Comparison of the morphology of the primary first molars and the forms of stainless steel crowns used in clinical practice.

This study aimed to assess the difference in the mesiodistal (MD) and buccolingual (BL) dimensions of primary first molars between Taiwanese boys and girls using a three-dimensional (3D) scanner (Microscribe G2 digitizer), record the coordinates in the 3D systems of Graph-R Project and reconstruct 3D images for subsequent analysis. We also determined whether the differences in these parameters between primary first molars and stainless steel crowns (SSC, 3M ESPE, No. 2-7) could be used as a reference for selecting a suitably-sized SSC and performing adjustments during restoration. The results indicated a statistically significant difference in the mesiodistal distance of lower primary first molar crowns between boys (7.75 ± 0.38 mm) and girls (7.41 ± 0.41 mm) (p < 0.05) but no differences in the mesiodistal distance of upper primary first molars between the two sexes. The mean mesiodistal distances of the upper and lower primary first molars of boys were close to SSC size 4 and 3, respectively, while those of girls were close to size 3 in both arches. Overall, the buccolingual distance between the first maxillary and mandibular molars of Taiwanese children was greater than the buccolingual distance between the 3M ESPE SSC. Reducing the buccolingual length of the abutment teeth might quickly help achieve a better fit, reduce chair time, and minimize patient discomfort. In addition, trimming the mesial and distal metal margins of SSCs might help reduce microleakage from the crown margins and improve its retention and survival rate. In conclusion, the 3D scanning and analysis method used in this study can serve as a reference for fabricating SSC to achieve better crown adaptation and improve dental procedures.

Prevalence of primate and interdental spaces for primary dentition in 3- to 6-year-old children in Taiwan.

BACKGROUND/PURPOSE: Spaced primary dentition plays a critical role in the eruption of permanent teeth and the establishment of ideal occlusion. A lack of these spaces in deciduous dentition may result in disproportionate jaw and tooth sizes. Additionally, spaced primary dentition is significantly affected by ethnic factors. However, few of these studies have been conducted in Asia. The purpose of this study was to investigate the prevalence of spaced primary dentition in Taiwan. METHODS: One hundred and forty-seven 3- to 6-year-old Taiwanese children (58 girls and 89 boys) were recruited for a cross-sectional study. Primate and interdental spaces were recorded by intraoral photos. The prevalence of spaced dentition was evaluated. The interpersonal agreement of spaced dentition between the upper and lower arches was also assessed. RESULTS: Most of the subjects had spaced primary dentition. The prevalence of primate space was 83.7% in the upper arch and 61.2% in the lower arch, whereas the prevalence of interdental space was 44.2% in the upper arch and 53.1% in the lower arch. The prevalence rates of interdental space and upper primate space were significantly higher in boys than in girls. Interdental spaces of the lower arch increased with age. CONCLUSION: Ethnic factors can affect the ratio of spaced dentition. Most of the 3- to 6-year-old Taiwanese children have spaced dentition. The boys have higher incidence of spaced dentition than the girls. Furthermore, primate space is more frequently found in the upper arch than in the lower arch, whereas interdental space is reversed.

Bite-force difference among obese adolescents in central Taiwan.

BACKGROUND/PURPOSE: Maximal bite force of the jaw can cause thorough food chewing and result in good digestion. Bite force is related to the health of the masticatory muscles. Muscle force is frequently affected by obesity in adolescence, however, little is known about how obesity influences the maximum bite force and the difference between genders. METHODS: Five hundred and seventy-seven adolescent students (292 girls and 285 boys), aged 13-16 years, from central Taiwan were recruited for a cross-sectional study in 2009. The maximum bite force, hand strength, triceps skin-fold fat thickness, serum level of testosterone, and body mass index (BMI) were measured. Dental health was evaluated based on malocclusion and dental caries. RESULTS: Bite force in girls was highest in the obese group (32.49 ± 19.13 kg, mean ± standard deviation), whereas in boys it was higher in the overweight group (41.89 ± 19.3 kg) than in the obese group (33.21 ± 17.12 kg). The prevalence of obesity was twofold higher in boys (14.39%) than in girls (7.88%). The mean serum level of testosterone increased with BMI in girls (p = 0.0172), whereas it decreased with BMI in boys (p = 0.0014). The relationships of serum testosterone level and bite force with BMI were similar in the two gender groups. CONCLUSION: The maximum bite force decreased in obese boys but increased in obese girls, which may be due to the sensitivity to testosterone being modulated by the fat level.

