Guidelines for the preparation of CAD/CAM ceramic inlays and partial crowns.

Ceramic inlays and partial crowns have become scientifically recognized posterior restorations. Their clinical effectiveness depends on the development of durable dental ceramics and luting materials as well as an effective bonding system. Therefore, these factors were in the focus of interest in the past. In contrast, only little attention was given to preparation techniques. However, current studies show that special preparation rules should be followed to ensure best fitting CAD/CAM ceramic restorations and long-lasting clinical success. This paper describes preparation requirements by means of detailed three-dimensional schematic drawings and then deduces the clinical procedure for the preparation of ceramic inlays and partial crowns with standardized preparation instruments.

Copy-milled all-ceramic Celay-InCeram crowns for modified CeraOne abutments: a technical report.

With single-tooth implant restorations, a divergence between implant and crown axes, a lack of interocclusal space, and supracrestal implant placement may result in fabrication problems for the prosthetic crown. It was found that the CeraOne abutment can be modified in three ways: (1) height reduction is possible; (2) a 15-degree taper can be applied; and (3) the cervical shoulder can be reduced in height with a chamfer remaining. For these modified abutments, the Celay-InCeram system was used to create individual, all-ceramic crowns for these modified abutments with improved esthetics.

Orbital reconstruction with individually copy-milled ceramic implants.

Diagnostic advances such as computed tomography and new surgical techniques have dramatically improved both the functional and aesthetic outcome of orbital reconstructions. Taking a further approach, we designed ceramic implants (Bioverit) on the basis of stereolithographic models. After copy milling a resin template with a commercially available dental unit (Celay), the prefabricated implants were inserted for reconstruction of the lamina papyracea (n = 1), zygomatic complex (n = 2), infraorbital floor (n = 5), and rim (n = 3). Intraoperatively, only slight modifications of the implants had to be performed. The results were encouraging, as all cases showed a good aesthetic and functional postoperative outcome. Preoperative evaluation of the osseous defect and prefabrication of the required implant reduced operating time and patient morbidity significantly.

All-ceramic crowns on modified CeraOne abutments: a case report.

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 Brånemark system was modified by selective grinding in the dental laboratory. Individual all-ceramic crowns were fabricated with the Celay In-Ceram system.

Slip-casting alumina ceramics for crown and bridge restorations.

The In-Ceram technique uses alumina ceramics and glass in a two-step firing procedure to create a high-strength core material for single-tooth restorations as well as small fixed partial dentures. Fine-grain alumina particles are sintered to form a porous substructure, which is infiltrated with molten glass. The combination of these two processes gives the material its outstanding properties. The sintering process is almost without shrinkage, providing an excellent fit, while the glass infiltration leaves practically no porosities, resulting in high strength.

Custom-made resin-bonded attachments supporting a removable partial denture using the spark erosion technique: a case report.

A removable partial denture supported by resin-bonded precision attachments was constructed for a patient with intraoral symptoms of a cleidocranial dysostosis. Because of the anatomic situation, the youth, and the preprosthetic orthodontic treatment of the patient, a conventional prosthetic solution seemed inappropriate. Custom-made attachments were constructed with the spark erosion technique. They were fixed to the abutment teeth with resin-bonded retainers. The combination of the resin-bonding technique with the modern technology of spark erosion thus allowed a conservative approach to the oral rehabilitation of a young patient.

Four year clinical study of glass-infiltrated, sintered alumina crowns.

The clinical outcome of 95 consecutively placed In-Ceram complete coverage crowns, 68 posterior and 28 anterior, all luted with conventional cements, was studied. In the 56 month observation period no total failure requiring replacement of a restoration occurred. The veneer of a molar single crown fractured, while its ceramic core remained intact. With four crowns, marginal caries was observed after 2-4.5 years. It was concluded from this clinical study that In-Ceram complete coverage all-ceramic crowns are indicated for anterior and posterior teeth.

Survival rate of In-Ceram restorations.

This paper reports on 76 consecutively placed In-Ceram restorations (61 complete-coverage crowns and 15 fixed partial dentures). Their survival rates were determined using the Kaplan-Meier method. During the 35-month observation period no crown failures occurred, a five-unit fixed partial denture fractured, and another fixed partial denture was removed because of periodontal complications. Thus, In-Ceram complete-coverage ceramic crowns are apparently indicated for anterior and posterior teeth. A larger number of subjects must be studied to assess the indication for all-ceramic fixed partial dentures.

Compressive strength of two modern all-ceramic crowns.

This study investigated the compressive strength of all-ceramic crowns manufactured using two recently introduced systems. The mean forces of fracture were 964 N for In-Ceram crowns, 814 N for paint-on IPS Empress crowns, and 750 N for layered IPS Empress crowns, compared with 1,494 N for metal ceramic crowns veneered on a nickel-chromium coping. The results indicate that clinical testing of these all-ceramic crowns is reasonable. Controlled, clinical, long-term evaluation is necessary to assess the safe application of these new crown systems.

[SEM study of failures in acid etched cast prosthodontics]. / Rasterelektronenmikroskopische Untersuchung von Misserfolgen in der Adhäsivprothetik.

Eight bonded prosthodontic units (mean wearing time 14 months), with 7 retainers spontaneously debonded during clinical use and 9 retainers removed by the dentist, have been studied by SEM. Since only bond fractures at the acrylic/metal interface and mixed fractures could be detected, it may be concluded that late failure is governed by processes at the interface between metal and acrylic. The lost retainers showed overgrowth of mainly rod-shaped bacteria, although one of the artificially removed retainers that was clinically stable beforehand, also exhibited bacterial overgrowth. This suggests that sequential debonding is possible; hence bonded retainers impart a longterm caries risk to abutment teeth.

