The International Journal of Prosthodontics, 04/2003

Purpose: This article describes the restorative management of two patients in whom the diagnosis of amelogenesis imperfecta was not made until young adulthood. Materials and Methods: Amelogenesis imperfecta is a variable developmental abnormality of the tooth enamel that affects relatively few persons. Previous case reports have focused largely on the early management of children and young adolescents. However, some patients may not be diagnosed correctly or may not request dental treatment until they are older, as with the two cases presented. In some instances, parents fail to appreciate the importance of early intervention. Results: Both patients required intensive preventive therapy and extensive restorative treatment over several years. The correct sequencing of treatment phases was required to achieve relief of pain and provide satisfactory function and esthetics. Conclusion: The two cases presented illustrate the degree of complexity that extended restorative treatments can involve, especially following severe tooth wear and poor bonding of restorations to the affected enamel.

Purpose: Persistent vegetative state is a form of wakefulness without awareness. This report describes a dental appliance for the treatment of sleep breathing disorders in this condition. The device can be easily inserted and removed by the patient's family or nurse. Materials and Methods: A 19-year-old woman had been in a persistent vegetative state since having hypoxic-ischemic encephalopathy because of cardiopulmonary arrest. Although she exhibited a sleep-wake cycle and normal respiration, she had sleep apnea and snoring, and produced snoring-like sounds even in an awake state. A three-piece device with Herbst attachments was fabricated to treat the symptoms. Overnight sleep studies were carried out to evaluate the effectiveness of the appliance. Results: The device could be handled by the patient's family. Snoring was satisfactorily reduced after insertion of the device. Sleep apnea, desaturation, and minimal oxygen saturation were markedly improved. Conclusion: If the family of a persistent vegetative state patient wishes to treat sleep-disordered breathing, the appliance may be helpful as an alternative to relieve the symptoms. The device could be applied for sleep apnea patients who experience difficulties using other types of oral appliances.

Purpose: The aim of the study was to determine the color and surface chemistry changes of two fiber-reinforced composites and one "advanced composite" as a function of an accelerated aging process by light exposure and water spray. Materials and Methods: Three composites (Artglass, Targis, and Conquest Sculpture) were assessed for color evaluation in three different shades and with XPS analysis. Four specimens of each shade were analyzed with the UV/VIS/NIR Spectrophotometer in reflectance to determine the baseline color for the CIE L*a*b* system. XPS spectra were obtained from three specimens for each material group. All sample disks were artificially aged in a weathering machine and exposed to water spray and a controlled irradiance xenon arc of 0.55 W/m2/nm measured at 340 nm for a total exposure time of 122 hours. L*a*b* and XPS analyses were repeated after the aging process for all specimens. Results: Artglass had "just perceptible," changes, with ΔE* between 1.8 and 2.7, while Conquest Sculpture showed, in all shades, "visually perceptible" changes from ΔE* 5 to 9. Targis had just perceptible as well as visually perceptible changes after aging. All materials showed decreased Ba and Si on the aged samples, while carbon increased. Conclusion: All materials tested underwent a surface change after the aging process. Artglass and Targis changed minimally into whitish/reddish and yellowish appearances, respectively. An organic-rich surface was produced by a combination of washout of filler particles and rearrangement of polymer molecules through diffusion.

Purpose: The aims of this study were to investigate the quality of written instructions given to dental laboratories for fabrication of chrome-cobalt removable partial dentures (RPD) in Ireland, and to examine the extent and nature of technical/laboratory support available for the fabrication of this prosthesis type. Materials and Methods: All dental laboratories listed in the commercial telephone book were contacted and invited to participate in the study. Written instructions received by dental technicians for fabrication of chrome-cobalt RPDs were examined for evidence of four design variables: denture base configuration, retention, support, and connector design. The use of diagrams was also examined. Results: Of 112 dental laboratories listed, 100 agreed to take part. Sixteen laboratories had the facilities to fabricate chrome-cobalt frameworks on their premises; 122 sets of written instructions were received. All four design variables were described in 10% (n = 12) of instructions, 7% (n = 9) contained reference to three variables, 13% (n = 16) contained reference to two variables, and 17% (n = 20) contained reference to one variable. No design features were prescribed in 53% (n = 65), and 5% (n = 6) requested the technician to design the prosthesis. Only 7% (n = 8) of instructions included a diagram. Conclusion: A high proportion of written instructions to dental laboratories regarding fabrication of chrome-cobalt RPDs contained no reference to the mentioned design variables.

