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1.
J Oral Maxillofac Surg ; 74(12): 2526-2531, 2016 Dec.
Article in English | MEDLINE | ID: mdl-27400143

ABSTRACT

PURPOSE: The purpose of this study was to describe the trends pertaining to the use of the fibula free flap for mandibular reconstruction during the past 10 years. MATERIALS AND METHODS: A systematic review for publications on the fibula free flap in mandibular reconstruction in the PubMed and Scopus databases was performed from January 1, 2005 until December 31, 2014. Publications were classified by topic, number of patients, and country of origin. The study period was split into 2 periods. The first 5-year period was compared with the second 5-year period. RESULTS: Eighty-five publications were identified. There was an increase in publications regarding restorative decision making (11 vs 9), surgical techniques (13 vs 6), outcomes (20 vs 10), and computer-aided design and computer-aided manufacturing (CAD-CAM; 8 vs 2) in the second 5-year period. The number of patients reported also increased in publications on surgical techniques (1,085 vs 59), outcomes (777 vs 254), bisphosphonate-related osteonecrosis of the jaw and osteoradionecrosis (165 vs 28), and CAD-CAM (65 vs 15) in the second 5-year period. The United States, India, China, and Europe produced most of the publications. CONCLUSIONS: In the past 10 years, there was a surge in publications on the use of the fibula free flap for mandibular reconstruction. There was a 1.8-fold increase in the number of publications and a 3.4-fold increase in the number of patients undergoing this method of mandibular reconstruction in the second 5-year period. Publications from the United States, India, and China contributed to a large increase in the number of patients in the second 5-year period. More interest in CAD-CAM technology was seen in the second 5-year period that was not seen in the first 5-year period.


Subject(s)
Fibula/transplantation , Free Tissue Flaps/statistics & numerical data , Mandibular Reconstruction/trends , Practice Patterns, Physicians'/trends , Bibliometrics , China , Europe , Free Tissue Flaps/trends , Humans , India , Mandibular Reconstruction/methods , United States
2.
Head Neck ; 45(8): 1894-1902, 2023 Aug.
Article in English | MEDLINE | ID: mdl-37255301

ABSTRACT

BACKGROUND: While a single-stage free-flap reconstruction is the preferred approach for oromandibular defects, a multistaged approach may be necessary in rare cases. These patients can still be effectively restored with functional and aesthetic improvements. METHODS: We report two cases with a history of bilateral failed fibula free flaps. We detail the multistaged reconstruction to repair these complex defects and discuss the considerations when planning such procedures. RESULTS: Both patients successfully underwent a staged reconstruction with an iliac crest osteocutaneous flap following either a rectus abdominis or pectoralis major myocutaneous flap. CONCLUSION: Oromandibular reconstruction is an expected outcome in the contemporary management of oral cavity cancer and osteoradionecrosis. However, complications do occur and can be devastating. In cases of bilateral failed fibula free flaps, a staged approach is a favorable option. Moreover, the iliac crest provides an important reconstructive option with the documented potential for implant born dental rehabilitation.


Subject(s)
Free Tissue Flaps , Mouth Neoplasms , Plastic Surgery Procedures , Humans , Free Tissue Flaps/surgery , Mouth Neoplasms/surgery , Fibula/transplantation , Ilium/surgery
3.
Craniomaxillofac Trauma Reconstr ; 15(3): 253-263, 2022 Sep.
Article in English | MEDLINE | ID: mdl-36081675

ABSTRACT

Study Design: case series. Objective: The restoration of defects in a single procedure with microvascular free flap reconstruction has become a mainstay of head and neck surgery. Yet in patients with complex defects and pre-existing comorbid medical conditions, a staged-reconstructive approach can enhance the safety of the procedure and improve the patient's outcome. Methods: We present 3 representative case examples of a larger series of patients who underwent reconstruction of major defects and discuss the usefulness of a staged-reconstructive approach in the management of complex patients. Results: All 3 patients, with an existing composite defect in the setting of prior radiation therapy, underwent successful staged-reconstructive surgery using a variety of free tissue and regional flap transfers. Conclusions: A staged approach facilitates the reconstruction of complex composite defects, increases vessel availability, and mitigates the risk of flap failure. Although this approach commits the patient to multiple procedures and a more prolonged plan of care, it is preferable to 1 operation in specific complex situations with adverse, high-risk clinical features.

