Digital design of open hollow obturator framework using existing dentures: A dental technique.

Computer-aided design and computer-aided manufacturing technology has been applied to the fabrication of maxillary obturator frameworks, both directly and indirectly. However, with earlier techniques, it was not possible to accurately determine the position of the framework conforming to the palate, an issue that has been resolved in current fabrication methods. Using the patient's existing denture, prosthodontists can determine where the framework should be positioned in the defect area. This allows the obturator bulb to be hollowed, thereby reducing weight and making adjustment easier. The most appropriate position for the finish line can be determined by accurately establishing the arrangement of the artificial teeth as well as the most appropriate polishing surface morphology. In maxillofacial prosthetics, restoring proper articulation and the swallowing function through rehabilitation is important, and determining the proper palatal morphology enables good tongue movement and facilitates the restoration of adequate function. The lighter weight contributes to protecting the remaining teeth and improves patient comfort.

Use of an occlusal ramp for rehabilitation after a mandibulectomy and its effects on mastication.

STATEMENT OF PROBLEM: Patients with a mandibular defect can develop mandibular deviation, resulting in a loss of or reduction in occlusal contact and ultimately loss of function. The occlusal ramp is a prosthesis used to help restore the masticatory function of such patients and is used particularly in the maxillofacial rehabilitation of patients with masticatory dysfunction resulting from mandibular deviation. The occlusal ramp is usually attached to a mandibular denture or worn as an independent device placed on the palate corresponding to the mandible that produces the offset. However, evidence of the effects of its use is sparse. PURPOSE: The purpose of this clinical study was to investigate the effects of occlusal ramp use in functional rehabilitation. MATERIALS AND METHODS: This study included 10 patients who had received mandibulectomies (5 men and 5 women; mean age 76.7 years, range 67 to 90 years) with deviation of the mandible. An occlusal ramp was fabricated for each participant as part of their maxillofacial prosthetic treatment. Masticatory performance was evaluated before and after the treatment by measuring glucose extraction while masticating a piece of gummy jelly. The Wilcoxon signed-rank test was used for statistical analysis (α=.05). RESULTS: The median masticatory performance score, represented as glucose concentration (mg/dL), was 82.45 before treatment and 115.45 after treatment, with an overall improvement of 33.00. Scores differed significantly before and after treatment (P=.005). Masticatory performance for each participant improved in the range of 17.7 to 103.3, highlighting the role that the occlusal ramp played in mastication, although with differing effects in each participant. CONCLUSIONS: Masticatory performance in participants with mandibular deviation after a mandibulectomy was significantly improved with an occlusal ramp. This suggests the effectiveness of using occlusal ramps in maxillofacial prosthetic treatment for the recovery of masticatory function in patients with mandibular deviation.

Use of digital technology in prosthesis fabrication for an elderly patient with a maxillectomy and severe trismus: A clinical report.

This clinical report describes a novel approach based on digital technology to fabricate a maxillofacial prosthesis for a 90-year-old woman with severe trismus who had undergone maxillectomy on the right side. The approach was safe, rapid, and less burdensome on this elderly patient, and the storage and communication of intraoral and maxillofacial prosthesis data without temporal and spatial constraints was helpful. A combination of digital and analog technology provided a maxillofacial prosthesis that improved the quality of life of this elderly patient with head and neck cancer and severe trismus.

Detailed speech evaluation including formant 3 analysis and voice visualization in maxillofacial rehabilitation: A clinical report.

Objective speech evaluation such as analysis of formants 1 and 2 and nasality measurement have been used in maxillofacial rehabilitation for outcome assessment. However, in some patients, those evaluations are insufficient to assess a specific or unique problem. This report describes the use of a new speech evaluation including formant 3 analysis and voice visualization in a patient with a maxillofacial defect. The patient was a 67-year-old man who had a maxillary defect that opened to the maxillary sinus and who had an unnatural voice even when wearing an obturator. Nasality was low and the frequency of formants 1 and 2 were normal even without the obturator. However, a low frequency of formant 3 and a shifted center of voice were observed. These results indicated that the unnatural voice was related to increased resonant volume in the pharynx rather than hypernasality. This patient demonstrates that advanced speech analysis can be useful for detecting the cause of speech disorder and planning maxillofacial rehabilitation.

