Postretention mandibular incisor stability after premolar serial extractions

The purpose of this study was to evaluate the mandibular incisor alignment in serial extraction cases, using the longitudinal dental cast records of the Burlington Growth Center as a control sample. Various parameters were investigated and the statistical differences determined between the treated and untreated groups. The results were also compared with data from serial extraction groups that subsequently had orthodontic treatment. Untreated subjects and subjects treated only with serial extractions showed similar longitudinal changes. However, the extraction group that also received orthodontic treatment appeared to show more lower incisor crowding long-term. No predictors for stability of clinical significance could be determined. Mechanotherapy influences the craniofacial and dentoalveolar dimensions, which appear to cause more long-term lower incisor crowding.

A longitudinal evaluation of extraction versus nonextraction treatment with special reference to the posttreatment irregularity of the lower incisors

A tendency exists in contemporary orthodontics to pursue a completely non-extraction philosophy. Moreover, it has been shown that the extraction versus non-extraction debate is still with us. Controversy exists as to which treatment decision will eventually lead to orthodontic stability. It is thus imperative to conduct investigations on long-term changes of the dentition in both treatment regimens. The present study serves as an example of such a longitudinal study. A random sample, inclusive of both extraction and non-extraction treatments, was examined with respect to long-term stability and an assessment was made as to whether one treatment option favors success over the other. It was concluded that the correct initial treatment choice will not only lead to correction of the malocclusion, but will also ensure clinically acceptable stability with no significant differences between extraction and non-extraction treatments.

Terminology: semantics of postorthodontic treatment changes in the dentition

Correct terminology eliminates confusion in communication between clinicians, as well as between clinician and patient. Long-term stability seems to be an elusive goal, because the terminology in this respect eludes to the various changes occurring in the posttreatment dentition. However, a stable orthodontic result can be achieved when the physiologic changes that naturally occur in the dentition are considered as part of the long-term result. Standardization of terminology is therefore important.

Optimization of a procedure for rebonding dislodged orthodontic brackets

The purpose of this study was to compare shear bond strength (SBS) of bonded and rebonded orthodontic brackets following a variety of commonly used conditioning treatments and using both light-cured and self-cured composite resin systems. Brackets debonded during the initial determination of SBS were rebonded after the removal of residual resin from enamel surfaces using five different treatments: (1) Remove residual resin using a tungsten carbide bur, re-etch enamel surface, then bond a new bracket; (2) Remove resin from the base mesh with micro-etching then rebond the same bracket, (3) Remove residual resin from the enamel surface using resin-removing pliers, recondition the enamel with an air-powder polisher, then bond a new bracket; (4) Remove residual resin using a rubber cup and pumice, then bond a new bracket; (5) Remove residual resin using pliers alone, then bond a new bracket. The results revealed that the light-cured system produced higher shear bond strength in the initial bond than the self-cured system (p<0.005). Reconditioning the enamel surfaces using a tungsten carbide bur and acid-etching gave the highest SBS (difference 5.8 MPa; p<0.01) and clinically favorable fracture characteristics. The data suggest that the optimal procedure for rebonding dislodged orthodontic brackets is to resurface the enamel using a tungsten carbide bur, acid-etch the enamel, and use a new or re-use an old bracket after microetching.

Combinations of etchants, composite resins, and bracket systems: an important choice in orthodontic bonding procedures

The objectives of this investigation were: (1) to compare the shear bond strengths (SBS) of metal, ceramic, and plastic brackets using different concentrations of maleic and phosphoric acid gels and aqueous solutions, and (2) to determine if a relationship exists between the type of acid etchant and the location of resin after debonding. A sample of 210 bovine incisors was divided among three different bracket groups (Victory series metal, Transcend 6000 ceramic, Spirit MB plastic). Prior to bonding, enamel was acid-etched using 37% phosphoric acid (H3PO4) gel and aqueous solution, 10% maleic acid gel and aqueous solution, 10% H3PO4 gel and aqueous solution, or 2% H3PO4 aqueous solution. SBS testing and the adhesive remnant index (ARI) score provided insight into the effects of the bonding process on enamel. Resin tags associated with each etchant type were inspected under scanning electron microscopy (SEM). Statistical analyses (level of significance, p = 0.05) of the data showed significant differences among groups. It was concluded that specific acid-composite-bracket combinations are recommended for use in clinical orthodontic practice in order to achieve efficient bonding.

