Abstinence phenomena of chronic cannabis-addicts prospectively monitored during controlled inpatient detoxification: cannabis withdrawal syndrome and its correlation with delta-9-tetrahydrocannabinol and -metabolites in serum.

OBJECTIVE: To investigate the course of cannabis withdrawal syndrome (CWS) within a controlled inpatient detoxification setting and to correlate severity of CWS with the serum-levels of delta-9-tetrahydrocannabinol (THC) and its main metabolites 11-hydroxy-delta-9-tetrahydrocannabinol (THC-OH) and 11-nor-delta-9-tetrahydrocannabinol-9-carboxylic acid (THC-COOH). METHODS: Thirty-nine treatment-seeking chronic cannabis dependents (ICD-10) were studied on admission and on abstinent days 2, 4, 8 and 16, using a CWS-checklist (MWC) and the Clinical Global Impression-Severity scale (CGI-S). Simultaneously obtained serum was analysed to its concentration of THC, THC-OH and THC-COOH. RESULTS: MWC peaked on day 4 (10.4 ± 4.6 from 39 points) and declined to 2.9 ± 2.4 points on day 16. Women had a significantly stronger CWS than men. The CWS was dominated by craving>restlessness>nervousness>sleeplessness. CGI-S peaked with 5 out of 7 points. On admission, THC and its metabolites did negatively correlate with the severity of CWS. There was no significant correlation afterwards, no matter if CWS was medicated or not. THC-OH in serum declined most rapidly below detection limit, on median at day 4. At abstinence day 16, the THC-levels of 28.2% of the patients were still above 1g/ml (range: 1.3 to 6.4 ng/ml). CONCLUSIONS: CWS increased and then decreased without any correlation between its severity and the serum-levels of THC or its main metabolites after admission. According to the CGI-S, most patients achieved the condition of 'markedly ill'. Serum THC-OH was most clearly associated with recent cannabis use. Residual THC was found in the serum of almost one-third of the patients at abstinence day 16.

[No opiates against cannabis hyperemesis syndrome]. / Keine Opiate gegen das Cannabis-Hyperemesis-Syndrom.

HISTORY AND CLINICAL FINDINGS: An otherwise healthy 25-year-old patient with heavy cannabis-abuse suffered from an undiagnosed cannabis hyperemesis syndrome (CHS) over years, which characteristically was resistant to usual antiemetics. In an apparently last attempt at healing, opiates (morphine, methadone) were administrated and improved the CHS, however, this led to an at least as equally distressing and painful opiate withdrawal syndrome. TREATMENT AND COURSE: In the controlled cannabis abstinence during the 2-week inpatient treatment of opiate addiction syndrome the CHS has not recurred. CONCLUSION: Opiates are not suited for the treatment of CHS because they are addictive and lead to respiratory depression in overdose.

Large molecules as anti-adhesive compounds against pathogens.

Anti-adhesive compounds are potential prophylactic tools in alternative treatment regimes against bacterial infection, as bacterial adhesion is commonly mediated by carbohydrate-protein interactions between surface adhesions of microorganisms and the host cell. The use of exogenous polyvalent, high-molecular carbohydrates and tannin-like plant-derived compounds should antagonize the adhesive interaction. A range of carbohydrates and carbohydrate- and proanthocyanidin-enriched plant extracts were screened for potential anti-adhesive effects against Helicobacter pylori, Campylobacter jejuni, Porphyromonas gingivalis and Candida albicans in different in-situ assays on primary tissue. The adhesion of H. pylori on human stomach tissue was effectively blocked by glucuronic acid-enriched polysaccharides from immature okra fruits (Abelmoschus esculentus). These compounds also had strong in-vitro effects against C. jejuni (inhibition up to 80%), but were ineffective in an in-vivo study in infected chicken broilers due to metabolism in the gastrointestinal system. Polysaccharides from Glycyrrhizia glabra, also enriched with glucuronic acid, showed strong anti-adhesive properties against H. pylori and P. gingivalis (inhibition 60-70%). Pelargonium sidoides extract, containing mainly polymeric proanthocyanidins, was effective against H. pylori in a dose-dependent manner. Due to the multifunctional adhesive strategy of C. albicans, no effective compounds were detected against this yeast. Structure-activity relationships are presented and the potential in-vivo use of carbohydrate-based anti-adhesives is discussed.

