Dental Materials Journal

Original Papers

Effects of photocuring strategy on bonding of dual-cure one-step self-etch adhesive to root canal dentin

Juthatip AKSORNMUANG, Masatoshi NAKAJIMA, Woraphong PANYAYONG, Junji T ...

2009 年 28 巻 2 号 p. 133-141
発行日: 2009年
公開日: 2009/08/14

DOIhttps://doi.org/10.4012/dmj.28.133

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This study evaluated the effects of light power density and light exposure time on regional bond strength of Clearfil DC Bond to root canal dentin. Post spaces were prepared in extracted premolars. Root canal dentin was treated with a dual-cure bonding system, Clearfil DC Bond, and light-cured for 10, 20, or 30 seconds using two halogen light curing units: Optilux 501 (830 mW/cm²) and Hyperlightel (1350 mW/cm²). Following which, all post spaces were filled with a dual-cure resin composite. After 24-hour storage, microtensile bond strengths (μTBS) at the coronal and apical regions were measured. At the coronal region, μTBS values were similar among all the experimental groups. At the apical region, bond strength improved when the curing time was extended to 30 seconds with Optilux 501, and likewise with Hyperlightel when curing time was extended to 20 or 30 seconds. In addition, significant differences in μTBS between the coronal and apical regions disappeared with prolonged curing times.

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Investigation of distortions around the cervical area of teeth restored with two kinds of crown materials

Chikako SUZUKI, Hiroyuki MIURA, Daizo OKADA, Wataru KOMADA, Munenaga M ...

2009 年 28 巻 2 号 p. 142-152
発行日: 2009年
公開日: 2009/08/14

DOIhttps://doi.org/10.4012/dmj.28.142

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The purpose of this study was to identify crown materials to decrease the stress concentrated at the cervical area of endodontically treated teeth. To this end, 14 extracted human mandibular premolars were divided into two groups for this study: complete cast crowns versus polymer-based crown and bridge material crowns. Both complete cast crowns (MC) and polymer-based crown and bridge material crowns (HC) were cemented with a glycidyl methacrylate-based resin cement (RC) to composite resin cores with glass fiber posts. Static loading was applied and distortion was measured with four pieces of strain gages attached to the marginal area. Findings showed that there was a large difference in distortion between crown and root in MC. On the other hand, distortions at the cervical area of crown and root were similar in HC.

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Combination with allogenic bone reduces early absorption of β-tricalcium phosphate (β-TCP) and enhances the role as a bone regeneration scaffold. Experimental animal study in rat mandibular bone defects

Makoto HIROTA, Yoshiro MATSUI, Nobuyuki MIZUKI, Teruki KISHI, Kei WATA ...

2009 年 28 巻 2 号 p. 153-161
発行日: 2009年
公開日: 2009/08/14

DOIhttps://doi.org/10.4012/dmj.28.153

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β-tricalcium phosphate (β-TCP) was grafted into rat mandibular bone defects to assess its potential as a scaffold material for bone regeneration. For this purpose, β-TCP (TCP), allogenic bone (Allograft), and allogenic bone combined with β-TCP (Combined) were employed as graft materials. To the left side of the graft materials in the bone defects, platelet-rich plasma (PRP) was added. The rats were sacrificed at one, three, and five weeks. Bone formation rate (BFR), remaining β-TCP rate (RTR), β-TCP absorption rate (TAR), whole amount of β-TCP (WTCP), and total rate of BFR and RTR (TBR) were measured. Combined showed equivalent BFR to Allograft at five weeks, and showed higher RTR at one week and higher BFR at five weeks than TCP. Combined with PRP showed higher TAR than that without PRP at three weeks. Therefore, combination with allogenic bone showed reduced β-TCP absorption, hence enhancing the role of β-TCP in bone regeneration. These findings suggested that β-TCP is a better scaffold for bone regeneration if its early absorption is reduced when used in combination with an osteogenic material.

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β-tricalcium phosphate and basic fibroblast growth factor combination enhances periodontal regeneration in intrabony defects in dogs

Yosei OI, Mikio OTA, Shigeki YAMAMOTO, Yoshihiro SHIBUKAWA, Satoru YAM ...

