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Ming-San Ma: From stem cells to Schwann cells – Potential applications of iPS cells and neural crest stem cells Onze zenuwvezels in het niet-centrale …
Mike Erdos:Genetic etiology of Type 2 Diabetes: From gene identification to functional genomics Door acht grote studies samen te voegen, zijn twaalf …
Jan van der Scheer: Low-intensity wheelchair training in inactive people with long-term spinal cord injury Twee keer per week rolstoelrijden met een …
Literature suggests that elimination of biofilm in active sites of a lesion could be sufficient to stimulate reparative mechanisms of a vital dentin-pulp complex. This supports a new minimal invasive approach of caries treatment. However, sufficient understanding of the biological mechanisms is needed to judge the status of the pulp. Indirect pulp treatment (IPT) is a minimal invasive approach of caries treatment where a thin dentin layer over a nearly exposed pulp is left. This should allow the pulp to recover and the tooth maintains its normal vitality and function. The periphery of the cavity should be clean at the DEJ to obtain a predictable site for bonding of restoration material. The active part of the deep carious lesion should be cleaned from biofilm, but dentin should be preserved as much as possible. IPT was introduced as a caries treatment in pediatric dentistry. It is now believed to be effective in adult patients as well. This translational study examines brush techniques used in IPT and analyses in vitro the macro-visual clinical features of dentin in extracted teeth with carious lesions.
The protocol for indirect pulp treatment in deep carious lesions is released at the Center for Oral Hygiene and Dentistry, Groningen in November 2013. It is written by Peters, Van der Sluis and Blanksma under authorization of Prof. Dr. F. Abbasa. Revision is demanded to specify the instructions of the brush technique. (Appendix I) The degree of bacterial infection in demineralized dentin with overlying biofim in proximity of the pulp is not evident3, whereas the conventional excavation procedures in deep carious lesions often lead to pulp exposure and significant tissue loss.63
Treatment complications and insufficient arrest of the caries progress may lead to additional pulp damage and eventually necrosis.4 Used criteria during excavation of dentin are tissue hardness and tissue stain. Criteria for biofilm removal with a brush in deep carious lesions should be reconsidered to update clinical decision making during treatment.3
Aim of this study
Evaluation of the visual and clinical effects of the brush technique used in IPT, as written in the protocol for “deep caries treatment” at Center for Oral Hygiene and Dentistry, Groningen, The Netherlands. Research question What is the determined visual (biofilm fluorescence) and clinical effect (remaining dentin) on dentin after brush technique is used to remove biofilm during IPT in deep carious lesions? Sub questions 1 What is the determined effect of brush technique on biofilm and dentin in deep carious lesions by means of QLF imaging? 2 What is the determined effect on RDT before and after brush technique in deep carious lesions? 3 Are changes in autofluorescence of biofilm and dentin related to changes in RDT? Null
Hypotheses 1 Brush technique is not related to changes in red/green fluorescence ratios of dentin and/or pathological biofilm considering time and speed of the brush technique. 2 Brush technique is not related to RDT considering time and speed of the brush technique. 3 Changes in autofluorescence are not related to changes in RDT.
The treatment cycle uses the brush technique for 10 seconds, cycles of 5 times for 2 seconds. Consequently white and violet light images are captured of samples in freshly extracted permanent human teeth with deep carious lesions. Two groups (n=25) with different speed of the brushes (1000rpm and 2000rpm) are investigated. Sample size was 49. The evaluation of the ratio in autofluorescence changes is measured with auto fluorescent images of the QLF-D camera. The evaluation of the remaining dentin thickness (RDT) is measured in millimeters of dentin covering the pulp in images of split samples. Analysis was done with rANOVA.
Results suggest that there is no effect of (interaction of) rotation speed and/or time on R/G values in autofluorescence of biomass and dentin during the brush technique, although a negative trend was observed within samples for time of brushing (p = 0.077). Time of brushing is associated within the samples with decrease in RDT within the limitations of this study (p = 0.000). This effect was seen most in the first 4 seconds, with an average reduction of 0.02 (mm/s). Association was not found between R/G values and RDT.
