Critical-sized marginal defects around implants in the rabbit mandible.

BACKGROUND: The mandible of the rabbit is considered a reliable model to be used to study bone regeneration in defects. The aim of the present study was to evaluate the formation of new bone around implants installed in defects of either 5 or 10 mm in the mandible of rabbits. MATERIALS AND METHODS: In 12 rabbits, 3 mm deep circumferential defect, either 5 or 10 mm in diameter, were prepared bilaterally and an implant was placed in the center. A collagen membrane was placed to close the entrance. After 10 weeks, biopsies were taken, histological slides were prepared, and different regions of the defects were analyzed. RESULTS: Similar amounts of new bone were found in both defects. However, most of the 5 mm defects were filled with new bone. New bone was observed closing the entrance of the defect and laid onto the implant surface. Only in a few cases the healing was incomplete. Despite a similar percentage of new bone found within the 10 mm defects, the healing was incomplete in most of the cases, presenting a low rate of bone formation onto the implant surface within the defect. Only one case presented the closure of the entrance. CONCLUSIONS: The dimensions of the defect strongly influenced the healing so that a circumferential marginal defect of 10 mm around an implant in the mandible body should be considered a critical-sized defect. The presence of the implant and of residues of teeth might have strongly influenced the healing.

Influence on marginal bone levels at implants equipped with blades aiming to control the lateral pressure on the cortical bone. An experimental study in dogs.

BACKGROUND: To avoid cortical compression, several implant systems have included in the protocol dedicated drills aimed at widening the cortical region of osteotomy. However, the manual execution of this operation does not guarantee the necessary precision. Hence, the present study aimed to determine the optimal size of the recipient site at the level of the alveolar crest in relation to the size of the coronal region of the implant to achieve the best healing result. MATERIALS AND METHODS: Blades of different diameters were incorporated into the coronal part of the implant to prepare the cortical region of the mandibular alveolar bone crest in different dimensions in relation to the collar of the implant. The differences in diameter of the blades in relation to the collar of the implant were as follows: one control group, -175 µm, and three test groups, 0 µm, + 50 µm, or + 200 µm. RESULTS: The marginal bone loss (MBL) at the buccal aspect was 0.7 mm, 0.5 mm, 0.2 mm, and 0.7 mm in the - 175 µm, 0.0 µm, + 50 µm, + 200 µm groups, respectively. The differences were statistically significant between group + 50 µm and control group - 175 µm (p = 0.019), and between + 50 µm and + 200 µm (p < 0.01) groups. The level of osseointegration at the buccal aspect was more coronally located in the test groups than in the control group, whereas the bone-to-implant contact percentage was higher in the + 50 µm and + 200 µm groups. However, these differences were not statistically significant. CONCLUSIONS: The lowest bone crest resorption and highest levels of osseointegration were observed in the 0.0 µm and + 50 µm groups. The cortical region where the blades had performed their cutting action showed regular healing with perfect hard and soft tissues sealing in all the groups. Cortical blades gathered bone particles, particularly in the + 200 µm group, which were incorporated into the newly formed bone. The results from the present experiment provide support to the use of blades that produce a marginal gap of 50 µm after implant insertion.

Variables Influencing Bone Formation After Transcrestal Sinus Floor Elevation: Radiographic and Tomographic Evaluations.

PURPOSE: To evaluate the influence of initial implant protrusion within the subantral space on hard tissue gain for implants placed simultaneously with transcrestal sinus floor elevation (TSFE) with a biomaterial. MATERIALS AND METHODS: A total of 50 implants were placed after TSFE in 44 patients using either a human demineralized bone matrix or a deproteinized bone mineral matrix. Intraoral radiographs were obtained before and immediately after surgery. CBCT scans were obtained at the last follow-up (mean: 6.6 years). RESULTS: The initial bone crest height was 4.6 ± 1.4 mm, and the initial protrusion of the implants above the sinus floor was 3.5 ± 1.4 mm. At the follow-up assessments, the hard tissue mean gain was 2.5 ± 1.5 mm, resulting in a mean residual protrusion of 1.1 ± 1.3 mm. Only 10 implants did not protrude above the apical level of hard tissue. Positive correlations were found between hard tissue gain and initial protrusion (r = 0.55; 95% CI: 0.32 to 0.72; P = .0001), between the initial and final protrusions (r = 0.38; 95% CI: 0.10 to 0.60; P = .007), and between the follow-up period and final protrusion (r = 0.35; 95% CI: 0.07 to 0.58; P = .012). CONCLUSIONS: The higher the initial protrusion was, the higher were the hard tissue gain and the final protrusion of the implant above the apical level of the hard tissue.