[Surface morphology of alloys treated with the Rocatec system]. / Zur Oberflächenmorphologie von mit dem Rocatec-System behandelten Legierungen.

The new Rocatec-System is propagated for improving the resin metal bond. With a tribotechnical blasting procedure a silicate layer is applied to the alloy surface. The resin is bonded to this layer with a silane coupling agent. This study investigates the alloy surface morphology alterations caused by the blasting procedures. The volume loss increases with blasting time, high gold alloys showing higher volume loss. Thin edges are deformed due to the high blasting pressure.

The influence of different cementation modes on the fracture resistance of feldspathic ceramic crowns.

One hundred twenty pressed feldspathic ceramic crowns were luted to 20 steel dies using six different cementation modes. Fracture resistance was tested under an angle of 45 degrees and was determined as the maximal fracture load. Crowns were tested with luting agent only (groups A and C) and after etching with hydrofluoric acid, silanating, and the application of a bonding agent (groups B, D, E, and F). The resulting means were: phosphate cement 294.3 (A) and 282.2 (B); glass-ionomer cement 217.2 (C) and 255.4 (D); resin composite 382.2 (E) and 687.6 (F). Statistical analysis revealed significantly greater fracture resistance (P < .01) of resin luted crowns. Bonding to the die almost doubled the fracture resistance. Conditioning of the inner surfaces of the crowns did not improve the fracture resistance of crowns luted using zinc phosphate or glass-ionomer cements.

[Comparison of two computer-aided recording systems: MT 1602 and Compugnath]. / Vergleich der computerunterstützten Registriersysteme MT 1602 und compugnath.

Two computer-aided jaw movement recording systems were compared with each other. The results showed that both systems work satisfactorily for use in reconstructive dentistry and TMJ diagnosis. It is, however, emphasized, that there are a number of shortcomings which may have a negative effect on the recordings.

Three-point bending strength of ceramics fused to cast titanium.

Titanium requires special ceramic systems for veneering. This study compared the three-point bending strength of three commercially available titanium ceramic systems with a NiCr-alloy with conventional ceramics. Three-point bend specimens 25 x 5 x 0.5 mm were cast from polyethylene patterns. After alpha-case removal, they were veneered with 8 x 5 x 1 mm of ceramics at the center of the bar. Specimens were tested in a universal testing machine without ageing, after thermocycling, and after 90 d storage in an electrolyte solution. Titanium-ceramic systems were found to have a significantly lower bond strength in comparison to the NiCr-ceramic system. One of the titanium ceramic systems had a significantly lower bond strength in comparison to the other systems investigated. It could be concluded that bonding between titanium and ceramics is obtainable; however, the achievable bonds strengths did not match the NiCr-ceramic control.

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.

Clinical follow-up study of ceramic veneered titanium restorations--three-year results.

Eighty-four titanium restorations having 125 ceramic veneers were placed for 32 patients. One hundred sixteen (93%) of the veneers could be reexamined after 21 to 41 months. Two of the restorations required removal because of a partial veneer loss. A Kaplan-Meier survival analysis was performed, giving a survival probability of .85 for single crowns and .59 for fixed partial dentures after a time interval of 30 months, regarding the veneer cracking or chipping. There was a significantly higher survival probability for single crowns than for fixed partial dentures (P=.001, logrank test). It was concluded that ceramic veneered titanium restorations should be limited to single crowns.

[Special ceramic hard substances as separating agents in cast-on procedures for the construction of precision attachments]. / Sonderkeramische Hartstoffe als Trennmittel für die Aufgusstechnik in der Geschiebeprothetik.

A new direct cast-on technology for the construction of telescopic crowns and precision attachments using non-precious alloys is described. Special ceramic hard substances, such as silicides and borides, are used as separating agents for the casting of the secondary structure. The application of the ceramic layers to the primary crown is accomplished with a chemical vapor deposition method. The layer thickness can be controlled and may range between some hundred nanometres and up to a few micrometres. The attainable gaps between primary and secondary casting range between 1 and 8 microns after separating and finishing.

Functional improvement of implant-retained ear epistheses with magnets and a retention clasp.

A method for enhanced retention and function of implant-retained ear epistheses is described. A cast bar containing two encapsulated magnets and a loop is retained on two retroauricular implants. The loop receives a clasp in the prosthesis and prevents its unintentional loss.

Determination of the minimum number of marginal gap measurements required for practical in-vitro testing.

STATEMENT OF PROBLEM: Gap measurements along margins are frequently used to assess the quality of single crowns. However, the number of gap measurements required for clinically relevant results in laboratory studies is not known. PURPOSE: This study estimated the minimum number of gap measurements on margins of single crowns to produce relevant results for gap analysis. METHODS AND MATERIAL: Ten all-ceramic crowns were fabricated on a master steel die. Gaps along crown margins were investigated in a scanning electron microscope on the master steel die without cementation and on replica dies after conventional cementation. Measurements were made in 100 microm steps according to 3 gap definitions. The initial number of measurements per crown (n = 230) was reduced to smaller subsets using both systematic and random approaches to determine the impact on the quality of results. RESULTS: On the data of gap definition 1, reduction from 230 to about 50 measurements caused less than +/-5 microm variability for arithmetic means. Analysis of standard errors showed slowly increasing values smaller than 3 microm, both indicating no relevant impact on the quality of results. Smaller data sizes yielded accelerated increase of standard errors and divergent variabilities of mean. The minimum of 50 measurements did not depend on gap definition or on cementation condition. CONCLUSION: Fifty measurements are required for clinically relevant information about gap size regardless of whether the measurement sites are selected in a systematic or random manner, which is far more than what current in vitro studies use.