Do Morphological Changes in the Anterior Mandibular Region Interfere with Standard Implant Placement? A Cone Beam Computed Tomographic Cross-Sectional Study.

OBJECTIVE: To determine the morphological features in the anterior mandibular region, the presence of lingual foramen and canal dimensions in Saudi subjects that would interfere with standard implant placement. METHODS: CBCT scans of patients seeking implant treatment were examined. Based on the dentition status, patients were categorized into edentulous (group I) and dentulous (group I). On the panoramic view, the distance between the two mental foramina was divided into vertical segments of 10 mm width. In each segment, vertical bone height and buccolingual thickness at three levels (alveolar crest, 5 mm, and 10 mm apical to the crest) were assessed. The lingual foramen prevalence and canal features were assessed as well. Comparisons between the two groups regarding the assessed parameters were performed using the t-test. The percentage of edentulous mandibles with thickness <6 mm corresponding to the standard implant diameter was also calculated. RESULTS: Following the inclusion and exclusion criteria, group I consisted of 45 subjects and group II comprised 26 subjects. Bone height and thickness at the crestal level were significantly less in edentulous (I) than dentate mandibles (II) (P < 0.0001). The lingual foramen was detected in 90% of patients. In both groups, males had significantly greater mandibular height than females (P=0.02 and 0.005). At the crestal level, the thickness was <6 mm in 50% of the anterior mandibular segments. CONCLUSION: Half of the edentulous patients may receive normal size implants in the anterior interforaminal segments, while the other half will be limited to narrow implants (3.5 mm and less). The lingual foramen location, canal size, and position may represent another limitation for implant placement in that segment.

Quality Evaluation of Zirconium Dioxide Frameworks Produced in Five Dental Laboratories from Different Countries.

PURPOSE: The aim of this study was to assess and compare quality as well as economic aspects of CAD/CAM high strength ceramic three-unit FDP frameworks ordered from dental laboratories located in emerging countries and Switzerland. MATERIAL AND METHODS: The master casts of six cases were sent to five dental laboratories located in Thailand (Bangkok), China (Peking and Shenzhen), Turkey (Izmir), and Switzerland (Bern). Each laboratory was using a different CAD/CAM system. The clinical fit of the frameworks was qualitatively assessed, and the thickness of the framework material, the connector height, the width, and the diameter were evaluated using a measuring sensor. The analysis of the internal fit of the frameworks was performed by means of a replica technique, whereas the inner and outer surfaces of the frameworks were evaluated for traces of postprocessing and damage to the intaglio surface with light and electronic microscopes. Groups (dental laboratories and cases) were compared for statistically significant differences using Mann-Whitney U-tests after Bonferroni correction. RESULTS: An acceptable clinical fit was found at 97.9% of the margins produced in laboratory E, 87.5% in B, 93.7% in C, 79.2% in A, and 62.5% in D. The mean framework thicknesses were not statistically significantly different for the premolar regions; however, for the molar area 4/8 of the evaluated sites were statistically significantly different. Circumference, surface, and width of the connectors produced in the different laboratories were statistically significantly different but not the height. There were great differences in the designs for the pontic and connector regions, and some of the frameworks would not be recommended for clinical use. Traces of heavy postprocessing were found in frameworks from some of the laboratories. The prices per framework ranged from US$177 to US$896. CONCLUSIONS: By ordering laboratory work in developing countries, a considerable price reduction was obtained compared to the price level in Switzerland. Despite the use of the standardized CAD/CAM chains of production in all laboratories, a large variability in the quality aspects, such as clinical marginal fit, connector and pontic design, as well as postprocessing traces was noted. Recommended sound handling of postprocessing was not applied in all laboratories. Dentists should be aware of the true and factitious advantages of CAD/CAM production chains and not lose control over the process.

Effects of Impression Coping Design, Impression Technique, and Dental Undercuts on the Accuracy of Implant Impressions Assessed by 3-Dimensional Optical Scanning: An In Vitro Study.