Orthodontic bonding with self-etching primer and self-adhesive systems.

The purpose of this study was to compare the tensile bond strengths of orthodontic brackets bonded to enamel using conventional multi-step adhesive, self-etching primer (SEP), which combines etching and priming into a single step, and self-adhesive systems, which combine etchant, primer, and adhesive. Metal brackets were bonded to 90 extracted human premolars according to three experimental protocols: group 1, conventional multi-step adhesive system; group 2, SEP; and group 3, self-adhesive system. All specimens were debonded using an Instron universal machine and failures between the tooth surface and bracket base were observed by scanning electron microscopy (SEM). The bracket bases were then analysed by mapping of energy-dispersive X-ray (EDX) spectrometry to calculate the distributive percentages of enamel or resin. The bond strength, percentage distribution, and calcium on the debonded interface were determined and analysed by one-way analysis of variance, and means were ranked by a Tukey interval, calculated at the 95 per cent confidence level. Group 1 produced the greatest bond strength, followed by groups 2 and 3. Group 3 showed the highest debonded interface between resin and enamel or within the resin itself, followed by groups 2 and 1. Groups 1 and 2 displayed significantly more debond failures at the interface between the bracket and the resin than group 3. More calcium particles were observed on the bracket base after debonding in group 3 than in groups 2 and 1. The simplified bonding procedures caused an undesirable decrease in tensile bond strength.

Bond strength of orthodontic light-cured resin-modified glass ionomer cement.

The purpose of this study was to compare the bond strengths and debonded interfaces achieved with light-cured resin-modified glass ionomer cement (RMGIC) and conventional light-cured composite resin. In addition, the effects of acid etching and water contamination were examined. One hundred human premolars were randomly divided into five equal groups. The mini Dyna-lock upper premolar bracket was selected for testing. The first four groups were treated with light-cured RMGIC with or without 15 per cent phosphoric acid-etching treatment and with or without water contamination preceding bracket bonding. The control samples were treated with the conventional light-cured Transbond composite resin under acid etching and without water contamination. Subsequently, the brackets were debonded by tensile force using an Instron machine. The modified adhesive remnant index (ARI) scores were assigned to the bracket base of the debonded interfaces using a scanning electron microscope. The bond strength and modified ARI scores were determined and analysed statistically by one-way analysis of variance and chi-square test. Under all four conditions, the bond strength of the light-cure RMGIC was equal to or higher than that of the conventional composite resin. The highest bond strength was achieved when using RMGIC with acid etching but without water contamination. The modified ARI scores were 2 for Fuji Ortho LC and 3 for Transbond. No enamel detachment was found in any group. Fifteen per cent phosphoric acid etching without moistening the enamel of Fuji Ortho LC provided the more favourable bond strength. Enamel surfaces, with or without water contamination and with or without acid etching, had the same or a greater bond strength than Transbond.

A comparative study of propofol alone and propofol combined with midazolam for dental treatments in special needs patients.

