Yooseok Shin

Color Changes of Teeth after Treatment with Various Mineral Trioxide Aggregate–based Materials: An Ex Vivo Study

INTRODUCTION Mineral trioxide aggregate (MTA) materials have been used for many years as a pulp therapy material. The most widely used product, ProRoot MTA (Dentsply, Tulsa, OK), has a major drawback in that it causes tooth discoloration. Alternatives have recently been developed such as ENDOCEM Zr (MARUCHI, Wonju, Korea) and RetroMTA (BioMTA, Seoul, Korea). The purpose of this study was to compare the discoloration of these various MTA-based materials. METHODS Discoloration of discs prepared from 4 different MTA-based materials (ProRoot MTA, MTA Angelus [Angelus, Londrina, PR, Brazil], ENDOCEM Zr, and RetroMTA) were observed at 15 and 30 minutes after exposure to light at an intensity of 1000 mA/cm(2). In a tooth model, 12 premolars were used per each group to retrofill the pulp chamber with MTA-based materials. The degree of discoloration was measured over a 16-week period using a digital spectrophotometer. RESULTS Distinct color changes were observed for discs made from ProRoot MTA and MTA Angelus, but no clear change was observed for those made from either ENDOCEM Zr or RetroMTA. In the tooth model, more distinct, time-dependent color changes were observed for teeth filled with ProRoot MTA and MTA Angelus than for those filled with ENDOCEM Zr and RetroMTA. CONCLUSIONS Less discoloration was observed with ENDOCEM Zr and RetroMTA (which contain zirconium oxide) than with ProRoot MTA and MTA Angelus (which contain bismuth oxide) in both of the test models used.

Evaluation of the shear bond strength of resin cement to Y-TZP ceramic after different surface treatments.

The purpose of this study was to evaluate the effect of various surface treatments on the shear bond strength of Y-TZP (Yttria-Tetragonal Zirconia Polycrystal) ceramics with zirconia primer and two different resin cements both containing 10-methacryloyloxydecyl dihydrogen phosphate (MDP). Zirconia blocks (LAVA, 3M ESPE, St. Paul, MN) were polished and assigned to five groups according to the surface treatment: (1) no further treatment (control); (2) airborne abrasion with Al2 O3 particles; (3) Z-PRIME Plus (Bisco, Schaumburg, IL) applied on polished zirconia; (4) Z-PRIME Plus applied on zirconia after airborne abrasion; and (5) tribochemical silica-coating performed with the CoJet system (3M ESPE) followed by application of ESPE®-Sil (3M ESPE). Each group was further divided into one of two resin cements: Panavia F2.0 (Kuraray, Kurashiki, Okayama, Japan) and Clearfil SA Luting (Kuraray). Resin cement placed inside a gel-cap was polymerized on the zirconia surface. Shear bond strength was tested with a universal testing machine at 0.5 mm/min. One-way analysis of variance and paired t-test were done. (p < 0.05), and scanning electron microscope (SEM) images were taken. Zirconia primer applied after airborne abrasion significantly increased the shear bond strength resulting in the highest value for both resin cements. Control groups for both cements showed the weakest value for shear bond strength. No significant differences were found between the shear bond strengths of the individual resin cements applied to zirconia surfaces treated the same way. In conclusion, the combined surface treatment of airborne abrasion followed by a zirconia primer is recommended for zirconia bonding with Panavia F2.0 and Clearfil SA Luting cements.

Comparative Study of Pulpal Responses to Pulpotomy with ProRoot MTA, RetroMTA, and TheraCal in Dogs' Teeth

INTRODUCTION This study was conducted to evaluate and compare pulpal responses to ProRoot MTA (Dentsply Tulsa Dental, Tulsa, OK), RetroMTA (Meta Biomed Co, Ltd, Seoul, Korea), and TheraCal (Bisco Inc, Schamburg, IL) in dog partial pulpotomy models. METHODS Partial pulpotomies were performed on 60 beagle teeth. The exposed pulp tissues were randomly capped with either ProRoot MTA (n = 15), RetroMTA (n = 15), TheraCal (n = 15), or interim restorative material as a negative control (n = 15). After 4 weeks, the teeth were extracted and processed for histologic and immunohistochemical examinations using osteocalcin and dentin sialoprotein. Calcific barrier formation, inflammatory reaction, and the odontoblastic layer were evaluated and scored in a blind manner. The areas of newly formed calcific barriers were measured for each group. RESULTS In most of the ProRoot MTA and RetroMTA specimens, continuous calcific barriers were formed, and the pulps contained palisading patterns in the odontoblastic layer that were free of inflammation. However, the TheraCal specimens had lower quality calcific barrier formation, extensive inflammation, and less favorable odontoblastic layer formation. Overall, areas of newly formed calcific barrier were higher in the ProRoot MTA and RetroMTA specimens than in the TheraCal specimens. Also, immunohistochemistry revealed that osteocalcin and dentin sialoprotein were more clearly visible in the ProRoot MTA and RetroMTA specimens than in the TheraCal specimens. CONCLUSIONS RetroMTA could provide an alternative to ProRoot MTA. Both materials produced favorable pulpal responses that were similar in nature, whereas TheraCal produced less favorable pulpal responses.

