The International Journal of Prosthodontics, 04/2001

Purpose: The purpose of this report is to describe a new technique to fabricate and deliver an implant-supported fixed prosthesis to the patient on the day of surgery, and to propose a protocol for the prosthodontic and dental laboratory procedures. Materials and Methods: The development of the Brånemark Novum prosthodontic protocol is reviewed, and clinical and dental laboratory assessments and methods are described. Results: The total treatment time to fabricate a permanent implant-supported fixed prosthesis in the mandible can be reduced to 1 day with the Brånemark Novum technique. The new method includes a precise surgical technique using drilling templates for predetermined implant positions, a rigid splinting of the implants immediately after placement, the use of a prefabricated titanium framework, and elimination of implant impression procedures. Conclusion: With the technique described in this report, it is possible to provide patients with a permanent implant-supported fixed prosthesis in the mandible on the day of implant surgery. Patient benefits are obvious, with drastically reduced total treatment time, lower cost, and fewer clinical visits.

Purpose: This article describes the development of a three-dimensional finite element model of a premolar based on a microscale computed tomographic (CT) data-acquisition technique. The development of the model is part of a project studying the optimal design and geometry of adhesive tooth-colored cusp-replacing restorations. Materials and Methods: The premolar was digitized with a micro CT scanner with a resolution of 13 µm. Surface contours were fitted to the various materials, after which a 3-D finite element mesh was constructed to the contours. To demonstrate the potential use of the resulting model, it was applied to a cusp-replacing resin composite restoration. Results: The stress patterns generated in the composite material were truly 3-D. Stress concentrations were found at the surface where the load was applied and in the vicinity of the dentin-composite bonding surface, where the interface had its complex geometry. Conclusion: The described procedure is an easy method to produce a highly detailed 3-D finite element model of a premolar with an adhesive cusp-replacing restoration.

Purpose: The recent development of several dental ceramic products has raised questions concerning the relative translucency potential of these materials. The objective of this study was to test the hypothesis that the contrast ratio of dental core and veneering ceramics is a linear function of ceramic thickness. Materials and Methods: Four groups of disk-shaped core ceramic specimens and four groups of veneering ceramic specimens (15 mm in diameter and 0.70, 1.10, 1.25, or 1.50 mm in thickness) were prepared for analysis. Five disks were randomly assigned to each of the eight groups. Four core ceramics were selected for study: (1) tetrasilicic fluormica glass ceramic, (2) quadruple-chain silicate glass ceramic, (3) barium silicate glass ceramic, and (4) sintered alumina. The four veneering ceramics included two feldspathic body porcelains, one fine-grained veneering porcelain, and one ultralow-fusing porcelain. Results: There were significant differences among the mean contrast ratio values of these materials. The most translucent group of the core materials was tetrasilicic fluormica glass ceramic, and the least translucent material was sintered alumina. The most translucent group among the veneering ceramics was one of the feldspathic ceramics (Ceramco), and the least translucent material for all thicknesses was the ultralow-fusing veneering ceramic (Duceram LFC). The mean contrast ratio values were significantly different at a thickness of 1.50 mm of the four core ceramic groups and among the four veneering ceramic groups. Conclusion: The results of this study indicate that the tetrasilicic fluormica glass ceramic is generally the most translucent core ceramic for thicknesses of 0.70, 1.10, and 1.25 mm, and Ceramco porcelain is the most translucent veneering ceramic. However, for a thickness of 1.50 mm, the quadruple-chain silicate glass ceramic was the most translucent core ceramic. The relationship between contrast ratio and thickness was linear for all ceramics except Vita VMK 68.

Purpose: The purpose of this retrospective multicenter study on implants combined with natural teeth was to investigate the implant survival rate and loss of marginal bone, as well as indications and complications pertinent to this form of implant therapy. Materials and Methods: The study comprised 185 implants in 111 patients from six different clinics in Sweden. Gathering of data, which were taken from patient records, followed a strict protocol. The registrations included indications for treatment, failure of implants, radiographs from baseline and follow-up, and information on complications. Results: The cumulative implant survival was found to be 95.4% (standard error 4.5%) up to 3 years of follow-up. The marginal bone level at baseline was lower in the maxilla compared with the mandible (P = .015), but any further loss did not differ between the jaws. The most severe complication other than loss of osseointegration (6/185) or periimplant infections (4/183) was intrusion of the abutment teeth, which occurred in 5% of the cases. In all instances, the intrusion was seen in constructions with nonrigid forms of connection between the implants and teeth. Conclusion: The tooth-implant supported prosthesis using the Brånemark system is in the short term an equally predictable treatment as the completely implant-supported prosthesis concerning implant survival and loss of marginal bone. When combining implants and teeth, a rigid form of connection should be used to prevent tooth intrusion.

