Statement of the Problem: Orthodontic proclination ofmandibular incisors to decompensate skeletal class IIImalocclusions before orthognathic surgery in patientswith thin periodontal biotype may cause gingival reces-sions. Connective tissue grafts to improve the periodon-tal morphology before orthodontic preparation wouldprevent this gingival compromise.

Materials and Methods: Twelve skeletal Class III pa-tients with thin periodontal biotype (5 males and 7 fe-males), ages between 14 and 34 (mean 20.3 y.o), un-derwent connective tissue graft on the buccal aspect ofthe mandible at the incisors level. Ten patients (10/12)received the grafts before the orthodontic treatment andtwo (2/12) at the time of orthognathic surgery. Thesetwo patients were in active orthodontic phase at thetime of our initial evaluation presenting gingival reces-sions in the inferior central incisors (1/2) and addition-ally in the right lateral incisor (1/2). All patients under-went oral hygiene and plaque control regimens through-out the study. Preoperative clinical evaluation includedvertical dimension of the clinical crown and gingivalthickness over the buccal bone cortex.

Under IV sedation and local anesthesia, a vestibularapproach was used to elevate a full thickness flap andexpose the buccal cortex of the anterior mandibularalveolar process. The connective tissue grafts were har-vested from the palate and positioned in the recipientsite fixating it with horizontal mattress sutures as far ascoronal as possible. In the two patients presenting re-cessions at the time of surgery an additional sulcularincision was made for a pedicle coronally repositionedflap combined with the free graft. Finally the wound wasclosed in a three layer fashion.

After surgery, control visits were weekly up to the firstmonth for oral hygiene and plaque control, then once amonth for 6 months. The same preoperative clinicalmeasurements were taken 3, 6, and 12 months post-operatively.

Method of Data Analysis: Forty eight anterior mandib-ular teeth and surrounding tissues were evaluated intwelve patients pre-operatively, three, six and twelvemonths postoperatively from August 2003 until January2007.

The vertical dimensions of the clinical crowns wereutilized to evaluate the soft tissue vertical loss for eachtooth at each period of time. The mean value for gingivalthickness over the buccal bone cortex and soft tissuevertical loss were calculated for all patients and com-pared with subsequent mean values.

A regression analysis was used to evaluate the effect ofthe thickness of gingival tissues on the preservation ofvertical soft tissue level. (P � 0.05 was considered sig-nificant)

Results: Four teeth (4/48) showed an increase of theclinical crown height (mean 1.2mm) at three monthspost-operatively evaluation, corresponding with the ac-

tive phase of the orthodontic treatment. However, thismeasure stayed stable until the 12 month follow-up. Fiveteeth (5/48) showed a decrease of the clinical crownheight after the coronally repositioned flap combinedwith the connective tissue graft (mean 2.5mm.) at the 12months follow up. The mean increase on the gingivalthickness was 2.3mm after one year follow up. A signif-icant relationship was found between the amount ofgingival thickness and the preservation of the verticalsoft tissue level throughout the study.

Conclusion: The use of connective tissue grafts toincrease the gingival thickness improves the periodontalbiotype. This seems to protect the gingival unit againstrecessions, particularly in the skeletal Class III patientand must be considered before any orthodontic procli-nations.

References

Årtun J, Krogstad O: Periodontal status of mandibular incisors fol-lowing excessive proclination. Am J Orthod Dentofac Orthop 91(3):225-232, 1987

Melsen B, Allais D: Factors of importance for the development ofdehiscences during labial movement of mandibular incisors: A retro-spective study of adult orthodontic patients. Am J Orthod DentofacOrthop 127 (5): 552-561, 2005

POSTER 115Soft Tissue Response to Implantation ofHybrid Poly(Propylene Fumarate)Scaffolds in a Critical Size MandibularDefectCharles Nguyen, MD, University of Texas HealthScience Center at Houston, Dental Branch, 6516 MDAnderson Blvd, Suite 2.059, Houston, TX 77030(Nguyen C; Young S; Kretlow J; Wong M; Mikos A)

Statement of the Problem: A special concern in oraland maxillofacial reconstruction is the potential expo-sure of grafted tissue to the external environment. Con-structs used to restore defects involving the jaws, orbits,nose and ears are potentially in direct contact with theoral cavity, sinuses (maxillary, ethmoidal and frontal),nasal passages and external environment. The design ofsynthetic bone grafting materials should encourage therapid development of lining tissue over the implant sur-face, forming a barrier to the external environment.

Poly(propylene fumarate) (PPF) is a polymer whichhas applications as a bone replacement biomaterial. Sev-eral advantages include its biodegradability into non-toxic products [1], its ability to undergo either thermalor photo-crosslinkage to form a stable scaffold constructand its hydrophobicity [2], which promotes protein ad-sorption and cell adhesion with respect to tissue in-growth during wound healing. This pilot study investi-gates the ability of soft tissue to regenerate across the

Scientific Poster Session

43.e66 AAOMS • 2007

implant surface. In order to simulate a common oraldefect, the post-extraction socket, the material was im-planted within a critical size mandibular defect in arabbit model. It was hypothesized that a PPF-based im-plant would allow for soft tissue growth over an intraoralcommunication with the underlying bone defect, form-ing a continuous layer as part of the normal healingprocess. Furthermore, it was predicted that the softtissue would remain intact over the polymer scaffold andthe defect site, without dehiscence or extrusion of theimplant.

