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1.  The effect of repeated firings on the color change of dental ceramics using different glazing methods 
PURPOSE
Surface color is one of the main criteria to obtain an ideal esthetic. Many factors such as the type of the material, surface specifications, number of firings, firing temperature and thickness of the porcelain are all important to provide an unchanged surface color in dental ceramics. The aim of this study was to evaluate the color changes in dental ceramics according to the material type and glazing methods, during the multiple firings.
MATERIALS AND METHODS
Three different types of dental ceramics (IPS Classical metal ceramic, Empress Esthetic and Empress 2 ceramics) were used in the study. Porcelains were evaluated under five main groups according to glaze and natural glaze methods. Color changes (ΔE) and changes in color parameters (ΔL, Δa, Δb) were determined using colorimeter during the control, the first, third, fifth, and seventh firings. The statistical analysis of the results was performed using ANOVA and Tukey test.
RESULTS
The color changes which occurred upon material-method-firing interaction were statistically significant (P<.05). ΔE, ΔL, Δa and Δb values also demonstrated a negative trend. The MC-G group was less affected in terms of color changes compared to other groups. In all-ceramic specimens, the surface color was significantly affected by multiple firings.
CONCLUSION
Firing detrimentally affected the structure of the porcelain surface and hence caused fading of the color and prominence of yellow and red characters. Compressible all-ceramics were remarkably affected by repeated firings due to their crystalline structure.
doi:10.4047/jap.2014.6.6.427
PMCID: PMC4279039  PMID: 25551001
Color change; Repeated firings; Glazing method; Dental ceramic
2.  Shear bond strength of a new self-adhering flowable composite resin for lithium disilicate-reinforced CAD/CAM ceramic material 
PURPOSE
The purpose of this study was to evaluate and compare the effects of different surface pretreatment techniques on the surface roughness and shear bond strength of a new self-adhering flowable composite resin for use with lithium disilicate-reinforced CAD/CAM ceramic material.
MATERIALS AND METHODS
A total of one hundred thirty lithium disilicate CAD/CAM ceramic plates with dimensions of 6 mm × 4 mm and 3 mm thick were prepared. Specimens were then assigned into five groups (n=26) as follows: untreated control, coating with 30 µm silica oxide particles (Cojet™ Sand), 9.6% hydrofluoric acid etching, Er:YAG laser irradiation, and grinding with a high-speed fine diamond bur. A self-adhering flowable composite resin (Vertise Flow) was applied onto the pre-treated ceramic plates using the Ultradent shear bond Teflon mold system. Surface roughness was measured by atomic force microscopy. Shear bond strength test were performed using a universal testing machine at a crosshead speed of 1 mm/min. Surface roughness data were analyzed by one-way ANOVA and the Tukey HSD tests. Shear bond strength test values were analyzed by Kruskal-Wallis and Mann-Whitney U tests at α=.05.
RESULTS
Hydrofluoric acid etching and grinding with high-speed fine diamond bur produced significantly higher surface roughness than the other pretreatment groups (P<.05). Hydrofluoric acid etching and silica coating yielded the highest shear bond strength values (P<.001).
CONCLUSION
Self-adhering flowable composite resin used as repair composite resin exhibited very low bond strength irrespective of the surface pretreatments used.
doi:10.4047/jap.2014.6.6.434
PMCID: PMC4279040  PMID: 25551002
Surface pretreatments; Shear bond strength; Vertise flow; Er:YAG laser; Tribochemical silica coating; CAD/CAM ceramic
3.  Effect of anatomic, semi-anatomic and non-anatomic occlusal surface tooth preparations on the adaptation of zirconia copings 
PURPOSE
To compare the accuracy of marginal and internal adaptation of zirconia (Zr) copings fabricated on anatomic (A), semi-anatomic (SA) and non-anatomic (NA) occlusal surface preparations.
MATERIALS AND METHODS
45 extracted bicuspid teeth were prepared for receiving zirconia crowns, with different occlusal preparation designs A=15, SA=15 & NA=15. The Zr copings were fabricated by using CAD4DENT, CAD/CAM. The copings were adjusted, cemented and were cross sectioned centrally from buccal cusp tip to lingual cusp tip into mesial and distal halves. The copings were examined under electron microscope at ×200 magnification and the measurements were recorded at 9 predetermined areas in micrometers.
RESULTS
Overall mean gap values for the three groups was found to be 155.93±33.98 µm with Anatomical Occlusal preparation design having the least gap value of 139.23±30.85 µm showing the best adaptation among the groups. Post Hoc Tukey's test showed a statistically significant difference (P=.007) between the means of gap for A & NA preparation designs. Measurements recorded at 9 predetermined points showed variations for the three groups.
CONCLUSION
Anatomical occlusal preparation designs resulted in better marginal and internal adaptation of Zr copings. There is a considerable variation between the measured marginal and internal gap values for the Zr copings fabricated by the (CAD4DENT-CAD/CAM). This variation may be associated with the lack of standardization of the preparation of teeth, computerized designing of the coping for each tooth, cement used, uniform pressure application during the cementation of the copings, sectioning of the copings and the microscopic measurements.
doi:10.4047/jap.2014.6.6.444
PMCID: PMC4279041  PMID: 25551003
Zirconia copings; Zirconia crowns; Marginal fit of zirconia crowns; Adaptation of zirconia crowns
4.  Effects of coloring procedures on zirconia/veneer ceramics bond strength 
PURPOSE
The most common failure seen in restorations with a zirconia core is total or layered delamination of the ceramic veneer. In the present study, the shear bond strengths between veneering ceramics and colored zirconia oxide core materials were evaluated.
