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Electrognathographic measurements on 18 patients with implant-attached mandibular complete dentures showed larger and more stable chewing patterns compared to their former dentures without implants. Strain gauge measurements revealed mechanical stress acting on the implants even during the fixation of the bar. In addition to simulating the periodontal ligament, the intramobile element (IME) of the IMZ system compensated minor, clinically undetectable mismatches inherent with technical procedures (casting, soldering). Although the implants are loaded with tensile and compressive stress, tensile stress dominated during the chewing process. The implants were also loaded during swallowing. This load reached half of the value of the chewing loads. [ABSTRACT FROM AUTHOR]

Overbite and overjet, especially high or low values, have been found in some studies to be associated with temporomandibular disorders (TMD). This study evaluates the relationship between overbite/overjet and three TMD self-report measures (pain, joint noises, limited mouth-opening). Subjects were from two population-based cross-sectional studies (3033 subjects). After adjustment for age and gender, high or low values of overbite were not associated with an increased risk of self-reported TMD pain as compared with a reference category of a normal overbite of 2 to 3 mm (-8 to -1 mm, odds ratio = 0.36, 95% confidence interval = 0.05-2.76; 6 to 15 mm, odds ratio = 1.08, 95% confidence interval = 0.68-1.72). Similar non-significant results were found for overjet and TMD pain, and for the association of overjet/overbite and joint noises or limited mouth-opening. This study provides the strongest evidence to date that there is no association between overbite or overjet and self-reported TMD. [ABSTRACT FROM AUTHOR]

Abstract Background The aim of the present study was to evaluate the recovery potential of the parotid glands after using either 3D-conformal-radiotherapy (3D-CRT) or intensity-modulated radiotherapy (IMRT) by sparing one single parotid gland. Methods Between 06/2002 and 10/2008, 117 patients with head and neck cancer were included in this prospective, non-randomised clinical study. All patients were treated with curative intent. Salivary gland function was assessed by measuring stimulated salivary flow at the beginning, during and at the end of radiotherapy as well as 1, 6, 12, 24, and 36 months after treatment. Measurements were converted to flow rates and normalized relative to rates before treatment. Mean doses (Dmean) were calculated from dose-volume histograms based on computed tomographies of the parotid glands. Results Patients were grouped according to the Dmean of the spared parotid gland having the lowest radiation exposure: Group I - Dmean < 26 Gy (n = 36), group II - Dmean 26-40 Gy (n = 45), and group III - Dmean > 40 Gy (n = 36). 15/117 (13%) patients received IMRT. By using IMRT as compared to 3D-CRT the Dmean of the spared parotid gland could be significantly reduced (Dmean IMRT vs. 3D-CRT: 21.7 vs. 34.4 Gy, p < 0.001). The relative salivary flow rates (RFSR) as a function of the mean parotid dose after 24 and 36 months was in group I 66% and 74%, in group II 56% and 49%, and in group III 31% and 24%, respectively. Multiple linear regression analyses revealed that the parotid gland dose and the tumor site were the independent determinants 12 and 36 months after the end of RT. Patients of group I and II parotid gland function did recover at 12, 24, and 36 months after the end of RT. Conclusions If a Dmean < 26 Gy for at least one parotid gland can be achieved then this is sufficient to reach complete recovery of pre-RT salivary flow rates. The radiation volume which depends on tumor site did significantly impact on the Dmean of the parotids, and thus on the saliva flow and recovery of parotid gland.

The rejection of composite veneerings in fixed partial dentures is primarily caused by the inadequacy of the bonds between the metal framework and the composite veneering. The development of improved veneering composites necessitates an investigation of their clinical suitability compared with ceramic materials. Nineteen patients with at least two suitable, adjacent natural teeth for crowning were treated with 64 high noble alloy crowns. The adjacent crowns were veneered with ceramic (IPS inline) and composite materials (SR Adoro). Seven follow-up examinations were carried out over a period of 10 years. The crowns were investigated for mechanical defects, periodontal parameters, and discolorations. The survival rates of the ceramic veneered metal crowns (CeMCs) and composite veneered metal crowns (CoMCs) at the 10-year follow-up were 87.1 and 87.9%, respectively. The success rates of the crowns after 10 years were 83.9% for CeMCs and 51.5% for CoMCs (log-rank test, p = 0.009). No significant differences between the groups were found in the periodontal parameters (Kruskal-Wallis one-way analysis of variance, ANOVA p ⟩ 0.05). After 10 years, discoloration patterns of the two materials differed significantly (Mann-Whitney-U-test, p = 0.017). Thus, despite the improvements associated with CoMCs, CeMCs remain the gold standard for veneered metal crowns., (Copyright© 2021 Dennis Barber Ltd.)

