applied sciences

Case Report 3D-Printed Surgical Guide for Crown Lengthening Based on Cone Beam Computed Tomography Measurements: A Clinical Report with 6 Months Follow Up

Abdulkareem Alhumaidan 1, Ayed Alqahtani 2 and Faisal al-Qarni 3,*

1 Department of Preventive Dental Sciences, College of Dentistry, Imam Abdulrahman Bin Faisal University, Dammam 31441, Saudi Arabia; [email protected] 2 King Fahad Specialist Hospital, Dammam 32253, Saudi Arabia; [email protected] 3 Department of Substitutive Dental Sciences, College of Dentistry, Imam Abdulrahman Bin Faisal University, Dammam 31441, Saudi Arabia * Correspondence: [email protected]



Received: 10 July 2020; Accepted: 11 August 2020; Published: 17 August 2020


Featured Application: When no prosthetic treatment is indicated, esthetic crown lengthening can be facilitated by fabricating a 3D printed surgical guide based on CBCT measurements and an intra oral scan.

Abstract: Excessive gingival display is a common clinical presentation that often requires surgical intervention. This report is for a patient for whom esthetic crown lengthening is indicated due to altered passive eruption. Cone beam computed tomography (CBCT) scan and an intraoral scan were used to design and print a single surgical guide which provided a reference for both gingivectomy and osteoectomy. A satisfactory outcome was obtained 6 months after surgery. The present technique provided a simplified method of generating a surgical guide with predictable results by relying on the existing tooth anatomy rather than diagnostic waxing. This technique is particularly useful when crowns or veneers are not indicated.

Keywords: crown lengthening; surgical guide; CBCT; CAD/CAM; 3D printing

1. Introduction Excessive gingival display, which can be due to altered passive eruption (APE) or gingival enlargement, results in short clinical crowns; this is a cause of common esthetic concern for many patients. Gingivectomy or esthetic crown lengthening with bone resection is often required to increase the clinical crown length and achieve acceptable esthetic outcomes [1]. The decision whether to perform bone resection is largely dependent on the location of the alveolar bone crest in relation to the cementoenamel junction. If the bone crest is at, or coronal to, the cementoenamel junction, then osseous resective surgery is indicated [2]. In order to locate the bone crest, bone sounding and periapical radiograph assessments are typically performed [3,4] However, these methods may be challenging and could provide inaccurate assessments [5]. Cone beam computed tomography (CBCT) has been suggested as a precise and reliable alternative approach for diagnosing APE [6]. To achieve adequate esthetic results, surgical guides are often utilized, and based on diagnostic waxing, made with acrylic resin or vaccuform transparent shells [7,8]. However, this technique has been reported to be sometimes inaccurate [9]. A recent report described a digital workflow in which

Appl. Sci. 2020, 10, 5697; doi:10.3390/app10165697 www.mdpi.com/journal/applsci Appl. Sci. 2020, 10, 5697 2 of 8 Appl. Sci. 2020, 10, x FOR PEER REVIEW 2 of 8 digital waxing was used to design the surgical guideguide for crown lengthening [[10].10]. The use of diagnostic diagnostic waxing is not necessary when no restorative treatmenttreatment isis indicated.indicated. Currently, there are no no known known studie studiess that that have have used used CBCT CBCT to to locate locate the the facial facial bone bone crest crest and and to designto design a digitally a digitally fabricated fabricated guide guide for for crown crown lengthening lengthening surgery. surgery. Therefore, Therefore, this this clinical report presents a patient with altered passive eruption, for whom CBCT was combined with digital scanning to make a single surgical guide for crowncrown lengthening.lengthening.

2. Case Case Report A 22-year-old female patient presented to the College of Dentistry clinics at Imam Abdulrahman Bin Faisal University with complaining of “a gummygummy smile” (Figure1 1).). UponUpon initialinitial examinationexamination thethe patient did not show any gingival tissues at rest, however on full smile, 4 mm of gingival band was shown below the lower border of the maxillary lip. The medical history of the patient did not show any relevant medical issues, while dental history revealed that patient had completedcompleted orthodontic teeth alignment with clear aligneraligner therapy 6 months earlier.

Figure 1. PreoperativePreoperative smile smile view showin showingg excessive gingival display.

