Immediate loading of implants in the edentulous mandible: a multicentre study.

PURPOSE: The aim of this prospective study was to investigate the two-year outcomes following immediate loading of mono-cortically engaged implants. MATERIALS AND METHODS: Thirty healthy mandible edentulous patients with an average age of 67.3 years and presenting with sufficient bony ridge at the mandible symphysis were included in the study. Four Astra Tech, Ti-Oblast® implants were installed between the mental foramina using the mono-cortical anchorage technique. The primary stability of the implants was assessed by resonance frequency analysis (RFA). After uni-abutments were placed, a temporary bridge was constructed and fixed the same day. The definitive bridges were installed 6 weeks after implant surgery. Five of 120 placed implants were lost in four patients during the first 6 weeks and these patients were excluded from the follow-up. The changes in marginal bone level (n = 20) were evaluated in Brazilian and Swedish groups at baseline, 6 weeks, 6 months, 12 months and 24 months. The RFA (n = 30) was evaluated at baseline, 6 weeks, 6 months, 12 months and 24 months postoperatively. RESULTS: Compared with baseline measurements, the postoperative values for marginal bone level (6 weeks, 6 months, 12 months and 24 months) were significantly reduced (p < 0.05), while no differences were observed in the RFA analysis (12 months and 24 months). CONCLUSIONS: The immediate loading of mono-cortically engaged implants in the edentulous mandible is safe and predictable and implant stability remains excellent after 2-year follow-up.

Bone Ceramic® at Implants Installed Immediately into Extraction Sockets in the Molar Region: An Experimental Study in Dogs.

PURPOSE: The aim of this paper was to study the healing of 1-1.4 mm wide buccal defects at implants placed immediately into extraction sockets (IPIES) filled with a mixture of synthetic hydroxyapatite (HA) 60% and beta-tricalciumphosphate (TCP) 40% or left with the clot alone and both covered with collagen membranes. MATERIAL AND METHODS: Eight Labrador dogs were used and implants were placed immediately into the extraction sockets of the first molar bilaterally. A mixture of synthetic HA 60% and beta-TCP 40% at the test or the clot alone at the control sites 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, biopsies harvested and processed for histomorphometric analysis. RESULTS: At the time of installation, residual buccal defects occurred that were 1.1 mm and 1.4 mm wide and 3 mm and 4 mm deep at the control and test sites, respectively. After 4 months of healing, the top of the bony crest and the coronal level of osseointegration were located respectively at 0.1 ± 1.8 mm and 1.5 ± 1.8 mm at the test, and 0.6 ± 1.6 mm and 1.2 ± 0.7 mm at the control sites apically to the implant shoulder. Bone-to-implant contact at the buccal aspect was 34.9 ± 25.9% and 36.4 ± 17.3% at the test and control sites, respectively. No statistically significant differences were found between test and control sites for any of the variables analyzed at the buccal aspects. CONCLUSIONS: The use of a mixture of synthetic HA 60% and beta-TCP 40% to fill residual buccal defects 1-1.4 mm wide at IPIES did not improve significantly the results of healing.

Fresh-frozen allografts combined with bovine bone mineral enhance bone formation in sinus augmentation.

We evaluated histologically, histomorphometrically, and tomographically the effects of the association of fresh-frozen bone allograft (FFB) with bovine bone mineral (BBM) in maxillary sinus floor augmentation. In total, 34 maxillary sinuses from 29 patients, with a mean age of 51.32 (±6.44) years, underwent sinus augmentation. Patients were divided into control and test groups (17 sinuses each). The controls were grafted with allograft bone, and the test group received a combination of FFB and BBM at a 2:1 ratio. After 6 months, bone samples were collected for histological and histomorphometric examinations. The implant survival rates were 93.02% (control group) and 100% (test group) at 6 months after functional loading. Median volumetric reductions of 28.32% (17.05-44.05) and 12.62% (5.65-16.87) were observed for the control and test groups, respectively. Statistically significant histomorphometric differences were found between the control and test groups regarding newly formed bone 12.54% (10.50-13.33) vs. 24.42% (17.62-35.92), p < 0.001, total bone 48.34% (39.03-54.42) vs. 61.32% (50.61-64.96), p = 0.007, and connective tissue 51.66% (45.57-60.97) vs. 39.30% (35.03-49.37), p = 0.007. The addition of BBM to allograft bone in maxillary sinus augmentation resulted in higher percentages of new bone formation and total bone, and permitted implant placement with a low rate of osseointegration failure at the 6-month follow-up.