4.
Laryngoscope ; 130(10): 2349-2353, 2020 10.
Article in English | MEDLINE | ID: mdl-31886884

ABSTRACT

OBJECTIVE: A subset of patients who undergo major palatomaxillary reconstruction do not initially achieve their intended oncologic and/or reconstructive goals and require additional surgery. We aim to detail the unique management considerations in this patient population. METHODS: We performed a retrospective review of patients who underwent palatomaxillary reconstruction by the senior author (m.l.u.) between 1998 and 2016. RESULTS: Twenty-one patients required multiple reconstructions. The median time to second reconstruction was 17 months. The most common reason for a second reconstruction was for recurrent disease (10 of 21), followed by functional/aesthetic reasons (7 of 21) and osteoradionecrosis (4 of 21). Four patients went on to have a third reconstruction, and two underwent a fourth. A total of 27 reconstructions were performed, consisting of 20 soft tissue free flaps, four vascularized bone free flaps, and three locoregional flaps. CONCLUSION: This patient cohort represents unique oncologic and reconstructive challenges. With long-term follow-up, multiple reconstructions may be required to optimize oncologic and functional/aesthetic outcomes. This is the first series of its kind that details the reasons for, as well as the outcomes of, patients who required multiple reconstructive procedures following initial palatomaxillary reconstruction. LEVEL OF EVIDENCE: 2B Laryngoscope, 130:2349-2353, 2020.


Subject(s)
Maxillary Diseases/surgery , Palate/surgery , Plastic Surgery Procedures/methods , Prosthodontics/methods , Aged , Esthetics , Female , Free Tissue Flaps , Humans , Male , Middle Aged , Recurrence , Reoperation , Retrospective Studies
5.
JAMA Otolaryngol Head Neck Surg ; 146(5): 437-443, 2020 05 01.
Article in English | MEDLINE | ID: mdl-32271362

ABSTRACT

Importance: Incorporation of patient perspectives, or patient-reported outcomes, in functional outcome measures has been gaining prominence in the literature on reconstructive surgery. Objective: To create and validate an instrument for measuring the main functional areas of concern for patients with head and neck cancer. Design, Setting, and Participants: This 4-phase mixed-methods qualitative study was conducted from July 1, 2013, to June 30, 2016, in a quaternary head and neck oncology center in Edmonton, Alberta, Canada. Patients were recruited from 3 Head and Neck Research Network sites: University of Alberta (Edmonton, Canada), Mount Sinai Health Network (New York, New York), and University of Turku Hospital (Turku, Finland). The inclusion criteria included 18 years of age or older, diagnosis of squamous cell carcinoma involving the subsites of the head and neck (ie, oral cavity, oropharynx, hypopharynx, and larynx), and at least 1 year since treatment completion. Those patients who were undergoing additional active treatment or with evidence of disease recurrence were excluded. Data were analyzed from July 1, 2013, to June 30, 2016. Main Outcomes and Measures: The primary outcome measures were the clinical correlation of the Edmonton-33 instrument scores with swallowing, speech, dry mouth, and chewing assessment outcomes. Results: In total, 10 patients with head and neck cancer (mean age, 59.6 years; 6 men [60%]) were included in phase 1 of the study, 5 patients (mean age, 55.2 years) were included in phase 2, 10 patients were included in phase 3, and 25 patients with head and neck cancer (mean age, 62.6 years; 14 men [56%]) participated in the phase 4 validation. The Edmonton-33 instrument scores correlated strongly with the swallowing scores of the MD Anderson Dysphagia Inventory (r = 0.77; 95% CI, 0.49-1.0), the European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire-Head and Neck 35 (EORTC QLQ-H&N35) (r = -0.73; 95% CI, -1.0 to -0.44), and the modified barium swallow test (r = -0.60; 95% CI, -0.94 to -0.25). The instrument scores were also strongly correlated with the Speech Handicap Index scores (r = -0.64; 95% CI, -0.97 to -0.31), word intelligibility scores (r = 0.61; 95% CI, 0.27-0.95), and sentence intelligibility scores (r = 0.55; 95% CI, 0.19-0.91). A moderate to strong correlation was observed between the Edmonton-33 instrument and the EORTC QLQ-H&N35 scores in the dry mouth (r = -0.54; 95% CI, -0.91 to -0.18) and chewing (r = -0.45; 95% CI, -0.84 to -0.06) domains. The factor loading values for the domains of swallowing, speech, dry mouth, and chewing were all greater than 0.3. The mean factor loading values for the items related to swallowing were 0.71 (95% CI, 0.62-0.80) and for the items related to speech were 0.76 (95% CI, 0.72-0.80). The mean factor loading values for the items related to dry mouth were 0.71 (95% CI, 0.59-0.83) and for those related to chewing were 0.77 (95% CI, 0.69-0.85). Conclusions and Relevance: The Edmonton-33 appears to be a validated instrument that will allow patients with head and neck cancer to assess and report their own functional outcomes. It could serve as a single comprehensive measure for functional outcomes.


