Faculty Publications (HBMCDM)

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Computer aided finite element model for biomechanical analysis of orthodontic aligners
(2022-08) Ghoneima, Ahmed; Abuzayda, Moosa
Objectives: To design a finite element (FE) model that might facilitate understanding of the complex mechanical behaviour of orthodontic aligners. The designed model was validated by comparing the generated forces — during 0.2-mm facio-lingual translation of upper left central incisor (Tooth 21) — with the values reported by experimental studies in literature. Materials and methods: A 3D digital model, obtained from scanning of a typodont of upper jaw, was imported into 3-matic software for designing of aligners with different thicknesses: 0.4, 0.5, 0.6, 0.7 mm. The model was exported to Marc/Mentat FE software. Suitable parameters for FE simulation were selected after a series of sensitivity analyses. Different element classes of the model and different rigidity values of the aligner were also investigated. Results: The resultant maximum forces generated on facio-lingual translation of Tooth 21 were within the range of 1.3–18.3 N. The force was direction-dependent, where lingual translation transmitted higher forces than facial translation. The force increases with increasing the thickness of the aligner, but not linearly. We found that the generated forces were almost directly proportional to the rigidity of the aligner. The contact normal stress map showed an uneven but almost repeatable distribution of stresses all over the facial surface and concentration of stresses at specific points. Conclusions A validated FE model could reveal a lot about mechanical behavior of orthodontic aligners. Clinical relevance: Understanding the force systems of clear aligner by means of FE will facilitate better treatment planning and getting optimal outcomes.
Considerations Regarding Dental Implant Site Preparation using Osseo densification Osteotomy. A Critical Review
(2020) Abuzayda, Moosa
Abstract: Conventional osteotomies for implant placement are typically prepared with implant drills originally designed for non-dental procedures. Such drill designs have proven efficacy for implant placement, resulting in good implant success rates over many years. Conventional drill designs used in oral implantology remove bone to create space for implant insertion. While these osteotomy drills effectively remove bone, they may not always create circumferential osteotomy sites. Therefore, implant insertion torques may be lower than ideal, possibly compromising primary implant stability (PIS). This in turn may adversely affect implant osseointegration (OI). Osteotomies performed in areas with narrow bone anatomy may also cause a dehiscence, which potentially further reduces PIS. Furthermore, additional bone grafting procedures may be required thereby prolonging healing time before implant restorations can be completed. More recently, a novel biomechanical bone preparation technique called “osseodensification” (OD) has been proposed. Unlike traditional dental implant drilling procedures, osseodensification does not remove bone tissue. Conversely, bone tissue is retained and compacted in outwardly expanding directions within the osteotomy preparation site. This is similar to the effect of a traditional hammer osteotome but with less adverse effects. When the OD bur is rotated at high speed in a counterclockwise direction, a dense bone tissue layer is created along the walls and base of the osteotomy site. The formation of this dense compacted bone layer may contribute towards faster OI by enhancing PIS. This review discusses the potential advantages of OD and critically evaluates the currently available literature investigating this interesting implant bed preparation technique.
Convergence angles of all-ceramic full crown preparations performed in Dubai private practice
(2018-12-01) Abdulla, Fahad; Hassan Khamis, Amar; Milosevic, Alexander; Abuzayda, Moosa
Background: This study aimed to determine the degree of taper and total occlusal convergence angles (TOC) for all-ceramic bonded crown preparations carried out by private practitioners in Dubai, UAE. Material and Methods: A convenience sample of all-ceramic crown preparations carried out by private dental practitioners were scanned (Carestream CS 3500) from casts and the digital images assessed. The degree of taper was measured on the axial walls of each crown preparation and the bucco-lingual and mesio-distal convergence angles subsequently calculated. Results: A total of 154 dentists prepared a total of 206 crown preparations (72 anterior, 134 posterior). The mean convergence angles mesio-distally for all preparations was 24.6° (sd 11.8º), and for the bucco-lingual it was 32.6° (sd 15.3°). The mean TOC was 28.6°. In anterior preparations, the mean bucco-lingual convergence angle was 38.8° (sd 12.2°) compared to 29.3° (sd 15.5°) for posterior preparations (p<0.001). Mean mesio-distal convergence anteriorly was 20.6° (sd 10.18°) compared to 26.7° (sd 12.16°) posteriorly (p<0.001). Distal and buccal taper were significantly greater on posterior teeth (<0.001) compared to anteriors whereas lingual taper was greater on anterior teeth (p<0.001). Mesial taper was not different. Premolars had significantly lower convergence values compared to other teeth. Conclusions: Bucco-lingual and mesio-distal convergence angles significantly exceeded the clinically acceptable convergence angle of between 10° and 22°. Greater axial taper is recommended for resin bonded all-ceramic crowns but reliance on adhesion in such preparations rather than parallelism may reduce retention and have increased biologic cost to pulp health.
