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OBJECTIVE: To determine if Pyk2-deficiency increases midpalatal suture bone mass and preserves sutural integrity after maxillary expansion. SETTING AND SAMPLE: Thirty-six male Pyk2 knockout (KO) and control (WT) mice at 6-weeks of age. MATERIALS AND METHODS: Mice received nickel-titanium spring expanders delivering 0g (no intervention control), 10g or 20g force for 14 days. High-resolution micro-CT was used to determine bone volume/tissue volume (BV/TV), sutural width and intermolar width. Effects on osteoclasts, chondrocytes and suture morphology were determined by histomorphometry. RESULTS: Pyk2-KO controls (0g) had 7% higher BV/TV compared with WT controls. Expanded Pyk2-KO maxillae also exhibited 12% (10g) and 18% (20g) higher BV/TV than WT mice. Although bone loss following expansion occurred in both genotypes, BV/TV was decreased to a greater extent in WT maxillae (−10% at 10g; −22% at 20g) compared with Pyk2-KO maxillae (−11% only at 20g) (p

Introduction The detailed mechanical and histologic properties of stainless steel miniscrew implants used for temporary orthodontic anchorage have not been assessed. Thus, the purpose of this study was to compare them with identically sized titanium alloy miniscrew implants. Methods Forty-eight stainless steel and 48 titanium alloy miniscrew implants were inserted into the tibias of 12 rabbits. Insertion torque and primary stability were recorded. One hundred grams of tensile force was applied between half of the implants in each group, resulting in 4 subgroups of 24 specimens each. Fluorochrome labeling was administered at weeks 4 and 5. When the rabbits were euthanized at 6 weeks, stability and removal torque were measured in half (ie, 12 specimens) of each of the 4 subgroups. Microdamage burden and bone-to-implant contact ratio were quantified in the other 12 specimens in each subgroup. Mixed model analysis of variance was used for statistical analysis. Results All implants were stable at insertion and after 6 weeks. The only significant difference was the higher (9%) insertion torque for stainless steel. No significant differences were found between stainless steel and titanium alloy miniscrew implants in microdamage burden and bone-to-implant contact regardless of loading status. Conclusions Stainless steel and titanium alloy miniscrew implants provide the same mechanical stability and similar histologic responses, suggesting that both are suitable for immediate orthodontic clinical loads.

Objective:To establish an association between patient personality traits and potential willingness to undergo various orthodontic treatments.Materials and Methods:One hundred adolescent individuals aged 12–16 years completed an anonymous electronic questionnaire via Survey Monkey. The 24-item questionnaire contained three major sections: patient demographics, a modified Big Five Inventory (BFI)-10 personality index, and a willingness to undergo treatment assessment. Multiple-variable linear regression analyses were used to determine the associations among age, gender, ethnicity, and the five personality traits simultaneously with willingness to undergo treatment. Statistical significance was set at P ≤ .05.Results:Ninety-six of the 100 individuals were included in the statistical analysis. Age, ethnicity, and gender failed to correlate with potential willingness to undergo orthodontic treatment. Several personality dimensions within the modified BFI-10 (agreeableness, conscientiousness, and neuroticism) were significantly associated with willingness to undergo various orthodontic treatments (P ≤ .05). Agreeableness demonstrated positive correlations with five treatment modalities, while both conscientiousness and neuroticism exhibited negative associations with a single treatment modality. Openness and extraversion were the only personality dimensions that failed to associate with any of the treatment modalities. Four of the nine treatment modalities had no association with patient demographics or a patient's personality dimensions.Conclusions:Personality traits are useful in predicting a patient's potential willingness to participate in various orthodontic treatments. The agreeableness dimension provided the most utility in predicting patient willingness. Age, ethnicity, and gender were not significant in predicting patient willingness.

The forces and moments supplied by braces determine the movement of tooth in orthodontic treatment, so clearly quantifying the force value is very important to formulate precise treatment plan. In recent decades, scholars have presented many articles about biomechanical research on orthodontic force. Based on investigations of these papers, techniques on orthodontic force stimulation including oral model (bone, PDL and teeth included) reconstruction and constitute model construction, methods in orthodontic force measurement including physical oral model fabrication and device architectures, and techniques on orthodontic force control such as the use of shape memory alloy and shape memory polymer as the wire material, are reviewed. At the end, the conclusions and future works are given.