Critical-sized marginal defects around implants treated with xenografts in rabbits.

BACKGROUND: Healing of critical-size defects is a well-known problem that has been challenged in several studies. The aim of the experiment was to evaluate bone formation and osseointegration of implants installed in critical defects of the mandibular body simultaneously grafted with Bio-Oss® or Cerabone®. MATERIAL AND METHODS: Defects, 10 mm wide and 3 mm deep, were prepared at both lateral aspects of the mandible in 12 rabbits. One implant was installed in the center of the defect, and bovine xenografts produced either at low (Bio-Oss®; Low-T) or high (Cerabone®; High-T) temperatures were used to fill the defects. A collagen membrane was placed to cover the sites. Healing was evaluated 10 weeks after surgery. RESULTS: In both groups, most sites showed optimal healing with closure of the coronal entrance of the defects. However, residual defects occupied by soft tissues and biomaterial particles were observed, even though generally limited to some regions of the defect. Osseointegration of the implant surface in the region of the defect was poor in both groups. CONCLUSIONS: Circumferential marginal critical-size defects around implants filled with bovine xenografts presented regions with a complete healing in both groups. However, the healing was not complete at all regions in most defects; therefore, a complete optimal healing of critical-size marginal defects cannot be predicted.

Mineralization and morphology of peri-implant bone around loaded and unloaded dental implants retrieved from the human mandible.

PURPOSE: Limited data is reported regarding the bone mineralization around dental implants in the first months from insertion. The study analyzed the peri-implant bone around loaded and unloaded implants retrieved from human mandible after 4 months from placement. METHOD: The composition and mineralization of human bone were analyzed through an innovative protocol technique using Environmental-Scanning-Electron-Microscopy connected with Energy-Dispersive-X-Ray-Spectroscopy (ESEM/EDX). Two regions of interest (ROIs, approximately 750×500 µm) for each bone implant sample were analyzed at the cortical (Cortical ROI) and apical (Apical ROI) implant threads. Calcium, phosphorus, and nitrogen (atomic%) were determined using EDX, and the specific ratios (Ca/N, P/N, and Ca/P) were calculated as mineralization indices. RESULTS: Eighteen implant biopsies from ten patients were analyzed (unloaded implants, n=10; loaded implants, n=8). For each ROI, four bone areas (defined bones 1-4) were detected. These areas were characterized by different mineralization degree, varied Ca, P and N content, and different ratios, and by specific grayscale intensity detectable by ESEM images. Bony tissue in contact with loaded implants at the cortical ROI showed a higher percentage of low mineralized bone (bone 1) and a lower percentage of remodeling bone (bone 2) when compared to unloaded implants. The percentage of highly mineralized bone (bone 3) was similar in all groups. CONCLUSION: Cortical and apical ROIs resulted in a puzzle of different bone "islands" characterized by various rates of mineralization. Only the loaded implants showed a high rate of mineralization in the cortical ROI.

Application of the break-even point to express the bone dynamics around implants.

PURPOSE: The aim of this study was to apply the break-even point concept to express the dynamics of bone formation and resorption around implants. METHODS: Published data on new bone and parent bone densities around implants from one human and three dog studies were selected and used for analysis. The break-even point (BEP) of the bone density (BD) was assessed. The BEP is the point at which, in a graph, the lines representing the formation of new bone and resorption of old bone intersect. BEP is expressed in time (x; days) of occurrence and percentage of bone (y; %) at which the break-even point occurs and illustrates the grade of bone modeling. The sooner the occurrence, the faster the bone formation in relation to the resorption of the old bone. RESULTS: In the marrow and cortical compartments, BEP of bone density occurred after 7.9 days (BD% 24.5%) and >30 days, respectively. Different surfaces presented similar BEP, ranging between 9.7 and 11.2 days (BD% 19.1-22.5%). BEP at implants installed in the human maxilla occurred after 29-30.4 days (BD% 28.3-29.6%). CONCLUSION: The present study showed that the parameters used to express the break-even point can provide information on the influence of the model used, surface characteristics, and bone quality on bone modeling/remodeling around implants.

