Deproteinized Bovine Bone Mineral or Autologous Bone at Dehiscence Type Defects at Implants Installed Immediately into Extraction Sockets: An Experimental Study in Dogs.

PURPOSE: The aim of this study was to evaluate bone regeneration at surgically created dehiscence buccal defects at implants placed immediately into extraction sockets (IPIES) of small dimensions filled with autogenous bone or deproteinized bovine bone mineral (DBBM) associated with a collagen membrane. MATERIALS AND METHODS: Eight Labrador dogs were used and implants were placed immediately into the extraction sockets of the second premolar. The buccal wall was subsequently removed to create a standardized defect, 4 mm wide coronally, 2 mm wide apically, and 6 mm high. Autogenous bone particles (AB) or DBBM granules were used to fill the defects. All surgical sites were subsequently covered by a resorbable collagen membrane and a non-submerged healing was allowed. After 4 months, the animals were euthanized and bone blocks harvested and processed for histomorphometric analysis. RESULTS: The bony crest at the buccal aspect (C) was located 2.3 ± 0.8 mm and 1.7 ± 0.7 mm apically to the implant shoulder (IS) at the AB and DBBM sites, respectively. The coronal levels of osseointegration at the buccal aspect (B) were located 2.7 ± 0.7 mm and 2.2 ± 1.0 mm apically to IS at the AB and DBBM sites, respectively. At the AB sites, the peri-implant mucosa was located 4.3 ± 0.9 mm, 4.7 ± 0.9 mm, and 2.0 ± 1.6 mm coronally to C, B, and IS, respectively. The corresponding values at the DBBM sites were 4.3 ± 0.6 mm, 4.8 ± 0.6 mm, and 2.5 ± 0.8 mm, respectively. No statistically significant differences were found. CONCLUSIONS: The treatment of surgically created buccal defects at IPIES sites using Bio-Oss® (Geistlich Biomaterials, Wolhusen, LU, Switzerland) or autogenous bone, concomitantly with a collagen membrane, engenders bone regeneration to a similar extent after 4 months of healing.

Hard and soft tissue changes around implants installed in regular-sized and reduced alveolar bony ridges. An experimental study in dogs.

OBJECTIVE: To study bony and soft tissue changes at implants installed in alveolar bony ridges of different widths. MATERIAL AND METHODS: In 6 Labrador dogs, the mandibular premolars and first molars were extracted, and a buccal defect was created in the left side at the third and fourth premolars by removing the buccal bone and the inter-radicular and interdental septa. Three months after tooth extraction, full-thickness mucoperiosteal flaps were elevated, and implants were installed, two at the reduced (test) and two at the regular-sized ridges (control). Narrow or wide abutments were affixed to the implants. After 3 months, biopsies were harvested, and ground sections prepared for histological evaluation. RESULTS: A higher vertical buccal bony crest resorption was found at the test (1.5 ± 0.7 mm and 1.0 ± 0.7 mm) compared to the control implants (1.0 ± 0.5 mm and 0.7 ± 0.4 mm), for both wide and narrow abutment sites. A higher horizontal alveolar resorption was identified at the control compared to the test implants. The difference was significant for narrow abutment sites. The peri-implant mucosa was more coronally positioned at the narrow abutment, in the test sites, while for the control sites, the mucosal adaptation was more coronal at the wide abutment sites. These differences, however, did not reach statistical significance. CONCLUSIONS: Implants installed in regular-sized alveolar ridges had a higher horizontal, but a lower vertical buccal bony crest resorption compared to implants installed in reduced alveolar ridges. Narrow abutments in reduced ridges as well as wide abutments in regular-sized ridges yielded less soft tissue recession compared to their counterparts.

A digital evaluation of alveolar ridge preservation at implants placed immediately into extraction sockets: an experimental study in the dog.

