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CLINICAL REPORT Treatment strategies for infraoccluded dental implants Nicola U. Zitzmann, DDS, PhD, a Dario Arnold, Med Dent, b Judith Ball, Dr Med Dent, c Daniel Brusco, Dr Med, Dr Med Dent, d Albino Triaca, Dr Med Dent, e and Carlalberta Verna, Prof Dr Med Dent f The use of dental implants to replace single missing teeth was established in the 1980s, and 97% success rates were reported at the 5-year follow- up. 1 At that time, it was already known that, in actively growing patients with on- going maxillary skeletal and dental growth, osseointegrated implants do not adapt to po- sitional changes of the natural dentition. Similar to ankylosed teeth, 2 implants remain stationary in the bone and do not follow the changes of the alveolar process with contin- uous eruption of the natural dentition. 3,4 This inability to move with the adjacent teeth causes deciencies in the alveolar bone and surrounding gingival tissues and leads to a discrepancy in the sagittal and transversal dimen- sion, described as infraocclusion or infraposition of the implant. 5 Vertical growth of the nasomaxillary complex with an anterior and downward displacement of the maxilla usually ceases at the age of 17 to 18 years in girls and somewhat later in boys. 6 However, implant infraposi- tioning has also been reported in patients who receive implants during adulthood 7-10 and is related to the continuous eruption of the teeth, which occurs even after occlusal contact is established. 11 From the age of 25 to 46 years, mens faces tend to grow more in posterior height, whereas womens faces tend to lengthen as the mandibular inclination increases and the maxilla elongates to compensate; this places women at greater risk of implant infraposition. 12,13 Particularly individuals with a hyperdivergent growth pattern (long face type) tend to have more pronounced maxillary growth and a backward rotation of the mandible in relation to the cranial base (SN line). The dentoalveolar complex follows this rotation to com- pensate, which enhances the vertical movement of the natural dentition. 6,11 Given these patterns of growth and eruption, an increased risk for infrapositioning of maxillary anterior single tooth implants has been documented, especially in young women and in patients with a long-face appearance. 7-9 Because asymmetry that results from an infrapositioned single-tooth implant in this region is most visible and esthetic impairment is pro- nounced, implant placement should be postponed, 14-16 a Professor, Department of Periodontology, Endodontology and Cariology, University of Basel, Basel, Switzerland. b Resident, Department of Orthodontics, University of Basel, Basel, Switzerland. c Senior Resident, Department of Orthodontics, University of Basel, Basel, Switzerland. d Private practice, Haus zur Pyramide, Zurich, Switzerland. e Private practice, Klinik Pyramide am See, Zurich, Switzerland. f Professor, Department of Orthodontics, University of Basel, Basel, Switzerland. ABSTRACT Single-tooth implants in the maxillary anterior region have the highest risk of esthetic complications from infrapositioning due to continuing maxillary growth and the eruption of adjacent teeth. Although the placement of anterior single-tooth implants should normally be postponed, partic- ularly girls and young women with a hyperdivergent growth pattern, if an infraposition of an implant is present, then thorough examination and strategic planning are required. According to the severity, the strategic treatment options are as follows: simple retention; adjustment or replacement of the implant restoration, possibly including adjacent teeth; surgical implant repo- sitioning by segmental osteotomy combined with osseodistraction; or submergence or removal of the implant. With the patient presented, an interdisciplinary approach that combined orthodontic alignment, surgical segmental osteotomy, distraction osteogenesis, and restorative features offered the opportunity to realign the adjacent teeth into the arch and to harmonize the gingival contour by means of continuous soft tissue enlargement and adaptation. (J Prosthet Dent 2015;113:169-174) THE JOURNAL OF PROSTHETIC DENTISTRY 169
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Page 1: Treatment strategies for infraoccluded dental … › 2015 › 04 › jpd-2015-vol...and alternative treatment options, including auto-transplantation, orthodontic space closure, or

CLINICAL REPORT

aProfessor, DbResident, DcSenior ResiddPrivate pracePrivate pracfProfessor, D

THE JOURNA

Treatment strategies for infraoccluded dental implants

Nicola U. Zitzmann, DDS, PhD,a Dario Arnold, Med Dent,b Judith Ball, Dr Med Dent,c

Daniel Brusco, Dr Med, Dr Med Dent,d Albino Triaca, Dr Med Dent,e and Carlalberta Verna, Prof Dr Med Dentf

