Palatonasal recess on medial wall of the maxillary sinus and clinical implications for sinus augmentation via lateral window approach

Anatomy of the Maxillary Sinus and the Role of CT Scans in Maxillary Sinus Augmentation Surgery

BACKGROUND

Detailed knowledge of sinus anatomy as well as timely identification through CT scans of the anatomic structures inherent to the maxillary sinus is required to avoid unnecessary surgical complications.

PURPOSE

To investigate sinus homeostasis, physiology, and anatomy; to review all anatomical-related risk factors for sinus membrane perforation; and to analyze the significance of preoperative and postoperative sinus CT scan imaging.

MATERIALS AND METHODS

Data from the recent literature on the above topics were explored.

RESULTS

Thinner membranes may not have sufficient mechanical strength to resist force during elevation or bone grafting, and thicker membranes may be associated with the presence of subclinical sinusitis. Increased thickness of an unhealthy membrane generally indicates a weaker membrane with a gelatinous texture, whereas thickening of a healthy membrane occurs at the periosteal layer level and can enhance its strength. Sinus membrane thickness, sinus septa, type of edentulism, and root position relative to the sinus cavity, residual bone height, sinus width, palatonasal recess angle, buccal wall thickness, zygomatic arch location, alveolar antral artery, and bone dehiscence may influence the clinical complexity of the surgery. There is no clear evidence of systematic negative outcomes related to sinus perforations. In patients with severely atrophic posterior maxillas, the possibility of lacerating the alveolar antral artery and/or detecting antral septa must be considered, especially when the residual ridge height is < 3 mm high. Transient edema and thickening of the sinus mucosal membrane typically resolve spontaneously. In cases of graft extrusion, conservative management could be considered for asymptomatic patients with healthy sinus and open ostium at the time of surgery. On the other hand, patients with symptoms should be referred. Radiographic evidence of implant protrusion into the sinuses is not always associated with complications.

CONCLUSIONS

Investigating sinus homeostasis and physiology, exploring the vascular anatomy within the maxillary sinus, identifying anatomical risk factors for sinus membrane perforation, and analyzing the significance of preoperative and postoperative sinus CT imaging provide a systematic and comprehensive framework for evaluating the complexity of maxillary sinus augmentation using a lateral approach.

Changes in Maxillary Sinus Structure Due to Tooth Loss and the Effects of Sex and Aging on CBCT Before Maxillary Sinus Augmentation: A Cross-Sectional Study of 120 Patients

Prosthesis for missing maxillary molars with dental implants often requires maxillary sinus augmentation owing to insufficient alveolar bone height. However, the anatomical structure of the maxillary sinus is a significant risk factor. This study used preoperative cone-beam computed tomography (CBCT) to investigate changes in the anatomical structure of the maxillary sinus due to tooth loss and conducted an epidemiological survey of Japanese people to determine the effects of gender and age on these changes. Preoperative CBCT scans were analyzed in patients aged ≥ 50 years with free-end maxillary molar edentulism involving ≥ 2 missing teeth seeking implant treatment. Statistical analyses were performed. One hundred and twenty participants (46 males, 74 females; mean age, 62.1 ± 7.4 years) with 3.0 ± 0.9 missing teeth and an existing bone volume of 6.2 ± 3.1 mm were included. Lateral wall thickness, sinus angle, sinus membrane thickness, maxillary sinus length and width, and the presence of the sinus septa significantly differed between missing and non-missing sides. Maxillary sinus height and sinus membrane thickness on missing side and maxillary sinus height and width on non-missing side varied significantly. Aging was associated with maxillary sinus length and width changes on the non-missing side in males, whereas no age-associated effects were identified in females. To ensure the safe execution of maxillary sinus augmentation, a thorough understanding of maxillary sinus anatomy is crucial prior to surgery.

Prevention and management of intra-operative complications in maxillary sinus augmentation: A review

Maxillary sinus floor elevation is usually performed in two different ways: the lateral approach involves the creation of a bony window on the maxillary sinus lateral wall, providing direct access to the sinus cavity for membrane elevation and subsequent graft placement, and the transcrestal approach is considered less invasive. The aim of this article is to describe, based on the literature, how to anticipate, avoid, and manage the intraoperative complications that can occur with both approaches. For both approaches, the most common complication is the sinus membrane perforation. For the lateral approach, an average frequency ranging from 15.7% to 23.1% is reported, but because of the better visibility, their management will be easier compared to the transcrestal approach. Mean perforation rate reported for the transcrestal approach is lower (3.1%-6.4%), but it should be noted that a significant number of perforations cannot be detected and managed given the blind nature of this technique. Anatomical parameters such as sinus width and buccal wall thickness may be a risk factor for one approach and not the other. As it is impossible to assess the resistance of the Schneiderian membrane, the transcrestal approach is more likely to lead to infectious complications in the event of perforation. Others, such as the risk of vascular damage, are encountered only with the lateral approach, which can be prevented easily by dissecting the alveolo-antral artery. For both approaches, prevention is essential and consists in analyzing the anatomy, mastering the surgical technique, and collaborating with the ENT to manage the essentially infectious consequences of intraoperative complications.

The influence of different extraction indications on the morphological changes in the maxillary sinus: A retrospective cohort study

AIMS

The comprehensive effects of maxillary posterior tooth extraction on the maxillary sinus (MS) morphology remain to be thoroughly elucidated. This retrospective cohort study aimed at evaluating the influence of different extraction indications on the morphological changes in the MS by utilizing cone-beam computed tomography (CBCT).