Subject(s)
Head and Neck Neoplasms/physiopathology , Head and Neck Neoplasms/therapy , Patient Reported Outcome Measures , Surveys and Questionnaires , Female , Humans , Male , Middle Aged , Qualitative Research , Quality of Life
6.
Laryngoscope ; 128(12): 2732-2739, 2018 12.
Article in English | MEDLINE | ID: mdl-30325025

ABSTRACT

OBJECTIVES/HYPOTHESIS: This study examined saliva weight over time and its association with diet and patient-rated swallowing, dry mouth, sticky saliva, and dysgeusia quality of life in head and neck cancer (HNCA) patients treated with surgery plus adjuvant chemoradiotherapy (CRT), or primary CRT. STUDY DESIGN: Prospective cohort study in an outpatient HNCA center setting. METHODS: Patients were seen pretreatment, and 1, 3, 6, 12, 24, and 36 + months post-treatment. All had newly diagnosed oral, oropharynx, nasopharynx, larynx/hypopharynx cancer from 2010 to 2016 and were to undergo surgery + CRT or primary CRT. Stimulated saliva weight was assessed with the Saxon test. Diet, eating, dry mouth, and dysgeusia quality of life were assessed and correlated with saliva weight, treatment modality, and tumor site. RESULTS: Saliva weight decreased the most within the first 3 months across treatment groups, except for the surgery + CRT group, which continued to decline. Similar trends were seen by tumor site. Performance Status Scale (PSS) Normalcy of Diet and all quality-of-life scores declined following treatment. The European Organization for Research and Treatment of Cancer Quality of Life Questionnaire Head and Neck-35 (EORTC QLQ-H&N35); Eating Assessment Tool (EAT-10); M. D. Anderson Dysphagia Inventory (MDADI) Composite, Global, and subdomain scores; and PSS Diet were significantly correlated with saliva weight. CONCLUSIONS: Saliva weight worsened post-treatment across groups and tumor site, with improvement by 36 + months. Saliva weight correlated with diet, eating quality of life and perception of dysgeusia across time points. Despite dose-sparing intensity-modulated radiation therapy, newer technologies are needed to preserve saliva production and maintain higher quality of life. LEVEL OF EVIDENCE: 2b Laryngoscope, 128:2732-2739, 2018.