Furthermore, there were no significantsignificant findingsfindings on the extra-oral examination and patient was normally asymmetrical. The The facial facial three three thirds thirds were analyzed and found to bebe normal.normal. A lateral cephalometric analysis confirmed confirmed absence of of vertic verticalal maxillary excess and dentoalveolar extrusion. extrusion. The maxillary lip length was 19 mm, the incisal display at rest was 4 mm, and the lip mobility was also assessed and found to be 6 mm. The clinical crown lengths of central incisors, lateral incisors, and canines teeth were 8 mm, 7 mm, and 8 mm, respectively.respectively. The gingival phenotype was assessed using thethe probe-transparency probe-transparency test4 test4 and and was determinedwas determined to be thick.to be A thick. CBCT scanA CBCT (CS9300; scan Carestream (CS9300; CarestreamHealth Inc., Health Kodak, Inc Rochester,., Kodak, NY, Rochester, USA) was NY, acquired USA) was to acquired analyze the to analyze level of the the level alveolar of the bone alveolar crest bonein relation crest in to relation the cementoenamel to the cementoenamel junction. juncti The radiographicon. The radiographic parameter parameter was set was as 90 set kVp as 90/4 kVp/4 mA/s, with voxel size 200 µm, according to manufacturer’s exposure settings with a field of view 10 5 cm mA/s, with voxel size 200 μm, according to manufacturer’s exposure settings with a field of view× 10 (diameter height). Based on the sagittal cross section of the maxillary anterior sextant, the distance × 5 cm (diameter× × height). Based on the sagittal cross section of the maxillary anterior sextant, the distancebetween between the bone the crest bone and crest the and respective the respective cementoenamel cementoenamel junction junction was at was a maximum at a maximum of 1.5 of mm 1.5 (Figuremm (Figure2). The 2). CBCTThe CBCT scan alsoscan showedalso showed that the that patient the patient had a had thick a buccalthick buccal cortex. cortex. Due to Due the to short the shortclinical clinical crowns crowns presentation, presentation, the squarish the squarish appearance appearance of the teeth,of the and teeth, the and aforementioned the aforementioned clinical clinicalfindings, findings, the patient the waspatient diagnosed was diagnosed with excessive with ex gingivalcessive gingival display display as a result as a of result altered of passivealtered passiveeruption eruption APE type APE 1 withtype a1 lowwith bone a low crest. bone Treatmentcrest. Treatment options options were were discussed discussed with with the patient the patient and andesthetic esthetic crown crown lengthening lengthening with with bone bone resection resection was proposed.was proposed. Appl. Sci. 2020, 10, x FOR PEER REVIEW 3 of 8 Appl. Sci. 2020, 10, 5697 3 of 8 Appl. Sci. 2020, 10, x FOR PEER REVIEW 3 of 8

Figure 2. Distance from cementoenamel junction to facial bone crest as measured on cone beam Figure 2. Distance from cementoenamel junction to facial bone crest as measured on cone beam computedFigure 2. Distancetomography from (CBCT). cementoenamel junction to facial bone crest as measured on cone beam computed tomography (CBCT). computed tomography (CBCT). 2.1. Desgin Desgin and 3D Printing of Surgical Guide 2.1. Desgin and 3D Printing of Surgical Guide An intraoral scanscan (TRIOS;(TRIOS; 3Shape) 3Shape) was was acquired acquired to to aid aid in in fabricating fabricating a surgical a surgical guide guide (Figure (Figure3a). 3a).Digital DigitalAn Imagingintraoral Imaging andscan and Communications(TRIOS; Communications 3Shape) was in in Medicine acquired Medicine (DICOM)to (DICOM) aid in fabricating files files were were a converted convertedsurgical guide toto Standard (Figure Tessellation3a). Digital LanguageImagingLanguage and (STL) (STL) Communications format format and and then thenin superimposed Medicine superimposed (DICOM) with STLwith files files STL were acquired files converted acquired from theto fromStandard intraoral the intraoralscanTessellation using scan coDiagnostiX Language using coDiagnostiX (STL) 9.7 software format 9.7(Dental softwareand then Wings (D suentalperimposed INC, Wings Montreal, INC, with Canada).Montreal, STL files Then Canada). acquired using Then thefrom design using the thesoftwareintraoral design scan (3Shape software using Premium coDiagnostiX(3Shape Dental Premium 9.7 System; software Dental 3Shape), (DSystentalem; the Wings 3Shape), level INC, of thethe Montreal, cementoenamellevel of Canada). the cementoenamel junction Then using was junctionmarkedthe design (Figurewas software marked3b) to (Figure guide(3Shape the 3b) Premium gingivectomy to guide Dental the gingivectomy incision System; line, 3Shape), followed incision the line, by level a followed second of the line by cementoenamel 3a mmsecond apical line to 3 mmthejunction cementoenamel apical was to markedthe cementoenamel junction (Figure line 3b) toto junction guideguide thethe line bonegingivectomy to guide resection. the boneincision The resection. virtual line, designfollowed The ofvirtual theby a surgical designsecond of guideline the 3 wassurgicalmm performedapical guide to the was accordingly. cementoenamel performed accordingly. junction line to guide the bone resection. The virtual design of the surgical guide was performed accordingly.

