Digital assessment of a retentive full crown preparation-An evaluation of prepCheck in an undergraduate pre-clinical teaching environment.

INTRODUCTION: Acquiring practical skills is essential for dental students. These practical skills are assessed throughout their training, both formatively and summatively. However, by means of visual inspection alone, assessment cannot always be performed objectively. A computerised evaluation system may serve as an objective tool to assist the assessor. AIM: The aim of the study was to evaluate prepCheck as a tool to assess students' practical skills and as a means to provide feedback in dental education. METHODS: As part of a previously scheduled practical examination, students made a preparation for a retentive crown on the maxillary right central incisor-tooth 11. Assessments were made four times by two independent assessors in two different ways: (a) conventionally and (b) assisted by prepCheck. By means of Cohen's kappa coefficient, agreements between conventional and digitally assisted assessments were compared. Questionnaires were used to assess how students experienced working with prepCheck. RESULTS: Without the use of prepCheck, ratings given by teachers differed considerably (mean κ = 0.19), whereas the differences with prepCheck assistance were very small (mean κ = 0.96). Students found prepCheck a helpful tool for teachers to assess practical skills. Extra feedback given by prepCheck was considered useful and effective. However, some students complained about too few scanners and too little time for practice, and some believed that prepCheck is too strict. CONCLUSION: prepCheck can be used to assist assessors in order to obtain a more objective outcome. Results showed that practicing with feedback from both prepCheck and the teacher contributes to an effective learning process. Most students appreciated prepCheck for learning practical skills, but introducing prepCheck requires enough equipment and preparation time.

Phase transformation and fracture load of stock and CAD/CAM-customized zirconia abutments after 1 year of clinical function.

OBJECTIVES: Functional loading and low-temperature degradation may give rise to impaired clinical long-term service of zirconia implant abutments. The aim of this study was to compare the fracture strength (primary outcome measure) and the volume percentage of monoclinic surface zirconia (m-ZrO2 ) of stock and CAD/CAM-customized zirconia implant abutments that functioned clinically for 1 year with geometrically identical pristine controls in an ex vivo experiment. MATERIAL AND METHODS: Twenty-three stock (ZirDesign™) and 23 CAD/CAM-customized (Atlantis™) zirconia implant abutments were retrieved after 1 year of clinical service. They were compared with pristine copies with respect to the volume fraction of the monoclinic phase using Raman spectroscopy and their fracture load by means of a single load-to-fracture test. Failure analysis was performed using optical and SEM microscopy. After verification of normal distribution, paired t tests were used for comparison of fracture loads between pristine and clinically aged specimen. All statistical tests employed a level of significance of α = 0.05. RESULTS: The fracture loads of the stock zirconia abutments were significantly (p < 0.05) reduced to 78.8% (SD 29.5%) after one year of clinical function. For the CAD/CAM abutments, no reduction in fracture load was found. No m-ZrO2 volume percentages beyond the detection threshold of 5% were observed in any of the samples. CONCLUSIONS: After 1 year of clinical service, no difference in fracture strength of the CAD/CAM-customized zirconia implant abutments could be demonstrated, whereas the stock zirconia abutments decreased considerably in fracture strength. No substantial tetragonal-to-monoclinic transformation was observed.

Adhesive Failure of Lava Ultimate and Lithium Disilicate Crowns Bonded to Zirconia Abutments: A Prospective Within-Patient Comparison.

PURPOSE: To demonstrate the influence of restorative material on the success of clinical bonding to zirconia. MATERIALS AND METHODS: A total of 50 participants with a single implant received screw-retained restorations; ie, Lava Ultimate (LU) crowns extraorally bonded to zirconia abutments. After 1 year, lithium disilicate (LDS) was used as an alternative restorative material. These restorations were also followed for 1 year. RESULTS: Forty LU restorations (80%) debonded within 1 year of clinical service, whereas no bonding failures occurred with LDS restorations. CONCLUSION: The choice of restorative material for single crowns luted to zirconia implant abutments strongly influences the incidence of bonding failures.

Fractography of clinically fractured, implant-supported dental computer-aided design and computer-aided manufacturing crowns.

