Evaluation of Stability of Implants Placed Simultaneously with Lateral Window Sinus Augmentation using Putty Alloplastic Bone Substitute: A Prospective Interventional Study

1. Lecturer, Department of Oral Surgery, Theerthanker Mahaveer Dental College and Research Centre, Moradabad, Uttar Pradesh, India. 2. Professor, Department of Periodontics, Postgraduate Institute of Dental Sciences, Rohtak, Haryana, India. 3. Senior Resident, Department of Periodontics, Postgraduate Institute of Dental Sciences, Rohtak, Haryana, India.

Abstract

Introduction: Lateral window sinus augmentation is done to augment the vertical sinus height for implant placement. Putty alloplasts have been used due to their longer resorption time and provide resistance to implant insertion. Although, widely used, the stability and bone loss around implants placed simultaneously following sinus augmentation with putty bone graft has not been evaluated.

Aim: To evaluate the effect of putty alloplastic bone substitute on implant stability.

Materials and Methods: A prospective interventional study was conducted in the Outpatient Department (OPD) of Oral and Maxillofacial surgery at SGT Dental College and Research Institute, Gurugram, Haryana, India. The duration of the study was two years and 11 months, from December 2014-November 2016. A total of 15 implants were placed simultaneously after lateral window sinus augmentation. Primary implant stablity measurements were done using Resonance Frequency Analysis (RFA). Vertical Bone Height (VBH), Maximum Insertion Torque (MIT) and Crestal Bone Loss (CBL) were measured till six months of follow-up. The data was analysed using standard statistical analyses with Shapiro-Wilk-test, Wilcoxon signed-rank test and Spearman’s correlation co-efficient.

Results: The mean age of the study participants was 58±3.04 years. A total of 15 implants were placed in 12 patients. Adequate primary stability was achieved with MIT >36 N/cm2 in 9/15 patients whereas, in 6/15 patients the MIT was ≤36 N/cm2. The implants showed 100% survival rate. Postoperative bone gain obtained was in the range of 7.89 mm to 11.9 mm, with a mean of 9.92 mm. Acceptable levels of implant stability were obtained after six months.

Conclusion: Within the limitations of the study, it can be concluded that, putty bone alloplast can serve as an adequate bone substitute in simultaneous implant placement after lateral window sinus augmentation and help in achieving stability.

Osseointegration, Sinus floor augmentation, Torque

Placement of dental implants in edentulous posterior maxilla can be challenging because of increased pneumatisation by the maxillary sinus resulting in a deficient hard tissue bed (1). Various surgical techniques like summer’s osteotome technique, lateral window technique, piezosurgery for sinus floor augmentation can be used depending upon the residual bone height. Osteotome technique with simultaneous placement of implants is performed, where more than 6 mm of residual bone is present and augmentation of about 3 to 4 mm is required. In case of more extensive pneumatisation, a bone window in the lateral wall is required to elevate the Schneiderian membrane and augment the sinus floor. This lateral window technique has been reported to deliver a significantly larger increase in bone height than the osteotome technique (2). Previous studies have established that, simultaneous implant placement can be done with lateral window sinus augmentation if a minimum bone height of 4-5 mm is present pre-operatively (3),(4).

Usually, the sinus cavity is augmented using autogenous bone grafts, biomaterials, or their combination. Intraoral autogenous bone grafts, though osteogenic, provide a significantly small volume of donor bone. In addition, they fail to yield predictable results owing to their faster resorption time. Hence, alternatives to autogenous bone grafts have been pursued. Alloplastic materials are synthetic biocompatible products developed to cover a broad range of indications. They come in a great variety of textures, particle size, shape and consistency. Bioactive synthetic bone graft putty is a commercially available product that is premixed and mouldable, which can be shaped and placed easily into osseous defect. It has four components: regular calcium phosphosilicate particles, smaller sized calcium phosphosilicate particles, binder composed of Phoshoethylene Glycol (PEG) and glycerin. Within hours of placement, Ca2+and PO42-ions along with soluble silica are released, forming a silica gel and hydroxyl carbonate apatite layer which recruits of osteoprogenitor cells (5).