ABSTRACTSingle-tooth implants in the maxillary anterior region have the highest risk of esthetic complicationsfrom infrapositioning due to continuing maxillary growth and the eruption of adjacent teeth.Although the placement of anterior single-tooth implants should normally be postponed, partic-ularly girls and young women with a hyperdivergent growth pattern, if an infraposition of animplant is present, then thorough examination and strategic planning are required. According tothe severity, the strategic treatment options are as follows: simple retention; adjustment orreplacement of the implant restoration, possibly including adjacent teeth; surgical implant repo-sitioning by segmental osteotomy combined with osseodistraction; or submergence or removal ofthe implant. With the patient presented, an interdisciplinary approach that combined orthodonticalignment, surgical segmental osteotomy, distraction osteogenesis, and restorative features offeredthe opportunity to realign the adjacent teeth into the arch and to harmonize the gingival contourby means of continuous soft tissue enlargement and adaptation. (J Prosthet Dent 2015;113:169-174)

The use of dental implants toreplace single missing teethwas established in the 1980s,and 97% success rates werereported at the 5-year follow-up.1 At that time, it wasalready known that, in activelygrowing patients with on-going maxillary skeletal anddental growth, osseointegratedimplants do not adapt to po-sitional changes of the naturaldentition. Similar to ankylosed

teeth,2 implants remain stationary in the bone and do notfollow the changes of the alveolar process with contin-uous eruption of the natural dentition.3,4 This inability tomove with the adjacent teeth causes deficiencies in thealveolar bone and surrounding gingival tissues and leadsto a discrepancy in the sagittal and transversal dimen-sion, described as infraocclusion or infraposition of theimplant.5

Vertical growth of the nasomaxillary complex withan anterior and downward displacement of the maxillausually ceases at the age of 17 to 18 years in girls andsomewhat later in boys.6 However, implant infraposi-tioning has also been reported in patients who receiveimplants during adulthood7-10 and is related to thecontinuous eruption of the teeth, which occurs evenafter occlusal contact is established.11 From the age of25 to 46 years, men’s faces tend to grow more inposterior height, whereas women’s faces tend to

epartment of Periodontology, Endodontology and Cariology, University of Bepartment of Orthodontics, University of Basel, Basel, Switzerland.ent, Department of Orthodontics, University of Basel, Basel, Switzerland.tice, Haus zur Pyramide, Zurich, Switzerland.tice, Klinik Pyramide am See, Zurich, Switzerland.epartment of Orthodontics, University of Basel, Basel, Switzerland.

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lengthen as the mandibular inclination increases andthe maxilla elongates to compensate; this placeswomen at greater risk of implant infraposition.12,13

Particularly individuals with a hyperdivergent growthpattern (long face type) tend to have more pronouncedmaxillary growth and a backward rotation of themandible in relation to the cranial base (SN line). Thedentoalveolar complex follows this rotation to com-pensate, which enhances the vertical movement of thenatural dentition.6,11

Given these patterns of growth and eruption, anincreased risk for infrapositioning of maxillary anteriorsingle tooth implants has been documented, especiallyin young women and in patients with a long-faceappearance.7-9 Because asymmetry that results froman infrapositioned single-tooth implant in this regionis most visible and esthetic impairment is pro-nounced, implant placement should be postponed,14-16

asel, Basel, Switzerland.

169

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Table 1. Treatment options for infrapositioned dental implants

Extent of Infrapositiona Treatment Option Indication Remarks

None or mild (<0.5 mm) Stabilization (fixed retention) Craniofacial growth has slowed downor stopped

Risk of open anterior occlusion or anterior-posteriorstep in mandible

Moderate (�1 mm)or severe (>1 mm)

Adjustment or replacement of implantrestoration (and/or adjacent teeth)

Restoration and/or adjacent teeth allowfor modifications

Minimally invasive adjustments

Severe (>1 mm) Surgical implant repositioning(segmental osteotomy) possiblywith distraction

Sufficient width of bony septa required(�3 mm); when soft tissueenlargement is required

Prolonged treatment time

Submerging implant Segmental osteotomy not feasibleand/or implant removal not indicated

Risk of soft tissue perforation and infection;more predictable with 2-part implants that enableremoval of transmucosal portion

Implant removal Augmentation and staged implantplacement and/or alternative restorativetreatments

Extended ridge defects, prolonged treatment time

aClassification according to Jemt et al,9 based on clinical assessment in sagittal dimension.

