Effect of post–orthognathic surgery condylar axis changes on condylar morphology as determined by 3-dimensional surface reconstruction

Objective: To evaluate the effect of postoperative condylar axis changes on mandibular condylar remodeling by comparing the condylar head in three-dimensional (3D) surface reconstructions before and after surgery in skeletal Class III deformities (one-jaw [mandibular setback] or two-jaw surgery), and also to determine the relationship between condylar inward rotation and condylar surface remodeling after orthognathic surgery.Materials and Methods:A retrospective analysis was conducted of 30 patients with skeletal Class III deformities who had received orthognathic surgery. Group 1 underwent one-jaw surgery (10 men, five women, age 22.4 ± 3.3 years), and group 2 underwent two-jaw surgery (10 men, five women, age 22.3 ± 2.2 years). Sixty condyles were reconstructed and superimposed pre- and postoperatively to compare the changes of condylar surfaces. The relation between the condylar axis change and the surface change using the Pearson correlation were investigated from the 3D image software.Results:Condylar surface changes before and after the surgery were significant. The postoperative inward rotation of the condyles was correlated with the average absolute deviation of the condyles, regardless of the surgery type (one- or 2-jaw surgery; r  =  .70, P < .05).Conclusion:After orthognathic surgery, condylar surface changes occurred, and condylar inward rotation was closely related to changes of condylar surface.     

Maxillary incisor inclination of skeletal Class III patients treated with extraction of the upper first premolars and two-jaw surgery: Conventional orthognathic surgery vs surgery-first approach

Objective:To investigate the differences in the amount and pattern of the maxillary incisor (MXI) inclination change in skeletal Class III patients treated with extraction of the maxillary first premolars (MXP1) and two-jaw surgery (TJS) between conventional orthognathic surgery (COS) and surgery-first approach (SFA).Materials and Methods:The study included 60 skeletal Class III patients who had normal maxillary position, prognathic mandible, and mild crowding in the maxillary arch (≤4 mm). The patients were divided into group 1 (COS, n  =  36) and group 2 (SFA, n  =  24). Lateral cephalograms were taken before treatment (T0), 1 month before surgery (T1), within 1 month after surgery (T2), and after debonding (T3) for COS patients and at T0, T2, and T3 for SFA patients. After measurement of the skeletodental variables, statistical analyses were performed.Results:During T0–T2, the amount of MXI inclination change (ΔU1-SN) in group 1 was significantly larger than that in group 2 (−12.8° vs −4.4°; P < .001). During T2–T3, ΔU1-SN in groups 1 and 2 occurred in opposite directions (3.8° vs −5.9°; P < .001). However, the total amount of ΔU1-SN during T0–T3 was not different between groups 1 and 2 (−9.0° vs −10.3°). At T3 the U1-SN values for groups 1 and 2, respectively, moved closer to normal according to the values of the normal range rate (all 83%), relative percentage ratio (102.4% and 100.1%), and achievement ratio (77.7% and 97.8%).Conclusions:The results of this study might provide basic data for predicting the amount and pattern of MXI inclination change in SFA for skeletal Class III TJS patients.     

Evaluation of canting correction of the maxillary transverse occlusal plane and change of the lip canting in Class III two-jaw orthognathic surgery

