The International Journal of Prosthodontics, 02/2004

Purpose: This article presents clinical guidelines for restoring structurally compromised teeth and dentitions to reduce the risk for fatigue-caused failures in connection with prosthetic reconstructions. Materials and Methods: Based on the best scientific evidence available and clinical expertise acquired through experience and practice, biomechanical principles are elucidated from a prosthetic aspect. Results: In prosthetic treatment in the structurally compromised dentition, all efforts need to be focused on protecting the abutments and reconstruction from future fatigue failures. A modified, "therapeutic" occlusion to avoid nonaxial forces may then be prudent. Conclusion: By lending the prosthesis a favorable occlusal design, the nonaxial forces may be markedly reduced, and the teeth, cement, and restorative materials will be less susceptible to fatigue failures.

Purpose: The aim of this investigation was to compare the biaxial flexural strength, its reliability, and the mode of fracture of bilayered disks made of two core materials (In- Ceram Alumina and In-Ceram Zirconia), both veneered with conventional feldspathic porcelain (Vita Alpha). Materials and Methods: One hundred forty specimens (monolithic and bilayered) of In-Ceram Alumina, In-Ceram Zirconia, and Vita Alpha were made and tested with the biaxial flexural test. Finite element analysis was used to estimate the maximum tensile stress at fracture. Data were analyzed with one-way ANOVA, Tukey HSD, and Weibull distribution. SEM was used to identify the initial crack and characterize the fracture mode. Results: All specimens with the core material on the bottom surface were statistically significantly stronger and more reliable than those with the porcelain on the bottom surface. Among them, In-Ceram Zirconia was stronger than In-Ceram Alumina. There was no statistically significant difference among groups when the porcelain underwent tension. Two different modes of fracture were observed in the bilayered samples according to which material was on the bottom surface. Conclusion: The material that underwent tensile stress dictated the strength, reliability, and fracture mode of the specimens. The design of the restorations and the actual distribution of the tensile stresses must be taken into account; otherwise, the significant contribution of stronger and tougher core materials to the performance of all-ceramic restorations may be offset by the weaker veneering porcelain.

Purpose: This study evaluated the assessment of attractiveness of standardized changes in incisor angulation of different tooth arrangements. Materials and Methods:Four sets of images showing the maxillary anterior teeth without lips against a black background were used for evaluation. Each set contained the original photograph, one computer-manipulated symmetric image, and four images with different standardized changes in incisor angulation (10 degrees). The judges, consisting of three groups (30 dental students, 30 medical students, 30 art students), ranked each photo set for attractiveness from 1 (most attractive) to 6 (most unattractive). Results: The mean ranking (in parentheses) showed that symmetric teeth with ideal axes (2.5) and changes in the angulation of one (2.8) or both (2.5) lateral incisors were significantly more attractive than the angulation of one (4.2) or both (4.6) central incisors. There were no differences between the groups of participants. All findings were reproducible. Conclusion: Tooth arrangements showing central incisors with ideal axes were more attractive. Slight changes in the angulation of one or both lateral incisors did not influence attractiveness negatively.

Purpose: This overview presents a description of organofunctional trialkoxysilane coupling agents (silanes), their chemistry, properties, use, and some of the main clinical experiences in dentistry. Materials and Methods: The main emphasis was on major dental journals that have been reviewed from 1958 up to the latest research news from 2002. A MEDLINE search with the key words "dental silanes" was used. Special silane literature and journals outside dentistry were also cited. Results: The main emphasis is on the use of silanes in prosthetic and restorative dentistry. Clinical relevance was based mainly on either short- or long-term tests. The interpretation of various results is not given, mainly because of controversial observations that may be very difficult to explain. Nevertheless, the majority of the clinical results pointed to silanes playing a significant role in the adhesion process. Silane reaction mechanisms were not entirely understood, and there exist several theories for bonding mechanisms for silanes and substrates. Conclusion: Dental materials offer a continuously challenging forum for silanes, and silanes will play an essential role in material development.