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and alternative treatment options, including auto-transplantation, orthodontic space closure, or aresin-bonded fixed dental prosthesis, should beconsidered.17,18

Treatment Strategy for Correcting ImplantInfrapositionTo assess the treatment requirements and to select theappropriate treatment to correct an infrapositionedimplant, a clinical and radiographic examination shouldinclude the following: the severity of the verticaldiscrepancy (infraposition) related to the equivalentcontralateral tooth and the position of the incisal edgeand gingival margin of the symmetric contralateral toothas references; the extent of transversal (bucco-oraldimension) changes of adjacent teeth, which possiblybecome trapped lingually to the stationary implantrestoration; the involvement of the opposing dentition,such as compensatory elongation; and 2- or 3-dimensional radiographs to estimate the width of thebone septum, particularly when bone segmentation forosseodistraction is considered.

Indications for treatment options depend on theseverity of infrapositioning and can be categorized ac-cording to their invasiveness (Table 1). Stabilizing theanterior dentition, including the implant with a fixedretainer is considered as a preventive measure to avoidchanges due to the continuing eruption of adjacent andopposing teeth. However, if growth continues, then theretention of the maxillary anterior dentition maintainsthe teeth in a stable position relative to the implant andpossibly causes an open occlusal relationship, or withcompensatory elongation of the mandibular incisors, asagittal step between the anterior and posterior dentitionmay be induced.

Modifying the implant restoration and/or thecontralateral tooth by grinding or even replacing theimplant crown is certainly the least-invasive treatmentoption and, therefore, the most frequently chosen,

THE JOURNAL OF PROSTHETIC DENTISTRY

particularly if the infraposition is minor. This modificationalso can include adjustments to the gingival contour, forinstance, by gingivectomy (Fig. 1). Surgical repositioningof the implant by segmental osteotomy,19 possibly incombination with osseodistraction for gradual move-ments of the bony segment and enlargement of the softtissues also is an option (Fig. 2) as is removing theimplant restoration, submerging the osseointegratedenossal implant portion, and fabricating a resin-bondedor conventional fixed dental prosthesis. Removing theimplant and either augmenting for staged implantplacement or performing an alternative restorativetreatment (resin-bonded or conventional fixed dentalprosthesis) also is an option.

Segmental osteotomy was described in the 1970s as away to correct the position of teeth that could notbe moved orthodontically.20,21 More recently, severalcase reports documented its application for surgicalimplant repositioning.19,22 Distraction osteogenesiscombines the segmental osteotomy with a subsequentslow movement along a fixed appliance to overcome thelimited stretchability of the deficient soft tissues and,therefore, to facilitate a greater translocation of themobilized segment. This procedure was originallydeveloped to reconstruct vertical alveolar bone defectsaccompanied by continuous soft tissue expansion23 andalso has been used to relocate an infrapositioned dentalimplant when the soft tissues have to be enlargedsimultaneously through continuous gradual traction ofthe bony segment.24,25 An interdisciplinary approach thatuses an external distractor stabilized with an orthodonticarch wire and that involves the maxillofacial surgeon, theorthodontist, and the restorative dentist is described withreference to a patient with progressive implantinfraposition.

CLINICAL REPORT

A 24-year-old woman reported dental trauma withavulsion of the left maxillary central incisor at the age of 7

Zitzmann et al

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Figure 1. Patient (age 32 years, 7 years after implant placement) with severe infraposition (2.5 mm) of implant at right central incisor position.Treatment planning comprised new restorations of both central incisors with preceding gingivectomy on facial aspect of left central incisor. A, Frontalview of clinical situation. B, Periapical radiograph. C, Maxillary anterior teeth assessed for esthetics.

Figure 2. Segmental osteotomy of bone surrounding infrapositionedimplant (left lateral incisor position) with parallel vertical incisions inpreparation for osseodistraction.

March 2015 171

years. The tooth had been repositioned but was removed3 years later because of external resorption and ankylosis.At the age of 14 years, skeletal growth ceased, and

Zitzmann et al

an implant (Standard plus, regular neck, 10 mm length;Straumann AG) was placed at the age of 17 years. Aftersoft tissue grafting, the implant restoration was deliveredat age 18 years. Six years later, the patient noticed thatthe implant restoration was no longer in occlusion andthat the implant shoulder was exposed, with gingivalrecession. Moreover, the adjacent teeth were now lingualto the implant crown.

