Active and Passive Mineralization of Bio-Gide® Membranes in Rat Calvaria Defects.

Bio-Gide® is a collagen membrane routinely used in guided bone regeneration. Recent studies have shown that this collagen membrane has osteoconductive properties, meaning that it can support the growth of new bone. However, it has also been observed that the collagen membrane has areas of mineralized fibers which can occur spontaneously and independently of osteoblasts. To better understand how this works, we established a model using minced collagen membranes to reduce the active mineralization of intact collagen membranes in favor of passive mineralization. We thus compared the original intact membrane with a minced collagen membrane in a 5 mm calvarial defect model in Sprague Dawley rats. After three weeks of healing, histology and microcomputed tomography (µCT) were performed. Histological analysis confirmed the osteoconductive properties, with new bone growing inside the intact collagen membrane. However, in minced collagen membranes, the osteoconductive properties were restricted to the defect margins. Interestingly, histology revealed large mineralized areas indicating passive mineralization with no signs of bone formation. In the µCT analysis, the intact collagen membranes caused a higher median mineralized volume (1.5 mm3) compared with the minced group (0.4 mm3), but this lacked significance (p = 0.09). The µCT analysis needs to be interpreted carefully, particularly in defects filled with minced membranes, considering that the mineralized tissue may not necessarily be bone but also the result of passive mineralization. Taken together, the findings suggest that Bio-Gide® collagen membranes support bone formation while also exhibiting potential for passive mineralization.

The Influence on Osseointegration of Immediate Functional Loading on Single Crowns: A Randomized, Double-Blind, Split Mouth Controlled Clinical Trial with Histomorphometric Evaluation.

PURPOSE: To evaluate the influence of immediate loading on osseointegration and bone density of implants installed in a healed alveolar bone crest and supporting single crowns. MATERIALS AND METHODS: Two solid titanium transmucosal mini-screws were inserted in the distal regions of the mandible in 14 patients. One mini-implant was immediately functionally loaded, whereas the other was left unloaded. After two months of healing, biopsies were retrieved and new bone, old bone, and total bone (new and old bone) were assessed. RESULTS: Histological examination was performed on biopsies This peer-reviewed, accepted manuscript will undergo final editing and production prior to print publication. from 12 patients (n=12). New bone-to-implant contact percentage (BIC%) was 40.3 ± 16.8 % and 55.1 ± 19.1 % (p=0.043) at the unloaded and loaded sites, respectively, while the total BIC% was 44.9 ± 17.0 % and 59.5 ± 18.8 %, respectively (p=0.034). The new bone density was 45.9 ± 11.6 % and 45.9 ± 16.7 % in the unloaded and loaded implants, respectively (p=0.622). CONCLUSIONS: Immediate loading positively affected bone apposition on the implant surface, while no effect on bone density was observed after 2 months of healing.

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.

Functionalizing Collagen Membranes with MSC-Conditioned Media Promotes Guided Bone Regeneration in Rat Calvarial Defects.

Functionalizing biomaterials with conditioned media (CM) from mesenchymal stromal cells (MSC) is a promising strategy for enhancing the outcomes of guided bone regeneration (GBR). This study aimed to evaluate the bone regenerative potential of collagen membranes (MEM) functionalized with CM from human bone marrow MSC (MEM-CM) in critical size rat calvarial defects. MEM-CM prepared via soaking (CM-SOAK) or soaking followed by lyophilization (CM-LYO) were applied to critical size rat calvarial defects. Control treatments included native MEM, MEM with rat MSC (CEL) and no treatment. New bone formation was analyzed via micro-CT (2 and 4 weeks) and histology (4 weeks). Greater radiographic new bone formation occurred at 2 weeks in the CM-LYO group vs. all other groups. After 4 weeks, only the CM-LYO group was superior to the untreated control group, whereas the CM-SOAK, CEL and native MEM groups were similar. Histologically, the regenerated tissues showed a combination of regular new bone and hybrid new bone, which formed within the membrane compartment and was characterized by the incorporation of mineralized MEM fibers. Areas of new bone formation and MEM mineralization were greatest in the CM-LYO group. Proteomic analysis of lyophilized CM revealed the enrichment of several proteins and biological processes related to bone formation. In summary, lyophilized MEM-CM enhanced new bone formation in rat calvarial defects, thus representing a novel 'off-the-shelf' strategy for GBR.