Early Osseointegration Events on Neoss® ProActive and Bimodal Implants: A Comparison of Different Surfaces in an Animal Model.

BACKGROUND: Cell interactions, adherence, and osseointegration at the bone-implant interface can be directly influenced by the surface properties of the titanium implant. PURPOSE: To characterize osseointegration of Neoss® implants with conventional (control group) and hydrophilic (test group) surface treatments. MATERIALS AND METHODS: Six Labrador dogs received Neoss implants with conventional and hydrophilic surfaces. The bone-implant interfaces were evaluated 1 and 4 weeks after implantation, and osseointegration was evaluated using histological, histomorphometric, fluorescence, and resonance frequency analyses. The surfaces were also subjected to topographic and hydrophilicity analyses. RESULTS: The topographic analyses revealed increased surface roughness in the test group compared with the control group (surface area roughness 0.42 and 0.78 µm, respectively, for control and test group surfaces; p ≤ .05). The wettability values were higher in the test group (contact angles 67.2° and 27.2° for the control and test group surfaces, respectively; p ≤ .05). Implants in the test group also exhibited better stability, more bone-implant contact, and increased bone area compared with implants in the control group. CONCLUSION: Neoss implants in the test group improved bone formation in the early stages of osseointegration compared with implants in the control group.

Effects of Photodynamic Process (PDP) in Implant Osseointegration: A Histologic and Histometric Study in Dogs.

BACKGROUND: The combination between photosensitivity substances with laser or light-emitting diode (LED) form the photodynamic therapy basis that consists of photosensitivity drug activated by low-frequency light. This mechanism is used in soft tissue healing process to improve the oxygen tension leading to a fast revascularization. PURPOSE: The objective of this study was to evaluate the effects of photosensitivity drugs activated through LED on osseointegration process. MATERIALS AND METHODS: Eight mongrel dogs underwent implant therapy in four mandibular bone defects using 5.0 mm trephine drill on each side of the mandible. The defects were randomly filled up with (1) Nano emulsion, (2) liposome, (3) blood clot, and (4) autogenous bone. LED with visible and infrared light were applied after 48/72 postoperative hours on four dogs and after 96/120 postoperative hours in the other four dogs. All the animals were euthanized at 15 days after surgery. Ground sections slides were prepared from the experimental site for histomorphometry and histological analysis. RESULTS: No difference was detected in the following parameters: bone-implant contact, bone inside the defect and crest level on LED 48/72. Significant difference was detected inside the defect when filled with autogenous bone (p = .0238) on LED 96/120. When LED 48/72 and LED 96/120 were compared, significant higher bone formation was detected when autogenous bone on bone-implant contact (p = .0043) and bone inside the defect (p = .0008) was used. CONCLUSION: The use of photosensitivity drugs activated by LED demonstrated a tendency to stimulate bone formation, similar to autogenous bone graft on later time point.

Treatment of circumferential defects with osseoconductive xenografts of different porosities: a histological, histometric, resonance frequency analysis, and micro-CT study in dogs.

