Influence of repeated insertion-removal cycles on the force and magnetic flux leakage of magnetic attachments: an in vitro study.

STATEMENT OF PROBLEM: Magnetic attachments are widely used in overdentures and maxillofacial prostheses. Because the patient will routinely have to insert and remove a removable prosthesis, the retentive force and magnetic flux leakage of the magnetic attachments after repeated insertion and removal must be evaluated to assess their clinical performance. PURPOSE: The purpose of this in vitro study was to investigate the retentive force and flux leakage of magnetic attachments after repeated insertion and removal. MATERIAL AND METHODS: Magfit EX600W magnet-keeper combinations (n=5) were used in this study. After 5000, 10,000, and 20,000 insertion-removal cycles, the retentive force of the magnetic attachments was measured 5 times at a crosshead speed of 5 mm/min with a universal testing machine. Magnetic flux leakage at 3 positions (P1, the upper surface of the magnet; P2, the lower surface of the keeper; and P3, the lateral side of the magnetic attachment set) was evaluated with a gaussmeter. Data were statistically analyzed by 1-way ANOVA (α=.05). The morphology of the abraded surfaces for both the magnet and the keeper was observed with an optical microscope (5×). RESULTS: The mean retentive force decreased significantly after 5000, 10,000, and 20,000 insertion-removal movements (P<.05). Significant differences of flux leakage were also observed at P1 after 5000 cycles and 10,000 cycles, at P2 after 5000 cycles, and at P3 after 5000, 10,000, and 20,000 insertion-removal cycles (P < .05). However, no significant differences in flux leakage were evident after 20,000 cycles at P1 and 10,000 cycles and 20,000 cycles at P2. CONCLUSIONS: Repeated insertion and removal influenced the retentive force and magnetic flux leakage of the magnetic attachments. Retentive force decreased significantly after repeated insertion-removal cycles, whereas the variation of magnetic flux leakage depended on refitting cycles and positions of the magnetic attachments.

Flavokawain B induces apoptosis of human oral adenoid cystic cancer ACC-2 cells via up-regulation of Bim and down-regulation of Bcl-2 expression.

Novel effective drugs are still urgently needed in the prevention and treatment of oral adenoid cystic carcinoma (ACC). In this study, we have assessed the antitumor potential and molecular mechanisms of flavokawain B (FKB) as a kava chalcone on the ACC-2 cell line in vitro. The results demonstrated that FKB could significantly inhibit the cell proliferation of ACC-2 in a dose-dependent manner that was associated with induced apoptosis and cell cycle G2-M arrest, and the half maximal inhibitory concentration (IC50) of flavokawain-B treatment for 48 h was estimated to be 4.69 ± 0.43 µmol/L. Mechanistically, FKB could induce the release of cytochrome c from mitochondria into the cytosol, and activate the cleavage of caspase-3 and, eventually, the poly(ADP-ribose) polymerase (PARP), in a dose-dependent manner, leading to marked apoptotic effect of ACC-2 cells. The apoptotic action of FKB was associated with the increased expression of proapoptotic proteins: Bim, Bax, Bak and a decreased expression of antiapoptotic Bcl-2. Among them, Bim expression was significantly induced by FKB, and knockdown of Bim expression by short-hairpin RNAs attenuated the inhibitory effect induced by FKB on ACC-2 cells. These results suggest Bim may be one of the potential transcriptional targets, and suggests the potential usefulness of FKB for the prevention and treatment of ACC.

Fluoridated hydroxyapatite/titanium dioxide nanocomposite coating fabricated by a modified electrochemical deposition.

Fluoridated hydroxyapatite/titanium dioxide nanocomposite coating was successfully fabricated by a modified electrochemical deposition technique. F(-) ions, nanoscaled TiO(2) particles and 6% H(2)O(2) was added into the electrolyte, and ultrasonication was also performed to prepare this nanocomposite coating. The microstructure, phase composition, dissolution rate, bonding strength and in vitro cellular responses of the composite coating were investigated. The results show that the composite coating was uniform and dense owing to the effects of H(2)O(2) and ultrasonication. The thickness of the composite coating was ~5 mum and scanning electron microscopy revealed that nanoscaled TiO(2) particles were imbedded uniformly between FHA crystals. The addition of F(-) and TiO(2) reduced the crystallite size and increased the crystallinity of HA in FHA/TiO(2) composite coating. In addition, the composite coating shows higher bonding strength and lower dissolution rate than pure HA coating, and the in vitro bioactivity of FHA/TiO(2) composite coating was not affected as compared with pure HA coating.

