Influence of abutment shape on peri-implant tissue conditions: A randomized clinical trial.

OBJECTIVE: To analyze the influence of 3-mm high abutments with different shapes (cylindrical abutment vs. wide abutment) on marginal bone-level changes (bone loss and bone remodeling). The influence of abutment shape on implant success, probing pocket depth (PPD), and bleeding on probing (BoP) was studied as secondary objectives. MATERIALS AND METHODS: Patients with a partially edentulous area requiring fixed dental prostheses by two implants in the posterior mandible or maxilla were included. The implants were 1 mm subcrestally placed, and osseointegration healing was submerged. Three-mm high abutments with two different shapes were randomly placed in second-stage surgery: cylindrical abutments (cylindrical group) and wide abutments (wide group). Marginal bone-level changes were measured using parallelized periapical radiographs at abutment placement, at definitive prosthesis placement, and at 1, 3, 6, and 12 months after loading. PPD and BoP were likewise measured at the control visits. RESULTS: Sixty-four dental implants in 25 patients were included. Statistically significant differences were found in bone-level changes. The cylindrical group exhibited less mean marginal bone remodeling (MBR) and marginal bone loss (MBL) than the wide group (p < .05). Moreover, the cylindrical group showed significantly less BoP (p < .05). CONCLUSION: Abutment shape had a significant influence upon marginal bone-level changes during the first 12 months. Cylindrical abutments caused less MBR and MBL than wide abutments. More clinical studies involving longer follow-ups and analyzing other abutment modifications are needed to improve our understanding of how abutments can affect peri-implant tissue stability.

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.

Radiological implications of crestal and subcrestal implant placement in posterior areas. A cone-beam computed tomography study.

BACKGROUND: Subcrestal implant placement has been suggested as a method that could contribute to maintain the periimplant soft and hard tissues in comparison with crestal placement. The objective of this study was to investigate the relationship between implant placement at different depths in the alveolar bone and (a) the thickness of the buccal bone plate (BBP); and (b) crestal cortical bone thickness, based on the use of cone-beam computed tomography (CBCT). MATERIAL AND METHODS: A cross-sectional study was performed, analyzing CBCT scans from the database of the Oral Surgery Unit of the University of Valencia. Individuals with single missing teeth in posterior sectors were included. Two trained dentists used a software application to plan implant placement at four different depths from the bone crest (from 0-2 mm subcrestal). The thickness of the BBP was measured at each established depth, tracing a line from the implant platform to the outermost part of the facial alveolar bone, and the ratio between the implant platform and cortical bone thickness was calculated. RESULTS: The study sample consisted of 64 patients. In the case of implants placed in a crestal position, the distance from the platform to the BBP was 1.99±1.10 mm. This distance increased significantly (p<0.001) with the planned implant placement depth, reaching an average of 2.90±1.22 mm when placement was 2 mm subcrestal. Subcrestal implant placement at this depth implied surpassing the cortical bone in 91% of the cases. CONCLUSIONS: Radiological planning of implant placement in a subcrestal position results in a greater distance from the implant platform to the BBP. In general terms, planning implant placement at a depth of 2 mm subcrestal surpassed the cortical bone in 91% of the cases. Key words:Subcrestal implant, cortical bone thickness, buccal bone plate, cone-beam computed tomography.

Sequential healing of the elevated sinus floor with different size of antrostomy: a histomorphometric study in rabbits.

PURPOSE: To study the influence of the access window dimensions on the healing at the antrostomy and within the augmented maxillary sinus. MATERIAL AND METHODS: A maxillary sinus augmentation was performed in twenty-four albino New Zealand rabbits. Antrostomies of 3 × 6 mm (small) or 5 × 6 mm (large) in dimensions were randomly prepared in each animal. A collagenated cortico-cancellous porcine bone was used to fill the elevated region, and an equine collagen membrane was placed on the antrostomies. Three different groups were formed, based on the time of euthanasia, i.e., 2, 4, and 8 weeks from surgery. RESULTS: No relevant changes of the height of the augmented sinus were detected over time. Mineralized bone increased between 2 and 4 weeks of healing while remained stable between 4 and 8 weeks. The highest amounts of new bone were found close to the sinus bone walls. No antrostomies were found healed with an even layer of corticalized bone, while large amounts of connective tissue were occupying the antrostomy in both groups. CONCLUSION: Antrostomies of different dimensions resulted in similar outcome in bone formation both in the antrostomy regions and within the elevated sinus.

