Effect of Aging on the Microstructure and Optical Properties of Translucent ZrO 2 Ceramics

Objectives

The development and placement of translucent zirconia ceramics on the dental materials market is in full swing. This research aimed to investigate how aging protocols affect the microstructure, color parameters and translucency of a new-generation monolithic zirconia ceramic.

Material and methods

Translucent zirconia ceramics KATANA-Zirconia STML with different surface treatments (as sintered - control, glazed, polished) was tested using two aging protocols (hydrothermal degradation in autoclave at 134 °C and 2 bars for three hours, chemical degradation in four-percent acetic acid at 80 °C for 16 hours) in order to examine phase composition using X-ray diffraction analysis and ΔE, ΔL and ΔC color parameters through spectrophotometry. The translucency parameter (TP) was calculated using parameters L*, a* and b* on a black and white surface.

Results

Regardless of the surface treatment, aging protocols did not cause a tetragonal-to-monoclinic phase transformation, although hydrothermal degradation in the autoclave transformed the hybrid tetragonal-cubic structure of all specimens to a tetragonal one. All polished and glazed specimens during chemical degradation demonstrated a significant color change ΔE. Lightness ΔL significantly changed in polished specimens aged in the autoclave. In all specimens, ΔC underwent a change manifested through statistically insignificant yellowing. None of the aging protocols altered the translucency of specimens.

Conclusions

Aging, regardless of the final surface treatment, did not manifest a monoclinic phase in the specimens. A tetragonal-cubic microstructure dominates. Unlike polishing, glazing the surface of translucent zirconia ceramics contributed to minor changes in color, lightness and chromaticity. The translucency of translucent zirconia ceramics remains stable regardless of aging and surface treatment.

The Effect of Aging on Composition and Surface of Translucent Zirconia Ceramic

Objectives

To examine the effect of two aging protocols on the chemical and phase composition as well as the surface state of monolithic translucent zirconia ceramics.

Material and Methods

Translucent zirconia ceramics KATANA-Zirconia STML with different surface treatments (no treatment, K1, K2; glazed, G1-G8; polished, P1-P8) underwent testing in order to examine how the two aging protocols (three-hour hydrothermal degradation in an autoclave at 134 °C and 2 bars: G1-G4, P1-P4, and sixteen-hour chemical degradation in four-percent acetic acid at 80 °C (ISO 6872): G5-G8, P5-P8) affect chemical composition, particularly the share of stabilizing yttrium oxide (Energy Dispersive X-Ray Fluorescence – EDXRF), phase composition (X-ray diffraction – XRD) and surface state in terms of roughness and gloss.

Results

Aging protocols did not affect the tested chemical composition stability of specimens and a high share of stabilizing yttrium-oxide (≥10% of total content), which correlates with the absence of monoclinic phase. A decrease in gloss on all specimens is statistically significant. Chemical degradation substantially increased the surface roughness of tested specimens.

Conclusions

Translucent monolithic zirconia demonstrated a stable chemical composition and resistance to tetragonal-to-monoclinic transformation. Surface gloss was significantly reduced, especially in polished specimens. Contrary to glazed specimens, the tested polished specimens manifested an increase in surface roughness. Glazing the surface of translucent monolithic zirconia produces better esthetic, tribological and hygienic effects than polishing.

Analysis of Translucency Parameter of Glass-Ceramics Fabricated by Different Techniques

THE PURPOSE

of the study was to analyse translucency parameter (TP values) of glass-ceramics fabricated by different techniques and investigate the effect of the corrosive medium on TP values.

MATERIALS AND METHODS

Three specimens of each type of IPS e.max ceramics (Ivoclar Vivadent, Schaan, Liechtenstein) were made in three colours (A2, C2 and B3) by three fabrication techniques (layering - e.max Ceram Dentin; heat-pressing - e.max Press; CAD/CAM - e.max CAD). Specimens were made in the form of plates (10 mm x 12 mm x 0.8 mm). CIE L*a*b* values were measured by a spectrophotometer (X-Rite DTP 20 Pulse, Neu Isenburg, Germany) before and after exposure to 4% acetic acid at 80 °C for 16 hours (ISO 6872) to calculate translucency parameter (TP values). Statistical data were analysed using the IBM SPSS 22 software.