Primary implant stability has been identified as a prerequisite to achieve osseointegration (6),(7),(8). This primary stability is critical at the time of implant insertion on grafted site also. Recently, Resonance-frequency Analysis (RFA) has been introduced to provide an objective measurement of implant stability and to monitor implant stability (9),(10),(11),(12),(13),(14),(15),(16),(17),(18). RFA is an effective method to measure changes in implant stability which may not be otherwise apparent clinically (10),(11),(14). It is postulated that, the putty material acts as a viscoelastic medium that transfers the resistance of cortical bony walls of the sinus to the inserted implant similarly, to the function of cancellous bone during implant placement in an intact ridge, thus, increasing its primary stability. Therefore, it is suggested that, the remaining available bone and putty both together constitute in obtaining the primary implant stability (19). It is important to know the role offered by putty alloplastic bone substitute in offering stability to implants placed in compromised conditions as that following lateral window sinus elevation. There are very few studies, which have evaluated the immediate stability of implants placed similarly (20),(21). So, the aim of present study was to evaluate the effect of putty alloplastic bone substitute on implant stability.

Material and Methods

The present prospective interventional study was conducted in the OPD of Oral and Maxillofacial Surgery at SGT Dental College and Research Institute, Gurugram, Haryana, India. The duration of the study was two years and 11 months, from December 2014-November 2016. The present study was approved by Institutional Ethics Committee (IEC) approval number SGT/IEC/2014/28 and ethical principles were followed in accordance with Helsinki declaration as modified in 2013 (22). Written informed consent was also obtained from all the patients.

The non probability convenient sampling was opted for the current study. After stringent inclusion and exclusion criteria, a total of 12 patients were recruited and 15 implants were placed in conjugation with lateral approach sinus elevation.

Inclusion criteria: Healthy male or female patients with inadequate bone height in the deficient posterior maxilla (presenting with edentulous, atrophic unilateral or bilateral maxillary arch with residual bone height less than 5 mm) who requires direct sinus lift with graft and implant placement.

Exclusion criteria: Patients with poor oral hygiene, chronic smoker, patient with systemic illness/systemic drugs that would affect postoperative healing, patient with acute and chronic sinus infections, patient unwilling for the follow-up, history of previous maxillary sinus surgery.

Study Procedure

Oral prophylaxis was done two weeks before the scheduled implant placement. The edentulous site and maxillary sinus were evaluated using Cone Beam Computed Tomography (CBCT) (Table/Fig 1)a,b and implants of suitable length were planned. Direct sinus lift procedure was performed by preparing an osteotomy in the buccal wall to access the schneiderian membrane (Table/Fig 1)c. The boundaries of the osteotomy were determined by the dimension of the maxillary sinus and the amount of elevation as deemed necessary from the preoperative evaluation. The membrane was separated from bone and gently elevated with blunt instruments. The sinus cavity was then filled using alloplastic bone graft material, putty alloplastic bone substitute (NovaBone Dental Putty; NovaBone Products, Alachua, FL). The preoperative residual bone height was ranged from 2 mm to 4.2 mm. All the implants were placed simultaneously with the sinus lift surgeries (Table/Fig 1)d. The implants were slowly torqued into prepared osteotomy site. Primary stability was recorded as the MIT achieved using a torque wrench for the placement of the implant in its final position followed by RFA values, by means of a transducer attached to the implant via a screw and frequency response analyser (OsstellTM device, Integration Diagnostic AB, Sweden) (23).