METHODS

One hundred and seventy-eight of maxillary posterior tooth extractions underwent CBCT scans before and after extraction using 3D Slicer software. Parameters such as maxillary sinus pneumatization (MSP, the primary outcome measure), buccal bone height (BBH), palatal bone height (PBH), mucosal thickness (MT), and other anatomical structures were measured for patients undergoing extraction due to periodontitis, periapical lesions, or tooth fracture. Multiple linear regression analysis was employed to assess the effect of extraction indications on the MS.

RESULTS

While the primary outcome, MSP, did not reveal statistically significant differences across various indications for tooth extraction (p > .05), extraction itself resulted in MSP (p < .05). The rate of this pneumatization was influenced by the position of the extraction site (p < .05). Additionally, baseline values of bone height and mucosal thickness showed an inverse correlation with the rate of change in these parameters following tooth extraction (p < .001).

CONCLUSIONS

Tooth extraction led to increased pneumatization of the maxillary sinus while simultaneously reducing bone height and mucosal thickness. However, these outcomes were not influenced by the reason for tooth extraction.

Middle meatal nasal recesses of the maxillary sinuses and dangerously modified nasal anatomy

Pneumatisation of the maxillary sinus (MS) is variable. The archived cone-beam computed tomography file of a 54-year-old female was retrospectively evaluated anatomically. Nasal or retrobullar recesses of the MSs (NRMS) were found. The MSs were bicameral. NRMSs extended from the postero-lateral chambers of the MSs into the lateral nasal walls. The right NRMS was reached superior to the middle turbinate and the ethmoidal bulla was applied on its anterior side. The left NRMS had two medial pouch-like ends, one beneath the ethmoidal bulla and the other on the anterior side of the basal lamella of the middle turbinate. Additional anatomical findings were the uncinate bulla, infraorbital recesses of the MS, maxillary recess of the sphenoidal sinus, and atypical posterior insertions of the superior nasal turbinates, maxillo-ethmoido-sphenoidal and ethmoido-sphenoidal. The NRMS is a novel finding and could lead to erroneous endoscopic corridors if not documented before the interventions.

Cone-beam computed tomography assessment of palatal-nasal recess of maxillary sinus in dentulous and edentulous subjects

Background

Implant placement in the posterior maxilla is challenging in the case of maxillary sinus pneumatization. Increasing the vertical dimension by grafting the sinus floor is a common surgical modality. Cone-beam computed tomography (CBCT) scans are used to assess the presurgical anatomic variations of the maxillary sinus and determine the difficulty that might be encountered while performing sinus elevation. The sinus membrane is elevated from both the lateral and mesial walls of the sinus. The location and angulation of the palatal-nasal recess (PNR) on the medial wall of the sinus could complicate the elevation of the sinus membrane in this region. This study aimed to assess the angulation of the PNR and its position with respect to the alveolar crest in dentulous and edentulous subjects in the 1st molar region on CBCT scans.

Materials and Methods

One hundred and fifty-two scans were selected from the department database. Sagittal sections including the 1st molar region were selected and measurements made. The PNR height was measured from the alveolar crest in millimeters and angulation in degrees and compared between the dentulous and edentulous groups.

Results

The dentulous group showed a statistically significant greater distance (10.4 ± 2.8 mm) between the alveolar crest and PNR as compared to the edentulous group (8.08 ± 3.1 mm). The edentulous group showed a statistically significant greater PNR angle (139.6o ± 13.6o) as compared to the dentulous group (133.4o ± 16.4o).

Conclusion

Maxillary sinuses with acute-angled PNR and lesser distance from the alveolar crest should be carefully evaluated to avoid complications such as membrane perforation during their elevation from the bony wall of the sinus.

Comprehensive sinus contour classification and its characteristics from radiographic examination: a cross-sectional study

OBJECTIVE

The aim of this study was to propose a comprehensive maxillary sinus (MS) contour classification system based on the evaluation of anatomical characteristics from cone beam computed tomography (CBCT) examination and investigate the relationship between sinus contours and sinus floor elevation (SFE).

METHODS

A total of 283 CBCT scans from patients who had single tooth loss in the posterior maxilla and underwent SFE were analyzed. The MS was classified at each tooth position. For buccal-palatal evaluation, the classification from Type A to E was narrow-taper, taper, ovoid, square, and irregular, respectively. For mesial-distal evaluation, the classification from Type 1 to 4 was flat, slope, concave, and septa, respectively. The major anatomical parameters evaluated were (1) residual bone height (RBH), (2) sinus width (SW), (3) maxillary sinus angle (MSA), (4) buccal dip angle (BDA), (5) palatonasal recess (PNR), and (6) sinus depth.

RESULTS

Eleven groups of MS contour were classified after detailed calculation. Differences in the RBH, MSA, BDA, and SW among different groups were statistically significant. The narrow-taper and slope MS (A2) group had the highest RBH (8.66 ± 0.77 mm), largest BDA (79.9° ± 3.18°), smallest MSA (19.8° ± 2.01°), and narrowest SW (6.30 ± 1.23 mm). The lowest RBH was in the square and concave sinus (D3) group (5.11 ± 2.70 mm). The ovoid and concave sinus (C3) group had the smallest BDA (50.64 ± 8.73 mm) and largest MSA (74.11° ± 11.52°). The square and flat MS (D1) group had the widest SW (19.13 ± 3.69 mm). A strongly significant positive correlation was observed between the SW and MSA (r = 0.67) and a strongly negative correlation between the SW and BDA (r = - 0.65). The prevalence of PNR (mean angle: 104.06° ± 16.83°, mean height: 14.72 ± 11.78 mm) was 38% and frequently observed in the ovoid and slope MS (C2) group.

