Showing papers in "International Journal of Prosthodontics in 2002"

A modified short version of the oral health impact profile for assessing health-related quality of life in edentulous adults.

Abstract: Purpose The aim of this study was to develop a shortened version of the Oral Health Impact Profile (OHIP) appropriate for use in edentulous patients and to evaluate its measurement properties. Materials and methods Data were collected from the Ontario Study of Older Adults and a longitudinal clinical trial of implant-retained prostheses undertaken in Newcastle Dental Hospital, UK. All subjects completed an OHIP at baseline, and UK subjects also completed an OHIP posttreatment. Using an item impact reduction method, a shortened version of the OHIP (called OHIP-EDENT) was derived from both datasets. Discriminant validity and responsiveness properties of this modified version were compared with OHIP-14 and OHIP-49. Results Using an item impact method of reducing the 49 OHIP items produced very similar subsets in both Canadian and British populations; the modified version had little overlap with the current short version (OHIP-14). Discriminant validity properties of OHIP-EDENT were similar to OHIP-14 and OHIP-49. Using effect sizes to assess sensitivity to change, OHIP-EDENT exhibited less susceptibility to floor effects than OHIP-14 and appeared to measure change as effectively as OHIP-49. Conclusion The modified shortened version of the OHIP derived in this study has measurement properties comparable with the full 49-item version. This modified shortened version may be more appropriate for use in edentulous patients than the current short version.

Masticatory function and patient satisfaction with implant-supported mandibular overdentures: a prospective 5-year study.

Abstract: Purpose The aim of this study was to assess the outcome of treatment with implant-supported mandibular overdentures in terms of biting and chewing, in entirely satisfied and not fully satisfied patients. Materials and methods Twelve edentulous patients who had worn dentures for at least 5 years participated. They were in good health but had retention problems with their mandibular dentures. First, all patients received new dentures. After 3 months, two Astra Tech implants were placed in the anterior part of the mandible, and 6 months later the abutments were connected. Patient assessment (questionnaire) and functional recordings (chewing ability, bite force, electromyographic activity) were performed with the new dentures, and again 3 months, 1 year, and 5 years after overdenture treatment. Results After treatment, all patients were able to comminute hard and tough food, the maximum bite force and the chewing activity increased in parallel, and the duration of the chewing cycle was reduced. Every patient felt improved function and reduction of chewing pain. However, the seven patients not fully satisfied with the function of the implant-supported mandibular overdentures were characterized by lower muscle activity, even before implant placement, than the entirely satisfied patients. Conclusion Implant-supported mandibular overdenture treatment permits better biting and chewing function than conventional complete dentures.

Effect of different artificial aging conditions on ceramic-composite bond strength.

Abstract: Purpose The purpose of this study was to evaluate the influence of different storage conditions on the bond strength of adhesive bonding systems to yttria-partially stabilized zirconia ceramic. Materials and methods Acrylic glass tubes filled with composite resin were bonded to ceramic disks. After sandblasting and ultrasonic cleansing of the ceramic samples, they were bonded using five bonding methods. Samples were tested for tensile bond strength following five different storage conditions: 3 days in distilled water at 37 degrees C, 31 days in distilled water at 37 degrees C, 37,500 thermocycles between 5 and 55 degrees C within 31 days, 150 days in distilled water at 37 degrees C, and 150 days in distilled water with 37,500 thermocycles performed at intervals. Results Mean resin bond strength values ranged from 7.7 to 41.9 MPa. There were statistically significant differences among groups, as revealed by the Kruskal-Wallis test. Some storage conditions influenced the resin bond strength statistically significantly, as revealed by the Wilcoxon rank sum test modified by Bonferroni-Holm. Conclusion Thermocycling had a much higher impact on the durability of the resin bond strength to zirconia ceramic than did water storage at a constant temperature.

Effect of ceramic surface treatment on tensile bond strength to a resin cement.

Abstract: Purpose The objective of this study was to test the following hypotheses: (1) hydrofluoric acid (HF)-treated ceramic surfaces produce the highest tensile bond strength to resin cements, independent of the ceramic microstructure and composition; and (2) the tensile bond strength test is appropriate for analysis of interfacial adhesion for ceramic-bonded-to-resin systems. Materials and methods Ceramic specimens were polished with 1-micron alumina abrasive and divided into four groups of 10 specimens for each of seven ceramic types. One of the following surface treatments was applied: (1) 10% ammonium bifluoride (ABF) for 1 minute; (2) 9.6% HF for 2 minutes; (3) 4% acidulated phosphate fluoride (APF) for 2 minutes; and (4) a silane coupling agent. The surface-treated areas were coated with an adhesive resin and bonded to a resin cement. Specimens were loaded to failure in tension using a testing machine. Tensile bond strength data were statistically analyzed, and fracture surfaces were examined to determine the mode of failure. Results Silane-treated surfaces showed statistically higher mean tensile bond strength values than surfaces treated with any etchant (HF, ABF, APF). HF produced statistically higher mean tensile bond strengths than ABF and APF. All failures occurred in the adhesion zone. Conclusion The tensile bond strength test is adequate for analysis of the adhesive zone of resin-ceramic systems. The chemical adhesion produced by silane promoted higher mean bond strength values than the micromechanical retention produced by any etchant for the resin-ceramic systems used in this study.

