The Accuracy of Digital Implant Impressions when Using and Varying the Material and Diameter of the Dental Implant Scan Bodies.

The effects of using and varying the material and diameter of implant scan bodies (ISBs) on the level of accuracy of digital implant impressions is unclear. The purpose of this study was to investigate these effects on the level of accuracy of scans made by an extraoral scanner (EOS) and intraoral scanner (IOS). A stone cast with two sets of ISBs was used. ISBs were made of titanium (TI) or polyether ether ketone (PEEK). Each set consisted of two narrow diameter (ND) and two regular diameter (RD) ISBs. Sixtysix scans were performed and imported into an inspection and metrology software to conduct the three-dimensional (3D) comparisons (N=140) and obtain root mean square (RMS) values. RMS values were analyzed with descriptive and inferential non-parametric statistics (α=.05). The use of ISBs did not improve the overall EOS and IOS scans accuracies. Also, varying the ISBs' diameter and material influenced the EOS and IOS accuracies. For the EOS, the precision in descending order was as follows RD TI, ND TI, RD PEEK, ND PEEK. In contrast, for the IOS an inverse relationship was noted. Finally, precision assessment should always be performed for any reference scanner under the proposed test conditions.

Comparison of Fit Between Zirconia and Metal Copings Fabricated Conventionally or Using Different CAD/CAM Techniques.

This study was designed to assess the fit of cobalt chromium copings fabricated using direct metal laser sintering and to compare with copings fabricated from nickel chromium (traditional casting) and zirconia (milled from partially sintered blanks). For both cobalt chromium and zirconia groups, impressions were generated using direct or indirect digitization. There were 5 experimental groups of 12 copings fabricated for a prepared maxillary right molar. The intimacy of fit (measured at the margin, axial wall and occlusal) was assessed using a replica method technique. The results showed that zirconia copings produced using direct digitization had significantly smaller marginal, axial and occlusal measurements compared to other groups (p⟨0.05). Nevertheless, all groups had a mean marginal gap within accepted clinical values. Though there was a decrease in the intimacy of fit from the margin to axial wall to the occlusal surface. It can be concluded that the fit of zirconia copings fabricated using direct digitization was significantly better than the other groups. However, it can be expected that further enhancement and refinement of additive technology such as direct metal laser sintering will offer clinicians a viable alternative to nickel chromium analogue production methods in the future.

Reduction of Tribocorrosion Products When Using the Platform-Switching Concept.

The reduced marginal bone loss observed when using the platform-switching concept may be the result of reduced amounts of tribocorrosion products released to the peri-implant tissues. Therefore, the purpose of this study was to compare the tribocorrosion product release from various platform-matched and platform-switched implant-abutment couplings under cyclic loading. Forty-eight titanium implants were coupled with pure titanium, gold alloy, cobalt-chrome alloy, and zirconia abutments forming either platform-switched or platform-matched groups ( n = 6). The specimens were subjected to cyclic occlusal forces in a wet acidic environment for 24 h followed by static aqueous immersion for 6 d. The amount of metal ions released was measured using inductively coupled plasma mass spectrometry. Microscopic evaluations were performed pre- and postimmersion under scanning electron microscope (SEM) equipped with energy-dispersive spectroscopy X-ray for corrosion assessment at the interface and wear particle characterization. All platform-switched groups showed less metal ion release compared with their platform-matched counterparts within each abutment material group ( P < 0.001). Implants connected to platform-matched cobalt-chrome abutments demonstrated the highest total mean metal ion release (218 ppb), while the least total mean ion release (11 ppb) was observed in the implants connected to platform-switched titanium abutments ( P ≤ 0.001). Titanium was released from all test groups, with its highest mean release (108 ppb) observed in the implants connected to platform-matched gold abutments ( P < 0.001). SEM images showed surface tribocorrosion features such as pitting and bands of fretting scars. Wear particles were mostly titanium, ranging from submicron to 48 µm in length. The platform-matched groups demonstrated a higher amount of metal ion release and more surface damage. These findings highlight the positive effect of the platform-switching concept in the reduction of tribocorrosion products released from dental implants, which consequently may minimize the adverse tissue reactions that lead to peri-implant bone loss.

