The International Journal of Prosthodontics, 05/2003

Purpose: This study examined patient satisfaction with conventional complete dentures and mandibular implant overdentures opposing conventional maxillary dentures 6 months after delivery. Materials and Methods: Sixty edentulous subjects (aged 65 to 75 years) were randomly assigned to either a mandibular conventional denture or an overdenture supported by two implants with ball-shaped retentive anchors. Patients rated their general satisfaction and other features of their prostheses, together with their ability to eat certain food items, on 100-mm visual analogue scales before assignment, and after 2 and 6 months. Results: Both treatment groups reported greater satisfaction with their new prostheses at 6 months. General satisfaction ratings were higher in the implant group than in the conventional denture group by approximately 36% (mean difference 22.3 mm). The implant group also rated comfort (mean difference 22.4 mm), stability (mean difference 28.5 mm), and ability to chew (mean difference 17.3 mm) significantly higher. Significantly higher scores were also given by the implant group for their ability to chew certain hard foods. A trend for an increase in the differences between the groups, in favor of the implant group, was observed between the 2- and 6-month recalls, although the increase was only significant for ease of cleaning. The primary influence on general satisfaction 6 months after the delivery of the prostheses was the provision of the two-implant overdenture. Conclusion: Edentulous seniors who received mandibular implant overdentures opposing a conventional denture rated their general satisfaction approximately 36% higher than did a comparable group provided with new conventional dentures.

Purpose: This study examined the influence of ceramic coping thickness on the maximum stresses that arise in a first premolar all-ceramic crown. Materials and Methods: Axisymmetric finite element models with different In-Ceram Alumina coping thicknesses (0.3, 0.6, and 0.9 mm) were examined. Models with and without resin lute were constructed. To all models, an identical axial load of 600 N was applied vertically downward, over an area around the crown's fissure. Results: The resulting peak tensile maximum principal stresses in each part of the crown existed below the fracture strengths of the respective materials making up the crown. This was true for all variations of core thickness, with and without resin lute. The peak tensile stresses in the coping, porcelain, and dentin decreased for an increase in core thickness. This was most evident in the porcelain and coping. Conclusion: The thickness of the ceramic core has a significant influence on the resulting stresses in the coping, porcelain, and dentin of this axially loaded crown.

Purpose: The aim of this study was to investigate whether systematic modifications of occlusal features or food consistency are suitable to reduce the loading of implants. Materials and Methods: Ten healthy subjects, each of whom had a gap in the chewing center (second premolar or first molar) of one lateral dental arch, were provided with fixed partial dentures (FPD) on two ITI implants. Strain gauges attached to the abutments recorded forces in three dimensions. In each person, the original FPD was successively replaced by three FPDs with different occlusal schemes: The first had steep cusps, the second had flat cusps, and the third had the same cuspal inclination as the first but a narrow occlusal surface. Subjects chewed gummy bears and bread as a tough and a soft bolus, respectively. Results: In chewing of gummy bears, the mean vertical forces of the three FPDs ranged between 264 and 284 N and were not significantly different. The mean bending moments amounted to 27 Ncm and 24 Ncm with steep and flat occlusal slopes, respectively. With the narrow occlusal surface, the bending moments were reduced by 48%, to a mean of 11 Ncm. Chewing of bread yielded similar relations with lower mean vertical forces and bending moments. Conclusion: Narrowing the orovestibular width of the occlusal surface by 30% caused a significant reduction of lateral force components. A reduced orovestibular width of the occlusal surface is recommended in unfavorable loading conditions. In addition, the chewing of soft food is suggested during the healing period in cases of immediate loading.

Purpose: The probability of failure under flexural load of veneered specimens of a unidirectional glass fiber-reinforced composite (FibreKor/Sculpture), a bidirectional glass fiber-reinforced composite (Vectris/Targis), a glass-infiltrated alumina (In-Ceram Alumina/Vita α), and a zirconia-reinforced glass-infiltrated alumina (In-Ceram Zirconia/Vita α) was investigated; a metal-ceramic (PG200/Vita Ω) system served as a control. Materials and Methods: Ten uniform beams of the veneered core materials were fabricated for each system and subjected to a three-point bending test. The data were analyzed using the Weibull method. The failure load of specimens at a 10% probability of failure (B10 load) was compared. The mode of failure was analyzed. Results: The B10 load of the systems investigated was not significantly different from that of the metalceramic system. FibreKor possessed significantly higher B10 load than Vectris, In-Ceram Alumina, and In-Ceram Zirconia. The B10 strength loads of Vectris, In-Ceram Alumina, and In-Ceram Zirconia were not significantly different from one another. Conclusion: The probability of FibreKor to fracture under a flexural load was significantly lower than that of Vectris, In-Ceram Alumina, or In-Ceram Zirconia.