ABSTRACT: Although dental treatment with sedation is performed increasingly in special needs patients, data on adding midazolam to intravenous propofol sedation are very limited for this group. The purpose of this study was to identify the factors and procedure time associated with the use of intravenous sedation with propofol alone or propofol combined with midazolam in dental patients with special needs.This was a retrospective data analysis. The sedation medications and relevant covariates, including demographic parameters, disability levels, oral health conditions, dental procedures, treatment time, and side effects, of 718 patients with special needs were collected between April 2013 and September 2014. The unfavorable side effects by sedation types were reported. Factors associated with procedure time and the sedation medications were assessed with multiple logistic regression analyses.Of 718 patients, 8 patients experienced unfavorable side effects (vomiting, sleepiness, or emotional disturbance) after the dental procedures; the rate was 0.6% in the 509 patients who received propofol only. In 209 patients who received propofol and midazolam, 2.4% experienced the side effects. Sedation time was associated with body mass index (BMI) < 25 (adjusted odds ratio [aOR] = 1.45, 95% confidence interval [CI]: 1.04-2.04) and the performance of multiple dental procedures (aOR = 1.44, 95% CI: 1.06-1.97) but not associated with the sedation types. A significant odds ratio for the combined use of propofol and midazolam was shown for adolescents (aOR = 2.22, 95% CI: 1.28-3.86), men (aOR = 2.05, 95% CI: 1.41-2.98), patients with cognitive impairment (aOR = 1.99, 95% CI: 1.21-3.29), and patients undergoing scaling procedures (aOR = 1.64, 95% CI: 1.13-2.39).With the acceptable side effects of the use of propofol alone and propofol combined with midazolam, multiple dental procedures increase the sedation time and the factors associated with the combined use of propofol and midazolam are younger age, male sex, recognition problems, and the type dental procedure in the dental treatment of patients with special needs.

Sex differences in anthropometric and cephalometric characteristics in the severity of obstructive sleep apnea syndrome.

INTRODUCTION: Craniofacial anatomic abnormalities related to structural narrowing of the upper airway have been reported in patients with obstructive sleep apnea syndrome (OSAS). The purpose of this study was to test whether there are sex differences in the relative contributions of specific anthropometric and cephalometric measurements of OSAS severity. METHODS: The subjects were Taiwanese patients who visited the Ear, Nose, and Throat Department of National Taiwan University Hospital with complaints of snoring or sleep apnea. The anthropometric, cephalometric, and overnight polysomnographic records of 109 subjects were evaluated. RESULTS: There are obvious sex differences in the craniofacial skeletal characteristics that contribute to OSAS severity. Male patients with the following risk factors are likely to have more severe type OSAS: increased neck size, inferiorly positioned hyoid bone, and greater anterior lower facial height. The risk factors related to the severity of OSAS in female patients include smaller posterior facial height and anteriorly positioned hyoid bone. CONCLUSIONS: To evaluate OSAS severity, different anthropometric and cephalometric measurements should be used for men and women. The craniofacial skeletal characteristics that contribute to OSAS severity were in the anterior lower portion of the profile in men and in the posterior portion of the profile in women.

Developmental changes in pharyngeal airway depth and hyoid bone position from childhood to young adulthood.

OBJECTIVE: (1) To test the hypothesis that there are no developmental changes in the pharyngeal airway depth and hyoid bone position from childhood to adulthood in normal Taiwanese persons, (2) to identify any sexual dimorphism, and (3) to find the predictive value of selective variables for the hyoid bone position. MATERIALS AND METHODS: Lateral cephalometric radiographs of 239 normal Taiwanese (132 females and 107 males; aged 7-27 years) were separated into three stages according to dental age. Twenty-three linear and 20 angular measurements were made in all subjects. Sexual dimorphism was analyzed by Student's t-test. Analysis of variance was used to compare the three stages in both genders. A stepwise regression analysis was carried out to predict the hyoid bone position. The level of significance for all analyses was set at P < .05. RESULTS: The pharyngeal airway depth increased from the mixed dentition stage to the permanent dentition stage in both genders. There was sexual dimorphism in the lower pharyngeal airway depth. The hyoid bone position showed an obvious difference in the permanent dentition stages between genders. The vertical position of the hyoid bone was associated with the mandibular morphology and position, but the relationship in males was reversed compared with that in females. CONCLUSIONS: The hypothesis was rejected. There are developmental changes in the pharyngeal airway depth and hyoid position from childhood to young adulthood. Sexual dimorphism appeared in the lower pharyngeal airway and the direction of change in the vertical position of the hyoid bone.

Cephalometric analysis of nonobese snorers either with or without obstructive sleep apnea syndrome.

