Sinus Width Analysis and New Classification with Clinical Implications for Augmentation

Treatment alternatives for the rehabilitation of the posterior edentulous maxilla

Rehabilitation of the edentulous maxilla with implant-supported fixed dental prostheses can represent a significant clinical challenge due to limited bone availability and surgical access, among other factors. This review addresses several treatment options to replace missing teeth in posterior maxillary segments, namely the placement of standard implants in conjunction with maxillary sinus floor augmentation, short implants, tilted implants, and distal cantilever extensions. Pertinent technical information and a concise summary of relevant evidence on the reported outcomes of these different therapeutic approaches are presented, along with a set of clinical guidelines to facilitate decision-making processes and optimize the outcomes of therapy.

Maxillary sinus floor augmentation: a review of current evidence on anatomical factors and a decision tree

Maxillary sinus floor augmentation using lateral window and crestal technique is considered as predictable methods to increase the residual bone height; however, this surgery is commonly complicated by Schneiderian membrane perforation, which is closely related to anatomical factors. This article aimed to assess anatomical factors on successful augmentation procedures. After review of the current evidence on sinus augmentation techniques, anatomical factors related to the stretching potential of Schneiderian membrane were assessed and a decision tree for the rational choice of surgical approaches was proposed. Schneiderian membrane perforation might occur when local tension exceeds its stretching potential, which is closely related to anatomical variations of the maxillary sinus. Choice of a surgical approach and clinical outcomes are influenced by the stretching potential of Schneiderian membrane. In addition to the residual bone height, clinicians should also consider the stretching potential affected by the membrane health condition, the contours of the maxillary sinus, and the presence of antral septa when evaluating the choice of surgical approaches and clinical outcomes.

Radiological changes in maxillary sinus morphology after lateral sinus floor augmentation

<b>Background:</b> Restoration of the masticatory function in patients with edentulous posterior maxilla is often challenging due to the severe atrophy of the alveolar ridges and proximity of the maxillary sinus, resulting in insufficient bone quantity for implant-supported dentures. <br><b>Aim:</b> The purpose of this study was to analyze the changes in Schneiderian membrane thickness after lateral sinus floor augmentation (LSFA) using cone beam computed tomography (CBCT). <br><b>Material and methods:</b> WLSFA procedures using different bone grafting materials were performed in 87 patients, operated on in two clinical institutions from 2016 to 2018. CBCT examination was performed in all patients before the LSFA procedure, at 1 month after surgery, and after 6 months, before implant placement or loading. <br><b>Results: </b>Minor r adiological changes in mucous membrane morphology were observed preoperatively in 17.1% of patients. Postoperative CBCT in the early postsurgical period demonstrated that the number of intact non-specific sinuses decreased significantly, i.e. from 86.7% to 26.7%. The number of cases with local hypertrophia of the mucous membrane increased from 20.3% to 26.7%. Mucosal thickening was observed in 41.7% vs 7.5%. The number of intact sinuses increased to 57.8%. The number of cases with local membrane hypertrophia also increased - to 37.4%. The number of cases with mucosal thickening or fluid accumulation decreased significantly to 11.8 and 5.3% respectively. In 2 cases the development of chronic sinusitis required secondary surgeries. <br><b>Conclusion:</b> The present retrospective study revealed that minor radiological changes in the morphology of the maxillary sinus mucosa were observed preoperatively in 17.1% of patients who underwent LSFA procedures. In the early and late postoperative period their frequency increased to 68.5% and 47.1%, respectively. However, the clinical signs of sinusitis developed only in 19.26% of patients. No significant correlations were found between the frequency and severity of postoperative radiological changes and residual bone height, sinus anatomy, initial state of the mucous membrane and type of the grafting material.

The effect of anatomy on osteogenesis after maxillary sinus floor augmentation: a radiographic and histological analysis

OBJECTIVES

To assess how anatomy and osteogenesis correlated with results of maxillary sinus floor augmentation (MSFA).

MATERIALS AND METHODS

Patients with partial edentulism and advanced atrophy of the posterior maxillae (≤ 4 mm residual bone height, RBH) underwent MSFA with sole deproteinized bovine bone matrix (DBBM) through a lateral approach. After a 6 to 9-month healing period, bone core biopsies were obtained from the sites of implant insertion for histological evaluation. The correlations between anatomical and histomorphometric variables were analyzed in a multiple regression model.

