Does Maximum Voluntary Clenching Force Pose a Risk to Overloading Alloplastic Temporomandibular Joint Replacement?-A Prospective Cohort Study.

PURPOSE: The amount of maximum voluntary clenching (MVC) force may influence functional loading at the polyethylene/metal bearing surfaces in alloplastic total temporomandibular joint replacement (TMJR). The aim of this study was to measure ipsilateral MVC and estimate the risk for revision due to overloading of the TMJR. METHODS: A prospective cohort study design was used to study patients who underwent alloplastic TMJR. The primary predictor was time after TMJR, the secondary predictors were age at TMJR placement, coronoidectomy, prior ipsilateral TMJ surgeries, TMJR design (custom, stock), and bite location. The primary outcome variable was MVC, the secondary outcome was need for TMJR revision. Data were collected preoperatively (T0), and 1 year (T1), 2 to 3 years (T2) and ≥4 years postoperatively (T3). Analysis of variance (ANOVA) with post hoc Tukey-HSD and regression analysis was used for statistical analysis. P < .05 was considered significant. RESULTS: Thirty-seven patients (58 TMJR) with unilateral (n = 16) and bilateral (n = 21) TMJR were enrolled; 8 males (12 TMJR) and 29 females (46 TMJR). Average age was 46.4 ± 14.9 years. MVC increased significantly over the observation period (P = .000). At all observation time points, age at TMJR placement and bite location significantly influenced MVC (P = .000). Coronoidectomy and prior ipsilateral TMJ surgeries did not demonstrate a significant influence on MVC. TMJR design influenced MVC significantly at T3 (P = .006). Regression analysis identified age as a significant factor for higher MVC. No TMJR required revision or replacement. CONCLUSIONS: Based on this study, ipsilateral MVC increases significantly after TMJR. However, since MVC is significantly lower than in healthy test-patients, a considerably lower functional loading at the polyethylene/metal bearing surfaces can be assumed. Lower loading at the TMJR bearing surfaces and at the cortical screw fixation sites suggest a potential longer lifespan compared to other artificial joints like hip and knee prostheses.

Unilateral, Alloplastic Temporomandibular Joint Reconstruction, Biomechanically What Happens to the Contralateral Temporomandibular Joint?-A Prospective Cohort Study.

PURPOSE: Unilateral alloplastic total temporomandibular joint reconstruction (TMJR) might influence the contralateral side joint function. This study's purpose was to estimate the risk for contralateral TMJR and the jaw function of the contralateral untreated temporomandibular joint (TMJ). PATIENTS AND METHODS: A prospective cohort study design was used for patients who underwent unilateral alloplastic TMJR. The primary predictor was time after TMJR, and the secondary predictors were pre-TMJR mandibular angle resection, prior ipsilateral TMJ surgeries, and TMJR design (custom, stock). The primary outcome variable was the need for contralateral TMJR. The secondary outcome variables were the results of jaw function-jaw tracking, maximum voluntary clenching, surface electromyography, and pressure pain thresholds (PPT) and patient's quality-of-life (oral health-related quality-of-life [OHrQoL]). Data were collected preoperatively (T0), and 1 year (T1), 2-3 years (T2), and ≥ 4 years postoperatively (T4). Analysis of variance with post hoc Tukey -HSD test and multiple linear regression analysis were used for statistical analysis. P < .05 was considered significant. RESULTS: Thirty-nine patients were enrolled, 15 males and 24 females, with an average age of 48.9 ± 16.2 years. Two patients (5.1%) required a contralateral TMJR. Contralateral condylar motion, incisal laterotrusion, and protrusion slightly decreased, while incisal opening (P = .003), rotation angle (P = .013), opening deflection, surface electromyography activity, maximum voluntary clenching (P = .01), PPTs, and OHrQoL all increased. Pre-TMJR mandibular angle resection had an impact on PPTs and subjective outcomes and prior ipsilateral TMJ surgeries on the opening rotation angle. CONCLUSIONS: Based on this study, bilateral TMJR does not appear necessary when the contralateral TMJ is healthy. Unilateral alloplastic TMJR is associated with improved contralateral jaw function and OHrQoL.

How Does a Unilateral Temporomandibular Joint Replacement Affect Bilateral Masseter and Temporalis Muscle Activity?-A Prospective Study.

