K.-A. Hiller

Responses of L929 mouse fibroblasts, primary and immortalized bovine dental papilla-derived cell lines to dental resin components

OBJECTIVEnThe use of adequate target cells for cytotoxicity testing of dental restorative materials has often been experimentally assessed with respect to the clinical relevance of the test results. In the present study, the responses in primary bovine dental papilla-derived cells (pulp cells) were compared with those in transformed dental papilla-derived cell lines and L929 mouse fibroblasts after exposure to various dental resin compounds.nnnMETHODSnPrimary bovine dental papilla-derived cells (CPC), tCPC B (CPC cells transformed with SV40 T-antigen), tCPC E (CPC cells transformed with E6/E7 oncogen), and L929 mouse fibroblast cells were exposed to various compounds of dental resin materials for 24 h, and cytotoxicity was determined using the MTT assay. Bis-GMA, UDMA, 1,6 hexane diol dimethacrylate (HDDM), TEGDMA, HEMA, MMA, camphorquinone (CQ), bisphenol A (BPA), and glycidyl methacrylate (GMA) were tested. Concentrations leading to 50% cell survival (TC50 values) were calculated from fitted dose-response curves.nnnRESULTSnThe simple ranking of the cytotoxic effects of the dental resin compounds in the four cell types was identical, and TC50 values determined in L929 cells here were consistent with findings by other authors using continuous cell lines. However, the concentrations of the resin compounds necessary for eliciting cytotoxic responses in the various cells were clearly different. The analyses of TC50 values of the resin compounds revealed a linear correlation between cell lines, and the overall sensitivities increased as follows: CPC=tCPC B<tCPC E<L929.nnnSIGNIFICANCEnThe low sensitivities of primary cells and transformed tCPC B cells compared with the continuous L929 cell line and the transformed tCPC E cells indicates the presence of specific structural and functional properties relevant in vivo. The differences between the transformed tCPC B and tCPC E cells may indicate modifications of cellular functions caused by the different transformation processes.

FDI World Dental Federation - clinical criteria for the evaluation of direct and indirect restorations. Update and clinical examples.

In 2007, new clinical criteria were approved by the FDI World Dental Federation and simultaneously published in three dental journals. The criteria were categorized into three groups: esthetic parameters (four criteria), functional parameters (six criteria), and biological parameters (six criteria). Each criterion can be expressed with five scores, three for acceptable and two for non-acceptable (one for reparable and one for replacement). The criteria have been used in several clinical studies since 2007, and the resulting experience in their application has led to a requirement to modify some of the criteria and scores. The two major alterations involve staining and approximal contacts. As staining of the margins and the surface have different causes, both phenomena do not appear simultaneously. Thus, staining has been differentiated into marginal staining and surface staining. The approximal contact now appears under the name approximal anatomic form as the approximal contour is a specific, often non-esthetic issue that cannot be integrated into the criterion esthetic anatomical form. In 2008, a web-based training and calibration tool called e-calib (www.e-calib.info) was made available. Clinical investigators and other research workers can train and calibrate themselves interactively by assessing clinical cases of posterior restorations, which are presented as high quality pictures. Currently, about 300 clinical cases are included in the database which is regularly updated. Training for 8 of the 16 clinical criteria is available in the program: Surface luster; Staining (surface, margins); Color match and translucency; Esthetic anatomical form; Fracture of material and retention; Marginal adaptation; Recurrence of caries, erosion, abfraction; and Tooth integrity (enamel cracks, tooth fractures). Typical clinical cases are presented for each of these eight criteria and their corresponding five scores.

