Accuracy of a cone beam computed tomography–guided surgical stent for orthodontic mini-implant placement

Objective:To validate the accuracy of a cone-beam computed tomography (CBCT)–guided surgical stent for orthodontic mini-implant (OMI) placement by quantitatively evaluating the difference between CBCT-prescribed and actual position of mini-implants in preoperative and postoperative CBCT images.Materials and Methods:A surgical stent was fabricated using Teflon-Perfluoroalkoxy, which has appropriate biological x-ray attenuation properties. Polyvinylsiloxane impression material was used to secure the custom-made surgical stent onto swine mandibles. CBCT scanning was done with the stent in place to virtually plan mini-implants using a three-dimensional (3D) software program. An appropriate insertion point was determined using 3D reconstruction data, and the vertical and horizontal angulations were determined using four prescribed angles. A custom-designed surveyor was used to drill a guide hole within the surgical stent as prescribed on the CBCT images for insertion of 32 OMIs. The mandibles with a surgical stent in place were rescanned with CBCT to measure the deviations between the virtual planning data and surgical results.Results:The difference between the prescribed and actual vertical angle was 1.01 ± 7.25, and the horizontal difference was 1.16 ± 6.08. The correlation coefficient confirms that there was no intrarater variability in either the horizontal (R  =  .97) or vertical (R  =  .74) vectors.Conclusions:The surgical stent in this study guides mini-implants to the prescribed position as planned in CBCT. Since the statistical difference was not significant, the surgical stent can be considered to be an accurate guide tool for mini-implant placement in clinical use.     

Fracture resistance of commonly used self-drilling orthodontic mini-implants

Objective:To investigate the fracture resistance of six commonly used self-drilling orthodontic mini-implants by comparing their respective fracture torques during insertion.Materials and Methods:Ninety self-drilling mini-implants from six manufacturers (Aarhus, Dual-Top, OrthoEasy, Tomas-pin, Unitek, and VectorTAS), with diameters ranging from 1.4 to 1.8 mm, were inserted into acrylic blocks using a custom-made insertion device. Insertion torques were measured using a 6-degree-of-freedom load cell fixed to the base of the acrylic blocks, and peak torques experienced at the time of fracture for each of the mini-implants were recorded. One-way analysis of variance (α  =  .05) was used to compare the fracture torques among the six different groups.Results:Statistical analysis revealed significant differences (P < .05) in the peak fracture torques among mini-implant groups. Mean fracture torques ranked as follows: Unitek (72 Ncm) > Tomas-pin (36 Ncm) > Dual-Top (32 Ncm) ≈ VectorTAS (31 Ncm) > OrthoEasy (28 Ncm) > Aarhus (25 Ncm), with significant differences found between all manufacturers, except for Dual-Top and VectorTAS.Conclusions:Mini-implants tested showed a wide range of torque at fracture depending on the manufacturer, with only a weak correlation between mini-implant diameter and fracture resistance. This torque should be considered at the time of mini-implant insertion to minimize the risk of implant fracture, especially in areas of high-density bone without predrilling.     

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.     

Dentoskeletal changes following mini-implant molar intrusion in anterior open bite patients

Objective:To evaluate skeletal and dental changes after intrusion of the maxillary molars in subjects with anterior open bite.Materials and Methods:This retrospective cephalometric study evaluated skeletal and dental changes resulting from the use of maxillary orthodontic mini-implants in 31 consecutively treated patients. Radiographs were taken at the start and end of maxillary molar intrusion to evaluate the associated changes. Statistical analysis was performed using a one-sample t-test.Results:The mean treatment observation time was 1.31 years (SD  =  2.03). The maxillary first molars (P  =  0.0026) and second molars (P  =  0.039) were intruded. However, the mandibular first molars (P  =  0.0004) and second molars (P  =  0.003) erupted in adolescent patients. Both the maxillary and mandibular first molars inclined distally (P  =  0.025 and P  =  0.044, respectively). The mandibular plane angle decreased (P  =  0.036), lower facial height decreased (P  =  0.002), and the occlusal plane angle increased (P  =  0.009). The overbite increased (P < .0001). The ANB angle decreased (P < .0001). Mandibular dental and skeletal changes were more apparent in adolescents, while adults tended toward maxillary changes.Conclusions:Vertical traction from orthodontic mini-implants reduces the maxillary posterior dentoalveolar height, thereby assisting orthodontic closure of anterior open bite. However, simultaneous eruption or extrusion of the mandibular molars should be controlled. Adolescent patients tend to demonstrate more favorable effects of mandibular autorotation than do adults.     