Objective:To compare the effect of canting correction in anterior maxillary transverse occlusal planes (AMTOP) and posterior maxillary transverse occlusal planes (PMTOP) on the change of lip canting (LC) in two-jaw surgery (TJS) cases.Materials and Methods:The samples consisted of eight young adult patients (three males and five females, mean age  =  24.1 ± 4.5 years) who had skeletal Class III malocclusion (CIII), facial asymmetry (FA), and LC and who underwent TJS. Two-dimensional lateral and posteroanterior cephalograms and three-dimensional facial scanning taken 1 week before (T1) and 6 months after TJS (T2) were combined using the Morpheus 3D program. Six linear and angular variables were measured and statistically analyzed.Results:When comparing the values of the linear and angular variables at the T1 and T2 stages there was significant canting correction of AMTOP (1.7 mm vs −0.3 mm; 3.0° vs 0.1°), PMTOP (3.5 mm vs 0.1 mm, 3.3° vs −0.1°), and LC (3.0 mm vs 0.7 mm, 4.7° vs 2.1°) (all P < .05). Although the angular change ratios (ΔLC/ΔAMTOP and ΔLC/ΔPMTOP) did not exhibit a significant difference (0.99 vs 0.83), the linear change ratio of ΔLC/ΔAMTOP was significantly higher than that of ΔLC/ΔPMTOP (1.67 vs 0.74, P < .05). The angular change of ΔLC showed a significant correlation with ΔAMTOP (r²  =  0.64; P < .05). However, the linear change of ΔLC was significantly correlated with both the angular and linear changes of ΔAMTOP (r²  =  0.62 and 0.66; both P < .05). Therefore, the amount of LC change was more related to the canting correction of AMTOP than to that of PMTOP.Conclusion:In TJS cases with CIII, FA, and LC, the amount of canting correction of the AMTOP should be considered to predict the actual LC change.     

Influence of unilateral maxillary first molar extraction treatment on second and third molar inclination in Class II subdivision patients

Objective:To assess the maxillary second molar (M2) and third molar (M3) inclination following orthodontic treatment of Class II subdivision malocclusion with unilateral maxillary first molar (M1) extraction.Materials and Methods:Panoramic radiographs of 21 Class II subdivision adolescents (eight boys, 13 girls; mean age, 12.8 years; standard deviation, 1.7 years) before treatment, after treatment with extraction of one maxillary first molar and Begg appliances and after at least 1.8 years in retention were retrospectively collected from a private practice. M2 and M3 inclination angles (M2/ITP, M2/IOP, M3/ITP, M3/IOP), constructed by intertuberosity (ITP) and interorbital planes (IOP), were calculated for the extracted and nonextracted segments. Random effects regression analysis was performed to evaluate the effect on the molar angulation of extraction, time, and gender after adjusting for baseline measurements.Results:Time and extraction status were significant predictors for M2 angulation. M2/ITP and M2/IOP decreased by 4.04 (95% confidence interval [CI]: −6.93, 1.16; P  =  .001) and 3.67 (95% CI: −6.76, −0.58; P  =  .020) in the extraction group compared to the nonextraction group after adjusting for time and gender. The adjusted analysis showed that extraction was the only predictor for M3 angulation that reached statistical significance. M3 mesial inclination increased by 7.38° (95% CI: −11.2, −3.54; P < .001) and 7.33° (95% CI: −11.48, −3.19; P  =  .001).Conclusions:M2 and M3 uprighting significantly improved in the extraction side after orthodontic treatment with unilateral maxillary M1 extraction. There was a significant increase in mesial tipping of maxillary second molar crowns over time.     

The short-term treatment effects of face mask therapy in Class III patients based on the anchorage device: Miniplates vs rapid maxillary expansion