MATERIALS AND METHODS
Zirconia discs (15 × 12 × 1.6 mm) were divided into 11 groups of 12 discs each. Groups were colored according to the Vita Classic scale: A3, B1, C4, D2, and D4. Each group was treated with the recommended shading time for 3 s, or with prolonged shading for 60 s, except for the control group. Samples were veneered with 3 mm thick and 3.5 mm in diameter translucent ceramic and subjected to shear test in a universal testing machine with a crosshead speed of 1 mm/min. One-way analysis of variance (ANOVA) and Tukey's HSD tests were used for comparisons of the groups having the same shading times. A paired t-test was used for groups of the same color (3 s/60 s).
RESULTS
Among the 11 groups investigated C4 (3 s) had the highest bond strength with a value of 36.40 MPa, while A3 (3 s) showed the lowest bond strength with a value of 29.47 MPa.
CONCLUSION
Coloring procedures can affect zirconia/ceramic bond strength. However, the results also showed that bond strengths of all the investigated groups were clinically acceptable.
doi:10.4047/jap.2014.6.6.451
PMCID: PMC4279042  PMID: 25551004
Bond strength; Veneering ceramic; Coloring pigments; Zirconia
5.  Comparative analysis of transmittance for different types of commercially available zirconia and lithium disilicate materials 
PURPOSE
Translucency and colour stability are two most important aspects for an aesthetic dental restoration. Glass ceramic restorations are popular amongst clinicians because of their superior aesthetic properties. In the last decade, zirconia has generated tremendous interest due to its favorable mechanical and biological properties. However, zirconia lacks the translucency that lithium disilicate materials possess and therefore has limitations in its use, especially in esthetically demanding situations. There has been a great thrust in research towards developing translucent zirconia materials for dental restorations. The objective of the study was to evaluate and compare the transmittance of a translucent variant of zirconia to lithium disilicate.
MATERIALS AND METHODS
Two commercially available zirconia materials (conventional and high translucency) and 2 lithium disilicate materials (conventional and high translucency) with standardized dimensions were fabricated. Transmittance values were measured for all samples followed by a microstructural analysis using a finite element scanning electron microscope. One way analysis of variance combined with a Tukey-post hoc test was used to analyze the data obtained (P=.05).
RESULTS
High translucency lithium disilicate showed highest transmittance of all materials studied, followed by conventional lithium disilicate, high translucency zirconia and conventional zirconia. The difference between all groups of materials was statistically significant. The transmittance of the different materials correlated to their microstructure analysis.
CONCLUSION
Despite manufacturers' efforts to make zirconia significantly more translucent, the transmittance values of these materials still do not match conventional lithium disilicate. More research is required on zirconia towards making the material more translucent for its potential use as esthetic monolithic restoration.
doi:10.4047/jap.2014.6.6.456
PMCID: PMC4279043  PMID: 25551005
Aesthetics; Lithium disilicate; Translucency; Transmittance; Zirconia
6.  Mechanical properties of zirconia after different surface treatments and repeated firings 
PURPOSE
This study investigated the influence of surface conditioning procedures and repeated firings on monoclinic content and strength of zirconia before cementation.
MATERIALS AND METHODS
Sintered bar-shaped zirconia specimens were subjected to no surface treatment (control), air abrasion, or grinding (n=21). Their roughness was evaluated using a profilometer, and microscope analysis was performed on one specimen of each group. Then, 2 or 10 repeated firings (n=10) were executed, the monoclinic content of specimens was analyzed by X-ray diffraction, and a three-point flexural strength test was performed. Surface roughness values were compared using one-way analysis of variance (ANOVA) and Tukey honestly significant difference (HSD) tests, the monoclinic content values were tested using Kruskal-Wallis and Mann-Whitney U tests, and the flexural strength values were tested using two-way ANOVA and Tukey HSD tests (P=.05). Spearman's correlation test was performed to define relationships among measured parameters.
RESULTS
Surface-treated specimens were rougher than untreated specimens and had a higher monoclinic content (P<.005), and the relationship between roughness and monoclinic content was significant (P<.000). Neither surface treatment nor firing significantly affected the flexural strength, but Weibull analysis showed that for the air-abraded samples the characteristic strength was significantly lower after the 10th firing than after the 2nd firing.
CONCLUSION
After firing, a negligible amount of monoclinic content remained on the zirconia surfaces, and rougher surfaces had higher monoclinic contents than untreated surfaces. Multiple firings could be performed if necessary, but the fracture probability could increase after multiple firings for rougher surfaces.
doi:10.4047/jap.2014.6.6.462
PMCID: PMC4279044  PMID: 25551006
Surface Treatment; Zirconium Oxide; Ceramics; X-ray diffraction; Flexural Strength
7.  Accuracy of 3D white light scanning of abutment teeth impressions: evaluation of trueness and precision 
PURPOSE
This study aimed to evaluate the accuracy of digitizing dental impressions of abutment teeth using a white light scanner and to compare the findings among teeth types.