Objective: To investigate three-dimensional microarchitecture and micromechanical properties of alveolar bone in the BoneCeramic grafting sites during orthodontic tooth movement. Materials and Methods: Sixty 5-week-old rats were randomly assigned into three groups to receive BoneCeramic, natural bovine cancellous bone particles (Bio-Oss), and no graft, respectively, after the extraction of the left maxillary first molar. After 4 weeks, the maxillary left second molar was moved into the extraction site for 28 days. Dynamic bone microstructures were evaluated using in vivo micro–computed tomography. Micromechanical properties and stress distribution of corresponding tissue were examined by nanoindentation and finite element methods. Mixed-model analysis of variance was performed to compare the difference among time points with Bonferroni post hoc tests at the significance level of P < .05. Results: The BoneCeramic group had the least amount of tooth movement and the highest bone volume fraction, tr...

The forces and moments supplied by braces determine the movement of tooth in orthodontic treatment, so clearly quantifying the force value is very important to formulate precise treatment plan. In recent decades, scholars have presented many articles about biomechanical research on orthodontic force. Based on investigations of these papers, techniques on orthodontic force stimulation including oral model (bone, PDL and teeth included) reconstruction and constitute model construction, methods in orthodontic force measurement including physical oral model fabrication and device architectures, and techniques on orthodontic force control such as the use of shape memory alloy and shape memory polymer as the wire material, are reviewed. At the end, the conclusions and future works are given.

Objective: To quantify the three-dimensional moments and forces produced by pretorqued nickel-titanium (NiTi) rectangular archwires fully engaged in 0.018- and 0.022-inch slots of central incisor and molar edgewise and prescription brackets. Materials and Methods: Ten identical acrylic dental models with retroclined maxillary incisors were fabricated for bonding with various bracket-wire combinations. Edgewise, Roth, and MBT brackets with 0.018- and 0.022-inch slots were bonded in a simulated 2 × 4 clinical scenario. The left central incisor and molar were sectioned and attached to load cells. Correspondingly sized straight and pretorqued NiTi archwires were ligated to the brackets using 0.010-inch ligatures. Each load cell simultaneously measured three force (Fx, Fy, Fz) and three moment (Mx, My, Mz) components. The faciolingual, mesiodistal, and inciso-occluso/apical axes of the teeth corresponded to the x, y, and z axes of the load cells, respectively. Each wire was removed and retested seven times. Three-way analysis of variance (ANOVA) examined the effects of wire type, wire size, and bracket type on the measured orthodontic load systems. Interactions among the three effects were examined and pair-wise comparisons between significant combinations were performed. Results: The force and moment components on each tooth were quantified according to their local coordinate axes. The three-way ANOVA interaction terms were significant for all force and moment measurements (P < .05), except for Fy (P > .05). Conclusion: The pretorqued wire generates a significantly larger incisor facial crown torquing moment in the MBT prescription compared to Roth, edgewise, and the straight NiTi wire.

OBJECTIVE: To test the effect of alcohol on force decay of elastomeric chains in vitro in order to determine if increasing alcohol concentrations results in an increased amount of elastomeric chain force decay. MATERIALS AND METHODS: A prospective laboratory study was completed to test the effect of alcohol exposure on orthodontic elastomeric chain. A total of 450 specimens were divided into five test groups. Two test groups were each exposed to different alcohol concentrations (14% and 26.9%) and the other two test groups were exposed to different commercially available mouth rinses (Cēpacol -14% alcohol and Listerine - 26.9% alcohol) for 60 seconds twice a day. The control group followed all of the same procedures but was only exposed to deionized (DI) water. Force measurements were taken at six time points (initial, 1 day, 7 days, 14 days, 21 days, and 28 days). RESULTS: There were no significant differences among groups at the initial time point (P = .52). Statistically significant effects of time on force decay were seen in all groups. All test groups showed significantly more force decay than the control group. Only a few statistically significant differences were observed when comparing force decay among the test groups. CONCLUSIONS: Alcohol causes an increase in force decay of elastomeric chain over time. A concentration dependence of alcohol on force decay of elastomeric chain was not observed.

