Remodeling of muscle fibers approaching the human myotendinous junction.

The myotendinous junction (MTJ) is at high risk of strain injuries, due to high amounts of energy that is transferred through this structure. The risk of strain injury is significantly reduced by heavy resistance training (HRT), indicating a remodeling capacity of MTJ. We investigated the degree of remodeling of muscle fibers near the human MTJ. In 8 individuals, samples were taken from the semitendinosus and gracilis MTJ and they were stained immunohistochemically for myonuclei (DAPI), fibroblasts (TCF7L2), and satellite cells (CD56). A high portion of the muscle fibers adjacent to the MTJ contained a centrally located myonucleus (47 ± 8%, mean ± SD) and half of the muscle fibers were CD56 positive. The number of satellite cells and fibroblasts were not higher than what has previously been reported from muscle bellies. The immunohistochemical findings suggest that the rate of remodeling of muscle fibers near the MTJ is very high. The finding that there was no increased number of satellite cells and fibroblasts could be explained as a dynamic phenomenon. The effect of HRT should be evaluated in a randomized setting.

Composition and adaptation of human myotendinous junction and neighboring muscle fibers to heavy resistance training.

The myotendinous junction (MTJ) is a common site of strain injury and yet understanding of its composition and ability to adapt to loading is poor. The main aims of this study were to determine the profile of selected collagens and macrophage density in human MTJ and adjoining muscle fibers, and to investigate whether heavy exercise loading would alter this profile. Fifteen individuals scheduled for anterior cruciate ligament repair surgery were randomized into three groups: control, acute or 4 weeks heavy resistance training. MTJ samples were collected from the semitendinosus and gracilis muscles and were sectioned and stained immunohistochemically for collagen types I, III, VI, XII, XIV, XXII, Tenascin-C and CD68. Macrophage density and distribution was evaluated and the amount of each collagen type in muscle and MTJ was graded. Collagen XXII was observed solely at the MTJ, while all other collagens were abundant at the MTJ and in muscle perimysium or endomysium. The endomysial content of collagen XIV, macrophages and Tenascin-C increased following 4 weeks of training. These findings illustrate the heterogeneity of collagen type composition of human MTJ. The increase in collagen XIV following 4 weeks of training may reflect a training-induced protection against strain injuries in this region.

The effect of preemptive and/or postoperative ibuprofen therapy for orthodontic pain.

The control of pain during orthodontic treatment is of vital interest to both clinicians and patients. Surprisingly, there has been limited research into the control of orthodontic pain, and there is no standard of care for controlling this discomfort. The purpose of this study was to compare the effectiveness of preemptive ibuprofen therapy, postoperative ibuprofen therapy, and a combination of the 2 therapies. Forty-one orthodontic patients aged 9 years 3 months to 16 years 11 months who were to undergo separator placement were enrolled in this prospective study. Patients were randomly assigned to 1 of 3 experimental conditions: (1) 400 mg ibuprofen taken orally 1 hour before separator placement and 400 mg ibuprofen taken orally 6 hours after the initial dose, (2) 400 mg ibuprofen taken orally 1 hour before separator placement and a lactose capsule taken orally 6 hours after the initial dose, or (3) a lactose capsule taken orally 1 hour before separator placement and 400 mg ibuprofen taken 6 hours after the initial placebo. The results revealed that preemptive ibuprofen therapy significantly decreased pain that was experienced 2 hours after separator placement and at bedtime. Beginning on day 2, there was a trend for patients who had taken both preemptive and postoperative ibuprofen doses to have lower pain scores compared with the other 2 groups. In conclusion, these data indicate that ibuprofen taken 60 minutes before separator placement alleviates pain at 2 hours and at bedtime after treatment. Further study with the use of additional postoperative doses is warranted.

An evaluation of preoperative ibuprofen for treatment of pain associated with orthodontic separator placement.

