > Ti 58.5 % > Z1 49.7 % > Z2 37.1 %; nBIC: Z3 57.2 % > Ti 46.5 % > Z1 32.3 % > Z2 29.3 %). Histomorphometrical analysis showed comparable mean BIC values in all groups at all healing periods without showing statistical differences (p > 0.05, unpaired t test, respectively). CONCLUSION: The bone tissue response throughout the healing periods was characterized by a constant bone remodeling accompanied by resorption of old bone in favor of new bone formation at both titanium and zirconia implants. Surface roughness had a positive effect on BIC, although not showing statistical significance. Due to the poor survival rate, the experimental zirconia implants investigated may not be suitable for clinical use. CLINICAL RELEVANCE: Zirconia has been introduced as an alternative biomaterial for dental implants. A profound knowledge about the bone tissue response at zirconia implant surfaces is necessary as it plays an important role for proper osseointegration and long-term stability.

Periodontally diseased tooth roots used for lateral alveolar ridge augmentation. A proof-of-concept study.

OBJECTIVES: To assess the efficacy of periodontally diseased tooth roots used as autografts for lateral ridge augmentation and two-stage early osseointegration of titanium implants. MATERIAL AND METHODS: Ligature-induced periodontitis lesions were established at the maxillary premolars in n = 8 foxhounds. Extracted, scaled and root planed pre-molar roots (PM-P) as well as retromolar cortical autogenous bone (AB) blocks were used for horizontal ridge augmentation of mandibular chronic-type defects. At 12 weeks, titanium implants were inserted and left to heal for another 3 weeks. Histological analyses included crestal ridge width (CW), augmented area (AA) and bone-to-implant contact (BIC). RESULTS: Both PM-P and AB grafts were gradually organized and replaced by newly formed bone. Median CW (PM-P: 3.83 versus AB: 3.67 mm), AA (PM-P: 10.18 versus AB: 9.82 mm(2) ) and BIC (PM-P: 50.00% versus AB: 35.21%) values did not reach statistical significance between groups (p > 0.05, respectively). Histologically, PM-P grafts were not associated with any inflammatory cell infiltrates. CONCLUSIONS: PM-P autografts may reveal a structural and biological potential to serve as an alternative autograft to AB.

Extracted tooth roots used for lateral alveolar ridge augmentation: a proof-of-concept study.

OBJECTIVES: To assess the efficacy of tooth roots used as autografts for lateral ridge augmentation and two-stage early osseointegration of titanium implants. MATERIAL & METHODS: The maxillary premolars were randomly assigned to either endodontic therapy (PM-E) or were left untreated (PM-C). Retromolar cortical autogenous bone (AB) blocks served as controls. PM-E/PM-C and AB were used for ridge augmentation at chronic-type defects in both lower quadrants (n = 8 foxhounds). At 12 weeks, titanium implants were inserted and left to heal for another 3 weeks. Histological analyses considered crestal ridge width (CW); augmented area (AA) and bone-to-implant contact (BIC). RESULTS: Both PM and AB grafts (exposures: AB = 3; PM-C = 4; PM-E = 7) were gradually involved in the bone remodelling process and associated with a replacement resorption. Median CW (PM-C: 2.70 versus AB: 3.30 mm; PM-E: 2.96 versus AB: 3.35 mm), AA (PM-C: 7.55 versus AB: 8.56 mm(2) ; PM-E: 11.20 versus AB: 6.60 mm(2) ) and BIC (PM-C: 36.96 mm versus AB: 64.10%; PM-E: 50.79 versus AB: 32.53%) values were comparable in both PM and AB groups (p > 0.05, respectively). CONCLUSIONS: Extracted tooth roots revealed a structural and biological potential to serve as an alternative autograft to autogenous bone. A higher exposure rate may be expected when using endodontically treated teeth.

Impact of plaque accumulation on the osseointegration of titanium-zirconium alloy and titanium implants. A histological and immunohistochemical analysis.

OBJECTIVES: To evaluate the impact of plaque accumulation on osseointegration at surface enhanced modified hydrophilic titanium-zirconium (TiZr) alloy and titanium (Ti) implants. MATERIALS AND METHODS: TiZr and Ti implants with a sand-blasted, acid etched, and chemically modified endosseous and a machined (M) transmucosal portion were bilaterally (i.e., one implant type on each side) inserted in the maxilla of six foxhounds. In a split-mouth design, experimental mucositis was induced at one randomly assigned side (NPC), while the contralateral side received mechanical plaque removal three times per week (PC). After 16 weeks, tissue biopsies were processed for histological (primary outcome: bone-to-implant contact [BIC]) and immunohistochemical (CD68) analysis. RESULTS: Mean BIC values varied between 81.96% (TiZrM) and 88.72% (TiM) in the NPC group, and between 87.88% (TiM) and 92.69% (TiZrM) in the PC group. Even though BIC values tended to be lower within the endosseous coronal compartment at NPC sites, within group (NPC vs. PC) comparisons failed to reach statistical significance at both types of implants. These non-BIC areas were not associated with any CD68 positive cells. CONCLUSIONS: Osseointegration of both TiZrM and TiM implants was not influenced by plaque accumulation in this experimental model.