An up to 15-year longitudinal study of 515 metal-ceramic FPDs: Part 1. Outcome.

Abstract: Purpose This study reports on the outcome of 515 metal-ceramic fixed partial dentures (FPD) involving 1,209 abutments and 885 pontics placed by one operator in a specialist prosthodontic practice between January 1984 and December 1997. Materials and methods Clinical and laboratory protocol was kept constant as much as was practical. Each FPD and abutment was given a subjective prognostic rating at the time of cementation. Patients were recalled in 1993 (review 1) and 1998 (review 2). Clinical examination by the author covered 85% of 342 FPDs at review 1 and 82% of 515 FPDs at review 2. At review 2, 37% had been in clinical service for 5 to 10 years (group b), and 34% had been in service for 10 to 15 years (group c). An objective classification protocol was used to assess outcome. Results At review 2, the FPDs had failure rates of 2%, 7%, and 11% in groups a, b, and c, respectively. There was a significant increase in the failure rate of group c at review 2 (11%) compared with review 1 (5%). Cumulative survival analysis indicated that FPDs have an expected survival rate of 96%, 87%, and 85% at 5, 10, and 15 years, respectively. The applied prognostic rating proved more accurate as clinical service time increased. Outcome was not related to number of units. Cantilevered FPDs, nonvital abutments, and anterior abutments had significantly greater failure rates. Of initially vital abutments, 2% were subsequently endodontically treated. Conclusion Tooth-supported FPDs have an expected survival rate of 85% at 15 years when the described clinical and laboratory protocol is applied.

Clinical study on the reasons for and location of failures of metal-ceramic restorations and survival of repairs.

Abstract: Purpose: A recently introduced technique, the Cojet system, using SiOx (Al2O3 coated with silisic acid), provides ultrafine mechanical retention by sandblasting, as well as a chemicophysical bond between the metal/ceramic and the composite resin. This study determined the reasons for and locations of failures of metal-ceramic restorations and evaluated the survival of the intraoral silica-coating system used for the repair of failed restorations. Materials and Methods: A total of 153 patients possessing 289 fractured crowns were involved in this study; 255 of these fractures were on fixed partial dentures, whereas 34 were on single crowns. The mean observation period was 34.6 months. The materials used for the repair process were ESPE-Sil for silane; Visiogem, Sinfony, and Dentacolor as opaquers; and Pertac II Aplitip, Sinfony, and Charisma as repairing composite resins. Results: The majority of the failures (65%) occurred in the anterior region. Sixty percent of the failures were observed at the labial, 27% at the buccal, 5% at the incisal, and 8% at the occlusal regions. The fractures were mainly in the maxilla (75%), predominantly at the labial surface. The overall cumulative survival rates of the repairs (89%) showed that the first failures happened mostly from 1 week to 3 months after the repair, without any difference between the composite resins. Conclusion: The original failures happened mainly during chewing function or because of accidents, iatrogenic factors, and surgical operations, whereas secondary failures after repair using intraoral silica coating and composite resin were due to trauma, chewing function, or lack of rubber dam application.

Mechanical properties of In-Ceram Alumina and In-Ceram Zirconia.

Abstract: Purpose: This study compared the mechanical properties of In-Ceram Zirconia and InCeram Alumina. Materials and Methods: Ninety-four disks and six bars were prepared with the slip-casting technique. The disks were used to assess biaxial flexural strength (piston on three ball), Weibull modulus, hardness, and fracture toughness with two methods: indentation fracture and indentation strength. The bars were used to measure elastic moduli (Young’s modulus and Poisson’s ratio). X-ray diffraction analysis of the specimens was carried out upon every step of the specimen preparation and of the fractured surfaces. Results: Mean biaxial flexure strengths of In-Ceram Alumina and InCeram Zirconia were 600 MPa (SD 60) and 620 MPa (SD 61), respectively. Mean fracture toughness measured according to indentation strength was 3.2 MPa · m 1/2 (SD 0.34) for InCeram Alumina and 4.0 MPa · m 1/2 (SD 0.43) for In-Ceram Zirconia. Mean fracture toughnesses of In-Ceram Alumina and In-Ceram Zirconia measured according to indentation fracture were 2.7 MPa · m 1/2 (SD 0.34) and 3.0 MPa · m 1/2 (SD 0.48), respectively. X-ray diffraction analysis showed that little phase transformation from tetragonal to monoclinic occurred when the specimens were fractured, supporting the existence of a modest difference of fracture toughness between the two ceramics. Conclusion: No statistically significant difference was found in strength. In-Ceram Zirconia was tougher (P < .01) than In-Ceram Alumina when tested according to indentation strength. However, no significant difference was found in the fracture toughness when tested with the indentation fracture technique. Int J Prosthodont 2002;15:339‐346.