Primary flap closure was achieved using a single interrupted suturing technique. Postoperative instructions such as, refraining from nose blowing and sucking with a straw were given. Patients were followed-up after one week for suture removal and to evaluate the soft tissue healing and then evaluated at three months and six months (Table/Fig 1)e,f Standardised Intra Oral Periapical Radiography (IOPA) X-rays were taken to evaluate the amount of postoperative VBH (POSVBH) and to assess the radiographic signs of osseointegration. RFA values were recorded again with the same technique at the 6th month follow-up. During surgery for each implant, the implant diameter; implant length; and the insertion torque were recorded and the RFA value with the ISQ scale. In each patient, mesial and distal implant crestal bone levels were evaluated by calibrated examination of periapical X-rays. The periapical radiographs were taken by using long-cone paralleling technique, and the measurements were scaled using known markers (i.e., the length of the implant) to correct possible elongation or foreshortening of measurements.

Resonance Frequency Analysis Buccolingually (RFBL), Resonance Frequency Analysis Mesiodistally (RFMD) were measured at baseline (immediately after implant placement) and 6th month follow-up. CBL Mesial (CBLM), CBL Distal (CBLD), Pre VBH, POSVBH were measured at baseline, three months and six months after placement. MIT was noted at the time of implant insertion.

Statistical Analysis

Data recorded was processed by standard statistical analysis in Statistical Package for Social Sciences (SPSS) software. The normality of distribution of data was examined by Shapiro-Wilk test. Data was found to be non normally distributed and hence, was subjected to non parametric test for statistical analysis. Intragroup comparison at two times interval was done using Wilcoxon signed-rank test and at three point intervals by Friedman analysis. Correlation between predictors and dependent variables was analysed by Spearman’s correlation analysis. The level of statistical significance was p<0.05.

Results

A total of 15 implants were placed in 12 patients (eight males and four females) with a mean age of 58±3.04 years (Table/Fig 2). The preoperative residual bone height ranged from 2 to 4.2 mm (mean 3.46±0.61). Adequate primary stability was achieved with MIT >36 N/cm2 in 9/15 patients (60%) whereas, the MIT was ≤36 N/cm2 in 6/15 implants placed (40%). In all the cases (100%) atleast 25 N/cm2 of MIT were achieved. Postoperative bone gain obtained was in the range of 7.89 mm to 11.9 mm, with a mean of 9.92 mm.

(Table/Fig 3) represents intragroup comparison of parameters at baseline, three months and six months. On intragroup comparison mesiodistal and buccolingual RFA was highly statistically significant (p=0.001). Mesial and distal crestal bone analysis was highly significant at baseline and six months follow-up (p=0.002 and 0.001, respectively). VBH gain was also statistically significant (p=0.001) with mean postoperative bone height 13.11±0.61 mm at three month follow-up and 12.67±0.67 mm at six months.

Spearman’s correlation in between various parameters (Table/Fig 4) revealed no significant correlation between RFA values and marginal bone loss.

Discussion

Several treatment options have been utilised in posterior maxillae to overcome the problem of inadequate bone quantity. The most conservative treatment is the insertion of short implants to avoid the need for entering the sinus cavity. However, the bone found in the posterior maxilla consists mostly of thin cortices and spongy cancellous compartments, hence, guarding the long-term success of short implants. The sinus lift procedure or sinus floor elevation, is an internal augmentation of the maxillary sinus, which is intended to increase the VBH in the lateral maxilla in order to facilitate the placement of implants (24). Even though, sinus lift procedures are well documented, very few studies were carried out to understand if, the bone grafted during a sinus lift is able to assure a good primary stability during implant insertion and if it is able to maintain this stability even after six months. The augmentation of the maxillary sinus induces the bone formation by promoting osteoconduction from surrounding bone and is dependent on the rate of revascularisation and osteoblast recruitment (25),(26). During organisation of granulation tissue, inconspicuous perivascular cells are activated which, ultimately form bone (27).

