Prediction of lifespan and assessing risk factors of large-sample implant prostheses: a multicenter study.

PURPOSE: This study aimed to analyze factors influencing the success and failure of implant prostheses and to estimate the lifespan of prostheses using standardized evaluation criteria. An online survey platform was utilized to efficiently gather large samples from multiple institutions. MATERIALS AND METHODS: During the one-year period, patients visiting 16 institutions were assessed using standardized evaluation criteria (KAP criteria). Data from these institutions were collected through an online platform, and various statistical analyses were conducted. Risk factors were assessed using both the Cox proportional hazard model and Cox regression analysis. Survival analysis was conducted using Kaplan-Meier analysis and nomogram, and lifespan prediction was performed using principal component analysis. RESULTS: The number of patients involved in this study was 485, with a total of 841 prostheses evaluated. The median survival was estimated to be 16 years with a 95% confidence interval. Factors found to be significantly associated with implant prosthesis failure, characterized by higher hazard ratios, included the 'type of clinic', 'type of antagonist', and 'plaque index'. The lifespan of implant prostheses that did not fail was estimated to exceed the projected lifespan by approximately 1.34 years. CONCLUSION: To ensure the success of implant prostheses, maintaining good oral hygiene is crucial. The estimated lifespan of implant prostheses is often underestimated by approximately 1.34 years. Furthermore, standardized form, online platform, and visualization tool, such as nomogram, can be effectively utilized in future follow-up studies.

Standardized multi-institutional data analysis of fixed and removable prosthesis: estimation of life expectancy with regards to variable risk factors.

PURPOSE: This study aims to assess and predict lifespan of dental prostheses using newly developed Korean Association of Prosthodontics (KAP) criteria through a large-scale, multi-institutional survey. MATERIALS AND METHODS: Survey was conducted including 16 institutions. Cox proportional hazards model and principal component analysis (PCA) were used to find out relevant factors and predict life expectancy. RESULTS: 1,703 fixed and 815 removable prostheses data were collected and evaluated. Statistically significant factors in fixed prosthesis failure were plaque index and material type, with a median survival of 10 to 18 years and 14 to 20 years each. In removable prosthesis, factors were national health insurance coverage, antagonist type, and prosthesis type (complete or partial denture), with median survival of 10 to 13 years, 11 to 14 years, and 10 to 15 years each. For still-usable prostheses, PCA analysis predicted an additional 3 years in fixed and 4.8 years in removable prosthesis. CONCLUSION: Life expectancy of a prosthesis differed significantly by factors mostly controllable either by dentist or a patient. Overall life expectancy was shown to be longer than previous research.

The effect of surface treatment and low-temperature degradation on flexural strength of additive manufactured zirconia.

This study aimed to assess the effect of low-temperature degradation (LTD) and surface treatment on the flexural strength of additive-manufactured (AM) zirconia by comparison to subtractive-manufactured (SM) zirconia. Disc-shaped zirconia specimens were fabricated using AM and SM technology, and each group was assigned to 3 subgroups according to the type of surface treatment: control, sandblasting (SB), and 9% hydrofluoric acid etching (HF). The groups were then further divided into 2 subgroups: unaged and aged. Biaxial flexural strength, crystal phase, surface topography, and surface roughness were measured to evaluate the mechanical properties. Statistical analyses were performed with 3-way ANOVA, followed by the comparison of means with Bonferroni post hoc analyses. The means and standard deviations of the biaxial flexural strength and Weibull parameters were calculated with descriptive statistics. All SM groups showed significantly greater flexural strength than the AM groups (p < .05), and LTD did not affect flexural strength except for the SMHF group (p < .05). After LTD, monoclinic phases (m-phase) were found in all groups, and SEM images showed grain pullout due to zirconia volume expansion in both control groups. Sandblasting significantly affected flexural strength (p < .05), whereas the HF group did not affect flexural strength except in the SMHF group after LTD (p < .05). No significant difference was observed in the surface roughness of AM compared to SM groups conditioned with the same surface treatment regardless of LTD. AM zirconia has comparable mechanical properties to SM zirconia, regardless of low-temperature degradation and surface treatment, which indicates the potential of the AM technique for clinical applications.

Effect of 9% Hydrofluoric Acid Gel Hot-Etching Surface Treatment on Shear Bond Strength of Resin Cements to Zirconia Ceramics.