OBJECTIVE: To compare with pristine sites bone resorption and soft tissue adaptation at implants placed immediately into extraction sockets (IPIES) in conjunction with deproteinized bovine bone mineral (DBBM) particles and a collagen membrane. MATERIAL AND METHODS: The mesial root of the third premolar in the left side of the mandible was endodontically treated (Test). Flaps were elevated, the tooth hemi-sectioned, and the distal root removed to allow the immediate installation of an implant into the extraction socket in a lingual position. DBBM particles were placed into the defect and on the outer contour of the buccal bony ridge, concomitantly with the placement of a collagen membrane. A non-submerged healing was allowed. The premolar on the right side of the mandible was left in situ (control). Ground sections from the center of the implant as well as from the center of the distal root of the third premolar of the opposite side of the mandible were obtained. The histological image from the implant site was superimposed to that of the contralateral pristine distal alveolus, and dimensional variation evaluated for the hard tissue and the alveolar ridge. RESULTS: After 3 months of healing, both histological and photographic evaluation revealed a reduction of hard and soft tissue dimensions. CONCLUSION: The contour augmentation performed with DBBM particles and a collagen membrane at the buccal aspects of implants placed IPIES was not able to maintain the tissue volume.

Sequential healing of the elevated sinus floor after applying autologous bone grafting: an experimental study in minipigs.

AIM: To describe the sequential healing after elevation of the maxillary sinus mucosa applying the lateral access technique with the use of autogenous bone grafting without membrane to occlude the osteotomy access. MATERIAL AND METHODS: Immediately after the elevation of the maxillary sinus Schneiderian membrane, applying the lateral access technique in 10 minipigs, autologous bone was harvested from the lateral aspect of the mandibular molar region and ground into particles with a bone mill. The space under the Schneiderian membrane was filled with this graft. No membranes were placed onto the access osteotomy. The healing was evaluated after 15, 30, 90 and 180 days. Paraffin sections were prepared and analyzed histologically. RESULTS: After 15 days of healing, the elevated area was mainly filled with provisional matrix, newly formed bone and some remnants of bone chips, and appeared reduced in volume compared with that at the time of surgery. After 30 days of healing, further shrinkage of the height of the elevated space was found, with similar percentages of the different tissue components. After 90 and 180 days, the area underneath the Schneiderian membrane appeared reduced in volume and condensed toward the base of the sinus. The bone tissues appeared to be more mature, both for the mineralized and the non-mineralized portions, while connective tissue occupied 20% of the space, most likely related to the lack of the use of a membrane occluding the access at the time of surgery. CONCLUSIONS: Suboptimal healing outcomes with respect to augmentation of the space under the sinus floor membrane were documented when autologous bone chips were used as a filler and no membrane was applied to cover the access.

Osseointegration at implants placed into delayed reimplanted roots: an experimental study in dogs.

AIM: To evaluate peri-implant bone repair of implants placed into the roots of delayed reimplanted teeth, in a process of ankylosis and external replacement resorption. MATERIAL AND METHODS: The third and fourth mandibular premolars of four (4) beagle dogs were used as experimental sites. The study was divided into three stages: stage 1 - endodontic and extraction/reimplantation session, stage 2 - decrowning session and stage 3 - implant placement. Two groups were identified: (I) immediate implants, including implants installed in fresh extraction sockets of the distal roots, and (II) experimental implants, including implants installed into the retained ankylotic mesial roots. In each group, 16 implants were planned to be inserted, but only 9 immediate implants and 12 experimental implants were used for analyses. Implants were intended to heal in a submerged mode. After 4 months of healing, the animals were sacrificed and ground sections were obtained for histomorphometric evaluation. RESULTS: Eleven of the twelve implants in the experimental group were found successful regarding clinical and radiographic aspects. For immediate implants, a lower BIC% was found at the coronal portion (BIC% 1 = 42.2%) compared with the three most coronal threads portion (BIC% 2 = 55.1). Also, experimental implants presented a lower BIC% at the coronal portion (BIC% 1 = 36.9%) compared with the three most coronal threads portion (BIC% 2 = 45.3). CONCLUSION: Comparison between groups showed a higher degree of BIC% and mineralization in immediate group compared with experimental group. The differences, however, did not yield statistical significance.

Influence of presence or absence of teeth adjacent to implants installed immediately into extraction sockets on peri-implant hard tissue levels: an experimental study in the dog.

