Magister Scientiae Dentium - MSc(Dent) / Introduction: Micro-leakage and enamel demineralization is still a major challenge in dental practice. It can lead to formation of demineralization lesions around and beneath the adhesive–enamel interface (Mali et al., 2006). Enamel demineralization adjacent to orthodontic brackets is one of the risks associated with orthodontic treatment. The prevention of demineralization during orthodontic treatment is therefore essential for aesthetic reasons and to circumvent the onset of caries. Aim: To assess micro-leakage and enamel demineralization around orthodontic direct attachments (brackets) using three different orthodontic cements. Materials and methods: In this in-vitro study, intact (non carious) extracted human premolars were used to compare the micro-leakage and enamel demineralization of three different cements (Fuji Ortho LC, Rely X luting 2 and Transbond XT). The dye penetration technique was used to evaluate micro-leakage on extracted human premolars. Micro-hardness testing was performed on 21 teeth to determine enamel demineralization. Sixty teeth were randomly divided into 3 groups of twenty teeth each. Direct attachments were cemented on each tooth using 3 different cements; Fuji Ortho LC (GC Fuji II LC GC Corporation Tokyo, Japan), (group 1), Rely X luting 2 cement (3M ESPE dental product, USA), (group 2), Transbond XT Light Cure (3M Unitek, Monrovia, Calif), (group 3). After the orthodontic direct attachments were fitted, they were exposed to 500 thermo-cycles between 5°C and 55°C, with a dwell time of 15 seconds in a buffered (pH 7) 1% methylene blue dye solution (Grobler et al, 2007). The specimens were viewed under a stereomicroscope (Nikon, Japan) at magnification of 40 times. Photographs of each specimen were taken with a Leica camera (Leica DFC 290 micro-systems, Germany) fitted onto a stereomicroscope. The ACDsee photo editing programme was used to transfer the photographs to a computer to measure the dye penetration along the enamel–adhesive and adhesive–bracket interfaces, both on the gingival and occlusal edge at × 40 magnification. For the demineralization sample, 21 teeth were divided into 3 groups of seven teeth each, where direct attachments were cemented using each of the 3 cements, group 1, Fuji Ortho LC (GC Fuji II LC GC Corporation Tokyo, Japan); group 2, Rely X luting 2 cement (3M ESPE dental product, USA) and group 3, Transbond XT Light Cure (3M Unitek, Monrovia, Calif). A digital hardness tester with Vickers diamond indenter (Zwick RoellIndentec (ZHV; Indentec UK) was used to measure surface micro-hardness of enamel before and after attaching the brackets. Ten indentations were made on the enamel surface of each tooth before bonding the brackets with a 300g load applied for 15 seconds to establish the baseline hardness value. After de-bonding the brackets, the hardness was measured again in the same area as mentioned above to determine the degree of enamel demineralization (softening). Result: The result showed statistically significantly lower levels of micro-leakage for Transbond XT (P= <0.001). The amount of micro-leakage on the margins was significantly higher in the gingival portion (P <0.05) as compared with the occlusal margin. Enamel micro-hardness tests before bonding using the three different cements showed that the variances are not significantly different (Chi-squared = 3.051, df = 2, p-value = 0.218). However, the micro-hardness tests done after bonding and thermo-cycling was statistically significantly different (Chi-squared = 13.435, df = 2, p-value = 0.001). Clearly, the Transbond XT group had less hardness, implying greater demineralization than the Fuji Ortho LC and Rely X luting 2 groups. Two sample t-tests show that mean value for the Fuji Ortho and Rely X luting 2 were not significantly different from each other (t = -0.636, df = 12, p-value = 0.537). The mean value for Transbond XT differed significantly from both the other two means: Transbond XT vs Fuji Ortho LC (t = 3.249, df = 6.9, p-value = 0.014). Transbond XT vs Rely X luting 2 (t = 3.493, df = 6.8, p-value = 0.011). Conclusions: This study showed that Fuji Ortho LC and Rely X luting 2 show more micro-leakage than Transbond XT. However Transbond XT had significant lower micro-leakage, less hardness (greater demineralization) than the Fuji Ortho LC and Rely X luting 2. This may have been due to the fluoride release which significantly reduces demineralization. Therefore the Fuji Ortho LC and Rely X luting 2 may be recommended for prevention of demineralization during orthodontic treatment.