Purpose: The aim of this retrospective study was to present the results of implant-supported telescopic prostheses in the mandible after removal of malignant tumors. Materials and Methods: Between 1991 and 2000, 24 patients with squamous cell carcinoma (16 irradiated, eight nonirradiated) underwent mandibular rehabilitation with implant-supported telescopic prostheses. A total of 111 dental implants were placed. Treatment complications were observed. The cumulative survival rates of the implants and prostheses were evaluated by lifetable analysis. Results: Within a mean follow-up period of 30 months (1 to 108 months), only three implants failed. All other implants are still in function. Of 24 patients, 23 were satisfied with their implant-supported telescopic restorations. Soft tissue, implant, or prosthetic complications occurred very rarely. The cumulative implant survival rate was about 97% and the cumulative prosthesis survival rate was about 95% at 9 years. Conclusion: Implants and implant-supported telescopic maxillofacial prostheses can successfully remain in function over a long period. Increased implant and prosthetic complications should not be expected. Therefore, telescopic implant attachments seem to be very useful as a treatment option for prosthetic restoration of the mandible in tumor patients.

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-µm 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°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.

Purpose: The suitable buccolingual width and the location of occlusal rest seats for removable partial dentures have not been scientifically established. The aim of the present study was to use three-dimensional geometric analysis to evaluate the effects of buccolingual width and the location of occlusal rest seats on load transmission to the abutments for tooth-supported removable partial dentures. Materials and Methods: A tooth-supported portion of a maxillary removable partial denture with two conventional circumferential cast clasps and an indirect retainer was analyzed. Occlusal loading of 100 N was applied to the buccal mesial cuspal incline 2.0 mm from the central fossa of the first molar or to the lingual mesial cuspal tip. Four combinations of position and width (wide, buccal shift, middle, and lingual shift) were simulated. Results: For buccal loading, the wide rests and buccal-shift rests produced lower tensile forces at the indirect retainer. For lingual loading, the buccal-shift rests produced the lowest compressive force to the anterior abutment. Conclusion: Based on the tooth-supported removable partial dentures that were analyzed, buccal shifting of the rest seats seems to be advantageous for load transmission to the abutments.

Purpose: Clinical damage, such as the fracture or abrasion of composite veneers, may cause the loss of a fixed partial denture (FPD). Intraoral methods may help in repairing and therefore lengthening the life span of the restoration. The aim of this in vitro study was to evaluate an intraoral method of repairing fractured FPDs made of two different fiber-reinforced composite framework systems. Materials and Methods: Shear bond strengths of a composite between two different fiber-reinforced composite frameworks were determined after five different mechanical surface treatments. A silicate-silane coating intraoral air-abrading system provided the most reliable bond strength values and was therefore used for treatment for the following veneer repair. The repair of 24 three-unit posterior FPDs was performed using a restorative composite resin. All FPDs were examined after simulating clinical service using thermocycling and mechanical loading. Fracture forces were determined for original FPDs and for FPDs after simulated intraoral repair. Results: The fracture strength of all original FPDs was about 900 N. After repair, a maximum decrease in strength of about 15% was determined. FPDs that were extremely damaged by cutting the framework showed the lowest results, with values of about 450 N. Conclusion: The repair of the fractured veneer of fiber-reinforced composite FPDs provided good results and therefore may lengthen the life span of damaged FPDs. The repair of the fractured frameworks showed good results but can only be recommended for limited temporary use.

Purpose: The addition of silicon carbide whiskers has been known to reinforce ceramics. This study compared the flexural strength of a glass-infiltrated alumina dental ceramic with various amounts of silicon carbide whiskers incorporated into the alumina matrix. Materials and Methods: Three groups with a total of 30 specimens were included: glass-infiltrated alumina dental ceramic with 0, 0.125, and 0.25 wt% silicon carbide whiskers. The flexural strength was measured using a three-point bending test, and the data were analyzed with one-way analysis of variance. Scanning electron microscopy was used to examine the fracture surfaces of all three materials. Results: There were no significant differences in the flexural strength among the three groups. Glass-infiltrated alumina dental ceramic failed predominantly by transgranular fracture and to a lesser degree by intergranular fracture. Conclusion: The addition of silicon carbide whiskers did not change the flexural strength of glass-infiltrated alumina dental ceramic.

Purpose: This article presents a review of the literature on factors that affect the resistance to fracture of post-core reconstructed teeth. Materials and Methods: Articles cited in a MEDLINE search were obtained from the journals and reviewed with respect to factors affecting fracture resistance of post-core reconstructed teeth. Results: A large part of the literature reviewed emphasizes the stress distribution during insertion of posts and during function. Other factors, like post length, post diameter, amount of remaining dentin, post material, post adaptability, post design, cement, core material, core and crown design, biocompatibility of post material, use of treated tooth, and load experienced by restored tooth, are also found to influence the fracture resistance of a reconstructed tooth. Of all the factors enumerated, crown design, occlusal forces, and use of the treated tooth are found to have direct impact on the longevity of the restored tooth. Conclusion: Literature indicates that (1) preservation of tooth structure is a must; (2) posts should not be used with the intention of reinforcing the tooth; (3) review of functional and parafunctional forces must be undertaken before restoring the tooth, as these will influence the prognosis; and (4) controlled prospective clinical studies evaluating each factor should be undertaken.

