The effect of surface treatment on the shear bond strength of luting cement to a glass-infiltrated alumina ceramic.

PURPOSE: The aim of this study was to evaluate the effect of three different surface treatments on the bond strength of four different luting cements--three bis-GMA-based resin cements and a compomer cement--to In-Ceram. MATERIALS AND METHODS: Eight In-Ceram samples were used for each experimental group. The samples were randomly assigned three treatment conditions: (1) etching for 90 seconds with 5% hydrofluoric acid gel, (2) sandblasting (110-micron Al2O3), and (3) tribochemical silica coating. All samples were silanated following the surface treatment. The luting cements were bonded to In-Ceram specimens using Teflon tubes. All samples were thermocycled for 5,000 cycles altering between 5 and 55 degrees C with 30-second dwell times. The shear bond strength values were measured in a universal testing machine with a cross-head speed of 1 mm/min. Analysis of variance was used to analyze data. RESULTS: The mean bond strengths varied between 1.2 and 24.7 MPa. CONCLUSION: Shear bond strength of compomer cement following tribochemical silica coating was significantly lower in comparison to resin cements. Luting of In-Ceram with various resins provided varying degrees of bond strengths that were significantly increased by the tribochemical silica-coating system.

A clinical evaluation of ceramic inlays bonded with different luting agents.

PURPOSE: The purpose of this study was to evaluate the clinical performance of a fired ceramic inlay system bonded with three different luting agents. MATERIALS AND METHODS: A total of 45 Ducera LFC ceramic inlays (12 in premolars, 33 in molars) were placed in 26 patients. Fifteen of the inlays were inserted with one of three different luting agents: (1) Variolink High Viscosity, (2) Enforce, and (3) Geristore. The restorations were evaluated for a period of 3 to 46 months, with a mean of 26.3 months after insertion using modified USPHS criteria. The evaluation period ended when the restoration had to be replaced due to fracture or secondary caries. Postoperative sensitivity was determined by direct questioning. Kaplan-Meier statistical analysis was used to calculate the survival rate of the inlays. Selected restorations were further evaluated indirectly with SEM. RESULTS: The fracture rates observed for Variolink, Enforce, and Geristore were 13%, 13%, and 33%, respectively. There was a high rate of early bulk fracture, seen mainly within 12 months, for inlays luted with Geristore. For all groups, secondary caries was found to be relatively low. The inlays in all luting agent groups showed acceptable color match and surface roughness scores during the whole evaluation period. SEM observation revealed that the deterioration of marginal adaptation was found to be more severe for inlays luted with Geristore, and that the rate of submargination was also higher for Geristore-luted inlays in comparison to those luted with Variolink and Enforce. CONCLUSION: The use of a polyacrylic acid modified glass ionomer, Geristore, resulted in a higher fracture rate and loss of marginal adaptation in fired ceramic inlays. The marginal adaptation of the luting agent was more durable at the enamel interface than that at ceramic interface.

Thermal cycling distortion of porcelain fused to metal fixed partial dentures.

STATEMENT OF PROBLEM: The initial fit of porcelain fused to metal restorations deteriorates during the firing cycle of porcelain. PURPOSE: This study evaluated thermal cycling distortion of 3-unit porcelain fused to metal frameworks at different firing stages. MATERIAL AND METHODS: A master model was designed to represent the 2 abutments of a 3-unit fixed partial denture replacing a missing mandibular molar. Standard techniques were used to fabricate 10 castings. Half of the copings were cast in a Ni-Cr alloy and the other half in a Pd-Cu alloy. Framework distortion was measured by means of inner fit changes, horizontal linear measurements of the framework length, and vertical fit changes of each retainer. Measurements were made (1) initially, (2) after degassing firing, and (3) after glaze firing. Differences between the firing cycles created distortion values of the retainers in 3 dimensions. Repeated measures ANOVA was used to analyze data statistically. RESULTS: Measured differences between the 2 firing stages ranged from -47 to 81.7 micrometer. For both alloy groups, retainers showed increase in vertical gap that implied poorer vertical fit after porcelain application. Mean values of inner fit change recorded for porcelain application firing were higher in magnitude than the values of metal-conditioning firing. In addition, no statistically significant differences were found among alloy types. CONCLUSIONS: A 3-dimensional distortion was observed both in Pd-Cu and Ni-Cr frameworks during porcelain firing cycle. The distortion seen after porcelain application firing was significantly greater than that seen after metal-conditioning firing. This result can be attributed to these factors, contamination of porcelain to the inner surface of metal coping and reduction in resilience of metal.

Effect of early water contact on solubility of glass ionomer luting cements.