MATERIALS AND METHODS
To assess precision, impressions of the canine, premolar, and molar prepared to receive all-ceramic crowns were repeatedly scanned to obtain five sets of 3-D data (STL files). Point clouds were compared and error sizes were measured (n=10 per type). Next, to evaluate trueness, impressions of teeth were rotated by 10°-20° and scanned. The obtained data were compared with the first set of data for precision assessment, and the error sizes were measured (n=5 per type). The Kruskal-Wallis test was performed to evaluate precision and trueness among three teeth types, and post-hoc comparisons were performed using the Mann-Whitney U test with Bonferroni correction (α=.05).
RESULTS
Precision discrepancies for the canine, premolar, and molar were 3.7 µm, 3.2 µm, and 7.3 µm, respectively, indicating the poorest precision for the molar (P<.001). Trueness discrepancies for teeth types were 6.2 µm, 11.2 µm, and 21.8 µm, respectively, indicating the poorest trueness for the molar (P=.007).
CONCLUSION
In respect to accuracy the molar showed the largest discrepancies compared with the canine and premolar. Digitizing of dental impressions of abutment teeth using a white light scanner was assessed to be a highly accurate method and provided discrepancy values in a clinically acceptable range. Further study is needed to improve digitizing performance of white light scanning in axial wall.
doi:10.4047/jap.2014.6.6.468
PMCID: PMC4279045  PMID: 25551007
White light scanner; Accuracy; Precision and trueness; Impression scanning; 3D shape data; Point cloud
8.  Influence of gag reflex on removable prosthetic restoration tolerance according to the patient section of the short form of the Gagging Problem Assessment Questionnaire 
PURPOSE
To assess removable prosthetic restoration tolerance according to the patient section of the short form of the Gagging Problem Assessment Questionnaire (GPA-pa SF) and the influence of gender, education level and prosthesis type and denture-related mucosal irritation on the GPA-pa SF scores before treatment and over a period of two months after prosthesis insertion.
MATERIALS AND METHODS
130 participants who required removable prosthesis were surveyed with a standard form that included questions regarding age, gender, education level, dental attendance, and prosthetic restoration type. Participants answered the GPA-pa SF before restoration (T0) and 1 day (T1), 2 days (T2), 15 days (T3), 1 month (T4), and 2 months (T5) after prosthesis insertion.
RESULTS
Of the 130 participants, 110 participants completed the prosthetic restoration procedure, but only 93 of these were able to use the prosthesis over the two-month period. The mean GPA-pa SF score obtained at T0 was higher than the scores obtained at the other periods in the total of the sample. Significant difference was present between mean scores obtained at T0-T1 and T2-T3 than scores obtained at other periods (P<.05). Female participants and participants with denture-related mucosal irritation had higher GPA-pa SF scores at all time points analysed. Significant difference was present between mean GPA-pa SF scores obtained at T2-T3 than scores obtained at other periods for females and participants with denture-related mucosal irritation (P<.05). Education level and prosthesis type did not significantly influence the GPA-pa SF score at any time point analysed (P>.05).
CONCLUSION
GPA-pa SF scores were higher before the restoration procedure began, and decreased over time with the use of prosthesis. Gender and denture-related mucosal irritation affected the GPA-pa SF scores.
doi:10.4047/jap.2014.6.6.474
PMCID: PMC4279046  PMID: 25551008
Gag reflex; Pharyngeal; Prosthodontics; Complete prosthesis; Partial prosthesis
9.  Faculty-supervised measurements of the face and of mandibular movements on young adults 
PURPOSE
The purpose of this study was to determine the average facial proportions and mandibular movement capacity of 316 first-year dental students who carefully recorded them on each other.
MATERIALS AND METHODS
This early exacting clinical experience was closely supervised by the authors in Columbus, Ohio during 1969-70. Five vertical and six horizontal distances were measured on each subject's face. An ala-tragus line and an occlusal line were drawn on the left side of the face to determine if these two lines were parallel. Measurements of mandibular movements involved maximum normal and hinge opening at the incisors and maximum amounts of right, left lateral and protrusive excursions of the mandible.
RESULTS
The ala width and distance between the tips of upper right and left canine cusps averaged (35.2 mm and 34.8 mm) but with very large individual variations. The distance between ala to occlusal plane lines was 29.9 mm at the tragus and 31.3 mm near the ala. The angle between orbitale and ala-tragus averaged 13.6 degrees.
CONCLUSION
The upper lip length was the most variable and the distance between the pupils was the most stable of the eleven facial measurements. The ala-tragus line and the occlusal plane lines were for all practical purposes parallel. Maximum jaw opening averaged 51.2 mm which was 3.0 times larger than maximal hinge opening of 17.2 mm. The maximum right plus left side jaw excursions (9.2 and 9.4 mm) totaled 18.6 mm, 2.3 times more than the 8.0 mm mean maximum forward protrusion.
doi:10.4047/jap.2014.6.6.483
PMCID: PMC4279047  PMID: 25551009
Measurements of the face; Anthropometry; Ala-tragus line; Occlusal plane; Maximum and normal mandibular openings and excursions
10.  Influence of abutment materials on the implant-abutment joint stability in internal conical connection type implant systems 
PURPOSE
This study evaluated the influence of abutment materials on the stability of the implant-abutment joint in internal conical connection type implant systems.