Impact of abutment microstructure and insertion depth on crestal bone changes at nonsubmerged titanium implants with platform switch.

OBJECTIVES: To assess the impact of microgrooved abutments and the insertion depth on crestal bone changes at titanium implants with platform switch. MATERIALS AND METHODS: A total of n = 3 titanium implants (conical abutment connection) were inserted in each hemimandible of n = 6 foxhounds with the implant shoulder (IS) located at either epicrestal, supracrestal (+1 mm), or subcrestal (-1 mm) positions and randomly (split-mouth design) connected with machined or partially microgrooved healing abutments. At 20 weeks, tissue biopsies were processed for histological (primary outcome: net bone loss - NET) analyses. RESULTS: Subcrestal positioning of IS tended to be associated with higher mean NET values (mm) at both machined (subcrestal [-0.72 ± 0.32] > epicrestal [-0.34 ± 0.21] > supracrestal [+0.20 ± 0.64]) and microgrooved (subcrestal [-0.48 ± 0.25] > epicrestal [-0.13 ± 0.54] > supracrestal [+0.33 ± 0.58]) abutments. However, these differences failed to reach statistical significance. CONCLUSIONS: The insertion depth may have a direct influence on crestal bone-level changes at both types of abutments investigated.

Healing of localized gingival recessions treated with coronally advanced flap alone or combined with either a resorbable collagen matrix or subepithelial connective tissue graft. A preclinical study.

OBJECTIVES: To histologically evaluate the effectiveness of a porcine derived collagen matrix (CM) and a subepithelial connective tissue graft (CTG) for coverage of localized gingival recessions. MATERIALS AND METHODS: Chronic single Miller Class I-like recessions were created at the buccal at the canines and at the third and fourth premolars in the upper and lower jaws of six beagle dogs. The defects were randomly treated with (1) coronally advanced flap surgery (CAF) + CM, (2) CAF + CTG, or (3) CAF alone. At 12 weeks, histometric measurements were made, e.g., between a reference point (N) - and the gingival margin (GM) - and the outer contour of the adjacent soft tissue (gingival thickness [GT]). RESULTS: The postoperative healing was uneventful in all animals. No complications such as allergic reactions, abscesses or infections were noted throughout the entire study period. All three treatments resulted in coverage of localized gingival recessions. The histological analysis failed to identify any residues of CM or CTG. The histometric measurements revealed comparable outcomes for N-GM and GT values for all three groups (CAF + CM: 1.04 ± 0.69 mm/0.68 ± 0.33 mm; CAF + CTG: 1.15 ± 1.12 mm/0.76 ± 0.37 mm; CAF: 1.43 ± 0.45 mm/0.79 ± 0.24 mm). CONCLUSIONS: In the used defect model, the application of CTG or CM in conjunction with CAF did not have an advantage over the use of CAF alone. CLINICAL RELEVANCE: The use of CAF alone is a valuable option for the treatment localized Miller Class I recessions.

Ridge preservation using a new 3D collagen matrix: a preclinical study.

OBJECTIVES: The success of ridge preservation techniques in reducing bone resorption is well documented, but no clear guidelines have been provided regarding the type of the biomaterial or technique to be used. This experimental animal study aimed at comparing the effectiveness of two ridge preservation techniques. MATERIALS AND METHODS: Following the extraction of the distal roots of the mandibular second and fourth premolars of four dogs, the sockets were preserved using a combination of a collagen membrane intimately covering the socket plus a collagen matrix or a collagen membrane alone. The mandibular quadrants were randomly assigned to one of the treatment groups. Histomorphometrical analyses as well as microscopic observations were performed. RESULTS: After 5 months of healing, the histological analysis revealed a similar picture of bone formation in both groups. No significant differences between the buccal and lingual dimensions were calculated between the two treatment groups. The mucosa covering the alveolar ridges is significantly more abundant in post-extraction sockets preserved with the double-layered approach. CONCLUSIONS: The double-layered approach used to treat post-extraction sockets may result in a better preservation of the mucosal seal than the single-layered approach. CLINICAL RELEVANCE: The use of the new collagen matrix associated with a collagen membrane could be a clinical option to preserve post-extraction ridges, especially when an improvement in soft tissue dimension and quality is desired. However, the cost-benefit ratio of this approach should be thoroughly evaluated in further studies.