(a) (b) (a) (b) Figure 3.3. ((aa)) Intraoral Intraoral scan scan of of the the maxillary maxillary jaw; jaw; (b) After (b) After superimposition superimposition of the CBCTof the and CBCT the intraoraland the intraoralscan,Figure the 3. cementoenamelscan,(a) Intraoral the cementoenamel scan junction of the andjunction maxillary future andbone jaw; future level(b) boneAfter marked. level superimposition marked. of the CBCT and the intraoral scan, the cementoenamel junction and future bone level marked. Data was transferred to a three-dimensional three-dimensional printer (Formlabs II; Formlabs Formlabs Inc., Inc., Somerville, Somerville, MD, MD, USA).Data TheThe was printerprinter transferred used used utilizes utilizes to a three-dimensional stereolithography stereolithography (SLA)printer (SLA) technology (Formlabs technology with II; Formlabs Laserwith SpotLaser Inc., size Spot Somerville, of 140size microns of MD,140 micronsandUSA). layer The and thickness printer layer thickness ofused 25–300 utilizes of microns. 25–300 stereolithography Themicrons. guide Th wase (SLA)guide printed wastechnology (Figure printed4) and with(Figure then Laser 4) checked and Spot then tosize ensure checked of 140 it tofitsmicrons ensure in the and it mouth fits layer in of the thickness the mouth patient of priorthe25–300 patient to startingmicrons. prior the Thto surgery.startinge guide wasthe surgery. printed (Figure 4) and then checked to ensure it fits in the mouth of the patient prior to starting the surgery. Appl. Sci. 2020, 10, x FOR PEER REVIEW 4 of 8 Appl. Sci. 2020, 10, 5697 4 of 8 Appl. Sci. 2020, 10, x FOR PEER REVIEW 4 of 8

Figure 4. 3D-printed surgical guide. Figure 4. 3D-printed surgical guide. 2.2. Surgical Surgical Procedure Procedure 2.2. Surgical Procedure Local anesthesia (xylocaine (xylocaine with with epinephrine epinephrine 1:100.000) 1:100.000) was was administered administered via via buccal buccal infiltration. infiltration. The guide Local was anesthesia then placed. (xylocaine Using with a 15c epinephrine blade and 1:100.000) fo followingllowing was the administeredupper border viaof the buccal window infiltration. of the guide,The guide an internalinternal was then bevelbevel placed. incision incision Using was was a made15c made blade from from and right right fo tollowing to left left first thefirst molar upper molar teeth border teeth (Figure (Figureof the5). Thewindow 5). guideThe guideof was the wasthenguide, then removed an removedinternal and abevel and second aincision second incision wasincision was made made was from inmade a right sulcular in to a leftsulcular fashion. first molarfashion. The secondary teeth The (Figure secondary flap 5). was The flap removed guide was removedusingwas then a Youger-Good usingremoved a Youger-Good and curette a second while curette incision visualizing while was visualizing themade new in crown athe sulcular new lengths crown fashion. (Figure lengths The6). (Figuresecondary 6). flap was removed using a Youger-Good curette while visualizing the new crown lengths (Figure 6).

Appl. Sci. 2020, 10, x FOR PEER REVIEW 5 of 8 Figure 5. Figure 5. SurgicalSurgical incision incision based on the guide. Figure 5. Surgical incision based on the guide.

Figure 6. Tooth length after gingival excision.

A full thickness mucoperiosteal flap was elevated past the mucogingival junction (Figure 7). The surgical guide was then placed again to determine the extent of osteoectomy needed (Figure 8), and the bone was marked with a round carbide bur. Using an end cutting carbide bur, osteoectomy was then performed; osteoplasty was performed after to remove buccal bone buttressing (Figure 9). The guide was then placed for a final check before internal vertical mattress sutures were placed using a monofilament non-resorbable material (5.0 Prolyne, Ethicon Inc, Somerville, NJ, USA) and hemostasis was ensured.

Figure 7. Mucoperiosteal flap elevated.