2009 年 28 巻 2 号 p. 162-169
発行日: 2009年
公開日: 2009/08/14

DOIhttps://doi.org/10.4012/dmj.28.162

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The combined effect of β-tricalcium phosphate and basic fibroblast growth factor was observed in the regeneration of periodontal tissue in dogs. For this purpose, either β-TCP and FGF-2 (β-TCP/FGF-2 group) or FGF-2 alone (FGF-2 group) was applied in intrabony defects. The control group received β-TCP alone. The tissues were histologically examined at 2, 4, or 8 weeks following treatment. The control group was characterized by incomplete, newly formed bone around β-TCP particles. The β-TCP/FGF-2 group showed a statistically significant increase in both new bone and cementum formation compared to the FGF-2-alone group (76.3% vs. 65.3%, p<0.01; 81.0% vs. 68.3%, p<0.01, respectively).
These findings suggested that β-TCP may be a suitable scaffold for FGF-2 and that the combination of β-TCP and FGF-2 can enhance bone and cementum formation.

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Behavior under impact of two polyvinyl acetate-polyethylene (PVA-PE) polymers and one elastomer — application to custom-made mouthguards

Philippe POISSON, Philippe VIOT, Julien PETIT

2009 年 28 巻 2 号 p. 170-177
発行日: 2009年
公開日: 2009/08/14

DOIhttps://doi.org/10.4012/dmj.28.170

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A drop tower was used to identify the mechanical behaviors of two polyvinyl acetate-polyethylene (PVA-PE) polymers and one elastomer used to fabricate custom-made mouthguards. The samples were in the form of either small cubes (edge length: 20 mm) or large cubes (edge length: 30 mm). Force and strain were recorded as functions of time, enabling a stress-strain analysis to be performed. In addition, a volume energy analysis was performed. While the three materials were viscoelastic, the stress-strain analysis showed that the PVA-PE polymers were more rigid than the elastomer, i.e., the same stress was reached with a lower strain. With the volume energy analysis, the two PVA-PE polymers were found to absorb a relatively large amount of energy with small sample deformations. Results of this study suggested that the mechanical properties of PVA-PE polymers are particularly useful and relevant for the fabrication of custom-made mouthguards.

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Surface analysis of commercially pure titanium implant retrieved from rat bone. part 1: Initial biological response of sandblasted surface

Kouichi WATANABE, Seigo OKAWA, Mitugu KANATANI, Kikuo HOMMA

2009 年 28 巻 2 号 p. 178-184
発行日: 2009年
公開日: 2009/08/14

DOIhttps://doi.org/10.4012/dmj.28.178

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To gain insight on the early biological response to commercial pure titanium (cpTi), the surface properties of cpTi implants retrieved from rat bone were examined by X-ray photoelectron spectroscopy (XPS). To this end, semi-cylindrical bullets, 1.1 mm in diameter and 3.5 mm in length, were implanted into the femurs of Wistar rats and then retrieved after either 3 hours or 7 days. Regardless of implantation interval, elements of Ti, O, C, and N were observed on the retrieved implants and that the thickness of the adsorbed film (mainly protein) was estimated to be about 2.5 nm. Small amounts of both Ca and P were also detected, whereby the Ca/P atomic ratios after 3 hours and 7 days were very small compared to that of hydroxyapatite. Furthermore, no correlation was found between the Ca and P distributions in the element maps. In conclusion, no calcium phosphate compounds were formed on the implant in vivo after 7 days.

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Effect of hybridization on bond strength and adhesive interface after acid-base challenge using 4-META/MMA-TBB resin

Tomohiro TAKAGAKI, Toru NIKAIDO, Satoko TSUCHIYA, Masaomi IKEDA, Richa ...

2009 年 28 巻 2 号 p. 185-193
発行日: 2009年
公開日: 2009/08/14

DOIhttps://doi.org/10.4012/dmj.28.185

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The purposes of this study were twofold, namely to evaluate: (1) the effect of hybridization on microtensile bond strength (μTBS) to dentin, and (2) the ultrastructure of the dentin-adhesive interface with 4-META/MMA-TBB resin after acid-base challenge. Dentin surfaces, which received no treatment (NT), 65% phosphoric acid (PA), or 10% citric acid-3% ferric chloride (10-3), were bonded with a 4-META/MMA-TBB resin. To evaluate dentin bond strength, μTBS test was performed at a crosshead speed of 1 mm/min. For ultrastructural evaluation of the adhesive interfaces, SEM was used to examine the interfaces of the bonded specimens after acid-base challenge. The μTBS of NT was not determined, while that of 10-3 was significantly higher than that of PA (p<0.05). With PA and 10-3, the hybrid layer was clearly observed, but no so for the acid-base resistant zone. Wall lesion was found in NT only.
In conclusion, hybridization is vital to improving μTBS to dentin and enhancing resistance at the adhesive interface against acid-base challenge.

