Appropriate laboratory testing in rheumatic diseases

Single-tooth implants were used to replace congenitally absent maxillary lateral incisors in a 17-year-old patient. The inclination of the alveolar process caused a severe discrepancy between the axes of the planned implant and the crown. To avoid the need for a labial screw opening in the crown or labial overcontouring, a CeraOne abutment of the Br?nemark system was modified by selective grinding in the dental laboratory. Individual all-ceramic crowns were fabricated with the Celay In-Ceram system.     

Replacing posterior teeth with freestanding implants: four-year prosthodontic results of a prospective study

This article presents prospective four-year prosthetic results of the placement of 432 posterior freestanding, conventionally cemented prosthetic tooth implants in posterior edentulous spaces using the Bicon Dental Implants system (Bicon Dental Implants). Over four years, 0.74 percent of the abutments loosened, 0.5 percent of the abutments fractured, and 2.47 percent of the crowns experienced porcelain fracture, (all porcelain fractures occurred at time of placement). This low rate of problems appears to make free-standing single-tooth implant restorations a reliable solution to treating posterior edentulism.     

Precision of fit: the Procera AllCeram crown

STATEMENT OF PROBLEM: Strength, color stability, and precision of fit are requirements for all-ceramic restorations. The Procera AllCeram crown system, composed of a densely sintered high-purity alumina core combined with a low fusing surface porcelain, appears to satisfy most of these requirements. However, evaluation of marginal fit has not been reported. PURPOSE: This study measured the precision of fit of the Procera AllCeram crown fabricated with Procera CAD/CAM technology for the premolar and molar teeth fit to a die. MATERIAL AND METHODS: Five ivorine maxillary first premolars and first molars were prepared for full-coverage crowns. Preparations were standardized with a convergence angle of 10 degrees, chamfer margins of 1.3 to 1.5 mm circumferentially, and occlusal reduction of 2.0 mm. AllCeram crowns were fabricated for the dies, and the fit of the crown to the die was determined by using a standardized procedure with a silicone impression material that served a dual role: (1) as a retrievable luting agent, and (2) to replicate the internal aspects of the crown. Laser videography was used to measure the gap dimension between the crowns and the dies at the marginal opening, the axial wall, the cusp tip, and the occlusal adaptation measurement locations. Mean gap dimensions and standard deviations (SDs) were calculated for marginal opening, internal adaptation, and precision of fit. RESULTS: Mean gap dimensions and standard deviations at the marginal opening for the premolar and molar crowns were 56.0 microns SD +/- 21 and 63.0 microns SD +/- 13 microns, respectively. The mean gap dimensions and SDs of the internal adaptation were 69.0 microns SD +/- 17 microns for axial wall, 48.0 microns SD +/- 12 microns for cusp tip, and 36.0 microns SD +/- 7 microns for occlusal adaptation for the premolar crowns; and 49.0 microns SD +/- 3 microns axial wall, 67.0 microns SD +/- 21 microns cusp tip, and 74.0 microns SD +/- 29 microns occlusal adaptation for molar crowns. Precision of fit and SDs for premolar and molar crowns were 52.0 microns SD +/- 19 microns and 63.0 microns SD +/- 20 microns, respectively. Mean marginal openings and precision of fit gap dimensions for the crown groups were not significantly different at the .05 level. However, gap dimensions that defined the internal adaptation at the measurement locations were different (P < or = .05). CONCLUSION: Mean gap dimensions for marginal openings, internal adaptation, and precision of fit for the crown groups were below 70 microns. These findings show that the crowns studied can be prescribed with confidence knowing that the precision of fit will consistently be less than 70 microns.     

