Excessive occlusal load on chemically modified and moderately rough titanium implants restored with cantilever reconstructions. An experimental study in dogs.

OBJECTIVE: To evaluate the outcomes of excessively loaded implants. MATERIAL AND METHODS: In five dogs, all mandibular premolars were extracted. After 3 months, six implants (three SLA® and three SLActive®) were placed (S). After 4 weeks, implants were restored: one single crown with stable occlusal contacts (SC), one crown and a cantilever unit with excessive occlusal contacts (OL), and a non-loaded implant (NL). Bleeding-on-probing (BoP), attachment level (AL), mucosal margin (GM) were assessed. Resonance frequency analysis (RFA) was assessed weekly. Standardized X-rays were taken at S, 4 and 24 weeks. RESULTS: Similar findings were observed for SLA® and SLActive® implants regarding PlI, GI, GM, AL, and BL. No significant differences were detected between baseline and 24-weeks or between treatment modalities for all clinical parameters (p > .05). Six months after loading, RFA values were significantly greater than at implant placement. No significant differences between treatment modalities were found. Linear radiographic measurements yielded similar results between SLA® and SLActive® implants. SLA® OL implants yielded a statistically significant gain on peri-implant bone density over all other groups (p = .012). Radiographic results were confirmed by descriptive histology. Technically, loosened occlusal screws occurred in 13.3% (SC = 3.3%; OL = 10%), while abutment fractures totalized 23.3% (SC = 6.6%; OL = 16.6%). CONCLUSIONS: Excessive occlusal load applied to implants (SLA® or SLActive®) restored with cantilevers did not cause loss of osseointegration or significant changes in their clinical, radiographic, or histologic outcomes. Early excessive occlusal load on SLA® implants promoted a gain in peri-implant bone density. Excessively loaded implants showed more technical complications.

Marginal healing using Polyetheretherketone as healing abutments: an experimental study in dogs.

OBJECTIVE: To evaluate the marginal soft and hard tissue healing at titanium and Polyetheretherketone (PEEK) healing implant abutments over a 4-month period. MATERIAL AND METHODS: In six Labrador dogs, all mandibular premolars and first molars were extracted. After 4 months of healing, flaps were elevated, and two implants were installed at each side of the mandible, one in the premolar and the other in the molar regions. Four different types of healing abutments were positioned on the top of each implant: (i) titanium (Ti); (ii) PEEK material bonded to a base made of titanium (Ti-P), randomly positioned in the premolar region; (iii) PEEK, pristine (P); and (iv) PEEK, roughened (P-R), randomly positioned in the molar region. The flaps were sutured to allow a non-submerged healing, and after 4 months, the animals were sacrificed and ground sections obtained for histological evaluation. RESULTS: A higher resorption of the buccal bone crest was observed at the PEEK bonded to a base made of titanium abutments (1.0 ± 0.3 mm) compared to those made of titanium (0.3 ± 0.4 mm). However, similar dimensions of the peri-implant mucosa and similar locations of the soft tissues in relation to the implant shoulder were observed. No statistically significant differences were seen in the outcomes when the pristine PEEK was compared with the roughened PEEK abutments. The mean apical extension of the junctional epithelium did not exceed the implant shoulder at any of the abutment types used. CONCLUSIONS: The coronal level of the hard and soft tissues allows the conclusion that the use of PEEK as healing abutments may be indicated.

Healing at implants placed in bone of different morphology: an experimental study in dogs.