Creating and analyzing digital scans of a mandibulectomy cast with simulated trismus.

STATEMENT OF PROBLEM: Trismus associated with maxillofacial defects resulting from tumor resection or radiotherapy can make dental treatment uncomfortable for patients. Using an intraoral scanner instead of making a conventional impression could help to make prosthetic rehabilitation more comfortable. However, limited information is available regarding the feasibility and accuracy of intraoral scanners for scanning mandibular defects. PURPOSE: The purpose of this in vitro study was to evaluate the feasibility and accuracy of using an intraoral scanner to digitize a cast of a mandibular defect under various simulated trismus conditions. MATERIAL AND METHODS: An intraoral scanner was used to scan the mandibular cast under different simulated degrees of trismus (mouth opening 10, 20, and 30 mm) and nontrismus (mouth opening 40 mm). The surface areas captured were compared. The datasets were loaded into a 3-dimensional (3D) evaluation software program and then superimposed for precision analysis and on reference data for trueness analysis. One-way analysis of variance was used to compare surface area captured, precision, and trueness of the measurement under the different mouth opening conditions (α=.05). RESULTS: The surface area for which 3D data were obtained by the intraoral scanner ranged from 3199.1 to 6161.6 mm2. The area differed significantly under all mouth opening conditions (P=.001), with a smaller scanned surface area captured in severe trismus (10 mm). Precision ranged from 0.032 to 0.056 mm, and trueness from 0.037 to 0.076 mm. No significant differences were seen in precision (P=.312), but significant differences were seen in trueness (P=.016) under all trismus conditions. CONCLUSIONS: Using an intraoral scanner appears feasible for digitizing mandibular defect casts with simulated mild and moderate trismus. The accuracy of the obtained data was clinically acceptable.

Effect of cut-out rescan procedures on the accuracy of an intraoral scanner used for digitizing an ear model: An in vitro study.

PURPOSE: The purpose of this study was to evaluate the impact of the rescanning of mesh holes of different diameters on the accuracy of an intraoral scanner (IOS) used to digitize an ear model. MATERIALS AND METHODS: An ear model was digitized using an intraoral scanner (Medit i500) to obtain a reference mesh. A baseline experimental scan was created by editing a duplicate of the reference mesh using the cut-out tool of the IOS software. Three equal groups were created based on the diameter of the cut-out areas: 2 mm (G1), 5 mm (G2), and 8 mm (G3) (n = 15). The cut-out areas were rescanned and a total of 45 digital files were exported. The discrepancy between the reference and the experimental digital scans was measured using the root mean square calculation (RMS). The data were analyzed by a Kruskal-Wallis test followed by a post hoc Dunn's test with Bonferroni correction. RESULTS: The trueness values ranged from 19.53 to 27.13 µm. There were significant differences in the RMS error values among the groups tested (p < 0.001) and post hoc multiple comparisons showed significant differences between the G1 and G2 groups (p = 0.04), G1 and G3 groups (p < 0.001), and G2 and G3 groups (p = 0.004). Overall, the precision values ranged from 4.93 to 7.73 µm and significant differences in the RMS values were only found between the G1 and G2 groups (p = 0.014). CONCLUSIONS: Mesh hole rescanning affected the scanning accuracy (trueness and precision) of the IOS tested. The larger the diameter of the mesh holes, the less the trueness of the IOS tested. The precision values seemed to be less affected compared with the trueness by the cut-out and rescanning procedures.

Digital acoustic analysis of the first three formant frequencies in patients with a prosthesis after maxillectomy.