Marginal accuracy of indirect provisional restorations fabricated on poly(vinyl siloxane) models

Indirect interim restorations have been traditionally fabricated on stone casts. Recently, flexible models fabricated from poly(vinyl siloxane) impression material have been suggested in place of stone casts. This study compared the marginal accuracy of indirect single-unit provisional restorations fabricated on stone casts with units made on poly(vinyl siloxane) impression material models. The mean marginal discrepancy of provisional restorations was compared for restorations fabricated from stone, low-viscosity poly(vinyl siloxane), and medium-viscosity poly(vinyl siloxane). Ten restorations were also fabricated directly on a master metal model (control). The mean marginal discrepancies were: control = 0.161 mm; stone model = 0.180 mm; low-viscosity poly(vinyl siloxane) = 0.245 mm; and medium-viscosity poly(vinyl siloxane) = 0.157 mm. The mean marginal discrepancy for the low-viscosity poly(vinyl siloxane) models was significantly higher than the other three groups. No significant difference was found between the control, stone cast, and medium-viscosity poly(vinyl siloxane) model groups.     

The influence of the impression tray on the accuracy of impressions for crown and bridge work--an investigation and review

OBJECTIVE: To evaluate the accuracy of working casts for crown and bridge restorations made from twin mix putty/wash silicone elastomeric impression materials using different types of stock tray. DESIGN: A master cast was made from ivorine teeth in a mandibular model. Three teeth were prepared for full crown restorations to simulate a single unit and a three unit bridge. Impressions were taken using four different types of impression tray and two different viscosities of silicone putty, together with a wash. Full metal crowns were constructed and seated on duplicate master casts and measurements made of the marginal discrepancies. SETTING: The work was carried out in a dental technology laboratory in a university department of restorative dentistry in 1995/1996. RESULTS: Metal and rigid plastic impression trays showed the least discrepancy (about 50 microns), the latter slightly greater with the normal putty than the soft one. Impressions taken with flexible plastic trays produced considerable discrepancy with both putties, approximately 210 microns and 180 microns respectively. CONCLUSIONS: Metal and rigid plastic stock trays give greater accuracy in the putty/wash silicone twin mix impression technique compared with flexible plastic ones for crown and bridge work. Those using the latter should be aware of their shortcoming in this respect.     

Effect of tooth surface roughness on marginal seating and retention of complete metal crowns

STATEMENT OF PROBLEM: Retention and marginal adaptation factors have major influence on the failure of cemented complete veneer crowns. PURPOSE: This study investigated the effect of axial surface roughness on the marginal seating and retention of silver-palladium crowns luted with zinc phosphate, glass ionomer, and resin cements. MATERIAL AND METHODS: Coarse and fine diamond stones were used to create various surface roughnesses of premolars. A milling machine was used to control the height and angle of the axial walls of tooth preparations. Ten cast metal crowns in 6 subgroups were luted with 3 cements (Phosphacap, Fuji Cap I, and Panavia 21). Marginal seating was recorded with a Digimatic indicator. Retention was determined by measuring the tensile force required to remove a metal crown with a Lloyd testing machine. RESULTS: Two-way analysis of variance revealed statistically significant differences (P <.001) in retention for both luting cements and surface roughness. No significant difference was recorded for marginal seating relative to roughness (P =.860) and interaction effects (P =.204). Tukey-HSD tests revealed substantial differences in retention among Phosphacap, Fuji Cap I, and Panavia 21 cements. Significant differences were not confirmed in marginal seating between Fuji Cap I and Phosphacap cements with coarse diamonds, and Phosphacap and Panavia 21 cements with fine diamonds. CONCLUSIONS: The best retention for complete metal crown was demonstrated for tooth preparations ground with coarse diamonds and cemented with Panavia 21 cement. Differences in axial surface roughness had no effect on the marginal seating of the complete metal crowns.     

The effect of adhesive luting agent-dentinal surface interactions on compressive strength of two types of all-ceramic crowns

This research compared the compressive strength of two types of all-ceramic crown (Hi-Ceram and Duceram) as affected by selected luting cements (Zn phosphate, glass ionomer and composite resin cement). Thirty crowns of similar size and shape were constructed (15 crowns of each tested material) to fit a standard posterior tooth preparation. Five crowns from each material were cemented by one of the tested cements. The cemented crowns were loaded until catastrophic failure. A two-way analysis of variance was performed and showed that the type of utilized cement had a significant effect on the compressive strength being that Panevia Ex. resin cement the most effective one followed by glass ionomer and then finally zn phosphate cement. Statistical analysis also showed that Hi-Ceram crowns were more resistant to occlusal load than Duceram.     