Purpose: The objective of this study was to compare two methods for reducing gagging induced by stimulation of the soft palate: table salt and nitrous oxide inhalation sedation. Materials and Methods: Fifteen healthy volunteers, eight men and seven women with a mean age of 20.6 years, were subjected to a gagging event three times using a large tablespoon to stimulate the soft palate: event 1 = spoon alone, event 2 = spoon and table salt on the tip of the tongue with a 30-minute break between events 1 and 2, and event 3 = spoon and nitrous oxide sedation on another day. Time in seconds was measured from the moment the spoon touched the soft palate until gagging was felt using a chronometer held by the subject. Results: The mean time for eliciting the gagging reaction was 7.7 seconds for the spoon alone, 8.9 seconds for the spoon and table salt, and 24.0 seconds for the nitrous oxide sedation. Nitrous oxide inhalation sedation significantly (P .001) reduced the gagging/retching reaction, whereas there was no significant time difference in gagging reaction between stimulation with the spoon alone or when table salt was added. Conclusion: Within the limits of this study, table salt did not seem to reduce the time to triggering the gag reflex, whereas nitrous oxide had a substantial effect.

Purpose: The aim of this study was to quantify masseter muscle deformation during palpation and to discuss the clinical significance of muscle palpation using magnetic resonance imaging (MRI) and the image-analysis procedure. Materials and Methods: Subjects were 10 male volunteers with a mean age of 26.8 years. MRIs were taken under two muscle conditions: compressed and noncompressed (control). By superimposing a compressed image on a noncompressed image, muscle deformation (the cross-sectional area, length of the surrounding area, thickness, circular convolution, compressed point, and anterior and posterior extension) was measured. Results: The cross-sectional area of the masseter muscle was diminished by 14%, circular convolution of the muscle was reduced by 31%, the length of the surrounding area was enlarged by 11%, and the thickness of the muscle was reduced by 6.7 mm because of compressing. Thus, the masseter muscle was compressed. An uneven stretch of the muscle caused by compression was observed at the same time. The anterior portion of the masseter muscles extended on average 10%, with great individual differences. On the other hand, posterior extension (3%) and its individual differences were small. Conclusion: The method used made it possible to quantify masseter muscle deformation. By compressing, the masseter muscles were deformed especially in the anterior direction but with great individual differences.

Purpose: This study compared the cuspal fracture resistances of posterior teeth restored with five different adhesive restorations. Materials and Methods: Eighty-four sound human molars were included in this study. Sample molars were divided into seven groups. The first five groups received mesio-occlusodistal cavity preparations and were restored with (1) amalgam combined with urethane dimethacrylate cement, (2) posterior composite, (3) direct composite inlay, (4) cast-metal inlay, and (5) complete ceramic inlay. The sixth and seventh groups were introduced in the study as controls. Samples of group 6 were prepared but were tested without restoration (prepared-only group). Samples of group 7 were intact teeth and were tested as unprepared. All samples were loaded axially until failure. Results: While the unprepared teeth had a significantly higher resistance than all other groups, the prepared-only teeth were the weakest. No significant differences were found in resistance to cuspal fracture among the restoration groups. Conclusion: The difference between the mean cuspal fracture resistance of the unprepared and prepared-only groups was statistically significant. Restoration groups were stronger than the prepared-only group. However, differences between the restoration groups were insignificant.

Purpose: The purpose of this study was to investigate whether the properties of the In-Ceram material are adequate for use in posterior three-unit fixed partial dentures (FPD) and to evaluate the clinical method regarding preparation technique, design, and choice of cement. Materials and Methods: Eighteen patients were treated with a total of 20 posterior three-unit FPDs according to the In-Ceram technique. The FPDs were constructed with bilateral support and one pontic and were all replacing one premolar or a molar (11 replacing premolars and 9 replacing molars). They were evaluated 6 months after delivery and then once yearly. Results: Eighteen of the 20 FPDs (90%) showed no defects at any of the follow-up examinations and were functioning well after 5 years. No caries or signs of gingivitis or periodontitis exceeding those found in the rest of the dentition were registered. Conclusion: The In-Ceram technique is, in a 5-year perspective and adopted for three-unit FPDs, an acceptable treatment alternative. Further studies must, however, be performed before the material can be recommended for more extensive restorations than the FPDs included in this study.