OBJECTIVE: To study osseointegration at implants installed using a standard bed preparation in sites of different bone morphology. MATERIAL AND METHODS: In six Labrador dogs, all mandibular premolars and first molars were extracted. After 4 months of healing, flaps were elevated, and two recipient sites were prepared in each side of the mandible, one in the second premolar and the other in the molar regions. Bone morphology and final insertion torque were evaluated. Healing abutments were applied, and the flaps were sutured to allow a non-submerged healing. After 4 months, the animals were sacrificed and ground sections were obtained for histomorphometric analyses. RESULTS: At the premolar sites, bone morphology Class 2 and at the molar regions Class 3 or 4 were identified. The final insertion torque was 50-55 Ncm at the premolar and 30-35 Ncm at the molar sites. Mean osseointegration in percentage reached 61.5 ± 11.5% and 63.3 ± 10.1% at the premolar and molar sites, respectively. Mineralized bone density evaluated from the implant surface up to a distance of about 0.6 mm lateral to the implant surface was 63.0 ± 7.4% and 65.4 ± 17.7% at the premolar and molar sites, respectively. CONCLUSIONS: Similar implant bed preparations performed at premolar and molar sites with different bone morphology, yielding insertion torque values of about 30-35 and 50-55 Ncm, respectively, did not affect osseointegration after 4 months at non-submerged implants.

Morphometric evaluation of the early stages of healing at cortical and marrow compartments at titanium implants: an experimental study in the dog.

OBJECTIVE: To study the early sequential stages of tissue composition in the cortical and marrow compartments of the alveolar bone crest at implants with a moderately rough surface. MATERIALS AND METHODS: Three month after tooth extraction in 12 Labrador dogs, full-thickness flaps were elevated in the edentulous region of the right side of the mandible and one implant was installed. The flaps were sutured to allow a fully submerged healing. The timing of the installations in the left side of the mandible and of sacrifices were scheduled in such a way to obtained biopsies representing the healing after 5, 10, 20, and 30 days. Ground sections (n = 6 per each healing period) were prepared, and the percentages of osteoid/new bone, old bone, new soft tissues (provisional matrix and primitive marrow), mature bone marrow, vessels, and other tissues (bone debris/particles and clot) were evaluated laterally to the implant surface up to a distance of about 0.4 mm from it. RESULTS: Osteoid/new bone was found after 5 days at percentages of 10.8 ± 4.3% at the marrow and 0.6 ± 0.6% at the cortical compartments. After 30 days, these percentages increased up to 56.4 ± 4.0% and 23.3 ± 6.1%, respectively. Old parent bone was resorbed between 5 and 30 days from 28.7 ± 10.9% to 14.9 ± 3.4% at the marrow (~48% of resorption) and from 81.2 ± 9.4% to 67.6 ± 5.6% at the cortical (~17% of resorption) compartments. All differences were statistically significant. CONCLUSION: Bone apposition to an implant surface followed a significantly different pattern in the compact and the marrow compartments around the implants. While in the compact compartments, bone apposition had to develop through the BMUs following resorption, it developed in very dense layers through an early apposition in the marrow compartments.

Radiographic evaluation of immediately loaded implants supporting 2-3 units fixed bridges in the posterior maxilla: a 3-year follow-up prospective randomized controlled multicenter clinical study.

OBJECTIVE: To compare the survival rate and alveolar bone levels at implants installed in healed sites and functionally loaded within 1 h from installation or after 3 months. MATERIAL AND METHODS: A total of 30 patients (17 male and 13 female) were recruited and 71 implants with a SLA(®) surface, 4.1 mm in diameter and 8-12 mm long, were installed in a fully healed alveolar ridge, 36 as test and 35 as control implants. The test implants were immediately loaded with a temporary reconstruction in proper occlusion, while the randomly selected control sites received the final reconstruction after 3 months. Radiographic bone levels were determined after implant installation, prosthesis delivery, and at annual intervals thereafter. RESULTS: One patient of the control and one patient of the test were excluded from evaluation. No further losses of implants or patients were seen up to the 3-year follow-up. Hence, data from 28 patients were accounted for. A total of 37 and 36 metal-ceramic crowns were provided at the test and control sites, respectively. No biological and technical complications were observed during the 3-year follow-up. Bone levels at the time of implant installation were at 1.6 ± 0.8 and 1.7 ± 0.9 mm from the implant shoulder at the test and control sites, respectively. At prosthesis delivery, the bone levels were located at 2.4 ± 0.7 mm at the control sites 3 months after implant placement. After 1 year of function, similar bone levels were observed at both sites, displaying 2.4 ± 1.0 and 2.5 ± 0.8 mm at the test and control sites, respectively. No differences were found in the subsequent observation periods. CONCLUSION: Survival rates and radiographic bone levels after 1, 2, and 3 years of observation did not differ between conventionally installed implants loaded immediately or delayed (after 3 months). Moreover, insertion torque values did not affect osseointegration.