PURPOSE: Total alloplastic temporomandibular joint replacement (TMJR) requires the detachment of the masseter muscle (MM) at its insertion to the lateral ramus and often the resection of the coronoid process (insertion of the temporalis muscle). There is little literature on how a detachment affects the muscles. The present study evaluates the long-term masticatory muscle activities and maximum voluntary bite force (MVC) in patients with unilateral TMJR. PATIENTS AND METHODS: Surface electromyography of the MM and anterior temporalis muscle during bite force testing and MVC were evaluated bilateral preoperatively (T0), 1 (T3), 2 (T4), 3 (T5), and 4 years (T6) postoperatively. The percentage overlapping coefficient (index of the symmetric distribution of muscular activity) was calculated. Differences between stock or custom devices were evaluated. RESULTS: Fourteen patients were enrolled, 4 males and 10 females, age 47.3 ± 14.3 years at TMJR placement. In 11 patients, the coronoid process was resected, 5 patients received stock, and 9 custom prostheses. After surgery, a trend in the improvement of bilateral surface electromyography activities and MVC was found without statistical significance for the side comparison or the time of the investigation. The percentage overlapping coefficient values showed postoperatively relative (>72%) symmetry in both muscles. Up to T5 on the TMJR side, MM showed higher activity when custom prostheses were used. There was no significant difference between stock and custom prostheses. CONCLUSIONS: The vertical (anterior) fibers of the temporalis muscle are preserved despite the resection of the coronoid process. The anterior temporalis muscle, as a synergist of the MM on the TMJR side, postoperatively partially assumes its abduction function. The detached MM appears to reattach. Generally, the bilateral increase in muscle activity and MVC of both muscles suggests regeneration of the investigated muscles. Custom prostheses seem to have an initial advantage for the reattachment of the MM compared with stock prostheses.

Age- and localization-dependent functional and psychosocial impairments and health related quality of life six months after OSCC therapy.

OBJECTIVES: The aim of the current study was to evaluate the functional and psychosocial impacts and changes in overall quality of life (QoL) following oral squamous cell carcinoma (OSCC) therapy in different age groups and in different oral locations. MATERIALS AND METHODS: The study assessed questionnaire responses from patients with OSCC (n = 1319) after 6 months of oncologic therapy, as collected in the DÖSAK Rehab Study. Oncological variables, dental status, sensory, QoL, psychosocial outcomes and coping strategies in younger (45-60 years) and older (61-100 years) patients were assessed for different OSCC locations including the entire oral cavity, maxilla, mandible and others besides the maxilla and mandible. RESULTS: Younger patients were generally less satisfied with their dental status and experienced more sensory and QoL impairments, as well as more psychological burden, compared to the older patients. Depending on the age group, different coping strategies were used. Oncologic therapy targeted to the mandible and other locations besides the maxilla and mandible led to the strongest sensory and QoL limitations. CONCLUSIONS: Regardless of age, oncologic OSCC therapy leads to profound sensory and psychosocial restrictions and to limitations in QoL. Reasons for the poorer functional and QoL outcomes in younger patients include a more invasive treatment and a lower psychosocial resilience. The identification of patients with depressive and dysfunctional coping strategies should be carried out for all ages, but especially in younger patients, in order to develop functional coping strategies through individualized counseling, treatment and rehabilitation. REGISTRATION OF CLINICAL TRIALS: Observational study, therefore not required.

Mandibular kinematics and maximum voluntary bite force following segmental resection of the mandible without or with reconstruction.

OBJECTIVES: The purpose was to analyze mandibular kinematics and maximum voluntary bite force in patients following segmental resection of the mandible without and with reconstruction (autologous bone, alloplastic total temporomandibular joint replacement (TMJ TJR)). MATERIALS AND METHODS: Subjects operated from April 2002 to August 2014 were enrolled in the study. Condylar (CRoM) and incisal (InRoM) range of motion and deflection during opening, condylar retrusion, incisal lateral excursion, mandibular rotation angle during opening, and maximum voluntary bite force were determined on the non-affected site and compared between groups. Influence of co-factors (defect size, soft tissue deficit, neck dissection, radiotherapy, occlusal contact zones (OCZ), and time) was determined. RESULTS: Twelve non-reconstructed and 26 reconstructed patients (13 autologous, 13 TMJ TJR) were included in the study. InRoM opening and bite force were significantly higher (P ≤ .024), and both condylar and incisal deflection during opening significantly lower (P ≤ .027) in reconstructed patients compared with non-reconstructed. Differences between the autologous and the TMJ TJR group were statistically not significant. Co-factors defect size, soft tissue deficit, and neck dissection had the greatest impact on kinematics and number of OCZs on bite force. CONCLUSIONS: Reconstructed patients (both autologous and TMJ TJR) have better overall function than non-reconstructed patients. CLINICAL RELEVANCE: Reconstruction of segmental mandibular resection has positive effects on mandibular function. TMJ TJR seems to be a suitable technique for the reconstruction of mandibular defects including the TMJ complex.

