Alveolar Buccal Bone Overbuilding Before Tooth Extraction: A Preclinical Study.

BACKGROUND: After tooth extraction, a physiological shrinkage of the alveolar ridge occurs. Applying a buccal overbuilding some months before tooth extraction may create a stiffer hard tissue that might protect the alveolar crest from resorption. Hence, the aim of this experiment was to evaluate the dimensional changes in the alveolar crest after buccal overbuilding performed before tooth extraction. MATERIALS AND METHODS: At the test sites, an alveolar crest overbuilding was performed on the buccal aspect of the distal root of the third premolar using xenograft covered with a collagen membrane. No treatment was applied at the control sites. After 3 months, the distal roots of both third premolars were extracted and implants were immediately installed into the alveolus allowing a non-submerged healing. After 3 months, biopsies were collected. RESULTS: At the histological analyses, no statistically significant differences in hard tissue dimensions were found. The buccal bone plate at the test sites presented a tendency of higher resorption compared to the control sites. However, if the contribution of the residues of biomaterial was considered, a higher volumetric gain was registered at the test than at the control sites. CONCLUSIONS: The buccal overbuilding performed before tooth extraction did not contribute to the preservation of the alveolar crest dimensions after extraction. This could be due to failure to incorporate the graft into the newly formed bone.

Healing Patterns of Non-Collagenated Bovine and Collagenated Porcine Xenografts Used for Sinus Floor Elevation: A Histological Study in Rabbits.

Objective: To compare healing of collagenated and non-collagenated xenografts used for maxillary sinus floor elevation. Materials and Methods: Two different xenografts were used: deproteinized bovine bone (DBBM group) and collagenated corticocancellous porcine bone (collagenated group). Healing was studied after 2, 4, and 8 weeks. The loss of dimensions of the elevated area and the percentages of new bone, xenograft remnants, osteoclastic zones, vessels, inflammatory infiltrates, and soft tissues were analyzed. Three regions were evaluated: close to the bone walls (bone wall region), subjacent the sinus mucosa (submucosa region), and the center of the elevated area (middle region). The primary variables were the percentage of new bone and xenograft remnants. Results: Between 2 and 8 weeks, the elevated areas showed a reduction of 16.3% and 52.2% in the DBBM and collagenated groups, respectively (p < 0.01 between the two areas after 8 weeks). After 8 weeks, the highest content of new bone was observed in the bone wall region, which was higher in the collagenated group than in the DBBM group (41.6% and 28.6%, respectively; p < 0.01). A similar quantity of new bone was found between the two groups in other regions. A higher percentage of vessels in all regions evaluated (p < 0.01) and soft tissue in the sub-mucosa region (p < 0.05) was found in the collagenated group than in the DBBM group. Conclusions: The present study showed that both xenografts allowed new bone formation. In comparison with the non-collagenated xenograft, the collagenated xenograft underwent higher resorption, resulting in greater shrinkage of the elevated space after sinus lifting and a higher content of new bone in the regions close to the bone walls. Clinical relevance: In this study, the region adjacent to the bone wall showed the highest new bone content. This region resembles the base of the sinus, closest to the sinus floor and walls, and is the most important region from a clinical point of view because it is where the implant will be installed. Residues of the biomaterial remained after 8 weeks of healing. Other reports have shown that these biomaterial residues may interfere with the integration of implants.

Comparison of histomorphometry and microCT after sinus augmentation using xenografts of different particle sizes in rabbits.

PURPOSE: The aim of the present experiment was to compare the data on new bone formation measured histologically and microtomographically in maxillary sinuses augmented with a xenograft with higher density and higher mineral content compared with the natural bone. The hypothesis was that histomorphometric and micro-computed tomography (microCT) analyses do not yield similar outcomes when a xenograft with higher density and mineral content compared with the natural bone is used. METHODS: In 18 rabbits, the maxillary sinus was augmented bilaterally using deproteinized bovine bone mineral (DBBM) xenograft granules of either 0.125-1 mm or 1-2 mm of dimensions. The rabbits were euthanized after 2, 4, and 8 weeks of healing. Comparisons were performed between microCT and histological analyses. RESULTS: After 2 weeks of healing, higher contents of bone were found at the histological compared with the microCT analyses in both sinuses, especially in the middle regions of the grafted sinus. Between 2 and 8 weeks of healing, new bone increased of about 21% at the histological analyses while, at the microCT, increased only about 4%. In the same period, the xenograft proportion decreased from 51.6 ± 4.9 to 45.3 ± 3.3% at the histological analyses while, at the microCT, the xenograft appeared to increase in percentages. CONCLUSION: Histological and microCT analyses yielded different outcomes when a xenograft with higher density and higher mineral content compared with the natural bone was used.

Horizontal Bone Augmentation in the Anterior Esthetic Area of the Maxilla Using a Flap Design Adapted from Mucogingival Surgery in Association with PLA Membrane and ß-TCP.

