Skip to main content
NCBI home page
The Angle Orthodontist logoLink to The Angle Orthodontist
. 2018 Oct 29;89(1):40–46. doi: 10.2319/012518-70.1

Failure rates for stainless steel versus titanium alloy infrazygomatic crest bone screws: A single-center, randomized double-blind clinical trial

Chris H Chang a, Joshua S Lin b, W Eugene Roberts c,✉
PMCID: PMC8137128  PMID: 30372127

Abstract

Objectives:

To compare failure rates for stainless steel (SS) and titanium alloy (TiA) bone screws (BSs) placed in the infrazygomatic crest (IZC).

Materials and Methods:

A total of 386 consecutive patients (76 male, 310 female; mean age 24.3 years, range 10.3–59.4 years) received IZC BSs (SS or TiA) via a double-blind, split-mouth design. BSs penetrated attached gingiva (AG) or moveable mucosa (MM) with 5 mm of soft tissue clearance. All BSs were immediately loaded and reactivated monthly with ≤14 oz (397 g or 389 cN) applied directly to the upper archwire bilaterally for 6 months to retract the maxilla to correct Class II or bimaxillary protrusion.

Results:

Of the 772 devices, there were 49 (6.3%) failures: 27 SS (7.0%) and 22 TiA (5.7%). The 1.3% difference was not statistically significant (P = .07). There was no significant relationship between SS or TiA failures relative to (1) right vs left side, (2) unilateral vs bilateral, or (3) age at failure. Significantly (P < .05) increased failure rates were noted for SS screws in only two subgroups: AG site (7.4%) and right side (7.8%). Unilateral failure occurred in 21 patients (5.4%), and bilateral failures occurred in 14 of the total 772 patients (1.8%).

Conclusions:

The overall success rate of 93.7% indicates that both SS and TiA are clinically acceptable for IZC BSs.

Keywords: Infrazygomatic crest, Bone screws, Skeletal anchorage, Stainless steel, Titanium alloy, Randomized clinical trial, Double blind, Split-mouth design, Predisposition to failure

INTRODUCTION

Retromolar osseointegrated implants are efficient extra-alveolar (E-A) temporary anchorage devices (TADs) in the posterior mandible,1 but they are expensive, require space in the arch, and are difficult to remove. Kanomi2 attempted to simplify the TAD concept by placing stainless steel (SS) interradicular (I-R) “mini-implants” between the roots of teeth. This approach was mimicked by many other types of small I-R titanium (Ti) or Ti alloy (TiA) miniscrews,3–5 but the I-R positioning of the devices interfered with the path of tooth movement6 and precluded routine movement of an entire dental arch as a segment.6,7 To conservatively manage skeletal malocclusions without extractions or orthognathic surgery, Chang et al.8 revived the E-A TAD concept by placing self-drilling SS bone screws (BSs) in the mandibular buccal shelf (MBS). SS was selected as the material rather than Ti or TiA because of its toughness (resistance to fracture) when placed in the dense cortical bone. None of 1680 MBS BSs fractured, and only 7.2% failed, but 1.9% of all patients experienced bilateral failures.8 Thus, 26.4% (1.9/7.2) of the overall failure experience suggested a genetic predisposition9 and/or a biomaterials problem, possibly related to SS (nickel) sensitivity.10

Success with the MBS stimulated interest in developing TADs for E-A anchorage in the posterior maxilla. The same 2 × 12-mm SS BSs (Figure 1) were installed at the base of the infrazygomatic crest (IZC; Figure 2), with a rotating screwdriver method (Figure 3).11–13 This unique surgical approach resulted in a TAD buccal to the roots of the maxillary molars, which was capable of providing extra-radicular (E-R) anchorage for retraction of individual maxillary teeth or the entire upper arch (Figure 4). Maxillary bone is less dense (Figures 3 and 4) than in the mandible,8 so the strength of SS may not be necessary for the posterior maxilla. It was hypothesized that TiA has adequate strength for the IZC, and the absence of nickel10 would result in a lower failure rate compared with SS, particularly for patients predisposed to failure. Therefore, the current research objectives were to assess unilateral and bilateral failure rates relative to (1) material (SS or TiA), (2) side of placement (right vs left), and (3) type of soft tissue at the site (ie, attached gingiva [AG] vs movable mucosa [MM]).

Figure 1.

