Customer Complaints as an Evaluation Tool Assessing the Performance and Clinical Suitability of Different Implant Design

Abstract

During an assessment of dental implant design effectiveness, most of the data are acquired from clinical or animal studies performed by researchers and clinicians. In order to represent scientific significance, those studies have to be properly designed, focusing on a precisely chosen aspect with inclusion and exclusion criteria. The last of these, especially, can create major limitations for the data collection. In order to create a reliable, complete overview of different implant suitability, the data from a single customer can also be a valuable input in dental science. The aim of the study was to compare if the type of implants returned corresponded with sales figures for this type of implant or if there were any differences in the number of complaints. Customer complaints regarding dental implants produced by the same manufacturer acquired from dental professionals from different countries were evaluated over a fixed period of time. After having compared the number of complaints regarding implants to the number of sold implants, it was evident that single-piece implants and those with a polished surface used for immediate loading were significantly less likely to generate customer complaints than conventional two-stage systems (p < 0.001) with rough surfaces and larger endosseous diameters.

1. Introduction

In the literature, the survival rates of implants are typically determined in studies undertaken by university researchers [1,2]. Such studies may have a doubtful base because inclusion and exclusion criteria at universities may be different in comparison to offices of private practitioners. Direct comparative studies between different approaches or even different implant technologies (e.g., Diskimplant^®, blades, one-piece, two-piece, Corticobasal^® implants) are not available. One of the possible explanations for such a situation is that specialists for alternative treatment strategies are usually not available in one center. The second is that, in most cases, university clinics are tied to one implant manufacturer as the medical equipment supplies are arranged through tenders.

Another problem is the definition of success criteria in clinical studies [3,4,5]. In a number of studies, only those implants that had reached at least the phase of the prosthetic treatment are counted as lost. Other authors include all implants consecutively placed. Data considering the intent-to-treat-principle are, to our knowledge, not available in dental implantology. Hence, the majority of studies are done with a small number of patients and usually only a few dozen or a few hundred dental implants. In the present study, the authors have chosen a different approach to assess the influence of implant design on the outcome of dental implant treatment. Based on the worldwide sales of 254,113 consecutive implants of all types manufactured by Dr. Ihde Dental AG, we have related the number of sold implants to the number of complaints that were made to the quality department of the manufacturer. The manufacturer encourages all customers to return failed or unusable implants by replacing those implants and other parts free of charge. There is no post-sales time limit for this warranty, i.e., such replacements will be done even after many years. As a result, we anticipate that the majority of customers will actually return any faulty implants. Returns of implants are delivered to the manufacturer directly or via a regional or national distributor. However, implants that were removed in a different office than where they were placed are unlikely to be returned to the producer. No limitations are stated in the manufacturer’s “manual for usage” regarding the implant used in the maxilla or mandible. In this one manufacturer offer are many different implant designs with different surfaces and loading protocols reflecting all the technological development in the field of dental implantology. As a result, we may expect that all implants were placed in the mandible and maxilla and that the dental specialist was able to choose the appropriate implant type for the particular patient. There is only one explicit rule that should be followed in all cases: load (splint) immediate loading systems within 72 h. The manufacturer encourages the treatment provider to use some of the implants (e.g., polished surface) even if severe periodontal conditions occur immediately following extractions and even in severely infected locations under local disinfection coverage [6]. To date, we have not found in the literature a product complaint analysis based on such a large group of implants. The aim of the study was to describe and compare the number of complaints from dental clinics regarding different implant designs and relate it to the sales figures, giving additional insight into the implant market.

2. Materials and Methods

The producer provides a wide range of implant designs, as presented in

Table 1. Analysis of sold versus returned implants for various implant designs.

