Microstructural Evaluation of the Mineralized Apical Barrier Induced by a Calcium Hydroxide Paste Containing Iodoform: A Case Report.

INTRODUCTION: A 65-year-old man had nonsurgical retreatment using an iodoform and calcium hydroxide paste in a maxillary left canine with persistent apical periodontitis. An apical mineralized barrier (AMB) was observed 3-months postoperatively. Unfortunately, the tooth was extracted due to a cementum tear. This provided an opportunity to analyze the AMB histologically, as there is a lack of previous reports on its microstructure. METHODS: After extraction and removal of the granulation tissue from the root surface, the canine was processed, and observed using micro-computed tomography (µCT) and light microscopy. Thereafter, the specimen was resin-embedded specimen was evaluated by scanning electron microscopy, micro-X-ray fluorescence spectroscopy and Raman spectroscopy to understand the mechanism and nature of the AMB formation during apical healing. RESULTS: Nonsurgical retreatment was clinically successful based on the absence of clinical symptoms of apical periodontitis and the radiographic presence of an AMB. The AMB was opaque and could be readily differentiated from dentin under a light microscope. Micro-computed tomography analysis revealed that the AMB had the same mineral density as dentin. Scanning electron microscopy revealed that the AMB had two distinct layers based on the size of the calcified particles. Elemental mapping using micro-X-ray fluorescence spectroscopy showed that the localization of calcium and phosphorus differed between AMB and other areas of biomineralization. Raman spectral mapping revealed that the surface layer of the AMB consisted of collagen, calcium carbonate, and hydroxyapatite. CONCLUSIONS: This study explored new analytical methods for elucidating the apical wound-healing process and the nature of the mineralized repair. The findings provided detailed information on the AMB highlighting a bilaminar structure with high calcium components higher on the inside and a brightness similar to cementum not dentin and the presence of hydroxyapatite.

Responses of MC3T3-E1 cells to three dental resin-based restorative materials.

This study aimed to examine the influences of three dental resin-based restorative materials on cells associated with hard tissue regeneration using osteoblastic MC3T3-E1 cells. A Bis-GMA-based resin composite [Clearfil AP-X (APX)], an MMA-based resin cement [Superbond C&B (SB)], and a resin-modified glass-ionomer [Fuji Ionomer Type II LC (LC)] were tested. A zinc oxide eugenol cement [Super EBA (EBA)] was included in the study for comparison. MC3T3-E1 cells were cultured on set materials for 3, 7, 14, or 21 days. Cell attachment and proliferation were observed by scanning electron microscopy, and mitochondrial dehydrogenase and alkaline phosphatase (ALP) activities of the cells were evaluated. Cell cultures on polystyrene tissue culture dishes served as controls. On APX and SB, cells demonstrated attachment, spreading, and proliferation similar to the controls. In contract, cells adhered and proliferated poorly on LC and EBA. The mitochondrial function and ALP activity of the cells were significantly suppressed (p < 0.05, Scheffe's F test) throughout the experimental period when cultured on LC or EBA, although APX and SB exhibited less inhibition. The results indicate that APX and SB are less toxic to proliferation and differentiation of MC3T3-E1, suggesting that a smaller influence on cementogenesis on these materials can be expected.

The relationship between the color of carious dentin stained with a caries detector dye and bacterial infection.

This in vitro study aimed to design a method for the objective evaluation of carious dentin using numerical values. This study also investigated the relationship between the color of carious dentin stained with a caries detector dye using this objective method and the rate of bacterial detection as detected by a polymerase chain reaction (PCR). In 15 molars with occlusal dentin caries and three extracted sound molars, dentin was removed in multiple steps with 300 microm removed each step. Before and after every removal, images of a color-matching sticker and carious surfaces stained with a caries detector dye were acquired simultaneously using a CCD camera and dentinal tissue samples were removed with a round bur. Next, corrected L*, a* and b* values of the carious surfaces (CIE 1976 L*a*b* color system) were calculated from the color changes of the stickers in the images. In addition, bacterial DNA in the dentinal tissue was detected by PCR. From evaluations of the receiver operating characteristic curves for the L*, a* and b* values, the L* value was determined to be a more useful parameter than a* or b* for detecting bacterial infection using the caries detector dye. The bacterial detection rates of carious dentin decreased as the L* values of carious dentin stained with the dye increased. When the L* values were more than 60, the dentin had no bacterial infection. This study clarified the relationship between the colors of lesions stained with a caries detector dye and the rates of bacterial detection.

