Comparative evaluation of the microhardness of 4 dental sealants

AIM

Aim of this study was the evaluation of the microhardness of 4 dental sealants polymerised with two different curing units.

METHODS

Twenty samples (5 x 5x 2 mm) were prepared with 4 different sealants; 10 samples for each group were polymerised with a plasma curing unit (Apollo 95 E DMD) and 10 with a halogen curing light (Heliolux DLX Vivadent ETS, Schaan, Liechtenstein). For each section 6 Vickers microhardness measurements were performed (VMHT 30A, Leica Wien, Austria), 3 on the surface exposed to the light and 3 on the opposite surface. After the baseline assessment all samples were stored in artificial saliva at 37 degrees C for 30, 60, 90, 180 and 360 days, and then analysed again with the microhardness indenter and observed under steromicroscope 10X (Leica DM2500 Wien, Austria). Data were then statistically analysed.

RESULTS

The hybrid composite Tetric flow (group IV) showed the higher microhardness values compared to the other tested materials (group I, II, III); surfaces exposed to curing light showed higher microhardness values than opposite surfaces. Moreover, a significant microhardness reduction was observed after 30 days; values remained unmodified after 60, 90, 180 and 360 days.

STATISTICS

Data were then statistically analysed with Anova test for repeated measures, with a global significance level of 0.05.

CONCLUSION

Because of the good mechanical properties of dental sealants they represent the first choice materials in pits and fissures sealing.

Influence of air abrasion and etching on enamel and adaptation of a dental sealant

AIM

Aim of this study was to evaluate the marginal microleakage of a dental sealant using different pre-treatment techniques of the enamel surface.

METHODS

Thirty extracted human intact teeth were selected and divided into 3 groups (n = 10) (1: acid etching with 37% orthophosphoric acid - 3M ESPE, St. Paul, Minnesota, USA; 2: air abrasion; 3: air abrasion + acid etching). The sealant (Helioseal, Vivadent Ivoclar AG, Liechtenstein) was applied into occlusal pits and fissures and light cured for 40 sec. All samples were thermocycled for 500 cycles (5 degrees -55 degrees C). Teeth were then immersed into a 2% methylene blue solution for 24 hrs and sectioned in a mesio-distal direction. Forty-eight sections were obtained for each group. Each section was analysed and photographed with a stereomicroscope (50x) assessing dye penetration (0: no dye penetration; 1: dye penetration restricted to the outer half of the sealant; 2: dye penetration restricted to the inner half of the sealant; 3: dye penetration into the underlying fissure).

STATISTICS

Data were statistically analysed (Mann-Whitney test).

RESULTS

Specimens prepared after air abrasion combined with acid etching showed lower microleakage expression if compared with the other two groups (p<0.01). Conclusion A combination of mechanical air abrasion and chemical acid etching represents an effective pre-treatment of enamel surface that may significantly reduce the risk of microleakage.

Surface roughness of three resin restorative materials after finishing and polishing

AIM

The surface roughness of 3 different resin restorative materials polymerized with a halogen and a plasma arc curing light, following finishing and polishing was evaluated in vitro.

METHODS

Using a metal mold, 10 block specimens were prepared from each material. A Mylar strip was placed on both sides of the mold. Five specimens from each material were cured with the halogen lamp, while the other 5 were polymerized with the plasma arc lamp. In both groups the surface exposed to curing light was finished and polished with the Enhance system (Dentsply). The opposite surface was not treated and served as a control. Both surfaces of each specimen were analyzed with a laser profilometer: the roughness average (R(a)) was evaluated. The Vickers microhardness of the polished surfaces was also calculated. All data were statistically analyzed with the Mann-Whitney test. A regression test was carried out to evaluate the possible correlation between roughness and microhardness.

RESULTS

The smoothest surfaces were obtained when composites were cured against a Mylar strip. Roughness was significantly increased in both groups in the treated surfaces. A significant correlation between roughness and microhardness could not be demonstrated.

CONCLUSIONS

This study demonstrated that the surface polymerized against a Mylar strip was the smoothest surface produced, while the roughness of the Mylar-formed surface was significantly increased by finishing and polishing. Surface roughness following polishing is material-dependent.