Background: To evaluate the accuracy of a computer numerical control (CNC) milled surgical guide for implant placement in edentulous jaws., Methods: Edentulous patients seeking implants treatment were recruited in this prospective cohort study. Radiographic guides with diagnostic templates were fabricated from wax-up dentures. Patients took cone-beam computed tomography (CBCT) wearing the radiopaque radiographic guides. Implant positions were virtually designed in the planning software based on the CBCT data, and the radiographic templates were converted into surgical guides using CNC milling technique. Forty-four implants were placed into 12 edentulous jaws following guided implant surgery protocol. Post-surgery CBCT scans were made for each jaw, and the deviations between the planned and actual implant positions were measured. Deviation of implant position was compared between maxilla and mandible, and between cases with and without anchor pins using independent t-test., Results: Nine patients (3 males and 6 females) with 12 edentulous jaws were recruited. The mean age of patients was 59.2 ± 13.9 years old. All 44 implants was placed without complication and survived, the mean three dimensional linear deviation of implant position between virtual planning and actual placement was 1.53 ± 0.48 mm at the implant neck and 1.58 ± 0.49 mm at the apex. The angular deviation was 3.96 ± 3.05 degrees. No significant difference was found in the deviation of implant position between maxilla and mandible (P = 0.28 at neck, 0.08 at apex), nor between cases with and without anchor pins (P = 0.87 at neck, 0.06 at apex)., Conclusions: The guides fabricated using the CNC milling technique provided comparable accuracy as those fabricated by Stereolithography. The displacement of the guides on edentulous arch might be the main contributing factor of deviation., Trial Registration: Chinese Clinical Trial Registry, ChiCTR-ONC-17014159 (July 26, 2017).

Objectives: Several in vitro studies have investigated the retention of double crowns with friction pins (DCP); however, clinical data on their long-term success have not been reported. We sought to evaluate the 5-year survival rate of DCPs in patients with severely reduced dentition (SRD) and not severely reduced dentition (NSRD)., Materials and Methods: A total of 158 patients were treated with 182 dentures on 520 abutment teeth between 2006 and 2016. The SRD group included 144 dentures that had been inserted on 314 abutment teeth. We evaluated the influence of age, sex, jaw, number, tooth vitality, and abutment teeth localization (according to Steffel's classification) on the 60-month survival rates of dentures and abutment teeth using the Kaplan-Meier estimator, logrank test, and Cox regression., Results: The cumulative 60-month survival rate was 84.3% (CI 77.1-91.5%) for all dentures; however, the survival rate in the SRD group (80.3%; CI 71.5-89.1%) was significantly lower than in the NSRD group (100%; p = 0.04). Dentures classified in Steffel's class A had the lowest survival rate (51.5%; CI 30.9-72.1%). Number, location, and vitality of the abutment teeth had a significant impact on survival rate., Conclusions: DCP dentures showed comparable clinical long-term success to double crown systems that have been previously reported in the literature. The number, localization, and vitality of abutment teeth had the greatest influence on the survival rates of denture and abutment teeth., Clinical Relevance: DCP dentures have an acceptable 5-year survival rate. Clinical treatment planning must take into account key factors associated with the prognosis of the abutment teeth.