BACKGROUND: Finding the most effective method of minimizing the gap effect in alveolar crest remodeling constitutes a clinical challenge for immediate implant technique. PURPOSE: To evaluate the effectiveness of osseoconductive xenografts with different porosities in the crestal bone region, with and without guided bone regeneration, over immediate implant installation. MATERIALS AND METHODS: Five bone defects (6 mm in diameter/4 mm depth) were prepared on one side of the mandibles of twelve dogs. Implants of 3.3 × 10 mm were installed on the mesial side of each defect, providing a 2.7-mm distal gap. Defects were randomly filled with autogenous bone, coagulum, a deproteinized bovine bone mineral (DBBM) block, a DBBM sponge, or DBBM granules. The same procedures were performed on the opposite side after 8 weeks. Collagen membranes were used to cover the defects on half of the sides. The animals were sacrificed after 8 weeks. The outcomes were evaluated by histology, histomorphometric analysis, resonance frequency analysis, and micro-CT analysis. RESULTS: The histomorphometry showed the DBBM sponge to provide similar bone formation to autogenous bone at 8 weeks without a membrane. The coagulum rendered better bone formation at 16 weeks (membrane) (p < .05). The DBBM block exhibited the poorest results between treatments (8 and 16 weeks, with or without membrane). Micro-CT analysis revealed increasing bone surface values in sites with DBBM granules, followed by the DBBM sponge (8 weeks without membrane) and autogenous bone at 8 weeks with membrane (p < .05). Porosity analysis of the biomaterials showed the highest number, volume, and surface area of closed pores in DBBM granules. The DBBM block presented the highest volume of open pores, open porosity, and total porosity. CONCLUSIONS: The high-porosity block (DBBM block) failed to provide greater bone repair within the defect. Biomaterials with lower porosity (DBBM sponge and granules) showed similar or higher bone formation when compared with autogenous bone.

Immunohistochemical, tomographic, and histological study on onlay bone graft remodeling. Part III: allografts.

OBJECTIVE: In the last decades aroused the interest for bone tissue bank as an alternative to autogenous grafting, avoiding donor sites morbidity, surgical time, and costs reduction. The purpose of the study was to compare allografts (ALg) with autografts (AUg) using histology, immunochemistry, and tomographic analysis. MATERIAL AND METHODS: Fifty-six New Zealand White rabbits were submitted to surgical procedures. Twenty animals were donors and 36 were actually submitted to onlay grafting with ALg (experimental group) and AUg (control group) randomly placed bilaterally in the mandible. Six animals of each group were sacrificed at 3, 5, 7, 10, 20, and 60 postoperative days. Immunolabeling was accomplished with osteoprotegerin (OPG); receptor activator of nuclear factor-k ligand (RANKL); alkaline phosphatase (ALP); osteopontin (OPN); vascular endothelial growth factor (VEGF); tartrate-resistant acid phosphatase (TRAP); collagen type I (COL I); and osteocalcin (OC). Density and volume of the grafts was evaluated on tomography obtained at the surgery and sacrifice. RESULTS: The ALg and AUg exhibited similar patterns of density and volume throughout the experiments. The intra-group data showed statistical differences at days 7 and 60 in comparison with other time points (P = 0.001), in both groups. A slight graft expansion from fixation until day 20 (P = 0.532) was observed in the AUg group and then resorbed significantly at the day 60 (P = 0.015). ALg volume remained stable until day 7 and decreased at day 10 (P = 0.045). The light microscopy analysis showed more efficient incorporation of AUg onto the recipient bed if compared with the ALg group. The immunohistochemical labeling picked: at days 10 and 20 with OPG in the AUg group and at day 7 with TRAP in the ALg group (P = 0.001 and P = 0.002, respectively). CONCLUSIONS: ALg and AUg were not differing in patterns of volume and density during entire experiment. Histological data exhibit more efficient AUg incorporation into recipient bed compared with the ALg group. Immunohistochemistry outcomes demonstrated similar pattern for both ALg and AUg groups, except for an increasing resorption activity in the ALg group mediated by TRAP and in the AUg group by higher OPG labeling. However, this latter observation does not seem to influence clinical outcomes.