Cyclosporin A specifically affects nuclear PLCbeta1 in immunodepressed heart transplant patients with gingival overgrowth

One of the most commonly observed adverse effects of cyclosporin A (CsA) is the development of gingival overgrowth (GO). Fibroblasts are involved in GO, but the question why only a percentage of patients undergoing CsA treatment shows this side-effect remains unanswered. In a previous study, CsA has been demonstrated to induce over-expression of phospholipase C (PLC) beta(1) in fibroblasts of patients with clinical GO, in cells from both enlarged and clinically healthy gingival sites. In this work, we assessed the expression of PLCbeta isoforms to investigate whether the exaggerated fibroblast response to CsA related to increased PLCbeta(1) expression could also be detected in CsA-treated patients without clinical signs of GO. Our results support the hypothesis of a multi-factorial origin of gingival overgrowth, including specific changes within the gingival tissues orchestrating fibroblastic hyper-responsiveness as a consequence of a long-term in vivo exposure to cyclosporin A.

Clinical evaluation of antibiotic prophylaxis before endodontic treatment of necrotic teeth

AIM

The efficacy of antibiotic prophylaxis before endodontic treatment of necrotic teeth in the prevention of post-treatment flare-up pain and swelling was evaluated.

METHODS

A total of 47 teeth with diagnosis of pulpal necrosis were selected in 39 patients, independently from the pre-operative symptomatology (painful or asymptomatic). Teeth were randomly divided into 2 groups. The first group (n=23) was given an antibiotic prophylaxis with 2 g amoxicillin 1 h before every appointment; the second group (n=24) did not receive any treatment (control group). The endodontic therapy was performed by shaping canals using the crown-down technique with hand devices, 5% sodium hypochlorite irrigations and 2 intermediate medications with Ca(OH)(2). Obturation was performed using randomly the vertical obturation technique or the no-stop wave technique. At the end of each appointment a questionnaire was given to each patient. The patient had to indicate if pain (absent, light, mild, severe) or swelling were present at 4, 8, 12, 24 h after every appointment. Data were statistically analysed with the Mann-Whitney, Wilcoxon and chi2 test.

RESULTS

Only a case of flare-up pain and swelling was found in a patient of the study group. The statistical analysis showed that there were no significant differences between the 2 groups.

CONCLUSIONS

An accurate endodontic treatment of necrotic canals is sufficient to guarantee an adequate control of post-treatment pain, with no need of antibiotic prophylaxis.

Reaction exothermia of 2 relining resins for temporary crowns

AIM

The aim of the study was to evaluate the reaction exothermia of 2 relining resins for temporary crowns. The resins used were Duralay, a methacrylate-based resin, and Protemp II, a bisacrylic resin.

METHODS

The coronal parts of an adult molar and of an impacted one were used. Abutments were obtained from the crowns, while the radicular part was sectioned in order to insert a thermocouple into the pulpal chamber. During the experiment the tooth with the polymerising resin was put into an oral cavity simulator to keep a constant temperature. The thermal increase during polymerisation of the 2 resins was recorded for 6 minutes at 5 seconds intervals and with 1 and 2.5 mm dentin thickness (n = 10). Data were statistically analysed by variance analysis with Scheffe test.

RESULTS

The intrapulpal thermal increase was significantly higher in relation to the type of resin (Duralay p < 0.0001), thickness (1 mm p < 0.0001) and type of dentin (young dentin p < 00001).

CONCLUSIONS

In order to protect the pulp, during the direct relining of a temporary crown, it is recommendable to choose the best combination among resin, type of dentin and its residual thickness, besides adequate cooling techniques.

[Actinomyces parotid infection after mandibular third molar extraction]

Actinomycosis is currently an uncommonly diagnosed human disease. The disease is a chronic suppurative infection caused by micro-organism from the Actinomyces group, most often Israelii. A patient with cervicofacial actinomycosis generally reports a history of recent dental treatment which, usually, involves extraction of a mandibular molar. The common initial signs and symptoms of infection (such as sudden onset of cervicofacial pain, swelling, erythema, edema and suppuration) can be absent. In this case report a 29-year-old man presented a mass in his left parotid area, 1 week after mandibular molar extraction. Echography and CT scans revealed a parotid abscess area. The needle-biopsy of swelling revealed infection due to Actinomyces. Therapy was started with intravenous cefazolin (fl 1g X 2 in 100 s.s. i.v.) and methylprednisolone (25 mg tablet, 1/die) for 9 days; 14 days after treatment suspension the lesion reappeared with a fistula and a new therapy was given (ceftriaxone 1 g/die and gentamicin 80 mg/i.m. for 3 weeks). To prevent a relapse, the patient received cefalexin 1 gx2/die per os for 4 weeks. After a follow-up of 1 year, the patient was still asymptomatic.