Radiographic localization of mandibular anesthesia landmarks

The objective of this study was to assess whether bony landmarks used for the standard inferior alveolar nerve block can be used to accurately determine the position of the mandibular foramen and whether panoramic radiographs are appropriate for this purpose. A total of 11 landmarks from 79 panoramic radiographs and 70 corresponding cases of oblique (45-degree) cephalometric radiographs were examined. Ten measurements of the distance from each landmark to the mandibular foramen, as well as 6 ratios from these distances, were calculated from all radiographs. The results showed that the position of the mandibular foramen was highly individualistic and not consistently related to traditional clinical landmarks. Panoramic radiographs were as good as oblique cephalometric radiographs for the locating of the mandibular foramen. No age or gender correlations were found. It was concluded that the mandibular foramen can be localized in panoramic radiographs but that its relation to bony landmarks is highly variable.

The effect of various storage methods and media on shear-bond strengths of dental composite resin to bovine dentine

A variety of media and methods have been used to store teeth used in bond-strength studies of resin restorative materials to dentine. This study examined the effect of 2 months of storage using 11 different methods and media on the shear-bond strength of Z100 resin composite to bovine dentine mediated by Scotchbond Multi Purpose adhesive. Freshly harvested teeth were used as controls. The results showed that 7 of the l1 storage methods or media were similar in shear-bond strengths and bond-failure characteristics. Four of the 11 methods (irradiation, or storage in thymol, methanol, and glutaraldehyde) resulted in significantly lower shear-bond strengths and atypical shear-bond failure, indicating that these are the least desirable methods of tooth storage for studies of this type. This study has further shown that if insufficient numbers of fresh teeth are available for studies of shear-bond strength, then freezing is the preferred method of storage for the registration of high shear-bond strengths. It is also apparent that further investigations are needed to examine what post mortem changes occur in dentine, whether these changes are modified by various storage conditions, and whether they have any significant effect on bonding of resin composites.

The relationship between bond strength and orthodontic bracket base surface area with conventional and microetched foil-mesh bases

The aim of this study was to test the effects on the shear bond strength by sandblasting bracket base surfaces, reducing base surface area, and etching enamel with various acid types. Four different base sizes, used as either standard (untreated), sandblasted or microetched were bonded with Phase II resin (Reliance Orthodontic Products, Inc.) in four groups of 12 bovine enamel specimens after enamel etching with phosphoric acid gel (37%), 37% phosphoric acid aqueous solution, 10% maleic acid gel, or 10% maleic acid aqueous solution. Storage of samples was for 7 days in distilled water at room temperature before shear bond testing with an Instron universal testing machine with a crosshead speed of 0.5 mm/min. Statistical analyses included the analysis of variance, the Student t test, and the Chi-square test at p < 0.05. An increase in shear bond strength was associated with sandblasting and microetching of foil-mesh bases for all base sizes (p < 0.05). No statistically significant difference in shear bond strength existed between the three larger base sizes, which indicated that shear bond strength is independent of surface area between 6.82 and 12.35 mm2. A reduction in bond strength was associated with the reduction of base surface area from 6.82 to 2.38 mm2 (p < 0.05). There appears to be no need to increase base surface area beyond 6.82 mm2. Aqueous maleic acid (10%) etching of the enamel was associated with the highest shear bond strength, with no statistically significant difference between the other three acids used.