Purpose: The objective of this cross-sectional study was to describe corresponding procedures for irreversible hydrocolloid and silicone impressions taught and used in European Union dental schools. Materials and Methods: A self-administered questionnaire requesting information about rinsing and disinfection methods was sent to each of the 373 heads of prosthodontic, pedodontic, and orthodontic departments in the 131 European Union dental schools. Response rate was 94%. Statistical analysis included chi-square or Fisher exact tests, and ANOVA or Kruskall-Wallis tests. Results: Of the responding departments, 92% systematically rinsed their impressions. Fifteen percent of the departments, mostly orthodontics, never disinfected irreversible hydrocolloid impressions, and 11% never disinfected silicone impressions. The immersion method was used by 65% for irreversible hydrocolloid impressions (73% for silicone), with a disinfection time of 10.3 ± 6.3 minutes (11.8 ± 7.4 for silicone). The disinfected impressions were not rinsed by 16% for irreversible hydrocolloid and 14% for silicone. Most departments used brand-name products. Conclusion: The same disinfection procedure for both irreversible hydrocolloid and silicone impressions was used by 78% of departments. There was great diversity, however, between departments in the procedure used for each impression material.

Purpose: This study investigated the emotional effects of tooth loss among community-dwelling elderly people in Hong Kong and compared the effects among edentulous and partially dentate elderly. Materials and Methods: A questionnaire study involved 233 southern Chinese elderly who were recruited and interviewed at social centers for elderly people throughout Hong Kong. Data were analyzed using chi-square or chi-square exact tests. Results: Twenty-two percent of the participants reported difficulty accepting tooth loss, with no difference between the edentulous and partially dentate. However, 95% stated that their confidence was unaffected. For more than half of elderly people, tooth loss had a negative effect on food choice and enjoyment of food, with removable denture wearers having greater restrictions. Avoiding going out, eating in public, and forming close relationships were less common problems. Twenty-two percent felt unprepared for the effects of tooth loss, and more than half said that better communication with the dentist would have helped. Conclusion: The emotional effects of tooth loss were not marked among elderly people, and there were no differences between edentulous and partially dentate individuals. However, significant disability was experienced because of restrictions in daily living activities. Restrictions were more severe in people who had lost enough teeth to necessitate denture wearing.

Purpose: The purpose of this follow-up study was to evaluate the stability of the screw joint in edentulous patients 1 year after treatment with implant-supported fixed prostheses (Brånemark system). Materials and Methods: A total of 20 patients were included, 10 treated in the maxilla and 10 in the mandible. The fixed prostheses were removed approximately 1 year after insertion, and the stability of the screw joints was evaluated using a rating scale based upon the CDA quality evaluation criteria of dental care. Results: All implant-supported fixed prostheses were recorded as stable before the prosthetic screws (gold screws) were unscrewed. "Unacceptable loosening" was observed in 4% of the prosthetic screws and in 29% of the abutment screws. Conclusion: In this study, only a few of the prosthetic screws showed unacceptable loosening after 1 year of function. The clinical relevance of the observed high occurrence of loose abutment screws could be questioned, as all fixed prostheses were initially recorded as stable.

Purpose: This article compares the cost of mandibular two-implant overdenture treatment to that of conventional denture treatment in an academic teaching hospital. Materials and Methods: Sixty edentulous patients (aged 65 to 75 years) participated in a randomized clinical trial. All patients received a new maxillary complete denture and either a mandibular conventional denture (n = 30) or an implant overdenture on two unsplinted implants (n = 30). Resource-based microcosting of direct and indirect costs (eg, expenses and time cost to patients) of all scheduled and unscheduled visits was conducted through 1 year following delivery of the prostheses. Results: Mean direct costs (1999 CD$) for scheduled visits in the implant and conventional groups were $2,332 and $814, respectively, and mean indirect costs were $1,150 and $810, respectively. Differences between the two groups were significant. Twenty-six patients in each group had unscheduled visits during the study at a median direct cost for the overdentures of $85 and $64 for the conventional dentures. Median indirect costs for unscheduled visits were $163 and $202, respectively. These differences were not significant. Mean total costs of the overdentures were $4,245 and $2,316 for the conventional dentures, and the between-group difference was significant. Conclusion: The direct cost of mandibular two-implant overdenture treatment was 2.4 times higher than that of conventional denture treatment. When indirect costs were added, the implant-to-conventional total cost ratio estimate was 1.8. These cost data can now be combined with estimates of the efficacy of the two types of prosthesis so practitioners and patients can make informed decisions about these prosthodontic treatment concepts.