Magnetic resonance imaging lesion analysis in neurofibromatosis type 1

The purpose of this prospective study was to investigate the clinical outcome and marginal bone resorption of three different endosseous implants placed in the anterior mandibles of 15 elderly patients. Eleven women and 4 men (ranging from 65 to 80 years, mean 71 years) had three different endosseous implants placed in the anterior mandible; one titanium plasma-sprayed cylinder implant (4-mm diameter), one titanium cylinder implant with hydroxyapatite coating (4-mm diameter), and one standard threaded titanium implant (3.75-mm diameter). Three months later, at the second-stage surgical procedure, ball abutments were connected and an overdenture was placed. At 12, 24, and 36 months, marginal bone resorption and Periotest values were recorded. None of the implants was lost in this period. An analysis of variance with repeated measurement was performed annually to test the existence of significant differences between the implants. When differences appeared, paired t tests were used to identify which differences were significant. Bonferroni multipliers were used to adjust for multiple testing. When marginal bone resorption was concerned, threaded titanium and hydroxyapatite-coated implants had significantly better scores than titanium plasma-sprayed cylinder implants. Periotest values for hydroxyapatite-coated implants were significantly better than test values for the other implants after 2 years. After 3 years significance was obtained between hydroxyapatite and screw-shaped implants only (P < .05). It was concluded that titanium plasma-sprayed cylinder implants have a less favorable prognosis than the other implants used in this study.     

Retrievable cemented crown options on implant-supported angled abutments: a case report

Nonaxial implant alignment often predicates the use of cemented of screw-retained angled abutments with inherent disadvantages, including reduced retrievability on screw loosening. The purposes of this article are to review the relative merits of cemented and screw-retained angled abutments and to present a method of ensuring retrievability of cemented angled abutments.     

New techniques for guiding catheter management during directional coronary atherectomy

In an uncontrolled retrospective recall study of 57 patients treated with conical crown retained dentures, 60 restorations (37 in the maxillae and 23 in the mandible jaw) with a mean wearing time of 30.1 months (range 4 to 76) were evaluated. Of the 248 abutments, eight (3.2%) had been lost. Clinically healthy mucosa was seen in 35 jaws. The marginal fit of the copings was judged to be good. No caries or new restorations were observed in 44 patients. Thirteen patients had 19 surfaces with new restorations and 20 surfaces with caries lesions. Of these 39 surfaces, 38 were located subgingivally.     

Anterior maxillary aesthetics utilizing all-ceramic restorations

The use of all-ceramic systems has increased significantly during recent years, due to the improved strength and the introduction of a new generation of dental adhesive agents and resin cements. Both factors permit reliable and predictable results in single jacket crown restorations in the maxillary anterior region. Due to their natural appearance, the all-ceramic materials, especially the glass ceramics, blend harmoniously with the oral environment and are particularly appreciated where aesthetics is a priority. The learning objective of this article is to demonstrate a routine utilization of all-ceramic systems in the maxillary anterior region, preceded by a proper case selection. Two clinical cases are used to illustrate the preparation procedure, the importance of well-integrated provisional restorations, and the accuracy in transferring provisional information onto the final jacket crowns.     

Antenatal sonographic diagnosis of club foot with particular attention to the implications and outcomes of isolated club foot

OBJECTIVE: This study assessed the clinical performance of dentin-bonded crowns, in which ceramic crowns are bonded to underlying dentin with a resin composite-based luting material and a dentin bonding agent. METHOD AND MATERIALS: Twenty-five patients who had received such restorations more than 1 year previously were recalled for evaluation of their crowns. RESULTS: Sixty dentin-bonded complete-coverage restorations were assessed. Forty-one of the crowns had been placed on incisor teeth. The mean time since placement of the restorations was 2.43 years. Fifty-seven of the 60 restorations were intact. The three failures had resulted from cracks in the restorations, which had not clinically debonded. No secondary caries was detected at the crown margins, and anatomic form was assessed as excellent for 56 crowns. Root canal treatment had been required in one case. Color match was rated very good for 47 crowns. All 25 patients were satisfied with their restorations. CONCLUSION: Dentin-bonded crowns may be found to have a low rate of failure and to provide a high level of patient satisfaction.     