Category	Implant Type	Returned Implants % (UCI; LCI)	Implant Design	Clinical Appearance	Endosseous Surface
1	KOS/GCS	0.13 (0.109; 0.155)	1-piece, immediate loading		sandblasted
2	BCS, GBC, Beces	0.03 (0.022; 0.050)	1-piece, immediate loading		Machined
3	Hexacone®	0.52 (0.455; 0.601)	2-piece, delayed loading		SA
4	SSO®, STI®	1.06 (0.907; 1.237)	2-piece, delayed loading		SA
5	STW, GIW	2.77 (1.946; 3.917)	2-piece, delayed loading		SA
6	Xign®(Xive-compatible)	0.54 (0.407; 0.701)	2-piece, delayed loading		SA
7	(disk implants); BOI®/TOI®	0.10 (0.033; 0.282)	1-piece, immediate loading		machined
8	TPG	0	2-piece, immediate loading		machined
9	Bone Level Plus (Straumann-like)	1.42 (1.090; 1.838)	2-piece, delayed loading		SA
10	STO, STC, (Straumann- like)	0.91 (0.650; 1.277)	2-piece, delayed loading		SA
11	Place® (GPL)	0.60 (0.223; 1.491)	2-piece, delayed loading		SA

. All implants, as well as their components, were manufactured, decontaminated, and packed in the same facility. The same equipment, raw materials, cleaners, personnel, and production procedures were used and followed throughout the process. Additionally, all the implants and their components were CE-marked and made in a facility that complies with ISO 13495 guidelines.

Data from the sales department and the quality department have been collated, and implant systems were split into the 4 following groups (after being checked for implant returns).

Group A: Included 1-piece implants with rough or machined surfaces

• KOS^®
• Strategic Implant^®, BCS^®, GBC^®, Beces^®
• BOI^®/TOI^®

Group B: 2-piece implants with rough or machined surfaces

• SSO, STI with max. neck Ø4.8 mm,
• STW^®, GTW^®
• Bone Level Plus
• Hexacone^®/GIH^®
• Place^®
• TPG^®

Group C: 1-piece implants with machined surface

• BCS^®/GBC^®/BECES^®
• TOI^®/BOI^®
• TPG^®

Group D: 2 -piece and single-piece implants with sandblasted or etched surfaces

• Standard cylindrical full screw implants (neck max. 4.8 mm, SSO, STI)
• Wide neck cylindrical full screw implants (STW^®, GTW^®)
• Bone level implant (Bone Level Plus)
• Internal Hex standard implant (Hexacone^®/GIH^®)
• Tri-Lobe Implants (Place^®)
• Compression screw implants (KOS^®)

Cross-tables, χ² tests odds ratios, and corresponding estimations of confidence intervals were used to analyze complaint rates (pc) between various groups (in the case of 2 × 2 tables). Additionally, category complaint rate confidence intervals were calculated. Implants with the same outer design but with different internal connections (e.g., full screws with an internal conus and full screw implants with an internal octagon) were assigned to the same group. The research period, which shows the time frame when implants were sold and specifics on sales of each system, cannot be fully disclosed due to the commercial interests of the manufacturer.

Exclusion Criteria

Implants that were returned due to problems with the insertion tool (e.g., defective insertion tools damaged implant connections) were excluded from the study

Implants that had never been placed and were returned with the attached holder were excluded, as the reason for return was opening the package.

3. Results

The results of n = 254,141 implants sold are shown in Table 1.

Group C consisted of n = 178,201 implants; the rest belonged to the two-piece group of implants. The overall return rate of implants was 0.282%. The estimated complaint rates and associated confidence intervals with respect to the overall return rate are shown in Figure 1. There were no complaints regarding polished two-piece implants designed mainly for the tubero-pterygoid region. However, only 350 sold pieces were included in the comparison. Rough implants with a large neck diameter (4.8 mm and larger) showed the highest complaint rate (2.77%). The complaint rate for single-piece basal screw implants (Category 2, Systems: BCS, BECES, GBC) was approx. 23.3 times lower than for all other two-piece implants. Prior to group analyses, categories 4 and 5, and 3, 6, and 11 (Table 1) were tested for significant within-group differences. Thereby, the comparison of categories 4 and 5 yielded significant differences in complaint rates, χ² (1) = 26.349, p < 0.001, whereas the results of comparing categories 3, 6, and 11 indicated no significant effects, χ² (2) = 0.119, n.s. Comparing categories 4 and 5 (pc = 1.182%) against category 10 (pc = 0.913%) showed no significant difference in complaint rates, χ² (1) = 1.818, n.s., OR = 1.297 (0.907; 1.853). However, when comparing implants in categories 4 and 5 against implants in categories 3, 6, and 11 (pc = 0.527%), the results indicated a significant difference in return rates, χ² (1) = 77.097, p < 0.001. The odds of observing a complaint in categories 4 and 5 were OR = 2.257 (1.875; 2.717) times higher than in categories 3, 6, and 11. When comparing category 4 (pc = 1.059%) against category 9 (pc = 1.418%), no significant difference emerged, χ² (1) = 3.440, n.s., OR = 0.745 (0.552; 1.005).