Background/Objectives: This study investigated the biomechanical properties and bone-implant intersurface response of machined and laser surface-treated stainless steel (SS) mini-screw implants (MSIs). Material and Methods: Forty-eight 1.3mm in diameter and 6mm long SS MSIs were divided into two groups. The control (machined surface) group received no surface treatment; the laser-treated group received Nd-YAG laser surface treatment. Half in each group was used for examining surface roughness (Sa and Sq), surface texture, and facture resistance. The remaining MSIs were placed in the maxilla of six skeletally mature male beagle dogs in a randomized split-mouth design. A pair with the same surface treatment was placed on the same side and immediately loaded with 200g nickel–titanium coil springs for 8 weeks. After killing, the bone-implant contact (BIC) for each MSI was calculated using micro computed tomography. Analysis of variance model and two-sample t test were used for statistical analysis with a significance level of P

Introduction BoneCeramic (Straumann, Basel, Switzerland) can regenerate bone in alveolar defects after tooth extraction, but it is unknown whether it is feasible to move a tooth through BoneCeramic grafting sites. The objective of this study was to investigate 3-dimensional real-time root resorption and bone responses in grafted sites during orthodontic tooth movement. Methods Sixty 5-week-old rats were randomly assigned to 3 groups to receive BoneCeramic, natural bovine cancellous bone particles (Bio-Oss; Geistlich Pharma, Wolhusen, Switzerland), or no graft, after the extraction of the maxillary left first molar. After 4 weeks, the maxillary left second molar was moved into the extraction site for 28 days. Dynamic bone microstructures and root resorption were evaluated using in-vivo microcomputed tomography. Stress distribution and corresponding tissue responses were examined by the finite element method and histology. Mixed model analysis of variance was performed to compare the differences among time points with Bonferroni post-hoc tests at the significance level of P Results The BoneCeramic group had the least amount of tooth movement and root resorption volumes and craters, and the highest bone volume fraction, trabecular number, and mean trabecular thickness, followed by the Bio-Oss and the control groups. The highest stress accumulated in the cervical region of the mesial roots. Conclusions BoneCeramic has better osteoconductive potential and induces less root resorption compared with Bio-Oss grafting and naturally recovered extraction sites.

To validate whether applying a well-defined initial three-dimensional (3D) load can create consistently expected tooth movement in patients.Twenty-one patients who needed bilateral canine retraction to close extraction space were selected for this split-mouth clinical trial. After initial alignment and leveling, two canines in each patient were randomly assigned to receive either translation (TR) or controlled tipping (CT) load. The load was delivered by segmental T-loops designed to give specific initial moment/force ratios to the canines in each treatment interval (TI), verified with an orthodontic force tester. Maxillary dental casts were made before canine retraction and after each TI. The casts were digitized with a 3D laser scanner. The digital models were superimposed on the palatal rugae region. The 3D canine displacements and the displacement patterns in terms of TR, CT, and torque were calculated for each TI.The method can reliably detect a TR displacement greater than 0.3 mm and a rotation greater than 1.5°. Ninety-two TIs had displacements that were greater than 0.3 mm and were used for further analysis. Most displacements were oriented within ±45° from the distal direction. The displacement pattern in terms of TR or CT was not uniquely controlled by the initial moment/force ratio.The initial load system is not the only key factor controlling tooth movement. Using a segmental T-loop with a well-controlled load system, large variations in canine displacement can be expected clinically.

Introduction Midpalatal suture expansion could induce osteogenesis to correct maxillary insufficiency; cartilage formation could also be induced, and lower-magnitude forces might generate a preferable response pattern. In this study, we aimed for an enhanced understanding of the cartilage formatting effects of expansion. Methods Thirty 6-week-old male C57BL/6 mice were randomly and evenly assigned to 3 groups; the animals in each group received a sustained suture expansion at 0, 10, and 20 g, respectively. Ten additional mice were fed the same as the baseline controls and received no expansion. After 7 days, the animals were killed; coronal paraffin sections were stained using toluidine blue and safranin-O. The proliferating cell nucleus antigen, the nuclear antigen Ki-67, alkaline phosphatase, and matrix metalloproteinase 13 expressions were visualized with immunohistochemistry. All data were analyzed statistically, and the differences were considered significant at P Results Compared with the control, the cartilage matrix volume was significantly increased by the 20-g expansion, showing increased cartilage matrix and hypertrophic chondrocytes with the highest matrix metalloproteinase 13 expression. The 10-g expansion formed condensed proliferating chondrocyte masses, within which the highest percentages of proliferating cell nucleus antigen and Ki-67 positive cells were present. The 10-g and the 20-g expansions equally intensified the alkaline phosphatase expression. Conclusions The lower expansion (10 g) promoted chondrocyte proliferation and induced a more preferable suture cartilage response pattern compared with the higher expansion (20 g), which just increased the cartilage matrix production.