MATERIALS AND METHODS
Internal conical connection type implants, cement-retained abutments, and tungsten carbide-coated abutment screws were used. The abutments were fabricated with commercially pure grade 3 titanium (group T3), commercially pure grade 4 titanium (group T4), or Ti-6Al-4V (group TA) (n=5, each). In order to assess the amount of settlement after abutment fixation, a 30-Ncm tightening torque was applied, then the change in length before and after tightening the abutment screw was measured, and the preload exerted was recorded. The compressive bending strength was measured under the ISO14801 conditions. In order to determine whether there were significant changes in settlement, preload, and compressive bending strength before and after abutment fixation depending on abutment materials, one-way ANOVA and Tukey's HSD post-hoc test was performed.
RESULTS
Group TA exhibited the smallest mean change in the combined length of the implant and abutment before and after fixation, and no difference was observed between groups T3 and T4 (P>.05). Group TA exhibited the highest preload and compressive bending strength values, followed by T4, then T3 (P<.001).
CONCLUSION
The abutment material can influence the stability of the interface in internal conical connection type implant systems. The strength of the abutment material was inversely correlated with settlement, and positively correlated with compressive bending strength. Preload was inversely proportional to the frictional coefficient of the abutment material.
doi:10.4047/jap.2014.6.6.491
PMCID: PMC4279048  PMID: 25551010
Preload; Interface stability; Abutment material; Implant; Compressive bending strength
11.  Techniques for dental implant nanosurface modifications 
PURPOSE
Dental implant has gained clinical success over last decade with the major drawback related to osseointegration as properties of metal (Titanium) are different from human bone. Currently implant procedures include endosseous type of dental implants with nanoscale surface characteristics. The objective of this review article is to summarize the role of nanotopography on titanium dental implant surfaces in order to improve osseointegration and various techniques that can generate nanoscale topographic features to titanium implants.
MATERIALS AND METHODS
A systematic electronic search of English language peer reviewed dental literature was performed for articles published between December 1987 to January 2012. Search was conducted in Medline, PubMed and Google scholar supplemented by hand searching of selected journals. 101 articles were assigned to full text analysis. Articles were selected according to inclusion and exclusion criterion. All articles were screened according to inclusion standard. 39 articles were included in the analysis.
RESULTS
Out of 39 studies, seven studies demonstrated that bone implant contact increases with increase in surface roughness. Five studies showed comparative evaluation of techniques producing microtopography and nanotopography. Eight studies concluded that osteoblasts preferably adhere to nano structure as compared to smooth surface. Six studies illustrated that nanotopography modify implant surface and their properties. Thirteen studies described techniques to produce nano roughness.
CONCLUSION
Modification of dental osseous implants at nanoscale level produced by various techniques can alter biological responses that may improve osseointegration and dental implant procedures.
doi:10.4047/jap.2014.6.6.498
PMCID: PMC4279049  PMID: 25558347
Intelligent surfaces; Sputtering; Superhydrophillic; Chemical vapor deposition; Osseointegration; Engineered surface
12.  The influence of systemically administered oxytocin on the implant-bone interface area: an experimental study in the rabbit 
PURPOSE
The purpose of this study was to assess the effect of systemically administered oxytocin (OT) on the implant-bone interface by using histomorphometric analysis and the removal torque test.
MATERIALS AND METHODS
A total of 10 adult, New Zealand white, female rabbits were used in this experiment. We placed 2 implants (CSM; CSM Implant, Daegu, South Korea) in each distal femoral metaphysis on both the right and left sides; the implants on both sides were placed 10 mm apart. In each rabbit, 1 implant was prepared for histomorphometric analysis and the other 3 were prepared for the removal torque test (RT). The animals received intramuscular injections of either saline (control group; 0.15 M NaCl) or OT (experimental group; 200 µg/rabbit). The injections were initiated on Day 3 following the implant surgery and were continued for 4 subsequent weeks; the injections were administered twice per day (at a 12-h interval), for 2 days per week.
RESULTS
While no statistically significant difference was observed between the two groups (P=.787), the control group had stronger removal torque values. The serum OT concentration (ELISA value) was higher in the OT-treated group, although no statistically significant difference was found. Further, the histomorphometric parameter (bone-toimplant contact [BIC], inter-thread bone, and peri-implant bone) values were higher in the experimental group, but the differences were not significant.
CONCLUSION
We postulate that OT supplementation via intramuscular injection weakly contributes to the bone response at the implant-bone interface in rabbits. Therefore, higher concentrations or more frequent administration of OT may be required for a greater bone response to the implant. Further studies analyzing these aspects are needed.
doi:10.4047/jap.2014.6.6.505
PMCID: PMC4279050  PMID: 25551011
Oxytocin; Removal torque test; Histomorphometric parameter; Dental implant
13.  Osteoblastic behavior to zirconium coating on Ti-6Al-4V alloy 
PURPOSE
The purpose of this study was to assess the surface characteristics and the biocompatibility of zirconium (Zr) coating on Ti-6Al-4V alloy surface by radio frequency (RF) magnetron sputtering method.