Computer-aided direct ceramic restorations: a 10-year prospective clinical study of Cerec CAD/CAM inlays and onlays.

Abstract: Purpose The objective of this follow-up study was to examine the performance of Cerec inlays and onlays in terms of clinical quality over a functional period of 10 years Materials and methods Of 200 Cerec inlays and onlays placed in a private practice between 1989 and early 1991, 187 restorations were observed over a period of 10 years The restorations were fabricated chairside using the Cerec-1 computer-aided design/manufacturing (CAD/CAM) method and Vita MK I feldspathic ceramic An adhesive technique and luting composite resin were used for seating the restorations After 10 years, the clinical performance of the restorations was evaluated using modified USPHS criteria The results were used to classify success and failure Results According to Kaplan-Meier analysis, the success rate of Cerec inlays and onlays dropped to 904% after 10 years A total of 15 (8%) failures were found in 11 patients Of these failures, 73% were caused by either ceramic fractures (53%) or tooth fractures (20%) The reasons for the remaining failures were caries (20%) and endodontic problems (7%) The three-surface Cerec reconstructions were found to have the most failures Conclusion The failure rate of 8% and the drop of the survival probability rate to 904% after 10 years of clinical service of Cerec-1 CAD/CAM restorations made of Vita MK I feldspathic ceramic appear to be acceptable in private practice This is particularly true in light of the very high patient satisfaction

Microstructure, composition, and etching topography of dental ceramics.

Abstract: Purpose Topographic analysis of etched ceramics provides qualitative surface structure information that affects micromechanical retention mechanisms. This study tested the hypothesis that the etching mechanism changes according to the type of etchant and the ceramic microstructure and composition. Materials and methods Quantitative and qualitative analyses of 15 dental ceramics were performed using scanning electron microscopy, back-scattered imaging, X-ray diffraction, optical profilometry, and wavelength dispersive spectroscopy based on Phi-Rho-Z correction. All ceramic specimens were polished to 1 micron with diamond compound, and the following etchants and etching times were used: ammonium bifluoride (ABF) for 1 minute, 9.6% hydrofluoric acid (HF) for 2 minutes, and 4% acidulated phosphate fluoride (APF) for 2 minutes. Results HF produced an irregular etching pattern in which pores were the characteristic topographic feature. ABF-etched ceramic surfaces showed mostly grooves, and APF etchant caused a buildup of surface precipitate. Core ceramics showed less topographic change after etching because of their high alumina content and low chemical reactivity. Conclusion The observations suggest that the etching mechanism is different for the three etchants, with HF producing the most prominent etching pattern on all dental ceramics examined.

A novel handy probe for tongue pressure measurement.

Abstract: Purpose: The purpose of this study was to develop a handy probe to measure tongue pressure without fear of radiation or infection. Materials and Methods: A probe was assembled using a small balloon, a stainless pipe, and a 1-mL disposable tuberculin-test syringe cylinder. The probe was pressurized to set the balloon diameter at approximately 18 mm. Forty-one subjects (16 men and 25 women, 24 to 84 years of age) participated. To record maximal voluntary tongue pressure, the subjects were asked to compress the balloon onto their palates as strongly as possible. To record deglutitious tongue pressure, 5 mL of water was measured and administered with a scaled 10-mL syringe and swallowed with the balloon in the mouth. Both types of pressure were recorded three times at 1-minute intervals. Peak values of each record were measured. Results: Individuals varied from 10 to 41 kPa in the maximal voluntary trial and 3 to 27 kPa in the deglutitious trial, with 5 and 7 kPa mean intraindividual ranges of reproducibility, respectively. A negative correlation to age was found for both types of pressure. No gender differences or effects of dentition were found. Conclusion: A disposable handy probe for measuring tongue pressure was developed and tested for clinical use. Despite the limited information acquired, we could see some quantitative aspects of tongue function conveniently and safely. Int J Prosthodont 2002;15:385‐388.

A survey of cusp fractures in a population of general dental practices.