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Effect of loading weight on bond durability of composite — type resin cement under cyclic impact test (part 2). Loading with light weight of 100 – 120 g

Masahiro OHSAWA, Mamoru FUJIWARA, Yoshihiko HAYASHI

2009 年 28 巻 2 号 p. 194-196
発行日: 2009年
公開日: 2009/08/14

DOIhttps://doi.org/10.4012/dmj.28.194

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The bond durability of composite-type resin cement was evaluated by means of cyclic impact tests using three different loads. In terms of experimental setup, a casting alloy, 12%Au-Pd-Ag, was used as the adherend and bonded to a cast block using a composite-type cement (Bistite II). A shear load — using plungers of three different weights at 100, 110, and 120 g — was dropped from a 3-mm height onto a small piece of the casting alloy until debonding. The cycle numbers that caused debonding were 1756±680 × 10⁴ times for 100 g, 1403±515 × 10⁴ times for 110 g, and 420±200 × 10⁴ times for 120 g, respectively. Therefore, the group loaded with 120 g showed a significantly lower value as compared to the other two groups. On the fracture mode of the cement, it was a bulk fracture regardless of the loading weight employed in this study — the same result obtained in a previous study where heavier weights were employed.

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Effects of attrition, prior acid-etching, and cyclic loading on the bond strength of a self-etching adhesive system to dentin

Koichi SHINKAI, Takashi EBIHARA, Manabu SHIRONO, Hideaki SEKI, Suguru ...

2009 年 28 巻 2 号 p. 197-203
発行日: 2009年
公開日: 2009/08/14

DOIhttps://doi.org/10.4012/dmj.28.197

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The purpose of this study was to evaluate the effects of dentin attrition, phosphoric acid etching, and cyclic loading on the microtensile bond strength (μTBS) of a self-etching adhesive system to dentin. Flat dentin surfaces of human molars were assigned to eight experimental groups based on those with or without attrition, prior acid-etching, and cyclic loading. Resin composite paste was placed and polymerized after the bonding procedure according to manufacturer's instructions. The specimens were subjected to μTBS testing at a crosshead speed of 0.5 mm/min. Results showed that the minimum mean value of μTBS was 14.9 MPa in the group without attrition and acid-etching but with loading, while the maximum mean value of μTBS was 40.0 MPa in the group without attrition and loading but with acid etching. Therefore, the value of μTBS to dentin without attrition was significantly decreased by cyclic loading but that to dentin with attrition was not affected.

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Photoelastic stress analysis of different post and core restoration methods

Masahiro YAMAMOTO, Hiroyuki MIURA, Daizo OKADA, Wataru KOMADA, David M ...

2009 年 28 巻 2 号 p. 204-211
発行日: 2009年
公開日: 2009/08/14

DOIhttps://doi.org/10.4012/dmj.28.204

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The aim of this study was to compare three types of post and core systems by analyzing the stress magnitude within the root. To this end, two-dimensional photoelastic simulation models of endodontically treated maxillary central incisors were fabricated. Three different types of post and core systems were selected for this study: composite resin post and core, composite resin core in combination with a glass fiber post, and conventional cast metal post and core. The fabricated models were observed in a transmission polariscope with the same loading force (400 N) on 45° palatal direction and the fringe orders registered were thereby analyzed. Results obtained in this study suggested that abutment build-up using composite resin core in combination with a glass fiber post model produced the lowest stress concentration and is hence effective in preventing stress concentration in the case of restored endodontically treated teeth.

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Bite force measurement system using pressure-sensitive sheet and silicone impression material

Katsuya ANDO, Yuji FUWA, Masahiro KUROSAWA, Takamasa KONDO, Shigemi GO ...

2009 年 28 巻 2 号 p. 212-218
発行日: 2009年
公開日: 2009/08/14

DOIhttps://doi.org/10.4012/dmj.28.212

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This study was conducted to reduce the bias in measured values caused by the thickness of materials used in occlusal examinations. To this end, a silicone impression material for bite force measurement and an experimental model of a simplified stomatognathic system were employed in this study. By means of this experimental model, results showed that the effect of bias toward the posterior arch could be reduced in the anterior-posterior distribution of bite forces and in the occlusal contact areas due to the thickness of the materials used in occlusal examinations.

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Three-dimensional finite element modeling from CT images of tooth and its validation

Kiyoshi TAJIMA, Ker-Kong CHEN, Nobusuke TAKAHASHI, Naoaki NODA, Yuki N ...