Survey on the use of CAD-CAM technology by UK and Irish dental technicians.

Statement of the problem Digital workflows (CAD/CAM) have been introduced in dentistry during recent years. No published information exists on dental technicians' use and reporting of this technology.Purpose The aim of this cross sectional survey was to identify the extent digital technology has infiltrated the workplace and to investigate the factors affecting the use of CAD-CAM technology by dental laboratory technicians within Ireland and the UK.Materials and methods A web-based questionnaire was composed (Opinio, Object Planet Inc. Oslo, Norway) and distributed to UK and Irish dental technicians. Answers to all questions were anonymous and grouped such that general information was gathered initially, followed by branching of the survey into two sections depending on whether or not the respondent worked with CAD-CAM technology. Results were compiled and statistical analysis (Fisher's Exact test, SPSS, IBM, Armonk, New York, USA) was performed in order to investigate any correlation between various demographic variables and the answers provided.Results The survey was distributed to 760 UK technicians and 77 Irish technicians. The total number of completed surveys was 105, which yielded a total response rate of 14%. Most technicians reported using some form of CAD/CAM aspect in the workflow, and this was more significant for technicians working in large laboratories. Most training received was company-led. Large laboratories were also significantly correlated with less outsourcing of CAD/CAM work and a change in dental material use leading to the increase of zirconia and the decrease of noble alloys. Dental technicians did not report any significant change in working relationships and staffing as a result of CAD/CAM incorporation. High initial investment cost was the most common reason quoted from non-users, along with the lack of such technology in their working environment.

Survey of UK dentists regarding the use of CAD/CAM technology.

Statement of the problem Digital workflows (CAD/CAM) have been introduced in dentistry during recent years. No published information exists on dentists' use and reporting of this technology.Purpose The purpose of this survey was to identify the infiltration of CAD/CAM technology in UK dental practices and to investigate the relationship of various demographic factors to the answers regarding use or non-use of this technology.Materials and methods One thousand and thirty-one online surveys were sent to a sample of UK dentists composing of both users and non-users of CAD/CAM. It aimed to reveal information regarding type of usage, materials, perceived benefits, barriers to access, and disadvantages of CAD/CAM dentistry. Statistical analysis was undertaken to test the influence of various demographic variables such as country of work, dentist experience, level of training and type of work (NHS or private).Results The number of completed responses totalled 385. Most of the respondents did not use any part of a digital workflow, and the main barriers to CAD/CAM use were initial costs and a lack of perceived benefit over conventional methods. Dentists delivering mostly private work were most likely to have adopted CAD/CAM technology (P <0.001). Further training also correlated with a greater likelihood of CAD/CAM usage (P <0.001). Most users felt that the technology had led to a change in the use of dental materials, leading to increased use of, for example, zirconia and lithium disilicate. Most users were trained either by companies or self-trained, and a third felt that their training was insufficient. The majority of respondents (89%) felt that CAD/CAM had a big role to play in the future.Conclusion Most of the respondents did not use any part of a digital workflow. However, the majority of surveyed dentists were interested in incorporating CAD/CAM into their workflow, while most believed that it will have a big role in the future. There are still some concerns from dentists about the quality of chairside CAD/CAM restorations while the costs are still in the main hugely prohibitive (especially for NHS dentistry).

Reporting quality of randomised controlled trials published in prosthodontic and implantology journals.