STATEMENT OF PROBLEM: Glass ionomer cements are susceptible to attack by moisture during the initial setting period that can result in an increased solubility. PURPOSE: This study was to evaluate the solubility of glass ionomer luting cements immersed in distilled water at early stages after mixing. MATERIAL AND METHODS: Four commercial glass ionomer cements were used (Ketac-Cem, Fuji Ionomer I; AquaCem; AquaMeron). For each material, 5 resin cement holders were made with 2 circular cavities (diameter = 5 mm; depth = 2 mm). One minute after start of mixing, the specimens were placed in a humidifier at 37 degrees C and 100% relative humidity. After 2, 5, and 8 minutes storage time, they were immersed in 50 mL of distilled water in a glass weighing bottle where they were stored for 3 hours at 37 degrees C. Next, the specimens were removed and the water was evaporated from the weighing bottle at 130 degrees C for 2 hours. The difference between the final and initial weights of the bottle was taken as amount of solubility. Data were analyzed by analysis of variance and Duncan's test. RESULTS: Solubility was greatest at 3 minutes immersion time and least at 9 minutes. The lowest cement loss was for AquaCem at 9 minutes immersion time (1.68 mg/cm2). The greatest loss was for Fuji Ionomer I after 3 minutes immersion time (14.98 mg/cm2). Solubility of cements decreased by 39% for Ketac-Cem, 61% for Fuji Ionomer I, 38% for AquaCem, and 37% for AquaMeron when the specimens were immersed in water 6 minutes after mixing. Comparison of all 4 cements revealed a relatively large difference between loss of substance from AquaCem and AquaMeron, and the 2 other conventional glass ionomer cements, Keta-cCem and Fuji Ionomer I. CONCLUSIONS: Increasing the time from start of mixing until immersion in water from 3 to 9 minutes resulted in a marked decrease in loss of substance from the surface of all 4 cements. Water-hardening glass ionomer cements (AquaCem and AquaMeron) were less sensitive to early water contamination.

Marginal adaptation of a sintered ceramic inlay system before and after cementation.

The long term clinical performance of porcelain inlays depends on a number of factors and the marginal adaptation is one of significant interest. The purpose of this in vitro study was to evaluate the marginal integrity of a sintered inlay technique (Ducera), before and after cementation. MOD cavities without bevels were prepared on 10 human mandibular molar teeth and porcelain inlays were fabricated according to the manufacturer's instructions. Inlays were evaluated microscopically for their adaptation to the occlusal and approximal margins of the tooth by means of a replica technique. Inlays were cemented with a dual-cured hybrid composite luting material (Enforce). After polishing, each tooth was sectioned in buccal/lingual and mesial/distal directions following the same procedure in the sectioning of replicas. The marginal gap and the thickness of exposed cement were measured at each section. The mean marginal gap of 71.83 +/- 8.93 microm recorded for the occlusal margin before cementation was significantly smaller than that of 105.6 +/- 39.33 microm calculated at the approximal margin. Following the cementation, the adaptation of the inlays at the occlusal margin was also found to be superior to that of the approximal margin. Comparison of mean gap values before and after cementation revealed that the marginal gap increased by 6.94 microm and 23.25 microm at the occlusal and approximal margins, respectively. Although polishing was performed after cementation, excess luting material was still observed, that caused an increase in the width of the exposed luting cement.

In vivo and in vitro evaluation of marginal integrity in ceramic inlays.

The marginal integrity is an important factor for the long-term success of ceramic inlays. The long term clinical performance of porcelain inlays depends on a number of factors of which the marginal adaptation is of significant interest. The aim of this study was to determine the margin quality of adhesively luted sintered porcelain inlays both in vivo and in vitro. MOD cavities without bevels were prepared on 10 extracted human mandibular molar teeth. Using the Ducera inlay system, inlays were fired on refractory dies and luted with a dual-curing composite resin. After polishing, each, tooth was sectioned in buccal/lingual and mesial/distal directions and marginal adaptation was assessed microscopically. The mean marginal gap of 78.77 +/- 14.85 microns recorded for occlusal margins was significantly smaller than that of 128.85 +/- 34.34 microns seen at the approximal margins. For in vivo evaluation, 25 fired porcelain inlays, including 7 onlays, were placed in Class II cavities. The assessment of the marginal adaptation of inlays was made according to the scaling system used by Aberg et al. (Acta Odontol Scand 1994; 52:140-149). In 19 of the clinical cases, the restoration was contiguous with the existing anatomic form. Both in vivo and in vitro evaluations showed the margin quality of porcelain inlays to be high.

Distortion of metal-ceramic fixed partial dentures resulting from metal-conditioning firing.

The aim of this study was to investigate the distortion of metal-ceramic prostheses that occurs during metal-conditioning firing and to examine whether the distortion might be controlled by embedding the castings in an investment bulk and applying a prior heat treatment. The distortion of palladium-copper and nickel-chromium frameworks was evaluated by means of inner fit and horizontal linear measurements of the framework length. There was no statistically significant difference between palladium-copper and nickel-chromium frame-works in the changes in inner fit. In addition, there was no statistically significant difference between the invested test group and the control group in changes in fit. However, the mean deformation in framework length recorded for invested palladium-copper frameworks (-20.20 microns) was significantly smaller than that recorded for control palladium-copper frameworks (52.20 microns).

Marginal fit changes during porcelain firing cycles.