Purpose: The aim of this study was to evaluate four recording materials (polyether, polyvinyl siloxane, acrylic resin, and wax) for their ability to accurately record, maintain, and reproduce the vertical interocclusal relationship. Materials and Methods: A metallic apparatus was used to represent the opposing arches; its epoxy resin duplicate represented the working casts. The vertical discrepancies produced because of the presence of the records were measured both after repositioning them on the metal apparatus and after transferring them onto the casts. Two-way ANOVA was performed. Results: Closure through the interocclusal recording materials produced small vertical discrepancies ranging from 24 to 74 µm. When repositioned on the apparatus, the vertical discrepancies were greater. The lowest discrepancy was displayed by polyvinyl siloxane (101 µm) and polyether (107 µm), and the greatest was displayed by wax (168 µm). When records were transferred onto casts, the discrepancies were approximately 0.5 mm, without significant differences among materials. Conclusion: Closure through interocclusal recording materials and removal and repositioning of the records on the apparatus produced small vertical discrepancies with clinically insignificant differences between the materials tested. When records of all materials tested were transferred onto casts, vertical discrepancies of approximately 0.5 mm were found, which is of clinical concern.

Purpose: This study evaluated the dynamic mechanical properties of silicone elastomers for maxillofacial applications and the influence of frequency and temperature on their properties. Materials and Methods: Seven currently used silicone maxillofacial prosthetic materials were used. Storage modulus, loss modulus, and loss tangent were determined over the frequency range from 0.01 to 100 Hz at both 23 and 37°C using a dynamic viscoelastometer. Contribution ratios of type of material, temperature, and frequency for each rheologic parameter were also determined. Results: Storage modulus, loss modulus, and loss tangent of all materials were greater at higher frequencies. Loss tangent and loss modulus were especially affected; the contribution ratios of frequency were 72% and 48%, respectively. These three rheologic parameters were insensitive to changes in temperature over the range tested; contribution ratios of temperature were less than 3%. There were significant differences in dynamic mechanical properties among the materials. Elasto Synsil showed higher storage modulus and loss modulus than the other materials (Cosmesil T001, Elastosil M3500, Episil, Ideal, Premium, Silskin 2000) at all frequencies and temperatures tested. Loss tangent values ranged from 0.02 to 0.20. Silicone maxillofacial prosthetic materials had almost no viscous component and exhibited elastic behavior. However, a wide range of ability in energy absorption was found among the materials. Conclusion: The results suggest that a maxillofacial prosthesis should have a laminate or hybrid structure consisting of both the material with a greater cushioning effect and that with a higher elastic recovery.

Purpose: The aim of this study was to verify the hypothesis that shortened dental arches constitute a risk to occlusal stability. Materials and Methods: Using cluster samples, 725 subjects with shortened dental arches comprising intact anterior regions and zero to eight occluding pairs of posterior teeth and 125 subjects with complete dental arches were selected. Subjects with shortened dental arches were classified into eight categories according to arch length and symmetry. Parameters for occlusal stability were interdental spacing, occlusal tooth wear, occlusal contact of incisors in intercuspal position, and vertical and horizontal overlap. Additionally, tooth mobility and overeruption of unopposed teeth were assessed. Influence of independent variables (dental arch category, age, gender, and residence) on the parameters for occlusal stability was assessed by oneway ANOVA and Tukey's multiple range tests. Results: Extreme shortened dental arches (zero to two pairs of occluding premolars) had significantly more interdental spacing, occlusal contact of incisors, and vertical overlap compared to complete dental arches. Occlusal wear and prevalence of mobile teeth were highest in these categories. The category with three to four occluding premolars had significantly more interdental spacing and, for the older age group, more anterior teeth in occlusal contact compared to complete dental arches. Age was consistently associated with increased changes in occlusal integrity. Conclusion: Signs of increased risk to occlusal stability seemed to occur in extreme shortened dental arches, whereas no such evidence was found for intermediate categories of shortened dental arches.

