Theses and Dissertations (Orthodontics)

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Arch dimension changes with a passive self-ligating system
(University of Pretoria, 2014-11) Choonara, S.; Dawjee, Salahuddien M.; vandenbergjj@mweb.co.za; Van den Berg, Johannes Jacobus
Recently, self-ligating brackets have gained popularity among clinicians around the world (Pandis et al., 2010, Berger, 2008). A passive self-ligating system utilizes a passive self-ligating slot, which is supposed to allow a low friction tooth movement environment (Harradine, 2008). The combination of thin super-elastic copper-nickel-titanium wires and 'low-friction systems' is claimed to be advantageous when leveling crowded dental arches (Tecco et al., 2009, Cattaneo et al., 2011). Some passive self-ligating systems even claim that there is less need for tooth extraction when using their system (Ormco, 2013, Scott et al., 2008). This raises the question of whether passive self-ligating systems achieve their results at the expense of overexpanded dental arches, which requires lifelong retention due to questionable stability. The aim of this study was to evaluate the arch dimension changes that occur after treatment with a 0,022" slot passive self-ligating system, and to compare the results with those obtained after treatment with a 0,018" slot conventional bracket system. Existing pre- and post treatment records of 31 anonymous patients (15 patients treated with passive self-ligating system, and 16 patients treated with a conventional bracket system) from a private orthodontic practice were subjected to examination and measurement. Dental casts were measured using a digital caliper up to a hundredth of a millimeter for changes in: intercanine-, interpremolar- and intermolar widths. Arch length was measured on a photocopied image (scale of 1:1) of the occlusal surfaces of the dental casts using the digital caliper. Results were compared between both the passive self-ligating system and conventional bracket system groups. The results indicated statistically significant increase for nearly all measured dimensions between pre- and posttreatment measurements within each group. Only the maxillary arch length in the passive self-ligating group, and both the maxillary- and mandibular arch lengths in the conventional bracket system group did not show statistically significant increase. When comparing the arch dimension changes between the two groups (after baseline correction), it was found that the passive self-ligating system showed statistically significantly more expansion than the conventional bracket system in the following dimensions: maxillary second interpremolar width, maxillary intermolar width, maxillary arch length, and mandibular intermolar width. Since preservation of original archform is important for posttreatment stability, and since overexpansion of dental arches are more prone to relapse (de la Cruz et al., 1995, Nojima et al., 2001), the cases treated with the passive self-ligating system might be more prone to relapse. However, no long-term studies on stability of passive self-ligating appliance systems are available at the present time. Until then, their implications on long-term stability will remain largely unknown. Further studies to investigate the arch dimension changes between a 0,022: slot passive self-ligating appliance system and a 0,022" slot conventional appliance system are recommended to evaluate whether similar trends between the two groups exist. Also, further research on long-term stability of passive self-ligating appliance systems are recommended.
Comparing two orthodontic brackets’ bond to fluorosed and non-fluorosed enamel - an in vitro study
(University of Pretoria, 2014) Dawjee, S.M.; Monehi, Serufe Emily
Orthodontic attachments must be able to bond to a wide range of tooth and prosthetic surfaces. Despite the high prevalence of fluorosis in many parts of South Africa (Louw A, Chikte U 1997), only limited information is available on the integrity of the bond between orthodontic brackets and fluorosed teeth. The objective of this study was to measure and compare Shear Bond Strengths (SBSs) of metal and ceramic orthodontic brackets on fluorosed and non-fluorosed teeth. One hundred and twenty (60 fluorosed and 60 non-fluorosed) extracted premolar teeth were divided into four groups A to D, consisting of 30 teeth in each group. BluGloo® was used as an orthodontic adhesive to bond brackets on the buccal surface of each tooth. The experimental groups consisted of Group A, in which Nu-Edge® metal brackets were used and Group B, in which InspireIce® ceramic brackets were bonded to fluorosed teeth. Group C and D consisted of Nu-Edge® metal brackets and InspireIce® ceramic respectively, bonded to non-fluorosed teeth. Bonding techniques were kept the same and standardised for all four groups. An Instron testing device was used to debond and measure the SBSs. SBSs were compared using ANOVA with posthoc analysis done using Dunnett’s C test for pairwise comparisons. Significance was set at P<0.05. The results showed that SBS of Group B>Group C>Group D>Group A. Ceramic brackets bonded to fluorosed teeth had the highest SBS with a mean of 15.78 (SD=9.07) Megapascals (MPa), while metal brackets bonded to fluorosed teeth produced the lowest SBS of 8.41 (SD=4.68) MPa. The SBSs of ceramic brackets bonded to fluorosed teeth was significantly higher than that of SBS of metal brackets bonded to fluorosed teeth, but not significantly different from SBSs obtained from either brackets bonded to non-flurosed teeth. The BluGloo adhesive if used to bond ceramic brackets to fluorosed teeth can produce adequate SBS for clinical use. The recommendation from this study is that ceramic brackets can be used efficiently to bond to fluorosed teeth. A follow up study should be carried out to assess the nature of enamel damage caused during debonding of flourosed teeth. This is a laboratory study and thus the clinical application should be interpreted with caution.
