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.

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.

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.

Horizontal mucosal thickness at implant sites as it correlates with the integrity and thickness of the buccal bone plate.

OBJECTIVES: To histologically assess the association between the horizontal mucosal thickness (MT) at implant sites with the integrity and thickness of the buccal bone plate in a canine model. MATERIALS AND METHODS: Two-piece titanium implants were placed at chronic-type lateral ridge defects. The resulting vestibular dehiscence-type defects (vertical dimensions of 2-8 mm) were left untreated. After a submerged healing period of 2 and 8 weeks (n = 6 fox hounds each), dissected blocks were processed for histomorphometrical analyses [e.g. MT, bone thickness (BT) and residual defect length]. RESULTS: Linear regression revealed significant associations between vestibular MT and BT values after 2 (R2  = 0.22, B = -0.37, P < 0.0001) and 8 weeks (R2  = 0.37, B = -0.45, P < 0.001) of healing. CONCLUSION: The present analysis has pointed to an inverse relationship between horizontal MT and BT values at the vestibular aspect of submerged titanium implants. MT was most pronounced in the absence of a buccal bone plate.

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.

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.

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.

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.

Immunohistochemical characteristics of regenerated bone after surgical therapy of advanced ligature-induced peri-implantitis defects.

OBJECTIVES: This study seeks to assess and compare immunohistochemical characteristics of regenerated and pristine bone areas following surgical therapy of advanced peri-implantitis. METHODS: At ligature-induced peri-implantitis defects, the intrabony component was filled with a natural bone mineral (NBM), and the supracrestal component was treated by either an equine bone block (EB) or implantoplasty. NBM and EB were soak-loaded with rhBMP-2 or sterile saline. Membrane (i.e., native collagen) protected sites were submerged for 12 weeks. Osteocalcin (OC) and transglutaminase 2 (TG2; angiogenesis) antigen reactivity was assessed within the augmented-(AA) and pristine bone (PB) areas at non-exposed sites (n = 39 defects). RESULTS: In all groups investigated, mean OC (AA, 0.5 ± 0.4 to 1.9 ± 2.9 %/PB, 1.7 ± 2.6 to 3.5 ± 6.5 %) and TG2 (AA, 0.6 ± 0.5 to 1.3 ± 1.5 %/PB, 0.5 ± 0.5 to 1.6 ± 1.9 %) values within AA did not significantly differ from those values assessed within PB (P > 0.05, respectively). CONCLUSIONS: AA formed in different treatment groups may not be considered as qualitatively (i.e., OC and TG2) compromised bone.

The impact of dis-/reconnection of laser microgrooved and machined implant abutments on soft- and hard-tissue healing.

OBJECTIVES: To (i) investigate the influence of different extensions of a laser microgrooved abutment zone on connective tissue attachment and (ii) assess the impact of a repeated abutment dis-/reconnection on soft- and hard-tissue healing. MATERIALS AND METHODS: Titanium implants were inserted epicrestally in the lower jaws of six dogs. Healing abutments with either partially (LP) or completely (LC) laser microgrooved margins or machined surface margins (M) were randomly allocated either to a single (1×)/repeated (2×) dis-/reconnection at 4 and 6 weeks (test), respectively, or left undisturbed (control). At 6 and 8 weeks, histomorphometrical (e.g. most coronal level of bone in contact with the implant [CBI], subepithelial connective tissue attachment [STC]) and immunohistochemical (Collagen Type-I [CI]) parameters were assessed. RESULTS: At control sites, LP/LC groups revealed lower mean CBL (8 weeks, 0.95 ± 0.51 vs. 0.54 ± 0.63 vs. 1.66 ± 1.26 mm), higher mean STC (8 weeks, 82.58 ± 24.32% vs. 96.37 ± 5.12% vs. 54.17 ± 8.09%), but comparable CI antigen reactivity. A repeated abutment manipulation was associated with increased mean CBL (8 weeks, 1.53 ± 1.09 vs. 0.94 ± 0.17 vs. 1.06 ± 0.34 mm), decreased STC (8 weeks, 57.34 ± 43.06% vs. 13.26 ± 19.04% vs. 37.76 ± 37.08%) and CI values. CONCLUSIONS: It was concluded that (i) LC>LP abutments enhanced subepithelial connective tissue attachment and preserved crestal bone levels, (ii) repeated abutment dis-/reconnection during the initial healing phase (4-6 weeks) may be associated with increased soft- and hard-tissue changes and (iii) LP and LC should be considered using a one abutment, one time approach.