Curing efficiency of different polymerization methods through ceramic restorations

Abstract The aim of this in vitro study was to examine the curing efficiency of three different polymerization methods through ceramic restorations by determination of the depth of cure and the universal hardness of a composite resin luting material. Therefore, 36 ceramic specimens [Empress 2 (Ivoclar), color 300, diameter 4xa0mm, height 2xa0mm] were prepared and inserted in steel molds (diameter 4xa0mm, height 6xa0mm) using a composite resin luting material [Variolink II (Vivadent)] with and without catalyst. The polymerization through six specimens of each group was done conventionally (40xa0s), by softstart polymerization (40xa0s), or by plasma arc curing (10xa0s). Depth of cure under the ceramic specimens was assessed according to ISO 4049. Additionally, universal hardness was determined at 0.5 and 1.0xa0mm from the ceramic using a universal testing machine (Zwick 14040). Curing without a catalyst, using conventional and softstart polymerization, resulted in greater hardness in both layers, compared to plasma arc curing. The use of a catalyst always produced a greater hardness and depth of cure with all polymerization methods. Depth of cure was always greater using conventional polymerization and softstart polymerization, compared to plasma arc curing. The curing efficiency of plasma arc curing through ceramic was lower compared to conventional and softstart-polymerization.

Patients with local adverse effects from dental alloys: frequency, complaints, symptoms, allergy

Abstract. Data on the prevalence of adverse effects from dental cast alloys and on the characteristics of the related patient groups are scarce. Therefore, the aim of the present study was to investigate patients in a defined part of Germany attributing oral complaints or symptoms to dental cast alloys. All dentists in the area of Eastern Bavaria (with 1xa0million inhabitants) were asked to send corresponding patients to our department during a 3-year period. Out of this collection, patients with complaints or symptoms in the oral cavity were recruited and characterized with regard to number, age and sex distribution, type of subjective complaints and objective intraoral symptoms, and allergy status based on an alloy analysis. Patients reporting to our department with suspected local adverse effects from dental cast alloys represented 0.01% of the population. Thirty-four percent of the patients were 50–59xa0years old, with females prevailing (76%). A great variety of subjective complaints was reported, which mainly resembles those reported by patients with adverse effects attributed to other dental materials like amalgam or denture base materials. The main objective intraoral symptoms were gingivitis, anomalies of the tongue (lingua plicata, lingua geographica), discoloration of the gingiva, redness of the palate or tongue and lichenoid reactions of the oral mucosa. In not more than 10% of the patients, allergy was diagnosed as contributing to the complaints or symptoms.

Retrospective clinical study and survival analysis on partial ceramic crowns: results up to 7 years.

Abstractu2002The purpose of the present study was to de-termine retrospectively the clinical performance of 42 all-ceramic partial crowns (PCCs) placed during the past 7 years. All patients (n=25) with partial ceramic crowns (n=49) placed by one experienced dentist between 1992 and 1999 were asked to take part in a clinical study, and 22 patients with 42 restorations agreed to do so. All partial ceramic crowns studied were fabricated using the IPS-Empress I all-ceramic system (Vivadent). The following luting composites were used for placing the restorations: 20 (47.6%) Variolink high viscosity (Vivadent), 3 (7.1%) Variolink ultra (Vivadent), 17 (40.5%) Dual Zement (Vivadent), and 2 (4.8%) Compolute (Espe). The partial ceramic crowns were examined clinically using the modified USPHS criteria. Of the 42 restorations, 40 (95.2%) were still in function without any need of replacement. One restoration (2.4%) had failed before starting the clinical study, and another one (2.4%) fractured during the study. Twenty-eight (66.7%) of the partial ceramic crowns evaluated were rated Alpha with respect to marginal adaptation. Twelve (28.6%) restorations were rated Bravo, no Charlie ratings were found and 2 (4.7%) restorations were rated Delta. The Kaplan-Meier analysis was used to calculate the survival rate. The probability of survival (95% confidence interval) for 7 years was 81% (66–96%). These data indicate that partial ceramic crowns may provide successful esthetic restorations in posterior teeth.

Metal content of saliva of patients with and without metal restorations.