Abstract: PURPOSE: This study was conducted to expand the knowledge on the incidence of complete cusp fractures of posterior teeth in Dutch general practices MATERIALS AND METHODS: During a 3-month period, data were obtained from 28 general practitioners, representing 46,394 patients For each new case of complete cusp fracture, clinicians recorded information using a standard form with questions relating to location of the fracture, cause of fracture, and restorative status of the tooth prior to the cusp fracture RESULTS: There were 238 cases of complete cusp fracture recorded The results of this study indicate an incidence rate of cusp fractures of 205 per 1,000 person-years at risk Molars were more frequently registered with cusp fractures than premolars (79% vs 21%) Maxillary molars presented more fractures of buccal cusps (66% vs 34%), while mandibular molars presented more fractures of lingual cusps (75% vs 25%) Almost 77% of the cases had been restored on three or more surfaces Statistical analysis revealed a positive correlation between history of endodontic treatment and subgingival fracture location Mastication was most frequently reported as the cause for fracture (54%), although one can argue whether the occlusal force was the cause or the immediate reason CONCLUSION: This study revealed that complete cusp fracture is a common phenomenon in dental practice and has shown differences in cusp fracture with respect to tooth type and restorative status of the tooth Teeth with a history of endodontic treatment are susceptible to unfavorable subgingival fracture locations

Measurement of masticatory forces and implant loads: a methodologic clinical study.

Abstract: Purpose The aim of this study was to measure vertical masticatory forces in vivo using a method that should be insensitive to the location of bite force impact. Materials and methods Two exchangeable implant abutments were equipped with strain gauges. In nine patients, the abutments were attached to implants supporting three-unit fixed partial dentures (FPD) in one mandibular chewing center. The signals of the two abutments were summed to give a force reading that was independent of the location of force impact along the FPD. In two subjects, an additional strain gauge was fixed under the pontic. With both setups, masticatory forces were measured in chewing of winegum. Results Total masticatory force displayed by the sum signal proved to be independent of the site of force application. Pontic strain gauges indicated only 42% or 84% of the force measured simultaneously by the corresponding sum signal of the abutments. In all nine patients, a mean total masticatory force of 220 N, with a maximum of 450 N, was found. The single abutments experienced mean loads of 91 N (anterior) and 129 N (posterior), with a maximum of 314 N. Conclusion Measuring chewing force via bending of a pontic involves the risk of underestimation. Masticatory forces obtained with a method that was insensitive to the site of force application were higher than forces found with some other setups.

An up to 5-year clinical evaluation of posterior in-ceram CAD/CAM core crowns.

Abstract: Purpose: This study evaluated the clinical performance of posterior CAD/CAM‐generated In-Ceram Alumina and In-Ceram Spinell core crowns. Materials and Methods: Nineteen InCeram Spinell core crowns (four premolars and 15 molars) and 24 In-Ceram Alumina core crowns (two premolars and 22 molars) in 21 patients were examined using modified USPHS criteria at baseline and after a mean service time of 39 ± 11 months. The crown copings were machined from Vitablocs In-Ceram Alumina and Vitablocs In-Ceram Spinell using the Cerec 2 CAD/CAM system. Results: Two molar In-Ceram Alumina core crowns fractured after respective service times of 14 and 17 months in the same patient. The Kaplan-Meier survival rate regarding fracture of the ceramic was 92% for In-Ceram Alumina and 100% for In-Ceram Spinell. At the follow-up examination, 80% alpha ratings and 18% beta ratings for In-Ceram Alumina core crowns and 84% alpha ratings and 15% beta ratings for In-Ceram Spinell core crowns were recorded. Conclusion: Despite the two fractures, the clinical quality of CAD/CAM-generated In-Ceram Alumina and In-Ceram Spinell posterior crowns was excellent. Within the limitations of this study, both types of crowns appeared to be feasible. Int J Prosthodont 2002;15:451‐456.

Color comparison of two shade guides.

Abstract: Purpose The aim of this study was to analyze color parameters and color compatibility of two randomly chosen Vita shade guides, as well as to propose possible clinical guidelines. Materials and methods Data were recorded using a colorimeter set to standard illuminant source C and the CIE L*a*b* system. A custom adapter system, which allowed a measuring area at the middle third of the tabs, was produced. Each of 42 tabs was recorded one time each on three different days. Color distribution was examined in diagrams whose coordinates were L*a*b* and L*C*H degree color coordinate pairs. Color coordinate ranges and coverage error were examined using the corresponding equations and statistical methods. Results The method repeatability was approximately delta E* = 0.1. Color difference ranges of Vitapan Classical and Vitapan 3D Master were 14.3 and 19.2, respectively. Color coordinate ranges of Vitapan Classical were as follows: delta L* = 12.8; delta a* = 1.7; delta b* = 9.0; delta C* = 9.0; and delta H degree = 7.4. Corresponding values for Vitapan 3D Master were delta L* = 15.3; delta a* = 3.4; delta b* = 16.3; delta C* = 16.6; and delta H degree = 10.5. Coverage error of Vitapan 3D Master to Vitapan Classical was 1.4 +/- 0.6, while vice versa it was 2.0 +/- 1.5. Conclusion Compared to Vitapan Classical, chromaticity ranges of Vitapan 3D Master were extended in the desired directions: hue was extended toward yellow-red, and saturation was extended toward more saturated tabs. Compared to Vitapan Classical, Vitapan 3D Master tabs were more uniformly spaced. The examined shade guides were found to be color compatible.