Purpose: The purposes of this study were to evaluate the shear bond strength of luting glass-ionomer cement to a dentin surface treated by pulsed Nd:YAG laser irradiation, and to prove the hypothesis that the bond strength of glass-ionomer luting cement to dentin is favorably altered after Nd:YAG laser irradiation. Materials and Methods: Sixty-four extracted human molars with an exposed flat dentin surface were divided into four groups (n = 16). After painting black ink on their surfaces, the teeth of groups 1, 2, and 3 were irradiated by an Nd:YAG laser at 1.064-µm wavelength at 1, 2, and 3 W, respectively; group 4 was untreated and served as a control. Some specimens of each group were used for morphologic and atomic analytic study, and the others were used for shear bond testing. The shear bond test was performed after cylindric titanium specimens were cemented with glass-ionomer cement on a circular dentin area and specimens were immersed in distilled water. The tested specimens were also morphologically investigated. Results: Shear bond strength of group 3 was significantly higher than that of the control group. Morphologic observation of the cement-dentin interface showed good adaptation of the luting cement to laser-treated dentin. Analysis of atomic contents on the dentin surface showed a significant increase of calcium:phosphorus ratio after laser irradiation. Conclusion: The dentin surface was modified morphologically and chemically, and the shear bond strength of glass-ionomer luting cement to dentin was increased by Nd:YAG laser irradiation at 3 W.

Purpose: The purpose of this study was to investigate the strength of the composite resin- denture tooth bond as affected by different tooth surface treatments. Materials and Methods: Spectrum TPH was condensed on 112 mandibular first molar acrylic resin and composite resin denture teeth, which received seven different treatments: Four groups were treated with Prime & Bond NT adhesive, and three groups were treated with One Step adhesive. Four groups (two of each adhesive category) were treated with Composite Activator and air abrasion. In one group, AeliteFlo was used just before the condensation of Spectrum TPH. Bond strength was evaluated with a shear test device on a Monsanto testing machine. The results were evaluated statistically with two-way ANOVA and the Scheffé method. Results: There was a significant interaction between denture tooth type and surface treatments. Bond strength of composite resin was greater to composite than to acrylic resin teeth when the bond was mediated only with adhesives. One Step adhesive and AeliteFlo resulted in a higher bond of composite resin to both types of teeth. Wetting tooth surfaces with Composite Activator did not increase the bond. Conclusion: When repairing denture teeth with composite resin and adhesives, the bond strength was higher with composite than with acrylic resin teeth, and there were differences between the adhesives used.

Purpose: The purpose of this study was to test the hypothesis that nucleation temperature significantly affects the fracture toughness of a fluorcanasite-based glass-ceramic. Materials and Methods: Sixty specimens were cut from a glass bar, polished, and randomly divided into six groups for nucleation treatment at temperatures of (1)520°C, (2)550°C, (3)580°C, (4)610°C, (5)640°C, and (6)670°C for 4 hours and a crystallization temperature of 850°C for 6 hours. A precrack was produced at the center of each bar, and the prepared specimens were subjected to three-point flexural loading with the cracked surface under tension using an Instron machine at a cross-head speed of 0.5 mm/min. Fracture toughness was calculated based on the indentation strength technique, and crystal volume fraction was determined by quantitative stereology of SEM images of each group of ceramic specimens. Results: The mean fracture toughness and crystal volume fraction ranged from 2.6 to 3.5 MPa·m1/2 and from 65% to 81%, respectively, within the limits of the nucleation temperatures investigated. ANOVA showed statistically significant differences among the test groups. Based on Duncan's multiple comparison test, significant differences in mean fracture toughness and crystal volume fraction were found among the following statistical subsets: groups 1 to 4, group 5, and group 6. Conclusion: Fracture toughness and crystal volume fraction of a fluorcanasite-based glass-ceramic were strongly influenced by nucleation temperature; the crystals precipitated during thermal processing are thought to be an important factor in increasing fracture toughness.