The brush technique has no effect on biofilm and dentin according to QLF imaging considering time, interaction of rotation speed and time and rotation speed self. Autofluorescence and RDT were not related. Within the limitations of this study, a statistically significant difference was found for the time the brush technique was used and decrease in RDT within samples. Use the brushtechnique for 4 seconds at low rotation speed (1000 or 2000 rpm).
The purpose of the present study was to answer the key question: what factors are decisive in the consideration of the current endocarditis prophylaxis directive and how do these factors determine the application in dentistry? Therefore, a literature review has been carried out.
Factors in balancing the prophylaxis were examined. The social relevance plays a major role, given the high mortality of the disease. The last few years, the prophylaxis directive has been criticized and amended several times.
This study focuses on the social and dental discussion, which includes the compliance of
dental professionals and the high probability of resistance to antibiotics due to the over prescription that might take place because of the prophylaxis. The search has been performed using PubMed, EMBASE, Web Of Science and Cochrane Central Register of Controlled Trials with the terms “(endocarditis AND dentistry) AND (bacteremia OR antibiotic
resistance OR compliance)”. A total of 33 articles were included after application of inclusion and exclusion criteria.
The results of this literature study show that patients with plaque and/or calculus have a greater chance of developing a bacteremia than patients without these aspects. The percentages of a bacteremia in various dental treatments are diverse. Once in every four years, a treatment procedure occurs where there is a possibility of the emergence of a bacteremia. A prophylactic antibiotic reduces the risk of a bacteremia.
If a professional is familiar with the prophylaxis, there is a large compliance. Antibiotics, however, are prescribed frequently when there is no indication and vice versa. Frequent use of amoxicillin leads to an increase of resistance although a bacteremia is not completely eliminated by this prophylaxis.
The relationship between dental treatments and infective endocarditis has not yet been
completely revealed. Studies have ascertained that only a small part of the infective endocarditis cases have been initiated by dental procedures. The burden of bacteremia after routine daily activity also surpasses the fugitive bacteremia after dental procedures. It is still unclear whether the possible damage and the cost of prescribing antibiotics outweigh the
Based on the data found in this literature study, several factors are decisive in the
consideration of the current prophylaxis guideline such as the development of a bacteremia, the compliance of dental professionals, the chance of resistance against antibiotics and the possible consequences of using these antibiotics. Further research about the existence of a
bacteremia after dental procedures is required to solve questions about these influencing factors. A possible adjustment in the current guideline may provide more clarity in the applicability.
The aim of this study is to determine the perception of visual attractivity of rhodium
coated brackets by adolescent orthodontic treated patients and their parents or their
For this study 50 minors (22 male and 28 female) and 50 parents or attendants (17
male and 33 female) were selected at the Orthodontic department of the University Medical Centre Groningen. The participants were shown four pictures of two types of brackets. Both types are identical in shape and size. The first type is coated with a rhodium layer, while the second type is not coated. The participants ranked the visual attractivity of the brackets on a Visual Analogue Scale. A Repeated Measures ANOVA was used for statistical analysis. The
significance level was set at α = 0,05.
Gender appeared to have no influence on perception of visual attractivity (p < 0,24).
Minors rated conventional brackets with an average of 4,95 with a standard deviation of 1,98, with respect to an average of 6,15 with a standard deviation of 1,98 for rhodium coated brackets. Adults rated the conventional brackets averagely on 3,87 with a standard deviation of 1,57. The rhodium coated brackets were rated on an average of 7,04 with a standard deviation of 1,49. The perception of visual attractivity is significantly influenced by the bracket type (p < 0,001). Adults appear to experience greater difference in visual attractivity than minors (p < 0,004).
Minors and their parent or attendants gave higher scores to rhodium coated brackets with regard to the visual attractivity in comparison to non-coated brackets. Adults
experienced a greater difference between the two types of brackets than minors. Gender appeared to have no influence on the perception of visual attractivity.
The try-in procedure of a ceramic restoration is an important step before it can be permanently cemented. The ceramic surface after etching can be contaminated by saliva during the try-in phase. There are little independent studies on the cleaning efficacy of Ivoclean. This study evaluated the bond strength of lithium disilicate to a composite resin with and without saliva contamination and with and without cleaning using Ivoclean or water.
