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.

Facial alveolar bone thickness and modifying factors of anterior maxillary teeth: a systematic review and meta-analysis of cone-beam computed tomography studies.

BACKGROUND: Understanding the anatomy of the facial alveolar bone (FAB), provides a prognostic tool for estimating the degree of dimensional ridge alterations after tooth extraction. This systematic review and meta-analysis aims to determine the FAB thickness and modifying factors of anterior maxillary teeth measured by CBCT scans. A secondary objective was to assess the facial distance from the cementoenamel junction (CEJ) to the bone crest. METHODS: An electronic search was made of Medline, Embase, Web of Science, Cochrane Library and Google Scholar up to December 2019. Studies that analyze and quantitatively compare FAB thickness at maxillary teeth by CBCT scans were included. The methodological quality of the included studies was appraised using the ROBINS-I tool and the overall meta-evidence certainty using the GRADE approach. A single means random-effects meta-analysis was performed to obtain the weighted mean for 95% confidence interval. A meta-regression of covariates and subgroup analysis was conducted. The nullity Qh test and I2 index for heterogeneity was estimated. RESULTS: 2560 potentially relevant articles were recorded from which 29 studies were selected for the qualitative analysis, including 17,321 teeth. Seventeen studies considered the facial bone crest, and 12 the CEJ as a reference point for their measurements. Mean FAB thickness was ≤ 1 mm in maxillary incisors and canines (0.75-1.05 mm) and 1-2 mm in premolars. Patients over 50 years of age, females and thin gingival phenotype was associated with thinner FAB at some apico-coronal locations of maxillary incisors and canines. The geographical setting was an effect modifier that could explain up to 87% of the heterogeneity in FAB thickness, being Asian populations that showed the lowest FAB thickness values. The CEJ-bone crest distance was 2-2.5 mm in all teeth analyzed. Population over 50 years of age exhibited greater CEJ-bone crest distances, and males also showed a trend for greater distance. Evidence certainty has shown moderate quality in most analysis subsets. CONCLUSIONS: Facial alveolar bone at anterior maxillary teeth is thin, heterogeneous in width along its apico-coronal dimensions, and increases in thickness in maxillary premolars. The CEJ-bone crest distance presented homogeneous and similar values in all teeth analyzed.

Relevance of Oxygen Concentration in Stem Cell Culture for Regenerative Medicine.

The key hallmark of stem cells is their ability to self-renew while keeping a differentiation potential. Intrinsic and extrinsic cell factors may contribute to a decline in these stem cell properties, and this is of the most importance when culturing them. One of these factors is oxygen concentration, which has been closely linked to the maintenance of stemness. The widely used environmental 21% O2 concentration represents a hyperoxic non-physiological condition, which can impair stem cell behaviour by many mechanisms. The goal of this review is to understand these mechanisms underlying the oxygen signalling pathways and their negatively-associated consequences. This may provide a rationale for culturing stem cells under physiological oxygen concentration for stem cell therapy success, in the field of tissue engineering and regenerative medicine.

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.

Influence of occlusal loading on peri-implant clinical parameters. A pilot study.

OBJECTIVES: To investigate the relation between occlusal loading and peri-implant clinical parameters (probing depth, bleeding on probing, gingival retraction, width of keratinized mucosa, and crevicular fluid volume) in patients with implant-supported complete fixed prostheses in both arches. MATERIAL AND METHODS: This clinical study took place at the University of Valencia (Spain) dental clinic. It included patients attending the clinic for regular check-ups during at least 12 months after rehabilitation of both arches with implant-supported complete fixed ceramo-metallic prostheses. One study implant and one control implant were established for each patient using the T-Scan®III computerized system (Tesco, South Boston, USA). The maxillary implant closest to the point of maximum occlusal loading was taken as the study implant and the farthest (with least loading) as the control. Occlusal forces were registered with the T-Scan® III and then occlusal adjustment was performed to distribute occlusal forces correctly. Peri-implant clinical parameters were analyzed in both implants before and two and twelve months after occlusal adjustment. RESULTS: Before occlusal adjustment, study group implants presented a higher mean volume of crevicular fluid (51.3 ± 7.4 UP) than the control group (25.8 ± 5.5 UP), with statistically significant difference. Two months after occlusal adjustment, there were no significant differences between groups (24.6 ± 3.8 UP and 26 ± 4.5 UP respectively) (p=0.977). After twelve months, no significant differences were found between groups (24.4 ± 11.1 UP and 22.5 ± 8.9 UP respectively) (p=0.323). For the other clinical parameters, no significant differences were identified between study and control implants at any of the study times (p>0.05). CONCLUSIONS: Study group implants receiving higher occlusal loading presented significantly higher volumes of crevicular fluid than control implants. Crevicular fluid volumes were similar in both groups two and twelve months after occlusal adjustment.