Reaction of rat pulp tissue to Carisolv 'new gel'--a histocytological evaluation.

BACKGROUND: This study was an histological examination of pulp tissue exposed to Carisolv 'new gel' after 1 to 28 days. METHODS: An occlusal cavity was prepared in 64 caries-free molar teeth of 16 Wistar rats. The roofs of the pulp chambers were perforated and Carisolv 'new gel' solution was placed onto the exposed pulps of 32 molar teeth for 20 minutes. Thirty-two contralateral molar teeth served as controls and were coated with an inert liquid containing isotonic saline solution and carmellose for 20 minutes as well. The pulps of all teeth were capped with Ca(OH)2 and the cavities were filled with a flowable composite in combination with a self-etching dentine adhesive. The animals were sacrificed after 1, 3, 7 and 28 days. Eight teeth per group and the time period were histologically examined, scored, and statistically evaluated (Wilcoxon-test). RESULTS: The results showed no statistically significant differences between the Carisolv group and the control group (p > 0.05). The observed pulp reaction was essentially the same as those reported in the past being typical for the effect of calcium hydroxide as a direct pulp capping agent. CONCLUSION: Compared to Ca(OH)2, Carisolv 'new gel' did not cause any different or additional pulp reaction in healthy teeth.

Regional odontodysplasia: a review of the literature and report of four cases.

Regional odontodysplasia (RO) is a rare dental anomaly involving both dentitions, mostly teeth of one quadrant. The characteristic findings are discolored soft teeth accompanied by gingivitis, swelling or abscess. Enamel and dentin are hypomineralised and hypoplastic, so that the 'ghost teeth' appear shadowy in radiographs with wide pulp chambers. The etiology is unknown. Epidemiological data is rare; 138 cases of RO have been published to date and reports on ultrastructure are few. An analysis of published cases of RO in the international literature is presented. The sex ratio of females to males was 1.7:1. The age at the time of diagnosis ranged between 4 and 23 years. The maxilla was more often affected (maxilla to mandible ratio 1.6:1). In 67 patients the deciduous and permanent dentitions were affected (47.1%). In 129 cases, affected teeth lay side by side. Missing tooth development was observed in 10.7%. Failure of tooth eruption of RO teeth occurred in 39.7%. In addition, four cases with RO which were collected over a period of more than 25 years are presented. Ultrastructural findings of one specimen are demonstrated.

Ultrastructural characterization of the implant/bone interface of immediately loaded dental implants.

Primary stability and an optimized load transfer are assumed to account for an undisturbed osseointegration process of implants. Immediate loaded newly designed titanium dental implants inserted in the mandible of minipigs were used for the characterization of the interfacial area between the implant surface and the surrounding bone tissue during the early healing phase. Histological and electron microscopical studies were performed from implant containing bone specimens. Two different load regimens were applied to investigate the load related tissue reaction. Histological and electron microscopical analysis revealed a direct bone apposition on the implant surfaces, as well as the attachment of cells and matrix proteins in the early loading phase. A striking finding of the ultrastructural immunocytochemical investigations was the synthesis and deposition of bone related proteins (osteonectin, fibronectin, fibronectin receptor) by osteoblasts from day one of bone/biomaterial interaction. Calcium-phosphate needle-like crystallites were newly synthesized in a time-related manner directly at the titanium surface. No difference in the ultrastructural appearance of the interface was found between the two loading groups. Our experimental data suggest that loading of specially designed implants can be performed immediately after insertion without disturbing the biological osseointegration process.

Development and evaluation of an experimental model for investigating the pathogenesis and therapeutic strategies of acute liver failure.

Because of the various etiologies of acute liver failure (ALF) a clinically relevant model must fulfill four criteria--reversibility, reproducibility, ALF-induced death, and a sufficient time interval for diagnosis and therapy between induction and death. In this study an experimental model was evaluated for these criteria. A total of 49 rats were randomized into seven groups: First, a pilot study was performed regarding the survival rate after different treatments: In group I, animals underwent a 70% liver resection. In group II, 70% liver resection was combined with ascending doses of postoperative endotoxin administration up to 400 microg/kg (group IIc). In group III, animals only underwent liver mobilization. In group IV, ALF was induced according to the protocol of group IIc, but with additional treatment of an endothelin-A-receptor (ETAR) antagonist. Animals in group V received only 400 microg endotoxin. After induction of ALF, all animals died within the first day, showing significantly elevated bilirubin and ammonium levels and severe damage to hepatocellular integrity. Application of the ETAR antagonist resulted in the survival of 6/7 animals until the 14th day; the biochemical and histomorphological changes were reversible. All other animals survived to the 14th day. A clinically relevant model of ALF in rats can be created by the combination of 70% liver resection and endotoxin application to produce an inflammatory component.

