Surgical maxillofacial treatment of obstructive sleep apnea

Obstructive sleep apnea is the most common sleep-related breathing disorder, with a surprisingly high prevalence. The treatment of choice is nasal continuous positive airway pressure (CPAP) ventilation during sleep, which has to be applied throughout the patient's whole life. Because of various underlying pathomechanisms in patients with certain craniofacial disorders--narrow posterior airway space and maxillary-mandibular deficiency--surgical therapy by craniofacial osteotomies seems possible. A series of 38 consecutive patients were treated by 10-mm maxillomandibular advancement by retromolar sagittal split osteotomy and Le Fort I osteotomy, respectively. Obstructive sleep apnea syndrome was improved considerably in all patients; there was no significant difference compared to the results under nasal CPAP. In 37 of 38 patients, the postoperative apnea-hypopnea index was reduced clearly to under 10 per hour, oxygen saturation rose, and sleep quality improved. This was achieved by maxillomandibular advancement of 10 mm without secondary refinements in all but 2 patients. In one patient, the apnea-hypopnea index could only be reduced to 20 per hour, probably because of insufficient maxillary advancement. These results indicate that successful surgical treatment is possible in a high percentage of selected patients with certain craniofacial characteristics. In addition to cardiorespiratory polysomnography, there should be routine cephalometric evaluation of all patients. Maxillomandibular advancement should be offered as an alternative therapy to all patients with maxillary and/or mandibular deficiency or dolichofacial type in combination with narrow posterior airway space.

Mandibular setback for surgical correction of mandibular hyperplasia--does it provoke sleep-related breathing disorders?

The question has arisen as to whether mandibular setback may possibly cause sleep-related breathing disorders (SRBD). To evaluate the possible effects of mandibular setback on posterior airway space (PAS), 16 consecutive patients were examined prospectively. All patients underwent surgical mandibular setback using bilateral sagittal split osteotomy. Polysomnographic evaluation for SRBD was performed according to the Marburg graded diagnostic protocol before and after surgery. Cephalometric analysis was performed preoperatively, and 1 week, 3 months, and 1 year postoperatively, with particular attention to pharyngeal changes. PAS decreased considerably in all patients. Nevertheless, the preoperative PAS was enlarged in all patients with mandibular hyperplasia compared to normal subjects. Despite the pharyngeal narrowing, there was no evidence of postoperative SRBD in any of these patients. SRBD as a consequence of mandibular setback may be rare; nevertheless, the pharyngeal airway does decrease.

Long-term follow-up after surgical treatment of obstructive sleep apnoea by maxillomandibular advancement

Obstructive sleep apnoea (OSA) is a common disorder with potentially serious consequences. If maxillary and mandibular deficiency, often in combination with a narrow posterior airway space is present, therapy of OSA by maxillomandibular osteotomy is possible. However, long-term follow-up of patients undergoing these procedures is lacking. We present the results of 15 OSA patients (1 female and 14 males), who underwent maxillomandibular advancement surgery with a follow-up of at least 2 yrs. Polysomnography was performed before surgery, after 6-12 weeks, and 1 and 2 yrs postoperatively. Mean apnoea/hypopnoea index (AHI) decreased from 51.4 events.h-1 before therapy to 5.0 events.h-1 6 weeks postoperatively, and was 8.5 events.h-1 after 2 yrs. Oxygen saturation significantly increased following surgery. After 2 yrs, the AHI was < 10 events.h-1 in 12 out of 15 subjects. No significant changes were found comparing the 6-12 weeks versus the 2 year follow-up data. The significant increase in stage 3/4 non-rapid eye movement (NREM) sleep and decrease in stage 1 NREM sleep, indicative of the restoration of normal physiological sleep structure, persisted in 14 of the 15 subjects 2 yrs postoperatively. Three patients, however, did not show satisfactory improvement 2 yrs postoperatively; two showed obstructive and one central respiratory events. This study demonstrates that maxillomandibular advancement is successful in a high percentage of patients carefully selected by cephalometric and polysomnographic investigation. Postoperative success has proved to be stable over a period of 2 yrs. Further preoperative evaluation seems necessary in patients with predominantly mixed or central apnoeas.

Obstructive sleep apnoea in acromegaly: the role of craniofacial changes

Obstructive sleep apnoea (OSA) is due to craniofacial changes and acromegaly. The question addressed by this study was whether growth hormone (GH) induced craniofacial changes might explain persisting OSA despite endocrine inactivity in acromegaly. Nineteen patients treated for acromegaly were examined cephalometrically for craniofacial changes and polysomnographically for OSA. Twelve patients proved to have OSA with an apnoea/hypopnoea index >15; seven patients showed no evidence of OSA at all. With respect to the endocrinological parameters, there were no differences between the two groups that would explain the presence or absence of OSA. Neither group differed with respect to sex, age, or body mass index. Craniofacial changes were predominantly found in the mandible. The group with OSA proved to have increased vertical, dolichofacial growth compared to those without OSA. Consecutively, in the OSA group the posterior airway space was narrowed, and the hyoid was displaced more caudally. Thus, it seems that craniofacial structures of patients with acromegaly and persisting obstructive sleep apnoea are different from those without obstructive sleep apnoea. Surgical corrections of pertaining acromegaly-induced craniofacial changes should be performed with an awareness of the individual craniofacial condition so as not to enhance obstructive sleep apnoea.