Materials and Methods:
Fifteen lithium disilicate discs (diameter: 17mm, thickness: 2mm) were divided at random in five groups, etched using 4.9% hydrofluoric acid and ultrasonic cleaned in demineralized water. Discs of group 1, 3 and 5 were contaminated with human saliva whereas groups 2 and 4 were left uncontaminated. The discs were cleaned with Ivoclean (G1-2), rinsed with water (G3) or underwent no cleaning (G4-5). All discs were treated with silane (Monobond Plus) followed by heat treatment and application of an unfilled resin (Adhese Universal). Tubes (N=60 and n=12 per group) filled with composite resin cement (Variolink Esthetic) were applied on each disk. All specimens underwent thermocycling (10.000 times, 5ºC to 55ºC). The shear bond strength (μSBS) was measured in a universal testing machine (1mm/min). The failure type was analyzed using a light microscope (x25). The results (MPa ± SD) were statistically analyzed with the one-way ANOVA and the post hoc analysis of Bonferroni. P-values smaller than 0.05 were considered significant.
Significant effects among the groups (p < 0.05) were observed on the bond strength (one-way ANOVA). Interaction terms were not significant (p > 0.05) for all groups (Bonferroni’s test). The bond strength of the group which was cleaned with Ivoclean after contamination (G1) showed a significant difference (p < 0.05) from the group which was not contaminated and cleaned with Ivoclean (G2). The group which was not cleaned after contamination (G5) showed a significant difference (p < 0.05) from the group which was not contaminated and cleaned with Ivoclean (G2). The group that was cleaned with Ivoclean after contamination (G1) showed no significant difference with the control group (G4) or the group that was not cleaned after contamination (G5). Adhesive failures between the cement and the substrate were observed in 63% of all specimens. Specimens that were not cleaned after the contamination with saliva, showed only adhesive failures (G5).
A residual layer of saliva after cleaning with Ivoclean led to a significant reduction of the bond strength. Cleaning with Ivoclean after saliva contamination of lithium disilicate did not lead to comparable bond strengths as uncontaminated lithium disilicate.
The aim of this study was to assess the esthetic outcome of immediate placed and/or immediate restored dental implants in an extraction socket in the anterior maxilla. Besides the focus of this study is on patient satisfaction. It was hypothesized that immediate placement and restoration is not inferior to conventional placement and/or restoration.
Materials and Methods
Eighty-two patients were randomly assigned to four different treatment groups. The groups differ from immediate/conventional placement to immediate/conventional restoration of implants. All implants were installed in extraction sockets with bony defects ranging from > 5mm. The patients were included when the unrestorable tooth was a tooth out of the upper esthetic area. The patients were able to give an informed consent. The esthetic outcome was objectively rated using the Pink Esthetic Score/White Esthetic Score (PES/WES) and the Implant Crown Aesthetic Index (ICAI) by a blinded researcher who had not been involved in the treatment. The subjective score was rated with the Visual Analog Scale (VAS).
Complete objective data was extracted from 73 patients. After one year an acceptable clinical PES/WES outcome was measured for 94% patients of group one, 94% of group two, 90% and 91% of group three and four. The total esthetic outcome was mainly influenced by the appearance of the implant crown (WES) and to a lesser extent by the peri-implant mucosa (PES). A significant difference in esthetic outcome was measured over time for every group. No significant difference was measured between the groups. Significant correlation was measured between both indices PES/WES and ICAI. Subjective outcome measures demonstrated a positive difference over time for one group.
Within the limitations of this study (sample size, follow-up duration), the results suggest that immediate placement of a restoration in a extraction socket with a bony defect of >/<5mm was not less favourable than conventional loading. This is in favour of the direct treatment way. Subjective results show really satisfied outcomes after one year.
The prevalence of erosive wear, especially among youngsters, is growing. Erosive wear is often the result of erosion in combination with abrasion and/or attrition. An erosive attack causes a softened top layer of enamel that is more vulnerable to wear. Research has shown that wear of eroded enamel increases with lower enamel hardness. The hardness of enamel is dependent on local chemistry and 3D composition, it varies over different parts of the enamel crown and decreases from the enamel surface inwards. The main objective of this study is to find out if erosion and erosive wear could be self-accelerating phenomena.