[Evaluation of colour differences in fiber post all-ceramic prosthetic restoration by spectrophotometry]

AIM

The aim of this study was to evaluate the influence of fiber post on all-ceramic prosthetic restorations, using the spectrophotometer Miniscan XE. Data were recorded according to the CIEL*a*b* system and the color difference (DE) was calculated.

METHODS

Carbon fiber Composipost (RTD) and quartz fiber Lightpost (RTD) posts were used. Square specimens (12x12 mm) were prepared using 9 #1 posts, covered with Z100 (3M) composite layers of different thickness (2, 3 and 4 mm) and color A3; 12x12 mm ceramic specimens (Finesse All Ceramic - 3M) of 2 and 3 mm thickness and color A3, were prepared using both opaque dentin and not.

RESULTS

With 2 and 3 mm thick ceramic layers, there was no color difference between carbon fiber specimens and quartz fiber specimens. Using the opaque dentin did not determine difference between groups.

CONCLUSION

In this study, according to results, a 3 mm thick ceramic layer always produced a DE<1, independently from the endodontic post. However, 2 mm thick ceramic layers were able to cover every kind of endodontic posts, even if with a DE=+/-1.6, and therefore are clinically acceptable.

Marginal microleakage in bonded amalgam restorations: a combined in vivo and in vitro study

PURPOSE

This study evaluated the marginal microleakage in bonded amalgam restorations in teeth extracted a month after restoration placement.

MATERIALS AND METHODS

Nine teeth in a patient scheduled for complete extraction were selected. In each tooth, a buccal prepared cavity was treated with Scotchbond Plus and filled with high copper amalgam. In four teeth, a lingual unlined restoration was also prepared as control. A month later, all the teeth were extracted; seven teeth were immersed for 48 hours in a 0.05% basic fucsine dye solution and then sectioned. Sections were observed with a stereomicroscope at 10X. Results were statistically evaluated using a nonparametric Mann-Whitney test for independent data. The remaining two teeth were sectioned and observed using a scanning electron microscope (SEM).

RESULTS

Stereomicroscopic analysis revealed that 80% of bonded specimens did not exhibit dye infiltration at the enamel margin; the same percentage of bonded specimens showed partial infiltration at the cervical margin. In the unlined control specimens, there was a complete dye infiltration at both margins. SEM analysis revealed a good adaptation between resin and tooth and between resin and amalgam.

CONCLUSION

Bonded amalgam restorations are effective in reducing marginal microleakage, particularly at the enamel margin.

Biocompatibility evaluation of dental metal alloys in vitro: expression of extracellular matrix molecules and its relationship to cell proliferation rates

The biocompatibility in vitro of dental biomaterials has been widely studied, with consideration of cell viability and cell proliferation rates. In the present study we evaluated the biocompatibility in vitro of three single-phase dental metal alloys, all provided by the same manufacturer. To this aim, we considered the percentage of proliferating cells revealed by 5-bromodeoxyuridine incorporation in human fibroblast cultures in the presence of these biomaterials, performing a short time test (72 h). These data were correlated with immunocytochemical expression of four molecules of the extracellular matrix, i.e., fibronectin, type I collagen, beta(1)-integrin subunit, and chondroitin sulfate, because the capability of cells to adhere to substrata is widely related to cell proliferation rates. Alloys presenting higher amounts of noble elements were more biocompatible even when they contained significant amount of both Ag and Cu. As regards the expression of the extracellular matrix molecules, the organization level of fibronectin in fibrils was correlated with higher cell proliferation rates, whereas no difference was detected for the expression of the other antigens. On these bases, we assume that expression of fibronectin could be a useful parameter in evaluation of biocompatibility in addition to cell proliferation capability.

Paresthesia of the mental nerve induced by periapical infection: a case report

Paresthesia can be a rare complication of infections of dental origin. This article presents a case of anesthesia/paresthesia caused by a periapical infection of the right mandibular second premolar. The sensory disturbance disappeared 2 weeks after conventional endodontic treatment associated with antibiotic therapy. Twelve months later, the tooth was still asymptomatic. The possible mechanisms responsible for paresthesia associated with periapical infection are discussed.