Sleep fragmentation and daytime vigilance in patients with OSA treated by surgical maxillomandibular advancement compared to CPAP therapy

Impaired vigilance is a frequent daytime complaint of patients with obstructive sleep apnoea (OSA). To date, continuous positive airway pressure (CPAP) is a well established therapy for OSA. Nevertheless, in patients with certain craniofacial characteristics, maxillomandibular advancement osteotomy (MMO) is a promising surgical treatment. Twenty-four male patients with OSA (pretreatment respiratory disturbance index (RDI) 59.3 SD +/- 24.1 events/h) participated in this investigation. The mean age was 42.7 +/- 10.7 years and the mean body mass index was 26.7 +/- 2.9 kg/m2. According to cephalometric evaluation, all patients had a narrow posterior airway space, more or less due to severe maxillary and mandibular retrognathia. All patients except two were treated first with CPAP for at least 3 months and afterwards by MMO. Two patients only tolerated a CPAP trial for 2 nights. Polysomnographic investigation and daytime vigilance were assessed before therapy, with CPAP therapy and 3 months after surgical treatment. Patients' reports of impaired daytime performance were confirmed by a pretreatment vigilance test using a 90-min, four-choice reaction-time test. The test was repeated with effective CPAP therapy and postoperatively. Daytime vigilance was increased with CPAP and after surgical treatment in a similar manner. Respiratory and polysomnographic patterns clearly improved, both with CPAP and after surgery, and showed significant changes compared to the pretreatment investigation. The RDI decreased significantly, both with CPAP (5.3 +/- 6.0) and postoperatively (5.6 +/- 9.6 events/h). The percentages of non-rapid eye movement Stage 1 (NREM 1) sleep showed a marked decrease (with CPAP 8.2 +/- 3.6% and after MMO 8.2 +/- 4.4% vs. 13.3 +/- 7.4% before treatment), whereas percentages of slow wave sleep increased significantly from 8.0 +/- 6.1% before therapy to 18.2 +/- 12.8 with CPAP and 14.4 +/- 7.3% after MMO. The number of awakenings per hour time in bed (TIB) was significantly reduced after surgery (2.8 +/- 1.3), compared to both preoperative investigation (baseline 4.2 +/- 2.0 and CPAP 3.4 +/- 1.5). Brief arousals per hour TIB were reduced to half with CPAP (19.3 +/- 20.0) and after MMO (19.7 +/- 13.6), compared to baseline (54.3 +/- 20.0). We conclude that the treatment of OSA by MMO in carefully selected cases has positive effects on sleep, respiration and daytime vigilance, which are comparable to CPAP therapy.

Experimental and quantum-chemical studies on the thermochemical stabilities of mercury carbodiimide and mercury cyanamide

Calorimetric dissolution measurements of the solid compounds mercury carbodiimide HgNCN(I) and mercury cyanamide HgNCN(II) in aqueous HCl that targeted at their thermochemical stabilities show the cyanamide species HgNCN(II) to be the more stable phase in terms of both enthalpy and Gibbs energy with an enthalpy difference of 2-3 kJ mol-1. While the stability ranking of HgNCN(I) and HgNCN(II) thus perfectly matches Pearson's HSAB concept, quantum-chemical stability predictions using common parametrizations of density functional theory appear to be fundamentally flawed. An analysis of the error is attempted on the basis of correlated wave functions for related molecules.

Vigilance transitions in reaction time test: a method of describing the state of alertness more objectively