FasL is a catabolic factor in alveolar bone homeostasis.

AIM: Fas ligand (FasL) belongs to the tumour necrosis factor superfamily regulating bone turnover, inflammation, and apoptosis. The appendicular and axial skeleton phenotype of mature Faslgld mice has been reported. The impact of FasL on the alveolar bone providing support for the teeth at mature stages under healthy and induced inflammatory conditions remains unknown. MATERIALS AND METHODS: We performed a phenotypical analysis of mice carrying the homozygous Faslgld mutation and wild-type (WT) mice (C57BL/6) under healthy conditions and upon ligature-induced periodontitis. After 12 days, micro-computed tomography analysis revealed the distance between the cement enamel junction and the alveolar bone crest. Additional structural parameters, such as the bone volume fraction (BV/TV) and the periodontal ligament space volume, were measured. Histological analyses were performed to visualize the catabolic changes at the defect site. RESULTS: Healthy Faslgld mice were found to have more periodontal bone than their WT littermates. Faslgld had no significant effect on inflammatory osteolysis compared to WT controls with ligatures. Histology revealed eroded surfaces at the root and in the inter-proximal bone in both strains. CONCLUSIONS: Our findings suggest that FasL is a catabolic factor in alveolar bone homeostasis but it does not affect the inflammatory osteolysis.

Influence of the use of autogenous bone particles to close the access window after maxillary sinus floor augmentation: a micro-computed tomography and positron emission tomography study in rabbits.

AIM: The purpose of this study was to evaluate using microCT and positron emission tomography (PET) analysis, the influence on bone healing of the placement of particulate autogenous bone in the antrostomy, and in the subjacent region after maxillary sinus elevation with xenograft. MATERIAL AND METHODS: The sinus mucosa was elevated in sixteen male New Zealand rabbits and they were both grafted with a collagenated cortico-cancellous porcine bone. The antrostomy and the near subjacent region were filled with either the same xenograft (control site) or with particulate autogenous bone (test site) harvested from the tibia. The antrostomies were covered with collagen membranes. MicroCT (measured in Hounsfield Units) and microPET (kBq/cm3) using sodium fluoride infiltration (18F-NaF) were performed at the time of euthanasia that was performed after 1 and 8 weeks of healing, using 8 animals in each group. The Wilcoxon test was used for analysis. RESULTS: At the microCT analysis, after 1 and 8 weeks of healing, no statistically significant differences were found between groups. Bone increased and xenograft decreased significantly between the two periods of healing. At the microPET analysis, the percentage of bone increased significantly over time in both test and control groups and no significant differences were found between groups. CONCLUSION: The placement of autogenous bone in the antrostomy and the subjacent region after maxillary sinus elevation did not enhance bone formation compared with sites where only xenograft was used. Both microCT and microPET showed increase bone formation over time.

Osseointegration at Implants Installed in Composite Bone: A Randomized Clinical Trial on Sinus Floor Elevation.

Osseointegration of implants installed in conjunction with sinus floor elevation might be affected by the presence of residual graft. The implant surface characteristics and the protection of the access window using a collagen membrane might influence the osseointegration. To evaluate these factors, sinus floor elevation was performed in patients using a natural bovine bone grafting material. The access windows were either covered with a collagen membrane made of porcine corium (Mb group) or left uncovered (No-Mb group) and, after six months, two mini-implants with either a moderate rough or turned surfaces were installed. After 3 months, biopsies containing the mini-implants were retrieved, processed histologically, and analyzed. Twenty patients, ten in each group, were included in the study. The two mini-implants were retrieved from fourteen patients, six belonging to the Mb group, and eight to the No-Mb group. No statistically significant differences were found in osseointegration between groups. However, statistically significant differences were found between the two surfaces. It was concluded that implants with a moderately rough surface installed in a composite bone presented much higher osseointegration compared to those with a turned surface. The present study failed to show an effect of the use of a collagen membrane on the access window.