OBJECTIVE: To determine if there is an indicator on the lateral cephalometric radiograph that can be used for the differential diagnosis of severe obstruct sleep apnea syndrome and simple snoring in nonobese young male adults. MATERIALS AND METHODS: The subjects were Taiwanese male patients with a complaint of snoring and/or sleep apnea, whose body mass index was less than 25 kg/m(2) and who were younger than 40 years old. Forty-six patients with severe obstructive sleep apnea and 36 patients with simple snoring were selected and underwent lateral cephalometric radiography, from which 24 linear and 34 angular measurements were calculated. Differences between the two groups were studied, and a discriminatory analysis was performed. RESULTS: Soft palate length, mandibular body length, tongue size, and distance from the hyoid bone to the mandibular plane were significantly larger in patients with severe obstructive sleep apnea syndrome. Of the original grouped cases, 76.5% were correctly classified using these five variables. The position of the hyoid bone in simple snorers was near the straight line from the third vertebra to the menton, whereas the position of the hyoid bone in severe obstruct sleep apnea syndrome patients was far below the line from the third vertebra to the menton. CONCLUSION: The position of the hyoid bone relative to the line from the third vertebra to the menton can be used as an indicator for a diagnosis of severe obstruct sleep apnea syndrome in nonobese young male Taiwanese adults.

Developmental changes of pharyngeal airway structures from young to adult persons.

This cross-sectional study investigated developmental changes of pharyngeal airway structures. The materials were comprised of 120 lateral cephalometric radiographs and were divided into three stages according to the dental age. Results indicated that the upper pharyngeal depth increased with age, whereas, the lower pharyngeal depth was established early in life. The pharynx increases its capacity predominantly by vertical expansion. The developmental changes in pharyngeal structures were signficantly greater in males than in females.

Factors associated with mandibular third molar eruption and impaction.

A retrospective study, using panoramic radiographs, was conducted on 152 Taiwanese (72 males and 80 females) to investigate mandibular third molar eruption and impaction. The following measurements were made: inclinations and mesiodistal crown widths of the mandibular molars, vertical and horizontal spaces between the distal surface of the second molar and the anterior surface of the ramus, lengths and widths of the mandibular ramus and body, the ramus inclination, the mandibular plane angle, and the mandibular gonial angle. Differences between non-impaction and impaction groups were studied, and the variables were analyzed with multivariate discriminatory analysis. Significant differences between the two groups were found; variables describing spaces between the anterior of the ramus and the distal of the mandibular second molar and tooth size appeared to be the primary contributors to the differences observed.

Morphology of the palatal vault of primary dentition in transverse view.

The purpose of this study was to investigate the transverse view of the morphology of the palatal vault in the primary dentition at the primary second molar level. Observations were obtained from 150 dental stone casts of normal children (78 boys and 72 girls; aged four to five years). Palatal width, palatal depth, arch width, and primary second molar angulation were measured. There were no significant differences in palatal depth and primary second molar angulation between boys and girls or between the right and left sides. However, girls had a statistically significantly narrower upper dental arch width and palatal width than did boys. Palatal widths on the left side were statistically significantly larger than those on the right side for both sexes. Asymmetry in the palatal width greater than two mm was present in 21.8% of boys and 16.7% of girls. There was a correlation between buccal tipping in the upper primary second molar and greater palatal width.

Dental crowding in primary dentition and its relationship to arch and crown dimensions.

PURPOSE: The purpose of this study was to compare dental arch size, mesiodistal and buccolingual crown widths, and crown shapes between 2 groups of children, 1 with anterior crowding in both dental arches and another with anterior spacing in both dental arches. METHODS: Sixty-one sets (27 crowded and 34 spaced arches) of dental casts of normal occlusions were examined. RESULTS: For both lower and upper arches, crowded arches had statistically significantly smaller arch widths than did the spaced arches. The buccolingual width of the upper second primary molar of the crowded arches was statistically significantly larger than that of the spaced arches. However, there were little significant differences between crowded and spaced arches in arch length, mesiodistal crown width, and crown shape. CONCLUSIONS: It can be concluded that the factor that determines whether a primary dental arch is crowded is the absolute width of the arch.

Positional changes of the upper canine and posterior teeth, hard palate, and sinus floor from primary to permanent dentition.