Objectives: This study aimed to evaluate the effects of endodontic treatment on the complication rate in abutment teeth following double crown treatment., Materials and Methods: Data of 233 patients supplied with 278 prostheses on 773 teeth were retrospectively analyzed. The 60-month cumulative complication rate for vital, root filled, and post and core reconstructed abutment teeth is calculated using the Kaplan-Meier method. Cox regression is performed to evaluate factors including age, sex, jaw, and tooth number., Results: After 60 months, the cumulative complication rate for all abutment teeth was 24.1% (CI: 19.7-28.5%). A significantly higher cumulative fracture rate (log-rank test, p < 0.001) was found for devital (51.7%; CI: 35.3-68.1%) compared to vital abutment teeth (20.6%; CI: 16.2-25%). Devital teeth restored with post and core reconstructions (46.3%; CI: 26.1-66.5%) showed a lower cumulative fracture rate than abutment teeth with only root fillings (60.9%; CI: 33.5-88.3%). Abutment teeth in severely reduced dentitions (≤ 3 teeth) were found to have significantly lower survival rates than abutment teeth in not severely reduced dentitions (≥ 4 teeth, p = 0.031, HR = 0.609)., Conclusion: Lower abutment teeth survival rates were associated with non-vitality and a reduced number of abutment teeth. Devital teeth with post and core reconstructions showed higher survival rates than root filled devital teeth., Clinical Relevance: After 5 years, devital teeth with double crowns have a fracture rate twice as high as vital teeth. This prognosis should be taken into account during treatment planning, especially in the severely reduced dentition.

Context: Impaired postural control in single-limb stance and aberrant drop-landing mechanics have been implicated separately as risk factors for noncontact anterior cruciate ligament (ACL) injury, but associations between these variables has not been reported., Objective: To determine whether there are associations between single-limb postural control and drop-landing mechanics., Setting: University motion-analysis laboratory., Design: Single-leg-landing kinematic and kinetic data were collected after participants dropped from a hang bar. Postural-control variables COP excursion and velocity were assessed during single-leg barefoot standing on a force platform., Participants: A convenience sample of 24 healthy women., Main Outcome Measures: Pearson product-moment correlation coefficients., Results: Strong associations were measured between maximal knee-abduction moment and COP excursion (r = .529, P = .003) and average COP velocity (r = .529, P = .003). Strong inverse associations were measured between minimum hip-flexion angle and COP excursion (r = -.521, P = .003) and average COP velocity (r = -.519, P = .003)., Conclusions: Participants with decreased postural control had higher knee-abduction moments and a more extended hip on landing, which have been implicated separately as risk factors for ACL injury. A longitudinal prospective analysis is needed to determine whether force-platform postural-control measures can identify athletes at risk for ACL injury.

Background: The aim of the present study was to evaluate the recovery potential of the parotid glands after using either 3D-conformal-radiotherapy (3D-CRT) or intensity-modulated radiotherapy (IMRT) by sparing one single parotid gland., Methods: Between 06/2002 and 10/2008, 117 patients with head and neck cancer were included in this prospective, non-randomised clinical study. All patients were treated with curative intent. Salivary gland function was assessed by measuring stimulated salivary flow at the beginning, during and at the end of radiotherapy as well as 1, 6, 12, 24, and 36 months after treatment. Measurements were converted to flow rates and normalized relative to rates before treatment. Mean doses (D(mean)) were calculated from dose-volume histograms based on computed tomographies of the parotid glands., Results: Patients were grouped according to the D(mean) of the spared parotid gland having the lowest radiation exposure: Group I - D(mean) < 26 Gy (n = 36), group II - D(mean) 26-40 Gy (n = 45), and group III - D(mean) > 40 Gy (n = 36). 15/117 (13%) patients received IMRT. By using IMRT as compared to 3D-CRT the D(mean) of the spared parotid gland could be significantly reduced (D(mean) IMRT vs. 3D-CRT: 21.7 vs. 34.4 Gy, p < 0.001). The relative salivary flow rates (RFSR) as a function of the mean parotid dose after 24 and 36 months was in group I 66% and 74%, in group II 56% and 49%, and in group III 31% and 24%, respectively. Multiple linear regression analyses revealed that the parotid gland dose and the tumor site were the independent determinants 12 and 36 months after the end of RT. Patients of group I and II parotid gland function did recover at 12, 24, and 36 months after the end of RT., Conclusions: If a D(mean) < 26 Gy for at least one parotid gland can be achieved then this is sufficient to reach complete recovery of pre-RT salivary flow rates. The radiation volume which depends on tumor site did significantly impact on the D(mean) of the parotids, and thus on the saliva flow and recovery of parotid gland., (© 2011 Hey et al; licensee BioMed Central Ltd.)

