Primary Stability Determination of Implants Inserted in Sinus Augmented Sites: 1-Step Versus 2-Step Procedure

Specific use of the implant stability quotient as a guide to improve healing for patients who had undergone rehabilitation with fixed implant-supported dental prostheses

PURPOSES

to develop a clinical approach to evaluating osteointegration around bone implants and try to determining which was the correct time of implant loading in different edentulous indications, that is, either properly positioned implants or implants "at risk", generally referred to as implants having increased probability of failure (namely those for which primary stability had been achieved via a time-consuming surgery).

MATERIALS

Several implant-supported rehabilitation strategies, with or without bone augmentation procedures, were performed in the upper and lower arches: From 2 to 5 months following implant placement, the prosthetic restorations were performed. A resonance frequency analyzer allowed clinicians to measure intraoperative and postoperative implant stability, then the values of the implant stability quotient, ISQ, ranging from 0 to 100, were registered. ISQs were ranked into 3 levels: Green (ISQ ≥ 70), Yellow (60 ≤ ISQ < 70), and Red (ISQ < 60). Groups were subjected to Pearson's χ2 analysis, with YATES correction when necessary, with a significance level of 0.05.

RESULTS

A total of 213 implants had been included. When the distribution of normalized values of ISQ registered for implants inserted in native bone and loaded at 2-3 months (5 Red, 19 Yellow, and 51 Green) was compared to that of native implants loaded after 4-5 months (4 Red, 20 Yellow, and 11 Green), a significative difference was found (p-value = 0.0037). At the time of loading, significance was lost. Significant clinical improvements on the distribution of normalized values of ISQ were apparent for both the implants placed in pristine and those placed in lifted sinuses; no significant differences were registered between the two groups.

CONCLUSION

At the loading time, implants considered to be at risk behaved similarly to the native sites for which the overall prosthetic workflow took about few; results confirmed that the mandibular implants appeared to have higher stabilities when compared to maxillary implants at both the intraoperative and the postoperative surveys.

The clinical significance of implant stability quotient (ISQ) measurements: A literature review

Implant stability quotients (ISQ values) are obtained in dental clinical practice on a non-invasive basis by resonance frequency measurement rapidly after surgical placement of implants. The ISQ-values are used as indicator for mechanical implant stability, and are believed to have predictive power for clinical outcome. It is the aim of this review to provide a synopsis of all factors described in the literature that influence ISQ measurements by performing an exhaustive literature review; moreover, this review aims at elucidating the key factors relevant for a rapid clinical predictive assessment. We searched systematically and exhaustively all major databases for publications relating to ISQ measurement methodology and for ISQ-influencing factor analyses. The reports identified were ordered in experimental (preclinical) studies and in clinical publications. We were able to identify 13 basic factors influencing ISQ-measurements. Among these, local bone quality, playing a key role in such measurements, was subdivided in four specific subfactors; thus a total of 17 individual factors was identified and reported to influence ISQ-measurements. A comprehensive list of these factors is provided in Table-form. A critical analysis points out that only 6 of these factors are of a sound predictive power useful for a rapid clinical assessment; and only two of these factors appear to have a well-documented scientific basis.

Relationship between cortical bone thickness and implant stability at the time of surgery and secondary stability after osseointegration measured using resonance frequency analysis

Purpose

It has been suggested that resonance frequency analysis (RFA) can measure changes in the stability of dental implants during osseointegration. This retrospective study aimed to evaluate dental implant stability at the time of surgery (primary stability; PS) and secondary stability (SS) after ossseointegration using RFA, and to investigate the relationship between implant stability and cortical bone thickness.

Methods

In total, 113 patients who attended the Tohoku University Hospital Dental Implant Center were included in this study. A total of 229 implants were placed in either the mandibular region (n=118) or the maxilla region (n=111), with bone augmentation procedures used in some cases. RFA was performed in 3 directions, and the lowest value was recorded. The preoperative thickness of cortical bone at the site of implant insertion was measured digitally using computed tomography, excluding cases of bone grafts and immediate implant placements.