Purpose: This retrospective longitudinal study evaluated the success of implant prosthetic rehabilitation with the Frialit-2 implant system. Materials and Methods: The study was performed with 504 patients, from two treatment centers, who had received a total of 1,554 implants between May 1990 and May 2001. The data of these patients, who received the implants in various regions and for various indications, were analyzed with respect to clinical, topographic, and radiographic parameters. The mean observation period was 6.2 years, with a maximum of 134 months. Results: A survival rate of 94.8% was found for all implants. The implant survival rate of 92.6% in the maxilla remained constant after 68 months of observation. In the mandible, the implant survival rate of 96.7% showed no changes after 76 months. Kaplan-Meier analysis identified jaw, occurrence of postoperative complications, and region as statistically significant factors influencing implant survival. Multivariate Cox regression showed that gender, occurrence of postoperative complications, and jaw were factors that increased the risk of implant loss. Statistically significant correlations were found between the incidence of implant loss and vertical bone loss adjacent to the implant at the time of second-stage surgery. Conclusion: Implant survival rate is influenced by implant site, gender, and occurrence of complications. On the whole, the Frialit-2 system proved successful in all areas of indication after long-term observation.

Purpose: Water sorption and dimensional stability of three fiber-reinforced composites were studied. Two composites (Vectris, FibreKor) were resin impregnated industrially, and one composite (Stick) was polymer preimpregnated but required further manual impregnation. Materials and Methods: Bar-shaped specimens of each material were prepared according to manufacturers' instructions. The water sorption and dimensional change of each specimen were calculated according to the change in its weight and dimension before and after immersion. Specimens were immersed in distilled water for 1, 7, 60, and 180 days. SEMs were taken to examine the quality of the fiber-matrix interface. The volume percentage of fiber content of each fiber-reinforced composite was experimentally estimated. Results: A general trend of increasing water sorption for each immersion period according to the material type was: Vectris FibreKor Stick. There were no significant differences in dimensional change among the materials and immersion periods. Conclusion: The preimpregnated fiber-reinforced composite (Stick) showed higher water sorption than the industrially impregnated fiber-reinforced composites (Vectris, FibreKor). Despite a variation in the water sorption of the fiber reinforced composites studied, all were within a 32 µg/mm3 criterion established by the ISO. The magnitude of dimensional change was small enough that it should not raise any significant clinical concern.

Purpose: This study measured the temperature increase induced by various types of curing units during resin cement polymerization under ceramic restorations. Materials and Methods: The resin cement was polymerized between a ceramic specimen (diameter 5 mm, height 2 mm) and a dentin disk (diameter 5 mm, height 1 mm) with a conventional halogen light, a high-intensity halogen light, a plasma-arc light, and a light-emitting diode unit. The temperature increase was measured under the dentin disk with a J-type thermocouple wire connected to a data logger. Ten measurements were carried out for each curing unit. Difference between starting and highest temperature readings was measured, and the 10 calculated temperature changes were averaged. Results: Temperature increase varied significantly depending on curing unit used. The plasma-arc light induced significantly higher temperature increases than any other curing unit. The light-emitting diode unit produced the lowest temperature changes. There were no statistically significant differences between the conventional and high intensity halogen curing units. Conclusion: Polymerization with curing units characterized by high energy output (plasma-arc light) caused higher temperature changes compared to other curing units, but the temperature increase detected was not viewed as critical for pulpal health.

Purpose: Incisal tooth wear may be a sign of long-term bruxing behavior. Bruxism is purported to be a risk factor for temporomandibular disorders (TMD). The aim of this population-based cross-sectional study was to determine if anterior tooth wear is associated with the self-report of TMD pain in children and adolescents. Materials and Methods: In a population sample of 1,011 children and adolescents (mean age 13.1 years, range 10 to 18 years; female 52%; response rate 85%), TMD cases were defined as subjects reporting pain in the face, jaw muscles, and temporomandibular joint during the last month according to RDC/TMD. All other subjects were considered controls. Incisal tooth wear was assessed in the clinical examination using a 0 to 2 scale (no wear, enamel wear, dentin wear) for every anterior permanent tooth. The mean wear score for the individuals was categorized into 0, 0.01 to 0.20, 0.21 to 0.40, and 0.41+. A multiple logistic regression analysis, controlling for the effects of age and gender, analyzed the association between the categorized summary wear score and TMD. Specifically, the hypothesis of a trend between higher tooth wear scores and higher risk of TMD was tested. Results: An odds ratio of 1.1 indicated, after adjusting for gender and age, no statistically significantly higher risk of TMD pain with higher tooth wear scores. Conclusion: Incisal tooth wear was not associated with selfreported TMD pain in 10- to 18-year-old subjects.

