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PubMed2003

Retained deciduous mandibular molars in adults: a radiographic study of long-term changes.

Management of retained deciduous second molars in the absence of permanent successors can be challenging. The purpose of this retrospective radiographic study was to examine long-term changes in retained deciduous mandibular second molars in adult patients. Specifically, we sought to answer the question, "If an adult has a retained deciduous mandibular second molar and a missing successor, is retaining the deciduous molar a viable treatment option?" From more than 6000 adult patients at the University of Iowa College of Dentistry, 20 were identified who initially had at least 1 retained deciduous mandibular second molar without a permanent successor and who had radiographs spanning 5 or more years after the initial visit. The mean (standard deviation) age at the initial examination was 36.1 (12.9) years, the mean age at the final examination was 48.5 (12.6) years, and the mean examination time span was 12.4 (7.7) years. Of the 28 retained deciduous molars initially identified, 24 (86%) continue to function. The remaining 4 were lost at a mean age of 51.0 (13.9) years and a mean time span after initial examination of 14.3 (10.0) years; this approximates the lifespan of some prosthetic appliances. These 4 mandibular deciduous molars were lost because of caries or periodontal breakdown. Furthermore, we found that the average shortening of all deciduous root lengths was negligible (0.16 mm), and only 6 teeth underwent a change in restoration status. Based on this study in adults and earlier studies in adolescents, we conclude that retaining healthy deciduous mandibular second molars is a viable treatment alternative.

Adult↗
PubMed2003

Arch width.

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Cuspid↗
PubMed2004

Comparison of arch forms between Korean and North American white populations.

The purpose of this study was to evaluate morphologic differences in the mandibular arches of Korean and North American white subjects. The subjects were grouped according to arch form (tapered, ovoid, and square) to compare the frequency distribution of the 3 arch forms between the ethnic groups in each Angle classification. The sample included 160 white (60 Class I, 50 Class II, and 50 Class III) and 368 Korean (114 Class I, 119 Class II, and 135 Class III) subjects. The most facial portion of 13 proximal contact areas was digitized from photocopied images of the mandibular dental arches. Clinical bracket points were calculated for each tooth according to mandibular tooth thickness data, and then 4 linear and 2 proportional measurements were taken. Arch width was statistically significantly smaller in the white group than in the Korean group, but arch depth did not differ. In the Korean group, the most frequent arch form was square, whereas in the white group the tapered arch form predominated. When the subjects were regrouped by arch form, the Korean arches had a tendency to be larger and deeper than the white arches within each of the 3 arch form types.

Adolescent↗
PubMed2005

Apical root resorption 6 months after initiation of fixed orthodontic appliance therapy.

INTRODUCTION: Individual predisposition might be a major reason for the observed variation in apical orthodontic root resorption. If so, resorption might be expressed during the initial stages of orthodontic therapy in patients at risk. METHODS: To explore this hypothesis, we evaluated standardized, digitized periapical radiographs made before treatment (T1) and at a mean period of 6.4 months (SD 0.9) after placement of maxillary incisor brackets (T2) in 290 patients (age range, 10.1 to 57.1 years at T1). Anamnestic and treatment parameters were recorded according to a protocol, and maxillary incisor irregularity was measured on T1 study models. RESULTS: The mean average root resorption for 4 incisors was 0.53 mm (SD 0.47), whereas the sample mean of the most severely resorbed tooth per patient was 1.18 mm (SD 0.86). A total of 4.1% of the patients had an average resorption of 1.5 mm or more, and 15.5% had at least 1 tooth with 2.0 mm or more resorption. The maximum amount of resorption was 4.4 mm. Multivariate linear regression showed that deviated root form and increased T1-to-T2 time period were risk factors for apical root resorption of the central incisors; normal root form and wide roots were preventive factors, with an explained variance of 14%. Similarly, long roots, narrow roots, and increased T1-to-T2 time period were risk factors for resorption of the lateral incisors, whereas normal root form was a preventive factor, with an explained variance of 24%. Parameters associated with use of rectangular wire, presence of incisor irregularity, and history of trauma were not identified as risk factors. Use of elastics was not included in the regression analyses. CONCLUSIONS: Root resorption can begin in the early leveling stages of orthodontic treatment. About 4.1% of patients studied had an average resorption of 1.5 mm or more of the 4 maxillary incisors, and about 15.5% had 1 or more maxillary incisors with resorption of 2.0 mm or more from 3 to 9 months after initiation of fixed appliance therapy. Although teeth with long, narrow, and deviated roots are at increased risk of resorption during this early stage, the explained variance of these risk factors is less than 25%.