A clinical and radiographic examination revealed thatthe implant infraposition was 2 mm sagitally (vertical) and3 mm facially. The gingival recession at the crown marginamounted to 4 mm (Fig. 3A-C). The width of the bonesepta on the mesial and distal measured 4 mm and 3 mm,whereas the bone that was apical to the implantmeasured only 3 mm, which is the minimum forsegmental osteotomy.26 Presurgically, a multibracketappliance was fixed from canine to canine to level theanterior dentition and to resolve the lingual displacementof the adjacent teeth. After 1 month, a 0.017×0.022stainless-steel wire with an apical bypass in the area of theimplant restoration was inserted. With the patient under

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Figure 3. Patient with severe infraposition of maxillary left central incisor implant. A, Frontal view of patient’s smile. B, Infrapositioned implant. C, Occlusalview, showing facial displacement of implant crown. D, Distractor in place after segmental osteotomy. E, Individualized abutment with fixation at adjacentteeth for torque application. F, Ceramic crown cemented. G, Occlusal view with retainer in place. H, Periapical radiograph after treatment was completed.

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local anesthesia, surgical access was accomplished by amesial and distal trapezoidal incision from the mucogin-gival margin to the vestibule, and preserving the papillarystructure. Soft tissues were mobilized by a tunnelingpreparation that protected the periosteum layerthat covered the implant segment. A segmental osteot-omy with parallel vertical incisions was performed with arotating surgical fissure bur and further extended throughthe medullary and palatal bone with thin osteotomes orchisels until the segment was mobilized. No access was

THE JOURNAL OF PROSTHETIC DENTISTRY

made from the palatal side to ensure adequate vascular-ization. To avoid bone obstructions during movement ofthe segment, the vertical osteotomies should be posi-tioned parallel or even convergent to the apical region.27

A custom-made external distraction device (Orthog-nathics GmbH) was adhesively cemented to the buccalsurface of the implant crown and to the heavy steel or-thodontic arch wire with light-polymerizing compositeresin (Fig. 3D). The distractor position and alignment,which determines the vector of movement of the

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Figure 3. (continued) Patient with severe infraposition of maxillary left central incisor implant. A, Frontal view of patient’s smile. B, Infrapositioned implant.C, Occlusal view, showing facial displacement of implant crown. D, Distractor in place after segmental osteotomy. E, Individualized abutment with fixation atadjacent teeth for torqueapplication. F, Ceramic crowncemented.G,Occlusal viewwith retainer inplace.H,Periapical radiographafter treatmentwascompleted.

March 2015 173

mobilized bone segment, should be planned according tothe required direction of displacement.27

After a 7-day latency period for callus formation, thedistraction of the implant-osseous block was initiatedwith 0.3 mm of activation per day. The distraction pro-cedure was monitored for 2 weeks until an implantextrusion of 4 mm with a palatal inclination of 4 mm wasachieved. The palatal surface and incisal edge of theimplant restoration were continuously adjusted to avoidocclusal interference. When the definitive position wasreached, the distractor was removed and replaced with abracket to facilitate small alignments with a 0.016×0.022Sentalloy wire (Dentsply Intl) for another 2 weeks.The fixed appliance and a 0.019×0.025 titanium-molybdenum alloy wire (Ormco) were then used toretain the distracted implant during the consolidationperiod of 3.5 months until bone healing was complete.After debonding the fixed orthodontic appliance, a splintretainer was used for interim stabilization during therestorative treatment.

The implant restoration and the angulated abutmentwere removed, and an impression was made at theimplant level. An individualized angulated titaniumabutment was combined with a zirconia coping to avoid agrayish discoloration in the marginal area and to facilitatean optimal contour of the crown margin along the un-dulation of the gingival margin. After clinical evaluation,the zirconia coping was adhesively cemented to theabutment by the laboratory technician. This abutment

Zitzmann et al

was then inserted by applying 30 Ncm torque with atemporary fixation on the adjacent teeth (Fig. 3E). Thescrew access was plugged with a small piece of cottonand white gutta percha (Dentsply Intl). A ceramic crown(IPS e.max; Ivoclar Vivadent) was adhesively cemented(RelyX Unicem; 3M ESPE) and excess cement removed.A fixed wire retainer was cemented onto the palatalsurfaces from canine to canine to ensure adequateretention (Fig. 3F-H).

