Immediate Ridge Augmentation Using Autogenous Tooth Root as a Block Graft in a Periodontally Hopeless Extraction Site: A Pilot Study

Dental implants are increasingly being accepted as a primary tooth replacement option owing to their property of preserving adjacent tooth structure and superior functional, biological, and aesthetic appeal. One of the most important factors for the success of dental implant therapy is favorable volume and architecture of available bone. The possible outcome of tooth extraction includes a resorption of alveolar bone which may result in loss of up to 40% of ridge height and 60% of ridge width along with soft tissue shrinkage during the first 6-month period.^1,2  A systematic review by Avila and colleagues³  compared the postextraction alveolar ridge volume with and without bone grafting and concluded that alveolar ridge preservation immediately after extraction is an effective way of limiting the physiologic ridge resorption.^3,4 

Teeth that have more than 50% of alveolar bone loss along with grade III mobility are considered to be periodontally hopeless and are indicated for extaction.⁵  The sockets of such teeth demonstrate a pre-existing periodontal bone loss which may further complicate the implant placement in such cases. The loss of bony walls in such cases make routine socket preservation techniques such as guided bone regeneration nonviable, and very few techniques have been described in literature pertaining to immediate augmentation of a periodontally hopeless socket. Desai and colleagues described a technique for reconstructing the periodontally hopeless extraction site with autogenous chin block graft and observed effective prevention of bone and soft tissue loss at the end of 6 months, which allowed for placement of implants.⁴ 

Autogenous bone is considered to be the gold standard for bone regeneration, however, its use is limited by factors such as an inadequate amount of donor bone, intra- and postoperative complications, unavoidable resorption, and second surgical site which increases the patient morbidity.^6,7  Tooth bone graft is a new autogenous bone grafting material that is biocompatible, mainly composed of hydroxyapatite that has a low crystalline structure with physicochemical characteristics similar to that of bone. It contains both minerals as well as organic components and promotes bone regeneration.⁷  Recently, extracted tooth roots were used as block autografts for lateral ridge augmentation and it was observed that they supported the staged early osseointegration of titanium implant by basal osseous graft integration at the recipient site followed by gradual graft resorption and replacement by new viable bone.⁸  Based on these results we hypothesized that extracted tooth roots may be used as an alternative to block grafts for immediate augmentation of periodontally hopeless tooth sockets.

In a thorough literature search we found no studies on immediate ridge augmentation using autogenous tooth as a block graft in periodontally hopeless extraction sites. Hence, the aim of the present study was to evaluate the efficacy of extracted tooth root as a block graft in reconstructing the periodontally hopeless extraction site planned for single implant placement both clinically and radiographically.

A total of 13 patients (11 women and 2 men) were selected for this prospective clinical study from the outpatient department. All the patients were explained the surgical procedure in detail prior to the commencement of the study. The treatment procedure was explained to every patient and written consent was obtained. The study was performed in accordance with the declaration of Helsinki and with the ethical approval from Institutional Ethical Committee (BDC/Exam/283/2016-17). Inclusion criteria for this study were patients in the age range of 18–45 years who were systemically healthy with good oral hygiene (plaque index 1.9) with a periodontally hopeless maxillary or mandibular single rooted tooth indicated for extraction.⁹  The tooth indicated for extraction had to be free of soft tissue recession and the adjacent teeth had to be periodontally healthy. Patients who were smokers, pregnant or lactating women, those on drugs affecting bone metabolism like bisphosphonates, and those not willing to participate were excluded from the study.

The patients' medical and dental histories were recorded. Prior to starting the procedure, intraoral periapical radiograph of the site indicated for surgery was done, as well as blood investigations like complete hemogram, random blood sugar, HIV, and hepatitis B. The phase I therapy was performed and the patients with satisfactory oral hygiene maintenance were considered for the study. A cone beam computerized tomography (CBCT) scan of the site of interest was recorded to evaluate the amount of residual bone width, and diagnostic casts were prepared. All the parameters like clinical photographs (Figure 1a, b), and clinical and radiographic ridge width were recorded at baseline and 6 months postaugmentation. The radiographic ridge width and apico-coronal defect depth was measured on CBCT scan using a fixed point (cemento enamel junction [CEJ]) as reference to evaluate the pre- and postoperative changes. The ridge width was measured at the crest of the bone and the apico-coronal defect depth was measured from the deepest point of the defect to the CEJ. This calculation was done with the help of Planmeca Romexis Viewer 3.5.1R Software (Asentajankatu, Helsinki, Finland) with 90 KVp, 10 mA, and exposure time of 12 seconds.