INTRODUCTION: The aim of this in vitro study was to evaluate the effect of the type and design of the impression copings on the accuracy of implant impressions in 2 different conditions. MATERIALS AND METHODS: A reference model with 2 implants inserted in bilateral mandibular canines was fabricated. The posterior teeth were inserted as tilted to simulate intra-oral undercuts. The teeth were eliminated to create an edentulous condition. Three different impression techniques were performed (open high retentive [OH], open low retentive [OL], closed [C]) for each condition. Total of 48 casts were made. Two scan-bodies were secured on each cast, scanned by an optical scanner. Then, they were compared to the scan of the reference model, and the calculated mean errors were analyzed with a 2-way ANOVA and Tukey test. RESULTS: There was no significant difference between the complete and partially edentulous groups (F = 3.252, P = 0.079). There was significant difference between the different designs of the impression copings (F = 31.789, P < 0.001) but the interaction between the dependent variables was not significant (F = 0.511, P = 0.603). CONCLUSIONS: The design of the impression copings was more important than the undercuts. The accuracy of the closed tray coping was greater than the low retentive coping and equal to the high retentive coping.

Technique to verify the accuracy of a definitive cast before the fabrication of a fixed dental prosthesis.

This report describes a straightforward technique for verifying the accuracy of a definitive cast by using a maximal intercuspation record fabricated from polyvinyl siloxane occlusal registration material. This precise verification method detects inaccurate casts before the dental prosthesis is fabricated, thus saving chairside and laboratory time while reducing the number of costly prosthesis remakes.

Evaluation of stress distributions occurring on zirconia and titanium implant-supported prostheses: A three-dimensional finite element analysis.

STATEMENT OF PROBLEM: Titanium implants have been successfully used to support fixed dental prostheses. Zirconia implants have been suggested as support for crowns, but information on their use to support partial fixed dental prostheses is limited. PURPOSE: The purpose of this finite element study was to evaluate the maximum principal, minimum principal, and von Mises stresses and their distributions on zirconia and titanium implant-supported, partial fixed dental prostheses located in the anterior maxillary region. MATERIAL AND METHODS: Zirconia and titanium implants (4 mm in diameter and 11. 5 mm in length) and prostheses made from 2 different materials (lithium disilicate and zirconia) were simulated, and 4 models were generated: Titan-IPS, Titan-Lava, Zircon-IPS, and Zircon-Lava. The maxillary bone was modeled as type 3 bone. The load was applied obliquely (534 N) and horizontally (76.5 N), and the stress values and distributions were examined. RESULTS: Under horizontal loading, stresses generated on the cortical bone in the Zircon models were lower than those in the Titan models. Under oblique loading, stress values were similar in the same implant material and stress type. For all types of stress among the models, the stress values that occurred on the trabecular bone were found to be similar under both horizontal and oblique loading. The maximum stress values on the bones, implants, cores, and veneers did not exceed the strength of the structures. CONCLUSIONS: Different stress values resulted from the different implant types. The prosthetic materials did not change the stress distributions in bone.

Understanding dental CAD/CAM for restorations--accuracy from a mechanical engineering viewpoint.

As is the case in the field of medicine, as well as in most areas of daily life, digital technology is increasingly being introduced into dental practice. Computer-aided design/ computer-aided manufacturing (CAD/CAM) solutions are available not only for chairside practice but also for creating inlays, crowns, fixed partial dentures (FPDs), implant abutments, and other dental prostheses. CAD/CAM dental practice can be considered as the handling of devices and software processing for the almost automatic design and creation of dental restorations. However, dentists who want to use dental CAD/CAM systems often do not have enough information to understand the variations offered by such technology practice. Knowledge of the random and systematic errors in accuracy with CAD/CAM systems can help to achieve successful restorations with this technology, and help with the purchasing of a CAD/CAM system that meets the clinical needs of restoration. This article provides a mechanical engineering viewpoint of the accuracy of CAD/ CAM systems, to help dentists understand the impact of this technology on restoration accuracy.

Standards, Regulation and Registration of Dental Laboratories. An Industry Update.

State dental associations are showing increased interest in maintaining current standards and regulations affecting the dental laboratory industry as mandated by the Food and Drug Administration. The domestic dental laboratory industry is being significantly stressed by foreign competition, rapid technology development and unprecedented consolidation, which are changing the way that prosthetic devices and restorations are manufactured and delivered to dentists. Of paramount importance to the prescribing dentist is the accurate documentation of the source and materials being used in prostheses being delivered to patients.