The force delivery of orthodontic buccal retractors of smaller diameter wires : an in vitro study
(University of Pretoria, 2010) Dr A du Toit; Prof P Hlongwa; upetd@up.ac.za; Mogoregi, Pitso Fairbridge
Load deflection rate (LDR) refers to the amount of force produced per unit deflection. A buccal retractor on a removable orthodontic appliance is commonly used to retract an upper canine. The traditional unsupported 0.7mm retractor is difficult to adjust and unstable in the vertical direction. Zietsman and Botha (2000) suggested a supported retractor by inserting the distal leg of a 0.5mm retractor in a tube which is soldered onto a molar clasp or continues into the palatal acrylic for more support. The aim of this study was to assess the force delivery of removable orthodontic buccal retractors of smaller diameter wires. In addition, the relation of load deflection rate (LDR) to coil type, wire diameter and wire length was also examined. Two different coils, the standard and reverse coil types, were made using three different wire sizes namely the 0.020, 0.022 and 0.028 inch diameter wires. The 0.028 inch diameter wire was used as a control. Unitek stainless steel wires were used. The wires were mounted on a modified measuring scale device based on the one used by Bass and Stephens (1970). The wires were deflected by using 40g weights at 14, 16, 18 and 20mm, and the deflections were read off on the ruler using a magnifying glass to the nearest quarter of a millimetre. The readings were recorded in a customised form and then transferred to a MS-Excel spreadsheet for further analysis. Means, standard deviations and distributions were calculated for all the variables. The interactions between the diameter, wire length and coil type were assessed and compared statistically using the student’s paired t-test. P values less than or equal to 0, 05 were considered significant. The results of the study showed that there was no statistically significant difference between the load deflection rate (LDR) values of the 0.020 and 0.022 wires. The LDR of the 0.028 diameter wire showed a statistically significant difference when compared to that of the 0.020 and 0.022 wires (P<0, 01). The results also showed that increasing the length of the wire decreased the LDR. The LDR is an indication of the force required per unit deflection. A wire with a high LDR value will transmit a high force for a short span of time compared to a wire with a low LDR value which will transmit a low force over a longer time. The results of the study indicated that smaller diameter wires yielded low LDR values when compared to the 0.028 diameter wire. The clinical relevance of this study could be pointed out to the ability of the smaller diameter wires to deliver lower forces over longer periods which might lead to an increase in rate of tooth movement. The recommendations from this study is that clinicians need to change the mindset when using removable appliances, as the current trends in fixed orthodontics focus is on use of lighter continuous forces, by using wires with low deflection rate to increase the rate of tooth movement. This was a laboratory study; therefore clinical application should be interpreted with caution.
The stability of the curve of spee and the overbite after orthodontic treatment
(University of Pretoria, 2004-11-07) Zietsman, S.T.; johan.hattingh@absamail.co.za; Hattingh, Johannes
The aim of orthodontic treatment is to provide the patient with a good static and functional occlusion. During research that was conducted to complete a seminar on the static and functional aspects of occlusion, the author discovered that there might be a discrepancy between the goals of an ideal static occlusion, and the goals of an ideal functional occlusion. An ideal static occlusion seemed to require a flat mandibular plane and a minimal amount of overbite after active orthodontic treatment, whereas an ideal functional occlusion required a curved mandibular plane and an overbite of 4 mm to prevent cusp interferences during functional mandibular movements. The rationale behind the excessively flat mandibular plane and minimal overbite after orthodontic treatment is to compensate for the tendency of the bite to deepen during the period following orthodontic treatment. This tendency to relapse causes uncertainty about the stability of orthodontic treatment. Little research has been dedicated to examining the long-term stability of the leveled curve of Spee. In addition, there seems to be a considerable amount of controversy surrounding the long-term stability of overbite correction after orthodontic treatment. The aim of this study was to evaluate the stability of the curve of Spee and the overbite following orthodontic treatment. In addition, the relationship between the curve of Spee and the presence of anterior guidance after a period of orthodontic retention, was examined. The relationship between the overbite and the presence of anterior guidance was also examined, and the results were used to predict an ideal value for the overbite to avoid possible dental cusp interferences. Standardized digital photographs of the dental casts of 40 subjects were taken at three different stages: before treatment (T1), after orthodontic treatment (T2), and three years (mean) post-treatment. Accurate electronic measurement of the curve of Spee, using computer software, was completed for all three stages. The overbite was measured with a dial caliper. Clinical evaluation of the functional occlusion, with special reference to anterior guidance, was performed on all the subjects. Statistical analysis was carried out in search of statistical significant changes between the various stages, and possible correlations between the different variables. The results indicated that the leveling of the curve of Spee is a stable treatment procedure. The overbite was less stable than the curve of Spee, and nearly half the amount of overbite correction obtained during treatment, relapsed in the three years (mean) post-treatment. No relationship was found between the curve of Spee and the presence of anterior guidance at T3. A highly significant relationship was found between the overbite and the presence of anterior guidance. Subjects with a small overbite seemed to be predisposed to posterior interferences during mandibular protrusion. An overbite of not less than 3mm was found to be a desirable feature after orthodontic retention in order to reduce potentially interfering contacts. More research is necessary to clarify the relationship between dental interferences and temporomandibular disorders (TMD).