Sequential healing at implants installed immediately into extraction sockets. An experimental study in dogs.

OBJECTIVE: To compare the sequential healing at implants installed in a healed alveolar bony ridge or immediately after tooth extraction without functional load. MATERIAL AND METHODS: In the mandible of 12 dogs, the mesial roots of the first molars were endodontically treated, the tooth hemisected, and the distal roots extracted. After 3 months, the mesial roots of the fourth premolars were endodontically treated, the tooth hemisected, and the distal roots extracted in one side of the mandible. Implants were placed immediately into extraction sockets (IPIES) of the fourth premolar and in the healed sites in the molar regions. Healing abutments were placed, and the flaps were sutured to allow a non-submerged healing. The time of surgery and of sacrifices were planned in such a way to obtain biopsies representing the healing after 1 and 2 weeks and 1 and 3 months, respectively. Ground sections were prepared for histological evaluation of tissues components on the implant surface and the coronal termination level of osseointegration (M-B). RESULTS: New bone apposition on the implant surface was slightly higher at the healed compared to the IPIES sites, being 7.4% and 4.1% after 1 week, and 67.3% and 65.3% after 3 months, respectively. Old bone was progressively resorbed, from 27.0% and 21.9% after 1 week, to 2.5% and 2.0% after 3 months, at healed and IPIES sites, respectively. M-B was 1.4 mm and 2.6 mm after 1 week, 1.2 mm and 1.2 mm after 3 months, at healed and IPIES sites, respectively. CONCLUSIONS: Similar patterns of sequential osseointegration were found at implants installed in healed alveolar bone or in alveolar sockets immediately after tooth extraction. The coronal termination level of osseointegration, that was different after 1 week, was found similar at the 3-month observation.

Bone healing at implants with different surface configurations: an experimental study in dogs.

OBJECTIVE: To study osseointegration of implants with surface modifications by the use of fluoroboric acid and/or H2 O2 installed in conventional sites or sites with circumferential marginal defects. MATERIAL AND METHODS: Four implants with different surfaces were used. One basic surface (ZirTi(®)) was sandblasted with zirconium microspheres and acid etched additionally with hydrofluoric acid. A second surface was treated with fluoroboric acid instead of hydrofluoric acid. The remainder of the other two surfaces was additionally treated with H2O2. The edentulous mandibles of 6 foxhound dogs were used to randomly install 8.5-mm-long implants with the different surfaces and to study the histological healing after 1 and 3 months. To study osteoconductivity, additional four recipient sites were prepared with the coronal region being widened so that a 4 mm deep and 0.85 mm wide marginal defect resulted after the placement of the four implants with different surfaces. No filler material or membranes were used, and a fully submerged healing was allowed for 3 months. RESULTS: At the conventional sites, new bone formation ranged between 68.5% and 74.9% after 1 month. After 3 months, bone-to-implant contact ranged from 72.6% at the ZirTi(®) surface to 84.1% at the fluoroboric acid-treated implants, the difference being statistically significant. At the sites with marginal defects, bone formation ranged from 0.77 mm at the surface treated with fluoroboric acid and H2O2 , to 1.93 mm at the surface treated with fluoroboric acid alone. CONCLUSIONS: Fluoroboric acid treatment alone of titanium implant surfaces resulted in improved osseointegration and osteoconductivity after 3 months.

Influence of immediate loading on healing of implants installed with different insertion torques--an experimental study in dogs.

