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Biomedical subjects

Hom-Lay Wang

Publications and source records attributed to Hom-Lay Wang.

At least 55 records · Page 3Linked to original sources
PubMed2005

Risk indicators for tooth loss due to periodontal disease.

BACKGROUND: Several risk indicators for periodontal disease severity have been identified. The association of these factors with tooth loss for periodontal reasons was investigated in this cross-sectional comparative study. METHODS: All extractions performed in 21 general dental practice clinics (25% of such clinics in Kuwait) over a 30-day period were recorded. Documented information included patient age and gender, medical history findings, dental maintenance history, toothbrushing frequency, types and numbers of extracted teeth, and the reason for the extraction. Reasons were divided into periodontal disease versus other reasons in univariate and binary logistic regression analyses. RESULTS: A total of 1,775 patients had 3,694 teeth extracted. More teeth per patient were lost due to periodontal disease than for other reasons (2.8 +/- 0.2 versus 1.8 +/- 0.1; P <0.001). Factors significantly associated with tooth loss due to periodontal reasons in logistic regression analysis were age >35 years (odds ratio [OR] 3.45; 95% confidence interval [CI] 2.79 to 4.26), male gender (OR 1.42; 95% CI 1.17 to 1.73), never having periodontal maintenance (OR 1.48; 95% CI 1.23 to 1.78), never using a toothbrush (OR 1.81; 95% CI 1.49 to 2.20), current or past smoking (OR 1.56; 95% CI 1.28 to 1.91), anterior tooth type (OR 3.23; 95% CI 2.57 to 4.05), and the presence of either of the following medical conditions: diabetes mellitus (OR 2.64; 95% CI 2.19 to 3.18), hypertension (OR 1.73; 95% CI 1.41 to 2.13), or rheumatoid arthritis (OR 4.19; 95% CI 2.17 to 8.11). CONCLUSION: Tooth loss due to periodontal disease is associated with the risk indicators of age, male gender, smoking, lack of professional maintenance, inadequate oral hygiene, diabetes mellitus, hypertension, rheumatoid arthritis, and anterior tooth type.

Adolescent↗
PubMed2005

Clinical response of azithromycin as an adjunct to non-surgical periodontal therapy in smokers.

BACKGROUND: Antibiotic therapy can be used in very specific periodontal treatment situations such as in refractory cases of periodontal disease found to be more prevalent in smokers. This study was designed to determine the efficacy of azithromycin (AZM) when combined with scaling and root planing (SRP) for the treatment of moderate to severe chronic periodontitis in smokers. METHODS: Thirty-one subjects were enrolled into a 6-month randomized, single-masked trial to evaluate clinical, microbial (using benzoyl- DL-arginine naphthylamine [BANA] assay), and gingival crevicular fluid (GCF) pyridinoline cross-linked carboxyterminal telopeptide of type I collagen (ICTP) levels in response to SRP alone or SRP + AZM. At baseline, patients who smoked > or =1 pack per day of cigarettes who presented with at least five sites with probing depths (PD) of > or =5 mm with bleeding on probing (BOP) were randomized into the test or control groups. At baseline and 3 and 6 months, clinical measurements (probing depth [PD], clinical attachment loss [CAL], and bleeding on probing [BOP]) were performed. GCF bone marker assessment (Ctelopeptide [ICTP] as well as BANA test analyses) were performed at baseline, 14 days, and 3 and 6 months. RESULTS: The results demonstrated that both groups displayed clinical improvements in PD and CAL that were sustained for 6 months. Using a subject-based analysis, patients treated with SRP + AZM showed enhanced reductions in PD and gains in CAL at moderate (4 to 6 mm) and deep sites (>6 mm) (P <0.05). Furthermore, SRP + AZM resulted in greater reductions in BANA levels compared to SRP alone (P <0.05) while rebounds in BANA levels were noted in control group at the 6-month evaluation. No statistically significant differences between groups on mean BOP and ICTP levels during the course of the study were noted. CONCLUSIONS: The utilization of AZM in combination with SRP improves the efficacy of non-surgical periodontal therapy in reducing probing depth and improving attachment levels in smokers with moderate to advanced attachment loss.