The Effect of Anticoagulants on Early Implant Failure: A Retrospective Cohort Study.

BACKGROUND: Anticoagulants (AC) are among the most often prescribed drugs in the world. Data regarding ACs' effect on the osseointegration of dental implants is lacking. PURPOSE: The aim of the present retrospective cohort study was to evaluate the effect of anticoagulants (AC) on early implant failure (EIF). The null hypothesis was that the use of AC increases the incidence of EIF. MATERIALS AND METHODS: The research included 687 patients who underwent 2971 dental implant placements in the department of oral and maxillofacial surgery in Rabin medical center, Beilinson hospital, by specialists in oral and maxillofacial surgery. The study group comprised 173 (25.2%) patients and 708 (23.8%) implants using AC. The rest of the cohort served as a control. A structured form was used to collect data at patient and implant level. EIF was defined as implant failure within a period of up to 12 months from loading. EIF was the primary outcome parameter. A logistic regression model was used to predict EIF. RESULTS: Implants placed in individuals ≥ 80 (odds ratio (OR) = 0.34, p = 0.05), and ASA 2/3 vs. ASA 1 individuals (OR = 0.30, p = 0.02/OR = 0.33, p = 0.03, respectively) had decreased odds of EIF, and implants in those using anticoagulants (OR = 2.64, p = 0.01) had increased odds of EIF. At the patient level, the odds of EIF in ASA 3 (OR = 0.53, p = 0.02) and IHD (OR = 0.40, p = 0.02) individuals decreased. In AF/VF (OR = 2.95, p = 0.01) individuals, EIF odds increased. CONCLUSIONS: Within the limitations of the present study, the use of AC is significantly associated with an increased likelihood of EIF: the OR was 2.64. Future research is required to validate and examine the prospective impact of AC on the osseointegration phenomena.

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.

Bioactivated Implant Surfaces Placed in Healed Sites or Extraction Sockets: A Preliminary Experimental Study in Dogs.

PURPOSE: To monitor the early bone reaction in a canine model to a conventional sandblasted and dual acid-etched implant surface (ABT), a nanostructured hydrophilic surface (Nano), a dry salt-bioactivated ultra-hydrophilic surface (Hydro), and a bioactivated nanosurface obtained from the addition of dry salts to the Nano surface (Nano-Active). MATERIALS AND METHODS: ABT, Nano, Hydro, and Nano-Active implants were placed in 12 dogs. A randomized split-mouth design was adopted. One implant of each type was placed in the mandible 3 months after tooth extraction in healed sites at the first molar region bilaterally. In the same session, the third and fourth premolars were extracted bilaterally and one implant of each type was immediately placed into the extraction socket. The dogs were euthanized at 14 and 28 days following surgery, and the peri-implant bone reaction was assessed histologically using Stevenel's blue and alizarin red in nondecalcified sections. RESULTS: The postoperative healing was uneventful. The 14-day histologic analysis reported nonsignificant results in terms of difference between the groups, while significant results were found 28 days after surgery. In fact, a significantly higher rate of new bone around the implant was reported in the Nano-Active compared to the Nano groups (51.0% ± 10.2% vs 36.0% ± 10.2%) and Hydro compared to the Nano groups (47.3% ± 10.7% vs 36.0% ± 10.2%). CONCLUSION: The results obtained indicate that new bone formed after 4 weeks demonstrated a tendency for dry salt-treated bioactivated surfaces to improve bone deposition in the interface in the early stages of healing; however, due to the limited number of dogs, the results failed to show a statistical significance. A study with a significantly larger group of animals should be performed in order to challenge the assumption that ultra-hydrophilic-surface implants might show higher bone-implant contact in immediate postextraction replacement.

Evaluation of Bone Response to a Nano HA Implant Surface on Sinus Lifting Procedures: Study in Rabbits.