MATERIALS AND METHODS
The zirconium films were developed on Ti-6Al-4V discs using RF magnetron sputtering method. Surface profile, surface composition, surface roughness and surface energy were evaluated. Electrochemical test was performed to evaluate the corrosion behavior. Cell proliferation, alkaline phosphatase (ALP) activity and gene expression of mineralized matrix markers were measured.
RESULTS
SEM and EDS analysis showed that zirconium deposition was performed successfully on Ti-6Al-4V alloy substrate. Ti-6Al-4V group and Zr-coating group showed no significant difference in surface roughness (P>.05). Surface energy was significantly higher in Zr-coating group than in Ti-6Al-4V group (P<.05). No difference in cell morphology was observed between Ti-6Al-4V group and Zr-coating group. Cell proliferation was higher in Zr-coating group than Ti-6Al-4V group at 1, 3 and 5 days (P<.05). Zr-coating group showed higher ALP activity level than Ti-6Al-4V group (P<.05). The mRNA expressions of bone sialoprotein (BSP) and osteocalcin (OCN) on Zr-coating group increased approximately 1.2-fold and 2.1-fold respectively, compared to that of Ti-6Al-4V group.
CONCLUSION
These results suggest that zirconium coating on Ti-6Al-4V alloy could enhance the early osteoblast responses. This property could make non-toxic metal coatings on Ti-6Al-4V alloy suitable for orthopedic and dental implants.
doi:10.4047/jap.2014.6.6.512
PMCID: PMC4279051  PMID: 25551012
Biocompatible materials; Surface-coated materials; Zirconium; Titanium; Surface properties; Cell proliferation
14.  Alveolar ridge preservation of an extraction socket using autogenous tooth bone graft material for implant site development: prospective case series 
This case series evaluated the clinical efficacy of autogenous tooth bone graft material (AutoBT) in alveolar ridge preservation of an extraction socket. Thirteen patients who received extraction socket graft using AutoBT followed by delayed implant placements from Nov. 2008 to Aug. 2010 were evaluated. A total of fifteen implants were placed. The primary and secondary stability of the placed implants were an average of 58 ISQ and 77.9 ISQ, respectively. The average amount of crestal bone loss around the implant was 0.05 mm during an average of 22.5 months (from 12 to 34 months) of functional loading. Newly formed tissues were evident from the 3-month specimen. Within the limitations of this case, autogenous tooth bone graft material can be a favorable bone substitute for extraction socket graft due to its good bone remodeling and osteoconductivity.
doi:10.4047/jap.2014.6.6.521
PMCID: PMC4279052  PMID: 25551013
Transplantation; Autologous; Extraction socket; Dental implants; Bone substitutes
15.  A prospective study on the effectiveness of newly developed autogenous tooth bone graft material for sinus bone graft procedure 
PURPOSE
The purpose of this prospective study was to evaluate the effectiveness of newly developed autogenous tooth bone graft material (AutoBT)application for sinus bone graft procedure.
MATERIALS AND METHODS
The patients with less than 5.0 mm of residual bone height in maxillary posterior area were enrolled. For the sinus bone graft procedure, Bio-Oss was grafted in control group and AutoBT powder was grafted in experimental group. Clinical and radiographic examination were done for the comparison of grafted materials in sinus cavity between groups. At 4 months after sinus bone graft procedure, biopsy specimens were analyzed by microcomputed tomography and histomorphometric examination for the evaluation of healing state of bone graft site.
RESULTS
In CT evaluation, there was no difference in bone density, bone height and sinus membrane thickness between groups. In microCT analysis, there was no difference in total bone volume, new bone volume, bone mineral density of new bone between groups. There was significant difference trabecular thickness (0.07 µm in Bio-Oss group Vs. 0.08 µm in AutoBT group) (P=.006). In histomorphometric analysis, there was no difference in new bone formation, residual graft material, bone marrow space between groups. There was significant difference osteoid thickness (8.35 µm in Bio-Oss group Vs. 13.12 µm in AutoBT group) (P=.025).
CONCLUSION
AutoBT could be considered a viable alternative to the autogenous bone or other bone graft materials in sinus bone graft procedure.
doi:10.4047/jap.2014.6.6.528
PMCID: PMC4279053  PMID: 25551014
Tooth; Bio-Oss; Sinus
16.  Comparable efficacy of silk fibroin with the collagen membranes for guided bone regeneration in rat calvarial defects 
PURPOSE
Silk fibroin (SF) is a new degradable barrier membrane for guided bone regeneration (GBR) that can reduce the risk of pathogen transmission and the high costs associated with the use of collagen membranes. This study compared the efficacy of SF membranes on GBR with collagen membranes (Bio-Gide®) using a rat calvarial defect model.
MATERIALS AND METHODS
Thirty-six male Sprague Dawley rats with two 5 mm-sized circular defects in the calvarial bone were prepared (n=72). The study groups were divided into a control group (no membrane) and two experimental groups (SF membrane and Bio-Gide®). Each group of 24 samples was subdivided at 2, 4, and 8 weeks after implantation. New bone formation was evaluated using microcomputerized tomography and histological examination.
RESULTS
Bone regeneration was observed in the SF and Bio-Gide®-treated groups to a greater extent than in the control group (mean volume of new bone was 5.49 ± 1.48 mm3 at 8 weeks). There were different patterns of bone regeneration between the SF membrane and the Bio-Gide® samples. However, the absolute volume of new bone in the SF membrane-treated group was not significantly different from that in the collagen membrane-treated group at 8 weeks (8.75 ± 0.80 vs. 8.47 ± 0.75 mm3, respectively, P=.592).