Effect of incision design on interproximal bone loss of teeth adjacent to single implants. A randomized controlled clinical trial comparing intrasulcular vs paramarginal incision.

PURPOSE: To evaluate the effect of incision design in implant surgery on interproximal bone loss of posterior teeth adjacent to interdental single implants, comparing intrasulcular and paramarginal incision. A further aim was to assess the influence of the incision technique on peri-implant bone remodeling. MATERIALS AND METHODS: A controlled randomized clinical trial was carried out in a University Clinic. All the patients received an interdental posterior single implant. The incision type was randomly divided into two groups: (a) intrasulcular or (b) paramarginal. Standardized periapical digital radiographs were made with the parallel technique and a silicone index individualized in each patient. Radiographs were made immediately after implant placement, at abutment connection, 6 and 12 months post-loading. Two radiographic reference points were detected at the interproximal aspect of the adjacent teeth: (A) the cementoenamel junction and (B) the most coronal aspect of the bone crest. The interproximal bone loss of the adjacent teeth was calculated as the difference from A to B between the different follow-up periods and baseline. Two different examiners evaluated the radiographic measurements twice. RESULTS: Sixty patients, each with one implant, were included, 30 in each group. A mean interproximal bone loss in teeth of 0.09 mm in the intrasulcular and 0.10 mm in the paramarginal group was found at 12 months post-loading. Mean peri-implant bone remodeling was 0.17 mm in the intrasulcular group and 0.15 mm in the paramarginal group. Differences between incision types were not statistically significant (p > .05). CONCLUSIONS: Both incision designs used to place interdental single implants resulted in minimum bone loss at the interproximal aspect of adjacent teeth. The incision design did not significantly influence the radiographically assessed interproximal bone loss nor peri-implant bone remodeling.

Accuracy of Implant Placement with Computer-Guided Surgery: A Systematic Review and Meta-Analysis Comparing Cadaver, Clinical, and In Vitro Studies.

PURPOSE: The aim of this systematic review was to analyze the accuracy of implant placement using computer-guided surgery and to compare virtual treatment planning and outcome in relation to study type (in vitro, clinical, or cadaver). A further objective was to compare the accuracy of half-guided implant surgery with that of full-guided implant surgery. MATERIALS AND METHODS: A PubMed search was performed to identify studies published between January 2005 and February 2015, searching the keywords "reliability AND dental implant planning" and "accuracy dental implant planning." Inclusion criteria were established a priori. Horizontal coronal deviation, horizontal apical deviation, angular deviation, and vertical deviation were analyzed. RESULTS: A total of 186 articles were reviewed, and 34 fulfilled the inclusion criteria. Information about 3,033 implants was analyzed in 8 in vitro studies (543 implants), 4 cadaver studies (246 implants), and 22 clinical studies (2,244 implants). Significantly less horizontal apical deviation and angular deviation were observed in in vitro studies compared to clinical and cadaver studies, but there were no statistically significant differences in apical coronal deviation or vertical deviation between the groups. Compared to half-guided surgery, full-guided implant surgery showed significantly less horizontal coronal deviation for cadaver studies, significantly less horizontal apical deviation for clinical studies, and significantly less angular deviation for both clinical and cadaver studies. CONCLUSION: Implant placement accuracy was lower in clinical and cadaver studies compared with in vitro studies, especially in terms of horizontal apical deviation and angular deviation. Full-guided implant surgery achieved greater accuracy than half-guided surgery.

Role of p16INK4a and BMI-1 in oxidative stress-induced premature senescence in human dental pulp stem cells.

Human dental pulp stem cells (hDPSCs) are a source for cell therapy. Before implantation, an in vitro expansion step is necessary, with the inconvenience that hDPSCs undergo senescence following a certain number of passages, loosing their stemness properties. Long-term in vitro culture of hDPSCs at 21% (ambient oxygen tension) compared with 3-6% oxygen tension (physiological oxygen tension) caused an oxidative stress-related premature senescence, as evidenced by increased ß-galactosidase activity and increased lysil oxidase expression, which is mediated by p16INK4a pathway. Furthermore, hDPSCs cultured at 21% oxygen tension underwent a downregulation of OCT4, SOX2, KLF4 and c-MYC factors, which was recued by BMI-1 silencing. Thus, p16INK4a and BMI-1 might play a role in the oxidative stress-associated premature senescence. We show that it is important for clinical applications to culture cells at physiological pO2 to retain their stemness characteristics and to delay senescence.