Orthodontic status and treatment need of 12-year-old children in South Africa : an epidemiological study using the dental aesthetic index
(University of Pretoria, 2004-11-07) Van Wyk, Philippus J.; robert.drummond@wol.co.za; Drummond, Robert John
The aim of this study was to evaluate the prevalence and severity of malocclusion and orthodontic treatment needs in a sample of 12-year-old South African school children using the Dental Aesthetic Index (DAI), and to assess the relationship between malocclusion and certain socio-demographic variables. The sample comprised 6142, 12-year-old children attending school in seven of the nine provinces of South Africa. For each subject the standard demographic information such as gender, population group, location type and employment status of the parents were collected, after which an intra-oral examination for occlusal status using the DAI was performed. The results showed that 47.7 per cent of the children in the sample presented with good occlusion or minor malocclusion, just over 52.1 per cent presented with identifiable malocclusion, a DAI score larger than 26. Of these, 21.2 per cent had definite malocclusion, 14.12 per cent had severe malocclusion and 16.89 per cent had very severe or handicapping malocclusion. Malocclusion as defined in this study was found to be significantly associated with the different provinces, the different population groups in South Africa, gender and dentition stage, but not with the location type or the employment status of parents. The results of the individual variables showed that anterior maxillary and mandibular irregularity occurred in more than 50 per cent of the sample. More than 40 per cent of the children examined showed signs of crowding. Spacing in the incisal segments occurred in almost 28 per cent of the sample and maxillary midline diastema was present in 16.66 per cent of the sample. At the age of 12 years, Black children, showed a higher prevalence of maxillary midline diastema, larger than 2mm, than their White, Coloured and Asian counterparts. A maxillary midline diastema, larger than 2mm, was more prevalent in 12-year-old females than in males. Thirty one per cent of the sample had an increased overjet larger than 3mm and a severe overjet of 6mm or more occurred in only 2.18 per cent of the sample. More Black 12-year-old children presented with an edge-to-edge anterior relationship and significantly less Black children had an increased overjet. Mandibular overjet affected only 10.43 per cent of the sample and was more prevalent in the late mixed dentition stage than in the early permanent dentition stage. Anterior openbite occurred in 7.7 per cent of the sample and ranged from 1mm to 8mm. Almost 44 per cent of the sample had a antero-posterior molar relation discrepancy. The results of this study indicated a high prevalence of malocclusion in 12-year-old South African children. The findings provide reliable base-line data regarding the prevalence, distribution and severity of malocclusion as well as useful epidemiological data on the orthodontic treatment needs of 12-year-old children in selected rural and urban areas in South Africa. The inclusion of occlusal traits as part of the index provided an opportunity to assess several occlusal characteristics in 12-year-old South African children, separately.
