Christopher Wyatt

Purpose: The study examined the accuracy of intraoral scanning of partially edentulous dental models. Materials and Methods: A mandibular dentoform with 16 individual acrylic teeth was used to remove specific dental units to create the four models of partially edentulous Kennedy classes. In all four situations, premolars (#34 & #44) were left to be used as reference points for accuracy assessments. The removed teeth sockets were filled with red wax, and each Kennedy class model was scanned ten times using a Trios 4 intraoral scanner (3Shape, Copenhagen, Denmark). These scans were compared to a reference digital scan of the fully dentate typodont model using an E4 laboratory benchtop scanner (3Shape, Copenhagen, Denmark). Comparisons were made using the CloudCompare alignment software. The best-fit alignment method was used to compare premolars #34 and #44 in all four Kennedy groups. Also, comparisons were made with the benchtop scan of the corresponding benchtop Kennedy scan at both premolars #34 and #44 and the edentulous ridges. The deviations from the benchtop scan were calculated as the root mean square (RMS) in mms, and the acceptable fit was ≤ 0.2 mm.Results: Intraoral scans of occlusal tables of #34 and #44 of all four partially edentulous Kennedy groups showed no statistically significant differences to the fully dentate benchtop scan and all had an acceptable fit. When compared to the corresponding benchtop scan, premolars #34 and #44 showed statistically significant differences between Kennedy Class II (0.061 ± 0.011 mm) and Class I (0.049 ± 0.008 mm) and between Class IV (0.05 ± 0.009 mm) and Class II. For the edentulous ridges, there was a statistically significant differences between Class I (0.072 ± 0.028 mm) and all other Kennedy Classes. Class I demonstrated the lowest accuracy and the accuracy values all measured within the acceptable threshold of 0.2 mm in both premolars and edentulous scans.Conclusions: Trios 4 intraoral scanner provided acceptable record of the remaining teeth and edentulous areas for all partially edentulous Kennedy groups.

View record

Objectives: The oral health needs of people who are frail are increasing with an aging population in Canada. The objective of this study was to explore the perceptions of dentists in British Columbia regarding their view of geriatric dentistry as a distinct scope of practice and in relation to special needs dentistry, a specialty for people with disabilities and medical conditions that require adaptations to access routine dental care. Methods: The research method that guided this study was interpretive description, which utilized a naturalistic inquiry amongst a purposeful sample and employed inductive analysis of semi-guided interviews to explore whether participants who were key informants in the dental profession perceived geriatric dentistry as a distinct scope of practice in dentistry within B.C. Qualitative data was coded and analyzed using a thematic approach. Results: A total of ten interviews were conducted. The participants perceived a geriatric patient as a person aging with frailty who is dependent on others to access oral health care. Participants expressed that general dentists in private practice had a preference to refer patients aging with frailty to a specialist or special service when treatment was outside their comfort level or when there were behavioural or other patient management challenges that were difficult to manage in the private practice setting. Participants perceived the ability to provide person-centered care through interprofessional collaboration was a core competency of geriatric dentistry which overlapped with special needs dentistry.Conclusion: The study found that participants perceived geriatric dentistry in B.C. as a distinct field from general dentistry that requires specialized knowledge and broader skill sets to address the patient management challenges associated with aging with frailty. Similar to special needs dentistry, geriatric dentistry requires person-centered care and emphasized the need for interprofessional collaboration in alternative care settings.

View record

Objectives: Frail older adults who reside in long-term care (LTC) facilities are among the most vulnerable to dental caries due to poor oral hygiene (OH), medication-related salivary hypofunction, diets high in carbohydrates, and limited access to dental care. Providing dental restorations for LTC patients is challenging and there is a lack of studies investigating the longevity of dental restorations in this cohort. Over the years, multiple dental restorative materials have been used to restore tooth anatomy in an aesthetic manner as well as to address dental caries prevention using fluoride-based materials. This study examined the longevity of direct bonded dental restorations placed in LTC patients. Specifically, we aimed to determine if there is a difference in survival between resin composite (RC) and glass ionomer cement (GIC) direct restorations in frail older adults residing in LTC. Methods: Tooth-coloured restorations placed in LTC patients between 2007-2012, within the University of British Columbia Geriatric Dentistry Program, were followed annually up to five years or until they incurred an event (i.e. re-restoration or tooth extraction), or the patient was lost to follow-up or deceased. Restoration status was documented within the Clinical Oral Disorder in Elders (CODE) Index annual oral health assessments. Mixed-effect logistic regression was calculated to determine hazard ratios, address within-patient correlation and measure the effect size of multiple covariates. Results: A total of 3,201 dental restorations placed in 846 LTC patients were followed. This cohort of patients had a mean age of 86 years, high levels of oral disease, systemic disease and polypharmacy, and had on average 2.5 carious teeth at presentation. Over 50% of patients were wheelchair-bound and had compromised ability to perform OH. The overall 5-year survival rate was 60.3% overall and there was no statistically significant difference in survival rates between RC and GIC restorations.Conclusion: Tooth-coloured dental restorations had reasonable longevity in LTC patients and had comparable survival to restorations placed in functionally independent, community-dwelling geriatric populations. No difference between RC and GIC was found with regards to restoration longevity in this population.