AIM: To evaluate the influence of the presence or absence of adjacent teeth on the level of the mesial and distal alveolar bony crest following healing at sites where implants were installed immediately into extraction sockets. MATERIAL AND METHODS: Six Labrador dogs were used. In the right side of the mandible, full-thickness flaps were elevated, and the second, third, and fourth premolars and first molars were extracted. In the left side of the mandible, endodontic treatments of the mesial roots of the third and fourth premolars as well as of the first molars were performed. Full-thickness flaps were elevated, the teeth were hemi-sected, and the distal roots were removed. The second premolars were extracted as well. Subsequently, implants were bilaterally installed with the implant shoulder flush with the buccal bony crest. Implants were placed in the center of the alveoli, but at the fourth premolars, they were placed toward the lingual bony plate of the alveoli. After 3 months of healing, the animals were euthanized and histological sections of the sites prepared. RESULTS: Larger bony crest resorption was observed at the test compared with the control sites, both at the bucco-lingual and mesio-distal aspects. The differences between test and controls for the coronal level of osseointegration were smaller than those for resorption. When data from all mesial and distal sites facing an adjacent tooth were collapsed and compared with those opposing an edentulous zone, lower bony crest resorption and deeper residual marginal defects were found at the sites with neighboring teeth. CONCLUSION: The extraction of teeth adjacent to a socket into which implants were installed immediately after tooth extraction caused more alveolar bone resorption both for the bucco-lingual and at the mesio-distal aspects compared with sites adjacent to a maintained tooth.

Deproteinized bovine bone mineral in marginal defects at implants installed immediately into extraction sockets: an experimental study in dogs.

AIM: To evaluate the influence of deproteinized bovine bone mineral (DBBM) particles concomitant with the placement of a collagen membrane on alveolar ridge preservation and on osseointegration of implants placed into alveolar sockets immediately after tooth extraction. MATERIAL AND METHODS: The pulp tissue of the mesial roots of (3) P(3) was removed in six Labrador dogs and the root canals were filled. Flaps were elevated in the right side of the mandible, and the buccal and lingual alveolar bony plates were exposed. The third premolar was hemi-sectioned and the distal root was removed. A recipient site was prepared and an implant was placed lingually. After implant installation, defects of about 0.6 mm wide and 3.1 mm depth resulted at the buccal aspects of the implant, both at the test and at the control sites. The same surgical procedures and measurements were performed on the left side of the mandible. However, DBBM particles with a size of 0.25-1 mm were placed into the remaining defect concomitant with the placement of a collagen membrane. RESULTS: All implants were integrated into mature bone. No residual DBBM particles were detected at the test sites after 4 months of healing. Both the test and the control sites showed buccal alveolar bone resorption, 1.8 ± 1.1 and 2.1 ± 1 mm, respectively. The most coronal bone-to-implant contact at the buccal aspect was 2 ± 1.1 an 2.8 ± 1.3 mm, at the test and the control sites, respectively. This difference in the distance was statistically significant. CONCLUSION: The application of DBBM concomitant with a collagen membrane to fill the marginal defects around implants placed into the alveolus immediately after tooth extraction contributed to improved bone regeneration in the defects. However, with regard to buccal bony crest preservation, a limited contribution of DBBM particles was achieved.

Bone healing pattern in surgically created circumferential defects around submerged implants: an experimental study in dog.

OBJECTIVE: To describe the healing of marginal defects below or above 1 mm of dimension around submerged implants in a dog model. MATERIAL AND METHODS: In 12 Labrador dogs, all mandibular premolars and first molars were extracted bilaterally. After 3 months of healing, full-thickness flaps were elevated in the edentulous region of the right side of the mandible. Two recipient sites were prepared and the marginal 5 mm were widened to such an extent to obtain, after implant installation, a marginal gap of 0.5 mm at the mesial site (small defect) and of 1.25 mm at the distal site (large defect). Titanium healing caps were affixed to the implants and the flaps were sutured allowing a fully submerged healing. The experimental procedures were subsequently performed in the left side of the mandible. The timing of the experiments and sacrifices were planned in such a way to obtain biopsies representing the healing after 5, 10, 20 and 30 days. Ground sections were prepared and histomorphometrically analyzed. RESULTS: The filling of the defect with newly formed bone was incomplete after 1 month of healing in all specimens. Bone formation occurred from the base and the lateral walls of the defects. A larger volume of new bone was formed in the large compared with the small defects. Most of the new bone at the large defect was formed between the 10- and the 20-day period of healing. After 1 month of healing, the outline of the newly formed bone was, however, located at a similar distance from the implant surface (about 0.4 mm) at both defect types. Only minor newly formed bone in contact with the implant, starting from the base of the defects, was seen at the large defects (about 0.8 mm) while a larger amount was detected at the small defects (about 2.2 mm). CONCLUSION: Marginal defects around titanium implants appeared to regenerate in 20-30 days by means of a distance osteogenesis. The bone fill of the defects was, however, incomplete after 1 month.