The purpose of the present study, was to assess the stability of implants placed with the proposed sinus augmentation technique and to study the relationship of VBH, Insertion torque, and the RFA values at the time of implant placement and followed-up to six months. A statistically significant increase in RFA (ISQ value) was noted (p=0.001) at six months follow-up. This finding is consistent with the finding of Sullivan D et al., (28). Two implants had ISQ values less than 40 at the time of implant placement. This increased thereafter at the time of six month follow-up. In the present study, statistically significant CBL was observed: mesially from 0.17±0.21 to 0.51±0.30 and distally from 0.15±0.18 to 0.58±0.33 at three months and six months, respectively. These findings fall well within the implant success criteria by Albrektsson T et al., (29). Though, in the present study, the crestal bone resorption mesially and distally showed grafted sinus height loss for each implant between follow-up time intervals; however, apexes of all implants were observed to be covered with grafted sinus floor and the reported loss in the VBH was due to CBL. The rapid initial bone loss in the present study might be the result of periosteal elevation, surgical trauma, and the osteotomy preparation of the recipient bed and stress concentration from tightening of the implant in less than 5 mm of remaining residual bone height. The average residual alveolar bone height was 3.46±0.61 mm preoperatively and after sinus floor augmentation, the increase in the residual bone height was in the range of 7.89 mm to 11.9 mm (mean 9.92 mm) with graft. The increase in post VBH was statistically very significant in the range of 12.67±0.67 mm after sinus floor augmentation over the period of six months following surgery. These findings were compatible with studies by Mazor Z et al., (30).

Despite CBL, the overall RFA values increased, which suggested that, the effect of bone loss was compensated by an increased interfacial stiffness resulting from bone formation and remodelling, due to the graft maturation and osseointegration (31). No preoperative VBH was found to be the predictive value for implant stability. Even though, patients had very less residual bone height pre-operatively, good stability could be attained with marked increase in RFA values within six months. Implants in soft bone with low primary stability showed a marked increase in stability in the current study. The Calcium Phosphosilicate (CPS) putty acted as a viscoelastic medium, which transferred the resistance of cortical bony walls of the sinus during placement of implant similarly to the function of cancellous bone, thus, increasing its primary stability. It is assumed that, the primary stability of the implant was obtained from its anchorage in the remaining crestal bone and the putty present in the augmented sinus cavity. The viscoelastic characteristics of the putty bone substitutes and their enhanced graft particle containment allowed the surgeon to have a better tactile sensation during the implant surgical procedure. Therefore, if sufficient primary stability can be obtained, a single stage approach with simultaneous implant placement is preferred, even in minimal residual alveolar bone.

In the present study, all the implants achieved acceptable stability (ISQ >55) with sinus augmentation at the end of six months, which signifies a safe level of stability (32). The bone height at baseline was not found to be the predictor of primary implant stability. The survival of implants placed was found to be 100% after six months of healing period. The simultaneous placement of implant in direct sinus lift thus, gives advantage of single stage surgery as being less invasive, more cost-effective, and saves time for the patients and a viable treatment option when primary stability can be assured.

Limitation(s)

Limitations of the study include the small sample size and limited follow-up period. Long-term prospective studies are required to verify the findings of the present study and provide definitive guidelines for simultaneous implant placement, along with direct sinus lift procedures.

Conclusion

Simultaneous implant placement with sinus elevation and putty alloplastic bone grafting can be considered as a viable option for implant placement in case of atrophic maxillae. Within the limitations of the present study, it can be concluded that, implant placement with sinus elevation and putty alloplastic bone grafts yields a sufficient degree of osseointegration, even in bare minimum residual bone height of 2 mm. Initial primary stability seems to be a more pivotal factor for implant survival, rather than residual VBH in isolation.

DOI and Others

DOI: 10.7860/JCDR/2023/61180.18127

Date of Submission: Nov 02, 2022
Date of Peer Review: Dec 07, 2022
Date of Acceptance: Mar 01, 2023
Date of Publishing: Jul 01, 2023

AUTHOR DECLARATION:
• Financial or Other Competing Interests: None
• Was Ethics Committee Approval obtained for this study? Yes
• Was informed consent obtained from the subjects involved in the study? Yes
• For any images presented appropriate consent has been obtained from the subjects. Yes

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EMENDATIONS: 7