Long-term outcomes of mandibular kinematics following class II malocclusion therapy with removable functional appliance therapy.

OBJECTIVE: To evaluate mandibular kinematics in class I adults following class II therapy with removable functional appliances (RFAs) during the growth period in comparison with orthodontically untreated class I and II individuals. METHODS: Condylar (CRoM) and incisal range of motion (InRoM), velocity during opening and closing, and the mandibular rotation angle were recorded using an ultrasound-based jaw-tracking system in 36 test patients (mean age = 28.03 ± 6.58 years). RESULTS: Significant group effects were found for CRoM towards the posterior in the right joint (p = 0.002) and InRoM towards the anterior (p = 0.043). The post hoc Tukey test indicates a significantly longer CRoM (posterior) for the right condyle in class II (p = 0.003) and RFA individuals (p = 0.023). DISCUSSION: The kinematic data imply greater dentoalveolar effects due to RFA therapy than adaptive remodeling of the temporomandibular joint. The class I relationship in the RFA group following treatment indicates stable long-term outcomes.

The influence of different registration positions on condyle displacement in symptomatic patients.

OBJECTIVE: This study aimed to evaluate effects of different registration positions on the condyle-disk position changes in the mandibular fossa in symptomatic individuals. STUDY DESIGN: Vertical and sagittal condyle position and thickness of the bilaminar zone were measured by magnetic resonance imaging during maximal intercuspation (MI) and with jigs in Gothic arch tracing guided centric relation (DIR method [Dynamics and Intraoral Registration]) and retruded contact position (RCP). Participants were 26 patients seeking treatment for temporomandibular disorders. Condyle and disk position in the fossa were calculated in the parasagittal plane. RESULTS: Significant differences were found for MI, DIR, and RCP for thickness of bilaminar zone and sagittal condyle position, dependent on diagnosis and registration position for vertical and sagittal condyle position and thickness of bilaminar zone. CONCLUSIONS: DIR position ensures the widest posterior space for the retrodiskal tissues and the slightest sagittal difference between condyle zenith and glenoid fossa.

Reproducibility of condyle position and influence of splint therapy on different registration techniques in asymptomatic volunteers.

The current study aims to analyze and quantify the effects of different registration techniques on the reproducibility of condyle position and the influence of stabilization splint therapy on the technique's reproducibility. Three-dimensional electronic-condylar-position analysis (EPA) with an ultrasound-based jaw-tracking system was recorded during intermaxillary registration of manually guided centric relation (CR), maximal intercuspation (MI), and clenching-force-dependent Gothic arch tracing guided centric relation (DIR method) before (T0) and after (T1) splint therapy. Patients were supplied with a stabilization splint for three months on the basis of the DIR registration. Participants were 26 asymptomatic volunteers with a mean age of 30.6 +/- 9.5 years. The registration technique was found to have a significant (p = 0.001) effect on condylar displacement in all axes before, and in X- and Y-axes after splint therapy. Condyles during DIR were found to be in a more anterior-inferior position compared with CR and MI, with the condyles in the latter position being likewise more anterior than in CR. There were significant (p < 0.03) differences in reproducibility of the condyle position dependent on the technique, both at T0 and T1. The DIR method showed the highest reproducibility, followed by MI and CR. There was no significant effect of time of investigation on the technique's reproducibility.

Maximum voluntary bite force in patients with alloplastic total TMJ replacement--a prospective study.

Alloplastic temporomandibular total joint replacement (TJR) for end-stage disease, congenital disorders and following ablative oncological surgery has been shown to reduce pain and improve function. The purpose was to assess the maximum voluntary bite force and maximum interincisal opening (MIO) in patients undergoing alloplastic total temporomandibular joint replacement (TJR). Seventeen patients with different diagnoses resulting in condylar hypomobility (8 patients; 15 joints) and condylar instability (9 patients; 12 joints) had undergone alloplastic TMJ reconstruction. Maximum voluntary bite force and MIO were measured at pre-operatively (T0), 2 (T1), 6 (T2) and 12 (T3) months. For ordinal data comparison at different time-points, the Wilcoxon signed-ranks test was used. There was a significant improvement in maximum voluntary bite force for both, patients with condylar hypomobility (P = 0.003) and condylar instability (P = 0.007). Analysis of MIO revealed a significant improvement at T3 (P = 0.002). Alloplastic TJR would appear to increase maximum voluntary bite force and MIO. Biomechanical integrity of the stomatognathic system and the ability of the patient to triturate food could be improved by alloplastic temporomandibular joint (TMJ) replacement.

