Ho Hyun Son

Translucency and masking ability of various opaque-shade composite resins.

OBJECTIVESnThe aims of this study were to evaluate the adequate thickness of opaque resins for situations such as an oral black cavity and discolored tooth structure, as well as the translucency of each opaque material at various thicknesses.nnnMETHODSnSix opaque-shade composite resins (Z-350 OA3, Amelogen Universal A2O, Esthet-X A2O, Esthet-X A4O, Charmfil UO, and Aelite Universal OA3) were prepared in metal molds with a hole of 8mm in diameter and various thicknesses (0.5mm, 1.0mm, 1.5mm, 2.0mm, 2.5mm, 3.0mm and 4.0mm). Four backgrounds (white tile, black tile, C4 shade porcelain and opaque resin itself) were used to determine the translucency parameter (TP) (between black and white backgrounds), and to mimic a black oral cavity (between black and opaque resin backgrounds) and a discolored tooth structure (between C4 and opaque resin backgrounds). Color measurements were made by a colorimeter to determine the CIELAB values of each specimen with each background and to calculate the TP and DeltaE* value difference among the specimens on the backgrounds.nnnRESULTSnTP and DeltaE* obtained between black and opaque resin backgrounds decreased in similar pattern as thickness increased. A C4 background was masked by resin thicknesses of 0.5-1.0mm, while a black background required thicknesses of 1.0-2.0mm.nnnSIGNIFICANCEnThis study can provide helpful guidelines for the esthetic restoration of discolored tooth structures or through and through class III and IV cavities with composite resin materials.

Thermal irritation of teeth during dental treatment procedures

While it is reasonably well known that certain dental procedures increase the temperature of the tooths surface, of greater interest is their potential damaging effect on the pulp and tooth-supporting tissues. Previous studies have investigated the responses of the pulp, periodontal ligament, and alveolar bone to thermal irritation and the temperature at which thermal damage is initiated. There are also many in vitro studies that have measured the temperature increase of the pulp and tooth-supporting tissues during restorative and endodontic procedures. This review article provides an overview of studies measuring temperature increases in tooth structures during several restorative and endodontic procedures, and proposes clinical guidelines for reducing potential thermal hazards to the pulp and supporting tissues.

The color change in artificial white spot lesions measured using a spectroradiometer.

ObjectivesThe purpose of this study was to determine the color of white spot lesions.Materials and methodsHuman premolars were subjected to a pH cycling to produce artificial caries lesions and classified into groups (nu2009=u200910/group): group 1, immersion in deionized water; group 2, pH cycling without fluoride (F) application; group 3, pH cycling with immersion in 1,000xa0ppm NaF solution; and group 4, pH cycling with immersion in 5,000xa0ppm NaF solution. CIE L*a*b* color parameters of the tooth were determined using a spectroradiometer at baseline, after demineralization and after pH cycling. The extent of demineralization was evaluated by scanning electron microscopy (SEM) and electron microprobe analysis (EPMA).ResultsSignificant degrees of color change (ΔE*) were observed after demineralization (pu2009<u20090.05). The changes were mainly due to an increase in lightness (L*) and a decrease in yellowness (b*). F application induced a significantly large ΔE* in group 4 (pu2009<u20090.05). The color reversal after remineralization was mostly due to the recovery of L*. SEM and EPMA verified that net mineral gains occurred in the subsurface lesions.ConclusionsThe initially white appearance of enamel caries was a result of changes of L* and b*. F treatment partially restored the color of white spot lesions.Clinical relevanceF-driven remineralization induced both mineral gains and esthetic enhancement of artificially produced enamel white spot lesions. The increase of L* and the decrease of b* contributed to the color changes.

Caries risk profile of Korean dental patients with severe intellectual disabilities.