Magister Chirurgiae Dentium - MChD / When faced with a failing or failed root treatment, the dentist must decide whether the tooth can be retreated and saved or extracted. The dentist's decision to retreat is often based on the x-ray presenting a failing root treatment. The dentist must be aware that there might be a number of factors that have contributed to the failure and which may preclude, following retreatment, a successful long term clinical function. The current study has been made to determine those factors that may influence the prognosis in order to assist the clinician in advising the patient of the best course of treatment. A literature review was made to determine and identify these factors and explain their relevance and influence on the healing process. The current study included identifying the factors described in the literature review and noting their influence on the prognosis following non-surgical retreatment. Retreatment of failed root treated teeth requires special knowledge and skill from the clinician in order to correct and manage the case. The current study was made in a clinical setting and compared results of retreatment with two types of rotary files on the market: progressive or variable taper (Pro Taper) with constant non-ISO 06 taper (K3). Clinical signs and symptoms were noted at the patient's presentation and following recalls at 1, 4 months and 1 year. The results were recorded and statistically analysed and the results were discussed. The results showed that out of 81 patients 10cases of retreatment were considered to have failed and 68 cases were considered to have been successful. Three patients did not return for their assessments and were therefore not considered in further results. There was a statistically significant (p<0.1 0) recording of deep periodontal pockets associated with teeth with failing root treatments (40%) and (13%) in the "Success" group. The two estimated proportions of "Sinus" present (60%) in the "Failure" group and 10% in the 'Success' group were significantly different (p<0.01). "Sinus present" in the "Success group" means in the initial clinical assessment before retreatment was initiated. The presence of a sinus at the One Year follow up signified a failure of the root retreatment (p<0.001). The two estimated proportions of "Occlusion" present (80% and 99%) in the "Failure" and "Success" group were significantly different (p<0.05). Therefore, teeth in "occlusion" were more within the "Success" group. 70% of those teeth that failed had pretreatment apical rarefactions of greater than 6mm diameter; whereas 76.5% of successful retreatments had areas less than 6mm diameter. The differences were significant according to Fisher's Exact Test (p<0.01). 44% of failed cases had areas of rarefaction described as "diffuse"; and 56% of failed cases had areas that were described as "well-defined". 95% of cases that were successful had areas described as "diffuse" and the rest were "welldefined". The differences between the success and failure categories were statistically significant (p<0.0 1). The two estimated proportions of "Post present" (0% and 31%) in the "Failure" and "Success" groups were significantly different (p<0.1 0). Therefore, the "Post was present" in many more cases within the "Success" group than in the "Failure" group. There was no difference between the Median "Crown/Root" ratios of the "Failure" (Median = 0.595) or "Success" groups (Median = 0.662) (Wilcoxon Test, p>O.10). Teeth with longer roots tend to lead to failure, however there was a considerable overlap between the distributions. Therefore the finding is that the Median length of the roots of the "Failures" is longer than that of the "Successes". (Wilcoxon Rank Sum Test, p-value = 0.0628). The results also indicated that previous short root filling preparation contributes to the final success of retreatment (Fisher Exact Test, p<0.05). There was a significant difference between the distribution of the "Failure" and "Success" (88.2%) groups (Fisher Exact Test, p<O.OI) in those cases with initial short obturated fillings. When comparing the outcome following the use of the two types of rotary files it was found that the "Successes" with K3 File (35 out of 41) was 85%; and with Protaper File (32 out of 36) 89%. The "Success" rate certainly was not different between the two file types. The conclusions drawn from the current study was not significantly different from those in the literature review and the overall results were of a similar nature with some minor changes. However it is clear that non-surgical root retreatment offers a good prognosis and should be included as an option for failed or failing root treatment.