Influence of implants with different sizes and configurations installed immediately into extraction sockets on peri-implant hard and soft tissues: an experimental study in dogs.

AIM: To study the influence on the healing of soft and hard peri-implant tissues when implants of different sizes and configurations were installed into sockets immediately after tooth extraction. MATERIAL AND METHODS: Transmucosal cylindrical implants, 3.3 mm in diameter in the control sites, and conical 5 mm in diameter in the test sites, were installed into the distal socket of the fourth mandibular premolars in dogs immediately after tooth extraction. After 4 months, the hard and soft tissue healing was evaluated histologically. RESULTS: All implants were integrated in mineralized mature bone. Both at the test and control sites, the alveolar crest underwent resorption. The buccal bony surface at the implant test sites (conical; 3.8 mm) was more resorbed compared with the control sites (cylindrical; 1.6 mm). The soft tissue dimensions were similar in both groups. However, in relation to the implant shoulder, the peri-implant mucosa was located more apically at the test compared with the control sites. CONCLUSION: The present study confirmed that the distance between the implant surface and the outer contour of the buccal alveolar bony crest influenced the degree of resorption of the buccal bone plate. Consequently, in relation to the implant shoulder, the peri-implant mucosa will be established at a more apical level, if the distance between the implant surface and the outer contour of the alveolar crest is small.

Bone regeneration at implants placed into extraction sockets of maxillary incisors in dogs.

AIM: To compare the influence of autologous or deproteinized bovine bone mineral as grafting material on healing of buccal dehiscence defects at implants installed immediately into the maxillary second incisor extraction socket in dogs. MATERIAL AND METHODS: In the maxillary second incisor sockets of 12 Labrador dogs, implants were installed immediately following tooth extraction. A standardized buccal defect was created and autologous bone particles or deproteinized bovine bone mineral were used to fill the defects. A collagen membrane was placed to cover the graft material, and the flaps were sutured to fully submerge the experimental areas. Six animals were sacrificed after 2 months, and six after 4 months of healing. Ground sections were obtained for histological evaluation. RESULTS: After 2 months of healing, all implants were osseointegrated. All buccal dehiscence defects were completely filled after 2 months irrespective of the augmentation material (autologous bone or Bio-Oss(®)) applied. Bone-to-implant contact (BIC) on the denuded implant surfaces was within a normal range of 30-40%. However, the newly formed tissue at 2 months was partially resorbed (>50% of the area measurements) after 4 months. CONCLUSIONS: Applying either autologous bone or deproteinized bovine bone mineral to dehiscences at implants installed immediately into extraction sockets resulted in high degree of regeneration of the defects with satisfactory BIC on the denuded implant surface.

Influence of various implant platform configurations on peri-implant tissue dimensions: an experimental study in dog.

AIM: To evaluate the influence (i) of various implant platform configurations and (ii) of implant surface characteristics on peri-implant tissue dimensions in a dog model. MATERIAL AND METHODS: Mandibular premolars and first molars were extracted bilaterally in six Labrador dogs. After 3 months of healing, two implants, one with a turned and a second with a moderately rough surface, were installed on each side of the mandible in the premolar region. On the right side of the mandible, implants with a tapered and enlarged platform were used, while standard cylindrical implants were installed in the left side of the mandible. Abutments with the diameter of the cylindrical implants were used resulting in a mismatch of 0.25 mm at the tapered implant sites. The flaps were sutured to allow a non-submerged healing. After 4 months, the animals were sacrificed and ground sections were obtained for histometric assessment. RESULTS: All implants were completely osseointegrated. A minimal buccal bone resorption was observed for both implant configurations and surface topographies. Considering the animals as the statistical unit, no significant differences were found at the buccal aspect in relation to bone levels and soft tissue dimensions. The surface topographies did not influence the outcomes either. CONCLUSIONS: The present study failed to show differences in peri-implant tissue dimensions when a mismatch of 0.25 mm from a tapered platform to an abutment was applied. The surface topographies influence a neither marginal bone resorption or peri-implant soft tissue dimension.