Development and Comparison of Conventional and 3D-Printed Laboratory Models of Maxillary Defects
(2023) Alanezi, Ahmad; Aljanahi, May; Moharamzadeh, Keyvan; Ghoneima, Ahmed; Tawfik, Abdel Rahman; Hassan Khamis, Amar; Abuzayda, Moosa
Background: Recording accurate impressions from maxillary defects is a critical and challenging stage in the prosthetic rehabilitation of patients following maxillectomy surgery. The aim of this study was to develop and optimize conventional and 3D-printed laboratory models of maxillary defects and to compare conventional and digital impression techniques using these models. Methods: Six different types of maxillary defect models were fabricated. A central palatal defect model was used to compare conventional silicon impressions with digital intra-oral scanning in terms of dimensional accuracy and total time taken to record the defect and produce a laboratory analogue. Results: Digital workflow produced different results than the conventional technique in terms of defect size measurements which were statistically significant (p < 0.05). The time taken to record the arch and the defect using an intra-oral scanner was significantly less compared with the traditional impression method. However, there was no statistically significant difference between the two techniques in terms of the total time taken to fabricate a maxillary central defect model (p > 0.05). Conclusions: The laboratory models of different maxillary defects developed in this study have the potential to be used to compare conventional and digital workflow in prosthetic treatment procedures.
Evaluation of Calcified Carotid Artery Atheromas Detected By Panoramic Radiograph among Patients with Type II Diabetes Mellitus
(2015) Jaber, Mohamed A; Shah, Maanas S.; Abuzayda, Moosa
Abstract: This study was designed to determine the prevalence of Carotid artery calcifications (CACs) of diabetic patients and compare it with normal non-diabetic individuals. Panoramic radiographs of 200 adult patients with type 2 diabetes (90 male and 110 females) (age range 16-79 years; mean age 40.54 years) and 200 controls (age-match, free of systemic diseases) were examined on panoramic radiographs for any unusual radiopacity adjacent to or just below the intervertebral space between C3 and C4. Statistical analysis was carried out using chi-squared and Fisher exact tests. Carotid artery calcifications (CACs) were higher in diabetic patients compared with normal healthy control and the statistical difference between the two groups was significant (Chi-square test = 10.82, P = 0.001). Twenty-five (16 females, 9 males) diabetic patients showed CACs, Mean age of diabetic patients with calcification was 47.11 years. Further analysis of this group showed that 60% of patients with CACs were smokers, 48% had hypertension and 25% were obese. In conclusion, our study shows that in patients with diabetes mellitus CACs can be detected by panoramic radiography and the patients may benefit from a referral to physicians for further evaluation and necessary management.
The Evaluation of Smile Design by Lay People and Dentists in the UAE
(2020) AlShamsi, Asmaa; Abuzayda, Moosa
Background and Objectives: Esthetics is characterized primarily by the smile, however, the smile comprises much more than the dental arch. Dental smile design preferences differ from one person to other based on different factors such as: social level, economic level, education level and ethnic origin. There is a lack of similar studies in the UAE. The purpose of this study is to determine which features of a smile are attractive as rated by lay people and dental professionals in the UAE. Material and Methods: A questionnaire survey of standardized images of smiles was distributed to 190 dental professionals including under-graduate students at Sharjah University and 190 lay people (teachers, employers, workers and patients relatives). A sample size calculation determined the sample as 380. The participants were not randomly selected and were not a representative sample of the UAE population but a convenience sample. The participants were all adults above the age of 17 years. The questionnaire had 7 separate aesthetic features with between 3 to 6 different standardized computer generated images for each feature. The different features included amount of tooth exposed, lip line height, buccal corridor and midline position. Results: There were a total of 380 participants with a mean age of 28.6 years (SD 7.9) of which 228 (60%) were female. Significantly more females compared to males preferred a convex smile irrespective of whether or not the upper teeth contacted the lower lip (p<0.01). Females tended to prefer low lip line compared to males but this was at the borderline of significance (p=0.067). Interestingly, more married respondents preferred the low lip line whereas unmarried respondents were evenly distributed between those liking an average and low lip line (p<0.05). The coincidence of dental and facial midlines would be expected as the preferred choice for both dental professionals and lay people but significantly more lay people preferred the smile that deviated to the right whereas dentists preferred midlines to be coincident (p<0.001). Furthermore, residents of Abu Dhabi, Dubai and Sharjah preferred the coincidence of midlines whereas the lay people from Fujairah preferred the right deviation of the dental midline. Over half the unmarried respondents had a significantly greater preference for midline coincidence but married respondents were more evenly split regarding this aspect of smile design (p<0.05). There were no preference differences for most of the smile design features as judged by dentists and lay people. Conclusion: There is general agreement between dentists and lay people regarding the most pleasing features of smile design. Females prefer a convex incisal curve that follows lip curvature and tend to prefer a low lip line. Coincidence of facial and dental midlines was expected to be preferred by both dentists and lay people but surprisingly this was not the case as lay people, married respondents and residents from Fujairah prefer a right deviation. Why should this preference for a smile with a deviated dental midline be regarded as attractive requires further research but may be influenced by tribal or other cultural factors.