Materials and methods.
Specimens were derived from 10 extracted third molars. Three test groups were formed, each containing one specimen of each molar. In the first group Vickers hardness tests and scratch tests were performed at increasing enamel depths until 1 mm subsurface. In the second and third testgroup additional erosive treatment was performed with 50 mM citric acid solution and apple juice respectively. The acquired results were processed using Excel and statistical analysis was performed using SPSS. The results of enamel hardness and erosion depth were analysed by means of One-way ANOVA statistical tests followed by a post-hoc Tukey test and linear regression. The scratch tests were analysed by means of linear regression, One-way ANOVA and a Pearson’s correlation. The relation between enamel hardness and erosion depth was analysed by means of One-way ANOVA with a post-hoc Tukey test and a Pearson’s correlation. For all statistical tests p < 0,05.
The hardness tests showed a significant decrease of enamel hardness with increasing enamel depth on both sound enamel, from 3,85 GPa (± 0,17) to 2,99 GPa (± 0,16), and eroded enamel; after treatment with citric acid from 2,45 GPa (± 0,26) to 1,98 GPa (± 0,20) and after treatment with apple juice from 2,69 GPa (± 0,20) to 2,10 GPa (±0,24). On sound enamel the decrease in hardness was quite linear, R2 being 0,69. The difference in hardness between sound and eroded enamel decreased significantly with increasing depth, there was however no significant difference in relative hardness loss after erosive treatment between enamel depths. The scratch test did not yield useful data on the softened toplayer of enamel and did not show a significant difference at different enamel depths. The erosion tests showed a significant increase of erosion depth with increasing enamel depth; after treatment with citric acid from 4,8 μm (± 1,2) to 9,7 μm (± 1,2) and after treatment with apple juice from 1,8 μm (± 0,7) to 2,9 μm (± 1,2). After treatment with citric acid a significant increase in erosion depth was observed with decreasing hardness, from 5,14 μm (± 1,46) to 8,53 μm (± 1,90), and a significant negative correlation of -0,54 was found between sound enamel hardness and erosion depth. A significant negative correlation of -0,27 between sound enamel hardness and erosion depth was observed after treatment with apple juice.
Discussion and conclusion.
Hardness values of both sound and eroded enamel decrease significantly with increasing enamel depth. The relative hardness loss after an erosive challenge remains the same with increasing enamel depth. Erosion depth increases significantly with increasing enamel depth. It appears that dental erosion and erosive wear are self-accelerating phenomena. Further research is required to validate these findings in vivo.
To analyse the esthetic appearance of a new ceramic implant in the anterior maxilla and to assess the students’ and laypeople’s ability to identify the implant in the mouth. Furthermore to analyse the satisfaction of patients regarding their implant esthetics over various periods of time.
Twenty patients were included in the present study. Inclusion criteria: a flapless, immediately placed Zirconia implant. Two measurements were set for evaluation of the esthetics: one measurement directly after placement of the final crown and one measurement further in time. The second measurement was divided into three arms: 1. 0,5-3 years, 2. 3 – 5.5 years and 3. 5,5 – 8 years. The Pink Esthetic Score (PES) and the White Esthetic Score (WES) for both measurents were evaluated through photographs taken in maximal occlusion. The mean PES and WES results were calculated. The statistically significant differences between measurement 1 and measurement 2 were calculated The significant statistical differences between measurement 1 and 2 were calculated for the whole study population and separately for the three separate groups (pared t-test, P<0,05). Furthermore 20 photographs from the included patients, taken at the first measurement, have been shown to 40 volunteers (20 laypersons and 20 dentistry students). They had 30 seconds to identify the implant in the photo. The percentage of non-identified implants and the difference between layperson and students was calculated (unpared t-test, P<0,05). A questionnaire with Visual Analogue Scale questions (VAS) concerning the esthetic perception of the implant was given to the included patients. The possibility of a correlation between the VAS-questionnaire and the PES/WES was investigated.
