A tissue engineered cell-occlusive device for hard tissue regeneration--a preliminary report.

Tissue engineering is an emerging discipline that applies engineering principles to create devices for the study, restoration, modification, and assembly of functional tissues and organs from native or synthetic sources. In the field of guided bone regeneration (GBR), cellular matter engineering has been applied, more or less successfully, to the development of biodegradable and bioresorbable devices with chemical, physical, or mechanical properties, structure, or form that permit active tissue integration with desirable cell types and tissue components. The employment of synthetic and naturally occurring polymers as well as sophisticated manufacturing technologies allow the tissue engineering of matrix configurations so that the biophysical limitations of mass transfer can be satisfied. The configuration of such a hybrid matrix can also be manipulated to vary the surface area available for cell attachment, as well as to optimize the exposure of the attached cells to nutrients. A biodegradable and bioresorbable device made of synthetic and natural polymers was engineered specifically for GBR procedures. The degradation and resorption kinetics as well as the mechanical properties give the device the potential to function as a carrier for bone growth factors. This innovative device was applied as a GBR membrane in a clinical investigation in seven patients.

Contribution of the periosteum to bone formation in guided bone regeneration. A study in monkeys.

The periosteum has been referred to as a protective barrier in the regeneration of bone defects. The objective of this study was to determine the contribution of periosteum as a natural barrier to bone formation in guided bone regeneration. Mucoperiosteal flaps were elevated bilaterally on the buccal aspect of the mandibular angle in 5 cynomolgus monkeys. Bleeding was induced by perforating the cortical bone. A hemispherical titanium mesh was fixed over the areas thus creating a void 5 mm in height between the mesh and the bone surface. One one side the mesh was covered with an ePTFE membrane (test side). The contralateral side did not receive further treatment (control side). After 4 month healing, histomorphometric analyses were used to determine the percentage of new bone in the void underneath the mesh, and the ratio between mineralized tissue and marrow spaces in new and old bone. The mean percentage of new bone tissue was 77.2 +/- 7.5% for the test sides and 68.6 +/- 8.4% for the control sides (P = 0.018, t-test). This new bone contained 80.0 +/- 3.6% mineralized tissue in the test group and 82.5 +/- 5.0% in the control group (P > 0.05, t-test). In both groups the newly formed bone exhibited significantly less mineralized tissue than the old bone (P < 0.05, t-test). It is concluded from this study that new bone formation was enhanced by the additional use of an ePTFE membrane under a periosteum-lined mucoperiosteal flap when space maintenance was excluded as a critical factor.

Utilization of the surgical microscope for advanced plastic periodontal surgery.

The increased demand for mucogingival aesthetics has required the optimization of periodontal procedures. Microsurgery is a minimally invasive technique that is performed with the surgical microscope and adapted instruments and suture materials. While this hardware and knowledge of various operations are necessary to achieve patient aesthetic expectations, clinicians must be willing to undergo an extended period of systematic training to become familiar with novel operating procedures and instruments. This article describes the application of the surgical microscope to provide enhanced perioplastic treatment.

Clinical and histologic evaluation of submerged and nonsubmerged hydroxyapatite-coated implants: a preliminary study in dogs.

A clinical and histologic study was performed to evaluate the differences in the healing of submerged and nonsubmerged hydroxyapatite-coated 2-piece implants. Three foxhounds were used for this evaluation. Mandibular premolars 1, 2, 3, and 4 were extracted. Three months later, 2 submerged implants were placed on one side of the mandible, and 2 nonsubmerged implants were placed on the other side of the mandible. After 3 months of healing, the submerged implants were exposed, and a third implant was placed on each side of the mandible in a nonsubmerged procedure. Clinical parameters were recorded, the animals were sacrificed 6 months after placement of the first implants, and histologic and histometric analyses were performed. Results of the evaluation of the clinical parameters showed only minor differences among the different treatment groups. Regarding the percentage of bone-to-implant contact of the different treatment groups, the submerged implants showed a bone-to-implant contact of 63.4%, the nonsubmerged implants showed 70.3% contact, and the late nonsubmerged implants demonstrated a bone-to-implant contact of 58.7%. The average distance from the implant neck to the first bone-to-implant contact (fBIC) for submerged implants was 0.58 mm, for nonsubmerged implants it was 1.09 mm, and it was 1.13 mm for late nonsubmerged implants. The vertical distance between the gingival margin and the apical extent of the junctional epithelium (aJE) varied from 1.14 mm to 1.28 mm in the different groups. The distance from the aJE to fBIC was 1.00 mm for the submerged group, 1.08 mm for the nonsubmerged group, and 1.00 mm for the late nonsubmerged group. Generally, it can be concluded that the clinical and the histologic behavior of submerged or nonsubmerged 2-piece implants utilized in this experiment do not differ.