Soft tissue facial profile assessment of 15-20 years old Tswana subjects
(University of Pretoria, 2010-08-26) Du Toit, A.; Hlongwa, P.; upetd@up.ac.za; Mzizana, Nondumiso Yvonne Helen
A well balanced and harmonious soft tissue profile is an important consideration in orthodontic diagnosis and treatment planning. The purpose of this study was to determine the soft tissue profile norms in Tswana subjects, compare the results with those of other ethnic groups and develop soft tissue “norms” or standards which may be useful as guides for diagnosis and treatment planning for Tswana orthodontic patients in South Africa. 420 subjects between the ages of 15-20 were randomly selected from their schools at no criteria. 102 Tswana (52 female and 50 male) and 50 non-Tswana subjects (25 female and 25 male) were selected according to criteria. The subjects were selected for excellence of occlusion, balanced facial proportion, complete dentition (third molars disregarded) dental Class I occlusion with normal overbite and overjet, minimal spacing or crowding, no history of orthodontic treatment and no gross caries. Various orthodontic analyses were used to measure and determine soft tissue facial profiles in both Tswana and non-Tswana subjects. Results were analysed statistically to determine the differences in facial profiles between Tswana and non-Tswana subjects and compare these to Caucasian and African-American norms. The results indicate that Tswana subjects had a flatter profile than non-Tswana subjects whose facial profiles were fuller. The study also indicates that the facial profile values established for Caucasian subjects are not applicable to Tswana and African-American subjects. The findings of the present study showed that when planning orthodontic treatment for Tswana subjects it may be useful to perhaps take into account some measurements which may be more appropriate. Copyright
Antimicrobial effectiveness of electro-chemically activated water as an endodontic irrigation solution
(University of Pretoria, 2007-01-05) Marais, J.T.; upetd@up.ac.za; Williams, Wayne Phillip
The use of sodium hypochlorite (NaOCI) as an endodontic irrigation solution is effective in eliminating microorganisms from the root canals of human teeth. The purpose of this in vitro study was to evaluate the antimicrobial effectiveness of electro-chemically activated water (ECA) as an endodontic irrigation solution. ECA is a solution comprising many different ions, molecules and radicals. Sixty caries-free, single root, adult, maxillary, anterior human teeth were used. The root canals were instrumented and irrigated with NaGCI in a similar method to that employed for in vivo root canal treatment. The external root surface of each tooth was sealed and the access cavity kept patent so that root canals could be inoculated with a suspension containing four bacterial. The teeth were randomly divided into four groups (n=15). Each group was irrigated ultrasonically, using solutions of distilled water (control), NaOCI (3.5%), and ECA, the latter at pH's 7.0 and 9.0 respectively. Antimicrobial effectiveness was established directly after irrigation and again seven days later, by counting colony forming units on blood agar plates and by spectrophotometric analysis. The surfaces of the root canals were visually examined by means of scanning electron microscopy. Large numbers of bacteria were present in the canals of teeth irrigated with distilled water. No bacteria were observed following irrigation with NaGCI. Neither of the ECA solutions were found to be effective against all the bacteria. Although some reduction in the number of bacteria was evident in the ECA groups, this was not statistically significant (p>0.05). Within the confines of this study ECA did not demonstrate antimicrobial effectiveness.
Effectiveness of manual toothbrushes in patients with fixed orthodontic appliances
(University of Pretoria, 2007-01-05) Kroon, Jeroen; upetd@up.ac.za; Laher, Ashraf
Please read the abstract in the section 00front of this document
The influence of orthodontic bracket base diameter and mesh size on bond strength
(University of Pretoria, 2007-01-05) Driessen, C.H.; Ferreira, Pierre D.; upetd@up.ac.za; Cucu, Marcel
Please read the abstract in the section 00front of this document
Development of an index for preventive and interceptive orthodontic needs (IPION)
(University of Pretoria, 2007-01-05) Van Wyk, Philippus J.; upetd@up.ac.za; Coetzee, Cobus Emelius
Please read the abstract in the section 00front of this document
Utilising radiographic incisor crown markers to determine incisor inclination on lateral headfilms - and experimental study on extracted teeth
(University of Pretoria, 2005-03-02) Zietsman, S.T.; dippies5@worldonline.co.za; Dippenaar, Alfred Meyer
Inaccuracy in landmark identification is regarded as the most important source of error in cephalometry. Better definition of landmarks should therefore contribute to better clinical decisions and research validity. This study primarily comprised of an ex vivo investigation on 50 extracted lower incisor teeth to determine whether radiopaque markers could be utilised to accurately assess lower incisor inclination. Fifty extracted lower incisor teeth were mounted onto a Perspex sheet. Radiopaque markers, manufactured from 1mm wide strips of lead film from used peri-apical radiographs, were attached to the crowns of the mounted teeth. A lateral cephalometric radiograph was taken in accordance to standard radiographic procedures (radiograph A). This showed the true inclination of the teeth. A second radiograph was taken with the roots obscured (radiograph B). Three observers traced the inclinations of the teeth on radiograph B (from incisor edge through the middle of the labio-lingual crown-root junction). The determination was done on two different occasions and the assessments compared with the true inclination. Comparative statistical analysis was applied to the readings and the results indicated that this method compared favourably with other methods to determine incisor inclination. In addition, clinical application of opaque markers to the teeth of patients demonstrated the following: it indicated exactly which tooth was being assessed, provided clear definition of the anatomical crown in the sagittal plane and served as a constant reference point for clinical, study model and cephalometric measurements. decisions and research validity. Opaque radiographic markers on teeth can contribute to more accurate cephalometric measurements in orthodontics, leading to better diagnoses, treatment planning and research validity.

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