Effects of Induced Malocclusion on Vertebral Alignment in Rats: A Controlled Study by CBCTs.

This study aimed to evaluate with CBCTs the alteration of vertebral alignment over time of induced malocclusion in rats. Crown pads increasing the vertical dimension of 0.5 mm were applied on the upper molars at one randomly selected side of the maxilla in rats (premature contact side) while the opposite side was left untreated (control side). Four groups were organized, ten animals each. In groups A, B, and C, the crowns were applied at time 0 (t-0). In group A, the crowns were removed after 2 weeks (t-2w) and euthanized after two more weeks, while in groups B and C, the animals were euthanized after 2 and 4 weeks (t-4w), respectively. No premature contacts were applied in group D. CBCTs were taken at t-0 in all animals before applying the crowns, at t-2w in group A before removing the crowns, and in all groups before the euthanasia. The changes in the iliac crest angle (ICA) that formed between the superior external margin of the iliac crest and the vertebral spine were evaluated. In groups A and B, after 2 weeks, the changes in ICA were statistically significant at p = 0.028 and p = 0.042, respectively. In group C, and in the control group D, the changes of ICA were not statistically significant (p = 0.058 and p = 0.414, respectively). In conclusion, the incease in monolateral occlusion in the molar region yielded a rotation of the lumbo-sacral segment towards the same side of the occlusal bite-raising.

Sinus Mucosa Thickness Changes and Ostium Involvement after Maxillary Sinus Floor Elevation in Sinus with Septa. A Cone Beam Computed Tomography Study.

BACKGROUND: A thickening of the sinus mucosa is observed after sinus floor augmentation. The objective of this retrospective study was to evaluate the influence of the presence of septa in the dimensional variation and ostium involvement over time of the Schneiderian mucosa after sinus floor augmentation. MATERIALS AND METHODS: Fifteen sinuses with septa (septa group) and 15 without (control group) were selected. CBCTs taken before surgery, and were analyzed after 1 week and after 9 months. Schneiderian membrane thickness changes over time and involvement of the ostium were evaluated. RESULTS: Four perforations occurred in the septa group and none in the control group. After 1 week of healing, the sinus mucosa thickness increased in height by 5.7 mm and 7.1 mm in the septa and control groups, respectively. In this period, the patency of the ostium decreased in both groups, and three infundibula were obstructed in the septa group, and five in the control group. The mucosa was thicker and the edema was closer to the ostium in the control compared to in the septa group. After 9 months of healing, the dimensions regressed to normal pattern and no obstruction of the infundibula were observed. No statistically significant differences were found between septa and control groups. CONCLUSIONS: after one week of healing, the sinus mucosa increased in dimensions in both septa and control groups. However, the sinus mucosa presented a tendency of being thicker and closer to the ostium, resulting in a higher number of infundibula obstructions, in the control group compared to in the septa group. After 9 months, the sinus mucosa regressed to normal dimensions and no obstructions of the infundibula were observed in any group.

The Impact on the Healing of Bioactivation with Argon Plasma of a Xenogeneic Graft with Adequate Fixation but Poor Adaptation to the Recipient Site: An Experimental Study in Rabbits.

