Melbourne Dental School - Research Publications

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    Complications and treatment errors in implant positioning in the aesthetic zone: Diagnosis and possible solutions
    Chen, ST ; Buser, D ; Sculean, A ; Belser, UC (WILEY, 2023-06)
    Incorrect implant positioning can lead to functional and aesthetic compromise. Implant positioning errors can occur in three dimensions: mesiodistal, corono-apical, and orofacial. Treatment solutions to manage adverse outcomes through positioning errors require an understanding of the underlying conditions and of those factors that may have led to the error being committed in the first place. These types of complications usually occur because of human factors. If errors do occur with adverse aesthetic outcomes, they are difficult and sometimes impossible to correct. Connective tissue grafts to reverse recession defects are only feasible in defined situations. The option to remove and replace the implant may be the only recourse, provided the removal process does not further compromise the site. Error in judgment by the clinician.
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    The relationship between facial bone wall defects and dimensional alterations of the ridge following flapless tooth extraction in the anterior maxilla
    Chen, ST ; Darby, I (WILEY, 2017-08)
    PURPOSE: To evaluate the relationship between defects of the facial socket wall at extraction and dimensional changes 8 weeks later in maxillary central and lateral incisor sockets. MATERIALS AND METHODS: A total of 34 consecutive patients requiring single tooth implants in the anterior maxilla (27 central and 7 lateral incisors) were evaluated. Orofacial external ridge, bone dimensions and the location of the socket bone crest were measured at extraction and again 8.5 ± 2.91 weeks later. The status of the facial bone wall was recorded at the same time points. RESULTS: At extraction, 16 of 34 sites (47%) had intact facial bone. There were fenestration defects at 9 of 34 sites (26.5%) and dehiscence defects at 9 of 34 sites (26.5%). A significant reduction (P < 0.001) in the external orofacial ridge dimension occurred (mesial 1.4 ± 1.30 mm or 12.1%, facial 2.5 ± 1.46 mm or 22.2%, distal 1.1 ± 0.83 mm or 10.5%), with greatest change at dehiscence (3.3 ± 1.80 mm or 28.4%) and fenestration sites (2.8 ± 1.40 mm or 24.9%). A significant reduction in orofacial bone dimension occurred (mesial 0.8 ± 0.80 mm or 9.3%, P < 0.001; facial 1.2 ± 1.03 mm or 18.3%, P < 0.001; distal 0.4 ± 0.65 mm or 5.5%, P < 0.01). Vertical resorption of the bone crest was most marked at the mid-facial aspect (1.4 ± 1.94 mm, P < 0.001). Initial fenestration defect sites demonstrated the greatest vertical dimensional change (2.9 ± 2.67 mm; P = 0.008). Of 16 sites with initially intact facial bone, 9 sites (56.3%) developed dehiscence defects after 8 weeks. Of the 9 initial sites with fenestration defects, 5 (55.6%) turned into dehiscence defects. All 9 sites with initial dehiscence defects healed with persistence of the dehiscence. CONCLUSIONS: Eight weeks after flapless extraction of maxillary central and lateral incisors, a reduction in the orofacial dimensions of the ridge was observed due to resorption of the facial bone of the socket. Tooth type (maxillary central incisor) and thin tissue phenotype significantly influenced the outcomes. The dimensional alterations were most pronounced at sites that initially had fenestration and dehiscence defects of the facial bone.
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    The influence of deproteinised bovine bone mineral on dimensional changes in the maxillary second incisor socket
    Raveendiran, N ; Chen, S ; Davies, H ; Fitzgerald, W ; Darby, I (WILEY, 2019-07)
    OBJECTIVES: To investigate the dimensional changes following the extraction of maxillary second incisors and to evaluate the influence of deproteinised bovine bone mineral on the healing outcomes. MATERIALS AND METHODS: The second maxillary incisors in nine dogs were extracted bilaterally in a minimally traumatic manner. Deproteinised bovine bone mineral with collagen (DBBMC) and a collagen matrix (CM) was placed in one socket with the contralateral socket left to heal naturally. After 3 months of healing, the dogs were sacrificed and the pre-maxilla resected. Cone beam computerised tomography scans (CBCTs) were obtained and the specimens prepared for histological preparation and analysis. Surface scans of study models taken pre- and post-extraction were digitally subtracted to analyse volumetric changes. RESULTS: All dogs healed uneventfully without any complications. No inflammation was seen, and DBBMC was well integrated into a network of mineralised tissues, bone marrow and connective tissue. The horizontal width of the buccal crest was found to be significantly greater in grafted sockets, but the vertical height to be similar. No significant difference was seen in regard to volumetric changes in sockets over 3 months post-extraction. CONCLUSION: Maxillary second incisor sockets of dogs grafted with DBBMC post-extraction had significantly greater horizontal width at the ridge crest compared with ungrafted sockets. Volumetric analysis revealed no significant difference between grafted and non-grafted sockets, suggesting possible soft tissue thickening post-extraction to counteract osseous resorption.