Objective: To observe the real-time microarchitecture changes of the alveolar bone and root resorption during orthodontic treatment. Materials and Methods: A 10 g force was delivered to move the maxillary left first molars mesially in twenty 10-week-old rats for 14 days. The first molar and adjacent alveolar bone were scanned using in vivo microcomputed tomography at the following time points: days 0, 3, 7, and 14. Microarchitecture parameters, including bone volume fraction, structure model index, trabecular thickness, trabecular number, and trabecular separation of alveolar bone, were measured on the compression and tension side. The total root volume was measured, and the resorption crater volume at each time point was calculated. Univariate repeated measures analysis of variance with Bonferroni corrections were performed to compare the differences in each parameter between time points with significance level at P < .05. Results: From day 3 to day 7, bone volume fraction, structure model index, trabecular thickness, and trabecular separation decreased significantly on the compression side, but the same parameters increased significantly on the tension side from day 7 to day 14. Root resorption volume of the mesial root increased significantly on day 7 of orthodontic loading. Conclusions: Real-time root and bone resorption during orthodontic movement can be observed in 3 dimensions using in vivo micro-CT. Alveolar bone resorption and root resorption were observed mostly in the apical third on day 7 on the compression side; bone formation was observed on day 14 on the tension side during orthodontic tooth movement.

Introduction Suture expansion stimulates bone growth to correct craniofacial deficiencies but has a high potential of treatment relapse. The objective of this study was to investigate whether there is a dose-dependent relationship between the recombinant human bone morphogenetic protein-2 (rhBMP-2) and bone formation during suture expansion. Methods Fifty 6-week-old male New Zealand white rabbits were randomly assigned to 5 groups to receive 0 (control), 0.01, 0.025, 0.1, or 0.4 mg/mL of rhBMP-2 delivered by absorbable collagen sponge placed over the interfrontal suture. The suture was expanded for 33 days by 200 g of constant force via a spring anchored with 2 miniscrew implants. Distance of suture expansion, suture volume, and cross-sectional area after expansion were measured using radiographs with bone markers and microcomputed tomography. Suture widths and mineralization appositional rates were calculated based on the widths between bone labels under an epifluorescent microscope. Software (Multilevel Win 2.0; University of Bristol, Bristol, United Kingdom) was used to model distance of suture expansion over time as polynomials to compare group differences. Wilcoxon signed rank tests were performed to compare the suture volume and cross-sectional area, mineral apposition rate, and suture width between groups. The significance level was set at P = 0.05. Results Whereas the sutures were expanded in all groups, sutures were expanded by significantly greater amounts in the control and the 0.01 mg/mL groups without fusing the sutures than in the 0.025, 0.1, and 0.4 mg/mL groups with fusing sutures. Compared with the controls, the 0.01 mg/mL group showed significantly lower suture volumes, cross-sectional areas, and suture widths after expansion. The mineral apposition rate was significantly higher in the 0.01 mg/mL group than in the controls from days 10 to 30. Conclusions The 0.01 mg/mL dose of rhBMP-2 delivered by absorbable collagen sponge can stimulate bone formation at the bony edges of the suture during suture expansion; however, higher concentrations cause suture fusion. With an appropriate concentration, rhBMP-2 might facilitate suture expansion for clinical uses.

Introduction Microdamage reduces bone mechanical properties and thus could contribute to implant failure. The objective of this study was to investigate whether the diameter of mini-implants affects linear microcrack generation and whether this differs between the mandible and the maxilla because of their contrasting cortical thicknesses. Methods Maxillary and mandibular quadrants of 5 dogs were randomly assigned to receive, in situ, no pilot drilling or mini-implant insertion (control), pilot drilling only without mini-implants, or pilot drilling plus a mini-implant of 1 of 3 diameters: 1.4 mm (n = 18), 1.6 mm (n = 18), and 2.0 mm (n = 18). Linear microcracks were assessed on basic fuchsin-stained sections by using epifluorescence microscopy. Results Pilot drilling without mini-implant insertion produced significantly higher linear microcrack burdens in the mandible compared with the maxilla. In the both the mandible and the maxilla, all implants produced higher linear microcrack burdens than did the controls, yet there were no differences between the 3 implant diameters. Conclusions Neither the diameter of the mini-implant nor the site of insertion (mandible vs maxilla) had a significant effect on the amount of linear microdamage adjacent to the implant when the implants were inserted after pilot drilling in situ.

