Chris Louca

Color related to ceramic and zirconia restorations: A review

The requirement to achieve natural looking restorations is one of the most challenging aspects of dentistry, and the shade matching of dental restorations with the natural dentition is a difficult task due to the complex optical characteristics of natural teeth. Dental porcelain is considered the reference material for prosthetic rehabilitation, but it is not easy to handle and aesthetic excellence is quite difficult to obtain. For these reasons, shade matching with dental porcelain is often considered to be more artistic than scientific. Shade matching is considered unpredictable due to several variables that may influence the final appearance of a restoration. In order to improve this situation, over the last decade new shade guides and instruments have been developed and the aesthetic aspects of dental porcelain have been further investigated. In this review some aspects of color selection and color reproduction have been examined. Color selection has advanced through the development of new shade guides and electronic shade taking devices, although visual assessment has still not been entirely replaced by electronic instruments. Color reproduction with dental porcelain has improved thanks to advances in the performance and knowledge of dental porcelain, but is still not easy to achieve. The difficulties of achieving good aesthetics with PFM restorations and the desire for metal free solutions have resulted in the increased use of zirconia. The unique optical properties of zirconia have introduced new opportunities for achieving superior aesthetics, however further research is required with this material.

Endodontic instrument fracture: causes and prevention

Endodontic file fracture has traditionally been considered an uncommon event; however, a recent perception of increased fracture incidence with rotary nickel-titanium (NiTi) instruments has emerged. It is essential for the clinician to understand the likelihood of instrument fracture and the reasons for this unfortunate occurrence. Removal of fractured files is both technically difficult and time consuming and therefore it is of key importance to limit the probability of fracture. Over the last ten years, a range of NiTi alloy modifications have been made by instrument manufacturers, with varying reports of success, in an attempt to reduce the likelihood of file separation. The aim of this review was to investigate the incidence and aetiology of file fracture as well as analysing recommended prevention protocols. Additionally, the effectiveness of alloy modifications in reducing the incidence of file fracture was considered. Analysis demonstrated that the bulk of the literature relating to instrument fracture is in vitro evidence, which limits its clinical relevance. The reported incidence of NiTi instrument fracture is similar to stainless-steel (SS) files; however, inconsistent methodologies hamper accurate comparison. NiTi instruments are reported to fail by torsional overload and/or flexural fatigue, with file fracture occurring principally in the apical third of the canal or with inappropriate use. Finally, operator skill, manufacturer modifications and limiting file reuse have been demonstrated to be significant in reducing fracture incidence indicating the importance of a prevention strategy.

An in vivo and in vitro investigation of the use of ICDAS, DIAGNOdent pen and CarieScan PRO for the detection and assessment of occlusal caries in primary molar teeth

ObjectivesThe aim of this study was to investigate the in vivo and in vitro validity of International Caries Detection and Assessment System (ICDAS), DIAGNOdent pen and CarieScan PRO in the detection and assessment of occlusal caries in primary teeth.MethodsSixty-four molars were assessed using all three systems under standardised in vivo conditions. They were then extracted and assessed by two examiners in vitro along with an additional 38 teeth (102 teeth in total from 45 children). Downer’s histological scoring criterion was the validation gold standard. Sensitivity, specificity, positive and negative likelihood ratios and area under the receiver–operator curves were calculated for all caries and dentine caries. Repeatability was analysed using Cohen’s Kappa and the performance of the systems between in vivo and in vitro settings by the same examiner were compared.ResultsICDAS showed the highest validity and repeatability. The DIAGNOdent pen’s overall clinical validity was comparable to that of ICDAS, but it demonstrated only moderate repeatability. CarieScan PRO had negligible validity in vivo, and there was no relationship between in vivo and in vitro parameters.ConclusionsThe in vivo results of ICDAS and DIAGNOdent pen were satisfactory and comparable to those obtained in vitro, with ICDAS performing better. The CarieScan PRO performed poorly under both conditions.Clinical relevanceICDAS should be the index of choice when detecting and assessing occlusal caries in the primary dentition, and in vitro data can be safely extrapolated in vivo. The DIAGNOdent pen must be employed with caution. Currently, the CarieScan PRO is unsuitable for use in the primary dentition.

Influence of coloring procedure on flexural resistance of zirconia blocks.