OBJECTIVE: To evaluate the influence of different insertion torques on healing of implants loaded immediately or left unloaded. MATERIAL AND METHODS: In six Labrador dogs, all mandibular premolars and molars were extracted. After 4 months of healing, flaps were elevated, and two implant sites were prepared at each side of the mandible. The distal sites were prepared conventionally while the mesial sites were underprepared by 0.3 mm. As a consequence, different final insertion torques of about 30 Ncm at the distal and >70 Ncm at the mesial sites were recorded. Healing abutments were applied to the left and transmucosal abutments to the right side. Flaps were sutured, crown preparation of the upper right second and third premolars was performed, and impressions were taken. Within 24 h, crowns were cemented both to implants and teeth in the right side of the mouth. After 4 months, the animals were sacrificed and ground sections obtained for histological evaluation. RESULTS: A higher buccal bony crestal resorption and a more apical position of the coronal level of osseointegration were found at the loaded compared with the unloaded sites. MBIC% and percentages of peri-implant mineralized tissue (MB%) were higher at the loaded compared with the unloaded sites. Moreover, a higher MBIC% was found at the lower compared with the higher final insertion torque. CONCLUSIONS: Immediate loading does not seem to have a negative effect on osseointegration. High torque values for the immediate loading procedures were not necessary. Probably, low torque values, were sufficient to obtain primary stability and hence may provide better osseointegration than high torque value.

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.

Influence on alveolar resorption of the buccal bony plate width in the edentulous ridge expansion (E.R.E.)--an experimental study in the dog.

OBJECTIVE: To compare the hard tissue changes at implants installed applying edentulous ridge expansion (E.R.E.) at sites with a buccal bony wall thickness of 1 or 2 mm. MATERIAL AND METHODS: In six Labrador dogs, the first and second maxillary incisors were extracted, and the buccal alveolar bony plates and septa were removed. After 3 months of healing, partial-thickness flaps were dissected, and the E.R.E. was applied bilaterally. Hence, an expansion of the buccal bony crest was obtained in both sides of the maxilla with a displacement of either a 1- or a 2-mm-wide buccal bony plate at the test and control sites, respectively. After 3 months of healing, biopsies were obtained for histological analyses. RESULTS: A buccal vertical resorption of the alveolar crest of 2.3 ± 0.8 and 2.1 ± 1.1 mm, and a coronal level of osseointegration at the buccal aspect of 2.7 ± 0.5 and 2.9 ± 0.9 mm were found at the test (1 mm) and control (2 mm) sites, respectively. The differences did not reach statistical significance. The mean values of the mineralized bone-to-implant contact (MBIC%) ranged from 62% to 73% at the buccal and lingual sites. No statistically significant differences were found. Horizontal volume gains of 1.8 and 1.1 mm were observed at the test and control sites, respectively, and the difference being statistically significant. CONCLUSIONS: Implants installed using the E.R.E. technique yielded a high degree of osseointegration. It is suggested that the displacement of buccal bony plates of 1 mm thickness is preferable compared with that of wider dimensions.

Use of sonic instruments for implant biopsy retrieval.

OBJECTIVE: To evaluate in vitro the quality of dental implant biopsies collected using trephines or a sonic instrument. METHOD: Sixty implants, 4 mm long and 2.4 mm in diameter, were installed in twelve fresh bovine ribs. Biopsies were collected after using three different methods for retrieval, 20 biopsies representing each group: (A) A trephine used concentrically; (B) a trephine used eccentrically; and (C) a sonic device (Sonosurgery(®) ). The time used for biopsy collection was recorded, and an evaluation of the quality of the biopsies obtained was performed. The specimens were subsequently prepared for ground sections, and tissue-to-implant contact percentages (TIC%) were evaluated in a stereomicroscope. RESULTS: Time needed for biopsy collection in Groups A and B was between 2 and 3 min, while in C, it amounted to 10-11 min. The differences between Group C and the other two groups were statistically significant (P < 0.00006). Group C showed significantly greater volumes of tissue around the apex of the implants compared with the other two groups (P < 0.027). Groups A and C showed biopsies with higher quality compared with Group B (P < 0.05). Group C presented a higher TIC% compared with the other two groups (P < 0.008). CONCLUSION: Compared with the use of trephines, the use of a sonic device for harvesting biopsies resulted in higher-quality biopsies and generated smaller residual defects. However, the harvesting was more time-consuming and was limited to one aspect of the implants.