Magnetic fields of 10mT and 120mT change cell shape and structure of F-actins of periodontal ligament cells.

Dental magnetic attachments, usually applied locally to oral cavities, produce stray fields (flux leakage) spreading in adjacent tissues. It has been found that human periodontal ligament (PDL) cells change their geometry and the structure of their cytoskeleton F-actins when the cell cultures are exposed to B-field strengths of B = 10mT and 120mT, respectively, which are similar to those generated by dental magnetic attachments. Analytically, after long-time exposures to B-fields for 12h, 36 h and 60 h, respectively, cytoskeleton F-actins are labeled with a fluorescent dye and observed under a laser scanning confocal microscope. The geometrical cell parameters of cell length and cell width and the fluorescence emission of labeled F-actins, respectively, were determined and subjected to an automatic image analysis using a special software. The results on cell shrinkage and filament reorganizations were statistically analyzed by the program ANOVA (P < 0.05). It was found that only long-time (hours) exposure to high fields in the order of 0.1T may produce tissue irritations during long-time medical treatments using open- and closed-field dental magnetic attachments.

The possible role of estrogen in the incidence of temporomandibular disorders.

Epidemiologic literatures suggest that temporomandibular joint disorders (TMD) are more prevalent in women than in men. It is affecting approximately 7-15% of the adult population in North America, and 80% of patients treated for TMD are women. The severity of symptoms is also related to the age of the patients. The gender and age distribution of TMD suggests a possible link between its pathogenesis and estrogen. It has been reported that estrogen could influence the development, restitution and metabolism of the temporomandibular joint and associated structures such as bone, cartilage and articular disc. Estrogen can also influence the regulative mechanism of pain. In this article, we will use the hypothesis that the overwhelming majority of patients treated for temporomandibular disorders are women and use the available literature to examine the role of estrogens in TMD.

Translucency of newly extracted maxillary central incisors at nine locations.

STATEMENT OF PROBLEM: In addition to color, translucency is one of the primary factors influencing the esthetics of a dental prosthesis. Due to difficulties in measuring the translucency of natural teeth, minimal data are available. PURPOSE: The purpose of this study was to measure the translucency of newly extracted maxillary central incisors and analyze the relationship between translucency, anatomic location, and age. MATERIAL AND METHODS: The translucency of 32 newly extracted maxillary central incisors was measured with a spectrocolorimeter (PR-650) at 9 locations on the tooth crown. These locations were identified by dividing the tooth incisally to cervically and medially to laterally in equal dimensions. The relationships between transmittance, locations, and age were analyzed by univariate analysis of variance (alpha=.05). RESULTS: The transmittance of maxillary central incisors ranged from 0.13% to 0.65%, which decreased from incisal to cervical (P<.05). Age also affected transmittance in certain locations of the crown; older teeth demonstrated higher transmittance (P<.05). CONCLUSIONS: Transmittance of the maxillary central incisor was variable at different locations of the crown and was positively correlated with age.

[Determination and Weibull analysis of the strength of dental veneering porcelains].

OBJECTIVE: To determine the strength of the veneering porcelain stored in artificial saliva. METHODS: Standard beams with a size of 3 mm x 2 mm x 20 mm made from the body, incisal, and translucent porcelains of SHOFU Vintage were stored in the artificial saliva for 30 days. Twenty samples from each material were tested for the strength by the 3-point flexural test at a crosshead speed of 0.5 mm. The data were analyzed by the two-parameter Weibull method. RESULTS: The strength, Weibull modulus (m) and characterization strength (male0) were (75.5 +/- 5.6) MPa, 17.3, and 77.6 MPa for Body porcelain, respectively; (73.6 +/- 5.0) MPa, 16.5, and 76.0 MPa for incisal porcelain, respectively; and (72.9 +/- 4.5) MPa, 16.1, and 75. 5 MPa for translucent porcelain, respectively. CONCLUSION: There are no differences in strength between the three dental porcelains. Weibull analysis describes the strength of the porcelains better than the average and standard deviation.