The PES has a maximum score of 14 and the WES has a maximum score of 10. The higher the score, the better the esthetic outcome. The PES/WES results from 20 patients were evaluated. The first measurement showed a mean PES of 12,8 (range, 11 to 14) and a mean WES of 8,5 (range, 2 to 10). The second measurement showed a mean PES of 12,8 (range, 8 to 14) and a mean WES of 8,6 (range, 6 to 10). Tests concerning the entire study population showed no statistically significant difference between measurement 1 and measurement 2. Within arm 1 a statistically significant difference was found between measurement 1 and measurement 2. Out of 40 volunteers, 74% laypeople and 56% the students did not recognize the implant correctly. Students were statistically significant better at recognizing the implant in the mouth. Eightteen of the 20 patients filled in the questionnaire, the mean assessment of esthetic satisfaction is 8,5 on a 0 – 10 point scale. No correlation was present between the outcome of the VAS-questionnaire and the PES/WES.
The PES/WES scores of the new Zirconia implant range from good to optimum and they are even better than previously described in literature. There is no statistically significant reduction of the PES/WES in a period of 8 years after placement of the permanent crown. It was shown that a high percentage of laypeople and students are not able to identify the implant in the mouth. Students are significantly better at recognizing the implant. Regarding the esthetics, patients are very satisfied with their implant.
The use of skeletal anchorage techniques in orthodontic treatments have been applied for only a relatively short period of time. Knowledge of complications, especially pain perception and aftereffects of these patients is limited and is mainly based on the clinical experience of the specialists carrying out these treatments.
The purpose of this study is to describe the (pain)perception of patients who have received skeletal bone anchors for the purpose of an orthodontic treatment. This includes bone anchors placed on the mandible and / or the maxilla. We also examined the aftereffects and complications that occur during or after treatment. Between 2005 and 2011, 105 patients (34 men, 71 women), aged between 11 and 64 years (mean age 23.6 years) who have had one or more bone anchors placed received a questionnaire. Using Visual Analog Scales (VAS scores) people were asked to mark their perceived amount of discomfort/pain.
Also, the type and amount of painkillers, complications and aftereffects have been documented.
A repeated measures ANOVA test was used to see whether there is a difference between the pain experienced by the group with anchors on the maxilla and the group with anchors on the mandible. Subsequently, a paired sample t-test is used to see between which days the pain levels significantly drop (p <0.05). Impediments by specific activities are measured the first 3 days after surgery and are processed in bar charts. Aftereffects, complications and pain relief were analyzed using descriptive statistics. Finally, the VAS-scores for overall satisfaction with treatment after 14 days were divided into five groups: very dissatisfied (0-19,9), dissatisfied (20-39,9), neutral (40-59,9), pleased (60-79,9) and very pleased (80-100).
Results show that there is no difference between the upper jaw and lower jaw groups p <0.05 [F (1.7, 152) = 0.252, p = 0.735]. Time has a significant positive effect on pain perception [F (1.7, 152) = 20.989, p = 0.000], with the greatest reduction in pain / discomfort between day 1 and day 2 after surgery (p = 0.023) In 89 (84.4% of the) patients no complications occurred. 7 patients developed an abscess after placement. Other complications were lip and cheek trauma by stinging anchors (4), sensory disturbances (2), epistaxis (1) and iatrogenic damage to radix (1). The failure rate is 0.54%.
About 25% indicated pain (due to) swelling of the lips and cheeks as the most bothersome aftereffect. The most painful activity after placement of the anchors is chewing solid hard foods, drinking is the least painful activity. A total of 94.6 percent of the patients had a neutral (17.2%), pleased (33.3%) or very pleased (44.1%) feeling about the treatment after 14 days.
Thus, the treatment of skeletal anchorage seems to be a good alternative to treatments with traditional anchorage treatment systems.
Internal fixation with surgical plates is often considered the treatment of choice when treating fractures of the mandibula. But in some clinical situations the biomechanical properties of conventional plates aren‟t sufficient to use them as an internal fixator. Results of in vitro studies in the late 90s showed that locking plates do have the biomechanical properties necessary in these cases and could be used as an alternative for conventional plates. A systematic review and meta-analysis were performed to review the evidence for the use of locking plates as an internal fixator in the treatment of mandibular fractures.
