Da-Yo Yuh

Factors Affecting Treatment Decisions and Outcomes of Root-Resected Molars: A Nationwide Study

BACKGROUND Treatment of furcation-involved molars presents a clinical challenge. This study retrospectively investigates the demographic parameters affecting treatment decisions and outcomes of root-resected molars using a nationwide population-based dataset. METHODS De-identified data from 471 eligible patients were obtained from a representative cohort composed of 1 million of Taiwans population. Demographic factors that influence treatment decisions and outcomes of root-resected teeth were examined. Cox regression was performed to statistically analyze the factors. RESULTS The overall survival rate for root-resected molars was 91.1%. The survival times of the extracted and surviving teeth were 303.0 ± 274.6 and 551.8 ± 327.2 days, respectively (P <0.001). The analyzed patient-related factors, such as living district, urbanization level, medical institution, and monthly income, have remarkable influence on treatment decisions; however, there is no statistically significant difference in survival rate between root-resected molars receiving flap surgery and those that do not (P = 0.504). After adjusting for other factors, patients aged >74 years have 3.33 times (hazard ratio = 3.33; 95% CI = 1.04 to 10.66; P = 0.043) higher rates of molar extraction than younger counterparts. CONCLUSIONS The overall survival rate of root-resected molars was satisfactory. Patients with advanced age (>74 years) had a higher risk of extraction occurrence on resected molars. Patient-related factors may influence the treatment decision of whether molars receive flap surgery. These findings suggest that demographic factors should be carefully evaluated before and after performing root-resection procedures because these factors may eventually impact the outcome of root-resected molars.

The national-scale cohort study on bisphosphonate-related osteonecrosis of the jaw in Taiwan

OBJECTIVES Osteonecrosis of the jaw (ONJ) is a potential side effect of bisphosphonate therapy. This Taiwanese national-scale cohort study aimed to investigate its incidence and risk of development by using a qualified control group with different demographic factors (age/gender), dental (tooth extraction/periodontal therapy) and medical (jaw radiotherapy) treatments, delivery routes (oral/intravenous), and diseases (diabetes/osteoporosis/cancer). METHODS Data (n=958,136) from January 1, 2006 through December 31, 2008 were sourced from the Longitudinal Health Insurance Database 2005 of Taiwan. Cases of BRONJ were identified by three criteria modified from the definition proposed by the American Association of Oral and Maxillofacial Surgeons. The Cox proportional-hazards regression model and Kaplan-Meier estimates were used to analyse the results. RESULTS The incidence densities of ONJ in the unexposed and bisphosphonate-exposed cohorts were estimated as 4.4 and 73.5 per 100,000 person-years, respectively (relative risk=16.8; 95% CI=6.0-37.5; P<0.001). Multivariate analysis revealed strong associations of delivery route, tooth extraction, and oral cancer with ONJ (hazard ratios=51.4 for oral bisphosphonates, 153.3 for intravenous bisphosphonates, 5.3 for tooth extraction, and 278.1 for oral cancer). CONCLUSIONS These results not only demonstrate the incidence and relative risk of bisphosphonate-related ONJ in Taiwan but also indicate that tooth extraction and oral cancer may have a major impact on its development. CLINICAL SIGNIFICANCE Physicians should be aware of individual patient risk factors before prescribing bisphosphonates. Bisphosphonate treatment is justified in the amelioration of life-threatening conditions in patients in whom ONJ would only affect quality of life.

The impact of medical institutions on the treatment decisions and outcome of root-resected molars: A retrospective claims analysis from a representative database