Purpose: The aim of this retrospective longitudinal study was to document the outcomes of resin-cemented ceramic inlays in patients treated in a private dental practice over up to 9 years. Materials and Methods: Fifty-two patients received in all 109 Mirage ceramic inlays, 59 in molars and 50 in premolars. Follow-up data were collected on 51 patients and 107 inlays. The mean time in situ was 6.3 years. Technical failures or dislodgments of the inlays were recorded, as well as clinical and radiographic signs of periodontal and periapical diseases or caries lesions. Results: During the follow-up period, 17 inlays had to be removed, 14 because of major fractures and 3 in teeth requiring endodontic treatment. The fractures were confined to 8 of the 51 patients available for follow-up and were significantly more common in molars than in premolars. Replacement of inlays was significantly more frequent in men than in women. During the study period, 20 further minor clinical interventions (eg, recementation of intact inlays, repair of minor fractures or caries defects) had been undertaken on the surviving inlays. Thus, major and minor complications together necessitated a total of 37 clinical interventions. The survival rate, based on the remaining 90 inlays still in situ, was 84%. Conclusion: In this material, the outcome of ceramic inlay therapy was influenced by both major and minor complications (35%). Eight of the 51 patients accounted for all the major fractures, implying that patient selection is an important determinant of the clinical outcome.

Purpose: The objective was to explore and gain insight into the sentiments surrounding tooth loss in a group of edentulous Saudis. Materials and Methods: Using a qualitative methodology, 44 edentulous patients who were receiving complete denture treatment were interviewed in private, in the Arabic language. Interviews were tape recorded and semistructured, following a list of predetermined and piloted topics, but dialogue also took place, with the freedom for both interviewer and interviewee to explore areas of interest. All recordings were transcribed, translated into English, and interpreted independently by two members of the team to identify the core themes associated with tooth loss. Results: The mean age of participants was 58.9 years (range 35 to 72 years), and they had been edentulous for a mean of 7.1 years (range 3 months to 22 years). The main themes related to tooth loss were unqualified acceptance, inevitability with old age, behavior changes with respect to eating comfort, aged appearance, self-responsibility, positively perceived benefits, high prosthetic expectations and reduced level of denture satisfaction, and some need for privacy. Conclusion: The lack of any outward indication that participants experienced bereavement suggests that outlook on life can influence the impact of tooth loss. Participants' unqualified acceptance of their edentulous fate, yet their clear need to "normalize" oral function, reflects a degree of pragmatism toward life events. The strong influence of religion in Saudi society is a possible factor in the sentiments expressed.

Purpose: The purpose of this study was to compare the maintenance requirements of implant-supported fixed prostheses with cantilever arms in edentulous jaws when opposed by fixed prostheses of similar design, by natural teeth, or by complete dentures. Materials and Methods: The maintenance requirements for the 5-year follow-up period were obtained by examining the dental records of 37 people. Six were provided with fixed prostheses in both arches, 22 with a fixed prosthesis in the mandible opposed by a complete denture, and 9 with a fixed prosthesis opposed by natural teeth. Everyone was treated with Nobel Biocare implants using standard implant and prosthetic protocols. Results: The denture teeth and acrylic resin were repaired on 44 occasions in the group with implants in both jaws, on 14 occasions in the group with implants opposed by natural teeth, and twice in the group in which the implants were opposed by a complete denture. The group with implants in both jaws was more likely to fracture the gold-alloy framework, which occurred on six occasions. The group with implants in both jaws was significantly different from the other two groups in relation to higher incidence of fracture of the teeth and gold-alloy framework. Conclusion: The maintenance requirements of implant-supported fixed prostheses with cantilever arms opposed by fixed prostheses of similar design were much greater than when opposed by natural teeth or complete dentures.

Purpose: This study evaluated the status of teeth adjacent to single-tooth implants in the anterior and posterior jaw during a follow-up of more than 3 years. Materials and Methods: Seventy-eight single-tooth implants and 148 adjacent teeth were followed for a mean of 58 months. Implant survival rate, peri-implant structures, and prosthetic complication rates were evaluated. Crowns and periodontal status of adjacent teeth were compared at crown placement and at the last examination. Horizontal distance from the implant edge to adjacent teeth was calculated and compared for anterior and posterior regions. The influence of approximal crestal bone resorption of the adjacent teeth was calculated using multivariate regression analysis. Results: The clinical findings for implants (one loss), periimplant structures, and prosthetic complication rates (three crown fractures) were excellent. There was a high proportion of intact adjacent teeth in both anterior and posterior regions at crown placement and at the follow-up examination. No adjacent teeth required extraction or endodontic treatment, and only four required restoration. Comparison of the periodontal status at crown placement and at follow-up revealed no differences for plaque and bleeding indices or for pocket depth of adjacent teeth. There was a significant influence of the horizontal distance on approximal bone loss in the closer distance of the anterior region, but not in the posterior region. Conclusion: The crown and periodontal status of teeth adjacent to single-implant restorations was excellent. The approximal bone crest reduction of the adjacent teeth was significantly influenced by the horizontal distance between the implant edge and neighboring tooth.