Comparison of osteoblast responses to hydroxyapatite and hydroxyapatite/soluble calcium phosphate composites.

Hydroxyapatite/soluble calcium phosphate composites (HAp/SCaP) are novel HAp-based materials with enhanced solubility that have been developed by annealing HAp in a vacuum. This study compared the effects of HAp and HAp/SCaP on osteoblast proliferation, differentiation, and mineralization using an MC3T3-E1 cell culture system. MC3T3-E1 cells were cultured on HAp or HAp/SCaP, and the number of attached cells and their morphology were examined. The influence of the extract from HAp/SCaP on osteoblast differentiation was determined by the measurement of alkaline phosphatase activity and reverse transcriptase-polymerase chain reaction analysis of the expression of osteoblastic markers. In addition, mineralization was evaluated by the staining of calcium deposits with Alizarin red. Attachment of a greater number of cells exhibiting no degeneration in their morphology was observed on HAp/SCaP compared with HAp after incubation for 7 days or more. Culturing cells with the extract from HAp/SCaP resulted in promotion of alkaline phosphatase activity, the expression of type I collagen, and bone-like tissue formation. The results of the present study indicate that HAp/SCaP shows greater ability in osteogenesis than HAp by increasing collagen synthesis and calcification of the extracellular matrix.

Optimal positioning for a dental operating microscope during nonsurgical endodontics.

The most comfortable positioning for a dental operating microscope (DOM) during nonsurgical endodontics for operators was investigated. Operators were categorized into 3 groups according to height. We recorded the time taken to obtain magnified images, and the angles of binoculars, microscope body, and the mirror to floor surfaces. For the group of shorter operators, observations were also made with an angled optics or a short objective lens (200 mm). It took longer to observe the mandibular molars than maxillary in every group. Although the differences in angles among each group were not remarkable for maxillary observation, we confirmed significant differences for the mandibular. Shorter operators had to adopt a strained position for mandibular observation in a standard setup but were more comfortable using angled optics or a short objective lens. By understanding the proper position, operators could learn to perform microendodontics more efficiently.

A two-year comparison of resin-based composite tunnel and Class II restorations in a randomized controlled trial.

PURPOSE: To evaluate the performance of total tunnel restoration with resin-based composites compared to Class II resin-based composite restorations in a randomized controlled clinical study. METHODS: 63 approximal carious lesions were restored in 38 patients by two experienced operators. The carious dentin and approximal demineralized enamel were completely removed for the tunnel restoration leaving the marginal ridge intact. The occlusal opening was enlarged to the center of the tooth to make access easy. Conservative cavity preparation was performed for the Class II restorations. All cavities were restored with Scotchbond Multipurpose Plus and Z250. At baseline, 1- and 2-year recalls, the restorations were evaluated clinically by two examiners using a modified USPHS rating system and radiographically for recurrent, caries. RESULTS: Both types of restorations performed well clinically, and there was no significant difference (P> 0.05) by the chi square test in any category. Recurrent caries was not detected. Only one tunnel restoration had to be replaced with a Class II restoration because of falling of the restoration with the marginal ridge after 2 years. However, no significant difference in the survival rates (P> 0.05) could be demonstrated between the restorations by the log-rank test.

Prognosis of intentional replantation of vertically fractured roots reconstructed with dentin-bonded resin.