Achilles tendon healing: long-term biomechanical effects of postoperative mobilization and immobilization in a new mouse model.

The aim of the study was to investigate the long-term effects of postoperative immobilization as opposed to mobilization on the biomechanical attributes of healing Achilles tendons in a new experimental mouse model. In 114 Balb-C-mice the left Achilles tendon was transected and sutured by the Kirchmayr-Kessler technique. The tendons healed either under postoperative immobilization effected by fixing the upper ankle joint in equinus position or under mobilization through a limited range of movement. The contralateral Achilles tendons served as internal control. All tendons were tested biomechanically at short intervals up to the 112th postoperative day in terms of load to failure [N], tendon deflection [mm] and tendon stiffness [N/mm], and were evaluated histologically after 8 and 112 days. Postoperative mobilization resulted in a continuous and significantly more rapid restoration of load to failure in comparison to the immobilization group. Tendon deflection was decreased by postoperative mobilization, whereas under immobilization it paradoxically increased still further in the later course. After 112 days the tendons of the mobilization group had regained their original tendon stiffness, whereas the tendons after immobilization reached only about half the values seen in the control tendons. Histologically, postoperative mobilization led to increased immigration of inflammatory cells in the early phase. In the late phase, as compared to immobilization, tendon structure was more mature, with fibre bundles arranged in parallel and interposed tendocytes. Tensile loading of the healing tendon by postoperative mobilization leads to fundamental changes in the biological process of tendon healing resulting in accelerated restoration of load to failure and reduced tendon deflection.

[Evaluating angiogenesis and osteogenesis modified by vascular endothelial growth factor (VEGF)]. / Beurteilung der Angiogenese und Osteogenese unter dem Einfluss von Vascular endothelial growth factor (VEGF).

PURPOSE: This intention of this study was to investigate the influence of controlled release of vascular endothelial growth factor (VEGF) on angiogenesis and osteogenesis in a mandibular defect model. METHODS: A total of 56 rabbits were operated and bicortical holes were placed in the mandible. The defects were filled with collagen type I implants, collagen implants complexed with 0.8-microgram VEGF165, or left without any filling. After 3, 7, 14, and 28 days specimens were taken and histologic, histomorphometric, and immunohistologic analyses were carried out concerning density of vessels, total surface of vessels, bone surface, and bone density. RESULTS: The number of vessels was increased in all groups up to 14 days, followed by physiologic regression in the control groups, whereas the study group showed persistently high numbers. The density of regenerated bone was significantly higher in the study group. CONCLUSION: The activation of angiogenesis using VEGF165 leads to more intensive angiogenesis and bone regeneration.

Histocytological evaluation of the reaction of rat pulp tissue to Carisolv.

OBJECTIVES: Carisolv is a viscous substance for the chemo-mechanical removal of caries. The aim of this study was to examine the tissue reactions of pulp and dentin tissue to Carisolv in vivo. METHODS: In 48 caries-free molars (24 Wistar rats, age: 3 months) an occlusal cavity was prepared. The roofs of the pulp chambers were perforated with a sharp probe and Carisolv solution was placed onto the exposed pulp of 24 molars for 1, 10 and 20 min. Twenty-four contralateral molars served as controls and were coated with an inert liquid containing isotonic saline solution, carmellose and erythrosin. RESULTS: After a contact period of 10 and 20 min in the experimental group, pulpal destruction of intercellular substance and cells including odontoblasts was observed up to a depth of 150 microm, in addition to the mechanical damage by perforation (e.g. dentin particles). The pulpal and predentin fibrils as well as the dentin fibrils appeared to be intact and did not differ from the controls. After a contact time of 1 min a weaker damage of pulp cells and odontoblasts, as well as intact fibrils in pulp, predentin and dentin could be observed. CONCLUSIONS: Radicals of Carisolv (OH- and OCI-) cause alkaline hydrolysis of cellular components but do not decompose collagenous tissue components.