Results

The mean implant stability quotient (ISQ) was 69.34±9.43 for PS and 75.99±6.23 for SS. The mandibular group had significantly higher mean ISQ values than the maxillary group for both PS and SS (P<0.01). A significant difference was found in the mean ISQ values for PS between 1-stage and 2-stage surgery (P<0.5). The mean ISQ values in the non-augmentation group were higher than in the augmentation group for both PS and SS (P<0.01). A weak positive correlation was observed between cortical bone thickness and implant stability for both PS and SS in all cases (P<0.01).

Conclusions

Based on the present study, the ISQ may be affected by implant position site, the use of a bone graft, and cortical bone thickness before implant therapy.

Relationship between implant stability measurements obtained by insertion torque and resonance frequency analysis: A systematic review

BACKGROUND

The primary stability of dental implants can be evaluated by insertion torque (IT) and resonance frequency analysis (RFA).

OBJECTIVE

Assess the supposed relationship between the IT and RFA.

MATERIALS AND METHODS

A systematic review was performed based on the PRISMA. The electronic search was performed in the PubMed, Web of Science, SCOPUS, Cochrane Library electronic, OVID, and Scielo databases. Manual searches were also performed. There was no restrictions regarding year of publication or language. The articles identified were assessed independently by 3 trained researchers. Clinical trials reporting the RFA values by means of implant stability quotient (ISQ) and IT were included.

RESULTS

The electronic and manual searches yielded 2017 studies. Twelve studies were included in the systematic review. There was no statistically significant correlation between ISQ and IT (r_s  = .366; P = .079). The quality of the evidence was downgraded by risk of bias and indirectness; and the certainty of the evidence was low.

CONCLUSION

IT and RFA are independent and incomparable methods of measuring primary stability. Is important for clinicians to define only one method of evaluation for each implant.

Sinus augmentation and concomitant implant placement in low bone-density sites. A retrospective study on an undersized drilling protocol and primary stability

BACKGROUND

Recently, a torque-measuring micromotor has been shown to provide a reliable, quantitative intraoperative evaluation of bone density and implant primary stability. This may be particularly useful for determining bone quality of residual bone and consequently the most appropriate site preparation in the posterior maxilla, where bone often is of low density and quality.

PURPOSE

This work aimed to assess the medium-term success of implants placed during 1-stage sinus augmentations using an undersized drilling protocol. In case of low bone density, the relationship between residual bone height (RBH) and primary stability was also investigated.

MATERIALS AND METHODS

Clinical records of patients who underwent sinus augmentation and concomitant implant placement following a 12.5% undersized drilling protocol were retrospectively analyzed. In all patients, bone density measured intraoperatively was ≤ 0.45 g/cm³ . A minimum of 60 months of follow-up was required for inclusion.

RESULTS

Records of 106 patients who received 253 implants were reviewed. No significant difference in the implant success rate was found for patients who had less than 4 mm of RBH and those who had more.

CONCLUSIONS

Underpreparation of the implant-placement sites enabled achievement of successful implant-supported rehabilitation of the posterior maxilla even when both RBH and bone density were low.

Multivariate linear regression analysis to identify general factors for quantitative predictions of implant stability quotient values

Objectives

This study identified potential general influencing factors for a mathematical prediction of implant stability quotient (ISQ) values in clinical practice.

Methods

We collected the ISQ values of 557 implants from 2 different brands (SICace and Osstem) placed by 2 surgeons in 336 patients. Surgeon 1 placed 329 SICace implants, and surgeon 2 placed 113 SICace implants and 115 Osstem implants. ISQ measurements were taken at T1 (immediately after implant placement) and T2 (before dental restoration). A multivariate linear regression model was used to analyze the influence of the following 11 candidate factors for stability prediction: sex, age, maxillary/mandibular location, bone type, immediate/delayed implantation, bone grafting, insertion torque, I-stage or II-stage healing pattern, implant diameter, implant length and T1-T2 time interval.

Results

The need for bone grafting as a predictor significantly influenced ISQ values in all three groups at T1 (weight coefficients ranging from -4 to -5). In contrast, implant diameter consistently influenced the ISQ values in all three groups at T2 (weight coefficients ranging from 3.4 to 4.2). Other factors, such as sex, age, I/II-stage implantation and bone type, did not significantly influence ISQ values at T2, and implant length did not significantly influence ISQ values at T1 or T2.