Purpose: The aim of this study was to compare the fracture strength of several commercial interim fixed partial denture (FPD) materials in an artificial oral environment. Materials and Methods: Twenty identical three-unit FPDs of the PMMA materials Trim and Cronsin and the composite-based materials Protemp 3 Garant, Protemp Garant, Luxatemp, and Tempofit were cemented on Co-Cr alloy dies. Ten FPDs of each material were stored for 14 days in distilled water and artificially aged. Ten FPDs of each material were stored for 24 hours in distilled water as a control group. Fracture resistance was determined using a testing machine. Results: The tested interim materials showed initial fracture values between 484 and 1,081 N. During artificial aging, the PMMA FPDs failed because of irreversible deflection. All Tempofit FPDs, four Luxatemp FPDs, two Protemp Garant FPDs, and one Protemp 3 Garant FPD failed because of fracture during artificial aging. The remaining FPDs showed fracture values of 759 N (Luxatemp), 772 N (Protemp Garant), and 956 N (Protemp 3 Garant). Conclusion: The PMMA FPDs and the composite Tempofit FPDs showed poor stability during artificial aging, whereas the highest strength values in combination with low fracture rates were found for the Protemp 3 Garant composite FPDs.

Purpose: This study evaluated the ability of five elastomeric impression materials to penetrate the gingival sulcus beyond the preparation margin. Materials and Methods: A model of brass and agar gel was made to simulate human sulci and clinical gingival conditions. Two addition-curing silicones, one condensation-curing silicone, one polyether, and one polysulfide were tested. Ninety impressions of the model were made, six impressions with each material with differing sulcular widths. The centers of sulcular extension of these impressions were found with a measuring microscope. Results: Two-way ANOVA showed significant differences among impression materials, sulcular widths, and their interactions. The penetration ability of polyether showed greater extension than the other materials, regardless of sulcular width. Polysulfide penetrated less than the two silicones with 0.2- and 0.1-mm sulcular widths but more with the narrow 0.05-mm sulcular width. Conclusion: These results suggest that the viscoelastic behavior of elastomers depends on the width of sulci. Moreover, the sulcus simulation model effectively contributes to the investigation of their characteristics.

Purpose: The purpose of this study was to compare elderly patients' satisfaction and oral health-related quality of life with mandibular two-implant overdentures and conventional dentures. Materials and Methods: Sixty edentulous subjects aged 65 to 75 years were randomly assigned to two groups treated with maxillary conventional dentures and either a mandibular conventional denture (n = 30) or an overdenture supported by two implants with ball retainers (n = 30). Subjects rated their general satisfaction, as well as other features of their dentures (comfort, stability, ability to chew, speech, esthetics, and cleaning ability), prior to treatment and 2 months postdelivery. Changes in ratings on the original Oral Health Impact Profile (OHIP) and its short form (OHIP-EDENT) were also used as indicators of oral health-related quality of life. Results: The primary outcome of this study, ratings of general satisfaction 2 months postdelivery, was significantly better in the group treated with mandibular two-implant overdentures ( P= .001). In addition, the implant group gave significantly higher ratings on comfort, stability, and ability to chew. Furthermore, using OHIPEDENT, subjects who received mandibular two-implant overdentures had significantly fewer oral health-related quality of life problems than did the conventional group. Conclusion: These short-term results suggest that mandibular two-implant overdentures combined with maxillary conventional dentures provide better function and oral health- related quality of life than conventional dentures.