Accuracy of intraoral digital impressions using an artificial landmark

Statement of problem Intraoral scanners have been reported to have limited accuracy in edentulous areas. Large amounts of mobile tissue and the lack of obvious anatomic landmarks make it difficult to acquire a precise digital impression of an edentulous area with an intraoral scanner. Purpose The purpose of this in vitro study was to determine the effect of an artificial landmark on a long edentulous space on the accuracy outcomes of intraoral digital impressions. Material and methods A mandibular model containing 4 prepared teeth and an edentulous space of 26 mm in length was used. A blue‐light light‐emitting diode tabletop scanner was used as a control scanner, and 3 intraoral scanners were used as experimental groups. Five scans were made using each intraoral scanner without an artificial landmark, and another 5 scans were performed after application of an artificial landmark (a 4×3 mm alumina material) on the edentulous area. The obtained datasets were used to evaluate trueness and precision. Results Without an artificial landmark on the edentulous area, the mean trueness for the intraoral scanner ranged from 36.1 to 38.8 &mgr;m and the mean precision ranged from 13.0 to 43.6 &mgr;m. With an artificial landmark on the edentulous area, accuracy was improved significantly: the mean trueness was 26.7 to 31.8 &mgr;m, and the mean precision was 9.2 to 12.4 &mgr;m. Conclusions The use of an alumina artificial landmark in an edentulous space improved the trueness and precision of the intraoral scanners tested.

In vivo quantitative evaluation of live and dead bacteria in root canal infection by using propidium monoazide with real-time PCR.

INTRODUCTION For selective detection of viable bacteria with molecular methods, propidium monoazide (PMA) treatment has been successfully applied to a wide range of bacteria. The purpose of this study was to compare the quantity of live cells with the total amounts of both live and dead cells before and after chemomechanical preparation by using PMA in combination with real-time polymerase chain reaction (qPCR). METHODS Twenty-one teeth with pulp necrosis and a periapical lesion were included. Bacterial sampling of the root canals was performed before (S1) and after (S2) chemomechanical root canal treatment. Each sample was separated into 2 different tubes. PMA was added to one of the tubes, and the other was left untreated. Then, DNA extraction and qPCR were performed. To evaluate the validity of the PMA treatment, the defined mixtures containing different ratios of live and dead cell suspensions of Enterococcus faecalis were either subjected to PMA treatment or not subjected to PMA treatment, followed by qPCR quantification. RESULTS A paired t test showed a highly significant difference in the mean threshold cycle values between S1 with and without PMA (P = .0002), and this difference (0.89) was similar to that (0.96) obtained from the samples consisting of 80% live cell suspension and 20% dead cell suspension of E. faecalis. The threshold cycle values between the S2 samples with and without PMA were also significantly different (P = .0134), and this difference (0.37) was similar to that obtained from the 100% live cell suspension of E. faecalis (0.42). CONCLUSIONS PMA in conjunction with qPCR appeared to be useful in analyzing the primary infections of root canals because there were significant amounts of dead bacteria in the root canals. Although the use of PMA treatment in post-preparation samples significantly reduced the detection of dead bacteria, this difference was still small, so further studies should be carried out to confirm the necessity of PMA treatment.

Characteristics of stem cells from human exfoliated deciduous teeth (SHED) from intact cryopreserved deciduous teeth

The aim of this study is to compare the characteristics of stem cells derived from human exfoliated deciduous teeth (SHED) from cryopreserved intact deciduous teeth with those of fresh SHED. In total, 20 exfoliated deciduous teeth were randomly divided into a fresh group (f-SHED; n = 11) and cryopreserved group (c-SHED; n = 9; stored for 1-8 months). Following thawing and separation of the pulp, the SHED cells were cultured, and the characteristics as mesenchymal stem cells were investigated using proliferation assays, cell-cycle analysis, colony-forming unit-fibroblast (CFU-F) assays, and flow cytometry analyses. Furthermore, differentiation into adipogenic and osteogenic lineages was investigated in vitro as well as in vivo via transplantation in mice. We found no significant differences between the two groups in the proliferation analyses, in the expression of mesenchymal stem cell markers, or in the adipogenic and osteogenic differentiation in vitro (p < 0.05). Furthermore, the in vivo transplantation results showed no significant differences in the quantity of bone tissue that formed or in histochemistry performance (p < 0.05). In conclusion, cryopreservation of intact exfoliated deciduous teeth appears to be a useful method for preserving SHED.