Figure 1

Open in a new tab

Bone screw specifications (SS or TiA).

Figure 2.

Figure 2

Open in a new tab

(a) An IZC bone screw (gold) is placed inferior to the zygomatic process relative to the second deciduous molar (E), first molar (6), and second molar (7). (b) Occlusal view of the maxilla shows the preferred site for an IZC BS (red dotted circle).

Figure 3.

Figure 3

Open in a new tab

(a) Orientation of the BS at the start of the installation procedure. (b) Penetration of the approximately 1-mm bone plate on the buccal surface. (c) Change in orientation in the frontal plane as the BS is rotated to place.

Figure 4.

Figure 4

Open in a new tab

(a) The completed installation procedure as illustrated in Figure 2. (b) The TAD is buccal to the roots of the maxillary molars. (c) A transverse cross section of the maxilla distinguishes between an extra-radicular vs interradicular insertion of a TAD. See text for details.

MATERIALS AND METHODS

This clinical research project was approved by the Indiana University Institutional Review Board (approval No. 1607517021) to compare identical BSs made of SS and TiA (Figure 1). A sample of 386 consecutive patients requiring bilateral IZC anchorage to retract the maxillary teeth agreed to participate. A total of 772 consecutive 2 × 12-mm OrthoBoneScrew TADs (Newton's A Ltd, Hsinchu City, Taiwan) were placed bilaterally in the IZCs of 76 males and 310 females, with a mean age of 24.3 years and a range of 10.3–59.4 years. According to a randomized split-mouth design (Figure 5), half of the IZC BSs (386) were made of 316LVM surgical SS, and the other half were composed of Ti6Al4V TiA. Pairs of SS and TiA screws were coded for the right and left sides and arranged in an alternating order, to ensure that equal numbers of each type were tested on the right and left sides in a uniform manner.

Figure 5.

Figure 5

Open in a new tab

Flow chart for the randomized clinical trial.

All screws were placed buccal to the roots of the maxillary molars (Figure 4) by the same clinician who had placed >1000 IZC BSs with a well-established, multicenter clinical procedure.11–16 After achieving local anesthesia, a sharp dental explorer was sounded through the soft tissue to mark the desired skeletal site, which is independent of the mucogingival junction (Figure 6). The type of soft tissue penetrated by the screw tip was scored as either AG or MM. The self-drilling BS (Figure 1) was oriented perpendicular to the buccal plate, and the screwdriver was turned clockwise to penetrate the approximately 1-mm-thick cortical plate (Figure 3a). As the screw penetrated the cortical plate (Figure 3b), the screwdriver was gradually rotated inferiorly about 60–70° to achieve a final insertion position buccal to the roots of the molars (Figure 3c). The final position of the screw head was about 5 mm superior to the soft tissue (Figure 6a), which was at about the level of the gingival crest or hooks of the buccal tubes as viewed from the buccal (Figure 6b).

Figure 6.

Figure 6

Open in a new tab

(a) About 5 mm of clearance from the head of the BS to the soft tissue surface is needed for effective hygiene. The mucogingival junction separates the AG from the MM. (b) An IZC bone screw anchors an elastomeric chain that is attached to the archwire mesial to the maxillary canine bracket.

For the present study, the maxillary teeth of each patient were retracted (Figures 7a–d). All BSs were immediately loaded and reactivated every 4 weeks with prestretched power chains,17 within the well-established force range for IZC BSs under routine conditions: 8–14 oz (227–397 g or 223–389 cN).11–16 As previously defined,11–16 the treatment force varied within the prescribed range according to the clinician's perception of bone density at the time of BS placement and the specific biomechanics required.

Figure 7.

Figure 7

Open in a new tab

(a) 0M: Left buccal view of a severe Class II malocclusion at the start of treatment. The canine discrepancy is marked with vertical lines. (b) 11M: Initiation of maxillary retraction with IZC anchorage. (c) 15M: Progress after 4 months of maxillary retraction. (d) 20M: Class I occlusion is achieved after 9 months of maxillary retraction.

All IZC BSs in this study were used as anchorage to retract the entire maxillary arch for at least 6 months (Figure 7c) to achieve a Class I occlusion (Figure 7d).12–16 According to a double-blind design, neither the patient, clinician, nor staff member was aware of the composition of any of the TADs until the code was broken at the end of the study. Once decoded, the TADs were sorted into four groups of 193 IZC BSs each: left SS, left Ti, right SS, and right Ti. Failure rates were calculated for each group and subgroup and tested for statistical significance with the chi-square test.