Background: This study analyzes the prognostic factors affecting the survival rate of root-resected molars by using a representative population-based dataset. Materials and Methods: A total of 635,216 eligible patients were enrolled from a representative cohort composed of one million of Taiwans population. The tooth-related factors influencing the survival rates of root-resected teeth were examined on 516 molars, in 492 patients. Cox regression was performed to statistically analyze the factors. Results: The overall survival rate for the root-resected molars was 91.7%. Of the analyzed factors with respect to root-resection procedures, whether or not concomitant flap surgery was performed in the medical institutions, the dental arch and tooth location demonstrated a considerable influence on the treatment and decision-making. The main reasons and results of root-resected molars receiving root-resection therapy in hospitals were the periodontal-compromised conditions, whereas, the root-resected molars that received root-resection therapy in private practice clinics were caused by caries/endodontic reasons. After adjusting for other factors, in the outcome of root-resected molars, a higher risk of extraction occurrence was seen in hospitals than in private practice clinics (hazard ratio = 2.03; 95% CI = 1.04 to 3.98; P = 0.039). Conclusions: Of the analyzed prognostic factors, medical institutions significantly affect the treatment decision and survival of root-resected molars. Therefore, a comprehensive evaluation, risk assessment, and treatment plan should be executed before the root-resection procedure is performed.

Therapeutic Effect of Combining Muscle Relaxant and Posture Correction in Patients with Myofascial Pain Dysfunction Syndrome of Temporomandibular Disorder

Background: Many studies have shown that poor posture may lead to myofascial pain dysfunction syndrome (MPDS) of the trunk. Forward head posture is one of the most common forms of poor posture, and is related to neck pain. Hence, the aim of this study was to estimate the influence of body posture on MPDS of the temporomandibular joint (TMJ). Methods: Twenty-six otherwise healthy adults with MPDS of the TMJ were enrolled in this study. Clinical examination was performed at three time-points: prior to the treatment, at the 2-week follow-up, and at the 4-week follow-up. The subjects received a muscle relaxant drug and adjustment of body posture. Variables such as visual analogue scale (VAS) score, shoulder angle (SA), cervical spine angle-coronal (CSA-c), and cervical spine angle-sagittal (CSA-s) were evaluated at each stage. Generalized estimating equations (GEE) were used to control for non-independence among observations. Results: There were significant improvements in VAS score (p ＜ 0.001), SA (p ＜ 0.001), CSA-c (p ＜ 0.001), and CSA-s (p ＜ 0.001) after treatment compared to the corresponding values obtained before treatment. Conclusions: Correcting body posture in conjunction with use of a muscle relaxant had an extremely therapeutic effect on patients with MPDS of TMJ. The improvement of the angle of sagittal cervical spine may have reduced the pain score, and we speculate that it is important to correct forward head posture when treating patients with MPDS of TMJ.

Er:YAG Laser for Surgical Crown Lengthening: A 6-Month Clinical Study

This study evaluated use of a solid-state laser to avoid the flap technique and suturing. An Er:YAG laser was used in 26 consecutive patients referred for osseous crown lengthening in 32 posterior teeth. The distance from the planned restoration margin to the alveolar crest (B) satisfied a 3-mm dentogingival complex. No tissue necrosis and no significant change in the distance from the gingival margin to B or probing depth were detected at 3 and 6 months. Minimally invasive Er:YAG laser surgery decreases the time needed to establish the gingival margin necessary for definitive restoration.

In Vitro Accuracy Assessment of a Surgical Navigation System for Dental Implantology

Objective: During the process of dental implantation, mistaken use of a surgical drill may cause damage to important anatomical structures. As a result, the use of computer-assisted systems to prevent damage has become commonplace among many dentists. Therefore, it is necessary to be aware of the accuracy of the surgical navigation system, and system accuracy is also an important reference for error range used by dentists in clinical practice. Materials and Methods: This study included the carrying out of an accuracy test on surgical navigation system and freehand drilling under an in vitro environment. Twelve dental implant plans were separately performed in two models; in addition, a surgical navigation system and freehand drilling were used in a simulated dental implant surgery. Furthermore, the accuracy of the planned and actual positions of the implants was assessed. Results: The entry lateral error of the surgical navigation system and freehand drilling was 0.73 ± 0.45 mm and 1.18 ± 0.25 mm, respectively; the apex lateral error was 0.71 ± 0.51 mm and 1.12 ± 0.49 mm, respectively; the apex longitudinal error always 0.25 ± 0.17 mm and 0.63 ± 0.43 mm, respectively; the total error was 0.78 ± 0.48 mm and 1.36 ± 0.44 mm, respectively; and the angular error was 2.09 ± 1.03 degrees and 8.58 ± 3.57 degrees, respectively. The results indicate that the error while using the surgical navigation system was smaller than the error of freehand drilling. Conclusion: This study included the assessment of drilling accuracy of the surgical navigation system in a gypsum model which revealed that the surgical navigation system was more accurate than freehand drilling; however, there are significant differences between the gypsum model and actual patients. Therefore, future clinical studies are warranted in order to provide more valuable data for reference.