RESULTS

IPS e.max Ceram Dentin had significantly the lowest TP values, and IPS e.max Press the highest TP values of all colours (A2, C2, B3), both prior and after exposure to acid (p<0.001). The difference in TP values among colours was evident in the IPS e.max Ceram Dentin material, both before and after exposure to acid with a great effect size (p<0.001; η2 = 0.702 and 0.741), and in the IPS e.max Press material (p<0.001, effect size 0.547 and 0.576). CAD/CAD specimens showed uniform TP values between three colours. Further, exposure to a corrosive medium did not result in a statistically significant change of TP values in any of the materials tested.

CONCLUSIONS

Different types of glass-ceramics showed significant difference in TP values both with respect to the fabrication technique and colour. Exposure to a corrosive medium did not result in a statistically significant change of TP values.

Prosthetic modalities used to treat cleft palate patients in a university clinic: a 10-year review

Cleft palate patients are not usually seen in general dental clinics, but this congenital anomaly is one of the most frequent of cases. General dental practitioners are usually unwilling or/and not sufficiently trained to treat such patients for whom rehabilitation and interdisciplinary cooperation is often needed. The aim of this study was to determine the incidence of prosthetic modalities most frequently used by licensed prosthodontists for prosthetic rehabilitation of cleft palate patients. Participants in this study were 56 cleft palate patients (aged 23-66 years) who received prosthetic treatment between 2000 and 2010. Patients' dental status and prosthetic modalities used were noted from patient records archived at Department of Prosthodontics, School of Dental Medicine, University of Zagreb. Data analyses revealed that combined prosthetic constructions (fixed + removable, p < 0.05) were the most frequently used. In a group of molar teeth, the most frequent fixed prosthetic modalities were crowns with rests; in a group of premolar teeth, telescopic crowns; on canines, metal ceramic crowns and telescopic crowns; and in a group of incisors, metal ceramic pontics (p < 0.05). Understanding the distribution of prosthetic modalities for cleft palate patients could serve to guide dental practitioners towards planning adequate prosthetic treatment for their patients since only a well-planned prosthetic therapy will result in satisfactory function and alleviation of the deformities.

Factors related to oral health related quality of life in TMD patients

The aims of the study were to determine the impact of temporomandibular disorders (TMD) on self-percieved oral health related quality of life (OHRQoL) and to compare OHRQoL of patients with TMD with a control group. A total of 81 TMD patients participated in a study group and 400 adults served as the control group. The mean OHIP summary scores were computed for all patients with the same diagnosis and the same subgroup of axis I according to the RDC/TMD exam form. The mean OHIP subscores for all seven domains of the OHIP questionnaire were compared between the study and the control group. The hierarchical linear regression model was used to assess the most important variables according to the RDC/TMD protocol that contribute to OHRQoL in TMD patients with the OHIP summary score as dependent variable. According to this study, TMD had a high association with reduced OHRQoL (p < 0.001). More diagnoses of axis I according to the RDC/TMD protocol (p < 0.001), higher age of TMD patients (p < 0.001) and diagnoses associated with limited jaw movements contributed to more impaired OHRQoL (p = 0.008 and p = 0.030, respectively). Female TMD patients had no significantly different OHRQoL compared to male patients (p = 0.436). According to regression analysis, higher age (p < 0.001), more physical diagnoses (p = 0.018) and diagnosis Ib (p = 0.169) explained 39.1% of the variability (p < 0.001) of the OHIP summary score in TMD patients.

Shear bond strength in zirconia veneered ceramics using two different surface treatments prior veneering

Aim of the study was to assess the effect of different surface treatments on the shear bond strength (SBS) of the veneering ceramics to zirconia core. In a shear test the influence of grinding and sandblasting of the zirconia surface on bonding were assessed. Statistical analysis was performed using SPSS statistical package (version 17.0, SPSS Inc., Chicago, IL, USA) and Microsoft Office Excel 2003 (Microsoft, Seattle, WA, USA). There was a significant difference between the groups considering shear bond strength (SBS) values, i.e. ground and sandblasted samples had significantly higher SBS values than only ground samples (mean difference = -190.67; df = 10, t = -6.386, p < 0.001). The results of the present study indicate that ground and sandblasted cores are superior to ground cores, allowing significantly higher surface roughness and significantly higher shear bond strength between the core and the veneering material.

