Mucosal adhesion phenomenon after maxillary sinus floor elevation: A preclinical study.

AIM: To describe the histological events that occur after maxillary sinus floor elevation when the elevated and undetached sinus mucosa are in close proximity or in contact with each other. MATERIALS AND METHODS: From 76 rabbits, 152 elevated maxillary sinuses were analyzed histologically. Sites without adhesions were classified as "No proximity," whereas the adhesion stages were divided into "Proximity," "Fusion," and "Synechia stages." The width of the pseudostratified columnar epithelium and the distance between the two layers of the elevated and undetached sinus mucosae were measured at various standardized positions. RESULTS: Thirty-one sites presenting with adhesions were found. Twelve sites were in the proximity stage," presenting cilia of the two epithelial layers that were shortened and interlinked within the mucous context. Hyperactivity of the goblet cells was also observed. In the other cases, the hyperplastic epithelium showed attempts to reach the contralateral mucosa. The 15 "fusion stage" sites presented regions with epithelial cells of the two mucosal layers that penetrated each other. Four sites presented "synechiae stages," represented by bridges of connective tissue connecting the two lamina propria. CONCLUSIONS: Close proximity or tight contact between the elevated and undetached mucosa adhering to the bone walls might occur after maxillary sinus floor elevation. This induced hyperplasia of the epithelial cells and adhesion of the two layers until synechiae formation.

Evaluation of Two Configurations of Hydroxyapatite and Beta-Tricalcium Phosphate in Sinus Grafts with Simultaneous Implant Installation: An Experimental Study in Rabbits.

BACKGROUND: This study aimed to evaluate peri-implant bone formation in rabbits after sinus grafting mediated by hydroxyapatite and beta-tricalcium phosphate (HA + ß-TCP) in granule or paste configurations, concomitant with immediate implant installation. MATERIAL & METHODS: Thirty-four rabbit maxillary sinuses were grafted with HA + ß-TCP, half of which were applied in a granule and half in a paste composition. Implant placement was performed simultaneously. At 7 and 40 days postoperatively, the animals were euthanized, and samples were prepared for tomographic, microtomographic, histological, histometric (hematoxylin and eosin staining, HE), and immunohistochemical (labeling of transcription factor Runx-2 [RUNX2], vascular endothelial growth factor [VEGF], osteocalcin [OCN], and tartrate-resistant acid phosphatase [TRAP]) analysis. Implant removal torque was also measured. RESULTS: On tomography, maintenance of sinus membrane integrity was observed in both the groups. Higher values of morphometric parameters evaluated by micro-CT were found in the "paste group" after seven days. At 40 days, there were no significant differences between the groups in most of the microtomographic parameters evaluated. In histological sections stained with HE, a higher percentage of newly formed bone was observed in the "granule group" after 40 days. Similar positive immunolabeling was observed for both RUNX2 and OCN in both the experimental groups. TRAP immunolabeling was similar in both groups as well. VEGF labeling increased in the "granule group", indicating a higher osteoconductive potential in this biomaterial. Similar removal torque values were observed in both groups. Thus, the two HA + ß-TCP configurations showed similar healing patterns of simultaneously installed implants adjacent to sinus floor elevation. However, significantly higher bone values were observed for the "granule configuration". CONCLUSIONS: The HA + ß-TCP granules and paste presentations showed favorable long-term healing results, with bone formation in similar quantities and quality adjacent to the implants.

Tomographic Assessment on the Influence of the Use of a Collagen Membrane on Dimensional Variations to Protect the Antrostomy After Maxillary Sinus Floor Augmentation: A Randomized Clinical Trial.

PURPOSE: To evaluate the dimensional variations after elevation of the maxillary sinus floor and the healing of the antrostomy left unprotected or protected by a collagen membrane. MATERIALS AND METHODS: Twenty patients were included in the study. After the elevation of the sinus mucosa, natural bovine bone was grafted into the elevated space. In 10 randomly selected patients, a native collagen membrane made of porcine corium was placed on the antrostomy (membrane group). In the other 10 patients, the antrostomy was left uncovered (no-membrane group). Cone beam computed tomography (CBCT) images were taken for all patients before surgery (T0), 1 week after sinus floor augmentation (T1), and after 9 months of healing (T2), and evaluations of dimensional variations over time of soft and hard tissues were performed. RESULTS: At T1, the elevation of the sinus floor in the middle aspect was 12.5 ± 3.8 mm and 11.9 ± 3.6 mm in the membrane and no-membrane groups, respectively. At T2, the reduction in height of the elevated space was 0.6 ± 0.9 mm and 0.8 ± 0.8 mm in the membrane and no-membrane groups, respectively. The elevated area decreased between ~10% and 11% in the membrane group and between ~15% to 20% in the no-membrane group. However, no statistically significant differences were found. CONCLUSION: The use of a collagen membrane to cover the antrostomy after sinus floor elevation did not produce significant clinical effects on dimensional variations over time.

Comparison of allografts and xenografts used for alveolar ridge preservation. A clinical and histomorphometric RCT in humans.