Avaliação da estabilidade do implante pela análise da frequência de ressonância: estudo in vivo com carregamento imediato e precoce em um modelo em cães / Evaluation of implant stability by means of resonance frequency analysis: an in vivo study with immediate and early loading in the dog model

Este estudo teve por objetivo avaliar a estabilidade de implantes de carga imediata ou precoce, em diferentes intervalos de tempo. Material e Métodos: foram extraídos os pré-molares mandibulares, bilateralmente, de oito cães e, após 12 semanas, cada cão recebeu seis implantes (três em cada lado da mandíbula). A carga foi aplicada em pares, em um implante de cada lado, sendo que o primeiro par recebeu carga imediata, o segundo par após sete dias, e o terceiro par após 14 dias. Em cada período, as medidas de estabilidade dos implantes foram realizadas por frequência de ressonância (ISQ). Após 12 semanas, uma nova leitura da estabilidade dos implantes foi realizada. A análise estatística foi feita usando modelo linear de efeitos mistos, que é uma generalização do modelo linear padrão (Anova). Diferenças foram consideradas significantes quando p < 0,05. Resultados: a estabilidade do implante mudou no decorrer do tempo para todos os protocolos de carga, apresentando aumento significativo na estabilidade final, mas as variações foram semelhantes para os três grupos estudados. Nos períodos de sete dias e 14 semanas, o protocolo de carga imediata apresentou menor estabilidade de implante do que os protocolos de sete e 14 dias. Conclusão: a estabilidade do implante diminui nos períodos iniciais após a cirurgia e aumenta no período de 14 semanas. A estabilidade dos implantes do protocolo de carga imediata é menor do que a dos protocolos de sete e 14 dias, sugerindo cautela para seu uso...

This study aimed to evaluate implant stability in function with immediate or early loading protocols at different time intervals. Material and Methods: The mandibular premolars of eight dogs were pulled bilaterally. After 12 weeks, each dog received 6 implants (3 at each mandibular side). Implant loading was performed for each implant pair according to the following periods: immediate (fi rst pair), 7 days later (second pair), 14 days later (third pair). Implant stability measurements were performed by means of resonance frequency for each period. After 12 weeks, new readings of implant stability were obtained. The statistical analysis was performed using a mixed linear model, which is a generalization of the standard linear model (Anova), with differences considered signifi cant at p<0.05. Results: Implant stability changed throughout time for all loading protocols, presenting a significant increase in fi nal stability values, but variations were similar for the three studied groups. At 7- and 14-week periods, immediate loading protocol presented lower implant stability than 7-day or 14-day protocols. Conclusions: Implant stability diminishes in the initial periods after surgery, and increases in a 14-week period. In the middle-term, there were no statistically significant differences in the stability of immediately-loaded implants, one or two weeks after implant placement...

Cirurgia de elevação da mucosa do seio maxilar: o uso de biomaterial é necessário? / Surgical elevation of maxillary sinus mucosa: is it necessary to use biomaterials?

A reabsorção óssea que ocorre após a extração dos dentes posteriores da maxila pode resultar em perdas ósseas severas verticais e/ou horizontais, comprometendo, assim, o planejamento de reabilitação com implantes naquela região. Inúmeras técnicas de enxertia têm sido descritas e utilizadas no intuito de restabelecer volume ósseo adequado para posterior instalação dos implantes. A técnica mais rotineira para restaurar a anatomia dessa região é o procedimento de aumento do assoalho do seio maxilar.

The bone resorption that occurs after extraction of maxillary posterior teeth may result in severe vertical and/or horizontal bone loss, compromising the planning of rehab with implants in that region. Numerous grafting techniques have been described and used aiming to restore adequate bone volume for posterior implants installation. The most used technique to restore the anatomy of this region is the procedure of maxillary sinus floor augmentation.

Periapical tissue response after use of intermediate restorative material, gutta-percha, reinforced zinc oxide cement, and mineral trioxide aggregate as retrograde root-end filling materials: a histologic study in dogs.