Vertical Bone Growth after Autotransplantation of Mature Third Molars: 2 Case Reports with Long-term Follow-up

Tooth autotransplantation is a viable treatment option for tooth replacement when a suitable donor tooth is available. These case reports described significant vertical bone growth after autotransplantation of a mature third molar. The left mandible third molars (n = 2) were transplanted to the missing tooth in the left mandible. The patient follow-up period was 10 years after transplantation. Clinical examination revealed no mobility of the transplanted tooth. Radiographic examination indicated that bone regeneration occurred around the transplanted tooth. Vertical bone growth was observed in the cervical area of the root surface and the recipient bone. In autotransplantation of mature teeth, long-term follow-up results indicate that vertical bone growth can be expected if viability of the periodontal ligament cells is maintained.

Influence of preparation design on fit and ceramic thickness of CEREC 3 partial ceramic crowns after cementation

Abstract Objective. This study investigated the influence of preparation design on the marginal and internal gap and ceramic thickness of partial ceramic crowns (PCCs) fabricated with the CEREC 3 system. Materials and methods. Sixteen extracted human mandibular molars were prepared according to two different preparation designs (n = 8): a retentive preparation design with traditional cusp capping (Group I) and a non-retentive preparation design with horizontal reduction of cusps (Group II). PCCs were fabricated from IPS Empress CAD with the CEREC 3 system. The parameters for luting space and minimum occlusal ceramic thickness were set to 30 μm and 1.5 mm, respectively. The fabricated PCCs were cemented to their corresponding teeth with self-adhesive resin cement and were then scanned by micro-computed tomography. The marginal and internal gaps were measured at pre-determined measuring points in five bucco-lingual and three mesio-distal cross-sectional images. The ceramic thicknesses of the PCCs were measured at the measuring points for cusp capping areas. Results. Group II (167.4 ± 76.4 μm) had a smaller overall mean gap, which included the marginal and internal gap measurements, than that of Group I (184.8 ± 89.0 μm). The internal gaps were larger than the marginal gaps, regardless of preparation design. Group I presented a thinner ceramic thickness in the cusp capping areas than the minimum occlusal ceramic thickness parameter of 1.5 mm. Conclusion. Preparation design had an influence on fit, particularly the internal gap of the PCCs. Ceramic thickness could be thinner than the minimum ceramic thickness parameter.

Evaluation of the marginal and internal discrepancies of CAD-CAM endocrowns with different cavity depths: An in vitro study

Statement of problem. The marginal and internal discrepancies of computer‐aided design and computer‐aided manufacturing (CAD‐CAM) endocrowns are unknown. Purpose. The purpose of this in vitro study was to evaluate the marginal and internal discrepancies of endocrowns with different cavity depths by measuring them with microcomputed tomography (&mgr;CT). Material and methods. Endocrowns (n=48) of 2 different cavity depths (2 mm and 4 mm) were fabricated in 2 different chairside CAD‐CAM systems (CEREC AC and E4D). A &mgr;CT scan was made before and after cementation. For analysis of the marginal and internal discrepancies, reference points were selected in 2‐dimensional views of 3 buccolingual cross‐sections and 3 mesiodistal cross‐sections. To calculate the total discrepancy volume, the &mgr;CT sections were reconstructed 3‐dimensional views, and changes in volume and surface area were examined. Statistical analysis was performed using 2‐way ANOVA with Bonferroni correction (&agr;=.05). Results. An endocrown with a 4‐mm cavity showed a larger marginal and internal volume than one with a 2‐mm cavity. Cementation did not show significant differences in total discrepancy thickness. Discrepancies on the pulpal floor were largest in other sites. Both chairside CAD‐CAM systems showed similar discrepancy in the endocrowns. Conclusions. Based on the present study, marginal and internal discrepancies increased depending on cavity depth. Cementation did not increase the dimension of the discrepancy between the restoration and the cavity wall. The discrepancy on the pulpal floor appeared to affect these results.

A randomized controlled trial of various MTA materials for partial pulpotomy in permanent teeth

OBJECTIVES The aim of this study was to evaluate and compare the clinical applicability of various MTA materials as partial pulpotomy materials in permanent teeth. METHODS Partial pulpotomy was performed on 104 permanent teeth from 82 people (mean 29.3±14.8years old), who met the inclusion criteria in randomized clinical trial. The teeth were divided into three groups: ProRoot MTA (n=33), OrthoMTA (n=36), RetroMTA (n=35). Clinical examination and radiographic comparison were carried out at 1, 3, 6 and 12 months after the treatment. Survival analysis was performed using the Kaplan-Meier survival curves and log rank tests. RESULTS Partial pulpotomy sustained a high success rate up to 1year with no significant differences in the outcomes treated with three MTA materials: ProRoot MTA, 96.0%; OrthoMTA, 92.8%; RetroMTA, 96.0%. The Kaplan-Meier survival function curves showed no significant differences among three groups concerning clinical and radiographic cumulative survival rates. In addition, no potential prognostic factors related to the success rate of partial pulpotomy among age, sex, tooth type, root apex status, the site and type of pulp exposure, and the type of restoration were observed in log rank analysis. CONCLUSIONS Partial pulpotomy with ProRoot MTA, OrthoMTA and RetroMTA had favorable results and clinical and radiographic results were not significantly different in three groups after 1year.