Background and Objectives: There is no consensus regarding the surface treatment method for achieving optimal bonding strength between zirconia and resin cements. We evaluated the effect of hot-etching with 9% hydrofluoric acid (HF) gel using the Zirconia Etchant Cloud System on zirconia surfaces and the consequent shear bond strength (SBS) of different resin cements to such surface-treated zirconia ceramics. Materials and Methods: Forty-five zirconia specimens were randomly assigned to surface-treatment groups (n = 15/group): no treatment (control, CT); sandblasting with 110-µm Al2O3 at an air pressure of 1 bar for 10 s (SB); hot-etching with 9% HF gel (HE). Post-treatment, specimens were examined using scanning electron microscopy (SEM) and surface roughness (SR) analysis. After treatment, self-adhesive resin cements (Maxcem Elite, MAZIC Cem, RelyX U200, 3M ESPE: Maplewood, MN, USA) were bonded to zirconia specimens, which were stored in distilled water at 37 °C for 24 h. All specimens were then subjected to SBS testing, using a universal testing machine, until failure. Data were analyzed using one-way analysis of variance and Tukey's post hoc test (α = 0.05). Results: In the SEM images, roughness was greater in SB than in HE specimens. Ra and Rt values were highest in SB, followed by HE, and CT specimens. HE specimens showed significantly higher SBS values than CT or SB specimens (p < 0.05). MAZIC Cem cement, with 10-methacryloyloxydcyl dihydrogen phosphate yielded the highest SBS values. Conclusions: Hot-etching with 9% HF gel in a safe shell formed uniformly small, defined holes on the zirconia surface and achieved significantly higher SBS values than sandblasting (p < 0.05). Zirconia prostheses can be bonded micromechanically with resin cement, without the deterioration of properties due to t-m transformation, using chemical acid etching with the Zirconia Etchant Cloud System.

Survival Rates and Clinical Outcomes of Implant Overdentures in Old and Medically Compromised Patients.

Studies on the survival rate of implant overdentures in medically compromised patients are limited because most studies exclude patients with systemic diseases affecting implant prognosis. This retrospective study aimed to evaluate the survival rate and clinical outcomes of dental implants used for overdentures in medically compromised patients. A total of 20 patients (9 men, 11 women; mean age: 67.55 ± 6.84 years, range: 53-81 years) were included. Fourteen patients had more than two systemic diseases, and nine patients had more than three systemic diseases. The mean follow-up period was 39.05 months. Of the 60 implants, 2 failed, resulting in an implant survival rate of 96.6%. No statistical differences were found in implant survival rates according to sex, age, implant diameter, restored arch, or opposing dentition (p > 0.05). A significant difference in mean marginal bone loss (MBL) was noted for restoring the arch (p = 0.022) and opposing dentition (p = 0.036). Implants placed in the mandible and with opposing removable partial dentures and complete dentures showed lower mean MBL. No significant differences in implant MBL were observed in terms of age, sex, or implant diameter (p > 0.05). Favorable clinical outcomes can be expected from implant overdentures using two or four implants in edentulous patients with systemic diseases by ensuring that the patients have a sufficient healing period and regular checkups.

The effect of missing teeth on dementia in older people: a nationwide population-based cohort study in South Korea.

BACKGROUND: To determine the effect of missing teeth on the risk of dementia onset among individuals who received tooth extractions and those who did not, based on the number of missing teeth. METHODS: We selected individuals who had not been diagnosed or treated for dementia between 2002 to 2011 from the National Health Insurance Service-Elderly Cohort Database (NHIS-ECD). We divided participants into two cohorts, a tooth extraction and non-extraction cohort, based on tooth loss from 2002 to 2011. After propensity score matching, there were 104,903 individuals in each cohort, and we included a total of 209,806 individuals in this study. Each cohort was grouped by sex, age, residential area, health insurance eligibility, income level, history of dental caries, history of periodontal treatment, and number of extracted teeth. We analyzed the relationship between dementia onset and these variables using logistic regression analysis. RESULTS: Individuals with tooth loss had a higher risk for dementia than those without tooth loss (odds ratio [OR] = 1.18; 95% confidence interval [CI]: 1.146-1.215). Regarding the incidence of dementia, the OR increased as the number of missing teeth and age increased, and the OR was higher for women (OR = 1.33; 95% CI: 1.286-1.367) than for men, and this difference was statistically significant (P < 0.01). The incidence of dementia decreased with periodontal treatment (OR = 0.96; 95% CI: 0.932-0.992) and increased with dental caries (OR = 1.07; 95% CI: 1.035-1.101). CONCLUSIONS: These results suggest that it is important to delay tooth loss and preserve the stable remaining teeth to help prevent dementia.