RESULTS

Forty-nine patients were recruited. One biopsy per patient was obtained from the augmented sinus. Thirty-seven bone core biopsies were intact and met the requirement for histomorphometry analysis. The mean (± standard deviation) percentages of vital bone (VB), remaining DBBM, and non-mineralized tissue were 18.25 ± 4.76%, 27.74 ± 6.68%, and 54.08 ± 6.07%, respectively. No statistically significant correlations were found between RBH and VB% (p = 0.44) or between sinus contour and VB% (p = 0.33). However, there was an inverse correlation between the sinus width (SW) and VB % (SW₁: R² = 0.13, p = 0.03; SW₂: R² = 0.15, p = 0.02).

CONCLUSIONS

After a healing period of 6-9 months, wider sinuses augmented with DBBM alone tended to have a lower proportion of new bone formation, while RBH and sinus contour did not appear to affect osteogenesis after MSFA.

CLINICAL RELEVANCE

This study emphasized the effect of anatomy on osteogenesis after MSFA. The result of the study may have an indication to the clinician that SW is a consideration when selecting the bone grafting material and deciding the healing period of MSFA.

The vertical course of bone regeneration in maxillary sinus floor augmentations: A histomorphometric analysis of human biopsies

Background

Maxillary sinus floor augmentation (MSFA) is a well‐established and predictable augmentation method in severely resorbed maxillae. However, data on the vertical course of bone graft consolidation within the maxillary sinus are rare. The aim of the present study was to quantify the vertical distribution of new bone formation (nBF) in MSFA and to characterize the vertical gradient of bone graft consolidation.

Methods

Eighty‐five human sinus biopsies were harvested 6 ± 1 months after MSFA. Histological thin‐ground sections were prepared and histomorphometrically analyzed. The volume of newly formed bone (nBV/TV) was measured in serial zones of 100 μm proceeding from the bottom of the sinus floor (SF) up to the apical top of the biopsy. The gradient of nBV/TV within the augmentation area was determined by the vertical distribution of nBV/TV along these zones.

Results

In the premolar region, nBV/TV slightly declined from 20.4% in the zone adjacent to the SF to 17.7% at a distance of 8 mm. The gradient was steeper in the molar region: nBV/TV decreased from 18.7% to 12.8%. This decline was even more distinct when the volume fraction and the height of the residual bone of the SF were low.

Conclusions

nBF follows a gradient from native bone of the SF towards the apical part of the augmentation area. The distance to primordial bone thus plays a critical role for bone regeneration in MSFA, particularly in the molar region.

Morphological Assessment of Maxillary Sinus Septa Variations with Cone-Beam Computed Tomography in a Turkish Population

Objective The purpose of this study was to measure and classify sinus septa variables (prevalence, numbers, heights, locations, orientations, and morphology) and to determine the effects of age, gender, and dental status on the presence of septa and also to evaluate the effects of septa on pathological mucosal thickening.

Materials and Methods A total of 2,000 patients were analyzed through conebeam computed tomography (CBCT). The total of 500 maxillary sinuses were included in this study. The number of maxillary sinus septa was determined on axial sections of CBCT images. Their locations, orientations, and morphologies were determined on both the axial and sagittal sections, and their heights were determined only on the sagittal sections. The influence of age, gender, dental status, and pathological mucosal thickening on the presence of septa was statistically analyzed. Mann–Whitney U-test and descriptive statistics were used for statistical analysis.

Results The average height of the determined 287 septa was measured as 7.36 mm. The highest rates of septa location, morphology, and orientation were found, respectively, in the middle region septa (57.49%), completed septa (75.95%), and transverse septa (93.37%). The effect of dental status, age, and gender on the presence of septa was not statistically significant ( p > 0.05).

Conclusion These high rates of findings support the importance of CBCT in the diagnosis of the variations of the maxillary sinus septa. Therefore, it is important to evaluate CBCT images of the relevant region to increase the success of surgical interventions in the maxillary posterior region and to eliminate possible complications.

Influence of residual bone height and sinus width on the outcome of maxillary sinus bone augmentation using anorganic bovine bone

OBJECTIVE

To evaluate the influence of the posterior residual bone height and sinus width on the outcome of maxillary sinus bone augmentation using anorganic bovine bone.

MATERIAL AND METHODS

Bilateral sinus bone augmentation was performed using anorganic bovine bone in 20 patients with residual bone height <2 mm in at least one site on each side. Trephine samples were removed at the implant insertion site 8 months after the grafting procedure, and histological and histomorphometric analyses were performed to examine the relative amount (%) of new bone, anorganic bovine bone, and soft tissue in the grafted area. Based on cone beam computed tomography evaluation, the sites of implant insertion were classified according to sinus width into narrow, average, and wide, and according to residual bone height into ≤2 and >2 mm.