A systematic review of CAD/CAM fit restoration evaluations.

The evolution and development of CAD/CAM systems have led to the production of prosthetic reconstructions by going beyond the use of traditional techniques. Precision adjustment of prosthetic elements is considered essential to ensure sustainable restoration and dental preparation. The purpose of this article was to summarise the current literature on the fitting quality of fixed prostheses obtained by CAD/CAM technology.

Laboratory quality assurance in the Department of Restorative Dentistry at the University of Illinois at Chicago, College of Dentistry.

PURPOSE: The purpose of this study was to evaluate data collected in University of Illinois at Chicago College of Dentistry (UIC COD) laboratory quality assurance (QA) forms, analyze the collected data, and create a report of the findings. The goals of the study were to (1) identify the most common mistakes occurring during laboratory and clinical procedures when performing prosthodontic treatment, (2) note the incidence and trends of mistakes made by D3, D4, and IDDP2 students, and (3) observe any differences in the types of mistakes made by D3, D4, and IDDP2. MATERIALS AND METHODS: QA data from June 1, 2007 to May 31, 2009 were evaluated based on forms gathered from the QA dental laboratory from all D3, D4, and IDDP2 students' submissions. All students had graduated from the UIC COD at the time of collection. Data were recorded for type of errors made in submission of laboratory work (Indirect Restorations [IR], Removable Partial Dentures [RPD], Complete Dentures [CD]), year of student in dental school (D3, D4, IDDP2), and frequency of rejection for each respective student. The frequency of common mistakes were pooled, evaluated, and reported by respective class year. RESULTS: The five most common laboratory submission errors for D3, D4, and IDDP2 students were nearly the same among student years for IR, RPD, and CD. D4 students had disproportionately higher numbers of work rejections compared to D3 and IDDP2 students. CONCLUSIONS: D4 students had a higher percentage of laboratory submission errors compared to D3 students for all laboratory procedures. There were similar types of errors noted between foreign-trained students (IDDP2) and domestically trained students (D3, D4).

[Contact wear related to single- and multi-unit dental prostheses]. / Contactslijtage in relatie tot kronen en bruggen.

Occlusal surfaces of teeth and restorations wear by repeated antagonistic contact. Two-body wear is the result of direct contact between occlusal surfaces. In cases of three-body wear, food is found between antagonistic teeth. Contact wear is expressed predominantly by abrasion and material fatigue. Erosion is a type of wear which does not involve direct antagonistic contact. Qualitative methods exist for registering occlusal tooth wear. Wear of restorations can be measured using casts. An obvious method for comparing rates of wear of restorative materials is laboratory research. This method has demonstrated that the wear rates of composite and enamel are similar. Cast metals and in particular ceramic wear less than enamel. The relation between oral factors and the rate of tooth wear is not always clear. Wellpolished surfaces of restorations wear less quickly and have less effect on the wearing of antagonistic teeth than rougher restoration surfaces.

Satisfaction Level among Patients Treated with Fixed Dental Prosthesis in a Tertiary Care Hospital: A Descriptive Cross-sectional Study.

INTRODUCTION: Dental treatment aims at correction of existing disease; prevention of future disease with rehabilitation of patient's lost functional capacity and aesthetics. Fixed dental prosthesis is any prosthesis that is cemented to a natural tooth or dental implants abutments that cannot be removed by patient. The success of prosthodontic treatment is related to prosthesis survival, with its ability to fulfil biologic and patient-evaluated objectives with patient satisfaction. This study is aimed to find the patient satisfaction with fixed prosthodontic treatment. METHODS: This descriptive cross-sectional study was done in a tertiary care hospital among 102 patients rehabilitated with fixed dental prosthesis from August to September 2019 after taking ethical approval from Institutional Review Committee of Kathmandu Medical College. (IRC No. 1207201918). Convenience sampling was done. The questionnaire assessed patient's satisfaction of fixed prosthesis on the basis of appearance, chewing ability, cleansibility, speech and awareness of oral hygiene measures for cleaning of the prosthesis. Data entry was done in Microsoft excel and analysed using Statistical Package for Social Sciences (SPSS)version 20.0, point estimate at 95% Confidence Interval was calculated along with frequency and proportion for binary data. RESULTS: The majority of the patients 87 (85.3%) were satisfied with their fixed prosthesis, at 95% confidence interval (93.5- 81%). Eighty one (79.4%) were satisfied with their chewing ability; 99 (97.1%) satisfied with their speech, 78 (76.4%) satisfied with appearance of fixed prosthesis. Ninety eight patients (96.1%) were aware of oral hygiene measures, out of which only 66 (67.3%) used interdental aids for cleaning of their fixed prosthesis. CONCLUSIONS: Several factors (chewing ability, appearance, speech, cleansibility of fixed prosthesis) had positive impact on overall satisfaction in majority of the patients. Dentists should continue to emphasise on the significance of maintaining good oral hygiene and use of interdental aids for the longevity of fixed prosthesis.