Effect of degree of conversion on in vivo biocompatibility of flowable resin used for bioprotection of mini-implants

Objective:To test the hypothesis that there is no difference between the biocompatibility and degree of monomer conversion of flowable resins used as bioprotective materials of orthodontic mini-implants.Materials and Methods:Forty-eight male Wistar rats were divided into four groups (n  =  12). Group Control (polyethylene), Group Wave, Group Top Comfort, and Group Filtek. The animals were sacrificed after time intervals of 7, 15, and 30 days and tissues were analyzed under optical microscopy for inflammatory infiltrate, edema, necrosis, granulation tissue, multinucleated giant cells, and collagen formation. The degree of conversion was evaluated by the Fourier method. Biocompatibility and degree of conversion were evaluated by the Kruskal-Wallis and Dunn tests, and analysis of variance and the Tukey test, respectively (P < .05).Results:An intense inflammatory infiltrate was observed on the seventh day, with Groups Top Comfort and Filtek differing statistically from Group Control (P  =  .016). Edema, necrosis, granulation tissue, and giant cells showed greater expressiveness at 7 days, without statistical difference between them (P > .05). For the presence of collagen fibers, Group Top Comfort was shown to differ statistically from Group Control (P  =  .037) at 15 days and from Groups Filtek and Control (P  =  .008) at 30 days. Monomer conversion ranged from 62.3% in Group Top Comfort at 7 days to 79.1% in Group Filtek at 30 days.Conclusions:The hypothesis was rejected. The resin Top Comfort demonstrated lower tissue repair capacity with a lower number of collagen fibers compared with Filtek and Wave resins. The resin Top Comfort showed the lowest conversion values during the experiment.     

Comparison of anterior and posterior mini-implant-assisted maxillary incisor intrusion: Root resorption and treatment efficiency

Objective:To compare, through cone-beam computed tomography (CBCT), the root resorption and treatment efficiency of two different mini-implant-assisted modalities in intruding the maxillary incisors.Materials and Methods:Thirty-two adults who had deep bite and elongated maxillary incisors were randomly allocated to two groups: anterior mini-implant group (AMG) and posterior mini-implant group (PMG). In the AMG, approximately 40 g of force was applied per side with elastic chains from mini-implants placed between the lateral incisors and canines and in the PMG, with beta-titanium wires from mini-implants placed between the second premolars and first molars. This study was conducted on CBCT scans taken before intrusion and after 4 months of intrusion. Data were analyzed by means of a paired t-test, independent t-test, and Pearson’s correlation test.Results:One patient was excluded from the AMG due to mini-implant loosening. While the incisors showed a significant reduction in length and volume, this amount was greater in the AMG, especially in the central incisors (P < .05). Together with the mean intrusion rates of 0.62 and 0.39 mm/mo in the AMG and PMG respectively, the center of resistance of the incisors showed distal movement with labial tipping; these changes were greater in the PMG (P < .001). Volumetric root resorption was correlated with the amount of intrusion (P < .05).Conclusions:Intrusion anchoring from posterior mini-implants is preferred in cases of upright incisors, as the use of such mechanics directs the roots into the spongiosa where they undergo less root resorption and more labial tipping.     