The aim of this study was to evaluate the bone response to two different implant surfaces on sinus lift procedures in rabbits. Bilateral sinus lifting with inorganic bovine bone associated with collagen membrane and immediate implantation were performed in 16 rabbits. Custom mini-implants were randomly installed in the prepared sites: one side received a double acid-etched (DAE) surface and the other a nano-hydroxyapatite (NHA) surface. The animals were euthanized 30 and 60 days after surgery, and biopsies were collected for microtomographic and histomorphometric analysis. After 30 days, no intra- and inter-group statistical differences were observed in microtomographic analysis, while at 60 days, bone analysis showed statistically significant differences between groups (p < 0.05) for all the evaluated parameters. Histomorphometric analysis showed, after 30 days, mean % of Bone-to-Implant Contact (BIC) for DAE and NHA of 31.70 ± 10.42% vs. 40.60 ± 10.22% (p > 0.05), respectively; for % of Bone Area Fraction Occupancy (BAFO), mean values were 45.43 ± 3.597% for DAE and 57.04 ± 5.537% for NHA (p < 0.05). After 60 days, mean %BIC and %BAFO for DAE and NHA implants were statistically significant (p < 0.05). The NHA surface showed superior biological features compared to the DAE treatment, promoting higher bone formation around the implants in an experimental model of bone repair in a grafted area.

Temporal and Permanent Changes Induced by Maxillary Sinus Lifting with Bone Grafts and Maxillary Functional Endoscopic Sinus Surgery in the Voice Characteristics-Systematic Review.

Sinus surgery procedures such as sinus lifting with bone grafting or maxillary functional endoscopy surgery (FESS) can present different complications. The aims of this systematic review are to compile the post-operatory complications of sinus elevation with bone grafting and FESS including voice changes, and to elucidate if those changes are either permanent or temporary. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) were used, and the literature was exhaustively searched without time restrictions for randomized and non-randomized clinical studies, cohort studies (prospective and retrospective), and clinical case reports with ≥4 cases focused on sinus lift procedures with bone grafts and functional endoscopic maxillary sinus surgery. A total of 435 manuscripts were identified. After reading the abstracts, 101 articles were selected to be read in full. Twenty articles that fulfilled the inclusion criteria were included for analysis. Within the limitations of this systematic review, complications are frequent after sinus lifting with bone grafts and after FEES. Voice parameters are scarcely evaluated after sinus lifting with bone grafts and no voice changes are reported. The voice changes that occur after FESS include a decreased fundamental frequency, increased nasality, and nasalance, all of which are transitory.

Effect of low-speed drilling without irrigation on osseointegration: an experimental study in dogs.

OBJECTIVE: To study the early phases of osseointegration at implants installed in sites prepared with either high rotational speed with irrigation or low rotational speed without irrigation. MATERIAL AND METHODS: After 3 months from tooth extraction, two implants were installed in one side of the mandible of twelve dogs. The osteotomies were prepared either at 60 rpm without irrigation or at 750 rpm with refrigeration. Biopsies were obtained after 4 and 8 weeks of healing, six animals each period for histological analyses. RESULTS: After 4 weeks of healing, new bone percentage in contact with the implant surface (BIC%) was 46.6 ± 7.3% and 43.1 ± 6.8% at the low- and high-speed sites, respectively (p = 0.345). After 8 weeks of healing, the fractions increased to 60.0 ± 11.1% and 60.2 ± 6.2%, respectively (p = 0.753). CONCLUSIONS: Implants installed in sites prepared using either low-rotational drilling without irrigation or high speed with irrigation presented similar amounts of osseointegration.

Fixation screw minimizes bone graft loss following autogenous lateral block graft augmentation: An experimental in vivo study.