Speech outcomes in patients rehabilitated with maxillary obturator prostheses after maxillectomy: a prospective study.

Abstract: PURPOSE: Speech outcome measurements are valuable in guiding treatment and determining the effectiveness of rehabilitation with a maxillary obturator prosthesis in individuals with palatal resection. Although speech outcome data exist in the literature for such patients, relatively few reports have used clinical tools designed to measure the acoustic, physiologic, and perceptual bases of speech. This investigation reports these measures for individuals rehabilitated with a maxillary obturator. MATERIALS AND METHODS: Speech measurements were collected prospectively at three clinical visit times (preoperative, postresection without an obturator, and with a definitive obturator) for 12 patients assigned to three groups based on the extent of their resection ( or = half the hard palate, hard and soft palates). Acoustic data were obtained with the Nasometer, aeromechanical data were collected with the PERCI-SARS, and perceptual ratings of speech intelligibility were obtained through listener analysis. RESULTS: Significant differences existed among the three treatments for all dependent variables and revealed that speech without an obturator is significantly different from the preoperative state, while speech with an obturator does not differ significantly from preoperative function. Individuals with soft palate involvement exhibited significantly poorer nasalance values than individuals with involvement of the hard palate only. CONCLUSION: Rehabilitation with a maxillary obturator is successful in restoring preoperative speech function. Rehabilitation of individuals with involvement of the soft palate may be more challenging.

Implant-retained prostheses for facial defects: an up to 14-year follow-up report on the survival rates of implants at UCLA.

Abstract: Purpose An analysis of retrospective data was conducted to establish the survival rates of osseointegrated implants used to retain orbital, nasal, and auricular prostheses over a 14-year period and to recommend guidelines in the restorative treatment of such facial defects. Materials and methods Included in this study were all patients who received implant-retained prostheses for auricular, nasal, or orbital defects from 1987 to 2001 in the Maxillofacial Clinics at the UCLA and City of Hope Medical Centers. Data were obtained from patient charts. Two methods were used to determine survival rates: (1) the percentage of the total exposed implants that survived was determined, and (2) life table analysis was used to calculate cumulative survival rates at different time intervals. Results A total of 207 implants were placed in 72 patients, and 182 implants had been uncovered. During the study period, 35 implants failed to integrate, and the survival rate for all exposed implants was 80%. Auricular implants showed the highest survival rate (95%), and orbital implants showed the lowest survival rate (53%). The life table analysis demonstrated a cumulative 6-year survival rate of 92% for auricular implants and 87% for piriform/nasal implants. In contrast, the survival rate for orbital implants showed a steady downward trend and reached 59% at 66 months. Conclusion It is possible to achieve high survival rates of implants in the auricular and piriform/nasal sites through careful presurgical and radiographic planning. The less favorable long-term survival of implants in the orbital rim, especially at irradiated sites, requires further study.

Changes in prosthetic screw stability because of misfit of implant-supported prostheses.

Abstract: Purpose The effect of two levels of prosthesis misfit on prosthetic screw stability was evaluated. Materials and methods Two levels of vertical discrepancies--100 and 175 microns--were introduced between an implant-supported complete denture and the terminal abutment. An implant-supported complete denture without vertical discrepancy served as a control. Cyclic load was delivered vertically on the cantilever portion of the prosthesis next to the terminal abutment for 48 hours for each trial. A total of seven sets of new screws were tested for each level of fit. Results The results revealed significant prosthetic screw instability at both the 100- and 175-micron levels of discrepancy. Conclusion Vertical discrepancies of 100 and 175 microns introduced between an implant-supported fixed complete denture and the terminal abutment resulted in significant prosthetic screw instability.

A study of the influence of occlusal factors and parafunctional habits on the prevalence of signs and symptoms of TMD.

Abstract: Purpose The purpose of this study was to investigate the prevalence of the clinical signs and symptoms of temporomandibular disorders (TMD) and the relationship between occlusal factors, parafunctional habits, and TMD in a young adult nonpatient population. Materials and methods A questionnaire including data from a history and clinical functional examination was used in the study. All 230 subjects were male recruits, from 19 to 28 years of age (mean 21.3 years). Results Thirty-eight percent of the subjects reported at least one symptom, while in 45% of the subjects at least one sign of TMD was recorded. Temporomandibular joint clicking (40%) and pain on palpation (34%) were the most commonly recorded signs. Multivariate logistic regression analysis showed several weak but statistically significant correlations between the occlusal factors, parafunctional habits, and TMD in this nonpatient population. TMD signs were thus weakly correlated with malocclusion traits (angle Classes II/1, II/2, III, and cross bite), interferences in retruded contact position, midline discrepancy > or = 2 mm, or = 5 mm, and parafunctional habits (teeth clenching and teeth grinding). Conclusion Some association between occlusal factors and TMD signs was found. However, this association cannot be considered unique or dominant in defining subjects with TMD in the population.