In vitro and in vivo mechanical stability of orthodontic mini-implants: Effect of sandblasted,large-grit,and anodic-oxidation vs sandblasted,large-grit,and acid-etching

Objective:To compare in vivo and in vitro mechanical stability of orthodontic mini-implants (OMIs) treated with a sandblasted, large-grit, and anodic-oxidation (SLAO) method vs those treated with a sandblasted, large-grit, and acid-etching (SLA) method.Materials and Methods:Fifty-four titanium OMIs (cylindrical shape, drill-free type; diameter  =  1.45 mm, length  =  8 mm, Biomaterials Korea Inc, Seoul, Korea) were allocated into control, SLA, and SLAO groups (N  =  12 for in vivo and N  =  6 for in vitro studies per group). In vitro study was carried out on a polyurethane foam bone block (Sawbones, Pacific Research Laboratories Inc, Vashon, Wash). In vivo study was performed in the tibias of Beagles (6 males, age  =  1 year, weight  =  10 to 13 kg; OMIs were removed at 8 weeks after installation). For insertion and removal of OMIs, the speed and maximum torque of the surgical engine were set to 30 rpm and 40 Ncm, respectively. Maximum torque (MT), total energy (TE), and near peak energy (NPE) during the insertion and removal procedures were statistically analyzed.Results:In the in vitro study, although the control group had a higher insertion MT value than the SLA and SLAO groups (P < .01), no differences in insertion TE and NPE or in any of the removal variables were noted among the three groups. In the in vivo study, the control group exhibited higher values for all insertion variables compared with the SLA and SLAO groups (MT, P < .001; TE, P < .01; NPE, P < .001). Although no difference in removal TE and removal NPE was noted among the three groups, the SLAO group presented with a higher removal MT than the SLA and control groups (P < .001).Conclusions:SLAO treatment may be an effective tool in reducing insertion damage to surrounding tissue and improving the mechanical stability of OMIs.     

Comparison of the fracture torque of different Brazilian mini-implants

This study evaluated fracture torque by torsion, in relation to the length and diameter of orthodontic mini-implants, to demonstrate their viability for clinical and experimental use based on the torque recommended by the manufacturers. The fractures at the moment of insertion, whose incidence in the literature is around 4%, are principally due to excessive force and the inability of the implant to resist rotational forces. Thirty orthodontic mini-implants of three commercial brands available in Brazil (Neodent 1.6 x 9 mm, Dentoflex 1.6 x 9 mm and Kopp 1.6 x 9 mm) were attached to a device made specifically for this research, leaving the mini-implants with sufficient stability. The miniimplants were submitted to torsion torque, using a digital torque wrench, until their breaking point. The values obtained with the test were submitted to analysis of variance and the Tukey test. The mean values of mini-implant ruptures were 26 N.cm for group A (Dentoflex), 25.4 N. cm for group B (Kopp) and 32.8 N.cm for group C (Neodent). From the Tukey test we could observe that the relationships between the means of the Dentoflex and Neodent groups, and between the Kopp and Neodent groups, were significant. Between the Dentoflex and Kopp groups, significance was nonexistent. All the values found in our research for fracture torque were higher than the limits recommended by the manufacturers for clinical use in orthodontics. The highest values were found in the Neodent group.     

Evaluation of the effect of force direction on stationary anchorage success of mini-implant with a lever-arm–shaped upper structure

Objective:To compare the effect of clockwise and counterclockwise torque on the primary stability of a mini-implant with a lever-arm–shaped upper structure.Materials and Methods:Twenty-four white rabbits were used for this study. Two screw-type mini-implants were placed in each tibia. In all, 96 screws were inserted. Two weeks later, a 2-N force was applied to the mini-implants without an upper structure in eight rabbits (control group). The mini-implants of the other 16 rabbits were loaded with an upper structure (experimental group). In the experimental group, the two left mini-implants were loaded in a clockwise direction (CW group) and the two right implants were loaded in a counterclockwise direction (CCW group). The rabbits were sacrificed at 1 week or 8 weeks after loading in both control and experimental groups. The removal torque value (RTV) was measured in 15 of 16 mini-implants in each group and the remaining implant was processed for histologic examination.Results:At 1 week there were no significant differences in the mean RTV between the control, CW, and CCW groups. At 8 weeks, the RTV was higher in the control and experimental groups than in the respective 1-week groups. At 8 weeks, there were no significant differences in the RTV between the control and CW groups, but the CCW group showed a lower RTV.Conclusions:CCW torque can decrease the stability of a mini-implant, whereas a CW torque has no effect.     