PubMed, Cochrane and Embase were searched from inception until March 2014 for randomized controlled trials which compared locking plates with conventional plates as an internal fixator in the treatment of mandibular fractures. The primary outcome was defined as the number of complications that occurred after surgical treatment. Based on title and abstract the publications were reviewed for eligibility for full text analysis. The full texts were analyzed for relevance with predetermined inclusion and exclusion criteria. For quality assessment both the Jadad scale and the CONSORT checklist for randomized controlled trials have been used. Data extraction was performed with a modified version of the Data Collection Form from the Cochrane Group. Statistical analysis was performed with RevMan 5 (version 5.2.11). A meta-analysis yielded the Relative Risk, the Risk Difference and the Number Needed to Threat together with the corresponding 95% confidence intervals.
The initial search yielded a total of 83 available publications. After analyzing and quality assessment, data was extracted out of 4 publications which were selected for meta-analysis. Meta-analysis revealed no statistical significant difference between locking plates and conventional plates as an internal fixator in the amount of complications that occurred after surgical treatment for mandibular fractures. Contrary to the primary outcome, the pooled data showed a statistical significant difference between the groups in the occurrence of occlusal discrepancies and need for postoperative MMF (p<0,05). Occlusal discrepancies occurred in 10,7% in the locking plate group and 30,7% in the control group. Postoperative MMF was necessary by 18,7% of the treated patients in the locking group and by 53,3% in the control group. Both the experimental as the control group consisted of the pooled data from 75 patients.
Quality assessment of the full texts revealed that none of available publications meet the predetermined quality requirements. Moreover, full text analysis with the CONSORT checklist for randomized controlled trials showed that there was a high risk of bias. A lot of items of the CONSORT checklist were inadequately reported or were missing in the selected publications. After minor adjustments of the inclusion criteria and the quality requirements meta-analysis could be performed. Because the included publications didn‟t meet the predetermined requirements, the results from the meta-analysis reported in this systematic review shouldn‟t be considered as solid evidence but mere indicative.
Meta-analyses reveals that the use of locking plates as an internal fixator in the treatment of mandibular fractures results in less occlusal discrepancies and diminishes the need for postoperative MMF. However, in the view of the general poor quality of the included publications, these results should be viewed with caution. Further randomized controlled trials with adequate follow-up are required to determine the benefits of locking plates over conventional plates as an internal fixator in the treatment of mandibular fractures.
Supporting a Removable Partial Denture (RPD) with implants can be beneficial to the many shortcomings associated with conventional RPD treatment. However it is also quite likely to increase treatment costs.
The aim of this study was to conduct a cost-effectiveness analysis comparing conventional RPD and Implant Supported Removable Partial Denture (ISRPD)
treatment in patients with a bilateral free-ending situation in the mandible.
Eleven patients were included, a new RPD was made and implant support was provided 3 months later. Opportunity costs and costs based on the national tariff structure where determined and compared to 3 outcome measures: oral health related quality of life measured using the OHIPNL49, a chewing ability test (Mixing Index) and perceived general health (SF-36) which was subsequently converted into Quality-adjusted Life Year’s (QALY’s). Outcome measures where determined at 3 moments in time: baseline (To), after having worn a newly made conventional RPD for 3 months (T1) and 3 months after the provision of implant support to the RPD (T2).
Results strongly depend on choice of outcome measure. When SF-36 is used as an outcome measure no incremental effect and thus added value was found. When MI or OHIP are used as outcome measures implant supported RPD’s provide better outcomes. A minimal importance
difference (MID) is only known for OHIP, making clinical relevance of MI difficult to determine.
Considering the clinical relevance of the gain in oral health related quality of life, supporting a RPD with implants is cost effective when a monetary threshold exceeding than €130 per OHIP point gained is adopted.
When endodontically treated teeth are extensive restored often there is a lot of coronal loss. To prevent recontamination of the root canal system and/or peri-apical space, restore function and morphology, it is important to restore the teeth after endodontically treatment. The endocrown is an adhesive bonded monolithic restoration, that uses the intracoronale space for retention. This space acts like an intern ferrule. The goal of this in vitro study was to compare the fracture resistance and mode of failure of untreated third molars and endocrowns made of two different materials. The null hypothesis was that the fracture strength and failure mode would not differ significantly.