STATEMENT OF PROBLEM: Prosthetic rehabilitation with an obturator can help to restore or improve the intelligibility of speech in patients after maxillectomy. The frequency of formants 1 and 2 as well as their ranges were initially reported in patients with maxillary defects in 2002, and the evaluation method that was used is now applied in clinical evaluation. However, the details of formant 3 are not known and warrant investigation because, according to speech science, formant 3 is related to the pharyngeal volume. Clarifying the formant frequency values of formant 3 in patients after maxillectomy would enable prosthodontists to refer to these data when planning treatment and when assessing the outcome of an obturator. PURPOSE: The purpose of this clinical study was to determine the acoustic characteristics of formant 3, together with those of formants 1 and 2, by using a digital acoustic analysis during maxillofacial prosthetic treatment. The utility of determining formant 3 in the evaluation of speech in patients after maxillectomy was also evaluated. MATERIAL AND METHODS: Twenty-six male participants after a maxillectomy (mean age, 63 years; range, 20 to 93 years) were included, and the 5 Japanese vowels /a/, /e/, /i/, /o/, and /u/ produced with and without a definitive obturator prosthesis were recorded. The frequencies of the 3 formants were determined, and their ranges were calculated by using a speech analysis system (Computerized Speech Lab CSL 4400). The Wilcoxon signed rank test was used to compare the formants between the 2 use conditions (α=0.05). RESULTS: Significant differences were found in the frequencies and ranges of all 3 formants between the use conditions. The ranges of all 3 formants produced with the prosthesis were significantly greater than those produced without it. CONCLUSIONS: Based on the findings, both the first 2 formants and the third formant were changed by wearing an obturator prosthesis. Because formant 3 is related to the volume of the pharynx, evaluation of this formant and its range can reflect the effectiveness of the prosthesis to seal the oronasal communication and help reduce hypernasality, suggesting the utility of formant 3 analysis in prosthodontic rehabilitation.

An indirect-direct technique with hot water for fabricating a cast metal crown under an existing removable partial denture.

Fracture or carious lesions in an abutment tooth may require the fabrication of a crown under an existing removable partial denture. Typically, once the crown has been fabricated, the prosthesis will need to be modified or refabricated. However, if the partial denture is in good clinical condition, special techniques may be applied to make the new crown fit the existing prosthesis. This article describes a straightforward indirect-direct technique for fabricating a cast metal crown under an existing removable partial denture with hot water. The technique does not require expertise or any special device and can be performed chairside by general dentists.

Two-piece detachable interlocking mold for low-dose-rate brachytherapy: A dental technique for radiotherapy prosthesis fabrication.

Brachytherapy is a type of radiotherapy used to eradicate malignancies in the head-and-neck region. Early-stage mucosal carcinomas, such as carcinomas of the hard palate and gingival mucosa, can be treated with low-dose-rate brachytherapy by using a radiotherapy prosthesis called a mold. Prosthodontists play a significant role in the design and fabrication of these molds, which deliver therapeutic doses to the primary lesion and protect adjacent tissues from radiation exposure. However, planning and observing ongoing treatment is difficult for radiation oncologists because the shield part cannot be removed from the carrier part or requires an attachment to do so. This article describes a technique for fabricating a 2-piece detachable interlocking mold without any special attachment for low-dose-rate brachytherapy.

Computerized optical scanning of ears: An in vitro evaluation with an intraoral scanner.

STATEMENT OF PROBLEM: Making conventional facial impressions can be uncomfortable for the patient and complicated for the prosthodontist. Using facial scanners to digitize faces is an alternative approach. However, the initial costs of the equipment have prevented their widespread use in dental practice, and the accuracy of ear scanning is unclear. PURPOSE: The purpose of this in vitro study was to investigate the accuracy of a widely used intraoral scanner for digitizing an ear model. MATERIAL AND METHODS: For reference, a silicone model of an ear was scanned with an industrial scanner. Then, the model was scanned 5 times with an intraoral scanner. Five conventional impressions of the model were made with a hydrocolloid impression material and poured with dental stone. The stone casts were then digitized with a desktop scanner. The data sets acquired with the 3 approaches were analyzed by using a 3-dimensional (3D) evaluation software program. Trueness and precision values were calculated for each approach. Linear mixed models with random intercepts were fitted to each sample to evaluate the effects of the impression method on mean deviations (α=.05). RESULTS: Mean ±standard deviation trueness and precision values were 0.097 ±0.012 mm and 0.033 ±0.015 mm, respectively, for the digital scan, and 0.092 ±0.022 mm and 0.081 ±0.024 mm for the conventional impression, showing a significantly lower deviation in precision for the digital approach (P<.001). CONCLUSIONS: The feasibility of digitizing an ear efficiently by using the investigated intraoral scanner was demonstrated, and similar trueness and significantly better precision values were achieved than when using conventional impressions. These promising results suggest the need for clinical investigations.