On the day of surgery all of the patients were prescribed Augmentin 625 mg (amoxicillin 500 mg + clavulanic acid, 125 mg; Gsk India, Mumbai, India) and Ketorol DT 10 mg (ketorolac; Gsk India) 1 hour prior to surgery as a prophylactic dose. Each patient was asked to mouth rinse with 0.2% chlorhexidine gluconate mouthwash (Dr Reddys Laboratories, Ltd, Hyderabad, India) for 30 seconds to reduce the bacterial load. Extraorally, the face was scrubbed using 5% povidone iodine (Win-Medicare Pvt, Ltd, New Delhi, India) as a precautionary measure.¹⁰ 

After administering appropriate amount of local anesthesia (lidocaine 2% with adrenaline 1:1 000 000; Dentsply, York, Pa), crevicular incisions were given around the tooth indicated for extraction and to the surfaces of adjacent teeth using a Bard Parker blade No. 15c (Osung, Houston, Tex). Atraumatic extraction of the periodontally hopeless teeth was carried out using a periotome (Figure 2a, b; Osung). A periotome was used along the long axis of the root to sever the periodontal fibres and other connective tissue attachment around the tooth. The instrument was kept in place for 30 seconds; this was repeated all around the tooth. When slight movement of the teeth was visible, extraction forceps were used for extraction. After extraction, vertical releasing incisions were given at the disto-buccal line angles on either side extending a few millimeters beyond the muco-gingival junction and connecting to the horizontal incision for proper accessibility and visibility. A full-thickness muco-periosteal flap was reflected buccally and palatally to expose about 3 mm of bone to be able to stabilize the tooth root graft and collagen membrane. After obtaining adequate visibility, the extracted socket was thoroughly curetted, debrided, and irrigated with sterile saline to remove all the granulation tissue and debris. To obtain a tension free primary closure periosteal releasing incision was given.

The extracted tooth was prepared as previously described.⁸  It was curetted properly to remove all debris and calculus. A straight bur (Mani Diamond burs: coarse, round end taper, head diameter 1.8 mm and length 10 mm) was used to remove cementum under copious irrigation until the underlying dentin was exposed. The tooth was then decapitated at the CEJ using a disc (Diamond disc) under copious saline irrigation and the pulp was extirpated with the K-file (10–20 mm, Dentsply, NY). The extracted tooth was trimmed according to the measured defect site to fit very closely over the recipient bone. After adequate trimming, the tooth root block was immersed in dentin cleansing solution (KometaBio, New Delhi, India) for 10 minutes followed by the buffer saline solution (Dulbecco's phosphate) for 2–3 minutes to obtain a graft free of all organic debris, resulting in a bacteria-free sterile graft.

The clinical ridge width was measured bucco-palatally using surgical vernier caliper (Insize, Ahmedabad, Gujrat, India). The prepared tooth root was adapted to the periodontally hopeless extraction site such that the margins of the auto tooth graft was within the alveolar housing, ensuring adequate blood supply and survival of the graft. The recipient site was analyzed for any bony irregularities and subsequently decortication was done with a drill of 1.2 mm to induce the bleeding. The auto tooth graft was stabilized with 1 or 2 titanium mini screws of 1.2 mm diameter (Biomaterial Korea, Seoul, Republic of Korea) of suitable length (8 mm or 10 mm) depending on the defect and available host bone thickness (Figure 4a). The grafted site was then packed with calcium phosphosilicate bone graft material (Novabone Morsels; Osteogenix, Lubbock, Tex) and was enclosed with resorbable collagen membrane (15×20 mm Matrix Flex, Oakland, NJ). To achieve sufficient stability the membrane was tucked underneath the palatal flap. The flaps were approximated with 4-0 Ethilon nonabsorbable sutures (Ethicon, New York, NY) with a combination of horizontal mattress sutures and simple interrupted sutures to obtain a tension free primary closure. The vertical incisions were approximated with interrupted sutures (Figure 4b).

The patients were prescribed antibiotics such as Augmentin 625 mg (amoxicillin 500 mg + clavulanic acid 125 mg three times a day) and analgesics Maxrel (diclofenac 50 mg + paracetamol 500 mg three times a day; Deys Medical Pvt, Ltd, Kolkata, India) for 5 days and were advised to apply an ice pack postoperatively for 12 hours. They were asked to report in case of any accidental bleeding or edema. The patients were instructed to avoid brushing at the surgical site for 10 days and use chlorhexidine gluconate 0.2% mouth rinse twice daily for 15 days. Oral hygiene instructions were reinforced. The patients were recalled after 14 days for suture removal and re-evaluation. Following this, the patient was kept under regular follow-up once a month for 6 months.