SUMMARY

Because of the potential for complications from infra-positioning, single-tooth implants in the maxillaryanterior should be postponed until mature adulthood. Ifimplant infrapositioning occurs, then surgical segmentalosteotomy, combined with orthodontic distractor fixa-tion, distraction osteogenesis (osseodistraction), andrestorative treatment, is a valuable option for main-taining the particular implant and improving the softtissue contour.

REFERENCES

1. Henry PJ, Laney WR, Jemt T, Harris D, Krogh PH, Polizzi G, et al.Osseointegrated implants for single-tooth replacement: a prospective 5-yearmulticenter study. Int J Oral Maxillofac Implants 1996;11:450-5.

2. Kawanami M, Andreasen JO, Borum MK, Schou S, Hjorting-Hansen E,Kato H. Infraposition of ankylosed permanent maxillary incisors afterreplantation related to age and sex. Endod Dent Traumatol 1999;15:50-6.

3. Cronin RJ Jr, Oesterle LJ, Ranly DM. Mandibular implants and the growingpatient. Int J Oral Maxillofac Implants 1994;9:55-62.

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4. Oesterle LJ, Cronin RJ Jr, Ranly DM. Maxillary implants and the growingpatient. Int J Oral Maxillofac Implants 1993;8:377-87.

5. Thilander B, Odman J, Grondahl K, Friberg B. Osseointegrated implants inadolescents. An alternative in replacing missing teeth? Eur J Orthod 1994;16:84-95.

6. Heij DG, Opdebeeck H, van Steenberghe D, Kokich VG, Belser U,Quirynen M. Facial development, continuous tooth eruption, and mesial driftas compromising factors for implant placement. Int J Oral Maxillofac Im-plants 2006;21:867-78.

7. Andersson B, Bergenblock S, Furst B, Jemt T. Long-term function of single-implant restorations: a 17- to 19-year follow-up study on implant infrapo-sition related to the shape of the face and patients’ satisfaction. Clin ImplantDent Relat Res 2013;15:471-80.

8. Bernard JP, Schatz JP, Christou P, Belser U, Kiliaridis S. Long-term verticalchanges of the anterior maxillary teeth adjacent to single implants in youngand mature adults. A retrospective study. J Clin Periodontol 2004;31:1024-8.

9. Jemt T, Ahlberg G, Henriksson K, Bondevik O. Tooth movements adjacent tosingle-implant restorations after more than 15 years of follow-up. Int JProsthodont 2007;20:626-32.

10. Thilander B, Odman J, Jemt T. Single implants in the upper incisor region andtheir relationship to the adjacent teeth. An 8-year follow-up study. Clin OralImplants Res 1999;10:346-55.

11. Iseri H, Solow B. Continued eruption of maxillary incisors and first molars ingirls from 9 to 25 years, studied by the implant method. Eur J Orthod 1996;18:245-56.

12. Bishara SE, Treder JE, Jakobsen JR. Facial and dental changes in adulthood.Am J Orthod Dentofacial Orthop 1994;106:175-86.

13. Pecora NG, Baccetti T, McNamara JA Jr. The aging craniofacial complex: alongitudinal cephalometric study from late adolescence to late adulthood. AmJ Orthod Dentofacial Orthop 2008;134:496-505.

14. Stenvik A, Zachrisson BU. Orthodontic closure and transplantation in thetreatment of missing anterior teeth. An overview. Endod Dent Traumatol1993;9:45-52.

15. Zitzmann NU, Krastl G, Hecker H, Walter C, Waltimo T, Weiger R. Strategicconsiderations in treatment planning: deciding when to treat, extract orreplace a questionable tooth. J Prosthet Dent 2010;104:80-91.

16. Zachrisson BU, Stenvik A. Single implants-optimal therapy for missing lateralincisors? Am J Orthod Dentofacial Orthop 2004;126:A13-5.