Objective:To compare the short-term treatment effects of face mask therapy with miniplates (FM-MP) and face mask therapy with rapid maxillary expansion appliance (FM-RME) in growing Class III malocclusion patients with maxillary hypoplasia.Materials and Methods:Twenty patients were allocated into two groups according to the anchorage device: FM-MP group (n  =  10; mean age  =  11.2 ± 1.2 years; miniplates in the zygomatic buttress area) and FM-RME group (n  =  10; mean age  =  10.7 ± 1.3 years; bonded or banded RME). The face mask was applied for 12 to 14 hours/day in both groups with a force of 400 g/side directed 30° downward and forward from the occlusal plane. Lateral cephalograms were taken before (T1) and after FM-MP or FM-RME therapy (T2). Skeletodental and soft-tissue variables were measured. Paired and independent t-tests were performed for statistical analysis.Results:Both groups exhibited significant forward movement of point A and posterior repositioning and opening rotation of the mandible from T2 to T1. The FM-MP group showed significant protraction of orbitale (ΔSNO), and the FM-RME group showed a decrease in overbite and an increase in Björk sum. Comparing the amount of changes between the two groups, the FM-MP group displayed greater forward movement of the maxilla than the FM-RME group (ΔSNA, ΔA to N perp, all P < .05). However, the FM-RME group exhibited a greater opening rotation of the mandible (ΔSNB, Björk sum, all P < .01; ΔPog to N-perp, P < .05) and labioversion of the maxillary incisors (ΔU1-FH, P < .05).Conclusion:FM-MP therapy induces a greater advancement of the maxilla, less posterior repositioning and opening rotation of the mandible, and less proclination of the maxillary incisors than FM-RME therapy.     

Asymmetric rapid maxillary expansion in true unilateral crossbite malocclusion: A prospective controlled clinical study

Objective:To investigate the short-term effects of the asymmetric rapid maxillary (ARME) appliance on the vertical, sagittal, and transverse planes in patients with true unilateral posterior crossbite.Materials and Methods:Subjects were divided into two groups. The treatment group was comprised of 21 patients with unilateral posterior crossbite (mean age  =  13.3 ± 2.1 years). Members of this group were treated with the ARME appliance. The control group was comprised of 17 patients with Angle Class I who were kept under observation (mean age  =  12.3 ± 0.8 years). Lateral and frontal cephalograms were taken before the expansion (T1), immediately after expansion (T2), and at postexpansion retention (T3) in the treatment group and at preobservation (T1) and postobservation (T2) in the control group. A total of 34 measurements were assessed on cephalograms. For statistical analysis, the Wilcoxon test and analysis of covariance were used.Results:The ARME appliance produced significant increases in nasal, maxillary base, upper arch, and lower arch dimensions (P < .01) and a clockwise rotation of the occlusal plane (P  =  .001).Conclusion:The ARME appliance created asymmetric increments in the transversal dimensions of the nose, maxilla, and upper arch in the short term. Asymmetric expansion therapy for subjects with unilateral maxillary deficiency may provide satisfactory outcomes in adolescents, with the exception of mandibular arch expansion. The triangular pattern of expansion caused clockwise rotation of the mandible and the occlusal plane and produced significant alterations in the vertical facial dimensions, whereas it created no displacement in maxilla in the sagittal plane.     

A prospective controlled evaluation of Class II division 1 malocclusions treated with fixed lingual mandibular growth modificator

Objective: To assess the net dentofacial effects of the fixed lingual mandibular growth modificator (FLMGM).Materials and Methods:The study sample comprised 38 patients with Class II/1 malocclusion and retrognathic mandible. All were in the pubertal growth spurt. Whereas FLMGM was applied to the treatment group (n  =  21, mean age  =  13.2 years), no treatment was performed on the control group (n  =  17, mean age  =  12.5 years). Skeletal and dentoalveolar changes were assessed on digital lateral cephalograms obtained at the beginning and end of the treatment/observation period of 8 months. Paired and independent t-tests were used to assess the differences within and between groups.Results:Maxillary growth was not affected by FLMGM treatment, which resulted in a significant overjet reduction of 4.1 mm, an increase in total mandibular length (Co-Gn) of 2.3 mm, chin advancement of 1.6°, and upper incisor retroclination of 4.0°. A reduction of 2.4° in ANB was largely due to an increase of 1.8° in SNB. Favorably, the lower incisors were obviously retroclined by 4.5°. The changes in the vertical skeletal relationships were negligible.Conclusion:FLMGM was effective in treating growing Class II/1 patients and produced favorable dentofacial effects, with the matched untreated sample showing minimal changes. Lower incisor retroclination was a benefit of FLMGM treatment.     