Immediate loading of implants installed in a healed alveolar bony ridge or immediately after tooth extraction: an experimental study in dogs.

OBJECTIVE: To compare the sequential healing at immediately loaded implants installed in a healed alveolar bony ridge or immediately after tooth extraction. MATERIAL AND METHODS: In the mandible of 12 dogs, the second premolars were extracted. After 3 months, the mesial roots of the third premolars were endodontically treated and the distal roots extracted. Implants were placed immediately into the extraction sockets (test) and in the second premolar region (control). Crowns were applied at the second and third maxillary premolars, and healing abutments of appropriate length were applied at both implants placed in the mandible and adapted to allow occlusal contacts with the crowns in the maxilla. The time of surgery and time of sacrifices were planned in such a way to obtain biopsies representing the healing after 1 and 2 weeks and 1 and 3 months. Ground sections were prepared for histological analyses. RESULTS: At the control sites, a resorption of the buccal bone of 1 mm was found after 1 week and remained stable thereafter. At the test sites, the resorption was 0.4 mm at 1-week period and further loss was observed after 1 month. The height of the peri-implant soft tissue was 3.8 mm both at test and control sites. Higher values of mineralized bone-to-implant contact and bone density were seen at the controls compared with the test sites. The differences, however, were not statistically significant. CONCLUSIONS: Different patterns of sequential early healing were found at implants installed in healed alveolar bone or in alveolar sockets immediately after tooth extractions. However, three months after implant installation, no statistically significant differences were found for the hard- and soft-tissue dimensions.

Healing of implants installed in over- or under-prepared sites--an experimental study in dogs.

OBJECTIVE: To study bone healing at implants installed with different insertion torques. MATERIAL AND METHODS: In six Labrador dogs, all mandibular premolars and first molars were extracted. After 4 months of healing, flaps were elevated, and two implant sites were prepared at each side of the mandible. In the right side of the mandible, the distal sites were prepared conventionally, while the mesial sites were over-prepared by 0.2 mm. As a consequence, a final insertion torque of ~30 Ncm at the distal and a minimal insertion torque close to 0 Ncm at the mesial sites were obtained. In the left sides of the mandible, however, the recipient sites were underprepared by 0.3 mm resulting in an insertion torque of ≥ 70 Ncm at both implants. Cover screws were applied, and flaps sutured to fully submerge the experimental sites. After 4 months, the animals were sacrificed and ground sections obtained for histological evaluation. RESULTS: The mineralized bone-to-implant contact was in the range of 55.2-62.1%, displaying the highest value at implants with ~30 Ncm insertion torque and the lowest value at the implant sites with close to 0 Ncm insertion torque. No statistically significant differences were revealed. Bone density was in the range of 43.4-54.9%, yielding the highest value at implants with ≥ 70 Ncm insertion torque and the lowest at the implant sites with close to 0 Ncm insertion torque. The difference between the sites of ~30 Ncm and the corresponding ≥ 70 Ncm insertion torque reached statistical significance. CONCLUSIONS: Similar amounts of osseointegration were obtained irrespective of the insertion torque applied. Moreover, implants installed in sites with close to 0 Ncm insertion torque may properly osseointegrate as well.

Sub-crestal positioning of implants results in higher bony crest resorption: an experimental study in dogs.