Systematic reviews showed possible esthetic complications with the use of traditional flap designs after guided bone regeneration (GBR) procedures in the esthetic zone and the aim of this case series was to analyze hard and soft tissue changes over 18 months after these procedures. Healthy subjects requiring tooth extraction and single-implant placement in the anterior maxilla were enrolled in the study. Three months after tooth extraction and ridge preservation, a prosthetic-driven implant was placed. The horizontal bone deficiency was treated with a resorbable bone graft substitute (beta tricalcium phosphate [ß-TCP]) and a bioresorbable polylactic acid (PLA) membrane. Primary closure was obtained by a novel coronally advanced flap adapted from mucogingival techniques. Final metal-free implant restorations were delivered 4 months after placement. Clinical measurements, pictures, and radiographs were acquired after delivery of the final restoration (T1) and at the 18-month follow-up (T2). Digital impressions were taken at the time of tooth extraction (T-1) and implant insertion (baseline; T0) and at T2. Marginal bone level changes were assessed by radiographic analysis, while soft tissue changes were evaluated with ExoCad software. Student t test for paired data was used to detect differences between the different time points. Twelve subjects (7 men and 5 women; mean age: 63.7 ± 14 years) completed the study and received 15 implants. All implants healed uneventfully and were clinically osseointegrated and stable, showing no sign of infection. No GBR complications were noted. Statistically significant ridge-width changes were observed after extraction (T-1 vs T0 = -1.72 ± 0.30 mm; P = .00001) and after horizontal GBR (T0 vs T2 = 1.41 ± 0.64 mm; P = .00001). Radiographic bone levels after implant placement remained stable T0 to T2 (0.09 ± 0.08 mm). Periodontal parameters never exceeded physiologic levels. It can be concluded that GBR using a bioresorbable PLA membrane and resorbable ß-TCP bone graft in conjunction with a coronally advanced flap is a predictable procedure for horizontal bone augmentation with simultaneous implant placement in the esthetic area.

Influence of the position of the antrostomy in sinus floor elevation assessed with cone-beam computed tomography: A randomized clinical trial.

AIM: The aim of the present study was to evaluate dimensional variations of augmented sinus volumes after sinus floor elevation using a lateral approach placing the antrostomy close to the sinus floor or more cranially to it. METHODS: Twenty-four healthy volunteers in need of sinus floor elevation were included in the study. The lateral approach was adopted placing the antrostomy randomly either close to the level of the sinus floor (group A) or approximately 3-4 mm cranially (group B). Cone-beam computed tomography (CBCT) was done before surgery (T0) and after 1 week (T1) and 9 months (T2), and analyses on dimensional variations were performed. RESULTS: CBCT of 10 patients per group were analyzed. At T1, the sinus floor was found to be elevated by 9.8 ± 2.1 mm in group A and 10.9 ± 1.9 mm in group B. At T2, shrinkage of 2.0 ± 1.7 mm in group A and 1.4 ± 2.5 mm in group B was observed. The area was reduced approximately 18-24% between T1 and T2. The sinus mucosa width increased by 4.3-5 mm between T0 and T1, and regained the original dimensions at T2. CONCLUSIONS: The more cranial the antrostomy, the greater the augmentation height after 9 months.

Histological and micro-computed tomography evaluations of newly formed bone after maxillary sinus augmentation using a xenograft with similar density and mineral content of bone: An experimental study in rabbits.

The objective of this study was to evaluate possible differences in the assessment of bone formation between histological and micro-computed tomography (CT) analyses in maxillary sinuses augmented with a xenograft with similar density and mineral content of bone. A collagen membrane was placed subjacent the elevated sinus mucosa at the test sites of 18 rabbits, and the elevated spaces were filled with xenograft. The antrostomy was covered with collagen membranes, bilaterally. Six rabbits per group were sacrificed after 2, 4, and 8 weeks of healing. Biopsies were retrieved and scanned in a high-resolution micro-CT at two different gray thresholds. Histological assessments were subsequently performed. At the histological analyses, bone increased over time, from 7.5 ± 2.4% to 27.0 ± 5.3%, between 2 and 8 weeks of healing. The highest content of bone was found close to the sinus bone walls, whereas the middle regions contained lower amounts. At the micro-CT analyses, discrepancies were found in bone content percentages compared with the histological analyses, especially after 2 weeks of healing and within the middle regions of the sinus, in which new bone was ~15-22% at the micro-CT analyses and only 1.6% at the histological evaluation. The outcomes of a micro-CT analysis performed in an early phase of healing may be altered when a resorbable bone substitute with similar density and mineral content of bone is applied.

Influence of a collagen membrane positioned subjacent the sinus mucosa following the elevation of the maxillary sinus. A histomorphometric study in rabbits.

OBJECTIVE: To evaluate the healing after elevation of the sinus mucosa when a collagen membrane was placed between the sinus mucosa and a xenograft used as filler. MATERIALS AND METHODS: Eighteen rabbits were used. Sinus mucosa elevation was performed bilaterally, and a collagen membrane was applied subjacent to the sinus mucosa only at a randomly selected test site. At both sites, a collagenated corticocancellous porcine bone was placed within the elevated space and the access window was covered with a collagen membrane. The animals were sacrificed after 2, 4, and 8 weeks of healing, six animals for group. Ground sections were prepared. RESULTS: At the histomorphometric evaluation, the elevated area after 2 and 8 weeks was 11.8 and 8.8 mm2 at the test, and 10.0 and 5.3 mm2 at the control sites, respectively. The available area was obtained subtracting the remaining area occupied by the membrane from the elevated area and, after 8 weeks, was 6.7 ± 0.9 mm2 . After 8 weeks of healing, the mineralized new bone within the elevated space was 18.2 ± 5.5% at the test and 26.7 ± 7.7% at the control sites. Within the available space at the test site, the percentage was 27.3 ± 7.0% after 8 weeks of healing. At 2 and 8 weeks of healing, within the elevated space, the xenograft proportion was 30.9 ± 4.4% and 6.9 ± 2.8% at the test, and 35.2 ± 7.3% and 9.6 ± 4.9% at the control sites, respectively. CONCLUSIONS: The placement of a collagen membrane subjacent the sinus mucosa did not reveal any major morphometric difference. The collagen membrane was not completely resorbed after 8 weeks.