Some "sealants" seal--a scanning electron microscopy (SEM) investigation

White spot lesions of enamel around orthodontic brackets as a result of demineralization have been well documented in the orthodontic literature. Various methods of treatment have been attempted to reduce or eliminate this danger. The purpose of this study was to evaluate, by means of scanning electron microscopy, the polymerization of the sealant layer around orthodontic brackets with direct and indirect methods of bonding. Twenty-four sound human lateral maxillary incisor teeth were collected, cleaned, divided equally into four groups A through D, and stored in 70% ethyl alcohol. Their buccal surfaces were pumiced, etched with 37% phosphoric acid for 1 minute, and washed under running water for 30 seconds. Metal brackets were bonded with the chemically cured BIS-GMA resin, Ortho Concise, as follows: group A, indirectly bonded with coping; group B, indirectly bonded without coping; and group C, directly bonded; light activated Transbond was used in group D, directly bonded brackets. After washing in alcohol for 20 seconds, all teeth were dried, and sectioned longitudinally, through the middle of the bracket. All were subjected to 5% hydrochloric acid for 30 seconds and then washed under running water for 30 seconds. After drying and sputter coating, the teeth were viewed under scanning electron microscopy. Groups A and D showed a sealant layer surrounding the brackets and covering the buccal enamel. Groups B and C showed total absence of a cured sealant layer around the brackets or surrounding enamel.(ABSTRACT TRUNCATED AT 250 WORDS)

Profile enhancement and cephalometric landmark identification

The reproducibility of two soft tissue landmarks (SN, V) and two anterior bony landmarks (A, ANS) was determined by three observers for three cephalometric techniques. The three techniques were aimed at soft tissue profile enhancement either by standard exposure control (technique 1), a hand-held metal shield covering the profile (technique 2), or a brass wedge in the collimator (technique 3). For each technique, the sample was restricted to 20 subjects with a skeletal convexity greater than +4 mm. The four landmarks were identified three times with 7-day intervals between readings. The figure-of-merit (or mean radius) method was used to assess the probability of "hitting" a target (landmark) area. The mean radius from the sample mean point of impact (MPI) ranged from 0.585 mm to 1.758 mm. For a specific landmark, the difference was never greater than 0.5 mm when grouped by observer and technique. No technique excelled in overall consistency for the identification of anterior bony and soft tissue landmarks. Techniques 1 and 3 produced the most consistent identification of points ANS and SN, but with no significant difference between the two techniques. Interacting factors prevented any recommendation regarding a preferential technique for the identification of points A and V. There is statistically no reason to recommend the use of a handheld, metal profile shield for more consistent landmark identification.

Malocclusion in patients presenting for orthodontic treatment

The Angle and Steiner classifications are used extensively in orthodontics. The prevalence of malocclusions in Caucasian patients living in the Western Cape was determined using both classifications and the degree of concordance of the data thus obtained was ascertained. A high prevalence of Angle Class I and II was found. No statistically significant differences could be demonstrated between the data obtained from the two systems although there were discrepancies. The implications of the findings are discussed and it is concluded that each classification system used on its own does not provide enough information for accurate diagnostic and treatment planning purposes.

A longitudinal evaluation of the anterior border of the dentition

Posttreatment changes of orthodontically treated dentitions are inherent to every orthodontic practice. Various studies have documented the ideal posttreatment dental and cephalometric norms that could pertain to stable long-term occlusal results. Clinically, changes in these parameters are often observed as mandibular incisor crowding. The purpose of this study was to evaluate the longitudinal changes in certain variables representing the anterior border of the dentition. Eighty-eight white subjects were assessed regarding stability of the dentition after edgewise orthodontic treatment. (44% nonextraction, 56% extraction) The following variables in proximity of the anterior limit of the dentition (overbite, overjet, mandibular arch length, upper and lower incisor position, Little irregularity index) were assessed and correlated with each other. The data were subjected to descriptive statistics, the Friedman test for significant changes and pairwise comparisons, and the Spearman correlation test. Mandibular intercanine width was not significantly altered during treatment, but although not significantly, p > 0.05 did decrease beyond the original measurement during posttreatment evaluation (mean 7 years after treatment). The other variables influenced by the orthodontic manipulation were all within normal ranges and remained stable. The arch length decreased significantly (p < 0.05) during the entire evaluation period and was the only variable not stable. It was concluded that: (1) sound treatment leads to attainment of ideal occlusal parameters, (2) mandibular intercanine expansion could lead to failure of results, (3) arch length change plays a major role in causing irregularity of mandibular incisors after treatment, and (4) patient education regarding posttreatment orthodontic changes is imperative.

