Pulpal regeneration and root development after subcutaneous transplantation of cryopreserved immature teeth in rats.

The purpose of this in vivo study was to investigate revascularization and root growth after autotransplantation of cryopreserved immature teeth. Immature molar teeth were extracted in 4-week-old Wistar rats. In the test group, teeth were cryopreserved for 1 week and transplanted subcutaneously to the abdomen. In the control group, teeth were transplanted subcutaneously immediately after extraction. Material was collected in test and control animals at intervals of 1, 2, 4 and 10 weeks post-transplantation and histological and microradiographical examination was performed. Results showed that during the first weeks after transplantation, pulpal repair was similar in both groups although degenerated pulpal tissue was replaced slower in cryopreserved teeth and some differences in types of hard tissue formation were found between test and control teeth. After 10 weeks, the differences in the regenerated pulpal tissue between cryopreserved and control teeth observed during the first weeks were no longer detectable. No root growth was detected microradiographically 10 weeks after transplantation in any of the transplanted teeth. The presence of dentin-like tissue in the pulp cavity of some autotransplanted cryopreserved teeth, suggests survival of pulpal tissue after cryopreservation.

[Orthodontics: interface between biology and biomechanics]. / Orthodontie: raakvlak tussen biologie en biomechanica.

As far as craniofacial development is concerned, the orthodontist is mainly interested in growth of the jaws, craniofacial growth patterns and physiologic backgrounds of bone remodelling after tooth displacement. In biomechanics, the principle "action is equal to reaction" is one of the most important issues to deal with. The art in orthodontics is to distribute the reaction forces or to use them on purpose in an attempt to achieve one of the treatment goals. Reaction forces can be neutralized intra-orally. In this respect the location of the center of resistance of the tooth or a group of teeth needs to be defined carefully in order to have a good understanding of the biomechanical principles of tooth displacement. The action forces can be neutralized extra-orally. When no reaction forces on other teeth are applied, there will be no side effects of the reaction forces on other teeth. Research on the biomechanical principles of the headgear does offer some clinical information. Recently in orthodontics, the use of implants has been introduced. It can be used to neutralize reaction forces intra-orally. Moreover, the implants can be used primarily as anchorage during orthodontic tooth movement and later on to replace missing teeth. Recent animal studies at our department have shown that non-axial loading of implants with forces higher than 5 Newton can be used.

Long-term fluoride release of some orthodontic bonding resins: a laboratory study.

OBJECTIVES: The present study compared the amounts and profiles of long term fluoride release from four commercial direct bonding resins (Light-Bond, Reliance Orthodontic Products; Rely.a. Bond, Reliance Orthodontic Products; Orthon, Orthon Dental Inc.; Fluor Ever, Macro-Chem Corporation) and one glass ionomer cement (Ketac-Cem, Espe). METHODS: The specimens were equilibrated in double-deionized water at 37 degrees C. At predetermined intervals, and up to 560 days, the fluoride concentration of the equilibrated solution was determined with a fluoride ion selective electrode. For Light-Bond and Rely.a. Bond two batches were studied and the amount of fluoride released in a 0.1 mol/L NaCl solution was also determined. Differences in the fluoride release profiles due to batch, type of solution and time were determined with a three-factor mixed design ANOVA with repeated measures on one factor. RESULTS: The fluoride release profiles of the orthodontic adhesives studied differ markedly. Initially, Fluor Ever and Ketac-Cem release comparable amounts of fluoride which are greater than those released by Orthon. After a few weeks the amounts of fluoride released by Ketac-Cem and Orthon become comparable, but are considerably higher than those released by Fluor Ever. During the first days of the elution, the amount of fluoride released by Light-Bond equals that of Orthon, but then decreases below the determination limit of the analytical method within half a year. No difference was found between the fluoride release profiles in water and the NaCl solution. However, the fluoride release profiles apparently depend on the batch. For Rely.a. Bond, the amount of fluoride released is smaller than the detection limit for the fluoride analysis. SIGNIFICANCE: The fluoride release of the orthodontic adhesives investigated markedly depends on the mechanisms responsible for the fluoride release process.