Electrophysiological recordings are considered a reliable method of assessing a person's alertness. The aim of this study was to show, firstly, that changes in alertness during a Reaction Time Test (RTT) can be determined with certain adaptive scoring stages but not with R&K scoring and secondly, that the different adaptive stages can explain findings in reaction time. In 17 male patients (50.8+/-9.7 years, Body-Mass Index (BMI) 31.9+/-5.1 kg/m2) diagnosed with Obstructive Sleep Apnea Syndrome (OSAS) (Respiratory Disturbance Index (RDI) 53.3+/-24.1 /h sleep) a 90 min daytime vigilance test was performed twice, after the diagnostic polysomnographic investigation and after two nights spent with nCPAP. After a computerised adaptive segmentation analysis, a visual rule-defined classification system categorised alertness into one of 12 adaptive scoring stages. 6 of the 12 stages are described by the alertness conditions comparable to WAKE and NREM1.4 stages are nearly classified as NREM2-4, Rapid Eye Movement (REM) and Movement Time (MT), and one stage reflects the increase of alertness from drowsiness. The typical stage of an alert subject increased significantly from a median of 65.9% before therapy to 80.8% in the second investigation. The percentages of clearly drowsy stages decreased significantly. In contrast, there were no significant changes in the percentages of sleep stages according to R&K criteria for both investigations. According to R&K criteria 178 of 398 failed reactions (Reaction time >10 s) occurred in stage WAKE. According to adaptive scoring, only 12 failed reactions appeared in the alert stage. During the other failed reactions the electrophysiological recordings showed decreases in alertness. Neither the visual assessment nor the descriptive statistical results of R&K scoring were helpful to interpret the patient's alertness condition. In contrast, the patients' increases in alertness with nCPAP could be described by the adaptive scoring stages. This method could be a very useful procedure, when an expert opinion is necessary. It also has an actual context to the discussion of the effectiveness of CPAP in the treatment of OSAS.

Is sleep bruxism in obstructive sleep apnea only an oral health related problem?

BACKGROUND

The etiology of sleep bruxism in obstructive sleep apnea (OSA) patients is not yet fully clarified. This prospective clinical study aimed to investigate the connection between probable sleep bruxism, electromyographic muscle tone, and respiratory sleep patterns recorded during polysomnography.

METHODS

106 patients with OSA (74 males, 31 females, mean age: 56.1 ± 11.4 years) were divided into two groups (sleep bruxism: SB; no sleep bruxism: NSB). Probable SB were based on the AASM criteria: self-report of clenching/grinding, orofacial symptoms upon awakening, abnormal tooth wear and hypertrophy of the masseter muscle. Both groups underwent clinical examination for painful muscle symptoms aligned with Temporomandibular Disorders Diagnostic Criteria (DC/TMD), such as myalgia, myofascial pain, and headache attributed to temporomandibular disorder. Additionally, non-complaint positive muscle palpation and orofacial-related limitations (Jaw Functional Limited Scale-20: JFLS-20) were assessed. A one-night polysomnography with electromyographic masseter muscle tone (EMG) measurement was performed. Descriptive data, inter-group comparisons and multivariate logistic regression were calculated.

RESULTS

OSA patients had a 37.1% prevalence of SB. EMG muscle tone (N1-N3, REM; P = 0.001) and the number of hypopneas (P = 0.042) were significantly higher in the sleep bruxism group. While measures like apnea-hypopnea-index (AHI), respiratory-disturbance-index (RDI), apnea index (AI), hypopnea-index (HI), number of arousals, and heart rate (1/min) were elevated in sleep bruxers, the differences were not statistically significant. There was no difference in sleep efficiency (SE; P = 0.403). Non-complaint masseter muscle palpation (61.5%; P = 0.015) and myalgia (41%; P = 0.010) were significant higher in SB patients. Multivariate logistic regression showed a significant contribution of EMG muscle tone and JFLS-20 to bruxism risk.

CONCLUSION

Increased EMG muscle tone and orofacial limitations can predict sleep bruxism in OSA patients. Besides, SB patients suffer more from sleep disorder breathing. Thus, sleep bruxism seems to be not only an oral health related problem in obstructive apnea. Consequently, interdisciplinary interventions are crucial for effectively treating these patients.

TRIAL REGISTRATION

The study was approved by the Ethics Committee of Philipps-University Marburg (reg. no. 13/22-2022) and registered at the "German Clinical Trial Register, DRKS" (DRKS0002959).

Structuring of bioactive glass surfaces at the micrometer scale by direct casting intended to influence cell response

Defect-free bioactive glass surfaces with a grooved microstructure at the low micrometer scale were achieved by a mold casting process. The process was applied to the well-known glass compositions 45S5 and 13–93. Such microstructured surfaces may exhibit especially favorable conditions for bone cell orientation and growth. The aim of the study was to assess the parameter range for a successful casting process and thus to produce samples suitable to investigate the interaction between structured surfaces and relevant cells. Viscous flow in its temperature dependence and thermal analysis were analyzed to identify a suitable process window and to design a manageable time-temperature process scheme. Counteracting effects such as formation of chill ripples, mold sticking and build-up of permanent thermal stress in the glass had to be overcome. A platinum gold alloy was chosen as mold material with the mold surface bearing the mother shape of the microstructure to be imprinted on the glass surface. First experiments studying the behavior of osteoblast-like cells, seeded on these microstructured glass surfaces revealed excellent viability and an orientation of the cells along the microgrooves. The presented results show that direct casting is a suitable process to produce defined microstructures on bioactive glass surfaces.