Purpose: To determine the influence of concomitant radiochemotherapy with cisplatin on parotid gland tissue complication probability., Methods and Materials: Patients treated with either radiotherapy (n = 61) or concomitant radiochemotherapy with cisplatin (n = 36) for head-and-neck cancer were prospectively evaluated. The dose and volume distributions of the parotid glands were noted in dose-volume histograms. Stimulated salivary flow rates were measured before, during the 2(nd) and 6(th) weeks and at 4 weeks and 6 months after the treatment. The data were fit using the normal tissue complication probability model of Lyman. Complication was defined as a reduction of the salivary flow rate to less than 25% of the pretreatment flow rate., Results: The normal tissue complication probability model parameter TD(50) (the dose leading to a complication probability of 50%) was found to be 32.2 Gy at 4 weeks and 32.1 Gy at 6 months for concomitant radiochemotherapy and 41.1 Gy at 4 weeks and 39.6 Gy at 6 months for radiotherapy. The tolerated dose for concomitant radiochemotherapy was at least 7 to 8 Gy lower than for radiotherapy alone at TD(50)., Conclusions: In this study, the concomitant radiochemotherapy tended to cause a higher probability of parotid gland tissue damage. Advanced radiotherapy planning approaches such as intensity-modulated radiotherapy may be particularly important for parotid sparing in radiochemotherapy because of cisplatin-related increased radiosensitivity of glands.

The aim was to improve the prediction rate of hyposalivation after using a modern 3D-conformal-radiotherapy-technique (3D-CRT) by sparing of the contralateral parotid gland. Between June 2002 and October 2006, 107 patients (90 male, 17 female, average age: 58 years) with squamous cell carcinoma of the head and neck were included in a prospective, non-randomized study. All patients were treated using 3D-CRT. Parotid function was assessed by measuring stimulated salivary flow before, during and at the end of radiotherapy, as well as 1, 6 and 12 months after radiotherapy. Measurements were converted to flow rates and normalized relative to that before treatment. Mean doses (D(mean)) were calculated from dose-volume histograms (DVHs) based on computed tomographies (CTs) for the left and right parotid gland separately. Patients were grouped according to the D(mean) of the lowest irradiated parotid gland. Group I included all patients who received a D(mean)<26Gy (n=23), group II D(mean) 26-40Gy (n=38) and group III D(mean)>40Gy (n=46). By the time of 6 months after irradiation, salivary flow rates decreased continuously during the therapy. In group I the flow rate decreased to 59%, in group II to 40% and in group III to 14%, p<0.05. One year after irradiation a recovery effect could be measured in all groups. A sufficient saliva flow rate can be proven if one parotid gland is spared with a D(mean) dose <26Gy. Approximately, one quarter of the participants showed a significant improvement.

Objective: To investigate the dimensional changes and the surface quality of dental impression materials after disinfection with 3 chemically different agents., Method and Materials: Four alginate impression materials and 1 addition silicone material were selected. The impressions were made from a brass model simulating a 3-unit fixed partial denture. The chemical disinfection was performed with 3 different disinfectants for 10 minutes. Three samples of each impression material and disinfectant agent were investigated. As a control, 3 impressions of each material were made without any disinfection. The casts were made with a type IV dental stone. For each cast, 6 diameters and 3 distances were measured. To evaluate the dimensional stability, measurements were taken at a magnification of 34X with a light microscope. The surface quality was recorded using a profilometer., Results: The dimensional change and surface quality differed minimally; however, statistically significant differences were found between alginate and addition silicone impression materials (ANOVA, P < .05). Casts from the silicone impressions were more accurate than the casts from alginate impressions., Conclusion: Different impression disinfection methods have only a marginal influence on dimensional stability and surface quality of dental casts. To achieve a higher precision, the use of an addition silicone can be recommended.