PURPOSE: To evaluate the impact on healing of bioactivation with argon plasma of a xenogeneic graft with adequate fixation but poor adaptation to the native host bone. MATERIALS AND METHODS: Xenogeneic grafts were either treated with argon plasma or left untreated and randomly secured with a titanium screw to both lateral aspects of the mandible angle of rabbits. A discrepancy was obtained between the xenograft and the mandible due to the convexity of the recipient site. Collagen membranes were placed on the grafts. Thirty animals were included and euthanized in groups of 10 after 2, 6, and 10 weeks, respectively. Histomorphometric evaluations were performed on ground sections. Newly formed bone was the primary outcome, while the distance between the peak of new bone inside the graft and the upper surface of the graft, the xenograft percentages, and the area of the xenograft were considered as secondary variables. The Wilcoxon test was applied for statistical analyses. RESULTS: After 2 weeks of healing, gaps of ~0.5 mm were observed at the interface between the graft and the recipient sites, and new bone was mainly located in the interface and within the inferior regions of the grafts. New bone increased over time in all regions, including those in the upper zones of the graft, reaching proportions of 20.3% ± 6.5% and 19.3% ± 7.4% (P = .484) after 10 weeks in the plasma and control groups, respectively. The mean distance between the peak of new bone inside the graft and the upper surface of the graft decreased between 2 and 10 weeks of healing from 1.4 mm to 0.4 mm and from 1.7 mm to 0.3 mm at the plasma and control sites, respectively. CONCLUSION: The xenogeneic grafts of both groups were incorporated into the recipient sites by newly formed bone that presented a growth close to the upper surface of the graft. The bioactivation with argon plasma did not improve healing.

Influence of Anatomical Parameters on the Dimensions of the Subantral Space and Sinus Mucosa Thickening after Sinus Floor Elevation. A Retrospective Cone Beam Computed Tomography Study.

BACKGROUND: Various anatomical parameters might influence the surgical approach for maxillary sinus floor elevation. The objective of the present study was to retrospectively evaluate the influence of anatomical parameters on the dimensions of the subantral space and of the sinus mucosa thickening after sinus floor elevation. MATERIAL AND METHODS: Seventy-eight maxillary sinuses in sixty-five patients were evaluated on cone beam computed tomographies taken before surgery and after one week (t1w) and nine months (t9m). Several parameters such as the distance XF between an axis parallel to the base of the nose (X-axes) and the sinus floor (F) were correlated with the height gain (IF) at t1w and t9m and the post-surgical edema. RESULTS: A weak significant positive correlation was observed between height gain vs. sinus height of interest (XF), the balcony, and the sinus floor angle. The post-surgical edema was influenced by the initial mucosa thickness and the xenograft used. CONCLUSIONS: Various parameters might affect height gain and sinus mucosa thickening after sinus floor elevation. The height of interest, the balcony, and the sinus floor angle showed significant correlations with height gain. The initial thickness of the mucosa and the biomaterial used influenced the post-surgical edema.

Osteoconductive properties of upside-down bilayer collagen membranes in rat calvarial defects.

BACKGROUND: Bilayer collagen membranes are routinely used in guided bone/tissue regeneration to serve as osteoconductive scaffolds and prevent the invasion of soft tissues. It is recommended to place the membranes with their dense layer towards the soft tissue and their porous layer towards the bony defect area. However, evidence supporting this recommendation is lacking. This study aimed to determine whether the alignment of bilayer collagen membranes has an effect on bone regeneration. METHODS: In two groups of ten male Sprague-Dawley rats each, a 5-mm calvarial defect was created. Thereafter, the defect was randomly covered with a bilayer, resorbable, pure type I and III collagen membrane placed either regularly or upside-down (i.e., dense layer towards bone defect). After 4 weeks of healing, micro-computed tomography (µCT), histology, and histomorphometry of the inner cylindrical region of interest (4.5 mm in diameter) were performed to assess new bone formation and the consolidation of the collagen membrane in the defect area. RESULTS: Quantitative µCT showed similar bone volume (median 8.0 mm3, interquartile range 7.0-10.0 vs. 6.2 mm3, 4.3-9.4, p = 0.06) and trabecular thickness (0.21 mm, 0.19-0.23 vs. 0.18 mm, 0.17-0.20, p = 0.03) between upside-down and regular placement, both leading to an almost complete bony coverage. Histomorphometry showed comparable new bone areas between the upside-down and regularly placed membranes, 3.9 mm2 (2.7-5.4) vs. 3.8 mm2 (2.2-4.0, p = 0.31), respectively. Both treatment groups revealed the same regeneration patterns and spatial distribution of bone with and without collagen fibers, as well as residual collagen fibers. CONCLUSIONS: Our data support the osteoconductive properties of collagen membranes and suggest that bone regeneration is facilitated regardless of membrane layer alignment.