Rehabilitation of an Extremely Edentulous Atrophic Maxilla with a Pseudoskeletal Class III Relationship
(2019) Yoon, Tae Ho; Abuzayda, Moosa
Summary: The skeletal class III relationship presents complex dentoalveolar problems, requiring multidisciplinary treatment. In edentulous people, severe atrophy of the jawbone simulates the clinical appearance of a skeletal class III relationship (pseudoskeletal class III), which presents major problems for rehabilitation. This article describes the rehabilitation of a 67-year-old patient with a pseudoskeletal class III relationship. The mandible was restored with two implant supported bar-retained overdentures using clips for retention. The extremely atrophic maxilla was restored with a combination of sinus augmentation, implant placement, and classic prosthodontic treatment using an electroformed mesostructured overdenture with swivel lock attachments on an implant-supported bar. By performing minimal augmentative and implant surgeries and using the possibilities and advantages of classic prosthetic dentistry, the clinical situation described here could be managed and the atrophic maxilla could be rehabilitated.
Survey of Dental Implant and Restoration Selection by Prosthodontists in Dubai
(2021) Abuzayda, Moosa; Milosevic, Alexander
Background: With various surgical and prosthetic component designs being introduced in dental implants, decisions have to be made when choosing a system and a certain prosthodontic protocol. A survey of implant prosthodontic specialists has not been previously performed in the Middle East. Aim. (is study aimed to determine selection criteria and choice of dental implants and restorations by prosthodontic specialists in the Emirate of Dubai, United Arab Emirates. Materials and Methods: A validated 16- item questionnaire was used in the survey which included demographic information, implant training and experience, implant treatment planning, implant restoration, and implant system preference. (e research protocol was approved by the Research and Ethics Committees of Hamdan Bin Mohammed College of Dental Medicine and Dubai Health Authority. Prosthodontists were identified from regulatory authority websites and contacted by e-mail with the questionnaire attached. Results: A total of 84.6% (77) of the registered prosthodontists in Dubai completed the questionnaire with 66.2% reported practicing implant dentistry. Out of which, 54.9% reported surgically placing dental implants and 45.1% restore them only prosthetically. Prefabricated metal abutments were the most commonly selected abutments for single crowns (76.0%) and for fixed dental prostheses (66.7%). Screw retention is preferred mostly for single crowns (68.0%) and fixed dental prostheses (74.0%). Locators were the most commonly selected type of attachment for implant-retained/supported overdentures (49.0%). Conventional loading was the most selected type of loading in all oral conditions. Conclusion: Within the limitations of this study, it can be concluded that most prosthodontists in Dubai practice implant dentistry and more than half surgically place dental implants. Prefabricated metal abutments are the most selected type of abutments. Most prosthodontists use screw-retained implant restorations and prefer locator attachments for implant-retained/supported overdentures. Conventional loading is the most preferred implant loading method in all oral conditions. Implant company/system selections are various and there is no major preference for a certain system. (e majority of prosthodontists select implant systems based on implant features, literature review, and simplicity of restorative kit.
The use of a customized mounting guide for Implant-Prosthetic Restoration of the Fully Edentulous Arch
(2017) Sotiropoulos, Evangelos; Yoon, Tae Ho; Abuzayda, Moosa
Abstract: Reconstruction of fully edentulous arches with implant-retained dentures requires thorough planning and precise registration of the interocclusal relationship, to achieve a successful treatment outcome. This technical report describes three representative approaches from a cohort of 89 fully edentulous arches in 69 patients who were treated with the described mounting guide technique. A technique of using a duplicated denture as a guide is described, which allows for the accurate transfer of the occlusal relationship and vertical dimensions, while facilitating the full-arch restoration process with implantretained fi xed or removable dentures and reducing the number of required in-office sessions.

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