Comparison of bioabsorbable and bioinert membranes for guided bone regeneration around non-submerged implants. An experimental study in the mongrel dog.

The aim of this clinical investigation was to evaluate the effect of guided bone regeneration around non-submerged implants using different barrier membranes. Five adult mongrel dogs were used in this investigation. After having all premolars extracted and implant osteotomies performed in the regions of the former premolars, buccal bone defects were created. Subsequently, 3 implants were placed and the defects treated with 1 of the following 3 modalities: a) guided bone regeneration using an expanded polytetrafluoroethylene membrane, b) guided bone regeneration using a bioabsorbable membrane made from a synthetic copolymer of glycolide and lactide and c) no membrane application. Following implant and membrane placement, the mucoperiosteal flaps were repositioned and tightly sutured around the neck of the implants allowing for a non-submerged healing. After a healing period of 6 months, the animals were sacrificed and the specimens processed for histologic evaluation. The clinical pre-treatment defects between the different treatment groups were not statistically different (bioinert membrane group: 4.9 mm; control group: 4.8 mm; bioabsorbable membrane group: 4.5 mm). The remaining histological defects after 6 months of healing amounted to approximately 2.5 mm in the bioinert membrane group, 5.7 mm in the control group and 6.0 mm in the bioabsorbable membrane group. A significant difference was observed between the bioinert membrane group and the other 2 groups. The mineralized bone-to-implant contact in the bioinert membrane group was 51.5%, in the control group 46.3% and in the bioabsorbable membrane group 37.5%. The values between the bioinert membrane group and the bioabsorbable membrane group were statistically different. The results of this study indicate that bone regeneration with bioinert e-PTFE membranes around non-submerged implants is possible. The utilized absorbable polyglycolic/polylactid membrane did not show any bone regenerative effect and the results did not differ from the control group without membrane application.

Functional and esthetic outcome enhancement of periodontal surgery by application of plastic surgery principles.

The closure of surgical wounds in a layer-by-layer fashion, a common principle of plastic surgery, is applied in this article to the field of periodontal surgery with the introduction of a new flap design. The suggested technique is indicated with all periodontal procedures that aim for hard and soft tissue augmentation (guided bone regeneration, mucogingival surgery, or plastic periodontal surgery) where passive, tension-free wound closure is fundamental for wound healing and a successful functional and esthetic outcome. By means of a series of incisions, buccal and lingual flaps are split several times; this results in a double-partial thickness flap and a coronally positioned palatal sliding flap, respectively. Thus, several tissue layers are obtained and the passive advancement of flaps becomes possible for the coverage of augmented areas. Wound closure with microsurgical suture material is accomplished in a multilayer approach, which ensures adaptation and closure of the outer tissue layers without any tension. Two case reports demonstrate the new plastic periodontal approach.

A single-incision technique to harvest subepithelial connective tissue grafts from the palate.

This article describes a new and simplified surgical approach to harvest subepithelial connective tissue grafts from the palate. For this procedure, only a single incision parallel to the gingival margin is used to access the donor site for graft preparation and harvesting. Grafts of variable size and thickness can be obtained. Since no band of epithelium is removed with the connective tissue graft the palatal donor site can heal with primary intention. No stents or hemostatic agents are necessary to cover the donor area postoperatively, and suturing can be reduced to a minimum. The harvesting technique is illustrated step by step, and the clinical application of connective tissue grafts harvested with the proposed method is demonstrated with the coverage of a gingival recession.

Reconstruction of the lost interproximal papilla--presentation of surgical and nonsurgical approaches.