Quantitative analyses of the biomineralization of different hard tissues.

The primary crystallites of the different developing hard tissues have an apatite structure. However, they have crystal lattice distortions representing an intermediate state between amorphous and fully crystalline. We have applied energy-filtering transmission electron microscopy in the selected area electron diffraction mode to analyse different stages of crystal formation in dentine, bone, enamel and inorganic apatite mineral. We have obtained quantitative information on the degree of crystal lattice distortion using the paracrystal theory of Hosemann and Bagchi. We have found that the early formed crystallites of the hard tissues being analysed have a paracrystalline character comparable to biopolymers. However, with maturation, the lattice fluctuations of the crystallites of the hard tissues bone, enamel and dentine decrease to form a typical (para)crystalline character. Also the decrease of the organic proportion in the matrix corresponds to the decrease of the lattice fluctuation of the crystallites in the different hard tissues during maturation.

Electrical stimulation influences mineral formation of osteoblast-like cells in vitro.

The aim of the present study was to assess the structure of newly formed mineral crystals after electrical stimulation of osteoblast-like cells in vitro. Pulsed electrical stimulation was coupled capacitively or semi-capacitively to primary osteoblast-like cells derived from bovine metacarpals. Computer calculations revealed that the chosen input signal (saw-tooth, 100 V, 63 ms width, 16 Hz repetition rate) generated a short pulsed voltage drop of 100 microV (capacitive coupled mode) and of 350 microV (semi-capacitive coupled mode) across the cell-matrix layer. Stimulated cultures showed an enhanced mineral formation compared to the non stimulated controls. In cultures exposed to capacitively coupled electric fields and in control cultures nodules and mineralized globules were found. Nodules with a diameter of less than 200 nm covered the cell surface, whereas mineral globules with a diameter of up to 700 nm formed characteristic mineral deposits in the vicinity of the cells similar to biomineral formations occurring in mineralizing tissues. In contrast, large rod-shaped crystals were found in cultures stimulated by semi-capacitive coupled electric fields, indicating a non-physiological precipitation process. In conclusion, osteoblasts in culture are sensitive to electrical stimulation resulting in an enhancement of the biomineralization process.

Mechanical tension in distraction osteogenesis regulates chondrocytic differentiation.

Differentiation of chondrocytes to cells of osteoblastic phenotype occurs during an interim period of bone development, fracture repair and distraction osteogenesis. To study the relationship between tension-stress and chondrogenesis, uniaxial strains (0 microstrains, 2000 microstrains, 20000 microstrains, 200000 microstrains, 300000 microstrains) were applied in a rabbit model of mandibular distraction osteogenesis. The results demonstrated that cell differentiation, apoptosis and tissue development in the newly formed gap tissue showed a correlation to the applied strain magnitudes. Only strains of 20000 microstrains resulted in a statistically significant (P<0.05) formation of cartilage struts with embedded chondrocyte-like cells. However, chondrocyte-like cells were rarely detected in samples distracted at lower or higher strain magnitudes. Osteoblasts appeared to replace cartilaginous matrix by mineralized bone matrix. The phenotypic change from chondrocytes to osteoblasts was accompanied by a decreased proteoglycan synthesis. a change in the expression from type II collagen towards type I and involved asymmetric cell divisions and apoptotic cell death. Therefore, we suggest that mechanical strain is an external stimulus responsible for phenotypic cell alterations.

Ultrastructural findings after intraarticular application of hyaluronan in a canine model of arthropathy.

We investigated the effect of intraarticularly applied hyaluronic acid (hyaluronan) on the cartilaginous structure of experimentally induced chondromalacia patellae in dogs. For the induction of chondromalacia, we used the Pond-Nuki technique, which involved severance and resection of the anterior cruciate ligament, as a canine model of arthropathy in 27 foxhounds (three groups of nine animals each). In a pilot study, we evaluated the effect of resection of the anterior cruciate ligament with no therapy. Patellar specimens were retrieved at 3, 6, and 12 weeks postoperatively. Subsequently, we compared a treatment group that received intraarticular injections of hyaluronan with a placebo group that received saline solution. The groups were compared at 3, 6, and 12 weeks postoperatively. Three animals from the treatment and placebo groups received five injections of hyaluronan during one of the 4-week intervals (weeks 3-6, 6-9, or 12-15). Specimens were retrieved 5 weeks after the last injection. In both groups, the uninvolved contralateral knee served as a control. The specimens were taken from the medial and lateral patellar poles. Histological analysis included light microscopy and transmission electron microscopy. The structural and ultrastructural changes were assessed qualitatively and were quantified with use of a modified Mankin score. Our results indicate that chondromalacia patellae may be induced with the Pond-Nuki technique. We found a significant reduction (p < 0.01) of cartilaginous lesions in the hyaluronan group compared with the placebo group. Our results suggest that intraarticularly applied hyaluronan is effective in delaying the degenerative process of cartilage degradation. Therefore, we conclude that the use of hyaluronan may be indicated during the early stages of chondromalacia.