Six months after surgery, the patients were re-evaluated. The ridge width and apico-coronal defect depth was recorded with a CBCT scan and the difference between preoperative and postoperative depth was calculated (Figure 5). The ridge width was measured at the alveolar crest on the sagittal section and the apico-coronal defect depth was measured using CEJ of the teeth adjacent to the grafted site as reference point (Figures 6, 7).⁴  After this, routine implant placement was carried out in all the patients (Figure 5d, f). During osteotomy preparation, a bone core was harvested using a trephine bur (Ossung; Houston, Tex) of diameter 2 mm which was sent for histological analysis (Figure 5c). All the implants were placed uneventfully and no additional bone grafting was required. Also, all the implants demonstrated sufficient primary stability as measured immediately after placement (insertion torque 32–50 Ncm). All the implants were subsequently provided with a prosthesis as performed routinely.

A standard proforma was maintained throughout the study period in which all the values were recorded. The values obtained for this study were analysed using SPSS software (Version 20.0; IBM, SPSS, Chicago, Ill) and it was found to have a normal distribution. A paired t test was used to compare pre- and post-changes in ridge width and defect depth. For this study, P value of .05 was considered to be statistically significant.

All patients completed the stipulated follow up period of 6 months and there were no dropouts from the study. After extraction, at baseline the mean alveolar ridge width was 2.3 ± 0.95 mm; immediately after grafting, 9.2 ± 1.68 mm; and 6 months postoperatively, 8.2 ± 1.14 mm. The mean difference in the clinical ridge width between baseline and 6 months postoperatively was 5.9 mm which was statistically significant (P = .001). After extraction, at baseline, the mean radiographic ridge width at the crest was 1.7 ± 0.79 mm and 6 months after ridge augmentation the mean value increased to 7.5 ± 1.66 mm. The mean difference in preoperative and postoperative alveolar ridge width was 5.8 mm, showing a gain in the width which was statistically significant (P = .001). The mean defect depth from a fixed reference point (CEJ of adjacent teeth) to the deepest point of the defect was 11.9 ± 1.51 mm and 6 months after ridge augmentation, the mean value decreased to 3.7 ± 1.03 mm. The mean difference in preoperative and postoperative defect depth was 8.2 mm which was a gain in the height and was statistically significant (P = .001; Table).

Histological analysis from the bone core obtained 6 months postoperatively demonstrated new bone formation along with complete organization. None of the sections demonstrated any remaining tooth graft particles (Figure 8).

Alveolar ridge resorption after extraction is inevitable and leads to major alveolar bone remodeling in the initial 3–6 months. This results in the dimensional alterations compromising the ideal prosthetic placement in the future.¹  In a systematic review by Tan et al,¹  they concluded that a periodontally hopeless tooth creates a challenging situation where there is alveolar bone loss of more than 50%, grade III mobility with complete buccal wall missing. Extraction of these teeth results in a poor volume of residual ridge due to pre-existing loss of alveolar bone as a consequence of chronic inflammatory nature of periodontal disease. This hampers the placement of implants in the future and thus, reconstruction of loss bone is indicated. Failing to do so at the time of extraction results in a severely deficient ridge, which again needs a two-step rehabilitation process for implant placement. This would include an augmentation procedure after the complete healing of the socket followed by a waiting period of 4–6 months, and then placement of implant. The rationale of this study was to assess the effectiveness of an immediate augmentation technique for a periodontally hopeless socket which helps in constructing sufficient bone for implant placement and would significantly reduce the treatment time and cost for the patient.⁴ 