Modern esthetic dentistry involves not only the restoration of lost teeth and their associated hard tissues, but increasingly the management and reconstruction of the encasing gingiva with adequate surgical techniques. The loss of interproximal dental papillae may cause functional, phonetic, and devastating esthetic problems. Complete and predictable restoration of lost interdental papillae remains one of the biggest challenges in periodontal reconstructive surgery. On reviewing the literature, publications involving surgical and nonsurgical techniques for papilla reconstruction are basically case presentations. Very little scientific data concerning long-term success and predictability of specific techniques has been published so far. Starting with facts about the anatomy and morphology of the interdental tissues, this article gives an overview of surgical and nonsurgical techniques to restore lost interproximal dental papillae.

Development and clinical application of titanium minipins for fixation of nonresorbable barrier membranes.

Clinical applications of the principle of guided bone regeneration in oral and maxillofacial surgery include preimplant reconstruction of atrophied bone defects and coverage of endosseous implants that were incompletely covered by bone through primary intention. Nonresorbable polytetrafluoroethylene membranes are used. Over the past several years, the use of periosteal sutures to fix membranes has been supplemental or replaced by the use of metallic fixation systems. Five-year clinical results with a membrane pin set developed for fixation of such membranes are reported. Application of the titanium pin limits the relative movement between the membrane and surrounding bone and/or between and surrounding soft tissue flaps. Moreover, the titanium pin expands the range of applications for such membranes, particularly to topographically complicated bone defects at sites where clinically secure and biologically functioning placement of the membrane is not always easy.

The effects of guided bone regeneration and grafting on implants placed into immediate extraction sockets. An experimental study in dogs.

Guided bone regeneration (gbr) for the treatment of insufficient bone volume around implants can be performed using membranes with or without grafting materials (i.e., autogenous, allogenous, xenogenous, or alloplastic grafts). A possible way to evaluate the quality of implant osseointegration is the torque necessary to remove implants from their bony housing. The aim of this study was to compare the torques necessary to remove dental implants from implant beds reconstructed with different bone substitutes and GBR or GBR alone in 6 adult mongrel dogs. All mandibular premolars were extracted and 3 extraction sockets on each side were enlarged using a trephine bur. A 13 mm titanium screw-type dental implant (3.75 mm diameter) was placed in each enlarged extraction socket so that only the apical 3 to 4 mm were engaged in bone. The 3 defects were then randomly treated with either 1) canine demineralized freeze-dried bone allograft (DFDBA) plus GBR using an expanded polytetrafluoroethylene membrane (DFDBA+GTAM); 2) bioabsorbable hydroxyapatite and GBR (HA+GTAM); or 3) GBR (GTAM alone). After 6 months, the torque to remove the implants was measured in 4 animals and analyzed using ANOVA. There were no statistically significant differences between the 3 groups (GTAM alone: 46.37+/-16.41 Ncm; HA+GTAM: 46.00+/-16.59 Ncm; DFDBA+ GTAM: 52.15+/-29.24 Ncm). In addition, the influence of early removal of barriers on the torque values was evaluated with the t-test. Comparing exposed versus retained membranes by treatment modality, the only statistically significant difference was found in the DFDBA+GTAM group. When the torque values of all implants with exposed and retrieved membranes were compared to all those with retained membranes a significant difference could be detected. Histologic sections were prepared from the 2 dogs not included in the removal torque testing. In the histometric analysis the GTAM alone group showed a mean mineralized bone-to-implant-contact of 27.1%, the DFDBA+GTAM group of 34.6%, and the HA+GTAM of 39.3%. The mineralized bone-to-implant-contact of the HA+GTAM group was significantly higher than that of the GTAM alone group. In addition, the mineralized bone-to-implant-contact was divided into an apical and coronal part using the apical seventh thread as the dividing landmark. In the apical region, there was no significant difference between the groups regarding mineralized bone-to-implant-contact. In the coronal part the mineralized bone-to-implant-contact of the GTAM alone group was significantly lower compared to the other 2 groups. Within the limits of this investigation, it can be concluded that the type of grafting material will not influence torque removal values, but that early membrane exposure and removal will negatively influence the torque measurements. The combination of GBR with a bone substitute increased the mineralized bone-to-implant contact.

Evaluation of a new bioresorbable barrier to facilitate guided bone regeneration around exposed implant threads. An experimental study in the monkey.