A custom-made brachytherapy applicator for recurrent endometrial and vaginal cancer: A dental technique for prosthesis fabrication.

The role of the prosthodontist in radiation therapy includes fabrication of radiation therapy prosthetic applicators. Brachytherapy is a form of cancer treatment that involves direct insertion of radioactive implants into the tissue. In the case of vaginal cancer, brachytherapy requires the radiation oncologist to use a device called an applicator. Conventional applicators have limitations in terms of the number of radiation tubes that can be inserted, positioning of the tubes, applicator misfit, and pain when inserted. A well-fitted applicator is needed to improve the orientation of the radiation source toward the target area and to reduce the amount of scatter radiation and tissue irritation. Using an appropriate dental material to make an impression can serve to achieve these aims. This article describes a technique for fabricating an acrylic resin custom-made applicator by using techniques used in dentistry.

Morphological comparison of artificial teeth position utilising denture space in glossectomy patients.

OBJECTIVE: This study aimed to compare the denture space of edentulous glossectomy patients with that of a control group from the perspective of artificial teeth positioning by using three-dimensional techniques. BACKGROUND: It is known that the shape of the denture space may be affected by tongue resection or reconstruction. However, the details of artificial teeth positioning in these patients remain unclear. MATERIALS AND METHODS: Six edentulous glossectomy patients aged 73-83 years and six normal participants aged 74-85 years participated in the study. Piezography was used to elucidate the characteristics of the denture space. For visualisation, piezographic records were scanned using cone beam computed tomography and the data were converted into stereolithographic format. Three-dimensional images of piezographic records were then constructed. Bucco-lingual widths of the mandibular occlusal surface were reproduced, and the camber line of the occlusal surface was set so as to simulate the position of the artificial teeth. The maximum chord of the occlusal surface on the left and right sides was recorded and measured. The discrepancy and ratio of the larger chord to the smaller chord between the right and left sides was calculated and subjected to statistical analyses using the Mann-Whitney U test. RESULTS: There were significant differences in discrepancy and ratio between the left and right in the control group and the glossectomy patients (P Ë‚ .01). The glossectomy patients showed a greater discrepancy and ratio than the control group. CONCLUSIONS: The simulated artificial teeth positions on the occlusal surface between the right and left side were asymmetric in glossectomy patients.

Color change of airborne particle-abraded acrylic resin surfaces: A palatography method.

STATEMENT OF PROBLEM: A palatogram aids prosthodontists and speech pathologists in evaluating the precise prosthetic treatment needed and the effectiveness of such treatment to improve speech intelligibility. Powder is commonly used to visualize tongue-palate contact, where wetted areas of powder in the oral cavity reveal such contact during palatography. However, discomfort and the risk of aspiration are among the shortcomings of this method, and an improved method is needed. PURPOSE: The purpose of this in vitro study was to examine the feasibility of a new method of palatography that uses airborne-particle-abraded acrylic resin so that wet areas can be easily distinguished from dry areas. MATERIAL AND METHODS: Seventy-two specimens of heat-polymerized acrylic resin were prepared in 6 different resin colors. After the specimens had been airborne-particle abraded, CIELab color values for each specimen were measured using a colorimeter under dry and wet conditions and recorded. Color difference (ΔE) was then computed, and a paired Student t test, 1-way analysis of variance, and multiple comparison using the Tukey post hoc analysis were applied (α=.05). RESULTS: A significant color difference was found between the 2 conditions in all acrylic resin specimens examined. Mean ΔE ranged from 5.58 to 6.76. CONCLUSIONS: The results indicated that an airborne-particle-abraded acrylic resin surface can show color differences made by wetting on palatograms.

Digitized Speech Characteristics in Patients with Maxillectomy Defects.