Clinical evaluations of cast gold alloy, machinable zirconia, and semiprecious alloy crowns: A multicenter study.

STATEMENT OF PROBLEM: Few studies have compared the marginal and internal fits of crowns fabricated from machinable palladium-silver-indium (Pd-Ag-In) semiprecious metal alloy. PURPOSE: The purpose of this clinical study was to evaluate and compare the marginal and internal fits of machined Pd-Ag-In alloy, zirconia, and cast gold crowns. MATERIAL AND METHODS: A prospective clinical trial was performed on 35 participants and 52 abutment teeth at 2 centers. Individuals requiring prosthetic restorations were treated with gold alloy or zirconia crowns (2 control groups) or Pd-Ag-In alloy crowns (experimental group). A replica technique was used to evaluate the marginal and internal fits. The buccolingual and mesiodistal cross-sections were measured, and a noninferiority comparison was conducted. RESULTS: The mean marginal gaps were 68.2 µm for the gold crowns, 75.4 µm for the zirconia crowns, and 76.9 µm for the Pd-Ag-In alloy crowns. In the 5 cross-sections other than the distal cross-section, the 2-sided 95% confidence limits for the differences between the Pd-Ag-In alloy crowns and the 2 control groups were not larger than the 25-µm noninferiority margin. The control groups displayed smaller internal gaps in the line angle and occlusal spaces compared with the Pd-Ag-In crown group. CONCLUSION: The marginal gaps of machinable Pd-Ag-In alloy crowns did not meet the noninferiority criterion in the distal margin compared with zirconia and gold alloy crowns. Nonetheless, all 3 crowns had clinically applicable precision.

Effect of topographical control by a micro-molding process on the activity of human Mesenchymal Stem Cells on alumina ceramics.

BACKGROUND: Numerous studies have reported that microgrooves on metal and polymer materials can affect cell adhesion, proliferation, differentiation and guidance. However, our knowledge of the cell activity associated with microgrooves on ceramics, such as alumina, zirconia, hydroxyapatite and etc, is very incomplete, owing to difficulties in the engraving of microgrooves on the hard surface of the base material. In this study, microgrooves on alumina were fabricated by a casting process using a polydimethylsiloxane micro-mold. The cell responses of Human Mesenchymal Stem Cells on the alumina microgrooves were then evaluated. RESULTS: Microgrooves on an alumina surface by micro-mold casting can enhance the adhesion, differentiation of osteoblasts as well as gene expression related to osteoblast differentiation. The ALP activity and calcium concentration of the cells on alumina microgrooves were increased by more than twice compared to a non-microgrooved alumina surface. Moreover, regarding the osteoblast differentiation of hMSCs, the expression of ALP, RUNX2, OSX, OC and OPN on the microgrooved alumina were all significantly increased by 1.5 ~ 2.5 fold compared with the non-microgrooved alumina. CONCLUSION: Altering the topography on alumina by creating microgrooves using a micro-molding process has an important impact on the behavior of hMSCs, including the adhesion, differentiation of osteoblasts and osteoblast-specific gene expression. The significant increase in hMSC activity is explained by the increasing of material transportation in parallel direction and by the extending of spreading distance in perpendicular direction.

Characterization of the enhanced bone regenerative capacity of human periodontal ligament stem cells engineered to express the gene encoding bone morphogenetic protein 2.