The purpose of this study was to examine the reporting quality of randomised controlled trials (RCTs) published in prosthodontic and implantology journals. Thirty issues of nine journals in prosthodontics and implant dentistry were searched for RCTs, covering the years 2005-2012: The Journal of Prosthetic Dentistry, Journal of Oral Rehabilitation, The International Journal of Prosthodontics, The International Journal of Periodontics & Restorative Dentistry, Clinical Oral Implants Research, Clinical Implant Dentistry & Related Research, The International Journal of Oral & Maxillofacial Implants, Implant Dentistry and Journal of Dentistry. The reporting quality was assessed using a modified Consolidated Standards of Reporting Trials (CONSORT) statement checklist. Data were analysed using descriptive statistics followed by univariable and multivariable examination of statistical associations (α = 0·05). A total of 147 RCTs were identified with a mean CONSORT score of 69·4 (s.d. = 9·7). Significant differences were found among journals with the Journal of Oral Rehabilitation achieving the highest score (80·6, s.d. = 5·5) followed by Clinical Oral Implants Research (73·7, s.d. = 8·3). Involvement of a statistician/methodologist was significantly associated with increased CONSORT scores. Overall, the reporting quality of RCTs in major prosthodontic and implantology journals requires improvement. This is of paramount importance considering that optimal reporting of RCTs is an important prerequisite for clinical decision-making.

Communication methods and production techniques in fixed prosthesis fabrication: a UK based survey. Part 1: communication methods.

STATEMENT OF THE PROBLEM: The General Dental Council (GDC) states that members of the dental team have to 'communicate clearly and effectively with other team members and colleagues in the interest of patients'. A number of studies from different parts of the world have highlighted problems and confirmed the need for improved communication methods and production techniques between dentists and dental technicians. AIM: The aim of this study was to identify the communication methods and production techniques used by dentists and dental technicians for the fabrication of fixed prostheses within the UK from the dental technicians' perspective. The current publication reports on the communication methods. MATERIALS AND METHODS: Seven hundred and eighty-two online questionnaires were distributed to the Dental Laboratories Association membership and included a broad range of topics. Statistical analysis was undertaken to test the influence of various demographic variables. RESULTS: The number of completed responses totalled 248 (32% response rate). The laboratory prescription and the telephone were the main communication tools used. Statistical analysis of the results showed that a greater number of communication methods were used by large laboratories. Frequently missing items from the laboratory prescription were the shade and the date required. The majority of respondents (73%) stated that a single shade was selected in over half of cases. Sixty-eight percent replied that the dentist allowed sufficient laboratory time. Twenty-six percent of laboratories felt either rarely involved or not involved at all as part of the dental team. CONCLUSION: This study suggests that there are continuing communication and teamwork issues between dentists and dental laboratories.

Communication methods and production techniques in fixed prosthesis fabrication: a UK based survey. Part 2: production techniques.

AIM: The aim of this study was to identify the communication methods and production techniques used by dentists and dental technicians for the fabrication of fixed prostheses within the UK from the dental technicians' perspective. This second paper reports on the production techniques utilised. MATERIALS AND METHODS: Seven hundred and eighty-two online questionnaires were distributed to the Dental Laboratories Association membership and included a broad range of topics, such as demographics, impression disinfection and suitability, and various production techniques. Settings were managed in order to ensure anonymity of respondents. Statistical analysis was undertaken to test the influence of various demographic variables such as the source of information, the location, and the size of the dental laboratory. RESULTS: The number of completed responses totalled 248 (32% response rate). Ninety percent of the respondents were based in England and the majority of dental laboratories were categorised as small sized (working with up to 25 dentists). Concerns were raised regarding inadequate disinfection protocols between dentists and dental laboratories and the poor quality of master impressions. Full arch plastic trays were the most popular impression tray used by dentists in the fabrication of crowns (61%) and bridgework (68%). The majority (89%) of jaw registration records were considered inaccurate. Forty-four percent of dental laboratories preferred using semi-adjustable articulators. Axial and occlusal under-preparation of abutment teeth was reported as an issue in about 25% of cases. Base metal alloy was the most (52%) commonly used alloy material. Metal-ceramic crowns were the most popular choice for anterior (69%) and posterior (70%) cases. The various factors considered did not have any statistically significant effect on the answers provided. The only notable exception was the fact that more methods of communicating the size and shape of crowns were utilised for large laboratories. CONCLUSION: This study suggests that there are continuing issues in the production techniques utilised between dentists and dental laboratories.

