Concurring opinion by Associate Judge MCLEESE at page 759.
Thompson, Associate Judge:
Petitioner Robert B. Johnson challenges the October 29, 2015, Superseding Decision and Final Order (the “Superseding Decision”) of the District of Columbia Board of Dentistry (the “Board” or the “D.C. Board”) that revoked his license to practice dentistry in the District of Columbia. For the reasons set out below, we remand for the Board to reconsider the sanction it imposed.
I.
On September 27, 2013, the Virginia Board of Dentistry (the “Virginia Board”), after conducting a two-day hearing, issued an order revoking petitioner’s license to [750]*750practice dentistry in Virginia. The order set out the Virginia Board’s findings on charges against petitioner based on the treatment of twenty-two patients over the course of a decade. On June 18, 2014, the D.C. Board issued a Notice of Intent to Take Disciplinary Action (“NOI”) based on the disciplinary action taken in Virginia.1 Based on the Virginia Board’s findings of fact, the NOI selectively charged petitioner with infractions in connection with the treatment of several patients in Virginia.
The D.C. Board conducted a hearing on August 27, 2014, during which it heard testimony from government expert witness Dr. Robert Caldwell, D.D.S., petitioner, and a few of petitioner’s former patients. The Board issued a Decision and Order on November 5,- 2014 (the “Original Decision”), in which it adopted all of the Virginia Board’s findings of fact, including findings relating to acts or omissions by petitioner that were not specified in the NOI, and revoked petitioner’s' license to practice dentistry in the District. Petitioner timely sought review of the Original Decision by this court. On July 16, 2015, this court granted a consent motion to remand the record for further proceedings “in light of [petitioner’s original] brief[,]” which asserted that the Board had erred in a number of respects, primarily by failing to “limit[ ] its inquiry into the specific charges contained in the District’s [NOI] ” and by “failing to consider whether the conduct at issue -in Virginia would have been grounds for taking disciplinary action in the-District[.]”2 Thereafter, on October 29, 2015, the Board issued its post-record-remand Superseding Decision, which is the subject of the instant review.
In the Superseding Decision, the Board adopted only those findings by the Virginia Board that were repeated in the NOI. After disposing of several pending motions (including a motion by petitioner to obtain information concerning a pending investigation by the Board into a complaint brought by a patient in the District of Columbia, which motion the Board denied), the Superseding Decision concluded that petitioner (who, the Board found, “practiced general dentistry and is a general dentist”) committed (in Virginia) the following acts or omissions, which it found are grounds for discipline in the District of Columbia:
• On September 9, 2010, [petitioner] injected into Patient' H’s sinus area [certain] homeopathic substances[;]
• On March 10, 2008 and August 11, 2009, [he] administered a series of injections of unspecified substances to Patient J’s sinus area without documenting the dental need for or diagnosis relating to such treatment;
• On August 18, 2010, [he] replaced the crown on Patient O’s tooth # 15 without documenting,a diagnosis as to the reason .for the replacement^]
• [His] treatment record for Patient R from April 2008 to December 2010 does not contain an initial or updated health history[;]
[751]*751• With respect to Patient T, from approximately 2003 to 2011, [his] records were devoid of an-initial, health history or subsequent updated history[;]
• [His] progress notes for Patient T end on July 22, 2009, but his billing for the patient indicates that he continued to provide treatment to her on multiple occasions after July 22, 2009[;]
• On September 26, 2005, ■ [he] removed amalgam from Patient K’s teeth # 3, 4, -29, 30, and 31 without an adequate dental indication for doing so (or any diagnosis of mercury poisoning, allergy, or related condition by a medical doctor)[;]
• On September 23, 2009, [he] provided injections of procaine, methyl, and folic acid into Patient O’s tonsils for pain. ... [and] [t]here was no documentation of a dental diagnosis for this treatment^]3
, • On July 29, 2009, [he] performed cranial myofascial therapy on Patient S without adequate dental diagnosis for doing so[;]