View record

Objectives: To study the effect of cementation on the marginal gap of lithium disilicate (LDS) crowns made with digital impression and manufacturing (DD), digital impression and traditional pressed manufacturing (DP) and traditional impression and manufacturing (TP).Methods: Ivorine typodont tooth #15 was prepared for an all-ceramic crown. The prepared tooth was scanned, and 45 dies were produced and used for fabricating 45 LDS crowns using three methods: DD, DP, and TP. Micro-CT was utilized to evaluate the 2D marginal gap before adjustment, after adjustment and after cementation. RelyX-Ultimate resin cement was used to cement the crowns on each of the 45 dies with 20 N application force using a universal material testing machine. The 2D vertical marginal gap (MG) evaluations were made at 20 designated positions along the crown margins. The results were analyzed using a linear mixed effect model with the interaction method x cementation as fixed effect, and crown as a random effect, as well as post hoc analysis (CI=95%).Results: Clinical adjustments of unacceptable crowns (4 from the TP and 2 from the DP) which showed at least 5 measurement points of MG of more than 120 μm resulted in reduction of the marginal gap to an acceptable level. Cementation resulted in an average increase in the marginal gap of 20 μm (95 % CI= 22-18), irrespective of the method of fabrication. All crowns had clinically acceptable crown margins, irrespective of the method of fabrication after cementation. Conclusion: Clinical adjustments to intaglio surface of crowns reduced MG, while cementation increased MG regardless of the method of fabrication. The DD group did not require any clinical adjustment prior to cementation. Only two crowns of the DP group and four crowns of the TP group required adjustment prior to cementation

View record

Purpose: The objectives of this study were to evaluate the clinical accuracy and reproducibilityof virtual inter-occlusal records of the CEREC intraoral scanning system. The presence orabsence of inter-occlusal contacts on multiple virtual occlusal records will be compared withconventional polyvinyl siloxane (PVS) inter-occlusal records.Materials and Methods: Three conventional inter-occlusal records followed by three virtualinter-occlusal records per side per participants were taken. Then three sites of close proximity(SCP) and three sites of clearance (SC) per side per participant were identified on the transilluminatedconventional PVS inter-occlusal records. A total of sixty SCP and SC were identifiedfor ten participants using the conventional PVS inter-occlusal records. The presence or absenceof these sites were analyzed using CloudCompare Software.Result: Sensitivity for the three-different virtual inter-occlusal records was between 82% and87%. Specificity was higher with values between 93% and 97%. Positive predictive values forthe three scans were 95%, 96%, and 93%, and the negative predictive values 84%, 86% and88%. Only 74% of the SCP were detected consistently with all three repeated scans and 92% ofthe SC were identified accurately with all the three scans.Conclusion: Accuracy of CEREC Omnicam intra-oral scanner is clinically acceptable, whilereproducibility is fair.

View record

Purpose: The aims of this study were to assess if virtual interocclusal records taken at different locations on the arch have an effect on the alignment of the virtual casts, and to assess whether quadrant scans and full arch scans have an effect on the alignment of the virtual casts when articulated using virtual interocclusal records. Materials and Methods: Three sites of close proximity (SCP) and three sites of clearance were identified in each sextant on mounted zirconia master models. SCP and SC were confirmed using shimstock foil and transillumination of an interocclusal impression. Full arch and quadrant scans of the master models were taken using an intra-oral scanner and different virtual interocclusal record were taken. SCP and SC on each virtual alignment produced by the intra-oral scanner were compared to each other, and to an independent software. Sensitivity, specificity, and predictive values were utilized for the comparison Results: A change in the location of the SCP was found depending on the location of the virtual interocclusal record. The intra-oral scanner software displayed contacts showed higher sensitivity and negative predictive value (92.86% and 84.21% respectively) when compared to the contacts displayed on the independent software (69.05% and 70.45% respectively). However, the intra-oral scanner software had lower specificity and PPV (41.03% and 62.90% respectively) compared to the independent software (79.49% and 78.38% respectively). Quadrant scans showed higher sensitivity when compared to full arch scans. Conclusion: There is a significant difference in occlusal contacts obtained from bite scans of different segments. This difference is more obvious in full arch scans, in which a “tilting effect” towards the site of the bite scan can be observed. Occlusal contacts obtained from bite scans taken for quadrant virtual arches exhibited higher sensitivity when compared to those obtained from bite scans taken for full virtual arches.