Pressure pain threshold and oral health-related quality of life implications of patients with alloplastic temporomandibular joint replacement--a prospective study.

PURPOSE: Alloplastic total temporomandibular joint replacement (TJR) for end-stage disease, congenital disorders, and after ablative surgery has been shown improve function and to decrease pain. The purpose of this study was to evaluate the pain pressure threshold (PPT) and oral health-related quality of life (OHRQoL) in patients undergoing alloplastic TJR. MATERIALS AND METHODS: Subjects requiring TJR from May 2007 through February 2011 were enrolled in the study. The PPT and OHRQoL were measured preoperatively and 2, 6, and 12 months postoperatively. The primary predictor variable was postoperative time (preoperatively and 2, 6, and 12 months postoperatively). The primary outcome variables were the PPT and OHRQoL. RESULTS: Seventeen subjects requiring TJR were enrolled in and completed the required 12-month follow-up. There was no difference in the PPT at any time point. There was a significant improvement in the OHRQoL domain of psychological discomfort (P = .04) at 12 months. Facial pain intensity, temporomandibular joint pain, mandibular function, and diet were also significantly improved at 12 months (P = .001). CONCLUSION: Alloplastic TJR appears to decrease pain, improve function and diet, and decrease psychological discomfort.

Mandibular kinematics in patients with alloplastic total temporomandibular joint replacement--a prospective study.

PURPOSE: The purpose was to analyze the mandibular patterns (condylar range of motion during opening; incisal range of motion during opening, lateral excursion, and protrusion; velocity during opening and closing; mandibular rotation angle during opening and closing) in patients with alloplastic total joint replacement (TJR). MATERIALS AND METHODS: Seventeen patients with different diagnoses resulting in condylar hypomobility (8 patients, 15 joints) and condylar instability (9 patients, 12 joints) had undergone alloplastic TJR. Data were recorded preoperatively and 2, 6, and at least 12 months postoperatively. For ordinal data comparison at different time points, the Wilcoxon signed-ranks test was used. RESULTS: Analysis of the kinematic data at least 12 months postoperatively showed in patients with condylar hypomobility a statistically significant increase in all measured data except the incisal range of motion lateral excursion. In patients with condylar instability, the results showed a statistically significant decrease for incisal range of motion protrusion and laterotrusion. A slight increase in condylar range of motion, incisal range of motion linear distance, and velocity during opening and closing was found. CONCLUSIONS: Even after successful alloplastic TJR, a complete restoration of normal joint function is not achievable. Nevertheless, the kinematic data indicate that alloplastic TJR results in an improved function in patients with joint hypomobility and in a decrease of abnormal hypermobility in patients with condylar instability.

Changes in condylar position using different types of splints with and without a chinstrap: a case-control study.

The aim of this case-control study was to analyze and quantify if there is a different mechanical effect of stabilization and pivot splints with uni- or bilateral pivot of different heights and with and without an additional chinstrap, on the vertical, sagittal, and horizontal condyle position. A stabilization splint and splints with unilateral or bilateral posterior pivot support of 0.6 mm or 1.9 mm height were used with and without a chinstrap individually adjusted to 5N per side. Electronic-condylar-position-analysis was performed using an ultrasound-based jaw-tracking system with an accuracy of 0.1 mm. Manual guided central position served as the reference point. Participants were 40 functional, asymptomatic volunteers with a mean age of 33.9 years. Main effect splint design (stabilization, uni-, bilateral pivot) was not significant. Pivoting height was reported as significant (p < or = 0.02) in all axes. Use of the chinstrap was significant (p < or = 0.03) in the X- and Y- axis, but not significant in the Z-axis. A post-hoc test revealed that use of a chinstrap led to significantly (p = 0.003) less anterior and significantly (p = 0.002) more inferior condyle displacement. Results indicate that the use of pivot splints only in combination with a chinstrap lead to a distractive effect of the condyles.

The influence of different registration techniques on condyle displacement and electromyographic activity in stomatognathically healthy subjects: a prospective study.