Human periodontal ligament stem cells (hPDLSCs) are considered an appropriate cell source for therapeutic strategies. The aims of this study were to investigate the sustainability of bone morphogenetic protein 2 (BMP2) secretion and the bone regenerative capacity of hPDLSCs that had been genetically modified to express the gene encoding BMP2 (BMP2). hPDLSCs isolated from healthy third molars were transduced using replication-deficient recombinant adenovirus (rAd) encoding BMP2 (hPDLSCs/rAd-BMP2), and the cellular characteristics and osteogenic potentials of hPDLSCs/rAd-BMP2 were analyzed both in vitro and in vivo. hPDLSCs/rAd-BMP2 successfully secreted BMP2, formed colonies, and expressed immunophenotypes similar to their nontransduced counterparts. As to their osteogenic potential, hPDLSCs/rAd-BMP2 formed greater mineralized nodules and exhibited significantly higher levels of expression of BMP2 and the gene encoding alkaline phosphatase, and formed more and better quality bone than other hPDLSC-containing or recombinant human BMP2-treated groups, being localized at the initial site until 8 weeks. The findings of the present study demonstrate that hPDLSCs/rAd-BMP2 effectively promote osteogenesis not only in vitro but also in vivo. The findings also suggest that hPDLSCs can efficiently carry and deliver BMP2, and that hPDLSCs/rAd-BMP2 could be used in an attractive novel therapeutic approach for the regeneration of deteriorated bony defects.

Effects of bone marrow-derived mesenchymal stem cells and platelet-rich plasma on bone regeneration for osseointegration of dental implants: preliminary study in canine three-wall intrabony defects.

Tissue engineering has been applied to overcome the obstacles encountered with bone regeneration for the placement of dental implants. The purpose of this study was to determine the bone formation ability of human bone marrow-derived mesenchymal stem cells (BMMSCs) and platelet-rich plasma (PRP) when applied separately or together to the intrabony defect around dental implants with a porous hydroxyapatite (HA) scaffold. Standardized three-wall intrabony defects (4 × 4 × 4 mm) were created at the mesial of each dental implant site in four mongrel dogs. Defects were then grafted with the following materials: HA + BMMSCs (HS group), HA + PRP (HP group), HA + BMMSCs + PRP (HSP group), and HA scaffold alone (HA group). The level of bone formation (bone density) and osseointegration (bone-to-implant contact [BIC]) in bone defects around the implants were evaluated by histological and histometric analysis at 6 and 12 weeks after the placement of implants. HA, HS, HP, and HSP groups generally showed an increase in bone density and BIC between 6 and 12 weeks, except BIC in the HS group. Although no statistically significant differences were found among HA, HS, HP, and HSP groups (p > 0.05), the highest level of bone density and BIC were observed in the HSP group after the 12-week healing period. Furthermore, the level of bone maturation was higher in the HSP group than in the other groups as determined histologically. The findings of this preliminary study suggest that BMMSCs and PRP combined with HA scaffold may provide additional therapeutic effects on bone regeneration and improve osseointegration in bone defects around dental implants.

The effect of resin cements and primer on retentive force of zirconia copings bonded to zirconia abutments with insufficient retention.

PURPOSE: The purpose of this study was to investigate the effect of resin cements and primer on the retentive force of zirconia copings bonded to zirconia abutments with insufficient retention. MATERIALS AND METHODS: Zirconia blocks (Lava, 3M ESPE, St. Paul, MN, USA) were obtained and forty sets of zirconia abutments and copings were fabricated using CAD/CAM technology. They were grouped into 4 categories as follows, depending on the types of resin cements used, and whether the primer is applied or not:Panavia F2.0 (P), Panavia F2.0 using Primer (PRIME Plus, Bisco Inc, Schaumburg, IL, USA) (PZ), Superbond C&B (S), and Superbond C&B using Primer (SZ). For each of the groups, the cementation was conducted. The specimens were kept in sterilized water (37℃) for 24 hours. Retentive forces were tested and measured, and a statistical analysis was carried out. The nature of failure was recorded. RESULTS: The means and standard deviations of retentive force in Newton for each group were 265.15 ± 35.04 N (P), 318.21 ± 22.24 N (PZ), 445.13 ± 78.54 N (S) and 508.21 ± 79.48 N (SZ). Superbond C&B groups (S & SZ) showed significantly higher retentive force than Panavia F2.0 groups (P & PZ). In Panavia F2.0 groups, the use of primer was found to contribute to the increase of retentive force. On the other hand, in Superbond C&B groups, the use of primer did not influence the retention forces. Adhesive failure was observed in all groups. CONCLUSION: This study suggests that cementation of the zirconia abutments and zirconia copings with Superbond C&B have a higher retentive force than Panavia F2.0. When using Panavia F2.0, the use of primer increases the retentive force.

Correlation between surface hydrophilicity and osteoblastic differentiation on microgrooved titanium substrata.

