Density of bone formed after sinus augmentation with Nanobone versus that of bone formed after sinus lift with tenting technique : Preliminary study

ABSTRACT

Aim: Comparing the density of bone formed after sinus lifting and augmentation with Nanobone graft to that of the newly formed bone after non-augmented sinus lifting with tenting technique.

Materials and Methods: A total of 12 maxillary sinuses requiring lifting and augmentation procedures were divided into two groups: Group 1: comprised six patients in which grafted maxillary sinus lifting with Nanobone graft procedures were performed, Group 2: comprised six patients in which non-grafted maxillary sinus lifting procedures were performed. Simultaneous implant placement was performed in both groups. Implants were left for six months after placement in bone to ensure complete osseointegration before loading. Results: Immediately post-operative, after 6 months and after 9 months, the mean bone density of grafted group showed statistically significantly higher value than non grafted group. This is due to the continued bone formation in the grafted group.

Conclusion: There is significant increase in density of bone formed after augmented sinus lifting with Nanobone more than that of newly formed bone after non-augmented sinus lifting in the first nine months after the maxillary sinus lifting operation with simultaneous implants placement.

Key Words: Bone density, implants, Nano-bone, tenting technique. Received: 05 January 2019, Accepted: 23 April 2019 Corresponding Author: Khaled M. Shawky, Department of Oral and Maxillofacial Surgery, Faculty of Oral and Dental Medicine, Cairo University, Tel.: 00201227542990, E-mail: [email protected]

ISSN: 2090-097X, January 2019, Vol. 10, No. 1 

INTRODUCTION

Numerous techniques have evolved to overcome the problem of reduced bone volume available in the posterior atrophic maxilla. The lateral window approach technique (Fig. 1)by the aid of Dentium Advanced Sinus Kit (DASK) (Fig. 2) is used for augmentation of the maxillary sinus with bone graft after sinus floor elevation and simultaneous creation of a new compartment between alveolar bone and floor of maxillary sinus. This new compartment may be filled with either autogenous graft, allografts, xenografts, or combination of them to maintain space for new bone formation[1-4].

Nanobone is a recently developed and approved granular material consisting of nanocrystalline HA embedded in a silica gel matrix, which offers several of the advantages of nanostructural biomaterials. Because of the open SiOH or SiO groups of polysilicic acid, the internal surface of this material is extremely large (about 84 m2/g).The interconnecting pores in the silica gel have sizes ranging from 10 to 20 nm, leading to material porosity of about 60%. The surface of the granules is very rough, thus creating an inter-connecting porous structure ranging from micrometer to millimeter dimensions. However, Nanobone has a high breaking strength of about 40 Mpa[5-9].

Bone formation occurs when sinus floor elevation is performed using a trans-alveolar osteotomy technique without placing any graft material in the maxillary sinus. In 1993, Boyne presented experimental results from a study in which implants were left without grafts to protrude 5 mm into the sinus floor and experienced bone formation. In 2004, Lundgren et al. showed evidence of bone formation around all installed implants after sinus lifting without grafting with bone, the blood clot was allowed to form in the sub-antral membrane space to act as a scaffold for new bone formation. The installed implants act as spacemaintaining device under the lifted membrane[10, 12].

 

 

 

 

 

MATERIALS AND METHODS

A total of 12 maxillary sinuses requiring lifting and augmentation procedures were divided into two groups:

• Group 1: comprised six patients in which grafted maxillary sinus lifting with Nanobone graft procedures were performed.

• Group 2: comprised six patients in which non-grafted maxillary sinus lifting procedures were performed.

• Data have been collected from twelve subjects, aged 36-56 years with mean age of 41.4 years and male: female ratio of five: seven

• Simultaneous implant placement was performed in both groups. Implants were left for six months after placement in bone to ensure complete osseointegration before loading.

• The subantral bone height should be at least 5mm from crest of the edentulous ridge to the base of the sinus membrane.

• Number of implants to be inserted in each edentulous side are from 2 to 3 implants to restore the area from canine distally.

Surgical Procedures:

1. Surgeries were operated under general anesthesia

2. Incision was made using a Bard Parker blade number 15 palatal to the crest of the ridge, extending distally 2 cm to the osteotomy site and continues anteriorly till the distal of the canine of the same side of the edentulous ridge.

3. Releasing mesiovertical incision was made at the anterior end of the incision for better visualization of the surgical field. A large bony window was made at the lateral sinus wall using dash bur and large round smooth bur under copious external irrigation

4. The osteotomy at the inferior aspect of the window was made at or as close to the level of superior aspect of residual alveolar bone height

5. Bony window made with dimensions of about 2 cm anteroposteriorly and 1.5 cm vertical cuts (Fig. 3)

6. The sinus membrane was detached from the margins of bony window using DASK.

7. Once the outline was completely detached, the sinus elevator was used to push the sinus membrane inside gently and dissect from the sinus floor so the membrane was completely free from inferior and medial aspects (Fig. 4).