RESULTS

Table 1 shows the overall failure incidence divided into SS and TiA groups vs age, sex, and clinical characteristics. A total of 49 of 772 (6.3%) BSs failed within 6 months. The distribution for materials (n = 386 each) was 27 SS (7.0%) and 22 TiA (5.7%; Tables 1 and 2); the difference of 1.3% was not statistically significant (P = .07; Figure 8). Collectively, there was no significant difference at the P < .05 probability level between SS and TiA for any of the following: (1) right (6.5%) vs left (6.2%) side, (2) unilateral (21 patients, 5.4%) vs bilateral (14 patients, 1.8% of 772 patients), or (3) age. The 35 patients experiencing failure had a mean age of 24.2 years (range 12.2–43.3 years) compared with the mean age of 24.3 years (range 10.3–59.4 years) for all subjects in the sample. The only significant differences in failure rates (P < .05) were SS in AG (7.4%) vs TiA in AG (5.1%), and SS on the right side (7.8%) vs TiA on the right side (5.2%; Table 2; Figure 9).

Table 1.

Baseline Characteristics of Patients: Sample Size and Number of Failures in the Stainless Steel (SS) and Titanium (Ti) Alloy Groups

 Total
 SS
 Ti Alloy
N = 772
 Failure n = 386
 Failure n = 386
 Failure
n = 49
 n = 27
 n = 22
Age (mean, range) 24.3 (10.3, 59.4) 24.2 (12.2, 43.3) 24.3 (10.3, 59.4) 23.6 (12.2, 39.1) 24.3 (10.3, 59.4) 24.9 (12.2, 43.3)
Sex
 Male 76 subjects n = 10 n = 76 n = 4 n = 76 n = 6
n = 152
 Female 310 subjects n = 39 n = 310 n = 23 n = 310 n = 16
n = 620
Mucosal type
 Right 386 25 193 15 193 10
 AG 191 12 92 7 99 5
 MM 195 13 101 8 94 5
 Left 386 24 193 12 193 12
 AG 194 12 96 7 98 5
 MM 192 12 97 5 95 7
Open in a new tab

Table 2.

With a Split-Mouth Design, Failure Rates (%) per Group Are Given According to Mucosal Type: Attached Gingiva (AG), Moveable Mucosa (MM), Right Side (R't), and Left Side (L't)

Failure Rate (%)
 AG (6.2)
 MM (6.5)
 R't (6.5)
 L't (6.2)
SS (7.0) 7.4 6.6 7.8 6.2
Ti (5.7) 5.1 6.4 5.2 6.2
Open in a new tab

Figure 8.

Figure 8

Open in a new tab

Overall failure rate (6.3%) is partitioned into SS (7.0%) and Ti (5.7%). The 1.3% difference between SS and Ti (TiA) was not significant (P = .07).

Figure 9.

Figure 9

Open in a new tab

Failure rates are shown for IZC bone screws placed in AG, MM, as well as on the right or left side. The only significant differences (P < .05) were for SS screws placed in AG and on the right side.

DISCUSSION

I-R miniscrews made of TiA have relatively high failure rates, so the data have often been reported as “success rates” from 57%–95%, with an average of about 84%.18–21 The most common E-R TADs are made of SS, and they are used as anchorage in the MBS and IZC regions to treat a broad variety of malocclusions.8,11–16 Most studies of I-R miniscrews had a higher failure rate in the mandible (19.3%) than in the maxilla (12.0%).18–21 In comparison, there was no significant difference between the failure rates for E-A BSs: 7.2% for MBS BSs in the posterior mandible8 compared with 7.0% for IZC BSs in the posterior maxilla (Figure 8).