• [He] also [in 2009] removed amalgam from Patient S’s teeth -without an adequate dental indication for doing so (or any diagnosis of mercury poisoning, allergy or related condition by a medical doctor).4
The Board found that “any of’ the above-described findings—relating. to “practicing outside the scope of his dental license,” “failing to conform to the standards of acceptable conduct and prevailing practice,” and “failure to properly maintain records” as required by regulation in the District of Columbia—-was “sufficient to warrant the imposition of disciplinary action” in the District of Columbia. Citing petitioner’s devotion to a “holistic approach toward the practice of dentistry[,]” the Board also found “that there are no restrictions, fines,, or courses that it could impose that would stop [petitioner] from crossing the line and engaging in practices that are beyond the scope of practice of dentistry and/or that fail to conform to the standards of acceptable conduct and prevailing practices of dentistry in the District of Columbia.” Quoting petitioner’s statement at the close of the hearing that he had “basically stopped doing” procedures when he learned that they were not acceptable in Virginia, the Board found that his testimony, which the Board called “disingenuous and self-serving,” “implie[d] that he continued doing these procedures in some manner or form, as opposed to full-stop cessation[,]” a fact that the Board found “undermine[d] his statements that he would not engage in conduct if he knew that it was not permissible.” The Board found that petitioner “knew or should have known that his conduct was not acceptable and that he ehose to offer these services to his patients anyway.” The Board explicitly [752]*752did not credit, and found “implausible,” petitioner’s testimony to the extent that it “attempt[ed] to convince th[e] Board that he provided services different from the ones documented in his records.”
The Board found that petitioner’s recordkeeping is “unreliable” and that the Board “would be unable to trust the content of [petitioner’s] records if it were to allow [him] to continue to practice and to attempt to monitor his conduct through an audit of his records in the future[,]” and cited the “lack[ ] [of] any assurances that if allowed to maintain his dentist license ... [petitioner] would not continue to practice beyond the scope of his District of Columbia license, fail to conform to the acceptable standards and prevailing practices of the profession, and fail to comply with the District’s recordkeeping requirements.” Finding “no lesser combination of sanctions ... that would sufficiently protect the citizens of the District of Columbia from [petitioner’s] impermissible dental practices[,]” the Board revoked petitioner’s District of Columbia dental license. It noted that revocation means that he is not eligible to apply for reinstatement for five years.
In the brief in support of his petition for review, petitioner asserts that the only NOI charges that were sustainable were those involving documentation failures, and that the charges set out in the NOI with regard to scope of practice and standards of practice were based on actions or omissions that would not have been sanc-tionable in the District of Columbia. He further argues that the Board made “numerous errors of law, applying Virginia rather than District of Columbia legal standards,” that the Board applied “vague practice standards,” improperly limited the presentation of evidence, and improperly denied his motion to obtain the results of the Board’s investigation into his complained-about conduct in the District of Columbia. Finally, he contends that even if all the charges are sustainable, the Board “reached a sanction that cannot be supported by substantial evidence.” Petitioner asserts that the Board, in issuing its Superseding Decision, primarily sought “to maintain the revocation,” and “simply justify the prior result,” rather than “begin the consideration ... afresh”5 after eliminating the defects in the Original Decision. “[T]hat error,” he argues, “still pervades [the Board’s] decision to use its most serious sanction.” He contends that the sanction the Board imposed reflects its “negative reaction to his ‘enthusiasm’ about holistic dentistry” and “biologic dentistry,”6 and exposes its willingness to decide the matter based on the full Virginia order “no matter the [differences between Virginia and District of Columbia law] or the evidence.”
II.