CONCLUSION
SF membranes successfully enhanced comparable volumes of bone regeneration in calvarial bone defects compared with collagen membranes. Considering the lower cost and lesser risk of infectious transmission from animal tissue, SF membranes are a viable alternative to collagen membranes for GBR.
doi:10.4047/jap.2014.6.6.539
PMCID: PMC4279054  PMID: 25551015
Silk; Bone regeneration; Membranes; Dental implants; Collagen; Guided tissue regeneration
17.  The influence of thread geometry on implant osseointegration under immediate loading: a literature review 
Implant success is achieved by the synergistic combination of numerous biomechanical factors. This report examines the mechanical aspect of implants. In particular, it is focused on macrodesign such as thread shape, pitch, width and depth, and crestal module of implants. This study reviews the literature regarding the effect of implant thread geometry on primary stability and osseointegration under immediate loading. The search strategy included both in vitro and in vivo studies published in the MEDLINE database from January 2000 to June 2014. Various geometrical parameters are analyzed to evaluate their significance for optimal stress distribution, implant surface area, and bone remodeling responses during the process of osseointegration.
doi:10.4047/jap.2014.6.6.547
PMCID: PMC4279055  PMID: 25551016
Dental implants; Implant macrodesign; Thread geometry; Primary stability; Immediate loading
18.  Focal epithelial hyperplasia arising after delivery of metal-ceramic fixed dental prosthesis 
Focal epithelial hyperplasia (FEH) is a human papillomavirus (HPV)-induced alteration of the oral mucosa that presents with a clinically distinct appearance. While other HPV-infected lesions such as squamous papilloma, verruca vulgaris, and condyloma acuminatum involve the skin, oral mucosa, and genital mucosa, FEH occurs only in the oral mucosa. The affected oral mucosa exhibits multiple papules and nodules with each papule/nodule being flat-topped or sessile. The affected region resembles the normal color of oral mucosa rather than appearing as a white color since the epithelial surface is not hyperkeratinized. Almost all cases present with multiple sites of occurrence. This rare, benign epithelial proliferation is related to low-risk HPV, especially HPV-13 and -32, and is not transformed into carcinoma. We report a case of FEH that arose on the attached gingiva of an East Asian male adult related to prosthesis without detection of any HPV subtype in HPV DNA chip and sequencing.
doi:10.4047/jap.2014.6.6.555
PMCID: PMC4279056  PMID: 25558348
Focal epithelial hyperplasia (FEH); Human papillomavirus (HPV); Attached gingiva; HPV DNA chip; Porcelain-fused to metal (PFM)
19.  Three dimensional finite element analysis of the stress distribution around the mandibular posterior implant during non-working movement according to the amount of cantilever 
PURPOSE
In case of large horizontal discrepancy of alveolar ridge due to severe resorption, cantilevered crown is usually an unavoidable treatment modality. The purpose of this study was to evaluate the clinical criteria for the placement of the aforementioned implant crown.
MATERIALS AND METHODS
The mandible model with 2 mm thick cortical bone and cancellous bone was fabricated from CT cross-section image. An external connection type implant was installed and cantilevered crowns with increasing offset of 3, 4, 5, 6, and 7 mm were connected. Vertical load and 30° oblique load of 300 N was applied and stress around bone and implant component was analyzed. A total of 14 cases were modeled and finite element analysis was performed using COSMOS Works (Solid works Inc, USA).
RESULTS
As for the location of the vertical load, the maximum stress generated on the lingual side of the implant became larger according to the increase of offset distance. When the oblique load was applied at 30°, the maximum stress was generated on the buccal side and its magnitude gradually decreased as the distance of the offset load increased to 5 mm. After that point, the magnitude of implant component's stress increased gradually.
CONCLUSION
The results of this study suggest that for the patient with atrophied alveolar ridge following the loss of molar teeth, von-Mises stress on implant components was the lowest under the 30° oblique load at the 5 mm offset point. Further studies for the various crown height and numbers of occusal points are needed to generalize the conclusion of present study.
doi:10.4047/jap.2014.6.5.361
PMCID: PMC4211052  PMID: 25352958
Finite element analysis; Implant prosthesis; Cantilever; Stress distribution
20.  Standardizing the evaluation criteria on treatment outcomes of mandibular implant overdentures: a systematic review 
PURPOSE
The aim of this review was to analyze the evaluation criteria on mandibular implant overdentures through a systematic review and suggest standardized evaluation criteria.
MATERIALS AND METHODS
A systematic literature search was conducted by PubMed search strategy and hand-searching of relevant journals from included studies considering inclusion and exclusion criteria. Randomized clinical trials (RCT) and clinical trial studies comparing attachment systems on mandibular implant overdentures until December, 2011 were selected. Twenty nine studies were finally selected and the data about evaluation methods were collected.