Purpose: This preliminary international survey compared provision of implant-retained overdentures to fixed implant-supported prostheses for edentulous mandibles. Materials and Methods: Questionnaires based on a 2001 Swedish study were sent to prosthodontists and specialist clinics in nine additional countries. Results: Response rate varied from 53% to 100% in 10 national surveys and should allow careful comparison of results. The relationship between implant overdentures and fixed implant-supported prostheses in treatment of edentulous mandibles varied much; in Sweden, the proportion of overdentures was 12%, whereas it was 93% in the Netherlands. In all countries, the most common reason for choice of the overdenture was reduced cost. In all but two countries, the majority of respondents thought that patients with implant overdentures were equally or more satisfied with overdentures as those with fixed implant-supported prostheses. Conclusion: There were great differences among the 10 countries in choice of implant treatment of the edentulous mandible. The relative proportion of mandibular overdentures to fixed prostheses was low in Sweden and Greece and varied from one to two thirds in the other countries, except the Netherlands.

Purpose: This study evaluated the marginal fit of experimental and custom-made fixed prosthetic restorations through a new 360-degree external examination. The minimum number of gap measurements required to produce relevant results for gap analysis was also investigated. Materials and Methods: The marginal fit of six experimental and eight custom-made crowns was observed microscopically by means of a mechanical device, and software was employed to measure the gap. Two crowns, chosen from among the 14 previously evaluated, were reanalyzed to determine the minimum number of gap measurements required to produce significant results for gap analysis. Results: The precision obtained with the custom-made crowns differed from that of the experimental specimens. The minimum number of measurements required to produce a sample mean value within ± 5 µm of the mean, calculated over 360 measurements, taking standard error of the means = 4 µm, was 18 for experimental and 90 for custom-made crowns, for both equidistant measurement spacing and randomly selected points. Conclusion: Differences in fit between experimental specimens and custom-made ones showed that experimental results might not always be obtained in clinical practice. Within the limitations of the protocol of this study, the minimum number of measurements required to ensure relevant results for gap analysis was 18 for experimental and 90 for custom-made crowns.

Purpose: This study assessed decayed/missing/filled teeth (DMFT), presence of occlusal units, and prevalence of shortened dental arches in a Tanzanian adult population. Materials and Methods: The dental state of samples of the Tanzanian population was studied. Oral examinations were conducted on 5,532 adults from rural and urban cluster samples. DMFT was related to age, gender, and residence. The pattern of tooth loss within dental arches was mapped, and the prevalence of shortened dental arches was estimated. Results: Mean DMFT scores increased gradually from 1.8 (20- to 29-year-olds) to 3.8 (50- to 59-year-olds). A steep increase was observed in the >= 60-year-olds (DMFT 8.1). "Missing" was the dominant component of DMFT. The mean number of present teeth ranged from 27 in the youngest to 20 in the oldest age group. Under 60 years of age, DMFT was significantly higher for women than for men. No differences were found between residence categories. Molars were more frequently decayed, missing, and mobile than premolars. Of all subjects, 41% had complete dental arches, 44% had interruptions (of these, 73% were in posterior regions only), and 15% had shortened dental arches; 0.5% were edentulous. Of the subjects with shortened dental arches, about 65% had at minimum three pairs of occluding premolars. Conclusion: An initial low DMFT rate increased after the age of 60 years. Molars had the highest risk of dental decay and were most frequently absent. Shortened dental arches develop as a consequence of the pattern of tooth decay and tooth loss, although interruptions were frequently seen in the posterior regions.