The aim of this study was to evaluate the effectiveness of a new bioresorbable barrier alone or in combination with BioOss for guided bone regeneration around dental implants with exposed implant threads. Five adult Macaca fascicularis monkeys were used in this investigation. After extraction of all premolars and first molars, two endosteal oral implants were installed in each quadrant and the bony defects were randomly treated with either: 1) placement of the new bioresorbable device alone (group 1); 2) placement of the new bioresorbable barrier in combination with BioOss (group 2); 3) placement of an ePTFE barrier in combination with BioOss (group 3); or (4) control (group 4). After a period of six months the animals were killed and the histological processing was performed. There was a significant difference in the amount of new bone regeneration around the implants between the four groups (i.e. groups 1, 2, 3 and 4) (P=0.0122). There was no difference, however, between group 2 and group 3. It can be concluded that the new bioresorbable barrier in combination with BioOss appears to obtain the same results in this type of bony defects as the grafting material in combination with an ePTFE barrier.

Changes in peri-implant tissues subjected to orthodontic forces and ligature breakdown in monkeys.

The aims of this investigation were to histologically evaluate in monkeys the effect of a repetitive mechanical trauma alone on the peri-implant tissues, and the effect of a repetitive mechanical trauma in combination with ligature-induced peri-implantitis on the peri-implant tissues. The study used 5 male cynomolgus monkeys. Prior to the start of the study, all premolars and the first and second molars in the mandible were extracted. After a healing period of 12 weeks, following tooth extraction, split/full thickness flaps were elevated on both sides of the mandible in order to expose the bony ridge. Four implants, of 3.75 mm in diameter and 7 mm in length, were then inserted on each side and the flaps were readapted and sutured in place. Following a healing period of 16 weeks, the second stage procedure was performed, impressions were taken, and custom-made crowns using a non-precious metal alloy were fabricated and inserted on all implants 4 weeks after abutment connection. At the same time peri-implantitis was induced on one side of the mandible by placing plaque-retentive ligatures around the implants. On the other side, an oral hygiene program consisting of thrice weekly brushing with a toothbrush and flour of pumice mixed with 2% chlorhexidine was initiated. Four months later, a repetitive mechanical trauma was initiated on implants 1 and 2 on both sides in the mandible. Consequently, a split mouth design was obtained: 1) test 1=ligature-induced peri-implantitis alone (LPNO); 2) test 2=ligature-induced peri-implantitits with a repetitive mechanical trauma (LPMT); 3) test 3=healthy peri-implant tissues with a repetitive mechanical trauma (MT); and 4) control (NO)=healthy peri-implant tissues with no repetitive mechanical trauma. Following 16 weeks of repetitive mechanical trauma the animals were sacrificed. Histologic observations and computed-assisted histometric and histomorphometric analyses were performed to determine the amount of peri-implant bone loss and the percentage of direct mineralized bone-to-implant contact around each endosseous oral implant. Histologically, all implants yielded osseointegration at the light microscopic level. There was a significant difference regarding the mean direct mineralized bone-to-implant contact length as a fraction of the total implant length between the healthy (i.e., MT and NO) and diseased sites (i.e., LPNO and LPMT) (P < 0.05). When comparing the percent of direct mineralized bone-to-implant contact for the 2 best threads of each implant and group, no significant difference (P=0.675) could be detected. Under the conditions of this study, the repetitive mechanical trauma showed no histologic effect on the peri-implant bone loss neither in healthy nor in diseased implant sites. The effects of excessive loading on osseointegration are presently not clearly understood. The key problem seems to be the determination when loading on implants exceeds the physiological range of bone adaptation which may then cause implant failure. Further research to elucidate this problem is essential.

Healing patterns in recession defects treated with ePTFE membranes and with free connective tissue grafts. A histologic and histometric study in the beagle dog.

This study focussed on the biologic success of 2 different procedures for root coverage. In the maxillary canines of 7 beagle dogs, buccal recessions were created and treated on one side with an ePTFE membrane (GTR-group) and on the contralateral side with a free connective tissue graft from the palate (CT-group). 2 areas served as negative controls. After 4 months of healing, histologic sections were processed and histologically analyzed. The evaluated parameters were coverage height, bone, cementum and connective tissue attachment regeneration, length of the epithelium, resorption, and ankylosis. Histologically, both GTR-group and CT-group produced more new bone, new cementum and new connective tissue attachment than the two control teeth. When histologically evaluated, the amount of new bone was more pronounced in the GTR-group than in the CT-group, however, no statistical differences in any of the evaluated parameters could be detected between the 2 procedures tested. Frequency and distribution of resorption and ankylosis were similar in the GTR-group and in the CT-group. Within the limits of this study, no differences in terms of the biologic rehabilitation between those recessions treated with ePTFE membranes and those treated with a free connective tissue graft could be found.