Denture relining as an indicator of residual ridge resorption

AIM

Residual ridges change in shape and reduce in size due to alveolar bone resorption. Therefore, the purpose was to investigate changes in denture base thickness (DBT) and interocclusal rest space (IRS) with regard to the denture relining procedure.

METHODS

The IRS and DBT were measured (before and after denture relining) in the case of 74 patients and their removable dental prostheses by using a precise sliding gauge. The DBT measuring was performed in 6 points for maxillary and in 3 points for mandibular removable dental prosthesis. The IRS values were measured as the distance (in mm) between the incisal edges of the maxillary and mandibular central incisors with patient's mandible in a physiological "rest position" with head and neck in the upright posture.

RESULTS

In a group of patients wearing maxillary and mandibular removable dental prosthesis mean values of DBT after denture relining were statistically significantly higher (p <0.05) in almost all measuring points. The IRS mean values after relining were statistically significantly lower (p <0.05). Statistically significant differences (p <0.05) of DBT were also observed in groups of "day-night time" and "day time" denture wearers, and in a group of patients for whom a period shorter than one year had passed since the last tooth extraction and the time when a functional impression for removable dental prostheses was taken.

CONCLUSION

The DBT and IRS values change after the denture relining procedure due to the alveolar bone resorption. Therefore, these measures could be used as resorption indicators in dental practice.

Patient's satisfaction with removable dentures after relining

AIM

To reveal patients' satisfaction with their old, usually poorly fitting dentures and the effect of denture relining to the patient's satisfaction.

METHODS

Thirty seven denture wearers participated in study by filling out questionnaires about their satisfaction with dentures before and after relining. In that way the data indicating the subjective patient's experience and satisfaction were collected.

RESULTS

Relined removable dentures included in study were on average 5.52 years (upper) or 4.86 years old (lower). Most of study participants (57%) were satisfied with their poor fitting dentures. Statistically significant was correlation between chewing discomfort and satisfaction, and the time elapsed from last tooth extraction to denture production. As this period was shorter, chewing discomfort was greater and satisfaction with chewing lower. Majority (53.3%) of denture wearers were considerably more satisfied with the chewing ability and felt better regarding the chewing discomfort after denture relining. Minority of the patients (22%) still used an adhesive for fixing the dentures after relining.

CONCLUSION

Denture relining affects patient's satisfaction with their dentures. After relining patient's masticatory function was improved, satisfaction with chewing ability and comfort were greater, and denture hygiene better. Denture relining should be performed in order to improve denture fitting to a denture bearing area, thus positively affecting patient's satisfaction with his denture(s).

Prosthetic rehabilitation of a patient with mandibular resection prosthesis using mini dental implants (MDIs)--case report

Physical disfigurement and functional impairments associated with facial trauma are a challenge to a prosthodontist, because even novel sophisticated surgical reconstructive techniques fail to provide adequate support for dental resection prosthesis. Therefore, different endosseous implants are often used as prosthesis-supporting elements. Manufacturers of dental implants have recently presented mini dental implants (MDIs) with diameter of only 1.8-2.4 mm. These implants allow very suitable prosthetic solutions within the range of their indications due to good osseointegration success rates, simple surgical technique, and immediate loading possibility. In this report, a case was presented for prosthetic rehabilitation including implantation of two Sendax type (IMTEC, Ardmore, Oklahoma, USA) MDIs in mental region, to obtain better retention and stability of the mandibular resection prosthesis and to improve function, phonation and aesthetics. The use of these implants, among aforementioned preferences, is also very cost-effective, so this implantation possibility should be taken into consideration during prosthetic treatment planning.

Oral hygiene and gingival health in patients with fixed prosthodontic appliances--a 12-month follow-up

