The International Journal of Prosthodontics, 04/1999

PURPOSE: The aim of the present article was to describe the treatment planning for an implant-supported maxillary fixed prosthesis and the clinical procedure involved, including the laboratory fabrication sequence. MATERIALS AND METHODS: If patients request a fixed prosthesis to restore the edentulous maxilla, it is essential to decide as soon as possible whether this prosthesis design can satisfy the requirements of esthetics, phonetics, comfort, and function. Thus, the crucial clinical factors need to be checked during examination. Furthermore, the relationships between ideal implant angulation, available bone, and intended crown should be assessed using reformatted computed tomography. RESULTS: In patients with minimal bone resorption and limited intermaxillary space, implants can usually be placed in the prosthetically driven implant position for a fixed prosthesis. To evaluate and optimize esthetics, biology, and function, a fixed provisional restoration should be inserted for a 6-month diagnostic period. The ideal provisional then serves as a guide for the final restoration. CONCLUSION: If clinical and radiologic diagnostics indicate that an implant-supported fixed complete denture is feasible, meticulous presurgical planning, precise execution of implant positioning, and a progressive prosthetic treatment sequence are required. The ceramometal fixed implant-supported restoration can then be established in an ideally prepared and matured oral environment.

PURPOSE: This study reports on the development and evaluation of a telemetry system for recording salivary pH. MATERIALS AND METHODS: The system used an iridium-oxide pH sensor (Metoxy sensor) and was housed inside a mandibular complete denture. It transmitted the data using the AM band (radio frequency of 12.3 MHz) and had a maximum power output of approximately 1 mW with a 3-V lithium battery (capacity 190 mAh). For the clinical evaluation, a 69-year-old woman who was edentulous and had no systemic disease was the subject. RESULTS: Under the conditions of the study, the system was able to operate for 19 hours. The maximum error of transmitted pH data values was pH 0.15 within the range from pH 5.0 to 9.0. The evaluation of the test subject showed that this system operated without problems, and that the pH levels responded appropriately. CONCLUSION: The developed system was shown to successfully record salivary pH, and it functioned as expected in a single test subject.

PURPOSE: This is a 2-year report from an ongoing prospective 5-year multicenter study. The aim of the study was to evaluate the short- and long-term clinical function of CerAdapt ceramic abutments supporting short-span fixed partial dentures (FPD). MATERIALS AND METHODS: Initially, 105 Brånemark System implants were placed in a total of 32 patients at 3 different clinics. After initial healing 103 implants remained. For the support of 36 FPDs, 53 ceramic and 50 titanium abutments were connected, 19 on ceramic and 17 on titanium abutments. RESULTS: All patients remained in the study after 2 years. There was a cumulative survival rate of 97.1% for implants and a cumulative success rate of 97.2% for FPDs (94.7% for ceramic and 100% for titanium abutment-supported FPDs). One of 53 ceramic but none of 50 titanium abutments failed, giving a cumulative success rate of 98.1% and 100%, respectively, for the abutments. Soft tissue around abutments and adjacent teeth appeared healthy. More crown margins were placed submucosally at titanium (31%) than at ceramic (14%) abutments, and the level of the periimplant mucosa was relatively stable in relation to the abutment/crown. No differences were seen between ceramic and titanium abutments regarding bleeding of the periimplant mucosa. There was a minimal marginal bone loss recorded after 1 year, which was slightly more at titanium (0.4 mm) than at ceramic (0.2 mm) abutments. All patients and dentists were satisfied with the achieved esthetic result and no FPD was remade because of compromised esthetics. CONCLUSION: So far the ceramic abutments have worked very well and the 2-year results have been very encouraging for CerAdapt abutments supporting short-span FPDs. However, ceramic materials tend to undergo static fatigue, and it is therefore important to wait for the 5-year results before making any more definite statement about the long-term prognosis for CerAdapt abutments.