PURPOSE: Accurate evaluation of speech characteristics through formant frequency measurement is important for proper speech rehabilitation in patients after maxillectomy. This study aimed to evaluate the utility of digital acoustic analysis and vowel pentagon space for the prediction of speech ability after maxillectomy, by comparing the acoustic characteristics of vowel articulation in three classes of maxillectomy defects. MATERIALS AND METHODS: Aramany's classifications I, II, and IV were used to group 27 male patients after maxillectomy. Digital acoustic analysis of five Japanese vowels-/a/, /e/, /i/, /o/, and /u/-was performed using a speech analysis system. First formant (F1) and second formant (F2) frequencies were calculated using an autocorrelation method. Data were plotted on an F1-F2 plane for each patient, and the F1 and F2 ranges were calculated. The vowel pentagon spaces were also determined. One-way ANOVA was applied to compare all results between the three groups. RESULTS: Class II maxillectomy patients had a significantly higher F2 range than did Class I and Class IV patients (p = 0.002). In contrast, there was no significant difference in the F1 range between the three classes. The vowel pentagon spaces were significantly larger in class II maxillectomy patients than in Class I and Class IV patients (p = 0.014). CONCLUSION: The results of this study indicate that the acoustic characteristics of maxillectomy patients are affected by the defect area. This finding may provide information for obturator design based on vowel articulation and defect class.

A chairside technique to add customized anterior acrylic resin teeth to a surgical obturator.

A surgical obturator may need to be modified during the healing process after tissue resection. Apart from relining the fitting surfaces to accommodate the healing wound and changes in the surrounding tissues, other modifications such as adding teeth are sometimes required to improve esthetics and speech. This article describes a chairside technique to add customized acrylic resin teeth to an existing surgical obturator.

Effect of Experimental Palatal Prosthesis on Voice Onset Time.

PURPOSE: Objective evaluation of a patient's speech is needed in prosthetic dentistry because the prostheses can affect the intelligibility of speech. Measurement of voice onset time is one evaluation method of consonant production used in phonetic science. The purpose of this study was to confirm the influence of a palatal prosthesis on consonant production by measuring voice onset time. MATERIALS AND METHODS: In this study, voice onset time was measured in 10 healthy women (mean age 26.5 years) under two conditions: with and without an experimental palatal prosthesis. In this study, voice onset time of /ta/ and /ka/ were used to determine the effect of wearing a palatal prosthesis; /pa/ was tested as a control, with the null hypothesis that voice onset time of /ta/ and /ka/ would not change when wearing a palatal prosthesis. RESULTS: Medial voice onset time of /pa/, /ta/, and /ka/ syllables without the palatal prosthesis was 22.5 ms, 19.5 ms, and 42.5 ms, whereas that with the palatal prosthesis was 22.5 ms, 23.5 ms, and 55.0 ms. Voice onset times for /ta/ and /ka/ were prolonged when wearing the experimental palatal prosthesis, whereas /pa/ showed no significant difference. CONCLUSION: Consonant production was affected by wearing a palatal prosthesis, and this change in sound was detected by measuring voice onset time.

Preschool and School Phases of Postmaxillectomy Prosthetic Rehabilitation in a Child: A Clinical Report.

This report describes the postmaxillectomy prosthetic rehabilitation of a child with maxillary chondrosarcoma over an 8-year period. Specifically, it (1) describes the planning and rehabilitation procedures carried out during the period from before the operation to the time when the patient started elementary school and (2) reports the results of evaluations of the patient's oral and psychosocial function conducted during the school phase. The prosthetic treatment plan was separated into two phases (the preschool and school phases) and was started prior to surgery, when an immediate surgical obturator was designed by the surgeons. After the operation, it was considered important to provide the patient and her mother with training regarding how the defect should be cleaned, trismus prevention, and how the prosthesis should be fitted. In addition, esthetic improvements and the ability to speak clearly were also targeted during treatment planning. After surgery, obturators were fabricated in a conventional manner and fitted at the ages of 2, 4, 6, 8, and 10 years. The patient's oral function during the use of the obturators was evaluated objectively. Marked improvements in oral function were seen during both treatment phases. The patient's ability to perform psychosocial functions at school also improved during the use of the obturators.