Patients undergoing orthodontic treatment can experience significant levels of pain. This study assessed the effectiveness of preoperative ibuprofen in reducing the incidence and the severity of pain after orthodontic separator placement. Sixty-three adolescent patients (mean age, 13 years) were included in this randomized, double-blind, placebo-controlled, prospective study. Patients were randomly assigned to 1 of 3 experimental conditions: (1) 400 mg of ibuprofen taken orally 1 hour before separator placement and a lactose placebo taken orally immediately after the appointment, (2) a lactose placebo taken orally 1 hour before separator placement and 400 mg of ibuprofen taken orally immediately after the appointment, or (3) a lactose placebo taken orally 1 hour before separator placement and again immediately after the appointment. The patient's level of discomfort was assessed with a visual analog scale at 2, 6, and 24 hours, as well as at 2, 3, and 7 days after placement of the orthodontic separators. An analysis of variance and Duncan's multiple range test revealed that 2 hours after their orthodontic appointment the patients who had taken ibuprofen 1 hour before separator placement had significantly less pain with chewing than did the patients who received either ibuprofen postoperatively or a placebo. Additional measures suggest a trend for less pain for this group of patients. These results support the use of pretreatment ibuprofen for patients requiring analgesics for orthodontic discomfort. Future study of the use of preemptive analgesics in orthodontics is warranted.

Effect of altering the type of enamel conditioner on the shear bond strength of a resin-reinforced glass ionomer adhesive.

The purpose of this study was to determine the effects of changing the type of enamel conditioner on the shear bond strength of a resin-reinforced glass ionomer within half an hour after bonding the bracket to the tooth. Freshly extracted human molars were collected and stored in a solution of 0.1% (weight/volume) thymol. The teeth were cleaned and polished. The teeth were randomly separated into 4 groups according to the enamel conditioner/etchant and adhesive used: group I, teeth were conditioned with 10% polyacrylic acid and brackets were bonded with a resin-reinforced glass ionomer adhesive; group II, teeth were conditioned with 20% polyacrylic acid and brackets were bonded with a resin-reinforced glass ionomer adhesive; group III, teeth were etched with 37% phosphoric acid and the brackets were bonded with a resin-reinforced glass ionomer adhesive; group IV, teeth were etched with 37% phosphoric acid and the brackets were bonded with a composite adhesive. The results of the analysis of variance comparing the 4 experimental groups (F = 24.87) indicated the presence of significant differences between the groups (P =.0001). In general, the shear bond strengths were significantly greater in the 2 groups etched with 37% phosphoric acid. This was true for both the resin-reinforced glass ionomer (X = 6.1 +/- 2.7 MPa) and the composite (X = 5.2 +/- 2.9 MPa) adhesives. On the other hand, the shear bond strengths were significantly lower in the two groups conditioned with polyacrylic acid. The bond strength of the resin-reinforced glass ionomer adhesive conditioned with 10% polyacrylic acid (X = 0.4 +/- 1.0 MPa) was significantly lower than the group conditioned with 20% polyacrylic acid (&xmacr; = 3.3 +/- 2.6 MPa). The present findings indicated that the bond strength of the resin-reinforced glass ionomer adhesive can be significantly increased in the initial half hour after bonding if the enamel is etched with 37% phosphoric acid instead of being conditioned with either 10% or 20% polyacrylic acid. The clinician needs to take these properties into consideration when ligating the initial archwires.

Effect of changing enamel conditioner concentration on the shear bond strength of a resin-modified glass ionomer adhesive.

The purpose of this study was to determine the effects on shear bond strength of changing the concentration of the enamel conditioner used with resin-reinforced glass ionomer. Shear bond strength was measured within 30 minutes after bonding. Forty-six freshly extracted human molars were collected and stored in a solution of 0. 1% (weight/volume) thymol. The teeth were cleaned and polished, then randomly separated into 2 groups. In group I, enamel was conditioned with a 10% polyacrylic acid solution before bonding. In group II, the enamel was conditioned with a 20% polyacrylic acid solution. The results of t test comparisons of the 2 experimental groups (t = 4.9) indicate significant differences (P =.001). Shear bond strength was significantly greater in the group conditioned with the 20% polyacrylic acid concentration (X = 3.3 +/- 2.6 MPa) than in the group conditioned with the 10% concentration (X = 0.4 +/- 1.0 MPa). The present findings indicated that the lower initial shear bond strength of resin-reinforced glass ionomer adhesive can be improved more than 8-fold when the concentration of the polyacrylic acid enamel conditioner is increased from 10% to 20%. The clinician needs to take these properties into consideration when ligating the initial archwires.