CONCLUSION

Despite certain characteristics at different tooth sites, the same tooth position was categorized differently using different classification systems, indicating large anatomical variations in the MS. The classification system proposed herein allows for classification based on general characteristics at a single tooth site, aiming to help surgeons in improving presurgical evaluation.

Anatomical Possibilities of the Alveolar Bone at the Upper Second Premolar Level

Background and Objectives: The upper posterior teeth are typically regarded as being exclusively inferior to the maxillary sinus (MS). The expansion of the nasal fossa above the maxillary alveolar base (MAB) needs better investigation. The hypothesis was raised that the MAB in the upper premolar region, which is usually addressed by surgeons for the elevation of the antral floor, is not exclusively beneath the MS. Therefore, we aimed to document the possible upper relations of the MAB as antral, nasal, or both. Materials and Methods: A total of 145 CBCT scans were used to study four types of MAB: type 1-antral; type 2-antral with a palatal recess; type 3-antral and nasal; type 4-nasal. In type 2, the orthoradial width of the alveolar bone, the rectilinear width of the antral floor, and the maximum depth of the palatal recess were measured. For type 3, the MAB width and the straight widths of the antral and nasal segments of the MAB were measured. Results: Type 1 was found in 67.24%, type 2 in 13.45%, type 3 in 16.21%, and type 4 in 3.1% of the 290 MSs investigated. Palatal recesses were found in 11.72% of the MSs on the right side and 15.17% of the MSs on the left side. Types 1 and 2 exhibited strongly statistically significant bilateral symmetry (Pearson's Chi2 = 86.42, p < 0.001). Type 3 correlated equally with contralateral types 1 and 3. The bilateral symmetry for types 1-3 was stronger in the males (Pearson's Chi2 = 47.83, p < 0.001) than in the females (Pearson's Chi2 = 56.96, p < 0.001). There were no statistically significant associations between sex and the unilateral anatomical type. Conclusions: The MAB in the upper second premolar area should not be considered to be exclusively antral during surgeries or in anatomical teaching.

Volumetric changes and graft stability after lateral window sinus floor augmentation: A randomized clinical trial

INTRODUCTION

The present investigation compared the stability and volumetric changes of two different grafting material used for lateral window sinus floor augmentation (LWSFA).

METHODS

Sixteen patients with a total 20 maxillary sinuses in need of LWSFA were included in the present study. The sinuses were grafted with either 100% anorganic bovine bone mineral (ABBM) alone (Group 1) or a mixture (0.8:1 ratio) of ABBM and mineralized cortical allograft (MCA) (Group 2). Cone beam computer tomography (CBCT) was obtained pre-operatively, and at 2-weeks, and 6-months after LWSFA to perform linear measurements including lateral window dimensions, sinus anatomy, residual bone height/thickness (RBH/RBT), and Schneiderian membrane thickness (SMT), among others. Three-dimensional segmentation analysis was used to evaluate changes of bone graft volume/height (GV/GH).

RESULTS

A total of 10 sinuses per group were included in the analysis. No statistically significant difference was found in between groups regarding mean reduction of GV (Group 1: 14.87% ± 16.60%, Group 2: 18.06% ± 9.81%, p = 0.33). Among the linear measurements, only SMT revealed a significant increase after 2-weeks more pronounce in Group 1 (8.70 mm) when compared with Group 2 (5.70 mm) with plausible effect upon LWSFA outcomes. Sinus width showed weak positive correlation with GH reduction after 6 months.

CONCLUSION

This study demonstrated that both ABBM alone and ABBM + MCA represent suitable alternatives for LWSFA with adequate graft stability as they revealed similar volumetric and linear dimensional changes 6 months postoperatively.

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.

Evaluation of maxillary palatal process pneumatization by cone-beam computed tomography

PURPOSE

The aim of this study is to investigate the pneumatization type of the palatal process (PTP) and angular and distance measurements of neighbouring structures on cone beam computed tomography (CBCT) images.

MATERIALS AND METHODS

400 maxillary sinuses (MS) of 200 patients (96 female; 104 male; mean age: 43.2) were retrospectively evaluated. PTP was divided into three as types 1,2 and 3 and evaluated at distances 4, 8, 16, and 24 mm posterior to incisive foramen. The sinus and alveolar ridge height, palatonasal recess angle (PRA) and palatal junction angle (PJA) were also measured and recorded.

RESULTS

PTP I (101, 25.3%) was the most frequent type, followed by PTP II (95, 23.8%), and the least was PTP III (4, 1%). In patients with PTP I, the alveolar ridge height in the 4 mm and 8 mm group was significantly higher than in the patients with PTP II and III (p<0.05). In patients with PTP I, PRA in the 4 mm and 16 mm groups was significantly higher than in patients with PTP II and III (p<0.05). Sinus and alveolar ridge height, PRA and PJA did not differ significantly between the right and left sides in the 4 mm, 8 mm, 16 mm, and 24 mm groups (p>0.05).

CONCLUSION

Knowing the anatomy of the MS is very important for a successful surgical procedure in this area. Anatomy and pathology of the MS can be understood more clearly in CBCT.