STATEMENT OF PROBLEM The white color of zirconia limits the possibility of a natural-looking restoration. Industrially precolored blocks and green-stage coloring liquids are used to obtain shaded zirconia. Several authors have reported that pigments may negatively affect the mechanical characteristics of the material. PURPOSE The purpose of this in vitro study was to investigate the effect of a recently marketed coloring system on the flexural strength (σ), Weibull characteristic strength (σ0), and Weibull modulus (m) of a zirconia for computer-aided design/computer-aided manufacturing (CAD/CAM) systems. MATERIAL AND METHODS Noncolored white blocks (In-Ceram YZ), industrially precolored blocks (In-Ceram YZ col. LL1p), and green-stage infiltration-shaded blocks in 4 colors (In-Ceram YZ Coloring Liquids) were tested. Industrially precolored specimens (n = 30) were assigned to the PREC group. Noncolored specimens were divided into 5 groups (n = 30). Group CNTR was not treated (control). Groups INF-N, INF-L, INF-M, and INF-I were subject to green-stage infiltration (neutral, light, medium, and intense, respectively). Specimens were tested in a 3-point bending apparatus following ISO 6872:2008 specifications. Data were analyzed by 1-way ANOVA. RESULTS The calculated flexural strengths (MPa) were CNTR 1232.56 ± 103.91; PREC 1215.16 ± 141.42; INF-N 1280.72 ± 160.10; INF-L 1218.92 ± 78.63; INF-M 1153.71 ± 176.80; and INF-I 1248.46 ± 111.73. No statistically significant differences were found among the tested groups (P = .195). CONCLUSIONS Unlike what has been reported for other combinations of zirconia and coloring liquids, the coloring technique tested in the present study did not negatively influence the flexural characteristics of the tested zirconia.

An in vitro comparison of tooth whitening techniques on natural tooth colour

Objective Tooth whitening has become a popular treatment regime but there is little quantitative evidence to compare techniques and so confusion may exist for the clinician as to which regime to prescribe for greatest efficacy. The aim of this study was to compare immediate and longer-term colour change on natural tooth colour in vitro, using five current tooth whitening techniques with blind matched control groups.Methods A total of 100 human teeth of matched size were cleaned, stored in sterile deionised water at 4°C then randomly allocated to one of the five active treatment groups or five matched control groups. The active treatments were: 10% carbamide peroxide (CP) × 60 min, 35% CP × 30 min or 35% hydrogen peroxide (HP) treatment × 30 min activated by one of three sources of energy (diode laser, halogen light, and plasma arc curing light). Tooth colour was analysed with a colorimeter before and after treatment: immediate, one week and nine months post-bleaching designed to generate tooth colour value (L*) according to the L*a*b system. The change in colour was determined as ΔL (the difference in the value of the colour) for each tooth, then the mean differences were obtained for each group and compared. Tooth surface temperature was monitored.Results Comparing active treatments with controls it was found that 10% CP, 35% CP, 35% HP with halogen provided significantly greater tooth whitening. Comparing the different treatments showed that 10% CP was significantly more effective (P <0.05) than all other treatments except 35% HP with halogen activation. The effect of each treatment regime over time showed that the 10% CP gave a significant gain immediately and one week later (P <0.05), however, all the whitening effects were lost over time following these single treatments. The temperature rise on the tooth surface was greatest when using laser activation during power whitening.Conclusion This study suggests that 10% CP is an effective technique for tooth whitening and can offer significant benefits over alternative regimes.

The impact of fractured endodontic instruments on treatment outcome.

Instrument fracture complicates the endodontic procedure by obstructing debridement, delaying treatment completion and affecting the patients dental experience. When a file fractures there are several treatment options that could be selected, however, the future management should be based on the effect of the fractured instrument on treatment outcome. The aim of the following review was to analyse the literature assessing the impact of endodontic instrument fracture, focusing on its influence on endodontic prognosis and treatment outcome. A comprehensive MEDLINE search including various keywords identified several publications that considered the variables. Analysis of the publications highlighted a paucity of quality long-term clinical outcome studies relating specifically to the influence of instrument fracture. The available studies demonstrated a wide variety of methodologies reporting conflicting findings; therefore, meaningful conclusions were difficult. Within the confines of the literature it appears that retained fractured instruments do not reduce the prognosis of endodontically treated teeth if apical periodontitis is absent, however, if disease is present healing is significantly reduced. Therefore, the stage at which an instrument fractures in infected cases appears likely to be significant as canal disinfection will be compromised accordingly. Considering the risks associated with file removal, perhaps this should only be attempted if apical disease is present. Although it is accepted that the nature of file fracture precludes integration into randomised prospective trials, there is a need for well designed long-term outcome studies investigating the influence of fractured files.