Evaluation of profile esthetic change with mandibular advancement surgery.

Our purpose was to investigate the impact of mandibular advancement surgery on profile esthetics and to attempt to define guidelines that could be of value to the clinician in predicting profile esthetic change. The sample consisted of 34 patients who had been treated with a combination of orthodontics and mandibular advancement surgery without genioplasty. Initial (pretreatment) and final (posttreatment) cephalometric radiographs of each patient were used to produce silhouette images and to quantify skeletal changes that occurred with surgery. The images were displayed randomly to lay persons and orthodontic residents who were asked to score the esthetics of each profile. On average, after mandibular advancement surgery, B point moved forward 5.0 mm (SD = 2.6 mm) and downward 4.7 mm (SD = 3.1 mm), and the ANB angle decreased 3.0 degrees (SD = 1.6 degrees ) Graphical analysis and results of paired t tests revealed that for patients with an initial ANB angle >/= 6 degrees, a consistent improvement in profile esthetics was seen following surgery (P

Effect of light-cure time on the initial shear bond strength of a glass-ionomer adhesive.

With the introduction of photosensitive (light-cured) restorative materials in dentistry, various methods were suggested to enhance the polymerization of these materials including layering and the use of more powerful light-curing devices. The purpose of this study was to determine the effects of increasing the light-cure time on the initial shear bond strength (in the first half hour) of a resin-modified glass-ionomer adhesive. Eighty-six teeth were divided into 4 groups according to either; (1) the adhesive system used, namely resin, reinforced glass ionomer, or composite, and (2) the light-cure time for the glass ionomer adhesive, namely 40, 45, and 50 seconds. The bonding approach followed the manufacturer's instructions unless otherwise specified. The results of the analysis of variance comparing the 4 experimental groups (F = 19.4) indicated the presence of significant differences between the groups (P =. 0001). In general, the shear bond strength was greater for the composite adhesive system (¿x(-) = 5.2 +/- 2.9 MPa), followed by the 2 groups bonded with the resin-reinforced glass-ionomer adhesive and light cured for 50 seconds (¿x(-) = 3.8 +/- 1.1 MPa) and 45 seconds (¿x(-) = 3.4 +/- 2.7 MPa). On the other hand, the shear bond strength was significantly lower for the group bonded with the glass ionomer adhesive and light cured for 40 seconds only (¿x(-) = 0.4 +/- 1.0 MPa). The present findings indicated the following: (1) the resin-reinforced glass-ionomer adhesive has a significantly lower shear bond strength in the first half hour after bonding when compared to a composite resin adhesive; (2) the initial bond strength of the glass-ionomer adhesive was significantly increased by increasing the light-cure time for an additional 5 to 10 seconds; (3) the mean increase in the shear bond strength between 5 and 10 seconds of additional light curing was not significant but the variability was less with the longer cure time.

Using standardized patients to assess presentation of a dental treatment plan.

In this new era of relationship-based care, involvement in treatment planning and goal setting is a high priority for patient satisfaction. This study reports on the use of standardized patients (SPs) in training third-year dental students to gather dental, medical, and psychosocial information from patients and to involve the patient in the decision-making process leading to the dental treatment plan. Among the skill areas measured, students were most successful in gathering dental information, with 94 percent of the students obtaining the complete set. Students were least successful in identifying the patient's goals for treatment (81 percent of the students identified the patients' goals). Students were most challenged by discussing sensitive topics with patients such as grief-related depression (25 percent of the students recognized and discussed such topics). It is important that dental schools familiarize students with patient issues and teach them how to talk effectively to patients about personal issues and to incorporate those issues into a discussion of the treatment plan for the patient. Standardized patients can be used effectively toward this end.

Comparison of the debonding characteristics of two innovative ceramic bracket designs.