The aim of this study was to assess and observe the oral hygiene and gingival condition in patients before and after fixed prosthodontic therapy through a 12-month period in combination with oral hygiene instructions. It was also analysed how factors, such as type of fixed prosthodontic appliance, constructive material, the position of a fixed partial denture (FPD) in the mouth, age and gender influenced oral hygiene. The dental arches were divided into three segments each and teeth and gingiva were examined using the Plaque and Gingiva Index by Silness and Löe, and for the mineralized deposits assessment the Calculus Index by Green and Vermillion was employed. The preliminary examination was conducted before the prosthodontic therapy, and the reexaminations were carried out 14 days, 1, 6 and 12 months after crown and/or FPD placement. A total of 93 subjects from the original study group of 146 patients attended all clinical examinations, while the rest was excluded. The sample consisted of 60 women, 33 men at age between 21 and 95 (average 51.8). A total of 39 patients had single crowns (C), 50 FPDs and 5 C+FPD. The frequency of plaque found during the preliminary visit was higher than that found in the other periods (p < 0.001). Patients with C showed better oral hygiene levels than patients with FPDs or C+FPDs (p = 0.001). Our results revealed no significant difference in oral hygiene status among patients with FPDs made of different materials (p = 0.083). The worst hygiene levels were found in patients with fixed prosthodontic appliances in both jaws (p = 0.012). Younger patients showed better hygiene levels than the older ones (p = 0.002). Our research showed that appropriate educational and motivational measures can lead to improved oral hygiene, even after FPD placement. Presumably, the oral health in a group of adult patients can be kept acceptable by providing a prophylactic oral hygiene program.

Effect of LGG yoghurt on Streptococcus mutans and Lactobacillus spp. salivary counts in children

The aim of this study was to establish effect of 14 day consumption of commercially available yoghurt containing Lactobacillus rhamnosus ATCC53103 - LGG (Bioaktiv LGG, Dukat, Croatia) on Streptococcus mutans and Lactobacillus spp. salivary counts in children. Twenty five patients, 6-10 yr old participated in the study. At the inclusion in the study caries risk for every patient was evaluated. The saliva samples were tested with chair side kits for saliva buffer capacity (CRT buffer, Vivadent, Schaan, Liechtenstein), S. Mutans and Lactobacillus counts (CRT bacteria test, Vivadent, Schaan, Liechtenstein). Seven, 14 and 30d after yoghurt consumption saliva samples were tested again with CRT buffer and CRT bacteria tests. Obtained data were analyzed using chi2 and Kruskal-Wallis tests. Results showed significant increase in saliva buffer capacity 30d after yoghurt consumption. S. Mutans salivary counts were significantly decreased after 30d. Significant differences in Lactobacillus counts were not observed. It could be concluded that daily consumption of yoghurt containing LGG have an inhibitory effect on oral pathogenic bacteria and may be beneficial in caries prevention.

Changing pattern of sensitization in Croatia to aeroallergens in adult population referring to allergy clinic during a period of 15 years

Published data indicate that during the last decades there is a possible change in the pattern of sensitization to different aeroallergens in adult population with atopy. The aim of this investigation was based on the hypothesis that during last 15 years there has been a change in the structure of prevalence of sensitization to different aeroallergens in adult population of Zagreb and its surroundings with atopy. Medical records from outpatient allergy clinic were screened for the period 1991-2004. We included 794 patients during years 1991-1994, 814 patients during years 1995-1999, and 969 patients during years 2000-2004. Following data were analyzed: age, gender, education level, residence, referral diagnosis, dominant symptoms, results of skin-prick test (SPT), total and specific serum immunoglobulin E. As risk factors for allergic sensitization we determined the decade of birth (p < 0.0001), male gender (p < 0.008), level of education (p < 0.0001), and place of residence (p < 0.05). Proportion of sensitized individuals to pollen significantly increased from the period 1991-1994 towards 2000-2004 (p < 0.001 for the trend) with a significant increase in the proportion of sensitized individuals to weed pollen (p = 0.002 for the trend) while the proportion of sensitized to other two groups of pollen (grasses and trees) was not significantly different. A significant increase in the proportion of sensitized individuals was determined for sensitization to ragweed pollen (p = 0.004 for the trend), and to mugwort (p = 0.005 for the trend). Despite all its limitations primarily based on the selection bias the results of this study are conclusive about the significant change in the proportion of sensitization to different aeroallergens and different pollen groups and individual pollen species during the investigated 15-year time interval.