Many in vitro studies have confirmed the corrosion of dental alloys. However, in vivo corrosion studies, for example, recording of the release of metal ions into saliva, are scarce, and data on the repeatability of the metal content measurements of saliva are lacking. The present study examined the metal content of saliva of patients with and without metal restorations and assessed the repeatability of these data. The composition of each patient’s oral cast alloys was analyzed using the energy-dispersive X-ray analysis of metal biopsy specimens and was compared to the metals found in saliva. Saliva analysis was performed using atomic absorption spectroscopy. Chemical analysis comprised the metals Ag, Au, Co, Cr, Cu, Fe, Ga, In, Ni, Pd, Pt, Sn, and Zn. The metals Ag, Cr, Cu, Fe, Ni, and Zn were found in saliva of patients without metal restorations, but these data showed statistically significant differences in the metal content between consecutively performed samples per patient. The metals Ag, Au, Cr, Cu, Fe, Ni, and Zn were identified in saliva of patients with metal restorations being higher in concentration than in control patients. In 77% of the cases at least one metal of the restoration was found in the patient’s saliva. However, the metal content showed statistically significant differences between replicate samples of the same patient taken at different times. The metal content of saliva is affected among other things by intraoral metal restorations, but present data do not support the idea that it is a reliable indicator for the systemic exposure to metals released from dental alloys.

Long-term clinical performance and longevity of gold alloy vs ceramic partial crowns

Cast gold partial crowns (CGPC) are an accepted means of restoring posterior teeth. For aesthetic reasons, gold alloys are being increasingly substituted with ceramics. The aim of the present study was to investigate retrospectively the long-term clinical performance and survival of CGPC and compare the results to the ones already reported for ceramic partial crowns (CPC). The CGPC group consisted of 42 patients (24 male, 18 female) randomly sampled from a total of 106 patients with CGPC, with one restoration per patient. The CPC group consisted of 22 patients with a total of 42 restorations. Both types of restoration were done by one experienced dentist. Another two experienced dentists who were not involved in performing the restorations rated both kinds of partial crowns using the modified United State Public Health Service (USPHS) criteria [14]. The Median age of the CGPC was 57xa0months (range 3–157) and of the CPC and 63xa0months (range 24–72). Forty-one (98%) of the CGPC and 27 (64%) of the CPC were placed in molars, the rest in premolars. In each group, 40 (95%) restorations were still functioning without any necessity of replacement. Two teeth with CGPC, in situ for 4.5 and 11xa0years, respectively, had been extracted for periodontal reasons. Two CPC fractured and had to be replaced after 2 and 6.5xa0years in situ. The USPHS criteria results were similarly good for the gold and ceramic groups. Kaplan-Meier analysis revealed survival probabilities of 72±21% and 96±4% after 13 and 7xa0years, respectively, for the CGPC. Survival of the CPC was 81±15% after 7xa0years. No statistically significant difference among survival functions of CGPC and CPC was found. From this data, it can be concluded that the longevity of CPC is not inferior to that of gold alloys. However, more long-term studies comparing the clinical performance and longevity of these two types of indirect restoration in the posterior region with larger numbers of restorations are desirable.

Partial ceramic crowns. Influence of preparation design and luting material on margin integrity—a scanning electron microscopic study

This in vitro study examines the effects of three preparation designs and different luting agents on the marginal integrity of partial ceramic crowns. One hundred forty-four extracted human molars were prepared according to the following preparation designs: A. Coverage of functional cusps, B. Horizontal reduction of functional cusps and C. Complete reduction of functional cusps. Partial ceramic crowns (Vita Mark II, Cerec 3 System) were bonded to the cavities with: Variolink II/Excite (Vivadent), Panavia F/ED primer (Kuraray), Dyract/Prime and Bond NT (Detrey/Dentsply), and Fuji Plus/GC cavity conditioner (GC). The specimens were exposed to thermocycling and mechanical loading. Marginal adaptation was assessed on replicas using quantitative margin analysis in the scanning electron microscope (SEM). Significant differences were observed between the preparation designs in general. Coverage of functional cusps with preparation of butt joints and use of Variolink as luting material showed a tendency toward the lowest values for compromised adhesion, especially within the dentin. Significant differences could be determined between luting systems: resin-modified glass ionomer cement (RMGIC) caused fracture of the restorations and revealed higher values than all other luting materials for compromised adhesion at ceramic-luting agent and tooth-luting agent interfaces. The dentin-luting material interface, in general, showed higher percentages of compromised adhesion (38–100%) than enamel- and ceramic-luting material interfaces (0–30%). In conclusion, the SEM data indicate that, with adhesively bonded partial ceramic crowns, retentive preparation is not contraindicated and the choice of luting material is more relevant than the preparation design. Margins below the cemento-enamel junction reveal significant loss of adhesion in spite of adhesive luting techniques. The RMGIC cannot be recommended as a luting material for feldspathic partial ceramic crowns.