Clinical performance of extended zirconia frameworks for fixed dental prostheses: two-year results.

The purpose of this prospective cohort study was to assess the performance of tooth-supported, extended zirconia, fixed dental prostheses (FDPs). Thirty FDPs with span-lengths between 36 and 46 mm (mean: 40.33 mm), four to seven units and with connector dimensions of approximately 9 mm(2) were inserted (19 in the posterior region, 11 including anterior teeth) using glass-ionomer cement and assessed (aesthetic evaluation, failures, hypersensitivity/tooth vitality, secondary caries, pocket depth, decementation and chipping) at baseline and after 2 years. Differences between baseline and 2-year recall were analysed using the Wilcoxon signed-rank test for matched pairs. There were five failures. One FDP revealed a core fracture at the base of the connector, probably caused by a damage induced during fabrication. Two FDPs had to be recemented, one abutment tooth had to be treated endodontically and one cohesive failure of the veneer was observed. There were no significant changes of pocket depth and hypersensitivity between baseline and 2-year recall. The aesthetics were rated as excellent by the patients at both baseline and recall. Two year clinical results of extended zirconia based FDPs with 9 mm(2) connectors are promising.

Marginal fit of 14-unit zirconia fixed dental prosthesis retainers.

The marginal fit of 14-unit fixed dental prosthesis retainers and single-crown copings fabricated by the same computer-aided design (CAD)/computer-aided manufacturing (CAM) system were evaluated in vitro hypothesizing that the marginal opening might be independent of the type of restoration. Eight ivorine maxillary teeth (FDI locations 27, 25, 23, 21, 11, 13, 15 and 17) were prepared to accommodate a 14-unit prosthesis. Ten fixed dental prosthesis retainers and 40 single-crown-copings were fabricated using Zeno CAD/CAM on 20 master dies. Four cross-sections were made from each tooth and the marginal gap dimensions were measured. One-way anova was used to test the difference between the experimental groups and two-way anova and a post hoc test (Student-Newman-Keuls) were carried out to determine the influence of the location of the abutment tooth and the measurement location within the abutment tooth in the experimental groups (P < 0.05). Mean marginal gap dimensions and standard deviations for fixed dental prosthesis retainers and single-crown copings were 25 +/- 29 and 13 +/- 12 microm, respectively. The type of restoration showed a significant influence (P < 0.001) on the marginal gap. The location of the abutment tooth (P < 0.001) and the measurement location (P < 0.001) exhibited significant influence on marginal gaps of fixed dental prosthesis retainers while no influence on single-crown copings could be detected. The highest marginal gaps were found at the palatal surface of the incisor and canine of the 14-unit fixed dental prosthesis retainers. Fourteen-unit fixed dental prosthesis showed significantly higher marginal openings than single crowns fabricated under the same conditions. However, both restorations showed clinically acceptable marginal openings.

[Adult orthodontics for a better prosthesis]. / L'orthodontie adulte pour une meilleure prothèse.

INTRODUCTION: Adult patients are seen more frequently in our orthodontic offices. Unlike the adolescent, the adult patient will often need a multidisciplinary approach due to tooth migrations secondary to extractions or periodontal disease. MATERIALS AND METHODS: This article will address the indications and orthodontic solutions to various restorative problems relative to the adult patient. Specific orthodontic mechanics aimed at facilitating and improving the prosthetic outcomes will be described and illustrated with clinical cases.