Subject(s)
Chemoradiotherapy, Adjuvant/adverse effects , Head and Neck Neoplasms/therapy , Postoperative Complications/epidemiology , Xerostomia/epidemiology , Deglutition , Female , Head and Neck Neoplasms/physiopathology , Humans , Male , Middle Aged , Postoperative Complications/etiology , Postoperative Period , Prospective Studies , Quality of Life , Saliva/metabolism , Time Factors , Treatment Outcome , Xerostomia/etiology
7.
Head Neck ; 40(8): 1639-1666, 2018 08.
Article in English | MEDLINE | ID: mdl-29537619

ABSTRACT

BACKGROUND: Palatomaxillary defects were historically restored with a prosthetic obturator; however, advances in local and free tissue transfer has provided a viable alternative for appropriately selected patients with palatomaxillary defects. METHODS: A retrospective chart review of patients who underwent palatomaxillary reconstruction by the lead author between 1998 and 2016 was conducted. Patients who were restored with a palatal obturator were excluded. RESULTS: One hundred forty patients were reconstructed with a total of 159 local, regional, and free flaps with a 96.7% success rate. Seventy-four patients (52.8%) underwent prosthodontic rehabilitation, with 183 implants placed and an 86% success rate. CONCLUSION: Palatomaxillary reconstruction applying a systematic approach, using a multitude of techniques, is a safe and effective way to restore patients without compromising the ability to maintain surveillance. Prosthodontic rehabilitation can be achieved in a high percentage of patients using dental implants, leading to optimal aesthetic and functional results.


Subject(s)
Bone Transplantation , Maxilla/surgery , Palate/surgery , Plastic Surgery Procedures/methods , Surgical Flaps , Adolescent , Adult , Aged , Aged, 80 and over , Dental Implants , Dental Restoration, Permanent , Female , Humans , Male , Maxillary Neoplasms/surgery , Middle Aged , Palatal Neoplasms/surgery , Retrospective Studies , Young Adult
8.
J Otolaryngol Head Neck Surg ; 46(1): 56, 2017 Sep 04.
Article in English | MEDLINE | ID: mdl-28870248

ABSTRACT

BACKGROUND: While aggressive treatment for oral cancer may optimize survival, decrements in speech and swallowing function and quality of life often result. This exploratory study investigated how patients recover their communicative function, swallowing ability, and quality of life after primary surgery [with or without adjuvant (chemo)radiation therapy] for tongue cancer over the course of the first year post-operation. METHODS: Patients treated for oral cancer at three institutions (University of Alberta Hospital, Mount Sinai Beth Israel Medical Center, and Turku University Hospital) were administered patient-reported outcomes assessing speech [Speech Handicap Index (SHI)], swallowing [(M.D. Anderson Dysphagia Inventory (MDADI)] and quality of life [European Organization for Research and Treatment of Cancer Quality of Life Questionnaire Head and Neck Module (EORTC-H&N35)]. Outcome measures were completed pre-operatively and at 1-, 6-, and 12-months post-operatively. RESULTS: One hundred and seventeen patients undergoing partial glossectomy with reconstruction participated in this study. Results indicated no significant differences in swallowing function (MDADI and EORTC-H&N35 subscales) between baseline and 6 months post-surgery and no significant differences in speech function (SHI subscales) between baseline and 1 year post-surgery. Most quality of life domains (EORTC-H&N35 subscales) returned to baseline levels by 1 year post-operation, while difficulties with dry mouth and sticky saliva persisted. A clear time trend of adjuvant (chemo)radiation therapy negatively affecting dry mouth scores over time was identified in this study, while negative independent effects of chemoradiation on MDADI swallowing, and EORTC-H&N35 swallowing, eating, and opening mouth subscales were found. CONCLUSIONS: Assessment time influenced patient-reported speech, swallowing, and quality of life outcomes, while treatment (by time) effects were found for only swallowing and quality of life outcomes. Results of the present study will help guide clinical care and will be useful for patient counseling on expected short and long-term functional and quality of life outcomes of surgical and adjuvant treatment for oral cavity cancer.