[nCPAP therapy and maxillary and mandibular osteotomy compared: attention during the day in obstructive sleep apnea]

11 patients with obstructive sleep apnea (OSA) and maxillary and mandibular characteristics participated. All patients received nCPAP therapy for at least 3 months. The surgical treatment principle consists of 10 mm maxillary and mandibulary advancement. Cardiorespiratory polysomnography (cPSG) control was assessed 3 months after surgical treatment. The daytime vigilance was investigated using a 90-min 4-choice reaction-time test. Patients reports of excessive daytime sleepiness (EDS) were confirmed by pre-treatment vigilance testing. Accordingly, daytime vigilance, respiratory and polysomnography patterns were improved with nCPAP and surgical treatment in a likewise manner. The tolerance to monotonous situations increased distinctly with nCPAP as well as after osteotomy. Surgical treatment of OSA in carefully selected cases has positive effects on sleep and daytime vigilance. There were no significant differences in the cPSG nor in vigilance tests with regard to nCPAP therapy.

[Actigraphy: methodological limits for evaluation of sleep stages and sleep structure of healthy probands]

Purpose of the investigation was to evaluate the differences of movement density during the sleep stages and waking. 22 diurnally active, healthy, male volunteers of mean age 30.7 (+/-Standard deviation +/- 3.3) years and a Body-Mass-Index 23.6 +/- 3.3 kg/m2 participated in the study. All subjects were recorded in the sleep lab via cardiorespiratory polysomnography and wrist actigraphy (Ambulatory Monitoring, Ardsley, USA) worn on the non-dominant hand, for two consecutive nights. The activity data, consisting of the number of zero crossings (NZC) were recorded in 1-minute periods. Sleep stages were scored visually according to standard criteria. EEG- and actigraphy data were converted to the same data format (European Feature Files). Attaching the actimetry data to the sleep stages was calculated mean NZC for every sleep stage and Wake. In spite of high differences in total individual NZC we observed that most NZC occurred during Wake. NREM 1 movement density was significantly higher in 19 recordings (86%) than in any other sleep stage. In 18 cases (82%) lowest movement density was found in NREM 3/4 with significant difference to all other sleep stages. Within 50% of the recordings were found decreasing activity in the following sequence of stages: Wake > NREM 1 > REM > NREM 2 > NREM 3/4 However, in all other cases there was a varying pattern of activity.

CONCLUSION

Although there is some correlation between motor activity and sleep stages, the predictive value of actimetry data analysis in the assessment of sleep structure appeared to be limited mainly by individual movement density, especially during REM and NREM 2.

A thermodynamic discourse on the dissolution behavior of bioactive glasses

The interaction between bioactive glass and body fluid is crucial for the special properties of this material, therefore a large number of experimental data is available in literature. However, a frame for systematic interpretation of these results in terms of understanding the mechanisms at the interface between glass and body medium and the relation between glass composition and dissolution behavior is still missing. For two multicomponent bioactive glasses, 45S5 and 13-93, the Gibbs energies of the glassy material on one side and their aqueous system on the other side were calculated individually. The difference between solid material and aqueous system further constitutes the pH dependent Gibbs energy of hydration, ∆Ghydr. The impact of glass compositions and glassy or crystalline state on ∆Ghydr is demonstrated referring to chemical durability. Along considerations regarding the aqueous system, the thermodynamic calculations proof the precipitation of hydroxyapatite inwater and simulated body fluid for a systemcontaining P2O5 and Ca2+. In the course of deriving the Gibbs energies for bioactive glass compositions via constitutional compounds, bioactive behavior is discussed from the point of coexisting equilibrium phases in the system of Na2O-CaO-SiO2.

[Influence of nCPAP therapy on bradycardic arrhythmias in sleep apnea]

In 5-10% of patients with sleep apnoea, AV conduction block or sinus arrest up to several seconds can be demonstrated. We studied the effect of nCPAP treatment on apnoea-associated heart blocks. 10 consecutive patients (9 m, 1 f) between 28-56 years of age (mean value 43.4 y) were studied. The diagnosis of sleep apnoea and nocturnal heart blocks during the first visit at the outpatient department were the only selection criteria. A standard polysomnography before and during nCPAP was performed. Mean pretreatment RDI was 91/h. Repetitive II degrees and III degrees AV conduction blocks were diagnosed in 2 patients (pts) and sinus arrest of 2 to 11 s in 8 pts at the study without therapy. 89.2% of heart blocks occurred during REM-sleep. In 8 pts a complete reversal of heart blocks could be demonstrated during nCPAP. In 2 pts heart blocks persisted at a reduced number during REM-sleep, mainly during ineffective nCPAP. In 80% of our pts nCPAP leads to a complete reversal of heart blocks. The indication for pacemaker implantation must be established on an individual basis.