Today, a substantial part of the dental crown production uses computer-aided design and computer-aided manufacturing (CAD/CAM) technology. A recent step in restorative dentistry is the replacement of natural tooth structure with pre-polymerized and machined resin-based methacrylic polymers. Recently, a new CAD/CAM composite was launched for the crown indication in the load-bearing area, but the clinical reality forced the manufacturer to withdraw this specific indication. In parallel, a randomized clinical trial of CAD/CAM composite crowns luted on zirconia implant abutments revealed a high incidence of failure within the first year of service. Fractured crowns of this clinical trial were retrieved and submitted to a fractographic examination. The aim of the case series presented in this article was to identify failure reasons for a new type of CAD/CAM composite crown material (Lava Ultimate; 3M Oral Care, St. Paul, Minnesota, USA) via fractographic examinations and analytical assessment of luting surfaces and water absorption behavior. As a result, the debonding of the composite crowns from the zirconia implant abutments was identified as the central reason for failure. The adhesive interface was found the weakest link. A lack of silica at the zirconia surface certainly has compromised the bonding potential of the adhesive system from the beginning. Additionally, the hydrolytic stress released from swelling of the resin-based crown (water absorption) and transfer to the luting interface further added to the interfacial stress and most probably contributed to a great extend to the debonding failure.

Osseointegration of a Zirconia Implant: A Histologic Assessment.

PURPOSE: The aim of this study was to describe the histologic and histomorphometric features of a retrieved, functional endosseous zirconia implant in a human subject. MATERIALS AND METHODS: A maxillary zirconia implant (ZV3) placed in a 52-year-old man was retrieved after 2 years of uncompromised service and prepared for light microscopic evaluation. RESULTS: Histologic examination demonstrated good osseointegration. Bone contact measurements revealed a mean percentage of bone-to-implant contact of 55.8% (SD 3.8%). CONCLUSION: The histologic data provide further evidence of the potential of zirconia implants to osseointegrate to a similar degree as titanium in humans.

Stock Versus CAD/CAM Customized Zirconia Implant Abutments - Clinical and Patient-Based Outcomes in a Randomized Controlled Clinical Trial.

BACKGROUND: Single-tooth replacement often requires a prefabricated dental implant and a customized crown. The benefits of individualization of the abutment remain unclear. PURPOSE: This randomized controlled clinical trial aims to study potential benefits of individualization of zirconia implant abutments with respect to preservation of marginal bone level and several clinical and patient-based outcome measures. MATERIAL AND METHODS: Fifty participants with a missing premolar were included and randomly assigned to standard (ZirDesign, DentsplySirona Implants, Mölndal, Sweden) or computer aided design/computer aided manufacturing (CAD/CAM) customized (Atlantis, DentsplySirona Implants, Mölndal, Sweden) zirconia abutment therapy. Peri-implant bone level (primary outcome), Plaque-index, calculus formation, bleeding on probing, gingiva index, probing pocket depth, recession, appearance of soft tissues and patients' contentment were assessed shortly after placement and one year later. RESULTS: No implants were lost and no complications related to the abutments were observed. Statistically significant differences between stock and CAD/CAM customized zirconia abutments could not be demonstrated for any of the operationalized variables. CONCLUSION: The use of a CAD/CAM customized zirconia abutment in single tooth replacement of a premolar is not associated with an improvement in clinical performance or patients' contentment when compared to the use of a stock zirconia abutment.

Clinical Bonding of Resin Nano Ceramic Restorations to Zirconia Abutments: A Case Series within a Randomized Clinical Trial.

BACKGROUND: New dental materials are introduced and promoted in the field without extensive clinical testing. Using those materials in a clinical setting might result in unacceptable early failure rates. PURPOSE: The purpose of this paper was to analyze bonding of a new dental restorative material to either zirconia stock abutments or zirconia customized abutments. MATERIALS AND METHODS: Fifty participants seeking single implant treatment were included in a prospective study. Resin Nano Ceramic (RNC, Lava Ultimate, 3M ESPE, Seefeld, Germany) crowns were digitally manufactured and extraorally bonded to either a stock or a customized zirconia abutment (ZirDesign and ATLANTIS, DENTSPLY Implants, Mölndal, Sweden) by means of a resin composite cement (RelyX Ultimate in combination with Scotchbond Universal, 3M ESPE), strictly following the manufacturer's recommendations. The final restorations were screw-retained to the implants and followed during 12 months. Primary outcome parameter was uncompromised survival of the restoration, and secondary outcome parameter was mode of failure. RESULTS: No implants were lost. The uncompromised survival rate of the RNC crowns bonded to zirconia abutments after 1 year of clinical service was only 14% (n = 7). Catastrophic failure occurred in three cases (6%), whereas bonding failure between RNC crowns and zirconia abutments occurred in 80% of the cases (n = 40) within the first year of service. No statistical significant difference in uncompromised survival rate could be identified between abutment types (χ2 = 1.495, p = .209). Uncompromised survival rate after 1 year was highly significantly different (χ2 = 104.173, p < .001) from a reference standard, which was set at 95%. CONCLUSION: RNC crowns luted to stock and customized zirconia implant abutments with the particular resin composite cement in this trial have a poor prognosis, regardless of the abutment type used.