Various implant designs based on the treatment protocol (immediate loading, two-stage, etc.) and surface properties (rough vs. polished surface) are presented in

Table 2. Grouping of various implant designs based on the treatment protocol (immediate loading, two-stage, etc.) and surface properties (rough vs. polished surface).

Group	Implant Surface and Design	Returned Number of Implants in %
group A	1-piece (rough and polished)	0.09
group A, including TPG system	immediate loading systems (1-piece and 1-piece)	0.09
group B	two-stage implants with SA/etched surface	0.73
excluded from group B	conical core, sandblasted/etched surface (Hexacone, Place, Xign)	0.91
group B, including TGP system	all implants with polished endosseous surface (1-piece, 2-piece)	0.70
group C	all implants with polished endosseous surface (1-piece, 2-piece)	0.04
group D	all implants with SA/etched surface (single-piece, two-piece)	0.39

. Complaint rates of categories 3, 6, and 11 (two-stage-implants with conical core and more aggressive threads) were significantly different compared to category 9 (Bone Level Plus), χ² (1) = 49.975, p < 0.001. Complaints in categories 3, 6, and 11 are OR = 0.368 (0.277; 0.490) times less likely to be observed than in category 9. Comparison of polished (pc = 0.037%) and rough (pc = 0.393%) surfaces yields a significant difference in complaint rates, χ² (1) = 245.130, p < 0.001. Thereby, the odds of observing complaints in the group of rough implants is OR = 10.777 (7.429; 15.630) times higher than for polished implants. With regard to implant design, two-piece implants (pc = 0.741%) showed significantly higher complaint rates than single-piece implants (pc = 0.089%), χ² (1) = 795.968, p < 0.001. The odds for implant complaints were OR = 8.408 (7.044; 10.040) higher for two-piece implants compared to single-piece implants. The implant’s core also shows a significant impact on the complaint rates, χ² (1) = 291.216, p < 0.001. Thereby, conical implants (pc = 0.309%) exhibit OR = 3.856 (3.266; 4.553) times lower odds of being returned compared to cylindrical implants (1.182%). Thread types are also significantly related to the outcome, χ² (3) = 982.317, p < 0.001. Aggressive threaded implants for 2nd-cortical engagement showed the lowest rates of complaint (pc = 0.033%), followed by compression screws (pc = 0.159%), cutting threads (pc = 0.527%), and cylindrical implants with minimal threads (pc = 1.229%). When comparing groups C and D against each other, it must be noticed that in group C mainly single-piece implants were found (99.7%), whereas the percentage of single-piece implants in group D was only 57.1%.

4. Discussion

As some implant manufacturers recognize the implant-return policy no matter the reason or circumstances, those data could be very valuable. From the clinical reality, we can assume that implant failure in most cases was because of implant-loading failure, which means that the implant was unable to work functionally. In the past, when not so many implant designs were available, patients were simply categorized based on relative and absolute contraindications for implant placement; nowadays, we rather use a low-, moderate-, or high-risk scale. Additionally, with the increased awareness in the field of biomaterials and the biology of bone-implant interference, implant features, such as shape and surface, are taken into consideration as important success factors [7,8,9]. On the other hand, remaining factors, such as the type of implant-abutment connections (internal and external hex, conical, trilobe, etc.), abutment neck diameter, time of loading, and many more, should be taken into consideration [10,11,12]. All of these can create a lot of confusion when it comes to a proper assessment of the reason for a treatment failure and how it can be corrected or improved. Moreover, this shows not only how diverse the patients are and how our approach has changed over the past years but also that an implant limitation in one case can be an advantage in another [13]. In the literature, there is still no consensus when it comes to the best implant surface for immediate loading [14]. According to Rocci et al., machined surface implants, in general, are presenting poorer results for immediate loading [14]. This statement may be accurate for implants inserted into spongious bone areas, but results from this study are not in agreement with the above, especially when it comes to implants with a cortical anchorage [15]. In the present study, the complaint rate for polished implants was the lowest among all designs; thus, our results are in agreement with studies conducted by other researchers focusing on the early or immediate loading of machined implants [16,17,18,19].