Accuracy of peri-implant bone thickness and validity of assessing bone augmentation material using cone beam computed tomography.

OBJECTIVES: The aim of this study was to evaluate the accuracy of measuring bone thickness surrounding dental implants and the reliability of assessing existence and completion of osseous integration of augmentation material using a cone beam computed tomography (CBCT) system. MATERIALS AND METHODS: In jaws of foxhounds, artificial defects were regenerated by guided bone regeneration and then dental implants were placed. After putting down the dogs, the jaws were separated from the bodies and exposed in a CBCT system. The bone thickness was measured on both buccal and oral sides of the implants at different levels. Every examiner evaluated existence and integration of bone augmentation materials (BAM) and the completeness of marginal implant covering. The same measurements and evaluations were performed at digital images of the corresponding histological sections. RESULTS: The mean and the standard deviation of the differences between radiological and histological measurements of peri-implant bone thickness were -0.22 mm and 0.77 mm, respectively. Sensitivity and specificity were 0.77 and 0.60 for existence of BAM, 0.59 and 0.74 for completed integration, and 0.39 and 0.71 for full covering of the implant surface. CONCLUSIONS: The present study indicates that the PaX Duo3D(®) CBCT system allows measurements of peri-implant bone thickness at an accuracy of half a millimeter, and--within limits--assessing the existence and integration of BAM. It is not possible to evaluate whether the implant is covered completely by hard tissue. CLINICAL RELEVANCE: Peri-implant bone thickness is a key factor for obtaining initial implant stability. The accuracy of its measurement has clinical impact. Radiological assessment of existence and integration of BAM would be of great benefit to the evaluation of augmentation procedures.

Impact of abutment material and dis-/re-connection on soft and hard tissue changes at implants with platform-switching.

OBJECTIVES: To assess the impact of abutment material and dis-/re-connection on soft and hard tissue changes at implants with platform-switching. MATERIAL & METHODS: Titanium implants (n = 12), placed epicrestally in the upper jaws of three dogs, were connected with titanium (Ti) and zirconium dioxide (ZrO(2) ) abutments (horizontal mismatch of 0.4 mm) and randomly allocated in a split-mouth design either to repeated (2x) dis-/re-connection at 4 and 6 weeks (test), respectively, or left undisturbed (control). At 8 weeks, histomorphometrical measurements were made between the mucosal margin (PM), implant shoulder (IS) and the apical extension of the long junctional epithelium (aJE),-the most coronal level of bone in contact with the implant (CBI). RESULTS: Repeated abutment manipulation was associated with increased mean PM-aJE and IS-CBI values at both Ti (1.82 ± 0.37-1.99 ± 0.40 mm and 0.72 ± 0.18-1.12 ± 0.60 mm) and ZrO(2) (1.90 ± 0.28-2.67 ± 0.67 mm and 0.22 ± 0.10-2.15 ± 0.77 mm) abutments at 8 weeks. These vertical dimensions were comparable at both vestibular and oral aspects. Between group comparisons, however, failed to reveal a significant difference between test and control sites. CONCLUSIONS: Repeated manipulation may be associated with dimensional changes of peri-implant soft and hard tissues formed at both non-matching Ti and ZrO(2) abutments.

Influence of two barrier membranes on staged guided bone regeneration and osseointegration of titanium implants in dogs: part 1. Augmentation using bone graft substitutes and autogenous bone.