Experimental peri-implant mucositis at different implant surfaces.

OBJECTIVES: To histologically and immunologically assess experimental peri-implant mucositis at surface enhanced modified (mod) hydrophilic titanium implants. MATERIALS AND METHODS: In a split-mouth design (n = 6 foxhounds), four different implants were inserted on each side of the maxilla: three titanium-zirconium alloy implants (TiZr) with either modSLA (sand-blasted, acid etched and chemically mod), modMA (machined, acid etched and chemically mod), or M (machined) surfaces in the transmucosal portion, and one titanium implant with a machined transmucosal portion (TiM). Experimental mucositis was induced at one randomly assigned side (NPC), whereas the contra-lateral maxillary side received mechanical plaque removal three times per week (PC). At 16 weeks, tissue biopsies were processed for histological (primary outcome: apical extension of the inflammatory cell infiltrate measured from the mucosal margin - PM-aICT) and immunohistochemical (CD68 antigen reactivity) analyses. Peri-implant sulcus fluid was analysed for interleukin (IL)-1ß, IL-8, matrix metalloproteinase (MMP)-8 and myeloperoxidase (MPO). RESULTS: Mean PM-aICT values varied between 1.86 (TiZrmodSLA) and 3.40 mm (TiM) in the UPC group, and between 0.88 (TiZrmodSLA) and 2.08 mm (TiZrM) in the PC group. Mean CD68, IL-1ß, IL-8, MMP-8 and MPO values were equally distributed between mod- and control implants in both NPC and PC groups. CONCLUSIONS: The progression of experimental mucositis was comparable at all implant surfaces investigated.

Treatment of soft tissue recessions at titanium implants using a resorbable collagen matrix: a pilot study.

OBJECTIVES: To histologically assess the effectiveness of a porcine-derived collagen matrix (CM) and a subepithelial connective tissue graft (CTG) for the coverage of single mucosal recessions at osseointegrated dental implants. MATERIALS AND METHODS: Chronic-type mucosal Miller Class I-like recessions (mean clinical defect height: 0.67 ± 0.33-1.16 ± 0.19 mm) were established at the buccal aspect of titanium implants with platform switch in six beagle dogs. The defects were randomly allocated to either (1) coronally advanced flap surgery (CAF) + CM, (2) CAF + CTG or (3) CAF alone. At 12 weeks, histomorphometrical measurements were made (e.g.) between the implant shoulder (IS) and the mucosal margin (PM) and IS and the outer contour of the adjacent soft tissue (mucosal thickness [MT]). RESULTS: All treatment procedures investigated were associated with an almost complete soft tissue coverage of the defect area (i.e. coronal positioning of PM relative to IS). Mean IS-PM and MT values tended to be increased in both CAF + CM (1.04 ± 0.74 mm/0.71 ± 0.55 mm) and CAF + CTG (0.88 ± 1.23 mm/0.62 ± 0.66 mm) groups when compared with CAF (0.16 ± 0.28 mm/0.34 ± 0.23 mm) alone. These differences, however, did not reach statistical significance. CONCLUSIONS: Within the limits of this pilot study, it was concluded that all treatment procedures investigated were effective in covering soft tissue recessions at titanium implants.

Impact of proangiogenic factors on organization and biodegradation of a collagen matrix. An immunohistochemical study in rats.

AIM: The aim of the present study was to investigate the impact of proangiogenic factors [erythropoetin (EPO), human growth hormone (HGH), fibroblast growth factor (FGF), and platelet derived growth factor (PDGF-BB)] on the organization and biodegradation of a porcine-derived collagen matrix (CM) in rats. MATERIAL AND METHODS: Collagen matrix specimens were soak-loaded either with EPO, HGH, FGF or PDGF-BB, each delivered in three concentrations (high, medium, low), and randomly allocated in unconnected subcutaneous pouches separated surgically on the back of 112 Wistar rats, which were divided into four groups (4, 7, 14 and 60 days of healing). Tissue biopsies were prepared for histological (e.g. CM thickness - TH, tissue contact - TC) and immunohistochemical (collagen type III - C3) analysis. RESULTS: Collagen matrix specimens of the control group were associated with an ingrowth of C3 fibres and subsequently an increase in TH at 7 (11%), 14 (20%) and 60 (21%). Factor application in different concentrations was commonly associated with a faster organization, but also significant biodegradation of CM at 7 (PDGF-M, FGF-M, HGH-H) and 14 days (EPO-H, HGH-L). All groups investigated revealed a comparable increase in mean TC values over time. CONCLUSION: Within the limits of the present study, it was concluded that all proangiogenic factors investigated were associated with a pronounced organization of CM by C3 fibres and a biodegradation of the matrix body. EPO may serve as an alternative to PDGF-BB.