2009 年 28 巻 2 号 p. 219-226
発行日: 2009年
公開日: 2009/08/14

DOIhttps://doi.org/10.4012/dmj.28.219

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The aim of this study was to develop a three-dimensional (3D) finite element (FE) model of a sound extracted human second premolar from micro-CT data using commercially available software tools. A detailed 3D FE model of the tooth could be constructed and was experimentally validated by comparing strains calculated in the FE model with strain gauge measurement of the tooth under loading. The regression coefficient and its standard error in the regression analysis between strains calculated by the FE model and measured with strain gauge measurement were 0.82 and 0.06, respectively, and the correlation coefficient was found to be highly significant. These results suggested that an FE model reconstructed from micro-CT data could be used as a valid model to estimate the actual strains with acceptable accuracy.

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Fluoride release and recharge characteristics of denture base resins containing surface pre-reacted glass-ionomer filler

Kazuko KAMIJO, Yoshiharu MUKAI, Takatoshi TOMINAGA, Izumi IWAYA, Fukue ...

2009 年 28 巻 2 号 p. 227-233
発行日: 2009年
公開日: 2009/08/14

DOIhttps://doi.org/10.4012/dmj.28.227

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The flexural strength, flexural modulus, and the amount of fluoride released from four experimental denture base resins containing 5, 10, 20 and 30 wt% surface pre-reacted glass-ionomer (S-PRG) filler added to the powder were evaluated.
The mean flexural strength of the experimental resins, except the 30 wt%, and the flexural modulus of all the resins, complied with ISO 1567 requirements.
In the 20 wt% resin, the amount of fluoride released in the initial phase was 1.88 μg/cm²/day, after which the level decreased. After recharging in a 9,000 ppm fluoride solution for eight hours, the level of released fluoride increased markedly to 40.21 μg/cm²/16hrs. Our results show that fluoride levels increased as a function of the S-PRG filler content. After the almost completely discharged resins were recharged, similar fluoride release occurred again.
These results suggest that denture base resins containing S-PRG filler have great recharge and release capabilities which may assist in preventing root caries of abutment teeth.

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Bone formation ability of carbonate apatite-collagen scaffolds with different carbonate contents

Ayumu MATSUURA, Takayasu KUBO, Kazuya DOI, Kazuhiko HAYASHI, Kouji MOR ...

2009 年 28 巻 2 号 p. 234-242
発行日: 2009年
公開日: 2009/08/14

DOIhttps://doi.org/10.4012/dmj.28.234

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Hydroxyapatite and carbonate apatites with different carbonate contents were synthesized, mixed with atelocollagen, and made into sponge scaffolds. The scaffolds were implanted into the bone sockets of the femurs of male New Zealand white rabbits for 2, 3, 12 and 24 weeks. carbonate apatite-collagen scaffold with 4.8 wt% carbonate content appeared to have similar crystallinity and chemical composition to human bone. When the scaffolds were implanted into the rabbit femurs, histological observation indicated that the carbonate apatites-collagen scaffolds with relatively higher carbonate contents were gradually deformed throughout the implantation period, and showed uniform surrounding bone after 24 weeks and could not be distinguished. The carbonate apatite-collagen scaffold with 4.8 wt% carbonate content showed the highest bone area ratio of all of the scaffolds. It is suggested that a carbonate apatite-collagen scaffold with carbonate content similar to that of human bone may have optimal bone formation ability.

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Technical Reports

Influence of irradiation conditions on the deformation of pure titanium frames in laser welding

Michio SHIMAKURA, Satoshi YAMADA, Misao TAKEUCHI, Koki MIURA, Joji IKE ...

2009 年 28 巻 2 号 p. 243-247
発行日: 2009年
公開日: 2009/08/14

DOIhttps://doi.org/10.4012/dmj.28.243

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Due to its ease of use in connecting metal frames, laser welding is now applied in dentistry. However, to achieve precise laser welding, several problems remain to be resolved. One such problem is the influence of irradiation conditions on the deformation of titanium frameworks during laser welding, which this study sought to investigate. Board-shaped pure titanium specimens were prepared with two different joint types. Two specimens were abutted against each other to form a welding block with gypsum. For welding, three different laser waveforms were used. Deformation of the specimen caused by laser welding was measured as a rise from the gypsum surface at the opposite, free end of the specimen. It was observed that specimens with a beveled edge registered a smaller deformation than specimens with a square edge. In addition, a double laser pulse waveform—whereby a supplementary laser pulse was delivered immediately after the main pulse— resulted in a smaller deformation than with a single laser pulse waveform.

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