The influence of Ni(II) on surface antigen expression in murine macrophages.

Biomedical alloys may release nickel ions during corrosion phenomena and, in addition to their interaction with oral tissues, these ions may also influence characteristic properties of the immune system cells. The aim of this study was to evaluate the effect of nickel chloride on the expression of functionally distinct surface antigens in murine RAW macrophages. The expression of the surface antigens CD14, CD40, MHC class I, MHC class II, CD80, CD86, CD54 was analyzed by flow cytometry. The bacterial endotoxin lipopolysaccharide (LPS) was used as a positive control to induce antigen expression. Cells were stimulated with NiCl(2) (0.1 and 0.5mm) in the presence and absence of LPS (0.1 or 25 microg/ml). After exposure periods of 6, 24 and 48 h, LPS caused a time- and dose-dependent increase in the expression of all surface antigens. CD14 expression was up-regulated by 0.1 microg/ml LPS by about 10-fold after 24h and 100-fold after 48 h. After 48 h, NiCl(2) alone up-regulated the expression of all surface antigens between 2- and 4-fold, while in cells stimulated by LPS, 0.1mm NiCl(2) was effective only on CD14, CD40 and MHC class I. Moreover, 0.5mm NiCl(2) even inhibited the LPS-induced expression of all surface antigens, except for CD54, which was still significantly up-regulated. These results show that nickel chloride is able to induce an up-regulation of surface antigen expression, but a high concentration may impair essential functions of macrophages stimulated by LPS.

Postoperative exposure of bioresorbable GTR membranes: effect on healing results

Abstract The goal of this investigation was to evaluate the effect of postoperative exposure of two different bioresorbable membranes on the guided tissue regeneration (GTR) healing results compared to nonexposed sites. In each of 25 patients one pair of contralateral intrabony lesions was treated either with polylactic acid (PLA) or polyglactin 910 (PG-910) membranes. Postoperative exposure occurred in 9 PLA and 13 PG-910 sites. Standardized clinical [papillary bleeding index (PBI), gingival recession (REC), probing pocket depth (PPD), probing attachment level (PAL)] and radiographic examinations (digital subtraction radiography) were performed immediately before (baseline) and 6 and 12 months postoperatively (p.o.). Subgingival bacterial samples from surgical sites were evaluated by culture at baseline, 6 weeks, and 6 and 12 months p.o. Six months after surgery the changes (Δ) of REC were significantly (P≤0.05) greater in exposed than in nonexposed sites, independently of the membrane material (median): exposed sites, ΔREC=–1 mm; nonexposed sites, ΔREC=0.0 mm. However, 12 months p.o. no significant differences were found due to a decrease in the initial recessions in exposed sites. Although a higher percentage of exposed than nonexposed sites harbored periodontal pathogens 6 weeks p.o. at the gingiva-faced membrane surface, membrane exposure did not have a significant negative effect on ΔPPD, ΔPAL, or radiographic bone density changes 6 and 12 months p.o. Both membranes showed significant gains in PAL and bone density in both exposed and nonexposed sites. In conclusion, this study demonstrates that with consistent infection control the postoperative exposure of PLA and PG-910 membranes has no significant negative effect on the regeneration outcome, although higher initial gingival recessions must be expected than in the nonexposed sites. However, in exposed sites plaque and infection control were clearly impeded by the rough, exposed membrane surfaces and by the initially negative gingival morphology.