Surface microgrooves and acid etching on titanium (Ti) have been proposed to enhance various cell behaviors. In this study, surface hydrophilicity, protein adsorption, and alkaline phosphatase activity of osteoblasts were analyzed and compared between microgrooved Ti, Ti with microgrooves and further acid etching, smooth Ti, and acid-etched smooth Ti. Correlations between the results of each experiment were analyzed using Pearson's correlation analysis, and the influential factor on alkaline phosphatase activity was determined using multiple stepwise regression analysis. Among groups, the Ti substrata with microgrooves and subsequent acid etching showed significantly greater surface hydrophilicity and alkaline phosphatase activity compared with smooth Ti, whereas the Ti substrata with only microgrooves showed the greatest protein adsorption. Multiple stepwise regression analysis determined the surface hydrophilicity of Ti as the influential factor on alkaline phosphatase activity. This study indicates that surface microgrooves and acid etching on Ti substrata enhance surface hydrophilicity, leading to increased alkaline phosphatase activity.

Texture direction of combined microgrooves and submicroscale topographies of titanium substrata influence adhesion, proliferation, and differentiation in human primary cells.

OBJECTIVE: This study aimed to identify the optimal micro- and submicroscale topographies of titanium (Ti) substrata that would most significantly influence adhesion, proliferation, and other activities of these cells. DESIGN: Truncated V-shaped microgrooves in 60 µm-wide and 10 µm-deep cross-sections with 0°, 30°, 60°, or 90° angles between the microgrooves and ridge-top submicroscale texture were created on the Ti substrata (designated NE60/10-0°, NE60/10-30°, NE60/10-60° and NE60/10-90°, respectively). Ground titanium with submicroscale texture but with no microgrooves was used as the control substratum, NE0. Scanning electron microscopic observation and the assays determining the cell adhesion, cell proliferation and osteoblast differentiation were performed. RESULTS: Cells more actively migrated into the microgrooves on NE60/10-30° than into the microgrooves on any other substrata tested, suggesting that the cells utilise the increased surface area of the substrata at the microscale level. NE60/10-0° and NE60/10-30° substrata generally enhanced adhesion, proliferation, alkaline phosphatase activity, and osteoblast differentiation of human primary cells when compared to other Ti substrata, and significant correlations were observed between these cellular activities. CONCLUSIONS: Here, we show that the contact guidance of human primary cells grown on Ti substrata can be controlled more by specific submicroscale textures on ridge tops than by the dimensions of surface microgrooves only. Also, the degree of angles created between the submicroscale textures and microgrooves on Ti substrata significantly affect cell adhesion, proliferation and differentiation in human primary cells.

Secondary closure of an extraction socket using the double-membrane guided bone regeneration technique with immediate implant placement.

PURPOSE: Immediate implantation presents challenges regarding site healing, osseointegration, and obtaining complete soft-tissue coverage of the extraction socket, especially in the posterior area. This last issue is addressed herein using the double-membrane (collagen membrane+high-density polytetrafluoroethylene [dPTFE] membrane) technique in two clinical cases of posterior immediate implant placement. METHODS: An implant was placed immediately after atraumatically extracting the maxillary posterior tooth. The gap between the coronal portion of the fixture and the adjacent bony walls was filled with allograft material. In addition, a collagen membrane (lower) and dPTFE membrane (upper) were placed in a layer-by-layer manner to enable the closure of the extraction socket without a primary flap closure, thus facilitating the preservation of keratinized mucosa. The upper dPTFE membrane was left exposed for 4 weeks, after which the membrane was gently removed using forceps without flap elevation. RESULTS: There was considerable plaque deposition on the outer surface of the dPTFE membrane but not on the inner surface. Moreover, scanning electron microscopy of the removed membrane revealed only a small amount of bacteria on the inner surface of the membrane. The peri-implant tissue was favorable both clinically and radiographically after a conventional dental-implant healing period. CONCLUSIONS: Secondary closure of the extraction socket and immediate guided bone regeneration using the double-membrane technique may produce a good clinical outcome after immediate placement of a dental implant in the posterior area.

Factors influencing osteoblast maturation on microgrooved titanium substrata.