Purpose: The aim of this prospective clinical trial was to compare peri-implant clinical and radiographic parameters following the placement of nonsubmerged two- and one-stage implants. Materials and Methods: Patients were randomly assigned to the IMZ group (20 patients receiving two IMZ two-stage implants in a one-stage procedure) or ITI group (20 patients receiving two ITI implants in the conventional one-stage procedure). The healing period was defined as an 18-week unloaded osseointegration period and a 1-year functional period during which maturation of bone took place. Twelve weeks after implant placement, fabrication of an overdenture with a bar-clip attachment system was started; it was placed at 18 weeks. Results: None of the implants were lost during the osseointegration period; one IMZ implant was removed during the functional period because of mobility. There was no significant difference in Gingival Index between the two groups at all evaluation periods. The mean bone loss during the functional period was 0.6 mm in both groups. A high number of healing abutments loosened in the IMZ group. Conclusion: Clinical and radiographic parameters of two-stage implants placed in a one-stage procedure and one-stage implants are comparable during the healing period. Healing abutments of the IMZ implant system loosen easily.

Purpose: The possibility of polymerizing glass fiber-reinforced composite (FRC) material into the root canal was preliminarily evaluated by determining the depth of light-initiated polymerization of FRC. Materials and Methods: The material used was polymerpreimpregnated E-glass fiber reinforcement, which was further impregnated with lightpolymerizable dimethacrylate monomer resin. The same resin without fiber reinforcement was used as a control. Six different lengths (range 4 to 24 mm) of lightprotected cylinders filled with the test materials were light polymerized from one end. The degree of monomer conversion was determined from the other end by FT-IR spectrometry. Infrared spectra were recorded at six time points from the beginning of polymerization. The microhardness of the test materials was measured from the lightexposure surface toward the other end of the cylinder. Results: Both groups showed a reduction in the degree of conversion with increased lengths of the cylinder. The FRC group showed a higher degree of conversion in the longest sample group compared to the resin group. Microhardness measurement confirmed the constant reduction of the degree of conversion by the reduced Vickers hardness values with increased cylinder length of the FRC. Conclusion: Generally, the glass FRC showed an almost equal degree of conversion after light curing as monomer resin without fibers. However, in the longest cylinders, FRC showed a slightly higher degree of conversion compared to resin only; this might be due to the fibers' ability to conduct light.

Purpose: Removable partial dentures (RPD) used to restore the severely shortened mandible may adversely affect the remaining natural teeth and are associated with a low prevalence of use. This pilot study investigated patient satisfaction following restoration of mandibular shortened dental arches. Materials and Methods: Sixty subjects with mandibular shortened dental arches entered a randomized controlled trial comparing two types of mandibular prostheses: bilateral free-end saddle RPDs and distal cantilever resin-bonded fixed partial dentures (FPD). Patient satisfaction was assessed using self-administered questionnaires before (baseline), 3 months after, and 1 year after provision of new prostheses. Results: Improvements in levels of general satisfaction with teeth, appearance of teeth, and perceived masticatory ability were significant for the FPD group. Significant improvements in perceived masticatory ability were noted for both groups. There were also significant improvements in perceived levels of comfort of mandibular prostheses in both groups. Changes in summary satisfaction scores indicated improved satisfaction for both treatment groups but suggested a larger clinical effect for the FPD group. Significant differences between treatment groups were not established. Conclusion: Patient-based outcomes reported suggested that resinbonded cantilever FPDs are an effective means of restoring the shortened mandibular dental arch in terms of patient comfort and acceptance.

Purpose: This study evaluated and compared the clinical performance of laser-welded titanium fixed partial implant-supported prostheses with that of conventional cast frameworks in the partially edentulous jaw. Materials and Methods: Forty-two patients provided with Brånemark system implants were arranged into two groups. Twenty-one patients (group A) were provided with a conventional cast ceramometal framework in one side of the jaw and a laser-welded titanium framework with low-fusing porcelain in the other side. In group B, 21 patients received a titanium framework prosthesis to replace a conventional implant prosthesis. Clinical and radiographic data were collected for 5 years. Results: Four implants and one titanium framework were lost during the follow-up period. The two framework designs did not show any significant differences with regard to implant or prosthesis survival ( P> .05). Few clinical complications were observed. In group A, marginal bone loss after 5 years was similar for both prosthesis designs, with an average of 0.1 mm and 0.3 mm in the maxilla and mandible, respectively. Basically, no bone loss was observed on average in group B. Furthermore, no significant relationship was observed between marginal bone loss and placement of prosthesis margin or prosthesis design. Conclusion: Except for an insignificant tendency toward a slightly higher incidence of small chips of porcelain veneers, laser-welded titanium frameworks presented an overall similar clinical performance as conventional cast frameworks in partial implant situations after 5 years.