Conclusions

These findings provide a rational basis for mathematical models to quantitatively predict the ISQ values of implants in clinical practice.

Maxillary Sinus Floor Augmentation Using Biphasic Calcium Phosphate and a Hydrogel Polyethylene Glycol Covering Membrane: An Histological and Histomorphometric Evaluation

PURPOSE

Maxillary sinus floor augmentation with a lateral approach is usually performed using a bone substitute covered with standard collagen or a synthetic barrier membrane to prevent soft tissue ingrowth within the bone graft. The purpose of this case series was to evaluate a polyethylene glycol (PEG) membrane with a hydrogel consistency, used to protect the lateral sinus anstrotomy, by analyzing the histological quality and histomorphometric quantity of newly formed bone (NB) in a maxillary sinus graft using biphasic calcium phosphate (BCP).

MATERIALS AND METHODS

Fifteen sinuses were grafted from 12 patients. Six months after the maxillary sinus floor augmentation, bone biopsies were harvested from 7 patients during the implant placement second-step surgery.

RESULTS

The histomorphometric evaluation of the 7 grafted sinuses showed mean values of 27.4 ± 4.6% for NB, 26.9 ± 5.4% for remaining BCP particles, and 45.7 ± 6.0% for connective tissue/bone marrow. No implant failure was observed in the 14- to 45-month follow-up period after maxillary sinus floor augmentation procedure and in the 8- to 39-month follow-up period after implant loading.

CONCLUSION

The use of a hydrogel PEG membrane to protect BCP proved to be a valuable grafting procedure to enhance the vital bone formation in the maxillary sinus floor augmentation procedure.

Two Composite Bone Graft Substitutes for Maxillary Sinus Floor Augmentation: Histological, Histomorphometric, and Radiographic Analyses

OBJECTIVE

To histologically, histomorphometrically, and radiographically compare clinical performance of 2 composite bone graft substitutes for maxillary sinus floor augmentation (MSFA).

MATERIALS AND METHODS

Partially or totally edentulous patients requiring MSFA underwent grafting procedures using a 2:1 mixture of biphasic calcium sulfate (CS) and deproteinized bovine bone (group CB) or biphasic CS and alloplast (group CA). Grafts were allowed to heal for 5 months before placing the implants. During implant surgery, bone samples were collected from grafted areas for histology and histomorphometry. Graft height was analyzed using cone beam computed tomography.

RESULTS

Sixteen patients completed the study. Mean percentages of new bone were 34.40% ± 18.91% and 36.71% ± 15.32% for the CA and CB groups, respectively; percentages of residual graft particles were 6.98% ± 5.09% and 5.52% ± 4.12%, respectively. The only significant finding was a greater graft height loss in the CA group (24.44% ± 6.52% vs 14.60% ± 4.58%).

CONCLUSION

Both graft substitutes were integrated in bone, confirming their biocompatibility and effectiveness for MSFA. The CB group showed less bone height loss than the CA group.

Mathematical evaluation of the influence of multiple factors on implant stability quotient values in clinical practice: a retrospective study

Objectives

The objective of this study is to mathematically evaluate the influence of multiple factors on implant stability quotient values in clinical practice.

Patients and methods

Resonance frequency analysis was performed at T1 (measured immediately at the time of implant placement) and at T2 (measured before dental restoration) in 177 patients (329 implants). Using a multivariate linear regression model, we analyzed the influence of the following eleven candidate factors: sex, age, maxillary/mandibular location, bone type, immediate/delayed implantation, bone grafting (presence or absence), insertion torque, I-/II-stage healing pattern, implant diameter, implant length, and T1–T2 time interval.

Results

The following factors were identified to significantly influence the implant stability quotient (ISQ) values at T1: insertion torque, bone grafting, I-/II-stage healing pattern, immediate/delayed implantation, maxillary/mandibular location, implant diameter, and sex. In contrast, the ISQ values at T2 were significantly influenced only by three factors: implant diameter, T1–T2 time interval, and insertion torque.