Shell technique using a rigid resorbable barrier system for localized alveolar ridge augmentation.

OBJECTIVES: To assess the safety and efficacy of a rigid synthetic barrier system in a shell technique for localized alveolar ridge augmentation. MATERIALS AND METHODS: Saddle-type defects (n = 4 each) were prepared in the lower jaws of six fox hounds. At two defects, the outer contours were reconstructed using polylactic acid (D and L isomers) (PDDL) pins welded to PDDL plates by ultrasound vibration and the defect area filled using either a natural bone mineral (NBM) or NBM + autogenous bone (AB) and covered by a native collagen membrane (CM). While the third defect was augmented using NBM+AB+CM, the fourth site was left untreated. At 14 weeks, dissected blocks were processed for histomorphometrical analysis [e.g., augmented area (AA)]. RESULTS: AA values (median in mm(2)) were significantly increased in all guided bone regeneration (GBR) groups [NBM+PDDL+CM (19.74) > NBM+AB+PDDL+CM (16.98) > NBM+AB+CM (16.66)] when compared with the untreated control sites (7.34). Histological analysis has pointed, in the absence of any foreign-body reactions, to biodegradation of both PDDL plates/pins and CM. CONCLUSIONS: (i) All GBR procedures investigated equally supported bone regeneration, (ii) the application of PDDL+CM may be associated with increased mineralized tissue MT and subsequently AA values than CM alone, and (iii) AB may not improve healing at NBM+PDDL+CM-treated sites.

Use of a self-curing resorbable polymer in vertical ridge augmentations - a pilot study in dogs.

AIM: The aim of the present study was to evaluate bone formation in vertical ridge augmentations using particulate bone grafting material stabilized by a resorbable polymer. MATERIAL AND METHODS: Three vertical defects were created in the maxillary alveolar ridge of six Beagle dogs 3 months after the removal of all premolars. One defect in each dog was filled with tricalciumphosphate/hydroxylapatite (TCP/HA) grafting material and stabilized using a poloxamer hydrogel (test group). Defects filled with grafting material only and covered with a collagen membrane as well as empty defects served as controls (controls 1 & 2). Bone formation in the defects was evaluated after 14 weeks of healing using histomorphometry on undecalcified thick-section specimens. RESULTS: There was no difference between the test group and the controls with respect to the amount of newly formed bone, percentage of bone fill, and bone density. The mean maximum bone height within the augmented area was the only parameter that was significantly higher in the test group compared with empty defects. The use of the poloxamer gel did not result in a better preservation of ridge shape compared with the group of augmentations covered with a collagen membrane. CONCLUSIONS: The use of a poloxamer gel for the stabilization of particulate bone grafting material in vertical ridge augmentations had no advantage compared with coverage of grafting materials with a collagen membrane.

Immunohistochemical analysis of staged guided bone regeneration and osseointegration of titanium implants using a polyethylene glycol membrane.

OBJECTIVES: This study aimed to immunohistochemically evaluate staged guided bone regeneration and osseointegration of titanium implants using two bone graft substitutes in combination with a polyethylene glycol (PEG) membrane in a dog model. MATERIALS AND METHODS: Saddle-type alveolar ridge defects were prepared in the lower jaws of 12 foxhounds and randomly filled with a natural bone mineral (NBM) or a biphasic calcium phosphate (SBC) and covered with an in situ gelling PEG membrane. After a healing period of 8 and 12 weeks (six animals each), modSLA titanium implants were inserted to heal in a submerged position. At 8 + 2 and 12 + 2 weeks, respectively, dissected blocks were processed for immunohistochemical analysis [osteocalcin (OC)]. RESULTS: After 8 + 2 weeks, mean OC values (%) tended to be higher in the NBM group (NBM, 32.7 ± 8.9%), but failed to reach statistical significance over the SBC group (SBC, 24.4 ± 6.6%). After 12 + 2 weeks, mean OC values decreased in both groups and was almost identical in both groups (NBM 1.6 ± 1.2%/SBC 2.1 ± 1.4%). CONCLUSION: It was concluded that all augmentation procedures investigated were characterised by a comparable OC activity during the process of bone regeneration and osseointegration of modSLA titanium implants.