Facial Alveolar Bone Width at the First and Second Maxillary Premolars in Healthy Patients: A Cone Beam Computed Tomography Study.

The purpose of this study was to analyze the thickness of the facial alveolar bone at the first and second maxillary premolars and determinate the percentage of premolars that reached 2 mm in width. A retrospective study was performed, analyzing cone beam computed tomography scans from the database of the Oral Surgery Unit of the University of Valencia. Patients with periodontal disease, orthodontic treatment, absence among the first maxillary molars, premolars with endodontic treatment, or prosthetic restorations were excluded. The facial alveolar bone width was measured at 1, 2, 3, and 5 mm apical to the vestibular bone peak. A total of 44 patients were included in the study, with 72 first premolars and 72 second premolars analyzed. A descriptive analysis was performed and the normal means were assessed using the Kolmogorov-Smirnov test. The average width of the facial alveolar bone at first and second maxillary premolars was respectively: 1.41 ± 0.50 and 1.72 ± 0.56 at 1 mm, 1.68 ± 0.72 and 2.23 ± 0.66 at 2 mm, 1.71 ± 0.89 and 2.43 ± 0.82 at 3 mm, 1.44 ± 1.00 and 2.31 ± 1.06 at 5 mm from the vestibular bone peak. The facial alveolar bone width at the second maxillary premolars was greater than at the first maxillary premolars at all points measured. This information should be taken in account when planning immediate implants. Further studies are needed to analyze bone resorption at maxillary premolars to better understand facial alveolar bone width influence in implant treatment.

Soft Tissue Response in Posterior Teeth Adjacent to Interdental Single Implants: A Controlled Randomized Clinical Trial Comparing Intrasulcular vs Trapezoidal Incision.

PURPOSE: To evaluate the soft tissue response in posterior teeth adjacent to interdental single implants comparing intrasulcular and trapezoidal incision, and to study their evolution over time. MATERIALS AND METHODS: A controlled randomized clinical trial was carried out in the Oral Surgery and Implantology Unit of a University Clinic. All the included patients received an interdental single implant (Frontier 2.45, Ilerimplant; Global Medical Implants). The incision type was randomized by sealed envelopes into two groups using the SPSS statistical package (SPSS): (1) intrasulcular or (2) trapezoidal incision. Probing depth and gingival recession at the mesial and distal teeth adjacent to the implant were measured before implant placement, 1 month after surgery, the day of the abutment connection, and at 6 months and 1 year postloading. Scar formation and papilla index were measured 1 month after surgery, and at 6 months and 1 year postloading. RESULTS: Forty patients with one implant per patient were included: 20 in the intrasulcular and 20 in the trapezoidal group. No statistical differences were found between incision types in the measured parameters (probing depth, recession, and interproximal papilla). When analyzing periodontal changes of the total sample, significant differences were found between implant placement and the 1-year follow-up in recession, scar formation, and papilla index. CONCLUSION: The incision type used to place a single interdental implant did not significantly influence the periodontal parameters of the adjacent teeth. Considering the whole sample, the values between implant placement and 1 year postloading showed significant differences in recession, scar formation, and papilla index over time.

Buccal bone crest dynamics after immediate implant placement and ridge preservation techniques: review of morphometric studies in animals.

PURPOSE: To review morphometric studies performed in animals assessing the dynamics of the buccal bone crest after immediate implant placement and ridge preservation techniques. MATERIAL AND METHOD: A bibliographic search in PubMed was performed. Studies that analyzed morphometrically in animals the buccal bone crest dynamics after immediate implant placement or ridge preservation techniques were included. Twenty-five studies met the inclusion criteria. RESULTS: Immediate implant placement does not prevent the resorption of the buccal bone crest. To minimize this resorption, 2 mm width of the buccal bone crest, palatal/lingual implant placement, and an adequate implant diameter for the width of the ridge are required. The regeneration of the gap after immediate implant placement limits the resorption of the buccal bone crest. Flap elevation and implant surface showed no relation with this resorption. Ridge preservation techniques associated with mucogingival surgery minimize buccal bone crest resorption. Biomaterials are more effective than autograft. CONCLUSIONS: Immediate implant placement does not prevent the resorption of the buccal bone crest after dental extraction. Ridge preservation techniques minimize this resorption.