STATEMENT OF PROBLEM: It is unclear whether different intermaxillary registration techniques are related to a physiological condylar position that permits neuromuscular equilibrium. PURPOSE: This study analyzes and quantifies the effects of different registration techniques on the condyle position and how the registration technique modulates bilateral masseter and anterior temporalis muscle electromyographic activity. MATERIAL AND METHODS: Three-dimensional electronic condylar position analysis (EPA) with an ultrasound-based jaw-tracking system and surface electromyographic activity (sEMG) was recorded during the registration of a manually guided centric relation (CR), maximal intercuspation (MI), and Gothic arch tracing guided centric relation (DIR method). Participants were 26 stomatognathically healthy volunteers (mean age, 30.6 ±9.5 years). Data were analyzed by 1-way ANOVA and post hoc Bonferroni correction (α=.05). RESULTS: EPA showed significant differences (P<.001) for CR, MI, and DIR in the vertical, sagittal, and horizontal axes. The condyle position during DIR was found to be significantly more anteriorly and inferiorly located than with CR (P<.001) and MI (P<.04). There were no significant differences in the mean muscle activity among CR, MI, and DIR. Muscular symmetry ranged from 63.87 to 81.47%. Significantly higher symmetry for the anterior temporalis (P=.03) and the masseter (P=.03) was found during the DIR than with CR. Torque coefficients (potential laterodeviating effect) were between 88.02% (CR) and 89.94% (MI). CONCLUSIONS: Registration technique significantly influenced the condyle position, while mean muscular activity was minimally affected. With respect to muscular balance and activation, the DIR position proved to be capable of inducing the greatest motor unit activity when compared with manually guided CR and MI.

Long-term results of endosteal implants following radical oral cancer surgery with and without adjuvant radiation therapy.

PURPOSE: The aim of this study was to analyze the long-term survival of implants and implant-retained prostheses in patients after ablative surgery of oral cancer with or without adjunctive radiation therapy. MATERIALS AND METHODS: Between 1997 and 2008, 66 patients who had undergone ablative tumor surgery in the oral cavity were treated with dental implants (n = 262). Thirty-four patients received radiation therapy in daily fractions of 2 Gy administered on 18 to 30 days. Implants were inserted in the maxilla (49; 18.7%) or mandible (213; 81.3%), in non-irradiated residual (65; 24.8%) or grafted bone (44; 16.8%) and in irradiated residual (15.6%) or grafted bone (39; 14.9%). Seventeen fixed protheses and 53 removable dentures (34 bar attachments, 9 telescopic and 10 ball retained dentures) were inserted. RESULTS: Mean follow-up after implant insertion was 47.99 (±34.31) months (range 12-140 months). The overall 1-, 5-, and 10-year survival rates of all implants were 96.6%, 96.6%, and 86.9%, respectively. Fourteen implants were lost in nine patients (5.3% of all implants); eight implants were primary losses, and five secondary losses because of an operation of tumor recurrence. There was no significantly lower implant survival for implants inserted into irradiated bone (p = .302), bone and/or soft-tissue grafts (p = .436), and maxilla or mandible (p = .563). All prosthetic restorations in patients without tumor recurrence could be maintained during the observation period. CONCLUSIONS: Implant survival is not significantly influenced by radiation therapy, grafts (bone and/or soft tissue), or location (maxilla or mandible). However, implants placed in irradiated bone exhibit a higher failure rate during the healing period than those placed in non-irradiated bone. No superstructure was particularly favorable. Osseointegrated implants can be used successfully in patients with prior history of ablative surgery with and without additional radiation therapy.

Optimization of the marginal gap of all-ceramic restorations and gold crowns by ultrasound activated, suspended Al2O3 powder.

PURPOSE: To evaluate if the use of ultrasound activated Al203 powder improved the fit especially of all-ceramic restorations. METHODS: 21 extracted teeth were prepared for 14 all-ceramic IPS Empress2 (IPS Empress2) restorations (four crowns, four partial crowns, two inlays, four veneers) and seven gold crowns (Degudent H). Each restoration was adjusted with a suspension of Al2O3 of 25 microm and 50 microm grit, respectively. The effect of the fitting adjustments was recorded with the silicone disclosing medium technique and measured at 11 points under the microscope in an interval of 0.4 mm. RESULTS: A significant (P < 0.001) improvement of the tight fit of all restorations by means of ultrasound activated Al2O3 powder was noticed. The approach of the restoration towards the prepared stump by the sonoerosive fitting correction was in the mean 201 +/- 60 microm in Empress2 restorations and 87 +/- 24 microm in gold crowns within a period of 10 minutes. SEM observation of the Empress2 specimens showed no microdamage after ultrasound machining.