Material and methods
Thirty extracted sound mandibular third molars were used in this study. The specimens were embedded and divided in three groups after randomization. Group 1 were the untreated specimens, and served as a control group (n=10). In group 2 the specimens were prepared and treated with an IPS e.max CAD endocrown. In group 3 the specimens were prepared and treated with an LAVA Ultimate endocrown (n=10) (n=10). Group 2 and 3 were scanned with CEREC, software 4.0 and decapitated 1mm above the CEJ and were endodontically treated. After preparation IDS was applied. With the use of CEREC the preparations were scanned and the restorations were milled according to the original morphology. The crowns were cemented with Variolink II. After placement of the crowns, all thirty specimens were thermocyled 10.000 times. The specimens were tested at a 90 degree angle to the long axis of the teeth, with the use of a static testing machine and loaded (1mm/min) until fracture occurred. The force (Newton) required for the fracture was documented in Excel. The mode of fracture was inspected visually and dived in to two categories, were the distinction between destructive and non-destructive was made. To analyze the fracture strength data the non-parametric Kruskal-Wallis test was used. After this test a post-hoc Mann-Whitney test was used with a Bonferroni correction α = 0.0167 (0.05/3). The mode of failure was analyzed with Fisher’s test.
A significant difference was found between the groups 1,2 and 3. The test could not show a significant difference between group 1 and group 2 (U=23.5, p 0.045).. Between group 1 and 3 (U= 10, r=-0.68, p= 0.002)., and group 2 and 3 (U= 13, r=-0.63, p= 0.004) a significant difference was seen. No significant difference was observed between the failure mode and the three groups.
There is a significant difference between the group of the untreated specimens and the group restored with endocrowns of Lava Ultimate. Also was the fracture resistance of the group restored with IPS e.max CAD significant higher than the group restored with the Lava Ultimate. No significant difference of mode of failure was found. The null hypothesis was partially rejected.
Exploratory study to look at the effect of a changing mA and exposure time and the associated quality of Cone Beam Computered Tomography (CBCT) images on the interpretation of the X-ray image for three different dento-alveolar indication areas of human cadavers: implant planning in the posterior upper jaw, implant planning in the posterior lower jaw and endodontic diagnosis.
Screenshots of the CBCT-scans were made from two human cadavers obtained with 1, 2, 3, 5 and 7 mA and 9.0 or 17.5 sec exposure time. 10 dentists with experience in CBCT diagnosis evaluated in four ways: (1) A forced choice for best picture between two X-rays on the ability to assess the full cortical bone of the maxilla, quality of the chosen image by a grade and indicating whether there’s a difference in the interpretation of the compared images. (2) and (3) the threshold for mA for the visibility of the Mandibular canalis at 9.0 and 17.5 sec exposure time. (4) The threshold for mA for the visibility of a second root canal in a tooth at 17.5 sec exposure time. Use was made of descriptive statistics.
At varying mA with similar exposure time, the higher the comparison in mA, the less observers chose the highest mA: for 1-3mA chose 96.7% 3 mA, for 3-5mA 5mA chose 85% (9.0 seconds); for 1-2 mA chose 100% 2mA, for 3-5mA chose 60% 5mA (17.5 sec). The average quality of 3-5mA(9.0 sec) was ‘sufficient’, the average quality of 3-5mA(17.5 sec) was ‘good’. At varying exposure time with equal mA: higher exposure was found to be superior (90-100%). The preference for X-ray images with an exposure time of 17.5 sec is higher at higher mA (50% at 1mA, 86.7% at 5mA). Threshold for CBCT of the mandible: 7 mA(9.0 sec) and 5mA(17.5 sec). Threshold for CBCT of root canal anatomy: ≥ 7 mA(17.5 sec)
The interpretation of the X-ray image of different observers differ more at higher mA and longer exposure time than at lower settings. At an exposure time of 17.5 seconds more difference was seen in the quality of the picture at higher mA than at lower mA. Possible perception plays a role in the interpretation of X-ray images. Threshold values depend on the structure to be imaged.