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Appl. Sci. 2020, 10, 5697 Figure 6. Tooth length after gingival excision. 5 of 8 Figure 6. Tooth length after gingival excision. A full thickness mucoperiosteal flap was elevated past the mucogingival junction (Figure 7). The surgicalAA fullfull guide thickness was then mucoperiosteal mucoperiosteal placed again flap to flap determine was was elevated elevated the pastextent past the of themucogingival osteoectomy mucogingival junctionneeded junction (Figure(Figure (Figure 8),7). andThe7). Thethesurgical surgicalbone guide was guide marked waswas then with then placed a placedround again carbide again to determine to bur. determine Us ingthe extentan the end extent of cutting osteoectomy of osteoectomy carbide needed bur, neededosteoectomy (Figure (Figure 8), wasand8), andthenthe thebone performed; bone was was marked osteoplasty marked with with a wasround a roundpe rformedcarbide carbide bur. after bur.Us toing remove Using an endan buccal cutting end cuttingbone carbide buttressing carbide bur, osteoectomy bur, (Figure osteoectomy 9). wasThe wasguidethen then performed; was performed; then placed osteoplasty osteoplasty for a final was wascheckperformed performed before after internal afterto remove vertical to remove buccal mattress buccal bone sutures bonebuttressing buttressing were (Figureplaced (Figure using9). The 9a). Themonofilamentguide guide was was then then non-resorbableplaced placed for fora final a finalmaterial check check before before(5.0 internalProlyne, internal vertical verticalEthicon mattress mattressInc, Somerville,sutures sutures were were NJ, placed placed USA) using using and a a monofilamenthemostasismonofilament was non-resorbable non-resorbableensured. material material (5.0 (5.0 Prolyne, Prolyne, Ethicon Ethicon Inc, Somerville, Inc, Somerville, NJ, USA) NJ, and USA) hemostasis and washemostasis ensured. was ensured.

Figure 7. Mucoperiosteal flap elevated. FigureFigure 7.7. Mucoperiosteal flap flap elevated. elevated.

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Figure 8. Surgical guide placed to determine level of osteoectomy. Figure 8. Surgical guide placed to determine level of osteoectomy.

FigureFigure 9.9. Bone level after osteoectomy and and osteoplasty. osteoplasty.

After surgery, the patient was instructed to take 600 mg ibuprofen 3 times/day for the first 7 days and to rinse with 0.12% chlorhexidine gluconate twice daily. On the 10th post-operative day, the patient presented for suture removal. Healing was uneventful (Figure 10). The patient then presented for recall at 6 weeks, and showed satisfactory outcomes at the 6 month follow-up (Figures 11 and 12).

Figure 10. At 10-day follow up.

Appl. Sci. 2020, 10, x FOR PEER REVIEW 6 of 8 Appl. Sci. 2020, 10, x FOR PEER REVIEW 6 of 8 Figure 8. Surgical guide placed to determine level of osteoectomy. Figure 8. Surgical guide placed to determine level of osteoectomy.

Figure 9. Bone level after osteoectomy and osteoplasty. Figure 9. Bone level after osteoectomy and osteoplasty. Appl. Sci. 2020, 10, 5697 6 of 8 After surgery, the patient was instructed to take 600 mg ibuprofen 3 times/day for the first 7 days Afterand to surgery, rinse with the 0.12%patient chlorhexidine was instructed gluconat to takee 600twice mg daily. ibuprofen On the 3 10thtimes/day post-operative for the first day, 7 daysthe patient Afterand to surgery, presentedrinse with the patient for0.12% suture waschlorhexidine removal. instructed Healingluconat to takeg 600wase twice mg uneventful ibuprofen daily. On (Figure 3 the times 10th/ day10). post-operative forThe the patient first 7 daysthenday, andthepresented patient to rinse for withpresented recall 0.12% at 6for chlorhexidine weeks, suture and removal. showed gluconate Healinsatisfac twicegtory daily.was outcomes uneventful On the 10that the (Figure post-operative 6 month 10). follow-up The day, patient the (Figures patient then presented11 and 12). for recall suture at removal. 6 weeks, Healingand showed was satisfac uneventfultory outcomes (Figure 10 at). the The 6 patientmonth thenfollow-up presented (Figures for recall11 and at 12). 6 weeks, and showed satisfactory outcomes at the 6 month follow-up (Figures 11 and 12).

Figure 10. At 10-day follow up. Figure 10. At 10-day follow up.

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Figure 11. Intra oral view (6 months after surgery). Figure 11. Intra oral view (6 months after surgery).

Figure 12. SmileSmile view view (6 (6 months months after surgery).