Evaluation of mandibular volume classified by vertical skeletal dimensions with cone-beam computed tomography

Objective:To investigate the relationship between anteroposterior and vertical differences in maxillofacial morphology and mandibular volume.Materials and Methods:Subjects comprised 213 Japanese adults (84 males and 129 females) who were divided into three groups based on mandibular basal arch (ANB) and Wits, measured in a cephalometric analysis: Class I (−1° ≤ ANB < 4°,−1 mm ≤ Wits < 0 mm), Class II (ANB ≥ 4°, Wits ≥ 0), and Class III (ANB <−1°, Wits <−1 mm). Subjects were also divided into three groups based on the mandibular plane angle (Mp), as follows: hypodivergent (Mp < 23°), normodivergent (Mp  =  23–30°), and hyperdivergent (Mp > 30°) groups. Mandibular volume was measured from cone-beam computed tomographic images that were analyzed using Analyze™ image processing software and compared among the three groups in each classification.Results:No significant differences were noted in mandibular volume among Classes I, II, and III. An inverse relationship was found between mandibular volume and Mp, and a significant difference was noted in mandibular volume between the hypodivergent and hyperdivergent groups.Conclusions:In addition to two-dimensional analysis, such as lateral cephalometry, three-dimensional information such as volume, provided by cone-beam computed tomography, contributes to a more detailed assessment of maxillofacial morphology.     

Cephalometric Characteristics of Korean Children with Class III Malocclusion in the Deciduous Dentition

Objective:To compare the cephalometric characteristics of children with Class III malocclusion to those of children with normal occlusion during the deciduous dentition phase.Materials and Methods:Cephalometric measurements of 27 children (mean age: 5.03 years) diagnosed with Class III malocclusion were compared with 32 children (mean age: 4.85 years) diagnosed with normal occlusion in the following four categories: sagittal skeletal analysis, vertical skeletal analysis, dentoalveolar analysis, and soft tissue analysis.Results:Significant differences were seen in all categories except vertical skeletal analysis. Sagittal skeletal measurements included ANB (Class III group: −0.91 ± 1.60; normal group: 5.28 ± 1.29), facial convexity (Class III group: 0.47 ± 4.32; normal group: 13.65 ± 3.44), Wits appraisal (Class III group: −5.54 ± 2.36; normal group: −0.84 ± 1.91), and A to N-perpendicular (Class III group: −2.94 ± 3.05; normal group: 0.78 ± 2.53). Dentoalveolar measurements included U1 to NA (Class III group: 11.98 ± 5.25; normal group: 8.12 ± 5.43), IMPA (Class III group: 81.34 ± 7.40; normal group: 86.57 ± 5.67), and interincisal angle (Class III group: 152.65 ± 8.82; normal group: 145.03 ± 7.34). Soft tissue measurements included soft tissue convexity (Class III group: 2.47 ± 4.20; normal group: 12.71 ± 3.95), nasofacial angle (Class III group: 22.68 ± 4.22; normal group: 26.24 ± 3.84), and upper lip to esthetic plane (Class III group: −0.65 ± 2.74; normal group: 3.07 ± 1.90).Conclusions: There are significant differences between the craniofacial patterns of normal children and those of children with Class III malocclusion that can be identified with cephalometric analysis as early as the deciduous dentition phase.     

Long-term evaluation of Class II subdivision treatment with unilateral maxillary first molar extraction