FasL Is Required for Osseous Healing in Extraction Sockets in Mice.

Fas ligand (FasL) is a member of the tumor necrosis factor (TNF) superfamily involved in the activation of apoptosis. Assuming that apoptosis is initiated after tooth extraction it is reasonable to suggest that FasL may play a pivotal role in the healing of extraction sockets. Herein, we tested the hypothesis of whether the lack of FasL impairs the healing of extraction sockets. To this end, we extracted upper right incisors of FasL knockout (KO) mice and their wildtype (WT) littermates. After a healing period of two weeks, bone volume over total volume (BV/TV) via µCT and descriptive histological analyses were performed. µCT revealed that BV/TV in the coronal region of the socket amounted to 39.4% in WT and 21.8% in KO, with a significant difference between the groups (p=0.002). Likewise, in the middle region of the socket, BV/TV amounted to 50.3% in WT and 40.8% in KO (p<0.001). In the apical part, however, no difference was noticed. Consistently, WT mice displayed a significantly higher median trabecular thickness and a lower trabecular separation when compared to the KO group at the coronal and central region of the socket. There was the overall tendency that in both, female and male mice, FasL affects bone regeneration. Taken together, these findings suggest that FasL deficiency may reduce bone regeneration during the healing process of extraction sockets.

Sinus Mucosa Thinning and Perforations after Sinus Lifting Performed with Different Xenografts: A Histological Analysis in Rabbits.

BACKGROUND: Experimental studies have shown a progressive thinning and perforations of the sinus mucosa associated with sharpened edges and the cutting projections of graft particles used simultaneously for maxillary sinus augmentation. Hence, the aim of the present study was to evaluate the damaging effects of two different bovine grafts on the sinus mucosa after sinus augmentation. METHODS: Twenty New Zealand rabbits received a bilateral sinus lifting using, as fillers, two different types of deproteinized bovine bone in granules, one processed at low temperature (low-T group), and the other at high temperature (high-T group). Thinned mucosa sites (<40 µm) and perforations were evaluated in the sinus mucosa that were in contact with graft granules after 2 and 10 weeks, in ten animals per period. RESULTS: After 2 weeks of healing, the number of thinned mucosa sites was 118 in the low-T group, and 149 in the high-T group (p = 0.191). At the 10-week assessment, the thinned sites increased to 237 and 195 sites, respectively. The numbers of sinus mucosa perforations after 2 weeks were eight and three in the low-T and high-T group, respectively. At the 10-week evaluation, the perforations increased to 19 in the low-T group, and to 14 in the high-T group. CONCLUSIONS: The contact with bovine xenografts yielded thinning and perforations of the sinus mucosa. Despite the differences in characteristics and dimensions, no differences were found between the two xenografts in the numbers of thinning mucosa sites and perforations. However, a trend of more events was found in the low-T compared to the high-T group.

An enigmatic soft tissue creeping phenomenon: The spontaneous peri-implant mucosa margin and papilla growth. A retrospective clinical study.

