Srinivas M. Susarla

Three-Dimensional Computed Tomographic Airway Analysis of Patients With Obstructive Sleep Apnea Treated by Maxillomandibular Advancement

PURPOSE To evaluate changes in airway size and shape in patients with obstructive sleep apnea (OSA) after maxillomandibular advancement (MMA) and genial tubercle advancement (GTA). MATERIALS AND METHODS This was a retrospective cohort study, enrolling a sample of adults with polysomnography-confirmed OSA who underwent MMA + GTA. All subjects who had preoperative and postoperative 3-dimensional computed tomography (CT) scans to evaluate changes in airway size and shape after MMA + GTA were included. Preoperative and postoperative sleep- and breathing-related symptoms were recorded. Descriptive and bivariate statistics were computed. For all analyses, P < .05 was considered statistically significant. RESULTS During the study period, 13 patients underwent MMA + GTA, of whom 11 (84.6%) met the inclusion criteria. There were 9 men and 2 women with a mean age of 39 years. The mean body mass index was 26.3; mean respiratory disturbance index (RDI), 48.8; and mean lowest oxygen saturation, 80.5%. After MMA + GTA, there were significant increases in lateral and anteroposterior airway diameters (P < .01), volume (P = .02), surface area (P < .01), and cross-sectional areas at multiple sites (P < .04). Airway length decreased (P < .01) and airway shape (P = .04) became more uniform. The mean change in RDI was -60%. CONCLUSIONS Results of this preliminary study indicate that MMA + GTA appears to produce significant changes in airway size and shape that correlate with a decrease in RDI.

Descriptive analysis of implant and prosthodontic survival rates with fixed implant-supported rehabilitations in the edentulous maxilla.

BACKGROUND This descriptive study reviewed the 1- to 15-year survival rates of fixed implant rehabilitations in the edentulous maxilla. METHODS An electronic search was conducted, and cohort studies with 1- to 15-year follow-ups were identified by two independent reviewers. The implant and prosthodontic survival rates were reviewed at 1-, 3-, 5-, 10-, and 15-year endpoints. Descriptive analysis includes surface characteristics, bone-augmentation procedure, prosthetic design, and implant number and distribution along the edentulous maxilla. RESULTS Thirty-three studies, including 1,320 patients and 8,376 implants, were selected for analysis. The overall calculated implant survival rates ranged from 94% (1 year) to 87.7% (15 years). The implant survival rates for rough-surface implants ranged from 97% (1 year) to 98% (15 years); machined implants showed survival rates of 92% to 87.7%; respectively. Implants placed in native bone had greater survival rates than those placed in augmented bone. The prosthodontic survival rate ranged from 98.2% at 1 year to 92.1% at the 10-year endpoint, and it was only influenced by the implant number and distribution. CONCLUSIONS Implants with rough surfaces showed a statistically higher survival rate than machined implants at all intervals. Implants placed in augmented bone had a statistically lower survival rate, except for rough-surface implants, for which no statistical difference between augmented and non-augmented bone survival rates was found. Machined implants showed a stable survival rate only when placed in native bone. When machined implants were placed in augmented bone, the survival rate decreased significantly at each study endpoint. The prosthetic design, veneering material, and the number of prostheses per arch had no influence on the prosthodontic survival rate. Implant number and distribution along the edentulous maxilla seemed to influence the prosthodontic survival rate.

Age-related changes of the upper airway assessed by 3-dimensional computed tomography.