Regeneration of gingival papillae after single-implant treatment

An index to assess the size of the interproximal gingival papillae adjacent to single implant restorations was described and preliminary tested in a pilot study of retrospective material comprising 25 crowns in 21 patients. The result indicated a significant spontaneous regeneration of papillae (P < .001) after a mean follow-up period of 1.5 years. Based on these results, the general conclusion was made that the proposed index allows scientific assessment of soft tissue contour adjacent to single-implant restorations. The results also indicated that soft tissue changed in a systematic manner during the time period between insertion of the crowns and follow-up 1 to 3 years later.     

In vitro milling accuracy and fit of 'natural inlays'

OBJECTIVE: This study aimed to investigate the milling behaviour of natural inlays (NI) dental restorations constructed from sound extracted teeth. This was done by comparing the milling accuracy and fit of NI to those of industrial porcelain inlays (PI), milled in the same way. METHODS: A calibration pro-inlay was used to mill three NI and three PI. These were cemented in six acrylic cavities reproduced from the calibration mould, using composite luting cement. No etching and bonding were done. After storage for 24 h in water at room temperature the specimens were sliced buccolingually in a standardised way. For each specimen, two sections were photographed under a light-microscope, resulting in enlarged pictures of the sections. An acetate matrix with the measurement points was placed over each picture in a standardised way. The interfaces between inlays and moulds were measured at 13 fixed points per section using computerised image analysis software. The mean vertical- and floor-interfaces were calculated for each picture, and the overall means were found for each group. Confidence intervals were used for comparison of the differences. The profiles of the milled materials were examined using scanning electron microscopy. RESULTS: There were no differences between NI and PI in the mean interfaces (NI, 102 +/- 8 micrometers; PI, 107 +/- 8 micrometers). Electron microscopy revealed no apparent differences in the profiles of the milled surfaces. CONCLUSION: These findings indicate that the milling accuracy and the fit of natural inlays and milled porcelain inlays are comparable.     

Procera: a new way to achieve an all-ceramic crown

The Procera System embraces the concept of computer-assisted design and computer-assisted machining to fabricate an all-ceramic crown composed of a densely sintered, high-purity aluminum oxide coping combined with a compatible veneering porcelain. Strength, precision of fit, color stability, cementation, and wear characteristics are among the many factors that concern clinicians when fabricating all-ceramic restorations with this new crown system. This article presents, in summary form, the data from the many studies on Procera AllCeram crowns that have been conducted at clinical and laboratory centers around the world. The evidence reported in these studies clearly demonstrates that the Procera AllCeram crown represents a combination of computer technology and creativity for which a positive prognosis can be made. Today its application is restricted to single crowns; however, with continued development, multiple unit all-ceramic anterior and posterior fixed partial dentures are clearly in the future.     

The fracture resistance of all-ceramic crowns on supporting structures with different elastic moduli

This in vitro study evaluated the fracture resistance of all-ceramic crowns as a function of the elastic modulus of the supporting die. All-ceramic crowns were made for dies with three different elastic moduli and two different crown lengths. The occlusal surface was loaded in compression with a 12.7-mm steel ball. The fracture load increased markedly with the increase in elastic modulus. The largest increase was seen when only the occlusal surface of the crown was covered. The characteristic fracture load of the complete-crown restorations was more than double that of the occlusal-cover restorations in the dies with the lowest modulus of elasticity, while for the dies with the highest modulus of elasticity the difference in the characteristic fracture load for the two configurations was not significant.     