Purpose: This work compared implant-supported fixed prostheses and overdentures in the edentulous mandible in a randomized prospective study of treatment results, clinical working hours, laboratory working hours, and laboratory costs including materials. Materials and Methods: Seventeen subjects agreed to participate. Three standard Brånemark implants were placed between the mental foramina in each patient. After the connection of standard abutments, subjects were randomly assigned to the fixed prosthesis group (n = 11) or overdenture group (n = 6). Subjects in the fixed group were provided with prostheses according to the All-in-One concept. Subjects in the overdenture group received a conventional denture retained by a Dolder bar system. Results: One implant was lost in the fixed prosthesis group after 1 year. A new implant was placed, and the prosthesis was refitted. Mean clinical working hours were 3.1 in the fixed prosthesis group and 4.1 in the overdenture group. Mean laboratory working hours were 12.5 in the fixed prosthesis group and 7.7 in the overdenture group. Total laboratory costs, including materials, were on average about US$1,700 for the fixed prosthesis and US$1,350 for the overdenture. Conclusion: A fixed implant-supported prosthesis in the edentulous mandible could be provided at about the same cost as an overdenture using the method described. Provided that the early survival results prove to be long lasting, the choice between a fixed and a removable prosthesis need not be a matter of economy.

Purpose: The purpose of this study was to measure patients' satisfaction and their preference between mandibular dentures with permanent silicone-based resilient denture liner (SR) and conventional heat-activated acrylic resin (AR), both opposed by acrylic resin-based maxillary complete dentures. Materials and Methods: Twenty-eight edentulous patients who had fulfilled selection criteria and provided informed consent were enrolled in this trial. Subjects were allocated randomly to either arm of cross-over groups (AR-SR/SR-AR), stratified by gender, using a random permuted block within the strata method. The AR-SR group received AR denture treatment followed by SR denture treatment. The SR-AR group received treatment in the reverse sequence. The primary outcome was patient satisfaction measured on 100-mm VAS, analyzed by two-way ANOVA and the Bonferroni multiple comparison as a post hoc test. The secondary outcome was patients' preference, evaluated by chi-square goodness-of-fit test. An intention-to-treat analysis was performed. Results: Twenty-five subjects were enrolled in the analysis. There were no significant differences between AR and SR dentures 1, 2, and 3 months after the completion of control. Eighteen of 25 patients preferred SR dentures. Conclusion: Although there were no significant differences in patient satisfaction ratings between the two types of dentures, a significant majority of patients preferred those with a resilient denture liner.

Purpose: The present follow-up study was carried out to evaluate the performance of Class II Cerec inlays after 10 years of clinical service. Materials and Methods: Sixty-six Class II CAD/CAM ceramic inlays were placed in 27 patients. Each patient received at least one inlay luted with a dual-cured resin composite and one inlay luted with a chemically cured resin composite. At the 10-year recall, 25 (93%) patients with 61 (92%) inlays were available for evaluation using a slight modification of the USPHS criteria. Results: Fifty-four (89%) of the 61 inlays reevaluated still functioned well at the 10-year recall. During the follow-up period, seven (11%) of the inlays required replacement because of: four inlay fractures, one cusp fracture, endodontic problems in one case, and postoperative symptoms in one case. All the replaced inlays had been luted with the dual-cured resin composite. The fractured inlays were all placed in molars. The estimated survival rate after 10 years was 89%, 77% for the dual-cured resin composite-luted inlays and 100% for the chemically cured resin composite-luted ones. The difference was statistically significant. Conclusion: Patient satisfaction with and acceptance of the Cerec inlays were high, and the performance after 10 years of clinical service was acceptable, especially regarding the inlays luted with the chemically cured resin composite. The properties of the luting agents seem to affect the longevity of the type of ceramic inlays evaluated.

Purpose: The aim of this study was to develop a simple technique to manufacture individualized ventilatory nasal masks for pediatric patients using materials and procedures commonly applied in dentistry. Materials and Methods: Three cases of pediatric patients who met with severe difficulties in their adaptation to commercially available nasal masks are described: one premature infant, one child diagnosed with achondroplasia, and one child with congenital central hypoventilation syndrome. Results: In each case, a light nasal mask was designed with two independent parts that become perfectly adapted to the patient's nose: one soft for the skin contact, and another rigid for dimensional stability. In all patients, adequate levels of ventilation were reached. Conclusion: This easy, inexpensive nasal mask fabrication technique can be used in a great number of patients, increasing the efficacy of individualized masks.