Materials and Methods: A unique porous-solid-poroustri-layered hybrid PPF scaffold was developed for implan-tation within an artificially created 10 mm diameter de-fect in the molar region of a rabbit mandible. The gingi-val epithelium overlying the defect was removed, creat-ing a direct communication with the oral cavity. Sixadult New Zealand White Rabbits each received a PPFscaffold implant, which was rigidly fixated with 1.0 mmtitanium plates and screws. The mandibles were har-vested after a 12 week period with the implants andsurrounding soft and hard tissue left intact for histomor-phometric analysis.

Method of Data Analysis: N/AResults: Histomorphometric analysis of the PPF sam-

ples exhibited a continuous soft tissue border along theimplant-tissue interface with regions of soft tissue in-growth into the porous surfaces of the hybrid PPF scaf-folds. No evidence of wound dehiscence was noted inany of the mandibles, and none of the scaffold implantsunderwent extrusion from the defect site. No osseoustissue in-growth was noted in the PPF samples at twelveweeks.

Conclusion: The present study suggests that PPF-basedscaffold constructs are conducive to soft tissue migrationacross the intraoral communication associated with acritical size mandibular defect and that such tissue re-mains intact to permit the natural healing process toproceed. While the oral environment presents manychallenges to healing tissue and despite the introductionof a foreign implant, PPF-based scaffolds appear to bebiocompatible, with minimal risk of dehiscence or ex-trusion based on our observations. The observation ofsoft tissue in-growth into the porous implant surfacesdemonstrates the potential for long-term implant bio-compatibility and the ability of the hybrid implant tocontribute toward mechanical retention of the overlyingsoft tissue flap. Further studies are required to assessPPF-based implants in oral and maxillofacial bioengineer-ing applications.

References

Vehof JW, Fisher JP, Dean D, van der Waerden JP, Spauwen PH,Mikos AG, Jansen JA. Bone formation in transforming growth factorbeta-1-coated porous poly(propylene fumarate) scaffolds. J BiomedMater Res. 2002 May;60(2):241-51

Fisher JP, Lalani Z, Bossano CM, Brey EM, Demian N, Johnston CM,

Dean D, Jansen JA, Wong ME, Mikos AG. Effect of biomaterial proper-ties on bone healing in a rabbit tooth extraction socket model.J Biomed Mater Res A. 2004 Mar;68(3):428-38

POSTER 116Implant Survival Rates in Patients Witha History of Implant Failure: Evaluationof an Implant Retreatment ProtocolJames M. Ryan, DDS, MS, 406 Beacon Hill Terrace,Gaithersburg, MD, 20878 (Melo M; Shafie H; Obeid G)

Statement of the Problem: Numerous studies haveexamined the factors associated with implant survivalhowever there is a paucity of data regarding the man-agement of implant failures and whether retreatment isassociated with an increased risk of implant failure. Pre-vious studies have investigated the role of implant sur-face characteristics on the outcome of implant retreat-ment. The purpose of this study was to evaluate thesurvival rates of dental implants placed as part of aretreatment protocol in a population of patients with ahistory of implant failure.

Materials and Methods: A retrospective review of allfailed dental implants placed between July 1, 2002 andJune 30, 2006 at the Washington Hospital Center wasperformed. Implant failure was defined as removal of theimplant. The survival rate of implants placed in a retreat-ment protocol was then analyzed. The criteria for sec-ondary implant survival was determined based on clini-cal and radiographic evidence of implant osseointegra-tion over a minimum six month follow-up period.

Method of Data Analysis: (Frequency reporting of im-plant survival as a percentage of implants placed in aretreatment protocol.)

Results: A total of 31 failed implants out of 598 totalimplants placed were identified during the specifiedinterval. According to a retreatment protocol, 22 im-plants were replaced in 13 patients in the same locationas the failed implant and followed for a minimum of sixmonths after surgery. Among implants placed as part ofour retreatment protocol, 20 implants in 12 patientssurvived and were loaded with a prosthesis. This corre-sponds to a 91% survival rate for implant retreatment.

Conclusion: Management of implant failures poses nu-merous challenges and evidence regarding the survivalrates of dental implants placed as part of a retreatmentprotocol is lacking. Here we report a survival rate forimplant retreatment that is comparable to primary im-plant placement and suggests that implant retreatment isa predictable option for patients with a history of previ-ous implant failure.

References

Alsaadi G, Quirynen M, van Steenberghe D. The importance ofimplant surface characteristics in the replacement of failed implants.Int J Oral Maxillofac Implants 2006; Mar-Apr;21(2): 270-4

Scientific Poster Session

AAOMS • 2007 43.e67