Suture compression is a widely used approach to inhibit maxillary growth; however, biological responses in sutures to compressive force are still unclear. The objective of this pilot study was to investigate the matrix metalloproteinase (MMP) expression and osteoclast activities during the midpalatal suture compression.56 six-week old male C57BL/6 mice were randomly assigned to the control and compression groups. The mice in the compression and control groups received helix springs bonded to the maxillary molars delivering initial compressive forces of 0.20 and 0N (no activation), respectively. On Days 1, 4, 7 and 14, animals were sacrificed and scanned using micro-computed tomography to quantify suture width and bone mineral density. Serial histological sections were stained with HE, TRAP, and immunohistochemistry to observe changes in bone resorption, osteoclast activities, and MMP-1, 8, and 13 expressions. Bone volume/total volume (Bv/Tv) ratio, osteoclast count, osteoclast covering area, and MMP expression intensity were measured. The Mann-Whitney and the Kruskal-Wallis tests with Bonferroni post-hoc corrections were performed to compare differences between groups and between time points in the same group at significant level of P0.05.Compared to the control, suture width in the compression group was significantly reduced on Day 1, but continuously widened with reduced bone mineral density afterwards. With MMP-1 and -13 evidently intensified expressions, osteoclast number and activities significantly increased, leading to reduced Bv/Tv ratio and progressive bone resorption from Days 4 to 14.Suture compression elevated the MMP-1 and 13 expressions, activated osteoclasts, reduced bone density, and induced bone resorption adjacent to the suture. It suggests that suture compression can be used for bone volume reduction.

While both intermittent and continuous forces are commonly used to expand sutures, it remains unclear which force is most effective. Using nickel-titanium (NiTi) open coil springs (50 g) and 3 mm long miniscrew implants (MSIs) for skeletal anchorage, intermittent and continuous forces were used to expand the midsagittal sutures in 18 New Zealand white juvenile male rabbits, 11 weeks of age, for 29 days. In the intermittent group, expansion forces of 50 g were delivered for 5 days (on) and paused for 1 day (off); the on/off cycles were repeated five times. Expansion forces of 50 g were delivered for 29 consecutive days in the continuous group. Longitudinal biometric and histomorphometric analyses were performed to evaluate sutural separation and bone formation using implanted tantalum bone markers and fluorescent bone labelling, respectively. Multilevel modelling procedures were undertaken to compare the groups and time intervals. Continuous forces produced significantly greater overall sutural separation (1.3 mm) than intermittent forces (0.8 mm). Although they were delivered over a period of time 86 per cent as long, intermittent forces produced only 61 per cent of the sutural separation of continuous forces. Between days 7 and 17, continuous forces resulted in significantly greater mineral apposition and bone formation rates than intermittent forces. Intermittent forces produced approximately 59 per cent as much mineral apposition and 61 per cent as much bone formation as continuous forces. Due to greater sutural separation and bone formation, continuous forces provide a more effective approach for separating sutures than intermittent forces.

Introduction The purpose of this study was to establish the causal relationships between expansion force magnitudes, sutural separation, and sutural bone formation. Methods Thirty-seven 6-week-old rabbits were randomly assigned to 4 force groups (0, 50, 100, or 200 g). Constant forces were delivered for 42 days by nickel-titanium open-coil springs to miniscrew implants (MSIs) placed in the frontal bone on both sides of the midsagittal suture. Inter-MSI and bone marker widths were measured biweekly to quantify sutural separation and MSI movements. Sutural bone formation was quantified based on the incorporation of fluorescent bone labels administered at days 18, 28, and 38. Results Nine of 74 MSIs failed between days 0 and 14, including 4 in the controls and 5 in the 50-g group. A decelerating curvilinear pattern of sutural separation was evident in the 50-g, 100-g, 200-g groups. Bone markers showed that sutural widths increased by 0.6, 3.2, 5.1, and 6.2 mm in the control, 50-g, 100-g, and 200-g groups, respectively. Except for the 200-g group, significantly greater amounts of bone formation were observed between days 18 and 28 than between days 28 and 38. Sutural bone formation also increased with increasing forces up to 100 g; there was no difference between the 100-g and the 200-g groups. Sutural separation explained 71% and 53% of the variations in bone formation between days 18 and 28 and days 28 and 38, respectively. Conclusions Within the limits of this study, sutural bone formation is directly related to the amount of sutural separation, which is in turn related to the amount of force applied. The results suggest that there is a level of induced sutural separation that provides the greatest amount of bone formation.