Predisposition to failure8 appears to affect all types of nonintegrated TADs. Uesugi et al.21 reported that the primary success rate for the initial insertion of I-R miniscrews was 80.4% (maxilla 82.6%, mandible 71.0%), but the secondary insertion success was only 44.2% (maxilla 46.6%, mandible 36.8%). These data support a predisposition to failure, particularly in the mandible, but the data are not directly comparable to E-A TADs because neither bilateral nor multiple failures were reported. Although E-A TADs had a much higher success rate (>92%), and there was little difference between the maxilla and mandible, predisposition to failure persists as evidenced by bilateral failures of 1.9% in the MBS8 and 3.6% for the IZC (present study). In the absence of a significant materials effect (present study), predisposition to failure appears to be predominantly genetic, which is similar to fracture nonunions9 and external apical root resorption.22 This potential complication is an important consideration for informed consent because alternate treatment methods may be desirable: extractions, headgear, and/or orthognathic surgery.

IZC Screw Failure

In several case reports,12–16 IZC screws were used as anchorage for retraction of the entire maxilla to correct Class II malocclusion and/or bimaxillary protrusion. Failure was defined as the inability of an IZC BS to serve as adequate anchorage to accomplish the intended orthodontic purpose for 6 months. This interval was the minimal anchorage requirement to retract the maxilla in the present sample. Additional study is indicated to determine the long-term failure rate relative to the overall anchorage needs for specific patients (Figure 7). Movement of an IZC BS within bone23,24 was not considered a failure if the device continued to provide the anchorage intended. TAD failures may include screw fracture, mobility, uncontrollable soft tissue inflammation, and/or host factors (pain or root damage). In this study, the only type of TAD failure was a loose (mobile) screw that exfoliated or was deemed too loose to provide effective anchorage.

SS vs TiA

SS has long been the material of choice for orthopedic applications requiring sharp self-drilling screws that are tough (resistant to fracture). In vivo comparison of SS and TiA (Ti) for nonintegrated TADs revealed there were no significant differences in the bone response.25,26 To avoid BS fractures, SS continues to be the preferred material for the MBS.8,23 TiA may be an adequate material for the MBS, but a specific fracture study is needed. In comparison with SS, TiA offered a slightly lower failure rate in AG and on the right side (Figure 9). Small differences in materials and site-specific failure rates may seem trivial, but they are important data for perfecting manufacturing and surgical procedures. The overall success rates for E-A TADs made of both materials exceeded 92%, so either SS or TiA are suitable for most clinical applications.

Chang et al.8 studied the role of soft tissue type (AG or MM) and sidedness on the failure of MBS BSs made of SS. There was no significant difference between AG and MM, but the overall failure rate was significantly greater on the left side (9.29%, P < .001). That problem was attributed to increased difficulty in placing an MBS screw on the left side for a right-handed surgeon. For the IZC, there were more SS failures on the right (15) compared with the left (12) side, but TiA failures were greater on the left (12) compared with the right (10) side. These small differences were not clinically relevant. Relative to E-R TAD sites, both SS and TiA have a high success rate (>92%), but continued study of other materials, screw design, and surgical methods are indicated because each variable may be relevant to specific sites under different conditions.

Stability of TADs

In addition to a high failure rate,18–21 I-R TADs may interfere with the desired path of tooth movement.6 E-A TADs avoid these problems, so they have evolved into a superior anchorage mechanism for the conservative management of severe skeletal malocclusion.7,8,23 However, the stability of nonintegrated TADs when loaded is problematic. In distinction to osseointegrated fixtures,27,28 nonintegrated screws move relative to basal bone when used for orthodontic anchorage.23,24 Bone labels for loaded TADs in monkeys (Melsen B. and Roberts WE., unpublished data) documented that firm, nonintegrated screws drifted within bone via a bone-modeling and remodeling mechanism similar to tooth movement.28 Remodeling of the cortical bone, supporting loaded 1.6-mm TiA screws, was much less compared with BSs with a larger diameter (3–3.5 mm).29 The latter are consistent with the dimensions of osseointegrated dental implants, which have a high remodeling rate (>300%/y) and that may be related to flexure at the bone-screw interface as a functional shear plane.27,28 Long-term osseointegration of prosthetic implants (>3 mm in diameter) is based on the biomechanics of interface flexure due to a mismatch in the modulus of elasticity of Ti or TiA and cortical bone.27,28 Additional research is needed to produce TADs <3 mm in diameter that heal with a modest degree of osseointegration to resist movement within supporting bone but still be easily removed with a conservative procedure after treatment.

CONCLUSIONS

  • Both SS and TiA are clinically acceptable materials for IZC BSs because the overall success rate was 93.7%.

  • Compared with TiA, SS IZC BSs have an insignificantly (P = .07) higher failure rate of 1.3%.