PURPOSE: Assess the role of tenting screws in the remodeling processes of autogenous bone blocks used for mandibular lateral augmentation in rabbits. METHODS: Eighteen rabbits, approximately 3.5-4.0 kg of weight and 4-5 months of age, were included in this study. One lateral side of the angle of the mandible was augmented with block autografts. Animals were euthanized after 7, 20 and 60 days of healing, respectively. Biopsies were taken for each period and specimens underwent microtomographic scanning. The total volume (TV, mm3), bone volume (BV: residual graft plus new bone, mm3), periimplant bone volume (PIBV), bone implant contact (BIC) along the screw and linear bone gain at five vertical points symmetrically dispersed from the fixation screw in the midline were measured. ANOVA and the t-test were performed. RESULTS: The total volume (TV) of autografts decreased between 7 and 60 days from 258.13±15.3 mm3 to 107.2 ± 17.5 mm3 (p < 0.05). Contraction rates of 58.5% were observed. BV was 52.8 ± 7.7 mm3, 27.2 ± 11.1 mm3, and 33.1 ± 2.8 mm3 after 7, 20, and 60 days of healing, respectively. PIBV and BIC remained unchanged along time demonstrating no contraction around the screw. Total linear bone gain demonstrated a total of 18% linear contraction after 60 days. Point 1, demonstrated no changes along time representing no resorption along time. Points 2 and 4 demonstrate a minimum linear contraction (10-15%) with borderline significance. Resembling the total results, contraction starts after 20 days. Points 3 and 5 demonstrate a statistically significant contraction (p<0.05) of 35-40% starting at 20 days. CONCLUSION: Tenting screws may reduce bone resorption symmetrically in a model of lateral block augmentation.

A Reliable Surgical Procedure for Sinus Floor Augmentation with Antral Pseudocysts.

An antral pseudocyst (AP) is a common well-defined 'dome-shaped' faintly radiopaque lesion of the maxillary sinus, and usually does not require treatment in asymptomatic patients. However, when sinus floor augmentation is required to increase bone volume for implant installation, the elevation of the sinus mucosa might drive the AP against the ostium. This might cause its obstruction and, as possible consequence, sinusitis. The purpose of this study was to investigate the clinical and tomographic conditions of APs to identify a predictable cyst removal that might allow a safety sinus floor augmentation. A total of 52 maxillary sinuses in 46 patients (mean age 55.1 years) presenting AP were examined by cone beam computed tomographies (CBCTs). A two-stage approach was applied. At the first surgery, the cystic lesions were further inspected by an endoscope through the antrostomy, and histopathological diagnosis of the removed tissues was carried out. After the confirmation of decrease of the swelling of sinus membrane by CBCT, the sinus floor augmentation was performed, at least four months after cyst removal. The color and transparency of the 86 cystic lesions were classified into 4 types. The whitish transparent cysts were 34 (39.5%), the yellowish transparent cysts were 18 (20.9%), the dark purple transparent cysts were 8 (9.3%) and the milky-white opaque cysts were 26 (30.2%). The contents of the 60 (69.8%) transparent cysts were serous fluid, but those of milky-white cysts were composed of viscous or elastic soft tissues, and the aspiration of the contents was unsuccessful. The analysis of the preoperative CBCT did not provide certainty on the contents of the cystic lesions. All cystic lesions were diagnosed as AP, and an infection was identified in one AP, presenting marked infiltration of the inflammatory cells. Considering the difficulties of performing a correct diagnosis of the AP content by a CBCT analysis, the risk of failure of the surgery that creates severe afflictions to the patients, and the necessity of a histological evaluation of the cyst, a two-stage surgery appeared to be the most reliable procedure.

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.

Incidence of Sinus Mucosa Perforations During Healing After Sinus Elevation Using Deproteinized Bovine Bone Mineral as Grafting Material: A Histologic Evaluation in a Rabbit Model.

PURPOSE: To examine the reaction of mucosa over time to a close contact with biomaterial after sinus elevation performed with deproteinized bovine bone mineral (DBBM) granules of two different sizes. MATERIALS AND METHODS: Bilateral sinus mucosa elevation was performed in 18 New Zealand rabbits through access on the nasal dorsum. DBBM with granule dimensions of either 1 to 2 mm (large group) or 0.250 to 1.0 mm (small group) were used to randomly fill the subantral hollow spaces. Biopsy specimens of the experimental sites from six animals in each group were obtained 2, 4, and 8 weeks after the surgery. RESULTS: The integrity of the sinus mucosa was clinically evaluated during surgery using a ×2.5 magnifying visual device. The sinus mucosa in contact with the biomaterial granules was found to be thinned compared with the pristine mucosa in all periods examined. Three hundred fifty-two thinned zones were found considering all 36 sinuses treated. Perforations of the sinus mucosa with extrusion of granules toward the sinus were observed, increasing in number over time. In the 8-week healing period, five perforations in three sinuses and eight perforations in four sinuses were found in the large and small groups, respectively. No differences were seen between the large and small groups. The differences between 2 and 8 weeks were statistically significant for the thinned mucosa width in both the large and the small groups and for the number of sinuses and perforations for the small group. CONCLUSION: Thinning zones and perforations of the sinus mucosa were seen increasing in number over time in regions in contact with graft granules in both the large and small groups.