SinusC-Net for automatic classification of surgical plans for maxillary sinus augmentation using a 3D distance-guided network

The objective of this study was to automatically classify surgical plans for maxillary sinus floor augmentation in implant placement at the maxillary posterior edentulous region using a 3D distance-guided network on CBCT images. We applied a modified ABC classification method consisting of five surgical approaches for the deep learning model. The proposed deep learning model (SinusC-Net) consisted of two stages of detection and classification according to the modified classification method. In detection, five landmarks on CBCT images were automatically detected using a volumetric regression network; in classification, the CBCT images were automatically classified as to the five surgical approaches using a 3D distance-guided network. The mean MRE for landmark detection was 0.87 mm, and SDR for 2 mm or lower, 95.47%. The mean accuracy, sensitivity, specificity, and AUC for classification by the SinusC-Net were 0.97, 0.92, 0.98, and 0.95, respectively. The deep learning model using 3D distance-guidance demonstrated accurate detection of 3D anatomical landmarks, and automatic and accurate classification of surgical approaches for sinus floor augmentation in implant placement at the maxillary posterior edentulous region.

How to avoid intraoperative and postoperative complications in maxillary sinus elevation

Maxillary sinus floor elevation, via the lateral approach, is one of the most predictable bone augmentation procedures performed in implant dentistry. but both intra- and postoperative complications can occur, and some of them are severe. Our aim is as follows: To review the pertinent literature on the topic, especially assessing the risk factors related to complications. To give clinical recommendations to minimize intra- and postoperative complications with the ultimate scope of improving the standard of clinical care and patient safety.

The influence of different forms of sinus membrane perforation on the prevalence of postoperative complications in lateral window sinus floor elevation: A retrospective study

BACKGROUND

Maxillary sinus membrane perforation (SMP) during lateral window sinus floor elevation (SFE) might be associated with postoperative complications (PC).

OBJECTIVES

To evaluate the prevalence of PC and clinical implant outcome for different forms of SMP with lateral window SFE.

MATERIAL AND METHODS

The prevalence of PC such as maxillary sinusitis, graft necrosis and wound infection was retrospectively evaluated for 434 lateral window SFE (334 patients) with 331 SFE (241 patients) without and 103 SFE (93 patients) with SMP. SMP was additionally classified into four subgroups regarding to membrane perforation size (small-moderate [<10 mm] vs. large [>10 mm]) and membrane biotype ([BT] thin vs. thick). Additionally, patient- and surgery-related risk factors affecting PC and the 1-year implant survival rate were evaluated for SFE without and with SMP and subgroups.

RESULTS

A significantly higher prevalence including significant odds ratios of PC such as maxillary sinusitis (10/103 [9.7%] vs. 4/331 [1.2%]; p < 0.021; OR: 8.85; p < 0.021) and graft necrosis (7/103[6.8%] vs. 1/103[0.3%]; p < 0.017; OR:7.43; p < 0.017) was found for SFE with than without SMP. The SMP subgroup with large size and thin BT involved significantly (p < 0.005) more PC (15/20[75%]) than all other SMP subgroups (5/20[25%]). For the risk factors evaluated the univariate analysis demonstrated differences of PC for the presence versus absence of SMP (p < 0.001) and for thin versus thick sinus mucosa (p < 0.038; p < 0.006) but not for sex, smoking, sinus septa and surgical stage. In the multivariate risk factors analysis, PC were significantly related to risk factors such as large size with thin BT (OR:18.049; p < 0.007). The 1-year implant survival rate did not differ between SFE without (99.5%) and with SMP (99.1%), regardless of successfully repaired subtype of SMP.

CONCLUSION

The synopsis of perforation size and membrane biotype is crucial in differentiating different forms of SMP assessing and anticipating different prevalences of PC in lateral window SFE.

Prevalence, risk factors, and repair mechanism of different forms of sinus membrane perforations in lateral window sinus lift procedure: A retrospective cohort study

OBJECTIVES

To evaluate prevalences, affecting risk factors and efforts for repair mechanism for different forms of sinus membrane perforations (SMP) during sinus floor elevation (SFE) using the lateral window technique (LWT).

MATERIAL AND METHODS

For 334/434 patients, SFE undergoing LWT prevalence of SMP was retrospectively evaluated including a subselection based on membrane perforation size (<10 mm: small-moderate/≥10 mm: large) and biotype (BT; thick BT/thin BT) into four subgroups (SMP1: thick BT/small-moderate; SMP2: thin BT/small-moderate; SMP3: thick BT/large; SMP4: thin BT/large). For the various subgroups, patient- and surgery-related/anatomic risk factors affecting SMP were evaluated and the scope of sinus membrane repair (SSMR) mechanisms rated with 1 (easy) to 5 (complex) was compared.

RESULTS

For 103/434 SMP (27.6%) in 93/334 patients (30.8%) the prevalence of various forms of SMP differed significantly (p < 0.001) among the four subgroups. SMP4 with a prevalence of 45.6% (n = 47) was the most frequent type, while SMP3 had low prevalence with 4.85% (n = 5). Small/moderate SMPs with thick (SMP1: n = 26) or thin BT (SMP2: n = 23) were seen in 26.2% and 23.3%, respectively. Univariate analysis showed significant differences between subgroups with large perforations (SMP3/SMP4) and those with small/moderate perforations (SMP1/SMP2) regarding anatomic risk factors such as residual ridge height (p = 0.023) and history of previous oral surgical interventions (OSI; p = 0.026). Most evidently, multivariate analysis showed that induction of large SMP with thin biotype (SMP4) was significantly affected by the presence of sinus septa (p < 0.022, OR: 2.415), reduced residual ridge height (p < 0.001, OR: 1.842), and previous OSI (p < 0.001, OR: 4.545). SSMR differed significantly (p < 0.001) between SMP4 (4.62 ± 0.49) and the subgroups SMP1 (1.11 ± 0.32), SMP2 (1.08 ± 028), and SMP3 (2.2 ± 0.55).