Subject(s)
Activities of Daily Living , Glossectomy/methods , Patient Reported Outcome Measures , Tongue Neoplasms/pathology , Tongue Neoplasms/surgery , Adult , Aged , Canada , Deglutition Disorders/etiology , Deglutition Disorders/physiopathology , Disability Evaluation , Glossectomy/adverse effects , Glossectomy/psychology , Humans , Linear Models , Longitudinal Studies , Male , Middle Aged , Neoplasm Invasiveness/pathology , Neoplasm Staging , Prospective Studies , Quality of Life , Plastic Surgery Procedures/methods , Risk Assessment , Speech Disorders/etiology , Speech Disorders/physiopathology , Xerostomia/etiology , Xerostomia/physiopathology
9.
Arch Otolaryngol Head Neck Surg ; 129(7): 775-80, 2003 Jul.
Article in English | MEDLINE | ID: mdl-12874081

ABSTRACT

BACKGROUND: Orodental rehabilitation of hemipalatomaxillectomy defects can be accomplished by using a prosthetic obturator or a vascularized bone-containing free flap. Whereas prosthetic obturation offers several advantages, including the opportunity for immediate dental restoration without the need for further surgery, vascularized bone grafts provide permanent closure of the oronasal communication and bone sufficient for the placement of osseointegrated implants. OBJECTIVE: To compare the functional and quality-of-life (QOL) outcomes in patients rehabilitated with a prosthetic obturator with defect-matched patients who underwent reconstruction with a vascularized bone-containing free flap. METHODS: Four hemipalatomaxillectomy patients rehabilitated with a tissue-borne prosthetic obturator were compared with 4 defect-matched hemipalatomaxillectomy patients who underwent reconstruction with a vascularized bone-containing free flap. All of the patients were objectively assessed for speech, mastication, and QOL. Functional status was assessed by mastication testing, voice analysis, and nasorhinometry. Swallowing-related QOL was assessed using a patient-reported, validated swallowing QOL questionnaire, and donor site morbidity was assessed using upper extremity and lower extremity questionnaires. RESULTS: Patients who underwent reconstruction with a vascularized bone-containing free flap achieved higher mastication and speech assessment scores with less oronasal reflux than defect-matched patients rehabilitated with a prosthetic obturator. Swallowing QOL and donor site assessments demonstrated that compared with their prosthetic counterparts, reconstruction patients enjoyed a better QOL without incurring significant donor site morbidity. CONCLUSIONS: Although palatomaxillary reconstruction with vascularized bone-containing free flaps requires a second operative site, this method of orodental rehabilitation of the hemipalatomaxillectomy defect can achieve superior functional and QOL outcomes relative to defect-matched patients rehabilitated with a prosthetic obturator.


Subject(s)
Mastication , Maxilla/surgery , Maxillofacial Prosthesis , Palatal Obturators , Quality of Life , Humans , Speech Intelligibility , Speech Perception , Surgical Flaps , Treatment Outcome
10.
JAMA Otolaryngol Head Neck Surg ; 139(4): 371-81, 2013 Apr.
Article in English | MEDLINE | ID: mdl-23599073