We will reverse the Board’s decision only if it is “[arbitrary, capricious, [753]*753an abuse of discretion, or otherwise not in accordance with law[.]” D.C. Code § 2-510(a)(3)(A) (2012 Repl.). “The [Board] must make findings on each material issue of fact; the factual findings must be supported by substantial evidence on the record as a whole; and the [Board’s] conclusions must flow rationally from those findings and comport with the applicable law.” Williamson v. District of Columbia Bd. of Dentistry, 647 A.2d 389, 394 (D.C. 1994) (internal citations omitted). Our review for abuse of discretion means that we must determine “whether the decision maker failed to consider a relevant factor, [or] ... relied upon an improper factor[.]” Johnson v. United States, 398 A.2d 354, 365 (D.C. 1979) (internal quotation marks omitted). We recognize that “on questions of credibility!,] the fact-finding of hearing officers is entitled to great weight.” Arthur v. District of Columbia Nurses’ Examining Bd., 459 A.2d 141, 146 (D.C. 1983) (internal quotation marks omitted). “We must be particularly deferential to the [Board’s] determination where the decision lies within the agency’s expertise!,]” and we are bound by factual findings “supported by substantial evidence on the record as a whole” even if we “may have reached a different result based on an independent review of the record.” Williamson, 647 A.2d at 394. We review an agency’s legal rulings de novo. District of Columbia Dep’t of Mental Health v. District of Columbia Dep’t of Emp’t Servs., 15 A.3d 692, 696-97 (D.C. 2011).
We recognize that “[a] licensing agency has broad discretion to suspend or revoke a license for reasonable cause in order to protect public health, safety, or morals!,]” and thus we review a sanction decision for abuse of discretion. Arthur, 459 A.2d at 147. As a general matter, “[w]here ... a sanction is within an agency’s statutory power to impose, an appellate court will not disturb the exercise of that discretion solely because that sanction is more severe than penalties levied in similar cases.” Kegley v. District of Columbia, 440 A.2d 1013, 1020 n.11 (D.C. 1982).
III.
Petitioner is correct that most of the instances of conduct charged in the NOI and determined by the Board to be grounds for discipline in the District of Columbia involved documentation failures (either no documentation of diagnosis, or patient records lacking initial or updated health histories).7 To the extent petitioner suggests that these “documentation failures” were merely minor infractions, we have no basis for accepting that claim. Deferring to the Board’s expertise,8 we accept its expressed view that recordkeep-ing infractions are not mere technical issues or minor violations, that proper recordkeeping practices are “essential for [754]*754the continuity of care of a provider’s patients” and “provide a window into the clinical judgment exercised at the time that the services were rendered,” and that petitioner’s omissions as found by the Virginia Board and set out in the NOI warrant reciprocal discipline. Cf. Faulkenstein v. District of Columbia Bd. of Med., 727 A.2d 302, 308 (D.C. 1999) (concluding that there was “no warrant to disturb the Board’s findings” where, inter alia, the evidence depicted Faulkenstein as having “a propensity for bad record-keeping” and the Board had grave doubts about his veracity).
We also cannot agree with petitioner that the only NOI charges that were sustainable were those involving documentation failures. For example, relying on testimony by Dr. Caldwell, the Board found, with reference to procedures the Virginia Board found petitioner performed on Patient H, that “injeetpng] a substance into a patient’s sinus”' (italics added) is not within the scope of the practice of dentistry in the District of Columbia and is a ground for disciplinary action under D.C. Code § 3-1205.14(a)(21) (2012 Repl.) (“Performs, offers, or attempts to perform services beyond the scope of those authorized by the license- held by the health professional”).9 Petitioner’s claim of error with respect to the conclusion that he committed a scope-of-practice violation is that the Board’s finding went beyond the finding of the Virginia Board, which used the phrase “into Patient H’s sinus area,” an ambiguous term that is consistent with the possibility (and petitioner’s explanation) that the injection was into the part, of the oral cavity near where the patient’s (presumably ailing) tooth projected into the sinus. In his testimony before the D.C. Board, petitioner noted the “anatomical proximity of the sinus to the roots of the maxillar molars.” In light of the Virginia Board’s ambiguous wording of the-finding as to Patient H, petitioner’s explanation was not necessarily, as the Board characterized it, an' effort to relitigate a fact resolved by the Virginia Board. Nevertheless, especially in light of the Virginia Board’s additional usage of the phrase “into Patient ... sinus area” when it found that petitioner performed an injection “into Patient D’s sinus area- to treat a sinus infection” (a matter not charged in the NOI), we are satisfied that the D.C. Board could reasonably infer that the Virginia Board’s finding about Patient H was also about an injection into the sinus itself (which petitioner acknowledges “would have been outside the scope of his dental license”). Cf. Williamson, 647 A.2d at 394 (“Our' function is to ascertain whether the inferences drawn by the administrative agency are within the reasonable boundaries prescribed by the facts.”' (internal quotation marks omitted)).