View record

Objectives: To describe the oral health-related lifestyle of Vancouver inner city elementary school-aged children and relate different aspects of their oral health-related lifestyle with demographic and socioeconomic factors. Methods: This cross-sectional study used a structured questionnaire with some open-ended items to survey 424 school-aged children in Vancouver inner city elementary schools (53.3% boys and 46.7% girls). There were two versions of the questionnaire: the shortened version was used for grades 1-3 and included only multiple choice questions while the comprehensive version for grade 4-7 comprised both structured and open-ended questions. In the questionnaire, different items were used such as ordinal, interval and qualitative to acquire information about different aspects of oral health-related knowledge, attitudes and behaviours. Results: Overall, there was a deficiency in oral-health related knowledge and corresponding behaviours in all age groups and both genders. Thus awareness about oral health in this cohort of children needs to be improved. The oral health-related lifestyle did not differ between boys and girls except for the interdental cleaning behaviour (P=0.033). Oral health-related lifestyle did not differ according to socio-demographic characteristics except for the difference in consumption of sugar-containing drinks among age groups (P0.001). The diet-related knowledge differed between children born inside and outside Canada (P0.050). Conclusion: Oral health-related knowledge, attitudes and behaviours among elementary school-aged children in inner-city Vancouver areas was deficient and professional guidance from oral health care workers concerning oral health self-care was lacking. There were no distinct socio-economic or demographic differences in lifestyle factors among the inner city Vancouver school-aged children.

View record

Elderly residents of long-term care facilities (LTC) have difficulty accessing dental services. Aiming to improve access for this population, the Geriatric Dental Program (GDP) was established by the UBC Faculty of Dentistry in 2002. Within the GDP, elderly LTC residents receive fee-for-service dental treatment. The objective of this research is to explore whether having access to the GDP services had an impact on the life of the patients’ relatives (family members). This research hopes to better understand how quality of health in relation to dental health extends to relatives who are responsible for the frail elderly patients who receive the dental care. Such understanding will contribute to our recognition of a more holistic and widespread impact of dental care access to all segments of our society.Methods: Data was collected through semi-structured, face-to-face, audio-recorded interviews with family members of elderly patients from the UBC-GDP. A purposive criterion sampling method was used to select the family members to participate in this study. The final number of participants was determined according to saturation procedures. Interview transcription and data coding procedures were conducted following Saldaña1. All interviews were transcribed verbatim. In a second step, NVivo software was used to code and organize the transcripts into different categories to develop themes. The analysis of the data followed a qualitative, interpretive Thematic Analysis.Results: Final analysis shows that family members are worried about their relatives’ oral health; they believe that it is difficult to find private dentists with geriatric expertise and to make appointments for their family members outside of UBC, and that the UBC program helped them in fulfilling this task. Moreover, the UBC-GDP made their life less stressful and relieved the burden of setting up appointments for their relatives making their life easier. Thus, the UBC GD program positively affected the life of relatives by improving access to dental care services for the growing geriatric segment of our Canadian society. Furthermore, this study shows that the UBC GD program not only improved the perceived oral health but also impacted the relatives’ life in a positive way.

View record

Purpose. The aim of this study was to determine and compare the marginal fit of crowns fabricated using digital and conventional methods.Materials and Methods. A maxillary right second bicuspid, set in a typodont (Frasaco, Greenville, N.C., USA), was prepared for a ceramic crown. The maxillary typodont was then digitized, using a 3Shape D700 lab scanner (3Shape Inc., New Jersey, N.Y., USA) and the digital file was used to mill a replica of the maxillary arch out of a monolithic block of yttria-stabilized zirconia, to serve as master model. Digital impressions of the prepared maxillary right second bicuspid were recorded using a 3M LAVA C.O.S. scanning unit. Scan files were exported as .STL files and e-mailed to the dental lab. Files were inputed (Core3dcentres®; Las Vagas, Nevada, USA) into a digital design workflow for digital articulation, digital wax-up, and design of the final crown. Fifteen crowns were produced by 5-axis milling IPS e.max® CAD (Ivoclar Vivadent, Liechtenstein) lithium disilicate glass-ceramic blocks. An additional fifteen IPS e.max® Press (Ivoclar Vivadent, Liechtenstein) lithium disilicate glass-ceramic crowns were produced using a conventional impression and laboratory fabrication methods. The original zirconia die was removed from the zirconia master model for evaluation of crown margins. Circumferential marginal gap measurements were taken at eight measurement locations: mesial, distal, buccal, palatal, and associated line angles. The marginal gap measurements were made to determine the vertical component of marginal gap, according to the definition of marginal fit.Results. A total of 240 images (2 groups, 15 crowns per group, 8 sites per crown) were recorded and measured. The overall mean vertical gap measurement for the digitally made crowns was (48 +/- 25) μm, which was significantly smaller than that for the conventionally made ones (74 +/- 47) μm. Conclusion. The fully digital fabrication methodology provides a better fitting crown margin than the conventional methodology.