  • SS screws placed in the AG and on the right side had a slight but significantly higher (P < .05) failure rate compared with TiA.

  • None of the 772 IZC BSs fractured or resulted in appreciable pain.

ACKNOWLEDGMENT

Thanks to Dr. Rungsi Thavarungkul for the beautiful illustrations. Thanks to Mr. Paul Head for proofreading this article.

REFERENCES

  • 1.Roberts WE, Nelson CL, Goodacre CJ. Rigid implant anchorage to close a mandibular first molar extraction site. J Clin Orthod. 1994;28:693–704. [PubMed] [Google Scholar]
  • 2.Kanomi R. Mini-implant for orthodontic anchorage. J Clin Orthod. 1997;31:763–767. [PubMed] [Google Scholar]
  • 3.Melsen B, Costa A. Immediate loading of implants used for orthodontic anchorage. Clin Orthod Res. 2000;3:23–28. doi: 10.1034/j.1600-0544.2000.030105.x. [DOI] [PubMed] [Google Scholar]
  • 4.Park HS, Kwon TG. Sliding mechanics with microscrew implant anchorage. Angle Orthod. 2004;74:703–710. doi: 10.1043/0003-3219(2004)074<0703:SMWMIA>2.0.CO;2. [DOI] [PubMed] [Google Scholar]
  • 5.Reynders RM. Low quality evidence on the stability of orthodontic mini-implants. Evid Based Dent. 2013;14:78–80. doi: 10.1038/sj.ebd.6400950. [DOI] [PubMed] [Google Scholar]
  • 6.Shih IY-H, Lin JJ-J, Roberts WE. Treatment of a Class III malocclusion with anterior crossbite and deepbite, utilizing infrazygomatic (IZC) bone screws as anchorage. Int J Orthod Implantol. 2015;40:2–14. [Google Scholar]
  • 7.Roberts WE, Viecilli RF, Chang CH, Katona TR, Paydar NH. Biology of biomechanics: finite element analysis of a statically determinate system to rotate the occlusal plane for correction of a skeletal Class III open-bite malocclusion. Am J Orthod Dentofacial Orthop. 2015;148:943–955. doi: 10.1016/j.ajodo.2015.10.002. [DOI] [PubMed] [Google Scholar]
  • 8.Chang C, Liu SS, Roberts WE. Primary failure rate for 1680 extra-alveolar mandibular buccal shelf mini-screws placed in movable mucosa or attached gingiva. Angle Orthod. 2015;85:905–910. doi: 10.2319/092714.695.1. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 9.Huang W, Zhang K, Zhu Y, Wang Z, Li Z, Zhang J. Genetic polymorphisms of NOS2 and predisposition to fracture non-union: a case control study based on Han Chinese population. PLoS One. 2018;13:e0193673. doi: 10.1371/journal.pone.0193673. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 10.Basko-Plluska JL, Thyssen JP, Schalock PC. Cutaneous and systemic hypersensitivity reactions to metallic implants. Dermatitis. 2011;22:65–79. [PubMed] [Google Scholar]
  • 11.Chang H-N, Hsiao H-Y, Tsai C-M, Roberts WE. Bone screw anchorage for pendulum appliances and other fixed mechanics applications. Semin Orthod. 2006;12:284–293. [Google Scholar]
  • 12.Shih IH-Y, Liao JJ-L. Esthetic considerations in orthodontics treatment case report: bimaxillary protrusion with severe gummy smile. News Trends Orthod. 2009;15:42–47. [Google Scholar]
  • 13.Chang H-W, Chang C, Roberts WE. Class II low angle case with bilateral first premolars crossbite. Int J Orthod Implantol. 2013;31:62–75. [Google Scholar]
  • 14.Lin C, Wu Y, Chang CH, Roberts WE. Bimaxillary protrusion and gummy smile corrected with extractions, bone screws and crown lengthening. Int J Orthod Implantol. 2014;35:40–60. [Google Scholar]
  • 15.Hsu YL, Chang CH, Roberts WE. The 12 applications of OrthoBoneScrew® on impacted teeth. Int J Orthod Implantol. 2011;23:34–49. [Google Scholar]