Effects of static magnetic fields on the voltage-gated potassium channel currents in trigeminal root ganglion neurons.

To evaluated the effects of moderate-intensity static magnetic fields (SMF) on two types of voltage-gated potassium channel (VGPC) currents: I(K,A) and I(K,V), whole-cell patch-clamp experiments were conducted on acute dissociated rat trigeminal root ganglion (TRG) neurons. The results demonstrated that 125 mT SMF could influence the inactivation kinetics of these two VGPC currents by altering the inactivation rate and velocity. No significant change was observed in the activation properties. These findings supported the hypothesis that biological membrane would be deformed in moderate-intensity SMF and the physiological characteristics of ion channels on the membrane would be influenced. The mechanism underlying the different effects of SMF on the I(K,A) and I(K,V) inactivation was also discussed.

Shrinkage and strength characterization of an alumina-glass interpenetrating phase composite for dental use.

OBJECTIVE: The aim of the study was to investigate the influence of temperature and time during partial-sintering (i.e. initial-stage sintering) on the shrinkage and strength of an alumina-glass dental composite. METHODS: The alumina slip and infiltrating glass were prepared for fabrication of an interpenetrating phase composite by melt-infiltration technology. Partial-sintering temperatures for the alumina body ranged from 1050 to 1200 degrees C (2 h) and at 1125 degrees C, the time was varied from 2 to 8 h. Partially sintered alumina preform were then infiltrated with melted glass at 1125 degrees C for 6h except for one group treated at 1100 degrees C for 6 h. RESULT: The composite demonstrated shrinkage not only during initial-stage sintering of the alumina but also during infiltration of glass into the alumina preform. Higher temperatures and longer times for alumina sintering led to greater shrinkage for the alumina preform and overall for the alumina-glass infiltrated composite. However, shrinkage during the infiltration stage was lower for alumina compacts having the highest initial-stage sintering shrinkage (1200 degrees C for 2 h or at 1125 degrees C for 6 and 8 h). Strength of the composite was not influenced when sintering temperatures and times were increased. SIGNIFICANCE: Shrinkage during both alumina sintering and glass infiltration must be taken into account for the overall shrinkage of the alumina-glass interpenetrating phase composite. Strength does not appear to be influenced by the changes in density or preform microstructure occurring during more extensive initial-stage sintering.

A self-disinfecting irreversible hydrocolloid impression material mixed with chlorhexidine solution.

OBJECTIVE: To examine the antibacterial effect and several physical properties of an irreversible hydrocolloid impression material mixed with chlorhexidine solution. MATERIALS AND METHODS: The experimental irreversible hydrocolloid specimens were prepared and allocated into four groups (Group0.1 g/L, Group0.2 g/L, Group0.5 g/L, Group1.0 g/L) according to the concentrations of chlorhexidine solution used as the mixing liquid. Specimens mixed with distilled water served as a control. The antibacterial effect, three-dimensional accuracy, flowability, and setting time were tested. Statistical analysis was performed using a one-way analysis of variance and a Tukey test, which was used for multiple comparisons (alpha=.05). RESULTS: Zones of growth inhibition were observed around the test specimens, but not around the control specimens, and there were significant intergroup differences in the diameters of the inhibition zones. In the accuracy test, no significant differences (P>.05) were detected among all the measurements for all groups, and the accuracy was clinically acceptable. Also, no significant differences in the flowability (P=.987) and setting time (P=.103) were detected. CONCLUSION: Chlorhexidine self-disinfecting irreversible hydrocolloid impression material can exhibit varying degrees of antibacterial activity without influencing the three-dimensional accuracy, flowability, and setting time.

[The research for magnetic attachments producing static magnetic fields to influence on cytoskeletons of human periodontal ligament cells].