Flexural strength of In-Ceram alumina and In-Ceram zirconia core materials.

Abstract: PURPOSE The study compared the flexural strength of In-Ceram alumina and In-Ceram zirconia systems. The probability of failure of the two glass-infiltrated ceramic core materials was analyzed with and without lamination with Vitadur-alpha porcelain. MATERIALS AND METHODS Ten uniform beams of core materials as well as 10 beams of laminated core materials were fabricated for In-Ceram alumina and In-Ceram zirconia. The samples were subjected to three-point bending tests. Flexural strength for both ceramic core materials was determined with and without their porcelain laminations. The strength data were analyzed using the Weibull method. Modes of failure for both systems were determined using scanning electron micrography. RESULTS The strength of the In-Ceram zirconia system was significantly higher than In-Ceram alumina when comparing their core materials with and without porcelain lamination. The failure mode for both systems was predominantly transgranular fracture of alumina platelets. CONCLUSION In-Ceram zirconia demonstrated higher flexural strength than In-Ceram alumina.

A multicenter interracial study of facial appearance. Part 1: A comparison of extraoral parameters.

Abstract: Purpose This article compares interracial or gender differences of six intraoral dental parameters among six racial groups (African American, Caucasian, Chinese, Hispanic, Japanese, and Korean). Materials and methods The same 253 patients participating in part 1 were included in this portion of the study to evaluate six intraoral parameters. The data were collected and analyzed using a one-way analysis of variance, followed by the Tukey-Kramer test for honestly significant difference when statistically significant differences were found (P Results Women displayed significantly more gingival tissue in four of the six races, and African Americans displayed significantly more gingival tissue than any other race. Women had significantly more missing teeth than men in three of the six races studied. Japanese subjects had significantly fewer missing teeth and smaller maxillary central incisors than all other groups except Caucasians. Women had significantly narrower maxillary central incisors in three of the races. There was a significantly higher prevalence of Angle Class III relationships in Chinese subjects. The Japanese had significantly more Class II molar relationships than other races. Conclusion Racial and gender differences were found in gingival tissue display, the number of missing teeth, maxillary right central incisor crown width, and Angle molar classification, but not in the amount of vertical or horizontal overlap of the anterior teeth.

Three-dimensional computerized stress analysis of commercially pure titanium and yttrium-partially stabilized zirconia implants.

Abstract: Purpose The purpose of this study was to use three-dimensional finite element analysis to analyze stress distribution patterns in Re-Implant implants made of commercially pure titanium (cpTi) and yttrium-partially stabilized zirconia (YPSZ). Materials and methods Two three-dimensional finite element analysis models of a maxillary incisor with Re-Implant implants were made, surrounded by cortical and cancellous bone. A porcelain-fused-to-metal crown for the cpTi implant and a ceramic crown for the YPSZ implant were modeled. Stress levels were calculated according to the von Mises criteria. Results Higher stresses were observed at the area where the implant entered the bone. Stresses were higher at the facial and lingual surfaces than the proximal ones. In cortical bone and at the junction of cortical and cancellous bone, stress distribution presented a pattern of alternating higher (4.0 to 5.0 MPa) and lower (1.3 to 2.0 MPa) stress areas. Higher stresses were found at the apical third of the implant-to-bone junction as well. Conclusion Re-Implant implants presented a pattern of low, well-distributed stresses along the entire implant-to-bone interface. YPSZ implants had very similar stress distribution to cpTi implants and may be viable esthetic alternatives, especially in maxillary anterior regions.

A comparison of three-dimensional finite element stress analysis with in vitro strain gauge measurements on dental implants.

Abstract: PURPOSE The purpose of this study was to evaluate the compatibility of three-dimensional finite element stress analysis and in vitro strain gauge analysis in the measurement of strains on a dental implant. MATERIALS AND METHODS Two vertically placed implants embedded in a poly(methyl methacrylate) model were used. Strain gauges were bonded to the cervical parts of the implants, and seven cement-retained fixed partial dentures were fabricated. A three-dimensional model of the strain gauge analysis model was constructed, and an additional model in which human bone simulation was provided was also constructed. A static vertical load of 50 N was applied at certain locations to simulate centrally positioned axial and laterally positioned axial loading for strain gauge analysis and three-dimensional finite element stress analysis. RESULTS Statistically significant increases in strain levels were recorded between loading types in the strain gauge analysis (P < .05). Strains obtained from strain gauge analysis were higher than for three-dimensional finite element stress analysis. There was a remarkable difference between the two finite element models under the conditions of laterally positioned axial loading. CONCLUSION There are differences regarding the quantification of strains between strain gauge analysis and three-dimensional finite element stress analysis. However, there is a mutual agreement and compatibility between three-dimensional finite element stress analysis and in vitro strain gauge analysis on the determination of the quality of induced strains under applied load.