Adolescent↗
PubMed2004

Appraising number and clinical significance of regression equations to predict unerupted canines and premolars.

A sound statistical or clinical reason for proposing several single linear regression equations (SLRE) for predicting unerupted canine and premolar tooth-width sums is needed. The purpose of this study was to develop a methodology to evaluate the number and the clinical significance of SLRE required. A 6-step methodology is presented that permits evaluating the number and the clinical significance of SLRE required for predicting unerupted canine and premolar tooth-width sums. It is important not only to evaluate the statistical need for specific SLRE in different populations, but also to state the clinical significance of their differences against commonly used SLRE.

Adolescent↗
PubMed2005

Long-term follow-up of severely resorbed maxillary incisors after resolution of an etiologically associated impacted canine.

BACKGROUND: Resorption of maxillary incisor roots because of an impacted canine is a well-recognized phenomenon that occurs in a surprisingly high proportion of patients with impacted canines. In this retrospective study, we studied a sample of patients in whom the resorption was particularly severe. METHODS: The sample consisted of 11 patients (age, 11.8 +/- 1.2 years) with 20 severely resorbed maxillary incisors. The amount of resorption was measured at the outset (T1), when the impacted canine was distanced from the incisor root area (T2), at the completion of the orthodontic treatment (T3), and at a follow-up appointment at least 1 year posttreatment (T4). RESULTS: A 17.2% increase in the crown/root ratio occurred due to aggressive continued resorption between T1 and T2. The resorption rate reduced to an almost insignificant level, despite continued and often appreciable orthodontic movement of the resorbed teeth from T2 to T3. CONCLUSIONS: Patients with impacted canines should be screened for resorption and the impacted tooth treated as soon as possible. The resorption process can be halted and the affected tooth moved orthodontically without further risk of resorption. In the long term, with early treatment, even severely resorbed teeth do not suffer from increased mobility or discoloration and might not require splinting.

Child↗
PubMed2005

Tooth-size ratio for patients requiring 4 first premolar extractions.

INTRODUCTION: The relationship between total mesiodistal widths of the maxillary and mandibular teeth is an important factor in orthodontic treatment planning. The purposes of this article are to report a mathematical tooth-size ratio specifically designed for patients needing the extraction of 4 first premolars and to compare the anterior "6" and overall "12" ratio values reported by Bolton with the calculated anterior "6" and overall "10" ratio values obtained from data in this study. METHODS: This study was conducted in 3 phases. In the first 2 phases, we used the peer assessment rating and ideal cephalometric norms to select 53 ideal posttreatment models of patients who had had 4 premolars extracted. In the third phase, the mean overall "10" ratio and the mean anterior "6" ratio were calculated for the selected models. Bolton's mean overall "12" (91.3%) and anterior "6" ratios (77.2%) were compared statistically with calculations derived from this study by using 1-sample t test. RESULTS: The mean overall "10" ratio and the mean anterior "6" ratio were found to be 89.28 +/- 1.07% and 77.68 +/- 1.12%, respectively. Although the difference in anterior ratio was not significantly different from Bolton's anterior "6" ratio, there was a statistically significant difference between Bolton's study and our study in overall ratio. CONCLUSIONS: The mathematical tooth size overall ratio of 89.28% was determined for patients requiring the extraction of 4 first premolars and is recommended for use in diagnosis and treatment planning.