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.

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.

Survival of implants placed with the osteotome technique: an update.

A literature review is made to analyze the survival of implants placed with the osteotome technique. A PubMed search was made based on the key words "osteotome AND dental implants", corresponding to publications between 1998-2008. The inclusion criteria were: a) a minimum of 10 patients; b) a minimum follow-up of 6 months; c) implants placed using the osteotome technique with or without indirect sinus lift; and d) specification of the implant number and survival rate. Sixty-four articles were identified, of which 20 met the inclusion criteria. A total of 2006 implants were placed in 1312 patients using the osteotome technique. The duration of follow-up after prosthetic loading ranged from 6-144 months. Indirect sinus lift was carried out in all but one of the studies. The residual crest height ranged from 2.8-12 mm, with a mean gain in bone after sinus lift of 2.5-5.1 mm. The time from implant placement to prosthetic loading varied from 1.5-9 months. The percentage implant survival rate was 85.1-100%. The survival rate of implants placed with the osteotome technique is high and does not differ with respect to implant placement with the conventional technique.

Influence of the Use of a Collagen Membrane Placed on the Bone Window after Sinus Floor Augmentation-An Experimental Study in Rabbits.

BACKGROUND: We studied the influence on healing of a resorbable membrane covering the osteotomy site after maxillary sinus grafting, evaluated in different regions of the augmented area. METHODS: Maxillary sinus augmentation was performed in 24 New Zealand rabbits. Osteotomy, 4 × 6 mm, were performed bilaterally. A collagenated cortico-cancellous porcine bone was used to fill the elevated region. A collagen membrane was randomly placed over the osteotomy site on one side (MG), and the other side was left uncovered (NMG). The animals were euthanized after 2, 4, and 8 weeks; and histomorphometric analysis was performed in eight different regions. RESULTS: New bone percentages were similar in both groups. There were no statistically significant differences. In MG, the overall percentages were 15.6 ± 7.3%, 22.9 ± 6.1%, and 24.9 ± 12.0% after 2, 4, and 8 weeks, respectively. In NMG, the percentages were 11.2 ± 4.5%, 24.1 ± 5.7%, and 24.5 ± 15.7%, respectively. The proportions of new bone in the various regions after 8 weeks were 31 ± 8.9% and 29.9 ± 9.1% in the bone walls region, 25 ± 10.1% and 32.8 ± 9.1% in the submucosa region, 22.6 ± 21.6% and 10.9 ± 11.5 in the middle region, 17.3 ± 14% and 13.4 ± 9.8% in the close-to-window region, and 21.8 ± 11.6%, 19.1 ± 6.4% in the osteotomy region-for MG and NMG, respectively. CONCLUSIONS: In both groups the greatest amounts of bone formation occurred near to the pre-existing bone walls, followed by the sub-mucosa region. The smallest amounts were found in the close-to-window region, followed by the central region. The placement of a collagen membrane to cover the osteotomy site did not influence the amount of new bone formation after sinus grafting.

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.

Influence of occlusal loading on peri-implant inflammatory cytokines in crevicular fluid: a prospective longitudinal study.