RESULTS

A total of 146 implants were installed and 103 biopsies were evaluated. New bone formation in sites classified as narrow (69 sites), average (19 sites), and wide (15 sites) was 28.5% ± 9.24, 28.9% ± 8.61, and 30.3% ± 7.80, respectively. The mean posterior maxillary residual bone height was 4.0 ± 2.43 mm, and 26 and 77 sites were classified as ≤2 and >2 mm, respectively. New bone formation was 26.2% ± 9.10 and 29.8% ± 8.67 for residual bone height ≤2 and >2 mm, respectively. The differences were non-significant.

CONCLUSIONS

Within the limitations of the present study, posterior residual bone height and sinus width were not factors with influence on new bone formation in sinuses grafted exclusively with anorganic bovine bone after 8 months of healing.

Variation in bucco-palatal maxillary sinus width does not permit a meaningful sinus classification

OBJECTIVES

The bucco-palatal sinus width (SW) appears as relevant factor for graft consolidation after maxillary sinus (MS) floor augmentation. The present study aimed to assess (a) SW at different height levels of posterior teeth, (b) possible factors influencing SW, and (c) whether a simple/meaningful sinus classification based on SW is possible.

METHODS

The following parameters were recorded on computed tomographies of 76 edentulous and 86 partially edentulous maxillary quadrants displaying 383 tooth sites in total: (a) alveolar ridge height, (b) -area, (c) -width 2 mm apical to the alveolar crest, (d) -width at the sinus floor, and (e) SW and sinus area at a level 2, 4, 6, 8, and 10 mm above the sinus floor. The possible influence of gender, tooth position [i.e., premolar (PM); molar (M)], tooth-gap extent, and residual alveolar ridge dimensions on SW was assessed. Further, based on percentiles of average values or on the frequency distribution of SW <10, 10-15, or >15 mm, it was attempted to classify the sinus at each given site into narrow, average, or wide.

RESULTS

Gender and tooth-gap extent presented no relevant impact on MS dimensions; however, significant differences were observed among the various tooth positions regarding all evaluated parameters. The lower the residual alveolar ridge, the wider the MS at 4-10 mm height, while the wider the residual alveolar ridge, the wider the MS. Large variation in SW classes among the different height levels within the same tooth position and among tooth positions within the same person was observed, irrespective of the threshold applied. Further, at a MS height of 10 mm at PM1, PM2, M1, and M2, SW was <10 mm in 68%, 33%, 0%, and 7% of the cases, respectively, while in 3%, 21%, 65%, and 57%, respectively, SW was >15 mm.

CONCLUSIONS

There is a large variation in SW depending on the height level within the sinus and on tooth position, which does not permit a simple/meaningful classification of each sinus as "narrow," "average," or "wide." Nevertheless, narrow sinuses (<10 mm) are rather prevalent in the premolar region, while wide sinuses (>15 mm) in the molar region; further, a wider and shorter residual alveolar ridge is associated with a wider SW.

Nonlinear Biomechanical Characteristics of the Schneiderian Membrane: Experimental Study and Numerical Modeling

Objective

The aim of this study is to quantify the nonlinear mechanical behavior of the Schneiderian membrane.

Methods

Thirty cadaveric maxillary sinus membrane specimens were divided into the elongation testing group and the perforation testing group. Mechanical experimental measurements were taken via ex vivo experiments. Theoretical curves were compared with experimental findings to assess the effectiveness of the nonlinear mechanical properties. The FE model with nonlinear mechanical properties was used to simulate the detachment of the Schneiderian membrane under loading.

Results

The mean thickness of the membrane samples was 1.005 mm. The mean tensile strength obtained by testing was 6.81 N/mm². In membrane perforation testing, the mean tensile strength and the linear elastic modulus were significantly higher than those in membrane elongation testing (P < 0.05). The mean adhesion force between the Schneiderian membrane and the bone was 0.052 N/mm. By FE modeling, the squared correlation coefficients of theoretical stress-strain curves for the nonlinear and linear models were 0.99065 and 0.94656 compared with the experimental data.

Conclusions

The biomechanical properties of the Schneiderian membrane were implemented into the FE model, which was applied to simulate the mechanical responses of the Schneiderian membrane in sinus floor elevation.