An in vitro study of factors affecting the primary stability of orthodontic mini-implants

Objectives:To evaluate the effects of mini-implant features (length, design, core diameter), insertion technique (insertion angle, cortical punch), and cortical bone depth and density on mini-implant primary stability. The effect of mini-implant reinsertion was also investigated.Materials and Methods:Two hundred and sixty Infinitas mini-implants of two lengths (9 mm and 6 mm), two core diameters (0.8 mm and 0.9 mm) for an external diameter of 1.5 mm, and four designs (two tapered, external diameter 1.5 mm; two cylindrical, external diameters 1.5 mm and 2.0 mm) were inserted into synthetic bone blocks, and the maximum insertion torque (MIT) was recorded. The cortical layer of the blocks varied in density (30 and 50 lb per cubic foot) and depth (1 mm and 2 mm). Three angles of insertion (90°, 75°, and 60°) and two methods of insertion (direct and cortical punch) were tested. Forty mini-implants were also removed and reinserted.Results:A significant increase in the average MIT occurred when cortical bone density increased and when mini-implants were reinserted. The 1.5 mm diameter cylindrical design had significantly lower MIT than the 1.5 mm tapered and the 2.0 mm cylindrical designs. The other variables did not have a significant effect on MIT.Conclusions:Mini-implants achieved greater primary stability in higher-density cortical bone, and the 1.5 mm diameter tapered and 2.0 mm cylindrical designs offered greater primary stability than the 1.5 mm cylindrical design. Reinserting mini-implants resulted in significantly increased MIT, possibly because of blunting of the threads.     

In vitro and in vivo biofilm adhesion to esthetic coated arch wires and its correlation with surface roughness

Objective:To evaluate the in vitro ability of esthetic coated rectangular arch wires to retain oral biofilms and in vivo biofilm formation on these wires after 4 and 8 weeks of clinical use and to correlate the findings with the surface roughness of these wires.Materials and Methods:Three brands of esthetic coated nickel-titanium (NiTi) arch wires were selected. Arch wires retrieved after 4 and 8 weeks of intraoral use were obtained from 30 orthodontic patients. Surface roughness (SR) was assessed with an atomic force microscope. In vitro adhesion assays were performed using Streptococcus mutans (MS), Staphylococcus aureus, and Candida albicans. The amount of bacterial adhesion was quantified using the colony-count method. Paired t-test, analysis of variance, post hoc Tukey''s test, and Pearson''s correlation coefficient test were used for statistical analysis at the .05 level of significance.Results:In vitro bacterial adhesion showed significant differences between wires in terms of MS adhesion (P  =  .01). All wires showed significant increases in SR (P  =  .001 after 4 weeks and .007 after 8 weeks) and biofilm adhesion (P  =  .0001 after 4 weeks and .045 after 8 weeks) after intraoral exposure. A significant positive correlation (P  =  .001 after 4 weeks and .05 after 8 weeks) was observed between these two variables in vivo, but the correlation was not significant for in vitro bacterial adhesion.Conclusions:SR and biofilm adhesion increased after intraoral use at all time intervals. There was a positive correlation between SR and biofilm adhesion in vivo only.     

Dental crowding: The role of genetics and tooth wear

Objective:To evaluate the role of genetics and tooth wear in the etiology of dental crowding through the analysis of a split indigenous Amazon population.Materials and Methods:Dental crowding prevalence (n  =  117), tooth wear (n  =  117), and inbreeding coefficient (n  =  288) were compared for both villages. A biometric investigation was performed by dental cast analysis of 55 individuals with no tooth loss. Mann-Whitney statistics, independent t-tests, and Fisher exact tests were used at P < .05.Results:A high coefficient of inbreeding was confirmed in the resultant village (F  =  0.25, P < .001). Tooth wear was not significantly different (P  =  .99), while a significantly higher prevalence of dental crowding was confirmed in the original village (PR  =  6.67, P  =  0.02). Forty dental arches (n  =  20) were examined in the new group, and only one (2.5%) had a dental crowding ≥5 mm. In the original villages, we found 20 arches (28.6%) with dental crowding. No difference was observed for tooth size, while larger dental arch dimensions explained a lower level of dental crowding in the resultant village.Conclusions:Our findings downplay the widespread influence of tooth wear, a direct evidence of what an individual ate in the past, on dental crowding and emphasize the role of heredity, exacerbated through inbreeding, in the etiology of this malocclusion.     