Orthodontic microabrasive reproximation

Reproximation (enamel stripping) is described in the literature as a clinical procedure for correction of tooth size deviations. The objective of this study was to qualitatively assess, by means of scanning electron microscopy, (1) the differences exhibited on enamel with mechanical and chemical methods of stripping, and (2) the effect of a synthetic calcifying solution on the etched enamel. Part 1. Sixty human anterior teeth (10 complete sets) that were previously stored in 70% ethanol were subdivided into groups I and II. The teeth in group I were divided into five sets of six teeth mounted in a plaster block in the anterior arch form. Each set was stripped with one of the following mechanical abrasive methods: garnet disks, tungsten carbide and fine diamonds burs, coarse and fine diamond burs, diamond wheel and 3M strips, diamond-coated metal and 3M strips. The teeth in group II were similarly treated, except each set was subjected to a further microabrasive chemical stripping with 37% phosphoric acid used in conjunction with 3M strips. The teeth were then prepared for scanning electron microscopy, viewed, and photographed under magnification. Part 2. Ten human central incisor teeth were etched and used to study the effect of remineralization solutions at various time intervals. The results showed that teeth stripped by routine mechanical abrasive methods exhibited deep furrows and roughness. The teeth that received mechanical and chemical abrasive treatments showed a flattened, etched surface free of furrows. These etched surfaces showed marked crystal growth at 5 and 10 hours after remineralization suggesting the possibility of repair of the chemically altered enamel surface.

Shear peel bond strengths of esthetic orthodontic brackets

Anecdotal reports of bracket fracture and tooth damage associated with the use of certain esthetic orthodontic brackets have been reported in the literature. With the advent of new esthetic orthodontic brackets, the need has arisen to test the claims of the manufacturers. The objectives of this study were to determine: (1) shear peel bond strengths (SPBS) of various debonded orthodontic brackets, (2) SPBS of these rebonded esthetic brackets with and without use of silane, and (3) fracture sites of all groups examined. Seventy-five noncarious human premolar teeth were randomly divided into five groups (A through E). The teeth were cleaned, stored in 70% ethyl alcohol, and mounted for testing in the Instron machine. The following brackets were bonded to the teeth with Ortho-Concise bonding resin: (A) metal brackets, (B) Silkon brackets, (C) Transcend 2000 brackets, (D) debonded Transcend 2000 brackets, and (E) debonded silanized Transcend 2000 brackets. After wet storage at 37 degrees C for 7 days, the SPBS of brackets were recorded, and fracture sites observed. There were statistically significant differences between the SPBS of metal brackets when compared with the Transcend 2000 and the Silkon brackets. These groups exhibited clinically acceptable SPBS. Debonded silanized Transcend 2000 brackets showed clinically unacceptable SPBS. Fracture sites of metal and Transcend 2000 brackets were resin-bracket, whereas Silkon brackets fracture sites were predominantly resin-enamel.

The frontal sinus and mandibular growth prediction

The skeletal growth patterns of 103 subjects with Class I and III malocclusions were cephalometrically analyzed as advocated by Ricketts el al. to assess abnormal mandibular growth. The surface area (mm2) of the frontal sinus was assessed by a Summagraphics decoder linked to a microcomputer. The results indicate that there is a significant correlation between maxillary length, mandibular length, symphysis width, condylar length, and frontal sinus size on a lateral cephalogram. The frontal sinus can possibly be used as an additional indicator when one is predicting mandibular growth.