Introduction The goal of this study was to evaluate whether human recombinant bone morphogenetic protein-2 (rhBMP-2) enhances sutural bone formation or causes premature sutural fusion. Methods Thirty 6-week-old rabbits underwent midsagittal sutural expansion. The animals were randomly assigned to receive 0 (control), 0.1 mg per milliliter, or 0.4 mg per milliliter of rhBMP-2, delivered by an absorbable collagen sponge placed over the suture. A 100-g constant force was delivered for 33 days by using a nickel-titanium spring to expand the suture between 2 miniscrew implants anchored in the frontal bone. At days 10, 20, and 30, sutural separation was evaluated and modeled over time as polynomials by using multilevel statistical procedures. Bone formation and sutural gaps were analyzed histomorphometrically between days 10 and 20 and days 20 and 30. Results The control group showed significantly greater overall sutural bone formation than did the 2 rhBMP-2 groups. Over time, bone formation decreased significantly in all groups. Between days 10 and 20, the 0.4 mg per milliliter group produced significantly more (58%) bone than did the 0.1 mg per milliliter group; there were no significant differences in bone formation between the 2 experimental groups between days 20 and 30. Both 0.1 and 0.4 mg per milliliter of rhBMP-2 in the absorbable collagen sponge caused premature fusion by forming a bony bridge connecting the ectocranial aspect of the sutural margins. Premature fusion significantly reduced sutural separation between 10 and 30 days (to 56% and 62% of control values for the 0.1 and 0.4 mg per milliliter groups, respectively). There were no significant differences in sutural separation between the 0.1 and 0.4 mg per milliliter groups. Conclusions Compared with the 0.1 mg per milliliter group, 0.4 mg per milliliter of rhBMP-2 accelerated sutural bone formation between days 10 and 20. After 10 to 20 days, rhBMP-2 in the absorbable collagen sponge caused premature sutural fusion, despite the constant expansion forces.

Introduction The goal of this study was to evaluate whether human recombinant bone morphogenetic protein-2 (rhBMP-2) enhances sutural bone formation or causes premature sutural fusion. Methods Thirty 6-week-old rabbits underwent midsagittal sutural expansion. The animals were randomly assigned to receive 0 (control), 0.1 mg per milliliter, or 0.4 mg per milliliter of rhBMP-2, delivered by an absorbable collagen sponge placed over the suture. A 100-g constant force was delivered for 33 days by using a nickel-titanium spring to expand the suture between 2 miniscrew implants anchored in the frontal bone. At days 10, 20, and 30, sutural separation was evaluated and modeled over time as polynomials by using multilevel statistical procedures. Bone formation and sutural gaps were analyzed histomorphometrically between days 10 and 20 and days 20 and 30. Results The control group showed significantly greater overall sutural bone formation than did the 2 rhBMP-2 groups. Over time, bone formation decreased significantly in all groups. Between days 10 and 20, the 0.4 mg per milliliter group produced significantly more (58%) bone than did the 0.1 mg per milliliter group; there were no significant differences in bone formation between the 2 experimental groups between days 20 and 30. Both 0.1 and 0.4 mg per milliliter of rhBMP-2 in the absorbable collagen sponge caused premature fusion by forming a bony bridge connecting the ectocranial aspect of the sutural margins. Premature fusion significantly reduced sutural separation between 10 and 30 days (to 56% and 62% of control values for the 0.1 and 0.4 mg per milliliter groups, respectively). There were no significant differences in sutural separation between the 0.1 and 0.4 mg per milliliter groups. Conclusions Compared with the 0.1 mg per milliliter group, 0.4 mg per milliliter of rhBMP-2 accelerated sutural bone formation between days 10 and 20. After 10 to 20 days, rhBMP-2 in the absorbable collagen sponge caused premature sutural fusion, despite the constant expansion forces.