Chooi Gait Toh

Strain measurements and fracture resistance of endodontically treated premolars restored with all-ceramic restorations

OBJECTIVES The aim of this study was to investigate the recovery of cuspal stiffness and fracture resistance in endodontically treated maxillary premolars restored with bonded ceramic inlays and onlays of various designs. METHODS Seventy intact premolars were selected for this study; six cavity designs were investigated: (i) mesio-occlusal-distal (MOD) inlay (I), (ii) MOD inlay with palatal cusp coverage (IPC), (iii) MOD onlay (O), (iv) MOD inlay with pulp chamber extension (IPE), (v) MOD inlay with palatal cusp coverage and pulp chamber extension (IPCPE), and (vi) MOD onlay with pulp chamber extension (OPE). Intact teeth acted as control. Strain gauges were attached to the buccal and palatal surfaces of the teeth to measure cuspal stiffness under static loading. All specimens were eventually subjected to compressive load to failure. Cuspal stiffness and fracture resistance data were analyzed using ANOVA and Tukey test. RESULTS The I and IPE restorations restored cuspal stiffness to 75% of the sound tooth value. The O and OPE restored teeth had stiffness values greater than that of a sound tooth. The I, IPC, O, IPE, IPCPE and OPE restored teeth demonstrated fracture strength values of 938N±113 N (s.d.), 1073N±176 N and 1317N±219 N, 893N±129 N, 1062N±153 N and 1347N±191 N respectively. CONCLUSIONS Within the limitations of this study, it was concluded that the all-ceramic onlay or inlay with palatal cusp coverage provided best biomechanical advantage in restoring an endodontically treated maxillary premolar tooth. CLINICAL SIGNIFICANCE The onlay approach which is more conservative compared to full coverage restoration is considered an appropriate approach to the restoration of endodontically treated maxillary premolars. The addition of a pulpal extension to the all-ceramic restorations, apart from being technically challenging, was not found to offer any biomechanical advantage to the restored teeth.

A survey of current practices among general dental practitioners in Manchester in 2002.

Aim The purpose of this study was to obtain data on current approaches for the restoration of endodontically treated teeth among general dental practitioners (GDPs) in Manchester, United Kingdom. Method A questionnaire containing 19 single-answer, multiple-choice type questions was mailed to 503 GDPs practising in the Greater Manchester area in January 2002. An explanatory covering letter and a stamped addressed return envelope were enclosed. The data obtained were processed using SPSS statistical software. Results Three hundred and fifty-one (70%) of the practitioners responded to the questionnaire. The restoration of root-filled teeth was normally undertaken within 1–2 weeks of completing root canal therapy by 63% of the practitioners. Only 35% of the GDPs used posts routinely in the restoration of root-filled anterior teeth; the corresponding figure for posterior teeth was 15%. While a cast, precious metal post was the preferred choice in the restoration of anterior teeth, the use of prefabricated posts and related techniques predominated in the restoration of posterior teeth. Composite resin was the most popular choice of material for core build-up procedures in anterior teeth. Amalgam tended to be favoured for core build-ups in posterior teeth. The majority of the practitioners (56%) routinely restored root-filled anterior teeth by means of porcelain-fused-to-metal crowns. Seventy-three per cent of the GDPs preferred to restore root-filled posterior teeth by means of a full veneer crown. Conclusions The results of this study suggest that the practitioners surveyed had a sound understanding of the principles involved in the restoration of endodontically treated teeth, with the possible exception of the need to establish a durable coronal seal as soon as possible after the placement of a root filling.

Subcutaneous reactions and degradation characteristics of collagenous and noncollagenous membranes in a macaque model

BACKGROUND collagenous and noncollagenous membranes have been investigated in many animal systems but their effects in the macaque model are unknown. OBJECTIVE to determine subcutaneous cellular reactions and degradation characteristics following implantation of collagenous and noncollagenous membranes in a macaque model. METHODS six adult male Macaca fascicularis, aged above 7 years, were used. Six commercially available collagenous (Bio-Gide [BG], Tissue Fleece [TFL] TissueFoil E forte [TFO], Lycoll [LC], Surgicoll [SG] and Tutodent [TU]) and two noncollagenous (Tabotamp [TA] and Gelita-Tampon [GT]) membranes (size 2 × 2 cm each) were implanted in unconnected subcutaneous pouches in the monkeys back and wounds were allowed to heal by primary intention. The total sample size for each membrane was six. Two monkeys were sacrificed for each experimental period of 4, 14 and 28 days. Explanted specimens were prepared for histologic and histomorphometric analysis. Digitized images of implant sites were systematically sampled using an Image Analyzer with a grid containing 35 intersection points. Four parameters were quantified: membrane degradation, foreign body reaction, tissue organization and vascularization. RESULTS biodegradation rate and vascularization scored higher in collagenous than in noncollagenous membranes. Except for TFL and TU, the remaining six membranes showed a moderately intense foreign body reaction at week 2. Tissue organization was initiated early in four out of six collagenous (TFL>LC>SG>TFO>BG>TU) compared with one of two noncollagenous (TA>GT) membranes. CONCLUSIONS the results suggest that differences in membrane structure and composition underlie their different cellular reactions and degradation characteristics.