[The dry skull model in orthodontics]. / Het droge schedelmodel in de orthodontie.

Orthodontic therapy aims to displace teeth by means of orthodontic appliances. Forces, applied on the teeth, induce remodeling of the alveolar process in upper and lower jaw resulting in a new position of the teeth into both jaws. In this publication an attempt has been made to test a model (dry skull model) which could provide a better understanding of the effect of force application on tooth and bone displacement. Initial tooth displacement (microscopical), right after force application, could give an indication for the longitudinal tooth displacement to be expected. Variables as the point of force application, the amount and direction of the force and the localisation of the centre of resistance are determining factors for the final tooth displacement. This study attempts to forecast the longitudinal tooth displacement by evaluating the initial displacement on the dry skull. Initial tooth displacement has been measured by means of laser measuring techniques (holography, speckle interferometry and laser reflection technique). These techniques are non-invasive (non-destructive testing) and permit the measurement of small tooth and bone displacements varying between 0.5 and 15 microns. According to the results of the animal studies, it became obvious that initial tooth and bone displacements are indicative for the longitudinal effect of the same sort of force application on a short time basis (5 to 8 weeks). The final conclusion is that initial tooth displacement measured on a dry skull has a predictive value for the longitudinal effect of orthodontic force application. Moreover, the creation of a finite element model looks very promising in this respect. More research is needed to test the finite element model further and to make it useful for testing the effect of force application on skull and tooth structures of a patient.

[Tooth transplantation: an extra dimension in orthodontics]. / Tandtransplantaties: een extra-dimensie in de orthodontie.

In the first part of the presentation, the content of orthodontics has been briefly explained by means of some clinical cases. The main part of the presentation consisted of discussing patient treatment by means of autogenous tooth transplantation with special emphasis on its indications and contra-indications. When a tooth transplantation is carried out properly, a success percentage of 90%, even forty years after treatment, can be expected. This high percentage has been reported in a recent study. The success of tooth transplantation is mainly due to the timing of the transplantation and the non-traumatic handling during surgery. According to the literature, the ideal moment for tooth transplantation is when half to three quarters of the root has been formed. One of the indications for tooth transplantation is the transplantation of a tooth in the cleft of a cleft palate patient. Two cleft palate patients have been presented in which tooth transplantation was carried out after bone grafting in the alveolar cleft. Finally some findings of a recent study, carried out at our department, dealing with cryopreservation of teeth before transplantation, has been presented. According to the findings of this study, cryopreservation, after removal of the pulp tissue does not inhibit the normal ingrowth of new pulp tissue after transplantation.

Apical root resorption of upper incisors during the torquing stage of the tip-edge technique.

The purpose of this study was to investigate whether treatment with the Tip-Edge appliance resulted in more apical root resorption (ARR) of the central and lateral incisors during the torquing (third stage) than the non-torquing phases (first two stages) of orthodontic treatment. The three stages of this orthodontic technique make it possible to examine the amount of root shortening during torque separately from other types of tooth movement. The ARR ratio was calculated in 31 Caucasian patients (20 females, 11 males), after the non-torquing stage of treatment and after the torquing phase, by analysing periapical radiographs taken at the beginning of treatment (T1), before the start of the torquing stage (T2), and at the end of treatment (T3). At T1, the mean age was 13 years 6 months (+/- 3 years 3 months). The mean, standard deviation and range of the ARR ratios were calculated and compared (P < 0.001). T-tests were performed to determine levels of significance, at different stages of treatment, between teeth with and without ARR (ARR ratio = 1). Root shortening at T3 was observed for 70 per cent of the central and 76 per cent of the lateral incisors. At T2, ARR was 48 and 53 per cent, respectively. Compared with T2, 38 per cent of the central incisors and 55 per cent of the lateral incisors showed ARR during the application of torque. At T3, the finding for both was 22 per cent. The mean ARR ratio for the central and lateral incisors was the same after the non-torquing stage of treatment but was significantly different from a tooth with no root resorption. After the torquing stage, the ARR ratio for the central incisors was 0.96 and for lateral incisors 0.92. At the end of treatment, the ratio was 0.89 and 0.85, respectively. This study revealed that both the central and the lateral incisors showed comparable amounts of ARR during the torquing and non-torquing stage of Tip-Edge treatment.