View record

The introduction of digital impressions into the field of dentistry has begun the era of entirely computer assisted crown fabrication. The aim of this study was to assess the internal fit of lithium disilicate crowns fabricated using this novel impression technology and to compare their fit to the fit of crowns obtained by traditional elastomeric impressions. Thus, 15 lithium disilicate crowns were fabricated using an entirely digital workflow (impression and fabrication), 15 lithium disilicate crowns were fabricated manually from digital impressions, and 15 lithium disilicate crowns were fabricated using a “traditional” manual process. For the fabrication of the crowns, tooth #15 was prepared for an all-ceramic restoration on an ivorine typodont, which in turn was digitized and a replica milled in zirconia. This master zirconia model and die were then utilized for the impression procedures. Duplicate dies of the master zirconia die were made in polyurethane, enabling the internal fit of each crown to be evaluated via micro CT analysis, due to the contrast in radioopacity between the ceramic, die and internal space. The total volume of the internal space (gap), the mean and maximum thickness of the gap, and the percentage of the gap that was at or below 120um thickness were calculated and evaluated statistically via one-way ANOVA, with post-hoc Scheffé analysis. The results demonstrated that the lithium disilicate crowns fabricated from digital impressions resulted in a smaller internal space, and therefore more intimate fit, in comparison to the lithium disilicate crowns fabricated via the traditional manual approach. Three-dimensional renderings of the internal space were also created, allowing for a descriptive analysis of the distribution of this internal space.

View record

Objectives: To describe the oral health-related lifestyle of Vancouver inner city elementary school-aged children and relate different aspects of their oral health-related lifestyle with demographic and socioeconomic factors. Methods: This cross-sectional study used a structured questionnaire with some open-ended items to survey 424 school-aged children in Vancouver inner city elementary schools (53.3% boys and 46.7% girls). There were two versions of the questionnaire: the shortened version was used for grades 1-3 and included only multiple choice questions while the comprehensive version for grade 4-7 comprised both structured and open-ended questions. In the questionnaire, different items were used such as ordinal, interval and qualitative to acquire information about different aspects of oral health-related knowledge, attitudes and behaviours. Results: Overall, there was a deficiency in oral-health related knowledge and corresponding behaviours in all age groups and both genders. Thus awareness about oral health in this cohort of children needs to be improved. The oral health-related lifestyle did not differ between boys and girls except for the interdental cleaning behaviour (P=0.033). Oral health-related lifestyle did not differ according to socio-demographic characteristics except for the difference in consumption of sugar-containing drinks among age groups (P0.001). The diet-related knowledge differed between children born inside and outside Canada (P0.050). Conclusion: Oral health-related knowledge, attitudes and behaviours among elementary school-aged children in inner-city Vancouver areas was deficient and professional guidance from oral health care workers concerning oral health self-care was lacking. There were no distinct socio-economic or demographic differences in lifestyle factors among the inner city Vancouver school-aged children.

View record

The purpose of this study was to evaluate what factors influence dentists in their decisionto provide services in long-term care facilities within British Columbia. The secondarypurpose was to determine if dentists practicing in rural areas of British Columbia aremore willing to provide services in LTC compared to dentists in urban areas. Also, toassess if there were any changes in opinions of dentists (practicing in Metro-Vancouver)in providing services to patients in long-term care compared to a similar study from 1985.A questionnaire was developed to determine views and opinions of general dentistspracticing in British Columbia with respect to the provision of services in long-term care.Eight hundred dentists from urban and rural areas of British Columbia were randomlyselected to participate in this study. The British Columbia Dental Association mailed apackage containing 3 questionnaires. The participants were to fill out one of thequestionnaires based on whether they treated, never treated or stopped treating patients inlong-term care. These questionnaires were faxed back to the British Columbia DentalAssociation. A reminder was sent out to the dentists 3 weeks after the initial mail-out.About thirty percent of those dentists surveyed responded with completed questionnairesfor analysis. Dentists who treated patients in long-term care reported that it was a part oftheir professional responsibility to provide services. The lack of a dental operatory andlack of experience/training in geriatric dentistry were primary concerns of dentists whonever provided services. Compared to 1985, dentists in 2008 showed increasedawareness for a need for dental services by patients in long-term care facilities. Dentistsin rural areas were more likely to be providing services to patients in long-term carefacilities, compared to dentists in urban areas. Dentists who never provided services inlong-term care facilities expressed interest in providing dental services.

View record