This cross-sectional study investigated normal positional changes of the upper permanent canine and posterior teeth, hard palate, and sinus floor in normal Taiwanese children from the deciduous to early permanent dentition. In total, 261 panoramic radiographs were used. During the observation period, almost all structures changed their positions toward the distal and occlusal direction. The vertical positional changes of crowns of all teeth were greater than those of the root apices through all developmental stages. There were small positional changes in the mesial surfaces of the crowns of the upper buccal teeth until their roots had formed. There were continuous positional changes in the crowns and root apices of the permanent molars during tooth development and eruption. There were no significant changes in tooth inclination for any of the buccal teeth, whereas there were conspicuous changes in tooth inclination for the permanent molars. The floor of the maxillary sinus remarkably changed its position in an occlusal direction during the active eruption period of the first molar and buccal teeth.

Panoramic radiographic findings of the mandibular growth from deciduous dentition to early permanent dentition.

The outlines of mandibular rami, condyles, coronoid process, and corpus in panoramic radiographs of normal children from deciduous to early permanent dentition were traced and digitized. Nine linear and four angular measurements were measured. During the observation period, the lengths for all the linear measurements increased, however, the angles for all the angular measurements decreased. The shape of condyle and gonion significantly correlated with the growth of ramus and corpus.

A study of growth changes in the mandible from deciduous to permanent dentition.

This cross-sectional study investigated mandibular developmental changes in untreated normal Taiwanese from the deciduous to permanent dentition. Differences in the mean values for ramus height and body length between males and females were statistically significant after eruption of the permanent second molars. SNB angles significantly increased and gonial and L1-MP angles significantly decreased from deciduous to permanent dentition in both sexes. The SN-MP angle in females significantly decreased and ramus inclination in males significantly increased from the early mixed to permanent dentition.

Panoramic radiographic findings of the mandibular foramen from deciduous to early permanent dentition.

The purpose of this study was to investigate the position of the mandibular foramen from deciduous (Hellman's stage IIA) to early permanent dentition (Hellman's stage IVA). Panoramic radiographs of 311 Taiwanese children were used. The results revealed that the distances between the mandibular foramen and ramus anterior plane were greater than those between the mandibular foramen and ramus posterior plane through all stages. The mean difference between them was the smallest (0.25 mm) in stage IIA and the greatest (1.18 mm) in stage IIIC. The distance from the mandibular foramen to the alveolar crest plane showed a little change from stage IIA (3.99 mm) to IVA (5.26 mm). The gonial angle had a negative correlation with the distances between the mandibular foramen and each mandibular border. Evaluation of the mandibular foramen from the oral aspect can be influenced by the degree of mouth opening.

Maximum bite force and related dental status in children with deciduous dentition.

Six hundred seventy-six Taiwanese children with deciduous dentition were sampled for maximum bite force and related dental status. Sixty-seven percent of children had at least one decayed tooth. The mean number of decayed teeth of all children was 2.97+/-3.58, and the mean plaque index of the right maxillary central incisor was 2.00+/-0.75. Twenty-seven percent of children had occlusal anomalies. Boys had a statistically significantly larger maximum bite force than did girls. Children with normal occlusion had statistically significantly larger maximum bite forces than did children with malocclusion. A statistically positive correlation was found between the number of decayed teeth and the plaque index. However, a statistically negative correlation was found between the number of decayed teeth and the maximum bite force and between the plaque index and the maximum bite force.

The positional changes of hyoid bone in children.

The purpose of this study was to investigate the developmental changes of the hyoid bone position in children from deciduous dentition to early permanent dentition. There was no sexual dimorphism in hyoid bone positions. The growth of the structures around the hyoid bone began to decline from late mixed dentition stage. During growth, Go-H was almost equal to C3-H and the hyoid bone was located near and above the line that connected C3 and Me.

Variations among the primary maxillary dental arch forms using a polynominal equation model.

This study identifies arch symmetry and describes arch form variations in normal primary maxillary dental casts. Sixty-two percent of casts had asymmetrical arches, and 38% had symmetrical arches. Six types of arch form were identified according to the ratio of arch width to length. There were more long types than short types. The rounded and short types tended to have a more-symmetrical arch than did the long type.