OBJECTIVE: The present research aimed to investigate that the static magnetic field (SMF) generated by dental magnetic attachments influenced on the cytoskeletons of human periodontal ligament cells (HPDLCs). METHODS: In vitro cultured HPDLCs were exposed to 10 mT and 120 mT SMF which simulated those of from the closed-field and open-field magnetic attachments respectively for 12-60 hours in a cellular SMF exposure system. The control group cells were cultured outside the SMF exposure system and were only exposed to geomagnetic field of about 0.03-0.07 mT. After finishing the SMF exposure, the cytoskeletons were observed under a laser scanning confocal microscope (LSCM). The image analysis software was utilized to measure and analyze the cell area, length/width ratios and the contents of F-actin of cells. RESULTS: There were certain changes observed in the cytoskeletons after HPDLCs exposed to 10 mT and 120 mT SMF for 12-60 hours. With the SMF strength increasing and the loading time extending, the cell microfilaments got ashorened change and a disordered arrangement inside cells, and the length/width ratios of cells decreased (P < 0.05). The areas of cells decreased after SMF loading for 60 hours (P < 0.05). The cell F-actin contents decreased after SMF loading for 12 hours (P < 0.05), but in the meantime there was no significant difference happening between the 36 or 60 hours SMF loading group and the control group (P > 0.05). CONCLUSION: In this study the SMF of magnetic attachments can lead the certain changes to the cytoskeletons in HPDLCs.

[Effects of static magnetic field on the activity of superoxide dismutase of human gingival fibroblasts].

OBJECTIVE: To investigate the effects of static magnetic fields (SMF) generated by the open-circuit and closed-circuit dental magnetic attachments on the enzymology of human gingival fibroblasts. METHODS: In this study, a cellular SMF exposure system developed by our department of prosthetic dentistry was used to impose the static magnetic force on the cultured human gingival fibroblasts in vitro. The activity of superoxide dismutase in those fibroblasts of the test group and that of the control group were measured and compared. RESULTS: No significant difference (P > 0.05) in superoxide dismutase activity was found between the groups when they were loaded with different intensity of magnetic fields or for different period of time. CONCLUSION: Under the conditions in this experiment, the static magnetic fields of the open-circuit magnetic attachments, and those of the closed-circuit ones as well, have no biological effects on the superoxide dismutase of human gingival fibroblasts.

[Effects of hypotonic solution on the proliferation, alkaline phosphatase activity and [Ca2+]i concentration of osteoblast-like cells].

OBJECTIVE: To investigate the effects of static-stretch from the hypotonic solution on the proliferation, alkaline phosphatase activity and [Ca2+]i in the osteoblast-like cells. METHODS: Mechanical loading was introduced by swelling in the hypotonic solution. In vitro cultured MG63 were incubated under continuous swelling of 277, 240 and 163mOsm for 2h, 4h, 8h, 12h, 24h and 48h. The cell proliferation was detected by MTT assay. ALPase and [Ca2+]i were determined by modified enzyme dynamic method and OCPC respectively. RESULTS: The cell proliferation, ALP activity and [Ca2+]i increased slowly under continuous static-stretch of 277 and 240mOsm. The cell proliferation was inhibited under 163mOsm, with a sharp increase of [Ca2+]i at 8h (11.383 +/- 0.111) and an increase of ALPase activity (0.326 +/- 0.002). CONCLUSION: The static-stretch induced from the hypotonic solution has an impact on the proliferation, differentiation, ALPase and Ca2+-ATPase of the MG63. The [Ca2+]i is correlated with the ALPase.

[A static magnetic field loading system for in vitro cultured cells].

Magnetic attachments have flux leakages, thus they will exert certain magnetic fields on the adjacent tissues when used in the patients' oral cavities. There are few research reports on the biological effects of the magnetic fields generated by magnetic attachments on human body. A cellular static magnetic field (SMF) loading system was developed in this study. By using this system, in vitro cultured human periodontal ligament cells (HPDLCs) were loaded with SMF simulating those of magnetic attachments. The cellular SMF loading system could produce constant SMF and the strength of the SMF is adjustable. The system is small and is able to exert SMF to cells cultured in different culture vessels such as culture dishes and culture plates, thus is suitable to researches in multiple biological items of cells. The results of the SMF loading experiment on HPDLCs showed that this cellular SMF loading system could effectively load cells with SMF of different strengths for different time in vitro. The development of this system has provided a useful tool for the researches on the cellular hiologioal effects of SMF.

[Compatibility between high-strength dental ceramic (type A) and vintage AL veneering porcelain].

