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.

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.

[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.

Unicoronal suture immobilization in the fetal rabbit.

Pre-clinical evaluation of surgical procedures aimed to correct craniosynostosis is ideally performed in species of small animals characterized by perinatal brain development, early skeletal maturation, and genuine synostosis in all newborns. It would be nearly impossible to breed such a colony to homozygosity, so most researchers have resorted to artificial postnatal suture immobilization. Our aim was to test the hypothesis that artificial immobilization of a unicoronal suture in the fetal rabbit (25 days of gestation) would result in neurocranial growth alterations similar to those seen in the 9-day postnatally immobilized or congenital synostotic rabbit models. The advantages of prenatal immobilization are that rabbits can undergo the tested corrective procedure at postnatal day 9. This age corresponds to a human age of 6 months and allows the deformity and the effects of its correction to be more readily detected. The heads of 25-day-old fetuses of five time-dated pregnant New Zealand white rabbits were exposed by hysterotomy. The left unicoronal suture of 4 fetuses in each litter was immobilized with a polyglactin suture piercing the frontal and parietal bone plates. The remaining two fetuses were sham-operated. Nine days after spontaneous delivery, all rabbits were marked with four titanium screws close to the sagittal and coronal sutures. Growth was recorded with dorsoventral cephalograms at 9 and 90 days. The group with the immobilized suture showed a small increase in growth across the sagittal sutures. However, the decreases in growth at the unicoronal suture in both the immobilized (5.41-mm difference with sham-treated group) and nonimmobilized (1.17-mm difference with sham-treated group) were significant. Fetal immobilization results in growth alterations similar to those observed after postnatal immobilization.

[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.

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.

Initial tooth displacement in vivo as a predictor of long-term displacement.

In the past, the dry skull has been used as a hypothetical model to test initial orthodontic and orthopaedic force systems. However, the question as to whether this hypothetical model can be used as a predictor of long-term displacements in vivo remains unanswered. In this study, an attempt was made to compare initial tooth displacement with the long-term effect after application of the force system for a longer period of time, in six adult dogs. Tooth displacement was obtained by applying a force by means of a coil spring (push) system. Following application of a force of 50 g in the first series (n = 3) and 80 g in the second series (n = 3), initial displacements were registered by means of speckle interferometry. The long-term displacement was registered by means of standardized cephalometry in the same dog by leaving the force system in place for 5 weeks. The mean values of the displacement vectors of the second premolars in the six dogs were compared. A paired t-test revealed no significant differences between the initial and long-term displacements in any of the dogs. The results show that both groups of measurements belong statistically to the same sample and that initial tooth displacement measured by means of speckle interferometry is a valuable predictor for forecasting long-term displacement in vivo after 5 weeks.

A multidisciplinary approach to the healing of cranial and residual maxillary cleft defects by means of allogenous demineralized osseous implants and polylactic acid casts in dogs.

OBJECTIVE: The aim of this study was to evaluate the healing of artificially induced bony defects in dogs by means of demineralized allogenous bone powder (DBP) implants covered with polyhydroxy lactic acid (PLA) casts compared with DBP implants without the casts. DESIGN: Prospective animal study. SETTING: Research university. SAMPLE: Following a pilot study in which two dogs were used, four mongrel dogs between the ages of 18 and 24 months and weighing approximately 20 kg were used as subjects. INTERVENTIONS: Each experimental animal had bilateral maxillary alveolar clefts created. In a later procedure, each defect was repaired with a DBP implant, half of which were covered with a PLA96 matrix. Each animal also had a circular defect created in each parietal bone that was immediately covered with DBP implants, half of which were similarly covered with a PLA96 disk. MAIN OUTCOME MEASURE: Repeated technetium-99m methylene-diphosphate (99mTC MDP) uptake measurements were performed to evaluate bone metabolism during the healing period, while at relevant intervals, radiographs were taken of the healing alveolar cleft defects to register bone repair. After 1 year, the animals were euthanized for macroscopic and histologic evaluation. RESULTS: Histologically, the grafts covered with PLA96 were at a more advanced stage of healing than those without, and the cranial defects similarly were more advanced in the healing process than the alveolar defects. Uptake of 99mTC MDP into the cranial implants was at its maximal level after 1 week and then gradually decreased until, after 7 weeks, it was not significantly different from zero. Cranial defects covered with a PLA95-enhanced implant showed a mean maximum count rate of 275, while the plain DBP side showed a mean maximal count rate of 150. Alveolar defects with the plain DBP implant showed a maximum count rate in the first week; those with the PLA95 enhanced implant showed maximum uptake during the second week. On both sides, there was a gradual decrease to the base value in the seventh week. The mean maximum count on the PLA96-enhanced side was 285, while on the plain DBP side, the corresponding value was 320. CONCLUSION: Although an advantage of the combination was established for parietal cranial defects, no advantage was seen for alveolar cleft defects in this experimental setup.