Cervical compomer restorations: the role of cavity etching in a 48-month clinical evaluation

Compomers are defined as polyacid-modified resin composites. They are supposed to combine the advantages of traditional glass-ionomer cements with resin composites. This study clinically evaluated a compomer in cervical cavities. Sixty cervical cavities in premolars and molars (24 with cervical caries and 36 with abrasions) randomly divided into two groups of 30 teeth (Group 1 and Group 2) were restored with Dyract (DeTrey-Dentsply, York, PA 17405-0872). The cavities of Group 2 were etched for 30 seconds with orthophosphoric acid before compomer application, while the Group 1 cavities received no treatment. All the restorations were evaluated every six months, up to 48 months: characteristics assessed according to USPHS-modified standards were retention, secondary caries, post-operative sensitivity, marginal adaptation and discoloration, color and wear. The Kaplan-Meier's survival analysis was performed. In both groups, retention was high without any statistically significant difference. No difference was found between the two groups for caries, post-operative sensitivity and wear--that all had a low incidence. Color was not perfectly matched, however, there was no statistically significant difference between the two groups. Marginal discoloration and marginal adaptation loss were significantly higher in non-etched group (p < 0.05). Clinically relevant failure required 17.2% of restorations in the non-etched group and 10% in the etched group to be replaced: this difference was not statistically significant. Dyract has an acceptable clinical behavior when used in cervical cavities. Its marginal adaptation is enhanced by etching.

[Enamel-dentinal adhesives in amalgam restorations. Review of the literature]

Amalgam is still the material most often used to restore posterior teeth, since it is easy to use, it has a low cost and a long clinical life. However, its use requires the solutions of several problems: lack of adhesion to tooth structure, marginal leakage, postoperative sensitivity and susceptibility to corrosion. In order to combine the advantages of dentinal adhesives with the excellent mechanical properties and good long clinical behaviour of amalgam, their use under amalgam restorations has been proposed. Adhesives improve marginal sealing and guarantee an additional retention to restorations, due to the formation of a layer linked with micromechanical bonds both to the tooth and the amalgam; they create a barrier that occludes dentinal tubules access, protecting the pulp. In this article the results of several in vitro studies performed to assess amalgam restorations properties are summarized. Present knowledge, based on an accurate literature review, allows to consider bonded amalgam restorations as a real progress in conservative dentistry: if long-term longitudinal studies, that are presently carried out, confirm the good short-term results, bonded restorations will represent the solution of choice for amalgam application.

Effectiveness of 1 mol L-1 citric acid and 15% EDTA irrigation on smear layer removal

AIM

The aim of this study was to evaluate in vitro the cleansing and smear layer removal capability of alternate canal irrigation with citric acid and NaOCl.

METHODOLOGY

Eighty-one teeth were divided into three groups on the basis of the type of instrumentation, namely, manual stainless steel, Ni-Ti mechanized ProFile .04 taper or MACXim. The groups were further divided on the basis of irrigation protocol: 5% NaOCl alone, NaOCl alternated with 1 mol L-1 citric acid solution or a combination of 15% EDTA and Cetrimide solution. After longitudinal sectioning, dentinal walls were microphotographed with scanning electron microscopy at x300 and x1000 magnifications. Qualitative and quantitative cleansing level evaluations were performed using computerized image analysis software. Data were statistically evaluated using Kruskal-Wallis analysis and t-test.

RESULTS

Qualitative evaluation at x300 and x1000 showed no statistically significant differences in cleansing ability between citric acid, EDTA and NaOCl groups. Quantitative evaluation of smear layer removal, measured as open tubules/total dentinal surface ratio, showed that 1 mol L-1 citric acid solution was comparable to EDTA (11.97% vs. 10.36%) (NS); in samples treated with ProFile .04 taper instruments citric acid was most effective (16.17%), whilst in the group treated with manual instrumentation EDTA and Cetrimide were the most effective (11.94%). Specimens irrigated with 5% NaOCl demonstrated significantly more cleansing than those obtained in the other two groups (P < 0.001).

CONCLUSIONS

1 mol L-1 citric acid solution was as effective in removing smear layer as EDTA, but was superior in specimens treated with ProFile .04 taper instruments.