Adult↗
PubMed2005

Effects of vitamin-B complex supplementation on periodontal wound healing.

BACKGROUND: Reports have demonstrated that nutrient supplements, in particular vitamin-B complex (Vit-B), can positively influence wound healing processes. However, limited information is available on the effects of Vit-B on periodontal wound healing. METHODS: A total of 30 patients (13 males, 17 females) presenting with generalized moderate to severe chronic periodontitis were enrolled in this study. All subjects presented > or = two teeth in the same sextant with probing depth (PD) > or =5 mm and bleeding upon probing (BOP) in need of access flap surgery (AFS). This study was a randomized, double-masked, placebo-controlled clinical trial. Subjects were instructed to take one capsule a day of either Vit-B (50 mg of the following: thiamine HCl, riboflavin, niacinamide, d-calcium pantothenate, and pyridoxine HCl; 50 microg each of d-biotin and cyanocobalamin; and 400 mcg of folate) or placebo for 30 days following AFS. Clinical attachment levels (CAL) and N-benzoyl-dl-arginine-2-naphthylamide (BANA) test scores were measured at baseline and at 90 and 180 days following surgical intervention. Assessments of the healing response were also performed using BOP, gingival index (GI), and plaque index (Pl) at baseline and 7, 14, 30, 90, and 180 days. The mean results of each parameter were averaged within a group. Differences between groups were analyzed by using repeated measures analysis of variance (ANOVA). RESULTS: Both groups experienced comparable levels of PD reduction following AFS (test: -1.57 +/- 0.34; control: -1.50 +/- 0.21). Changes in mean CAL were more favorable in Vit-B supplemented subjects (test: +0.41 +/- 0.12; control: -0.52 +/- 0.23; P = 0.024). Stratified data demonstrated significantly better results for the test group in both shallow (test: -0.08 +/- 0.03; control: -1.11 +/- 0.27; P = 0.032) and deep sites (test: +1.69 +/- 0.31; control: +0.74 +/- 0.23; P = 0.037). No significant differences were observed between groups regarding PI, GI, and BOP. BANA test values were significantly reduced in both groups after surgical treatment and no significant differences were noted between groups. CONCLUSION: Vitamin B-complex supplement in combination with AFS resulted in statistically significant superior CAL gains when compared to placebo.

Adult↗
PubMed2005

Periodontal regeneration.

Untreated periodontal disease leads to tooth loss through destruction of the attachment apparatus and tooth-supporting structures. The goals of periodontal therapy include not only the arrest of periodontal disease progression,but also the regeneration of structures lost to disease where appropriate. Conventional surgical approaches (e.g., flap debridement) continue to offer time-tested and reliable methods to access root surfaces,reduce periodontal pockets, and attain improved periodontal form/architecture. However, these techniques offer only limited potential towards recovering tissues destroyed during earlier disease phases. Recently, surgical procedures aimed at greater and more predictable regeneration of periodontal tissues and functional attachment close to their original level have been developed, analyzed, and employed in clinical practice. This paper provides a review of the current understanding of the mechanisms, cells, and factors required for regeneration of the periodontium and of procedures used to restore periodontal tissues around natural teeth. Targeted audiences for this paper are periodontists and/or researchers with an interest in improving the predictability of regenerative procedures. This paper replaces the version published in 1993.

Absorbable Implants↗
PubMed2005

Histomorphometric comparison of three bioabsorbable GTR barrier membranes in the canine model.

Guided tissue regeneration (GTR) using bioabsorbable barrier membranes has shown promising and somewhat predictable clinical results. However, limited information is available on the stages of histologic healing when these types of barriers are used. Therefore, the aim of this study was to compare three currently available bioabsorbable GTR barriers (type 1 collagen, polylactide/polyglycolide copolymer, and citric acid copolymer) for the treatment of surgically created periodontal dehiscences in dogs. Eight three-walled periodontal dehiscences were surgically created in the mandibles of six beagle dogs (four on each side of the jaw). The periodontal dehiscences were randomly assigned to receive one of the three barriers. One defect was left untreated to serve as a control. Histomorphometric analyses were conducted at 4 and 12 weeks. Data were analyzed using the Student-Fisher test. The membrane-treated group had a statistically significant increase in new bone formation and connective tissue attachment compared to the nontreated control sites. However, no statistical difference was noted among the various membranes. In addition, no difference was found between test and control sites when new cementum was examined. Sites treated with barrier membranes achieved greater bone regeneration than nontreated control sites in the canine model.