Clinical anatomy and palpability of the inferior lateral pterygoid muscle.

STATEMENT OF PROBLEM: The intraoral palpation technique of the inferior belly of the inferior lateral pterygoid (ILP) muscle is a standard diagnostic examination method for temporomandibular joint dysfunction syndrome, although different studies have revealed inconsistent results. PURPOSE: This study assessed the feasibility of the ILP muscle palpation by a simulated clinical setting. MATERIAL AND METHODS: Three dentists performed a bilateral palpation of the ILP muscle in 53 fresh and unfixed human cadavers and decided whether the muscle was palpable or unpalpable. In a second step, it was observed through the dissected infratemporal fossa, whether the examiner's finger did or did not touch the ILP muscle by simulating the performed palpation. Palpatory findings were supplemented by 1-dimensional measurements for determination of topographic relations of the ILP muscle within the infratemporal fossa. For statistical analysis, sensitivity, specificity, and negative and positive predictive values of the palpation technique were calculated. Interexaminer agreement was estimated with the kappa value. RESULTS: In 86 of 106 dissected specimens, a superficial fascicle of the medial pterygoid muscle was found in direct proximity to the ILP muscle. In these cases, a residual distance of 7.8 +/- 3.2 mm remained between the ILP muscle and buccinator fascia indented by the tip of the examiner's finger. In 10 of 20 specimens with an absent superficial fascicle, the finger was able to reach the ILP muscle. CONCLUSION: It is recommended that the ILP muscle palpation technique should no longer be considered as a standard clinical procedure because it is nearly impossible to palpate the ILP muscle anatomically and because the risk of false-positive findings (by palpation of the medial pterygoid muscle) is high.

Periosteally derived osteoblast-like cells differentiate into chondrocytes in suspension culture in agarose.

Pluripotent cells from the periosteal layer adjacent to cortical bone attain an osteoblast-like phenotype in culture when reaching confluence in monolayer. It is unknown whether such newly differentiated osteoblast-like cells preserve the chondrogenic potential characteristics for stem cells derived from the periosteum. Primary osteoprogenitor cells derived from bovine metacarpal periosteum were differentiated into alkaline phosphatase-positive osteoblast-like cells by an established monolayer culture protocol. After transfer into suspension culture in agarose gels, the cells differentiated into chondrocytes demonstrated by the production of collagen II, but not of collagen I, as well as alkaline phosphatase activity was abated. Contrarily, with continuation of monolayer culture, the cells maintained their osteoblast-like phenotype and secreted large amounts of collagen I and a minor quantity of collagen III and V. The alkaline phosphatase activity steadily increased during the entire culture period of 2 weeks. Thus, our culture techniques can serve as useful tools to study mechanisms of differentiation by modulating the phenotypic potential of osteogenic cells. The results presented here support the notion that the extracellular environment strongly influences the cell type and its metabolism.

The effect of magnitude and frequency of interfragmentary strain on the tissue response to distraction osteogenesis.