OBJECTIVE: To compare peri-implant soft- and hard-tissue integration at implants installed juxta- or sub-crestally. Furthermore, differences in the hard and soft peri-implant tissue dimensions at sites prepared with drills or sonic instruments were to be evaluated. MATERIAL AND METHODS: Three months after tooth extraction in six dogs, recipient sites were prepared in both sides of the mandible using conventional drills or a sonic device (Sonosurgery(®)). Two implants with a 1.7-mm high-polished neck were installed, one with the rough/smooth surface interface placed at the level of the buccal bony crest (control) and the second placed 1.3 mm deeper (test). After 8 weeks of non-submerged healing, biopsies were harvested and ground sections prepared for histological evaluation. RESULTS: The buccal distances between the abutment/fixture junction (AF) and the most coronal level of osseointegration (B) were 1.6 ± 0.6 and 2.4 ± 0.4 mm; between AF and the top of the bony crest (C), they were 1.4 ± 0.4 and 2.2 ± 0.2 mm at the test and control sites, respectively. The top of the peri-implant mucosa (PM) was located more coronally at the test (1.2 ± 0.6 mm) compared to the control sites (0.6 ± 0.5 mm). However, when the original position of the bony crest was taken into account, a higher bone loss and a more apical position of the peri-implant mucosa resulted at the test sites. CONCLUSIONS: The placement of implants into a sub-crestal location resulted in a higher vertical buccal bone resorption and a more apical position of the peri-implant mucosa in relation to the level of the bony crest at implant installation. Moreover, peri-implant hard-tissue dimensions were similar at sites prepared with either drills or Sonosurgery(®).

Influence of bone marrow on osseointegration in long bones: an experimental study in sheep.

AIM: To evaluate the influence of yellow bone marrow on osseointegration of titanium oral implants using a long bone model. MATERIAL AND METHODS: The two tibiae of eight sheep were used as experimental sites. Two osteotomies for implant installation were prepared in each tibia. At the control sites, no further treatments were performed while, at the test sites, bone marrow was removed from the osteotomy site with a curette to an extent that exceeded the implant dimensions. As a result, the apical portion of the implants at the control sites was in contact with bone marrow while, at the test sites, it was in contact with the blood clot. After 2 months, the same procedures were performed in the contralateral side. After another month, the animal was sacrificed. Ground sections were obtained for histological analysis. RESULTS: After 1 month of healing, no differences between test and control sites were found in the apical extension of osseointegration and the percentage of new bone-to-implant contact. However, after 3 months of healing, a higher percentage of new bone-to-implant contact was found at the test compared to the control sites in the marrow compartment. The apical extension of osseointegration, however, was similar to that found at the 1-month healing period both for test and control sites. CONCLUSIONS: Osseointegration appeared to be favored by the presence of a blood clot when compared to the presence of yellow fatty bone marrow. Moreover, the contact with cortical bone appeared to be a prerequisite for the osseointegration process in the long bone model.

Healing at implant sites prepared conventionally or by means of Sonosurgery ®. An experimental study in dogs.

OBJECTIVE: To compare peri-implant tissue healing at implants installed in sites prepared with conventional drills or a sonic device. MATERIAL AND METHODS: In six Beagle dogs, the mandibular premolars and first molars were extracted bilaterally. After 3 months, full-thickness muco-periosteal flaps were elevated and recipient sites were prepared in both sides of the mandible. In the right side (control), the osteotomies were prepared using conventional drills, while, at the left side (test), a sonic device (Sonosurgery(®)) was used. Two implants were installed in each side of the mandible. After 8 weeks of non-submerged healing, biopsies were harvested and ground sections prepared for histological evaluation. RESULTS: The time consumed for the osteotomies at the test was more than double compared to the conventional control sites. No statistically significant differences were found for any of the histological variables evaluated for hard and soft tissue dimensions. Although not statistically significant, slightly higher mineralized bone-to-implant contact was found at the test (65.4%) compared to the control (58.1) sites. CONCLUSIONS: Similar healing characteristics in osseointegration and marginal hard tissue remodeling resulted at implants installed into osteotomies prepared with conventional drills or with the sonic instrument (Sonosurgery(®)).