  • 16.Chang CH. Clinical applications of orthodontic bone screw in Beethoven Orthodontic Center. Int J Orthod Implantol. 2011;23:50–51. [Google Scholar]
  • 17.Kin KH, Chung CH, Choy K, Lee JS, Vanarsdall RL. Effects of prestretching on force degradation of synthetic elastomeric chains. Am J Orthod Dentofacial Orthop. 2005;128:477–482. doi: 10.1016/j.ajodo.2004.04.027. [DOI] [PubMed] [Google Scholar]
  • 18.Berens A, Wiechmann D, Dempf R. Mini- and micro-screws for temporary skeletal anchorage in orthodontic therapy. J Orofac Orthop. 2006;67:450–458. doi: 10.1007/s00056-006-0601-1. [DOI] [PubMed] [Google Scholar]
  • 19.Viwattanatipa N, Thanakitcharu S, Uttraravichien A, Pitiphat W. Survival analyses of surgical miniscrews as orthodontic anchorage. Am J Orthod Dentofacial Orthop. 2009;136:29–36. doi: 10.1016/j.ajodo.2007.06.018. [DOI] [PubMed] [Google Scholar]
  • 20.Schatzle M, Mannchen R, Zwahlen M, Lang NP. Survival and failure rates of orthodontic temporary anchorage devices: a systemic review. Clin Oral Implants Res. 2009;20:1351–1359. doi: 10.1111/j.1600-0501.2009.01754.x. [DOI] [PubMed] [Google Scholar]
  • 21.Uesugi S, Kokai S, Kanno Z, Ono T. Prognosis of primary and secondary insertions of orthodontic miniscrews: what we have learned from 500 implants? Am J Orthod Dentofacial Orthop. 2017;152:224–231. doi: 10.1016/j.ajodo.2016.12.021. [DOI] [PubMed] [Google Scholar]
  • 22.Al-Qawasmi RA, Hartsfield JK, Jr, Everett ET, et al. Genetic predisposition to external root resorption in orthodontic patients: linkage and association of the interleukin 1B gene. Am J Orthod Dentofac Orthop. 2003;123:242–252. doi: 10.1067/mod.2003.42. [DOI] [PubMed] [Google Scholar]
  • 23.Lin JJ. 2 mm bone screw vs. MIA. Int J Orthod Implantol. 2008;9:1–5. [Google Scholar]
  • 24.Liou EJ, Pai BC, Lin JC. Do miniscrews remain stationary under orthodontic forces? Am J Orthod Dentofacial Orthop. 2004;126:42–47. doi: 10.1016/j.ajodo.2003.06.018. [DOI] [PubMed] [Google Scholar]
  • 25.Gritsch K, Laroche N, Bonnet JM. In vivo evaluation of immediately loaded stainless steel and titanium orthodontic screws in a growing bone. PLoS One. 2013;8:e76223. doi: 10.1371/journal.pone.0076223. [DOI] [PMC free article] [PubMed] [Google Scholar]
  • 26.Brown RN, Sexton BE, Gabriel Chu TM, et al. Comparison of stainless steel and titanium alloy orthodontic miniscrew implants: a mechanical and histologic analysis. Am J Orthod Dentofacial Orthop. 2014;145:496–504. doi: 10.1016/j.ajodo.2013.12.022. [DOI] [PubMed] [Google Scholar]
  • 27.Chen J, Esterle M, Roberts WE. Mechanical response to functional loading around the threads of retromolar endosseous implants utilized for orthodontic anchorage: coordinated histomorphometric and finite element analyses. Int J Oral Maxillofac Implants. 1999;14:282–289. [PubMed] [Google Scholar]
  • 28.Roberts WE. Bone physiology, metabolism and biomechanics in orthodontic practice. In: Graber LW, Vanarsdall RL Jr, Vig KWL, editors. Orthodontics: Current Principles and Techniques 5th ed. St Louis, Mo: Elsevier Mosby; 2012. pp. 287–343. [Google Scholar]
  • 29.Francis JC, Oz U, Cunningham LL, Huja PE, Kryscio RJ, Huja SS. Screw-type device diameter and orthodontic loading influence adjacent bone remodeling. Angle Orthod. 2017;87:466–472. doi: 10.2319/041316-302.1. [DOI] [PMC free article] [PubMed] [Google Scholar]

Articles from The Angle Orthodontist are provided here courtesy of Edward H Angle Education and Research Foundation, Inc

RESOURCES