Guided bone regeneration around dental implants in the atrophic alveolar ridge using a bioresorbable barrier. An experimental study in the monkey.

The aim of this study was to evaluate guided bone regeneration (GBR) around dental implants placed in atrophic alveolar ridges using an experimental, nonporous bioresorbable barrier. In 8 Rhesus monkeys, the maxillary canines and lateral incisors were extracted bilaterally and the remaining alveoli were reduced to create atrophic ridges. After a healing period of 3 months, soft tissue expansion was performed using a subperiosteal tissue expander. After 1 month of tissue expansion, and IMZ implant was placed in the atrophic ridge on each side in such a way that its coronal 4 mm to 5 mm remained circumferentially exposed above the bone level. The test implants were covered with a bioresorbable barrier made of poly (D,L-lactid-co-trimethylencarbonate) in a 70/30 ratio, whereas the control implants were covered with a nonresorbable expanded polytetrafluoroethylene (e-PTFE) barrier. The e-PTFE barriers were stabilized with titanium minipins while the bioresorbable barriers were analogously fixed using bioresorbable minipins made of poly (L-lactid-co-D,L-lactid) 70/30. Clinical healing progressed uneventfully in both groups and no soft tissue dehiscences occurred. Histometric and histomorphometric analyses were performed 5 months post surgery. Both test and control implants exhibited direct bone-to-implant contact to variable extents. The mean direct mineralized bone-to-implant contact length fraction was 32% of the total implant length in the test sites and 58% in the control sites. Control sites exhibited significantly greater bone fill compared to the experimental sites (P < 0.001). Histologic observations of test specimens demonstrated a moderate inflammatory reaction related to the degradation and resorption products of the barrier. In conclusion, the nonresorbable e-PTFE GBR barrier was found to be superior to the bioresorbable barriers tested in the present investigation.

Guided periodontal tissue regeneration in interproximal intrabony defects following treatment with a synthetic bioabsorbable barrier.

This study evaluated guided periodontal tissue regeneration (GPTR) wound healing in interproximal intrabony periodontal defects following surgical treatment with a synthetic bioabsorbable barrier made from a copolymer of glycolide and lactide. Periodontal lesions were induced around the mandibular central incisor teeth of 10 adult male rhesus monkeys using orthodontic elastics. Once similar contralateral interproximal defects had been created, the elastics were removed and an oral hygiene program was initiated and maintained until completion of the study. Three weeks after commencing oral hygiene, flap surgery was performed in the mandibular incisor region and the root surfaces were thoroughly scaled and root planed to the apical portion of the defects. On the test sites, a bioabsorbable barrier was placed over the entire interproximal periodontal defect. Control sites did not receive a barrier. Five months after surgery, the animals were sacrificed and the teeth with their supporting periodontium were processed for light microscopic evaluation. Postoperative clinical healing progressed uneventfully and was similar in both control and test sites. Histologic observations from control specimens indicated reparative healing characterized by a long junctional epithelium with limited cementum and bone formation. Test specimens exhibited significantly more new connective tissue attachment, cementum deposition, and bone formation than the control sites (P < 0.001). The barriers had been completely resorbed with no apparent adverse effect on periodontal wound healing. It was concluded that this bioabsorbable barrier facilitated GPTR wound healing in interproximal intrabony periodontal defects.

Guided periodontal tissue regeneration in Class II furcation defects following treatment with a synthetic bioabsorbable barrier.