Immediate implantation in infected tooth sockets

Although immediate implantation has not been previously recommended in infected sites, it is now becoming a procedure of choice in modern implant dentistry. We report a case of a 65-year-old male patient, who required multiple tooth extractions in the lower jaw and fabrication of a new overdenture in the lower jaw and a complete denture in the upper jaw. Immediate implantation in infected tooth sockets followed extraction. Two NobelReplace Tapered implants (Nobel BioCare, Zürich, Switzerland), one 13 mm long and 4.3 mm wide and the other 13 mm long and 5.0 mm wide, were placed in the position 33 and 43. The site was sutured and a temporary denture was fabricated by adjusting the old denture. After a period of three months the implant site was reopened and healing abutments were placed. Impressions were made using the Impregum Penta Soft (3M ESPE, St. Paul, Minn, USA) polyether material. Ball Abutment Titanium" was used as a patrix attachment and a matrix was inserted into the denture. Clinical examination and x-ray analysis after six months showed no significant changes of the implants. Bone resorption was within standard values. Although it is still a controversial subject, immediate implantation in infected sites can be a safe and predictable procedure if surgical protocols are followed. However, further research is needed to draw firm conclusions.

Decreasing of residual alveolar ridge height in complete denture wearers. A five year follow up study

The resorption of the residual alveolar ridges is a chronic and continuous process of bone remodeling. The aim of this study was to analyse the rate of residual ridge resorption at different sites in the both jaws in complete denture wearers, through a five-year period of denture wearing. Residual ridge changes were measured on successive lateral cephalograms at 5 measurement points of the maxilla and the mandible. The first lateral radiograph was obtained at the delivery of complete dentures. The second lateral cephalogram was obtained after five years of denture wearing. Measurements were performed using a calibrated grid. The results of this study showed the existence of a significant alveolar ridge resorption at all five measurement points of the maxilla and the mandible. The observed variables, such as body mass index and the night time denture wearing had no significant influence on the rate of residual alveolar ridge resorption (p > 0.05). The duration of edentulousness had a significant influence on the rate of residual ridge resorption with significantly higher amounts of alveolar bone height decrease in those patients who had lost the last remaining teeth more recently.

A study of the surface topography and roughness of glazed and unglazed feldspathic ceramics

The aim of this study was to obtain the 3-D qualitative and quantitative nanoscale data of the surface topography and surface roughness of glazed and unglazed feldspathic ceramics. Twelve samples composed of Ni-Cr alloy (Wiron 99, Bego Germany) and feldspathic ceramics (IPS Classic, Ivoclar-Vivadent, Schaan, Liechtenstein) were prepared, and divided into two groups, dependent of the surface final finishing; 6 unglazed and 6 glazed samples. The surface of the samples was recorded and analysed by atomic force microscopy (AFM, Veeco Instruments, Santa Barbara, CA, U.S.A.). According to the results of this study, unglazed ceramic surface is significantly rougher than the glazed one, showing significantly higher root mean square (RMS), mean roughness (Ra) and maximum height (Z range values) (p < 0.01), higher crystallites with sharper peaks and deeper pores. The roughness parameters of the unglazed samples were almost twice or even more higher than of the glazed samples. Exposed unglazed ceramic surfaces can therefore promote antagonistic tooth wear.

Optoelectronic pantography diagnostics of temporomandibular disorders in patients with bruxism

Temporomandibular disorders (TMD) is a joint term that encompasses a number of clinical symptoms that involve the teeth, masticatory musculature and temporomandibular joints (TMJ). They are a frequent cause of orofacial medical conditions. The aetiology of disorders is complex and individual etiologic factors are not sufficiently defined. Bruxism, in its centric or eccentric form, is becoming a frequent problem for dentists. The purpose of this study is to show factors of the condyle leading in patients with bruxism by optoelectronic pantography, and to establish the possibility of using optoelectronic pantography in the diagnostic procedure of TMD. Patients were selected (N = 42), with incomplete sets of teeth, without prosthodontic appliances and with traces and symptoms of TMD. After completing the history questionnaire a clinical check up and plaster cast analysis patients with bruxism were selected (N = 22) and without bruxism (N = 20). During the study optoelectronic String-condylocomp LR3, Dentron, D-Höchberg (software JAWS 30) was used. This study showed the possibility of applying optoelectronic pantography in TMD diagnostics and compares history, clinical and condylographic parameters in TMD patients with and without bruxism. Optoelectronic pantography enables us, by using relatively easy methods, to determine a more accurate diagnosis, highly important when choosing therapeutic methods and control of the aforementioned disorders.

Metal-ceramic bond: how to improve?