OBJECTIVE: To investigate the interface bond strength and compatibility between High-Strength Dental Ceramic (type A) and Vintage AL veneering porcelain. METHODS: Twenty bar-shape specimens (ten Vintage AL and ten Vitadur alpha) were fabricated, and shear test was conducted to determine the bond strength. A bilayered composite (1 mm core ceramic and 0.8 mm Vintage AL) was prepared and then fractured for scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analysis. Ten all-ceramic anterior crowns were fabricated and the temperatures of thermal shock resistance were tested. RESULTS: The mean values of the bond strength measured were (55.52 +/- 14.64) MPa and (59.37 +/- 13.93) MPa for Vintage AL and Vitadur alpha respectively (P>0.05). SEM showed tight connection between the High-Strength Dental Ceramic (type A) and the veneering porcelain. Element diffusion was also confirmed by energy dispersive spectroscopy (EDS) analysis. The temperature of thermal shock resistance of this system was (179 +/- 15) degrees C. CONCLUSION: Vintage AL veneering porcelain has good thermal and chemical compatibility with High-Strength Dental Ceramic (type A).

[Study on the interface of Ti-porcelain fused under different surface treatment].

OBJECTIVE: This study was made to observe the topography and ionic diffusion of the elements titanium, silicon, et cetera in the Ti-porcelain interface area which was pretreated with different methods. METHODS: Ti-bond porcelain was fused on commercial pure titanium (CPT) with 8 different pretreatment methods; according to the temperature of the preoxidation, there were 300 degrees C, 400 degrees C, 500 degrees C and 600 degrees C groups, and based on the oxidizing-time in the air, there were 5 min, 15 min, 2 h and 24 h groups. The topography and ionic diffusion of elements in the Ti-porcelain interface area were observed with scanning electron microscopy (SEM) and electron probe microanalysis (EPMA) respectively. RESULTS: There were clefts and exfoliations in the 500 degrees C pre-oxidation group and 600 degrees C pre-oxidation group in SEM images. The distribution of titanium in the interlayer in EPMA images decreased from the titanium surface to porcelain, which was opposite to the distribution of silicon. CONCLUSION: The clefts and exfoliations suggested the position of the fracture and brittleness of alpha-Ti[o] layer. The widths of ionic diffusion in the eight groups were different, but it was difficult to measure and compare them exactly.

[The study of the colorimetric characteristics of the cobalt-chrome alloys abutments covered by four different all-ceramic crowns by using dental spectrophotometer].

OBJECTIVE: This study aims to evaluate the optical data of the different sites of the cobalt-chrome (Co-Cr) alloy abutments covered by four different all-ceramic crowns and the color difference between the crowns and target tab using a digital dental spectrophotometer. METHODS: Ten Co-Cr alloy abutments were made and tried in four different groups of all-ceramic crowns, namely, Procera aluminia, Procera zirconia, Lava zirconia (Lava-Zir), and IPS E.max glass-ceramic lithium disilicate-reinforced monolithic. The color data of the cervical, body, and incisal sites of the samples were recorded and analyzed by dental spectrophotometer. The CIE L*, a*, b* values were again measured after veneering. The color difference between the abutments covered by all-ceramic crowns and A2 dentine shade tab was evaluated. RESULTS: The L* and b* values of the abutments can be increased by all of the four groups of all-ceramic copings, but a* values were decreased in most groups. A statistical difference was observed among four groups. After being veneered, the L* values of all the copings declined slightly, and the values of a*, b* increased significantly. When compared with A2 dentine shade tab, the ΔE of the crowns was below 4. CONCLUSION: Four ceramic copings were demonstrated to promote the lightness and hue of the alloy abutments effecttively. Though the colorimetric baseline of these copings was uneven, veneer porcelain can efficiently decrease the color difference between the samples and thee target.

Laboratory evaluation of a new denture adhesive.