Bicuspid↗
PubMed2005

Intra-arch occlusal indicators of crowding in the permanent dentition.

INTRODUCTION: The objective of this study was to identify the intra-arch occlusal characteristics that best discriminated 3 groups with different grades of dental arch discrepancies. This cross-sectional analysis was conducted in Lima, Peru, in 2003. METHODS: Intra-arch measurements were made on 150 sets of dental casts of high school students (aged 12-16; 75 boys, 75 girls). Stepwise multiple discriminant analysis (SMDA) was used to obtain a better understanding of the morphological relationships between tooth and dental-arch variables and their relationship with crowding. RESULTS: Mesiodistal tooth sizes and crown proportions of some teeth differed among significantly crowded, mild-to-moderately crowded, and spaced dental arches. Buccolingual tooth sizes were similar in the 3 groups. Of the arch dimensions evaluated, only intermolar arch width and arch length differed between the groups. An SMDA was developed to classify dental-arch discrepancies in the permanent dentition based on several intra-arch occlusal characteristics. The variable with the highest discriminatory capability between groups was arch length. When arch length was taken out of the SMDA, the explanatory capability from the variability on the dental arch discrepancies diminished from 51% to 14%. When the remaining arch dimension variable (intermolar width) was taken out, the explanatory capability diminished more (from 14% to 8%). CONCLUSIONS: Although other tooth-size and arch dimensions are indicators of crowding, arch length is the most important factor.

Adolescent↗
PubMed2005

Intermaxillary tooth size discrepancy and mesiodistal crown dimensions for a Turkish population.

INTRODUCTION: The aims of this study were to determine the size of individual permanent teeth, tooth-size ratios for the maxillary and mandibular dentitions, and sex differences for those variables in a Turkish population, and to compare the figures obtained with those of the Bolton analysis. METHODS: The data were derived from dental casts of 150 Turkish subjects (72 men, mean age 22.09 +/- 3.11 years; 78 women, mean age, 21.11 +/- 2.08 years) with normal occlusions. The mean, standard deviation, and minimum and maximum values were calculated for individual tooth size, and overall and anterior ratios, separately for men and women. To determine whether there are sex differences in intermaxillary tooth size discrepancies, an independent samples t test was performed. RESULTS: The mesiodistal dimensions of the maxillary teeth showed greater variability than the mandibular teeth, with the first molar dimensions having the greatest variability. The overall and anterior ratios were found to be 89.88 +/- 2.29 and 78.26 +/- 2.61, respectively. A statistically significant sex difference was found only in overall ratio (P < .001). According to Bolton's mean values, a discrepancy in the overall ratio was found in 18% of Turkish normal occlusion subjects, and anterior ratios outside 2 standard deviations from the Bolton mean were found in 21.3% of our sample. CONCLUSIONS: These findings indicate that population-specific standards are necessary for clinical assessments. Bolton's original data do not represent Turkish people, and therefore it is appropriate to use Turkish norms in daily orthodontic practice for Turkish patients.

Adult↗
PubMed2006

Influence of buccal segment size on prevention of side effects from incisor intrusion.

INTRODUCTION: Deep overbite can be corrected by maxillary incisor intrusion. The purpose of this study was to determine whether the size of the maxillary buccal segment influences the amount of steepening, extrusion, or narrowing of the buccal segments, or the rate of intrusion that occurs with maxillary incisor intrusion. METHODS: Twenty patients, 9 to 14 years of age, seeking treatment at a private practice, were divided into 2 groups. Patients in the long buccal-segment group had maxillary buccal segments that included the canines, both premolars, and the first molars. In the short buccal-segment group, the buccal segments consisted of only the maxillary first molars. Patient records were taken at the beginning and end of maxillary incisor intrusion. RESULTS: Intermolar width increased slightly in the short buccal-segment group and decreased slightly in the long buccal-segment group. More steepening of the buccal segment occurred in the short buccal-segment group, and more proclination of the anterior segment in the long buccal-segment group. The size of the buccal segment had no influence on the rate of incisor intrusion or on the amount of buccal-segment extrusion. In both groups, the mean amount of incisor intrusion exceeded 2 mm. CONCLUSIONS: A buccal segment that extends from canine to first molar will help minimize the side effects of incisor intrusion.