The purposes of this study were to establish normative data for airway size and shape and to evaluate differences associated with age and sex using 3-dimensional (3-D) imaging. Patients being evaluated by computed tomography (CT) for pathologic conditions not related to the airway were included. Using 3-D Slicer (Harvard Surgical Planning Laboratory, Brigham and Womens Hospital, Boston, MA), a software program, digital 3-D CT reconstructions were made and parameters of airway size analyzed: volume (VOL), surface area (SA), length (L), mean cross-sectional area (mean CSA), minimum retropalatal (RP), minimum retroglossal (RG), minimum cross-sectional area (min CSA), and lateral (LAT) and anteroposterior (AP) retroglossal airway dimensions. Evaluation of airway shape included LAT/AP and RP/RG ratios, uniformity (U), and sphericity, a measure of compactness (&PSgr;). Children were stratified by stage of dentition: primary, 0 to 5 years; mixed, 6 to 11 years; permanent, 12 to 16 years; and adults, older than 16 years. Differences in airway parameters by age and sex were analyzed. Forty-six CT scans (31 males) were evaluated. Adults had larger (VOL, SA, L, mean CSA, and LAT), more elliptical (increased LAT/AP, P = 0.01), less uniform (U, P = 0.02), and less compact (decreased &PSgr;, P = 0.001) airways than children. Among children, those in the permanent dentition demonstrated greater VOL (P < 0.01), SA (P < 0.01), L (P < 0.01), and mean CSA (P < 0.01) than those in the primary dentition. There were no gender differences in airway parameters. Understanding differences in 3-D airway size and morphology by age may serve as a basis for evaluation of patients with obstructive sleep apnea and may help to predict and to evaluate outcomes of treatment.

Three-Dimensional Computed Tomographic Analysis of Airway Anatomy in Patients With Obstructive Sleep Apnea

PURPOSE To identify abnormalities in airway size and shape that correlate with the presence and severity of obstructive sleep apnea (OSA). MATERIALS AND METHODS This was a retrospective case series of patients undergoing treatment of OSA who had preoperative computed tomographic (CT) scans of the upper airway available. Patients who had undergone CT scanning for nonairway pathologic features during the same period served as the controls. Digital 3D-CT reconstructions were made and 12 parameters of airway size and 4 of shape were analyzed. The posterior airway space, middle airway space, and hyoid to mandibular plane distance were measured on the lateral cephalograms of the patients with OSA. Bivariate analysis was used to identify the factors associated with the presence and severity of OSA as measured by the respiratory disturbance index (RDI). Multiple regression analysis identified the factors that correlated with the RDI. RESULTS Of the 44 patients with OSA, 15 (10 men and 5 women) had pre- and postoperative CT scans available. In addition, 17 patients (11 men and 6 women) were used as controls. The airway length was significantly increased in the patients with OSA (P < .01). On bivariate analysis, the length, lateral/retroglossal anteroposterior dimension ratio and genial tubercle to hyoid bone distance were associated with the RDI (P < .03). On multiple regression analysis, length (P < .01) had a positive correlation and the lateral/retroglossal anteroposterior dimension ratio (P = .04) an inverse correlation with the RDI. CONCLUSIONS The results of this study indicate that the presence of OSA is associated with an increase in airway length. Airways that were more elliptical in shape and mediolaterally oriented (greater lateral/retroglossal anteroposterior dimension ratio) had a decreased tendency toward obstruction.

Three-dimensional computed tomographic analysis of airway anatomy.

PURPOSE To test the reliability of a 3-dimensional computed tomographic (3D-CT) analysis of airway size and shape and to correlate the 3D-CT findings with lateral cephalometric measurements. MATERIALS AND METHODS Fifteen pairs of preoperative maxillofacial 3D-CT scans and digital lateral cephalograms of patients treated for obstructive sleep apnea were used in the present study. Digital 3D-CT reconstructions were created and 12 measurements of airway size and 4 of shape were analyzed. The posterior airway space (PAS), middle airway space, and hyoid to mandibular plane distances were measured on the cephalograms. We then randomly selected 5 CT scans and 5 cephalograms which were analyzed blindly on 5 separate occasions by 2 investigators (Z.A., J.T.) to establish the intraclass correlation coefficients for inter- and intraexaminer reliability. All 15 pairs of images were used to compute the Pearson correlation coefficients to establish the relationship between the CT and cephalometric measurements. RESULTS The intra- and interexaminer reliabilities were high for all CT (0.86 to 1.0 and 0.89 to 1.0, respectively; P < .001) and cephalometric measurements (0.84 to 1.0 and 0.91 to 0.99, respectively; P < .001). The CT measurements retroglossal anteroposterior dimension and distance between the genial tubercle and hyoid exhibited a positive correlation with the PAS (r = .60, P = 02 and r = .54, P = .04, respectively), and the lateral/anteroposterior dimension demonstrated an inverse correlation (r = -.68, P = .01) with the PAS. CONCLUSION The results of the present study indicate that the 3D-CT and lateral cephalometric measurements we selected are reliable and reproducible. The only cephalometric measurement that exhibited any correlation with the CT parameters was PAS.