Further, the Board relied on Dr. Caldwell’s testimony to find that petitioner engaged in conduct that “failed to conform to standards of acceptable conduct and prevailing practices within the practice of dentistry in the District of Columbia” within the meaning of D.C. Code § 3-1205.14(a)(26) (“Fails to conform to standards of acceptable conduct and prevailing practice within a health profession”). That was the D.C. Board’s conclusion about petitioner’s use of procaine (which Dr. Cald[755]*755well testified “is not currently used in the practice of dentistry in the District of Columbia” and his “performance of cranial myofascial therapy” “without an adequate dental diagnosis for doing so.” Petitioner argues with some force that the Virginia Board deems cranial myofascial therapy to be “quackery” and therefore would never find any “dental diagnosis” “adequate” to justify it (even though, he correctly asserts, Dr. Caldwell acknowledged that he performs such therapy and testified that it is not improper when supported by an adequate diagnosis). However, even if we assume that the D.C. Board erred in treating the Virginia Board’s finding pertaining to petitioner’s performance of cranial myo-fascial therapy as a basis for discipline in the District of Columbia, we are still left with the Board’s conclusion, supported by Dr. Caldwell’s testimony, that petitioner’s use of procaine would have been a deviation from acceptable dental practice in our jurisdiction and is a basis for discipline here.
The Board also relied on Dr. Caldwell’s testimony that petitioner “failed to conform to standards of acceptable conduct and prevailing practices within the practice of dentistry in the District of Columbia” when he removed amalgam from the teeth of Patient K in 2005 “without an adequate dental indication for doing so (or any diagnosis of mercury poisoning, allergy, or related condition)”; Petitioner argues that it was unfair for the Board to infer that he made no diagnosis just because, as charged in the NOI, he failed to document a diagnosis in the patient’s record (and he asserts that he “always found defects in the amalgam removed”). We are satisfied, however, that to the extent the Board drew an inference of the absence of a dental diagnosis as to Patient K, it did not do so unreasonably. Cf. Williamson, 647 A.2d at 395 (holding that the licensing board’s conclusion that “because there was no notation of a prescription in a patient’s record[,] this indicated that, the prescription was issued for a. reason outside a legitimate medical purpose” was not arbitrary or capricious).
We do agree with petitioner, however, that the Board relied on legally insufficient evidence in concluding that his conduct in.2009,.when he removed amalgam from the teeth of Patient S “without an adequate dental indication for doing so or any diagnosis of mercury poisoning, allergy, or related condition,” was “conduct that would be grounds for disciplinary action in the District of Columbia.” As petitioner notes, 17 DCMR § 4213.44, added in 2007 (see 54 D.C. Reg. 3514, 3520 (Apr. 20, 2007)), provides that .“[a] dentist shall not remove amalgam restorations containing mercury from patients who. are' not allergic to mercury for the alleged-purpose of removing toxic substances from the body, when such treatment is performed solely at the recommendation or suggestion of the dentist,” (italics added).10 Another regulation, also added in 2007 contemplates that a dentist might remove amalgam without a dental indication therefor if the dentist has obtained “appropriate informed consent from the patient,” which includes advising the patient that “(a) [t]he National Institutes of Health has determined that there are no verifiable systemic health benefits resulting from the [756]*756removal of mercury amalgam restorations; and (b) [t]he removal of sound or serviceable mercury amalgam restorations may significantly affect the integrity of the tooth.” 17 DCMR § 4213.45. Prior to 2007, there was no D.C. regulation pertaining to removal of amalgam.
As the D.C. Board acknowledged, the Virginia Board made no finding about whether petitioner removed amalgam from the teeth of Patient S solely at petitioner’s suggestion or recommendation (and similarly made no finding about whether the removal was with the patient’s informed consent). In the absence of a finding that petitioner removed the amalgam without a dental indication therefor and did so at his sole recommendation or suggestion (rather than, for example, at each patient’s request), the Board had an inadequate basis for concluding that the Virginia infraction provided a basis for discipline in the District of Columbia. Dr. Caldwell’s testimony that “removal of amalgam of a patient without adequate dental indication for removal [is] a basis for discipline of a dentist in the District of Columbia” was not a sufficient basis for the Board to apply a standard-of-practice limitation that went beyond that specified in § 4213.44, the standard-of-conduct regulation specifically addressing amalgam removal.
