The minipig intraoral dental implant model: A systematic review and meta-analysis

Objectives The objective of this report was to provide a review of the minipig intraoral dental implant model including a meta-analysis to estimate osseointegration and crestal bone remodeling. Methods A systematic review including PubMed and EMBASE databases through June 2021 was conducted. Two independent examiners screened titles/abstracts and selected full-text articles. Studies evaluating titanium dental implant osseointegration in native alveolar bone were included. A quality assessment of reporting was performed. Random-effects meta-analyses and meta-regressions were produced for bone-implant contact (BIC), first BIC, and crestal bone level. Results 125 out of 249 full-text articles were reviewed, 55 original studies were included. Quality of reporting was generally low, omissions included animal characteristics, examiner masking/calibration, and sample size calculation. The typical minipig model protocol included surgical extraction of the mandibular premolars and first molar, 12±4 wks post-extraction healing, placement of three narrow regular length dental implants per jaw quadrant, submerged implant healing and 8 wks of osseointegration. Approximately 90% of studies reported undecalcified incandescent light microscopy histometrics. Overall, mean BIC was 59.88% (95%CI: 57.43–62.33). BIC increased significantly over time (p<0.001): 40.93 (95%CI: 34.95–46.90) at 2 wks, 58.37% (95%CI: 54.38–62.36) at 4 wks, and 66.33% (95%CI: 63.45–69.21) beyond 4 wks. Variability among studies was mainly explained by differences in observation interval post-extraction and post-implant placement, and implant surface. Heterogeneity was high for all studies (I2 > 90%, p<0.001). Conclusions The minipig intraoral dental implant model appears to effectively demonstrate osseointegration and alveolar bone remodeling similar to that observed in humans and canine models.


Rationale
3 Describe the rationale for the review in the context of existing knowledge. p. 3, l.

15-22
Objectives 4 Provide an explicit statement of the objective(s) or question(s) the review addresses. p. 3, l. 31-33

METHODS
Eligibility criteria 5 Specify the inclusion and exclusion criteria for the review and how studies were grouped for the syntheses. p. 4, l.

9-22
Information sources 6 Specify all databases, registers, websites, organisations, reference lists and other sources searched or consulted to identify studies. Specify the date when each source was last searched or consulted.
p.3, l39-p4,l7 p. 3, l. 36 Search strategy 7 Present the full search strategies for all databases, registers and websites, including any filters and limits used. p. 3, l. 35page 4 l. 4 Selection process 8 Specify the methods used to decide whether a study met the inclusion criteria of the review, including how many reviewers screened each record and each report retrieved, whether they worked independently, and if applicable, details of automation tools used in the process.

33-37
Data collection process 9 Specify the methods used to collect data from reports, including how many reviewers collected data from each report, whether they worked independently, any processes for obtaining or confirming data from study investigators, and if applicable, details of automation tools used in the process.

39-43
Data items 10a List and define all outcomes for which data were sought. Specify whether all results that were compatible with each outcome domain in each study were sought (e.g. for all measures, time points, analyses), and if not, the methods used to decide which results to collect.
p. 4, l. 24-31; p. 5, l 2-6 10b List and define all other variables for which data were sought (e.g. participant and intervention characteristics, funding sources). Describe any assumptions made about any missing or unclear information.
p. 4, l. 40-p.5 l 6 Study risk of bias assessment 11 Specify the methods used to assess risk of bias in the included studies, including details of the tool(s) used, how many reviewers assessed each study and whether they worked independently, and if applicable, details of automation tools used in the process.

41-43
Effect measures 12 Specify for each outcome the effect measure(s) (e.g. risk ratio, mean difference) used in the synthesis or presentation of results. p. 5, l. 8-12 Synthesis methods 13a Describe the processes used to decide which studies were eligible for each synthesis (e.g. tabulating the study intervention characteristics and comparing against the planned groups for each synthesis (item #5)).

NA
13b Describe any methods required to prepare the data for presentation or synthesis, such as handling of missing summary statistics, or data conversions.
p. 5, l. 2-6 13c Describe any methods used to tabulate or visually display results of individual studies and syntheses.
p. 4, l. 41, sup Table 3 and 4 13d Describe any methods used to synthesize results and provide a rationale for the choice(s). If meta-analysis was performed, describe the model(s), method(s) to identify the presence and extent of statistical heterogeneity, and software package(s) used.

Item # Checklist item
Location where item is reported 13e Describe any methods used to explore possible causes of heterogeneity among study results (e.g. subgroup analysis, meta-regression).

8-15
13f Describe any sensitivity analyses conducted to assess robustness of the synthesized results. p. 5, l.

15-16
Reporting bias assessment 14 Describe any methods used to assess risk of bias due to missing results in a synthesis (arising from reporting biases). Figure 2a; sup Table 4 Certainty assessment 15 Describe any methods used to assess certainty (or confidence) in the body of evidence for an outcome. NA

Study selection
16a Describe the results of the search and selection process, from the number of records identified in the search to the number of studies included in the review, ideally using a flow diagram.
p. 5, l. 22-28; Fig. 1 16b Cite studies that might appear to meet the inclusion criteria, but which were excluded, and explain why they were excluded. p. 5, l. 25-27; sup. Table  2 Study characteristics 17 Cite each included study and present its characteristics. sup Table  3 Risk of bias in studies 18 Present assessments of risk of bias for each included study. Figure 2a; sup Table  4 Results of individual studies 19 For all outcomes, present, for each study: (a) summary statistics for each group (where appropriate) and (b) an effect estimate and its precision (e.g. confidence/credible interval), ideally using structured tables or plots.

Results of syntheses
20a For each synthesis, briefly summarise the characteristics and risk of bias among contributing studies. Figure 2a; sup Table  4 20b Present results of all statistical syntheses conducted. If meta-analysis was done, present for each the summary estimate and its precision (e.g. confidence/credible interval) and measures of statistical heterogeneity. If comparing groups, describe the direction of the effect. Table 1, Table 2, Table 3 20c Present results of all investigations of possible causes of heterogeneity among study results. Table 1,  Table 2, Table 3 20d Present results of all sensitivity analyses conducted to assess the robustness of the synthesized results. Table 1,  Table 2,  Table 3 Reporting biases 21 Present assessments of risk of bias due to missing results (arising from reporting biases) for each synthesis assessed. Figure 2a,

Item # Checklist item
Location where item is reported 2b; sup Table 4 Certainty of evidence 22 Present assessments of certainty (or confidence) in the body of evidence for each outcome assessed. NA

Discussion
23a Provide a general interpretation of the results in the context of other evidence. p. 7, l. 12-26 23b Discuss any limitations of the evidence included in the review. p. 8, l. 37-50 23c Discuss any limitations of the review processes used. p. 9, l.

OTHER INFORMATION
Registration and protocol 24a Provide registration information for the review, including register name and registration number, or state that the review was not registered. NA 24b Indicate where the review protocol can be accessed, or state that a protocol was not prepared. NA 24c Describe and explain any amendments to information provided at registration or in the protocol. NA Support 25 Describe sources of financial or non-financial support for the review, and the role of the funders or sponsors in the review. p. 1 PDF proof fin disclosure Competing interests 26 Declare any competing interests of review authors.
p. 1, l. 26 Availability of data, code and other materials 27 Report which of the following are publicly available and where they can be found: template data collection forms; data extracted from included studies; data used for all analyses; analytic code; any other materials used in the review. For more information, visit: http://www.prisma-statement.org/