Dimensional changes in soft tissues around dental implants following free gingival grafting: an experimental study in dogs.

OBJECTIVE: To study the buccal dimensional tissue changes at oral implants following free gingival grafting, with or without including the keratin layer, performed at the time of implant installation into alveolar mucosa. MATERIAL AND METHODS: The mandibular premolars and first molars were extracted bilaterally in six Beagle dogs. In the right side of the mandible (Test), flaps were first elevated, and the buccal as well as part of the lingual masticatory mucosa was removed. An incision of the periosteum at the buccal aspect was performed to allow the flap to be coronally repositioned. Primary wound closure was obtained. In the left side, the masticatory (keratinized) mucosa was left in situ, and no sutures were applied (Control). After 3 months of healing, absence of keratinized mucosa was confirmed at the test sites. Two recipient sites were prepared at each side of the mandible in the region of the third and fourth premolars. All implants were installed with the shoulder placed flush with the buccal alveolar bony crest, and abutments were connected to allow a non-submerged healing. Two free gingival mucosal grafts were harvested from the buccal region of the maxillary canines. One graft was left intact (gingival mucosal graft), while for the second, the epithelial layer was removed (gingival connective tissue graft). Subsequently, the grafts were fixed around the test implants in position of the third and fourth premolars, respectively. After 3 months, the animals were euthanized and ground sections obtained. RESULTS: Similar bony crest resorption and coronal extension of osseointegration were found at test and control sites. Moreover, similar dimensions of the peri-implant soft tissues were obtained at test and control sites. CONCLUSIONS: The increase in the alveolar mucosal thickness by means of a gingival graft affected the peri-implant marginal bone resorption and soft tissue recession around implants. This resulted in outcomes that were similar to those at implants surrounded by masticatory mucosa, indicating that gingival grafting in the absence of keratinized mucosa around implants may reduce the resorption of the marginal crest and soft tissue recession.

Osseointegration of implants with dendrimers surface characteristics installed conventionally or with Piezosurgery®. A comparative study in the dog.

AIM: The first aim of the present experiment was to compare bone healing at implants installed in recipient sites prepared with conventional drills or a piezoelectric device. The second aim was to compare implant osseointegration onto surfaces with and without dendrimers coatings. MATERIAL AND METHODS: Six Beagles dogs were used in this study. Five implants with two different surfaces, three with a ZirTi(®) surface (zirconia sand blasted, acid etched), and two with a ZirTi(®)-modified surface with dendrimers of phosphoserine and polylysine were installed in the right side of the mandible. In the most anterior region (P2, P3), two recipient sites were prepared with drills, and one implant ZirTi(®) surface and one coated with dendrimers implants were installed at random. In the posterior region (P4 and M1), three recipient sites were randomly prepared: two sites with a Piezosurgery(®) instrument and one site with drill and two ZirTi(®) surface and one coated with dendrimers implants installed. Three months after the surgery, the animals were sacrificed for histological analysis. RESULTS: No complications occurred during the healing period. Three implants were found not integrated and were excluded from analysis. However, n = 6 was obtained. The distance IS-B at the buccal aspect was 2.2 ± 0.8 and 1.8 ± 0.5 mm, while IS-C was 1.5 ± 0.9 and 1.4 ± 0.6 mm at the Piezosurgery(®) and drill groups, respectively. Similar values were obtained between the dendrimers-coated and ZirTi(®) surface implants. The BIC% values were higher at the drill (72%) compared to the Piezosurgery(®) (67%) sites. The BIC% were also found to be higher at the ZirTi(®) (74%) compared to the dendrimers-coated (65%) implants, the difference being statistically significant. CONCLUSION: This study has revealed that oral implants may osseointegrate equally well irrespective of whether their bed was prepared utilizing conventional drills with abundant cooling or Piezosurgery(®). Moreover, the surface coating of implants with dendrimers phosphoserine and polylysine did not improve osseointegration.