Objective:To evaluate the long-term effects of asymmetrical maxillary first molar (M1) extraction in Class II subdivision treatment.Materials and Methods:Records of 20 Class II subdivision whites (7 boys, 13 girls; mean age, 13.0 years; SD, 1.7 years) consecutively treated with the Begg technique and M1 extraction, and 15 untreated asymmetrical Class II adolescents (4 boys, 11 girls; mean age, 12.2 years; SD, 1.3 years) were examined in this study. Cephalometric analysis and PAR assessment were carried out before treatment (T1), after treatment (T2), and on average 2.5 years posttreatment (T3) for the treatment group, and at similar time points and average follow-up of 1.8 years for the controls.Results:The adjusted analysis indicated that the maxillary incisors were 2.3 mm more retracted in relation to A-Pog between T1 and T3 (β  =  2.31; 95% CI; 0.76, 3.87), whereas the mandibular incisors were 1.3 mm more protracted (β  =  1.34; 95% CI; 0.09, 2.59), and 5.9° more proclined to the mandibular plane (β  =  5.92; 95% CI; 1.43, 10.41) compared with controls. The lower lip appeared 1.4 mm more protrusive relative to the subnasale-soft tissue-Pog line throughout the observation period in the treated adolescents (β  =  1.43; 95% CI; 0.18, 2.67). There was a significant PAR score reduction over the entire follow-up period in the molar extraction group (β  =  −6.73; 95% CI; −10.7, −2.7). At T2, 65% of the subjects had maxillary midlines perfectly aligned with the face.Conclusions:Unilateral M1 extraction in asymmetrical Class II cases may lead to favorable occlusal outcomes in the long term without harming the midline esthetics and soft tissue profile.     

Measurement of mini-implant stability using resonance frequency analysis

Objective:To investigate whether resonance frequency analysis (RFA) is suitable to measure orthodontic mini-implant stability. Implant size significantly affects the level of resonance frequency. Regarding the operating mode of RFA, it has to be proven whether the resonance frequency of mini-implants in bone fits the range of frequency emitted by the Osstell ISQ device.Material and Methods:For this purpose the SmartPegs in the Osstell ISQ device were modified to fit with the inner screw thread of orthodontic mini-implants, and 110 mini-implants were inserted into porcine pelvic bone. RFA was performed parallel and perpendicular to the run of superficial bone fibers. A suitability test, Periotest, was also performed in the same directions. Compacta thickness was measured using cone-beam computed tomography. Correlation tests and linear regression analysis were carried out between the three methods.Results:The RFA showed a mean Implant Stability Quotient value of 36.36 ± 2.67, and the Periotest mean value was −2.10 ± 1.17. The differences between the two directions of measurement were statistically significant (P > .001) for RFA and the Periotest. There was a high correlation between RFA and the Periotest (r  =  −0.90) and between RFA and compacta thickness (r  =  0.71). The comparison between the Periotest and compacta thickness showed a correlation coefficient of r  =  −0.64.Conclusion:The present results suggest that RFA is feasible as a measurement method for orthodontic mini-implant stability. As a consequence, it could be used for clinical evaluation of current stability and allow stability-related loading of mini-implants to reduce the failure rate.     

Comparison of pharyngeal airway volume among different vertical skeletal patterns: A cone-beam computed tomography study

Objective:To test the null hypothesis that there are no significant differences in pharyngeal airway volumes among adult patients with different vertical skeletal patterns and a clinically normal sagittal skeletal pattern using cone-beam computed tomography (CBCT).Material and Methods:The study sample consisted of 100 adult patients (45 men and 55 women; mean age  =  24.0 ± 5.3 years) with a normal sagittal skeletal pattern divided into three groups according to the vertical skeletal patterns: high angle (32 patients: 15 women and 17 men), low angle (34 patients: 14 women and 20 men), and normal angle (34 patients: 16 women and 18 men) groups. Nasopharyngeal, oropharyngeal, and total airway volumes of patients in all vertical groups were calculated. Group differences were analyzed using one-way analysis of variance and post hoc Tukey tests.Results:Nasopharyngeal airway volume in the high-angle group (mean  =  6067.9 ± 1693.9 mm³) was significantly lower than that of the low- and normal-angle groups (P < .01). Oropharyngeal airway volume was highest in the low-angle group (mean  =  15,957.6 ± 6817.2 mm³) and significantly decreased in the control (mean  =  11,826.1 ± 4831.9 mm³; P  =  .008) and high angle (mean  =  10,869.1 ± 4084.1 mm³; P  =  .001) groups. Total airway volume was highest in the low-angle group (mean  =  24,261.6 ± 8470.1 mm³) and lowest in the high-angle group (mean  =  16,937.0 ± 5027.4 mm³; P < .001).Conclusion:The null hypothesis was rejected. Significant differences were found in pharyngeal airway volumes among different skeletal vertical patterns.     