OBJECTIVE: The objective of the study was to evaluate the relation between occlusal loading and peri-implant crevicular fluid cytokine expression in patients with implant-supported complete fixed prostheses in both arches. MATERIAL AND METHODS: A prospective longitudinal clinical study was performed at a university clinic. Fifteen patients were selected and 11 were included. All patients had bimaxillary implant-supported complete fixed ceramo-metallic prostheses loaded at least 12 months before the beginning of the study. Allocation was established for each patient using a computerized occlusal analysis system. The test implant was the maxillary implant closest to the point of highest occlusal loading. The maxillary implant with least loading was the control implant. Occlusal adjustment was performed using a round diamond burr. This occlusal distribution was verified with the occlusal analysis system. Expression of cytokines from peri-implant crevicular fluid (TNF-α, IL-10, IL-6, IL-1ß, IL-8) were recorded and analyzed in both test and control implants before (baseline: T0) and 2 (T1) and 12 months (T2) after occlusal adjustment. The Brunner-Langer non-parametric test was performed. RESULTS: At T0, the expression of IL-10 was significantly higher in the test group implants (p = 0.018). Between T0 and T1, the expression of all the cytokines decreased in the implants of both groups with statistically significant differences, except for TNF (p = 0.271). When comparing both groups at T1, there was no statistically significant difference in any of the analyzed cytokines. At T2, TNF-α suffered when compared with baseline, a statistical decrease in both study and control implants (p < 0,001). At T2, there were no statistically significant differences between groups in any of the cytokines analyzed. CONCLUSIONS: Implants with higher occlusal load presented higher expression of IL-10 in peri-implant crevicular fluid. Occlusal adjustment produced a decrease in the expression of all the analyzed cytokines, both in test and control implants.

Influence of the use of autogenous bone particles to close the access window after maxillary sinus floor augmentation: an experimental study in rabbits.

AIM: To study the influence on the healing of the placement of particulate autogenous bone in the antrostomy and in the subjacent region after maxillary sinus elevation. MATERIAL AND METHODS: Sixteen New Zealand rabbits were undergone to bilateral maxillary sinus floor augmentation with 4 × 4 mm antrostomy dimension. The sinus mucosa was elevated, and the space obtained was filled with xenograft. In the test site (treated sites), autogenous bone was harvested from the tibia and was placed either in the antrostomy and the subjacent region while the control site was left untreated. Antrostomy was covered bilaterally with collagen membranes. Animals were euthanized after 1 and 8 weeks of healing, with 8 rabbits in each group. Histomorphometric evaluations were done. The Wilcoxon test is used for statistical analysis, for a 5% statistical significance. RESULTS: After 1 week of healing, the new bone proportion in the antrostomy was 7.7 ± 11.2% and 6.1 ± 6.4% in the treated and untreated sites, respectively. In the subjacent region (close-to-window region), hardly any new bone was assessed. In the elevated region, 2.7-2.8% of total new bone was found in both sites. In the antrostomy region, after 8 weeks of healing, 35.5 ± 20.9% of new bone in the treated sites, and 28.6 ± 24.1% in the untreated sites was observed (p = 0.499). In the close-to-window region, the respective proportions were 25.8 ± 16.1% and 17.6 ± 16.3% (p = 0.018). In the elevated region, the total new bone reached fractions of 27.9 ± 12.9% and 23.6 ± 15.2% in the treated and untreated sites, respectively (p = 0.128). CONCLUSIONS: The placement of autogenous bone in the antrostomy and the subjacent region after maxillary sinus elevation, slightly enhanced bone formation compared with sites only grafted with xenograft. Though, only the subjacent close-to-window region showed a statistical significance at 8 weeks of healing. Despite the limitations of the present study, due to its preclinical nature, findings should be extrapolated to humans with caution.

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.

Influence of perforation of the sinus membrane on the survival rate of implants placed after direct sinus lift. Literature update.