Is it cost-beneficial to society? Measuring the economic worth of dental residency training.

This study estimated whether continued programming of a highly specialized four-year dentistry residency training in Saudi Arabia was cost-beneficial. We utilized a purposive sampling to administer a survey to trainees in major cities. Additionally, we used publically available market information about general practitioners. We employed Benefit-Cost Analysis accounting approach as a conceptual framework. Using general practitioners as the base category, we grouped overall social analytical perspectives into resident trainees and rest of society. The residency program was cost-beneficial to trainees, realizing an estimated return of SR 4.07 per SR 1 invested. The overall societal return was SR 0.98 per SR 1 invested, slightly shy of a bang for the buck, in part because the public sector largely runs the training. Benefits included increased earnings and enhanced restorative dentistry skills accruing to trainees; increased charitable contributions and programming-related payments accruing to programs and the public; and practice-related payments accruing to governmental, professional, and insurance agencies. Rest of society, notably government underwrote much of the cost of programming. A sensitivity analysis revealed the results were robust to uncertainties in the data and estimation. Our findings offer evidence to evaluate whether continued residency training is cost-beneficial to trainees and potentially to overall society.

Quality Assurance in Custom Dental Devices: A Technologist's Perspective.

Manufacturing of custom-made dental devices such as removable dentures, fixed prosthodontics and orthodontics are subject to the requirements of the Medical Devices Directive (MDD). Many dental laboratories often enhance these requirements by implementing quality assurance procedures that then provide enhanced consistency. this paper provides a dental technologist's view of some of the systems currently being used in dental laboratories to provide a quality assured product and associated issues.

Qualitative evaluation of elderly home residents' fixed and removable prostheses in relation to the ADL index.

UNLABELLED: Functional diversity and biopsychosocial state is a significant issue, which greatly influences elderly oral health and state of fixed and removable prostheses. OBJECTIVES: The goal of the investigation was to evaluate the quality of fixed and removable prostheses in a group of elderly home residents in relation to the ADL index. METHODS: The group consisted of 175 institutionalised elderly, mean age 76.8 years. Special care need was assessed on ADL scale. To evaluate the quality and need for replacement of fixed and removable prostheses Karlsson's and modified Nevalainen et al. indices were used. RESULTS: Spearman's correlation analysis showed significant correlation of ADL index scores and both Karlsson's index values (rho=-0.468, p<0.01) as well as for modified Nevalainen's indices (rho=-0.572, p<0.01). Lower ADL score was correlated with poorer oral hygiene and condition of fixed or removable dentures. It was determined that 87% of the examined patients were in objective need of fixed, removable or combined prosthodontic treatment. CONCLUSIONS: The study showed that lower ADL index scores of functionally dependent elderly patients correlate with poorer condition of fixed and removable prostheses and greater need of fixed, removable or combined prosthodontic treatment.

Development of effectiveness of care and use of services measures for dental care plans.

OBJECTIVES: Standardized measures to assess clinical aspects of the performance of managed dental care plans are not available. This project sought to develop and evaluate measures for effectiveness of care and use of services that could be calculated using a plan's administrative data. METHODS: Two panels of stake holders representing dental plans, purchasers, and dental providers participated in a modified Delphi process to refine initial sets of effectiveness of care and use of services measures modeled after HEDIS measures for medical care. The refined measures were then pilot tested in two dental health maintenance organizations. RESULTS: The development process resulted in specification of seven effectiveness of care measures assessing disease activity classification, and prevention and outcomes for caries, periodontal disease, and tooth loss. Six use of services measures focusing on prophylaxes, third molar surgery, preventive, restorative, prosthetic, surgical, and endodontic care also were specified. Pilot testing of the measures indicated reasonable reliability and sensitivity, but also demonstrated the need for supervision or auditing of the process. CONCLUSIONS: These standardized measures for dental care plan performance are available for immediate use. However, because the measures depend on diagnostic information (periodontal probing data and diagnoses associated with restorative treatments) in the administrative data set, their adoption will require changes in most plans' data systems and data collection policies.