This study evaluated the caries risk profile of patients with severe intellectual disabilities (IDs) who received dental treatment under general anesthesia. One hundred and two patients with ID [ID group, mean age (SD); 23.8(9.3)] and 100 healthy patients without ID [NID group, mean age (SD); 23.19(3.3)] were included. Medication, disability type, oral hygiene maintenance, and cooperation of the patients were investigated. Dietary habits, plaque index, mutans streptococci counts, fluoride availability, and salivary buffering were scored and analyzed using the Cariogram. The mean chance of avoiding caries (SD) was 28.1(20.4) in the ID group and 54.7(18.4) in the NID group. The ID group had significantly higher numbers of decayed and missing teeth, but fewer filled teeth than the NID group (p < .05). Significant disparities existed in the distributions of all caries-related factors except for mutans streptococci counts between the two groups (p < .05). The low chance to avoid future caries in ID patients was closely associated with insufficient oral hygiene maintenance (p < .05). Fluoride availability was strongly associated with the chance of avoiding caries in the ID group. Dental patients with severe ID exhibited a higher risk of developing caries than normal patients. Among several caries-related factors, insufficient oral hygiene maintenance and low fluoride availability most contributed to the high risk.

Caries risk profiles of Korean dental patients using simplified Cariogram models

Abstract Objectives. The objective of this study was to compare the caries risk profiles obtained from the simplified Cariogram models and the conventional Cariogram model of Korean dental patients. Materials and methods. Data required for a caries risk assessment with the Cariogram were collected from 80 young adult patients (mean: 23 years old). Three different simplified Cariogram models were produced with exclusion of either or both salivary secretion rate and lactobacilli count: group 1, conventional model; group 2, both salivary secretion rate and lactobacilli count excluded; group 3, salivary secretion rate excluded; group 4, lactobacilli count excluded. Results. The mean chance of avoiding caries in group 1 (55.5%) was not significantly different from those in groups 2 and 3. Also four caries-related sectors of the Cariogram (diet, bacteria, susceptibility and circumstance) in group 1 were not significantly different than in groups 2 and 3. Group 4 showed significant differences from group 1 in the mean chance of avoiding caries and the diet, susceptibility and circumstance sectors (p < 0.05). Significant correlations were detected between all risk factors and their corresponding risk sectors (p < 0.05). Also there were significant correlations between each risk factor and the chance of avoiding caries, except for the amount of plaque, in groups 1, 2 and 3 (p < 0.05). Conclusions. The simplified Cariogram model without salivary secretion rate and lactobacilli count did not significantly change the outcome produced from the conventional model. However, single exclusion of lactobacilli count noticeably changed the caries risk profile.

Elemental analysis of the fluoride varnish effects on root caries initiation

Objectives: The usage of fluoride varnish for a moderate to low caries-risk group has not been well validat- ed. This study aimed to evaluate the preventive and therapeutic efficacies of fluoride varnish on the initiat- ed root caries. Materials and Methods: Ten premolars were sectioned into quarters, further divided into two windows, one of which was painted with Fluor Protector (1,000 ppm fluoride, Ivoclar Vivadent). An initial lesion with a well-preserved surface layer was produced by pH cycling. Scanned line analysis using energy dispersive spectrometry determined the weight percentages of Ca and P in the demineralized layer. Scanning Electron microscopy and confocal laser scanning microscopy (CLSM) evaluated the varnish-applied root surfaces. Results: The mean lesion depth (SD) was 12.3 (2.6) μ m (single cycling) and 19.6 (3.8) μ m (double cycling). Double cycling extended the lesion depth, but induced no more mineral loss than single cycling ( p < 0.05). The mean weight percentages of Ca and P between groups with and without varnish were not sig- nificantly different (p < 0.05). A CLSM showed varnish remained within 15 μ m of the surface layer. Conclusions: When a mild acid challenge initiated root tissue demineralization, the application of low-con- centration fluoride varnish did not influence the lesion depth or the mineral composition of the subsurface lesion. (J Kor Acad Cons Dent 2011;36(4):290-299.)

Bonding of the silane containing multi-mode universal adhesive for lithium disilicate ceramics