The marginal fit changes that occur during the procelain firing cycles of palladium-copper and nickel-chromium copings both with shoulder and chamfer finish lines were investigated with scanning electron microscopy. Three copings from each alloy test group were used as nonporcelainized controls. Comparisons of the firing cycles revealed a greater change during the degassing stage, and the opaque firing caused a decrease in marginal gap. There was a small increase in gap size after firing body porcelain. The marginal fit change for the palladium-copper copings (19.39 microns) during degassing was significantly greater than that for the nickel-chromium copings (8.65 microns). However, no significant differences were found when the effects of margin design and porcelain proximity to fit of metal-ceramic crowns were compared.

Processing dentures using a microwave technique.

In this research the technique of curing denture base acrylic resins by microwave energy was investigated with respect to polymerization method, hardness, mechanical and physical properties. Twenty-one different polymerization methods were used by varying radiation power and curing time. The Vickers hardness test was applied to the samples which were polymerized. The average value was found to be 22.46 VHN (Vicker hardness number), that is, almost the same as conventionally cured acrylic. The recommended polymerization method of curing acrylic was 3 min at 550 W in a microwave oven. Mechanical and physical tests were applied to the samples which were cured by the recommended polymerization method. The average transverse load to fracture value was found to be 7.6 kg, and the transverse deflection value was 1.5 mm at 3500 g, and 2.9 mm at 5000 g. Water sorption of acrylic resin cured by microwave energy was 0.72 mg cm-2 and the solubility rate in water was 0.038 mg cm-2. Results conformed with the ADA specification. The findings showed that acrylic resin cured by microwave energy is more resistant to mechanical failure than conventionally cured acrylic and this technique can safely be applied to the production of denture bases.

Marginal distortion of metal-ceramic restorations during the porcelain firing procedure.

The fit of a metal-ceramic casting deteriorates during the firing of a porcelain facing. Although many factors have been reported as the cause of these distortion phenomena, studies of marginal distortion associated with firing metal-ceramic restorations have yielded mixed results. The effect of firing cycles on distortion of a metal-ceramic coping was examined on 0.5 mm thick palladium-copper copings with shoulder marginal finish lines. It was found that the distortion produced in the first stage of firing was greater than at other stages. The marginal distortion seen on the porcelain veneered margin was not significantly different from the distortion on the non-veneered margin. These two results demonstrate that thermal contraction stresses due to porcelain contraction are probably not the primary cause of coping distortion. The internal surfaces of the copings were examined for contamination with porcelain particles and porcelain contamination was detected with an energy dispersive spectrometer analysis. The distortion produced during the porcelain veneering procedure was due to porcelain contamination on the internal surfaces of the copings. A convenient method is necessary to remove porcelain from the internal surfaces of completed restorations.

Hemifacial microsomia and hypodontia: a case report.

A 6-year-old girl with hemifacial microsomia was examined. Abnormalities found were: severely malformed pinna of the right ear, right malar hypoplasia and unilateral mandibular hypoplasia. Dental examination revealed normal intraoral soft tissues with all deciduous teeth present. Radiographic examination disclosed that the maxillary and mandibular right and left second premolars were not developing. The mandibular ramus was short in length and the mandibular condyle had not developed on the right. The patient had no renal, cardiac or skeletal anomalies and her hearing was normal. No previous publications have been located which report the association of hypodontia and hemifacial microsomia.

The fit of all-ceramic crowns cemented with different luting agents.

In this article the fit of all-ceramic crowns, cemented with different luting agents (zinc phosphate and resin cements), was investigated using a scanning electron microscope. The marginal opening of all-ceramic crowns cemented with zinc phosphate cement was 111.9 +/- 40.6 microns which was significantly greater than the 46.7 +/- 12.9 microns marginal opening of Cerestore crowns cemented with resin cement. Total film thicknesses of the cements were not uniform and there were certain discrepancies from margins to walls and to tip due to the die spacer.

The prevalence of Candida albicans in complete denture and removable partial denture wearers: a comparative study.

In this study, 60 complete denture wearers, 53 removable partial denture wearers and 50 dentate subjects were examined to determine the Candidal carrier state. The influence of local factors such as denture type, smoking habits and sex on Candidal carrier rate were investigated. Wearing complete or removable partial denture was determined as an important factor increasing Candidal carrier rate. Cigarette smoking is another factor which increases Candidal growth in complete denture and removable partial denture wearers. In contrast to denture wearers Candidal carrier rate was considerably less on dentate smokers. Candidal colonization rate was found to be higher on the dorsum of the tongue. This suggests that the tongue is the primary oral reservoir of Candida albicans in the mouth.

[Marginal fit of porcelain-fused-to-metal crowns: a comparative study of metal and porcelain butt margin]. / Metal destekli porselen kronlarda, metalve basamak porseleni marjinal uyumlarinin karsilastirilmasi.

Marginal openings and shoulder fit of porcelain butt margins and metal butt margins of porcelain fused-to-metal crowns have been investigated. Crown restorations were constructed directly onto the prepared teeth with 1 mm. square shoulder. Marginal openings and shoulder fit of labial surface and the cross-section of shoulder area then observed using optical microscope. Marginal fit was found better in porcelain fused-to-metal crowns with porcelain butt margin and also practically invisible neutrally-coloured join between crown and prepared tooth, was achieved with shoulder porcelain.