Noteworthy Abstracts of

Fracture resistance of three porcelain-layered

Ferrari M, Giovannetti A, Carrabba M, Bonadeo GDent Mater 2014;30:e163-8

Objectives. Chipping is the most frequent clinical failure ofcompletely understood and different possible reasons have bfracture resistance of 3 different CAD/CAM zirconia frame d

Methods. Thirty extracted sound premolars were divided intoimpressions were taken. Three zirconia frame designs (Aadvcontour (flat design, FD); wax-up as for porcelain-fused-to-mconstant the thickness of the overlying porcelain veneering (Atechnique (Initial Zr, GC). Crowns were cemented utilizingwater storage at 37�C, using a universal testing machine (1 mcentral fossa in a direction parallel to the longitudinal axis ofDigital photographs of the specimens were taken in order tofracture strength were statistically analyzed (One-Way Analy

Results. Load at fractures differed significantly among the grresistance 1721.6 (488.1) N than PFM 1004.6 (321.3) N andfailures occurred in 80% of AG, 70% of PFM, and 50% of F

Significance. Anatomically guided zirconia frames resisted sign

Reprinted with permission of the Academy of Dental Materi

THE JOURNAL OF PROSTHETIC DENTISTRY

17. Kern M, Sasse M. Ten-year survival of anterior all-ceramic resin-bondedfixed dental prostheses. J Adhes Dent 2011;13:407-10.

18. Zitzmann NU, Scherrer S, Ozcan M, Bühler J. R W, Krastl G. Resin-bondedrestorations: A strategy for managing anterior tooth loss in adolescence.J Prosthet Dent 2015. http://dx.doi.org/10.1016/j.prosdent.2014.09.028.

19. Toscano N, Sabol J, Holtzclaw D, Scott T. Implant repositioning by segmentalosteotomy: a case series and review. Int J Periodontics Restorative Dent2011;31:e102-8.

20. Burk JL Jr, Provencher RF Jr, McKean TW. Small segmental and unitoothostectomies to correct dentoalveolar deformities. J Oral Surg 1977;35:453-60.

21. Epker BN, Paulus PJ. Surgical-orthodontic correction of adult malocclusions:single-tooth dento-osseous osteotomies. Am J Orthod 1978;74:551-63.

22. Poggio CE, Salvato A. Implant repositioning for esthetic reasons: a clinicalreport. J Prosthet Dent 2001;86:126-9.

23. Jensen OT, Cockrell R, Kuhike L, Reed C. Anterior maxillary alveolardistraction osteogenesis: a prospective 5-year clinical study. Int J Oral Max-illofac Implants 2002;17:52-68.

24. Oduncuoglu BF, Alaaddinoglu EE, Oguz Y, Uckan S, Erkut S. Repositioning aprosthetically unfavorable implant by vertical distraction osteogenesis. J OralMaxillofac Surg 2011;69:1628-32.

25. Watzek G, Zechner W, Crismani A, Zauza K. A distraction abutment systemfor 3-dimensional distraction osteogenesis of the alveolar process: technicalnote. Int J Oral Maxillofac Implants 2000;15:731-7.

26. Guerrero CA, Laplana R, Figueredo N, Rojas A. Surgical implant reposi-tioning: a clinical report. Int J Oral Maxillofac Implants 1999;14:48-54.

27. Kofod T, Wurtz V, Melsen B. Treatment of an ankylosed central incisor bysingle tooth dento-osseous osteotomy and a simple distraction device. Am JOrthod Dentofacial Orthop 2005;127:72-80.

Corresponding author:Dr Nicola U. ZitzmannDental School, Hebelstrasse 3CH-4056 BaselSWITZERLANDEmail: [email protected]

Copyright © 2015 by the Editorial Council for The Journal of Prosthetic Dentistry.

the Current Literature

CAD/CAM zirconia frame designs

, Rengo C, Monticelli F, Vichi A

zirconia crowns. Causes of chipping have not beeneen considered. The study was aimed at evaluating theesigns veneered with porcelain.

3 groups (n=10). Chamfer preparations were performed,a, GC) were realized: reproduction of the abutmentetal crowns (PFM); anatomically guided, designed to keepG). Porcelain veneering was made with pressure layeringa self-adhesive resin cement (G-Cem, GC). After a 24-hm crosshead speed), crowned teeth were loaded in the

the tooth. Load at fracture was recorded in Newtons (N).assess failure patterns. Between-group differences insis of Variance, Tukey test, p<0.05).

oups (p=0.004). AG exhibited significantly higher fractureFD 1179.5 (536.2) N, that were comparable. RepairableD specimens.

ificantly higher loads than flat and PFM-like frame designs.

als.

Zitzmann et al