Two new ceramic brackets-one designed with a metal-lined arch wire slot and the other with an epoxy resin base-have been recently introduced. The new brackets are thought to combine the esthetic advantages of ceramics and the functional advantages of debonding metal brackets. The purpose of this study was to compare the following: 1) the shear bond strength of the 2 brackets, and 2) the bond failure location when the brackets are debonded with pliers. Sixty-one Clarity (3M Unitek) collapsible ceramic brackets and 66 MXi (TP Orthodontics, Inc) brackets were bonded to the teeth with the same bonding system. The Zwick Universal Test Machine (Zwick Gm bH & Co) was used to determine the shear bond strength force levels needed to debond the brackets. The appropriate pliers also were used to debond both types of brackets to determine the mode of bond failure that will be encountered clinically. After debonding, all the teeth and brackets were examined with 10x magnification. Any adhesive that remained after the bracket removal was assessed according to the Adhesive Remnant Index. The findings indicated that the shear bond strength of the Clarity ceramic brackets was significantly greater than that of the MXi ceramic brackets. However, both brackets exhibited forces that were adequate for clinical use. The Adhesive Remnant Index scores for both the shear test and the plier debonding indicated a similar bond failure pattern when the 2 ceramic brackets were compared with each other. This suggests that, when these brackets are debonded with the Weingart (Ormco) and ETM (Ormco) pliers, there was a greater tendency for most of the adhesive to remain on the enamel surface. In conclusion, the most efficient method to debond the MXi ceramic bracket is by placing the blades of the ETM 346 pliers between the bracket base and the enamel surface. On the other hand, the most efficient method of debonding the Clarity bracket is by using the Weingart pliers and applying pressure to the tiewings. When the 2 ceramic brackets were debonded as recommended here, most of the residual adhesive remained on the enamel surface, a pattern similar to the one observed previously with metal brackets. The failure at the bracket-adhesive interface decreases the probability of enamel damage but necessitates the removal of more residual adhesive after debonding.

Changes in root length from early to mid-adulthood: resorption or apposition?

A significant number of adults are seeking orthodontic treatment, therefore, it is important to determine the normal changes in root length (resorption or apposition) that occur at this stage of maturation, specifically between early and mid-adulthood. The purpose of the study was to determine on a longitudinal basis the changes in root length between 25 and 45 years of age in a normative untreated population. Two sets of complete mouth surveys were available at early and mid-adulthood, on a total of 26 subjects (12 males and 14 females). Each set consisted of at least 18 periapical radiographs. On each set of radiographs, the roots of 28 teeth were measured including incisors, canines, premolars, and first and second molars, in both the maxillary and mandibular arches. Root length was measured as the perpendicular from the root apex to a line connecting the mesial and distal points of the cementoenamel junction of each tooth. A total of 1456 teeth (1664 roots) were measured; 672 teeth in males and 784 teeth in females. Allowable intraexaminer and interexaminer measurement variability was predetermined at 0.5 mm. Paired and Student t tests were used to determine: (1) whether significant changes occurred with age; (2) whether there were differences between males and females for the incisors, canines, premolars, and molars; and (3) whether there were differences between the right and left sides. Statistical significance was predetermined at P

Geometric and densitometric standardization of intraoral radiography through use of a modified XCP system.

OBJECTIVE: The purposes of this study were to examine the density correction afforded by curve-fitting algorithms and to investigate whether the device we developed significantly improves the reliability of longitudinal alveolar process bone radiographic density measurements. STUDY DESIGN: Stepwedges were radiographed over a range of impulse settings, and curve-fitting algorithms were fitted to sets of step images on each digitized film. Differences between the actual thicknesses of an alternate set of steps and their corresponding thickness estimates were calculated. Next, clinicians made periapical radiographs from interproximal bony sites on a dry skull using our imaging device. Differences in bone densities between corresponding regions of interest taken 1 week apart were calculated. RESULTS: Analysis of variance and Duncan's Multiple Range test demonstrated that piecewise linear, third-degree polynomial, and fourth-degree polynomial curves provided significantly better estimates of stepwedge thickness than did sigmoid or first degree polynomial-curves (P < .05) and that the differences between repeat bone density measurements made with density correction were significantly less than those made without density correction (P < .05). CONCLUSIONS: Piecewise linear, third-degree polynomial, and fourth-degree polynomial curve-fitting algorithms provided the best densitometric correction. The use of our imaging device increased the reliability of longitudinal bone density measurements.

Shear bond strength of composite, glass ionomer, and acidic primer adhesive systems.