There is no particular treatment established to preserve vertically fractured teeth. We evaluated the long-term prognosis of the intentional replantation of 26 vertically fractured roots after reconstruction with 4-META/MMA-TBB dentin-bonded resin. Replanted teeth were evaluated according to clinical criteria and radiographic examinations for periods ranging from 4 to 76 months. Eighteen cases were functional and retained, with six fully successful; the others needed further observation. Eight cases failed to respond to treatment because of refracture, recurrence of gingival inflammation, or both. Longevity was calculated as 88.5% at 12 months after replantation, 69.2% at 36 months, and 59.3% at 60 months. All failures occurred in premolar and molar teeth. Longitudinal fractures extending more than 2/3 from the cervical portion toward the apex showed significantly shorter longevity compared with fractures within the 2/3 area (log-rank test, p = 0.02). Intentional replantation of vertically fractured roots reconstructed with dentin-bonded resin may be considered for incisors as an alternative to extraction, although the long-term success is not optimal.

Cytotoxicity of dentin conditioners and primers on human periodontal ligament cells in vitro.

PURPOSE: To examine the cytotoxicity of dentin conditioners and primers on human periodontal ligament (PDL) cells in vitro. MATERIALS AND METHODS: Primary PDL cells were plated in 96 well culture plates and exposed to 100 microL of test solutions. Undiluted Cavity Conditioner (CC), Vitremer Primer (VP), Uni-Etch (UE), All-Bond 2 (AB), Gluma conditioner (GC), and Gluma primer (GP) were examined at full strength and at 1/100 and 1/1000 dilutions in culture medium. Cytotoxicity of the undiluted material was determined immediately following exposure of the cells to the test substance. Cytotoxicity of the diluted materials was determined immediately following a 300-second exposure of the cells to the test solution, as well as 24 hours after removal of the test solution. Cytotoxicity was expressed as lactate dehydrogenase activity retained within the cells following exposure divided by the activity in unexposed control cells. RESULTS: Exposure to each undiluted test substance resulted in severe damage to the cells (78.2-100%). At 1/100 dilution, only exposure to UE resulted in significant cytotoxicity (72.9%) immediately following removal of the solution. But significant cytotoxicity (21-100%) was evident in cells 24 hours after removal of each of the materials. At 1/1000 dilution, exposure to UE (14.8%) and GP (27.2%) resulted in mild cytotoxicity. Twenty-four hours after removal of the solutions, there was a mild but significant cytotoxic effect of each of the test substances (18.5-49.4%).

Polymerization contraction stresses of resin-based composite restorations within beveled cavity preparations of Class I restorations.

PURPOSE: To evaluate internal stresses resulting from polymerization of resin-based composite materials in cavity preparations beveled at the internal line angles or the cavosurface margin, compared with those in conventional butt-joint box-shaped cavity preparations. MATERIALS AND METHODS: Contraction stress generated in resin-based composite restorations placed in an experimental cavity preparation model was determined using micro-photoelastic analysis. Three types of cavity preparations simulating Class I restorations with bevels at internal line angles (1 mm and 2 mm deep), and at the cavosurface margin (2 mm deep) were prepared in a posterior composite model in order to obtain no marginal defect with the restorative composite. The transparent restorative composite was bulk-filled into the preparations and light-cured for 80 seconds. Specimens 2 mm thick for micro-photoelastic analysis were cut perpendicular to the long axis of the preparation. Fringe patterns for directions and magnitudes of stresses were obtained using transmitted and reflected polarized light. Then, the photoelastic stress analysis was performed to examine stresses in the preparations. The data were statistically compared with the previous data in conventional butt-joint box-shaped preparations by ANOVA and Scheffé's F test (P < 0.05). RESULTS: In 1 and 2 mm deep internal beveled cavity preparations, the maximum principal stress lines were parallel to the wall at the straight internal bevels. In the preparation with a round bevel at the cavosurface margin, the stress distribution in the bulk of the preparation was similar to that in the butt-joint preparation. Maximum stress values in 1 and 2 mm deep internal beveled preparations were 12.2 +/- 0.2 MPa and 18.8 +/- 2.8 MPa, respectively. For 2 mm-deep preparation, the maximum stress values in the internal beveled preparations were significantly lower than those values in butt-joint box-shaped cavity preparations. Maximum stress values in the preparations with the bevel at the cavosurface margin were 22.7 +/- 1.0 MPa, and were not significantly different from those values observed in the butt-joint preparations.