The purpose of this study was to evaluate guided periodontal tissue regeneration (GPTR) wound healing in Class II furcation defects following surgical treatment with a synthetic bioabsorbable barrier manufactured from a copolymer of glycolide and lactide. Periodonal lesions were induced in four adult male rhesus monkeys around the mandibular first, second, and third molar teeth using orthodontic elastics. After obtaining approximately 30% bone loss, the elastics were replaced by a stainless steel wire which had a projection extending into the furcation. Once similar contralateral Class II furcation defects had been created, the wires were removed, and an oral hygiene program was initiated and maintained until completion of the study. Three weeks after commencing oral hygiene, flap surgery was performed in the mandibular molar region and the root surfaces were thoroughly scaled and root planed to the apical portion of the defects. A bioabsorbable barrier was then placed to cover the furcation defects on one side of the jaw (i.e., test sites). No barriers were placed on the contralateral molars (i.e., control sites). Five months after surgery, the animals were sacrificed and the teeth with their supporting periodontium were processed for light microscopic evaluation. Clinical healing progressed normally and was similar in both groups. Histologic observations from control specimens indicated repair with epithelium and connective tissue occupying the majority of the furcation defects. Test specimens exhibited definitive evidence of regeneration with significantly greater new connective tissue attachment, cementum deposition, and bone formation than the control sites (P < 0.001). It was concluded that this bioabsorbable barrier facilitated GPTR wound healing in Class II furcation defects.

Treatment of peri-implantitis using guided bone regeneration and bone grafts, alone or in combination, in beagle dogs. Part 2: Histologic findings.

The aim of this study was to histologically evaluate and compare the treatment of ligature-induced peri-implantitis using guided bone regeneration, two bone grafts alone, or guided bone regeneration combined with one of the two bone graft materials. Mandibular premolars and first molars in seven beagle dogs were extracted. After placement of Brånemark implants and connection of abutments, experimental peri-implantitis was induced. Flap surgery was performed, abutments were removed, and implant surfaces were treated with an air-powder abrasive unit. Bony defects were randomly treated with either (1) debridement only; (2) debridement plus resorbable hydroxyapatite; (3) debridement plus canine demineralized freeze-dried bone; (4) debridement plus guided bone regeneration; (5) debridement plus resorbable hydroxyapatite and guided bone regeneration; or (6) debridement plus canine demineralized freeze-dried bone and guided bone regeneration. Four months after surgery, a flap was elevated and the barriers were removed. One month later, the animals were sacrificed, and the implants with their supporting peri-implant tissues were processed for histologic evaluation. Guided bone regeneration procedures resulted in the greatest amount of new bone formation, followed by bone grafts alone, and flap debridement. There was no significant difference between guided bone regeneration and both guided bone regeneration/graft combinations in terms of bone regeneration; however, the guided bone regeneration/graft combinations resulted in a greater amount of "reosseointegration" than all of the other treatments. Therefore, the combination of guided bone regeneration with either demineralized freeze-dried bone or resorbable hydroxyapatite appears to be the treatment of choice for plaque-induced peri-implant defects.

Maxillary sinus augmentation using different grafting materials and dental implants in monkeys. Part I. Evaluation of anorganic bovine-derived bone matrix.

The aim of this study was to evaluate clinically, histologically and histometrically the use of anorganic bovine bone matrix (i.e. Bio-oss) as a grafting material for maxillary sinus augmentation procedures. In 4 adult male rhesus monkeys (i.e. Macaca mulatta) the 1st, 2nd and 3rd maxillary molars on one side of the jaws were extracted. The remaining bone between the alveolar crest and the bottom of the sinus was then reduced to 3-4 mm. After 3 months, maxillary sinus augmentation procedures were performed on one side of the jaws in each monkey and the sinuses were grafted with the bovine bone matrix. At that time, 2 IMZ pure titanium plasma coated implants were immediately placed into the augmented sinuses (i.e. simultaneous implants-loaded group). After 4 months, 2 additional similar implants were placed into these previously augmented sinuses (i.e. delayed implants-loaded group). Four months later, the abutment connection was performed and all 4 implants were loaded with a gold-alloy bridge for 6 months (i.e. until sacrifice of the animals). The contralateral side of each monkey received the same treatment with the exception that the extractions were performed 7 months after those in the opposite side and that the implants in this side were not loaded. Thus, 2 additional study groups (i.e. simultaneous implants-unloaded group and delayed implants-unloaded group) were obtained. Clinically, all loaded implants were stable at the day of sacrifice. Histologically, the grafted sinuses exhibited significant bone formation with integration of the bovine bone matrix particles to the new bone. Direct mineralized bone-to-implant contact was greater for the delayed implant placement groups than for the implants installed simultaneously with the sinus augmentation. Furthermore, the percentage of direct mineralized bone-to-implant contact was greater in the residual bone than in the augmented area. It was concluded that the anorganic bovine bone matrix facilitated bone formation and implant osseointegration in the augmented sinuses and that the delayed implant placement in combination with the sinus augmentation procedure seemed to be preferable.