Purpose: To stabilize overdentures, a wide range of attachments to implants is suggested. Although there is evidence that denture stability is an important factor for patient satisfaction, there are no data on how these attachments may reduce denture mobility. It was the purpose of this study to compare the effects of different types of attachments on the mobility of implant-stabilized overdentures in vitro, designing a measurement device that could also be used in vivo., Materials and Methods: On an acrylic model with 2 implants in the canine areas, magnets were fixed to one of the implant abutments. Four Hall-effect devices were attached to the denture opposite the magnet, which allowed contact-free measurements of denture movements., Results: In vitro experiments loading an overdenture showed very small, largely insignificant differences in denture mobility when different bar or ball attachments were used. Geometric aspects of load application were more important than the choice of attachment., Conclusion: The measurements gave no guide to the choice of an attachment. The similarity of the attachments must be confirmed by in vivo measurements.

Pumice is a potential source of infection for the dental technician and of cross-contamination between different dentures and patients. In this study, the number of microorganisms in two different combinations of pumice and disinfectant was compared with a conventional mixture of pumice and water. The results revealed that under practical conditions the mix of Steribim (pumice containing benzoic acid added by the manufacturer) with water reduced the number of bacteria by 99% compared with a mix of a conventional pumice and water. The addition of an antiseptic product that contained octenidine as active agent to conventional pumice reduced the number of microorganisms by 99.999%.

Sintered metals have been developed recently for the construction of metal ceramic crowns (Degusint U). An unbalanced, randomized double-blind study was conducted to compare the gingival response to artificial crowns with sintered noble metal margins and cast noble metal margins (Degudent U) by measuring the sulcus-fluid-flow rate (SFFR) in highly motivated patients. In a prior study marginal opening of 20 microns were recorded for cast metal crowns, whereas two sintered metal crowns had marginal openings of 40 microns. Three metal ceramic crowns (Renaissance, Degusint U, and Degudent U for the copings and VMK 68 porcelain) with subgingival margins were prepared and fabricated for 12 intact natural teeth. The SFFR was measured for teeth with artificial crowns and adjacent natural teeth after provisional insertion of each crown. Significantly elevated SFFRs were recorded for all artificial crowns compared with the adjacent natural teeth, but there were no variations recorded for the different types of crown margins.

Light curing composite resins became the preferred material in treating carious or traumatic lesions of anterior teeth. Attempts to improve the properties of these materials lead to the development of hybrid composites with an amount of anorganic fillers of more than 80 weight %. It was the purpose of this study to investigate whether composites with higher amounts of anorganic filler show better properties than those with lower amounts of filler. Eight commercial and two experimental composites have been tested for their resistance to abrasion by simulated toothbrushing, polymerization shrinkage, water sorption, porosity, and surface quality. The results showed no correlation between the amount of anorganic filler on the one hand and tested properties on the other. The amount of anorganic filler is no quality criterium per se, the properties of a composite are rather influenced by composition and quality of the organic matrix, even if the amount of anorganic fillers increases to more than 80 weight %.

Traditional elastomeric impression materials, four recently developed "hydrophilic" silicones and a hydrocolloid have been tested for their accuracy of reproduction by use of indirect measurements via plaster dies and for their wettability by means of the sessile drop method. The new silicones are reproducing the original model as exactly as the traditional elastomers. The impression techniques have a stronger influence on the results than the impression materials. Although the new silicones are more hydrophilic than the traditional elastomers, they do not reach the wettability of a hydrocolloid. The results of the indirect measurements and the results of the contact angle measurements are corresponding to the results of other investigations and to literature data of bubble counts of plaster dies made of different impression materials.

The need for disinfection of dental impressions is generally postulated. While many disinfectants for elastomeric impression materials have been recommended for at least ten years, several authors recently described suitable disinfectants for alginate impressions. Disinfectants for reversible hydrocolloid materials are in the phase of practical testing, and show promising first results. Under practical and scientific aspects further investigations are necessary to evaluate standards and standardized testing procedures.