In this study, we demonstrate surfaces with various dimensions of microgrooves fabricated by photolithography and subsequent acid etching that enhance various characteristics of titanium. Microgrooves with truncated V-shape in cross-section from 15 to 90 microm widths enabled us to report their exclusive effects on altering the surface chemistry and on enhancing the surface hydrophilicity, serum protein adsorption and osteoblast maturation on titanium substrata in a microgroove dimension-dependent manner. Further, acid etching and measurement direction separately affected the surface hydrophilicity results. By multiple correlation and regression analyses, surface chemistry, surface hydrophilicity and serum protein adsorption were determined to be the significant influential factors on osteoblast maturation. Within the limitations of this study, we conclude that combined submicron- and microtopography with relevant micro-dimension and structure enhance various characteristics of titanium, including surface hydrophilicity, which act as the essential factors influencing the osteoblast maturation on microgrooved titanium substrata.

Evaluation of Spinal Fusion Using Bone Marrow Derived Mesenchymal Stem Cells with or without Fibroblast Growth Factor-4.

OBJECTIVE: In this study, the authors assessed the ability of rat bone marrow derived mesenchymal stem cells (BMDMSCs), in the presence of a growth factor, fibroblast growth factor-4 (FGF-4) and hydroxyapatite, to act as a scaffold for posterolateral spinal fusion in a rat model. METHODS: Using a rat posterolateral spine fusion model, the experimental study comprised 3 groups. Group 1 was composed of 6 animals that were implanted with 0.08 gram hydroxyapatite only. Group 2 was composed of 6 animals that were implanted with 0.08 gram hydroxyapatite containing 1 x 10(6)/ 60 microL rat of BMDMSCs. Group 3 was composed of 6 animals that were implanted with 0.08 gram hydroxyapatite containing 1 x 10(6)/ 60 microL of rat BMDMSCs and FGF-4 1 microG to induce the bony differentiation of the BMDMSCs. Rats were assessed using radiographs obtained at 4, 6, and 8 weeks postoperatively. After sacrifice, spines were explanted and assessed by manual palpation, high-resolution microcomputerized tomography, and histological analysis. RESULTS: Radiographic, high-resolution microcomputerized tomographic, and manual palpation revealed spinal fusion in five rats (83%) in Group 2 at 8 weeks. However, in Group 1, three (60%) rats developed fusion at L4-L5 by radiography and two (40%) by manual palpation in radiographic examination. In addition, in Group 3, bone fusion was observed in only 50% of rats by manual palpation and radiographic examination at this time. CONCLUSION: The present study demonstrates that 0.08 gram of hydroxyapatite with 1 x 10(6)/ 60 microL rat of BMDMSCs induced bone fusion. FGF-4, added to differentiate primitive 1 x 10(6)/ 60 microL rat of BMDMSCs did not induce fusion. Based on histologic data, FGF-4 appears to induce fibrotic change rather than differentiation to bone by 1 x 10(6)/ 60 microL rat of BMDMSCs.

Surface microgrooves and acid etching on titanium substrata alter various cell behaviors of cultured human gingival fibroblasts.

OBJECTIVE: This study aimed to investigate the influence of surface microgrooves and acid etching on titanium substrata on cell proliferation and gene expression of cultured human gingival fibroblasts. MATERIAL AND METHODS: Ti substrata with various dimensions of microgrooves and further acid etching comprised four experimental groups (E15/3.5, E30/5, E60/10, and E90/15), whereas smooth and acid etched Ti discs were both used as control (NE0 and E0). The chemical composition of the control and experimental cp Ti substrata was analyzed by X-ray photoelectron spectroscopy (XPS). Cell proliferation, gene expression, and protein expression of cultured human gingival fibroblasts were analyzed between all groups using bromodeoxyuridine (BrdU) assay, reverse-transcriptase polymerase chain reaction (RT-PCR), and Western blotting, respectively. RESULTS: The XPS results showed that the Ti substrata used in this study showed no significant differences in the expression of surface chemical composition. BrdU assay showed that cell proliferation was significantly increased in E60/10 compared with that in any other group. In RT-PCR, E60/10 was noted to increase the expression of various genes involved in cell-matrix adhesion and adhesion-dependent cell cycle progression. In Western blotting, increased expression of fibronectin and Rho A was noted in E60/10 compared with that in NE0 or E15/3.5. CONCLUSION: This study indicates that surface microgrooves 60 mum in width and 10 mum in depth, and further acid etching on Ti substrata trigger the proliferation and alter the expression of both genes and proteins in cultured human gingival fibroblasts.