Conclusion

Among the eleven candidate factors, seven key factors were found to influence the T1-ISQ values, while only three key factors influenced the T2-ISQ values. Both T1 and T2-ISQ values were found to be influenced by implant diameter and insertion torque. T1 was influenced specifically by the sex of the patient, the location (maxillary or mandibular), the implantation mode (immediate/delayed implantation), the healing stage, and the absence or presence of bone graft materials.

Biomechanical evaluation of oversized drilling technique on primary implant stability measured by insertion torque and resonance frequency analysis

Background

This study evaluated the influence of implant site preparation depth on primary stability measured by insertion torque and resonance frequency analysis (RFA).

Material and Methods

Thirty-two implant sites were prepared in eight veal rib blocks. Sixteen sites were prepared using the conventional drilling sequence recommended by the manufacturer to a working depth of 10mm. The remaining 16 sites were prepared using an oversize drilling technique (overpreparation) to a working depth of 12mm. Bone density was determined using cone beam computerized tomography (CBCT). The implants were placed and primary stability was measured by two methods: insertion torque (Ncm), and RFA (implant stability quotient [ISQ]).

Results

The highest torque values were achieved by the conventional drilling technique (10mm). The ANOVA test confirmed that there was a significant correlation between torque and drilling depth (p<0.05). However, no statistically significant differences were obtained between ISQ values at 10 or 12 mm drilling depths (p>0.05) at either measurement direction (cortical and medullar). No statistical relation between torque and ISQ values was identified, or between bone density and primary stability (p >0.05).

Conclusions

Vertical overpreparation of the implant bed will obtain lower insertion torque values, but does not produce statistically significant differences in ISQ values.

Key words:Implant stability quotient, overdrilling, primary stability, resonance frequency analysis, torque.

Modified protocol of the intraoral welding technique for immediate implant-supported rehabilitation of the edentulous maxilla

PURPOSE

The aim of this study was to report the outcomes of a treatment option of immediate loading with intraoral welding on only 4 implants for the restoration of patients with maxillary edentulism.

MATERIALS AND METHODS

Seventeen consecutive patients were rehabilitated with 2 parallel and 2 tilted implants in the maxilla. Immediately after implant placement, angulated abutments were screwed on the implants to create better parallelism among the implants; thereafter, a titanium bar was intraorally welded to the welding pins to create a superstructure that rigidly splinted the implants. A fixed full-arch durable prosthesis was delivered on the same day of the surgery. The patients were followed for 26.5 months on average.

RESULTS

During the follow-up time, 2 implants were lost giving an implant survival rate of 97%. Nonetheless, all the prostheses remained in function and the prosthetic success was 100%.

CONCLUSIONS

The rehabilitation of the edentulous maxilla with an immediately loaded full-arch prosthesis, obtained through intraoral welding on only 4 implants, is a functionally and esthetically successful treatment.

Fresh-frozen allografts combined with bovine bone mineral enhance bone formation in sinus augmentation

We evaluated histologically, histomorphometrically, and tomographically the effects of the association of fresh-frozen bone allograft (FFB) with bovine bone mineral (BBM) in maxillary sinus floor augmentation. In total, 34 maxillary sinuses from 29 patients, with a mean age of 51.32 (±6.44) years, underwent sinus augmentation. Patients were divided into control and test groups (17 sinuses each). The controls were grafted with allograft bone, and the test group received a combination of FFB and BBM at a 2:1 ratio. After 6 months, bone samples were collected for histological and histomorphometric examinations. The implant survival rates were 93.02% (control group) and 100% (test group) at 6 months after functional loading. Median volumetric reductions of 28.32% (17.05-44.05) and 12.62% (5.65-16.87) were observed for the control and test groups, respectively. Statistically significant histomorphometric differences were found between the control and test groups regarding newly formed bone 12.54% (10.50-13.33) vs. 24.42% (17.62-35.92), p < 0.001, total bone 48.34% (39.03-54.42) vs. 61.32% (50.61-64.96), p = 0.007, and connective tissue 51.66% (45.57-60.97) vs. 39.30% (35.03-49.37), p = 0.007. The addition of BBM to allograft bone in maxillary sinus augmentation resulted in higher percentages of new bone formation and total bone, and permitted implant placement with a low rate of osseointegration failure at the 6-month follow-up.