Cephalometric Measurement of Upper Airway Length Correlates With the Presence and Severity of Obstructive Sleep Apnea

PURPOSE The purpose of this study was to measure upper airway length (UAL) on lateral cephalograms and to assess its relationship with the presence and severity of obstructive sleep apnea (OSA). MATERIALS AND METHODS Using a case-control study design, the investigators enrolled a sample of cases defined as adult subjects with OSA and controls who were adult patients with skeletal Class II malocclusions. The primary predictor variable was UAL. Other variables were demographic and cephalometric parameters. The respiratory disturbance index (RDI) was used to measure disease severity in cases. Bivariate analyses were computed to evaluate the associations between predictor and outcome variables. Multiple regression analyses were used to provide adjusted measures of association, controlling for the effects of confounders/effect modifiers. Diagnostic test characteristics were computed for threshold airway lengths. P ≤ .05 was considered statistically significant. RESULTS The sample consisted of 96 cases with OSA (76 males) and 56 controls without OSA (36 males). OSA subjects were older, were predominately male, and had higher body mass indexes and longer and narrower airways (P < .05). After controlling for confounding variables, UALs ≥ 72 mm for males and ≥ 62 mm for females were significantly associated with the presence of OSA (P = .03). The sensitivity and specificity of UAL as a diagnostic test for OSA were ≥ 0.8. UAL was strongly correlated with RDI (disease severity) in males (r = 0.72, P < .01) and moderately correlated with RDI in females (r = 0.52, P < .01). CONCLUSION Increased upper airway length was correlated with the presence and severity of OSA in this sample of adult patients.

Biomechanics of the upper airway: Changing concepts in the pathogenesis of obstructive sleep apnea.

Obstructive sleep apnea (OSA) is a disorder characterized by repetitive, episodic collapse of the pharyngeal airway. Over the last two decades, understanding of the pathophysiology of sleep disordered breathing, which includes OSA, has improved. Once thought to be predominately related to anatomic constriction of the maxillomandibular complex, central nervous system regulation of breathing is now recognized as a significant contributor to the pathogenesis of OSA. Ventilator control, the central response to chemoreceptor phenomena, has important implications for oral and maxillofacial surgeons who treat OSA, particularly for patients who appear refractory to treatment with maxillomandibular advancement (MMA). The purpose of this article is to review the biomechanics of the upper airway as it relates to the pathophysiology of OSA, to discuss emerging concepts of ventilator control mechanisms in normal sleep versus sleep-disordered breathing and to discuss the concept of complex sleep apnea, a new category of sleep disordered breathing with both obstructive and central features.

Delayed versus immediate loading of implants: survival analysis and risk factors for dental implant failure.