We also note that while the Board found two instances of sanctionable conduct (injections into the patients’ sinus area) that it labeled scope-of-practice violations (but see note 9 supra regarding the factual allegation as to Patient J), it repeatedly emphasized Dr. Caldwell’s testimony that injections into the tonsils (which petitioner was found to have done in the case of Patient 0) are “not within the scope of general dentistry practice in the District of Columbia.” (italics added). During the hearing, the Board Chair remarked that “[u]nder the laws of the District of Columbia[,] general dentists are not treating the tonsils.” (italics added). The Board returned to the subject of tonsil injections in explaining its decision on what sanction to impose, referring to the “superior cervical ganglion” (which petitioner testified is “right behind the tonsil”) and stating that petitioner “knew or should have known that his conduct was not acceptable and that he chose to offer these services to his patients anyway.”
Although the Board’s decision does not formally treat the tonsil injections for Patient 0 as a scope-of-practice violation that was a basis for discipline in the District of Columbia, the Board’s frequent mention of this leaves us with the impression that it was a significant factor in the Board’s determination that reciprocal discipline was warranted. Yet, neither D.C. Code § 3-1201.02(5) (2012 Repl.), which defines the “[p]ractice of dentistry,”11 nor 17 DCMR § 4217, the regulation on “unauthorized [dental] practice,” defines or uses the terms “general dentistry” or “general dentist”'—meaning that Dr. Caldwell’s testimony about the scope of “general dentistry” arguably lacks a legal anchor. Given Dr. Caldwell’s acknowledgment that “[t]here are dentists who by skill or training or expertise in a certain area may go beyond what general dentistry does and that might include the tonsils[,]” and the absence of evidence that this practice is not “[c]ommonly used in dental practice in the United States” and “[c]urrently taught in [American Dental Association-accredited] United States dental schools or dental residency programs!,]” 17 DCMR [757]*757§ 4217.1(b)-(c), we must agree with petitioner that the Board, which charged the tonsil-injection incident as a lack-of-docu-mentatioii-of-diagnosis violation, could not properly sanction it as an additional scope-of-practiee violation. Uncharged conduct, even if it would constitute a violation of District of Columbia law, cannot form the basis for imposition of a sanction. See D.C. Code 3-1205.14(a)(3).
IV.
We now turn to petitioner’s challenge to the sanction the Board imposed: license revocation, with the opportunity to apply for reinstatement only after five years. For two primary reasons, we conclude that we must remand this matter to the Board for reconsideration of the sanction.
The first reason relates to the fact that the Board imposed the sanction in a decision after a remand, to which it consented so that it could correct errors in its original analysis. In this circumstance, the Board “was bound to deal with the problem afresh, performing the function delegated to it[,]” SEC v. Chenery Corp., 332 U.S. 194, 200-01, 67 S.Ct. 1760, 91 L.Ed. 1995 (1947), and it was obligated not to merely “redraft[ ] ... [its] conclusions to ... reinforce [its original] decision.” Ait-Ghezala v. District of Columbia Bd. of Zoning Adjustment, 148 A.3d 1211, 1218 (D.C. 2016); see also Zhang, 834 A.2d at 106 (“[W]e direct that the Board not simply justify the prior result, but rather begin the consideration of Zhang’s application afresh in light of this decision.”). We note that in the Original Decision, having adopted all of the Virginia Board’s scores of findings (designated “a” through “kkkk”), the Board purported to impose a sanction “identical” to the sanction the Virginia Board had imposed (revocation). The Board endorsed the concept of discipline “mirrorfing] that imposed by the original disciplining jurisdiction^]” explaining that it is “a helpful tool for the Board to consider that general legal principles support the adoption of an identical- (or mirroring) sanction as the starting point.”