[Orthodontics based on a new scientific method of evaluating results: "evidence-based"]. / L'orthodontie basé sur une nouvelle méthode scientifique d'evaluation des résultats: l'"evidence-based".

In the orthodontic literature, randomized clinical trials are used to establish standards for the comparison of different clinical approaches. The balancing effect produced in a randomized study makes it possible to attribute the differences in results achieved clearly to treatment and not to variations in the biological characteristics of the patients involved. Recently, most randomized studies in orthodontics have been devoted to testing the hypothesis that some orthodontic appliances exert orthopedic effects that modify dento-facial growth. The authors propose definitions of "orthopedic effects" and of "dento-alveolar changes" and discuss the difficulties encountered in measuring them. They also review clinical studies published over the past 10 years on the correction of Class II malocclusions, on the problems of expansion and also report on Class IIl disorders. In addition they assess the problems associated with these clinical studies such as the ethical requirement of assuring that control groups receive treatment as appropriate for their maladies as that delivered to patients under study, the high cost of carrying them out, the relatively long delay before results can be evaluated, the difficulties of measuring all the different parameters involved, and the need to assemble large enough samples. To sum up, one can conclude that, because of all these impediments, randomized clinical studies have not as yet delivered the hope for benefit of collecting enough "evidence based" information for the orthodontic profession to deliver better treatment to its patients.

Apical root resorption of upper incisors caused by intrusive tooth movement: a radiographic study.

The purpose of the study was to investigate whether root resorption of the upper incisors occurs during intrusion of maxillary incisors. It examines the possibility of a relationship between the amount of root shortening and duration of the intrusive force. The ratio of root length before and after intrusion was compared in 20 patients. In 66 incisors with an intrusion period of 29 weeks, an intrusion of 3.6 mm was performed. The control group consisted of 15 patients who underwent no orthodontic treatment. Consequently, 58 incisors had no intrusion. The follow-up time between 2 measurements was +/- 28 weeks. The findings clearly showed root shortening after intrusion. A mean resorption of 18% of the original root length was found. In comparison, none of the control patients showed root shortening. No correlation has been found between the amount of resorption and the amount and duration of intrusion. In combination with the apical deflection of the root, the nasal floor was occasionally a limiting factor for intrusion and this may have caused root resorption.

The marginal polishing of Ion Ni-Chro crowns: a preliminary report.

Although several publications about the stainless steel crown are available, only a few studies were found by which the effect of the crowns on gingival health was investigated. Webber suggested that there were no gingival changes after placement of the stainless steel crown. Goto, however, found that gingivitis occurred around most of the crowns. The highest incidence was noticed around the crowns with the poorest marginal adaptation. Henderson showed that the poorer the crown fit, the greater the plaque accumulation and the more severe the gingivitis. Myers also found that gingivitis was associated with poor crown adaptation. In the investigation by Peterson, attention was drawn to the polishing of stainless steel crowns before placement. Following the results of our small pilot study, it was clear that polishing of the crown margins is a very important procedure. It was found that the use of abrasive wheels followed by silicon rubbers was the most satisfactory. Independently, we can state that careful polishing of the crown margins is a "must" to prevent gingivitis.

Orthopedics in orthodontics: Fiction or reality. A review of the literature--Part II.

This study covers articles dealing with orthopedic treatment of Class III malocclusions, transversal deficiencies, and orthopedically induced changes in animal studies. An attempt has been made to discuss the whole group of orthopedic changes and their effects in the long-term. We want to emphasize that all orthopedic appliances have an important value in clinical orthodontics. There is, however, little scientific evidence so far to support the idea that they have any permanent orthopedic effect.

Orthopedics in orthodontics: Part I, Fiction or reality--a review of the literature.

The purpose of this review is to investigate the orthopedic effect of functional appliances such as activators and Herbst appliances, and the orthopedic effect of extraoral traction appliances. A systematic review of mostly English-language orthodontic articles reporting treatment of Class II malocclusions with different orthopedic appliances was carried out. According to this review, only Herbst therapy was able to change mandibular growth to a clinically significant extent. In part II of this study, the long-term effect of these changes will be evaluated.