Anatomic Considerations to Harvest Subepithelial Connective Tissue Grafts from the Palate on the Three-Dimensional Reconstruction of Cone Beam Computed Tomography

Objectives: Biotype conversion around both natural teeth and implants with subepithelial connective tissue graft (SCTG) has been advocated. The harvesting procedure should be carefully conducted to avoid violating the greater palatine neurovascular bundle (GPB). The GPB, which comprises the greater palatine artery, vein, and nerve, travels through the pterygopalatine fossa, passes through the pterygopalatine canal, and exits into the greater palatine foramen (GPF). This study assessed the accuracy of predicting the location of the GPF and measured the thickness of the palatal masticatory mucosa and the distance from the GPB in the posterior palatal area, using cone beam computerized tomography (CBCT). Methods: CBCT images of 21 patients (13 men and 8 women, 22~46y) were evaluated retrospectively. The inclusion criterion was complete dentition from the maxillary first premolar to the third molar (first premolar: P1, first molar: M1, second molar: M2, area between second molar and third molar: M2-M3, third molar: M3, distal area of third molar: M3D). The distance from the cemento-enamel junction (CEJ) of the P1 and M1 to the GPB (P1d and M1d, respectively) was defined as the safe zone of the palate. The perpendicular distance from the middle P1d and M1d to the palatine bone was defined as the thickness of the palate (P1t and M1t, respectively). Foramen of transversal diameter (FTD) is the transverse diameter of the GPF. The location of the GPF in relation to the tooth and the distance from the CEJ to GPF (M3d) was also determined. Results: The most frequent location of the GPF was M3 (59.5%), followed by M2-M3 (26.2%) and M3D (14.3%). The mean diameter of FTD was 3.4±0.7mm. The mean M3d was 14.6±1.4mm. P1d and M1d were 12.1±1.4mm and 13.3±1.4mm, respectively. P1t and M1t were 3.7±0.5mm and 3.6±0.8mm, respectively. No significant difference was observed between P1d and M1d, but significant difference was noted between P1t and M1t. Conclusion: The thickness of palatal masticatory mucosa increased from the first premolar but decreased at the first molar region. The results of this study can assist clinicians in planning the location for harvesting SCTG on the hard palate.

Position and Incidence of the Mental Foramen in the 3-Dimensional Reconstruction of Cone-Beam Computed Tomography

Objectives: Paralysis of the mental nerve is one of the principle surgical complications when placing implants in the mental foramen region. Therefore, identifying the mental foramen is crucial for surgical procedures.Methods: This study was conducted using 3-dimentional (3D) computed tomographic (CT) analysis on both sexes. The mental foramen was present in 224 CT images of bilateral mandibles of Taiwanese patients. The criteria for including foramen in this study are as follows: (1) age and sex; (2) no missing mandibular teeth of the canine to first molar regions; (3) no pathologic findings between the teeth and the mandibular mental foramen; and (4) no participants with altered tooth positions from the original location, caused by orthognathic surgery and orthodontic treatment.Results: The findings indicated that the most common position for the mental foramen was in line with the longitudinal axis of the second premolar (54.9%), followed by a location between the second premolar and the first molar (22.3%). The right and left foramen were bilaterally symmetrical in the recorded position (61.6%). The mental foramen was symmetrically located on the right and left sides. No significant difference existed between men and women in position.Conclusion: The mental foramen was most often in line with the second premolar, detected using cone-beam computed tomography (CBCT). Knowledge of the mental foramen position is crucial for placing osseointegrated implants in the mandibular second premolar region.