Maxillary anterior alignment stability in Class I and Class II malocclusions treated with or without extraction

Objective:To compare the postretention stability of maxillary incisors alignment in subjects with Class I and II malocclusion treated with or without extractions.Materials and Methods:The sample comprised 103 subjects with initial maxillary anterior irregularity greater than 3 mm and was divided into four groups: group 1 comprised 19 patients with Class I malocclusion treated with nonextraction (mean initial age = 13.06 years); group 2 comprised 19 patients with Class II malocclusion treated with nonextraction (mean initial age = 12.54 years); group 3 comprised 30 patients with Class I malocclusion treated with extractions (mean initial age = 13.16 years); group 4 comprised 35 patients with Class II malocclusion treated with extractions (mean initial age = 12.99 years). Dental casts were obtained at three different stages: pretreatment (T1), posttreatment (T2), and long-term posttreatment (T3). Maxillary incisor irregularity and arch dimensions were evaluated. Intergroup comparisons were performed by one-way analysis of variance followed by Tukey tests.Results:In the long-term posttreatment period, relapse of maxillary crowding and arch dimensions was similar in all groups.Conclusion:Changes in maxillary anterior alignment in Class I and Class II malocclusions treated with nonextractions and with extractions were similar in the long-term posttreatment period.     

Response of the maxillary dentition to a statically determinate one-couple system with tip-back mechanics: A prospective clinical trial

Objective:To quantify the effects of tip-back mechanics on the maxillary first molars and incisors.Materials and Methods:Sixteen subjects with Class II end-on malocclusion were treated with an intrusion arch to achieve distalization of the maxillary molar through tip-back mechanics. Lateral cephalograms were taken prior to molar tip-back (T1), after molar tip-back (T2), and after molar root uprighting (T3). Data were analyzed using the Friedman’s and Wilcoxon signed rank tests to evaluate differences in time points (P ≤ .016).Results:The maxillary first molar distalized 1.53 mm (P = .001) with 6.65° (P = .001) of distal tipping and 0.86 mm (P = .001) of extrusion at T2. Minor relapse of the first molar (mesial direction) was seen at T3. The maxillary incisors flared labially 0.4 mm, and the incisor root apex moved palatally 1.19 mm (P = .005) at T2. At T3, the incisor root apex moved palatally 1.5 mm (P = .003) from T1. An angular change from T1 of 3.31° (P = .008) and 3.53° (P = .014) was seen at T2 and T3, respectively, as a result of palatal root movement of the maxillary incisors.Conclusions:A significant amount of distalization of maxillary molars was attained at the crown level with tip-back mechanics. Palatal root angulation change was significant in the incisors with minimal anteroposterior movement of the incisal edge.     