Surprisingly, implants that are “Straumann-compatible” have a high proportion of complaints. These implants’ design provides little macro-retention, and their cylindrical shape prevents spongy bone from being compressed while the implant is inserted [20]. The endosseous design of such devices has a significant impact on their success rate [21,22]. The performance of implants with essentially little thread retention (Category 4, threads 0.15 mm thicker than the core) is inferior to implants with the same connection but greater compression threads and conical design (Category 10, threads 0.25 mm thicker than the core). Single-piece compression screw implants with rough surfaces (Category 1) achieve significantly better results than two-stage implants with the same type of surface (Category 10), which is not in agreement with the paper of Limirio et al. However, they did not focus exclusively on immediate loading but rather on marginal bone loss and survival rate [23]. It appears that many dental professionals specializing in implantology simply follow the mainstream without giving appropriate thought to, for example, the true qualities of an implant design or how different designs and loading protocols cope with guided bone-regeneration materials. Future research should focus on comparing the results of this study with previous studies that followed a specific cohort of implant recipients. The findings of this study demonstrate that the rates of problems can fit the statistics on immediate or early loading found in the existing literature [24]. According to our findings, it may be concluded that there is no “good” or “poor” dental implant manufacturer; instead, the complaint rate (and hence, the “success” rate) is directly related to the implant design. Standard healing times for two-stage systems, with the exception of TGP, are 3 months for the mandible and 5–6 months for the maxilla. According to Kopp and Kopp, lateral basal implants show better performance in periodontally compromised patients. Further, if implants are placed right after extractions, the manufacturer does not restrict the use of a Strategic Implant^® system to sites that are devoid of periodontal involvement [25]. A number of implants in this study were sent back, including cemented and screwed-on prosthetic restorations. This shows that the sample size of this study comprised both early losses of unloaded implants as well as losses that happened during the implants’ utilization period. Based on the finding from this study, it can be hypothesized that the number of a particular implant type’s sales reflects its popularity, but the complaint rates may reflect its actual effectiveness. In the authors’ opinion, complaints from dental specialists and the return of the implants can be an added value when designing new implants and should be taken into consideration when a specific implant design success rate is evaluated.

5. Limitations

We cannot be certain that all missing implants are actually returned, which is one of the restrictions. Implants removed in a different office are unlikely to be returned to the original manufacturer. The fact that practitioners can clean, re-sterilize, and reuse polished implants exactly as they do with machined or polished fracture-plates used in traumatology, may be a contributing factor in the very favorable results for these implants. Even though reusing implants is not recommended in the usage guidelines, it is possible that these implants will not be returned to the manufacturer. Bivariate statistics are used to compare complaint rates. It is possible that there were confounding effects from outside factors and/or interactions among implant-related factors.

6. Conclusions

Within the limitations of the study’s methodology, the following conclusions can be drawn:

• Implants with polished endosseous surfaces and cortical engagement had the lowest rate of customer complaints, with only 0.04% of such implants being returned.
• Single-piece implants intended for instant loading have substantially lower complaint rates than “two-stage systems,” particularly when endosseous parts are “rough”
• Compared to cylindrical core implants with tiny threads, conical core implants show a 3.8-times reduced complaint rate.
• Compared to other thread types and to all other implants, aggressively threaded implants created for engagement in the second cortical have the lowest percentage of complaints (0.03%).