Objectives This study evaluated the influence of a multi-mode universal adhesive (MUA) containing silane (Single Bond Universal, 3M EPSE) on the bonding of resin cement to lithium disilicate. Materials and Methods Thirty IPS e.max CAD specimens (Ivoclar Vivadent) were fabricated. The surfaces were treated as follows: Group A, adhesive that did not contain silane (ANS, Porcelain Bonding Resin, Bisco); Group B, silane (S) and ANS; Group C, hydrofluoric acid (HF), S, and ANS; Group D, MUA; Group E, HF and MUA. Dual-cure resin cement (NX3, Kerr) was applied and composite resin cylinders of 0.8 mm in diameter were placed on it before light polymerization. Bonded specimens were stored in water for 24 hours or underwent a 10,000 thermocycling process prior to microshear bond strength testing. The data were analyzed using multivariate analysis of variance (p < 0.05). Results Bond strength varied significantly among the groups (p < 0.05), except for Groups A and D. Group C showed the highest initial bond strength (27.1 ± 6.9 MPa), followed by Group E, Group B, Group D, and Group A. Thermocycling significantly reduced bond strength in Groups B, C, and E (p < 0.05). Bond strength in Group C was the highest regardless of the storage conditions (p < 0.05). Conclusions Surface treatment of lithium disilicate using HF and silane increased the bond strength of resin cement. However, after thermocycling, the silane in MUA did not help achieve durable bond strength between lithium disilicate and resin cement, even when HF was applied.

Information resources and material selection in bonded restorations among Korean dentists.

PURPOSEnTo elucidate how dentists access knowledge sources when choosing adhesive agents for bonded restoration and whether these resources influenced the selection of materials.nnnMATERIALS AND METHODSnA national survey was carried out involving dentists in South Korea. The questionnaire included the status of the operator, clinical techniques, and materials. A total of 12,193 e-mails were distributed, 2632 were opened by recipients, and 840 responses were collected.nnnRESULTSnFor primary information resources in material selection, 55.8% (n = 469) of the responders mentioned continuing education. This selection criteria varied according to the working status of the clinician (p < 0.0001). The choice of bonding system was influenced by of the length of the career (p < 0.0001), and the preferred bonding systems differed according to the source of the information (p = 0.035).nnnCONCLUSIONnThe popular bonding systems were not ranked according to the bonding strategy, but a preference was found for specific brands or manufacturers. To decrease the confusion of clinicians related to the selection of bonding materials, evidence-based guidelines need to be comprehensibly organized and efficiently approached in clinics.

PULP TISSUE REGENERATION AND ROOT FORMATION OF PERMANENT TEETH WITH PULPAL/PERIAPICAL DISEASES

Numerous cases about additional growth of roots or pulp tissue regeneration by using various intracanal medicaments in immature permanent teeth with periapical or pulpal disease have been reported. The underlying mechanism has not been clearly delineated, but it has been widely accepted that undifferentiated mesenchymal cells and stem cells are involved. Moreover, the growth and deposition of osteoid or cementoid tissues have been observed in regenerated pulp and roots. This new and non-invasive treatment has brightened the future of endodontics, and enlarged the vision of regenerative root canal treatment with multi-potent stem cells and various tissue engineering techniques. [J Kor Acad Cons Dent 35(4):238-245, 2010]

Influence of rebonding procedures on microleakage of composite resin restorations

During a composite resin restoration, an anticipating contraction gap is usually tried to seal with low-viscosity resin after successive polishing, etching, rinsing and drying steps, which as a whole is called rebonding procedure. However, the gap might already have been filled with water or debris before applying the sealing resin. We hypothesized that microleakage would decrease if the rebonding agent was applied before the polishing step, i.e., immediately after curing composite resin. On the buccal and lingual surfaces of 35 extracted human molar teeth, class V cavities were prepared withthe occlusal margin in enamel and the gingival margin in dentin. They were restored with a hybrid composite resin Z250 (3M ESPE, USA) using an adhesive AdperTM Single Bond 2 (3M ESPE). As rebonding agents, BisCover LV (Bisco, USA), ScotchBond Multi-Purpose adhesive (3M ESPE) and an experimental adhesive were applied on the restoration margins before polishing step or after successive polishing and etching steps. The infiltration depth of 2% methylene blue into the margin was measured using an optical stereomicroscope. The correlation between viscosity of rebonding agents and mciroleakage was also evaluated. There were no statistically significant differences in the microleakage within the rebonding procedures, within the rebonding agents, and within the margins. However, when the restorations were not rebonded, the microleakage at gingival margin was significantly higher than those groups rebonded with 3 agents (p < 0.05). The difference was not observed at the occlusal margin. No significant correlation was found between viscosity of rebonding agents and microleakage, except very weak correlation in case of rebonding after polishing and etching at gingival margin (r = -0.326, p = 0.041).