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    Marginal bone level and survival of short and standard-length implants after 3 years: An Open Multi-Center Randomized Controlled Clinical Trial
    Zadeh, HH ; Gulje, F ; Palmer, PJ ; Abrahamsson, I ; Chen, S ; Mahallati, R ; Stanford, CM (WILEY, 2018-08)
    OBJECTIVES: The present multi-center randomized controlled clinical trial sought to compare the marginal bone level (MBL) changes and survival of 6- and 11-mm implants. MATERIAL AND METHODS: Ninety-five patients receiving a total of 209 dental implants were enrolled. Subjects were randomly allocated to two cohorts: test (4.0 × 6 mm; N = 108) or control (4.0 × 11 mm; N = 101) implant groups. To be randomized, all edentulous sites were anatomically qualified to receive 11 mm implant. Two to three implants were placed in maxillary or mandibular posterior regions and loaded with splinted provisional restoration after 6 weeks and definitive restoration 6 months thereafter. Test and control implants were followed by clinical and radiographic examinations on an annual basis up to 3 years. RESULTS: Radiographic assessment of MBL 3 years after loading revealed the bone to be located at 0.27 mm (±0.40) and 0.44 mm (±0.74) apical to the implant platform in the test and control groups, respectively. During the 3 years of follow-up since loading, 0.04 mm (±0.43) MBL gain and 0.02 mm (±0.76) of MBL loss were observed in the 6-mm (test) and 11-mm (control) groups, respectively. The MBL's for test and control were significantly different (p = 0.000) in favor of short implants. The cumulative survival rates from placement after 3 years were 96% and 99% for the 6- and 11-mm implants, respectively, with no statistical significance. CONCLUSIONS: Reconstruction of partially edentulous posterior maxilla or mandible with 6- or 11-mm implants led to stable marginal bone level and high implant survival rate after 3 years.
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    Peri-implant diseases and conditions: Consensus report of workgroup 4 of the 2017 World Workshop on the Classification of Periodontal and Peri-Implant Diseases and Conditions
    Berglundh, T ; Armitage, G ; Araujo, MG ; Avila-Ortiz, G ; Blanco, J ; Camargo, PM ; Chen, S ; Cochran, D ; Derks, J ; Figuero, E ; Hammerle, CHF ; Heitz-Mayfield, LJA ; Guy, H-B ; Iacono, V ; Koo, K-T ; Lambert, F ; McCauley, L ; Quirynen, M ; Renvert, S ; Salvi, GE ; Schwarz, F ; Tarnow, D ; Tomasi, C ; Wang, H-L ; Zitzmann, N (WILEY, 2018-06)
    A classification for peri-implant diseases and conditions was presented. Focused questions on the characteristics of peri-implant health, peri-implant mucositis, peri-implantitis, and soft- and hard-tissue deficiencies were addressed. Peri-implant health is characterized by the absence of erythema, bleeding on probing, swelling, and suppuration. It is not possible to define a range of probing depths compatible with health; Peri-implant health can exist around implants with reduced bone support. The main clinical characteristic of peri-implant mucositis is bleeding on gentle probing. Erythema, swelling, and/or suppuration may also be present. An increase in probing depth is often observed in the presence of peri-implant mucositis due to swelling or decrease in probing resistance. There is strong evidence from animal and human experimental studies that plaque is the etiological factor for peri-implant mucositis. Peri-implantitis is a plaque-associated pathological condition occurring in tissues around dental implants, characterized by inflammation in the peri-implant mucosa and subsequent progressive loss of supporting bone. Peri-implantitis sites exhibit clinical signs of inflammation, bleeding on probing, and/or suppuration, increased probing depths and/or recession of the mucosal margin in addition to radiographic bone loss. The evidence is equivocal regarding the effect of keratinized mucosa on the long-term health of the peri-implant tissue. It appears, however, that keratinized mucosa may have advantages regarding patient comfort and ease of plaque removal. Case definitions in day-to-day clinical practice and in epidemiological or disease-surveillance studies for peri-implant health, peri-implant mucositis, and peri-implantitis were introduced. The proposed case definitions should be viewed within the context that there is no generic implant and that there are numerous implant designs with different surface characteristics, surgical and loading protocols. It is recommended that the clinician obtain baseline radiographic and probing measurements following the completion of the implant-supported prosthesis.