Absorbable Implants↗
PubMed2004

The zinc finger mutation C417R of I-kappa B kinase gamma impairs lipopolysaccharide- and TNF-mediated NF-kappa B activation through inhibiting phosphorylation of the I-kappa B kinase beta activation loop.

The activation of the I-kappaB kinase (IKK) complex by TNF or LPS stimulates phosphorylation and degradation of I-kappaBalpha, leading to the nuclear translocation of NF-kappaB. The IKK complex is mainly composed of two catalytic subunits, IKKalpha and IKKbeta, and a chaperon subunit IKKgamma. Although IKKgamma does not have catalytic activity, it is essential for IKK activation induced by multiple stimuli. Importantly, the key residue cysteine 417 at the zinc finger domain of IKKgamma has been found to be mutated to arginine (IKKgammaC417R) in a human genetic disorder called the anhydrotic ectodermal dysplasia with immunodeficiency. To understand the underlying mechanisms of immunodeficiency, we examined whether the IKKgammaC417R mutant modified IKK activation and NF-kappaB transcription stimulated by LPS or TNF in human monocytes. We found that overexpression of IKKgammaC417R severely impaired LPS- and TNF-induced I-kappaBalpha phosphorylation and degradation in a dominant-negative fashion. Also, LPS- and TNF-induced NF-kappaB transcription was inhibited by IKKgammaC417R. The reconstitution of IKKgamma, but not IKKgammaC417R, in IKKgamma-deficient cells restored NF-kappaB signaling, indicating the zinc finger structure of IKKgamma plays a key role in IKK activation. Moreover, C417R mutation in IKKgamma abolished both LPS- and TNF-induced phosphorylation of the activation loop of IKKbeta. Collectively, our results indicated that the zinc finger structure of IKKgamma plays a key role in LPS- and TNF-induced NF-kappaB activation. The anhydrotic ectodermal dysplasia with immunodeficiency patients' immunodeficiency may be associated with NF-kappaB defect in response to bacterial stimulation.

Active Transport, Cell Nucleus↗
PubMed2004

Creation of interimplant papillae through a split-finger technique.

PURPOSE: The purpose of this pilot study is to propose a technique, the split-finger approach, to preserve/promote papillae formation. MATERIALS AND METHODS: Twenty-one patients with 39 implants consecutively placed in the maxillary anterior region were evaluated at 6 months to 1 year after prosthodontic restoration. The implants evaluated included 16 single-tooth implants, 1 2-unit implant prosthesis, 2 4-unit tooth implants, 1 6-unit prostheses, and 1 7-unit restoration. The papillae were recorded as 0 = no papillae; 1 = < or =50% of the gingival embrasure height; 2 = >50% but <100% of embrasure height; 3 = 100% closure of the proximal space; and 4 = overgrowth of the interproximal tissue. RESULTS: Data from this pilot study showed no class 0, class 1, or class 4 interproximal papillae after the final restoration. The 16 single-tooth restorations and 32 papillae had an average mesial papilla score of 3 and an average of 2.82 for the distal interproximal space. The average papilla score of the other implant papillae sites were 2.7 at 6 months to 1 year. A lower papilla score was noted in interimplant papillae. CONCLUSIONS: The proposed split-finger technique could serve as a clinically useful alternate procedure to promote/augment papillae formation around dental implants.

Dental Implants↗
PubMed2004

Rationale for the application of immediate load in implant dentistry: Part I.

Immediate loading in implant dentistry is increasing in popularity as a clinical procedure. A scientific rationale of immediate occlusal loading of the implant support system should emphasize methods to decrease surgical trauma during implant placement and to decrease bone loading trauma during the early loading period. The surgical trauma may be reduced by decreasing heat generation and pressure necrosis. The early loading trauma may be decreased by decreasing the bone strain adjacent to the implant interface. Greater microstrain conditions in bone increase the remodeling rate of bone. The higher the remodeling rate, the weaker the bone and the more risk of occlusal overload. Occlusal overload may lead to implant failure. Since strain is directly related to stress, methods to decrease stress are beneficial. In the present report, the stress-reducing influences include increasing the number of implants.