Metal-ceramic restorations include the positive features of metal (strength, durability and stability) and ceramics (esthetics). The strong bond on the metal-ceramic interface is the basic prerequisite for the durability of the metal-ceramic restoration. The heating of metal construction results in the diffusion of certain atoms (tracers) on the surface. There they react with atmospheric oxygen creating in oxides which remain on the cast surface, because the reversible diffusion is prevented. Atoms of silica in ceramic are bound with these oxides as a result of which a metal-tracer-ceramic compound is formed and a chemical bond is realised. In addition to forming an oxide layer, the oxidation heat treatment (OHT) is applied for all alloys in order to remove the entrapped gas and eliminate surface contaminants. Surface metal preparation before porcelain application may also affect the bond strength of metal and ceramics. Roughened surface by sandblasting enables mechanical interlocking and an increased surface for bonding metal and ceramics. Applying a bonding agent may improve the quality of the bond of certain metal-ceramic restorations. Due to the continued oxidation of titanium and creation of a non-adherent oxide layer, the bond strength between titanium and ceramics is weak, which is attempted to be resolved by firing in an argon atmosphere.

Failures in fabrication and treatment using ceramic crowns

Dental ceramics is a constituent prosthodontic material with excellent aesthetic properties. It is stable, does not change shape, color or size, and is biotolerant. Treatment with ceramic restorations is a standard procedure in modern fixed prosthodontics. Because of its multiphase structure and the thermal processes it undergoes during the making of a fixed prosthodontic replacement, ceramics is highly sensitive to small failures in fabrication. These failures can develop into cracks that can ultimately cause fracture of restorations in use. This is why each phase of restoration in a dental practice and a dental laboratory requires professional skill. Selection of a definite ceramic system for a specific clinical case is more important than with other constituent materials. Patient selection, oral hygiene, masticatory force, as well as proper maintenance of instruments and devices for the fabrication of ceramic replacements are all important.

Selection of appropriate artificial frontal teeth size using dimensions of hard palate

Eighty dentate students participated as a study group and another 74 as a control group. The aim was to determine a possibility to reconstruct maxillary frontal teeth dimensions by use of certain hard palate dimensions. The height (IH) and the incisal (IW), contact point (CtW) and cervical width (CW) of maxillary central incisors (MCI), hamular width (HW) and the distance between the incisive papilla and the palatine foveas (IP-FP) were measured on the maxillary casts. CtW of maxillary lateral incisors and canines were measured too. In the study group the ratios were computed: HW/IW (5.71), HW/CtW (5.69), HW/CW (5.51) and IP-FP/IH (4.76). These ratios were multiplied by incisor's dimensions (obtained from the control group) to calculate the hard palate dimensions. No significant differences were obtained between the calculated and the measured (study group) hard palate dimensions. Furthermore, there was no significant difference between the HW and the Sum of contact-point widths of all maxillary frontal teeth (p > 0.05) in the both groups. The results revealed: 1. MCI width and height might be calculated by dividing dimensions of a patient's hard palate and appropriate ratio; 2. hamular width dimension can be used as a selection guide for the sum of contact-point widths of six maxillary frontal teeth.

Expression of contact allergy in undergoing prosthodontic therapy patients with oral diseases

AIM

Contact allergy is a postponed reaction of hypersensitivity where a localised cutaneous or mucosal lesion occurs due to a recurrent contact with an allergen. Placement of a fixed or removable prosthetic replacement into the oral cavity causes corrosive processes on the surface of the restoration and discharge of ions, which as haptens can induce allergic reactions. The purpose of this study was to examine occurrence of allergies to basic and auxiliary restorative dental materials in patients with lichen, stomatitis and stomatopyrosis by means of an epicutaneous allergy test.

METHODS

The study included 32 patients with a fixed and/or removable replacement and 7 patients with one of the mentioned diagnoses, but without any replacement. Testing was conducted using a standard method (patch test), and hypersensitivity to 13 most common allergens in prosthodontics was examined.

RESULTS

The research results revealed higher frequency of positive allergic reactions in persons with the mentioned diseases and with a restoration. Patients with lichen indicated positive patch test in the majority of cases. The allergens of nickel, cobalt and chromium demonstrated the highest score of positive results, and negative score was found for dibutylphthalate and HH mix. Stomatopyrosis was more common in persons with hypersensitivity to chromium. A lower incidence of positive allergic reactions to epoxide resins was found in female than in male subjects.

CONCLUSIONS

The epicutaneous (patch) test performed in the subjects examined in this study, showed that the majority of positive reactions was caused by mixes of nickel, cobalt and chromium; however, unwanted reactions also to other auxiliary materials used in dental practice should also be considered.