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    Alveolar ridge preservation and early implant placement at maxillary central incisor sites: A prospective case series study
    Chen, ST ; Darby, I (WILEY, 2020-09)
    PURPOSE: To assess whether alveolar ridge preservation (ARP) with 90% deproteinized bovine bone mineral in a 10% collagen matrix (DBBMC) and resorbable type I/III porcine collagen matrix (CM) maintains sufficient bone volume for early implant placement 8-10 weeks after extraction of maxillary central incisors. MATERIALS AND METHODS: In this case series study of 10 consecutively enrolled patients, sockets of maxillary single central incisors requiring extraction and early implant placement were grafted with DBBMC/CM. Ridge dimensions were measured pre-extraction and just prior to implant placement. RESULTS: Alveolar ridge preservation maintained sufficient bone volume for implants to be placed in all sites. Compared to pre-extraction, there was a significant reduction in the orofacial dimensions of the ridge (1.4 ± 1.07 mm; 13.2% reduction) and bone (0.7 ± 0.67 mm; 9.3%) at the coronal midfacial region. A significant reduction in apicocoronal height of the crestal bone at midfacial (1.2 ± 0.78 mm) and palatal aspects was observed. On CBCT, a statistically significant reduction in alveolar ridge area occurred (10.9 ± 13.42 mm2 ; 12.2% reduction). To optimize aesthetic outcomes, 9/10 sites required additional low volume grafting at the coronal region, whereas one site required more extensive grafting due to a facial bone dehiscence. At 1-year, the implant survival rate was 100% and median Pink Esthetic Score (PES) was 10 (range 9-13). CONCLUSIONS: ARP using DBBMC/CM maintains sufficient bone volume for early implant placement 8.9 ± 0.97 weeks later, with a 100% survival rate 1 year after restoration.
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    Primary stability and healing outcomes of apically tapered and straight implants placed into fresh extraction sockets. A pre-clinical in vivo study
    Ellis, R ; Chen, S ; Davies, H ; Fitzgerald, W ; Xu, J ; Darby, I (WILEY, 2020-08)
    OBJECTIVES: To compare the stability of apically tapered and straight (non-tapered cylindrical) implants at the time of immediate placement and to histologically evaluate the healing outcomes after 6 weeks. MATERIALS AND METHODS: The second maxillary incisors were extracted bilaterally in nine dogs. After randomization, apically tapered and straight implants with a 3.3 mm shoulder diameter were inserted into the extraction sockets. The implant stability quotient (ISQ) of the implants was recorded after placement. Peri-implant defects on the buccal aspect were filled with deproteinized bovine bone mineral and covered with resorbable type I/III porcine collagen matrix. After 6 weeks of healing, sections were prepared for histological and morphometric analysis. RESULTS: All implant sites healed uneventfully. The apically tapered implants had significantly higher ISQ values compared to straight implants at placement (p = .009). The histomorphometric outcomes 6 weeks following implant placement in both experimental groups were similar, except in the apico-palatal region. Apically tapered implants demonstrated significantly less percentage bone-to-implant contact (p = .035) in the apico-palatal region. At both implant types, substantial corono-apical resorption of the buccal bone wall was noted in the coronal 2 mm of the implant. CONCLUSION: Apically tapered implants had significantly higher ISQ values at immediate placement compared to straight implants. The healing outcomes and remodelling of the buccal bone wall were similar for both implant designs. In the apico-palatal region, there was less %BIC at the implant surface at apically tapered implants compared to straight implants.
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    Comparison of 6-mm and 11-mm dental implants in the posterior region supporting fixed dental prostheses: 5-year results of an open multicenter randomized controlled trial
    Gulje, FL ; Meijer, HJA ; Abrahamsson, I ; Barwacz, CA ; Chen, S ; Palmer, PJ ; Zadeh, H ; Stanford, CM (WILEY, 2021-01)
    OBJECTIVE: The aim of this multicenter, randomized controlled trial was to compare the clinical and radiographic outcomes of 6-mm or 11-mm implants, placed in the posterior maxilla and mandible, during a 5-year follow-up period. MATERIALS AND METHODS: Ninety-five patients with adequate bone height for 11-mm implants, were randomly allocated to a 6-mm group (test group with short implants) or an 11-mm group (control group with standard-length implants). Two or three implants of the same length were placed in each patient and after 6 weeks loaded with a splinted provisional restoration. This was followed by definitive splinted restoration 6 months after implant placement. Clinical and radiographic parameters, including the occurrence of complications were recorded. RESULTS: A total of 49 patients were enrolled to receive 6-mm implants (n = 108) and 46 patients to receive 11-mm implants (n = 101). Three implants (two of 6 mm and one of 11 mm in length) were lost before loading and one 6-mm implant after 15 months of function, and one 11-mm implant was lost during the first year of function. The 5-year survival rates were 96.0% and 98.9% in the 6-mm and 11-mm group, respectively. The mean marginal bone level changes 5 years post-loading were 0.01 ± 0.45 mm (bone gain) in the 6-mm group and -0.12 ± 0.93 mm (bone loss) in the 11-mm group (p = .7670). Clinical parameters, including plaque, bleeding on probing and pocket probing depth were not significantly different between the groups, and also technical complications were low. CONCLUSION: The clinical and radiographic outcomes of 6-mm short and 11-mm standard-length implants were not different during a 5-year evaluation period.