Adolescent↗
PubMed2005

A new way of analyzing occlusion 3 dimensionally.

This article introduces a new method for 3-dimensional dental cast analysis, by using a mechanical 3-dimensional digitizer, MicroScribe 3DX (Immersion, San Jose, Calif), and TIGARO software (not yet released, but available from the author at hayasaki@dent.kyushu-u.ac.jp ). By digitizing points on the model, multiple measurements can be made, including tooth dimensions; arch length, width, and perimeter; curve of Spee; overjet and overbite; and anteroposterior discrepancy. The bias of the system can be evaluated by comparing the distance between 2 points as determined by the new system and as measured with digital calipers. Fifteen pairs of models were measured digitally and manually, and the bias was evaluated by comparing the variances of both methods and checking for the type of error obtained by each method. No systematic errors were found. The results showed that the method is accurate, and it can be applied to both clinical practice and research.

Bias↗
PubMed2006

Validity, reliability, and reproducibility of plaster vs digital study models: comparison of peer assessment rating and Bolton analysis and their constituent measurements.

INTRODUCTION: The objective of this validation study was to compare standard plaster models (the current gold standard for cast measurements) with their digital counterparts made with emodel software (version 6.0, GeoDigm, Chanhassen, Minn) for the analysis of tooth sizes and occlusal relationships--specifically the Bolton analysis and the peer assessment rating (PAR) index and their components. METHODS: Dental casts were poured from 24 subjects with 8 malocclusion types grouped according to American Board of Orthodontics categories. Measurements were made with a digital caliper to the nearest 0.01 mm from plaster models and with the software from the digital models. A paired samples t test was used to compare reliability and validity of measurements between plaster and digital methods. RESULTS: Reproducibility of digital models via the concordance correlation coefficient was excellent in most cases and good in some. Although statistically significant differences in some measurements were found for the reliability and validity of the digital models via the average mean of the absolute differences of repeated measurements, none was clinically significant. Grouping of the measurements according to the 8 American Board of Orthodontics categories produced no significant difference (Kruskal-Wallis test). No measurement associated with Bolton analysis or PAR index made on plaster vs digital models showed a clinically significant difference. The PAR analysis and its constituent measurements were not significantly different clinically between plaster and emodel media. CONCLUSIONS: Preliminary results did not indicate that digital models would cause an orthodontist to make a different diagnosis of malocclusion compared with plaster models; digital models are not a compromised choice for treatment planning or diagnosis.

Computer Simulation↗
PubMed2005

Craniofacial and dentofacial development in pigs fed soft and hard diets.

INTRODUCTION: Several authors have found a correlation between reduced chewing activity and malocclusion. In animal experiments, it has been possible to correlate a diet of low chewing resistance to narrower arches, which predispose the subject to crowding and irregular teeth. METHODS: In this study, 17 pigs were weaned at 5 weeks of age and divided into 2 groups according to diet and housing. The soft-diet, indoor group was housed in conventional pens, and the animals were fed aliquots of barley and oats with soya and a mineral-vitamin premix added. The food was mixed with water at a dry matter content of about 25%. The hard-diet, outdoor group was kept outdoors; the pigs were fed solid food and also ate organic matter in the soil. All pigs were killed at 22 months of age. The skulls were dissected, and transverse and sagittal craniofacial and dentofacial dimensions were measured. RESULTS: Chewing hard food caused considerable occlusal and approximal attrition in the experimental animals. The dental arches were shorter due to this attrition and to mesial migration of the molars and premolars. The approximal attrition also reduced the tendency for crowding and rotation of the teeth. Posterior crossbite was more common among the hard-chewing animals. CONCLUSIONS: The increase in arch width in the hard-diet animals reported in the literature was not duplicated in this study. On the contrary, the soft-diet pigs had significantly wider arches than the hard-diet animals. This was most pronounced in the premolar region and could be the result of an atypical tongue habit, caused by the nonphysiologic feeding of the pigs. The soft-diet pigs also had a greater tendency to postnormal occlusion, especially in the canine region.