RESULTS
Evaluation criteria could be classified into 4 groups (implant survival, peri-implant tissue evaluation, prosthetic evaluation, and patient satisfaction). Among 29 studies, 21 studies presented implant survival rate, while any studies reporting implant failure did not present cumulative implant survival rate. Seventeen studies evaluating peri-implant tissue status presented following items as evaluation criteria; marginal bone level (14), plaque Index (13), probing depth (8), bleeding index (8), attachment gingiva level (8), gingival index (6), amount of keratinized gingiva (1). Eighteen studies evaluating prosthetic maintenance and complication also presented following items as evaluation criteria; loose matrix (17), female detachment (15), denture fracture (15), denture relining (14), abutment fracture (14), abutment screw loosening (11), and occlusal adjustment (9). Atypical questionnaire (9), Visual analog scales (VAS) (4), and Oral Health Impact Profile (OHIP) (1) were used as the format of criteria to evaluate patients satisfaction in 14 studies.
CONCLUSION
For evaluation of implant overdenture, it is necessary to include cumulative survival rate for implant evaluation. It is suggested that peri-implant tissue evaluation criteria include marginal bone level, plaque index, bleeding index, probing depth, and attached gingiva level. It is also suggested that prosthetic evaluation criteria include loose matrix, female detachment, denture fracture, denture relining, abutment fracture, abutment screw loosening, and occlusal adjustment. Finally standardized criteria like OHIP-EDENT or VAS are required for patient satisfaction.
doi:10.4047/jap.2014.6.5.325
PMCID: PMC4211048  PMID: 25352954
Denture; Overlay; Mandibular prosthesis; Dental implants; Outcome assessment; Patient satisfaction
21.  The effects of dentin bonding agent formulas on their polymerization quality, and together with tooth tissues on their microleakage and shear bond strength: an explorative 3-step experiment 
PURPOSE
Bonding agents (BA) are the crucial weak link of composite restorations. Since the commercial materials' compositions are not disclosed, studies to formulize the optimum ratios of different components are of value. The aim of this study was to find a proper formula of BAs.
MATERIALS AND METHODS
This explorative experimental in vitro study was composed of 4 different sets of extensive experiments. A commercial BA and 7 experimental formulas were compared in terms of degree of conversion (5 experimental formulas), shear bond strength, mode of failure, and microleakage (3 experimental formulas). Statistical analyses were performed (α=.05). The DC of selected formula was tested one year later.
RESULTS
The two-way ANOVA indicated a significant difference between the shear bond strength (SBS) of two tissues (dentin vs. enamel, P=.0001) in a way that dentinal bonds were weaker. However, there was no difference between the four materials (P=.283). The adhesive mode of failure was predominant in all groups. No differences between the microleakage of the four materials at occlusal (P=.788) or gingival (P=.508) sites were detected (Kruskal-Wallis). The Mann-Whitney U test showed a significant difference between the microleakage of all materials (3 experimental formulas and a commercial material) together at the occlusal site versus the gingival site (P=.041).
CONCLUSION
A formula with 62% bisphenol A-glycidyl methacrylate (Bis-GMA), 37% hydroxy ethyl methacrylate (HEMA), 0.3% camphorquinone (CQ), and 0.7% dimethyl-para-toluidine (DMPT) seems a proper formula for mass production. The microleakage and SBS might be respectively higher and lower on dentin compared to enamel.
doi:10.4047/jap.2014.6.5.333
PMCID: PMC4211049  PMID: 25352955
Dentin bonding agents; Polymerization; Degree of conversion; Shear bond strength; Microleakage; Mode of failure; H-NMR spectroscopy; FT-IR spectroscopy
22.  Flexural strengths of implant-supported zirconia based bridges in posterior regions 
PURPOSE
Impact forces in implant supported FDP (fixed dental prosthesis) are higher than that of tooth supported FDPs and the compositions used in frameworks also has a paramount role for biomechanical reasons. The aim of this study was to evaluate the flexural strength of two different zirconia frameworks.
MATERIALS AND METHODS
Two implant abutments with 3.8 mm and 4.5 mm platform were used as premolar and molar. They were mounted vertically in an acrylic resin block. A model with steel retainers and removable abutments was fabricated by milling machine; and 10 FDP frameworks were fabricated for each Biodenta and Cercon systems. All samples were thermo-cycled for 2000 times in 5-55℃ temperature and embedded in 37℃ artificial saliva for one week. The flexural test was done by a rod with 2 mm ending diameter which was applied to the multi-electromechanical machine. The force was inserted until observing fracture. The collected data were analyzed with SPSS software ver.15, using Weibull modulus and independent t-test with the level of significance at α=.05.
RESULTS
The mean load bearing capacity values were higher in Biodenta but with no significant differences (P>.05). The Biodenta frameworks showed higher load bearing capacity (F0=1700) than Cercon frameworks (F0=1520) but the reliability (m) was higher in Cercon (m=7.5).
CONCLUSION
There was no significant difference between flexural strengths of both zirconia based framework systems; and both Biodenta and Cercon systems are capable to withstand biting force (even parafunctions) in posterior implant-supported bridges with no significant differences.
doi:10.4047/jap.2014.6.5.346
PMCID: PMC4211050  PMID: 25352956
Implant-supported prosthesis; Zirconia; Flexural strength; Weibull modulus
23.  Characteristics and response of mouse bone marrow derived novel low adherent mesenchymal stem cells acquired by quantification of extracellular matrix 
PURPOSE
The aim of present study was to identify characteristic and response of mouse bone marrow (BM) derived low-adherent bone marrow mesenchymal stem cells (BMMSCs) obtained by quantification of extracellular matrix (ECM).