PURPOSE: To investigate the periapical tissue response of 4 different retrograde root-filling materials, ie, intermediate restorative material, thermoplasticized gutta-percha, reinforced zinc oxide cement (Super-EBA), and mineral trioxide aggregate (MTA), in conjunction with an ultrasonic root-end preparation technique in an animal model. MATERIALS AND METHODS: Vital roots of the third and fourth right mandibular premolars in 6 healthy mongrel dogs were apicectomized and sealed with 1 of the materials using a standardized surgical procedure. After 120 days, the animals were sacrificed and the specimens were analyzed radiologically, histologically, and scanning electron microscopically. The Fisher exact test was performed on the 2 outcome values. RESULTS: Twenty-three sections were analyzed histologically. Evaluation showed better re-establishment of the periapical tissues and generally lower inflammatory infiltration in the sections from teeth treated with the intermediate restorative material and the MTA. New root cement on the resected dentin surfaces was seen on all sections regardless of the used material. New hard tissue formation, directly on the surface of the material, was seen only in the MTA sections. There was no statistical difference in outcome among the tested materials. CONCLUSIONS: The results from this dog model favor the intermediate restorative material and MTA as retrograde fillings when evaluating the bone defect regeneration. MTA has the most favorable periapical tissue response when comparing the biocompatibility of the materials tested.

Short implants (6 mm) installed immediately into extraction sockets: an experimental study in dogs.

AIM: To evaluate the effect of implant length (6 mm vs.11 mm) on osseointegration (bone-to-implant contact) of implants installed into sockets immediately after tooth extraction. MATERIAL AND METHODS: In six Labrador dogs, the pulp tissue of the mesial roots of (3) P(3) was removed and the root canals were filled. Flaps were elevated bilaterally, the premolars hemi-sectioned and the distal roots removed. Recipient sites were prepared in the distal alveolus and a 6 mm or an 11 mm long implant was installed at the test and control sites, respectively. Non-submerged healing was allowed. After 4 months of healing, block sections of the implant sites were obtained for histological processing and peri-implant tissue assessment. RESULTS: No statistically significant differences were found between test and control sites both for hard and soft tissue parameters. The bone-to-implant contact evaluated at the apical region of the implants was similar as well. Although not statistically significant, the location of the top of the bony crest at the buccal aspect was more apical in relation to the implant shoulder at the test compared with the control sites (2.0 ± 1.4 and 1.2 ± 1.1 mm, respectively). CONCLUSIONS: Shorter implants (6 mm) present with equal osseointegration than do longer implants (11 mm).

Implant osseointegration in circumferential bone defects treated with latex-derived proteins or autogenous bone in dog's mandible.

BACKGROUND: In sites with diminished bone volume, the osseointegration of dental implants can be compromised. Innovative biomaterials have been developed to aid successful osseointegration outcomes. PURPOSE: The aim of this study was to evaluate the osteogenic potential of angiogenic latex proteins for improved bone formation and osseointegration of dental implants. MATERIALS AND METHODS: Ten dogs were submitted to bilateral circumferential defects (5.0 × 6.3 mm) in the mandible. Dental implant (3.3 × 10.0 mm, TiUnite MK3™, Nobel Biocare AB, Göteborg, Sweden) was installed in the center of the defects. The gap was filled either with coagulum (Cg), autogenous bone graft (BG), or latex angiogenic proteins pool (LPP). Five animals were sacrificed after 4 weeks and 12 weeks, respectively. Implant stability was evaluated using resonance frequency analysis (Osstell Mentor, Osstell AB, Göteborg, Sweden), and bone formation was analyzed by histological and histometric analysis. RESULTS: LPP showed bone regeneration similar to BG and Cg at 4 weeks and 12 weeks, respectively (p ≥ .05). Bone formation, osseointegration, and implant stability improved significantly from 4 to 12 weeks (p ≤ .05). CONCLUSION: Based on methodological limitations of this study, Cg alone delivers higher bone formation in the defect as compared with BG at 12 weeks; compared with Cg and BG, the treatment with LPP exhibits no advantage in terms of osteogenic potential in this experimental model, although overall osseointegration was not affected by the treatments employed in this study.