Avaliação do padrão de reparação óssea ao redor de implantes submersos: estudo experimental em cães / Bone healing pattern around submerged implants: an experimental study in dogs

Objetivo: estudar as fases iniciais da regeneração óssea de implantes instalados sobre a crista óssea alveolar desdentada. Material e Métodos: Em 12 cães labradores, foram extraídos bilateralmente todos os pré-molares inferiores e primeiros molares. Após 3 meses de regeneração, foi realizada a incisão sobre o rebordo alveolar desdentado do lado direito da mandíbula e descolamento do retalhos de espessura total. Foram instalados dois implantes e finalizado com a suturas dos retalhos para permitir a regeneração totalmente submersa. Posteriormente, foram realizados os mesmos procedimentos experimentais no lado esquerdo da mandíbula. Os sacrifícios dos animais foram planejados de forma a obter biópsias com pós-operatórios de 5, 10, 20 e 30 dias. Um implante de cada lado da mandíbula foi processado laboratorialmente para cortes histológicos em tecido mineralizado (inclusão em resina) e outro para cortes histológicos em tecido desmineralizado (inclusão em parafina). Resultados: Foi observada apenas uma reação celular importante ao redor do implante no compartimento da medula óssea. Observou-se a formação de matriz óssea provisória e, posteriormente, osso esponjoso ao redor e em contato com o implante. O contato osso-implante melhorou durante os períodos de regeneração avaliados. Conclusão: Com este estudo pode-se mostrar que a preparação do sítio cirúrgico e a instalação do implante produziram reação celular evidente no osso circunjacente. No compartimento da medula óssea, a aposição de matriz óssea provisória e formação de osso esponjoso ocorreram sequencialmente durante o primeiro mês de pós- operatório. Na região em que o osso apresentou contato com a superfície do implante, os processos de remodelação óssea (reabsorção e aposição óssea) ocorreram através da intervenção das BMUs (Bone Multicellular Units)

Objective: the purpose of the present study was to evaluate the early phases of bone response to implants installed in edentulous alveolar bony crest. Material & Method: In 12 Labrador dogs, all mandibular premolars and first molars were extracted bilaterally. After 3 months of healing, full-thickness flaps were elevated in the edentulous region of the right side of the mandible. Two implants were installed and the flaps were sutured to allow a fully-submerged healing. The experimental procedures were subsequently performed in the left side of the mandible. The timing of the experiments and sacrifices were planned in such a way to obtain biopsies representing the healing after 5, 10, 20, 30 days. One implant from each side of the mandible was processed for ground sections and the other for paraffin sections. Results: only an important cellular reaction was observed around the implant in the bone marrow compartment. Provisional matrix and, subsequently, woven bone were formed around and in contact with the implant. Bone-to-implant contact improve duign the healing period. Conclusions: In conclusion, the present experiment showed that site preparation and implant placement produced an evident cellular reaction within the surrounding bone. In the bone marrow compartment, provisional matrix apposition and woven bone formation occurred sequentially during the first month of healing. Where mineralized bone was in contact with the implant surface, bone remodeling processes (bone resorption and apposition) occurred through the intervention of BMUs (Bone Multicellular Units)

Avaliação do padrão de reparação óssea ao redor de implantes submersos: estudo experimental em cães / Bone healing pattern around submerged implants: an experimental study in dogs