OBJECTIVES: To assess the influence of two barrier membranes and two bone graft substitutes mixed with autogenous bone (AB) on staged guided bone regeneration and osseointegration of titanium implants in dogs. MATERIALS AND METHODS: Four saddle-type defects each were prepared in the upper jaw of six fox hounds and randomly filled with a natural bone mineral (NBM)+AB and a biphasic calcium phosphate (SBC)+AB and allocated to either an in situ gelling polyethylene glycol (PEG) or a collagen membrane (CM). At 8 weeks, modSLA titanium implants were inserted and left to heal in a submerged position. At 8+2 weeks, dissected blocks were processed for histomorphometrical analysis (e.g., treated area [TA], bone-to-implant contact [BIC]). RESULTS: The mean TA values (mm(2) ) and BIC values (%) tended to be higher in the PEG groups(TA: NBM+AB [10.4 ± 2.5]; SBC+AB [10.4 ± 5.8]/BIC: NBM+AB [86.4 ± 20.1]; SBC+AB [80.1 ± 21.5]) when compared with the corresponding CM groups (TA: NBM+AB [9.7 ± 4.8]; SBC+AB [7.8 ± 4.3]/BIC: NBM+AB [71.3 ± 20.8]; SBC+AB [72.4 ± 20.3]). A significant difference was observed for the mean TA values in the SBC+AB groups. CONCLUSION: It was concluded that all augmentation procedures investigated supported bone regeneration and staged osseointegration of modSLA titanium implants. However, the application of PEG may be associated with increased TA values.

Influence of two barrier membranes on staged guided bone regeneration and osseointegration of titanium implants in dogs. Part 2: augmentation using bone graft substitutes.

OBJECTIVES: To assess the influence of two barrier membranes and two bone graft substitutes on staged guided bone regeneration and osseointegration of titanium implants in dogs. MATERIALS AND METHODS: Saddle-type defects were prepared in the lower jaws of 6 fox hounds and randomly filled with a natural bone mineral (NBM) and a biphasic calcium phosphate (SBC) and allocated to either an in situ gelling polyethylene glycol (PEG) or a collagen membrane (CM). At 8 weeks, modSLA titanium implants were inserted and left to heal in a submerged position. At 8+2 weeks, respectively, dissected blocks were processed for histomorphometrical analysis (e.g., mineralized tissue [MT], bone-to-implant contact [BIC]). RESULTS: The mean MT values (mm2) and BIC values (%) tended to be higher in the PEG groups (MT: NBM [3.4±1.7]; SBC [4.2±2]/BIC: NBM [67.7±16.9]; SBC [66.9±17.8]) when compared with the corresponding CM groups (MT: NBM [2.5±0.8]; SBC [2.3±1.6]/BIC: NBM [54.1±22.6]; SBC [61±8.7]). These differences, however, did not reach statistical significance. CONCLUSION: It was concluded that all augmentation procedures investigated supported bone regeneration and staged osseointegration of modSLA titanium implants.

Surgical therapy of advanced ligature-induced peri-implantitis defects: cone-beam computed tomographic and histological analysis.

OBJECTIVES: To evaluate radiological bone level (RBL) (i.e. cone-beam computed tomography) and histological bone levels (HBL) as well as re-osseointegration [bone-to-implant contact (BIC)] after surgical resective (i.e. implantoplasty) and/or regenerative therapy of advanced ligature-induced peri-implantitis in dogs. MATERIAL AND METHODS: At all defect sites (n=6 dogs, n=48 implants), the intrabony component was filled with a particulate bovine-derived natural bone mineral (NBM). The supracrestal component was treated by either the application of an equine bone block (EB) or implantoplasty. In a split-mouth design, NBM and EB were soak-loaded with recombinant human bone morphogenetic protein (rhBMP)-2 or sterile saline. All sites were covered by a native collagen membrane and left to heal in a submerged position for 12 weeks. RESULTS: A premature wound exposure was observed at nine defect sites. Mean RBL and HBL values were lowest in the P+rhBMP-2 group, reaching statistical significance when compared with the EB group. Mean BIC values were comparable in all groups. Within-group comparisons commonly revealed a close correlation between RBL and HBL values. CONCLUSIONS: It was concluded that (i) in all groups the investigations failed to predictably obtain complete defect resolution, (ii) the surgical procedure was associated with high exposure rates, and (iii) RBL was closely correlated with HBL.

Biodegradation of different synthetic hydrogels made of polyethylene glycol hydrogel/RGD-peptide modifications: an immunohistochemical study in rats.