Dental Implantation, Endosseous↗
PubMed2004

Rationale for the application of immediate load in implant dentistry: part II.

Immediate loading of an implant interface has been used for completely and partially edentulous patients. A biomechanical rationale to decrease the initial risk of overload is reasonable, because implant failure and overload has been well established. This article addresses methods to decrease stress to the transitional restoration. Forces may be influenced by patient factors, implant position, cantilever forces, occlusal load direction, occlusal contact intensity, and diet. The surface area of load distribution may be increased by implant size, implant design, and surface condition of the implant body. A blend of these factors affects the amount of stress to the developing implant interface and hence may affect the risk of immediate occlusal loading for implant prostheses.

Alveolar Process↗
PubMed2004

Socket augmentation: rationale and technique.

The consequences of exodontia include alveolar bone resorption and ultimately atrophy to basal bone of the edentulous site/ridges. Ridge resorption proceeds quickly after tooth extraction and significantly reduces the possibility of placing implants without grafting procedures. The aims of this article are to describe the rationale behind alveolar ridge augmentation procedures aimed at preserving or minimizing the edentulous ridge volume loss. Because the goal of these approaches is to preserve bone, exodontia should be performed to preserve as much of the alveolar process as possible. After severance of the supra- and subcrestal fibrous attachment using scalpels and periotomes, elevation of the tooth frequently allows extraction with minimal socket wall damage. Extraction sockets should not be acutely infected and be completely free of any soft tissue fragments before any grafting or augmentation is attempted. Socket bleeding that mixes with the grafting material seems essential for success of this procedure. Various types of bone grafting materials have been suggested for this purpose, and some have shown promising results. Coverage of the grafted extraction site with wound dressing materials, coronal flap advancement, or even barrier membranes may enhance wound stability and an undisturbed healing process. Future controlled clinical trials are necessary to determine the ideal regimen for socket augmentation.

Alveolar Bone Loss↗
PubMed2004

Management and prevention of retrograde peri-implant infection from retained root tips: two case reports.

Fracture of root tips in the maxillary premolar region is not an uncommon finding because of the high incidence of bifid and root dilacerations. Therefore, a retained root tip may serve as a nidus of infection when a dental implant is placed. The likely result is the development of an implant periapical lesion. This case report shows the successful management of a rapidly developing implant periapical lesion caused by an undetected retained root tip. Initially, systemic antibiotics failed to subdue the infection. A retained root fragment was retrieved surgically, together with the implant, and a new wide-body implant was engaged with DFDBA mixed with tetracycline. A 5-month follow-up showed increased radiographic density, and clinical reentry revealed the formation of bone with a hard consistency. The second case demonstrates the management of a retained root tip via a guided bone regeneration technique when it is detected prior to or during implant placement. Finally, a systematic therapeutic approach is proposed based on 17 case reports on implant periapical lesion management.

Aged↗
PubMed2004

Implant plastic surgery: a review and rationale.

Implant dentistry has been established as a predictable treatment modality with high clinical success rates. Esthetic considerations of implant restorations have been gaining increased interest over the years. The role of periodontal plastic surgical procedures in the creation and maintenance of peri-implant soft tissue heights to facilitate better esthetics has become more popular. The available plastic surgery procedures and their clinical applications are reviewed in this article. Emphasis is placed on factors to consider for proper case selection and ideal treatment planning.

Alveoloplasty↗
PubMed2004

Effect of enamel matrix derivative on collagen guided tissue regeneration-based root coverage procedure.