Fig. 3: Clinical photographs showing flap reflection and creation of a bony window in the edentulous maxillary region opposite to the maxillary sinus (the sinus membrane can be seen through the bony window)

Fig. 4: The use of sinus elevator to push the sinus membrane inside gently and dissect from the sinus floor

8. The implant site was marked using a surgical template and osteotomy was performed using pilot drill with copious amount of coolant to guide the rest of the drills in correct positions and angulations.

9. The surgical stent was removed then drills were used in a sequential manner till the required diameter for the fixture was reached.

10. Patients were divided into two groups: For group 1: Nanocrystalline hydroxyapatite (ArtossNanobone) was prepared by mixing the graft granules with saline.The graft material was placed at the superior aspect of the sinus and against the medial aspect of the grafted compartment created in the sinus cavity (Fig. 5). [or group 2, no graft was placed.

Fig. 5: Clinical photographs showing condensation of the Nanobone graft before (B) and after (C) implants placement below the elevated maxillary sinus

 

11. For both groups, the implants were inserted into the prepared osteotomy sites (Fig. 6).

Fig. 6: Clinical photographs showing implants placed under the elevated maxillary sinus

12. The sinus freer was held in place carrying the sinus membrane upwards to avoid any unvisualized tension from the implant on the sinus membrane.

13. For group 1, the rest of the graft material was condensed around the implant to fill the defect.

14. The cover screws of the implants were placed. The flap was then repositioned and the edges were sutured in an interrupted mattress suture using resorbable suture material.

15. Inserted implants were left for six months in bone to ensure complete osseointegration before loading.

Radiographic assessment:

Postoperative panoramic radiographs and computerized tomography (CT) scan of 0.6 mm cuts axial, reformatted sagittal and coronal cuts with two mm interval were performed two weeks after the surgery and other scans were performed later after six and nine months.

CT analysis:

Bone height and density were assessed in comparable standardized sagittal cuts from CT scans performed two weeks after surgery, six months after surgery and nine months after the surgery (three months after implants loading). Analysis of bone height using linear measurements extended from the line of demarcation visible the native bone and grafted bone or newly formed bone to the end of the graft while being perpendicular to the alveolar ridge and an average mean value in millimeters was calculated. Analysis of bone density by taking five random readings for densities using rectangular shapes with specified area of the native bone and newly formed bone of both groups then an average mean value was calculated in Hounsfield units (HU) (Figure 7).

Fig. 7: computerized tomography scans of a case that have undergone grafted sinus lifting on the left side and non-grafted sinus lifting on the right side showing CT number in HU.

 

Statistical analysis:

Comparisons between the changes in bone density within the members of each group separately and between the two groups in term of mean and standard deviation were performed. Paired t-test was used to study the changes by time in each group. Student’s t-test was used to study the changes in bone density between the two groups. The significance level was set as P

 

RESULTS I.

Clinical Results:

1. Pre-operative Clinical Data:

All the patients received detailed clinical examination: no abnormalities in soft or hard tissue had been recorded. All the patients had a health overlying keratinized mucosa. All patients had been examined radiographically through ConebeamCT. One patient had a maxillary sinus septum that was apparent in the panoramic view in the molar region.

2. Operative Clinical Data

Patients had been operated under general anaesthesia. All the patients underwent maxillary sins lift using lateral antrostomy approach. No complication had been recorded during the operation.

3. Post-Operative Follow-Up Clinical Data

All the patients had been examined periodically during the follow period up to nine months. All the patients had completed the scheduled follow up. Swelling was observed in all patients during the first week post operatively and was completely resolved by the seventh– nineth post-operative day. All the patients had removed the sutures after tenfourteen days. Healing was uneventful in all patients.

4. Bone density

Immediately post-operative, after 6 months and after 9 months, the mean bone density of grafted group showed statistically significantly higher value than non grafted group as showed in Fig. 8 

Fig. 8: Bar chart comparing the change in bone density between the two groups.

 

DISCUSSION

Two main techniques were reported by Summers for maxillary sinus augmentation; the crestal and lateral approaches. The most commonly used one is the lateral approach, which is indicated when the subantral bone height is 5mm as was the case with patients included in this study[13,14]. Lateral sinus lift is reported to have several advantages. It provides direct vision of the sinus membrane, and it can be carried out with or without the use of a graft or filling material[15, 22]. In lateral sinus lift, the buccal cortex can be either preserved or totally removed[23]. Whether to preserve the buccal wall of the window or not is controversial. The design of the window is a key factor for a successful sinus lift procedure. Traxler and colleagues recommended a small size window to ensure adequate endosseous arterial anastomosis[24]. However, we found nothing to support any negative effect of the increased window size on the healing process in our study. 

CONCLUSION

There is significant increase in density of bone formed after augmented sinus lifting with Nanobone more than that of newly formed bone after non-augmented sinus lifting in the first nine months after the maxillary sinus lifting operation with simultaneous implants placement.

 

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Fuente: omx.journals.ekb.eg