CONCLUSION

The most frequently found type of SMP had characteristics of thin biotype and large size associated with risk factors such as sinus septa, reduced residual ridge, and previous surgical interventions and required challenging repair mechanisms assessing clinical impact.

Radioanatomic study of maxillary sinus palatal process pneumatization

OBJECTIVES

To perform a detailed analysis of palatal process pneumatization (PPP) on cone beam computed tomography (CBCT) images.

METHODS

This study consisted of 376 maxillary sinuses of 188 patients aged 22-88 years who had maxillary CBCT scans. The radioanatomy of the PPP was evaluated at distances 4, 8, 16, and 24 mm posterior to incisive foramen. The types of PPP were classified as follows: type I: maxillary sinus palatal process non-gasified; type II: palatal process gasification into the nasal floor, but not more than half of the width of the nasal floor; and type III: palatal process gasification into the nasal floor more than half of the width of nasal floor. Sinus opening angle (SOA), palatonasal recess angle (PNRA), palatal junction angle (PJA), and palatal depth measurement (PDM) were the evaluated parameters.

RESULTS

Among the identified 1315 PPPs, type I PPP (880, 66.92%) was the most frequently observed, followed by type II (426, 32.4%), and the least observed was type III PPP (9, 0.68%). There was no significant difference between SOA and PJA according to the types of PPP (p > 0.05). The difference between PNRA and PDM of type I and type II PPP showed a statistically significant difference (p < 0.05). Type I PPP was the most encountered with the highest PDM, and PNRA was narrower in type III than in type II PPP.

CONCLUSION

Physicians must be aware of these variations to prevent possible complications during surgery because 33.08% of the maxillary sinuses showed extensive pneumatization through the palatal process.

Flapless Localised Management of Sinus Floor (LMSF) for trans-crestal sinus floor augmentation and simultaneous implant placement. A retrospective non-randomized study: 5-year of follow-up

Background

Trans-crestal sinus lift procedures are well established.

Purpose

to retrospectively analyse the efficacy of a flapless trans-crestal maxillary sinus floor elevation and simultaneous dental implant placement based on the Localised Management of Sinus Floor (LMSF) technique suitable for cases with sufficient width of keratinized tissue and of crestal bone but insufficient vertical dimensions of the bone below the sinus.

Materials and methods

71 sinus elevations with simultaneous implant placement were performed on 52 consecutive patients. Following an initial pilot bur transmucosal perforation, the Magnetic Mallet was used with progressively larger osteotomes. The mallet osteotomes are initially directed palatally, towards the cortex of the medial wall of the sinus, below the palato-nasal recess (PNR) and then redirected in a more vertical direction to create the final osteotomy for implant placement.

Results

No significant complications were reported in the post-operative phase. The cumulative success rate during the observation period was 95%. All successful implants were successfully loaded with metal-ceramic or monolithic zirconia crowns and bridges and remained in function during the observation period.

Conclusions

Flapless Localised Management of Sinus Floor (LMSF) is a safe and effective surgical technique with minimal risks and with the advantage of low morbidity. Also, only native bone is used for augmentation and there is no need for additional grafting.

Sinus Mucosa Thickness Changes and Ostium Involvement after Maxillary Sinus Floor Elevation in Sinus with Septa. A Cone Beam Computed Tomography Study

Background: A thickening of the sinus mucosa is observed after sinus floor augmentation. The objective of this retrospective study was to evaluate the influence of the presence of septa in the dimensional variation and ostium involvement over time of the Schneiderian mucosa after sinus floor augmentation. Materials and Methods: Fifteen sinuses with septa (septa group) and 15 without (control group) were selected. CBCTs taken before surgery, and were analyzed after 1 week and after 9 months. Schneiderian membrane thickness changes over time and involvement of the ostium were evaluated. Results: Four perforations occurred in the septa group and none in the control group. After 1 week of healing, the sinus mucosa thickness increased in height by 5.7 mm and 7.1 mm in the septa and control groups, respectively. In this period, the patency of the ostium decreased in both groups, and three infundibula were obstructed in the septa group, and five in the control group. The mucosa was thicker and the edema was closer to the ostium in the control compared to in the septa group. After 9 months of healing, the dimensions regressed to normal pattern and no obstruction of the infundibula were observed. No statistically significant differences were found between septa and control groups. Conclusions: after one week of healing, the sinus mucosa increased in dimensions in both septa and control groups. However, the sinus mucosa presented a tendency of being thicker and closer to the ostium, resulting in a higher number of infundibula obstructions, in the control group compared to in the septa group. After 9 months, the sinus mucosa regressed to normal dimensions and no obstructions of the infundibula were observed in any group.

Influence of Anatomical Parameters on the Dimensions of the Subantral Space and Sinus Mucosa Thickening after Sinus Floor Elevation. A Retrospective Cone Beam Computed Tomography Study

BACKGROUND

Various anatomical parameters might influence the surgical approach for maxillary sinus floor elevation. The objective of the present study was to retrospectively evaluate the influence of anatomical parameters on the dimensions of the subantral space and of the sinus mucosa thickening after sinus floor elevation.

MATERIAL AND METHODS

Seventy-eight maxillary sinuses in sixty-five patients were evaluated on cone beam computed tomographies taken before surgery and after one week (t1w) and nine months (t9m). Several parameters such as the distance XF between an axis parallel to the base of the nose (X-axes) and the sinus floor (F) were correlated with the height gain (IF) at t1w and t9m and the post-surgical edema.

RESULTS

A weak significant positive correlation was observed between height gain vs. sinus height of interest (XF), the balcony, and the sinus floor angle. The post-surgical edema was influenced by the initial mucosa thickness and the xenograft used.