Resin bond strength to densely sintered alumina ceramic.

Abstract: PURPOSE The aim of this in vitro study was to investigate the resin bond strength and durability of adhesive bonding systems to densely sintered, pure aluminum oxide ceramic. MATERIALS AND METHODS Acrylic glass tubes filled with composite resin were bonded to industrially manufactured alumina ceramic disks with an ultrasonically machined surface. Groups of 20 samples were bonded in an alignment apparatus using five different bonding methods. Subgroups of 10 bonded samples were tested for tensile strength following storage in distilled water at 37 degrees C for either 3 or 150 days. In addition, the 150-day samples were thermocycled 37,500 times. The statistical analyses were made by the Kruskal-Wallis test, followed by multiple pairwise comparison of the groups using the Mann-Whitney test. RESULTS The mean bond strength of a bis-GMA composite resin to sandblasted alumina ceramic was relatively high after 3 days, at 20 MPa. Additional silanization or tribochemical silica coating and silanization did not enhance the bond strength (18 to 20 MPa) and failed spontaneously over long-term storage. However, using a composite resin containing a special adhesive phosphate monomer, a statistically significantly higher and durable bond strength to the sandblasted alumina ceramic surface was achieved after 3 days (50 MPa) and after 150 days of storage (46 MPa). CONCLUSION A durable bond strength to pure alumina ceramic was achieved only by using a composite resin containing an adhesive phosphate monomer after sandblasting the ceramic surface.

The effectiveness of seven denture cleansers on tea stain removal from PMMA acrylic resin.

Abstract: Purpose In this study, seven denture cleansers were evaluated for their mode of action of tea stain removal from Perspex acrylic resin material. Materials and methods Perspex acrylic resin specimens were stained using a combination of chlorhexidine and tea solution. The specimens were also treated with saliva to form an initial pellicle layer and facilitate the uptake of the stain. The capacity for stain removal was determined by measuring the optical density of the treated specimens by using a spectrophotometer. These were then exposed, for 5 minutes, to seven denture cleansers to demonstrate the percentage stain-removal ability of each cleanser. The same procedure was applied for roughened Perspex acrylic resin specimens. Water was used as a control in the two parts of the experiment. Results The products containing alkaline hypochlorite had the highest ability for removing stain from the acrylic resin material together with a bleaching effect. The results varied when the same denture cleansers were used on the roughened Perspex surface, and this was attributed to the presence of irregularities and porosities on the blocks. Conclusion Denture cleansing agents containing hypochlorite and Boots Denture Cleaning Powder (constituents not stated by the manufacturer) exhibited the ability to remove stain from the denture base materials most effectively. Irregularities and porosities present on the denture surface played a major role in reducing the activity of denture cleaning agents and hence increased stain and plaque retention.

A review of clinical and technical considerations for fixed and removable implant prostheses in the edentulous mandible.

Abstract: Purpose The aim of the present article is to review some of the technical treatment options for implant prostheses restoring the edentulous mandible, mainly based on the Branemark system. Materials and methods Clinical and technical aspects are discussed for the three established concepts: (1) implant-supported fixed prosthesis, (2) removable implant-supported overdenture, and (3) combined implant-retained and soft tissue-supported overdenture prosthesis. Results The framework of an implant-supported fixed screw-retained prosthesis can be processed in gold, Co-Cr alloy, or titanium with casting, laser-welding, or milling techniques. To improve the stability and retention of a conventional complete denture, one to four implants are indicated, and unsplinted (single attachments) or splinted designs (bar systems) can be applied. The design of the overdenture prosthesis must be carefully planned according to the requirements to ensure adequate stability and optimal form, contour, and esthetics, and the patient's best comfort. Conclusion A large variety of different treatment modalities exist for both the fixed and removable mandibular implant prosthesis. Clinical and technical aspects should be considered at the beginning of the treatment to: (1) select the optimal implant position, (2) establish an adequate number of functional units, (3) select the appropriate retainers, and (4) apply the best technique for framework processing and veneering.

Evaluation of a newly developed visual shade-matching apparatus.