OBJECTIVES: The aim of the present retrospective study was to evaluate papillae filling rate and buccal margins coronal growth in implant-supported prostheses which were over-contoured at the apical buccal third to form a rearmost collar zone, thus mimicking a false root. MATERIAL AND METHODS: The influence of adjacent elements, teeth, implants, or pontics was examined. One-hundred and three crowns have been assessed in photographs taken on 61 patients after prosthesis delivering and at last follow-up (mean 2.8 years). The Jemt index was adopted to evaluate papillae growth at the baseline and follow-up as follows: 0, absence of papilla; 1, less than half of interdental embrasure height; 2, more than half of interdental embrasure height; 3, fully papilla filled interdental embrasure. Index score 4, papilla hyperplasia was not included. Moreover, the coronal growth (or recession) of buccal mucosa in implant-supported crowns was assessed. RESULTS: At baseline, a total of 29 papillae had a 0 score, while only two scored 3 with complete papilla formation. On follow-up, only one papilla scored 0, while 46 scored 3 with complete interdental embrasures filling. The highest papilla score was registered from first year crown insertion and likewise in interdental embrasures located between two implants or implants and pontics. Moreover, the buccal margin growth was observed in almost 80% of crowns. Such findings seem to indicate that buccal margin and papilla around implant-supported crowns presented a coronal growth over time, especially during its first year. The average papilla growth between two implants was no lower than that observed in papilla present between implants and natural teeth. CONCLUSIONS: Recessed areas at collar of implant-supported prostheses appear to positively influence papillae and buccal margin growth, especially in its first year. Papilla growth between two implants was similar to that observed between implants and natural teeth.

The Influence on Healing of Bony Window Elevated Inward in the Sinus Cavity as Cortical Bone Graft: A Histomorphometric Study in Rabbit Model.

PURPOSE: To evaluate the influence on healing of the bony window elevated inward in the sinus cavity as a cortical bone graft. MATERIALS AND METHODS: Eighteen rabbits were included in the experiment. At the test sites (bony window), the antrostomy was prepared and the remaining bony window was elevated together with the sinus mucosa. At the control sites, the bony window was gently detached before the sinus mucosa elevation and discarded. The space obtained was grafted with deproteinized bovine bone mineral (DBBM). A collagen membrane was positioned on the antrostomy at both sides. The rabbits were euthanized after 2, 4, and 8 weeks in groups of six each. Histologic analyses in different regions of the elevated space were carried out, and a Wilcoxon test was used to estimate differences. Microcomputed tomography (microCT) analyses were also performed. RESULTS: After 2 weeks of healing, higher proportions of new bone were found in the test group compared with the control group due to the higher amount of bone formed in the region subjacent to the sinus mucosa. In this region, higher amounts of new bone were also found in the test group after 4 (P = .028) and 8 weeks of healing (P = .345). After 8 weeks of healing, the percentage of new bone was higher at the control sites compared with the test sites, with the proportions being 25.4% ± 3.2% and 21.3% ± 6.1%, respectively. In this period of evaluation, the bony window contributed with 20.1% ± 5.3% of vital bone in the test group. A fraction of 60.4% ± 10.8% of its surface was surrounded by new bone. In the microCT analysis, after 8 weeks of healing, fractions of 22.3% ± 1.6% and 22.2% ± 0.7% of bone were found in the test and control groups, respectively. CONCLUSION: The presence of the bony window positively influenced the healing in the elevated space, especially in the submucosa region. The bony window was vital and incorporated into newly formed bone.

Involvement of the maxillary sinus ostium (MSO) in the edematous processes after sinus floor augmentation: a cone-beam computed tomographic study.

BACKGROUND: After sinus floor augmentation, a thickening of the sinus mucosa has been described. The aim of the present study was to evaluate the involvement of the maxillary sinus ostium in the edematous processes after a sinus floor augmentation procedure. METHODS: Seventy-two cone-beam computerized tomographies (CBSTs) were taken before sinus floor augmentation and after 1 week and 9 months from surgery and analyses. Sinus mucosa thickness and area, ostium diameter and patency, and extension of the post-surgical transient mucosal thickening in relation to the ostium were evaluated on the CBCTs for all three periods. The term "virtual" when referring to sinus mucosa thickness and area was introduced because of the edema and bleeding that both contributed to a transient thickening and additional elevation of the sinus mucosa. RESULTS: The mean virtual thickness of the sinus mucosa was 2.7 ± 4.0 mm, 7.7 ± 7.1 mm, 1.7 ± 2.0 mm before surgery, and after 1 week and 9 months. The virtual mucosa area was 37.2 ± 52.5 mm2, 184.5 ± 153.8 mm2, and 34.0 ± 50.7 mm2. The ostium diameter at the three periods evaluated was 1.8 ± 0.5 mm, 1.1 ± 0.6 mm, 1.5 ± 0.8 mm, respectively. Three infundibula (4.2%) were found out of patency before surgery while this number increased to 14 (19.4%) after 1 week. Nine months after surgery, only one infundibulum (1.4%) was out of patency, however, without presenting signs of sinus pathologies. The extension of the mucosal edema on the palatal sinus was reduced after 9 months of healing. CONCLUSIONS: One week after sinus floor augmentation, the maxillary sinus mucosa increased in dimensions and in several cases involved the ostium, reducing its diameter and producing a transient loss of patency. After 9 months of healing, the initial conditions were recovered.