Several advanced techniques and combinations of grafting materials have been tried and tested over the years for the successful regeneration of bone in an immediate postextraction site. Among all the grafts, autogenous bone is considered to be the gold standard as it is not only osteoconductive but also contains live osteoblasts which helps in osteogenesis.¹¹  However, it has certain limitations such as second surgical site, donor site morbidity, and limited availability of bone.⁴  In a recent literature review, Cicciù and colleagues¹¹  have discussed the various alternatives to autogenous bone graft including alloplasts, xenografts, and allografts, and mentioned their various indications and limitations. The concept of auto tooth graft is gaining attention due to the physiochemical properties similar to autogenous bone. The rationale for using autogenous tooth root in our study was based on the previous studies by Kim and colleagues and Schwarz and colleagues.^7,8,12  The properties of extracted teeth derived from patients were analyzed, and it was observed that the crown portion was composed of high-crystalline calcium phosphate minerals (mainly hydroxyapatite) with higher Ca/P ratio while the root portion was mainly composed of low-crystalline calcium phosphates with relatively low Ca/P ratio.¹²  It was concluded that the root portion has low crystallinity and a greater percentage of other organic materials, and hence can be suitable as bone graft compared to the crown portion.¹³ 

A clinical study was done to evaluate the efficacy of autogenous tooth bone graft compared to that of anorganic bovine bone (Bio-Oss, Geistlich, Switzerland). In postextraction alveolar bone augmentation, there was a comparable increase in vertical dimensions in the autogenous tooth bone graft group at 6 months postextraction. There was no difference found on comparison of autogenous demineralized dentin matrix derived from an extracted tooth and anorganic bovine bone. Both were found to be equally effective in terms of change in vertical dimension, ISQ values, and histomorphometric new bone formation when used for grafting of the extraction sockets. Thus, the results of this study very clearly suggest the effectiveness of autogenous tooth graft material and therefore they can be considered a feasible option for alveolar bone augmentation following dental extraction.¹⁴  Schwarz and colleagues¹⁵  performed another study comparing the autogenous tooth roots to that of autogenous bone blocks for lateral alveolar ridge augmentation following two-stage implant placement. They observed no statistical difference at crestal width after 6 months between 2 groups as both allowed for a successful implant placement. Thus, they concluded that tooth root may serve as an alternative viable substitute to other block grafts in lateral alveolar ridge augmentation.¹⁵  No studies have been conducted which assess the augmentation of a periodontally hopeless extraction site using extracted autogenous tooth root. Based on these findings we hypothesized that tooth root block graft can be used to augment the socket of a periodontally hopeless tooth.

In our study, we selected a total of 13 patients (11 women and 2 men) within the age group 18–45 years having single rooted maxillary and mandibular teeth with hopeless periodontal prognosis and indicated for extraction. CBCT of the experimental site was taken prior to and 6 months after surgical procedure. The periodontally hopeless tooth was atraumatically extracted by using periotome under local anesthetic. This instrument helps in extracting the tooth by causing less trauma to the surrounding thin alveolar bone plates and minimally lacerating the soft tissue, thus helping in preserving the extraction socket. Thorough curettage and debridement of the defect was done. Improper debridement may result in major graft resorption as the residual inflammatory tissue increases the acid phosphatase activity due to the low pH environment of the socket, thus hampering the bone regeneration process.¹⁶  Bleeding was induced from the osseous base to increase the participation of endosteal bone forming cells in the wound.¹⁷  This helps to trigger the regional acceleratory phenomena, which is known to stimulate new bone formation and graft incorporation.¹⁸ 

The extracted tooth was processed to remove all debris, calculus and the layer of cementum exposing the underlying dentin. According to Schwarz et al¹⁵  the removal of cementum layer will improve the ankylosis between the graft and the defect site. The underlying dentin is kept exposed since the physiochemical properties of dentin are similar to those of alveolar bone. The tooth was decapitated at the CEJ and the pulp was extirpated.¹⁵  This was followed by trimming and stabilization of prepared tooth root graft with titanium screws to stabilize the graft to avoid any micromotion which may hamper healing of the graft.

The clinical and radiographic ridge width postoperatively after 6 months was significantly more than the baseline suggesting definite gain in ridge width. There was a slight decline in clinical ridge width from immediate postoperative to 6-months postoperative which was statistically not significant. This can be attributed to the natural bone remodeling during the healing process as tooth roots have both 55% inorganic and 45% organic material which is quite similar to bone. The major component of the inorganic material contains 4 types of calcium phosphate (eg, hydroxyapetite, tricalcium phosphate, amorphous calcium phosphate, and octacalcium phosphate) which are distributed evenly and help in active mineral metabolism.¹⁹  The organic components include bone morphogenetic protein and several other proteins which have osteoinduction capacity, including the type I collagen identical to that found in alveolar bone.⁸  Results obtained in our study are in agreement with the study conducted by Kfir et al²⁰  where they extracted a periodontally hopeless tooth and the site was immediately augmented using platelet rich fibrin and titanium mesh. The authors achieved sufficient bone after augmentation without any additional guided bone regeneration.²⁰  Another study was conducted by Desai et al⁴  where the authors used chin block graft for immediate ridge augmentation after extraction of periodontally hopeless teeth. They also achieved significant gain in ridge width preventing bone loss as well as soft tissue collapse.⁴  The apico-coronal defect depth was reduced from baseline to postoperative after 6 months, suggesting reduction in defect depth which was statistically highly significant. These are in accordance with the findings obtained by Desai et al⁴  where they found sufficient gain in the defect by using chin block for augmenting periodontally hopeless extraction site. Schwarz and colleagues²¹  demonstrated that the periodontally diseased tooth roots were gradually organized and replaced by newly formed bone.