Antibacterial activity and bonding characteristics of an adhesive resin containing antibacterial monomer MDPB.

OBJECTIVES: The aims of this study were to investigate the antibacterial activity of an adhesive resin incorporating the antibacterial monomer 12-methacryloyloxydodecylpyridinium bromide (MDPB) as well as its bonding characteristics in terms of bond strength into dentin and curing ability. METHODS: An experimental adhesive resin was prepared by incorporation of 2.5% MDPB into proprietary adhesive (LB Bond), and the inhibitory effect of cured specimen against the growth of Streptococcus mutans on its surface was determined. Bond strength to human dentin and degree of conversion of the experimental adhesive in combination with 1, 2, or 5% MDPB-containing primers, which were previously reported to possess bactericidal effect, were evaluated by conventional tensile bond strength test and Fourier transformation infrared spectroscopy. RESULTS: The cured experimental adhesive exhibited an inhibitory effect on S. mutans growth, reducing the number of bacteria to approximately 3% of control adhesive without MDPB. Tensile bond strength of experimental adhesive was not significantly different from that of the control (p>0.05), and use in combination with MDPB-containing primer did not show any adverse influence on bond strength. The degree of conversion of the bonding system was not different (p>0.05) between control and experimental adhesive irrespective of addition of MDPB into primer. SIGNIFICANCE: These results indicate that an adhesive resin with antibacterial activity after curing could be produced by incorporation of MDPB without influencing bond strength or curing performance, suggesting that the comprehensive bonding system including MDPB-containing primer and adhesive should be highly effective in its antibacterial effect before and after curing.

Internal root resorption associated with inadequate caries removal and orthodontic therapy.

This case report presents a case of internal root resorption originating from inadequate caries removal and orthodontic therapy in maxillary right lateral incisor in a 13-yr-old female. A preoperative, panoramic radiograph taken at the orthodontic office showed no evidence of resorption, however, the composite restoration in the coronal portion was inadequate. During 4 months of nickel titanium orthodontic wire activation, the patient suffered spontaneous pain. Periapical radiographs revealed internal root resorption in the middle third of the root. Endodontic treatment was accomplished and coronal restorations were completed with composite resin. Periodical radiograph examination as well as orthodontic treatment was continued. The tooth was clinically and radiographically healthy at the 18-month follow-up. The importance of the preoperative radiographic examination as well as radiographs during orthodontic treatment is affirmed.

Short-term evaluation of intentional replantation of vertically fractured roots reconstructed with dentin-bonded resin.

The purpose of this study was to evaluate intentional replantation of vertically fractured roots reconstructed with dentin-bonded resin. Twenty vertically fractured teeth were extracted intentionally and reconstructed with 4-META/MMA-TBB dentin-bonded resin. After reconstruction, the teeth were replanted into the original sockets. The replanted teeth were evaluated by clinical criteria and radiographic examination. The observation periods ranged between 4 and 45 months. Longevity was calculated by the Kaplan-Meier method, and factors that had significant influence on the longevity were analyzed with the Log rank test at a 95% level of confidence. From this short-term observation, 14 of 20 cases were functioned in the oral environment. Of these 14 cases, 6 could be considered truly successful and 8 cases needed further observation. The other six cases were total failures and were extracted. The longevity was calculated as 83.3% at 12 months and 36.3% at 24 months. Teeth with thin roots or with longitudinal fractures extending over 2/3 of the root from the cervical portion toward the apex showed significantly lower longevity. It was concluded that this method had the potential to preserve vertically fractured teeth.