Purpose: The purpose of this follow-up study was to quantify the change in the periimplant mucosal level after treatment of edentulous patients with fixed prostheses on osseointegrated endosseous implants. Materials and Methods: Twenty patients were included in the study: 10 were treated in the maxilla, and 10 were treated in the mandible. Both groups had fixed prostheses on osseointegrated Brånemark implants. Periimplant mucosal level was measured with a calibrated probe after removal of the prostheses at the 1-year follow-up. These measurements were compared to those made on the original master casts. Results: A larger mean retraction (-) was observed in the mandible (-1.6 mm) compared to the maxilla (-0.8 mm), but there was great variation. The individual values varied from -4.5 to +1.0 mm in the mandible and from -6.0 to +6.0 mm in the maxilla. Conclusion: Peri-implant soft tissue recession occurs during the first year in edentulous jaws after treatment with implant-supported fixed prostheses and more so in the maxilla than the mandible.

Purpose: The aim of this study was to investigate the changes in interocclusal distance during the pronunciation of /m/ and /s/ sounds in the Portuguese language, in partially edentulous patients before and after insertion of new dentures. Materials and Methods: Subjects were divided into a control group consisting of 18 completely dentate patients and an experimental group consisting of 18 patients who were edentulous in the maxilla and classified as Kennedy Class I in the mandible. The experimental group had new dentures placed and the occlusal vertical dimension corrected. A magnetic jaw-tracking device measured the interocclusal distance during pronunciation of the /m/ and /s/ phonemes. Interocclusal distance evaluations were carried out in a single session for the control group. In the experimental group, the measurements were carried out before insertion of new dentures; immediately after insertion; and after 6 and 24 hours; 2 days; 1 and 2 weeks; 1, 2, 3, and 6 months; and 1 year. Results: Comparison between groups revealed significant difference in interocclusal distance for the /m/ sound both before and after insertion of dentures up to 2 months. For the /s/ phoneme, there was no difference between the groups before prosthesis insertion, or after 3, 6, and 12 months of prosthesis use. There were significant differences for the /m/ sound only at 6 and 12 months after new denture insertion, and for the /s/ sound at all periods evaluated. Conclusion: Insertion of new dentures, with the vertical dimension corrected, changes the interocclusal distance of speech during phonation of /m/ and /s/ sounds.

Purpose: This in vitro study investigated the marginal adaptation and fracture resistance of heat-pressed glass-ceramic and fiber-reinforced composite molar crowns luted with resin, resin-modified glass-ionomer, or zinc-oxide-eugenol-free cements. Materials and Methods: A total of 24 heat-pressed all-ceramic and 24 glass fiber-reinforced composite crowns were constructed and cemented using the above-mentioned luting agents (eight crowns per cement). The restorations were thermocycled and mechanically stressed, and fracture resistance was determined. Marginal adaptation was evaluated before and after stress application using semiquantitative analysis in a scanning electron microscope. Results: All-ceramic and fiber-reinforced composite crowns reached the highest fracture resistance after stress application in combination with the resin cement. When luted with resin-modified glass-ionomer or zinc-oxide-eugenol-free cements, the fracture resistance of all-ceramics decreased significantly, while the fiber-reinforced composite crowns maintained their fracture resistance level; the lowest values were found for zinc-oxideeugenol -free cements. The marginal adaptation remained unchanged after stress for allceramics and fiber-reinforced composite restorations if they were luted with resin cements. Luting with resin-modified glass-ionomers significantly deteriorated the marginal adaptation after stress application, with the exception of the crown-cement interface of all-ceramics. Conclusion: The highest fracture resistance and marginal adaptation were found for all-ceramic and glass fiber-reinforced composite molar crowns if they were luted with resin cement.