Color match of two different ceramic systems to selected shades of one shade guide

STATEMENT OF PROBLEM There are no consistent indications given by dental manufacturers on how to layer ceramics to achieve a color match to a shade selected from a dental shade guide. The technique for ceramic layering relies primarily on the skill and experience of ceramists and is not easily predictable. PURPOSE The purpose of this study was to evaluate, using a clinical spectrophotometer, the ability to color match shades selected with the 3D-Master shade guide using 2 different ceramic systems. MATERIAL AND METHODS Two ceramic systems were selected for this study, the VITA Omega 900 and VITA VM 13. For both systems, shades 2M3, 3M2, 4M2 of the VITA 3D-Master shade guide were selected. Thirty ceramic discs, 15 mm in diameter, were fabricated with different layer thickness ratios of opaque dentin, dentin, and enamel, maintaining a constant overall thickness. A clinical spectrophotometer (VITA Easyshade) was used for color comparison. The measured ΔE values were statistically analyzed with a 3-way ANOVA and the Tukey HSD test (α=.05). RESULTS The 3-way ANOVA showed that the ceramic system (P<.001), the selected shade (P<.001), and the layering scheme all significantly influenced the ΔE values (P<.001). CONCLUSIONS Both VITA VM 13 and VITA Omega 900 ceramic systems showed a color match with the shades 2M3, 3M2, and 4M2 of the VITA 3D-Master shade guide to be within the limits for clinical acceptability (ΔE≤ 3.3). VM 13 showed a statistically better color match. The layering scheme influenced the definitive color of the restoration.

An investigation of complete denture teaching in the UK: Part 1 - A survey of undergraduate teaching

Aim This paper is the first in a series of two that investigate the undergraduate teaching of complete dentures in the UK.Materials and methods A questionnaire was sent by email to 13 UK dental schools enquiring about the number of hours spent in the lecture theatre, laboratory and clinic. The schools were also asked to give their views about the preparedness of the new graduates for dealing with complete dentures in general practice.Results There was great disparity between schools in the overall number of lectures delivered. Two schools claimed 28 hours and the remainder varied between 6-15 hours. Four schools devoted more time to laboratory work whereas three schools spent more time in the clinic. One school reported no dedicated clinical time for complete dentures. There appears to be a regional variation with northern UK dental schools spending more time on the teaching of complete dentures. The quota for complete dentures varied from three in most schools to eight in one school and none in another. Comments from the dental schools varied from a reported lack of suitable complete denture cases, to concerns with insufficient curricular time devoted to the subject and a subsequent lack of clinical competence on graduation. Some schools have integrated complete denture teaching into the general prosthodontic course as it is considered inappropriate to teach different aspects of prosthetics in isolation.Conclusion Competence in complete dentures falls short of what is expected. With a single exception all the schools seem to have low expectations for their undergraduate students to be practically trained and experienced in the production of complete dentures. Despite the advent of implants and the introduction of clinical dental technicians, there is and will continue to be a need for the competent treatment of the edentulous population by general practitioners.

BDJ UCL Eastman CPD programme: an online survey

Objective To ascertain from participants of the BDJ UCL Eastman CPD programme its value to their professional endeavours, and in particular to determine whether they would object to making it more robust especially in the way that the CPD hours are achieved.Design An online questionnaire survey.Method Participants were encouraged to complete an online survey of nine questions by 31 July 2012.Results Of the 3,292 participants who began the survey, it was completed by 3,070 (93.2%). Of those, 2,952 (91.1%) thought that additional learning tools would be helpful. The ability to resubmit incorrect answers was preferred by 2,549 (80.1%) of the respondents. Two thousand two hundred and fourteen participants (69.9%) raised no objection to making the scoring system more robust and 953 (30.1%) objections to this proposition were recorded. Ninety-eight percent (3,128) favoured the regular inclusion and flagging of core subjects and 95% of these respondents thought it would be useful to record these separately. The most preferred method of obtaining verifiable CPD was cited by 1,075 (39.5%) participants as reading journals followed by attending lectures and hands-on courses. The BDJ was the preferred journal to achieve both verifiable and general CPD. Most participants (1,930; 67.7%) use a home computer to take part in this initiative while a significant minority use tablets and smart-phones.Conclusion This survey showed that the BDJ UCL Eastman CPD journal-based verifiable CPD programme remains a popular method of fulfilling the GDC regulations and that the majority of participants are in favour of making the process more rigorous.

The Use of Picture Cards to Elicit Postgraduate Dental Student Feedback

The aim of this study was to elicit information about the use of picture cards to stimulate student feedback following a postgraduate dental course. Twenty-nine general dental practitioners (GDPs) volunteered for the study. Following an explanation of how this style of feedback worked, students were asked to choose a picture card from those available and use that image to stimulate their feedback. An independent interviewer introduced the topic and gathered comments in the form of qualitative data, generated by pre-formed questions. 93% (n = 26) questionnaires were completed and returned. 77% (n = 20) GDPs reported enjoying giving their feedback by ‘picture card’ technique; 83% (n = 20) reported this form of feedback stimulated their thoughts. Qualitative data were analysed thematically. Some GDPs felt the picture cards helped them formulate their feedback, others felt being able to give feedback to a third party they did not know was beneficial and giving feedback as a group was helpful. This novel approach of using picture cards to stimulate feedback was well received by these GDPs. A mixed result as to the value of this style of feedback was evident. A group feedback session facilitated by a stranger was considered to be a valuable approach to take.