MATERIALS AND METHODS
Non-adherent cells acquired by ECM coated dishes were termed low-adherent BMMSCs and these cells were analyzed by in vitro and in vivo methods, including colony forming unit fibroblast (CFU-f), bromodeoxyuridine (BrdU), multi-potential differentiation, flow cytometry and transplantation into nude mouse to measure the bone formation ability of these low-adherent BMMSCs. Titanium (Ti) discs with machined and anodized surfaces were prepared. Adherent and low-adherent BMMSCs were cultured on the Ti discs for testing their proliferation.
RESULTS
The amount of CFU-f cells was significantly higher when non-adherent cells were cultured on ECM coated dishes, which was made by 7 days culturing of adherent BMMSCs. Low-adherent BMMSCs had proliferation and differentiation potential as adherent BMMSCs in vitro. The mean amount bone formation of adherent and low-adherent BMMSCs was also investigated in vivo. There was higher cell proliferation appearance in adherent and low-adherent BMMSCs seeded on anodized Ti discs than machined Ti discs by time.
CONCLUSION
Low-adherent BMMSCs acquired by ECM from non-adherent cell populations maintained potential characteristic similar to those of the adherent BMMSCs and therefore could be used effectively as adherent BMMSCs in clinic.
doi:10.4047/jap.2014.6.5.351
PMCID: PMC4211051  PMID: 25352957
Bone marrow mesenchymal stem cells; Quantification; Low-adherent; Non-adherent cells; Extracellular matrix; Bone formation
24.  A comparative study on the bond strength of porcelain to the millingable Pd-Ag alloy 
PURPOSE
The porcelain fused to gold has been widely used as a restoration both with the natural esthetics of the porcelain and durability and marginal fit of metal casting. However, recently, due to the continuous rise in the price of gold, an interest towards materials to replace gold alloy is getting higher. This study compared the bond strength of porcelain to millingable palladium-silver (Pd-Ag) alloy, with that of 3 conventionally used metal-ceramic alloys.
MATERIALS AND METHODS
Four types of metal-ceramic alloys, castable nonprecious nickel-chrome alloy, castable precious metal alloys containing 83% and 32% of gold, and millingable Pd-Ag alloy were used to make metal specimens (n=40). And porcelain was applied on the center area of metal specimen. Three-point bending test was performed with universal testing machine. The bond strength data were analyzed with a one-way ANOVA and post hoc Scheffe's tests (α=.05).
RESULTS
The 3-point bending test showed the strongest (40.42 ± 5.72 MPa) metal-ceramic bond in the nonprecious Ni-Cr alloy, followed by millingable Pd-Ag alloy (37.71 ± 2.46 MPa), precious metal alloy containing 83% of gold (35.89 ± 1.93 MPa), and precious metal alloy containing 32% of gold (34.59 ± 2.63 MPa). Nonprecious Ni-Cr alloy and precious metal alloy containing 32% of gold showed significant difference (P<.05).
CONCLUSION
The type of metal-ceramic alloys affects the bond strength of porcelain. Every metal-ceramic alloy used in this study showed clinically applicable bond strength with porcelain (25 MPa).
doi:10.4047/jap.2014.6.5.372
PMCID: PMC4211053  PMID: 25352959
Metal ceramic alloys; Palladium-silver alloy; Bending test; Porcelain bond strength
25.  Optimization of growth inducing factors for colony forming and attachment of bone marrow-derived mesenchymal stem cells regarding bioengineering application 
PURPOSE
These days, mesenchymal stem cells (MSCs) have received worldwide attention because of their potentiality in tissue engineering for implant dentistry. The purpose of this study was to evaluate various growth inducing factors in media for improvement of acquisition of bone marrow mesenchymal stem cells (BMMSCs) and colony forming unit-fibroblast (CFU-F).
MATERIALS AND METHODS
The mouse BMMSCs were freshly obtained from female C3H mouse femur and tibia. The cells seeded at the density of 106/dish in media supplemented with different density of fetal bovine serum (FBS), 1α, 25-dihydroxyvitamin (VD3) and recombinant human epidermal growth factor (rhEGF). After 14 days, CFU-F assay was conducted to analyze the cell attachment and proliferation, and moreover for VD3, the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay was additionally conducted.
RESULTS
The cell proliferation was increased with the increase of FBS concentration (P<.05). The cell proliferation was highest at the density of 20 ng/mL rhEGF compared with 0 ng/mL and 200 ng/mL rhEGF (P<.05). For VD3, although the colony number was increased with the increase of its concentration, the difference was not statistically significant (P>.05).
CONCLUSION
FBS played the main role in cell attachment and growth, and the growth factor like rhEGF played the additional effect. However, VD3 did not have much efficacy compare with the other two factors. Improvement of the conditions could be adopted to acquire more functional MSCs to apply into bony defect around implants easily.
doi:10.4047/jap.2014.6.5.379
PMCID: PMC4211054  PMID: 25352960
Bone marrow mesenchymal stem cells; Cell proliferation; Fetal bovine serum; 1α; 25-dihydroxyvitamin; Recombinant human epidermal growth factor

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