ABSTRACT

IMPORTANCE: Functional recovery for patients who undergo maxillomandibular reconstruction with vascularized bone free flaps (VBFFs) is potentially more attainable with computer-assisted implant rehabilitation. This prosthodontic-driven approach uses software planning and surgical templates for implant placement supporting fixed dental prostheses (FDP). Implant success with immediate load (IL) provisional and definitive FDP restorations in VBFFs is reported for the first time in a patient cohort. OBJECTIVES: To determine implant success for FDP restorations and IL restorations. To determine factors that may influence success and predictability to provide FDP restorations in VBFFs. DESIGN: A retrospective medical chart review was conducted of patients who underwent VBFF reconstruction and computer-assisted planning (CP) for FDP implant rehabilitation. This study was conducted with approval from the institutional review board at Beth Israel Medical Center, New York, New York. SETTING: Clinical procedures were conducted in operating room and outpatient facilities in a tertiary referral medical center. PARTICIPANTS: Twenty-eight consecutive patient treatments were reviewed. Inclusion criteria for all patients were VBFF reconstruction and CP for FDP restoration prior to stage 1 implant surgery. Patients were evaluated for implant success, surgical templates, IL provisional restorations, and prosthodontic framework design. A comparison is made between patients with IL provisional restorations and those patients who did not receive an immediate restoration. MAIN OUTCOMES AND MEASURES: Implants that achieved osseointegration and used for prosthetic reconstruction determined success. Prosthodontic design considerations included whether the patient received an IL provisional restoration and 3 categories of FDP metal framework design. RESULTS Ninety-nine implants of 116 implants placed were used for prosthetic restorations, achieving an 85.4% success rate. Twenty-five of 28 patients received FDP restorations. Thirteen of 28 patients received IL provisional restorations at stage 1 implant surgery. Fifty of 56 implants were successful (89.3%) in the IL group. CONCLUSIONS: Computer-assisted implant rehabilitation of reconstructed defects can achieve superior results to provide FDP and IL provisional restorations. This prosthodontic-driven approach also uses unique framework design to account for mandible height discrepancy after fibula free flap reconstruction. Patient management for FDP rehabilitation is also dependent on radiation status, soft-tissue modification, and patient selection.


Subject(s)
Bone Transplantation/methods , Dental Implantation, Endosseous/methods , Dental Prosthesis, Implant-Supported/methods , Free Tissue Flaps , Mandibular Reconstruction/methods , Maxilla/surgery , Surgery, Computer-Assisted/methods , Adolescent , Adult , Aged , Child , Female , Fibula/transplantation , Humans , Male , Mandible/surgery , Middle Aged , Osseointegration , Retrospective Studies , Young Adult
13.
J Otolaryngol Head Neck Surg ; 39(5): 523-31, 2010 Oct.
Article in English | MEDLINE | ID: mdl-20828515

ABSTRACT

BACKGROUND: Functional outcomes assessment has become increasingly important in informing treatment decisions in the area of head and neck cancer. However, consistency of assessment methods across studies has been lacking. For the literature to inform clinical decision making, consensus regarding outcomes measurements is necessary. OBJECTIVE: The Head and Neck Research Network (HNRN) was founded in January 2008 to become a conduit for high-quality research in the area of functional outcomes in patients with head and neck defects. The present study surveyed experts in functional outcomes assessment to determine what are considered the most important tools for assessing speech and swallowing and what background patient characteristics are important to capture. DESIGN, PARTICIPANTS, AND MEASURES: Respondents to the online survey included 54 participants with a background in speech-language pathology, with the majority of respondents from the United States, Canada, and the United Kingdom. RESULTS AND CONCLUSIONS: The results from the survey indicated that clinicians consider both subjective and objective measures as important to use when assessing function. More advanced technical tools were often rated as less important; however, it also was noted that clinicians were most often not able to access these tools or were unfamiliar with them.


Subject(s)
Biomedical Research/methods , Deglutition/physiology , Head and Neck Neoplasms/physiopathology , Outcome Assessment, Health Care , Quality of Life , Surveys and Questionnaires , Canada/epidemiology , Europe/epidemiology , Female , Head and Neck Neoplasms/epidemiology , Head and Neck Neoplasms/therapy , Humans , Male , Morbidity , Retrospective Studies , United States/epidemiology
14.
Head Neck ; 26(9): 808-14, 2004 Sep.
Article in English | MEDLINE | ID: mdl-15350027

ABSTRACT

BACKGROUND: Although prosthetic obturation is the "gold standard" for restoration of hard-palate defects, obturators can be problematic. We present 10 cases of palatal reconstruction with the radial forearm free flap and compare patient satisfaction with defect-matched patients rehabilitated with prosthetic obturation. METHODS: Twelve patients who underwent radial forearm free flap (RFFF) reconstruction of a hard-palate defect and eight patients, with similar-sized defects who were rehabilitated with a prosthetic obturator, were evaluated for donor site and recipient site complications, diet, and patient satisfaction. RESULTS: All the patients in both groups were able to resume an unrestricted diet with normal mastication and articulation. Both groups achieved equivalent satisfaction scores with regard to appearance, chewing, and taste; however, the patients reconstructed with an RFFF reported higher satisfaction scores in speech, comfort, convenience, and social interaction. CONCLUSIONS: RFFF reconstruction of hard-palate defects provides a functional alternative to conventional prosthetic obturators.