PURPOSE: The purpose of this study was to develop a material with low polymerization shrinkage for resin patterns to improve the fit of a long superstructure to implants. MATERIALS AND METHODS: Three different chemical substances were added at 1, 2, 3, 5, 10, and 20 wt% to the liquid component of a self-curing acrylic resin. Specimens for measuring shrinkage during self curing were prepared in a metal mold that took the form of a conical cavity with slightly tapered walls. The specimens were prepared using three different methods: (1) a brush-on technique, (2) an injection method, and (3) an injection-press method. The percentage of linear shrinkage was calculated from the protrusion of the specimen from the bottom of the cavity. RESULTS: The injection-press method and the brush-on method gave the lowest polymerization shrinkage results (P 0.05). The standard deviation of the former method was smaller than that of the latter. The linear shrinkage in the injection-press method decreased with the increase of the powder-to-liquid ratio (P 0.05). All three additives reduced shrinkage to about 1/3 of the shrinkage of the basic resin using the injection-press method and a 2.00:1.00 powder-to-liquid ratio. CONCLUSION: The addition of three different chemical substances to liquid reduces linear shrinkage to about 1/3 of the shrinkage of the original self-curing acrylic resin.

PURPOSE: The purpose of this study was to compare the effect of seven different alloy surface treatments on the bond strength of the porcelain-metal interface. MATERIALS AND METHODS: Three layers of opaque porcelain and a measured thickness of dentin porcelain were applied to nickel-chromium alloy. A tensile bond strength test was used. RESULTS: The alloy surface treatment that exhibited the highest bond strength was sandblast + surface grinding + sandblast + de-gas, whereas the alloy surface treatment that exhibited the lowest bond strength was sandblast + surface grinding + sandblast + steam cleaning + de-gas. There was a significant difference between the two methods (P 0.05). CONCLUSION: It was concluded that de-gassing the alloy prior to porcelain application increased the bond strength and excess surface grinding of the alloy reduced bond strength; steam cleaning the alloy surface prior to de-gassing and porcelain application also significantly reduced the bond strength.

PURPOSE: The objective of this study was to assess and compare patients' and clinicians' judgments of the esthetic outcome of implant-supported single-tooth replacements. MATERIALS AND METHODS: In all, 29 patients with 41 single implant-supported crowns in the maxillary anterior region participated in the study. The esthetic outcome of the implant-supported crowns was assessed by the patients and by 5 prosthodontists by means of a questionnaire in which various esthetics-related variables were addressed and responded to using visual analogue scales. Multiple regression analyses were used to evaluate the influence of the variables on the overall satisfaction with the implant-supported crown. RESULTS: Most variables in the patients' assessments revealed mean values above 90% and median values close to 100%. No single factor used in the multiple regression analysis was found to influence a patient's satisfaction with appearance of the crown at a statistically significant level. The clinicians' degree of satisfaction was for all variables lower than that of the patients. In 89% of the cases the clinicians could correctly locate the single implant-supported crown. Among the variables assessed, surrounding soft tissue appearance and form of the crown had the strongest influence on the clinician's overall satisfaction with the appearance of the crown. CONCLUSION: Appreciation of the esthetic outcome of the single implant-supported crowns was rated higher by the patients than by the prosthodontists. Furthermore, factors considered by professionals to be of significance for the esthetic result of the restorative treatment may not be of decisive importance for the patient's satisfaction.

PURPOSE: The purpose of this study was to evaluate both marginal and overall adaptation of 4 adhesively luted ceramic inlay systems. MATERIALS AND METHODS: A total of 40 extracted teeth were restored with mesio-occlusodistal ceramic inlays using 4 different techniques: Colorlogic, IPS Empress, Celay direct, and Celay indirect. After cementation with a resin luting agent, the samples were sectioned along a mesiodistal line passing through the center of the restoration. The thickness of the cement was measured at the margins and at several points along the inside of the restorations by means of a stereomicroscope fitted with a measuring grid. RESULTS: The results were analyzed by one-way analysis of variance. The marginal precision of IPS Empress and Colorlogic inlays averaged below 50 microns. Marginal precision of Celay inlays averaged between 110 and 130 microns. IPS Empress and Celay inlays showed a uniform distribution of the cement along the entire prepared surface. Colorlogic inlays showed an uneven distribution of the cement film. CONCLUSION: IPS Empress inlays showed the best clinical features compared to Colorlogic and Celay inlays.