Histological analysis of the bone core, which was obtained 6 months postoperatively, demonstrated formation of new organized native bone. No remnants of the tooth block graft were observed. This can be attributed to several factors. The first factors is the time elapsed since the grafting, which was more than 6 months. In their study, Schwarz and colleagues used similar tooth block graft for lateral alveolar ridge augmentation in foxhounds and observed that at 15 weeks, the block graft was completely resorbed and replaced by nonmineralized tissue which was being replaced by woven bone.²¹  However, in our study, the core sample was obtained at 6 months postoperatively. This time lapse would be enough for resorption of the grafted block material and formation of bone to take place. Also, the core sample was obtained from the osteotomy site, ie, the centre of the grafted area. This area is not in the vicinity of the site where the tooth block graft was placed, ie, the buccal wall of the socket. Hence, it is possible that any remaining graft material would be present near the buccal wall of the ridge and hence, was effectively excluded from the biopsy sample.

The advantages of using tooth bone graft as a block graft are multifold. Because it is an autograft, there is no possibility of graft rejection or cross infection. The graft is the extracted tooth itself and hence there is no second surgical site. It has been demonstrated histologically that the healing of a tooth bone graft is associated with basal osseous graft integration at the recipient site and gradual graft resorption and replacement by new viable bone. When carefully performed, tooth bone block graft is efficient to reconstruct the lost alveolar bone for future implant placement. When the site was reopened for implant placement good integration into the host bone and increase in the ridge width was observed. However complete integration took around 6 months. This time could have decreased if the block was demineralized or perforated.

Few alternatives to this technique for immediate augmentation of periodontally hopeless sockets have been described in the literature. These include either a block autograft such as chin/ramus or platelet rich fibrin or composite of particulate autograft with anorganic bovine bone with titanium mesh.^4,20,22  Another possible alternative could be augmentation using an allogenic cortical lamina.²³  In a study by Herford and colleagues,²⁴  use of rhBMP2 along with distraction osteogenesis demonstrated encouraging results to manage alveolar defects. Clinically, when faced with a deficient/periodontally hopeless socket, it is always be prudent to think of immediate augmentation especially in a site indicated for future implant placement. This kind of planning would save the patient a lot of treatment time and cost and significantly enhance the dimensions of the residual ridge. However, studies on management of compromised sockets are few and more research is required.

Possible complications of the current technique may include graft exposure, graft infection or graft nonunion. Graft exposure can be prevented by careful selection of cases with good tissue biotype along with minimal loss of soft tissue on the tooth indicated for extraction which will facilitate primary wound closure. Proper instrumentation of the extracted root surface and following the graft processing protocol thoroughly would minimize the chances of infection of the graft. Also, thorough cementum removal and close adaptation of the graft to the recipient bed ensuring minimal micromotion using titanium screws would facilitate good union between the graft and host bed.

The limitations of this technique include the presence of a healthy tooth root free of caries and restorations which may not be frequently present. Also, root canal treated teeth may not be ideal for this technique. The case selection is highly specific and should be in such a way that only one bony socket plate is missing and either buccal plate or palatal plate is present to support the graft and ensure good vascularity. The technique also mandates the use of minimum diameter mini-screws, preferably 1.2 mm, to fix the tooth root to the underlying bone. Use of larger diameter screws may increase the chances of fracture of the tooth root block graft. Also, the absence of a control group and limited sample size can be considered limitations of the study design. Further studies with a larger sample size and longer follow up are required to validate the results of this study.

Within the limitations of the present study, it can be concluded that immediate ridge augmentation using autogenous tooth root block graft can be effective option in managing the periodontally hopeless extraction site indicated for implant placement.

Abbreviations

CBCT:

cone beam computerized tomography

CEJ:

cemento enamel junction

The authors report no conflicts of interest.