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.

Tomographic, histological, and immunohistochemical evidences on the use of N-butyl-2-cyanoacrilate for onlay graft fixation in rabbits.

BACKGROUND: The bone tissue responses to Cyanoacrylate have been described in the literature, but none used N-butyl-2-cyanoacrilate (NB-Cn) for bone graft fixation. PURPOSE: The aims of the study were: (a) to analyze the bone grafts volume maintenance fixed either with NB-Cn or titanium screw; (b) to assess the incorporation of onlay grafts on perforated recipient bed; and (c) the differences of expression level of tartrate-resistant acid phosphatase (TRAP) protein involved in bone resorption. MATERIALS AND METHODS: Eighteen New Zealand White rabbits were submitted to calvaria onlay grafting on both sides of the mandible. On one side, the graft was fixed with NB-Cn, while on the other hand the bone graft was secured with an osteosynthesis screw. The computed tomography (CT) was performed just after surgery and at animals sacrifice, after 1 (n = 9) and 6 weeks (n = 9), in order to estimate the bone grafts volume along the experiments. Histological sections of the grafted areas were prepared to evaluate the healing of bone grafts and to assess the expression of TRAP protein. RESULTS: The CT scan showed better volume maintenance of bone grafts fixed with NB-Cn (p ≤ 0.05) compared with those fixed with screws, in both experimental times (analysis of variance). The immunohistochemical evaluation showed that the TRAP expression in a 6-week period was significantly higher compared with the 1-week period, without showing significant difference between the groups (Wilcoxon and Mann-Whitney). Histological analysis revealed that the NB-Cn caused periosteum damage, but provided bone graft stabilization and incorporation similar to the control group. CONCLUSION: The perforation provided by screw insertion into the graft during fixation may have triggered early revascularization and remodeling to render increased volume loss compared with the experimental group. These results indicate that the NB-Cn possesses equivalent properties to titanium screw to be used as bone fixation material in osteosynthesis.

Magnesium-enriched hydroxyapatite at immediate implants: a histomorphometric study in dogs.

AIM: To evaluate the influence of magnesium-enriched hydroxyapatite (MHA) (SintLife(®)) on bone contour preservation and osseointegration at implants placed immediately into extraction sockets. MATERIAL AND METHODS: In the mandibular pre-molar region, implants were installed immediately into extraction sockets of six Labrador dogs. MHA was placed at test sites, while the control sites did not receive augmentation materials. 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: After 4 months of healing, one control implant was not integrated leaving n=5 test and control implants for evaluation. Both at the test and the control sites, bone resorption occurred. While the most coronal bone-to-implant contact was similar between test and control sites, the alveolar bony crest outline was maintained to a higher degree at the buccal aspect of the test sites (loss: 0.7 mm) compared with the control sites (loss: 1.2 mm), even though this difference did not reach statistical significance. CONCLUSIONS: The use of MHA to fill the defect around implants placed into the alveolus immediately after tooth extraction did not contribute significantly to the maintenance of the contours of the buccal alveolar bone crest.

Flap vs. "flapless" surgical approach at immediate implants: a histomorphometric study in dogs.

AIM: To compare the remodeling of the alveolar process at implants installed immediately into extraction sockets by applying a flap or a "flapless" surgical approach in a dog model. MATERIAL AND METHODS: Implants were installed immediately into the distal alveoli of the second mandibular premolars of six Labrador dogs. In one side of the mandible, a full-thickness mucoperiosteal flap was elevated (control site), while contra-laterally, the mucosa was gently dislocated, but not elevated (test site) to disclose the alveolar crest. After 4 months of healing, the animals were sacrificed, ground sections were obtained and a histomorphometric analysis was performed. RESULTS: After 4 months of healing, all implants were integrated (n=6). Both at the test and at the control sites, bone resorption occurred with similar outcomes. The buccal bony crest resorption was 1.7 and 1.5 mm at the control and the test sites, respectively. CONCLUSIONS: "Flapless" implant placement into extraction sockets did not result in the prevention of alveolar bone resorption and did not affect the dimensional changes of the alveolar process following tooth extraction when compared with the usual placement of implants raising mucoperiosteal flaps.