The aim of this paper was to review the procedures adopted when a perforation of the sinus membrane takes place during a direct sinus lift for filling with bone graft; and the survival of implants in those cases in which perforation of the sinus membrane occurred. A bibliographical search in PUBMED was carried out of articles published from 1997 to 2008, with the key words "sinus perforation" and "membrane perforation". All articles specifying the two following criteria were included: (a) procedure in the case of perforation of the sinus membrane during direct sinus lift; and (b) the number and survival rate of implants placed in direct sinus lift with perforated and non perforated membrane. Six articles fulfilled the inclusion criteria. In all the articles the sinus lift was continued when a perforation of the sinus membrane took place. In maxillary sinus lift procedures with perforation of the membrane a 88.6% implant survival rate was obtained, and in maxillary sinus lifts with intact membrane the survival rate rose to 98%. In case of small perforation of the sinus membrane, it is possible to continue with the procedure; there is no consensus on the procedure when a perforated membrane is to be repaired, but the method of choice according to the majority of authors is to use a reservable membrane. In the case of large perforation, there is no consensus either, although the majority of authors choose to abandon the procedure. The survival of the implants diminishes when they are placed in sinus lifts with perforated membrane.

Bone-Healing Pattern on the Surface of Titanium Implants at Cortical and Marrow Compartments in Two Topographic Sites: an Experimental Study in Rabbits.

This study evaluates the bone-healing patterns on the surface of titanium implants at the cortical and marrow compartments of bicortically-installed implants in the diaphysis and metaphysis of rabbit tibiae. In 27 New Zealand rabbits, two implants, one for each macro-design and with equal resorbable blasted media (RBM) implant surfaces, were randomly implanted in the diaphysis or metaphysis of each tibia. The flaps were sutured to allow submerged healing. The animals were sacrificed after two, four, or eight weeks, with nine weeks used for the period of healing. Ground sections were prepared and analyzed. No statistically significant differences were found between the two groups for newly formed bone in contact with the implant surface after two, four, and eight weeks of healing. Bone apposition in the marrow compartment was slightly higher in the diaphysis compared to metaphysis regions across healing stages. Despite the limitations of the present study, it can be concluded that new bone apposition was better than average in the cortical compartment as compared to the marrow compartments. Bone morphometry and density may affect bone apposition onto the implant surface. The apposition rates were slightly better at both the cortical and marrow compartments in diaphysis as compared to metaphysis sites. The new bone formation at the marrow compartment showed slightly better increasing values at diaphysis compared to metaphysis implantation sites.

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.

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.

Influence of Partial O2 Pressure on the Adhesion, Proliferation, and Osteogenic Differentiation of Human Dental Pulp Stem Cells on ß-Tricalcium Phosphate Scaffold.

PURPOSE: To analyze, in vitro, the influence of O2 pressure on the adhesion, proliferation, and osteogenic differentiation of human dental pulp stem cells (DPSC) on ß-tricalcium phosphate (ß-TCP) scaffold. MATERIALS AND METHODS: DPSC, positive for the molecular markers CD133, Oct4, Nestin, Stro-1, and CD34, and negative for CD45, were isolated from extracted third molars. Experiments were started by seeding 200,000 cells on ß-TCP cultured under 3% or 21% O2 pressure. No osteogenic medium was used. Eight different cultures were performed at each time point under each O2 pressure condition. Cell adhesion, proliferation, and differentiation over the biomaterial were evaluated at 7, 13, 18, and 23 days of culture. Cell adhesion was determined by light microscopy, proliferation by DNA quantification, and osteogenic differentiation by alkaline phosphatase (ALP) activity analysis. RESULTS: DPSC adhered to ß-TCP with both O2 conditions. Cell proliferation was found from day 7 of culture. Higher values were recorded at 3% O2 in each time point. Statistically significant differences were recorded at 23 days of culture (P = .033). ALP activity was not detectable at 7 days. There was, however, an increase in ALP activity over time in both groups. At 13, 18, and 23 days of culture, higher ALP activity was recorded under 3% O2 pressure. Statistical differences were found at day 23 (P = .014). CONCLUSION: DPSC display capacity of adhering to ß-TCP under 3% or 21% O2 pressure conditions. Cell proliferation on ß-TCP phosphate is significantly higher at 3% than at 21% O2 pressure, the most frequently used O2 tension. ß-TCP can itself promote osteogenic differentiation of DPSC and is enhanced under 3% O2 compared with 21%.

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.