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.

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.

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.

Adipose-Derived Stem Cells as a Tool for Dental Implant Osseointegration: an Experimental Study in the Dog.

The biological interaction between the jaw bones and dental implant is fundamental for the long-term success of dental implant placement. Nevertheless, the insufficient bone volume remains a major clinical problem, especially in case of immediate dental implant. Using a canine model, the present study proves the regenerative potential of adipose- derived stem cells (ADSCs) to repair peri-implant bone defects occurring in immediate dental implant placement. In six labradors, all mandibular premolars and the first molars were extracted bilaterally and three months later dental implants were installed with a marginal gap. The marginal defects were filled with hydroxyapatite (HA)-based scaffolds previously seeded with ADSCs. After one month of healing, specimens were prepared for histological and histomorphometric evaluations. Histological analyses of ground sections show that ADSCs significantly increase bone regeneration. Several new vessels, osteoblasts and new bone matrix were detected. By contrast, no inflammatory cells have been revealed. ADSCs could be used to accelerate bone healing in peri- implant defects in case of immediate dental implant placement.