Animals↗
PubMed2006

Can crown-root ratio predict premolar eruption?

INTRODUCTION: The purpose of this study was to establish a method to prospectively predict the eruption of mandibular second premolars with panoramic radiographs. This technique could be used clinically to optimize the timing of comprehensive treatment, detect abnormalities of development and eruption, or effectively estimate eruption timing and determine the need for early intervention because of caries or defects of the deciduous dentition. METHODS: Three hundred one white children from an orthodontic practice in Alaska between the ages of 6 and 16 years were examined and monitored with serial panoramic radiographs until all premolars had erupted. Eruption of the mandibular second premolar was predicted at the first examination based on the panoramic radiograph. When the mandibular second premolar erupted, a researcher measured the crown length to crown-plus-root length ratio on the radiograph using the Simpson and Kunos scale, and the prospectively predicted timing of eruption was compared with the actual timing. RESULTS AND CONCLUSIONS: The Simpson and Kunos scale allowed a rapid assessment for predicting the time of eruption of mandibular second premolars. The mean age of eruption of the mandibular second premolar in these children was 12.5 years.

Adolescent↗
PubMed2005

New, fast, and accurate procedure to calibrate a 2-dimensional digital measurement method.

Traditionally, dental casts have been measured by hand, with conventional calipers. Today, several digital methods are available for automatically measuring tooth size, but their accuracy depends on proper calibration. The purpose of this article is to introduce a fast and accurate procedure to calibrate a previously introduced 2-dimensional computerized system of measuring mesiodistal tooth size and calculating overall and anterior Bolton ratios. In this calibration method, the cast is digitized while sitting on a sheet of graph paper. The magnification of the paper in 2 axes can be easily calculated and hence the magnification of the dental cast digital image.

Calibration↗
PubMed2005

Long-term stability of combined rapid palatal expansion-lip bumper therapy followed by full fixed appliances.

INTRODUCTION: The purpose of this study was to evaluate the long-term postretention stability of rapid palatal expansion-lip bumper therapy followed by full fixed appliances. METHODS: The sample included 20 treated patients (11 women and 9 men) who were recalled to obtain postretention records. The subjects were out of retention for a minimum of 4 years and an average of 7.9 years. They had begun treatment in the late mixed dentition at a mean age of 11.1 with considerable incisor crowding but, on average, no tooth size-arch length discrepancies. Pretreatment, posttreatment (mean age, 13.6 years), and postretention (mean age, 24.3 years) models were digitized, and the computed measurements were compared with untreated reference data. RESULTS: The majority of treatment increases in maxillary and mandibular arch dimensions were statistically significant (P < .05) and greater than expected for untreated controls. Although many measurements decreased postretention, net gains were maintained for 21 of the 30 measurements evaluated. The notable exception was arch perimeter, which decreased to less than pretreatment values. Postretention incisor irregularity increased 0.5 +/- 1.2 mm in the maxillary arch and 1.1 +/- 1.5 mm in the mandibular arch. CONCLUSIONS: Based on the good long-term stability observed in this study, we concluded that use of rapid palatal expansion-lip bumper expansion therapy in the late mixed dentition followed by full fixed appliances is an effective form of treatment for patients with up to moderate tooth size-arch length discrepancies.

Child↗