Orientation of handle for successful prosthetic treatment in patients with an anatomic compromise after a maxillectomy.

This clinical technique provides a key procedure for successful prosthetic treatment in patients with an anatomical compromise after a maxillectomy. When making a preliminary impression, the clinician must keep the handle of the stock tray parallel to the patient's interpupillary line extraorally to maintain the correct position of the tray and to make a record of the inclination of the occlusal plane. This simple consideration during this first step of making a preliminary impression can be an important guide for both dentists and dental technicians. Information about the correct positioning of the tray and the inclination of the occlusal plane obtained by using a stock tray handle will greatly reduce the stress experienced by dentists, dental technicians, and patients during the fabrication of the prosthesis and will ultimately lead to successful prosthetic treatment in patients with anatomic compromise resulting from a maxillectomy.

Investigation of nutritional status using the Mini Nutritional Assessment-Short Form and analysis of the relevant factors in patients with head and neck tumour.

OBJECTIVE: The aims of this study were to reveal the nutritional status of patients after head and neck tumour treatment by using the Mini Nutritional Assessment-Short Form (MNA-SF) and to analyse the factors affecting nutritional status in patients with head and neck tumour. BACKGROUND: Elderly patients with loss of teeth and maxillary/mandibular bone due to head and neck tumour treatment could be at high risk of malnutrition. However, there are few reports on the nutritional status of these patients. MATERIALS AND METHODS: Forty-six participants (average age 74.7 years) were selected from patients who visited the maxillofacial prosthetics clinic of Tokyo Medical and Dental University Hospital Faculty of Dentistry in Japan. Nutritional status was evaluated using the MNA-SF. Multiple regression analysis was used to identify predictors affecting MNA-SF score. The candidate explanatory variables were age, sex, maxillofacial prosthesis use, number of residual teeth, resection side, neck dissection and treatment option. RESULTS: The results showed that approximately half of the patients were at risk of malnutrition, and a regression equation for MNA-SF score was developed using two predictors: maxillofacial prosthesis use and neck dissection. CONCLUSION: Use of a maxillofacial prosthesis can improve nutritional status. On the other hand, a medical history of neck dissection can decrease nutritional status.

Rehabilitation of a Bilateral Maxillectomy Patient with a Free Fibula Osteocutaneous Flap and with an Implant-Retained Obturator: A Clinical Report.

A 47-year-old man underwent surgical resection and reconstruction with a fibula osteocutaneous flap. After the surgery, a surgical obturator was placed and adjusted. After flap healing, a conventional obturator was fabricated with polymethyl methacrylate resin and retained by the anatomical undercuts around the reconstructed fibula bone flap and the posterior part of the defect. As the defect shape changed with time, a second conventional obturator was fabricated and fitted. No further recurrence of myoepithelioma was observed for 2 years, and the patient was satisfied with the obturator during mastication and speech; however, despite having no major complaints, the patient found it difficult to chew on the right side, and the obturator was displaced slightly downward when the mouth was opened wide and shifted when chewing hard and sticky food. Thus, an implant-retained obturator was suggested to provide better retention and stability. Four dental implants were therefore placed into the fibula bone, although one did not osseointegrate because either primary stability was insufficient or overload was affected in the nonloaded implant environment and was replaced. After fitting custom abutments with a magnet, an implant-retained obturator was placed, and the patient was satisfied with the outcome. During 3 years of follow-up, no issues were noted with the implant bodies, abutments, obturator, or reconstructed site. The conventional obturator was displaced slightly downward when the patient opened his mouth wide, and it shifted when chewing hard and sticky food because there was limited fibula bone at the reconstruction site and more available posteriorly. For better retention and stability, the implant-retained obturator was fabricated with a custom abutment and magnetic retention. The patient was satisfied with the results, as improved implant retention increased the stability of the prosthesis. This clinical report describes the rehabilitation of a bilateral maxillectomy patient with a free fibula osteocutaneous flap and an implant-retained obturator. The patient's oral functions were improved when the prosthesis was stabilized by means of dental implants and custom abutments.