PURPOSE: This study characterized the effect of water immersion on the strength of denture polymers. MATERIALS AND METHODS: Four denture-base polymers and four denture-reline polymers were tested for flexural strength at proportional limits (FSpl) at 24 hours and at monthly intervals. The equilibrium strength of each polymer was estimated. RESULTS: The denture polymers took from 24 hours to 4 months to reach their equilibrium strength. The equilibrium strengths of the denture polymers were significantly different. CONCLUSION: Water immersion affected the strength of most denture polymers. Different denture polymers behaved differently in response to water immersion.

PURPOSE: The purpose of this study was to estimate which occlusion offers the best conditions of pressure distribution on the supporting structure under a complete denture when crushing food. MATERIALS AND METHODS: Simulated maxillary and mandibular complete dentures with three different posterior occlusal schemes - fully balanced occlusion, lingualized occlusion, and monoplane occlusion - were fabricated. Eight pressure transducers were placed in the basal surface of a mandibular denture. The pressure distribution on the mandibular edentulous mouth model with 1.5-mm-thick artificial tissue under a complete denture was recorded when crushing three different foods: soft food (kamaboko), peanuts, and carrot. The mean pressure values at each measurement point and the force required for each test were compared using one-way analysis of variance with P or = 0.05 representing statistical significance. RESULTS: The required force for crushing a soft food or carrot in the left molar region in monoplane occlusion was significantly larger than that required in fully balanced occlusion or lingualized occlusion. In crushing soft food, fully balanced occlusion showed significantly higher pressure values on the working side than in monoplane occlusion or lingualized occlusion. In crushing the carrot, the pressure values in fully balanced occlusion and in lingualized occlusion were significantly lower than those in monoplane occlusion. CONCLUSION: These results demonstrate that with fully balanced occlusion and lingualized occlusion a large occlusal force is not needed for crushing hard food, and the stress to the supporting tissues is smaller than with monoplane occlusion.

PURPOSE: This study evaluated some mechanical properties of 2 newly introduced, addition-type silicone prosthetic elastomers (Cosmesil and Episil). MATERIALS AND METHODS: The properties evaluated were tensile strength, modulus at 100% elongation, elongation at break, tear strength, and hardness. The properties tested were selected because of their clinical significance for fabricating facial prostheses. RESULTS: Episil showed greater tensile strength (P = 0.0002), elastic modulus (P = 0.0001), hardness (P = 0.0002), and tear strength (P = 0.0004) than Cosmesil material. Cosmesil exhibited a higher elongation at break (P = 0.0002) than Episil. CONCLUSION: Cosmesil and Episil showed reasonable properties as facial prosthetic elastomers and neither was superior for all properties tested. Both materials showed favorable combinations of elongation at break and tear strength.

PURPOSE: The purpose of this clinical pilot study was to describe a photogrammetric technique to determine implant positions in the oral cavity, and to test and compare this technique to conventional impression/master cast procedures for fabrication of titanium frameworks with a computer numeric-controlled (CNC) milling technique. MATERIALS AND METHODS: Implant positions were recorded by means of conventional impressions/master casts as well as intraoral 3-dimensional photogrammetric measurements in 2 patients who were provided with 5 Brånemark implants each in the edentulous mandible. For each patient 2 titanium frameworks were made by means of a CNC milling technique (All-in-One). Both frameworks had an identical design, but the orientations of the framework cylinder fit surfaces were machined either from measurements from the master casts or from the intraoral photogrammetric measurements. The frameworks were tried for fit in the oral cavity and on the master casts. RESULTS: Both cases showed different precision of fit when comparing the 2 frameworks on the master casts. One of the 2 photogrammetric frameworks was not considered acceptable when tried on the models. In the oral cavity, however, all 4 frameworks presented comparable fit, and all were accepted for clinical use. CONCLUSION: The clinical experiences with try-in of the 4 different frameworks indicated that the photogrammetric technique could be a valid option for conventional impressions when using CNC milling fabrication in implant dentistry. The different results from the model and oral examinations also imply the difficulties of assessing clinical fit when testing fit at the master cast level only.