CONCLUSIONS

Various parameters might affect height gain and sinus mucosa thickening after sinus floor elevation. The height of interest, the balcony, and the sinus floor angle showed significant correlations with height gain. The initial thickness of the mucosa and the biomaterial used influenced the post-surgical edema.

Three-dimensional CBCT based evaluation of the inferior part of the maxillary sinus: Retrospective Study

The maxillary sinus is the largest of the four paranasal sinuses in humans, and its close proximity to the teeth means that caution is required during dental treatment. In particular, implant surgeries involving the maxillary posterior teeth should include evaluating the inferior part of the maxillary sinus. The purpose of this study is to evaluate the differences by comparing the inferior part of the maxillary sinus based on the nasal cavity floor (NCF) between patients (male 30, female 30) genders through the use of the three-dimensional (3-D) program that can facilitate 3-D visualizations. The present study results obtained from 3-D visualizations using cone beam computed tomography (CBCT) data showed that the inferior part of the maxillary sinus was mostly larger in males than in females. In addition, the utilization of 3-D visualization data was more likely to assure accuracy than when using data obtained by two-dimensional (2-D) imaging. Therefore, 3-D visualizations of the inferior part of the maxillary sinus will contribute to accurate analyses of its anatomical structure during implant surgery and other operations. Further studies utilizing 3-D visualization will yield useful fundamental data and guidelines for future research.

Risk factors in lateral window sinus elevation surgery

Maxillary sinus augmentation is the most predictable of the pre-prosthetic surgical procedures. There are, however, known and well-documented complications that can and do occur. The most common are the intraoperative complications of sinus membrane perforation and bleeding, and the postoperative complications of sinus graft infections, sinus infections, and sinusitis. The majority of these complications can be prevented, or their incidence greatly reduced, through a thorough understanding of maxillary sinus anatomy, the multifaceted etiologies of these conditions, and the steps that can be taken to avoid them. This volume of Periodontology 2000 will discuss both the preoperative and intraoperative procedures that will prevent these untoward outcomes and the necessary treatment modalities that will limit their adverse effects.

Tomographic evaluation of the influence of the placement of a collagen membrane subjacent to the sinus mucosa during maxillary sinus floor augmentation: a randomized clinical trial

Aim

To study the influence of a collagen membrane placed subjacent to the sinus mucosa on the dimensional changes of augmented maxillary sinus floor.

Methods

Twenty patients were recruited in the study and randomly assigned to two groups. After the elevation of the maxillary sinus mucosa, a collagen membrane with standardized dimensions was placed at the test sites subjacent to the sinus mucosa and the elevated space was filled with a xenograft, both at test and control sites. A collagen membrane was then used to cover the antrostomy at both sites, and sutures were applied to close the wounds. Cone beam computed tomographies (CBCTs) were taken for all patients before surgery (T0), after 1 week from sinus floor augmentation (T1), and after 9 months of healing (T2). Dimensional changes over time of soft and hard tissues were evaluated on the CBCTs.

Results

After 1 week of healing, the sinus floor was elevated by 10.0 ± 2.8 mm and 10.6 ± 2.5 mm at the no-membrane and membrane groups, respectively. After 9 months of healing, a similar reduction of the height was observed in both groups, providing a total vertical augmentation of 8.6 ± 2.8 mm at the no-membrane sites and 9.1 ± 3.1 mm at the membrane sites. After 9 months of healing, the hard tissues subjacent to the sinus mucosa appeared to be partially corticalized in three patients in the no-membrane group and in six patients in the membrane group.

Conclusions

The use of collagen membranes subjacent to the sinus mucosa did not influence the dimensional variations of the augmented regions and the clinical outcomes after 9 months of healing also in absence of perforations.

Anatomical analyses for maxillary sinus floor augmentation with a lateral approach: A cone beam computed tomography study

BACKGROUND

Various anatomical references and structures should be analyzed prior approaching a surgery in the maxillary sinus. The objective of the present study was to evaluate the anatomical structures and references involved in sinus floor elevation with a lateral approach.

MATERIALS AND METHODS

Seventy-five patients planned for sinus floor elevation were included in the study. Eighty-eight maxillary sinuses were evaluated using cone beam computed tomographies (CBCTs). The nasal floor was used as main reference (X) and sinus mucosa width, bone crest height, palatal-nasal recess angle (PNR), sinus width at the level of the nasal floor, distance from the nasal floor to the base of the sinus (X-F), position of the posterior superior alveolar artery (PSAA height) and diameter (PSAA diameter), lateral bone wall width at 3mm (LW 3mm) and 9mm (LW 9mm) from the base of the sinus (F), patency of the ostium (OP), and presence and position of septa have been evaluated.

RESULTS

The mean dimensions and standard deviations were the following: mucosa thickness was 2.0±1.4mm, bone crest height 2.8±1.4mm, distance X-F 8.3±1.9mm, PNR angle 135.5±23.1, sinus width 12.6±4.2mm, X-F 8.3±1.9mm, PSAA height 14.4±2.9mm, PSAA diameter 1.1±0.4mm, LW 3mm 1.5±1.2, LW 9mm 1.3±0.6mm, OP 1.9±0.4mm. Septa were present in 19.3% of the sinuses evaluated and were located mostly in the molar region.

CONCLUSIONS

In conclusion, the analysis of the CBCT before sinus floor elevation allows the identification of anatomical structures and references that might be used for the planning of the surgical approach, aiming to improve the outcome of the treatment and to avoid possible complications.

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.