Influence of etched microgrooves of uniform dimension on in vitro responses of human gingival fibroblasts.

OBJECTIVE: The purpose of this study was to investigate the influence of titanium (Ti) substrata with etched surface microgrooves on in vitro responses of human gingival fibroblasts. MATERIAL AND METHODS: Commercially pure Ti discs with surface microgrooves 15, 30, and 60 microm in width were fabricated using photolithography. Microgrooves 15 microm in widths were designed to be 3.5 microm in depth, whereas microgrooves 30 and 60 microm in width varied between 5 and 10 microm in depth. The entire surface of the microgrooved Ti substrata was further acid etched and used as the five experimental groups in this study (E15/3.5, E30/5, E30/10, E60/5, and E60/10), whereas the smooth and acid-etched Ti discs were both used as the control (NE0 and E0). Human gingival fibroblasts were cultured on all groups of substrata on successive timelines. Fibroblast adhesion and morphology was analyzed using confocal laser scanning microscopy (CLSM). Cell adhesion and proliferation were analyzed and compared using crystal violet staining and sulforhodamine B protein staining assays, respectively. RESULTS: In CLSM, the cells in E30/10 and E60/10 were observed to be able to readily descend into and form focal adhesions inside the microgrooves, whereas the cells in E15/3.5 were mostly found on the ridge tops. Cell adhesion was significantly increased in E60/10 compared with that in NE0 or E0 at 4-h incubation. Cell proliferation was significantly increased in E60/10 and E15/3.5 compared with NE0 or E0 after 72 and 96 h of culture. CONCLUSION: This study indicates that Ti substrata with etched microgrooves 60 microm in width and 10 microm in depth significantly enhance human gingival fibroblast adhesion and proliferation.

In vivo study on hydroxyapatite scaffolds with trabecular architecture for bone repair.

The objective of this research was to investigate the bone formation and angio-conductive potential of hydroxyapatite (HA) scaffolds closely matched to trabecular bone in a canine segmental defect after 3 and 12 weeks post implantation. Histomorphometric comparisons were made between naturally forming trabecular bone (control) and defects implanted with scaffolds fabricated with micro-size (M-HA) and nano-size HA (N-HA) ceramic surfaces. Scaffold architecture was similar to trabecular bone formed in control defects at 3 weeks. No significant differences were identified between the two HA scaffolds; however, significant bone in-growth was observed by 12 weeks with 43.9 +/- 4.1% and 50.4 +/- 8.8% of the cross-sectional area filled with mineralized bone in M-HA and N-HA scaffolds, respectively. Partially organized, lamellar collagen fibrils were identified by birefringence under cross-polarized light at both 3 and 12 weeks post implantation. Substantial blood vessel infiltration was identified in the scaffolds and compared with the distribution and diameter of vessels in the surrounding cortical bone. Vessels were less numerous but significantly larger than native cortical Haversian and Volkmann canals reflecting the scaffold architecture where open spaces allowed interconnected channels of bone to form. This study demonstrated the potential of trabecular bone modeled, highly porous and interconnected, HA scaffolds for regenerative orthopedics.

An in vivo comparison of working length determination by only root-ZX apex locator versus combining root-ZX apex locator with radiographs using a new impression technique.

OBJECTIVE: The objective of this study was to compare, in vivo, the accuracy of working length determination using only the Root-ZX electronic apex locator versus adjusting Root-ZX measurements after obtaining a working length radiograph. STUDY DESIGN: The working length was determined in 25 premolar root canals using Root-ZX and K-files were fixed at these positions. Radiographs were acquired and interpreted, and the recorded working length measurement was adjusted, if necessary, for a combined measurement. The teeth were then extracted in an effort to determine the position of the file tip to the root canal constriction. On the basis of the position of the file tip to the apical foramen, polyvinylsiloxane impressions of the root apex were taken, or the root was imbedded in acrylic resin and ground in order to measure the position of the file tip to the apical constriction. RESULTS: The Root-ZX alone detected the apical constriction within +/- 0.5 mm in 84% of the samples (21 of 25 canals). However, 96% (24 of 25 canals) were within this range when the combination of Root-ZX and radiographs was used. We noted no statistical significance between these 2 methods (P > .05). CONCLUSION: Using a Root ZX Electronic Apex Locator combined with radiographs is recommended for the determination of working length, although there was no statistical significance between those 2 groups in this study.