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    Early implant placement in ridge preserved extraction sockets: A pre-clinical in vivo study
    Rodriguez-Ortiz, G ; Chen, S ; Davies, H ; Fitzgerald, W ; Darby, I (WILEY, 2021-06)
    OBJECTIVES: The aim was to analyse the outcomes of early implant placement after 6 and 12 weeks of healing in ridge preserved sites in a canine model. MATERIALS AND METHODS: Implants were placed in second maxillary incisors sites in 9 dogs 6 weeks after grafting of the sockets with 90% deproteinized bovine bone mineral in 10% collagen matrix (DBBMC) and closure with resorbable type I/III porcine collagen matrix (PCM). The implants were randomly assigned to 6 (T6) and 12 (T12) weeks of healing. RESULTS: The percentage of bone-to-implant contact (%BIC), old bone, new bone and residual DBBMC was similar between T6 and T12. In relation to the implant shoulder (IS), the original bone crest (IS-ROB) was more apical on the buccal than the palatal side. The regenerated bone crest (IS-C) and IS-ROB were similar between groups. However, the distance from IS to first bone-to implant contact (IS-fBIC) was significantly less in T12 compared with T6 (p = .022; Wilcoxon signed-rank test). The bucco-palatal ridge dimensions between T6 and T12 were similar. CONCLUSIONS: This study confirms that implants can successfully be placed early in ridge preserved maxillary second incisor sites and are osseointegrated by 6 weeks. There were significantly lower IS-fBIC values at 12 weeks than at 6 weeks on the buccal aspect. The original buccal bone crest underwent greater corono-apical resorption than the palatal crest. The %BIC, relative proportions of mineralized tissues and dimensions of the alveolar ridge demonstrated stability between 6 and 12 weeks of healing.
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    Submerged and transmucosal healing yield the same clinical outcomes with two-piece implants in the anterior maxilla and mandible: interim 1-year results of a randomized, controlled clinical trial
    Haemmerle, CHF ; Jung, RE ; Sanz, M ; Chen, S ; Martin, WC ; Jackowski, J ; Ivanoff, C-J ; Cordaro, L ; Ganeles, J ; Weingart, D ; Wiltfang, J ; Gahlert, M (WILEY-BLACKWELL, 2012-02)
    OBJECTIVES: To test whether or not transmucosal healing at two-piece implants is as successful as submerged placement regarding crestal bone levels and patient satisfaction. MATERIAL AND METHODS: Adults requiring implants in the anterior maxilla or mandible in regions 21-25, 11-15, 31-35 or 41-45 (WHO) were recruited for this randomized, controlled multi-center clinical trial of a 5-year duration. Randomization was performed at implantation allowing for either submerged or transmucosal healing. Final reconstructions were seated 6 months after implantation. Radiographic interproximal crestal bone levels and peri-implant soft tissue parameters were measured at implant placement (IP) (baseline), 6 and 12 months. Patient satisfaction was assessed by a questionnaire. A two-sided t-test (80% power, significance level α=0.05) was performed on bone-level changes at 6 and 12 months. RESULTS: One hundred and twenty-seven subjects were included in the 12-month analysis (submerged [S]: 52.5%, transmucosal [TM]: 47.2%). From IP to 6 months, the change in the crestal bone level was -0.32 mm (P<0.001) for the S group and -0.29 mm (P<0.001) for the TM group. From IP to 12 months, bone-level changes were statistically significant in both groups (S -0.47 mm, P<0.001; TM -0.48 mm, P<0.001). The mean differences of change in the bone levels between the two groups were not statistically significant at either time point, indicating the equivalence of both procedures. For both groups, very good results were obtained for soft tissue parameters and for patient satisfaction. CONCLUSIONS: Transmucosal healing of two-piece implants is as successful as the submerged healing mode with respect to tissue integration and patient satisfaction within the first 12 months after IP.