Initial orthopaedic displacement compared with longitudinal displacement of the maxilla after a forward force application. An experimental study in dogs.

The aim of this study was to compare the initial orthopaedic displacement of the maxilla in vivo and the longitudinal changes after a forward force application. The sample consisted of five 1-year-old dogs. An anterior force of 5 N on the maxilla was applied by a coil spring system pushing between Brånemark implants and a maxillary splint. The initial displacement of the maxilla after force application was measured by means of speckle interferometry. The longitudinal displacement of the maxilla after a force application during 8 weeks was measured by superimposing standardized lateral cephalograms. The initial, as well as the longitudinal, displacement of the maxilla of the dogs was in a forward direction with some counterclockwise rotation. There was no statistical difference between the initial and longitudinal displacement. The biological response after force application during 8 weeks can be predicted by the initial orthopaedic displacement.

White spot formation under orthodontic bands cemented with glass ionomer with or without Fluor Protector.

The purpose of this study was to determine whether an additional application of Fluor Protector before band cementation with glass ionomer cement reduces white spot formation compared with band cementation with glass ionomer cement. In the in vitro study, 80 premolars were divided in half, creating a control and a test group. All specimens were divided into four different groups to simulate different clinical situations and stored in a demineralizing solution to induce white spot formation. In the in vivo investigation, 18 orthodontic patients were incorporated in the study. One lower and one upper first molar band (randomly selected) were coated with Fluor Protector and then cemented with a glass ionomer cement (test group). The other two uncoated first molars were cemented with glass ionomer cement and served as the control group. The application of Fluor Protector in combination with Aquacem did not contribute to a reduction of white spot formation underneath molar bands compared with the use of Aquacem for banding.

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.

Effect of electric toothbrushes versus manual toothbrushes on removal of plaque and periodontal status during orthodontic treatment.

This study compared the effectiveness of three different types of electric toothbrushes, i.e., Interplak, Philips, and Rotadent, with a manual multitufted toothbrush (Blend-a-Med), in removing supragingival plaque and in preventing the development of gingivitis in adolescent patients with fixed orthodontic appliances. A single blind, cross-over, clinical trial was carried out in 36 adolescent patients, randomly divided into four equal groups. Every group tested each type of toothbrush, in a different sequence. Plaque and gingival scores were recorded at baseline and after 1 and 2 months of the test period. All patients received a professional prophylaxis after each clinical evaluation, except during the test period. The analysis of the data was performed with the nonparametric Friedman test. The results demonstrated, in essence, for all parameters that the manual toothbrush was the most effective. Of the three electric toothbrushes tested, the Philips toothbrush seemed to give slightly better results than the Interplak toothbrush, whereas Rotadent very clearly gave results inferior to all others. Personal preference on the four toothbrushes used revealed that the group as a whole least preferred a manual brush. However, the answers on the questionnaire did not always show a logical consistency. Therefore it should be interpreted with some caution.

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.

Comparative shear bond strength of some orthodontic bonding resins to enamel.

The aim of this study was to compare the in vitro bond strength, to bovine enamel measured in shear, of the orthodontic adhesives Lee Insta-bond (LiB), Rely-a-Bond (RaB), Right-on (Ro), Concise precoating method (Cc), Concise mixed method (CaB), Super-C (Sc), and Orthon (Or), and of the glass ionomer cement Ketac-Cem (KC). The fracture surfaces after debonding were also examined in order to determine the sites of failure. The results indicate that there is a significant difference between the shear bond strength obtained with the different adhesives so that the mean shear bond strength decreases in the order [Ro approximately Cab approximately Sc] > [LiB approximately RaB approximately Cc] > Or > KC. Moreover, for Cab and Sc it was found that the shear bond strength varies depending on the location on the bovine tooth. The failure site was essentially at the resin-bracket interface, except for Concise, where only 50 per cent of the cases failed at the resin-bracket interface.

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.