In vitro release of metal ions from a gold-platinum alloy in saliva-simulated conditions

The aim of this study was to evaluate the behavior of high-noble gold-platinum alloy samples (18 + 8 Rafinerija plemenitih kovina, Zagreb, Hrvatska), in a phosphate buffer pH 6.0. The aim of the study was to determine the type and amount of released metal ions from the alloy, and to evaluate how the time of exposure to the phosphate buffer pH 6.0 influences the release of metal ions from the alloy. Manufacturer samples 8.0 x 6.5 x 1.0 mm in size, with a surface area of 133 mm2 were used. The release of metal ions from the tested alloy was measured in ten time periods (after 1, 2, 3, 4, 5, 6, 7, 14, 21 and 30 days). Six samples were used (n = 6) for each time period that the alloy was in the solution, which means that a total of 60 samples was analyzed. Solutions, in which the samples were placed, were analyzed with the inductively coupled plasma atomic emission spectrometer (ICP-AES, JY 50P, Jobin-Ywon, France). It was found that four metal ions were released; zinc ions (Zn), chromium ions (Cr), copper ions (Cu) and iron ions (Fe). The most released ions from the gold-platinum alloy were those of zinc (Zn), and the least released were those of iron (Fe) (p < 0.01). The results of the study show that the time the tested alloy spent in the phosphate buffer pH 6.0 solution has an effect on the release of ions (p < 0.01).

Screening of fixed prosthodontic dentures after five years of use in relation to material and construction

The aim of this study was to screen patients with fixed prosthodontic appliances that were in oral cavity for a period of 5 years or more and to assess clinically and radiologically root caries, gingival recession, pocket formation, alveolar ridge resorption, as well as gingival (GI) and plaque index (PI). The aim also was to find out the differences between materials and constructions, between abutment and non-abutment teeth, and to find out the need for replacement. A total of 260 patients and their orthopantomograms were examined, with a total of 2,265 teeth, 610 being bridge abutments and 246 being crowns. The most frequent were metal+ acrylic veneer crowns or bridges. Root caries was found under the abutments in 10-20%; however abutments with ceramic crowns had the lowest percentage of caries (p < 0.01). Alveolar ridge resorption, pocket formation deeper than 3 mm and gingival recession of various degree was found in 50% of the cases, again with the lowest percentage of ceramic-fused-to-metal appliances (p < 0.01). Pocket depth was registered in significantly higher percentage in metal-acrylic veneer appliances compared to natural teeth (p < 0.01), while there was no significant difference between metal-ceramic appliances and natural teeth (p > 0.05). Although the worst findings were recorded for metal- + acrylic veneer crowns for PI, no significant difference existed between crowns of different material or non-abutment teeth (p > 0.05). There was statistically significant difference between abutments with metal + acrylic veneer crowns, full metal crowns, metal ceramic crowns and non-abutments for GI scores. Higher percentage of scores 0 and 1 was recorded for metal ceramic crowns and non-abutments and significantly higher percentage of scores 2 and 3 was recorded for metal + acrylic veneer crowns and full metallic crowns. Almost 50% of metal-ceramic abutments had no pathologic findings. Almost 30% of the patients needed replacement, or even some abutments to be extracted and therefore a new prosthodontic appliance.

Some periodontological parameters in patients with oesophagogastric passage insufficiency

The aim of this study was to examine the state of oral hygiene (OHI), the presence of tooth calculus and the condition of the gingiva on the group of 101 patient with oesophagogastric passage insufficiency. The control was group of 78 examines without clinical signs of oesophagogastric disease. The plaque was visualised by plaque revelator and recorded on each tooth. The calculus and condition of gingiva was determined according to the modified instruction of WHO, 1987. Both parameters were determined for each sextant of upper and lower jaw. The results of the OHI on the patients with oesophagogastric passage insufficiency (0.3, SD 0.126) was statistically different (p < 0.01) in comparison with control group (0.51, SD 0.25). Pathological changes of gingiva were more prominent in patient with insufficiency and that difference was statistically significant (p < 0.05). Calculus was more evident in control group but statistically insignificant (p < 0.1). The data show that insufficiency of oesophagogastric passage can cause pathological changes of gingiva while the lower OHI and less prominent calculus could be explained probably by better oral hygiene of patients because of bad taste in mouths.