The purpose of this study was to determine the shear bond strengths of orthodontic brackets bonded with one of three methods: (1) a glass ionomer adhesive with a 20% polyacrylic acid enamel conditioner; (2) a composite resin adhesive used with 37% phosphoric acid etchant and a conventional primer; or (3) the same composite resin used with an acidic primer that combines the etchant with the primer in one application. The brackets were bonded to the teeth according to one of three protocols. Group I teeth were etched with 37% phosphoric acid and bonded with Transbond XT (3M Unitek, Monrovia, Calif) following the manufacturer's instructions. Group I acted as the control group. Group II teeth were etched with an acidic primer (Clearfil Liner Bond 2. J.C. Moritta Kuraway, Japan) that contains both the acid (Phenyl-P) and the primer (HEMA and dimethacrylate) and was placed on the enamel for 30 seconds; the adhesive used to bond the brackets was Transbond XT as in Group I. Group III teeth were etched with 20% polyacrylic acid and the brackets were bonded with Fuji Bond LC (G.C. America, Chicago, Ill). A steel rod with one flattened end was attached to the crosshead of a Zwick test machine (Zwick GmbH & Co, Ulm, Germany). An occlusogingival load was applied to the bracket, producing a shear force at the bracket-tooth interface. The results indicated that the resin/phosphoric acid adhesive system (control group) provided the strongest shear bond strength x = 10.4 +/- 2.8 MPa). The glass ionomer adhesive system provided a significantly lower bond strength (x = 6.5 +/- 1.9 MPa). The least shear bond strength was present when the acidic primer was used with an orthodontic adhesive (x = 2.8 +/- 1.9 MPa). In the present study, the use of either a fluoride-releasing glass ionomer or an acidic primer in combination with an available orthodontic composite adhesive resulted in a significantly reduced shear bond strength when compared with that of the conventional composite resin adhesive system. At the present time, the orthodontist and the patient are better served by using phosphoric acid/composite resin adhesive system or other equivalent systems that provide a clinically reliable bond strength between the bracket, the adhesive, and the enamel surface.

A pilot study of dental students' esthetic perceptions of computer-generated mild dental fluorosis compared to other conditions.

OBJECTIVES: Few studies have considered people's opinions about the esthetics of dental fluorosis. Assessments of fluorosis esthetics can be confounded by differences in a number of clinical factors, including tooth shape, color, contour, and gingival status. This pilot study compared esthetic perceptions of mild fluorosis and other conditions using computer-generated images made from a base set of normal appearing teeth. METHODS: Entering dental students (n = 61) completed questionnaires about four sets of paired photographs. Three sets consisted of fluorotic teeth (very mild to mild) versus other conditions (diastema, isolated enamel opacity, "normal"/control) and the other pair compared two presentations of mild fluorosis (generalized versus limited to incisal one-third). Six questions, both qualitative and quantitative, were asked about each pair of photographs. RESULTS: Mild fluorosis was assessed less favorably than normal/control, midline diastema was less favorable than mild fluorosis, and mild fluorosis was less favorable than isolated opacity. CONCLUSIONS: This approach allows fluorosis to be better compared with other oral conditions because the images are standardized. Additional research with this method is warranted, including more variations in conditions, more comparisons, and other study populations.

Prediction of mandibular growth rotation: assessment of the Skieller, Björk, and Linde-Hansen method.

The purpose of this investigation was to assess the method proposed by Skieller, Björk, and Linde-Hansen in 1984 to predict mandibular growth rotation. Our sample consisted of 40 randomly selected, untreated, adolescent subjects representative of the patient population generally encountered in orthodontic practice. The four independent variables identified in the Skieller study as having the highest predictive value (mandibular inclination, intermolar angle, shape of the lower border of the mandible, and inclination of the symphysis) were identified on initial lateral cephalograms. The proposed regression equations were applied and predicted mandibular rotations obtained. Final lateral cephalograms made 6 years after the initial profile radiographs were superimposed and actual mandibular rotation recorded. The observed and predicted rotations were compared and regression analyses performed to determine the amount of variability in observed values accounted for by the four variables individually and in combination. Only 5.6% of the variability in mandibular growth rotation could be accounted for using the four variables individually. Only 9% of the variability could be accounted for with a combination of the variables. In addition, we performed a Monte Carlo analysis, which mirrored the Skieller analysis but used random numbers instead of actual cephalometric data, to determine if the Skieller results may simply have capitalized on chance. Using the same forward stepwise selection procedure with a rejection level of P >.1, we found after 5000 simulations that a mean of 84% and a median of 94% of mandibular growth rotation variability could be accounted for using meaningless data in the Skieller analysis. This result was comparable to the Skieller value of 86%. In conclusion, information derived from pretreatment lateral cephalograms using the Skieller, Björk, and Linde-Hansen method does not permit clinically useful predictions to be made in a general population relative to the direction of future mandibular growth rotation.