Maxillary sinus augmentation using different grafting materials and osseointegrated dental implants in monkeys. Part II. Evaluation of porous hydroxyapatite as a grafting material.

The aim of this study was to evaluate clinically, histologically and histometrically the use of porous hydroxyapatite (i.e. Interpore-200) as a bone grafting material for maxillary sinus augmentation procedures. In 4 adult male rhesus monkeys (i.e. Macaca mulatta) the 1st, 2nd and 3rd maxillary molars on one side of the jaws were extracted and the remaining bone between the alveolar crest and the bottom of the sinus was reduced to 3-4 mm. After 3 months, maxillary sinus augmentation procedures were performed on one side of the jaws in each monkey, and the sinuses grafted with the porous hydroxyapatite. Two IMZ titanium plasma-sprayed cylinder implants were then immediately placed into the augmented sinus (i.e. simultaneous implants-loaded group). After 4 months, 2 additional similar implants were placed into the previously augmented sinuses (i.e. delayed implants-loaded group). Four months later, the abutment connection was performed and all 4 implants were loaded with a gold-alloy bridge for 6 months (i.e. until sacrifice). The contralateral side of each monkey received the same treatment with the exception that the extractions were performed 7 months after those in the opposite side and that the implants in this side were not loaded. Thus, 2 additional study groups (i.e. simultaneous implants-unloaded group and delayed implants-unloaded group) were obtained. Clinically, all loaded implants were stable at the day of sacrifice. Histologic analysis demonstrated a significant amount of new bone formation in the augmented sinuses. Porous hydroxyapatite graft particles appeared to be integrated to the new bone. The percentage of direct mineralized bone-to-implant contact in the augmented area was greater on the delayed-placed implants than on the simultaneously-placed implants. Also, the percentage of direct mineralized bone-to-implant contact was greater in the residual bone than in the augmented area. It was concluded that this porous hydroxyapatite bone graft enhanced bone formation and bone-to-implant contact in the augmented sinuses and that the delayed implant placement in combination with the sinus augmentation procedure appears to result in a higher percentage of direct mineralized bone-to-implant contact.

Maxillary sinus augmentation using different grafting materials and dental implants in monkeys. Part IV. Evaluation of hydroxyapatite-coated implants.

The aim of this study was to evaluate clinically, histologically and histometrically the use of hydroxyapatite-coated dental implants in conjunction with maxillary sinus augmentation procedures. In 4 adult male Rhesus monkeys (Macaca mulatta) the 3 maxillary molars on 1 side of the jaws were extracted and the remaining bone between the alveolar crest and the floor of the sinus was reduced to 3-4 mm. After 3 months, maxillary sinus augmentation procedures were performed in each monkey and the sinuses were grafted with a porous hydroxyapatite bone graft (Interpore-200). At the same time, 2 hydroxyapatite-coated cylinder implants (IMZ) were immediately placed into the augmented sinuses (i.e. simultaneous-implants-loaded group). Four months later, 2 additional similar implants were placed into the previously augmented sinuses (i.e. delayed-implants-loaded group). After 4 months, the abutment connection was performed and all 4 implants were loaded with a gold-alloy bridge for 6 months (i.e. until sacrifice of the animals). The contralateral side of each monkey received the same treatment with the exception that removal of the maxillary molars was performed 7 months after those in the opposite side, and that the implants in this side were not loaded. Thus, 2 additional study groups (i.e. simultaneous-implants-unloaded group and delayed-implants-unloaded group) were obtained. Clinically, all loaded and unloaded implants were stable the day of sacrifice. Histologically, the grafted sinuses exhibited a significant amount of new bone formation with integration of the porous hydroxyapatite graft particles and hydroxyapatite-coat of the dental implants to the new bone. Histometric analysis indicated that on the loaded side the implants placed simultaneously with the sinus lift procedure exhibited greater direct mineralized bone-to-implant contact than the delayed placed implants. In addition, the percentage of direct mineralized bone-to-implant contact was significantly greater in the residual bone in comparison to the augmented area in all groups. Loading of the implants exhibited a positive effect on the percentage of direct mineralized bone-to-implant contact in the augmented area. It could be concluded that hydroxyapatite-coated implants may be of benefit when used in conjunction with sinus augmentation procedures.