PURPOSE: Bone regeneration is believed to be partially controlled by the applied local mechanical strain. To test whether the magnitude or frequency of discontinuous traction regulates the tissue response, defined daily strains were applied on mandibular osteotomies using an implanted mechanical distractor. MATERIALS AND METHODS: Unilateral mandibular osteotomies were performed in skeletally immature rabbits (n = 36). and distraction was done by applying 2,000, 20,000, 200,000, or 300,000 microstrains once or 10 times (2,000, 20,000 microstrains) per day, respectively. Sham-operated animals (n = 6), serving as controls, underwent frame application and osteotomy without distraction. At the end of the distraction process, the newly formed tissue was evaluated histomorphometrically by the use of a well-defined scoring system of bone-forming indices. RESULTS: The highest bone-forming indices were detected in the osteotomized, nondistracted group and in samples exposed to a physiologic strain (2,000 microstrains). Application of hyperphysiologic strains (200,000 and 300,000 microstrains) resulted in the formation of fibrous tissue and decreased bone-forming indices. Using Kruskal-Wallis tests, a statistically significant relationship was found between the bone-forming indices and the applied strain magnitudes. Scanning and transmission electron microscopic examinations showed osteoblastic differentiation and early mineral deposition in samples distracted up to 20,000 microstrains, whereas higher strain magnitudes led to the formation of fibroblast-like cells surrounded by collagen fibrils and only slight mineralization. Multiple strain applications (10 cycles/d vs 1 cycle/d) did not alter the histomorphometric indices or ultrastructural morphology significantly but increased the amount of newly formed tissue. CONCLUSIONS: These results suggest that the magnitude and not the frequency of mechanical loading controls the differentiation of bone cells and the subsequent formation of bone tissue.

Three-dimensional visualization and quantification of the mandibular articular surface by optical profilometry.

The aim of this study was to introduce a nondestructive optical technique for the quantitative assessment of natural biological surfaces as demonstrated with the example of the articular surface of the human temporomandibular joint. The computer-assisted quantitative evaluation of the surface is realized by the acquisition of three-dimensional images via the optical technique of phase measuring profilometry. After mathematical processing of the data set the resulting image can be visualized as three-dimensional object surface reconstructions or as grid surfaces from which arbitrary sections may easily be extracted. From such single sections we can calculate a value that represents the degree of height deviations of the section profile and can be regarded as a parameter for the surface roughness. Further quantitative information about the surface topography is provided by the Fourier transform analysis of the profiles. The Fourier spectrum contains information about the spatial distribution of roughness-causing protuberances along the overall surface. As an example one healthy condyle and one remodeled condyle from macerated cadaver mandibles were investigated. For the two samples evaluated we calculated a mean surface roughness of the entire articular surface with a value of 0.03 +/- 0.005 mm for the healthy condyle with its smooth surface and a value of 0.14 +/- 0.009 mm for the remodeled condyle. We recommend optical profilometry as a sophisticated technique for a more objective and quantitative pathological classification of articular surfaces and similar objects.

Quantitative electron spectroscopic diffraction analyses of the crystal formation in dentine.

Newly formed apatitic crystallites of different hard tissues consist, according to our investigations, of chains composed of nanometre-sized particles (islands, dots) arising at nucleating sites of the collagenous and noncollagenous matrix macromolecules. In dentine these islands coalesce rapidly in longitudinal direction to form needle-like crystallites which further coalesce to ribbon-like crystallites. We have concluded that the centre-to-centre distances between these islands represent the distances between the nucleating sites of the matrix macromolecules. We have applied energy-filtering transmission electron microscopy in the selected area electron diffraction mode at different stages of crystal formation in dentine and have obtained quantitative information of the degree of crystal disorder on the basis of the paracrystal theory. The fluctuation of the lattice plane distances in c-axis direction decreases, proceeding from the region near the dentine/predentine border to the dentine/enamel border.

Strain-related bone remodeling in distraction osteogenesis of the mandible.

Distraction osteogenesis has become a mainstay in craniofacial surgery. However, there are several unresolved problems concerning the biology of bone regeneration. We investigated the biomechanical effects of mandibular lengthening in 32 rabbits on a cellular and histologic level. The mandible was subjected to a corticotomy, held in a neutral position for 4 days, and then lengthened at various strain rates and frequencies for 10 days. Radiographic, histologic, and electron microscopic examinations showed a strain-related bone regeneration. Application of physiologic strain rates (2000 microstrains or 0.2 percent) led to a bridging of the artificial fracture exhibiting woven ossification, whereas at 20,000 microstrains trabecular bone formation was demonstrated. In contrast, hyperphysiologic strain magnitudes (200,000 microstrains and 300,000 microstrains) showed a fibrous tissue formation. Multiple strain applications (10 cycles/day versus 1 cycle/day) increased the width of the distraction gap without changing the stage of bone regeneration. The gradual distraction of bone in physiologic magnitudes at higher frequencies seems to be desirable for a bony differentiation and may help to improve clinical applications.