Restorative Dentistry & Endodontics

Marginal microleakage of cervical composite resin restorations bonded using etch-and-rinse and self-etch adhesives: two dimensional vs. three dimensional methods: Maryam Khoroushi, Ailin Ehteshami; Restor Dent Endod 2016;41(2):83-90. Published online April 18, 2016; DOI: https://doi.org/10.5395/rde.2016.41.2.83

Abstract PDF PubReader ePub: Objectives
This study was evaluated the marginal microleakage of two different adhesive systems before and after aging with two different dye penetration techniques.
Materials and Methods
Class V cavities were prepared on the buccal and lingual surfaces of 48 human molars. Clearfil SE Bond and Single Bond (self-etching and etch-and-rinse systems, respectively) were applied, each to half of the prepared cavities, which were restored with composite resin. Half of the specimens in each group underwent 10,000 cycles of thermocycling. Microleakage was evaluated using two dimensional (2D) and three dimensional (3D) dye penetration techniques separately for each half of each specimen. Data were analyzed with SPSS 11.5 (SPSS Inc.), using the Kruskal-Wallis and Mann-Whitney U tests (α = 0.05).
Results
The difference between the 2D and 3D microleakage evaluation techniques was significant at the occlusal margins of Single bond groups (p = 0.002). The differences between 2D and 3D microleakage evaluation techniques were significant at both the occlusal and cervical margins of Clearfil SE Bond groups (p = 0.017 and p = 0.002, respectively). The difference between the 2D and 3D techniques was significant at the occlusal margins of non-aged groups (p = 0.003). The difference between these two techniques was significant at the occlusal margins of the aged groups (p = 0.001). The Mann-Whitney test showed significant differences between the two techniques only at the occlusal margins in all specimens.
Conclusions
Under the limitations of the present study, it can be concluded that the 3D technique has the capacity to detect occlusal microleakage more precisely than the 2D technique.

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The effect of the amount of interdental spacing on the stress distribution in maxillary central incisors restored with porcelain laminate veneer and composite resin: A 3D-finite element analysis: Junbae Hong, Seung-Min Tak, Seung-Ho Baek, Byeong-Hoon Cho; J Korean Acad Conserv Dent 2010;35(1):30-39. Published online January 31, 2010; DOI: https://doi.org/10.5395/JKACD.2010.35.1.030

This study evaluated the influence of the type of restoration and the amount of interdental spacing on the stress distribution in maxillary central incisors restored by means of porcelain laminate veneers and direct composite resin restorations.

Three-dimensional finite element models were fabricated to represent different types of restorations. Four clinical situations were considered. Type I, closing diastema using composite resin. Labial border of composite resin was extended just enough to cover the interdental space; Type II, closing diastema using composite resin without reduction of labial surface. Labial border of composite resin was extended distally to cover the half of the total labial surface; Type III, closing diastema using composite resin with reduction of labial surface. Labial border of the preparation and restored composite resin was extended distally two-thirds of the total labial surface; Type IV, closing diastema using porcelain laminate veneer with a feathered-edge preparation technique. Four different interdental spaces (1.0, 2.0, 3.0, 4.0 mm) were applied for each type of restorations.

For all types of restoration, adding the width of free extension of the porcelain laminate veneer and composite resin increased the stress occurred at the bonding layer. The maximum stress values observed at the bonding layer of Type IV were higher than that of Type I, II and III. However, the increasing rate of maximum stress value of Type IV was lower than that of Type I, II and III.

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A comparison of canal centering abilities of four root canal instrument systems using X-ray micro-computed tomography: Hye-Suk Ko, Heyon-Mee You, Dong-Sung Park; J Korean Acad Conserv Dent 2007;32(1):61-68. Published online January 31, 2007; DOI: https://doi.org/10.5395/JKACD.2007.32.1.061

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The purpose of this study was to compare the centering abilities of four root canal instrument systems and the amounts of dentin removed after root canal shaping using them.

The mesial canals of twenty extracted mandibular first molars having 10 - 20° curvature were scanned using X-ray micro-computed tomography (XMCT)-scanner before root canals were instrumented. They were divided into four groups (n = 10 per group). In Group 1, root canals were instrumented by the step-back technique with stainless steel K-Flexofile after coronal flaring. The remainders were instrumented by the crown-down technique with Profile (Group 2), ProTaper (Group 3) or K3 system (Group 4). All canals were prepared up to size 25 at the end-point of preparation and scanned again. Scanned images were processed to reconstruct three-dimensional images using three-dimensional image software and the changes of total canal volume were measured. Pre- and post-operative cross-sectional images of 1, 3, 5, and 7 mm from the apical foramen were compared. For each level, centering ratio were calculated using Adobe Photoshop 6.0 and image software program.

ProTaper and K3 systems have a tendency to remove more dentin than the other file systems. In all groups, the lowest value of centering ratio at 3 mm level was observed. And except at 3 mm level, ProTaper system made canals less centered than the other systems (p < 0.05).

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Evaluation of canal preparation with Ni-Ti rotary files by micro computed tomography: Jeong-Ho Lee, Mi-Ja Kim, Chang-In Seok, Woo-Cheol Lee, Seung-Ho Baek; J Korean Acad Conserv Dent 2004;29(4):378-385. Published online July 31, 2004; DOI: https://doi.org/10.5395/JKACD.2004.29.4.378

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The purpose of this study was to compare the effects of preparation with GT files and profiles .04 in shaping of root canals and reconstruct the three-dimensional root canal system using micro computed tomography.

40 canals of the extracted human mandibular molars were used, and randomly distributed into two experimental groups. In group 1, canals were prepared by GT files. In group 2, Profiles .04. were used. Apical preparation size was #30.

For each tooth pre and post operative cross-sectional images were obtained by the micro CT at 50 micron intervals. Pre and post operative cross-sectional images of 1, 2, 3, 5, and 8mm from the apex were compared. For each section, canal area and centering ratio were determined. For each tooth pre- and post-operative root canal volume from the furcation to the apex of the roots was calculated by three-dimensional image software. Following results were obtained:

1. At 8mm from the apex, area of dentin removed by GT rotary file was significantly larger than that by Profile .04. And at the other levels there was not a significant difference.

2. There was a trend for GT rotary file to remain more centered in the canals than Profile .04 at all levels. But at 3mm level, there was a statistically significant difference.

3. In root canal volume increments after instrumentation, there was no significant difference between two groups.

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