Abstract: PURPOSE This study evaluated a newly developed visual shade-matching apparatus, Shademat Visual+, as well as the influence of tab arrangement, clinician gender, and years in practice on shade-matching quality. MATERIALS AND METHODS A group of 129 color-normal evaluators-dental students and general dentists-matched the shade of four ceramometal crowns using the Vitapan Classical shade guide. Crowns were positioned onto the upper member of an artificial head and fastened to the headrest of the dental chair or Shademat Visual+. Shade tabs were arranged according to the manufacturer's suggestion or according to deltaE* in relation to the "lightest" tab and divided into groups (alternative arrangement). The evaluators matched the shade of four ceramometal crowns both in daylight and using the Shademat Visual+ artificial light source. The color coordinates were determined using digital image analysis. Based on deltaE* values, each shade-matching result was ranked from 1 (the worst match) to 16 (the best match) points. RESULTS The evaluators achieved a better result in Shademat Visual+ trials than in daylight trials (13.2 points vs 12.4 points; P < .001). For the same ceramometal crown, 12.7 points were recorded in daylight trials with the manufacturer-suggested arrangement, and 13.7 were recorded with the alternative arrangement (P< .001). Corresponding values for Shademat Visual+ trials were 13.6 points and 14.6 points, respectively (P< .001). Female-male and student-dentist evaluator differences were not significant. CONCLUSION The Shademat Visual+ apparatus enabled better shade-matching results than daylight. The alternative tab arrangement enabled better results than the manufacturer-suggested one. Gender and years in practice did not influence shade-matching quality.

Implant-supported welded titanium frameworks in the edentulous maxilla: a 5-year prospective multicenter study.

Abstract: Purpose This study evaluated the 5-year clinical and radiographic performance of fixed implant-supported maxillary prostheses with either welded titanium or conventional cast-gold alloy frameworks. Materials and methods Fifty-eight consecutive patients were provided with 349 osseointegrated Branemark system implants in the edentulous maxilla at six different implant centers. Twenty-eight of the patients received, at random, prostheses with laser-welded titanium frameworks, and the remaining 30 patients had prostheses with conventional cast-gold alloy frameworks. Clinical and radiographic data were collected for 5 years after prosthesis placement. Results The titanium and cast-gold framework groups exhibited similar cumulative survival and success rates (CSR). The 5-year implant CSR from time of placement was 91.4% and 94.0%, respectively, and from prosthesis delivery the rate was 94.9% and 95.6%, respectively. The corresponding 5-year prosthesis CSRs were 96.4% and 93.3%. One patient from each group lost all the implants and turned to complete dentures within the first year of function. Another patient with a cast-gold framework had the prosthesis replaced after 4 years, basically because of problems with the veneering material. No fractures of implant components were observed during the follow-up period. Bone loss was on average 0.59 mm (SD 0.97 mm) during 5 years, with no statistical difference between the two groups. Conclusion Welded titanium frameworks presented a similar favorable clinical performance as conventional cast-gold alloy frameworks in fixed implant-supported prostheses in the edentulous maxilla after 5 years in function. Implant failures were concentrated in only a few patients in each study group.

Removable partial denture design: a need to focus on hygienic principles?

Abstract: Purpose The purpose of this study was to critically analyze important hygienic/secondary prophylactic and biomechanical aspects of removable partial denture (RPD) design. Materials and methods The literature related to traditional biomechanical design and open/hygienic design of RPDs was discussed by the authors at a 2.5-day workshop. The written report was circulated among the authors until a consensus was reached. Results There is little scientific support for most of the traditional design principles of RPDs, nor has patient satisfaction shown any correlation with design factors. However, there is evidence that an open/hygienic design is more important than biomechanical aspects for long-term oral health. The biomechanical importance of some components is questioned, e.g., indirect retention and guiding planes. Alternative connector designs that reduce risks of tissue injury are described. Direct retainers and pontics are discussed in relation to the possibilities they offer for gingival relief. Conclusion Greater attention should be paid to RPD design principles that minimize the risks of tissue injury and plaque accumulation in accordance with modern concepts of preventive dentistry.

Optical data acquisition for computer-assisted design of facial prostheses.

Abstract: Purpose The conventional impression technique for manufacturing facial prostheses has the disadvantage of deforming the soft tissues because of the tension caused by the impression material, as well as causing discomfort to the patient. The purpose of this study was to establish a system that allows contact-free reproduction of the facial surface combined with computer-assisted design and fabrication of facial prostheses. Materials and methods Three-dimensional data of the facial surface were obtained using an optical acquisition system based on the method of phase-measuring profilometry. A sensor head with a fringe projector and two CCD cameras for photogrammetric triangulation were used in connection with a PC for measurement control and data evaluation. Software for computer-assisted design of the facial surface to be reconstructed was developed. A prototype facial prosthesis was fabricated using stereolithography. The system was tested using a modified puppet head. First clinical tests were performed with a patient who had undergone maxillofacial surgery including the resection of one eye. Results Three-dimensional data acquisition and imaging allow visualization of a whole face without causing tension or neuromuscular reaction. As surface brightness is also part of the digital model, it is even more realistic than a plaster cast. The stereolithographic object showed good marginal fit and satisfactory shape. Conclusion The presented technique allows three-dimensional data reproduction of the facial surface, computer-assisted design of a facial prosthesis, and transfer to a rapid prototyping unit. The system has obvious advantages over conventional impression techniques. Further clinical trials are planned to evaluate the clinical success of the technique.