Analysis of smile esthetics in American Board of Orthodontic patients

Objective:To investigate the common denominators of an esthetically pleasing smile in patients who were considered to be successfully treated upon the submission to American Board Orthodontics (ABO) clinical examination.Material and Methods:A total of 462 patients were examined. Ninety subjects that fulfilled the inclusion criteria were included. Standardized digital smile photographs of the subjects were rated by 30 panel members, including orthodontists, general dentists, and parents of orthodontic patients, using a numeric version of the visual analog scale. Three groups were formed using the mean esthetic score ± standard deviation range: unattractive (n  =  21), average (n  =  47), and attractive (n  =  22) smiles. Eleven smile characteristics were digitally measured on the photographs and compared between the groups using one-way analysis of variance and χ² tests. Additionally, regression analyses were used to investigate the association of the smile characteristics with the esthetic score.Results:A significant difference was found between the three groups for the comparison of smile arc relationship (P < .001). When all the variables used in this study were entered in the regression analysis, a positive association was found (r  =  0.658; r²  =  0.434; P < .001). Additionally, two models were defined using stepwise regression. The first model included the smile arc (r  =  0.478; r²  =  0.228; P < .001), and the second model had both the smile arc and right gingival display/visible dentition display ratio (r  =  0.567; r²  =  0.321; P < .001).Conclusions:A harmonious smile arc relationship and less gingival display during a smile are significantly associated with smile attractiveness in patients considered successfully treated according to ABO standards.     

Comparisons of soft tissue chin thickness in adult patients with various mandibular divergence patterns

Objective:To evaluate the association between soft tissue at the chin (STC) thickness and mandibular divergence.Materials and Methods:Nongrowing patients seeking orthodontic treatment (n  =  190; 113 women and 77 men), who had an average age of 26.94 years (range  =  18.10–53.50 years), were stratified in four subgroups based on cephalometric mandibular plane inclination to anterior cranial base (MP/SN): low  =  MP/SN ≤ 27° (n  =  48); medium-low  =  27° < MP/SN ≤ 32° (n  =  60); medium-high  =  32° < MP/SN < 37° (n  =  37); and high  =  MP/SN ≥ 37° (n  =  45). The STC thicknesses were measured at pogonion (Pog), gnathion (Gn), and menton (Me). Group differences were evaluated with two-way analysis of variance and Student''s t-test. The Pearson product moment correlation gauged associations between parameters.Results:The STC values were greater in men than women (P < .02) and were smaller in the high group (7.47 ± 2.42 mm) than in all other groups at Gn (mean values  =  9.00 mm < STC < 9.58 mm; P < .001) and at Me (high group  =  6.30 ± 1.89 mm; other groups  =  7.15 mm < STC< 7.57 mm; P  =  .011).Conclusion:The STC is thinner at Gn and Me in hyperdivergent facial patterns, apparently in contrast to Pog. This differential thickness warrants focused research as it implies that it is possible (1) to vertically grow hard tissues impinging on the inferior soft tissue envelope in patients with severe hyperdivergence and (2) to plan for genioplasty in such patients when more advancement of the chin might be needed to compensate for the increased vertical height.     

Mini-implant stability at the initial healing period: A clinical pilot study

Objective:To evaluate the changes of mini-implant stability over the initial healing period in humans.Material and Methods:A sample of 19 consecutively treated patients (mean age 15.5 ± 7.3 years) was examined. In each patient, a mini-implant of a size of 2 × 9 mm was inserted into the anterior palate. Implant stability was assessed using resonance frequency analysis (RFA) immediately after insertion (T0), 2 weeks later (T1), 4 weeks later (T2), and 6 weeks later (T3). Insertion depth (ID) and the maximum insertion torque (IT) were measured. Data were tested for correlations between RFA, ID, and IT. All RFA values were tested for statistically significant differences between the different times.Results:The mean ID was 7.5 ± 0.6 mm, and the mean IT was 16.8 ± 0.6 Ncm. A correlation was found between RFA and ID (r  =  .726, P < .0001), whereas no correlations between RFA and IT or between IT and ID were observed. From T0 to T1, the stability (36.1 ± 6.1 implant stability quotient [ISQ]) decreased nonsignificantly by 4.9 ± 6.1 ISQ values (P > .05). Between T1 and T2, the stability decreased highly significantly (P < .001) by 7.9 ± 5.9 ISQ values. From T2 on, RFA remained nearly unchanged (−1.7 ± 3.5 ISQ; P > .05).Conclusions:Mini-implant stability is subject to changes during the healing process. During weeks 3 and 4, a significant decrease of the stability was observed. After 4 weeks, the stability did not change significantly.