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.

Two-Year Follow-Up of 4-mm-Long Implants Used as Distal Support of Full-Arch FDPs Compared to 10-mm Implants Installed after Sinus Floor Elevation. A Randomized Clinical Trial.

BACKGROUND: In edentulous patients, bone resorption cannot allow the installation of standard implants and it is demanded to use short implants in the residual alveolar bone or longer implants in grafted bone. AIM: To compare the survival and bone level changes of standard plus short 4-mm implants used as distal support of a maxillary full-arch fixed dental prostheses (FDPs) with standard (10-mm) implants placed in association with a bilateral sinus floor augmentation procedure. MATERIAL AND METHODS: Full-arch FDPs supported by six implants were randomly placed in both groups. In the control group, all implants were 10 mm long and 4.1 mm in diameter. The distal implant in both sides of the maxilla was installed after 4 months from bilaterally sinus floor elevation. In the test group (short group), the distal implant in both sides of the maxilla was 4 mm long and 4.1 mm in diameter. No sinus floor elevations were performed in the test group. Clinical assessments and X-rays were taken at prosthesis delivering and after 6, 12, 18, and 24 months. Patient-reported outcome measures (PROMs) were also evaluated before surgery and after 6, 12, and 24 months. RESULTS: The changes over time of the bone level for the short implants were -0.01 ± 0.11 mm, -0.04 ± 0.13 mm, -0.17 ± 0.29 mm, and -0.28 ± 0.37 mm after 6, 12, 18, and 24 months from prosthesis delivering, respectively. For the standard implants, bone changes were -0.21 ± 0.33 mm (p = 0.103), -0.30 ± 0.32 mm (p = 0.023), -0.40 ± 0.37 mm (p = 0.144), and -0.54 ± 0.49 mm (p = 0.128), respectively. A statistically relevant difference was found only at 12 months after loading between the two groups. CONCLUSIONS: Similar results on implant survival rate and marginal bone loss were observed for the short and standard implants, placed in association with a bilateral sinus floor augmentation procedure, used as distal support of a maxillary full-arch FDP. A statistically relevant difference was found only at 12 months after loading between the two groups (p = 0.023).

Sinus mucosa thinning and perforation after sinus augmentation. A histological study in rabbits.

AIM: To evaluate the modifications and possible perforations of the sinus mucosa lining graft particles and implant surfaces after sinus lifting. MATERIAL AND METHODS: Twelve New Zealand rabbits underwent a bilateral sinus lifting using either autogenous bone harvested from the tibia (AB; autogenous bone group) or deproteinized bovine bone mineral (DBBM group) as filler. Implants were simultaneously installed. Thinned sites (<40 µm) and perforations were histologically evaluated at the sinus mucosa in contact with the graft and with the implant after 7 and 40 days of healing. RESULTS: The mean width of the pristine mucosa was ~70-80 µm. After 7 days of healing, the sinus mucosa in contact with the graft presented fourteen thinned sites in the AB group (mean width 28.8±12.8 µm) and fifty-nine in the DBBM group (mean width 22.2±5.2 µm). No perforations of the mucosa were seen in the AB group while six perforations distributed in two sinuses were found in the DBBM group. After 40 days, only one thinned mucosa and no perforations were observed in the AB group while ninety-six thinned mucosa sites were shared by six sinuses (19.2±3.8 µm), and 3 perforations by two sinuses in the DBBM group. Few sites of the mucosa were in contact with the implant apex and threads after 7 days of healing. However, after 40 days, twelve thinned mucosa sites were seen in four sinuses in the AB groups (mean width ~19 µm) and 5 in two sinuses in the DBBM group (mean width ~20 µm). Perforations were seen in two sinuses in the AB group, and in one sinus in the DBBM group. CONCLUSIONS: The sinus mucosa might be damaged by a close contact with graft particles and implant surface.