A clinical trial comparing the failure rates of two orthodontic bonding systems.

A clinical trial was carried out to compare the failure rates of a visible light-cured fluoride-releasing material with a chemically cured adhesive. Fifty patients were used for the trial and 762 brackets were bonded in a split-mouth experimental design. Bracket failures were reported over the full period of orthodontic treatment. Statistical data analysis was carried out by means of chi 2 tests. The results of this study indicate that brackets, bonded with a chemically cured material (Lee Insta-bond, Lee Pharmaceuticals, EI Monte, Calif.), showed significantly fewer failures than brackets bonded with the light-cured material (Orthon, Orthon Dental Inc., Victoria, Canada). When the site of bond failure was evaluated in an overall manner, there were significantly more lower than upper, and more posterior than anterior bond failures.

A clinical evaluation of the effectiveness of a fluoride-releasing visible light-activated bonding system to reduce demineralization around orthodontic brackets.

The presence of decalcification (white spots) after the removal of orthodontic appliances still remains a problem. A method to deliver fluoride to the area beneath and around the bonded attachments, independent of patient compliance, could be very helpful. Therefore special attention is being currently directed to the so-called "fluoride releasing bonding adhesives." A clinical trial was carried out to compare the effect of a visible light-cured fluoride-releasing (F-releasing) material with a chemically cured nonfluoride resin on white spot formation during fixed orthodontic therapy. Fifty patients entered the trial, and 762 brackets were bonded in a crossover design. Intraoral slides were taken before and after treatment and were evaluated for white spot formation. Statistical data analysis was carried out by means of a chi-square test. The results of this clinical study indicate that there was no significant difference between the decalcification rates for both types of adhesives. When the appearance of white spots was evaluated in an overall manner, there was significantly more upper than lower decalcification.

[Radiographic follow-up of primary molars following sclerosing amputation]. / Radiografische kontrole van melkmolaren na scleroserende amputatie.

The effects of pulpotomy with the formocresol technique (Tempophore) were studied in a sample of 72 patients between 3 and 9 years of age. A total of 137 primary molars were treated and a longitudinal radiographical follow-up was executed with an interval of 4 months. Eighteen pulpotomies (13%) failed; in twelve of them an interradicular abscess was developing and 6 of them failed by internal resorption. It was striking that a rather great number of the failures occurred under 3 years of age and in patients older than 9 years. A second remarkable result was the higher frequency of failures in the mandible (18%) than in the maxilla (4%). This study reveals that the pulpotomy by formocresol is a successful therapy, by which primary molars with extensive carious lesions can be preserved until their usual time of shedding.

The effects of class II elastic force on a dry skull measured by holographic interferometry.

A method was developed for measuring bone displacements due to orthodontic forces. By means of holographic interferometry, the effects of Class II elastics on a dry skull were investigated. The bone deformation induced by the elastic force was studied on double-exposed holograms and also by the live fringe method. The results of this study reveal that sutures in the skull behave as weak structures, creating an interruption in the fringe pattern. With regard to the nasofrontal suture, the main movement, as could be expected, was an anteroposterior displacement. Related to the first molar, chosen as the anchorage unit, the vertical displacement was most pronounced. Furthermore, according to the findings of this study, the zygomaticotemporal suture was behaving as a hinge axis in a transversal direction. The method developed seems to be suitable for measuring bone displacements qualitatively as well as quantitatively.

Evaluation of intrusive mechanics of the type "segmented arch" on a macerated human skull using the laser reflection technique and holographic interferometry.