New classification of maxillary sinus contours and its relation to sinus floor elevation surgery

BACKGROUND

It is complicated to select an appropriate sinus floor elevation and the procedure for sinus floor elevation lacks of consensus. Sinus contour plays an important role in choosing a surgery approach. But there are still no published articles revealing the influence of sinus contours to sinus floor elevation surgery.

PURPOSE

We propose a new classification depending on sinus contours from cone-beam computed tomography (CBCT), analyze clinical characters of different types, and investigate the relationship between sinus contours and sinus floor elevation.

MATERIALS AND METHODS

We divide sinus into five categories: narrow tapered, tapering, ovoid, square, and irregular. For the first four types, subtypes are classified into three categories: without recess, with buccal-sinus-recess (BSR), and with palate-nasal-recess (PNR). For irregular type, subtypes are classified into three categories: tooth protruding into sinus floor, irregular floor, and septa/exostosis on sinus floor. Then the distribution features of sinuses of 698 patients are described. Sinus widths are measured at second premolar, first and second molar on both sides, and are compared among different types and subtypes.

RESULTS

Narrow tapered sinus occupies 88% at second premolar sites, while tapered sinus occupies almost 50% at first and second molar sites. At second premolar and first molar sites, 62% are without recess types. While 92% are without recess types at second molar. Sinuses with BSR present in only three of 3765 sites. There is an increasing trend of sinus width from narrow tapered to irregular type. Sinus width of the group with recesses is significantly higher than the one without recess. At the end, we provide corresponding treatment recommendations for each sinus types and subtypes.

CONCLUSION

This is the first classification system that gives treatment recommendations for sinus floor elevation surgery based on sinus contours. The classification system is consistent, easy to visualize, and practicable.

Morphometric analysis of sinus depth in the posterior maxilla and proposal of a novel classification

The aim of this study was to analyse the posterior maxillary sinus based on its extension into the alveolar process and to provide a simple clinical classification. A retrospective cohort study was conducted in CT scans of 200 dentate and 200 edentulous patients (100 women and 100 men, respectively). After manual placement of 12 reference points morphometric analysis was performed and sinus depth, residual alveolar ridge height (RH) and the sinus opening angle were calculated. Sinuses were classified according to the quartiles of sinus depth: class I (above the hard palate), class II (0–6 mm below the hard palate) and class III (>6 mm below the hard palate). Sinus depth was found to be a reliable anatomical landmark and did not vary significantly between gender (p = 0.8940) or dentition groups (p = 0.9723). Alveolar height varied significantly between sinus classes (p < 2 × 10⁻¹⁶) and dentition groups (p < 2 × 10⁻¹⁶) but not between genders (p = 0.5178). The sinus opening angle was significantly different between sinus classes (p < 2.2 × 10⁻¹⁶) but not between gender or dentition groups. We propose a novel classification built upon the quartiles of sinus depth, dividing the sinuses into three classes. Our classification is the first one that represents the anatomy of the patient independent of gender and dentition.

Influence of Lateral-Medial Sinus Width on No-Grafting Inlay Osteotome Sinus Augmentation Outcomes

PURPOSE

Intrasinus new bone formation (BF) has been observed after no-grafting osteotome sinus augmentation, and it is hypothesized to be influenced by the dimensions of the maxillary sinus. The aim of this clinical trial is to evaluate the influence of lateral-medial sinus width (SW) on no-grafting osteotome sinus augmentation outcomes using cone-beam computed tomography.

PATIENTS AND METHODS

All patients recruited for this prospective study were treated with no-grafting osteotome sinus augmentation with simultaneous implant placement. Cone-beam computed tomography was obtained before, immediately after, and 6 months after the surgical procedure to use for measurements. Descriptive statistics were calculated and univariate, bivariate, and multivariate analysis were conducted to evaluate the influence of average SW and other relevant factors on procedure outcomes, including new BF, residual bone resorption (BR), and change of peri-implant bone height (CPBH).

RESULTS

A total of 48 implants placed in 32 elevated sinuses of 29 patients were included. The average SW was 11.3 ± 1.8 mm. Intrasinus BF measured 1.7 ± 0.9 mm at 6 months after surgery. The amount of BR was 0.3 ± 0.9 mm, and CPBH was calculated as 1.3 ± 1.3 mm. Multivariate analysis showed a negative correlation between SW and BF (r = -0.469, P = .001), as well as between SW and CPBH (r = -0.562, P = .001). A positive correlation was discovered between SW and BR (r = 0.311, P = .027) in general.

CONCLUSIONS

The lateral-medial SW was observed to have a negative correlation with new BF and CPBH after no-grafting osteotome sinus augmentation.