A novel technique for measurement of orthodontic mini-implant stability using the Osstell ISQ device

Objectives: To develop and validate a method for application of the Osstell ISQ device in the assessment of mini-implant stability.Materials and Methods: An adaptor was developed for attachment of Osstell''s SmartPeg onto a variety of orthodontic mini-implants. For validation of the adaptor, Benefit mini-implants were inserted into bone blocks that mimicked different stability conditions. The Osstell device was used to assess mini-implant stability with the adaptor (test measurement) and conventional SmartPeg attachment (gold-standard measurement). Implant stability quotient (ISQ) values were assessed for agreement, repeatability, and reproducibility.Results: Strong positive correlations were found between ISQ values obtained using the novel adaptor and the conventional attachment. Repeatability and reproducibility of ISQ values with the adaptor were similar to those obtained with the conventional attachment.Conclusions: A method was developed and validated to assess the stability of orthodontic mini-implants using the Osstell system. The novel mini-implant adaptor provided repeatable and reproducible measurements of mini-implant stability, which agreed with those obtained using a conventional SmartPeg attachment. This adaptor permits noninvasive stability assessment of various designs of mini-implants, most of which are incompatible with the conventional SmartPeg attachment.     

Does cortical thickness influence the primary stability of miniscrews?: A systematic review and meta-analysis

Objective:To investigate whether there is evidence to support the association between cortical thickness (CtTh) and the primary stability of mini-implants (MI).Materials and Methods:A search was performed including articles published until September 2013. The inclusion criteria comprised observational clinical studies conducted in patients who received monocortical MI for orthodontic anchorage and in vivo or ex vivo experimental studies performed to evaluate the primary stability of MI, studies that evaluated the association between CtTh and MI primary stability, CtTh measurement performed numerically, and MI primary stability evaluated by implant stability quotient value, Periotest value , pull-out strength, or insertion torque. Studies conducted exclusively in artificial bone or finite elements were excluded.Results:Abstract and title reading identified 15 possible articles to be included. After reading the complete text, three were excluded. One article was found by hand searching and another excluded for an overlapping sample. Finally, 12 articles were selected. A positive correlation was found between primary stability and CtTh when studies that evaluated primary stability through PS were grouped (r  =  .409) and when studies that evaluated stability in humans were grouped (r  =  .338).Conclusions:There is a positive association between MI primary stability and CtTh of the receptor site. However, there is still a lack of well-designed clinical trials.     

Long-term durability of orthodontic mini-implants

The current study aimed at examining surface and chemical composition changes of retrieved mini-implants after different periods of service as aids of anchorage for orthodontic patients. This study examined 72 retrieved orthodontic self-tapping and self-drilling mini-implants, 1.7 mm in diameter and 8 mm in length (OrthoEasy system, Forestadent, Pforzheim, Germany) from 36 adult orthodontic patients (18 men and 18 women, mean age = 23 years). The retrieved mini-implants were divided into 3 groups according to service period: 3–6 months (3M–6M) group, 6–12 months (6M–12M) group, and 12–24 months (12M–24M) group, with 24 mini-implants in each group. The control group (As Received) comprised of 24 unused mini-implants of the same type (AR group). All mini-implant heads and threaded bodies were examined for chemical characterization and topographical features by SEM–EDS. The average weight percentages for the following elements Ti, Al, and O₂ were obtained and compared among the 4 groups. There was significant decrease in titanium content and deterioration for the surface properties for all parts of the mini-implants after being used inside patients’ oral cavities for more than 6 months p < 0.05. The period of mini-implant service inside patients’ oral cavities should not exceed 6 months.     