Purpose: This article presents a novel manufacturing approach that integrates laser surface digitizing/scanning and computer-aided design and manufacturing (CAD/CAM) to achieve automated fabrication of spatially and anatomically accurate extraoral facial prostheses. Materials and Methods: Contrary to the approach in part 1 for fabricating positive replicas of prostheses, the approaches presented here are focused on designing and producing negative molds of the final prostheses using CAD, rapid prototyping, and rapid tooling techniques. The molds were applied directly to cast the final prostheses, thereby eliminating conventional flasking and investing procedures. Results: Three different facial prostheses were produced to evaluate the proposed approach for prosthesis production. The advantages of this alternative manufacturing approach over the approach presented in part 1 and conventional techniques are discussed. The limitations encountered with the integrated manufacturing system are highlighted. Conclusion: With the new techniques, reduced patient discomfort, minimal dependence on the artistic skills of the prosthetist, and short turnaround times for prosthesis production can be expected.

Purpose: The purpose of this study was to examine the flexural strength and elastic modulus of a new fiber-reinforced composite used for the fabrication of inlay-retained fixed partial dentures (FPD). Materials and Methods: A total of six materials were used: Vectris, FibreKor, and an experimental material, BR-100, were the types of glass fiber preimpregnated with resin used for making the frameworks; Targis, Sculpture, and Estenia were used as the veneering composites. Five specimens of each material were prepared. Flexural strength and elastic modulus were determined using the three-point bending test. In addition, laminate specimens were fabricated by combination of the veneering composite and framework materials (Targis/Vectris, Sculpture/FibreKor, and Estenia/BR-100), and fracture loads of these specimens were determined. Laminate specimens were fabricated with three different framework thicknesses for Estenia/BR-100. Results: Estenia had the greatest strength and highest modulus of elasticity of the veneering composites. All three framework materials had flexural strength values (567 to 686 MPa) more than three times as great as those of the veneering composites (132 to 193 MPa). Of the laminate specimens, the Estenia/BR-100 with a framework thickness of 1.0 mm had a fracture load more than 50% greater than Targis/Vectris and Sculpture/FibreKor. Conclusion: The combination of the experimental framework material BR-100 and the composite Estenia showed higher fracture loads than the other combinations tested.

Purpose: The purpose of this study was to investigate the clinical and radiographic outcome of a prospective 5-year longitudinal multicenter test of a simplified implantology concept comprising an abutment-free implant system (Cresco) and a new method for fabrication of passively fitting superstructures, the Cresco Ti Precision method. Materials and Methods: The tests were carried out at three different centers. Sixty partially or completely edentulous patients were restored by fixed implant-supported superstructures fabricated according to the Cresco Ti Precision method. In all, 215 Cresco implants were placed for the support of the superstructures. For various reasons, eight patients (13%) could not be followed through the 5 years. The radiographic measurements were recorded from radiographs exposed perpendicular to the implants. Results: The initial implant failure rate (during the healing phase) was 2%, and the survival rate after loading was 98%. The mean peri-implant bone loss was 0.29 mm (SD 0.57). Of the measured sites, 71% showed a crestal bone loss of less than 0.5 mm. Very few mechanical complications were observed. This was attributed to the passively fitting superstructures. Conclusion: The results from the present multicenter test demonstrated that the abutment-free Cresco implantology concept is a reliable alternative method for implant-supported fixed prosthetic rehabilitation of edentulous and partially edentulous jaws.

Purpose: Systems of recording jaw movements that are used in prosthodontics and orthodontics are too expensive and complicated for daily clinical diagnosis. This pilot study presents the development of a simple system using a camcorder and motion-capturing software. Materials and Methods: Markers to detect jaw movement were attached to the mandibular incisors of a subject. A mirror was assembled beside the subject's face to detect anteroposterior movement. Jaw movements were recorded by a home digital camcorder. Movements of the markers were analyzed by motion-capturing software and transferred to 3-D data. The results were compared with those of a conventional system. To examine the accuracy of the measurements, the markers were placed on a computer-controlled x-y working stage and displaced. The positions of the markers were measured and analyzed, then compared with the true values indicated by the x-y working stage. Results: The trajectories of the mandibular incisors recorded by the new system were very similar to those of the conventional system. On measurement accuracy, the mean differences between the measured and true values of the vertical and transverse movements were 0.07 mm (SD 0.03) and 0.06 mm (SD 0.04), respectively. On anteroposterior movement, the difference was 0.11 mm (SD 0.05). Conclusion: This new system can be useful for simple recording of jaw movements with satisfactory accuracy.