Objetivo: estudar as fases iniciais da regeneração óssea de implantes instalados sobre a crista óssea alveolar desdentada. Material e Métodos: Em 12 cães labradores, foram extraídos bilateralmente todos os pré-molares inferiores e primeiros molares. Após 3 meses de regeneração, foi realizada a incisão sobre o rebordo alveolar desdentado do lado direito da mandíbula e descolamento do retalhos de espessura total. Foram instalados dois implantes e finalizado com a suturas dos retalhos para permitir a regeneração totalmente submersa. Posteriormente, foram realizados os mesmos procedimentos experimentais no lado esquerdo da mandíbula. Os sacrifícios dos animais foram planejados de forma a obter biópsias com pós-operatórios de 5, 10, 20 e 30 dias. Um implante de cada lado da mandíbula foi processado laboratorialmente para cortes histológicos em tecido mineralizado (inclusão em resina) e outro para cortes histológicos em tecido desmineralizado (inclusão em parafina). Resultados: Foi observada apenas uma reação celular importante ao redor do implante no compartimento da medula óssea. Observou-se a formação de matriz óssea provisória e, posteriormente, osso esponjoso ao redor e em contato com o implante. O contato osso-implante melhorou durante os períodos de regeneração avaliados. Conclusão: Com este estudo pode-se mostrar que a preparação do sítio cirúrgico e a instalação do implante produziram reação celular evidente no osso circunjacente. No compartimento da medula óssea, a aposição de matriz óssea provisória e formação de osso esponjoso ocorreram sequencialmente durante o primeiro mês de pós- operatório. Na região em que o osso apresentou contato com a superfície do implante, os processos de remodelação óssea (reabsorção e aposição óssea) ocorreram através da intervenção das BMUs (Bone Multicellular Units)

Objective: the purpose of the present study was to evaluate the early phases of bone response to implants installed in edentulous alveolar bony crest. Material & Method: In 12 Labrador dogs, all mandibular premolars and first molars were extracted bilaterally. After 3 months of healing, full-thickness flaps were elevated in the edentulous region of the right side of the mandible. Two implants were installed and the flaps were sutured to allow a fully-submerged healing. The experimental procedures were subsequently performed in the left side of the mandible. The timing of the experiments and sacrifices were planned in such a way to obtain biopsies representing the healing after 5, 10, 20, 30 days. One implant from each side of the mandible was processed for ground sections and the other for paraffin sections. Results: only an important cellular reaction was observed around the implant in the bone marrow compartment. Provisional matrix and, subsequently, woven bone were formed around and in contact with the implant. Bone-to-implant contact improve duign the healing period. Conclusions: In conclusion, the present experiment showed that site preparation and implant placement produced an evident cellular reaction within the surrounding bone. In the bone marrow compartment, provisional matrix apposition and woven bone formation occurred sequentially during the first month of healing. Where mineralized bone was in contact with the implant surface, bone remodeling processes (bone resorption and apposition) occurred through the intervention of BMUs (Bone Multicellular Units)

Influence of lateral pressure to the implant bed on osseointegration: an experimental study in dogs.

AIM: To study osseointegration and bone-level changes at implants installed using either a standard or a reduced diameter bur for implant bed preparation. MATERIAL AND METHODS: In six Labrador dogs, the first and second premolars were extracted bilaterally. Subsequently, mesial roots of the first molars were endodontically treated and distal roots, including the corresponding part of the crown, were extracted. After 3 months of healing, flaps were elevated and recipient sites were prepared in all experimental sites. The control site was prepared using a standard procedure, while the test site was prepared using a drill with a 0.2 mm reduced diameter than the standard one used in the contra-lateral side. After 4 months of healing, the animals were euthanized and biopsies were obtained for histological processing and evaluation. RESULTS: With the exception of one implant that was lost, all implants were integrated in mineralized bone. The alveolar crest underwent resorption at control as well as at test sites (buccal aspect ∼1 mm). The most coronal contact of bone-to-implant was located between 1.2 and 1.6 mm at the test and between 1.3 and 1.7 mm at the control sites. Bone-to-implant contact percentage was between 49% and 67%. No statistically significant differences were found for any of the outcome variables. CONCLUSIONS: After 4 months of healing, lateral pressure to the implant bed as reflected by higher insertion torques (36 vs. 15 Ncm in the premolar and 19 vs. 7 Ncm in the molar regions) did not affect the bone-to-implant contact.