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.

Collagen membranes at immediate implants: a histomorphometric study in dogs.

AIM: To evaluate the influence of resorbable membranes on hard tissue alterations and osseointegration at implants placed into extraction sockets in a dog model. MATERIAL AND METHODS: In the mandibular premolar region, implants were installed immediately into the extraction sockets of six Labrador dogs. Collagen-resorbable membranes were placed at the test sites, while the control sites were left uncovered. 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: After 4 months of healing, a control implant was not integrated (n=5). Both at the test and at the control sites, bone resorption occurred. While the most coronal bone-to-implant contact was similar between the test and the control sites, the alveolar bone crest outline was maintained to a higher degree at the buccal aspect of the test sites (loss: 1.7 mm) compared with the control sites (loss: 2.2 mm). CONCLUSIONS: The use of collagen-resorbable membranes at implants immediately placed into extraction sockets contributed to a partial (23%) preservation of the buccal outline of the alveolar process.

Hard tissue formation adjacent to implants of various size and configuration immediately placed into extraction sockets: an experimental study in dogs.

OBJECTIVES: To evaluate the influence of implant size and configuration on osseointegration in implants immediately placed into extraction sockets. MATERIAL AND METHODS: Implants were installed immediately into extraction sockets in the mandibles of six Labrador dogs. In the control sites, cylindrical transmucosal implants (3.3 mm diameter) were installed, while in the test sites, larger and conical (root formed, 5 mm diameter) implants were installed. After 4 months of healing, the resorptive patterns of the alveolar crest were evaluated histomorphometrically. RESULTS: With one exception, all implants were integrated in mineralized bone, mainly composed of mature lamellar bone. The alveolar crest underwent resorption at the control as well as at the test implants. This resorption was more pronounced at the buccal aspects and significantly greater at the test (2.7+/-0.4 mm) than at the control implants (1.5+/-0.6 mm). However, the control implants were associated with residual defects that were deeper at the lingual than at the buccal aspects, while these defects were virtually absent at test implants. CONCLUSIONS: The installment of root formed wide implants immediately into extraction sockets will not prevent the resorption of the alveolar crest. In contrast, this resorption is more marked both at the buccal and lingual aspects of root formed wide than at standard cylindrical implants.

Influence of implant positioning in extraction sockets on osseointegration: histomorphometric analyses in dogs.

AIM: To evaluate the influence of implant positioning into extraction sockets on osseointegration. MATERIAL AND METHODS: Implants were installed immediately into extraction sockets in the mandibles of six Labrador dogs. In the control sites, the implants were positioned in the center of the alveolus, while in the test sites, the implants were positioned 0.8 mm deeper and more lingually. After 4 months of healing, the resorptive patterns of the alveolar crest were evaluated histomorphometrically. RESULTS: All implants were integrated in mineralized bone, mainly composed of mature lamellar bone. The alveolar crest underwent resorption at the control as well as at the test sites. After 4 months of healing, at the buccal aspects of the control and test sites, the location of the implant rough/smooth limit to the alveolar crest was 2 + or - 0.9 mm and 0.6 + or - 0.9 mm, respectively (P<0.05). At the lingual aspect, the bony crest was located 0.4 mm apically and 0.2 mm coronally to the implant rough/smooth limit at the control and test sites, respectively (NS). CONCLUSIONS: From a clinical point of view, implants installed into extraction sockets should be positioned approximately 1 mm deeper than the level of the buccal alveolar crest and in a lingual position in relation to the center of the alveolus in order to reduce or eliminate the exposure above the alveolar crest of the endosseous (rough) portion of the implant.