OBJECTIVE: The ideal denture adhesive demonstrates a neutral or slightly basic pH, satisfactory bonding load, and minimal toxicity to the oral mucosa. The purpose of this study was to evaluate the properties of a new denture adhesive (Comfort-DA, developed by the authors). METHODS: Comfort-DA was evaluated in the laboratory to determine the clinical effect of pH, bonding strength, and cytotoxicity. Firstly, the material was diluted at 1.0, 2.0, 3.3, 5.0, and 10% concentrations. Then the pH values were measured at 1-, 2-, 3-, 4-, 5-, 6-, and 8-hour intervals. Secondly, bonding load test was performed between acrylic resin samples on a universal testing machine. An existing product, Fittydent, was used as a control. Finally, the cytotoxicity of several dilutions of Comfort-DA was recorded with a MTT assay on human oral fibroblast cells. Cell viability was recorded by optical density after culturing in an atmosphere of 5% CO2 and 95% air at 37 degrees C for 2, 3 and 4 days, respectively. Wells containing fresh medium alone served as controls. All the results were compared with ANOVA or Tukey intervals (alpha = 0.05). RESULTS: Comfort-DA remained above the critical pH for hydroxyapatite (pH 6.5) in all dilutions throughout the study. Results of bonding strength test indicated that Comfort-DA was significantly stronger than Fittydent (p < 0.05). The statistical analysis of results for cytotoxicity showed that Comfort-DA only displayed slight cytotoxicity. SIGNIFICANCE: The generally favorable laboratory performance of Comfort-DA formulations indicates that this product may be an efficacious denture adhesive.

[Measurements of the flux densities of static magnetic fields generated by two types of dental magnetic attachments and their retentive forces].

OBJECTIVE: To measure and analyze the flux densities of static magnetic fields generated by two types of commonly used dental magnetic attachments and their retentive forces, and to provide guidance for the clinical application of magnetic attachments. METHODS: A digital Gaussmeter was used to measure the flux densities of static magnetic fields generated by two types of magnetic attachments, under four circumstances: open-field circuit; closed-field circuit; keeper and magnet slid laterally for a certain distance; and existence of air gap between keeper and magnet. The retentive forces of the magnetic attachments in standard closed-field circuit, with the keeper and magnet sliding laterally for a certain distance or with a certain air gap between keeper and magnet were measured by a tensile testing machine. RESULTS: There were flux leakages under both the open-field circuit and closed-field circuit of the two types of magnetic attachments. The flux densities on the surfaces of MAGNEDISC 800 (MD800) and MAGFIT EX600W (EX600) magnetic attachments under open-field circuit were 275.0 mT and 147.0 mT respectively. The flux leakages under closed-field circuit were smaller than those under open-field circuit. The respective flux densities on the surfaces of MD800 and EX600 magnetic attachments decreased to 11.4 mT and 4.5 mT under closed-field circuit. The flux density around the magnetic attachment decreased as the distance from the surface of the attachment increased. When keeper and magnet slid laterally for a certain distance or when air gap existed between keeper and magnet, the flux leakage increased in comparison with that under closed-field circuit. Under the standard closed-field circuit, the two types of magnetic attachments achieved the largest retentive forces. The retentive forces of MD800 and EX600 magnetic attachments under the standard closed-field circuit were 6.20 N and 4.80 N respectively. The retentive forces decreased with the sliding distance or with the increase of air gap between keeper and magnet. CONCLUSION: The magnetic attachments have flux leakages. When they are used in patients' oral cavities, if keeper and magnet are not attached accurately, the flux leakage will increase, and at the same time the retentive force will decrease. Therefore the keeper and magnet should be attached accurately in clinical application.

Adenovirus encoding BMP-7 immobilized on titanium surface exhibits local delivery ability and regulates osteoblast differentiation in vitro.

OBJECTIVE: The local delivery of growth factors such as bone morphogenetic protein-7 (BMP-7) into the tissues around dental implants may improve their osseointegration. We have designed a new method of attaching BMP-7 to a titanium surface and assessed both the retention of the BMP-7 and its effect on osteoblast differentiation. DESIGN: Adenoviral vector expressing BMP-7 was attached to dental titanium discs by hexon-specific antibodies in a type I collagen-avidin gel. FITC-labelled secondary antibody was used to measure the continuing adherence of the coating after repeated rinsing. Osteoblasts were harvested and seeded on the titanium discs. Gene transduction efficiency and targeting ability were assessed after 24h. Surface morphology was observed by SEM. Cell proliferation and alkaline phosphatase (ALP) activities were measured. RESULTS: The anti-adenohexon antibody adhered strongly to the collagen-avidin gels. BMP-7 gene expression was localized precisely to cells growing on the gels bound by the hexon-specific antibody. Osteoblasts on the titanium containing Ad-BMP-7 had a higher ALP activity than those without Ad-BMP-7. CONCLUSIONS: This study describes a novel technique for the precise attachment of BMP-7 to titanium surfaces. The process may enhance the osseointegration of dental implants.