Resistance to Immediate Orthodontic Loading of Surface-Treated Mini-Implants

Objective:To test the hypothesis that there is no difference in the stability and resistance to orthodontic forces of immediately loaded sandblasted and acid-etched (SAE) mini-implants and those of machined-surface implants of the same size and shape.Materials and Methods:Two types of mini-implants were used in the tibiae of 44 rabbits; some had an SAE surface and some had machined surfaces. Orthodontic loading of 150 g was applied immediately after placement. The success rates and maximum removal torque values (RTVs) of 412 mini-implants were recorded and compared immediately after placement, 3 days after placement, and 1, 6, and 10 weeks after placement. The RTV data were analyzed using multiple regression analysis to evaluate differences with respect to surface treatment, loading, and loading periods (P < .05). Multiple comparisons using the Scheffé method were performed to evaluate the RTVs for the subsequent loading periods.Results:Thirteen mini-implants failed during the experimental period. The SAE group had a higher RTV than the machined group, and there was significant difference in RTVs in accordance with loading periods (P < .001). However, there was no significant RTV difference between loaded and unloaded mini-implants.Conclusions:The hypothesis was supported. Both SAE mini-implants and machined mini-implants can be loaded immediately and experience similar success rates. RTVs were higher for the SAE mini-implants than for the machined mini-implants. The latter finding suggests that, for immediate loading, SAE mini-implants may provide more stable retention than machined mini-implants.     

Evaluation of orthodontic mini-implant placement: a CBCT study

Background

Optimal positioning of orthodontic mini-implants is essential for a successful treatment with skeletal anchorage. This study aims to compare the accuracy of two-dimensional radiographs with a cone beam computed tomography (CBCT) for mini-implant placement.

Methods

An ideal site for mini-implant placement at the buccal interradicular space between the second premolar and the first molar was determined for 40 sites (in 13 patients aged 14 to 28 years) by using CBCT data. The mini-implant placement procedure was then divided into two groups. In CBCT group, mini-implants were placed at the sites determined from CBCT data. In RVG group, mini-implants were placed with the help of two-dimensional digital radiographs and a custom made guide. Postplacement CBCT scans were obtained to determine the accuracy of the mini-implant placement. The results were statistically analyzed with a Mann-Whitney test.

Results

A statistically significant difference (p value = 0.02) was observed between the two groups for deviation from an ideal height of placement of the mini-implants. Deviations in mesiodistal positioning and angular deviation showed a statistically non-significant difference. Three out of twenty mini-implants in the RVG group showed root contact in the mandibular arch that may be attributed to the narrower interradicular space and reduced accessibility in the mandibular posterior region.

Conclusions

Although CBCT provides an accurate three-dimensional visualization of the interradicular space, the two-dimensional intraoral radiograph of the interradicular area provides sufficient information for mini-implant placement. Considering the amount of radiation exposure and cost with the two techniques, it is recommended to use two-dimensional radiographs with a surgical guide for a routine mini-implant placement.     

The effect of changes in primary attending doctor coverage frequency on orthodontic treatment time and results

Objective:To determine whether changes in primary attending (PA) doctor coverage frequency caused an increase in orthodontic treatment time or a decrease in the quality of treatment results in a postgraduate orthodontic clinic. The effect of T1 Peer Assessment Rating (PAR) scores on PA doctor coverage frequency, treatment times, and results was also evaluated.Materials and Methods:A sample of 191 postorthodontic subjects was divided into three groups based on PA doctor coverage (high, medium, or low). Treatment times, treatment results, and other variables were compared between the three PA coverage groups. Additionally, the sample was divided into three groups based on T1 PAR scores. Attending coverage frequency, treatment times, and results were compared between the T1 PAR groups.Results:No statistically significant differences were found in treatment time (P  =  .128) or results (P  =  .052). There were no statistically significant differences in the mean scores for T1 PAR (P  =  .056), T2 PAR (P  =  .602), patient age at T1 (P  =  .747), total appointments (P  =  .128), missed appointments (P  =  .177), or cancelled appointments (P  =  .183). Statistically significant differences were found between the low T1 PAR group and the medium and high T1 PAR groups (attending coverage, P  =  .008; results, P < .001; treatment time, P  =  .001).Conclusions:Under the conditions of this study, variations in PA doctor coverage frequency did not lengthen orthodontic treatment or reduce the quality of treatment results. Low T1 PAR scores were associated with less PA coverage, less change in PAR, and shorter treatment times.