Indications for palatal sinus lift: Case series

Background:

Open sinus lift is indicated in posterior maxilla when subantral bone is insufficient for insertion of dental implants. Lateral approach is the most used technique. Sometimes, this surgery is difficult due to thick buccal bone or other anatomic variations of maxillary sinus.

Aim:

The aim of this study was to determine cases that palatal approach open sinus lift is indicated.

Settings and Design:

This study was a retrospective study.

Materials and Methods:

Archive files of Dental Implant Department of Mashhad Dental School were searched for palatal sinus lift. The reason for patients was noticed. Pre- and post-operative radiographs were evaluated.

Results:

Ten patients with palatal approach sinus lift were included. Seven patients had previous insufficient sinus lift, one patient had acute palatonasal recess, and two other patients had thick buccal bone.

Conclusion:

Palatal approach is maxillary open sinus lift is a useful auxiliary in patients with heavy buccal vestibule scar, thick buccal bone, deep palatonasal recess, and for reentry augmentation.

The implications of different lateral wall thicknesses on surgical access to the maxillary sinus

The objective of this study was to measure the topographic thickness of the lateral wall of the maxillary sinus in selected Asian populations. Measurements were made on the lateral walls of maxillary sinuses recorded using CBCT in a convenient sample of patients attending an Asian teaching hospital. The points of measurement were the intersections between the axes along the apices of the canine, first premolar, and second premolar and along the mesiobuccal and distobuccal apices of the first and second molars and horizontal planes 10 mm, 20 mm, 30 mm and 40 mm beneath the orbital floor. The CBCT images of 109 patients were reviewed. The mean age of the patients was 33.0 (SD 14.8) years. Almost three quarters (71.8%) of the patients were male. The mean bone thickness decreased beginning at the 10-mm level and continuing to 40 mm below the orbital floor. Few canine regions showed encroachment of the maxillary sinus. The thickness of the buccal wall gradually increased from the canine region (where sinus encroachment of the canine region was present) to the first molar region, after which it decreased to the thickness observed at the canine region. The buccal wall of the maxillary sinus became thicker anteroposteriorly, except in the region of the second molar, and thinner superoinferiorly. These changes will affect the approach used to osteotomize the lateral sinus wall for oral surgery and for the sinus lift procedure.

Schneiderian Membrane Thickness and Clinical Implications for Sinus Augmentation: A Systematic Review and Meta-Regression Analyses

BACKGROUND

Schneiderian membrane thickness (SMT) has been regarded as a key factor for influencing membrane perforation, which may jeopardize the final clinical outcome of sinus augmentation. Hence, this systematic review aims at studying the mean SMT and further investigating patient-related factors that may affect SMT. As a secondary goal, the association between SMT and membrane perforation rate was studied.

METHODS

Three independent reviewers in several databases, including MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, and Cochrane Oral Health Group Trials Register databases, conducted electronic and manual literature searches. This review was written and conducted according to the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) and MECIR (Methodological Expectations of Cochrane Intervention Reviews) guidelines. Quantitative assessment was performed for articles that met the inclusion criteria to investigate the mean SMT, its contributing factors, and the influence on membrane damage and surgical complications.

RESULTS

Thirty-one studies that reported maxillary SMT were considered for qualitative analysis. Nineteen were further meta-analyzed. Overall mean ± SE SMT was 1.17 ± 0.1 mm (95% confidence interval [CI] = 0.89 to 1.44). Although mean SMT for the three-dimensional radiography (3DR) group was 1.33 mm (95% CI = 1.06 to 1.60), for the histology group, it was 0.48 mm (95% CI = 0.12 to 1.1). Random-effects model showed that, although there is a trend for thicker SMT as determined using 3DR compared with histologic analysis, such difference did not reach statistical significance (P = 0.15). Also, regression analyses demonstrated that the variables periodontitis (P = 0.13) and smoking (P = 0.11) showed thicker SMT. Inconclusive data were obtained when correlating SMT and perforation rate, although it seems that thicker SMT might be more prone to perforation (P = 0.14).

CONCLUSIONS

SMT is, on average, 1 mm in patients seeking sinus augmentation. Three-dimensional technologies overestimate approximately 2.5 times SMT when compared with histologic analysis. Periodontitis and smoking may result in thickening of the sinus membrane. However, current data were inconclusive to link SMT to the rate of membrane damage.

Long-term Evaluation of Peri-implant Bone Level after Reconstruction of Severely Atrophic Edentulous Maxilla via Vertical and Horizontal Guided Bone Regeneration in Combination with Sinus Augmentation: A Case Series with 1 to 15 Years of Loading

BACKGROUND

To the best of the authors' knowledge, there is very limited clinical data on the outcomes of simultaneous guided bone regeneration (GBR) for horizontal and/or vertical bone gain for the reconstruction of severely atrophic edentulous maxilla. Therefore, the purpose of the clinical series presented herein was to clinically evaluate long-term horizontal and vertical bone gain, as well as implant survival rate after reconstruction of severely atrophic edentulous maxillary ridges.

MATERIAL AND METHODS

Sixteen patients (mean age: 64.6 ± 14.6 years of age) were consecutively treated for vertical and/or horizontal bone augmentation via GBR in combination with bilateral sinus augmentation utilizing a mixture of autologous and anorganic bovine bone. Implant survival, bone gain, intraoperative/postoperative complications and peri-implant bone loss were calculated up to the last follow-up exam.