Subject(s)
Forearm/surgery , Palate, Hard/surgery , Patient Satisfaction , Plastic Surgery Procedures/methods , Surgical Flaps , Female , Humans , Male , Middle Aged , Palatal Neoplasms/surgery , Palatal Obturators , Palate, Hard/pathology , Treatment Outcome
15.
J Prosthet Dent ; 90(3): 276-81, 2003 Sep.
Article in English | MEDLINE | ID: mdl-12942062

ABSTRACT

STATEMENT OF PROBLEM: Irreversible hydrocolloid is widely used as an impression material for fabrication of extraoral maxillofacial impressions. A disadvantage of irreversible hydrocolloid, however, is its limited working time. PURPOSE: This study tested the compression strength (elastic recovery) and working and setting times for an irreversible hydrocolloid impression material after a retarder was added. MATERIAL AND METHODS: The irreversible hydrocolloid (Jeltrate) was mixed with water in a standard water/powder mixture of 18 mL (1 unit) of water and 7 g (1 unit) of the impression material. Test specimens (n = 3) were prepared by adding 2, 4, 6, and 8 drops of monobasic sodium phosphate (the retarder) to each. Three other specimens, to which no retarder was added, served as the control. Specimens were prepared according to the American National Standards Institute/American Dental Association's specification no.18 guidelines for irreversible hydrocolloid impression material. Immediately after the specimens were prepared, the flat end of a polished rod of poly(methyl methacrylate) was placed in contact with its exposed surface and quickly withdrawn. The working-time experiment was a pass/fail test conducted 30 seconds before the initial setting time. The initial setting time was established as extending from the start of the mix to the time when the impression material no longer adhered to the end of the rod. To determine how the compressive strength of the modified irreversible hydrocolloid (with retarder added) compared with that of the control, the mean stress at maximum load (Mpa) was analyzed. The compressive strength (MPa) was calculated. Statistical analysis consisted of descriptive statistics and regression analyses. RESULTS: The results of this experiment demonstrated that the elastic recovery of the irreversible hydrocolloid did not change with the addition of sodium phosphate (2 to 8 drops). The percent recovery with was 95.95% +/-.42%, 96.33% +/-.82%, and 96.28% +/-.53% for 0 (control), 2 and 8 drops, respectively. Average setting times for control specimens were 2 minutes 20 seconds +/- 0 seconds for the control specimen (0 drops) to 11 minutes 20 seconds +/- 1 minute 50 seconds for the test specimen with 8 drops. There was a direct relationship (R(2) = 0.85) between the number of drops added and the setting time. All control specimens and test specimens containing 2, 4, 6, and 8 drops of monobasic sodium phosphate produced acceptable levels of elastic recovery (> or =95%). CONCLUSION: Within the limitations of this study, predictable longer working and setting times were demonstrated for the irreversible hydrocolloid specimens with 1 to 8 drops of the sodium phosphate solution tested. The specimens with 8 drops of retarder solution exhibited variable setting times and would not be suitable for clinical use. The compressive strength of the modified irreversible hydrocolloid material tested was compromised because of the addition of sodium phosphate solution; however, recovery from deformation remained satisfactory as retarder solution was added.


Subject(s)
Colloids/chemistry , Dental Impression Materials/chemistry , Alginates/chemistry , Compressive Strength , Dental Stress Analysis , Elasticity , Materials Testing , Maxillofacial Prosthesis , Organic Chemicals , Phosphates , Regression Analysis , Time Factors
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