AIM: The aim of the present study was to investigate the pattern of biodegradation of different polyethylene glycol (PEG) hydrogel/RGD-peptide modifications in rats. MATERIAL AND METHODS: Two different hydrogels were employed: (i) a combination of four-arm PEG-thiol, M(n)=2.3 kDa, and eight-arm PEG-acrylate, M(n)=2.3 kDa (PEG1); and (ii) a combination of four-arm PEG-thiol, M(n)=2.3 kDa, and four-arm PEG-acrylate, M(n)=15 kDa (PEG2). Both PEG1 and PEG2 were either used alone or combined with a nine amino acid cys-RGD peptide (RGD). A non-cross-linked porcine type I and III collagen membrane [BioGide (BG)] served as control. Specimens were randomly allocated in unconnected subcutaneous pouches separated surgically on the back of 60 wistar rats, which were divided into six groups (1, 2, 4, 8, 16, and 24 weeks). Specimens were prepared for histological (tissue integration, foreign body reactions, biodegradation) and immunohistochemical (angiogenesis) analysis. RESULTS: All materials investigated revealed unimpeded and comparable tissue integration without any signs of foreign body reactions. While BG exhibited transmembraneous blood vessel formation at 1 week, all PEG specimens were just surrounded by a well-vascularized connective tissue. The hydrolytic disruption of PEG1 and PEG1/RGD specimens was associated with an ingrowth of blood vessels at 4 weeks. Biodegradation times were highest for PEG1 (24 weeks)>PEG1/RGD (16 weeks)>BG (4 weeks)>PEG2=PEG2/RGD (2 weeks). CONCLUSION: Within the limits of the present study, it was concluded that (i) all materials investigated revealed a high biocompatibility and tissue integration, and (ii) hydrogel biodegradation was dependent on PEG composition.

Dentointegration of a titanium implant: a case report.

PURPOSE: This case illustrates a pulp tissue-induced dentointegration of a titanium implant. MATERIALS AND METHODS: One commercially available titanium implant with a sand-blasted and acid-etched surface was placed in the maxilla of a foxhound where the palatinal root of the previously (i.e., 8 weeks) removed first molar was unintentionally retained. After 8 weeks of nonsubmerged healing, the dissected block was prepared for immunohistochemical (osteocalcin) and histomorphometrical analysis. RESULTS: A reparative hard tissue had formed within the artificially opened pulp canal. Also, the external layer of the exposed dentin due to the root fracture during tooth removal further developed into an atubular reparative dentin thus establishing a close contact with the adjacent titanium implant surface. The entire contact zone was demarcated by an intense osteocalcin antigen reactivity. A thin layer of osteocementum originated from the root surface and superimposed implant integration in the peripheral areas. Mean contact of osteodentin/osteocementum to the implant surface was 67.4 %, whereas bone-to-implant contact at the vestibular aspect was 63.5 %. CONCLUSION: The present case report provides the first histological evidence for a pulp tissue-induced dentointegration of a titanium implant.

Measurement of mini-implant stability using resonance frequency analysis.

OBJECTIVE: To investigate whether resonance frequency analysis (RFA) is suitable to measure orthodontic mini-implant stability. Implant size significantly affects the level of resonance frequency. Regarding the operating mode of RFA, it has to be proven whether the resonance frequency of mini-implants in bone fits the range of frequency emitted by the Osstell ISQ device. MATERIAL AND METHODS: For this purpose the SmartPegs in the Osstell ISQ device were modified to fit with the inner screw thread of orthodontic mini-implants, and 110 mini-implants were inserted into porcine pelvic bone. RFA was performed parallel and perpendicular to the run of superficial bone fibers. A suitability test, Periotest, was also performed in the same directions. Compacta thickness was measured using cone-beam computed tomography. Correlation tests and linear regression analysis were carried out between the three methods. RESULTS: The RFA showed a mean Implant Stability Quotient value of 36.36 ± 2.67, and the Periotest mean value was -2.10 ± 1.17. The differences between the two directions of measurement were statistically significant (P > .001) for RFA and the Periotest. There was a high correlation between RFA and the Periotest (r  =  -0.90) and between RFA and compacta thickness (r  =  0.71). The comparison between the Periotest and compacta thickness showed a correlation coefficient of r  =  -0.64. CONCLUSION: The present results suggest that RFA is feasible as a measurement method for orthodontic mini-implant stability. As a consequence, it could be used for clinical evaluation of current stability and allow stability-related loading of mini-implants to reduce the failure rate.