Soft tissue profile changes from 5 to 45 years of age.

The purpose of this study was to describe the changes in five soft tissue parameters that are commonly used by orthodontic practitioners in their diagnosis and treatment planning as well as in their evaluation of profile changes that occur with growth and orthodontic treatment. The subjects in this study were 20 males and 15 females for whom lateral cephalograms were available between 5 and 45 years of age. The parameters evaluated were two angles of facial convexity, the Holdaway soft tissue angle, and the relationship of the upper and lower lips to Rickett's esthetic line. Descriptive statistics for the absolute and incremental changes were collected on a yearly basis between 5 and 17 years of age as well as at early (25 years) and middle (45 years) adulthood. Growth profile curves were constructed for each parameter to describe the age-related changes in the five parameters for both males and females. The analysis of variance was used to compare the absolute and incremental changes both longitudinally and cross-sectionally. Significance was predetermined at P

Comparison of two nonradiographic methods of predicting permanent tooth size in the mixed dentition.

The determination of the tooth size-arch length discrepancy in the mixed dentition requires an accurate prediction of the mesiodistal widths of the unerupted permanent teeth. Three approaches have been used to estimate the mesiodistal crown widths of unerupted canines and premolars: (1) measurements from erupted teeth, (2) measurements from radiographs, and (3) a combination of measurements from erupted teeth and from radiographs of unerupted teeth. The purpose of this study was to compare two mixed dentition prediction methods that do not require the use of periapical radiographs of the unerupted permanent teeth. The two methods compared were the Tanaka/Johnston and the Boston University Prediction approaches. Records on 33 male and 22 female subjects who were participants in the Iowa Longitudinal Growth Study were used in the present study. The findings indicated that on the average the Tanaka/Johnston approach slightly overestimated the tooth size of the unerupted teeth (mean = 1.1 +/- 0.9 mm). On the other hand, the Boston University approach slightly underestimated the tooth size of the unerupted teeth (mean = -0.1 +/- 1.2 mm). The findings further indicated that there were statistically significant correlations between the predicted and actual tooth size. In general the r values were higher for the Tanaka/Johnston method than with the Boston University approach. The error involved in the use of the predicted equations was expressed as the standard error of the estimate. The present findings indicated that the standard error of the estimate for Tanaka/Johnston prediction equations ranged between 0.67 and 0.92 mm and the corresponding values for the Boston University equations ranged between 0.92 and 1.02 mm. Depending on the stage of dental development, i.e., which deciduous and permanent teeth are present, the Tanaka/Johnston approach can be used when the four mandibular incisors have completely erupted, whereas the Boston University approach can be used when all the deciduous canines and first molars are still present.

The effect of microetching on the bond strength of metal brackets when bonded to previously bonded teeth: an in vitro study.

The purpose of this in vitro study was to answer the following questions for three different metal brackets: (1) when rebonding a previously bonded tooth, how do shear bond strengths compare for new brackets, new microetched brackets, and debonded microetcher cleaned brackets? and (2) how do the different bracket types compare with respect to the time required to remove composite resin from their bonding pads with a microetcher? Ninety human premolars and canines previously debonded of metal brackets were randomly assigned to 9 groups of 10 teeth each. New, new etched, and debonded etched cleaned brackets of each type were bonded with composite resin onto teeth, and the bonds tested to failure for shear bond strength. An analysis of variance and Duncan's multiple range test were used to compare bracket/enamel bond strength. Within each bracket type no significant differences were found between mean bond strengths for new, new etched, and debonded etched conditions, a finding that supports the use of microetching to clean accidentally debonded brackets. Mean times for removal of resin from bonding pads with a microetcher varied from 9.3 seconds to 11.9 seconds, with bracket (M) requiring significantly less time for removal of resin.