Digital versus analog complete-arch impressions for single-unit premolar implant crowns: Operating time and patient preference.

STATEMENT OF PROBLEM: Digital impression-making techniques are supposedly more patient friendly and less time-consuming than analog techniques, but evidence is lacking to substantiate this assumption. PURPOSE: The purpose of this in vivo within-subject comparison study was to examine patient perception and time consumption for 2 complete-arch impression-making methods: a digital and an analog technique. MATERIAL AND METHODS: Fifty participants with a single missing premolar were included. Treatment consisted of implant therapy. Three months after implant placement, complete-arch digital (Cerec Omnicam; Sirona) and analog impressions (semi-individual tray, Impregum; 3M ESPE) were made, and the participant's opinion was evaluated with a standard questionnaire addressing several domains (inconvenience, shortness of breath, fear of repeating the impression, and feelings of helplessness during the procedure) with the visual analog scale. All participants were asked which procedure they preferred. Operating time was measured with a stopwatch. The differences between impressions made for maxillary and mandibular implants were also compared. The data were analyzed with paired and independent sample t tests, and effect sizes were calculated. RESULTS: Statistically significant differences were found in favor of the digital procedure regarding all subjective domains (P<.001), with medium to large effect sizes. Of all the participants, over 80% preferred the digital procedure to the analog procedure. The mean duration of digital impression making was 6 minutes and 39 seconds (SD=1:51) versus 12 minutes and 13 seconds (SD=1:24) for the analog impression (P<.001, effect size=2.7). CONCLUSIONS: Digital impression making for the restoration of a single implant crown takes less time than analog impression making. Furthermore, participants preferred the digital scan and reported less inconvenience, less shortness of breath, less fear of repeating the impression, and fewer feelings of helplessness during the procedure.

Noninvasive restoration of severe erosion by means of CAD/CAM indirect composite occlusal restorations: a technical note.

The use of new materials and computer-aided design/computer-aided manufacturing techniques can help dental practitioners efficiently treat dental erosion in a predictable manner. If the vertical dimension of occlusion has to be increased, the static and dynamic occlusion need to be reorganized. This article presents and documents a practical, digital approach to such treatment and discusses possible merits as they relate to treatment time, ease of treatment, and predictability.

The discoloring effects of food on the color stability of esthetic brackets--an in-vitro study.

AIM: The purpose of this study was to investigate the discoloring effect of certain foods on the color stability of esthetic brackets made of different materials. MATERIAL AND METHODS: Ten specimens of six different tooth-colored brackets were immersed for 10 days at 37 degrees C in various solutions (de-ionized water, tea, coffee, red wine, orange juice, curry and cress) or exposed to accelerated photo-aging (150 KJ/ m(2), 340 nm). Using the Easyshade device, the brackets were analyzed at the beginning of the experiment and after ultrasound-cleaning daily thereafter for ten days according to CIELCh coordinates lightness, chroma and hue. Our results were evaluated using the SPSS-12.0 statistical program and subjected to the Kruskal-Wallis and/or Mann-Whitney U tests. RESULTS: The results can be divided into three types of reactions. The brackets exposed to UV light, cress or orange juice showed no visible discoloration. The measured color differences remained in the same range as the measurements for brackets in the control group. All brackets immersed in red wine, tea or coffee showed similar reactions, with a sharp increase in discoloration after 5 days (corresponding to high consumption). In the curry solution, the brackets made of polyoxymethylene became immediately discolored; all other bracket types showed no visible reaction. CONCLUSIONS: This in-vitro test can only simulate the actual intra-oral situation, but the results seem to demonstrate that the consumption of certain foods greatly influences to what extent the color of tooth-colored brackets changes.