BACKGROUND: Several types of bone grafts are used in ridge preservation procedures. PURPOSE: To compare the healing of allografts and xenografts applied for alveolar ridge preservation. MATERIALS AND METHODS: Twenty volunteers in need of extraction of a single-rooted tooth prior to implant installation were randomized into two groups. One group received a deproteinized cancellous bovine bone xenograft embedded in a 10% collagen matrix and the other a demineralized freeze-dried cortical bone allograft. A collagen membrane was used to cover the grafts, flaps were sutured. At baseline and 6 months later, clinical measurements including vertical and horizontal bone dimensions were taken. Histomorphometric analysis was performed. RESULTS: Both groups showed shrinkage of bone dimensions. At mesial, center and distal sites, the vertical changes in dimension were -0.6, 0.5, and -0.1 mm for the allograft and -1.1, -0.4, and -0.9 mm for the xenograft. The horizontal changes in dimensions were -1.4 mm for the allograft and -2.6 mm for the xenograft. New bone and residual graft material were 25.5 ± 10.1% and 33.8 ± 9.4% at the allograft and 35.3 ± 16.8% and 22.2 ± 13.4% at the xenograft sites. None of the differences was statistically significant. CONCLUSION: Both grafting materials are suitable for the preservation of the alveolar ridge.

Wound healing of osteotomy defects prepared with piezo or conventional surgical instruments: a pilot study in rabbits.

AIM: The aim of the present study was to evaluate and compare the wound-healing process following osteotomies performed with either conventional rotary burs or piezoelectric surgery in a rabbit model. METHODS: Two types of osteotomy window defects of the nasal cavities were prepared on the nasal bone of 16 adult New Zealand white rabbits with either a conventional rotary bur or piezo surgery. The defects were covered with a resorbable membrane. Four animals were killed at 1, 2, 3, and 5 weeks after the surgical procedure, respectively. Histological and morphometric evaluations were performed to assess the volumetric density of various tissue components: the blood clot, vascularized structures, provisional matrix, osteoid, mineralized bone, bone debris, residual tissue, and old bone. RESULTS: Significantly more bone debris was found at 1 week in the conventionally-prepared defects compared to the piezo surgically-prepared defects. At 2 and 3 weeks, a newly-formed hard tissue bridge, mainly composed of woven bone, was seen; however, no statistically-significant differences were observed. At 5 weeks, the defects were completely filled with newly-formed bone. CONCLUSION: The defects prepared by piezo surgery showed a significantly decreased proportion of bone debris at 1 week, compared to conventional rotary bur defect.

Healing of buccal dehiscence defects at implants installed immediately into extraction sockets - an experimental study in dogs.

AIM: To evaluate the influence of implant positioning into extraction sockets on bone formation at buccal alveolar dehiscence defects. MATERIAL AND METHODS: In six Labrador dogs the pulp tissue of the mesial roots of (4) P(4) was removed and the root canals were filled. Flaps were elevated bilaterally, the premolars hemi-sectioned and the distal roots removed. The implants were placed in contact with either the buccal (test site) or with the lingual (control site) bony wall of the extraction sockets. Healing abutments were affixed and triangular buccal bony dehiscence defects, about 2.7 mm deep and 3.5 mm wide, were then prepared. No regenerative procedures were done and a 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: After 4 months of healing, the bony crest and the coronal border of osseointegration at the test sites were located 1.71 ± 1.20 and 2.50 ± 1.21 mm apically to the implant shoulder, respectively. At the control sites, the corresponding values were 0.68 ± 0.63 and 1.69 ± 0.99 mm, respectively. The differences between test and control reached statistical significance (P < 0.05). Residual marginal bone defects were found both at the test and control sites. A statistically significant difference between test and control sites was only found at the lingual aspects (depth 2.09 ± 1.01 and 1.01 ± 0.48 mm, respectively). Similar heights of the buccal biological width were observed at both sites (about 5.1 mm). CONCLUSIONS: The placement of implants in a lingual position of the extraction sockets allowed a higher degree of bone formation at buccal alveolar dehiscence defects compared with a buccal positioning.

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).

Early healing after elevation of the maxillary sinus floor applying a lateral access: a histological study in monkeys.

AIM: To describe the early healing within the void obtained after the elevation of the sinus mucosa and simultaneous implant installation without the use of any grafting material in monkeys. MATERIAL AND METHODS: Implants were installed simultaneously with the elevation of the maxillary sinus using the lateral approach in eight monkeys without the use of grafting material. The healing after 4, 10, 20 and 30 days was evaluated in the area distal to the implants. Paraffin sections were prepared and analyzed using qualitative histological methods. RESULTS: The healing process was initiated by the formation of a coagulum and followed by a provisional matrix and woven bone. Subsequently, a parallel-fiber bone replaced woven bone. The dimension of the elevated area shrank during the healing process. Sprouts of woven bone, present to a moderate extent after 4 days, were more numerous after 10 and 20 days. Newly formed bone originated from the sinus walls and septa, while there was no evidence of participation of the Schneiderian membrane in this process. After 30 days, the window access appeared to be closed by a layer of newly formed trabecular bone. CONCLUSIONS: The coagulum that filled the void distal to the implant after simultaneous elevation of the sinus floor gave rise to newly formed bone. However, the void occupied by the coagulum shrank substantially. The Schneiderian membrane did not provide a basis for new bone formation in the early phase of healing.

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.