BACKGROUND: Enamel matrix derivative (EMD) has been shown to promote periodontal wound healing and/or regeneration when applied to tooth root surfaces in soft tissue dehiscence models. In addition, guided tissue regeneration (GTR)-based root coverage using collagen membrane (GTRC) has shown promising results. However, limited information is available regarding how EMD may influence GTRC outcome. METHODS: Twenty-six patients with Miller's Class I or II gingival recession defects of 2.5 mm were recruited for the study. Subjects were randomly assigned to receive either EMD + collagen (EMDC; test group) or collagen membrane (GTRC; control group). Clinical parameters, including plaque index (PI), gingival index (GI), relative clinical attachment levels (RCAL) to the stent, recession depth (RD), recession width (RW), probing depth (PD), gingival tissue thickness (GTT), and width of keratinized gingiva (KG) were assessed at baseline, and 3 and 6 months after surgery. A repeated measure of analysis of variance (ANOVA) was used to determine differences between treatment groups and time effect. RESULTS: Both treatments (GTRC and EMDC) resulted in a statistically significant decrease in RD and RW between baseline and 6 months (P <0.05). However, no difference was noted between treatment groups. The percent of root coverage after 6 months was 75% for GTRC and 63% for EMDC. Complete 100% root coverage was achieved in five patients in the GTRC group, compared to only one patient in the EMDC group. There was a statistically significant gain (P <0.05) in the clinical attachment level (CAL) between baseline and 6 months in both groups, as reflected on the RCAL data. No other significant differences were noted on other clinical parameters (PD, GTT, KG, GI, and PI). CONCLUSIONS: GTR-based root coverage utilizing collagen membrane, with or without enamel matrix derivative, can be successfully used in obtaining gingival recession coverage. The application of EMD during GTRC procedures did not add additional benefit to the final clinical outcome.

Absorbable Implants↗
PubMed2004

Treatment of gingival recession using a collagen membrane with or without the use of demineralized freeze-dried bone allograft for space maintenance.

BACKGROUND: Studies utilizing collagen membranes for guided tissue regeneration (GTR)-based root coverage procedures have reported promising results. However, creating and maintaining space underneath the membrane remains a challenge. Therefore, the purpose of this clinical trial was to determine whether the addition of bone graft (i.e., demineralized freeze-dried bone allograft [DFDBA]) significantly affects the outcome of collagen membrane GTR-based root coverage procedures. METHODS: Twenty patients participated. One Miller's Class I or II recession defect per patient was treated with a collagen membrane covered by a coronally positioned flap. Half of the patients also had DFDBA placed under the membrane. Clinical parameters recorded included: recession depth, recession width, width of keratinized tissue, clinical attachment level, and probing depth, measured to the nearest 0.5 mm. Presurgery and postsurgery (6-month) data were compared using Student's paired t test for parametric data and the Wilcoxon matched pairs test for non-parametric data. RESULTS: Guided tissue regeneration with collagen (COLL) and collagen + DFDBA (COBA) both resulted in statistically significant (P <0.05) reductions in recession depth (2.1 +/- 0.9 mm and 2.5 +/- 0.5 mm), recession width (1.5 +/- 1.7 mm and 2.2 +/- 1.6 mm), increase in keratinized tissue (0.7 +/- 0.8 mm and 1.2 +/- 1.0 mm), and gain of clinical attachment level (2.1 +/- 1.0 mm and 3.0 +/- 1.0 mm), when comparing 6-month data to baseline. Mean root coverage was 68.4 +/- 15.2% with COLL and 74.3 +/- 11.7% with COBA. However, there were no statistically significant differences between groups for recession depth, recession width, width of keratinized tissue, clinical attachment level, and probing depth. CONCLUSIONS: Both techniques are effective in attaining root coverage. Although root coverage tended to be better with the addition of DFDBA, the difference was not statistically significant. Further studies with a larger sample size are needed to determine whether adding DFDBA to GTR-based procedures using collagen membranes is of any benefit.

Adult↗
PubMed2004

Morphometric analysis of implant-related anatomy in Caucasian skulls.