Solitary fibrous tumor of the prostate

The aim of this retrospective study was to record patients' satisfaction with fixed metal ceramic bridges and crowns made by dental students and to evaluate the functioning and condition of the bridges and crowns clinically and radiologically. Out of the 60 patients treated at the Institute of Dentistry during 1984-85, 30 patients attended the follow-up examination (16 women, mean age 39, range 23-62 years and 14 men, mean age 44, range 26-65 years). The anamnestic data and data regarding treatment procedures were collected from the patient files. The patients had been supplied with 41 crowns and 24 bridges (mean 3.9 units, range 3-6 units), which included 61 abutments and 33 pontics or cantilever extensions (abutment/pontic ratio 1.85: 1). Marginal fidelity was unsatisfactory in 13% of the crowns and bridges and gingival bleeding and pockets of 4-6 mm were noted in 27% and 12% of cases, respectively. None of the subjects had caries in the abutments.     

Establishing soft tissue integration with natural tooth-shaped abutments

The disparity in dimensions between implant fixtures and the exposed extraction sockets has resulted in the development of anatomically shaped abutments. Systems have been recently introduced that facilitate the fabrication of abutments to the configuration of natural teeth in the anterior maxilla. These systems permit development of an aesthetic emergence profile and contours for easy access in maintenance of oral hygiene of maxillary anterior single-tooth implant-supported restorations. The rationale for the development, indications, advantages, and clinical utilization of a recently introduced abutment system is discussed.     

New players and puzzles in the Hedgehog signaling pathway

STATEMENT OF PROBLEM: Esthetic demands of patients and practitioners for an all-ceramic crown in both anterior and posterior regions of the dental arches has prompted the development of the Procera AllCeram crown. Long-term clinical trials that evaluate the strength and naturalness of the Procera AllCeram crown are lacking. PURPOSE: This prospective study was initiated to evaluate the clinical performance of 100 Procera AllCeram crowns after 5 years in service. MATERIAL AND METHODS: One hundred Procera AllCeram crowns were fabricated for 58 patients (20 men and 38 women). Patients were treated by 4 general dental practitioners. Crown placement involved both the anterior and posterior regions of the dental arches. Crowns were examined at baseline and once a year during the 5 years that followed and evaluated at each appointment with the California Dental Association's quality assessment system. RESULTS: Of the 97 crowns remaining in the study after 5 years, only 3 crowns had experienced a fracture through the veneering porcelain and the aluminum oxide coping material. Two additional crowns were replaced as a result of fractures of only the veneering porcelain. One crown was replaced as a result of recurrent caries. All remaining crowns were ranked as either excellent or acceptable for surface/color, anatomic form, and marginal integrity. CONCLUSION: The 5-year clinical observations and ranking with the California Dental Association's quality assessment criteria supported the conclusion that Procera AllCeram crowns may be used in all areas of the mouth.     

Marginal fit consistency of copy-milled all-ceramic crowns during fabrication by light and scanning electron microscopic analysis in vitro

The aim of this study was to evaluate the marginal fit of copy-milled Celay In-Ceram crowns after different fabrication steps and to compare light-microscopic with scanning-electron-microscopic data. A master steel die of an upper middle incisor with a shoulder preparation and a rounded inner line angle was used. Impressions were taken to produce 10 working stone dies. One crown per working die was manufactured. The evaluation of the external marginal gap was performed on the master steel die by using a light microscope and a computerized video image analysis system after copy milling (A), glass infiltration (B), and veneering (C). Approximately 3900 readings were taken. In a final series the veneered crowns were measured by using a scanning electron microscope (Cs), yielding approximately 1000 readings. The results obtained were: A mean, 25.1 microm; s.d., 5.1 microm; range, 2.5-76.8 microm: B mean, 20.6 microm; s.d., 2.3 microm; range, 2.5-76.1 microm: C mean, 18.3 microm; s.d., 4.1 microm; range, 2.5-87.2 microm: Cs mean, 23.0 microm; s.d., 7.6 microm; range, 0.0-94.5 microm. The results were statistically evaluated using the t-test. The differences found between the series did not show practical relevance. Therefore, it is concluded that the manufacturing steps after copy milling have no obvious influence on the external marginal gap width. Scanning electron microscopic data seem to confirm the light-microscopic results. Hence, we expect that the Celay In-Ceram method yields a clinically acceptable marginal fit.