By contrast, in the Superseding Decision, having concluded that discipline was warranted with respect to only a fraction of the Virginia Board’s findings and with respect to only ten of the twelve Virginia Board findings recited in the NOI (see supra note 4), and without having heard any additional evidence that might justify a harsher sanction even on fewer sustained charges, the Board imposed the very same sanction it had imposed in the Original Decision (for what it then called “the staggering number of [petitioner’s] conduct that constitute^] violations of the District laws”).12 The Board did so even though, for example, it no longer cited (as it had in the Original Decision), as a basis for discipline in the District, the Virginia Board’s finding that the patient the Virginia Board referred to as “Patient I” had “suffered significant [“actual”] harm when his infection was not diagnosed and properly treated, forcing him to seek emergency care,” and even though no finding of actual harm was entailed in any of the [758]*758findings the Board concluded warranted disciplinary action here. We acknowledge that the Board was “free on remand to reach the same result on different grounds[,]” City of Charlottesville v. Fed. Energy Regulatory Comm’n, 774 F.2d 1205, 1212 (D.C. Cir. 1985) (internal quotation marks omitted), but these facts do not give us assurance that, on remand, the Board actually considered the sanction afresh.13
. We note in this regard that although the NOI charged petitioner with only a fraction of the charges that had been sustained by the Virginia Board, the D.C. Board was not precluded from considering petitioner’s other Virginia infractions in considering what sanction to impose, especially to the extent that the Board viewed the Virginia findings as pertinent to petitioner’s willingness -to abide by -the practice limitations and standards of this jurisdiction as one of its licensees.14 That-said, to the extent such infractions were not shown to be grounds for discipline in the District; we caution that they cannot properly be the driving force of the Board’s sanction decision, lest the Board fail to adhere to the limitations of its authority under D.C. Code § 3-1205.14(a)(3). The Assistant Attorney General properly recommended that, “any sanction ... be consistent with the violations that are stated and proved in the [NOI],’’15
The second reason for remand is that our analysis above concludes that [759]*759there was an insufficient basis for reciprocal discipline based on petitioner’s removal of amalgam from Patient S’s teeth, at least with respect to the 2009 infraction, and an insufficient evidentiary basis for (apparently) treating the tonsil injection as a scope-of-practice violation. Our case law establishes that “remand is required ... if substantial doubt exists whether the agency would have made the same ultimate finding with the error removed.” Arthur, 459 A.2d at 146. “[Ujnless we can be sure that the Board would have based its ruling on a lesser number [of bases for revocation than it found to exist,]” we cannot affirm. Faulkenstein, 727 A.2d at 304 (quoting Salama v. District of Columbia Bd. of Med., 578 A.2d 693, 700 (D.C. 1990)).
Given our disposition of this matter, we do not address petitioner’s remaining arguments. But “[s]ince we must remand, we take this opportunity to point out certain deficiencies in the findings and conclusions of the [Board].” Bakers Local Union No. 118 v. District of Columbia Bd. of Zoning Adjustment, 437 A.2d 176, 180 (D.C. 1981); see also Caison v. Project Support Servs., Inc., 99 A.3d 243, 250 (D.C. 2014). We have two points in mind. First, the Board faulted petitioner for not having “contacted the Board for clarification” if he “truly wanted to know what conduct was permissible” “prior to facing disciplinary action before this Board” (which, again, was based on his conduct in Virginia). At oral argument, counsel for the District of Columbia was unable to say whether the Board issues advisory opinions about whether certain practices are or are not permissible. The Board’s criticism was misplaced if the Board would not have given an advisory opinion regarding petitioner’s dental practice in Virginia.
Second, the Board stated that petitioner’s “conduct and practice in the District” were not relevant to the Board’s intent to take reciprocal action based on the Virginia revocation, thus reiterating a ruling that it made during the hearing and that may reasonably have caused petitioner to limit his presentation. Yet, in explaining the sanction it chose, the Board faulted petitioner—-unfairly, it seems to us—for failing to “address whether he has continued to remove amalgam without an adequate dental indication, to replace crowns without documenting a diagnosis, to perform cranial myofascial therapy without adequate dental diagnosis, or to fail to maintain appropriate records” in the District of Columbia.
V.
This matter is remanded to the Board for it to reconsider the appropriate sanction in light of this opinion.
So ordered.