3. Discussion Surgical guides are usually fabricated as a reference for crown lengthening procedures, especially when anterior teeth are involved. When using Vacuform shells or an acrylic mock-up, diagnostic waxing is required to anticipate the future crown length and to act as a guide for soft tissue incision and freehand osteoectomy. In contrast, the technique presented provides guides for both gingival and bone resection; thus, it facilitates the surgical procedure and provides predictable outcomes. This is important for avoiding unnecessary bone removal, which may result in root exposure and tooth sensitivity. The use of a digital workflow to fabricate a surgical guide has been reported recently [10], where the surgical guide was designed based on a digital wax-up. In this report, the CBCT scan was used to locate the cementoenamel junction and the surgical guide was designed and printed accordingly; this technique eliminates the need for diagnostic waxing when restorative treatment is not indicated. In some patients, when maxillary anterior teeth have incisal wear followed by compensatory eruption, the cementoenamel junction is more coronal than expected. Performing esthetic crown lengthening in such patients based on a diagnostic wax-up can cause excessive removal of soft tissues, which may in turn result in root exposure, mandating a restorative treatment that was otherwise not planned. Using a precise outline of the anatomical cementoenamel junction location of the patient can compensate for the variability among patients and reduce the chance of under- or over- contouring of hard and soft tissues. However, additional clinical studies are needed to confirm the reliability and repeatability of this technique.

4. Conclusions This clinical report describes a method to design and print a surgical guide for esthetic crown lengthening based on the cementoenamel junction level, which was outlined using CBCT.

Author Contributions: Conceptualization, A.A. (Abdulkareem Alhumaidan) and A.A. (Ayed Alqahtani); data curation, A.A. (Abdulkareem Alhumaidan); writing—original draft preparation, F.a.-Q. and A.A. (Abdulkareem Alhumaidan); writing—review and editing, F.a.-Q., A.A. (Ayed Alqahtani) and A.A. (Abdulkareem Alhumaidan); All authors have read and agreed to the published version of the manuscript.

Funding: This research received no external funding.

Acknowledgments: The authors would like to thank Ayham Chaban, Charismatic Dental Lab for his valuable contributions during guide fabrication.

Conflicts of Interest: The authors declare no conflict of interest. Appl. Sci. 2020, 10, 5697 7 of 8

3. Discussion Surgical guides are usually fabricated as a reference for crown lengthening procedures, especially when anterior teeth are involved. When using Vacuform shells or an acrylic mock-up, diagnostic waxing is required to anticipate the future crown length and to act as a guide for soft tissue incision and freehand osteoectomy. In contrast, the technique presented provides guides for both gingival and bone resection; thus, it facilitates the surgical procedure and provides predictable outcomes. This is important for avoiding unnecessary bone removal, which may result in root exposure and tooth sensitivity. The use of a digital workflow to fabricate a surgical guide has been reported recently [10], where the surgical guide was designed based on a digital wax-up. In this report, the CBCT scan was used to locate the cementoenamel junction and the surgical guide was designed and printed accordingly; this technique eliminates the need for diagnostic waxing when restorative treatment is not indicated. In some patients, when maxillary anterior teeth have incisal wear followed by compensatory eruption, the cementoenamel junction is more coronal than expected. Performing esthetic crown lengthening in such patients based on a diagnostic wax-up can cause excessive removal of soft tissues, which may in turn result in root exposure, mandating a restorative treatment that was otherwise not planned. Using a precise outline of the anatomical cementoenamel junction location of the patient can compensate for the variability among patients and reduce the chance of under- or over-contouring of hard and soft tissues. However, additional clinical studies are needed to confirm the reliability and repeatability of this technique.

4. Conclusions This clinical report describes a method to design and print a surgical guide for esthetic crown lengthening based on the cementoenamel junction level, which was outlined using CBCT.

Author Contributions: Conceptualization, A.A. (Abdulkareem Alhumaidan) and A.A. (Ayed Alqahtani); data curation, A.A. (Abdulkareem Alhumaidan); writing—original draft preparation, F.a.-Q. and A.A. (Abdulkareem Alhumaidan); writing—review and editing, F.a.-Q., A.A. (Ayed Alqahtani) and A.A. (Abdulkareem Alhumaidan). All authors have read and agreed to the published version of the manuscript. Funding: This research received no external funding. Acknowledgments: The authors would like to thank Ayham Chaban, Charismatic Dental Lab for his valuable contributions during guide fabrication. Conflicts of Interest: The authors declare no conflict of interest.

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