Twelve different systems of intrusion, based on the principle of the "segmented arch," were evaluated on a macerated human skull. The number of teeth involved in the anterior unit and the location of the application points of intrusive force were considered to be variables. Initial displacements of the anterior teeth after loading were registered by means of the laser reflection technique and double exposure holographic recordings. An attempt was made to define "this" intrusive system, achieving the most genuine intrusion (for definition, see text) without flaring of the teeth. When two central incisors were incorporated in the sectional wire, strong torque forces appeared, especially when the intrusive forces seized more distally. When four or six anterior teeth were pinned in the sectional wire, tooth movement seemed to be under better control. When the six front teeth were incorporated in the sectional wire, the center of resistance (for definition, see text) was located more to the distal side of the canines. It seemed more difficult, however, to define the center of resistance of the four incisors; it was situated approximately distal to the lateral incisors. In some of the intrusive systems, the teeth underwent independent mesial or distal rotations. This was easily observed with the laser measuring techniques used.

The interaction between reaction forces and stabilization systems during intrusion of the anterior teeth and its effect on the posterior unit.

The aim of this research is to attain a better understanding of the initial reaction forces induced by an intrusion mechanism (acting on the anterior teeth) on the posterior unit and to examine how these forces can be neutralized. The experiments were performed on the dentition of a dry human skull and initial tooth displacements were registered by means of two laser measuring techniques, namely holographic interferometry and the laser reflection technique. It was established that of all reaction forces induced by the intrusion arch, distal tipping of the first molars is the most pronounced. A transpalatal bar connecting the teeth does not counteract this movement. The stabilization of the posterior unit with a transpalatal bar, buccal sectionals, and high-pull headgear proved to be the most effective technique.

Comparative study of 2 electric and 2 manual toothbrushes in patients with fixed orthodontic appliances.

The objective of this prospective single-blind crossover clinical trial was to evaluate the efficacy of 4 toothbrushes in 33 children undergoing fixed appliance orthodontic therapy. The toothbrushes included in this study were the Braun Oral-B 3D Plaque Remover (Kronberg, Germany), the Philips-Jordan HP 510 (Philips Domestic Appliances, Groningen, The Netherlands), the Lactona orthodontic toothbrush (Bergen op Zoom, The Netherlands), and the Oral-B Advantage Control Grip (Braun); the first 2 are electric, and the last 2 are manual. Every patient tested each type of toothbrush in a randomly designed sequence. Plaque and gingival scores were recorded at baseline and after every 4-week test period. All patients received professional prophylaxis after each clinical evaluation. The data were analyzed with the Friedman test, which showed no significant differences among the 4 brushes for any of the parameters measured. The Wilcoxon signed rank test, comparing the plaque and the gingival scores between the upper and lower jaw for each brush, indicated that plaque removal was more efficient in the lower jaw than in the upper.

The use of 'Fluor Protector', a fluoride varnish, as a caries prevention method under orthodontic molar bands.

The aim of this study was to determine whether Fluor Protector, a fluoride varnish, applied to molars before orthodontic banding could prevent white spot formation. In the in vitro study 93 human premolars were used, divided in five different groups, representing different clinical situations. Each tooth was sliced in half, one as a control and the other as a test specimen. All tooth halves were stored in a demineralizing solution, in an attempt to induce white spot formation. In the in vivo study 104 molars (52 controls and 52 tests) of 28 orthodontic patients were involved. The 'split-mouth technique' was used. After evaluation of the results of both studies, it is evident that Fluor Protector is very effective in the prevention of white spot formation under molar bands.

The integumental profile: a reflection of the underlying skeletal configuration?

The aim of this study was twofold: (1) to evaluate the importance of the level of training in orthodontics when estimating skeletal configuration by visual inspection of the soft tissue profile, and (2) to evaluate a possible discrepancy between integumental profile (IP) and skeletal class (SC). Four test groups comprising 10 orthodontists (O), 10 senior assistants (S), 10 junior assistants (J), and 10 dentists (D) assessed horizontal and vertical skeletal pattern from a series of slides of 100 patients. The assessments were repeated after a 1-month interval. Cephalometric analysis was also carried out by using a number of conventional analyses. Analysis of the results with Levene's test, two factor mixed-design variance analysis, and Newman-Keuls' Multiple-Range test showed that (1) orthodontists, independent of their level of training, are more consistent in assessing an IP than dentists; (2) assessments were more consistent for sagittal profile than for vertical profile; (3) sagittally the Wits' appraisal corresponds best with IP, and (4) vertically the Steiner analysis corresponds best with IP.