The effect of prosthetic margin location on caries susceptibility. A systematic review and meta-analysis.

BACKGROUND: The prosthetic margin location relevant to the free gingival margin may influence the incidence of secondary caries due to the differences that exist between the micro-environment within the gingival crevice compared to the rest of the oral environment. OBJECTIVE: The purpose of this study was to systematically review the effect of prosthetic margin placement on caries susceptibility of abutment teeth. METHOD: Two independent authors identified cohort studies using MEDLINE, EMBASE, CDSR, CENTRAL, Google Scholar and Scopus through March 2012. Reference lists were also scanned. Included studies had to report on caries incidence with regard to location of prosthetic margins, with a minimum follow-up period of two years. RESULTS: A total of 5,541 references were identified and, after application of the inclusion criteria, 22 studies were included in the systematic review. Random-effects meta-analysis could be made in two studies, in which secondary caries incidence did not differ between margins placed subgingivally compared to equi- or supragingivally placed margins for a follow-up period up to ten years. Indications were found of a possible lower secondary caries rate at 15 years of follow up, based on one study. CONCLUSION: This systematic review and meta-analysis failed to detect a significantly different secondary caries rate of subgingivally located prosthetic margins in the short to mid-term (≤10 years). Due to the small number and the limitations of the included studies the results do not provide conclusive evidence as to the effect of prosthetic margin placement on the incidence of secondary caries.

The influence of age on tooth supported fixed prosthetic restoration longevity. A systematic review.

OBJECTIVE: The purpose of this study was to investigate the possible influence of age on the longevity of tooth supported fixed prosthetic restorations, using a systematic review process. DATA SOURCES: To identify relevant papers an electronic search was made using various databases (MEDLINE via Pubmed, EMBASE, The Cochrane Register of RCTs, the database of abstracts of Reviews of Effects-DARE), augmented by hand searching of key prosthodontic journals (International Journal of Prosthodontics, Journal of Prosthetic Dentistry and Journal of Prosthodontics) and reference cross-check. STUDY SELECTION: Assessment and selection of studies identified were conducted in a two phase procedure, by two independent reviewers utilizing specific inclusion and exclusion criteria. The minimum mean follow-up time was set at 5 years. RESULTS: The initial database search yielded 513 relevant titles. After the subsequent filtering process, 22 articles were selected for full-text analysis, finally resulting in 11 studies that met the inclusion criteria. All studies were classified as category C according to the strength of evidence. Meta-analysis was not possible due to the non-uniformity of the data available. The final studies were presented with conflicting results. The majority of the final studies did not report a statistically significant effect of age on fixed prostheses survival, whilst only one study reported poorer prognosis for elderly patients, and two studies reported poorer prognosis for middle-aged patients. CONCLUSIONS: The results of this systematic review showed that increased age of patients should not be considered as a risk factor for the survival of fixed prostheses. Although the majority of studies did not show any effect of age on the survival of fixed prostheses, there was some evidence that middle-aged patients may present with higher failure rates.

Time course of serial cystatin C levels in comparison with serum creatinine after application of radiocontrast media.

BACKGROUND: The delayed increase of creatinine after radiocontrast application is a potential reason for overlooking radiocontrast nephrotoxicity. Cystatin C may be more useful to rapidly assess a decrease in glomerular filtration rate (GFR). We compared cystatin C and creatinine to examine their kinetics after application of radiocontrast media. PATIENTS AND METHODS: Forty-one patients (60.8 +/- 8.8 years, 68% males) with normal to subnormal GFR scheduled for coronary angiography (27% with angioplasty), were studied for serum cystatin C and creatinine levels before, 5 h, 24 h and 48 h after angiography. Furthermore, alpha1-microglobulin was checked for evidence of tubular damage. RESULTS: At 5 hours after angiography, there was no significant change compared to baseline in either serum creatinine nor cystatin C. In comparison with the value immediately before coronary angiography, the increase of cystatin C achieved a maximum at 24 h after the application of the contrast agent (+7.2%). Within 48 h, cystatin C decreased to the level before angiography. Serum creatinine increased at 24 h (+7.7%) and continued to increase at 48 h (+11.3%). CONCLUSION: Cystatin C increases earlier after radiocontrast application compared with creatinine. Therefore, cystatin C needs to be investigated as a potential early marker for nephrotoxicity, especially in the upcoming setting of short-time hospitalizations for coronary angiographies and interventions. Thus, further studies in patients with renal failure undergoing radiocontrast application are warranted to assess the usefulness of cystatin C in respect of an earlier detection of radiocontrast nephrotoxicity.