RESULTS

Overall, 122 dental implants were placed into augmented sites and have been followed from 12 to 180 months (mean: 76.5 months). Implant survival was 100% (satisfactory survival rate of 97.5%). Mean bone gain was 5.6 mm (max: 9 mm; min: 3 mm) While vertical bone gain was 5.1 ± 1.8 mm; horizontal bone gain was 7.0 ± 1.5 mm. No intraoperative/postoperative complications were noted. Mean peri-implant bone loss values were consistent within the standards for implant success (1.4 ± 1.0 mm). At patient-level, only one patient who had three implants presented with severe peri-implant bone loss.

CONCLUSION

Complete reconstruction of an atrophied maxilla can be successfully achieved by means of guided bone regeneration for horizontal and/or vertical bone gain including bilateral sinus augmentation using a mixture of anorganic bovine bone and autologous bone.

The influence of sinus membrane thickness upon membrane perforation during lateral window sinus augmentation

OBJECTIVES

To investigate: (1) sinus membrane thickness in patients receiving lateral window sinus augmentation via cone-beam computed tomography (CBCT) and (2) the influence of Schneiderian membrane thickness upon membrane perforation during lateral window approach.

MATERIAL AND METHODS

A total of 73 subjects with 81 sinus lift procedures between years 2010 and 2013 were recruited consequently. Each patient selected had CBCT images in initial and immediately after surgery. The values and correlation between variables of membrane thickness, perforation rate, membrane morphology, residual bone height, and elevated bone height were evaluated.

RESULTS

The mean thickness of the Schneiderian membrane was 1.32 ± 0.87 mm. Perforation rate was lowest (7.14%) when membrane thickness was 1-1.5 mm. As membrane became thicker (≥2 mm) or thinner (<1 mm), the perforation rate increased abruptly. When examined the membrane thickness category, Class B (between ≥1 mm and <2 mm) had the lowest perforation rate. Statistically significant correlation was found between the perforation and the membrane thickness. The amount of the remaining bone height did not significantly correlate to the membrane thickness nor influence the membrane perforation.

CONCLUSIONS

This study demonstrated that membrane thickness was related to the sinus perforation during lateral window sinus augmentation. The perforation rate was lowest when the membrane thickness was 1-1.5 mm.

Implant success remains high despite grafting voids in the maxillary sinus

OBJECTIVES

Given that the nature and presence of voids present within grafted sinuses following maxillary sinus elevation procedures were not known, nor was the contribution of these factors to implant success, the purpose of this study was to investigate these parameters and their relationship to implant success.

MATERIALS AND METHODS

This study evaluated data from 25 subjects who had a lateral window maxillary sinus augmentation procedure. Cone-beam computed tomography (CBCT) was performed at baseline and 4 months after surgery. CBCT images were used to evaluate grafted sites prior to implant placement. Using CBCT images, three examiners independently measured bone-grafted areas (BG), void areas (V), and percentage of void areas (V%) from six different sections within grafted sites. The six sections were defined as a cross-sectional (CS) midpoint, CS mesial point, CS distal point, horizontal section (HS) low point, HS midpoint, and HS high point. Implant success was also determined.

RESULTS

The calculated V% (V/BG) for the CS midpoint, CS mesial point, CS distal point, HS low point, HS midpoint, and HS high point were 5.30 ± 6.67%, 5.79 ± 8.51%, 6.67 ± 7.12%, 2.07 ± 2.56%, 5.30 ± 6.62%, and 4.92 ± 5.17% respectively. Implant success after 6 months of follow-up approximated 100%.

CONCLUSIONS

Although voids within grafts varied in terms of distribution and size, the V% within the HS low point were significantly smaller compared to those within the CS midpoint and CS distal point, which had the most intra-subject V%. Thus, more attention should be given to the distal aspect of the sinus when compacting graft materials in the lateral wall sinus augmentation procedure. Implant success was not influenced by the existence of voids as implant success remained high.

Maxillary sinus lateral wall thickness and morphologic patterns in the atrophic posterior maxilla

BACKGROUND

The aim of the present study is to examine the sinus lateral wall thickness (LWT) of atrophic posterior maxilla (<10 mm) of patients with complete and partial edentulism and determine the influence of residual ridge height (RH), sex, and age on maxillary LWT.

METHODS

Four hundred fourteen measures were taken from 140 consecutive patients that met the inclusion criteria. On the selected sagittal section, a built-in digital caliper recorded in millimeters the RH and LWT (a perpendicular line at 3, 5, 7, 10, 13, and 15 mm from the lowest point of the sinus floor). Edentulous spans were further classified as complete edentulous atrophic maxilla (CEM) and partial edentulous atrophic maxilla (PEM). The mixed linear model was used to test the effects of sex, type of edentulism, edentulous span, and RH on the measurement of the LWT of the sinus.

RESULTS

Mean LWT for PEM was 1.71 ± 0.12 mm, and for CEM, 1.57 ± 0.07 mm (P = 0.01). The mixed model yielded significant effect of edentulous span (P = 0.048) and interactions among type of edentulism and edentulous span (P <0.001) and edentulous span by RH (P <0.01). Age and RH were positively associated with LWT; however, they did not interact with RH, sex, or type of edentulism. RH has been shown to correlate with edentulous span (P <0.001) and type of edentulism (P = 0.01). The longer the edentulous span, the thinner the LWT. Similarly, RH was larger for PEM (6.85 ± 0.34 mm) than CEM (5.69 ± 0.26 mm).

CONCLUSIONS

The maxillary sinus lateral wall tends to increase in thickness from the second premolar to the second molar and from 5 mm up to 15 mm. In addition, RH, presence of teeth adjacent to the edentulous atrophic ridge, and age were shown to influence maxillary sinus LWT.