PURPOSE The purpose of this study was to estimate 1-year survival for delayed versus immediately loaded implants and identify risk factors for implant failure. MATERIALS AND METHODS This was a retrospective cohort study, consisting of a sample of subjects who had greater than or equal to 1 Bicon dental implant (Bicon, Boston, MA) placed over a 13-year period. The primary predictor variable was method of implant loading: delayed (3 to 6 months after placement) or immediately after insertion. Secondary predictor variables were classified as demographic, anatomic, implant/abutment, and reconstructive. The outcome variable was implant failure, defined as removal of the implant, and was recorded as months of survival. Descriptive, Kaplan-Meier, and univariate Cox proportional hazards statistics were computed. Univariate associations with P <or= .15 and biologically relevant variables (eg, age, gender) were included in a marginal multiple Cox regression model. In the multiple model, a P value of <or= .05 was considered statistically significant. RESULTS The study sample consisted of 677 subjects who had 2,349 delayed-loaded dental implants and 178 patients who had 477 immediate-loaded implants. The unadjusted 1-year survival estimates for the delayed and immediate loading groups were 95.5% and 90.3%, respectively (P < .01). In the marginal multiple Cox regression model, immediate loading, current tobacco use, maxillary implants, and shorter implants were associated with failure (P <or= .05). CONCLUSION In this study, implants loaded immediately were 2.7 times (after adjusting) more likely to fail at 1 year compared with delayed-loaded implants.

Does Computed Tomographic Assessment of Inferior Alveolar Canal Cortical Integrity Predict Nerve Exposure During Third Molar Surgery

PURPOSE To evaluate the association between computed tomographic (CT) assessment of inferior alveolar nerve (IAN) canal cortical integrity and intraoperative IAN exposure. MATERIALS AND METHODS This was a retrospective cohort study. The study sample included patients considered at high risk for IAN injury based on panoramic findings. The primary predictor variable was IAN canal integrity (intact or interrupted) assessed on coronal CT images. The secondary predictor variable was length of the cortical defect, in millimeters. The primary outcome variable was intraoperative visualization of the IAN. Other variables were demographic and operative parameters. Bivariate and multiple logistic regression analyses were used to evaluate the unadjusted and adjusted associations between the cortical integrity and IAN exposure. Diagnostic test characteristics were computed for cortical integrity and threshold cortical defect size. A P value < or = 0.05 was statistically significant. RESULTS The sample consisted of 51 subjects (57% female) with a mean age of 35.2 +/- 12.8 years. Of the 80 third molars available for evaluation, 52 third molars (64.1%) had evidence of loss of cortical integrity. The mean cortical defect length was 2.9 +/- 2.6 mm. Loss of cortical integrity had a high sensitivity (> or = 0.88) but low specificity (< or = 0.49) as a diagnostic test for IAN visualization. A cortical defect size > or = 3 mm was associated with an increased risk for intraoperative IAN visualization with a high sensitivity and specificity (> or = 0.82). CONCLUSION Cortical defect size on a maxillofacial CT has a high sensitivity and specificity for predicting intraoperative IAN exposure during third molar removal.

Candida albicans adherence to surface-modified denture resin surfaces.

PURPOSE The purpose of this study was to investigate two innovative methods in reducing adhesion of Candida albicans to denture base resins through modification of the surface characteristics of denture resin by incorporation of surface charge and application of a self-bonding polymer on denture resins. MATERIALS AND METHODS Three groups were tested [Group 1: control, pure poly(methyl methacrylate) (PMMA); Group 2: modified PMMA (mPMMA) with 16% methacrylic acid; Group 3: pure PMMA coated with self-bonding polymer (SBP)]. Twenty resin specimens for each group were polymerized, and four experimental subgroups for each surface type were devised, consisting of 2, 4, 6, and 12 days of incubation in C. albicans suspension. The surface area of adherent C. albicans stained with Grams crystal violet was examined under a light microscope at 400x magnification. Four areas were photographed on each block, one on each quadrant. The images were analyzed using Scion Image 1.63 software to calculate the percent surface area containing adherent C. albicans. Kruskal-Wallis test and Tukeys honest significant difference (HSD) procedure were used to compare the groups. RESULTS At day 2, the modified resin had statistically significantly lower levels of Candida than both the control group and the SBP group (p<or= 0.036). Both the mPMMA group and SBP group had statistically significantly lower levels of Candida accumulation at days 4, 6, and 12, compared to the control. CONCLUSIONS The amount of C. albicans adhering to the resin surfaces reduced significantly with modification of surface charge and application of self-bonding polymer. Modification of surface characteristics of polymeric biomaterials is an effective method in reducing adhesion of C. albicans to PMMA surfaces.