Purpose: The aim of this study was to test the utility and validity of a newly developed EMG-based bruxism recording system, which allowed high-resolution digital recordings of the masseter EMG in the patient's home environment and systematic discrimination of artifact signals with the aid of semiautomated software. Materials and Methods: First, simulated bruxism and nonbruxism signals were recorded in two subjects; a total of 72 signals were obtained. Two independent scorers were shown these signals and asked to differentiate bruxism from nonbruxism signals. Second, EMG recordings were actually performed in 56 subjects for six consecutive nights. Using 10 randomly selected recordings, data cleaning was performed by the two scorers to remove any EMG artifact signals, and five bruxism event outcome variables (duration per event, hour, and night, and number per hour and night) were obtained twice with a 7-day interval. Results: The signal differentiation test using signals recorded during simulated tasks revealed that 97% of simulated bruxism and 87% of nonbruxism signals were recognized accurately by the scorers. A total of 317 night recordings, 94% of the scheduled recording nights, were successfully completed by 56 subjects without any substantial difficulty. The results of analysis of intraclass correlation coefficient of outcome variables scored by the two scorers revealed that intrascorer reproducibility varied between .70 and .97. The intraclass correlation coefficients for interscorer reliability were >= .84. Conclusion: This EMG-based bruxism recording system has high utility and reasonable accuracy and precision.

Purpose: The purpose of this study was to ascertain the influence of dental appearance upon subjective ratings of personal characteristics, specifically social competence, intellectual ability, and psychologic adjustment. Materials and Methods: A cross-sectional analytic interview study was conducted with 201 undergraduates. Each participant was asked to make judgments about the personal characteristics of the subject of a single color photograph. Eight photographs of four different men were used, each with one of two degrees of dental status (visible disease, no visible disease). Outcome measures were participants' judgments of the social competence, intellectual ability, and psychologic adjustment of the subjects of the photographs. Results: Participants judged subjects with less dental disease to be more socially competent, to show greater intellectual achievement, and to have better psychologic adjustment. Conclusion: In the absence of other information, the judgments an individual makes concerning the personal characteristics of others are influenced by dental appearance.

Purpose: This article presents a novel manufacturing approach that integrates laser surface digitizing/scanning and computer-aided design (CAD) and manufacturing (CAM) to achieve automated fabrication of spatially and anatomically accurate extraoral facial prostheses. Materials and Methods: Topologic data of the patient's face, including the site of deformity and the anatomy of a healthy "donor" organ, were acquired using laser surface digitizing. Two different CAD data manipulation techniques were developed to alleviate problems encountered in laser-digitized data sets. To reduce patient involvement, fitting of the prosthesis was conducted using a computer model of the patient's face. Once finalized, rapid prototyping techniques were employed to fabricate a master pattern to cast the final prosthesis. Results: Three case studies involving different facial prostheses were conducted to evaluate the integrated manufacturing system. The results demonstrated the many advantages of the system for facial prosthesis production. Conclusion: With the new manufacturing approach, 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 determine the influence of margin design and taper abutment angle on the stresses developed in all-ceramic first premolar crowns. Materials and Methods: Four margin designs and three taper abutment angles were independently incorporated into models examined by finite element analysis. A 600-N force was applied vertically downward. Results: The taper abutment angle had a significant influence on the greatest peak tensile maximum principal stresses (σ11) in the coping (16.8% change in stress for an 8-degree variation in taper angle). The margin design had significant influence on the highest peak tensile σ11 in the dentin (60% difference in stress between designs) and lesser significance in the cement (30%). All calculated values of the highest peak tensile σ11 were considerably lower than the fracture strengths of the respective materials in which the stresses resided. Conclusion: A smaller taper abutment angle and a larger chamfer radius (equivalent to the modified light chamfer) are recommended to reduce the magnitude of the greatest peak tensile σ11 based on the finite element modeling conducted.