BACKGROUND: Sequelae related to implant placement/advanced bone grafting procedures are a result of injury to surrounding anatomic structures. Damage may not necessarily lead to implant failure; however, it is the most common cause of legal action against the practitioner. This study aimed to describe morphological aspects and variations of the anatomy directly related to implant treatment. METHODS: Morphometric analyses were performed in 22 Caucasian skulls. Measurements of the mental foramen (MF) included height (MF-H), width (MF-W), and location in relation to other known anatomical landmarks. Presence or absence of anterior loops (AL) of the inferior alveolar nerve (IAN) was determined, and the mesial extent of the loop was measured. Additional measurements included height (G-H), width (G-W), thickness (G-T), and volume (G-V) of monocortical onlay grafts harvested from the mandibular symphysis area, and thickness of the lateral wall (T-LW) of the maxillary sinus. The independent samples t test, and a two-tailed t test with equal variance were utilized to determine statistical significance to a level of P < 0.05. Multiple regression analyses were performed to determine if each one of these measurements was affected by age and gender. RESULTS: The most common location of the MF in relation to teeth was found to be below the apices of mandibular premolars. The mean MF-H was 3.47 +/- 0.71 mm and the mean MF-W was 3.59 +/- 0.8 mm. The mean distance from the MF to other anatomical landmarks were: MF-CEJ = 15.52 +/- 2.37 mm, MF to the most apical portion of the lower cortex of the mandible = 12.0 +/- 1.67 mm, MF to the midline = 27.61+/- 2.29 mm, and MF-MF = 55.23 +/- 5.34 mm. A high prevalence of AL was found (88%); symmetric occurrence was a common finding (76.2%), with a mean length of 4.13 +/- 2.04 mm. The mean size of symphyseal grafts was: G-H = 9.45 +/- 1.08 mm, G-W = 14.5 +/- 3.0 mm, and G-T = 6.15 +/- 1.04 mm, with an average G-V of 857.55 +/- 283.97 mm3 (range: 352 to 1,200 mm3). The mean T-LW of the maxillary sinus was 0.91 +/- 0.43 mm. CONCLUSION: Implant-related anatomy must be carefully evaluated before treatment due to considerable variations among individuals, in order to prevent injury to surrounding anatomical structures and possible damage.

Aged↗
PubMed2004

Effects of implant thread geometry on percentage of osseointegration and resistance to reverse torque in the tibia of rabbits.

BACKGROUND: Dental implant thread geometry has been proposed as a potential factor affecting implant stability and the percentage of osseointegration. Therefore, the aim of this prospective, randomized, parallel arm study was to evaluate the effects of dental implant thread design on the quality and percent of osseointegration and resistance to reverse torque in the tibia of rabbits. METHODS: Seventy-two custom-made, screw-shaped, commercially pure titanium implants (3.25 mm diameter x 7 mm length) were placed in the tibiae of 12 white New Zealand rabbits. Each tibia received three implants of varying thread shapes: one with a V-shaped, one with a reverse buttress, and one with a square thread design. The rabbits were sacrificed following an uneventful healing period of 12 weeks. Implants in the right tibiae underwent histologic and histomorphometric assessments of the bone-to-implant contact (BIC) and the radiographic density of surrounding bone, while implants in the left tibiae were used for reverse-torque testing. Differences between the three thread designs were examined using analysis of variance (ANOVA). RESULTS: Data showed that the square thread design implants had significantly more BIC and greater reverse-torque measurements compared to the V-shaped and reverse buttress thread designs, while no differences were found in radiographic bone density assessments. CONCLUSION: These results indicate that the square thread design may be more effective for use in endosseous dental implant systems.

Analysis of Variance↗
PubMed2004

"Sandwich" bone augmentation technique: rationale and report of pilot cases.

The aim of this article is to present a new technique for augmentation of deficient alveolar ridges and/or correction of osseous defects around dental implants. Current knowledge regarding bone augmentation for treatment of osseous defects prior to and in combination with dental implant placement is critically appraised. The "sandwich" bone augmentation technique is demonstrated step by step. Five pilot cases with implant dehiscence defects averaging 10.5 mm were treated with the technique. At 6 months, the sites were uncovered, and complete defect fill was noted in all cases. Results from this pilot case study indicated that the sandwich bone augmentation technique appears to enhance the outcomes of bone augmentation by using the positive properties of each applied material (autograft, DFDBA, hydroxyapatite, and collagen membrane). Future clinical trials for comparison of this approach with other bone augmentation techniques and histologic evaluation of the outcomes are needed to validate these findings.

Adult↗