Effect of lack of plaque control after the surgical treatment of peri-implantitis at surfaces with different characteristics: an experimental study in dogs.

OBJECTIVE: The aim of the present study was to evaluate the effect of the induction of peri-implantitis and of plaque accumulation on implants with different surface characteristics after the surgical treatment. MATERIAL AND METHODS: All mandibular premolars and first molars were extracted bilaterally in six dogs. After 3 months, two non-submerged implants were installed, each with either a hydrophilic sandblasted and acid-etched surface stored in saline solution (SLActive) or an acid-etched and modified with calcium ions surface (UnicCa). After 3 months, ligatures were placed in the sulcus around the implants to induce an experimental peri-implantitis and plaque accumulation was allowed. After 3 months, ligatures were removed and, after one more month of plaque accumulation, a surgical treatment was performed using gauzes soaked in saline and irrigations. X-rays were taken at this stage. Plaque control maintenance was established at the control sites, while plaque accumulation was allowed at the test sites (plaque sites). After 5 months, biopsies were obtained. Marginal bone levels were compared between x-rays and histological assessments. RESULTS: At the time of peri-implantitis treatment, two SLActive implants were lost. At the euthanasia, seven more implants were lost only in the plaque group, one control and six test implants. The calculated mean values of the marginal bone level of the two surfaces at the treatment were 3.65 ± 1.71 mm in the control group, and 3.65 ± 1.76 mm in the plaque group (p = 0.463). The additional marginal bone loss after 5 months from surgical treatment was 0.67 ± 0.67 mm (UnicCa, 0.48 ± 1.06 mm and SLActive, 0.79 ± 2.10 mm) and 3.11 ± 1.38 mm (UnicCa, 2.67 ± 1.87 mm and SLActive, 3.94 ± 2.11 mm) for the control and plaque groups, respectively (p = 0.028). CONCLUSIONS: The lack of plaque control after the surgical treatment of the peri-implantitis strongly influenced the marginal bone loss.

Influence of the Dimensions of the Antrostomy on Osseointegration of Mini-implants Placed in the Grafted Region After Sinus Floor Elevation: A Randomized Clinical Trial.

PURPOSE: To evaluate the osseointegration of mini-implants placed in grafted sinuses with lateral windows of two different dimensions. MATERIALS AND METHODS: Sinus floor augmentation was performed in volunteers using a lateral window. The antrostomy was systematically prepared with a height of either 8 mm (large group) or 4 mm (small group). After 6 months of healing, mini-implants were placed in the grafted region. Biopsy specimens including the mini-implants were harvested 3 months after placement. RESULTS: Twenty biopsy specimens, 10 from each group, were suitable for the histologic analysis. Similar amounts of new bone-to-implant contact were obtained in both the large (41.1% ± 19.5%) and the small (42.8% ± 13.2%) groups (P = .940). Small percentages of residues of xenograft were found in contact with the implant surface, with 0.6% ± 1.1% in the large group and 5.9% ± 9.5% in the small group (P = .098). The new bone density around the implants was 31.7% ± 8.2% and 34.0% ± 7.9% in the large and small groups, respectively (P = .623). CONCLUSION: The dimensions of the antrostomy did not influence the histologic healing of implants placed 6 months after sinus floor augmentation.