Dimensional profile of oral mucosa around combined tooth-implant-supported bridgework in macaque mandible.

PURPOSE A stable oral mucosa is crucial for long-term survival and biofunctionality of implants. Most of this evidence is derived from clinical and animal studies based solely on implant-supported prosthesis. Much less is known about the dimensions and relationships of this soft tissue complex investing tooth-implant-supported bridgework (TISB). The aim here was to obtain experimental evidence on the dimensional characteristics of oral mucosa around TISB with two different abutment designs. METHODS Sixteen 3-unit TISB were constructed bilaterally in the mandible of eight adult Macaca fascicularis. An implant system with a standard progressive thread design was the bone-anchoring implant in the second mandibular molar region while the second mandibular premolar served as the natural tooth abutment. Eight implants were connected with the tapered abutment, the remaining with butt-joint abutment, in a split-mouth design. These were allowed to functional load for 6 months before sacrification for histomorphometry. Six soft tissue indices were scored: coronal gingival mucosa-to-implant top distance (DIM); sulcus depth (SD); junctional epithelium (JE); connective tissue contact (CTC); implant top to first bone-to-implant contact distance (DIB); and biologic width (BW=SD+JE+CTC); corresponding parameters in the natural tooth abutment were also measured. RESULTS Mucosal dimensions in tapered implants (*BW=3.33±0.43; SD=1.03±0.24; JE=1.08±0.13; CTC=1.22±0.23 mm) were comparable with those of natural tooth abutments (BW=3.04±0.18; SD=0.93±0.1; JE=0.78±0.1; Attachment=1.33±0.09 mm), but differed from butt-joint implants (*BW=4.88±1.24; SD=1.47±0.38; JE=1.49±0.4; CTC=1.92±0.93 mm) (*P<0.05). CONCLUSIONS Results suggested that soft tissue dimensions around TISB are influenced by the implant-abutment interface and abutment material used. Mucosa investing tapered abutment tends to recapitulate soft tissue physiologic dimensions of natural tooth.

Factors associated with faculty participation in research activities in dental schools

BACKGROUND To quantify participation in dental research activities in Malaysia, and investigate its association with socio-demographic and professional characteristics, and perceptions of research and development (R&D) culture. MATERIALS AND METHODS Dental academics in Malaysian dental schools were invited to complete a questionnaire by email and post. The survey comprised questions on research activities in the past 12 months, socio-demographic and professional characteristics, and the R&D Culture Index. Principal components factor analysis was carried out to confirm the factor structure of the R&D Culture Index. Chi-square test was used to identify association of research activities with R&D culture, and socio-demographic and professional characteristics. Binary logistic regression was carried to identify predicators of research activities. RESULTS Of 256 potential participants contacted, 128 (50%) useable responses were returned. Three R&D Culture factors accounting for 57.4% of variance were extracted. More positive perception of R&D Support was associated with Malaysians (0.025) and those employed in Government schools (0.017). R&D Skills and Aptitude were associated with older respondents (0.050), PhD qualification (0.014) and more years in academia (0.014). R&D Intention was associated with any of the socio-demographic characteristics. Thirty (23.4%) respondents reported a peer-review research publication in the past 12 months, which was associated with having a PhD (OR 12.79, CI 1.28-127.96), after adjustment in regression analyses. DISCUSSION Postgraduate research training should be encouraged to promote participation in research activities. R&D culture did not appear to impact on research productivity. Other factors such as individual attitudinal interests should be studied.

Cementum status in natural teeth opposing implant-borne bridgework in Macaca fascicularis.

OBJECTIVE The objective of this study was to investigate the cementum status in natural teeth opposing implant-supported bridgework. METHODS Maxillary premolars and molars opposing immediate-loading (IL) and delayed-loading (DL) mandibular implant-supported bridgework in 4 Macaca fascicularis were harvested after 3 months of functional loading. Another 2 monkeys without mandibular fixed prostheses served as control. The cervical (CCW) and apical cementum width (ACW), and resorption craters (RCs) were measured. RESULTS No significant differences were observed between test and control groups for mean CCW (control = 26.79 ± 3.28, IL = 21.29 ± 9.12, and DL = 20.32 ± 5.65 μm) and for ACW (control = 937.97 ± 353.74, IL = 955.26 ± 720.05, and DL = 750.56 ± 517.26 μm) (P > .05). In test and control monkeys, RCs were uncommon and showed no significant differences in width (control = 0.71 ± 0.38, IL = 1.02 ± 0.49, DL = 0.85 ± 1.02 mm) and depth (control = 0.15 ± 0.07, IL = 0.25 ± 0.40, DL = 0.22 ± 0.15 mm) (P > .05). CONCLUSIONS Present findings suggest that implant-supported bridgework does not produce any adverse effects on the cementum of opposing natural teeth after 3 months of functional loading.