Periodontal considerations in removable partial denture treatment: a review of the literature.

PURPOSE: A critical review of the literature on the periodontal considerations in removable partial denture (RPD) treatment is presented. MATERIALS AND METHODS: A MEDLINE search was conducted for studies pertaining to the effects of RPDs on the periodontal tissues during the various phases of prosthetic treatment. The review included both in vivo and in vitro studies. RESULTS: The use of RPDs leads to detrimental qualitative and quantitative changes in plaque. There seems to be a lack of information regarding the effects of RPDs on the status of periodontally compromised abutments. A number of studies, mainly in vitro, have failed to agree on the ideal RPD design. Clinical trials have shown that if basic principles of RPD design are followed (rigid major connectors, simple design, proper base adaptation), periodontal health of the remaining dentition can be maintained. CONCLUSION: Removable partial dentures do not cause any adverse periodontal reactions, provided that preprosthetic periodontal health has been established and maintained with meticulous oral hygiene. Frequent hygiene recalls and prosthetic maintenance are essential tools to achieve a good long-term prognosis. More prospective clinical trials are needed on the effect of RPDs on the condition of periodontally involved abutment teeth.

Shear bond strength of techniques for bonding esthetic veneers to metal.

STATEMENT OF PROBLEM: New composites with improved qualities have been introduced to the dental profession as alternatives to porcelain. There is concern about the strength and reliability of new metal-resin bonding systems when these composites are used as esthetic veneers over metal frameworks. PURPOSE: This in vitro study compared the shear bond strength of 2 metal-resin bonding techniques with the bond strength of conventional porcelain fused-to-metal (PFM). Effects of water storage and thermocycling were also evaluated. MATERIAL AND METHODS: Ninety disks, cast in a medium gold, high noble PFM alloy, were divided equally into 6 groups, and received 3 treatments for veneering: conventional feldspathic porcelain on 1 group, and a composite (Artglass) bonded to the metal, using 2 metal-resin bonding techniques. Specimens were tested in shear, half of them after a 24-hour dry storage at room temperature and the rest after 10-day storage in normal saline solution at 37 degrees C and thermocycling. Fractured specimens were evaluated under x10 magnification to determine the nature of failure. Statistical analysis was performed with 2-factor analysis of variance (ANOVA). RESULTS: Mean shear bond strength values before and after wet storage and thermocycling were 29.66 and 22.91 MPa for the PFM group; 21.43 and 17.92 MPa for the Siloc group; and 19.34 and 15.64 for the etched group, respectively. The PFM group exhibited significantly higher bond strength values compared with the other 2 groups (P<.001). All groups showed a significant decrease in bond strength values after wet storage and thermocycling (P<.001). CONCLUSION: Wet storage and thermocycling caused a significant decrease in shear bond strength of all specimens. Shear bond strength of conventional feldspathic PFM was significantly higher than that of the 2 metal-resin bonding techniques tested. The 2 latter techniques did not reveal any statistically significant differences.

A new approach to fabricating the occlusal surfaces of removable prostheses.

A procedure is introduced to fabricate the occlusal surfaces of removable prostheses that oppose ceramic restorations or ceramic denture teeth. It involves the use of a heat-processed glass ceramic material in the form of onlays over the plastic denture teeth. This procedure provides for more wear compatibility, improved esthetics, and individualized occlusion.